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Biomedical subjects

C Shen

Publications and source records attributed to C Shen.

At least 73 records · Page 4Linked to original sources

Experience journals: using computers to share personal stories about illness and medical intervention.

Medical advances make it increasingly possible for children with previously fatal illness to live and thrive. However, a significant number still experience repeated operations, hospitalization, and invasive procedures, or need special care at home. Many do so with little or no intervention to help them and their families cope with the emotional stresses involved. One significant source of emotional and cognitive support is the community of patients and families who have experienced similar medical procedures. However, in spite of a general willingness to share experiences, communication among patients and families is usually limited. To facilitate this process, we are investigating the use of computer technology to record, organize, and display stories about the experiences of families with children who have been treated for cardiac and neurological illness at Children's Hospital, Boston. We are asking children and their families to record text and multimedia vignettes describing some aspect of their illness, coping strategies, or care that might be useful to others. These contributions will be available for browsing at a secure World-Wide-Web site. However, economic realities preclude reliance on a professional site administrator to organize and monitor what we hope to be a rapidly growing Web site with a large, distributed authorship. The need to make the Web site fully accessible to users who have varying familiarity with computers and Web browsing imposes further constraints. We are therefore developing software to automate the process of managing and organizing an easily accessed Web site that contains an "Experience Journal." We describe this software, the rationale for its development, and our plans for its use in the coming year.

Adolescent↗

[Nucleotide sequence analysis of a species specific probe by an inserted fragment from recombinant plasmid pCX7 of L. interrogans sensu stricto serovar lai].

The etiological agents of leptospirosis are the pathogenic leptospires (L. interrogans sensu lato) which can be divided into 223 serovars organized into 23 serogroups. The serovar remains the basic taxon, but serotyping may now be accomplished and recognized by acceptable methods. Complementary molecular approaches are being used extensively to assess genetic relatedness amongst leptospires with restriction endonuclese analysis (REA), pulse field gel electrophoresis (PFGE) and DNA-DNA hybridization as well established tools. However, the method is cumbersome and unsuitable for routine application. To develop a sensitive and specific method for identification of pathogenic leptospires, a genomic library of L. interrogans sensu stricto serovar lai was constructed with the plasmid vector pUC9. A recombinant plasmid, designated pCX7 which has homologous fragment of pathogenic leptospires was screened from the bank. pCX7 could recognize pathogenic leptospiral DNA fragment 1.7 kb of strain 017 without cross hybridization to nonpathogenic leptospiral DNA. Inserted fragment of pCX7 DNA sequencing was performed by Dr. Yan Zhengxin (Max-Plank-Institut fur Biology, Tubingen, Germany). Insert fragment was cloned into pBluescript and sequenced by using ABI(Applied Bio. Systems, Model 373A). Nucleotide sequences were analyzed by Dr. Xiao Jianguo (Texas University Medical School and School of Public Health, Center for Infectious Diseases) using a suit of computer program (NIH). One open reading frame of 306 nucleotids were identified. There were identifiable initiation codons, terminators, pribnow box and sextama box within the sequenced regions. These results further confirmed that the little homology between L. interrogans sensu strito and L. borgpeterseni serovar javanica, L. inadai serovar ranarun and serovar manhao (L. genomospecies 2), L. biflexa serovar patoc, L. illini. pCX7 DNA probe could provide a base for identification and classification of leptospires.

DNA, Bacterial↗

[Study on a new method for spectrophotometry].

In this paper, the relation between absorbance difference and concentration was measured by the ultraviolet spectrophotometer and computer made P-E company of U.S.A. The basic goal is to prove that the standard absorption curve method can be replaced by the new method, in which the sample was put in standard room and the standard material in sample room. Utilizing this method can minimize the error, most importantly, can measure the higher concentration sample, which can not be measured by the standard curve method. The new method does not require a Linear deltaA-c linear relationship.

