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Biomedical subjects

A Vermeulen

Publications and source records attributed to A Vermeulen.

At least 91 records · Page 5Linked to original sources
PubMed1991

Hormonal effects of a 5 alpha-reductase inhibitor (finasteride) on hormonal levels in normal men and in patients with benign prostatic hyperplasia.

Finasteride is a potent competitive 5 alpha-reductase inhibitor, active at a dose as low as 1 mg/day. After a single dose, the effects on 5 alpha-reductase last as long as 7 days. Both hepatic and target tissue 5 alpha-reductase are inhibited. Plasma testosterone and estradiol are unaffected and luteinizing hormone levels do not change. During chronic treatment with finasteride 5 mg/day, the effects on 5 alpha-reductase are maintained. Since the only significant effect of chronic finasteride therapy appears to be 5 alpha-reductase inhibition, and testosterone or estradiol levels are not affected, neither libido nor potency is lost. Testosterone is the active androgen at the muscular level; therefore, muscular catabolism is not expected.

5-alpha Reductase Inhibitors↗
PubMed1991

Influence of age on the responsiveness of the gonadotrophs to luteinizing hormone-releasing hormone in males.

The mechanisms that most likely underly the attenuated response of plasma LH to antiopioids or antiestrogens and the reduced frequency of large amplitude LH pulses in elderly men are decreased LHRH release and/or decreased sensitivity of the gonadotrophs to LHRH. To test the latter hypothesis, the LH response, measured both as bioactivity (B) and immunoactivity (IR), to increasing doses of LHRH ranging from 0.625-5 micrograms, administered as an iv bolus, was evaluated in 10 young (20-45 yr old) and 10 elderly (64-78 yr old) monks. Both basal B- and IR-LH levels were significantly higher in elderly men. The maximal response to each dose was similar in young and elderly men when measured as IR-LH, but the B-LH response was higher in elderly men. The B/IR LH ratio increased with increasing LH levels. The mean half-life of plasma IR-LH in the elderly was significantly longer than that in the group of young men and significantly longer than the mean half-life of B-LH. It is concluded that the sensitivity of the gonadotrophs to LHRH is not decreased in elderly men. This suggests that the attenuated response of LH levels to antiopioids and antiestrogens, respectively, as well as the reduced number of spontaneous high amplitude LH pulses in elderly men may, instead, be the consequence of the release of a decreased mass of LHRH at each pulse.

Adult↗
PubMed1991

Are high-performance young women athletes doomed to become low-performance old wives? A reconsideration of the increased risk of osteoporosis in amenorrheic women.

Osteoporosis and athletic amenorrhea are now well-established findings in top level women athletes. Specifically trabecular bone appears to be affected. Since these two phenomena seem to occur simultaneously, questions have been raised as to the underlying mechanisms and whether physical exercise, which had been proven to exert a positive beneficial effect under normal conditions, should be held responsible. Although hypo-estrogenic status, body composition, and nutritional deficiency have been offered as possible explanations, none of these can be solely regarded as completely satisfactory. As for athletic amenorrhea itself, low estrogens are probably secondary to other phenomena and may only be related indirectly to osteoporosis. Whether they interfere with nutritional uptake is obscure. Possibly, endogenous opioid peptides are involved as an unnegligible mediator. As an important practical consequence it should be pointed out that osteoporosis in women athletes will be only detected incidentally; a fact which could obstruct timely intervention, though whether therapy is necessary remains open to discussion. The discovery that amenorrheic athletes subject to more severe training have a higher bone density than less engaged amenorrheic colleagues, can only be in favor of physical exercise, even under these conditions.

Aging↗
PubMed1990

Neuroendocrine regulation of pulsatile luteinizing hormone secretion in elderly men.

