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Biomedical subjects

R H Smith

Publications and source records attributed to R H Smith.

At least 235 records · Page 13Linked to original sources
PubMed1970

Biological responses of Habrobracon to spaceflight.

Since the interaction of the parasitic wasp Habrobracon with the space environment could not be prejudged, we decided to test approximately 30 different parameters of a genetic, mutational, biochemical, behavioral, and physiological character in the one spaceflight we had at our disposal. These parameters were examined at six different exposures of gamma-radiation (including 0 dose) in flight, resulting in about 180 different endpoints in all. The most profound effects of spaceflight in conjunction with radiation were decreased hatchability and enhanced fecundity of eggs exposed to spaceflight at different stages of oogenesis. The interpretation we favor is that these two endpoints are reflections of chromosomal non-disjunction in the former case and inhibition of cell division in the latter. Our most comprehensive study of mutagenesis was on sperm, where dominant lethality, recessive lethality, translocations, and visible mutations were assayed; the only effect found was a threefold enhancement of the recessive lethal mutation frequency in the non-irradiated sperm in the orbited Habrobracon males. Behavioral and biochemical differences were found. Mating activity of orbited males was severely disrupted and xanthine dehydrogenase activity was sharply decreased in the irradiated flight animals, an unexpected observation. Postflight experiments were like the ground-based control experiments in all aspects but one. Under conditions of vibration similar to those encountered during the launch and re-entry, the mutation frequency in the sperm increased by a factor of three over that of the non-vibrated control.

Animals↗
PubMed1969

Mutational responses of insects in the Biosatellite II experiment.

Genetic effects associated with space flight include mutation induction by the space flight itself, and enhancements or antagonisms of radiation-induced mutations. The conditions of space flight vary in mutagenic effectiveness from no response at all to responses nine times that found in ground-based controls. The test systems follow the sensitivity pattern: spermatogonial translocations > oogonial and oocyte nondisjunction > recessive lethality of stages in spermatogenesis > dominant lethality of stages in spermatogenesis. Large enhancing and antagonistic effects of space flight in conjunction with radiation were observed in the Biosatellite II experiment. The most surprising one was the elimination of the effect of 2500 R by space flight in Habrobracon oogonia where the effects of 500 R normally can be easily observed. Two sets of parameters are considered in attempts to explain the responses: (1) the nature of the biological targets, and (2) the particular conditions of space flight that are responsible for the effects.

Animals↗