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Biomedical subjects

Z Shen

Publications and source records attributed to Z Shen.

At least 109 records · Page 6Linked to original sources
PubMed2000

[Effect of kidney tonifying and circulation promoting compound on transcription of T-cell apoptosis related Fas and FasL genes in aged rats].

OBJECTIVE: To probe the molecular mechanism for down-regulation of T-cell apoptosis by Kidney tonifying compound (KTC) in aged rats. METHODS: GAPDH was used as an internal control gene, and semi-quantitative analysis of the transcription of Fas and FasL genes was performed by using RNase protection assay. RESULTS: The Fas/GAPDH and FasL/GAPDH optical density (OD) ratios was 0.81 +/- 0.17 and 0.84 +/- 0.12 in the aged control group, and 0.36 +/- 0.16 and 0.26 +/- 0.12 in the young control group, the difference between the two groups was significant. In the circulation promoting group, the parameters were 0.99 +/- 0.36 and 0.94 +/- 0.33 which were not significantly different as compared with those in the aged control group (P > 0.05). In the two Kidney tonifying groups, the Fas/GAPDH OD ratio was 0.78 +/- 0.11 and 0.78 +/- 0.20, respectively, and no significant difference was observed as compared with those in the aged control group. However the FasL/GAPDH OD ratios in the two kidney tonifying group were 0.71 +/- 0.21 and 0.68 +/- 0.15, which were lower than those in the aged control group (P < 0.01). CONCLUSION: The negative regulation of FasL gene expression may be one of the molecular mechanisms of KTC in down-regulating excessive apoptosis of T-cell in aged rats.

Aging↗
PubMed2000

[Study on production of poly-beta-hydroxybutyrate by recombinant strain VG1(pTU14)].

Cloning and expression of Vitreoscilla hemoglobin gene (vgb) and lambda phage lytic genes (S-RRz) in production of Poly-beta-hydroxybutyrate(PHB) was studied in different Escherichia coli hosts such as E. coliJM105, E. coliJM109 and VG1. In the recombinant strains, VG1(pTU14) was a superior one which simultaneously contained three exogenes including vgb, S-RRz and PHB biosynthesis genes(phbCAB). The experimental results showed that after 82 hours fed-batch cult ure in LBG medium in shaking flask, cell concentration of VG1(pTU14) could reach 25.9 g/L, which was the highest PHB production ever reported, and till 52 h PHB content could be higher than 95%. Additionally, inducible cell lysis was also attained successfully in recombinant VG1(pTU14) accompanying with its high cell density culture. Therefore, VG1(pTU14) is a novel potential strain with promising prospect in industrial production of PHB.

Bacterial Proteins↗
PubMed1999

Leukocytes utilize myeloperoxidase-generated nitrating intermediates as physiological catalysts for the generation of biologically active oxidized lipids and sterols in serum.

The initiation of lipid peroxidation and the concomitant formation of biologically active oxidized lipids and sterols is believed to play a central role in the pathogenesis of inflammatory and vascular disorders. Here we explore the role of neutrophil- and myeloperoxidase (MPO)-generated nitrating intermediates as a physiological catalyst for the initiation of lipid peroxidation and the formation of biologically active oxidized lipids and sterols. Activation of human neutrophils in media containing physiologically relevant levels of nitrite (NO(2)(-)), a major end product of nitric oxide (nitrogen monoxide, NO) metabolism, generated an oxidant capable of initiating peroxidation of lipids. Formation of hydroxy- and hydroperoxyoctadecadienoic acids [H(P)ODEs], hydroxy- and hydroperoxyeicosatetraenoic acids [H(P)ETEs], F(2)-isoprostanes, and a variety of oxysterols was confirmed using on-line reverse phase HPLC tandem mass spectrometry (LC/MS/MS). Lipid oxidation by neutrophils required cell activation and NO(2)(-), occurred in the presence of metal chelators and superoxide dismutase, and was inhibited by catalase, heme poisons, and free radical scavengers. LC/MS/MS studies demonstrated formation of additional biologically active lipid and sterol oxidation products known to be enriched in vascular lesions, such as 1-hexadecanoyl-2-oxovalaryl-sn-glycero-3-phosphocholine, which induces upregulation of endothelial cell adhesion and chemoattractant proteins, and 5-cholesten-3beta-ol 7beta-hydroperoxide, a potent cytotoxic oxysterol. In contrast to the oxidant formed during free metal ion-catalyzed reactions, the oxidant formed during MPO-catalyzed oxidation of NO(2)(-) readily promoted lipid peroxidation in the presence of serum constituents. Collectively, these results suggest that phagocytes may employ MPO-generated reactive nitrogen intermediates as a physiological pathway for initiating lipid peroxidation and forming biologically active lipid and sterol oxidation products in vivo.

