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Biomedical subjects

B S Ramakrishna

Publications and source records attributed to B S Ramakrishna.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effect of shiga toxin on NaCl transport in rat distal colon.

BACKGROUND: Shiga toxin causes net fluid secretion in rabbit jejunum by selectively targeting, and inhibiting protein synthesis in, absorptive villous cells. The effect of Shiga toxin on the colon, where it is presumably produced, is not known. This study was undertaken to investigate the effect of Shiga toxin on the rat distal colon. METHODS: Net absorption of water and Na was determined by in vivo perfusion of closed loops of rat colon pre-exposed to Shiga toxin or saline. Unidirectional and net fluxes of 22Na and 36Cl were measured in vitro under voltage-clamp conditions across rat distal colon mucosa pre-exposed to Shiga toxin. Shiga toxin binding to sections of rat distal colon was localized by immunohistochemistry. Protein synthesis was measured in surface and crypt colonocytes with 3H-leucine incorporation. RESULTS: In the in vivo perfusion studies net absorption of Na and water was increased in Shiga toxin-treated colon compared with controls (P < 0.01). In the studies carried out in vitro, J(net)Na and J9net)Cl across Shiga toxin-treated mucosa were found to be significantly higher than in control tissue (P < 0.001 and P < 0.01, respectively). Net absorption of Na or Cl did not increase further in the presence of 25 mM butyrate, indicating the absence of short-chain fatty acids (SCFA)-linked NaCl absorption in Shiga toxin-treated colon. Moreover, Shiga toxin-treated colon failed to respond to theophylline, which induced secretion in the normal colon. Immunohistochemistry showed Shiga toxin binding to crypt cells but not to surface cells in the distal colon. Shiga toxin inhibited protein synthesis (by 27.3%) in crypt cells but not in surface cells (P < 0.05). CONCLUSIONS: An unexpected increase in water and NaCl absorption was noted in Shiga toxin-treated rat distal colon, which appears to result from selective effects of the toxin on secretory crypt cells.

Animals↗
PubMed1999

Response of wild-type mutants of Vibrio cholerae O1 possessing different combinations of virulence genes in the ligated rabbit ileal loop and in Ussing chambers: evidence for the presence of additional secretogen.

Five wild-type mutant strains of Vibrio cholerae serogroup O1 that lacked the CTX virulence cassette, or contained a natural deletion of a virulence gene within the CTX virulence cassette, or possessed an additional virulence gene, along with a prototype toxigenic strain representing the El Tor classical biotypes were examined by in-vivo and in-vitro methods to determine their enterotoxic potential. The ability of whole cells and culture supernates of the strains to cause fluid accumulation in the rabbit ileal loop model revealed a pattern consistent with the presence of the various virulence gene(s), with those possessing the intact CTX virulence cassette being the most secretogenic. Culture supernates of strains without the CTX virulence cassette or the strain with an incomplete cassette were also able to evoke mild to moderate fluid accumulation in the rabbit ileal loop. Of the various media used, AKI and brain heart infusion broth appeared to support the production of a hitherto unknown secretogenic factor, because culture supernates of the non-toxigenic V. cholerae O1 strains showed higher fluid accumulation ratios when grown in these media than in the others. To confirm that the fluid accumulation elicited by these strains in the ileal loop was due to enterotoxin activity, the effect of supernate of the strains was examined in rabbit small intestine mounted on Ussing chambers. Increases in short circuit current and tissue conductance, as compared with the medium control, were observed even with the strains that did not possess the CTX virulence cassette, confirming their ability to disrupt the function of intestinal tissue. From these studies, it was concluded that strains of V. cholerae O1 devoid of the CTX virulence cassette were still able to elicit a secretory response in the ileal loop and displayed enterotoxic activity in an in-vitro experimental model.

Animals↗
PubMed1999

Collagenous gastritis and collagenous colitis: a report with sequential histological and ultrastructural findings.

The case is reported of a young adult man with collagenous gastritis, an extremely rare disorder with only three case reports in the English literature, who subsequently presented with collagenous colitis. Sequential gastric biopsies showed a notable increase in thickness of the subepithelial collagen band. Ultrastructural study of gastric and rectal mucosa showed the characteristic subepithelial band composed of haphazardly arranged collagen fibres, prominent degranulating eosinophils, and activated pericryptal fibroblasts.

