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H Zhang

Publications and source records attributed to H Zhang.

At least 289 records · Page 16Linked to original sources
PubMed2001

Modeling the third loop of short-chain snake venom neurotoxins: roles of the short-range and long-range interactions.

The influence of long-range interactions on local structures is an important issue in understanding protein folding process and protein structure stability. Using short-chain snake venom neurotoxin as a model system, we have studied the conformational properties of eight different loop III sequences either in the environment of one of the short-chain neurotoxin, erabutoxin b (PDB ID 1nxb), or in free state by Monte Carlo simulated annealing method. The surrounding protein structure was found to be crucial in stabilizing the loop conformation. Although all the eight peptides prefer type V beta turn in solution, three of them (KPGI, KPGV, KSGI) turn to type II beta turn and the other five (KKGI, KKGV, KNGI, KQGI, and KRGV) are confined to more rigid type V beta turn conformation in the protein structure. Using flexible tetra-glycine-peptide to screen the backbone conformational space in the protein environment also validates the results. This study shows that long-range interactions do contribute to the stability and the types of conformation for a surface loop in protein, while short-range interactions may only provide candidate conformations, which then have to be filtered by the long-range interactions further.

Amino Acid Motifs↗
PubMed2001

Fluorometric determination of 2'-beta-fluoro-2',3'-dideoxyadenosine 5'-triphosphate, the active metabolite of a new anti-human immunodeficiency virus drug, in human lymphocytes.

A sensitive precolumn derivatization method has been developed to measure the 5'-triphosphate of 2'-beta-fluoro-2',3'-dideoxyadenosine (F-ddA, lodenosine), a new anti-HIV drug, in human lymphocytes by HPLC using fluorescence detection. Reaction of chloroacetaldehyde with F-ddA triphosphate in extracts from human lymphocytes produces a highly fluorescent etheno adduct. This derivative is then separated and quantitated by reverse-phase paired-ion chromatography. Degradation of natural nucleic acid ribosides, such as ATP, using periodate oxidation simplifies the chromatogram and minimizes interference with detection of the target analyte. This method, modeled using cultured MOLT-4 T-lymphocytes, achieves a linear detector response for peak area measurements over the range 2.5 to 22.5 pmol (50-450 nM using 50 microl sample). Analyte recovery is greater than 90%, and the method achieves a limit of detection and limit of quantitation of 1.4 and 2.5 pmol per HPLC injection (50 microl sample containing cellular extract from 2.5 x 10(6) cells), respectively. Application of this method to measure F-ddATP in peripheral blood mononuclear cells from HIV-infected patients treated with F-ddA at 3.2 mg/kg twice daily for 22 days shows F-ddATP levels which range from 1.5 to 3.5 pmol/10(6) cells.

Anti-HIV Agents↗
PubMed2001

Regional brain and ventricular volumes in Tourette syndrome.

BACKGROUND: The pathophysiology of Tourette syndrome (TS) is thought to involve disturbances in cortico-striato-thalamo-cortical circuitry. The morphological characteristics of the cortical and associated white matter portions of these circuits have not been previously examined in TS subjects. METHODS: High-resolution anatomical magnetic resonance images were acquired in 155 TS and 131 healthy children and adults. The cerebrums and ventricles were isolated and then parcellated into subregions using standard anatomical landmarks. RESULTS: For analyses that included both children and adults, TS subjects were found to have larger volumes in dorsal prefrontal regions, larger volumes in parieto-occipital regions, and smaller inferior occipital volumes. Significant inverse associations of cerebral volumes with age were seen in TS subjects that were not seen in healthy controls. Sex differences in the parieto-occipital regions of healthy subjects were diminished in the TS group. The age-related findings were most prominent in TS children, whereas the diminished sex differences were most prominent in TS adults. Group differences in regional ventricular volumes were less prominent than in the cerebrum. Regional cerebral volumes were significantly associated with the severity of tic symptoms in orbitofrontal, midtemporal, and parieto-occipital regions. CONCLUSIONS: Broadly distributed cortical systems are involved in the pathophysiology of TS. Developmental processes, sexual dimorphisms, and compensatory responses in these cortical regions may help to modulate the course and severity of tic symptoms.

