摘要:

SUMMARYA microbiological assay for serum folic acid activity usingLactobacillus caseias the test organism is described. The method uses ascorbic acid to protect the folic acid‐like activity of serum and is sensitive enough to differentiate between sera from normal and folic acid‐deficient subjects without overlap. One hundred normal sera have been assayed and fall within the range 2·7–18·5 mμg./ml. There does not appear to be a significant difference between male and female serum levels.

ISSN:0004-945X    

DOI:10.1038/icb.1962.48

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYThe metabolism of chylomicron triglycerides containing predominantly palmitic, oleic and linoleic acids has been studied in intact rats and in isolated perfused rats’ livers using14C‐labelled chylomicrons. In intact rats infused continuously with labelled chylomicrons the rate of excretion of14CO2reached a relative plateau during the second hour of the infusion. The rate of excretion of14CO2in the third and fourth hours of the infusion showed that about 40 p.c. of the labelled fat was converted to CO2as it was infused. It was found that significantly less palmitic acid was oxidized to CO2than oleic or linoleic acids. This difference was, however, small. About 4 p.c. of the radioactivity of the infused labelled fat underwent recycling and subsequent oxidation once the relative plateau was reached.In experiments with perfused livers there was no significant difference in the rate of uptake or oxidation of palmitic, oleic or linoleic acids incorporated into chylomicrons. Significantly more linoleic acid than oleic or palmitic acid was incorporated into the phospholipids of the perfusate. The results showed that the rate of oxidation of palmitic, oleic or linoleic acids incorporated into chylomicrons can be used as a measure of the overall rate of oxidation of chylomicron triglycerides.

ISSN:0004-945X    

DOI:10.1038/icb.1962.49

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYThe relationship between peak tension developed during a twitch in isolated rabbit papillary muscle and the frequency and pattern of stimulation has been examined. The muscle was subjected to a short train of stimuli followed by n single α‐stimulus; this pattern of stimuli was repeated at regular intervals. The experimental variables were the frequency and number of stimuli in the train, the time interval after the end of the train and the α‐stimulus, and the rest period between each stimulus pattern. The peak tension of the response to the α‐stimulus as a function of these four variables was determined in a number of ways and a tentative mathematical model is formulated which describes this aspect of the results.The response to the stimuli of the train is considered in relationship to the model and the form of model which could describe these and other results is discussed.

ISSN:0004-945X    

DOI:10.1038/icb.1962.50

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYThe effect of menadione on the reduction of methaemoglobin by normal and glucose‐6‐phosphate dehydrogenase‐deficient (G6PD‐deficient) human erythrocytes has been studied. With glucose as substrate, menadione caused an increased rate of methaemoglobin reduction in normal but not in G6PD‐deficient erythrocytes. With lactate, menadione produced enhanced methaemoglobin reduction in both normal and G6PD‐deficient erythrocytes.The effect of menadione appeared somewhat similar in nature to that produced by methylene blue, but of lesser degree and shorter duration. Evidence was presented to show that menadione‐induced methaemoglobin formation may complicate the kinetics of methaemoglobin reduction, particularly with higher concentrations of menadione and lower initial concentrations of methaemoglobin.It was suggested that menadione enhances the reduction of methaemoglobin mainly by catalysing reduced nicotinamide‐adenine dinucleotide phosphate‐dependent reduction of methaemoglobin, but also under certain circumstances by stimulating one or more reduced nicotinamide‐adenine dinucleotide‐dependent pathways of methaemoglobin reduction.

ISSN:0004-945X    

DOI:10.1038/icb.1962.51

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYUsing anin vitrophagocytic system, stimulation of macrophage activity following exposure of mouse peritoneal cells to glyceryl trioleate (triolein) suspension has been found. The stimulation is time‐ and dose‐dependent, maximum effects on 2 × 106cells being obtained with 50 μg. triolein for 60 minutes. Larger doses of triolein are not immediately stimulatory but following prolonged incubation the cells eventually develop significant activity. The stimulation is due to contact between the cells and triolein particles and is independent of the degree of opsonization of the organisms by normal animal sera.

ISSN:0004-945X    

DOI:10.1038/icb.1962.52

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYThere is a striking similarity in the psychomotor effects of reserpine and bulbocapnine. Details are given for a simple behavioural test for measuring psychomotor activity. It was found that methyl phenidate has some potency as an antagonist to the catatonic‐like action of bulbocapnine. Iproniazid was ineffective.

ISSN:0004-945X    

DOI:10.1038/icb.1962.53

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYThe effect of suspensions of saturated fatty acids or oleic acid on the coagulation of plasma and on the release of plasma kinin was determined by quantitative methods. The activity of the saturated series (C8‐C22) increases enormously with the length of the carbon chain. Oleic acid is practically inactive. Evidence is presented that the reaction is mediated by adsorption and activation of Hageman factor by the fatty acid micelles. The differences between the activity of the fatty acids are related to the physical conditions at the surface of the particles.

ISSN:0004-945X    

DOI:10.1038/icb.1962.54

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYFemale Wistar rats were found to be more susceptible to the lethal effect of d‐tubocurarine than were male rats of the same strain and age. The LD50of d‐tubocurarine administered intraperitoneally was estimated as 0·256 mg./kg. body weight for female rats and 0·328 mg./kg. for male rats.Sedative doses of sodium amytal were found to protect against the lethal effect of relatively large single doses of d‐tubocurarine. However, doses of sodium amytal repeated over several days had the opposite effect and increased the susceptibility of rats to small doses of d‐tubocurarine. The effect of amytal appears not to be due to sedation.Rats given several doses of d‐tubocurarine at or above the LD50did not show any biochemical or histological evidence of liver damage. Long courses of frequent injections of d‐tubocurarine at lower dose rates than the LD50did not result in any detectable enzymological dysfunction of, or histopathological change in, the liver. It is concluded that although d‐tubocurarine is potentially hepatotoxic by virtue of its effectin vitroon liver mitochondria it is such a highly specific neuromuscular blocking agent at such low dose rates that, under usual conditions, animals die from neuromuscular paralysis before the alkaloid enters the liver in sufficient quantities to cause damage.

ISSN:0004-945X    

DOI:10.1038/icb.1962.55

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY

摘要:

SUMMARYA high proportion of the batches of monkey kidney cells commercially available in Australia carry a haemadsorbing virus, the properties of which are described. The virus appears to be identical with or very closely related to SV‐5. Since diagnostic laboratories usually rely on the haemadsorption technique for the isolation of the viruses of para‐influenza, influenza and mumps from the respiratory tract of man and animals, the presence of this agent may seriously complicate the interpretation of results. The problem can be partially overcome by the routine incorporation of SV‐5 antiserum in cell culture media. However, since SV‐5 appears also to cause human infection, it is not practicable to try to isolate this virus from man in tissue which already contains it. For this and other reasons discussed it is suggested that monkey kidney can no longer be considered the tissue of choice for the isolation of respiratory viruses and should be replaced by another cell type.

ISSN:0004-945X    

DOI:10.1038/icb.1962.56

出版商:Nature Publishing Group    

年代:1962

数据来源: WILEY