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Biomedical subjects

A Vermeulen

Publications and source records attributed to A Vermeulen.

At least 145 records · Page 8Linked to original sources
PubMed1985

Fat tissue: a steroid reservoir and site of steroid metabolism.

Sex steroid concentrations and 17 beta-hydroxy-steroid dehydrogenase and aromatase activities were determined in fat tissue removed at surgery or, in order to allow comparisons in different sites, postmortem. Except for dehydroepiandrosterone (DHEA) sulfate (DHEAS), there existed a positive tissue/plasma gradient for all steroids studied (testosterone, androstenedione, DHEA, androstenediol, estrone, and estradiol), suggesting androgen uptake and estrogen synthesis in situ. Androgen concentrations did not vary according to site of origin of fat tissue, except that the DHEAS concentration was significantly lower in abdominal sc and omental fat than in breast, pericardial, or sc pubic fat. Tissue androgen concentrations were positively correlated with their plasma concentrations, but tissue and plasma estrogen concentrations were not correlated. All tissue steroid concentrations, with the exception of estradiol in men, decreased with age. Aromatase activity [androstenedione----estrone; mean maximum velocity, 7.4 +/- 3.7 (+/- SD) fmol estrone/mg protein . h] did not vary between sexes or with site of origin of fat tissue. 17 beta-Hydroxysteroid dehydrogenase activity (estradiol----estrone, mean maximum velocity 9.8 +/- 5.4 pmol/mg protein . h) was higher in fat from women than in that from men, higher in premenopausal than in postmenopausal women, and higher in omental than in sc fat. Its activity was noncompetitively inhibited in vitro by DHEA and DHEAS in near-physiological concentrations, and the enzyme activity was inversely correlated (P less than 0.001) with the tissue DHEA and DHEAS concentrations. We conclude that fat tissue is an important steroid hormone reservoir, that it is the site of active aromatase and 17 beta-hydroxysteroid dehydrogenase, and that tissue DHEA(S) may have a modulating effect on tissue estrogen production.

17-Hydroxysteroid Dehydrogenases↗
PubMed1985

Influence of age on steroid concentrations in skin and striated muscle in women and in cardiac muscle and lung tissue in men.

In order to investigate whether androgen concentrations vary as a function of age in all tissues and organs and whether the sexual differences in plasma androgen levels are reflected in tissue concentrations, testosterone (T), 5 alpha-androstane-17 beta-ol, 3-one (DHT), 5 alpha-androstane-3 alpha,17 beta-diol (Adiol), and 4-androstene-3,17-dione (Adion) concentrations were measured postmortem in lung tissue and myocardium of men aged 16-87 yr. The results were compared to values obtained previously in other tissues. Similar measurements were made in various tissues (labia majora, clitoris, pubic skin, thigh skin, striated muscle) from women aged 16-87 yr. In cardiac tissue of men, T was quantitatively the most important androgen and concentrations of DHT and Adiol were low, reflecting low 5 alpha-reductase activity; in lung tissue, T and Adion were found in similar concentrations, with lower levels of 5 alpha-reduced metabolites. In both cardiac and lung tissue, androgen concentrations decreased significantly with age. In women, androgen concentrations were highest in specific androgen target tissues (labia majora, clitoris) and lowest in thigh skin and striated muscle. The ratios of the 5 alpha-saturated metabolites (DHT plus Adiol) to T or to T + Adion, respectively, parallel total androgen concentrations, whereas the Adiol to DHT ratio, a parameter of 3 alpha-reductase activity, was highest in striated muscle and thigh skin and lowest in androgen target tissues (labia majora and clitoris). In women tissue concentrations of all androgens decreased significantly with age in nearly all tissues studied. As expected tissue androgen concentrations were lower in women than in men, but in androgen target tissues such as the clitoris or labia majora, concentrations were little lower than in scrotal skin. We conclude that in both men and women androgen target tissues contain high androgen concentrations and high 5 alpha-reductase activity; moreover androgen concentrations in target tissues are similar in both sexes. In both sexes tissue androgen concentrations decreased with age in most tissues, but in target tissues the decrease was more pronounced in women than in men.

