Search PubMed⌕ Search

Biomedical subjects

L C Tang

Publications and source records attributed to L C Tang.

At least 73 records · Page 4Linked to original sources
PubMed1984

Lack of effect of exogenous prolactin on the fertilizing capacity of human spermatozoa in vitro.

The effect of exogenous prolactin (PRL) on the fertilizing capacity of human spermatozoa in vitro was evaluated by the zona-free hamster ova penetration assay. Bovine and ovine PRL, in both physiological and pharmacological concentrations, failed to increase the penetration after 5 hr of incubation in vitro. The percent motility of spermatozoa was not influenced by PRL during the incubation period. Exogenous PRL does not affect the fertilizing capacity of human spermatozoa in vitro. The role of prolactin, normally present in seminal plasma and female reproductive tract fluid, in the human spermatozoal capacitation process merits further investigation.

Animals↗
PubMed1984

Transient hyperprolactinaemia in human menopausal gonadotropin induction of ovulation.

In 20 anovulatory patients who were normoprolactinaemic, 12 developed transient hyperprolactinaemia when they were treated with human menopausal gonadotropin (hMG) for induction of ovulation. The hyperprolactinaemia was probably due to the increased oestrogen production effect on some susceptible patients. The pregnancy rate was found to be lower in those who developed this condition. The dosage of hMG required was found to be significantly higher in this group. The importance of recognizing this transient hyperprolactinaemia and the probably role of Bromocriptine are discussed. Further study is suggested.

Adult↗
PubMed1984

A personal and scientific biography of Dr. George C. Cotzias.

George Cotzias was a person of towering dimensions, with a great brain, a great sense of humor, a great loyalty and a great pride. A giant of 6'2", he made an immediate impact on all who met him, for his physical and intellectual force were wedded to courage, vision, and an extraordinary capacity to share and to motivate others. He was at one and the same time vigorous and opinionated , gentle, kind and sensitive. Courage and challenge were part of Cotzias ' makeup. He shared dreams, ambitions and built towers in the sky with his friends and colleagues. The vitality and love, the enthusiasm and praise, the roar of indignation and the boom of laughter: he was a Zorba of science, with warm friends all around the earth, doctors and scientists, barbers and taxi drivers, poets and musicians, children and all the women in the world.

Brain Chemistry↗
PubMed1984

Effect of propranolol on human spermatozoal in vitro hamster ova penetration.

The effect of (D,L)-propranolol at various concentrations (3.4 X 10(-6) to 3.4 X 10(-3) M) on human spermatozoal motility and zona-free hamster ova penetration was studied in vitro. Propranolol, in 10(-4) M concentration, completely abolished the spermatozoal motility and hamster ova penetration. No significant effect was observed on the spermatozoal motility and the hamster ova penetration efficiency with concentrations of the agent as low as 3.4 X 10(-6) M. The blocking action of propranolol on the in vitro penetration of hamster ova appears to be a direct consequence of the depressive effect of this drug on spermatozoal motility.

Animals↗
PubMed1983

Effects of androgens on fertilizing capacity of human spermatozoa.

The potential functions of testosterone and 5 alpha-dihydrotestosterone, the androgens normally present in human seminal plasma, on human spermatozoal physiology were evaluated by studying the effects of these two steroid hormones on the in vitro fertilizing capacity of human spermatozoa. Spermatozoa collected from presumably fertile men were washed in BWW medium and incubated with different concentrations (0, 100, 250, 500, 1000 pg/ml) of testosterone or 5 alpha-dihydrotestosterone for 5 hr before insemination of the zona-free hamster ova. Penetration of the zona-free hamster ova was scored 6 hr later and the results were analyzed statistically. Both testosterone and 5 alpha-dihydrotestosterone, at the concentrations tested, significantly decreased the in vitro penetration of the denuded hamster ova in comparison to the controls (p less than 0.05). A dose-dependent response was also observed for the 5 alpha-dihydrotestosterone tested. These findings indicate that exogenous testosterone and 5 alpha-dihydrotestosterone can inhibit the fertilizing capacity of human spermatozoa in vitro, and suggest that the androgens normally present in human seminal plasma may serve, in part, to prevent premature spermatozoal capacitation before the spermatozoa reach the site of fertilization in vivo.

