Biomedical subjects

R M Batt

Publications and source records attributed to R M Batt.

At least 109 records · Page 6Linked to original sources

PubMed1987

Comparison of the biochemical changes in the jejunal mucosa of dogs with aerobic and anaerobic bacterial overgrowth.

Subcellular biochemical changes in the jejunal mucosa have been compared in dogs with either aerobic or anaerobic bacterial overgrowth to explore relationships between composition of the flora and mucosal damage. Affected animals comprised 17 German shepherd dogs with chronic diarrhea or weight loss, or both. Analysis of duodenal juice demonstrated aerobic overgrowth in 10 cases, most frequently comprising enterococci and Escherichia coli, and obligate anaerobic overgrowth in 7 cases, most frequently including Clostridia spp. Histologic changes were minimal; however, examination of peroral jejunal biopsy specimens by sucrose density gradient centrifugation revealed specific biochemical abnormalities. In the dogs with aerobic overgrowth, there was a selective loss of brush border alkaline phosphatase activity, and gamma-glutamyl transferase activity was increased, whereas activities of disaccharidases and aminopeptidase N were unaltered. In contrast, anaerobic overgrowth was associated with a reduction in brush border density, indicative of a considerable fall in the glycoprotein-to-lipid ratio of the brush border membrane, whereas brush border enzyme activities were unaltered. There was a loss of peroxisomal catalase activity in dogs with aerobic overgrowth, and an indication of mitochondrial disruption in dogs with anaerobic overgrowth, but little evidence for damage to other subcellular organelles. These findings demonstrate that aerobic and anaerobic overgrowth may be associated with distinct but different mucosal abnormalities particularly affecting the brush border membrane.

Alkaline Phosphatase↗

PubMed1987

Organ culture of rabbit ileum as a model for the investigation of the mechanism of intestinal damage by enteropathogenic Escherichia coli.

Organ culture of rabbit ileum has been established as a model for the investigation of the mechanism of intestinal damage by enteropathogenic Escherichia coli (EPEC). Loops of rabbit ileum were filled in vivo with saline, non-enteropathogenic P-fimbriate E coli (PFEC), or EPEC. After 45 minutes the loops were washed, then mucosal biopsies were taken and cultured for up to 48 hours. The earliest changes discernable by electron microscopy were observed at 18 hours postinfection, at which time EPEC were closely adherent to the surface of enterocytes at the base of microvilli, some of which were elongated. By 24 hours postinfection there were large areas of brush border effacement with pedestal formation around the EPEC. No such damage was seen in biopsies from the control loops (saline, PFEC), and intracellular ultrastructure was extremely well preserved in all preparations for up to 48 hours. While there were no differences at eight hours, biochemical analyses at 24 hours postinfection showed a marked increase in the release of brush border enzymes into the culture medium from EPEC-infected explants compared to explants from the control loops. These findings provide morphological and biochemical evidence for damage to the microvillus membrane by EPEC, and validate organ culture of rabbit ileum as a model for the investigation of EPEC-pathogenicity.

Alkaline Phosphatase↗

PubMed1987

C-reactive protein in dogs.

Serum concentrations of C-reactive protein (CRP) in dogs with various diseases or undergoing various procedures were measured by specific immunoassay. In 20 healthy dogs from various sources, values were all less than 5 mg/L, but in 22 healthy dogs from a single source, values ranged from less than 5 mg/L in 14 dogs and from 8 to 67 mg/L in 8 dogs. Increased concentrations of serum CRP were attained 24 hours after injection of casein (n = 9; median 188 mg/L), ovariohysterectomy (n = 11; median, 144 mg/L), or elective, nonacute orthopedic surgery (n = 10; median, 83 mg/L). After inoculation of Leptospira interrogans serovar canicola (n = 5), the behavior of serum CRP as an acute-phase reactant provided a sensitive and precise objective reflection of in vivo response. The CRP concentration in random single-serum samples from 73 dogs with other inflammatory and noninflammatory disorders ranged from normal (less than 5 mg/L) to 246 mg/L and generally correlated with the extent and activity of disease.

Animals↗

PubMed1986

Ultrastructural and biochemical changes in human jejunal mucosa associated with enteropathogenic Escherichia coli (0111) infection.

