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Biomedical subjects

H Dai

Publications and source records attributed to H Dai.

At least 91 records · Page 5Linked to original sources
PubMed1997

Requirements for urology and renal dialysis PC-based telemedicine applications: comparative analysis.

The Imaging Science and Information Systems (ISIS) Center of the Department of Radiology at Georgetown University Medical Center (GUMC) has been developing technical requirements for different telemedicine applications. This paper details the process through which those technical requirements are determined and shows how they may differ substantially, depending on the clinical need. This information is presented in light of two telemedicine applications being undertaken at GUMC: a urology application for the management of patients with surgical stone disease and a nephrology application for monitoring of renal dialysis patients.

Humans↗
PubMed1997

[Changes of plasma endothelium-derived relaxing factor and endothelin-1 in patients with chronic cor pulmonale at exercise test].

OBJECTIVE: The authers investigated the levels of plasma EDRF-nitric oxide (NO) and ET-1 in 10 cases of cor pulmonale at exercise. METHODS: Using the technologies of cardiac catheter, radioimmunization and biochemical analysis. RESULTS: The level of plasma NO was lower in group A (mean pulmonary artery pressure (mPAP) < 2.67 kPa) than in group B (mPAP > or = 2.67 kPa) at rest; the content of plasma NO increased more markedly in group A than in group B during exercise; there was no change in the content of ET-1 in both groups; mPAP strongly correlated with plasma NO or ET-1 in both groups. CONCLUSIONS: The patients with cor pulmonale at early stage may be in a state of compensated release of NO, but its release reserve has been reduced.

Aged↗
PubMed1997

The study of IL-1 beta, TNF-alpha, IL-6 gene expression and plasma levels on hemodialysis before and after dialyzer reuse.

OBJECTIVE: To investigate the biocompatibility of dialyzer reuse. METHODS: Twenty-two hemodialysis patients were randomized into cuprophan (CU, 7), polymethylmethacrylate (PMMA, 7) and polysulphone (PS, 8) membrane groups to observe IL-1 beta, TNF-alpha, IL-6 gene expression and their plasma levels by using themselves as control with enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. RESULTS: Plasma levels of interlukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) were 14.07 +/- 3.32 pg/ml, 67.41 +/- 19.79 pg/ml, 83.67 +/- 40.34 pg/ml; 12.80 +/- 3.01 pg/ml, 49.65 +/- 9.75 pg/ml, 33.36 +/- 12.14 pg/ml and 14.41 +/- 3.16 pg/ml, 80.56 +/- 23.22 pg/ml, 48.14 +/- 16.01 pg/ml, respectively, after patients dialyzed with CU, PMMA and PS membranes. Plasma cytokine levels decreased after reuse compared with those before reuse in each group. But no significant difference was found between them (P > 0.05); the levels of IL-1 beta, TNF-alpha, IL-6 gene expression after reuse were 5.61 +/- 0.33, 2.11 +/- 0.12, 5.04 +/- 0.19%; 2.43 +/- 0.19, 1.29 +/- 0.11, 3.48 +/- 0.20% and 2.48 +/- 0.20, 1.24 +/- 0.11, 3.22 +/- 0.20% respectively by in situ hybridization, and 0.92 +/- 0.07, 0.63 +/- 0.05, 0.53 +/- 0.05; 0.61 +/- 0.06, 0.47 +/- 0.04, 0.37 +/- 0.03 and 0.59 +/- 0.05, 0.44 +/- 0.04, 0.38 +/- 0.03 by RT-PCR, respectively. After reuse there was significant decrease as compared with that before reuse (P < 0.001, P < 0.005 and P < 0.05, respectively). CONCLUSIONS: This suggested reprocessing dialyzer with formaldehyde reduced cytokine release and gene expression in peripheral blood mononuclear cells and enhanced dialyzer biocompatibility. It would be beneficial to reduce the dialysis cost and may reduce the complication related to a long term hemodialysis.

Adult↗
PubMed1997

[Induction of apoptosis in human ovarian cancer cell line HO-8910 by transforming growth factor beta 1].

