Biomedical subjects

J Tan

Publications and source records attributed to J Tan.

At least 127 records · Page 7Linked to original sources

PubMed1999

[A comparison of serological and high resolution DNA methods for HLA-B40 cross-reactive groups typing].

OBJECTIVE: To compare the high-resolution DNA typing method with serological method for HLA-B40 cross-reactive groups (CREG) typing in Chinese population. METHODS: A total of 199 consecutive samples were entered into the study, including 177 identified serologically as B40 CREG positive, 12 ambiguous and 10 negative controls. Double-blind typing for HLA-B40 CREG was carried out using PCR-SSP high-resolution DNA typing and serological one-step monoclonal antibody technique, respectively. RESULTS: In 3 of the samples serological typing could not be performed owing to poor cell viability, while in 1 PCR-SSP typing could not be done owing to poor DNA. Among samples that were successfully typed by both methods, all alleles of HLA-B40 CREG could be accurately distinguished by PCR-SSP. It was proved that PCR-SSP was a high-sensitivity and high-specificity technique. However, serology showed 11.2% misassignments. The overall time for serological typing was 2 hours, and for DNA typing, 5 hours. The percentages of HLA-B40 CREG alleles in Chinese population were 67.4% for B60, 20.8% for B61, 9.6% for B4801 and 2.2% for B4005. CONCLUSION: High resolution PCR-SSP typing for HLA-B40 CREG could be used in routine clinical practice with a greater precision than serology.

Cross Reactions↗

PubMed1999

[Experimental study on protective effect of Chinese herbal medicine on glucocorticoid receptor].

OBJECTIVE: To probe the relationship of glucocorticoid receptor and some Chinese medicinal herbs. METHODS: The models of Qi-Yang exhaustion and Qi-Yin exhaustion were made with hemorrhagic rats and heat-stressed rats respectively. The effect of Shenfu Decoction (SFD) and Shengmai Powder (SMP) on plasma glucocorticoid (GC) and its receptor (GcR) in hepatic cytosol of the models were measured respectively. RESULTS: The activity of GcR decreased in both models, while their blood level of GC increased markedly. SFD and SMP showed no regulating effect on blood GC, but displayed obvious up-regulation on GcR level in both models. CONCLUSION: SFD and SMP could up-regulate the activity of GcR in Qi-Yang and Qi-Yin exhaustion models.

Animals↗

PubMed1999

[Changes of transmembrane ion transport in essential hypertensives with familial histories].

OBJECTIVE: To investigate the effects of heredity on transmembrane ion transport in essential hypertension (EH). METHODS: 52 essential hypertensives were divided into two groups, 23 with positive family history (FH(+)) and 29 with negative family history (FH(-)). The rate constant of ouabain-sensitive sodium efflux ((o)K(os)) was measured as the half of the increase in erythrocyte Na(+) concentration during incubation with ouabain for 2 hours, (o)K(os) was calculated by an equation and the maximal rate (Vmax) of red cells Na(+)/H(+) exchange was determined as the Na(+) influx promoted by an outward H(+) gradient. Intracellular Na(+) concentration was measured with flame photometry and (45)Ca(2+) influx in ATP-depleted red cells with liquid scintillation counting. RESULTS: The red cell Na(+)/H(+) exchange and (45)Ca(2+) in-flux were significantly higher but the (o)K(os) lower in both the FH(+) and FH(-) groups than in the controls. FH(+) group demonstrated a significantly higher (o)K(os) and lower Ca(2+) influx as compared with those in FH(-) group. In FH(+) group, systolic blood pressure was positively correlated with age, while diastolic blood pressure positively correlated with (45)Ca(2+) influx. CONCLUSION: Our data show a genetic contribution to abnormal membrane transport in hypertension. There is a defect in membrane permeability to Ca(2+) and a greater exchangeable pool of cytosolic free Ca(2+) in FH(+) group that participate in the pathogenesis of inherited hypertension.

