Biomedical subjects

Z Shen

Publications and source records attributed to Z Shen.

At least 19 recordsLinked to original sources

PubMed2002

Alpha-glucosidase inhibition from a Chinese medical herb (Ramulus mori) in normal and diabetic rats and mice.

Alpha-glucosidase inhibitors are oral antidiabetic drugs. A traditional Chinese medical herb, Sangzhi (Ramulus mori), appears to have properties similar to those of alpha-glucosidase inhibitors. The effects of an aqueous extract of Shangzhi (SZ) were studied in normal and alloxan diabetic rats and mice, and these results compared with those for acarbose, an alpha-glucosidase inhibitor. In our grade-dose studies, SZ was found to lower and prolong the zenith of blood glucose concentration (ZBG) after sucrose or starch loading and stabilize blood glucose levels in fasting normal and alloxan diabetic mice. After 2 weeks of SZ administration with high-calorie chow or a normal diet, the fasting and non-fasting blood glucose concentrations in alloxan diabetic mice and rats were decreased. In alloxan rats, the blood fructosamine concentration was lowered. Results for acarbose and SZ were similar. These indicate that SZ has alpha-glucosidase inhibitory effects.

Alloxan↗

PubMed2002

Multiple transcription factor profiling by enzyme-linked immunoassay.

Transcription factor-DNA interactions have been widely studied in the regulation of gene expression. We have established an enzyme-linked immunoassay platform to quantify specific transcriptionfactor-DNA interactions. In our assay, dsDNA immobilized on a 96-well plate captures the transcriptionfactor from the nuclear extract of mammalian cells. The DNA-bound transcription factor is detected and quantified by enzyme-linked immunoassay using a transcription factor-specific antibody. We have profiled multiple transcription factors involved in inflammation including NFkappaB p50, NFkappaB p65, c-Rel, c-Fos, CREB-1, and ATF-2. When compared with the traditional electrophoretic mobility shift assay, the enzyme-linked immunoassay shows a 10-fold higher sensitivity, eliminates the use of radioactivity, allows for a high-throughput format, and is faster.

Activating Transcription Factor 2↗

PubMed2001

Overexpression of human RAD51 and RAD52 reduces double-strand break-induced homologous recombination in mammalian cells.

Double-strand breaks (DSBs) can be repaired by homologous recombination (HR) in mammalian cells, often resulting in gene conversion. RAD51 functions with RAD52 and other proteins to effect strand exchange during HR, forming heteroduplex DNA (hDNA) that is resolved by mismatch repair to yield a gene conversion tract. In mammalian cells RAD51 and RAD52 overexpression increase the frequency of spontaneous HR, and one study indicated that overexpression of mouse RAD51 enhances DSB-induced HR in Chinese hamster ovary (CHO) cells. We tested the effects of transient and stable overexpression of human RAD51 and/or human RAD52 on DSB-induced HR in CHO cells and in human cells. DSBs were targeted to chromosomal recombination substrates with I-SceI nuclease. In all cases, excess RAD51 and/or RAD52 reduced DSB-induced HR, contrasting with prior studies. These distinct results may reflect differences in recombination substrate structures or different levels of overexpression. Excess RAD51/RAD52 did not increase conversion tract lengths, nor were product spectra otherwise altered, indicating that excess HR proteins can have dominant negative effects on HR initiation, but do not affect later steps such as hDNA formation, mismatch repair or the resolution of intermediates.

Animals↗

PubMed2001

Interaction with BRCA2 suggests a role for filamin-1 (hsFLNa) in DNA damage response.

