Biomedical subjects

M Shen

Publications and source records attributed to M Shen.

At least 19 recordsLinked to original sources

PubMed2006

Influence of the Plasmodium falciparum P-glycoprotein homologue 1 (pfmdr1 gene product) on the antimalarial action of cyclosporin.

BACKGROUND AND OBJECTIVES: The immunosuppressant cyclosporin A and a number of other cyclosporins have potent and selective antimalarial activity. Their exact mechanism of antimalarial action is unknown but the structure-activity relationships for malarial parasite inhibition and immunosuppression differ markedly. The 3'-keto derivative of cyclosporin D (valspodar) is particularly potent against the human malarial parasite Plasmodium falciparum in culture but causes negligible immunosuppression. Multidrug resistance in mammalian cancer cells, the result of overproduction of the P-glycoprotein, can be reversed by certain cyclosporins, particularly valspodar. We therefore investigated the possibility that the antimalarial target of cyclosporin might be a P-glycoprotein homologue. P. falciparum P-glycoprotein homologue 1 (Pgh1; the pfmdr1 gene product) is located in the digestive vacuole (DV) membrane of the parasite. Its function is unknown but it modulates the susceptibility of parasites to quinolines and related antimalarial drugs, including quinine, mefloquine, halofantrine and chloroquine, and to artemisinin. METHODS AND RESULTS: Here we demonstrate that (i) sequence polymorphisms in pfmdr1 altered the susceptibility of parasites to cyclosporin A and (ii) pfmdr1-overexpressing strains were slightly less susceptible to the drug. Furthermore, we found synergistic antimalarial interactions between cyclosporin A and quinine, mefloquine or halofantrine and antagonism between cyclosporin A and chloroquine. However, we were unable to detect a direct interaction between cyclosporin and Pgh1. CONCLUSIONS: The amino acid sequence and copy number of Pgh1 may influence cyclosporin susceptibility as a result of a direct interaction between the drug and the protein, or via indirect effects on the physiology of the DV.

Animals↗

PubMed2006

Long-term outcome and neuroradiological findings of 31 patients with 6-pyruvoyltetrahydropterin synthase deficiency.

Tetrahydrobiopterin (BH(4)) deficiency is an autosomal recessive disorder caused by enzyme defects in the biosynthesis or recycling of BH(4). Patients with BH(4) deficiency present with severe neurological signs and symptoms and require a different treatment from classical phenylketonuria. During the last 12 years, 31 cases of BH(4) deficiency were identified in our department. They were all classified as 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency. They were diagnosed at the ages of 2.5-48 months and treated with BH(4), L-dopa and 5-hydroxytryptophan immediately after diagnosis. The average development quotients (DQ) at diagnosis and after treatment for more than 3 years were 53+/- 16, and 78+/- 15, respectively. A significant negative correlation was observed between the level of the DQ and the age at which treatment was commenced (r = -0.751, p = 0.002). Developmental profiles were uneven. Language, adaptability and at later age mathematics were particularly weak areas. Only two patients achieved a good performance in mathematics. Eleven patients who were treated with drugs from ages of 2.9-48 months had neuroradiological scanning. Computed tomography disclosed calcification in lentiform nuclei in one patient and magnetic resonance imaging disclosed delayed myelination and abnormal high intensity signal in cerebral white matter in all of them. Even though most of abnormalities were reversible, small patchy or spotted areas were still present on these regions after treatment for 10-46 months. In summary, our study supports the substantial efficacy of the current therapeutic approach in PTPS deficiency of normalizing amine neurotransmitters with three drugs as early as possible. For the first time, calcifications could be detected in patients with PTPS deficiency. Abnormalities in white matter on magnetic resonance imaging were not related to clinical manifestations and most were reversible.

Brain↗

PubMed2006

Mycophenolic acid upregulates B7-DC expression on dendritic cells, which is associated with impaired allostimulatory capacity of dendritic cells.

