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At least 19 recordsLinked to original sources
PubMed1977

Studies on intestinal adenosine triphosphatases. II. Stabilitiies in different rat subcellular fractions.

Subcellular fraction (brush border, mitochondria, microsomes and plasma membranes) are isolated from the rat intestinal epithelial cells. A comparison was made between the effect of cold storage, freeze-thawing, heating and of some chemicals (DMSO, DTT, glycerol, sucrose) on the stability of Mg2+ and (Na+-K+) dependent ATPases in these fractions in order to determine possible difference linked to the localization in the enterocyte. Enzymatic activities were found more stable at -20 degrees C than at +4 degrees C. Microsomal (Na+-K+)-ATPase increased in activity until the 8th day, then declined. Brush border (Na+-K+)-ATPase was the least resistant of all fractions. For Mg2+-ATPase, that from mitochondria was that had lost much more activity (84%) in 15 days at +4 degrees C. With freeze-thawing there was a comparable decrease in all activities (20-35%). by heating between 35 and 60 degrees C, Mg2+-ATPase was shown to be more heat resistant than (Na+-K+)-ATPase. The addition of some stabilizing chemicals (DMSO, glycerol, sucrose) improved the heat stability of the two enzymes: better results were obtained with glycerol for Mg2+-ATPase and sucrose for (Na+-K+)-ATPase. These differences might be due to the compositon in membraine lipids or to the nature of the enzymes studied.

Adenosine Triphosphatases↗
PubMed1975

Phosphatidate phosphohydrolase and palmitoyl-coenzyme A hydrolase in cardiac subcellular fractions of hyperthyroid rabbits and cardiomyopathic hamsters.

Activities of phosphatidate phosphohydrolase and palmitoyl-CoA hydrolase were determined in cardiac subcellular fractions prepared from rabbits which has received tri-iodothyronine and from hamsters with hereditary cardiomyopathy (strain BIO 14.6). 1. Both mitochondrial and microsomal fractions of hyperthyroid rabbit hearts produced 4-5 times as much diacylglycerol 3-phosphate from glycerol 3-phosphate and palmitate as did those of euthyroid hearts. 2. Phosphatidate phosphohydrolase, measured with phosphatidate emulsion, was activated by 1mm-Mg(2+) in all but the mitochondrial fraction of euthyroid rabbit hearts. The activation was more pronounced in subcellular fractions isolated from hyperthyroid hearts, so that the measured activities were significantly increased above those of the controls. The highest activity was found in the microsomal and lysosomal fractions. 3. In the absence of Mg(2+) during incubation, the difference in phosphohydrolase activities between eu- and hyper-thyroid states was not significant. 4. The phosphohydrolase of subcellular fractions of control hamsters did not respond to addition of 0.5-8.0mm-Mg(2+). The enzyme from cardiomyopathic hearts was slightly inhibited by this bivalent cation and therefore significant increases in activity were observed only in the absence of Mg(2+) from the assay system. 5. The rate of reaction by soluble phosphatidate phosphohydrolase was similar regardless of the nature of the substrate. Both when microsomal-bound phosphatidate was used as the substrate and when phosphatidate suspension was used, the activity of soluble enzyme was lower than that of the microsomal and lysosomal enzymes measured with phosphatidate suspension; this was especially so when the assay was carried out in the absence of Mg(2+). Neither tri-iodothyronine nor cardiomyopathy influenced the soluble phosphohydrolase activity in the two species. 6. Neither tri-iodothyronine nor cardiomyopathy significantly changed palmitoyl-CoA hydrolase activities in subcellular fractions. 7. Microsomal diacylglycerol acyltransferase and myocardial triacylglycerol content were also unchanged in the hyperthyroid state.

Acid Phosphatase↗
PubMedDate not supplied

[Distribution of gamma-hexachlorcyclohexane in subcellular fractions of the liver and brain].

The character of the gamma-HCCH distribution in the subcellular fractions of the liver and brain of albino rats with peroral threefold introduction of the compound in doses of 34 mg/kg (1/5 LD50) and in a dose of 1.7 mg/kg (1/100 LD50) for a space of 1, 3 and 6 months was investigated. It was found that gamma-HCCH penetrates the cells of the liver and brain and is non-uniformly distributed among subcellular fractions, viz. nuclear, mitochondrial and supernatant. Both in acute and chronic experiments the greatest amounts of the preparation were found in the nuclear fraction of the cell. The established features distinguishing the accumulation and distribution of the preparation in the subcellular fractions of the liver and brain explain the previously elicited biochemical and physiological shifts occurring in the organism after entrance of gamma-HCCH thereinto.

