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At least 1,711 records · Page 95Linked to original sources
PubMed2001

Molecular studies of the molluscan response to digenean infection.

A classical body of knowledge regarding molluscan immunobiology has developed over the years that indicates an important role for both soluble hemolymph proteins and hemocytes in internal defense. The incorporation of powerful molecular approaches into the toolkit of the molluscan immunobiologist holds considerable promise for allowing a more precise description of the molecules and processes involved. Recent discoveries indicate that the molluscan internal defense system has components that are simultaneously both tantalizingly similar to, and different from, molecules functioning in a defense context in other phyla. Study of molecular components of the internal defense systems of molluscs promises to be a rewarding and surprising field.

Animals↗
PubMed1975

The development of the primitive epithelium and true tegument in the cercaria of Schistosoma mansoni.

The formation of the final cercarial tegument of Schistosoma mansoni is preceded by that of a so-called primitive epithelium. The primitive epithelium is derived from the tegument of the daughter sporocyst. The final cercarial tegument is formed from peripherally located somatic cells of the cercarial embryo, which expand and coalesce beneath the primitive epithelium. The primitive epithelium degenerates and disappears. The ultrastructure of both epithelia in the course of the development of the cercaria is described in detail. Possible functions are discussed.

Animals↗
PubMed1988

Chemical signals of fish skin for the attachment response of Acanthostomum brauni cercariae.

The chemical signals of the skin surface of fish, which stimulate the attachment responses of Acanthostomum brauni cercariae, were identified by offering chemicals and fish-skin extracts in agarose substrates to the cercariae. Smaller molecules such as amino acids, fatty acids, monosaccharides, electrolytes, urea, and carbonate solutions did not stimulate attachments, but hyaluronic acid had some effects. Bovine submaxillary glycoproteins had a strong stimulating activity that disappeared after neuraminidase digestion. The stimulating components of the skin surface of fish were hydrophilic substances with molecular weights of more than 10,000. They were sensitive to neuraminidase digestion but not to hyaluronidase digestion and thus can be identified as glycoproteins. A. brauni cercariae respond only to the complete glycoprotein molecules and not to their monosaccharide components. The known attachment triggers of other cercariae are small molecules. Large glycoproteins as host signals for A. brauni cercariae may be an adaptation to muddy habitats, where various substances with low molecular weights may interfere with the host identification.

Amino Acids↗
PubMed1987

Late development and fertility of adult worms derived from gamma-irradiated first-stage larvae of Angiostrongylus cantonensis.

Effects of gamma ray irradiation on the first-stage larvae of Angiostrongylus cantonensis were studied. Compared to the non-treated controls, infection of rats with third-stage larvae which developed from irradiated first-stage larvae resulted in reduced recovery rates of adults. There was also a change in the male-female adult worm ratio and a reduction in larval output per female in relation to increasing irradiation dosage. Morphological changes in the adults were noted.

Angiostrongylus↗
PubMed1979

[Sequence of reconversion of the sporocysts of Schistosoma mansoni producing cercariae, to the production of new generations of sporocysts (author's transl)].

During the life cycle of Schistosoma mansoni the production of sporocysts of a higher order than secondary is a normal mode of larval multiplication which intervenes in asexual reproduction of the parasite. The sequence of reconversion of sporocysts producing cercariae to those producing sporocysts III, IV, etc... can be divided into three principal steps: (1) cessation of cercariae production; (2) degeneration of cercariae contained in the sporocyst, and (3) production of the new generation of sporocysts. Degeneration of intrasporocystic larval material seems to be an indispensable step for the new orientation of production. The signifance of this method os multiplication in the ecology of transmission is discussed.

Animals↗
PubMed1985

[Morpho-anatomic and functional sectorization of Schistosoma mansoni daughter sporocysts].

During the larval development of S. mansoni in the snail host, morpho-anatomic changes occur in the daughter sporocyst by a sectorization of this larval stage. Three sectors can be distinguished: an anterior zone with a well-differentiated birth pore; dilated zones containing the developing cercariae; constricted zones without cercarial embryo. The photonic and electronic microscopical study shows variations in the tegumental structure of these sectors. This evolution of the daughter sporocysts is discussed in relation with the dynamics of larval stages and the replication process of sporocysts.

