Against “Revolution” and “Evolution”

Those standard historiographic themes of evolution and revolution need replacing. They perpetuate mid-Victorian scientists history of science. Historians history of science does well to take in the long run from the Greek and Hebrew heritages on, and to work at avoiding misleading anachronism and teleology. As an alternative to the usual evo-revo themes, a historiography of origins and species, of cosmologies (including microcosmogonies and macrocosmogonies) and ontologies, is developed here. The advantages of such a historiography are illustrated by looking briefly at a number of transitions the transition from Greek and Hebrew doctrines to their integrations by medieval authors; the transition from the Platonist, Aristotelian, Christian Aquinas to the Newtonian Buffon and to the no less Newtonian Lamarck; the departures the early Darwin made away from Lamarcks and from Lyells views. Issues concerning historical thinking about nature, concerning essentialism and concerning classification are addressed in an attempt to challenge customary stereotypes. Questions about originality and influence are raised, especially concerning Darwins tree of life scheme. The broader historiography of Darwinian science as a social ideology, and as a worldview, is examined and the scope for revisions emphasised. Throughout, graduate students are encouraged to see this topic area not as worked out, but as full of opportunities for fresh contributions.     

Steroid hormones and the brain: Linking “nature” and “nurture”

Contrary to earlier belief, the genetic constitution of each cell of the body (nature) is subject to modulation by environmental factors (nurture) which act throughout the life of the organism to shape the individual characteristics. The nervous system adapts and changes with the environment that the organism experiences through genomic activity controlled by chemical messengers from other nerve cells and from endocrine secretions. The nervous system expresses receptors for a number of circulating hormones, and the location of these hormone receptors has revealed a great deal about the neuroanatomy of neuroendocrine and behavioral control processes. The brain controls the endocrine system through the hypothalamus and pituitary gland, and it responds to circulating hormones throughout each stage of life. These effects begin during early development (eg., sexual differentiation of the brain; effects of maternal or neonatal stress). They continue in adult life in response to cyclic events (eg., season of year; time of day, controlling reproduction and daily activity-sleep rhythms of behavior); and they also include the behavior of other animals which alters hormone output. Hormones also operate during the aging process and under conditions which induce neural damage such as hypoxia and stress. This overview summarizes involvement of steroid hormones of gonads and adrenals in many of these processes and also examines the features of the genomic activity which is modified by these hormones. This area of research is fruitful because it brings together molecular, anatomical, physiological and behavioral approaches in an attempt to understand the longterm plasticity of the nervous system.This overview article, written in recognition of the contributions to neuroscience by Professor Holger Hydén, is based upon a Presidential Special Lecture delivered by the author at the Society for Neuroscience Meeting in Washington, D.C., on November 11, 1986     

Darwinian selection and “altruism”

Models are proposed for evolution at a single locus affecting altruistic behavior in which genotypic fitnesses are Darwinian and frequency (but not density) dependent. The fitnesses are composed, either in a multiplicative or an additive way, of factors which depend on the receipt and donation of altruistic behavior. The factors are determined from the matrices of conditional probabilities which describe the genotypes of relatives. Since selection occurs, these probabilities are in terms of genotype frequencies. The relationship between the risk to helper and benefit to recipient which allows altruism to evolve is shown to depend on the kinship coefficient between helper and helped, the particular fitness function proposed and the degree of dominance of the altruism. The commonly accepted criteria of W. D. Hamilton [J. Theor. Biol.7 (1964), 1–16, 17–52] apply only in the additive case. A second class of models of social cooperation independent of relationship and its evolutionary dynamics are discussed.     

“Realism” and “relevance” in gaming simulations

How useful are gaming simulations for the study of problems that interest human ecologists? Anatol Rapoport, a principal contributor to the development of game theory, raised this issue with the editors of Human Ecology,who in turn invited him to express his views in print. In brief, Dr. Rapoport calls into question the real-world applicability of gaming simulations, and explores its limitations. The educational function of simulation, he argues, should not be confused with the research aims of laboratory experimentation. The addition of “realistic” conditions in a gaming simulation merely complicates the experiment and reduces its theoretical significance. It does, however, have some pedagogical utility, whose implications have not yet been adequately taken into account. Dr. Rapoport considers this matter with reference to the problem of “social traps,” such as the “tragedy of the commons,” an issue which concerns many human-ecology researchers.     

GABA and “neuro-cardiovascular” mechanisms

One has only to recall that GABA appears to be a major inhibitory neurotransmitter in the vertebrate central nervous system (CNS), that it exerts a hypotensive action upon systemic administration, that it is present in the blood, that its actions are antagonized by bicuculline and picrotoxin and facilitated by benzodiazepines, and that receptors for GABA exist in cerebral blood vessels, to consider that GABA is somehow involved in cardiovascular regulation. One might even postulate that influences upon GABA-ergic mechanisms are involved in that dangerous sequence of biological activities: environmental stress → anxiety → atherosclerosis and hypertension, the latter of which represent major health problems of man. Herein, some evidence that appears to support this view will be presented.     