Aged↗

PubMed1999

[The diagnostic value of perforin and granzyme B genes mRNA expression in acute rejection after hamster to rat orthotopic liver transplantation].

OBJECTIVE: To explore the mRNA expression of perforin and granzyme B genes activated by cytotoxic T lymphocytes (CTL) for monitoring early acute rejection after liver transplantation. METHODS: The mRNA expression of perforin and granzyme B genes in grafts after gold hamster to rat liver transplantation was examined by reverse transcriptase polymerase chain reaction. Histological findings were studied comparatively, and isogenic rat liver transplantation was the control. RESULTS: The mRNA expression of perforin and granzyme B genes began to be up-regulated on the day 3 after transplantation, when no histologic evidence of rejection was found. Levels of expression significantly increased after day 4 and persisted through the whole course of rejection. In contrast, the control group showed no expression of mRNA for perforin and granzyme B. CONCLUSIONS: The determination of mRNA expression of perforin and granzyme B genes are useful to early diagnosis of acute rejection of liver transplantation.

Acute Disease↗

PubMed1999

[The effects of moderate acute normovolemic hemodilution on intestinal oxygen supply and consumption in anesthetized cats].

OBJECTIVE: To study the effects of moderate acute normovolemic hemodilution on the intestinal blood perfusion and oxygen supply in cats. METHODS: 15 domestic male cats were hemodiluted with Haemaccel. HR, MAP, lactate concentration in superior mesenteric vein (LAC), superior mesenteric artery blood flow (SMABF), superior mesenteric artery and venous blood gas analysis were recorded and the intestinal oxygen delivery (DO(2)), oxygen consumption (VO(2)) and oxygen extraction (EO(2)) were calculated before and after hemodilution. RESULTS: SMABF increased obviously (P < 0.05), intestinal DO(2) and EO(2) did not change (P > 0.05) but VO(2) increased (P < 0.05), and LAC in superior mesenteric vein did not increase. CONCLUSIONS: Moderate acute normovolemic hemodilution with Haemaccel do not alter intestinal oxygen delivery by increasing the superior mesenteric blood flow. It means that intestinal mucosa ischemia does not happen during moderate acute normovolemic hemodilution.

Animals↗

PubMed1999

[Effect of manganese on the brain extrapyramidal development of rat offspring].

The effect of manganese (Mn) exposure on the behavior and extrapyramidal system of offspring were studied. Pregnant rats and their offspring in the experimental group were exposed to manganese from drinking water containing 2 g/L (low Mn-exposed group) or 10 g/L (high Mn-exposed group) of MnCl2 respectively. The latent period for running from the center field to any arm of Elevated Plus Arm Maze of both low and high Mn-exposed group was significantly reduced. But the latent period for reaching the platform above the water in Morris Water Maze of the Mn-exposed group was not different from that of control group. There was a significant increase in the areas, glial fibrillary acid protein(GFAP) immunoreactivity and the average proportional densities of GFAP-positive elements in nucleus caudate and accumbens in the high Mn-exposed group, and a significant reduction in the tyrosine hydroxylase immunoreactivity (TH) and average proportional densities of TH-positive elements in substantia nigra, ventral tegmentum area of midbrain and nucleus caudate in the high Mn-exposed group.

Animals↗

PubMed1999

[DNA typing for HLA-A by polymerase chain reaction with sequence-specific primers].

