Endocrine function of the heart. Structure and biological properties of peptides secreted by the heart atrium

Apart from the generally known functions, the heart has also an endocrine function. Atrial cardiocytes, being typical secretory cells, release peptide hormones into the blood stream: atrial natriuretic peptide containing 28 amino acids and cardiodilatin. The structure of atrial peptides was determined. It was shown that both peptides were derived from their common precursor, a protein containing 151 amino acids. The presence of specific receptors is demonstrated on plasmatic membranes of cells of kidney epithelium, arterial smooth muscle, arterial endothelium, kidney cortex and hypophysis. The interaction of atrial peptides with these receptors activates the guanylate cyclase system. The biological action of atrial peptides manifests itself in the quick, massive and instantaneous increase of diuresis and electrolyte excretion, elevated clearance of creatinine, decrease of kidney vascular resistance, intensification of glomerular filtration, inhibition of stimulated secretion of aldosterone, relaxation of blood vessels, elimination of arterial and intestinal spasm induced by various endogenous and exogenous vasoconstrictors and in correction of kidney hypertension. Various radioimmunoassays for the presence of atrial peptides in human plasma were developed; it was shown that in patients with congestive heart failure the content of atrial peptides is increased.     

Mechanism of directional selectivity of neurons with complex receptive fields in the cat visual cortex

Spatio-temporal interactions within complex receptive fields in the cat visual cortex were investigated by sequential presentation of two stationary stimuli. When two stimuli were presented in phase (on-on or off-off) in the order corresponding to preferred direction of movement, facilitation or weak inhibition of the response to the second stimulus was observed, whereas if it corresponded to zero direction of movement, the response was strongly inhibited. In the case of stimulation out of phase (on-off or off-on), in the order corresponding to the preferred direction of movement, considerable inhibition of the response to the second stimulus was observed, whereas in the opposite order, facilitation or weak inhibition was observed. The strength of interaction between different parts of the field depended on the distance between them and the duration of the interval between stimuli. Directional selectivity of "complex" neurons is thus ensured by asymmetry of spatio-temporal interactions between receptive field inputs of the same type. Interactions between inputs of different types, arising when a multiedge stimulus (bar, grating) can be used by the visual system to distinguish an object from the background and to assess changes in size of objects and the relative velocity of their movement.V. Kapsukas State University, Vilnius. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 505–512, July–August, 1984.     

European checkerspots (Melitaeini: Lepidoptera,Nymphalidae) are not aposematic – the point of view of great tits (Parus major)

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Antitumor efficacy of combined gene and radiotherapy in animals

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Structure of reciprocal connections in visual cortical areas 17 and 18 in cats

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Neuronal connections of ocular dominance columns in the cortex of monocularly deprived cats

We have investigated the developmental changes of intrahemispheric neuronal connections of the areas 17 & 18 ocular dominance columns in monocularly deprived cats. Single cortical columns were microiontophoretically injected with horseradish peroxidase and 3D reconstruction of retrogradely labelled cells' region was done. Ocular dominance of injected columns and their coordinates in the visual field map were determined. In area 17 it was shown that for non-deprived eye the connections of columns that are driven via the crossed pathways were longer than connections of columns driven via uncrossed ones, and in both cases they were longer than connections in intact cats. The connections of deprived eye columns are significantly reduced. We have observed some changes in the spatial organization of long-range connections in area 17 for columns driven by the non-deprived eye (more rounded shape of regions of labeled cells, non-uniform distribution of cells within it). Maximal length of such connections did not exceed the length of connections in strabismic cats. We speculate that the length of cell axons providing for the horizontal connections of cortical columns has some intrinsic limit that does not depend on visual stimulation during the critical period of development.     

Changes in the expression of monoaminergic genes under the influence of repeated experience of agonistic interactions: from behavior to gene

The role of genetic and environmental factors as well as brain neurochemistry in regulating aggressive and submissive behaviors in animals are considered. We present a review of data on changes in brain monoaminergic activity (synthesis, catabolism, receptors) and on the expression of monoaminergetic genes under repeated daily agonistic confrontations in male mice. A repeated experience of aggression was shown to result in the total activation of the dopaminergic system and the inhibition of the serotonergic one. This was accompanied by a decrease in the mRNA level of the catechol-O-methyltransferase gene in the midbrain and an increase of the mRNA level of the dopamine transporter and tyrosine hydroxylase genes in the ventral tegmental area of aggressive male mice. Repeated experience of social defeats produced dynamic changes in the serotonergic system of some brain areas and an increase of the mRNA level of the serotonin transporter and monoamine oxidase A genes in the midbrain raphe nuclei. Theoretical and methodological possibilities of the proposed ethological approach for studying molecular mechanisms of agonistic behavior are discussed in the context of the fundamental problem of investigating the ways of regulation from behavior to gene.     

The peptidase activity of a cellular extract of the causative agent of plague

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