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Biomedical subjects

Jun Chen

Publications and source records attributed to Jun Chen.

At least 343 records · Page 19Linked to original sources
PubMed2003

[Analyses on the trace elements of soils in geo-authentic and non-authentic production areas of Flos lonicearae].

OBJECTIVE: To analyse the trace elements presented in the same germplasm of Flos Lonicerae with the soil in different producing areas of crude drugs and to investigate, the relationship between the trace elements and the characteristics of the geo-authentic Flos Lonicerae in the soil and crude drugs. METHOD: The analyses on the trace elements of soil and crude drugs were made by ICP-AES. RESULT: The contents of Sr, K, Na, Mg and Ca were higher in the geo-authentic areas, and the contents of Ca, Sr and Fe were higher, but the Cr and Pb were lower in the geo-authentic Flos Lonicerae. The geo-authentic crude drugs had a strong tendency to accumulate P and Cu. CONCLUSION: There are no direct relationship between the concentrations of trace elements in Flos Lonicerae and those in their corresponding soil. There are good relationship between the absorption and accumulation of Ca and Cr, Co, Na and Fe; Zn and Co, Cr, Mn; Na and Co; Mg and Mn.

China↗
PubMed2003

[Study on the pollination characteristic of Cistanche deserticola].

OBJECTIVE: To study the Pollination Characteristic of C. deserticola. METHOD: Four pollination methods were used, cross pollination coming different plant, cross pollination in one plant, wind pollination and no-pollination. RESULT: Cross pollinations coming different plant are fructiferous. The average fructication rate of cross pollination coming different plant is 94.1%; the average fructication rate of cross pollination in one plant is 52.2%; The seed qulitity of cross pollination coming different plant is better than the cross pollination in one plant. CONCLUSION: Cross pollinations coming different plant have a high quantity and quality of seeds of C. deserticola.

Cistanche↗
PubMed2003

[Applied studies of biological control techniques on healthful Chinese crude drugs].

Medicinal plants always suffer from diseases and pests in their cultivation and growing, and the yield and quality are reduced. At present, chemical pesticide is mainly used to control the diseases and pests. The long-term use and over-use of pesticide result in pesticide residue, pests resistance to pesticide, water and soil pollution and other environmental contamination. It is necrssary to provide the integrated pests management, including new technology of biological control for developing green drug. This project makes research on the following aspects: 1. Applied studies on bethyloid wasp (Scleroderma guani) control for stem borer; 2. To develop Trichoderma spp. and use it to control the diseases of medicinal plants; 3. Applying Agro-antibiotics 120 to control phytophthora root rot of ginseng; 4. Researches on application of entomopathogenic nematodes against ten-spotted lema (Lema decempuntata) et al.

Animals↗
PubMed2003

[Biological effect of seed-coating in Carthamus tinctorins].

OBJECTIVE: To study the Biological effect of seed-coating in Carthamus tinctorins. METHOD: Two kinds of seedcoating chemicals SCF1 and SCF2 were used in this experiment, the seed YM-99 and 27981-99 were coated by three kinds of ratio of seedcoating chemicals to seed. It was investigated that the germination energy and germination percentage in the room and the emergence rate, seedling stage growing, pest in the field. RESULT: Seedoating can improve the emergence rate and seedling stage growing, it also can effectively control aphid, rust and virosis during the growing period in C. tinctorins. CONCLUSION: Seedcoating has significant biological effect in C. tinctorins.

Carthamus↗
PubMed2003

[An experimental study of cellular mechanic properties of intestinal epithelial cells by micropipette aspiration].

OBJECTIVE: To further understand the mechanic properties of the Intestinal Epithelial cells (IEC). METHODS: The viscoelastic properties of the IEC-6 were determined by micropipette aspiration. RESULTS: The elastic coefficient K1 was 436.21 +/- 89.64 dyn/cm2 and K2 was 298.37 +/- 75.16 dyn/cm2. The visous coefficient micro was 15.94 +/- 4.93 dyn/(sec x cm2). CONCLUSION: The elastic component reflects the degree of initial deformation of the IEC and makes a notable impact on the deformation of the IEC. The viscous component reflects the time dependency of the deformation of the IEC and influences the velocity of the IEC deformation.