Leydig cell function is driven by LH, secreted in a pulsatile manner by the anterior pituitary in response to episodic discharge of hypothalamic LHRH into the pituitary portal circulation, under control of a yet to be defined neural mechanism, the "hypothalamic LHRH pulse generator". The normal aging process in elderly men is accompanied by a decline in Leydig cell function. Whereas primary testicular factors undoubtedly play an important role in the decrease of circulating (free) testosterone levels with age, recent studies demonstrated that aging also affects the central compartment of the neuroendocrine cascade. Hypothalamic alterations comprise changes in the regulation of the frequency of the LHRH pulse generator with an inappropriately low frequency relative to the prevailing androgen impregnation and opioid tone, and with an increased sensitivity to retardation of the LHRH pulse generator by androgens. As observed by some authors in basal conditions and by others after endocrine manipulations. LH pulse amplitude seems also to be reduced in elderly men as compared to young subjects. This is most probably the consequence of a reduction in the amount of LHRH released by the hypothalamus. Indeed, challenge of the gonadotropes with low, close to physiological doses of LHRH in young and elderly men reveals no alterations in pituitary responsiveness when looking at either the response for immunoreactive LH or bioactive LH. Deconvolution analysis on data obtained after low-dose LHRH suggests a markedly prolonged plasma half-life of LH in elderly men, a finding which may explain the paradoxical increase of mean LH levels in face of the reduced or unchanged frequency and amplitude of LH pulses.

Aging↗
PubMed1990

Plasma lipid and lipoprotein levels in obese post-menopausal women: effects of a short-term low-protein diet and exercise.

Obesity is associated with an increased prevalence of cardiovascular and cerebrovascular disease, probably mediated by the induction of an atherogenic lipid profile. Since few data are available concerning plasma lipid levels and the effects of short-term dieting on these parameters in obese postmenopausal women, we studied plasma lipid and lipoprotein levels in such women and also the effects on these levels of a short-term hypocaloric low-fat diet combined with a moderately intense physical exercise programme. Plasma triglycerides and low-density-lipoprotein cholesterol (LDL-C) levels were significantly higher, whereas high-density-lipoprotein cholesterol (HDL-C) and apoprotein A1 (ApoA1) levels, as well as the HDL-C/LDL-C and ApoA1/ApoB ratios, were significantly lower in moderately to severely obese women (Body Mass Index greater than 30, n = 26) than in non-obese post-menopausal controls. A short-term (4 week) protein-sparing modified fast diet, providing 400 calories (1675 J), resulted in a mean weight loss of 7.7 +/- 2.8 (S.D.) kg. While plasma cholesterol, LDL-C and ApoB levels decreased by approximately 25% and reached the levels recorded in normal controls, ApoA2 decreased by 20%. HDL-C and HDL2-C levels remained unchanged and as a consequence the HDL-C/LDL-C and the ApoA1/Apob ratios increased, indicating a shift towards a less atherogenic lipid profile. No correlation was observed between weight loss and changes in lipid or lipoprotein levels. It was concluded that a hypocaloric, low-fat diet combined with our physical exercise programme, resulted in the normalization of plasma lipids within 4 weeks.

Adult↗
PubMed1990

Possibilities and limitations of techniques of assisted reproduction for the treatment of male infertility.

Since relatively few spermatozoa are needed for oocyte fertilization during gamete intra-Fallopian transfer (GIFT) or in-vitro fertilization (IVF), these methods have been applied in couples with infertility due to male causes. Forty-six couples with male factor infertility were enrolled in this study and results were compared with those attained in 48 couples treated with the same techniques for other than male causes. Overall, GIFT resulted in 26% ongoing pregnancies. GIFT seems to be particularly successful when the sperm concentration is 20 x 10(6)/ml or more, but sperm motility and/or morphology are poor. Nine pregnancies occurred out of 26 GIFT cycles in 18 cases selected on this basis. The ongoing pregnancy rate after IVF was 16% per patient. The latter treatment should be attempted in male immune infertility and in cases with a low sperm concentration, with or without abnormal sperm motility and/or morphology. In these circumstances, five pregnancies were attained out of 28 cycles in 14 cases. For similar sperm concentrations, the conception rate per cycle attained with techniques of assisted reproduction was more than twice that attained with conventional treatment of male infertility.

Female↗
PubMed1990

Reduced forearm bone mineral content and biochemical evidence of increased bone turnover in women with euthyroid goitre treated with thyroid hormone.

