Biomedical subjects

Min Chen

Publications and source records attributed to Min Chen.

At least 109 records · Page 6Linked to original sources

PubMed2005

Protective mechanisms of a metalloporphyrinic peroxynitrite decomposition catalyst, WW85, in rat cardiac transplants.

Nitric oxide (NO) derived from inducible NO synthase has been implicated in cardiac rejection. However, little is known about the role of the reactive nitrogen species peroxynitrite. We examined the protective actions of a peroxynitrite decomposition catalyst, WW85, in an experimental model of acute cardiac rejection. Heterotopic, abdominal transplantation of rat donor hearts was performed. Groups included isografts, allografts, or allografts treated with WW85, cyclosporine, or cyclosporine + WW85. We determined graft survival, histological rejection, and graft function (by in situ sonomicrometry). Intragraft biochemical analysis of cytokines and proapoptotic and antiapoptotic gene expression using reverse transcriptase-polymerase chain reaction were determined. Treatment with WW85 or cyclosporine alone prolonged graft survival, improved graft function, and decreased histological rejection. Graft survival was further significantly (P < 0.001) enhanced by combination treatment. A decrease was also shown in nitrotyrosine, poly(ADP-ribose) polymerase (PARP) activation, and lipid peroxide formation by WW85 that was potentiated when given in combination with cyclosporine. Benefits could not be ascribed to changes in intragraft myeloperoxidase activity. Only combination therapy produced significant decreases in inflammatory cytokine gene expression, suggesting that WW85 acted primarily downstream of these stimuli. In general, WW85 had no direct action on expression of the proapoptotic gene, Fas ligand; however, WW85 given alone or with cyclosporine enhanced expression of antiapoptotic genes Bcl-2 and Bcl-xL. Collectively, these findings suggest a protective action of the peroxynitrite decomposition catalyst WW85 on graft rejection that is independent of any action on leukocyte sequestration and cytokine gene expression. Rather, effects seem to be downstream on decreased protein nitration, decreased lipid peroxidation, and decreased PARP activation.

Animals↗

PubMed2005

Ecology: a niche for cyanobacteria containing chlorophyll d.

The cyanobacterium known as Acaryochloris marina is a unique phototroph that uses chlorophyll d as its principal light-harvesting pigment instead of chlorophyll a, the form commonly found in plants, algae and other cyanobacteria; this means that it depends on far-red light for photosynthesis. Here we demonstrate photosynthetic activity in Acaryochloris-like phototrophs that live underneath minute coral-reef invertebrates (didemnid ascidians) in a shaded niche enriched in near-infrared light. This discovery clarifies how these cyanobacteria are able to thrive as free-living organisms in their natural habitat.

Animals↗

PubMed2005

Influence of structure on binding of chlorophylls to peptide ligands.

Four classes of chlorophyll (Chl), a, b, c, and d, are involved in photosynthesis within cyanobacteria, algae, and plants. These classes have different evolutionary origins, chemical properties, and biological functions. Our results demonstrate that peptide-bound ligands provided by the imidazole group of histidine and the charge-compensated glutamate-arginine ion pair readily form coordination bonds with Chls a and d but do not interact significantly with Chls b and c. These ligands are apparently not sufficiently strong Lewis bases to displace strongly coordinated water from Chls b and c. These differences determine specificity of binding of Chls in light-harvesting complexes and play an important role in assembly of stable Chl-protein complexes, which has had a profound impact on the evolution of photosynthetic organisms.

Amino Acid Sequence↗

PubMed2005

Expression and immunoactivity of chimeric particulate antigens of receptor binding site-core antigen of hepatitis B virus.

