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Biomedical subjects

H J Dulce

Publications and source records attributed to H J Dulce.

At least 19 recordsLinked to original sources
PubMed1981

Evaluation of a sensitive radioimmunoassay of plasma corticotropin using commercial reagents.

A radioimmunological method for the sensitive estimation of plasma corticotropin immunoreactivity (ACTH) using commercially available reagents is presented. The method involves silica extraction of corticotropin from plasma, desorption with acid protein solution, neutralization and subsequent radiomimmunoassay (RIA). [125I]corticotropin is added as internal standard to the plasma sample. The amounts of corticotropin extractable with silica differed considerably between the plasma samples of individual subjects. There were marked differences in the affinity of five different corticotropin standards to the antiserum used. The detection limit of the method was found to be 1.47 pmol/l. Blanks arising in water and in charcoal stripped serum were lower than the detection limit. Precision and accuracy were within the range commonly achieved for RIA-methods. Morning levels of normal subjects ranged from 6.5-10.9-18.5 pmol/l. Hydrocortisone infusion suppressed plasma corticotropin from 12.6 +/- 6.4 (S.D.) to 4.4 +/- 3.1 (S.D.) pmol/l. Infusion of metyrapone increased corticotropin levels from 7.3 +/- 4.2 (S.D.) to 15.3 +/- 6.0 (S.D.) pmol/l.

Adrenocorticotropic Hormone↗
PubMed1980

Specific and practicable assessment of urinary free cortisol by combination of automatic high-pressure liquid chromatography and radioimmunoassay.

An assay for the specific measurement of urinary free cortisol excretion is described. The method involves a simple solid-phase extraction, automatic high pressure liquid chromatography (HPLC) and radioimmunological quantification. The concurrent study on antigenically interfering compounds in the organic extract of urine revealed that non-specific immunoreactivities with a chromatographic behaviour very similar to cortisol are present in urine, which are not attributable to the steroids commonly studied for cross-reactivity. Non-chromatographed values are about twice as high as those chromatographed by HPLC. Correlation between them was significant (r = 0.98). Precision and accuracy of the present method are within the range commonly achieved by radioimmunoassay methods. The normal range of urinary free cortisol excretion was found to be 28--117 nmol/24 h (n = 128). The present method, suitable for routine purposes, provides a basis for external quality control of urinary cortisol estimations, which is inadequate with the non-specific methods usually applied.

Chromatography, High Pressure Liquid↗
PubMed1980

Interferences in the radioimmunological determination of urinary free cortisol.

The magnitude of interferences arising in the radioimmunological assessment of urinary free cortisol is studied (a) by comparing cortisol immunoreactivities from crude urine, after organic solvent extraction of different selectivity and after additional chromatography by high pressure liquid chromatography (HPLC) and (b) by evaluation of the profile of immunoreactivity resulting from the fractions eluted by HPLC. Three antisera from different sources have been investigated. Values of cortisol-immunoreactivity in crude urine were about six times and values of a simple dichloromethane extract about three times higher than values obtained after HPLC. The main part of the interfering compounds arising in organic extracts have a polarity similar to cortisol, which cannot be easily eliminated by simple solvent extraction procedures. Specific estimation of urinary cortisol by radioimmunoassay requires a preceding chromatographic technique of high efficiency, such as HPLC, which represents an adequate tool for the routine laboratory.

Chromatography, High Pressure Liquid↗
PubMed1979

Comparison of different high-performance liquid chromatographic systems for the purification of adrenal and gonadal steroids prior to immunoassay.

The high-performance liquid chromatography of nineteen hormonal steroids with special respect to its suitability for routine purification of these steroids from crude, organic extracts of biological fluids prior to final quantitation by immunoassay has been studied. In all systems the gradient elution technique was applied. Separation of steroids has been investigated using different stationary phases chemically coated with non-polar, hydroxyl, NO2 and CN groups. Reproducibility of retention times was studied on a stationary phase coated with hydroxyl groups (DIOL column) using different organic eluents. Coefficients of variation range from 0.76 to 8.16%. Reproducibility was shown to be unequivocally better in the gradient part than in the isocratic part of the chromatographic run. In contrast to the other steroids, 18-hydroxylated steroids were more or less unstable in certain systems studied. As to resolution and reproducibility, the DIOL column run with an n-hexane-dioxane gradient has been shown to be superior to the other systems studied.

