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X F Wang

Publications and source records attributed to X F Wang.

At least 163 records · Page 9Linked to original sources
PubMed1988

In vivo functional analysis of in vitro protein binding sites in the immunoglobulin heavy chain enhancer.

We have systematically investigated the functional role of protein binding sites within the mouse immunoglobulin heavy chain enhancer which we previously identified by in vitro binding studies (1,2). Each binding site was deleted, mutant enhancers were cloned 3' of the chloramphenicol acetyl transferase gene in the vector pA10CAT2 and transfected into plasmacytoma cells. We demonstrate that the newly identified site E, located at 324-338 bp, is important for enhancer function; previously identified sites B(uE1), Cl(uE2), C2(uE3) and C3 were also shown to be important for enhancer activity. Sites A and D are not required for IgH enhancer function, as assayed by our methods. Thus, including the octamer site, six protein binding sites which bind at least six different proteins are important for enhancer function in vivo.

Animals↗
PubMed1988

Absence of TGF-beta receptors and growth inhibitory responses in retinoblastoma cells.

The responses of retinoblastoma tumor cells and normal retinal cells to various growth inhibitory factors were examined. Whereas fetal retinal cells were highly sensitive to the antimitogenic effects of transforming growth factor beta 1 (TGF-beta 1), retinoblastoma tumor cell lines were all resistant to this factor. Binding assays and affinity labeling of these cells with radioiodinated TGF-beta 1 revealed that the cells did not have TGF-beta receptors. The retinoblastoma cells lacked the three affinity-labeled proteins of 65, 95, and 300 kilodaltons typically seen in human cell lines and thus differed from normal retinal cells and from other types of neuroectodermal tumors that display the normal pattern of receptors. Loss of TGF-beta receptors, which is a rare event among tumor cells, may represent one mechanism through which these cells escape from negative control and form retinoblastomas.

Cell Division↗
PubMed1988

The effects of radiotherapy on the immune system of patients with nasopharyngeal carcinoma.

We report on 123 patients with nasopharyngeal carcinoma whose immune status was measured at the time of diagnosis, the day radiotherapy was completed, and then 2-3 months and 6-8 months after completion of radiotherapy. Immunological tests performed included the lymphocyte transformation test, the erythrocyte-rosette formation test (ERFT), the 29 degrees C erythrocyte-rosette formation test (29 degrees C ERFT), lymphocyte counts (lymphocytes/mm3 and percentage of lymphocytes), levels of serum immunoglobulins (IgG, IgA, IgM), complement (C3) and circulating immune complexes (CIC), the antinuclear antibody test and a skin test using phytohaemagglutinin (PHA). There were statistically significant differences in all tests (except C3) between patients and normal controls. Marked differences were seen in the lymphocyte count, ERFT, and 29 degrees C ERFT after radiotherapy (p less than 0.01). The diameters of induration of the PHA skin tests were less than those before radiotherapy (p less than 0.01). There were higher incidences of recurrence and metastases in the patients with high levels of CIC and low numbers of lymphocytes in the peripheral blood after radiotherapy. Cellular immunity remained at a low level 8 months after radiotherapy.

Antibodies, Antinuclear↗
PubMed1988

Effectiveness of amodiaquine, sulfadoxine-pyrimethamine, and combinations of these drugs for treating chloroquine-resistant falciparum malaria in Hainan Island, China.

The study was carried out in 1985-86 in Hainan Island where Plasmodium falciparum is resistant to chloroquine. Fifty cases of falciparum malaria were treated with 1800 mg amodiaquine for 3 days: the cure rate was 65.3%, and the mean time to clear fever and asexual parasitaemia was 30.7 and 60.3 hours, respectively; 34.7% of cases showed RI or RII recrudescence, and one patient's temperature did not come down to normal within 7 days.Twenty-one cases were treated with sulfadoxine-pyrimethamine (1500 mg and 75 mg, respectively): 19 were cured, I showed RI and another had an S or RI response; the mean time for fever control was 56.1 hours.Fifty cases were treated with amodiaquine plus sulfadoxine and 49 received amodiaquine plus sulfadoxine-pyrimethamine: the cure rate was 97.9% and 100%, respectively; the mean time for fever clearance was 25.0 and 25.7 hours and for parasite clearance 57.1 and 52.8 hours, respectively. These drug combinations gave much better results for cure and for symptom control than amodiaquine or sulfadoxine-pyrimethamine alone, and may be considered for treatment of chloroquine-resistant falciparum malaria.