English Abstract↗

Structure-activity relationships for a novel series of pyrido[2,3-d]pyrimidine tyrosine kinase inhibitors.

Screening of a compound library for inhibitors of the fibroblast growth factor (FGFr) and platelet-derived growth factor (PDGFr) receptor tyrosine kinases led to the development of a novel series of ATP competitive pyrido[2,3-d]pyrimidine tyrosine kinase inhibitors. The initial lead, 1-[2-amino-6-(2,6-dichlorophenyl)pyrido[2,3-d]pyrimidin-7-yl]-3- tert-butylurea (4b, PD-089828), was found to be a broadly active tyrosine kinase inhibitor. Compound 4b inhibited the PDGFr, FGFr, EGFr, and c-src tyrosine kinases with IC50 values of 1.11, 0.13, 0.45, and 0.22 microM, respectively. Subsequent SAR studies led to the synthesis of new analogs with improved potency, solubility, and bioavailability relative to the initial lead. For example, the introduction of a [4-(diethylamino)butyl]amino side chain into the 2-position of 4b afforded compound 6c with enhanced potency and bioavailability. Compound 6c inhibited PDGF-stimulated vascular smooth muscle cell proliferation with an IC50 of 0.3 microM. Furthermore, replacement of the 6-(2,6-dichlorophenyl) moiety of 4b with a 6-(3',5'-dimethoxyphenyl) functionality produced a highly selective FGFr tyrosine kinase inhibitor 4e. Compound 4e inhibited the FGFr tyrosine kinase with an IC50 of 0.060 microM, whereas IC50s for the inhibition of the PDGFr, FGFr, EGFr, c-src, and InsR tyrosine kinases for this compound (4e) were all greater than 50 microM.

Animals↗

Characterization of zinc-substituted cytochrome c by circular dichroism and resonance Raman spectroscopic methods.

Iron(III) in cytochrome c is replaced with zinc(II) by a modification of a method published by others, and the procedure is described in full detail. Three forms of cytochrome c-those containing iron(III), iron(II), and zinc(II)-are examined by circular dichroism spectroscopy and resonance Raman spectroscopy. Spectra of both kinds show that introduction of zinc(II) ions does not appreciably alter the overall structure and conformation of cytochrome c. Resonance Raman spectra indicate the size of the porphyrin "core" that is inconsistent with six-coordination and consistent with five-coordination. Unlike the iron(III) and iron(II) ions, which are bound to two axial ligands (His 18 and Met 80), the zinc(II) ion in cytochrome c seems to be bound to only one, most probably His 18. Evidence pertaining to the question of axial coordination is discussed.

Animals↗

Adenosine A1 receptor promotion of multinucleated giant cell formation by human monocytes: a mechanism for methotrexate-induced nodulosis in rheumatoid arthritis.

OBJECTIVE: To determine why methotrexate (MTX) exacerbates rheumatoid nodules in some patients, despite the effective suppression of synovial inflammation. METHODS: Phorbol myristate acetate (PMA)-induced differentiation of monocytes into multinucleated giant cells was used as an in vitro model to study the effects of adenosine on nodulosis. RESULTS: MTX at 200-2,000 nM or the adenosine A1 agonist N5-cyclopentyl adenosine (CPA) (10(-12) to 10(-9) M) or the A2 antagonist 3,7-dimethyl-1-propargylxanthine markedly enhanced giant cell formation, whereas the adenosine A1 antagonist 8-cyclopentyl-dipropylxanthine completely reversed these effects. PMA, CPA, and MTX induced adenosine release by cultured monocytes at concentrations consistent with those associated with predominantly A1 effects. Furthermore, surface expression of A1 receptors was found to remain unchanged on the differentiating cells throughout the culture period. CONCLUSION: Agents that inhibit adenosine A1 receptors might be useful in the treatment of MTX-induced rheumatoid nodulosis, while still potentiating the A2-mediated antiinflammatory effects of MTX on synovitis.

