|
| ||
|
|
||
Cell Division (cell + division)
Kinds of Cell Division Terms modified by Cell Division Selected AbstractsKinematic Analysis of Leaf Growth in Grasses: A Comment on Spatial and Temporal Quantitative Analysis of Cell Division and Elongation Rate in Growing Wheat Leaves under Saline ConditionsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2009Hans Schnyder [source] Spatial and Temporal Quantitative Analysis of Cell Division and Elongation Rate in Growing Wheat Leaves under Saline ConditionsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 1 2008Yuncai Hu Abstract Leaf growth in grasses is determined by the cell division and elongation rates, with the duration of cell elongation being one of the processes that is the most sensitive to salinity. Our objective was to investigate the distribution profiles of cell production, cell length and the duration of cell elongation in the growing zone of the wheat leaf during the steady growth phase. Plants were grown in loamy soil with or without 120 mmol/L NaCl in a growth chamber, and harvested at day 3 after leaf 4 emerged. Results show that the elongation rate of leaf 4 was reduced by 120 mmol/L NaCl during the steady growth phase. The distribution profile of the lengths of abaxial epidermal cells of leaf 4 during the steady growth stage shows a sigmoidal pattern along the leaf axis for both treatments. Although salinity did not affect or even increased the length of the epidermal cells in some locations in the growth zone compared to the control treatment, the final length of the epidermal cells was reduced by 14% at 120 mmol/L NaCl. Thus, we concluded that the observed reduction in the leaf elongation rate derived in part from the reduced cell division rate and either the shortened cell elongation zone or shortened duration of cell elongation. This suggests that more attention should be paid to the effects of salinity on those properties of cell production and the period of cell maturation that are related to the properties of cell wall. [source] Cell division in magnetotactic bacteria splits magnetosome chain in halfJOURNAL OF BASIC MICROBIOLOGY, Issue 4 2010Sarah S. Staniland Abstract Cell division in magnetotactic bacteria has attracted much interest, speculation and hypothesis with respect to the biomineralised chains of magnetic iron-oxide particles known as magnetosomes. Here we report direct Transmission Electron Microscopy (TEM) evidence that division occurs at a central point of the cell and the chain, cleaving the magnetosome chain in two. Additionally, the new magnetosome chain relocates rapidly to the centre of the daughter cell and the number of magnetosomes is directly proportional to the cell length, even during the division part of the cell cycle. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] SEXUAL REPRODUCTION, MATING SYSTEM, AND PROTOPLAST DYNAMICS OF SEMINAVIS (BACILLARIOPHYCEAE)1JOURNAL OF PHYCOLOGY, Issue 5 2002Victor A. Chepurnov Cell division, the mating system, and auxosporulation were studied in the marine epipelic diatom Seminavis cf. robusta Danielidis & D. G. Mann. The interphase protoplast contains two girdle-appressed chloroplasts, each with an elongate bar-like pyrenoid, and also a central nucleus, located in a bridge between two vacuoles. Before cell division, the chloroplasts divide transversely and translocate onto the valves. The nucleus relocates to the ventral side for mitosis. After cytokinesis and valve formation, the chloroplasts move back to the girdle, showing a constant clockwise movement relative to the epitheca of the daughter cell. Seminavis cf. robusta is dioecious, and sexual reproduction is possible once cells are less than 50 ,m. In crosses of compatible clones, gametangia pair laterally, without the formation of a copulation envelope, and produce two gametes apiece. The intensity of sexualization increases as cells reduce further in size below the 50-,m threshold. At plasmogamy, the gametangia dehisce fully and the gametes, which were morphologically and behaviorally isogamous, fuse in the space between the gametangial thecae. The auxospore forms a transverse and longitudinal perizonium. After expansion is complete, there is an unequal contraction of the protoplast within the perizonium, creating the asymmetrical shape of the vegetative cell. Apart from this last feature, almost all characteristics exhibited by the live cell and auxospores of Seminavis agree with what is found in Navicula sensu stricto, supporting the classification of both in the Naviculaceae. Haploid parthenogenesis and polyploid auxospores were found, lending support to the view that change in ploidy may be a significant mechanism in diatom evolution. [source] Spatio-temporal changes in cell division, endoreduplication and expression of cell cycle-related genes in pollinated and plant growth substances-treated ovaries of cucumberPLANT BIOLOGY, Issue 1 2010F. Q. Fu Abstract We investigated the temporal and spatial changes in