I defend a new conception of the particular-universal distinction based on considerations about what David Lewis calls ‘amphibians’. I argue, first, that given the possibility of amphibians, two recently popular conceptions of the particular-universal distinction, namely the repeatability conception and the duplicability conception, are both objectionable since they are biased in one way or another. I then propose a more flexible conception that solves this problem by regarding amphibians as belonging to a sui generis sort of property (...) distinct from what I call ‘strong universals’ and ‘strong tropes’. Finally, I respond to some objections directed at this new account. (shrink)

Anuran amphibian metamorphosis is an immunologically interesting period. For the investigator, it provides an unusual opportunity for analyzing both humoral regulation of the immune response and the development and maintenance of self‐tolerance. Some of the questions one can ask are: Why don't immunocompetent larvae destroy antigenically disparate adult cells as they differentiate within them during metamorphosis? Do the dramatic hormonal changes occurring during this period regulate immunological function? How do animals in metamophorsis protect themselves from their immunologically hostile environment?

Here we review and discuss the link between regeneration capacity and tumor suppression comparing mammals (embryos versus adults) with highly regenerative vertebrates. Similar to mammal embryo morphogenesis, in amphibians (essentially newts and salamanders) the reparative process relies on a precise molecular and cellular machinery capable of sensing abnormal signals and actively reprograming or eliminating them. As the embryo's evil twin, tumor also retains common functional attributes. The immune system plays a pivotal role in maintaining a physiological balance to provide (...) surveillance against tumor initiation or to support its initiation and progression. We speculate that susceptibility to cancer development in adult mammals may be determined by the loss of an advanced regenerative capability during evolution and believe that gaining mechanistic insights into how regenerative capacity linked to tumor suppression is postnatally lost in mammals might illuminate an as yet unrecognized route to cancer treatment. (shrink)

It is posited that the initiating event of amphibian regeneration of a limb, is retrodifferentiation* of what are to become the developing cells of the blastema. These cells reiterate a larval or premetamorphic ontogenic repertoire, induced by elevated levels of prolactin with adequate innervation. Subsequent redifferentiation of the blastema cells occurs, controlled by thyroxine and innervation.This temporal displacement of cellular morphologic characters in regeneration should be looked upon as a function of the ability to reiterate larval characters and subsequently metamorphose. (...) If correct, this would explain why amphibians which metamorphose only once, lose the ability to postmetamorphically regenerate. An exception to this,Xenopus laevis, an anuran which can epimorphically regenerate, to some extent, will be discussed.[/p]. (shrink)

The concept of positional information is applied to a large amount of data obtained previously in experiments on developing and regenerating amphibian limbs. Only the proximo-distal axis of the limb is considered. It is shown that the concept provides a simple, unitary hypothesis which satisfactorily accounts for the experimental data, and may moreover suggest meaningful new approaches. It is suggested that the boundaries of the bipolar limb system lie in the girdle skeleton and at the distal end of the limb, (...) respectively, and that it is the apical epidermis of the growing or regenerating limb which defines the distal boundary conditions. A relatively stable gradient of positional information is assumed to be set up in the mesoderm . It is further shown that the differentiated limb retains its positional information and upon amputation imparts it to the base of the blastema. To explain an apparent discrepancy between the developing and the regenerating limb, it is proposed that dedifferentiation of mesodermal limb tissues upon amputation entails a change of positional value in the mesenchyme. Consequently, the amputation level does not once and for all specify the positional value at the proximal end of a mass of blastemal mesenchyme, particularly when the mesenchyme is transplanted in such a way that its linear size decreases or increases. (shrink)

This study investigated how seventh-grade students rate their fear of, and disgust toward, amphibians in comparison to some other nonhuman animal species. For the purpose of evaluating these variables, a questionnaire with open-ended and self-report questions was used. The study found that direct experience of animals significantly affects students’ self-reported fear and disgust ratings. Boys generally reported less fear and disgust toward animals than girls. With regard to amphibians, students expressed relatively high disgust, but low fear. There were (...) no differences in disgust ratings between boys and girls. Also, a majority of students reported having no direct experience of amphibians, and their attitudes hovered between negative and neutral. Factor analysis placed amphibians in a category of disgust-relevant animals. The other two categories that emerged were interpreted as fear-relevant animals and companion animals. The study concluded that education should place greater importance on allowing students to experience a variety of different animal species directly in order to foster positive change in their feelings and attitudes toward them, and at the same time to build on their understanding of animals. (shrink)

