Biomedical subjects

M Xu

Publications and source records attributed to M Xu.

At least 163 records · Page 9Linked to original sources

PubMed2000

[Perioperative changes of plasma ET-1 in patients undergoing coronary artery bypass grafting and the effect of nitroglycerin].

OBJECTIVE: To observe the dynamic changes of the plasma ET-1 and the effect of low dose nitroglycerin in patients with coronary artery bypass surgery. METHODS: 40 patients with coronary artery bypass surgery were divided into group A and B. Group B received intravenous nitroglycerin 1 microg x kg(-1) x min(-1) perioperatively. We used RIA to assay the plasma ET-1 level. All the hemodynamic parameters were recorded by the Swan-Ganz catheter. RESULTS: The preoperative plasma ET-1 level in patients with coronary artery disease was significantly higher than the normal level. Five minutes after cardiopulmonary bypass in these patients the plasma ET-1 level was increased significantly until 6 to 8 hours after operation. The increased plasma ET-1 level in group B was less than in group A. There was a positive correlation between the plasma ET-1 level and the mean pulmonary pressure in group A 2 and 8 hours after operation. CONCLUSION: In patients undergoing coronary artery bypass surgery, the increased plasma ET-1 level may be partly due to the influence of cardiopulmonary bypass. Low dose of nitroglycerin is beneficial to these patients.

Coronary Artery Bypass↗

PubMed2000

[Anisodamine in prevention and treatment of sepsis of severely burned patients].

OBJECTIVE: To observe the preventive effect of anisodamine on possible sepsis of patients with major burns and the effect of anisodamine on patients with sepsis. METHODS: Forty-two patients with extensive burn admitted to our burn institute from April 1998 to November 1999 were divided randomly into two groups: treatment group (T group) and control group (C group). In the T group, all 20 patients received fluid resuscitation regimen with anisodamine, and in the C group, 22 patients received the regimen with no anisodamine. A tonometry catheter was positioned in the stomach, connecting with the automatic gas analysis machine (Datex-Engstrom Corporation, Dutch) for determining gastric intramucosal pH (pHi). The plasma concentrations of diamine oxidase (DAO) and endotoxin were measured. Correlation analysis between pHi, DAO and endotoxin were made respectively during early stage of postburn. All the parameters in 7 patients with sepsis before and after administration of anisodamine were compared with those in 6 patients with sepsis without use of anisodamine. RESULTS: The incidence of sepsis in the T group was lower (20.0%) than that in C group (40.9%). The gastric pHi value in the early period of postburn was significantly higher in the T group than in the C group (P < 0.05). Concurrently, the plasma concentrations of DAO and endotoxin were significantly lower in the T group than in the C group (P < 0.05 or 0.01). A significant negative correlation was seen between the gastric pHi and respective values of DAO, endotoxin (P < 0.05 or 0.01). There were a decrease in gastric pHi, and an increase in plasma DAO and endotoxin level in patients with septic episode; however all the parameters after administration of anisodamine were improved compared with those in septic patients without use of anisodamine. CONCLUSIONS: Intestinal ischemic injury plays an important role in provoking sepsis during early postburn period. Anisodamine is effective in restoring intestinal circulation both in the shock phase and after the development of sepsis.

Adolescent↗

PubMed2000

[Clinical use of acellular allogenic dermis or acellular porcine dermis with split-thickness autologous skin graft in 119 cases].

OBJECTIVE: To observe the effect of acellular allogenic dermis or acellular porcine dermis together with split-thickness autologous skin graft on coverage of deep burn wound and the wound of scar excision. METHODS: Acellular allogenic dermis or acellular porcine dermis produced by our unit, with split-thickness autologous skin graft, were used in repairing various wounds in 119 cases. The take rate of various wounds was compared, and the take rate of wounds in which autologous skin from different sites was used to cover either acellular allogenic dermis or acellular porcine dermis was also compared. Histological examination and follow-up were made in some cases. RESULTS: After tangential excision, eschar excision and scar excision, the wounds were covered with either allogenic acellular dermis or porcine acellular dermis and autologous split-thickness skin. The take rate was found to be (93.4 +/- 3.4)%, (92.1 +/- 4.6)%, (94.5 +/- 3.5)%, respectively. There was no a significant difference in take rate (P > 0.05). No significant difference in take rate between the transplantation of allogenic acellular dermis with autologous split-thickness skin and transplantation of porcine acellular dermis with autologous split-thickness skin was found (P > 0.05). When autologous split-thickness skin harvested from the trunk or extremities was used, the take rate was (93.1 +/- 4.8)%, (89.0 +/- 6.2)%, respectively, whereas the take rate was only about 70% - 80% when skin harvested from the scalp was used. The take rate was only about 40% when acellular allogenic dermis and autologous micro-skin graft were used to cover the wound. Histological examination 19 months after the transplantation revealed normal structure. Collagenous fibers were orderly arranged. There was no apparent hyperplasia of collagenous fibers. Hair follicles, sweat glands and other skin appendages were not found in the healed area. Grossly, no obvious pigmentation was seen, the surface was smooth with slight wound contraction, and the consistency was flexible. CONCLUSION: Acellular allogenic split-thickness dermis or acellular porcine split-thickness dermis with autologous split-thickness dermis for coverage of deep burn wound and the wound of scar excision is an ideal material.

