Biomedical subjects

M Mathan

Publications and source records attributed to M Mathan.

At least 19 recordsLinked to original sources

PubMed2001

Epidemiological and laboratory investigations of outbreaks of diarrhoea in rural South India: implications for control of disease.

Two epidemics of acute, watery diarrhoea in villages in North Arcot district, India, were investigated. The attack rates were 10.03 and 15.53 per 100 population, the median duration was 5 days and enteric pathogens were present in 56.8% and 60.3% of specimens from the two villages, but no predominant pathogen was identified. Examination of stools from a 20% age-stratified random sample of the population of one of the villages after the epidemic found 22.9% of asymptomatic subjects excreted bacterial enteric pathogens. Despite the high background of enteric pathogen carriage, the isolation rates for shigellae, enteropathogenic Escherichia coli and Shiga-toxin producing E. coli were significantly higher (P < 0.001, P < 0.02, P < 0.05) during the epidemic. The epidemics may have been caused by faecal contamination of well water following rain. Point-of-use techniques for water disinfection may be most effective for preventing such outbreaks, but further research into the development of appropriate technology is required.

Adolescent↗

PubMed2000

Butyrate and glucose metabolism by colonocytes in experimental colitis in mice.

BACKGROUND/AIMS: Impaired colonocyte metabolism of butyrate has been implicated in the aetiopathogenesis of ulcerative colitis. Colonocyte butyrate metabolism was investigated in experimental colitis in mice. METHODS: Colitis was induced in Swiss outbred white mice by oral administration of 4% dextran sulphate sodium (DSS). Colonocytes isolated from colitic and normal control mice were incubated with [(14)C]butyrate or glucose, and production of (14)CO(2), as well as of intermediate metabolites (acetoacetate, beta-hydroxybutyrate and lactate), was measured. The effect of different substrate concentrations on oxidation was also examined. RESULTS: Butyrate oxidation (micromol/h per mg protein; mean (SEM)) was significantly reduced in DSS colitis, values on day 7 of DSS administration being 0.177 (0.007) compared with 0.406 (0.035) for control animals (p<0.001). Glucose oxidation (micromol/h per mg protein; mean (SEM)) on day 7 of DSS administration was significantly higher than in controls (0.06 (0.006) v 0.027 (0.004), p<0.001). Production of beta-hydroxybutyrate was decreased and production of lactate increased in DSS colitis compared with controls. Increasing butyrate concentration from 10 to 80 mM enhanced oxidation in DSS colitis (0.036 (0.002) to 0.285 (0.040), p<0.001), although it continued to remain lower than in controls. Surface and crypt epithelial cells showed similar ratios of butyrate to glucose oxidation. When 1 mM DSS was added to normal colonocytes in vitro, it did not alter butyrate oxidation. The initial histological lesion of DSS administration was very patchy and involved crypt cells. Abnormal butyrate oxidation became apparent only after six days of DSS administration, at which time histological abnormalities were more widespread. CONCLUSIONS: Colonocyte metabolism of butyrate, but not of glucose, is impaired in DSS colitis, and may be important in pathophysiology. Histological abnormalities preceded measurable defects in butyrate oxidation.

Animals↗

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↗

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

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

Light and electron microscopic findings in rhinosporidiosis after dapsone therapy.

Morphological findings in serial nasal mucosal biopsies from three cases of rhinosporidiosis on dapsone therapy were compared with biopsies from 33 patients taken before dapsone or surgical treatment was initiated. All biopsies were examined by light microscopy and five by electron microscopy. Counts of histologically intact and degenerated organisms showed a decreasing proportion of intact forms with treatment.

Dapsone↗

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↗

PubMed1996

Isolation of Vibrio cholerae O139 from the drinking water supply during an epidemic of cholera.

