Chromatin degradation in the death of thymic lymphocytes induced by radiation or dexamethasone: the necessity for a stage of preliminary proteolysis

Proteolytic activity in a protein fraction of a rat thymocyte nuclear matrix was found to increase 1-2 h after gamma-irradiation or administration of dexamethazone. Cycloheximide did not prevent the observed protease activation. Neither histons nor thymocyte nuclear matrix proteins were subjected to proteolysis after exposure to radiation or the hormone. Such proteolysis inhibitors as phenylmethylsulfonyl fluorine, trasilol, and partly leupeptine inhibited nuclear DNA degradation in irradiated and dexamethazone treated thymus lymphocytes. In all appearance, this effect was not due to Ca/Mg-dependent endonuclease inactivation. The same was observed in the system of autolytic chromatin degradation in isolated thymocyte nuclei.     

Selective medium with nalidixic acid for isolating antibiotic-producing Actinomyces

The majority of actinomycetes belonging to various genera proved to be resistant to nalidixic acid concentrations having an inhibitory effect on bacteria with trailing growth i.e. B. subtilis and B. mycoides. The bacteria prevented isolation of actinomycetes as pure cultures. The use of a selective medium with nalidixic acid for isolation of soil actinomycetes resulted in 20 per cent increase in the number of the actinomycetes isolated as pure cultures. Preliminary treatment of the soil samples with calcium carbonate under moist conditions followed by the inoculation to the medium with nalidixic acid made it possible to increase isolation of actinomycetes at most 100-fold. With this complex method 495 actinomycete cultures were isolated, their antibiotic properties were studied and their taxonomic position at the genus level was determined. The complex method including the preliminary treatment of soil samples with calcium carbonate followed by inoculation to the selective medium with nalidixic acid is efficient and may be recommended for screening organisms producing new antibiotics.     

Influences of thigh cuffs on the cardiovascular system during 7-day head-down bed rest.

Thigh cuffs, presently named "bracelets," consist of two straps fixed to the upper part of each thigh, applying a pressure of 30 mmHg. The objective was to evaluate the cardiac, arterial, and venous changes in a group of subjects in head-down tilt (HDT) for 7 days by using thigh cuffs during the daytime, and in a control group not using cuffs. The cardiovascular parameters were measured by echography and Doppler. Seven days in HDT reduced stroke volume in both groups (-10%; P < 0.05). Lower limb vascular resistance decreased more in the cuff group than in the control group (-29 vs. -4%; P < 0.05). Cerebral resistance increased in the control group only (+6%; P < 0.05). The jugular vein increased (+45%; P < 0.05) and femoral and popliteal veins decreased in cross-sectional area in both groups (-45 and -8%, respectively; P < 0.05). Carotid diameter tended to decrease (-5%; not significant) in both groups. Heart rate, blood pressure, cardiac output, and total resistance did not change significantly. After 8 h with thigh cuffs, the cardiac and arterial parameters had recovered their pre-HDT level except for blood pressure (+6%; P < 0.05). Jugular vein size decreased from the pre-HDT level (-21%; P < 0.05), and femoral and popliteal vein size increased (+110 and +136%, respectively; P < 0.05). The thigh cuffs had no effect on the development of orthostatic intolerance during the 7 days in HDT.     

Cell wall teichoic acids from Streptomyces daghestanicus VKM Ac-1722T and Streptomyces murinus INA-00524T

The structure of cell wall teichoic acids was studied by chemical methods and NMR spectroscopy in the type strains of two actinomycete species of the "Streptomyces griseoviridis" phenetic cluster: Streptomyces daghestanicus and Streptomyces murinus. S. daghestanicus VKM Ac-1722T contained two polymers having a 1,5-poly(ribitol phosphate) structure. In one of them, the ribitol units had alpha-rhamnopyranose and 3-O-methyl-alpha-rhamnopyranose substituents; in the other, each ribitol unit was carrying 2,4-ketal-bound pyruvic acid. Such polymers were earlier found in the cell walls of Streptomyces roseolus and Nocardiopsis albus, respectively; however, their simultaneous presence in the cell wall has never been reported. The cell wall teichoic acid of Streptomyces murinus INA-00524T was is a 1,5-poly(glucosylpolyol phosphate), whose repeating unit was [-6)-beta-D-glucopyranosyl-(1 --> 2)-glycerol phosphate-(3-P-]. Such a teichoic acid was earlier found in Spirilliplanes yamanashiensis. The 13C NMR spectrum of this polymer is presented for the first time. The results of the present investigation, together with earlier published data, show that the type strains of four species of the "Streptomyces griseoviridis" phenetic cluster differ in the composition and structure of their teichoic acids; thus, teichoic acids may serve as chemotaxonomic markers of the species.     

