Biomedical subjects

Hao Chen

Publications and source records attributed to Hao Chen.

At least 109 records · Page 6Linked to original sources

PubMed2004

Laser-induced time-resolved photoacoustic calorimetry study on photo-dissociation of human and bovine oxyhemoglobin.

The dynamics of the enthalpy and volume changes related to the photo-dissociation of oxygen from human and bovine oxyhemoglobin are investigated by nanosecond time-resolved photoacoustic calorimetry (PAC). The values of enthalpy and volume change associated with the above process are deltaH = 37.8 +/- 3 kcal/mol, deltaV = 5.0 +/- 1 ml/mol for human HbO(2); and deltaH = 35.7 +/- 3.5 kcal/mol, deltaV = 4.8 +/- 1 ml/mol for bovine HbO(2), respectively. A possible explanation for the similar values between both human and bovine oxyhemoglobin is proposed. In addition, the PAC results for human HbO(2) and HbCO are compared and discussed.

Acoustics↗

PubMed2004

Brain-derived neurotrophic factor reduces TrkB protein and mRNA in the normal retina and following optic nerve crush in adult rats.

Brain-derived neurotrophic factor (BDNF) is a well-known retinal neuroprotectant, but its effectiveness is limited: higher doses do not yield increased cell survival, multiple applications are not additive, and long-term delivery does not reverse, ganglion cell death. These limitations might reflect either injury- or BDNF-induced retinal changes in TrkB, the high affinity tyrosine kinase receptor used by BDNF. Retinal levels of TrkB protein and mRNA were measured in rats following intravitreal application of BDNF alone, optic nerve crush alone, and both. Full-length receptor protein levels (TrkB.FL) were determined by Western blot analysis and mRNA (trkB.FL) levels were measured using RNAse protection assay (RPA). BDNF alone produced a rapid and prolonged decrease in normal retina TrkB.FL. Nerve crush also resulted in decreased TrkB.FL, but the reduction was not apparent before 2-week post-crush. BDNF applied at the time of the crush yielded reductions in TrkB.FL similar to that of BDNF alone. With respect to TrkB mRNA levels, injection of BDNF into normal eyes and optic nerve crush alone showed bell-shaped patterns of change: approximately 50% below normal at 24-h post-procedure, approximately 50% above normal at 3 days, normal at 7 days, and approximately 50% below normal at 2-week post-procedure. When BDNF and nerve crush were combined, trkB-FL levels reached 90% of normal 1-week post-crush/injection. The data suggest that the limitation of BDNF in promoting ganglion cell survival following optic nerve injury results, in part, due to drug-induced down-regulation of the full-length TrkB receptor needed to activate intracellular pathways.

Animals↗

PubMed2004

Liver biopsy in evaluation of complications following liver transplantation.

AIM: To analyze the role of liver biopsies in differential diagnosis after liver transplantation. METHODS: A total of 50 biopsies from 27 patients with liver dysfunction out of 52 liver transplantation cases were included. Biopsies were obtained 0-330 d after operation, in which, 44 were fine needle biopsies, another 6 were wedge biopsies during surgery. All tissues were stained with haemotoxylin-eosin. Histochemical or immunohistochemical stain was done. RESULTS: The rate of acute rejection in detected cases and total transplantation cases was 48.2% and 25.0%, chronic rejection rate in detected cases and total transplantation cases was 14.8% and 7.7%, preservation-reperfusion injury in detected cases and total transplantation cases was 25.9% and 13.5%, hepatic artery thrombosis rate in detected cases and total transplantation cases was 11.1% and 5.8%, intrahepatic biliary injury rate in detected cases and total transplantation cases was 7.4 % and 3.8%, CMV infection rate in detected cases and total transplantation cases was 3.7% and 1.9%, hepatitis B recurrence rate in detected cases and total transplantation cases was 3.7% and 1.9%, the ratio of suspicious drug-induced hepatic injury in detected cases and total transplantation cases was 11.1% and 5.8%. CONCLUSION: Acute rejection and preservation-reperfusion injury are the major factors in early liver dysfunction after liver transplantation. Hepatic artery thrombosis and prolonged cold preservation may result in intrahepatic biliary injury. Acute rejection and viral infection may involve in the pathogenesis of chronic rejection. Since there are no specific lesions in drug-induced hepatic injury, the diagnosis must closely combine clinical history and rule out other possible complications.