OBJECTIVE: To investigate the mechanism of inhibitory effects of Transforming Growth Factor beta 1 (TGF-beta 1) on human ovarian cancer cell in vitro. METHODS: The possibility of induction of apoptosis in human ovarian cancer cell line HO-8910 cells after treatment with TGF-beta 1 was studied by using methods of DNA electrophoresis, P1-staining, TdT-mediated dUTP-x nick end labeling and flow cytometer assay (FCM); and the kinetic change of expression of c-myc was also studied by relative quantified RT-PCR. RESULTS: DNA-strand nicks were present in cells after treatment with TGF-beta 1 at the final concentration of 20 ng/ml for 36 hours. The percent of labeled cells reached 75.55% on the time of 48 hours, PI staining-FCM assay also showed subdiploid peak of apoptotic cells at the same time. The typical apoptotic DNA ladder was present in genomic DNA preparation after treatment with TGF-beta 1 for 60 hours, meanwhile, the expression of c-myc in cells started to decrease beginning at treatment for 9 hours. CONCLUSIONS: TGF-beta 1 can induce apoptosis in HO-8910; such an inductive effect may occur mainly in G0/G1 phase. The effects of TGF-beta 1 on the inhibited expression of c-myc and on the enhancement of cAMP concentration may also play important roles in the process of apoptotic induction.

Apoptosis↗
PubMed1997

[The changes of lipid metabolism and hemorrheology in intrahepatic cholestasis during pregnancy].

OBJECTIVE: To identify the influence of the increased level of serum cholyglycine (CG) on lipid metabolism and hemorrheology in patients with intrahepatic cholestasis during pregnancy (ICP). METHODS: The concentrations of serum CG, total cholesterol (CH), triglycerides (TG), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), high shear and low shear of blood specific viscosity (HS and LS), plasma specific viscosity (PV) and hematocrit (HCT) were measured in 68 cases of primiparas with single pregnancy and 30 healthy nonpregnant women respectively. The group of ICP was composed of 35 cases with CG > 6 mumol/L, the group of normal pregnancy, 33 cases with CG < 6 mumol/L. RESULTS: The means of CG and the lipidic parameters in the two pregnant groups were significantly higher than those in the non-pregnancy group (P < 0.02-0.001) except the means of HDL-C between the groups of ICP and non-pregnancy. The levels of LDL-C, LDL-C/HDL-C, LS, PV and HCT in the ICP were significantly higher than those in the normal pregnancy group (P < 0.02-0.001). CONCLUSIONS: There are significant changes of lipid metabolism and hemorrheology in patients with ICP. However, these changes could be corrected after pregnancy termination, when the level of serum CG returned to normal. The results suggest that the pathophysiologic changes of ICP are associated with increased level of serum CG.

Adult↗
PubMed1996

Crystalline Ropes of Metallic Carbon Nanotubes

Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200degreesC. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C5v symmetry and an open edge stabilized by triple bonds.

Journal Article↗
PubMed1996

Glutathione S-transferases in the Japanese quail: tissue distribution and purification of the liver isozymes.