In mid-1994, the public water supply was investigated in a medium-sized town in south India during an epidemic of cholera due to Vibrio cholerae O139. Vibrio cholerae O139 was isolated from the public water supply including one of the wells supplying the town, the central overhead tank, and domestic taps connected to the public supply. Following chlorination, the organism was no longer isolated from the water supply and the epidemic subsided. This demonstration of V. cholerae O139 in the drinking water supply of a town underlines the need for adequate treatment of the water supply.

Adolescent↗

PubMed1994

Alteration of colonic absorption by long-chain unsaturated fatty acids. Influence of hydroxylation and degree of unsaturation.

Unabsorbed dietary unsaturated fatty acids may cause diarrhea in patients with steatorrhea, but their ability to cause colonic fluid secretion is not known. The present study investigated the effect of several dietary long-chain unsaturated fatty acids on colonic absorption and morphology in the rat colon in vivo. The fatty acids tested induced concentration-dependent net water secretion. The ability of these fatty acids to induce net water secretion varied as follows: linolenic acid (18:3) > linoleic acid (18:2), ricinoleic acid (18:1 OH) > oleic acid (18:1), palmitoleic acid (16:1). Net absorption of sodium and chloride were decreased in fatty acid perfusions. Mucosal activity of sodium potassium adenosine triphosphate and adenyl cyclase were not significantly altered by fatty acids. Epithelial cell damage was noted and correlated with the ability of the fatty acid to induce fluid secretion. Unsaturated fatty acids induce epithelial cell damage and fluid secretion in the colon, their effect being related to the degree of unsaturation.

Adenylyl Cyclases↗

PubMed1993

Medical therapy of rhinosporidiosis with dapsone.

Clinical, histopathological and ultrastructural studies in three cases of rhinosporidiosis show complete remission of infection within one year of therapy with dapsone. Light and electron microscope studies confirmed arrest of the maturation of the spores and accentuated granulomatous response with fibrosis following dapsone therapy.

Administration, Oral↗

PubMed1992

Colonoscopic study of 50 patients with colonic tuberculosis.

Fifty patients with colonic tuberculosis are reported in whom a colonoscopic diagnosis confirmed by histological examination was possible in 40. Bacteriological studies did not increase the diagnostic yield. Abdominal pain was the most common symptom (90%) and an abdominal mass the most common abnormal physical finding (58%). A nodular mucosa with areas of ulceration was the usual colonoscopic finding. Ileocaecal disease was found in 16, ileocaecal and contiguous ascending colon disease in 14, segmental colonic tuberculosis in 13, ileocaecal disease and non-confluent involvement of another part of the colon in five, and pancolitis in two patients. This report emphasises that colonoscopy is a useful procedure for diagnosing colonic tuberculosis and that segmental colonic tuberculosis is not uncommon.

Biopsy↗

PubMed1991

Melanosis of the esophagus. An endoscopic, histochemical, and ultrastructural study.

Endoscopic, histological, and ultrastructural features of 21 cases of esophageal melanosis are described. These cases were detected during 1000 consecutive routine upper gastrointestinal endoscopies. Staining characteristics and ultrastructure of the pigment contained in the endoscopically visible lesions were found to be similar to those of true melanin.

Adult↗

PubMed1987

The morphogenesis of the human Paneth cell. An immunocytochemical ultrastructural study.

In human duodenal mucosa Paneth cells originate away from the base of crypts and migrate towards the base during maturation. The earliest cells in the Paneth cell lineage could be identified by labelling of lysozyme in the Golgi apparatus. Specific labelling for lysozyme was present in the rough endoplasmic reticulum, Golgi apparatus, condensing vacuoles, granules and many lysosomes of mature Paneth cells. The maturation of the Paneth cell is accompanied by an increase in the content of lysozyme in the secretory granules and with senescence lysozyme diffuses into the cytoplasm.

Cell Differentiation↗

PubMed1987

Aetiology and clinical features of acute childhood diarrhoea in an outpatient clinic in Vellore, India.