Acute Disease↗

PubMed2004

Protective effect of doxorubicin induced heat shock protein 72 on cold preservation injury of rat livers.

AIM: To observe the protective effect of heat shock protein 72 (HSP 72) induced by pretreatment of doxorubicin (DXR) on long-term cold preservation injury of rat livers. METHODS: Sprague-Dawley rats were administered intravenously DXR at a dose of 1 mg/kg body mass in DXR group and saline in control group. After 48 h, the rat liver was perfused with cold Linger's and University of Wisconsin (UW) solutions and then was preserved in UW solution at 4 degrees for 24, 36 and 48 h. AST, ALT, LDH and hyaluronic acid in preservative solution were determined. Routine HE, immunohistochemical staining for HSP 72 and electron microscopic examination of hepatic tissues were performed. RESULTS: After 24, 36 and 48 h, the levels of AST, ALT and hyaluronic acid in preservative solution were significantly higher in control group than in DXR group (P<0.05), while LDH level was not significantly different between the 2 groups (P>0.05). Hepatic tissues in DXR group were morphologically normal and significantly injured in control group. HSP 72 was expressed in hepatocytes and sinusoidal endothelial cells in DXR group but not in control group. CONCLUSION: Pretreatment of DXR may extend the time of rat liver cold preservation and keep liver alive. The expression of HSP 72 in liver can prevent hepatocytes and sinusoidal endothelial cells from long-term cold preservation injury.

Animals↗

PubMed2004

Tyrosol is a quorum-sensing molecule in Candida albicans.

The human fungal pathogen Candida albicans shows a significant lag in growth when diluted into fresh minimal medium. This lag is abolished by the addition of conditioned medium from a high-density culture. The active component of conditioned medium is tyrosol, which is released into the medium continuously during growth. Under conditions permissive for germ-tube formation, tyrosol stimulates the formation of these filamentous protrusions. Because germ-tube formation is inhibited by farnesol, another quorum-sensing molecule, this process must be under complex positive and negative control by environmental conditions. The identification of tyrosol as an autoregulatory molecule has important implications on the dynamics of growth and morphogenesis in Candida.

Base Sequence↗

PubMed2004

Reduction of nitroaromatics to arylnitrenium ions by vinyl halide cations.

The title reduction of nitroaromatics ArNO(2) by vinyl halide radical cations CH(2)[double bond]CH-X(+*)(X = Cl or Br) to form arylnitrenium ions ArNH(+) involves a change in oxidation number of nitrogen from +3 to -1. This novel reaction provides a new route for the generation of arylnitrenium ions, a highly selective method for the detection of explosives in mixtures, and offers clues to the carcinogenic activity of nitroaromatics in vivo.

Journal Article↗

PubMed2004

[Infection after cardiac transplantation: prevention and management].

OBJECTIVE: To explore and sum up the characteristics of infection after cardiac transplantation and to discuss the prophylaxis and management. METHOD: From May 2000 to April 2003, 36 patients received orthotopic heart transplantation, the clinical data were observed and analyzed. RESULTS: Infection occurred in 2 (6%) cases, both belonged to lung infection caused by human cytomegalovirus. The 2 cases were cured by ganciclovir intravenously. CONCLUSION: Good prophylactic method may decrease post cardiac transplantation infection significantly. It is very important to early diagnose and treat infection.

Adolescent↗

PubMed2004

High-performance liquid chromatographic method for simultaneous determination of sophoridine and matrine in rat plasma.