Biomechanical Phenomena↗
PubMed2003

[Study on the production condition of extraction in combination hydrolysis in situ for isolating diosgenin].

OBJECTIVE: To study the production technology of extraction in combination hydrolysis in situ for isolating diosgenin from Dioscorea nipponica by orthogonal design. METHOD: The optimum production conditions were investigated with the recovery of diosgenin as an index by extraction in combination hydrolysis in situ, and were compared with the traditional method. RESULT: Extraction in combination hydrolysis in situ conducted in 1.5 mol x L(-1) sulfuric acid of water containing 75% isopropanol at 100 degrees C for 4.5 h could get higher recovery of diosgenin than traditional methods. CONCLUSION: This production technology can get higher recovery of diosgenin, and it is simple, time and money saving.

Dioscorea↗
PubMed2002

Survivin enhances Aurora-B kinase activity and localizes Aurora-B in human cells.

Survivin, one of the most tumor-specific gene products, has been implicated in both anti-apoptosis and cytokinesis. However, the mechanism by which survivin regulates these two different processes is still elusive. Here, we show that survivin binds to the catalytic domain of Aurora-B. We demonstrate that in the presence of survivin, Aurora-B phosphorylates histone H3 much more efficiently than in the absence of survivin in a cell-free system. Furthermore, we confirm that cells lacking survivin due to survivin antisense oligonucleotide-treatment have lower Aurora-B kinase activity, whereas cells overexpressing survivin have higher Aurora-B kinase activity. We also provide evidence that depletion of survivin by survivin antisense oligonucleotide treatment causes significant reduction of endogenous phosphorylated histone H3 and mislocalization of Aurora-B. These results indicate that survivin stimulates Aurora-B kinase activity and helps correctly target Aurora-B to its substrates during the cell cycle, thus providing a mechanism as to how survivin exerts its function in human cells.

Animals↗
PubMed2002

Distinct BAG-1 isoforms have different anti-apoptotic functions in BAG-1-transfected C33A human cervical carcinoma cell line.

BAG-1 protein can be expressed as four isoforms of 50, 46, 33 and 29 kDa with different subcellular localizations, which may have different functions in anti-apoptosis, but the exact mechanism remains unclear. We constructed BAG-1 full length and deletion mutated plasmids in a pCR3.1 vector and established stable transfections of BAG-1 isoforms in low BAG-1 expressing C33A cells. Treatment of the transfected cells with cisplatin, staurosporine, paclitaxel and doxorubicine showed that BAG-1 p50, p46 and p33 isoforms enhanced the resistance to apoptosis. BAG-1 p50, p46 and p33 exhibited different degrees of apoptosis inhibition in the transfected cells and BAG-1 p46 isoform had the most pronounced effect on anti-apoptosis. BAG-1 p29 failed to protect the transfected cells from apoptosis. Resistance to apoptosis by BAG-1 isoforms was correlated with decreased caspase-3 activation. We also detected the expression of Bax, Bak, p53, Bcl-2, Bcl-X(L), AIF and MRP1 by Western blots. Bcl-2 protein expression was significantly increased in p50, p46 and p33 transfected cells, while the expression of Bax, Bak, p53, Bcl-X(L) and MRP1 was essentially unchanged. These in vitro results suggest that distinct isoforms of BAG-1 have different anti-apoptotic functions and their functions may be correlated to increased Bcl-2 expression.

Apoptosis↗
PubMed2002

Differential effect of peripheral glutamate (NMDA, non-NMDA) receptor antagonists on bee venom-induced spontaneous nociception and sensitization.

This study aimed to investigate the role of peripheral N-methyl-d-aspartate (NMDA) and non-NMDA receptor on (1). spontaneous nociception and (2). on sensitization induced by subcutaneous (s.c.) injection of bee venom (0.2mg/50 micro l) in rats. Peripheral s.c. administration of the competitive NMDA receptor antagonist dl-2-amino-5-phosphonovaleric acid (AP5), the non-competitive NMDA receptor channel blocker MK-801, and the competitive non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were performed before (pre-treatment) and after (post-treatment) bee venom-induced inflammation. Pre-treatment with AP5 (10mM, 50 micro l) and both pre-treatment and post-treatment with MK-801 (2mM, 50 micro l) into the same area of the bee venom injection site markedly reduced the bee venom-increased spontaneous responses of wide-dynamic range (WDR) neuron of the spinal cord. Post-treatment with the same dose of AP5 as well as pre-treatment and post-treatment with CNQX (5mM, 50 micro l) did not produce any inhibitory effects. Additionally, the role of peripheral NMDA and non-NMDA receptors on bee venom-induced mechanical allodynia and hyperalgesia were investigated and assessed by the paw withdrawal reflex to the innocuous and noxious mechanical stimulation. Peripheral administration of AP5, but not CNQX, reduced mechanical allodynia and hyperalgesia. The data suggest that the peripheral NMDA receptor, but not non-NMDA receptor, plays a pivotal role in the bee venom-induced persistent nociception and hyperexcitability.