cell division, endoreduplication and expression of cell cycle-related genes in developing cucumber fruits at 0,20 days after anthesis (DAA). Cell division was intense at 0,4 DAA and then decreased until to 8 DAA. Meanwhile, endoreduplication started at 4 DAA and increased gradually to 20 DAA, accompanied by an increase in fruit weight. Cell division was mainly observed in the exocarp, while endoreduplication occurred mostly in the endocarp and pulp. Among the six cell cycle-related genes examined, two mitotic cyclin genes (CycA and CycB) and CDKB had the highest transcript levels within 2 DAA, while transcripts of two CycD3 genes and CDKA peaked at 4 DAA and 20 DAA, respectively. Naphthaleneacetic acid (NAA), N -(2-chloro-4-pyridyl)- N'-phenylurea (CPPU) and 24-epibrassinolide (EBR) all induced parthenocarpic growth as well as active cell division, and enhanced transcripts of cell cycle-related genes. In comparison, gibberellic acid (GA3) had little effect on the induction of parthenocarpy and transcripts of cell cycle-related genes. These results provide evidence for the important roles of cell division and endoreduplication during cucumber fruit development, and suggest the essential roles of cell cycle-related genes and plant growth substances in fruit development. [source] Proteomic profiling of tumor cells after induction of telomere dysfunctionPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2009Stefan Zimmermann Dr. Abstract Cell division in the absence of telomerase causes progressive telomere shortening which ultimately leads to telomere dysfunction and initiation of genome instability. In order to identify factors related to loss of telomere function, the effects of telomerase inhibition on the proteome of five tumor cell lines were followed by SELDI-TOF-MS. Five differentially expressed protein peaks (p<0.01) were found in a total of 60 clones of five cell lines representing four tissues (lung, breast, prostate, and colon) in which telomerase was inhibited by retroviral overexpression of a dominant negative (DN) mutant of human telomerase reverse transcriptase (hTERT). Among these, a 11.3,kDa peak diminished in DN-hTERT clones was identified as histone H4 by nanoflow-HPLC-MS/MS. Immunoblot analysis not only confirmed the decline of histone H4, but also of other core histone proteins including histone H3. Furthermore, upregulation of several cytokeratins was found to be associated with telomere attrition. In conclusion, loss of telomere function is associated with alterations in the proteome which may represent novel biomarkers for the detection of replicative senescence. [source] Developmental stages, larval and post-larval growth of angelwing clam Pholas orientalisAQUACULTURE RESEARCH, Issue 7 2009Beewah Ng Abstract Angelwing clam were induced to spawn by thermal stimulation. Mature eggs measured 50 ,m in diameter. Cell division occurred within 36 min after fertilization. Mobile trochophore larvae were seen after 12 h and larvae developed within 18 h. Reared on a diet of Isochrysis galbana the larvae reached the umbo stage in 6,7 days. On day 10 the foot could be seen and settlement occurred if a suitable substrate was present. The larvae completed metamorphosis into juveniles within 20 days after settling. [source] Crystallization and preliminary X-ray crystallographic analysis of MinE, the cell-division topological specificity factor from Helicobacter pyloriACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2010Gil Bu Kang Cell division in Gram-negative bacteria is driven by the formation of an FtsZ ring at the division site. MinE regulates the proper placement of the FtsZ ring at mid-cell by blocking the inhibitory action of the MinCD complex. Diffraction data were collected at 2.8,Å resolution from a native crystal of full-length Helicobacter pylori MinE. The crystal belonged to space group P64. Assuming the presence of two molecules in the asymmetric unit, the calculated Matthews coefficient was 2.58,Å3,Da,1, which corresponds to a solvent content of 52.3%. For MAD phasing, a four-wavelength data set was collected at 3.0,Å resolution. [source] Novel interactors and a role for supervillin in early cytokinesis,CYTOSKELETON, Issue 6 2010Tara C. Smith Abstract Supervillin, the largest member of the villin/gelsolin/flightless family, is a peripheral membrane protein that regulates each step of cell motility, including cell spreading. Most known interactors bind within its amino (N)-terminus. We show here that the supervillin carboxy (C)-terminus can be modeled as supervillin-specific loops extending from gelsolin-like repeats plus a villin-like headpiece. We have identified 27 new candidate interactors from yeast two-hybrid screens. The interacting sequences from 12 of these proteins (BUB1, EPLIN/LIMA1, FLNA, HAX1, KIF14, KIFC3, MIF4GD/SLIP1, ODF2/Cenexin, RHAMM, STARD9/KIF16A, Tks5/SH3PXD2A, TNFAIP1) co-localize with and mis-localize EGFP-supervillin in mammalian cells, suggesting associations in