Adolescent↗

PubMed2000

[Inhibition of monocytes adhesion to the intima of arterial wall by local expression of antisense monocyte chemotactic protein-1].

OBJECTIVE: To study the mechanism of monocyte recruitment in atherogenesis and to clarify the effect of monocyte chemotactic protein-1 (MCP-1) in this process. METHODS: Femoral arteries isolated from the rabbits which had been fed with a high cholesterol diet and locally perfused with MM-LDL within the artery beforehand, were used as the models. Antisense MCP-1cDNA was transferred into the arterial wall by injecting recombinant LNCX-anti-MCP-1/liposomal complex in the femoral sheath and the periarterial tissue. RESULTS: Expression of antisense MCP-1 mediated by recombinant LNCX plasmid/lipsomal complex gene transfer enabled to inhibit MCP-1 gene expression and adhesion of monocyte to the intima. CONCLUSION: MCP-1 plays an important role on the recruitment of monocytes in the arterial wall, which provides a potential clue in developing a gene therapy project for the prevention and treatment of atherogenesis.

Animals↗

PubMed2000

[Study on the modulation of the inflammatory response in mouse hepatic vasculitis with sodium selenite and vitamin E antioxidants].

OBJECTIVE: To identify the regulatory effect of sodium selenite and vitamin E on complement-neutrophil-reactive oxygen species (ROS)-activation feedback mechanism-mediated inflammatory response. METHODS: The modulation of inflammatory response through the complement-neutrophil-ROS-activation feedback cycle with sodium selenite and alpha-tocopherol was verified both in vitro tests by chemiluminescense technique and complement fixation to detect ROS production and complement activation as well as in vivo mouse hepatic vasculitis models to test for the regulation of the inflammatory response. RESULTS: Convincing results were observed as the incidence of hepatic vasculitis dropped from 100% in the control group down to 20% in the seleno-antioxidant vitamin E treated group, indicating down regulation of the inflammatory response. CONCLUSIONS: Elucidation of the mechanism of complement mediated inflammatory response is a promising area for new therapeutic developments in the modulation of inflammatory response. This study suggests that selenium, vitamin E and other antioxidants may be the useful therapeutic agents in those disorders in which upregulation of inflammatory response has been implicated, e.g. ischemia, reperfusion injury, severe sepsis, rheumatoid arthritis and hepatitis.

Animals↗

PubMed2000

[P15(INK4B) gene methylation in malignant hematopoietic diseases].

OBJECTIVE: To study the effect of operative region hypermethylation gene in human malignant hematopoietic tumors. METHODS: The abnormal methylation rate of P(15)(INK4B) gene 5'CpG island in 68 cases of malignant hematopoietic tumor samples were determined by methylation specific PCR using bisulfite modified DNA. RESULTS: The methylation rates of P(15)(INK4B) were 84%, 0, 50% and 75%, respectively, for 25 cases of acute myeloid leukemia (AML), 15 chronic myeloid leukemia (CML), 16 myelodysplastic syndrome (MDS) and 12 multiple myeloma (MM). P(15)(INK4B) gene was frequently methylated in patients with high risk MDS and early stage of MM. CONCLUSION: Hypermethylation of P(15)(INK4B) gene is one of the main causes of its inactivation. Hypermethylation of CpG island was closely related to the development of malignant hematopoietic diseases.

Acute Disease↗

PubMed2000

[A study on thermal decomposition mechanism and quality analysis of pearl powder].

