Thirty-six infertile couples underwent treatment by in-vitro fertilization. In 16 couples (group 1) the male partner was positive for antisperm antibodies measured by direct mixed antiglobulin reaction, direct immunobead test, and serum and/or seminal plasma tray agglutination test. In 20 couples (group 2) the men had no such antibodies. Men with poor sperm motility were excluded. The female partners had no antisperm antibodies, and in the controls (group 2) infertility was due to a known female factor. The fertilization rate in couples without antisperm antibodies (group 2) was 72.7% compared to 50.5% when the men had antibodies. However, the pregnancy rate per embryo transfer was not significantly different in the two groups (46.1% in group 1, 33.3% in group 2). This indicates that antisperm antibodies in the male interfere with sperm--egg fusion and subsequent fertilization but once fertilization has occurred, the pregnancy rate remains the same.

The shedding pattern of the protozoan parasite, Blastocystis hominis, is investigated in man and in experimental animal infections. The shedding pattern of the vacuolar and cystic forms of Blastocystis hominis in infected individuals have been shown in the present study to be irregular. The study shows that there is marked fluctuation in the shedding of the parasite from day to day, varying from as high as 17 to 0 per x40 microscopic field. The cystic stages when estimated in 8 Blastocystis-infected individuals ranged from as high as 7.4x10(5) cysts per gram of stool to 0. The shedding of cystic and vacuolar forms observed over a period of 20 days in experimentally-infected Wistar rats were not only shown to be irregular but the amount varied from host to host. The study has important diagnostic implications in that the stool samples must be collected more than once from patients showing clinical signs and symptoms to eliminate the cause of it to Blastocystis. The study also shows that there are asymptomatic individuals who pass a large amount of cysts as such individuals should be treated to prevent transmission to others.

No abstract

In recent years, a growing number of reports have suggested that the protozoan parasite, Blastocystis hominis (Brumpt 1912), is a pathogenic cause of diarrhoea. It is imperative, however, that more studies are conducted on the various human isolates of the parasite before incriminating it is a pathogen. In our laboratory we maintain human and animal isolates of Blastocystis using the monophasic medium Iscove's Modi®ed Dulbecco Medium (IMDM) as established by Ho et al. (1993), but maintaining continuous cultures is tedious, time consuming and expensive, and the parasites may be prone to genetic drift. There is therefore a need to cryopreserve these isolates before biochemical, molecular and other biological studies can be undertaken. However, very little is known about the cryopreservation of this parasite.The cryopreservation protocol described by Zierdt (1991), who used dimethylsulphoxide (DMSO) to cryopreserve Blastocystis, demanded extreme care, especially during the process of slow cooling and the subsequent maintenance of parasites in liquid nitrogen. In our previous study (Suresh et al., in press), we showed that the cryoprotective ability of glycerol and mannitol to preserve Blastocystis was enhanced when DMSO was added. We used a protocol which was simpler than that described by Zierdt (1991), but the parasite recovery from this cryopreservation medium upon reculture was low, despite an initially high parasite concentration (200´10 6 ml). The original culture medium had to be supplemented with 20% horse serum to successfully recover cryopreserved parasites after deep freezing.The present paper reports for the ®rst time a protocol for the cryopreservation of Blastocystis using fetal calf serum. The medium was prepared by adding 3.5 ml fetal calf serum (Gibco) to 7.5 ml glycerol and 89 ml minimum essential medium (MEM). The fetal calf serum used was non-heat-inactivated serum. The medium was then dispensed into 20-ml universal bottles and stored at A20°C until use.An axenic culture of B. hominis (isolate C), previously obtained from a Blastocystis-infected patient was continuously maintained in IMDM (Gibco) with 10% horse serum in anaerobic chambers at 37°C (Ho et al. 1993). Parasites, mostly vacuolar forms from anaerobic cultures of axenic isolate C, were centrifuged and the sediments containing the parasites were pooled. The concentration was made up to 50´10 6 , 100´10 6 and 200´10 6 of vacuolar forms in IMDM.Twenty preparations of each parasite concentration were placed in 2-ml cryovials (Nunc) containing the above-mentioned medium and were then allowed to stand at room temperature for 30 min. They were then placed in a polystyrene box and transferred to a A20°C freezer for 2 h. Polystyrene boxes containing these cryovials were then stored at A70°C overnight before transfer to liquid nitrogen for storage.Batches of cryovials were maintained for 2 and 8 weeks in liquid nitrogen and then thawed at 37°C in a water bath for 1.5±2 min. The cryovial contents were quickly transferred under sterile conditions t...

No abstract