A high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of sophoridine and matrine in rat plasma. Sophoridine and matrine in the resulting supernatant of the plasma deproteinized with acetonitrile containing an internal standard (acetanilide) were directly determined by reversed-phase HPLC and ultraviolet detection. The result of limits of quantitation for matrine and sophoridine were 200 and 350 ng/mL in plasma, respectively, and recovery of both analytes was greater than 98%. The assay was linear from 250 to 4000 ng/mL for matrine and from 500 to 8000 ng/mL for sophoridine. Variation over the range of the standard curve was less than 15%. The method was used to determine the concentration-time profiles of matrine and sophoridine in the plasma following oral administration of Kexieling tablets, which is one of the preparations of Kudouzi at a dose equivalent to 30 and 60 mg/kg of matrine and sophoridine, respectively.

Alkaloids↗

PubMed2004

Dissociation of ionized benzophenones investigated by the kinetic method: effective temperature, steric effects and gas-phase CO+* affinities of phenyl radicals.

Ionized benzophenones ([PhC(O)PhY](+*); Y = 4 - NO(2), 4 - CF(3), 4-F, 4-Br, 4-Me, 3,4-diMe, 4-OH, 4-OMe, 2-Cl, 2-Me, 2-OH, 2,6-diMe) undergo competitive dissociation upon collision-induced dissociation (CID) at 20 eV collision energy to generate benzoyl cations ([PhCO](+) and [YPhCO](+)) and phenyl radicals (Ph(*) and YPh(*)). For the para-substituted benzophenones, the natural logarithm of the abundance ratio of the benzoyl cations [ln([PhCO(+)]/[YPhCO(+)])] is found to correlate linearly with the calculated CO(+*) affinities of the phenyl radicals Ph(*) and YPh(*). A deviation from linearity is observed for the ortho-substituted isomers. This is probably due to a significant intramolecular steric interaction between the carbonyl group and the ortho substituent which prevents the formation of a stable planar system. An observed shift in the intercept relative to the origin is interpreted as the result of a systematic error in the calculated CO(+*) affinities and this effect is minimized by calculations at a higher level. The dissociation of ionized para-substituted benzophenones is associated with a relatively high effective temperature of 1816 +/- 41 K, calculated from the slope of the kinetic method plot, a value that is consistent with a covalent bond in the activated ion. In addition, Delta(DeltaS(CO(+) )), the dissociation entropy of the benzoyl cations to form CO(+*) and the aryl radical, is found to be about 4 J mol(-1) K(-1) by employing the extended version of the kinetic method.

Journal Article↗

PubMed2004

Meerwein reaction of phosphonium ions with epoxides and thioepoxides in the gas phase.

Phosphonium ions are shown to undergo a gas-phase Meerwein reaction in which epoxides (or thioepoxides) undergo three-to-five-membered ring expansion to yield dioxaphospholanium (or oxathiophospholanium) ion products. When the association reaction is followed by collision-induced dissociation (CID), the oxirane (or thiirane) is eliminated, making this ion molecule reaction/CID sequence a good method of net oxygen-by-sulfur replacement in the phosphonium ions. This replacement results in a characteristic mass shift of 16 units and provides evidence for the cyclic nature of the gas-phase Meerwein product ions, while improving selectivity for phosphonium ion detection. This reaction sequence also constitutes a gas-phase route to convert phosphonium ions into their sulfur analogs. Phosphonium and related ions are important targets since they are commonly and readily formed in mass spectrometric analysis upon dissociative electron ionization of organophosphorous esters. The Meerwein reaction should provide a new and very useful method of recognizing compounds that yield these ions, which includes a number of chemical warfare agents. The Meerwein reaction proceeds by phosphonium ion addition to the sulfur or oxygen center, followed by intramolecular nucleophilic attack with ring expansion to yield the 1,3,2-dioxaphospholanium or 1,3,2-oxathiophospholanium ion. Product ion structures were investigated by CID tandem mass spectrometry (MS(2)) experiments and corroborated by DFT/HF calculations.

Journal Article↗

PubMed2004

Meisenheimer complexes bonded at carbon and at oxygen.

