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991.
992.
Kohzaburo Fujikawa‐Yamamoto Xianwen Luo Minoru Miyagoshi Hiroko Yamagishi 《Journal of cellular physiology》2010,223(2):369-375
Pentaploid H1 (ES) cells (5H1 cells) were accidentally obtained through one‐cell cloning of octaploid H1 (ES) cells (8H1 cells) that were established from tetraploid H1 (ES) cells (4H1 cells) polyploidized using demecolcine. The number of chromosomes of 5H1 cells was 100, unlike the 40 of diploid H1 (ES) cells (2H1 cells), 80 of 4H1, and 160 of 8H1 cells. The durations of G1, S, and G2/M phases of 5H1 cells were 3, 7, and 6 h, respectively, almost the same as those of 2H1, 4H1, and 8H1 cells. The cell volume of 5H1 cells was half of that of 8H1 cells, suggesting that 5H1 cells were created through abnormal cell divisions of 8H1 cells. The morphology of growing 5H1 cells was a spherical cluster similar to that of 2H1 cells and differing from the flagstone‐like shape of 4H1 and 8H1 cells. Pentaploid solid tumors were formed from 5H1 cells after interperitoneal injection into the mouse abdomen, and they contained endodermal, mesodermal, and ectodermal cells as well as undifferentiated cells, suggesting both that the DNA content of 5H1 cells was retained during tumor formation and that the 5H1 cells were pluripotent. The DNA content of 5H1 cells was stable in long‐term culturing as 2H1 cells, meaning that 5H1 and 2H1 cells shared similarities in DNA structure. The excellent stability of the DNA content of 5H1 cells was explained using a hypothesis for the DNA structure of polyploid cells because the pairing of homologous chromosomes in 5H1 cells is spatially forbidden. J. Cell. Physiol. 223: 369–375, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
993.
Sze‐Ying Ng Chi‐Hou Chin Yuen‐Ting Lau Jialie Luo Chun‐Kit Wong Zhao‐Xiang Bian Suk‐Ying Tsang 《Journal of cellular physiology》2010,224(1):165-177
Embryonic stem cells (ESCs) possess two unique characteristics: self‐renewal and pluripotency. In this study, roles of voltage‐gated potassium channels (Kv) in maintaining mouse (m) ESC characteristics were investigated. Tetraethylammonium (TEA+), a Kv blocker, attenuated cell proliferation in a concentration‐dependent manner. Possible reasons for this attenuation, including cytotoxicity, cell cycle arrest and differentiation, were examined. Blocking Kv did not change the viability of mESCs. Interestingly, Kv inhibition increased the proportion of cells in G0/G1 phase and decreased that in S phase. This change in cell cycle distribution can be attributed to cell cycle arrest or differentiation. Loss of pluripotency as determined at both molecular and functional levels was detected in mESCs with Kv blockade, indicating that Kv inhibition in undifferentiated mESCs directs cells to differentiate instead of to self‐renew and progress through the cell cycle. Membrane potential measurement revealed that Kv blockade led to depolarization, consistent with the role of Kv as the key determinant of membrane potential. The present results suggest that membrane potential changes may act as a “switch” for ESCs to decide whether to proliferate or to differentiate: hyperpolarization at G1 phase would favor ESCs to enter S phase while depolarization would favor ESCs to differentiate. Consistent with this notion, S‐phase‐synchronized mESCs were found to be more hyperpolarized than G0/G1‐phase‐synchronized mESCs. Moreover, when mESCs differentiated, the differentiation derivatives depolarized at the initial stage of differentiation. This investigation is the first study to provide evidence that Kv and membrane potential affect the fate determination of ESCs. J. Cell. Physiol. 224:165–177, 2010 © 2010 Wiley‐Liss, Inc. 相似文献
994.
Meng Luo Xia Liu Yuangang Zu Yujie Fu Su Zhang Liping Yao Thomas Efferth 《Chemico-biological interactions》2010,188(1):151-160
Cajanol (5-hydroxy-3-(4-hydroxy-2-methoxyphenyl)-7-methoxychroman-4-one) is an isoflavanone from Pigeonpea [Cajanus cajan (L.) Millsp.] roots. As the most effective phytoalexin in pigeonpea, the cytotoxic activity of cajanol towards cancer cells has not been report as yet. In the present study, the anticancer activity of cajanol towards MCF-7 human breast cancer cells was investigated. In order to explore the underlying mechanism of cell growth inhibition of cajanol, cell cycle distribution, DNA fragmentation assay and morphological assessment of nuclear change, ROS generation, mitochondrial membrane potential (ΔΨm) disruption, and expression of caspase-3 and caspase-9, Bax, Bcl-2, PARP and cytochrome c were measured in MCF-7 cells. Cajanol inhibited the growth of MCF-7 cells in a time and dose-dependent manner. The IC50 value was 54.05 μM after 72 h treatment, 58.32 μM after 48 h; and 83.42 μM after 24 h. Cajanol arrested the cell cycle in the G2/M phase and induced apoptosis via a ROS-mediated mitochondria-dependent pathway. Western blot analysis showed that cajanol inhibited Bcl-2 expression and induced Bax expression to desintegrate the outer mitochondrial membrane and causing cytochrome c release. Mitochondrial cytochrome c release was associated with the activation of caspase-9 and caspase-3 cascade, and active-caspase-3 was involved in PARP cleavage. All of these signal transduction pathways are involved in initiating apoptosis. To the best of our knowledge, this is the first report demonstrating the cytotoxic activity of cajanol towards cancer cells in vitro. 相似文献
995.
