摘要:

Treatment of L1210 ascites tumors in vivo with combinations of 9-β-D-arabinosyladenine and 6-methyladenine nucleosides repressed cell growth by approximately 30%. This repression was measured by the volume of accumulated cells after 6 days of treatment with these compounds. No significant increase of the survival time of L1210 tumor-bearing mice was obtained when the mice were treated under identical conditions. Incubation of TA3 or L1210 ascites cells in vitro with 6-methyIadenosine inhibited the deamination of added arabinosyladenine by 95% for TA3 and 50% for L1210. The cleavage of adenosine or deoxyadenosine in the presence of arabinosyladenine was unaffected. Incorporation of C14-adenine or C14-uracil into the DNA of TA3 cells was inhibited when arabinosyladenine and the four natural deoxynucleosides were incubated in vitro. This inhibition was relieved specifically by adenosine but not by deoxyadenosine. Arabinosyladenine affected the uptake of C14-amino acids into the proteins of TA3 cells and liver. Elevation or depression of incorporation varied with the amino acid used. Incorporation of arabinosyladenine-C14into the RNA of subcellular components of TA3 and liver cells was greatest in the nuclear and soluble fractions.

ISSN:0008-4018    

DOI:10.1139/o65-001

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

The inhibition byL-α-glycerophosphate of the reduction of dihydroxyacetone phosphate by crystalline rabbit muscle NAD+-linkedL-α-glycerophosphate dehydrogenase has been examined. As a result of the measurement of the absorbance at 340 mμ in a photometric test system at 26° containing 0.08–2.0 mMdihydroxyacetone phosphate, 0.14 mMNADH, and 1–1.5 μg crystalline enzyme in 1.5 ml 10 mMEDTA −0.1 Mphosphate buffer at pH 7-0, the apparent Michaelis constant (Km) for dihydroxyacetone phosphate was found to be 0.363 mM(± 0.025 S.E.).L-α-Giycerophosphate, but notD-α-glycerophosphate, acted as a competitive inhibitor in this system with an apparent inhibition constant (Ki) of 0.575 mM(± 0.030). Substitution of 50 mMtriethanolarnine buffer for the 0.1 Mphosphate buffer lowered theKmto 0.088 mM(± 0.019) and theKito 0.240 mM(± 0.013). To study the enzyme at lower NADH concentrations, a fluorometric system containing 20–75 μMNADH, 5–370 μMDHAP, and 0.5–2.0 μg enzyme in 1 ml 2 mMEDTA −50 mMtriethanolarnine buffer, pH 7.0 at 23°, was used. The apparentKmfor dihydroxyacetone phosphate andKiforL-α-glycerophosphate were 0.075 μM(± 0.020) and 0.186 mM(± 0.006) respectively, at a NADH concentration of 75 μM. Lowering the NADH concentration to 20 μMfurther decreased the apparentKmandKivalues to 0.039 mM(± 0.008) and 0.056 mM(± 0.007) respectively.A consideration of the concentrations of dihydroxyacetone phosphate andL-α-glycerophosphate in muscle during contraction suggests that the competitive inhibition of cytoplasmicL-α-glycerophosphate dehydrogenase by its product,L-α-glycerophosphate, may influence the pathway of triose phosphate utilization and also the coupling, by way of theL-α-glycerophosphate cycle, of cytoplasmic NADH-generating reactions to the mitochondrial respiratory chain.

ISSN:0008-4018    

DOI:10.1139/o65-002

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Tracer doses of tritiated testosterone were injected into four healthy men, followed by urine collection and by an assay for estrone, estradiol, androsterone, etiocholanolone, dehydroepiandrosterone, and Δ16-androstenol, and by an assay for radioactivity in each of these fractions. The androstenol fraction contained very little tritium, which indicated that most of it was not derived from the miscible testosterone pool. Maximum testosterone production rates were calculated from the urinary estrone and estradiol data, the results indicating testosterone turnovers of 1 to 3 mg per day. Comparison with testosterone production rates for healthy men, which were reported by other investigators using different methods, indicated that most, if not all, of the estrone and estradiol produced by the four subjects was derived from the miscible testosterone pool.

ISSN:0008-4018    

DOI:10.1139/o65-003

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Extraction of freeze-dried cod fillets with 1,2-dichloroethane resulted in destruction of cystine and histidine and in interference with the release of cystine, histidine, and methionine by pancreatic digestion. The reaction was pH dependent, occurring most readily under slightly alkaline conditions. The thioether S,S′-ethylenebiscysteine was synthesized by reacting cysteine and 1,2-dichloroethane. Alkylation of reduced wool or fish solids, and subsequent hydrolysis, yielded a sulfur-containing compound with the sameRfvalue as the synthetic thioether. The thioether appeared devoid of biological activity forL.mesenteraidesP-60,Tetrahymena pyriformisW., and the rat. It was cleaved by autoclaving, but was stable to acid hydrolysis.The evidence suggested that sulfhydryl groups of protein can be alkylated by 1,2-dichloroethane to produce thioether linkages, with a resultant decrease in nutritional value.

