Biomedical subjects

Q X Chen

Publications and source records attributed to Q X Chen.

At least 19 recordsLinked to original sources

PubMed2002

In vitro spontaneous parthenogenetic activation of golden hamster oocytes.

Parthenogenetic activation is a major hurdle to be cleared for the examination of the human sperm chromosome after intracytoplasmic injection (ICSI) into golden hamster oocytes. Various factors that affect spontaneous activation of hamster oocytes were, therefore, investigated in this study. We collected cumulus-oocyte complexes (COC) from the oviducts of superovulated females and washed them thoroughly with Ca2+-containing or Ca2+-free TALP-HEPES medium (handling media). We cultured oocytes with intact cumulus or those without cumulus (removed by previous hyaluronidase treatment) in Ca2+-containing or -free m-TALP-3 for 6 or 12 h before examining for their activation. Among the oocytes recovered 17 h post-hCG, 92-94% were parthenogenetically activated by 6 h of in vitro culture. Activation rate in the oocytes collected at 13.5 h post-hCG (53%) was significantly (P < 0.05) lower than that in the oocytes collected 17 h post-hCG (92%), indicating that the spontaneous activation rate increased as the oocytes became older. Both cumulus-intact and cumulus-free oocytes had similar (P > 0.05) activation rates when cultured in vitro, suggesting that hyaluronidase treatment had no effect on the rate of oocyte activation. Omission of Ca2+ from the handling medium also had no effect on the activation of the oocytes. The rate of spontaneous activation of the oocytes cultured in calcium-free medium for 6 (9%) and 12 h (16%) was significantly (P < 0.01) lower than that (94%) of the control oocytes cultured in Ca2+-containing medium, implying a positive influence of Ca2+ on in vitro activation of hamster oocytes. When we cultured the oocytes first in calcium-free medium for 6 h, and then in calcium-containing medium for 6 h, 94% were activated, which is comparable to the rate for oocytes continuously cultured in Ca2+-containing medium. This indicates that the inhibition of hamster oocyte activation in Ca2+-free medium is reversible and can be used to control spontaneous activation of golden hamster oocytes.

Animals↗

PubMed2001

Inhibition kinetics of green crab (Scylla serrata) alkaline phosphatase by zinc ions: a new type of complexing inhibition.

The Tsou method was used to study the kinetic course of inactivation of green crab alkaline phosphatase by zinc ions. The results show that the enzyme was inactivated by a complexing scheme which has not been previously identified. The enzyme first reversibly and quickly binds Zn(2+) and then undergoes a slow reversible course to inactivation and slow conformational change. The inactivation reaction is a single molecule reaction and the apparent inactivation rate constant is for a saturated reaction being independent of Zn(2+) concentration if the concentration is sufficiently high. The microscopic rate constants of inactivation and the association constant were determined from the measurements.

Alkaline Phosphatase↗

PubMed2001

Axillary osmidrosis treated by partial removal of the skin and subcutaneous tissue en bloc and apocrine gland subcision.

BACKGROUND: Axillary osmidrosis can be treated with many methods, but local surgery is the treatment of choice. METHODS: Forty-three patients (32 females and 11 males, average age 20.3 years) were treated by partial removal of the skin and subcutaneous tissue en bloc and follicular clipping of the adjacent area. All operations were performed with local anesthesia in an outpatient setting. RESULTS: Follow-up ranged from 2 to 47 months (mean: 13.4 months). Forty-one patients (95%) had good results, two (5%) were fair, and none were poor. No recurrences were seen. The wound complication rate was 3.5% for axillae and 7% for patients. There were no scar contractures or limitations of arm abduction. CONCLUSION: This combined surgical method can eliminate malodor and has a low wound complication and recurrence rate. Though the transient and conspicuous scar is the chief drawback of this method, it is a simple, safe, effective and inexpensive method for treating axillary osmidrosis.

Adolescent↗

PubMed2001

[Exogenous pGH gene localization on chromosomes of the transgenic pigs].

The pUC19-OMT plasmids were cut by Ssp 1 and the products in 900 bp were recovered from low-melting agarose gel and used as probes which were labeled by Digoxigenin. After being denatured, the probes were dropped on the chromosome samples which were also denatured to anneal with them. The anti-digoxigenin antibodies labeled with colloidal gold were used to act with the chromosome samples. In order to localize the exogenous pGH genes(porcine growth hormone gene) on chromosomes detected with optical microscope and improve the sensitivity, digoxigen gold signals are amplified by silver precipitation. After calculating the number of silver grains on every chromosome under the optical microscope, we analyzed the data with statistical methods. The results show that the integrating sites of exogenous pGH genes are very different among the positives. However, it is clear that the exogenous genes in one are always of the tendency to integrate in one specific site on a certain chromosome. These data are of great significance for studying the site-specific integration and the expression efficiency of exogenous genes in the future research.

