Neuronal Gap Junctions in Cortical Columns and Nuclei of the Ventral Thalamus of Rats

Functional cortical columns and nuclei of the ventral thalamus play a key role in processing of sensory information; therefore, detailed studies on formation of neuron-to-neuron gap junctions in these areas are of great theoretical and practical importance. In the present study, we applied electron-microscopy methods to examine the structure and specific distribution of interneuronal gap junctions in the cortical layer IV and thalamic nuclei, including VPM, RTN, Pom, and VPL. In the cortex, we found more interneuronal gap junctions than in thalamic nuclei. In all structures studied we revealed and described axo-dendritic, dendrodendritic, and “mixed” synapses. We report on the axo-dendritic gap junctions for the first time. It is suggested that this type of contacts plays some functional role in local synchronization of neuronal activity within one ensemble on the presynaptic level.     

Experimental study of the morphogenesis of nutmeg fibrosis of the liver]

Partial structure of the inferior vena cava over the diaphragm carried out experimentally in dogs let to blood stasis in the liver. Biopsy material obtained at different experimental periods demonstrated that fibrosis began to develop from the central and collective veins as a result of proliferation of the fibroblasts of the vein adventitita and "emigration" of the fucsinophilic fibers into the adjacent parenchyma. In parallel there occurred a neoformation of the connective tissue in the areas of hemorrhages and necroses associated with proliferation of the Kupffer's cells. Nutmeg fibrosis proved to have a cellular genesis and as associated with increased tropocollagen activity of fibroblasts.     

Interhemispheric asymmetry of positive emotional reactions in rats

Interhemispheric asymmetry of positive emotional reactions was studied in rats: satisfaction of drinking need and self-stimulation. Successive inactivation of the hemispheres was carried out by potassium spreading depression. Switching off of the right as well as the left hemispheres symmetrically influenced the whole quantity of the water, drunk by the rats to a full thirst satisfaction, i. e. the magnitude of need. However, at different stages of drinking need satisfaction an interhemispheric asymmetry was observed: under a strong drinking motivation the right hemisphere dominated, under a weak motivation--the left one. Switching off of the right hemisphere lowered the frequency of self-stimulation of the lateral hypothalamus and switching off the left one heightened it, testifying to the dominance of the right hemisphere in the reaction of self-stimulation. This reaction was also characterized by asymmetry of the lateral hypothalamus nuclei; reactivity to hemispheres inactivation (decreasing or increasing of self-stimulation frequency) of the right nucleus was more expressed than that of the left one.     

Purification and some catalytic properties of phosphoglucomutase from maize leaves

Phosphoglucomutase (EC 2.7.5.1, PGM) was purified to homogeneity from maize (Zea mays L.) leaves. The enzyme had specific activity 11. 7 U/mg protein and molecular mass (determined by gel-chromatography) of 133 +/- 4 kD. The molecular mass of PGM subunits determined by SDS-electrophoresis was 66 +/- 3 kD. The enzyme had Km for glucose-1-phosphate and glucose-1,6-diphosphate of 20.0 +/- 0.9 and 16.0 +/- 0.8 &mgr;M, respectively. Concentrations of glucose-1-phosphate and glucose-1,6-diphosphate above 3 and 0.4 mM, respectively, cause substrate inhibition. The enzyme activity was maximal at pH 8.0 and temperature 35 degreesC. Magnesium ions activate the enzyme and manganese ions inhibit it. 3-Phosphoglycerate is an uncompetitive inhibitor of the enzyme (Ki = 1.22 +/- 0.05 mM). Fructose-6-phosphate, 6-phosphogluconate, and ADP activate PGM, whereas ATP, UTP, and AMP inhibit the enzyme. Citrate was also a potent inhibitor, inhibitory effects of isocitrate and cis-aconitate being less pronounced.     

Comparison of Worm Control Strategies in Grazing Sheep in Denmark

Control of nematode parasites with reduced reliance on the use of anthelmintics was studied in 16 ewes with suckling twin lambs on contaminated pasture in Denmark. Ewes and lambs were treated with albendazole at turn-out 3 May. Ewes were removed from the groups on 26 July, and lambs were slaughtered on 11 October. The animals were allocated to 4 groups of 8 lambs and their 4 ewes. Group TS was treated with albendazole at weeks 3, 6 and 8 after turnout and set-stocked; group TM was similarly treated but moved to clean pasture in conjunction with the last drenching; group US was untreated and set-stocked, and group UM was left untreated but moved to clean pasture week 8 after turn-out. Supplementary feed was offered in June and August due to scarcity of pasture. Strategic treatments of ewes and lambs weeks 3, 6 and 8 after turn-out, with or without a move to clean pasture, were highly effective in controlling nematode infections for most of the season. This was reflected in better weight gains and carcass characteristics in the treated compared to untreated lambs, resulting in an average increase in the value of the product by 36%. The effect of moving without treatment (UM) on faecal egg counts was limited but peak pasture infectivity was reduced to less than 10% compared to the set-stocked group and weight gains of lambs were significantly better despite poor feed availability in late season. The study showed that under set-stocked conditions repeated anthelmintic treatments of both ewes and lambs in early season may ensure sufficient nematode control whereas moving animals to clean pasture without dosing was less efficient. The latter may, however, still be a viable option in organic and other production systems where routine use of anthelmintics is banned, particularly if weaning and moving are combined or a second move is performed.     

Phytohemagglutinin--a modulator of activity of cytochrome P-450-dependent enzymes of hepatocyte and immunocyte membranes

The phytohemagglutinin effect in vivo on monooxygenase activity depends on the type of the cells under study (thymocytes, splenocytes, macrophages, hepatocytes) and on the period after lectin injection. Variations of monooxygenase activities associated with different forms of cytochrome P-450 are established to have a number of peculiarities in isolated hepatocytes as compared to those in the liver microsome fraction. These differences are supposed to be due to the effect of nonmicrosomal cytochrome P-450. The results obtained are discussed with regard for phytohemagglutinin effect on systems regulating activity of cytochrome P-450-dependent monooxygenases.     

Evaluation of the apron as a taxonomic trait in ixodid ticks of the genus Dermacentor Koch (Ixodoidea, Ixodidae)

Study of the apron in 9 species of the genus Dermacentor from the fauna of the USSR has revealed differencies in its structure. The subgenus Dermacentor (s. str.) differs from two other subgenera both in the shape of the apron itself and in the shape of the postgenital sclerite and setae of perigenital area. Close species within each of two other subgenera differ in apron proportion, shape and size of denticles along its hind edge, and sometimes in their number. Inspite of the statistically reliable interspecific differences in apron structure a wide range of individual variability of some details and geographical specificity of samples from various places of the area were observed in species with a vast area.