Nosotres, biólogues, ecologistas y otres profesionales dedicados a proteger la vida, les escribimos con una solicitud urgente. Les pedimos muy comedidamente que su organización o institución emita un comunicado oficial condenando la crisis en curso y abordando los impactos ambientales y humanitarios en Palestina.

This paper starts briefly presenting the “ontological pillars” above which Gustavo Bueno’s philosophical materialism stands as a discontinous materialism. After this, I analyze some important philosophical problems related to the ontological idea of discontinuity, such as the classical problems about Diodorus Cronus’ Master Argument and the future contingents, the “relationship between the brain and the mind”, and the ontological structure of death. Finally, this paper analyzes the utility of offering a new tipology of the main types of ontological discontinuities that (...) we can find in reality. Since Bueno’s philosophy holds the discontinous structure of matter, my paper defends the convenience of solving these problems in the future in order to expand the philosophical capacity of this worldview. (shrink)

Explaining the behaviour of ecosystems is one of the key challenges for the biological sciences. Since 2000, new-mechanicism has been the main model to account for the nature of scientific explanation in biology. The universality of the new-mechanist view in biology has been however put into question due to the existence of explanations that account for some biological phenomena in terms of their mathematical properties (mathematical explanations). Supporters of mathematical explanation have argued that the explanation of the behaviour of ecosystems (...) is usually provided in terms of their mathematical properties, and not in mechanistic terms. They have intensively studied the explanation of the properties of ecosystems that behave following the rules of a non-random network. However, no attention has been devoted to the study of the nature of the explanation in those that form a random network. In this paper, we cover that gap by analysing the explanation of the stability behaviour of the microbiome recently elaborated by Coyte and colleagues, to determine whether it fits with the model of explanation suggested by the new-mechanist or by the defenders of mathematical explanation. Our analysis of this case study supports three theses: (1) that the explanation is not given solely in terms of mechanisms, as the new-mechanists understand the concept; (2) that the mathematical properties that describe the system play an essential explanatory role, but they do not exhaust the explanation; (3) that a non-previously identified appeal to the type of interactions that the entities in the network can exhibit, as well as their abundance, is also necessary for Coyte and colleagues’ account to be fully explanatory. From the combination of these three theses we argue for the necessity of an integrative pluralist view of the nature of behaviour explanation when this is given by appealing to the existence of a random network. (shrink)

Background: Several countries have recently changed their model of consent for organ donation from opt-in to opt-out. We undertook a systematic review to determine public knowledge and attitudes towards these models in Europe. Methods: Six databases were explored between 1 January 2008 and 15 December 2017. We selected empirical studies addressing either knowledge or attitudes towards the systems of consent for deceased organ donation by lay people in Europe, including students. Study selection, data extraction, and quality assessment were conducted by (...) two or more reviewers independently. Findings: Awareness of the consent model was lower in opt-out countries than in opt-in countries. A majority of the public agrees with opt-in, regardless of the law in their own country. There are ambivalent attitudes regarding the opt-out system. The public tend to prefer opt-in and mandatory choice over opt-out when several options are offered. Interpretation: The assumption that people in opt-out countries are aware of the legal requirements to be excluded from the pool of potential donors is not supported by the results of this review. This is a concern, since ignorance hinders people's autonomy regarding organ donation decision-making. Higher awareness of consent model in opt-in countries may reflect greater efforts to inform the public through campaigns to motivate donation. Legal moves towards opt-out are at odds with people's expressed preferences. Main limitations of this review are the lack of data from some countries, study population heterogeneity, and methodological shortcomings. (shrink)

Since 1968, the irreversible loss of functioning of the whole brain, called brain death, is assimilated to individual’s death. The almost universal acceptance of this neurological criterion of death had decisive consequences for the contemporary medicine, such as the withdrawal of mechanical ventilation in these patients and organ retrieval for transplantation. The new criterion was successfully accepted in part because the assimilation of brain death state to death was presented by medicine --and acritically assumed by most of societies-- as a (...) scientific and objective fact. Nevertheless, many people do not think that the patients suffering brain death are actually dead. We show here that those people are not necessarily wrong. It can be argued that, in fact, the justification of the neurological criterion is not scientific but moral. We outline the thesis that the problem surrounding the vital status of brain dead patients is due to a confusion between factual and normative questions. Furthermore, we claim that the donation of organs and the withdrawal of life-support could be ethically acceptable even if the patients suffering brain death are considered as alive. As an alternative to the dead donor rule, we propose a justification for organ donation of brain-dead patients based on the (moral) concepts of harm and consent : what truly justifies the procurement of organs on those patients is not that they are dead, but that they wish to donate their organs and that, since they have irreversibly lost their brain, they cannot be harmed. (shrink)

Objectives To increase postmortem organ donation rates, several countries are adopting an opt-out (presumed consent) policy, meaning that individuals are deemed donors unless they expressly refused so. Although opt-out countries tend to have higher donation rates, there is no conclusive evidence that this is caused by the policy itself. The main objective of this study is to better assess the direct impact of consent policy defaults per se on deceased organ recovery rates when considering the role of the family in (...) the decision-making process. This study does not take into account any indirect effects of defaults, such as potential psychological and behavioural effects on individuals and their relatives. -/- Design Based on previous work regarding consent policies, we created a conceptual model of the decision-making process for deceased organ recovery that included any scenario that could be directly influenced by opt-in or opt-out policies. We then applied this model to internationally published data of the consent process to determine how frequently policy defaults could apply. -/- Main outcome measures We measure the direct impact that opt-in and opt-out policies have per se on deceased organ recovery. -/- Results Our analysis shows that opt-in and opt-out have strictly identical outcomes in eight out of nine situations. They only differ when neither the deceased nor the family have expressed a preference and defaults therefore apply. The direct impact of consent policy defaults is typically circumscribed to a range of 0%–5% of all opportunities for organ recovery. Our study also shows that the intervention of the family improves organ retrieval under opt-in but hinders it under opt-out. -/- Conclusions This study may warn policy makers that, by emphasising the need to introduce presumed consent to increase organ recovery rates, they might be overestimating the influence of the default and underestimating the power granted to families. (shrink)

Background Consent policies for post-mortem organ procurement (OP) vary throughout Europe, and yet no studies have empirically evaluated the ethical implications of contrasting consent models. To fill this gap, we introduce a novel indicator of governance quality based on the ideal of informed support, and examine national differences on this measure through a quantitative survey of OP policy informedness and preferences in seven European countries. -/- Methods Between 2017–2019, we conducted a convenience sample survey of students (n = 2006) in (...) Austria (AT), Belgium (BE), Denmark (DK), Germany (DE), Greece (GR), Slovenia (SI) and Spain (ES), asking participants about their donation preferences, as well as their beliefs and views about the policy in place. From these measures, we computed indices of informedness, policy support, and fulfilment of unexpressed preferences, which we compared across countries and consent systems. -/- Results Our study introduces a tool for analyzing policy governance in the context of OP. Wide variation in policy awareness was observed: Most respondents in DK, DE, AT and BE correctly identified the policy in place, while those in SI, GR and ES did not. Respondents in opt-out countries (AT, BE, ES and GR) tended to support the policy in place (with one exception, i.e., SI), whereas those in opt-in countries (DE and DK) overwhelmingly opposed it. These results reveal stark differences in governance quality across countries and consent policies: We found a preponderance of informed opposition in opt-in countries and a general tendency towards support–either informed or uninformed–in opt-out countries. We also found informed divergence in opt-in countries and a tendency for convergence–either informed or uninformed–among opt-out countries. -/- Conclusion Our study offers a novel tool for analyzing governance quality and illustrates, in the context of OP, how the strengths and weaknesses of different policy implementations can be estimated and compared using quantitative survey data. (shrink)

Sacrificial dilemmas such as the trolley problem play an important role in experimental philosophy (x-phi). But it is increasingly argued that, since we are not likely to encounter runaway trolleys in our daily life, the usefulness of such thought experiments for understanding moral judgments in more ecologically valid contexts may be limited. However, similar sacrificial dilemmas are experienced in real life by animal research decision makers. As part of their job, they must make decisions about the suffering, and often the (...) death, of many non-human animals. For this reason, a context-specific investigation of so-called “3R dilemmas” (i.e., dilemmas where there is a conflict between the principles of replacement, reduction, and refinement of the use of animals in research) is essential to improve the situation of both non-human animals and human stakeholders. An approach well suited for such investigation is experimental philosophical bioethics (“bioxphi”), which draws on methods similar to x-phi to probe more realistic, practical scenarios with an eye to informing normative debates and ethical policy. In this article, we argue for a need to investigate 3R dilemmas among professional decision-makers using the tools of bioxphi. In a first step, we define 3R dilemmas and discuss previous investigations of professionals’ attitudes in such cases. In a second step, we show how bioxphi is a promising method to investigate the whys and hows of professional decision-making in 3R dilemmas. In a last step, we provide a bioxphi template for 3R dilemmas, give recommendations on its use, explore the normative relevance of data collected by such means, and discuss important limitations. (shrink)