Amphibians that undergo a metamorphosis provide an unparalleled opportunity to investigate how skeletal shape is generated, preserved, and transformed in development. Their pharyngeal arch (PA) cartilages, which support breathing and feeding behaviors, form embryonically from cranial neural crest cells, grow isometrically at larval stages, and abruptly change shape during metamorphosis. Further, the shape changes occur in three different ways: some adult cartilages form de novo, others emerge from within resorbing larval cartilages and some larval cartilages reshape themselves at the (...) cellular level. Isometric growth followed by abrupt shape change is unique to amphibian PA cartilages, which suggests that the origin and evolution of amphibian metamorphosis has been influenced by the tissue properties of cartilage. This essay reviews the functional role of the PA skeleton in frogs and salamanders and presents a mechanistic framework for understanding how its shape is generated, preserved, and transformed at the levels of cell behavior and specification mechanisms. (shrink)

Amphibian metamorphosis is a post‐embryonic process that systematically transforms different tissues in a tadpole. Thyroid hormone plays a causative role in this complex process by inducing a cascade of gene regulation. While natural metamorphosis does not occur until endogenous thyroid hormone has been synthesized, tadpoles are competent to respond to exogenous thyroid hormone shortly after hatching. In addition, even though the metamorphic transitions of individual organs are all controlled by thyroid hormone, each occurs at distinct developmental stages. Recent molecular studies (...) suggest that this competence of premetamorphic tadpoles to respond to the hormone and the developmental stage‐dependent regulation of tissue‐specific transformations are determined in part by the levels of thyroid hormone receptors and the concentrations of cellular free thyroid hormone. In addition, at least two genes, encoding a cytosolic thyroid hormone binding protein and a 5‐deiodinase, respectively, are likely to be critical players in regulating cellular free thyroid hormone concentrations. This review discusses how all of these molecuar components coordinate to induce amphibian metamorphosis in a correct spatial and temporal manner. These studies provde us with general clues as to how and why tissues become competent to respond to hormonal signals. (shrink)

In this paper we try to answer the question whether diffusion is a possible mechanism to explain mesoderm induction in Amphibians. First the embryological data are discussed and a hypothesis for mesoderm formation is set forth. The blastula being essentially a hollow sphere, we assume that the induction mechanism in an embryo at the blastula stage can be simulated by diffusion-reaction processes on spherical surfaces. A model is constructed for the simple case when the source is held constant with (...) respect to time, the decay proportional to the concentration and the diffusion coefficient a constant, From simulation we find a (best) value for the decay constant to be 6 × 10–5/sec and for the diffusion constant to be 0.24 × 10– 6 cm2/sec. The relation between the parameters is derived from an analytic solution for the diffusion process on a spherical surface with a continuously producing point source and the concentration proportional to the decay. The form and regulative properties of the steady concentration gradient are discussed. (shrink)

The emerging view of early dorso‐ventral patterning of amphibian embryos is that two opposing gradients of dorsalising and ventralising secreted factors are necessary. while several transcription factors acting upstream or downstream of the dorsalising molecules have been identified, until recently little was known about the transcriptional response to ventralising signals. Now two groups describe the identification of related homeodomain proteins, Xvent‐1 and Vox, which are able to convert dorsal cells of Xenopus embryos into more ventral ones(1,2).

