Showing papers in "Journal of Parasitology in 1980"

Macrophagelike hemocytes of resistant biomphalaria glabrata are cytotoxic for sporocysts of schistosoma mansoni in vitro

Abstract: When Schistosoma mansoni miracidia penetrate resistant individuals of the intermediate host snail Biomphalaria glabrata, the sporocyst is encapsulated by hemocytes (macrophagelike cells of the snail circulation) and killed. In our in vitro model the same fate requires only sporocysts and snail hemolymph. However, when cultured in plasma alone (cell-free hemolymph), sporocysts remain viable for more than 3 days, regardless of whether the plasma is from susceptible or resistant snails. When hemolymph is used from susceptible snails, the sporocysts retain a normal healthy appearance. Furthermore, the parasite appears to express an offensive response to the hemocytes of susceptible snails. Ultrastructural study reveals that resistant-strain hemocytes destroy the parasite tegument; within 24 hr the sporocyst is damaged severely throughout. This cell-mediated, internal, defensive response of an invertebrate host closely resembles antibody-dependent, cell-mediated damage to schistosomula in mammalian hosts.

Some corrections of coccidian (Apicomplexa: Protozoa) nomenclature.

Abstract: The following nomenclatural corrections and changes are introduced for the coccidia. NEW SPECIES: Cryptosporidium rhesi from the rhesus monkey Macaca mulatta; Cryptosporidium serpentis from the snakes Elaphe guttata, Elapha subocularis, Crotalus horridus, and Sanzinia madagascarensis; Eimeria perazae from the lizard Cnemidophorus l. lemniscatus; and Eimeria tarichae from the salamander Taricha toirosa. NEW COMBINATIONS: Orcheobius carinii for Cariniella carinii from the frog Leptodactylus ocellatus; Schellackia iguanae for Lainsonia iguanae from the iguana Iguana iguana; Schellackia weinbergi for Haemogregarina weinbergi from the lizard Tupinambis nigropunctatus; Dorisa harpia for Dorisiella harpia from the bat Harpiocephalus harpia lasyurus; Barrouxia labbei for Echinospora labbei from the centipedes Lithobius mutabilis and L. pyrenaicus; and Barrouxia ventricosa for Echinospora ventricosa from the centipede Lithobius hexodus. The generic names Lainsonia and Gordonella are synonymized with Schellackia; Echinospora with Barrouxia; and Cariniella with Orcheobius.

Identification of the structural component in the cyst wall of Entamoeba invadens.

Abstract: Cyst walls of Entamoeba invadens were isolated and purified. Both whole cysts and purified walls appeared intensely fluorescent when stained with Calcofluor white M2R. Examination of positive replicas of purified cyst walls with the electron microscope revealed the presence of a microfibrillar structure. The main sugars detected in acid hydrolysates from the walls were hexosamines. X-ray diffraction analysis of purified cyst walls demonstrated that the crystalline polymer present was chitin.

Experimental infection of the squirrel monkey (saimiri sciureus) with plasmodium falciparum

Abstract: Seventy-six squirrel monkeys, Saimiri sciureus, caught in Guyana and French Guiana, were examined for their susceptibility to infection with a strain of Plasmodium falciparum. Twenty-nine serial transfers were performed, both in splenectomized and intact animals. After a period of "adaptation," the strain became more virulent for the squirrel monkey and high parasitemias were obtained regularly in splenectomized animals. Frequently, such infections led to the death of infected animals. In intact squirrel monkeys, a consistent parasitemia was observed in most animals, but with a less regular pattern and a lower level of infection. Cultivation of infected erythrocytes from squirrel monkeys and human erythrocytes confirmed that the parasite had kept its infectivity for human cells after a long period of serial syringe-transfers in the squirrel monkey, and that the virulence for the Saimiri remained unchanged after 1-mo, in vitro progagation in human erythrocytes. All erythrocytic forms of the schizogonic cycle were observed in the bloodstream, and there was a certain synchronicity of the cycle. Gametocytes were not detected in infected animals nor in in vitro cultures derived from the parasitized squirrel monkey blood. Our results indicate that the squirrel monkey can be a useful host in the laboratory for studies on P. falciparum, and it may become more important as the supply of other species of monkeys diminishes.