Goal: To assess public knowledge and attitudes towards the family’s role in deceased organ donation in Europe. -/- Methods: A systematic search was conducted in CINHAL, MEDLINE, PAIS Index, Scopus, PsycINFO, and Web of Science on December 15th, 2017. Eligibility criteria were socio-empirical studies conducted in Europe from 2008 to 2017 addressing either knowledge or attitudes by the public towards the consent system, including the involvement of the family in the decision-making process, for post-mortem organ retrieval. Screening and data collection (...) were performed by two or more independent reviewers for each record. -/- Results: Of the 1482 results, 467 studies were assessed in full-text form, and 33 were included in this synthesis. When the deceased has not expressed any preference, a majority of the public support the family's role as a surrogate decision-maker. When the deceased expressly consented, the respondents' answers depend on whether they see themselves as potential donors or as a deceased's next-of-kin. Answers also depend on the relationship between the deceased and the decision-maker(s) within the family, and on their ethnic or cultural background. -/- Conclusions: Public views on the authority of the family in organ donation decision-making require further research. A common conceptual framework and validated well-designed questionnaires are needed for future studies. The findings should be considered in the development of Government policy and guidance regarding the role of families in deceased organ donation. (shrink)

Families play an essential role in deceased organ procurement. As the person cannot directly communicate his or her wishes regarding donation, the family is often the only source of information regarding consent or refusal. We provide a systematic description and analysis of the different roles the family can play, and actions the family can take, in the organ procurement process across different jurisdictions and consent systems. First, families can inform or update healthcare professionals about a person’s donation wishes. Second, families (...) can authorize organ procurement in the absence of deceased’s preferences and the default is not to remove organs, and oppose donation where there is no evidence of preference but the default is to presume consent; in both cases, the decision could be based on their own wishes or what they think the deceased would have wanted. Finally, families can overrule the known wishes of the deceased, which can mean preventing donation, or permitting donation when the deceased refused it. We propose a schema of 4 levels on which to map these possible family roles: no role, witness, surrogate, and full decisional authority. We conclude by mapping different jurisdictions onto this schema to provide a more comprehensive understanding of the consent system for organ donation and some important nuances about the role of families. This classificatory model aims to account for the majority of the world’s consent systems. It provides conceptual and methodological guidance that can be useful to researchers, professionals, and policymakers involved in organ procurement. (shrink)

Despite the central presence of materialism in the history of philosophy, there is no universal consensus on the meaning of the word “matter” nor of the doctrine of philosophical materialism. Dictionaries of philosophy often identify this philosophy with its most reductionist and even eliminative versions, in line with Robert Boyle’s seventeenth century coinage of the term. But when we take the concept back in time to Greek philosophers and forward onto our own times, we recognize more inclusive forms of materialism (...) as well as complex interplays with non-materialist thought about the place of matter in reality, including Christian philosophy and German idealism. We define philosophical materialism in its most general way both positively (the identification of reality with matter understood as changeability and plurality) and negatively (the negation of disembodied living beings and hypostatized ideas). This inclusive approach to philosophical materialism offers a new light to illuminate a critical history of the concept of matter and materialism from Ancient Greece to the present that is also attentive to scientific developments. By following the most important connections and discontinuities among theoretical frameworks on the idea of matter, we present a general thread that offers a rich and plural, but highly cohesive, field of investigation. Finally, we propose building on rich non-reductionist materialist philosophies, such as Mario Bunge’s systemic materialism and Gustavo Bueno’s discontinuous materialism, to elaborate powerful theoretical alternatives to both physicalism and spiritualism. (shrink)

This paper analyses the arguments for and against what we have called automatic organ procurement model in relation to the organs of the deceased. For this purpose, this work provides empirical evidence to assess the potential impact of this model on donation rates and on public opinion. Specifically, we examine first the reasons supporting this model, with special reference to utilitarian and justice arguments. On the other hand, we analyse both the approaches based on the violation of pre mortem and (...) post mortem interests opposing this theoretical model and the rejection the model would generate in the population. Finally, we point out the aspects that, in our opinion, should be exhaustively regulated if this model were implemented. In particular, we refer to the legal status of the human body, the treatments for end-of-life patients, the incentives for health professionals and the recognition of the right to conscientious objection. (shrink)

Throughout the biological and biomedical sciences there is a growing need for, prescriptive ‘minimum information’ (MI) checklists specifying the key information to include when reporting experimental results are beginning to find favor with experimentalists, analysts, publishers and funders alike. Such checklists aim to ensure that methods, data, analyses and results are described to a level sufficient to support the unambiguous interpretation, sophisticated search, reanalysis and experimental corroboration and reuse of data sets, facilitating the extraction of maximum value from data sets (...) them. However, such ‘minimum information’ MI checklists are usually developed independently by groups working within representatives of particular biologically- or technologically-delineated domains. Consequently, an overview of the full range of checklists can be difficult to establish without intensive searching, and even tracking thetheir individual evolution of single checklists may be a non-trivial exercise. Checklists are also inevitably partially redundant when measured one against another, and where they overlap is far from straightforward. Furthermore, conflicts in scope and arbitrary decisions on wording and sub-structuring make integration difficult. This presents inhibit their use in combination. Overall, these issues present significant difficulties for the users of checklists, especially those in areas such as systems biology, who routinely combine information from multiple biological domains and technology platforms. To address all of the above, we present MIBBI (Minimum Information for Biological and Biomedical Investigations); a web-based communal resource for such checklists, designed to act as a ‘one-stop shop’ for those exploring the range of extant checklist projects, and to foster collaborative, integrative development and ultimately promote gradual integration of checklists. (shrink)

It is a matter of fact that Europe is facing more and more crucial challenges regarding health and social care due to the demographic change and the current economic context. The recent COVID-19 pandemic has stressed this situation even further, thus highlighting the need for taking action. Active and Assisted Living technologies come as a viable approach to help facing these challenges, thanks to the high potential they have in enabling remote care and support. Broadly speaking, AAL can be referred (...) to as the use of innovative and advanced Information and Communication Technologies to create supportive, inclusive and empowering applications and environments that enable older, impaired or frail people to live independently and stay active longer in society. AAL capitalizes on the growing pervasiveness and effectiveness of sensing and computing facilities to supply the persons in need with smart assistance, by responding to their necessities of autonomy, independence, comfort, security and safety. The application scenarios addressed by AAL are complex, due to the inherent heterogeneity of the end-user population, their living arrangements, and their physical conditions or impairment. Despite aiming at diverse goals, AAL systems should share some common characteristics. They are designed to provide support in daily life in an invisible, unobtrusive and user-friendly manner. Moreover, they are conceived to be intelligent, to be able to learn and adapt to the requirements and requests of the assisted people, and to synchronise with their specific needs. Nevertheless, to ensure the uptake of AAL in society, potential users must be willing to use AAL applications and to integrate them in their daily environments and lives. In this respect, video- and audio-based AAL applications have several advantages, in terms of unobtrusiveness and information richness. Indeed, cameras and microphones are far less obtrusive with respect to the hindrance other wearable sensors may cause to one’s activities. In addition, a single camera placed in a room can record most of the activities performed in the room, thus replacing many other non-visual sensors. Currently, video-based applications are effective in recognising and monitoring the activities, the movements, and the overall conditions of the assisted individuals as well as to assess their vital parameters. Similarly, audio sensors have the potential to become one of the most important modalities for interaction with AAL systems, as they can have a large range of sensing, do not require physical presence at a particular location and are physically intangible. Moreover, relevant information about individuals’ activities and health status can derive from processing audio signals. Nevertheless, as the other side of the coin, cameras and microphones are often perceived as the most intrusive technologies from the viewpoint of the privacy of the monitored individuals. This is due to the richness of the information these technologies convey and the intimate setting where they may be deployed. Solutions able to ensure privacy preservation by context and by design, as well as to ensure high legal and ethical standards are in high demand. After the review of the current state of play and the discussion in GoodBrother, we may claim that the first solutions in this direction are starting to appear in the literature. A multidisciplinary debate among experts and stakeholders is paving the way towards AAL ensuring ergonomics, usability, acceptance and privacy preservation. The DIANA, PAAL, and VisuAAL projects are examples of this fresh approach. This report provides the reader with a review of the most recent advances in audio- and video-based monitoring technologies for AAL. It has been drafted as a collective effort of WG3 to supply an introduction to AAL, its evolution over time and its main functional and technological underpinnings. In this respect, the report contributes to the field with the outline of a new generation of ethical-aware AAL technologies and a proposal for a novel comprehensive taxonomy of AAL systems and applications. Moreover, the report allows non-technical readers to gather an overview of the main components of an AAL system and how these function and interact with the end-users. The report illustrates the state of the art of the most successful AAL applications and functions based on audio and video data, namely lifelogging and self-monitoring, remote monitoring of vital signs, emotional state recognition, food intake monitoring, activity and behaviour recognition, activity and personal assistance, gesture recognition, fall detection and prevention, mobility assessment and frailty recognition, and cognitive and motor rehabilitation. For these application scenarios, the report illustrates the state of play in terms of scientific advances, available products and research project. The open challenges are also highlighted. The report ends with an overview of the challenges, the hindrances and the opportunities posed by the uptake in real world settings of AAL technologies. In this respect, the report illustrates the current procedural and technological approaches to cope with acceptability, usability and trust in the AAL technology, by surveying strategies and approaches to co-design, to privacy preservation in video and audio data, to transparency and explainability in data processing, and to data transmission and communication. User acceptance and ethical considerations are also debated. Finally, the potentials coming from the silver economy are overviewed. (shrink)

