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Biomedical subjects

W Zhang

Publications and source records attributed to W Zhang.

At least 721 records · Page 40Linked to original sources
PubMed1999

[Association expression of genes encoding gst of Schistosoma japonicum and enterotoxigenic Escherichia coli].

AIM: To study the association expression of two genes encoding GST of Schistosoma japonicum and K99 of enterotoxigenic Escherichia coli. METHODS: PCR technique was used to gain the K99 gene. After digestion with BamH I and EcoR I, the gene was cloned into the plasmid vector pUC18 by using recombinant DNA techniques. The other target gene of GST in pSj5 plasmid was obtained by EcoR I digestion, and was then ligated into the recombinant plasmid pUC18-K99. The expressed product was assayed by SDS-PAGE, Western blotting, reversal IHA, ELISA and transmission electron microscopy. RESULTS: Co-expression product of around 50 kDa was obtained. The protein was recognized by anti-GST and anti-K99 antibodies (ELISA and IHA), and acted as pilus on the surface of transformed DH5 alpha E. coli bacteria. CONCLUSION: Co-expression of the genes encoding GST and K99 was successfully achieved.

Animals↗
PubMed1999

[Aminoglycoside ototoxicity associated with mitochondrial DNA mutation].

OBJECTIVE: To confirm the effect of genetic susceptibility to aminoglycoside ototoxicity. METHOD: Mitochondrial DNA (mtDNA) from 62 members of 9 aminoglycoside induced deafness families was analysed by PCR-Restriction endonuclease digestion. RESULT: The nucleotide 1555A-->G mutation in 12S rRNA gene of mtDNA was identified in 20 members of 5 families. CONCLUSION: These findings indicate that this mutation is a molecular basis for genetic susceptibility to the ototoxic effect of aminoglycosides. The relationship between the audiovestibular changes and genetic susceptibility to aminoglycoside ototoxicity and the pathogenetic mechanism of susceptible deafness are discussed. The possibility that other gene mutations can also predispose to aminoglycoside ototoxicity is proposed.

Adolescent↗
PubMed1999

[Detection of telomerase activity in gastric cancer and adjacent tissues].

OBJECTIVE: To study the telomerase activity in chinese gastric cancer and their adjacent tissues and to explore the possibility of telomerase as a tumor biological marker. METHODS: Telomerase activity was analyzed in 42 primary gastric cancers and their adjacent tissues and 1 benign gastric lesion by a PCR-based telomerase repeat amplification protocol assay. RESULTS: The result showed 88.1% (37/42) gastric cancerous specimens displayed telomerase activity. However, only 2 of 42 tissue samples adjacent to the gastric cancer showed telomerase activity. However our results indicated that 1 benign gastric lesion sample expressed telomerase activity. CONCLUSIONS: The results indicated that the detection of telomerase activity might be a useful method in the diagnosis of gastric cancer.

Humans↗
PubMed1999

[Clinical significance of detecting telomerase activity in ascites cells from patients with ovarian carcinoma].

OBJECTIVE: The purpose was to investigate the clinical significance of telomerase activity for tumor diagnosis in ascites cells from patients with ovarian carcinoma. METHODS: Thirty ascites specimens from patients with ovarian tumor were examined for telomerase activity by PCR-based TRAP (telomeric repeat amplification protocol) method, and the result of detection was compared with the cytological diagnosis. RESULTS: Telomerase activity was detected in ascites cells from patients with ovarian tumor in 19 of the 20 cytologic-possitive specimens and in 3 of the 7 cytologic-negative specimens and in all the 3 cytologic-suspicious specimens. The positive rate in 30 ascites samples by cytological examination and by the detection of telomerase activity was 66.67% (20/30), and 83.33% (25/30), respectively. CONCLUSIONS: The result suggested that measuring telomerase activity in ascites cells would be helpful to cytological examination in diagnosis of patients with ovarian carcinoma.

Ascites↗
PubMed1999

[Studies on the chemical constituents of essential oil from roots and rhizomes of Patrinia rupestris].