Animals↗
PubMed1999

Proteolytic enzymes as a limitation for pulmonary absorption of insulin: in vitro and in vivo investigations.

In vitro biodegradation of insulin in lung cytosol and subcellular pellets of normal and diabetic rats was investigated. Rat lung was homogenized and subcellular fractions were isolated by ultracentrifugation. Degradations of [125I]-insulin after incubation with lung cytosol or subcellular pellets was determined using the trichloroacetic acid method. The results show that insulin is highly degraded in cytosol and subcellular pellets. Cytosolic insulin degradation was strongly inhibited by bacitracin or sodium cholate. The degradation of insulin in the lung cytosol from diabetic rats was significantly less than from normal rat. The lung protease activity reached a maximum at pH 7.4. Enzyme inhibitors like bacitracin and sodium cholate noticeably enhanced the relative pharmacological bioavailability of insulin when given intratracheally with insulin to normal rats. Acidic insulin solutions (pH 3.0) had more pronounced hypoglycaemic effects than neutrol solution (pH 7.0). These in vitro and in vivo results suggest that the proteolytic enzymes in the lung limit pulmonary delivery of insulin. The coadministration of protease inhibitors would be a useful approach for improving the pulmonary absorption of insulin.

Absorption↗
PubMed1999

Formation of nitric oxide-derived oxidants by myeloperoxidase in monocytes: pathways for monocyte-mediated protein nitration and lipid peroxidation In vivo.

Protein nitration and lipid peroxidation are implicated in the pathogenesis of atherosclerosis; however, neither the cellular mediators nor the reaction pathways for these events in vivo are established. In the present study, we examined the chemical pathways available to monocytes for generating reactive nitrogen species and explored their potential contribution to the protein nitration and lipid peroxidation of biological targets. Isolated human monocytes activated in media containing physiologically relevant levels of nitrite (NO(2)(-)), a major end product of nitric oxide ((*)NO) metabolism, nitrate apolipoprotein B-100 tyrosine residues and initiate LDL lipid peroxidation. LDL nitration (assessed by gas chromatography-mass spectrometry quantification of nitrotyrosine) and lipid peroxidation (assessed by high-performance liquid chromatography with online tandem mass spectrometric quantification of distinct products) required cell activation and NO(2)(-); occurred in the presence of metal chelators, superoxide dismutase (SOD), and scavengers of hypohalous acids; and was blocked by myeloperoxidase (MPO) inhibitors and catalase. Monocytes activated in the presence of the exogenous (*)NO generator PAPA NONOate (Z-[N-(3-aminopropyl)-N-(n-propyl)amino]diazen-1-ium-1,2- diolate) promoted LDL protein nitration and lipid peroxidation by a combination of pathways. At low rates of (*)NO flux, both protein nitration and lipid peroxidation were inhibited by catalase and peroxidase inhibitors but not SOD, suggesting a role for MPO. As rates of (*)NO flux increased, both nitrotyrosine formation and 9-hydroxy-10,12-octadecadienoate/9-hydroperoxy-10,12-octadecadieno ic acid production by monocytes became insensitive to the presence of catalase or peroxidase inhibitors, but they were increasingly inhibited by SOD and methionine, suggesting a role for peroxynitrite. Collectively, these results demonstrate that monocytes use distinct mechanisms for generating (*)NO-derived oxidants, and they identify MPO as a source of nitrating intermediates in monocytes.

