Mechanisms of changes in human hemodynamics under the conditions of microgravity and prognosis of postflight orthostatic stability

The mechanisms of hemodynamic responses to orthostatic stresses and orthostatic stability (OS) of cosmonauts were studied before and after short-and long-term spaceflights (SFs) using orthostatic tests, as well as before, during, and after SFs using ultrasonic methods in tests with exposure to lower body negative pressure (LBNP). The capacitance and distensibility of the veins of the lower extremities were studied using occlusive air plethysmography before, during, and after SFs of different durations. A stay in microgravity has been proved to result in detraining of, mainly, the vascular mechanisms of compensating orthostatic perturbations. It has been established that the decrease in OS under the influence of microgravity is determined by a reduction of the vasoconstrictive ability of large blood vessels of the lower extremities; an increase in venous distensibility and capacitance of the legs; and an impairment of blood flow regulation, which leads to a cerebral blood flow deficit in orthostatic stresses, and of the initial individual OS before the flight. The results of preflight studies of hemodynamics by ultrasonic methods at LBNP and the data of orthostatic tests before SFs make it possible to predict the degree of decrease of OS after an SF proceeding in the normal mode. At the same time, the data of ultrasonic blood flow examination provide more a accurate estimation of OS and make it possible to assess the physiological reserves of hemodynamic regulation and to reveal the loss of regulation capacity even in cases where integrated indices (heart rate and blood pressure) are within the normal ranges.     

Effect of the lymphocytosis-stimulating factor from Bordetella pertussis on murine lymphoid and hemopoietic cells

Effect of B. pertussis lymphocytosis-promoting factor (LPF) on the lympho-hematopoietic system of mice was studied. The injection of LPF was shown to sharply enhance endogenous colony formation and to induce a severe depletion of thymus cells, reaching its maximum of day 4. Thymocytes obtained on day 2 or 3 after the injection of LPF produced a suppressive effect on endogenous colony formation. The proliferative activity of hematopoietic stem cells sharply increased under the influence of LPF, though it had no radioprotective action. On the following day after the injection of LPF a steep rise in the number of hematopoietic stem cells was observed in the blood of mice: their content increased 20-fold in comparison with the control level. These data may be important for the evaluation of the side effects of pertussis vaccine on the lympho-hematopoietic system.     

The cluster method in conducting epidemiological research

The Expanded Programme on Immunization (EPI) whose goal is to reduce morbidity and mortality by providing children with immunizations against diphtheria, pertussis, tetanus, poliomyelitis, measles, and tuberculosis continually faces the problem of documenting immunization coverage rates. Therefore the EPI seeks simple, effective, and inexpensive methods of evaluation which could be implemented in different countries. An example of such a method is a simplified cluster sampling technique of estimation of immunization coverage through the examination of 210 children, selected randomly as 30 groups of 7 children each. In 1978-1984 more than 1000 immunization coverage surveys were performed all over the world, mainly in developing countries. In a modified way this method is also used to collect data on morbidity and mortality of certain EPI target diseases as well as diarrhoeal diseases.     

Antibodies against calcium-regulating hormones in infectious-allergic forms of bronchial asthma

Antibodies to calcitonin, parathyroid hormone and cortisol are detected in acute stage of infection-caused bronchial asthma. The appearance of antibodies is paralleled by marked hypercalcaemia. The antibodies may bind excessive hormones in the blood, preventing further hormonal imbalance. Ten-day treatment with glucocorticoids decreased the amount of antibodies possibly due to normalization of hormonal secretion and restoration of their balance. As a result, calcium blood levels returned to normal.     

Metyrapone - reduced cytochrome P-450 complex: A specific method for the determination of the phenobarbital inducible form of rat hepatic microsomal cytochrome P-450

Using homogeneous cytochrome P-450, we have shown that the well-known metyrapone-dithionite reduced cytochrome P-450 complex is specific for the cytochrome P-450b induced by phenobarbital. A linear relationship was observed between the absorbance of metyrapone-reduced cytochrome P-450 complex and the one of CO-reduced cytochrome P-450 complex, the usual method for the determination of cytochrome P-450. A method has been proposed for the specific determination of the cytochrome P-450b.     

Molecular control of rabbit follicular testosterone production. Role of protein and RNA after stimulation with luteinizing hormone.

The time and dose dependence of the relationship between uptake of labelled precursors into protein and RNA and production of testosterone by rabbit follicles was examined. Although testosterone production was stimulated by luteinizing hormone at concentrations between 0.1 and 10 microgram/ml, the uptake of [3H]leucine into protein was significant only when the concentration of luteinizing hormone was greater than 2.5 microgram/ml. Increased production of testosterone was observed within 15 min of stimulation with luteinizing hormone whereas uptake of [3H]leucine was only significant at 90 min. Puromycin (40 microgram/ml) and cycloheximide (10 microgram/ml) in the presence of luteinizing hormone inhibited the synthesis of both testosterone and protein. However, lower concentrations of puromycin (0.1, 1 and 10 microgram/ml) and cycloheximide (1 microgram/ml) had no effect on luteinizing hormone-induced testosterone production but significantly inhibited protein synthesis by 58, 37, 31 and 71%, respectively. Actinomycin D (20, 80 and 160 microgram/ml) alone and in combination with 5 microgram luteinizing hormone/ml severely inhibited uptake of [3H]uridine into RNA without affecting testosterone production. However, with 1 microgram actinomycin/ml, testosterone production was significantly (P less than 0.01) greater than in the presence of luteinizing hormone alone. These results cast doubt on the obligatory role of RNA and protein synthesis in rabbit ovarian follicular steroidogenesis.