[The rate of gluconeogenesis and the activity of its key enzymes in the kidneys of the developing chick embryo]. / Skorost' gliukoneogeneza i aktivnost' ego kliuchevykh fermentov v pochkakh razvivaiushchegosia zarodysha kuritsy.

The rate of glucose formation from lactate was studied in tubules isolated from the kidneys of chick embryos of different age and for one- and two-day-old chickens. Changes in the activity of the key enzymes of gluconeogenesis have also been followed in the chick embryo kidneys. The rate of gluconeogenesis markedly increased after hatching. Changes in the rate of gluconeogenesis during embryogenesis are correlated with those in the activity of key enzymes of this process: phospho(enol) pyruvate carboxykinase, fructose-1,6-bisphosphatase, and glucose-6-phosphatase. Glucose-6-phosphatase was shown to be polyfunctional in the kidneys of chick embryos and chickens: in addition to hydrolysis of glucose-6-phosphate with formation of glucose, the enzyme is capable of phosphorylating glucose with the help of phosphate donors, carbamyl-phosphate and pyrophosphate.

[The enzymes of fructose metabolism in the liver of chick embryos]. / Fermenty obmena fruktozy v pecheni zarodyshei kur.

The activity of fructose cycle enzymes remains practically constant in chick embryonic liver during ontogenesis. Change in ratio of aldolase A to B activities was detected. It is suggested that fructose enters the cycle via the sorbitol pathway in which aldose reductase and sorbitol dehydrogenase are involved.

[The activity of alpha-ketoglutarate dehydrogenase and succinate dehydrogenase in the liver of the developing chick embryo. The relation to the rate of the tricarboxylic acid cycle]. / Aktivnost' al'fa-ketoglutaratdegidrogenazy i suktsinatdegidrogenazy v pecheni razvivaiushchegosia zarodysha kuritsy. Sviaz' so skorost'iu tsikla trikarbonovykh kislot.

Succinate dehydrogenase and alpha-ketoglutarate dehydrogenase activities were determined in the liver of chick embryos and one and two day old chickens. The succinate dehydrogenase activity remained unchanged throughout development. The alpha-ketoglutarate dehydrogenase activity decreased by the end of embryogenesis and increased after hatching. The alpha-ketoglutarate dehydrogenase activity as an index of rate of the tricarboxylic acid cycle is discussed.

[Rate of gluconeogenesis in the hepatocytes of the developing chick embryo]. / Skorost' gliukoneogeneza v gepatotsitakh razvivaiushchegosia zarodysha kuritsy.

The rate of glucose formation from lactate was determined in the hepatocytes isolated from the liver of developing chick embryos and one day old chickens. The maximum rate of gluconeogenesis is observed in the hepatocytes of 16-17 day old chick embryos. A sharp fall in the rate of gluconeogenesis is noted in the hepatocytes of the embryos before hatching. It decreases still further in one day old chickens. The patterns of the gluconeogenesis rate are similar both for endogenous precursors and lactate.

[Role of polyfunctional glucose-6-phosphatase in the liver carbohydrate metabolism of the developing chick embryo]. / Rol' polifunktsional'noi gliukozo-6-fosfatazy v uglevodnom obmene pecheni razvivaiushchegosia émbriona kuritsy.

Glucose-6-phosphatase was shown to be polyfunctional in the liver of the developing chick embryo. Changes in the activity of glucose-6-phosphate phosphohydrolase did not correlate with the rate of gluconeogenesis. The activity of this enzyme increased from the 16th to the 20th day of embryogenesis. The activities of pyrophosphate-glucose phosphotransferase, carbamyl-phosphate-glucose phosphotransferase did not change during embryogenesis. The ratio of the activities of phosphohydrolase and phosphotransferases was characterized by the predominance of the phosphohydrolase activity. The values of latency of phosphohydrolase and phosphotransferases did not correlate with the rate of gluconeogenesis. Glucose-6-phosphate phosphohydrolase was found not only in the microsomal, but in the nuclear fraction as well. KM(G6P) of the enzyme of the nuclear fraction differed from KM of the microsomal enzyme.

[Correlation between [NAD+]:[NADH] and the "phosphate potential" in liver cytoplasm of developing chicken embryos]. / Sootnoshenie mezhdu [NAD+]:[NADH] i "fosfatnym potentsialom" v tsitoplazme pecheni razvivaiushchegosia émbriona Kuritsy.

No correlation between the changes in the ratios of [NAD+]:[NADH] and [ATP]/[ADP] . [HPO4(2-)] in liver cytoplasm of developing chicken embryos was found. The [ATP]/[ADP] . [HPO4(2-)] ratio depends on the rate of gluconeogenesis. The [NAD+]:[NADH] ratio remains unchanged up to hatching and is then decreased 2-fold, the [ATP]/[ADP] . [HPO4(2-)] ratio being unchanged. The experimental and theoretical values of the "phosphate potential" show a coincidence.

[Interrelationship between two kinetic forms of pyruvate kinase in chicken liver during ontogenesis]. / Sootnhoshenie mezhdu dvumia kinticheskimi formami piruvatkinazy v pecheni kuritsy v ontogeneze.

