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Biomedical subjects

W Qin

Publications and source records attributed to W Qin.

At least 73 records · Page 4Linked to original sources
PubMed1997

Molecular cloning and functional analysis of polyphosphoinositide-dependent phospholipase D, PLDbeta, from Arabidopsis.

A novel plant phospholipase D (PLD; EC 3.1.4.4) activity, which is dependent on phosphatidylinositol 4,5-bisphosphate (PIP2) and nanomolar concentrations of calcium, has been identified in Arabidopsis. This report describes the cloning, expression, and characterization of an Arabidopsis cDNA that encodes this PLD. We have designated names of PLDbeta for this PIP2-dependent PLD and PLDalpha for the previously characterized PIP2-independent PLD that requires millimolar Ca2+ for optimal activity. The PLDbeta cDNA contains an open reading frame of 2904 nucleotides coding for a 968-amino acid protein of 108,575 daltons. Expression of this PLDbeta cDNA clone in Escherichia coli results in the accumulation of a functional PLD having PLDbeta, but not PLDalpha, activity. The activity of the expressed PLDbeta is dependent on PIP2 and submicromolar amounts of Ca2+, inhibited by neomycin, and stimulated by a soluble factor from plant extracts. Sequence analysis reveals that PLDbeta is evolutionarily divergent from PLDalpha and that its N terminus contains a regulatory Ca2+-dependent phospholipid-binding (C2) domain that is found in a number of signal transducing and membrane trafficking proteins.

Amino Acid Sequence↗
PubMed1997

Control of pupal fat body disappearance in the female black blow fly, Phormia regina (Meigen) by the brain and the corpus allatum.

Neck-ligation, brain implantation, allatectomy, methoprene treatment, and ovariectomy indicated that the disappearance of pupal fat body cells in newly emerged adult female blow fly, Phormia regina, is controlled by the brain and the corpus allatum (CA). Absence of brain or CA greatly lowered the rate of fat body cell disappearance (i.e. death). Dependency on the CA decreased from 0 to 36h post-emregence, indicating that the CA was active during the earlier part of this timespan. Methoprene treatment enhanced pupal fat body cell disappearance in allatectomized females. Brain implantation restored the rate of pupal fat body cell disappearance in neck-ligated flies. Brains from day 1 sugar-fed flies proved to be more effective than those from day 2 sugar-fed flies, indicating that there may be a window after adult emergence that allows the brain to act directly or indirectly on the death of pupal fat body cells. Ovariectomy did not alter the rate of pupal fat body cell death in test animals. Dying pupal fat body cells were smaller in size, less dense (i.e. did not sink in saline like normal pupal fat body cells), and stickier (i.e. attached to other tissues tighter) than the healthy cells. A possible role played by ecdysteroids is also discussed.

Journal Article↗
PubMed1997

Chemiluminescence flow system for vanadium(v) with immobilized reagents.

A chemiluminescence (CL)-based system for vanadium(v) combined with flow-injection analysis is described. The analytical regents, luminol and hexacyanoferrate(II), were both immobilized on an anion-exchange resin column. When a volume of phosphoric acid was passed through the column, these two reagents were eluted from the resin and then mixed with a vanadium(v) stream under acidic conditions. By means of the fast oxidation reaction between vanadium(v) and hexacyanoferrate(II), vanadium(IV) and hexacyanoferrate (III) were generated, both of which catalyzed the oxidation of luminol by dissolved oxygen in aqueous alkaline solution to produce CL. The CL emission intensity was correlated with the standard vanadium (v) concentration in the range from 1.0 x 10(-2) to 10 micrograms cm-3, and the detection limit was 5.4 x 10(-3) micrograms cm-3 vanadium (v). Interfering metal ions co-existing in sample solutions could be effectively separated on-line by a cation-exchange column placed upstream. A complete analysis, including sampling and washing, could be performed in 1 min with a relative standard deviation of less than 5%. The system was stable for over 100 analyses and was applied successfully to the determination of vanadium in geochemical and human hair samples.

Flow Injection Analysis↗
PubMed1997

[Antibacterial activity in vitro and clinical use of sulperazon].

