| Using [U-13C]glucose and 2H2O tracers, we present a novel method to estimate the sources of plasma glucose from gastric absorption, gluconeogenesis from phosphoenol pyruvate (PEP), gluconeogenesis from glycerol, or glycogenolysis after an oral glucose load. A 13C NMR method was adapted to measure the contributions of oral glucose and endogenous glucose to plasma glucose. A 2H NMR method was used to subdivide endogenous glucose into contributions from glycogen, PEP and glycerol. Rats were fasted for 24 hr and glucose (2 g/kg; enriched with [U-13C]glucose to 5% or 10%) was loaded by oral gavage. 2H2O (2 mL) was injected into the intraperitoneal cavity immediately after the glucose load. Individual animals were sacrificed at 30-min intervals over a 3-hr period and whole blood and liver samples were collected. Plasma glucose was converted to monoacetone glucose and analyzed by 1H-, 2H-NMR, and J-resolved heteronuclear single quantum coherence (J-HSQC) spectroscopy. Liver fructose 2,6-bisphosphate (Fru-2,6-P2) and glycogen were assayed enzymatically. The gastric contribution to plasma glucose reached ∼50% at 30 min after the glucose load and gradually decreased thereafter. The contribution of gluconeogenesis to plasma glucose was significant, ranging ∼6--7 mM throughout the study period, whereas the contribution from glycogenolysis was small. Liver Fru-2,6-P2 increased ∼10 fold shortly after the glucose load, reached a maximum at 60 min, then dropped to baseline levels by 150 min. Liver glycogen repletion was brisk throughout the study, reaching ∼30 mumol/g at 3 hr and gluconeogenesis remained active even in the presence of high liver Fru-2,6-P2. Thus, Fru-2,6-P2 does not inhibit gluconeogenesis significantly in 24hr fasted rats after an oral glucose load.;Practicum Two. The analysis of steroidal molecules on dietary supplements using a GC/MS system and a LC/ESI-MS system was presented. Sterols and saponins in wild yam extracts, orchic substances, Tribulus terrestris, and a commercial product (T.T.-LRTM) were analyzed.;Practicum One. The fabrication, characterization, and implementation of imaging fiber electrode (IFE)sensors specific for NADH is presented. IFE sensors represent the first union in which electrogenerated chemiluminescence (ECL) imaging is performed through the actual sensor itself. (Abstract shortened by UMI.)... |
