Glycogen Formation Research Articles

On the formation of glycogen and trehalose in baker's yeast

More glycogen and trehalose is formed in aerobically incubated baker's yeast than under anaerobic conditions, glucose being a more favourable source of sugar than maltose. The regulation of the formation of glycogen in aerobic incubations of non-proliferating baker's yeast in the presence of glucose can be explained by the action of the activators and inactivators (Rothman & Cabib, 1967). The level of ATP in the cell does not affect the formation of trehalose in the same way as it influences the formation of glycogen. The incubation temperature chosen can be used to manipulate the relative proportions of glycogen and trehalose in baker's yeast. 30°C is the optimum for the formation of glycogen, and at 45°C none at all is formed. The inhibition of the biosynthesis of glycogen is not, at least primarily, a consequence of the effect of the elevated temperature on the enzymes taking part in the formation of glycogen. The optimum temperature for the formation of trehalose is 45°C, and at this temperature baker's yeast containing as much as 20% trehalose can be obtained.

The Effects of Human Chorionic Somatomammotropin and Estradiol on Gluconeogenesis and Hepatic Glycogen Formation in the Rat

The Effects of Human Chorionic Somatomammotropin and Estradiol on Gluconeogenesis and Hepatic Glycogen Formation in the Rat

Glycogen Metabolism in Glycogen-rich Erythrocytes

Abstract High concentrations of red blood cell glycogen were visualized by electron microscopy and demonstrated biochemically in amylo-1,6-glucosidase- and phosphorylase-deficient red blood cells. Glycogen concentration decreased as a function of cell age. Similar incorporation rates of 14C-U-glucose into glycogen were observed in amylo-1,6-glucosidase-deficient and normal erythrocytes, characterized by an initial rise, followed by a plateau formation reflecting a steady state between glycogen synthesis and breakdown. A different pattern of kinetics was observed in phosphorylase-deficient cells, which in view of the lack of the degradative enzyme showed a continuous linear increase in radioactive glycogen formation leveling off only after exhaustion of substrate. Evidence that in amylo-1,6-glucosidase-deficient red blood cells the main metabolic activity affects the outer branches of the glycogen molecule was obtained directly by β-amylolytic degradation of the radioactive glycogen molecule and indirectly by a chase experiment substituting radioactive with nonlabeled glucose. Normal glycogen synthetase activity was found in all cases of amylo-1,6-glucosidase examined except in one family in which an unexpected low affinity of the enzyme to glycogen was found. The observation that both amylo-1,6-glucosidase- and phosphorylase-deficient red blood cells retain the capacity to incorporate glucose into glycogen indicates that glycogen synthesis in erythrocytes proceeds along the UDPG glycogen synthetase pathway and is not a result of a reverse activity of any of the degradative enzymes.

The action of insulin of glycogen synthesis in rat diaphragm from intracellular and extracellular glucose

Rat hemidiaphragms were loaded with [U-14C] glucose at 2°C and subsequently incubated at 37°C with non-labeled glucose or [14C] glucose in the presence or absence of insulin. The incorporation of isotope into glycogen and lactate was determined. The results showed that insulin markedly stimulated the synthesis of glycogen from extracellular glucose while it had no effect on incorporation of isotope into glycogen from intracellular glucose. Lactate formation was not influenced by insulin. It was concluded that glucose transport in muscle is linked to glycogen sythesis and that insulin preferentially directs glucose entering the cell toward the formation of glycogen.

Gluconeogenesis and hepatic glycogen formation in relation to the rat estrous cycle.

Gluconeogenesis and hepatic glycogen formation in relation to the rat estrous cycle.

Culture of human fetal liver.

