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Biomedical subjects

M M Weiser

Publications and source records attributed to M M Weiser.

At least 37 records · Page 2Linked to original sources
PubMed1989

In vitro electrophysiological effects of cimetidine, prostaglandin E2 and acetylcholine on the rabbit gastric mucosa.

The electrophysiological effects of cimetidine, cytoprotective dose of prostaglandin E2 (PGE2) and acetylcholine were determined in parallel in Ussing-chambered rabbit fundic and antral mucosal preparations. In the fundic mucosal preparations both cimetidine and PGE2 caused an increase in transmucosal potential difference (PD) and in short-circuit current (ISC); the transepithelial resistance (Rt) was essentially unchanged. Addition of acetylcholine to the pretreated fundic preparations produced further gradual increases in PD and ISC; cimetidine pretreatment delayed this effect of acetylcholine. In contrast to fundic mucosa, cimetidine did not cause any electrical change of the antral preparation but decreases in PD, Rt and ISC were detected after the addition of PGE2. Acetylcholine produced a rapid initial PD elevation followed by a PD drop of both antral tissues independent of pretreatment. These findings suggest that both cimetidine and PGE2 generated electrical hyperpolarisation of rabbit fundic mucosa. These changes may be favourable for mucosal protection. No "beneficial" electrical changes were detected on the antral mucosa after administration of cimetidine and PGE2. Acetylcholine increased the effects of other stimuli on the fundic mucosa. In the rabbit antral mucosa acetylcholine generated biphasic changes of electrical properties.

Acetylcholine↗
PubMed1988

Identification and isolation of the phosphorylated intermediate of the calcium pump in rat intestinal basolateral membranes.

Transport of Ca2+ by the ATP-dependent Ca2+ pump has been demonstrated previously in rat intestinal basolateral-membrane vesicles. To identify the Ca2+-pump protein, duodenal basolateral membranes were phosphorylated with [gamma-32P]ATP in the presence of Ca2+ and La3+, under conditions conducive for maximal formation of the phosphorylated intermediate of the Ca2+ pump. Four major phosphoprotein bands were seen on autoradiograms of acidic SDS/polyacrylamide gels; the properties of a phosphoprotein (pp) at 130 kDa (pp130) were consistent with those expected for the plasma-membrane Ca2+ pump. This phosphoprotein was markedly enhanced by La3+, exhibited the characteristics of an acyl-phosphate bond, was preferentially phosphorylated from ATP and inhibited by micromolar concentrations of vanadate. Another phosphoprotein of 115 kDa possibly represented the endoplasmic reticulum Ca2+ pump or a fragment of pp130. Other phosphoproteins of 75 and 95 kDa were predominantly expressions of alkaline phosphatase. Formation of pp130 was highest in duodenal basolateral-membrane preparations when compared with those of jejunum and ileum or other subcellular fractions. A similar correlation between Ca2+-pump activity and pp130 formation was not found in membranes from villus-tip and crypt cells or in vitamin D-deficient animals. pp130 was isolated as a single phosphoprotein by calmodulin-affinity chromatography. We conclude that pp130 represents the phosphorylated intermediate of the rat intestinal basolateral-membrane Ca2+ pump, which can be separated from other phosphoproteins using its properties as a calmodulin-binding protein.

Animals↗
PubMed1987

Distribution, purification and characterization of rat intestinal UDPgalactose: N-acetylglucosaminyl(beta 1----4)galactosyltransferase.

Rat intestinal UDPgalactose: N-acetylglucosaminyl(beta 1----4)galactosyltransferase activity was studied as to its intestinal and villus-to-crypt distribution, and then purified and characterized. Rapid UDPgalactose hydrolysis was noted in the duodenum and jejunum; little to no breakdown was detected in the distal ileum, cecum and proximal colon. Product analysis suggested that UDPgalactose hydrolysis was due to nucleotide-sugar pyrophosphatase and galactose-1-phosphate phosphatase activities; ileum appeared to have little of the first activity and none of the latter. An aboral gradient of galactosyltransferase activity was noted, activity being 3-4-fold higher in the ileum, cecum and proximal colon. Total homogenate exogenous acceptor galactosyltransferase activities showed no villus-crypt differences but activity measured with intact isolated cells demonstrated higher activity with crypt cells; this was particularly evident in the ileum. Galactosyltransferase activity was purified from ileal-colonic mucosa. An over 4000-fold purification with 75 percent yield was achieved. Only one band of approx. 70-75 kDa was noted on sodium dodecyl sulfate polyacrylamide electrophoresis. As with other eukaryotic galactosyltransferase activities, there was an absolute requirement for Mn2+; the concentration required for half maximal activity was only 2.5 microM and higher concentrations did not inhibit. The Km for UDPgalactose was 30 microM.

