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Biomedical subjects

D Gao

Publications and source records attributed to D Gao.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Experimental research of gene therapy for human gliomas with vascular endothelial growth factor(165) antisense RNA].

OBJECTIVE: To investigate the feasibility of gene therapy for human gliomas with vascular endothelial growth factor(165) (VEGF(165)) antisense RNA. METHODS: The eukaryotic expression vector of antisense VEGF(165) was constructed and identified. Then the vector was transfected into human glioma cells (SHG44). The biological characteristics and tumorigenesis of SHG44 cells before and after transfection were inspected and compared. The changes were detected by Western blot, immunohistochemistry, micrangium counting, electron microscopy and flow cytometry. RESULTS: The eukaryotic expression vector pcDNA-AVEGF(165) was successfully constructed and transfected into SHG44 glioma cells. The characterstics of the cells were not influenced by the expression of antisense gene. The capability of tumorigenesis and angiogenesis of the transfected cells in nude mices was greatly reduced (tumour end volume, experiment group 212 mm(3); control group 7 897 mm(3); P < 0.01; Blood vessel counting: experiment group, 5.50; control group 11.22; P < 0.01 ). CONCLUSION: The angiogenesis and tumor growth of human gliomas are effectively inhibited by VEGF(165) antisense RNA. This experiment lays a foundation for solid tumor-specific gene therapy.

Animals↗
PubMed2000

[Ultrasonically guided radio-frequency ablation of liver tumors with a clustered electrode: a report of 100 cases].

OBJECTIVE: To evaluate the efficacy of ultrasonically guided radio-frequency (RF) thermal ablation of liver tumors with a clustered electrode. METHODS: Clinical records of 100 consecutive patients who underwent RF tissue ablation 120 times were analysed. Image data, tumor size, clinic manifestation, and AFP value before and after the procedure were compared. RESULTS: A hundred cases at 10 days, thirty at 30 days, ten at 60 days after the procedure were subjected to color ultrasonography and CT scans, respectively. The tumor size decreased by 20% at 10 days in 70% patients, decreased by 30% at 30 days in 80% patients, decreased by 50% at 60 days in 3 patients. AFP value decreased in 50% of patients, no operative death was noted, and the rate of operative complication was 23% after ablation. CONCLUSION: Ultrasound guided RF thermal ablation of hepatic tumors is safe, applicable and effective.

Adolescent↗
PubMed2000

[An experimental study of immune mediating action of T-lymphocyte subsets on recurrent herpetic stromal keratitis].

OBJECTIVE: To investigate the role of T-lymphocyte subsets in the recurrent herpetic stromal keratitis (SK). METHODS: In a recurrent SK NIH mouse model, rat monoclonal antibodies were used to selectively deplete in vivo the CD(+)(4) and CD(+)(8) T-lymphocytes in mice, and the effects of the subsets on recurrent herpetic SK were evaluated. RESULTS: As measured by flow cytometry, in the mice treated with GK1.5, > 90% of CD(+)(4) T cells were depleted; and in the mice treated with H-35, > 95% of CD(+)(8) T cells were depleted. Depletion of CD(+)(4) T cells could halt the recurrence of SK, reduce the severity of recurrent SK and impair the delayed type hypersensitivity. In contrast, depletion of CD(+)(8) T cells had no effect on the outcome of the disease. Histopathologic examination of the recurrent SK demonstrated that the stromal inflammation in CD(+)(8) T-cell depleted and control mice was characterized by extensive lymphocyte and polymorphonuclear leukocyte infiltration, but only occasional lymphocytes were observed in CD(+)(4) T-cell depleted mice. CONCLUSION: The results provide evidence that recurrent herpetic SK represents an immunopathologic process mediated by CD(+)(4) T cells.

Animals↗
PubMed2000

[Research of toxin and plasmids of Saccharomyces cerevisiae].