vivo. Supervillin-interacting sequences within BUB1, FLNA, HAX1, and MIF4GD also mimic supervillin over-expression by inhibiting cell spreading. Most new interactors have known roles in supervillin-associated processes, e.g. cell motility, membrane trafficking, ERK signaling, and matrix invasion; three (KIF14, KIFC3, STARD9/KIF16A) have kinesin motor domains; and five (EPLIN, KIF14, BUB1, ODF2/cenexin, RHAMM) are important for cell division. GST fusions of the supervillin G2-G3 or G4-G6 repeats co-sediment KIF14 and EPLIN, respectively, consistent with a direct association. Supervillin depletion leads to increased numbers of bi- and multi-nucleated cells. Cytokinesis failure occurs predominately during early cytokinesis. Supervillin localizes with endogenous myosin II and EPLIN in the cleavage furrow, and overlaps with the oncogenic kinesin, KIF14, at the midbody. We conclude that supervillin, like its interactors, is important for efficient cytokinesis. Our results also suggest that supervillin and its interaction partners coordinate actin and microtubule motor functions throughout the cell cycle. © 2010 Wiley-Liss, Inc. [source] Actin-like protein 1 (ALP1) is a component of dynamic, high molecular weight complexes in Toxoplasma gondii,CYTOSKELETON, Issue 1 2010Jennifer L. Gordon Abstract Apicomplexan parasites, such as Toxoplasma gondii, rely on actin-based motility for cell invasion, yet conventional actin does not appear to be required for cell division in these parasites. Apicomplexans also contain a variety of actin-related proteins (Arps); however, most of these not directly orthologous to Arps in well-studied systems. We recently identified an apicomplexan-specific member of this family called Actin-Like Protein 1, (ALP1), which plays a role in the assembly of vesicular components recruited to the inner membrane complex (IMC) of daughter cells during cell division. In addition to its enrichment at daughter cell membranes, ALP1 is localized throughout the cytoplasm both diffusely distributed and concentrated in clusters that are detected by fluorescence microscopy, suggesting it forms complexes. Using quantitative optical imaging methods, including fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP), we demonstrated that ALP1 is a component of a large complex, and that it readily exchanges between diffusible and complex-bound forms. Sedimentation and density gradient analyses revealed that ALP1 is found in a freely soluble state as well as high molecular weight complexes. During cell division, ALP1 was dynamically associated with the IMC, suggesting it rapidly cycles between freely diffusible and complex forms during daughter cell assembly. © 2009 Wiley-Liss, Inc. [source] Myosin Vb localises to nucleoli and associates with the RNA polymerase I transcription complexCYTOSKELETON, Issue 12 2009Andrew J. Lindsay Abstract It is becoming increasingly clear that the mammalian class V myosins are involved in a wide range of cellular processes such as receptor trafficking, mRNA transport, myelination in oligodendrocytes and cell division. Using paralog-specific antibodies, we observed significant nuclear localisation for both myosin Va and myosin Vb. Myosin Vb was present in nucleoli where it co-localises with RNA polymerase I, and newly synthesised ribosomal RNA (rRNA), indicating that it may play a role in transcription. Indeed, its nucleolar pattern was altered upon treatment with RNA polymerase I inhibitors. In contrast, myosin Va is largely excluded from nucleoli and is unaffected by these inhibitors. Myosin Vb was also found to physically associate with RNA polymerase I and actin in co-immunoprecipitation experiments. We propose that myosin Vb serves a role in rRNA transcription. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Dynamics of bacterial cytoskeletal elementsCYTOSKELETON, Issue 11 2009Peter L. Graumann Abstract Bacterial cytoskeletal elements are involved in an astonishing spectrum of cellular functions, from cell shape determination to cell division, plasmid segregation, the positioning of membrane-associated proteins and membrane structures, and other aspects of bacterial physiology. Interestingly, these functions are not necessarily conserved, neither between different bacterial species nor between bacteria and eukaryotic cells. The flexibility of cytoskeletal elements in performing different tasks is amazing and emphasises their very early development during evolution. This review focuses on the dynamics of cytoskeletal elements from bacteria. