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Biomedical subjects

R Q Zhang

Publications and source records attributed to R Q Zhang.

At least 19 recordsLinked to original sources
PubMed2001

Presence of gonadotropin-releasing hormone (GnRH) and its mRNA in rat pancreas.

Gonadotropin-releasing hormone (GnRH) has been reported to exist in many non-hypothalamic tissues, such as the placenta, gonads, and mammary glands, while there still have been no reports concerning the existence and expression of GnRH in the mammalian digestive system. Immunocytochemistry and in situ hybridization results show that GnRH molecule and GnRH mRNA are both exclusively distributed in exocrine pancreas, and RT-PCR result further proves that GnRH transcription units do exist in the pancreas, which possess the same sequence as the hypothalamus GnRH mRNA. Quantitative analysis indicates that mRNA levels in rat pancreas remain at a low level (less than 10% of that in hypothalamus) without sexual or developmental difference. This is the first report suggesting the existence and gene expression of GnRH in rat pancreas.

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

Two-phase unfolding pathway of ribonuclease A during denaturation induced by dithiothreitol.

The dynamics of the unfolding process of bovine pancreatic ribonuclease A (RNase A) unfolded by dithiothreitol (DTT) at a low concentration of 1:30 were investigated in alkaline phosphate-buffered saline solutions at 303K and 313K by using proton nuclear magnetic resonance ((1)H NMR) spectra. Three NMR spectral parameters including Shannon entropy, mutual information, and correlation coefficient were introduced into the analysis. The results show that the unfolding process of RNase A was slowed to the order of many hours, and the kinetics of the unfolding pathway described by the three parameters is best fit by a model of two consecutive first-order reactions. Temperature greatly influences the rate constants of the unfolding kinetics with different temperature effects observed for the fast and the slow processes. The consistencies and the differences between the three sets of parameters show that they reflect the same relative denaturation pathway but different spectra windows of the unfolding process of RNase A. The results suggest that the unfolding process of RNase A induced by low concentrations of DTT is a two-phase pathway containing fast and slow first-order reactions.

Animals↗
PubMed2001

Gene expression of gonadotropin-releasing hormone and its receptor in rat pancreatic cancer cell lines.

The regression of experimental and clinical pancreatic cancers by treatment with gonadotropin-releasing hormone (GnRH) agonists or antagonists has been repeatedly reported and is usually presumed to result from the creation of a sex steroid deficiency. There are, however, indications that GnRH analogs can also suppress the growth of the tumor cells in vitro and that specific binding sites for GnRH are present on membranes of these cells. The regulatory role of GnRH in rat pancreatic adenocarcinoma was investigated by examining the gene for GnRH and GnRH receptor (GnRH-R) in two pancreatic tumor cell lines (AR42J and ARIP). Reverse transcriptase polymerase chain reaction and Southern blot analysis indicated both GnRH-mRNA and GnRH-R-mRNA transcripts in the two cell lines. This is the first report raising the possibility of an autocrine/paracrine role for GnRH in rodent malignant pancreas.

Animals↗
PubMed2000

Dynamic accumulation and degradation of poly(3-hydroxyalkanoate)s in living cells of Azotobacter vinelandii UWD characterized by (13)C NMR.

The synthesis and degradation of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-hydroxyvalerate) (P(HB-co-HV)) by Azotobacter vinelandii UWD were investigated using natural abundance solution (13)C nuclear magnetic resonance (NMR) in vivo in shake flask culture and in fermenter culture. The synthesis and the degradation of poly(3-hydroxyalkanoate)s (PHA) monomers hydroxybutyrate (HB) and hydroxyvalerate (HV) had different rates. The amount of HB and HV increased dramatically in the initial degradation stage. The results suggest that the intracellular PHA of strain UWD was the subject of dynamic metabolic processing. (13)C NMR in vivo analysis provided a rapid, easy, accurate, non-destructive method to obtain valuable information on the metabolism of PHA.

Azotobacter vinelandii↗
PubMed2000

Molecular cloning and expression of a phospholipid hydroperoxide glutathione peroxidase homolog in Oryza sativa.

A cDNA encoding putative phospholipid hydroperoxide glutathione peroxidase (PHGPX) was isolated from rice using rapid amplification of cDNA ends. This cDNA, designated ricPHGPX, includes an open reading frame encoding a protein of 169 amino acids which shares about 60% and 50% amino acid sequence identity with plant and mammalian PHGPXs, respectively. The gene is expressed at a relative high level in flag leaves and the expression can be markedly induced by oxidative stress, suggesting that the product of the gene plays a key role in defense against oxidative damage in rice.

Amino Acid Sequence↗
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

Production of polyesters consisting of medium chain length 3-hydroxyalkanoic acids by Pseudomonas mendocina 0806 from various carbon sources.