En los últimos tiempos el derecho ambiental ha ganado un puesto importante en el ámbito jurídico, hecho que refleja la preocupación que hoy se tiene por la relación del hombre con su entorno. Desde hace quince años, la Universidad Colegio Mayor de Nuestra señora del Rosario, por intermedio de su Facultad de Jurisprudencia y concretamente de la Especialización y la línea de investigación en Derecho Ambiental, ha propuesto a través de diversos proyectos avanzar en el conocimiento y análisis del ordenamiento (...) jurídico ambiental, aportando así al desarrollo, estructura y consolidación de esta rama jurídica. Bajo estos parámetros, el objetivo de esta publicación es hacer algunas reflexiones en torno a distintos temas que dentro del derecho público impactan o influyen al derecho ambiental y responder a los enormes desafíos que se presentan en la materia. Por tanto, el programa quiere contribuir desde la academia al diálogo crítico y propositivo que permita dar solución a los problemas encontrados en la aplicación del derecho ambiental. En el primer capítulo, Gloria Amparo Rodriguez describe los ordenamientos jurídicos constitucionales de Colombia, Ecuador y Bolivia a fin de analizar la forma en que cada uno de ellos consagra el derecho a un ambiente sano. A continuación, Martha Ovalle y Zelba Nidia Castro de Perez realizan un estudio de los principios de precaución y prevención, exponiendo su alcance, su fundamento desde el derecho internacional y cómo vienen siendo entendidos por nuestro ordenamiento jurídico, tanto jurisprudencial como legal. Luis Adolfo Diazgranados se ocupa de la responsabilidad de los funcionarios públicos en materia ambiental, para lo cual realiza un análisis de los deberes consagrados en la normatividad vigente. Continuando con esta temática, el profesor Jorge Agudo Gonzalez, de la Universidad Autónoma de Madrid, explora la incidencia del ambiente y los recursos naturales en los procesos contractuales, a fin de mostrar cómo estas materias se han constituido en variable fundamental en el devenir de la formación, celebración y ejecución de los contratos, desde un punto de vista crítico, los aspectos importantes del proceso sancionatorio ambiental, evidenciando las falencias y vacios del a Ley 1333 de 2009. Jairo Cabrera plantea algunas reflexiones sobre la responsabilidad, valiéndose de la doctrina internacional, sobre la problemática de la reparación por daño ambiental. Por su parte, Leonardo Güiza Suárez explica el régimen general de la responsabilidad ambiental en el ordenamiento jurídico a partir del daño de los bosques naturales y su incidencia sobre los derechos humanos. Andres Gomez Rey, desde la teoría del acto administrativo, desarrolla el análisis crítico del régimen jurídico de las aguas superficiales en el derecho ambiental. Giovani J. Herrera Carrascal realiza una disertación sobre los recursos naturales y el ambiente como elementos del espacio público que a su vez constituye en un componente del medio ambiente urbano a partir de la jurisprudencia y de las competencias respectivas. Por último, Marybell Ochoa Miranda trate el tema de los residuos hospitalarios en Colombia, exponiendo su régimen jurídico, las competencias de las autoridades ambientales, los deberes que en estos asuntos tienen los ciudadanos, proponiendo lineamientos para avanzar en la consolidación de la gestión integral de residuos hospitalarios y similares. (shrink)

Perez-Rodriguez and de la Fuente (2017) assume that although human races do not exist in a biological sense (“geneticists and evolutionary biologists generally agree that the division of humans into races/subspecies has no defensible scientific basis,” they exist only as “sociocultural constructions” and because of that maintain an illusory reality, for example, through “racialized” practices in medicine. Agreeing with the main postulates formulated in the article, we believe that the authors treat this problem in a superficial manner and (...) have failed to capture the current state of the field of knowledge in science and the humanities. In our commentary, we want to highlight two main omissions, and to notice three important implications for “a postracial medicine.”. (shrink)

Esta investigación retoma la obra de Gabriel García Márquez, Noticia de un secuestro (1996), con la volición de cuestionar la idea de Estado nación que está inmersa en el libro. Para ello, es necesario entender que la naturaleza del texto exige un conocimiento amplio al lector o al intérprete, puesto que su contenido revela datos multidisciplinarios. Además, es insoslayable realizar un análisis discursivo de la historia de ese contexto y cotejar con pasajes del mismo libro. Para facilitar esta labor, la (...) extrapolación de conceptos del teórico Luis Rodríguez Manzanera será de utilidad, ya que él despliega definiciones de Criminología, un tema frecuente en la obra. Verbigracia, la macrocriminalidad, una noción que él postula, permite que se comprenda la complexión del periodo histórico finisecular del siglo XX en Colombia, etapa que le corresponde a Noticia de un secuestro. Por otro lado, es menester dilucidar que este estudio no se reduce a lo literario, lo histórico y lo criminológico, sino que abarca distintas disciplinas, por lo que la exigencia en la consolidación epistemológica e interpretativa estará demostrada consuetudinariamente, sin obviar la inmanencia de la obra. Este tipo de análisis interdisciplinarios ya ha sido trabajado desde los Estudios Culturales, tal como se constata en las investigaciones de Richard Johnson (2000) o Néstor García Canclini (1997). De igual modo, el intento de establecer lineamientos y conexiones entre disciplinas como las de Literatura y Derecho ya ha sido desarrollado por Stanley Fish (1986), Faustino Martínez (2005), Carlos Pérez (2006) y Denise Schalet (2014). A diferencia de estos abordajes ya estudiados, el objetivo de esta investigación es detectar y fundamentar cómo se articula una propuesta ideológica desde una configuración que reanuda elementos históricos y literarios. En específico, lo que se busca es argumentar por qué fracasó implícitamente un proyecto sociopolítico de democracia y progreso, a partir de un panorama de violencia, narcoterrorismo, corrupción, negociaciones ilícitas, transgresión a los derechos humanos e inseguridad ciudadana. Con todo ello, esta tesis de maestría terminará siendo fructuosa para análisis postremos de discursos que tienen como esencia un soporte multidisciplinario. (shrink)

Brought to you by: Crop X editors: Jonathan Alexander Perez, Harmony Smith, Corinne Tendorf, David Turturo, and Derek Rahn Williams. Faculty Advisor: David Turturo; Crop X team included: Chaimae Alehyane, Zachary S. Casey, Suzanna Brinez, Jacob Brown, Elizabeth George, Francisco Javier Muniz Ituarte, Brodey Myers. -/- Credits: Huckabee College of Architecture; Graphic Designers: Studio BLDG (Blossom Liu + Danny Gray); English Editor: Luke Studebaker; Spanish Translator: Jessie Forbes; Printer: Die Keure. Cover Photo: Derek Williams. -/- Generously supported by (...) the Graham Foundation for Advanced Studies in the Fine Arts and the Huckabee College of Architecture, Texas Tech University. (shrink)

