scholarly journals Studies on glycogen synthesis in pigeon liver homogenates. Incorporation of hexose into glycogen

1967 ◽  
Vol 105 (2) ◽  
pp. 505-513 ◽  
Author(s):  
V. N. Nigam ◽  
A. Fridland
Keyword(s):  
Oxidative Phosphorylation ◽  
Microsomal Fraction ◽  
Glycogen Synthesis ◽  
Liver Homogenate ◽  
Glucose Starvation ◽  
Optimum Conditions ◽  
Liver Homogenates ◽  
Pigeon Liver ◽  
Glycogen Formation ◽  
Stimulation Of

Liver homogenates of avian species, but not of mammals, form glycogen from glucose, mannose, fructose and galactose. Incorporation of labelled glucose, fructose and mannose, but not of labelled galactose, into glycogen is diluted isotopically by unlabelled glucose. Except for fructose, glycogen formation from other substrates by pigeon liver homogenates compares favourably with that from the same substrates in pigeon liver slices. Optimum conditions for glycogen synthesis from glucose by pigeon liver homogenate are: medium of incubation, 0·175m-sucrose–45mm-potassium chloride−15mm-glycylglycine buffer, pH 7·5; concentration of substrate, 15mm; concentration of tissue, less than 120mg./ml.; temperature of incubation, 37–43°; atmosphere, oxygen. Uncouplers of oxidative phosphorylation, Ca2+, EDTA, PPi, 2-deoxyglucose 6-phosphate and microsomal fraction of rat liver are inhibitory to glycogen synthesis from glucose. Starvation of pigeons for 24 and 48hr. leads to a slight stimulation of glycogen synthesis in their liver homogenates as compared with fed controls. Pigeon liver homogenates can be separated into subcellular fractions that on reconstitution can synthesize glycogen. All the enzymes of the glycogen pathway except soluble high-Km glucokinase are present in pigeon liver.

scholarly journals Studies on glycogen synthesis in pigeon liver homogenates. Glycogen synthesis from glucose monophosphates and uridine diphosphate glucose

1967 ◽  
Vol 105 (2) ◽  
pp. 515-519 ◽  
Author(s):  
V. N. Nigam
Keyword(s):  
Time Course ◽  
Initial Rate ◽  
Glycogen Synthesis ◽  
Uridine Diphosphate ◽  
Cytoplasmic Fraction ◽  
Uridine Diphosphate Glucose ◽  
Diphosphate Glucose ◽  
Liver Homogenates ◽  
Pigeon Liver ◽  
Glycogen Formation

Comparative time-course studies of glycogen synthesis from glucose 6-phosphate, glucose 1-phosphate and UDP-glucose show that glucose 1-phosphate forms glycogen at an initial rate faster than that obtained with glucose 6-phosphate and UDP-glucose. After 5min. the rates from glucose monophosphates are considerably slower. 2,4-Dinitrophenol decreases glycogen synthesis from both glucose monophosphates, whereas arsenate and EDTA increase glycogen synthesis from glucose 1-phosphate and inhibit the reaction from glucose 6-phosphate, galactose and galactose 1-phosphate. Mitochondria-free pigeon liver cytoplasmic fraction forms less glycogen from glucose monophosphates than does the whole homogenate. 2-Deoxyglucose 6-phosphate inhibits glycogen synthesis from glucose monophosphates. Glycogen formation from UDP-glucose is relatively unaffected by dinitrophenol, by arsenate, by EDTA, by 2-deoxyglucose 6-phosphate and by the removal of mitochondria from the whole homogenate.

Role of glucose-1-phosphate and glucose-6-phosphate in glycogen synthesis by pigeon liver homogenate

1976 ◽  
Vol 7 (6-7) ◽  
pp. 327-333 ◽  
Author(s):  
Enrique Figueroa ◽  
Iris Peirano ◽  
Margarita Vega ◽  
Patricio Vega
Keyword(s):  
Glycogen Synthesis ◽  
Liver Homogenate ◽  
Pigeon Liver

scholarly journals Bile acids of snakes of the subfamily Viperinae and the biosynthesis of C-23-hydroxylated bile acids in liver homogenate fractions from the adder, Vipera berus (Linn.)

1976 ◽  
Vol 153 (2) ◽  
pp. 343-350 ◽  
Author(s):  
S Ikawa ◽  
A R Tammar
Keyword(s):  
Bile Acids ◽  
Microsomal Fraction ◽  
Liver Homogenate ◽  
Mitochondrial Fraction ◽  
Sodium Cholate ◽  
Vipera Berus ◽  
C 23 ◽  
Liver Homogenates ◽  
Generating System ◽  
Cholanic Acid