SummaryA method for the preparation of collagen-substrate cultures of human fetal liver is described. The growth and long-term maintenance of differentiated hepatic parenchymal cells in these cultures from liver tissue from human fetuses of 8 to 18 wk gestation is described. Satisfactory outgrowth of hepatic parenchymal cells was obtained from fetuses of 12 to 18 wk gestation, while outgrowth of cells from an 8 wk fetus was less satisfactory and the cells degenerated within 2 wk. Outgrowing cells demonstrated the typical morphology and arrangement of hepatic parenchymal cells and glycogen formation was readily demonstrated. Mitotic figures were observed during the first 2 wk of culture and foci of cells in the granulocytic and erythrocytic series were prominent during this period. Addition of hydrocortisone to the media resulted in a marked reduction of fibroblastic growth surrounding the colonies of hepatic parenchymal cells, even after prolonged culture. Culture of human fetal liver in Gelfoam-sponge or...

Dynamics of metabolism of normal and virus-transformed chick cells in culture.

Application of steady-state tracer technique to normal and transformed cells in tissue culture allows quantitation of intracellular pool sizes of many metabolites and determination of rate of carbon flow along diverse paths. Using a unique apparatus to control the environmental conditions, we show that the glucose carbon flow into tricarboxylic acid cycle intermediates and amino acids is unchanged upon transformation. The increased glycogen formation and glycolysis varies with the glucose concentration in the medium, correlates with the faster glucose transport of transformed cells, and cannot be explained by a difference in growth rate alone.

Reappraisal of the ultrastructure of the human endometrial glandular cell.

SummaryA survey of the ultrastructure of histologically normal endometrial biopsies from 30 women at various stages of the menstrual cycle was made. The nucleus and nucleolus showed morphological variations in the different phases of the cycle which could be correlated with the changing metabolic needs of the cytoplasm. During the ovulatory phase, glycogen, giant mitochondria and nucleolar basket formation were observed and the functional morphology of the latter two organelles is discussed. The secretory phase was characterized by the apocrine and merocrine secretion of glycogen and glycoprotein, as well as by age changes and ultimate cellular breakdown.

Sex steroid influence on hepatic gluconeogenesis and glucogen formation.

Hepatic gluconeogenesis and glycogen formation were studied in female rats following 21 days of parenterally administered sex steroids to assess the effects of these hormones on liver carbohydrate metabolism and their role in the development of insulin antagonism during pregnancy. Estradiol, progesterone or the two hormones in combination were administered in sesame oil, and control rats received oil alone. Daily dosages of estradiol and progesterone did not exceed 5 μg or 5 mg, respectively. 128 Animals were subdivided into 2–hr and 24–hr fasted groups. Percentage conversion of intravenous alanine— U–14C or pyruvate–3–14C into glucose–14C was followed over a 30 min interval. Suppression of this conversion was most consistently produced with the combined regimen in association with increased percentages of precursor radioactivity appearing in hepatic glycogen. Plasma insulin concentrations were significantly increased in all sex steroidtreated animals relative to control values as was the liver glycogen c...

Parallel stimulation of sugar transport and glycogen formation by a synthetic insulin-dextran complex in diaphragms.

The effects of a soluble insulin—dextran complex on the distribution of l-14C—L—arabinose and on the incorporation of U—14C—D—glucose into glycogen were examined in rat “intact” hemidiaphragm preparations. The complex was prepared by coupling crystalline bovine insulin covalently with dextran (av mol wt, 40,000). The insulin—dextran caused the acceleration of glycogen formation in parallel with the facilitation of sugar transport in quite a similar manner to that of native insulin, although insulin—dextran was to some extent less potent than native insulin in both of the above actions. The present results indicate that insulin exerts its effects on glycogenesis under conditions precluding the entry of the hormone into the cell. The binding of insulin with the cell membrane structures not only stimulates transmembrane sugar transport but initiates a propagation of events by which glycogen formation system is directly stimulated within the cell. (Endocrinology 91: 1442, 1972)

Role of different precursors in the synthesis of liver glycogen during cortisol administration.