Adolescent↗
PubMed1987

Deletions of a DNA sequence in retinoblastomas and mesenchymal tumors: organization of the sequence and its encoded protein.

Retinoblastoma is a childhood tumor that can arise because of mutant alleles acquired as somatic or germinal mutations. The mutant allele can be carried in the germ line. The mutations creating these alleles act by inactivating copies of a recessive oncogene located within band q14 of chromosome 13 and termed the RB1 locus. We have reported isolation of a cDNA fragment that recognizes chromosomal sequences possessing many of the attributes of the retinoblastoma gene associated with the RB1 locus. We now report that this segment is additionally the target of somatic mutations in mesenchymal tumors among patients having no apparent predisposition to retinoblastoma and no previous evidence of retinoblastoma. These tumors provide additional evidence that the cloned sequences are representative of a gene that is a frequent target of inactivation during tumorigenesis. Sequence analysis of this cDNA provides little insight into its normal functional role.

Amino Acid Sequence↗
PubMed1986

SV40 enhancer-binding factors are required at the establishment but not the maintenance step of enhancer-dependent transcriptional activation.

We have used temperature-sensitive COS cells to design delayed competition experiments in which competition for simian virus 40 (SV40) enhancer factors occurs after enhancer-dependent transcription has been established. The results demonstrate that competition for SV40 enhancer-binding factors has no effect on enhancer-dependent transcription after transcription has been established at the SV40 early promoter. These data show that the enhancer and factors that bind to it are involved in the establishment of stable transcription complexes, although they do not show whether enhancer factors are an integral part of the transcription complexes. Furthermore, the results of delayed competition experiments with a replicating test plasmid are consistent with the possibility that enhancer-dependent stable transcription complexes could be maintained after DNA replication.

Binding, Competitive↗
PubMed1985

Host-mediated selection of influenza virus receptor variants. Sialic acid-alpha 2,6Gal-specific clones of A/duck/Ukraine/1/63 revert to sialic acid-alpha 2,3Gal-specific wild type in ovo.

Human and animal influenza A isolates of the H3 serotype preferentially bind SA alpha 2,6Gal or SA alpha 2,3Gal linkages (where SA represents sialic acid), respectively, on cell-surface sialyloligosaccharides. Previously, we have demonstrated selection of SA alpha 2,3Gal-specific receptor variants of several human viruses which differed from the parent viruses by a single amino acid at residue 226 of the hemagglutinin which is located in the receptor binding pocket (Rogers, G. N., Paulson, J.C., Daniels, R.S., Skehel, J.J., Wilson, I.A., and Wiley, D.C. (1983) Nature 304, 76-78). In this report, the selection in the reverse direction was accomplished starting with a SA alpha 2,3Gal-specific avian virus, A/duck/Ukraine/1/63 (H3N7), yielding SA alpha 2,6Gal-specific variants that exhibit the receptor binding properties characteristic of the human isolates. Selection was again mediated at residue 226 of the hemagglutinin, in this case changing from Gln in the parent virus to Leu in the variants. Although the SA alpha 2,6Gal-specific avian virus variants were stable to passage in MDCK cells, they exhibited dramatic reversion to the SA alpha 2,3Gal-specific phenotype of the parent virus during a single passage in chicken embryos. This was in contrast to the SA alpha 2,6Gal-specific human virus isolates which were stable to passage in both hosts. The reversion of the avian virus variants in eggs provides compelling evidence for host-mediated selection of influenza virus receptor variants.

Animals↗
PubMed1985

The endogenous immunoglobulin heavy chain enhancer can activate tandem VH promoters separated by a large distance.

The availability of a clone containing two linked immunoglobulin heavy chain variable region genes located 15.8 kb apart has allowed us to study the functional capabilities of the immunoglobulin heavy chain transcriptional enhancer element in its normal chromosomal context. In plasmacytoma J606 the 3' VH gene is joined to D and J gene segments, located within 1.7 kb of the heavy chain enhancer, and expressed; the 5' VH gene is 17.5 kb from the enhancer in J606 DNA. Run-on transcription in isolated nuclei demonstrated specific transcription of the 5' VH gene in J606 that was 60% that of the expressed 3' VH gene. No other enhancer elements are detectable closer to the 5' VH gene than the known heavy chain enhancer. Thus, the heavy chain enhancer appears to be capable of activating transcription of a VH promoter located 17.5 kb away and of activating two tandem VH promoters.

Animals↗