Self-sustained rhythmic spike and wave activity and response of glial and nerve cells in the cat sensorimotor cortex

During acute experiments on unanesthetized cats, immobilized with myorelaxants, it was found that during rhythmic stimulation (8–14 Hz, duration: 10 sec) of the ventroposterolateral thalamic nucleus brief hyperpolarization is succeeded by depolarization in the pyramidal neurons of the sensorimotor cortex. Following this depolarization, rhythmic (approximately 3 Hz) paroxysmal depolarizing shifts in membrane potential are produced by ending stimulation, succeeded by protracted hyperpolarization and termination of rhythmic wave activity. Depolarization only is observed in glial cells, however, while hyperpolarization sets in after hyperpolarization is completed in the neurons. It is suggested that long-term changes in the membrane potential of cortical cells could make some contribution to the setting up and termination of rhythmic spike and wave activity.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 319–325, May–June, 1986.     

Dynamics of the growth and maturation of oocytes and follicles in the ovaries of the cow

Chromosome despiralization and nucleolus vacuolization have been studied during the oocyte intensive growth. Oocyte and nucleolus growth has been found to stop at the secondary antral follicles with the diameter more than 1000 mkm. Chromosomal and nucleolar activity decreases at this stage. Chromosomes condense and concentrate around the nucleolus and chromatine mass (karyosphere) forms.     

Correlation between the amplitude of action potentials and the rate of conduction along axons of the output cells of the sensomotor cortex

Antidromic responses of neighbouring neurones in micro-areas of the sensorimotor cortex to the stimulation of fibers of the pyramidal tract as well as of the red nucleus and thalamic nuclei VPL and MGB, were studied in acute experiments on unanesthetized immobilized cats. Depending on the velocity of conduction along the axon, the neurones of all the categories were divided into fast and slow cells. When examining the two neuronal groups most differing in AP amplitude (N1 and N3), it was found that N1 neurones were mainly fast-conducting and N3 neurones-- slow-conducting. The conclusion is made that at multineuronal recording, each of the examined categories of the output neurones is characterized by positive correlation between AP amplitude and the axon conduction velocity and consequently, the size of the cell.     

Investigation on the Assimilation of Nitrogen by Maize Roots and the Transport of Some Major Nitrogen Compounds by Xylem Sap

The uptake and assimilation of nitrate and ammonia have been studied in Zea mays. Nitrogen-starved maize roots are capable of accumulating a potential capacity for nitrogen uptake and assimilation. Reestablishment of nitrogen supply leads to intense uptake, reaching 154 % of the reference variant level after 24 hours when nitrate is supplied, and 121 % when ammonia is supplied. After 24 hours the insoluble nitrogen fraction accounts for 80, 54 and 55 % of the total taken up in the PK + NO₃^-, PK + NH₄⁺ and NPK variants respectively.     

Isolation of Actinomycetales from the soil of Kazakhstan on selective media with antibiotics

About 3000 actinomycetes were isolated from various soil samples collected in 11 regions of Kazakhstan. 62.7 per cent of them proved to be antagonists. For isolation of the strains, selective media supplemented with antibiotics were used. Kanamycin promoted growth of Actinomadura and Nocardia. Rubomycin promoted growth of Actinomadura. Tavromycetin and roseofungin were used as selective agents for the first time. Tavromycetin favoured isolation of Actinomadura and Nocardia. Roseofungin favoured isolation of Actinomadura. Light chestnut and serozemic soils were the most rich in antagonists (67.1 and 61.3 per cent, respectively) while saline and chestnut soils were the poorest in antagonists (32.2 and 30.6 per cent, respectively). Actinomadura were more frequent in light-chestnut light-loamy and serozemic soils. Half of the antibiotics isolated in the form of concentrates were identified with the known antibiotics or classified as belonging to various groups. A culture producing a novel antibiotic was isolated.     

Pharmacokinetics of kanamycin during targeted delivery to the liver in erythrocyte ghosts in animals with experimental acute cholecystitis

Pharmacokinetics of kanamycin was studied after its targeted delivery to the liver in autological erythrocyte ghosts on 25 noninbred dogs with experimental acute cholecystitis in comparison to the routine intravenous administration of the antibiotic in solution. Kanamycin concentrations in the tissues of the liver, pancreas, spleen, kidneys and lungs as well as in bile and blood serum were determined by the agar diffusion method 24, 48 and 72 hours after the last administration. It was found that the targeted delivery of kanamycin in blood shadows made it possible to provide high concentrations of the antibiotic for prolonged periods in the liver and biliary ducts and to more efficiently arrest the clinical manifestations of acute cholecystitis as well as normalize the laboratory indices. The data showed that using blood shadows as a reliable system for targeted delivery of antibiotics to the liver was advisable in purulent inflammatory affections of the biliary ducts.