Understanding aging and how it affects an organism's lifespan is a fundamental problem in biology. A hallmark of aging is stem cell senescence, the decline of functionality, and number of somatic stem cells, resulting in an impaired regenerative capacity and reduced tissue function. In addition, aging is characterized by profound remodeling of the immune system and a quantitative decline of adequate immune responses, a phenomenon referred to as immune‐senescence. Yet, what is causing stem cell and immune‐senescence? This review discusses experimental (...) studies of potentially immortal Hydra which have made contributions to answering this question. Hydra transcription factor FoxO has been shown to modulate both stem cell proliferation and innate immunity, lending strong support to a role of FoxO as critical rate‐of‐aging regulator from Hydra to human. Constructing a model of how FoxO responds to diverse environmental factors provides a framework for how stem cell factors might contribute to aging. (shrink)

Hydra are remarkable because they are immortal. Much of immortality can be ascribed to the asexual mode of reproduction by budding, which requires a tissue consisting of stem cells with continuous self‐renewal capacity. Emerging novel technologies and the availability of genomic resources enable for the first time to analyse these cells in vivo. Stem cell differentiation in Hydra is governed through the coordinated actions of conserved signaling pathways. Studies of stem cells in Hydra, therefore, promise critical insights of general relevance (...) into stem cell biology including cellular senescence, lineage programming and reprogramming, the role of extrinsic signals in fate determination and tissue homeostasis, and the evolutionary origin of these cells. With these new facts as a backdrop, this review traces the history of studying stem cells in Hydra and offers a view of what the future may hold. (shrink)

Current work in experimental biology revolves around a handful of animal species. Studying only a few organisms limits science to the answers that those organisms can provide. Nature has given us an overwhelming diversity of animals to study, and recent technological advances have greatly accelerated the ability to generate genetic and genomic tools to develop model organisms for research on host–microbe interactions. With the help of such models the authors therefore hope to construct a more complete picture of the mechanisms (...) that underlie crucial interactions in a given metaorganism (entity consisting of a eukaryotic host with all its associated microbial partners). As reviewed here, new knowledge of the diversity of host–microbe interactions found across the animal kingdom will provide new insights into how animals develop, evolve, and succumb to the disease. (shrink)

Peptides serve as important signalling molecules in development and differentiation in the simple metazoan Hydra. A systematic approach (The Hydra Peptide Project) has revealed that Hydra contains several hundreds of peptide signalling molecules, some of which are neuropeptides and others emanate from epithelial cells. These peptides control biological processes as diverse as muscle contraction, neuron differentiation, and the positional value gradient. Signal peptides cause changes in cell behaviour by controlling target genes such as matrix metalloproteases. The abundance of peptides in (...) Hydra raises the question of whether, in early metazoan evolution, cell–cell communication was based mainly on these small molecules rather than on the growth‐factor‐like cytokines that control differentiation and development in higher animals. BioEssays 23:420–427, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

Cells in the basal metazoan phylum Cnidaria are characterized by remarkable plasticity in their differentiation capacity. The mechanism controlling asymmetric cell divisions is not understood in cnidarians or in any other animal group. PIWI proteins recently have been shown to be involved in maintaining the self‐renewal capacity of stem cells in organisms as diverse as ciliates, flies, worms and mammals. Seipel et al.1 find that, in the cnidarian Podocoryne carnea, the Piwi homolog Cniwi is transcriptionally upregulated when the polyp generates (...) buds, which will develop into medusae. Since transdifferentiation of striated muscle cells to smooth muscle cells also activated Cniwi expression, Cniwi appears to play a crucial role in differentiation events. The discovery should facilitate elucidation of the poorly understood factors that control asymmetric cell divisions at the beginning of animal evolution. BioEssays 26:929–931, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Ecological developmental biology (eco‐devo) explores the mechanistic relationships between the processes of individual development and environmental factors. Recent studies imply that some of these relationships have deep evolutionary origins, and may even pre‐date the divergences of the simplest extant animals, including cnidarians and sponges. Development of these early diverging metazoans is often sensitive to environmental factors, and these interactions occur in the context of conserved signaling pathways and mechanisms of tissue homeostasis whose detailed molecular logic remain elusive. Efficient methods for (...) transgenesis in cnidarians together with the ease of experimental manipulation in cnidarians and sponges make them ideal models for understanding causal relationships between environmental factors and developmental mechanisms. Here, we identify major questions at the interface between animal evolution and development and outline a road map for research aimed at identifying the mechanisms that link environmental factors to developmental mechanisms in early diverging metazoans.Also watch the Video Abstract. (shrink)

Cover Photograph: Transgenic Hydra provide insights of general relevance into stem cell biology. The image shows a mass culture of transgenic Hydra expressing EGFP in all of their ectodermal epithelial cells. See article by Thomas C. G. Bosch pp. 478–486.