Adolescent↗
PubMed2001

Gelation behaviour of konjac glucomannan with different molecular weights.

The deacetylation and gelation of konjac glucomannan (KGM) following alkali addition was investigated by Fourier transform infrared, while the rheological properties of KGM with different molecular weights were studied by dynamic viscoelastic measurements in shear mode and penetration force tests. It was found that gelation occurred after significant deacetylation had taken place. Rheometrical studies revealed that KGM with different molecular weights exhibited different gelation characteristics in small amplitude oscillatory shear flow. For the samples of fractionated KGM with lower molecular weights, a decrease in both the storage shear modulus (G') and loss shear modulus (G") was observed during gelation at temperatures above 75 degrees C. It is suggested that the decrease results from the wall slip between sample and measuring geometry owing to a rapid gelation process with syneresis and/or disentanglement of molecular chains adsorbed on the surface of parallel plates from those located in the bulk. Penetration force tests were employed to confirm the occurrence of slippage and thereby no decreases in rigidity of samples were observed during gelation. For the native KGM samples decreases in G' and G" during gelation were not observed, and it is suggested that this is due to the effect of the higher molecular weight and increased solution viscosity of these samples on the gelation kinetics.

Acetylation↗
PubMed2001

Analysis of genetic alterations in primary nasopharyngeal carcinoma by comparative genomic hybridization.

To identify genetic alterations associated with the development and progression of human nasopharyngeal carcinoma (NPC), 57 tumors were analyzed by comparative genomic hybridization (CGH). In 47 cases, chromosomal imbalances were found. Several recurrent chromosomal abnormalities were identified in the present study. The most frequently detected chromosomal gains involved chromosome arms 12q (24 cases, 51%), 4q (17 cases, 36%), 3q (16 cases, 34%), 1q (15 cases, 32%), and 18q (15 cases, 32%). Common regions of gain involved 12q13--q15, 4q12--q21, and 3q21--q26. High-copy-number increases of chromosomal materials were detected in four chromosomal regions, 3q21--q26.2, 4p12--q21, 8p, and 12q14--q15. The most frequently detected loss of chromosomal materials involved chromosome arms 16q (26 cases, 55%), 14q (21 cases, 45%), 1p (20 cases, 43%), 3p (20 cases, 43%), 16p (19 cases, 40%), 11q (17 cases, 36%), and 19p (16 cases, 34%). The most common regions of loss involved 14q24--qter, 1pter--p36.1, 3p22--p21.3, 11q21--qter, and the distal region of 19p. Genomic alterations detected by CGH were compared and found to be largely consistent with those identified in banding analysis and loss of heterozygosity studies. However, several previously unrecognized recurrent alterations were also identified in the present study, including gain of 4q and 18q, and loss of 16q, 14q, and 19p. In addition, gain of 1q, 8q, 18q, and loss of 9q showed a statistically significant association with advanced clinical stages (P < 0.05). Identification of recurrent sites of chromosomal gain and loss identify regions of the genome that may contain oncogenes or tumor suppressor genes, respectively, which may be involved in the tumorigenesis of NPC. Published 2000 Wiley-Liss, Inc.

Adult↗
PubMed2001

Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component: association with inhibition of p27 accumulation.

The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [(3)H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10- to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation. Mol. Carcinog. 30:37-46, 2001.

Animals↗
PubMed2001

Proteomic characterization of early-stage differentiation of mouse embryonic stem cells into neural cells induced by all-trans retinoic acid in vitro.

