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Biomedical subjects

X Chu

Publications and source records attributed to X Chu.

At least 19 recordsLinked to original sources
PubMed1999

The nociceptin receptor-mediated inhibition of the rat rostral ventrolateral medulla neurons in vitro.

The recently available antagonist selective for novel nociceptin receptor, [Phe1 psi(CH2-NH)Gly2]NC(1-13)NH2, was utilized in this study to verify specificity of nociceptin receptor in mediating the nociceptin-induced inhibition of electrical activity of neurons in the rostral ventrolateral medulla of rat brain slices. Perfusion of nociceptin (10 nM) considerably reduced spontaneously firing frequency of the medullary neurons. Co-perfusion of [Phe1 psi(CH2-NH)Gly2]NC(1-13)NH2 (10 microM) completely blocked the nociceptin-induced depression of the neuronal activity. Blocking effect of [Phe1 psi(CH2-NH)Gly2]NC(1-13)NH2 was concentration-dependent. However, the nociceptin antagonist did not modify basal, and opioid peptide enkephalin-depressed, firing rates of the neurons. In contrast to [Phe1 psi(CH2-NH)Gly2]NC(1-13)NH2, the non-selective opioid receptor antagonist naloxone (10 microM) failed to affect the nociceptin inhibition even though naloxone at a lower concentration (1 microM) readily blocked enkephalin-induced depression of the neuronal activity. These data indicate that the nociceptin-induced inhibition of spontaneous discharge of the rostral ventrolateral medulla neurons is specifically mediated by [Phe1 psi(CH2-NH)Gly2]NC(1-13)NH2-sensitive nociceptin receptors distinct from typical naloxone-sensitive opioid receptors.

Animals↗
PubMed1999

Unique regulation of CYP17 expression in the trophectoderm of the preattachment porcine blastocyst.

Expression of the gene encoding cytochrome P450 17alpha-hydroxylase, CYP17, is necessary for adrenal and gonadal steroidogenesis in most species. However, some animals, such as the pig, express CYP17 in the trophectoderm of the preattachment blastocyst, an event associated with estrogen synthesis and the establishment of pregnancy. How trophoblastic expression of CYP17 is regulated in the porcine blastocyst remains unknown and forms the basis of the following studies. The porcine CYP17 gene, including the complete coding and several kilobases of 5'-flanking regions, was cloned and sequenced. Blastocysts were examined by Northern analysis to verify the level of CYP17 transcript, and tissue-specific expression in the trophectoderm was confirmed by in situ hybridization. Primer extension, S1 nuclease protection, and 5'-rapid amplification of cDNA ends confirmed a common proximal transcription start site in adrenals and gonads (-48 bp) but identified a unique distal start site used in porcine trophectoderm (-182 bp). Additionally, reporter analysis of the CYP17 regulatory region demonstrated that constructs (-27 to -718 bp) were unresponsive to forskolin when expressed in porcine trophoblast cells, suggesting that trophoblast may not be able to respond to cAMP induction of this gene. The identification of this distal, previously undescribed, transcriptional start site suggests that unique mechanisms control the expression of CYP17 in porcine trophectoderm and possibly other genes important in implantation and early placental development.

Adrenal Cortex↗
PubMed1998

Stress-induced neuroendocrine modulation of viral pathogenesis and immunity.

Physical restraint (RST) was used to examine the interactions among the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic nervous system, and the immune response to infection. In these studies, mice were infected with either herpes simplex virus (HSV) or influenza A/PR8 virus so that the impact of neuroendocrine activation could be assessed on disease pathophysiology and anti-viral immunity. RST suppressed lymphadenopathy in draining lymph nodes, reduced mononuclear cellular infiltration in the lungs, and suppressed virus-specific cytokine and cytolytic T-cell responses. Blockade of type II glucocorticoid receptors (by RU486) restored cellularity and cytokine responses to both organs in restraint-stressed, infected mice. Thus, the HPA axis modulated cell trafficking and T-cell cytokine responses. However, RU486 treatment failed to restore cytolytic T-cell responses. Blockade of beta-adrenergic receptors (by nadolol), in combination with RU486 treatment, fully restored cytolytic T-cell responses, suggesting that catecholamines were involved in suppressing the virus-specific CD8+ cytolytic T-cell response. RST also modulated the local development or expression of antibody-secreting cells (ASC) in the lungs draining lymph nodes, and spleen following infection of restrained mice. RST significantly suppressed the number of virus-specific ASC (IgM, IgG and subclasses IgG1 and IgG2a) in the lungs, mediastinal (MLN) lymph nodes and spleen, while it enhanced the responses in the superficial cervical (SCV) lymph nodes. This observation of differential modulation of ASC responses in the MLN and SCV lymph nodes supports the concept of tissue-specific immunoregulation in response to stress.

