Second contribution to the knowledge of the larvae of the Raviniini (Diptera, Sarcophagidae) based on observations using scanning electron microscope

First and second instar larvae of some Sarcophagidae (Diptera) of the tribe Raviniini are described on observations with a scanning electron microscope.

A contribution to the study of acute schistosomiasis (an experimental trial)

In an attempt to establish an experimental model of acute schistosomiasis, sequential histological changes were investigated in the skin, lung, liver and spleen of mice infected with 30 or 100 cercariae of Schistosoma mansoni according to four sets of experiments: single infection, repeated infections, unisexual infection and infection in mice born from infected mothers. Animals were killed every other day from exposure up to 50 days after infection. Only mild, isolated, focal inflammatory changes were found before the appearance of mature eggs in the liver, even when repeated infections were made. Severe changes of reactive hepatitis and splenitis appeared suddenly when the first mature eggs were deposited, around the 37th to 42nd day after infection. The mature eggs induced lytic and coagulative necrosis of hepatocytes around them which was soon followed by dense infiltration of eosinophils. So, mature egg-induced lesions appeared as the major factors in the pathogenesis of acute schistosomiasis in mice. Mice born from infected mothers were apparently able to rapidly modulate the egg-lesions, forming early fibrotic granulomas. The murine model of acute schistosomiasis appeared adequate for the study of pathology and pathogenesis of acute schistosomiasis.

Third contribution to the knowledge of the Raviniini (Diptera, Sarcophagidae), based on observations of the larvae, using scanning electron microscope

L1, L2 and L3 of Oxysarcodexia paulistanensis (Mattos), L3 of O. confusa Lopes, L2 of Ravinia belforti (Prado & Fonseca) and L2 of Oxyvinia excisa (Lopes) were described and figured using scanning electron microscope.

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.

The significance of variation in the susceptibility of Schistosoma mansoni to the antischistosomal drug oxamniquine

Clinical and laboratory evidence is reviewed which shows that there is a great deal of variation in the susceptibility of Schistosoma mansoni to oxamniquine. This variation occurs both among endemic regions and within endemic regions in Brazil and Kenya. It is genetically controlled. It is suggested that the parasite possesses a large capacity for developing resistance to the drug and that resistance will develop where sufficient drug pressure is maintained.

A contribution to the study of simulium and Culicoides of Rio de Janeiro: monthly incidence and biting activity

During March 1984 to February 1985, we captured simuliids and biting midges in the National Park of Tijuca, Rio de Janeiro. A study on monthly incidence and biting activity and their correlation to air temperature, relative humidity, and rainfall was made.