Animals↗
PubMed1976

Proteolytic activity of subcellular fractions from Streptomyces griseus no. 45-H.

Subcellular fractions were prepared from Streptomyces griseus No. 45-H at different stages of life cycle, and their proteolytic activity was examined. The highest proteolytic activity was found in the 24- and 72- h-old vegetative hyphae, the lowest in the resting spores. Spores contained about 9--30% of the proteolytic activity of vegetative cells. At the age of 16 h about 80%, at 26 h 70%, at 72 h 40%, and in spores about 60% of the proteolytic activity was particulate. The greatest part of the proteolytic activity could be inhibited by EDTA, lower levels of serine and sulfhydryl protease activities were detected in the cell-free extracts of vegetative cells.

4-Chloromercuribenzenesulfonate↗
PubMed1975

Insulin degradation by isolated fat cells and their subcellular fractions.

Isolated frt cells and purified subcellular fractions of fat cells have been shown to degrade insulin to biologically inactive trichloroacetic-acid-soluble fragments. Further study of this activity has revealed the following characteristics: 1 Most of the insulin-degrading enzymes are intracellular, inaccessible to insulin or trypsin when fat cells are intact. More that 90 per cent of the recovered activity is found in the high-speed supernatant (cytosol) when cell fractionation studies are performed. 2. The plasma membrane contains significant insulin-degradative capacity, as shown by tryptic digestion of intact cells and cell fractionation. 3. The pH optimum of the cell-membrane insulin-degrading site is more acid than that of the cytosol activity, but the tow enzyme systems are similar with regard to substrate specificity, response to metabolic inhibitors, and elution volume of degradation products on gel filtration. 4. The plasma-membrane-degrading activity differs from the specific insulin-binding site with regard to saturation kinetics, optimum temperature, substrate specificity, sensitivity to sulfhydryl-blocking agents, and trypsin snesitivity.

Adipose Tissue↗
PubMed1976

Ca-activated ATPase activity in subcellular fractions of mouse pancreatic islets.

Ca-stimulated ATPase activity has been demonstrated in homogenates of mouse pancreatic islets. On subcellular fractionation Ca-ATPase activity was found in secretory granules, mitochondria, and microsomes, but not in the postmicrosomal fractions. Highest specific activity was found in the granules. In all active subcellular fractions two Km(Ca) values for Ca-ATPase around 7.0 X 10(-6) and 1.8 X 10(-7) M were estimated. Assuming an ATP hydrolysis:Ca pumping ratio of 1:2, the highest capacity for active Ca transport was found in secretory granules and mitochondria. Concentrations of 40 mM or higher of Na and 10(-5) M cyclic AMP inhibited Ca-ATPase in all subfractions. Caffeine at a concentration of 10 mM inhibited Ca-ATPase significantly in secretory granules and microsomes. Also MG-ATPase activity was demonstrated in the various subfractions. This activity was compared with that of Ca-ATPase at identical concentrations of free metal ions and in the absence or presence of various inhibitors. It was concluded that high-affinity Ca-ATPase and Mg-ATPase are two different enzymic entities. Ca-ATPase may tentatively be assumed to participate in active transport of Ca between intracellular compartments and to constitute a Ca-accumulating system which returns the cytosolic free Ca concentration to the resting state after stimulation of the beta-cells by secretagogues. This enzyme may therefore play a significant role in regulation of insulin release.

4-Chloromercuribenzenesulfonate↗
PubMed1976

Preparation of subcellular fractions from rat liver: comparison of the Polytron with the Dounce homogenizer.

The PolytronR and Dounce homogenizers have been evaluated for preparation of homogenates of rat liver prior to isolation of subcellular fractions by differential centrifugation. Marker enzymes used to evaluate the subcellular fractions included cytochrome oxidase, monoamine oxidase, D-amino acid oxidase, acid phosphatase, glucose-6-phosphatase, ethyl morphine demethylase, and lactate dehydrogenase. No significant difference in the distribution of enzymes (percent recovery or specific activity) was observed between the two methods of homogenization. In addition, there were no significant differences in the ultrastructural appearances and respiratory control ratios of the mitochondrial fractions prepared by the two methods of homogenization.

