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PubMed1999

Internal defenses of the snail Biomphalaria glabrata.

The three populations of hemocytes and the fixed phagocytes of Biomphalaria glabrata show different affinities for the following injected foreign materials: ferritin, horseradish peroxidase, zymosan particles, latex beads, and live bacteria. Ferritin and horseradish peroxidase, which are internalized by micropinocytosis, induce a moderate activation of hemocytes. Particles trigger a strong activation that consists of mobilization of the cytoskeleton, with formation of pseudopodia and filopodia and modifications of the plasma membrane that enable hemocytes to adhere together, as in encapsulations. Phagocytosis of zymosan and live bacteria induces alterations in mitochondria that may reflect changes in the respiratory activity. Phagocytosis of particles follows different processes: fixed phagocytes ingest latex beads of two different sizes according to the "zipper model", which implies sequential binding between phagocyte receptors and opsonized ligands; zymosan particles are ingested by medium-size hemocytes by a variant of the zipper model in which a limited close contact between cell and particle resembles focal contacts in cell spreading; bacteria or large latex beads are ingested by large hemocytes without apparent close contact following a "trigger model" which resembles macropinocytosis.

Animals↗
PubMed1999

Internal defenses of the snail Biomphalaria glabrata.

Injection of foreign particles (zymosan, latex beads, living bacteria) and substances (ferritine, horseradish peroxidase) in Biomphalaria glabrata induces the rapid appearance of tubular double-helical filaments in the hemolymph. This rapid induction may be due to the polymerization of precursor proteins of the hemolymph. Tubular helical filaments are also observed in normal snails, especially in the hemal spaces of the proximal kidney; they seem to belong to the extracellular matrix and form bundles of a few parallel units associated with fine fibrils. Hemocytes adhere to these bundles by means of the filopodia tip or by small areas of the cell surface; consequently, they may become temporarily sedentary in the hemal spaces. The deposition of helical filaments seems increased in ageing snails and in snails parasitized by Echinostoma caproni.

Animals↗
PubMed1983

Identification of antigenically distinct hemocyte subpopulations in Biomphalaria glabrata (Gastropoda) using monoclonal antibodies to surface membrane markers.

Five monoclonal antibodies (mABs) against surface antigens on circulating, glass-adherent hemocytes of the snail, Biomphalaria glabrata, were produced by somatic cell hybridization methods. Two mABs (IID2.6-Bg and IID4.8-Bg) are pan-hemocytic, reacting uniformly with epitopes shared by all adherent hemocytes. Determinants recognized by these mABs also are present in soluble form and appear to be associated with a hemoglobin-depleted ultracentrifuged fraction of snail hemolymph. Hybridoma-derived mABs IIC6.8-Bg and VB10.3-Bg recognize hemocyte surface epitopes expressed by only 50-60% of the adherent cell population. These mABs also are reactive with soluble hemolymph antigens but apparently recognize determinants which are different from the IID2.6-Bg and IID4.8-Bg reactive sites. Another antigenically distinct hemocyte subpopulation is recognized by mAB IID7.1-Bg. Epitopes that are reactive with this mAB differ from the previously described determinants by their asymmetrical distribution on the surface of positive cells and the absence of soluble antigenic components in hemolymph. Furthermore, unlike the other mABs, the prevalence of hemocytes staining with IID7.1-Bg antibodies differed between two strains of B. glabrata. Results of this study clearly demonstrate that circulating B. glabrata hemocytes, consisting of a single, predominant population of adherent cells, is composed of several distinct antigenic subpopulations based on the specific binding of anti-hemocyte mAB probes. Our successful application of hybridoma techniques to the study of molluscan hemocyte surface antigens underscores further the great potential usefulness of this method in analysing the molecular basis of hemocyte reactivity.

Animals↗
PubMed1984

An ultrastructural study of the effect of parasitism by larval Schistosoma mansoni on the calcium reserves of the host, Biomphalaria glabrata.

The tissues of Biomphalaria glabrata contain three types of calcium cells which can be differentiated by their location and the size and number of their contained corpuscles. X-ray analysis has confirmed the presence of calcium and magnesium in the corpuscles. Molluscs containing the larval stages of Schistosoma mansoni at 40 days post infection show disintegration of the calcareous corpuscles in Type-A calcium cells and erosion of the inner surface of the shell.

Animals↗
PubMed1976

A light and electron microscope study on oogenesis in the freshwater pulmonate snail Biomphalaria glabrata.

