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Biomedical subjects

F Meng

Publications and source records attributed to F Meng.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Low-tensioned and "b"-like ileocystoplasty].

OBJECTIVE: To perfectly solve the urine-kept and urinary problems of the vesical cancer patients after vesicoectomy. METHODS: We performed low-tensioned and "b"-like ileocystoplasty in 16 patients. RESULTS: After the operation, new vesica urinaria worked well in keeping and emptying urine-urine through the urethra. Residual urine test, chemical test and urography showed that there were no disturbance of body water and electrolyte metetabolism, no reterograde urine in the ureter, no uracratia, and no damage to renal function. CONCLUSIONS: Ileocystoplasty can be used clinically.

Aged↗
PubMed1999

[Evaluation of immunochromatographic test in the diagnosis of Plasmodium falciparum and Plasmodium vivax].

AIM: To evaluate the effectiveness of immunochromatographic test(ICT) in detecting Plasmodium falciparum and Plasmodium vivax in malaria endemic areas. METHODS: ICT was used to detect P. falciparum and P. vivax among patients with fever in the outpatient clinics by comparason with thick blood smear method. RESULTS: The sensitivity of ICT to detect P. falciparum and P. vivax was 96.7% and 90.4%, respectively. The specificity of ICT was 98.6%, and the coincidence rate was 94.7%. There is no cross reaction between P. falciparum and P. vivax. CONCLUSION: ICT could detect P. falciparum and P. vivax simutaneously, being more rapid and simple than blood smear method.

Animals↗
PubMed1998

Affected enzyme activities in Alzheimer's disease are sensitive to antemortem hypoxia.

Many enzyme activities in Alzheimer's disease (AD) are changed. Some of these enzyme activities are related to certain neurotransmitter systems. Enzymes in the brain can also be sensitive to antemortem hypoxia. In the present study it was determined if enzyme activities that are altered in AD are also subject to alteration by antemortem hypoxia. As an indicator of antemortem hypoxia brain lactate concentration was used. Enzyme activities measured were those of prolyl endopeptidase (PE), aminopeptidase (AP), phosphatidylinositol (PI) kinase, phosphatidylinositol phosphate kinase, alpha-ketoglutarate dehydrogenase (alpha-KGDH), choline acetyltransferase and beta-glucuronidase. All of these enzyme activities have been measured in AD patients before and several of them have been found to be decreased. In accordance with previous findings, PE, alpha-KGDH and ChAT activities were reduced in AD patients. PI kinase and beta-glucuronidase activities, however, were not reduced, contrary to previous findings. All enzyme activities, except that of beta-glucuronidase, correlated with brain lactate concentration, suggesting that antemortem hypoxia has a major influence on the activity of enzymes in the brain. PE, AP, alpha-KGDH and ChAT activities were still different between AD and control samples when these were matched for lactate concentration. The enzyme activities that were changed in AD were also significantly correlated with lactate concentration, an indicator of antemortem hypoxia, in brain specimens. This suggests that antemortem hypoxia and AD have some factor in common that may be responsible for changes in enzyme activities. Since both PE and alpha-KGDH are known to be sensitive to oxidative stress this factor could be oxidative stress.

Adult↗
PubMed1998

A beta 1 integrin signaling pathway involving Src-family kinases, Cbl and PI-3 kinase is required for macrophage spreading and migration.

We have used mutant macrophages which are deficient in expression of Src-family kinases to define an integrin signaling pathway that is required for macrophage adhesion and migration. Following ligation of surface integrins by fibronectin, the p120(c-cbl) (Cbl) protein rapidly becomes tyrosine phosphorylated and associated with the Src-family kinases Fgr and Lyn. In hck-/-fgr-/-lyn-/- triple mutant cells, which are defective in spreading on fibronectin-coated surfaces in vitro and show impaired migration in vivo, Cbl tyrosine phosphorylation is blocked, Cbl protein levels are low, adhesion-dependent translocation of Cbl to the membrane is impaired and Cbl-associated, membrane-localized phosphatidylinositol 3 (PI-3)-kinase activity is dramatically reduced. In contrast, adhesion-dependent activation of total cellular PI-3 kinase activity is normal in mutant cells, demonstrating that it is the membrane-associated fraction of PI-3 kinase which is most critical in regulating actin cytoskeletal rearrangements that lead to cell spreading. Treatment of wild-type cells with the Src-family-specific inhibitor PP1, Cbl antisense oligonucleotides or pharmacological inhibitors of PI-3 kinase blocks cell spreading on fibronectin surfaces. These data provide a molecular description for the role of Src-family kinases Hck, Fgr and Lyn in beta 1-integrin signal transduction in macrophages.