In addition to its effects on lymphocytes, mycophenolic acid (MPA) may inhibit the allostimulatory capacity of dendritic cells (DC) via unknown mechanisms. B7-H1 and B7-DC surface markers on DC negatively regulate T-cell responses via the receptor PD-1. In this study, we sought to investigate whether B7-H1 and B7-DC are responsible for the inhibitory functions of MPA on DC. Mouse bone marrow-derived DC were cultured with recombinant granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 in the presence or absence of MPA (0.01 micromol and 0.1 micromol). The DC phenotype was assessed by flow cytometry, their immunostimulatory capacity measured by mixed lymphocyte reaction (MLR), and cytokine production by ELISA. The results showed that MPA not only inhibited the expression of major histocompatibility complex (MHC) class II and costimulatory molecules CD80 and CD86 but upregulated B7-DC expression on mature DC induced by LPS. These findings were associated with a reduced allostimulatory ability and an altered cytokine secretion pattern of DC. Thus, we suggest that MPA upregulates B7-DC expression during DC maturation induced by LPS in vitro, an effect that may be responsible for MPA-mediated inhibitory effects on the allostimulatory capacity of DC.

Animals↗

PubMed2006

Living environment and schooling of children with HIV-infected parents in southwest China.

A cross-sectional household survey was conducted in Longchuan County, China, to study the lives of children with HIV-infected parents. Registered HIV-infected drug users and their households were approached and information about the living environment of children < or =15 years of age was collected. Of the 266 households interviewed, there were 213 children < or =15 years old. Forty percent of the children had lost at least one parent. Most of the children resided in a household with low economic status and a high dependency ratio. One-half of the children experienced discordant family relations, family anxiety and shame. Compared to orphans, non-orphans and their families were less likely to receive social support from the community. Orphans and older children were less likely to attend school and more likely to be truant if enrolled in school. Findings in the current study suggest that many children whose parents are infected with HIV or have died from HIV are living in stressful environments with minimal support from the community. Efforts should be taken to provide support and supervision to these children.

Absenteeism↗

PubMed2006

B7-H1 expression is upregulated in peripheral blood CD14+ monocytes of patients with chronic hepatitis B virus infection, which correlates with higher serum IL-10 levels.

Chronicity in hepatitis B virus (HBV) infection is maintained by increased type 2 T-helper cell response, possibly because of increased interleukin-10 (IL-10) productions. B7-H1 can negatively regulate T-cell responses via its receptor, programmed death 1. Ligation of B7-H1 to T-cells can result in the preferential secretion of IL-10. In this study, we investigated whether there was an upregulated expression of B7-H1 in peripheral blood mononuclear cells in patients chronically infected by HBV and further explored the correlation between B7-H1 expression and serum interleukin 2, interferon-gamma, IL-10, HBeAg, alanine aminotransferase (ALT) levels and viral load. Fifty-five patients with chronic HBV infection and 20 healthy controls (HCs) were enrolled in the present study. The results showed that in patients with chronic hepatitis B CD14+ monocytes but not CD3+ and CD19+ cells had a significantly increased expression of B7-H1 compared with HCs, which positively correlates with serum IL-10 levels and the presence of HBeAg and negatively correlates with serum ALT levels. In conclusion, chronic HBV patients harbour an increased B7-H1 expression in CD14+ monocytes compared with controls, which may be responsible for the increased serum IL-10 levels. This might be an important way by which HBV evades an adequate immune response, leading to viral persistence and disease chronicity.

Adult↗

PubMed2004

Complete nucleotide sequence of Kashmir bee virus and comparison with acute bee paralysis virus.

The complete nucleotide sequence of a novel virus is presented here together with serological evidence that it belongs to Kashmir bee virus (KBV). Analysis reveals that KBV is a cricket paralysis-like virus (family Dicistroviridae: genus Cripavirus), with a non-structural polyprotein open reading frame in the 5' portion of the genome separated by an intergenic region from a structural polyprotein open reading frame in the 3' part of the genome. The genome also has a polyadenylated tail at the 3' terminus. KBV is one of several related viruses that also includes acute bee paralysis virus (ABPV). Although KBV and ABPV are about 70 % identical over the entire genome, there are considerable differences between them in significant areas of the genome, such as the 5' non-translated region (42 % nucleotide identity), between the helicase and 3C-protease domains of the non-structural polyprotein (57 % amino acid identity) and in a 90 aa stretch of the structural polyprotein (33 % amino acid identity). Phylogenetic analyses show that KBV and ABPV isolates fall into clearly separated clades with moderate evolutionary distance between them. Whether these genomic and evolutionary differences are sufficient to classify KBV and ABPV as separate species remains to be determined.