Apolipoprotein B-100↗
PubMed1999

Early repair treatment of electrical burns and recovery of tendons and nerves. Report of 194 operations.

A new approach to treatment of electrically burned tendons and nerves by primarily covering with skin or myocutaneous flaps is recommended. Between 1964 and 1989, 194 operations using the new approach were performed on 147 patients, of which 179 operations were successful and only 15 procedures resulted in infection. Among 42 cases involving the wrist, the rate of functional recovery of the electrically burned tendons was 97.6%; the rate of recovery in 21 cases of electrically burned peripheral nerves was 80.9%.

Burns, Electric↗
PubMed1999

One-Dimensional Electronic Structure and Suppression of d-Wave Node State in (La(1.28)Nd(0.6)Sr(0.12))CuO(4).

Angle-resolved photoemission spectroscopy was carried out on (La(1.28)Nd(0.6) Sr(0.12))CuO(4), a model system of the charge- and spin-ordered state, or stripe phase. The electronic structure contains characteristic features consistent with other cuprates, such as the flat band at low energy near the Brillouin zone face. However, the low-energy excitation near the expected d-wave node region is strongly suppressed. The frequency-integrated spectral weight is confined inside one-dimensional segments in the momentum space (defined by horizontal momenta &cjs3539;k(x)&cjs3539; = pi/4 and vertical momenta &cjs3539;k(y)&cjs3539; = pi/4), deviating strongly from the more rounded Fermi surface expected from band calculations. This departure from the two-dimensional Fermi surface persists to a very high energy scale. These results provide important information for establishing a theory to understand the charge and spin ordering in cuprates and their relation with high-temperature superconductivity.

Journal Article↗
PubMed1999

[Biological characteristics of human fetal esophageal epithelial cell line immortalized by the E6 and E7 gene of HPV type 18].

OBJECTIVE: Biological features including proliferation, differentiation and cell death of SHEE cell line, an immortalized epithelium of the fetal esophageal epithelium induced by HPV 18 E6E7 AAV, were studied. METHODS: SHEE cell line being cultured for more than 50 passages, were cultured in 199 growth medium and were examined by light, electron and fluorescence microscopy for growth rate, morphological features and chromosome analysis, by flow cytometry for cell proliferative dynamics, by immunohistochemistry for Ki67 and cytokeratin, and by terminal DNA transferase label (TUNEL) for apoptosis. RESULTS: At the 20th passage, the SHEE cell remained monolayer, anchorage-dependent and attachment-inhibited growth. The growth curve showed proliferative phase 3-8th days, top-plate phase 9-10th days and attenuative phase after 10th days. Proliferative index(PIx) 34.0%, mitotic index (MI) 2.74% (1.20%-4.80%), apoptotic index (AI) 1.30%-6.90%, chromosome analysis mainly 46 (44-54/nucleus) and DNA distribution in diploidy were calculated and described. The tonofilament expression in cell cytoplasm by electron-microscopy and positive reaction of cytokeratin by immunochemistry showed differentiative character of squamous epithelium. The cell apoptosis occured in the proliferative phase and especially increased in attenuative phase. CONCLUSION: Of biological behaviors, the SHEE cells are close to the basal cells of their original fetal esophageal mucosa keeping proliferative and differentiative potency. This study suggests that the cell death (including cell apoptosis) may be an important factor in studying of cell growth regulation and it may be an research area for cellular biological behaviors.

Cell Division↗
PubMed1999

Thalidomide stimulates T cell responses and interleukin 12 production in HIV-infected patients.

