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Biomedical subjects

Y F Yang

Publications and source records attributed to Y F Yang.

At least 73 records · Page 4Linked to original sources
PubMed1994

Diagnosis of fungemia in bone marrow transplantation patients by examination of peripheral blood smears.

Two patients who received BMT for treatment of severe aplastic and AML-M2, developed fungemia during leukopenia. The organisms responsible for the infections were Candida parapsilosis and Rhodotorula glutinis, respectively. Early diagnosis of fungemia in these two patients was made by visualization of fungal blastospores in peripheral blood (PB) smears. These two cases illustrate that cytologic examination of PB smears is a useful method for early detection of fungus infection in BMT patients with leukopenia and unexplained fever in spite of appropriate antibiotic treatment.

Adolescent↗
PubMed1994

The induction of multidrug resistance in human cervical carcinoma cell lines by estrogenic hormones.

The role of estrogenic hormones on the induction of drug resistance was studied in cervical cancer cell lines, SiHa and Caski. After the cells were inoculated with estradiol (E2) or diethylstilbestrol (DES) in various dosages, the cell survival rates with adriamycin treatment were examined by MTT (3-[4,5-dimethyl-thiazole-2-yl]-2,5-diphenyl-tetrazolium-bromide) test and the intracellular accumulation of adriamycin was evaluated by flow cytometry. In the same condition, the expression of multidrug resistance gene-1 (mdr-1 gene) was detected either by Northern blot hybridization for mdr-1 mRNA or by immunoblot for P-glycoprotein 170. The data in this study indicated that estrogenic hormones had the capacity to induce drug resistance in cervical carcinoma cell lines. When cells were treated with estrogenic hormones and adriamycin simultaneously, the intracellular accumulation of adriamycin declined and corresponded with the drug resistance. Since the expression of the mdr-1 gene induced by E2 or DES results in drug resistance, it is suggested that the mdr-1 gene in SiHa cells may contain the estrogenic responsive element (ERE) in its regulatory region. However, the mechanism of drug resistance induced by estrogenic hormones in Caski cells is different from SiHa cells due to the absence of mdr-1 gene expression. Despite that, this experiment may provide a model to investigate the relationships between estrogenic hormones and drug resistance in other female genital cancers.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

[Experimental study on anti-abortional effect of yunkang oral liquid].

Yunkang oral liquid (YK) had an obviously anti-abortional effect on the abortional testing model of both rats and mice, which was induced by acupuncture and oxytocin (P < 0.05, P < 0.01); there is no statistic difference between the effect of progesterone and the effect of YK. The results showed that YK could relax obviously the uteri of both rats and mice in vitro and the uteri of rabbits in vivo. It also could antagonize the effects of oxytocin and acetylcholine on animals uteri in vivo and in vitro (P < 0.01, P < 0.05). The acute toxicologic test showed the maximal tolerance dose of ig. in mice and rats were higher than 240 g/kg and 96 g/kg respectively. The LD50 in mice (ip.) was 61.56 +/- 5.29 g/kg (p = 0.95). Subacute toxicologic test for 8 weeks of continuous drug feeding among rats did not show obvious toxicity. Mutagenicity test also showed negative results. Feeding to pregnant rats with YK did not result in teratogenicity to the offsprings. The growth and development, memory of filial generations were not affected, either. So Yunkang oral liquid, a Chinese compound recipe, has a safe and reliable effect of anti-abortion.

Abortion, Spontaneous↗
PubMed1994

Establishment and characterization of the transfectable golden hamster embryo fibroblast cell line.

A diploid, continuous cell line, Golden Hamster Embryo Fibroblast-III (GHEF-III), which had been passaged for one year, was established essentially by a 3T3 protocol from primary culture of 14-day-gestation Golden Hamster embryo fibroblast cells. The cultured fibroblast exhibited monolayer growth and had contact inhibition. In morphological identification by light microscope (LM), transmission electron microscope (TEM) and immunofluorescence examination (IF), these multipolar and spindle-shaped cells had a large ovoid nucleus, enriched rER and mitochondria in the cytoplasm. On the other hand, the vimentin presented in the cell with a random network and capped around the nucleus. The results indicated that the cultured GHEF-III cells were fibroblast in origin. The cells were free of bacterial and mycoplasma contamination. The doubling time in GHEF-III was about 15 hours. Chromosomal analysis of GHEF-III presented a diploid stem cell line with a modal number of 44. No evidence of transformation of GHEF-III was shown by properties of contact inhibition, no colony formation in soft agar, and no tumor growth in nude mice. The transformation of GHEF-III after transfection with pT24-C3, an oncogenic plasmid, was shown by the evidence of loss of contact inhibition, growth in low serum medium, colony formation in soft agar and tumor growth in nude mice. In vitro transformation testing of these cells may provide valuable data in studying the role of tumor transforming genes in carcinogenesis. Owing to the genetic stability and less spontaneous transformation, this GHEF-III cell line can be utilized as a source of recipient cells in transfection assay.