5' Untranslated Regions↗

PubMed2003

Quantitative analysis of binary adsorbed protein films by time of flight secondary ion mass spectrometry.

Time of flight secondary ion mass spectrometry (ToF-SIMS) is an ideal technique for the analysis of adsorbed protein films because of its surface sensitivity and chemical specificity. In this study, we examined ToF-SIMS with the multivariate calibration method partial least squares regression (PLSR) for the determination of the relative abundance of the components in binary protein films adsorbed onto mica, PTFE, and heptyl amine plasma polymer substrates. These results have been compared with independently measured 125I-radiolabeled protein adsorption experiments. By applying PLSR to the ToF-SIMS data, the relative abundance of the components in the binary adsorbed protein films was quantified, and the agreement between the ToF-SIMS and 125I-radiolabeling data was measured by the root mean square prediction error (RMSPE). Differences in protein quantification by PLSR and 125I-radiolabeling ranged from 5 to 25 mass % RMSPE and were highly dependent on the structure of the adsorbed protein film, the substrate surface chemistry and morphology, and the number of latent variables retained in the PLSR model. The limit of detection for the minor component in the adsorbed protein film was found to be approximately 10 mass %. This study demonstrates that the combination of ToF-SIMS and multivariate calibration provide complementary information to 125I-radiolabeling about the composition and structure of binary adsorbed protein films.

Adsorption↗

PubMed2001

The effects of surface chemistry and adsorbed proteins on monocyte/macrophage adhesion to chemically modified polystyrene surfaces.

Monocytes and macrophages play critical roles in inflammatory responses to implanted biomaterials. Monocyte adhesion may lead to macrophage activation and the foreign body response. We report that surface chemistry, preadsorbed proteins, and adhesion time all play important roles during monocyte adhesion in vitro. The surface chemistry of tissue culture polystyrene (TCPS), polystyrene, Primaria, and ultra low attachment (ULA) used for adhesion studies was characterized by electron spectroscopy for chemical analysis. Fibrinogen adsorption measured by (125)I-labeled fibrinogen was the lowest on ULA, higher on TCPS, and the highest on polystyrene or Primaria. Monocyte adhesion on protein preadsorbed surfaces for 2 h or 1 day was measured with a lactate-dehydrogenase method. Monocyte adhesion decreased over time. The ability of preadsorbed proteins to modulate monocyte adhesion was surface dependent. Adhesion was the lowest on ULA, higher and similar on TCPS or polystyrene, and the highest on Primaria. Monocyte adhesion on plasma or fibrinogen adsorbed surfaces correlated positively and linearly to the amount of adsorbed fibrinogen. Preadsorbed fibronectin, immunoglobulin G, plasma, or serum also promoted adhesion compared with albumin preadsorbed or uncoated surfaces. Overall, biomaterial surface chemistry, the type and amount of adsorbed proteins, and adhesion time all affected monocyte adhesion in vitro.

Adsorption↗

PubMed2001

Functional cloning of Src-like adapter protein-2 (SLAP-2), a novel inhibitor of antigen receptor signaling.