In the freshwater snail Biomphalaria glabrata the formation and composition of yolk granules and the role of the follicle cells were studied by histochemical and electron microscopical techniques. The rough endoplasmic reticulum and the Golgi apparatus appeared to be involved in yolk formation, which is a continuous process throughout oogenesis. From the very beginning of yolk formation two main types of yolk granules were distinguished morphologically. However, with histochemical and enzyme cytochemical methods no differences were observed between these types. The granules acquire lysosomal enzymes after oviposition, indicating that their main function is probably digestion of perivitelline fluid, which contains nutrients for the developing embryo. Yolk formation and the activity of the follicle cells were studied in successive stages of oogenesis by quantitative electron microscopy. The data strongly suggest that the follicle cells are involved in the formation of the follicular cavity and hence in the ovulation process.

Animals↗
PubMed1977

Spermatogenesis and the role of Sertoli cells in the freshwater snail Biomphalaria glabrata.

The various stages of spermatogenesis and the Sertoli cells of Biomphalaria glabrata were studied with histochemical and electron microscope techniques. During spermatogenesis a manchette of microtubules is formed around the nucleus and the mid-piece of the spermatids. This manchette becomes helically coiled and probably plays an important role in the spiralisation of the nucleus and of the mitochondrial sheath. During spermatogenesis so-called chromatoid bodies (CB) occur, which consist of arginine-rich proteins. These CB disintegrate during the early spermatid stage. The results suggest that the CB are either involved in histone transition or in the formation of microtubules. The remaining cytoplasm of the spermatids is phagocytised by the Sertoli cells. Apparently this process of phagocytosis is an important part of the mechanism of spermiation. Morphological measurements of the Sertoli cells showed that the relative volume of most organelles decrease during spermatogenesis, indicating a general decrease in cell activity. Possible functions of the Sertoli cells, such as transportation and nutrition of spermatogenic cells and hormone production, are discussed. It is concluded on the basis of the histochemical and ultrastructural observations that the Sertoli cells are involved in the nutrition of spermatogenic cells. It seems unlikely that they are hormone producing cells.

Animals↗
PubMed1977

[The ketone bodies in the hemolymph of Biomphalaria glabrata under starvation and infection with Schistosoma mansoni (author's transl)].

The metabolism of the snail Biomphalaria glabrata stressed by five days' starvation as well as by infection with Schistosoma mansoni was examined with regard to the metabolism of ketone bodies. Previous studies in the metabolism of this host--parasite relationship always resulted in changes in the same direction with starvation as well as with infection. Contrary to that the concentration of acetoacetate and beta-hydroxybutyrate measured in the hemolymph decreased significantly with starvation but increased significantly with infection. The following problems concerning the ketone body metabolism are discussed: on the one hand the differences between infected and starved snails, and on the other hand the differences between the snails and the mammals as well as in the invertebrates so far investigated.

Acetoacetates↗
PubMed1977

Experimental double infection of Biomphalaria glabrata snails with Angiostrongylus cantonensis and Schistosoma mansoni.

Two groups of Biomphalaria glabrata snails primarily infected with Angiostrongylus contonensis were secondarily exposed to infection with Schistosoma mansoni. To investigate any anatagonistic effect of the first infection on a superimposed one and to compare to singly and non-infected snails, a series of experiments was undertaken in which snails were individually exposed, variously, to 1,000 and 2,000 first-stage larvae of A. cantonensis and then to 5 and 10 miracidia of S. mansoni 1 day and 3 weeks later. Snails became infected with S. mansoni in both groups of snails with double infections and shed cercariae after the same incubation period as in the singly infected groups. The number of snails shedding cercariae simultaneously was similar in single and double infection groups during the first two weeks of shedding, after which this number decreased somewhat in doubly infected groups. Snails with double infection showed higher cumulative mortality rates than in snail groups with single infection with either A. cantonensis or S. mansoni. Therefore, initial infection of B. glabrata with A. cantonensis produced no inhibitory or retarding effect on subsequent infection of snails with S. mansoni.

Animals↗
PubMed1975

The effect of some biological and physical factors on infection of Biomphalaria glabrata with Angiostrongylus cantonensis.

Several biological and physical factors which may influence infection of Biomphalaria glabrata snails with the first stage larvae of Angiostrongylus cantonensis were studied. These factors were: the size of snails, the number of first stage larvae to which snails were exposed, the age of larvae, individual exposure compared with mass exposure of snails, the length of exposure period and the effect of temperature and light. The results showed that young snails, 2 mm in diameter, became infected with significantly smaller numbers of third stage larvae than larger snails (4, 8, 12 and 16 mm). No significant differences in the intensity of infection were evident between the larger size groups. The number of third stage larvae recovered from snails was directly related to the number of first stage larvae to which the snails were exposed. The mean percentage recovery per snail was more or less constant regardless of the infective dose. First stage larvae showed a slight reduction in their survival rate within 7 and 4 days, at 24 degrees C and 26 degrees C respectively, after which a sharp decrease in their survival rate occurred. However, the infectivity of larvae was progressively reduced from the second day at these two temperatures. The mean intensity of infection in snails was independent of whether the infection was by mass or individual exposure. The average number of first stage larvae entering a snail was greatest during the first half hour of exposure, this decreased considerably during the second half hour, and thereafter the number of larvae which entered a snail was low. It was concluded that 26 degrees C was the optimal temperature for infection and that the presence or absence of light had no effect on the infection.

