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Biomedical subjects

X Wang

Publications and source records attributed to X Wang.

At least 361 records · Page 20Linked to original sources
PubMed2001

[Keratin 17 gene mutation in patients with steatocystoma multiplex].

OBJECTIVE: To study the relationship between steatocystoma multiplex (SCM) and keratin 17 gene mutation. METHODS: The keratin 17 gene mutation in the cDNA of cystic tissue of 5 patients of SCM and in the DNA in peripheral blood of 25 patients with SCM from a SCM family was studied by direct sequencing of the RT-PCR products, nested PCR, and restricted fraction length polymorphism (RFLP) analysis. Thirty-nine blood specimens from the unaffected members of that family were collected and tested too. Ten DNA pool specimens and other 2000 DNA pool specimens of normal individuals outside that SCM family were used as controls. RESULTS: In the base 428, 94(th) codon in keratin 17 gene in the cDNA of patients' cystic tissue, R94C mutation, a G-->A mutation, was detected Nested PCR, and restricted enzyme Acil polymorphism analysis showed that in the DNA specimens of peripheral blood of patients a mutated allele lacking enzyme cutting locus was detected, thus causing an uncut band with 200 bp while the corresponding allele was cut and caused two bands with 108 bp and 92 bp. In the DNA pool specimens of normal controls only these two bands with 108 bp and 92 bp were observed. CONCLUSION: The R94C mutation in keratin 17 gene is one of the genetic bases of SCM in Chinese. The results of this study provide scientific data for genetic diagnosis and counseling of SCM.

Adolescent↗
PubMed2001

[Expression of telomerase subunits and its relationship with telomerase activity in nasopharyngeal carcinoma].

OBJECTIVE: To study the expression of telomerase subunits and its relationship with telomerase activity in nasopharyngeal carcinoma. METHODS: The expression of telomerase subunits and the telomerase activity were examined in the same sample from nasopharyngeal carcinoma (NPC) as well as from chronic inflammation of nasopharyngeal epithelium (CINE) with RT-PCR and PCR-ELISA respectively. RESULTS: (1) hTERT mRNA was expressed in 38 of 43 cases of NPC (88%), and in none of the 16 cases of CINE (0%) (P < 0.05). (2) hTR was expressed in 39 of the 43 cases of NPC (90.7%),and in 14 of the 16 cases of CINE (87.5%) (P < 0.05). TP1 mRNA was expressed in 38 of the 43 cases of NPC (88%), and in 14 of the 16 cases of CINE (87.5%). There was no statistically significant difference between the expression of hTR and TP1 mRNA in NPC and their expression in CINE (P > 0.05). (3) Telomerase activity was detected in 37 of the 43 cases of NPC (86%) and in none of the 16 cases of CINE (0%) (P < 0.05). There was a significant correlation between the expression of hTERT mRNA in NPC and CINE (P < 0.05). No correlation was observed between telomerase activity and the expression of hTR and TP1 mRNA (P > 0.05). (5) No correlation was observed between the clinicopathological features of NPC and CINE (such as clinical stage and lymph node metastasis) and the expression of any of the telomerase subunits (P > 0.05). CONCLUSION: The expression of hTERT may play a critical role in regulation of telomerase activity, and detection of hTERT mRNA might be useful for clinical diagnosis of NPC.

Carcinoma, Squamous Cell↗
PubMed2001

Effects of all-trans-retinoic acid and arsenic trioxide on the hemostatic disturbance associated with acute promyelocytic leukemia.

