Biomedical subjects

Xiao-Ming Zhu

Publications and source records attributed to Xiao-Ming Zhu.

8 recordsLinked to original sources

PubMed2006

Endothelium-dependent and -independent relaxation induced by pinocembrin in rat aortic rings.

The aim of present study was to evaluate the vasorelaxant effects of the flavonone pinocembrin and its possible mechanisms in isolated rat aortic rings. Pinocembrin (5 approximately 100 microM) induced relaxation in aortic rings pre-contracted with norepinephrine (NE, 1 microM) or KCl (60 mM), with pEC(50) value 4.37+/-0.02 and 4.52+/-0.04. Pretreatment with pinocembrin (30 or 50 microM) also inhibited contractile responses to NE and KCl. The vasorelaxant effect of pinocembrin relied on intact endothelium partially, and incubation with n(omega)-nitro-l-arginine methyl ester (l-NAME, 100 microM) or methylene blue (10 microM) significantly inhibited the effect, however indomethacin (5 microM) had no influence on the action. In endothelium-denuded rings, the vasorelaxant effect of pinocembrin was reduced by glibenclamide (10 microM), tetraethylammonium (5 mM) and 4-aminopyridine (100 microM). Pinocembrin also reduced NE-induced transient contraction in Ca(2+)-free solution and inhibited contraction induced by increasing external calcium in Ca(2+)-free medium plus 60 mM KCl. Our results suggest that pinocembrin induces relaxation in rat aortic rings through an endothelium-dependent pathway, involving NO-cGMP, and also through an endothelium-independent pathway, opening K(+) channels and blockade of Ca(2+) channels.

Animals↗

PubMed2006

Specific peptide patterns of follicular fluids at different growth stages analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Human follicular fluid (HFF) has been suggested to influence oocyte development potential, and some of HFF proteins may be potential markers for oocyte maturation during follicular development. Using matrix-assisted laser desorption /ionization-time of flight mass spectrometry (MALDI-TOF MS), the presence of specific peptide peaks in HFF which could represent the follicle development potential was evaluated. HFF from different developmental stages were first digested and the resultant peptide mixtures were directly analyzed by MALDI-TOF MS. It was shown that the frequencies of specific peaks demonstrated higher reproducibility than peak intensities after multiple measurements (>or=6 times) per sample. Using this approach, a reliable peak list for each different sample could be generated by combining the information from multiple measurements. By comparing the peak lists from different samples at different growth stages, we found that 5 specific peaks appeared in the 100% frequency category of 6 replicates in all the HFF samples containing mature oocyte. Similarly, such 25 peptide peaks were also identified for HFF containing immature oocyte. These specific peaks could be used to distinguish HFF from different stages as biomarkers related to follicle development and maturation. After searching the protein database, some proteins that are known to be involved in the development and maturation of oocyte were identified, such as apolipoprotein A-I, collagen type IV, integrin, et al. Identification of such proteins in our experiment further proved that the direct analysis of tryptic digests could be of practical value.

Female↗

PubMed2006

50-Hertz electromagnetic fields induce gammaH2AX foci formation in mouse preimplantation embryos in vitro.

Effects of electromagnetic fields (EMFs) on DNA damage in mammals are still controversial. In the present study, the effects of EMFs on DNA damage in preimplantation mouse embryos in vitro were investigated by using gammaH2AX foci formation, a new sensitive indicator for detecting DNA double-strand breaks (DSBs). The data obtained demonstrated that EMFs decreased the cleavage rate of preimplantation mouse embryos. This decreasing effect of EMFs was related to the DNA-damaging effect indicated by the induction of gammaH2AX foci formation in preimplantation mouse embryos. The inducing effects of EMFs on gammaH2AX foci formation could be inhibited by the treatment of noise MFs or wortmannin, a phosphatidylinositol 3-kinase (PI3K) family inhibitor. Furthermore, the data obtained also showed that EMFs could activate the DNA damage-repair mechanism by recruiting repair factor Rad50 to the damaged DNA sites to repair the corresponding DNA damage. These findings suggest that EMFs could cause DNA damage in preimplantation embryos in vitro and that the adverse effects of EMFs on development might at least partly act through DNA damage. The DNA damage induced by EMFs could be at least partly repaired by the natural activation of DNA damage-repair mechanism or prevented by the simultaneous treatment of noise magnetic fields.