The carbon-bonded gas-phase Meisenheimer complex of 2,4,6-trinitrotoluene (TNT) and the nitromethyl carbanion CH(2)NO(2)(-) (m/z 60) is generated for the first time by chemical ionization using nitromethane as the reagent gas. Collision-induced dissociation (CID) of the Meisenheimer complex furnishes deprotonated TNT, a result of the higher gas-phase acidity of TNT than nitromethane. The formation of Meisenheimer complexes with CH(2)NO(2)(-) in the gas phase is selective to highly electron-deficient compounds such as dinitrobenzene and trinitrobenzene and does not occur with organic molecules with lower electron-affinity such as methanol, methylamine, propionaldehyde, acetone, ethyl acetate, chloroform, toluene, m-methoxytoluene, and even nitrobenzene and p-fluoronitrobenzene. As such, the reaction allows selective detection of TNT in mixtures. Meisenheimer complexes between CH(2)NO(2)(-) and the three dinitrobenzene isomers display distinctive fragmentations. The oxygen-bonded sigma-complex of TNT with the deprotonated hemiacetal anion CH(3)OCH(2)O(-) (m/z 61), represents a different type of Meisenheimer complex. It displays characteristic fragmentation involving loss of HNO(2) upon CID. The combination of a selective ion/molecule reaction (Meisenheimer complex formation) followed by a characteristic CID process provides a second novel and highly selective approach to the detection of TNT and closely related compounds in mixtures. The assay is readily implemented using neutral loss scans in a triple quadrupole mass spectrometer. Gas-phase reactions of denitrosylated TNT with benzaldehyde produce the corresponding dihydrofuran in an aldol condensation, a result that parallels the corresponding condensed-phase reaction.

Journal Article↗

PubMed2004

Generation of arylnitrenium ions by nitro-reduction and gas-phase synthesis of N-heterocycles.

Nitro-reduction by the vinyl halide radical cation CH2 = CH-X+* (X = Cl or Br) converts nitroaromatics into arylnitrenium ions, significant intermediates in carcinogenesis, and the present study reports on the scope and regioselectivity of this versatile reaction. The reaction is general for different kinds of substituted nitroaromatics; para/meta substitutents have little effect on the reaction while ortho substitutents result in low yields of arylnitrenium ions. The phenylnitrenium ion PhNH+ can be generated by chemical ionization (CI) of nitrobenzene using 1,2-dichloroethane as the reagent gas or by atmospheric pressure chemical ionization (APCI) of 1,2-dichloroethane solution doped with nitrobenzene. The chemical reactivities of the arylnitrenium ions include one-step ion/molecule reactions with nucleophiles ethyl vinyl ether and 1,3-dioxolanes, respectively, involving the direct formation of new CN bonds and synthesis of indole and benzomorpholine derivatives. The indole formation reaction parallels known condensed phase chemistry, while the concise morpholine-forming reaction remains to be sought in solution. The combination of collision-induced dissociation (CID) with novel ion/molecule reactions should provide a selective method for the detection of explosives such as TNT, RDX and HMX in mixtures using mass spectrometry. In addition to the reduction of the nitro group, reduction of methyl phenyl sulfone PhS(O)2Me to the thioanisole radical cation PhSMe+* occurs using the same chemical ionization reagent 1,2-dichloroethane. This probably involves an analogous reduction reaction by the reagent ion CH2 = CH-Cl+*.

Benzoxazines↗

PubMed2004

The tandem complex of BEL and KNOX partners is required for transcriptional repression of ga20ox1.