The authors have established a method of DNA typing for HLA-A antigen in Chinese by using polymerase chain reaction with sequence-specific primers (PCR-SSP). HLA-A alleles were successfully typed in all clinical samples and 36 standard DNAs by PCR-SSP. A total of 635 A antigens were typed in 345 donor-recipients, including 55 homozygotes and 290 heterozygotes. Twenty alleles of HLA-A were accurately distinguished by DNA typing. No false positive or false negative typing results were obtained. Reproducibility was 100%. The overall time of DNA typing was 5 hours. The typing results were concordant with the results of UCLA Tissue Typing Lab. Comparative study of HLA-A typing was carried out using PCR-SSP and standard serology. The results showed that the discrepancy rate of serology was 9.0%, containing 13 individuals incorrectly interpreted by serology and 16 serological "blanks" turned out to be a definable alleles by PCR-SSP. In conclusion, DNA typing for HLA-A by PCR-SSP has proved to be a high-resolution, high-specificity, rapid and accurate technique, suitable for clinical application with a greater precision than serology.

Alleles↗

PubMed1999

Expression of ICAM-1 and LFA-1 molecules in relation to renal allograft rejection in rats.

OBJECTIVE: The purpose of this study was to assess the renal graft expression of ICAM-1 (intercellular adhesion molecule-1) and LFA-1 (lymphocyte function-associated antigen-1) molecule with relation to graft rejection. METHODS: Rat kidney transplantation was performed according to the procedure of Kamada with some modification. Experimental rats were divided into 5 groups. The survival time of recipient rats and function of grafts after renal transplantation were observed. The sections of renal graft were stained for monoclonal antibody ICAM-1 and LFA-1, and then quantification of ICAM-1 and LFA-1 expression was accomplished by computer image analysis. RESULTS: ICAM-1 and LFA-1 increased significantly in the renal allograft rejection group as compared with the non-rejection groups (P<0.05). CONCLUSION: Both biopsy of renal graft and monitoring of ICAM-1 and LFA-1 are useful tools in diagnosing and treating acute rejection.

Animals↗

PubMed1999

[Prediction the octane number of gasoline by near infrared spectra analysis].

The feasibility of predicting the octane number by the near infrared spectra analysis technique in the quantitative analysis was investigated. 12 calibration gasoline samples and 4 prediction samples were collected and their absorption spectra were measured with a high precision model Lambda 19 scanning spectrophotometer. Based on the multivariate statistic model, stagewise regression and partial least squares were selected. A model of the correlation behavior between the spectra and octane number was established and calibrated, and then the prediction of octane number is made. The prediction error is +/-1.0 octane number in the best analysis results.

Gasoline↗

PubMed1998

S-Nitroglutathione, a product of the reaction between peroxynitrite and glutathione that generates nitric oxide.

Peroxynitrite (ONOO-) has been shown in studies on vascular relaxation and guanylate cyclase activation to react with glutathione (GSH), generating an intermediate product that promotes a time-dependent production of nitric oxide (NO). In this study, reactions of ONOO- with GSH produced a new substance, which was characterized by liquid chromatography, ultraviolet spectroscopy, and electrospray tandem mass spectrometry. The mass spectrometric data provided evidence that the product of this reaction was S-nitroglutathione (GSNO2) and that S-nitrosoglutathione (GSNO) was not a detectable product of this reaction. Further evidence was obtained by comparison of the spectral and chromatographic properties with synthetic standards prepared by reaction of GSH with nitrosonium or nitronium borofluorates. Both the synthetic and ONOO-/GSH-derived GSNO2 generated a protonated ion, GSNO2H+, at m/z 353, which was unusually resistant to decomposition under collision activation, and no fragmentation was observed at collision energy of 25 eV. In contrast, an ion at m/z 337 (GSNOH+), generated from the synthetic GSNO, readily fragmented with the abundant loss of NO at 9 eV. Reactions of ONOO- with GSH resulted in the generation of NO, which was detected by the head space/NO-chemiluminescence analyzer method. The generation of NO was inhibited by the presence of glucose and/or CO2 in the buffers employed. Synthetic GSNO2 spontaneously generated NO in a manner that was not significantly altered by glucose or CO2. Thus, ONOO- reacts with GSH to form GSNO2, and GSNO2 decomposes in a manner that generates NO.

Chromatography, High Pressure Liquid↗

PubMed1998

Regulation of mammalian pyruvate dehydrogenase alpha subunit gene expression by glucose in HepG2 cells.

