Biomedical subjects

D Hu

Publications and source records attributed to D Hu.

At least 55 records · Page 3Linked to original sources

PubMed2000

Differences of four catechins in cell cycle arrest and induction of apoptosis in LoVo cells.

(-)-Epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG), and (-)-epicatechin (EC) were found to have different cytotoxicities to human colon carcinoma LoVo cells. EGCG and EGC suppressed the growth of LoVo cells in dose-dependent manner; ECG and EC, however, had no obvious effects. At lower concentrations, EC did seem to promote slight proliferation. Similarly, EGCG and EGC, rather than ECG and EC, were found to induce apoptosis in LoVo cells. Moreover, EGCG, EGC, and ECG arrested G(1) phase in the cell cycle progression, whereas EC resulted in S phase arrest. We suggest that there are differences in the cytotoxicities of the four catechins to LoVo cells. They exert the effects by inducing apoptosis and regulating the cell cycle.

Apoptosis↗

PubMed2000

Unmasking electronic energy transfer of conjugated polymers by suppression of O(2) quenching

The photochemistry of poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) has been found to be highly dependent on the presence of O(2), which increases singlet exciton quenching dramatically. Spectroscopy on isolated single molecules of MEH-PPV in polycarbonate films that exclude O(2) reveals two distinct polymer conformations with fluorescence maxima near 555 and 580 nanometers wavelength, respectively. Time-resolved single-molecule data demonstrate that the 580-nanometer conformation exhibits a "landscape" for intramolecular electronic energy relaxation with a "funnel" that contains a 580-nanometer singlet exciton trap at the bottom. The exciton traps can be converted to exciton quenchers by reaction with O(2). Conformationally induced, directed-energy transfer is arguably a critical dynamical process that is responsible for many of the distinctive photophysical properties of conjugated polymers.

Journal Article↗

PubMed2000

Collapse of stiff conjugated polymers with chemical defects into ordered, cylindrical conformations

The optical, electronic and mechanical properties of synthetic and biological materials consisting of polymer chains depend sensitively on the conformation adopted by these chains. The range of conformations available to such systems has accordingly been of intense fundamental as well as practical interest, and distinct conformational classes have been predicted, depending on the stiffness of the polymer chains and the strength of attractive interactions between segments within a chain. For example, flexible polymers should adopt highly disordered conformations resembling either a random coil or, in the presence of strong intrachain attractions, a so-called 'molten globule'. Stiff polymers with strong intrachain interactions, in contrast, are expected to collapse into conformations with long-range order, in the shape of toroids or rod-like structures. Here we use computer simulations to show that the anisotropy distribution obtained from polarization spectroscopy measurements on individual poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] polymer molecules is consistent with this prototypical stiff conjugated polymer adopting a highly ordered, collapsed conformation that cannot be correlated with ideal toroid or rod structures. We find that the presence of so-called 'tetrahedral chemical defects', where conjugated carbon-carbon links are replaced by tetrahedral links, divides the polymer chain into structurally identifiable quasi-straight segments that allow the molecule to adopt cylindrical conformations. Indeed, highly ordered, cylindrical conformations may be a critical factor in dictating the extraordinary photophysical properties of conjugated polymers, including highly efficient intramolecular energy transfer and significant local optical anisotropy in thin films.

Journal Article↗

PubMed2000

Identification of Grb10 as a direct substrate for members of the Src tyrosine kinase family.

Treatment of cells with insulin and protein tyrosine phosphatase inhibitors such as vanadate and pervanadate resulted in the tyrosine phosphorylation of Grb10, a Src homology 2 (SH2) and pleckstrin homology domain-containing adaptor protein which binds to a number of receptor tyrosine kinases including the insulin receptor (IR). Although Grb10 binds directly to the kinase domain of the IR, our data show that Grb10 is not a direct substrate for the IR tyrosine kinase. Consistent with this finding, Grb10 tyrosine phosphorylation in cells was inhibited by herbimycin A, a relatively specific inhibitor for members of the Src tyrosine kinase family, and by the expression of dominant negative Src or Fyn. In addition, Grb10 tyrosine phosphorylation was stimulated by expression of constitutively active Src or Fyn in cells and by incubation with purified Src or Fyn in vitro. The insulin stimulated or Src/Fyn-mediated tyrosine phosphorylation in vivo was significantly reduced when Grb10 tyrosine 67 was changed to glycine. This mutant form of Grb10 bound with higher affinity to the IR in cells than that of the wild-type protein, suggesting that tyrosine phosphorylation of Grb10 may normally negatively regulate its binding to the IR. Our data show that Grb10 is a new substrate for members of the Src tyrosine kinase family and that the tyrosine phosphorylation of the protein may play a potential role in cell signaling processes mediated by these kinases. Oncogene (2000).