ISSN:0008-4018    

DOI:10.1139/o65-004

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Increases in the specific activities of undine and deoxyuridine phosphorylases of slices of regenerating rat liver were found 4 hours after incubation in tissue-culture medium containing uridine or 6-azauridine. These increases were not found when the tissue-culture medium contained either 8-azaguanine or puromycin, or when it lacked amino acids. Although both uridine and 6-azauridine were more effective in increasing the specific activity of uridine phosphorylase than that of deoxyuridine phosphorylase, azauridine was more effective than uridine in increasing the specific activities of both enzymes.In time studies, in which slices of regenerating rat liver were incubated in tissue-culture medium containing optimal concentrations of uridine, the specific activities of the two enzymes reached maximum levels at 3–4 hours. Puromycin prevented these increases.

ISSN:0008-4018    

DOI:10.1139/o65-005

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Carboxypeptidase A releases histidine and tyrosine from horse oxy- and deoxy-hemoglofoins; carboxypeptidase B releases arginine only. In both cases, action is more rapid with the oxygenated form.Frozen storage appears to alter the structure of hemoglobin, permitting the two enzymes together to digest further into the protein.Leucine aminopeptidase had no detectable effect on horse hemoglobin.

ISSN:0008-4018    

DOI:10.1139/o65-006

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

The properties of two different cholinesterases present in the organophosphorus-insecticide-resistant Leverkusen strain and its susceptible counterpart were investigated and compared. The cholinesterase of the Leverkusen resistant strain is characterized by a low sensitivity to organophosphate inhibitors, as is represented by an increase in the enzyme-inhibitor affinity constant (KI). This statement is in accordance with the finding that the ratio of the Michaelis constants for the two cholinesterases is 4, whereas the ratio of the respective maximum velocities (vmax) was only 1.2. Since those organophosphate inhibitors are known to attack only the esteratic site of the cholinesterase, the above finding can be interpreted to mean that the cholinesterase of the resistant strain possesses an abnormally weak esteratic site in terms of its affinity for the substrate as well as for the inhibitor. To investigate the extent of alteration of the esteratic site, a series of organophosphate poisons was tested against these cholinesterases. It was found that the interstrain difference was maximal with the shortest dialkyl side chain of the phosphorus atom, and that the difference decreased with the increase in the dialkyl carbon chain length. Similar findings were made when eholinesters with different acyl groups were tested as substrates. Propionylcholine was hydrolyzed at a faster rate than acetylcholine in both mite strains, and distinct interstrain differences in the cholinesterase activity towards these substrates were observed; with butyrylcholine, however, this interstrain difference was undetectable. Properties of mite cholinesterase were compared with those of insect and mammalian cholinesterases.

ISSN:0008-4018    

DOI:10.1139/o65-007

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Water-soluble proteins and enzymes of human skeletal and smooth muscle were separated by vertical-zone electrophoresis in starch gel and compared with those of human liver and kidney. Thirteen bands of proteins were detected with amido black in skeletal muscle, five of which were also detected in smooth muscle. Various substrates and inhibitors were used in efforts to identify enzymes. Ten bands of esterase activity were detected in skeletal muscle, and nine in smooth muscle. One zone, characteristic of serum cholinesterase, was believed to be due to serum contained in the tissue. A zone of isozymic esterases found in skeletal and smooth muscle was similar to a zone in human liver and kidney and reacted like an acetylesterase. Other esterase bands, which showed a marked hydrolysis of α-naphthyl butyrate, were similar to aliesterases of renal tissue. Observations on alkaline phosphatase, acid phosphatase, aminopeptidase, lactate dehydrogenase, and catalase were recorded for comparison with the data on esterases.

ISSN:0008-4018    

DOI:10.1139/o65-008

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Cellulases fromA.terreusandP.variabilewere isolated and purified nearly 100-fold. Enzyme production reached a maximum on the seventh day of incubation. The properties and activities of the purified cellulases were studied. At constant enzyme concentration, the activity increased with the increase in substrate concentration but the percentage of the substrate hydrolyzed decreased. Of the two purified cellulases, that fromA.terreusseemed to be a purer product and was tested for its homogeneity and enzymic nature. A unienzymic nature was indicated by the observation that no resolution of the enzyme could be effected by electrophoresis. Standard solubility and diffusion tests gave no indication of heterogeneity in the purified cellulase; this finding was confirmed by the presence of only one peak in both gel filtration and ion-exchange chromatography. Random splitting of α-cellulose and carboxymethylcellulose (CMC) was indicated.

ISSN:0008-4018    

DOI:10.1139/o65-009

出版商:NRC Research Press    

年代:1965

数据来源: NRC

摘要:

Uredospores ofPuccinia graminisvar.triticiwere incubated in phosphate buffer (pH 6.2) containing pelargonic acid-1-C14. After 3 hours 97.5% of the tracer was assimilated. Fifty-five percent of this was released as C14O2and 36.2% was incorporated into the spores. About one-half of the carbon-14 in the spores was soluble in ethanol and water, whereas nearly a third was ether extractable. The amino acid and carbohydrate fractions contained about equal amounts of carbon-14 and together accounted for two-thirds of the radioactivity in the ethanol–water extract. The organic acids were also radioactive. Glutamic acid, γ-aminobutyric acid, aspartic acid, and alanine were the most highly labelled amino acids. Fifty-three percent of the radioactivity in glutamic acid was found in carbon 1 and 46% in carbon 5. This distribution suggests β-oxidation of pelargonic acid to acetyl CoA and extensive utilization of the latter by means of the glyoxylate cycle.

ISSN:0008-4018    

DOI:10.1139/o65-010

出版商:NRC Research Press    

年代:1965

数据来源: NRC