In order to approach antibacterial activity in vitro and the efficacy of Sulperazon (SPZ) (sulbactam/cefoperazone), the sensitivity tests of 1,372 strains from clinical isolated bacteria to 17 antibiotics including SPZ were determined. The Gram negative bacteria occupied 1,035 strains (75.4) and Gram positive 337 strains (24.6%). 50 episodes of infections of major respiratory system in 43 patients were treated by SPZ. 58% of bacterial infections occurred in hematologic malignant diseases and solid tumors patients. 24% of 50 episodes were in neutropenia status. The positive rate of bac-terial cluteres was 56% in the series. 1.0-2.0 g SPZ was administered twice a day for 5-18 days, 56% of them was more than seven days (28/50 episodes). The results of susceptibility tests showed that sensitive rates were most high and the nesistant rates of SPZ were lower than these of to common Gram negative and Gram positive bacteria in third-generation cephalosporins. The efficacy rate of SPZ in clinical use was 84% (42/50 episodes), bacterial clearance rate was 89% (25/28 episodes). Three cases (6%) had temporary elevation and other adverse reactions of SPZ were not seen.

Adolescent↗
PubMed1997

[Surgical correction of penile torsion].

To treat the physiological dysfunction and psychic disturbances of the patients with penile torsion, a variety of surgery were used to eliminate its abnormality. A modificed of Nesbit procedure was used to correct the major malformation, several parallel ellipsoid patches which axis forms an angle of 45-degree with that of the penis were removed from the tunica albuginea on the convex side of the corpora cavernosa. Besides, stitches were necessary to suture the tunica albuginea to the opposite pubis. It was suitable plicate the tunica albuginea on the convex side of the corpora cavernosa for mild case. The penises of the patients had a normal appearance at both flexible and errect conditions during a 3-month follow-up. Penile torsion could be corrected satisfactorily by shortening the convex side of the corpora cavernosa with excision of ellipsoids or plication of the tunica albuginea, which angulates 45-degree with the penile axis.

Adult↗
PubMed1997

[Chemical constituents of rhizoma Pinelliae pedatisecta].

Five compounds were isolated from the alkaloid extract of Rhizoma Pinelliae Pedatisecta and their structures were determined as pedatisectine F(I), hypoxanthine (II), erythritol (III), uridine (IV) and pedatisectine G (V), of which I and V are new compounds, while II, III and IV were found in this plant for the first time.

Alkaloids↗
PubMed1997

[Differential regulation of dopamine receptors on pre- and postsynaptic Na+, K(+)-ATPase in rat striatum].

The pre- and postsynaptic membranes isolated from rat striatum were used to investigate the regulation of dopamine receptors on striatal Na+, K(+)-ATPase in these membranes. The activity of Na+, K(+)-ATPase was determined by colorimetric method. Dopamine (DA) was found to inhibit the Na+, K(+)-ATPase activity on postsynaptic membranes in a concentration-dependent manner with a IC50 value of 4.6 mumol.L-1. This inhibitory effect was reversed by either selective D1 receptor antagonist SCH23390 or selective D2 receptor antagonist spipernone. The inhibitory effect similar to DA was produced by combination with selective D1 receptor agonist SKF38393 and selective D2 receptor agonist LY171555. In contrast, under the same experimental conditions, DA (10(-8)-10(-5) mol.L-1) was shown to activate the activity of Na+, K(+)-ATPase on presynaptic membranes in a concentration-dependent manner. Meanwhile, the stimulatory effect was reversed by spiperone alone rather than by SCH23390. These results show the differential regulation of presytnaptic and postsynaptic DA receptors on Na+, K(+)-ATPase in rat striatum.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1996

Functional organization of saposin C. Definition of the neurotrophic and acid beta-glucosidase activation regions.

Saposin C is an essential co-factor for the hydrolysis of glucosylceramide by acid beta-glucosidase in mammals. In addition, prosaposin promotes neurite outgrowth in vitro via sequences in saposin C. The regional organization of these neurotrophic and activation properties of saposin C was elucidated using recombinant or chemically synthesized saposin Cs from various regions of the molecule. Unreduced and reduced proteins were analyzed by electrospray-mass spectrometry to establish the complement of disulfide bonds in selected saposin Cs. Using saposin B as a unreactive backbone, chimeric saposins containing various length segments of saposin B and C localized the neurotrophic and acid beta-glucosidase activation properties to the carboxyl- and NH2-terminal 50% of saposin C, respectively. The peptide spanning residues 22-31 had neurotrophic effects. Molecular modeling and site-directed mutagenesis localized the activation properties of saposin C to the region spanning residues 47-62. Secondary structure was needed for retention of this property. Single substitutions of R and S at the conserved cysteines at 47 or 78 diminished but did not obliterate the activation properties. These results indicate the segregation of neurotrophic and activation properties of saposin C to two different faces of the molecule and suggest a topographic sequestration of the activation region of prosaposin for protection of the cell from adverse hydrolytic activity of acid beta-glucosidase.

