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Biomedical subjects

O Lantto

Publications and source records attributed to O Lantto.

At least 19 recordsLinked to original sources
PubMed1983

Identification of thyroxine in human breast milk by gas chromatography-mass spectrometry.

In several previous publications it has been reported that human breast milk contains significant amounts of T4. Great differences in concentrations were found by different authors. In all these publications T4 was assayed by RIA, and it seems probable that the varying results obtained are due to varying specificity of the antibodies used in the assay. Definite demonstration of the presence of T4 in breast milk requires a more specific method than RIA. In the present work we have used combined gas chromatography-mass spectrometry. T4 was isolated from human breast milk by combined anion- and cation-exchange chromatography. The purified material was treated with HCl in methanol and trifluoroacetic acid anhydride and was analyzed by single-ion monitoring of the ions at m/e 983, m/e 870, and m/e 799, major ions in the mass spectrum of the N,O-bis(trifluoroacetyl) methyl ester of T4. Significant peaks confirmed the presence of T4 in human milk. The estimated concentration was less than 10 ng/ml. Attempts were made to quantitate the T4 by selected ion monitoring of the ions at m/e 870 and m/e 822 after addition of monobromotriiodothyronine as internal standard. According to this latter method, the concentration of T4 in four samples of centrifuged breast milk was less than 4 ng/ml. The possible physiological significance of the finding is discussed.

Acetonitriles↗
PubMed1983

Assay of cortisol with a radioimmunoassay method calibrated by isotope dilution-mass spectrometry. A Nordic collaborative study.

A reference method for serum cortisol, based on isotope dilution-mass spectrometry (ID-MS), was compared with a modified commercial RIA method. The modification solely concerned the calibration standards used in the RIA method. These were replaced by a series of human serum samples, in which the concentration of cortisol had been determined by the reference ID-MS method. The samples were selected so as to cover the whole range of the standard curve. Serum samples from healthy, untreated subjects with cortisol concentrations 270-1134 nmol/l were analysed with the ID-MS calibrated RIA method in four laboratories, one in each of the four Nordic countries. The results from two of the four laboratories did not differ significantly from the ID-MS values (P less than 0.05), whereas the results from the other two laboratories differed slightly. The mean values based on results from all four laboratories were almost identical with the values obtained with the reference method. In addition, serum samples from 11 patients with endocrine disorders with cortisol concentrations 31-916 nmol/l were analysed in three of the four laboratories. In three of the samples significant differences were observed between the values obtained with the ID-MS and the ID-MS calibrated RIA method. The value obtained with the ID-MS calibrated RIA was however always more accurate than the corresponding value obtained with RIA with the use of a commercial calibration standard. Advantages of the present model in increasing the accuracy of routine analysis by RIA are discussed. The possibility is further discussed that the ID-MS calibrated RIA method may be used as a 'secondary reference method'.

Adult↗
PubMed1982

Gradients of monoamine metabolites and cortisol in cerebrospinal fluid of psychiatric patients and healthy controls.

Amine metabolites and cortisol were measured in four consecutive 3 ml samples of lumbar cerebrospinal fluid (CSF). There were pronounced concentration gradients for both 5-hydroxyindoleacetic acid and homovanillic acid, and there was no difference in the gradients of 11 controls and 17 psychiatric patients (10 depressed). As there was a close correlation between the mean of the first two fractions and the mean of all four fractions, a concentration obtained in 6 ml can be used to calculate that in a 12 ml CSF sample. In psychiatric patients there was a slight, but statistically significant concentration gradient for 3-methoxy-4-hydroxyphenylglycol (unconjugated as well as conjugated). No gradient was found for cortisol in CSF.

Body Height↗
PubMed1982

Radioimmunoassay and lipid-chromatographic analysis for free cortisol in urine compared with isotope dilution--mass spectrometry.

I compared results by three different routine methods for analysis for urinary cortisol with those by a highly specific reference method based on isotope dilution--mass spectrometry (i). A "high-performance" liquid-chromatographic method (II) gave the most comparable results (regression coefficient 0.86, intercept 9 nmol/L). For some urines much lower values were obtained by I than by II. Two radioimmunoassay (III) methods, one involving direct assay and one involving extraction, gave less-accurate results (regression coefficients of 1.87 and 1.52 and intercepts of 86 and 12 nmol/L, respectively, although values obtained by III and by I correlated well (r = 0.95-0.99), indicating a relation between the free cortisol and the compounds interfering in III. The apparent accuracy for the extraction method was previously assayed by I (regression coefficient 0.90, intercept 6 nmol/L). All four methods investigated showed a statistically significant sex-related difference in 24-h urinary cortisol excretion; evidently such a finding should be a prerequisite in any such method proposed for routine use.

Adult↗
PubMed1982

Simultaneous determination of prednisolone and cortisol in serum by HPLC and by isotope dilution--mass spectrometry.

