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Biomedical subjects

Rong Yang

Publications and source records attributed to Rong Yang.

At least 37 records · Page 2Linked to original sources
PubMed2005

[125I seed implantation in sphincter preservation for treatment of low rectal cancer].

OBJECTIVE: To evaluate the effects of (125)I seed implantation in sphincter preservation for treatment of low rectal cancer. METHODS: Seventy-six patients with low rectal cancer were randomly divided into 2 group: group A, 17 males and 13 females, aged 48.5 +/- 2.4, receiving rectostomy and anal sphincter preservation and group B, 24 males and 22 females, aged 49.4 +/- 2.6, receiving modified TME and anal sphincter preservation combined with brachytherapy by (125)I seed implantation. Two to four weeks after operation chemotherapy with 5-FU/CF were performed. Follow-up was carried out 6, 12, 24, and 36 months after operation. RESULTS: The local recurrence rates 6, 12, 24, and 36 months after operation were 0%, 11.1%, 14.3%, and 23% respectively in the group A, and all 0% in the group B (P < 0.05 for the rate 36 months later). The survival rates 6, 12, 24, and 36 months after operation were 100%, 100%, 85.7%, and 76.7% respectively in the group A, and were 100%, 100%, 97.1%, and 93% respectively in the group B (P < 0.05 for the rate 36 months later). The functions of defecation and erection were better in the group B and the symptom of pain was improved better in the group A too (all P < 0.05). CONCLUSIONS: Safe, simple, and effective, surgery with sphincter preservation combined with brachytherapy in low rectal cancer is one of the ideal methods for treatment of low rectal cancer.

Adenocarcinoma↗
PubMed2005

Loop conformation and dynamics of the Escherichia coli HPPK apo-enzyme and its binary complex with MgATP.

Comparison of the crystallographic and NMR structures of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) suggests that the enzyme may undergo significant conformational change upon binding to its first substrate, ATP. Two of the three surface loops (loop 2 and loop 3) accounting for most of the conformational differences appear to be confined by crystal contacts, raising questions about the putative large-scale induced-fit conformational change of HPPK and the functional roles of the conserved side-chain residues on the loops. To investigate the loop dynamics in crystal-free environment, we carried out molecular dynamics and locally enhanced sampling simulations of the apo-enzyme and the HPPK.MgATP complex. Our simulations showed that the crystallographic B-factors underestimated the loop dynamics considerably. We found that the open-conformation of loop 3 in the binary complex is accessible to the apo-enzyme and is the favored conformation in solution phase. These results revise our previous view of HPPK-substrate interactions and the associated functional mechanism of conformational change. The lessons learned here offer valuable structural insights into the workings of HPPK and should be useful for structure-based drug design.

Adenosine Triphosphate↗
PubMed2005

Stereochemical assignment, antiinflammatory properties, and receptor for the omega-3 lipid mediator resolvin E1.

The essential fatty acid eicosapentaenoic acid (EPA) present in fish oils displays beneficial effects in a range of human disorders associated with inflammation including cardiovascular disease. Resolvin E1 (RvE1), a new bioactive oxygenated product of EPA, was identified in human plasma and prepared by total organic synthesis. Results of bioaction and physical matching studies indicate that the complete structure of RvE1 is 5S,12R,18R-trihydroxy-6Z,8E,10E,14Z,16E-EPA. At nanomolar levels, RvE1 dramatically reduced dermal inflammation, peritonitis, dendritic cell (DC) migration, and interleukin (IL) 12 production. We screened receptors and identified one, denoted earlier as ChemR23, that mediates RvE1 signal to attenuate nuclear factor-kappaB. Specific binding of RvE1 to this receptor was confirmed using synthetic [(3)H]-labeled RvE1. Treatment of DCs with small interference RNA specific for ChemR23 sharply reduced RvE1 regulation of IL-12. These results demonstrate novel counterregulatory responses in inflammation initiated via RvE1 receptor activation that provide the first evidence for EPA-derived potent endogenous agonists of antiinflammation.

Amino Acid Sequence↗
PubMed2005

Recent advances in atomic-scale spin-polarized scanning tunneling microscopy.

