Further studies on sister-chromatid exchange frequency in users of hormonal contraceptives

Women using an estrogen-progestogen combination contraceptive exhibited an increased frequency of sister-chromatid exchange (SCE), supporting our previous observation. These elevated SCE frequencies tended to decline 3 months after the discontinuation of the pill. Women using a progestogen injectable contraceptive, on the other hand, had unaltered SCE rates. The analysis, in vitro; of mitomycin-C-induced SCE frequencies in women using either the combination or the progestogen injectable contraceptives showed significantly higher rates of induced SCE.     

Use of Medroxyprogesterone Acetate as a Contraceptive in conjunction with Early Postpartum Rubella Vaccination

During a 12-month period 170 women received early postpartum rubella vaccination. An injectable “depot” progestogen was given to each of these patients for contraceptive purposes at the same time as the vaccine was administered. Subsequent observations showed that the progestogen was effective as a contraceptive in this context and that it did not appear to affect the immune response of the patients to the vaccine.     

Male contraception: expanding reproductive choice

The development of steroid-based oral contraceptives had revolutionized the availability of contraceptive choice for women. In order to expand the contraceptive options for couples by developing an acceptable, safe and effective male contraceptive, scientists have been experimenting with various steroidal/non-steroidal regimens to suppress testicular sperm production. The non-availability of a long-acting androgen was a limiting factor in the development of a male contraceptive regimen since all currently tested anti-spermatogenic agents also concurrently decrease circulating testosterone levels. A combination regimen of long-acting progestogen and androgen would have advantage over an androgen-alone modality since the dose of androgen required would be much smaller in the combination regimen, thereby decreasing the adverse effects of high steroid load. The progestogen in the combination regimen would act as the primary anti-spermatogenic agent. Currently, a number of combination regimens using progestogen or GnRH analogues combined with androgen are undergoing trials. The side effects of long-term use of androgens and progestogens have also undergone evaluation in primate models and the results of these studies need to be kept in view, while considering steroidal regimens for contraceptive use in men. Efforts are also being made to popularize non-scalpel vasectomy and to develop condoms of greater acceptability. The development of contraceptive vaccines for men, using sperm surface epitopes not expressed in female reproductive tract as source, still requires considerable research efforts.     

Assessment of Incremental Dosage Regimen of Combined Oestrogen-Progestogen Oral Contraceptive

Eighty-six women of proved fertility used an incremental dosage regimen of a combined oral contraceptive for a total of 570 cycles over one year. A daily tablet containing 50 μg of ethinyloestradiol and 50 μg D-norgestrel was taken for 11 days and a daily tablet containing 50 μg ethinyloestradiol and 125 μg D-norgestrel for the next 10 days. Withdrawal bleeding occurred during the tabletfree interval of seven days. The new preparation proved to be an efficient contraceptive, well tolerated, and with few side effects. Women who had gained weight while taking other oral contraceptives lost weight when they changed to the new preparation. The regimen allowed a significant reduction in the cycle dose of progestogen, and these results suggest that a further reduction in the cycle dose of both oestrogen and progestogen may be possible without losing contraceptive efficiency.     

Hormonal contraception

The combination hormonal contraceptive pill consisting of a fixed ratio of a progestational compound to an estrogenic compound administered from the 5th to 25th day of the cycle approaches 100% in efficacy. Cycle control is excellent and is related to the mechanism of action. The progestogen plus estrogen of the combination pill inhibit the hypothalamic-anterior pituitary-ovarian axis, thus insuring almost complete inhibition of ovulation and endogenous steroid hormone biosynthesis. The lack of endogeneous hormone is not critical since the pill replaces the lost hormones particularly as to uterine endometrial stimulation so that the tissue is prepared for a bleed on treatment withdrawal. The carefully timed hormonal replacement ensures excellent cyclicity. Although suppression of ovulation may be continued for years, cessation of treatment is followed by a return to normal hormonal function and fertility.Variants of the combination treatment include a once-a-month pill and a once-a-month injectable preparation. Both formulations are based on combinations of a progestogen plus estrogen.A high degree of efficacy approaching that seen for the combination pill has been achieved with a sequential regimen. In this procedure an estrogen alone is administered for 5 to 15 days while a mixture of estrogen plus a progestational agent is administered for the balance of the 20 days of treatment. Withdrawal of treatment brings on a bleed in 2 to 5 days. The mechanism of of antifertility is similar to that of the combination pill.Contraceptive efficiency of a high order may be attained with a small continuous dose of a progestational agent. The pregnancy rate and cyclicity are acceptable but not as good as that of the combination or sequential regimens. The pure progestogen treatment has been adapted to a pseudo post-coital therapy where one sexual contact requires one pill usually within 1 to 3 hours of the event. Thus far a reasonable efficacy has been established but as much as 33% of the cycles may be less than 20 days in length.A Single injection of a progestogen can produce effective antifertility for 90 days. This treatment is efficacious but the early treatment periods may involve considerable irregular bleeding and after repeated use ammenorrhea may be a problem.A true post-coital treatment has not been established. However, for emergency use 4 to 6 days of treatment with high doses of estrogen is highly effective in preventing pregnancy. The mechanism may involve speeding of ova transport thus preventing implantation.     