AIM: To improve the immunogenicity of receptor binding site of hepatitis B virus (HBV) on preS1 antigen using HBV core antigen as an immuno-carrier. METHODS: One to 6 tandem copies of HBV preS1 (21-47) fragment were inserted into HBcAg at the sites of aa 78 and 82, and expressed in E.coli. ELISA, Western blot and animal immunization were used to analyze the antigenicity and immmunogenicity of purified particulate antigens. The ability to capture HBV by antibodies elicited by chimeric particles was detected with immuno-capture PCR. RESULTS: Recombinant antigens CI, CII, CIII carrying 1-3 copies of HBV preS1 (21-47) individually could form virus-like particles (VLPs), similar to HBcAg in morphology. But recombinant antigens carrying 4-6 copies of HBV preS1 (21-47) were poorly expressed in E.coli. Chimeric antigens were lacking of immunoreactivity with anti-HBc monoclonal antibodies (McAbs), but still reserved good immunoreactivity with anti-HBe McAbs. CI, CII, CIII could strongly react with anti-preS1 McAb, suggesting that preS1 (21-47) fragment was well exposed on the surface of chimeric VLPs. Three chimeric VLP antigens (CI, CII and CIII) could stimulate mice to produce high-level antibody responses, and their immunogenicity was stronger than non-particulate antigen 21-47*6, containing 6 copies of preS1 (21-47). Mouse antibodies to CI, CII and CIII were able to capture HBV virions in immuno-capture PCR assay in vitro. CONCLUSION: Chimeric particulate antigens of receptor binding site-core antigen of HBV can elicit strong antibody responses to preS1. They have a potential to be developed into prophylactic or therapeutic vaccines against HBV infection.

Animals↗

PubMed2005

Structure of a large photosystem II supercomplex from Acaryochloris marina.

Acaryochloris marina is a prochlorophyte-like cyanobacterium containing both phycobilins and chlorophyll d as light harvesting pigments. We show that the chlorophyll d light harvesting system, composed of Pcb proteins, functionally associates with the photosystem II (PSII) reaction center (RC) core to form a giant supercomplex. This supercomplex has a molecular mass of about 2300 kDa and dimensions of 385 A x 240 A. It is composed of two PSII-RC core dimers arranged end-to-end, flanked by eight symmetrically related Pcb proteins on each side. Thus each PSII-RC monomer has four Pcb subunits acting as a light harvesting system which increases the absorption cross section of the PSII-RC core by almost 200%.

Cyanobacteria↗

PubMed2005

Formation of nucleoplasmic protein aggregates impairs nuclear function in response to SiO2 nanoparticles.

Despite of their exponentially growing use, little is known about cell biological effects of nanoparticles. Here, we report uptake of silica (SiO(2)) nanoparticles to the cell nucleus where they induce aberrant clusters of topoisomerase I (topo I) in the nucleoplasm that additionally contain signature proteins of nuclear domains, and protein aggregation such as ubiquitin, proteasomes, cellular glutamine repeat (polyQ) proteins, and huntingtin. Formation of intranuclear protein aggregates (1) inhibits replication, transcription, and cell proliferation; (2) does not significantly alter proteasomal activity or cell viability; and (3) is reversible by Congo red and trehalose. Since SiO(2) nanoparticles trigger a subnuclear pathology resembling the one occurring in expanded polyglutamine neurodegenerative disorders, we suggest that integrity of the functional architecture of the cell nucleus should be used as a read out for cytotoxicity and considered in the development of safe nanotechnology.

Cell Division↗

PubMed2005

Recruitment of topoisomerase I (Scl-70) to nucleoplasmic proteasomes in response to xenobiotics suggests a role for altered antigen processing in scleroderma.

OBJECTIVE: Scleroderma, also known as systemic sclerosis (SSc), is a chronic, life-threatening autoimmune disease characterized by a wide spectrum of manifestations and a variable evolution. The presence of particular antinuclear antibodies is often predictive of the clinical expression and prognosis of the disease, but the molecular mechanisms of the immune responses remain unclear. Recently, we have shown xenobiotic-induced recruitment of nuclear autoantigens to proteasomes in the cell nucleus in cell culture and in animal models in correlation with a unique autoantibody response. In this study, we attempted to validate our findings in patients with SSc. METHODS: Using indirect immunofluorescence microscopy, run-on replication and transcription assays, immunoblotting, and proteasome activity assays, we analyzed the nuclear structure, function, and proteasomal proteolysis in HEp-2 cells treated with xenobiotics or left untreated. Blood dendritic cells (DCs) were isolated from 30 patients with SSc and age- and sex-matched control subjects to determine the subcellular localization of SSc autoantigens in relation to proteasomes. RESULTS: Xenobiotics induced a relocation of the SSc autoantigen DNA topoisomerase I (Scl-70, topo I) to nucleoplasmic clusters, where proteasomes degrade topo I. Colocalization of topo I with proteasomes occurred exclusively in DCs from patients with SSc who developed antibodies against this autoantigen. Neither centromeres nor other SSc autoantigens colocalized with proteasomes in DCs from patients with SSc or from control subjects. CONCLUSION: Alteration of nuclear structure and function by xenobiotics induces recruitment of the nuclear autoantigen topo I for proteasomal processing. This event may, in turn, lead to subsequent presentation of the resulting peptides on the cell surface and the autoimmune responses against topo I in SSc.