Animals↗
PubMed1987

The distribution and partial characterization of UDPgalactose: N-acetylgalactosamine mucin galactosyltransferase activity from rat small intestine and its sensitivity to Zn2+.

UDPgalactose: N-acetylgalactosamine mucin galactosyltransferase activity of the rat intestine was studied and purified using asialo-ovine submaxillary mucin as the acceptor substrate and inhibitors to suppress UDPgalactose breakdown by pyrophosphatase activities particularly prevalent in the duodenal-jejunal regions. Despite adequate suppression of UDPgalactose breakdown, significant intestinal region differences of mucin galactosyltransferase activity were observed. Elevations of activity were observed in the duodenum and distal ileum of the small intestine and the cecum and proximal colon; these elevations in activity correspond to areas of increased mucin production. Similarly, mucin galactosyltransferase activity of duodenal cells isolated along a crypt-to-villus axis showed a moderate increase (67.7%) in activity associated with cells in the crypt region. Small intestine mucin galactosyltransferase activity was purified 800-fold using a series of ion exchange (DEAE-Sepharose), gel filtration (S-200 Sephacryl) and affinity chromatographic steps to isolate the mucin galactosyltransferase activity from a Triton X-100/Nonidet P-40 extract of homogenized cells obtained by scraping everted intestines. The partially purified enzyme showed two distinct protein bands of 81.5 and 50 kDa and a faint band at 53.3 kDa. Kinetic analysis gave an apparent Km of 152 microM for UDPgalactose. The enzyme showed optimal activity with Mn2+ (20 mM) and partial activities using a number of other divalent cations. Higher concentrations of Mn2+ were slightly inhibitory. Mucin galactosyltransferase activity was inhibited by more then 90% in the presence of Zn2+ (4 mM) and this inhibition could not be reversed by additional Mn2+. Addition of Zn2+ (4 mM) to assays containing Mn2+ (20 mM) did not cause appreciable UDPgalactose breakdown, as measured by high-voltage paper electrophoresis, suggesting that Zn2+ inhibition is not a result of pyrophosphatase activation. In addition, Zn2+ does not appear to activate a protease or glycosidase activity in the partially purified enzyme preparation which could hydrolyze the galactosylated product prior to isolation.

Galactosyltransferases↗
PubMed1987

Serum antibodies to cow's milk proteins in ulcerative colitis and Crohn's disease.

Serum antibodies of immunoglobulin G, immunoglobulin M, and immunoglobulin A isotypes to five major proteins of cow's milk, casein, bovine serum albumin, alpha-lactalbumin, beta-lactoglobulin A, and beta-lactoglobulin B, were measured using enzyme-linked immunosorbent assay in 51 patients with ulcerative colitis, 49 with Crohn's disease, and 20 age-matched controls. Immunoglobulin G and immunoglobulin M antibodies to cow's milk proteins were significantly elevated in patients with inflammatory bowel disease as compared to controls. In contrast, no significant increase in immunoglobulin A antibodies to 3 of 5 proteins was noted. The increased titers of antibodies to milk proteins seem to be specific and not due to a polyclonal immunoglobulin activation, as naturally occurring blood group antibodies were not elevated in patients with ulcerative colitis and Crohn's disease. A good correlation of disease activity, as measured by serum alpha 1-acid glycoprotein concentrations, and immunoglobulin G and immunoglobulin A antibody titers against certain cow's milk proteins could be demonstrated in Crohn's disease, but not ulcerative colitis. These findings suggest that production of antibodies to cow's milk proteins reflects specific immunization with these antigens. The study of antibody isotypes and correlation with disease activity may provide better insight into the immune response to dietary antigens and its possible role in the pathogenesis of inflammatory bowel diseases.