Trypanosoma cruzi (chagas) (protozoa: kinetoplastida) in invertebrate, reservoir, and human hosts of the lower rio grande valley of texas

Abstract: Small trypomastigotes, morphologically identical to Trypanosoma cruzi, were observed in the feces of 19 of 84 (22.6%) triatomid insects (Triatoma gerstaekeri and Triatoma sanguisuga) examined in south Texas in 1977 to 1978. In the summer, an estimated 247 Triatoma sp. per hectare occurred in wooded areas of Cameron Co. and 384 per hectare in similar areas of Hidalgo Co., Texas. Trypanosoma cruzi was cultured from or observed in the blood of seven of 30 Neotoma micropus (23.3%) and from possibly, previously unreported rodent hosts: Perognathus hispidus (4 of 25, 16.7%); Liomys irrorattus (1 of 11, 9.0%); Onychomys leucogaster (1 of 9, 11.1%). The sera of 382 other wild and domestic mammals were examined for antibody to T. cruzi by indirect hemagglutination assay (IHA). Fifty-two (13.6%) had positive titers of 1:128 or greater. Indirect hemagglutination assay was performed on 500 randomly se- lected, local human residents. Twelve (2.4%) positive titers of 1:128 or greater were identified and four of the 12 (0.8%) were confirmed IHA and/or CF (complement fixation) positive by the Center for Disease Control (CDC), Atlanta, Georgia. Four of the 12 positive individuals submitted to culture and microscopic examination of follow-up blood samples, all of which were negative. Trypanosoma cruzi incidence in invertebrate (22.6%) and rodent hosts (9.0-23.3%) was similar to pre- vious studies in south Texas, other areas of the USA, and many areas of South America where it is endemic in humans. The apparent occurrence in local humans (2.4%) was higher than similar studies in the USA. These data confirm the presence of T. cruzi in this area and indicate the possibility of human infection.

Biology and pathogenesis of the coccidium Eimeria funduli infecting killifishes.

Abstract: Epizootics of Eimeria funduli involved estuarine killifishes (Fundulus grandis, F. pulvereus, F. similis, and F. heteroclitus) in Mississippi, Alabama, and Virginia. All of more than 500 specimens examined of F. grandis from Mississippi during 1977 though 1979 had infections, regardless of age, sex, or season collected. Oocysts occurred primarily in the liver and pancreas, replacing up to 85% of both those organs. Infrequent sites of infection were fatty tissue of the body cavity, ovary, intestine, and caudal peduncle. Living fish did not discharge oocysts. Eimeria funduli is the first known eimerian to require a second host. To complete the life cycle, an infective stage in the grass shrimp Palaemonetes pugio had to be eaten. In 6-mo-old killifish reared in the laboratory at 24 C, young schizonts were first observed in hepatic and pancreatic cells 5 days postfeeding, followed by first generation merzoites by day 10, differentiation of sexual stages during days 15 to 20, fertilization between days 19 and 26, sporoblasts from days 25 to 30, and sporozoites about day 60. Unique sporopodia developed on sporocysts by day 35 when still unsporulated. Temperatures of 7 to 10 C irreversibly halted schizogony. Both schizogony and sporogony progressed slower as age of host increased. When infective shrimp in doses ranging from 1 to 10% of a fish's body weight were eaten, the level of intensity of resulting infections did not differ significantly. Pathogenesis followed a specific sequence, with the host response apparently unable to contend with extensive infections as seen typically in nature and in our experiments. Premunition was indicated. When administered Monensin orally, infected fish exhibited a reduction in oocysts by 50 to 70% within 20 days as compared with untreated fish. Furthermore, infected killifish exclusively on a diet of TetraMin for 3 mo completely lost their infections.

Ultrastructural comparison of cysts and zoites of Toxoplasma gondii, Sarcocystis muris, and Hammondia hammondi in skeletal muscle of mice.

