Ultrastructural analysis of rat articular cartilage following treatment with dexamethasone and glycosaminoglycan-peptide complex.

This ultrastructural study describes a stereological analysis of rat articular cartilage, with and without exposure to dexamethasone and a chondroprotective drug used in the treatment of osteoarthritis. Normal rat cartilage was found to contain 27.6 x 10(4) chondrocytes/mm3 which occupied approximately 10% of the cartilage tissue, and the organelle content of each chondrocyte was calculated to be about 20% of the cytoplasmic volume.

Accumulation of poliovirus proteins in uninfected isolated HEp-2 cell nuclei in vitro.

Poliovirus (type 1, Mahoney) proteins preferentially inhibited in vitro RNA polymerase II activity in uninfected isolated HEp-2 cell nuclei, as demonstrated by electron microscopic autoradiography. Structural integrity of the nuclei and preincubation of nuclei and poliovirus proteins in vitro prior to addition of [3H]-UTP were prerequisites for differential inhibition. During in vitro incubation, [3H]-labeled poliovirus proteins were shown to accumulate in the uninfected isolated nuclei.

Intracellular distribution of poliovirus proteins and the induction of virus-specific cytoplasmic structures.

In a susceptible cell, enteroviruses induce a vesiculated region (the "virus-induced vesicles") which is both the site of viral RNA synthesis as well as the site referred to morphologically, as the "cytopathic effect." Proteins of poliovirus (type I, Mahoney) were shown to migrate into the region of the virus-induced vesicles of infected HEp-2 cells. Five proteins (P2-5b, P3-4b, P3-6a, P3-7c, P3-9) were found to be associated with the vesicles themselves, either as intrinsic membrane protein (P3-9) or in a soluble form within the vesicles (P3-4b, P3-7c, and, partially, P3-6a) or bound to a DOC-resistant structure (P2-5b and a small amount of P3-6a).

Poliovirus-induced inhibition of host RNA synthesis studied in isolated HEp-2 cell nuclei.

Nuclei isolated from uninfected HEp-2 cells synthesized RNA for 60 to 90 min. The individual RNA polymerase activities were determined by alpha-amanitin differential inhibition and the RNA products characterized by electron microscope (EM) autoradiography and sucrose gradient centrifugation. In nuclei prepared from poliovirus-infected cells, the capacity to synthesize RNA in vitro decreased with time after infection.

Accumulation of poliovirus proteins in the host cell nucleus.

Poliovirus (type 1, Mahoney) proteins were transported into the nuclei of HEp-2 cells, as demonstrated by means of electron microscopic autoradiography. Quantitative determinations of the proteins by electrophoresis showed that the relative amounts of precursor proteins (1a, 3b, 1b), of some of the intermediate polypeptides (3a, 3c, 5b, 2), and of one end product (VP1) were higher in the nucleus than in the cytoplasm. Other proteins (VPO, VP2, X, 4, 6a) were found in the same relative amounts in the nucleus as in the cytoplasm, whereas two proteins (VP3 and 6b) were excluded from the nucleus.