We used single-photon absorptiometry to assess forearm bone mineral content (BMC/BW) (arbitrary units normalized for bone width) at a proximal site (PBMC/BW) and at a more distal site (DBMC/BW) in 60 women treated with 25-50 micrograms T3 or 50-100 micrograms T4 for euthyroid goitre, in 13 untreated goitre patients, and in 2 controls matched for age and menopausal state for each goitre patient. BMC/BW was not significantly different between untreated goitre patients and controls. In 36 premenopausal patients, treated for 5.8 +/- 5.4 years (mean +/- SD) a slight decrease in PBMC/BW of about 5% compared to controls to controls was observed (PBMC/BW 1.42 +/- 0.19 vs 1.49 +/- 0.13, P less than 0.05). In 24 postmenopausal patients, treated for 10.0 +/- 5.8 year, a 20% deficit in BMC/BW compared to controls was found (DBMC/BW 0.80 +/- 0.18 vs 1.06 +/- 0.20, P less than 0.001 and PBMC/BW 1.14 +/- 0.20 vs 1.42 +/- 0.19, P less than 0.001). Biochemical indices of bone metabolism in 43 pre and post-menopausal patients and 43 controls showed in the patients a higher serum alkaline phosphatase activity (AP) (P less than 0.01 and P less than 0.05 and serum osteocalcin (NS and P less than 0.05). AP was negatively correlated with TSH levels and, in postmenopausal patients, with DBMC/BW and PBMC/BW. Our results suggest that treatment of euthyroid women with moderate doses of thyroid hormone increases bone turnover with clear adverse effects on bone mineral status in postmenopausal patients.

Adult↗
PubMed1990

Value of sperm characteristics and the result of in-vitro fertilization for predicting the outcome of assisted reproduction.

The outcome of procedures for assisted reproduction, namely in-vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT) were used as end-points to assess the capacity of particular sperm characteristics to predict the fertilizing potential of semen. In addition, the result of IVF performed with spare oocytes from the GIFT procedure, was used to predict the pregnancy outcome of GIFT. The power of sperm characteristics to predict the outcome of assisted reproduction procedures was poor. With regard to the outcome of IVF, sperm morphology was the best discriminant. The threshold value of 16% normal sperm morphology could be used as a good predictor of successful IVF, but could not be applied as a criterion to reject an IVF trial. For the latter purpose, the limit of 5% sperm with normal morphology should be used. The proportion of sperm with grade A motility in native semen provided the best discrimination between GIFT-fertile and GIFT-infertile cases. A negative result from IVF performed with spare oocytes was 93% accurate in predicting unsuccessful outcome of GIFT. Hence, diagnostic IVF is the most sensitive assay for male fertility. The occurrence of oocyte fertilization during IVF predicts a successful outcome of GIFT in only 50% of cases. Hence, a negative result in IVF indicates that semen is almost certainly infertile, but a positive result does not guarantee the successful outcome of GIFT.

Adult↗
PubMed1990

Effects of a short-term (4 weeks) protein-sparing modified fast on plasma lipids and lipoproteins in obese women.

The aim of this study was to evaluate the effects of a short-term (4 weeks) protein-sparing modified fast (PSMF) diet of 400 cal on plasma lipids and lipoproteins in a group (n = 51) of pre- and postmenopausal women with moderately severe obesity (body mass index greater than 30) as well as the eventual relations of plasma lipids to the type of fat distribution. Women with android-type obesity had higher plasma cholesterol, low-density lipoprotein cholesterol (LDL-C), apoprotein B (apoB) and glucose levels and lower high-density lipoprotein cholesterol (HDL-C) levels and HDL-C/LDL-C ratio than women with gynoid-type obesity. Besides waist-hip ratio (WHR), also age was an important determinant of HDL-C and HDL-C/LDL-C. PSMF for 4 weeks caused a 20% decrease in plasma cholesterol, LDL-C and apoB levels but also a decrease of HDL-C, apoA1 and apoA2. Nevertheless the HDL-C/LDL-C ratio increased, and, overall, PSMF resulted in less atherogenic profile of plasma lipids. Weight loss was independent of WHR but somewhat higher in premenopausal women (mean 10 kg) than in postmenopausal women (mean 8 kg), suggesting a more important energy deficit in pre- than in postmenopausal women. No correlation was observed between the importance of weight loss and the changes in plasma lipid levels: this indicates that the normalization of plasma lipids is the consequence of the diet itself and not secondary to weight loss.

