Detailed pollution map of an area highly contaminated by mercury containing wastewater from an organic chemical factory in People's Republic of China.
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Chemical Industry↗
Biomedical subjects
L Mei
Publications and source records attributed to L Mei.
Relationship between leached total mercury and leached methylmercury from soil polluted by mercury in wastewater from an organic chemical factory in the People's Republic of China.
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Chemical Industry↗
Mercury distribution in farmlands downstream from an acetaldehyde producing chemical company in Qingzhen City, Guizhou, People's Republic of China.
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Acetaldehyde↗
Distribution of methylmercury in an area polluted by mercury containing wastewater from an organic chemical factory in China.
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Chemical Industry↗
Evaluation of functional ovarian reserve in 60 patients.
Diminished ovarian reserve is a condition occurring in women at any adult age, although it is more frequent in women in their 30s and in couples with unexplained subfertility. Different tests are employed to diagnose the problem. The most common are basal tests for FSH, LH, oestradiol and inhibin B, or dynamic endocrine tests such as the clomiphene citrate challenge test and gonadotrophin analogue stimulating test. In recent years, great attention has been devoted to direct tests such as the antral follicle count and ovarian biopsy results. The basal FSH concentration is the most common test utilized for ovarian screening. An abnormal value is correlated with a decrease in pregnancy rate and an increase in cycle cancellation rate. Among other basal endocrine tests, inhibin concentrations appear promising, although more data are necessary before this can be included in clinical practice. The clomiphene citrate challenge test can unmask patients who might have not been detected by basal FSH screening alone, and appears to be more sensitive than day 3 FSH alone. A prospective study was performed on the simultaneous application of various markers of ovarian reserve (FSH, LH, oestradiol, inhibin B, antral follicle count) in the natural cycle preceding assisted reproductive therapy, in 60 women. The present study suggests that counting ovarian follicles by ultrasound appears, at the moment, the most reliable test of ovarian reserve, although it is influenced by subjective factors and more studies are needed in order to confirm its predictive value.
Adult↗
Clinical and endocrinological effects of 6 months of metformin treatment in young hyperinsulinemic patients affected by polycystic ovary syndrome.
Most patients with polycystic ovary syndrome (PCOS) have hyperinsulinemia; thus it has been postulated that insulin-lowering drugs, such as metformin, might be a useful long-term choice. We evaluated the effects of 6 months' administration of metformin on clinical and endocrine indices in PCOS patients. Forty-two hyperinsulinemic women with PCOS were continuously treated with metformin for 6 months. Gonadotropins, androgens (testosterone and androstenedione), insulin, sex hormone binding globulin (SHBG), lipid profile and clinical indices (menstrual length, body mass index (BMI), Ferriman-Gallwey score and waist/hip ratio (WHR)) were studied before and after metformin treatment. All women experienced a normalization of menstrual cycle length (reduction rate, 36.9%), a significant decrease in luteinizing hormone, insulin and androgen levels and an increase in SHBG plasma concentrations, with a concomitant decrease in cycle length and WHR. Significant changes were observed in the lipid profile. According to baseline androgen levels, patients were divided into two groups: 20 normoandrogenic and 17 hyperandrogenic women. The greatest decline of androgens, BMI and Ferriman-Gallwey score was observed in hyperandrogenic patients. Lowering of androgenicity was independent of BMI. Significant changes in lipid profile were observed in both groups after metformin treatment. These results suggest that metformin is effective in decreasing hyperandrogenism, mainly by reducing insulin levels. This leads to an improvement of clinical manifestations of PCOS and, in particular, of hyperandrogenism.
Adolescent↗
Signal transduction in neuronal migration: roles of GTPase activating proteins and the small GTPase Cdc42 in the Slit-Robo pathway.
The Slit protein guides neuronal and leukocyte migration through the transmembrane receptor Roundabout (Robo). We report here that the intracellular domain of Robo interacts with a novel family of Rho GTPase activating proteins (GAPs). Two of the Slit-Robo GAPs (srGAPs) are expressed in regions responsive to Slit. Slit increased srGAP1-Robo1 interaction and inactivated Cdc42. A dominant negative srGAP1 blocked Slit inactivation of Cdc42 and Slit repulsion of migratory cells from the anterior subventricular zone (SVZa) of the forebrain. A constitutively active Cdc42 blocked the repulsive effect of Slit. These results have demonstrated important roles for GAPs and Cdc42 in neuronal migration. We propose a signal transduction pathway from the extracellular guidance cue to intracellular actin polymerization.
