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Biomedical subjects

X L Chen

Publications and source records attributed to X L Chen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Expression of matrix metalloproteinase-2, tissue inhibitors of metalloproteinase-1, -3 at the implantation site of rhesus monkey during the early stage of pregnancy.

We have examined the expression of MMP-2, TIMP-1, and TIMP-3 mRNA at the implantation site of rhesus monkeys during early stage of pregnancy using in situ hybridization and Northern blot analysis. The results indicate that MMP-2 mRNA was mainly localized in the chorinoic villi and epithelial plaque, suggesting that MMP-2 may be involved in the process of epithelial plaque and trophoblast invasion. TIMP-3 was specifically expressed in the cells around the spiral arteries and maternal-fetal interface. Therefore, TIMP-3 may be the main inhibitor that restricts the trophoblast invasion. The TIMP-1 mRNA was detected in trophoblast villi and maternal decidua; however, its distribution was not cell-specific, suggesting a general role in the protection of trophoblast villi and maternal decidua from proteolysis by the MMPs secreted by themselves.

Animals↗
PubMed2001

Signal transduction from bradykinin, angiotensin, adrenergic and muscarinic receptors to effector enzymes, including ADP-ribosyl cyclase.

Muscarinic acetylcholine receptors in NG108-15 neuroblastoma x glioma cells, and beta-adrenergic or angiotensin II receptors in cortical astrocytes and/or ventricular myocytes, utilize the direct signaling pathway to ADP-ribosyl cyclase within cell membranes to produce cyclic ADP-ribose (cADPR) from beta-NAD+. This signal cascade is analogous to the previously established transduction pathways from bradykinin receptors to phospholipase Cbeta and beta-adrenoceptors to adenylyl cyclase via G proteins. Upon receptor stimulation, the newly-formed cADPR may coordinately function to upregulate the release of Ca2+ from the type II ryanodine receptors as well as to facilitate Ca2+ influx through voltage-dependent Ca2+ channels. cADPR interacts with FK506, an immunosuppressant, at FKBP12.6, FK506-binding-protein, and calcineurin, or ryanodine receptors. cADPR also functions through activating calcineurin released from A-kinase anchoring protein (AKAP79). Thus, some G(q/11)-coupled receptors can control cADPR-dependent modulation in Ca2+ signaling.

ADP-ribosyl Cyclase↗
PubMed2001

[MK-801 attenuates NOS expression and NO content in the spinal cord of rats with inflammatory pain].

Using NADPH-d histochemistry, the effect of NMDA receptor antagonist MK-801 on the expression of nitric oxide synthase (NOS) in the dorsal horn of the spinal cord was investigated during inflammatory pain and hyperalgesia induced by injection of formalin into the right hind paw. The course of the change in the nitric oxide (NO) content of the lumbar intumescence was observed by measuring the ratio of nitrate/nitrite (NO3T/NO2T) and also the end product of NO. The results showed that the NOS expression and NO contents significantly increased 24 h after formalin injection, which were substantially inhibited when MK-801 was intrathecally injected 15 min prior to formalin injection or 12 h after formalin injection. The results suggest that the increases in the expression of NOS and NO contents in the dorsal horn of the spinal cord are mediated by activation of NMDA receptors during pain and hyperalgesia after formalin injection.

Animals↗
PubMed2001

Involvement of pressure-related mechanism in activation of inducible nitric oxide synthase.

The goal of this study was to clarify the relationship between blood pressure and inducible nitric oxide synthase (iNOS) activity. Different levels of blood pressure were obtained by long-term (six days) intravenous infusion of different concentrations (0.3%-8%) of NaCl solution to normal SD rats. iNOS activity assay and measurement of urinary nitrate/nitrite (UNOx), an index of NO production of the whole body, were carried out by isotope-labeled L-arginine conversion rate measurement and Greiss Reaction respectively. Groups of normotensive and hypertensive rats including normal Wistar rats, normal Sprague-Dawley (SD) rats, high NaCl-induced hypertensive rats (NaHR) and spontaneously hypertensive rats (SHR) were used to detect the changes in iNOS protein under normotension and hypertension by Western blotting. iNOS activity of aorta and kidney tissues and UNOx increased more significantly in hypertensive animals than in the normotensive control ones. Accordingly, iNOS protein in the aortas of NaHR and SHR increased by 149% and 261% respectively. It is suggested that in addition to cytokine and bacterial products etc, blood pressure is also an effective regulatory factor involved in iNOS activation and expression.

