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Biomedical subjects

L X Wang

Publications and source records attributed to L X Wang.

At least 37 records · Page 2Linked to original sources
PubMed1996

A fluorometric assay of ceramide glycanase with 4-methylumbelliferyl beta-D-lactoside derivatives.

4-Methylumbelliferyl 6'-O-benzyl-beta-D-lactoside (6'Bn-MU-Lac) and some related compounds were synthesized via different selective reactions including phase-transfer glycosylation. Their suitability as substrates for a fluorometric assay of ceramide glycanase (CGase) was evaluated. Among others, the 6'Bn-MU-Lac, which is resistant to exogalactosidase, was found to be a suitable substrate for routine assay of the CGase activity. For American leech CGase, the K(m) value is 0.232 mM at pH 5.

Animals↗
PubMed1996

Bradykinin B2 receptors on skeletal muscle are coupled to inositol 1,4,5-trisphosphate formation.

To determine the presence of bradykinin receptors in skeletal muscle, we examined in both displacement and saturation studies the binding of [125I-Tyr8]bradykinin or [3H]bradykinin in three types of skeletal muscle preparations: membrane fractions from guinea pig hindlimb quadriceps, dog semimembranosus and semitendinosus muscles, and L8 rat skeletal muscle myoblasts. Scatchard analysis of [125I-Tyr8]bradykinin x bradykinin competition binding demonstrated specific bradykinin binding of 4.9 and 3.2 fmol/mg protein in dog and guinea pig skeletal muscle preparations, respectively. Unlabeled bradykinin specifically displaced [125I-Tyr8]bradykinin with IC50 values of 36.5 +/- 6 and 118.0 +/- 16.0 pmol/l from dog and guinea pig muscle membranes, respectively. The B2 bradykinin receptor antagonist HOE 140 and the B1 bradykinin receptor antagonist des-Arg9[Leu8]bradykinin displaced the binding of [3H]bradykinin from dog membranes with IC50 values of 0.38 and 217.3 nmol/l, respectively, suggesting that bradykinin binds to a B2-type receptor. In addition, unlabeled bradykinin competed with [3H]bradykinin for binding to dog skeletal muscle membrane preparations in a biphasic manner. To assess whether this represents multiple bradykinin receptor subtypes present in skeletal muscle homogenates or several affinity states of a single binding site, we examined bradykinin receptors on a pure skeletal muscle system, the L8 neonatal rat skeletal muscle myoblast cell line. These myoblasts also contain specific [3H]bradykinin-binding sites with a Bmax of 271 fmol/mg protein and a Kd of 0.83 nmol/l. Competitive agonist binding curves were biphasic (high-affinity IC50 = 3.9 pmol/l, low-affinity IC50 = 22.6 nmol/l) in the absence of guanosine 5'-O-(3-thio-trisphosphate) (GTP gamma S); they shifted to a model of one affinity (8.1 nmol/l) in the presence of GTP gamma S. Because the enzyme neutral endopeptidase 24.11 is an important kininase in skeletal muscle, we examined the effect of the neutral endopeptidase inhibitor phosphoramidon on the binding of bradykinin to dog skeletal muscle membranes. We found that phosphoramidon decreased the apparent Bmax from 7.3 to 5.8 fmol/mg protein. In addition, in this cell line we investigated the action of bradykinin on phosphoinositide hydrolysis. Inositol 1,4,5-trisphosphate (IP3) was measured with a radioreceptor assay. Bradykinin (0.1 nmol/l to 1 mumol/l) induced IP3 formation in a dose-dependent manner (EC50 = 1.42 nmol/l) from a basal level of 72.8 +/- 16 pmol/mg protein to 433 +/- 35.5 at the highest (1 mumol/l) concentration. We conclude that bradykinin B2 receptors are expressed in skeletal muscle. Phosphoinositide hydrolysis upon stimulation of this receptor is an indicator of intracellular signal transduction. Part of the bradykinin binding in skeletal muscle is due to interaction with the enzyme neutral endopeptidase.

Animals↗
PubMed1996

Kininase II-type enzymes. Their putative role in muscle energy metabolism.

