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Biomedical subjects

C Gao

Publications and source records attributed to C Gao.

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

Preliminary evaluation of a new dental implant design in canine models.

Problems with crestal bone resorption and bone adaptation to dental implants in compromised and weak bone present clinical challenges due to insufficient bone volume. Mathematical models have shown that a new, square-thread, dental implant design increases functional surface area and reduces shear loading at the implant interface. The aim of this investigation was to evaluate the ability of bone to grow between the threads of the new implant and its general biocompatibility in a canine model. Test implants were placed in the mandibles of four beagle dogs after posterior partial edentulism. Three months after implantation, the animals received independent fixed partial dentures, were followed for an additional 6 months, and then euthanized for histological analyses. Analyses revealed that bone grew between the threads and closely apposed the new implant design. Histological observations also revealed that the inferior aspect of the test implant threads were apposed by more bone than the coronal aspect, suggesting a biological advantage for the compressive load transfer mechanism of the new implant design. The results of this study revealed that the new implant design became osseointegrated with bone growing between the threads of the device.

Animals↗
PubMed2000

Structure-activity relationships of sialogogic heptapeptides analogous to physalaemin.

OBJECTIVES: The rationale behind this study was to determine in detail which amino acids in physalaemin are crucial to its sialogogue activity, with a view of synthesizing new sialogogues which might be of use in the treatment of dry mouth. METHODS: With the progressive elimination of amino acids, one by one, from the C- and N-terminal regions, 126 heptapeptides were newly synthesized by the multipin peptide method, for comparison with II naturally occurring tachykinins. RESULTS: The C-terminal amide in position II was essential for salivation, but not the pyrolidine group or the N-terminal amino acid residues in positions I to 4. In 18 heptapeptides in which M in position II (MII) was replaced by another amino acid, one by one, none caused salivation. In 18 heptapeptides, in which L10 or G9 was replaced, three peptides caused salivation but none had significantly increased secretory activities. In 18 heptapeptides in which Y8 was replaced, four caused salivation but only one (I) had significantly increased secretory activity. In 18 heptapeptides in which F7 was replaced, only Y caused salivation but with significantly reduced secretory activity. In contrast, in 18 heptapeptides in which K6 and N5 were replaced, most caused salivation and some of them had significantly increased secretory activities. CONCLUSIONS: It is concluded that the sequence FYGLM-NH2 conserved in the C-terminal region of physalaemin is optimal, that amides in position II and F7 are very important for salivation, but that K6 and N5 can be replaced by some other amino acids, resulting in increased secretory activities.

Amino Acids↗
PubMed2000

Surface photo-grafting of polyurethane with 2-hydroxyethyl acrylate for promotion of human endothelial cell adhesion and growth.

Cytocompatible polyurethane (PU) surface was prepared by photo-grafting 2-hydroxyethyl acrylate (HEA) onto the membrane surface. Graft polymerization was conducted by combining the use of the photo-oxidation and irradiation grafting. PU membrane was photo-oxidized to introduce the hydroperoxide groups onto the surface, then the membrane, immersed previously in monomer solution, was irradiated under UV light. The ATR-FTIR spectra, element spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM) and water contact angle characterized the grafted copolymers and verified the occurrence of graft polymerization. The results showed that UV irradiation could realize the graft polymerization effectively and the grafting was confined within the surface layer. The grafted membrane showed minimal surface morphology. Human umbilical vein endothelial (HUVE) cells were seeded on the grafted surface. The performance of the surface in cell attachment and growth correlated with the oxygen content and mainly the carbonyl content on the surface. Cells were spread more extensively and grew faster on the surface with a higher oxygen content.

Acrylates↗
PubMed2000

LHRH neuronal migration: heterotypic transplantation analysis of guidance cues.

During embryonic development, the olfactory placode (OP) differentiates into the olfactory epithelium (OE). Luteinizing hormone-releasing hormone (LHRH) neurons migrate out of the OE in close association with the olfactory nerve (ON) to the telencephalon. LHRH neuronal migration and ON extension to the telencephalon may be independent events which are correlated but do not represent a causal relationship. However, we hypothesize that LHRH neurons are dependent on ON axons to migrate to the brain. To test this hypothesis, we ablated the right trigeminal placode and replaced it with an OP from another chick embryo. After several days' additional incubation, the embryos were fixed, sectioned, and immunostained with antibodies against LHRH or N-CAM. The ectopic OPs were well integrated into the host and developed into relatively normal appearing OEs. The ONs extended from the OE to several different sites: the lateral rectus of the eye, the ciliary ganglion, and the trigeminal ganglion. In all cases, LHRH neurons were found in the OE and ON, regardless of where the ON terminated. When the ON extended to the trigeminal ganglion, LHRH neurons could clearly be seen entering the metencephalon. Our results support the idea that LHRH neurons are dependent on the ON for guidance as they appear to follow the nerve even when it extends away from the brain. The cues which direct the ON and LHRH neurons to the telencephalon do not appear to be unique to this brain region.

