Biomedical subjects

H Ding

Publications and source records attributed to H Ding.

At least 37 records · Page 2Linked to original sources

PubMed2003

Putative protein markers in the sera of men with prostatic neoplasms.

OBJECTIVE: To describe the preliminary identification of serum proteins that may be diagnostic markers in prostate cancer. PATIENTS AND METHODS: The study included 11 men referred for treatment of localized prostate cancer, 12 with benign prostatic hyperplasia (BPH) and 12 disease-free controls. For serum protein analysis, the protein-chip array surface-enhanced laser desorption/ionization (SELDI) technique was used (Ciphergen Biosystems, Fremont, CA). SELDI combines protein-chip technology with time-of-flight mass spectrometry, and offers the advantages of speed, simplicity and sensitivity. RESULTS: Three protein peaks were identified in the serum of men with prostate cancer and BPH, but not in controls, with relative molecular masses of 15.2, 15.9 and 17.5 kDa. These three proteins were significantly associated with BPH and prostate cancer when compared with controls (P = 0.001, 0.004, and 0.011, respectively, Kruskal-Wallis test). Interestingly, the 17.5 kDa protein was more abundant in five men with stage T1 prostate cancer than in eight with stage T2 (P = 0.016, two tailed Mann-Whitney U-test corrected for ties). CONCLUSIONS: These proteins, particularly the 15.9 kDa one, may be used for the diagnosis or monitoring of prostate cancer and differentiation from BPH, and have the potential for antibody-based chip SELDI-TOF technology. Identified proteins may be targets for immunotherapy.

Biomarkers, Tumor↗

PubMed2002

A matrix-assisted laser desorption/ionization time-of-flight based method for screening the 1691G --> A mutation in the factor V gene.

A point mutation, 1691 G --> A in the coagulation factor V gene results in an Arg506 --> Gln amino acid substitution in the factor V molecule. This mutation, defined as factor VLEIDEN, results in activated protein C (APC) resistance and is the most common genetic risk factor for familial thrombophilia. A new mini-sequencing method using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was developed for the screening of the 1691G --> A substitution in factor V. In this method, a fragment of genomic DNA containing the 1691st base is first amplified, followed by mini-sequencing in the presence of dGTP and ddATP, ddCTP, and ddTTP. In this manner, the primer is extended by one base from one allele and two bases from the other allele. The extended products are analyzed using MALDI-TOF mass spectrometry. The base at position 1691 is identified based on the number of nucleotides added. We have used this method to genotype 16 APC-resistant patients previously identified by conventional methods and 11 normal control samples. The genotypes of all samples were correctly identified. This method is accurate, fast, and potentially allows for simultaneous multiplex genotyping of a number of mutation sites associated with thrombophilia and clot formation.

Activated Protein C Resistance↗

PubMed2002

RT-PCR heteroduplex analysis permits differentiation of transgene and host gene expression in a transgenic animal model.

In transgenic animal models, the conservation of DNA sequences between the transgene and the host wild-type gene can complicate the evaluation of the expression of each gene. The potential for gene silencing may complicate matters further. Here we report the use of RT-PCR heteroduplex analysis to differentiate the expression of a transgene and its homologous wild-type, even when these genes are very similar in their respective DNA sequences. We designed RT-PCR primers to amplify identically sized 243-bp fragments within the DNA binding domain of the p53 gene from both human and mouse mRNA samples. Ten samples from human p53 (273H) transgenic mice and 10 samples from wild-type controls were tested. Heteroduplex bands were formed in all transgenic samples but were absent from all wild-type samples. In addition, RT-PCR heteroduplex analysis was able in one sample to differentiate a silenced transgene from its wild-type allele, without the assistance of sequencing or labeling. In summary, the RT-PCR heteroduplex analysis is easy to use and has the ability to screen a large number of samples in a short time. The RT-PCR heteroduplex analysis is especially useful for the detection of expression when a transgene and the host homologous endogenous allele are too conserved in sequence to design species-specific RT-PCR primers.

Animals↗

PubMed2001

Increased expression of unmethylated CDKN2D by 5-aza-2'-deoxycytidine in human lung cancer cells.

