Biomedical subjects
Publications and source records attributed to R Krishnan.
A simple method is described for labelling cells with fluorescein and using them in artificial mixtures to assess cell separation procedures. The method facilitates the examination of the variables in a separation procedure. It is thus possible to tailor a separation procedure (for example panning with monoclonal antibody) to suit the specific requirements of the experiment.
The pattern and frequency of neurovegetative symptoms was studied in 57 patients with chronic pain. Seventy-nine percent of these patients had a diagnosable depressive illness, but endogenous depression was rare (5%). Patients with chronic pain were divided into major depressives, minor/intermittent depressives and patients with no depression. A control group of nonendogenous major depressives without pain was also utilized. Major depressives differed from the other two chronic pain groups in that there was more frequent or severe early waking, weight loss, anorexia, diminished libido and initial insomnia. Diurnal variation of mood was not a characteristic of major depression with chronic pain, and did not differ in frequency from the other two chronic pain groups. Major depressives exhibited a profile of neurovegetative symptoms very similar to that found in the control group of major depressives. Over one-third of minor/intermittent depressed patients with chronic pain exhibited atypical (reversed) vegetative symptoms of hyperphagia and weight gain. This finding, together with our review of the literature, suggests an important and previously unrecognized link between atypical depression and chronic pain.
The authors evaluated four sets of diagnostic criteria, the Newcastle Index, DSM-III, RDC, and the Michigan Diagnostic Index, for the diagnosis of melancholia. Forty-nine depressed inpatients, all of whom met RDC for major depression, also received consensus diagnostic assessment for melancholia. The dexamethasone suppression test (DST) was administered before drug treatment began. Results showed that the sensitivity of the DST ranged from 39% to 48%, specificity from 80% to 100%, and diagnostic confidence from 66% to 100%. All four scales received validation, but DSM-III showed the lowest specificity and predictive value.
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Anniversary reactions as precipitants of manic episodes are reported to be relatively common, while manic onset within a week of bereavement ("funeral mania") has been considered rare. Three cases of funeral mania are described to illustrate that this phenomenon may be more frequent than has been thought.
The immunogenic efficacy of inactivated (Salk) poliovirus vaccine (IPV) was evaluated in infants in India, in view of the high frequency of vaccine failure after immunization with oral (Sabin) poliovirus vaccine (OPV). A total of 150 infants, aged 6-45 weeks, were given 3 doses of IPV, with intervals of 4 or 8 weeks between doses. The effect on the antibody response of child's age, presence of maternal antibody before immunization, and interval between doses was assessed. The overall seroconversion rates to poliovirus types 1, 2, and 3 were 99%, 89%, and 91%, respectively. Seroconversion rates to types 2 and 3, and antibody titres to types 1 and 2, were higher (i) in infants given vaccine doses at 8-week intervals and (ii) in those without detectable maternal antibody. The seroconversion rates in infants without maternal antibody, who were given IPV at 8-week intervals, were 100%, 100%, and 96.2% to poliovirus types 1, 2, and 3, respectively. Thus the immunogenic efficacy of IPV was found to be satisfactory.
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A young female patient had juvenile laryngotracheobronchial papillomatosis. Metastasizing squamous cell carcinoma developed in this patient without any prior irradiation. The case is extremely unusual and exhibits multifocal in situ and microinvasive changes in the bronchial papillomas.
The changes induced by dietary xylitol in the gastrointestinal tract of the rat were investigated in relation to the phenomenon of vitamin-sparing. Within 18 days of consuming a synthetic diet, deficient in thiamin, riboflavin and pyridoxine, rats ceased to grow and began to lose weight rapidly. If xylitol was then included in the diet (10% w/w), the effect of the vitamin-deficient diet on growth was reversed. Moreover, within 3 days of the rats ingesting xylitol, the metabolism of this sugar polyol by the caecal microflora was increased 17-fold and the caecal concentrations of thiamin and thiamin pyrophosphate were increased 5-fold. Increases were also observed in the caecal size, the weight of the caecal contents, and the weight of the caecal wall. In contrast to the rapid changes observed within the caecum, liver thiamin pyrophosphate levels did not rise until 6-12 days after the feeding of xylitol, at which time the rats had begun to gain weight. The caecal contents were shown to contain facultative bacteria which have the ability to metabolise and grow on xylitol and which can, at the same time, synthesise thiamin. Species of the genera Klebsiella, Serratia and Micrococcus which have this ability were isolated from the caecal contents of rats. It is assumed that coprophagy is the means by which the thiamin and other vitamins synthesised by enteral bacteria become available to the host, although some absorption from the caecum cannot be excluded.