ATP-Binding Cassette Transporters↗

PubMed2006

Ovarian stimulation with GnRH agonist, but not GnRH antagonist, partially restores the expression of endometrial integrin beta3 and leukaemia-inhibitory factor and improves uterine receptivity in mice.

BACKGROUND: The impact of different ovarian stimulation (OS) protocols on endometrial receptivity remains controversial. In this study, the effects of different OS on the expression of endometrial integrin beta3 subunit and leukaemia-inhibitory factor (LIF) during the implantation window and the implantation rate in mice were investigated. METHODS: Three OS protocols were used, involving either pregnant mare's serum gonadotrophin (PMSG) alone, PMSG plus GnRH agonist or PMSG plus GnRH antagonist. Uterus samples were collected at 48 h after OS or ovulation and were detected with immunohistochemistry, Western blot and RT-PCR analyses. Normal embryos at gestation day 4 were transferred into the uteri of mice in the control and OS groups. RESULTS: All OS groups showed a significant decrease in the expression of both the endometrial integrin beta3 subunit and LIF during the implantation window and the implantation rate. Among the three OS groups, GnRH agonist-treated mice showed a higher endometrial integrin beta3 subunit and LIF expression and a higher implantation rate. No significant difference was found in the measured indices between the GnRH antagonist and PMSG groups. CONCLUSIONS: OS may inhibit the expression of endometrial integrin beta3 subunit and LIF and impair endometrial receptivity in mice. OS with GnRH agonist, but not GnRH antagonist, may partially restore the endometrial physiological secretion and improve uterine receptivity.

Animals↗

PubMed2006

A novel SNP at exon 17 of INSR is associated with decreased insulin sensitivity in Chinese women with PCOS.

To investigate the association of single-nucleotide polymorphisms (SNPs) in exon 17 of the insulin receptor (INSR) gene with insulin resistance and INSR beta-subunit expression in polycystic ovary syndrome (PCOS) patients, a case-control study was carried out in an academic endocrinology clinic of China. One hundred and nine Chinese patients with PCOS and 107 healthy Chinese women as control were recruited. Their leukocytes and red blood cells were separated from blood samples, for SNP analysis with single-stranded conformation polymorphism and for the INSR beta-subunit expression detection by western blot analysis, respectively. A novel T/C SNP at codon Cys1008 (position 3128 of NM_000208) of INSR was found in two allele genotypes, i.e. the homozygous CC and the heterozygous TC. A higher frequency of the mutant homozygous CC was observed in the PCOS women with PCOS than that in the controls (21.1 versus 5.6%, P < 0.01). In contrast with the women with wild-type genotype, a significantly lower insulin sensitivity index in the women with each of the two mutant genotypes was revealed (CC: 0.335 +/- 0.026/TC: 0.346 +/- 0.027 versus TT: 0.367 +/- 0.029, P < 0.05). No relationship was found between the novel SNP and the INSR beta-subunit expression. We concluded that the novel T/C SNP at codon Cys1008 of INSR is associated with decreased insulin sensitivity in Chinese women with PCOS and that the association is not by the change of synthesis or secretion of INSR beta-subunit, but most possibly by the effects of this novel SNP on the function of INSR beta-subunit.

Adult↗

PubMed2004

Changes in GABA transporters in the rat hippocampus after kainate-induced neuronal injury: decrease in GAT-1 and GAT-3 but upregulation of betaine/GABA transporter BGT-1.

