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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.

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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.(AU)

O presente estudo teve como objetivo contribuir para o conhecimento sobre a interação parasita-vetor associada à infecção por Trypanosoma cruzi (Chagas, 1909) em Panstrongylus megistus (Burmeister, 1835), importante vetor da doença de Chagas no Brasil. A prevalência e a intensidade da infecção por T. cruzi, a incidência de metaciclogênese e a frequência de fenótipos nucleares presentes em túbulos de Malpighi foram investigadas em ninfas de P. megistus criadas à temperatura de 28 °C e submetidas a choque térmico por 1 hora a 40 °C, dois dias após alimentação em camundongos infectados com T. cruzi II (linhagem Y). A análise realizada 45 dias pós-infecção revelou que tanto nos insetos submetidos ao choque térmico como nos respectivos controles a frequência de epimastigotos se apresentava muito maior do que a dos tripomastigotos; a prevalência da infecção não foi alterada pelo choque térmico. Menos epimastigotos e tripomastigotos foram encontrados nos insetos submetidos ao choque térmico, indicando que a multiplicação e a metaciclogênese dos parasitas possam ser afetadas com o estresse. Nos espécimes infectados, o choque térmico induziu aumento na frequência de núcleos com descompactação da heterocromatina, uma resposta de sobrevivência celular ao estresse, e não afetou a sobrevivência propriamente dita do inseto. Os efeitos da infecção e do choque térmico, especialmente sobre a multiplicação e a metaciclogênese de T. cruzi, e a resistência ao choque térmico desenvolvidos pelas ninfas de P. megistus são indicativos de que devam ser considerados quando se buscam condições adequadas de criação em laboratório de insetos infectados.(AU)

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OBJECTIVE: To assess the knowledge, attitudes, and behavior associated with cadaver organ donation and transplantation among medical students and physicians. PATIENTS AND METHODS: We randomly selected 350 medical students, 150 physicians, and 150 intensive care unit physicians. Each completed a questionnaire consisting of 9 self-administered items, from which we gathered data about their knowledge about brain death and criteria for the diagnosis of brain death; their hypothetical behaviors, assuming willingness to donate their own or their family's organs; their trust in physicians; and their confidence in a diagnosis of brain death made by physicians. RESULTS: We observed that knowledge about brain death increased with medical education level; the best results were noted in intensive care unit physicians. Agreement to transplant organs from brain-dead donors (odds ratio [OR], 4.58), confidence in brain-death diagnosis by physicians (OR, 2.17), and knowledge about criteria for the diagnosis of brain death (OR, 2.26) were predictors of willingness to donate one's own organs. CONCLUSION: Enhanced medical knowledge of and involvement in donation are needed to achieve cadaver organ donation.

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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.

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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 (0 degree C, 5 degrees C, 35 degrees C, or 40 degrees C for 1 h) preceded a severe one (0 degree C or 40 degrees C for 12 h), separated by intervals of 8, 18, 24, and 72 h at 28 degrees C (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, 35 degrees C) or even longer (preliminary shock, 40 degrees C) between sequential shocks, significant values were verified in adults only for shock intervals of up to 8 h (preliminary shock, 40 degrees C). While findings for nymphs exhibited considerable cold-shock tolerance under conditions in which preliminary shocks were given at 5 degrees C or 0 degree C and the periods between shocks were up to 72 h long, the adults were shown to be capable of acquiring a substantial tolerance response to a more severe cold shock only when the preliminary shock was given at 0 degree C 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.

