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Biomedical subjects

R M Batt

Publications and source records attributed to R M Batt.

At least 19 recordsLinked to original sources
PubMed1997

Surface properties of diarrhoeagenic Escherichia coli isolates.

The surface properties of various Escherichia coli isolates associated with diarrhoeal illness were compared by aqueous partitioning between polyethylene glycol (PEG) and Dextran phases. Two well characterised strains of enteropathogenic E. coli (EPEC) were found to be very hydrophobic, based on the critical polymer concentration. EPEC strain E2348 cured of the EPEC adherence factor (EAF) plasmid had much reduced surface hydrophobicity. Partitioning of a series of diarrhoeagenic E. coli strains demonstrated that the majority of EAF+ EPEC strains were significantly more hydrophobic than EAF- EPEC strains. E. coli strains defined as enteroaggregative on the basis of hybridisation with a specific DNA probe showed much greater heterogeneity in their partitioning behaviour, possibly indicating that the AAF/I pili were not expressed in all strains. The E. coli K-12 strain used as a transformation host for adhesion studies had very low surface hydrophobicity but had a detectable negative charge. No alteration in these properties was observed when transformed with EPEC and recombinant plasmids known to specify adherence to tissue culture cells.

Agglutination Tests↗
PubMed1997

Canine major histocompatibility complex genes DQA and DQB in Irish setter dogs.

Information about genetic variation within the canine major histocompatibility complex (MHC) class II genes is limited. In common with most other vertebrate species the canine MHC, or DLA, includes genes which are homologous to human DR, DQ, and DP. Recently, at least one functional DLA DQ gene-pair has been characterized, but so far systematic screening efforts have been lacking. In the present study, we sequenced both cDNA and genomic clones derived from DLA DQ genes of Irish setter dogs. This breed was of interest, since it shows a high prevalence of gluten sensitive enteropathy (GSE), which may be a useful animal model for celiac disease (CD) of man. Interestingly, few of the alleles found in Irish setters were identical to those previously detected in other breeds. Three novel DLA DQA and four novel DLA DQB alleles were discovered in 19 unrelated dogs. Strong association between certain HLA DQ alleles and CD of man prompted us to screen the DQ alleles of members of a family of gluten-sensitive Irish setter dogs. No haplotypes or alleles were shared by all affected dogs, but one frequent haplotype in this family was also detected in an unrelated gluten-sensitive Irish setter; this haplotype was absent in the healthy dogs. This observation warrants further investigation by screening the DQ alleles of a large population of unrelated gluten-sensitive Irish setters.

Alleles↗
PubMed1996

Growth and propagation of normal rat intestinal epithelial cells.

A combination of mild proteolytic digestion and selective growth stimulation has been used to isolate and propagate adult rat intestinal epithelial cells with a finite life span. Growth of these cells on a variety of matrices and on mesenchymal cells has resulted in the expression of brush border enzymes including sucrase-isomaltase, aminopeptidase N, and alkaline phosphatase. Examination of the cells at the electron microscopic level has revealed that although these cells express key brush border enzymes, they do not have a fully formed brush border. These findings suggest that the expression of brush border enzymes and structural proteins represent distinct stages of enterocyte differentiation that are under separate transcriptional and temporal control.

Alkaline Phosphatase↗
PubMed1996

Urinary excretion by dogs of intravenously administered simple sugars.

Seven simple sugars, commonly used in intestinal function tests, were simultaneously administered intravenously to dogs and their urinary excretion was measured to assess their potential for metabolic degradation. Lactose, lactulose and 3-O-methyl-D-glucose were excreted unchanged, but small proportions of palatinose and sucrose were not, and were assumed to have been metabolised. More than half of the administered D-xylose and a quarter of L-rhamnose was not excreted and was assumed to have been metabolised. These findings may be significant for the interpretation of differential sugar absorption tests and the D-xylose tolerance test.

3-O-Methylglucose↗
PubMed1996

Enteric bacteria: friend or foe?