We performed a placebo-controlled study to evaluate the effects of immunomodulatory treatment with thalidomide on HIV levels, TNF-alpha levels, and immune status of 31 HIV-infected individuals, after temporary suppression of viral replication with antiretroviral drugs. Treatment with a combination of zidovudine and lamivudine (ZDV/LMV) for 14 days resulted in a median decline in plasma viremia of 1.94 log10 RNA equivalents/ml. After discontinuation of ZDV/LMV, thalidomide therapy (200 mg/day for 4 weeks) did not retard the prompt return of HIV titers to the pretreatment levels, and had no effect on plasma levels of TNF-alpha. In contrast, thalidomide treatment resulted in significant immune stimulation. We observed increased levels of plasma soluble IL-2 receptor, soluble CD8 antigen, and IL-12 (p < 0.01 for all parameters), as well as increased cutaneous delayed-type hypersensitivity reactions to recall antigens (p < 0.01) in thalidomide-treated patients. These changes were associated with a median increase in HIV titer of 0.2 log10 RNA equivalents/ml in the thalidomide-treated group (p < 0.05), which resolved after stopping the drug. Further studies were performed in vitro to elucidate the mechanism of thalidomide-induced immune stimulation. When purified T cells from HIV-infected individuals were stimulated by immobilized anti-CD3 in the presence of thalidomide, a costimulatory effect of the drug was observed, resulting in increased production of IL-2 and IFN-gamma, and increased T cell-proliferative responses. Further experiments showed that thalidomide increased IL-12 production by antigen-presenting cells in a T cell-dependent manner. Our findings suggest a potential application for thalidomide as a novel immune adjuvant in HIV disease.

Adult↗
PubMed1999

Evidence for SH3 domain directed binding and phosphorylation of Sam68 by Src.

Sam68 is a 68 kDa protein that associates with and is phosphorylated by the c-Src kinase at mitosis. It contains a KH domain implicated in RNA binding and several proline-rich motifs that resemble known SH3 binding sites. The SH3 domains of c-Src, phosphatidylinositol 3-OH kinase, phospholipase C-gamma and Grb2 protein (containing two SH3 domains), but not other SH3 domains tested, were capable of binding Sam68 in vitro. Synthetic peptides corresponding to the proline motifs of Sam68 inhibited with different efficiencies the binding of SH3 domains to Sam68 suggesting that the proline motifs of Sam68 function as specific SH3 domain binding sites. Mutation of Sam68 SH3 binding sites further indicated that the SRC SH3 domain mediates binding of Src to unphosphorylated Sam68. Phosphorylation of Sam68 by Src kinase was inhibited when the Src SH3 binding site of Sam68 was mutated or when corresponding peptides were added to in vitro kinase reactions indicating that binding of the Src SH3 domain to a specific site near the amino-terminus of Sam68 (including residues 38 - 45: PPLPHRSR) facilitates phosphorylation of Sam68 by the Src kinase domain. Sam68-based proline peptides had no effect on the phosphorylation of another in vitro substrate of Src, enolase. These results suggest that Src effectively mounts Sam68 through its SH3 domain, possibly as a mechanism to position the kinase domain close to substrate tyrosine residues in the carboxyl-half of the protein.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Modulation of TEL transcription activity by interaction with the ubiquitin-conjugating enzyme UBC9.

The E-26 transforming specific (ETS)-related gene TEL, also known as ETV6, is involved in a large number of chromosomal rearrangements associated with leukemia and congenital fibrosarcoma. The encoded protein contains two functional domains: a helix-loop-helix (HLH) domain (also known as pointed domain) located at the N terminus and a DNA-binding domain located at the C terminus. The HLH domain is involved in protein-protein interaction with itself and other members of the ETS family of transcription factors such as FLI1. TEL is a transcription factor, and we and others have shown that it is a repressor of gene expression. To understand further the role of TEL in the cell, we have used an in vivo interaction system to identify proteins that interact with TEL. We show that a protein, UBC9, interacts specifically with TEL in vitro and in vivo. UBC9 is a member of the family of ubiquitin-conjugating enzymes. These enzymes usually are involved in proteosome-mediated degradation; however, our data suggest that interaction of TEL with UBC9 does not lead to TEL degradation. Our studies show that UBC9 binds to TEL exclusively through the HLH domain of TEL. We also show that TEL expressed as fusion to the DNA-binding domain of Gal4 completely represses a Gal4-responsive promoter, but that the coexpression of UBC9 in the same system restores the activity of the promoter. Targeted point mutation of conserved amino acids in UBC9 essential for enzymatic ubiquitination of proteins does not affect interaction nor transcriptional activity. Based on our data, we conclude that UBC9 physically interacts with TEL through the HLH domain and that the interaction leads to modulation of the transcription activity of TEL.