Graphical AbstractCIFAR's Humans & the Microbiome program is a multidisciplinary group of biological, clinical, and social scientists who explore the links between microbiome biology and sociocultural, historical, evolutionary, and environmental aspects of human existence that may impact the microbiome or be impacted by it. In this focus issue, members of the program focus on topics ranging from decoding the link between nutrition, the microbiome and human developmental, metabolic, and immune health and aging, to understanding past changes in the environment and (...) microbiome. The image depicts a population of bacteria (green) in association with the epithelia tissues (magenta and blue), perhaps the most common type of symbiosis in humans and other animals. Image contribution: Tara Essock-Burns. DOI: 10.1002/bies.201900130. (shrink)

While largely studied because of their harmful effects on human health, there is growing appreciation that bacteria are important partners for invertebrates and vertebrates, including man. Epithelia in metazoans do not only select their microbiota; a coevolved consortium of microbes enables both invertebrates and vertebrates to expand the range of diet supply, to shape the complex immune system and to control pathogenic bacteria. Microbes in zebrafish and mice regulate gut epithelial homeostasis. In a squid, microbes control the development of the (...) symbiotic light organ. These discoveries point to a key role for bacteria in any metazoan existence, and imply that beneficial bacteria‐host interactions should be considered an integral part of development and evolution. (shrink)

Here we evaluate our current understanding of the function of the nervous system in Hydra, a non‐bilaterian animal which is among the first metazoans that contain neurons. We highlight growing evidence that the nervous system, with its rich repertoire of neuropeptides, is involved in controlling resident beneficial microbes. We also review observations that indicate that microbes affect the animal's behavior by directly interfering with neuronal receptors. These findings provide new insight into the original role of the nervous system, and suggest (...) that it emerged to orchestrate multiple functions including host‐microbiome interactions. The excitement of future research in the Hydra model now relies on uncovering the common rules and principles that govern the interaction between neurons and microbes and the extent to which such laws might apply to other and more complex organisms. (shrink)

The conference explored an extraordinary diversity of aging strategies in organisms ranging from short‐lived species to “immortal” animals and plants. Research on the biological processes of aging is at the brink of a revolution with respect to our understanding of its underlying mechanisms as well as our ability to prevent and cure a wide variety of age‐related pathologies.

A reality-design gap in the conceptualization and practice of digital agriculture has been systematically reported in the literature. This condition is favored by the lack of understanding and inclusion of local worldviews around digital technologies. Informed by Amartya Sen’s capabilities approach, this study looks to bring stories of local appropriation to the spotlight. Based on a qualitative approach that included data collected through interviews with 73 households, the authors explored the way in which two selected communities of Colombian coffee growers (...) are engaged in the use of digital technologies in material and symbolic ways. Three emergent themes—a relational way of farming, (dis)connected machines, and nurtured families and communities – articulate multiple interactions between farmers, farms, institutional programs, and technologies, that originate local forms of digitalization (and non-digitalization). This study points out the relevant role of situated ideas of development in positioning technologies in or out of the farm, and broader digitalization agendas in or out of farmers’ life projects. At the same time, it presents a critique of notions of universality that drive unquestioned quests for technification. In contrast, building on a relational perspective, this study calls for embracing a perspective of multiplicity within notions of development and innovation. (shrink)

Humans’ indigenous microbes strongly influence organ functions in an age‐ and diet‐dependent manner, adding an important dimension to aging biology that remains poorly understood. Although age‐related differences in the gut microbiota composition correlate with age‐related loss of organ function and diseases, including inflammation and frailty, variation exists among the elderly, especially centenarians and people living in areas of extreme longevity. Studies using short‐lived as well as nonsenescent model organisms provide surprising functional insights into factors affecting aging and implicate attenuating effects (...) of microbes as well as a crucial role for certain transcription factors like forkhead box O. The unexpected beneficial effects of microbes on aged animals imply an even more complex interplay between the gut microbiome and the host. The microbiome constitutes the major interface between humans and the environment, is influenced by biosocial stressors and behaviors, and mediates effects on health and aging processes, while being moderated by sex and developmental stages. (shrink)

