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At least 55 records · Page 3Linked to original sources
PubMed1994

Impaired in vivo insulin secretion in response to non-glucidic secretagogues in adult rats after neonatal streptozotocin.

In the perfused pancreas of adult rats that were injected with streptozotocin (STZ) during the neonatal period, the release of insulin caused by glucose is more severely affected than that evoked by other secretagogues. We have now examined whether a comparable situation prevails in vivo. In anesthetised rats, the 0-10 min plasma insulin incremental area recorded after intravenous glucose administration (2.8 mumol/g body wt) was severely decreased in STZ rats, with a K value for glucose utilization of 1.9 +/- 0.2 x 10(-2)/min, as compared with control rats, with a K value of 4.4 +/- 0.4 x 10(-2)/min. At the 2nd min of the test, the plasma insulin increment was about 5 times lower in STZ than control rats. After glibenclamide administration (0.1 nmol/g body wt), the insulin incremental area was 3 times lower in STZ than control rats. Relative to the post-prandial readings, the plasma glucose concentration was decreased to the same extent, however, in control and STZ rats injected with glibenclamide. The secretory response to succinic acid methyl ester (SAM; 1.0 mumol/g body wt) was virtually abolished in the STZ rats. In the latter animals, SAM also failed to enhance the hypoglycemic action of glibenclamide in contrast to the situation found in control rats. Iterative intraperitoneal administration of SAM (1.0 mumol/g body wt) thrice daily for 7-10 days failed to improve significantly the insulin secretory response to glucose or glibenclamide, whether in control or STZ rats. These findings indicate that the altered metabolism of glucose in the B cell of STZ rats coincides with an impaired secretory response to glibenclamide and SAM, as possibly attributable, in part at least, to a loss of the modulating action of glucose upon the secretory response to the hypoglycemic sulfonylurea and succinate ester.

Animals↗
PubMed2005

Topographical localisation of glucidic residues and their variations in the canine zona pellucida during folliculogenesis.

In the present ultrastructural study, horseradish peroxidase-labelled lectins, in conjunction with antiperoxidase antibody and protein A-gold, were used to characterise and localise the oligosaccharide sequences of zona pellucida glycoproteins at different stages of follicular development in the canine ovary. Deacetylation and sialidase digestion were also performed before lectin cytochemistry. The zona pellucida of oocytes present in unilaminar primary follicles reacts with WGA- and RCA-I-lectins. The zona pellucida of oocytes present in bilaminar and trilaminar secondary follicles displays positivity to WGA, RCA-I, Con-A, UEA-I, and sialidase/SBA. This labelling pattern persists in the zona pellucida of oocytes present in antral tertiary follicles with the exception of WGA and RCA-I reactive sites which are differently distributed throughout the zona pellucida. The topographical distribution of these carbohydrates is not uniform throughout the zona pellucida, indicating the regionalization of oligosaccharide chains within three concentric bands of the zona matrix: an inner surface close to the oocyte plasma membrane, an intermediate portion and an outer layer in contact with the follicular cells. Our results demonstrated variations in the presence and distribution of the carbohydrate residues in the canine zona pellucida during different stages of follicular growth. We also observed the presence of vesicles in both the ooplasm and granulosa cells, showing a similar lectin binding pattern to that of the zona pellucida.

Animals↗
PubMed1999

Glucose and non-glucidic nutrients exert permissive effects on 2-keto acid regulation of pancreatic beta-cell function.

Insulin-releasing effects of straight and branched chain 2-keto acids were assessed using clonal glucose-responsive beta-cells. Pyruvic acid (PA), 2-ketovaleric acid (KV), 2-ketoisovaleric acid (KIV) or 2-keto-3-methylvaleric acid (KMV) dose-dependently promoted the stimulatory effects of D-glucose, whereas 2-ketobutyric acid (KB) did not affect insulin release. The stimulatory 2-keto acids also promoted the stimulatory activity of D-glyceraldehyde, L-leucine or L-arginine. Responses to PA, KV, KIV or KMV were significantly reduced by transport inhibition with 2-cyano-3 hydroxycinnamate, glucokinase inhibition with mannoheptulose or metabolic inhibition with sodium azide or sodium cyanide. Membrane hyperpolarisation with K+ depletion or diazoxide reduced insulin output, but failed to abolish secretory responses to KV, KIV and KMV. Secretory effects of these 2-keto acids also persisted in beta-cells depolarised with high KCl and glucose. Voltage-dependent Ca2+ channel blockade, with verapamil, or depletion of extracellular Ca2+ abolished the secretory activity of 2-keto acids. Collectively, these results indicate that glucose and metabolisable nutrients exert permissive effects on 2-keto acid-induced insulin release. In addition, KV, KIV and KMV can regulate beta-cell function at least partially independently of K+-ATP channel activity, both through their mitochondrial metabolism and regulation of Ca2+ influx.