Killer toxin from Saccharomyces cerevisiae SK was isolated by ultrafiltration of culture supernatants and purified by poly(ethylene glycol). The toxin migrates as one single protein band on SDS-PAGE and its molecular weight is 15 kD. The SK toxin has the greatest lethal effect on the sensitive yeast strain in the lat-lag phase. Extraction and purification of killer heretity factor(dsRNA) from SK found that M-dsRNA plasmid and L-dsRNA plasmid have different molecular lengths being 1.7 kb and 4.0 kb.

Killer Factors, Yeast↗
PubMed1999

The gon-1 gene is required for gonadal morphogenesis in Caenorhabditis elegans.

In wild-type Caenorhabditis elegans, the gonad is a complex epithelial tube that consists of long arms composed predominantly of germline tissue as well as somatic structures specialized for particular reproductive functions. In gon-1 mutants, the adult gonad is severely disorganized with essentially no arm extension and no recognizable somatic structure. The developmental defects in gon-1 mutants are limited to the gonad; other cells, tissues, and organs appear to develop normally. Previous work defined the regulatory "leader" cells as crucial for extension of the gonadal arms (J. E. Kimble and J. G. White, 1981, Dev. Biol. 81, 208-219). In gon-1 mutants, the leader cells are specified correctly, but they fail to migrate and gonadal arms are not generated. In addition, gon-1 is required for morphogenesis of the gonadal somatic structures. This second role appears to be independent of that required for leader migration. Parallel studies have shown that gon-1 encodes a secreted metalloprotease (R. Blelloch and J. Kimble, 1999, Nature 399, 586-590). We discuss how a metalloprotease may control two aspects of gonadal morphogenesis.

Animals↗
PubMed1999

Molecular packing groups and ab initio crystal-structure prediction.

Ab initio crystal structure prediction can proceed by minimization of the packing energy of Z independent molecules per cell, or alternatively by energy minimization taking one molecule as independent and Z - 1 molecules as related by assumed space-group symmetry. In the former method, a large number of positional variables must be considered. In the latter method, a large number of space groups must be considered. An alternative, more efficient, procedure is proposed, where it is recognized that values of Z and the number of molecules in the asymmetric unit, Z', impose restrictions on possible space groups. Examples of application of this method to crystal structure prediction are given.

Journal Article↗
PubMed1999

IL-12 administered during Chlamydia psittaci lung infection in mice confers immediate and long-term protection and reduces macrophage inflammatory protein-2 level and neutrophil infiltration in lung tissue.

Protection against infections with the intracellular bacterium Chlamydia spp. requires Th1-polarized CD4+ T cell immunity. In BALB/c mouse lung infections, immediate innate and nascent Chlamydia-specific immune responses following intranasal inoculation of Chlamydia psittaci strain B577 were modulated by 7-day i.p. administration of murine rIL-12, the initiation cytokine for Th1 immunity. Treatment with IL-12 reduced the severity of chlamydial pneumonia, abolished mortality (37.5% in untreated mice), and significantly reduced numbers of chlamydial organisms in lungs. On day 4 after inoculation, the neutrophil:macrophage ratio in bronchointerstitial pneumonias was 1.96 in untreated mice and 0.51 in IL-12-treated mice. This immediate, IL-12-mediated shift in innate inflammatory phenotype was correlated with a significant reduction of lung concentrations of the neutrophil chemoattractant macrophage inflammatory protein (MIP)-2 (putative murine homologue of human IL-8), monocyte chemotactic protein-1, and TNF-alpha; and a reduction in MIP-1alpha and IFN-gamma, at high-dose infection only, and IL-12-independent IL-10 levels. Chlamydia-specific Ab titers and Ig isotype ratios indicated an IL-12-dependent Th1 shift. Recall responses of IL-12-primed mice to secondary chlamydial lung infection eliminated chlamydiae more effectively and generated a lung cytokine profile conducive to perpetuation of the Th1 memory population. These data support the hypothesis that genetic differences in endogenous IL-12 production and response pathways could determine disease outcomes characterized by poor chlamydial clearance and a purulent inflammatory infiltrate vs effective elimination of chlamydiae in a macrophage-dominated response.

