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991.
Rho GTPases regulate axon growth through convergent and divergent signaling pathways 总被引:10,自引:0,他引:10
Rho GTPases are essential regulators of cytoskeletal reorganization, but how they do so during neuronal morphogenesis in vivo is poorly understood. Here we show that the actin depolymerization factor cofilin is essential for axon growth in Drosophila neurons. Cofilin function in axon growth is inhibited by LIM kinase and activated by Slingshot phosphatase. Dephosphorylating cofilin appears to be the major function of Slingshot in regulating axon growth in vivo. Genetic data provide evidence that Rho or Rac/Cdc42, via effector kinases Rok or Pak, respectively, activate LIM kinase to inhibit axon growth. Importantly, Rac also activates a Pak-independent pathway that promotes axon growth, and different RacGEFs regulate these distinct pathways. These genetic analyses reveal convergent and divergent pathways from Rho GTPases to the cytoskeleton during axon growth in vivo and suggest that different developmental outcomes could be achieved by biases in pathway selection. 相似文献
992.
Kintner DB Su G Lenart B Ballard AJ Meyer JW Ng LL Shull GE Sun D 《American journal of physiology. Cell physiology》2004,287(1):C12-C21
The ubiquitously expressed Na(+)/H(+) exchanger isoform 1 (NHE1) functions as a major intracellular pH (pH(i)) regulatory mechanism in many cell types, and in some tissues its activity may contribute to ischemic injury. In the present study, cortical astrocyte cultures from wild-type (NHE1(+/+)) and NHE1-deficient (NHE1(-/-)) mice were used to investigate the role of NHE1 in pH(i) recovery and ischemic injury in astrocytes. In the absence of HCO(3)(-), the mean resting pH(i) levels were 6.86 +/- 0.03 in NHE1(+/+) astrocytes and 6.53 +/- 0.04 in NHE1(-/-) astrocytes. Removal of extracellular Na(+) or blocking of NHE1 activity by the potent NHE1 inhibitor HOE-642 significantly reduced the resting level of pH(i) in NHE1(+/+) astrocytes. NHE1(+/+) astrocytes exhibited a rapid pH(i) recovery (0.33 +/- 0.08 pH unit/min) after NH(4)Cl prepulse acid load. The pH(i) recovery in NHE1(+/+) astrocytes was reversibly inhibited by HOE-642 or removal of extracellular Na(+). In NHE1(-/-) astrocytes, the pH(i) recovery after acidification was impaired and not affected by either Na(+)-free conditions or HOE-642. Furthermore, 2 h of oxygen and glucose deprivation (OGD) led to an approximately 80% increase in pH(i) recovery rate in NHE1(+/+) astrocytes. OGD induced a 5-fold rise in intracellular [Na(+)] and 26% swelling in NHE1(+/+) astrocytes. HOE-642 or genetic ablation of NHE1 significantly reduced the Na(+) rise and swelling after OGD. These results suggest that NHE1 is the major pH(i) regulatory mechanism in cortical astrocytes and that ablation of NHE1 in astrocytes attenuates ischemia-induced disruption of ionic regulation and swelling. 相似文献
993.
Unbiased mapping of transcription factor binding sites along human chromosomes 21 and 22 points to widespread regulation of noncoding RNAs 总被引:76,自引:0,他引:76
994.
A less competent murine in vitro maturation (IVM) model was achieved by shortening the standard duration of in vivo PMSG stimulation from 48 to 24 h and selecting only naked/partially naked GV oocytes from a mixture of large and small follicles. Porcine granulosa coculture enhanced meiotic maturation within such a less competent model (37.3% versus 23.1%, P<0.05), while no significant enhancement was observed with macaque and murine granulosa coculture. Culture of porcine granulosa on extracellular matrix (ECM) gel resulted in a more differentiated morphology, but did not significantly further enhance the beneficial effects it already had on meiotic maturation. Increased concentrations of serum as well as the supplementation of gonadotrophins and follicular fluid within the culture milieu did not enhance IVM under both cell-free and coculture conditions. Porcine granulosa-conditioned medium also enhanced meiotic maturation (36.5% versus 26.7%, P<0.05), which was not diminished upon freeze-thawing (35.8% versus 22.6%, P<0.05). Enhancement of meiotic maturation by porcine granulosa coculture did not however translate to significant improvements in developmental competence, as assessed by in vitro fertilization (IVF) and embryo culture to the blastocyst stage, followed by total cell counts. ECM gel had a detrimental effect on fertilization and developmental competence, even though it had no detrimental effect on meiotic maturation itself. 相似文献
995.
