On the dependence of nuclear oxidative phosphorylation on glycolysis in isolated rat thymus nuclei

Résumé Les expériences présentées montrent qu'il est possible d'inhiber au maximum la glycolyse des noyaux isolés du thymus de rat, sans influencer la respiration et la synthèse d'ATP. Elles suggèrent ainsi que, dans ces noyaux, la phosphorylation oxydative ne dépend pas forcément de la glycolyse.     

Kinetics of insulin secretion in response to glucose by isolated islands of Langerhans from the fetal rat]

Isolated islets of Langerhans from 21.5 day-old foetal Rats were studied in a perifusion system in vitro. The overall dynamics of insulin release by the foetal islets in response to glucose 13.9 mM is biphasic and qualitatively similar to that obtained with islets of adult Rats. The magnitude of the initial phase of insulin secretion is similar for the foetal and adult islets. The second phase is fourfold higher in the adult than in the foetus. The response of foetal islets occurs, 45 to 60 sec. after the increase of glucose concentration in the medium and a maximum insulin release for the first phase is obtained with a lag period of 2 min. The difference between foetal and adult islets is essentially quantitative.     

Preparation of isolated cells from rat heart

Summary Suspensions of isolated cells from rat heart were prepared and the data for viability and yield are given. Glucose uptake by the cells was mediated by a carrier system.The technical assistance of Mr.E. T. Potter, Mr.K. D. Patel and Mr.M. Griffin is gratefully acknowledged.     

Effect of methotrexate on glycolysis of leukemia L 1210 cells cultivated in vitro]

Methotrexate, at non lethal doses, alters the glycolysis of leukaemic L 1210 cells. Glucose uptake and lactate excretion are increased but lactate/glucose ratio remains constant. The activity of glycolytic enzymes in the cytoplasm is increased and the level of intracellular ATP is greatly enhanced.     

Effect of fatty acids on fetal rat bone in culture

Zusammenfassung Nachweis, dass Fettsäuren (Palmitin-, Stearin- und Ölsäuren) in sehr niedrigen Konzentrationen die Kalziumabgabe und die Knochenresorption in fötalen Ratten in vitro fördern.

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The studies were supported by USPHS grant No. AM 11262. The albumin monomer was kindly supplied by Drs.J. Brand andL. Raisz.     

Cyclic nucleotide levels in the perfused rat heart subjected to hypoxia

Summary Isolated rat hearts were subjected to hypoxic perfusion on a recirculating Langendorff apparatus. Following a 30-min-period of aerobic stabilization the hearts were perfused for 30 min with media equilibrated with 84% N₂, 12% O₂ and 4% CO₂. At the end of the hypoxic period myocardial concentrations of cyclic AMP and cyclic GMP were determined by radioimmunoassay. Exposure to hypoxia resulted in a significant increase in cyclic AMP (p<0.01) and a decrease in cyclic GMP (p<0.05) as compared to hearts perfused for 60 min with media gassed with 96% O₂, 4% CO₂.Acknowledgment. We gratefully acknowledge the excellent technical assistance provided by Mrs Inger O. Boggs and Miss Patricia C. Hannigan. This work was supported in part by U. S. Public Health Service grant HL 14661 from the National Heart and Lung Institute, and by a grant from the Central Ohio Heart Chapter.     

Cyclic nucleotide levels in the perfused rat heart subjected to hypoxia.

Isolated rat hearts were subjected to hypoxic perfusion on a recirculating Langendorff apparatus. Following a 30-min-period of aerobic stabilization the hearts were perfused for 30 min with media equilibrated with 84% N2, 12%O2 and 4% CO2. At the end of the hypoxic period myocardial concentrations of cyclic AMP and cyclic GMP were determined by radioimmunoassay. Exposure to hypoxia resulted in a significant increase in cyclic AMP (p less than 0.01) and a decrease in cyclic GMP (p less than 0.05) as compared to hearts perfused for 60 min with media gassed with 96% O2. 4% CO2.     

Hydrochloric acid secretion of fetal rat gastric mucosa]

In Rat, spontaneous secretion of hydrochloric acid by gastric mucosa takes place before birth. From day 20 of gestation until birth, the pH of gastric content markedly decreases, reaching 3 pH-units in newborns. During this period, Cl- concentration in gastric juice increases, while p-CO2 remains constant.     

Effect of spironolactone on p-nitrophenol glucuronidation in isolated rat hepatocytes

The effect of spironolactone (SP) on p-nitrophenol (PNP) glucuronidation was studied in isolated rat hepatocytes with appropriate viability conditions. A significant increase of protein concentration and PNP glucuronidation was found in the hepatocytes from SP-treated rats. Increased enzyme activity apparently was related to the SP dose. The results favor the conclusion that SP may induce PNP glucuronidation in the hepatocyte.     

The effect of insulin on the glycolysis and glycogen content of beating rat heart cells in the primary culture

Zusammenfassung An pulsierenden Rattenherzzellen in der Primärkultur wurde die Insulinwirkung auf die Glykolyse und den Glykogengehalt untersucht.     

Regulation of isolated rat hepatocyte volume in hypoosmotic media]

Isolated hepatocytes behave like osmometers immediately after an incubation in hypo-osmotic media. During long-term incubation periods they recover their normal volume either in the absence or in the presence of ouabain. The volume regulation is parlty due to a decrease in intracellular potassium and amino acid contents.     

Evolution of myocardial glycolysis in perinatal rats]

Glycolysis was assessed in the Langendorff perfused rat heart during the perinatal period. Glucose uptake, lactate production, 14C-glucose incorporation into glycogen, tissue content content of glycogen, lactate and high energy phosphates were measured in the foetus of 21.5 days post co?tum and in the newborn of 1 and 7 days post partum. Glycogen synthesis and anaerobic glycolysis were found to be more active in the foetal heart and to decrease during the first neonatal week.     

Effect of nonprotein thiols on protein synthesis in isolated rat hepatocytes

The ability of nonprotein thiols to modulate rates of protein synthesis was investigated in isolated rat hepatocytes. Addition of cysteine stimulates protein labelling by [¹⁴C] Leucine. Glutahione depletion, induced by in vivod administration of L-buthionine sulfoximine and diethylmaleate, did not alter the effect of cysteine, although it decreased the rate of protein synthesis by 32%. The effect of cysteine on protein synthesis does not seem to be related to a perturbatin of the redox state of the NAD⁺/NADH system or to changes in the rate of gluconeogenic pathway. The following observations indicate that cysteine may stimulate protein syntheis by increasing intracellular levels of aspartate: 1. Amino-oxyacetate, an inhibitor of pyridoxyal-dependent enzymes, inhibits protein labelling and decreases aspartate cellular content, whereas most amino acids accumulate or remain unchanged; 2. Cysteine, in the absence or in the presence of amino-ocycetate, stimulates protein labelling and induces aspartate accumulation, although mot amino acids diminish or remain unchanged.     

Effect of glucagon on ethanol oxidation in isolated rat liver cells

Summary Addition of glucagon 5 min after ethanol was found to stimulate the rate of ethanol oxidation in hepatocytes isolated from starved rats. This stimulation is of the same order of magnitude as that mediated by asparagine. The glucagon effect is suppressed by antiproteolytic agents such as insulin or NH₄Cl. The stimulatingeffect of glucagon on ethanol oxidation is probably liked to enhanced proteolysis andan elevated glutamate level in the hepatocytes.Acknowledgments. this investigation was supported by grants from the Institut de la Santé de la Recherche Médicale, the Scientific Council of the Faculté de Médecine Paris-Ouest and the Ecole Pratique des Hautes Etudes (3rd section).