Administration, Intranasal↗
PubMed1999

Antinociceptive properties of fenfluramine, a serotonin reuptake inhibitor, in a rat model of neuropathy.

Fenfluramine is an indirect agonist of 5-hydroxytryptamine (5-HT) receptors that acts by evoking 5-HT release and blocking 5-HT reuptake in neuronal cells. The current study compared the antinociceptive properties of fenfluramine with those of the tricyclic antidepressants amitriptyline and desipramine in rat models of acute, persistent, and neuropathic pain. In a rat model of neuropathic pain produced by tight ligation of the L(5)/L(6) spinal nerves, i.v. bolus injection of fenfluramine resulted in a dose-dependent and long-lasting (>4 h) blockade of mechanical allodynia (ED(50) = 3.5 mg/kg; 95% confidence interval, 2.2-5.4 mg/kg) and cold allodynia (ED(50) = 2.4 mg/kg; 95% confidence range, 1.2-4.6 mg/kg). Fenfluramine also prevented tonic pain evoked by the s.c. injection of dilute (5%) formaldehyde solution (formalin), into the dorsal hindpaw. The i.v. administration of amitriptyline (4.7 mg/kg) or desipramine (13.5 mg/kg) at maximum tolerated doses did not block either allodynia in rats with spinal nerve ligation-induced painful neuropathy or tonic pain in the formalin test. Fenfluramine had differential effects on acute behavioral responses to noxious thermal (heat), chemical (5% formaldehyde solution), and mechanical stimuli; it completely inhibited nociceptive behavior in the acute phase of the formaldehyde solution test and partially inhibited licking and jumping responses in the hot-plate test but did not alter nociceptive thresholds in either the paw pressure test or the tail immersion test. Intracerebroventricular bolus injection of 240 microg of fenfluramine significantly increased mechanical allodynia thresholds; however, the same dose administered spinally by intrathecal bolus injection was ineffective. The inhibitory effects of fenfluramine on mechanical allodynia (and tonic pain behavior in the formaldehyde solution test) were prevented by pretreatment with 10 mg/kg metergoline, a selective antagonist of 5-HT receptors, but not with the mu-opioid receptor antagonist naloxone. These results suggest that fenfluramine produces analgesia in the formaldehyde solution test and the spinal nerve ligation model of neuropathic pain by potentiating, at least in part, supraspinal 5-HT mediated processes.

Analgesics↗
PubMed1999

Cloning and sequencing of the fragment of angiostatin K (1-3) gene.

OBJECTIVE: To secure anti-endotheliocyte hyperplasia functional fragment of human angiostatin K (1-3) gene. METHODS: As the template of leukocytotic cDNA, functional fragment of human angiostatin K (1-3) cDNA was amplified by PCR, cloned into the vector pGEM-3Zf, and sequenced according to Dye primer sequencing kit. RESULTS: The functional fragment of angiostatin K (1-3) cDNA (859 bp) was obtained by PCR and determined by sequencing. CONCLUSION: The angiostatin K (1-3) gene has been cloned. The gene is of great significance in tumor-antiangiogenesis therapy.

Angiogenesis Inhibitors↗
PubMed1999

[The novel copolymer coated capillary columns of electrophoresis and their applications to separation of proteins].

The copolymer of acrylonitrile, methyl acrylate, hydroxy ethyl acrylate (ZB-004), the copolymer of acrylonitrile, methyl acrylate, hydroxy ethyl acrylate, acrylamide (ZB-014) and the copolymer of acrylonitrile, hydroxy ethyl acrylate (ZB-016) were coated on the inner surface of fused-silica capillaries by just filling the capillary with solutions containing these copolymers followed by flushing the capillary with nitrogen. The physically adsorbed layer can reduce both protein adsorption and electroosmotic flow in the pH range of 3-5. Electroosmotic flow decreased by raising the concentrations of the copolymers. Separation performance of ZB-004 layer is better than those of other two layers due to its low hydrophilicity, but with higher pH values, appreciable peak deformation and increase in electroosmosis were observed. The intra day and inter day migration reproducibility were investigated in terms of relative standard deviation (RSD) with four basic proteins at pH 4.0. The RSDs of the intra day migration times were less than 2%. The RSDs of the inter day migration times were less than 4%. At pH 5.0, the RSDs of the migration times in two ZB-004-coated capillaries made on two different days were less than 1%. Separation efficiencies of four basic proteins in a ZB-004-coated capillary which stored in a buffer (pH 4.0) for fifteen days after being used for 14 days decreased 15%. These coatings were stable and exhibited reproducible separations from intra day, inter day and inter column under acidic conditions.