The BRCA2 tumor suppressor plays significant roles in DNA damage response. The human actin binding protein filamin-1 (hsFLNa, also known as ABP-280) participates in orthogonal actin network, cellular stress responses, signal transduction, and cell migration. Through a yeast two-hybrid system, an in vitro binding assay, and in vivo co-immunoprecipitations, we identified an interaction between BRCA2 and hsFLNa. The hsFLNa binding domain of BRCA2 was mapped to an internal conserved region, and the BRCA2-interacting domain of hsFLNa was mapped to its C terminus. Although hsFLNa is known for its cytoplasmic functions in cell migration and signal transduction, some hsFLNa resides in the nucleus, raising the possibility that it participates in DNA damage response through a nuclear interaction with BRCA2. Lack of hsFLNa renders a human melanoma cell line (M2) more sensitive to several genotoxic agents including gamma irradiation, bleomycin, and ultraviolet-c light. These results suggest that BRCA2/hsFLNa interaction may serve to connect cytoskeletal signal transduction to DNA damage response pathways.

BRCA2 Protein↗

PubMed2001

A mixed-valence manganese(III)-manganese(IV) di-mu-oxo complex, [(cyclam)MnO]2(ClO4)2(NO3).

The title dinuclear di-mu-oxo-bis[(1,4,8,11-tetraazacyclotetradecane-kappa(4)N)manganese(III,IV)] diperchlorate nitrate complex, [Mn(2)O(2)(C(10)H(24)N(4))(2)](ClO(4))(2)(NO(3)) or [(cyclam)MnO](2)(ClO(4))(2)(NO(3)), was self-assembled by the reaction of Mn(2+) with 1,4,8,11-tetraazacyclotetradecane in aqueous media. The structure of this compound consists of a centrosymmetric binuclear [(cyclam)MnO](3+) unit, two perchlorate anions and one nitrate anion. While the low-temperature electron paramagnetic resonance spectra show a typical 16-line signal for a di-mu-oxo Mn(III)/Mn(IV) dimer, the magnetic susceptibility studies also confirm a characteristic antiferromagnetic coupling between the electronic spins of the Mn(IV) and Mn(III) ions.

Journal Article↗

PubMed2001

Resolution of structural isomers of sialylated oligosaccharides by capillary electrophoresis.

The resolution of structural isomers in mixtures of oligosaccharides is often challenging. Capillary electrophoresis was employed to separate three sets of structural isomers of sialylated oligosaccharides found in human milk and bovine colostrum. Different running buffers were necessary to achieve optimal baseline resolution. To resolve 3'- and 6'-sialyllactoses, 0.2 M aqueous sodium phosphate containing 40% methanol as an organic modifier was used as a running buffer. To resolve 3'- and 6'-sialyllactosamines, 0.4 M aqueous sodium phosphate without organic modifier was used. Baseline resolution of sialyllacto-N-tetraose-a and -b and sialyllacto-N-neotetraose-c was achieved with a 0.4 M Tris-HCl buffer containing 250 mM sodium dodecyl sulfate and 10% methanol as the organic modifier. Thus, each of these sets of structural isomers of sialylated oligosaccharides required a unique running buffer with respect to buffer type, concentration, pH, presence of organic modifiers, and surfactants. Similar electrophoresis conditions may be useful for resolving and analyzing other structural isomers of acidic oligosaccharides by capillary electrophoresis.

Carbohydrate Conformation↗

PubMed2001

Degradation of dye solution by an activated carbon fiber electrode electrolysis system.

Degradation of 29 dyes by means of an activated carbon fiber (ACF) electrode electrolysis system was performed successfully. Almost all dye solutions tested were decolorized effectively in this ACF electrolysis process. Internal relationships between treatment mechanisms and chemical composition of the dye have been discussed in this paper. Generally, it is shown that higher solubility leads to greater degradation in the process. Dyes with many -SO3-, COO-, -SO2NH2, -OH, hydrophilic groups, and azo linkages are susceptible to reduction. However, dyes with many -C=O, -NH-and aromatic groups, and hydrophobic groups, tend to be adsorbed. For dyes with -SO3-, COOH and -OH groups, if their molecules linearly spread in solution and have a significant tendency to form colloids by hydrogenous bonding, they also tend to be adsorbed and flocculated. Typical dynamic electrolysis of dye Acid Red B, Vat Blue BO and Disperse Red E-4B shows how the two major mechanisms, degradation and adsorption, act differently during treatment. Reduction occurs evenly during treatment. During the dominant adsorption process, after certain amount of iron is generated, colloid precipitation occurs and TOC and color are rapidly removed.