Animals↗

PubMed2000

Three novel TBX5 mutations in Chinese patients with Holt-Oram syndrome.

Holt-Oram syndrome (HOS) is an autosomal dominant syndrome that comprises upper limb and cardiac defects. The gene responsible for HOS, TBX5, was isolated and many mutations have been identified in HOS patients. We analyzed 11 Chinese HOS patients (7 from three families and 4 sporadic cases) for TBX5 mutation by single strand conformation polymorphisms (SSCPs). Three SSCP changes were detected in two of the three familial cases and one sporadic case. Sequence analysis identified three novel, heterozygous mutations in TBX5: a frameshift mutation caused by one base deletion [C416del] in one family, a mis-sense mutation (Gln49Lys) induced by a base substitution (C145A) in another family, and the other mis-sense mutation (Ile54Thr) by T161C in one sporadic case. The patients with the frameshift mutations had severer clinical manifestations that involved aplasia/hypoplasia of the arm and thumbs, while those with the mis-sense mutations presented with milder anomalies such as absent or hypoplastic thumbs but without arm abnormalities. These observations may support a genotype-phenotype correlation in HOS patients with TBX5 mutation.

Amino Acid Substitution↗

PubMed2000

The HIV epidemic in the Amazon Basin is driven by prototypic and recombinant HIV-1 subtypes B and F.

This paper describes genetic subtypes of HIV-1 found in blood samples from 31 HIV-1-infected people who visited the Counseling and Testing AIDS Center of Instituto de Medicina Tropical in Manaus, Brazil. Manaus, the main city in Brazil's Amazon Basin, is also the closest urban connection for more than 100,000 Indians living in the rain forests of this region. Although to date there is no evidence of increased incidence of HIV-1 infection among the indigenous population, our understanding of both the prevalence and nature of the epidemic in the region as a whole is limited. From the 31 samples analyzed by C2V3 sequencing, we found almost equal proportions of HIV-1 strains belonging to subtype B (n = 16; 51.6%) and subtype F (n = 15; 48.4%), a finding that differs from results from previous studies conducted in urban areas of southeastern Brazil. We also observed the presence of the GWGR amino-acid sequence in the critical tetra-peptide crown of the env V3 loop in the HIV-1 subtype B samples analyzed. Among these samples, we also found 14 mosaic genomes (45.16%) in which different combinations of subtypes B, C, and F were identified between the p24 gag, pro, and env regions. Our data support the hypothesis that the Amazonian HIV-1 infections linked to the urban epidemic in southeastern Brazil. The genetic diversity and the prevalence of mosaic genomes among the isolates in our study confirm an integral role of recombination in the complex Brazilian epidemic.

Adult↗

PubMed2000

Probing the structure of the PI-SceI-DNA complex by affinity cleavage and affinity photocross-linking.

The PI-SceI protein is an intein-encoded homing endonuclease that initiates the mobility of its gene by making a double strand break at a single site in the yeast genome. The PI-SceI protein splicing and endonucleolytic active sites are separately located in each of two domains in the PI-SceI structure. To determine the spatial relationship between bases in the PI-SceI recognition sequence and selected PI-SceI amino acids, the PI-SceI-DNA complex was probed by photocross-linking and affinity cleavage methods. Unique solvent-accessible cysteine residues were introduced into the two PI-SceI domains at positions 91, 97, 170, 230, 376, and 378, and the mutant proteins were modified with either 4-azidophenacyl bromide or iron (S)-1-(p-bromoacetamidobenzyl)-ethylenediaminetetraacetate (FeBABE). The phenyl azide-coupled proteins cross-linked to the PI-SceI target sequence, and the FeBABE-modified proteins cleaved the DNA proximal to the derivatized amino acid. The results suggest that an extended beta-hairpin loop in the endonuclease domain that contains residues 376 and 378 contacts the major groove near the PI-SceI cleavage site. Conversely, residues 91, 97, and 170 in the protein splicing domain are in close proximity to a distant region of the substrate. To interpret our results, we used a new PI-SceI structure that is ordered in regions of the protein that bind DNA. The data strongly support a model of the PI-SceI-DNA complex derived from this structure.