The normal gastrointestinal tract contains an enormous number of aerobic and anaerobic bacteria which normally enjoy a symbiotic relationship with the host but can have adverse effects with local and systemic consequences. The small intestine constitutes a zone of transition between the sparsely populated stomach and the luxuriant bacterial flora of the colon. Regulation of the intestinal flora depends on complex interactions between many factors including secretion of gastric acid, intestinal motility, biliary and pancreatic secretions, local immunity, the surface glycocalyx and mucus layer, and diet. Microbial interactions are also important, and can involve alterations in redox potential, substrate depletion and production of substances such as bacteriocins that inhibit bacterial growth. The beneficial effect of the normal enteric flora include the competitive exclusion of potentially pathogenic organisms, and the production of nutrients such as short-chain fatty acids (which represent an important energy source for the colonic mucosa) and vitamins. Detrimental effects of the enteric flora include competition for calories and essential nutrients, particularly by bacteria located in the small intestine, and a capacity to damage the mucosa, in some circumstances causing or contributing to inflammatory bowel disease. These problems can be accentuated by interference with the physiological regulation of intraluminal bacteria allowing overgrowth by a normal resident, or colonisation by transient pathogens. The pathophysiological consequences may involve direct damage to the intestinal mucosa, and bacterial metabolism of intraluminal constituents, for example forming deconjugated bile acids and hydroxylated fatty acids which stimulate fluid secretion. Additional problems arise if there is interference with the mucosal barrier since this can result in increased passage of bacteria and bacterial products stimulating mucosal inflammation, while bacterial translocation can result in bacteraemia and septicaemia. Problems associated with bacterial pathogens are illustrated by the properties of the spectrum of pathogenic Escherichia coli, some of which facilitate long-term colonisation by adherence to the surface or invasion of enterocytes.

Animals↗
PubMed1996

Intestinal permeability and function in dogs with small intestinal bacterial overgrowth.

Small intestinal bacterial overgrowth (SIBO) has been reported to occur commonly in dogs with signs of chronic intestinal disease. There are usually few intestinal histological changes, and it is uncertain to what extent bacteria cause mucosal damage. The aim of this study was to apply a differential sugar absorption test for intestinal permeability and function to the objective assessment of intestinal damage in dogs with SIBO. Studies were performed on 63 dogs with signs of chronic small and, or, large bowel disease, in which SIBO (greater than 10(5) total or greater than 10(4) anaerobic colony forming units/ml) was diagnosed by quantitative culture of duodenal juice obtained endoscopically. None of the dogs had evidence of intestinal pathogens, parasites, systemic disease or pancreatic insufficiency. differential sugar absorption was performed by determining the ratios of urinary recoveries of lactulose/rhamnose (L/R ratio, which reflects permeability) and D-xylose/3-O-methylglucose (X/G ratio, which reflects intestinal absorptive function) following oral administration. Dogs with SIBO comprised 28 different breeds, including 13 German shepherd dogs. SIBO was aerobic in 18/63 dogs (29 per cent), and anaerobic in 45/63 (71 per cent). Histological examination of duodenal biopsies showed no abnormalities in 75 per cent, and mild to moderate lymphocytic infiltrates in 25 per cent of the dogs. The L/R ratio was increased (greater than 0.12) in 52 per cent, and the X/G ratio reduced (less than 0.60) in 33 per cent of the dogs. Differential sugar absorption was repeated in 11 dogs after their four weeks of oral antibiotic therapy. The L/R ratio declined in all 11 dogs (mean +/- SD pre: 0.24 +/- 0.14; post: 0.16 +/- 0.11; P < 0.05), but changes in the X/G ratio were more variable. These findings show that SIBO is commonly associated with mucosal damage not detected on histological examination of intestinal biopsies, and that changes in intestinal permeability following oral antibiotics may be used to monitor response to treatment.

Administration, Oral↗
PubMed1995

Small intestinal bacterial overgrowth in dogs with chronic intestinal disease.