The Mn3N2 (010) surface has been studied using spin-polarized scanning tunneling microscopy at the atomic scale. The principle objective of this work is to elucidate the properties and potential of this technique to measure atomic-scale magnetic structures. The experimental approach involves the use of a combined molecular beam epitaxy/scanning tunneling microscopy system that allows the study of atomically clean magnetic surfaces. Several key findings have been obtained. First, both magnetic and non-magnetic atomic-scale information has been obtained in a single spin-polarized image. Magnetic modulation of the height profile having an antiferromagnetic super-period of c = 12.14 A (6 atomic rows) together with a non-magnetic superstructure having a period of c/2 = 6.07 A (3 atomic rows) was observed. Methods of separation of magnetic and non-magnetic profiles are presented. Second, bias voltage-dependent spin-polarized images show a reversal of the magnetic modulation at a particular voltage. This reversal is clearly due to a change in the sign of the magnetic term in the tunnel current. Since this term depends on both the tip's as well as the sample's magnetic local density of states, the reversal can be caused by either the sample or the tip. Third, the shape of the line profile was found to vary with the bias voltage, which is related to the energy-dependent spin contribution from the 2 chemically inequivalent Mn sites on the surface. Overall, the results shown here expand the application of the method of spin-polarized scanning tunneling microscopy to measure atomic-scale magnetic structures.

Algorithms↗
PubMed2005

[Expression of nerve growth factor in cavernous tissue and its effects on the treatment of rats with diabetic erectile dysfunction].

OBJECTIVE: To investigate the content of nerve growth factor (NGF) in penis of rats with diabetic erectile dysfunction (DED) and apply rhNGF to treat the DED rat model to study the pathogenesis mechanism of DED and treatment effects by NGF for DED rat model. METHODS: Fifty adult male SD rats were randomly selected to make up diabetic models. After 8 weeks, the mRNA and protein levels of NGF in rat penis were detected. Then the rest of rats were divided into 5 groups: normal control group, non-treated diabetes group, NGF treatment group, insulin treatment group, NGF plus insulin treatment group. After 8 weeks of treatment, intracavernous pressure (ICP) was measured. The content of neuronal nitric oxide synthase (nNOS) in the erectile tissue was also value- ated by immunohistochemistry staining. RESULTS: Compared with those of normal control group, the mRNA content of NGF and protein in the penis of non-treated diabetic rats is increased significantly. Compared with non-treated diabetic group, ICP was much higher in the treated groups which received NGF or/and insulin therapy, and the changes in nNOS staining of those groups were the same. CONCLUSION: The injury of pelvic splanchnic nerves in advanced stage of diabetes may lead to DED, which may be relevant to the abnormal of NGF level or the NGF receptors. The increased extent of NGF in penis of rat with DED suggests that erectile nerves be severely damaged by diabete and the increase of producing NGF couldn't compensate the needs for reproduction of the nerve fibers. The ability of combination of NGF with its receptor may also be damaged. It is helpful to use exogenous NGF to lessen the partly neuropathy and improve the erectile dysfunction of diabetic rats. The abnormal of NGF may play an important role in the pathogenesis of diabetic ED and its treatment.

Animals↗
PubMed2005

[The results of surgery on HIV carriers with urinary system disease].

OBJECTIVE: To approach characteristics of performing operation on HIV carriers with urinary system diseases. METHODS: To summarize author's experiences of surgery on 41 HIV carriers suffering urinary system diseases abroad from April 1996 to May 2004. RESULTS: The 41 HIV carriers received HAART and were performed with corresponding operations, followed up from 4 to 30 months post-operatively. The 31 carriers have recovered well up to date, while 4 carriers died of AIDS. Among them, 2 patients with penis cancer who received a partial peotomy and a patient with renal tuberculosis receiving left nephrectomy were died of AIDS within 4-8 months after operations whose CD4+ T lymphocyte number was below 0.2 x 10(9)/L. CONCLUSION: Prior to operation, HIV carriers should receive HAART ordinarily to control copy of the virus. The CD4+ T lymphocyte number is important for selecting a proper time for operation and deciding the further after surgery. We also take note to CD4+ T lymphocyte number to monitor progress of the AIDS. For those HIV carriers, endourologic surgery and laparoscopy should be taken so far as possible. Meanwhile, medical stuffs must pay more attention to preventing occupational infection during surgery.

Adult↗
PubMed2004

A trimeric HIV-1 fusion peptide construct which does not self-associate in aqueous solution and which has 15-fold higher membrane fusion rate.

