Biomedical subjects

J Shen

Publications and source records attributed to J Shen.

At least 73 records · Page 4Linked to original sources

PubMed2001

Constitutive expression of ErbB-2 in gallbladder epithelium results in development of adenocarcinoma.

Overexpression of ErbB-2 in the basal layer of biliary tract epithelium led to the development of gallbladder adenocarcinoma in 100% of transgenic mice by 3 months of age. In addition, tumors developed in other parts of the biliary tree (e.g., cholangiocarcinoma). Adenocarcinoma of the gallbladder appeared to arise via a stepwise process involving hyperplasia, adenoma formation, and then adenocarcinoma formation. Increased ErbB-2/epidermal growth factor receptor heterodimer formation, activation of mitogen-activated protein kinase, and up-regulation of cyclooxygenase-2 levels (mRNA and protein) were observed in gallbladder epithelium of these mice. These mice represent a unique new animal model for studying biliary tract carcinogenesis.

Adenocarcinoma↗

PubMed2001

[Microvascular decompression for hemifacial spasm: experience of 215 cases].

OBJECTIVE: To investigate the relationship between pre-operational etiological diagnosis of medically intractable hemifacial spasm (HFS) and patterns of offending vessels and the curative effect of microvascular decompression (MVD). METHODS: Two hundred and fifteen patients with medically intractable HFS underwent MVD under general anesthesia. Pre-operative MRI examination was made for all cases to exclude space occupying lesion and magnetic imaging tomographic angiography (MRTA) was conducted for 145 cases of them instead of routine MRI. RESULTS: Routine MRI failed to provide information about offending vessels except for ruling out mass lesions whereas MRTA revealed the offending vessels with a positive rate of 82.8%, thus helping make correct diagnosis and operation decision. Follow-up of more than two years showed that the surgical intervention achieved a high relief rate of 91.2% without major complication, and with a low recurrence rate of only 3.5% after averaging more than two years' follow-up. CONCLUSION: Pre-operative MRTA can replace conventional MRI as a best approach for pre-operational etiological diagnosis of facial spasm. It helps perceive the offending vessels before operation. Skilled microsurgical technique along with correct recognition and mobilization of offending vessels are a must to assure MVD a high efficacious and low risk treatment of choice for HFS patients.

Adult↗

PubMed2001

APP processing and synaptic plasticity in presenilin-1 conditional knockout mice.

We have developed a presenilin-1 (PS1) conditional knockout mouse (cKO), in which PS1 inactivation is restricted to the postnatal forebrain. The PS1 cKO mouse is viable and exhibits no gross abnormalities. The carboxy-terminal fragments of the amyloid precursor protein differentially accumulate in the cerebral cortex of cKO mice, while generation of beta-amyloid peptides is reduced. Expression of Notch downstream effector genes, Hes1, Hes5, and Dll1, is unaffected in the cKO cortex. Although basal synaptic transmission, long-term potentiation, and long-term depression at hippocampal area CA1 synapses are normal, the PS1 cKO mice exhibit subtle but significant deficits in long-term spatial memory. These results demonstrate that inactivation of PS1 function in the adult cerebral cortex leads to reduced Abeta generation and subtle cognitive deficits without affecting expression of Notch downstream genes.

Alzheimer Disease↗

PubMed2001

Transcriptional transactivation by selected short random peptides attached to lexA-GFP fusion proteins.

BACKGROUND: Transcriptional transactivation is a process with remarkable tolerance for sequence diversity and structural geometry. In studies of the features that constitute transactivating functions, acidity has remained one of the most common characteristics observed among native activation domains and activator peptides. RESULTS: We performed a deliberate search of random peptide libraries for peptides capable of conferring transcriptional transactivation on the lexA DNA binding domain. Two libraries, one composed of C-terminal fusions, the other of peptide insertions within the green fluorescent protein structure, were used. We show that (i) peptide sequences other than C-terminal fusions can confer transactivation; (ii) though acidic activator peptides are more common, charge neutral and basic peptides can function as activators; and (iii) peptides as short as 11 amino acids behave in a modular fashion. CONCLUSIONS: These results support the recruitment model of transcriptional activation and, combined with other studies, suggest the possibility of using activator peptides in a variety of applications, including drug development work.

Journal Article↗

PubMed2001

Kinetics study of a selenium-containing ScFv catalytic antibody that mimics glutathione peroxidase.