Adolescent↗
PubMed1985

Demonstration of nodules in the normal thyroid by echography.

An ultrasound examination was performed of the normal thyroid in 300 patients (164 males and 136 females). Small echoic nodules were demonstrated in 19% of the patients and fluid-filled masses in 6%. Echoic nodules occurred frequently (greater than 40%) in the seventh decade. 71% of the nodules were situated in the right lobe.

Adolescent↗
PubMed1985

Self blood glucose monitoring: evaluation of Haemo-Glukotest 20-800R, Visidex I and Reflolux.

Trained staff-members evaluated the accuracy of Haemo-Glukotest 20-800R (= HG 20-800R), Visidex I and Reflolux in 135 blood glucose measurements. A glucose-oxidase method was used as reference method. Although the correlation between the 3 methods tested was excellent, more detailed analysis revealed for all methods a clear deviation from the real blood glucose, especially in the low blood glucose range. This might result in an inappropriate adaptation of the insulin dose, when the estimated blood glucose is used in connection with a classic algorithm. Apart from this limitation, Reflolux had the best accuracy, followed by HG 20-800R. If stored in a desiccated tube, the HG 20-800R strip can be reliably re-read (visually or with Reflolux) even after 7 days. Visidex I is unsuitable for storage and re-reading.

Blood Glucose↗
PubMed1984

Inhibition of adenylate cyclase activity of human thyroid membranes by gangliosides.

Gangliosides inhibit basal, thyrotropin-induced and fluoride-induced adenylate cyclase activity of human thyroid membranes in physiological conditions. In contrast neutral glycolipids, phospholipids and neuraminic acid containing oligosaccharides show no effect. The efficacy of inhibition is more dependent upon the position of the sialic acid residues than upon their absolute number. In general gangliosides with disialyl groups are more inhibitory than those with single sialyl moieties. The inhibitory effects of the individual gangliosides on the two modes of stimulation are parallel. This parallelism suggests that the inhibitory effect is located at the postreceptor level and that the gangliosides interact directly with the adenylate cyclase system. A possible role of thyroid membrane gangliosides as suppressive cofactors of adenylate cyclase is discussed in relation to recent findings of stimulating anti-ganglioside antibodies in Graves' disease.

Adenylyl Cyclase Inhibitors↗
PubMed1984

Leydig cell function in normal men: effect of age, life-style, residence, diet, and activity.

The decrease of plasma testosterone (T) in old age may be inherent to the aging process or secondary to environmental factors such as stress, minor illness, physical inactivity, etc. We determined plasma T, apparent free T, and gonadotropin levels in healthy men (n = 71), aged 26-90 yr living under identical conditions, i.e. as monks in a monastery. We found a highly significant age-dependent decrease in morning and mean 24-h T and apparent free T levels and a moderate increase in gonadotropin levels; the nycthemeral variation in plasma levels was, however, decreased in the elderly. In a larger group of healthy normal men (n = 302), smokers had higher T levels than nonsmokers in all age groups; values were similar whether older men lived in a geriatric institution or in their home. Diet had no discernable effect on T levels, whereas in young men plasma T levels decreased more in response to stress such as hypoglycemia or myocardial infarction than in elderly subjects. Moderate physical training in men, convalescing from myocardial infarction, did not alter consistently plasma T levels. We conclude that the age-associated decrease in plasma T levels is inherent to the aging process.

Adult↗
PubMed1984

Diabetes mellitus in dogs: relationship of obesity to glucose tolerance and insulin response.