Animals↗
PubMed1998

Controlling signaling with a specifically designed Gi-coupled receptor.

We are developing a system to control G protein signaling in vivo to regulate a broad range of physiologic responses. Our system utilizes G protein-coupled peptide receptors engineered to respond exclusively to synthetic small molecule ligands and not to their natural ligand(s). These engineered receptors are designated RASSLs (receptor activated solely by a synthetic ligand). We have made two prototype RASSLs that are based on the human kappa opioid receptor. Small molecule drugs that activate the kappa receptor are nonaddictive and safe to administer in vivo. Binding and signaling assays reveal 200-2000-fold reductions in the ability of our RASSLs to bind or be activated by dynorphin, an endogenous peptide ligand of the kappa opioid receptor. In a high-throughput signaling assay, these prototype RASSLs expressed in Chinese hamster ovary K1 cells showed little or no response to a panel of 21 opioid peptides but still signaled normally in response to small molecule drugs such as spiradoline. Activation of a RASSL by spiradoline also caused proliferation of rat-1a tissue culture cells. These data provide evidence that G protein-coupled receptors can be made into RASSLs. The potential in vivo applications for RASSLs include the positive enrichment of transfected cells and the development of new animal models of disease.

Adenylyl Cyclases↗
PubMed1998

A Comparative Study of Surface Fractality between Polymeric and Particulate Titania Aerogels

The surface fractality was studied for polymeric and particulate titania aerogels prepared via CO2 supercritical drying of titania lyogels. The surface fractal dimensions of these mesoporous aerogels were determined from their nitrogen adsorption isotherms by means of the Frenkel-Halsey-Hill method and the thermodynamic method. The results from these distinctly different methods have been found to be similar; the fractal surfaces of particulate aerogels are slightly more irregular than those of polymeric aerogels. The difference in the surface morphology between the two types of aerogels, observed with scanning electron microscopy, can be attributed to the difference between the proposed mechanisms for formation of polymeric and particulate lyogels. Copyright 1998 Academic Press. Copyright 1998Academic Press

Journal Article↗
PubMed1998

Acetylcholine-induced and nitric oxide-mediated vasodilation in burns.

Microvascular endothelial cells actively participate in local regulation of blood flow and blood-tissue exchange by producing various vasoactive substances including nitric oxide (NO). This study examined microcirculatory changes in the early stage of thermal injury and the NO-related mechanisms. Resistance arterioles of rat cremaster muscle were observed using intravital microscopy. Arteriolar diameter and flow velocity were measured and flow rate was calculated after administration of various vasoactive agonists in burns. In fluid-resuscitated rats with stable systemic blood pressure, microvascular caliber and blood flow were not significantly altered in the first hour following a 25% total body surface area full-thickness scald burn. Topical application of acetylcholine (ACh), an endothelium-dependent vasodilator, increased arteriolar diameter and flow rate in a dose-dependent fashion. The dose-responsive effects of ACh were significantly greater in burned rats than in sham-burned rats, and the augmentation was blocked by inhibition of NO production with NG-monomethyl-l-arginine (L-NMMA). Topical application of adenosine, an endothelium-independent vasodilator, and sodium nitroprusside, an exogenous NO donor, markedly increased arteriolar diameter and flow rate. The effects were not significantly different in burned and sham-burned animals, and the adenosine-induced vasodilation was not blocked by L-NMMA. These data suggest that endothelium-dependent and NO-mediated arteriolar dilation is enhanced in the early stage of thermal injury. This effect may play an important role in the pathophysiological events of microcirculation and blood-tissue exchange in burns.

Acetylcholine↗
PubMed1998

Clinical research on the therapeutic effect of the electro-acupuncture treatment in patients with depression.