Animals↗
PubMed1998

Profound inhibition of cardiomotor neurons in the rat rostral ventrolateral medulla by nociceptin (orphanin FQ).

Nociceptin (orphanin FQ), the newly discovered endogenous ligand for the opioid receptor like-1 receptor, profoundly inhibited spontaneous discharges of neurons in the rostral ventrolateral medulla (RVLM) in rat brain slices. This inhibition was concentration-dependent (0.3, 1, 3 and 10 nM) and insensitive to pharmacological blockade of traditional opioid receptors by naloxone. Moreover, nociceptin injected into the RVLM (10 nM, 0.1 microliter) in anesthetized rats decreased arterial blood pressure and heart rate by 31% and 15%, respectively. The data obtained in vitro and in vivo suggest that nociceptin has powerful effects on the RVLM neurons involving central control of cardiovascular activity. The negative regulation of cardiovascular activity by nociceptin is not mediated through typical naloxone-sensitive opioid receptors.

Animals↗
PubMed1998

Multiplicity of biliary excretion mechanisms for the camptothecin derivative irinotecan (CPT-11), its metabolite SN-38, and its glucuronide: role of canalicular multispecific organic anion transporter and P-glycoprotein.

A frequent dose-limiting effect of irinotecan (CPT-11) is its gastrointestinal toxicity (diarrhea), which is thought to be related to biliary excretion of CPT-11 and its metabolites. Accordingly, we have investigated the mechanism of biliary excretion of these compounds. In vivo pharmacokinetic studies revealed that the biliary excretion of the four anionic forms of CPT-11 and its metabolites was reduced in Eisai hyperbilirubinemic rats, which carry a mutation of the hepatic canalicular multispecific organic anion transporter (cMOAT) gene. The protein encoded by this gene is expressed on the bile canalicular membrane and is responsible for the transport of organic anions into bile. Detailed analysis using isolated liver bile canalicular membrane vesicles to identify transport systems showed that cMOAT is responsible for biliary excretion of the low-affinity component of the carboxylate form of CPT-11 and the high-affinity component of both the lactone and carboxylate forms of SN-38 glucuronide. The carboxylate form of SN-38 is transported by cMOAT alone. Transport of the high-affinity component of CPT-11 was inhibited by verapamil and PSC-833, but their effect on the transport of its low-affinity component was minimal. In addition, ATP dependence in the uptake of CPT-11 by membrane vesicles obtained from a P-glycoprotein (P-gp)-overexpressing cell line was observed. Thus P-gp may be responsible for transport of the high-affinity component of the carboxylate form of CPT-11.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

An Expression for the Dispersion Force between Colloidal Particles

A result for the integral of R-12 over two spheres of radii a and b is given. This result, together with Hamaker's result for the integral of R-6, leads to an expression for the integral of the Lennard-Jones potential over two spheres that is suitable for calculations involving colloidal particles.

Journal Article↗
PubMed1997

[Purification and some properties of superoxide dismutase from Fusarium moniliform].

Superoxide dismutase from Fusarium moniliform was purified by the steps including heating, ammonium sulfate fractionation, Sephedax G-100 gel filtration and DEAE-Sephadex A-50 chromatography. The results showed that the enzyme was a Mn-SOD with the specific activity of 2640 U/mg and had two homogenous subunits whose molecular mass were 14.5 kD. The wave length of max. absorbing peak in ultraviolet spectrum was 276 nm which was not similar with other resource of SOD. The composition of amino acid was also analyzed.

