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Biomedical subjects

N A Schmidt

Publications and source records attributed to N A Schmidt.

At least 19 recordsLinked to original sources
PubMed1989

Application of diethylstilbestrol dipropionate in bulls. I. Excretion of residues in urine and faeces and histological and immunohistochemical changes in the prostate.

In this experiment 20 one year old bulls received a single intramuscular injection of the anabolic preparation diethylstilbestrol dipropionate (DES-DP) (an oil preparation or an emulsion). Four animals received a corresponding placebo. The application of DES-DP to bulls caused characteristic histological alterations in the peripheral glandular epithelium of the prostate, which could be observed until four weeks after treatment. The value of histological investigation as a screening method was, however, limited by the occurrence of only few metaplastic lesions and a rapid recovery. By contrast, immunohistochemistry using a polyclonal cytokeratin antiserum K40 appeared to be a specific and very sensitive method to detect oestrogen-induced lesions in the prostate. In only two animals, six weeks after injection with the DES-emulsion, false-negative results were obtained, demonstrating the potential value of this screening method. The excretion of DES in the urine and faeces was monitored using radioimmunoassay following chromatographic purification of the urine and faeces extracts. The excretion of DES in urine was faster for animals of the oil group. The DES content in urine decreased to the 1 microgram/l level after 42 days (emulsion group) or 70 days (oil group). The excretion in faeces was comparable to that in urine. After day 21 the excretion patterns of the two excreta were indistinguishable.

Animals↗
PubMed1989

Steroid profile for urine: reference values.

We describe a project, participated in by 24 institutions in The Netherlands and Belgium, to determine normal reference values for steroids in urine by capillary gas chromatography. Urine samples from 288 healthy volunteers were analyzed in triplicate. Reference values, expressed in mumol/24 h, were determined for androsterone, etiocholanolone, dehydroepiandrosterone, 11-keto-androsterone, 11-keto-etiocholanolone, 11-hydroxyandrosterone, 11-hydroxyetiocholanolone, pregnanediol, pregnanetriol, 11-desoxytetrahydrocortisol, tetrahydrocortisone, tetrahydrocortisol, allo-tetrahydrocortisol, and 17-keto- and 17-hydroxysteroids. We also determined reference ratios for etiocholanolone/androsterone, tetrahydrocortisone/tetrahydrocortisol, and tetrahydrocortisol/allo-tetrahydrocortisol; an upper limit of a discriminant function to establish polycystic ovarian disease; and reference values for 24-h urine volume and creatinine excretion. Reference values were determined separately for men and women, each in six age categories: 0-3 months, 4 months-12 years, 13-16 years, 17-50 years, 51-70 years, and older than 70 years. We conclude that these reference values are reliable and form a basis for quantitative interpretation of steroid profiles.

Adolescent↗
PubMed1989

Correction of instrument- and reagent-based differences in determination of the International Normalized Ratio (INR) for monitoring anticoagulant therapy.

As recommended by the World Health Organization, standardization of prothrombin time assays involves conversion of prothrombin times into International Normalized Ratios (INR). We investigated the effect of two different methods (Nycomed's Thrombotest, and Instrumentation Laboratory's PT-fibrinogen) and three coagulation instruments (Schnitger & Gross, KC-10, and ACL) on calculations of INR. The INR plots showed considerable scatter of individual values around the regression lines when the two different methods were compared. Systematic differences in the outcome of INR calculation were related to the use of the different coagulation instruments. Prothrombin times obtained with the different instruments were linearly correlated. We used the bias of these lines to correct results for both the patients' samples and the reference samples. This correction yielded INR values from the different instruments that agreed well.

Anticoagulants↗
PubMed1986

The effect of age, weight-related parameters and hormonal contraceptives on andrological assays.