A peptide construct (FPtr) was synthesized which mimics the biologically relevant topology of fusion peptide (FP) domains of the trimeric HIV-1 gp41 envelope protein. The FP domains play a critical role in gp41-catalyzed fusion of viral and host cell membranes which is a key step in viral infection. The FPtr construct contains three FP strands chemically bonded at their C-termini through lysine side chains. Analytical ultracentrifugation demonstrated that FPtr does not self-associate in aqueous solution and therefore models the expected FP topology of gp41. Comparative functional fusion assays were carried out using FPtr, FPdm (a cross-linked FP dimer construct), and FPmn (FP monomer). The derived fusion rate constants order ktr > kdm > kmn, and the ratio ktr/kmn has values in the range of 15-40. These results suggest that there is strong correlation of the fusion rate with the biologically relevant trimeric FP topology.

Amino Acid Sequence↗
PubMed2004

Use of moving optical gradient fields for analysis of apoptotic cellular responses in a chronic myeloid leukemia cell model.

To facilitate quantitation of cellular apoptotic responses to various antineoplastic agents, a laser-based technology, Optophoresis, has been developed to provide analysis of cells without any need for labeling or cell processing. Optophoresis is defined as the analysis of the motion of cells, where the motion is either induced or modified by a moving optical gradient field, which produces radiation pressure forces on the cells in an aqueous suspension. Quantitation of the induced motion provides a basis for distinguishing one population of cells from another. One Optophoretic technique, Fast Scan, measures the distribution of distances traversed by a population of cells when exposed to a fast-moving optical gradient. Fast Scan was validated using a cell-based model of chronic myeloid leukemia treated with Gleevec, a specific inhibitor of aberrant Bcr-Abl protein kinase. The Optophoretic measurements were quantitatively comparable to reference assays with regard to drug selectivity and potency and to target specificity, demonstrating the suitability of this technology for pharmaceutical and clinical applications.

Antineoplastic Agents↗
PubMed2004

Defective lipoxin-mediated anti-inflammatory activity in the cystic fibrosis airway.

In cystic fibrosis, dysregulated neutrophilic inflammation and chronic infection lead to progressive destruction of the airways. The underlying mechanisms have remained unclear. Lipoxins are anti-inflammatory lipid mediators that modulate neutrophilic inflammation. We report here that lipoxin concentrations in airway fluid were significantly suppressed in patients with cystic fibrosis compared to patients with other inflammatory lung conditions. We also show that administration of a metabolically stable lipoxin analog in a mouse model of the chronic airway inflammation and infection associated with cystic fibrosis suppressed neutrophilic inflammation, decreased pulmonary bacterial burden and attenuated disease severity. These findings suggest that there is a pathophysiologically important defect in lipoxin-mediated anti-inflammatory activity in the cystic fibrosis lung and that lipoxins have therapeutic potential in this lethal autosomal disease.

Cystic Fibrosis↗
PubMed2004

The tautomerism of Omeprazole in solution: a 1H and 13C NMR study.

The tautomerism of 5(6)-methoxy-2-([(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl] sulfinyl)-1H-benzimidazole (omeprazole) was determined in solution, K(T) = 0.59 in THF at 195 K, in favor of the 6-methoxy tautomer. The assignment of the signals was made by comparison with its two N-methyl derivatives in acetone-d6 and through theoretical calculations of the absolute shieldings (GIAO/DFT/6-311++G**).

Carbon Isotopes↗
PubMed2004

Herbimycin A inhibits angiogenic activity in endothelial cells and reduces neovascularization in a rat model of retinopathy of prematurity.

The pathogenesis of retinopathy of prematurity involves dysregulated angiogenesis resulting in pre-retinal growth of new vessels. Inhibition of tyrosine kinase-dependent pro-angiogenic signals may provide a rational therapeutic approach to the reduction of pre-retinal neovascularization. Vascular endothelial growth factor stimulates endothelial cell mitogenesis, differentiation and migration, by binding and activating the receptor tyrosine kinases vascular endothelial growth factor receptor-1 and vascular endothelial growth factor receptor-2. One of the vascular endothelial growth factor receptor substrates implicated in vascular endothelial growth factor signal transduction is c-Src. The ability of herbimycin A, a c-Src-selective tyrosine kinase inhibitor, to inhibit vascular endothelial growth factor-induced bovine retinal microvascular endothelial cell proliferation and tube formation was investigated. The ability of the compound to inhibit pathologic angiogenesis was tested in a rat model of retinopathy of prematurity. Exposure of neonatal rats to oxygen concentrations cycling between 10 and 50% induced severe pre-retinal neovascularization in all rats. Some of the eyes of these variable oxygen-exposed rats were herbimycin A-injected or vehicle-injected 1 or 3 days post-oxygen exposure while some eyes were non-injected. All rats were sacrificed for assessment 6 days post-exposure. Herbimycin A inhibited both vascular endothelial growth factor-induced bovine retinal microvascular endothelial cell proliferation and capillary tube formation in a dose-dependent manner. Injection of herbimycin A into oxygen-treated rats 1 day post-oxygen exposure produced a 63% decrease in pre-retinal neovascularization relative to vehicle (P = 0.0029). There was a 41% decrease in pre-retinal neovascularization in herbimycin-injected eyes relative to vehicle-injected eyes 3 days post-oxygen (P = 0.031). Pre-retinal neovascularization was reduced in vehicle-injected eyes relative to non-injected eyes at both injection times. There were no significant differences in retinal vascular area between any of the experimental groups. Based on the results of this study, herbimycin A inhibits endothelial cell proliferation and tube formation at non-toxic concentrations and reduces pre-retinal neovascularization in a rat model of retinopathy of prematurity. Reduction of angiogenesis by the inhibition of tyrosine kinase activity may be a viable route to the development of effective chemotherapies applicable to eye disease.