The last decade has seen a dramatic increase in studies on the development, function and evolution of asymmetries in vertebrates, including amphibians. Here we discuss current knowledge of behavioral and anatomical asymmetries in amphibians. Behavioral laterality in the response of both adult and larval anurans to presumed predators and competitors is strong and may be related, respectively, to laterality in the telencephalon of adults and the Mauthner neurons of tadpoles. These behavior lateralities, however, do not seem to correlate (...) with visceral asymmetries in the same animals. We briefly compare what is known about the evolution and development of asymmetry in the structure and function of amphibians with what is known about asymmetries in other chordate and non‐chordate groups. Available data suggest that the majority of asymmetries in amphibians fall into two independent groups: (1) related to situs viscerum and (2) of a neurobehavioral nature. We find little evidence linking these two groups, which implies different developmental regulatory pathways and independent evolutionary histories for visceral and telencephalic lateralizations. Studies of animals other than standard model species are essential to test hypotheses about the evolution of laterality in amphibians and other chordates. BioEssays 26:512–522, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Retrieval efficiencies of paper-based references in journals and other serials containing 10 scientific names of fossil amphibians were determined for seven major search engines. Retrievals were compared to the number of references obtained covering the period 1895—2006 by a Comprehensive Search. The latter was primarily a traditional library-based search which involved intensive work from 2002—2007. Only a few references originally obtained by search engines were included. Retrieval efficiencies were calculated by comparison to the number obtained through the Comprehensive Search (...) (assumed to be 100%). All percent retrievals were quite low (mean = 11.3%, range = 4.0—22.9%). For all seven search engines combined (duplicate references excluded), the percent retrieval was only 40.7%. There was also retrieval inefficiency and bias of the search engines in: sampling over time, the top five journals containing the most references, the top five most prolific authors, and non-English references. Consequently, all seven search engines were unsatisfactory for retrieval of references for our scientific research. (shrink)

Perspectives on the difficult topic of the evolution of language can be differentiated to a large extent based on how much relevant continuity or discontinuity they see between humans and nonhuman animals. In general, biologists and psychologists tend to have a broad definition of “language” that highlights significant continuities, whereas linguists tend to define “language” more narrowly, in accord with their emphasis on the uniqueness of human capacities. This article examines the value of Whitehead's innovative theory of language, which is (...) grounded in his account of the fundamental symbolic element in basic perceptual processes, mainly for understanding the continuities between animal and human perceptual and symbolic activity but also for accommodating the discontinuity, or at least the pivotal difference, evident in the full flowering of human language. It will focus particularly on applying Whitehead's approach to gain a new understanding of the emergence, with the rise of amphibians, of the first vocalization in the history of life. (shrink)

Regenerative medicine promises to greatly impact on human health by improving repair outcomes in a range of tissues and injury contexts. Successful therapies will rely on identifying both intrinsic and extrinsic biological circuits that control wound healing, proliferation, cell survival, and developmental cell fate. Animals such as the zebrafish and the salamander display powerful examples of near‐perfect regeneration and scar‐free healing in a range of injury contexts not attained in mammals. By studying regeneration in a range of highly regenerative species (...) that maintain regenerative potential throughout life, many instructive and permissive factors have been identified that could assist in the development of regenerative therapies. This review highlights some of the recent observations in immune regulation, epigenetic regulation, stem cell mobilization, and regenerative signatures that have improved our understanding of the regenerative process. Potential opportunities in harnessing this knowledge for future translation into the clinic are discussed. (shrink)

The mesoderm is the region of the embryo that gives rise to muscle, blood and connective tissues; it becomes segregated from the ectoderm and endoderm at gastrulation. Embryological studies have revealed, however, that the potential for certain embryonic cells to become part of the mesoderm is established well before gastrulation, most likely through an extracellular signalling process termed ‘induction’. The recent characterization of mesoderm‐specific mRNAs and proteins now permits an analysis of the very earliest events involved in the specification of (...) the mesoderm at the molecular level. Such experiments should contribute to our understanding of the mechanisms involved in controlling cell differentiation. (shrink)

New methods of marking cells enable single clones to be followed during embryonic development. They can be used for the construction of fate maps and for the investigation of induction and determination.