The steady-state kinetics study and some enzymatic characterization of a selenium-containing scFv catalytic antibody (Se-scFv2F3) were carried out. A novel reaction formula of this abzyme-catalyzed reaction was proposed and a rate equation was obtained according to the formula. The constants in the equation were compared with Dalziel's parameters and the exact meanings of these constants were analyzed. The obtained kinetics parameters from the kinetics study of Se-scFv2F3 were analyzed and compared with those of native glutathione peroxidase.

Antibodies, Catalytic↗

PubMed2001

Increased inducible nitric oxide synthase expression contributes to myocardial dysfunction and higher mortality after myocardial infarction in mice.

BACKGROUND: Inducible nitric oxide synthase (iNOS) is expressed in the myocardium after myocardial infarction (MI) and in heart failure. Its pathophysiological role in these conditions, however, is not clear. We hypothesized that increased NO production from iNOS expression causes myocardial dysfunction and results in higher mortality after MI. METHODS AND RESULTS: MI was induced by left coronary artery ligation in iNOS(-/-) mutant and wild-type mice. Mortality was followed up for 30 days. MI resulted in a significant increase in mortality in both iNOS(-/-) and wild-type mice compared with sham operation (P<0.01). Mortality was significantly decreased and LV myocardial contractility was increased, however, in iNOS(-/-) mice compared with the wild-type mice (P<0.05). Five days after MI, myocardial iNOS mRNA expression, plasma nitrate and nitrite concentrations, and myocardial and plasma nitrotyrosine levels were significantly increased in wild-type compared with iNOS(-/-) mutant mice (P<0.05). Both basal LV +dP/dt and its response to dobutamine were significantly increased in iNOS(-/-) compared with the wild-type mice (P<0.05). CONCLUSIONS: Increased NO production from iNOS expression contributes to myocardial dysfunction and mortality after MI in mice.

Animals↗

PubMed2001

alpha-Synuclein occurs in lipid-rich high molecular weight complexes, binds fatty acids, and shows homology to the fatty acid-binding proteins.

alpha-Synuclein (alphaS) is a 140-residue neuronal protein that forms insoluble cytoplasmic aggregates in Parkinson's disease (PD) and several other neurodegenerative disorders. Two missense mutations (A53T and A30P) are linked to rare forms of familial PD. The normal function of alphaS is unknown, and cultured cell systems that model its modification from soluble monomers to aggregated forms have not been reported. Through a systematic centrifugal fractionation of mesencephalic neuronal cell lines and transgenic mouse brains expressing wild-type or A53T human alphaS, we observed unusual, previously unrecognized species of alphaS that migrate well above the 17-kDa monomeric form in denaturing gels. Incubation at 65 degrees C of high-speed cytosols from cells or brains revealed a modified alphaS species migrating at approximately 36 kDa and an extensive higher molecular mass alphaS-reactive smear. Extraction of the cytosols with chloroform/methanol or with a resin (Lipidex 1000) that binds fatty acids resulted in a similar pattern of higher molecular mass alphaS forms. On the basis of this effect of delipidation, we reexamined the primary structure of alphaS and detected a motif at the N and C termini that is homologous to a fatty acid-binding protein signature. In accord, we found that purified human alphaS binds oleic acid, with an apparent K(d) of 12.5 microM. We also observed an enhanced association of A53T alphaS with microsomal membranes in both mesencephalic cells and transgenic mouse brains. We conclude that alphaS has biochemical properties and a structural motif that suggest it is a novel member of the fatty acid-binding protein family and may thus transport fatty acids between the aqueous and membrane phospholipid compartments of the neuronal cytoplasm.

Amino Acid Sequence↗

PubMed2001

The gene ygdP, associated with the invasiveness of Escherichia coli K1, designates a Nudix hydrolase, Orf176, active on adenosine (5')-pentaphospho-(5')-adenosine (Ap5A).

ygdP, a gene associated with the invasion of brain microvascular endothelial cells by Escherichia coli K1 (Badger, J. L., Wass, C. A., and Kim, K. S. (2000) Mol. Microbiol. 36, 174-182), the primary Gram-negative bacterium causing meningitis in newborns, has been cloned and expressed in E. coli. The protein, YgdP, was purified to near homogeneity and identified as a member of the Nudix hydrolase subfamily of dinucleoside oligophosphate pyrophosphatases. It catalyzes the hydrolysis of diadenosine tetra-, penta-, and hexa-phosphates with a preference for diadenosine penta-phosphate, from which it forms ATP and ADP. The enzyme has a requirement for a divalent metal cation that can be met with Mg2+, Zn2+, or Mn2+ and, like most of the Nudix hydrolases, has an alkaline pH optimum between 8.5 and 9. This is the second identification of a gene associated with the invasiveness of a human pathogen as a member of the Nudix hydrolase subfamily of dinucleoside oligophosphate pyrophosphatases, and an examination of homologous proteins in other invasive bacteria suggests that this may be a common feature of cellular invasion.