Acrylamide↗
PubMed1999

[Expression of xylose isomerase gene(xylA) in Saccharomyces cerevisiae from Clostridium thermohydrosulfuricum].

The Clostridium thermohydrosulfuricum xylA gene encoding xylose(glucose) isomerase was cloned in the yeast expression vector pMA91 under the control of the PGK promoter, resulting in pBX-1, and transformed into Saccharomyces cerevisiae. Production of recombinant xylose isomerase was seen in the a Coomassie stained SDS-PAGE gel and the molecular mass was estimated to be 43 kD. The recombinant xylose isomerase showed the highest activity at 85 degrees C and pH7. The specific activity under these condition was 1.0 U/mg protein. At 30 degrees C and 40 degrees C, the relative activity was reduced to 3.7% and 11%, respectively, of the maximum.

Aldose-Ketose Isomerases↗
PubMed1999

[Synthesis of methyl ester of aliphatic acid under irradiation of ultraviolet and mass spectra (MS) analysis].

A new method was introduced here to prepare methyl ester of aliphatic acid under irradiation of ultraviolet. Analysis was performed for the MS spectra of 19 products, by which Mclafferty rearrangements were discussed of methyl ester of aliphatic acid with two kinds of gamma-H in details. The regularity of Mclafferty rearrangement was established for the same kind of methyl ester with the increase of the carbon chain.

English Abstract↗
PubMed1998

Binding affinity of Cu(II)-VP-16 (etoposide) complex and its analogues to DNA and hydroxyl radical generation during DNA strand breaks.

Conformational effects and affinities of VP-16 (etoposide) and its derivatives to DNA in the presence of Cu(II) ion were examined by circular dichroic (CD) spectra. The Cu(II)/Cu(I) redox kinetics and the hydroxyl radical (.OH) generation from the Cu(II)-complexes were estimated by the stopped-flow kinetics. Based on the results, DNA-cleaving activity of Cu(II)-complexes of VP-16 has been shown to be related with binding affinity of the complex to DNA, Cu(II)/Cu(I) redox and .OH generation, emphasising the mechanism of generated .OH attack to DNA.

Animals↗
PubMed1998

The gene 4 of rice yellow stunt rhabdovirus encodes the matrix protein.

The complete nucleotide sequence of the gene 4 of rice yellow stunt rhabdovirus (RYSV) was determined from cDNAs corresponding to the viral genomic RNA. Gene 4 is 913 nucleotides (nt) long, comprising a 17-nt untranslated 5' region, a 786-nt open reading frame encoding a polypeptide with a molecular mass of 29,125 Da, and a 110-nt untranslated 3' region. Western blot analysis of the RYSV proteins using the antiserum raised against the protein expressed from the cloned gene in Escherichia coli indicates that gene 4 encodes the M protein of RYSV. Comparisons of the deduced amino acid sequence of the M protein of RYSV with those of other rhabdoviruses revealed no significant homologies. However, it shared a similar basic property and a similar distribution of charges with the other rhabdovirus matrix proteins and showed a relatively closer relationship to the sonchus yellow net virus (SYNV) M1 protein.

Amino Acid Sequence↗
PubMed1998

Water and DMSO membrane permeability characteristics of in-vivo- and in-vitro-derived and cultured murine oocytes and embryos.