The gamma-aminobutyric acid (GABA) transporters GAT-1, GAT-2, GAT-3, and BGT-1 have been cloned and identified according to their differential amino acid sequences and pharmacologic properties. In contrast to GAT-1, -2, or -3, BGT-1 is capable of utilizing both GABA and betaine as substrates. Betaine has been suggested to be a protective osmolyte in the brain. Because changes in expression of GABA transporters/BGT-1 might result in alterations in levels of GABA/betaine in the extracellular space, with consequent effects on neuronal excitability or osmolarity, the present study was carried out to explore expression of GABA transporters in the rat hippocampus after kainate-induced neuronal injury. A decrease in GAT-1 and GAT-3 immunostaining but no change in GAT-2 staining was observed in the degenerating CA subfields. In contrast, increased BGT-1 immunoreactivity was observed in astrocytes after kainate injection. BGT-1 is a weak transporter of GABA in comparison to other GABA transporters and the increased expression of BGT-1 in astrocytes might be a protective mechanism against increased osmotic stress known to occur after excitotoxic injury. On the other hand, excessive or prolonged BGT-1 expression might be a factor contributing to astrocytic swelling after brain injury.

Animals↗

PubMed2004

A light and electron microscopic study of betaine/GABA transporter distribution in the monkey cerebral neocortex and hippocampus.

The present study aimed to elucidate the distribution of betaine/gamma-aminobutyric acid (GABA) transporter-1 (BGT-1) in the normal monkey cerebral neocortex and hippocampus by immunoperoxidase and Immunogold labelling. BGT-1 was observed in pyramidal neurons in the cerebral neocortex and the CA fields of the hippocampus. Large numbers of small diameter dendrites or dendritic spines were observed in the neuropil. These made asymmetrical synaptic contacts with unlabelled axon terminals containing small round vesicles, characteristic of glutamatergic terminals. BGT-1 label was observed in an extra-perisynaptic region, away from the post-synaptic density. Immunoreactivity was not observed in portions of dendrites that formed symmetrical synapses, axon terminals, or glial cells. The distribution of BGT-1 on dendritic spines, rather than at GABAergic axon terminals, suggests that the transporter is unlikely to play a major role in terminating the action of GABA at a synapse. Instead, the osmolyte betaine is more likely to be the physiological substrate of BGT-1 in the brain, and the presence of the transporter in pyramidal neurons suggests that these neurons utilize betaine to maintain osmolarity.

Animals↗

PubMed2003

Multi-factorial role of GnRH-I and GnRH-II in the human ovary.

Normal ovarian functions are regulated by a wide variety of endocrine hormones, local paracrine and autocrine factors, which functionally interact with each other in a highly coordinated fashion. Recent findings have demonstrated that both forms of gonadotropin-releasing hormone (GnRH-I and GnRH-II) are expressed in various compartments of the human ovary including the granulosa-luteal cells, ovarian surface epithelial cells and ovarian tumors, and their expressions have been shown to be tightly regulated by gonadal steroids and gonadotropins. Functionally, these neuropeptides exert diverse biological effects in the ovary via binding to their cognate receptors, supporting the notion that these peptides act as paracrine and autocrine factors in modulating local ovarian functions. In this review, we will summarize recent literatures regarding the regulation of GnRH-I and GnRH-II gene expressions in the human ovary, and discuss the possible signal transduction mechanisms by which these hormones exert their actions in the gonad. Recent cloning of the second form of the GnRH receptor (GnRH-II receptor) in primates and other vertebrates demonstrated that it was structurally, and thus, functionally distinct from the GnRH-I receptor. Cell proliferation studies showed that GnRH-II inhibited the growth of human ovarian cancer cells that express GnRH-II but not GnRH-I receptor, indicating that the GnRH-II binding sites are functional in these cells. However, it remains unknown if GnRH-II receptor is expressed as a full-length, properly processed and functional gene transcript in humans, and its potential physiological roles such as differential regulation of gonadotropin secretion, neuroendocrine modulation and female sexual behavior await further investigation.

Amino Acid Sequence↗