Under the influence of Malthus's law of population growth: Darwin eschews the statistical techniques of Aldolphe Quetelet

Charles Darwin, James Clerk Maxwell, and Francis Galton were all aware, by various means, of Aldolphe Quetelet’s pioneering work in statistics. Darwin, Maxwell, and Galton all had reason to be interested in Quetelet’s work: they were all working on some instance of how large-scale regularities emerge from individual events that vary from one another; all were rejecting the divine interventionistic theories of their contemporaries; and Quetelet’s techniques provided them with a way forward. Maxwell and Galton all explicitly endorse Quetelet’s techniques in their work; Darwin does not incorporate any of the statistical ideas of Quetelet, although natural selection post-twentieth century synthesis has. Why not Darwin? My answer is that by the time Darwin encountered Malthus’s law of excess reproduction he had all he needed to answer about large scale regularities in extinctions, speciation, and adaptation. He didn’t need Quetelet.     

Yeast ornithine decarboxylase and antizyme form a 1:1 complex in vitro: Purification and characterization of the inhibitory complex

Saccharomyces cerevisiae antizyme (AZ) resembles mammalian AZ in its mode of synthesis by translational frameshifting and its ability to inhibit and facilitate the degradation of ornithine decarboxylase (ODC). Despite many studies on the interaction of AZ and ODC, the ODC:AZ complex has not been purified from any source and thus clear information about the stoichiometry of the complex is still lacking. In this study we have studied the yeast antizyme protein and the ODC:AZ complex. The far UV CD spectrum of the full-length antizyme shows that the yeast protein consists of 51% β-sheet, 19% α-helix, and 24% coils. Surface plasmon resonance analyses show that the association constant (K_A) between yeast AZ and yeast ODC is 6 × 10⁷ (M⁻¹). Using purified His-tagged AZ as a binding partner, we have purified the ODC:AZ inhibitory complex. The isolated complex has no ODC activity. The molecular weight of the complex is 90 kDa, which indicates a one to one stoichiometric binding of AZ and ODC in vitro. Comparison of the circular dichroism (CD) spectra of the two individual proteins and of the ODC:AZ complex shows a change in the secondary structure in the complex.     

Individual differences, density dependence and offspring birth traits in a population of red deer

Variation between individuals is an essential component of natural selection and evolutionary change, but it is only recently that the consequences of persistent differences between individuals on population dynamics have been considered. In particular, few authors have addressed whether interactions exist between individual quality and environmental variation. In part, this is due to the difficulties of collecting sufficient data, but also the challenge of defining individual quality. Using a long-established study population of red deer, Cervus elaphus, inhabiting the North Block of the Isle of Rum, and three quality measures, this paper investigates how differences in maternal quality affect variation in birth body mass and date, as population density varies, and how this differs depending on the sex of the offspring and the maternal quality measure used. Significant interactions between maternal quality, measured as a hind's total contribution to population growth, and population density are reported for birth mass, but only for male calves. Analyses using dominance or age at primiparity to define maternal quality showed no significant interactions with population density, highlighting the difficulties of defining a consistent measure of individual quality.     

Spatial and temporal variation in the vegetation of dune slacks in relation to the ground water régime

Summary The aim of the study presented here is to determine the relation between the vegetation and the ground water régime in the dune slacks on the island of Voorne. A distinction is made between the spatial and the temporal variation in the vegetation. On the basis of data from a transect the relation between the spatial variation and the water-table is determined. With respect to the temporal variation data recorded on permanent plots were used. Both the variation in space and that in time proved to be related to differences in the ground water régime. The supposition is put forward that the amount of variation in time depends on the height of site relative to the water-table.Contribution to the Symposium of the Working Group on Succession Research on Permanent Plots held at Yerseke, the Netherlands, October 1975.Nomenclature of phanerogams follows Heukels & van Ooststroom 1975, Flora van Nederland, 18e druk Wolters-Noordhoff, Groningen; that of bryophytes Margadant 1959, Mossentabel, 3e druk, Amsterdam.The author is very much indebted to Mr. P.A. Bakker, Society for the Preservation of Nature reserves in the Netherlands, for the use of the 1966 relevé of site 46, and to Mr. W. Smant for his assistance in field work and the preparation of the data.     

Migration of connective tissue-derived cells is mediated by ultra-low concentration gradient fields of EGF

The directed migration of cells towards chemical stimuli incorporates simultaneous changes in both the concentration of a chemotactic agent and its concentration gradient, each of which may influence cell migratory response. In this study, we utilized a microfluidic system to examine the interactions between epidermal growth factor (EGF) concentration and EGF gradient in stimulating the chemotaxis of connective tissue-derived fibroblast cells. Cells seeded within microfluidic devices were exposed to concentration gradients established by EGF concentrations that matched or exceeded those required for maximum chemotactic responses seen in transfilter migration assays. The migration of individual cells within the device was measured optically after steady-state gradients had been experimentally established. Results illustrate that motility was maximal at EGF concentration gradients between .01- and 0.1-ng/(mL.mm) for all concentrations used. In contrast, the number of motile cells continually increased with increasing gradient steepness for all concentrations examined. Microfluidics-based experiments exposed cells to minute changes in EGF concentration and gradient that were in line with the acute EGFR phosphorylation measured. Correlation of experimental data with established mathematical models illustrated that the fibroblasts studied exhibit an unreported chemosensitivity to minute changes in EGF concentration, similar to that reported for highly motile cells, such as macrophages. Our results demonstrate that shallow chemotactic gradients, while previously unexplored, are necessary to induce the rate of directed cellular migration and the number of motile cells in the connective tissue-derived cells examined.