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Biomedical subjects

C F Yang

Publications and source records attributed to C F Yang.

At least 109 records · Page 6Linked to original sources
PubMed1987

Uridylylation of the genome-linked protein of poliovirus in vitro is dependent upon an endogenous RNA template.

The properties of an in vitro replication system derived from a membrane fraction (crude replication complex, CRC) of poliovirus-infected HeLa cells were examined. This system was capable of producing the nucleotidyl-proteins VPg-pU and VPg-pUpU. Due to high intrinsic phosphoesterase(s) activity and endogenous nucleoside triphosphate pools the yield of labeled product was low. Treatment of CRC with DEAE-cellulose and addition of an ATP generating system resulted in a dramatic increase in the level of nucleotidyl-proteins formed. The capacity to form VPg-pU and VPg-pUpU could be completely abolished by pretreatment of CRC with nuclease, an observation suggesting that the uridylylation of VPg is a template-dependent reaction.

Genes, Viral↗
PubMed1987

Analysis of RNA synthesis of type 1 poliovirus by using an in vitro molecular genetic approach.

Membranous crude replication complexes (CRC) were isolated from poliovirus-infected HeLa cells as recently described (N. Takeda, R.J. Kuhn, C.-F. Yang, T. Takegami, and E. Wimmer, J. Virol. 60:43-53, 1986). Viruses used to produce the CRC were poliovirus type 1 (Mahoney), [PV-1(M)], poliovirus type 1 (Sabin) [PV-1(S)], and four in vitro recombinants that were constructed from infectious cDNA clones. RNA synthesis in CRC was studied. No end-linked, full-length double-stranded poliovirus RNA was detected in CRC regardless of whether nonionic detergent (Nonidet P-40) was added prior to incubation. Synthesis of VPg-pU and VPg-pUpU, two nucleotidyl proteins presumed to be involved in the initiation of RNA synthesis, was slower at 30 degrees C in CRC induced by PV-1(S) than by PV-1(M). This observation was used to design a pulse-chase experiment whose result suggested that synthesis of VPg-pUpU occurred by uridylylation of VPg-pU. Synthesis of VPg-pU(pU) was thermosensitive in CRC induced by PV-1(S). With CRC of recombinant viruses, the thermosensitive block covaried to nucleotide substitutions in PV-1(S) that mapped to the virus-induced RNA polymerase 3Dpol. We conclude that plus-stranded RNA synthesis in CRC does not proceed via hairpin structures. The results of VPg-pU----VPg-pUpU synthesis are consistent with a model in which VPg-pU is the primer of RNA synthesis mediated by 3Dpol. The data suggest that uridylylation of VPg or a precursor thereof may be catalyzed by 3Dpol itself, a mechanism resembling events occurring in adenovirus DNA replication.

HeLa Cells↗
PubMed1986

Initiation of poliovirus plus-strand RNA synthesis in a membrane complex of infected HeLa cells.

An in vitro poliovirus RNA-synthesizing system derived from a crude membrane fraction of infected HeLa cells was used to analyze the mechanism of initiation of poliovirus plus-strand RNA synthesis. This system contains an activity that synthesizes the nucleotidyl proteins VPg-pU and VPg-pUpU. These molecules represent the 5'-terminal structure of nascent RNA molecules and of virion RNA. The membranous replication complex is also capable of synthesizing nucleotidyl proteins containing nine or more of the poliovirus 5'-proximal nucleotides as assayed by the formation of the RNase T1-resistant oligonucleotide VPg-pUUAAAACAGp or by fingerprint analysis of the in vitro-synthesized RNA. Incubation of preformed VPg-pUpU with unlabeled nucleoside triphosphates resulted in the formation of VPg-pUUAAAACAGp. This reaction, which appeared to be an elongation of VPg-pUpU, was stimulated by the addition of a soluble fraction (S-10) obtained from uninfected HeLa cells. Preformed VPg-pU could be chased into VPg-pUpU in the presence of UTP. Our data are consistent with a model that VPg-pU can function as a primer for poliovirus plus-strand RNA synthesis in the membranous replication complex and that the elongation reaction may be stimulated by a host cellular factor.

Cell Membrane↗
PubMed1986

Benign hydrocephalus in infants. A computed tomographic and clinical correlative study.

During the past 3 years we studied benign hydrocephalus in 7 infants, who presented symptoms of macrocrania and mild psychomotor retardation. Computed tomography (CT) revealed dilatation of CSF space resembling brain atrophy or subdural effusion. These children were observed clinically and were found gradually to restore to normal with regard to CT changes, as well as clinically. These patients were compared with another group of patients with subdural effusion or hematoma who needed tapping or shunting.

Brain↗
PubMed1982

Percutaneous transluminal angioplasty for limb salvage.

Thirty patients with end-stage atherosclerosis, being considered for amputation, were treated by percutaneous transluminal angioplasty (PTA). All had very poor run-off, and none was a candidate for arterial reconstruction. Occluded segments of the iliac, femoral, popliteal, and tibial arteries measuring up to 21 cm were recanalized, resulting in an increased ankle/brachial systolic pressure index despite significant distal occlusive disease. Ischemic symptoms were relieved in 22 patients, and the overall limb salvage rate (2- to 17-month follow-up) was 73%.

Aged↗