The microbiome of human hair follicles (HFs) has emerged as an important player in different HF and skin pathologies, yet awaits in‐depth exploration. This raises questions regarding the tightly linked interactions between host environment, nutrient dependency of host‐associated microbes, microbial metabolism, microbe‐microbe interactions and host immunity. The use of simple model systems facilitates addressing generally important questions and testing overarching, therapeutically relevant principles that likely transcend obvious interspecies differences. Here, we evaluate the potential of the freshwater polyp Hydra, to dissect (...) fundamental principles of microbiome regulation by the host, that is the human HF. In particular, we focus on therapeutically targetable host‐microbiome interactions, such as nutrient dependency, microbial interactions and host defence. Offering a new lens into the study of HF – microbiota interactions, we argue that general principles of how Hydra manages its microbiota can inform the development of novel, microbiome‐targeting therapeutic interventions in human skin disease. (shrink)

Meet the Metaorganism is a web‐based learning app that combines three fundamental biological concepts (coevolution, community dynamics, and immune system) with latest scientific findings using the metaorganism as a central case study. In a transdisciplinary team of scientists, information designers, programmers, science communicators, and educators, we conceptualized and developed the app according to the latest didactic and scientific findings and aimed at setting new standards in visual design, digital knowledge transfer, and online education. A content management system allows continuous integration (...) of new findings, which enables us to expand the app with the dynamics of the research field. Students can thus gain a close insight and connection to current research, and at the same time learn that knowledge is not static but grows dynamically. Especially in the realm of the easily accessible metaorganism research, visualization plays an essential role to keep complex processes understandable and memorable. Meet the Metaorganism is freely available online and can be accessed here: www.metaorganism.app. (shrink)

The evidence compiled in the target article demonstrates that the assumptions of cultural group selection theory are often met, and it is therefore a useful framework for generating plausible hypotheses. However, more can be said about how we can test the predictions of CGS hypotheses against competing explanations using historical, archaeological, and anthropological data.

Issues of reliability are claiming center-stage in the epistemology of machine learning. This paper unifies different branches in the literature and points to promising research directions, whilst also providing an accessible introduction to key concepts in statistics and machine learning – as far as they are concerned with reliability.

Das Netz der Kultur bildet eine kommunikative Medialität, in der sich Freiheitsspielräume des menschlichen Lebens eröffnen.

Zu den bedeutendsten Leistungen der Friedensschrift Kants für die Entwicklung der Völkerrechtsidee gehört die Zurückweisung der bisherigen Leitvorstellung eines ius ad bellum. Unmißverständlich formuliert er: „Bei dem Begriffe des Völkerrechts, als eines Rechts zum Kriege, läßt sich eigentlich gar nichts denken“ . Eine internationale Rechtsordnung müsse dem Ziele dauerhafter Friedenssicherung dienen, und in einem Bund freier Völker soll dieser zwischenstaatliche Konsens institutionalisiert werden.

This paper explores structuralism as a way to model theories from scientific practice. As a case study I analyzed a theory about the dynamics of the basal ganglia, a part of the brain that is involved in Parkinson's disease. After introducing the case study I explore how to structurally represent qualitative assumptions about disease, intervention and dynamical systems in general. I further explicate the structure of the basal ganglia theory in detail, how it explains Parkinson's disease and how it implies (...) treatments. I close with a consideration of how a structuralist representation could be useful in practice to explore and develop theories with the aid of a computer. (shrink)

Looking back on it, it seems almost incredible that so many equally educated, equally sincere compatriots and contemporaries, all drawing from the same limited stock of evidence, should have reached so many totally different conclusions---and always with complete certainty.

Thomas Reid, the Scottish natural and moral philosopher, was one of the founding members of the Aberdeen Philosophical Society and a significant figure in the Scottish Enlightenment. Reid believed that common sense should form the foundation of all philosophical inquiry. He criticised the sceptical philosophy propagated by his fellow Scot David Hume and the Anglo-Irish bishop George Berkeley, who asserted that the external world did not exist outside the human mind. Reid was also critical of the theory of ideas (...) propagated by Locke and Descartes, arguing that it was incompatible with physical and experiential facts. For Reid, our senses demonstrate that the external world must exist, and this work is organised in chapters examining each of the senses in turn. The book, based on his lectures, was first published in 1764 when Reid was a regent professor at King's College, Aberdeen, and was reissued in 1818. (shrink)

