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Biomedical subjects

S M Karim

Publications and source records attributed to S M Karim.

At least 55 records · Page 3Linked to original sources
PubMed1981

Inhibition of serum oxytocinase activity by prostaglandins.

The effect of prostaglandins (PGs) and other compounds on human serum oxytocinase (EC 3.4.11.3) activity in vitro was studied by a sensitive assay using S-benzyl-L-cysteine-p-nitroanilide as substrate. PGE1, PGE2 and PGF2 alpha significantly inhibited serum oxytocinase activity in a dose-related manner and in decreasing order of potency. cGMP, 8-bromo-cGMP, indomethacin, polyphloretin phosphate, hypertonic saline and urea were also active. cAMP, db-cAMP, 8-bromo-cAMP, db-cGMP, 5'-AMP, 5'-ADP, 5'-ATP, 5'-GDP, 5'-GTP, aspirin, sodium salicylate, paracetamol, theophylline and IBMX did not inhibit the enzyme activity. The results suggest that the oxytocic action of prostaglandins may be due, at least in part, to an inhibition of oxytocinase activity.

Aminopeptidases↗
PubMed1981

Control of gonadotrophin secretion by steroid hormones in castrated male transsexuals. II. Effects of androgens alone and in combination with oestradiol on the secretions of FSH and LH.

Twenty-nine infusions in twenty castrated male transsexual volunteers were carried out over a period of 7 h with subjects lying in the supine position. The effects of different doses of testosterone and its 5 alpha-reduced metabolites as well as the effect of testosterone in combination with oestradiol on gonadotrophin secretion were evaluated. Different and varying degrees of suppression of plasma levels of FSH and LH were observed. The infusions of 2.4 mg testosterone, 5 alpha-androstan-3 alpha-17 beta-diol (3 alpha-diol), 5 alpha-androstan-3 beta-17 beta-diol (3 beta-diol) but not dihydrotestosterone (DHT) caused significant suppression of LH. FSH, on the other hand was not significantly inhibited by the androgens at this rate. At higher doses all four androgens suppressed LH secretion significantly. FSH was similarly suppressed by the androgens except by DHT. A differential effect on FSH and LH secretions was noted with the combined regime of testosterone and oestradiol. The combined regime did not cause a significantly higher degree of FSH suppression compared with either 200 microgram of oestradiol or 12 mg of testosterone infused alone. The level of LH, however, was suppressed to a greater extent than either of the hormones when given alone. The inhibitory effect of testosterone demonstrated in this study could be due to the parent hormone or its 5 alpha-reduced metabolites. Pharmacological doses of testosterone could exert a greater degree of LH suppression through its conversion to oestradiol. It is likely that oestradiol and testosterone act on gonadotrophin secretion through different mechanisms and that they have an additive suppressive effect on the secretion of LH but not FSH. The potencies for the androgens to suppress gonadotrophin secretion can be ranked as: 3 alpha-diol = 3 beta-diol greater than testosterone greater than dihydrotestosterone.

Androgens↗
PubMed1981

Recovery of hypophyseal-testicular function from sex steroid treatment and the pituitary response to castration in male transsexuals.

Twenty-one male transsexuals who had been on steroid hormone therapy for at least 1 year volunteered for this investigation. Their hormone profiles after stopping sex steroid hormone treatment for periods ranging from 2 to 70 days were examined. Based on their testosterone levels before the sex-reassignment operation which includes castration, penectomy and the construction of an artificial vagina, two separate groups can be distinguished; those with low (group A) and the other with normal (group B) levels. The gonadotrophins levels in group A and group B were (respectively) significantly (P less than 0.05) lower and higher than corresponding levels in a group of normal males. Castration had caused elevations of FSH and LH in both groups. Although the increment rates were different, both groups attained the same maximum levels of FSH and LH. Within each group, the patterns of FSH and LH responses to castration were similar. However, differences in rates and time of significant elevation of FSH and LH were noted. These observations indicate that there is a delay between the cessation of steroid treatment and the recovery of testicular and hypophyseal functions. Testicular function seems to be altered by steroid treatment since excessive secretions of FSH and LH are needed to produce normal testosterone levels. The secretions of FSH and LH are controlled in some ways by the same mechanisms, while they, in other respects, are controlled by different factors.