996.
Functional interaction of human neutrophil peptide-1 with the cell wall precursor lipid II 总被引:1,自引:0,他引:1
Defensins constitute a major class of cationic antimicrobial peptides in mammals and vertebrates, acting as effectors of innate immunity against infectious microorganisms. It is generally accepted that defensins are bactericidal by disrupting the anionic microbial membrane. Here, we provide evidence that membrane activity of human α-defensins does not correlate with antibacterial killing. We further show that the α-defensin human neutrophil peptide-1 (HNP1) binds to the cell wall precursor lipid II and that reduction of lipid II levels in the bacterial membrane significantly reduces bacterial killing. The interaction between defensins and lipid II suggests the inhibition of cell wall synthesis as a novel antibacterial mechanism of this important class of host defense peptides. 相似文献
997.
998.
999.
Variations in sulfation of heparan sulfate (HS) affect interaction with FGF, FGFR, and FGF-HS-FGFR signaling complexes. Whether structurally distinct HS motifs are at play is unclear. Here we used stabilized recombinant FGF7 as a bioaffinity matrix to purify size-defined heparin oligosaccharides. We show that only 0.2%-4% of 6 to 14 unit oligosaccharides, respectively, have high affinity for FGF7 based on resistance to salt above 0.6M NaCl. The high affinity fractions exhibit highest specific activity for interaction with FGFR2IIIb and formation of complexes of FGF7-HS-FGFR2IIIb. The majority fractions with moderate (0.30-0.6M NaCl), low (0.14-0.30M NaCl) or no affinity at 0.14M NaCl for FGF7 supported no complex formation. The high affinity octasaccharide mixture exhibited predominantly 7- and 8-sulfated components (7,8-S-OctaF7) and formed FGF7-HS-FGFR2IIIb complexes with highest specific activity. Deduced disaccharide analysis indicated that 7,8-S-OctaF7 comprised of DeltaHexA2SGlcN6S in a 2:1 ratio to a trisulfated and a variable unsulfated or monosulfated disaccharide. The inactive octasaccharides with moderate affinity for FGF7 were much more heterogenous and highly sulfated with major components containing 11 or 12 sulfates comprised of predominantly trisulfated disaccharides. This suggests that a rare undersulfated motif in which sulfate groups are specifically distributed has highest affinity for FGF7. The same motif also exhibits structural requirements for high affinity binding to dimers of FGFR2IIIb prior to binding FGF7 to form FGF7-HS-FGFR2IIIb complexes. In contrast, the majority of more highly sulfated HS motifs likely play FGFR-independent roles in stability and control of access of FGF7 to FGFR2IIIb in the tissue matrix. 相似文献
1000.
Inactivation of the cyclic nucleotide signal in granulosa cells depends on a complex array of cyclic nucleotide phosphodiesterases (PDE). In order to examine the role of PDE in cyclic AMP (cAMP) signaling in granulosa cells, the present study examined the expression of PDE4D proteins and regulation of cAMP-PDE activities in cultured rat granulosa cells. The results of immunoblot analyses showed that two predominant PDE4D subtypes of approximately 80 and 70 kDa appeared when immature rat granulosa cells were treated with FSH. However, these two new subtypes presumed to be PDE4D proteins were not influenced by treatments of DETA/NO, cGMP and PKB inhibitor, LY294002. Immature rat granulosa cells treated with medium alone displayed low cAMP-PDE activity throughout 48 h of culture while those treated with FSH (2 ng.mL-1) showed a marked increase in cAMP-PDE activity between 6 and 12 h of culture, followed by a decline. The findings from the present study indicate that the increased cAMP-PDE activity by FSH is mainly related to the changes of PDE4D protein levels. However, the inhibitory effects of NO on cAMP accumulation in rat granulosa cells are not via the increased cAMP-PDE activity. 相似文献