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Biomedical subjects

T C Wong

Publications and source records attributed to T C Wong.

At least 73 records · Page 4Linked to original sources
PubMed1985

Cloned DNA of defective avian sarcoma virus mutant LA46 encodes the cis-acting temperature-sensitive defect in replication.

Avian defective sarcoma virus mutant LA46 carries a temperature-sensitive defect in replication and transformation. To elucidate this defect, we cloned the integrated provirus of LA46. By DNA-mediated transfection, the cloned DNA induced fusiform-transformed foci in chick embryo fibroblasts without helper virus. LA46-encoded transformation-specific protein p105 was expressed in these transformants in the absence of helper virus-encoded proteins. Superinfection of the transformed cells with different helper viruses resulted in the rescue of pseudotypes. All the rescued pseudotypes retained the temperature-sensitive phenotype in virus replication and transformation, suggesting that the defect was due to a cis-acting lesion in the LA46 genome. Restriction enzyme comparison between LA46 and wild-type virus revealed sequence differences near the 5' and 3' termini of the LA46 genome, including the long terminal repeat regions.

Animals↗
PubMed1985

The promoter of the long terminal repeat of feline leukemia virus is effective for expression of a mouse H-2 histocompatibility gene in mouse and human cells.

DNA-mediated gene transfer techniques have been used to study the effectiveness of a novel construction involving the feline leukemia virus long terminal repeat (FeLV LTR) for expressing the mouse H-2 Ld gene in mouse and human cells. In this construction, the transcription initiation (promoter) and termination (polyadenylation) functions of the FeLV LTR have been split by insertion of a promoterless H-2 gene between them. An S1 nuclease assay has been developed that makes it possible to measure accumulated LdRNA against a background of endogenous major histocompatibility antigen RNAs in mouse and human cells. In mouse cells, the H-2 Ld gene was expressed at approximately equal levels (measured as accumulated RNA) when driven either by its own promoter or by the FeLV LTR construction. In human cells, expression at the RNA level was highest when driven by the FeLV LTR. We conclude that the FeLV LTR construction is useful for expressing foreign genes in human cells.

Animals↗
PubMed1984

The combining site of anti-I Ma (group 1).

Evidence is provided that the trisaccharide beta DGal(1----4)beta DGlcNAc(1----6)beta DGal is bound by the monoclonal anti-I Ma antibody beginning with a basically nonpolar cleft at the surface of the protein which comes into contact with a weakly polar region of the trisaccharide that extends from the C-5 methylene group of the reducing unit about the surfaces involving the acetamido grouping and the OH-3' of the beta DGlcNAc unit intramolecularly hydrogen bonded to the O-5'' of the nonreducing beta DGal unit and up to the C-5'' methylene group. The combining site then terminates with a polar grouping at its periphery which is disposed to react with OH-6'' and likely OH-4'' in a highly specific manner. The hydroxyl groups at positions 1, 2, 3, 4, 6', 3'' and 4'' remain in contact with the aq. phase. This conclusion was deduced from the relative potencies as inhibitors of a wide number of synthetic compounds that bear varying structural relationships to the trisaccharide. It appears that the stability of the complex is mainly related to attractive interactions between two large complementary and essentially hydrophobic surfaces relative to those when these surfaces are exposed to water.

Antibodies, Monoclonal↗
PubMed1981

Avian reticuloendotheliosis virus: characterization of genome structure by heteroduplex mapping.

The genome structure of defective, oncogenic avian reticuloendotheliosis virus (REV) was studied by heteroduplex mapping between the full-length complementary DNA of the helper virus REV-T1 and the 30S REV RNA. The REV genome (5.5 kilobases) had a deletion of 3.69 kilobases in the gag-pol region, confirming the genetic defectiveness of REV. In addition, REV lacked the sequences corresponding to the env gene but contained, instead, a contiguous stretch (1.6 to 1.9 kilobases) of the specific sequences presumably related to viral oncogenicity. Unlike those of other avian acute leukemia viruses, the transformation-specific sequences of REV were not contiguous with the gag-pol deletion. Thus, REV has a genome structure similar to that of a defective mink cell focus-inducing virus or a defective murine sarcoma virus. An additional class of heteroduplex molecules containing the gag-pol deletion and two other smaller deletion loops was observed. These molecules probably represented recombinants between the oncogenic REV and its helper virus.

