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Biomedical subjects

L Verdonck

Publications and source records attributed to L Verdonck.

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

Prolactinomas, testosterone-binding globulin, and androgen metabolism.

To study the mechanism by which PRL might influence the metabolism of androgens, the testosterone-binding capacity of testosterone-estradiol-binding globulin (TeBG) as well as the free testosterone (T) fraction were determined in patients with prolactinoma. In untreated patients with prolactinoma, the TeBG capacity was decreased and the free T fraction was increased. Whereas in males, the plasma (free) T concentration was decreased, the apparent free T concentration was increased in women. The increased free T fraction had as a consequence an increase in MCRs of both T and 5 alpha-androstan-17 beta-ol-3-one; the MCR of androstenedione was normal. It is concluded that besides the well known factors, such as estrogens, androgens, and thyroid hormones, PRL appears, at least in prolactinoma patients, to influence the TeBG level.

Adenoma↗
PubMed1981

The nitrogen requirements of Gluconobacter, Acetobacter and Frateuria.

The nitrogen requirements of 96 Gluconobacter, 55 Acetobacter and 7 Frateuria strains were examined. Only some Frateuria strains were able to grow on 0.5% yeast extract broth or 0.5% peptone broth. In the presence of D-glucose or D-mannitol as a carbon source, ammonium was used as the sole source of nitrogen by all three genera. With ethanol, only a few Acetobacter strains grew on ammonium as a sole nitrogen source. Single L-amino acids cannot serve as a sole source of carbon and nitrogen for growth of Gluconobacter, Acetobacter or Frateuria. The single L-amino acids which were used by most strains as a sole nitrogen source for growth are: asparagine, aspartic acid, glutamine, glutamic acid, proline and alanine. Some Acetobacter and Gluconobacter strains deaminated alanine, asparagine, glutamic acid, threonine, serine and proline. No Frateuria strain was able to develop on cysteine, glycine, threonine or tryptophan as a sole source of nitrogen for growth. An inhibitory effect of valine may explain the absence of growth on this amino acid. No amino acid is "essential" for Gluconobacter, Acetobacter or Frateuria.

Acetobacter↗
PubMed1978

Sex hormone concentrations in post-menopausal women.

Plasma sex hormone concentrations (testosterone, (T), androstenedione (A), oestrone (E1) and oestradiol (E2) were measured in forty post-menopausal women more than 4 years post-normal menopause. Correlations between these and age, years post-menopause (YPM), degree of obesity and fat mass respectively were studied. T and A, as well as E1 and E2 were positively correlated (P less than 0.01), but no statistically significant correlation between A and E1 was observed. Sex hormone concentrations in this group of postmenopausal women (greater than 4YPM) did not show any variation as a function of age, with the possible exception of E2 which showed a tendency to decrease in the late post-menopause. E1 and to a lesser extent E2 as well as the E1/A ratio were significantly corelated with degree of obesity or fat mass, suggesting a possible role of fat tissue in the aromatization of androgens. Neither the T/A nor the E2/E1 ratios were correlated with fat mass, suggesting that the reduction of 17 oxo-group does not occur in fat tissue. The E1/A ratio was significantly higher than the reported conversion rate of A in E1. This might suggest the existence of an additional precursor of plasma E1.

Age Factors↗
PubMed1976

Plasma androgen levels during the menstrual cycle.

Utilizing RIA methods, T, DHT, delta 4, and DHEA levels were determined daily during a complete cycle in 15 normal young women with apparently normal ovulatory cycles. T, DHT, and delta 4 levels showed statistically significant cyclical variations, with highest values in the periovulatory period and lowest values in early follicular and late luteal phase. DHEA levels showed random variations during the cycle. The failure to detect these variations by some authors may be related to the relatively large interindividual variation in plasma levels.

Adolescent↗