Canadian Science Publishing
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Effects of various conditions on the movement of carbon atoms derived from glucose into and out of protein in rat brain The time course of entry of radioactive carbon from intravenously administered [U-14 C]-glucose into protein in five brain regions in rats was studied using an automatic amino acid analyzer coupled, through a flow cell, with a scintillation counter. Radioactivity appeared in protein-bound alanine and in glutamic and aspartic acids and, more slowly and to a much lesser extent, in serine, proline, and glycine; none was detected in any other bound amino acids. There appear to be two main groups of proteins, one of which turns over more slowly than the other. In pentobarbital narcosis, radioactivity in protein-bound alanine increased but no other changes were obvious. In convulsions induced by pentylenetetrazol or picrotoxin, and during hypoxia, the entry of radioactive carbon into protein-bound alanine, glutamic acid, and aspartic acid decreased. At 24 h after the injection of radioactive glucose, radioactivity in free amino acids had almost completely disappeared in normal animals though protein remained radioactive. Pentobarbital narcosis did not affect this situation. Radioactivity was released from protein into free amino acids during hypoxia, during convulsions induced by pentylenetetrazol, picrotoxin, or oxygen at high pressure, and after insulin treatment. Evidence was obtained that free alanine occurs in more than one pool.
Canadian Science Publishing - Tập 48 Số 3 - Trang 236-243 - 1970
Glycerolipid metabolism in Ascaris lumbricoides Homogenates of ovarian tissue from the pig roundworm Ascaris lumbricoides rapidly incorporate fatty 14 C-acids, fatty 14 C-acyl-CoA derivatives, glucose, and glycerol into lipid, the most highly labeled fraction after prolonged incubation periods being the triglycerides (except with glucose). Data from studies on the time course of incorporation of these precursors is consistent with the operation of the phosphatidic acid – diglyceride pathway for biosynthesis of these lipids. However, formation and acylation of monoglyceride may also contribute to their synthesis. Determination of the composition and labeling pattern of the triglyceride species indicated that some species turn over more rapidly than others, perhaps reflecting different metabolic roles. In these experiments, only small amounts of the precursors were incorporated into phospholipids other than phosphatidic acid.
Canadian Science Publishing - Tập 46 Số 10 - Trang 1167-1173 - 1968
Decreased monoamine oxidase activity in liver of iron-deficient rats Chronic nutritional deficiency of iron in the rat results in a decrease of 18–31% in the monoamine oxidase activity of the liver. Prolonged feeding of a diet low in copper was without effect on the enzyme, although the concentration of ceruloplasmin in the plasma and of copper in the liver declined.Possible roles of iron in the action of monoamine oxidase are discussed. The inhibitory actions of three iron-chelating agents on monoamine oxidase preparations are consistent with a function of iron in the oxidation of monoamines.
Canadian Science Publishing - Tập 47 Số 11 - Trang 999-1002 - 1969
Studies on Spermatogenesis in Rats. I. Application of the Sedimentation Velocity Technique to an Investigation of Spermatogenesis A sedimentation velocity chamber at unit gravity (Staput fractionation) was employed to separate cells obtained from suspensions of testes from adult rats, and the differential cell count was determined to estimate the sedimentation profiles of cell populations in various fractions. The incorporation of thymidine-3 H into acid-insoluble portions of cell fractions was measured at varying times following the intratesticular administration of thymidine. The kinetic profiles of thymidine-3 H incorporation into spermatogonia, primary spermatocytes, spermatids, and spermatozoa were compared with radioautographs prepared from histological sections of testes obtained from the same animals. Good correlations were observed between radioactivity peaks in Staput fractions and grain localization in cells of the spermatogenesis cycle at varying time periods after thymidine-3 H injection. Data obtained with the Staput technique can be rapidly quantitated. The limits of the Staput fractionation technique for the separation of cells from the rat testis were evaluated with respect to the possible isolation of homogeneous populations for biochemical studies, and to the currently more amenable separation of heterogeneous classes of cells for kinetic studies. The usefulness of the method was validated for application to subsequent investigations.
Canadian Science Publishing - Tập 49 Số 7 - Trang 753-760 - 1971
Steroid Metabolism by the Immature Rat Testis Treatment of hypophysectomized immature male rats with luteinizing hormone (LH) greatly increased the metabolism of both 4-[14 C]progesterone and 4-[14 C]testosterone by testicular homogenates. Prolactin, either alone or in combination with LH, did not influence the metabolism of either substrate. Progesterone was metabolized to 17α-hydroxyprogesterone, androstenedione, 5α-pregnan-3,20-dione, 3α-hydroxy-5α-pregnan-20-one, and 3β-hydroxy-5α-pregnan-20-one. Testosterone was metabolized to dihydrotestosterone and 5α-androstan-3α,17β-diol. On the basis of these observations it is suggested that LH stimulated the 5α-reductase(s) of the immature rat testis. Testis homogenates from immature rats with intact pituitaries were incubated with 4-[14 C]3α-hydroxy-5α-pregnan-20-one. Rapid conversion to androsterone was observed, with the formation of a compound chromatographically identical with 3α, 17α-dihydroxy-5α-pregnan-20-one as an apparent intermediate. These findings demonstrate the ability of the rat testes to form androsterone from progesterone by a pathway that does not involve testosterone.