OBJECTIVE: To establish a rapid and convenient method for distinguishing genuine from sham of pearl powder as well as appraising its quality preliminarily. METHOD: Thermogravimetry and differential thermogravimetry. RESULT: The TG and DTG curves can be divided into two characteristic regions. The first step ranges from 250 to 380 degrees C with a weight loss of about 3%, resulting from the denaturalization and decomposition of organic matter in the powder; and the second step from 600 to 780 degrees C with a weight loss of about 40% resulting from the decomposition of calcium carbonate in the powder. CONCLUSION: According to the two characteristic regions on TG and DTG curves along with corresponding parameters, pearl powder can be appropriately authenticated. Being related directly to the contents of organic matter in pearl powder, the first step is an important criterion for quality appraisal.

Animals↗

PubMed2000

[Determination of resibufogenin in xinli pills by RP-HPLC].

A method has been developed for the quantitative determination of Resibufogenin in Xinli pills by RP-HPLC. The stainless steel column(200 x 4.6 mm) was packed with ODS-3 (particle size 5 microns). The mobile phase was a mixture of methanol-water (60:40). The flow rate was 1 ml/min. The column temperature was 30 degrees C. The detection wavelength was 299 nm. The retention time for recibufogenin was 5.6 min. The average recovery for resibufogenin was 99.9%. The linear calibration curve for resibufogenin was obtained in the range 53.0-159.0 micrograms with the correlation coefficient 0.9998.

Amphibian Venoms↗

PubMed2000

[HPLC quantitative analysis of berberine absorpted with macroporous resin in Rhizoma Coptidis and its preparation zuo jin wan].

Absorptive ability and elution program of macroporous resin to the berberine in the Rhizoma Coptidis and its preparation Zuo Jin Wan (containing Rhizoma Coptidis and Fructus Evodiae) were explored. The extract of 70% MeOH of samples were disolved in water, then alkalized to pH 12 with ammonia solution. The berberine was absorpted by the macroporous resin, the washed off water soluble impurity with alkalescent water, and eluted with 50% MeOH containing 0.5% H2SO4. The results of quantitative analysis of the berberine by HPLC were satisfied.

Adsorption↗

PubMed1999

DNA fragmentation factor 45-deficient cells are more resistant to apoptosis and exhibit different dying morphology than wild-type control cells.

The DNA fragmentation factor 45 (DFF45) is a subunit of a heterodimeric DNase complex critical for the induction of DNA fragmentation in vitro. To understand the in vivo role of DFF45 in programmed cell death, we measured the expression of DFF45 during mouse development and compared DNA fragmentation and viability of DFF45-deficient cells with wild-type control cells after activation of apoptosis. We found that DFF45 is ubiquitously expressed throughout mouse development. Moreover, DFF45-deficient thymocytes are resistant to DNA fragmentation with in vivo dexamethasone treatment. Furthermore, primary thymocytes from DFF45 mutant mice are also more resistant to apoptosis than wild-type control cells on exposure to several apoptotic stimuli. Dying DFF45-deficient thymocytes exhibit different morphology than wild-type control cells in that they show reduced degree of chromatin condensation, absent nuclear fragmentation, intranuclear cytoplasmic invagination, and striking nuclear chromatin conglutination after release from disintegrating cells. These results indicate that DFF45 is essential during normal apoptosis.

Animals↗

PubMed1999

Steroid-induced conformational changes of rat glucocorticoid receptor cause altered trypsin cleavage of the putative helix 6 in the ligand binding domain.

Steroid-induced changes in receptor protein conformation constitute a logical means of translating the variations in steroid structures into the observed array of whole cell biological activities. One conformational change in the rat glucocorticoid receptor (GR) can be readily discerned by following the ability of trypsin digestion to afford a 16-kDa fragment. This fragment is seen after proteolysis of steroid-free receptors but disappears in digests of either glucocorticoid- or antiglucocorticoid-bound receptors. The location of this cleavage site has now been located unambiguously as R651, in helix 6 of the ligand binding domain, by a combination of point mutagenesis, arginine specific protease digestion, and radiochemical sequencing. This 16-kDa species, corresponding to amino acids 652-795, was non-covalently associated with another, approximately 17-kDa species that was determined to be amino acids 518-651 after a comparison of co-immunoprecipitated fragments from wild type and two chimeric receptors. These assignments revise our earlier report of amino acids 537-673 being the 16-kDa fragment and suggest that sequences of the entire ligand binding domain are required for high affinity and specificity binding. This was supported by the observation that trypsin digestion of the steroid-free R651A mutant GR gave rise to the 30-kDa meroreceptor (amino acids 518-795), which displayed wild type affinity. This 30-kDa species is thus the smallest non-associated fragment of GR possessing wild type steroid binding affinity. This suggests that other GR regions do not influence steroid binding affinity. The above results are reminiscent of those observed for the estrogen receptor. However, unlike the estrogen receptor or the more closely related progesterone receptor, the precise proteolytic cleavage points of both the steroid-free and -bound GR fall within regions that are predicted, on the basis of X-ray crystal structures of related receptors, to be alpha-helical and resistant to proteolysis. Thus, the tertiary structure of the GR ligand binding domain may be distinctly different from that of estrogen and progesterone receptors.