A case of prolonged diarrhoea following Escherichia coli 0111 gastroenteritis is reported. Electron microscopy of the jejunal biopsy revealed effacement of the brush border and attachment of bacteria by pedestal formation. Specific activities of brush border enzymes showed marked depression of disaccharidases, zinc-resistant alpha-glucosidase, and alkaline phosphatase. In contrast, marker enzymes for basolateral membranes and endoplasmic reticulum were unaffected. The biochemical changes support the pathogenic mechanism suggested by ultrastructural studies previously reported.

Biopsy↗

PubMed1985

Lysosomal localisation of cobalamin during absorption by the ileum of the dog.

The subcellular distribution of cobalamin during absorption in the dog ileum has been studied using analytical subcellular fractionation. Animals dosed orally with cyano[57Co]cobalamin were killed 2 h later, and postnuclear supernatant fractions prepared from homogenates of the ileal mucosa were subjected to isopycnic centrifugation on reorientating sucrose density gradients. Marker enzymes for the principal subcellular organelles and cyano[57Co]cobalamin were assayed in the gradient fractions. At 2 h, the distribution of cyano[57Co]cobalamin exhibited a major lysosomal localisation with only 30% of the counts being recovered in the soluble fractions. This observation was confirmed by preparing postnuclear supernatant fractions in digitonin, which selectively disrupted lysosomes and released their contents into the soluble fractions. Lysosomal localisation during passage through the ileal enterocyte strongly supports absorption of cobalamin by a process of receptor-mediated endocytosis in the dog.

Animals↗

PubMed1985

Copper toxicosis and tolerance in the rat. III. Intracellular localization of copper in the liver and kidney.

Male rats fed a 3 g/kg copper diet were killed sequentially up to 14 weeks. Copper in liver and kidney cortex was identified histochemically and assayed in homogenates and gradient fractions following analytical subcellular fractionation on reorientating sucrose density gradients. Copper accumulated fastest in the liver postnuclear (PNS) supernatant fraction which became saturated at 2 weeks; there was a distinct localization of copper in hepatic lysosomes which displayed progressively enhanced fragility. Rapid accumulation of copper then occurred in liver and kidney nuclear (N) fractions, peak copper concentrations coinciding with hepatic and renal tubular necrosis. Copper accumulated slowly up to 4 weeks and was maintained to 14 weeks in the cytosol of the proximal renal tubules from which it appeared to be excreted. Subsequently liver copper declined in both liver fractions and kidney (N) fractions; hepatic lysosomes regained stability, regeneration of liver and kidney occurred, and the rats were tolerant to continued copper administration. These findings do not support a primary role for copper-loaded lysosomes in the genesis of cell injury, but suggest that nuclear saturation may be the destabilizing event. Recovery is associated with changes in the subcellular distribution of copper within liver and kidney and renal excretion of excess.

Animals↗

PubMed1985

Wheat-sensitive enteropathy in Irish setter dogs: possible age-related brush border abnormalities.

The pathogenesis of a wheat-sensitive enteropathy was explored in a litter bred from two Irish setters with a naturally occurring enteropathy. Jejunal biopsies from all eight progeny exhibited morphological changes comparable to those in the parents, while biochemical abnormalities appeared to be related to age. In biopsies obtained from the first group of four dogs at eight months, the activities of alkaline phosphatase and of leucyl-2-naphthylamidase were almost undetectable while disaccharidases were unaltered. In contrast, analytical subcellular fractionation of biopsies obtained from the second group of four dogs at nine months showed that specific activities now reflected a major deficiency of brush border alkaline phosphatase, and normal brush border leucyl-2-naphthylamidase accompanied by elevated soluble activity. Further studies are indicated to determine whether these findings represent an age-related abnormality affecting specific microvillus membrane proteins.

Age Factors↗

PubMed1984

Biochemical changes in the jejunal mucosa of dogs with a naturally occurring enteropathy associated with bacterial overgrowth.