Cytosolic glutathione S-transferase (GST) activities toward 1-chloro-2,4-dinitro-benzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), ethacrynic acid (EA), 1,2-epoxy-3-(p-nitrophenoxyl)propane (EPNP), trans-4-phenyl-3-buten-2-one(t-PBO), delta 5-androstene-3,17-dione (ASD) and trans-stilbene oxide (t-SO); cytosolic glutathione peroxidase activity toward cumene hydroperoxide (CuOOH); and microsomal GST activity toward CDNB were examined in liver, kidney, brain, and lung of adult male and female Japanese quail. In all cases, the renal specific activity per milligram protein was higher than the hepatic activity and was the highest among the four tissues examined. No consistent sex differences in GST activity were observed. The GSTs were purified from quail liver cytosol by S-hexylglutathione and glutathione affinity chromatography. Total GSTs eluted from the S-hexylglutathione affinity column were further separated by chromatofocusing, and the microheterogeneity of the GST isozymes was shown by high-resolution native isoelectrofocusing (IEF) in polyacrylamide slab gels and by SDS-PAGE. Five subunits were identified: QL1 (30.5 kDa), QL2 (27.2 kDa), QL3a (26.8 kDa), QL3b (26.5 kDa), and QL4 (25.5 kDa). Western blot analysis revealed that QL1 and QL2 reacted with antibodies raised against the rat Mu class GSTs (Yb1 and Yb2), and QL3a and QL3b reacted with those raised against the Alpha class (rat Ya and mouse a). Substrate specific activity of each isoform was determined with CDNB, DCNB, CuOOH, EA, t-PBO, ASD, and t-SO. QL3a and QL3b have high reactivity toward CuOOH, while QL1 and QL2 showed high activity toward t-SO. The N-terminal amino acid sequence of QL2 was identical to that of the chicken Mu class GST subunit CL2. However, no sequence was obtained with QL1 due to possible N-terminal blockage.

Amino Acid Sequence↗
PubMed1996

Characterization of polyion counterion interactions in cartilage by 23Na NMR relaxation.

Nuclear quadrupole relaxation is a sensitive measure of electrolyte environments. We used the relaxation of 23Na to probe mobile ion-matrix interactions and the electrostatic structure of the polyelectrolyte extracellular matrix of cartilage. Specifically, we measured spin-lattice and spin-spin relaxation times of 23Na in bovine nasal cartilage at 132 MHz under several conditions. Matrix fixed charge density was reduced by protonating anionic sites and by matrix digestion with trypsin and the relaxation times compared to controls. Under all conditions studied, measured longitudinal relaxation was monoexponential with values ranging from 16-32 msec. Transverse relaxation exhibited biexponential behavior in all cartilage samples with a fast component in the range of 2 to 5 ms and a slow component between 16 and 53 ms. Reduction in matrix fixed charge density in all cases led to a decrease in the relaxation rates. The results suggest a two-site model for Na+ ions in cartilage and a relaxation mechanism involving both polyion segmental motion and counterion diffusion. In the context of ion condensation theory, the implication of a two-site model is that the mean polyion-polyion spacing may be less than 0.7 nm. The mean polyion-counterion spacings were estimated by calculating correlation times and quadrupole coupling constants. These spacings were found to be 0.5-0.7 nm.

Animals↗
PubMed1996

Decision rules of listeners in spectral-shape discrimination with or without signal-frequency uncertainty.

A correlation technique was used to assess the decision rules of three listeners in two cases of spectral-shape discrimination tasks. In one case the signal frequency was fixed, and in the other it was randomly varied within each block of trials. In order to estimate the decision rule of the listeners, the experimenter superimposed random level perturbations on each frequency component upon each stimulus presentation. Over many trials, correlation coefficients were computed between the random perturbations and the binary responses of the listeners, and were expressed as a function of signal level. For both the fixed- and random-signal cases, the measured correlation functions were in reasonably good agreement with those predicted based on the likelihood-ratio decision rules. Thus the listeners appeared to use information nearly optimally in discriminating spectral shapes. This investigation demonstrated that the correlation technique can be used to reveal the decision rules for cases where the decision statistics are nonlinear functions of the observations.

Auditory Perception↗
PubMed1996

Phase independence of pitch produced by narrow-band sounds.

Three listeners matched the pitch of a simple tone to that of narrow-band complex signals having different phases. The pitch matches were independent of the phases; the frequency of the simple tone approximately equaled the center of gravity of the power spectrum of each complex signal. This result is inconsistent with a model that calculates the pitch of a waveform as the average of instantaneous frequency weighted by the envelope of the waveform.

Humans↗
PubMed1996

The optimum decision rules in the same-different paradigm.

In this paper we derive the optimum (likelihood-ratio) decision statistic for a same-different paradigm. The likelihood ratio is dependent on the degree of correlation between the two observations on each trial. For the two extreme cases in which the observations are either independent or highly correlated, the optimum decision rule is identical to each of two previously suggested decision rules. For these two cases, the receiver-operating characteristic (ROC) curves are calculated. Finally, an experimental procedure is suggested for assessing the decision rule actually used by the observer in a same-different task.

