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Biomedical subjects

D R Langslow

Publications and source records attributed to D R Langslow.

At least 19 recordsLinked to original sources
PubMed1978

Hepatic gluconeogenesis in chickens.

Gluconeogenesis by isolated hepatocytes resulted in glucose release but insignificant rates of glycogen synthesis. The effectiveness of precursors was similar for hepatocytes from fed and starved chickens except for impaired gluconeogenesis from pyruvate when compared to lactate in lactate starved chicken hepatocytes. The impairment was caused by limitations in cytosolic NADH production as a result of the mitochondrial location of phosphoenolpyruvate carboxykinase in chicken liver. The order of effectiveness of precursors on hepatic gluconeogenesis was generally similar to the effects of precursors on increasing the plasma glucose concentration in vivo. The exceptions were caused by interactions with other precursors in vivo. The alteration of the NADH/NAD+ ratio by ethanol and ATP/ADP ratio by adenosine could play significant roles in the control of precursor conversion to glucose. Physiological glucagon concentrations stimulated gluconeogenesis from precursors entering the pathway both above and below the level of triose phosphates, and its effect were mimicked by dibutyryl cyclic AMP. Previous results on the effects of precursor and glucagon injection on the plasma glucose concentration of chickens in vivo can largely be explained by effects at the hepatic level. Isolated chicken and rat hepatocytes share many common features. Qualitatively the ordering of gluconeogenic effectiveness was similar but quantitive differences existed as a result of differing activities and cellular locations of enzymes. Neither preparation readily synthesised glycogen and the sensitivity to glucagon was similar.

Amino Acids↗
PubMed1978

The use of viable hepatocytes to study the hormonal control of glycogenolysis in the chicken.

The rapid isolation of high yields of parenchymal cells from chicken liver is described. Stringent tests of viability show that the isolated hepatocytes are both structurally and metabolically similar to those in intact liver. During incubation viability decreased and the significance of this change on the interpretation of metabolic experiments is discussed. Lactate was a much more effective gluconeogenic precursor than pyruvate even in the presence of additional reducing equivalents. Hepatocytes isolated from fed chickens produced glucose from glycogen degradation. Glycogenolysis was stimulated by glucagon, dibutyryl cyclic AMP and adrenaline. Half maximal glucagon effects were elicited by physiological concentrations of the hormone. Glucagon and dibutyryl cyclic AMP stimulated glucagon, dibutyryl cyclic AMP and adrenaline their action was not additive to that of adrenaline.

Adenosine Diphosphate↗
PubMed1978

Glucose phosphorylation and dephosphorylation in chicken liver.

1. Glucokinase was absent from chicken liver and only the low Km hexokinases, inhibited by AMP, ADP but not ATP, were present. 2. The Km of chicken liver glucose-6-phosphatase for glucose-6-phosphate was reduced from 5.65 to 3.75 mM following starvation, and the enzyme was inhibited by glucose. 3. Starvation of chickens for 24 hr slightly lowered the hexokinase activity and doubled glucose-6-phosphatase activity; it did not change subcellular distribution of the enzymes. Oral glucose rapidly restored the activities to fed values. 4. It was concluded that glucose uptake into, and efflux from, chicken hepatocytes, was regulated by the activity and kinetic characteristics of glucose-6-phosphatase and by the glucose-6-phosphate concentration, and that the hexokinases had little regulatory function.

Animals↗