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S K Nath

Publications and source records attributed to S K Nath.

At least 37 records · Page 2Linked to original sources
PubMed1994

A sustained outbreak of Clostridium difficile in a general hospital: persistence of a toxigenic clone in four units.

OBJECTIVE: To evaluate the endemicity and epidemiology of toxigenic Clostridium difficile in a sustained outbreak of antibiotic-associated diarrhea. SETTING: University-affiliated, 465-bed tertiary care teaching hospital with adjacent cancer clinic in Hamilton, Ontario. DESIGN: From August 8, 1991, through August 31, 1993, a total of 187 cases were investigated for epidemiologic analysis of toxigenic C difficile from stool cultures, to identify the endemic clone(s). To assess the nature of contamination, cultures of inanimate surfaces in the patient environment from the four most affected units (medical teaching, nonteaching medical, hematologic oncology, and the intensive care unit) were processed for C difficile. The 229 clinical strains and 24 environmental strains isolated were typed by numerical analysis of SDS-PAGE protein patterns. RESULTS: A majority (81%) of cases in the epidemiologic analysis were associated with a toxigenic electrophoretic (EP) type 1 C difficile that was identical to the strain first isolated from an index case that occurred 18 months before the start of this study. Culture and typing of the C difficile strains from the inanimate surfaces in the four most affected units showed that the patient environment was contaminated with the toxigenic EP type 1 organism. Six other strains that occurred infrequently among cases also were found in the environment. CONCLUSIONS: A single predominant toxigenic clone has been implicated in a sustained outbreak of antibiotic-associated diarrhea that affected elderly patients. The "endemic" clone transmitted for the 25-month study period was linked to an index case shedding a toxigenic EP type 1 strain that occurred 21 months prior to the initial outbreak on the medical teaching unit. The patient environment in the affected units was found to be contaminated with the same clone, possibly due to shedding of organisms by fecally incontinent symptomatic patients. The extrinsic factors contributing to the endemic transmission of this one clone still are not well understood.

Bacterial Typing Techniques↗
PubMed1994

Investigation of an outbreak of Clostridium difficile infection in a general hospital by numerical analysis of protein patterns by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

One hundred forty-five cultures of Clostridium difficile, including strains from an apparent nosocomial outbreak of infection, were characterized by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins. Each protein pattern was characterized by the presence of one to three dense bands which were highly reproducible. The first 100 strains (in chronological order) were used as the basis for a numerical analysis which divided the strains into 17 phenons (EP types 1 to 17). The protein patterns of the remaining 45 strains were identified to type by comparing their individual patterns against a data base made up of the protein patterns of the first 100 strains. EP type 1 was the most common, with 70 of 139 (50%) patient isolates having this pattern type, and it accounted for 26 of 35 strains (74%) from patients in a medical teaching ward from which the outbreak was believed to have originated. This type was also found as a high proportion of isolations in a number of other medical and oncology wards, but the majority of these isolates occurred subsequent to the isolations on the initial outbreak ward. This technique can therefore provide a method for tracing the possible spread of epidemic strains in hospitals and other institutions and may contribute to a better understanding of the epidemiology of C. difficile.

Adolescent↗
PubMed1994

Relation between chloride secretion and intracellular cyclic adenosine monophosphate in a cloned human intestinal cell line HT-29 cl 19A.

The relation between the intracellular cyclic adenosine monophosphate (cAMP) content and the electrogenic chloride secretion induced by cholera toxin was studied in secretory HT-29 cl 19A cell monolayers. Cells were treated by the mucosal addition of cholera toxin (5 micrograms/ml) for 10, 45, or 90 minutes in Ussing chambers. After 10 minutes, the mean (SEM) intracellular cAMP content (3.2 (0.2) pmol/mg protein) and short circuit current (Isc) (1.9 (0.3) microA.cm-2) did not differ significantly from the corresponding basal values. At 45 minutes, a significant increase in the Isc (22.2 (5.7) microA.cm-2) was accompanied by a significant elevation in cAMP (10(1.7) pmol/mgh protein). At 90 minutes, when the stimulated Isc plateaued (35.2 (5.2) microA.cm-2), the cAMP value (99.2 (23.8) pmol/mg protein) increased further. The protein kinase C (PKC) activity of the cells was not affected by cholera toxin. Treatment of cell monolayers by different concentrations of DbcAMP (10(5), 5 x 10(-5), 10(-3) M) showed that the minimal concentration of DbcAMP (serosal) which significantly increased the Isc (delta 4.5 microA.cm-2) was 10(-4) M, and that this was accompanied by an increase in cAMP of delta 6.7 pmol/mg protein: Compared with DbcAMP, cholera toxin stimulated the Isc (at 45 minutes) to a much higher degree with a comparable elevation of cAMP. It is concluded that in cl 19A cells there is a threshold value of increase in intracellular cAMP that induces chloride secretion. Cholera toxin stimulated chloride secretion can be explained predominantly by an increase in intracellular cAMP that is unrelated to PKC activity.

