PubMed Health⌕ Search

Biomedical subjects

J S Whitehead

Publications and source records attributed to J S Whitehead.

At least 19 recordsLinked to original sources
PubMed1983

Alterations in membrane sugars during epidermal differentiation: visualization with lectins and role of glycosidases.

Differentiation in keratinizing epithelia involves the orderly transformation of basal germinal cells into an exterior cornified layer. We have employed rhodamine-conjugated lectins to visualize distinctive changes in the localization of keratinocyte membrane glycoconjugates during epidermal differentiation. The dermis, basement membrane, and epidermal cell membranes stained positively for mannose, alpha- and beta-galactose, N-acetyl-glucosamine, and sialic acid. In contrast, only the viable epidermis demonstrated N-acetyl-galactosamine, while alpha-L-fucose staining was limited to the upper stratum spinosum and stratum granulosum. Neuraminidase treatment extended the binding of certain lectins, e.g., peanut agglutinin, to regions of the skin that otherwise did not label. Whereas the granular cell membranes displayed the largest number of carbohydrates, these sugars could no longer be visualized after granular cells differentiated into the stratum corneum. Loss of lectin staining may be attributable to the presence of a family of sugar-specific glycosidases that we obtained from granular and cornified cell cytosol fractions. Finally, as further support for sugar deletion during cornification, we found that glycosphingolipids are hydrolyzed to ceramides coincident with both loss of lectin staining and the emergence of glycosidase activity. These results suggest: 1) that carbohydrates on keratinocyte cell membranes can be used as markers of epidermal differentiation, and 2) that removal of cell surface sugars during cornification may be due to the action of specific glycosidases in the outer epidermis.

Acetylglucosamine↗
PubMed1982

Muscarinic acetylcholine receptors of the small intestine and pancreas of the rat: distribution and the effect of vagotomy.

1. The distribution of muscarinic cholinergic receptors (mAChR), detected by atropine-inhibitable binding of [3H] quinuclidinyl benzilate, was examined in membrane fractions of pancreas, small intestinal muscle, mucosa, villi and crypts of sham-operated and vagotomized rats. 2. Specific (atropine inhibitable) [3H] quinuclidinyl benzilate binding was greater to the ileal mucosa than to jejunal mucosa or to duodenal mucosa, but binding crypt and villus fractions was not significantly different. This distribution of specific [3H] quinuclidinyl benzilate binding suggests that cholinergic mucosal innervation is more important in the ileum than the jejunum. 3. Vagotomy produced a decrease in the amount of specific [3H] quinuclidinyl benzilate binding to duodenal mucosa only, suggesting that parasympathetic denervation of the small intestine does not cause mucosal hypersensitivity to acetylcholine by an increase in mAChR.

Acetylcholine↗
PubMed1980

Effects of sodium butyrate and dimethylsulfoxide on biochemical properties of human colon cancer cells.

Sodium butyrate and dimethylsulfoxide (DMSO) have marked effects on the growth, morphology, and biochemistry of two human colonic adenocarcinoma cell lines in culture. Doubling times were increased between 18% and 660% while cell viability was unaffected. Both cell lines formed colonies in soft agar in the absence of butyrate of DMSO, but no colonies were observed in the presence of these agents. However, no differences in in vivo tumorigenicities, when cells were implanted in athymic mice, were seen following treatment. Gross morphological alterations including cell enlargement, process formation, and cellular flattening occurred during culture in butyrate or DMSO. Acrylamide gel electrophoresis in sodium dodecyl sulfate revealed no change in membrane protein constituents, but autoradiographic analysis of membrane glycoproteins demonstrated differences between treated and untreated cells. Ganglioside compositions were altered, and a sialyltransferase required for the synthesis of GM3 ganglioside was elevated by butyrate. Although cytoplasmic aminooligopeptidase remained unaffected by butyrate or DMSO, brush border-associated activity was enhanced by butyrate. Alkaline phosphatase also rose dramiatically during culture in butyrate but was not enhanced by DMSO.

Adenocarcinoma↗
PubMed1980

Interaction of Escherichia coli K88 antigen with porcine intestinal brush border membranes.

