Physical forces constrain the depth distribution of the abundant native mussel Elliptio complanata in lakes

1. Unionid mussels often account for a large portion of benthic biomass and contribute to nutrient cycling and sediment processes, but are thought to be limited to shallow areas (<2–3 m). 2. The depth distribution and body size of Elliptio complanata were compared in seven Canadian Shield lake basins of different sizes to test what factors determine the upper and lower limit of their depth range. Specifically, I tested whether (i) the upper range of their distribution is limited by exposure to winds and wave action and (ii) the lower range of their distribution is limited by the depth of the thermocline or by the boundary of mud deposition. 3. The average depth distribution of E. complanata shifted to greater depths in larger lake basins. When comparing individual transects, maximum mussel density was found deeper at more exposed sites. Mussel size decreased with increasing depth and was larger, on average, in larger lake basins. These results suggest that physical forces limit the upper range of mussel distribution in lakes. 4. The maximum depth at which mussels were found in different lakes was closely related to thermocline depth. However, mussels were commonly observed below the predicted depth of the mud deposition boundary. The thermocline limits the lower range of mussel distribution in lakes, probably by limiting food availability and by determining water temperature. Substratum type does not limit the lower distribution of mussels. 5. These results suggest that unionid mussels are present in the deeper parts of the littoral zone, especially in large lakes. Therefore, comparisons of mussel populations between sites and between lakes would be biased unless the full depth distribution of these mussels is considered. These results also suggest that long‐term changes in the thermal structure of lakes could affect the range of unionid mussel populations and their functional role in littoral ecosystems.     

Rod-shaped inclusions in the heart and brain in the experimental alcoholization of rats

Experiments were made on rat alcoholized by inhalation. Electron microscopy of the myocardium and brain cortex showed the dystrophically altered cells of these organs to contain unusual rod-shaped and sagittal cytoplasmic inclusions unrelated to organelles and having a certain structural similarity to alcoholic hyaline detected in men. The necessity of further studies to identify the inclusions in question is discussed.     

Host preferences of Palaearctic Culicoides biting midges: implications for transmission of orbiviruses

Feeding success depends on host availability, host defensive reactions and host preferences. Host choice is a critical determinant of the intensity at which pathogens are transmitted. The aim of the current study was to describe host preferences of Palaearctic Culicoides species (Diptera: Ceratopogonidae) Latreille using traps baited with the five different host species of poultry, horse, cattle, sheep and goat. Collections were carried out nightly in July and August 2009 in western France with three replicates of a 5 × 5 randomized Latin square (five sites, five hosts). Moreover, an ultraviolet (UV) light/suction trap was operated during host‐baited collections to correlate Culicoides biting rates and UV light/suction trap catches. A total of 660 Culicoides belonging to 12 species, but comprised mainly of Culicoides scoticus Downes and Kettle, Culicoides dewulfi Goetghebuer and Culicoides obsoletus Meigen, were collected on animal baits. Abundance was highest for the horse, which accounted for 95% of all Culicoides caught, representing 10 species. The horse, the largest bait, was the most attractive host, even when abundance data were corrected by weight, body surface or Kleiber's scaling factor. Culicoides obsoletus was the only dominant species attracted by birds. Both C. scoticus and C. dewulfi were collected mainly from the upper body of the horse. Finally, the quantification of host preferences allows for discussion of implications for the transmission of Culicoides‐borne pathogens such as bluetongue virus.     

Effect of polyamine synthesis inhibitors separately and in combination with epidermal growth factor on fusion of lysosomes with phagosomes and F-actin level in mouse peritoneal macrophages

Effects of polyamine (PA) synthesis inhibitors--alpha-difluoromethylornithinchloride (DFMO) and alpha-methylornithinchloride (MO)--separately or in combination with the epidermal growth factor (EGF)--on lysosome-phagosome fusion (P-LF) and F-actin content in murine peritoneal macrophages were studied using fluorescent dye Acridine orange for lysosome labelling, FITC-phalloidin for F-actin, and yeast cells as a target. DFMO and MO significantly inhibited P-LF and decreased F-actin content in murine peritoneal macrophages. A combination of DFMO and MO with EGF failed to inhibit P-LF or to decrease F-actin content in these cells. The results obtained with DFMO and MO suggested new cellular targets of their effects. These results may be extended to cancer research to provide a rationale for clinical trials using combinations of EGF with DFMO or MO.     

