Responses of single units in the bat cochlear nuclei to simultaneously presented cones

Investigation of single unit responses in the cochlear nuclei of bats (Vespertilionidae) to pure-tone and frequency-modulated stimuli overlapping in time showed that most (85%) of them respond to combination tones f₂–f₁ and 2f₁–f₂ (f₁ is the filling frequency of the first and f₂ of the second cone) resulting from nonlinearity in the auditory system. As a rule responses appeared whenever the frequency of the combination tone was close to the characteristic frequency of the neuron, regardless of the filling frequency of the basic tones. It is postulated that nonlinearity in the auditory system may lie at the basis of analysis of complex frequency-modulated stimuli.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 10, No. 3, pp. 252–260, May–June, 1978.     

The structure of partly decondensed metaphase chromosomes

The technique of freeze-drying was applied to examine the submicroscopic organisation of metaphase chromosomes from Chinese hamster after removal of bivalent cations with EDTA and removal of histone HI with 0,6 M NaCl. Treated chromosomes increased in size, and nucleosomal filaments appeared at the periphery of the chromosomes. Removal of bivalent cations is accompanied with the appearance of regularly organized structures of the beads-on-a-string type. The regular organization of the fibers is damaged as soon as histone H1 is removed. After decondensation in a 0,6 M NaCl solution the metaphase chromosomes were treated with staphylococcal nuclease in situ on EM grids and the residual structures analysed using electron microscopy. Nucleohistone fibers were visible at the periphery of the chromosomes at the beginning of digestion. After complete elimination of the nucleohistone fibers in the course of digestion the remaining proteinaceous material was represented by aggregates of irregular shape and of varying size. These were either concentrated along the central axis of the chromatids or, at the final step of digestion, scattered evenly over the entire area that had been occupied by the chromosome. Presumably, in the chromosome prior to digestion, the material did not form an integral protein structure similar to a scaffold in dehistonised and spread chromosomes. An alternative interpretation for the fragmentation of protein material in the chromosome considers possible degradation of the protein scaffold in the course of digestion.     

Inhibition of mitochondrial ATP-synthetase by redox-agents]

Effects of phenol and phenothiazine on ATP synthesis and electron transport in submitochondrial particles were studied. Nitrophenols and phenothiazines inhibited ATP synthesis without notable effect on electron transport. On the contrary chlorphenols equally decreased the velocities of electron transport and ATP synthesis. The inhibitors studied showed the properties of electron acceptors in relation to the radicals, their acceptor properties corresponding to their ability to inhibit ATP synthesis.     

Epinephrine potentiates activation of human platelets by low density lipoproteins

Low density lipoproteins activate phosphoinositide turnover, increase free cytoplasmic calcium concentration and stimulate phosphorylation of 20- and 47-kDa proteins in blood platelets. All these effects are substantially potentiated by epinephrine.     

Streptomycin-3"-phosphotransferases from streptomycin-resistant cells of Escherichia coli strains

Streptomycin-3"-phosphotransferases were isolated and purified from E. coli cells containing plasmids 836, pBS52 or R6K, which determine the microorganisms resistance towards streptomycin and dihydrostreptomycin. Phosphorylation of the 3"-hydroxylic group of dihydrostreptomycin was demonstrated by [13C]-NMR spectrometry. It was shown that streptomycin-3"-phosphotransferase, whose synthesis is determined by plasmid 836 (as well as by plasmid R6K), differs from the analogous enzyme, whose synthesis is operated by plasmid pBS52 in some properties, e. g. dependence of the initial reaction rate on concentrations of antibiotics and ATP, pH-optimum, sensitivity to the buffer ionic strength, stability, etc. Besides, the antiserum against streptomycin-3'-phosphotransferase detected by plasmid pBS52 does not produce cross immunological reactions with the other enzyme.     

Ampicillin concentration in the blood when administered by jet injection and needle-syringe methods]

The studies were carried out on 50 persons. Ampicillin was administered with the help of a jet injector B1-2 and needle syringe in doses of 250 or 500 and 500 mg respectively. When the drug was administered by infusion, its maximum blood levels were achieved earlier than after needle-syringe administration of the drug and were higher (22.83+/-4.10 and 6.3+/-0.09 gamma/ml respectively). Even when ampicillin was administered with the help of the injector in a dose of 250 mg its blood levels were much higher than those after needle-syringe administration in a dose of 500 mg. After jet infusion the prolongation of the drug retention time in the blood at therapeutical levels was observed as compared to the needle-syringe administration.     

The effect of disconnecting the hippocampus from the septum on the activity of septal neurons]

Extracellular recording of neuronal activity was performed in the medial and lateral septal nuclei (MS and LS) in unanaesthetized rabbits after coagulation of septo-hippocampal connections. The MS neuronal activity had many pathological features. The LS activity was normal in every respect. Spontaneous activity, reactivity to sensory stimuli and main characteristics of responses to sensory stimuli were preserved in LS (and in a part of MS neurones). Sensory effects were augmented in intensity and duration, the number of neurones in LS with theta-bursts increased twofold, theta-bursts were more regular, than in control animals. These effects may be explained by an increase of ascending RF influences, which is supported by the fact of outstanding similarity between sensory and reticular effects in septal neurones after hippocampal disconnection. The number of units with inhibition of activity in response to sensory stimuli decreased, habituation of responses was absent. That means that hippocampal influences are necessary for the organization of inhibitory phenomena in the septum, and, above all, for processes of gradual habituation.     

Sensory characteristics of the cortical input of the hippocampus, the dentate fascia]

Investigation of sensory reactions of the neurones of the dentate fascia was performed in unanaesthetized rabbits. Spontaneous activity usually consisted of long aperiodic high-frequency bursts with silent periods between them. Multimodal convergence was observed in 76% of records. Responses to sensory stimuli constituted three nearly equal groups: 1 -- tonic inhibitory reactions; 2--phasic (equal to stimulus duration) activatory responses; 3--simple "specific" responses of on-type, sometimes with secondary phasic components. In one microelectrode track, perpendicular to the double lamina of granular cells, all neurones usually responded in the same fashion.