Animals↗
PubMed2000

[One of the etiological factors of digestive tract cancers in Chinese: the missense mutation Val384Asp in the hMLH1 gene].

OBJECTIVE: To investigate the etiological role of Val384Asp in the hMLH1 gene, which may be a polymorphism in Chinese, in colorectal, gastric and esophageal cancers. METHODS: Genomic DNA extracted from normal tissues were subjected to analysis in exon 12 of the hMLH1 gene by single strand conformation polymorphism(SSCP) followed by DNA sequencing of aberrant bands in 101 colorectal, 79 gastric and 76 esophageal cancer patients; in 79 and 76 first degree relatives of gastric cancer and esophageal cancer patients respectively; and in 100 healthy control individuals. RESULTS: Six percent of Chinese healthy individuals were the carriers of Val3 84Asp in the hMLH1 gene. There were significant differences in the frequencies of Val384Asp in the hMLH1 gene between the patients with colorectal cancer at young age(<45 years) and the control individuals (P<0.05), and between the gastric cancer patients with family history, the first degree relatives and the control group (P<0.05 and P<0.01 respectively). No difference was found between the esophageal cancer patients, their relatives and healthy controls. CONCLUSION: The alleles frequency of Val384Asp in the hMLH1 gene in Chinese is three percent. This missense mutation may play a part in the etiology of colorectal and gastric cancers in Chinese.

Adaptor Proteins, Signal Transducing↗
PubMed2000

[Ordination analysis on relationship between bryophyte distribution and climatic factors].

Based on the data of climate and bryoflora in 21 mountainous regions of China, 61 moss families, 23 genera of Dicranaceae, 17 species of genus Campylopus and 35 species of genus Dicranum were analyzed by Canonical Correspond Analysis(CCA) and Detrended Canonical Correspond Analysis (DDCA) to reveal their distribution relationships with nine climatic factors, including annual average temperature, January average temperature, July average temperature, annual average rainfall, annual average fog days, annual average frost days and annual average light hours. The similarity of geographical elements among nine mountains in China and their relationships with climatic factors were also analyzed. The methods of applying DDCA and CCA to analyze the relationships between bryophyte and climatic factors were thus introduced. The studies indicate that CCA and DCCA are applicable in florology and phytogeography.

Bryopsida↗
PubMed2000

[Population growth, distribution pattern and sampling technique of Thrips palmi on eggplant].

Population growth of Thrips palmi Karny on eggplant (Solanum melongena L.) were analyzed by mathematical models. The rate of population increase (r) of the adults and immature (instars 1-2) T. palmi were estimated to be 0.0630 and 0.0801 respectively in the open fields, and 0.0983 and 0.1036 respectively in the greenhouse. K value of logistic curve of T. palmi was estimated to be 33.90 in the greenhouse, and 23.50 in the open fields. The relationship between mean crowding (M*) and mean density (M) of T. palmi per eggplant leaf were estimated by Iwao's M*-M regression. The regression equation of adult and immature T. palmi on eggplant were: M* = 0.6011 + 1.468M and M* = 7.2515 + 2.064M respectively. The regression equation of the number of adult and immature was M* = 7.5138 + 1.9119M. When the population density of the adults and immature T. palmi per eggplant leaf were 10 to 100, the number of sampling should be 78 to 44.

Animals↗
PubMed2000

Basic and clinical study on the antithrombotic mechanism of glycosaminoglycan extracted from sea cucumber.

