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M Y Wang

Publications and source records attributed to M Y Wang.

At least 73 records · Page 4Linked to original sources
PubMed1996

Rapid and near-complete resolution of moyamoya vessels in a patient with moyamoya disease treated with superficial temporal artery-middle cerebral artery bypass.

Several groups have reported partial resolution of moyamoya vessels following surgical revascularization in pediatric patients, but angiographic documentation of near-complete resolution has been poor. We report here a case of a 5-year-old boy who underwent bilateral superficial temporal artery-middle cerebral artery bypass combined with unilateral encephaloduroarteriosynangiosis who demonstrated near-complete resolution of moyamoya vessels and a dramatic improvement in cerebral perfusion as measured by xenon-enhanced CT. The resolution of moyamoya networks may serve as an indicator of successful surgical revascularization.

Blood Flow Velocity↗
PubMed1995

Lipid hydroperoxide-induced endogenous DNA adducts in hamsters: possible mechanism of lipid hydroperoxide-mediated carcinogenesis.

DNA of livers or kidneys of rodents contain endogenously modified nucleotides of as yet unknown structure or function. As part of our examination of the origin of endogenous DNA modifications, we examined polar adducts of hamster liver and kidney DNA by 32P-postlabeling analysis (central and upper cuts) and compared them to adducts generated by incubation of DNA with [9Z,11E,(13S)]-13-hydroperoxyoctadecadienoic acid or with malondialdehyde. The central and upper cuts of DNA adduct maps of intact female retired breeder hamsters contained one and three adducts called C1, U1, U2, and U3, respectively, which cochromatographed with similar adducts in DNA incubated with the hydroperoxide or with malondialdehyde. Concentrations of adducts C1, U1, and U2 in organs of 1-month-old hamsters were lower than those in the 5-month-old female retired breeder hamsters. Adduct concentrations increased in tandem with lipid peroxide concentrations in livers and kidneys of hamsters treated with carbon tetrachloride compared to controls. A linear dependence of the concentrations of adducts on those of lipid peroxides was demonstrated independent of the treatment conditions or the organ examined. The polar endogenous adducts U1, U2, and U3 were identified by cochromatography in five different chromatographic systems with adducts induced by linoleic hydroperoxide or malondialdehyde. Adducts U1, U2, or U3 were also formed by incubating malondialdehyde with dAMP or with dGMP, respectively. The dependence of adduct concentrations in vivo on lipid peroxide levels are taken as evidence that decomposition products of lipid peroxides such as malondialdehyde induced endogenous DNA adducts in intact animals. Moreover, these adducts may mediate carcinogenic processes induced by chemicals which raise lipid peroxide levels.

Age Factors↗
PubMed1995

Induction by estrogens of lipid peroxidation and lipid peroxide-derived malonaldehyde-DNA adducts in male Syrian hamsters: role of lipid peroxidation in estrogen-induced kidney carcinogenesis.

Estrogen-induced kidney carcinogenesis in male Syrian hamsters has previously been postulated to be mediated by free radicals generated by redox cycling of catecholestrogen metabolites. As part of our examination of this hypothesis, we have studied the induction of lipid peroxidation and lipid peroxide-derived malondialdehyde (MDA)-DNA adducts in kidney and liver of hamsters treated with single injections of diethylstilbestrol (DES) or with estradiol (E2) implants for various lengths of time. Treatment of hamsters with 50 and 100 mg/kg DES increased concentrations of both lipid hydroperoxides and of MDA-DNA adducts. In hamsters treated with E2 implants for up to 50 days, lipid peroxide levels in liver were double control values 3 h after hormone implantation, and then decreased to plateau values of 30% over controls. Those in kidney rose to 2- to 3-fold above controls 3 days after hormone implantation and then decreased to plateau values of 51% above controls. MDA-DNA adduct levels were two or three times higher than those of controls in liver and kidney of hamsters treated with hormone implants for 3 and 7 days. Renal lipid peroxide concentrations were raised by chronic treatment with E2, but not by weakly carcinogenic estrogens ethinylestradiol or 2-fluoroestradiol. In contrast, MDA-DNA adduct levels were raised by all three steroidal estrogens 3 days after estrogen implantation. The increases in lipid peroxides and in MDA-DNA adducts in estrogen-treated hamsters support a mechanism of carcinogenesis by free radical generation via redox cycling of catcholestrogen metabolites. Lipid peroxides are postulated to play a dual role in estrogen-induced carcinogenesis, (i) as cofactors for cytochrome P450-mediated formation of catecholestrogen metabolites and their redox cycling, and (ii) as precursors of MDA, a DNA adduct-forming endogenous electrophile.