The fimbria-associated Escherichia coli antigen, K88, was purified to homogeneity as determined by polyacrylamide gel electrophoresis and immunodiffusion. This polymeric antigen consists of noncovalently linked subunits, containing little or no carbohydrate, and has a monomeric molecular weight of 23,000. When a binding assay employing differential filtration was used, K88 formed complexes with isolated porcine intestinal brush border membranes. The formation of complexes was inhibited by glycoproteins with terminal N-acetylglucosamine and N-acetylgalactosamine residues and to a lesser extent by free N-acetylhexosamines. These amino sugars may play a role in the interaction of this pathogenic strain of E. coli with the intestinal epithelia of pigs.

Animals↗
PubMed1980

An inhibitor of lymphocyte proliferation produced by a human colonic adenocarcinoma cell line in culture.

The culture fluid taken from a human colonic adenocarcinoma cell line, SKCO-1, inhibited mitogenic stimulation of mouse lymphocytes measured by reductions in blast information or [3H]thymidine uptake. The inhibitor was not cytotoxic to lymphocytes nor did it alter the growth rates of 21 other cell lines examined. However, the in vitro growth rates of two murine lymphoid tumor lines were also markedly reduced by the SKCO-1 medium. The tumor cell culture media could be added up to 40 hr after concanavalin A stimulation and still effect complete inhibition of [3H]thymidine uptake. A similar inhibition was observed for phytohemagglutinin (from red kidney bean), lipopolysaccharide, and mixed lymphocyte response assays. The inhibitor has a molecular weight of greater than 100,000 and is stable to heat and ultraviolet radiation, but is destroyed by mild periodate oxidation. The inhibitor may play a role in immunosuppression.

Adenocarcinoma↗
PubMed1978

Protein digestion and absorption in the rat.

1. A randomly labelled 14C protein was synthesized in order to investigate the site and rate of digestion and absorption of dietary protein in the rat. 2. A liquid test meal consisting of protein and a non-absorbable marker, 51CrCl3, was administered to rats which were then sacrificed at intervals up to 4 hr after ingestion of the meal. Analysis of intestinal contents showed that as gastric emptying proceeded, the meal moved rapidly to the distal two thirds of the small intestine. 3. Protein digestion and absorption occurred predominantly in this area over a period of 1-2 hr. 4. Amounts of endogenous protein present in the small intestine never exceeded amounts of exogenous protein during maximum absorption of exogenous protein (0-1 hr). At later time periods (2-4 hr), however, more endogenous than exogenous protein was detected in the intestinal lumen. 5. It is concluded that the digestion and absorption of dietary protein is a rapid process, taking place in the distal two-thirds of the small intestine. Endogenous protein levels do not exceed exogenous protein levels until after the bulk of exogeneous protein is absorbed.

Animals↗
PubMed1977

Human plasma uridine diphosphate galactose-glycoprotein galactosyltransfertase. Purification, properties and kinetics of the enzyme-catalysed reaction.

The soluble galactosyltransferase of human plasma catalysed the transfer of galactose from UDP-galactose to high- and low-molecular-weight derivatives of N-acetylglucosamine, forming a beta-1-4 linkage. The enzyme was purified by using (NH4)2SO4 precipitation and affinity chromatography on an alpha-lactalbumin-Sepharose column. The galactosyltransferase was maximally bound to this column in the presence of N-acetylglucosamine, and the enzyme was eluted by omitting the amino sugar from the developing buffer. The molecular weight of the enzyme was estimated to be 85000 by gel filtration. The assay conditions for optimum enzymic activity was 30 degrees C and pH7.5. Mn2+ ion was found to be an absolute requirement for transferase activity. The Km for Mn2+ was 0.4 mM and that for the substrate, UDP-galactose, was 0.024 mM. The Km for the acceptors was 0.21 mM for alpha1-acid glycoprotein and 3.9 mM for N-acetylglucosamine. In the presence of alpha-lactalbumin, glucose became a good acceptor for the enzyme and had a Km value of 2.9 mM. Results of the kinetic study indicated that the free enzyme reacts with Mn2+ under conditions of thermodynamic equilibrium, and the other substrates are added sequentially.

Chromatography, Paper↗
PubMed1976

A simple quantitative method to determine short chain fatty acid levels in biological fluids.

A simple method has been developed for quantitative acetic, propionic, isobutyric, butyric, isovaleric, valeric, isocaproic, and caproic acids in intestinal fluids, feces and blood. The method utilizes extraction with ether and gas chromatography. It is accurate over a wide range of SCFA concentrations and appears to be applicable to any biological fluid.