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Kinesin-5 is not essential for mitotic spindle elongation in DictyosteliumCYTOSKELETON, Issue 11 2008Irina Tikhonenko Abstract The proper assembly and operation of the mitotic spindle is essential to ensure the accurate segregation of chromosomes and to position the cytokinetic furrow during cell division in eukaryotes. Not only are dynamic microtubules required but also the concerted actions of multiple motor proteins are necessary to effect spindle pole separation, chromosome alignment, chromatid segregation, and spindle elongation. Although a number of motor proteins are known to play a role in mitosis, there remains a limited understanding of their full range of functions and the details by which they interact with other spindle components. The kinesin-5 (BimC/Eg5) family of motors is largely considered essential to drive spindle pole separation during the initial and latter stages of mitosis. We have deleted the gene encoding the kinesin-5 member in Dictyostelium, (kif13), and find that, in sharp contrast with results found in vertebrate, fly, and yeast organisms, kif13, cells continue to grow at rates indistinguishable from wild type. Phenotype analysis reveals a slight increase in spindle elongation rates in the absence of Kif13. More importantly, there is a dramatic, premature separation of spindle halves in kif13, cells, suggesting a novel role of this motor in maintaining spindle integrity at the terminal stages of division. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] In vivo phosphorylation of regulatory light chain of myosin II in sea urchin eggs and its role in controlling myosin localization and function during cytokinesisCYTOSKELETON, Issue 2 2008Ryota Uehara Abstract Phosphorylation of myosin regulatory light chain (RLC) at Ser19 (mono-phosphorylation) promotes filament assembly and enhances actin-activated ATPase activity of non-muscle myosin, while phosphorylation at both Ser19 and Thr18 (di-phosphorylation) further enhances the ATPase activity. However, it has not well been addressed which type of phosphorylation is important in regulating myosin during cytokinesis. Here, we investigated subcellular localization in sea urchin eggs of mono-phosphorylated and di-phosphorylated RLC by both quantitative biochemical and spatiotemporal cytological approaches. Mono-phosphorylated RLC was dominant in the equatorial cortex throughout the whole process of cytokinesis. Inhibition of myosin light chain kinase (MLCK) decreased mono-phosphorylated RLC both in the cortex and in the cleavage furrow, and blocked both formation and contraction of the contractile ring. Two different types of ROCK inhibitor gave inconsistent results: H1152 blocked both RLC mono-phosphorylation in the cleavage furrow and contraction of the contractile ring, while Y27632 affected neither the mono-phosphorylation nor cell division. These results suggest that there may be other targets of H1152 than ROCK, which is involved in the RLC phosphorylation in the cleavage furrow. Furthermore, it was revealed that localization of myosin heavy chain in the cleavage furrow, but not in the cortex, was perturbed by inhibition of RLC mono-phosphorylation. These results suggested that RLC mono-phosphorylation by more than two RLC kinases play a main role in regulation and localization of myosin in the dividing sea urchin eggs. Cell Motil. Cytoskeleton 2007. © 2007 Wiley-Liss, Inc. [source] Myosin localization during meiosis I of crane-fly spermatocytes gives indications about its role in divisionCYTOSKELETON, Issue 2 2003Rosalind V. Silverman-Gavrila Abstract We showed previously that in crane-fly spermatocytes myosin is required for tubulin flux [Silverman-Gavrila and Forer, 2000a: J Cell Sci 113:597,609], and for normal anaphase chromosome movement and contractile ring contraction [Silverman-Gavrila and Forer, 2001: Cell Motil Cytoskeleton 50:180,197]. Neither the identity nor the distribution of myosin(s) were known. In the present work, we used immunofluorescence and confocal microscopy to study myosin during meiosis-I of crane-fly spermatocytes compared to tubulin, actin, and skeletor, a spindle matrix protein, in order to further understand how myosin might function during cell division. Antibodies to myosin II regulatory light chain and myosin II heavy chain gave similar staining patterns, both dependent on stage: myosin is associated with nuclei, asters, centrosomes, chromosomes, spindle microtubules, midbody microtubules, and contractile rings. Myosin and actin colocalization along kinetochore fibers from prometaphase to anaphase are consistent with suggestions that acto-myosin forces in these stages propel kinetochore fibres poleward and trigger tubulin flux in kinetochore fibres, contributing in this way to poleward chromosome movement. Myosin and actin colocalization at the cell equator in cytokinesis, similar to studies in other cells [e.g., Fujiwara and Pollard, 1978: J Cell Biol 77:182,195], supports a role of actin-myosin interactions in contractile ring function. Myosin and skeletor colocalization in prometaphase spindles is consistent with a role of these proteins in spindle formation. After microtubules or actin were disrupted, myosin remained in spindles and contractile rings, suggesting that the presence of myosin in these structures does not require the continued presence of microtubules or actin. BDM (2,3 