Adult↗
PubMed1987

Calcium transport by rat duodenal villus and crypt basolateral membranes.

Rat duodenal cells were isolated sequentially to give fractions enriched for villus and crypt cells. From each of these fractions, basolateral-enriched membrane vesicles were prepared and ATP-dependent calcium uptake was studied. Calcium uptake was sensitive to temperature, was inhibited by vanadate and by A23187, and was lower in vitamin D-deficient animals. In normal animals, calcium transport was approximately twofold greater in villus-tip than in crypt cell-fraction basolateral membranes though the affinity of the uptake for calcium was similar (Km = 0.3 microM). In vitamin D-deficient animals, the crypt-to-villus gradient was reduced, and in all fractions, calcium transport was similar to or lower than that in the crypts of normal animals. Six hours after vitamin D-deficient animals were repleted with 1,25-dihydroxycholecalciferol, a significant increase in calcium transport by everted gut sacs was present; however, basolateral calcium transport was significantly increased in only the mid-villus fractions, and no change was seen in the villus-tip fractions. Thus vitamin D appears necessary for the development of increased basolateral membrane calcium pump activity in duodenal villus cells, but not all cells in vitamin D-deficient rats are able to respond to 1,25-dihydroxycholecalciferol.

Adenosine Triphosphate↗
PubMed1987

In vitro translation of rat intestinal RNA prepared from isolated villus and crypt cells and from the epithelium-denuded intestine. Synthesis of intestinal basement membrane.

RNA purified from rat intestinal epithelial cells, obtained as isolated cell fractions of a villus-to-crypt gradient, were shown to be capable of directing peptide synthesis in a cell-free system. Analysis of products have demonstrated differences between villus and crypt and between jejunum and ileum. RNA purified from epithelium-denuded intestine was also shown to be capable of directing cell-free protein synthesis. Precipitation of products by antisera to rat IBM showed differences between epithelial and nonepithelial cells. Anti-laminin derived from mouse EHS sarcoma laminin precipitated products synthesized, in vitro, only by nonepithelial intestinal cells. Further studies on the control of the synthesis of rat IBM should provide valuable information on the relative contributions of epithelial and nonepithelial cells to the synthesis of basement membrane components of this organized tissue system.

Animals↗
PubMed1986

Intestinal basolateral membrane Ca-ATPase activity with properties distinct from those of the Ca-pump.

The Ca-pump in rat intestinal basolateral membranes had been studied previously as vesicular ATP-dependent Ca-uptake. In the present studies, Ca-stimulated ATP hydrolysis (Ca-ATPase activity) was measured and found to differ from the Ca-pump in having higher activity and being insensitive to vanadate. Whereas the pump was specific for ATP, hydrolytic activity was found with ATP, GTP or ADP but not with AMP or p-nitro-phenyl-phosphate. In contrast to Ca-pump activity, Ca-ATPase activities were similar for different intestinal segments, for duodenal villus/crypt cell-fractions and for vitamin D-deficient animals. Thus, as usually measured, intestinal basolateral membrane Ca-ATPase activity is not equivalent to the Ca-pump.

Adenosine Diphosphate↗
PubMed1986

Preparation of subcellular membranes from rat intestinal scrapings or isolated cells. Different Ca2+ binding, nonesterified fatty acid levels, and lipolytic activity.

Basolateral, brush-border, and Golgi-enriched subcellular membrane fractions, prepared from homogenates of rat small intestinal mucosa obtained by scraping, had unusually high concentrations of nonesterified fatty acids. These fatty acids appear to be responsible for the large amount of calcium binding, an effect that previously was shown to be reduced in vitamin D deficiency. In contrast, basolateral and Golgi membranes prepared from isolated cells had low levels of nonesterified fatty acids and calcium binding. Intermediate levels were found with isolated cells that were not put through the usual washing procedures. Addition to homogenates of scrapings of a lipase inhibitor, diethyl-p-nitrophenyl phosphate, reduced calcium binding and nonesterified fatty acids to levels similar to those in membranes prepared from isolated cells. Phospholipase A activity was low in homogenates of isolated cells and high in scrapings; this was reduced in intestinal scrapings of vitamin D-deficient rats. Ileal membranes had more calcium binding than duodenal membranes, and ileal homogenates also had greater phospholipase A activity. Preparation of subcellular membranes from rat intestinal scrapings can result in altered lipid composition, probably due to lipolytic enzyme activity; in addition to increasing cation-binding, these high levels of fatty acids may affect other membrane properties and enzyme function.