Adsorption↗

PubMed2001

Prolonged hypoglycemic effect of insulin-loaded polybutylcyanoacrylate nanoparticles after pulmonary administration to normal rats.

Insulin-loaded polybutylcyanoacrylate nanoparticles were prepared by emulsion polymerization. The mean diameter of the nanoparticles was 254.7 nm with a polydispersity of 0.064. The associating ratio of insulin to the nanoparticles reached 79.1%. Studies on in vitro release kinetics showed that release profiles can be modeled using a biexponential function and the burst effect was obvious. After various doses of insulin-loaded nanoparticles were intratracheally given to normal rats, significant decrease of glucose level was achieved at each dose group from 5 to 20 IU kg-1. The minimum blood glucose concentration reached 46.9%, 30.4% and 13.6% of the initial level after pulmonary delivery of 5, 10 and 20 IU kg-1 insulin-loaded nanoparticles to normal rats, respectively. The time to reach the minimum blood glucose level (Tmin) was 4, 4 and 8 h for three doses, respectively. The duration of glucose level below 80% of insulin-loaded nanoparticles was much longer than that of insulin solution at every dose. Relative pharmacological bioavailability of insulin-loaded nanoparticles by pulmonary administration was 57.2% over the same formulation by subcutaneous administration.

Animals↗

PubMed2001

Functional analysis and intracellular localization of p53 modified by SUMO-1.

p53 tumor suppressor is a subject of several post-translational modifications, including phosphorylation, ubiquitination and acetylation, which regulate p53 function. A new covalent modification of p53 at lysine 386 by SUMO-1 was recently identified. To elucidate the function of sumoylated p53, we compared the properties of wild type p53 and sumoylation-deficient p53 mutant, K386R. No differences were found between wild type p53 and K386R mutant of p53 in transactivation or growth suppression assays. Moreover, overexpression of SUMO-1 has no effect on p53-regulated transcription. Biochemical fractionation showed that sumoylated p53 is localized in the nucleus and is tightly bound to chromatin structures. p53 and SUMO-1 co-localized in PML nuclear bodies in 293 cells and the nucleoli in MCF7 and HT1080 cells. However, sumoylation-deficient p53 mutant showed a similar pattern of intranuclear localization, suggesting that SUMO-1 does not target p53 to subnuclear structures. These data indicate that SUMO-1 modification of p53 at lysine 386 may not be essential for p53's cellular localization, transcriptional activation, or growth regulation.

Amino Acid Sequence↗

PubMed2001

Effects of all-trans-retinoic acid and arsenic trioxide on the hemostatic disturbance associated with acute promyelocytic leukemia.

To study the in vivo effect of all-trans-retinoic acid (ATRA) and arsenic trioxide (As(2)O(3)) on the expression of tissue factor (TF) and the other hemostatic disturbance, a series of parameters were measured either in bone marrow blasts or plasma from acute promyelocytic leukemia (APL) patients. The plasma parameters were measured by ELISA or chromogenic studies. The TF transcription was assessed using reverse transcription-polymerase chain reaction (RT-PCR) technique. The results indicated that the blast cell procoagulant activity (PCA), TF antigen of APL cell lysate, as well as the transcription of APL TF mRNA elevated at diagnosis, were reduced after ATRA or As(2)O(3) therapy. The plasma level of P-selectin, TF, thrombin-antithrombin complex (TAT), soluble fibrinmonomer complex, thrombomodulin (TM), tissue factor pathway inhibitor (TFPI), plasmin-antiplasmin complex, tissue plasminogen activator (t-PA) activity, urokinase plasminogen activator (u-PA) and its receptor (u-PAR), and D-dimer (D-D) significantly increased. Fibrinogen (Fg), antigen level of protein C (PC), plasminogen (PLG) activity, alpha(2)-plasminogen inhibitor activity (alpha(2)-PI), and plasminogen activator inhibitor (PAI) activity were decreased at diagnosis. The protein C activity (PC:A) and protein S (PS) remained unchanged. All the parameters were restored to normal ranges after complete remission (CR) except elevation of TF and TAT in both groups, as well as PC:A, PS, and t-PA in the ATRA group. In conclusion, there existed activation of platelets and consumption of anticoagulants as well as activation of coagulation and fibrinolytic system before treatment. Both ATRA and As(2)O(3) therapy downregulated the expression of TF mRNA, decreased the PCA and TF level in APL cells, significantly inhibited coagulation activation, corrected secondary hyperfibrinolysis and the other hemostatic abnormalities, and thus greatly improved the bleeding symptom in early stage of the treatment.