To study the in vivo effect of all-trans-retinoic acid (ATRA) and arsenic trioxide (As(2)O(3)) on the expression of tissue factor (TF) and the other hemostatic disturbance, a series of parameters were measured either in bone marrow blasts or plasma from acute promyelocytic leukemia (APL) patients. The plasma parameters were measured by ELISA or chromogenic studies. The TF transcription was assessed using reverse transcription-polymerase chain reaction (RT-PCR) technique. The results indicated that the blast cell procoagulant activity (PCA), TF antigen of APL cell lysate, as well as the transcription of APL TF mRNA elevated at diagnosis, were reduced after ATRA or As(2)O(3) therapy. The plasma level of P-selectin, TF, thrombin-antithrombin complex (TAT), soluble fibrinmonomer complex, thrombomodulin (TM), tissue factor pathway inhibitor (TFPI), plasmin-antiplasmin complex, tissue plasminogen activator (t-PA) activity, urokinase plasminogen activator (u-PA) and its receptor (u-PAR), and D-dimer (D-D) significantly increased. Fibrinogen (Fg), antigen level of protein C (PC), plasminogen (PLG) activity, alpha(2)-plasminogen inhibitor activity (alpha(2)-PI), and plasminogen activator inhibitor (PAI) activity were decreased at diagnosis. The protein C activity (PC:A) and protein S (PS) remained unchanged. All the parameters were restored to normal ranges after complete remission (CR) except elevation of TF and TAT in both groups, as well as PC:A, PS, and t-PA in the ATRA group. In conclusion, there existed activation of platelets and consumption of anticoagulants as well as activation of coagulation and fibrinolytic system before treatment. Both ATRA and As(2)O(3) therapy downregulated the expression of TF mRNA, decreased the PCA and TF level in APL cells, significantly inhibited coagulation activation, corrected secondary hyperfibrinolysis and the other hemostatic abnormalities, and thus greatly improved the bleeding symptom in early stage of the treatment.

Adolescent↗
PubMed2001

The kinase DYRK phosphorylates protein-synthesis initiation factor eIF2Bepsilon at Ser539 and the microtubule-associated protein tau at Thr212: potential role for DYRK as a glycogen synthase kinase 3-priming kinase.

The substrate specificity of glycogen synthase kinase 3 (GSK3) is unusual in that efficient phosphorylation only occurs if another phosphoserine or phosphothreonine residue is already present four residues C-terminal to the site of GSK3 phosphorylation. One such substrate is the epsilon-subunit of rat eukaryotic protein-synthesis initiation factor 2B (eIF2Bepsilon), which is inhibited by the GSK3-catalysed phosphorylation of Ser(535). There is evidence that GSK3 is only able to phosphorylate eIF2Bepsilon at Ser(535) if Ser(539) is already phosphorylated by another protein kinase. However, no protein kinases capable of phosphorylating Ser(539) have so far been identified. Here we show that Ser(539) of eIF2Bepsilon, which is followed by proline, is phosphorylated specifically by two isoforms of dual-specificity tyrosine phosphorylated and regulated kinase (DYRK2 and DYRK1A), but only weakly or not at all by other 'proline-directed' protein kinases tested. We also establish that phosphorylation of Ser(539) permits GSK3 to phosphorylate Ser(535) in vitro and that eIF2Bepsilon is highly phosphorylated at Ser(539) in vivo. The DYRK isoforms also phosphorylate human microtubule-associated protein tau at Thr(212) in vitro, a residue that is phosphorylated in foetal tau and hyperphosphorylated in filamentous tau from Alzheimer's-disease brain. Phosphorylation of Thr(212) primes tau for phosphorylation by GSK3 at Ser(208) in vitro, suggesting a more general role for DYRK isoforms in priming phosphorylation of GSK3 substrates.

Animals↗
PubMed2001

TFIIH action in transcription initiation and promoter escape requires distinct regions of downstream promoter DNA.

TFIIH is a multifunctional RNA polymerase II general initiation factor that includes two DNA helicases encoded by the Xeroderma pigmentosum complementation group B (XPB) and D (XPD) genes and a cyclin-dependent protein kinase encoded by the CDK7 gene. Previous studies have shown that the TFIIH XPB DNA helicase plays critical roles not only in transcription initiation, where it catalyzes ATP-dependent formation of the open complex, but also in efficient promoter escape, where it suppresses arrest of very early RNA polymerase II elongation intermediates. In this report, we present evidence that ATP-dependent TFIIH action in transcription initiation and promoter escape requires distinct regions of the DNA template; these regions are well separated from the promoter region unwound by the XPB DNA helicase and extend, respectively, approximately 23-39 and approximately 39-50 bp downstream from the transcriptional start site. Taken together, our findings bring to light a role for promoter DNA in TFIIH action and are consistent with the model that TFIIH translocates along promoter DNA ahead of the RNA polymerase II elongation complex until polymerase has escaped the promoter.

Base Sequence↗
PubMed2001

Chromatin structure mapping in Saccharomyces cerevisiae in vivo with DNase I.