Summary Two interacting three amino acid loop extension (TALE) proteins of potato, StBEL5 (Solanum tuberosom BEL 5) and POTH1 (potato homeobox 1), mediate developmental processes by regulating phytohormone levels. Overexpression of either partner alone increased tuber yields by lowering gibberellin (GA) levels and increasing cytokinins. Gel shift assays demonstrated that StBEL5 and POTH1 bind to the regulatory region of ga20 oxidase1 (ga20ox1) from potato, a gene encoding a key enzyme in the GA biosynthetic pathway. In tandem, StBEL5 and POTH1 had a greater binding affinity for the ga20ox1 promoter than either protein alone. The StBEL5-POTH1 heterodimer bound specifically to a composite 10-bp sequence, containing two TGAC cores. Using a transcription assay, StBEL5 and POTH1 suppressed the activity of the ga20ox1 promoter by more than 50%. Dominant negative constructs containing the protein-binding domains of StBEL5 or POTH1 blocked the repression activity of StBEL5 or POTH1, respectively. The mutated ga20ox1 promoter that could be bound by the StBEL5 or POTH1 proteins individually but not by the StBEL5-POTH1 heterodimer also abolished the repression activity of StBEL5, POTH1, and the StBEL5-POTH1 heterodimer. These results indicate that the tandem interaction of StBEL5 and POTH1 is essential for regulation of the expression of their target gene.

Base Sequence↗

PubMed2004

[Research on relationships of gastric cancer with serum trace elements, Helicobacter pylori and COX-2 in gastric tissue].

The relationships of gastric cancer with serum trace elements, helicobacter pylori (HP) and COX-2 in gastric tissue were investigated. We took 50 blood samples from the gastric cancer patients in Hexi region (the gastric cancer group), and 50 blood samples from healthy volunteers (control group) and detected the level of trace elements, the rate of HP infection, and the expression of COX-2 in gastric tissue. The results showed the levels of Cu/Zn, Fe in the serum of the gastric cancer group were higher than those of the control group respectively(P < 0.05, 0.01), and the levels of Zn, Mn were lower than those of the control group respectively (P < 0.05, 0.01). The data on Zn were submitted to multi-variate non-conditional logistic analysis. The rate of HP infection and the positive expression of COX-2 were 88% and 78% respectively in the gastric cancer group, 42.0% and 0 in the control group (P < 0.01). These findings suggest that the decrease of Zn in serum may be a precancerous factor of gastric cancer development which induces HP infection and the higher expression of COX-2 and hence may lead to the development of gastric cancer. Detecting the trace elements could conduce to the diagnosis of gastric cancer. Regulating the level of trace element in the patient can be an effective chemoprophylaxis for gastric cancer.

Adult↗

PubMed2004

Expression of hepatitis B virus antigen and Helicobacter pylori infection in gastric mucosa of patients with chronic liver disease.

BACKGROUND: It is common for the gastroendoscopist to find patients infected simultaneously with hepatitis B virus (HBV) and Helicobacter pylori (H pylori). Considering that HBV infection is linked to hepatocellular carcinoma and H pylori to gastric cancer, we investigated the incidence in this kind of patients in the northern Jiangsu Province, China. Rational management of these patients was also discussed. METHODS: Seventy-two patients including 28 patients with chronic hepatitis B and 44 patients with post hepatitis B liver cirrhosis served as observation group. Thirty patients with gastritis but without liver disease were included as controls. Diagnostic endoscopy was performed in all the patients. Three biopsy specimens were taken from the pyloric antrum 3 cm from the pyloric ring. Urease test staining of hematoxylin and eosin or fuchsin, and immunohistochemical analysis of H pylori IgG antigen and HBV antigen (HBsAg, HBcAg) were performed. RESULTS: The extent and intensity of chronic inflammation were identified in 95.5% (42/44) of the antrum mucosa of the patients with cirrhosis and in 92.9% (26/28) of the patients with chronic hepatitis. The expression of H pylori in the mucosa was found in 29 of the 42 patients with cirrhosis associated with antrum inflammation (69.0%). The expression of H pylori was observed in 20 of the 26 patients with chronic hepatitis combined with antrum inflammation (76.9%). No significant difference existed between the cirrhosis group and the chronic hepatitis group. The rates of HBV antigen expression in the H pylori positive and negative gastric antrum mucosa were 69.8% (37/53)and 73.7% (14/19), respectively (P>0.05). CONCLUSIONS: Over-expression of HBV antigen (HBsAg and HBcAg) coexists with the expression of H pylori antigen in the H pylori infected gastric mucosa. Difficult clearance of HBsAg and HBcAg from gastric epithelial cells may be related to persistent H pylori infection. Early treatment of H pylori infection may be beneficial to the prognosis of patients with chronic liver disease.