Amino Acid Sequence↗
PubMed1996

Effects of M1 and M2 receptor agonists and blockers on dog respiration.

AIM: To study the effects of M1 and M2 receptor agonists and blockers on dog respiration. METHODS: Using thoracic respiratory transducer and RM-86 multipurpose polygraph to determine respiratory rate (RR), tidal volume (TV), and minute ventilation volume (MVV), and DH-100G blood gas analysis instrument to analyze pO2, pCO2 and pH. RESULTS: Pilocarpine (Pil, an M1-R subtype agonist) 0.5, 1, and 2 mg.kg-1 iv caused increases in RR, MVV, and pO2, and a decrease in pCO2. The excitatory effects of Pil were antagonized by pretreatment with pirenzepine (Pir, 3 mg.kg-1, iv) and scopolamine (Sco, 2 mg.kg-1, iv). The iv injections of a novel M2-R subtype agonist, 6 beta-acetoxy nortropane (6 beta-AN) 2, 5, and 20 micrograms.kg-1 caused decreases in RR, MVV, and pO2 and an increase of pCO2. The actions of 6 beta-AN were antagonized by iv pretreatment with AF-DX116 ¿11-2 [[2-[(diethylamino)methyl]-1-piperidinyl] acetyl]-5, 11-dihydro-6H[2,3-b][1,4]benzodiazepine-6-one, 0.5 mg.kg-1¿ and atropine (Atr, 2 mg.kg-1). Similar results were obtained when smaller doses of Pil (0.2, 0.4, and 0.8 mg.kg-1) and 6 beta-AN (0.25, 0.5, and 1 microgram.kg-1) were injected into the vertebral artery. Pir and Sco also antagonized the excitatory effects of Pil, and AF-DX116 and Atr antagonized the inhibitory effects of 6 beta-AN on respiration. CONCLUSION: Stimulating M1-R of the respiratory center caused excitation of the respiration while stimulating the M2-R subtype caused inhibition of the respiration.

Animals↗
PubMed1995

The role of histidines 26 and 33 in the structural stabilization of cytochrome c.

Comparative studies of the importance of the two histidines of rat cytochrome c that are not ligands of the heme iron, for the stability of the protein, were carried out by site-directed mutagenesis. Histidine 26 was substituted by valine and the resulting effects on the stability of the Met-80-sulfur to heme iron bond to changes in pH and temperature, and of the global stability of the protein to unfolding in urea solutions, were measured. It is suggested that the loss of the hydrogen bond between the His-26 imidazole and the backbone amide of Asn-31 caused the observed decreases in local stability; and that, in addition, the elimination of the hydrogen bond between this imidazole and the carbonyl of Pro-44 resulted in an increase of the mobility of the lower loop (residues 41-47) on the right side of the protein and of its distance from the middle loop (residues 26-31), probably leading to greater hydration of the interior right side of the molecule. These changes resulted in a decrease in the global stability of the protein. Further mutation of Asn-52 to Ile led to a total recovery of the wild-type stability of the sulfur-iron bond, and a partial restoration of the global stability of the protein. Substitution of Phe for His-33 did not alter the sulfur-iron bond but caused a pronounced increase in the global stability of the protein. It is suggested that this effect results from hydrophobic interaction of the Phe-33 side chain with the lower loop on the right side of the protein. Such an interaction also explains the observation that the same mutation reversed the loss of global stability caused by substitution of Val to His-26, but did not restore the strength of the sulfur-iron bond that this mutation had brought about.

Amino Acid Sequence↗
PubMed1995

Organization and fine structure of a pacemaker derived from fetal rat myocardium.

