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At least 1,225 records · Page 68Linked to original sources
PubMed1988

[Introduction of modified hexose residues into O-specific polysaccharides of Salmonella of serotype E, B, C2 and C3 using synthetic nucleotide sugars].

A series of synthetic nucleotide sugars have been studied as monosaccharide donors in the biosynthetic assembly of the O-antigen repeating units of Salmonella sero-groups E, B, C2 and C3. UDP-Tal did not serve as a substrate of galactosyl phosphate transferase, and GDP-Tal did not substitute GDP-Man in mannosyltransferase reactions. dTDP-L-Man proved to be a substrate of rhamnosyl transferases; GDP-2dMan, GDP-3dMan, GDP-D-Rha and GDP-Glc served as substrates for mannosyltransferases. The modified tri- and tetrasaccharide derivatives can be converted into the modified O-specific polysaccharides after incubation with Salmonella membranes.

Antigens, Bacterial↗
PubMed1988

Reassessment of the translocation hypothesis by kinetic studies on hexose transport in isolated rat adipocytes.

The effect of insulin and factors which have insulin-like activity on the kinetic parameters of 3-O-methyl-D-glucose (MeGlc) transport in rat adipocytes were assessed. Carrier-mediated uptake of MeGlc was estimated by the difference in the amounts of [14C]MeGlc and L-[3H]glucose taken up in cells under equilibrium exchange conditions at 37 degrees C. The Km and Vmax values in basal cells were 17.4 mM and 0.24 nmol/10(6) cells/s, respectively. Removal of endogenous adenosine by adenosine deaminase resulted in a 26% decrease in the basal rate due to a slight increase in the Km (19.6 mM) and a decrease in the Vmax value (0.20 nmol/10(6) cells/s). The maximum concentration (10 nM) of insulin decreased the Km to approximately one-half of the basal (7.1 mM) concomitant with an 8.5-fold increase in the Vmax value (2.04 nmol/10(6) cells/s). Submaximal concentrations (50 and 150 pM) of insulin, N6-phenylisopropyladenosine (1 microM), mechanical agitation of cells by centrifugal force (160 x g), low temperature (15 degrees C), 12-O-tetradecanoylphorbol-13-acetate (1 microM), and hydrogen peroxide (10 mM) all decreased the basal Km value to a range of 13.5-7.3 mM, concomitant with a 1.7-7.4-fold increase in the Vmax. A possible explanation for the alterations in the kinetic parameters may be that insulin and other factors cause the translocation of the mobile low-Km glucose transporters from an intracellular site to the cell surface, where the stationary high-Km transporters are located. Thus, when the Km and Vmax values of the hypothetical high-Km transporters were assumed to be 20 mM and 0.20 nmol/10(6) cells/s, respectively, and the Km of the low-Km transporters was assumed to be 7 mM, the theoretical Km decreased from 20 to 7.5 mM as the Vmax of the low-Km transporters increased from near 0 to 2.0 nmol/10(6) cells/s. The relation between empirical Km and Vmax values as affected by several agents and conditions followed closely the relation predicted by the above two-transporter model.

3-O-Methylglucose↗
PubMed1977

The endocrine pancreas in early alloxan diabetes. Including study of the alloxan inhibitory effect of feeding and some hexoses.

Starved animals were sensitive to alloxan, whereas a more or less inhibitory effect towards alloxan was observed in fed animals, and in starved animals pretreated with glucose, mannose or fructose, but not in those pretreated with galactose. The islets of starved controls possessed larger B-cell mitochondria than those of fed ones. The earliest B-cell changes in the alloxan-treated animals were localized to the mitochondria which showed swelling, and disruption of inner and occasionally outer membranes. Later, many mitochondria were disintegrated, and the endoplasmic reticulum and Golgi complex disorganized. The secretory granules were preserved, although sometimes with atypical configuration, in degenerating but non-necrotic B-cells, suggesting that insulin stored in granules is not released until the cells are necrotic. Finally, frank necrosis was seen in some B-cells, whereas others were unaffected. The Ca2+-precipitation studied by pyroantimonate technique and x-ray analysis differed in the B-cells of the alloxan-treated animals from that in the controls; the former animals exhibited no or only sparse precipitation in mitochondria and secretory granules, but a rich precipitation in the cytoplasmic ground substance, whereas the precipitation in the controls mainly was localized to mitochondria and secretory granules. The primary site of alloxan action in the B-cells is believed to be localized to the mitochondria.

