Morphofunctional changes in the small intestine epithelium of the frog <Emphasis Type="Italic">Rana temporaria</Emphasis> in the course of hibernation

The structure and function of small intestine epithelium have been studied in overwintering frogs at various stages of hibernation. Experiments on the in vitro absorption of arginine vasotocin (AVT) have shown that the epithelium ability for absorption of this nonapeptide without hydrolysis persists during hibernation. However, there is a decline in AVT absorption observed in January–February and later on (as compared with that in October–December) which is most pronounced in March–April. Changes in the epithelial structure appear by midwinter and are growing towards spring. In April–May, enterocyte height decreased by 33%, microvilli length by 40%, and number of mitochondria by 57% relative to the values at the beginning of hibernation. The absence of signs of breakdown attests to the adaptive nature of the observed changes. The dynamics of the studied parameters reveals morphological and functional plasticity of small intestinal epithelium in Rana temporaria over the hibernation period.     

Probing the role of copper in the biosynthesis of the molybdenum cofactor in <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis>

The crystal structure of Cnx1G, an enzyme involved in the biosynthesis of the molybdenum cofactor (Moco) in Arabidopsis thaliana, revealed the remarkable feature of a copper ion bound to the dithiolene unit of a molybdopterin intermediate (Kuper et al. Nature 430:803-806, 2004). To characterize further the role of copper in Moco biosynthesis, we examined the in vivo and/or in vitro activity of two Moco-dependent enzymes, dimethyl sulfoxide reductase (DMSOR) and nitrate reductase (NR), from cells grown under a variety of copper conditions. We found the activities of DMSOR and NR were not affected when copper was depleted from the media of either Escherichia coli or Rhodobacter sphaeroides. These data suggest that while copper may be utilized during Moco biosynthesis when it is available, copper does not appear to be strictly required for Moco biosynthesis in these two organisms.     

Changes in the diet of the coastal cod <Emphasis Type="Italic">Gadus morhua marisalbi</Emphasis> in the Kandalaksha Gulf of the White Sea under conditions of increased abundance of three-spined stickleback <Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>

The data on feeding of coastal cod Gadus morhua marisalbi in the area of the Chupa Bay (Kandalaksha Gulf of the White Sea) are presented. In the food spectrum of cod, over 25 cm long fish and their eggs dominated (77.5% by frequency of occurrence and 91.7% by weight). Other groups of food organisms occupied a secondary place. Among fish, three-spined stickleback Gasterosteus aculeatus was the most prominent food item in the diet of cod (48.3% by weight). The published data on long-term changes of the diet of cod are considered, which are mostly related to considerable fluctuations of the abundance of three-spined stickleback in the White Sea. It is shown that, at present, three-spined stickleback again plays an important role in the diet of the White Sea cod     

Estimation of the biological age in females of the Taiga tick <Emphasis Type="Italic">Ixodes persulcatus</Emphasis> by changes in the body shape and the surface of the integument

A method of visual estimation of the biological age of living hungry tick females by visible changes in the depth of the marginal groove and the structure of the alloscutum cuticle during natural ageing is developed. In recently activated individuals, the body is convex and the marginal groove is exposed, demonstrating distinctly visible cuticular microfolds. In attenuated ticks, the body is flattened and the marginal fold overlays the marginal groove, concealing cuticular microfolds.     

Developmental changes in the effects of prostaglandin E<Subscript>2</Subscript> in the chicken ductus arteriosus

Prostaglandin E₂ (PGE₂) is the major vasodilator prostanoid of the mammalian ductus arteriosus (DA). In the present study we analyzed the response of isolated DA rings from 15-, 19- and 21-day-old chicken embryos to PGE₂ and other vascular smooth muscle relaxing agents acting through the cyclic AMP signaling pathway. PGE₂ exhibited a relaxant response in the 15-day DA, but not in the 19- and 21-day DA. Moreover, high concentrations of PGE₂ (≥3 μM in 15-day and ≥1 μM in 19-day and 21-day DA) induced contraction of the chicken DA. The presence of the TP receptor antagonist SQ29,548, unmasked a relaxant effect of PGE₂ in the 19- and 21-day DA and increased the relaxation induced by PGE₂ in the 15-day DA. The presence of the EP receptor antagonist AH6809 abolished PGE₂-mediated relaxation. The relaxant responses induced by PGE₂ and the β-adrenoceptor agonist isoproterenol, but not those elicited by the adenylate cyclase activator forskolin or the phosphodiesterase 3 inhibitor milrinone, decreased with maturation. High oxygen concentrations (95%) decreased the relaxation to PGE₂. The relaxing potency and efficacy of isoproterenol and milrinone were higher in the pulmonary than in the aortic side of the DA, whereas no regional differences were found in the response to PGE₂. We conclude that, in contrast to the mammalian situation, PGE₂ is a weak relaxant agent of the chicken DA and, with advancing incubation, it even stimulates TP vasoconstrictive receptors.     

