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Biomedical subjects

C Y Cheng

Publications and source records attributed to C Y Cheng.

At least 199 records · Page 11Linked to original sources
PubMed1982

Partial characterization of human spermatozoal phosphodiesterase and adenylate cyclase and the effect of steroids on their activities.

In sonicated human spermatozoa, phosphodiesterase hydrolyzed adenosine 3':5'-monophosphate (cAMP) at 20.80 +/- 3.23 nmoles/10(8)sperm/20 min at 37 degrees C (50 microM cAMP, initially). In human semen, about 60% of the phosphodiesterase activity was in the spermatozoa. Both polyacrylamide gel electrophoresis and DEAE-cellulose column chromatography indicated that there are at least 5 isozymes of phosphodiesterase. Various steroids were tested at a concentration of 2 micrograms/ml for their effects on phosphodiesterase activity in semen. None was found to have any significant effect. In sonicated human spermatozoa, adenylate cyclase synthesized cAMP at 0.02-2.11 nmoles/10(8)sperm/20 min at 37 degrees C (1 mM ATP, initially) depending on the availability of Mn2+ and caffeine in the assay mixture. Mn2+ was demonstrated to be a potent adenylate cyclase activator in human spermatozoa and its effect on human sperm adenylate cyclase was found to be dose-dependent. Cholera toxin, at a concentration of 20 micrograms/ml, had no effect on human sperm adenylate cyclase activity after it had been incubated with the intact spermatozoa for between 5 min and 5 h at 37 degrees C before the sperm were homogenized and the rate of cAMP formation assayed. In addition, human sperm adenylate cyclase decayed rapidly at 37 degrees C. Of various steroids tested at a concentration of 2 micrograms/ml for their effects on human sperm adenylate cyclase activity, only oestradiol-17 beta showed a significant effect, elevating the rate of cAMP formation by about 30%.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1981

Effects of steroids on the in vitro forward migration of human spermatozoa.

The effects of 14 steroids at concentrations between 0.1 and 10 micrograms/ml on human spermatozoal forward migration in vitro were tested. Oestradiol-17 beta at a concentration of 0.1 microgram/ml significantly activated spermatozoal forward migration in ejaculated human semen. However, the effect of oestradiol-17 beta at concentrations of 2 and 10 micrograms/ml on ejaculated human sperm motility was not significantly different from the control where no steroid was added. Progesterone, testosterone, oestriol, oestrone, oestradiol-17d, and ethinyl oestradiol significantly inhibited human spermatozoal forward migration at concentrations of 10 micrograms/ml. Chlormadinone acetate and medroxyprogesterone acetate at concentrations of 2 and 10 micrograms/ml significantly inhibited human spermatozoal forward migration, while norethynodrel, ethynodiol diacetate, norgestrel and lynoestrenol significantly inhibited human spermatozoal forward migration at concentrations between 0.1 and 10 micrograms/ml. However, norethindrone had no demonstrable effect on human spermatozoal forward migration at the above concentrations.

Dose-Response Relationship, Drug↗
PubMed1981

The binding of sex steroids to human spermatozoa. An autoradiographic study.

The locations of steroid binding sites with specificities for 17 beta-oestradiol, progesterone and testosterone have been examined on human spermatozoa by autoradiography. The binding sites were not evenly distributed over the entire surface of human spermatozoa. They were more densely located on the midpiece of the tail, less on the head and neck, and least on the principal- and end pieces of the tail. The binding sites for 17 beta-oestradiol were specific, with 3H-17 beta-oestradiol being displayed by unlabelled 17 beta-oestradiol, but less readily displaced by either progesterone or testosterone. The binding sites for testosterone were less specific than those for 17 beta-oestradiol or those for progesterone. Both 17 beta-oestradiol and progesterone were good competitors for testosterone binding sites, while the binding of 3H-progesterone was easily displaced by 17 beta-oestradiol, but less readily displayed by testosterone. Since there was preferential binding of these steroids to the mid-piece, and strong competition for binding between 17 beta-oestradiol and progesterone, these studies appear to provide information on the sites of action for the reported effects of these and related steroids on spermatozoal motility, migration and metabolism.