Abstract: Cysts of Hammondia hammondi and Toxoplasma gondii in skeletal muscle of mice were compared at the ultrastructural level with cysts of Sarcocystis muris. Cysts of H. hammondi and T. gondii were similar, except for the size of the cystozoite, which was about 4 to 5 /im in H. hammondi, but about 7 to 8 ,tm in T. gondii. Both cysts were limited by a relatively smooth, but intensely folded, primary cyst wall, under which a zone of granular ground substance was always present. No secondary cyst walls were observed around the parasitized fiber. Both cysts differed from Sarcocystis cysts, which possessed a thick primary cyst wall, septa, and metrocytes that were found to persist even in old cysts. Septa were not found in cysts of H. hammondi or T. gondii, probably because of the uniformly close packing of the parasites inside the cysts and the absence of metrocytes. All these findings indicate that one can distinguish Toxoplasma and Hammondia from Sarcocystis on a morphological basis, but that there are no significant morphologic differences between the cysts of Hammondia and Toxoplasma. The generic distinction is based on the distribution of zoites and cysts in organs in intermediate and definitive hosts, and by the distinctive cycles. Hammondia hammondi, described by Frenkel and Dubey (1975), is an intestinal coccidium of cats. The coccidium forms cysts, similar to those of Sarcosporidia and Toxoplasma gondii, in striated muscles of intermediate hosts such as mice. Isolations have been reported from the central United States, Hawaii (Wallace, 1975), and Germany (Rommel and Seyerl, 1976). Hammondia hammondi forms cysts principally in skeletal muscle, and its life cycle is obligatorily heteroxenous. Thus, cats can be infected only with tissue cysts of H. hammondi from the intermediate hosts, and not with oocysts from its own feces; mice can be infected only with sporozoites, and not with zoites from the tissue cysts of mice. Toxoplasma gondii, on the other hand, forms cysts with about equal frequency in nervous tissue, skeletal muscle, heart muscle, and commonly, in smooth muscle and various other tissues, and its life cycle may be homoxenous or heteroxenous. Received for publication 8 December 1978. * Institut fur Zoologie II der Universitat Dusseldorf, D-4000 Dusseldorf, Federal Republic of Germany. Research supported by the Deutsche Forschungsgemeinschaft. t Department of Pathology and Oncology, The University of Kansas Medical Center, Kansas City, Kansas 66103. Research supported by a Humboldt Foundation Senior Scientist Award and Research Grant AI-07489 from the National Institute of Allergy and Infectious Diseases. The cycles of Hammondia and the Sarcosporidia are superficially similar. However, young H. hammondi cysts are infectious, whereas sarcocysts must mature before they infect the final host. Hammondia hammondi is distinguished by the occurrence of asexual multiplication in the gut of cats, the final host, preceding gamogony, whereas in Sarcocystis species, the cystozoites develop directly into gametocytes. Furthermore, in the genus Hamm ndia, oocysts are shed unsporulated, like those of T. gondii, whereas sarcosporidian oocysts always develop sporocysts with sporozoites prior to being shed. Apart from these important biological differences, all three genera form intracellular cysts in striated muscles of mice, and these cysts look similar by light microscopy. Therefore, we wanted to study and compare skeletal muscle cysts of H. hammondi by means of electron microscopy, and to compare them with cysts of a Sarcocystis species and of T. gondii (Senaud and Mehlhor, 1974; Mehlhorn et al., 1976; Sheffield et al., 1977). MATERIALS AND METHODS

Trypanosoma cruzi-induced suppression of the primary immune response in murine cell cultures to t-cell-dependent and -independent antigens

Abstract: In vitro antisheep erythrocyte (SRBC) and antitrinitrophenyl (TNP) antibody responses of spleen cells obtained from C57BL/6 mice infected with Trypanosoma cruzi were reduced as early as 6 days postinfection and not detectable after 18 days of infection. Lymph node cells had normal antibody responses to SRBC and TNP in vitro until the 11th day of infection, after which responses were diminished. By day 31 of infection, lymph node cells were unresponsive to both SRBC and TNP in vitro. Not only were the antibody responses of spleen and lymph node cells to T-cell-dependent and -independent an- tigens progressively reduced as the period of infection increased, but in addition, the effect of lymphoid cell density and antigen dose on antibody production underwent several sequential changes. As the infection advanced, low densities of cultured lymphoid cells and low doses of antigen were ineffective in eliciting a detectable immune response, whereas high densities of lymphoid cells and high doses of antigen resulted in responses approximately equivalent to that observed with normal cells under the same conditions. Results of cell mixing studies have shown that a plastic-adherent, macrophagelike cell plays a major role in the suppressed humoral responses observed in this host-parasite system. A number of viral, bacterial, protozoal, and metazoal infections of mammals effect states of nonspecific immunosuppression in their hosts. In some of these host-parasite relation-

