Inputs to the hormonal control of egg development in Rhodnius prolixus

This paper re-examines existing data on the environmental inputs governing egg production in Rhodnius prolixus. Feeding has a direct effect on egg production such that the product of the unfed weight of the female times the weight of the blood meal is a good predictor of the number of eggs produced. Mating modifies this input, so that mated females produce more eggs. Egg production is governed by the corpus allatum, and indirect evidence suggests that the number of eggs producted by a female is a function of the length of time that juvenile hormone is secreted by the corpus allatum. The input which determines the times at which the corpus allatum is switched off originates in the stretch induced by the amount of the meal remaining in the crop, modified by the matedness status of the female. The precise nature of the sensors detecting stretch is not yet clear, but the integrity of the dorsal aorta is essential to the transmission of the information. These data are related to the survival strategy for Rhodnius.

Granulomatous hypersensitivity to Schistosoma mansoni egg antigens in human Schistosomiasis: I. Granuloma formation and modulation around polyacrylamide antigen-conjugated beads

We have developed an in vitro model of granuloma formation for the purpose of studying the immunological components of delayed type hypersensitivity granuloma formation in patients infected with Schistosoma mansoni. Our data show that 1) granulomatous hypersensitivity can be studied by examining the cellular reactivity manifested as multiple cell layers surrounding the antigen conjugated beads; 2) this reactivity is a CD4 cell dependent, macrophage dependent, B cell independent response and 3) the in vitro granuloma response is antigenically specific for parasite egg antigens. Studies designed to investigate the immune regulation of granulomatous hypersensitivity using purified populations of either CD4 or CD8 T cells have demonstrated the complexity of cellular interactions in the suppression of granulomatous hypersensitivity. The anti-S. mansoni egg immune responses of individual patients with chronic intestinal schistosomiasis can be classified either as soluble egg antigen (SEA) hypersensitive with maximal granulomatous hypersensitivity or SEA suppressive with activation of the T cell suppressor pathway with effective SEA granuloma modulation. Our data suggest that T cell network interactions are active in the generation of effective granuloma modulation in chronic intestinal schistosomiasis patients.

Extra-tissular Schistosoma mansoni egg granulomata in the peritoneal cavity of mice

The presence of Schistosoma mansoni eggs surrounded by inflammatory cells were detected within the peritoneal cavity of experimentally infected mice. The histological and ultrastructural analysis revealed the predominantly macrophagic composition of these structures. The presence of epithelioid cells, macrophages in different stages of activation and the architectural pattern of the cells, characterize these structures as extra-tissular true granulomas. Granulomas much similar to those observed in the peritoneal cavity of infected mice were also detected after the intraperitoneal injection of viable eggs in non-infected mice. Collagen fibers were observed in between the inflammatory cells of granulomas obtained 10 weeks after infection and 48 hours after the injection of viable eggs into the peritoneal cavity. In later times of infection or injection the amount of collagen fibers increases resulting in a typical pattern of healed schistosoma egg granulomas. The possible influence of the immune response on the genesis of the granulomatous reaction as well as the influence of the vascularized connective tissue on this process is discussed.

Scanning electron microscopy of the egg and the first instar larva of Dermatobia hominis (Diptera, cuterebridae)

The egg and the first instar larva of Dermatobia hominis were described based on observation with a scanning electron microscope.

Morphological observations on the egg and first instar larva of Metacutereba apicalis (Diptera: Cuterebidae)

Descriptions are given of the egg and first intar larvar of Metacutereba apicalis (Diptera: Cuterebridae) when viewed by light and scanning electronic microscopes.

Morphology of the EGG of Sarcodexia lambens (Diptera: sarcophagidae)

The egg of Sarcodexia lambens (Diptera: Sarcophagidae) is described on the basis of scanning electron microscopy.

Sarcopromusca pruna (Diptera: Muscidae) as an egg transport host of Dermatobia hominis (Diptera: Cuterebridae) in the cacau region of Bahia, Brazil

Sarcopromusca pruna appears to be the predominant transport host for Dermatobia hominis eggs among cattle herds in central eastern Bahia, Brazil. In the study area, two seasonal peaks of S. Pruna abundance coincide with those of Dermatobia, from mid July through late September and from mid November until early January, two periods of moderate monthly rainfall between anual extremes. Among more than 26,000 flies examined during the study, 75 (all female S. pruna) bore Dermatobia eggs. Certain aspects of Dermatobia behavior and ovoposition habits in the field are also discussed.

Short and long-term effects of azadirachtin A on development and egg production of Rhodnius prolixus

Azadirachtin A was given through a blood meal to 4th-instar larvae and to adult females of Rhodnius prolixus. Development (ecdysis) and egg production were inhibited in a dose-dependent manner. Long-term experiments with subsequent four feedings on azadirachtin-free blood were performed with 4th-instar larvae and with adult females. Only in the low-dose azadirachtin larval groups (0.01 and 0.1 microng/ml of blood), development was partially restored; after a single 1.0 microng/ml treatment about 50% of the treated larvae were still alive 120 days later without any adult emergence. Similarly fed females had a dose-dependent lower survival and egg deposition rate. The results are discussed in relation to the mode of azadirachtin A action.