butanedione, 2 monoxime) treatment that inhibits chromosome movement and cytokinesis also altered myosin distributions in anaphase spindles and contractile rings, consistent with the physiological effects, suggesting also that myosin needs to be active in order to be properly distributed. Cell Motil. Cytoskeleton 55:97,113, 2003. © 2003 Wiley-Liss, Inc. [source] Post-karyokinesis centrosome movement leaves a trail of unanswered questionsCYTOSKELETON, Issue 3 2002Young Y. Ou Abstract The centrosome is a complex structure composed of a large number of proteins (pericentriolar material, PCM) usually organized around a pair of centrioles (or a centriole duplex). This structure is capable of nucleating and organizing microtubules, duplication, and motility. In general, episodes of dramatic centrosome movement correlate with periods of cellular reorganization and nowhere is cellular reorganization more apparent, or more important, than in the periods before and after cell division. It is now clear that centrosome movement occurs not only prior to cell division but also at its completion, in concert with cytokinesis. The focus of this review is the newly emerging picture of centrosome activity during the post-karyokinesis period and the role that this activity might play in the transition of cells from mitosis to interphase. Cell Motil. Cytoskeleton 51:123,132, 2002. © 2002 Wiley-Liss, Inc. [source] Inhibitors of purine and pyrimidine synthesis: mycophenolate, azathioprine, and leflunomideDERMATOLOGIC THERAPY, Issue 4 2002Daniel Mimouni The major goal in the treatment of autoimmune blistering diseases has changed from simply keeping the patient alive to suppressing disease while maintaining quality of life and minimizing drug side effects. Researchers and clinicians are constantly seeking steroid-sparing agents that would allow a dose reduction in corticosteroids with no loss of benefit. Purine and pyrimidine base inhibitors are commonly used for this purpose. These drugs act by inhibiting cell division and inducing cell death. The pharmacologic and clinical aspects of azathioprine, mycophenolate mofetil, and leflunomide are discussed in this review. [source] TSC-box is essential for the nuclear localization and antiproliferative effect of XTSC-22DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 3 2007Akiko Hashiguchi Transforming growth factor- ,1-stimulated clone 22 (TSC-22) encodes a leucine zipper-containing protein that is highly conserved among various species. Mammalian TSC-22 is a potential tumor suppressor gene. It translocates into nuclei and suppresses cell division upon antiproliferative stimuli. In human colon carcinoma cells, TSC-22 inhibits cell growth by upregulating expression of the p21 gene, a cyclin-dependent kinase (Cdk) inhibitor. We previously showed that the Xenopus laevis homologue of the TSC-22 gene (XTSC-22) is required for cell movement during gastrulation through cell cycle regulation. In this report, we investigated the molecular mechanism of the antiproliferative effect of XTSC-22. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis suggested that XTSC-22 did not affect the expression levels of the p21 family of Cdk inhibitors or other cell cycle regulators. Analysis of deletion mutants of XTSC-22 revealed that nuclear localization of the N-terminal TSC-box is necessary for cell cycle inhibition by XTSC-22. Further experiments suggested that p27Xic1, a key Cdk inhibitor in Xenopus, interacts with XTSC-22. Because p27Xic1 is a cell cycle inhibitor with a nuclear localization signal, it is possible that XTSC-22 suppresses cell division by translocating into the nucleus with p27Xic1, where it may potentiate the intranuclear action of p27Xic1. [source] Activator of G-protein signaling in asymmetric cell divisions of the sea urchin embryoDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 9 2006Ekaterina Voronina An asymmetric fourth cell division in the sea urchin embryo results in formation of daughter cells, macromeres and micromeres, with distinct sizes and fates. Several lines of functional evidence presented here, including pharmacological interference and dominant negative protein expression, indicate that heterotrimeric G protein Gi and its interaction partner, activator of G-protein signaling (AGS), are necessary for this asymmetric cell division. Inhibition of Gi signaling by pertussis toxin interferes with micromere formation and leads to defects in embryogenesis. AGS was isolated in a yeast two-hybrid screen with G,i as bait and was expressed in embryos localized to the cell cortex at the time of asymmetric divisions. Introduction of exogenous dominant-negative AGS protein, containing only G-protein regulatory (GPR) domains, selectively prevented the asymmetric division in normal micromere formation. These results support the growing evidence that AGS is a universal regulator of asymmetric cell divisions in embryos. [source] Cleavage-like cell division and explosive increase in cell