Adult↗
PubMed1999

Endoscopic mucosal biopsies are useful in distinguishing granulomatous colitis due to Crohn's disease from tuberculosis.

BACKGROUND: Intestinal tuberculosis and Crohn's disease are chronic granulomatous disorders that are difficult to differentiate histologically. AIMS: To characterise distinctive diagnostic features of tuberculosis and Crohn's disease in mucosal biopsy specimens obtained at colonoscopy. METHODS: Selected histological parameters were evaluated retrospectively in a total of 61 biopsy sites from 20 patients with tuberculosis and 112 biopsy sites from 20 patients with Crohn's disease. The patients were chosen on the basis of clinical history, colonoscopic findings, diagnostic histology, and response to treatment. RESULTS: The histological parameters characteristic of tuberculosis were multiple (mean number of granulomas per section: 5.35), large (mean widest diameter: 193 microm), confluent granulomas often with caseating necrosis. Other features were ulcers lined by conglomerate epithelioid histiocytes and disproportionate submucosal inflammation. The features characteristic of Crohn's disease were infrequent (mean number of granulomas per section: 0.75), small (mean widest diameter: 95 microm) granulomas, microgranulomas (defined as poorly organised collections of epithelioid histiocytes), focally enhanced colitis, and a high prevalence of chronic inflammation, even in endoscopically normal appearing areas. CONCLUSIONS: The type and frequency of granulomas, presence or absence of ulcers lined by epithelioid histiocytes and microgranulomas, and the distribution of chronic inflammation have been identified as histological parameters that can be used to differentiate tuberculosis and Crohn's disease in mucosal biopsy specimens obtained at colonoscopy.

Adult↗
PubMed1999

Enteric pathogens in southern Indian HIV-infected patients with & without diarrhoea.

This study was undertaken to determine the carriage rate of various enteric pathogens in southern Indian patients with HIV infection, both with and without diarrhoea. Stool from 111 consecutive HIV-positive patients (50 without and 61 with diarrhoea) was examined by microscopy and culture. Jejunal biopsy and fluid examination were carried out if diarrhoea persisted, with negative stool examination. Enteric pathogens were detected from stool in 57.4 per cent of diarrhoeal patients compared to 40 per cent of those without diarrhoea (P > 0.05). Jejunal biopsy and fluid examination provided 11 additional diagnoses. Protozoa accounted for 71.8 per cent of all pathogens isolated. Isospora was significantly more common in patients with (11/61) than in those without (2/50) diarrhoea (P < 0.05). Bacterial pathogens were isolated more commonly from patients with diarrhoea (12/61 compared to 2/50, P < 0.05). Isolation rate of pathogens was higher from patients with diarrhoea for more than 2 wk, compared to those with less than 2 wk duration. Remission of diarrhoea either spontaneously or with symptomatic therapy was observed in 22 patients with acute diarrhoea. A high enteric carriage of a number of pathogens was noted in HIV patients without diarrhoea, but I. belli and bacterial enteropathogens were more likely to be associated with diarrhoea.

Adult↗
PubMed1998

Characterization of non-membrane-damaging cytotoxin of non-toxigenic Vibrio cholerae O1 and its relevance to disease.

The non-membrane-damaging cytotoxin which causes dramatic cell rounding of cultured HeLa cells was purified to homogeneity from a clinical strain (WO5) of non-toxigenic Vibrio cholerae O1 Inaba belonging to the E1 Tor biotype. The purified protein has a denatured molecular weight of 35 kDa and a native molecular weight of approximately 37 kDa indicating the monomeric nature of the protein. The 15 N-terminal amino acid sequence of non-membrane-damaging cytotoxin showed complete homology to the hemagglutinin protease previously purified and characterized from V. cholerae O1. Purified non-membrane-damaging cytotoxin from V. cholerae O1 was immunologically and biochemically identical to that previously purified from V. cholerae O26. Non-membrane-damaging cytotoxin was found to be enterotoxic in rabbit ileal loop assay inducing accumulation of non-hemorrhagic fluid at 100 micrograms and elicited a concentration dependent increase in short circuit current and tissue conductance of rabbit ileal mucosa mounted on Ussing chambers. A significant serum immunoglobulin G response against non-membrane-damaging cytotoxin was elicited by patients infected with V. cholerae O139 but not with V. cholerae O1. These properties make non-membrane-damaging cytotoxin a potential virulence factor of V. cholerae which should be taken into consideration while making live, attenuated recombinant vaccine strains against cholera.