The aetiology of acute diarrhoea was investigated in 245 children less than 3 years old in a paediatric outpatient clinic in southern India. In 55% of the children organisms were found in the stools, and one quarter were infected with multiple organisms. Viruses, enteropathogenic E. coli, shigella and campylobacter species accounted for 75% of all isolates. Cholera and helminthiasis were rare, and no child had amoebiasis. Clinical findings were useful in the diagnosis of shigella and rotavirus infection only. Children with shigellosis had classical dysentery, and a greater number of stools; they were unlikely to be breast-fed, to be less than 6 months old, or to have watery stools. Rotavirus infections were characterized by vomiting. Only 20% of the 245 children had an infection which could be treated effectively with antimicrobials.

Campylobacter Infections↗

PubMed1985

Transitional diarrhoea in newborn infants.

A self-limited acute fluid diarrhoea was seen in 80 of 3550 (2.2%) live-born infants not kept in a nursery in this hospital. Rotavirus and enteropathogenic serotypes of E. coli were detected with equal frequency with and without diarrhoea. It is suggested that this self-limited episode of diarrhoea occurring soon after birth is not necessarily due to rotavirus infection but could also be due to failure of adaptation to enteral feeding and microbial colonization during this transitional period.

Breast Feeding↗

PubMed1985

A correlative study of etiology, clinical features and rectal mucosal pathology in adults with acute infectious diarrhea in southern India.

For detailed etiological studies we isolated invasive enteric bacterial pathogens in 16, non-invasive pathogens in 13 and no pathogens in 11 of 40 adults with untreated acute diarrhea of less than 5 days duration at a tertiary care hospital in southern India. It was possible to establish a system for the objective assessment of the clinical severity of illness. Hemorrhage in the rectal mucosal lamina propria. especially pericryptal, was a striking feature in rectal biopsies. This was associated with a vascular lesion with endothelial damage. The prevalence of the vascular lesion did not correlate with the etiological agents or the severity of the histological abnormality in the rectal mucosa. However, there was a good correlation between the presence of vascular abnormalities and clinical severity. While the vascular changes could be the result of non-specific trauma to the rectal mucosa due to diarrhea, it is suggested that they may have an as yet unknown role in determining clinical severity.

Adult↗

PubMed1984

Isolation and identification of enteroviruses from faecal samples in a differentiated epithelial cell line (HRT-18) derived from human rectal carcinoma.

A human rectal carcinoma-derived differentiated epithelial cell line, HRT-18, was inoculated with faecal samples in an attempt to grow coronavirus-like particles (CVLP), which are widely prevalent in human stools in southern India. While CVLP did not grow in this cell line, a variety of enteroviruses were isolated from 48 of the 114 stool samples from healthy controls and patients with diarrhoea. The results suggest that human gastrointestinal tumour-derived differentiated epithelial cells in continuous culture may be useful for the primary isolation of enteroviruses and merit further study.

Adult↗

PubMed1983

Studies of intestinal lymphoid tissue. VII. The secondary nature of lymphoid cell "activation" in the jejunal lesion of tropical sprue.

Morphometric techniques were used in the evaluation of lymphocyte morphology and activity in tropical sprue. jejunal biopsies from control subjects (8), patients with epidemic disease (7), patients with endemic disease (11), and subjects who had recovered from sprue (4) were analyzed blindly. In patients with sprue, lymphocytes were increased significantly within crypt (but not surface) epithelium. Immunoblasts (greater than 6 mu in diameter) were increased by 5% over control subjects. Group means for lymphocytic mitotic indexes were also significantly raised, while flux ratios only differed significantly between endemic sprue patients and control subjects. The lymphocytic infiltration was distributed focally in the upper crypt and crypt-villus interzones. Analysis of epidemic cases (presenting within 4-28 days) revealed detectable changes in lymphocyte behavior only after 3 weeks' illness, whereas mucosal lesions and malabsorption were already established during the first week. These data indicate that lymphocyte activation, suggestive of a local cell-mediated immune reaction, does occur in tropical sprue but is secondary to damage already inflicted on enterocytes and their function.

Adult↗