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Weightlessness produces adaptive and maladaptive changes in the respiratory system. We assessed the effects of 30-day antiorthostatic hanging as a model of microgravity on the water balance in the lungs and surface activity and phospholipid composition of pulmonary surfactant in C57Bl/6 mice. Long-term antiorthostatic hanging increased water content in the lungs and reduced surface-active properties of the surfactant. This was accompanied by an increase in the content of alveolar phospholipids and changes in their fractional composition (increase in the relative content of lysophosphatidylcholine and phosphatidylethanolamine).

White male rats with the body mass of 180-220 grams were distributed into the open-field active (presumably stress-resistant) and open-field inactive (presumably stress vulnerable) groups for a 10-day experimental suspension with the purpose to evaluate the surfactant activity in bronchoalveolar lavages, total phospholipids and their fractions, and water balance in the lung. In modeled microgravity, augmented blood filling of the rat's lung increases the alveolar phospholipid content and alters the phospholipid fractional composition in the pulmonary surfactant. Ten-day suspension raises pulmonary surfactant activity to a greater extent in stress-resistant animals rather than in their stress vulnerable peers.

The kinetics of active transport of an organic acid (fluorescein) through the membranes of the choroid plexus from the lateral ventricules of the brain of rabbit was studied both morphologically and functionally. It was shown that fluorescein is actively translocated through the apical and basal membrane of the epithelium and is accumulated in blood capillaries at a concentration exceeding one order of magnitude that in the incubation medium. The kinetic curves displaying saturation and the demonstration of inhibition by other acids shows that a specific carrier is involved in the transfer across the membrane. The active transport of fluorescein at 20 degrees C was found to be sodium independent. Total exclusion of sodium from the incubation medium does not change the Michaelis constant (Km) and maximal velocity (V). The active transport depends on the operation of (Na+ + K+)-ATPase as energy source but obviously no specific complexes with the participation of sodium are involved.

The antigenic and immunogenic properties of five ts mutants of neurovaccinia virus with markedly reduced pathogenicity for laboratory animals as compared with "wild" type virus were studied. The antigenic and immunogenic activities of the mutants correlated with their capacity to reproduce in the skin of the inoculated animals. When similar doses of UV-inactivated mutants were used for immunization of rabbits, significant differences (more than 100-fold) in their antigenic activity were found. When rabbits were immunized with active virus, neutralizing antibody in titer of 1:800 protected all the immunized animals against intracerebral challenge with log 4.0 LD50 of neurovaccinia virus. On the other hand, the neutralizing antibody formed in response to inoculation of UV-inactivated virus did not protect the immunized animals in titers exceeding 1:2560. A correlation between the antibody titer for "extracellular" virus and immunity in vaccinated rabbits has been demonstrated.

Fifty-seven temperature-sensitive (ts) mutants of a neurotropic variant of vaccinia virus were obtained. A comparison of the effectiveness of 6 different mutagens showed that in in vivo experiments nitrosomethylurea induced 10%, nitrosoguanidine 8%, and bromodeoxyuridine 2.5% ts mutants. In vitro, at the same degree of inactivation, UV irradiation, hydroxylamine and nitrous acid induced 2.5% ts mutants. Out of 49 mutants studied, 27 had a DNA+ phenotype, 19 a DNA+/-and 3 a DNA- phenotype. Under permissive conditions, two thirds of all the mutants tested formed thermolabile virions. In experiments on genetic recombination, the recombination frequency between different pairs was from 2.8 to 57%. Seven of the mutants were plotted on the virus genetic map in a certain sequence.