Amino Acid Sequence↗

PubMed2001

Kinetics study of a selenium-containing ScFv catalytic antibody that mimics glutathione peroxidase.

The steady state kinetic study and some enzymic characterization of a selenium-containing scFv catalytic antibody (Se-scFv2F3) was carried out. A novel reaction formula of this abzyme-catalyzed reaction was proposed and a rate equation was gotten according to the formula. The constants in the equation were compared with Dalziel's parameters and the exact meanings of these constants were analyzed. The gotten kinetics parameters from the kinetics study of Se-scFv2F3 were analyzed and compared with that of native glutathione peroxidase.

Antibodies, Catalytic↗

PubMed2001

Unwinding the molecular basis of the Werner syndrome.

Werner syndrome (WS) is an autosomal recessive disease manifested by the premature onset of age-related phenotypes, including diseases such as atherosclerosis and cancer. This mimicry of normal aging with the possible exception of central nervous system manifestations has made it a focus of recent molecular studies on the pathophysiology of aging. In culture, cells obtained from patients with WS are genetically unstable, characterized by an increased frequency of nonclonal translocations and extensive DNA deletions. The WS gene product (WRN) is a DNA helicase belonging to the RecQ family, but is unique within this family in that it also contains an exonuclease activity. In addition to unwinding double-stranded DNA, WRN helicase is able to resolve aberrant DNA structures such as G4 tetraplexes, triplexes and 4-way junctions. Concordant with this structure-specificity, WRN exonuclease preferentially hydrolyzes alternative DNA that contains bubbles, extra-helical loops, 3-way junctions or 4-way junctions. WRN has been shown to bind to and/or functionally interact with other proteins, including replication protein A (RPA), proliferating cell nuclear antigen (PCNA), DNA topoisomerase I, Ku 86/70, DNA polymerase delta and p53. Each of these interacting proteins is involved in DNA transactions including those that resolve alternative DNA structures or repair DNA damage. The biochemical activities of WRN and the functions of WRN associated proteins suggest that in vivo WRN resolves DNA topological or structural aberrations that either occur during DNA metabolic processes such as recombination, replication and repair, or are the outcome of DNA damage.

ATPases Associated with Diverse Cellular Activitie↗

PubMed2001

Essential role for Gab2 in the allergic response.

Dos/Gab family scaffolding adapters (Dos, Gab1, Gab2) bind several signal relay molecules, including the protein-tyrosine phosphatase Shp-2 and phosphatidylinositol-3-OH kinase (PI(3)K); they are also implicated in growth factor, cytokine and antigen receptor signal transduction. Mice lacking Gab1 die during embryogenesis and show defective responses to several stimuli. Here we report that Gab2-/- mice are viable and generally healthy; however, the response (for example, degranulation and cytokine gene expression) of Gab2-/- mast cells to stimulation of the high affinity immunoglobulin-epsilon (IgE) receptor Fc(epsilon)RI is defective. Accordingly, allergic reactions such as passive cutaneous and systemic anaphylaxis are markedly impaired in Gab2-/- mice. Biochemical analyses reveal that signalling pathways dependent on PI(3)K, a critical component of Fc(epsilon)RI signalling, are defective in Gab2-/- mast cells. Our data identify Gab2 as the principal activator of PI(3)K in response to Fc(epsilon)RI activation, thereby providing genetic evidence that Dos/Gab family scaffolds regulate the PI(3)K pathway in vivo. Gab2 and/or its associated signalling molecules may be new targets for developing drugs to treat allergy.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Lewis rat pancreas, but not cardiac xenografts, are resistant to anti-gal antibody mediated hyperacute rejection.

