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Biomedical subjects

G Cheng

Publications and source records attributed to G Cheng.

At least 55 records · Page 3Linked to original sources
PubMed2001

CD40 is a cellular receptor mediating mycobacterial heat shock protein 70 stimulation of CC-chemokines.

The 70 kDa mycobacterial heat shock protein (Mtb HSP70) stimulates mononuclear cells to release CC-chemokines. We now show that this function of Mtb HSP70, but not human HSP70, is dependent on the cell surface expression of CD40. Deletion of the CD40 cytoplasmic tail abolished, and CD40 antibody inhibited, Mtb HSP70 stimulation of CC-chemokine release. Mtb HSP70 stimulated THP1, KG1 cells, and monocyte-derived dendritic cells to produce RANTES. Specific binding of CD40-transfected HEK 293 cells to Mtb HSP70 was demonstrated by surface plasmon resonance. Coimmunoprecipitation of Mtb HSP70 with CD40 indicates a physical association between these molecules. The results suggest that CD40 is critical in microbial HSP70 binding and stimulation of RANTES production.

Bacterial Proteins↗
PubMed2001

A Schiff base is a major DNA adduct of crotonaldehyde.

Previous studies have demonstrated that the reaction of crotonaldehyde with DNA produces Michael addition products, and these have been detected in human tissues as well as tissues of untreated laboratory animals. A second class of crotonaldehyde-DNA adducts releases 2-(2-hydroxypropyl)-4-hydroxy-6-methyl-1,3-dioxane (paraldol, 12) upon hydrolysis, and these adducts are quantitatively more significant than the Michael addition adducts in vitro. In this study, we demonstrate that the major source of the paraldol-releasing DNA adducts of crotonaldehyde is a Schiff base. Reaction of crotonaldehyde with DNA, followed by treatment with NaBH(3)CN and enzyme hydrolysis, resulted in the formation of N(2)-(3-hydroxybutyl)dG (10), identified by its UV, MS, and proton NMR. Reactions of crotonaldehyde or paraldol with dG demonstrated that the Schiff base precursor to N(2)-(3-hydroxybutyl)dG is N(2)-(3-hydroxybutylidene)dG (7), identified by UV, LC-APCI-MS, and MS/MS. Four isomers of N(2)-(3-hydroxybutylidene)dG were observed. The (R)- and (S)-isomers were identified by reactions of chiral paraldol with dG; each existed as a pair of interconverting (E)- and (Z)-isomers. These data indicate that the structure of the major Schiff base DNA adduct in crotonaldehyde-treated DNA is N(2)-(3-hydroxybutylidene)dG (7). This adduct is unstable at the nucleoside level and accounts for more than 90% of the paraldol released from crotonaldehyde-treated DNA. However, the adduct is stable in DNA and therefore is a likely companion to the Michael addition adducts in human DNA.

Aldehydes↗
PubMed2001

Reactions of 2,6-dimethyl-1,3-dioxane-4-ol (aldoxane) with deoxyguanosine and DNA.

In a recent study, we identified several new DNA adducts of the carcinogen acetaldehyde, including N(2)-(2,6-dimethyl-1,3-dioxan-4-yl)deoxyguanosine (N(2)-aldoxane-dG, 2). Our goal in this study was to investigate further the formation of 2 by allowing 2,6-dimethyl-1,3-dioxane-4-ol (aldoxane, 5) to react with dG and DNA. Aldoxane is readily formed by trimerization of acetaldehyde. The reaction of aldoxane with dG and DNA produced diastereomers of N(2)-aldoxane-dG (2) as observed in the reactions of acetaldehyde with dG and DNA, supporting the intermediacy of aldoxane in their formation. Unexpectedly, however, an array of other adducts was formed in these reactions, including 3-(2-deoxyribos-1-yl)-5,6,7,8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)one (3), 2-amino-7,8-dihydro-8-hydroxy-6-methyl-3H-pyrrolo[2,1-f]purine-4(6H)one (13), N(2)-(3-hydroxybutylidene)dG (9), N(2)-[(2-hydroxypropyl)-6-methyl-1,3-dioxane-4-yl]dG (14), and N(2)-ethylidene-dG (1). Adduct 1 was the major product and was found to be quite stable in DNA. The adducts result from a cascade of aldehydes, e.g., 2-butenal (crotonaldehyde, 12), 3-hydroxybutanal (7) and its dimer (2-hydroxypropyl)-6-methyl-1,3-dioxane-4-ol (paraldol, 6), and acetaldehyde, produced from aldoxane under the reaction conditions. The reactions of aldoxane with dG and DNA were compared with those of paraldol. The paraldol reactions gave products resulting from reactions of dG and DNA with paraldol, 3-hydroxybutanal, and crotonaldehyde (adducts 3, 13, and 9) but the products of the aldoxane and acetaldehyde reactions (adducts 1 and 2) were not observed, indicating that paraldol is more stable under the reaction conditions than is aldoxane. The results of this study provide new insights about the formation of DNA adducts from aldehydes via condensation products of the latter.