Animals↗

PubMed2001

Kinetics of complexing activation by the magnesium ion on green crab (Scylla serrata) alkaline phosphatase.

As with mammalian enzymes, green crab (Scylla serrata) alkaline phosphatase can be activated by Mg2+ through a time-dependent course. The activation is mainly a Vmax effect. Tsou's method was used to study the kinetic course of activation. The results show that the enzyme was activated by a complexing scheme that had not been previously identified: the enzyme first reversibly and quickly binds Mg2+ and then undergoes a slow reversible course to activation, with a relatively high activation energy (78 +/- 4 kJ/mol) and a slow conformational change. The activation reaction is a single molecule reaction, and the apparent activation rate constant is independent of Mg2+ concentration if the concentration is sufficiently high. The microscopic rate constants of activation and the association constant were determined from the measurements. The proposed scheme may also be applied to the Mg2+ activation mechanism for mammalian enzyme, to explain why the activation rate is time-dependent and not diffusion controlled. Substrate binding was also shown to affect the activation rate constant.

Alkaline Phosphatase↗

PubMed2000

Kinetics of inhibition of beta-glucosidase from Ampullarium crossean by bromoacetic acid.

The kinetics of inhibition of beta-glucosidase from Ampullarium crossean by bromoacetic acid (BrAc) has been studied. The results show that the enzyme can be irreversibly and completely inactivated at high BrAc concentration, while at low BrAc concentration, inhibition of the enzyme is a slow, reversible reaction. The microscopic rate constants for the reactions of BrAc with the enzyme were determined. The presence of the substrate offers obvious protection of the enzyme against inhibition by BrAc. The above results suggest that the histidine residue is essential for activity and is situated at or near the active site of the enzyme.

Acetates↗

PubMed2000

Effect of metal ions on the activity of green crab (Scylla serrata) alkaline phosphatase.

Green crab (Scylla serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme, which catalyzes the nonspecific hydrolysis of phosphate monoesters. The present paper deals with the study of the effect of some kinds of metal ions on the enzyme. The positive monovalent alkali metal ions (Li(+), Na(+) and K(+)) have no effect on the enzyme; positive bivalent alkaline-earth metal ions (Mg(2+), Ca(2+) and Ba(2+)) and transition metal ions (Mn(2+), Co(2+), Ni(2+) and Cd(2+)) activate the enzyme; heavy metal ions (Hg(2+), Ag(+), Bi(2+), Cu(2+) and Zn(2+)) inhibit the enzyme. The activation of magnesium ion on the enzyme appears to be a partial noncompetitive type. The kinetic model has been set up and a new plot to determine the activation constant of Mg(2+) was put forward. From the plot, we can easily determine the activation constant (K(a)) value and the activation ratio of Mg(2+) on the enzyme. The inhibition effects of Cu(2+) and Hg(2+) on the enzyme are of noncompetitive type. The inhibition constants have been determined. The inhibition effect of Hg(2+) is stronger than that of Cu(2+).

Alkaline Phosphatase↗

PubMed2000

Inhibition kinetics of green crab (Scylla serrata) alkaline phosphatase activity by dithiothreitol or 2-mercaptoethanol.

Green crab (Scylla serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme which catalyzes the nonspecific hydrolysis of phosphate monoesters. Some pollutants in seawater affect the enzyme activity causing loss of the biological function of the enzyme, which affects the exuviating crab-shell and threatens the survival of the animal. The present paper studies the effects of thiohydroxyal compounds on the activity of green crab alkaline phosphatase. The results show that thiohydroxyal compounds can lead to reversible inhibition. The equilibrium constants have been determined for dithiothreitol (DTT) and mercaptoethanol (ME) binding with the enzyme and/or the enzyme-substrate complexes. The results show that both DTT and ME are non-competitive inhibitors. The kinetics of enzyme inactivation by ME at low concentrations has been studied using the kinetic method of the substrate reaction. The results suggest that at pH 10.0, the action of ME on green crab ALP is first quick equilibrium binding and then slow inactivation. The microscopic rate constants were determined for inactivation and reactivation. The rate constant of the forward inactivation (k(+0)) is much larger than that of the reverse reactivation (k(-0)). Therefore, when the ME concentration is sufficiently large, the enzyme is completely inactivated.

Alkaline Phosphatase↗

PubMed2000

Effects of oxodiperoxovanadate (V) complexes on the activity of green crab (Scylla serrata) alkaline phosphatase.