DNA hypermethylation of CpG islands in the promoter region of genes is associated with transcriptional silencing. Treatment with hypo-methylating agents can lead to expression of these silenced genes. However, whether inhibition of DNA methylation influences the expression of unmethylated genes has not been extensively studied. We analysed the methylation status of CDKN2A and CDKN2D in human lung cancer cell lines and demonstrated that the CDKN2A CpG island is methylated, whereas CDKN2D is unmethylated. Treatment of cells with 5-aza-2'-deoxycytidine (5-Aza-CdR), an inhibitor of DNA methyltransferase 1, induced a dose and duration dependent increased expression of both p16(INK4a) and p19(INK4d), the products of CDKN2A and CDKN2D, respectively. These data indicate that global DNA demethylation not only influences the expression of methylated genes but also of unmethylated genes. Histone acetylation is linked to methylation induced transcriptional silencing. Depsipeptide, an inhibitor of histone deacetylase, acts synergistically with 5-Aza-CdR in inducing expression of p16(INK4a) and p19(INK4d). However, when cells were treated with higher concentrations of 5-Aza-CdR and depsipeptide, p16(INK4a) expression was decreased together with significant suppression of cell growth. Interestingly, p19(INK4d) expression was enhanced even more by the higher concentrations of 5-Aza-CdR and depsipeptide. Our data suggest that p19(INK4d) plays a distinct role from other INK4 family members in response to the cytotoxicity induced by inhibition of DNA methylation and histone deacetylation.

Azacitidine↗

PubMed2001

Coherent quasiparticle weight and its connection to high-T(c) superconductivity from angle-resolved photoemission.

We study the doping and temperature dependence of the single-particle coherent weight, z(A), for high- T(c) superconductors Bi(2)Sr(2)CaCu(2)O(8+x) using angle-resolved photoemission. We find that at low temperatures the coherent weight z(A) at (pi,0) is proportional to the carrier concentration x and that the temperature dependence of z(A) is similar to that of the c-axis superfluid density. We show that, for a wide range of carrier concentration, the superconducting transition temperature scales with the product of the low-temperature coherent weight and the maximum superconducting gap.

Journal Article↗

PubMed2001

Microscopic electronic inhomogeneity in the high-Tc superconductor Bi2Sr2CaCu2O8+x.

The parent compounds of the copper oxide high-transition-temperature (high-Tc) superconductors are unusual insulators (so-called Mott insulators). Superconductivity arises when they are 'doped' away from stoichiometry. For the compound Bi2Sr2CaCu2O8+x, doping is achieved by adding extra oxygen atoms, which introduce positive charge carriers ('holes') into the CuO2 planes where the superconductivity is believed to originate. Aside from providing the charge carriers, the role of the oxygen dopants is not well understood, nor is it clear how the charge carriers are distributed on the planes. Many models of high-Tc superconductivity accordingly assume that the introduced carriers are distributed uniformly, leading to an electronically homogeneous system as in ordinary metals. Here we report the presence of an electronic inhomogeneity in Bi2Sr2CaCu2O8+x, on the basis of observations using scanning tunnelling microscopy and spectroscopy. The inhomogeneity is manifested as spatial variations in both the local density of states spectrum and the superconducting energy gap. These variations are correlated spatially and vary on the surprisingly short length scale of approximately 14 A. Our analysis suggests that this inhomogeneity is a consequence of proximity to a Mott insulator resulting in poor screening of the charge potentials associated with the oxygen ions left in the BiO plane after doping, and is indicative of the local nature of the superconducting state.

Journal Article↗

PubMed2001

L-cysteine-mediated destabilization of dinitrosyl iron complexes in proteins.

