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Biomedical subjects

K Horn

Publications and source records attributed to K Horn.

At least 55 records · Page 3Linked to original sources
PubMed1993

Assessment of acute parathyroid responsiveness to high calcium dialysate in uremic patients.

The response of the parathyroid glands to dialysis-induced changes in calcium has been studied in 83 normocalcemic patients receiving maintenance hemodialysis. Predialysis concentrations of intact parathyroid hormone (iPTH) were normal in 13 patients; 70 patients had increased iPTH levels of different degrees. All patients had analytically significant changes in total serum calcium (2.3 +/- 0.2 vs 2.8 +/- 0.2 mmol/l) without additional parenteral calcium loading during a standard dialysis session with a dialysis solution of 1.75 mmol calcium chloride. During hemodialysis the concentration of iPTH fell in 77 patients and was normalized in 48 of these patients. The remaining 6 patients showed no or an inadequate response (less than 30% suppression of predialysis iPTH) to the increase in Ca. Parathyroidectomy was performed in patients with refractory iPTH secretion. Histological evidence of marked parathyroid hyperplasia was obtained in all these patients. All patients with normal or partial responsiveness of the parathyroids tolerated at least small doses of 1.25 (OH)2-vitamin D3. Quantification of predialysis and postdialysis iPTH concentrations is a useful and simple method for identifying those uremic patients with true autonomy of the parathyroid glands at an early stage.

Adolescent↗
PubMed1992

A comparison of sporozoite and cyst merozoite surface proteins of Sarcocystis.

Surface labeling of Sarcocystis muris and S. suicanis sporozoites with N-hydroxysuccinimide biotin led to the detection of major membrane proteins with relative molecular weights of 29 and 30 kDa, respectively. Immunoblots of Sarcocystis sporozoite proteins probed with sera from infected hosts or with polyclonal monospecific antibodies generated against membrane antigens of cyst merozoites (noncorresponding stages) showed cross-reactivity between the two developmental stages (cyst merozoites and sporozoites) as well as between the species S. muris and S. suicanis. Two-dimensional gel electrophoresis resulted in the identification of isoforms of the sporozoite membrane antigens, with isoelectric points ranging from pH 4.7 to pH 6.4 for S. muris and from pH 4.7 to pH 5.2 for S. suicanis. The molecular masses, the charge heterogeneity, and the immunological reactivity of the surface proteins of Sarcocystis sporozoites were similar to those of cyst merozoites of both species.

Animals↗
PubMed1992

Results of the multicenter evaluation of the CEDIA cortisol assay.

The present paper describes the multicenter evaluation of the CEDIA Cortisol test for total cortisol. The observed linearity of the test was between 1.2 and 50 micrograms/dL cortisol. The limit of detection was calculated as 1.2/dL. Imprecision studies covering the diagnostically relevant range (5-20 micrograms/dL cortisol) yielded coefficients of variation between 1.7-8.9% (within-run) and 2.7-10.5% (between-day). An interlaboratory survey using 41 human samples and three control sera demonstrated that the new CEDIA Cortisol assay has a good interlaboratory transferability. Method comparison studies between the CEDIA Cortisol test and EIA, FIA, FPIA, and various RIAs yielded an acceptable level of agreement and concordant results in most cases. Low cross-reactivity of the antibody used in the new cortisol assay was observed with precursors or metabolites of cortisol. Especially, dexamethasone did not cross-react. However, prednisolone, 6-methylprednisone, and corticosterone showed cross-reactivities. No limitation by endogenous interferences was observed. The CEDIA Cortisol assay permits the precise, fast and sufficiently specific determination of cortisol. Furthermore, it offers the advantages of a non-radioactive assay and can be performed conveniently on Boehringer Mannheim/Hitachi analyzers in combination with routine clinical chemistry.

Humans↗
PubMed1991

Purification of in vitro excysted Sarcocystis sporozoites by passage through a modified DE 52 anion-exchange column.

A method of purifying Sarcocystis sporozoites following in vitro excystation is described. After passage of sporozoites through a modified DE 52 anion-exchange cellulose column, the mean recovery was 88% for S. capracanis, 71% for S. hircicanis, 77% for S. ovicanis and 74% for S. arieticanis. Most of the sporozoites were motile, and the parasite suspension was free of excystation debris.

Animals↗
PubMed1991

Spatial vision of the cat: variation with eccentricity.