At an unknown point in mammalian development, cardiac precursor cells become committed to the cardiocyte phenotype. Certain of these are believed to specialize further into pacemaker cardiocytes. By culturing explanted embryonic ventricles into in vivo organ culture (Tucker DC, Snider C, Woods WT Jr: Pediatr Res 23:637-642, 1988), we observed pacemaker cells arising apparently from cardiocytes. We hypothesized that this event can be triggered by intercellular attachments, innervation, vascularization, or other factors. The present study was designed to test the hypothesis that primitive ventricular cells in the tubular heart can organize into an anatomically and electrophysiologically distinct pacemaker structure in the absence of innervation or vascularization from extrinsic sources. Developing ventricles of tubular hearts from 10-d-old rat embryos (n = 22) were excised and incubated in culture dishes. Within each explant, a group of cells organized into a uniform cluster (diameter, 150 +/- 50 microns) after 8 +/- 2 d in culture. These cells resembled immature conduction system cells and had electrophysiologic features similar to those of mature pacemaker cells. Single-cell action potentials and impulse conduction patterns proved that the pacemaker cluster was the dominant pacemaker for the entire explant. These results confirm that, in the absence of extrinsic nerves and blood vessels, culture of the tubular ventricle elicits formation of an organized pacemaker, resembling the mature cardiac pacemaker and suggesting that contact with the culture dish surface or some other factor triggers conversion of cardiocytes to the pacemaker phenotype.

Action Potentials↗
PubMed1995

[Inhibitory effect and mechanism of scopolamine on respiration].

In conscious rabbits, dogs and anaesthetized dogs, the respiratory frequency (FR), tidal volume (Vt) and minute ventilation (Vm) were determined in order to confirm whether the respiratory effect of scopolamine is stimulatory or inhibitory. Arterial blood samples were taken intermittently and analyzed for Po2, Pco2 and pH. When scopolamine was injected i.c.v., i.a. and i.v., the decrease of FR, Vt, Vm and Po2 and the increase of Pco2 were observed in two animals. When the drug was given in clinical doses used for treating respiratory failure, the effect was seen still observable. The results indicate that scopolamine inhibits respiration. Moreover, it was observed that excitatory effect of pilocarpine on respiration can be antagonized by scopolamine, but the inhibitory effect of 6 beta-acetoxy nortropane can not be antagonized, on the contrary, can be coordinated. The above results suggest that respiratory inhibition induced by scopolamine may be related to blocking M1-R of the respiratory center.

Animals↗
PubMed1994

Overexpression of protein kinase C-zeta stimulates leukemic cell differentiation.

A function for protein kinase C-zeta (PKC-zeta), a member of the phorbol ester nonresponsive atypical protein kinase C subfamily, in modulating differentiation was examined in the leukemic U937 cell. Transfected U937 cells stably overexpressing PKC-zeta displayed a longer doubling time, lower saturation density at confluency, and an increase in adherence to plastic as compared to control cells. PKC-zeta cells expressed a more differentiated phenotype as assessed by changes in morphology, surface antigen expression, and lysosomal enzyme activities and were distinct from parental U937 cells stimulated to differentiate by exposure to phorbol esters. In contrast to parental U937 cells, PKC-zeta cells constitutively expressed mRNA transcripts for c-jun and a low mobility AP-1 binding activity. Thus, PKC-zeta overexpression stimulates a type of phenotypic differentiation that differs significantly from maturation occurring upon activation of other PKC subfamilies induced by phorbol ester treatment. Increased expression of the c-jun protooncogene and an increase in AP-1 binding activity in PKC-zeta cells provides a potential mechanism for explaining the altered differentiation status of this cell.

Antigens, CD↗
PubMed1994

[Inhibitory effect of 6 beta-acetoxy nortropane on respiration].

6 beta-AN (6 beta-acetoxy nortropane), a novel selective M2-receptor agonist, caused decrease in FR, TV, MVV and pO2 and increase of pCO2 when intravenous injection of 10 micrograms.kg-1 in conscious rabbits or 2, 5, 20 micrograms.kg-1 in conscious dogs was given (P < 0.05 or 0.01). The inhibitory effect on MVV exhibited a dose-dependent relationship. Small doses of 6 beta-AN icv (0.5, 1, 2, 4 micrograms.kg-1 in the conscious rabbits) and iva (0.25, 0.5 and 1.0 micrograms.kg-1 in anesthetized dogs) decreased FR, TV, MVV and pO2 and increased pCO2 as well. These results were reversed after administration of AF-DX116 and enhanced after administration of pirenzepine. Thus, it appears that the inhibitory action of 6 beta-AN on respiration might be related to stimulation of the inhibitory M2 cholinergic receptor in respiratory center.