The subcellular biochemical features of a naturally occurring enteropathy in the dog associated with bacterial overgrowth have been examined. Affected animals comprised a group of 10 German Shepherd dogs with raised serum folate and reduced vitamin B12 concentrations, mild steatorrhoea, reduced xylose absorption, and normal exocrine pancreatic function. Culture of duodenal juice showed bacterial overgrowth with mixed flora, most frequently including enterococci and Escherichia coli. Examination of peroral jejunal biopsies revealed predominantly minimal histological but distinct biochemical abnormalities in the mucosa. The specific activity of alkaline phosphatase was decreased, isopycnic density gradient centrifugation showing a marked loss particularly of the brush border component of enzyme activity. In contrast, gamma-glutamyl transferase activity was enhanced in brush border fragments of slightly increased modal density, but there were no changes in the activities of the carbohydrases, zinc-resistant alpha-glucosidase, maltase, sucrase, and lactase or of the peptidase, leucyl-2-naphthylamidase. Activities of lysosomal enzymes were increased and there was evidence for enhanced lysosomal fragility and mitochondrial disruption. The activities and density gradient distributions of marker enzymes for basal-lateral membranes, endoplasmic reticulum and peroxisomes were essentially unaltered. These findings show that bacterial colonisation of the proximal small intestine may be associated with specific alterations in microvillus membrane proteins and provide biochemical evidence for intracellular damage to the enterocytes.

Animals↗

PubMed1984

Isolation and characterization of C-reactive protein from the dog.

Using calcium-dependent affinity chromatography on Sepharose-bearing, covalently-coupled pneumococcal C-polysaccharide, a protein was isolated from the serum of dogs that had undergone general anaesthesia and major surgery. This protein was confirmed as the canine analogue of C-reactive protein (CRP) in other species by virtue of its electron microscopic appearance, subunit composition and behaviour as an acute phase reactant. Dog CRP had an apparent molecular weight of approximately 100,000 and was composed of five subunits of approximately 20,000 MW each. Two of the five subunits in each molecule were glycosylated. Negatively stained preparations had the typical cyclic pentameric disc-like structure of proteins of the pentraxin family, and in some preparations had a tendency to form stacks. Serum from normal healthy dogs of various strains usually contained less than 5 mg/l of CRP but, following the stimulus of major surgery, an increase in the CRP concentration was first detected at 4 hr.

Animals↗

PubMed1984

Morphological and biochemical studies of a naturally occurring enteropathy in the Irish setter dog: a comparison with coeliac disease in man.

A naturally occurring enteropathy was identified in Irish setter dogs and wheat-sensitivity was demonstrated in a litter bred from two of the affected animals. The morphological and biochemical features of this enteropathy are described and compared to coeliac disease in man. Affected animals comprised 10 dogs that presented with poor weight gain or weight loss, with or without diarrhoea. Exocrine pancreatic function was normal and culture of duodenal juice demonstrated no marked bacterial overgrowth. Serum vitamin B12 concentrations were unaltered, but in some cases low serum and erythrocyte folate concentrations and reduced xylose absorption provided indirect evidence for proximal small intestinal disease. Examination of peroral jejunal biopsies revealed patchy morphological changes within individual animals, comprising predominantly partial, but in one case subtotal, villous atrophy. Brush border enzymes were selectively altered: the specific activities of alkaline phosphatase, leucyl-2-naphthylamidase and of zinc-resistant alpha-glucosidase were reduced by approximately 40 per cent, while activities of maltase, sucrase, lactase and gamma-glutamyl transferase were unaltered. Activity of a lysosomal enzyme was increased and there was evidence for enhanced lysosomal fragility. The activity of malate dehydrogenase, with a dual mitochondrial and cytoplasmic localisation, was decreased but there were no changes in the activities of marker enzymes for basal-lateral membranes, endoplasmic reticulum or peroxisomes. These findings, particularly the specific biochemical abnormalities, were comparable to those in partially treated coeliac disease in man; however, a specific role for wheat in the pathogenesis of the disease has yet to be defined.

Animals↗

PubMed1984

Relative deficiency of serum IgA in the german shepherd dog: a breed abnormality.

Serum immunoglobulin concentrations in clinically healthy German shepherd dogs were compared with those in mongrel dogs and Irish setters. Serum IgA concentrations were significantly lower in the German shepherd dogs than in the other two groups, while there were no differences in the concentrations of IgM or IgG. These findings suggest that production of IgA by gut associated lymphoid tissue may be abnormally low in the German shepherd dog.

Animals↗

PubMed1983

Bacterial overgrowth associated with a naturally occurring enteropathy in the German shepherd dog.