Small intestinal bacterial overgrowth (SIBO) was diagnosed by quantitative bacterial culture of duodenal juice samples obtained endoscopically in 41 of 80 dogs that were admitted with chronic diarrhea, vomiting, or weight loss. Thirteen dogs had aerobic bacterial overgrowth, most frequently comprising Escherichia coli, staphylococci, and enterococci, and 28 dogs had mixed anaerobic overgrowth, most frequently including Clostridium and Bacteroides spp. Affected dogs comprised 23 breeds, including 10 German Shepherd Dogs and median age at diagnosis was 2 years (range, 6 months to 11 years). High serum folate and low serum cobalamin concentrations had fair specificity (79 and 87%, respectively), but low sensitivity (51 and 24%, respectively) in detecting SIBO. Histologic examination of duodenal biopsy specimens did not reveal abnormalities (26/41 dogs), or revealed mild to moderate lymphocytic (12/41) or eosinophilic (2/41) infiltrates, or lymphosarcoma (1/41). Oral antibiotic treatment was effective in 77% (23/30 dogs), but prolonged treatment (> 4 weeks) was required to control signs and prevent recurrence in 50% (15/30). Corticosteroids were used alone in a dog with eosinophilic enteritis and in combination with antibiotics in 4 dogs with marked gastrointestinal lymphocytic/plasmacytic infiltrates. This study suggested that SIBO may be observed in dogs of many breeds, without an obvious primary cause, and that, although results of indirect tests may be suggestive of SIBO, bacterial culture of duodenal juice samples remains necessary for definitive diagnosis.

Animals↗
PubMed1995

Effects of concanavalin A and pokeweed lectins on microvillar membrane proteins during the organ culture of rabbit intestinal mucosa.

The effects of pokeweed lectin (PWL) and concanavalin A (Con A) on microvillar membrane (MVM) proteins during the organ culture of rabbit ileal explants for 24 hours were compared with the known effects of enteropathogenic Escherichia coli (EPEC). PWL resulted in the accelerated release of brush border enzymes into the culture medium, accompanied by decreased tissue activities and an increase in the total activity present in the tissue and culture medium. Con A had less effect on the release and tissue activities of brush border enzymes and the total activity was not increased. Sucrose density gradient centrifugation of the culture medium showed that MVM enzymes were predominantly particulate, consistent with their release as vesicles. Centrifugation of ileal explants showed that PWL, but not Con A, resulted in a decrease in the modal density of the brush border which was consistent with a lower glycoprotein-to-lipid ratio. These findings suggest that PWL, in common with EPEC, may cause the disruption and vesiculation of microvilli and the compensatory stimulation of MVM protein synthesis.

Animals↗
PubMed1995

Characterization of microvillar membrane proteins of dog small intestine by two-dimensional electrophoresis.

A method for analysing microgram amounts of microvillar membranes by two-dimensional electrophoresis (protein mapping) is described, and has been used to characterize the microvillar proteins of the small intestine of German shepherd, corgi, and beagle dogs. Detergent-solubilized microvillar membranes were radiolabelled with 14C and separated by isoelectric focussing followed by SDS-PAGE. Proteins were detected fluorographically and glycoproteins by lectin-affinity staining. The microvillar hydrolases alkaline phosphatase and dipeptidyl aminopeptidase IV were identified by active-site labelling and aminopeptidase N by immunoprecipitation. Changes following pancreatic duct diversion were consistent with accumulation of pro-sucrase-isomaltase and diminished expression of the sucrase and isomaltase subunits. Cytoskeletal proteins were concentrated in the core fraction remaining after extraction of microvillar membranes with Triton X-100. There were no consistent differences between dogs of different breed, and the canine protein maps were similar to the human.

Alkaline Phosphatase↗
PubMed1995

A stable isotope study of zinc kinetics in Irish setters with gluten-sensitive enteropathy.

The short-term kinetics of Zn turnover were studied in Irish setters with gluten-sensitive enteropathy and control dogs following intravenous injection of 0.25 mg 96.5% enriched 70ZnCl2. The 70Zn enrichment of serum was found closely to obey two-compartment kinetics and the derived two-compartment decay equation was used to calculate the size and turnover of the two initial rapidly exchanging pools of body Zn. In normal Irish setters isotopic Zn initially equilibrates with a pool (a) of size 1.27 (SD 0.46) mumol/kg and then with a second pool (b) of size 6.83 (SD 1.72) mumol/kg. The fractional turnover of pool (b) was approximately one eighth that of pool (a). Enteropathic dogs showed no reduction in the size of either rapidly exchangeable Zn pool, reduction in serum Zn concentration or abnormality in Zn balance and hence these results do not support the possibility of an underlying Zn deficiency in this disorder.