TRANSPORTE DE GAMETAS, FERTILIZAÇÃO E SEGMENTAÇÃO -/- • _____OBJETIVO -/- O entendimento do desenvolvimento embrionário nos estágios iniciais, desde a deposição dos espermatozoides na fêmea, passando pela fertilização deste no ovócito e na formação do zigoto, é de suma importância para diferenciar especialistas em reprodução e manejo reprodutivo no mercado de trabalho e, também, durante a vida acadêmica. Compreender os processos que levam à formação do zigoto na fêmea é essencial para avaliar a capacidade reprodutiva dos animais e, mediante técnicas, (...) avaliar o trato reprodutivo da fêmea e o desenvolvimento do embrião até a formação do feto e, por fim, em um novo animal sadio na propriedade. Com esse trabalho, o estudante de veterinária ou zootecnia, que deseja se aprofundar na fisiologia da reprodução animal, identificará os mecanismos que são envolvidos no transporte dos gametas, bem como os processos que estes últimos devem completar para alcançar a fertilização e para desencadear as divisões iniciais do embrião. -/- • _____INTRODUÇÃO -/- A fertilização ou fecundação é o processo pelo qual os gametas masculino (espermatozoide) e feminino (ovócito) se fundem para gerar um novo indivíduo. Seu êxito depende da culminação adequada dos diferentes processos que devem sofrer os gametas durante sua maduração e percurso; do transporte oportuno destes no trato reprodutivo da fêmea, assim como de uma série de adaptações dos órgãos genitais internos da mãe. A segmentação refere-se às primeiras divisões celulares do embrião. -/- • _____TRANSPORTE DO OVÓCITO -/- O ovócito que é liberado na ovulação, e que se encontra coberto pelas células do cumulus (figura 1), é capturado pela fímbria do infundíbulo ao aderir aos cílios. Esse processo é altamente eficaz, inclusive em espécies onde os ovários possuem várias formações globosas, por exemplo nas porcas, onde os ovidutos capturam entre 95 e 100% dos ovócitos que são ovulados. As contrações das camadas musculares do oviduto e o movimento intenso dos cílios da mucosa faz com que as secreções fluam em direção ao útero, transportando assim o complexo cumulus-ovócito. Esse transporte é relativamente rápido até alcançar a junção da ampola com o istmo (que é considerado o local de fertilização do espermatozoide e ovócito) a partir do qual se torna lento. Devido a fêmea estar em estro, o processo está sob controle endócrino, isto é, controle hormonal através do estradiol. Nas fêmeas domésticas, ao contrário das mulheres, o transporte ao longo do oviduto é extremamente eficiente, pois os embriões passam para o útero sem dificuldade, de modo que gestações ectópicas (tubárias ou em cavidade) são quase inexistentes. A égua, frequentemente, retém por muito tempo os ovócitos não fertilizados no oviduto, provavelmente devido a não secreção de substâncias (como a prostaglandina E) que poderiam favorecer sua passagem, como se propõe que aconteça com os embriões. A figura 2 apresenta um ovócito com suas respectivas estruturas. Figura 1: ovócitos de uma vaca madurados in vitro. Nota-se as células do cumulus que os recobre. -/- Figura 2: estruturas do ovócito de uma ovelha que se encontra na etapa de ovócito secundário, depois da ovulação. Elaborado pelo autor. • _____TRANSPORTE ESPERMÁTICO -/- Para que os espermatozoides sejam capazes de fertilizar o ovócito, deverão sofrer uma série de mudanças bioquímicas e morfológicas ao longo de sua passagem pelo aparelho reprodutor tanto masculino como feminino. Uma vez produzidos na parede do túbulo seminífero, os espermatozoides são liberados em direção ao lúmen tubular e transportados passivamente para uma estrutura ramificada conhecida como rede testicular (rete testis). Dessa rede são conduzidos em direção ao epidídimo passando através de 10 a 20 ductos eferentes localizados no polo superior do testículo. O epidídimo é dividido em três seções denominadas cabeça, corpo e cauda; é constituído por um só ducto longo e tortuoso que continua com o canal deferente. Ao final desemboca nas ampolas seminais, no ducto ejaculatório e na uretra. As funções do epidídimo são as de maduração, transporte e armazenamento dos espermatozoides. O transporte através do epidídimo é lento, aproximadamente de 10 dias em touros, e segue sendo passivo. Os espermatozoides tomados da cabeça do epidídimo são ainda imaturos e incapazes de fertilizar, enquanto os armazenados na cauda são completamente maduros. Durante o trânsito pelo epidídimo os espermatozoides adquirem motilidade e o potencial para fertilizar, o acrossomo é remodelado e a gota citoplasmática migra para o flagelo e é liberada. Quando um macho ejacula com muita frequência, é possível observar espermatozoides com gota citoplasmática no sêmen, já que não há tempo suficiente para que completem sua maduração. Os espermatozoides são expulsados fora do organismo durante a cópula, na masturbação ou em emissões espontâneas. Na ejaculação, os espermatozoides que se encontram suspensos nos fluidos do testículo e do epidídimo, misturam-se ao chegar na uretra com as secreções das glândulas acessórias para formar o sêmen. Essas secreções denominadas plasma seminal, proporcionam substâncias para manter o metabolismo energético das células espermáticas, e integram suas membranas elementos que impedem uma capacitação prematura. Durante a cópula, o sêmen é depositado na vagina ou no útero, variando entre as espécies (tabela 1). Na monta natural, geralmente, o serviço ocorre no momento propício, já que está definido pela fase do ciclo estral em que a fêmea é receptiva ao macho. No entanto, na inseminação artificial, é o macho que deverá determinar o momento ideal, e para isso é importante considerar a vida média dos gametas, ao qual é muito curta no caso dos ovócitos (tabela 1). -/- Tabela 1: local de depósito do sêmen, volume da ejaculação e vida média dos gametas. Espécie Local de deposição Volume (ml) Velocidade de ejaculação Vida média do ovócito Vida média do espermatozoide Bovinos Intravaginal 2 1 – 3 seg 8 h 30 – 48 h Caninos Intravaginal 2 – 30 (10 média) 6 – 45 min 48 – 72 h 9 – 11 d Equinos Intrauterina 50 – 200 20 – 60 seg 6 – 8 h 72 – 120 h Humanos Intravaginal 3 - - 5 – 6 d Ovinos Intravaginal 1 1 – 2 seg 16 – 24 h 30 – 48 h Suínos Intrauterina 200 – 400 5 – 20 min 8 – 10 h 24 – 48 h Onde d = dias; h = horas. A vida fértil do ovócito é muito curta, portanto, o momento do serviço é de grande importância para obter altos índices de fertilização. -/- Independentemente do local em que os espermatozoides sejam depositados no aparelho reprodutor feminino, serão expostos às secreções genitais e sofrem uma série de mudanças em seu trajeto até o local de fertilização antes de penetrar no ovócito. Nas espécies em que o sêmen é depositado na parte cranial da vagina, uma parte do mesmo penetra através da cérvix, enquanto outra parte é eliminada do aparelho genital da fêmea, em pouco tempo, através do fluxo retrógrado. O meio vaginal não é adequado e imobiliza os espermatozoides em pouco tempo, pelo qual deverão entrar no útero onde o ambiente é mais propício. O transporte espermático na fêmea é o resultado da alta contratilidade, do movimento ciliar e o fluido do aparelho genital durante o estro, ao qual está sob controle endócrino e do sistema nervoso. Esse transporte é favorecido pelas características especiais do muco estral, cujas moléculas formam uma espécie de canais que facilitam a passagem dos espermatozoides. Pelo contrário, durante a fase lútea seu transporte é dificultado. Além do meio vaginal, a cérvix também atua como barreira natural para limitar a passagem dos espermatozoides, diminuindo assim a possibilidade de polispermia. Funciona, também, como um filtro que seleciona os espermatozoides aptos dos que não o são, uma vez que somente os primeiros possuem uma motilidade vigorosa que lhes permite passar pelo muco altamente hidratado. Na vaca a cérvix é considerada como um reservatório espermático. Quando atravessam a cérvix, os espermatozoides seguem sua deslocação tanto por movimento próprio como pelas contrações uterinas e tubárias. Nas espécies em que o local de depósito do sêmen do macho na fêmea é intrauterino, como equinos, a principal barreira que os espermatozoides enfrentam é a união ou junção útero-tubárica. A união entre o útero e o oviduto (istmo do oviduto) serve como reservatório funcional dos espermatozoides nas espécies domésticas. Poucos minutos depois da cópula, é possível encontrar alguns espermatozoides no oviduto, que é conhecido como fase de transporte rápido. No entanto, esses espermato-zoides não são os que participam do processo de fertilização e podem apresentar certas anormalidades. Existe um segundo tipo de transporte denominado fase sustentada, a qual consiste na migração prolongada dos espermatozoides em direção as partes mais craniais do aparelho genital feminino, que conduzem à colonização do reservatório funcional e na liberação gradual dos espermatozoides dos reservatórios espermáticos, incluindo este último. O reservatório do istmo fornece aos espermatozoides um ambiente propício, protegendo-os contra a fagocitose, prolongando assim a sua viabilidade. Aqui os esper-matozoides permanecem aderidos a superfície das células ciliadas do epitélio até a finalização de sua capacitação, depois da qual são liberados quando alteram seu padrão de motilidade flagelada, fenômeno conhecido como hipermotilidade, e migram em ondas em direção ao local da fertilização. Dos milhões de espermatozoides ejaculados, somente alguns milhares alcançarão o istmo do oviduto e um número sumamente pequeno será encontrado nas imediações do ovócito no momento da fertilização. -/- • _____CAPACITAÇÃO ESPERMÁTICA E REAÇÃO ACROSSÔMICA -/- A capacitação é um processo gradual e essencial para a fertilização. Os espermato-zoides devem passar por um dado tempo de “incubação” no aparelho genital da fêmea e sofrer uma série de mudanças antes de serem capazes de fecundar o ovócito. A capacita-ção dos espermatozoides começa quando eles entram em contato com as secreções do aparelho genital da fêmea e termina no istmo do oviduto. Durante esse percurso a superfície da cabeça do espermatozoide se modifica já que algumas moléculas como o colesterol são removidas da membrana plasmática, aumentando sua fluidez e alterando suas propriedades bioquímicas. Entre outras coisas, essa reorganização dos lipídios facilita a entrada de cálcio extracelular pelos canais iônicos e ocasiona a desestabilização da membrana, tornando-a mais fusogênica. Também são eliminados outros fatores (conhecidos genericamente como fatores descapacitantes) que expõem receptores membranais indispensáveis para a realização da união entre o espermatozoide e o ovócito durante a fertilização. Os espermatozoides capacitados apresentam um padrão de hipermotilidade e uma maior atividade metabólica, características que devem obter para que sejam capazes de penetrar as camadas do ovócito. A capacitação é necessária para que ocorra a reação acrossômica. A reação acrossomal ou acrossômica (RA) é um fenômeno de exocitose que é desencadeada pela ligação entre as proteínas e receptores localizados na membrana do espermatozoide e a zona pelúcida do ovócito (figura 3). Envolve a fusão da membrana plasmática do espermatozoide com a membrana externa de seu acrossomo; formando, assim, pequenas vesículas, cujo conteúdo de enzimas hidrolíticas, como a hialuronidase e a acrosina, é liberado em direção ao seu exterior, facilitando a penetração da zona pelúcida. A adesão do espermatozoide à zona pelúcida é específica da espécie e depende de glicoproteínas presentes na membrana dos ovócitos maduros; a cabeça do espermatozoide se une com essas glicoproteínas mediante receptores específicos e atravessam em direção oblíqua a zona pelúcida até chegar ao espaço perivitelino. Nos mamíferos, particularmente em roedores e nos humanos, algumas dessas glicoproteínas são conhecidas como ZP1, ZP2 e ZP3. Pensa-se que a união da membrana espermática a esta última é o que desencadeia a reação acrossomal. Posteriormente, as vilosidades do ovócito entram em contato com o espermatozoide e a membrana presente na secreção equatorial da cabeça do espermatozoide, que tem proteínas fusogênicas específicas, une-se a membrana plasmática do ovócito, fusionando-se e permitindo a entrada do núcleo