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The effects of simultaneous administration of thiamine, niacin or vitamin B12 with vitamin E on plasma vitamin E levels were studied in 20 adult male volunteers belonging to the low socio-economic class. The effect of vitamin E on the nutritional status of pyridoxine, riboflavin and thiamine as judged by the erythrocyte enzymes, aspartate aminotransferase, glutathione reductase and transketolase, respectively was also studied. None of the members of the B-complex vitamins studied here had any effect on plasma vitamin E levels. This was in contrast to the observation made earlier that pyridoxine and riboflavin can reduce plasma vitamin E. There was a transient reduction in both the basal and stimulated activities of erythrocyte aspartate aminotransferase, the significance of which needs further investigation.
The mechanism of adaptation to dietary carbohydrates was investigated by examining cellular metabolism in the liver and gut lumen. The inclusion of 10% (w/w) glucose, fructose, sucrose, xylose, sorbitol, xylitol or arabitol in the diet of rats for 7 days had essentially no effect on the ability of liver homogenates to produce 14CO2 from labelled glucose, fructose, xylose, sorbitol or xylitol. Moreover, no major changes were observed in the activities of hepatic enzymes. In these studies, diarrhoea and caecal distension were only observed in those rats receiving dietary sugar alcohols. Rats were also fed 0, 2.5, 5, 10, and 20% (w/w) xylitol in their diets for periods ranging from 1 to 14 days. These diets caused no significant changes in 16 of the commonly assessed blood parameters which included liver function tests. Xylitol feeding, however, caused distension, caecal gas production, decreases in the pH of caecal contents, the appearance of a fluffy layer in the centrifuged specimens of caecal contents, and diarrhoea. These changes were directly related to the concentration of xylitol in the caecal contents. After various periods, and depending on the concentration of xylitol in the diet, the rats underwent an adaptation which reduced the incidence of diarrhoea. In the short term, dietary xylitol does not affect the function of the liver or the gut wall, but causes an adaptation within the gut microflora. This adaptation leads to the increased ability of gut microflora to utilise xylitol, followed by a subsequent reduction in the caecal osmotic load and diarrhoea.
The effect of dietary xylitol on the ability of the rat caecal flora to metabolise xylitol was investigated. Xylitol metabolism in micro-organisms has generally been assessed in terms of pH change and acid production which are often insensitive in demonstrating low rates of substrate utilisation. Using a rapid and sensitive radioisotopic assay, in which 14CO2 production from [U-14C] xylitol was measured, it was possible to show that the caecal microflora obtained from rats can metabolise xylitol. This activity was increased 10, 15, 30 and 40-fold in the caecal flora taken from rats fed diets containing 2.5,5,10 and 20% xylitol, respectively. Using the caecal microflora of normally fed rats, the order of 14CO2 production from 14C-labelled sugars and sugar alcohols was glucose greater than fructose greater than xylose greater than sorbitol greater than or equal to xylitol. The feeding of glucose and fructose did not alter the 14CO2 producing activities, whereas xylose feeding increased xylose metabolism, sorbitol feeding increased sorbitol and xylitol metabolism, xylitol feeding increased sorbitol, xylose and its own metabolism and arabitol feeding increased xylose and sorbitol metabolism. Marked changes were also observed in the population of the caecal flora of xylitol-fed rats, with increases in the number of gram-positive bacteria, compared to rats on a normal diet. Possible mechanisms for these effects involve mutation, selection of micro-organisms capable of metabolising sugar alcohols, and the induction of enzymes involved in sugar alcohol metabolism.
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The tridentate pedicellaria of Salmacis bicolor consists of calcareous head and stalk, connected by a muscular neck regions. Head, neck and stalk are covered by a thin cuticle, which is non-mineralized and soft. Both the cuticle and the organic fraction of the calcareous region are resistant to acids and alkalis. Histochemical studies reveal that both the cuticle and the organic matrix of the calcified head and stalk contain protein, polysaccharide and lipids. The lipid content of the organic fraction of the mineralized matrix recalls the spicules of Pluteus larva reported in an earlier study. The protein component of the cuticle and that of the organic matrix slightly differ in that the former is rich in aromatic amino acids, namely tyrosine and tryptophane. Both cuticle protein and the protein of the organic matrix lack sulphur containing aminoacids. Another feature of similarity between the cuticle and the organic matrix is that both contain acid mucopolysaccharide and neutral mucopolysaccharide components. The role of acid mucopolysaccharide in calcification is discussed. The neutral mucopolysaccharide has been suggested to be similar to chitin, and its significance is discussed. Unlike the skeletal elements of other invertebrates, the cuticle and the organic matrix of pedicellariae are devoid of any phenolic compounds.
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