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In this study, we addressed the effects of N limitation in Bradyrhizobium japonicum for its association with soybean roots. The wild-type strain LP 3001 grew for six generations with a growth rate of 1.2 day(-1) in a minimal medium with 28 mM mannitol as the carbon source and with the N source [(NH(4))(2)SO(4)] limited to only 20 microM. Under these conditions, the glutamine synthetase (GS) activity was five to six times higher than in similar cultures grown with 1 or 0.1 mM (NH(4))(2)SO(4). The NtrBC-inducible GSII form of this enzyme accounted for 60% of the specific activity in N-starved rhizobia, being negligible in the other two cultures. The exopolysaccharide (EPS) and capsular polysaccharide (CPS) contents relative to cell protein were significantly higher in the N-starved cultures, but on the other hand, the poly-3-hydroxybutyrate level did not rise in comparison with N-sufficient cultures. In agreement with the accumulation of CPS in N-starved cultures, soybean lectin (SBL) binding as well as stimulation of rhizobial adsorption to soybean roots by SBL pretreatment were higher. The last effect was evident only in cultures that had not entered stationary phase. We also studied nodC gene induction in relation to N starvation. In the chromosomal nodC::lacZ fusion Bj110-573, nodC gene expression was induced by genistein 2.7-fold more in N-starved young cultures than in nonstarved ones. In stationary-phase cultures, nodC gene expression was similarly induced in N-limited cultures, but induction was negligible in cultures limited by another nutrient. Nodulation profiles obtained with strain LP 3001 grown under N starvation indicated that these cultures nodulated faster. In addition, as culture age increased, the nodulation efficiency decreased for two reasons: fewer nodules were formed, and nodulation was delayed. However, their relative importance was different according to the nutrient condition: in older cultures the overall decrease in the number of nodules was the main effect in N-starved cultures, whereas a delay in nodulation was more responsible for a loss in efficiency of N-sufficient cultures. Competition for nodulation was studied with young cultures of two wild-type strains differing only in their antibiotic resistance, the N-starved cultures being the most competitive.

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The survival and molting incidence of fifth-instar nymphs of Panstrongylus megistus (Burmeister, 1835), a vector of Chagas' disease, were investigated following sequential heat shocks in which a mild shock (35 or 40 degrees C, 1 h) preceded a more drastic one (40 degrees C, 12 h). The shocks were separated by 8-, 18-, 24-, or 72-h periods at 28 degrees C. The heat-shock tolerance response was more effective when the first shock was given at 40 degrees C. When the period between shocks was 18 h, the tolerance to sequential shocks (in terms of specimen survival) weakened, which suggested a transient control of the process that enables the organism to circumvent the unfavorable effects of severe shock. In terms of molting incidence, the heat-shock tolerance was only demonstrated when the period between the first shock at 40 degrees C for 1 h and the second shock at 40 degrees C for 12 h was > or = 24 h. These results are the first to demonstrate the induction of heat-shock tolerance in a blood-sucking hemipteran.

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The survival and molting incidence were studied in the insect, Panstrongylus megistus, following sequential cold shocks in which a milder shock at 0 or 5 degrees C for 1 h preceded a more severe shock (0 degrees C, 12 h). The shocks were separated by intervals of 8, 18, 24, and 72 h at 28 degrees C. The survival rate after sequential shocks was identical to that of unshocked controls. Cold-shock tolerance differed from heat-shock tolerance since the latter varied with the time between shocks and was much more transient. Sequential cold shocks produced a higher molting incidence when the first shock was given at 0 compared to 5 degrees C. This response was more rapid than that to sequential heat shocks. Cold-shock tolerance in P. megistus may involve heat-shock proteins, although other protective mechanisms may also occur concurrently. This is the first report of cold-shock tolerance in a blood-sucking hemipteran.

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The nuclear phenotypes of Malpighian tubule epithelial cells of 5th instar male nymphs of the blood-sucking insect Panstrongylus megistus were studied immediately after a short (1 h) cold shock at 0 degrees C, and 10 and 30 days later. The objective was to compare the responses to a cold shock with those known to occur after hyperthermia in order to provide insight into the cellular effect of cold in this species. Nuclei which usually exhibited a conspicuous Y chromosome chromocenter were the most frequent phenotype in control and treated specimens. Phenotypes in which the heterochromatin was unravelled, or in which there was nuclear fusion or cell death were more abundant in the shocked specimens. Most of the changes detected have also been found in heat-shocked nymphs, except for nuclear fusion which generates giant nuclei and which appeared to be less effective or necessary than that elicited after heat shock. Since other studies showed that a short cold shock does not affect the survival of more than 14% of 5th instar nymphs of P. megistus with domestic habit and can induce tolerance to a prolonged cold shock, heat shock proteins proteins are probably the best candidates for effective protection of the cells and the insects from drastic damage caused by low temperature shocks.

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Soybean seed lectin stimulates adsorption of Bradyrhizobium japonicum to its host roots. Pretreatment of the rhizobia with soybean seed lectin for at least 6-12 h previous to their interaction with the plants was required to detect the stimulatory effect. This activity could be observed with as few as 1000 soybean seed lectin molecules per bacterium, and required specific carbohydrate binding. Infectivity and competitiveness for nodulation were also stimulated by preincubation of the rhizobia either with soybean seed meal extract or soybean seed lectin, the extract being more effective in enhancing competitiveness.