Acetaldehyde↗
PubMed2001

Reactions of alpha-acetoxy-N-nitrosopyrrolidine with deoxyguanosine and DNA.

We investigated the reactions of alpha-acetoxy-N-nitrosopyrrolidine (alpha-acetoxyNPYR) with dGuo and DNA. Alpha-acetoxyNPYR is a stable precursor to the major proximate carcinogen of NPYR, alpha-hydroxyNPYR (3). Our goal was to develop appropriate conditions for the analysis of DNA adducts of NPYR formed in vivo. Products of the alpha-acetoxyNPYR-dGuo reactions were analyzed directly by HPLC or after treatment of the reaction mixtures with NaBH3CN. Products of the alpha-acetoxyNPYR-DNA reactions were released by enzymatic or neutral thermal hydrolysis of the DNA, then analyzed by HPLC. Alternatively, the DNA was treated with NaBH3CN prior to hydrolysis and HPLC analysis. The reactions of alpha-acetoxyNPYR with dGuo and DNA were complex. We have identified 13 products of the dGuo reaction-6 of these were characterized in this reaction for the first time. They were four diastereomers of N2-(3-hydroxybutylidene)dGuo (20, 21), 7-(N-nitrosopyrrolidin-2-yl)Gua (2), and 2-(2-hydroxypyrrolidin-1-yl)deoxyinosine (12). Adducts 20 and 21 were identified by comparison to standards produced in the reaction of 3-hydroxybutanal with dGuo. Adduct 2 was identified by its spectral properties while adduct 12 was characterized by comparison to an independently synthesized standard. With the exception of adduct 2, all products of the dGuo reactions were also observed in the DNA reactions. The major product in both the dGuo and DNA reactions was N2-(tetrahydrofuran-2-yl)dGuo (10), consistent with previous studies. Several other previously identified adducts were also observed in this study. HPLC analysis of reaction mixtures treated with NaBH3CN provided improved conditions for adduct identification, which should be useful for in vivo studies of DNA adduct formation by NPYR.

Carcinogens↗
PubMed2001

Human T-cell leukemia virus type I tax protein induces the expression of anti-apoptotic gene Bcl-xL in human T-cells through nuclear factor-kappaB and c-AMP responsive element binding protein pathways.

