Dara M. Bier

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"New" glucose production has been measured in 54 infants and children for the first time by continuous three-to-four-hour influsion of the safe, nonradioactive tracer 6,6-dideuteroglucose. The use of combined gas chromatography--mass spectrometry with monitoring of selected ions allowed deuterium enrichment in blood glucose to be measured on microliter(More)
To determine the plasma epinephrine thresholds for its metabolic and hemodynamic actions and plasma epinephrine metabolic clearance rates, 60-min intravenous epinephrine infusions at nominal rates of 0.1, 0.5, 1.0, 2.5, and 5.0 microgram/min were performed in each of six normal human subjects. These 30 infusions resulted in steady-state plasma epinephrine(More)
To study glutamate and glutamine kinetics, 4-h unprimed intravenous infusions of L-[15N]glutamate, L-[2-15N]glutamine, and L-[5-15N]-glutamine were administered to healthy young adult male subjects in the postabsorptive state. Arterialized-venous blood samples were drawn and analyzed for glutamate and glutamine 15N enrichments. The fractional turnover rates(More)
Leucine metabolism in vivo can be determined from a primed, continuous infusion of L-[1-13C]leucine by measuring, at isotopic steady state, plasm [-13C]leucine enrichment, expired 13CO2 enrichment, and CO2 production rate. With an appropriate priming dose of L-[1-13C]leucine and NaH13CO3, isotopic steady state is reached in less than 2 h, and the infusion(More)
Muscle mass and function are improved in the elderly during resistance exercise training. These improvements must result from alterations in the rates of muscle protein synthesis and breakdown. We determined the rate of quadriceps muscle protein synthesis using the in vivo rate of incorporation of intravenously infused [13C]leucine into mixed-muscle protein(More)
To quantitate alanine and lactate gluconeogenesis in postabsorptive humans and to test the hypothesis that muscle is the principal source of these precursors, we infused normal volunteers with [3-14C]lactate, [3-13C]alanine, and [6-3H]glucose and calculated alanine and lactate incorporation into plasma glucose corrected for tricarboxylic acid cycle carbon(More)
To assess the mechanisms responsible for increased gluconeogenesis in noninsulin-dependent diabetes mellitus (NIDDM), we infused [3-14C]lactate, [3-13C]alanine, and [6-3H]glucose in 10 postabsorptive NIDDM subjects and in 9 age- and weight-matched nondiabetic volunteers and measured systemic appearance of alanine and lactate, their release from forearm(More)
Insulin resistance for glucose metabolism in skeletal muscle is a key feature in non-insulin-dependent diabetes mellitus (NIDDM). Which cellular effectors of glucose metabolism are involved is still unknown. We investigated whether transmembrane glucose transport in vivo is impaired in skeletal muscle in nonobese NIDDM patients. We performed euglycemic(More)
To explore leucine metabolism in relation to leucine intake, five young adult men received an L-amino acid diet that supplied 40, 30, 20, and 10 mg leucine.kg-1.d-1 for 6 d. A stable-isotope-tracer infusion study was then conducted for 5 h while subjects received an intragastric infusion of the test diet. Primed, constant infusions of L-[1-13C]leucine(More)