The paraxial structure of the flagellum of trypanosomatidae

Abstract: The flagella of several Trypanosomatidae (Trypanosoma cruzi, Herpetomonas samuelpes- soai, Leptomonas samueli, Herpetomonas megaseliae, and Crithidia harmosa) were studied. Besides the axoneme, they have a filamentous, latticelike structure, the paraxial or paraflagellar rod. This structure was not observed in the flagellum of the intracellular spheromastigote form of Trypanosoma cruzi, but it appeared when the transformation of epimastigote and trypomastigote stages occurred. Cross sections of the flagella show that the paraxial structure maintains a fixed position relative to the axonemal microtubules, being localized in a region comprised between doublets 4 and 7. Flagella of T. cruzi and H. samuelpessoai were isolated using the detergent lubrol PX. Most of them did not have a flagellar membrane. However, the paraxial structure remained associated with the axoneme. By negative staining, short projections were seen connecting the paraxial structure to the axonemal microtubules. The paraxial structure did not stain with phosphotungstic acid as occurs with the peripheral doublet micro- tubules, but it is formed by microfilaments longitudinally oriented in relation to the axoneme crossed in two directions by oblique filaments which make an angle of 45? with the longitudinal ones.

Methods for detecting Babesia microti infection in wild rodents.

Abstract: We compared various methods for detecting Babesia microti infection in white-footed mice (Peromyscus leucopus) captured in enzootic regions of Massachusetts. The most sensitive method tested involved inoculating blood from wild rodents into hamsters. One month postinoculation proved to be the optimal time for microscopically examining blood of inoculated hamsters. With this method, as few as 300 organisms produced patent infection. Prior splenectomy of hamsters did not increase susceptibility to infection. For direct study of captured animals, a Giemsa-stained, thin blood-film prepared from the ani- mal's tail was the most convenient method tested. However, this method detected only 61% of infections identified by hamster inoculation.

Contracaecum multipapillatum (=C. robustum) from fishes and birds in the northern Gulf of Mexico.

Abstract: of the sediment in 1 cc of sterile saline. The results were expressed per mouse. White cell counts for 10 noninfected mice in the second group were 10.5 (+2.04) x 106 per animal, whereas the count in the third group of control mice was 6.4 (+3.5) x 106 leukocytes per mouse. The respective coefficients of variation were 0.19 and 0.55. This indicates a recovery of 64% higher cell counts and a reproducibility 2.8 times greater for the dye method. The mean volume of peritoneal fluid in noninfected mice was 0.28 (?0.08) cc. In 10 infected mice examined by the technique described, the data were 17.1 (?4.1) x 106 white cells, 56.0 (?12.01) x 106 trophozoites, and 1.09 (?0.18) cc of peritoneal exudate per mouse. The dye method provides an accurate assessment of cell and parasite number in the peritoneal cavity by the use of Evans blue as a dilution stain marker. Spectrophotometric absorption curve for the stain showed good absorption at 610 nm. At this wavelength, the yellow color of the FCS was minimal. Evans blue had no noticeable effect on the viability of parasites under the conditions employed. This technique also provides good resolution of differences in cell number and liquid volume in the peritoneum between infected and noninfected mice owing to the marked development of ascites in mice inoculated with T. gondii intraperitoneally. The ability to obtain cell and parasite counts for each infected mouse has an advantage in host-parasite studies by providing a more direct measure of the infection itself than parameters based on number per unit volume. The injected volume (V) may be altered as desired without change in the results, because it is substituted in the equation for the new value. Varying amounts may be especially useful in the evaluation of T. gondii infection in mice of different ages or between different rodent species. The present method has been applied successfully in experiments with a large number of mice. Calculations can be performed with a single desk-top calculator program, cutting down the time of repetitive calculations.

Endogenous development of the swine coccidium, Isospora suis Biester 1934.