We report the effect of glucose on the expression of the gene encoding the pyruvate dehydrogenase (E1) alpha subunit (E1alpha) in human hepatoma (HepG2) cells. Total pyruvate dehydrogenase complex activity as well as the levels of protein and mRNA of the E1alpha subunit were significantly increased in HepG2 cells cultured in medium containing 16.7 mM glucose compared with 1.0 mM glucose for a period of 4 weeks. The level of E1alpha mRNA was elevated approx. 2-fold in HepG2 cells cultured for 24 h in medium containing 16.7 mM glucose compared with 1 mM glucose. This effect was specific to glucose and independent of insulin. Nuclear run-on assays and promoter analysis indicate that the glucose-induced increases in the levels of E1alpha mRNA in HepG2 cells are due to increased transcription of the human E1alpha (PDHA1) gene. Mutational analysis of the E1alpha promoter region has identified two regions, from -78 to -73 bp (CCCCTG) and from -8 to -3 bp (GCGGTG), that are responsible for the effect of glucose on promoter activity; the former exhibits a larger effect. These two sequences represent new variations of the carbohydrate-response element that has been identified in other genes. The stimulation of E1alpha promoter activity by glucose was abolished by okadaic acid at 100 nM but not at 5 nM, suggesting that glucose-mediated regulation of pyruvate dehydrogenase complex E1alpha gene transcription involves a phosphorylation/dephosphorylation mechanism, possibly involving protein phosphatase-1.

Chloramphenicol O-Acetyltransferase↗

PubMed1998

Interaction of amelogenin with hydroxyapatite crystals: an adherence effect through amelogenin molecular self-association.

At the secretory stage of tooth enamel formation the majority of the organic matrix is composed of amelogenin proteins that are believed to provide the scaffolding for the initial carbonated hydroxyapatite crystals to grow. The primary objective of this study was to investigate the interaction between amelogenins and growing apatite crystals. Two in vitro strategies were used: first, we examined the influence of amelogenins as compared to two other macromolecules, on the kinetics of seeded growth of apatite crystals; second, using transmission electron micrographs of the crystal powders, based on a particle size distribution study, we evaluated the effect of the macromolecules on the aggregation of growing apatite crystals. Two recombinant amelogenins (rM179, rM166), the synthetic leucine-rich amelogenin polypeptide (LRAP), poly(L-proline), and phosvitin were used. It was shown that the rM179 amelogenin had some inhibitory effect on the kinetics of calcium hydroxyapatite seeded growth. The inhibitory effect, however, was not as destructive as that of other macromolecules tested. The degree of inhibition of the macromolecules was in the order of phosvitin > LRAP > poly(L-proline) > rM179 > rM166. Analysis of particle size distribution of apatite crystal aggregates indicated that the full-length amelogenin protein (rM179) caused aggregation of the growing apatite crystals more effectively than other macromolecules. We propose that during the formation of hydroxyapatite crystal clusters, the growing apatite crystals adhere to each other through the molecular self-association of interacting amelogenin molecules. The biological implications of this adherence effect with respect to enamel biomineralization are discussed.

Amelogenin↗

PubMed1998

Alzheimer's beta-amyloid peptides induce inflammatory cascade in human vascular cells: the roles of cytokines and CD40.