Quantitative and qualitative bacteriological studies were performed on duodenal juice from 19 dogs with chronic small intestinal disease. Bacterial overgrowth was demonstrated in seven German shepherd dogs with minimal histological but specific biochemical abnormalities in the jejunal mucosa. Most frequently this overgrowth comprised bacteria of the normal flora, particularly Escherichia coli and enterococci, but these were occasionally accompanied by bacteria rarely present in the proximal small intestine of the normal dog, particularly Clostridium species. In most cases this overgrowth was associated with raised serum folate and reduced serum vitamin B12 concentrations, a finding consistent with the capacity of many enteric bacteria to synthesise folate and bind vitamin B12.

Animals↗

PubMed1983

Subcellular biochemical studies of a naturally occurring enteropathy in the dog resembling chronic tropical sprue in human beings.

Subcellular biochemical features of a naturally occurring enteropathy in the dog resembling chronic tropical sprue in human beings were examined. Affected dogs had reduced xylose absorption and low concentrations of serum folate, RBC folate, and serum vitamin B12. Histologic examination of peroral jejunal biopsy specimens revealed villous atrophy and a variable infiltration of lymphocytes and plasma cells in the lamina propria. Biochemical assessment of the principal subcellular organelles was achieved by the assay of specific marker enzymes in homogenized jejunal biopsy specimens and in the gradient fractions after isopyknic centrifugation on continuous sucrose-density gradients. Activities of brush-border marker enzymes were reduced. However, there was no change in the equilibrium density of this organelle, indicating that these quantitative brush-border changes were not accompanied by an alteration in the composition of the microvillous membrane. Activities of lysosomal enzymes were increased, and there was evidence of enhanced lysosomal fragility and a proliferation of the endoplasmic reticulum. These findings were consistent with an impairment of the functional capacity of the small intestinal mucosa and implicated lysosomes and the endoplasmic reticulum in the disease process.

Animals↗

PubMed1983

Quantitation of small intestinal structure and function in unthrifty piglets.

Litters of piglets were weighed at birth, weaning and five weeks later; pairs of thrifty and unthrifty weaned pigs were identified. Small intestinal structure and function were studied in 28 eight-week-old age-matched littermate pairs and in 16 weight-matched littermates. A comparison of age-matched piglets showed changes in mucosal structure in unthrifty piglets, a slight reduction in absorptive function but no biochemical evidence of small intestinal disease. Morphometric studies of weight-matched piglets revealed no differences between thrifty and unthrifty piglets, suggesting that the differences in the age-matched groups may have been an effect of body-weight. If unthrifty pigs grew slowly as a result of small intestinal damage and malfunction immediately after weaning no evidence of it remained when they were studied five weeks later.

Animals↗

PubMed1983

Evaluation of preformed Percoll and reorientating sucrose density gradient centrifugation for the analytical subcellular fractionation of dog liver.

A low-speed supernatant from dog liver was prepared and subjected to analytical subcellular fractionation using either preformed Percoll or reorientating sucrose density gradient centrifugation. In Percoll the following organelles, with marker enzymes and modal densities between brackets, were characterised: plasma membrane (alkaline phosphatase, 5' nucleotidase, gamma-glutamyl transferase, 1.039); endoplasmic reticulum (neutral alpha-glucosidase, 1.039); lysosomes (N-acetyl-beta-glucosaminidase, 1.087; alpha-mannosidase, 1.081) peroxisomes (catalase, 1.045) and mitochondria (succinate dehydrogenase, 1.081). In sucrose alkaline phosphatase had a bimodal particulate distribution (1.120, 1.187) distinct from that of 5' nucleotidase (1.160) and of gamma-glutamyl transferase (1.173). Other modal densities were: endoplasmic reticulum (1.187), lysosomes (1.227, 1.200), peroxisomes (1.213) and mitochondria (1.187). Further resolution was achieved by homogenisation in digitonin which disrupted lysosomes and, in sucrose, selectively increased the densities of the plasma membrane components. Both procedures therefore achieved distinct but quite different resolutions of organelles and should prove valuable for investigating subcellular pathology.

Animals↗

PubMed1982

Response of the small intestinal mucosa to oral glucocorticoids.

