Biomedical subjects

D Tang

Publications and source records attributed to D Tang.

At least 55 records · Page 3Linked to original sources

PubMed2000

Sociocultural contexts of anthropophobia: a sample of Chinese youth.

BACKGROUND: Anthropophobia, a subtype of social phobia, is prevalent in Chinese and Japanese societies. This study investigated sociocultural influences on the course of this culturally specific mental disorder. METHOD: One hundred and fifty subjects, including 50 anthropophobic, 50 neurasthenic, and 50 community subjects, were interviewed in Beijing, China for the assessment of their early life experiences (child-parent relationships and sexual experiences), collectivism disposition, sexual attitudes, and communication behaviors. Logistic and linear regression analyses were performed to examine significant predictors of the occurrence and the symptom level of anthropophobia. RESULTS: Regression models explained 69% of variance in the diagnosis and 57% of variance in the symptom level of anthropophobia among anthropophobic and community subjects. They also explained 48% and 47% of variance respectively in the diagnosis and the level of symptoms among anthropophobic and neurasthenic subjects. Anthropophobic subjects had more problematic relationships with parents than did community and neurasthenic subjects. They also exhibited significantly stronger characteristics of collectivism than did community subjects. Sexual contact with a non-family member prior to age 19 and a feeling of discomfort when interacting with the opposite sex were significantly associated with the diagnosis and symptom level of anthropophobia. CONCLUSIONS: It was concluded that anthropophobic subjects' early sexual experiences and need for parental approval shaped their conformity to social norms and negative sexual attitudes, which were reinforced by the collective-orientated cultural environment, and contributed to the development of anthropophobia.

Adult↗

PubMed2000

Mutational analyses of restriction endonuclease-HindIII mutant E86K with higher activity and altered specificity.

We have performed mutational analyses of restriction endonuclease HindIII in order to identify the amino acid residues responsible for enzyme activity. Four of the seven HindIII mutants, which had His-tag sequences at the N-termini, were expressed in Escherichia coli, and purified to homogeneity. The His-tag sequence did not affect enzyme activity, whereas it hindered binding of the DNA probe in gel retardation assays. A mutant E86K in which Lys was substituted for Glu at residue 86 exhibited high endonuclease activity. Gel retardation assays showed high affinity of this mutant to the DNA probe. Surprisingly, in the presence of a transition metal, Mo(2+) or Mn(2+), the E86K mutant cleaved substrate DNA at a site other than HindIII. Substitution of Glu for Val at residue 106 (V106E), and Asn for Lys at residue 125 (K125N) resulted in a decrease in both endonucleolytic and DNA binding activities of the enzyme. Furthermore, substitution of Leu for Asp at residue 108 (D108L) abolished both HindIII endonuclease and DNA binding activities. CD spectra of the wild type and the two mutants, E86K and D108L, were similar to each other, suggesting that there was little change in conformation as a result of the mutations. These results account for the notion that Asp108 could be directly involved in HindIII catalytic function, and that the substitution at residue 86 may bring about new interactions between DNA and cations.

Aspartic Acid↗

PubMed2000

Evaluation of sound propagation models used in bottom volume scattering studies

The proper evaluation of sound propagation between sources/receivers and scatterers is important in characterizing bottom volume scattering. In this article, several sound propagation models used in bottom volume scattering studies are evaluated and their results compared to the exact solution obtained through a numerical wave number integration technique. It is found that Hines' approach [J. Acoust. Soc. Am. 88, 324-334 (1990)] works well for the two isovelocity half-space case except when the grazing angle is close to the critical angle. The far-field approximation, given by Ivakin [Sov. Phys. Acoust. 32(6), 492-496 (1986)] and Mourad and Jackson [J. Acoust. Soc. Am. 94, 344-358 (1993)], has a performance depending upon the sound speed structure in the sediment. For an isovelocity slow bottom, it agrees well with the exact solution. However, discrepancies arise for an isovelocity fast bottom or a bottom with a complex sound speed structure. In addition, the appropriateness of using the equivalent surface scattering strength as a function of grazing angle in volume scattering characterizations is studied. In conclusion, precautions need to be taken in modeling both the propagation effects and the scattering mechanisms associated with the bottom volume scattering process.

