不同放牧强度下短花针茅荒漠草原植被的空间异质性

分析不同放牧强度下植物群落中物种的空间分布特征, 有助于阐明群落在放牧胁迫下的演替规律。该研究基于幂函数法则, 探讨了不同放牧强度下短花针茅(Stipa breviflora)荒漠草原群落植物的频率和空间异质性。结果表明: 不同放牧强度下物种空间分布与幂函数法则能很好地吻合; 不同物种空间异质性具有特异性, 随着放牧强度的增加, 提高群落空间异质性的物种分别由无芒隐子草(Cleistogenes songorica)、冷蒿(Artemisia frigida)、短花针茅、银灰旋花(Convolvulus ammannii)等多个物种逐渐转变为以无芒隐子草、短花针茅为主的少数物种, 同时, 物种空间异质性大于群落空间异质性的物种数逐渐减少。     

Calcium-induced calcium release mediates all-or-nothing responses of mesenchymal stromal cells to noradrenaline

By using Ca²⁺ imaging and Fluo-4 dye, we examined the capability of certain agonists of G-protein coupled receptors to stimulate Ca²⁺ signaling in cultured mesenchymal stromal cells (MSC) derived from the human adipose tissue. In particular, a small subpopulation (～5%) MSC was found to respond to noradrenaline with Ca²⁺ transients. The all-or-nothing fashion was characteristic of adrenergic Ca²⁺ signaling in MSC, that is, while at low concentrations noradrenaline stimulated undetectable Ca²⁺ transients, virtually maximal responses were elicited by this agonist at any concentration above the threshold of 100–200 nM. In some experiments, MSC were loaded with the photosensitive Ca²⁺ chelator NP-EGTA to produce local or global jumps in cytosolic Ca²⁺ concentration by virtue of Ca²⁺ uncaging. Global uncaging eliciting a high enough Ca²⁺ jump triggered a Ca²⁺ transient in the MSC cytoplasm, which was similar to a noradrenaline response kinetically and by magnitude. When Ca²⁺ uncaging was produced locally, it initiated a Ca²⁺ signal that traveled along a cell with a speed that exceeded an expected one by two orders of magnitude, should Ca²⁺ signal transfer be mediated merely by passive Ca²⁺ diffusion in the presence of Ca²⁺ buffer. These findings implicated Ca²⁺-induced Ca²⁺ release (CICR) as a mechanism amplifying local Ca²⁺ signals in MSC. Of Ca²⁺ targets involved in CICR, the ryanodine receptor and IP₃ receptor are only known. The inhibitory analysis revealed IP₃ receptors to be principally responsible for CICR in MSC, whereas a contribution of ryanodine receptors was negligible. Altogether, our results suggest that an initial noradrenaline-dependent rise in cytosolic Ca²⁺ stimulates, should it reach the threshold level, IP₃ receptors, thereby triggering an avalanche-like Ca²⁺ release from Ca²⁺ stores and underlying the all-or-nothing dependence of cellular responses on the agonist concentration.     

Heavy Metal Contents in Tissues of Dominant Species of the Benthos and in Bottom Sediments of Zolotoi Rog Bay, Sea of Japan

Data on heavy metal contents in polychaetes and free-living nematodes inhabiting the bottom sediments of Zolotoi Rog Bay near the port of Vladivostok are reported. Chronically high contents of heavy metals (Fe, Cu, Zn, and Cd) were found in the bottom sediments and in the infauna. The levels of some toxic elements in tissues of the polychaete Dorvillea (Schistomeringos) japonica inhabiting polluted sediments of Zolotoi Rog Bay were higher than in worms of this species from relatively clean areas of the Sea of Japan. Similar high concentrations of Fe were found in the polychaete Capitella capitata and the nematode Oncholaimium ramosum. The highest concentrations of Fe, Zn, Cu, and Cd were found in tissues of the free-living nematode O. ramosum. Chronic heavy pollution of the bottom sediments leads to a decrease in the biodiversity of the infauna and to specific metal-tolerant communities.Original Russian Text Copyright © 2005 by Biologiya Morya, Davydkova, Fadeeva, Kovekovdova, Fadeev.     

Effects of a medium pH on the ability of Chinese hamster cells to repair radiation injuries]

In experiments with Chinese hamster cells at exponential and stationary growth phases, it has been shown that the postirradiation incubation of irradiated cells in a medium with low pH (up to 6.0) promotes the recovery of cells from potentially lethal damages; it has also been found that the recovery from sublethal radiation damages does not depend on the medium pH. The long-term incubation of nonirradiated cells with low pHc causes death of part of cells.     

Intensification of antibacterial and antiviral nonsusceptibility and of the immune response with an officinal RNA preparation]

Sodium nucleinate increased essentially the insusceptibility of mice to pathogenic escherichia, strain O26, Pr. vulgaris, Ps. aeruginosa, Ser. marcescens, and produced a total stimulating effect on the nonspecific bacterial resistance; analogous stimulating activity was found in the homologous low polymeric RNA from the liver. Sodium nucleinate intensified the insusceptibility of the animals to the tick-born encephalitis and encephalomyelitis viruses, and increased the antibody-forming cells count. The side-effect of heat-inactivated vaccine from pathogenic escherichia was reduced in animals inoculated with sodium nucleinate preliminarily.     

Peculiarities of the contour feather microstructure in the Cordovidae family

The results of comparative electron microscope study of the fine structure of the definitive contour feathers of ten Crows species (Perisoreus infaustus, Garrulus glandarius, Cyanopica cyanus, Pica Pica, Podoceus panderi, Nucifraga caryocatactes, Corvus monedula, C.frugilegus, C. cornix, C. corax) are presented. The results of the research allowed us to conclude that crows, along with the traditional elements of feather architectonics, have a number of species-specific microstructure characteristics that are taxonomically important.