Are women (simply) adult human females? Dictionaries suggest that they are. However, philosophers who have explicitly considered the question invariably answer no. This paper argues that they are wrong. The orthodox view is that the category *woman* is a social category, like the categories *widow* and *police officer*, although exactly what this social category consists in is a matter of considerable disagreement. In any event, orthodoxy has it that *woman* is definitely not a biological category, like the categories *amphibian* or (...) *adult human female*. -/- In the first part, a number of arguments are given for the view that women are adult human females; the second part turns to rebutting the main objections. Finally, a couple of morals are briefly noted: one for activist sloganeering, and one for ameliorative projects that seek to change the meaning of ‘woman’. (shrink)

On April 19, 2024, the New York Declaration on Animal Consciousness was announced at the “Emerging Science of Animal Consciousness” conference held at New York University. The New York Declaration is an effort to showcase a scientific consensus on the presence of conscious experiences across all vertebrates (including reptiles, amphibians, and fish) and many invertebrates (at least including cephalopods, decapod crustaceans, and insects). Scientifically, the New York Declaration marks a significant advancement for humanity. However, it also brings heightened awareness (...) to the moral challenges associated with animals that have conscious experiences (or phenomenal consciousness). This article will discuss philosophical approaches to the moral issue of killing sentient beings, thereby highlighting an existing moral dilemma in human society: In sustaining human survival, a species considered to have morality, we have to violate our own moral standards by killing other species with intrinsic value, consciousness, or sentience. This moral dilemma has long been present in human society. Various solutions have been proposed and implemented in practice to address this issue, such as the non-violence and vegetarian approach of Buddhism, the application of Islamic law and sacred rituals to animals in Islam, animal rights movements and voluntary extinction in Western countries, and the technology producing meat using animal cells. However, despite these approaches, we have not yet been able to fully resolve the dilemma, as sentient beings continue to be killed for our survival. We believe the most feasible solution is to change the current food consumption culture, build an eco-surplus culture to mitigate climate change, prevent deforestation, and promote peace. (shrink)

Regeneration in arthropods and amphibians follows an analogous principle making comparisons between the two phyla possible.Larval arthropods and amphibians possess powers of epimorphic regeneration which wane for many species of these phyla with the completion of metamorphosis or the cessation of moulting. In those species which retain, post-maturationally, the ability to form a regenerative blastema, larval characteristics are carried into the adult and reproductive stages of these organisms. These include many species of: urodeles, ametabolous insects, crustaceans, myriapods and (...) arachnids. The long-standing distinction between embryonic regulation and true epimorphosis would thus appear to be a difference of degree rather than kind. (shrink)

How consciousness appeared much earlier in evolutionary history than is commonly assumed, and why all vertebrates and perhaps even some invertebrates are conscious. How is consciousness created? When did it first appear on Earth, and how did it evolve? What constitutes consciousness, and which animals can be said to be sentient? In this book, Todd Feinberg and Jon Mallatt draw on recent scientific findings to answer these questions—and to tackle the most fundamental question about the nature of consciousness: how does (...) the material brain create subjective experience? After assembling a list of the biological and neurobiological features that seem responsible for consciousness, and considering the fossil record of evolution, Feinberg and Mallatt argue that consciousness appeared much earlier in evolutionary history than is commonly assumed. About 520 to 560 million years ago, they explain, the great “Cambrian explosion” of animal diversity produced the first complex brains, which were accompanied by the first appearance of consciousness; simple reflexive behaviors evolved into a unified inner world of subjective experiences. From this they deduce that all vertebrates are and have always been conscious—not just humans and other mammals, but also every fish, reptile, amphibian, and bird. Considering invertebrates, they find that arthropods (including insects and probably crustaceans) and cephalopods (including the octopus) meet many of the criteria for consciousness. The obvious and conventional wisdom–shattering implication is that consciousness evolved simultaneously but independently in the first vertebrates and possibly arthropods more than half a billion years ago. Combining evolutionary, neurobiological, and philosophical approaches allows Feinberg and Mallatt to offer an original solution to the “hard problem” of consciousness. (shrink)