ABSTRACT The rate of label incorporation of various precursors into liver glycogen and exhaled carbon dioxide was investigated in rats 3, 6, 24 and 48 hours after cortisol injection. The glycogen concentration in the liver attained its maximum 24 hours after the hormone injection, whereas the total radioactivity of glycogen from [1-14C] glucose, [1–3-14C] lactate and [1,2-14C] glycerol reached the highest level during 3 to 6 hours and then remained within the subnormal limits 24 hours after the injection. The label incorporation from [1-14C] glycine into liver glycogen reached a maximum 6 to 24 hours after the hormone injection, coinciding in time with the maximum increase of the glycogen concentration in the liver. Hence, amino acids play a more important role in glycogen formation as compared with other precursors; thus they seem to be the main substrates in cortisol-induced gluconeogenesis. Cortisol produced no effect on [1,2-14C] glycerol oxidation, but the hormone increases oxidation of other labelled substrates involved in exhaled carbon dioxide.

Effect of insulin on pyruvate and glucose metabolism of beating mouse heart cells

Beating myocardial cells from 1 to 5-day old mice maintained in tissue culture can convert [U- 14C]glucose, [2- 14C]pyruvate and [1- 14C]octanoate to carbon dioxide. Single component porcine insulin stimulated only the oxidation of pyruvate without enhancing glycogen or lactic acid formation. The effect of insulin on pyruvate does not require glucose. It is suggested that insulin increases the oxidation of pyruvate by the activation of pyruvic dehydrogenase in these beating heart cells.

Glycogen Metabolism following Ultraviolet Irradiation

Using mini pigs as experimental animals, histochemical and biochemical changes in glycogen metabolism following UV light irradiation were investigated. The most remarkable change observed in the first 4 hours post irradiation was a decrease in the glycogen concentration. This decrease might be due to the release of lysosomal α-glucosidase. After the first 4 hours there was a sharp increase in the percent of glycogen synthetase present in the I-form (peak at 10 hours) and in the rate of glycogen formation. This was followed by a peak of glycogen concentration at approximately 15 hours after irradiation.

Separation of glycogen formation and aminotransferase activity induced by cortisol in fetal rat liver.

Fetal rat liver in organ culture formed glycogen and tyrosine aminotransferase (TAT) in response to 2 X 10–6M cortisol. Introduction of decaborane suppressed the increase in TAT, but did not prevent glycogen formation from glucose. When glucose was omitted, explants made TAT but not glycogen in response to cortisol. Fetal liver explants incorporated label from L—alanine—U–14C into glucose and glycogen to a small extent and thus showed gluconeogenic capability. This process was not affected by decaborane or cortisol. Cortisol diverted the products of gluconeogenesis to glycogen and away from glucose. The steroid caused a rise in aspartate aminotransferase that was prevented by decaborane. Alanine aminotransferase levels were unaffected by either steroid or decaborane. It is concluded that cortisol stimulated glycogen synthesis by a mechanism which did not involve gluconeogenesis or an effect on aminotransferases. (Endocrinology91: 257, 1972)

Occurrence of intramitochondrial glycogen in canine myocardium after prolonged anoxic cardiac arrest

Intramitochondrial glycogen deposits were observed in viable cardiac muscle cells of dogs sacrificed 2 to 4 weeks following prolonged periods of normothermic anoxic cardiac arrest induced by aortic cross-clamping during total cardiopulmonary bypass. These deposits were not observed in control dogs, in dogs which died several hours to 8 days after the anoxic period, or in cardiac biopsies taken immediately before and immediately after the anoxic period. The intramitochondrial glycogen deposits were located in the outer mitochondrial compartment, and varied from few to large numbers of granules that almost completely filled the mitochondria. These granules occurred in the monoparticulate (β) form and usually were slightly larger than the extramitochondrial β glycogen granules. Both intra- and extramitochondrial glycogen gave a strongly positive reaction with the periodic acid-thiosemicarbazide-silver proteinate method of Thiéry for the demonstration of polysaccharides; glycogen granules in both locations were extracted from ultrathin sections by amylase. Although intramitochondrial glycogen deposits have been described in a few patients with cardiomyopathies, the present study suggests that such deposits indicate a type of response to injury rather than a specific type of cardiomyopathy. It is suggested that the three factors responsible for the occurrence of intramitochondrial glycogen deposits in cardiac muscle cells following anoxic cardiac arrest are: (i) solubilization of the enzymes of glycogen metabolism during the anoxic period: (ii) increased permeability, due to anoxic damage, of the outer mitochondrial membrane; and (iii) diffusion of the solubilized enzymes of glycogen synthesis into the mitochondria with subsequent formation of glycogen.

