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Z Velkov

Publications and source records attributed to Z Velkov.

At least 19 recordsLinked to original sources

Disorders of ventricular contractility and electrogenesis in the early stage of endotoxin shocked rabbits.

This is a report on ventricular contractility and electrogenesis disorders in rabbits, following intravenous injection of E. coli endotoxin at a dose of 2 mg.kg-1. At the 30th min, the right ventricular contractility indices (dP/dtmax)/P and [(dP/dt)/P]max had lower values, whereas end diastolic pressure (EDP), right ventricular systolic pressure (RVSP) and P(dP/dtmax) showed higher values compared to the initial ones. Most of the left ventricular contractility indices tested showed significantly lower values at the 30th and 60th min of the registration. In the scalar orthogonal ECG leads, at the 5th min an increased Qz amplitude, and at the 60th min an increased Rz amplitude, a decreased Ry amplitude, and QRS complex widening and bradicardia, were registered. In the spatial magnitude curve an increased amplitude of the main vectors of ventricular depolarization was documented. The changes in electrogenesis are interpreted first and foremost by the presence of hemodynamic disorders. The inference is reached that both left and right ventricular dysfunction have been already formed during the initial stage of endotoxin shock.

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Changes in rabbit cardiac function during fulminant endotoxin shock.

Septic shock in humans is usually characterized by severe changes in the left ventricular function, while little is known about the dysfunction of the right ventricle. Rabbits were injected intraventricularly with endotoxin from Escherichia coli at a dose of 2 mg/kg following catheterization of both heart ventricles with the purpose of measuring their pressure, and determining a number of contractility indices. In the animals in which endotoxin shock developed very rapidly and death occurred between the 60th and the 90th min (shock development is called fulminant), we established significant changes in the function of both ventricles. At the 20th min, the intraventricular pressure, EDP and P-(dP/dtmax) increased, indicating a tension lead of the right ventricle. At the same time, there was a decrease in plus dP/dtmax, minus dP/dtmax, (dP/dtmax)/P and [(dP/dt)/P]max, considered evidence for impaired contractility and relaxation of the right ventricular myocardium. During the subsequent observation periods, some of the contractility indices returned to normal. At the 20th min, a reduction of intraventricular pressure, P-(dP/dtmax), plus dP/dtmax, minus dP/dtmax and (dP/dt)P was registered in the left ventricle. Pronounced bradycardia was observed from the 30th min to the end of the experiments. Fulminant endotoxin shock in rabbits occurs as a result of the impaired function of the right ventricle attributed to tension leading and endotoxin-induced biventricular myocardial dysfunction.

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Immunohistochemical and electron microscope studies of rat islets of Langerhans one month after adult thymectomy.

Ultrastructural and quantitative immunocytochemical studies of rat pancreata were carried out 1 month after adult thymectomy. The proportions of insulin-, glucagon-, and somatostatin-immunoreactive cells in the pancreas were estimated on paraffin sections using the unlabelled peroxidase-antiperoxidase method. Relative islet volume, islet size and number were determined on hematoxylin and eosin stained sections. A moderate increase of the islet volume on account of size was found in the pancreas of the thymectomized rats. The proportion of insulin-immunoreactive cells was also elevated. Ultrastructural studies showed a rich supply of secretory granules in most beta-cells. Mixed beta-endocrine-acinar cells were often observed. Mitotic figures were found in single beta-cells. The blood glucose level was in the normal range. The findings suggest a moderate stimulation of beta-cell secretory activity after thymectomy which is not associated with elevated blood glucose levels.

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A study of ventricular electrogenesis and contractility in acute pressure overload of the right heart ventricle.

A model of fat embolism induced acute pressure overload of rabbit right ventricle of heart is presented. A decrease in right ventricular contractility is registered as early as the first minutes after loading. Changes in spatial magnitude and polar coordinates of vectors of ventricular depolarization, and myocardial ischemia manifestations are recorded. The changes in electrogenesis described are attributed basically to ensuing development of hemodynamic disorders.

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Time course changes in blood glucose and insulin levels of thymectomized rats.

The endocrine function of the thymus and its relations to other endocrine glands have been discussed in the scientific literature. Blood glucose contents (assayed on a 'Beckman' glucoanalyzer by the glucoseoxidase method) and serum insulin level (using radioimmunoassay) were studied in male Wistar rats--1, 2, 3, 4, 5, 6, 9, and 12 months after adult thymectomy. The results obtained demonstrated that the thymectomy provoked increase of insulin level accompanied by phasic decrease of blood glucose in comparison to age matched controls. Correlation between insulin and glucose levels in the thymectomized rats was not found. The results support the hypothesis of functional interrelations between the thymus and the endocrine pancreas.

