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Biomedical subjects

I F Lau

Publications and source records attributed to I F Lau.

At least 55 records · Page 3Linked to original sources
PubMed1978

Endocrinological and physiological features after steroid treatment of male rats.

The effects of medroxyprogesterone acetate (Provera), testosterone propionate (TP), ethinyl estradiol (EE), and ethynodiol diacetate (ED) treatments on sperm population in different segments of the male rat reproductive tract, reproductive organ weights, circulating androgens and fertility were studied. Ten microgram TP given for five days reduced the sperm population and organ weights. A marked reduction in the number of sperm and reproductive organ weights was observed in males orally treated with estrogens. Only long-term (20 days) treatment with Provera (1 mg/day) significantly reduced sperm population and reproductive organ weights. Combination of TP and Provera resulted in a more pronounced reduction in sperm counts and organ weights. Among steroids studied, estrogen was the only compound which suppressed fertility and circulating steroid levels.

Androgens↗
PubMed1977

Determination of seven unconjugated steroids in the blood and seminal plasma of the fertile male rabbit.

Seven unconjugated steroids were measured in the blood and seminal plasmas of fertile male rabbits by radioimmunoassay. The blood plasma testosterone concentration was 4--5 times that of the seminal plasma. Dehydroepiandrosterone, estrone and 17beta-estradiol were found in measurable amounts in the blood plasma; however, these steroid levels were slightly lower in seminal plasma. Androstenedione and 5alpha-dihydrotestosterone were present in equal quantities in both the seminal and blood plasmas. By contrast, seminal plasma pregnenolone level was about twice that of the blood plasma. The determination of seminal plasma steroids may lend itself as a complementary assessment to blood steroid determinations for the evaluation of the normal function of various reproductive organs.

Androstenedione↗
PubMed1976

The inhibition of the conversion of testosterone into 5alpha-dihydrotestosterone in the reproductive organs of the male rat.

The inhibition of testosterone 5alpha-reductase activity by 3-oxo-4-androstene-17beta-carboxylic acid in the male reproductive organs of the rat was demonstrated in vitro. The medium for incubation of caput epididymis showed the highest concentration of 5alpha-dihydrotestosterone (5alpha-DHT) whereas the highest concentration of testosterone (T) was recorded in medium for incubation of decapsulated testis after two hours of incubation. The 3-oxo-4-androstene-17beta-carboxylic acid (1.58 X 10(-5)M) inhibited the conversion of T to 5alpha-DHT in all the organs tested (testis, caput and cauda epididymis and ventral prostate) under identical incubation conditions.

5-alpha Reductase Inhibitors↗
PubMed1976

Temporal changes in circulating steroids during prostaglandin F2alpha induced abortion in the rat and rabbit.

The serum levels of progesterone (delta4P), 20alpha-dihydroxyprogesterone (20alpha-DHP), pregnenolone (delta5P) and estrogens at different time intervals during Silastic-PVP-PGF2alpha tube induced midterm abortion were measured by radioimmunoassay in the rat and rabbit. The concentrations of delta4P and delta5P were significantly reduced but that of 20alpha-DHP was increased significantly as early as 20 hours after PGF2alpha treatment. Estrogen levels showed slight reduction in the rat but remained unchanged in the rabbit. The ratio of delta4P/20alpha-DHP recorded were 2.15 and 16.86 (pretreatment) and dropped to 0.08 and 0.37 (60 hours after insertion of Silastic-PVP-PGF2alpha tube) in the rat and rabbit, respectively. These findings suggest that the suppression of circulating delta4P by PGF2alpha might be the result of a reduced precursor (delta5P) pool size as well as changes in the enzymic systems responsible for the formation and conversion of delta4P. It is still to be determined if changes in estrogen levels in the rat have any bearing on abortion induced by PGF2alpha.

Abortion, Induced↗
PubMed1976

Relationship between oestrogen, prostaglandin F2alpha and histamine in delayed implantation in the mouse.

Treatment of pregnant mice ovariectomized on day 3 (23.00-2330 h) with progesterone (1 mg/day/mouse, from day 4 through 11 post coitum (p.c.)) and oestrogen (single injection of 0.05 mug on day 8 p.c.) induced implantation in all the animals. Implantation was inhibited in animals following three subcutaneous injections of indomethacin given on the morning and afternoon of day 8 and the morning of day 9 p.c. A single injection of histamine on day 8 p.c. partially compensated the effect of indomethacin. A complete reversal of the antifertility effect of indomethacin was achieved following intraperitoneal administration of histamine (2 mug at noon of day 8 p.c.) and PGF2alpha (20 mug on the morning and afternoon of day 8 p.c.). This study suggests that in the mouse uterus indomethacin impairs the physiological changes which are required for the decidual cell formation and implantation. It is likely that an injection of oestradiol in the progesterone treated ovariectomized mice triggers the release of PGF2alpha and histamine and that these compounds are involved in the chain of events leading to implantation of blastocysts.

Animals↗
PubMed1975

Induction of temporary sterility in female hamsters by an intraperitoneal silastic-PVP-PGF2alpha tube.

