Prevalence and intensity of infection, metacyclogenesis and nuclear phenotypes in Panstrongylus megistus (Burmeister, 1835) after ingestion of Trypanosoma cruzi (Chagas, 1909) II and subjection to heat shock.

This study aimed to contribute to our knowledge of the parasite-vector interaction associated with Trypanosoma cruzi (Chagas, 1909) infection in Panstrongylus megistus (Burmeister, 1835), an important vector of Chagas' disease in Brazil. The prevalence and intensity of T. cruzi infection, the incidence of metacyclogenesis and the frequency of nuclear phenotypes in Malpighian tubules were investigated in nymphs of P. megistus, reared at 28 °C and subjected to heat shock (40 °C, 1 hour) two days after infection with T. cruzi II (Y strain). Following the 45-day post-infection period, the frequency of epimastigotes was much higher than that of trypomastigotes in both heat-shocked and non-shocked insects, and the prevalence of infection was not altered by heat shock. Fewer epimastigotes and trypomastigotes were found in the infected insects subjected to the heat shock, indicating that the multiplication and metacyclogenesis of the parasites were affected by the stress. In infected specimens heat shock promoted an increased frequency of cell nuclei with heterochromatin decondensation, a cell survival response to stress, and did not affect insect survival. The effects of infection and heat shock, especially on the multiplication and metacyclogenesis of T. cruzi, and the observed resistance to heat shock developed by P. megistus nymphs are suggestive that they should be considered when adequate conditions for rearing these infected insects in the laboratory are pursued.

Eye pigments of the blood-sucking insect, Triatoma infestans Klug (Hemiptera, Reduviidae).

The pigmentation of black (wild) and red (mutant) eyes of Triatoma infestans was studied spectrophotometrically and compared with red-eyed (wild) and white-eyed (mutant) forms of Drosophila melanogaster. The spectral absorption profiles of the black and red eye pigments of T. infestans were similar to each other and to that of the wild-type eyes of D. melanogaster. The similarity to the wild form of D. melanogaster indicated that both eye forms of T. infestans contained ommochromes of the xanthommatin type, a finding confirmed by ascending paper chromatography. Pteridines, melanins, and ommins were not detected as eye pigments in T. infestans. The eye color difference in T. infestans was assumed to be a function of the xanthommatin concentration, with a smaller content of ommochrome in red eyes, although this probably did not affect the insect's visual acuity. These data support other findings regarding the similarities between black- and red-eyed specimens of T. infestans for other characteristics.

Eye pigments of the blood-sucking insect, Triatoma infestans klug (Hemiptera, Reduviidae)

A pigmentação de olhos pretos (forma selvagem) e vermelhos (forma mutante) de Triatoma infestans foi estudada por espectrofotometria e comparada à de olhos vermelhos (selvagem) e brancos (mutante) de Drosophila melanogaster. Os perfis do espectro de absorção dos pigmentos de olho preto e vermelho de T. infestans foram semelhantes entre si e ao dos olhos de tipo selvagem de D. melanogaster. A similaridade com a forma selvagem de D. melanogaster indicou que ambos os tipos de olho de T. infestans continham omocromos do tipo xantomatina, o que foi confirmado por cromatografia ascendente em papel. Não foram detectadas pteridinas, melaninas e ominas como pigmentos de olho em T. infestans. A diferença na cor de olho em T. infestans foi considerada uma função da concentração de xantomatina, sendo menor o conteúdo de omocromo nos olhos vermelhos, embora isso provavelmente não afete a acuidade visual do inseto. Esses resultados estão de acordo com dados de outros autores quanto a semelhanças envolvendo outras características entre espécimes de olho preto e vermelho de T. infestans.

Experimentally induced heat- and cold-shock tolerance in adult Panstrongylus megistus (Burmeister) (Hemiptera, Reduviidae)

The survival rate of domestic male and female adult Panstrongylus megistus was studied after sequential heat and cold shocks in order to investigate shock tolerance compared to that previously reported for nymphs. Sequential shocks were such that a milder shock (0ºC, 5ºC, 35ºC, or 40ºC for 1 h) preceded a severe one (0ºC or 40ºC for 12 h), separated by intervals of 8, 18, 24, and 72 h at 28ºC (control temperature). The preliminary thermal shock induced tolerance to the more severe one, although tolerance intensity depended on the initial shock temperature and the interval between treatments. Despite the observed tolerance, the survival rate for insects subjected to both shocks decreased when compared to that of individuals subjected to a single mild shock. When tolerance differed with sex, females showed greater values than males. In contrast to the response detected in nymphs, for which higher heat tolerance values were sustained for intervals of up to 24 h (preliminary shock, 35ºC) or even longer (preliminary shock, 40ºC) between sequential shocks, significant values were verified in adults only for shock intervals of up to 8 h (preliminary shock, 40ºC). While findings for nymphs exhibited considerable cold-shock tolerance under conditions in which preliminary shocks were given at 5ºC or 0ºC and the periods between shocks were up to 72 h long, the adults were shown to be capable of acquiring a substancial tolerance response to a more severe cold shock only when the preliminary shock was given at 0ºC and shock interval surpassed 18 h. It is assumed that the mechanisms involved in the cellular protection of P. megistus under sequential temperature shocks (heat shock protein action?) may loose effectiveness with insect development.

Distribuiçäo e índice de infecçäo natural de triatomíneos capturados na regiäo de Campinas, Säo Paulo, Brasil / Distribution and index of natural infection of Triatominae captured in the region of Campinas, Säo Paulo, Brazil

Entre 1974 e 1981 em 53 municípios pertencentes à regiäo administrativa de Campinas, SP, foram coletados pela SUCEN e encaminhados ao laboratório de Mogi-Guaçu, 36.406 triatomíneos, dos quais foram examinados 33.131 exemplares; destes, foram observados 3.176 (9,60%) infectados pelo T. cruzi. No referente ao local de captura, constatou-se que 4.516 (12,40%), foram encontrados nas casas, sendo 1.827 (40,46%) habitantes e a grande maioria, 30.460 exemplares (83,67%) coletados em anexos de diferentes tipos e os 1.429 (3,92%) restantes em focos silvestres. A espécie predominante foi o P. megistus, com 33.263 exemplares capturados e também aquela de maior índice de infecçäo pelo T. cruzi (10,26%)