In an effort to identify novel therapeutic targets for autoimmunity and transplant rejection, we developed and performed a large-scale retroviral-based functional screen to select for proteins that inhibit antigen receptor-mediated activation of lymphocytes. In addition to known regulators of antigen receptor signaling, we identified a novel adaptor protein, SLAP-2 which shares 36% sequence similarity with the known Src-like adaptor protein, SLAP. Similar to SLAP, SLAP-2 is predominantly expressed in hematopoietic cells. Overexpression of SLAP-2 in B and T cell lines specifically impaired antigen receptor-mediated signaling events, including CD69 surface marker upregulation, nuclear factor of activated T cells (NFAT) promoter activation and calcium influx. Signaling induced by phorbol myristate acetate (PMA) and ionomycin was not significantly reduced, suggesting SLAP-2 functions proximally in the antigen receptor signaling cascade. The SLAP-2 protein contains an NH2-terminal myristoylation consensus sequence and SH3 and SH2 Src homology domains, but lacks a tyrosine kinase domain. In antigen receptor-stimulated cells, SLAP-2 associated with several tyrosine phosphorylated proteins, including the ubiquitin ligase Cbl. Deletion of the COOH terminus of SLAP-2 blocked function and abrogated its association with Cbl. Mutation of the putative myristoylation site of SLAP-2 compromised its inhibitory activity and impaired its localization to the membrane compartment. Our identification of the negative regulator SLAP-2 demonstrates that a retroviral-based screening strategy may be an efficient way to identify and characterize the function of key components of many signal transduction systems.

Adaptor Proteins, Signal Transducing↗

PubMed2001

The stability of tetramine, morphine and meperidine in formalin solution.

The stability of tetramine, morphine and meperidine in formalin solution is an important factor for drug analysis in forensic investigation. In this paper, the tissues (liver, kidney, lung and heart) from poisoned rabbits were immersed in 50 ml 10% formalin solutions for 4 months before examination. We compared the levels of tetramine, morphine, meperidine and the main metabolite normeperidine, measured by GC/NPD or GC-MS, in frozen rabbit tissues, formalin-fixed rabbit tissues, and formalin solution. There was a decrease in the levels of tetramine, morphine, meperidine in formalin-preserved tissues compared with the levels of these drugs in the frozen tissues. It is suggested that the formalin-fixed tissues and formalin solution should be analyzed at the same time to assure the accurate results.

Animals↗

PubMed2001

RGS18 is a myeloerythroid lineage-specific regulator of G-protein-signalling molecule highly expressed in megakaryocytes.

Myelopoiesis and lymphopoiesis are controlled by haematopoietic growth factors, including cytokines, and chemokines that bind to G-protein-coupled receptors (GPCRs). Regulators of G-protein signalling (RGSs) are a protein family that can act as GTPase-activating proteins for G(alphai)- and G(alphaq)-class proteins. We have identified a new member of the R4 subfamily of RGS proteins, RGS18. RGS18 contains clusters of hydrophobic and basic residues, which are characteristic of an amphipathic helix within its first 33 amino acids. RGS18 mRNA was most highly abundant in megakaryocytes, and was also detected specifically in haematopoietic progenitor and myeloerythroid lineage cells. RGS18 mRNA was not detected in cells of the lymphoid lineage. RGS18 was also highly expressed in mouse embryonic 15-day livers, livers being the principal organ for haematopoiesis at this stage of fetal development. RGS1, RGS2 and RGS16, other members of the R4 subfamily, were expressed in distinct progenitor and mature myeloerythroid and lymphoid lineage blood cells. RGS18 was shown to interact specifically with the G(alphai-3) subunit in membranes from K562 cells. Furthermore, overexpression of RGS18 inhibited mitogen-activated-protein kinase activation in HEK-293/chemokine receptor 2 cells treated with monocyte chemotactic protein-1. In yeast cells, RGS18 overexpression complemented a pheromone-sensitive phenotype caused by mutations in the endogeneous yeast RGS gene, SST2. These data demonstrated that RGS18 was expressed most highly in megakaryocytes, and can modulate GPCR pathways in both mammalian and yeast cells in vitro. Hence RGS18 might have an important role in the regulation of megakaryocyte differentiation and chemotaxis.

Amino Acid Sequence↗

PubMed2001

[Histopathological changes of prostate cancer after castration therapy and correlative factors].