Amino Acids↗
PubMed1997

[Studies on the changes of morphometry and neuropeptide of spinal neurons after peripheral nerve injury].

To observe the change of morphology and neuropeptide in the spinal neurons in order to clarify the functional state after injury of peripheral nerves is especially in the late stage. Sciatic nerves were cut with their proximal segments in the preparation of a model of peripheral nerve injury. Combination of horseradish peroxidase retrograde tracing immunohistochemistry and computer image analysis the changes in the morphometry of the perikarya of ventral horn neurons of the spinal cord, the quantitative changes of substance P (SP). Calcitonin gene-related peptide (CGRP) in dorsal horn and CGRP and choline acetyransferase (CHAT) in ventral horn of the spinal cord were examed. The results showd: (1) At the 3rd week after injury, swollen perikarya of the ventral horn neurons were observed, subseauently the swelling of perikarya was decreased tile the 6th week the neurons recovered to their normal size. At the 12th week the neurons were generally stable in their size, shortening of the dendrites was seen in 27% of the neurons. (2) The dendrites of the neurons progressively contracted till at the 12th week 53% of them were degenerated. The results of the 24th week were similar to the that at the 12th week. (3) CGRP in the ventral horn of the spinal cord was elevated to the highest point after 1 week of injury, that lasting for 4 weeks and 8 weeks later, the lever of CGRP returned to normal. From 20th to 24th week, there was no obvious changes of CHAT in the ventral horn of the spinal cord during observation. (4) SP went to the lowest point in the dorsal horn during 2-6 weeks, then recovered slowly, and beiny normal again after 16 weeks, however, CGRP was changed slightly. The results indicated that although a series of degenerating changes occurred in the neurons of the spinal cord during the late peripheral nerve injury, but the functional activity of the central meurons still was maintained at a certain level.

Animals↗
PubMed1997

[Peripheral nerve injury as a complication from orthopedic operation].

Nerve injury following operation is one of the main causes of the iatrogenic peripheral nerve injury. In order to learn lessons from these cases, one hundred and seven cases of peripheral nerve injury complicated with the orthopedic operations were analyzed. Forty-four cases were cutting injury during operation, made up 41% of all cases and 27 cases were stretch and compression injury, made up 25%. The involved nerves included 41 radial nerves and 24 common peroneal nerves, composing 60.7% of all nerve injury. The operations responsible were mainly the bone and joint operations, which made up 81%. The cause, prophylaxis, diagnosis and treatment were discussed. The rich appropriate knowledge of anatomy and responsibility of the surgeon were emphasized in order to prevent the occurrence of complication. Once the injury was suspected, diagnosis should be made promptly and effective treatment should be performed in time.

Adolescent↗
PubMed1996

Attractive Interaction between Similarly Charged Colloidal Particles

The pair interactions between the charged colloidal particles dispersed in a solvent are studied theoretically by the integral equation method. The pair potential of the mean forces, accounting for the effective pair interaction between colloidal particles, is calculated from the solution of the Ornstein-Zernike equation with the mean spherical approximation (MSA). An attractive interaction was found between two similarly charged colloidal particles in contrast with the purely repulsive force predicted by the Debye-Huckel theory. Such an attractive interaction provides physical insight for the "condensed" phenomena in charged colloidal dispersions, that is, the coexistence of a "condensed" phase and an "expanded" phase (voids). At the higher concentration and charge on colloidal particles, the effective pair interaction becomes oscillatory.

Journal Article↗
PubMed1996

Polymer agglutination-based piezoelectric immunoassay for the determination of complement III.