Actins↗
Nerve growth factor uses Ras/ERK and phosphatidylinositol 3-kinase cascades to up-regulate the N-methyl-D-aspartate receptor 1 promoter.
We reported previously that nerve growth factor (NGF) up-regulates activity of the N-methyl-D-aspartate receptor 1 (NR1) promoter. We have explored the pathways and nuclear targets of NGF signaling in regulating the NR1 promoter. PD98059 and wortmannin, but not rapamycin, significantly attenuated NGF-induced transcriptional activity from an NR1 promoter-luciferase construct. Coexpressing constitutively active forms of Ras, Raf, or MAPK/ERK kinase 1 (MEK1) increased promoter activity dramatically. The MEK1-induced increase was largely prevented by mutations of the tandem GC boxes in the promoter. Promoter activity was also increased significantly by coexpressed GC box-binding proteins (Sp1, 3, or 4) in nonstimulated PC12 cells. Either an extracellular signal-regulated kinase-1 (ERK1)- or Sp1-specific antibody coprecipitated Sp1 with ERKs, and the coprecipitation was enhanced significantly by NGF treatment of PC12 cells. ERK2 also incorporated radioactivity of [gamma(32)P]ATP into recombinant Sp1. However, ERK2-treated Sp1 and PC12 nuclear extracts or nuclear extracts from NGF-treated cells exhibited reduced binding to the promoter or a consensus GC box. Our results suggest that NGF utilizes both the Ras/ERK and phosphatidylinositol 3-kinase pathways to up-regulate NR1 promoter activity and that Sp1 is a novel substrate of NGF-activated ERKs. NGF-increased NR1 promoter activity may involve a complicated mechanism of Sp1 phosphorylation and possible transcription factor exchange.
Androstadienes↗
Phosphotyrosines 627 and 659 of Gab1 constitute a bisphosphoryl tyrosine-based activation motif (BTAM) conferring binding and activation of SHP2.
A major Grb2-associated binder-1 (Gab1) binding partner in epidermal growth factor (EGF)-stimulated cells is protein-tyrosine phosphatase (PTPase) SHP2, which contains tandem SH2 domains. The SHP2 PTPase activity is required for activation of the extracellular signal-regulated kinase (ERK) subfamily of mitogen-activated protein (MAP) kinase by EGF. To investigate the mechanism by which Gab1 and SHP2 mediate ERK activation, we characterized the Gab1-SHP2 interaction. We found that both Tyr-627 and Tyr-659 of Gab1 were required for SHP2 binding to Gab1 and for ERK2 activation by EGF. Far Western blot analysis suggested that the tandem SH2 domains of SHP2 bind to Gab1 in a specific orientation, in which the N-SH2 domain binds to phosphotyrosine (Tyr(P))-627 and the C-SH2 domain binds to Tyr(P)-659. When assayed with peptide substrates, SHP2 PTPase was activated by a bisphosphopeptide containing both Tyr(P)-627 and Tyr(P)-659, but not by monophosphopeptides containing Tyr(P)-627 or Tyr(P)-659 or a mixture of these monophosphopeptides. These results suggest that Tyr(P)-627 and Tyr(P)-659 of Gab1 constitute a bisphosphoryl tyrosine-based activation motif (BTAM) that binds and activates SHP2. Remarkably, while a constitutively active SHP2 (SHP2DeltaN) could not rescue the defect of a SHP2-binding defective Gab1 (Gab1FF) in ERK2 activation, expression of a Gab1FF-SHP2DeltaN chimera resulted in constitutive activation of ERK2 in transfected cells. Thus, physical association of activated SHP2 with Gab1 is necessary and sufficient to mediate the ERK mitogen-activated protein kinase activation. Phosphopeptides derived from Gab1 were dephosphorylated by active SHP2 in vitro. Consistently, substrate-trapping experiments with a SHP2 catalytic inactive mutant suggested that Gab1 was a SHP2 PTPase substrate in the cells. Therefore, Gab1 not only is a SHP2 activator but also is a target of its PTPase.