Autoradiography↗
PubMed1981

The binding of oestradiol-17beta to human spermatozoa - an electron microscope autoradiographic study.

The location of steroid binding sites with specificity for oestradiol-17beta at an ultrastructural level has been examined on human spermatozoa by electron microscope autoradiography. About 75% of the 438 gains produced by 3H-oestradiol-17beta, and counted on electron microscope autoradiographs, were found over the plasma membrane or within 1000 A of it. This study provides evidence suggesting that the plasma membrane is a site of action of oestradiol-17beta in human spermatozoa.

Autoradiography↗
PubMed1981

Effect of cAMP, Mn2+, and phosphodiesterase inhibitors on human sperm motility.

The effects of cyclic adenosine monophosphate (cAMP), MnCl2, caffeine, and theophylline at concentrations of 10 mM on human sperm motility and forward migration in vitro were tested. cAMP was effective in activating human spermatozoal motility and forward migration after incubation with the spermatozoa for 3 hr or more and 5 hr, respectively, whereas caffeine and theophylline were effective in activating sperm motility after incubation with the spermatozoa for 1 hr or more. Caffeine and theophylline significantly activated sperm forward migration only after incubation with the sperm for 5 hr. MnCl2, a potent sperm adenylate cyclase activator, had no significant effect in improving human sperm motility and forward migration.

Caffeine↗
PubMed1980

Activation of spermatozoal forward migration in vitro by hydrocortisone.

The effects of hydrocortisone and cortisone on spermatozoal motility in vitro were tested Hydrocortisone at concentrations of 50, 100 and 1000 nmoles/ml was effective in activating in vitro the forward migration and the motility of boar spermatozoa recovered from the cauda epididymidis. Where boar epididymal spermatozoa were incubated with hydrocortisone at concentrations of 50, 100 and 1000 nmoles/ml for between 0 and 24 h at 25 degrees C in vitro, the spermatozoal motility was significantly higher than where no hydrocortisone was added. With ejaculated boar spermatozoa, hydrocortisone at concentrations of 100 and 1000 nmoles/ml increased the spermatozoal motility for between 0 and 2 h and at concentration of 50 nmoles/ml increased spermatozoal motility for between 2 and 24 hr at 25 degrees C in vitro. After 4 incubation, the effect of hydrocortisone at a concentration of 100 nmoles/ml on boar ejaculated sperm motility was not significantly different from the control. But, hydrocortisone at a concentration of 1000 nmoles/ml inhibited for forward migration of boar ejaculated sperm after it had been incubated with the sperm for 6 h. Cortisone, although structurally similar to hydrocortisone, had no significant effect in improving the motility of boar spermatozoa. Both hydrocortisone and cortisone had no demonstrable effect on the forward migration and the motility of human spermatozoa in vitro.

Animals↗
PubMed1980

Mitogenic activity and plasminogen activator in harvest fluid concentrates from mammary cells in culture.

Harvest fluid concentrates (HFC's) from three human mammary tumor cell lines (T47D), HSO578T, and MDA-MB-157), one nontumorigenic human mammary cell line (HBL-100), and one mouse mammary tumor cell line (MCG-T14) stimulated thymidine incorporation in confluent quiescent BALB/c 3T3 cells in a dose-dependent manner. HFC's from all of the cell lines also exhibited plasminogen activator activity. Levels of mitogenic activity and plasminogen activator in the HFC preparations were not correlated with cell growth potential or with the amount of protein which was recovered in the HFC's. High levels of mitogenic activity and plasminogen activator in the HFC's from HBL-100 cells suggested that the production of these biological activities is not a unique feature of tumorigenic mammary cells. The HFC's from three human cell lines (T47D), HS0578T, MDA-MB-157) exhibited high levels of mitogenic activity but low levels of plasminogen activator. This suggested that plasminogen activator is not the source of the mitogenic activity in the HFC's from these cells. The HFC's from a human mammary carcinoma line, BT-20, contained very low levels of mitogenic activity and plasminogen activator. In addition, BT-20 HFC's inhibited the mitogenic activity of fetal bovine serum in a dose-dependent manner. It is proposed that BT-20 cells are the source of a macromolecular inhibitor of serum mitogens.