Embryonic stem (ES) cells are totipotent stem cells, which can differentiate into various kinds of cell types, including neurons. They are widely used as a model system for investigating mechanisms of differentiation events during early mouse development. In this study, proteomic techniques were used to approach the protein profile associated with the early-stage differentiation of ES cells into neuronal cells induced by all-trans retinoic acid (ATRA) in vitro. In comparison of the protein profile of parent ES cells with that of ES-derived neural-committed cells, which was induced by ATRA for four days, 24 differentially displayed protein spots were selected from two-dimensional electrophoresis (2-DE) gels for further protein identification by pepide mass fingerprinting (PMF). Nine proteins were known to being involved in the process of neural differentiation and/or neural survival. Of those, alpha-3/alpha-7 tubulin and vimentin were down-regulated, while cytokeratin 8, cytokeratin 18, G1/S-special cyclin D2, follistatin-related protein, NEL protein, platelet-activating factor acetylhydrolase IB alpha-subunit, and thioredoxin peroxidase 2 were upregulated during differentiation of ES cells to neural cells. Additionally, other 12 protein (five upregulated and seven downregulated) spots associated with ES cell differentiation into neuronal cells were not matched to known proteins so far, implicating that they might be novel proteins. The results above indicated that the molecular mechanisms of differentiation of ES cells to neural cells in vitro might be similar to those of other neural systems in vitro and identified that proteomic analysis is an effective strategy to comprehensively unravel the regulatory network of differentiation.

Animals↗
PubMed2001

Chromosomal DNA from a variety of bacterial species is present in synovial tissue from patients with various forms of arthritis.

OBJECTIVE: We and others have reported the presence of Chlamydia and other bacterial species in joint specimens from patients with reactive arthritis (ReA). The present study was conducted to investigate whether bacteria other than those specified by diagnostic criteria for ReA could be identified in synovial fluid (SF) or tissue from patients with various arthritides, and whether the presence of such organisms corresponds to particular clinical characteristics in any patient set or subset. METHODS: DNA in synovial biopsy samples and SF obtained from 237 patients with various arthritides, including ReA, rheumatoid arthritis, and undifferentiated oligoarthritis, was assayed by polymerase chain reaction (PCR) using "panbacterial" primers; we chose only samples known to be PCR negative for Chlamydia, Borrelia, and Mycoplasma species. PCR products were cloned, and cloned amplicons from each sample were sequenced; DNA sequences were compared against all others in GenBank for identification of bacterial species involved. RESULTS: Ten percent of patient samples were PCR positive in panbacterial screening assays. Bacterial species identified belonged to the genera Neisseria, Acinetobacter, Moraxella, Salmonella, Pseudomonas, and others. Thirty-five percent of PCR-positive patients showed the presence of DNA from more than a single bacterial species in synovium; overall, however, we could identify no clear relationship between specific single or multiple bacterial species in the synovium and any general clinical characteristics of any individual or group of patients. CONCLUSION: This analysis provides the first systematic attempt to relate bacterial nucleic acids in the synovium to clinical characteristics, joint findings, and outcomes. Many patients with arthritis have bacterial DNA in the joint, and, in some cases, DNA from more than a single species is present. However, except for 1 case of a control patient with staphylococcal septic arthritis, it is not clear from the present study whether the synovial presence of such organisms is related to disease pathogenesis or evolution in any or all cases.

Acinetobacter↗
PubMed2001

Jumping translocations are common in solid tumor cell lines and result in recurrent fusions of whole chromosome arms.

Jumping translocations (JTs) and segmental jumping translocations (SJTs) are unbalanced translocations involving a donor chromosome arm or chromosome segment that has fused to multiple recipient chromosomes. In leukemia, where JTs have been predominantly observed, the donor segment (usually 1q) preferentially fuses to the telomere regions of recipient chromosomes. In this study, spectral karyotyping (SKY) and FISH analysis revealed 188 JTs and SJTs in 10 cell lines derived from carcinomas of the bladder, prostate, breast, cervix, and pancreas. Multiple JTs and SJTs were detected in each cell line and contributed to recurrent unbalanced whole-arm translocations involving chromosome arms 5p, 14q, 15q, 20q, and 21q. Sixty percent (113/188) of JT breakpoints occurred within centromere or pericentromeric regions of the recipient chromosomes, whereas only 12% of the breakpoints were located in the telomere regions. JT breakpoints of both donor and recipient chromosomes coincided with numerous fragile sites as well as viral integration sites for human DNA viruses. The JTs within each tumor cell line promoted clonal progression, leading to the acquisition of extra copies of the donated chromosome segments that often contained oncogenes (MYC, ABL, HER2/NEU, etc.), consequently resulting in tumor-specific genomic imbalances. Published 2001 Wiley-Liss, Inc.

