H.W. Gordon Baker

Bio: H.W. Gordon Baker is an academic researcher from Prince Henry's Institute of Medical Research. The author has contributed to research in topics: Artificial insemination & Pregnancy rate. The author has an hindex of 4, co-authored 5 publications receiving 120 citations.

Andrology: Relationship between stimulated hyperactivated motility of human spermatozoa and pregnancy rate in donor insemination: a preliminary report

Abstract: The proportion of spermatozoa exhibiting the vigorous motility behaviour termed 'hyperactivation' (HA) has been shown to be increased following removal of seminal plasma and stimulation with chemical agents such as pentoxifylline. The aim of this study was to examine the relationship between the proportion of HA in cryopreserved semen samples from sperm donors and the corresponding pregnancy rates achieved by donor insemination. Cryopreserved samples from 20 men were incubated in the presence or absence of 3 mM pentoxifylline for 1 h and the %HA determined in each sample. The relationship between pregnancy rate, the proportion of HA spermatozoa in control and pentoxifylline-treated groups and the change in %HA following pentoxifylline treatment (delta HA) as well as the mean semen characteristics for each donor [sperm count, motility (%), motility index, normal morphology (%), post-thaw motility (%) and post-thaw motility index] were examined by logistic regression of the occurrence of clinical pregnancy with each insemination. Both delta HA and mean post-thaw motility index were significantly related to pregnancy rates and together accounted for 64% of the observed variation in pregnancy rates.

A pre-coital pill? A preliminary in vitro study.

Abstract: The use of the progestogen-only pill as a ‘pre-coital contraceptive’ was tested by in vitro studies of sperm-mucus interaction. The results suggest that a single tablet of levonorgestrel 30 μg, or norethisterone 350 μg, was effective in preventing sperm migration in the cervical mucus about 12 hours later. This suggests that the progestogen-only pill may be effective as a ‘morning before pill’.

A critical review of the physiological importance and analysis of sperm movement in mammals

Abstract: The identification of human sperm hyperactivated motility has potential importance in sperm function tests, as well as in quality control assays and in reproductive toxicology investigations. However, relatively little is known about this phenomenon and the variety of definitions used for hyperactivation has led to a great deal of confusion as to its occurrence and physiological relevance. This presentation is a critical review of a number of aspects of hyperactivated motility, including its identification and potential role(s) in mammalian fertilization. The initial sections of the review consider the mechanisms involved in the development and maintenance of mammalian sperm motility, and the structural and functional changes in spermatozoa which occur during transport through the female reproductive tract. The methods available for the quantification of aspects of sperm movement are also discussed, with an historical overview of sperm movement analysis.

Hyperactivated Motility in Sperm

Abstract: Contents Hyperactivation is a movement pattern seen in sperm at the site and time of fertilization in mammals. It may be critical to the success of fertilization, because it enhances the ability of sperm to detach from the wall of the oviduct, to move around in the labyrinthine lumen of the oviduct, to penetrate mucous substances and, finally, to penetrate the zona pellucida of the oocyte. The movement of hyperactivated sperm appears different under different physical conditions and in different species, but basically it involves an increase in flagellar bend amplitude and, usually, beat asymmetry. Presumably, a signal or signals exist in the oviduct to initiate hyperactivation at the appropriate time; however, none has yet been identified with certainty. While the signal transduction cascade regulating hyperactivation remains to be completely described, it is clear that calcium ions interact with the axoneme of the flagellum to switch on hyperactivation. Although hyperactivation often occurs during the process of capacitation, the two events are regulated by somewhat different pathways.

Predictive value of normal sperm morphology in intrauterine insemination (IUI): a structured literature review

Abstract: The aim of the study was to conduct a structured review of the literature published on the use of normal sperm morphology, as an indicator of male fertility potential in intrauterine insemination (IUI) programmes. Published literature in which normal sperm morphology was used to predict pregnancy outcome in IUI during the period 1984-1998 was reviewed. In total, 421 articles were identified via Medline searches. Eighteen provided data that could be tabulated and analysed. Eight of the analysed studies provided sufficient data for statistical analysis, six studies used the Tygerberg 'strict' criteria, and two the WHO guidelines (1987, 1992). A meta-analysis of the six studies in the strict morphology group yielded a risk difference (RD) between the pregnancy rates achieved in the patients below and above the 4% strict criteria threshold of -0.07 (95% CI: -0.11 to 4.03; P<0.001). The WHO criteria group (1987, 1992) had insufficient data to be analysed. Meta-analysis showed a significant improvement in pregnancy rate above 4% threshold for strict criteria. Accurate evaluation of normal sperm morphology results should be an integral part of evaluating the male factor.

Declining gonadal function in elderly men

Abstract: Ageing in men is accompanied by a progressive decline of gonadal function with, in particular, a decline of total and free testosterone (T) plasma levels resulting in a significant proportion of elderly men over age 60 years presenting with subnormal T levels compared with the levels in young adults. A great interindividual variation in T levels is observed in elderly men, a variability explained in part by physiological variables and differences in life style, while associated acute or chronic diseases may accentuate the age-related decline of T levels. The progressive decrease of plasma T levels has been shown to result from both primary testicular changes and altered neuroendocrine regulation of Leydig cell function. At present, little is known about the clinical relevance of the relative hypoandrogenism of elderly men and there is an urgent need for more longitudinal studies, which may clarify a possible role of decreased T levels in the modulation of the clinical consequences of ageing in men. In view of the lack of relevant controlled clinical trials having careful assessment of the risks and benefits of androgen replacement therapy in elderly men, this treatment should be reserved for selected patients with clinically and biochemically manifest hypogonadism, after careful screening for contraindications.