Fiodor Dostoievski rasga el alma humana hasta dejarla herida por el sufrimiento, la culpa y el aislamiento. Y, sin embargo, la derrota no gana la batalla. La escritora sureña estadounidense Carson McCullers escribe sobre la soledad y la miseria del sur de los Estados Unidos con una mirada atenta a los paisajes desolados de la Rusia de Fiodor Dostoievski, no sólo físicos sino esencialmente metafísicos. Esta autora que ya leyó al maestro ruso a los 13 años explora las entrañas humanas (...) desde un terreno rural, desolador, inhóspito y desafortunado, con diferencias raciales, sobreexposición de alcohol y con un concepto de bien moral interno que aparece como una pulsión constante e inagotable. En esta aproximación queremos destacar cómo el misterio del mal, pero también el acto de la voluntad y la incomunicación, son aspectos que unen a ambos autores, especialmente en dos de sus obras maestras, Crimen y Castigo y El corazón es un cazador solitario, respectivamente. (shrink)

The application of machine-learning technologies to medical practice promises to enhance the capabilities of healthcare professionals in the assessment, diagnosis, and treatment, of medical conditions. However, there is growing concern that algorithmic bias may perpetuate or exacerbate existing health inequalities. Hence, it matters that we make precise the different respects in which algorithmic bias can arise in medicine, and also make clear the normative relevance of these different kinds of algorithmic bias for broader questions about justice and fairness in healthcare. (...) In this paper, we provide the building blocks for an account of algorithmic bias and its normative relevance in medicine. (shrink)

Cette étude essaye d’établir qu’il y a deux notions très différentes de « fondation » à l’œuvre dans les Recherches logiques de Husserl. Dans la IIIème Recherche, où le terme est formellement introduit, lorsqu’il se demande quels sont les contenus qui peuvent exister d’une manière autonome (indépendants) et lesquels peuvent exister uniquement en tant que moments d’autre chose (dépendants), Husserl suit ce que j’appelle un « modèle ontologique ». Selon ce modèle, le concret possède une priorité sur à l’abstrait qui (...) est fondé en lui. Dans la VIème Recherche, en revanche, Husserl s’oriente principalement sur un « modèle gnoséologique » qui voit le complexe comme fondé sur ce qui est relativement simple, étant donné que les expériences d’ordre supérieur (telles les perceptions de types d’objets plus complexes) sont « fondées sur » des expériences plus simples, bien qu’elles ne puissent pas y être réduites. L’exemple principal ici est celui des intuitions catégoriales : fondées sur les intuitions sensibles, elles n’y sont pas réductibles. Mais cette distinction entre deux sens différents du terme de « fondation » peut également nous aider à mieux comprendre de nombreuses thèses husserliennes plutôt controversées. Par exemple, elle peut nous permettre de mieux comprendre dans quelle mesure faire l’expérience d’un être humain comme un tout se fonde sur l’expérience d’un corps physique, et cela même si l’étant que nous rencontrons inclut à la fois des aspects corporels et des aspects spirituels – les deux étant vus, d’une manière essentielle, comme des moments de cette unique personne qui fait l’objet de notre expérience. (shrink)

En la obra de Hegel la filosofía de lo bello es eminentemente filosofía del espíritu. Uno de los temas insoslayables acerca de la belleza es su presencia en la naturaleza y en el arte. En las Lecciones de Estética la belleza del arte se pondera como la más excelente. En este punto la postura hegeliana diverge llamativamente de la de Schelling; quien trató explícitamente de la relación de las artes plásticas con la naturaleza, como consta en el texto que lleva (...) este tema por título (generalmente llamado “discurso de la academia”). Su propuesta es clara: la superioridad de la naturaleza frente a las artes plásticas. Lo más interesante de esta disputa no es el desacuerdo en sí mismo, sino las argumentaciones que uno y otro autor alegan a favor de sus tesis respectivas. (cuánto se parece y cuánto divergen) A través de ellas se pueden ver los diversos matices en torno a los conceptos de belleza y de espíritu. A esta cuestión es a lo que se dedicará esta comunicación: a analizar brevemente algunos argumentos de ambos autores acerca de la belleza en la naturaleza y en el arte. A lo largo de este artículo se lleva a cabo una comparación de textos, de algunas discrepancias concretas: en todas ellas lo llamativo es cómo son a la vez tan cercanos y tan contrarios. Tanto para Schelling como para Hegel, la belleza es del espíritu: lo más bello es lo que está penetrado de espíritu y es vivificado por él. Pero más allá de estos principios comunes hay mil matices que acaban desembocando en dos posturas contrapuestas. (shrink)