Gentle handling of mammals , and lizards , but not of frogs and fish elevated the set-point for body temperature, i.e., produced an emotional fever, achieved only behaviourally in lizards. Heart rate, another detector of emotion in mammals, was also accelerated by gentle handling, from ca. 70 b/min to ca. 110 b/min in lizards. This tachycardia faded in about 10 min. The same handling did not significantly modify the frogs’ heart rates. The absence of emotional tachycardia in frogs and its (...) presence in lizards , together with the emotional fever exhibited by mammals and reptiles, but not by frogs or fish, would suggest that emotion emerged in the evolutionary lineage between amphibians and reptiles. Such a conclusion would imply that reptiles possess consciousness with its characteristic hedonic dimension, pleasure. The role of sensory pleasure in decision making was therefore verified in iguanas placed in a motivational conflict. To be able to reach a bait , the iguanas had to leave a warm refuge, provided with standard food, and had to venture into a cold environment. The results showed that lettuce was not necessary to the iguanas and that they traded off the palatability of the bait against the disadvantage of the cold. Thus, the behaviour of the iguanas was possibly produced, as it is in humans, through the maximization of sensory pleasure. Altogether, these results may indicate that the first elements of mental experience emerged between amphibians and reptiles. (shrink)

Recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. These include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. There are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori (...) association between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. Moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. It might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. However, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. Here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an “evolutionarily stable strategy” under “social” pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species. Key Words: asymmetry; brain evolution; brain lateralization; development; hemispheric specialization; laterality; lateralization of behavior; social behavior; theory of games. (shrink)

This study of the patterns of the keeping of herpetofauna animals and associated animal welfare issues among secondary school pupils in the United Kingdom suggests that a large proportion of the animals kept as companion animals by this group are indigenous species. In comparison with purchased species, these captured animals, even those normally long-lived, appear to suffer a high rate of mortality. Relatively large numbers of escape- and food-related deaths among these animals imply that many are not furnished with suitable (...) vivaria or adequate care. Traded reptile and amphibian species were reported to have been kept by nearly 40% of the students who said they had kept herpetofauna, and the proportions of most taxa reflected their availability in shops. Data concerning students' opinions about their own care-knowledge appeared to support the general conclusion that students have much to learn about keeping reptiles and amphibians. These findings are considered in relation to issues of animnl welfare and herpetofauna conservation. Their ramifications for school-based education about reptiles and amphibians are also discussed. (shrink)

A nationwide survey that included personal interviews in 1,021 households studied the incidence, species, and numbers of nonhuman animals kept in Costa Rican households. A total of 71% of households keep animals.The proportion of households keeping dogs is 3.6 higher than the proportion of households keeping cats . In addition to the usual domestic or companion animals kept in 66% of the households, 24% of households keep wild species as pets. Although parrots are the bulk of wild species kept as (...) pets, there is vast species diversity, including other birds, reptiles, mammals, amphibians, fishes, and invertebrates - typically caught in their natural habitat to satisfy the pet market. The extraction from the wild and the keeping of such animals is by-and-large illegal and often involves endangered species. Costa Ricans, in a conservative estimate, keep about 151,288 parrots as pets. More than half the respondents have kept a psittacid at some point in their lives. Pet keeping is a common practice in Costa Rican society, and its incidence is high by international standards. (shrink)

Les conditions dans lesquelles on peut susciter expérimentalement, chez les Amphibiens, une lèvre blastoporale surnuméraire ont été rappelées. Une interprétation a été esquissée en se basant sur des recherches plus récentes de microstructure, d'embryologie moléculaire et de cytochimie.The various techniques, by which a secondary blastoporal lip can be obtained in Amphibians have been recorded. Their intelligence is more or less increased by recent information due to electromicroscopy, molecular embryology and cytochemistry.

