摘要:

When rats were fed 1% potassium nitrite in diets containing carotene or vitamin A, their livers contained less vitamin A than those of control rats. After prolonged feeding of potassium nitrite the total amount of vitamin A stored in the liver after a single dose of carotene or vitamin A was reduced, whereas there was no reduction after the administration of vitamin A aldehyde. Ingestion of nitrite did not affect the ability of rate to store vitamin A in the liver nor alter the rate of disappearance of the vitamin from the liver. It is suggested that dietary nitrite degrades carotene and vitamin A in the digestive tract before their absorption, and does not affect the conversion of carotene, the transport of the vitamin, nor the function of the liver.

ISSN:0008-4018    

DOI:10.1139/o66-001

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Acid-soluble extracts were made of cells ofBacillus subtilisgrown on a medium containing glycine-2-14C as a labeled precursor. Paper chromatography of the extracts with propan-2-ol:H2O:NH3as solvent and radioautography of the chromatograms showed that if growth of the cells was inhibited by including actinomycin D in the medium, two radioactive ultraviolet-absorbing components appeared close to the origin of the chromatograms. Only traces were present in control cells not inhibited by the antibiotic. Spectrophotometry of eluted material indicated that these were compounds of guanine, and electrophoresis and phosphorus determinations provided evidence that they were guanosine triphosphate and guanosine diphosphate. Further evidence for this was obtained y comparing them with authentic nucleotides by thin-layer chromatography and by showing that treatment with phosphomonoesterase liberated guanosine. The presence of other components in the acid-soluble fractions was observed and two have been identified tentatively. One may be cytidine diphosphate, which is more strongly radioactive in the control cells. The second, which appears to be radioactive inosinic acid, was present in the inhibited cells but not in the control material.

ISSN:0008-4018    

DOI:10.1139/o66-002

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The effect of 9-β-D-arabinofuranosyladenine triphosphate on the incorporation of thymidine monophosphate-14C into DNA by cell-free extracts of TA3 ascites tumor cells has been studied. Arabinosyl adenine triphosphate is a non-competitive inhibitor of DNA polymerase in TA3 cells. TheKiis 9 × 10−5 M. This effect reasonably accounts for the ability of the compound to inhibit the growth of several ascites tumors in mice.

ISSN:0008-4018    

DOI:10.1139/o66-003

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The hypoglycemic agents hypoglycin A and phenformin lower the ATP levels of slices of rat kidney and liver in vitro. These agents, as well as dinitrophenol, interfere with glucose production by kidney and liver slices in the presence of pyruvate or of various intermediate compounds of glycolysis. There is evidence that the activities of fructose-1,6-diphosphatase and glucose-6-phosphatase may be indirectly affected by these agents.

ISSN:0008-4018    

DOI:10.1139/o66-004

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Rapeseed oil was fed to rats at a level as high as 73% of the calories (48% by weight) of the diet, and there was no mortality in 7 weeks. This is in contrast to a report by an earlier investigator that there was complete mortality in an average of 17 days. The animals survived because the oil was gelatinized with ethyl cellulose before it was mixed into the diet, to prevent settling of the solid ingredients. When the fat levels were high, animals on the diets with rapeseed oil consumed less food and grew less than those on comparable diets with soybean oil. On the basis of caloric efficiency and ability to support growth, however, rapeseed oil was essentially equivalent to soybean oil. Thus the earlier report of the toxicity of rapeseed oil is attributable to the unpalatable form in which it was fed, and not to the oil itself. Levels of cholesterol in the blood and liver were similar whether the rats consumed diets containing rapeseed oil or soybean oil, whereas the adrenal cholesterol was increased when rapeseed oil was fed.