Because of the importance of bradykinin in improving heart function in some conditions or in enhancing glucose uptake by skeletal muscle, we investigated kininases in these tissues. In P3 fraction of the heart and skeletal muscles, angiotensin I-converting enzyme (ACE) and neutral endopeptidase 24.11 (NEP) are the major kininases, as determined first with specific substrates and second with bradykinin. ACE activity was highest in guinea pig heart (2.7 +/- 0.07 mumol.h-1.mg protein-1) but decreased in other species in this order: dog atrium, rat heart, dog ventricle, and human atrium. The specific activity of NEP was lower: 0.45 mumol.h-1.mg protein-1 in cultured neonatal cardiac myocytes and varying between 0.12 and 0.05 mumol.h-1.mg protein-1 in human, dog, rat, and guinea pig heart. In the skeletal muscle P3, ACE was most active in guinea pig and rat (1.2 and 1.1 mumol.h-1.mg protein-1, respectively) but less so in dog (0.09 mumol.h-1.mg protein-1). NEP activity was higher in dog P3 (0.28 mumol.h-1.mg protein-1) but lower in rat and guinea pig (0.19 and 0.1 mumol.h-1.mg protein-1, respectively). Continuous density gradient centrifugation enriched NEP activity in dog and rat (from 0.3 to 1.0 and 0.49 mumol.h-1.mg protein-1, respectively). Immunoprecipitation with antiserum to purified NEP proved the specificity of the rat enzyme. Bradykinin (0.1 mmol/l) was inactivated in the presence and absence of inhibitors by rat skeletal muscle NEP, as measured by high-performance liquid chromatography. Here, 36% of the activity was caused by NEP and 19% by ACE. In radioimmunoassay (bradykinin 10 nmol/l), 46 and 55% of kininase in rat and dog skeletal muscle P3, respectively, was due to ACE; 36 and 28%, respectively, was due to NEP. Aside from these enzymes, an aminopeptidase in rat P3 also inactivates bradykinin. Thus, in conclusion, heart and skeletal muscle membranes contain kininase II-type enzymes, but their activity depends on the species.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Single-domain angiotensin I converting enzyme (kininase II): characterization and properties.

Somatic angiotensin I converting enzyme (ACE; kininase II) has two active sites, in two (N and C) domains. We studied the active centers with separate N-domain ACE (N-ACE), testicular C-domain ACE (germinal ACE) and, as control, renal somatic ACE. Germinal ACE cleaved the nonapeptide bradykinin about two times faster than N-ACE in 20 mM Cl-. Bradykinin1-7 was hydrolyzed further to bradykinin1-5 by N-ACE four times faster in the absence of Cl-, but at 300 mM Cl- the C-domain hydrolyzed it twice as fast. The hematopoietic system regulatory peptide acetyl-Ser-Asp-Lys-Pro was split to two dipeptides by N-ACE, depending on the chloride concentration, 8 to 24 times faster than by germinal ACE; at 100 mM Cl-, the Kcat with N-ACE was eight times higher. One millimolar 1-fluoro-2,4-dinitrobenzene inhibited germinal ACE 96% but it inhibited N-ACE by only 31%. [3H]Ramiprilat was displaced by other unlabeled ACE inhibitors to establish their relative affinities. Captopril had the lowest IC50 (0.5 nM) with N-ACE and the highest IC50 (8.3 nM) with the germinal ACE. The IC50 values of ramiprilat and quinaprilat were about the same with both active sites. The association and dissociation constants of [3H]ramiprilat indicated faster association with and faster dissociation from N-ACE than from germinal ACE. After exposure to alkali or moderate heat, somatic ACE was cleaved by plasmin and kallikrein, releasing N-ACE and apparently inactivating the C-domain. These studies affirm the differences in the activity, stability and inhibition of the two active sites of ACE.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

[(Sp)-8-chloroadenosine 3',5'-cyclophosphate induced differentiation on human leukemia HL-60 cells].