Base Sequence↗

PubMed2000

The effect of different interventional treatment on P-Glycoprotein in different histopathological types and grades of primary hepatocellular carcinoma.

To study the effect of the different interventional treatment on P-Glycoprotein (Pgp) in different histopathological types of primary hepatocellular carcinoma (PHC), 98 surgically and histologically verified PHC specimens were obtained. The patients included 57 patients treated by surgical resection alone and 41 patients receiving second-stage surgical resection after four kinds of interventional treatment. SABC immunohistochemical staining with a monoclonal antibody against human Pgp was used to observe the Pgp in all specimens. The positive rate of Pgp was 100% in group of chemotherapy alone (P < 0.05), 62.5% in group of chemotherapy combined with iodized oil (P > 0.05), 46.6% in group of chemotherapy combined with iodized oil and spongia gelatini absorbens (Sga) (P > 0.05), 18.18% in group of chemotherapy combined with Ethanol-iodized-oil and Sga (P < 0.05) and 52.63% in group of surgical resection alone. The positive rate of Pgp varied with different histopathological types, with rate of clear cell PHC being the lowest, and that of poorly differentiated or undifferentiated PHC the highest. The positive rate of Pgp was increased as pathological grades increased. Overexpression of Pgp may be responsible for the intrinsic and acquired drug resistance of PHC. Multidrug resistance (MDR) varied with different histological types. Therapy of PHC should be tailored according to individual. Local chemotherapy combined with ethanol-iodized-oil and Sga embolization may become a new way to overcome MDR of PHC.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2000

Antioxidative stress response in workers exposed to carbon disulfide.

OBJECTIVE: To study the effects of carbon disulfide (CS2) on antioxidative stress systems of exposed workers. METHODS: Enzyme-linked immunosorbent assay (ELISA) and thiobarbituric acid test (BAT) were conducted on 67 exposed workers and 88 controlled ones in a viscose rayon factory to determine their serum cuprozinc-superoxide dismutase (CuZnSOD) and malonyldialdehyde (MDA) levels. RESULTS: The average levels of CuZnSOD in workers exposed to CS2 both above and below 10 mg/m3 were higher than those in the control group (P < 0.0001), showing some dose-effect and dose-response relationships. SOD levels increased when the exposure index (EI) was less than 300, and remained at a high level at the range of 300 to 900. When EI was higher than 900, SOD tended to decrease. Meanwhile, the serum MDA levels increased. Both CS2 concentrations and exposure time contribute to the MDA levels. CONCLUSIONS: CS2 exposure could influence the stress response of the oxidative-antioxidative system of workers. Increased SOD levels could be considered as the stress response of antioxidative system to CS2 exposure in the early stages, and the influence of CS2 on SOD might be bi-directional. SOD and MDA might become objective indices in workers' health surveillance. The role of these two indices in the intoxication mechanism still needs to be clarified.

Adult↗

PubMed2000

5-Fluorouracil-induced apoptosis in cultured oral cancer cells.