Nitric oxide is a signaling molecule in intercellular communication as well as a powerful weapon used by macrophages to kill tumor cells and pathogenic bacteria. Here, we show that when Escherichia coli cells are exposed to nitric oxide, its ferredoxin [2Fe-2S] cluster is nitrosylated, forming the dinitrosyl iron complex with a characteristic EPR signal at g(av) = 2.04. Such formed ferredoxin dinitrosyl iron complex is efficiently repaired in E. coli cells even in the absence of new protein synthesis. However, the repair activity is completely inactivated once E. coli cells are disrupted, indicating that repairing the ferredoxin dinitrosyl iron complex requires cellular reducing equivalents. In search of such cellular factors, we find that l-cysteine can effectively eliminate the EPR signal of the ferredoxin dinitrosyl iron complex and release the ferrous iron from the complex. In contrast, N-acetyl-l-cysteine and reduced glutathione are much less effective. l-Cysteine seems to have a general function, since it can also remove the otherwise stable dinitrosyl iron complexes from proteins in the cell extracts prepared from the E. coli cells treated with nitric oxide. We propose that l-cysteine is responsible for removing the dinitrosyl iron complexes from the nitric oxide-modified proteins into which a new iron-sulfur cluster will be reassembled.

Cysteine↗

PubMed2001

Astrocyte-specific expression of activated p21-ras results in malignant astrocytoma formation in a transgenic mouse model of human gliomas.

Activation of the p21-ras signaling pathway from aberrantly expressed receptors promotes the growth of malignant human astrocytomas. We developed a transgenic mouse astrocytoma model using the glial fibrillary acidic protein (GFAP) promoter to express oncogenic V(12)Ha-ras, specifically in astrocytes. The development of GFAP-immunoreactive astrocytomas was directly proportional to the level of V(12)Ha-ras transgene expression. Chimeras expressing high levels of V(12)Ha-ras in astrocytes died from multifocal malignant astrocytomas within 2 weeks, whereas those with moderate levels went to germ-line transmission. Ninety-five percent of these mice died from solitary or multifocal low- and high-grade astrocytomas within 2-6 months. These transgenic astrocytomas are pathologically similar to human astrocytomas, with a high mitotic index, nuclear pleomorphism, infiltration, necrosis, and increased vascularity. Derivative astrocytoma cells are tumorigenic upon inoculation in another host. The transgenic astrocytomas exhibit additional molecular alterations associated with human astrocytomas, including a decreased or absent expression of p16, p19, and PTEN as well as overexpression of EGFR, MDM2, and CDK4. Cytogenetic analysis revealed consistent clonal aneuploidies of chromosomal regions syntenic with comparable loci altered in human astrocytomas. Therefore, this transgenic mouse astrocytoma model recapitulates many of the molecular histopathological and growth characteristics of human malignant astrocytomas in a reproducible, germ-line-transmitted, and high-penetrance manner.

Animals↗

PubMed2001

Lipid and signal peptide-induced conformational changes within the C-domain of Escherichia coli SecA protein.

SecA ATPase is an essential component of the Sec-dependent protein translocation machinery. Upon interaction with the plasma membrane containing SecYE, preprotein, and ATP, SecA undergoes cycles of membrane insertion and retraction resulting in the translocation of segments of the preprotein to the trans side of the membrane. To study the structural basis of SecA function, we employed fluorescence spectroscopy along with collisional quenchers with a set of SecA proteins containing single tryptophan substitutions. Our data show that among the seven naturally occurring tryptophan residues of Escherichia coli SecA, only the three tryptophan residues contained within the C-domain contributed significantly to the fluorescence signal, and they occupied distinct local environments in solution: Trp723 and Trp775 were found to be relatively solvent accessible and inaccessible, respectively, while Trp701 displayed an intermediate level of solvent exposure. Exposure to increased temperature or interaction with model membranes or signal peptide elicited a similar conformational response from SecA based upon the fluorescence signals of the SecA-W775F and SecA-W723F mutant proteins. Specifically, Trp775 became more solvent exposed, while Trp723 became less solvent accessible under these conditions, indicating similarities in the overall conformational change of the C-domain promoted by temperature or translocation ligands. Only Trp701 did not respond in parallel to the different conditions, since its solvent accessibility changed only in the presence of signal peptide. These results provide the first detailed structural information about the C-domain of SecA and its response to translocation ligands, and they provide insight into the conformational changes within SecA that drive protein translocation.

Adenosine Triphosphatases↗

PubMed2001

Sonographic diagnosis of pancreatic islet cell tumor: value of intermittent harmonic imaging.