espermático ao citoplasma (figura 4). A capacitação dos espermatozoides é fundamental para o êxito da fertilização, uma vez que apenas os aptos estarão perfeitos e íntegros para que a união e percepção das glicoproteínas presentes nos mesmos possam ocorrer de forma ideal para a penetração deste no ovócito, fertilizá-lo e formar um zigoto. Figura 3: estrutura do espermatozoide. Nota: a membrana é acrossomal e não acrossonal. Elaborado pelo autor. -/- Figura 4: eventos que ocorrem durante a fertilização. A – depois de passar através das células do cumulus, o espermatozoide entra em contato com a zona pelúcida, onde receptores da membrana plasmática reconhecem as proteínas da zona pelúcida; B – é desencadeada, então, a reação acrossomal; C – para que o espermatozoide penetre na zona pelúcida; D – ao atravessar a zona pelúcida e entrar no espaço perivitelino, a cabeça do espermatozoide entra em contato com a membrana vitelina; ambas membranas se fusionam graças ao reconhecimento de proteínas fusogênicas que estão no segmento equatorial. E – ocorre, então, que o núcleo do espermatozoide penetra no citoplasma do ovócito; uma das consequências da fusão da membrana com a cabeça do espermatozoide é a reação cortical, em que os grânulos corticais do ovócito liberam seu conteúdo em direção ao espaço perivitelino, o que resulta na alteração da estrutura da zona pelúcida e da membrana vitelina para bloquear a polispermia. Elaborado pelo autor. • _____CONSEQUÊNCIAS DA PENETRAÇÃO -/- Bloqueio da polispermia -/- A fusão das membranas dos gametas durante a penetração permite a entrada da fosfolipase C zeta (PLCζ) – fator solúvel que provém do espermatozoide – que desencadeia liberação e oscilações de Ca2+ no retículo endoplasmático. Isso, por sua vez, provoca a migração e fusão dos grânulos corticais, com a consequente liberação de enzimas, que mudam tanto a estrutura da zona pelúcida (por exemplo a inativação de ZP3), como a da membrana vitelina. Desse modo, impede-se que outros espermatozoides as penetrem, evitando assim a polispermia (figura 5). -/- Figura 5: os grânulos corticais que encontram-se na periferia do citoplasma, debaixo da superfície da membrana do ovócito, migram e fusionam-se sobre a mesma, liberando seu conteúdo no espaço perivitelino imediatamente depois da penetração do espermatozoide. A – como conse-quência, tanto a membrana vitelina como a zona pelúcida são modificadas, impedindo a entrada de mais espermatozoides, o que evita a polispermia. B – o ovócito retoma, então, sua segunda divisão meiótica, que ocasiona a expulsão do segundo corpúsculo polar, e na formação dos pronúcleos feminino e masculino. C – continuando, os pronúcleos migram, suas membranas se dissolvem e os cromossomos de ambos se condensam e se unem. Completa-se, assim, a singamia e forma-se, então, o zigoto. Elaborado pelo autor baseado nos livros de embriologia e fisiologia da reprodução conforme vida bibliografia. -/- Ativação do ovócito e formação de pronúcleos -/- Na maioria das fêmeas domésticas, com exceção da cadela, o ovócito encontra-se suspenso na metáfase II da segunda meiose no momento da ovulação. A entrada da PLCζ do espermatozoide no citoplasma do ovócito, e a consequente liberação de Ca2+, faz com que o ovócito se ative, terminando a segunda divisão meiótica e expulse o segundo corpo polar. Posteriormente, o material nuclear do ovócito se reorganiza para formar o pronú-cleo feminino. Entretanto, a membrana nuclear do espermatozoide se dissolve, a cromatina descondensa-se, as protaminas são substituídas por histonas, e se forma uma nova membrana nuclear, dando lugar ao pronúcleo masculino. -/- Singamia -/- Uma vez que os pronúcleos feminino e masculino são formados, migram para o centro do ovócito, aproximam-se, suas membranas se dispersam e os cromossomos paternos e maternos se associam, com o qual recupera a condição diploide e dá origem ao zigoto (figura 5). -/- • _____DESENVOLVIMENTO EMBRIONÁRIO -/- Poucas horas após a fertilização ocorre a primeira divisão do zigoto em duas, depois em 4, 8, 16 e 32 células, denominadas blastômeros. Essas divisões mitóticas são conhecidas como divisões de segmentação ou clivagem (figura 6), uma vez que são realizadas sem aumento do citoplasma, de modo que com cada divisão os blastômeros se tornam menores. A partir das 16 células o embrião se chama mórula, e é visto como uma massa celular compacta. A compactação deve-se a informação de proteínas de ligação entre os blastômeros. O embrião acumula líquido em seu interior, formando uma cavidade denominada blastocele. Esse processo é conhecido como blastulação; o embrião, assim, passa a ser chamado de blastocisto. Nessa etapa é possível diferenciar duas populações de células embrionárias: a massa celular interna, embrioblasto ou botão embrionário (que dará origem ao embrião), e a massa celular externa, células superficiais ou trofoblasto, do qual se originam a maioria das membranas fetais. Ao continuar a multiplicação das células e a acumulação de líquido, o blastocisto aumenta de tamanho, convertendo-se em blastocisto expandido. A zona pelúcida torna-se mais fina e, finalmente, o embrião eclode; isto é, o embrião é liberado da zona pelúcida. -/- • _____FERTILIZAÇÕES ATÍPICAS -/- Polispermia -/- É a penetração de dois ou mais espermatozoides no óvulo. Esta condição é letal nos mamíferos, já que o número cromossômico desse zigoto é maior que 2n, o envelheci-mento do ovócito da porca, como consequência do serviço tardio, favorece a apresentação da polispermia, por isso, é comum ver números de nascimentos de média de 10 a 12 leitões por parição nessa espécie. Nas aves, no entanto, a penetração de mais de um espermatozoide é normal, embora apenas um pronúcleo masculino se formará, fundindo-se com o feminino. -/- Figura 6: etapas do processo de segmentação/clivagem. Fonte: aula de reprodução da professora Domenica Palomaris, UFT. -/- Ginogênese -/- É o desenvolvimento de um embrião a partir de um óvulo normal fecundado por um espermatozoide, mas sem a fusão dos cromossomos masculinos com os da fêmea. A função do espermatozoide, nesse caso, é a de ativação do ovócito para que este inicie seu desenvolvimento, mas não há fusão com o núcleo do espermatozoide. Ocorre em plantas, em nematódeos e em algumas espécies de peixes, por exemplo a Poecilia formosa, espécie em que os ovócitos das fêmeas são ativados por machos de outra espécie relacio-nada. -/- Partenogênese -/- Consiste no desenvolvimento do embrião sem a participação do espermatozoide. Ocorre em alguns insetos, o zangão, por exemplo, é partenogenético. Também pode apresentar-se em perus, cujos embriões são machos e, geralmente, morrem antes da eclosão. -/- • _____GÊMEOS -/- Existem dois tipos de gêmeos: idênticos ou monozigóticos e os não idênticos ou dizigóticos. -/- Idênticos ou monozigóticos -/- Originam-se do mesmo zigoto, sendo assim, possuem o mesmo genótipo e um fenótipo similar e, portanto, são do mesmo sexo. Em laboratório é possível gerá-los ao seccionar uma mórula em duas ou mais partes, por meio de um micromanipulador. Uma vez que possuem o mesmo genótipo, os produtos resultantes são clones. -/- Não idênticos ou dizigóticos -/- Provêm da fertilização de dois óvulos distintos por espermatozoides diferentes. Possuem, portanto, genótipos e fenótipos diferentes, e podem ser de sexo diferente. -/- REFERÊNCIAS BIBLIOGRÁFICAS -/- ALBERTS, Bruce et al. Biologia molecular da célula. Artmed Editora, 2010. AUSTIN, Colin Russell; SHORT, Roger Valentine. Reproduction in Mammals, Book I: Germ Cells and Fertilization. 1982. BEARDEN, Henry Joe et al. Reproducción animal aplicada. México: Manual Moderno, 1982. BOSCH, P.; WRIGHT JR, R. W. The oviductal sperm reservoir in domestic mammals. Archivos de medicina veterinaria, v. 37, n. 2, p. 95-105, 2005. CAPALLEJAS, Roberto Brito; RODRÍGUEZ, Lourdes Tagle. Fisiología de la reproducción animal: con elementos de biotecnología. Editorial Félix Varela, 2010. CROXATTO, Horacio B. Physiology of gamete and embryo transport through the fallopian tube. Reproductive biomedicine online, v. 4, n. 2, p. 160-169, 2002. CUPPS, Perry T. (Ed.). Reproduction in domestic animals. Elsevier, 1991. DIEDRICH, Smidt et al. Endocrinología y Fisiología de la Reproducción de los Animales Zootécnicos. 1972. DUKES, Henry Hugh; SWENSON, Melvin J.; REECE, William O. Dukes fisiologia dos animais domésticos. Editora Guanabara Koogan, 1996. FERREIRA, A. de M. Reprodução da fêmea bovina: fisiologia aplicada e problemas mais comuns (causas e tratamentos). Juiz de Fora: Minas Gerais–Brasil, p. 422, 2010. HAFEZ, Elsayed Saad Eldin; HAFEZ, Bahaa. Reprodução animal. São Paulo: Manole, 2004. HUNTER, Ronald Henry Fraser. The Fallopian tubes in domestic mammals: how vital is their physiological activity?. Reproduction Nutrition Development, v. 45, n. 3, p. 281-290, 2005. HUNTER, R. H. F.; RODRIGUEZ‐MARTINEZ, H. Capacitation of mammalian spermatozoa in vivo, with a specific focus on events in the Fallopian tubes. Molecular Reproduction and Development: Incorporating Gamete Research, v. 67, n. 2, p. 243-250, 2004. GALINA, Carlos; VALENCIA, Javier. Reproducción de los animales domésticos. 2006. HOPPER, Richard M. (Ed.). Bovine reproduction. John Wiley & Sons, 2014. HYTTEL, Poul; SINOWATZ, Fred; VEJLSTED, Morten. Embriologia veterinária. Elsevier Brasil, 2012. KÖLLE, Sabine; REESE, Sven; KUMMER, Wolfgang. New aspects of gamete transport, fertilization, and embryonic development in the oviduct gained by means of live cell imaging. Theriogenology, v. 73, n. 6, p. 786-795, 2010. MCKINNON, Angus O. et al. (Ed.). Equine reproduction. John Wiley & Sons, 2011. OLIVERA, Martha et al. El espermatozoide, desde la eyaculación hasta la fertilización. Revista Colombiana de Ciencias Pecuarias, v. 19, n. 4, p. 426-436, 2006. PLANT, Tony M.; ZELEZNIK, Anthony J. (Ed.). Knobil and Neill's physiology of reproduction. New York: Academic Press, 2014. RODRIGUEZ-MARTINEZ, Heriberto. Role of the oviduct in sperm capacitation. Theriogenology, v. 68, p. S138-S146, 2007. SAAVEDRA LEOS, María Dolores. Estudio de la composición de los gránulos corticales y del oolema de ovocitos porcinos y bovinos madurados y fecundados in vitro. Proyecto de investigación:, 2010. SENGER, Phillip L. et al. Pathways to pregnancy and parturition. Current Conceptions, Inc, 2004. SUAREZ, Susan S. The oviductal sperm reservoir in mammals: mechanisms of formation. Biology of Reproduction, v. 58, n. 5, p. 1105-1107, 1998. VALENCIA MÉNDEZ, Javier de J. Fisiología de la reproducción porcina. 1986. -/- FIXAÇÃO DO ASSUNTO -/- 1. Defina e diferencie fertilização e segmentação. -/- 2. Disserte sobre o transporte do ovócito. Por que no istmo o transporte do ovócito se torna lento? -/- 3. Fale sobre a eficiência do transporte do gameta no trato genital da fêmea e sobre a retenção de ovócitos pela égua. -/- 4. Defina as células do cumulus e explique seu papel sobre o ovócito. -/- 5. Quais as estruturas que compõem o ovócito? Qual a função de cada uma? -/- 6. Todos os ovócitos das fêmeas domésticas são iguais? Justifique. -/- 7. Disserte sobre o papel dos hormônios e das secreções sobre o transporte do ovócito no trato genital da fêmea. -/- 8. Disserte sobre o transporte do espermatozoide. Por que há transporte rápido e lento dos espermatozoides? -/- 9. Fale sobre o local de deposição do sêmen nas espécies domésticas e como esse influen-cia na eficiência da reprodução. -/- 10. Por que a vida média do espermatozoide canino é maior que as outras espécies? -/- 11. Quais as mudanças que os espermatozoides precisam sofrer para conseguir êxito na fertilização e por quê? -/- 12. Defina fase de transporte rápido, fase sustentada e hipermotilidade. Qual a importân-cia de cada um? -/- 13. Como ocorre a reação acrossômica? -/- 14. O que é polispermia e como ocorre seu bloqueio? 15. Como ocorre a ativação do ovócito e como se formam os pronúcleos? -/- 16. O que é e qual a importância da singamia? -/- 17. Disserte sobre as divisões de segmentação e qual a importância destas para o êxito da reprodução. -/- 18. Defina e diferencia mórula e blastocisto. -/- 19. Defina e diferencie ginogênese e partenogênese. -/- 20. Qual o papel endócrino e quais hormônios e enzimas atuam sobre o transporte de gametas, sobre a fertilização e sobre a segmentação? (shrink)