The roles of redox processes in pea nodule development and senescence

Nodule senescence is triggered by developmental and environmental cues. It is orchestrated through complex but poorly characterized genetic controls that involve changes in the endogenous levels of reactive oxygen species (ROS) and antioxidants. To elucidate the importance of such redox control mechanisms in pea root nodule senescence, redox metabolites were analysed throughout nodule development in a commercial pea variety ( Pisum sativum cv. Phoenix) inoculated with a commercial rhizobial strain ( Rhizobium leguminosarum bv. viciae ). Although a strong positive correlation between nitrogenase activity and nodule ascorbate and glutathione contents was observed, the progressive loss of these metabolites during nodule senescence was not accompanied by an increase in nodule superoxide or hydrogen peroxide. These oxidants were only detected in nodule meristem and cortex tissues, and the abundance of superoxide or hydrogen peroxide strongly declined with age. No evidence could be found of programmed cell death in nodule senescence and the protein carbonyl groups were more or less constant throughout nodule development. Pea nodules appear to have little capacity to synthesize ascorbate de novo . l -galactono-1, 4-lactone dehydrogenase (GalLDH), which catalyses the last step of ascorbate synthesis could not be detected in nodules. Moreover, when infiltrated with the substrates l -galactono-1, 4-lactone or l -gulonolactone, ascorbate did not accumulate. These data suggest that ROS, ascorbate and glutathione, which fulfil well recognized, signalling functions in plants, decline in a regulated manner during nodule development. This does not necessarily cause oxidative stress but rather indicates a development-related shift in redox-linked metabolite cross-talk that underpins the development and aging processes.     

Localization of acid organelles in frog skeletal muscle fibers

By means of fluorescent and phase-contrast microscopy the distribution of acid membrane organelles in normal and vacuolated frog skeletal muscle fibers has been studied. The vacuolation of the T-system was produced by loading and subsequent removal of glycerol (80-110 mM), or it appeared as a result of Zenker's necrosis. Acridine orange (AO) was used as a marker for acid intracellular compartments. AO accumulated in granules localized near the nuclear poles (more seldom around the nucleus)' and in the intermyofibrillar spaces. Typically the AO granules make up short longitudinal chains or regular pairs, where the distances between neighboring granules are short-dated to sarcomere lengths. Almost all granules emit in red, but about one third of them simultaneously emit in green, which is characteristic of AO monomers. In the vicinity of necrotic boundary or under the influence of brefeldin A, a green component of fluorescence appears in most granules. Treatment with monensin leads to granule disappearance. Vacuoles accompanying the glycerol treatment or developing of necrosis do not accumulate AO and exert no effect on the localization of AO-granules. The nature of cellular organelles accumulating AO in skeletal muscle fibers is discussed.     

Peptide synthesis in organic media with the use of subtilisin 72 immobilized on a poly(vinyl alcohol) cryogel

Subtilisin 72 serine protease (EC 3.4.21.14) immobilized on a poly(vinyl alcohol) cryogel was used as a catalyst in the syntheses of N-protected peptide p-nitroanilides of the general formulas Z(or Boc)-Xaa-Phe-pNA (Xaa = Leu or Ala), Z-Ala-Xaa-Yaa-pNA (Xaa = Leu or Ala; Yaa = Leu or Phe), and Z-Ala-Ala-Xaa-Yaa-pNA (Xaa = Leu, Arg, or Gly; Yaa = Phe, Leu, Gly, Asp, or Glu). The syntheses were carried out in DMF-acetonitrile mixtures. A number of protected di-, tri-, and tetrapeptides were prepared in yields up to 99%. The syntheses were found to retain stereoselectivity under the conditions studied. The activation of carboxyl group of the acylating component was shown to have a positive effect upon the coupling rate. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2005, vol. 31, no. 6; see also http://www.maik.ru.     

Lysosomal glycosidase activity in cultured human fibroblasts

A study was made of the activity of 3 lysosomal glycosidases -beta-D-galactosidase (K. P. 3.2.1.23), alpha-L-fucosidase (K. P. 3.2.1.51), N-acetyl-beta-D-hexosoaminidase (K. P. 3.2.1.52) depending on the time after subcultivation and duration of the passage of human skin embryonal and postembryonal fibroblasts. It was established that changes in the specific activity of the enzymes should be calculated with reference to the cell rather than to protein whose amount might vary considerably. It was also found that for measuring the specific activity of enzymes, of great importance are the procedures of cell removal from the base layer (by mechanical scraping off or by trypsin solution) and the regimen of the homogenization of cell preparations.