Adipose Tissue↗
PubMed1990

Serum tumor necrosis factor levels in patients with infectious disease and septic shock.

The role of tumor necrosis factor (TNF-alpha) in the pathogenesis of septic shock has been assessed by daily measurements of serum TNF-alpha levels in 60 patients admitted to the medical intensive care unit. All patients in the study had infectious disease and were at risk for the development of sepsis and septic shock. Sepsis was diagnosed in 34 patients, 24 of whom died (six within the first 24 hours). The 26 patients who did not evolve toward sepsis served as a control group. The clinical condition of all patients was monitored by daily APACHE II scoring. Blood was drawn once a day and additional samples were taken in patients whose clinical condition underwent sudden deterioration. TNF-alpha levels were measured with a commercially available immunoradiometric assay. At time of patient admission, TNF-alpha levels were higher in the group with sepsis than in the control group (median 79 iqr 329 vs median 0.5 iqr 5; p less than 0.001). In the group with sepsis, extremely high TNF-alpha levels were found in patients who died within 24 hours. These patients had TNF-alpha levels of 917 iqr 755 pg/ml, whereas the patients who died more than 24 hours after admission had TNF-alpha levels of 58 iqr 59 pg/ml. Survivors had lower TNF-alpha levels (26 iqr 347 pg/ml). APACHE II scores correlated with TNF-alpha levels in the total sepsis group (Spearman rank correlation coefficient 0.477; p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Infections↗
PubMed1989

Hormonal effects of an orally active 4-azasteroid inhibitor of 5 alpha-reductase in humans.

The objective of this study was to estimate the minimum in vivo effective oral dose and duration of action of the competitive 5 alpha-reductase inhibitor MK-906, a 4-azasteroid, in humans. Plasma dihydrotesterone (DHT), 5 alpha-androstane-3 alpha,17 beta-diol (AD), and its glucuronide (ADG), as well as urinary androsterone (A) and 5 alpha-pregnane-3 alpha,11 beta, 17 alpha,21-tetrol-20-one (aH4F) were determined in 54 healthy young men before and up to 7 days after a single morning dose of the compound. Twenty-four hours after a single 5- to 40-mg dose (n = 24), plasma DHT levels decreased by a mean of +/- 65%, with slow recovery of DHT levels. Seven days later, DHT remained decreased by +/- 15%. Plasma AD levels decreased to a similar degree, whereas ADG levels decreased by about 75%, indicating inhibition of target tissue 5 alpha-reductase. Testosterone levels did not show any significant variations. The A as well as aH4F excretion in the 24-hour urine test following drug administration decreased by 65%, indicating inhibition of the hepatic 5 alpha-reductase. After a single dose of 1.5 or 0.5 mg, DHT levels decreased by 50% 24 hours after administration, returning to normal within 5-7 days; at this dose, urinary A and aH4F excretion decreased by 50%. A single dose of 0.2 mg appeared to be slightly active as a 5 alpha-reductase inhibitor, but no statistically significant effect on DHT levels was observed after administration of a single 0.04-mg dose. It is concluded that MK-906 is a highly effective 5 alpha-reductase inhibitor in vivo. The effect on plasma DHT lasts for several days after administration of a single oral dose. The data suggest that both hepatic and extrasplanchnic 5 alpha-reductases are inhibited.

5-alpha Reductase Inhibitors↗
PubMed1989

Medical, social and psychological recovery after cardiac rehabilitation.

A multidisciplinary study was undertaken to determine the number of patients that recovered, deteriorated or remained unchanged during a cardiac rehabilitation programme, as assessed in medical, social and psychological terms. In addition, the relationship between the medical, social and psychological aspects of recovery were investigated. Criteria for improvement, deterioration and an unchanged condition had been developed for the different aspects of recovery. These criteria were based on the degree of change during the rehabilitation programme (expressed in an effect size index) and the outcome at completion of the programme (expressed in terms of good, moderate or poor according to external standards). Although more patients improved than deteriorated, quite a few patients remained unchanged in medical, social or psychological condition. We conclude that cardiac rehabilitation might not be necessary for some patients and is not sufficient for others. Further, the relationship between the several aspects of recovery investigated was found to be weak.

Adaptation, Psychological↗