Contributions to the sociology and chorology of contrasting plant communities in the southern part of the ‘Wienerwald’ (Austria)

Five plant communities contrasting in successional status and human impact from the southern part of the ‘Wienerwald’ (Austria) are analyzed using vegetation relevés, spectra of area types and a newly proposed disjunction quotient. A climax community (Asperulo-Fagetum), a subclimax community (Querco-Carpinetum s.l.), an anthropogenous substitute community (Mesobromion) and two natural, non-climax permanent communities (Euphorbio saxatilis-Pinetum nigrae and Fumano-Stipetum eriocaulis) are recognized. The disjunction quotient is defined as the number of partial (discontinous) areas divided by the size of the total area of distribution of a species. In particular, the average disjunction quotients of the species in the first two communities reflect relatively table environments only slightly influenced by man, with many ancient, stable taxa. These communities are characterized by species with well-delimited, stable distribution areas. The species in the Mesobromion community have very low average disjunction quotients as its component species are widely and continuously distributed and are often promoted by man. In contrast to these communities, the species linked to the natural permanent, non-climax communities of extreme habitats, have high distribution quotients i.e. small, disconinuous areas; this illustrates the relic character of these plant communities and of the eastern edge of the Alps is a whole. Using the highly variable disjunction quotient of all species and communities examined, the concepts of climax and permanent communities (of different origin) are discussed with regard to European conditions.     

The influence of contact guidance on the orientation of colonies of subcultured vascular smooth muscle cells

Summary Subcultures of smooth muscle cells derived from rat thoracic aorta were grown on plane plastic substrata and on plastic substrata having ridges molded in them by a heated, ruled template. The cells were found to have a very high degree of contact guidance when distributed sparsely on the ridged substrata. When the cell density increased multilayered, elongated colonies formed. On plane substrata these were irregular, curved, and disposed in all directions. On the ridged substrata, however, the colonies were straight, evenly spaced, and positioned at right angles to the ridges. Supported by Grant MT1011 from the Medical Research Council of Canada.     

The effect of costs associated with toxin production in a competitive system

In this paper, we study a two-species competitive system where both the species produce toxin against each other at some cost to their growth rates. A much wider set of outcomes is possible for our system. These outcomes are important contrasts to competitive exclusion or bistable attractors that are often the outcomes for competitive systems. We show that toxin helps to gain an advantage in competition for toxic species whenever the cost of toxin production remains within some moderate value; otherwise it may result in the extinction of the species itself.     

Studies onMadhuca butyraceae seed proteins

DefattedMadhuca butyraceae seeds contain 24% of crude protein and 10.4% of saponins. The solubility ofMadhuca seed proteins was determined in water and NaCl as a function of pH and minimum solubility occurred at pH 4.0. The proteins consist of three components with S_20,w values of 2.2, 9.8 and 15.4. On gel filtration the proteins gave three peaks and on diethylaminoethyl cellulose chromatography they resolved into two components. Thein vitro digestibility ofMadhuca seed protein was found to be 69% when assayed with a pepsin-pancreatin system.     

A Search for Discrete Cholinergic Nuclei in the Human Ventral Forebrain

Abstract: Slices cut from five frozen human brains were dissected into 2-mm cubes and assayed for choline acetyltransferase (ChAT) activity and protein content. A pattern of enrichment of ChAT activity was found ventral to the anterior commissure; this finding is consistent with the location of the enzyme in the cells of the nucleus basalis of Meynert. The region beneath the anterior commissure was the only place a discrete enrichment of activity could be found, and the precise topography of the enrichment was somewhat variable from brain to brain. The results are discussed in the light of recent knowledge concerning the source of the cortical cholinergic innervation.     

Membrane electrical parameters in turtle bladder measured using impedance-analysis techniques

Summary Equivalent-circuit impedance analysis experiments were performed on the urinary bladders of freshwater turtles in order to quantify membrane ionic conductances and areas, and to investigate how changes in these parameters are associated with changes in the rate of proton secretion in this tissue. In all experiments, sodium reabsorption was inhibited thereby unmasking the electrogenic proton secretion process. We report the following: (1) transepithelial impedance is represented exceptionally well by a simple equivalent-circuit model, which results in estimates of the apical and basolateral membrane ionic conductances and capacitances; (2) when sodium transport is inhibited with mucosal amiloride and serosal ouabain, the apical and basolateral membrane conductances and capacitances exhibit a continual decline with time; (3) this decline in the membrane parameters is most likely caused by subtle time-dependent changes in cell volume, resulting in changes in the areas of the apical and basolateral membranes; (4) stable membrane parameters are obtained if the tissue is not treated with ouabain, and if the oncotic pressure of the serosal solution is increased by the addition of 2% albumin; (5) inhibition of proton secretion using acetazolamide in CO₂ and HCO ₃ ^– -free bathing solutions results in a decrease in the area of the apical membrane, with no significant change in its specific conductance; (6) stimulation of proton transport with CO₂ and HCO ₃ ^– -containing serosal solution results in an increase in the apical membrane area and specific conductance. These results show that our methods can be used to measure changes in the membrane electrophysiological parameters that are related to changes in the rate of proton transport. Notably, they can be used to quantify in the live tissue, changes in membrane area resulting from changes in the net rates of endocytosis and exocytosis which are postulated to be intimately involved in the regulation of proton transport.     

Localization of99mTc in bone by means of autoradiography

The uptake of two different preparations of^99mTechnetium-methylene diphosphonate in fetal rat calvaria is compared. The localization of^99mTc after administration of^99mTc(Sn)-MDP and^99mTc-MDP showed equal distribution in autoradiography.     

Protein diffusion in crowded electrolyte solutions

We report on a combined cold neutron backscattering and spin-echo study of the short-range and long-range nanosecond diffusion of the model globular protein bovine serum albumin (BSA) in aqueous solution as a function of protein concentration and NaCl salt concentration. Complementary small angle X-ray scattering data are used to obtain information on the correlations of the proteins in solution. Particular emphasis is put on the effect of crowding, i.e. conditions under which the proteins cannot be considered as objects independent of each other. We thus address the question at which concentration this crowding starts to influence the static and in particular also the dynamical behaviour. We also briefly discuss qualitatively which charge effects, i.e. effects due to the interplay of charged molecules in an electrolyte solution, may be anticipated. Both the issue of crowding as well as that of charge effects are particularly relevant for proteins and their function under physiological conditions, where the protein volume fraction can be up to approximately 40% and salt ions are ubiquitous. The interpretation of the data is put in the context of existing studies on related systems and of existing theoretical models.