Adolescent↗

PubMed2001

Desorption/ionization on silicon (DIOS): a diverse mass spectrometry platform for protein characterization.

Since the advent of matrix-assisted laser desorption/ionization and electrospray ionization, mass spectrometry has played an increasingly important role in protein functional characterization, identification, and structural analysis. Expanding this role, desorption/ionization on silicon (DIOS) is a new approach that allows for the analysis of proteins and related small molecules. Despite the absence of matrix, DIOS-MS yields little or no fragmentation and is relatively tolerant of moderate amounts of contaminants commonly found in biological samples. Here, functional assays were performed on an esterase, a glycosidase, a lipase, as well as exo- and endoproteases by using enzyme-specific substrates. Enzyme activity also was monitored in the presence of inhibitors, successfully demonstrating the ability of DIOS to be used as an inhibitor screen. Because DIOS is a matrix-free desorption technique, it also can be used as a platform for multiple analyses to be performed on the same protein. This unique advantage was demonstrated with acetylcholine esterase for qualitative and quantitative characterization and also by its subsequent identification directly from the DIOS platform.

Acetylcholine↗

PubMed2001

Heteronuclear nuclear magnetic resonance assignments, structure and dynamics of SUMO-1, a human ubiquitin-like protein.

The structure of a ubiquitin-like protein, small ubiquitin-related modifier-1 (SUMO-1), was earlier determined using homonuclear nuclear magnetic resonance (NMR) spectroscopy, since the spectral quality of the protein was not suitable for heteronuclear NMR data collection. In this study, a slightly different construct of the SUMO-1 gene was used for protein over-expression. The protein purified from this construct showed high spectral qualities, therefore, multi-dimensional heteronuclear NMR data for a dynamic study and structural determination were acquired. The structure of SUMO-1 obtained in this study differs in several respects from the structure obtained from homonuclear NMR data. Furthermore, structural differences were observed between the new SUMO-1 and ubiquitin structures. These differences may be important for SUMO-1-specific recognition in cells. Additionally, relaxation parameters indicate that SUMO-1 undergoes highly anisotropic tumbling in solution and that the long amino (N)-terminal sequence of SUMO-1 is highly dynamic with increasing flexibility towards the end.

Escherichia coli↗

PubMed2001

Eosinophil peroxidase catalyzes bromination of free nucleosides and double-stranded DNA.

Chronic parasitic infections are a major risk factor for cancer development in many underdeveloped countries. Oxidative damage of DNA may provide a mechanism linking these processes. Eosinophil recruitment is a hallmark of parasitic infections and many forms of cancer, and eosinophil peroxidase (EPO), a secreted hemoprotein, plays a central role in oxidant production by these cells. However, mechanisms through which EPO may facilitate DNA oxidation have not been fully characterized. Here, we show that EPO effectively uses plasma levels of bromide as a cosubstrate to brominate bases in nucleotides and double-stranded DNA, forming several stable novel brominated adducts. Products were characterized by HPLC with on-line UV spectroscopy and electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS). Ring assignments for brominated purine bases as their 8-bromo adducts were identified by NMR spectroscopy. Using stable isotope dilution LC/ESI/MS/MS, we show that while guanine is the preferred purine targeted for bromination as a free nucleobase, 8-bromoadenine is the major purine oxidation product generated following exposure of double-stranded DNA to either HOBr or the EPO/H(2)O(2)/Br(-) system. Bromination of nucleobases was inhibited by scavengers of hypohalous acids such as the thioether methionine, but not by a large molar excess of primary amines. Subsequently, N-monobromoamines were demonstrated to be effective brominating agents for both free nucleobases and adenine within intact DNA. A rationale for selective modification of adenine, but not guanine, in double-stranded DNA based upon stereochemical criteria is presented. Collectively, these results suggest that specific brominated DNA bases may serve as novel markers for monitoring oxidative damage of DNA and the nucleotide pool by brominating oxidants.