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The nuclear phenotypes of Malpighian tubule epithelial cells of male nymphs of the blood-sucking insect, Panstrongylus megistus, subjected to short- and long-duration heat shocks at 40oC were analyzed immediately after the shock and 10 and 30 days later. Normal nuclei with a usual heterochromatic body as well as phenotypes indicative of survival (unravelled heterochromatin, giants) and death (apoptosis, necrosis) responses were observed in control and treated specimens. However, all nuclear phenotypes, except the normal ones, were more frequent in shocked specimens. Similarly altered phenotypes have also been reported in Triatoma infestans following heat shock, although at different frequencies. The frequency of the various nuclear phenotypes observed in this study suggests that the forms of cell survival observed were not sufficient or efficient enough to protect all of the Malpighian tubule cells from the deleterious effects of stress. In agreement with studies on P. megistus survival following heat shock, only long-duration shock produced strongly deleterious effects.

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Survival and molting incidence were studied after heat (40 degrees C) and cold (0 degree C) shocks in specimens of Panstrongylus megistus with the aim of establishing its response to temperature stress under laboratory rearing conditions and to understand occasional changes in the biological characteristics of specimens captured in nature. The response to the thermal shocks was found to vary as a function of the temperature and duration of the shock, developmental phase and sex of the specimens, and in certain cases, the insect habit and nourishment conditions. P. megistus specimens were found to be less resistant to the heat shock assay than Triatoma infestans, another reduviid species. The short cold shock affected survival of P. megistus more than did the heat shock, survival of fully-nourished specimens being preferential. The response of adults to the short cold shock was affected by sex, males being generally less resistant. The insect sylvatic habit was found to seldom affect the thermal shock response established for specimens with domestic habit. A decrease in molting frequency and sometimes a slowdown of the molting rate were found after the short heat and cold shocks, possibly promoted by change in hormonal balance, and differing from patterns reported for T. infestans. The results indicate that no generalization should be made for different reduviid species in terms of the effects of temperature shocks.

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The mineral, lean, and fat contents of the human body may be not only allometrically but also functionally associated. This report evaluates the influence of muscle mass on bone mass and its age-related changes by investigating these and other variables in both genders in the different stages of reproductive life. We have analyzed the dual-energy X-ray absorptiometry (DEXA)-determined whole-body mineral content (TBMC), lean body mass (LBM), and fat body mass data (FBM) of 778 children and adolescents of both genders, aged 2-20 years [previously reported in Bone 16(Suppl.): 393S-399S; 1995], and of 672 age-matched men and women, aged 20-87 years. Bone mass (as assessed by TBMC) was found to be closely and linearly associated with muscle mass (as reflected by LBM) throughout life. This relationship was similar in slope and intercept in prepubertal boys and girls. However, while keeping the same slope of that relationship (50-54 g increase in TBMC per kilogram LBM): (1) both men and women stored more mineral per unit of LBM within the reproductive period than before puberty (13%-29% and 33%-58%, respectively); (2) women stored more mineral than age-matched men with comparable LBM (17%-29%) until menopause; and (3) postmenopausal women had lower values of bone mineral than premenopausal women, similar to those of men with comparable LBM. Men showed no age effect on the TBMC/LBM relationship after puberty. Multiple regression analyses showed that not only the LBM, but also the FBM and body height (but not body weight), influenced the TBMC, in that decreasing order of determining power. However, neither the FBM nor body height could explain the pre/postpubertal and the gender-related differences in the TBMC/LBM relationship. Accordingly: (1) calculated TBMC/LBM and FBM-adjusted TBMC/LBM ratios were lower in girls and boys from 2-4 years of age until puberty; (2) thereafter, females rapidly reached significantly higher ratios than age-matched men until menopause; and (3) then, ratios for women and age-matched men tended to equalize. A biomechanical explanation of those differences is suggested. Sex hormones or related factors could affect the threshold of the feedback system that controls bone remodeling to adapt bone structure to the strains derived from customary mechanical usage in each region of the skeleton (bone "mechanostat"). Questions concerning whether the mineral accumulation in women during the reproductive period is related or not to an eventual role in pregnancy or lactation, or whether the new bone is stored in mechanically optimal or less optimal regions of the skeleton, are open to discussion.

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