Animals↗
PubMed1998

The ability of enteric diarrhoeal pathogens to ferment starch to short-chain fatty acids in vitro.

BACKGROUND: Short-chain fatty acids (SCFA), produced in the normal colon by bacterial fermentation, are decreased in acute diarrhoea. This may have deleterious effects on epithelial function in the colon. METHODS: The ability of several diarrhoeal pathogens to produce SCFA when incubated with starch in vitro was studied. Isolated pathogens were incubated for 24 h with either no added substrate, glucose, or starch under anaerobic conditions, and SCFA were quantitated by gas-liquid chromatography. RESULTS: Unlike the normal colonic flora, the pathogens produced acetate but not propionate or butyrate. D-Lactate was also produced by all the pathogens studied. When the pathogens were incubated in anaerobic medium containing starch, significantly greater amounts of acetate and significantly lesser amounts of lactate were produced. CONCLUSIONS: The inability of enteric pathogens to produce butyrate may impair epithelial cell function, whereas production of D-lactate may enhance mucosal damage in diarrhoeal disease. The presence of luminal starch may be helpful in shifting the fermentation profile to a more favourable pattern.

Butyrates↗
PubMed1998

Mucosal mitochondrial function and antioxidant defences in patients with gastric carcinoma.

BACKGROUND: Cancer cells have alterations in energy metabolism due to defective mitochondrial function. This may be due to generation of excessive free radicals and/or defective antioxidant enzyme systems. The aim of the present study was to assess mitochondrial function and antioxidant defences in the gastric mucosa of patients with gastric carcinoma (CA). METHODS: Gastric mucosal mitochondrial function was assessed by means of the reduction of tetrazolium dye (MTT), and levels of antioxidants such as glutathione S-transferase (GST), catalase, superoxide dismutase (SOD), and thiols were measured in biopsy specimens taken from the tumour mucosa (TM) and tumour-free (TF) mucosa, 2 cm away from the tumour, in 49 patients with gastric CA and compared with that in 54 controls. In a further 10 patients with gastric CA, these studies were done on TM and TF mucosa 2 cm and > or = 5 cm away from the tumour. In 10 patients and 5 controls, specimens were obtained for electron microscopy as well. Helicobacter pylori infection was diagnosed by means of histology. RESULTS: MTT reduction and GST and SOD activities were significantly decreased in TM and TF mucosa in patients with CA compared with controls (P < 0.01). The levels of thiols and catalase activity were significantly increased in CA as compared with controls (P < 0.01). H. pylori positivity did not influence most of these variables but did give significant decrease in MTT reduction in CA (TF) mucosa (P=0.01) and significant increase in thiol levels in CA (TM) mucosa (P=0.04). Electron microscopy showed mitochondrial alterations in tumour cells in all patients and in adjacent mucosa of 10%-50% of the cells. CONCLUSIONS: 1) In gastric CA the cancer mucosal cells and the non-involved cells adjacent to the tumour have defective mitochondrial function, which may be due to altered antioxidant defences and possibly altered free radical formation. 2) Ultrastructural mitochondrial abnormalities are shown to parallel these biochemical abnormalities.

Adult↗
PubMed1998

Butyrate and glucose metabolism in isolated colonocytes in the developing rat colon.