In Xenopus, as in all amphibians and possibly in vertebrate embryos in general, mesoderm formation and the establishment of the dorsoventral axis depend on inductive cell interactions. Molecules involved in mesoderm induction include FGF which acts predominantly as a ventrolateral inducer, the TGF‐β homolog activin which can induce all types of mesoderm, and members of the Wnt family which have powerful dorsalizing effects. Early effects of inducer action include the activation of regulatory genes. Among such genes, particular interest is (...) focused on three genes encoding putative transcription factors that are expressed specifically in the Spemann organizer region of the gastrula. Expression of one of these genes, goosecoid, has been shown to be sufficient to elicit the formation of a dorsal axis including head and notochord in the embryo. (shrink)

The first round about ‘The myth of ASCOT and its rival ASCO2.T: tech-noetic vs. techno-logic’ exposed the hazard in colliding obsolete disciplinary categories under outdated procedures. The orthodox jurisdiction of Ars Electronica and CERN in Collide@CERN, one of the most prominent ongoing programmes of this kind, does not eliminate the risk of missing the target by operating with categories of artists and scientists. Art is one of those disciplines with a long expired warranty, but with decay on its periphery that (...) is turning into fertile forefront territories. Fresh temporary categories are marking and spreading over these uncharted territories and sensibly interconnecting with peripheries of other disciplines. The ex-artist that is reborn in this peripheral transdisciplinary zone can be provisionally categorized as a polyphibian for its features to be carefully studied. Like amphibians, a polyphibian can coherently transcend from one medium to another, in between and beyond the disciplines. In order to research the implications of such ‘categorical’ mutations, a readymade was submitted to the organization of Collide@CERN under the licence of R. Mutt. Namely, the readymade ASCOTT (Apparatus with Super COnducting Thought Transduction) dubbed also ASCO2.T is needed as the second-order upgrade of the existing plan for ASCOT (Apparatus with Super COnducting Toroids) invented by the scientists for CERN. As is expected from the reputation of R. Mutt’s readymades – this submission was ignored and refused in just the same quiet manner as his most notorious one. But if society would not provide salons for the refused artists (Salon des Refuses) right next to the salons under the scrutiny of academically established artists, there would be no mutations and no evolution in art. Such mutations of the artist into a ‘complex and widely distributed system’ at the dispersing fringes of decomposing art was already predicted by R. Ascott. Polyphibians are the species surviving the ripening metamorphosis of disciplines by taking refuge in the unexplored transdisciplinary buffer zone. This is the only zone where a confrontation of ASCOT technology with tech-noetics of ASCO2.T is possible. The refused unknown demands not a Salon but the Interval of Suspended Judgement. In the sequel to the first round of this debate, the Interval of Suspended Judgement will be investigated. (shrink)

Studies of the G2 to M transition in amphibian oocytes, in combination with in vitro mitotic systems and yeast genetic analysis, have significantly contributed to our understanding of the mechanisms by which M‐phase is regulated. Historically, oocyte maturation has provided a number of valuable initial observations, but the biochemical elucidation of cell cycle control mechanisms has proved more tractable in cell‐free extracts of frog eggs which reproduce aspects of early embryogenic mitosis. Recent experiments examining the importance of protein synthesis in (...) the maturing oocyte have highlighted some important differences between mitosis and meiosis. Additional controls found in meiosis but not embryonic mitosis, are similar to controls found in somatic cells. This suggests that understanding the differences, as well as the similarities, between meiosis in the oocyte and mitosis in the early embryo will help us to learn more about the way in which cells enter and leave mitosis. (shrink)

Summary Is it possible to discover the critical realist foundations of Gestalt theory in Berlin comparative musicology (vergleichende Kunstwissenschaft) associated above all with Erich M. von Hornbostel? The balance of natural science explanation and phenomenal experience is a useful model for overcoming Eurocentrism in comparative ethnomusicology, relying both on third-person tools and indigenous music systems. This paper uses Gestalt critical realist epistemology and methodology and a portrayal of the strata making up the understanding of a musical act with chemico-physical, phenomenal (...) and cultural components to create an “amphibian” ethnomusicology. Using this framework it is possible to understand Hornbostel and Sachs’ musical instrument classification system and Hornbostel’s account of “primitive” music as strata in a Gestalt explanatory system. The potential binding agent through the strata is isomorphism. (shrink)