OBJECTIVE: To study the histopathological changes of prostate cancer after castration therapy among Chinese and correlative factors. METHODS: Needle biopsy specimens and prostatectomy specimens were obtained from 17 cases of prostate cancer and examined by light microscopy and image analysis system. RESULTS: Glandular atrophy, cytoplasmic vacuolization, nuclear pyknosis, and relative increase of stroma could be seen after orchectomy. There was a close correlation between atrophy of neoplastic tissue in prostate gland and patients' age (P < 0.05). The atrophy of neoplastic tissue in prostate gland was not correlated with the serum PSA, tumor staging and grading before castration therapy (P > 0.05). CONCLUSION: Castration is effective for treatment of prostate cancer, especially among the elderly patients. It is important for pathologists to recognize the histopathological changes in the prostectomy specimens made untypical by castration.

Age Factors↗

PubMed2001

[Study on expression of PCNA and estrogen, progesterone receptors in endometrial carcinoma].

OBJECTIVE: To investigate the proliferating ability of tumor cells in 74 cases with endometrial carcinoma (EMC), as well as define the correlation between clinical pathology, prognostic features and estrogen receptor (ER), progesterone receptor (PR). METHODS: Proliferating cell nucleus antigen (PCNA) and ER/PR content were examined using immunohistochemical assay. RESULTS: PCNA was expressed in both benign hyperplasia and EMC, but positive rate in the latter was significantly higher than that in the former (82.4% vs 30.0%) (P < 0.01). EMC well differentiated had lower proliferating index (PI) score than those moderately and poorly differentiated(P < 0.001), and the PI score was negatively related to the grade of differentiation(r = -0.52, P < 0.01). PI score in early cases (I/II) was significantly lower than that in advanced ones(III/IV) (P < 0.05), and the PI score was positively related to the clinical stages (r = 0.55, P < 0.01). Positive rates of ER, PR were 66.2% (49/74) and 75.7%(56/74) respectively, expression of PCNA was negatively related with ER and PR(r = -0.42, -0.51, respectively, P < 0.05). CONCLUSIONS: EMC cells with poorer differentiation or in more advanced stages have faster proliferating ability and aggressive biological behavior. Expression of PCNA combined with detection of ER/PR not only apts to retrospective study, but also has some prognostic value.

Adult↗

PubMed2001

p15(PAF), a novel PCNA associated factor with increased expression in tumor tissues.

Proliferating cell nuclear antigen (PCNA) is an essential protein in both DNA replication and DNA damage repair. A novel 15 kD protein, p15(PAF), was identified as a PCNA-associated factor in a yeast two-hybrid screen using PCNA as the bait. p15(PAF) is localized primarily in the nucleus. p15(PAF) shares the conserved PCNA binding motif with several other PCNA binding proteins including CDK inhibitor p21. Overexpression of p15(PAF) competes with p21-PCNA binding. Mutation of this motif in p15(PAF) abolished its PCNA-binding activity. Notably, p15(PAF) expression in several types of tumor tissues was significantly increased, especially in esophageal tumors. Like PCNA, p15(PAF) may possess prognostic significance in a broad array of human cancers.

Amino Acid Sequence↗

PubMed2001

Molecular cloning and characterization of DEC2, a new member of basic helix-loop-helix proteins.

DEC1 is a basic helix-loop-helix (bHLH) protein related to Drosophila Hairy, Enhancer of split and HES, and involved in the control of proliferation and/or differentiation of chondrocytes, neurons, etc. We report here the identification and characterization of human, mouse and rat DEC2, a novel member of the DEC subfamily. DEC2 had high (97%) and moderate (52%) similarities in the bHLH region and the Orange domain with DEC1, respectively. However, DEC2, but not DEC1, had alanine and glycine-rich regions in the C-terminal half. Unlike Hairy, Enhancer of split and HES, DEC2 lacked the WRPW motif for interaction with the corepressor Groucho. The DEC2 gene was mapped to human chromosome 12p11.23-p12.1, mouse chromosome 6 G2-G3 and rat chromosome 4q43 distal-q4, where the conserved linkage homology has been identified among these species. Unlike DEC1, which was broadly expressed in many tissues, DEC2 showed a more restricted pattern of mRNA expression. The DEC subfamily proteins may play an important role in tissue development.