Abstract: The endogenous development of Isospora suis Biester 1934 is described in piglets inoculated with 150,000 or 200,000 sporulated oocysts. Endogenous stages developed within villous epithelial cells throughout the small intestine. Two distinct types of meronts were seen in tissue sections. Type I meronts, which were seen at 3 days postinoculation, were binucleate, elongate, and 10.5 by 4.7 micron. They produced two to 14 Type I merozoites per parasitophorous vacuole. Type I merozoites were 10.0 by 3.6 micron. They produced two to 14 Type I merozoites per parasitophorous vacuole. Type I merozoites were 10.0 by 3.6 micron. Type II meronts, which were seen at 4 days postinoculation, were elongate and contained three to 12 nuclei. Type II meronts were 11.4 by 5.3 micron, and one to four were found per parasitophorous vacuole. Type II merozoites were 6.3 by 2.1 micron, and three to 16 were found per parasitophorous vacuole. The peak of asexual development occurred 4 days postinoculation. Fully developed microgamonts, macrogamonts, and oocysts were seen 5 days postinoculation. The prepatent period was 5 days, and the patent period was 5 to 8 days. No extraintestinal stages were seen.

Light and electron microscopic study on developmental stages of Babesia canis within the gut of the tick Dermacentor reticulatus.

Abstract: The initial developmental stages of Babesia canis within the gut of the vector tick, Derma- centor reticulatus, were studied by means of light and electron microscopy. Large quantities of varying "spiky-rayed" stages and a few ovoid stages without any protrusions were observed after lysis of the engorged canine erythrocytes. The transformation of spherical erythrocytic stages into "spiky-rayed" forms was initiated inside the intact erythrocytes. The significance of all developmental stages in a hypothetical life cycle of Babesia species is discussed. In 1906 Koch described so-called "Strah- lenk6rper" (ray bodies) in the gut of female ticks as developing stages of the genera Ba- besia and Theileria. In the following years, however, many contradictory conclusions were published (for review, see Riek, 1964) concerning the absence or presence of these stages in the life cycle of piroplasms. How- ever, Schein et al. (1975) and Mehlhorn and Schein (1976) confirmed Koch's observations

The Chesson strain of Plasmodium vivax in Aotus monkeys and anopheline mosquitoes.

Abstract: The Chesson strain of Plasmodium vivax was studied in Aotus trivirgatus monkeys. Parasitemia in intact and splenectomized animals was similar to that reported for this strain in man. Comparative infectivity studies with mosquitoes fed on infected monkeys indicated that the most susceptible was Anopheles freeborni, followed by An. balabacensis, An. culicifacies, An. maculatus, An. atroparvus, An. stephensi, An. quadrimaculatus, and An. albimanus. Transmissions via sporozoites from An. maculatus was demonstrated on two occasions; prepatent periods were 30 and 32 days.

Parasitemia and tissue infection in sheep fed Toxoplasma gondii oocysts.

Abstract: The distribution of Toxoplasma gondii in blood and other tissues of nine adult sheep experimentally infected with T. gondii oocysts was studied by inoculation of mice with ovine tissues. Parasitemia was detected in five sheep 6 to 11 days after inoculation (DAI) and lasting usually for 1 to 2 days. Toxoplasma gondii was isolated from numerous internal organs of five sheep killed between 7 and 28 DAI and from eight organs of a sheep killed 64 DAI. Of the three sheep killed 117, 118, and 119 DAI, T. gondii was isolated only from brain, heart, diaphragm, skeletal muscle, and intestine. Skeletal muscle was infected in all sheep. More mice became infected after inoculation with chronically infected tissues digested in 1% trypsin than undigested tissues. Results indicate that skeletal muscle and brain should be used for parasitological surveys in sheep.

Properties and drug sensitivity of adenosine triphosphatases from Schistosoma mansoni.

Abstract: The hydrolysis of ATP was measured in the presence of schistosome homogenates and var- ious cations. The enzyme was stimulated strongly by either Ca2+ or Mg2+. Na+ added to the activation by Ca2+. A minor (17%) component was Na+ + K+ + Mg2+-dependent and ouabain-sensitive. Praziquantel, niridazole, oxamniquine, and hycanthone had no direct effect on the ATPase activity of schistosome homogenates. When schistosomes were pretreated with these drugs in vitro, washed thoroughly, and then homogenized, hycanthone, praziquantel, and oxamniquine caused a reduction in ATPase content of the worms. Niridazole did not share this effect. These results suggest that antischistosomal drugs did not directly inhibit ATPase, but did reduce ATPase in whole worms, possibly by removing or damaging the tegument, which is thought to contain most of the ATPase activity. In vitro ATPase measurements may be a useful indicator of pharmacologic activity of some types of drugs.

Geographic variation in helminth parasites from the digestive tract of Tennessee raccoons, Procyon lotor.