Animals↗
PubMed1995

Application of organ culture of small intestine to the investigation of enterocyte damage by equine rotavirus.

We used organ culture of jejunal mucosal explants obtained from ponies aged between 2 and 12 months to study enterocyte damage by group A strains of equine rotavirus. Electron microscopy of jejunal explants maintained for < or = 48 h in the presence of organ culture medium alone showed that enterocytes were structurally intact and had a densely packed brush border and overlying mucus. Similarly, examination of explants maintained in the presence of rotavirus for 48 h revealed no apparent ultrastructural abnormalities. However, obvious replication and assembly of virus in enterocytes had occurred following exposure to equine rotavirus strains H2 (three of eight occasions), trypsin-activated H2 (two of four), L338 (five of five), and EQ124 (two of two), although brush borders and intracellular organelles appeared unaltered. Despite the absence of obvious ultrastructural damage, analytical subcellular fractionation showed that rotavirus infection can result in decreased activities of microvillar membrane enzymes, with a particular loss of the main brush border peak of modal density 1.21 g/ml. These findings demonstrate that organ culture of small intestine may be applied to the investigation of rotavirus pathogenicity; they further suggest that certain strains impair enterocyte function by affecting the turnover of microvillar membrane proteins.

Alkaline Phosphatase↗
PubMed1995

Intestinal permeability testing in dogs with diet-responsive intestinal disease.

Fifteen dogs with signs of small and, or, large bowel disease that responded clinically to an exclusion diet were studied, using differential sugar absorption as an objective parameter of the mucosal response to the diet. Intestinal permeability and function were assessed by determining the urinary excretion ratios of lactulose/rhamnose and xylose/3-O-methylglucose, respectively, following oral administration of a mixture of these four sugars. Five dogs, all retrievers, were tentatively diagnosed as having dietary hypersensitivity, based upon resolution of clinical signs and normalisation of high intestinal permeability following an exclusion diet and recurrence of signs (in four of five dogs) upon challenge with the original diet. The fifth dog did not become symptomatic when challenged, but intestinal permeability increased. The remaining 10 dogs were diagnosed as having food intolerance, based upon clinical improvement on an exclusion diet, relapse on challenge with their original diet, but lack of improvement in intestinal permeability. These findings suggest that a differential sugar absorption test may be useful to determine the reasons for clinical response to exclusion diets. Demonstration of increased intestinal permeability with subsequent normalisation following an exclusion diet may be useful in the diagnosis of dietary hypersensitivity, while persistent abnormalities in intestinal permeability are suggestive of underlying intestinal disease and food intolerance.

Analysis of Variance↗
PubMed1995

Subcellular pathologic features of glucocorticoid-induced hepatopathy in dogs.

Dogs are particularly susceptible to development of glucocorticoid-induced hepatopathy, but the mechanisms are not well understood. We investigated the pathogenesis of glucocorticoid hepatopathy by examining sequential morphologic and biochemical changes in the liver of dogs during steroid administration. Six adult Beagles were given prednisolone acetate (4mg/kg of body weight, once daily for 24 days IM). Serum samples and percutaneous liver biopsy specimens were obtained before the start of the study (treatment day [TD] 0) and at TD 5, 10, 15, and 25. There were significant (P < 0.05) and progressive increases in serum activities of alkaline phosphatase, gamma-glutamyltransferase, and alanine transaminase. Light microscopic changes in liver biopsy specimens included progressive hepatocellular swelling and vacuolation. Electron microscopy revealed glycogen accumulation, peripheral displacement of organelles, and prominent dilatation of bile canaliculi, compared with findings at TD 0. Liver biopsy specimens taken at TD 25 had significantly (P < 0.05) increased activities of the plasma membrane enzymes, alkaline phosphatase and gamma-glutamyltransferase, and 5'-nucleotidase was significantly (P < 0.001) decreased. Subcellular fractionation on reorientating sucrose density gradients revealed high-density peaks of alkaline phosphatase and gamma-glutamyltransferase, compatible with a specific increase in the biliary canalicular component of the enzyme activities. Neutral alpha-glucosidase activity was shifted to the denser fractions, indicative of an increase in the proportion of rough to smooth endoplasmic reticulum and consistent with enhanced synthesis of plasma membrane proteins. There also was evidence for progressive increase in fragility of intracellular organelles, particularly lysosomes. These findings indicate that glucocorticoid hepatopathy in dogs is associated with progressive alterations not only to the plasma membrane, but also to other subcellular organelles.

