Schistosoma mansoni: chemoreception through n-acetyl-d-galactosamine-containing receptors in females offers insight into increased severity of schistosomiasis in individuals with blood group A.

The role of exposed surface carbohydrates in chemoreception in Schistosoma mansoni females was investigated in vitro. Sexually mature females were treated with peanut (PNA), soybean (SBA) or wheat germ (WGA) agglutinin, and their migration in response to excretory-secretory (ES) products of males was measured in a bioassay system. Random distribution of untreated and lectin-treated females was similar (p=>0.05). PNA-treated females were unresponsive for 1.0 h, after which they exhibited slight repulsion to ES products. SBA-treated females did not respond to ES products for 3.0 h. WGA-treated females were unresponsive for 1.5h, after which they exhibited slight attraction to male ES products. Attempts were made to restore chemoattraction by using specific sugar inhibitors of lectin-binding; chemoattraction was best restored in n-acetyl-d-galactosamine (GalNAc)-treated females. These data suggest that GalNAc-containing receptors, possibly GP50, the major SBA-binding schistosome glycan, mediate chemoreception in schistosome females. These findings may explain the observed differences in morbidity between individuals with different blood groups. Individuals with blood group B or O may afford partial protection because of their natural anti-A or by mounting a more efficient antibody response directed against GalNAc-containing structures shared by blood group A red blood cells.

Pellioditis pellio: Substituted phenolic compounds as chemoattractants.

Vanillin, vanillic acid, and other related compounds are chemoattractants either for nematodes or arthropods. We tested vanillin, vanillic acid, and 2,4-dihydroxybenzaldehyde in an in vitro bioassay system for their ability to attractPellioditis pellio males and females. Females were not attracted to any of the three compounds tested. Males responded to vanillin and vanillic acid, but not to 2,4-dihydroxybenzaldehyde. Males responded to vanillin and vanillic acid when these compounds were present at 10(-5) M concentration. Vanillin at 10(-3) and 10(-7) M concentrations was not attractive.

Schistosoma mansoni: a chemoattractive factor released by males and its receptor in females.

Chemoattraction between developing (23- to 28-day-old) and adult (10- to 12-week-old) Schistosoma mansoni males and females has been described previously. We report here on in vitro attraction of mature worms to released products of worms of the opposite sex. In the absence of a stimulus worms migrated randomly and did not show any preference in their orientation. Males were not significantly attracted to released products of females. Females exhibited greatest attraction to released products of males, and some attraction to the lipid fraction of released products of males. The aqueous fraction of male-released products slightly repelled females. Prior exposure to released products of males rendered females unresponsive to subsequent exposure, suggesting receptor saturation. These findings have important potential implications for the control of schistosomiasis by intercepting attraction and mating between males and females.

Chemoattraction inPellioditis pellio (Nematoda: Secernentia) in the presence and absence of barriers.

Pellioditis pellio (Nematoda) adults showed heterosexual chemoattraction and female homosexual chemoattraction in an in vitro bioassay without barriers. Male-to-female heterosexual, but no homosexual chemoattraction, was observed whenM r 25,000 pore size dialysis tube chimneys (barriers) were used to restrain female attractor worms. Less attraction was seen whenM r 12,000 pore size barriers were used. The results suggest the presence of at least two types of chemoattractant for this species and that at least one heterosexual chemoattractant is betweenM r 12,000 and 25,000.

Schistosoma mansoni: female-dependent lipid secretion in males and corresponding changes in lipase activity.

Eight to 10-week old Schistosoma mansoni males from unisexual infections were examined histochemically for neutral lipids and lipase activity. In addition, in situ fixed pairs were examined for lipase activity. Neutral lipid content of males from unisexual infections was variable and lipase activity was minimal. Following 1 h incubation at 37 degrees C in Earle's balanced salt solution (EBSS) in which females had previously been maintained for 1 h, males showed moderate increase in lipid content and diminished lipase activity. In contrast, unisexually developed males incubated for 1 h with females from bisexual infections showed increased lipid accumulation and lipase activity. Unisexually developed males incubated for 1 h in EBSS showed both lipid accumulation and release from the dorsal surface. Worm-pairs fixed in situ showed greater lipase activity in females than in males. These observations suggest that a factor(s) released by females affects the physiology of males.

