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Biomedical subjects

X Tang

Publications and source records attributed to X Tang.

At least 289 records · Page 16Linked to original sources
PubMed1992

Generation of 19 STS markers that can be anchored at specific sites on human chromosome 21.

Sequence-tagged sites (STSs) are short stretches of DNA that can be specifically detected by the polymerase chain reaction (PCR) and can be used to construct long-range physical maps of chromosomal DNA. These STSs can be detected by PCR assays developed by reference to data obtained from the sequencing of restriction fragment length polymorphism-DNA markers for chromosome 21, which were derived from recombinant lamba-phage and plasmid clones made from DNA of a human-hamster hybrid cell line. In this report, we describe the generation of 19 new STSs that are specific for human chromosome 21.

Base Sequence↗
PubMed1992

Phenotypic conversion of SV40-immortalized human diploid fibroblasts to senescing cells by introduction of an antisense gene for SV40-T antigen.

Normal human lung fibroblast diploid cells, WI-38, become senescent after a definite number of divisions. VA-13 is a line of immortalized cells established by transformation of WI-38 cells by SV40 virus. To determine whether SV40 large T (SV40-T) antigen is essential for this immortalization of WI-38 cells we introduced an antisense gene for T antigen into VA-13. Two morphologically different types of antisense transformant (VA-AS5-8 and VA-AS37-8) were obtained. In both antisense transformants the expression of T antigen was reduced by more than 70% as compared to that in the parent cells. The morphology of the antisense transformants indicated a partial conversion to the senescent phenotype of WI-38. The relative number of cells in the S phase of the antisense transformants was decreased as compared to that in cultures of VA-13 and about 50% of cells were at G1/0. The doubling time of the transformants was prolonged to close to the doubling time of WI-38. The level of expression of retinoblastoma protein (pRB) complexed with SV40-T antigen of the antisense transformants was significantly decreased although the level of total pRB was much higher than that in VA-13. The pRB was present exclusively in the underphosphorylated form. Thus, the decreased level of formation of the complex between SV40-T and pRB or the underphosphorylation of pRB may explain the suppression of growth of antisense transformants. Together, these results show that an antisense gene for SV40-T antigen can efficiently block the cell proliferation and the cell immortalization of VA-13 cells.

Antigens, Polyomavirus Transforming↗
PubMed1992

Inhibition of expression of a mouse alpha-globin gene by plasmids that include antisense oligonucleotides.

Plasmid-borne DNAs, corresponding to 68-base oligodeoxynucleotides, synthesized in the antisense or sense configuration and based on the nucleotide sequences of various regions of the mouse alpha-globin mRNA, were introduced with the gene for xanthine-guanine phosphoribosyl transferase from E. coli (Ecogpt) into mouse erythroleukemia (MEL) cells by protoplast fusion. Specific inhibition of the synthesis of alpha-globin was observed only in the cells transformed with the plasmids with antisense 68-mers that corresponded to the cap site as well as the site of initiation of translation of alpha-globin mRNA (Oligo-A); Other plasmids with antisense 68-mers that corresponded to the regions of the exon/intron junctions, the individual exons, or the 3' untranslated region were ineffective. This antisense RNA efficiently reduced the production of alpha-globin to 9-18% of the endogenous level after induction with hexylmethylene-bis-acetoamide (HMBA). Moreover, most of the antisense transformants did not show any decrease in the expression of the c-myc gene at the early phases of differentiation of MEL cells. Thus, we propose a hypothesis that the early decline in levels of c-myc mRNA may be independent of and uncoupled from the program of globin synthesis during the differentiation of MEL cells.

Acetamides↗
PubMed1992

Utilization of the protoplast fusion technique to explore directional altering lincomycin producing microorganism.

Interspecific protoplast fusion between Streptomyces lincolnensis var. lincolnensis (LM gamma, CTC gamma, producing lincomycin) protoplast and Streptomyces aureofaciens (LM gamma, CTC gamma, producing chlorotetracycline) protpolast which had been treated with UV radiation 40 min for inactivation was performed with PEG 6000, the fusants were obtained by directly selecting from the regeneration plates containing CTC 50 micrograms/ml, the fusion frequency was about 9.05 x 10(-5). From many fusants, only 4 stable recombinants were obtained. These species produced antibiotics which are different from lincomycin and chlorotetracycline. Preliminary identification of the antibiotic synthesized by one of the recombinants suggests that its basic structure might be similar to that of lincomycin. The fermentation product of recombinant No. 2 showed new chromatographic spot which is similar to that of clindamycin. Though the products remain to be identified further, this strategy seems to be worthy of exploring for screening new antibiotics.

Anti-Bacterial Agents↗
PubMed1992

[Veno-valvulectomy and primary in situ arteriolization of the great saphenous vein for the treatment of ischemic lower limbs].

After the study of the valvular distribution of 18 cadaveric great saphenous veins, we performed microsurgically great saphenous veno-valvulectomy and primary in situ veno-arteriolization for 18 severely ischemic limbs of 17 patients of these patients, 14 had thromboangiitis obliterans, and 3 arteriosclerosis. 16 patients were followed up for 14 to 32 months after operations. The results were excellent. The procedure is a good alternative for the treatment of extensive arterial occlusive disease of the lower limbs.

Adult↗
PubMed1992

[The effect of stimulating the auricular liver-gall acupoint with electrode on synaptic of nucleus originis dorsalis nervi vagi in rabbits].

In this experiment, several ultrastructural parameters of Gray's type I synapses in nucleus originis dorsalis nervi vagi were observed and quantitatively analysed by use of electron microscopy in condition gallbladder contraction by stimulating the auricular liver-gall acupoint of rabbits with electrode. It was found that the synaptic contact length was increased extremely significantly, and the postsynaptic thickening length lengthened significantly. There were no changes in the area and the perimeter of presynaptic bouton as well as synaptic vesicle density. The percentages of synaptic perforation and negative synaptic interface tended towards increase. But there were no differences in synapses of positive and straight interface. It is suggested that the nucleus is involved in the regulation of gallbladder activity induced by auricular acupoint stimulation.

Acupuncture Points↗
PubMed1992

[Transcranial magnetic motor evoked potentials (MEP) and somatic sensory evoked potentials (SEP) in the management of cervical spondylitic myelopathy (CSM)].

Fourteen CSM patients with clinical findings of myelopathy had their diagnoses proved with MRI imaging and at operation. There were a control group of 28 normal subjects for MEP and another control group of 32 for SEP. The results of the study showed that 72.7% had MEP abnormality with prolongation of the central motor conduction time (CMCT) in 7 cases and absence of motor action potentials after C7 stimulation in one of the 11 patients. In 2 patients with prolongation of CMCT, normal SEPs were found in the same arm while 1 patient showed directly a reversal of the results. The short-term follow-up study in 10 patients showed normalization of the prolonged CMCT in one and reappearance of motor action potentials with C7 stimulation in another. The authors considered that the non-invasive and painless, transcranial magnetic stimulation of the motor pathways might be useful in the assessment and management of CSM patients and better than the electrical stimulation.

Adult↗