Ng WK 《Acta cytologica》2003,47(6):1045-1049
BACKGROUND: Cytoplasmic eosinophilia in breast tumors is due mainly to abundance of secretory granules, lysosomes and/or mitochondria. Diffuse cytoplasmic hyalinization caused by intermediate filaments has not been described before. CASES: Two cases of pure mammary mucinous carcinoma occurred with marked cytoplasmic hyalinization among 556 wide excision/mastectomy specimens of mammary ductal carcinoma, either in situ or invasive, encountered at Pamela Youde Nethersole Eastern Hospital, Hong Kong, during the period from 1994 to the end of 2001. Preoperative fine needle aspiration cytology was available in 1 case, showing cohesive clusters and micropapillae of tumor cells in abundant background mucin. The tumor cells had low mitotic activity and possessed round to oval nuclei, solitary macronucleoli; ample, eosinophilic cytoplasm and discrete cell borders. Cytoplasmic granularity, intracytoplasmic vacuoles or "cometlike" cells were not found. Histologic examination of the surgical specimens in both cases revealed pure mucinous carcinoma with diffuse and marked cytoplasmic hyalinization. There was no evidence of peritumoral lymphovascular permeation or regional lymph node metastasis. Ultrastructural examination showed minimal secretory activity, with abundant, loose aggregates of intermediate filaments in the cytoplasm. There was a relative paucity of other organelles. CONCLUSION: Diffuse cytoplasmic hyalinization is a peculiar morphologic change in mammary ductal carcinoma and apparently unique to pure mucinous carcinoma. Recognition of this phenomenon may help to avoid misdiagnosis of other types of ductal carcinoma with cytoplasmic eosinophilia, such as apocrine carcinoma and ductal carcinoma with neuroendocrine differentiation, which sometimes are also associated with pools of extracellular mucin. 相似文献
996.
OBJECTIVE: To describe the thin-layer cytology (if available) and histologic findings of warty (condylomatous) carcinoma of the cervix, with molecular analysis for HPV screening. STUDY DESIGN: The authors reviewed the clinical features, thin-layer cytology (if available) and histologic findings of all cases of warty carcinoma of the cervix encountered at Pamela Youde Nethersole Eastern Hospital, Hong Kong, during the 4-year period January 1998-April 2002. Molecular techniques for HPV screening using polymerase chain reaction were carried out on thin-layer cytology specimens or paraffin-embedded tumor tissue. RESULTS: Three cases of warty carcinoma of the cervix were encountered during the study period. Thin-layer preparations (Autocyte, TriPath Imaging, Burlington, North Carolina, U.S.A.) were available for 2 of them, and both were of moderate cellularity. There were small, cohesive clusters and syncytial sheets of tumor cells with vague papillary configurations. Dispersed squamous carcinoma cells and necrotic tumor debris (diathesis) were focally present in the background. The tumor cells were polygonal to elongated and contained oval nuclei, coarse chromatin and sometimes distinct nucleoli. Dyskeratotic tumor cells with bizarre shapes were also noted. Characteristically, there were also many koilocytes demonstrating extreme nuclear atypia and increased nuclear/cytoplasm ratio. These koilocytic cells possessed pleomorphic nuclei, distinct nucleoli and perinuclear cytoplasmic halos. Histologic examination of the tumor biopsies showed classic features of warty carcinoma, with papillary architecture, obvious koilocytic cytopathic change and focal stromal invasion. Molecular analysis confirmed the presence of HPV DNA in all the samples. CONCLUSION: Although koilocytes are rarely found in cervical cytology specimens of conventional squamous cell carcinoma, they are characteristically observed in warty carcinoma. A correct cytologic diagnosis is possible if one pays attention to the extreme koilocytic atypia, focal papillary configurations and otherwise classic features of squamous cell carcinoma. Abundance of koilocytes does not necessarily rule out invasive malignancy. 相似文献
997.