OBJECTIVE: To study the chemical constituents of the essential oil from the roots and rhizomes of Patrinia rupestris. METHOD: The essential oil was extracted by steam distillation. The components were separated and identified by gas chromatography mass spectrometry and elucidated on the standard mass spectral data. Gas chromatography showed their percentages by area normalization method. RESULTS: Seventeen constituents were identified which make up 74.57% of the oil. CONCLUSION: Transcaryophyllene (38.41%) was the main constituent, and other constituents include alpha-gurjunene, caryophyllene oxide, humulene, 9,12-octadecadienoic acid, etc.

Gas Chromatography-Mass Spectrometry↗
PubMed1999

[Effects of the centipede aqueous extract on animal gastrointestinal function].

In order to investigate the mechanism of Centipede on the function of animal gastrointestinal digestion, we studied the effects of cetipede aqueous extract on animal digestion, secretion and intestional movement. The results showed that the Centipede extract increased the volume of gastric juice and acid, activity of pepsin, volume of pancreatic juice and protein in rat. The Centipede extract also accelerated the mice intestinal movement. The above results revevaled that Centipede could regulate the function of the gastrointestinal digestion, secretion and movement.

Animals↗
PubMed1999

[A new anaesthetic method of intraocular surgery: anaesthesia at infrafascia bulbi].

OBJECTIVE: To probe the advantage, indications and its mechanism of anaesthesia at intraocular operation with infrafaseia bulbi anaesthetic (IBA) technique. METHODS: 456 eyes were operated with the anaesthesia in infrafascia bulbi, including 77 eyes for phacoemulsification intraocular lens implantation, 346 eyes for modern surgical extracapsular cataract extraction and intraocular lens implantation, 33 eyes for trabeculectomy. 2 ml of mixture of 2% Lidocaine and 0.75% Bupivacaine were injected at infratemporal near bulbi conjunctiva of limbus through the blunt silicone canal, which entered the fascia bulbi via a small incision and reached the equator of the eyeball. When the injection of the mixture filled up the fascia bulbi the surgery could be performed. RESULTS: IBA applied in 456 eyes had shown the same effect as posterior fascia bulbar and peripheral fascia bulbar anaesthesia. IBA is a safe method. CONCLUSION: It is avoided the mechanical injure to optic nerve, artery, vein, muscle and wall of eyeball with IBA using blunt silicone injecting canal. It is proved in our clinical practice that this is a saft and efficient local anaesthetic method.

Aged↗
PubMed1999

Attenuation of WAF1/Cip1 expression by an antisense adenovirus expression vector sensitizes glioblastoma cells to apoptosis induced by chemotherapeutic agents 1,3-bis(2-chloroethyl)-1-nitrosourea and cisplatin.

Previous studies have shown that the negative cell cycle regulator WAF1/Cip1 is often overexpressed in human gliomas and that WAF1/Cip1 overexpression renders glioma cells resistant to chemotherapy agents. In this study, we investigated whether down-regulation of WAF1/Cip1 would sensitize gliomas to chemotherapy. An adenoviral vector expressing antisense WAF1/Cip1 was constructed and used to infect D54 glioma cells, which express a high level of endogenous WAF1/Cip1. After D54 cells were infected with antisense WAF1/Cip1 adenovirus, Western blotting revealed a significant decrease in the WAF1/Cip1 protein level. Down-regulation of WAF1/Cip1 alone resulted in the cells rounding up and detaching from plates. Electron microscopy revealed some nuclear fragmentation in antisense WAF1/Cip1-infected cells, indicating the initiation of apoptosis. The antisense WAF1/Cip1-infected cells were then treated with the chemotherapeutic agents 1,3-bis(2-chloroethyl)-1-nitrosourea and cisplatin. Other cells were infected with sense WAF1/Cip1 adenovirus or control virus and served as controls. Trypan blue exclusion assay revealed significant cell death in antisense WAF1/Cip1-infected cells. In situ end-labeling assay by flow cytometry revealed that many cells died of apoptosis. Our results show that the attenuation of WAF1/Cip1 expression initiated glioma cell death and sensitized glioma cells to apoptosis induced by 1,3-bis(2-chloroethyl)-1-nitrosourea and cisplatin. Thus, blocking WAF1/Cip1 production may serve as a useful chemosensitization regimen for treating glioma.

