Morphological evidence for a permeability barrier in the testis and spermatic duct of Gymnotus carapo (Teleostei: Gymnotidae).

Cell-cell interactions play essential roles in the regulation of gametogenesis. The involvement of junctional complexes in permeability barriers, for example, provides structural and physiological support for male germ-cell development. This study describes morphological characteristics of the reproductive system of Gymnotus carapo, a neo-tropical freshwater fish widely distributed in South and Central America, focusing on the detection of permeability barriers using morphological and biochemical approaches. Ultrastructural analysis of testes treated with the lanthanum nitrate exclusion technique showed that the tracer penetrated the interstitial compartment of the testis, surrounding and appearing within cysts containing spermatogonia and spermatocytes in early stages of meiosis, but was not detected in the spermatid cysts or inside the lumen of spermatogenic tubules. These results suggest the presence of a permeability barrier that is stabilized after meiosis is completed and serves to protect the haploid cells from the vascular system. In the spermatic-duct region, the tracer was obstructed near the lumen of the duct. Junctional complexes and focal tight junctions between adjacent cells were observed in the testis and spermatic duct. Freeze-fracture methods indeed confirmed the presence of tight junctions, which were visualized as parallel rows of individual particles between adjacent cells. More evidence supporting the existence of a permeability barrier was gathered from differences observed in the electrophoretic protein profiles of testis and spermatic-duct fluids compared to blood plasma. Together, these observations demonstrate the existence of a permeability barrier formed by tight junctions in the testis and spermatic duct of G. carapo.

Atomic force microscopy as a tool for the study of the ultrastructure of trypanosomatid parasites.

Here, we describe the methodology currently used to analyze the structural organization of protozoa of the Trypanosomatidae family by atomic force microscopy. The results are compared with those obtained using light, scanning, and transmission electron microscopy.

Atomic force microscopy: a tool to analyze the structural organization of pathogenic protozoa.

The fine structure of parasitic protozoa has been the subject of intense investigation with the use of electron microscopy. The recent development of atomic force microscopy (AFM) and all of the techniques associated with AFM has created new ways to further analyze the structure of cells. In this review, the various, presently-available modalities of AFM are discussed, as well as the results obtained in analysis of: (i) the structure of intact and detergent-extracted protozoa; (ii) the surface of infected cells; (iii) the structure of parasite macromolecules; (iv) the measurement of surface potential; and (v) force spectroscopy, the measurement of elasticity and ligand-receptor interactions.

Envelope lipid-packing as a critical factor for the biological activity and stability of alphavirus particles isolated from mammalian and mosquito cells.

Alphaviruses are enveloped arboviruses. The viral envelope is derived from the host cell and is positioned between two icosahedral protein shells (T = 4). Because the viral envelope contains glycoproteins involved in cell recognition and entry, the integrity of the envelope is critical for the success of the early events of infection. Differing levels of cholesterol in different hosts leads to the production of alphaviruses with distinct levels of this sterol loaded in the envelope. Using Mayaro virus, a New World alphavirus, we investigated the role of cholesterol on the envelope of alphavirus particles assembled in either mammalian or mosquito cells. Our results show that although quite different in their cholesterol content, Mayaro virus particles obtained from both cells share a similar high level of lateral organization in their envelopes. This organization, as well as viral stability and infectivity, is severely compromised when cholesterol is depleted from the envelope of virus particles isolated from mammalian cells, but virus particles isolated from mosquito cells are relatively unaffected by cholesterol depletion. We suggest that it is not cholesterol itself, but rather the organization of the viral envelope, that is critical for the biological activity of alphaviruses.

Rattus norvegicus as a model for persistent renal colonization by pathogenic Leptospira interrogans.

Leptospirosis continues to be a disease with a poorly understood pathogenesis. The experimental rat model is amenable for the investigation of leptospiral dissemination, tropism, persistence of renal colonization and factors related to disease resistance. In this study, Wistar rats were infected intraperitoneally with virulent Leptospira interrogans serovar Copenhageni strain Fiocruz L1-130. The detection of leptospires in tissue samples was based on culture, silver staining and immunofluorescence techniques. An inoculum of 10,000 leptospires induced colonization in 50% of rats and colonization persisted for the 4-month period of the study. Dissemination kinetics revealed that renal colonization took place 7-9 days after infection, with no underlying histopathology. The peak leptospiral load occurred on day 5 post-infection, followed by rapid clearance in all tissues except the kidneys, where dense leptospiral aggregates persisted in the renal tubules. We conclude that the experimental rat model is suitable for studies contributing towards the understanding of the mechanisms of colonization and resistance to severe disease in leptospirosis.

[HIV patients' understanding of information on antiretroviral therapy]. / Compreensão de informações relativas ao tratamento anti-retroviral entre indivíduos infectados pelo HIV.

To assess the understanding of information related to antiretroviral therapy among HIV-infected patients enrolled in public AIDS services (Belo Horizonte, Minas Gerais State, Brazil), a cross-sectional analysis was carried out, based on interviews with patients after initial provision of antiretroviral drugs. The study evaluated the information on antiretroviral therapy provided by healthcare professionals and the patients' level of understanding in relation to prescription information. This level was classified as insufficient if there was disagreement of more than 30.0% between the information reported by the patient and the written prescription. Divergence between prescriptions and information reported by 358 interviewed patients was observed. The level of understanding regarding the prescribed antiretroviral was obtained, and 26.3% of patients displayed insufficient understanding. The results show an important proportion of patients with misunderstanding of information regarding antiretroviral therapy, mainly those with limited schooling and low income. It is necessary to bolster strategies to increase quality of recommendations provided to these patients. Improving the multidisciplinary team approach to patient care should help reverse the observed situation.

Compreensão de informações relativas ao tratamento anti-retroviral entre indivíduos infectados pelo HIV / HIV patients' understanding of information on antiretroviral therapy

Para avaliar a compreensão das informações sobre a terapia anti-retroviral entre portadores do HIV/AIDS atendidos em serviços públicos de referência, em Belo Horizonte, Minas Gerais, Brasil, foi realizada análise transversal por meio de entrevistas com pacientes, após a primeira dispensação de anti-retrovirais. A orientação recebida dos profissionais de saúde e o nível de compreensão pelo paciente foram investigados, sendo este classificado como insuficiente se houvesse discordância igual ou superior a 30,0 por cento entre a resposta do paciente e a informação contida na prescrição para itens selecionados. Divergências entre as informações da prescrição e as relatadas pelos 358 pacientes foram observadas. O nível de compreensão das informações sobre anti-retrovirais prescritos foi classificado como insuficiente para 26,3 por cento. Os resultados obtidos revelam proporção importante de pacientes com lacunas na compreensão de informações sobre a terapêutica anti-retroviral combinada. É necessário implementar estratégias para aumentar a qualidade das orientações fornecidas a esses pacientes. O enfoque multidisciplinar no atendimento aos pacientes poderá contribuir para reverter a situação observada.