Aging↗

Decreases in left ventricular contractility during endotoxin shock in rabbits.

The participation of the heart in shock syndrome formation during endotoxin shock is a problem still awaiting solution. The task undertaken is to assess the work of the left ventricle and arterial pressure in rabbits before and after endotoxin injection at a dose of 2 mg.kg-1. Heart rate is the first to reach significantly lower values--at 30 min (p less than 0.05). At 45 min, there are significant reductions in dP/dtmax (p less than 0.01), (dp/dt)/P40 (p less than 0.001), LVP (p less than 0.05), and increase in dP/dtneg (p less than 0.02). Both the systolic and diastolic blood pressures were significantly decreased at 60 min. The data obtained warrant the assumption that impaired myocardial contractility plays a part in the formation of shock syndrome in rabbits exposed to endotoxin.

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Effect of calcium blocking agent verapamil on blood pressure, ventricular contractility, parathyroid hormone, calcium and phosphorus in plasma, catecholamines, corticosterone and plasma renin activity in spontaneously hypertensive rats.

In four-month-old spontaneously hypertensive rats (SHR) the effect of a calcium blocking agent verapamil on blood pressure, ventricular contractility indices, parathyroid hormone (PTH), plasma renin activity (PRA), plasma and adrenal corticosterone content and catecholamines in hypothalamus, myocardium and adrenal gland was evaluated. Calcium and phosphorus in plasma were also determined. Verapamil treatment resulted in a significant decrease in systolic and diastolic blood pressure and a reduction in maximum left ventricular pressure. Verapamil exerted a negative inotropic effect, evaluated by a decrease in dP/dt max and dP/dt neg. PRA was elevated, calcium tended to decrease, and no changes in PTH and phosphorus were found. The hypotensive effect of verapamil in SHR was accompanied by a decrease in plasma and adrenal corticosterone content, and a fall in catecholamine concentration in adrenal glands and myocardium.

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Changes in the connective tissue components of the aorta in thymectomized rats.

The character and essence of changes taking place in the connective tissue matrix of the vascular wall under the effect of thymus deficiency are not well enough clarified. The aim of the study was to assess the content of collagen, elastin, total glucosamines, total glycoproteins, total nonfibrillar protein and total protein in the aorta total glycoproteins, total nonfibrillar protein and total protein in the aorta of adult thymectomized rats of the Wistar strain and in control animals over a 12-month post-thymectomy period. The amount of collagen and elastin augments both in connection with the aging process (after 2-4 months), and as a result of thymectomy. Glycoproteins show an increase starting from the third month in the controls, and from the fifth month in thymectomized animals. Glucosamines display a fluctuating decrease parallel to aging in either of the groups under study. The content of total protein and nonfibrillar protein reveals no differences worthy of notice. It is reasonable to assume the existence of a correlation between thymus activity and metabolism of the connective tissue components in the vascular wall of rats.

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Effect of captopril on some ventricular contractility indices in spontaneously hypertensive rats (SHR).

Two groups of SHR were treated with captopril (Squibb): the first group (1 month old)--30 mg/kg i.p. twice daily for 77 days, and the second group (8 months old)--20 mg/kg p.o. twice a day for 23 days. The recording of electrocardiogram (ECG), systolic blood pressure (SBP), diastolic blood pressure (DBP), and some isometric indices of the left-ventricular contractility indicate that in all treated animals the values of most of the parameters are considerably lowered compared to the controls. The ratio between velocity of pressure increase and intraventricular pressure/equal to 50 mmHg--(dP/dt)/ICP50/does not change significantly. It can be concluded that in SHR, captopril practically does not influence the inotropic condition of the myocardium.

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[Characteristics of the aortic rheogram (an experimental study)].

The authors aim to describe aortic rheogram and examine its changes under the influence of some agents, to compare with the phases of the heart activity and to explain the origin of the curve. They use experimental animals (cats), to whom aortic rheogram is recorded by means of a probe-electrode, as well as atreiral blood pressure, phonocardiogram and electrocardiogram. The changes in the aortic rheogram are recorded after elevation or diminition of arterial blood pressure (medicamentous and mechanical), replacement of a part of the abdominal aorta with nonelastic prothesis and application of a model heart-aorta-vascular bed, in which the "systolic volume" is changeable as well as the "peripheral vascular resistance". The authors come to the conclusion that the aortic rheogram, recorded by a probe-electrode, is a reflection of the fluctuations in the volume velocity of the blood flow. Furthermore the general amplitude of the curve is in direct dependence of the systolic volume of the left ventricle. The peripheral vascular resistance and elasticity of the aortic wall do not affect substantially the form and amplitude of the rheogram. The value of the mean arterial blood pressure itself does not influence the form and the value of the curves.

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