We describe a case of nonfunctioning islet cell tumor of the pancreas diagnosed preoperatively by intermittent harmonic power Doppler imaging and digital subtraction gray-scale harmonic imaging and the use of the contrast agent SH U 508A (Levovist). Hypervascularity and tumor perfusion were clearly demonstrated with both harmonic imaging techniques in the early arterial phase. Sonographic findings were confirmed by other modalities and by histopathologic examination.

Adenoma, Islet Cell↗

PubMed2001

Cholesterol biosensors prepared by layer-by-layer technique.

The analysis of formation, deposition and characterization of cholesterol oxidase (COX) layer-by-layer films were performed. Initially, a layer of polyanion, poly(styrene sulfonate) (PSS) was adsorbed followed by a layer of polycation, poly(ethylene imine) (PEI) on each solid substrate from aqueous solutions. The alternating layers were formed by consecutive adsorption of polycations (PEI) and negatively charged proteins (COX) and cholesterol esterase (CE). A strong interaction between protein and polyelectrolyte improves the stability of the alternating multilayer; however, it can change a native protein conformation and impair the protein activity. The PSS/PEI/COX, PSS/PEI/COX/PEI/CE, PSS/PEI/COX-CE/PEI etc. layered structures were prepared on the surface of a platinum electrode, ITO coated glass plate, quartz crystal microbalance, quartz plates, mica and silicon substrates. Optical and gravimetric measurements based on an ultraviolet-visible absorption spectroscopy and a quartz crystal microbalance revealed that the enzyme multilayers thus prepared consist of molecular layered of the proteins. The surface morphology of such bilayer films was investigated by using atomic force microscopy. The electrochemical redox processes of the enzyme-layered films deposited either on platinum or ITO coated glass plate were investigated. The response current of cholesterol oxidase electrode with concentration of cholesterol was investigated at length.

Biosensing Techniques↗

PubMed2001

Mouse astrocytoma models: embryonic stem cell mediated transgenesis.

The development of rational and targeted therapies for human astrocytomas is heavily dependent on our knowledge of its molecular pathogenesis, combined with the generation of appropriate pre-clinical mouse models. The ability to manipulate the mouse genome. which is nearing completion and is highly homologous to its human counterpart, has significantly accelerated our ability to create transgenic mouse models that replicate the pathological and molecular characteristics found in human astrocytomas. These models should serve to further our knowledge of the molecular pathogenesis of human astrocytomas, and serve as useful reagents to test conventional and novel therapeutics.

Animals↗

PubMed2001

Senescent expression of genes coding tropoelastin, elastase, lysyl oxidase, and tissue inhibitors of metalloproteinases in rat vocal folds: comparison with skin and lungs.

Histology studies indicate that vocal elastin content accumulates with age, suggesting possible contribution of elastin to age-associated voice changes. However, the underlying mechanism remains unclear. Using a reverse-transcriptase polymerase chain reaction (RT-PCR), mRNA levels of tropoelastin, elastase, lysyl oxidase, and tissue inhibitors of metalloproteinases (TIMP-1 to TIMP-4) were measured in vocal folds, tail skin, and lungs of rats at ages 1.5 +/- 0.5 weeks (neonatal), 6.0 +/- 0.5 months (adult), and 24 +/- 0.5 months (elderly). Vocal expression of both tropoelastin and lysyl oxidase peaks during the neonatal stage, followed by a significant decrease. Gene expression for elastase in the vocal folds of adult rats is not dissimilar to the neonatal levels. The levels in the elderly rots, however, show marked increase, to as much as 201% of the neonatal levels (p < .05). On the other hand, there is no conspicuous age-dependent variation in vocal expression of TIMPs. Gene expression of tropoelastin was similar in rat skin, lung, and vocal folds. In summary, compared to what is found in adult rats, there is a significant up-regulation in the expression of vocal elastase in the elderly animals in the presence of unchanged vocal expression of tropoelastin, lysyl oxidase, and TIMPs. As senescence occurs in both adult and elderly rats, tropoelastin and elastase expression are most affected. Gene expression for proteins affecting the amount of elastin in the vocal fold extracellular matrix does vary with age. These results may not be directly applicable to humans, because biomechanical forces experienced by human folds are likely different than those experienced by rats. However, in the absence of biomechanical forces experienced by humans, rat lungs, skin, and vocal folds display similar profiles of expression of genes coding the above-mentioned molecules. Similar profiles of expression for elastin genes across different tissue types not sharing similar environments suggests a common mechanism influencing senescence of these tissues. Human folds likely share a common similar mechanism of senescence with other organ systems, although organ-specific factors (oscillation, mechanical forces) are also likely operating.

