scholarly journals Potassium ion-stimulated and sodium ion-dependent adenosine diphosphate–adenosine triphosphate exchange activity in a kidney microsomal fraction

1972 ◽  
Vol 129 (3) ◽  
pp. 775-779 ◽  
Author(s):  
Shailesh P. Banerjee ◽  
Shirley M. E. Wong
Keyword(s):  
Exchange Rate ◽  
Guinea Pig ◽  
Exchange Reaction ◽  
Microsomal Fraction ◽  
Atp Hydrolysis ◽  
Adenosine Diphosphate ◽  
Sodium Ion ◽  
Pig Kidney ◽  
Stimulation Of ◽  
Exchange Activity

1. K+ did not affect the Mg2+-dependent transphosphorylation but markedly increased the Na+-stimulated ADP–ATP exchange rate mediated by a microsomal fraction from guinea-pig kidney. 2. Rb+, Cs+, NH4+ and Li+ were equally effective in stimulating the Na+-dependent ADP–ATP exchange activity. 3. Treatment of the microsomal fraction with N-ethylmaleimide or increased concentrations of Mg2+ prevented stimulation of the Na+-dependent exchange reaction by K+. 4. Ouabain (2.5μm) inhibited ATP hydrolysis by 33% but did not decrease the K+-stimulated Na+-dependent ADP–ATP exchange rate. 5. A possible mechanism for stimulation of exchange activity by K+ is discussed.

scholarly journals Glutamine synthesis from glucose and ammonium chloride by guinea-pig kidney tubules

1994 ◽  
Vol 297 (1) ◽  
pp. 69-74 ◽  
Author(s):  
C Michoudet ◽  
M F Chauvin ◽  
G Baverel
Keyword(s):  
Glucose Metabolism ◽  
Guinea Pig ◽  
Carbon Skeleton ◽  
Kidney Cortex ◽  
Physiological Concentration ◽  
Pig Kidney ◽  
Glucose Carbon ◽  
Glutamine Synthesis ◽  
Stimulation Of

1. At a physiological concentration (5 mM), glucose was found to be metabolized by isolated kidney cortex tubules prepared from fed guinea pigs. 2. The release of 14CO2 from [U-14C]glucose indicated that oxidation of the glucose carbon skeleton represented about 50% of the glucose removed; significant amounts of lactate and glutamine also accumulated. 3. Addition of 0.1-10 mM NH4Cl led to a dose-dependent stimulation of glucose metabolism which was accompanied by a large increase in lactate and glutamine accumulation and, to a lesser extent, in glucose oxidation. 4. Comparison of the release of 14CO2 from [1-14C]- and [6-14C]glucose indicates that, in both the absence and the presence of NH4Cl, the pentose phosphate shunt was only a minor pathway of glucose metabolism. 5. The central role of pyruvate carboxylase in the conversion of glucose carbon into glutamine carbon was demonstrated by using a bicarbonate-free medium and measuring the fixation of 14CO2 from [14C]bicarbonate, which was recovered mostly at C-1 of glutamine plus glutamate. 6. The NH4Cl-induced stimulation of glucose removal was secondary not only to increased glutamine synthesis, as shown by the effect of methionine sulphoximine, an inhibitor of glutamine synthetase, but also to the stimulation of phosphofructokinase activity by NH4Cl. 7. Renal arterio-venous difference measurements revealed that, in vivo, the guinea-pig kidney removed glucose from the circulating blood, which suggests that glucose carbon may contribute to the carbon skeleton of the glutamine released by this organ.

scholarly journals SWR1C catalyzes H2A.Z deposition by coupling ATPase activity to the nucleosome acidic patch

2021 ◽  
Author(s):  
Nathan Gioacchini ◽  
Craig L Peterson
Keyword(s):  
Atpase Activity ◽  
Exchange Reaction ◽  
Chromatin Remodeling ◽  
Essential Role ◽  
Atp Hydrolysis ◽  
Histone H2a ◽  
Rich Region ◽  
Biochemical Assays ◽  
Nucleosomal Histone ◽  
Exchange Activity

The SWR1C chromatin remodeling enzyme catalyzes the ATP-dependent exchange of nucleosomal histone H2A for the histone variant H2A.Z, a key variant involved in a multitude of nuclear functions. How the 14-subunit SWR1C engages the nucleosomal substrate remains largely unknown. Numerous studies on the ISWI, CHD1, and SWI/SNF families of chromatin remodeling enzymes have demonstrated an essential role for the nucleosomal acidic patch for remodeling activity, however a role for this nucleosomal epitope in nucleosome editing by SWR1C has not been tested. Here, we employ a variety of biochemical assays to demonstrate an essential role for the nucleosomal acidic patch in the H2A.Z exchange reaction. Nucleosomes lacking acidic patch residues retain the ability to stimulate the ATPase activity of SWR1C, implicating a role in coupling the energy of ATP hydrolysis to H2A/H2B dimer eviction. A conserved arginine-rich region within the Swc5 subunit is identified that interacts with the acidic patch and is found to be essential for dimer exchange activity. Together these findings provide new insights into how SWR1C engages its nucleosomal substrate to promote efficient H2A.Z deposition.