The value of the r coefficient for pyruvate kinase (rate at 1.5 mM of phosphoenolpyruvate per rate at 0.4 mM of phosphoenolpyruvate), i.e. ratio between the enzyme forms possessing the Michaelis-Menten and cooperative kinetics, in chicken liver during ontogenesis was found to be different. The embryonic liver contains predominantly the form with the cooperative kinetics, while in the livers of 1- and 10-day-old chickens the content of the other form is increased. In the livers of adult chicken the correlation between the two forms is that typical for 10-day-old chicken.

[Independence of the (NAD+):(NADH) ratio from the adenylic system in the liver cytoplasm of the developing chick embryo]. / Nezavisimost' otnosheniia (NAD+):(NADH) ot adenilovoi sistemy v tsitoplazme pecheni razvivaiushchegosia zarodysha kuritsy.

No dependence was found between the index of the adenylic system phosphorylated state (ATP) : (ADP) (HPO2-4), the ratios (ATP) : (ADP) and (ATP : (ADP + AMP), on one hand, and the ratio (NAD+) : (NADH) in the cytoplasm, on the other one. The maximum value of the ratio (ATP) : (ADP) (HPO2-4) was observed on the 17th day of development and correlated with the maximum rate of gluconeogenesis. The ratio (NAD+) : (NADH) in the cytoplasm suffered no changes until hatching and decreased twice thereafter.

[Factors regulating gluconeogenesis in chick embryo liver]. / Faktory reguliatsii gliukoneogeneza v pecheni kurinykh embrionov.

The ratio NAD+/NADH in cytoplasm and mitochondria of chicken embryo liver does not change up to the stage of hatching. After the hatching this ratio decreases 2-fold in both cytoplasm and mitochondria. The hatching is also accompanied by the decrease of total and mitochondrial contents of oxaloacetate and of oxaloacetate/malate ratio, the activity of citrate synthase and the ratio acetyl-CoA/CoA being unchanged.

[Activity of pyruvate dehydrogenase in embryonic and postnatal chicken liver]. / Aktivnost' piruvatdegidrogenazy v embrional'noi pecheni kuritsy.

The activity of pyruvate dehydrogenase (EC 1.2.4.1) in chicken liver embryos remains constant up to the stage of hatching, and is increased by 50-70% during the first days of postnatal development and 6-7-fold on the ninth day. The enzyme activity in adult chickens is approximately equal to that in embryonic liver. The system of pyruvate dehydrogenase activation is labile; however, it may be stabilized by an addition of serum to embryonic liver homogenates. The amount of the inactive form of pyruvate dehydrogenase in embryonic liver makes up to approximately 50% of total activity. No stabilizing effect of the serum on the pyruvate dehydrogenase from young and adult chicken liver was observed.

[Characteristics of the activity of "satellite" enzymes of gluconeogenesis in the oocytes and embryos of loach]. / Osobennosti aktivnosti "satellitnykh" fermentov gliukoneogeneza v ootistakh i zarodyshakh v'iuna

The activity of "satellite" enzymes related to gluconeogenesis has been measured in the oocytes and embryos at the early stages of loach (Misgurnus fossilis L.) embryogenesis. The activity of pyruvate dehydrogenase increase during oocyte maturation by 30%, remains constant at the cleavage and blastula stages and decreased on the onset of gastrulation. In the both oocytes and embryos pyruvate dehydrogenase has been found only in the active form. The activity of citrate synthase, malate dehydrogenase and pyruvate carboxylase remained constant during oocyte maturation and et all early stage of embrional development. Citrate lyase and "malic"-enzyme were not found, Oocyte maturation is followed by a considerable increase in the malate and oxalacetate content, the level of pyruvate and acetyl-CoA being found invariable.

[NAD+/NADH ratio in the mitochondria of the oocytes and ova of groundling, Misgurnus fossilis (L.)]. / Otnoshenie (NAD+)/(NAD-H) v mitokhondriiakh ootsitov i iaits v'iuna Misgurnus fossilis (L.)

The ratio NAD+/NAD-H was detemined in mitochondria of the loach oocytes and eggs on the basis of concentrations of the glutamate dehydrogenase reaction intermediates. This ratio increases 6 times upon the oocyte maturation. The importance of this ratio in the metabolism of oocyte and embryo is discussed.

[Control of pyruvate dehydrogenase in loach embryo oocytes]. / Osobennosti kontrolia piruvatdegidrogenazy v ootsitakh i zarodyshakh v'iuna.

The activity of pyruvate dehydrogenase (PDH) increases during the oocyte maturation in the loach Misgurnus fossilis due, apparently, to the decrease of pyruvate utilization in the reactions of gluconeogenesis. The activity of PDH decreases twice at the stage of gastrula. These changes in the PDH activity are not related to intertconversion of the enzyme active and inactive forms of PDH; the total PDH of oocytes and embryos is in the active form only.

[The relationship between the (NAD+)/(NAD-H) ratio and the adenylate system in the cytoplasm of loach oocytes and embryos]. / Zavisimost' mezhdu otnosheniem (NAD+)/(NAD-H) i adenilovoi sistemoi v tsitoplazme ootsitov i zarodyshei v'iuna

The dependence was found between the phosphorylated state of the adenylic system (ATP)/(ADP) (HPO42-) and the ratio (NAD+)/(NAD-H) during the maturation of the loach (Misgurnus fossilis L.) oocytes which is accompanied by the cessation of gluconeogenesis and onset of gycogenolysis. The twofold decrease of the value of phosphorylated state of the adenylic system is correlated with the twofold decrease of the value of the ratio (NAD+)/(NAD-H).