Adrenal Cortex Hormones↗
PubMed1979

Characteristics of transcriptionally active and inactive neuronal and nonastrocytic glial rat brain chromatin fractions.

Rapid and reliable fractionation of neuronal and nonastrocytic glial (NAG) cerebral rat brain chromatin in transcribable and repressed portions was achieved employing the DNAase II/Mg++-solubility method of Gottesfeld et al. (1974). Compositional and transcriptional properties of these fractions have been investigated. Compared to transcriptionally repressed fractions, template-active neuronal and NAG chromatin fractions are associated with an increased content of nonhistone chromosomal (NHC-) proteins. Both of the transcribable as well as both of the repressed fractions are strikingly different in their composition as assessed by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Comparative acid urea gel electrophoretic patterns of histones revealed that histone fraction H 1 is almost completely absent in actively transcribed neuronal chromatin and reduced in the corresponding NAG fraction while in template-inactive neuronal and NAG chromatin all five main histone fractions are present in equal amounts. The total number of RNA initiation sites available for exogenously added homologous RNA polymerase on template-active and -inactive neuronal and NAG chromatin was quantitatively measured under assay conditions completely eliminating reinitiation. Unlike the template-active neuronal and NAG fractions which are differently enriched in RNA initiation sites, transcriptionally more repressed neuronal and NAG fractions demonstrated a minimal ability to initiate RNA synthesis. Under assay conditions allowing repeated initiation of RNA chains at the same initiation site, rat brain RNA polymerase molecules were found to utilize neuronal initiation sites more frequently than NAG ones.

Animals↗
PubMed1978

Studies on the regulation of RNA synthesis in neuronal and glial nuclei isolated from rat brain.

In searching for regulatory mechanisms involved in the cell-specific neuronal and glial transcription a cell-free transcriptional system has been developed using neuronal and glial rat brain chromatin and partially purified neuronal and glial nuclear rat brain RNA polymerases. Both free and chromatin-bound (engaged) neuronal and glial RNA polymerase fractions were separated from isolated neuronal and glial rat brain nuclei to determine their transcriptive efficiency. A double number of RNA initiation sites was measured on the neuronal when compared to the glial chromatin, independently of whether the neuronal or the glial RNA polymerase preparation was used for the determination. Structural modification of the neuronal and glial chromatin template by acetylation with acetyl-coenzyme A leads to an increase of the total number of RNA initiation sites available for exogenously added rat brain RNA polymerase. This indicates that acetylation of chromatin-bound proteins is capable to render primarily restricted gene sequences transcriptable. A positive correlation exists between the extent of acetate uptake by neuronal and glial chromatin-bound histone fractions and the extent of the increase of the number of RNA initiation sites is specifically related to histone acetylation rather than to acetylation of any other chromatin protein. Significant information in this respect could be achieved by dissociation of chromatin into its principal components and selectively reconstituting DNA with specifically acetylated histone and non-histone proteins.

Animals↗
PubMed1978

[Influence of oxianthraquinones on the crystallization of calcium oxalate and calcium phosphate: dissolution of calciumcontaining urinary calculi (author's transl)].

Ruberythric acid and alizarin glucuronide, the biologic secretion product obtained from the alizarin derivative, stop the crystallization of calcium oxalate and calcium phosphate in the physiologic milieu of the urine. This effect is thought to be due to a soluble alizarin glucuronide: calcium chelate (2:1 mol). From this finding, we deduce that the solubility of calcium oxalate and calcium phosphate in the urine of humans can be increased through the oral administration of oxianthraquinone.

Anthraquinones↗