Animals↗
PubMed1994

Effects of chronic phorbol ester treatment on protein kinase C activity, content, and gene expression in the human monoblastoid U937 cell.

Immediate and sustained signal transduction is involved in mediating phorbol ester-induced changes in growth and differentiation. Activation of protein kinase C (PKC) is the initial step in phorbol ester-induced signal transduction. By virtue of preferential down-regulation of individual isoforms and generation of proteolytically derived kinase activities, the signal transduced by sustained activation of this pathway may differ substantially from that generated initially upon application of the phorbol ester. To examine the effect of chronic phorbol ester-induced activation of this pathway, the relationship between PKC activity/content and AP-1 binding activity and gene expression was studied in the U937 cell. Phorbol ester-induced differentiation of the U937 cell into a monocyte/macrophage-like cell requires sustained activation of the PKC pathway. AP-1 binding activity was enhanced by 12-O-tetradecanoylphorbol-13-acetate (TPA) and in a temporally dependent manner, with conversion of a high to low mobility band shift occurring after a 12-h exposure to TPA. After a 72-h exposure, AP-1 binding activity was maximally increased by 1 nM TPA and remained elevated to a similar degree even after treatment with 600 nM TPA. Enhanced AP-1 binding activity was dependent upon continuous exposure to TPA and was not secondary to differentiation. A 72-h treatment with one nM TPA maximally increased expression of c-jun, krox-24, and jun-B mRNA transcripts. Exposure to higher TPA concentrations decreased the content of these transcripts. Maximal expression of collagenase and plasminogen activator receptor transcripts required exposure to much higher TPA concentrations (100 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1993

Reaction of aspirin with cysteinyl residues of lens gamma-crystallins: a mechanism for the proposed anti-cataract effect of aspirin.

Incubation of lens crystallins with aspirin inhibits the development of opacities caused by cyanate. Cyanate-induced opacities are thought to be due to carbamylation of the lysyl residues which causes a decrease in the protein charge and subsequent conformational changes that permit disulfide bonding. Because aspirin can also react with lysyl residues, it has been proposed that the aspirin inhibition of cataractogenesis is due to acetylation of the lysyl residues which would block their reaction with cyanate. However, acetylation of lysyl residues also lowers the protein charge and would be expected to effect changes in protein conformation similar to those caused by carbamylation. Therefore, acetylation of the lysyl residues is not a satisfactory explanation for the inhibitory effect of aspirin on lens opacification. Our investigations of the reactions of cyanate and aspirin with bovine gamma II-crystallins show that the cysteinyl residues are also carbamylated and acetylated at pH 7.4. At this pH, the carbamylation at the cysteinyl residues is reversible, leading to regeneration of the thiol group and disulfide bonding. In contrast, the acetylation at cysteinyl residues is stable at pH 7.4 and can prevent disulfide bonding. This difference in stability explains how cyanate promotes, and aspirin inhibits, cataractogenesis.

Acetylation↗
PubMed1993

The reaction of bovine lens alpha A-crystallin with aspirin.

Acetylation of the lysines of bovine lens alpha A-crystallin has been examined after 0-48-hr incubations of whole alpha-crystallins in 100 mM aspirin. The alpha A-crystallins were isolated after the incubation, proteolytically digested into peptides which were separated by reversed phase HPLC and analysed by mass spectrometry. For the reaction conditions used in this investigation, acetylated lysyl residues were the principal products. The extent of acetylation was quantified from the intensities of the peaks in the fast atom bombardment mass spectra of the modified and unmodified peptides. The modified lysine containing peptides demonstrated that all seven lysyl residues of alpha A-crystallin reacted with aspirin; the extent of acetylation at each lysyl residue varied. Plots of the extent of acetylation vs. time were used to calculate rate constants for the reaction at each lysyl residue. The rate constant for the acetylation of Lys 166, the most reactive, was about seven times greater than for Lys 88, the least reactive. These rate constants were used to calculate the yield of predicted products for the reaction of alpha-crystallin with therapeutic concentrations of aspirin. Comparison of the yield of acetylated alpha-crystallin with the yield of carbamylated alpha-crystallin that might occur due to renal failure indicates that aspirin is not likely to be an effective inhibitor of cataract due to carbamylation of lysyl residues.

Acetylation↗