Schistosoma mansoni: onset of chemoattraction in developing worms.

Heterosexual chemoattraction studies on juvenile worms showed that 20- and 21-day-old worms do not attract each other, whereas 23- and 28-day-old worms are attracted to each other and pair with worms of the opposite sex. This onset of chemoattraction in vitro corresponds to the time when worms begin pairing in vivo. The ability of single worms to locate each other and mate is presumably mediated by chemoreceptors.

Schistosoma mansoni: characterization of clones maintained by the microsurgical transplantation of sporocysts.

Five male and 5 female clones of Schistosoma mansoni were established and maintained for 3 yr by the serial microsurgical transplantation of sporocysts from infected to uninfected Biomphalaria glabrata snails. The clones were initially derived from 10 randomly selected snails with monomiracidial infections. Clones were characterized by several criteria, including their infectivities for mice and snails, their cercarial outputs, and their ability to produce immunity in mice. The mean infectivities of individual clones in mice ranged from 26 to 44%, and were highly consistent within each clone. The infectivities of cloned sporocysts in snails ranged from 44 to 100% and were also highly consistent within clones. Mean cercarial outputs from individual clones ranged from 450 to 4,300 per snail. In mice, clones differed significantly from each other in their ability to immunize and in their susceptibility to immunity. Each clone was unique and did not appear to differ with time or subpassaging through snails, suggesting that the differences had a genetic basis.

Intra- and interspecific chemoattraction studies onSchistosoma mansoni, S. japonicum, andS. haematobium in the absence of barriers.

Heterosexual intra- and interspecific chemoattraction studies were done in polycarbonate chambers without barriers using 8- to 10-week-oldSchistosoma mansoni from mice, 10-week-oldSchistosoma japonicum from hamsters, and 14-week-oldSchistosoma haematobium from hamsters. Experiments were done for up to 4 hr at 37 °C in a humidified incubator. Single worms were not attracted to decoys or heat-killed worms. Heterosexual intraspecific and interspecific attraction was significant at all time points with all combinations. No clear differences were apparent between intra- and interspecific attraction. Differences between same and differentS. japonicum orS. haematobium pairs were not significant at any time point.

Schistosome behavior in vitro.

Schistosome adults attract each other in vitro and the attraction is chemically mediated. InSchistosoma mansoni adults, excretory-secretory (ES) products of worms of one sex attract worms of the opposite sex, and at least the lipophilic fraction is attractive. Intra- and interspecific attraction occurs inSchistosoma mansoni, S. japonicum, andS. haematobium adults. Current knowledge of schistosome behavior in vitro is reviewed.

Chemical communication in adult schistosomes.

Lipids released bySchistosoma mansoni adult males attract females in vitro. Lipid release is modulated by the presence of other worms. AlthoughS. mansoni males release lipid when paired with females, the release is enhanced when they are separated.S. japonicum adults release more free sterols when incubated individually than when incubated together. Similarly, individually incubatedS. haematobium males release more free sterols than when incubated in groups. However,S. haematobium females incubated in groups release more free fatty acids than do equal numbers of males or pairs incubated in groups. There is evidence thatS. mansoni adult females concomitantly accumulate and release cholesterol in the absence of an exogenous supply, although de novo synthesis of cholesterol in schistosomes has not yet been demonstrated. Schistosomula and adult schistosomes incorporate exogenous lipids. Lipids are incorporated chiefly through the tegument. Cholesterol is transferred between males and females.

Schistosoma haematobium: neutral lipid composition and release by adults maintained in vitro.

