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91.
Effect of sodium butyrate on mammalian cells in culture: A review   总被引:10,自引:0,他引:10  
Summary Sodium butyrate produces reversible changes in morphology, growth rate, and enzyme activities of several mammalian cell types in culture. Some of these changes are similar to those produced by agents which increase the intracellular level of adenosine 3′,5′-cyclic monophosphate (cAMP) or by analogs of cAMP. Sodium butyrate increases the intracellular level of cAMP by about two fold in neuroblastoma cells; therefore, some of the effects of sodium butyrate on these cells may in part be mediated by cAMP. Sodium butyrate appears to have properties of a good chemotherapeutic agent for neuroblastoma tumors because the treatment of neuroblastoma cells in culture causes cell death and “differentiation”; however, it is either innocuous or produces reversible morphological and biochemical alterations in other cell types.  相似文献   
92.
Animal cells initiate cytokinesis in parallel with anaphase onset, when an actomyosin ring assembles and constricts through localized activation of the small GTPase RhoA, giving rise to a cleavage furrow. Furrow formation relies on positional cues provided by anaphase spindle microtubules (MTs), but how such cues are generated remains unclear. Using chemical genetics to achieve both temporal and spatial control, we show that the self-organized delivery of Polo-like kinase 1 (Plk1) to the midzone and its local phosphorylation of a MT-bound substrate are critical for generating this furrow-inducing signal. When Plk1 was active but unable to target itself to this equatorial landmark, both cortical RhoA recruitment and furrow induction failed to occur, thus recapitulating the effects of anaphase-specific Plk1 inhibition. Using tandem mass spectrometry and phosphospecific antibodies, we found that Plk1 binds and directly phosphorylates the HsCYK-4 subunit of centralspindlin (also known as MgcRacGAP) at the midzone. At serine 157, this modification creates a major docking site for the tandem BRCT repeats of the Rho GTP exchange factor Ect2. Cells expressing only a nonphosphorylatable form of HsCYK-4 failed to localize Ect2 at the midzone and were severely impaired in cleavage furrow formation, implying that HsCYK-4 is Plk1's rate-limiting target upstream of RhoA. Conversely, tethering an inhibitor-resistant allele of Plk1 to HsCYK-4 allowed furrows to form despite global inhibition of all other Plk1 molecules in the cell. Our findings illuminate two key mechanisms governing the initiation of cytokinesis in human cells and illustrate the power of chemical genetics to probe such regulation both in time and space.  相似文献   
93.
Epigenetic mechanisms of plant stress responses and adaptation   总被引:3,自引:0,他引:3  
Epigenetics has become one of the hottest topics of research in plant functional genomics since it appears promising in deciphering and imparting stress-adaptive potential in crops and other plant species. Recently, numerous studies have provided new insights into the epigenetic control of stress adaptation. Epigenetic control of stress-induced phenotypic response of plants involves gene regulation. Growing evidence suggest that methylation of DNA in response to stress leads to the variation in phenotype. Transposon mobility, siRNA-mediated methylation and host methyltransferase activation have been implicated in this process. This review presents the current status of epigenetics of plant stress responses with a view to use this knowledge towards engineering plants for stress tolerance.  相似文献   
94.
Horseshoe crabs are the only extant xiphosurans and are believed to be morphologically unchanged for more than 200 million years. Of the four extant species namely, Limulus polyphemus, Tachypleus tridentatus, Tapinauchenius gigas and Carcinoscorpius rotundicauda, the latter three are found in Asian waters. Recent evidences showed that Asian horseshoe crabs are facing serious threats such as degradation of their spawning grounds and habitat, environmental pollution, overexploitation as a culinary delicacy and biomedical bleeding practices. Baseline data on the distribution and existing population of the wild horseshoe crabs remain poorly known in several Asian regions. Several studies have clearly revealed that pressure due to over-fishing of wild stock has increased tremendously in the last decade. Due to an increase in demand for Tachypleus Amebocyte Lysate (TAL) analogous to Limulus Amebocyte Lysate (LAL) in the United States, there is an urgent need to comprehensively address their fishing and conservation measures in the Asian region. This review addresses the overall studies on three species of Asian horseshoe crabs in relation to their fishing practices, local exploitation of their wild stock either for human consumption (or) by biomedical industries. The authors have structured the discussion on an international scale to address the existing problems in fishing and conservation of horseshoe crabs. Since no specific regulatory force or legislative protection act or a policy to preserve their natural stock are available to this date, this paper strongly recommends representative countries to include horseshoe crabs under their wildlife protection act to avoid further unsustainable exploitation of their wild populations.  相似文献   
95.
The present investigation attempt to analyze the biosorption behavior of novel biosorbent, Araucaria heterophylla (green plant) biomass, for removal of Pb+2 from solution as the function of initial metal ion concentration, pH, temperature, sorbent dosage and biomass particle size. The maximum biosorption was found to be 95.12% at pH 5 and biosorption capacity (qe) of Cd+2 is 9.643 mg/g. The Langmuir and Freundlich equilibrium adsorption isotherms were studied and observed that Freundlich model is best fit than the Langmuir model with correlation coefficient of 0.9927. Kinetic studies indicated that the biosorption process of Cd+2 followed well pseudo second order model with R2 0.999. The process is exothermic and, spontaneous. The chemical functional groups –OH, CH2 stretching vibrations, C?O of alcohol, C?O of amide, P?O stretching vibrations, –CH, were involved in the process. The XRD pattern of the A. heterophylla was found to be mostly amorphous in nature. The SEM studies showed Pb+2 biosorption on selective grains of the biosorbent. It was concluded that A. heterophylla leaf powder can be used as an effective, low cost, and environmentally friendly biosorbent for the removal of Pb+2 from aqueous solution.  相似文献   
96.