Adenosine↗

Photoelastic analysis of miniplate osteosynthesis for mandibular angle fractures.

OBJECTIVE: The purpose of this study was to reassess Champy's findings, which were instrumental in justifying the theory of tension band plating for mandibular angle fractures. STUDY DESIGN: Ten anatomically correct mandibles were fabricated with a photoelastic resin. In five mandibles, angle fractures were created and fixed with a superior border miniplate; five uncut mandibles served as controls. Each mandible was loaded in a manner that simulated physiologic conditions. The internal stress patterns were preserved within the models by completing a stress freezing cycle. RESULTS: The stress patterns in the experimental mandibles virtually replicated the patterns seen in the controls. Stress fringes were present surrounding the outer screws, indicating that these screws were subjected to pull-out forces. CONCLUSIONS: There is greater force on the outer screws that may contribute to fixation failure. The theory of tension band plating for mandibular angle fractures is accurate but Champy's model is oversimplified.

Birefringence↗

Effect of magnesium sulfate on the development of cystic periventricular leukomalacia in preterm infants.

To determine if magnesium sulfate has an effect on the development of cystic periventricular leukomalacia in preterm infants, this retrospective case control study was conducted. There were 23,382 infants born at three teaching hospitals in the metropolitan New York area from January 1992 to December 1994. Four hundred ninety-two infants met our entrance criteria. Criteria included a birth weight < 1750 g, survival to at least 7 days of life and at least one cranial ultrasound after 7 days of life. Infants exposed to magnesium sulfate in utero were less likely to develop periventricular leukomalacia. Two of 18 (11%) infants with periventricular leukomalacia were exposed to magnesium sulfate in-utero compared to 14 of 36 controls (39%) (p = 0.035) (OR = 0.196, 95% CI = 0.039-0.988). Pre-eclampsia as an independent factor was not associated with a reduced risk (p = 0.251) (OR = 0.294, 95% CI = 0.033-2.65). Preterm infants exposed to antenatal magnesium sulfate were found to have a reduced risk of developing cystic periventricular leukomalacia.

Anticonvulsants↗

DNA vaccination with the major outer-membrane protein gene induces acquired immunity to Chlamydia trachomatis (mouse pneumonitis) infection.

The efficacy of DNA vaccination for prevention of Chlamydia trachomatis infection was studied using the murine model of pneumonia induced by the mouse pneumonitis (MoPn) isolate of C. trachomatis. Intramuscular DNA immunization with two chlamydial genes, one that encodes the major outer-membrane protein (MOMP) and one that encodes a cytoplasmic enzyme (cytosine triphosphate [CTP] synthetase) were tested. The MOMP DNA vaccine but not the CTP synthetase DNA vaccine generated significant delayed-type hypersensitivity and serum antibodies to MoPn elementary bodies and reduced the peak growth of MoPn by >100-fold following lung challenge infection. MOMP DNA immunization suggests a new approach to vaccine development for prevention of human chlamydial infection.

Animals↗

[A primary study of the association of human leucocyte antigen and osteosarcoma].

OBJECTIVE: To study the association of human leucocyte antigen and osteosarcoma in Chinese Han nationality. METHODS: The frequencies of HLA-A,B,DR,DQ locus antigens were tested in a group of 25 osteosarcoma patients and in a control group of 250 healthy persons by using complement-dependent microlymphocytoxity technique. The members of both groups were of Chinese Han nationality. Their results were compared statistically. RESULTS: The frequency of HLA-B35 was 0.400 in patient group and 0.048 in the control group. The relative risk of suffering from osteosarcoma in persons carrying HLA-B35 was 13.220 times as high as that in those without this antigen (P < 0.01). Patients with HLA-B13 had 12.048 fold increase in relative risk with poor prognosis compared to those without this antigen (P < 0.05). A tendency of worst prognosis was seen in patients who carried both HLA-B13 and HLA-B35, but patients with HLA-B40 had 7.057 times better relative safety for good prognosis than those without that antigen (P < 0.05). CONCLUSION: HLA-B35 is in close linkage to osteosarcoma susceptible gene in Chinese Han nationality. HLA-B13 and HLA-B40 may be separately related to the malignant and resistant genes of osteosarcoma.