Carcinoma↗
PubMed2001

Tree-based linkage and association analyses of asthma.

Tree-based linkage analyses and association studies are introduced and applied for two data sets on asthma from Genetic Analysis Workshop 12. Consistent and strong evidence of linkage and association to markers on chromosomes 1 and 11 is revealed. Linkage to chromosome 16 in one data set and association with D6S276 in the other data set are also detected.

Adult↗
PubMed2001

Nitric oxide and Coxsackievirus B3 myocarditis: differential expression of inducible nitric oxide synthase in mouse heart after infection with virulent or attenuated virus.

Increased expression of inducible nitric oxide synthase (iNOS) has been found in inflammatory myocardial disease and increased production of nitric oxide (NO) has both an inhibitory effect on virus replication and a cytotoxic effect on host cells. To investigate the relationship between severity of enteroviral myocarditis and iNOS expression, a characterised murine model was infected with either cardiovirulent or an attenuated Coxsackievirus B3 and myocardial samples were collected on Day 7. The ability of these viruses to induce NOS expression was compared by measurement of iNOS enzyme activity and localisation of iNOS protein or peroxynitrite, a product of excessive NO production. In accordance with previous reports, high expression of iNOS was detected in mice infected with the cardiovirulent virus. The iNOS protein was located mainly in infiltrating macrophages in and around foci of necrotic myofibres where viral genomic RNA was detected. In contrast, the level of iNOS expression was significantly lower in mice infected with the attenuated virus. This correlates with fewer and smaller myocarditic lesions and less infiltrating cells in the heart. iNOS was not detected in mock-infected mice by the above assays. These findings suggest that one mechanism of attenuation may be associated with the reduced ability of the variant to induce NOS expression in the heart. This also confirms a cytotoxic role for NO in the pathogenesis of Coxsackievirus B3-induced myocarditis.

Animals↗
PubMed2001

Identification of TNF-alpha-sensitive sites in HCMVie1 promoter.

Viral vectors using the human cytomegalovirus immediate-early promoter (HCMVie1 promoter) are potentially efficient tools for gene delivery in vivo to diverse cell types. We previously demonstrated that two cytokines, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (INF-gamma), inhibited transgene expression from this promoter in skeletal and cardiac myocytes. In this study, electrophoretic mobility shift assays (EMSAs) were performed to identify the TNF-alpha response elements from the HCMVie1 promoter. The results show that TNF-alpha enhances the interaction of nuclear proteins from the C2C12 myocyte line with a single restricted segment of the HCMVie1 promoter. In vitro DNase I footprinting defined precisely the sites of interaction to two elements: nucleotides -1 to 0 and +24 to +36 relative to a transcription initiation cap homologous in the HCMVie1 promoter. These sites contain homologous sequences for cap initiation site (82%) and NFkappaB (62%) sites, respectively. Specificity was further ascertained by competitive EMSAs with wild-type and mutant oligonucleotide probes. Southwestern blotting showed that three proteins (45, 30, and 20 kDa) bound to this TNF-alpha-sensitive element, separately. However, EMSAs failed to prove a role for Yin Yang-1 (YY-1), NFkappaB (p65), or NFkappaB (p50) in binding to these sites. Our results provide evidence for two novel sites in the HCMVie1 promoter that are targets for TNF-alpha enhanced binding of transcription factors.

Antigens, Viral↗
PubMed2001

Experimental characterization of intermolecular multiple-quantum coherence pumping efficiency in solution NMR.

The behavior of intermolecular multiple-quantum coherences in a variety of simple liquids with different chemical and magnetic properties is investigated experimentally and modeled by numerical simulations based on modified Bloch equations. The effects of spin concentration, temperature, intramolecular conformational flexibility, chemical exchange, and spin-spin coupling on the formation of high-order coherences are examined. It is shown that any process that makes the Larmor frequency time-dependent may interfere with the formation of these coherences. Good agreement is achieved between experiments and simulation, using independently known values of the magnetization density, the rate constants for translational diffusion, spin-spin and spin-lattice relaxation, and radiation damping.