Action Potentials↗
PubMed2002

Position of aromatic residues in the S6 domain, not inactivation, dictates cisapride sensitivity of HERG and eag potassium channels.

Unintended block of HERG K+ channels is a side effect of many common medications and is the most common cause of acquired long QT syndrome associated with increased risk of life-threatening arrhythmias. The molecular mechanism of high-affinity HERG block by structurally diverse compounds has been attributed to pi-stacking and cation-pi interactions of a drug (e.g., cisapride) with specific aromatic amino acid residues (Tyr-652 and Phe-656) in the S6 alpha-helical domain that face the central cavity of the channel. It also has been proposed that strong C-type inactivation of HERG facilitates or is the primary determinant of high-affinity drug binding. The structurally related, but noninactivating eag channel is insensitive to HERG blockers unless inactivation is induced by specific amino acid mutations [Ficker, E., Jarolimek, W. & Brown, A. M. (2001) Mol. Pharmacol. 60, 1343-1348]. Here we examine the relative importance of inactivation vs. positioning of S6 aromatic residues in determining sensitivity of HERG and eag channels to block by cisapride. The repositioning of Tyr-652 or Phe-656 along the S6 alpha-helical domain of HERG reduced sensitivity of channels to block by cisapride. Moreover, independent of inactivation, repositioning of the equivalent aromatic residues in Drosophila eag channels induced sensitivity to block by cisapride. These findings suggest that positioning of S6 aromatic residues relative to the central cavity of the channel, not inactivation per se determines drug block of HERG or eag channels.

Amino Acid Sequence↗
PubMed2002

Bid-mediated mitochondrial pathway is critical to ischemic neuronal apoptosis and focal cerebral ischemia.

We have investigated the role of the BH3-only pro-death Bcl-2 family protein, Bid, in ischemic neuronal death in a murine focal cerebral ischemia model. Wild-type and bid-deficient mice of inbred C57BL/6 background were subjected to 90-min ischemia induced by left middle cerebral artery occlusion followed by 72-h reperfusion. The volume of ischemic infarct was significantly smaller in the bid-deficient brains than in the wild-type brains, suggesting that Bid participated in the ischemic neuronal death. Indeed, following the ischemic treatment there was a significant reduction of apoptosis in the ischemic areas, particularly in the inner infarct border zone (the penumbra), of the bid-deficient brains. In addition, activation of Bid in the wild-type brains could be readily detected at approximately 3 h after ischemia, as evidenced by its proteolytic cleavage and translocation to the mitochondria as determined using Western blot analysis and immunofluorescence staining. Correspondingly, mitochondrial release of cytochrome c could be detected around the same time Bid was cleaved in the wild-type brains. However, no significant cytochrome c release was detected in the bid-deficient brains until 24 h later. This suggests that, although the mitochondrial apoptosis pathway might be activated by multiple mechanisms during focal cerebral ischemia, Bid is critical to its early activation. This notion was further supported by the finding that caspase-3 activation was severely impaired in the bid-deficient brains, whereas activation of caspase-8 was much less affected. Taken together, these data suggest that Bid is activated early in neuronal ischemia in a caspase-8-dependent fashion and that Bid is perhaps one of the earliest and most potent activators of the mitochondrial apoptosis pathway. Thus, the role of Bid in the induction of ischemic neuronal death may render this molecule an attractive target for future therapeutic intervention.

Animals↗
PubMed2002

Mutations at positions 547-553 of rat glucocorticoid receptors reveal that hsp90 binding requires the presence, but not defined composition, of a seven-amino acid sequence at the amino terminus of the ligand binding domain.