Adenine↗

PubMed2001

Porous silicon as a versatile platform for laser desorption/ionization mass spectrometry.

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) is a novel method for generating and analyzing gas-phase ions that employs direct laser vaporization. The structure and physicochemical properties of the porous silicon surfaces are crucial to DIOS-MS performance and are controlled by the selection of silicon and the electrochemical etching conditions. Porous silicon generation and DIOS signals were examined as a function of silicon crystal orientation, resistivity, etching solution, etching current density, etching time, and irradiation. Pre-and postetching conditions were also examined for their effect on DIOS signal as were chemical modifications to examine stability with respect to surface oxidation. Pore size and other physical characteristics were examined by scanning electron microscopy and Fourier transform infrared spectroscopy, and correlated with DIOS-MS signal. Porous silicon surfaces optimized for DIOS response were examined for their applicability to quantitative analysis, organic reaction monitoring, post-source decay mass spectrometry, and chromatography.

Journal Article↗

PubMed2001

Inhibition of breast and brain cancer cell growth by BCCIPalpha, an evolutionarily conserved nuclear protein that interacts with BRCA2.

BRCA2 is a tumor suppressor gene involved in mammary tumorigenesis. Although important functions have been assigned to a few conserved domains of BRCA2, little is known about the longest internal conserved domain encoded by exons 14-24. We identified a novel protein, designated BCCIPalpha, that interacts with part of the internal conserved region of human BRCA2. Human BCCIP represents a family of proteins that are evolutionarily conserved, and contain three distinct domains: an N-terminus acidic domain (NAD) of 30-60 amino acids, an internal conserved domain (ICD) of 180-220 amino acids, and a C-terminus variable domain (CVD) of 30-60 amino acids. The N-terminal half of the human BCCIP ICD shares moderate homology with regions of calmodulin and M-calpain, suggesting that BCCIP may also bind Ca. Human cells express both a longer, BCCIPalpha, and a shorter, BCCIPbeta, form of the protein, which differ in their CVD. BCCIP is a nuclear protein highly expressed in testis. Although BCCIPbeta expression is relatively consistent in cancer cells, the expression of BCCIPalpha varies in cancer cell lines. The BCCIPalpha gene is located at chromosome 10q25.3-26.2, a region frequently altered in brain and other cancers. Furthermore, expression of BCCIPalpha inhibits breast and brain cancer cell growth, but fails to inhibit HT1080 cells and a non-transformed human skin fibroblast. These results suggest that BCCIPalpha is an important cofactor for BRCA2 in tumor suppression.

Amino Acid Sequence↗

PubMed2001

CCR7 expression and memory T cell diversity in humans.

CCR7, along with L-selectin and LFA-1, mediates homing of T cells to secondary lymphoid organs via high endothelial venules (HEV). CCR7 has also been implicated in microenvironmental positioning of lymphocytes within secondary lymphoid organs and in return of lymphocytes and dendritic cells to the lymph after passage through nonlymphoid tissues. We have generated mAbs to human CCR7, whose specificities correlate with functional migration of lymphocyte subsets to known CCR7 ligands. We find that CCR7 is expressed on the vast majority of peripheral blood T cells, including most cells that express adhesion molecules (cutaneous lymphocyte Ag alpha(4)beta(7) integrin) required for homing to nonlymphoid tissues. A subset of CD27(neg) memory CD4 T cells from human peripheral blood is greatly enriched in the CCR7(neg) population, as well as L-selectin(neg) cells, suggesting that these cells are incapable of homing to secondary lymphoid organs. Accordingly, CD27(neg) T cells are rare within tonsil, a representative secondary lymphoid organ. All resting T cells within secondary lymphoid organs express high levels of CCR7, but many activated cells lack CCR7. CCR7 loss in activated CD4 cells accompanies CXC chemokine receptor (CXCR)5 gain, suggesting that the reciprocal expression of these two receptors may contribute to differential positioning of resting vs activated cells within the organ. Lymphocytes isolated from nonlymphoid tissues (such as skin, lung, or intestine) contain many CD27(neg) cells lacking CCR7. The ratio of CD27(neg)/CCR7(neg) cells to CD27(pos)/CCR7(pos) cells varies from tissue to tissue, and may correlate with the number of cells actively engaged in Ag recognition within a given tissue.

