Effect of Deficiency of Dietary Nitrogen on Cellulose Digestibility and Nitrogen-Fixing Flora Activity in Sibling Vole Microtus rossiaemeridionalis

The effect of feed composition on nitrogen-fixing activity of the symbionts living in the digestive tract of sibling vole Microtus rossiaemeridionalis was experimentally studied. In the control, the rodents were allowed to select any of three feeds: protein-rich, protein-free with low cellulose content, and protein-free with high cellulose content. The voles consumed the food in a proportion corresponding to 16% of protein and about 6% of cellulose. Exclusion of the protein-rich food considerably increased cellulose consumption (up to 12%) and digestibility (from 35 to 64%). The changes in the consumed feed composition were reflected in localization of nitrogenase activity in the digestive tract: the control level of nitrogen-fixing activity in the cecum was three times that in the proventriculus, while an inverse proportion was observed in the experimental groups. In all cases, the colon was the major locus of nitrogen fixation.     

Allozyme Variability among Populations of Three Species of Brush-Furred Mice (Lophuromys,Rodentia, Muridae) from the Bale Mountains National Park (Ethiopia)

Allozyme variability was examined in populations of three endemic species of the species complex Lophuromys flavopunctatussensu lato: L. chrysopus, L. brevicaudus, and L. melanonyx. These species replace each other in adjacent altitudinal belts of the Bale Massif in Ethiopia. A deficit of heterozygotes at several loci was found in most samples of all species studied. Moreover, the samples included animals homozygous for two or three minor alleles and heterozygous for alleles that are rare and unique for the given species. It is suggested that the Bale Massif are inhabited by numerous genetically isolated populations of eachLophuromys species, which exchange genes at an extremely low rate. Genotypic disequilibrium observed in most samples is explained by the fact that most sampling localities comprise ranges of two and more micropopulations. In our view, microgeographic subdivision of the populations is caused by recurrent fragmentation of habitats during the Pleistocene glaciation of the Bale Massif and subsequent prolonged isolation of local populations. Gene drift accompanying these processes resulted in high genetic differentiation of the local populations, which probably persisted until the present. Geographical isolation of the Bale Massif, its uniquely diverse ecological conditions, and extraordinary allozyme structure of the Lophuromys populations suggest that these populations represent remnants or direct descendants of relic local populations.     

Concentration and size distribution of plant fiber in the digestive tract of muroid rodents

The weight parameters that characterize the size and the degree of fullness of fermentation chambers (forestomach and cecum), namely, the weight of the walls and the content of these organs, and the concentration and size distribution of fibers in the chyme have been investigated in five muroid rodent species (Arvicola terrestris, Microtus oeconomus, Microtus arvalis sp., Clethrionomys glareolus, and Sylvaemus flavicollis). No distinct regularities were observed in the above-mentioned parameters of the forestomach. These parameters of the cecum were generally found to be in good agreement with the conventional concept of dietary specialization of the rodent species under investigation, but the results have provided a more precise assessment of the role of dietary fiber in the diet of free-living rodents under specific environmental conditions.     

Control of Aerobic Training with Individualized Physical Loads

A method was used for organizing training for aerobic working capacity. Its salient feature was individualization of the main components of the training process: dosing of the physical load at a level of 90–95% of the anaerobic threshold and optimizing the duration of rest on the basis of revealing the phase of superrecovery of the aerobic working capacity. The study, which enrolled 64 healthy males and females aged 16–20 years, provided evidence for the high effectiveness of the method. After 12 weeks of training, the anaerobic threshold, the systolic work index, and the results of Cooper’s 12-min test increased, respectively, by 9.7, 24, and 16% in the males and by 9.2, 32, and 25% in the females. The method of organizing the training process is proposed not only for the development of aerobic working capacity in healthy individuals but also for primary and secondary prophylaxis of cardiovascular diseases such as arterial hypertension and atherosclerosis.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 131–133.Original Russian Text Copyright © 2005 by El’chaninova, Varshavskii, Ladanov, Kalachev, Filippova.     

Study of the intermolecular association of poly(G).poly(c) and poly(dG).poly(dC) in solutions by methods of 1H to 3H exchange and electron microscopy

The kinetic of 1H leads to 3H exchange between water and C(8)H-groups of the guanylic residues in poly(G) . poly(C) and poly(dG) . poly(dC) was investigated within the temperature range from 30 to 90 degrees in 0.5 M NaCl (pH 7.2). It was shown that the exchange in freshly dissolved preparations at temperatures lower than 50 degrees proceeds faster than that in the case of GMP. According to the ylide mechanism of the exchange reaction the observed acceleration of the exchange is considered as a consequence of associates formation in poly(G) . poly(c) and poly(dG) . poly(dC) solutions at temperatures lower than 50 degrees. Associates are stabilized by intermolecular hydrogen bonds in which N(7) atoms of guanylic residues take part. The increase of the temperature is accompanied by gradual disappearance of the exchange acceleration. The retardation of exchange, which is characteristic of most non-associated double-stranded polynucleotides and nucleic acids is observed at the temperatures above 60 degrees. The retardation points to thermal destruction of the associates at temperatures higher than 50 degrees. The associates which are characterized by ordered structure including several "side by side" arranged double-stranded molecules were observed by electron microscopy. The addition of EDTA to solutions as well as the increase of temperature leads to destruction of the associates whereas the addition of Mg2+ makes the associates more stable.     

Lipid Peroxidation and Antioxidant Enzyme Activity in Response to Interval Hypoxic Training

This study revealed the metabolic parameters of reactive oxygen species, including erythrocyte superoxide dismutase, catalase, and glutathione peroxidase activity, and oxidative stress markers, including total prooxidant activity and plasma concentration of thiobarbituric acid reactive substances, in response to 14-day interval hypoxic training (IHT). The study included healthy subjects and patients with essential hypertension, who had a decreased activity of the main antioxidant enzymes due to a marked oxidative stress, as revealed by previous studies. In all subjects, the oxidative stress markers decreased and the enzyme activity increased in four days after the IHT course. However, the differences in metabolism of the reactive oxygen species between the patients and the healthy subjects persisted. It is suggested that, even with a different antioxidant enzyme system baseline, IHT may contribute to adaptive activity of this system.     

Functional Diversity of Morphologically Similar Digestive Organs in Muroidea Species

Biology Bulletin - We examine possible ways of functional adjustment of morphologically similar alimentary tracts in rodents with different dietary specializations. We study the structure of...