Palaeoenvironmental and palaeoclimatic reconstruction of the Middle to Late Pleistocene sequence of Scladina Cave (Namur,Belgium) using the small-mammal assemblages

The habitat weighting, the bioclimatic model methods and the Simpson diversity index are applied to the small-mammals assemblage of Scladina Cave (border between High and Middle Belgium) in order to reconstruct the environmental and climatic fluctuations that are reflected on the Middle to Late Pleistocene sequence of the cave. The small-mammal data analyzed come from two surveys carried out at the entrance of the cave and allow us to identify within the section one cold episode: a dry, cool phase in the upper part of the sequence (probably associated with the MIS 3). The environmental and climatic data show an alternation of open meadows and woodland formations through both sequences, punctuated by peaks in local watery environments together with lower temperatures and higher precipitations rates than at present. Finally, a comparison of the small-mammal fossil assemblage from the studied surveys with the small-mammals assemblage from the Holocene deposits of Scladina Cave shows that layers related with MIS 5 temperate sub-stages (MIS 5c and MIS 5a) present environmental characteristics similar to those prevailing nowadays (a landscape dominated by woodland formations and water streams) in the area surrounding the cave. This is coherent with the available chronostratigraphic datasets on this part of the sequence, suggesting the record of the humid and temperate phases at the beginning of the Late Pleistocene.     

Frequencies of interspecific shell exchanges between hermit crabs

Frequencies of interspecific shell exchange due to shell fighting were determined for a number of species pairs of hermit crabs from several different locations. Frequencies were determined in the laboratory using a standardized experimental design. Results suggest that most individuals of most species are able to retain adequate or good quality shells in the presence of members of another species occupying poor quality shells. High frequencies of shell exchange always seem to be associated with very asymmetric relationships in which one member of the species pair is clearly dominant over the other. Dominant species usually attain larger sizes than subordinates, are found lower in the intertidal habitat, and are less abundant.     

Why don't predators have positive effects on prey populations?

Summary Three mechanisms by which increasing predation can increase prey population density are discussed: (1) Additional predation on species which have negative effects on the prey; (2) Predation on consumer species whose relationship with their own prey is characterized by a unimodal prey isocline; (3) Predation on species which adaptively balance predation risk and food intake while foraging. Possible reasons are discussed for the rarity of positive effects in previous predator-manipulation studies; these include the short-term nature of experiments, the large magnitudes of predator density manipulation, and various sources of bias in choice of system and interpretation of results.     

NEW EXPERIMENTS ON ANOMALOUS OSMOSIS

1. It is impossible to reproduce Loeb''s observations on anomalous osmosis with membranes prepared from relatively pure brands of collodion, whereas positive effects can be obtained using collodion containing acidic impurities. 2. The inactive (purer) collodion membranes may be activated by oxidation with NaOBr solution. 3. Properly oxidized membranes give much greater anomalous osmotic effects than those described by Loeb.     

THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR : I. THE BEHAVIOR AND PROPERTIES OF COMMERCIAL COLLODION

1. The electrochemical behavior of membranes prepared from commercial collodion preparations varies widely, some preparations showing very high, other ones very low electrochemical efficiency ("activity"). 2. The electrochemical activity of a collodion membrane depends entirely upon impurities of an acidic nature contained in the collodion used for casting the membrane. 3. The active acidic impurities are substantially due to partial oxidation which occurs in the manufacturing process. Sulfuric acid compounds; e.g., acid sulfuric acid esters play only a minor rôle, if any. 4. The electrochemical behavior of collodion membranes in solutions of strong electrolytes is decisively dependent upon the acidic groups built permanently into the collodion surfaces. Preferential ion adsorption plays only a minor, if any, rôle.     

Seasonal variations in oviductal morphology of the painted turtle,Chrysemys picta

Histology of each of the five segments of the oviduct of the female turtle Chrysemys picta was described for successive intervals throughout their annual cycle. Uterine and glandular segments showed marked seasonal variations in the extent and content of the submucosal and epithelial glands. Submucosal glands were most prominent in preovulatory and postovulatory animals (May to June), regressing in late summer (oviposited animals) and recrudescing the following spring. These changes correlated with variations in the muscularis layer, the number of uterine epithelial blebs, oviductal vascularity, and the presence of eosinophils in cervical segment cross-sections. These cyclic seasonal changes are discussed in relationship to reported seasonal changes in gonadal steroids in this species. Hormonal control was corroborated by oviductal response to estradiol-17β injected (1 mg/kg daily for 2 weeks) into mature, reproductively inactive (winter) animals. This treatment induced increases in glandular activity, vascularity, and distribution of eosinophils comparable to those of reproductively active (summer) animals.     

Ecological structure of a pelagic seabird community in the Southern Ocean

Summary The pelagic avifauna (excluding penguins) of the African sector (30°S–70°S, 20°W–40°E) of the Southern Ocean is described quantitatively, based on 3,005 10-min observation of seabirds during seven oceanic cruises in April 1979 – April 1980. The avifauna is characterized according to species richness, diversity, abundance and biomass. These indices are correlated with groups of birds ordered into principal diet and feeding-method classes. Birds eating either plankton, cephalopods or a mixed diet accounted for 51, 23 and 22% of the total avifaunal abundance and 22, 49 and 25% of the total biomass, respectively. Piscivores were represented poorly. Planktivores were especially abundant south of the Antarctic Convergence and, to a lesser extent, at the sub-Tropical Convergence. Cephalopod-eaters were most abundant north of the sub-Tropical Convergence. The greatest abundance of omnivores occurred where planktivores and cephalopod-eaters were least abundant. The distribution of the planktivores and cephalopodeaters is related tentatively to the availability of the birds' principal prey.     

A MULTIPHASIC SCREENING SURVEY IN SAN JOSE

In the interest of economy and of better service to the persons examined, three screening tests of a kind usually made separately were combined and applied in a single examination of 945 employees in four industrial establishments. Miniature x-ray films of the chest were taken, blood specimens drawn and urine samples obtained so that studies and tests might be made to determine the presence of pulmonary or cardiac disease, syphilis, kidney disease, or diabetes. The history of each person examined was taken.Through this multiphasic survey, 13 cases of significant disease previously unknown to the patient were discovered. Sixteen cases of significant disease, previously known, were also disclosed; and in several such cases treatment was begun or resumed.The results in case finding were considerably greater than those of the customary screening for a single disease.     

CD4+ T lymphocyte-induced target cell detachment. A model for T cell-mediated lytic and nonlytic inflammatory processes.

We have been exploring the hypothesis that T lymphocytes have the potential to mediate immune damage through nonlytic disruption of tissue organization. In this report, we have examined the ability of purified, primary cultures of alloreactive CD4+ T cells to mediate Ag-specific target cell detachment and/or lysis of L cell lines transfected with MHC class II determinants. Using this model, we demonstrate that: 1) MHC class II-specific CD4+ T cells can cause detachment as a distinct event of the E:T interaction, although the pathways or mechanisms involved appear to be different from those utilized by MHC class I-specific CD8+ T cells; 2) detachment and lysis by CD4+ T cells are distinct activities that involve different functional requirements: 3) CD4+ T cell-induced detachment is initiated by direct cell-cell interaction, independent of TNF-alpha/beta; 4) CD4+ T cell-mediated lysis can be accomplished by TNF-alpha/beta-dependent and independent pathways; and 5) the nature of a particular target cell response to alloreactive CD4+ T cell attack reflects its intrinsic susceptibility to one or more potential effector mechanisms.