The IV glucose-tolerance test was performed in 71 diabetic dogs (fasting glycemia greater than 6.70 mmol/L) and in 20 healthy dogs. All diabetic dogs were characterized by various degrees of glucose intolerance as expressed by an abnormal glucose disappearance coefficient. On the basis of the fasting plasma insulin concentration (Io), insulin peak response (IPR), the insulinogenic index (delta I/delta G), and the total insulin secretion (TIS), the diabetic dogs were classified, as follows: Type I dogs (n = 32) which had the severe clinical signs of diabetes and an absence of certain diagnostic responses: Io, IPR, delta I/delta G, and TIS. Type II dogs (n = 15) which also had marked diabetic signs and an absence of IPR, delta I/delta G, and TIS responses. The dogs were further subdivided into obese and nonobese groups; the Io was within acceptable limits in the nonobese group (n = 8), but was markedly increased in the obese group (n = 7). Type III dogs (n = 24) had no diabetic signs and a fasting plasma glucose less than 12 mmol/L. They were also subdivided into obese and nonobese groups. The nonobese dogs (n = 13) had Io values within acceptable limits and decreased IPR, delta I/delta G, and TIS. In contrast, the obese dogs had increased Io, IPR, delta I/delta G, and TIS. Statistical analyses indicated that the TIS and IO were highly significant linear functions of obesity.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1984

Improved fertility after varicocele correction: fact or fiction?

Fertility after varicocele correction by embolization of the vena spermatica in 62 subjects was compared with fertility in an untreated group (n = 20) of subjects with varicocele. One year after varicocele correction of infertile males with oligozoospermia, asthenozoospermia, or teratozoospermia but normal follicle-stimulating hormone levels, 15 of 62 had achieved a pregnancy; in the untreated group, 8 had achieved a pregnancy. Comparison of results by cumulative pregnancy rate analysis reveals that the pregnancy rate was only marginally higher in the treated group. Varicocele correction induced only a modest improvement of sperm quality; the severity of varicocele had no influence either on sperm characteristics or on the outcome of treatment. It is concluded that the effects of varicocele correction on the pregnancy rate can be seriously doubted and that large-scale prospective studies are urgently required to determine whether or not varicocele correction improves the pregnancy rate and which subjects could eventually benefit from the treatment.

Adult↗
PubMed1983

Improved liquid chromatographic determination of serum cortisol with double internal standardization compared to radioimmunoassay and fluorometry, and evaluated by isotope dilution/mass spectrometry.

A sensitive and specific high-performance liquid chromatographic (HPLC) method for the determination of cortisol in only 200 microliters of serum is described. Cortisol and two internal standards, 19-nortestosterone (IS1) and 6 alpha-methylprednisolone (IS2) are extracted with dichloromethane and analyzed on a C18 reversed-phase column eluted with a mobile phase of methanol:water at a flow rate of 0.75 ml/min. Ultraviolet absorption at 254 nm is used for detection and quantitation is performed by peak height ratio measurement. Using 200 microliters of serum, the lower limit of detection for cortisol is 10 ng/ml, the analytical recovery is 104 +/- 3.6% (n = 8), and the day-to-day precision was 1.69% at a level of 90 ng/ml (n = 16). Cortisol values obtained by this method were generally lower than those obtained by radioimmunoassay or by fluorometry. A serum pool was analyzed both by HPLC and by isotope dilution/mass spectrometry (ID/MS). A mean value of 90.1 ng/ml was obtained by HPLC (n = 16, CV = 1.7%), whereas ID/MS yielded a mean of 90.8 ng/ml (n = 28, CV = 0.4%). These results clearly demonstrate the high specificity and the accuracy of the HPLC procedure. The use of two internal standards not only compensates for losses during the sample manipulation but also prevents erroneous results in case of medication by either of these two products.

Chromatography, High Pressure Liquid↗
PubMed1983

Diuretic effect of slow-release furosemide in elderly patients.