Amino Acid Substitution↗

PubMed1999

Chemoprevention studies of heterocyclic amine-induced colon carcinogenesis.

The cooking of meat and fish produces heterocyclic amine mutagens, including 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Chronic administration of PhIP or IQ to the F344 rat induces tumors at several sites, including adenocarcinomas of the colon, and short-term treatment leads to the formation of colonic aberrant crypt foci (ACF). We have used these end-points to identify potential chemopreventive agents that might be effective against heterocyclic amine colon carcinogens. Typically, IQ or PhIP were administered to groups of 10-15 rats by oral gavage on alternating days in weeks 3 and 4, and ACF were scored after 8, 12, or 16 weeks or tumors were detected at 52 weeks. To distinguish between 'blocking' and 'suppressing' agents, potential inhibitors were administered during the initiation or post-initiation phases, respectively, and subsequent studies focused on the inhibitory mechanisms. Among the most effective inhibitors identified to date, and their major mechanisms, were the following: chlorophyllin (molecular complex formation); indole-3-carbinol (inhibition and induction of cytochromes P450 and phase II enzymes); green and black tea catechins (induction of UDP-glucuronosyl transferase, inhibition of NADPH-cytochrome P450 reductase, scavenging of reactive intermediates); and conjugated linoleic acids (inhibition of cytochrome P450 and prostaglandin H synthase).

Animals↗

PubMed1999

Expression, DNA-binding specificity and transcriptional regulation of nuclear factor 1 family proteins from rat.

Nuclear factor 1 (NF1) family proteins, which are encoded by four different genes (NF1-A, NF1-B, NF1-C and NF1-X), bind to the palindromic sequence and regulate the expression of many viral and cellular genes. We have previously purified NF1-A and NF1-B from rat liver as factors that bind to the silencer in the glutathione transferase P gene, and have also reported the repression domain of NF1-A. In the present study we cloned five cDNA species (NF1-B1, NF1-B2, NF1-B3, NF1-C2 and NF1-X1) and compared their expression profiles and the affinity and specificity of the DNA binding of these NF1 family members. By Northern blot analysis, we found that the expression profiles of the NF1s are indistinguishable in the various tissues of the rat. The DNA-binding affinities of NF1-A and NF1-X are higher than those of NF1-B and NF1-C, whereas all four NF1 proteins showed the same DNA-binding specificity. Transfection analyses revealed that the function of NF1-B on the transcriptional regulation differed between NF1-B isoforms and was affected by the factor(s) that bind to the promoter regions. In addition, we identified the transcriptional regulatory domain of NF1-B, which is enriched with proline and serine residues.

Amino Acid Sequence↗

PubMed1999

Phe310 in transmembrane VI of the alpha1B-adrenergic receptor is a key switch residue involved in activation and catecholamine ring aromatic bonding.

Pharmacophore mapping of adrenergic receptors indicates that the phenyl ring of catecholamine agonists is involved in receptor binding and activation. Here we evaluated Phe310, Phe311, and Phe303 in transmembrane VI (TMVI), as well as Tyr348 in TMVII of the alpha1B-adrenergic receptor (alpha1B-AR), which have been implicated in a catechol-ring interaction. Neither catecholamine docking studies nor mutagenesis studies of Phe311, Phe303, or Tyr348 supported a role for these residues in catechol-ring binding. By contrast, docking studies indicated that the Phe310 side chain is well positioned to interact with the catechol-ring, and substituted cysteine accessibility method studies revealed that the side chain of the 310, but not 311 residue, is both solvent accessible and directed into the agonist-binding pocket. Also, saturation mutagenesis of both Phe310 and Phe311 revealed for the former, but not for the latter, a direct relationship between side chain volume and agonist affinity, and that aromaticity is essential for wild-type agonist binding, and for both wild-type agonist potency and efficacy. Moreover, studies of Phe310 mutants combined with a previously described constitutively active alpha1B-AR mutant, A293E, indicated that although not required for spontaneous receptor isomerization from the basal state, R, to a partially activated conformation R', interaction of Phe310 with catecholamine agonists is essential for isomerization from R' to the fully activated state, R.