Most methods for assessment of chromatin structure involve chemical or nuclease damage to DNA followed by analysis of distribution and susceptibility of cutting sites. The agents used generally do not permeate cells, making nuclear isolation mandatory. In vivo mapping strategies might allow detection of labile constituents and/or structures that are lost when chromatin is swollen in isolated nuclei at low ionic strengths. DNase I has been the most widely used enzyme to detect chromatin sites where DNA is active in transcription, replication or recombination. We have introduced the bovine DNase I gene into yeast under control of a galactose-responsive promoter. Expression of the nuclease leads to DNA degradation and cell death. Shorter exposure to the active enzyme allows mapping of chromatin structure in whole cells without isolation of nuclei. The validity and efficacy of the strategy are demonstrated by footprinting a labile repressor bound to its operator. Investigation of the inter-nucleosome linker regions in several types of repressed domains has revealed different degrees of protection in cells, relative to isolated nuclei.

Animals↗
PubMed2001

Structure of the C-domain of human cardiac troponin C in complex with the Ca2+ sensitizing drug EMD 57033.

Ca(2+) binding to cardiac troponin C (cTnC) triggers contraction in heart muscle. In heart failure, myofilaments response to Ca(2+) are often altered and compounds that sensitize the myofilaments to Ca(2+) possess therapeutic value in this syndrome. One of the most potent and selective Ca(2+) sensitizers is the thiadiazinone derivative EMD 57033, which increases myocardial contractile function both in vivo and in vitro and interacts with cTnC in vitro. We have determined the NMR structure of the 1:1 complex between Ca(2+)-saturated C-domain of human cTnC (cCTnC) and EMD 57033. Favorable hydrophobic interactions between the drug and the protein position EMD 57033 in the hydrophobic cleft of the protein. The drug molecule is orientated such that the chiral group of EMD 57033 fits deep in the hydrophobic pocket and makes several key contacts with the protein. This stereospecific interaction explains why the (-)-enantiomer of EMD 57033 is inactive. Titrations of the cCTnC.EMD 57033 complex with two regions of cardiac troponin I (cTnI(34-71) and cTnI(128-147)) reveal that the drug does not share a common binding epitope with cTnI(128-147) but is completely displaced by cTnI(34-71). These results have important implications for elucidating the mechanism of the Ca(2+) sensitizing effect of EMD 57033 in cardiac muscle contraction.

Calcium↗
PubMed2001

Multibit gates for quantum computing.

We present a general technique to implement products of many qubit operators communicating via a joint harmonic oscillator degree of freedom in a quantum computer. By conditional displacements and rotations we can implement Hamiltonians which are trigonometric functions of qubit operators. With such operators we can effectively implement higher order gates such as Toffoli gates and C(n)-NOT gates, and we show that the entire Grover search algorithm can be implemented in a direct way.

Journal Article↗
PubMed2001

Purification and characterization of three antifungal proteins from cheeseweed (Malva parviflora).

Three potent antimicrobial proteins were purified from cheeseweed (Malva parviflora) seeds. These antimicrobial proteins, named CW-3, CW-4, and CW-5, showed different antimicrobial spectrum and potency compared to the two heterologous antimicrobial proteins (CW-1 and CW-2) purified previously. CW-3 and CW-4 possess antimicrobial activities against Phytophthora infestans (Pi), but not Fusarium graminearum (Fg). A database search indicated that CW-3 shares high homology to cotton vicilin, an abundant seed storage protein. CW-4 shares homology to 2S albumin, another seed storage protein from cotton. CW-5 has antimicrobial activity against Fg, but no activity against Pi was observed at protein concentration up to 50 ppm. Under low salt condition, CW-5 showed potent antimicrobial activity against Fg, but under high salt condition, the antimicrobial activity was drastically diminished. Database search indicated that CW-5 has high homology to a lipid transfer protein from grape. The IC(50) values of the three purified antimicrobial proteins under both low and high salt conditions were determined. The isolation of five antimicrobial proteins for the first time from a single plant source provides further understanding of the plant innate defense system and insight on how plants evolve their complex and complementary antimicrobial system that is important in the early stage of development.