Animals↗
PubMed1983

Stimulation of the zona-free hamster ova penetration efficiency by human spermatozoa after 17 beta-estradiol treatment.

17 beta-Estradiol (E2) stimulated the zona-free hamster ova penetration by human spermatozoa from both fertile and subfertile men after 5 hours of incubation in vitro. For spermatozoa samples from fertile men, the mean penetration rates increased significantly (P less than 0.05), from 35.6% +/- 3.5% (control) to 60.1% +/- 5.8% (E2 = 50 ng/ ml) and 50.5% +/- 2.6% (E2 = 100 ng/ml), respectively. E2 also increased the mean penetration rates of spermatozoa samples from subfertile men significantly (P less than 0.05), from 10.2% +/- 1.8% (control) to 30.5% +/- 7.2% (E2 = 50 ng/ml) and 33.1% +/- 6.6% (E2 = 100 ng/ml), respectively. These findings indicate that E2 can affect the fertilizing ability of human spermatozoa in vitro.

Animals↗
PubMed1983

Hyperprolactinaemic amenorrhoea in Hong Kong.

In a retrospective study of 595 patients attending the Menstrual Disorder Clinic from January, 1978 to December, 1981, 92 patients (15.5%) had raised serum prolactin (PRL) levels (greater than 25 ng/ml) on 2 or more separate occasions with a mean (+/- S.E.M.) value of 67.1 +/- 2.5 ng/ml. Galactorrhoea was found in 27.2% of the hyperprolactinaemic patients. Primary amenorrhoea was observed in 1 patient (1.1%) with serum PRL level of 68 ng/ml. Secondary amenorrhoea of longer than 6 months' duration occurred in 61 patients (66.3%) with mean PRL level 84.2 +/- 3.3 ng/ml. The 30 patients (32.6%) with irregular menstruation had a mean PRL level of 47.2 +/- 3.3 ng/ml. Investigations revealed that 43 patients (46.7%) had idiopathic hyperprolactinaemia, 14 patients (15.4%) had drug induced hyperprolactinaemia and 1 patient (1.1%) had hypothyroidism; 18 patients (19.5%) had suspected pituitary microadenoma and 16 patients (17.2%) had abnormal radiographic findings. Bromocriptine treatment was given to 38 patients, 13 with abnormal tomographic findings (mean serum PRL greater than 100ng/ml); 18 with suspected pituitary microadenoma (mean serum PRL 94 +/- 2.7 ng/ml) and 7 with idiopathic hyperprolactinaemia (mean serum PRL 65 +/- 4.7 ng/ml). All patients (38/38) responded to treatment with restoration of menstruation and cessation of galactorrhoea within 1 to 3 months. Mean PRL level was 21.6 +/- 5.2 ng/ml at the time of response. Thirteen patients subsequently became pregnant and all delivered healthy babies.

Adenoma↗
PubMed1983

Stimulation of the human spermatozoal fertilizing ability by dibutyryl 3',5'-CAMP and theophylline in vitro.

The stimulation of the human spermatozoal fertilizing ability by dibutyryl 3',5'-CAMP (diCAMP) and theophylline in suspected fertile and subfertile semen samples was demonstrated with the zona-free hamster ova penetration test. The penetration rates for the untreated (control) fertile and subfertile samples were 30% and 17%, respectively. DiCAMP increased the penetration rates to 54% and 37% (with 5 mM diCAMP) and to 46% and 36% (with 10 mM diCAMP) in the fertile and subfertile samples, respectively; theophylline increased the penetration rates to 56% and 35% (with 10 mM theophylline) and to 49% and 42% (with 20 mM theophylline) in the fertile and subfertile samples, respectively. These results indicate that diCAMP and theophylline can affect the fertilizing ability of human spermatozoa in vitro.

Animals↗
PubMed1983

Immunoreactive LHRH-like factor in human seminal plasma.

Luteinizing hormone releasing hormone (LHRH)-like factor was detected in human seminal plasma by radioimmunoassay. The concentrations of immunoreactive LHRH in all semen samples tested (n = 46) ranged from 31 pg/ml to 71 pg/ml. Total content per ejaculate (pg) varied between 58 pg and 329 pg. There were no significant differences (p greater than 0.05) in the concentrations or total contents of immunoreactive LHRH-like factor between normospermic, oligospermic, and azoospermic semen samples.

