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Biomedical subjects

F Loré

Publications and source records attributed to F Loré.

At least 37 records · Page 2Linked to original sources
PubMed1982

Effect of the administration of 1,25-dihydroxyvitamin D3 on serum levels of 25-hydroxyvitamin D in postmenopausal osteoporosis.

Serum concentrations of 25-hydroxyvitamin D were measured in a group of women with symptomatic postmenopausal osteoporosis, before and after long-term treatment with physiological doses of 1,25-dihydroxyvitamin D3. A competitive protein binding assay was used, which included a chromatographic step. The treatment resulted in a significant decrease in serum 25-hydroxyvitamin D levels that were higher than normal in basal conditions, the mean values before and after therapy being 27.7 ng/ml (+/- 17.1 SD) and 19.7 ng/ml (+/- 12.7), respectively. These findings seem to confirm the hypothesis that an inadequate product-inhibition of liver 25-hydroxylase is responsible for the increased basal levels of 25-hydroxyvitamin D found in postmenopausal osteoporosis.

25-Hydroxyvitamin D 2↗
PubMed1981

[Seasonal rhythm in 25-hydroxyvitamin D blood levels].

A retrospective study of the serum concentrations of 25-hydroxyvitamin D was performed over a one-year period, using data from 158 healthy subjects aged 40-80 years. Serum 25-hydroxyvitamin D was determined by competitive protein binding assay; the method included a chromatographic step. A noticeable seasonal variation was observed, with a maximum in summer.

25-Hydroxyvitamin D 2↗
PubMed1981

Serum levels of 25-hydroxyvitamin D in postmenopausal osteoporosis.

Serum concentrations of 25-hydroxy-vitamin D were measured in a group of women with symptomatic postmenopausal osteoporosis, assessed by bone biopsy. A competitive protein binding assay was used, which included a chromatographic step. Accurate surveys of dietary or therapeutic vitamin D intake and light environment were obtained in each patient. Women with severe postmenopausal osteoporosis were found to have significantly (P less than 0.001) higher serum levels of 25-hydroxyvitamin D than age-matched normal women, the mean values being 27.5 ng/ml (+/- 13.6 SD) and 9.2 ng/ml (+/-5.7), respectively. The authors hypothesize that the reduction in 1,25-dihydroxyvitamin D, recently reported in postmenopausal osteoporotic women, might be responsible for the increased serum levels of 25-hydroxyvitamin D through an inadequate product inhibition of liver vitamin D 25-hydroxylase.

25-Hydroxyvitamin D 2↗
PubMed1980

Influence of the extraction technique in the assay of serum 25-hydroxyvitamin D.

Various extraction procedures for the assay of serum 25-hydroxyvitamin D were compared in order to investigate their specificity and accuracy. Extraction with chloroform/methanol followed by chromatography on silicic acid columns was chosen as the reference method. The dried extracts and eluates from column chromatography were used in a competitive protein binding assay. The values obtained using the different extraction procedures without chromatography did not differ significantly, but were constantly higher than the values obtained using the reference method. These results confirm the necessity of a chromatographic step after extraction of samples in the assay of serum 25OHD,, since all the techniques tested 25OHD together with other substances which interfere with the competitive binding assay. Ethanol extraction gave the best recoveries; furthermore this technique is also very simple, therefore it could be considered the best extraction procedure in the assay of 25OHD.

Calcifediol↗
PubMed1980

Evaluation of sera of various origin as sources of binding protein for the assay of 25-hydroxyvitamin D.

The affinity for 25-hydroxycholecalciferol (25OHD3) of transport proteins present in sera of various origin was estimated by means of Scatchard plots, using tritiated 25OHD3 as the tracer. Normal and rachitic rat sera showed the highest affinities, human sera showing lower association constants. Serum from normal rats is therefore to be considered the most suitable source of binding protein for the assay of 25-hydroxyvitamin D.

Animals↗
PubMed1980

Comparative study of chromatographic and non-chromatographic procedures in the assay of serum 25-hydroxyvitamin D.

Chromatographic and non-chromatographic procedures in the assay of serum 25-hydroxyvitamin D are compared. Samples extracted with chloroform/methanol were analysed using a competitive protein binding assay, with or without prior chromatography. Non-chromatographic methods constantly gave higher values than chromatographic methods. It is concluded that chromatography is an essential step in the preparation of extracts for the assay of 25-hydroxyvitamin D.

Animals↗
PubMed1980

Technical problems in the assay of serum 25-hydroxyvitamin D.

Various methods to enhance the solubility of 25-hydroxyvitamin D in the aqueous buffer used for competitive protein binding assay are compared. The problem of non-specific binding caused by the addition of various substances to the buffer to prevent loss of 25-hydroxyvitamin D from the reaction mixture is also evaluated. Bovine albumin at the concentration of 0.2-0.4 g % seems to represent the best solution of the above problems, since it exerts a good solubilizing effect on 25-hydroxyvitamin D with low non-specific binding counts.

Hydroxycholecalciferols↗
PubMed1980

[Determination of 25-hydroxycholecalciferol in the blood by means of protein binding competition].

A competitive binding-protein assay for 25-hydroxycholecalciferol, is described in which serum from vitamin D deficient rats is used as the source of binding protein. Serum samples after extraction are chromatographed using silicic acid. Bovine albumin is used in the buffer as a protein stabilizer and lipid solubilizer, at a concentration shown to enhance the reproducibility of the assay without interfering in the binding properties of 25-hydroxycholecalciferol. The method appears to be sufficiently sensitive for clinical studies even in vitamin D deficiency.

Animals↗
PubMed1978

[Gas chromatographic determination of urinary 17-ketosteroids in normal adults of various ages].

The excretion of individual urinary 17-ketosteroids, pregnanediol and pregnanetriol, as measured in 98 healthy adults subdivided into groups according to age and sex, by means of a gas chromatographic analysis method based on enzymatic hydrolysis, extraction with ethyl ether, and conversion of the extracted steroids into trimethylsilyl ethers. The results showed that age and sex substantially influence the steroid pattern. Metabolites with 5-alpha configuration are predominant in young subjects; those with 5-beta configuration are pre-eminent in the more advanced ages, particularly in women. Metabolites with definite androgenous significance (C19O2-17KS) decline rapidly with advancing age, while the C19O3-17KS undergo a lesser decrease.

17-Ketosteroids↗
PubMedDate not supplied

Seasonal variation in urinary excretion of cyclic AMP in healthy people.

In a group of healthy young men and women the daily urinary excretion of cyclic adenosine 3', 5'-monophosphate (cAMP), calcium, hydroxyproline and the renal threshold phosphate concentration were evaluated at monthly intervals during 1 yr. A significant seasonal variation in cAMP urinary excretion was demonstrated, with a maximum occurring in spring and a minimum in winter. A clear annual rhythm was also observed when the other above parameters were considered. These findings are of importance in the interpretation of urinary cAMP values in clinical situations, and in the study of bone metabolism.

Adult↗