Architecture and human-built structures are embedded with speciesist practices of domination over the environment, where humans are considered special and superior to other species. This (hu)man exceptionalism has driven architecture and the built environment to be conceived in opposition to ‘nature’, dominating natural terrains and consequently displacing or instrumentalizing the many other species that are given little to no ethical consideration. This way of intervening in the world is leading to the existential questions that must be posed given our global (...) climate crisis. A reframing of human intervention as ‘built environment’ placed in opposition to the ‘natural environment’ of supposedly passive nature, is urgently needed. The motivation for this paper is rooted in a deep concern for the role of humans in the climate crisis and a realization that architecture as a discipline is complicit in elevating the human category above all other beings in nature. There are biases embedded in the practices and teaching of architecture that need to be interrogated and reflected upon, starting with the role models and ideals that we unwittingly operate within. To contextualize the idea of human exceptionalism in architecture, we will explore deep-seeded ideals in architecture linked to the concept of Rectitude as a form of ‘rightness’ -or correct- mode of intervening in the world, conceptualized by Western men as a human-centric practice distinct from nature-made. Supported by Ecofeminist thought, the aim is to open alternative models for world-building and housing humans on earth living in its sixth extinction. (shrink)

En nuestro artículo, analizaremos las diferencias y similitudes que podemos encontrar en el uso de diagramas entre dos prácticas matemáticas de la antigüe-dad. Mostraremos que no existe un solo uso posible de éstos, sino que tienen que considerarse como herramientas de razonamiento creadas y manipuladas de acuerdo con los propósitos de cada tradición. Argumentaremos que las diferencias en los procedimientos y organizaciones del conocimiento que ambas tradiciones presentan no implican ningún tipo de valoración acerca de su mayor o menor "matematicidad", (...) ya que ambas tradiciones llegaron a resultados matemáticos suficientemente generales y precisos, hecho que es característico de investigaciones matemáticas a un nivel teórico. (shrink)

Pérez Carballo adopts an epistemic utility theory picture of epistemic norms where epistemic utility functions measure the value of degrees of belief, and rationality consists in maximizing expected epistemic utility. Within this framework he seeks to show that we can make sense of the intuitive idea that some true beliefs—say true beliefs about botany—are more valuable than other true beliefs—say true beliefs about the precise number of plants in North Dakota. To do so, however, Pérez Carballo argues that we must (...) think of the value of epistemic states as consisting in more than simply accuracy. This sheds light on which questions it is most epistemically valuable to pursue. (shrink)

Bourrat and Griffiths :33, 2018) have recently argued that most of the evidence presented by holobiont defenders to support the thesis that holobionts are evolutionary individuals is not to the point and is not even adequate to discriminate multispecies evolutionary individuals from other multispecies assemblages that would not be considered evolutionary individuals by most holobiont defenders. They further argue that an adequate criterion to distinguish the two categories is fitness alignment, presenting the notion of fitness boundedness as a criterion that (...) allows divorcing true multispecies evolutionary individuals from other multispecies assemblages and provides an adequate criterion to single out genuine evolutionary multispecies assemblages. A consequence of their criterion is that holobionts, as conventionally defined by hologenome defenders, are not evolutionary individuals except in very rare cases, and for very specific host-symbiont associations. This paper is a critical response to Bourrat and Griffiths’ arguments and a defence of the arguments presented by holobiont defenders. Drawing upon the case of the hologenomic basis of the evolution of sanguivory in vampire bats, I argue that Bourrat and Griffiths overlook some aspects of the biological nature of the microbiome that justifies the thesis that holobionts are evolutionarily different to other multispecies assemblages. I argue that the hologenome theory of evolution should not define the hologenome as a collection of genomes, but as the sum of the host genome plus some traits of the microbiome which together constitute an evolutionary individual, a conception I refer to as the stability of traits conception of the hologenome. Based on that conception I argue that the evidence presented by holobiont defenders is to the point, and supports the thesis that holobionts are evolutionary individuals. In this sense, the paper offers an account of the holobiont that aims to foster a dialogue between hologenome advocates and hologenome critics. (shrink)

