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At least 577 records · Page 32Linked to original sources
PubMed1994

Interaction between tubulin and the viral matrix protein of vesicular stomatitis virus: possible implications in the viral cytopathic effect.

The matrix (M) protein of vesicular stomatitis virus has been shown to induce the rounding of cells. Experiments were performed in order to define the mechanism by which M protein could cause this cytopathic effect (CPE). Immunofluorescence experiments performed on infected cells indicate that cellular rounding coincides with the disruption of the microtubular network. Immunoprecipitation of M protein or tubulin in infected cell extract demonstrates an association of these two proteins in vivo. We show that M protein is capable of interacting in vitro with tubulin in both its polymerized and nonassembled forms. Studies using proteolytically cleaved proteins indicate that this interaction occurs via the highly basic N-terminal domain of M protein and the highly acidic C-terminal region of tubulin. Furthermore, a thermosensitive mutant (tsG33) containing a mutation in the matrix protein gene which is unable to induce CPE at nonpermissive temperature interacts with tubulin with a lower affinity. These results demonstrate that M protein interacts with tubulin in vivo and in vitro and strongly suggest that CPE is caused by this interaction.

Animals↗
PubMed1997

Nontranslatability and dissimilar behavior in plants and protoplasts of viral RNA and movement protein complexes formed in vitro.

It was found that the fusion (His)6-movement proteins (MPs) of two tobamoviruses (TMV UI and a crucifer-infecting tobamovirus, crTMV) were efficient nonspecific translational repressors. The in vitro translation of viral RNAs was blocked by incomplete 30K MP-RNA complexes formed at the MP:RNA molar ratios of 100-150:1. Similar results were obtained with the barley stripe mosaic hordeivirus (BSMV)-encoded 58K MP; however, the translation inhibiting activity of the 58K MP was manifested only in the presence of magnesium. By contrast, the 25K MP of potato virus X (PVX) was incapable of forming MP-RNA complexes under experimental conditions used and did not inhibit in vitro translation. The translation repressing ability correlated with the level of MP affinity to RNA. The complexes of the 30K MP and 58K MP with TMV RNA were not infectious in isolated protoplasts; however, they were infectious in indicator plants. Reduction of MP affinity to RNA resulted in translatability of MP-TMV RNA complexes that apparently was due to their destabilization. Thus, the deletion mutant DEL4 MP formed MP-TMV RNA complexes that were translatable in vitro, infectious to protoplasts and plants. In contrast to this, the complexes of TMV RNA with the mammalian RNA-binding protein p50 were nontranslatable and noninfectious to either protoplasts or intact plants. These results implied that nontranslatable MP-RNA complexes which could not replicate in the primary infected cells were converted into a translatable and replicatable form in the course of passage through plasmodesmata in planta.

Collodion↗
PubMed1993

How are myosin fragments bound to nitrocellulose film?

In an attempt to identify the binding sites of myosin fragments to the nitrocellulose film in a flow cell, proteolytic digestion was performed of myosin fragments bound to the substrate. Chymotryptic digestion of papain.Mg-subfragment-1 (S1) showed that a large proportion of S1 were bound near the tail and that the digestion site was protected for some S1. The binding of S1 near the tail was also confirmed by the production of extra long subfragment-2 (S2) by chymotryptic digestion of heavy meromyosin (HMM). Papain digestion of HMM released slightly smaller HMM from the substrate and impaired the motility at the same time. Hence, the motility of HMM is supported largely by those bound to the substrate near the C terminus. These results demonstrate the importance of flexible regions of myosin in generating active movements.

Binding Sites↗
PubMed2000

Detection of PrP(Sc) in subclinical BSE with the paraffin-embedded tissue (PET) blot.

The appearance of a new variant of CJD (vCJD) in young patients has caused considerable public concern and there is evidence that this novel disease is caused by the same agent as BSE. BSE is a prion disease that became epidemic in the UK, with a peak incidence in January 1993. New test systems should aim to identify BSE-infected cattle early in the incubation period. We compared the established histological and immunohistochemical methods and the Western blot method used by Prionics with the PET blot method that detects prion PrP(Sc) deposits in formalin-fixed and paraffin-embedded tissue. Investigating the obex region with the PET blot, all BSE cases were detectable and no false positive cases occurred. From the Swiss culling program, five clinically healthy cattle out of 1761 were identified as incubating BSE. With the PET blot method four of them showed the same PrP(Sc) deposition pattern that was seen in clinical BSE, though less conspicuous. In one of the five cases, PrP(Sc) was restricted to two brain stem nuclei, a pattern that was reported to be the first manifestation of PrP(Sc) deposits in the brain after peripheral infection and one that occurs after half of the incubation time. In this case, histology and Western blot were negative.

Animals↗
PubMedDate not supplied

Permeable collagen-glycosaminoglycan cross-linked copolymers for the study of biological responses of cocultured Sertoli and spermatogenic cells.