OBJECTIVE: To investigate the antithrombotic mechanism of glycosaminoglycan (GAG) extracted from sea cucumber. METHODS: We studied the effects of GAG on the coagulant pathway by measuring cloting time. The antithrombin mechanism of GAG was checked by assaying its effects on the thrombin activity in normal human pooled plasma, purified human heparin cofactor II system and antithrombin III system. The effects of GAG on the assembly, dispersion, and structure of fibrin gels as well as on the activity of plasmin were studied by means of turbidimetry, electron microscopy, and chromogenic substrate assay. We studied the effect of GAG on the expression and transcription of tissue factor (TF) and thrombomodulin (TM) in LPS (lipopolysaccharide)-stimulated human umbilical vein endothelial cells (HUVECs), and used heparin as a control. HUVECs were treated with different concentrations of GAG (1 microgram/ml, 5 micrograms/ml, and 10 micrograms/ml respectively) and 5 micrograms/ml heparin as a control together with LPS (1 microgram/ml). After incubation for 6 hours, TF and TM were investigated by ELISA and the mRNA study was carried out by RT-PCR. In a clinical trail, a series of variables were observed before and after treatment with GAG in patients recovering from cerebral ischemic stroke or suffering from ischemic heart disease. RESULTS: The TT and APTT were significantly prolonged by GAG (0.1 microgram/ml). GAG inhibited thrombin activity in the presence of HCII with a second order rate constant of 1.14 x 10(7) m-1.min-1, which was 4.6 times higher than that of ATIII. GAG significantly inhibited the polymerization of fibrin monomer and enhanced the activity of plasmin in a concentration dependent manner. GAG could impair TF mRNA expression and up-regulate TM mRNA expression. The result of clinical trail showed that the fat metabolism was enhanced in addition to the anticoagulant and the blood viscosity reducing effects. No side-effect was found. CONCLUSIONS: GAG mainly affected on the intrinsic pathway of blood coagulation. GAG was similar to dermatan sulfate both in the efficiency and in the mechanism of antithrombin. The acceleration of colt lysis by GAG depended on its ability to increase the activity of plasmin, to inhibit the polymerizing of fibrin monomer, and consequently, to alter the architecture of the fibrin net work. This effect on HUVECs appears to be at a transcriptional level and might be relevant for the antithrombotic action of GAG. GAG possess anticoagulant activity in vivo and it is a promising drug for antithrombotic therapy.

Animals↗
PubMed2000

[Study on the relations between HLA-DRB 1 alleles and Helicobacter pylori infection].

OBJECTIVE: In order to study the relation between human leukocyte antigen (HLA) DRB1 alleles and Helicobacter pylori (Hp) infection. METHODS: Hp-IgG antibody from 46 gastric cancer (GC), 75 esophageal cancer and 100 population-based controls were identified by Hp-IgG quantitative enzyme immunoassay. Biotest HLA-DRB enzyme linked probe hybridization assay kit (low resolution) was used to identify DRB1 alleles. RESULTS: (1) Frequency of DRB1 * 08 was significantly higher in Hp-IgG positive group than in Hp-IgG negative group (13.1% vs 4.4%, chi(2) = 11.14, P < 0.001). Frequency of DRB1 * 12 was significantly lower in Hp-IgG positive group than in Hp-IgG negatives (5.4% vs 11.3%, chi(2) = 4.49, P < 0.05). (2) Frequency of DRB1 * 02 in GC was significantly higher than that of controls. Frequency of DRB1 * 07 in GC was significantly lower than that of controls. However, neither the frequency of DRB1 * 02 between Hp-IgG positive and Hp-IgG negative groups nor the frequency of DRB1 * 07 between Hp-IgG positive and Hp-IgG negative groups showed significant differences in GC and controls. CONCLUSIONS: (1) HLA-DRB1 * 08 might serve a genetic risk factor for Hp infection while DRB1 * 12 might play a role of protecting effect against Hp infection. (2) DRB1 * 02 might be a genetic risk factor for GC while DRB1 * 07 might play a role of protecting effect against GC. However, the relations between DRB1 * 02, DRB1 * 07 and GC were not associated with Hp infection.

Alleles↗
PubMed2000

[The effect of Shenmai injection on the expression of TNFalpha mRNA of the macrophages in scalded mice].