Effects of thiols and disulfides on glucose utilization and insulin action in the isolated rat diaphragm

The actions of 2,2′-dithiodipyridine (DTP) and dithiothreitol (DTT) on glucose utilization and lactate formation by rat diaphragm were studied in vitro. The disulfide DTP had no significant effect on glucose utilization in the absence of insulin but inhibited the effect of insulin on glucose utilization and increased lactate formation and breakdown of glycogen by the tissue. The interference by DTP with the action of insulin could be reversed by the sulfhydryl compound DTT. DTT stimulated glucose utilization and net lactate formation by rat diaphragm. This effect of the sulfhydryl compound was different from that of insulin in that it commenced not immediately but only after about 30 min of incubation. In contrast to insulin, DTT decreased rather than increased glycogen synthesis. When the muscle was under the influence of both insulin and a high concentration of DTT, the initial insulin effect was not abolished. However, after about 30 min of incubation, the rate of glucose utilization was the same with DTT alone as with DTT plus insulin, and the muscle appeared to be under the influence mainly of DTT.

ASPECTS OF FRUCTOSE METABOLISM IN NORMAL MAN

Abstract. In normal subjects infusion of fructose (1 g/kg/hr) for 4 hrs resulted in an increase in the glycogen content of the m. quadriceps femoris of 3.3 g/kg wet muscle (muscle samples obtained by needle biopsy). This was equal to the amount of glycogen formed after a glucose infusion of the same magnitude. In muscle depleted of glycogen by exercise, infusion of glucose resulted in twice as much glycogen formed, as did a fructose infusion. Formation of liver glycogen was much higher after fructose than after glucose infusion (liver samples obtained by Menghini biopsy). Studies by hepatic vein catheterization indicated that glucose formation by the liver was insufficient to account for the synthesis of muscle glycogen, which presumably occurred directly from fructose taken up by the muscle.The occurrence of high lactic acid concentrations in blood resulting from infusion of fructose could be partly abolished by simultaneous infusion of amino acids, thus lessening the risk of lactic acidosis.

Glycogen Formation from Glycols and their Esters in the Livers of Chicks

Glycogen Formation from Glycols and their Esters in the Livers of Chicks

Effects of histological and electron microscopical fixatives on the insulin content of the rat pancreas.

SUMMARY The effects of chemical fixatives such as the aldehydes, as well as ethanol, on the insulin content of the rat pancreas were studied. Although there was some loss of insulin after the use of all the fixatives investigated it was found that glutaraldehyde preserved the greatest amount of the hormone at both room and low temperature. Insulin was still preserved in the pancreas after glutaraldehyde fixation even after the complete preparation of the tissue for histology or electron microscopy. The insulin extracted from the pancreas after fixation in formaldehyde was still biologically active and it enhanced the formation of glycogen in the rat diaphragm.

Cation transport and metabolism as a function of salinity in the excised gill of Carcinus maenas

1. 1. Intracellular concentrations of sodium and potassium were measured in the excised gill of Carcinus maenas in media of different ionic compositions as a function of salinity. 2. 2. The increase in respiration observed with decrease in salinity was independent of the activity of the conventional Na +/K + linked pump. 3. 3. No evidence was obtained to suggest that the energy for the Na +/K + pump was supplied by glycolysis. 4. 4. Evidence is presented which shows that the ionic composition of the medium has a pronounced effect on respiration, lactic acid and carbon dioxide production and the formation of glycogen and glucose.