BACKGROUND: The objective of this study was to evaluate the role of anti-Gal Abs and non-anti-Gal Abs in hyperacute rejection (HAR) of concordant pancreas xenografts compared with heart xenografts. In addition, we tested whether rejection of Lewis rat pancreas grafts was T-cell dependent and could be prevented by anti-T-cell treatment. METHODS: To determine the role of anti-Gal Abs in the induction of HAR, Lewis rat pancreas and heart xenografts were transplanted into alpha1,3Galactosyltransferase knockout (GT-Ko) mice treated with normal human serum (NHS) or hyperimmune serum, or into presensitized GT-Ko mice. To investigate whether rejection of pancreas xenograft was mediated by a T-cell dependent response, Lewis rat pancreas grafts were transplanted into streptozotocin (STZ)-induced diabetic GT-Ko mice treated with FK506, anti-CD4 mAbs (GK1.5), and thymectomy. Antidonor-specific IgM and IgG and anti-Gal Abs were analyzed by flow cytometry. Rejected and long-term surviving pancreas xenografts were assessed by functional (blood glucose) and histopathological examination. RESULTS: HAR of Lewis rat pancreas xenografts could not be induced by NHS (0.4 ml), whereas NHS (0.2 ml) resulted in HAR of Lewis heart xenografts. Infusion of Lewis rat-specific hyperimmune serum (0.2 ml) resulted in HAR of Lewis rat pancreas xenografts. In addition, second Lewis rat pancreas grafts were hyperacutely rejected by presensitized GT-Ko mice. Immunohistochemical staining showed a low expression of Galalpha1,3Gal antigen in the endocrine tissue compared with that in the cardiac grafts. The levels of anti-Gal Abs in pancreas xenograft transplantation did not increase in GT-Ko mice after pancreas xenograft transplantation that was significantly increased after heart transplantation. FK506 treatment induced long-term survival of Lewis pancreas xenografts (mean survival time (MST) >90 days). Anti-CD4 treatment delayed rejection of Lewis rat pancreas xenografts with MST of 34.3 days, whereas anti-CD4, in combination with thymectomy, synergistically prolonged survival of pancreas xenograft (MST=70.4 days). CONCLUSION: Pancreas xenograft is resistant to anti-Gal Abs-induced HAR but is susceptible to anti-donor specific Abs. Rejection of Lewis pancreas xenograft in STZ-induced, diabetic, GT-Ko mice is T-cell dependent.

Acute Disease↗

PubMed2001

The antiangiogenic property of docetaxel is synergistic with a recombinant humanized monoclonal antibody against vascular endothelial growth factor or 2-methoxyestradiol but antagonized by endothelial growth factors.

Numerous chemotherapeutic agents have been shown to have an inhibitory effect on endothelial cell proliferation and migration, and tubule formation. In this study, we examined the antiangiogenic activity of docetaxel. Docetaxel inhibited endothelial cell proliferation and tubule formation in vitro in a dose-dependent fashion. Docetaxel treatment also inhibited angiogenesis in an in vivo Matrigel plug assay. The endothelial stimulating factors, vascular endothelial cell growth factor (VEGF) and basic fibroblast growth factor are able to protect endothelial cells from the antiangiogenic properties of docetaxel. This protective effect can be overcome by a recombinant humanized monoclonal antibody directed against VEGF in both in vitro and in vivo models. Similarly, combination of docetaxel with the antiangiogenic agent 2-methoxyestradiol also overcomes the protective effect of VEGF in both in vitro and in vivo models. These data suggest that microenvironmental factors (e.g., local release of VEGF and basic fibroblast growth factor) could play a role in decreasing the antiangiogenic effects of docetaxel, whereas agents such as 2- methoxyestradiol and recombinant humanized monoclonal antibody directed against VEGF may reverse this protective effect.

2-Methoxyestradiol↗

PubMed2001

Repression of transcription of the p27(Kip1) cyclin-dependent kinase inhibitor gene by c-Myc.

Upon engagement of the B Cell Receptor (BCR) of WEHI 231 immature B cells, a drop in c-Myc expression is followed by activation of the cyclin-dependent kinase inhibitor (CKI) p27(Kip1), which induces growth arrest and apoptosis. Here, we report inverse patterns of p27 and c-Myc protein expression follow BCR engagement. We present evidence demonstrating, for the first time, that the p27(Kip1) gene is a target of transcriptional repression by c-Myc. Specifically, the changes in p27 protein levels correlated with changes in p27 mRNA levels, and gene transcription. Induction of p27 promoter activity followed BCR engagement of WEHI 231 cells, and this induction could be repressed upon co-transfection of a c-Myc expression vector. Inhibition of the TATA-less p27 promoter by c-Myc was also observed in Jurkat T cells, vascular smooth muscle, and Hs578T breast cancer cells, extending the observation beyond immune cells. Consistent with a putative Inr element CCAGACC (where +1 is underlined) at the start site of transcription in the p27 promoter, deletion of Myc homology box II reduced the extent of repression. Furthermore, enhanced repression was observed upon transfection of the c-Myc 'super-repressor', with mutation of Phe115 to Leu. The sequences mediating transcriptional activity and c-Myc repression were mapped to bp -20 to +20 of the p27 gene. Finally, binding of Max was shown to facilitate c-Myc binding and repression of p27 promoter activity. Overall, these studies identify the p27 CKI gene as a new target whereby c-Myc can control cell proliferation, survival and neoplastic transformation.