Bucladesine↗
PubMed1994

Genetic epidemiology of vitiligo: multilocus recessivity cross-validated.

Vitiligo is a dermatological disorder characterized by hypopigmentary patches that tend to become progressive over time. There are reports of extensive familial aggregation. A genetic model for this disorder was earlier proposed by us. This model postulates that recessive alleles at multiple unlinked autosomal loci interact epistatically in the pathogenesis of vitiligo. The present family study was primarily undertaken to cross-validate the proposed genetic model. Data on 194 families from the United States were collected. Each family was ascertained through an affected proband. Analyses of these data reveal that approximately 20% of probands have at least one first-degree relative afflicted with vitiligo. All types of first-degree relatives of probands show a significant risk of developing vitiligo. Results of segregation and robustness analyses reveal that the genetic model postulated by us previously is the most parsimonious model for the present family data set.

Adolescent↗
PubMed1993

Leu143 in the putative fourth membrane spanning domain is critical for amiloride inhibition of an epithelial Na+/H+ exchanger isoform (NHE-2).

A family of Na+/H+ exchanger isoforms (called NHE1, NHE2, and NHE3) which exhibits a wide range of amiloride sensitivity has recently been cloned and characterized. A part of the domain, which determines amiloride sensitivity in the epithelial Na+/H+ exchanger isoform, NHE2, was identified by site-directed mutagenesis and functional studies using cDNAs stably expressed in a fibroblast cell line. It has previously been reported that AR300, an amiloride resistant mutant of the ubiquitous Na+/H+ exchanger isoform, NHE1, is 30-fold more resistant to methylpropyl amiloride (MPA) compared to NHE1 and contains a single amino acid substitution of L167F in the fourth putative transmembrane helix, which corresponds to L143 in NHE2. Therefore, in the present study point mutational substitutions were introduced into the equivalent of this fourth transmembrane helix of rabbit NHE2 (including Y144F; L143F; L143F and Y144F) to mimic the corresponding amino acids in NHE1, NHE3 (another epithelial isoform) and AR300, respectively. NHE2/L143F (mimicking NHE3) increased the IC50 for amiloride by 5-fold and for ethylisopropyl amiloride (EIPA) by 20-fold. Similarly, NHE2/L143F and Y144F (mimicking AR300) increased the resistance to both amiloride and EIPA by 10-fold. On the other hand, NHE2/Y144F (mimicking NHE1) did not affect the sensitivity to amiloride or EIPA, and this mutant, like wild type NHE2, is partially resistant to EIPA. Thus, amino acid 143 of NHE2 is critical for, but is not the only amino acid responsible for, amiloride and EIPA inhibition of Na+/H+ exchange. That none of the mutations studied altered the Na+ affinity of these Na+/H+ exchangers further suggests that amiloride binding and Na+ transport sites are not identical.

Amiloride↗
PubMed1993

Pattern of familial aggregation of vitiligo.

BACKGROUND AND DESIGN: Vitiligo is a disorder whose cause is not well understood. This study was undertaken to clarify whether genetic factors are involved in the pathogenesis of vitiligo. Data on 160 white kindreds living in the United States have been collected. Each family was ascertained through a proband afflicted with vitiligo. The nature and extent of familial aggregation and other relevant epidemiologic features have been determined. RESULTS: The mean age at onset of vitiligo is about 19 years in male and about 24 years in female individuals. The percentage of probands reporting one or more first-degree relatives also afflicted with vitiligo is 20%. Children of probands are found to be afflicted about 1.7 times more commonly than other first-degree relatives. The relative risk (RR) for vitiligo is about 7 for parents, about 12 for siblings, and about 36 for children. For second-degree relatives, the RR varies between 1 and 16. Relative risks for all first- and second-degree relatives, except uncles and grandsons, are significant at the 5% level. In families in which one or more relatives of the proband are afflicted with vitiligo, the intrafamilial correlation of ages at onset of vitiligo is moderate (0.6). No statistically significant effect (at the 5% level) of parental age at first childbirth was seen on the proportion of offspring afflicted with vitiligo. No significant association of some commonly related diseases (eg, thyroid disorder or alopecia areata) was observed with vitiligo or with a family history of vitiligo. CONCLUSIONS: The extent of familial aggregation of vitiligo is statistically significant. The pattern of relationship between RR and degree of kinship indicates involvement of genetic factors, although it is not consistent with single-locus mendelian transmission.