Age Factors↗

PubMed2001

Senescent expression of genes coding collagens, collagen-degrading metalloproteinases, and tissue inhibitors of metalloproteinases in rat vocal folds: comparison with skin and lungs.

In humans, vocal tissue stiffness increases with age, suggesting a possible contribution of age-associated variations in vocal fold collagen turnover to voice senescence. The underlying mechanisms remain to be explored. With the use of reverse-transcriptase polymerase chain reaction (RT-PCR), collagen subtypes expressed in rat vocal folds were determined, and messenger RNA (mRNA) levels of collagens (types I, III, IV, and V), collagen-degrading proteinases (collagenase 3, gelatinase A and B), and tissue inhibitors of metalloproteinases (TIMP-1 to TIMP-4) were measured in vocal folds of neonatal, adult, and elderly rats. Collagens I, III-VIII, XV, XVII, and XVIII are abundantly expressed, whereas collagens II, IX, X, and XI are absent in rat vocal folds. Messenger RNA levels of collagens I, III, IV, and V and collagen-degrading proteinases in the vocal folds of the adult rats are significantly lower than those in the neonates. These mRNA levels show further decline in the vocal folds of the elderly rats, but only the decrease in mRNA levels of collagens I and V significantly differ from the adult levels. There are no marked age-related alterations in vocal fold levels of TIMP mRNAs, and the tissue variation in the gene expression of the aforementioned molecules is minute. Rat vocal folds display tissue-specific expression of collagen genes. Diminished gene expression for collagens and proteinases and unchanged gene expression for TIMPs indicate a slowdown in collagen turnover that may increase the cross-linking of collagen molecules. This observation may explain in part the stiffness that occurs with aging in human vocal folds.

Aging↗

PubMed2001

Expression and hypoxic regulation of angiopoietins in human astrocytomas.

Vascular endothelial growth factor (VEGF) is a major inducer of tumor angiogenesis and edema in human astrocytomas by its interaction with cognate endothelial-specific receptors (VEGFR1/R2). Tie1 and Tie2/Tek are more recently identified endothelial-specific receptors, with angiopoietins being ligands for the latter. These angiogenic factors and receptors are crucial for the maturation of the vascular system, but their role in tumor angiogenesis, particularly in astrocytomas, is unknown. In this study, we demonstrate that the angiopoietin family member Ang1 is expressed by some of the astrocytoma cell lines. In contrast to VEGF, Ang1 is down regulated by hypoxia. Ang2 was not overexpressed. Expression profiles of low-grade astrocytoma specimens were similar to those of normal brain, with low levels of Ang1, Ang2, and VEGF expression. Glioblastoma multiforme expressed higher levels of Angl, but not to the same degree as pseudopalisading astrocytoma cells around necrotic and hypoxic zones expressed VEGF, as shown in previous studies. Ang2 expression in the highly proliferative tumor vascular endothelium was also increased, as was phosphorylated Tie2/Tek. The expression profile of these angiogenic factors and their endothelial cell receptors in human glioblastomas multiforme was similar to that in a transgenic mouse model of glioblastoma multiforme. These data suggest that both VEGF and angiopoietins are involved in regulating tumor angiogenesis in human astrocytomas.

Angiopoietin-1↗

PubMed2001

Non-invasive quantitative assessment of oxidative metabolism in quadriceps muscles by near infrared spectroscopy.