Adenoviridae↗
PubMed1998

Structure-function relationships in a type I antifreeze polypeptide. The role of threonine methyl and hydroxyl groups in antifreeze activity.

Several analogs of an alanine-rich, alpha-helical type I antifreeze polypeptide from the winter flounder were synthesized and studied to evaluate the role of threonine residues on antifreeze activity. In this series, the four Thr residues in the wild type polypeptide were substituted with from one to four Ser, allo-Thr, or Val residues. Circular dichroism studies determined that these substitutions did not significantly diminish alpha-helicity. Thermal hysteresis data showed that substitution of Thr by Ser resulted in moderate to complete loss of antifreeze activity, depending on the number and position of the substituted Thr residue(s). Replacement by Val, in confirmation of other recent reports, or by allo-Thr had a much less detrimental effect on activity though there were qualitative differences in activity between the mutants and the wild type AFP. Based on these results, we propose that both the methyl and hydroxyl groups of Thr, particularly of the central two Thr residues, Thr13 and Thr24, play key roles in the ice-binding properties of the antifreeze peptide. Specifically, the methyls participate in hydrophobic interactions with ice, which provide the driving force for binding and stability, whereas the hydroxyls and other polar residues control binding specificity and impart additional stability through hydrogen bonding.

Amino Acid Sequence↗
PubMed1998

Molecular basis of T cell inactivation by CTLA-4.

CTLA-4, a negative regulator of T cell function, was found to associate with the T cell receptor (TCR) complex zeta chain in primary T cells. The association of TCRzeta with CTLA-4, reconstituted in 293 transfectants, was enhanced by p56(lck)-induced tyrosine phosphorylation. Coexpression of the CTLA-4-associated tyrosine phosphatase, SHP-2, resulted in dephosphorylation of TCRzeta bound to CTLA-4 and abolished the p56(lck)-inducible TCRzeta-CTLA-4 interaction. Thus, CTLA-4 inhibits TCR signal transduction by binding to TCRzeta and inhibiting tyrosine phosphorylation after T cell activation. These findings have broad implications for the negative regulation of T cell function and T cell tolerance.

Abatacept↗
PubMed1998

Mutagenesis studies of human red opsin: trp-281 is essential for proper folding and protein-retinal interactions.

Human red and green opsins contain a strikingly large number of tryptophan residues. These tryptophans are highly conserved among all red and green opsins. To investigate possible roles of these tryptophans in folding and structure, we have systematically replaced each tryptophan of human red opsin. When expressed in COS cells, wild-type red opsin undergoes N-linked glycosylation, forms a light-sensitive pigment with absorption maximum at 560 nm upon reconstitution with 11-cis-retinal, and is transported to the plasma membrane. We used the extent of glycosylation, pigment generation, and intracellular localization of mutant red opsins as our criteria for assessing the effect of substitution. Replacement of eight tryptophans, Trp-59, Trp-90, Trp-149, Trp-152, Trp-183, Trp-191, Trp-195, and Trp-243, with Phe or Ala did not affect the wild-type phenotype significantly. However, replacement of Trp-5 and Trp-51 in the putative N-terminal domain and Trp-142, Trp-177, Trp-179, and Trp-281 in the transmembrane domain with Phe had profound effects, indicating that these substitutions affected red opsin folding. Judged by the severity of the effects, we propose that Trp-5, Trp-51, Trp-177, and Trp-281 are important for red opsin folding. Although substitution of Trp-281 with Phe and Cys did not permit normal glycosylation and transport, substitution with Tyr and His permitted these processes but resulted in blue-shifted pigment. Thus, polar aromatics appear to substitute for Trp-281 to allow red opsin folding. The large spectral shift indicates that Trp-281 is essential for the proper interaction of the protein with 11-cis-retinal.

Amino Acid Sequence↗
PubMed1998

Intrastriatal and intraventricular injections of oligodeoxynucleotides in the rat brain: tissue penetration, intracellular distribution and c-fos antisense effects.