Animals↗
PubMed2001

Interactions of the antimalarial drug mefloquine with the human cardiac potassium channels KvLQT1/minK and HERG.

Mefloquine is a quinoline antimalarial drug that is structurally related to the antiarrhythmic agent quinidine. Mefloquine is widely used in both the treatment and prophylaxis of Plasmodium falciparum malaria. Mefloquine can prolong cardiac repolarization, especially when coadministered with halofantrine, an antagonist of the human ether-a-go-go-related gene (HERG) cardiac K+ channel. For these reasons we examined the effects of mefloquine on the slow delayed rectifier K+ channel (KvQT1/minK) and HERG, the K+ channels that underlie the slow (I(Ks)) and rapid (I(Kr)) components of repolarization in the human myocardium, respectively. Using patch-clamp electrophysiology we found that mefloquine inhibited KvLQT1/minK channel currents with an IC50 value of approximately 1 microM. Mefloquine slowed the activation rate of KvLQT1/minK and more block was evident at lower membrane potentials compared with higher ones. When channels were held in the closed state during drug application, block was immediate and complete with the first depolarizing step. HERG channel currents were about 6-fold less sensitive to block by mefloquine (IC50 = 5.6 microM). Block of HERG displayed a positive voltage dependence with maximal inhibition obtained at more depolarized potentials. In contrast to structurally related drugs such as quinidine, mefloquine is a more effective antagonist of KvLQT1/minK compared with HERG. Block of KvLQT1/minK by mefloquine may involve an interaction with the closed state of the channel. Inhibition by mefloquine of KvLQT1/minK in the human heart may in part explain the synergistic prolongation of QT interval observed when this drug is coadministered with the HERG antagonist halofantrine.

Animals↗
PubMed2001

Inhibitory effect of aminoguanidine on bleomycin-induced pulmonary toxicity in rat.

AIM: To observe the inhibitory effect of aminoguanidine (AG) on the pulmonary toxicity induced by bleomycin A5 (BLM-A5) in rat. METHODS: The contents of hydroxyproline, nitrite/nitrate (NO2-/NO3-), and malondialdehyde (MDA), which reflect fibrosis, nitric oxide (NO) production, and hyperoxidative injury of lung, were investigated by colorimetry. Histologic and morphometric examination of lung was also carried out on histological sections stained with hematoxylin and eosin (HE). RESULTS: (1) The content of hydroxyproline in lung and MDA in out-going pulmonary blood (OPB) increased from 14 d to 30 d after intratracheal administration of BLM-A5. Collapsed alveoli and fibrotic areas were seen and a lot of fibroblasts appeared in the lung interstitum of the rats 30 d after BLM-A5. (2) The NO2-/NO3- content increased in supernatant of alveolar macrophage culture and in OPB. (3) The increment of hydroxyproline in lung and MDA in OPB induced by BLM-A5 was alleviated by aminoguanidine (AG, 20 mg.kg-1 . d-1, ip). AG also reduced the histologic and morphometric changes in lung interstitum. (4) The augment of NO2-/NO3- in OPB was blocked by AG. CONCLUSION: AG had inhibitory effect on pulmonary injury and fibrosis induced by BLM-A5, and the inhibitory effect was related to the decrease of NO production in lung.

Animals↗
PubMed2001

[Increase in amount and affinity of adenosine receptor in rat hippocampal cellular membranes induced by cerebral ischemic preconditioning and its protective effects on the neurons].

To determine the role of adenosine (ADO) receptor in the induction of brain ischemic tolerance, changes in amount and affinity of ADO receptor in rat hippocampal cellular membranes after transient ischemia were investigated using radioligand binding method. Ischemia for 6 min resulted in an apparent delayed neuron death (DND) in the hippocampus, while ischemia for 3 min did not cause DND. Preconditioning ischemia for 3 min could apparently decrease DND caused by ischemia for 6 min after the preconditioning at an interval of 1 d reperfusion. In correspondence with the histological changes, ischemia for 3 min caused an increase in amount and affinity of ADO receptor at 1 or 3 days after reperfusion (P<0.05 vs sham), while ischemia for 6 min caused a decrease in the amount and an increase in the affinity (P<0.05 vs sham). Compared with the rats suffering from ischemia for 6 min followed by reperfusion for 4 h and 1 or 3 d, the amount and affinity of ADO receptor increased in rats with preconditioning ischemia (3 min) 1 d before the ischemia for 6 min. The above results showed that cerebral ischemic preconditioning increased the amount and affinity of ADO receptor in hippocampal cellular membranes, and resisted the down-regulating of ADO receptor caused by severe ischemia, suggesting an important role of the increase in amount and affinity of ADO receptor in the induction of brain ischemic tolerance.