Journal Article↗

PubMed2000

Three-dimensional density spectra of sandy sediments

Power spectra of density variability for sandy sediments offshore Panama City, Florida, are estimated and modeled using digital x-ray computed tomography images of sediment structure. Spectral analysis reveals that while shell pieces and mud mixtures are the main contributors to density variability at large scales, intrinsic density variability associated with sand grain contacts dominates at small scales. The power spectrum of sandy sediments is modeled by an analytic form that consists of two power-law components, one associated with the shell and mud contributions and the other with the intrinsic density variability of sand. The dominant term has a much higher power-law exponent than previously reported. Implications for the scattering of high-frequency sound in sandy sediments are discussed.

Journal Article↗

PubMed2000

Mutation detection in the human HSP7OB' gene by denaturing high-performance liquid chromatography.

Variances, particularly single nucleotide polymorphisms (SNP), in the genomic sequence of individuals are the primary key to understanding gene function as it relates to differences in the susceptibility to disease, environmental influences, and therapy. In this report, the HSP70B' gene is the target sequence for mutation detection in biopsy samples from human prostate cancer patients undergoing combined hyperthermia and radiation therapy at the Dana-Farber Cancer Institute, using temperature-modulated heteroduplex analysis (TMHA). The underlying principles of TMHA for mutation detection using DHPLC technology are discussed. The procedures involved in amplicon design for mutation analysis by DHPLC are detailed. The melting behavior of the complete coding sequence of the target gene is characterized using WAVEMAKER software. Four overlapping amplicons, which span the complete coding region of the HSP70B' gene, amenable to mutation detection by DHPLC were identified based on the software-predicted melting profile of the target sequence. TMHA was performed on PCR products of individual amplicons of the HSP70B' gene on the WAVE Nucleic Acid Fragment Analysis System. The criteria for mutation calling by comparing wild-type and mutant chromatographic patterns are discussed.

Chromatography, High Pressure Liquid↗

PubMed2000

The relationship between genetic damage from polycyclic aromatic hydrocarbons in breast tissue and breast cancer.

A number of polycyclic aromatic hydrocarbons (PAH) are widespread environmental contaminants that cause mammary cancer experimentally. We investigated whether exposure and susceptibility to PAH, as measured by PAH-DNA adducts in breast tissue, are associated with human breast cancer. We carried out a hospital-based case-control study using immunohistochemical methods to analyze PAH-DNA adducts in tumor and nontumor breast tissue from cases and benign breast tissue from controls. The subjects were white, African-American and Latina women without prior cancer or treatment, including 119 women with breast cancer and 108 with benign breast disease without atypia. PAH-DNA adducts measured in breast tumor tissue of 100 cases and in normal tissue from 105 controls were significantly associated with breast cancer (OR=4.43, 96% CI 1.09-18.01) after controlling for known breast cancer risk factors and current active and passive smoking, and dietary PAH. There was substantial interindividual (17-fold) variability in adducts overall, with 27% of cases and 13% of controls having elevated adducts. The odds ratio for elevated adducts in tumor tissue compared with control tissue was 2.56 (1. 05-6.24), after controlling for potential confounders. Adduct levels in tumor tissue did not vary by stage or tumor size. Among 86 cases with paired tumor and nontumor tissue, adducts levels in these two tissues were highly correlated (r=0.56, P<0.001). However, the corresponding associations between case-control status and adducts measured in nontumor tissue from 90 cases and in normal tissue from 105 controls were positive but not statistically significant. Overall, neither active nor passive smoking, or dietary PAH were significantly associated with PAH-DNA adducts or breast cancer case-control status. These results suggest that genetic damage reflecting individual exposure and susceptibility to PAH may play a role in breast cancer; but more research is needed to determine whether the findings are relevant to causation or progression of breast cancer.