Animals↗
PubMedDate not supplied

[Fucose and other neutral hexoses in the feces of patients with nonspecific ulcerative colitis].

Secretion of glycoproteins with protective mucus of large intestine was studied by means of estimation of the carbohydrate components in feces of patients with unspecific ulcerous colitis. A decrease in daily excretion with feces of glycoproteins and glycopeptides was detected in these patients as well as in the patients with chronic pancreatitis. Under conditions of unspecific ulcerous colitis distinct from chronic pancreatitis content of fucoglycoproteins, main chemical protectors of gastrointestinal tract, was primarily decreased. The defect of large intestine mucus might be responsible for impairment of barrier function of the intestinal mucose and to contribute to ulcer development.

Adolescent↗
PubMed1985

Intestinal uptake of hexoses and fatty acids in tumor-bearing rats.

An in vitro technique was used to examine the rate of uptake of varying concentrations of glucose, galactose, and a homologous series of saturated fatty acids into the jejunum of control rats and Noble rats bearing prostatic tumor variants of primary human prostatic adenocarcinoma 52. Both groups of animals were healthy, eating and gaining weight normally. The uptake of acetic and butyric acid was reduced in tumor-bearing rats, but the uptake of four medium chain-length fatty acids was unchanged. The similar value of the incremental change in free energy in the control and tumor-bearing animals indicates similar passive permeability properties of the jejunum in the two groups. The uptake of varying concentrations of glucose and galactose was similar in the control and in the tumor-bearing animals. It is concluded that there are only subtle changes in nutrient uptake in tumor-bearing rats that are eating and gaining weight normally. It is suggested that any alteration in nutrient absorption which might occur in the cachectic tumor-bearing animal is probably due to alterations in food intake or body weight, rather than due to a direct effect of the tumor on the intestine.

Adenocarcinoma↗
PubMed1985

Effect of two defined formula diets on jejunal and colonic uptake of hexoses in control and ileal resected rabbits.

An in vitro technique was used to measure the jejunal and colonic uptake of glucose and galactose in sham-operated control (CONT) rabbits and in animals with a surgical resection of the distal half of the small intestine (RES) performed six weeks previously. CONT and RES were fed ad libitum or pair-fed amounts of standard Purina chow, or ad libitum amounts of Ensure or Flexical HN for two weeks. Flexical NH differs from Ensure in its higher content of carbohydrate, essential fatty acids and polyunsaturated fatty acids but lower total dietary content of fat. The ad libitum chow-fed animals gained weight whereas the animals fed the defined formula diets lost weight. Weight gain was greater in RES than CONT fed chow, and weight loss was greater in RES than CONT fed Ensure or Flexical HN. Despite these differences in body weight, the dry and wet weights of the jejunum, and the adherent mucosal fluid volumes remained unchanged in CONT and RES fed the different diets. The intestinal morphology was unaffected by feeding Ensure or Flexical HN to control animals, whereas the villus cell size, villus and mucosal surface areas were lower in resected rabbits fed these diets than in resected animals fed chow. Glucose uptake was greatest in CONT and RES fed Flexical HN. Glucose uptake was higher in RES than CONT fed chow or Ensure but was lower in RES than CONT fed Flexical HN. In CONT fed Flexical HN, there was a lower value of the apparent Michaelis constant, Km*, and a higher value of the apparent passive permeability coefficient (Pd*) than in animals fed chow or Ensure. In RES there was lower Pd* in Ensure and Flexical HN-fed rabbits than in those fed chow, but the Km* was lower and the maximal transport rate, Jdm, was higher in animals given Flexical HN. The colonic uptake of glucose and the jejunal uptake of galactose was also influenced by feeding Ensure and Flexical HN. These differences in uptake in animals fed Ensure or Flexical-HN could not be explained by differences in body weight gain, since a different pattern of changes in glucose and galactose uptake was observed in CONT or RES rabbits exposed to restricted chow intake.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