Extendend chromatin fibers in spermatozoa of apis mellifera (HYMENOPTERA, APOIDEA)

The flow of chromatin from the nuclei of mouse liver cells and spermatozoa after treatment with concentratedsaline and detergent solutions under the simultaneous action of gravity results in the formation of extendedchromatin fibers (ECF). In mouse somatic nuclei, the increase in chromatin condensation is accompaniedby a decrease in the frequency of ECF formation. Since tightly packed chromatin with a very lysine-richhistone variant that resembles somatic H1 histones occurs in honey bee spermatozoa, we examined theformation of ECF in sperm cells of Apis mellifera, and compared the findings with data for mouse cells.Freshly prepared smears of fixed and unfixed semen from A. mellifera were lysed under the action of gravity,stained with toluidine blue at pH 4.0, and examined with polarized and unpolarized light. A protocol usingunfixed preparations and a short lysis period that resulted in abundant ECF production in mouse hepatocytes(which contain loosely-packed chromatin) and sperm cells produced ECF in only a few spermatozoa of A.mellifera. In contrast, a protocol using fixed preparations and a long lysis period produced fewer ECFs inthe former two cell types and no ECF formation in honey bee spermatozoa. The limited chromatin fluidityin A. mellifera spermatozoa may reflect their special DNA-protein composition and organization in the cellnuclei, the participation of nuclear matrix elements, a less effective disruption of the nuclear envelope andplasmalemmal components during lysis, and/or cytoplasmic spatial constraints resulting from particularitiesin the acrosomal complex.

Extended chromatin fibers in mouse testicular spermatozoa

Since in mouse spermatozoa the somatic histones are replaced by other basic proteins and there are changes in the chromatin supraorganization, different patterns of extended chromatin fiber (ECF) formation would be expected compared with those formed by somatic cells that were previously studied. In this study, we investigated the formation of ECF in mouse testicular spermatozoa after lysis with 2 M NaCl plus 1 por cento Triton X-100, and under the action of gravity. ECFs were observed under polarized light in fixed and unfixed spermatozoa subjected to lysis in a vertical position and stained with toluidine blue at pH 4.0. In unfixed preparations, all of the sperm nuclei showed ECFs, whereas in fixed preparations 60 por cento of the cells had ECF. The latter frequency was much higher than that previously reported for mouse hepatocytes. Even in cells that did not produce ECFs in vertically and horizontally lysed preparations, an ordered reorganization of the chromatin was observed after lysis. The faint positive response to acid fast green at the nuclear periphery in spermatozoa that did not develop ECF after lysis was assumed to represent residual protamine and nuclear matrix proteins. The high frequency of mouse sperm cell nuclei with ECF probably reflected the extraction of protamines from the DNA-protein complexes of sperm cell nuclei facilitated by the specific lysis protocol.

Survival and molting incidence after heat and cold shocks in Panstrongylus megistus burmeister

Survival and molting incidence were studied after heat (40ºC) and cold (0ºC) 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 an 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 preferencial. 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 affected 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 changes 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.

Detecçäo de atividade fosfatásica alcalina em túbulos de malpighi de Triatoma infestans klug / Detection of alkalina phosphatase in malpighian tubules of Triatoma infestans klug

Atividade fosfatásica alcalina foi detectada nas células distais e proximais dos túbulos de Malpighi de Triatoma infestans pelo método de Gömöri. Nas células distais, a atividade fosfatásica alcalina detectada em "concreçöes" laminares é sugerida como estando relacionada ao processo de calcificaçäo dessas estruturas e/ou ao mecanismo de esgotamento de reservas de glicogênio contíguas às mesmas. A atividade enzimática no citoplasma das células proximais é atribuída ao transporte de fosfatos ou cálcio. Por outro lado, a presença de fosfatases alcalinas nos núcleos está possivelmente relacionada à atividade nucleolar

Mg2+ - dependent ATPase activity investigated in heterochromatin, euchromatin and nucleoli of Triatoma infestans

Foram demonstradas ATPases dependentes de Mg2+ com procedimentos citoenzimatológicos, a nível da microscopia de luz na eucromatina e nucléolo, mas näo na heterocromatina de núcleos poliplóides de ninfas, durante o desenvolvimento de Triatoma infestans. A nível da microscopia eletrônica, a eucromatina näo exibe o produto da reaçäo, um achado que é atribuído a ligeiras diferenças na metodologia quando comparado com aqueles da microscopia luz. Presume-se que as ATPases detectadas na eucromatina estejam relacionadas com as atividades de transcriçäo