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.     

Tumor vascular signals in renal masses: detection with Doppler US

The vascularity of 49 renal masses (26 malignant and 23 benign lesions) was investigated with duplex Doppler ultrasound. Doppler signals obtained at the margins of renal masses were defined as "tumor signals" when the Doppler-shifted frequency of the lesion exceeded the frequency shift in the ipsilateral main renal artery. These exceeded 2.5 kHz with a 3-MHz insonating frequency. Among the 26 renal masses that subsequently proved to be malignant, tumor signals were obtained in 15 of 18 (83%) untreated renal cell carcinomas, in three of four Wilms tumors, and in two patients with metastases to the kidney, but not in the one patient with lymphoma. None of the 23 benign renal masses demonstrated tumor signals. Tumor vascularity in malignant lesions gives rise to abnormal, high-velocity, Doppler-shifted signals that can help in the differential diagnosis of renal masses.     

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.