(Sp)-octyl 8-chloroadenosine 3',5'-cyclophosphate(OCC), a newly synthesized cAMP analog, strongly induced growth inhibition and differentiation in human leukemia HL-60 cells. The effects were dose- and time-dependent and irreversible. In flow cytometry, OCC brought about a block at the G1 phase of HL-60 cell cycle. Determined by incorporation assay, OCC was shown to strongly inhibit DNA synthesis without affecting the synthesis of RNA and protein in HL-60 cells. OCC activated the protein kinase A(PKA) in the cytosol of HL-60 cells and inhibited its binding to cAMP. The activities of PKA in the cytosol of HL-60 cells treated with OCC were more significantly increased than those in control cells. It can be concluded that OCC binds itself to PKA in competition with cAMP and, as a result, activates PKA.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Synthesis of 1D-(1,3,5/2,4)-4-acetamido-5-amino-1,2,3-cyclohexanetriol and its incorporation into a pseudo-disaccharide.

The synthesis of the title compound and 1D-(1,3,5/2,4)-4-acetamido-5-amino-3-O-(beta-D-glucopyranosyluronic acid)- 1,2,3-cyclohexanetriol [sequence: see text] is described. Starting from methyl 2-acetamido-2-deoxy-alpha-D-glucopyranoside 2L-(2,4,5/3)-4-acetamido-3-benzoyloxy-2-benzyloxy-5- hydroxycyclohexanone [sequence: see text] was prepared via a series of transformations including the regioselective ring opening of the benzylidene acetal and the mercury(II)-catalyzed carbocyclic ring closure reaction of 5-enopyranoside. Stereoselective reduction of ketone 11 with NaBH(OAc)3 gave 1D-(1,2,4/3,5)-2-acetamido-3-O-benzoyl-4-O-benzyl-1,3,4,5- cyclohexanetetrol [sequence: see text] (88%), which was then converted into 1D-(1,3,5/2,4)-4-acetamido-5-azido-3-O-benzoyl-2-O- benzyl-1-O-pivaloyl-1,2,3-cyclohexanetriol [sequence: see text] through selective 5-OH protection, 1-O-mesylation, and subsequent azide displacement. Saponification and hydrogenation of this gave the title compound. Selective O-debenzoylation with 1.1 equiv of K2CO3 in MeOH gave 1D-(1,3,5/2,4)-4-acetamido-5-azido-2-O-benzyl-1-O- pivaloyl-1,2,3-cyclohexanetriol [sequence: see text] (73%). Glycosylation of this compound with methyl (2,3,4-tri-O-acetyl-alpha-D-glucopyranosyl bromide) uronate in Ch2Cl2, using silver triflate as the promoter, afforded 1D-(1,3,5/2,4)-4-acetamido-5-azido-2-O-benzyl-3-O-(methyl 2,3,4-tri-O-acetyl-beta-D-glucopyranosyluronate)-1-O- pivaloyl-1,2,3-cyclohexanetriol [sequence: see text] and subsequent hydrogenation of this compound gave the basic pseudo-disaccharide.

Carbohydrate Sequence↗
PubMed1995

[A study on the implementation of primary chemotherapy to pulmonary tuberculosis with positive bacillus].

A cohort study on chemotherapy implementation program with regards to newly detected bacillus positive pulmonary tuberculosis patients in 132 medical units was carried out. Results showed that a) one year sputum negative conversion rate was 80%; b) only 48.1% of the patients had received the standardization six--month short--course chemotherapy regimens promoted by M. O. H; c) among 60% of the patients the duration of treatment had been too long; d) the two--year relapse rate of initial drug--resistant patients was 7.6%. The result suggested that the standardized chemotherapy program should be strenghened.

Antitubercular Agents↗
PubMed1995

[Study on geographic distribution of smear-positive pulmonary tuberculosis with trend-surface analysis].

The Trend-surface Analysis method was used to study the geographic distribution of smear-positive pulmonary tuberculosis prevalence in China. The prevalence data used in this article was cited from Nation-wide Tuberculosis Surveys in 1979 and 1990. The results showed that smear-positive pulmonary tuberculosis prevalence had obvious characteristics of geographic distribution and the characteristics had been changed within 11 years. In a word, the smear-positive pulmonary tuberculosis prevalence distribution tallies with their quality of tuberculosis control.