Biomarkers↗

PubMed2001

Fatty acid composition of lysophosphatidic acid and lysophosphatidylinositol in plasma from patients with ovarian cancer and other gynecological diseases.

OBJECTIVE: We previously reported that plasma levels of total lysophosphatidic acid (LPA) represented a potential biomarker for ovarian cancer and other gynecological cancers [1]. However, total LPA is composed of different LPA species with distinct fatty acid chains. The major objective of the current study, therefore, was to determine whether one or more specific fatty acid LPA species was associated with disease or disease staging. If this was determined, these species could be useful in further improving the sensitivity and/or specificity of this biomarker for the diagnosis and/or prognosis of the disease. Because lysophosphatidylinositol (LPI) co-migrates with LPA, this study represents the analysis of combined molecular species from both lysolipid classes. METHODS: The patient population, sample collection, and analyses have been reported previously [1]. Lipids were hydrolyzed from the LPA band on thin-layer chromatography plates. The following individual fatty acid species were analyzed by gas chromatography: palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2), arachidonic acid (20:4), and docosahexaenoic acid (22:6). The LPA/LPI fatty acid composition levels were analyzed and compared with disease status. RESULTS: Distinct plasma LPA/LPI fatty acid chain species were not associated with ovarian or other gynecological cancers, compared to patients with benign gynecological disease or healthy controls. However, an increased presence of unsaturated fatty acids in plasma LPA/LPI was found in patients with late-stage or recurrent ovarian cancer and possibly with other gynecological cancers. CONCLUSIONS: Analysis of individual fatty acid species present in plasma LPA/LPI do not appear to enhance the sensitivity or specificity of total LPA/LPI as a marker for gynecological cancer detection. However, our results suggest that increased LPA/LPI species with unsaturated fatty acid chains may be associated with late-stage or recurrent ovarian cancer.

Adult↗

PubMed2001

Chemical forms of Pb, Zn and Cu in the sediment profiles of the Pearl River Estuary.

The chemical forms of heavy metals (Pb, Zn and Cu) in sediment cores of the Pearl River Estuary were studied using a sequential chemical extraction method. The isotope ratios of 206Pb/207Pb in various chemical fractions were also measured to assess the potential Pb sources. Zinc and Cu were mainly associated with the residual fraction. The Fe-Mn oxide and organic/sulphide fractions were the next important phases for Zn and Cu, respectively. For Pb, different chemical partitioning patterns were found among different sediment cores. Most Pb was associated with the residual fraction in the sediments. In some sediment profiles, the major phase of Pb in the top layers was the Fe-Mn oxide fraction. The proportion of Pb in the Fe-Mn oxide fraction decreased significantly with increasing depth. Among the different depths, the 206Pb/207Pb isotope ratios in the residual fraction remained fairly stable, with a mean value of 1.202, which may represent the natural background value. The 206Pb/207Pb ratios in the exchangeable fraction were the lowest among the five fractions, particularly in top sediments, showing the anthropogenic inputs of heavy metals from recent rapid industrial development in the surrounding region. For the other three non-residual fractions, there was a similar trend of increasing 206Pb/207Pb ratios down the profile. Results from this study are useful in assessing both the chemical changes for heavy metals in marine sediments and the potential of heavy metal release into the water environment of an estuary area.

China↗