Animals↗
PubMed2001

Promotion of pulmonary fibroblast proliferation and apoptosis by sodium nitroprusside.

The effects of nitric oxide (NO) donor sodium nitroprusside (SNP) on the proliferation and apoptosis and on Bcl-2, Bax and p53 proteins of pulmonary fibroblasts were investigated by using MTT cleavage assay, agarose gel electrophoresis and flow cytometric analysis. The results showed increases in the optical density (550 nm) of MTT cleavage assay, the number of cells and the proliferation index (PI), in comparison with the control. The number of apoptotic cells was also increased, though the percentage of apoptotic cells was too low to reveal oligonucleosomal fragmentation of characteristic ladder pattern, which is associated with apoptosis. In the meantime, the level of Bcl-2 decreased and that of Bax increased, while the p53 remained unchanged. These results suggest that exogenous NO has a dual effect on proliferation and apoptosis; and the action of NO on pulmonary fibroblasts is mainly proliferative. Down regulation of Bcl-2 and up regulation of Bax are implicated in the molecular mechanisms of this action.

Animals↗
PubMed2001

[Effect of rhubarb on intestinal immune associated secretion in healthy mice and in burn mice].

OBJECTIVE: To explore the therapeutic mechanism of rhubarb (sennosides) in protecting intestinal muco-membranous barrier by observing the change of intestinal immune associated secretion (IIAS) in mice before and after burn and the enhancing effect of rhubarb on it in healthy and in burn mice. METHODS: Bal b/c mice were divided into 4 groups. Group A (n = 8), untreated healthy mice; Group B (n = 11), healthy mice treated with 10% rhubarb decoction 12 ml/kg, once every 6 hrs; Group C (n = 7), the mice with 30% back full-thickness burn and no treatment was given; Group D (n = 9), the mice with 30% back full-thickness burn and treated with 10% rhubarb decoction 12 ml/kg, once every 6 hrs. The animals were killed 24 hrs after burn, the intestinal juice was collected after intestinal lavage, and centrifuged for determination of IgA, total protein, C3 and high density lipoprotein. RESULTS: IgA content in intestinal juice of Group A, B, C and D were 93.5 +/- 13.7 mg/L, 150.8 +/- 44.6 mg/L, 43.4 +/- 21.5 mg/L and 59.8 +/- 19.3 mg/L respectively, suggesting that it was significantly reduced by burn (P < 0.05), while rhubarb decoction could increase it in either healthy or burn mice (P < 0.05). The other immune associated substance, such as total protein, C3 and high density lipoprotein in intestinal juice were also increased significantly after rhubarb decoction treatment. CONCLUSION: Rhubarb could increase the reduced intestinal juice IgA content in mice caused by burn, it may be an important mechanism of rhubarb in protecting muco-membranous barrier.

Adjuvants, Immunologic↗
PubMed2000

NF- kappa B independent suppression of endothelial vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 gene expression by inhibition of flavin binding proteins and superoxide production.

Oxidation-reduction (redox) coupled mechanisms play an important role in the regulation of cell surface adhesion molecule expression. In endothelial cells membrane-bound NADH/NADPH oxidase is a significant source of intracellular superoxide (O(2)(-)) production. We explored the role of flavin containing proteins such as NADH/NADPH oxidase in the induction of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) gene expression in human aortic endothelial cells (HAECs) and human dermal microvascular endothelial cells (HMECs). Treatment of HAECs by tumor necrosis factor- alpha (TNF- alpha, 100 U/ml) for 1 h induced a 31% increase in O(2)(-)production within 5 min as determined by lucigenin chemiluminescence analysis of whole cells (n=4, P<0.05). Pretreatment with the NADH/NADPH oxidase inhibitor diphenylene iodonium (DPI, 40 microm) for 1 h inhibited O(2)(-)production. DPI also inhibited TNF and LPS-induced VCAM-1 and ICAM-1 cell surface expression and TNF- alpha, LPS, or IL-1 beta induced VCAM-1 and ICAM-1 mRNA accumulation. However, DPI did not inhibit TNF- alpha -induced activation of nuclear NF- kappa B-like binding activity in HAECs and HMECs. Furthermore, DPI did not inhibit TNF- alpha induced transactivation of NF- kappa B-driven VCAM-1 and HIV-LTR promoter gene constructs in transiently transfected HMECs. These data suggest that flavin binding proteins such as NADH/NADPH oxidase can regulate VCAM-1 gene expression independent of NF- kappa B. Furthermore, intracellular O(2)(-)generation is not necessary for NF- kappa B activation or for transactivation of NF- kappa B driven promoters.