Thin-layer chromatographic analyses showed that the major neutral lipid fractions of whole-worm extracts of male and female adult Schistosoma haematobium were free sterols, triacylglycerols and sterol esters. Worm-free incubates of adult worm-pairs contained free sterols only. The major fractions of worm-free incubates from separated worms were free fatty acids and free sterols; traces of triacylglycerols and sterol esters were also detected. Females incubated in a group of ten released more free fatty acids than ten incubated singly. Males incubated singly released more free sterols than a similar number incubated in a group. Females released more free sterols than males.

The uptake, localization and transfer of [4-14C]cholesterol in Schistosoma mansoni males and females maintained in vitro.

Schistosoma mansoni male and female adults incorporated [4-14C]cholesterol in vitro. Males incorporated about three times more cholesterol than females. The major sites of cholesterol deposition in males were the tegument and parenchyma. The tegument and vitelline glands were the primary sites of cholesterol accumulation in females. In males, dorsal tegument showed greater cholesterol uptake than ventral tegument. Radiolabelled males and females transferred cholesterol to unlabelled members of the opposite sex.

Schistosoma mansoni: long-term maintenance of clones by microsurgical transplantation of sporocysts.

Schistosoma mansoni sporocysts originally derived from monomiracidially infected Biomphalaria glabrata snails were serially transplanted into the cephalopedal sinus of anesthetized snails by the microsurgical implantation of fragments of parasitized hepatopancreas and ovotestis. Three to six passages each of five male and five female clones were maintained for as long as 2.0 years. Of the recipient snails which survived surgery, 87% released cercariae, usually beginning 5-7 weeks after surgery. The percentage of snails which released cercariae increased with successive passages. The mean survival time of surgically infected snails after cercarial emergence began was 9.2 +/- 0.5 weeks, nearly the same as that of miracidially infected snails. Longevities of snails infected with male or female clones were similar. Recipient snail size and age did not influence cloning success. Beginning 5 weeks from the onset of cercarial emergence large numbers of cercariae (a mean of 3900/snail from male clones and 1300/snail from females) were obtained during each shedding period. These results clearly demonstrate that the microsurgical transplantation of sporocysts is a practical means of maintaining and expanding populations of genetically homogeneous schistosomes (clones).

Schistosoma mansoni: adult worm chemoattraction with barriers of specific molecular weight exclusions.

Chemoattraction studies were done with Schistosoma mansoni adults from mice. To test for attraction or repulsion, some worm pairs were separated mechanically and the individuals placed in polycarbonate chambers. Experiments were done at 37 C and chambers contained dialysis tube chimneys. In all cases, heterosexual attraction occurred when one worm, but not two worms, were placed in the chimneys. Unperforated chimneys with specific molecular weight (Mr) exclusions were compared with perforated chimneys to study heterosexual attraction. Attraction was similar in designs using perforated chimneys and those with 50,000 and 12,000 Mr exclusions, but none was seen in chimney designs with 1000 Mr exclusions.

Densitometric thin-layer chromatographic analyses of cholesterol inSchistosoma mansoni (Trematoda) adults and their excretory-secretory products.

Densitometric thin-layer Chromatographic analysis was used to quantitate cholesterol in 6-week-old male, female, and worm-pairs ofSchistosoma mansoni, and their excretory-secretory (E-S) products. Males extracted immediately after removal from mice had 1.2-1.5 µg cholesterol/worm, whereas those incubated for 0.5 hr in Earle's balanced solution at 37 ° C contained 0.8-1.5 µg cholesterol/ worm. Females extracted immediately after removal from hosts contained 130 ng cholesterol/worm. Females accumulated considerable cholesterol during incubation and had 420 ng cholesterol/ worm at 0.5 hr. Worm-pairs extracted at 0 hr had 1.9-2.8 µg cholesterol/pair and 1.2-1.5 µg cholesterol/ pair when extracted at 0.5 hr postincubation. Following incubation for 0.5 hr, males released 12-28 ng cholesterol/ worm (average 21), females released 8-13 ng cholesterol/ worm (average 11), and worm-pairs released 3-13 ng cholesterol/worm-pair (average 8).