Animals↗
PubMed1995

Granulocyte colony-stimulating factor improves myelopoiesis and host defense in fulminant intra-abdominal sepsis in rats.

The therapeutic efficacy of granulocyte colony-stimulating factor (G-CSF) was studied in a model of fulminant sepsis in rats. Polymicrobial peritonitis was induced by a 4 mm cecal perforation and 10 micrograms/kg recombinant human G-CSF was given intravenously every 12 h, with the first dose at sepsis induction or 4 h post-induction. Rats were sacrificed at various intervals throughout sepsis to measure levels of neutrophil progenitors in the bone marrow and neutrophils and bacteria in blood and peritoneal fluid. Sepsis gave a sustained neutropenia and bacteremia, but did not affect numbers of blast- or GM-colonies, and only a delayed and moderate proliferation of G-clones was seen. Treatment with G-CSF at sepsis induction improved myelopoiesis by doubling the numbers of GM- and G-progenitors at 12 and 24 h post-induction. Concentrations of neutrophils increased twofold in blood and 5-fold in peritoneal fluid, while bacteria counts in the same compartments declined logarithmically. Mortality was 92% in untreated sepsis and declined to 46% when G-CSF therapy was started at sepsis induction, and to 42% following 4 h delayed therapy.

Acute Disease↗
PubMed1994

All-trans retinoic acid directly inhibits granulocyte colony-stimulating factor-induced proliferation of CD34+ human hematopoietic progenitor cells.

In this study we examine the effects of retinoids on purified CD34+ human hematopoietic progenitor cells. All-trans retinoic acid inhibited granulocyte colony-stimulating factor (G-CSF)-induced proliferation of CD34+ cells in short-term liquid cultures in a dose-dependent fashion with maximal inhibition of 72% at a concentration of retinoic acid of 1 mumol/L. Although no significant effects were observed on granulocyte-macrophage CSF (GM-CSF)--interleukin-3--or stem cell factor (SCF)-induced proliferation, the combinations of G-CSF and each of these cytokines were all inhibited. Moreover, retinol (3 mumol/L) and chylomicron remnant retinyl esters (0.1 mumol/L) in concentrations normally found in human plasma also had inhibitory effects. Single-cell experiments showed that the effects of retinoic acid were directly mediated. Retinoids also significantly inhibited G-CSF-induced colony formation in semisolid medium, with 88% inhibition observed at a concentration of retinoic acid of 1 mumol/L. However, we did not observe any effects of retinoic acid on G-CSF-induced differentiation as assessed by morphology and flowcytometry. Similar to previous findings using total bone marrow mononuclear cells, we observed a stimulation of GM-CSF-induced colony formation after 14 days. We also observed a stimulatory effect of low doses of retinoic acid (30 nmol/L) on blast-cell colony formation on stromal cell layers. Taken together, the data indicate that vitamin A present in human plasma has inhibitory as well as stimulatory effects on myelopoiesis.

Adult↗
PubMed1994

Identification of fatty acid hydroperoxide cofactors in the cytochrome P450-mediated oxidation of estrogens to quinone metabolites. Role and balance of lipid peroxides during estrogen-induced carcinogenesis.