Human T-cell leukemia virus type I (HTLV-I) is the etiologic agent of adult T-cell leukemia (ATL), which is an aggressive form of human T-cell malignancy. The viral protein, Tax, immortalizes human T-cells and inhibits various types of apoptosis, and is thought to play crucial roles in the development of ATL. We have recently demonstrated that Tax induces the constitutive expression of the anti-apoptotic protein, Bcl-xL, in a mouse T-cell line. The mouse, however, is not a natural host of HTLV-I, and HTLV-I does not induce this malignancy in mice. We thus examined whether Tax also activates the expression of Bcl-xL in human T-cells. Expression of Tax in a human T-cell line, Jurkat, induced the expression of the Bcl-xL gene, but did not significantly affect the expression of the other apoptosis-related genes, Bcl-2 and Bax. Transient transfection assays showed that Tax stimulated human Bcl-xL promoter activity in Jurkat cells. Deletion of the two potential nuclear factor (NF)-kappaB binding sites in the human Bcl-xL promoter significantly decreased Tax-induced transactivation. In addition to NF-kappaB, Tax activates transcription through the c-AMP responsive element binding protein (CREB). Tax mutants segregating these two pathways showed that both the NF-kappaB and CREB pathways of Tax are required for maximum activation of a human Bcl-xL promoter, nevertheless, NF-kappaB alone was sufficient for that of a mouse Bcl-xL promoter. Northern blot analysis showed that all the human T-cell lines expressing Tax had higher levels of Bcl-xL mRNA than HTLV-I-uninfected ones. Furthermore, the sample from one patient with ATL expressed higher levels of Bcl-xL mRNA compared with levels from uninfected peripheral blood mononuclear cells. Our results suggest that Tax induces the expression of Bc-xL through the NF-kappaB and CREB pathways in HTLV-I-infected human T-cells, and then inhibits apoptosis, and such inhibition is necessary for the infected cells to advance to the leukemia in vivo.

Apoptosis↗
PubMed2001

Compositional and functional changes of pulmonary surfactant in a guinea-pig model of chronic asthma.

Recent studies have found that severe surfactant dysfunction occurs during an asthma attack, but the changes in surfactant in a guinea-pig model of chronic asthma have not been studied. We therefore analysed the surfactant recovered from guinea-pigs after repeated inhalation of ovalbumin to see if the surfactant recovered from chronic asthmatic lungs would be intrinsically altered. Guinea pigs immunized through repeated inhalation of aerosolized ovalbumin (OA) were exposed to the antigen once a week for a month. Twenty-four hours after the last challenge the alveolar wash was recovered. We calculated saturated phosphatidylcholine (Sat-PC) and total protein (TP) pool sizes in alveolar spaces. Surfactant subtype conversion of large aggregate surfactant (LA) to small aggregate surfactant was studied in vitro by means of the surface area cycling technique. The phospholipid composition of LA was analysed by thin layer chromatography and the surface activity of LA was also determined. We found decreased surfactant pool sizes, decreased ratio of Sat-PC to TP in alveolar lavages in asthma groups, and surface activity of the surfactant recovered from asthmatic lungs to be inferior to that of the controls. Accelerated surfactant subtype conversion in vitro was also noted in the lungs of asthmatic animal models. In addition, the changes in phospholipid compositions which were similar to the pattern of acute lung injury suggested that alveolar inflammation might be involved in the pathogenesis of chronic asthma. These results indicate that surfactant is intrinsically abnormal in chronically asthmatic lungs.

Analysis of Variance↗
PubMed2001

Successful engraftment in two adult patients with severe aplastic anemia using nonmyeloablative conditioning followed by unrelated HLA-mismatched cord blood transplantation.

Umbilical cord blood as an alternative source of hematopoietic stem cells and nonmyeloablative conditioning are very exciting new developments in transplantation. We report here mixed chimerism in two adult patients with severe aplastic anaemia using nonmyeloablative conditioning and two-antigen mismatched cord blood transplantation resulting in satisfactory clinical response. Our results suggest that such transplant is possible with minimal toxicity.

Adolescent↗
PubMed2001

Nonaspiration puncture biopsy for suspected thoracic cavum tumor: experience of 2,010 clinical cases.

In our hospital from October 1980 to February 2000, 2,010 patients with suspected thoracic cavum cancer were diagnosed by nonaspiration puncture with multiple-hole type and surface trough-type biopsy needles. The positive rate of cytology or pathology examination for lesions in pleura, mediastinum, and lung tissue were 88.6% (148/167), 83% (297/358), and 80.2% (1,191/1,485), respectively. The mean positive rate in all cases was 81.4% (1,636/2,010). Complications rates for pneumothorax or hemoptysis were 1.3% and 0.8%, respectively, in this group. Such revised puncture needles have been used by us in various organs, such as brain tumors, metastatic lymph nodes of head and neck cancers, malignant disease of breast, liver, kidney, prostate, rectum and bone, etc. The use of such nonaspiration puncture needles is very simple, safe, and effective; even for beginners with this technique, the rate of successful diagnoses is fairly high.