Adolescent↗

Experimental study on biodynamic response to vibration in human and animals.

In order to study the characteristics of human dynamic response to vibration, 56 subjects were exposed to vibration on X, Y and Z axes. It showed that there were two resonance peaks of most local parts of the human body. The curves of transmissibility are essentially the same in all the subjects. It was found that resonance frequencies of the human body decreased with increase of G levels of vibration. These characteristics were also proved in animals. Using three-level artificial neural network, common reflective relation of the resonance frequency with height and weight of the human body and exciting acceleration were obtained. The above findings might be applicable to studies of vibration ergonomics.

Acceleration↗

High prevalence of antiphospholipid antibodies in patients taking procainamide.

OBJECTIVE: To determine whether antiphospholipid antibodies (aPL) are more prevalent in cardiac patients taking procainamide than in a control population of similar elderly cardiac patients and to determine whether these antibodies react in an ELISA in which the primary antigen is beta 2-glycoprotein I (beta 2-GPI). METHODS: aPL and antibodies to beta 2-GPI were measured in 66 patients taking procainamide from a Veterans Administration Medical Center population and a control group of 30 similar cardiac patients not taking procainamide. RESULTS: 21% of the patients taking procainamide and no control patients were found to have moderate to high aPL. There were similar results in an assay that measured anti-beta 2-GPI in the absence of exogenous phospholipids. aPL were associated with antinuclear antibodies and antihistone antibodies but not with diabetes or clinical manifestations of drug related lupus. There was no increase in cholesterol or past thrombotic history associated with aPL, but there was a frequent history of noncardiac thrombosis in patients taking procainamide (25.7%). CONCLUSION: The predictive significance of procainamide induced aPL remains unknown but beta 2-GPI dependent aPL may be of some concern in this elderly population already at high risk for thrombosis.

Adult↗

Effects of mutations in plastocyanin on the kinetics of the protein rearrangement gating the electron-transfer reaction with zinc cytochrome c. Analysis of the rearrangement pathway.

We study, by flash kinetic spectrophotometry on the microsecond time scale, the effects of ionic strength and viscosity on the kinetics of oxidative quenching of the triplet state of zinc cytochrome c (3Zncyt) by the wild-type form and the following nine mutants of cupriplastocyanin: Leu12Glu, Leu12Asn, Phe35Tyr, Gln88Glu, Tyr83Phe, Tyr83His, Asp42Asn, Glu43Asn, and the double mutant Glu59Lys/Glu60Gln. The unimolecular rate constants for the quenching reactions within the persistent diprotein complex, which predominates at low ionic strengths, and within the transient diprotein complex, which is involved at higher ionic strengths, are equal irrespective of the mutation. Evidently, the two complexes are the same. In both reactions, the rate-limiting step is rearrangement of the diprotein complex from a configuration optimal for docking to the one optimal for the subsequent electron-transfer step, which is fast. We investigate the effects of plastocyanin mutations on this rearrangement, which gates the overall electron-transfer reaction. Conversion of the carboxylate anions into amide groups in the lower acidic cluster (residues 42 and 43), replacement of Tyr83 with other aromatic residues, and mutations in the hydrophobic patch in plastocyanin do not significantly affect the rearrangement. Conversion of a pair of carboxylate anions into a cationic and a neutral residue in the upper acidic cluster (residues 59 and 60) impedes the rearrangement. Creation of an anion at position 88, between the upper acidic cluster and the hydrophobic patch, facilitates the rearrangement. The rate constant for the rearrangement smoothly decreases as the solution viscosity increases, irrespective of the mutation. Fittings of this dependence to the modified Kramers's equation and to an empirical equation show that zinc cytochrome c follows the same trajectory on the surfaces of all the plastocyanin mutants but that the obstacles along the way vary as mutations alter the electrostatic potential. Mutations that affect protein association (i.e., change the binding constant) do not necessarily affect the reaction between the associated proteins (i.e., the rate constant) and vice versa. All of the kinetic and thermodynamic effects and noneffects of mutations consistently indicate that in the protein rearrangement the basic patch of zinc cytochrome c moves from a position between the two acidic clusters to a position at or near the upper acidic cluster.