A piezoelectric immunoassay technique, which is based on the detection of agglutination of antibody- or antigen-bearing polymer by an immunoreaction using a piezoelectric quartz crystal, has been developed for the determination of complement III (C3). Anti-C3 antibodies were physically adsorbed onto the carboxymethyl cellulose polymer by hydrogen bonds. The agglutination of the (anti-C3 antibody)-bearing polymer by immunoreaction caused a viscosity change of the solution, which could be monitored by a piezoelectric quartz crystal. The effect of experimental conditions such as the polymer concentration, the antibody dilution ratio and the reaction temperature on the frequency response were investigated. The linear ranges for C3 concentration determined by the end-point method and the initial rate method were 22.0-43.2 micrograms ml-1 and 22.0-49.1 micrograms ml-1, respectively. Other antigens presenting in serum did not interfere with the determination of C3. Analytical results of ten clinical specimens obtained using the developed technique were in satisfactory agreement with those given by the rate diffusion turbidimetry. With a simple regeneration method devised, the crystal can be used repeatedly with acceptable reproducibility.

Complement C3↗
PubMed1995

Identification of Streptomyces violaceoruber Tü22 genes involved in the biosynthesis of granaticin.

A 50 kb region of DNA from Streptomyces violaceoruber Tü22, containing genes encoding proteins involved in the biosynthesis of granaticin, was isolated. The DNA sequence of a 7.3 kb fragment from this region, located approximately 10 kb from the genes that encode the polyketide synthetase responsible for formation of the benzoisochromane quinone skeleton, revealed five open reading frames (ORF1-ORF5). The deduced amino acid sequence of GraE, encoded by ORF2, shows 60.8% identity (75.2% similarity) to a dTDP-glucose dehydratase (StrE) from Streptomyces griseus. Cultures of Escherichia coli containing plasmids with ORF2, on a 2.1 kb BamHI fragment, were able to catalyze the formation of dTDP-4-keto-6-deoxy-D-glucose from dTDP-glucose at 5 times the rate of control cultures, confirming that ORF2 encodes a dTDP-glucose dehydratase. The amino acid sequence encoded by ORF3 (GraD) is 51.4% identical (69.9% similar) to that of StrD, a dTDP-glucose synthase from Streptomyces griseus. The amino acid sequence encoded by ORF4 shares similarities with proteins that confer resistance to tetracycline and methylenomycin, and is suggested to be involved in transporting granaticin out of the cells by an active efflux mechanism.

Amino Acid Sequence↗
PubMed1995

Polymerase chain reaction analysis of the Xba I polymorphism of the human complement C4 genes provides evidence for strong haplotype conservation.

The genes coding for the two isotypes of the fourth component of human complement, C4A and C4B, are located between the HLA-B and -DR loci of the MHC. We studied the linkage relationship of the previously described XbaI RFLP to obtain further insight into the evolution of the tandemly arranged C4 genes. Using exon-specific PCR amplification followed by restriction analysis and direct DNA sequencing, the polymorphic site could be located in exon 40 of the C4 gene (cDNA position 5095). The polymorphism does not change an amino acid residue. Using nested PCR amplification with isotype-specific primers to amplify either C4A or C4B alleles the haplotype arrangement of the XbaI sites in both isotypic C4 genes was analyzed independently. It was observed that the XbaI restriction site was either present or absent in both C4 genes of a given haplotype. In a study of 106 Caucasian haplotypes, only two different haplotypes could be identified carrying a C4A gene with and a C4B gene without the XbaI restriction site. Also, the XbaI site could only be detected in long C4 genes possessing the 6.5-kb insertion in intron 9. Our findings provide evidence that the mutation creating the XbaI polymorphism occurred in an ancestral C4 gene already carrying the long intron 9. The duplicating resulting in the presence of two isotypic genes, C4A and C4B, must have taken place subsequently giving rise to haplotypes with or without the XbaI site.

Base Sequence↗
PubMed1995

Piezoelectric immunosensor for the detection of immunoglobulin M.

A piezoelectric immunosensor has been developed for the determination of human IgM. The crystals are AT-cut and have a basic resonant frequency of 9 MHz. Immobilization of goat antihuman IgM antibodies to the crystals' surfaces was accomplished via a CNBr-activated copolymer coating of 2-hydroxyethyl methacrylate and methylmethacrylate. The IgM piezoelectric immunosensor can be used for the human IgM determination in the range 5-93 micrograms ml-1. The analytical results given by this approach were in satisfactory agreement with those given by the single radical immunodiffusion procedure. The sensitivity, specificity and reproducibility of this immunosensor were investigated. Further, the valent value of goat antihuman IgM antibody binding with human IgM antigen and the affinity constant of immunoreaction in this experimental system were studied. After washing with tetrahydrofuran, a crystal can be re-used 20 times without detectable loss of sensitivity.