Accumulating evidence suggests that beta-amyloid (Abeta)-induced inflammatory reactions may partially drive the pathogenesis of Alzheimer's disease (AD). Recent data also implicate similar inflammatory processes in cerebral amyloid angiopathy (CAA). To evaluate the roles of Abeta in the inflammatory processes in vascular tissues, we have tested the ability of Abeta to trigger inflammatory responses in cultured human vascular cells. We found that stimulation with Abeta dose-dependently increased the expression of CD40, and secretion of interferon-gamma (IFN-gamma) and interleukin-1beta (IL-1beta) in endothelial cells. Abeta also induced expression of IFN-gamma receptor (IFN-gammaR) both in endothelial and smooth muscle cells. Characterization of the Abeta-induced inflammatory responses in the vascular cells showed that the ligation of CD40 further increased cytokine production and/or the expression of IFN-gammaR. Moreover, IL-1beta and IFN-gamma synergistically increased the Abeta-induced expression of CD40 and IFN-gammaR. We have recently found that Abeta induces expression of adhesion molecules, and that cytokine production and interaction of CD40-CD40 ligand (CD40L) further increase the Abeta-induced expression of adhesion molecules in these same cells. These results suggest that Abeta can function as an inflammatory stimulator to activate vascular cells and induces an auto-amplified inflammatory molecular cascade, through interactions among adhesion molecules, CD40-CD40L and cytokines. Additionally, Abeta1-42, the more pathologic form of Abeta, induces much stronger effects in endothelial cells than in smooth muscle cells, while the reverse is true for Abeta1-40. Collectively, these findings support the hypothesis that the Abeta-induced inflammatory responses in vascular cells may play a significant role in the pathogenesis of CAA and AD.

Alzheimer Disease↗

PubMed1998

LIGHT, a novel ligand for lymphotoxin beta receptor and TR2/HVEM induces apoptosis and suppresses in vivo tumor formation via gene transfer.

LIGHT is a new member of tumor necrosis factor (TNF) cytokine family derived from an activated T cell cDNA library. LIGHT mRNA is highly expressed in splenocytes, activated PBL, CD8(+) tumor infiltrating lymphocytes, granulocytes, and monocytes but not in the thymus and the tumor cells examined. Introduction of LIGHT cDNA into MDA-MB-231 human breast carcinoma caused complete tumor suppression in vivo. Histological examination showed marked neutrophil infiltration and necrosis in LIGHT expressing but not in the parental or the Neo-transfected MDA-MB-231 tumors. Interferon gamma (IFNgamma) dramatically enhances LIGHT-mediated apoptosis. LIGHT protein triggers apoptosis of various tumor cells expressing both lymphotoxin beta receptor (LTbetaR) and TR2/HVEM receptors, and its cytotoxicity can be blocked specifically by addition of a LTbetaR-Fc or a TR2/HVEM-Fc fusion protein. However, LIGHT was not cytolytic to the tumor cells that express only the LTbetaR or the TR2/HVEM or hematopoietic cells examined that express only the TR2/HVEM, such as PBL, Jurkat cells, or CD8(+) TIL cells. In contrast, treatment of the activated PBL with LIGHT resulted in release of IFNgamma. Our data suggest that LIGHT triggers distinct biological responses based on the expression patterns of its receptors on the target cells. Thus, LIGHT may play a role in the immune modulation and have a potential value in cancer therapy.

Apoptosis↗

PubMed1998

Broadened clinical utility of gene gun-mediated, granulocyte-macrophage colony-stimulating factor cDNA-based tumor cell vaccines as demonstrated with a mouse myeloma model.

Effective immunization against the murine B16 melanoma by a nonviral approach in which a gene gun is used to transfer GM-CSF cDNA into tumor cells has been described. We have extended this nonviral approach by using the poorly immunogenic murine myeloma MPC11 model. Vaccination with the transfected, GM-CSF-expressing MPC11 cells induced a potent antitumor cytotoxic T lymphocyte response associated with tumor rejection in the majority of the test mice. Furthermore, nearly 100% (27 of 28) of the tumor-free mice were able to reject a tumor rechallenge. While this approach is clinically attractive because of minimal tissue manipulation/culturing and the absence of infectious agents, a number of tested human primary tumors, including myeloma cells, have failed to produce high levels of GM-CSF after gene gun transfection. To circumvent the low transfection efficiency in certain human tumor cells, we showed that combining irradiated tumor cells to provide tumor antigens together with gene gun-transfected fibroblasts to provide GM-CSF induced effective tumor rejection. We also report that normal human skin fibroblasts transfected by the gene gun produce high levels of human GM-CSF (250 ng/10(6) cells/24 hr). These results suggest that combining irradiated tumor cells with gene gun-transfected fibroblasts results in antitumor immune responses and may allow for a wider application of this approach to cancer immunotherapy.