Antigen Presentation↗

PubMed2005

Separation and determination of carnosine-related peptides using capillary electrophoresis with laser-induced fluorescence detection.

A capillary electrophoresis (CE) method with laser-induced fluorescence (LIF) detection was developed for the separation and detection of carnosine-related peptides (carnosine, anserine, and homocarnosine). A sensitive and fluorogenic regent, 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde (CBQCA) was selected as a precapillary labeling reagent for imidazole dipeptides to form isoindole derivatives. The optimized molar ratio between CBQCA and peptide was found to be 75:1, and 50 mmol/L borate buffer (pH 9.2) was used for the derivatization in order to achieve good efficiency. Three imidazole dipeptides were baseline-separated within 20 min by using 112 mmol/L sodium borate (pH 10.4-10.8) as running buffer. Concentration detection limits (signal-to-noise ratios) for carnosine, anserine, and homocarnosine were 4.73, 4.37, and 3.94 nmol/L, respectively. This method has been applied to the analysis of human cerebrospinal fluid (CSF) and meat dry powder of pig and sheep. Recoveries were in the range of 82.9-104.8% for homocarnosine in CSF. For carnosine and anserine, the recoveries are 98.3% and 80.2% in meat dry powder of pig and 111.2% and 112.8% in meat dry powder of sheep, respectively.

Adolescent↗

PubMed2005

Modification of plant N-glycans processing: the future of producing therapeutic protein by transgenic plants.

Transgenic plants are regarded as one of the most promising systems for the production of human therapeutic proteins. The number of therapeutic proteins successfully produced in plants is steadily arising. However, the glycoproteins normally produced from plants are not the same as native therapeutic proteins produced from mammals or humans. In addition to in vitro enzymatic modeling glycoproteins, there are two gene manipulation strategies to humanize plant N-glycans connected to the glycoproteins. One is retaining the recombinant glycoproteins in endoplasmic reticulum (ER), the site where few specific modifications of N-glycans occurs. The other is inhibiting the plant endogenous Golgi glycosyltransferase and/or adding new glycosyltransferase from mammalians. In this review, the biosynthesis of N-glycans in plants, the modification of the plant N-glycans processing will be discussed.

Endoplasmic Reticulum↗

PubMed2005

Sonographic features of lethal multiple pterygium syndrome at 14 weeks.

Lethal multiple pterygium syndrome is a rare inherited disorder. Previous reports suggest that the diagnosis may be based on prenatal sonographic demonstration of severe limb flexion, absence of fetal motion, and a large cystic hygroma in the second and third trimesters. We present the sonographic features and postmortem features of a fetus with lethal multiple pterygium syndrome at 13 weeks of gestation, which shows that the condition can possibly be diagnosed in the first trimester of pregnancy.

Abnormalities, Multiple↗

PubMed2005

Synthesis of complex carbohydrates and glyconjugates: enzymatic synthesis of globotetraose using alpha-1,3-N-acetylgalactosaminyltransferase LgtD from Haemophilus infuenzae strain Rd.

