The electrophysiological characteristics and behavioral manifestations of hippocampal and thalamic spreading depression]

Behavioral manifestations of spreading depression (SD) were compared with SD electrophysiological characteristics in these structures. Carbon electrodes were suitable for recording DC slow potential changes in freely moving animal. It was shown that short (0.1 s) high-frequency (200 Hz) electrical stimulation of thalamus and hippocampus with intensity 50-300 microA easily triggered SD wave in these structures in narcotized and awake rats. The threshold of SD occurrence in dorsal hippocampus was the same or sometimes lower than that of the primary afterdischarge. Penetrating SD into ventral hippocampus provoked long latency seizure discharge and wet-dog shakings in awake rats. Intensity of locomotor activity accompanying bilateral hippocampal SD exceeded orienting response significantly. Contrary to hippocampus, thalamic SD was usually subseizure and unilateral phenomenon and had a clear tranquil effect on the rat locomotor activity. It was found that the rats didn't change the compartment preference after 20-45 SD waves in the thalamus or in the hippocampus.     

Study of the kinetics of thermoinactivation of lysyl-tRNA-synthetase from the liver of x-irradiated rats

A study was made of the kinetics of thermoinactivation of lysyl-tRNA-synthetase isolated from rat liver at early times of radiation damage development after the effect of a minimum absolutely lethal X-radiation dose (0.21 C/kg). The thermostability of a dimer form of the enzyme was shown to be higher than that of a monomer. It was established that substrates had a stabilizing effect on the enzyme during thermoinactivation. On the basis of the data obtained from the studies in the kinetic properties of the enzyme and the thermoinactivation a conclusion is made that lysyl-tRNA-synthetase is stabilized during subunit aggregation. The thermostability of the enzyme was decreased by irradiation.     

PCR-based cDNA library construction: general cDNA libraries at the level of a few cells.

A procedure for the construction of general cDNA libraries is described which is based on the amplification of total cDNA in vitro. The first cDNA strand is synthesized from total RNA using an oligo(dT)-containing primer. After oligo(dG) tailing the total cDNA is amplified by PCR using two primers complementary to oligo(dA) and oligo(dG) ends of the cDNA. For insertion of the cDNA into a vector a controlled trimming of the 3' ends of the cDNA by Klenow enzyme was used. Starting from 10 J558L micron3 myeloma cells, total cDNA was synthesized and amplified approximately 10(5) fold. A library containing 10(6) clones was established from 1/6 of the amplified cDNA. Screening of the library with probes for three genes expressed in these cells revealed a number of corresponding clones in each case. The longest obtained clones contained inserts of 1.5 kb length. No sequences originating from carriers or from rRNA was found in 14 randomly picked clones.     

Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans

Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and D. simulans for two common allozyme forms, as well as for several other less common variants. Parallel latitudinal clines in the frequencies of the common EST6-F and EST6-S allozymes in these species have previously been interpreted in terms of a shared amino acid polymorphism that distinguishes the two variants and is subject to selection. Here we compare the sequences of four D. simulans Est-6 isolates and show that overall estimates of nucleotide heterozygosity in both coding and 5' flanking regions are more than threefold higher than those obtained previously for this gene in D. melanogaster. Nevertheless, the ratio of replacement to exon silent-site polymorphism in D. simulans is less than the ratio of replacement to silent divergence between D. simulans and D. melanogaster, which could be the result of increased efficiency of selection against replacement polymorphisms in D. simulans or to divergent selection between the two species. We also find that the amino acid polymorphisms separating EST6- F and EST6-S in D. simulans are not the same as those that separate these allozymes in D. melanogaster, implying that the shared clines do not reflect shared molecular targets for selection. All comparisons within and between the two species reveal a remarkable paucity of variation in a stretch of nearly 400 bp immediately 5' of the gene, indicative of strong selective constraint to retain essential aspects of Est-6 promoter function.      

Responses of neurons of the frog nucleus isthmi to optic nerve stimulation

Responses of single units in the region of the nucleus isthmi were investigated in frogs immobilized with diplacin by means of extracellular capillary liquid microelectrodes. The neurons of this region were not spontaneously active and, after electrical stimulation of the contralateral optic nerve with a single pulse, they gave a single spike discharge with a minimal latent period of 20–110 msec. On increasing the strength of stimulation from threshold to maximal these latent periods were significantly reduced, indicating marked development of summation processes in the corresponding neuronal pathway. Only 14% of the neurons (7 of 57) discharged in response to stimuli exciting myelinated but not exciting unmyelinated optic fibers. All neurons were characterized by instability of the latent period of the evoked discharge; consequently, they were not excited antidromically. The possible functional role of the nucleus isthmi region in the Anura is discussed.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 33–40, January–February, 1977.     

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.     

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.     

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.