Animals↗

Glial cell-specific differences in repair of O6-methylguanine.

Normal and malignant cells of the oligodendrocyte lineage show increased sensitivity to alkylating agents compared to astrocytes. One of the most mutagenic DNA lesions formed following exposure to alkylating agents is O6-alkylguanine. To determine whether the increased sensitivity to nitrosoureas seen in oligodendrocytes is due to decreased repair capacity for O6-alkylguanine, removal of this lesion from DNA was assessed in primary cultures of rat oligodendrocytes, astrocytes, and microglia. Glial cells were exposed to 1 mM N-methyl-N-nitrosourea for 1 h and allowed 8 or 24 h for repair. Repair was evaluated using an immunoslot blot technique and a monoclonal antibody which recognizes O6-methylguanine (O6MeGua). Astrocytes removed O6MeGua more efficiently (approximately 80% in 24 h) than either oligodendrocytes (approximately 20%) or microglia (approximately 4%). Determination of O6-alkylguanine-DNA-alkyltransferase (AT) activity revealed that astrocytes contain 0.4 pmol/mg protein, which is average by comparison to other cell types. Both oligodendrocytes and microglia exhibited very low levels of AT (oligodendrocytes, 0.08; microglia, 0.01 pmol/mg protein). These data are the first to show that within different populations of glial cells, O6MeGua adduct removal is substantially reduced in both oligodendrocytes and microglia. Rapid removal of O6MeGua in astrocytes coupled with persistence of this mutagenic lesion in oligodendrocytes following exposure of the developing central nervous system to nitrosoureas could contribute to the observed formation of oligodendrogliomas. Inefficient removal of O6MeGua in oligodendrogliomas might also account for their response to chemotherapeutic regimens involving alkylating agents such as procarbazine, lomustine, and carmustine. The lack of repair of O6MeGua in microglia suggests that primary lymphomas of the central nervous system might be sensitive to treatment with alkylating drugs whose toxicity depends on repair of this adduct.

Alkylating Agents↗

Control of beta1 integrin function. Localization of stimulatory epitopes.

The beta1 integrins can be expressed on the surface of cells in a latent form, which is activated by a variety of stimuli. As an approach to examining the transition to an active receptor, a panel of stimulatory antibodies to beta1 were produced and characterized. These antibodies induced adherence of the T-leukemic cell line Jurkat to collagen and fibronectin. Competitive antibody binding assays indicated the existence of at least three distinct epitope clusters A (B3B11, JB1B, 21C8), B (B44, 13B9), and C(N29) defined by the indicated antibodies. Two antibodies to the A site, JB1B and B3B11, were shown to localize to positions 671-703 and 657-670, respectively, of the beta1. This region is located in an area encompassing a predicted disulfide bond between linearly distant cysteines in beta1 (Cys415-Cys671). The homologous region of the beta3 integrin (490 690 and 602 690) has been shown to be one of the sites recognized by stimulatory antibodies to ligand-induced binding sites. The present results indicate the existence of multiple stimulatory regions and suggest considerable homology between the locations of beta1 and beta3 regulatory sites.

Amino Acid Sequence↗

Local infusion of FGF-saporin reduces intimal hyperplasia.