Serum levels of dehydroepiandrosterone-sulfate (DHEA-S), testosterone (T), sex hormone binding globulin (SHBG), T/SHBG ratio and the calculated free T were evaluated in healthy female blood donors. The influence of age and weight-related parameters were studied together with the effects of 9 different oral contraceptives. A gradual decrease with age of DHEA-S, T, T/SHBG and free T levels were observed. The Quetelet index showed a significant negative correlation with the androgen levels except for the T/SHBG ratio. In the females using contraceptives, DHEA-S levels were only significantly decreased in the group using Depo-provera. Most contraceptive users had slightly lowered T levels. Marvelon and Ministat induced an increase in the SHBG levels. Androstenedione (A) levels were studied for some of the contraceptives (Ministat, Marvelon, Lyndiol, Depoprovera); levels were found to be significantly lower than in normal premenopausal women. A highly significant correlation was demonstrated between DHEA-S and the T, T/SHBG and free T levels in the serum of 106 normal women.

Age Factors↗
PubMed1985

Steroid profiling--an update.

Extraction of steroids from urine with C18 solid-phase extraction cartridges results in an extract containing impurities. If, during the extraction of hydrolyzed urine, an amino (NH2) column is placed in series with the C18 column, then one obtains a sample that is sufficiently clean for gas-chromatographic analysis. Analytical recovery of dehydroepiandrosterone from urine is considerably decreased by the use of increasing amounts of Helix pomatia enzyme preparation. Extraction of the steroid conjugates from urine with C18 columns before the hydrolysis stage is essential for hydrolysis with an amount of enzyme preparation that suffices for complete splitting of the polar steroid conjugates but not so much as to cause insufficient analytical recovery of dehydroepiandrosterone.

Animals↗
PubMed1983

The need for a sufficient number of low level sera in comparisons of different serum vitamin B12 assays.

Eight radiochemical methods for the assay of vitamin B12 in serum were compared with the microbiological assay with Lactobacillus leichmannii ATCC 7830 using 198 individual sera of patients. There was a good agreement between the results of most samples with some kits and the microbiological assay. However, especially in the sera of vitamin B12-deficient patients large discrepancies between the results could occur. These variations were due to both the kits used and the performance of the assays in different laboratories. A sufficient number of non-pooled sera of vitamin B12-deficient patients should be included in investigations to validate radiochemical methods.

Biological Assay↗
PubMed1976

Automation in the hematology laboratory.

In the routine laboratory for hematology conflicting results may be obtained for the red blood cell parameters with the Coulter Counter Model S. These parameters2) are: mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC). When the values of the MCHC are above 36 g/dl something must be wrong with the blood sample of the patient. One of the reasons can be agglutination e.g. by cold agglutinins. The blood sample should be reanalysed before and after heating for 1 hour at 37 degrees C. If the values change: cold agglutinins are present; if no change occurs paraproteins, or other disturbing factors, such as bilirubin or high leucocyte levels, will be found. MCH values may also be high in some cases e.g. if the red blood cells are coated with antibodies (Coombs test positive) or after ingestion of medicines like Azathioprine. These examples show that it is possible in some cases to correlate immunological findings with the red blood cell parameters. In addition to the results with the Coulter Counter Model S, some observations on the Hemalog (Technicon) are also presented.

Blood Cell Count↗
PubMed1975

A systematic investigation on the Hemalog.

The Hemalog system is an automated hematological instrument. From one sample this instrument determines the value for platelets (PBC), white blood cells (WBC), red blood cells (RBC), hemoglobin (Hb) and the hematocrit simultaneously. Moreover the system calculates the derived values: the mean cell volume (MCV), mean cell hemoglobin (MCH) and the mean cell hemoglobin concentration (MCHC). The values were investigated for cross sample contamination, coincidence, reproducibility, and compared with other methods. From this comparative study we can conclude that the Hemalog is a suitable and reliable instrument for hematological determination.

Autoanalysis↗
PubMed1975

Quality control in hematology by means of values from patients.

The results of the analyses which were obtained with the Hemalog for the determination of platelets, white blood cells, red blood cells, hemoglobin and hematocrit were statistically analysed for the quality control of the determinations. Now that the testing method has been applied for 6 months, it appears from the results that it is extremely suitable for the determination of hemoglobin, red blood cells and the hematocrit and, to a lesser extent, for white blood cells and platelets.

Autoanalysis↗