Chemotherapy is commonly used to treat advanced oral squamous cell carcinoma (SCC) and is known to kill cancer cells through apoptosis. Our hypothesis states that 5-fluorouracil (5FU) also kills cultured oral epithelial cells through programmed cell death or apoptosis. Cultured oral cancer cells were exposed to an optimum dose of 20 mg/ml of 5FU. Cells were analyzed for changes in cell cycle distribution and induction of cell death including apoptosis. Normal control, human papilloma virus-immortalized (PP), ATCC SCC cell line (CA1) and two primary oral SCC cell lines (CA3 and -4) were studied. Inhibition of apoptosis by a pan-caspase inhibitor was used. SYTO 11 flow cytometry showed increased apoptosis in all 5FU-treated cell cultures compared to untreated controls. The results show biological variation in apoptotic response. CA1 had the lowest apoptotic rate of the cancer cell lines at 1.5%. Next lowest was CA3, followed by CA4 and PP. In addition, alteration in the G1 and S phase fractions were found. Untreated CA1 showed 28% G1, 53% S compared to 43% G1, and 40% S of treated. We investigated the pathway of apoptosis using the pan-caspase inhibitor IDN-1529 by methylthiazolyl diphenyl tetrazolium bromide (MTT) colorimetric analysis. Results showed mild inhibition of cell death when cells were incubated with 50 microM IDN-1529 for 24 h. This suggests a probable caspase-dependent apoptotic pathway. In conclusion, our data suggest that 5FU induces oral cancer cell death through apoptosis and that biological variation exists between normal and cancer cells and between different types of cancer cells themselves. Our data indicate that cultures of a useful in vitro model for chemosensitivity assays are possible. Our results also suggest a caspase-dependent pathway for chemocytotoxicity in oral SCC.

Antimetabolites, Antineoplastic↗

PubMed2000

Left ventricular tachycardia originating near the left main coronary artery.

Eight patients with idiopathic ventricular tachycardia (VT) underwent mapping and radiofrequency ablation. Mapping showed VT originating in the high posterolateral left ventricular outflow tract in proximity to the left main and proximal circumflex coronary arteries. Ablation was not attempted due to this proximity to the left main and proximal circumflex coronary arteries. Ablation was not attempted due to this proximity in 2 patients and limited in 1 patient. It was successful in VT suppression in 5 of 6 patients.

Adult↗

PubMed2000

ART restorations and sealants placed in Chinese school children--results after three years.

OBJECTIVES: These were to assess whether ART restorations and sealants could be provided to children in a school environment in China, to assess patient acceptability of the ART approach, and to evaluate on a longitudinal basis the treatments performed. METHODS: This study was conducted in Deyang, Sichuan Province, in western China. A total of 294 ART restorations were placed in 197 children and 191 fissure sealants were placed in 140 children by five middle-level dentists in four secondary schools. Standard instruments and procedures for ART were used. The restorative material used was a high-strength glass-ionomer (Ketac-Molar, ESPE). The treatments were evaluated annually after placement by the same examiner who had not been involved in the placement of the restorations nor sealants using explorers and mouth-mirrors. At the 3-year examination an independent external examiner evaluated the restorations using USPHS criteria. RESULTS: Most of the children did not report discomfort during treatment and 92% were willing to receive ART restorations again. The cumulative 1-year and 3-year survival rates of small Class I restorations were 99% and 92% respectively. The corresponding figures for large Class I restorations were 90% and 77%. After 3 years, 72% of the sealants were either partially or completely retained. Only 2% of the sealed teeth developed fissure caries and these involved teeth where the sealants had been lost. Similar success rates were found using USPHS criteria. CONCLUSIONS: The ART approach for preventing and treating tooth decay in Chinese school children was shown to be appropriate, effective and acceptable. The 3-year survival rates of the restorations were high but were related to the size and type of the restoration.

Adolescent↗

PubMed2000

Mutations of PVRL1, encoding a cell-cell adhesion molecule/herpesvirus receptor, in cleft lip/palate-ectodermal dysplasia.

Cleft lip, with or without cleft palate (CL/P), is one of the most common birth defects, occurring in 0.4 to 2.0 per 1,000 infants born alive. Approximately 70% of CL/P cases are non-syndromic (MIM 119530), but CL/P also occurs in many single-gene syndromes, each affecting a protein critical for orofacial development. Here we describe positional cloning of the gene responsible for an autosomal recessive CL/P-ectodermal dysplasia (ED) syndrome (CLPED1; previously ED4; ref. 2), which we identify as PVRL1, encoding nectin-1, an immunoglobulin (Ig)-related transmembrane cell-cell adhesion molecule that is part of the NAP cell adhesion system. Nectin-1 is also the principal cell surface receptor for alpha-herpesviruses (HveC; ref. 7), and the high frequency of CLPED1 on Margarita Island in the Caribbean Sea might result from resistance of heterozygotes to infection by these viruses.