3T3 Cells↗
PubMed1993

cAMP analogs prevent activation-induced apoptosis of T cell hybridomas.

Activation of T cell hybridomas through their TCR leads to secretion of IL-2, inhibition of proliferation, and apoptosis. The identification of various inhibitors that prevent activation-induced T cell death (AICD) has helped identify several essential events in apoptosis. For example, inhibition of AICD by dexamethasone indicates a connection between these two programmed death pathways. In this study, we have investigated the interaction between the cAMP signal transduction pathway and the activation- or glucocorticoid-induced cell death. cAMP induced DNA fragmentation in thymocytes. T cell hybridomas displayed different sensitivity to cAMP. Regardless of its cAMP sensitivity, programmed cell death promoted by anti-CD3 or Ag in hybridoma was prevented by the presence of cAMP analogs. In contrast, cAMP had no effect on glucocorticoid-induced T cell death. The inhibitory effect of cAMP on AICD was unlikely to be due to quenching of T cell activation signals, because cAMP added 1 h after T cell activation could still prevent cell death. In addition, the increased binding of AP-1, NF-AT, and NF-kappa B during T cell activation was not significantly affected by cAMP. The presence of the inhibitory cAMP-mediated signals, together with the glucocorticoid-induced pathway, suggest there are at least two distinct mechanisms regulating AICD in immature lymphocytes.

Amino Acid Sequence↗
PubMed1993

[Platelet neuropeptide Y and its vasoconstriction effect in rat].

Specific radioimmunoassay showed that in rat neuropeptide Y (NPY) immuno-reactivities (IR) in platelets and platelet rich plasma (PRP) were respectively 90 +/- 16 ng/10(7) platelets and 93 +/- 19 ng/ml. Both values were much greater than those in the plasma (1.2 +/- 0.1 ng/ml, P < 0.001) and platelet poor plasma (PPP) (1.7 +/- 0.3 ng/ml, P < 0.001). The NPY-IR in rat platelets eluted at the same position as authentic NPY on reverse phase HPLC. The NPY-IR in the platelets prepared from the PRP aggregated maximally by collagen reduced to 34 +/- 5 ng/10(7) platelets, while the NPY-IR in the PPP prepared from the same PRP increased to 26 +/- 4 ng/ml. PPP 1.6 ml prepared from the aggregated PRP induced contraction of isolated rat caudal arteries with the maximal tension of 380 +/- 80 mg; while the maximal contraction induced by 1.6 ml of the same PPP pretreated with NPY anti-serum was only 190 +/- 40 mg (P < 0.001). Authentic NPY 1 nmol/L did not cause any contraction. The results indicate that rat platelets contain a high concentration of NPY, which can be released during irreversible platelet aggregation. The NPY released can potentiate vasoconstriction responses induced by co-released substances during platelet aggregation.

Animals↗
PubMed1992

[Analysis of the correlations between immunological changes and syndrome groups in patients with immunological thrombocytopenic purpura (ITP)].

To study the relationship between the immunological changes and syndrome (Zheng,) groups by TCM of ITP, the T-lymphocyte subsets, B-lymphocyte, NK cell, platelet-associated IgG (PAIgG, PAIgA, PAIgM) and antiplatelet-autoantibodies (GPIIb, GPIIIa, GP I b) of 66 patients with ITP were assisted using APAAP and ELISA method separately. It was found that the T-lymphocyte subsets, PAIg and syndrome groups of ITP were closely related. From the group of blood-heat (Xuerewangxing) to the group of deficiency of both Qi and blood, the group of asthenia of both Spleen and Kidney, the group of deficiency of Liver-yin and Kidney-yin, and the group of deficiency Yin and Yang Ts lymphocyte successfully increased (from 29. 0 +/- 8.0% to 47.2 +/- 10.0%), Th/Ts ratio declined (from 1.35 +/- 0.60% to 0.69 +/- 10%), PAIg increased gradually except for PAIgM,PAIgG of the group of deficiency Yin and Yang. Only the Th of the group of asthenia of both Spleen and Kidney among 5 syndrome groups was decreased significantly and contrary to the group of deficiency of Liver-Yin and Kidney-Yin. These results indicated that every syndrome group has specific characteristics, and immunological changes of ITP could have prognostic value.