Biosensing Techniques↗
PubMed1995

St14 (DXS52) VNTR in the Chinese population and its application to genetic diagnosis of haemophilia A.

The variable number of tandem repeats (VNTR) of St14 (DXS52) on the human X-chromosome was analysed using the polymerase chain reaction (PCR) method. Screening of 78 X-chromosomes in 56 healthy Chinese individuals revealed the existence of at least seven different alleles in the the Chinese population, the corresponding amplified fragments and frequencies being 700 bp (60.3%), 1220 bp (1.3%), 1300 bp (2.6%), 1390 bp (11.5%), 1570 bp (12.8%), 1630 bp (6.4%) and 1690 bp (5.1%). Total theoretical heterozygous rate was 60%. Compared to Caucasians, this Chinese population showed a markedly higher occurrence of low molecular weight fragments and a relatively low occurrence of high molecular weight fragments. Study of this polymorphism in 14 suspected haemophilia A carriers revealed half of them to be heterozygous. Thus, St14 VNTR analysis by PCR should prove to be a useful tool in the genetic diagnosis of haemophilia A in China.

Asian People↗
PubMed1995

Length polymorphism of the human complement component C4 gene is due to an ancient retroviral integration.

The fourth component of the complement system, C4, is encoded by two highly homologous MHC-linked genes expressing the two isotypes C4A and C4B. A gene size polymorphism (either 22.5 or 16 kb) has been described which depends on the presence or absence of a 6.5-kb insertion in intron 9 of the C4 gene. By sequencing a C4A-specific lambda clone from a human genomic library containing the long intron 9 as well as PCR-amplified DNA containing the short intron, the DNA sequences of both introns were determined. The long and short introns have lengths of 6,787 bp and 415 bp, respectively. The sequence of the short intron is almost identical (96%) to the corresponding parts of the long intron. At position 282 of the short intron, a 6,372-bp insertion is present in the long intron which has all characteristics of a full-length endogenous retrovirus. The proviral DNA is flanked by two 6-bp target site repeats. The orientation of the proviral sequence is opposite to that of the C4 coding strand. Long terminal repeats (LTRs) of 548 bp were found at both ends of the provirus. A TATA box and an SV40 enhancer core as well as a polyadenylation signal are present in the LTR. A 5' primer binding site for lysine tRNA was identified. The strongest sequence homologies were found in comparison to human endogenous retrovirus (HERV-K): between 65-88% for gag, pol and env genes. However, a search for open reading frames in these regions indicated the presence of multiple stop codons in all three reading frames.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Composition↗
PubMed1994

[Site-directed mutagenesis of Lac Z gene in Escherichia coli and the kinetic properties of the mutated enzymes].

Glutamic acid at position of 537 of beta-D-galactosidase coded by Lac Z gene was substituted with Aspartic acid, Glutamine and Valine using synthetic oligonucleotide probes. Compared to native enzyme, the kcat values for substrate ONPG were 0.13%, 0.0006% and 0.0035% for Asp-537, Gln-537 and Val-537 mutated enzymes respectively. The Km values were of the same order of magnitude, either native or mutated enzymes. The substrate analog, IPTG was a strong inhibitor of each of the substituted enzymes, as in the case of native enzyme. The transition state analogs, 2-NH2-galactose and L-ribose were almost the same effects for the mutated enzymes as for the normal enzyme. The nucleophili, Azide, did not activate the mutated enzymes as in the case of Glu-461 substituted in beta-D-galactosidase. The effect of methanol on the mutated enzymes was less than on native enzyme. The order of the thermal stability was native enzyme > Asp-537 > Gln-537 > Val-537 enzymes. Overall, the evidence strongly supports the suggestion that Glu-537 is an essential residue of beta-D-galactosidase.

Base Sequence↗