Glucocorticoid receptors (GRs) must heterocomplex with hsp90 to have an open steroid binding cleft that can be accessed by steroid. We reported that a seven-amino acid sequence (547-553 of rat GR) overlapping the amino-terminal end of the ligand binding domain is required for hsp90 binding to GR. We have now conducted saturation mutagenesis of this sequence, which appears to be part of the surface where the ligand binding cleft merges with the surface of the ligand binding domain. No single point mutation causes significant changes in any of a variety of biochemical and biological properties in addition to hsp90 binding. A triple mutation (P548A/T549A/V551A) increases by >100-fold the steroid concentration required for half-maximal induction without affecting the level of maximal induction or coactivator response. Interestingly, this triple mutant displays reduced binding of steroid and hsp90 in whole cells, but it possesses wild type affinity for steroid and normal hsp90 binding capacity under cell-free conditions. This phenotype of a dramatic shift in the dose response for transactivation would be expected from an increase in the rate of disassembly of the triple mutant GR.hsp90 heterocomplex in the cell. Mutation of the entire seven-amino acid region to CAAAAAC maintains the presence of a critical alpha-helical structure and heterocomplex formation with hsp90 but eliminates steroid binding and transcriptional activation, thus disconnecting hsp90 binding from opening of the ligand binding cleft and steroid binding.

Animals↗
PubMed2002

Studies on the synthesis of a G-rich octaoligoisonucleotide (isoT)2(isoG)4(isoT)2 by the phosphotriester approach and its formation of G-quartet structure.

The octaoligoisonucleotide (isoT)2(isoG)4(isoT)2 (I), consisting of isonucleoside units 6'-O-allyl-4'-deoxy-4'-(nucleobase)-2',5'-anhydro-L-mannitol, was synthesized by the phosphotriester approach in solution phase. Based on CD spectra and capillary electrophoresis, it was confirmed that iso-oligomer I could form a parallel intermolecular G-quadruplex structure. K+, Na+ and Li+ can prompt the formation of G-quartet structures and stabilize them. The effective order of these cations is K+ > Na+ > Li+.

Chromatography, High Pressure Liquid↗
PubMed2002

In Vivo Delivery of a Bcl-xL Fusion Protein Containing the TAT Protein Transduction Domain Protects against Ischemic Brain Injury and Neuronal Apoptosis.

Bcl-xL is a well characterized death-suppressing molecule of the Bcl-2 family. Bcl-xL is expressed in embryonic and adult neurons of the CNS and may play a critical role in preventing neuronal apoptosis that occurs during brain development or results from diverse pathologic stimuli, including cerebral ischemia. In this study, we used a novel approach to study the potential neuroprotective effect of Bcl-xL as a therapeutic agent in the murine model of focal ischemia/reperfusion. We created a Bcl-xL fusion protein, designated as PTD-HA-Bcl-xL, which contains the protein transduction domain (PTD) derived from the human immunodeficiency TAT protein. We demonstrated that this fusion protein is highly efficient in transducing into primary neurons in cultures and potently inhibited staurosporin-induced neuronal apoptosis. Furthermore, intraperitoneal injection of PTD-HA-Bcl-xL into mice resulted in robust protein transduction in neurons in various brain regions within 1-2 hr, and decreased cerebral infarction (up to approximately 40%) in a dose-dependent manner, as determined at 3 d after 90 min of focal ischemia. PTD-HA-Bcl-xL was effective even when it was administered after the completion of ischemia (up to 45 min), and the protective effect was independent of the changes in cerebral blood flow or other physiological parameters. Finally, as shown by immunohistochemistry, Western blotting, and substrate-cleavage assays, PTD-HA-Bcl-xL attenuated ischemia-induced caspase-3 activation in ischemic neurons. These results thus confirm the neuroprotective effect of Bcl-xL against ischemic brain injury and provide the first evidence that the PTD can be used to efficiently transduce a biologically active neuroprotectant in experimental cerebral ischemia.

Animals↗
PubMed2002

Glycated collagen I induces premature senescence-like phenotypic changes in endothelial cells.

