The role of purinergic neurotransmission in various cardiovascular reflexes.

In urethane-anaesthetized rats the effects of alpha-adrenoceptor antagonists and desensitization of P2-purinoceptors with alpha,beta-methylene ATP on the pressor reflex responses were investigated. Pressor responses were elicited by electrical stimulation of the central end of the sciatic nerve, by asphyxia and by occlusion of the common carotid artery. Responses to sciatic nerve stimulation and to asphyxia, but not those to carotid artery occlusion were entirely suppressed by dihydroergotamine and phentolamine. Under the action of dihydroergotamine the sinocarotid reflex decreased by over 70% in 40% of the experiments. In 60% of experiments the response was only slightly reduced or even augmented, but it was entirely inhibited by subsequent desensitization with alpha,beta-methylene ATP. The magnitude of response to sciatic nerve stimulation was almost unaffected by alpha,beta-methylene ATP, while the response to carotid occlusion was decreased by 40-50%. The recovery of purinoceptor sensitivity to alpha,beta-methylene ATP was accompanied by restoration of the sinocarotid reflex. It is suggested that purinergic neurotransmission plays a considerable role in the pressor sinocarotid reflex, while in the pressor response to stimulation of somatic afferents its role is negligible.     

A comparative study of the pharmacokinetics and pharmacodynamics of bonnecor]

The pharmacokinetics and pharmacodynamics of bonnecor were studied simultaneously in animals with experimental arrhythmia. It was shown that irrespective of the animal species and individual features of the drug elimination kinetics the level of bonnecor concentration correlated with the antiarrhythmic effect. The data on the excretion of bonnecor and its metabolites in the urine in the dog and man were obtained. The decrease of bioavailability at oral administration of bonnecor was demonstrated to be related to its intensive conversion in metabolite M-I.     

Age changes in vasomotor reflexes and ultrastructure of sympathetic neurons in rats after chemical desympathization

The number of cells in the sympathetic ganglia of rats was reduced by means of guanethidine to 30% (group 1) and to 1% (group 2) of normal. In rats aged 2 months pressor responses to asphyxia and to stimulation of the femoral nerve were absent. In the animals of group 1 (but not of group 2) recovery of the reflexes was observed at the age of 4 months. An increase in the number of neurofibrils was demonstrated in the neurons surviving guanethidine treatment, indicating growth of the axon of these cells. Investigation of responses to the indirect sympathomimetic tyramine revealed an increase in the number of effector sympathetic endings at the periphery at the age of 4 months in the animals of group 1. It is suggested that restoration of reflex responses in the animals of this group at the age of 4 months took place on account of growth and branching of the axons of the surviving nerve cells, as a result of which the density of the effector innervation at the periphery was restored.     

Sympathetic neurons in the superior cervical ganglion are more numerous in SHR and Wistar-Kyoto rats than in wistar rats

Department of Physiology of Man and Animals, Faculty of Biology, Moscow University. Laboratory of Pathophysiology, Research Institue of Pediatrics, Academy of Medical Sciences of the USSR. Department of General Biology, N. I. Pirogov Second Moscow Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR M. Ya. Studenikin.) Translated from Byullet en' Éksperimental'noi Biologii i Meditsiny, Vol. 108, No. 11, pp. 620–622, November, 1989.     

The chromosomes ofFestuca pratensis Huds. (Poaceae): fluorochrome banding,heterochromatin and condensation

The karyotype of meadow fescueFestuca pratensis Huds. (2n=14) has been studied by means of fluorescence banding techniques. At-enriched heterochromatic bands were revealed in the metaphase chromosomes 1–6. A single GC-rich band was associated with the chromosome 2 secondary constriction. Delay of condensation of the heterochromatic regions was discovered. The heterochromatic bands reported are markers which allow identification of all meadow fescue chromosomes.     

Mutational analysis of the SOX9 gene in campomelic dysplasia and autosomal sex reversal: lack of genotype/phenotype correlations

It has previously been shown that, in the heterozygous state, mutations in the SOX9 gene cause campomelic dysplasia (CD) and the often associated autosomal XY sex reversal. In 12 CD patients, 10 novel mutations and one recurrent mutation were characterized in one SOX9 allele each, and in one case, no mutation was found. Four missense mutations are all located within the high mobility group (HMG) domain. They either reduce or abolish the DNA-binding ability of the mutant SOX9 proteins. Among the five nonsense and three frameshift mutations identified, two leave the C-terminal transactivation (TA) domain encompassing residues 402-509 of SOX9 partly or almost completely intact. When tested in cell transfection experiments, the recurrent nonsense mutation Y440X, found in two patients who survived for four and more than 9 years, respectively, exhibits some residual transactivation ability. In contrast, a frameshift mutation extending the protein by 70 residues at codon 507, found in a patient who died shortly after birth, showed no transactivation. This is apparently due to instability of the mutant SOX9 protein as demonstrated by Western blotting. Amino acid substitutions and nonsense mutations are found in patients with and without XY sex reversal, indicating that sex reversal in CD is subject to variable penetrance. Finally, none of 18 female patients with XY gonadal dysgenesis (Swyer syndrome) showed an altered SOX9 banding pattern in SSCP assays, providing evidence that SOX9 mutations do not usually result in XY sex reversal without skeletal malformations.      

Effect of Transmural Pressure on Constrictor Reactions of Caudal Artery in Hypotensive and Hypertensive Rats

Clipping of the abdominal aorta distally to the renal arteries produces a persistent decrease in blood pressure in hindquarter vessels by 35-40%. On week 6-7 postoperation, the reactions of the caudal artery perfused in vitro under constant pressure to norepinephrine were studied. At transmural pressure of 150 mm Hg, the vascular responses in hypotensive rats were reduced compared to those in normotensive control. By contrast, the responses of hypertensive vessels were more pronounced at 75 mm Hg even after deendothelization.