Long-acting hormonal contraceptives for women

Following the development and widespread use of oral hormonal contraceptives, it became evident that alternative long-acting delivery systems would be required to improve contraceptive practice in some cultural settings where injectable or subdermal routes of administration are preferred. Nowadays, long-acting contraceptives constitute an important option in family planning services in many parts of the world. Indeed, two long-acting injectable contraceptives containing just a synthetic progestogen (depot-medroxyprogesterone acetate (DMPA) and norethisterone enantate (NET-EN)) have been in clinical practice for more than 20 years. The World Health Organization's (WHO) Special Programme of Research in Human Reproduction, in collaboration with the U.S. National Institute of Child Health and Human Development (NICHD) and universities primarily in developing countries undertook a synthesis programme aimed at producing an improved injectable preparation by developing new derivatives of known steroids. One such compound (levonorgestrel 17-butanoate) is now at the stage of Phase II clinical testing. In addition, the Special Programme has developed and improved once-a-month injectable formulations and assessed their safety and efficacy in diferent countries worldwide. After large scale clinical testing, at least two prgestogen-estrogen combinations have reached the point of introductory trials.     

Effects of Progestogen Oral Contraception with Norethisterone on Blood Clotting and Platelets

The effects on clotting tests and platelet function of six months'' continuous administration of the 19-norsteroid, progestogen-only contraceptive, norethisterone, have been studied in four groups of women. In a group of women who have not previously taken oral contraceptive no acceleration of clotting or platelet factors was found, but in contrast a tendency to reduced coagulability was observed. Women who had previously been taking combined oestrogen-progestogen preparations showed reduced clotting and platelet parameters when norethisterone was substituted. No changes in clotting or platelets were found in women who changed from 17-acetoxysteroid progestogen chloramadinone acetate or in a group of women started postpartum.     

Sister chromatid exchange in newborns

Summary Siter chromatid exchanges (SCE) were analyzed in the cord and postnatal blood of controlled groups of low and high birth weight infants to detect possible associations between abnormal birth weight and SCE frequency. Structural chromosome aberration rates had previously been evaluated for all infants, and possible correlations between aberration and SCE rates were sought.No correlation was found between neonatal or postnatal SCE frequency and birthweight, nor was there evidence of association of chromosome aberration rates with SCE frequency. In all groups of infants, however, mean postnatal SCE frequencies were significantly lower than mean neonatal SCE frequencies.     

Effect of tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate on induction of sister-chromatid exchanges in Chinese hamster V79 cells treated with mutagens

The effect of a tumor promoter, 12-O-tetradecanoyl-phorbol 13-acetate (TPA) alone and in combination with mitomycin C (MMC) or cyclophosphamide (CPP) on the induction of sister-chromatid exchanges (SCE) in Chinese hamster V79 cells was investigated. TPA alone at various doses and durations caused no increase of SCE frequency. MMC either at the dose of 0.03 or 0.003 μg/ml alone or in combination with TPA (2 μg/ml) all caused a significant increase of SCE frequencies. There was no difference in SCE frequencies between the cultures treated with MMC alone at 0.03 μg/ml and those treated with MMC plus TPA. However, cultures treated with MMC at 0.003 μg/ml plus TPA had significantly and consistently higher SCE frequencies than those treated with MMC alone at all durations. Treatment of CPP at 1 μg/ml activated by S9 mix caused significant increase of SCE frequencies. Surprisingly, the cultures treated with CPP, S9 mix plus TPA (2 μg/ml) caused a drastic reduction of SCE frequencies as compared to those treated with CPP and S9 mix only at all durations. These results indicate that TPA alone had no effect on SCE in V79 cells. TPA enhanced the SCE induction in V79 cells treated with MMC at a low dose, i.e. 0.003 μg/ml, but it inhibited SCE induction in cultures treated with the indirect mutagen CPP. Thus, TPA has no direct effect on genetic materials but it may indirectly alter the effects of a mutagen.     