Electroacupuncture (EA) stimulation has been found to influence the brain (norepinephrine metabolism in experimental animals). Preliminary clinical research has shown that EA treatment is as effective as amitriptyline for patients with depression. In this study, two consecutive clinical studies on the treatment of depression with EA are conducted. The first study was double blind placebo controlled, in which 29 depressed inpatients were recruited. Patients were randomly divided into three groups: EA + placebo; amitriptyline; and EA + amitriptyline. They received EA and/or amitriptyline treatment for 6 weeks. The Hamilton Rating Scale for Depression, Clinical Global Impression and ASBERG scales for the side effect of antidepressants were used to evaluate the therapeutic efficacy and side effects. Based on the results and research protocol of the first study, a multi-centered collaborative study was conducted, in which 241 inpatients with depression were recruited. Patients were randomly divided into two treatment groups: the EA + placebo and the amitriptyline groups. The results from both studies showed that the therapeutic efficacy of EA was equal to that of amitriptyline for depressive disorders (P > 0.05). Electro-acupuncture had a better therapeutic effect for anxiety somatization and cognitive process disturbance of depressed patients than amitriptyline (P < 0.05). Moreover, the side effects of EA were much less than that of amitriptyline (P < 0.001). The article suggested that EA treatment was an effective therapeutic method for depressive disorders. Particularly, it was a treatment of choice for depressed patients who were unable to comply with the classic tricyclic antidepressants because of their anticholinergic side effects. The possible mechanism of EA treatment is discussed.

Adult↗
PubMed1998

Creating a functional opioid alkaloid binding site in the orphanin FQ receptor through site-directed mutagenesis.

Although much has been learned about the mechanisms of ligand selectivity between different opioid receptor subtypes, little is known about the common opioid binding pocket shared by all opioid receptors. The recently discovered orphanin system offers a good opportunity to study the mechanisms involved in the binding of opioid versus nonopioid ligands. In the current study, we adopt a "gain of function" approach aimed at shifting the binding profile of the orphanin FQ receptor toward that of the opioid receptors. After two rounds of mutagenesis, several orphanin FQ receptor mutants can be labeled with the opiate alkaloid [3H]naltrindole and show greatly increased affinities toward the opiate antagonists naltrexone, nor-binaltrophine HCl, and (-)-bremazocine. These orphanin FQ receptor mutants also display stereospecificity similar to that of opioid receptors. Furthermore, the orphanin FQ receptor mutant that has the best affinities toward the opioid alkaloids shows, in the presence of GTP and high salt concentration, an affinity-shift profile similar to that of the delta receptor. Most strikingly, the same mutant exhibits naltrindole-sensitive etorphine-stimulated [35S]guanosine-5'-O-(3-thio)triphosphate binding, whereas the effect of etorphine on GTP binding cannot be inhibited by naltrindole in the wild-type receptor. Our results indicate that 1) several residues in the orphanin FQ receptor are critical to its selectivity against the opiate alkaloids, particularly antagonists; and 2) mutating these residues to those of the opioid receptor at the corresponding position preserves the agonist/antagonist nature of opiate alkaloids as they interact with the mutant receptor. It is reasonable to hypothesize that the corresponding residues in the opioid receptors may form a functional common binding pocket for opiate alkaloids. These findings may be helpful to medicinal chemists in designing ligands for the orphanin FQ receptor based on the structure of the opiate alkaloids.

Amino Acid Substitution↗
PubMed1998

Construction and application of MCBL plate for facilitation of chromosome recombination in fungi.

A medium with camphor and benomyl MCBL plate was designed and constructed based on the proposed mechanism that d-camphor could induce the fusion of nuclear membrane while benomyl could induce the nondisjunctional recombination of chromosome in fungi. This so-called co-induction plate consisted of 0.1% d-camphor (W/V) and 0.5 microgram/L benomyl contained in Czapek's minimal medium. The precautions to be taken in the construction procedure of this plate was described in detail. One typical example of intergeneric fusion-cross, Aspergillus niger x Trichoderma reesei, was investigated, comparing the ratios of genotypes and phenotypes of fusant progenies produced by the co-induction of MCBL plate and by the step-by-step induction with camphor and benomyl separately. The results showed that the heterodiploid state was extremely transient and the recombinant haploid was hardly obtained when induced by the routine step-by-step method, whereas the ratios of apparent diplodization and nondisjunctional recombinant haplodization among all types of varied segregates on MCBL plate were greatly improved, compared with those on the routine plates containing single reagents, which indicated that the transient heterodiploid could be grasped and transformed further into nondisjunctional recombinant haploid when co-induced on the MCBL plate. The age of regenerated mycelium to be induced was found to have a dominant influence on the co-induction effects of MCBL plate. The mechanism of co-induction by MCBL plate and its promising applications were discussed.

Aspergillus niger↗
PubMed1998

[Treatment of portal hypertension by using pericardial vascular disconnection and mesocaval side-to-side shunting].