Lipid hydroperoxide-supported metabolic redox cycling between diethylstilbestrol (DES) or catechol-estrogens and their corresponding quinones has been postulated previously to play a role in estrogen-induced toxicity and carcinogenesis. As part of an examination of this postulate, we investigated (a) the effectiveness of various lipid hydroperoxides as oxidants in microsome-mediated quinone formation, and (b) the dependence of DES oxidation to quinone on lipid hydroperoxide levels in liver and kidney of hamsters. Kinetic analyses of the lipid hydroperoxide-mediated conversion of DES to DES quinone revealed that of the peroxides tested (9Z,11E,13(S))-13-hydroperoxyoctadecadien-1-oic acid was the most powerful oxidant (Vmax = 10.5 nmol min-1; Km = 21.3 microM) followed by (5(S),6E,8Z,11Z,14Z)-5-hydroperoxyeicosatetra en-1-oic acid (Vmax = 1.0 nmol min-1; Km 10.0 microM). The other pure fatty acid hydroperoxide isomers or mixtures had a lower affinity for the enzyme (Km values ranging from 23.1 to 130 microM) and/or lower maximal velocity (Vmax values ranging from 0.2 to 7.0 nmol min-1). Levels of Z,Z-dienestrol, which arises from spontaneous rearrangement of DES quinone, were not affected in liver of hamsters treated with estradiol implants for 9 days and an injection of 20 mg/kg DES but increased in kidney by 120% over levels observed in animals without implants (5.5 and 12.1 nmol/g of wet tissue, respectively). Z,Z-Dienestrol concentrations correlated directly with lipid hydroperoxide concentrations in liver and kidney of control and estradiol-treated hamsters. The increased conversion of DES to quinone in kidney compared with that in liver was catalyzed by comparable activities of cytochrome P450 IA, the enzyme family catalyzing this oxidation. These results demonstrated that the oxidation of DES to quinone was directly dependent on the lipid hydroperoxide levels in the organ of metabolic conversion in addition to the enzyme activity catalyzing this reaction. The elevated lipid hydroperoxide levels in kidney of estrogen-treated hamsters indicate enhanced estrogen quinone formation and therefore enhanced generation of free radicals by metabolic redox cycling of estrogens in this organ prior to the appearance of malignancy.

Animals↗
PubMed1994

Developmental expression of poly(A) binding protein mRNAs during spermatogenesis in the mouse.

The poly(A) binding protein (PABP), a conserved protein that binds to the 3' poly(A) tail on mRNAs in eukaryotic cells, has been implicated in the regulation of mRNA stability and translation. Two PABP cDNAs with different sequences were isolated from mouse testis cDNA libraries. The predicted amino acid sequence of one, PABP1, is nearly identical (98.9%) to human liver PABP, while 80% of the amino acids of the second, PABPt, are identical to mouse and human PABPs. Northern blots reveal that there is one major PABP mRNA species in liver, muscle, kidney, and brain, two in spleen, and at least four in testis. The levels of PABP mRNA in testis are 5-10-fold higher than in these somatic tissues, but surprisingly the vast majority of all PABP mRNA size variants sediment more slowly than single ribosomes, indicating strong translational repression. Reverse transcriptase-polymerase chain reaction assays demonstrate that PABPt mRNAs are abundant only in testis. Northern blots of RNAs purified from highly enriched spermatogenic cells show that the high levels, multiple sizes of PABP mRNAs, and the PABPt mRNA are present in meiotic and early haploid spermatogenic cells, and are sharply reduced in late haploid cells. Comparison of the binding of PABP1 and PABPt to poly(A) Sepharose in vitro revealed subtle differences, even though PABPt contains substitutions for highly conserved aromatic amino acids that are thought to be necessary for binding to poly(A). The existence of two PABP isoforms in mouse spermatogenic cells could influence cytoplasmic gene expression during spermatogenesis.

Amino Acid Sequence↗
PubMed1994

Identification of chicken liver glucose transporter.

A cDNA, Ch-GT2, encoding a glucose transporter was cloned by screening a chicken liver lambda gt11 cDNA library and by modified polymerase chain reaction (PCR) techniques. The encoded protein is highly homologous to rat and human GLUT 2. Within the predicted amino acid sequence, there are 12 putative transmembrane helices with a relatively large exofacial hydrophilic loop between transmembrane segments 1 and 2, which is characteristic of mammalian GLUT 2. Expression of Ch-GT2 gene in E. coli results in sixfold increase in the uptake of 2-deoxy-D-glucose uptake, and this increment can be reduced by incubation with phloretin. Thus, Ch-GT2 is a bona fide chicken liver glucose transporter. A deletion mutant generated by PCR was expressed in bacteria and shown to be functional, indicating that the N-terminal seven amino acid residues of Ch-GT2 is not essential for transport of glucose. From Northern blot analysis, Ch-GT2 is prominently expressed in chicken liver with a transcript of 4.0 kb, but not in chicken brain and heart, suggesting that distinct types of glucose transporters are present in various chicken tissues.

Amino Acid Sequence↗
PubMed1994

Continuous insect cell (Sf-9) culture with aeration through sparging.