Analysis and Evaluation of the Functional State of the Cardiovascular System in Cosmonauts during Long-term Spaceflights

Forty-four cosmonauts participating in 28 main long-term (73–438 days) missions on the Mirorbital station performed functional tests with graded physical exercise using a bicycle ergometer. There were two types of this functional load. The cosmonauts that participated in the first eight main missions performed a two-step exercise with a total load power of 1150 W. In the remaining cosmonauts, the exercise was three-step, with a total power of 1350 W. The results obtained during the flight were compared with the results of the same tests performed before the flight, which served as control values for each cosmonaut. To estimate the load tolerance, the heart rate (HR), systolic blood pressure, stroke volume (SV), cardiac output (CO), and cardiac index were analyzed. The data were grouped according to the load, taking into account the type of blood circulation for each group before and during the flight. The ratio between different types of blood circulation was found to change during the flight. The responses to both types of exercises before the flight were less favorable in the cases of the hyperkinetic type of circulation. In these cases, the dominance of the chronotropic function of the heart determined the increase in CO. In the cases of the hypo- and eukinetic types of circulation, the response to the exercise was close to normotonic. In microgravity, irrespective of the circulation type and the exercise, the mechanism of the CO formation changed: the effect of HR was dominant, and there was no increase in SV. Insufficient venous return to the chambers of the heart is the main cause of the decreased response of SV to exercises during spaceflight.     

Cell wall teichoic acids from Streptomyces daghestanicus VKM Ac-1722T and streptomyces murinus INA-00524T

The structure of cell wall teichoic acids was studied by chemical methods and NMR spectroscopy in the type strains of two actinomycete species of the Streptomyces griseoviridis phenetic cluster: streptomyces daghestanicus and streptomyces murinus. S. daghestanicus VKM Ac-1722^t contained two polymers having a 1,5-poly(ribitol phosphate) structure. In one of them, the ribitol units had -rhamnopyranose and 3-O-methyl--rhamnopyranose substituents; in the other, each ribitol unit was carrying 2,4-ketal-bound pyruvic acid. Such polymers were earlier found in the cell walls of Streptomyces roseolus and Nocardiopsis albus, respectively; however, their simultaneous presence in the cell wall has never been reported. The cell wall teichoic acid of Streptomyces murinus INA-00524^T was a 1,5-poly(glucosylpolyol phosphate), whose repeating unit was [-6)--D-glucopyranosyl-(12)-glycerol phosphate-(3-P-]. Such a teichoic acid was earlier found in Spirilliplanes yamanashiensis. The ¹³C NMR spectrum of this polymer is presented for the first time. The results of the present investigation, together with earlier published data, show that the type strains of four species of the Streptomyces griseoviridis phenetic cluster differ in the composition and structure of their teichoic acids; thus, teichoic acids may serve as chemotaxonomic markers of the species.Translated from Mikrobiologiya, Vol. 74, No. 1, 2005, pp. 48–54.Original Russian Text Copyright © 2005 by Streshinskaya, Kozlova, Alferova, Shashkov, Evtushenko.     

Monitoring of the cardiac and vascular response to LBNP during the 14 day spaceflight "Cassiopee"

The objective of the present experiment was to monitor in real time the cardiac and the peripheral response to inflight LBNP. The second objective was to detect and quantify hemodynamic signs of orthostatic tolerance inflight by measuring the heart rate, blood pressure, cardiac and regional hemodynamics during LBNP.