Although embryo cryopreservation is routine for many mammalian species, it is important to know how the fundamental cryobiology of these cells changes with development. Progressive cleavage divisions result in a reduction in the blastomere surface area available for water and cryoprotectant mass transport. Therefore, the membrane permeability of murine oocytes, zygotes, 2-cell, 4-cell, and 8-cell embryos to water (Lp), and dimethylsulphoxide (PDMSO), and the reflection coefficient, sigma (sigma) were determined. Oocytes or zygotes were recovered, cumulus cells removed, then cultured until use. Oocytes and embryos were immobilized and perfused with treatment solutions at 24 degrees C. Osmotically induced cell volume changes over time were videotaped followed by image analysis. The Lp values in the presence of dimethylsulphoxide (DMSO) were 0.77, 0.81, 0.94, 0.86, and 1.10 microm/min/atm, and the PDMSO values were 1.85, 2.04, 2.41, 1.95, and 1.25x10(-3) cm/min for oocytes, zygotes, 2, 4, and 8-cell embryos respectively. The Lp values in the presence of DMSO were significantly (P < 0.05) higher than those in the absence of DMSO. Treating the whole embryo as a single osmotic entity leads to significantly (P < 0.05) elevated PDMSO estimates relative to those based upon measurements of individual blastomeres. These data indicate that both Lp and PDMSO estimates are lower when predicted on an individual blastomere basis. The data also show that neither Lp nor PDMSO differ among oocytes, zygotes, 2-cell and 4-cell embryos. However, the significantly higher Lp and lower PDMSO of the 8-cell stage support the hypothesis that fundamental cryobiological differences may require developmental stage-specific embryo cryopreservation protocols.

Animals↗
PubMed1998

Expression of the extracellular domain of the human immunodeficiency virus type 1 envelope protein and its fusion with beta-galactosidase in Saccharomyces cerevisiae.

Two envelope glycoprotein gene fragments were cloned from the proviral genome of the HXB2 isolate of human immunodeficiency virus (HIV). For the production of the two domains of the envelope gene product these cloned gene fragments were inserted into an Escherichia coli-yeast inducible shuttle vector fused to the galactokinase (GAL1) promoter. Cell extracts from strains of Saccharomyces cerevisiae harboring these two vectors (pYENV1 and pYENV2) were found to contain a specific protein with a size of 50 kDa when induced by galactose, while the protein could not be detected in extracts from control cells containing only the E. coli-yeast vector in the presence of galactose. Furthermore, another expression plasmid coding for fusion proteins from the majority of the external envelope glycoprotein (gp120) moiety and a large part of the beta-galactosidase was constructed. Antibodies from HIV type 1-positive sera could react with recombinant fusion polypeptides. Transformants could produce this fusion protein to a level of about 1.6% of the total protein content, as deduced from beta-galactosidase activity.

Cloning, Molecular↗
PubMed1998

Protective effects of baicalein against cell damage by reactive oxygen species.

Baicalein (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one), a naturally occurring flavonoid, was found to prevent human dermal fibroblast cell damage induced by reactive oxygen species such as hydrogen peroxide (H2O2), tert-butyl hydroperoxide (BuOOH) and superoxide anions (.O2-) in a concentration-dependent manner, and was more effective than the iron chelator, deferoxamine, hydroxyl radical (.OH) scavengers such as dimethyl sulfoxide (DMSO) and ethanol (EtOH), the lipid peroxidation chain blocker, alpha-tocopherol (Vit. E) and the xanthine oxidase inhibitor, allopurinol. To probe the mechanism of cell defense, the reaction of baicalein with oxygen free radicals was investigated using electron spin resonance (ESR) spectrometry. Baicalein decreased the signal intensities due to the 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin adducts of .OH, .O2- and tert-butyl peroxyl (BuOO.) radicals in a concentration-dependent manner. The IC50 values, which are the 50% inhibition concentrations of baicalein for the free radicals, were 10, 45 and 310 microM, respectively. These results suggested that baicalein possesses free radical scavenging ability which prevents the fibroblast damage induced by these free radical species.

Cyclic N-Oxides↗