Diabetic vasculopathy is central to the development of diverse cardiovascular, renal, retinal, and neurological complications of diabetes. We previously demonstrated that growth of endothelial cells on glycated extracellular matrix proteins (collagen and matrigel) results in a significant decrease in cell proliferation. In the present study, we show that early-passage human umbilical vein endothelial cells (HUVECs) grown on glycated collagen (GC) express hallmarks of premature cell senescence, ie, increase in the proportion of cells expressing senescence-associated beta-galactosidase activity, apoptotic rate, and p53 and p14(AFR) expression, but in contrast to replicative senescence, display neither attrition of telomeres nor decrease in telomerase activity. An increased frequency of prematurely senescent cells was similarly observed in vivo in aortae of young Zucker diabetic rats, compared with lean controls. NO production by HUVECs grown on GC was decreased, despite a 3-fold increase in eNOS expression and was associated with the increased nitrotyrosine-modified proteins. Development of premature senescence of HUVECs on GC could be prevented and reversed by treatments with the peroxynitrite scavenger, ebselen, eNOS intermediate N(omega)-hydroxy-L-arginine (NOHA), or superoxide dismutase mimetic Mn-TBAP. Concomitant with the reversal of senescence, ebselen, and NOHA each restored NO production to levels observed with HUVECs grown on unmodified collagen. Our findings indicate that diabetes mellitus in vivo and GC exposure in vitro elicit premature senescence of the vascular endothelium, a process with distinct pathogenetic mechanisms. Premature senescence of the vascular endothelium is hypothesized to be an important contributor to diabetic vasculopathy and a consequence of reduced NO availability, peroxynitrite, and/or superoxide excess.

Animals↗
PubMed2002

Mechanism of Galpha i-mediated inhibition of type V adenylyl cyclase.

The topology of mammalian adenylyl cyclase reveals an integral membrane protein composed of an alternating series of membrane and cytoplasmic domains (C1 and C2). The stimulatory G protein, Galpha(s), binds within a cleft in the C2 domain of adenylyl cyclase while Galpha(i) binds within the opposite cleft in the C1 domain. The mechanism of these two regulators also appears to be in opposition. Activation of adenylyl cyclase by Galpha(s) or forskolin results in a 100-fold increase in the apparent affinity of the two domains for one another. We show herein that Galpha(i) reduces C1/C2 domain interaction and thus formation of the adenylyl cyclase catalytic site. Mutants that increase the affinity of C1 for C2 decrease the ability of Galpha(i) to inhibit the enzyme. In addition, Galpha(i) can influence binding of molecules to the catalytic site, which resides at the C1/C2 interface. Adenylyl cyclase can bind substrate analogs in the presence of Galpha(i) but cannot simultaneously bind Galpha(i) and transition state analogs such as 2'd3'-AMP. Galpha(i) also cannot inhibit the membrane-bound enzyme in the presence of manganese, which increases the affinity of adenylyl cyclase for ATP and substrate analogs. Thus homologous G protein alpha-subunits promote bidirectional regulation at the domain interface of the pseudosymmetrical adenylyl cyclase enzyme.

Actins↗
PubMed2002

Curcumin enhances cytotoxicity of chemotherapeutic agents in prostate cancer cells by inducing p21(WAF1/CIP1) and C/EBPbeta expressions and suppressing NF-kappaB activation.

BACKGROUND: The modulatory effects and molecular mechanisms of curcumin (CCM) on the cytotoxicity of chemotherapeutic agents to prostate cancer cells were explored. METHODS: The combined effects of CCM and chemotherapeutic agents were examined by three different administration schedules (one concurrent and two sequential treatments) in two androgen-independent prostate cancer (AIPC) cells (PC-3 and DU145). Alteration of cell cycle progression, protein levels, and transcriptional activation in PC-3 cells were assayed by flow cytometry, Western blotting, and gel shift assay, respectively. RESULTS: The combined effects of CCM --> chemotherapeutic agent schedule showed the greatest synergistic cytotoxicity when compared to the other two schedules in both cells. CCM induced a significant G1 arrest in PC-3, which may be mediated by the induction of p21(WAF1/CIP1) and C/EBPbeta. Moreover, CCM was able to inhibit both the constitutional and TNF-alpha-induced NF-kappaB activation in a time-dependent manner. CONCLUSIONS: The incorporation of CCM into cytotoxic therapies may be a promising strategy for the treatment of AIPC.

Antineoplastic Agents↗