Decision Making↗
PubMed1996

The optimum decision rules for the oddity task.

This paper presents the optimum decision rule for an m-interval oddity task in which m-1 intervals contain the same signal and one is different or odd. The optimum decision rule depends on the degree of correlation among observations. The present approach unifies the different strategies that occur with "roved" or "fixed" experiments (Macmillan & Creelman, 1991, p. 147). It is shown that the commonly used decision rule for an m-interval oddity task corresponds to the special case of highly correlated observations. However, as is also true for the same-different paradigm, there exists a different optimum decision rule when the observations are independent. The relation between the probability of a correct response and d' is derived for the three-interval oddity task. Tables are presented of this relation for the three-, four-, and five-interval oddity task. Finally, an experimental method is proposed that allows one to determine the decision rule used by the observer in an oddity experiment.

Decision Making↗
PubMed1996

[The effects of growth factors on gene expressions in human ovarian cancer cell line HO-8910].

The effects of EGF and TGF beta 1 on onco gene expressions was studied by RT-PCR technique in an ovarian cancer cell line HO-8910. The results showed that TGF beta 1 could inhibit mRNA expression of TGF beta 1 gene and that of c-myc, EGFR and c-erbB2 genes in HO-8910 cells in vitro. However, EGF could enhance the mRNA expressions of c-myc, c-erbB2 and EGFR to various extents, but inhibit that of TGF beta 1 gene.

Cystadenocarcinoma↗
PubMed1995

L-DOPA and psychosis: evidence for L-DOPA-induced increases in prefrontal cortex dopamine and in serum corticosterone.

L-DOPA can often induce psychotic reactions during treatment for Parkinson's disease. This study was undertaken to assess, in an animal model of Parkinson's disease, the impact of L-DOPA treatment on two potential biological risk factors for psychosis, namely, an increase in prefrontal cortex dopamine and an increase in the stress-related hormone corticosterone. Hemiparkinsonian rats with unilateral 6-hydroxydopamine (6-OHDA) lesions which resulted in severe unilateral denervation of dopamine neurons were treated with either saline or 25 mg/kg L-DOPA methyl ester (with 2 mg/kg carbidopa). Serum L-DOPA concentrations were found to be positively and highly correlated with serum corticosterone, with medial prefrontal cortex dopamine and with the dopamine metabolite homovanillic acid. Serum L-DOPA, however, was found not to be correlated with serum or brain concentrations of serotonin, 5-hydroxyindoleacetic acid, or norepinephrine. These findings support the possibility that chronic L-DOPA treatment can expose parkinsonian patients to two significant risk factors for psychosis: 1) increased levels of prefrontal cortex dopamine, and 2) increased levels of serum corticosterone.

Animals↗
PubMed1995

Purification of crotonyl-CoA reductase from Streptomyces collinus and cloning, sequencing and expression of the corresponding gene in Escherichia coli.

A crotonyl-CoA reductase (EC 1.3.1.38, acyl-CoA:NADP+ trans-2-oxidoreductase) catalyzing the conversion of crotonyl-CoA to butyryl-CoA has been purified and characterized from Streptomyces collinus. This enzyme, a dimer with subunits of identical mass (48 kDa), exhibits a Km = 18 microM for crotonyl-CoA and 15 microM for NADPH. The enzyme was unable to catalyze the reduction of any other enoyl-CoA thioesters or to utilize NADH as an electron donor. A highly effective inhibition by straight-chain fatty acids (Ki = 9.5 microM for palmitoyl-CoA) compared with branched-chain fatty acids (Ki > 400 microM for isopalmitoyl-CoA) was observed. All of these properties are consistent with a proposed role of the enzyme in providing butyryl-CoA as a starter unit for straight-chain fatty acid biosynthesis. The crotonyl-CoA reductase gene was cloned in Escherichia coli. This gene, with a proposed designation of ccr, is encoded in a 1344-bp open reading frame which predicts a primary translation product of 448 amino acids with a calculated molecular mass of 49.4 kDa. Several dispersed regions of highly significant sequence similarity were noted between the deduced amino acid sequence and various alcohol dehydrogenases and fatty acid synthases, including one region that contains a putative NADPH binding site. The ccr gene product was expressed in E. coli and the induced crotonyl-CoA reductase was purified tenfold and shown to have similar steady-state kinetics and electrophoretic mobility on sodium dodecyl sulfate/polyacrylamide to the native protein.