The lipopolysaccharide of capsule-deficient Haemophilus infuenzae strain Rd contains an N-acetylgalactosamine residue attached to the terminal globotriose moiety in the Hex5 glycoform. Genome analysis identified an open reading frame, HI1578, referred to as LgtD, whose amino acid sequence shows a significant level of similarity to those of a number of bacterial glycosyltransferases involved in lipopolysaccharide biosynthesis. To investigate its function, overexpression and biochemical characterization were performed. Most of the protein was obtained in a highly soluble and active form. Standard glycosyltransferase assay, high-performance liquid chromatography (HPLC), and liquid chromatography (LC)/mass spectrometry (MS) show that LgtD is an N-acetylgalactosaminyltransferase with high donor substrate specificity, and globotriose is a highly preferred acceptor substrate for the enzyme.

Amino Acid Sequence↗

PubMed2005

Characterization of anti-mesangial cell antibodies and their target antigens in patients with lupus nephritis.

The pathogenetic mechanisms of lupus nephritis (LN) remain to be elucidated. In our previous study, autoantibodies against human glomerular mesangial cells (HMC) were identified in sera of most patients with lupus nephritis. The current study is to investigate the binding characteristics of anti-mesangial cell antibodies to human mesangial cell membrane. Serum samples were collected from 54 patients with renal biopsy proven lupus nephritis, 12 patients with systemic lupus erythematosus without clinical renal involvement, and 15 healthy subjects. Membrane proteins were obtained from in vitro cultured HMC by sonication and sequential centrifugation. DNase I were employed to remove DNA fragments in sera and membrane protein preperation and IgG F(ab')2 was obtained by pepsin digestion. Western Blot analysis was used to characterize the antibody and antigen interaction. In results, 25 of 54 (46.3%) sera from patients with lupus nephritis had anti-mesangial cell antibodies targeted at 74 kDa, 63 kDa, 52 kDa and 42 kDa protein bands of HMC membrane. Only four of 12 (33.3%) sera from patients without renal involovement recognized the protein bands at 74 kDa and 63 kDa, but not 52 kDa and 42 kDa. DNase treatment of the HMC membrane and the sera did not affect the binding. IgG F(ab')2 from sera of 10 patients with positive anti-mesangial cell antibodies could still bind the 63 kDa protein. In conclusion, anti-mesangial cell antibodies from sera of patients with lupus nephritis could bind membrane proteins of HMC directly without a DNA bridge and the binding was through antigen-antibody interation. Anti-mesangial cell antibodies might play some role in the pathogenesis of lupus nephritis(LN).

Antigen-Antibody Reactions↗

PubMed2005

Photosynthetic apparatus of antenna-reaction centres supercomplexes in oxyphotobacteria: insight through significance of Pcb/IsiA proteins.

In this Review we give an overview of the structure and function of the membrane-bound photosynthetic antenna reaction centre complexes present in oxyphotobacteria. We summarise how variations in the organisation of these complexes have enabled oxyphotobacteria to exploit different ecological niches and discuss the evolutionary relationships of the IsiA/Pcb family of pigment-binding proteins.

Evolution, Molecular↗

PubMed2005

Poly (ADP) ribose polymerase inhibition improves rat cardiac allograft survival.

BACKGROUND: Heart transplantation is an accepted treatment modality for end-stage heart failure. However, acute cellular rejection (ACR) continues to be a morbid complication. Recently a novel mechanism of inflammatory allograft injury has been characterized which involves overactivation of the nuclear enzyme poly (ADP-ribose) polymerase (PARP). In the present studies, we compared the efficacy of INO-1001, a novel, potent PARP inhibitor, in limiting ACR with and without adjuvant low-dose cyclosporine (CSA). METHODS: Heterotopic heart transplantation was performed utilizing Brown-Norway strains as donors and Lewis rats as recipients. Groups received daily intraperitoneal injections of: vehicle, low-dose CSA, low-dose INO-1001, high-dose INO-1001, and low-dose CSA combined with high-dose INO-1001. Additional animals were sacrificed on postoperative Day 5 for histologic assessments of allograft inflammation, including immunohistochemistry for nitrotyrosine and poly (ADP-ribose) (the product of PARP) staining. RESULTS: PARP inhibition significantly prolonged allograft survival relative to vehicle controls. The combination of low-dose CSA and INO-1001 resulted in a marked increase in allograft survival and significant reductions in allograft rejection scores. This was associated with decreased nitrotyrosine and PAR staining in transplanted cardiac allografts. CONCLUSIONS: Pharmacologic inhibition of INO-1001 prolongs allograft survival in a dose-dependent fashion in a rodent model of heart transplantation. PARP inhibitors may permit reductions in the dose of CSA needed for adequate immunosuppression after heart transplantation.