Biopsy, Needle↗
PubMed2001

Enflurane actions on spinal cords from mice that lack the beta3 subunit of the GABA(A) receptor.

BACKGROUND: Gamma-aminobutyric acid type A (GABA(A)) receptors are considered important in mediating anesthetic actions. Mice lacking the beta3 subunit of this receptor (beta3-/-) have a higher enflurane minimum alveolar concentration (MAC) than wild types (+/+). MAC is predominantly determined in spinal cord. METHODS: The authors measured three population-evoked responses in whole spinal cords, namely, the excitatory postsynaptic potential (pEPSP), the slow ventral root potential (sVRP), and the dorsal root potential. Synaptic and glutamate-evoked currents from motor neurons in spinal cord slices were also measured. RESULTS: Sensitivity of evoked responses to enflurane did not differ between +/+ and -/- cords. The GABA(A) receptor antagonist bicuculline significantly (P < 0.05) attenuated the depressant effects of enflurane on pEPSP, sVRP and glutamate-evoked currents in +/+ but not -/- cords. The glycine antagonist strychnine elevated the pEPSP to a significantly greater extent in -/- than in +/+ cords, but the interactions between strychnine and enflurane did not differ between -/- and +/+ cords. CONCLUSIONS: Similar enflurane sensitivity in spinal cords from -/- and +/+ mice was coupled with a decreased role for GABA(A) receptors in mediating the actions of enflurane in the former. This finding implies that other anesthetic targets substitute for GABA(A) receptors. Increase in glycine receptor-mediated inhibition was found in -/- cords, but the glycine receptor does not appear to be a substitute anesthetic target. This mutation thus led to a quantitative change in the molecular basis for anesthetic depression of spinal neurotransmission in a fashion not predicted by the mutation itself. The results argue against an immutable dominant role for GABA(A) receptors in mediating spinal contributions to MAC.

Anesthetics, Inhalation↗
PubMed2001

AlaArg motif in the carboxyl terminus of the gamma(1)34.5 protein of herpes simplex virus type 1 is required for the formation of a high-molecular-weight complex that dephosphorylates eIF-2alpha.

The gamma(1)34.5 protein of herpes simplex virus (HSV) type 1 functions to prevent the shutoff of protein synthesis mediated by the double-stranded-RNA-dependent protein kinase PKR. This is because gamma(1)34.5 associates with protein phosphatase 1 (PP1) through its carboxyl terminus, forming a high-molecular-weight complex that dephosphorylates the alpha subunit of translation initiation factor eIF-2 (eIF-2alpha). Here we show that Val193Glu and Phe195Leu substitutions in the PP1 signature motif of the gamma(1)34.5 protein abolished its ability to redirect PP1 to dephosphorylate eIF-2alpha and replication of mutant viruses was severely impaired. The gamma(1)34.5 protein, when expressed in Sf9 cells using a recombinant baculovirus, was capable of directing specific eIF-2alpha dephosphorylation. Deletions of amino acids 258 to 263 had no effect on activity of gamma(1)34.5. However, deletions of amino acids 238 to 258 abolished eIF-2alpha phosphatase activity but not PP1 binding activity. Interestingly, deletions in the AlaArg motif of the carboxyl terminus disrupted the high-molecular-weight complex that is required for dephosphorylation of eIF-2alpha. These results demonstrate that gamma(1)34.5 is functionally active in the absence of any other HSV proteins. In addition to a PP1 binding domain, the carboxyl terminus of gamma(1)34.5 contains an effector domain that is required to form a functional complex.

Alanine↗
PubMed2001

MEKK1 is essential for DT40 cell apoptosis in response to microtubule disruption.