OBJECTIVE: To prevent post-operative bleeding, to maintain the blood supply to the liver from the portal vein and to reduce the incidence of hepatic encephalopathy. METHOD: The blood vessel was cut around the cardial opening and the venae cavae was anastomosed in 37 patients with portal hypertension. RESULT: The success rate of surgery was 100%. The free portal pressure (FPP) was 3.16 +/- 0.581 kPa, which was lower than the FPP (3.91 +/- 0.642 kPa) before operation (P < 0.01). Follow-up for 5 to 22 months showed that liver function recovered from III to I in 5 patients, and from III to II in 7. Ascites disappeared in all and varix improved in 82.9% patients. CONCLUSION: Cutting flow combined with fraction flow can effectively maintain the blood supply to the liver in treating portal hypertension.

Adolescent↗
PubMed1998

[The intergeneric compatibility of heredity and expression for cellulase genomes between Aspergillus niger and Trichoderma reesei].

By using the developed display techniques of cellulase isozymes and the RAPD-PCR analysis guided by a deduced universal sequence of cellulase genes, the polymorphisms of genomic DNA fingerprints and cellulase isozymes were compared among three typical stable recombinants (3a, 3b, A7-1) and their two parents (Aspergillus niger AMS11, Trichoderma reesei QM9414) in order to provide the molecular evidence of gene recombination, to demonstrate the compatibility of heredity and expression of intergeneric genomes, and to assay on the molecular fundamentals of hybridization dominance. The results showed that in these recombinant strains the recombinantal fingerprints of genomic DNA could be stablly hereditary and the expression of recombinantal CMCase (carboxymethylcellulase) and beta GLase (beta-glucosidase) could be compatibly enhanced. The diversity of molecular fundamentals of cellulase hybridization dominance were (1) the compatible co-existence and enhanced expression of some hereditary beta GLase-coding genes from two parents in recombinant 3b; and (2) the compatibly enhancement of expression between the hereditary genes encoding beta GLase and CMCase from two parents, resulting in the dramatic increase of proteins of corresponding isozymes in recombinants 3a and A7-1. Based on these, a proposal model for the double synergism on cellulase activity in vitro and on its biosynthesis in vivo mediated by beta GLase was suggested. A practical method for assaying on the molecular fundamentals and the stability of hybridization dominance of recombinants was thereby established in this study.

Aspergillus niger↗
PubMed1998

[Part of biological activity of peptidoglycan from Streptococcus lactis SB900].

Peptidoglycan of Streptococcus lactis SB900(LABPG) was isolated. It's chemical composition was analyzed and part of biological activity was examined. The PG contained 9.84% protein, 0.871 mumol/m NAG, 1.14 mumol/mg NAM. The amino acids of relatively high concentrations were Ala, Glu, Asp and their concentrations were 1.046, 0.775, 0.304 mumol/mg respectively. Using mice as subject, the animal experiment confirmed that LABPG was non-toxic and safe. Effect of i.p. LABPG 0.5 mg/mouse on the phagocytic function were studied. It was suggested that the phagocytic activity of PM phi had markedly enhanced, the activity of serum lysozyme was increased significantly. YC-Rosette experiment suggested that the activity of C3b receptors of PM phi were increased and the YC-Rosette forming ratio were higher than controls. The difference was significant by statistical analysis. Therefore, it is considered that LABPG was able to activate M phi and improve immune function in mice.

Animals↗
PubMed1997

A critical role for Syk in signal transduction and phagocytosis mediated by Fcgamma receptors on macrophages.

Receptors on macrophages for the Fc region of IgG (FcgammaR) mediate a number of responses important for host immunity. Signaling events necessary for these responses are likely initiated by the activation of Src-family and Syk-family tyrosine kinases after FcgammaR cross-linking. Macrophages derived from Syk-deficient (Syk-) mice were defective in phagocytosis of particles bound by FcgammaRs, as well as in many FcgammaR-induced signaling events, including tyrosine phosphorylation of a number of cellular substrates and activation of MAP kinases. In contrast, Syk- macrophages exhibited normal responses to another potent macrophage stimulus, lipopolysaccharide. Phagocytosis of latex beads and Escherichia coli bacteria was also not affected. Syk- macrophages exhibited formation of polymerized actin structures opposing particles bound to the cells by FcgammaRs (actin cups), but failed to proceed to internalization. Interestingly, inhibitors of phosphatidylinositol 3-kinase also blocked FcgammaR-mediated phagocytosis at this stage. Thus, PI 3-kinase may participate in a Syk-dependent signaling pathway critical for FcgammaR-mediated phagocytosis. Macrophages derived from mice deficient for the three members of the Src-family of kinases expressed in these cells, Hck, Fgr, and Lyn, exhibited poor Syk activation upon FcgammaR engagement, accompanied by a delay in FcgammaR-mediated phagocytosis. These observations demonstrate that Syk is critical for FcgammaR-mediated phagocytosis, as well as for signal transduction in macrophages. Additionally, our findings provide evidence to support a model of sequential tyrosine kinase activation by FcgammaR's analogous to models of signaling by the B and T cell antigen receptors.