Animals↗

PubMed2001

Analgesic domains of interferon-alpha.

Interferon-alpha (IFNalpha) is not only an immunoregulatory factor, but is also an analgesic molecule. We ever reported that there exist distinct domains in IFNalpha molecule that mediate immune and analgesic effects respectively and inferred that the analgesic domain locates around the 122nd Tyr residue of IFNalpha molecule in the tertiary structure. After the 36th Phe residue, which was located closely to the 122nd Tyr residue in the tertiary structure, was mutated to Ser using site-directed mutagenesis, the analgesic activity of this mutant lost completely, but the antiviral activity of IFNalpha still maintained 40.5% of wild type IFNalpha. The results suggest that the 36th Phe residue is one of the constituent for the analgesic domain of IFNalpha and inferred that the analgesic domain of IFNalpha consists of the 122nd Tyr and the residues around the 122nd in the tertiary structure, which include the 36th Phe.

Analgesics↗

PubMed2001

A novel glutathione peroxidase mimic with antioxidant activity.

Many diseases are associated with the overproduction of hydroperoxides that inflict cell damage. A novel cyclodextrin derivative, 6A,6B-diseleninic acid-6A',6B'-selenium bridged beta-cyclodextrin (6-diSeCD), was synthesized to be a functional mimic of glutathione peroxidase (GPX) that normally removes these hydroperoxides. The mimic had high catalytic GPX activity of 13.5 U/micromol, which is 13.6-fold higher than ebselen (PZ51), and was chemically and biologically stable in vitro. Antioxidant activity was studied by ferrous sulfate/ascorbate-induced mitochondria damage model system. These data show that the mimic has great antioxidant activity. Such mimics may result in better clinical therapies for diseases mediated by hydroperoxides.

Animals↗

PubMed2001

Surface-enhanced Raman spectra study of metal complexes of N-D-glucosamine beta-naphthaldehyde and glycine and their interaction with DNA.

Copper(II), zinc(II), cobalt(II) and cobalt(III) complexes of N-D-glucosamine beta-naphthaldehyde (C17H19O6N, NG) and glycine were synthesized. The four novel metal complexes, Cu(II)C19H28O11N2(CuGNG), Zn(II)C19H24O9N2 (ZnGNG), Co(II)C19H28O11N2(Co(II)GNG) and Co(III)C21H29O12N2(Co(III)GNG) were characterized by means of infrared (IR), electronic absorption spectroscopy and NMR etc. The surface-enhanced Raman spectra of the four complexes and their interaction with DNA were studied. By comparison of the surface-enhanced Raman spectra (SERS), the information of the four complexes' SER active sites and adsorption orientation were obtained. Combined with fluorescence spectra of Ethidium bromide (EthBr) DNA system, we concluded that none of the four complexes intercalate into DNA and that the presence of the glycine ligand lowered the anticancer activity of NG series complexes.

Animals↗

PubMed2001

Crystal structure of human cyclin-dependent kinase 2 in complex with the adenine-derived inhibitor H717.

Cyclin-dependent kinases (CDKs) are regulatory proteins of the eukaryotic cell cycle. They act after association with different cyclins, the concentrations of which vary throughout the progression of the cell cycle. As central mediators of cell growth, CDKs are potential targets for inhibitory molecules that would allow disruption of the cell cycle in order to evoke an antiproliferative effect and may therefore be useful as cancer therapeutics. We synthesized several inhibitory 2,6,9-trisubstituted purine derivatives and solved the crystal structure of one of these compounds, H717, in complex with human CDK2 at 2.6 A resolution. The orientation of the C2-p-diaminocyclohexyl portion of the inhibitor is strikingly different from those of similar moieties in other related inhibitor complexes. The N9-cyclopentyl ring fully occupies a space in the enzyme which is otherwise empty, while the C6-N-aminobenzyl substituent points out of the ATP-binding site. The structure provides a basis for the further development of more potent inhibitory drugs.

Adenine↗