Aorta↗
PubMed2000

A novel method for the determination of total protein in human serum by near infrared fluorescence recovery.

A novel fluorometric method has been developed for the determination of total protein in human serum with a new near-IR reagent as a fluorescence probe, based on the fluorescence recovery of the cyanine-CTAB system in the presence of protein. Maximum fluorescence is produced with maximum excitation and emission wave-lengths at 765 and 812 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0.4-12.0 microg/mL for protein. The detection limit is 70 ng/mL, and the relative standard deviation of six replicate measurements is 1.14% for 6.0 microg/mL protein. The results are satisfactory.

Animals↗
PubMed2000

Cationic cyanine as a near-infrared fluorescent probe for the determination of nucleic acids.

A new method with a cationic near-IR cyanine as fluorescent probe was developed for the determination of nucleic acids. The near-IR cyanine shows maximum excitation and emission wavelengths at 765 and 790 nm, respectively, in aqueous solution. The method is based on the fluorescence decrease of near-IR cyanine in the presence of nucleic acids. Under optimal conditions, the ratio of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of nucleic acids over the range 0.10-1.2 microg/mL for CT (calf thymus) DNA or SM (salmon sperm) DNA, and 0.10-1.6 microg/mL for yeast RNA. The detection limits were 30 ng/mL for CT DNA, 25 ng/mL for SM DNA and 70 ng/mL for yeast RNA. The relative standard deviation (n = 6) was 2.1% for 500 ng/mL CT DNA, 2.4% for 500 ng/mL SM DNA and 2.7% for 500 ng/mL yeast RNA, respectively.

Carbocyanines↗
PubMed2000

[RP-HPLC determination of MBAMT and its decomposition product].

This paper presents a method of reversed-phase high performance liquid chromatography to determine N,N-methylene-bi-(2-amino-5-mercapto-1,3,4-thiodiazole) (MBAMT) and its decomposition product 2-amino-5-mercapto-1,3,4-thiodiazole (AMT). Recoveries of MBAMT and AMT were 91% and 94% respectively. The detectable limits of them in water samples were 7.19 nmol/L for MBAMT and 2.87 nmol/L for AMT. The resolution between the peaks of MBAMT and AMT was 2.5. The column efficiency and the sensitivity of this method were significantly better in comparison with normal phase chromatography.

English Abstract↗
PubMed2000

[The clinical value of laryngeal image analysis with two methods].

OBJECTIVE: To analyze normal and pathological glottal image quantitatively with computed image technique, and try to calculate the absolute value of the laryngeal parameter. METHOD: The glottal image parameters of 60 normal adults, 60 cases of vocal polyps and 40 unilateral vocal fold paralysis(UVFP) patients were measured and analyzed, including the relative and absolute maximum or minimum glottal area, that is Amax(r), Amin(r), Amax(a) and Amin(a) respectively. RESULT: Amin(r) of females was larger than that of males; and both were larger than zero. He and she were equal in Amin(a) and Amax(r), while Amax(a) of males was larger than that of females. Compared with normal adults, Amin(r) of the patients with vocal polyp increased, and Amax(r) of UVFP patients diminished, while their Amin(r) increased. CONCLUSION: Laryngeal image could be analyzed quantitatively with computer assisted fibrolaryngoscopy. Normal adults have incomplete glottal closure to certain degree, and the level is different between sexes. The patients with vocal polyp and UVFP have relevant pathological glottal image.

Adult↗
PubMed1999

Angiotensin II induces vascular cell adhesion molecule-1 expression in rat vasculature: A potential link between the renin-angiotensin system and atherosclerosis.