1. Analysis of bile salts of four snakes of the subfamily Viperinae showed that their bile acids consisted mainly of C-23-hydroxylated bile acids. 2. Incubations of 14C-labelled sodium cholate (3 α, 7 α, 12 α-trihydroxy-5 β-cholan-24-oate) and deoxycholate (3 α, 12 α-dihydroxy-5 β-cholan-24-oate) with whole and fractionated adder liver homogenates were carried out in the presence of molecular oxygen and NADPH or an NADPH-generating system. The formation of C-23-hydroxylated bile acids, namely bitocholic acid (3 α, 12 α, 23xi-trihydroxy-5 β-cholan-24-oic acid) and 3 α, 7 α, 12 α, 23 ξ-tetrahydroxy-cholanic acid (3 α, 7 α, 12 α, 23 ξ-tetrahydroxy-5 β-cholan-24-oic acid), was observed mainly in the microsomal fraction and partly in the mitochondrial fraction. 3. Biosynthetic pathways of C-23-hydroxylated bile acids are discussed.

scholarly journals Glycogen synthesis by hepatocytes from diabetic rats

1979 ◽  
Vol 182 (3) ◽  
pp. 727-734 ◽  
Author(s):  
S Golden ◽  
P A Wals ◽  
F Okajima ◽  
J Katz
Keyword(s):  
Rat Liver ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Active Form ◽  
Diabetic Rats ◽  
Liver Homogenates ◽  
Glucagon Injection ◽  
Glycogen Formation ◽  
In Cells

Hepatocytes prepared from streptozotocin- and alloxan-diabetic rats starved for 24 h contain 0.5–2% wet wt. of glycogen. Glycogen synthesis in the hepatocytes from such rats, after prior depletion of the glycogen by glucagon injection, was studied. As distinct from cells from normal animals, there was no glycogen synthesis from glucose as sole substrate, even at concentrations of 60 mM. When supplied with glucose, a gluconeogenic precursor (lactate, dihydroxyacetone or fructose), and with glutamine there was concurrent synthesis of glucose and of glycogen. Without glutamine there was little or no glycogen synthesis. The rate of glycogen formation was in the same range as for cells from control rats. Glutamine addition markedly activated glycogen synthase in cells of starved diabetic rats, but there was no effect on phosphorylase. We obtained very little synthesis of glycogen with hepatocytes from fed diabetic rats, whereas with normal animals, synthesis by such cells equals or exceeds that obtained from starved rats. The conversion of synthase b (inactive) into the active form was studied in rat liver homogenates. The activation of the synthase in cells from starved diabetic rats is somewhat less than that from normal animals, but that from fed diabetic rats is markedly decreased compared with that in livers of fed control animals or that of starved diabetic animals.

Secretagogue-induced changes in subcellular Ca2+ distribution in isolated pancreatic acini

1981 ◽  
Vol 240 (2) ◽  
pp. G130-G140
Author(s):  
R. L. Dormer ◽  
J. A. Williams
Keyword(s):  
Atomic Absorption Spectrometry ◽  
High Speed ◽  
Microsomal Fraction ◽  
Absorption Spectrometry ◽  
Subcellular Fractionation ◽  
Differential Centrifugation ◽  
Zymogen Granules ◽  
Pancreatic Acini ◽  
Induced Changes ◽  
Stimulation Of

In a prior study, we demonstrated that pancreatic secretagogues increased both the uptake into and washout of 45Ca2+ from isolated mouse pancreatic acini. The net result of these processes was an initial fall in total acinar cell Ca2+ content. In the present study, we have employed subcellular fractionation of acini under conditions that minimized posthomogenization redistribution of Ca2+ in order to localize those organelles involved in intracellular Ca2+ fluxes. Homogenization and differential centrifugation of acini, preloaded with 45Ca2+ and subjected to a period of washout, showed that carbachol induced an increased loss of 45Ca2+ from all fractions isolated. The high-speed microsomal fraction lost 45Ca2+ to a greater extent than did whole acini; measurement of total Ca2+ by atomic absorption spectrometry showed a net loss of Ca2+ from this fraction. Purification of the lower-speed fractions indicated that carbachol increased 45Ca2+ exchange with both zymogen granules and mitochondria, but net Ca2+ levels in these organelles were unchanged. It was concluded that stimulation of pancreatic acini by carbachol results in the release of calcium from a microsomal compartment leading to a rise in cytoplasmic Ca2+, increased exchange with granule and mitochondrial Ca2+, and increased efflux of Ca2+ from the cell.

Cholesterol Metabolism and Vitamin B6. III. The Stimulation of Hepatic Cholesterogenesis in the Vitamin B6-Deficient Rat

1971 ◽  
Vol 49 (8) ◽  
pp. 933-935 ◽  
Author(s):  
C. M. Hinse ◽  
P. J. Lupien
Keyword(s):  
Vitamin B6 ◽  
Cholesterol Metabolism ◽  
Krebs Cycle ◽  
Pool Size ◽  
Liver Slices ◽  
Liver Homogenates ◽  
The Difference ◽  
Hepatic Cholesterogenesis ◽  
Stimulation Of

The rate of incorporation of labeled acetate into cholesterol by liver slices of pyridoxine-deficient rats was found to be three times that of control rats; with liver homogenates the difference between the two groups was even greater. Using the CO2 trapping technique, a 30% decrease in the hepatic acetate pool size was observed in pyridoxine-deficient rats and a 20% increase in pair-fed rats. Activity of the Krebs cycle was decreased by a third in the pair-fed rats.

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