Robyn C. Johnston

Bio: Robyn C. Johnston is an academic researcher from Prince Henry's Institute of Medical Research. The author has contributed to research in topics: Artificial insemination & Sperm. The author has an hindex of 4, co-authored 4 publications receiving 155 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.

Sperm preparation for ART.

Abstract: The onset of clinical assisted reproduction, a quarter of a century ago, required the isolation of motile spermatozoa. As the indication of assisted reproduction shifted from mere gynaecological indications to andrological indications during the years, this urged andrological research to understand the physiology of male germ cell better and develop more sophisticated techniques to separate functional spermatozoa from those that are immotile, have poor morphology or are not capable to fertilize oocytes. Initially, starting from simple washing of spermatozoa, separation techniques, based on different principles like migration, filtration or density gradient centrifugation evolved. The most simple and cheapest is the conventional swim-up procedure. A more sophisticated and most gentle migration method is migration-sedimentation. However, its yield is relatively small and the technique is therefore normally only limited to ejaculates with a high number of motile spermatozoa. Recently, however, the method was also successfully used to isolate spermatozoa for intracytoplasmic sperm injection (ICSI). Sperm separation methods that yield a higher number of motile spermatozoa are glass wool filtration or density gradient centrifugation with different media. Since Percoll® as a density medium was removed from the market in 1996 for clinical use in the human because of its risk of contamination with endotoxins, other media like IxaPrep®, Nycodenz, SilSelect®, PureSperm® or Isolate® were developed in order to replace Percoll®. Today, an array of different methods is available and the selection depends on the quality of the ejaculates, which also includes production of reactive oxygen species (ROS) by spermatozoa and leukocytes. Ejaculates with ROS production should not be separated by means of conventional swim-up, as this can severely damage the spermatozoa. In order to protect the male germ cells from the influence of ROS and to stimulate their motility to increase the yield, a number of substances can be added to the ejaculate or the separation medium. Caffeine, pentoxifylline and 2-deoxyadenosine are substances that were used to stimulate motility. Recent approaches to stimulate spermatozoa include bicarbonate, metal chelators or platelet-activating factor (PAF). While the use of PAF already resulted in pregnancies in intrauterine insemination, the suitability of the other substances for the clinical use still needs to be tested. Finally, the isolation of functional spermatozoa from highly viscous ejaculates is a special challenge and can be performed enzymatically to liquefy the ejaculate. The older method, by which the ejaculate is forcefully aspirated through a narrow-gauge needle, should be abandoned as it can severely damage spermatozoa, thus resulting in immotile sperm.

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.