Biomedical subjects
Publications and source records attributed to S C Sharma.
Cellular radiosensitivity parameters of the track structure theory of Katz and co-workers are evaluated from a sum of squares minimizing computer program for nonlinear models. Based on these observations, suggestions are presented for efficient experiment design for the determination of these parameters from track-segment bombardments of high LET radiations.
Fifty healthy male volunteers, 21-34 yr of age, normally resident at altitudes less than 1,000 m, were airlifted to 3,658 m. Urinary excretion of catecholamines was measured at sea level (198 m) and on the 1st, 2nd, 4th, and 10th day of a stay at high altitude. The symptoms observed on exposure to high altitude were assigned arbitrary scores. The volunteers could, on this basis, be divided into "symptomatic" and "asymptomatic" groups. The two groups showed a markedly different pattern of urinary catecholamines excretion on exposure to high altitude and on return to sea level. Significant increase in the catecholamine excretion was observed in the symptomatic group only. A possible role for enhanced sympathoadrenal activity in the etiopathogenesis of high-altitude illnesses is postulated.
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From cellular radiosensitivity parameters and theoretical particle-energy spectra in tissue, of the secondary particles from neutron and negative pion irradiations, RBE-Dose relations have been calculated. The theoretical results are compared with clinical and radiobiological data for normal tissue, tumours and cells in culture. Formulae for calculation, cellular parameters and the needed properties of equivalent 'track-segment bombardments' are given, for several mammalian cells irradiated with pions and with neutrons of several energies.
A case is reported, apparently the first of its kind in the literature, of a female child in which there were not only pigmented lesions of incontinentia pigmenti but also hypopigmented lesions of incontinentia pigmenti achromians. The title incontinentia pigmenti et achromians is suggested for this combined disorder. The child also had associated lesions in the form of nail dystrophy, delayed dentition and epilepsy.
The oral adminitration of Tamoxifen on Days 2,3 and 4 after mating, or on Day 2 only, was found to prevent the oestrogen-dependent surface-coat change of the late preimplantation blastocyst in the mouse. It is suggested that his is an antioestrogenic manifestation and that ist is, at least in part, responsible for the drug's known antifertility effect.
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