Effect of hyaluronidase on the quantum content and binomial p and n parameters of neuromuscular transmission in frogs

In the frog dermo-sternal muscle hyaluronidase (0.01--0.1%) caused e.p.p. amplitude and quantum content of transmission to fall when acting in a solution containing 1 mM Ca2+ and 4 mM Mg2+. The change in the quantum content was related to a decrease in binomial parameter n, the probability of mediator p release increased in the first moments of the enzyme action. With the prolongation of hyaluronidase action, negative values of p appeared. Hyaluronidase caused an increase in e.p.p. amplitude and in quantum content of transmission when acting in a solution containing 8 mM Ca2+ and d-tubocurarine. It was suggested that hyaluronidase modifies the normal calcium exchange between the bulk solution and the unstirred layer near nerve terminal membrane thus affecting the transmission.     

Compensation in behavioral disorders in rats receiving 5,7-DHT neonatally and by transplantation of embryonic raphe nucleus tissue

In 62 male Wistar rats the influence was studied of the transplanted embryonal tissue of raphe nuclei (NR) on the mechanisms of compensation of disturbances of exploratory activity, sensory attention, learning and emotional reactivity induced by neonatal injection of 5,7-DHT. In histochemical studies by Falk-Hillarp method the presence of yellow fluorescence confirmed the specificity of transplanted 5-HT neurones. It is found that NR transplantation causes in animals after 3 months recovery of orienting reaction to sensory stimuli, reduces rats reactivity in the open field, restores the ability to discrimination of emotionally positive influence, disturbed by neonatal injection of 5,7-DHT. The obtained data show the possibility of compensation of behaviour disturbances caused by chronic deprivation of 5-HT system activity by transplantation in the neocortex parenchyma of the embryonal tissue, containing serotoninergic neurones.     

Functional integration of the nervous tissue of the rat following xenotransplantation into the brain of a rabbit

Surviving grafts of the nervous tissue taken from the septum and hippocampus of rat embryos and xenotransplanted into the rabbit's brain were observed in 4 out of 6 animals 2-3 months after surgery. The grafts contacted the neocortex or hippocampus of the recipients. Extracellular recording of neuronal activity in the grafts revealed spontaneous discharges with normal patterns and without any signs of pathology. Electrical stimulation of the recipients' brain (contralateral hippocampus, mesencephalic reticular formation, posterior cingulate cortex) induced changes of spontaneous discharges in 41% of the units in the grafts. Diffuse tonic shifts of the level of discharge were usually observed, though driving effects (in two units) were also encountered. Reactions to sensory stimulation of the recipients were observed in 61% of grafted units. Excitatory and inhibitory reactions, tonic, phasic and specific on-effects were evoked mainly by auditory and somatosensory stimuli. The data show the possibility of integration of xenografted tissue with the brain of the recipient and of its participation in processing of sensory information.     

The spontaneous neuronal activity of the hippocampus during the modulation of the theta rhythm by cholinergic substances]

Background activity of the hippocampal neurons, extracellularly recorded in waking chronic rabbits, was analysed in control state and after systemic injection of physostigmine and scopolamine. Similar analysis was done in the hippocampus chronically deprived of ascending brain stem afferents. Cholinergic drugs controlled the number of hippocampal neurons with theta-modulation and the degree of its stability but not the frequency. Activation of cholinergic theta-rhythm resulted also in regularization of activity with suppression of delta-modulation and complex spike discharges; its blockade was accompanied by the opposite changes. Both drugs shifted the level of background activity in the majority of neurons, but the overall mean frequency did not vary between the states. Regression analysis demonstrated significant negative correlations with dominating decrease in the level of activity in high-frequency neurons ( > 25 sp/s) and its increase in low-frequency ones ( < 25 sp/s) after injection of both drugs. Stability of the overall mean frequency and uniformity of its shifts presumably indicate that the frequency, unlike the pattern of the background activity, is not directly controlled by the cholinergic septal input.     

Effect of flanking regions on the expression of the human interleukin-2 chromosomal gene in a murine myeloma cell line]

A human interleukin-2 (IL-2) gene was isolated from genomic DNA library. The isolated gene with 5'- and 3'-flanking sequences of various lengths was inserted into plasmids derived from the retroviral vector pPSneo. The recombinant plasmids were transfected into myeloma X63Ag8-653 cells. The transfected cells, harbouring the IL-2 gene with the shortened (to position -165) or totally deleted 5'-flanking sequence, constitutively expressed biologically active IL-2. Deletion of 3'-flanking region on did not affect the IL-2 expression.     

Spreading depression produced in the thalamus,hippocampus, and caudate nucleus by electrical stimulation of the parietal cortex in rats

The parameters of cortical electrical stimulation (ES) producing synaptically-operated spreading depression (SD) were determined in rats. Waves of SD were regularly triggered in the thalamus by brief, high frequency ES (0.02–0.05 sec; 200–500 Hz) of the parietal cortex. Monitoring by EEG confirmed the lack of accompanying convulsive activity in the cortex and the subcortical structures investigated. Use of Nembutal-induced anesthesia led to a higher minimum threshold for onset of SD, without preventing short-latency thalamid SD. Stimulating the parietal cortex was less effective for synaptic excitation of hippocampal and caudate SD. Hippocampal, unlike thalamic SD, was accompanied by spells of epileptiform activity, most pronounced at certain points in the onset and decline of the SD wave. These brief convulsive episodes were not the cause but the result of SD to a large extent. The low, subconvulsive threshold of synaptically triggered subcortical as well as cortical structures should therefore be taken into account when considering the functional significance of the SD reaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 36–44, January–February, 1990.