Cholinesterases and cell proliferation in “nonstratified” and “stratified” cell aggregates from chicken retina and tectum

Summary Dissociated single cells from chicken retina or tectum kept in rotation-mediated cell culture aggregate, proliferate and establish a certain degree of histotypical cellto-cell relationships (sorting out), but these systems never form highly laminated aggregates (nonstratified R- and T-aggregates). In contrast, a mixture of retinal plus pigment epithelial cells forms highly stratified aggregates (RPE-aggregates, see Vollmer et al. 1984). The present comparative study of stratified and nonstratified aggregates enables us to investigate the process of cell proliferation uncoupled from that of tissue stratification. Here we try to relate these two basic neurogenetic processes with patterns of expression of cholinesterases (AChE, BChE) during formation of both types of aggregates.During early aggregate formation, in both stratified and nonstratified aggregates an increased butyrylcholinesterase activity is observed close to mitotically active cells. Quantitatively both phenomena show their maxima after 2–3 days in culture. In contrast, AChE-expression in all systems increases with incubation time. In nonproliferative areas, in the center of RPE-aggregates, the formation of plexiform layers is characterized initially by weak BChE and then strong AChE-activity. These areas correspond with the inner (IPL) and outer (OPL) plexiform layers of the retina in vivo. Although by sucrose gradient centrifugation we find that the 6S- and the fiber-associated 11S-molecules of AChE are present in all types of aggregates, during the culture period the ratio of 11S/6S-forms increases only in RPE-aggregates, which again indicates the advanced degree of differentiation within these aggregates.It is thus demonstrated that cholinesterases first correlate with neuronal cell proliferation and later with stratification, which indicates functions of both enzymes during both developmental periods.Abbreviations AChE acetylcholinesterase - BChE butyrylcholinesterase - iso-OMPA specific inhibitor of BChE - BW 284C51 specific inhibitor of AChE - IPL inner plexiform layer - OPL outer plexiform layer     

“Sunbursts” and “christiesomes”: Cellular fragments in normal cow and goat milk

Summary Goats' milk includes numerous cell fragments (christiesomes) which originate from the mammary secretory cells, contain well preserved endoplasmic reticulum, mitochondria and lipid droplets, and are responsible for the considerable triglyceride synthesising capacity of fresh goat milk. Cows' milk shows a few such particles only after repeated oxytocin-aided milkings. Cows' milk does contain quite different particles which have a dense content with a few small vesicles and numerous microvillus-like protrusions on one side (sunbursts). These have not been found in goats milk. Cytoplasmic particles similar to sunbursts have been found on the surface of the mammary secretory epithelium. It is suggested that they are residues of dead cells.     

Synthesis of “Reversed” and “Double Headed” Nucleosides

Abstract

The synthesis of several partially and fully deprotected “reversed” nucleosides are described starting from “reversed” 5-iodouracil-1-yl nucleoside 1. The preparation of a novel purine-purine and mixed purine-pyrimidine “double headed” nucleosides via “reversed” purine nucleoside 12 is also described.     

Differential expression of “Fe-repressible” and “growth-rate-sensitive” proteins in Neisseria meningitidis and Neisseria gonorrhoeae

By varying growth conditions, we were able to differentiate (SDS-PAGE) between true Fe-repressible proteins and growth-rate-sensitive proteins (GSP's) (60-110 Kd) in outer membranes of iron-starved meningococci and gonococci. Immunological characterization with monoclonal antibodies raised against the GSP's revealed (GIRA) crossreactivity between different GSP's. On the basis of common epitopes, two groups of proteins could be distinguished. Immuno-electron-microscopy showed that proteins of both groups were exposed at the cell surface.     

Information, evolution and “error-friendliness”

Information can be conceived as being composed of two complementary components: novelty and confirmation. Whenever either of the two is zero, information is zero. Genetic information too requires both novelty and confirmation. Evolution can be seen as the history of diversification. Selection alone reduces diversity. Recessivity appears to serve as a mechanism to protect diversity against selection. So does the geographical and behavioural “separation” of species. Both recessivity and separation can be seen as “error-friendly”, a broader concept that is supportive of diversity, learning and further evolution. The principle should also be obeyed in technological systems. Received: 4 October 1997 / Accepted in revised form: 26 August 1998     

“Theory” in Theory and Practice

A central obstacle to accepting evolution, both among students and the general public, is the idea that evolution is “just a theory,” where “theory” is understood in a pejorative sense as something conjectural or speculative. Although scientists and textbooks constantly explain that the scientific use of “theory” is quite different, the pejorative use continues to cause confusion, in part because of its deep roots in a popular, Baconian, understanding of science. A constructivist approach, whereby students are helped to examine the adequacy of their preconceptions about “theory” for themselves and to revise or replace them appropriately, is recommended.