Contemporary biological research has suggested that some host–microbiome multispecies systems (referred to as “holobionts”) can in certain circumstances evolve as unique biological individual, thus being a unit of selection in evolution. If this is so, then it is arguably the case that some biological adaptations have evolved at the level of the multispecies system, what we call hologenomic adaptations. However, no research has yet been devoted to investigating their nature, or how these adaptations can be distinguished from adaptations at the (...) species-level (genomic adaptations). In this paper, we cover this gap by investigating the nature of hologenomic adaptations. By drawing on the case of the evolution of sanguivory diet in vampire bats, we argue that a trait constitutes a hologenomic adaptation when its evolution can only be explained if the holobiont is considered the biological individual that manifests this adaptation, while the bacterial taxa that bear the trait are only opportunistic beneficiaries of it. We then use the philosophical notions of emergence and inter-identity to explain the nature of this form of individuality and argue why it is special of holobionts. Overall, our paper illustrates how the use of philosophical concepts can illuminate scientific discussions, in the trend of what has recently been called metaphysics of biology. (shrink)

The purpose of this article is to offer a reconstruction of the moral theory defended by Callicles in Plato’s Gorgias, aided by other contemporary texts that contribute to explain and refine such a theory. The first step of this reconstruction is to show that Callicles offers a perspectivist theory of moral judgements, according to which moral judgements can be issued from two radically distinct perspectives, the contractual and the natural one. The second step is to show that Callicles makes use (...) of a peculiar conception of nature that allows him to claim that certain natural rights and privileges stemming from the natural perspective of valuation must override those rights stemming from the contractual perspective. The resulting theory, as well as being worthy of philosophical interest, does not appear to be vulnerable to most of the objections advanced by the dominant interpretations, nor does it entail the implausible sort of hedonism that Plato attributes to Callicles in this dialogue. (shrink)

Holobionts are symbiotic assemblages composed by a host plus its microbiome. The status of holobionts as individuals has recently been a subject of continuous controversy, which has given rise to two main positions: on the one hand, holobiont advocates argue that holobionts are biological individuals; on the other, holobiont detractors argue that they are just mere chimeras or ecological communities, but not individuals. Both parties in the dispute develop their arguments from the framework of the philosophy of biology, in terms (...) of what it takes for a “conglomerate” to be considered an interesting individual from a biological point of view. However, the debates about holobiont individuality have important ontological implications that have remained vaguely explored from a metaphysical framework. The purpose of this paper is to cover that gap by presenting a metaphysical approach to holobionts individuality. Drawing upon a conception of natural selection that puts the focus on the transgenerational recurrence of the traits and that supports the thesis that holobionts are units of selection, we argue that holobionts bear emergent traits and exert downward powers over the entities that compose them. In this vein, we argue, a reasonable argument can be made for conceiving holobionts as emergent biological individuals. (shrink)

Symbiosis plays a fundamental role in contemporary biology, as well as in recent thinking in philosophy of biology. The discovery of the importance and universality of symbiotic associations has brought new light to old debates in the field, including issues about the concept of biological individuality. An important aspect of these debates has been the formulation of the hologenome concept of evolution, the notion that holobionts are units of natural selection in evolution. This review examines the philosophical assumptions that underlie (...) recent proposal of the hologenome concept of evolution, and traces those debates back in time to their historical origins, to the moment when the connection between the topics of symbiosis and biological individuality first caught the attention of biologists. The review is divided in two parts. The first part explores the historical origins of the connection between the notion of symbiosis and the concept of biological individuality, and emphasizes the role of A. de Bary, R. Pound, A. Schneider and C. Merezhkowsky in framing the debate. The second part examines the hologenome concept of evolution and explores four parallelisms between contemporary debates and the debates presented in the first part of the essay, arguing that the different debates raised by the hologenome concept were already present in the literature. I suggest that the novelty of the hologenome concept of evolution lies in the wider appreciation of the importance of symbiosis for maintaining life on Earth as we know it. Finally, I conclude by suggesting the importance of exploring the connections among contemporary biology, philosophy of biology and history of biology in order to gain a better understanding of contemporary biology. (shrink)

Laura Specker Sullivan (2022) makes a fairly compelling case for the value of the perspectives of Buddhist practitioners in neuroethics. In this study, Tibetan Buddhist monks have been asked, among other things, whether consciousness, in brain-injured patients in a minimally conscious state, entails a duty to preserve life. In our view, some of the participants’ responses could be used to inform the bioethical debate on death determination.

1. The Bundle Theory I shall discuss is a theory about the nature of substances or concrete particulars, like apples, chairs, atoms, stars and people. The point of the Bundle Theory is to avoid undesirable entities like substrata that allegedly constitute particulars. The version of the Bundle Theory I shall discuss takes particulars to be entirely constituted by the universals they instantiate.' Thus particulars are said to be just bundles of universals. Together with the claim that it is necessary that (...) particulars have constituents, the fundamental claim of the Bundle Theory is: (BT) Necessarily, for every particular x and every entity y, y constitutes x if and only ify is a universal and x instantiates y. 2 The standard and supposedly devastating objection to the Bundle Theory is that it entails or is committed to a false version of the Principle of Identity of Indiscernibles (Armstrong 1978: 91, Loux 1998: 107), namely: (Pll) Necessarily, for all particulars x and y and every universal z, if z is instantiated by x if and only if z is instantiated byy, then x is numerically identical with y. The most famous counterexample to the Identity of Indiscernibles is that put forward by Max Black, consisting of a world where there are only two iron spheres two miles apart from each other, having the same diameter, temperature, colour, shape, size, etc (Black 1952: 156). Let us from now on think of the properties of the spheres in this world as universals. The possibility of this world, which I shall hereafter refer to as 'Black's world', makes (Pll) false.' And according to common philosophical opinion this means that the Bundle Theory is false.. (shrink)

Political philosophy in the last decades has turned away from universal narratives of progress, on grounds that these narratives produce exclusion and justify domination. However, the universal values that underlie emancipatory political projects seem to presuppose universal history, which explains its persistence in some contemporary political philosophers committed to such projects. In order to find a response to the paradox according to which universal history is inherently exclusionary and yet necessary to uphold universal values, I examine the contrast between Adorno’s (...) and Lyotard’s perspectives on the problem of writing history ‘after Auschwitz’. For both philosophers, Auschwitz interrupts our fundamental normative and cognitive values, because any attempt to identify the meaning of the camps by means of these values misunderstands the suffering that took place in them. Yet this interruption produces a feeling that calls for the institution of new universal normative values. For Adorno, this value is a purely negative command to act in such a way that Auschwitz does not repeat itself. For Lyotard, by contrast, it is the demand to invent new idioms that make it possible to find meaning in Auschwitz. (shrink)

States restrict immigration on a massive scale. Governments fortify their borders with walls and fences, authorize border patrols, imprison migrants in detention centers, and deport large numbers of foreigners. Unjust Borders: Individuals and the Ethics of Immigration argues that immigration restrictions are systematically unjust and examines how individual actors should respond to this injustice. Javier Hidalgo maintains that individuals can rightfully resist immigration restrictions and often have strong moral reasons to subvert these laws. This book makes the case that (...) unauthorized migrants can permissibly evade, deceive, and use defensive force against immigration agents, that smugglers can aid migrants in crossing borders, and that citizens should disobey laws that compel them to harm immigrants. Unjust Borders is a meditation on how individuals should act in the midst of pervasive injustice. (shrink)

Philippe Huneman has recently questioned the widespread application of mechanistic models of scientific explanation based on the existence of structural explanations, i.e. explanations that account for the phenomenon to be explained in virtue of the mathematical properties of the system where the phenomenon obtains, rather than in terms of the mechanisms that causally produce the phenomenon. Structural explanations are very diverse, including cases like explanations in terms of bowtie structures, in terms of the topological properties of the system, or in (...) terms of equilibrium. The role of mathematics in bowtie structured systems and in topologically constrained systems has recently been examined in different papers. However, the specific role that mathematical properties play in equilibrium explanations requires further examination, as different authors defend different interpretations, some of them closer to the new-mechanistic approach than to the structural model advocated by Huneman. In this paper, we cover this gap by investigating the explanatory role that mathematics play in Blaser and Kirschner’s nested equilibrium model of the stability of persistent long-term human-microbe associations. We argue that their model is explanatory because: i) it provides a mathematical structure in the form of a set of differential equations that together satisfy an ESS; ii) that the nested nature of the ESSs makes the explanation of host-microbe persistent associations robust to any perturbation; iii) that this is so because the properties of the ESS directly mirror the properties of the biological system in a non-causal way. The combination of these three theses make equilibrium explanations look more similar to structural explanations than to causal-mechanistic explanation. (shrink)

This paper aims to offer a new argument in defence bacterial species pluralism. To do so, I shall first present the particular issues derived from the conflict between the non-theoretical understanding of species as units of classification and the theoretical comprehension of them as units of evolution. Secondly, I shall justify the necessity of the concept of species for the bacterial world, and show how medicine and endosymbiotic evolutionary theory make use of different concepts of bacterial species due to their (...) distinctive purposes. Finally, I shall show how my argument provides a new source of defence for bacterial pluralism. (shrink)

In this chapter, we will summarize recent empirical results highlighting how different groups of people solve pure coordination games. Such games are traditionally studied in behavioural economics, where two people need to coordinate without communicating with each other. Our results suggest that coordination choices vary across groups of people, and that people can adapt flexibly to these differences in order to coordinate between groups. We propose that pure coordination games are a useful empirical platform for studying aspects of mindshaping. Drawing (...) on existing psychological literature on alignment during interactions, we suggest that experience of successful interaction leads people to develop aligned intuitions about what is relevant and appropriate that support coordination when interaction and communication is not possible. Consistent with arguments made in the literature on mindshaping we believe that such alignment is more important for coordination than mindreading inferences about mental states, and indeed that mindreading is instead a form of coordination behaviour that is dependent upon intuitive alignment. (shrink)