A novel collagen-glycosaminoglycan (C-GAG) substrate was developed to overcome the optical opacity of a HATF nitrocellulose substrate and to provide a more physiological permeable substrate for cocultured Sertoli and spermatogenic cells. Cocultures were prepared on optically transparent C-GAG discs attached to a polyester mesh to facilitate handling. Sertoli cells displayed a cuboidal-to-columnar shape; a large number of spermatogonia and primary spermatocytes connected by intercellular bridges were associated with basolateral and apical surfaces of Sertoli cells up to 12 days after plating. Rat Sertoli-spermatogenic cell cocultures have been used for testing the effect of toxicants on rat spermatogenesis in vitro. In our initial studies, we tested the effects of the toxicant gossypol on spermatogenic cells cocultured with Sertoli cells on non-permeable (plastic) and permeable substrates (HATF nitrocellulose) under both standard culture conditions and during perifusion after achieving a continuous electrical-resistant cell monolayer. A selective mitochondrial structural damage was observed in spermatogenic cells (spermatogonia and spermatocytes) but not in the coexisting Sertoli cells. This damage was time- (15-60 min) and dose-dependent (0.1-10 microM) and developed more rapidly under perifusion conditions. Similar mitochondrial damage was reported in the intact animal but required higher concentrations (mg) and longer administration time (months) for detection. Studies are in progress to evaluate the effect of additional toxic chemical agents on functional properties of Sertoli and spermatogenic cells in cocultures prepared on various classes of C-GAG substrates.

Animals↗
PubMed1986

Characterization of intermediate filaments and their structural organization during epithelium formation in pigmented epithelial cells of the retina in vitro.

Retinal pigmented epithelial cells of chicken have circumferential microfilament bundles (CMBs) at the zonula adherens region. Isolated CMBs are polygons filled with a meshwork composed primarily of intermediate filaments; they show three major components of 200 000, 55 000, and 42 000 daltons in SDS-gel electrophoresis. Here we have characterized the 55 000-dalton protein immunochemically and ultrastructurally. Immunoblotting and immunofluorescence microscopy have shown that the 55 000-dalton protein is an intermediate filament protein, vimentin. Vimentin filaments changed their distribution during differentiation of pigmented epithelial cells in culture. The protein in the elongated cells showed a fibroblast-type pattern of intermediate filaments. During epithelium formation, the filaments were uniformly distributed and formed a finer meshwork at the apical level. In pigmented epithelial cells that differentiated and matured in culture, vimentin and actin exhibited their characteristic behavior after treatment with colcemid. In the central to basal region of the cell, intermediate filaments formed thick perinuclear bundles. In the apical region, however, intermediate filaments changed in organization from a nonpolarized meshwork to a polarized bundle-like structure. Simultaneously, new actin bundles were formed, running parallel to the intermediate filaments. This suggests that there is some interaction between microfilaments and intermediate filaments in the apical region of these cells.

Actin Cytoskeleton↗
PubMed1986

Immunocytochemical localization of a rhodopsin-like protein in the lipochondria in photosensitive neurons of Aplysia californica.

Polyclonal antibodies directed against squid opsin were used in immunocytochemical and immunoblot experiments to identify a rhodopsin-like protein in photosensitive neurons of Aplysia. Aldehyde-fixed abdominal and cerebral ganglia were embedded in paraffin for peroxidase anti-peroxidase analysis or used whole for immunofluorescence studies. Ganglia were embedded in Lowicryl K4M for electron-microscope immunocytochemistry. In both the cerebral and abdominal ganglia, light-microscope immunocytochemical results showed reaction product deposited around the neuronal cell periphery corresponding in position to the lipochondria. In the abdominal ganglion, the giant cell R2, located in the right rostral quarter, and neurons in the right caudal quarter were consistently labeled with anti-opsin. Electron-microscopic studies demonstrated ferritin-labeling of the lipochondria in R2 and other immunoreactive neurons. Immunoblot analysis of R2 and cerebral neuron extracts was used to identify two prominent immunoreactive protein bands at 85 000 and 67 500 molecular weight.

Animals↗
PubMed1985

The alpha and gamma subunits of 7S nerve growth factor are present in excess concentrations in the mouse submandibular gland.

The 7S nerve growth factor molecule, found in the mouse submandibular gland, is comprised of three distinct protein subunits named alpha, gamma and beta-NGF. In this paper, radioimmunoassays specific for each subunit were used to measure the concentrations of these subunits in homogenates of mouse submandibular gland. It was determined that there were excess concentrations of both the alpha and gamma subunits, more than enough to bind all of the beta-NGF in the gland to form 7S-NGF. The radioimmunoassay data was confirmed by gel filtration experiments. In the gel filtration experiments, the excess alpha and gamma subunits eluted at positions which would indicate that these excess subunits were free and not bound in the 7S-NGF complex. The identity of the excess alpha and gamma subunits was substantiated by ion exchange chromatography, isoelectric focusing polyacrylamide gels and immunoblotting experiments. In conclusion, there are considerable quantities of alpha and gamma subunits present in the submandibular gland which are not bound to beta-NGF. The functional significance of these excess concentrations of the alpha and gamma subunits is not known.

Animals↗