Algorithms↗
PubMed2001

Radiofrequency ablation for eradication of pulmonary tumor in rabbits.

BACKGROUND: Radiofrequency ablation (RFA) has emerged as an alternative for surgery in clinical oncology. This animal experiment was conducted to evaluate the feasibility of RFA in the treatment of pulmonary tumor. METHODS: Eighteen rabbits with pulmonary implantation of VX2 tumors were divided into two groups. Group A (n = 12) was treated with RFA by using a cooled-tip electrode technique. Group B (n = 6) received sham operation. The therapeutic efficacy was evaluated by survival rate, magnetic resonance imaging (MRI), postmortem microangiography, and histology. RESULTS: All animals in group B died within 3 months after tumor implantation. Tumor eradication was achieved in 9 of 12 rabbits (75.0%) in group A, of which 4 rabbits survived longer than 3 months free of disease and another 5 rabbits were found free of viable tumor when sacrificed. One rabbit was subjected to incomplete tumor ablation and two rabbits suffered from local tumor relapse and/or lung metastasis. The 3-month survival rate of RFA-treated rabbits was significantly higher (P < 0.01) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of five characteristic concentric zones, which corresponded to central needle track (zone A), tumor coagulation (zone B), pulmonary parenchyma coagulation (zone C), peripheral hemorrhage (zone D), and inflammatory layer (zone E) on histology. CONCLUSIONS: Eradication of pulmonary tumor could be achieved with current RFA technique in rabbits. MRI is a useful modality for assessment of lung tumor ablation.

Angiography↗
PubMed2001

Time course of inducible nitric oxide synthase activity following endotoxin administration in dogs.

An increased production of nitric oxide (NO) via the inducible isoform of NO synthase (iNOS) has been incriminated in the pathogenesis of septic shock. Since the time course of iNOS activity is not known during endotoxic shock in dogs, we measured iNOS activity, estimated by the rate of conversion of (14)C-arginine to (14)C-citrulline in the absence of calcium, in the heart, lung, liver, kidney, and gut at 1, 2, 3, 4, and 6 h after a bolus of Escherichia coli endotoxin (2 mg/kg, iv), in the dog. This model, including generous fluid administration, is associated with typical features of human septic shock, including low systemic vascular resistance, altered myocardial function and limited oxygen extraction capability. An increase in iNOS activity was observed at 4 h in the liver (0.24 vs 0.04 mU/mg/min) and at 6 h in the heart (0.26 vs 0.09 mU/mg/min). These findings may contribute to a better delineation of the involvement of NO in endotoxic shock, and to the evaluation of the therapeutic effects of NO inhibitors.

Animals↗
PubMed2001

Purification and characterization of human cell--cell adhesion molecule 1 (C-CAM1) expressed in insect cells.

The cell--cell adhesion molecule 1 (C-CAM1) plays an important role as a tumor suppressor for prostate cancer. Decreased expression of C-CAM1 was detected in prostate, breast, and colon carcinoma. Reexpression of C-CAM1 in prostate and breast cancer cell lines was able to suppress tumorigenicity in vivo. These observations suggest that C-CAM1 may be used as a marker for cancer detection or diagnosis. To generate monoclonal antibodies specific to C-CAM1, we have overexpressed full-length human C-CAM1 in Sf9 cells using a baculovirus expression system. The protein was purified 104-fold using nickel affinity chromatography. About 0.4 mg purified C-CAM1 was obtained from 200 mg of infected cells. When the purified protein was digested with peptidyl-N-glycosidase, the apparent mobility of the protein on SDS--PAGE changed from 90 to 58 kDa, which is close to the molecular weight predicted from the cloned cDNA sequence. This observation suggests that C-CAM1 was glycosylated on asparagine residues when expressed in Sf9 cells. Western blotting and internal protein sequencing analysis confirmed that the purified protein is human C-CAM1. Biochemical and functional assays indicate that this protein expressed in Sf9 cells displays characteristics similar to those of native protein, including adhesion function and glycosylation modification. Using this protocol, sufficient quantity of this protein can be produced with purity suitable for monoclonal antibody generation and biochemical study.

Adenosine Triphosphatases↗