According to one of Leibniz's theories of contingency a proposition is contingent if and only if it cannot be proved in a finite number of steps. It has been argued that this faces the Problem of Lucky Proof , namely that we could begin by analysing the concept ‘Peter’ by saying that ‘Peter is a denier of Christ and …’, thereby having proved the proposition ‘Peter denies Christ’ in a finite number of steps. It also faces a more general but (...) related problem that we dub the Problem of Guaranteed Proof . We argue that Leibniz has an answer to these problems since for him one has not proved that ‘Peter denies Christ’ unless one has also proved that ‘Peter’ is a consistent concept, an impossible task since it requires the full decomposition of the infinite concept ‘Peter’. We defend this view from objections found in the literature and maintain that for Leibniz all truths about created individual beings are contingent. (shrink)

The hologenome concept of evolution is a hypothesis about the evolution of animals and plants. It asserts that the evolution of animals and plants was partially triggered by their interactions with their symbiotic microbiomes. In that vein, the hologenome concept posits that the holobiont (animal host + symbionts of the microbiome) is a unit of selection. -/- The hologenome concept has been severely criticized on the basis that selection on holobionts would only be possible if there were a tight transgenerational (...) host-genotype-to-symbiont-genotype connection. As our current evidence suggests that this is not the case for most of the symbiont species that compose the microbiome of animals and plants, the opportunity for holobiont selection is very low in relation to the opportunity for selection on each of the species that compose the host microbiome. Therefore, holobiont selection will always be disrupted ‘from below’, by selection on each of the species that compose the microbiome. -/- This thesis constitutes a conceptual effort to defend philosophically the hologenome concept. I argue that the criticism according to which holobiont selection requires tight transgenerational host-genotype-to-symbiont-genotype connection is grounded on a metaphysical view of the world according to which the biological hierarchy needs to be nested, such that each new level of selection includes every entity from below. Applied to hologenomes, it entails that the hologenome is a collection of genomes, and selection of hologenomes is assumed to entail cospeciation of the host with the species that constitute its microbiome. -/- Against that interpretation, I propose the ‘stability of traits’ account, according to which hologenome evolution is the result of the action of natural selection in a non-nested hierarchical world. In that vein, hologenome evolution does not entail cospeciation, and thus it does not require tight transgenerational host-genotype-to-symbiont-genotype connection. By embracing a multilevel selection perspective, I argue that hologenome evolution results from the simultaneous action of natural selection on each of the lineages that compose the microbiome, and on the assemblage composed by the host genome plus the functional traits of its microbiome. Hologenome selection occurs when the evolution of the traits of the microbiome result from their effects on the fitness of the host, and it can take the form of multilevel selection 1, or multilevel selection 2. In both cases, hologenome selection entails the evolution of microbiome traits, as well as evolution of the host genome, rather than cospeciation of lineages. (shrink)

The notion of a correct appreciation of nature, like the one put forward in Carlson’s environmental account, has been rejected by many other authors in the aesthetics of the natural environment. Their critics challenge the idea that only scientific cat- egories can ground the aesthetic appreciation of nature as nature, and they hold that there is not a correct way of appreciating nature. However, they may share with Carlson the idea of correctness under an objectivist paradigm of aesthetic appreciation, according (...) to which correctness means the adequation of the experi- ence to properties of the object. My aim in the article is to claim that it is necessary to endorse an aesthetic standard of correctness that takes into consideration the subjective character of aesthetic appreciation. An aesthetic standard of correct- ness implies universal assent, or validity for everyone in Kantian terms, in place of an objectivist notion. This notion of correctness permits the inclusion of expressive perception of nature as an essential form of aesthetic appreciation. (shrink)

Many political theorists argue that immigration restrictions are unjust and defend broadly open borders. In this paper, I examine the implications of this view for individual conduct. In particular, I argue that the citizens of states that enforce unjust immigration restrictions have duties to disobey certain immigration laws. States conscript their citizens to help enforce immigration law by imposing legal duties on these citizens to monitor, report, and refrain from interacting with unauthorized migrants. If an ideal of open borders is (...) true, these laws are unjust. Furthermore, if citizens comply with their legal duties, they contribute to violating the rights of migrants. We are obligated to refrain from contributing to rights-violations. So, citizens are obligated to disobey immigration laws. I defend the moral requirement to disobey immigration laws against the objection that disobedience to the law is excessively risky and the objection that citizens have political obligations to obey the law. (shrink)

States heavily restrict immigration, and many people violate these restrictions. For example, unauthorized immigrants cross borders without official permission, and other actors, such as people smugglers, assist them in doing so. How should we evaluate resistance to immigration law from a moral perspective? In this article, I survey recent work on the ethics of resisting immigration law. In particular, I examine three categories of resistance to immigration law as the following: unauthorized immigration, people smuggling, and citizens' resistance to laws that (...) prohibit them from assisting or interacting with unauthorized immigrants. (shrink)

El artículo analiza el papel del resentimiento en la Teoría de los sentimientos morales de Adam Smith y su conexión con el proceso de la simpatía mutua por medio del cual el “espectador imparcial” asume plenamente el resentimiento de la víctima, al considerar que su pasión se rige por los principios de la propiedad y la justicia. Se sostiene que el resentimiento no solo cumple un rol central en la teoría del castigo de Adam Smith, en la medida en que (...) permite retribuir, disuadir y rehabilitar al victimario sino que, además, aporta a la discusión contemporánea sobre el perdón y la reconciliación, pues convoca la posibilidad de superar el resentimiento y restablecer las relaciones sociales entre el agresor y la víctima. (shrink)

Several political theorists argue that states have rights to self-determination and these rights justify immigration restrictions. Call this: the self-determination argument for immigration restrictions. In this article, I develop an objection to the self-determination argument. I argue that if it is morally permissible for states to restrict immigration because they have rights to self-determination, then it can also be morally permissible for states to deport and denationalize their own citizens. We can either accept that it is permissible for states to (...) deport and denationalize their own citizens or reject the self-determination argument. To avoid this implication, we should reject the self-determination argument. That is, we should also reject the conclusion that rights to self-determination can justify any significant immigration restrictions. (shrink)

According to an influential view, when it comes to representing reality, some words are better suited for the job than others. This is elitism. There is reason to believe that the set of the best, or elite, words should not be redundant or arbitrary. However, we are often forced to choose between these two theoretical vices, especially in cases involving theories that seem to be mere notational variants. This is the riddle of redundancy: both redundancy and arbitrariness are vicious, but (...) there are cases in which one must be picked. Logical realists admit that there are some logical constants among the elite words. This leads to awkward questions, such as which among conjunction and disjunction is elite. In this paper, I show how the riddle of redundancy arises for logical realists, and offer a solution. This approach requires us to change how we represent negation. Instead of using some particular symbol, we represent negation by flipping formulae over the horizontal axis. (shrink)

ABSTRACTPeople smugglers help transport migrants across international borders without authorization and in return for compensation. Many people object to people smuggling and believe that the smuggling of migrants is an evil trade. In this paper, I offer a qualified defense of people smuggling. In particular, I argue that people smuggling that assists refugees in escaping threats to their rights can be morally justified. I then rebut the objections that people smugglers exploit migrants, have defective motivations, and wrongly violate the law. (...) My conclusion is that people smuggling is sometimes a permissible way of helping refugees to evade unjust immigration restrictions and compelling states to bear their fair share of the global refugee population. (shrink)

ABSTRACT Do Buddhist philosophical commitments support a particular theory of well-being? Most authors who have examined this question argue that Buddhist ideas are compatible with multiple theories of well-being. In this paper, I contend that one tradition of Buddhist philosophy—Abhidharma—does imply a specific theory of welfare. In particular, Abhidharma supports hedonism. Most Ābhidharmikas claim that only property-particulars called dharmas ultimately exist and I argue that an Abhidharmic theory of well-being should only refer to these properties. Yet the only dharmas that (...) could plausibly be intrinsically good are phenomenal properties that are good in virtue of how they feel. Thus, the only intrinsically good things are pleasures. I defend this surprising conclusion from various interpretative objections and show that my argument can also inform contemporary philosophical debates about welfare. (shrink)

The classification of preserved hypothalamic activity in brain death and brainstem death as functional or non-functional has become a subject of debate. While proponents of the neurological criterion claim that these activities lack functional significance (Shemie et al. 2014), Nair-Collins and Joffe (2023) argue for their functional physiological role. However, the interpretation of the term "function" within the medico-legal framework, where death is characterized by the irreversible cessation of all brain functions, remains unclear. -/- My intention here is not to (...) engage in a debate over the validity of different viewpoints regarding the functional significance of preserved activities in the hypothalamus or the heart. Rather, I aim to highlight the critical importance of exploring and defining the concept of function in medicine, which currently lacks clarity. My point is that, whatever our position in the brain death debate, reaching a consensus on this conceptual matter would minimize misunderstandings and establish a robust foundation for further insightful analysis. (shrink)