A study of the relationship between the energy contents of Schistosoma mansoni cercariae and their death during penetration of mammalian host skin

Molecular cloning and characterization of Schistosoma japonicum aldose reductase

Antioxidant defense is an essential mechanism for schistosomes to cope with damage from host immune-generated reactive oxygen species. The evaluation of the effects of aldose reductase, an important enzyme that may be involved in this system, has long been neglected. In the present study, aldose reductase of Schistosoma japonicum (SjAR) was cloned and characterized. The activity of SjAR was assessed in vitro and was suppressed by the reported inhibitor, epalrestat. RT-PCR analysis revealed that SjAR was expressed at each of the development stages analyzed with increased levels in cercariae. The results also showed that SjAR was expressed at higher levels in adult male worms than in adult female worms. Indirect enzyme-linked immunosorbent assay and western blot analysis indicated that the purified recombinant SjAR (rSjAR) protein displayed a significant level of antigenicity. Immunolocalization analysis revealed that SjAR was mainly distributed in the gynecophoral canal of adult male worms. BALB/c mice immunized with rSjAR induced a 32.91 % worm reduction compared to the adjuvant group (P < 0.01). Moreover, a 28.27 % reduction in egg development in the liver (P > 0.05) and a 42.75 % reduction in egg development in the fecal samples (P < 0.05) were also observed. These results suggested that SjAR may be a potential new drug target or vaccine candidate for schistosomes.

The relationship between the age of Schistosoma mansoni cercariae and their ability to penetrate and infect the mammalian host

The ability of the cercariae of Schistosoma mansoni to penetrate the tails of mice was shown to remain constant throughout their lives. However, their capacity to establish themselves and then reach maturity decreased as they aged. The abdominal route of penetration produced consistently higher maturation rates than the tail route. Significantly different maturation rates were obtained by modifying the standard tail infection technique. Evidence is presented that age-related mortality of schistosomula occurs within 24 h of penetration and may be associated with the exhaustion of energy reserves during the penetration of the stratum corneum. The relationship of this age-related mortality to 'mass mortality' is discussed.

An examination of the skin phase of schistosome migration using a hamster cheek pouch preparation

A living hamster cheek pouch preparation has been used to study the skin phase of schistosomulum migration. Between 0 and 16 h post-exposure schistosomula become increasingly difficult to see and lateral movement in the skin ceases. Up to 50 h post-exposure they remain poorly visible. They lie in fluid-filled lacunae within the epidermis, external to the basement membrane. The first schistosomula enter the dermis from 40 h post-exposure, approximately half having done so by 52.5 h. Coincidentally, they can be more easily distinguished from surrounding tissue. Up to 91% of original penetrants have been observed alive in pouch tissue at 65 h post-exposure. Since only 26% eventually mature in the hepatic portal system there would appear to be considerable attrition subsequent to the skin phase of migration. The mean diameter of venules penetrated was 22.7 micrometers and the mean time taken to penetrate was 8.01 h. The majority of schistosomula left the pouch between 60 and 80 h post-exposure.