Amino Acid Sequence↗

PubMed2000

Effects of obesity and body fat distribution on lipids and lipoproteins in nondiabetic American Indians: The Strong Heart Study.

OBJECTIVES: To examine the relationship between obesity and lipoprotein profiles and compare the effects of total obesity and central adiposity on lipids/lipoproteins in American Indians. RESEARCH METHODS AND PROCEDURES: Participants were 773 nondiabetic American Indian women and 739 men aged 45 to 74 years participating in the Strong Heart Study. Total obesity was estimated using body mass index (BMI). Central obesity was measured as waist circumference. Lipoprotein measures included triglycerides, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, apolipoprotein AI (apoAI), and apolipoprotein B (apoB). Partial and canonical correlation analyses were used to examine the associations between obesity and lipids/ lipoproteins. RESULTS: Women were more obese than men in Arizona (median BMI 32.1 vs. 29.2 kg/m2) and South Dakota and North Dakota (28.3 vs. 28.0 kg/m2), but there was no sex difference in waist circumference. Men had higher apoB and lower apoAI levels than did women. In women, when adjusted for center, gender, and age, BMI was significantly related to HDL cholesterol (r = -0.24, p < 0.001). There was a significant but weak relation with apoAI (r = -0.14, p < 0.001). Waist circumference was positively related to triglycerides (r = 0.14, p < 0.001) and negatively related to HDL cholesterol (r = -0.23, p < 0.001) and apoAI (r = -0.13, p < 0.001). In men, BMI was positively correlated with triglycerides (r = 0.30, p < 0.001) and negatively correlated with HDL cholesterol (r = -0.35, p < 0.001) and apoAI (r = -0.23, p < 0.001). Triglycerides increased with waist circumference (r = 0.30, p < 0.001) and HDL cholesterol decreased with waist circumference (r = -0.36, p < 0.001). In both women and men there was an inverted U-shaped relationship between obesity and waist with LDL cholesterol and apoB. In canonical correlation analysis, waist circumference received a greater weight (0.86) than did BMI (0.17) in women. However, the canonical weights were similar for waist (0.46) and BMI (0.56) in men. Only HDL cholesterol (-1.02) carried greater weight in women, whereas in men, triglycerides (0.50), and HDL cholesterol (-0.64) carried a large amount of weight. All the correlation coefficients between BMI, waist circumference, and the first canonical variable of lipids/lipoproteins or between the individual lipid/lipoprotein variables and the first canonical variable of obesity were smaller in women than in men. Triglycerides and HDL cholesterol showed clinically meaningful changes with BMI and waist circumference in men. All lipid/lipoprotein changes in women in relation to BMI and waist circumference were minimal. DISCUSSION: The main lipoprotein abnormality related to obesity in American Indians was decreased HDL cholesterol, especially in men. Central adiposity was more associated with abnormal lipid/lipoprotein profiles than general obesity in women; both were equally important in men.

Adipose Tissue↗

PubMed2000

Effect of brief exposure to mitomycin C on cultured human nasal mucosa fibroblasts.

PURPOSE: To observe the effect of mitomycin C (MMC) on cultured human nasal mucosa fibroblasts. METHODS: Cultured human nasal mucosa fibroblasts were exposed to MMC (0.1-0.4 mg/ml) for 1 to 5 minutes. The viability of the fibroblasts was determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay; DNA fragmentation (apoptosis) by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL); apoptotic percentage by flow cytometry; and morphology by light microscopy. RESULTS: A portion of the fibroblasts survived the mitomycin treatment and showed evidence of regrowth within 2 to 3 days. These cells reached confluence in 5 to 7 days. The inhibition rates by MTT assay of 0.4 mg/ml MMC for 5-minute exposures was 31.3%. Dose-response effect was noted with the lower concentrations and shorter exposure times where the inhibition rates were lower (but not significantly so). DNA fragmentation was observed in fibroblasts 24 hours after MMC exposure (0.4 mg/ml) for 5 minutes compared with normal control. The apoptotic rate of fibroblasts treated by 0.4 mg/ml MMC was significantly higher than the control (p < 0.05). CONCLUSIONS: Short MMC exposure times have a variable cytotoxic effect and inhibit proliferation of cultured nasal mucosa fibroblasts. MMC also can induce apoptosis with a 5-minute exposure time. Therefore, it is possible that MMC has a complex effect in dacryocystorhinostomy.