Abstract: The stomachs and intestinal tracts of 253 raccoons, Procyon lotor, were examined for helminth parasites. Sixteen species of helminths were found including eight trematodes, two cestodes, five nematodes, and one acanthocephalan. Fourteen of these helminths are new geographic records for the state of Tennessee. Multivariate statistical techniques were used to analyze two-state and multistate character sets. Matrices of correlation among characters were computed and the first three principal components were extracted, accounting for 79.7% and 66.5% of the variation in the respective character sets. Three-dimensional projections of Tennessee's eight geographic localities onto two-state and multistate principal components demonstrated that raccoons in western localities were parasitized most heavily by Atriotaenia procyonis. Mesocestoides variabilis, Gnathostoma procyonis, and Pharyngostomoides procyonis. Parallelorchis diglossus, Euparyphium beaveri. Eurytrema procyonis, Euryhelmis squamala, Molineus barbatus, and Macracanthorhynchus ingens were most common to P. lotor from eastern areas.

Injury induced by Trypanosoma congolense adhesion to cell membranes.

Abstract: Trypanosoma congolense binds to erythrocytes and the walls of the microvasculature. Ex- periments were conducted to determine if the attachment of T. congolense, alone or in combination with antitrypanosome antibody, was damaging to host cells. Bovine erythrocytes were labelled with 5'Cr and incubated with T. congolense to promote adhesion. Plasma from the same donor as the red blood cells was added to the erythrocyte-trypanosome aggregates and the release of 51Cr measured. There was a two- to threefold increase in 51Cr release when trypanosomes were lysed by antibody-complement interaction following adhesion to the erythrocyte. The erythrocytes were not damaged by trypanosome binding in the absence of antibody or complement. A similar mechanism may operate in vivo because experiments demonstrated an increased vascular permeability of mesenteric vessels, a site of T. congolense attachment to the microcirculation. These results suggest that the adhesion of T. congolense to host cells, followed by an immune response to the parasite, may damage the infected host by "innocent bystander" mecha- nisms.

Ornithodoros (alectorobius) amblus (Acarina: Ixodoidea: Argasidae): identity, marine bird and human hosts, virus infections, and distribution in Peru.

Abstract: Ornithodoros (Alectorobius) amblus Chamberlin 1920, adults previously were described inadequately. Practically nothing was known regarding the identity, hosts, distribution, and biology of this species. We redescribe both sexes, describe the nymph and larva, and present criteria for differentiating these stages from those of other members of the O. (A.) capensis group in the Western Hemisphere. Samples were collected from 13 localities on the Pacific coast and on offshore islands of Peru. Hosts recorded are the Peruvian Brown Pelican, Peruvian Booby, Blue-footed Booby, Red-legged Cormorant, Guanay Cormorant, and Inca Tern. These birds are not long-distance migrants and more widely distributed species of the O. (A.) capensis group have not been found parasitizing them. The life cycle is characteristic of the O. (A.) capensis group; the first nymphal instar does or does not feed. Humans are attacked eagerly by O. (A.) amblus and suffer afterward from severe inflammation and "incredible" pruritus, and possibly from more severe illness. Viruses infecting this tick are Punta Salinas (Hughes serogroup, family unclassified) and Huacho (Reoviridae, genus Orbivirus, Kemerovo serogroup). Dense tick populations cause breeding birds to desert numerous nests; thus, O. (A.) amblus is economically important to the Peruvian guano industry. Certain spiders and lizards may prey on this tick.

Measurement of cytolytic antibody in experimental Chagas' disease using a terminal radiolabeling procedure.

Abstract: The onset and development of anti-Trypanosoma cruzi cytolytic antibody during the course of infection were examined in two strains of mice that differ in their susceptibility to T. cruzi. The relative amounts of cytolytic antibody in the sera of mice were determined by a terminal radiolabeling procedure that measures the amount of 3H-thymidine incorporatedinto culture-form parasites that survive treatment with antibody and complement. The results showed that low levels of anti-T. cruzi cytolytic antibody developed during the course of infection in mice, and that there was no apparent difference in cytolytic antibody responses during the acute phase of infection in relatively resistant C57BL/6 mice and highly susceptible C3H(He)mice.

In vitro pairing of Echinostoma revolutum (Trematoda) metacercariae and adults, and characterization of worm products involved in chemoattraction.

