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R Blomstrand

Publications and source records attributed to R Blomstrand.

At least 37 records · Page 2Linked to original sources
PubMed1980

Use of isotope dilution--mass spectrometry for accuracy control of different routine methods used in clinical chemistry.

Serum from patients was pooled, filtered, dispensed and frozen. The serum pool obtained was used for accuracy control in twenty-one participating laboratories in the Stockholm area. Mean values (state of art values) were obtained for creatinine, cholesterol, glucose, urea and uric acid. These values were compared with values obtained with highly accurate reference methods, based on isotope dilution--mass fragmentography. The most marked difference was found in the case of determination of creatinine. It is suggested that immediate access to such a well-defined human serum might decrease the need for conventional interlaboratory control programmes.

Blood Glucose↗
PubMed1980

Interlaboratory evaluation of four RIA kits for determination of plasma cortisol, with special reference to accuracy: influence of matrix in calibration standards.

We used four RIA kits for determination of plasma cortisol to assay 12 plasma samples in four laboratories, and compared the results with those obtained with a highly accurate method based on isotope dilution/mass spectrometry. All kits (Farmos, NEN, Sorin, and Clinical Assays) showed 10-50% deviation from the comparison method in the normal range (200-700 nmol/L). The inter- and intralaboratory imprecision (CV) ranged between 8-27% and 5-11%, respectively. Possible explanations for this low accuracy are discussed. Retention of an intact biological matrix in the calibration standards seems to be one prerequisite for accuracy.

Humans↗
PubMed1979

Pyrazoles as inhibitors of alcohol oxidation and as important tools in alcohol research: an approach to therapy against methanol poisoning.

4-Methylpyrazole, in a dose producing inhibition of alcohol dehydrogenase (alcohol:NAD(+) oxidoreductase, EC 1.1.1.1), was given alone or together with ethanol (10%) as sole drinking fluid to growing rats for up to 38 weeks. Their weight curves remained normal. Electron microscopy of liver, kidney, and heart revealed no changes related to treatment. Hematologic analysis showed normal values for blood and bone marrow. Several clinical chemical parameters showed no impairment of liver or kidney function, except for an enhancement of the microsomal drug-metabolizing activity after concurrent administration of 4-methylpyrazole and ethanol. A study on rats receiving 4-methylpyrazole and ethanol indicated a mutual interaction of the two compounds or the metabolites, leading to increased concentration in the blood of the compounds and reduced formation of 4-hydroxymethylpyrazole, the primary metabolite of 4-methylpyrazole. In monkeys, elimination of 4-methylpyrazole followed a linear course. 4-Hydroxymethylpyrazole accumulated to a level of at most 10% of that of 4-methylpyrazole. Concurrent administration of methanol inhibited the elimination of 4-methylpyrazole about 25%, and 4-methylpyrazole produced a profound inhibition of the oxidation of methanol. 4-Methylpyrazole, at a level in the plasma of more than 10 muM, prevented accumulation of the toxic metabolite formic acid in methanol-poisoned monkeys, and repeated injections of 4-methylpyrazole abolished methanol toxicity in monkeys receiving lethal doses of methanol. The present investigation indicates that 4-methylpyrazole, with its low toxicity and strong inhibition of alcohol oxidation, is a valuable tool for experimental studies of alcohol metabolism and its effects. It illustrates the usefulness of the monkey as a model to study 4-methylpyrazole activity and toxicity in light of its possible use for treating methanol poisoning in human beings.

Alcoholism↗
PubMed1978

Mass fragmentographic determination of docosenoic acid in rapeseed oils.

A highly sensitive and accurate reference method for determination of docosenoic acid (mainly erucic acid, 22:1n-9) in different rapeseed oils is described. A fixed amount of [1-14C] erucic acid methyl ester (about 1 microgram) is added to a fixed amount of oil. After treatment with sodium methoxide/methanol reagent and extraction with hexane, the amount of unlabeled erucic acid is determined from the ratio between the recordings at m/e 320 and m/e 322 obtained after analysis with a combined gas chromatograph-mass spectrometer equipped with an MID (multiple ion detector). The two ions used correspond to the M-32 peak in the mass spectrum of unlabeled and [1-14C] labeled erucic acid methyl ester. The relative standard deviation of the method is about 1.8%. The method was compared with a gas chromatographic method for determination of erucic acid.