number of neonatal gonocytesDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2004Yasuhiro Sakai Based on previous conventional quantitative observations of rat testes, it was proposed that large numbers of gonocytes degenerate after birth and this notion was widely accepted. However, many studies show that neonatal gonocytes display high levels of mitotic activity. In order to resolve the apparent contradiction of increased mitotic activity in gonocytes despite a decrease in their numbers at the neonate stage, quantitative analysis using a marker of suitably higher resolution is required. It has been shown that the vasa protein could be used as a marker of germ cells. In this study, quantitative changes in gonocytes were re-examined using a germ-cell-specific marker in order to delineate more clearly the process of development from gonocytes to spermatogonia after birth. The vasa -positive cells, which correspond to gonocytes and spermatogonia, increased exponentially after birth. This observation suggests that all gonocyte divide actively after birth and do not degenerate as previously believed. Surprisingly, the cell volume of gonocytes decreased during their division. The largest population size was 2000,4000 µ3 at day 2, 1000,2000 µ3 at day 4 and 500,1000 µ3 at day 6. This finding suggests that gonocytes divide in a similar way to cleavage, which can be considered a special mode of fertilized eggs. Judging from the growth of seminiferous tubules and the degree of volume reduction, 60% of the contribution rate is estimated to be due to ordinal cell growth, and 40% due to volume reduction as in cleavage of a fertilized egg. This unique cleavage-like division may contribute to the supply of large numbers of spermatogonia. [source] Members of the Plag gene family are expressed in complementary and overlapping regions in the developing murine nervous systemDEVELOPMENTAL DYNAMICS, Issue 3 2005Sharmila Alam Abstract In the developing nervous system, cell fate specification and proliferation are tightly coupled events, ensuring the coordinated generation of the appropriate numbers and correct types of neuronal and glial cells. While it has become clear that tumor suppressor genes and oncogenes are key regulators of cell division in tumor cells, their role in normal cellular and developmental processes is less well understood. Here we present a comparative analysis of the expression profiles of the three members of the pleiomorphic adenoma gene (Plag) family, which encode zinc finger transcription factors previously characterized as tumor suppressors (Zac1) or oncogenes (Plag1, Plag-l2). We focused our analysis on the developing nervous system of mouse where we found that the Plag genes were expressed in both unique and overlapping patterns in the central and peripheral nervous systems, and in olfactory and neuroendocrine lineages. Based on their patterns of expression, we suggest that members of the Plag gene family might control cell fate and proliferation decisions in the developing nervous system and propose that deciphering these functions will help to explain why their inappropriate inactivation/activation leads to tumor formation. Developmental Dynamics 234:772,782, 2005. © 2005 Wiley-Liss, Inc. [source] Centrosome amplification induced by the antiretroviral nucleoside reverse transcriptase inhibitors lamivudine, stavudine, and didanosineENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 8 2009Mia Yu Abstract In cultured cells, exposure to the nucleoside reverse transcriptase inhibitor (NRTI) zidovudine (AZT) induces genomic instability, cell cycle arrest, micronuclei, sister chromatid exchanges, and shortened telomeres. In previous studies, we demonstrated AZT-induced centrosome amplification (>2 centrosomes/cell). Here, we investigate centrosome amplification in cells exposed to other commonly used NRTIs. Experiments were performed using Chinese Hamster ovary (CHO) cells, and two normal human mammary epithelial cell (NHMEC) strains: M99005 and M98040, which are high and low incorporators of AZT into DNA, respectively. Cells were exposed for 24 hr to lamivudine (3TC), stavudine (d4T), didanosine (ddI), and thymidine, and stained with anti-pericentrin antibody. Dose response curves were performed to determine cytotoxicity and a lower concentration at near plasma levels and a 10 fold higher concentration were chosen for the experiments. In CHO cells, there was a concentration-dependent, significant (P < 0.05) increase in centrosome amplification for each of the NRTIs. In NHMEC strain M99005, an NRTI-induced increase (P < 0.05) in centrosome amplification was observed for the high concentrations of each NRTI and the low doses of 3TC and ddI. In NHMEC strain M98040, the high doses of ddI and d4T showed significant increases in centrosome amplification. Functional viability of amplified centrosomes was assessed by arresting microtubule nucleation with nocodazole. In cells with more than two centrosomes, the