OBJECTIVE: To explore the effect of Shenmai injection on the expression of TNFalpha mRNA of peritoneal macrophages in scalded mice. METHODS: BALB/c mice inflicted with 11% TBSA III degree scalding injury were employed as the model. Shenmai injection was composed of 100 mg of red ginseng and 100 mg of lily turf root in 1 ml injection solution and was administered to mice via peritoneal injection in a dose of 2.5 ml per kilogram of mice body weight per day for 5 days. The expression of TNFalpha mRNA was determined by semi-quantitative RT-PCR. RESULTS: The expression of macrophage TNFalpha mRNA was significantly increased in the scalded mice, while the expression was obviously lowered after the administration of Shenmai injection (P < 0.01) to scalded mice and the survival rate of the scalded mice was thus markedly increased (P < 0.05). CONCLUSION: The beneficial effect of Shenmai injection on the scalded mice might be related to its inhibitory effect on the hyperexpression of macrophage TNFalpha mRNA. Shenmai injection could lower down the expression of TNFalpha in scalded mice and raise the survival rate of scalded mice.

Animals↗
PubMed2000

[Identification and functional analysis of NIFA from Mesorhizobium huakuii 159].

The nifA gene from Mesorhizobium huakuii 159 was identified and sequenced. An open reading frame coding for 44734D. NifA protein would detected. Comparison of the deduced amino acid sequence with other NifA proteins revealed the presence of the conserved central domain and the C-terminal DNA-binding domains. But the predicted M. huakuii NifA protein lacked a N-terminal domain that is present in the homologous proteins. Mutants with Nif- phenotype were obtained by site-directed Tn5 mutagenesis. A nifA constitutively expressed plasmid was constructed, and this plasmid could activate the nifH expression in YMC11.

Amino Acid Sequence↗
PubMed1999

Activation of p53 in MDM2-overexpressing cells through phosphorylation.

Overexpressed MDM2 inactivates wild-type (wt) p53 in various human tumors. However, whether and how the wild-type p53 can be activated by anticancer drug treatment in the presence of excess MDM2 is still unclear. In the present study, we showed that the topoisomerase II inhibitor of widely used anticancer drugs etoposide and doxorubicin activated wt p53 in BL2, a Burkitt's lymphoma cell line which overexpressed MDM2. Activation of p53 was followed by apoptosis in BL2 cells, while the same drug treatment did not induce apoptosis in Raji cells, another Burkitt's lymphoma cell line which carried mutant p53. Activation of p53 was accompanied by phosphorylation of p53 at Ser-15 and elevated p21 and MDM2, both of which were at least partly blocked by wortmannin, a kinase inhibitor against proteins with a PI3 kinase domain. Although MDM2 protein was rapidly cleaved and degraded after anticancer drug treatment, cotreatment with caspase inhibitor Z-VAD blocked degradation, while wt p53 remained activated, suggesting MDM2 degradation not to be essential for the activation of p53. Treatment with proteasome inhibitor stabilized p53 without being further phosphorylated. This p53 was co-immunoprecipitated with MDM2, but p53 activated by etoposide or doxorubicin barely complexed with MDM2. These results suggest that the wild-type p53 in MDM2-overexpressing cells can be activated by anticancer drugs through phosphorylation of p53, alleviating inhibitory action by MDM2, and activating caspases which in turn downregulates MDM2. The activation of p53 in MDM2-overexpressing tumor cells, which does not require the downregulation of MDM2, may have important implications in cancer therapy.

Antineoplastic Agents↗
PubMed1999

Phage-display library selection of high-affinity human single-chain antibodies to tumor-associated carbohydrate antigens sialyl Lewisx and Lewisx.

mAbs against tumor-associated carbohydrate antigens have the potential to play a prominent role in cancer immunotherapy. However, it has not been possible to fully exploit the clinical utility of such antibodies primarily, because those of adequate affinity could be derived only from murine sources. To address this problem, we prepared a single-chain Fv (scFv) antibody library from the peripheral blood lymphocytes of 20 patients with various cancer diseases. Completely human high-affinity scFv antibodies were then selected by using synthetic sialyl Lewisx and Lewisx BSA conjugates. These human scFv antibodies were specific for sialyl Lewisx and Lewisx, as demonstrated by ELISA, BIAcore, and flow cytometry binding to the cell surface of pancreatic adenocarcinoma cells. Nucleotide sequencing revealed that at least four unique scFv genes were obtained. The Kd values ranged from 1.1 to 6.2 x 10(-7) M that were comparable to the affinities of mAbs derived from the secondary immune response. These antibodies could be valuable reagents for probing the structure and function of carbohydrate antigens and in the treatment of human tumor diseases.

Amino Acid Sequence↗
PubMed1999

Making artificial antibodies: a format for phage display of combinatorial heterodimeric arrays.

