Participation of neurofilament proteins in axonal dark degeneration of rat's optic nerves.

Neurofilaments (NF) are neuronal intermediate filaments formed by three different subunits: high (NF-H), medium (NF-M) and light (NF-L). They are responsible for the determination and maintenance of axon caliber. Accumulation of NF or their immunoreactive products are components of several neurodegenerative disease lesions, such as neurofibrillary tangles, Lewy bodies and the spheroids of amyotrophic lateral sclerosis. Also, cytoskeletal breakdown is one of the first ultrastructural changes occurring after nerve crush or section. In the present study, Wistar rats were subjected to bilateral enucleation to induce Wallerian degeneration of optic nerve fibers and perfused 24 h, 48 h and 1 week later. Optic nerve segments were processed for electron microscopy (EM), light microscopy immunofluorescence (LM) and immunoelectronmicroscopy (IEM) for NF subunit detection. LM for NF of control nerves showed a slightly different pattern and intensity for each subunit, with more intense staining of NF-M and NF-H and less intense staining of NF-L. This reaction did not change considerably at 48 h, but was severely reduced 1 week after enucleation. Results of EM showed fibers in: (1) partial cytoskeleton degeneration or (2) watery degeneration or (3) dark degeneration. The number of dark degenerating axons was statistically higher at the latest time-interval studied. Neurofilament clumping areas and dark degenerating axons showed positive immunostaining for the three neurofilaments subunits when examined by IEM. These results suggest that dark degenerating axons develop from areas of neurofilament aggregation. We may also conclude that NF proteins participate in the process of axonal dark degeneration.

A continuous lineage of rat adenohypophysis stromal cells: characterisation and effects on GH(3)B(6) prolactin-secreting cell behaviour.

Although some studies have shown a possible modulation of the stroma on the hormonal secretion, it is not clear as to what are the requirements for these cellular interactions. In the present work, a homogeneous and continuous lineage of rat adenohypophysis stromal cells (APS9 cells) obtained from rat adenohypophysis primary culture was established. Using immunocytochemical methods and electron microscopy, we have characterised APS9 cells as elongated fibroblastoid-like cells with intercellular contacts, expressing alpha-smooth muscle actin, type IV collagen and laminin. By biochemical procedures, higher amounts of chondroitin sulphate and heparan sulphate were found in the pericellular and extracellular compartments of APS9 cell culture. In order to evaluate the possible effects of APS9 cell on GH(3)B(6) prolactin-secreting cell survival and/or proliferation, we established co-culture and proliferation assays. When GH(3)B(6) cells were cultivated on APS9 cell substrate, they displayed an organisation of many cellular cords strongly attached and covering all the stromal cell area, establishing punctual interactions or extensive surface associations between adjacent cells. Prolactin immunoreactivity appeared to be more scattered throughout the cytoplasm and accumulated in its periphery. When plated on glass coverslips, on newborn rat skin fibroblasts, on murine haematopoietic bone marrow stroma cell line or on murine foetal liver stroma cell line, GH(3)B(6) cells changed their organisation and presented a decrease in cell number and adherence to the substrate. Our results showed that the APS9 cell/GH(3)B(6) cell interactions favour cell growth and probably PRL secretion, and raises questions about the specificity of different organs and/or animal species stromas on the hormone secretion.

Ultrastructural aspects of the human T-lymphotropic virus type I (HTLV-I) in Brazil

Nowadays, Brazil may be considered an endemic area for HTLV-I infection. Several studies showed a high incidence of HTLV-I infection among the general population and different groups such as blood donors, hemophiliacs, hematological and neurological patients. Cases of adult T-cell leukemia/lymphoma as well as tropical spastic paraparesis/HTLV-I associated myelopathy have been already described. Therefore the use of different technical approaches, to characterize Brazilian HTLV strains has become important. HTLV particles were characterized and recognized by the use of transmission electron microscopy in lymphocyte cocultures. The ultra-structural analysis revealed typical virus particles close to the lymphocyte membrane. The immunoelectron microscopy allowed the identification of the virus as HTLV, a type C oncovirus, group HTLV-BLV. The ethanol phosphotungstic acid technique showed structures similar to the virus budding process and the routine preparations have contributed to the analysis of the first virus-cell interaction events. Structures related to the endocytic route HTLV entrance are also pointed out.

Structural and cytochemical localization of the endoplasmic reticulum in the electrocyte of electrophorus electricus

Vesículas com vários diâmetros variando entre 0.06 e 0.6 micronm e localizadas em torno do núcleo, bem como na proçäo mais periférica, foram observadas no electrócito do peixe elétrico Electrophorus electricus. Tais vesículas foram consideradas como componentes de retículo endoplasmático do eletrócito uma vez que observaçöes citoquímicas demonstraram a presença de glicose-6-fosfatase na membrana dessas vesículas. Esta idéia é reforçada por resultados obtidos com o uso da técnica do pirantiminiato de potássio e análise espectroscópica de elétrons, que mostrou a presença da Ca++ na membrana das vesiculas

Structural and cytochemical localization of the endoplasmic reticulum in the electrocyte of electrophorus electricus

Vesículas com vários diÔmetros variando entre 0.06 e 0.6 micronm e localizadas em torno do núcleo, bem como na proþõo mais periférica, foram observadas no electrócito do peixe elétrico Electrophorus electricus. Tais vesículas foram consideradas como componentes de retículo endoplasmático do eletrócito uma vez que observaþ÷es citoquímicas demonstraram a presenþa de glicose-6-fosfatase na membrana dessas vesículas. Esta idéia é reforþada por resultados obtidos com o uso da técnica do pirantiminiato de potássio e análise espectroscópica de elétrons, que mostrou a presenþa da Ca++ na membrana das vesiculas (AU)