We examined the grating acuity and contrast sensitivity of cats whose eye position was monitored with a scleral search-coil technique. During each trial, the cat was required to maintain fixation on a laser spot and respond to the presence or the absence of a grating by pressing a right or left pedal. With this procedure, acuity was measured along the horizontal and vertical meridian over a range of eccentricities in the nasal, temporal, superior, and inferior retina. In addition, contrast sensitivity for stationary and drifting gratings was measured for the temporal retina along the horizontal meridian. Acuity in area centralis reached about 3.5 cycle/deg and declined by 0.5 octaves at 4 deg and by about 1.3 octaves at 16-deg eccentricity in the nasal retina. The acuity was higher in the nasal than temporal retina. At all eccentricities, spatial resolution exceeded the resolution limit derived from Y (alpha)-cell properties. Contrast sensitivity also decreased as the eccentricity increased when the target size was held constant. The slope of sensitivity-eccentricity function was relatively shallow for a low spatial frequency (0.30 cycle/deg) with sensitivity decreasing by a factor of 1.5-2 at 8-deg eccentricity. The slope of the sensitivity falloff for high spatial-frequency gratings (1.2 cycle/deg) was steeper, with a 5-10-fold difference in sensitivity between 0 and 8 deg. By varying the target size, we determined that the summation area in the cat is about a factor of 3 smaller in area centralis than a 16-deg eccentricity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The determination of thyroxine and thyroxine uptake with new homogeneous enzyme immunoassays using Boehringer Mannheim/Hitachi analysis systems.

New homogeneous enzyme immunoassays for the determination of thyroxine and thyroxine uptake have been developed. The CEDIA assays are based on the cloned enzyme donor immunoassay technology, which involves fragments of beta-galactosidase prepared by genetic engineering. The assays have been adapted for Boehringer Mannheim/Hitachi analysers. The CEDIA T4/T Uptake assays were evaluated in eleven clinical chemistry laboratories on various Boehringer Mannheim/Hitachi analysis systems, using a 2-point calibration. The analytical range of the T4 test was 10 to 258 nmol/l thyroxine. The T uptake test had a measuring range between 20-50%. Depending on the concentration of the analyte (samples from hypo-, eu- or hyperthyroid patients), mean coefficients of variation ranged from 1.8 to 4.8% within-run and from 4.1 to 6.5% between-run for the T4 assay. Even better coefficients of variation were obtained for the T uptake assay (1.4 to 2.3% within-run, 2.8 to 3.3% between run). The relative inaccuracy of the CEDIA assays with respect to values assigned by other tests was satisfactory in various control sera. The T4 assay was compared with one radioimmunoassay, one enzyme immunoassay and one fluorescence polarisation immunoassay. Slopes ranging from 0.9 to 1.1 and intercepts ranging from -10 to +10 nmol/l thyroxine were obtained with two exceptions. The results of the T uptake test correlated reasonably with those of other thyroxine-binding methods. No interference was observed with icteric and lipaemic sera. Haemoglobin up to 4 g/l had no significant influence. Results of the CEDIA T Uptake test are mainly used for calculation of the free thyroxine index, in which the thyroxine value is corrected for variations of thyroxine-binding protein concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoanalysis↗
PubMed1991

Environmental medicine.

Four theses appear as the focal point of the paper: 1. Variability and specificity of medical protection of the environment, 2. Interdisciplinary character of the medical environment protection, 3. Medical protection of the environment within the powers of the public health services, 4. Medical protection of the environment as a nationwide issue.

Environmental Exposure↗
PubMed1991

[Carbon disulfide excretion in urine--a biological exposure test for the workplace and environmental concentration ranges].

The biological control procedure for carbon disulphide (CS2), the determination of free and bound CS2 in urine--a procedure already applied to hygienic surveillance--were modified by using gas chromatography and sulphide selective detection (FPD). The results obtained by the changed biological monitoring test in workplace and environmental surveillance are present and discussed. For CS2 concentrations at workplaces in the range of 8-54 mg/m3 a correlation coefficient of r = 0.56 (n = 11, p less than 0.07) was calculated for the mathematical connection of CS2 shift exposure and CS2 content in urine. For environmental exposures in the range of the CS2 immision short term threshold value (MIKK) of 0.03 mg/m3 the procedure may discriminate significantly exposure load from naturally occurring CS2 background.

Adult↗
PubMed1990

Influence of ozone and acid mist on the contents of gibberellic acid (GA(3)) in spruce needles (Picea abies) (L.) Karst.

The phytohormone GA(3) in needles from 4-year-old Norway spruce trees was analyzed after treatment with ozone and acid mist in environmental chambers under controlled conditions. GA(3) was extracted with methanol from the lyophilized material. Subsequent purification steps included the use of polyvinylpyrollidone (PVP), cartridge reversed-phase purification, ethylacetate extraction and HPLC. The GA(3) was determined in the methylated form by means of a highly specific and sensitive enzyme immunoassay. Higher GA(3) contents were detected in young needles (year 1987) as compared to older ones (year 1986). However, no statistically significant differences were found in the GA(3) levels between the controls and the needles of trees which were treated with increased levels of ozone and acidic mist.

Journal Article↗