Adolescent↗
PubMed1993

Comparative effects of nicotinic acid and nicotinamide on cholera toxin-induced secretion in rabbit ileum.

Nicotinic acid reduces the cholera-toxin induced fluid secretion in experimental animals but its toxicity at high doses prevent its therapeutic use in patients suffering from cholera. This study aimed to determine whether nicotinamide, the non toxic amide derivative of nicotinic acid, is as effective as nicotinic acid in inhibiting cholera toxin induced intestinal secretion in vivo. Four intestinal loops, with their blood supply intact, were isolated in 30 rabbits and injected with either (i) 30 mM mannitol, (ii) 30 mM mannitol + 10 micrograms cholera toxin, (iii) 30 mM glucose, or (iv) 30 mM glucose + 10 micrograms cholera toxin. These rabbits were then randomly assigned to three groups receiving intraluminally either 100 mg/kg of nicotinic acid, 100 mg/kg of nicotinamide, or 10 ml/kg of Ringer solution. Measurement of intestinal fluid accumulation showed that nicotinic acid, but not nicotinamide, significantly reduced cholera toxin induced intestinal secretion.

Animals↗
PubMed1992

[15N]- and [14C]glutamine fluxes across rabbit ileum in experimental bacterial diarrhea.

L-Glutamine (Gln) fluxes and the effects of Gln on Na and Cl transport were studied across the ileum of healthy and rabbit diarrheagenic Escherichia coli (RDEC-1)-infected weanling rabbits. Stable ([alpha-15N]Gln) and radioisotopic ([U-14C]Gln) tracers provided identical estimates of Gln transport both in healthy (H) and infected (I) rabbits. RDEC-1 infection, however, decreased net Gln flux [Jnet[14C]Gln = 682 +/- 147 (H) vs. 278 +/- 63 (I); Jnet[15N]Gln = 739 +/- 160 vs. 225 +/- 110 nmol.h-1.cm-2] due to a reduction in mucosal-to-serosal flux. After addition of Gln, increases in net Na absorption [delta Jnet[15N]Gln = 1.87 +/- 0.45 (H) vs. 0.70 +/- 0.27 (I) microeq.h-1.cm-2] and short-circuit current (delta Isc) [1.80 +/- 0.40 (H) vs. 0.74 +/- 0.14 (I) microeq.h-1.cm-2] were also reduced in infected rabbits. Addition of glucose after Gln, however, stimulated Na absorption further. These results indicate that 1) Gln is actively absorbed as intact Gln molecule across rabbit ileum; 2) Gln stimulates an electrogenic Na absorption in a 1:2 ratio that may be further stimulated by glucose; and 3) in RDEC-1 infection electroneutral NaCl absorption, intact Gln absorption, and electrogenic stimulation of Na absorption by glutamine are reduced.

Animals↗
PubMed1992

Urinary excretion of iodide and fluoride from supplemented food grade salt.

Iodide and fluoride supplemented food grade salt (NaCl) is a common source of these two micronutrients. In a pilot study, we investigated whether increased intake of NaCl supplemented with iodide (I-) and fluoride (F-) results in their higher bioavailability. Twelve healthy adult human volunteers ingested increasing quantities (1, 3, 6 and 9 g) of NaCl with usual diet over 8 days. Sodium (Na+), I- and F- were measured in 24 hour urine specimen. During the 4 day basal period when no additional NaCl was ingested, ingestion of NaCl calculated from urinary Na+ concentration and diuresis was 8.25 +/- 0.67 g/24 h. During the same period 0.11 +/- 0.01 and 0.61 +/- 0.04 mg of I- and F- respectively were excreted in the urine per 24 h. Increased ingestion of supplemented NaCl resulted in higher urinary excretion of sodium while urinary creatinine remained stable. 92% of I- and 40% of F- contained in the additional amount of NaCl ingested were excreted in the urine. These results indicate that with increased ingestion of supplemented (I- and F-) NaCl, almost the totality of I- is excreted in the urine while fluoride is either incompletely absorbed or retained by the body to a higher extent. I- and F- supplemented NaCl is, therefore, an effective vehicle to provide these micronutrients when ingested with diet.

Adolescent↗
PubMed1992

Rh segregation distortion: an artifact of ascertainment bias?