The gene VII protein (pVII) and gene IX protein (pIX) are associated closely on the surface of filamentous bacteriophage that is opposite of the end harboring the widely exploited pIII protein. We developed a phagemid format wherein antibody heavy- and light-chain variable regions were fused to the amino termini of pVII and pIX, respectively. Significantly, the fusion proteins interacted to form a functional Fv-binding domain on the phage surface. Our approach will be applicable to the display of generic peptide and protein libraries that can form combinatorial heterodimeric arrays. Consequently, it represents a first step toward artificial antibodies and the selection of novel biological activities.

Amino Acid Sequence↗
PubMed1999

Intramuscular injection of an adenoviral vector expressing hepatocyte growth factor facilitates hepatic transduction with a retroviral vector in mice.

Retroviral vectors can result in therapeutic and stable levels of expression of proteins from the liver. However, most retroviral vectors transduce only dividing cells, and hepatocytes are normally quiescent. The goal of this study was to determine if an adenoviral vector could transiently express hepatocyte growth factor (HGF) in order to induce hepatocyte replication and facilitate retroviral vector transduction of the liver. Intramuscular injection of an adenoviral vector that expressed human HGF from the cytomegalovirus promoter (Ad.CMV.HGF) resulted in moderate levels of HGF in blood and liver, and replication of 3 to 12% of hepatocytes. No cytopathic effect was observed in the liver, and a control adenoviral vector induced no or lower levels of replication. When a retroviral vector expressing beta-galactosidase cDNA was injected into a peripheral vein during the peak period of hepatocyte replication induced by intramuscularly administered Ad.CMV.HGF, 8% of hepatocytes were transduced. We conclude that intramuscular injection of Ad.CMV.HGF is a safe and effective way to induce transient systemic expression of HGF and hepatocyte replication, and to facilitate transduction of hepatocytes with a retroviral vector.

Adenoviridae↗
PubMed1999

Lipopolysaccharide potentiates the effect of hepatocyte growth factor on hepatocyte replication in rats by augmenting AP-1 activity.

The liver regenerates by replication of differentiated hepatocytes after damage or removal of part of the liver. Although several growth factors and signaling pathways are activated during regeneration, it is unclear as to which of these are essential for hepatocyte replication. We show here that low- (1 mg/kg) and high- (10 mg/kg) dose hepatocyte growth factor (HGF) induced replication of 2.1% and 11.1% of hepatocytes in rats, respectively. Lipopolysaccharide (LPS), an inducer of the acute phase response, augmented hepatocyte replication in response to low- and high-dose HGF by 4- and 2-fold, respectively. HGF alone induced moderate levels of c-Jun-N-terminal kinase (JNK) and p44/p42 mitogen-activated protein kinase (MAPK), resulting in moderate levels of AP-1-DNA binding activity. The combination of LPS + HGF increased JNK and AP-1-DNA binding activity more than levels seen with LPS or HGF alone. The activation of Stat3 that was observed after administration of LPS + HGF, but not HGF alone, could contribute to increased transcription of AP-1 components. Because phosphorylation of the c-Jun component of AP-1 by JNK increases its ability to activate transcription, the AP-1 in hepatocytes from animals treated with LPS + HGF may be more active than in rats treated with LPS or HGF alone. LPS may contribute to hepatocyte replication by potentiating the effect of HGF on the activation of both AP-1-DNA binding and transcriptional activity.

Acute-Phase Proteins↗
PubMed1999

Establishment and cellular characteristics of a hepatocyte cell line (OUMS-31) derived from an acatalasemic mouse.

Liver cell lines with very low catalase activity were established from an acatalasemic mouse. Hepatocytes isolated by a collagenase-liver-perfusion technique were cultured in Williams' E medium supplemented with 10% fetal bovine serum. The acatalasemic liver cell line showed approximately 20% of the catalase activity of a normal mouse liver cell line, whereas its glutathione peroxidase activity was approximately equal to that of the normal liver cell line. DNA sequence analysis of this cell line showed the same mutation in the catalase gene as is seen in the acatalasemic mouse. Our observation of intracellular content of hydrogen peroxide (H2O2) radical and increased susceptibility of the cells to H2O2 were compatible with the existence of low catalase activity in the acatalasemic mouse. This hepatocyte cell line should be useful for studying effects of oxidative radical stress at the cellular level.

Acatalasia↗