Biomedical subjects
Publications and source records attributed to H Singh.
An alternate co-polymer of styrene and maleic anhydride was dissolved in dimethylsulphoxide and injected into the vas deferens of rats. The polymer was retained in the vas deferens and the morphological changes detected were confined to the mucosa. When the polymer was removed by flushing dimethylsulphoxide, the mucosal structure became normal within 2 weeks.
To investigate abnormalities in peripheral nerve myelin in experimental diabetes, we studied the effects of the proteolytic enzymes trypsin and alpha-chymotrypsin on the proteins of this membrane, obtained from the sciatic nerves of normal rats and from animals made diabetic with streptozotocin. The dominant effect of the proteolytic enzymes was to incompletely degrade the major membrane protein (mol. wt. 28,000), with the appearance of new protein (mol. wt. 20,000). Using myelin isolated from the nerves of diabetic animals, the reaction was approximately one-half that of the controls (P less than 0.01) for both enzymes. When, however, the myelin protein affected by trypsin and chymotrypsin was isolated from the membrane and then incubated with the proteolytic enzyme, its proteolysis was complete and took place at the same rate in the diabetic animals and controls. These findings suggest that, in this model of experimental diabetes, there is an alteration in the structure of peripheral nerve myelin that inhibits interaction between the protein in the membrane bilayer and two water soluble proteolytic enzymes. This alteration could not be demonstrated in protein isolated from the membrane, suggesting that the change relates to the interaction of the protein and other components of myelin, rather than to chemical alteration in the protein per se.
Sixty welders (20 each from Plants A, B, and C) and 20 control subjects were investigated for the possible occurrence of manganese poisoning among welders exposed to the welding fumes containing this metal. Ten, 9, and 5 welders from Plants B, C, and A, respectively, were diagnosed as suspected cases of early manganese poisoning. The diagnosis was based on the proof of overexposure to manganese by the findings of increased urinary levels of this metal, signs of early neurological involvement, and increased contents of serum calcium. These results are discussed in relation to the manganese concentration in the air around the welder's breathing zones.
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The effects of insecticides containing either an organophosphate parathion (Paramar M 50) or an organochlorine aldrin (Aldrin) on the survival, ovarian 32P-uptake and the gonadotrophic potency of the pituitary gland and blood serum in Heteropneustes fossilis were studied for 4 weeks. Aldrin was found to be more Paramar M 50. Reduced ovarian 32P uptake and a significantly decreased level of total gonadotrophin in the pituitary gland and blood serum were seen when fish were kept either in SC (safe concentration) or in LC(I)50 (a concentration that had been found to kill half the fish in 96 h) of Aldrin and Paramar M 50. The data suggest that those insecticides retarded gonadotrophin secretion which in turn reduced ovarian 32P uptake.
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The effect of 2/3 hepatectomy in the adult rat on the specific and total activities of two lysosomal endopeptidases, cathepsins B1 and D, has been examined. The specific activity of both enzymes fell rapidly following hepatectomy when compared to paired, sham-operated controls. When changes in total protein were compared to changes in cathepsins B1 and D, all three decreased in a parallel fashion for the first 18 h. At 24 h, total liver protein increased rapidly while cathepsins B1 and D continued to decrease. Cathepsin B1 fell to a level of 12% of non-operated control levels at 36 h, while total protein was already back to 40% of control levels. In contrast to the decreases in the activities of the cathepsins, there was an increase in the activities of lactate dehydrogenase and malate dehydrogenase during the first two days of regeneration. The clear lag in replacement of the cathepsins relative to other liver proteins following partial hepatectomy suggests that cathepsin activity is selectively controlled and that lowering the levels of cathepsins B1 and D may play an important role in the decreased degradation of protein seen during the early phases of liver regeneration.
Cerebrospinal fluid pressure (CSFP) by lumbar puncture, systemic blood pressure (BP) and pulse rate (PR) were measured for 15 minutes during the induction phase of general anaesthesia in seven groups of six healthy female patients each. Intravenous drugs, thiopentopne 5 mg . kg-1, alfathesin 50 microliters . kg-1 and diazepam 0.5 mg . kg-1 given in 10 to 20 seconds caused a fall of CSFP and BP, whereas ketamine 2 mg . kg-1 and a three-minute induction with halothane three per cent, trichloroethylene one per cent, or methoxyflurane 0.75 per cent caused a sharp highly significant but short-lived rise of CSFP. Unlike ketamine, trichlorethylene and methoxyflurane, halothane caused a simultaneous significant fall of BP. To rule out apprehension as the cause of the rise of CSFP with inhalation agents a second challenge was given with similar concentrations of the vapours while patients were asleep. These still produced a sharp and significant rise of CSFP.
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