Adolescent↗
PubMed1991

Rat liver c-erb A beta 1 thyroid hormone receptor is a constitutive activator in yeast (Saccharomyces cerevisiae): essential role of domains D,E and F in hormone-independent transcription.

To assess thyroid hormone receptor (TR)-mediated activation of transcription in yeast in the presence or absence of thyroid hormone (T3), we developed a co-expression system using a TR-beta 1 expression vector and a reporter plasmid containing a 16 base pair palindromic thyroid hormone response element (TRE) upstream from a proximal CYC1 promoter that was fused to the beta-galactosidase lac Z gene of Escherichia coli. Although TR-beta 1 functions as a repressor in most mammalian systems, using our system we observed a unique thyroid hormone-independent transcriptional response indicating that wild TR-beta 1 acted as a constitutive activator in yeast; the addition of 1 microM T3 induced a moderate but significant (p less than 0.01) 25-40% further increase in transcriptional activity. Using a series of rat TR-beta 1 mutant constructs, we found that deletion of domain D and portions of E completely eliminated transcriptional activity, whereas truncations of domain F and E permitted a partial (20-40%) response compared to wild TR-beta 1 in the presence or absence of T3. These observations indicate that TR-beta 1 functions as an activator in yeast and that domains D,E and F play important interactive roles in its hormone-independent gene activation with the D domain likely being the most essential. Furthermore, our results suggest that the different transcriptional property of TR-beta 1 in yeast compared to mammalian cells i.e. activator vs repressor function, is likely determined by transcriptional factor differences which are dependent upon cellular origin.

Amino Acid Sequence↗
PubMed1991

Identification and characterization of the functional amino acids at the active center of pig liver thioltransferase by site-directed mutagenesis.

By using site-directed mutagenesis techniques, the essential amino acids at the catalytic center of porcine thioltransferase (glutaredoxin) were determined. Seven oligonucleotides were designed, synthesized, and used to construct mutants, ETT-C22S, ETT-C25S, ETT-C25A, ETT-R26V, ETT-K27Q, ETT-R26V: K27Q, and ETT-C78S:C82S, by altering their codons in pig liver thioltransferase cDNA/M13mp18 clones. Each of the thioltransferases was purified to homogeneity and its dithiol-disulfide exchange, and dehydroascorbate reductase activities were compared with those of the wild-type (ETT). Evidence was obtained that Cys22 was essential for catalytic activity, and the extremely low pKa value of its sulfhydryl group was facilitated primarily by Arg26. The role of Lys27 at the active center was different from that of Arg26 and may be important in stabilizing the E.S intermediate by electrostatic forces. The second pair of cysteines, Cys78 and Cys82, nearer the C terminus, were not directly involved in the active center, but may play a role in defining the native protein structure. The replacement of the original Cys with a Ser at position 25 increased rather than decreased the enzyme activity, suggesting that the proposed intramolecular disulfide bond between Cys22 and Cys25 is not necessary for the catalytic mechanism of the Ser25 mutant, but does not rule out such a mechanism for the wild-type enzyme.

Amino Acid Sequence↗
PubMed1991

Catalytic mechanism of thioltransferase.

To evaluate potential catalytic mechanism for thioltransferase thiol-disulfide exchange reactions, seven pig liver mutants were constructed by site-directed mutagenesis. All the expressed enzymes, including wild-type and mutants with the exception of the inactive mutant, ETT-C22S, were variably inhibited by iodoacetamide, and similar results were obtained when these enzymes were preincubated with GSH. However, when preincubated with S-sulfocysteine or hydroxyethyl disulfide, the activity of the enzymes was totally or partially protected against inhibition by iodoacetamide, with the exception of the mutants, ETT-C25S and ETT-C25A. When simultaneously pretreated with GSH and S-sulfocysteine, all enzymes were highly protected. Isoelectric focusing analysis of the above preincubation mixtures showed that different enzyme-substrate intermediates occurred. Using radioactively labeled substrates, [U-14C]cystine and [glycine-2-3H] GSH, enzyme-substrate intermediates were detected. These data indicate that reduced thioltransferase reacts first with disulfide substrates, then with a thiol substrate, e.g. GSH. The formation of either enzyme-substrate mixed disulfide or protein intramolecular disulfide protected the enzyme from inactivation by iodoacetamide. Based on the experimental results, alternative methods of the catalytic mechanism for thioltransferases are proposed.