Animals↗
PubMed1976

Calcium accumulation and enzymatic activities of subcellular fractions from aortas and ventricles of genetically hypertensive rats.

Subcellular fractions were obtained from aortas and ventricles of 6-month-old spontaneously hypertensive and normotensive Wistar rats by the use of differential and sucrose density gradient centrifugation. These preparations were studied to determine what alterations in calcium accumulation and enzymatic activities might be associated with hypertension. The total amount of calcium accumulation (in the presence of ATP and 17 muM free calcium) by the plasma membrane-enriched fraction from hypertensive rat aortas significantly less than that from normotensive rats (11.3 +/- 0.4 vs 16.2 +/- 1.6 mumol of calcium/g of protein, n = 8). In contrast the specific activities of the plasma membrane marker enzymes, 5'-nucleotidase and phosphodiesterase I, were 80% and 40% greater, respectively, in the hypertensive than in the normotensive fractions. On the other hand, various fractions from ventricles of the two types of rats were generally similar in enzyme activities and calcium accumulation. The decreased rate of relaxation of aortas from spontaneously hypertensive rats may be caused by the decreased rate of calcium transport demonstrated in this study.

Animals↗
PubMed1976

Calcium uptake by subcellular fractions of human umbilical artery.

Two different mechanisms for the active accumulation of Ca2+ by subcellular fractions of human umbilical artery are described. One, located in the mitochondrial fraction, was induced by exogenous ATP or respiratory substrates (ADP and succinate) and was inhibited by azide. The other, located in the microsomal fraction, was induced by ATP and potentiated by oxalate, but not inhibited by azide. Increasing ATP concentrations up to 4-5 mM increased microsomal Ca2+ accumulation, whereas increasing ATP concentration above 2-3 mM caused inhibition of mitochondrial Ca2+ uptake. Although changing pH from 7.4 to 7.2 had no effect on mitochondrial Ca2+ accumulation, it doubled microsomal uptake. Neither adenosine 3',5'-monophosphate nor guanosine 3',5'-monophosphate in the presence or absence of protein kinase and kinase modulator affected Ca2+ uptake by or phosphorylation of the subcellular fractions. Partially purified protein kinases from umbilical and beef skeletal muscle contained a component(s) distinguishable from the kinase on the basis of its heat stability that enhanced ATP-induced Ca2+ uptake by mitochondrial fractions from the umbilical artery. It is suggested that alterations in Ca2+ sequestration induced by changes in ATP concentration and intracellular pH in mitochondrial and microsomal fractions, respectively, could play a role in the control of arterial patency and closure with changes in PO2.

Adenosine Triphosphate↗
PubMed1975

Phosphatidate phosphohydrolase and palmitoyl coenzyme A hydrolase in cardiac subcellular fractions.

The characteristics of the two enzymes related to fatty acid esterifaction were studied in order to provide fundamental information leading to further understanding of the control of myocardial glyceride formation. Palmitoyl-CoA hydrolase and phosphatidate phosphohydrolase are both distributed unevenly among heart subcellular fractions. The activity of the latter enzyme in subcellular fractions changes independently in response to Mg2+ addition and in response to thyroid hormone treatment of animals.

Animals↗
PubMed1978

NADPH-oxidation activities in subcellular fractions isolated from resting or phagocytozing human polymorphonuclears.

Using a fluorometric assay for the determination of oxidized pyridine nucleotides (NAD[P]+), total and cyanide-resistant NADPH-oxidative activities have been measured in subcellular fractions isolated from resting and phagocytosing human polymorphonuclears. Enzymatic activies responsible for the oxidation of the NADPH have been recovered in the heavy particles (15,000g/15 min), the low-density particles (100,000g/30 min), and the cytosolic fraction. Stimulation of the cells with opsonized zymosan had a different effect on the NADPH-oxidative activities of these subcellular fractions, which suggests the involvement of various types of enzymatic systems in the oxidation of NADPH. The cytosolic fraction interacted strongly with the enzymatic activities occurring in the sedimentable fractions and is therefore thought to play a central role in the regulation of the activation of the oxidative metabolism associated with phagocytosis.

Cell Fractionation↗
PubMedDate not supplied

[Localization of retinylphosphatase activity in subcellular fractions of rat liver].

