Ca2+-dependent stimulation of muscle and liver phosphorylase kinase by heparin

• 1.1. Heparin stimulates the activity of nonactivated and activated skeletal muscle phosphorylase kinase in a Ca²⁺-dependent manner.
• 2.2. The stimulatory effect of heparin on the activity of nonactivated phosphorylase kinase is also expressed in the presence of calmodulin and glycogen. Heparin acted in synergism with glycogen.
• 3.3. Heparin increases the affinity of phosphorylase kinase to Ca²⁺ 5–12 fold depending upon the activation conditions.
• 4.4. Ca²⁺ influences the stimulation of liver phosphorylase kinase by heparin in a similar way.

     

Activation of neutrophils NADPH oxidase by PMA: Cytosol activity is translocated in phorbol-primed neutrophils

• 1.1. Translocation of cytosol activity in phorbol-primed neutrophils was studied.
• 2.2. Prior exposure of PMA or FMLP could potentiate the oxidative response by subsequent heterogeneous stimulus, FMLP or PMA.
• 3.3. In FMLP-primed neutrophils, the cytosol had almost the same activity as resting one and cytosol activity was not eluted from the membrane.
• 4.4. In PMA-primed neutrophils, however, the cytosol had less activity and cytosol activity was correspondingly eluted from the membrane.
• 5.5. These observations suggested that cytosol activity was translocated in PMA-primed cells.

     

Protoporphyrin-induced Photohemolysis : Differences related to the subcellular distribution of protoporphyrin in erythropoietic protoporphyria and when added to normal red cells

• 1.1. When protoporphyrin is added to normal red cells it distributes to about 30% in the stroma and 70% in the cytosol. By comparison, in erythropoietic protoporphyria red cell protoporphyrin is found to more than 95% in the cytosol.
• 2.2. At equimolar concentrations of protoporphyrin the photohemolysis is much more severe in normal red cells with exogenous protoporphyrin than in red cells from patients with erythropoietic protoporphyria.
• 3.3. The photohemolysis is markedly enhanced when D₂O is used as solvent instead of H₂O.
• 4.4. The results suggest that the photodamage is determined by the ability of susceptible structures to accumulate porphyrins, the partition of porphyrins between lipophilic and hydrophilic structures and the longevity of singlet oxygen in lipophilic environments.

     

Association of cytosolic lipids with fatty acid synthase from lactating mammary gland

• 1.1. Membrane-free cytosol contained over 4% of both the total lipids and phospholipids present in homogenates of lactating rat mammary gland, and much of this lipid was associated with a high molecular weight complex isolated from cytosol by gel exclusion chromatography or by density gradient centrifugation.
• 2.2. This complex principally consisted of polypeptides with apparent molecular weights of 220 and 116kDa. Lipids associated with this complex were transferred to endoplasmic reticulum and to intracellular lipid droplet precursors of milk lipid globules upon incubation in a cell-free system.
• 3.3. This lipoprotein complex was abundant in cytosol from lactating mammary gland, but was diminished in amount in cytosol from involuted mammary glands. The 220 kDa constituent of this complex was identified as the monomer of fatty acid synthase.
• 4.4. These results suggest that fatty acid synthase complex in lactating mammary gland may function in transfer of lipids necessary for formation or growth of lipid droplet precursors of milk lipid globules.

     

Studies on lipid peroxidation in rat liver by copper deficiency

• 1.1. Copper deficiency in rats results in a 2-fold increase in the level of lipid hydroperoxides in liver mitochondria and microsomes.
• 2.2. The specific activity of cupro-zinc Superoxide dismutase decreases up to 30% while that of the mangano-enzyme is not changed.
• 3.3. Glutathione peroxidase activity as well as catalase activity are suppressed in both cytosol and mitochondrial fractions from copper-deficient rat liver.

     

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Nucleoside monophosphoramidate hydrolase from rat liver: Purification and characterization

• 1.1. Adenosine 5'-phosphoramidate hydrolase of 29 kDa was isolated from rat liver cytosol.
• 2.2. It consisted of two subunits of 14 kDa.
• 3.3. It hydrolyzed nucleoside 5'-monophosphoramidates into nucleoside 5'-monophosphates and ammonia, while it did not hydrolyze adenylyl phosphoramidate, adenylyl imidodiphosphate and N-phosphorylated compounds like phosphocreatine, N^ω-phosphoarginine, 6-phospholysine and 3-phosphohistidine.
• 4.4. Divalent cations and cyclic AMP had no effect on the hydrolytic activity.

     

The assembly of the DNA complex present in chick embryo cell cytosol

• 1.1. Chromatography of chick embryo fibrobast cytosol labelled with [³H]thymidine or [³H]uridine precursors has shown the presence of early labelled DNA and RNA eluting at a position corresponding to a relative molecular mass of approximately 1.5–10⁵.
• 2.2. The early DNA-RNA (heteroduplex?) then moves progressively to a higher molecular weight peak, relative molecular mass approximately 10⁶.
• 3.3. The process appears similar in cytosol from cultured cells and from whole aminiotically labelled chick embryo: consequently the cytosolic DNA complex is not an artefact of cell culturing.
• 4.4. The relative contribution of artefactual and specific cytosol-associated DNA material is discussed: it is concluded that while both are present in cytosol as prepared, it is possible to discriminate between specific and artefactual DNA material.

     

Purification and partial characterization of the alkaline phosphatase from Allolobophora caliginosa

• 1.1. A purification of the enzyme from the starting material was achieved by means of butanol and acetone fractionations and, successively, by DEAE cellulose and Sephadex G-200 chromatographies.
• 2.2. Two enzymatic forms were separated; they showed various similar characteristics but differed greatly in specific activity.
• 3.3. It is probable that in A. caliginosa a sole alkaline phosphatase form exists and the less active fraction is partly denatured enzyme.
• 4.4. It is not completely possible to exclude the existence of two isoenzymes.