Green crab (Scylla serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme that catalyzes the nonspecific hydrolysis of phosphate monoesters. The effects of some pollutants in seawater on the activity of the enzyme will result in the loss of the biological function of the enzyme, which will affect the exuviating crab shell and threaten the survival of the animal. In the present paper, the effects of four oxodiperoxovanadate (V) complexes on the activity of green crab alkaline phosphatase have been studied. The results show that these vanadate derivatives can lead to reversible inactivation. The equilibrium constants for binding of inhibitors with the enzyme and/or the enzyme-substrate complexes have been determined. The results show that sodium (2,2;-bipyridine)oxodiperoxovanadate, pV(bipy), and potassium oxodiperoxo-(1,10-phenanthroline)vanadate, pV(phen), are competitive inhibitors, while potassium picolinato-oxodiperoxo-vanadate, pV(pic), and oxalato-oxodiperoxovanadate, pV(ox), are mixed-type inhibitors. These results suggest that pV(bipy) is a considerably more potent competitive inhibitor than pV(phen) and that the competitive inhibition effect of pV(pic) is stronger than that of pV(ox), but the non-competitive inhibition effect of pV(ox) is stronger than that of pV(pic).

2,2'-Dipyridyl↗

PubMed2000

Effect of methanol on the activity and conformation of acid phosphatase from the prawn Penaeus penicillatus.

Prawn (Penaeus penicillatus) acid phosphatase (EC 3.1.3.2) catalyzes the nonspecific hydrolysis of phosphate monoesters. The effects of some pollutants in sea water on the enzyme activity results in the loss of the biological function of the enzyme, which leads to disruption of phosphate metabolism in cells. This paper analyzes the effects of methanol on the activity and conformation of prawn acid phosphatase. The results show that low concentrations of methanol can lead to reversible inactivation. Inhibition of the enzyme by methanol is classified as non-competitive inhibition, and the inhibition constant (Ki) is 8.5%. Conformational changes of the enzyme molecule in methanol solutions of different concentrations were measured using fluorescence emission, differential UV-absorption, and circular dichroism spectra. Increased methanol concentrations caused the fluorescence emission intensity of the enzyme to increase. The ultraviolet difference spectra of the enzyme denatured with methanol had two negative peaks, at 222 and 270 nm, and a positive peak at 236 nm. The changes in the fluorescence and ultraviolet difference spectra reflected the changes of the microenvironments of tryptophan and tyrosine residues of the enzyme. The CD spectrum changes of the enzyme show that the secondary structure of the enzyme also changed some. These results suggest that methanol is a non-competitive inhibitor and the conformational integrity of the enzyme is essential for its activity.

Acid Phosphatase↗

PubMed2000

Kinetics of inhibition of green crab (Scylla serrata) alkaline phosphatase by vanadate.

Green crab (Scylla serrata) alkaline phosphatase is a metalloenzyme that catalyzes the nonspecific hydrolysis of phosphate monoesters. The kinetics of inhibition of the enzyme by vanadate has been studied. The time course of the hydrolysis of p-nitrophenyl phosphate catalyzed by the enzyme in the presence of different Na3VO4 concentrations showed that, at each Na3VO4 concentration, the rate decreased with increasing time until a straight line was approached, the slopes of the straight lines being the same for all concentrations. The results suggest that the inhibition of the enzyme by Na3VO4 is a slow, reversible reaction with fractional residual activity. The microscopic rate constants were determined for the reaction of the inhibitor with the enzyme. As compared with Na2HPO4 (Ki = 0.95 mM), Na2HAsO4 (Ki = 1.10 mM), and Na2WO4 (Ki = 1.55 mM), the results suggest that Na3VO4 (Ki = 0.135 mM) is a considerably more potent inhibitor than other inhibitors.

Alkaline Phosphatase↗

PubMed1999

Effect of ethanol on the activity and conformation of Penaeus penicillatus acid phosphatase.

The effect of ethanol on the activity of Penaeus penicillatus acid phosphatase has been studied. The results show that ethanol significantly inhibits enzyme activity as a non-competitive inhibitor, with Ki 8.75%. The conformational changes of the enzyme molecule induced by ethanol were followed using fluorescence emission, ultraviolet difference and circular dichroism (CD) spectra. Increasing the ethanol concentration caused the fluorescence emission intensity of the enzyme to increase. The ultraviolet difference spectra of the enzyme denatured with ethanol had two negative peaks at 220 and 278 nm, and a positive peak at 240 nm. Increasing the ethanol concentration produced a small shoulder peak at 287 nm in addition to the increases in the negative magnitudes of the 220 and 278 nm peaks. The changes of the fluorescence and ultraviolet difference spectra reflected the changes of the microenvironments of the tryptophan and tyrosine residues of the enzyme. The CD spectrum changes of the enzyme show that the secondary structure of the enzyme also changed. The results suggest that ethanol is a non-competitive inhibitor and the conformational integrity of the enzyme is essential for its activity.