The recent conjugation of the potent ribosome-inactivating protein saporin (SAP) with basic fibroblast growth factor (FGF2) to form recombinant (r)FGF2-SAP permits increased selectivity of this mitoxin for cells exhibiting upregulated FGF receptors. Systemic administration of rFGF-SAP in therapeutic doses, however, may be associated with significant liver toxicity. In this blinded study, we used a local boundary layer infusion approach to increase local drug concentration while minimizing the risk of side effects. Six dogs underwent bilateral carotid endarterectomies. Expanded polytetrafluoroethylene infusion devices, blindly primed with rFGF2-SAP to one artery or vehicle to the contralateral vessel, were anastomosed proximal to the injured segments so that each animal served as its own control. rFGF2-SAP (2 microgram/kg/day) or vehicle (5 microl/hr) was continuously delivered for 14 days from an osmotic reservoir, through the wall of the graft infusion device. Euthanasia was carried out at 14 days and the processed arteries were blindly analyzed for intimal thickening and cellular proliferation. All dogs survived until sacrifice with no clinical side effects. Liver function tests at euthanasia were not significantly altered when compared to baseline values. Intimal area in rFGF2-SAP-treated vessels averaged 0.31 +/- 0.10 mm2 versus 0.57 +/- 0.24 mm2 in the control segments (P = 0.02), a relative reduction of 46%. Cell proliferation, however, was not significantly different at 14 days postendarterectomy (2.40 +/- 1.31% vs 2.39 +/- 0.45%). From this study it can be concluded that locally delivered rFGF2-SAP reduces intimal hyperplasia and that the boundary layer infusion strategy is an effective means for delivering high local drug concentration while minimizing systemic drug effects.

Amino Acid Sequence↗

Large-scale purification and characterization of recombinant fibroblast growth factor-saporin mitotoxin.

In order to produce sufficient quantities of fibroblast growth factor-saporin (rFGF-2-SAP) mitotoxin for preclinical evaluation in models of diseases such as cancer and restenosis, we have undertaken the large-scale expression, purification, and characterization of the recombinant molecule. The fusion gene encoding rFGF-2-SAP was cloned into the inducible pET 11a expression vector and transformed into Escherichia coli strain BL21 (DE3). The transformants were grown using a fed-batch fermentation until the A600 reached 85. At this stage, induction of the expression of the fusion protein led to the production of approximately 2.2 mg/liter per A600 unit. The soluble mitotoxin was purified to homogeneity from cell lysates via expanded bed adsorption chromatography followed by cation-exchange, heparin-affinity, and size-exclusion chromatography. Purified rFGF-2-SAP contained less than 0.5 EU/mg of endotoxin, as determined by gel clot analyses. The highly purified rFGF-2-SAP retained the toxin's ability to inhibit protein synthesis as measured in a cell-free system and was cytotoxic to a number of normal and neoplastic cell lines bearing FGF receptors. Binding studies establish that the fusion protein exerts its effects via the FGF high-affinity receptor.

Binding, Competitive↗

The epidemiology of Chlamydia trachomatis within a sexually transmitted diseases core group.

Female sex workers in Nairobi were prospectively evaluated for risk factors of incident Chlamydia trachomatis infection. Independent risk factors included cervical ectopy (P=.007), gonococcal infection (P=.002), human immunodeficiency virus (HIV) seropositivity (P=.003), HIV seroconversion (P=.001), and duration of prostitution (P=.002). Eighteen different C. trachomatis outer membrane protein (omp1) genotypes were identified, with the allelic composition of the C. trachomatis population changing significantly over time (P=.005). Seventeen of 19 reinfections > or = 6 months apart were with different C. trachomatis omp1 genotypes. Women with HIV infection had an increased proportion of visits with C. trachomatis infection (P=.001) and an increased risk of reinfection (P=.008). Overall, the data demonstrate significant fluctuations in the genotype composition of the C. trachomatis population and a reduced rate of same-genotype reinfection consistent with the occurrence of strain-specific immunity.

Amino Acid Sequence↗