     

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Cellular and intracellular localization of catalase and acid phosphatase in the midgut of Lumbricus terrestris L.: A cell fractionation study

• 1.1. Cellular and intracellular localization of catalase and acid phosphomonoesterase in the midgut of Lumbricus terrestris was studied by use of tissue fractionation.
• 2.2. At least 60–70% of the catalase resides in the chloragocyte cytosol and the remaining 30–40% resides in gut epithelium peroxisomes.
• 3.3. One of the main functions of the chloragocyte catalase is probably scavenging for H₂O₂ arising from the interaction between blood heme-protein and oxygen.
• 4.4. A simple method for the histochemical detection of cytosol catalase is proposed.
• 5.5. About 10% of the gut acid phosphatase resides in chloragocyte lysosomes. The chloragosomes contain no acid phosphatase.

     

Stability to sodium dodecyl sulphate of the proteinase fromArmillaria mellea: Use for fragmentation of insoluble proteins

• 1.The proteinase fromArmillaria mellea showed no activity towards the low molecular weight substratesN-acetylglycyl-l-lysinemethyl ester,N-α-toluenesulphonyl-l-lysinemethyl ester andN-α-benzoyloxycarbonyl-l-lysinemethyl ester or towards the tetrapeptide tuftsin.

• 2.The enzyme retained the ability to degrade bovine serum albumin after treatment with sodium dodecyl sulphate (SDS) at 50°C.

• 3.Rapid fragmentation of an insoluble protein byA. mellea proteinase occurred when SDS was added to the incubation mixture but virtually no fragmentation occurred in the absence of SDS.

     

Stimulatory effect of amp on the copper ion dependent oxidation of adrenaline to adrenochrome

• 1.1. AMP markedly activated copper ion dependent oxidation of adrenaline to adrenochrome. It is proposed that a Cu(II)-AMP chelate forms a reactive complex with adrenaline.
• 2.2. AMP did not affect copper stimulated oxidation of noradrenaline, dopamine and l-dopa.

     

Control of pyruvate kinase flux during gluconeogenesis in isolated liver cells

• 1.1. With pyruvate as the gluconeogenic substrate, pyruvate kinase flux, estimated isotopically, and lactate formation were inhibited by glucagon, but only slightly affected by epinephrine.
• 2.2. The glucagon effect was unchanged in the absence of calcium.
• 3.3. Ethanol increased lactate formation from pyruvate, but depressed pyruvate kinase flux.
• 4.4. These results support the role of pyruvate kinase m the cyclic mechanism which transfers mitochondrial reducing hydrogen to the cytosol.
• 5.5. Glucagon and, to a lesser degree, epinephrine inhibit lactate formation from fructose or dihydroxyacetone.
• 6.6. Ethanol also inhibits lactate formation from these substrates, suggesting the possibility that NADH may in some manner regulate pyruvate kinase flux.

     

Identification of a glycoprotein complex containing a glycogen synthase isozyme in Ascaris Suum obliquely-striated muscle

• 1.1. A glycogen/protein complex which contains the major portion of glycogen synthase activity in Ascaris suum muscle has been purified.
• 2.2. The complex contains two proteins which can be dissociated from a glycoprotein component.
• 3.3. The glycoprotein contains glycogen-like domains and is resistant to trypsin digestion.
• 4.4. The glycogen synthase activity in the purified complex catalyzes glycogen synthesis in the absence of exogenous glycogen, but demonstrates an absolute glucose 6-phosphate requirement for activity.
• 5.5. The data support the hypothesis that this isozyme of glycogen synthase is significantly different from the cyclic AMP-regulated enzyme.

     

Characteristics of tubulin aggregation by tubulin-binding proteins from brain and by synthetic polycations

• 1.1. A basic fraction from brain cytosol was found to contain two or more tubulin-binding proteins, able to induce aggregation of tubulin accompanied by hydrolysis of GTP.
• 2.2. In some respects tubulin aggregation by the brain proteins was similar to its aggregation by polylysine.
• 3.3. The burst of GTP hydrolysis accompanying tubulin aggregation by polylysine had the following characteristics: enhanced by salt and abolished by low temperature; not stoichiometric with the amount of tubulin precipitated and actually maximal at relatively low polylysine concentration; uncoupled temporally from aggregation, which occurred over a much shorter interval.

     

Potassium balance in freshwater-adapted xtrout Oncorhynchus mykiss

• 1.1. Potassium loss occurs through the gills of trout.
• 2.2. This loss is compensated by intestinal absorption.
• 3.3. During a fasting period, branchial regulation appears after 2–3 days.
• 4.4. The maintenance of potassium balance is discussed as a function of experimental conditions.

     

The breakdown of Tetrahymena ribosomes by lysosomal enzymes: Inhibition by cytosol

• 1.1. Extracts from Tetrahymena lysosomes contained acid RNase and proteinase. At pH 7.4 there was appreciable proteinase activity which was inhibited by a heat-stable protein present in cell sap.
• 2.2. Lysosomal enzymes rapidly converted 80S ribosomes to subunits at pH 7.4. Hydrolysis of ribosomal RNA was very slow at pH 7.4 but rapid at pH 5.0.
• 3.3. These reactions were inhibited by proteinase inhibitors and by cell sap, but the latter was relatively ineffective at pH 5.0.
• 4.4. It seems unlikely that ribosome breakdown in vivo is initiated by the release of lysosomal enzymes into the cytosol.