Amino Acid Sequence↗

PubMed2001

Biochemical properties of heat-treated valvular bioprostheses.

BACKGROUND: Preliminary studies showed that heat treatment of glutaraldehyde preserved valvular bioprostheses mitigates calcification. This study was carried out to define the physicochemical characteristics of the heat-treated tissues to elucidate the mechanism involved in the mitigation. METHODS: Glut bovine pericardium or porcine valve samples were treated at 50 degrees C in a 0.625% glutaraldehyde solution for 2 months. Some samples underwent assay for shrinkage temperature, moisture content, ninhydrin test, and acid hydrolysis, and other samples were incubated in human serum for 3 days and then analyzed by electrophoresis to study protein adsorption. RESULTS: Heat treatment mitigated calcification without adversely affecting shrinkage temperature (84.81 degrees C versus 83.95 degrees C) and moisture content (78.68% versus 78.71%). A significant reduction in free amino groups (0.15 versus 0.37 mol NH2/mol collagen) and a significant increase in resistance to acid hydrolysis were observed. Total protein content was similar, but significant differences were found for four proteins adsorbed in the tissues (167, 45, 11.6, and 10 kDa). CONCLUSIONS: The anticalcification effect of heat treatment may be attributed to structural changes, lipid extraction, increased resistance, and modifications of the type and concentration of the proteins adsorbed in the tissue.

Adsorption↗

PubMed2001

Protein adsorption of calcified and noncalcified valvular bioprostheses after human implantation.

BACKGROUND: The incidence of calcification of porcine valve bioprostheses shows important, and as yet unexplained, variations. Previous studies by others showed that osteopontin and osteocalcin are expressed in calcified porcine valve bioprostheses. However, no study has yet explored other proteins that could also be involved. METHODS: Twelve porcine valve bioprostheses were retrieved from 12 patients and were separated into two groups. Group 1 (n = 6) had early calcification after 4 to 9 years (mean, 6+/-2.3 years). The mean age of the patients at the time of implantation was 46+/-9 years. Group 2 (n = 6) had no calcification after 8 to 14 years (mean, 12+/-2.8 years). The mean age was 47+/-13.4 years. These valves were analyzed by electrophoresis, and the bands were quantified by densitometry. RESULTS: A 14-kd protein showed a 50% increase in the calcified group. A 31-kd protein found in the calcified group was not detected in the noncalcified group. Three other proteins (45, 39, and 28 kd) showed reduced adsorption in the calcified group. CONCLUSIONS: Important differences were found in the proteins adsorbed in calcified and noncalcified bioprostheses after implantation in patients. Besides osteopontin and osteocalcin, several other proteins may play a role in the process of calcification of valvular bioprostheses.

Adsorption↗

PubMed2001

Protein adsorption in glutaraldehyde-preserved bovine pericardium and porcine valve tissues.

BACKGROUND: Proteins adsorbed by bioprosthetic tissues after implantation play a major role in the process of calcification. We investigated whether there are differences in protein adsorption between bovine pericardial and porcine valvular tissues that could correlate with the differences observed clinically. METHODS: Glutaraldehyde-treated bovine pericardial and porcine valve samples were implanted subcutaneously in rats and retrieved 1 month after implantation. Total protein content was assessed by Lowry's method. Qualitative analysis was performed by polyacrylamide gel electrophoresis. Quantitative analysis was performed by densitometry. RESULTS: Total protein content showed a higher protein concentration in porcine valve tissue than in pericardial tissue: 149+/-22.6 microg/mg dry tissue versus 108+/-12.7 microg/mg dry tissue (38% increase). In pericardial tissue, four protein bands (17, 16, 15.5, and 13.5 kd) showed decreased concentration when compared with porcine valve tissue, whereas one band (11 kd) showed increased concentration. CONCLUSIONS: Significant differences were found in protein content between bovine pericardial and porcine valve tissues. Correlations with clinical findings may lead to a better understanding of the mechanism involved in the process of calcification, particularly the role played by the structure of the tissues.

Adsorption↗