Mitochondrial Oxidation of p-N, N-Dimethylamino-β-Phenethylamine (DAPA)

1975 ◽  
Vol 33 ◽  
pp. 458-459
Author(s):  
W. Allen Shannon ◽  
Hannah L. Wasserkrug ◽  
andArnold M. Seligman
Keyword(s):  
Guinea Pig ◽  
Oxidase Activity ◽  
Amine Oxidase ◽  
Histochemical Demonstration ◽  
Guinea Pig Heart ◽  
Pig Kidney ◽  
Cytoplasmic Vacuoles ◽  
Liver And Kidney ◽  
Mitochondrial Oxidation ◽  
Amine Oxidase Activity

The synthesis of a new substrate, p-N,N-dimethylamino-β-phenethylamine (DAPA)3 (Fig. 1) (1,2), and the testing of it as a possible substrate for tissue amine oxidase activity have resulted in the ultracytochemical localization of enzyme oxidase activity referred to as DAPA oxidase (DAPAO). DAPA was designed with the goal of providing an amine that would yield on oxidation a stronger reducing aldehyde than does tryptamine in the histochemical demonstration of monoamine oxidase (MAO) with tetrazolium salts.Ultracytochemical preparations of guinea pig heart, liver and kidney and rat heart and liver were studied. Guinea pig kidney, known to exhibit high levels of MAO, appeared the most reactive of the tissues studied. DAPAO reaction product appears primarily in mitochondrial outer compartments and cristae (Figs. 2-4). Reaction product is also localized in endoplasmic reticulum, cytoplasmic vacuoles and nuclear envelopes (Figs. 2 and 3) and in the sarcoplasmic reticulum of heart.

INCORPORATION OF IODIDE INTO ORGANIC COMPOUNDS IN THE GUINEA PIG THYROID

1963 ◽  
Vol 43 (1) ◽  
pp. 110-118 ◽  
Author(s):  
R. Ekholm ◽  
T. Zelander ◽  
P.-S. Agrell
Keyword(s):  
Guinea Pig ◽  
Protein Binding ◽  
Organic Compounds ◽  
Guinea Pigs ◽  
Microsomal Fraction ◽  
Thyroid Tissue ◽  
Particulate Fraction ◽  
Supernatant Fraction ◽  
Hydrolysis Of

ABSTRACT Guinea pigs, kept on a iodine-sufficient diet, were injected with Na131I and the thyroids excised from 45 seconds to 5 days later. The thyroid tissue was homogenized and separated into a combined nuclear-mitochondrial-microsomal fraction and a supernatant fraction by centrifugation at 140 000 g for one hour. Protein bound 131iodine (PB131I) and free 131iodide were determined in the fractions and the PB131I was analysed for monoiodotyrosine (MIT), diiodotyrosine (DIT) and thyroxine after hydrolysis of PB131I. As early as only 20 minutes after the Na131I-injection almost 100% of the particulate fraction 131I was protein bound. In the supernatant fraction the protein binding was somewhat less rapid and PB131I values above 90% of total supernatant 131I were not found until 3 hours after the injection. In all experiments the total amount of PB131I was higher in the supernatant than in the corresponding particulate fraction. The ratio between supernatant PB131I and pellet PB131I was lower in experiments up to 3 minutes and from 2 to 5 days than in experiments of 6 minutes to 20 hours. Hydrolysis of PB131I yielded, even in the shortest experiments, both MIT and DIT. The DIT/MIT ratio was lower in the experiments up to 2 hours than in those of 3 hours and over.

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.

scholarly journals THE METABOLISM OF DIHYDROXYPHENYLALANINE BY GUINEA PIG KIDNEY EXTRACTS

1949 ◽  
Vol 179 (3) ◽  
pp. 1037-1048
Author(s):  
Robert E. Clegg ◽  
Robert.Ridgely. Sealock
Keyword(s):  
Guinea Pig ◽  
Pig Kidney
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