The continuous growth of Spodoptera frugiperda Sf-9 cells in a 250-ml blown-glass jacketed spinner flask under a direct air sparging environment was investigated. Even at 220 ml working volume (about 90% of total volume), this spinner flask provided good mixing and oxygenation as demonstrated by a higher cell density compared with fermentor cultures. This eliminates a common limitation of the traditional spinner flask, namely much lower cell density at high working volume. Furthermore, this spinner flask has been run with Sf-9 cell culture at five different dilution rates and two different air sparging rates at steady state, demonstrating its utility in research applications where cell size, metabolic activity and environmental conditions can be constantly maintained. In addition to demonstrating the utility of the reactor, three novel points are made in this report. First, cell density in continuous cultures is increased significantly due to a high agitation rate and, especially, air sparging rate, which is seldom used in animal cell or insect cell culture. Second, there is no apparent difference in the specific death rate at two different sparging rates (0.0093 vvm and 0.0125 vvm). Finally, we have maintained Sf-9 cells for more than 4 months in a continuous culture using a serum-free medium without loss of recombinant protein expression in infected cells.

Aerobiosis↗
PubMed1994

[Responses of motoneurons to ventrolateral funiculus stimulation in neonate rat spinal cord slices].

Intracellular recordings were made from 25 antidromically identified motoneurons (MNs) in the transverse thoracolumbar spinal cord slices (500 microns) of neonate rats (7-16 d). In more than 80% MNs, depolarization potentials (EPSP) with latency of 1.2 +/- 0.2 ms could be evoked by focal stimulation (0.1 ms, 1-20 V, 0.1 Hz) of ventrolateral funiculus. When recorded at resting potential of -70 +/- 6 mV, the time-to-peak, amplitude, half-decay time and duration of EPSPs to suprathreshold stimuli were respectively, 2.6 +/- 0.4 ms, 13 +/- 3 mV, 5.3 +/- 1.6 ms and 31 +/- 8 ms. The EPSPs were graded in consummate to stimulus intensity and upon reaching threshold depolarization, action potentials were initiated. Relatively constant latency of EPSPs was observed in spite of varying stimulus frequency from 0.1 to 5 Hz. Upon increasing stimulation frequency > 20 Hz, EPSPs began to decrease and finally disappeared. In 3 MNs tested, the mean reversal potential of EPSPs was -8 mV. Low Ca/high Mg solution consistently attenuated but Mg-free solution enhanced the EPSPs. EPSPs were reversibly depressed by kynurenic acid (0.5-1 mmol/L) and partially inhibited by ketamine (50-100 mumol/L). The findings of the present investigation suggest that MNs are excited by the descending fibers in ventrolateral funiculus possibly via excitatory amino acid transmitters.

Action Potentials↗
PubMed1994

[Facilitation of cholinergic transmission by huperzine A in toad paravertebral ganglia in vitro].

Using the intracellular recording techniques of toad paravertebral ganglia (PVG), the effects of cholinesterase inhibitor huperzine A (Hup-A), an alkaloid first isolated from Huperzia serrata (Thunb) Trev in China, on the synaptic transmission were studied. In 30 PVG cells tested, no remarkable changes in membrane potential and input resistance were observed during superfusion of Hup-A 0.3 or 1 mumol.L-1 for 15 min. The rate of orthodromic action potential evoked by preganglionic stimulation was increased by Hup-A 0.3 or 1 mumol.L-1 (n = 12, P < 0.05), and much faster, stronger, and longer in action at 50 or 100 mumol.L-1 (n = 11). The amplitude and duration of exogenous acetylcholine-, but not carbachol-, induced depolarization were increased (P < 0.05). It is concluded that Hup-A is a selective and potent cholinesterase inhibitor, by which action it facilitates the cholinergic transmission of PVG neurons.

Acetylcholine↗
PubMed1994

[Long-lasting afterhyperpolarization of sympathetic preganglionic neurons of neonate rat spinal cord slices].

Intracellular recordings of antidromically identified sympathetic preganglionic neurons (SPNs) were made in thoracolumbar spinal cord slices from neonate rats (7-16 days). In the SPNs population, a 7-20 mV long-lasting afterhyperpolarization (11-AHP) lasting for 1 to 10 s following spike potential could be recorded in part of the neurons and the 11-AHPs was usually preceded by a fast component lasting shorter than 400 ms. With decrease of membrane resistance during 11-AHP, membrane potential-dependent property was observed and the calculated reversal potential was -90 to -100 mV. The results indicate that the 11-AHPs are effective in the control of firing frequency of SPNs.