Animals↗
PubMed1986

Localization of chloride secretion in rabbit colon: inhibition by anthracene-9-carboxylic acid.

The substituted aromatic compound anthracene-9-carboxylic acid (A-9-C) was used to inhibit active Cl- secretion by the epithelium of short-circuited rabbit distal colon. Tissues were mounted in Ussing chambers and stimulated to secrete Cl- by the addition of 1 mM dibutyryl adenosine 3',5'-cyclic monophosphate to the serosal bath. Results of 36Cl-flux measurements showed that the addition of 0.1 mM A-9-C to the mucosal bath inhibited Cl- secretion by 48%. The site of Cl- secretion was determined by using conventional micro-electrodes to show that the cells of the crypt regions, and not the surface epithelial cells, responded to A-9-C by an increase in apical membrane fractional resistance from 0.75 to 0.80 and a hyperpolarization of the apical membrane from -64 to -68 mV (P less than 0.05). The sulfhydryl reagent dithiothreitol was added to the mucosal tissue bath to remove the mucus produced by goblet cells of the crypt regions of these tissues. The time for maximal inhibition of Cl- secretion by A-9-C was decreased from 30 to 15 min by removal of the mucus barrier. The effects of A-9-C on the crypt cells, as well as the effect of mucus on the inhibitory action of this compound, demonstrate that the crypt region is the site of Cl- secretion.

Animals↗
PubMed1986

Lack of circulating immune complexes in inflammatory bowel disease.

Multi-organ involvement and especially extraintestinal manifestations have suggested an immune complex-mediated pathogenesis of ulcerative colitis and Crohn's disease. Using various techniques controversial data have been reported on the incidence and levels of circulating immune complexes and their correlation to clinical presentation. Sera of 131 patients with inflammatory bowel disease (78 Crohn's disease, 53 ulcerative colitis) representing a wide spectrum of disease activity, treatment and presence or absence of extraintestinal manifestations were tested for circulating immune complexes using Raji cell indirect immunofluorescence assay, Raji cell radioimmunoassay, C1q solid phase assay and polyethylene glycol precipitation coupled with measurements of optical density and subsequent immunoelectrophoresis or radial immunodiffusion. Circulating immune complexes in low concentrations were observed in a small number of patients with inflammatory bowel disease, the frequency and concentrations being slightly higher in patients with Crohn's disease than in those with ulcerative colitis. No association of concentrations of circulating immune complexes with disease activity or presence of extraintestinal manifestations could be demonstrated. These data do not support the claim for a major role of circulating immune complexes in the pathogenesis of inflammatory bowel disease.

Adolescent↗
PubMed1986

Autoimmune disease induced by oral administration of mercuric chloride in Brown-Norway rats.

Only few reports are available on the consequences of chronic oral administration of low doses of mercuric chloride (HgCl2). Forty Brown-Norway rats received 150 micrograms HgCl2/100 g body weight 3 times a week by gavage or by i.m. injection with 100 micrograms twice per week. After 2 weeks of oral HgCl2 administration, the rats lost weight and hair. Phases of proteinuria were observed in weeks 5-8 and then continuously from week 12 until the end of the experiment at week 39. Antibodies binding to renal, intestinal, and vascular basement membrane developed after 2 weeks; circulating immune complexes were detectable in increasing titers starting at week 3. There were linear deposits of IgG, IgM, and IgA in the glomerular basement membrane and tubular basement membrane, and along the intestinal basement membrane. After week 11, the first granular immune deposits were observed in renal and intestinal basement membranes. Light microscopy showed thickening of glomerular basement membrane, mesangial matrix, and tubular basement membrane. In addition, interstitial nephritis was observed in some animals. Interestingly, kidney involvement was as severe in the orally as the i.m.-treated animals.

Administration, Oral↗
PubMed1986

Expression of developmentally regulated crypt cell antigens in human and rat intestinal tumors.