Animals↗

PubMed2005

Proteasomal processing of nuclear autoantigens in systemic autoimmunity.

Autoimmune diseases are believed to rise from a breakdown of tolerance and a deregulation of the immune system to discriminate effectively between "self" and "non-self". Although the origins of autoimmunity and the factors leading to overt autoimmune diseases are largely unclear, genetic background, hormones, and environmental agents are found to be involved. The production of autoantibodies against distinct "self"-proteins of the cell nucleus constitutes one of the autoimmune manifestations that characterize systemic autoimmunity. While molecular mechanisms of anti-nuclear autoimmune responses remain poorly understood, processing and presentation of intracellular autoantigens to T cells constitutes a central issue in the generation of antigen-driven autoimmunity. Intracellular proteins, including nuclear autoantigens, are degraded by the proteasomal pathway that clears away endogenous proteins, regulates numerous cellular processes, and delivers immunocompetent peptides to the antigen presenting machinery. Since antigen processing is a key step for the maintenance of peripheral tolerance, in this article, we discuss the role of proteasome-dependent antigen processing in systemic autoimmunity.

Animals↗

PubMed2005

Stress-associated changes in the steady-state expression of latent Epstein-Barr virus: implications for chronic fatigue syndrome and cancer.

Antibodies to several Epstein-Barr virus (EBV)-encoded enzymes are observed in patients with different EBV-associated diseases. The reason for these antibody patterns and the role these proteins might play in the pathophysiology of disease, separate from their role in virus replication, is unknown. In this series of studies, we found that purified EBV deoxyuridine triphosphate nucleotidohydrolase (dUTPase) can inhibit the replication of human peripheral blood mononuclear cells in vitro and upregulate the production of TNF-alpha, IL-1beta, IL-6, IL-8, and IL-10. It also enhanced the ability of natural killer cells to lyse target cells. The EBV dUTPase also significantly inhibited the replication of mitogen-stimulated lymphocytes and the synthesis of IFN-gamma by cells isolated from lymph nodes and spleens obtained from mice inoculated with the protein. It also produced sickness behaviors known to be induced by some of the cytokines that were studied in the in vitro experiments. These symptoms include an increase in body temperature, a decrease in body mass and in physical activity. The data provide a new perspective on how an early nonstructural EBV-encoded protein can cause immune dysregulation and produce clinical symptoms observed in patients with chronic fatigue syndrome (CFS) separate from its role in virus replication and may serve as a new approach to help identify one of the etiological agents for CFS. The data also provide additional insight into the pathophysiology of EBV infection, inflammation, and cancer.

Animals↗

PubMed2005

Size-fractionated thorium isotopes (228Th, 230Th, 232Th) in surface waters in the Jiulong River estuary, China.