Alkylating Agents↗

PubMed2000

Effect of MCI-154, a calcium sensitizer, on calcium sensitivity of myocardial fibers in endotoxic shock rats.

This study was designed to investigate the effect of a calcium sensitizer on the Ca2+ sensitivity of myocardial fibers in endotoxic shock rats. Right ventricular papillary muscles from sham shock or endotoxic shock rats were skinned by incubation in saponin solution. Forces of the skinned muscles were recorded when they were activated sequentially by different pCa (-log[Ca2+]) activating solutions with or without positive inotropic agents. Tension-pCa relationship curve of skinned fibers delineated the affinity of troponin C(TnC) for Ca2+ and the medium value pCa50 (pCa required for producing 50% of maximal Ca2+-activated tension) was taken as the quantitative index of Ca2+ sensitivity of TNC. It was found that the maximal Ca2+ activated tension (Tmax) was lower, tension-pCa relationship curve was shifted rightward, and the pCa50 was reduced significantly in endotoxic shock group compared with that of sham shock group. Milrinone could not counteract the above abnormalities. However, when skinned right ventricular papillary fibers from endotoxic shock rats were dealt with activating solutions containing 1 x 10(-5) M MCI-154, the Tmax was significantly increased, the tension-pCa relationship curve was shifted leftward. The pCa50 in MCI-154 group was increased to an extent similar to that of sham shock group and markedly higher than the values of endotoxic shock group and milrinone group. Furthermore, such effects of MCI-154 were concentration dependent. It can been concluded that the sensitivity of cardiac contractile proteins to Ca2+ in endotoxic shock rats is decreased. MCI-154, a calcium sensitizer, can significantly reverse the decreased sensitivity and increase Tmax of myocardial muscles from endotoxic shock rats.

Animals↗

PubMed2000

Suppression of sodium current by arachidonic acid in atrial myocytes from patients with coronary heart disease.

This study was designed to examine the effects of arachidonic acid (AA) on atrial myocytes from patients with coronary heart disease. The patch clamp technique was used to record sodium current in human atrial myocytes, before and after administration of intracellular AA. The suppression of sodium current induced by AA was voltage- and dose-dependent, with an IC50 of 10.3 microM. The activation curves of relative conductance in absence versus presence of AA, 10 microM, nearly overlapped. The 50% channel activation was at 40.8 +/- 2.7 mV in the control state versus 42.5 +/- 3.1 mV in presence of AA (n = 10, P > 0.05). AA at 10 microM shifted the steady-state inactivation relationship significantly, from 94.5 +/- 3.4 mV to 116.6 +/- 4.1 mV (n = 11, P < 0.01) at the 50% channel inactivation point. The 50% recovery time from the inactivation state was significantly longer in the presence of 10 microM AA (27.3 +/- 1.7 ms), than in the control state (5.9 +/- 0.4 ms n = 8, P < 0.01). In conclusion, AA suppressed the sodium current and prolonged the duration of recovery from inactivation in atrial myocytes from patients with coronary heart disease.

Aged↗

PubMed2000

Assembly of double-shelled, virus-like particles in transgenic rice plants expressing two major structural proteins of rice dwarf virus.

Rice dwarf virus (RDV) is a double-shelled particle that contains a major capsid protein (P8), a major core protein (P3), several minor core proteins, and viral genomic double-stranded RNA. Coexpression of P8 and P3 in transgenic rice plants resulted in formation of double-shelled, virus-like particles (VLPs) similar to the authentic RDV particles. The VLPs were not detected in transgenic rice plant cells expressing P8 alone. This in vivo result suggests that P8 interacted with P3 and that these two proteins provide the structural integrity required for the formation of VLPs in rice cells independently of other structural proteins, nonstructural proteins, or viral genomic double-stranded RNAs.

Capsid↗