A reference method for the simultaneous assay of cortisol and prednisolone by isotope dilution-mass spectrometry has been developed. A fixed amount of 2H4-labelled cortisol is added to a fixed amount of serum. The mixture is then extracted, converted into methoxime-trimethylsilyl derivative, and subjected to analysis by combined gas chromatography-mass spectrometry. The ions at m/e 603, m/e 605 and m/e 609 are followed through the gas chromatography. These ions correspond to the M-31 ions in the mass spectrum of methoxime-trimethylsilyl ether derivative of prednisolone, unlabelled cortisol and 2H4-cortisol, respectively. With the use of a standard curve, the concentration of prednisolone can be calculated from the ratio between the peak at m/e 603 and the peak at m/e 609 and the concentration of cortisol can be calculated from the ratio between the peak at m/e 605 and the peak at m/e 609. The coefficient of variation was about 2% with respect to determination of prednisolone and about 3% with respect to determination of cortisol. This method was compared with a routine method based on high-performance liquid chromatography (HPLC) The coefficient of variation was 2-3% with respect to determination of cortisol and 1-3% with respect to determination of prednisolone. There was a good correlation between the isotope dilution method (x) and the HPLC method (y). In the assay of serum prednisolone the regression analysis gave the following equation: y = 1.02x -69 nmol/l, r = 0.99. In the assay of serum cortisol, the regression equation was: y = 1.07x-14 nmol/l, r = 0.95. It is concluded that the HPLC-method, used for routine determination of cortisol and prednisolone, has an accuracy sufficient for its intended use.

Chromatography, High Pressure Liquid↗
PubMed1981

Accuracy of some routine method used in clinical chemistry as judged by isotope dilution-mass spectrometry.

Serum from patients was pooled, filtered, dispensed, and frozen. This pooled specimen was used for accuracy control in 64 participating laboratories in Sweden. Mean values ("state-of-the-art" values) were obtained for creatinine, cholesterol, glucose, urea, uric acid, and cortisol. These values were compared with values obtained with highly accurate reference methods based on isotope dilution-mass spectrometry. Differences were marked in the case of determination of creatinine and cortisol. Concerning the other components, the differences between the state-of-the-art value and the values obtained with the reference methods were negligible. Moreover, the glucose oxidase and the oxime methods for determination of glucose and urea were found to give significantly lower values than the hexokinase and urease methods, respectively. We conclude that methods with a higher degree of accuracy are required for routine determination of creatinine and cortisol.

Blood Chemical Analysis↗
PubMed1980

Rhythmic changes in estriol excretion during pregnancy.

Different biologic rhythms with effect on one and the same parameter may cause a complicated signal pattern in which no regularity can be visually identified. In this study an autocorrelation function approach, well established in the interpretation of electroencephalograms, was shown to be applicable also in the interpretation of processes with few points of observation. This technique, used on the excretion of estriol in urine, reveals several rhythms with wavelengths between 6 and 72 hours. Interference between these signals may explain the irregular visual appearance of plots of subsequent estriol determinations and the considerable rise and fall of urinary estriol excretion during pregnancy. The presence of two independent sources of the rhythms is suggested. It is concluded that the complicated and individual rhythmic changes in urinary excretion of estriol results in a low diagnostic specificity for fetoplacental malfunction of this component.

Circadian Rhythm↗
PubMed1980

Cortisol in the CSF of depressed and suicidal patients.

Cortisol concentrations in CSF were measured by radioimmunoassay in healthy controls, depressed patients, patients who had attempted suicide but were not depressed, and obsessive-compulsive patients. The factors that contributed most to the variance in CSF cortisol levels were a diagnosis of depression, height, and important life changes during the six months preceding the investigation. Depression was by far the most important factor. The depressed patients had significantly higher CSF cortisol levels than the controls. In obsessive-compulsive and depressed patients treated with clomipramine hydrochloride, the levels were significantly correlated with mean urinary cortisol excretion. Of the three monoamine metabolites measured, only 5-hydroxy-indoleacetic acid level was weakly correlated with CSF cortisol level. This correlation was confined to the depressed patients and could be accounted for by the common correlation with height.

Adjustment Disorders↗
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

Total cortisol and L/S-ratio in amniotic fluid in late pregnancies complicated by diabetes mellitus.

68 samples of amniotic fluid from 47 women with varying severity of diabetes mellitus and 48 samples from 43 normal women were obtained in the 31st to 40th week of pregnancy before onset of labour. The concentration of total cortisol and the L/S-ratio in amniotic flud were determined and related to gestational age. There was a continous rise of total cortisol with advancing gestational age in the diabetic pregnancies similar to that found in normal pregnancy. Diabetic pregnancies were associated with slightly lower amniotic fluid cortisol levels without significant difference to values found in normal pregnancy. The severity of the disease did not affect the cortisol levels in amniotic fluid. There was no correlation between total cortisol levels and L/S-ratios in amniotic fluid. Determination of total cortisol in amniotic fluid can thus not replace measurements of L/S-ratios to predict fetal lung maturation.

Amniotic Fluid↗
PubMed1978

Total and free cortisol in amniotic fluid during late pregnancy.

Total cortisol levels were measured in 81 samples of amniotic fluid obtained from 72 patients in the third trimester of pregnancy; 19 of them had pre-eclampsia and the remainder had no pre-eclampsia, hypertension or renal disease. In accordance with previous studies, there was a rise in the concentration of amniotic fluid cortisol with advancing gestation; the rise was steepest after 40 weeks, the amniotic fluid cortisol levels invariably being above 700 nmol/l between 41 and 43 weeks of pregnancy. Amniotic fluid cortisol may thus be of value in diagnosing postmaturity. A relatively low correlation was found between total cortisol levels and lecithin/sphingomyelin ratios in amniotic fluid unless results were ranked for gestational age. Total cortisol concentrations in amniotic fluid obtained from patients with pre-eclampsia were significantly higher than in controls. The concentration of free cortisol in amniotic fluid changed much less than total cortisol. Thus total cortisol should be measured in studies of the fetal capacity to synthesize corticosteroids.

Amniotic Fluid↗
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↗