Abstract: In vitro pairing studies were done on chemically excysted metacercariae and on adults of Echinostoma revolutum maintained in vitro in agar-Locke's petri dish cultures at 39 + 1 C for up to 24 hr. Whereas newly excysted metacercariae did not pair, both immature and mature adults showed signif- icant pairing. Adult echinostomes confined in dialysis sacs emitted excretory-secretory (ES) products which significantly attracted single echinostome adults in vitro. Only the lipophilic fraction of ES products was found to elicit attraction. Preparative TLC analysis of adult echinostomes produced three major bands, as follows: I (phospholipids); II (free sterols); and III (free fatty acids + triglycerides). When tested in vitro, only the free sterol fraction significantly attracted single adult echinostomes. TLC and GLC analyses of free sterols of E. revolutum have indicated that cholesterol is the major free sterol.

Echinostome cercarial penetration and metacercarial encystment as mortality factors for a second intermediate host, Biomphalaria glabrata.

Abstract: Cercarial penetration and metacercarial encystment of Echinostoma liei in Biomphalaria glabrata caused high mortality of juvenile snails (3-8 mm in diameter) after 4 to 6 days of continuous exposure to about 150 cercariae per snail per day Larger snails (10-13 mm) withstood cercarial penetration longer, significant mortality appearing 16 days after exposure Life-table analysis showed that the snail mortality rate per age interval increased with increasing exposure to echinostome penetration Single exposures of 3- and 6-mm snails to 500 cercariae caused 97% mortality for the former and 84% for the latter within 2 days Snails surviving the first 2 days did not suffer further mortality when infected with as many as 488 metacercariae Thus, mortality seems to result from penetration and early stages of encystment, rather than the presence of large numbers of metacercariae in the pericardial region Growth of 3-mm snails exposed to 10 or 100 cercariae and of 6-mm snails to 500 cercariae was significantly less than the growth of unexposed controls after 20 days Cercariae rapidly located the snails, 90% penetrating within 1 hr when individual, 6-mm snails were exposed to 100 cercariae in 5 ml of water The high rate of cercarial penetration needed to cause snail mortality suggests that echinostome pen- etration and encystment will not cause much mortality of snail intermediate hosts in nature unless the density of echinostome cercariae is high For several species of echinostome trema- todes, cercariae released from the first inter- mediate snail host must penetrate another freshwater mollusc Development continues when the cercariae encyst as metacercariae, often localized in the pericardial sac and ad- jacent kidney The range of second interme- diate hosts may include the same species of snail used as the first intermediate host, as well as a broad range of other aquatic mol- luscs Even the same individual snail may be penetrated by cercariae issuing from that host

Characteristics of antischistosomal benzodiazepine binding sites in Schistosoma mansoni.

Abstract: The benzodiazepines, clonazepam and Ro 11-3128, have been identified as antischistosomal drugs (Stohler, 1978). Using (14C) Ro 11-3128 or (3H) clonazepam, we were able to demonstrate that male S. mansoni can specifically bind these labeled drugs. The binding sites on this parasite displayed char- acteristics of saturability and low affinity. The affinity of various benzodiazepines for the binding site on intact schistosomes correlated with their antischistosomal efficacy. Binding was markedly altered by agents known to destroy membrane integrity. Combined with previous studies (Pax et al., 1978), this work sug- gests that a specific, benzodiazepine binding site may be located on the epidermis of male S. mansoni. It has been reported that certain benzodi- azepine derivatives (e.g., clonazepam or Ro 11-3128) are effective antischistosomal com- pounds (Stohler, 1978). It appears that the mode of the antischistosomal action of these compounds may result from their effect upon the musculature of this parasite, because it has been noted that the parasite remains con- tracted and immobile when incubated in the presence of low concentrations of these com- pounds (Pax et al., 1978). Because the effects of these drugs are so rapid and easy to detect, as compared to the action of most antischis- tosomals, we have attempted to identify and characterize the binding site in this parasite which mediates the action of these drugs. Us- ing ('4C) Ro 11-3128 or (3H) clonazepam, we were able to identify a low affinity, benzodi- azepine binding site in intact worms or ho- mogenates of male schistosomes. My results suggest, as determined by criteria established for receptor identification (Bert, 1978), that the Ro 11-3128 binding site in intact schisto- somes may be the receptor that mediates the pharmacological action of these drugs.