Vinblastine and other microtubule-damaging agents, such as nocodazole and paclitaxel, cause cell cycle arrest at the G2/M transition and promote apoptosis in eukaryotic cells. The roles of these drugs in disrupting microtubule dynamics and causing cell cycle arrest are well characterized. However, the mechanisms by which these agents promote apoptosis are poorly understood. We disrupted the MEKK1 kinase domain in chicken bursal B-cell line DT40 by homologous recombination and have shown that it is essential for both vinblastine-mediated apoptosis and vinblastine-mediated c-Jun N-terminal protein kinase activation. In addition, our data indicate that vinblastine-mediated apoptosis in DT40 cells requires new protein synthesis but does not require G2/M arrest, suggesting that vinblastine-mediated cell cycle arrest and apoptosis are two independent processes.

Animals↗
PubMed2001

A549 cells can express interleukin-16 and stimulate eosinophil chemotaxis.

Alveolar epithelial cells produce many types of chemokines such as regulated on activation, normal T cells expressed and secreted (RANTES), eotaxin induced by interleukin (IL)-1 beta, or tumor necrosis factor (TNF)-alpha and may contribute to allergic disease by recruiting eosinophils. However, identification of the eosinophil chemotacic activity (ECA) release from A549 cells, an alveolar type II cell line, has not yet been completed. Recently, IL-16 was also reported to be a potent chemotactic stimulus for CD4(+) T lymphocytes and eosinophils in asthma and other pulmonary diseases. To test the possibility that alveolar epithelial cells produce IL-16, we analyzed RNA and culture supernatant from A549 cells by reverse transcription/ polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The release of ECA from A549 cells was assessed using a blind-well chemotactic chamber. IL-16 release was increased in a concentration-dependent manner by stimulation with IL-1 beta or TNF-alpha. A549 cells also expressed IL-16 messenger RNA. The combination of IL-4 and IL-1 beta or TNF-alpha had an additive effect on IL-16 production. The release of ECA was induced by IL-1 beta or TNF-alpha in a dose-dependent manner. The combination of these cytokines had a greater effect than one alone. The blockade of eotaxin and IL-16 caused 70% inhibition of ECA, but anti-RANTES antibodies only caused 30% inhibition and anti-IL-8 antibodies failed to affect inhibition. These findings suggest a role for chemokines released by alveolar epithelial cells in the recruitment of eosinophils into the lung in pulmonary disorders such as asthma and interstitial lung diseases, and suggested that eotaxin and IL-16 are potent and effective eosinophil chemoattractants.

Base Sequence↗
PubMed2001

Suppressive effect of tranilast on interleukin-5 prolonged eosinophils survival via apoptosis.

Tranilast has long been used clinically to treat allergic diseases such as bronchial asthma. To further clarify the antiinflammatory machanism, we examined the ability of tranilast to counteract the prolongation of eosinophil survival induced by interleukin (IL)-5. Tranilast reduced the IL-5 prolonged survival of eosinophils at the concentration range of 30 microg/ml to 100 microg/ml. The DNA extracted from eosinophils cultured with tranilast showed signs of fragmentation that was comparable with apoptosis. Electron-microscopic analysis of activated eosinophils cultured with 100 microg/ml of tranilast also revealed morphologic features of apoptosis. These data suggest that tranilast may act in vivo on activated eosinophils to reduce inflammation in allergic diseases.

Anti-Allergic Agents↗
PubMed2001

[Using fluorescence PCR analysis for early diagnosis and carriers detection of Chinese Wilson's disease].

OBJECTIVE: To diagnose the pre-symptomatic cases of Chinese Wilson's disease(WD) and detect the potential carriers by using fluorescence PCR technique. METHODS: Screening the high frequency spot Arg778Leu of WD gene mutation in 66 Chinese WD patients, 55 healthy family members and 30 controls, and selecting 3 random samples (2 from WD patients, 1 from controls) for DNA sequencing to testify the accuracy of fluorescence PCR. RESULTS: Among 66 Chinese WD cases, 5 were found homozygous for mutation of Arg778Leu and 21 were compound heterozygous; the gene mutation rate was totally 39.4%. Out of 55 healthy family members, 12 were found heterozygous, and it was confirmed that 11 of these 12 individuals were WD gene carriers but not pre-symptomatic patients. The results of direct DNA sequencing consisted with those results detected by fluorescence PCR. CONCLUSION: The Arg778Leu mutation in exon 8 is the high frequency spot of Chinese Wilson's disease gene. Fluorescence PCR analysis is a rapid, accurate gene diagnostic method and demonstrates a high detecting rate.