Gonadotropin-Releasing Hormone↗
PubMed1979

The beta-adrenergic responses in isolated splenic capsule area of several species of animals.

In isolated splenic capsules of mouse, rat, guinea pig, rabbit, cat and dog, either a single or a cumulative dose of l- and dl-isoproterenol at a concentration higher than l0(-9) M, induced a relaxation which was inhibited or blocked with pretreatment of 10(-5) M propranolol. At a concentration of 5 x 10(-6) M to 10(-5) M 1- and dl-isoproterenol, an inverse contraction was induced, and such response was prevented or reversed to one of relaxation in the presence of 10(-5) M phentolamine. Application of 10(-5) M epinephrine produced a strong contraction and such was reversed to one of relaxation after addition of 10(-4) M phentolamine. This relaxation was reduced or blocked with pretreatment of 10(-5) M propranolol. Thus, it was confirmed that both alpha- and beta-receptors exist in the splenic capsule area of these different species.

Animals↗
PubMed1978

Morphine sulfate stimulates the adenylate cyclase in mouse caudate nuclei.

The effect of several concentrations of morphine on the activity of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing): EC 4.6.1.1.] was measured in homogenates of caudate nuclei of mice. Morphine stimulated the enzyme at 500 micron and inhibited slightly at 5 micron. Morphine stimulation was blocked by naloxone. Depending on its dose, morphine also increased or decreased the stimulating effect of dopamine on the dopamine-sensitive adenylate cyclase activity of caudate homogenate. Like dopamine, morphine'e effect on the adenylate cyclase activity was increased or decreased, respectively, by pretreating the animals with poly(I).poly(C) or with chloramphenicol. Thus, both dopamine and morphine appear to act on the same receptor. This "new" receptor differs from the one described by Snyder et al. and others, who demonstrated only binding affinity and no enzymatic activity. These data indicate that certain functions of the opiates might be mediated through the dopamine-sensitive adenylate cyclase of the caudate nuclei, which are the dopamine receptors in the brain.

Adenylyl Cyclases↗
PubMed1977

Levodopa, fertility, and longevity.

High concentrations of the dopaminergic drug levodopa (L-dopa, L-3,4-dihydroxphenylalanine) administered to mice in their diet affected fertility to a moderate degree and prolonged the mean life-span by a maximum of 50 percent.

Animals↗
PubMed1977

Opposing effects of dopaminergic to cholinergic compounds on a cerebral dopamine-activated adenylate cyclase.

In contrast to antipsychosis drugs which inhibit the dopamine-activated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] of caudate nucleus, dopaminergic drugs for treatment of Parkinson's disease stimulate this cyclase. Stimulants and inhibitors of cholinergic neurons inhibited this adenylate cyclase activity competitively and specifically. Thus, the mechanism by which dopaminergic medications ameliorate the effects of Parkinson's disease includes activation of the dopamine-sensitive adenylate cyclase. Excessive activation might be present during the psychotic episodes seen in patients with parkinsonism who are overtreated. The enzymatic effects of the drugs that affect cholinergic mechanisms seem to be generally in keeping with the pharmacological reciprocity between psychoses and extrapyramidal function, except for the anticholinergic ones which inhibited this cyclase although they can be hallucinogenic.

Adenylyl Cyclases↗
PubMed1977

Quantitative correlation of dopamine-dependent adenylate cyclase with responses to levodopa in various mice.

We obtained 12 groups of mice with widely different neurological responses to levodopa by selecting them from different strains and submitting some of them to pretreatments. We scored the symptoms evoked by a standardized dose of levodopa in one subgroup from each group. We tested another subgroup for activation of an adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] by a standardized dose of dopamine added to homogenates of the caudate nuclei of the brains of these mice. Both sets of tests were performed randomly. When the accruing two sets of data were plotted against each other there emerged a straight line which fitted the data with a coefficient of correlation of 0.97 (P less than 0.0001). The dopamine-dependent activity of the adenylate cyclase of the brain was thus shown to be a determinant of the neurological responses of intact animals to a dopaminergic drug.

Adenylyl Cyclases↗