Current status of fertility control methods in India

Approximately 48.2% of couples of 15 to 49 years of age practice family planning methods in India. Female sterilization accounts for 34.2%, with male sterilization declining from 3·4% in 1992–93 to 1·9% in 1998–99. Use of the condom increased to 3·1% from 2·4%. There is an urgent need for research to develop new contraceptive modalities especially for men and also for women and to make existing methods more safe, affordable and acceptable. Current efforts in India to develop a male contraceptive are mainly directed towards (i) development of antispermatogenic agents to suppress sperm production, (ii) prevention of sperm maturation, (iii) prevention of sperm transport through vas deferens or rendering these sperm infertile and (iv) prevention of sperm deposition. Research work in the field of prevention of sperm transport through vas deferens has made significant advances. Styrene maleic anhydride (SMA) disturbed the electrical charge of spermatozoa leading to acrosome rupture and consequent loss in fertilizing ability of sperm. A multicentre phase-III clinical trial using SMA is continuing and it is hoped that the SMA approach would be available in the near future as an indigenously developed injectable intra-vasal male contraceptive. The safety and efficacy of available oral contraceptives were evaluated. An indigenously developed oral contraceptive ‘Centchorman’, which is a nonsteroidal, weakly estrogenic but potently antiestrogenic, was found to be safe and effective and is now being marketed in India since 1991 as a ‘once a week’ pill. Cyclofem and Mesigyna have been recommended as injectable contraceptives with proper counselling and service delivery by Indian studies. It has been recommended that these injectable contraceptives be added to the existing range of contraceptive methods available in the National Family Planning Programme. Based on the Indian studies CuT 200 was also recommended. Studies have indicated the advantage of intrauterine devices (IUD); they are long acting, relatively easily removed and fertility returns rapidly after their removal. Recent studies have recommended CuT 200 for use up to 5 years. The combination of some plant products i.e.Embelia ribes, Borax andPiper longum has been found to be safe and effective as a female contraceptive and the results of phase-I clinical trials are encouraging. Research work is going on in the country in various areas with special reference to hormonal contraceptive — a three monthly injectable contraceptive, immuno-contraceptives, antiprogestins, etc.     

Excessive chromosome fragility and abundance of sister-chromatid exchanges induced by UV in an Indian muntjac cell line defective in postreplication (daughter strand) repair

Two UV-hypersensitive animal cell mutants defective in postreplication recovery (daughter strand synthesis) display quite different patterns of induced sister-chromatid exchange (SCE). One, an SV40-transformed Indian muntjac cell (SVM), shows extremely high frequencies of SCE after UV; induced exchanges can be measured after UV doses as low as 0.01 J/m2. This cell also displays exaggerated levels of induced and spontaneous chromosome aberrations. By contrast SCE rates in the Chinese hamster cell mutant, UV-1, are essentially normal. In both SVM and UV-1, however, there is a clear correlation between the cell density and spontaneous frequencies of SCE, a feature which could be related to the observed density-dependent rate of DNA maturation.     

In vivo sister chromatid exchange analysis of a mouse plasmacytoma cell line NP-38

In vivo sister chromatid exchange (SCE) frequencies have been compared between the mouse plasmacytoma NP-38 and normal bone marrow cells of the host BALB/c mouse. NP-38 cells, transplanted subcutaneously showed a two-fold increase in SCEs (4.35-5.76/cell) compared with the bone marrow cells of the host (1.65-2.14/cell). Such an increase in SCE rates was also observed in NP-38 cells metastasized in spleen, bone marrow, liver, or mesentery, upon inoculation of NP-38 cells by intravenous injection. Even in such tumor-bearing mice, the SCE rates of the bone marrow cells were equivalent to the SCE level found in uninfected mice. These results indicate that the high SCE incidence in NP-38 cells is an inherent characteristic of this tumor cell line.     