China↗
PubMed1995

The synthesis and biological activities of oligodeoxynucleotides that are covalently linked to psoralen at their 5' ends.

Four oligodeoxynucleotides (15-mers), designated 13 through 16, and the corresponding conjugates, designated 17 through 20, in which psoralen was covalently linked to the 5' end of each oligonucleotide were synthesized. Compounds 16 and 20 contained a sequence that was complementary to part of the first four codons and the upstream sequence close to the ribosome-binding site of c-Ha-ras mRNA. Compounds 16 and 20 inhibited the growth of cells that had been transformed by the c-Ha-ras plasmid, with accompanying suppression of the expression of the activated c-Ha-ras oncogene. The antisense oligonucleotides 16 and 20 also appeared to cause partial reversion of the major phenotypic characteristics of transformed cells, which included inhibition of anchorage-independent growth. Compound 20, which contained psoralen, was a more efficient inhibitor of the growth of transformed cells than compound 16 without psoralen, a result that suggests psoralen might have increased the ability of the oligodeoxynucleotides to enter the cells.

Amino Acid Sequence↗
PubMed1994

Autoimmune sera react with multiple epitopes on recombinant 52 and 60 kDa Ro(SSA) proteins.

OBJECTIVE: To determine the reactivity of recombinant 52 and 60 kDa Ro(SSA) (Ro) proteins with sera from 3 subsets of patients with Ro autoantibody associated disease. METHODS: Complementary DNA (cDNA) clones that encode the human 52 and 60 kDa Ro autoantigens were isolated by the polymerase chain reaction and utilized to express recombinant glutathione S-transferase (GST) fusion proteins. Double immunodiffusion (ID) defined Ro positive autoimmune sera from 12 patients with neonatal lupus erythematosus (NLE), 16 with subacute cutaneous lupus erythematosus (SCLE) and 12 with primary Sjögren's syndrome (SS) were tested by enzyme linked immunosorbent assay (ELISA) against the recombinant 52 and 60 kDa Ro fusion proteins. RESULTS: Seventy-five percent of NLE, 56% of SCLE and 83% of SS sera reacted with the 52 kDa fusion protein. Seventy-five percent of NLE, 63% of SCLE and 83% of SS sera reacted with the 60 kDa fusion protein. Seventeen percent of NLE sera, 25% of SCLE sera and 8% of SS sera were nonreactive to both full length fusion proteins. Eight (57%) of 14 ID defined Ro negative NLE, SCLE and SS sera were reactive with both Ro fusion proteins by ELISA: ELISA studies with recombinant 52 and 60 kDa Ro protein fragments revealed at least 2 major epitopes on each Ro protein. A fragment of the 52 kDa Ro protein that contains a putative leucine zipper motif reacted with 100% of ID defined Ro positive SS sera. CONCLUSION: Our data demonstrate that the ID assay and the recombinant Ro ELISA together are more sensitive in detecting Ro antibodies than either assay alone, and that multiple epitopes are present on both Ro proteins.

Autoantigens↗
PubMed1994

A report on selective radiofrequency ablation of dual atrioventricular node pathways in 34 cases.

Selective ablation of slow pathway by radiofrequency (RF) current in 34 patients with atrioventricular (AV) node pathways and tachycardia was performed with two methods in our section; posterior approach was used in the first 12 patients, the slow pathways were ablated successfully. Inferior approach was performed in the other 22 patients. Slow pathways were interrupted in 14 patients. Retrograde fast pathways and/or slow pathways were ablated in 6 patients. Retrograde fast pathways and slow pathways were abolished and antegrade fast pathways were injured transitorily in 2 cases. The total procedure time was shorter, RF applications were fewer by inferior approach than by posterior approach (P < 0.05). Both antegrade and retrograde conduction of fast pathways had not been affected after slow pathways were ablated (P > 0.05). After a mean of 8 months follow-up, two patients recurred and were ablated successfully again. We come to the conclusion that inferior approach might be a preferable method compared with posterior approach; the slow pathways is the compact node and its posterior input of transitional cells; the retrograde fast pathway may be the anterior superficial group of transitional cells and is not always in the same location of antegrade fast pathway.