Adult↗

PubMed2000

Impact of aging and hyperbaric oxygen in vivo on guinea pig lens lipids and nuclear light scatter.

PURPOSE: To measure lipid compositional and structural changes in lenses as a result of hyperbaric oxygen (HBO) treatment in vivo. HBO treatment in vivo has been shown to produce increased lens nuclear light scattering. METHODS: Guinea pigs, approximately 650 days old at death, were given 30 and 50 HBO treatments over 10- and 17-week periods, respectively, and the lenses were sectioned into equatorial, cortical, and nuclear regions. Lipid oxidation, composition, and structure were measured using infrared spectroscopy. Phospholipid composition was measured using (31)P-NMR spectroscopy. Data were compared with those obtained from lenses of 29- and 644-day-old untreated guinea pigs. RESULTS: The percentage of sphingolipid approximately doubled with increasing age (29-544 days old). Concomitant with an increase in sphingolipid was an increase in hydrocarbon chain saturation. The extent of normal lens lipid hydrocarbon chain order increased with age from the equatorial and cortical regions to the nucleus. These order data support the hypothesis that the degree of lipid hydrocarbon order is determined by the amount of lipid saturation, as regulated by the content of saturated sphingolipid. Products of lipid oxidation (including lipid hydroxyl, hydroperoxyl, and aldehydes) and lipid disorder increased only in the nuclear region of lenses after 30 HBO treatments, compared with control lenses. Enhanced oxidation correlated with the observed loss of transparency in the central region. HBO treatment in vivo appeared to accelerate age-related changes in lens lipid oxidation, particularly in the nucleus, which possesses less antioxidant capability. CONCLUSIONS: Oxidation could account for the lipid compositional changes that are observed to occur in the lens with age and cataract. Increased lipid oxidation and hydrocarbon chain disorder correlate with increased lens nuclear opacity in the in vivo HBO model.

Aging↗

PubMed2000

The association between glutathione S-transferase M1 genotype and polycyclic aromatic hydrocarbon-DNA adducts in breast tissue.

A major goal in molecular epidemiology is to identify preventable environmental risk factors and susceptible subpopulations. In a hospital-based molecular epidemiological case-control study of breast cancer, we investigated the relationship between DNA damage from exposure to polycyclic aromatic hydrocarbons (PAHs) and susceptibility attributable to inherited deletion of the xenobiotic detoxifying gene, glutathione S-transferase M1 (GSTM1). Prior to breast surgery, women (n = 227) were enrolled and interviewed and donated a blood sample. PAH-DNA adduct levels were measured by immunohistochemistry in breast tissue samples retrieved from pathology blocks, and GSTM1 genotype was determined by PCR using WBC DNA. The GSTM1 analysis included 95 cases and 87 benign breast disease controls. GSTM1 genotype was not associated with breast cancer case-control status (odds ratio = 0.73; 95% confidence interval, 0.37-1.44). However, the GSTM1 null genotype predicted PAH-DNA adduct levels in malignant (beta = 0.407; P = 0.003) and nonmalignant (beta = 0.243; P = 0.05) breast tissue from cases. This relationship was not seen in tissue from controls (beta = 0.095; P = 0.341). When tissue from controls was compared with tumor tissue from cases, there was a significant case-control difference in PAH-DNA adduct levels among women who were GSTM1 null. There was no such case-control difference among women who were homozygous or heterozygous for GSTM1. There was an interaction between GSTM1 and case-control status on adduct levels in breast tissue (P = 0.002). The results suggest that genetic susceptibility to the formation of PAH-DNA adducts in breast tissue may play a role in breast cancer development.

Adult↗

PubMed2000

Involvement of macrophage migration inhibitory factor (MIF) in experimental uric acid nephropathy.