Castration↗
PubMed1981

Adrenoreceptors in the human penis.

1. Adrenaline, noradrenaline and phenylephrine caused contraction of the corpus cavernosum muscle of the human penis. These sympathomimetic amines did not product inhibitory effects even in the presence of the alpha-adrenoreceptor blocker, phentolamine. The effect of dopamine was similar to that produced by these three sympathomimetic amines. Higher doses of isoprenaline and salbutamol also contracted this preparation. 2. Cocaine and guanethidine enhanced the motor response to adrenaline, noradrenaline and phenylephrine while the action of dopamine was blocked by these two drugs. 3. The motor response to adrenaline, noradrenaline and phenylephrine was antagonized by phentolamine and often potentiated by the beta-adrenoreceptors blocking drug, propranolol. The contractions produced by high doses of salbutamol and isoprenaline were also abolished by phentolamine. These findings indicate that the motor response to sympathomimetic amines is the result of activation of alpha-adrenoreceptors in the corpus cavernosum muscle. 4. At low doses, isoprenaline and salbutamol relaxed the corpus cavernosum muscle strip. The inhibitory action was blocked by low concentrations of the beta-adrenoreceptor antagonist, propranolol but not by practolol (beta 1-adrenoreceptor antagonist) and butoxamine (beta 2-adrenoreceptor antagonist). beta-adrenoreceptors are present in the corpus cavernosum muscle but these are unlikely to be either of the beta 1 or beta 2 type. The possible existence of a third type of beta-adrenoreceptor is suggested.

Catecholamines↗
PubMed1980

Platelet and other effects of carboprostacyclin--a stable prostacyclin analogue.

Carboprostacyclin, a chemically stable analogue of prostacyclin (PGI2) is 12.5 and 25.0 times respectively weaker than PGI2 in inhibiting ADP-induced aggregation of baboon and human platelets in vitro. Carboprostacyclin was also 28.5 times weaker as a vasodepressor than PGI2 in anaesthetised baboons. Intravenous and oral administration of carboprostacyclin in baboons resulted in ex-vivo inhibition of ADP-induced platelet aggregation at doses that did not produce changes in blood pressure or heart rate. Like PGI2, carboprostacyclin contracted guinea pig tracheal chain preparation in vitro but decreased histamine induced lung resistance in anaesthetised guinea pigs. Both PGI2 and carboprostacyclin relaxed the human respiratory tract smooth muscle in vitro.

Administration, Oral↗
PubMed1980

Control of gonadotrophin secretion by steroid hormones in castrated male transsexuals. I. Effects of oestradiol infusion on plasma levels of follicle-stimulating hormone and luteinizing hormone.

Twenty-four infusions of oestradiol (E2) in graded doses ranging from 0--200 micrograms administered over a period of 7 hours were carried out in eleven healthy male transsexuals who had undergone sex reassignment at least 3 months previously. Plasma levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and E2 were analysed by radioimmunoassay, while sex hormone binding globulin (SHBG) was measured using 3H-testosterone as the saturating ligand. Infusion of 5--200 micrograms of E2 raised plasma E2 to levels ranging from 38.4--367.8 pg/ml which present 83%--800% of levels found in a control group of sixty-three normal males. SHBG capacity remained unchanged at all doses of E2 studied. No change in plasma levels of FSH and LH was observed in control infusions and infusion of 5 micrograms of E2. From 10 micrograms-200 micrograms, suppression of plasma levels of FSH was noted at the 5--7 hour period. The suppression increased up to 20 micrograms and thereafter the levels of FSH remained constant. On the other hand, the suppression of LH increased up to the highest E2 dose (200 micrograms) studied. Further, significant suppression of LH occurred earlier than the 5--7 hours as the dose of E2 increased. These observations are consistent with the conclusions that: (1) E2 plays a part in the regulation of secretion of FSH and LH in men; and (2) at doses higher than physiological, E2 exerts a differential effect on the secretion of FSH and LH.

Castration↗
PubMed1980

Plasma concentration of steroid hormones after intravenous infusion of testosterone in castrated male transsexuals.