Pseudomonas mendocina strain 0806 was isolated from oil-contaminated soil and found to produce polyesters consisting of medium chain length 3-hydroxyalkanoates (mclPHAs). The monomers of mclPHAs contained even numbers of carbon atoms, such as 3-hydroxyhexanoate (HHx or C6), 3-hydroxyoctanoate (HO or C8), and/or 3-hydroxydecanoate (HD or C10) as major components when grown on many carbon sources unrelated to their monomeric structures, such as glucose, citric acid, and carbon sources related to their monomeric structures, such as myristic acid, octanoate, or oleic acid. On the other hand, PHA containing both even and odd numbers of hydroxyalkanoates (HA) monomers was synthesized when the strain was grown on tridecanoic acid. The molar ratio of carbon to nitrogen (C/N) had a significant effect on PHA composition: the strain produced PHAs containing 97-99% of HD monomer when grown in a glucose ammonium sulfate medium of C/N<20, and 20% HO, and 80% of the HD monomer when growth was conducted in media containing C/N>40. It was demonstrated that the HO/HD ratio in the polymers remained constant in media with a constant C/N ratio, regardless of the glucose concentration. Up to 3.6 g/L cell dry weight containing 45% of PHAs was produced when the strain was grown for 48 h in a medium containing 20 g/L glucose with a C/N ratio of 40.

Glucose↗
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↗
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↗
PubMed1998

Studies on the localization of 5-hydroxytryptamine and its receptors in human placenta.

The localization of 5-hydroxytryptamine (5-HT) and its receptors in human placenta was studied under light and electron microscopy using immunohistochemistry and in situ hybridization. The syncytiotrophoblast, cytotrophoblast, stromal cells and decidual cells in human placentae all appeared to be 5-HT immunoreactive. The 5-HT immunoreactive material was distributed in cytoplasm with negative nuclei. The 5-HT immunoreactive material was also found in capillary endothelium. Trophoblast cells cultured in serum-free medium also showed 5-HT immunoreactivity in the cytoplasm. Fetal white blood cells and both syncytiotrophoblast and cytotrophoblast in human placenta showed 5-HT receptor immunoreactivity and 5-HT1A receptor mRNA hybridized signal was also detected in cytoplasm. The stromal cells and capillary endothelium in placental villi and maternal decidual cells all showed 5-HT receptor immunoreactivity in cytoplasm. The small flattened vesicles and large dense cored vesicles within trophoblast cells showed electron-dense 5-HT receptor immunoreactivity using immunoelectron microscopy. These results suggest that human placenta may not only produce 5-HT but also be a 5-HT target organ, and that 5-HT may not only play roles in placental development and pregnancy maintenance by paracrine and autocrine interactions but may also take part in regulating fetal development.

Adult↗
PubMed1994

Regulatory action of Astragalus saponins and buzhong yiqi compound on synthesis of nicotinic acetylcholine receptor antibody in vitro for myasthenia gravis.

With overall analysis of symptoms and signs of myasthenia gravis (MG) basing on "Pi (Spleen) Deficiency" [symbol: see text] theory and with years of our clinical experience in treating MG, we performed a pharmacological study of Astragalus saponins and Buzhong Yiqi Compound (Tonic granulae invigorating vital energy) in 14 peripheral blood mononuclear cell (PBMNC) cultures from 10 MG patients. PBMNG from two groups of patients given dexamethasone (Dxm) and cobalt 60 (60Co) treatment were used as controls. The results showed that water soluble Astragalus saponins significantly reduced the titer of nicotinic acetylcholine receptor antibodies (nAchR-Ab) in the cell culture supernatants, from 418.8-2328 to nil in 6 cases, and from 1143-1235 to 43-157 fmol/ml in 2 cases, and that Buzhong Yiqi compound also had inhibitory immunoregulatory action.

Adolescent↗
PubMed1989

In vivo measurement of total body magnesium and manganese in rats.

Mg and Mn are essential minerals in many biological processes. Thus knowledge of their absolute amounts and how those amounts may be altered is important. In the past the in vivo measurement of Mg in animals was limited by both the poor geometry of the counting system and the requirement for multiple counts of the animal over several hours. We have developed a neutron activation technique for the direct in vivo measurement of total body Mg and Mn in the rat. The counting system adapted for the technique has a response that is relatively invariant (+/- 2.5%) to differences in body size. A least-squares curve fitting technique was developed that requires only a single 5-min count of the animal. Our in vivo values for body Mg and Mn were in excellent agreement (+/- 2.0%) with the results of total carcass analysis using atomic absorption. Longitudinal changes in total body Mg and Mn were examined in vivo in two groups of animals maintained on test diets that contained different amounts of Mg.

Activation Analysis↗