A prospective clinical trial investigating the efficacy of a method of preparing subpopulations of antibody-free spermatozoa from the ejaculates of antibody-positive patients.

Couples undergoing in vitro fertilization treatment (IVF) were invited to take part in a controlled prospective clinical trial. The aim was to determine the effect on the fertilization rate of a technique devised to obtain an antibody-free preparation of spermatozoa from an antibody-positive ejaculate. Oocytes collected during IVF were allocated into one of two groups, ensuring that quality and maturity were comparable in each. One group, the control, was inseminated with Percoll-processed spermatozoa. The experimental group was inseminated with identical numbers of Percoll-processed spermatozoa which had been treated to obtain an antibody-free preparation. The treatment was found to have no beneficial effect on the fertilization rate at IVF. Laboratory studies were also performed on the ejaculates of antibody-positive volunteers to determine whether this treatment led to any effects, whether beneficial or detrimental, on sperm function. Membrane integrity was found to be unaffected, as was the percentage of spermatozoa undergoing the spontaneous acrosome reaction following overnight incubation. The percentage of spermatozoa undergoing the ionophore-induced acrosome reaction following treatment, however, was higher than that of the controls. The results of sperm-zona pellucida binding studies were equivocal. The findings indicated that the treatment procedure could not be justified for use in IVF, but may be beneficial for intrauterine insemination.

Investigation of the association between the presence of cytoplasmic residues on the human sperm midpiece and defective sperm function.

Defective sperm function has been identified as one of the most common causes of human infertility. The aim of this investigation was to identify whether the presence of retained cytoplasm on the human sperm midpiece is associated with defective sperm function. Statistical analysis of data demonstrated a strong negative correlation between the presence of residual cytoplasm on the midpiece of spermatozoa in the inseminate and fertilization rate during IVF. Significant negative correlations were also identified between the percentage of spermatozoa in the ejaculate bearing cytoplasmic residues and (i) spermatozoa having membrane integrity and (ii) sperm concentration. A highly significant positive correlation was also revealed between the percentage of spermatozoa in the ejaculate with membrane integrity and the percentage of motile spermatozoa. These correlations suggest that retained cytoplasm is a cause of subfertility. Measurements of the percentage of spermatozoa bearing residual cytoplasm in the IVF inseminate could provide the basis for a simple predictive test before IVF.

Fine structure mapping and complementation studies of the metD methionine transport system in Salmonella typhimurium.

A fine structure deletion map of the metD region of the chromosome of Salmonella typhimurium responsible for a high-affinity methionine transport system has been constructed. Complementation tests involving the introduction of metD+DNA contained in a pUC8 vector into metD strains indicated the presence of four complementation groups in the metD region. This suggested that the methionine system belongs to the osmotic shock-sensitive class of transport system, and therefore should possess a periplasmic methionine-binding protein and several membrane proteins. But a deletion mutation covering all known metD point mutations did not affect the level of a methionine binding activity in osmotic shock fluids, suggesting either that the deletion did not extend into the gene encoding the binding protein, or that the binding activity is not associated with the metD system. Possible reasons for the failure to isolate mutations in the gene for the binding protein are discussed.

Selection of an antibody-free population of spermatozoa from semen samples of men suffering from immunological infertility.

Ejaculates from infertile men with significant levels of antisperm antibodies were processed in vitro, in an attempt to prepare sub-populations of antibody-free spermatozoa. Semen samples were processed on a discontinuous Percoll gradient and the resultant sperm preparation was treated with immunobeads. Selection of antibody-free spermatozoa was achieved: less than 10% of the resulting spermatozoa showed binding to immunobeads after treatment in all cases investigated. The overnight survival of these antibody-free spermatozoa was comparable to, or better than, that of the untreated antibody-coated sample obtained from the Percoll gradient. The fertility potential of these treated spermatozoa is currently under investigation.