Chromatography, Gas↗
PubMed1976

Isolation and characterization of three unusual membrane glycopeptides present in rat intestinal endoplasmic reticula.

Three glycopeptides have been isolated from the mucosal homogenates of the rat small intestine without using proteolysis. These glycopeptides appear to be localized exclusively in the membranes of the endoplasmic reticula. Although they have similar molecular weights of about 2550 and have similar amino acid compositions, they differ in the carbohydrate constituents. The major glycopeptide has 2 mol glucose per polypeptide chain while the two other glycopeptides contain 1 mol fucose, mannose and galactose with either 1 or 2 mol glucose. No hexosamine or sialic acid was detected in any of the glycopeptides. An unusual physical property was found associated with these glycopeptides. Below pH 6.5 they formed a precipitate which prevented them from diffusing through a dialysis membrane and allowed them to be rapidly purified following solubilization from the membrane. These glycopeptides appear to represent a new group of heretofore uncharacterized membrane constitutents which may play a role in some function specific for the endoplasmic reticula.

Amino Acids↗
PubMed1975

Differential binding to Sepharose-Con A of B12-binding proteins from human gastric juice.

Human gastric juice was found to contain at least two vitamin B-12 binding substances. One of the proteins which formed a complex with B12 was found to bind to a column containing Sepharose-ConA. Since the protein which bound to Sepharose-ConA was absent in the gastric juice of pernicious anemia patients it was concluded that this protein was intrinsic factor. The ability of intrinsic factor to bind to Sepharose-ConA offers a potential means by which intrinsic factor could be separated from other B-12 binding proteins in gastric juice. The ConA binding properties of intrinsic factor might be exploited in the development of a diagnostic test for pernicious anemia.

Anemia, Pernicious↗
PubMed1975

Short chain fatty acids in rats with jejunal blind loops. I. Analysis of SCFA in small intestine, cecum, feces, and plasma.

The luminal and plasma levels of short chain fatty acids (SCFA), products of bacterial fermentation, were measured in rats with surgically produced, self-filling blind loops located in the proximal small intestine. High levels of acetic, propionic, and butyric acids were detected in the blind loop segment and in the distal small bowel, regions which in normal and sham-operated rats contain no SCFA. Isobutyric, isovaleric, and valeric acids were also present. Feeding or fasting made little difference in the amount or composition of luminal SCFA. Although the amount of SCFA in each animal varied, the ratio of these acids was relatively constant. The ceca of the blind loop rats had relatively less acetic acid (48% of total SCFA) than did normal rats (64%) and proportionately more isobutryic, isovaleric, and valeric acids. The concentrations of SCFA increased in the feces of blind loop rats. The acetic acid concentration was 50% higher in blind loop rat feces; propionic, isobutryic, and isovaleric acids were elevated to a greater extent. The total output of most of the SCFA was also of acetic acid (137 +/- 32 mug per ml), the rest being isovaleric (5.2 +/- 2.6 mug per ml) and isobutyric (1.4 +/- 0.7 mug per ml) acids. Blind loop animals had nearly twice the concentration of acetic acid in the plasma (240 +/- 29 mug per ml) as normal animals, while the other acids were unchanged. The present study suggests that endogenous substances may be important substrates for the production of SCFA in the intestinal lumen. The high levels of SCFA in the small intestine and in feces and the substantial increase in the concentration of acetic acid in thvergrowth syndrome if the same relationships were found in man.

Animals↗
PubMed1975

Studies on the binding of amylopectin sulfate with gastric mucin.

Amylopectin sulfate, a sulfated polysaccharide that has an antipeptic property, was examined for its ability to bind gastric mucins. After chemically cross-linking the amylopectin sulfate into an insoluble gel, its binding with mucins isolated from antral and fundic mucosa of canine stomachs was studied with chromatography. A component present in both mucin fractions bound to the amylopectin sulfate gel below pH 4.5. This binding was reversible, and the complex dissociated above pH 5. Similar binding properties were found with soluble amylopectin sulfate. The component of the mucine which bound to amylopectin sulfate differed from the one which did not bind in its electrophoretic mobility and in its higher proportion of basic amino acids and a lower hexosamine, serine, and threonine content. This study suggests that amylopectin sulfate may bind to gastric mucins only under conditions of low pH.

Amino Acids↗