Category Archives: Human Reproduction

BACKGROUND

Semenogelin (Sg), the main protein of human semen coagulum, prevents sperm capacitation. The objective of this study was to examine the role of Sg and its mechanism of action.

METHODS AND RESULTS

Sg blocked sperm capacitation triggered by various stimuli, via inhibition of superoxide anion (O₂•–; luminescence assay) and nitric oxide (NO•; tested using diaminofluorescein) generation. Triton-soluble and -insoluble sperm fractions contained Sg and Sg peptides (immunoblotting), the level of which decreased with initiation of capacitation. This drop was prevented by superoxide dismutase and NO• synthase inhibitor and was reproduced by addition of O₂•– and NO•. Zinc (Zn²⁺) blocked and a zinc chelator (TPEN) promoted the decline in Sg levels. There was a decreased labelling of Sg on the head in capacitating spermatozoa with the two fixation techniques tested (immunocytochemistry). Reactive oxygen species (ROS) (O₂•– and NO•) caused, these changes, and zinc prevented them. Spermatozoa quickly internalized Sg upon incubation and Sg was then rapidly degraded in a zinc-inhibitable manner.

CONCLUSIONS

Sg blocked capacitation mainly via inhibition of ROS generation. Spermatozoa appeared permeable to Sg and processed Sg in a zinc-inhibitable fashion. ROS themselves could promote sperm disposal of Sg which maybe one of the mechanisms that allows initiation of capacitation.

BACKGROUND

Previous research has demonstrated an association between economic contraction at both the individual and aggregate level, and adverse health outcomes. Proposed mechanisms include increased psychosocial stress and loss of resources. The aim of this review is to assess the quantity, validity and consistency of empirical evidence examining economic contraction and birth outcomes.

METHODS

Empirical, English-language articles examining the effects of economic change at either the aggregate or individual level on birthweight, length of gestation, neonatal mortality and the secondary sex ratio were identified using PubMed and ISI Web of Knowledge. Studies were organized by level of analysis and birth outcome and evaluated for internal and external validity.

RESULTS

One individual-level study reported a strong association between individual shift to inadequate employment and decreased birthweight. Of seven aggregate-level studies on birthweight, five exhibited moderate to strong validity but reported inconsistent findings. Similarly, findings from five studies (four with moderate to strong validity) examining rates of neonatal mortality reported inconsistent findings. Three of four moderate to strong studies reported a reduced secondary sex ratio following economic contraction.

CONCLUSIONS

Associations between economic contraction and birthweight, neonatal mortality and the secondary sex ratio remain speculative. Consensus on methodology is needed to compare findings across studies. Further research on economic contraction and the secondary sex ratio, as well as individual-level birthweight and length of gestation, is warranted.

BACKGROUND

An ectopic pregnancy is a pregnancy which occurs outside of the uterine cavity, and over 98% implant in the Fallopian tube. Tubal ectopic pregnancy remains the most common cause of maternal mortality in the first trimester of pregnancy. The epidemiological risk factors for tubal ectopic pregnancy are well established and include: tubal damage as a result of surgery or infection (particularly Chlamydia trachomatis), smoking and in vitro fertilization. This review appraises the data to date researching the aetiology of tubal ectopic pregnancy.

METHODS

Scientific literature was searched for studies investigating the underlying aetiology of tubal ectopic pregnancy.

RESULTS

Existing data addressing the underlying cause of tubal ectopic pregnancy are mostly descriptive. There are currently few good animal models of tubal ectopic pregnancy. There are limited data explaining the link between risk factors and tubal implantation.

CONCLUSIONS

Current evidence supports the hypothesis that tubal ectopic pregnancy is caused by a combination of retention of the embryo within the Fallopian tube due to impaired embryo-tubal transport and alterations in the tubal environment allowing early implantation to occur. Future studies are needed that address the functional consequences of infection and smoking on Fallopian tube physiology. A greater understanding of the aetiology of tubal ectopic pregnancy is critical for the development of improved preventative measures, the advancement of diagnostic screening methods and the development of novel treatments.