Animals↗
PubMed1981

Genetic variation among laboratory strains of the planorbid snail Biomphalaria glabrata.

Isozymes of laboratory strains of Biomphalaria glabrata have been studied by starch gel electrophoresis. Methods are outlined for adaptation of this technique to the genetic study of these snails. Twenty-eight presumptive gene loci have been identified. Twelve invariant enzymes were observed. Sixteen loci displayed some polymorphism within or among the strains. These polymorphisms were generally widespread among strains from Brazil, Puerto Rico, St. Lucia, and the Dominican Republic. A high degree of intrastrain polymorphism was noted even in some presumably inbred laboratory strains. Crosses between strains were used to demonstrate the genetic basis for the patterns observed at 9 of the 16 polymorphic loci.

Animals↗
PubMed1976

Alcohol dehydrogenase of Biomphalaria glabrata (Molusca: Pulmonata): polymorphism, genetic analysis, and interspecific variations.

Alcohol dehydrogenase of Biomphalaria glabrata has been characterized by electrophoresis, substrate specificities, and other physiochemical means. It exists as a multiple molecular form possessing a minimum number of three bands in ovotestis, five in digestive gland, and six in albumen gland. Each organ shows characteristic electrophoretic forms which differ in substrate specificities and the response to the organomercurial inhibitor p-hydroxymercuribenzoate. Mercaptoethanol treatment has no effect on any electrophoretic form. Genetic analyses of the electrophoretic variants show that three different loci are responsible for the synthesis of the various electrophoretic forms observed in this species. Different species vary in their electrophoretic patterns. A possible role of alcohol dehydrogenase isozymes in the phylogenetic relationship among three species, B. glabrata, B. tenagophila, and B. straminea, has been discussed.

Alcohol Oxidoreductases↗
PubMed1985

Genetics of Biomphalaria glabrata: linkage analysis of genes for pigmentation, enzymes, and resistance to Schistosoma mansoni.

The snail, Biomphalaria glabrata, is a major intermediate host of the human blood fluke, Schistosoma mansoni, in the Americas. The inheritance and linkage relationships of a gene enabling adult snails to resist infection by a Puerto Rican strain of the parasite were analyzed using two laboratory stocks that differed in susceptibility, pigmentation, and five electrophoretically detectable enzyme markers. Segregation ratios in second-generation intraspecific hybrids between susceptible (M-stock) and resistant (10-R2-stock) snails indicate that the susceptibility gene is not linked to the enzyme (ACON-1, ACP, EST-2, PEP-2, PGD) or pigmentation loci studied. These seven loci assort independently of one another. Observed rates of infection among F1 and F2 progeny are consistent with Richards' finding that adult susceptibility to the PR-1 strain of S. mansoni is controlled by a single locus with resistance dominant. No association between allozymes of acid phosphatase and snail susceptibility to PR-1 was seen in the snail-parasite combinations studied.

Animals↗
PubMed1987

Intermediate host (Biomphalaria alexandrina) antigens partly protect against subcutaneous infections with cercariae of Schistosoma mansoni but are ineffective in infections by percutaneous invasion.

Mice were immunized against hepatopancreas homogenate of Biomphalaria alexandrina, using Al(OH)3 as adjuvant, and challenged by subcutaneous (s.c.) injection of Schistosoma mansoni cercariae, percutaneous invasion of cercariae and intravenous (i.v.) injection of mechanically prepared schistosomula of different ages. Significantly reduced (about 50%) numbers of adult S. mansoni were found 42 days after challenge in immunized animals infected by s.c. injection of cercariae. Protective effects were detectable as early as 4 days after infection when the numbers of schistosomules in the lungs were reduced in immunized animals. However, immunized animals lacked protective immunity against S. mansoni when infected via the percutaneous route with cercariae or by i.v. injection of schistosomules of different ages. Experiments show that immunization of hosts against intermediate host antigens does not protect against S. mansoni infection via the natural route.

Animals↗
PubMed1981

Schistosoma mansoni: effect on growth, fertility, and development of distal male organs in Biomphalaria glabrata exposed to miracidia at different ages.

