Comparative effects of amygdala and central gray matter of the midbrain on lateral hypothalamic unit activity

The effect of stimulation of the stria terminalis, the main afferent component of the amygdalo-hypothalmic system, and of the central gray matter and tegmentum of the midbrain on lateral hypothalamic unit activity was investigated in acute experiments on rats. Five types of unit responses were discovered: phasic excitation and inhibition, tonic activation and inhibition, and a biphasic response. In response to stimulation of the stria terminalis and lateral hypothalamus mainly inhibitory responses (62.7%) were recorded. As a result of stimulation of the central gray matter most lateral hypothalamic neurons (87%) were activated. Convergence of influences from the amygdala and tegmentum was observed on 14.4% of responding neurons. The structures had an antagonistic action on most (84.6%) of the lateral hypothalamic neurons tested.Institute of Physiology, Siberian Branch, Academy of Medical Sciences of the USSR, Novosibirsk. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 25–32, January–February, 1977.     

Functional properties of locust locomotor muscles

The ultrastructure of the muscle fibers and the electrical constants and responses of the membrane to microapplication of L-glutamate and acetylcholine were investigated in the longitudinal flight muscle and the flexor tibiae ofLocusta migratoria migratorioides. The twitch flight muscle differs from the slower leg muscle in the smaller size of its sarcomeres and the lower values of the space attenuation factor of the electrotonic potential, time constant, and resistance of the membrane. Microapplication of sodium L-glutamate at strictly definite points of the fibers of both muscles evoked depolarization responses of the membrane. In experiments on normal and denervated muscle, during microapplication of acetylcholine, changes in the level of the membrane potential were never observed. It is concluded that L-glutamic acid is the excitatory mediator of the twitch and slow muscle systems of insects.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 532–538, September–October, 1977.     

Morphological changes in axodendritic synapses of the leech during blocking of conduction in medium with reduced ionic concentration

Reactive changes were found by supravital staining with methylene blue in the synaptic system of the neuropil ofHirudo officinalis. They consist of marked bead-like deformation of the presynaptic portions, enlargement of the terminal structures, initial decolarization of the isthmuses between the boutons, and the clearer demonstration of the neurofibrils in the expanded postsynaptic dendrites. In a specially treated preparation of clearly identifiable axodendritic synapses of the leech it was shown that these changes reach a considerable magnitude when electrical activity in the ventral chain is blocked. This fact suggests that, together with other factors, they participate in the development of the conduction block.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 613–618, November–December, 1977.     

Quantitative histochemical study of monoamine oxidase in the rabbit hippocampus

The distribution of monoamine oxidase activity in the rabbit hippocampus was studied by quantitative histochemical analysis. The presence of monoamine oxidase activity was found in str. lacunosum-moleculare of areas CA₁ and CA₂ of the hippocampus and in str. moleculare of the dentate fascia. A strong positive reaction was found in layers containing many myelinated fibers (the alveus and Shaffer's collaterals). However, when the reaction was carried out without substrate, considerable deposition of diformazan was observed in these layers. These observations and the ability of myelin to reduce nitro-BT spontaneously, described in the literature, suggest that the positive Glenner's reaction in the alveus and Shaffer's collaterals is not specific. The deposition of diformazan in the layer of pyramidal and granular neurons likewise is nonspecific, as is confirmed by the results of experiments with preincubation in iproniazid and with incubation without substrate.Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 9, No. 2, pp. 135–141, March–April, 1977.     

EPSPs of masseter motoneurons evoked by stimulation of low-threshold infraorbital nerve afferents in cat