Acid Phosphatase↗

PubMed1999

Kinetics of inhibition of green crab (Scylla serrata) alkaline phosphatase by L-cysteine.

The inhibition of alkaline phosphatase from green crab (Scylla serrata) by L-cysteine has been studied. The results show that L-cysteine gives a mixed-type inhibition. The progress-of-substrate-reaction method previously described by Tsou [(1988), Adv. Enzymol. Related Areas Mol. Biol. 61, 391-436] was used to study the inactivation kinetics of the enzyme by L-cysteine. The microscopic rate constants were determined for reaction of the inhibitor with the free enzyme and the enzyme-substrate complex (ES) The results show that inactivation of the enzyme by L-cysteine is a slow, reversible reaction. Comparison of the inactivation rate constants of free enzyme and ES suggests that the presence of the substrate offers marked protection of this enzyme against inactivation by L-cysteine.

Alkaline Phosphatase↗

PubMed1999

Kinetics of inhibition of green crab (Scylla serrata) alkaline phosphatase by sodium (2,2'-bipyridine) oxodiperoxovanadate.

Green crab (Scylla serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme, which catalyzes the nonspecific hydrolysis of phosphate monoesters. The kinetics of inhibition of the enzyme by sodium (2, 2'-bipyridine) oxodiperoxovanadate, pV(bipy), has been studied. The time course of the hydrolysis of p-nitrophenyl-phosphate catalyzed by the enzyme in the presence of different pV(bipy) concentrations showed that at each pV(bipy) concentration, the rate decreased with increasing time until a straight line was approached, the straight line slopes are the same for all concentrations. The results suggest that the inhibition of the enzyme by pV(bipy) is a slow, reversible reaction with fractional remaining activity. The microscopic rate constants are determined for the reaction of inhibitor with the enzyme.

2,2'-Dipyridyl↗

PubMed1999

Inhibitors of green crab (Scylla serrata) alkaline phosphatase.

Green crab (Scylla serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme which catalyzes the nonspecific hydrolysis of phosphate monoesters. The effects of several inhibitors on its activity have been studied. The results show that Na2HPO4, Na2HAsO4 and Na2WO4 are competitive inhibitors, L-phenylalanine is an uncompetitive inhibitor, while L-cysteine is a mixed-type inhibitor. The equilibrium constants were determined for inhibitor binding. The order of potency was Na2HPO4 (KI = 0.95 mM) > Na2AsO4 (1.10 mM) > Na2WO4 (1.55 mM).

Alkaline Phosphatase↗

PubMed1999

[A study of genetic character and foreign OMT/PGH gene integration in transgenic swine].

By using isotopic and non-isotopic in situ hybridization on chromosomes, the locus on chromosomes of foreign OMT/PGH gene was analyzed in eight transgenic pigs (G0, G1,G2 and G3). The research result is as follows: (1) The foreign genes could integrated on chromosomes of pig and the foreign integrated randomly; (2) the foreign genes integrated on chromosomes were transmissible through generations; (3) the locus on chromosomes of foreign gene was relatively stable in alternation of generations in transgenic swine.

Animals↗

PubMed1998

The effects of N-thiophosphoryl amino acids on the activity of green crab (Scylla Serrata) alkaline phosphatase.

Green crab (Scylla Serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme which catalyzed the nonspecific hydrolysis of phosphate monoesters. In the present paper, the effects of several N-thiophosphoryl amino acids on the activity of green crab alkaline phosphatase have been studied. The results show that these derivatives of amino acids can lead to reversible inactivation. The equilibrium constants for inhibitors binding with the enzyme and/or the enzyme-substrate complexes have been determined. The obtained results show that both N-thiophosphoryl-Cys and N-thiophosphoryl-Glu were non-competitive inhibitors, while other five N-thiophosphoryl amino acids were un-competitive inhibitors. For the un-competitive inhibitors, the inhibition strength follows the order N-thiophosphoryl-Ile > -Val > -Lys > -Ala > -Tyr. Compared with respective free amino acids, it can be seen that N-thiophosphorylation of the amino acids increased their inhibition strength except the N-thiophosphoryl-Cys.

Alkaline Phosphatase↗

PubMed1998

Kinetics of inhibition of Penaeus penicillatus acid phosphatase by bromoacetic acid.

The kinetics of inhibition of penaeus penicillatus acid phosphatase by bromoacetic acid has been studied. The results show that inhibition of the enzyme by bromoacetic acid is a slow, reversible reaction. The microscopic rate constants for the reaction of inhibitor with the enzyme were determined. The presence of the substrate offers marked protection of this enzyme against inhibition by bromoacetic acid. The above results suggest that the histidine residue is essential for activity and are situated at the active site of the enzyme.

Acetates↗