Amino Acid Motifs↗
Erbin is a protein concentrated at postsynaptic membranes that interacts with PSD-95.
Neuregulin is a factor essential for synapse-specific transcription of acetylcholine receptor genes at the neuromuscular junction. Its receptors, ErbB receptor tyrosine kinases, are localized at the postjunctional membrane presumably to ensure localized signaling. However, the molecular mechanisms underlying synaptic localization of ErbBs are unknown. Our recent studies indicate that ErbB4 interacts with postsynaptic density (PSD)-95 (SAP90), a PDZ domain-containing protein that does not interact with ErbB2 or ErbB3. Using as bait the ErbB2 C terminus, we identified Erbin, another PDZ domain-containing protein that interacts specifically with ErbB2. Erbin is concentrated in postsynaptic membranes at the neuromuscular junction and in the central nervous system, where ErbB2 is concentrated. Expression of Erbin increases the amount of ErbB2 labeled by biotin in transfected cells, suggesting that Erbin is able to increase ErbB2 surface expression. Furthermore, we provide evidence that Erbin interacts with PSD-95 in both transfected cells and synaptosomes. Thus ErbB proteins can interact with a network of PDZ domain-containing proteins. This interaction may play an important role in regulation of neuregulin signaling and/or subcellular localization of ErbB proteins.
Adaptor Proteins, Signal Transducing↗
Regulation of CDC42 GTPase by proline-rich tyrosine kinase 2 interacting with PSGAP, a novel pleckstrin homology and Src homology 3 domain containing rhoGAP protein.
Proline-rich tyrosine kinase 2 (PYK2), a tyrosine kinase structurally related to focal adhesion kinase (FAK), is implicated in regulating cytoskeletal organization. However, mechanisms by which PYK2 participates in and regulates cytoskeletal organization remain largely unknown. Here we report identification of PSGAP, a novel protein that interacts with PYK2 and FAK and contains multiple domains including a pleckstrin homology domain, a rhoGTPase-activating protein domain, and a Src homology 3 domain. PYK2 interacts with PSGAP Src homology 3 domain via the carboxyl-terminal proline-rich sequence. PSGAP is able to increase GTPase activity of CDC42 and RhoA in vitro and in vivo. Remarkably, PYK2, but not FAK, can activate CDC42 via inhibition of PSGAP-mediated GTP hydrolysis of CDC42. Moreover, PSGAP is localized at cell periphery in fibroblasts in a pleckstrin homology domain-dependent manner. Over expression of PSGAP in fibroblasts results in reorganization of cytoskeletal structures and changes of cellular morphology, which requires rhoGTPase-activating activity. Taken together, our results suggest that PSGAP is a signaling protein essential for PYK2 regulation of cytoskeletal organization via Rho family GTPases.
Amino Acid Sequence↗
Inhibition of PYK2-induced actin cytoskeleton reorganization, PYK2 autophosphorylation and focal adhesion targeting by FAK.
Focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2) are structurally related tyrosine kinases. They are implicated in regulating actin cytoskeleton organization, a process critical for cell migration, mitosis and tumor metastasis. In this paper, we demonstrate that, although both PYK2 and FAK were expressed and colocalized at focal adhesions in fibroblasts, microinjection of PYK2, but not FAK, in Swiss 3T3 fibroblastic cells led to reorganization of focal adhesions and cell rounding. PYK2-mediated actin cytoskeleton reorganization required the PYK2 N terminus, the focal adhesion targeting (FAT) domain, catalytic activity and autophosphorylation. Remarkably, FAK suppressed PYK2-mediated reorganization of focal adhesions and cell rounding. In addition, FAK inhibited PYK2 autophosphorylation and focal adhesion targeting, which might contribute to FAK-mediated suppression of PYK2's phenotypes. Further analyses demonstrated that the inhibition of PYK2 autophosphorylation required the FAK N terminus but not FAK tyrosine phosphorylation. The FAK FAT domain seemed to be critical for FAK-mediated suppression of PYK2 focal adhesion targeting. Taken together, these results demonstrate that FAK could inhibit PYK2 autophosphorylation, focal adhesion targeting and actin cytoskeleton reorganization, suggesting that the balance between FAK and PYK2 tyrosine kinases is important for regulating cellular morphology, cell migration and cell growth.