We have determined the time course, the spatial spread in brain tissue, and the intracellular distribution of biotin- and fluorescein-labeled phosphorothioate oligodeoxynucleotides (ODNs) following single injections into the rat striatum or the lateral ventricle. These time and space parameters were correlated with the ability of c-fos phosphorothioate antisense ODNs to suppress the induction of Fos protein by cocaine. A rapid and dose-dependent tissue penetration of labeled ODNs was observed following either intrastriatal or intraventricular injections of a constant sample volume. Inspection of tissue sections by confocal microscopy uncovered a distinct change in the intracellular disposition of labeled ODNs during the 24 h post-injection period. At 1, 6 and 12 h, the vast majority of the fluorescent signal was confined to the interstitial spaces throughout the zone penetrated by ODNs. Neuronal nuclei displayed faint labeling along the outer portion of the nucleus at 1 and 6 h post-injection. At these time-points, ODNs were not detected in the cytoplasm. By 16 h, ODNs were barely detectable in the extracellular space and absent from neuronal nuclei. Instead, ODNs were seen in large cytoplasmic granules of neurons throughout the tissue zone penetrated by the ODNs. Experiments with intrastriatal injections of antisense ODNs to c-fos mRNA revealed Fos suppression between 3 and 12 h, but not at 16 and 24 h. This combined analysis has revealed that (1) restricted tissue penetration by ODNs limits their antisense effects on protein expression, and (2) depletion of extracellular ODNs and sequestration of c-fos antisense ODNs into large intracellular granules coincides with the loss of their biological activity.

Animals↗
PubMed1998

Lymphotactin gene-modified bone marrow dendritic cells act as more potent adjuvants for peptide delivery to induce specific antitumor immunity.

Dendritic cells (DC) are regarded as attractive candidates for cancer immunotherapy. Our aim is to improve the therapeutic efficacy of DC-based tumor vaccine by augmenting DC preferential chemotaxis on T cells. Mouse bone marrow-derived DC were transduced with lymphotactin (Lptn) gene by adenovirus vector. The supernatants from Lptn gene-modified DC (Lptn-DC) were capable of attracting CD4+ and CD8+ T cells in a chemotaxis assay, whereas their mock control could not. Lptn expression of Lptn-DC was further confirmed by RT-PCR. Lptn-DC were pulsed with Mut1 peptide and used for vaccination. Immunization with the low dose (1 x 10(4)) of Mut1 peptide-pulsed DC induced weak CTL activity, whereas the same amounts of Mut1 peptide-pulsed Lptn-DC markedly induced specific CTL against 3LL tumor cells. A single immunization with 1 x 10(4) Mut1 peptide-pulsed Lptn-DC could render mice resistant to a 5 x 10(5) 3LL tumor cell challenge completely, but their counterpart could not. The protective immunity induced by Mut1 peptide-pulsed Lptn-DC depends on both CD4+ T cells and CD8+ T cells rather than NK cells in the induction phase and depends on CD8+ T cells rather than CD4+ T cells and NK cells in the effector phase. Moreover, the involvement of CD28/CTLA4 costimulation pathway and IFN-gamma are also necessary. When 3LL tumor-bearing mice were treated with 1 x 10(4) Mut1 peptide-pulsed Lptn-DC, their pulmonary metastases were significantly reduced, whereas the same low dose of Mut1 peptide-pulsed DC had no obvious therapeutic effects. Our data suggest that Lptn-DC are more potent adjuvants for peptide delivery to induce protective and therapeutic antitumor immunity.

Adenoviridae↗
PubMed1998

Generation of fiber-mutant recombinant adenoviruses for gene therapy of malignant glioma.