Brassica↗
PubMed1978

Effect of different dietary triglycerides on 7alpha-hydroxylation of cholesterol and other mixed-function oxidations.

The effect of a diet containing triglycerides of different fatty acid composition on hepatic 7alpha-hydroxylation of cholesterol was studied. 7alpha-Hydroxylation of exogenous as well as endogenous cholesterol was significantly lower in the liver of rats fed trilinolein and triolein than in those fed tripalmitin and trierucin. The concentration of cytochrome P-450 in liver microsomes was significantly lower in the rats fed tripalmitin and trierucin than in those fed triolein and trilinolein. The inhibitory effect of triolein and trilinolein on 7alpha-hydroxylation of cholesterol and the stimulatory effect of these triglycerides on the concentration of cytochrome P-450 was not due to the small amounts of peroxides present in the unsaturated triglycerides. Thus addition of the antioxidant butylated hydroxyanisol did not change the general pattern with respect to 7alpha-hydroxylation and concentration of cytochrome P-450. However, a diet consisting of peroxidized linoleic acid further decreased 7alpha-hydroxylation of cholesterol. The difference between the effect obtained with triolein and trilinolein on the one hand and trierucin and tripalmitin on the other was observed also in experiments with lower concentrations of fat in the diet and in experiments with different lighting conditions and feeding patterns. The inverse relation between cytochrome P-450 and 7alpha-hydroxylation of cholesterol, as well as results obtained with substrates for mixed-function oxidation other than cholesterol suggest that most of the changes observed due to the different diets are specific for 7alpha-hydroxylation of cholesterol. The level of cholesterol 7alpha-hydroxylase activity was found to be better related to the degree of absorption of fat than to total amount of absorbed fat or degree of unsaturation of the fat. The results are discussed in relation to previous knowledge concerning mechanisms regulating biosynthesis of bile acid.

Animals↗
PubMed1976

The use of mass fragmentography in the evaluation of routine methods for glucose determination.

A highly specific and accurate mass fragmentographic reference method for determination of serum glucose is described. A fixed amount of hepta-deuterated glucose is added to a fixed amount of serum. The mixture is lyophilized, converted into the penta-trimethylsilyl-methyloxime derivative and subjected to analysis with a combined gas chromatograph - mass spectrometer equipped with a MID-unit (multiple ion detector). The amount of unlabeled glucose was determined from the ratio between recordings at m/e 319 and 323. The two ions used correspond to the base peak in the mass spectrum of derivative of unlabeled and hepta-deuterium labeled glucose, respectively. The relative standard deviation of the method was 1.9%. The method was compared with different enzymatic methods based on the hexokinase reaction and the glucose oxidase reaction. Of the different methods tested, a glucose oxidase method with determination of maximal rate of consumption of oxygen gave results most close to the results of the reference method.

Blood Glucose↗
PubMed1976

Determination of serum triglycerides by mass fragmentography.

A mass fragmentographic reference method for determination of serum triglycerides is described. A fixed amount of a mixture of [1,1,2,3,3-2H5]glycerol tripalmitate and [1,1,2,3,3-2H5]glycerol trioleate (500 nmol) is added to a fixed amount of serum (250 mul) and extracted with chloroform/methanol (2 : 1, v/v). The triglycerides are isolated by means of thin-layer chromatography. The glycerol obtained after acid hydrolysis is converted into the tri-trimethylsilyl derivative and the amount of unlabeled glycerol is determined from the ratio between the recordings at m/e 218 m/e 222, obtained after analysis with a gas chromatograph-mass spectrometer equipped with an MID (multiple ion detector). The two ions correspond to the peak at M--90 and M--91 in the mass spectrum of the tri-trimethylsilyl derivative of unlabeled and (1,1,2,3,3-2H5)-labeled glycerol. The relative standard deviation of the method in the range 0.4--5.8 mmol/l was 2.4%. A fully enzymatic routine method for determination triglycerides was compared with the mass fragmentographic reference method. There was a good correlation between the two methods (r = 0.995) and the regression coefficient was 1.19.