Vegetation of the aquatic and marshland habitats in the Orava region,including the first records of <Emphasis Type="Italic">Potametum alpini,Potametum zizii</Emphasis> and <Emphasis Type="Italic">Ranunculo-Juncetum bulbosi</Emphasis> in the territory of Slovakia

The vegetation of the aquatic and marshland habitats of the Orava region (north of Slovakia) was studied in 2009, using traditional phytosociological methods. Sixteen aquatic and eighteen marsh plant communities were described within 96 phytosociological relevés by using TWINSPAN with the application of the dominance principle. Three associations, Potametum alpini, Potametum zizii and Ranunculo-Juncetum bulbosi, were found as new communities for Slovakia. Myriophylletum verticillati, Potametum nodosi, Potametum graminei and Alisma gramineum community were recorded in the northernmost localities in Slovakia. Among marsh communities, Calletum palustris is very rare, both in the Orava region and in Slovakia as a whole. According to Ellenberg’s indicator values (EIV), moisture was evaluated as the main ecological gradient. Plant communities are ordered along the first Detrended Correspodence Analysis (DCA) axis in a typical hydroseries (Potametea → Lemnetea → Phragmition communis → Phalaridion arundinaceae, Oenanthion aquaticae and Sparganio-Glycerion → Magnocaricion elatae). The second DCA axis was most correlated with EIV for nutrients. Among the five directly measured ecological characteristics (temperature, pH and conductivity of water, water depth, and substrate type), conductivity of water (0.44, P < 0.01) and substrate type (0.32, P < 0.05) were the statistically significant variables explaining the variability along the first DCA axis.     

Serotoninergic Mechanism in the Central Link of the Shadow Reflex in <Emphasis Type="Italic">Lymnaea stagnalis</Emphasis> L.

The study was performed on effects of serotonin and its antagonists (mianserin, propranolol, and metergoline) on efferent electrical activity in nerves cervicalis superior, cervicalis inferior, and columellaris innervating muscles withdrawing body of Lymnaea stagnalis into the shell. Serotonin had a dual effect on the off-reactions caused by rhythmical light stimulation of mollusc skin. The number of responses to series of stimuli increased at serotonin concentrations of about 10⁻⁸-10⁻⁷ M and decreased at its higher concentrations. In many cases, serotonin antagonists also had a dual effect depending on their concentration. All studied substances slightly affected duration and latent period of individual off-responses. Serotoninergic regulation is suggested to participate in central chains of the pond snail defensive shadow reflex.__________Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 2, 2005, pp. 134–138.Original Russian Text Copyright © 2005 by Samarova, Zhukov, Sudoplatov.     

Morphometric variations of the skull in the Gray Wolf (<Emphasis Type="Italic">Canis lupus</Emphasis>) in Iran

The Gray Wolf is a wide ranging carnivore in Iran, absent only in the central deserts and Dasht-e Lut. This study was carried out to verify whether, despite their high mobility, individual wolves belonging to different populations show morphological variations in the skull. We collected 48 skulls from various regions of Iran and measured 24 variables on the cranium. These primary variables were then used to generate six indices to examine any variations in the shape of the skulls collected in different regions of the country. Although the largest skulls collected for this study originated in the mountainous regions of the northwest, northeast, and west, principle component analysis (PCA) did not result in a meaningful difference in the size and shape of wolf skulls in different regions of Iran. Our results confirm that the minor morphological variations of the skull in wolves of Iran are not an evidence for the separation of wolf populations in different regions or the existence of various subspecies in the country. This uniformity can be explained by the strong gene flow among populations as well as high mobility of the wolf that facilitates movement of individuals between populations.