BACKGROUND: Deposition of uric acid in the kidney can lead to progressive tubulointerstitial injury with granuloma formation. We hypothesized that uric acid crystal deposition may induce granuloma formation by stimulating local expression of macrophage migration inhibitory factor (MIF), which is a known mediator of delayed type hypersensitivity (DTH). MATERIALS AND METHODS: A model of acute uric acid nephropathy was induced in rats by the administration of oxonic acid (an inhibitor of uricase), together with uric acid supplements. MIF expression and local cellular response were examined by in situ hybridization and immunohistochemistry. RESULTS: Kidney tissue examined at 35 days posttreatment showed widespread tubulointerstitial damage with intratubular uric acid crystal deposition and granuloma formation. Tubules within the areas of granuloma showed a six-fold increase in MIF mRNA, compared with uninvolved areas by in situ hybridization. Moreover, the areas of increased MIF mRNA expression correlated with sites of dense accumulation of macrophages and T cells, and these cells were activated when assessed by the expression of interleukin-2R (IL-2R) and (MHC) class II. Interestingly, cytoplasmic staining for MIF protein in the uric acid (UA) crystal-associated granulomatous lesions was reduced, indicating a rapid MIF secretion by damaged tubules and macrophages secondary to uric acid crystal stimulation. This was confirmed by the demonstration of a marked increase in urinary MIF protein by Western blot analysis. Control rats fed either a normal diet or only oxonic acid had no discernible evidence of renal disease by routine light microscopy and minimal tubular expression of MIF mRNA and protein. CONCLUSIONS: These data suggest that intrarenal granulomas in urate nephropathy may be the consequence of a crystal induced DTH reaction mediated by MIF.

Animals↗

PubMed2000

Different Wnt-5A gene expressions in the renal cell carcinoma GRC-1 cell line during the cell cycle.

OBJECTIVE: To investigate the gene expression at transcription level of growth factor Wnt-5A in different phase during the cell cycle. METHODS: We synchronized the renal cell carcinoma GRC-1 cell line by double thymidine blocks and high-pressure N2O gae methods and amplified Wnt-5A cDNAs from different phase using Semi-quantitative RT-PCR (reverse transcriptase polymerase chain reaction). The PCR products were electrophoresized on the agrose gel and detected by Gel Doc 1000 computer controlled system integrating the volumes of each band, representing the intensities of all pixels in a defined band. RESULTS: The different mRNA expressions of growth factor Wnt-5A was detected in RCC GRC-1 cell line. In S phase, the highest level of Wnt-5A transcript was observed, and in G1 and M phase, medial and lowest, respectively. The differences between S and M stages were statistically significant (P < 0.05). CONCLUSION: Growth factor Wnt-5A has the potential effect on tumorigenesis. It contributes to all phases during cell cycle but in S phase especially.

Carcinoma, Renal Cell↗

PubMed2000

[Monitor visual function with flash visual evoked potential during orbital surgery].

OBJECTIVE: To evaluate the feasibility and reliability of monitoring visual function with flash visual evoked potential (FVEP) during orbital surgery. METHOD: The visual function of 82 cases was monitored during orbital surgery with FVEP. Of these cases, the intraoperative and postoperative visual functions (IOVF and POVF) were compared. RESULTS: Sixty-nine cases were successfully monitored. Sixty-seven cases obtained the accordance of IOVF and POVF, and there were false positive in 1 case and false negative in 1 case. CONCLUSION: Intraoperative monitoring of visual function with FVEP can show the surgical injury of the optic nerve and unsuitable procedures, and decrease the surgical blind rate.

Adolescent↗

PubMed2000

[Microsatellite instability in urine sediments from patients with transitional cell carcinoma of bladder and its clinical value].