Ng WK 《Acta cytologica》2003,47(2):141-148
OBJECTIVE: To describe the thin-layer cytology and diagnostic pitfalls of papillary squamotransitional cell carcinoma of the cervix, with clinical and histologic correlation. STUDY DESIGN: The author reviewed the clinical findings, thin-layer cytology and histologic features of papillary squamotransitional cell carcinoma of the cervix encountered at Pamela Youde Nethersole Eastern Hospital, Hong Kong, during the 4-year period January 1998-March 2002. Strict histologic criteria (basaloid/transitional cell-like cells constituted > 70% of the tumor cell population and papillary/anastomosing, frondlike structures seen in > 70% of tumor tissue in superficial biopsies) were employed in defining this entity. RESULTS: During the study period, 10 biopsy cases of carcinoma of the lower female genital tract (9 in cervix and 1 in vagina) fulfilled the above histologic criteria. Six of them had thin-layer cytology performed The preparations were often of moderate to high cellularity and contained three-dimensional, arborizing, papillary clusters of basal/parabasal cells. Discernible fibrovascular cores were sometimes identified. Occasionally at the papillary surface, the basaloid cells were aligned horizontally. High-power cytology of the tumor cells ranged from bland-looking to high grade squamous intraepithelial lesions (HSILs) and sometimes squamous cell carcinoma. Mitotic figures were commonly identified. Tumor diathesis and dyskeratotic cells were occasional. Koilocytosis was not observed. Subsequent tumor biopsies showed evidence of stromal invasion in 3 cases. CONCLUSION: Papillary squamotransitional cell carcinoma has a distinctive appearance in thin-layer cytologic preparations. The predominance of bland-looking basaloid cells or HSIL cells, together with scantiness of tumor diathesis and carcinoma cells, may lead to underdiagnosis. Recognition of the subtle cytologic features and clinical correlation are essential in arriving at a correct diagnosis. 相似文献
998.
During embryo implantation in species with hemochorial placentation, such as the mouse and human, trophoblast cells of the attached blastocyst penetrate the luminal epithelium of the endometrium before invasion into the endometrial stroma. Signs of apoptosis were demonstrated in luminal endometrial epithelial cells (EEC) adjacent to the trophoblast cells; however, the signaling mechanisms leading to apoptosis in EEC remain unclear. Because mitogen-activated protein kinases (MAPK) were shown to mediate apoptosis in several model systems and found to be activated in the uterus during decidualization, the possible involvement of MAPK during trophoblast-EEC interactions was studied. By coculturing BeWo human trophoblast spheroids with RL95-2 human EEC monolayers to mimic the blastocyst-endometrial interaction, we found that most spheroids rapidly attached to EEC monolayers and then progressively expanded, with marked dislodgment of EEC adjacent to the spreading trophoblast cells. Immunoblotting analysis showed that both p38 MAPK and extracellular signal-regulated kinase (ERK) were activated in EEC after coculture. However, only SB203580 (a p38 MAPK inhibitor), but not PD98059 (an ERK inhibitor), inhibited trophoblast outgrowth on EEC monolayers through the suppression of p38 MAPK activation in EEC. Furthermore, trophoblast expansion caused prominent EEC apoptosis at the spheroid-EEC interface, as detected by annexin V labeling and valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (which binds activated caspases) staining, and SB203580 significantly decreased the percentage of apoptotic cells. Our results, based on a model of human trophoblast-EEC interactions, establish that trophoblast cells cause activation of p38 MAPK in EEC and, consequently, induce apoptosis and displacement of EEC, a process that may facilitate implantation. 相似文献
999.
Wang M Ng KK Cherney MM Chan L Yannopoulos CG Bedard J Morin N Nguyen-Ba N Alaoui-Ismaili MH Bethell RC James MN 《The Journal of biological chemistry》2003,278(11):9489-9495
X-ray crystal structures of two non-nucleoside analogue inhibitors bound to hepatitis C virus NS5B RNA-dependent RNA polymerase have been determined to 2.0 and 2.9 A resolution. These noncompetitive inhibitors bind to the same site on the protein, approximately 35 A from the active site. The common features of binding include a large hydrophobic region and two hydrogen bonds between both oxygen atoms of a carboxylate group on the inhibitor and two main chain amide nitrogen atoms of Ser(476) and Tyr(477) on NS5B. The inhibitor-binding site lies at the base of the thumb domain, near its interface with the C-terminal extension of NS5B. The location of this inhibitor-binding site suggests that the binding of these inhibitors interferes with a conformational change essential for the activity of the polymerase. 相似文献
1000.
METHODS AND RESULTS: We introduce a new method to discover many diversified and significant rules from high dimensional profiling data. We also propose to aggregate the discriminating power of these rules for reliable predictions. The discovered rules are found to contain low-ranked features; these features are found to be sometimes necessary for classifiers to achieve perfect accuracy. The use of low-ranked but essential features in our method is in contrast to the prevailing use of an ad-hoc number of only top-ranked features. On a wide range of data sets, our method displayed highly competitive accuracy compared to the best performance of other kinds of classification models. In addition to accuracy, our method also provides comprehensible rules to help elucidate the translation between raw data and useful knowledge. 相似文献