Androstadienes↗
PubMed1997

Lipopolysaccharide (LPS)-induced macrophage activation and signal transduction in the absence of Src-family kinases Hck, Fgr, and Lyn.

Lipopolysaccharide (LPS) stimulates immune responses by interacting with the membrane receptor CD14 to induce the generation of cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, and IL-6. The mechanism by which the LPS signal is transduced from the extracellular environment to the nuclear compartment is not well defined. Recently, an increasing amount of evidence suggests that protein tyrosine kinases especially the Src-family kinases Hck, Fgr, and Lyn, play important roles in LPS signaling. To directly address the physiological function of Hck, Fgr and Lyn in LPS signaling, a genetic approach has been used to generate null mutations of all three kinases in a single mouse strain. hck-/-fgr-/-lyn-/- mice are moderately healthy and fertile; macrophages cultured from these mice express normal levels of CD14 and no other Src-family kinases were detected. Although the total protein phosphotyrosine level is greatly reduced in macrophages derived from hck-/-fgr-/-lyn-/- mice, functional analyses indicate that both elicited peritoneal (PEMs) and bone marrow-derived macrophages (BMDMs) from triple mutant mice have no major defects in LPS-induced activation. Nitrite production and cytokine secretion (IL-1, IL-6, and TNF-alpha) are normal or even enhanced in hck-/-fgr-/-lyn-/- macrophages after LPS stimulation. The development of tumor cell cytotoxicity is normal in triple mutant BMDMs and only partially impaired in PEMs after LPS stimulation. Furthermore, the activation of the ERK1/2 and JNK kinases, as well as the transcription factor NF-kappaB, are the same in normal and mutant macrophages after LPS stimulation. The current study provides direct evidence that three Src-family kinases Hck, Fgr, and Lyn are not obligatory for LPS-initiated signal transduction.

Animals↗
PubMed1997

Cloning and characterization of cDNAs encoding the integrin alpha2 and alpha3 subunits from Xenopus laevis.

Integrins containing the alpha2 and alpha3 subunits associate with the beta1 subunit to form distinct receptors with partially overlapping adhesive specificities. We report the cloning and sequence of cDNAs that encode the Xenopus orthologues of integrins alpha2 and alpha3 and the expression of these subunits during embryogenesis. Integrin alpha2 and alpha3 mRNAs are first expressed in the dorsal mesoderm and developing notochord at gastrulation. We also show that alpha3 mRNAs are expressed in the entire marginal zone of gastrulae dorsalized with LiCl but that this localization is lost in embryos ventralized by ultraviolet light. Immunoblots reveal that the alpha3 protein is expressed throughout early development, however, the alpha2 protein is not detected until late tailbud stages. Injection of full-length alpha3 transcripts into the animal poles of fertilized eggs results in embryonic defects in paraxial mesoderm attributed to the failure of somites to form segments. Injection of the alpha3 transcripts into the vegetal pole and overexpression of a 5'-truncated alpha3 control construct have no apparent affect on development or somite formation. These data suggest that normal position-specific expression of integrins is important in maintaining the proper organization of tissues during early amphibian morphogenesis.

Amino Acid Sequence↗
PubMed1997

Characterization of the B lymphocyte populations in Lyn-deficient mice and the role of Lyn in signal initiation and down-regulation.

Lyn-deficient mice were generated to analyze the role of Lyn in B cell antigen receptor (BCR) signaling. These mice had a reduced number of peripheral B cells with a greater proportion of immature cells and a higher than normal turnover rate. Aged lyn-/- mice developed splenomegaly, produced autoantibodies, and had an expanded population of B lymphoblasts of the B1 lineage. Splenic B cells from young lyn-/- mice initiated early BCR signaling events, although in a delayed fashion. Unexpectedly, lyn-/- B cells exhibited an enhanced MAP kinase activation and an increased proliferative response to BCR engagement. Stimulation of lyn-/- B cells with intact and F(ab')2 anti-IgM revealed defects in at least two mechanisms that negatively regulate BCR signaling, one of which involves Fc gammaRIIb1.

Aging↗