OBJECTIVE: To investigate the expression of microsatellite instability in transitional cell carcinoma of bladder and to detect its diagnostic value. METHODS: Urine samples from 35 patients with transitional cell carcinoma of bladder (TCC) were analyzed by PCR method. 25 patients were followed up to detect microsatellite instability in their urine sediments. RESULTS: Microsatellite changes (including MSI and LOH) were detected in 88.6% of urine sediments (31 of 35 patients). Microsatellite changes were detected in urine sediments of 10 of 12 patients with tumor recurrence, in which the existence of tumor cells in the urine of 3 patients had been correctly predicted before cystoscopic evidence from 3 to 6 months. CONCLUSION Microsatellite analysis of urine sediment may be a novel and potentially clinical tool for the diagnosis and follow-up of bladder cancer patients.

Adult↗

PubMed2000

[Impact of glutamine of gut permeability and clinical prognosis on the aging patients undergoing gastric-intestinal operation].

OBJECTIVE: To evaluate the impact of parenteral nutrition supplemented glutamine on aging patients undergoing gastric-intestinal operation. METHODS: 30 patients above 60 years old undergoing gastric-intestinal operation, a randomized double-blind protocol was designed, divided into two groups, received impact isocaloric parenteral nutrition. The study group received alanyl-glutamine [0.5 g/(kg.d)]. To observe plasma amino acids profile, nitrogen balance, intestinal permeability and clinical prognosis, examine clinical chemistry variables and observe the adverse reactions in order to find out its safety. RESULTS: The patients in both groups were comparable prior to the operation. The plasma glutamine level of study group is higher than the control group, it's cumulative nitrogen balance values were prior to the control group, L/M ratio was lower than the control group. The complications related to infection was observed more in the control group. No adverse reaction was observed in both groups. CONCLUSIONS: Ala-Gln-supplemented PN improved nitrogen balance and maintained intestinal permeability, reduced complications.

Aged↗

PubMed1999

Mediated, amperometric biosensor for glucose-6-phosphate monitoring based on entrapped glucose-6-phosphate dehydrogenase, Mg2+ ions, tetracyanoquinodimethane, and nicotinamide adenine dinucleotide phosphate in carbon paste.

In this study, an amperometric carbon paste biosensor is developed for glucose-6-phosphate (G6P) monitoring which is based on entrapped Mg2+ ions, G6P dehydrogenase, NADP+ polyethylenimine (PEI) and the electroactive mediator, tetracyanoquinodimethane (TCNQ). The calibration line had a slope of 1.55 x 10(-5) A. M-1 with a correlation coefficient of 0.9965. The limit of detection (defined as three times the standard deviation of the response of the electrode to blank phosphate buffer injections (noise)) of the G6P biosensor was 5.0 x 10(-5) M. The application of this biosensor for monitoring G6P in human blood using the standard addition method is also demonstrated. A two-parameter empirical equation which adequately describes the deactivation of the biosensor steady-state response with time is also proposed.

Biosensing Techniques↗

PubMed1999

Identification and structure characterization of a Cdk inhibitory peptide derived from neuronal-specific Cdk5 activator.

The activation of cyclin-dependent kinase 5 (Cdk5) depends on the binding of its neuronal specific activator Nck5a. The minimal activation domain of Nck5a is located in the region of amino acid residues 150 to 291 (Tang, D., Chun, A. C. S., Zhang, M., and Wang, J. H. (1997) J. Biol. Chem. 272, 12318-12327). In this work we show that a 29-residue peptide, denoted as the alphaN peptide, encompassing amino acid residues Gln145 to Asp173 of Nck5a is capable of binding Cdk5 to result in kinase inhibition. This peptide also inhibits an active phospho-Cdk2-cyclin A complex, with a similar potency. Direct competition experiments have shown that this inhibitory peptide does not compete with Nck5a or cyclin A for Cdk5 or Cdk2, respectively. Steady state kinetic analysis has indicated that the alphaN peptide acts as a non-competitive inhibitor of Cdk5. Nck5a complex with respect to the peptide substrate. To understand the molecular basis of kinase inhibition by the peptide, we determined the structure of the peptide in solution by circular dichroism and two-dimensional 1H NMR spectroscopy. The peptide adopts an amphipathic alpha-helical structure from residues Ser149 to Arg162 which can be further stabilized by the helix-stabilizing solvent trifluoroethanol. The hydrophobic face of the helix is likely to be the kinase binding surface.