Amino Acid Sequence↗
PubMed2001

An intronic poly (AT) polymorphism of the DNA repair gene XPC and risk of squamous cell carcinoma of the head and neck: a case-control study.

Inherited polymorphisms of DNA repair genes may contribute to variations in DNA repair capacity and genetic susceptibility to cancer. In a hospital-based case-control study of 287 non-Hispanic white patients with newly diagnosed SCCHN and 311 control subjects matched on age, sex, ethnicity, and smoking status, we investigated the role of a newly identified variant allele of XPC, XPC-PAT+. We found that the frequency of the XPC-PAT+ allele was higher in the cases (0.409) than in the controls (0.333; P = 0.007). Fifty cases (17.4%) and 37 controls (11.9%) were XPC-PAT+/+, and 135 (47.0%) cases and 133 controls (42.8%) were XPC-PAT+/-. XPC-PAT+/- and XPC-PAT+/+ subjects were at significantly increased risk for SCCHN [adjusted odds ratios = 1.44 and 1.85, respectively (95% confidence intervals, 1.01-2.05 and 1.12-3.05, respectively; trend test, P = 0.007)]. We did not find ethnic difference in the frequency of XPC-PAT+ allele among four groups aged between 19 and 75 years: non-Hispanic whites, 294; African-Americans, 178; Hispanic-Americans, 103; and native Chinese, 119 (0.333, 0.281, 0.296, and 0.353, respectively). The case-control findings support the hypothesis that the XPC-PAT+ allele may contribute to the risk of developing SCCHN.

Aged↗
PubMed2001

[Effects of cigarette smoke extract on the expression of beta-catenin and tyrosine phosphorylation in airway epithelial cells].

OBJECTIVE: To explore the possible mechanism of injury by smoking and its repairing, the effects of cigarette smoke extract on the expression of beta-catenin (beta-cat), c-Src and level of phosphoric tyrosine in airway epithelial cells (AEC). METHODS: Pig AECs were cultured in vitro. After CSE and tyrphostin 25 exposure, (1) the expression of beta-cat was determined by immunocytochemical stain in 300 randomly selected AECs of each group, (2) the level of phosphoric tyrosine, content of c-Src and beta-cat mRNA in AECs were evaluated by immunocytochemical stain, in situ hybridization and image analysis in 30 randomly selected AECs of each group. RESULTS: After exposure to CSE for 4 hours and 24 hours, the levels of phosphoric tyrosine were 1.51 and 3.44 times of that of the control groups of the same time (P < 0.0001) respectively; the ratio of positive stain of beta-cat on membrane was markedly lower than that in the control groups (78.3% vs 83.3%, 77.7% vs 81.3%, P < 0.0001), and the cytoplasmic content of c-Src decreased 47.9% and 51.4% (P < 0.0001) compared with the control groups of the same time, respectively. While dealt with CSE and tyrphostin 25 together, the level of phosphoric tyrosine, the expression of beta-cat and c-Src resembled those in normal control. Contends of beta-cat mRNA decreased in the both two situations (P < 0.0010). CONCLUSION: CSE decreased the membranous expression of beta-cat and increased the level of tyrosine phosporylation of AECs. The change of beta-cat expression might mediate the airway epithelial injuries caused by smoking, and tyrphostin 25 might prevent such injuries through inhibiting the tyrosine kinase.

Animals↗
PubMed2001

Reaction path of phosphofructo-1-kinase is altered by mutagenesis and alternative substrates.

Escherichia coli phosphofructokinase (PFK) has been proposed to have a random, nonrapid equilibrium mechanism that produces nonallosteric ATP inhibition as a result of substrate antagonism. The consequences of such a mechanism have been investigated by employing alternative substrates and mutants of the enzyme that produce a variety of nonallosteric kinetic patterns demonstrating substrate inhibition and sigmoid velocity curves. Mutations of a methionine residue in the sugar phosphate binding site produced apparent cooperativity in the interaction of fructose 6-phosphate. Cooperativity could also be seen with native enzyme using a poorly binding substrate, fructose 1-phosphate. With an alternative nucleotide, 1-carboxymethyl-ATP, coupled with a mutation that introduced a negative charge in the nucleotide binding site, one could observe substrate inhibition by fructose 6-phosphate and apparent cooperativity in the interaction with nucleotide. Furthermore, the use of a phosphoryl donor, gamma-thiol-ATP, which greatly reduced the catalytic rate, apparently facilitated the equilibration of all binding reactions and eliminated ATP inhibition. These unusual kinetic patterns could be interpreted within the random, steady-state model as reflecting changes in the rates of particular binding and catalytic events.