Animals↗
PubMed2004

[Progress in gene therapy of liver cirrhosis].

Liver cirrhosis is a common progressive pathological lesion in the late stage of chronic liver disease, which is characterized by disorganization of normal hepatic structure of regenerative nodules and hyperplasia of fibrotic tissues. In recent years, with the development of molecular biology, the molecular mechanisms underlying liver cirrhosis has been revealed more and more, which makes the therapy at the gene level possible. The ideal strategy for the treatment of liver cirrhosis should include prevention of fibrogenesis, stimulation of hepatocyte proliferation and reorganization of the liver architecture. Several gene therapy approaches for treatment of liver cirrhosis have been developed by transfer of some genes of cytokines and enzymes (e.g. HGF, TGF beta 1R, MMPs). These gene therapies can inhibit fibrogenesis and hepatocyte apoptosis and also produce resolution of fibrosis in the cirrhotic liver. Thus, gene therapy may be potentially useful for the treatment of liver cirrhosis, which is otherwise fatal and untreatable by conventional therapy.

Animals↗
PubMed2004

[Study on the expression of nm23-M1/NDPK a during the blastocyst adhesiveness in the mouse endometrium].

The nm23 gene was originally identified as a metastasis suppressor gene by differential hybridization of non-metastatic and metastatic clones of murine K-1735 melanoma cell lines. Subsequently, other highly homologous genes were characterized and shown to code for nucleoside diphosphate kinase (NDPK) isotypes. These enzymes have been evidenced in a wide variety of organisms. In human, up to eight distinct but highly related genes have been discovered. The nm23-H1 and nm23-H2 gene products share 88% identity and are about 95% and 98% identical to the murine nm23-M1 and nm23-M2 proteins respectively. A number of data indicate that nm23 family, initially documented as metastasis suppressors in some cancer types, are involved in the control of normal development, differentiation and apoptosis. The trophoblast cells of blastocyst and of the normal first-trimester placenta share some phenotypic similarities with malignant cells, such as rapid proliferation and ability to invade neighbouring tissues, including basement membrane, during the process of implantation and placental development, but do not have the ability for unlimited growth or metastasis, as few trophoblast cells can be identified in the deciduas, and trophoblasts rarely penetrate the maternal blood vessels. Although some data indicate that nm23 family play an important role in regulation of reproductive processes, little is know about its actual mechanism. In our studies, we performed RT-PCR, Western blot and immunohistochemical analyses of nm23-M1/NDPK A expression during the blastocyst adhesiveness in the mouse endometrium. The nm23-M1 mRNA expression was shown progressive increase in D5 mice endometrium by RT-PCR, which was consistent with the result obtained by Western blot and immunohistochemistry. It is suggested that nm23-M1/NDPK A was involved in the process of blastocyst implantation.

Animals↗
PubMed2003

Optical forces for noninvasive cellular analysis.

A novel, noninvasive measurement technique for quantitative cellular analysis is presented that utilizes the forces generated by an optical beam to evaluate the physical properties of live cells in suspension. In this analysis, a focused, near-infrared laser line with a high cross-sectional intensity gradient is rapidly scanned across a field of cells, and the interaction of those cells with the beam is monitored. The response of each cell to the laser depends on its size, structure, morphology, composition, and surface membrane properties; therefore, with this technique, cell populations of different type, treatment, or biological state can be compared. To demonstrate the utility of this cell analysis platform, we evaluated the early stages of apoptosis induced in the U937 cancer cell line by the drug camptothecin and compared the results with established reference assays. Measurements on our platform show detection of cellular changes earlier than either of the fluorescence-based Annexin V or caspase assays. Because no labeling or additional cell processing is required and because accurate assays can be performed with a small number of cells, this measurement technique may find suitable applications in cell research, medical diagnostics, and drug discovery.