Amino Acid Sequence↗

PubMed1999

Cycloheximide-induced T-cell death is mediated by a Fas-associated death domain-dependent mechanism.

Cycloheximide (CHX) can contribute to apoptotic processes, either in conjunction with another agent (e.g. tumor necrosis factor-alpha) or on its own. However, the basis of this CHX-induced apoptosis has not been clearly established. In this study, the molecular mechanisms of CHX-induced cell death were examined in two different human T-cell lines. In T-cells undergoing CHX-induced apoptosis (Jurkat), but not in T-cells resistant to the effects of CHX (CEM C7), caspase-8 and caspase-3 were activated. However, the Fas ligand was not expressed in Jurkat cells either before or after treatment with CHX, suggesting that the activation of these caspases does not involve the Fas receptor. To determine whether CHX-induced apoptosis was mediated by a Fas-associated death domain (FADD)-dependent mechanism, a FADD-DN protein was expressed in cells prior to CHX treatment. Its expression effectively inhibited CHX-induced cell death, suggesting that CHX-mediated apoptosis primarily involves a FADD-dependent mechanism. Since CHX treatment did not result in the induction of Fas or FasL, and neutralizing anti-Fas and anti-tumor necrosis factor receptor-1 antibodies did not block CHX-mediated apoptosis, these results may also indicate that FADD functions in a receptor-independent manner. Surprisingly, death effector filaments containing FADD and caspase-8 were observed during CHX treatment of Jurkat, Jurkat-FADD-DN, and CEM C7 cells, suggesting that their formation may be necessary, but not sufficient, for cell death.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Size fractionation of bacterial capsular polysaccharides for their use in conjugate vaccines.

We have developed a chromatographic method suitable for the fractionation of polysaccharides having a negatively charged group. The method permits the removal of all those polysaccharide fragments having a short sequence and which are likely unsuitable for conjugate vaccine construction. The selected polysaccharide fragments can be used to produce glycoconjugate vaccines containing a restricted saccharide polydispersion. We have applied this chromatographic method to three different antigens, Haemophilus influenzae type b and Neisseria meningitidis group A and group C polysaccharides. The method is easily adapted for manufacturing purposes.

Antigens, Bacterial↗

PubMed1999

Lipid composition, membrane structure relationships in lens and muscle sarcoplasmic reticulum membranes.

Membrane lipid composition varies in different tissues and species. Since a defined lipid composition is essential to the function of many membranes, the relationship between membrane lipid composition and structure was determined using infrared and Raman spectroscopy in four membranes containing a calcium pump: rabbit fast and slow twitch muscle sarcoplasmic reticulum and human and bovine lens fiber cell membranes. We found that membrane sphingolipid and phosphatidylcholine content were correlated to a decrease and increase, respectively, in the infrared lipid CH2 symmetric stretching band frequency. We interpret the change in frequency as a change in lipid hydrocarbon chain structural order. This was confirmed by Raman order parameters. The high degree of hydrocarbon chain saturation found in the variable amide chains of sphingolipids is likely to account for this correlation. Lipid phase transition temperature and cooperativity also correlated to sphingolipid and phosphatidylcholine content, and are the forces defining the order in at physiological temperature in the samples studied. Ca(2+)-ATPase caused an increase in the CH2 symmetric stretching frequency in fast twitch muscle sarcoplasmic reticulum (interpreted as an increase in hydrocarbon chain disorder), but had no effect on slow twitch muscle sarcoplasmic reticulum lipid hydrocarbon chain structure. In the natural systems studied, we find that it is the lipid hydrocarbon chain saturation that defines lipid hydrocarbon chain order.

Animals↗