BACKGROUND: Cardiovascular ischemic events may occur more frequently in hypertensive patients with activated renin-angiotensin systems. We tested the hypothesis that angiotensin II (Ang II) may contribute to atherosclerosis by increasing expression of vascular inflammatory genes such as vascular cell adhesion molecule-1 (VCAM-1). METHODS AND RESULTS: Rats infused with norepinephrine or Ang II for 6 days developed similar hypertensive responses, but only Ang II-treated rats exhibited significant increases in aortic VCAM-1 protein and mRNA expression. Oral losartan treatment (50 mg. kg(-1). d(-1)) inhibited Ang II-induced hypertension and aortic VCAM-1 mRNA expression. Ang II treatment significantly increased VCAM-1 mRNA expression in cultured rat aortic smooth muscle cells (RASMCs). Ang II also induced nuclear NF-kappaB-like binding activity and transactivated an NF-kappaB-driven VCAM-1 promoter. Losartan and proteasome inhibitors blocked Ang II-induced NF-kappaB activation and VCAM-1 mRNA accumulation. IkappaB-alpha overexpression in RASMCs inhibited Ang II-induced VCAM-1 promoter transactivation. CONCLUSIONS: Ang II may contribute to atherogenesis by activation of VCAM-1 through proteasome dependent, NF-kappaB-like transcriptional mechanisms.

Angiotensin II↗
PubMed1999

Analysis of a 762-bp proximal leptin promoter to drive and control regulation of transgene expression of growth hormone receptor in mice.

Transgenic (TG) mice expressing porcine GH receptor (pGHR) directed by a 762-bp proximal leptin promoter were used to analyze the capability of the promoter to drive and regulate pGHR expression in vivo. Transgene expression occurred in inguinal, retroperitoneal, and epididymal/parametrial fat depots in both male and female TG mice, but not in wild type (WT) mice. pGHR transgene was also expressed in liver, heart, kidney, muscle, lung, and brain. Levels of pGHR transgene mRNA were higher in tissues other than adipose tissue. Fasting reduced leptin mRNA levels in adipose; however, pGHR transgene expression was not affected in either adipose or muscle. These results suggest (1) the region between +3 and -759 bp of the leptin promoter is able to drive gene expression in vivo, (2) this region may not be responsible for adipose tissue specificity of leptin expression, and (3) this region may not be responsible for negative regulation of leptin gene expression during fasting.

Adipose Tissue↗
PubMed1999

Expression of leptin mRNA and CCAAT-enhancer binding proteins in response to insulin deprivation during preadipocyte differentiation in primary cultures of porcine stromal-vascular cells.

The aim of this study was to examine the correlation between CCAAT-enhancer binding proteins (C/EBPs) and leptin gene expression in response to insulin deprivation in preadipocytes and adipocytes. Adipose tissue from 7 d-old pigs was digested enzymatically and stromal-vascular (S-V) cells were seeded and plated for 3 d in fetal bovine serum (FBS) with dexamethasone (DEX) followed by 6 d (Days 3-9) in serum-free medium with insulin (850 nM or 10 nM), transferrin, and selenium. During FBS+DEX treatment (Days 0-3) a large number of preadipocytes develop with no lipid accretion. In contrast, preadipocyte number does not change with lipid accretion during insulin treatment (Days 3-9). Total RNA and cells were harvested from S-V cultures after periods with and without insulin after FBS+DEX. Northern-blotting and Western blot analysis were used to study leptin mRNA and C/EBP protein expression in cultures, respectively. Insulin deprivation from Days 3-4 reduced leptin mRNA and C/EBP-alpha protein expression. Treatment with 850 nM or 10 nM insulin from Days 3-9 induced leptin mRNA and C/EBP-alpha expression at a similar level. In cultures treated with 10 nM insulin from Days 3-7, leptin and C/EBP-alpha expression were reduced markedly by insulin deprivation from Days 7-9, but were restored by insulin treatment for 6 hr before harvesting. The restoration of leptin expression by insulin was blocked by cycloheximide treatment. However, C/EBP-beta protein levels did not change regardless of insulin deprivation. Insulin deprivation from Days 7-9 in cultures treatedwith 850 nM insulin from Days 3-7 did not influence C/EBP-alpha or leptin mRNA expression, whereas C/EBP-alpha and leptin expression were reduced after treating these cultures with 1.5 uM okadaic acid for 45 min before harvesting on Day 9. However, cycloheximide treatment for 6 hr before harvesting did not reduce leptin mRNA expression. These results suggest that 1) leptin expression is positively correlated with C/EBP-alpha expression, and 2) the maintenance of leptin expression after insulin deprivation in 850 nM insulin-treated cultures on Day 9 may be associated with the presence of C/EBP-alpha expression and/or activation.

Adipocytes↗