2-Hydroxyphenethylamine↗

PubMed1999

Dopamine D3 receptor mutant and wild-type mice exhibit identical responses to putative D3 receptor-selective agonists and antagonists.

Previous studies using a variety of drugs with different affinities for the dopamine (DA) D3 receptor suggested that this receptor is involved in regulating motor activity and hypothermia. However, the in vivo selectivity of many of these compounds has been repeatedly questioned. To examine the precise roles of the DA D3 receptor in motor activity and hypothermic responses, we used mutant mice lacking the DA D3 receptor to evaluate the in vivo effects of several putative D3 receptor-selective agonists and antagonists. Using automated photocell activity chambers, we observed that the decreases in locomotor activity produced by putative D3 receptor-selective agonists as well as increases in locomotor activity produced by putative D3 receptor antagonists are identical in D3 receptor mutant and wild-type mice. In addition, the hypothermia produced by the putative D3 receptor-selective agonist PD 128907 is identical in both groups of mice. Based on these findings, we propose that D3 receptors are unlikely to be involved in these effects and we caution that the putative D3 ligands that have been used to reach conclusions regarding the functional roles of D3 receptors lack the necessary in vivo selectivity to support such conclusions.

Animals↗

PubMed1999

Endogenous noradrenergic tone controls symptoms of allodynia in the spinal nerve ligation model of neuropathic pain.

Endogenous inhibitory controls were studied in the spinal nerve ligation model of neuropathic pain. Atipamezole, a selective alpha2-adrenoceptor antagonist, produced both mechanical and cold allodynia in those rats which had not developed clear neuropathic symptoms. The same doses (50 microg i.t. or 1 mg/kg s.c.) did not increase the severity of symptoms in rats which had developed them. The opioid receptor antagonist naloxone (20 microg i.t. or 1 mg/kg s.c.) had no effect on the neuropathic symptoms. These results indicate that mechanical and cold allodynia are under endogenous noradrenergic rather than opioidergic control in this model of neuropathic pain.

Adrenergic alpha-Antagonists↗

PubMed1999

Sum rules and interlayer conductivity of high-Tc cuprates

Analysis of the interlayer infrared conductivity of cuprate high-transition temperature superconductors reveals an anomalously large energy scale extending up to midinfrared frequencies that can be attributed to formation of the superconducting condensate. This unusual effect is observed in a va- riety of materials, including Tl2Ba2CuO6+x, La2-xSrxCuO4, and YBa2Cu3O6.6, which show an incoherent interlayer response in the normal state. Midinfrared range condensation was examined in the context of sum rules that can be formulated for the complex conductivity. One possible interpretation of these experiments is in terms of a kinetic energy change associated with the superconducting transition.

Journal Article↗

PubMed1999

Paradoxical locomotor behavior of dopamine D1 receptor transgenic mice.

The behavioral effects of augmenting dopamine D1 receptor expression in the brain were investigated in mice incorporating additional copies of the mouse D1 receptor gene. Two transgenic lines showed increases in brain D1 receptor binding sites, which were greatest in extrastriatal regions. The full D1 agonist SKF 81297, when administered systemically to control animals, stimulated a dose-dependent increase in locomotor activity. In contrast, in D1 receptor overexpressing transgenic mice, this drug caused a marked suppression of locomotion due to a decrease in the frequency of movement initiation. Amphetamine and cocaine induced comparable locomotor activation in both transgenic animals and their control littermates. In the transgenic animals, D1 agonist-induced rearing and climbing behaviors were suppressed. However, on rotarod testing, the agonist-treated transgenic and control mice performed comparably, indicating that sensorimotor coordination was unaffected. These studies demonstrate that altering the levels of D1 receptor expression reverses the effects of D1 agonism on locomotor initiation and rearing.

Animals↗