China↗

PubMed2004

[In-vitro refolding and biotinylation of soluble HLA-A2-peptide complex].

AIM: To refold and biotinylate HLA-A2-peptide complex in-vitro. METHODS: The BirA substrate peptide (BSP) containing H chain of HLA-A2 and beta(2m) were expressed highly as insoluble aggregates in E.coli, and then the two subunits were refolded to form an HLA-A2-peptide complex by dilution method in the presence of an antigenic peptide (NH(2)-CLGGLLTMV-COOH of EB virus latent membrane protein 2A LMP2A). Then the BirA enzyme was used to biotinylate the refolded complex. The refolded and biotinylated products were detected by ELISA and Western blot with mAb W6/32 and rabbit anti-human beta(2m) antibody and streptavidin. RESULTS: The refolded complex was composed of H chain aggregate, HLA-A2-peptide complex and beta(2m). Both HLA-A2-peptide complex and the H chain aggregate could be biotinylated. CONCLUSION: The refolding and biotinylation of HLA-A2-peptide complex were successfully performed and the products were confirmed by our practical immunological method. This study laid the foundation for the preparation of HLA-peptide tetramer and artificial antigen presenting cells.

Biotinylation↗

PubMed2004

[The cytokine secretion of peripheral blood mononucleocytes from patients infected with HCV].

AIM: To detect the levels of cytokines secreted by PBMC from patients infected with HCV after culture for 72 hours in-vitro, so as to reflect the immune state of the HCV-infected patients. METHODS: The levels of cytokines in the culture supernatant of PBMCs were detected by ELISA. RESULTS: (1)Compared with the cytokine level of normal control, the levels of IFN-gamma, TNF-alpha, and IL-10 of HCV patients notably increased while IL-2, IL-4, and IL-12 were not detected in the culture supernatant of PBMCs from both normal control and HCV patients after culture for 72 hours. (2)There was no statistic difference in secretion of cytokines among the patients with mild, and moderate chronic hepatitis, and compensated or uncompensated cirrhosis. CONCLUSION: (1)PMBCs from the HCV-infected patients tend to secret Th2 type cytokines. (2)Lack of the IL-2 secretion from PBMCs of HCV patients may account for the immune escape of HCV.

Adolescent↗

PubMed2004

[Perforin and granzyme B expression in liver allograft rejection].

OBJECTIVE: To investigate the expression of perforin and granzyme B in rejection response following liver transplantation, and evaluate their roles to be used as predictive markers of rejection. METHODS: The expression of perforin and granzyme B in liver biopsies obtained from liver allograft recipients was determined by immunohistochemistry. Biopsies were classified into two groups-no evidence of rejection and rejection-according to Histopathologic criteria. The relationship between the perforin/granzume B expression and acute rejection was analyzed. RESULTS: From 19 patients, thirty-five liver biopsies were obtained after liver transplantation. Among them, nineteen samples were diagnosed as rejection response. The frequencies of perforin and granzyme B expression in rejection group were 100% (19/19) and 94.7% (18/19), respectively. While those in no rejection group were 25.0% (4/16) and 12.5 (2/16), respectively. In most rejected samples, perforin and granzyme B were expressed simultaneously. Only three samples showed perforin expression alone, while no samples demonstrated granzyme B expression alone. There was a close relationship between perforin/granzyme B expression and liver allograft rejection. CONCLUSION: Perforin and granzyme B expression seemed to be related to the development of acute rejection following liver transplantation, and might be served as sensitive and reliable markers in diagnosing acute rejection in early stage.

Adult↗