BACKGROUND: The newborn colon is devoid of microflora, in that bacterial colonization is established after birth. Short chain fatty acids, products of bacterial fermentation, are the major energy source for colonocytes. Because it is not known whether colonocytes in the newborn can metabolize butyrate, this was examined in newborn and infant rat colon. METHODS: Isolated colonocytes from rats of different perinatal ages were incubated with 14C-labeled butyrate or glucose in vitro. Complete oxidation was estimated by the production of 14C-labeled carbon dioxide, whereas intermediate metabolites were measured enzymatically. RESULTS: Oxidation of butyrate (in micromoles per hour per milligram of protein) was highest in newborns (5.83+/-1.76), declining to 1.32+/-0.28 at day 10 and to 0.34+/-0.04 in adult rats. Glucose oxidation was also highest at birth (0.39+/-0.23), with a minor increase at approximately day 20 (weaning period) before decreasing to adult levels (0.05+/-0). Butyrate oxidation was substantially higher than was glucose oxidation in all age groups. Production of metabolic intermediates paralleled substrate oxidation. Acetoacetate production was 4.35+/-2.68, 2.07+/-1.29, and 0.27+/-0.09 nmol/hr per milligram of protein in newborns, at postnatal day 10, and in adults, respectively. The corresponding values for beta-hydroxybutyrate were 3.62+/-3.35, 0.2+/-0.07, and 0.09+/-0.03 nmol/hr per milligram of protein; and L-lactate production was 0.54+/-0.52, 0.06+/-0.04, and 0.02+/-0 micromol/hr per milligram of protein respectively. CONCLUSIONS: Neonatal rat colon epithelial cells resemble adult colonocytes in their preference for butyrate as a metabolic substrate, indicating a constitutive expression of this property.

3-Hydroxybutyric Acid↗
PubMed1998

Uncooked rice powder in oral rehydration solution: an alternative to glucose or cooked rice powder.

Glucose-based or rice-based ORS is the standard treatment in acute dehydrating diarrhoea. However, glucose may not be easily available in remote villages and the rice needs to be cooked for rice-based ORS. We embarked on a study to examine whether uncooked rice powder could be used as an alternative to glucose or cooked rice powder in ORS. Initially, 50 adult male patients (aged 18 to 55 yr) were randomized to receive glucose-ORS or uncooked rice ORS, in two equal groups. Subsequently, 20 male children (aged 3 to 12 yr) were also enrolled in the study and received either WHO-ORS or study ORS. All the adult patients and the children could be successfully rehydrated with ORS containing uncooked rice powder. As compared to WHO-ORS, the study ORS significantly reduced stool output (6.60 +/- 1.24 vs. 5.88 +/- 1.34 l), ORS intake (9.17 +/- 1.54 vs 8.24 +/- 1.69 l) and duration of diarrhoea (45.68 +/- 6.91 vs 41.32 +/- 6.03 h). In children also similar results were obtained. No clinical complication (e.g., vomiting, abdominal pain etc.) or abnormality in serum electrolyte concentrations was encountered either in the adults or in the children. Uncooked rice powder containing ORS can be considered as an alternative to glucose-based ORS or rice-based ORS.

Adolescent↗
PubMed1998

Immunoproliferative small intestinal disease in South India: a clinical and immunomorphological study.

Immunoproliferative small intestinal disease (IPSID), a proliferative disorder affecting the intestinal immune system, has only been reported sporadically in India. Fifteen patients with malabsorption syndrome who were diagnosed to have IPSID were included in this study. Mucosal biopsies from all patients, full thickness surgical biopsies from 10 and autopsy material from four patients were examined by light microscopy and immunohistochemistry. The patients were predominantly young (aged 16-36 years) and male (13 of 15). Diarrhoea, weight loss, vomiting and abdominal pain were the major symptoms. The upper small bowel was involved in all cases. Involvement of large bowel was detected antemortem in three patients, but was found in all autopsied patients. Involvement of the stomach was noted in one patient at autopsy. Mesenteric lymph nodes were involved in all patients who underwent laparotomy. The plasmacytic infiltrate was uniformly positive for alpha-heavy chain, and either negative for light chain production or showed monotypic light chain production. Some of the blasts were also positive for alpha-heavy chain. Three patients died before therapy could be commenced. One patient with stage A disease is alive and clinically free of disease at 7 years. Of the remainder, there have been four long-term survivors with chemotherapy. Immunoproliferative small intestinal disease occurs in southern India and has characteristics similar to that in other parts of the world. Early diagnosis may improve outcome in this disease.