BACKGROUND: Near infrared spectroscopy can be used in non-invasive monitoring of changes in skeletal muscle oxygenation in exercising subjects. OBJECTIVE: To evaluate whether this method can be used to assess metabolic capacity of muscles. Two distinctive variables abstracted from a curve of changes in muscle oxygenation were assessed. METHODS: Exercise on a cycle ergometer was performed by 18 elite male athletes and eight healthy young men. A measuring probe was placed on the skin of the quadriceps muscle to measure reflected light at two wavelengths (760 and 850 nm), so that the relative index of muscle oxygenation could be calculated. Exercise intensity was increased from 50 W in 50 W increments until the subject was exhausted. During exercise, changes in muscle oxygenation and blood lactate concentration were recorded. The following two variables for assessment of muscle oxygenation were then abstracted and analysed by plotting curves of changes in muscle oxygenation: the rate of recovery of muscle oxygen saturation (R(R)) and the relative value of the effective decrease in muscle oxygenation (D(eff)). RESULTS: Data analysis showed a correlation between muscle oxygenation and blood lactate concentration at the various exercise intensities and verified the feasibility of the experiment. Data for the athletes were compared with those for the controls using the Aspin-Welch test of significance; t = 2.3 and 2.86 for R(R) and D(eff) respectively. There were significant differences (p = 0.05) between the athletes and the control group with respect to these two variables. CONCLUSION: R(R) and D(eff) may be distinctive variables that can be used to characterise muscle oxidative metabolism during human body movement.

Adult↗

PubMed2001

Evaluation of posttreatment response of hepatocellular carcinoma with contrast-enhanced coded phase-inversion harmonic US: comparison with dynamic CT.

PURPOSE: To assess the reliability of contrast material-enhanced real-time gray-scale ultrasonography (US) in evaluating posttreatment response of hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Fifty HCC nodules were examined with contrast-enhanced coded phase-inversion harmonic US before and after treatment. Intratumoral vascularity was assessed with continuous imaging in the early arterial phase and with interval-delay scanning to depict tumor parenchymal flow during the blood pool phase. Vascular findings at US were compared with those at dynamic computed tomography (CT). RESULTS: In 50 HCC nodules before treatment, positive enhancement of tumor vessels and tumor parenchymal flow (stain) were observed in 47 (94%) and 46 (92%), respectively. Either tumor vessel or stain was visualized with coded harmonic US in 49 of 50 nodules. Eighty-one coded harmonic US studies were performed in 49 posttreatment HCC nodules. Compared with dynamic CT, the sensitivity, specificity, and accuracy of coded harmonic US in helping to detect positive enhancement in pretreatment HCC were 98% (49 of 50), 100% (50 of 50), and 98% (49 of 50), respectively. After treatment, positive enhancement of tumor vascularity was observed in 39 (48%) of 81 posttreatment studies, and no enhancement was observed in others (52%). Coded harmonic US demonstrated partial and no enhancement of tumor vascularity in four and one nodule, respectively; after transcatheter arterial embolization with iodized oil, evaluation of tumor vascularity with dynamic CT was difficult because of the presence of oil. CONCLUSION: With enhancement, coded harmonic US depicted tumor vascularity by showing tumor vessels in a real-time fashion at continuous imaging and tumor parenchymal flow at interval-delay scanning.

Adult↗

PubMed2001

Hepatocellular carcinoma: depiction of tumor parenchymal flow with intermittent harmonic power Doppler US during the early arterial phase in dual-display mode.

PURPOSE: To assess the effectiveness of contrast material-enhanced intermittent harmonic Doppler ultrasonography (US) in depicting tumor vessels and tumor parenchymal flow (stain) in hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Fifty-eight patients with 65 HCC nodules were examined by using intermittent harmonic power Doppler US and digital subtraction harmonic B-mode US, both with intravenous administration of SH U 508A. Vascular findings at early arterial phase harmonic US were classified as positive enhancement or nonenhancement, depending on the tumor vascularity relative to the surrounding liver parenchyma. These results were compared with those of three-phase helical dynamic computed tomography (CT). RESULTS: For hypervascular HCCs, there was excellent depiction of tumor vessels and tumor stain with the two intermittent harmonic US methods. The sensitivity and specificity for depiction of tumor vascularity were 93% (41 of 44 nodules) and 100% (21 of 21), respectively, with intermittent harmonic power Doppler US and 86% (38 of 44) and 100% (21 of 21), respectively, with subtraction US, as compared with these values at dynamic CT. Attenuation was an important factor in the depictability of tumor vascularity at harmonic US. CONCLUSION: Contrast-enhanced intermittent harmonic US enables noninvasive demonstration of tumor vessels and especially tumor stain in HCC.

Adult↗