Adult↗
PubMed1994

[Effect of recombinant human growth factors: recombinant human interleukin-6, recombinant human granulocyte-macrophage colony-stimulating-factor and recombinant human erythropoietin on normal human hematopoietic progenitor cells].

The effect of recombinant human growth factors: rhIL-6, rhGM-CSF and rhEPO on normal human hematopoietic progenitor cells was studied by using liquid and semisolid culture systems. The results showed that the expanding folds of progenitor cells after culturing with the three growth factors were 4.3 +/- 0.6, 9.4 +/- 0.9 and 13.7 +/- 1.0 respectively, being markedly higher than those of control (2.4 +/- 0.7, P < 0.01. In the presence of IL-6 alone, no CFU-E colony was observed and only CFU-GM colonies were formed in the semisolid culture. When IL-6 was added with EPO, the number of CFU-E colonies was significantly higher than that of EPO alone (P < 0.01). In the presence of IL-6 plus GM-CSF or IL-6 plus GM-CSF and EPO, CFU-Mix colonies were observed. Moreover, the total number of colonies was significantly higher than that of IL-6 or GM-CSF alone (P < 0.01). It is suggested that IL-6 is an important hematopoietic regulator. IL-6 may act on hematopoietic progenitor cells to enhance their proliferation. The target cells of IL-6 are the same as those of GM-CSF. IL-6 has synergistic action with EPO and GM-CSF, to enhance erythropoiesis with EPO and proliferation of multipotential progenitor cells with rhGM-CSF and EPO. However, the mechanism of the synergism between IL-6 and other growth factors is still unknown.

Adolescent↗
PubMed1994

Endocardial mapping and radiofrequency catheter ablation of multiple atrioventricular accessory pathways.

UNLABELLED: Among 174 patients with Wolff-Parkinson-White syndrome, 13 (17.5%) had multiple atrioventricular (AV) accessory pathway. Twenty-one of the 29 pathways were identified by baseline electrophysiologic study and eight were found after the radiofrequency ablation of the initial ones. Bilateral ablation approach was tried in four patients and unilateral approach in nine. Twenty-seven of the pathways (93.1%) were eliminated permanently after a mean of 32 +/- 14 pulses of current delivery. There were no complications. The pulses was more and the procedure took more time (3.6 +/- 0.8 hr) in the group compared to those in single pathway ablation (14 +/- 11 and 2.1 +/- 0.8 hr respectively, P < 0.05). The success rate was identical in the two patient populations (93.1% vs 94.0%, P > 0.05). However, the recurrence in multiple pathway ablation (7.6%) was more than that in single pathway ablation (1.9%, P < 0.01). CONCLUSION: radiofrequency catheter ablation is a safe and effective modality for tachyarrhythmias mediated by multiple accessory pathways.

Adult↗
PubMed1993

Catheter radiofrequency ablation of slow pathway in patients with atrioventricular nodal re-entrant tachycardia.

Selective ablation of slow pathway by radiofrequency current in 12 patients with atrioventricular (AV) nodal dual pathway and tachycardia was performed in our section. A large-tip ablation catheter was positioned around the ostium of the coronary sinus. The slow pathways of all the 12 patients were abolished permanently. Both the antegrade and retrograde conduction of fast pathway was not affected. There was no recurrence after 178 days follow-up.

Adult↗
PubMed1993

Survey of 160 centenarians in Shanghai.

One hundred and sixty centenarians were discovered and followed up for 7 years (1982-88) in Shanghai. The proportion of centenarians in the population was non-significantly greater in the urban than in the rural area and centenarians were in general increasing in both areas over the years. The factors promoting longevity were good medical care and benevolent attention from family members. Autopsy was performed in eight centenarians revealing the main causes of death as pneumonia and cancer.

Activities of Daily Living↗