Actins↗
The value of ultrasonographic examination of the uterine cervix in predicting post-term pregnancy.
OBJECT: To assess whether transvaginal ultrasound is helpful in predicting the post-term onset of labor (> or = 1 weeks). SETTING: Antenatal clinic of a University hospital and referral center. SUBJECT AND MEHODS: One hundred and twenty singleton uncomplicated pregnancies in primiparous women were enrolled at 37 weeks of gestation. Ultrasound examination of the cervical length by a transvaginal probe was performed at recruitment and at weekly intervals until 40 completed weeks. Subjects were divided into Group A (those with spontaneous onset of labor < or = 1 completed weeks) and Group B (those not in labor by that date). RESULTS: Eighty women delivered < or = 41 completed weeks, forty were not in labor by that date. The cervix was significantly shorter at 39 and 40 weeks in group A, but no particular cervical length was predictive of post-term delivery. DISCUSSION: There is a significant difference in cervical length in women delivering at term compared with those due to have a post-term delivery. This difference is significant from 39 weeks of gestation onwards. We speculate that targeted transvaginal ultrasound may be useful in predicting the post-term onset of labor and possibly in assisting its active management.
Cervix Uteri↗
[Neuregulin/ErbB signal transduction pathway in the development of nervous system].
Neuregulins are a family of structurally-related polypeptides encoded by four distinct genes. Three isoforms of neuregulin (NRG1, 2, and 3) are highly expressed in the developing and adult brain, among which NRG1 is best characterized. NRG1 has multiple functions essential for the development of the nervous system. It promotes growth and differentiation of glial cells and regulates the migration of cerebellar granule cells along radial glial fibers. During synaptogenesis, NRG1 induces the expression of acetylcholine receptor at the neuromuscular junction and in CNS, and expression of the NMDA receptor NR2C subunit and GABAA receptors in cerebellar granule cells. Recent studies indicate that NRG receptors are densely distributed in the postsynaptic membrane, suggesting that NRGs may play an important role in synaptic plasticity. We review recent progress in studies of NRG, their functions, and signaling mechanisms.
Animals↗
Inhibition of malignant trophoblastic cell proliferation in vitro and in vivo by melatonin.
Melatonin inhibited thymidine incorporation into human choriocarcinoma JEG-3 cells at physiological and pharmacological concentrations in the present study. Gene expression of MT2 receptor, but not that of mt1 receptor, was detected in JEG-3 cells by reverse transcription-polymerase chain reaction (RT-PCR). The gene expression profile of the two human melatonin receptor subtypes in JEG-3 cells was identical to that previously reported for JAr cells, whose proliferation had also been shown to be similarly inhibited by physiological and pharmacological concentrations of melatonin. In contrast, melatonin had no effect on thymidine incorporation into 3A-Sub-E cells (a transformed trophoblast cell line), in which gene expression of both receptor subtypes could not be detected. The data suggest that in human placental trophoblasts, a correlation may exist between MT2 receptor gene expression and the direct anti-proliferative action of melatonin. Although melatonin has been reported to induce G1/S delay in cell cycle progression of JAr cells, no significant changes in the percentages of JEG-3 cells in different cell cycle phases upon melatonin treatment was recorded by flow cytometric analysis. This indicates that G1/S transition delay is probably not an important cellular mechanism in the direct anti-proliferative action of melatonin on human JEG-3 cells in vitro. Furthermore, melatonin inhibited the growth of both JAr and JEG-3 xenograft tumors in athymic nude mice, and prolonged the survival of those animals that developed choriocarcinoma. While the number of apoptotic tumor cells was not increased by melatonin, the pineal hormone induced significant decreases in the numbers of JAr and JEG-3 cells expressing proliferating cell nuclear antigen (PCNA) and cyclin A in the tumors. Taking into account both the in vitro and in vivo findings, it is likely that the inhibitory effect of melatonin on choriocarcinoma JAr and JEG-3 cell proliferation in vivo is largely a direct action of the hormone on the tumor cells.
Animals↗
Requirement of SHP2 binding to Grb2-associated binder-1 for mitogen-activated protein kinase activation in response to lysophosphatidic acid and epidermal growth factor.