The expression of 5 antigens specific for adult intestinal crypt cells and defined by monoclonal antibodies prepared to surface membrane components of the human colon tumor cell line CaCo-2 was studied during fetal and postnatal development of Sprague-Dawley rat small and large intestines. In the small intestine, all epithelial cells were stained during fetal life; antigen distribution became restricted to the crypt and lower villus cells in suckling animals and to the crypt cells after weaning. In the colon, these antigens could be detected only during a short period of development, comprising the last 3-4 days of fetal life and the first 8-10 days after birth. Expression of the antigens defined by this group of antibodies was investigated in rat intestinal tumors induced by 1,2-dimethylhydrazine (CAS: 540-73-8) and in normal and diseased human colons. In rats, these antigens were detected in all poorly and moderately differentiated adenocarcinomas of the small and large intestines. In most specimens, antigen distribution was not uniform; intensely stained areas were surrounded by completely negative tumor regions. Antigen expression was less intense in well-differentiated tumors, and about half of the tumors were negative for antigen expression. A similar pattern of expression of these antigens was observed in all human colonic adenocarcinomas examined; all samples of normal colon, benign polyps, and inflammatory bowel diseases examined were negative. These results suggest that this group of monoclonal antibodies recognizes oncofetal rat antigens expressed in chemically induced rat intestinal tumors and human colonic adenocarcinomas.

1,2-Dimethylhydrazine↗
PubMed1985

Decrease by cycloheximide of calcium binding and nonesterified fatty acids in rat-intestinal Golgi-enriched membrane fractions.

Rat intestinal Golgi-enriched membrane fractions bind more Ca2+ than do basolateral and microvillus-enriched membrane fractions, and this uptake is reduced by vitamin D-deficiency. The effect of the protein synthesis inhibitor, cycloheximide, on this Ca2+ binding was determined in rat fed a normal, vitamin D-sufficient diet. Cycloheximide, 1.5 mg/kg, rapidly reduced protein synthesis (measured by [3H]leucine incorporation) to 12% of control values within 15 min, but Ca2+ binding diminished gradually to 50% of control values by 60 min. Ca2+ transport across gut sacs was also decreased. The reduction in Ca2+ binding was not due to an alteration in vesicle morphology or to a direct effect of cycloheximide. Nonesterified (free) fatty acids, the probable binding sites for Ca2+ in these membrane fractions, were reduced by cycloheximide to 48% of control values by 60 min. There was no significant change in total lipid phosphate. Cycloheximide may affect the synthesis of proteins necessary for the presence of nonesterified fatty acids in these Golgi membranes.

Animals↗
PubMed1985

Arteriovenous malformations as a cause of gastrointestinal bleeding: the importance of triple-vessel angiographic studies in diagnosis and prevention of rebleeding.

Arteriovenous malformations of the gastrointestinal tract are a source of upper and lower gastrointestinal bleeding. We studied 40 patients with arteriovenous malformations. Eighteen percent had single lesions in either the distal transverse colon or the left colon (the angiographic distribution of the inferior mesenteric artery). Seventeen percent had concomitant colonic and extracolonic arteriovenous malformations. Only 6% of those who underwent surgery for removal of arteriovenous malformations rebled. We also studied the incidence of angiodysplastic lesions of the colon of 159 patients over the age of 55 with lower gastrointestinal bleeding; associated arteriovenous malformations were present in 21%. These data suggest: that to evaluate arteriovenous malformations as a cause of gastrointestinal bleeding, one must perform inferior and superior mesenteric and celiac angiography; the incidence of rebleeding is reduced when triple-vessel selective visceral angiography precedes surgical removal of arteriovenous malformations; and the incidence of associated arteriovenous malformations approaches that of diverticulosis in elderly patients with lower gastrointestinal bleeding.

Adult↗
PubMed1985

Heterotopic gastric mucosa: a case report.

A case of heterotopic gastric mucosa in discrete nodules of the duodenum is presented. Its radiographic and endoscopic appearance is described. The light and electron microscopic features are analyzed. Ultrastructural examination of its organization, cellular and subcellular components revealed similarities to normal fundic gastric mucosa. The histological and clinical differences between heterotopic gastric mucosa and duodenal metaplastic change are discussed.

Choristoma↗