ISSN:0008-4018    

DOI:10.1139/o66-005

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The disturbance in lipid metabolism caused by deficiency of dietary choline in rats was investigated with H3-palmitic acid as a tracer. The incorporation of radioactivity into blood triglycerides, as compared to that in choline-supplemented controls, showed a striking decline in rats taken at intervals during the development of choline deficiency. This was partially corrected by choline re-feeding for 2 days and was normal after 4 days of choline re-feeding. Both the total amounts and the radioactivities of phosphatidyl choline in the liver and total phospholipids in the plasma were reduced in choline deficiency and were restored by choline re-feeding, whereas phosphatidyl ethanolamine in the liver was not affected. The findings confirm that the fatty liver of choline deficiency is the result of an impairment in the transport of triglyceride from the liver, and support the hypothesis that it occurs because of a restriction in the synthesis of phosphatidyl choline which is required for lipoprotein formation.A marked reduction in the transformation of14C-ethanolamine into phosphatidyl choline was evident in choline deficiency, but most of the increase in liver phosphatidyl choline which occurred subsequent to choline re-feeding appeared to be from synthesis by the direct (CDP-choline) pathway.

ISSN:0008-4018    

DOI:10.1139/o66-006

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Human and rabbit erythrocytes suspended in a Ringer phosphate solution can synthesize adenine nucleotides from glucose if exogenous adenine is added. The quantity of nucleotide synthesized approaches a maximum when the concentration of adenine is 0.15 mMand of glucose 8.5 mM. Most of the nucleotide that is synthesized is ATP. With giucose-1-14C, glucose-2-14C, and glucose-6-14C respectively and human erythrocytes, the counts per minute (c.p.m.) obtained in the corresponding nucleotides were in the ratio of 1.7:2.5:1. With rabbit red cells and glucose labeled respectively in the C-1 and C-6 positions, the ratio of the c.p.m. was 1.7:1. When human erythrocytes were incubated with labeled glucose,14CO2was obtained only from glucose tagged in the C-1 position, and the quantity produced was not altered by the addition of adenine. Analysis of the ratios of C-1:C-2:C-6 from glucose in the nucleotides and in CO2leads to the conclusion that the pentose of the nucleotides is formed by oxidative decarboxylation of carbon-1 of glucose and by the transformation of glucose to pentose via the reaction catalyzed by transketolase, with the latter predominating.

ISSN:0008-4018    

DOI:10.1139/o66-007

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The oxidation of added dihydro-nicotinamide-adenine dinucleotide (NADH) by rat liver mitochondria in the presence of different concentrations of magnesium was studied.It was found that, in the absence of added magnesium, NADH was oxidized rapidly by isolated rat liver mitochondria. The addition of either magnesium or ATP strongly inhibited the oxidation of NADH.The inhibition of NADH oxidation induced by magnesium was not released by the addition of a phosphate acceptor, but it was partially released by the addition of ATP at concentrations lower than that of magnesium. As the concentration of ATP increased over that of magnesium, its releasing effect tended to disappear.Similarly, the inhibition of NADH oxidation induced by ATP was partially released by the addition of magnesium at concentrations lower than that of ATP. As the magnesium concentration increased over that of ATP, its releasing effect diminished and eventually caused a greater inhibition than that produced by ATP alone.It is suggested that conditions similar to those described in the oxidation of added NADH by isolated rat liver mitochondria might also occur in the intact cell.

ISSN:0008-4018    

DOI:10.1139/o66-008

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Extracts of conidia of thetd3mutant strain ofNeurospora crassadid not develop pseudo-tryptophan synthase enzyme activity under conditions leading to formation of the activity by equivalent extracts of thewild typestrain. The defect in extracts of thetd3mutant appears to be located in the microsome fraction. The latter is unable to interact effectively with a component of thetd3mutant "post-microsome" fraction which will support in vitro development of the enzymic activity when supplemented with microsomes from other strains ofN.crassa.

ISSN:0008-4018    

DOI:10.1139/o66-009

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Some factors affecting steroid production by rat adrenals in vitro have been studied. Aldosterone production by normal glands increases linearly for at least 20 hours of incubation, whereas corticosterone production reaches a plateau after 4 hours. Aldosterone production by adrenals from rats kept on 1% NaCl as drinking fluid for 8 days does not increase after the second hour of incubation. Varying the volume of Krebs–Ringer bicarbonate medium (containing a given amount of tracer 4-14C-progesterone) does not alter the endogenous production of aldosterone or corticosterone, but the specific activity of these compounds decreases as the volume of Krebs–Ringer bicarbonate increases. The significance of these findings is discussed.

ISSN:0008-4018    

DOI:10.1139/o66-010

出版商:NRC Research Press    

年代:1966

数据来源: NRC