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At least 217 records · Page 12Linked to original sources
PubMed1984

The fine structure of cytoplasmic inclusions in brain and other visceral organs in Sandhoff disease.

This paper describes an 11-month-old male who died of Sandhoff disease. Diagnosis was based on detection of cherry red spots and total deficiency of hexosaminidase A and B activities. Sections of the brain revealed swollen neuronal cells and their degeneration and disappearance, leaving a distorted cortical architecture. Ultrastructurally, numerous inclusions showing concentric lamellar or stacked lamellar profiles were found in ballooned neuronal cells, astrocytes and histiocytes. The parafoveal retina in the region of the cherry red spot contained ballooned ganglion and amacrine cells filled with PAS and LFB positive granules. Electron microscopically, these cells showed a greater accumulation of inclusions with stacked lamellar profiles, than the concentric lamellar ones, of classically membranous cytoplasmic bodies (MCB). Hepatocytes and Kupffer cells and epithelial cells of renal glomeruli contained pleomorphic inclusions. Biochemical analysis by thin-layer chromatography of lipid extracts from the cerebral cortex showed a marked increment of the GM2 fraction, without an increase in globoside.

Brain↗
PubMed1985

Effect of viral infection on host protein synthesis and mRNA association with the cytoplasmic cytoskeletal structure.

We studied the association of several eucaryotic viral and cellular mRNAs with cytoskeletal fractions derived from normal and virus-infected cells. We found that all mRNAs appear to associate with the cytoskeletal structure during protein synthesis, irrespective of their 5' and 3' terminal structures: e.g., poliovirus that lacks a 5' cap structure or reovirus and histone mRNAs that lack a 3' poly A tail associated with the cytoskeletal framework to the same extent as capped, polyadenylated actin mRNA. Cellular (actin) and viral (vesicular stomatitis virus and reovirus) mRNAs were released from the cytoskeletal framework and their translation was inhibited when cells were infected with poliovirus. In contrast, actin mRNA was not released from the cytoskeleton during vesicular stomatitis virus infection although actin synthesis was inhibited. In addition, several other conditions under which protein synthesis is inhibited did not result in the release of mRNAs from the cytoskeletal framework. We conclude that the association of mRNA with the cytoskeletal framework is required but is not sufficient for protein synthesis in eucaryotes. Furthermore, the shut-off of host protein synthesis during poliovirus infection and not vesicular stomatitis virus infection occurs by a unique mechanism that leads to the release of host mRNAs from the cytoskeleton.

Actins↗
PubMed1981

Reassembly of flagellar B (alpha beta) tubulin into singlet microtubules: consequences for cytoplasmic microtubule structure and assembly.

B(alpha beta) tubulin was obtained from a homogeneous class of microtubules, the incomplete B subfiber of sea urchin sperm flagellar doublet microtubules, by thermal fractionation. The thermally derived soluble B tubulin fraction (100, 000 g-h) repolymerizes in vitro, yielding microtubule-like structures. The microtubule-associated protein (MAP) composition and certain assembly parameters of thermally derived B tubulin are different from those reported for sonication-derived flageller tubulin and purified vertebrate tubulin. The "microtubules" reassembled from thermally prepared B tubulin are composed of 12-15 protofilaments (73% possess 14 protofilaments). A certain number possess a single "adlumenal component" applied to their inside walls, regardless of the number of protofilaments. Following the first cycle of polymerization, 81% of the B tubulin and essentially 100% of the MAPs remain cold insoluble. Evidence suggests that B tubulin assembles faithfully into a B lattice, creating a j seam between two protofilaments that are laterally bonded in a A-lattice configuration. The significance of these seams is discussed in relation to the mechanism of microtubule assembly, the stability of observed ribbons of protofilaments, and the three-dimensional organization of microtubule-associated components.

Animals↗
PubMed1984

The structure of cytoplasm in directly frozen cultured cells. I. Filamentous meshworks and the cytoplasmic ground substance.

Cultured fibroblasts or epithelial cells derived from Xenopus laevis embryos were directly frozen, freeze-substituted by an improved method, and then either critical-point-dried and viewed as whole mounts, or embedded and thin sectioned. In thin regions of these cells, where ice crystal artifacts are absent, the cytoplasm consisted of a dense, highly interconnected meshwork of filaments, embedded in a finely granular ground substance. The meshwork in directly frozen, intact cells was compared with that in cells that were lysed (physically, with detergents, or with filipin), or fixed with glutaraldehyde before freezing. Although filaments tended to be less numerous in lysed cells, their overall organization was the same as that in intact cells. However, fixation with glutaraldehyde before freezing distorted the meshwork to variable degrees depending on the osmolarity of the fixation buffer, and also obscured the granular ground substance which is obvious in directly frozen cells. With optimal preparative methods, the cytoplasm of these directly frozen cells is shown to consist of a cytoskeleton composed of discrete interwoven filaments interconnected by numerous finer filaments and a readily extractable granular matrix which presumably represents aggregations of cytoplasmic proteins.

Animals↗