Perspectives of contraceptive choices for men

Apart from condoms and vasectomy, which have several limitations of their own, no other methods of contraception are available to men. Various chemical, hormonal, vas based and herbal contraceptives have been examined and few of them have reached the stage of clinical testing. Promising leads have been obtained from testosterone buciclate/undecanoate, alone or in combination with levonorgestrel butanoate or cyproterone acetate, RISUG, an injectable intravasal contraceptive and a few herbal products, particularly the seed products of Carica papaya. It is feasible that an ideal male contraceptive, that meets out all the essential criteria will be made available to the community in the near future.     

Genotoxic effects of thiram evaluated by sister-chromatid exchanges in human lymphocytes

The purpose of this investigation was to study the genotoxic potential of thiram (CAS No. 137-26-8) using an in vitro sister-chromatid exchange (SCE) assay with human lymphocytes. The results indicate that thiram and its metabolites increase the SCE frequencies 2-fold over those observed in the negative controls. The standard inducers cyclophosphamide and ethyl methanesulfonate increased SCE frequencies 10- and 4-fold, respectively, over untreated levels.     

Epilepsy and Oral Contraception

A controlled cross-over trial in 20 epileptic women, receiving regular anticonvulsant therapy showed that an oral contraceptive with a low oestrogen/ progestogen content had no significant effect on the average frequency of fits compared with identical dummy tablets.     

Blood pressure and contraceptive use

In a survey of 461 women routinely attending family planning clinics those taking oral contraceptives had significantly higher mean systolic and diastolic blood pressures than those using non-hormonal contraception. There appeared to be a dose-response relation of blood pressure to the progestogen component of two oral contraceptives with an identical 30 μg ethinyloestradiol component. This supports the idea that the progestogen as well as the oestrogen component has an aetiological role in the rise in blood pressure. There was a significant correlation of blood pressure with duration of current use of oral contraceptive but not with total duration of use. There was also a significant negative correlation of blood pressure with time since oral contraceptives were last taken, and women who had stopped using oral contraceptives over a month previously had similar blood pressures to those who had never taken them. In women taking oral contraceptives those who had either a history of hypertension in pregnancy or a family history of hypertension had significantly higher mean blood pressures than those who did not. Both systolic and diastolic blood pressures correlated independently with weight and body mass index, but controlling for the effect of this and age did not affect the above relations. No significant differences in mean blood pressures were found between different ethnic groups, and there was no relation of blood pressure to reported marital state, social class, parity, smoking, or alcohol use.Any oral contraceptive that has a less adverse effect on blood pressure has implications for general prescribing policy; thus even small differences in the progestogen contents of low-dose oestrogen pills may be important.     

Bimodal distribution of sensitivity to SCE induction by diepoxybutane in human lymphocytes. II. Relationship to baseline SCE frequency

Environmental and genetic factors have been implicated as important sources of individual variation in baseline sister-chromatid exchange (SCE) frequency in humans. The current study was designed to test whether the frequency of baseline SCEs in 58 normal blood donors is associated with previously observed variations in SCE frequencies induced by diepoxybutane (DEB). Because 12 subjects were current cigarette smokers and smoking is known to be an in vivo inducer of baseline SCE frequencies, we specifically tested whether higher baseline SCE frequencies in smokers would be associated with in vitro sensitivity to SCE induction by DEB. Analysis of variance showed that DEB-induced SCE frequencies were significantly associated with baseline SCE frequencies; those who were sensitive to SCE induction by DEB were more likely to have higher baseline SCE frequencies. This effect, however, was independent of in vivo induction of SCE by smoking. Chromosomal sensitivity to the induction of SCE by DEB explained approx. 15-20% of the variation in baseline SCE. This was similar in magnitude to the effect of cigarette smoking. Because increased sensitivity to DEB-induced SCEs is common in normal blood donors (approx. 24%) and is associated with an increase in baseline SCEs, it should be investigated as a source of bias and/or a potential marker of sensitivity to environmental mutagens in future cytogenetic studies.     

The control of follicular wave development for self-appointed embryo transfer programs in cattle.