Adolescent↗
PubMed1997

Circulating antioxidants in ulcerative colitis and their relationship to disease severity and activity.

Oxygen free radicals produced by neutrophils are important in the pathogenesis of mucosal damage in ulcerative colitis. Vitamin A, vitamin E and cysteine in the plasma can scavenge free radicals. In the present study, plasma levels of vitamin A, vitamin E, cysteine, cystine and protein-bound cysteine were measured in active ulcerative colitis before and immediately after treatment of the active disease, and correlated with disease severity, extent and activity. Plasma vitamin A and cysteine were significantly reduced in active ulcerative colitis compared with controls. Levels of vitamin E, cystine and protein-bound cysteine were not significantly altered in active ulcerative colitis. Vitamin A and cysteine concentrations returned to normal levels (P < 0.05) within 2 weeks of treating active colitis. There were significant negative correlations between clinical severity and the plasma concentrations of vitamin A and cysteine. Plasma cysteine levels also correlated inversely to disease extent. Depletion of the circulating antioxidants, vitamin A and cysteine, in active ulcerative colitis is likely to be important in the pathophysiology of the disease.

Adolescent↗
PubMed1997

An epidemic of diarrhoea in south India caused by enteroaggregative Escherichia coli.

A diarrhoeal epidemic in a village close to Vellore was investigated in January 1996. Faecal samples were obtained from 20 subjects with diarrhoea and from 11 individuals without diarrhoea (controls) and were examined for bacterial, viral and parasitic enteropathogens. Water samples from all sources in the village were analysed. The epidemic affected all age groups (overall attack rate 15%). The mean duration of diarrhoea was 11 days. Individuals who consumed water exclusively from a borewell had a lower relative risk (RR) of disease (0.14, 95% Cl 0.02-1.01) compared to users of two open wells (RR 6.93, Cl 0.99-48.66 and RR 7.81, Cl 1.02-59.79, respectively). No conventional bacterial enteropathogens were isolated from the stool samples. Enteroaggregative Escherichia coli (EAggEC) were identified in the stool of 11 of 20 subjects with diarrhoea, and in 1 of 11 control samples (P = 0.02). All the EAggEC isolates from the patients had identical antibiotic sensitivity patterns and produced a toxin in Ussing chamber studies. Serotyping indicated that all the EAggEC from individuals with diarrhoea belonged to one or other of two serotypes. All water samples had high coliform counts and E. coli were cultured from the two open wells but not from the borewell. The evidence suggests that EAggEC was responsible for this outbreak of diarrhoea. EAggEC should be considered as a possible pathogen in unexplained diarrhoeal outbreaks in developing countries.

Adolescent↗
PubMed1997

Gastrointestinal problems in the elderly.

Improvements in nutrition and health care have led to increased life expectancy in our country, which occasioned this review of gastrointestinal problems in the elderly. Some gastrointestinal symptoms may be secondary to age-related physiological changes (e.g., presbyoesophagus). Certain diseases (e.g., diverticulosis) may be more common in the elderly. On the other hand, the elderly may have unusual presentations of common diseases (e.g., complicated peptic ulcer disease). Each of these types of problems has been detailed in this review. Included is a preliminary analysis of hospitalised elderly patients which illuminates serious gastrointestinal problems afflicting the elderly in India.

Aged↗
PubMed1997

An outbreak of food poisoning in Tamil Nadu associated with Yersinia enterocolitica.

An outbreak of food poisoning in a Tamil Nadu village, affecting 25 of 48 individuals who participated in a feast, was investigated. The risk of developing illness was associated with consumption of buttermilk (relative risk 3.8). None of the food items consumed during the feast was available for analysis. Toxin-producing Y. enterocolitica (serotype 3, biotype 4) was grown from 1 of 11 stool samples from affected individuals, as well as from a water sample from the source used to dilute the buttermilk. High titres of antibody of Yersinia were detected in 2 of 12 patients but in neither of the two groups of controls. Toxin production was noted in buttermilk incubated for 6 h with Y. enterocolitica. This is the first report from India of a food poisoning outbreak associated with this organism.

Adolescent↗