DNA-Binding Proteins↗
PubMed1999

Constitutive cell surface association between CD4 and CCR5.

HIV-1 entry into cells involves formation of a complex between gp120 of the viral envelope glycoprotein (Env), a receptor (CD4), and a coreceptor. For most strains of HIV, this coreceptor is CCR5. Here, we provide evidence that CD4 is specifically associated with CCR5 in the absence of gp120 or any other receptor-specific ligand. The amount of CD4 coimmunoprecipitated with CCR5 was significantly higher than that with the other major HIV coreceptor, CXCR4, and in contrast to CXCR4 the CD4-CCR5 coimmunoprecipitation was not significantly increased by gp120. The CD4-CCR5 interaction probably takes place via the second extracellular loop of CCR5 and the first two domains of CD4. It can be inhibited by CCR5- and CD4-specific antibodies that interfere with HIV-1 infection, indicating a possible role in virus entry. These findings suggest a possible pathway of HIV-1 evolution and development of immunopathogenicity, a potential new target for antiretroviral drugs and a tool for development of vaccines based on Env-CD4-CCR5 complexes. The constitutive association of a seven-transmembrane-domain G protein-coupled receptor with another receptor also indicates new possibilities for cross-talk between cell surface receptors.

3T3 Cells↗
PubMed1999

The binding interface between an E2 (UBC9) and a ubiquitin homologue (UBL1).

Human UBC9 is a member of the E2 (ubiquitin conjugation enzyme) family of proteins. Instead of conjugating to ubiquitin, it conjugates with a ubiquitin homologue UBL1 (also known as SUMO-1, GMP1, SMTP3, PIC1, and sentrin). UBC9 has been shown to be involved in cell cycle regulation, DNA repair, and p53-dependent processes. The binding interfaces of the UBC9 and UBL1 complex have been determined by chemical shift perturbation using nuclear magnetic resonance spectroscopy. The binding site of UBL1 resides on the ubiquitin domain, and the binding site of UBC9 is located on a structurally conserved region of E2. Because the UBC9-UBL1 system shares many similarities with the ubiquitin system in structures and in conjugation with each other and with target proteins, the observed binding interfaces may be conserved in E2-ubiquitin interactions in general.

Humans↗
PubMed1999

A cell surface mucin specifically expressed in the midgut of the malaria mosquito Anopheles gambiae.

An invertebrate intestinal mucin gene, AgMuc1, was isolated from the malaria vector mosquito Anopheles gambiae. The predicted 122-residue protein consists of a central core of seven repeating TTTTVAP motifs flanked by hydrophobic N- and C-terminal domains. This structure is similar to that of mucins that coat the protozoan parasite Trypanosoma cruzi. Northern blot analysis indicated that the gene is expressed exclusively in the midgut of adult mosquitoes. A length polymorphism and in situ hybridization were used to genetically and cytogenetically map AgMuc1 to division 7A of the right arm of the second chromosome. The subcellular localization of the encoded protein in tissue culture cells was examined by using a baculovirus vector to express AgMuc1 protein tagged with the green fluorescent protein (GFP). The results indicated that this protein is found at the cell surface and that both hydrophobic domains are required for cell surface targeting. We propose that AgMuc1 is an abundant mucin-like protein that lines the surface of the midgut microvilli, potentially protecting the intestinal epithelium from the proteinase-rich environment of the gut lumen. An intriguing possibility is that, as an abundant surface protein, AgMuc1 may also interact with the malaria parasite during its invasion of the mosquito midgut.