Multi-protein complexes, termed “inflammasomes,” are known to contribute to neuronal cell death and brain injury following ischemic stroke. Ischemic stroke increases the expression and activation of nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) Pyrin domain containing 1 and 3 (NLRP1 and NLRP3) inflammasome proteins and both interleukin (IL)-1β and IL-18 in neurons. In this study, we provide evidence that activation of either the NF-κB and MAPK signaling pathways was partly responsible for inducing the expression and activation of NLRP1 and NLRP3 inflammasome proteins and that these effects can be attenuated using pharmacological inhibitors of these two pathways in neurons and brain tissue under in vitro and in vivo ischemic conditions, respectively. Moreover, these findings provided supporting evidence that treatment with intravenous immunoglobulin (IVIg) preparation can reduce activation of the NF-κB and MAPK signaling pathways resulting in decreased expression and activation of NLRP1 and NLRP3 inflammasomes, as well as increasing expression of anti-apoptotic proteins, Bcl-2 and Bcl-xL, in primary cortical neurons and/or cerebral tissue under in vitro and in vivo ischemic conditions. In summary, these results provide compelling evidence that both the NF-κB and MAPK signaling pathways play a pivotal role in regulating the expression and activation of NLRP1 and NLRP3 inflammasomes in primary cortical neurons and brain tissue under ischemic conditions. In addition, treatment with IVIg preparation decreased the activation of the NF-κB and MAPK signaling pathways, and thus attenuated the expression and activation of NLRP1 and NLRP3 inflammasomes in primary cortical neurons under ischemic conditions. Hence, these findings suggest that therapeutic interventions that target inflammasome activation in neurons may provide new opportunities in the future treatment of ischemic stroke.  相似文献   
97.
Slit, which mediates its function by binding to the Roundabout (Robo) receptor, has been shown to regulate neuronal and CXCR4-mediated leukocyte migration. Slit-2 was shown to be frequently inactivated in lung and breast cancers because of hypermethylation of its promoter region. Furthermore, the CXCR4/CXCL12 axis has been reported recently to be actively involved in breast cancer metastasis to target organs such as lymph nodes, lung, and bone. In this study, we sought to characterize the effect of Slit (=Slit-2) on the CXCL12/CXCR4-mediated metastatic properties of breast cancer cells. We demonstrate here that breast cancer cells and tissues derived from breast cancer patients express Robo 1 and 2 receptors. We also show that Slit treatment inhibits CXCL12/CXCR4-induced breast cancer cell chemotaxis, chemoinvasion, and adhesion, the fundamental components that promote metastasis. Slit had no significant effect on the CXCL12-induced internalization process of CXCR4. In addition, characterization of signaling events revealed that Slit inhibits CXCL12-induced tyrosine phosphorylation of focal adhesion components such as RAFTK/Pyk2 at residues 580 and 881, focal adhesion kinase at residue 576, and paxillin. We found that Slit also inhibits CXCL12-induced phosphatidylinositol 3-kinase, p44/42 MAP kinase, and metalloproteinase 2 and 9 activities. However, it showed no effect on JNK and p38 MAP kinase activities. To our knowledge, this is the first report to analyze in detail the effect of Slit on breast cancer cell motility as well as its effect on the critical components of the cancer cell chemotactic machinery. Studies of the Slit-Robo complex may foster new anti-chemotactic approaches to block cancer cell metastasis.  相似文献   
98.
Abnormal activation of the Wnt/β-catenin signaling pathway and subsequent upregulation of β-catenin driven downstream targets—c-Myc and cyclin D1 is associated with development of breast cancer. The objective of our study was to determine if curcumin could modulate the key elements of Wnt pathway in breast cancer cells; an effect that might underscore its usefulness for chemoprevention/treatment of this malignancy. Curcumin showed a cytotoxic effect on MCF-7 cells with 50% inhibitory concentration (IC50) of 35 μM; while IC50 for MDA-MB-231 cells was 30 μM. Treatment with low cytostatic dose of 20 μM curcumin showed G2/M arrest in both breast cancer cells. The effect of curcumin (20 μM) treatment on expression of Wnt/β-catenin pathway components in breast cancer cells (MCF-7 and MDA-MB-231) was analyzed by immunofluorescence and Western blotting. Curcumin was found to effectively inhibit the expression of several Wnt/β-catenin pathway components—disheveled, β-catenin, cyclin D1 and slug in both MCF-7 and MDA-MB-231. Immunofluorescence analysis showed that curcumin markedly reduced the nuclear expression of disheveled and β-catenin proteins. Further, the protein levels of the positively regulated β-catenin targets—cyclin D1 and slug, were downregulated by curcumin treatment. The expression levels of two integral proteins of Wnt signaling, GSK3β and E-cadherin were also altered by curcumin treatment. In conclusion, our data demonstrated that the efficacy of curcumin in inhibition of cell proliferation and induction of apoptosis might occur through modulation of β-catenin pathway in human breast cancer cells.  相似文献   
99.
Aims Studies of the climatic responses of plant assemblages via vegetation-based environmental reconstructions by weighted averaging (WA) regression and calibration are a recent development in modern vegetation ecology. However, the performance of this technique for plot-based vegetation datasets has not been rigorously tested. We assess the estimation accuracy of the WA approach by comparing results, mainly the root mean square error of prediction (RMSEP) of WA regressions for six different vegetation datasets (total species, high-frequency species and low-frequency species as both abundance and incidence) each from two sites.  相似文献   
100.
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