Apoptosis↗
PubMed2003

Synthesis, enhanced fusogenicity, and solid state NMR measurements of cross-linked HIV-1 fusion peptides.

In the HIV-1 gp41 and other viral fusion proteins, the minimal oligomerization state is believed to be trimeric with three N-terminal fusion peptides inserting into the membrane in close proximity. Previous studies have demonstrated that the fusion peptide by itself serves as a useful model fusion system, at least to the hemifusion stage in which the viral and target cell lipids are mixed. In the present study, HIV-1 fusion peptides were chemically synthesized and cross-linked at their C-termini to form dimers or trimers. C-terminal trimerization is their likely topology in the fusogenic form of the intact gp41 protein. The fusogenicity of the peptides was then measured in an intervesicle lipid mixing assay, and the assay results were compared to those of the monomer. For monomer, dimer, and trimer at peptide strand/lipid mol ratios between 0.0050 and 0.010, the final extent of lipid mixing for the dimer and trimer was 2-3 times greater than for the monomer. These data suggest that the higher local concentration of peptide strands in the cross-linked peptides enhances fusogenicity and that oligomerization of the fusion peptide in gp41 may enhance the rate of viral/target cell membrane fusion. For gp41, this effect is in addition to the role of the trimeric coiled-coil structure in bringing about apposition of viral and target cell membranes. NMR measurements on the membrane-associated dimeric fusion peptide were consistent with an extended structure at Phe-8, which is the same as has been observed for the membrane-bound monomer in the same lipid composition.

Amino Acid Sequence↗
PubMed2003

A point-charge force field for molecular mechanics simulations of proteins based on condensed-phase quantum mechanical calculations.

Molecular mechanics models have been applied extensively to study the dynamics of proteins and nucleic acids. Here we report the development of a third-generation point-charge all-atom force field for proteins. Following the earlier approach of Cornell et al., the charge set was obtained by fitting to the electrostatic potentials of dipeptides calculated using B3LYP/cc-pVTZ//HF/6-31G** quantum mechanical methods. The main-chain torsion parameters were obtained by fitting to the energy profiles of Ace-Ala-Nme and Ace-Gly-Nme di-peptides calculated using MP2/cc-pVTZ//HF/6-31G** quantum mechanical methods. All other parameters were taken from the existing AMBER data base. The major departure from previous force fields is that all quantum mechanical calculations were done in the condensed phase with continuum solvent models and an effective dielectric constant of epsilon = 4. We anticipate that this force field parameter set will address certain critical short comings of previous force fields in condensed-phase simulations of proteins. Initial tests on peptides demonstrated a high-degree of similarity between the calculated and the statistically measured Ramanchandran maps for both Ace-Gly-Nme and Ace-Ala-Nme di-peptides. Some highlights of our results include (1) well-preserved balance between the extended and helical region distributions, and (2) favorable type-II poly-proline helical region in agreement with recent experiments. Backward compatibility between the new and Cornell et al. charge sets, as judged by overall agreement between dipole moments, allows a smooth transition to the new force field in the area of ligand-binding calculations. Test simulations on a large set of proteins are also discussed.

Algorithms↗
PubMed2003

Absence of R24C mutation of the CDK4 gene in leukemias and solid tumors.

A mutation of the p16(INK4a)-binding domain of the cyclin dependent kinase 4 (CDK4) gene, R24C, has been reported in some cases of melanoma. This mutation prevented binding of the CDK4 inhibitor p16(INK48) to CDK4. To determine the relevance of the mutation, we performed polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis in diverse types of human leukemias and solid tumors. No mobility shifts indicating sequence alterations were observed in 273 tumors and 49 cell lines from diverse kinds of tumors These results suggest that in contrast to melanoma, in many other types of human neoplasms the mutation of the CDK4 gene is very rare. To better understand these findings, we randomly mutagenized the CDK4 gene and used the yeast two-hybrid method to screen for CDK4 mutants that had lost the ability to bind to p16(INK4a). Sequence analysis and in vitro kinase assays showed that most of the mutations that disrupted interactions with p16(INK4) also knocked out the activity of CDK4. This result may explain the rareness of CDK4 mutations in human tumors.

Cell Line, Tumor↗