3T3 Cells↗

PubMed1998

High incidence of gastropharyngeal and gastroesophageal reflux after total laryngectomy.

BACKGROUND: Gastroesophageal reflux (GER) appears to be related to laryngeal carcinoma. Little is known about GER and gastropharyngeal reflux (GPR) in the laryngectomized patient. Therefore, GER and GPR were studied in laryngectomized patients. METHODS: In 11 patients, 24-hour double-probe pH monitoring was performed in an ambulant setting. An optic fiberscope was used for the accurate positioning of the proximal probe in the upper esophageal sphincter. RESULTS: In 9 of 11 patients pathologic GPR was found. Four of these 9 patients had reflux in upright and supine position, 5 patients had reflux only in upright position. CONCLUSIONS: A high incidence of GPR in laryngectomized patients was found. These results raise the question whether all laryngectomized patients should be investigated for reflux and in the presence of pathologic reflux findings should be treated with reflux prophylaxis.

Aged↗

PubMed1998

Biocompatibility of poly(etherurethane urea) containing dehydroepiandrosterone.

Poly(etherurethane urea) (PEUU) elastomers, with their broad range of mechanical properties and high biocompatibility, are used clinically for medical applications. However, the possibility exists for the ether soft segment of PEUU to degrade in long-term uses. To retard degradation, antioxidants that scavenge reactive oxygen intermediates are added. In this study, we incorporated dehydroepiandrosterone (DHEA), which functions by the alternate mechanism of modulating or down-regulating adherent macrophage activity, to retard the biodegradation of PEUUs. Biocompatibility of PEUU samples containing 1% DHEA, 5% DHEA, and 5% vitamin E (alpha-tocopherol) by weight were studied in vivo and in vitro. The biocompatibility was initially evaluated by examination of the inflammatory cellular exudate. Compared to PEUU without additives and PEUU with 5% vitamin E, the addition of 5% DHEA to PEUU caused a decrease in the total leukocyte exudate concentration at 4 days. The addition of 5% DHEA also caused lower macrophage adhesion and FBGC formation compared to the other materials at 7 days. Despite these short-term effects, the biocompatibility at later time points (14, 21, and 70 days) was similar for all materials. Transmission infrared analysis of the materials revealed that more than 70% of the DHEA had leached out of the samples by 3 days implantation. Furthermore, through attenuated total reflectance Fourier transform analysis and scanning electron microscopy, it was determined that unlike vitamin E, DHEA did not enhance long-term PEUU biostability. The effect of DHEA on inflammatory cell activity appeared to be dose dependent, with improved biocompatibility in vivo for higher loading levels of DHEA, but the overall effect was limited owing to the rapid diffusion of the water-soluble DHEA from the PEUU.

Animals↗

PubMed1998

Lack of effect of oral choline supplement on the concentrations of choline metabolites in human brain.

Recent reports suggest that oral choline supplement may alter the cerebral choline/creatine (Cho/Cr) ratio and might be used to treat neurodegenerative disorders of cholinergic transmission. Using both 1H and 31P MRS, we reexamined the Cho/Cr ratio and quantified cerebral choline and its major constituents: phosphoethanolamine (PE), phosphorylcholine (PC), glycerophosphorylethanolamine (GPE), and glycerophosphorylcholine (GPC). In the four brain locations examined, no significant increases in Cho/Cr, [Cho], or in its major constituents were found in response to an oral challenge of 50 mg/kg of choline bitartrate. Oral choline did not significantly affect human cerebral metabolism in the short term.

Administration, Oral↗