Action Potentials↗
PubMed1993

Impaired fibrinolysis in patients with Blackfoot disease.

Blackfoot disease is a unique endemic and chronic progressive arteriosclerotic vascular disease in southwest area of Taiwan. In this study, we determined the plasma levels of tissue plasminogen activator (tPA), plasminogen activator inhibitor (PAI), urokinase plasminogen activator (uPA), and von Willebrand factor (vWF) antigen in Blackfoot disease patients, in comparison with normal controls from non-endemic areas and the endemic area, Putai. Blackfoot disease patients had mean tPA antigen level of 7.9 ng/ml (n = 27) which was significantly lower (p < 0.05) than both the normal controls with 11.0 ng/ml (n = 20) and the Putai normal controls with 9.7 ng/ml (n = 39). However, the mean PAI-1 antigen level in the patient group was 41.2 ng/ml (n = 28) which was significantly higher (p = 0.0001) than both the normal controls with 19.7 ng/ml (n = 23) and the Putai normal controls with 21.3 ng/ml (n = 40). Furthermore, in the patient group, a significantly lower (p < 0.005) mean uPA antigen level (2.3 ng/ml, n = 18) was noted as compared with that in the normal controls (3.2 ng/ml, n = 14). No significant difference was observed in vWF antigen level between patients and normal controls. This study suggests that a reduced capacity for fibrinolysis is associated with Blackfoot disease.

Adult↗
PubMed1993

The effect of intravenous infusion of prostaglandin E1 on cutaneous microcirculation in black foot disease.

In order to evaluate the effect of an intravenous infusion of prostaglandin E1 (PGE1), 80 micrograms/day for two weeks, on microcirculatory vasculature in seven patients (M:F = 3:4, age 60-78) with black foot disease (a peripheral vascular disease of undefined etiology), we applied laser Doppler velocimetry to measure the maximal cutaneous microcirculatory flow (LDF) at a proximal site near gangrenous ulcers of the foot. Maximal flow was induced by local warming to 42 degrees C with a modified laser Doppler heating probe. Three phasic measurements were recorded, i.e., during pretreatment, treatment and follow-up with the separation interval being two weeks. The net maximal LDF (LDF at 42 degrees C minus LDF at room temperature) increased from 8.8 +/- 4.0 to 11.9 +/- 4.0 volt, p < 0.05. Cutaneous vascular conductance (CVC) was calculated as LDF/mean BP. Mean BP showed no significant change before or after treatment. Net CVC was changed from 7.5 +/- 3.1 to 11.9 +/- 4.0 volt/100 mmHg, p < 0.05. The LDF dropped significantly during the two-week period between treatment and follow-up in five subjects (10.8 +/- 3.4 vs 4.6 +/- 1.8, p < 0.05), while the follow-up LDF was close to the control data (4.6 +/- 1.8 vs 6.3 +/- 2.2, p = NS). Hence, we conclude that PGE1 may beneficially enhance microcirculatory blood flow in black foot disease through direct vasodilatory effects.

Aged↗
PubMed1993

Timed dose-response relationship of depressive action of ouabain on toad heart contraction in vitro.

Timed dose-response relationship (TDRR) of depressive action of ouabain (Oua) 0.01-30 mmol.L-1 on toad heart contraction in vitro was studied by simultaneous recordings of mechanical tension and electrocardiography. It was found that the inhibition of contraction tension, the latency, the half equilibrium time of depression, and the cardioplegia time (CPT) were all concentration-dependent (P < 0.01). The EC50 +/- L95 of Oua was 35 +/- 8 mumol.L-1, in which L95 is the average 95% confidence limit. The TDRR data of latency or CPT were fitted to the hyperbolic 4-parameter model II weighted with the square of SE inversely: Y = 25.9492(7.2757)/(1nX + 23.5906)(6.2757) + 72.7732 for latency and Y = 20637.37/(1nX + 3.0947)(3.5907) + 196.7069 for CPT. It was concluded that the hyperbolic type of TDRR was present in Oua depressive action on the toad heart contraction in vitro.

Animals↗