Corticofugal influences on the neurons of different regions of the hypothalamus

Responses of the neurons of the lateral and ventromedial hypothalamic regions (HL andHvm, respectively), as well as of the area of the dorsal hypothalamus (aHd) and the projection region of the medial forelimb bundle (MFB), evoked by stimulation of the proreal cortex (field 8), cingular cortex (field 24), pyriform lobula (periamigdalar cortex), and hippocampus (CA3) were studied in acute experiments on cats under ketamine anesthesia. Distributions of the latent periods of the responses recorded from hypothalamic neurons at stimulation of the above cortical structures were analyzed. The responses were classified into primary excitatory and primary inhibitory. Stimulation of the proreal gyrus evoked four times more excitatory responses than inhibitory responses. With stimulation of the cingular gyrus, the ratio of excitatory/inhibitory responses was 1.5∶1. Stimulation of the pyriform cortex evoked activatory and inhibitory responses with a similar probability. With hippocampal stimulation, inhibitory responses appeared two times more frequently than excitatory reactions. The hypothalamus was found to be a zone of wide convergence: one-half of all responding neurons in theHL andHvm responded to stimulations of two or more tested cortical zones. In 26% of the cells, only excitatory convergence was observed, while in 10% only inhibitory convergence was found; 21% of the cells revealed mixed convergence.     

Cyclic kinetics and mathematical expression of the primary immune response to soluble antigen

The injected dose of antigen determines not only the duration of its persistence in the injection site but also the intensity of plasma cell response in the regional lymph node. It was found that the logarithmic sum of antigen quantity in the injection site was related to the sum of cell response values, the correlation coefficient approaching 1. The antigen-lymphoid system interrelations appear to obey Weber-Fechner’s law for afferent systems of the organism. The sum of plasma cells appeared to be in direct connection with the logarithm of the dose injected, with antigen persistence in the injection site and also with the tangent of the acute angle adjoining the ordinate. The basic components of the primary immune response of the organism to soluble antigen,viz. logarithm of the dose injected, antigen persistence in the injection place, plasma cell quantity, tangent of the acute angle, transition modulus from antigen to plasma cells, are interconnected by rather simple equations, which represent the structural elements of the mathematical model described in the text.     

Electrophysiological analysis of corticofugal influences on preoptic neurons

Evoked potential (EPs) and responses of the medial (MPO) and lateral (LPO) preoptic region (RPO) and adjacent structures of the hypothalamus to stimulation of the prefrontal (area 8) and cingulate (area 24) cortex, piriform lobe (periamygdaloid cortex), and hippocampus (area CA3) were investigated in acute experiments on cats under ketamine anesthesia. The most pronounced EPs were observed in the RPO after stimulating the piriform and cingulate cortex. A close relation was found between neuronal responses and EP components. The majority of neurons responding to stimulation of various cortical structures were localized in the LPO, where primarily excitatory responses dominate. The MPO contained somewhat fewer neurons responding to cortical stimulation, and the dominant response here was primarily inhibitory. The ratio of inhibitory and excitatory responses in the LPO was 0.6:1 and in the MPO 5.8:1. Primarily in-inhibitory responses dominated also in the LPO zone adjacent to the bed nucleus stria terminalis (BST) and primarily excitatory in the region surrounding the supraoptic nucleus (SO) (respective ratios 4.9:1 and 0.7:1). The RPO is a broad convergence zone, where 3/4 of the neurons responded to stimuli of two and more cortical regions.A. M. Gorky Medical Institute, Ukrainian Minstry of Health, Donetsk. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 709–719, November–December, 1991.     

Immobilization of Saccharomyces yeast cells on electret polyethylene films

The method of electret-thermal analysis developed in dielectric physics has been applied to monitor bioelectric phenomena that accompany the immobilization of microorganisms on electret substrates. A spectrum of thermo stimulated currents for biofilms consisting of immobilized Saccharomyces cells has been obtained. The spectrum represents a halo in the region of 30-90 degrees C. The immobilization of Saccharomyces cells on electret polyethylene films results in their depolarization that is recorded on the spectra of thermostimulated currents as a reduction of the current peak corresponding to the polyethylene melting point. A hypothesis has been put forward that explains the phenomenon by the absorption of the electric energy of polarized substrates by the cells for the occurrence of metabolic reactions.     

Responses of neurons of the frontal area of the cortex of the rabbit to electric stimulation of certain limbic-mesencephalic structures after administration of substance P

In rabbits tested on behavioural reactions by electrical stimulation of certain limbic-midbrain structures, intravenous injection of substance P (30 mcg/kg) led after 10 min of silent period to a decrease of spontaneous neuronal activity in the frontal cortex. Convergence of excitations arising from the lateral hypothalamus, the dorsal hippocampus and the midbrain reticular formation was also found to decrease after the substance P injection. Analysis of neuronal responses allowed to establish that substance P markedly changed the ascending excitations of the lateral hypothalamus and was less effective for the influences from the midbrain reticular formation.     

Changes in the sorption of the antigens of the causative agent of typhoid on erythrocytes in the dynamic immune response

The study of the adsorption capacity of erythrocytes in 4 strains of mice was made. According to the results of the determination of the background capacity of erythrocytes, the strains of mice, opposite with respect to the sorption of S. typhi Vi- and O-antigens, were selected. After the immunization of these mice with the killed culture of S. typhi, the process of the sorption of the antigen on erythrocytes showed a characteristic kinetics. The course of immune response was characterized by specific changes in the adsorption capacity of erythrocytes in all strains of mice: the increase of this capacity on week 1 was followed by its sharp drop on weeks 3-4 and its subsequent restoration to the initial level by weeks 7-8. The non-specific stimulation of the host had no essential influence on the kinetics of the fixation of S. typhi antigens on erythrocytes. Experiments with the passive immunization of the animals revealed that different receptors take part in the process of the sorption of Vi-antigen on erythrocytes, some of these receptors being related to antibodies.     

Free calcium concentrations in the nerve endings in the brain of rats with spontaneous hypertension

Fluorescent indicator Quin-2 was used for the determination of free calcium (Ca2+in) in synaptosomes incubated in the normal medium and media where sodium is replaced by potassium or choline. At external calcium concentration of 1 mM, Ca2+in in all three media was 20-30% higher in synaptosomes of spontaneously hypertensive rats (SHR) than in control animals. At external calcium concentration of 5 mM, the increase in Ca2+in values induced by K+-depolarization in sodium- or choline-containing media was 50-80% higher in synaptosomes of SHR. These differences are suggested to be the basis for the mechanism of increased peripheral chain activity in the sympathetic nervous system in primary hypertension.