Growth, egg laying rate, and mortality of Biomphalaria glabrata (Portorican strain), maintained in groups of two, after exposure at different ages (1, 2, 4, 6, 8 weeks) to three miracidia each of Schistosoma mansoni (Liberian strain) were determined. The findings in infected snails were compared with those in exposed but uninfected (negative) and in unexposed snails. Younger snails were infected at higher rates, and these showed a significantly increased mortality. Young infected snails grew much slower than negative or unexposed snails; older infected snails grew at about the same rate as negative or control snails. A growth acceleration was not observed in parasitized animals. When prepatency to a high extent passed before sexual maturity, infected snails did not lay any eggs. In later infections the numbers of eggs dropped below those in healthy snails by the second week after exposure. Snails were dissected 15 weeks after exposure. Development of male reproductive organs (prostate gland, preputium plus penis sheath), in relation to shell diameter, was retarded particularly in animals infected before sexual maturity and highly retarded in growth. In larger animals the organs reached approximately their definitive size. Parasitized snails were partially deformed by an enlargement of their shell apertures on the right side.

Aging↗
PubMed1981

Experimental epidemiology of schistosomiasis. II. Prepatency of Schistosoma mansoni in Biomphalaria glabrata at diurnally fluctuating temperatures.

The basic hyperbolic relationship established between constant water temperatures and the length of the prepatent period in the snail was tested as diurnally fluctuating temperatures, stimulating natural conditions. Diurnal temperature variations are generally summed up by S. mansoni according to the time-temperature product and are independent of the shape of the temperature curve. Using a simple hyperbolic formula, the time of prepatency can be calculated for temperatures ranging from 16 degrees C to 32 degrees C. The developmental rate (reciprocal of the prepatency period) within this range is a linear function of the mean environmental temperature. Biomphalaria glabrata and S. mansoni survive well at temperature peaks as high as 40.5 degrees C or as low as 11.5 degrees C, if they are given as part of a diurnal sinusoidal or trapezoidal temperature programme. At fluctuating temperatures decreasing to low values of about 11 degrees to 14 degrees C, however, the parasite's development was up to 27% faster than predicted. Apparently the development in the low temperature range does not follow the basic hyperbolic relationship, and even below the so-called "developmental null point" of 14.2 degrees C some development of S. mansoni takes place. For practical purposes, an empirical compensation of the deviation at low temperatures is proposed. Instead of the real mean of the diurnal temperature cycle, the mean between 14.2 degrees C and the daily maximum can be used as the basis for calculation, regardless of the time with temperatures below 14.2 degrees C.

Animals↗
PubMed1984

Effects of temperature on the larval development of Angiostrongylus cantonensis in the intermediate host, Biomphalaria glabrata.

The effects of temperature on the larval development of Angiostrongylus cantonensis in Biomphalaria glabrata were studied under controlled conditions. When B. glabrata were maintained at different, constant temperatures, the first-stage larvae developed to third-stage larvae between 20 degrees and 31 degrees C. The velocity of development to the third-stage in the snail depended on the relationship, Y = -0.1281 + 0.0081 X (Y velocity of development; X rearing temperature). The "threshold of development" was 15.8 degrees C and the thermal constant 123 degree-days. It is concluded that there might be a possibility of A. cantonensis spreading to temperate regions in the world, if, in addition to the temperature, other factors allowed the completion of the life cycle of this worm.

Angiostrongylus↗
PubMed1986

Quantification of parasite development in the host-parasite system Biomphalaria glabrata and Schistosoma mansoni.

The visceral mass of Biomphalaria glabrata uninfected or infected with Schistosoma mansoni was serially sectioned. The amount of hepatopancreas tissue and of parasite tissue was quantified. In pool-infected snails the volume of the whole visceral mass increased very significantly until week 6 and then decreased. Due to the growing parasites the volume of the visceral mass in infected snails was at most times higher when compared with uninfected snails of the same dimensions. Two weeks p.i. there was a permanent and significant increase of parasite tissue until week 6. During this time the amount of hepatopancreas tissue still increased. From this time onwards till week 12 the proportion of parasite tissue remained rather constant, indicating a kind of regulation, whereas the hepatopancreas tissue decreased to about one-third of the volume found in uninfected snails of the same shell diameter. Compared with infections by a single miracidium there was a significant increase in parasite tissue after infection with two miracidia. Infections with more miracidia (5, 10, and 20) gave no significant further increase. This also demonstrates a kind of regulation. Mortality rate, growth rate and egg production were studied during an infection period of 12 weeks.

Animals↗
PubMed1989

Alterations in hemolymph components in Biomphalaria glabrata during long-term infection with Schistosoma mansoni.

Total protein, hemoglobin, glucose, and urea concentrations in hemolymph of Biomphalaria glabrata were studied during a 12-week infection of the snails with Schistosoma mansoni. The results suggest an equilibrium between host and parasite metabolism, which is reached after about 6 weeks of infection. During the period studied, the protein spectrum of infected snails showed no difference in quality compared with that of noninfected snails; all fractions were present, and no additional fractions appeared. Only the lipoprotein fraction increased fourfold in the 1st week of infection, decreasing during the 2nd week to concentrations that were also found in noninfected individuals. No further significant alterations could be detected until week 12 postinfection (PI).

Animals↗