Canadian Science Publishing - Tập 52 Số 9 - Trang 744-750 - 1974
Identification and Distribution of Tryptamine in the Rat A procedure for the quantitative measurement of tryptamine in mammalian tissues is described. The amine is isolated by ion-exchange chromatography, converted to its dansyl derivative, further purified by thin-layer chromatography, and quantitated by the mass-spectrometric integrated ion current technique using an isotopically labelled internal standard.The concentrations of tryptamine in some tissues of male Wistar rats were (ng/g ± S.D.): brain 0.50 ± 0.07, heart 0.62 ± 0.10, kidney 8.04 ± 2.10, liver 0.73 ± 0.07, lung 0.54 ± 0.18, and spleen 0.43 ± 0.14. In the brain, the hypothalamus contained 0.94 ± 0.22, the cerebellum 0.27 ± 0.02, the stem 0.24 ± 0.06, the caudate nucleus 2.93 ± 1.14, and the "rest" 0.32 ± 0.05 ng/g (mean ± mean deviation).
Canadian Science Publishing - Tập 52 Số 6 - Trang 447-451 - 1974
An investigation of factors influencing mitotic G2 delay in synchronous cultures of human kidney cells after X-irradiation Factors affecting mitosis have been studied in human kidney T-cells synchronized by two exposures to 7.5 mM thymidine. Biochemical measurements were correlated with the position of the cells in the cell cycle from S to mitosis. Anaerobic conditions during S, although not inhibition of respiration, prevented cells from progressing to mitosis. ATP production is largely anaerobic and glycolytic metabolism is sufficient for a cell to complete mitosis once it has entered G2 or prophase. Both RNA and protein synthesis are required in G2 for the initiation of cell division, while treatment with carbon monoxide or thiol blocking agents also prevents mitosis.Postirradiation mitotic delay is greater for cells irradiated in G2 than for cells irradiated in S. This G2 delay is reversible if the cells are blocked in S by addition of excess thymidine. Pretreatment with 5–15 mM cysteamine largely protected irradiated cells from mitotic delay. Cysteine at a concentration of 20 mM and AET at 10 mM were only weakly protective, while 20 mM mercaptoethanol was ineffective. All these compounds added after irradiation were ineffective. Anoxia during irradiation had a slight protective effect. Mitotic delay was enhanced by lowered concentrations but not reduced by elevated concentrations of calcium, while agmatine before or after irradiation was without protective effect.The protein thiol content of cells increases from S to a maximum at metaphase, while the nonprotein thiol content is unchanged. X-irradiation of up to 500 R has no effect on the protein or nonprotein thiol content of the cell up to mitosis. The intracellular ATP content is maximal for cells in G2 , then falls subsequently to mitosis. Irradiation slows this premitotic accumulation of ATP. The respiration rate per cell is constant up to mitosis then drops sharply following division. Irradiation has no effect on respiration. Decreased specific activities of DNA from cells irradiated in S and incorporating 3 H-TdR post-irradiation over a 2-h period suggest a pool effect as the mechanism of reduced thymidine incorporation. No evidence could be obtained for any significant breakdown of DNA following irradiation. Prolonged DNA synthesis following irradiation is not considered to be the primary reason for mitotic delay. The radiation block is located less than 30 min before the onset of prophase and is possibly correlated with a condensation mechanism of the chromatin strands.
Canadian Science Publishing - Tập 47 Số 3 - Trang 237-249 - 1969
Studies on Mammalian and Molluscan Steroid Sulfatase. Solubilization and Properties Steroid sulfatase from the microsomal fraction of rat liver exhibits properties which are suggestive of an allosteric type of enzyme. The kinetics of dehydroisoandrosterone sulfate cleavage are normal while the cleavage of cholesterol sulfate presents a cooperative effect beyond 0.8 × 10−6 M at the protein concentration used. This abnormal kinetic behavior is normalized by the addition of an analogue of this substrate, sodium lauryl sulfate. This analogue elicits a biphasic effect on the cleavage of cholesterol sulfate while the cleavage of dehydroisoandrosterone sulfate and pregnenolone sulfate is inhibited at all of the concentrations tested.Using polyacrylamide gel electrophoresis in the presence of sodium lauryl sulfate, the molecular weight of what is believed to be the monomeric form of the enzyme was estimated to be approximately 23 000.Steriod sulfatase from Helix pomatia cleaves the sulfate of dehydroisoandrosterone while cholesterol sulfate remains intact. This enzyme was found to have a molecular weight near or below 50 000 and was isolated as a single band of sulfatase activity by polyacrylamide gel electrophoresis.
Canadian Science Publishing - Tập 49 Số 2 - Trang 234-242 - 1971
The Assay of Cholesterol Sulfate in Biological Material by Enzymatic Radioisotopic Displacement A technique is described for the measurement of cholesterol sulfate (CS) which is based upon the displacement of labelled CS from a placental sulfatase enzyme system by the addition of unlabelled CS isolated from various biological sources.From the extent of this displacement by unknown samples of CS and by reference to standard curves, the concentration of CS in the biological samples can be calculated. This assay method is relatively simple, rapid, and sensitive (nanogram level) and provides values which are in good agreement with those obtained by a double isotope derivative assay. Levels of CS in human plasma, erythrocytes, semen, and saliva have been determined. This sterol sulfate appears to be a ubiquitous entity although its biological function remains to be determined. Certain aspects of its possible physiological role in the organism are discussed.
Canadian Science Publishing - Tập 50 Số 3 - Trang 277-286 - 1972
A methodology for the production of carbohydrate-specific antibody 8-Methoxycarbonyloctyl glycosides are recommended as precursors for the preparation of artificial antigens that possess strongly immunodominant carbohydrate antigenic determinants. The preparation and immunochemical properties of a selected number of these antigens are reported to demonstrate the high levels of hapten-specific antibodies that are normally achieved using standard immunization schedules. The method, based on glycoside synthesis, promises to make available a wide spectrum of well defined antigens and the homologous antibodies.
Canadian Science Publishing - Tập 55 Số 5 - Trang 507-512 - 1977
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