Animals↗
PubMed1979

The effect of steroids on the in vitro migration of washed human spermatozoa in modified Tyrode's solution or in fasting human blood serum.

In modified Tyrode's solution, 17 beta-estradiol at concentrations between 0.1 microgram/ml and 320 nmoles/ml was effective in increasing human spermatozoal forward migration. 17 alpha-Estradiol, although structurally similar to 17 beta-estradiol, had no effect on human spermatozoal motility. DL-Norgestrel at concentrations between 0.1 migrogram/ml and 320 nmoles/ml inhibited spermatozoal motility. These stimulatory and inhibitory effects were not observed when fasting human blood serum was used as a penetration medium in place of the modified Tyrode's solution. Also, the motility of spermatozoa suspended in fasting human blood serum was better than that of spermatozoa suspended in modified Tyrode's solution or in seminal plasma. These observations indicated that there is a component(s) of fasting human blood serum which increases spermatozoal motility and can counteract the activation or inhibition of spermatozoal motility by 17 beta-estradiol or DL-norgestrel at the concentrations used here.

Blood↗
PubMed1979

Isolation and characterization of mutations in the structural gene for protease III (ptr).

Escherichia coli mutants defective in protease III were isolated by enzyme assays of heavily mutagenized colones. One mutant produced thermolabile enzyme, and it is presumed to have a mutation in the structural gene of protease III. Two other mutants mapping at the same site had less than 5% of the wild-type protease III level. The genetic locus of these mutations, designated ptr, was located at approximately 60 min on the E. coli linkage map based on its high frequency (70%) of contransduction by P1 with argA. Strains with less than 5% of the wild-type protease III activity grew normally and degraded nonsense fragments of beta-galactosidase at wild-type rates.

Chromosome Mapping↗
PubMed1976

Comparison of rapid versus slow decompression of the distended urinary bladder.

Experiments are described showing that urinary retention with its associated increased intravesical pressure and overstretching of the bladder wall can lead to loss of capillary and tissue integrity. Our findings indicate that the severity of damage to the bladder wall prior to catheterization determines the degree of hemorrhage after bladder decompression and not the rate of emptying.

Animals↗
PubMed1975

Mucosal uptake in vitro of cholesterol from bile salt and surfactant solutions.

That bile salts are required for intestinal absorption of cholesterol is well known, but the mechanism of action is elusive. Substitution of other surfactant micelles and inclusion of fatty acid or monoglyceride variably influenced sterol transport. In this study, rat jejunal mucosal sheets were exposed for 1-2 min to 10 mM micellar solutions of taurodeoxycholate, dodecylsulfate, Tween 80 or cetyltrimethylammonium bromide containing cholesterol, 0.25 mM. Monoolein and/or oleic acid were variably added. Cholesterol influx was insignificant in all solubilizers without additives. With taurodeoxycholate, addition of monoolein progressively enhanced influx from 13 nmoles/cm-2 per hour to 29 nmoles/cm-2 per hour (0.67-5.4 mM monoglyceride). Oleic acid, 3 mM, was as effective as 5.4 mM monoolein. Oleic acid, 3 mM, added to monoolein 3 mM maximized influx (42 nmoles/cm-2 per hour). With cetyltrimethylammonium bromide, monoolein 0.67 mM enhanced influx to 13 nmoles/cm-2 per hour but further additions of monoolein with or without oleic acid had no added effect. Additives had no material effect on the insignificant influx from the other anionic or nonionic surfactants. These results are not explained by differences in cholesterol, monoolein or oleic acid partition or in micellar sizes. Specific interactions of bile salt and fatty acid or monoglyceride with the plasma membrane are postulated in cholesterol absorption.

Animals↗