Ultrastructure of the egg of Muscina stabulans and Synthesiomyia nudiseta (Diptera: Muscidae)

The eggs of Muscina stabulans and Synthesiomyia nudiseta are morphologically described, based on scanning electron microscope (SEM).

Schistosomiasis mansoni in three localities of western lowland of the state of Maranhão before and after mass treatments

A cross-sectional study for schistosomiasis was carried out in the localities of Aliança, Alegre and Coroatá (districts of Cururupu, São Bento and São João Batista, respectively) in the lowland of the state of Maranhão, after respectively 13, 11 and 4 mass treatments with oxamniquine in the period of ten years (1977-1987). The study included clinical and quantitative fecal examination, skin test for Shistosoma mansoni infection, evaluation of man-water contact of the total population (829 persons) in the three localities and other epidemiological investigations such as infection rate and dynamics of the snail population. After 13 mass treatments in Aliança, the prevalence of S. mansoni infection was reduced from 57.9% to 7.4%. In Coroatá with 11 mass treatments the prevalence fell from 69.2% to 12.8% and in Alegre, with only 4 mass treatments there was pratically no reduction in prevalence: 22.9% to 21%. After mass treatments the type II hepatointestinal clinical form was 10.8% in Aliança, 17.9% in Alegre and 18% in Coroatá. The hepatosplenic (type III) form was not seen in Aliança and Coroatá but unexplanably it was 7.6% in Alegre. There was no correlation between the egg load elimination and the clinical forms.

The role of egg antigens, cytokines in granuloma formation in murine schistosomiasis mansoni

The induction of granuloma formation by soluble egg antigens (SEA) of Schistosoma mansoni is accompanied by T cell-mediated lymphokine production that regulates the intensity of the response. In the present study we have examined the ability of SDS-PAGE fractioned SEA proteins to elicit granulomas and lymphokine production in infected and egg-immunized mice. At the acute stage of infection SEA fractions (<21, 25-30, 32-38, 60-66, 70-90, 93-125, and > 200 kD) that elicited pulmonary granulomas also elicited IL-2, IL-4 lymphokine production. At the chronic stage a diminished number of fractions (60-66, 70-90, 93-125, and > 200 kD) were able to elicit granulomas with an overall decrease in IL-2, IL-4 production. Granulomas were elicited by larval-egg crossreactive and egg-specific fractions at both the acute and chronic stage of the infection. Examination of lymphokine production from egg-immunized mice demonstrated that as early as 4 days IL-2 was produced by spleen cells stimulated with <21, 32-38, 40-46, 93-125, and >200 kD fractions. By 16 days, IL-2production was envoked by 8 of 9 fractions. IL-4 production at 4 days in response to all fractions was minimal while at 16 days IL-4 was elicited with the < 21, 25-30, 50-56, 93-125, and > 200 kD fractions. The present study reveals differences in the range of SEA fractions able to elicit granulomas and IL-2, IL-4 production between acute and chronic stages of infection. Additionally, this study demonstrates sequential (IL-2 followed by IL-4) lymphokine production during the primary egg antigen response.

Cross-sectional and evolutive studies of schistosomiasis mansoni in untreated and mass treated endemic areas in the southeast and northeast of Brazil

Cross-sectional and evolutive studies on schistosomiasis mansoni were carried out before and after mass treatment in the endemic areas of Capitao Andrade and Padre Paraíso, state of Minas Gerais, Riachuelo, state of Sergipe, Alhandra, state of Paraíba, and Aliança, Alegre and Coroatá, lowland of the state of Maranhao, Brazil, in the last eighteen years. The studies included clinical and fecal examination by the Kato-Katz quantitative technique, skin testfor Schistosoma mansoni infection, evaluation of man-water contact and other epidemiological investigations such as infection rate and dynamic of the snail population. Results showed: (1) Higher prevalence of S. mansoni infection, greater egg load elimination and higher and earlier morbidity of the chronic froms of the disease in the southeast areas of Capitao Andrade and Padre Paraíso; (2) The incidence of hepatosplenic form is higher in some family clusters, in whites and mullattos in all the endemic areas but develop earlier in the southeast; (3) The prevalence and morbidity of schistosomiasis are decreasing both in the mass treated northeast and in the untreated southeast areas; (4) The mass treatment reduces rapidily the prevalence of the infection and the morbidity of the disease but can not control it because of the frequent reinfections due to the intensity of man-water contact.

Egg-laying induced by insemination in Biomphalaria snails

Contrasting with many populations of Biomphalaria glabrata and B. straminea previously dealt with in this laboratory, which when reared in isolation deposit self-fertilized eggs without apparent restraint, isolated individuals of the former species from São Sebastião do Passé, Bahia state, and of the latter from Porto Alegre, Rio Grande do Sul state, show a high degree of self-sterility, laying egg capsules with a few usually abortive, rarely viable egg cells, or just jellylike masses without egg cells. When two individuals are paired they readily copulate, usually withing 24 hr deposit one of more egg capsules containing many eggs, and egg-laying continues up to exhaustion of stored allosperm. So far this aspect of reproductive biology has been only observed in a number of populations of the planorbid species Helisoma duryi, and should be viewed as a populational rather than specific characteristic. Since sterility is not overcome by courtship, copulation and insemination by individuals of a different species, the stimulating factor that causes ovulation in the studied self-sterile individuals is considered to be present in the conspecific allosperm.