Gas Chromatography-Mass Spectrometry↗
PubMed1976

Determination of serum urea by mass fragmentography.

A mass fragmentographic method of high accuracy for determination of serum urea is described. A fixed amount of [15N2]urea is added to a fixed amount of serum, then the urea is converted into 5,5-diallyl barbituric acid by coupling with diallyl malonic acid diethyl ester. The barbiturate is then transferred from an alkaline water phase into an organic phase containing methyl iodine by ion-pair extraction using tetrabutyl ammonium as the positive counterion. The amount of urea is determined from the ratio between the recordings at m/e 236 and m/e 238 obtained after analysis with a combined gas chromatograph-mass spectrometer equipped with an MID-unit (multiple-ion detector). The two ions used correspond to the molecular peak in the mass spectrum of the methyl derivative of unlabeled and labeled 5,5-diallyl barbituric acid, respectively. The relative standard deviation of the method was 3.6%. A comparison between the mass fragmentographic method and a routine method for determination of serum urea based on the urease-Berthelot reaction gave a high correlation (r = 0.99) and a regression coefficient of 0.95.

Barbiturates↗
PubMed1976

Toward absolute methods in clinical chemistry: application of mass fragmentography to high-accuracy analyses.

We review recently developed reference methods based on mass fragmentography (specific ion monitoring) with use of isotope-labeled internal standard, for determination of cholesterol, triglycerides, urea, glucose, cortisol, progesterone, and testosterone. With an optimal ratio between standard and material to be determined, the relative standard deviation of these methods, based on duplicate determinations, is between 1.3 and 2.7%. The very high specificity of the methods, in combination with the fact that the ratio between labeled and unlabeled molecules is determined with a high degree of accuracy, makes it likely that the most significant errors in the methods are related to errors in pipetting. The possibility is discussed that these methods might be developed into "absolute" or "definitive" methods by subjecting each individual step in the determination to a detailed analysis with respect to possible error. We also discuss some of the consequences of the different reference methods on the choice of routine methods.

Blood Glucose↗
PubMed1975

Validation of routine methods for serum progesterone determination using mass fragmentography.

A mass fragmentographic reference method for determination of serum progesterone is described. A fixed amount of [4-14C]progesterone (usually 7.5 ng) is added to a fixed amount of serum (usually 1 ml) and extracted with hexane. The extract is purified by means of thin-layer chromatography. The purified progesterone is converted into the dienol heptafluorobutyrate derivative by treatment with heptafluorobutyric acid anhydride. The amount of unlabeled progesterone is determined from the ratio between the recordings at m/e 510 and m/e 512 obtained after analysis with a combined gas chromatograph-mass spectrometer equipped with a MID-unit (multiple ion detector). The two ions used correspond to the molecular peak in the mass spectrum of the dienol heptafluorobutyrate derivative of unlabeled and labeled progesterone, respectively. The relative standard deviation of the method was 3.7% provided that serum progesterone concentration was in the range 10-70 nM. Two radioimmunoassay techniques with commercial kits were compared with the mass fragmentographic method. The correlation coefficient obtained was 0.93 and 0.76 respectively, and the regression coefficient 0.93 and 1.05, respectively.

Adult↗
PubMed1975

Validation of methods for determination of urinary estriol during pregnancy using mass fragmentography.

A specific and accurate method for determination of urinary estriol during pregnancy is described. After acid hydrolysis of 1 ml urine, a fixed amount of [2,4-2H2] estriol (usually 15 mug) is added and the mixture is extracted with diethyl ether. The extracted estriol is converted into the tri-trimethylsily derivative and the amount of unlabeled estriol is determined from the ratio between the recordings at m/e 504 and m/e 506 obtained after analysis with a gas chromatograph-mass spectrometer equipped with an MID (multiple ion detector). The two ions used correspond to the molecular peak in the mass spectrum of unlabeled and (2,4-2H2)-labeled tri-trimethylsilyl derivative, respectively. The relative standard deviation of the method was about 6%. The method was compared with a photometric method using the Kober reaction and the gas liquid chromatographic method used in routine analysis. There was a good correlation in both cases and the regression coefficient was 1.5 and 1.3, respectively.

Estriol↗