Our expanding knowledge of the control of follicular wave dynamics during the bovine estrous cycle has resulted in renewed enthusiasm for the prospects of precisely controlling the follicular and luteal dynamics and finely controlling the time of ovulation. Follicular wave development can be controlled mechanically by ultrasound-guided follicle ablation or hormonally by treatments with GnRH or estradiol and progestogen/progesterone in combination. Treatment of cattle with GnRH in combination with prostaglandin F2 alpha (PGF) 7 d later and a second GnRH 48 h after PGF (known as Ovsynch) has resulted in acceptable pregnancy rates after fixed-time AI in lactating dairy cows and in recipients in which embryos were transferred without estrus detection. Alternatively, treatments with estradiol and progestogen/progesterone-releasing devices resulted in synchronous emergence of a new follicular wave and, when a second estradiol treatment was given 24 h after device removal, synchronous ovulation and high pregnancy rates to fixed-time AI. Self-appointed embryo transfer (without estrus detection) using estradiol and progesterone treatments have resulted in pregnancy rates comparable with those obtained with recipients transferred 7 d after estrus. Furthermore, estradiol and progesterone treatments combined with PGF and eCG (given 1 d after the expected time of wave emergence) have resulted in high rates of recipients selected for transfer (84.6%) and an overall pregnancy rate of 48.7% (recipients pregnant/recipients treated). Estradiol and progestogen/progesterone treatments have also been widely used for self-appointed superstimulation protocols with equivalent embryo production to that of donor cows superstimulated using the traditional approach beginning 8 to 12 d after estrus. In summary, exogenous control of luteal and follicular development facilitates the application of assisted reproductive technologies in cattle by offering the possibility of planning the superstimulation of donors and synchronization of recipients at a self-appointed time, without the necessity of estrus detection and without sacrificing results.     

Contraceptive use and efficacy in a genetically counseled population

Abstract

This paper reports contraceptive use and efficacy rates among 648 married women aged 15 to 44 who had received genetic counseling six months previously. Over half (53.5 per cent) of the counseled population were using non‐surgical contraception; 20 per cent were pregnant or postpartum; 10 per cent were seeking to become pregnant; 11 per cent were sterilized. Only 4.5 per cent were neither using contraceptives nor seeking to become pregnant. Women who were certain about their reproductive intentions after counseling utilized contraceptives effectively, with only two pregnancies at six months among those seeking to delay wanted pregnancies and only one pregnancy among those seeking to prevent pregnancy. This represents six‐month contraceptive failure rates of 4.3 and 2.1 per cent respectively for the two groups, rates similar to those with comparable intentions in the U. S. population at large. A distinguishing characteristic of the genetically counseled group was that 32 per cent of contraceptive users reported that their reproductive intentions were uncertain after counseling. The six‐month pregnancy rate in this uncertain group was 10 per cent.     

Suppression of ovulation in Nile Hippopotamus (Hippopotamus amphibious) using melengestrol acetate‐treated feed or high dose Depo‐Provera injection

Analysis of fecal progestogen profiles during Depo‐Provera injection (1,200 mg; DEPO, Pfizer Inc., New York, NY), melengestrol acetate (MGA) in feed (2 or 3 mg/head/day), and a combination treatment (DEPO+MGA) are presented for nine captive female Nile hippos housed at Disney's Animal Kingdom in Florida. All tested treatments reduced fecal progestogen elevations successfully to durations consistent with prevention of ovulation for a portion of the treatment period. Percentage of treatment months with suppression of luteal phases indicative of ovulation was maximal for high‐dose MGA (91.7±13.9%) and DEPO+MGA (91.7±20.4%), followed by DEPO injection alone (69.2±13.9%) and low‐dose MGA (57.6±33.2%). Both 1,200 mg DEPO and low‐dose MGA (2.0 mg/day) treatments were insufficient to prevent an apparent seasonal breakthrough of ovarian activity from June–August 2002. Although luteal phases were observed, no females conceived during those months. Overall, in 133.5 treatment months with females housed with an adult male, one female conceived during the transition period between treatments. After cessation of contraceptive treatment, average latency to first normal ovarian cycle was 80.6±19.5 days (range = 22–179 days). Up to 12 months post‐treatment, however, successive cycles were often irregular with evidence of short periods of anovulation and shortened luteal phases in all females monitored. In conclusion, high dose and combination treatments were most successful in preventing progestogen increases indicative of ovulation in hippos. Zoo Biol 26:259–274, 2007. © 2007 Wiley‐Liss, Inc.