Grb2-associated binder-1 (Gab1) is a multisite docking protein containing a pleckstrin homology (PH) domain, multiple potential tyrosine phosphorylation sites, and several proline-rich sequences. Gab1 becomes tyrosine-phosphorylated in cells stimulated with growth factors, cytokines, and ligands for G protein-coupled receptors. A major Gab1-binding protein detected in cells treated with extracellular stimuli is the tyrosine phosphatase, SHP2. Although the role of SHP2-Gab1 interaction in cell signaling has not yet been characterized, SHP2 is known to mediate mitogen-activated protein (MAP) kinase activation induced by the epidermal growth factor (EGF). However, the mechanism by which the SHP2 phosphatase exerts a positive signaling role remains obscure. In this study, we prepared Gab1 mutants lacking the SHP2 binding site (Gab1Y627F), the phosphatidylinositol 3-kinase (PI3K) binding sites (Gab1DeltaPI3K), and the PH domain (Gab1DeltaPH). Expression of Gab1Y627F blocked the extracellular signal-regulated kinase-2 (ERK2) activation by lysophosphatidic acid (LPA) and EGF. Conversely, expression of the wild-type Gab1 in HEK293 cells augmented the LPA receptor Edg2-mediated ERK2 activation. Whereas the PH domain was required for Gab1 mediation of ERK2 activation by LPA, it was not essential for EGF-induced ERK2 activation. Expression of Gab1DeltaPI3K had no apparent effect on ERK2 activation by LPA and EGF in the cells that we have examined. These results establish a role for Gab1 in the LPA-induced MAP kinase pathway and clearly demonstrate that Gab1-SHP2 interaction is essential for ERK2 activation by LPA and EGF. These findings also suggest that the positive role of SHP2 in the MAP kinase pathway depends on its interaction with Gab1.
Animals↗
Expression of PSD-95/SAP90 is critical for N-methyl-D-aspartate receptor-mediated thermal hyperalgesia in the spinal cord.
PSD-95/SAP90, a molecular scaffold protein, attaches the N-methyl-D-aspartate receptor to cellular signaling pathways through PSD-95/DLG/Z0-1 domain interactions at neuronal synapses.(5,9) This suggests that PSD-95/SAP90 might be involved in many physiological and pathophysiological actions triggered via the N-methyl-D-aspartate receptor in the central nervous system. Here, we present evidence that suppression of the expression of PSD-95/SAP90 in the spinal cord significantly attenuated facilitation of the tail-flick reflex triggered through N-methyl-D-aspartate receptor activation but not baseline tail-flick reflex latency. Moreover, PSD-95/SAP90's messenger RNA and protein were enriched in the spinal cord and selectively distributed in the superficial dorsal horn, where PSD-95/SAP90 overlapped with the N-methyl-D-aspartate receptor. In spinal cord neurons, PSD-95/SAP90 interacted with the N-methyl-D-aspartate receptor subunits 2A/2B. It is indicated that activation of the N-methyl-D-aspartate receptor in spinal hyperalgesia results in association of the N-methyl-D-aspartate receptor with PSD-95/SAP90 and that PSD-95/SAP90 is required for noxious thermal hyperalgesia triggered via the N-methyl-D-aspartate receptor at the spinal cord level. The present findings may provide novel insights into the mechanisms for persistent sensitization of the somatosensory system.
Animals↗
Regulation of neuregulin signaling by PSD-95 interacting with ErbB4 at CNS synapses.
Neuregulins (NRGs) and their receptors, the ErbB protein tyrosine kinases, are essential for neuronal development, but their functions in the adult CNS are unknown. We report that ErbB4 is enriched in the postsynaptic density (PSD) and associates with PSD-95. Heterologous expression of PSD-95 enhanced NRG activation of ErbB4 and MAP kinase. Conversely, inhibiting expression of PSD-95 in neurons attenuated NRG-mediated activation of MAP kinase. PSD-95 formed a ternary complex with two molecules of ErbB4, suggesting that PSD-95 facilitates ErbB4 dimerization. Finally, NRG suppressed induction of long-term potentiation in the hippocampal CA1 region without affecting basal synaptic transmission. Thus, NRG signaling may be synaptic and regulated by PSD-95. A role of NRG signaling in the adult CNS may be modulation of synaptic plasticity.
Animals↗