Recombinant adenovirus (Adv)-mediated gene transduction is a powerful technology for cancer gene therapy. In this article, we report the generation of a fiber-mutant Adv vector, using the Adv genomic DNA-terminal protein complex (DNA-TPC) cotransfection method. First, a fiber-mutant construct in a plasmid carrying the right-side two-thirds of the human adenovirus type 5 (Ad5) genome (pTR) was cotransfected with Ad5 DNA-TPC, yielding the recombinant Adv with the desired fiber mutation. The DNA-TPC from the mutant Adv was then utilized to produce a second-step recombinant Adv with an expression cassette in the place of E1. By this procedure, we generated a fiber mutant, F/K20, that has a linker and a stretch of 20 lysine residues added at the C terminus of the fiber. By using Adv carrying a reporter lacZ gene (AxCAZ2) with either F/K20 or wild-type fiber (F/wt), we examined the transduction efficiency of F/K20-Adv. No significant difference in the transduction efficiency between F/K20 and F/wt-Adv was observed for a human fibroblast line, WI-38, or various tumor cell lines, including melanoma, prostate, esophageal, and pancreatic cancer lines. In clear contrast, F/K20-Adv showed a remarkably enhanced efficiency in genetic transduction of human glioma cells. In all four human glioma lines tested, the multiplicities of infection (MOIs) for transduction of 50% of the population (ED50) were decreased with F/K20-Adv compared with F/wt-Adv: 7-fold for T98G, 14-fold for U251, 9-fold for U373, and 42-fold for U87 cells. Therefore, we attempted to apply F/K20-Adv for gene therapy of malignant glioma. Glioma cells infected with F/K20-Adv carrying genes for interleukin 2 or interleukin 12 produced a high level of each cytokine at a much lower MOI than did cells infected with F/wt-Adv. Infection with F/K20-Adv carrying the wild-type p53 tumor suppressor gene resulted in an enhanced level of p53 protein expression and an increased incidence of F/K20-Adv in transduction efficiency for malignant glioma, providing promising tools for gene therapy.

Adenoviridae↗
PubMed1998

Ultrastable mesostructured silica vesicles

A family of mesoporous molecular sieves (denoted MSU-G) with vesiclelike hierarchical structures and unprecedented thermal (1000 degreesC) and hydrothermal stabilities (more than 150 hours at 100 degreesC) associated with high SiO4 cross-linking was prepared through a supramolecular assembly pathway that relies on hydrogen bonding between electrically neutral gemini surfactants of the type CnH2n+1NH(CH2)2NH2 and silica precursors derived from tetraethylorthosilicate. The vesicle shells are constructed of one or more undulated silica sheets that are about 3 nanometers thick with mesopores (average diameters from 2.7 to 4.0 nanometers) running both parallel and orthogonal to the silica sheets, which makes the framework structure bicontinuous and highly accessible. Catalytic metal ion centers [for example, Ti(IV) and Al(III)] have been incorporated into the framework with the retention of hierarchical structure.

Journal Article↗
PubMed1998

Modification of phosphorothioate oligonucleotides yields potent analogs with minimal toxicity for antisense experiments in the CNS.

There is increasing evidence that phosphorothioate oligonucleotides infused into the brain can cause a host of undesired side effects which compromise the antisense experiment. In studies on the corticotropin releasing factor type-2 receptor, several phosphorothioate oligonucleotides administered intraventricularly produced significant weight loss in rats. Four different phosphodiester and phosphorothioate oligonucleotide analogs were examined to identify molecules which could eliminate these side effects while maintaining good potency for antisense inhibition. Of these, chimeric oligonucleotides consisting of a mixed phosphodiester-phosphorothioate backbone, and having 2'-methoxyribonucleotide modifications in 60% of the oligonucleotide were the most optimal. Rats treated with these chimeric oligonucleotides gained weight at rates identical to that of saline-treated controls. In addition, the antisense oligonucleotide but not the mismatch control sequence reduced corticotropin releasing factor type-2 receptor binding of 125iodo-sauvagine in the lateral septum by 40-60% after 5 daily injections. Increasing the dosing period to 9 days reduced receptor binding by 78%. Reductions in protein binding were accompanied by comparable reductions in the in situ hybridization signal of the corticotropin releasing factor type-2 receptor mRNA. However, when an oligonucleotide analog incapable of supporting ribonuclease H activity was used, neither protein nor RNA binding levels were changed compared to saline-treated controls. These results suggest that ribonuclease H or enzymes with similar activity are critical to the antisense inhibition observed in the lateral septum.

Amphibian Proteins↗