Alanine Transaminase↗
PubMed1995

Subcellular biochemical changes during the development of the small intestine of pony foals.

To examine the postnatal development of equine small intestine, biopsy specimens of jejunal mucosa from 8 ponies, between 6 and 28 weeks old, were subjected to analytical subcellular fractionation and assay of organelle marker enzymes. Fractionation revealed a reduction in the particulate brush border component of beta-galactosidase (lactase) activity between 6 and 28 weeks, and a corresponding increase in soluble activity, although the reduction in mean specific activity was not significant. There also was a decrease in the proportion of brush border to soluble aminopeptidase N activity, a relative loss of brush border gamma-glutamyltransferase activity, and a considerable decrease in the specific activity of alkaline phosphatase throughout the gradient fractions. In contrast, there were marked increases in activities of alpha-glucosidase (maltase) and sucrase in the older ponies, accompanied by considerable changes in the intracellular distribution of particulate alpha-glucosidase activity, which was predominantly associated with endoplasmic reticulum at 6 weeks, whereas the large increase in activity observed by 28 weeks was clearly associated with the brush border. The modal density of brush borders also increased with age, suggestive of an increase in the glycoprotein-to-lipid ratio of the microvillar membrane. In contrast to these brush border changes, there was relatively little alteration in the activities or density distributions of marker enzymes for endoplasmic reticulum, basolateral membranes, mitochondria, or lysosomes. These findings indicate that maturation of equine intestinal epithelium during the first few months of life results in major changes in the properties and enzyme composition of enterocyte brush borders.

Aging↗
PubMed1994

Diarrhoea and increased intestinal permeability in laboratory beagles associated with proximal small intestinal bacterial overgrowth.

Repeated episodes of diarrhoea were seen in 4 laboratory beagles after experimental renal surgery and feeding a modified diet. Small intestinal bacterial overgrowth (SIBO) was suspected by exclusion of other causes and measurement of plasma folate. SIBO was confirmed by quantitative duodenal bacteriology. Beagles with SIBO can show no clinical signs, experimental stress and dietary change may have been reasons why these 4 beagles exhibited clinical signs with SIBO. Despite normal gut histology an increase in gut permeability was found using sugar absorption tests. This increased permeability had the potential to cause variations in drug absorption during experimental studies.

Animals↗
PubMed1993

A novel HPLC method for the simultaneous quantification of monosaccharides and disaccharides used in tests of intestinal function and permeability.

The quantification of monosaccharides and disaccharides used as probes in intestinal function and permeability tests can be technically demanding, detracting from the value of this approach to the indirect assessment of intestinal damage. In this study, a procedure is described for the simultaneous quantification of rhamnose, lactulose, 3-O-methyl-D-glucose and xylose in urine by HPLC using an anion exchange column with pulsed amperometric detection. This method is relatively fast and simple to perform, requiring no pre-treatment of urine samples or post-column derivatization. Accuracy and precision of determinations are illustrated by analytical recoveries (mean percentage +/- S.D., CV., n = 30) for multiple batch analyses of a diluted urine sample containing 20 mg/l of rhamnose (100 +/- 6.8, 6.2%), lactulose (100 +/- 6.1, 5.5%), 3-O-methyl-D-glucose (98 +/- 5.9, 5.5%) and xylose (104 +/- 7.1, 6.5%). Linearity of standard curves indicated that the lower limit for accurate quantification was 0.1 mg/l for all four sugars. Urinary recoveries following oral administration of these sugars to control dogs were determined as a baseline for the investigation of intestinal damage in this species and comparison of chromatograms illustrated enhanced permeability in dogs with gluten-sensitive enteropathy.

3-O-Methylglucose↗