Animals↗
PubMed1986

Infectivity and development of the gamma-irradiated first stage larvae of Angiostrongylus cantonensis.

Effects of gamma-ray irradiation on the first-stage larvae of Angiostrongylus cantonensis were studied. There was a significant reduction in the infectivity of the 10,000 R-irradiated larvae to intermediate host snails compared to other groups. In the final host infection, both the worm populations and worm body length of irradiated groups differed markedly from those of the non-irradiated control.

Angiostrongylus↗
PubMed1986

Comparison of two Egyptian strains of Schistosoma mansoni in hamsters.

In human infection with Schistosoma mansoni from Beni-Suef, the eggs were encountered more frequently in the urine of patients than in infection with S. mansoni from Giza, where eggs were passed into the stool. A comparative study of the two strains of S. mansoni from Beni-Suef and Giza has been carried out in golden hamster. Consistent strain differences were observed. The Beni-Suef strain proved to have lower worm recovery and different egg distribution patterns in tissues of infected hamsters. Worms of both sexes of this strain were larger in size and required a longer period to reach maturity. Hence, the prepatent period was prolonged. Significant differences between the two strains were also noted in the number of eggs per worm. A lower mortality rate and a longer survival time were encountered in hamsters infected with the Beni-Suef strain.

Animals↗
PubMed1995

Immunoelectron microscopical localization of a circulating antigen in the excretory system of Schistosoma mansoni. Ultrastructural localization studies of the excretory system of S. mansoni.

In this study the excretory system of Schistosoma mansoni was ultrastructurally examined with a recently described monoclonal antibody (mAb) against a circulating antigen. In previous studies this mAb was found to have affinity for the excretory system. Strong immunoreactivity was found on the flagella of the flame cells and of the collecting ducts throughout the worm. The eggshell and the space between the miracidium and the eggshell showed strong reactivity with a declining gradient towards the exterior, suggesting a secretion process. In cercariae, immunoreactivity was restricted to the tegument, whereas in schistosomula the labeling pattern resembled that of the adult worm, demonstrating positive reactivity of the flame cells and no immunostaining of the tegument. This stage-dependent differential expression of different antigens in the excretory system and in the tegument could suggest a maturation process of the excretory system.

Animals↗
PubMed1993

Immune defense and eosinophilia in congenitally IgE-deficient SJA/9 mice infected with Angiostrongylus costaricensis.

The roles of IgE in protective immunity and eosinophilia in Angiostrongylus costaricensis infection were examined by comparing IgE-deficient SJA/9 mice and IgE-producing SJL/J mice. In primary infection, mean total IgE levels increased to a maximum of 390 ng/ml, which was more than 10 times greater than the 29 ng/ml measured preinfection in SJL/J mice but less than the 10 ng/ml found in SJA/9 mice throughout the experiment. Immune defense as determined by recovery of adult worms and eosinophilia were similar in SJL/J and SJA/9 mice. Protective immunity was induced by infection with A. costaricensis followed by treatment with levamisole for 4-6 days postinfection. After the challenge infection, the numbers of adult worms and eosinophils in SJA/9 mice were not significantly different from those in SJL/J mice. Anti-A. costaricensis IgE antibody was not detected in either strain of mice during the experiment. These results indicate that A. costaricensis infection induced the production of IgE not specific for parasite antigens in IgE-producing mice. Potentiated nonspecific IgE played no significant role in immune defense and eosinophilia.

Angiostrongylus↗
PubMed1995

Time course of the effect of praziquantel on Schistosoma mansoni attachment in vitro: comparison with its effects on worm length and motility.

We report herein that praziquantel inhibits the capacity of adult male Schistosoma mansoni to attach to the bottom of a glass dish and produces a diminution of worm length and motility, acting under a similar concentration and time dependency. After removal of 1 microM praziquantel from the medium, the worms progressively recuperated their initial length and motility without recovering their attachment capability. The absence of calcium or presence of 1 microM verapamil did not change the praziquantel-induced effect on worm attachment, causing only a transient decrease in worm length and motility. The present data indicate that the diminution of motility induced by praziquantel results from the progressive contraction of the longitudinal musculature of the worm. In contrast, the loss of attachment should not be causally related to the contraction of the worm since these two praziquantel-induced effects have distinct patterns of response under some experimental conditions.

Animals↗