On the basis of Rh blood group data on mother-child pairs collected from the maternity clinic of a hospital in Chile, Valenzuela and Harb postulated that there is a significant segregation distortion at the Rh locus. For data collected from a hospital, biases of ascertainment cannot be ruled out. For the Rh blood group locus, there is a strong possibility of preferential admission of Rh(-) pregnant women, especially of those Rh(-) women with Rh(+) husbands. We show that the evidence of segregation distortion vanishes when the possibility of such preferential admissions are taken into account.

Adult↗
PubMed1990

Quantification of protein transcytosis in the human colon carcinoma cell line CaCo-2.

The transepithelial absorption of food-type proteins has been shown to proceed by endocytosis along two functional pathways: a minor direct pathway allowing transport of intact protein and a major lysosomal degradative pathway. The human colon carcinoma cell line CaCo-2 grown on Millipore filters was used here further to characterize these pathways by measuring HRP transport across the cell monolayer in Ussing chambers. In the apical-basal direction, this transport mainly occurred along the degradative pathway and was inhibited at 4 degrees C (7.41 +/- 1.26 pmoles/h.cm2 vs. 27.40 +/- 8.91 at 37 degrees C). The amount conveyed via the direct pathway was very small (0.89 +/- 0.35 pmoles/h.cm2) and did not diminish at 4 degrees C (1.43 +/- 0.59 pmoles/h.cm2). In the basal-apical direction, HRP transport along the degradative pathway at 37 degrees C was similar to the apical-basal value and was inhibited at 4 degrees C (16.40 +/- 4.05 vs. 2.72 +/- 2.52 pmoles/h.cm2), but along the direct pathway, it was eight times the apical-basal value (8.36 +/- 3.11 pmoles/h.cm2) and was inhibited at 4 degrees C (2.43 +/- 0.78 pmoles/h.cm2). Intact HRP fluxes were not correlated with the electrical resistance of the filters, indicating transport via a transcellular route. Monensin at 10(-5) M did not affect direct or degradative transport in the apical-to-basal direction. These results suggest that in CaCo-2 cells HRP undergoes bidirectional transcytosis by a fluid-phase mechanism, but the extent of degradation during that transport varies according to the membrane (apical or basal) where it is presented.

Biological Transport↗
PubMed1990

Human intestinal cell lines as in vitro tools for electrolyte transport studies with relevance to secretory diarrhoea.

Intestinal cells from human colorectal adenocarcinomas have been established in culture as monolayers of homogeneous polarised cells on permeable filters with various degrees of cell differentiation. These cell lines allow to avoid some of the difficulties of studying water and electrolyte transport through whole intestinal tissue or isolated intestinal cells. Cell lines, such as Caco-2, T-84, HT-29, HRT-18 which exhibit electrogenic chloride secretion induced by various hormones, neurotransmitters, enterotoxins, and other chemical compounds, can be used to study basic biochemical mechanism and their interrelation in the process of chloride secretion which is associated with many diarrhoeal diseases. Identification and use of cell lines having absorptive properties will equally contribute to the understanding of absorptive processes, their regulation and biochemical basis. Cell lines in which both secretory and absorptive processes coexist are valuable for understanding the complex interrelation of the two principal processes of transport mechanism including its biochemical and molecular correlates. Intestinal cell lines can also be used for screening efficacies of potential secretagogues and antisecretagogues.

Adenocarcinoma↗
PubMed1989

Food-based oral rehydration salt solution for acute childhood diarrhoea.

The efficacy in acute childhood diarrhoea of oral rehydration therapy (ORT) based on staple foods (maize, millet, wheat, sorghum, rice, or potato) was compared with that of standard ORT based on glucose. 266 children aged 1-5 years, with a history of acute diarrhoea for 48 h or less, moderate to severe dehydration, and no complications, were assigned to treatment with one of the food-based oral rehydration salt solutions (ORS) or standard ORS. The mean stool output over the first 24 h of treatment in the group receiving standard ORS was significantly higher than that of any other treatment group, and the groups receiving food-based ORT showed substantial reductions in stool output compared with the standard ORT group. Abnormalities in electrolyte concentrations were corrected in all treatment groups with similar efficiency. The digestibility of the food-based ORS was assessed by the stool pH, glucose content before and after acid hydrolysis, and osmolality; there were no significant differences between the standard ORS and food-based ORS groups. Food-based ORT should be more acceptable to users in developing countries since the mixtures are similar to traditional weaning foods and since, unlike standard ORT, it reduces stool output substantially.

Acute Disease↗