Thorium isotopes (228Th, 230Th, 232Th and 234Th) are useful tracers for studying particle dynamics and trace element scavenging in marine environments. In this study, surface waters were collected along a salinity gradient from the Jiulong River estuary, China, for determination of activity concentrations of 228Th, 230Th and 232Th in different size fractions, namely, the >53 microm, 10-53 microm, 2-10 microm, 0.4-2 microm, 10 kDa-0.4 microm and the <10 kDa fractions. Our results indicated that the activity concentrations of 228Th, 230Th and 232Th in the Jiulong River estuarine waters were significantly higher than most of the previously reported values in coastal and oceanic seawaters, suggesting a higher lithogenic U and Th contribution from the Jiulong River Basin. When normalized to the particulate mass concentration, the activity concentrations of the three thorium isotopes decreased with increasing particle size, demonstrating the important role of surface areas of particles in controlling the scavenging of thorium from the water column. The partitioning of three thorium isotopes showed a common characteristic, i.e., the >53 microm fraction had the least share (0-1%), while the 10-53 microm fraction had the largest share of Th isotopes. The average value of the 230Th/232Th activity ratio (230Th/232Th)(A.R.) increased from 0.8 in the >53 microm fraction to 3.7 in the 10 kDa-0.4 microm fraction, indicating that the radiogenic Th isotopes are preferentially scavenged by the small size particles. (230Th/232Th)(A.R.) in the <10 kDa and 10 kDa-0.4 microm fractions were similar, however, suggesting a similar chemical composition and/or equilibrium partitioning between the low molecular weight and colloidal Th. It was very interesting to note that the geochemical behaviors of the three Th isotopes were different from each other. Dissolved 228Th had the highest concentration in the mid-salinity region, showing a non-conservative behavior with additional input. In contrast, dissolved 232Th showed a concave profile, indicating a net removal of 232Th during the mixing of fresh water with seawater. The behavior of Th isotopes in the <10 kDa fraction followed those in the dissolved phases. The difference in geochemical behaviors among three Th isotopes was ascribed to their different sources in the estuary.

China↗

PubMed2005

Poly(adenosine diphosphate ribose) polymerase inhibition modulates spinal cord dysfunction after thoracoabdominal aortic ischemia-reperfusion.

OBJECTIVE: Spinal cord injury (SCI) remains a source of morbidity after thoracoabdominal aortic reconstruction. These studies were designed to determine whether PJ34, a novel ultrapotent inhibitor of the nuclear enzyme poly(adenosine diphosphate ribose) polymerase (PARP) could modulate neurologic injury after thoracic aortic ischemia reperfusion (TAR) in a murine model of SCI. METHODS: Forty-one anesthetized male mice were subject to thoracic aortic occlusion (11 minutes) through a cervical mediastinotomy followed by 48 hours of reperfusion (TAR) under normothermic conditions. PJ34-treated mice (PJ, n = 12) were given 10 mg/kg PJ34 intraperitoneally 1 hour before ischemia and 1 hour after unclamping. The control group (UN, n = 21) received normal saline intraperitoneally 1 hour before ischemia and 1 hour after unclamping. Sham animals (n = 10) were subject to thoracic aortic exposure with no aortic clamping and similar intraperitoneal normal saline injections. PARP-1-/- (KO, n = 8) mice were subjected to the same conditions as the UN mice. Blinded observers rated murine neurologic status after TAR by using an established rodent paralysis scoring system. Murine spinal cords were subjected to cytokine (GRO-1) protein analysis as a marker of inflammation and immunohistochemical analysis (hematoxylin-eosin and PAR staining). Paralysis scores (PS) and GRO-1 levels were compared with analysis of variance, and survival data were compared with chi 2 . RESULTS: Immediately after TAR, UN and PJ mice had severe neurologic dysfunction (PS = 5.8 +/- 0.1 and 4.6 +/- 0.6, respectively; P > .05), which was significantly worse than the KO mice (PS = 1.0 +/- 0.7, P < .001). After 6, 24, and 48 hours KO mice had no discernable neurologic injury (PS = 0). Six hours after TAR, PJ mice significantly improved (PS = 1.1 +/- 0.73, P < .001) and remained improved at 24 (PS = 0.7 +/- 0.6) and 48 hours (PS = 0.6 +/- 0.6). UN mice did not improve their PS, and Sham mice showed no neurologic abnormality at any time during these experiments. The mortality at 48 hours was 0% for PJ and KO mice, 43% for UN (P = .012), and 0% for Sham. GRO-1 levels were significantly decreased in PJ and KO versus UN mice (UN, 583 +/- 119 vs PJ, 5.8 +/- 0 vs KO, 5.3 +/- 1.4 mg/pg; P < .0001). Immunohistochemistry showed evidence of decreased PAR staining and ventral motor neuron injury in PJ mice. CONCLUSIONS: Genetic deletion of PARP or inhibition of its activity (PJ34) rescued neurologic function in mice subjected to TAR. PARP inhibition might represent a novel therapeutic approach for prevention of SCI after TAR.

Animals↗