These studies explored the effects of oral pharmacological doses of glucocorticoids on the normal small intestine of the adult rat. Short-term (7 days) prednisolone had little effect on mucosal structure or cell kinetics but enhanced the maximum absorptive capacities of the jejunum and ileum for galactose. This was due to an increase in carrier-mediated transport in the individual enterocytes and not to a change in the cell population. Activities of brush border enzymes were elevated and turnover studies indicated an increased rate of synthesis of brush border proteins associated with an enhanced glycoprotein content of the microvillus membrane. Subcellular fractionation studies demonstrated a large increase in the membrane-bound ribosomal RNA content of the enterocytes consistent with an enhanced synthesis of membrane proteins. These findings implicate a direct action of prednisolone on the enterocytes to increase their absorptive and digestive capacities by the induction of specific functional proteins. These effects on the absorptive and digestive functions of the small intestine were sustained with long-term (28 days) prednisolone feeding. An equivalent long-term oral dose of betamethasone-17-valerate, a locally rather than a systemically active glucocorticoid, had a similar effect on the enterocytes. However, an inhibition of crypt cell turnover resulted in a marked hypoplasia and hence no net change in the functional capacity of the mucosa. These findings emphasise the separate and opposing actions of glucocorticoids on the adult mucosa, on the one hand to stimulate enterocyte function, but on the other to reduce the enterocyte population. The predominant activity appears to be a function of each individual steroid. The predominant stimulatory action of prednisolone was further emphasised by investigating the effects of this glucocorticoid on the adapted ileum following jejunal resection. Indeed, short-term prednisolone enhanced the adaptive hyperplasia in the ideal remnant by increasing the functional capacity of the expanded population of enterocytes.

Adaptation, Physiological↗

PubMed1982

Role of serum folate and vitamin B12 concentrations in the differentiation of small intestinal abnormalities in the dog.

Serum folate and vitamin B12 concentrations have been measured in 53 dogs presented for an investigation of malabsorption. Abnormal concentrations have permitted the differentiation of animals with small intestinal disease into three main groups, each with distinct biochemical abnormalities in the jejunal mucosa. The first group had reduced folate and vitamin B12 concentrations. Jejunal biopsies revealed marked villous atrophy and generalised biochemical abnormalities in the brush borders, lysosomes and endoplasmic reticulum. The second group had reduced folate but normal vitamin B12 concentrations and although histological changes were minimal there were specific biochemical changes confined to the brush borders. In the third group, increased folate and reduced vitamin B12 concentrations suggested a bacterial overgrowth in the proximal small intestine. Minor histological changes were accompanied by marked biochemical changes in brush borders and lysosomes. A group of animals with severe exocrine pancreatic insufficiency had increased mean folate but reduced mean vitamin B12 concentrations. These changes are consistent with bacterial overgrowth, but could be due to defective degradation of a B12-binding protein.

Animals↗

PubMed1981

Specificity of the BT-PABA test for the diagnosis of exocrine pancreatic insufficiency in the dog.

Exocrine pancreatic insufficiency in the dog has been assessed by the oral administration of the synthetic peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA), a specific substrate for pancreatic chymotrypsin. The subsequent assay of PABA in either the plasma or the urine clearly differentiated control animals from those with exocrine pancreatic insufficiency (EPI), the results being unaffected by combination of this pancreatic function with a xylose absorption test. Possible interference with the specificity of the peptide test for the diagnosis of EPI was examined in six animals with small intestinal disease. In a group of four animals, with features resembling chronic tropical sprue in man, the results were comparable to those of the control group. In the fifth case, however, the results were indistinguishable from those of the EPI group, the estimation of sodium PABA absorption and the assay of proteolytic activity in the duodenal juice demonstrating that this was due to defective hydrolysis of the peptide. In the sixth case, diffuse intestinal lymphosarcoma and a marked villous atrophy were associated with an apparent reduction in the absorption of sodium PABA. However, although the plasma PABA concentrations following oral BT-PABA were subnormal, they were distinctly higher than those of the EPI group. These findings suggest that small intestinal abnormalities do not affect PABA absorption sufficiently to interfere with the specificity of the peptide test for the detection of severe EPI in the dog. This insufficiency may occasionally be secondary to small intestinal disease.

4-Aminobenzoic Acid↗