Animals↗
PubMed1991

Selective association of a fragment of the knob protein with spectrin, actin and the red cell membrane.

The knob protein of Plasmodium falciparum is essential for the formation of knob-like protrusions on the host erythrocyte membrane. A functional domain of the knob protein was identified. This peptide formed stable complexes with the two major red cell skeletal proteins, spectrin and actin. When introduced into resealed normal erythrocytes, the peptide associated selectively with the cytoplasmic surface of the membrane and formed knob-like electron dense deposits. Knobs are thought to play an important role in the immunopathology of P. falciparum infections. Our findings provide a first step towards understanding the molecular basis for selective membrane changes at knobs.

Actins↗
PubMed1991

Neuroendocrine carcinomas associated with squamous cell carcinomas of the uterine cervix: light and electron microscopic observations in two cases.

Small cell carcinomas are rare in cervical cancers and appear to be a heterogeneous group of tumors. Neuroendocrine carcinoma of the cervix, one subtype of small cell carcinomas of the cervix, can be identified by characteristic light and electron microscopic criteria. Two cases of neuroendocrine carcinomas associated with squamous cell carcinomas of the uterine cervix are reported in which electron microscopic studies were performed. The presence of small dense-core membrane-bound granules (120 to 160 nm) in cytoplasmic process under electron microscopic observation confirmed the diagnosis of neuroendocrine carcinoma of the cervix. The coexistence of electron dense-core membrane-bound granules, abundant tonofibrils, and desmosomes within the cancer cells, suggests that these tumors may have derived from the multipotential precursor cells with neuroendocrine and squamous differentiation. Because neuroendocrine carcinomas appear to have the highest incidence of recurrence and the poorest prognosis, it is necessary to distinguish these neoplasms from squamous cell carcinomas of the cervix. Literature about neuroendocrine carcinomas of the cervix is also reviewed.

Carcinoma, Small Cell↗
PubMed1990

Mammalian thioltransferase (glutaredoxin) and protein disulfide isomerase have dehydroascorbate reductase activity.

Homogeneous native and recombinant porcine liver thioltransferase (glutaredoxin), bovine thymus and human placenta thioltransferase (glutaredoxin) were examined for dehydroascorbate reductase activity (EC 1.8.5.1) involving the direct catalytic reduction of dehydroascorbic acid (DHA) by glutathione. Each enzyme had substantial activity with apparent Km and Vmax for dehydroascorbate between 0.2 and 2.2 mM and 6-27 nmol min-1, respectively, and for gluathione between 1.6 and 8.7 mM and 11-30 nmol min-1, respectively. In the presence of purified bovine liver thioredoxin reductase, homogeneous bovine liver thioredoxin failed to reduce DHA to ascorbic acid as measured by NADPH oxidation. Highly purified bovine liver protein disulfide isomerase (PDI) reacted directly with DHA and GSH to catalyze the reduction of DHA to ascorbic acid. The apparent Km for DHA was 1.0 mM and the Vmax was 8 nmol min-1, and for GSH were 3.9 mM and 14 nmol min-1, respectively. These results suggest that thioltransferase and PDI contribute to the regeneration of oxidized ascorbic acid in mammalian cells, and based on their cellular location, thioltransferase is proposed to be the major cytoplasmic activity, whereas interaction of DHA with microsomal membrane PDI may catalyze regeneration of ascorbic acid and initiate oxidation of intralumenal protein thiols to disulfides.

Animals↗
PubMed1990

In vivo expression of rat liver c-erbA beta thyroid hormone receptor in yeast (Saccharomyces cerevisiae).

To study thyroid hormone receptor (TR), we developed an in vivo expression system in yeast by using a copper-responsive yeast metallothionein promoter and ubiquitin-fusion protein technology. The cDNA encoding full-length rat liver TR beta was expressed under the control of copper. The [125I]T3 binding activities to yeast extracts were significantly correlated with the added copper sulfate into the medium. Partially purified TR from the transformed yeast had a high hormone binding affinity (Kd = 0.34) for T3 and could bind thyroid hormone response element in gel retardation analysis.

Animals↗