Base Sequence↗
PubMed1980

Assembly of avian reticuloendotheliosis virus: association of the core precursor polypeptide with the intracellular ribonucleoprotein complex.

A virus-specific ribonucleoprotein complex is present in the cytoplasm of reticuloendotheliosis virus-transformed chicken bone marrow cells. This ribonucleoprotein complex contains viral reverse transcriptase activity and may represent a precursor to the budding virion. The major viral polypeptide associated with the ribonucleoprotein complex was a polypeptide with a molecular weight of 63,000. This protein exhibited a precursor-product relationship with the major reticuloendotheliosis virus structural core protein p29. Core polypeptides were not associated with the intracellular ribonucleoprotein complex. Thus, p29 was incorporated into the virion in the form of its precursor Pr63. The cleavage of Pr63 in the ribonucleoprotein complex was accomplished either during the budding process of shortly after the release of particles from the cell.

Animals↗
PubMed1979

Electrocardiographic voltage changes during hyperthyroidism.

Electrocardiograms of 67 thyrotoxic patients were studied. Subsequent electrocardiograms during euthyroidism in 16 patients permitted an analysis of voltage changes. Decreases in voltages after radioiodine therapy were significant (P less than 0.01) for the P wave in lead, V1, R wave in leads II, AVF, V4, V5, and V6, maximal RS wave, and maximal R wave and were present in all but one patient. Criteria for left ventricular hypertrophy (sum of S wave in V1 plus R wave in V5 or V6 greater than 35 mm), present in 21% of patients, regressed in all five patients who had later electrocardiograms during euthyroidism. Left ventricular hypertrophy or high-voltage R waves in the absence of usual causes may suggest the presence of hyperthyroidism. The concept that cardiac voltage is determined in part by thyroid hormone is reviewed; this relationship may be the basis for increased voltage in hyperthyroidism as well as decreased voltage in hypothyroidism.

Adult↗
PubMed1978

Isolation and characterization of a virus-specific ribonucleoprotein complex from reticuloendotheliosis virus-transformed chicken bone marrow cells.

Chicken bone marrow cells transformed by reticuloendotheliosis virus (REV) produce in the cytoplasm a ribonucleoprotein (RNP) complex which has a sedimentation value of approximately 80 to 100S and a density of 1.23 g/cm3. This RNP complex is not derived from the mature virion. An endogenous RNA-directed DNA polymerase activity is associated with the RNP complex. The enzyme activity was completely neutralized by anti-REV DNA polymerase antibody but not by anti-avian myeloblastosis virus DNA polymerase antibody. The DNA product from the endogenous RNA-directed DNA polymerase reaction of the RNP complex hybridized to REV RNA but not to avian leukosis virus RNA. The RNA extracted from the RNP hybridized only to REV-specific complementary DNA synthesized from an endogenous DNA polymerase reaction of purified REV. The size of the RNA in the RNP is 30 to 35S, which represents the subunit size of the genomic RNA. No 60S mature genomic RNA was found within the RNP complex. The significance of finding the endogenous DNA polymerase activity in the viral RNP in infected cells and the maturation process of 60S virion RNA of REV are discussed.

Animals↗
PubMed1976

Fine structure of oocyst transformation and the sporozoites of Leucocytozoon dubreuili.

The sporogonic stages of Leucocytozoon dubreuili in the midgut and salivary glands of the simuliid vectors was studied by electron microscopy. Young uninucleate oocysts have a pellicle that initially resembles that of the ookinete. Numerous electron-dense bodies and microtubules in the peripheral cytoplasm may be involved in the formation of the cyst wall. The dense bodies appear to give rise to the amorphous material of the wall. The tubules which run circumferentially beneath the oocyst's boundary probably serve as a skeletal support for the cell surface during deposition of the wall material.

Animals↗