834 resultados para Ultrastructure


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Conselho Nacional de Desenvolvimento Científico e Tecnologico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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We aimed to standardize a protocol to suppress spermatogenesis in the characiform fish, Astyanax altiparanae, for future use as a host in germ cell transplant research, opening opportunities for a range of studies, such as spermatogenesis analyses and transgenesis because this species presents livestock characteristics to be used as a biological model. The effects of the chemotherapeutic busulfan (formulated as Myleran), which is used as medicine, therefore not as toxic to humans manipulation as analytical grade busulfan (Fluka) used in previous studies, were evaluated at physiological temperature of 28 °C, ideal for growth and reproduction of A altiparanae, and also at increased temperature 35 °C. The temperature groups were divided into three treatment groups: busulfan, DMSO only, and an untreated control. Macroscopic, histologic, stereological, and ultrastructure analysis showed that, at 28 °C, busulfan did not cause depletion of germ cells in A altiparanae. However, at 35 °C, sterilization was observed 3 weeks after the initial application. Similar results were obtained with maintenance of fish at 35 °C for a longer period with no accompanying Myleran treatment. This procedure allows reduction in stress and lower mortality resulting from manipulation during busulfan injection and is also suitable for mass treatment because large numbers of fish can be incubated in warm water.

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The phylogenetic relationships among tick species (Acari: Ixodida) have been revisited by several researchers over the last decades. Two subfamilies, Rhipicephalinae (Ixodidae) and Ornithodorinae (Argasidae), deserve special attention. The male reproductive system morphology, as well as the ultrastructure of the germ cells, may provide important information for phylogeny and systematics of metazoan groups, with spermatozoa exhibiting characters that can be used for this purpose. With that information in mind, this study aimed at evaluating, through a comparative analysis, the morphology of the male reproductive systems and germ cells of ticks species Rhipicephalus sanguineus and Ornithodoros rostratus. In order to do that, histology and scanning electron microscopy techniques were used. The results have shown that despite the similarities in the general morphology of the male reproductive system among studied Ixodida so far, there are morphological differences among the species studied herein, mainly the U-shaped testis (ancestral character) in O. rostratus and the pair testes (derived character) in R. sanguineus, and the general morphology of germ cells (spermatids V). Besides that, the morphological changes observed during the spermiogenesis appear to be different between the species studied here, probably characterizing the two families considered. The data generated in this study showed the importance of comparative internal morphology studies, mainly in regard to spermatology, despite the morphological data obtained herein not being enough to product a cladogram (sperm cladistics), it was already possible to observe clear differences among families Argasidae and Ixodidae in regard to the organization of their male reproductive systems and concerning the external morphology of spermatids. Data yet to be obtained through transmission electron microscopy techniques will allow the application of spermiocladistics and spermiotaxonomy as tools for tick systematics.

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Studies of morphological and ultrastructural alterations in target organs have been useful for evaluating the sublethal effects of biopesticides regarded as safe for non-target organisms in ecotoxicological analyses. One of the most widely used biopesticides is neem oil, and its safety and compatibility with natural enemies have been further clarified through bioassays performed to analyze the effects of indirect exposure by the intake of poisoned prey. Thus, this study examined the cellular response of midgut epithelial cells of the adult lacewing, Ceraeochrysa claveri, to neem oil exposure via intake of neem oil-contaminated prey during the larval stage. C. claveri larvae were fed Diatraea saccharalis eggs treated with neem oil at concentrations of 0.5%, 1% and 2% throughout the larval stage. The adult females obtained from these treatments were used at two ages (newly emerged and at the start of oviposition) in morphological and ultrastructural analyses. Neem oil was found to cause pronounced cytotoxic effects in the adult midgut, such as cell dilation, emission of cytoplasmic protrusions, cell lysis, loss of integrity of the cell cortex, dilation of cisternae of the rough endoplasmic reticulum, swollen mitochondria, vesiculated appearance of the Golgi complex and dilated invaginations of the basal labyrinth. Epithelial cells responded to those injuries with various cytoprotective and detoxification mechanisms, including increases in cell proliferation, the number of calcium-containing cytoplasmic granules, and HSP 70 expression, autophagic processes and the development of smooth endoplasmic reticulum, but these mechanisms were insufficient for recovery from all of the cellular damage to the midgut. This study demonstrates that neem oil exposure impairs the midgut by causing sublethal effects that may affect the physiological functions of this organ, indicating the importance of studies of different life stages of this species and similar species to evaluate the safe and compatible integrated use of biopesticides.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The Amazon River prawn Macrobrachium amazonicum is endemic to tropical South America and is being intensively exploited by artisanal fisheries in Brazil. Limited information is available about the nutritional requirements of M. amazonicum, although the production of this species is now technically feasible. The digestive process in this species is still unclear and investigation into the digestive cells of its hepatopancreatic epithelium is required. Thus, the hepatopancreas from 15 specimens were fixed in Karnovsky Solution and processed for Transmission Electron Microscopy. Our results indicate that E cells are located at the distal portion of the hepatopancreatic tubule and are involved in mitotic activity. The cylindrical R cells are sparse and are only found in the proximal portion of the hepatopancreatic tubule. According to its ultrastructural characteristics, this cell is involved in pinocytosis. M cells are generally found near the R cells. The F cells are scattered throughout the length of the hepatopancreatic tubules, and B cells are observed mainly in the proximal and middle regions. F cells and B cells are likely related to, respectively, the synthesis of enzymes and the intracelular digestion. R- and M cells are probably related to material storage. Thus, these findings provide basic information on the cell types that perform protein digestion in M. amazonicum, and will be useful in further nutritional research. The identification and characterization of digestive cells is an important step towards understanding the digestive mechanisms.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)