Adolescent↗
PubMed2001

Provision of phenotype-matched blood units: no need for pre-transfusion antibody screening.

BACKGROUND AND OBJECTIVES: The Hong Kong government is planning to introduce an electronic smart identity card for all seven million citizens in 2003. If the smart card contains the full red cell phenotype/genotype of the individual, it may be possible to transfuse phenotype-matched blood units without pre-transfusion antibody screening. We conducted a feasibility study. DESIGN AND METHODS: Red cell phenotype was determined for 407 donor blood units and 493 patients for whom an antibody screen had been ordered. The computer program selected phenotype-matched blood from the donor stock for the patients according to actual transfusion request. For patients with a positive antibody screen, full crossmatching was carried out with the computer-selected phenotype units. The frequencies of the various red cell phenotypes in the population were calculated from Red Cross data of antigen frequencies. The probabilities of finding at least one unit of phenotype-matched blood from a 300-unit hospital stock and a 4,000-unit Red Cross stock were determined for each phenotype. Cost analysis was performed. RESULTS: Ninety-two out of 493 patients received a total of 395 blood units. The required number of phenotype-matched blood units could be found for 92 patients using a 300-unit pool and for all patients using a 4,000-unit pool. We calculated that phenotype-matched blood could be provided for more than 98% of patients without antibody screening. The total cost of the project is US$ 98 million with potential savings of US$ 14 million per year. INTERPRETATION AND CONCLUSIONS: It is feasible and cost-effective to transfuse patients with phenotype-matched blood without antibody screening using a smart card system.

Blood Group Antigens↗
PubMed2001

Investigation of infection risk and the value of urine endotoxin during extracorporeal shock wave lithotripsy.

OBJECTIVE: To clarify the infection risks and the value of endotoxin determination in urine during extracorporeal shock wave lithotripsy (ESWL). METHODS: According to the distribution and complications of upper urinary calculi, 164 patients were divided into five groups. Group A consisted of 48 patients with 1 to 4 renal calculi, which were or less than 2 cm in diameter. Group B was composed of 24 patients with renal calculus larger than 2 cm in diameter or one to multiple renal calculi. Group C was composed of 22 patients with 1 to 3 renal calculi accompanied by 1 to 2 ureteric calculi. Group D consisted of 51 patients with 1 to 3 ureteric calculi that were 0.5 to 1.2 cm in diameter, respectively. Group E included 19 patients with complicated renal calculus, such as casting and staghorn renal calculus. Urine and blood samples of these patients were obtained before and after ESWL, respectively. Their urine samples were proven sterile prior to treatment. All samples were cultured for bacteria and investigated for endotoxin concentration by the limulus lysate test. RESULTS: No significant difference in serum endotoxin was noted before and after ESWL. Blood bacterial cultures were all negative in all patients after ESWL, similar to those before ESWL. Significant increases in urine endotoxin after ESWL compared with that before ESWL in patients of Groups B, C and E were observed, respectively (P < 0.05). There was no significant difference in urine endotoxin after ESWL compared with that before ESWL in patients of Groups A and D. The positive incidences of urine bacterial culture were significantly increased (P < 0.05) in Groups B and C and very significantly increased (P < 0.01) in Group E compared with those in Groups A and D. CONCLUSIONS: Urinary infection risk following ESWL was lower in patients with one to several renal calculi, which were less than 2 cm in diameter and did not interfere obviously with the urine flow or in patients with 1 to 3 ureteric calculi that were 0.5 to 1.2 cm in diameter. The risk was higher in those with complicated calculi, such as casting, staghorn renal calculus, renal calculus larger than 2 cm in diameter or renal calculi accompanied by ureteric calculi. For patients with higher infection risk after ESWL, prophylactic antibiotics are necessary even if bacteriuria is not present before ESWL. Endotoxin determination in urine is a reliable, sensitive and simple method for the diagnosis of bacterial infection in patients undergoing ESWL.

Adolescent↗