Ten male transsexuals who had surgical operations for sex-reassignment at least three months previously were given intravenous infusion of 2.4 mg (7 subjects) or 12 mg (3 subjects) testosterone over a period of seven hours. In both groups, plasma levels of testosterone and oestradiol measured by radioimmunoassay were significantly elevated one hour after the start of the infusion and remained raised throughout the infusion period. With the lower rate of infusion, plasma levels of testosterone rose from 0.6 ng/ml to 7.4 ng/ml, oestradiol from 16.2 pg/ml to 22.4 pg/ml while levels of androstenedione remained unchanged. When 12 mg testosterone was infused, the level of this hormone was elevated from 0.5 ng/ml to 29.6 ng/ml, while oestradiol increased from 16.5 pg/ml to 45.0 pg/ml. These results indicate that when physiological doses of testosterone are infused, conversion to oestradiol contributes to approximately 13.5% of total circulating oestradiol in men.

Castration↗
PubMed1979

Effects of some prostaglandin E1 analogues on guinea pig and human respiratory tract.

The effects of (a) 4, 5, 6-trinor-3, 7-inter-m-phenylene PGE1 methyl ester, (b) 4, 5, 6 trinor-3, 7-inter-m-phenylene 3 oxa PGE1 and (c) 4, 5, 6 trinor-3, 7-inter-m-phenylene 3 oxa PGE1 methyl ester on human and guinea pig respiratory tract muscle in vitro and in vivo have been studied. All the analogues relaxed the isolated preparations of guinea-pig tracheal chain, human tracheal, bronchial and bronchiolar muscles and decreased histamine-induced lung resistance in the anaesthetised guinea pig. On some preparations the effects of the analogues were more pronounced than those of PGE1. The results suggest that some of the inter-m-phenylene analogues of PGE1 may be bronchodilators in asthmatics.

Airway Resistance↗
PubMed1979

Effect of 17 phenyl PGF2 alpha on nasal patency in man.

The effect of three different doses (12.5 microgram, 25 microgram and 50 microgram) of 17 phenyl PGF2 alpha on nasal patency in fourteen patients with vasomotor rhinitis was studied on separate occasions. In all subjects the three doses of the prostaglandin analogue increased nasal patency for varying duration. With the 50 microgram single dose the duration of action ranged between three hours and more than seven hours. There were no side effects in most of the patients.

Dinoprost↗
PubMed1979

The effect of clomiphene on uncastrated and castrated male transsexuals.

Clomiphene was administered at a daily dose of 100 mg for 5 consecutive days to two groups of male subjects. There were three uncastrated male transsexuals (Group A) and nine castrated male transsexuals (Group B). In the uncastrated subjects Clomiphene enhanced the secretion of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T) starting from day 3 of treatment. The magnitude of the increment ranged from 150%--250% over the mean basal plasma level for LH, 113%--262% for FSH and 12%--68% for T. In contrast, Clomiphene suppressed both FSH and LH in the castrated subjects. Equal suppression of both the gonadotrophins were observed. The levels of FSH and LH in plasma on day 3 were suppressed to 66.4% and 66.2% of their respective mean basal levels. Two days after the termination of treatment, suppressions were maintained. These results suggest that Clomiphene acts as an anti-oestrogen in uncastrated male transsexuals and in castrated male transsexuals who have subphysiological levels of oestradiol it acts as a weak oestrogen.

Adult↗
PubMed1979

In vitro C-20, 22 desmolase regulation of pregnenolone supply in first trimester human placenta.

Homogenates of first trimester human placentae were incubated with [26-14C]chloresterol. Using reverse-isotope dilution analysis [14C]isocaproic acid was isolated and characterized. A progressive increase in [14C]isocaproic acid formation with increasing gestation suggestive of a regulatory mechanism at the C-20, 22 desmolase site in the supply of placental pregnenolone was noted.

Caproates↗
PubMed1978

Termination of second trimester pregnancy with intra-muscular administration of 16 phenoxy-omega-17,18,19,20 tetranor PGE2 methylsulfonylamide.

A new prostaglandin analogue, 16 phenoxy-omega-17,18,19,20 tetranor PGE2 methylsulfonylamide was used for the termination of second trimester pregnancy in 60 patients. The drug was injected intramuscularly in doses of 0.5 mg 4 hourly, 1 mg 8 hourly or 1 mg 6 hourly for a maximum of 36 hours. Fifty five patients aborted. The incidence of gastrointestinal side effects was low and there were no complications.

Abortion, Induced↗