The discovery by Hans Spemann of the “organizer” tissue and its ability to induce the formation of the amphibian embryo's neural tube inspired leading embryologists to attempt to elucidate embryonic inductions’ underlying mechanism. Joseph Needham, who during the 1930s conducted research in biochemical embryology, proposed that embryonic induction is mediated by a specific chemical entity embedded in the inducing tissue, surmising that chemical to be a hormone of sterol-like structure. Along with embryologist Conrad H. Waddington, they conducted research aimed at (...) the isolation and functional characterization of the underlying agent. As historians clearly pointed out, embryologists came to question Needham's biochemical approach; he failed to locate the hormone he sought and eventually abandoned his quest. Yet, this study finds that the difficulties he ran into resulted primarily from the limited conditions for conducting his experiments at his institute. In addition, Needham's research reflected the interests of leading biochemists in hormone and cancer research, because it offered novel theoretical models and experimental methods for engaging with the function of the hormones and carcinogens they isolated. Needham and Waddington were deterred neither by the mounting challenges nor by the limited experimental infrastructure. Like their colleagues in hormone and cancer research, they anticipated difficulties in attempting to establish causal links between complex biological phenomena and simple chemical triggering. (shrink)

The discovery by Hans Spemann of the “organizer” tissue and its ability to induce the formation of the amphibian embryo’s neural tube inspired leading embryologists to attempt to elucidate embryonic inductions’ underlying mechanism. Joseph Needham, who during the 1930s conducted research in biochemical embryology, proposed that embryonic induction is mediated by a specific chemical entity embedded in the inducing tissue, surmising that chemical to be a hormone of sterol-like structure. Along with embryologist Conrad H. Waddington, they conducted research aimed at (...) the isolation and functional characterization of the underlying agent. As historians clearly pointed out, embryologists came to question Needham’s biochemical approach; he failed to locate the hormone he sought and eventually abandoned his quest. Yet, this study finds that the difficulties he ran into resulted primarily from the limited conditions for conducting his experiments at his institute. In addition, Needham’s research reflected the interests of leading biochemists in hormone and cancer research, because it offered novel theoretical models and experimental methods for engaging with the function of the hormones and carcinogens they isolated. Needham and Waddington were deterred neither by the mounting challenges nor by the limited experimental infrastructure. Like their colleagues in hormone and cancer research, they anticipated difficulties in attempting to establish causal links between complex biological phenomena and simple chemical triggering. (shrink)

Although estrogens are widely considered circulating “sex steroid hormones” typically associated with female reproduction, recent evidence suggests that estrogens can act as local modulators of brain circuits in both males and females. The functional implications of this newly characterized estrogen signaling system have begun to emerge. This essay summarizes evidence in support of the hypothesis that the rapid production of estrogens in brain circuits can drive acute changes in both the production and perception of acoustic communication behaviors. These studies have (...) revealed two fundamental neurobiological concepts: (1) estrogens can be locally produced in brain circuits, independent of levels in nearby circuits and in the circulation and (2) estrogens can have very rapid effects within these brain circuits to modulate social vocalizations, acoustic processing, and sensorimotor integration. This vertebrate‐wide span of research, including vocalizing fishes, amphibians, and birds, emphasizes the importance of comparative model systems in understanding principles of neurobiology. (shrink)

Three experiments, adopting an evolutionary biology perspective, investigated subjects’ inferences about living things. Subjects were told that different enzymes help regulate cell function in two taxa and asked which enzyme a third taxon most likely uses. Experiment 1 and its follow-up, with college students, used triads involving amphibians, reptiles, and mammals (reptiles and mammals are most closely related evolutionarily) and plants, fungi, and animals (fungi are more closely related to animals than to plants). Experiment 2, with 10th graders, also (...) included triads involving mammals, birds, and snakes/crocodilians (birds and snakes/crocodilians are most closely related). Some subjects received cladograms (hierarchical diagrams) depicting the evolutionary relationships among the taxa. The effect of providing cladograms depended on students’ background in biology. The results illuminate students’ misconceptions concerning common taxa and constraints on their willingness to override faulty knowledge when given appropriate evolutionary evidence. Implications for introducing tree thinking into biology curricula are discussed. (shrink)