Stimulation of the infraorbital nerve at strengths 1.4–2.5 times higer than the threshold of excitation of A fibers in cats anesthetized with chloralose and pentobarbital evoked EPSPs with an amplitude up to 3.0 mV and a duration of 9–15 msec in 69% of masseter motoneurons after 1.5–3.0 msec. These EPSPs were complex and formed by summation of simpler short-latency and long-latency EPSPs. The short-latency EPSPs appeared in response to infraorbital nerve stimulation at 1.1–1.5 thresholds and had a slow rate of rise (2.5–4.5 msec, mean 3.7±0.4 msec), low amplitude (under 2.0 mV), and short duration (5–6 msec). Their latent period varied from 1.5 to 3.0 msec (mean 2.1±0.2 msec). The shortness of the latent period and its constancy during stimulation of the nerve at increasing strength, and also the character of development of facilitation and inhibition of the EPSP during high-frequency stimulation suggests that these EPSPs are monosynaptic. The slow rate of rise suggested that these EPSPs arise on distal dendrites of the motoneurons. Long-latency EPSPs appeared 7–9 msec after stimulation of the infraorbital nerve at 1.1–1.5 thresholds. Their amplitude reached 1.5–2.0 mV and their duration 7–9 msec. The long duration of the latent period combined with low ability to reproduce high-frequency stimulation (up to 30/sec) points to the polysynaptic origin of these EPSPs.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 583–591, November–December, 1977.     

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.     

UV-sensitivity and repair of UV-damages in Salmonella of wild type.

Summary The UV-sensitivity of wild type Salmonella strains has been compared to that of wild type E. coli and its UV-sensitive mutants. Many wild type Salmonella strains are 4–5 times more sensitive than wild type E. coli and their inactivation curve is similar to that for E. coli with a mutation in the polA gene. Alkaline sucrose gradient centrifugation has shown a deficiency of these strains in normal excision repair of UV-damaged DNA. This deficiency is not a Salmonella genus feature because one strain as resistant as wild type E. coli was found. This resistant strain showed normal excision repair in alkaline sucrose gradient centrifugation experiments. The possible influence of plasmids and mutations in repair genes on the ability of Salmonella to repair UV-damaged DNA is discussed.     

The modulation of the induction of ornithine decarboxylase by spermine,spermidine and diamines

Extremely low concentrations of putrescine, spermidine and spermine added to the extracellular medium of cultures of mammalian cells inhibit the induction of ornithine decarboxylase activity despite 100- to 1,000-fold greater intracellular polyamine concentrations. The diamines, 1,2-diaminoethane, 1,3-diaminopropane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,10-diaminodecane, 1,12-diaminododecane also inhibit ornithine decarboxylase at all concentrations tested (greater than 10^?6 M). In contrast, 10^?6 M to 10 ^?3 M 1,8-diaminooctane, the alkyl analog of spermidine, enhances ornithine decarboxylase activity. The concentraton of putrescine required to inhibit the activity of ornithine decarboxylase by 50% is a characteristic of each cell line; however, it varies by as much as 1,000-fold among the five cell lines we have tested (L1210 leukemic, H35 hepatoma, N18 neuroblastoma, W256 carcinosarcoma and 3T3 fibroblasts). The antizyme to ornithine decarboxylase can be induced in all these cells by high (di)(poly)amine concentrations. Based on these and other experiments we suggest a working hypothesis: that the polyamines regulate ornithine decarboxylase activity through two different sites that may be interrelated; a sensitive membrane-mediated site that responds to minute fluctuations of extracellular polyamine levels and a coarse site which may be intracellular or membrane associated that responds to larger fluctuations of intracellular polyamine levels. The consequences of such a control mechanism operating within the whole organism are discussed.     

Recessive nonsense-suppression in yeast: Involvement of 60S ribosomal subunit

Summary The ribosomal protein patterns of recessive suppressor strain and parent strain of Saccharomyces cerevisiae were analyzed by two-dimensional polyacrylamide gel electrophoresis. About 30 protein spots were found for ribosomal proteins of small subunit for both mutant and parent strain. These patterns do not differ from each other neither in intensity of staining, nor in mobility of spots. 41 protein spots were found in electrophoregrams of 60S ribosomal proteins both from parent strain and recessive suppressor strain. The electrophoretic picture of the 60S proteins from the parent and mutant strains is similar except the intensity of staining of the L30 spot. This protein is present in 60S subunit of suppressor strain and completely absent or only weakly stained on electrophoregrams of ribosomal proteins of parent strain. The possible relationships between the content of L30 protein and the mechanism of recessive suppression in yeast are discussed.