Adenosine Diphosphate↗
PubMed2001

Development of scoliosis following pinealectomy in young chickens is not the result of an artifact of the surgical procedure.

Pinealectomy in young chickens consistently results in scoliosis, which has many characteristics similar to those seen in adolescent idiopathic scoliosis. The mechanism underlying this phenomenon remains a mystery and it is not yet entirely clear whether some unidentified aspect of the extensive surgery is the major factor rather than the removal of the pineal gland. Four different types of pinealectomy surgery were performed on young chickens as well as deliberate damage to the cerebral cortex which simulated the extreme of any accidental damage that might occur during surgery. Scoliosis was assessed from weekly radiographs. No differences in incidence of scoliosis, degree of severity, or pattern of curve development were observed for any of the experimental groups when compared with controls. In all groups approximately 55% of the chickens developed scoliosis that progressed rapidly. Different pinealectomy procedures and deliberate damage to the cerebral cortex produce scoliosis in young chickens with the same incidence and characteristics. This suggests strongly that the mechanism behind the phenomenon is due to the removal of the pineal gland and not some artifact of the extensive surgery. The pinealectomy model in young chickens is proving to be a good model for studying AIS in humans. An understanding of the mechanism underlying this phenomenon has the potential to provide further insights into the etiology of AIS and can lead to the development of novel treatment methods.

Animals↗
PubMed2001

A study of interleukin-1 cluster genes in susceptibility to and severity of multiple sclerosis.

In this explorative study, interleukin-1 (IL-1) receptor antagonist (IL-1RA; polymorphism of variable number of tandem repeats: VNTR), IL-1alpha (-889), IL-1beta (-511) and IL-1beta (+3953) polymorphisms were studied in relation to susceptibility to and severity of multiple sclerosis (MS), in 93 MS patients and 400 normal controls. No associations were found for any polymorphisms, alone or in combination. However, in our MS cohort, females were found to be IL-1RA allele 2 carriers more frequently than males (33/49 vs. 16/44, p = 0.0028). Using a cohort of 109 controls, IL-1RA allele 2 carriers were more frequently women with MS than control women (33/49 vs. 23/43, odds ratio (OR) = 2.19, 95% confidence interval (CI) 1.02-4.72, p = 0.043, P(C) = ns). The data suggest that the IL-1 cluster genes make no major contribution to MS, but the tentative association between IL-1RA allele 2 and susceptibility of MS in women warrants further studies.

Adult↗
PubMed2001

Weekly dosing with the platelet-derived growth factor receptor tyrosine kinase inhibitor SU9518 significantly inhibits arterial stenosis.

The platelet-derived growth factor (PDGF) ligands and their receptors have been implicated as critical regulators of the formation of arterial lesions after tissue injury. SU9518 (3[5-(5-bromo-2-oxo-1,2-dihydroindol-3-ylidenemethyl)-2,4-dimethyl-1H-pyrrol-3-yl]propionic acid) is a novel synthetic indolinone that potently and selectively inhibits the cellular PDGF receptor kinase and PDGF receptor-induced cell proliferation. Inhibition of PDGF receptor phosphorylation in cell-based assays occurs within 5 minutes after drug exposure and persists for >6 hours after drug removal. The pharmacokinetics indicate plasma levels that exceeded the effective concentration required to inhibit the PDGF receptor in cells for up to 8 hours or 7 days after a single oral or subcutaneous administration, respectively. In the rat balloon arterial injury-induced stenosis model, once-daily oral or once-weekly subcutaneous administration of SU9518 reduced intimal thickening of the carotid artery (ratio of neointimal to medial area, 1.94+/-0.38 versus 1.03+/-0.29 [P<0.01] 2.21+/-0.32 versus 1.34+/-0.45 [P<0.01], respectively). These studies provide the rationale to evaluate PDGF receptor tyrosine kinase inhibitors, including inhibitors related to the indolinone, SU9518, for the treatment of arterial restenosis.

3T3 Cells↗