Acyl-CoA Dehydrogenases↗
PubMed1995

The Drosophila schnurri gene acts in the Dpp/TGF beta signaling pathway and encodes a transcription factor homologous to the human MBP family.

Decapentaplegic (dpp), a TGF beta-related ligand, plays a key role in Drosophila development. Although dpp receptors have been isolated, the downstream components of the signaling pathway remain to be identified. We have cloned the schnurri (shn) gene and show that it encodes a putative zinc finger transcription factor homologous to the human major histocompatibility complex-binding proteins 1 and 2. Mutations in shn affect multiple events that require dpp signaling as well as the transcription of dpp-responsive genes. Genetic interactions and the strikingly similar phenotypes of mutations in shn and the dpp receptors encoded by thick veins and punt suggest that shn plays a downstream role in dpp signaling.

Amino Acid Sequence↗
PubMed1995

Antibody reactivity to the HRES-1 endogenous retroviral element identifies a subset of patients with systemic lupus erythematosus and overlap syndromes. Correlation with antinuclear antibodies and HLA class II alleles.

OBJECTIVE: To evaluate the correlation between the presence of antibodies to an endogenous retroviral element-encoded nuclear protein autoantigen, HRES-1, and the presence of other antinuclear antibodies and HLA class II alleles in patients with systemic lupus erythematosus (SLE) and overlap syndromes. METHODS: Antibody reactivities to native and recombinant proteins and synthetic peptides were assessed by counterimmunoelectrophoresis, enzyme-linked immunosorbent assay, and Western blotting. HLA class II alleles were determined by oligonucleotide typing. RESULTS: Forty-eight percent of the 153 patients with autoimmune disease, and 52% of the subgroup with SLE, had HRES-1 antibodies. In contrast, 3.6% of 111 normal donors, and none of 42 patients with the acquired immunodeficiency syndrome or 50 asymptomatic human immunodeficiency virus 1-infected patients, had HRES-1 antibodies. Chi-square analyses revealed a significant association between anti-HRES-1 and anti-RNP and an inverse correlation between HRES-1 and Ro/La autoantibodies in patients with SLE or overlap syndromes. Antigenic epitopes of HRES-1 and the retroviral gag-related region of the 70-kd protein component of U1 small nuclear RNP, which share 3 consecutive highly charged amino acids (Arg-Arg-Glu), an additional Arg, and functionally similar Arg/Lys residues, represent cross-reactive epitopes between the two proteins. Selective removal of HRES-1 antibodies from sera of HRES-1-seropositive/RNP-seropositive patients by absorption on recombinant HRES-1/glutathione-S-transferase-conjugated agarose beads had no effect on anti-RNP reactivities. A comparative multivariate analysis of HLA class II genes revealed a differential segregation of DQB1 alleles in HRES-1-seropositive versus HRES-1-seronegative patients (P = 0.04). While a relative increase of DQB1*0402 among HRES-1-seropositive patients was noted across ethnic groups (P = 0.02), a decrease of DQB1*0201 and DQB1*0301 was found in white HRES-1-seropositive patients (P = 0.04). CONCLUSION: Autoantibodies to HRES-1 are detectable in a distinct subset of patients with autoimmune disease, primarily in those who do not have antibodies to Ro and La. Anti-HRES-1 and anti-RNP reactivities are mediated by cross-reactive but separate antibody molecules. HLA-DQB genes, rather than HLA-DRB or DQA genes, may have a more significant influence on generation of these antinuclear autoantibodies.

Alleles↗