To compare the natriuretic and diuretic effects of a slow-release and a standard formulation of furosemide, 18 elderly patients with stable congestive heart failure were hospitalized and treated with one of these formulations in a double blind randomized trial. Patients received placebo on the first 2 days, furosemide on the third day and placebo again on the last 2 days of the study. In patients receiving the standard formulation mean urine output was increased only on the day of active treatment. However, in patients who had received the slow-release preparation, increased urine excretion was seen both on the day of active treatment and on the subsequent day. The total diuresis (0-48 h) in the 2 groups was equal, but a peak diuresis (0-6 h) was seen only in patients on the standard formulation of furosemide. Sodium excretion followed the pattern of urine excretion. Furosemide in a slow-release formulation offers advantages in maintenance therapy in congestive heart failure, especially in elderly patients.

Aged↗
PubMed1983

Effects of cardiac rehabilitation after myocardial infarction: changes in coronary risk factors and long-term prognosis.

Prognosis during 5 years of follow-up after first myocardial infarction (MI) in a group of men (aged 40 to 55 years) was related to risk factors determined at the time of MI. Progression of coronary artery disease (CAD) was measured by the occurrence of severe angina pectoris, recurrent myocardial infarction, and cardiac death. Only smoking and serum cholesterol level influenced prognosis. It was possible to identify a subgroup (patients smoking less than 20 cigarettes/day and having a cholesterol level of less than 7.0 mmoles/L) with low risk for progression of CAD. A randomly applied 6-week rehabilitation program shortly after MI was associated with a 50% decrease in progressive CAD when compared to the control group. Since only a slight decrease in cholesterol levels was found in the rehabilitation group, a direct effect of the rehabilitation program could thus not be excluded because the second important risk factor, smoking, did not show differences between the two groups. The smoking habits at the time of MI determined the continuation of cigarette smoking and rehabilitation did not influence smoking habits.

Adult↗
PubMed1983

Androgen and precursor levels in serum and testes of adult rats under basal conditions and after hCG stimulation.

In adult male Wistar rats, serum and testicular concentration of testosterone (T), estradiol (E2), dihydrotestosterone (DHT), 5 alpha-androstane 3 alpha, 17 beta-diol (Adiol), and their precursors were measured under basal conditions as well as 4 and 8 h respectively after i.m. injection of 100 I.U. of hCG. Under basal conditions T (203 +/- 30 (SE) ng/dl) was quantitatively by far the most important serum steroid, followed by progesterone (P) (76.5 +/- 12 ng/dl), 17-hydroxyprogesterone (170HP) (37.3 +/- 4.1 ng/dl), androstenedione (A) (24.6 +/- 2.5 ng/dl) and pregnenolone (P5) (22.9 +/- 4 ng/dl). Estradiol (E2) was present in a low concentration (1.06 +/- 0.26 ng/dl). In the testes, T was quantitatively the most important steroid (89 +/- 7.2 ng/g), followed by 5 alpha-androstane-3 alpha-17 beta-diol (Adiol) (26.5 +/- 2.8 ng/g) whereas 170HP (11.8 +/- 1.0 ng/g), P (11.5 +/- 1.0 ng/g) and P5 (16.6 +/- 1.8 ng/g) were present in roughly the same concentration, concentrations of A, DHT, dehydroepiandrosterone (DHEA), 17 hydroxy-pregnenolone (170HP5) and androst-5-ene-3 beta-17 beta-diol (D5diol) being much lower; E2 (0.06 +/- 0.01 ng/g) was hardly detectable. Within 4-8 h after hCG stimulation, serum androgen concentrations increased by a factor of 4-12, except for DHEA and D5diol (X2), and E2 (X 1.5). Intratesticular androgens and delta 4 steroid precursors increased by a factor of 5-10, delta 5 precursors by a factor of 2-4 and E2 by a factor of 2, the data tending to confirm that the delta 4 pathway is preferred over the delta 5 pathway. After hCG the relative increase of T precursors was the most important for P, suggesting that 17 hydroxylation might be the rate limiting step in T biosynthesis.

Androgens↗