In the female hamster, temporary sterility for a period of 10 or 15 days was induced by an intraperitoneal Silastic-PVP-tube containing 3.5 or 1.0 mg of PGF2alpha, respectively. All Silastic-PVP-PGF2alpha tube hearing animals regained fertility and delivered normal litters at various times after the placement of the tube. The release rate of 3-H-PGF2alpha from the Silastic-PVP tube was described and their potential use as a drug delivery system discussed.

Animals↗
PubMed1975

Prostaglandin F2alpha: modification of its abortifacient effect by depo-estradiol cypionate in rats.

Insertion of a Silastic-PVP implant containing 150 mug PGF2alpha into one of the uterine horns or administration of a single subcutaneous injection of 4 mug of Depo-Estradiol Cypionate (ECP) did not induce abortion in pregnant rats. However, a combined treatment with 150 mug of PGF2alpha in a Silastic-PVP implant and 4 mug of ECP induced abortion in all treated rats. Apparently, ECP stimulated endogenous production of PGF and consequently enhanced the effect of the administered 150 mug of PGF2alpha. The release of 3H-PGF2alpha from Silastic-PVP implants was faster after intrauterine or intraperitoneal than after subcutaneous insertion. The release rate of 3H-PGF2alpha from Silastic-PVP implants in vitro was comparable to that observed after subcutaneous placement of similar implants. It is suggested that administration of estrogen combined with PGF2alpha might shorten the interval between treatment with PGF2alpha and abortion. Moreover, a Silastic-PVP implant would lend itself as a better method of administration, releasing PGF2alpha locally, slowly, and continuously.

Abortifacient Agents↗
PubMed1975

Effects of indomethacin and prostaglandin F2alpha on parturition in the hamster.

In the hamster administration of indomethacin twice a day on days 14 to 16 of pregnancy delayed the onset of parturition; a delay of 5 and 8 hours was observed following treatments of 300 or 600 mug/injection of indomethacin, respectively. Injection of PGF2alpha to the indomethacin treated hamsters on day 15 of pregnancy, on the other hand, advanced the onset of parturition. Treatments of indomethacin and/or PGF2alpha did not affect the duration of parturition.

Animals↗
PubMed1975

Effect of indomethacin, an inhibitor of prostaglandin biosynthesis on the length of pseudopregnancy in rats and hamsters.

Pseudopregnancy (PSP) in rats was significantly lengthened after subcutaneous administration of 0.2-1.0 mg indomethacin/day, starting on day 5 of PSP. Injections of 1 mg indomethacin on days 5 and 6 or days 7 and 8, as well as a single injection of 2 mg indomethacin on day 6, also produced a significant increase of the duration of PSP. In hamsters, doses of 300-500 mug indomethacin per day starting on day 5 of PSP did not alter the length of PSP, but a significant prolongation varying from 11 to more than 30 days was observed after a treatment with 1 mg of indomethacin daily. It was further observed that the ovaries of hamsters autopsied on day 31 of PSP were very small and the uteri resembled those of ovariectomized animals. It is concluded that indomethacin lengthens pseudopregnancy in both rats and hamsters and that the latter species showed a more variable response. It seems that chronic administration of indomethacin in hamsters caused a long-lasting suppression of ovarian hormone production.

Animals↗
PubMed1975

Effect of indomethacin on blood plasma levels of LH and testosterone in male rats.

Treatment of adult male rats with indomethacin, an inhibitor of prostaglandin (PG) synthesis, caused a significant decrease in LH and testosterone levels in the blood plasma and in the weight of the seminal vesicles, but the weight of the testes and ventral prostate, the levels of FSH in the plasma and fertility were not affected. The concentration of PGF in the blood plasma of the treated animals was reduced, even though measurable amounts of PGs were present in every group. The results of this study, together with the known effects of PG administration on LH release, suggest that the reduction of plasma LH levels in rats injected with indomethacin was due to decreased PG synthesis. It appears that PGs are normally involved in the regulation of LH release.

Animals↗
PubMed1975

Prostaglandin F2-alpha for induction of midterm abortion: a comparative study.

The action of prostaglandin F2alpha (PGF2-alpha) to induce midterm abortion in rabbits, rats, hamsters, and mice using different methods and routes of administration was studied. Administration of PGF-alpha in a Silastic-PVP implant was more effective than was the parenteral injection at the same dose levels. The efficacy of PGF2alpha was optimum when deposited locally in the uterine lumen as a Silastic-PVP implant, a condition comparable to a continuous intra-amniotic or extra-amniotic administration of PGF2alpha in women. It is possible that the insertion of a Silastic-PVP implant into the uterine lumen results in a continuous PGF2alpha release and a high local PGF2alpha concentration which minimizes such factors as dilution and the short half life displayed in the general circulation. PGF2alpha contained in a Silastic-PVP implant and inserted into the uterine lumen may effectively induce abortion with a comparatively lower dose than that necessary for parenteral routes of administration.

Abortion, Induced↗