Amino Acid Sequence↗
PubMed1999

Nonlinear indicial response of complex nonstationary oscillations as pulmonary hypertension responding to step hypoxia.

This paper is devoted to the quantization of the degree of nonlinearity of the relationship between two biological variables when one of the variables is a complex nonstationary oscillatory signal. An example of the situation is the indicial responses of pulmonary blood pressure (P) to step changes of oxygen tension (DeltapO2) in the breathing gas. For a step change of DeltapO2 beginning at time t1, the pulmonary blood pressure is a nonlinear function of time and DeltapO2, which can be written as P(t-t1 | DeltapO2). An effective method does not exist to examine the nonlinear function P(t-t1 | DeltapO2). A systematic approach is proposed here. The definitions of mean trends and oscillations about the means are the keys. With these keys a practical method of calculation is devised. We fit the mean trends of blood pressure with analytic functions of time, whose nonlinearity with respect to the oxygen level is clarified here. The associated oscillations about the mean can be transformed into Hilbert spectrum. An integration of the square of the Hilbert spectrum over frequency yields a measure of oscillatory energy, which is also a function of time, whose mean trends can be expressed by analytic functions. The degree of nonlinearity of the oscillatory energy with respect to the oxygen level also is clarified here. Theoretical extension of the experimental nonlinear indicial functions to arbitrary history of hypoxia is proposed. Application of the results to tissue remodeling and tissue engineering of blood vessels is discussed.

Animals↗
PubMed1999

A nanomechanical device based on the B-Z transition of DNA.

The assembly of synthetic, controllable molecular mechanical systems is one of the goals of nanotechnology. Protein-based molecular machines, often driven by an energy source such as ATP, are abundant in biology. It has been shown previously that branched motifs of DNA can provide components for the assembly of nanoscale objects, links and arrays. Here we show that such structures can also provide the basis for dynamic assemblies: switchable molecular machines. We have constructed a supramolecular device consisting of two rigid DNA 'double-crossover' (DX) molecules connected by 4.5 double-helical turns. One domain of each DX molecule is attached to the connecting helix. To effect switchable motion in this assembly, we use the transition between the B and Z forms of DNA. In conditions that favour B-DNA, the two unconnected domains of the DX molecules lie on the same side of the central helix. In Z-DNA-promoting conditions, however, these domains switch to opposite sides of the helix. This relative repositioning is detected by means of fluorescence resonance energy transfer spectroscopy, which measures the relative proximity of two dye molecules attached to the free ends of the DX molecules. The switching event induces atomic displacements of 20-60 A.

Biomechanical Phenomena↗
PubMed1999

Evolution of chitin-binding proteins in invertebrates.

Analysis of a group of invertebrate proteins, including chitinases and peritrophic matrix proteins, reveals the presence of chitin-binding domains that share significant amino acid sequence similarity. The data suggest that these domains evolved from a common ancestor which may be a protein containing a single chitin-binding domain. The duplication and transposition of this chitin-binding domain may have contributed to the functional diversification of chitin-binding proteins. Sequence comparisons indicated that invertebrate and plant chitin binding domains do not share significant amino acid sequence similarity, suggesting that they are not coancestral. However, both the invertebrate and the plant chitin-binding domains are cysteine-rich and have several highly conserved aromatic residues. In plants, cysteines have been elucidated in maintaining protein folding and aromatic amino acids in interacting with saccharides [Wright HT, Sanddrasegaram G, Wright CS (1991) J Mol Evol 33:283-294]. It is likely that these residues perform similar functions in invertebrates. We propose that the invertebrate and the plant chitin-binding domains share similar mechanisms for folding and saccharide binding and that they evolved by convergent evolution. Furthermore, we propose that the disulfide bonds and aromatic residues are hallmarks for saccharide-binding proteins.

Amino Acid Sequence↗