Animals↗
PubMed1997

Intranasal immunization of mice with Echinococcus granulosus surface antigens iscoms evokes a strong immune response, biased towards glucidic epitopes.

The present work describes the preparation and characterization of iscoms from tegumental antigens of Echinococcus granulosus protoscoleces, and their use as immunogens in mice by intranasal and subcutaneous routes. Iscoms given at 10 mg doses evoke a significant antibody response when administered i.n. and a strong and long lasting antibody response by s.c. route. The Ag administered i.n. in a non-adjuvanted form as a booster was not immunogenic. The i.n. route of immunization induced higher IgA serum titre in relation to IgG than the s.c. route and antisera of slightly higher avidity. Also, ten fold lower IgG2a/IgG1 and ten fold higher IgG3/IgG1 ratios were observed for the i.n. protocol compared to the s.c. one. Moreover, the mucosal route of immunization induced more efficiently antibodies of both isotypes directed to carbohydrate epitopes. The differences between immune response generated by i.n. and parenteral immunizations should be taken into consideration, particularly in those cases in which protective antigens are glycosylated.

Administration, Intranasal↗
PubMed2002

Glucidic determinants expressed by the digestive apparatus of Umbrina cirrosa (L.) fries as revealed by lectin histochemistry.

Glycoconjugates present in the various parts of the digestive apparatus (oesophagus, stomach, intestine) of 27, 34 and 44 days-old Umbrina cirrosa (L.) fries were characterised by means of lectin histochemistry in conjunction with sialidase digestion and KOH treatment. High amounts of carbohydrates were detected especially in goblet cells of the oesophagus. Positivity obtained with the various lectins in oesophagus, stomach and intestine did not change during the development of the fries examined. D-Gal and D-GalNAc appeared to occupy a terminal position in oligosaccharidic chains whereas they are linked to sialic acid residues in adult subjects, which suggests an incomplete chemical structure of the glycoconjugates secreted by the digestive apparatus of fries.

Animals↗
PubMed1990

Intestinal calcium transfer and alkaline phosphatase activity in relation with vitamin D and glucide diet.

For four weeks after weaning, rats were fed either on a diet without any calcium utilization factors (-D) or on the same diet with cholecalciferol (+D) or sorbitol (S). In the -D group, blood calcium levels decreased whilst alkaline phosphatase activities in blood and bone were increased. For +D and S groups, these parameters were normal. Using everted or in situ ligatured loops, calcium transfer from a CaCl2 + 45Ca solution was measured in the duodenum, the jejunum and in the ileum. Alkaline phosphatase activity from these regions was also measured. For the three diets and for all regions of the intestine, there was a good correlation between calcium transfer and phosphatase activity. These values were higher in the duodenum than in the ileum or jejunum, and also higher in the ileum in the +D group than in the -D and S groups although this was not significant. These low levels in the S group which were, sometimes, even lower than those seen in the -D group contrasted with blood and bone levels of alkaline phosphatase, which were normal for the S and +D groups. There was also a discrepancy between the low values found for both phosphatase activity and calcium transfer in rats S in the experiments where the calcium transfer assay was carried out in calcium solution and those found in experiments were both calcium and carbohydrate were present. In the latter, enhanced levels of intestinal phosphatase activity were observed, as well as a marked, albeit delayed, increase in intestinal calcium transfer. Onset latency and rapid offset are reminiscent of induction of bacterial enzymes by carbohydrates.

Alkaline Phosphatase↗