Features of corticofugal effects of the motor area of the cortex on processing of heterogeneous afferentation in the parafascicular complex of the thalamus in the cat

Evoked potentials to somatic and visual stimuli were recorded in the parafascicular complex (parafascicular nuclei--centrum medianum--Pf--CM) of the thalamus of cats anaesthetized by nembutal. Cooling of the motor cortex was also used. The influence of the motor cortex on processing of the visual and somatic afferent signals at the thalamic level was found to be direct but different by its character. The motor cortex exerted unidirectional facilitatory modulatory action of a tonic type on the processing of visual afferentation and general facilitatory influence against the background of which particular excitatory and inhibitory effects were seen which it exerted on the processing of somatic signals. Episodically the motor cortex completely controlled the afferent inputs activated by somatic impulses. The motor cortical area non-equally influenced afferentation of the same modality forming the different components of the evoked potentials in Pf--CM. On the base of our present and earlier obtained data an idea has been formed of existence of a general principle of differentiated influences of polysensory areas on heterogeneous afferentation on nonspecific and association thalamic nuclei, and of realization of these influences through separation of functionally isolated subsystems in descending pathways. Each of the subsystems by closing separate thalamo-cortical circuits might transmit signals of a single modality.     

Neurophysiologic analysis of the bilateral organization of the associative parietal regions of the neocortex in the cat

In cats under Nembutal anesthesia, impulses come to the parietal areas of both hemispheres, which, when evoked by unilateral stimulation of fore- and hind-paws, converge at the same cortical points forming early components of associative responses (ECAR). In responses to contralateral paws' stimulation, individual interhemispheric functional asymmetry is shown. The influence of the contralateral parietal area on the ipsilateral one is more strong than the reverse effect. In contrast to ECAR formation on the contralateral side as a result of the arrival of impulses of specific genesis along the "classical" lemniscal tract,--the signals of the same type participating in the initiation of ECAR in the ipsilateral hemisphere, on their way form a relay in the thalamus and the same zone of the opposite side via the interthalamic commissure and callosal body, correspondingly. It is suggested that along with the arrival of impulses through the mentioned crossed tracts, ECAR generation in the ipsilateral parietal cortex involves impulses, coming through the uncrossed channel of the extralemnisc tract.     

Polysensory properties of the horizontal region of the diagonal bundle from the cat forebrain

Sharply different wave forms and parameters of averaged evoked potentials (EP) in response to single visual and somatic stimuli were observed in the same points of the horizontal limb nucleus of the diagonal band (NDB) in cats under nembutal anesthesia. The existence of heterogenic EPs in NDB makes it possible to consider this part of the nucleus as a polysensory structure. Decreased EP latency, as compared to that in the neocortex, indicates that heterogenic impulses reach NDB by higher speed Ways than the cortex. The comparison of NDB EP refractory periods during paired stimulation of one or different sensory systems shows that polyvalent impulses affect independently functioning neuronal populations. It is suggested that a common principle of specific heterogenic signals arrival to distinct neuronal complexes exists for polysensory structures at different levels of the central nervous system.     

Effect of decreasing hydrodynamic resistance of a polymer on localization of sclerotic plaques. A model study]

Flow structure and wall shear stress and the changes in these parameters induced by the administration of a drag-reducing polymer polyethylene oxide WSR-301 at a concentration of 10(-5) g/ml were studied in a glass tube with a T-junction by the laser Doppler anemometry technique. The pattern of wall shear stresses is in a good agreement with the data, obtained for rabbits in [1]. For tubes with rigid walls, the location of plaques corresponds to regions of a high wall shear stress.     

Effect of glucocorticoids on the endocrine system of the pancreas of the pigeon and rat after a food load

The level of 35S-methionine incorporation (in 15, 30 min, 1, 2, 3, 6, 12, 24 h) has been investigated in A- and B-cells of the pigeon and rat pancreatic islets against the background of excessive injection of hydrocortisone. The pigeon and rat A- and B-endocrinocytes respond in a similar was to the excess of hydrocortisone. An accelerated elimination of the isotope from the pigeon A- and B-endocrinocytes is noted, while in the rat the effect of the excessive hydrocortisone is opposite.     

Relation between reaction time and the characteristics of a motor act

The connection of reaction time (RT) with spatial-temporal motor parameters was studied in humans. Duration of the motor act was set by experimenter. In response to the signal the tested person pressed one or two buttons according to instruction. The interval between these pressings corresponded to the time of performing the movement. It is shown, that RT significantly depends on the regime of work, duration of movement, and distance between buttons: with greater distances such dependence becomes significant. It is suggested that dependence of RT upon various motor act parameters is determined by differences in the levels of brain structures activation and in spatial-temporal organization of the movement.     

Comparative study of appearance of water-soluble antigens and brain esterase fractions in ontogenesis of two strains of rats

By means of immunoelectrophoresis of rat brain, 12 water-soluble antigens were detected, five of which were found to be specific to the brain. Histochemical reactions have identified two antigens that are not specific to the brain, lactate dehydrogenase and esterase. By means of enzymoelectrophoresis, 14 esterase fractions were determined. An immunoautoradiographic study of the synthesis of some antigens specific to the brain was carried out. It was found that rats responding to sound by epileptic seizures develop more slowly than normal rats. In particular, in rats resistant to auditory stimulus the antigenic spectrum typical of the brain of the adult rat (12 antigens) is formed by day 14 of postnatal life, while in rats of the sensitive strain this pattern takes 17 days to completely form. The last brain-specific antigen for rats susceptible to audiogenic epilepsy appears on day 17, while this antigen is present in normal rats on day 14. Fast-moving esterase fractions are detected earlier in ontogenesis in rats resistant to sound than in sensitive rats.     

Autoantibodies to the thrombocytes and erythrocytes in HIV-infected patients

In 48 patients with HIV infection were tested for the presence of autologous and allogenic antibodies to red blood cells with the use of Coombs' direct and indirect tests. 18 HIV-infected patients had IgG antibodies to thrombocytes, circulating in the blood (detected by the method of EIA) and bound to thrombocytes (detected by the method of RIA). In 5 out of 48 patients Coombs' direct test yielded positive results with red blood cells. 6 out of 18 examined patients had an elevated content of thrombocyte-bound antibodies. The presence of cross reactions between gp120 of human immunodeficiency virus and gp3a thrombocytes led to the formation of antithrombocyte antibodies and, consequently, to a decrease in the number of thrombocytes.     

Yeast biodiversity in hydromorphic soils with reference to grass-Sphagnum swamp in Western Siberia and the hammocky tundra region( Barrow, Alaska)]

The microbiological analysis of 78 samples taken from a boreal bog in Western Siberia and from a tundra wetland soil in Alaska showed the presence of 23 yeast species belonging to the genera Bullera, Candida, Cryptococcus, Debaryomyces, Hanseniaspora, Metschnikowia, Mrakia, Pichia, Rhodotorula, Saccharomyces, Sporobolomyces, Torulaspora, and Trichosporon. Peat samples from the boreal bog were dominated by eurytopic anamorphic basidiomycetous species, such as Rhodotorula mucilaginosa and Sporobolomyces roseus, and by the ascomycetous yeasts Candida spp. and Debaryomyces hansenii. These samples also contained two rare ascomycetous species (Candida paludigena and Schizoblastosporion starkeyi-henricii), which so far have been found only in taiga wetland soils. The wetland Alaskan soil was dominated by one yeast species (Cryptococcus gilvescens), which is a typical inhabitant of tundra soils. Therefore, geographic factors may serve for a more reliable prediction of yeast diversity in soils than the physicochemical or ecotopic parameters of these soils.