In the first trimester the extravillous cytotrophoblast cells occlude the uterine spiral arterioles creating a low oxygen environment early in pregnancy, which is essential for pregnancy success. Paradoxically, shallow trophoblast invasion and defective vascular remodelling of the uterine spiral arteries in the first trimester may result in impaired placental perfusion and chronic placental ischemia and hypoxia later in gestation leading to adverse pregnancy outcomes. The hypoxia inducible factors (HIFs) are key mediators of the response to low oxygen. We aimed to elucidate mechanisms of regulation of HIFs and the role these may play in the control of placental differentiation, growth and function in both normal and pathological pregnancies. The Pubmed database was consulted for identification of the most relevant published articles. Search terms used were oxygen, placenta, trophoblast, pregnancy, HIF and hypoxia. The HIFs are able to function throughout all aspects of normal and abnormal placental differentiation, growth and function; during the first trimester (physiologically low oxygen), during mid-late gestation (where there is adequate supply of blood and oxygen to the placenta) and in pathological pregnancies complicated by placental hypoxia/ischemia. During normal pregnancy HIFs may respond to complex alterations in oxygen, hormones, cytokines and growth factors to regulate placental invasion, differentiation, transport and vascularization. In the ever-changing environment created during pregnancy, the HIFs appear to act as key mediators of placental development and function and thereby are likely to be important contributors to both normal and adverse pregnancy outcomes.

BACKGROUND

Female cancer patients are offered ‘banking’ of gametes before starting fertility-threatening cancer therapy. Transplants of fresh and frozen ovarian tissue between healthy fertile and infertile women have demonstrated the utility of the tissue banked for restoration of endocrine and fertility function. Additional methods, like follicle culture and isolated follicle transplantation, are in development.

METHODS

Specialist reproductive medicine scientists and clinicians with complementary expertise in ovarian tissue culture and transplantation presented relevant published literature in their field of expertise and also unpublished promising data for discussion. As the major aims were to identify the current gaps prohibiting advancement, to share technical experience and to orient new research, contributors were allowed to provide their opinioned expert views on future research.

RESULTS

Normal healthy children have been born in cancer survivors after orthotopic transplantation of their cryopreserved ovarian tissue. Longevity of the graft might be optimized by using new vitrification techniques and by promoting rapid revascularization of the graft. For the in vitro culture of follicles, a successive battery of culture methods including the use of defined media, growth factors and three-dimensional extracellular matrix support might overcome growth arrest of the follicles. Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation. Large animals, including non-human primates, are essential working models.

CONCLUSIONS

Experiments on ovarian tissue from non-human primate models and from consenting fertile and infertile patients benefit from a multidisciplinary approach. The new discipline of oncofertility requires professionalization, multidisciplinarity and mobilization of funding for basic and translational research.

BACKGROUND

Although prescription drug use is common during pregnancy, the human teratogenic risks are undetermined for more than 90% of drug treatments approved in the USA during the past decades. A particular birth defect may have its origins through multiple mechanisms and possible exposures, including medications. A specific pathogenic process may result in different outcomes depending upon factors such as embryonic age at which a drug is administered, duration and dose of exposure and genetic susceptibility. This review focuses on the teratogenic mechanisms associated with a number of medications.

METHODS

We used three methods to identify the teratogenic mechanisms of medications: the MEDLINE and EMBASE databases, two recent books on teratogenic agents and a list of drugs classified as U.S. Food and Drug Administration class D or X. Mechanisms were included only if they are associated with major structural birth defects and medications that are used relatively frequently by women of reproductive age.

RESULTS

We identified six teratogenic mechanisms associated with medication use: folate antagonism, neural crest cell disruption, endocrine disruption, oxidative stress, vascular disruption and specific receptor- or enzyme-mediated teratogenesis. Many medications classified as class X are associated with at least one of these mechanisms.

CONCLUSIONS

Identifying teratogenic mechanisms may not only be relevant for etiologic and post-marketing research, but may also have implications for drug development and prescribing behavior for women of reproductive age, especially since combinations of seemingly unrelated prescription and over the counter medications may utilize similar teratogenic mechanisms with a resultant increased risk of birth defects.