Enzymic hydrolysis of retinyl phosphate in subcellular fractions of the rat liver has been investigated. A quantitative method of measuring activity of retinyl phosphatase has been developed. The method is based on the isolation of labeled retinol, the substance formed from chemically synthesized labeled retinyl phosphate through enzymatic hydrolysis. It has been shown that the major quantity of retinyl phosphatase activity (75%) with a specific activity of 80 micrograms retinyl phosphate hydrolyzed for 30 min/mg protein at 30 degrees C occurs in plasmatic membranes.

Animals↗
PubMed1978

The distribution of dietary plant sterols in serum lipoproteins and liver subcellular fractions of rats.

Rats were fed plant sterols containing campesterol and beta-sitosterol in the differerent proportions, and their distribution in serum lipoproteins and in liver subcellular fractions was determined. In serum lipoproteins, the percentage as well as the concentration of plant sterols increased with the increase in the density of lipoproteins. Thus, high density lipoprotein (HDL) contained the highest and very low density lipoprotein (VLDL), the lowest. Also, there were distinct differences in the ratio of campesterol to sitosterol among lipoproteins, it was the highest in VLDL and lowest in HDL. Quantitatively, more than 75% of campesterol and 80% of sitosterol were carried in HDL; the values were significantly different from those of cholesterol (ca. 70%) in relation to total cholesterol. The distribution of plant sterols in liver subcellular fractions was virtually the same with that of cholesterol. Both nuclei and microsomes contained approximately 40% of total plant sterols.

Animals↗
PubMed1976

Effects of hypolipidemic agents on lipid synthesis in subcellular fractions from Tetrahymena pyriformis.

Lipid synthesizing systems have been prepared from subcellular fractions of Tetrahymena pyriformis, GL. These fractions, the mitochondrial fraction, the microsomal fraction and the soluble cell fraction, have been characterized as to cofactors and cations required for optimal lipid synthesis. The effects of hypolipidemic agents on lipid synthesis by all fractions are presented.

Acetates↗
PubMed1976

(3H)-isoproterenol binding to subcellular fractions of mouse parotid: relationship to cyclic nucleotide formation and the stimulation of DNA synthesis.

(3H) Isoproterenol binding to subcellular fractions of mouse parotid: Relationship to cyclic nucleotide formation and the stimulation of DNA synthesis. (Unión the (3H) Isoproterenol a fracciones subcelulares de parótida de ratón y su relacón con la formacón de nucleótidos cíclicos y la estimulación de la síntesis de DNA). Arch. Biol. Med. Exper. 10: 105-114, 1976. Tritiated isoproterenol binds to all subcellular fractions of mouse parotid but 70% of the binding is to the nuclear fraction. Binding to other mouse tissues was less than to the parotid. The patterns of binding did not correlate with the distribution of adenylate cyclase, guanylate cyclase or catechol-O-methyl transferase among the fractions or tissues nor with the extent of response in stimulation of DNA synthesis among the tissues. Inhibition of (3H) Isoproterenol binding to parotid fractions by catecholamine analogs was studied. There was no correlation between their ability to inhibit binding and the ability of the analogs themselves to raise cyclic AMP levels or stimulate DNA synthesis.

Adenosine Monophosphate↗
PubMedDate not supplied

[Peptide hydrolase activity in rabbit brain subcellular fractions under conditions of adrenalectomy and administration of hydrocortisone and ACTH].

Adrenalectomy and administration of hydrocortisone and ACTH are shown to induce no changes in the total activity of neutral peptide-hydrolase in both homogenates and brain subcellular fractions. The absence of adrenalectomy and hormone administration effect on the total peptide-hydrolase activity in homogenates is established simultaneously with its essential changes in the brain subcellular fractions. A decrease in the enzymic activity of the mitochondrial-lysosomal fraction (MLF) following adrenalectomy is observed side by side with its increase in a soluble fraction. Hydrocortisone and ACTH administration cause an increase in the acid peptide-hydrolase activity in MLF and its decrease in the brain soluble and microsomal fractions of adrenalectomized rabbits. The degree of solubilization of MLF acid and neutral peptide-hydrolase by detergent triton X-100 after adrenalectomy is increased. Hydrocortisone and ACTH administration, on the contrary, decrease a degree of solubilization of the brain MLF peptide-hydrolase in adrenalectomized animals.

Adrenalectomy↗