ability to recover microtubule nucleation was similar to that of unexposed cells. We conclude that centrosome amplification is a consequence of exposure to NRTIs and that cells with centrosome amplification are able to accomplish cell division. Environ. Mol. Mutagen., 2009. © 2009 Wiley-Liss, Inc. [source] Effect of mangiferin on radiation-induced micronucleus formation in cultured human peripheral blood lymphocytesENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2005Ganesh Chandra Jagetia Abstract Irradiation causes a variety of lesions in important biomolecules of the cell through generation of free radicals leading to genomic instability. DNA strand breaks, acentric fragments, or defective kinetochores are manifested as micronuclei after the first cell division. Chemicals that can trap free radicals may reduce the deleterious effects of ionizing radiation. Mangiferin (MGN), a glucosylxanthone derived from Mangifera indica (mango), was investigated for its ability to reduce the frequency of radiation-induced micronucleated binucleate cells (MNBNCs) in cultured human peripheral blood lymphocytes (HPBLs). HPBL cultures were pretreated with 0, 5, 10, 20, 50, and 100 ,g/ml of MGN for 30 min before exposure to 3 Gy of 60Co ,-radiation. The maximum decline in radiation-induced micronuclei was observed at a concentration of 50 ,g/ml MGN; thereafter, a nonsignificant elevation in MNBNC frequency was observed at 100 ,g/ml MGN. Since the lowest MNBNC frequency was observed for 50 ,g/ml MGN, dose-response studies were undertaken using this concentration. Irradiation of HPBLs with 0, 1, 2, 3, or 4 Gy of ,-radiation caused a dose-dependent elevation in the MNBNC frequency, while treatment of HPBLs with 50 ,g/ml MGN 30 min before radiation resulted in significant declines in these frequencies. MGN alone did not alter the proliferation index. Irradiation caused a dose-dependent decline in the proliferation index, while treatment of HPBLs with 50 ,/ml MGN significantly elevated the proliferation index in irradiated cells. MGN treatment reduced hydrogen peroxide-induced lipid peroxidation in HPBLs in a concentration-dependent fashion. In cell-free studies, MGN inhibited the induction of ·OH (hydroxyl), O2·, (superoxide), DPPH (1,1-diphenyl-2-picrylhydrazyl), and ABTS·+ (2,2-azino-bis-3-ethyl benzothiazoline-6-sulphonic acid) radicals in a dose-dependent manner. The results of this study indicate that MGN possesses radioprotective properties by suppressing the effects of free radicals. Environ. Mol. Mutagen. 45:000,000, 2005. © 2005 Wiley-Liss, Inc. [source] Swarmer cell differentiation in Proteus mirabilisENVIRONMENTAL MICROBIOLOGY, Issue 8 2005Philip N. Rather Summary Under the appropriate environmental conditions, the Gram-negative bacterium Proteus mirabilis undergoes a remarkable differentiation to form a distinct cell type called a swarmer cell. The swarmer cell is characterized by a 20- to 40-fold increase in both cell length and the number of flagella per cell. Environmental conditions required for swarmer cell differentiation include: surface contact, inhibition of flagellar rotation, a sufficient cell density and cell-to-cell signalling. The differentiated swarmer cell is then able to carry out a highly ordered population migration termed swarming. Genetic analysis of the swarming process has revealed that a large variety of distinct loci are required for this differentiation including: genes involved in regulation, lipopolysaccharide and peptidoglycan synthesis, cell division, ATP production, putrescine biosynthesis, proteolysis and cell shape determination. The process of swarming is important medically because the expression of virulence genes and the ability to invade cells are coupled to the differentiated swarmer cell. In this review, the genetic and environmental requirements for swarmer cell differentiation will be outlined. In addition, the role, of, the, differentiated, swarmer, cell, in, virulence and its possible role in biofilm formation will be discussed. [source] Phenotypical variation in a toxic strain of the phytoplankter, Cylindrospermopsis raciborskii (nostocales, cyanophyceae) during batch cultureENVIRONMENTAL TOXICOLOGY, Issue 6 2001Peter R. Hawkins Abstract A nonaxenic strain of Cylindrospermopsis raciborskii Woloszynska (AWT 205) was grown in batch culture, with and without nitrate as the primary N source. Rapid log-phase growth with nitrate was 1.0 doubling/day versus 0.3 doubling/day without nitrate. Cylindrospermopsin (CYN) production was measured by HPLC. The rate of intracellular CYN production matched cell division rate for both the diazotrophies at cell densities less than 107 cell/ml. At cell density >107 cell/ml, additional resource limitation in batch culture slowed log-phase growth to 0.04 division/day and cell division and CYN production decoupled. Intracellular CYN concentration increased at a rate of 0.08 doubling/day, twice the cell division rate. Extracellular CYN as a proportion of the total CYN increased from 20% during the rapid growth phase, to 50% during the slow growth phase. The total CYN yield from cultures grown out to stationary phase (55 days) exceeded 2 mg CYN/l. C. raciborskii cells in log-phase growth, exposed to 1 ppm copper (as copper sulphate), lysed within 24 hours. After copper treatment, all CYN was in the filterable fraction. These findings imply that in naturally occurring blooms of C. raciborskii, the movement of intracellular CYN into solution will be the greatest during stationary phase, when intracellular concentrations are highest and cell lysis is more frequent. The application of algicides that promote cell lysis will exacerbate this effect. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 460,467, 2001 [source] Exposure of pacific herring to weathered crude oil: Assessing effects on ova,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2000Mark G. Carls Abstract In order to determine if exposure to Exxon Valdez oil would adversely affect progeny, reproductively mature Pacific herring were confined in water contaminated with weathered crude oil. Progeny were generally not affected by a 16-d parental exposure to initial aqueous concentrations of ,58 ,g/L total polynuclear aromatic hydrocarbons (PAHs), yielding concentrations of up to 9.7 ,g/g in ova. In contrast, previous research indicated that a 16-d direct exposure of herring eggs to similarly weathered oil was detrimental to developing embryos at total initial PAH concentrations of 9 ,g/L. Progeny of exposed fish could have been insulated from toxic effects for two reasons. First, as an apparent result of partitioning and metabolism in parental tissues, lower concentrations and less toxic PAHs were preferentially accumulated by ova (primarily naphthalenes; 84,92%). Second, peak exposure concentrations occurred before cell differentiation. The opposite was true for directly exposed eggs; the more toxic multi-ring PAHs (e.g., phenanthrenes and chrysenes) and alkyl-substituted homologues were accumulated, and internal concentrations increased during cell division, differentiation, and organ development. Thus, Pacific herring embryos are more critically sensitive to oil pollution than are gametes. [source] Identification of a Chr 11 quantitative trait locus that modulates proliferation in the rostral migratory stream of the adult mouse brainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2010Anna Poon Abstract Neuron production takes place continuously in the rostral migratory stream (RMS) of the adult mammalian brain. The molecular mechanisms that regulate progenitor cell division and differentiation in the RMS remain largely unknown. Here, we surveyed the mouse genome in an unbiased manner to identify candidate gene loci that regulate proliferation in the adult RMS. We quantified neurogenesis in adult C57BL/6J and A/J mice, and 27 recombinant inbred lines derived from those parental strains. We showed that the A/J RMS had greater numbers of bromodeoxyuridine-labeled cells than that of C57BL/6J mice with similar cell cycle parameters, indicating that the differences in the number of bromodeoxyuridine-positive cells reflected the number of proliferating cells between the strains. AXB and BXA recombinant inbred strains demonstrated even greater variation in the numbers of proliferating cells. Genome-wide mapping of this trait revealed that chromosome 11 harbors a significant quantitative trait locus at 116.75 ± 0.75 Mb that affects cell proliferation in the adult RMS. The genomic regions that influence RMS proliferation did not overlap with genomic regions regulating proliferation in the adult subgranular zone of the hippocampal dentate gyrus. On the contrary, a different, suggestive locus that modulates cell proliferation in the subgranular zone was mapped to chromosome 3 at 102 ± 7 Mb. A subset of genes in the chromosome 11 quantitative trait locus region is associated with neurogenesis and cell proliferation. Our findings provide new insights into the genetic control of neural proliferation and an excellent starting point to identify genes critical to this process. [source] Multi-directional differentiation of doublecortin- and NG2-immunopositive progenitor cells in the adult rat neocortex in vivoEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Yasuhisa Tamura Abstract In the adult mammalian brain, multipotent stem or progenitor cells involved in reproduction of neurons and glial cells have been well investigated only in very restricted regions; the subventricular zone of the lateral ventricle and the dentate gyrus in the hippocampal formation. In the neocortex, a series of in vitro studies has suggested the possible existence of neural progenitor cells possessing neurogenic and/or gliogenic potential in adult mammals. However, the cellular properties of the cortical progenitor cells in vivo have not been fully elucidated. Using 5,-bromodeoxyuridine labeling and immunohistochemical analysis of cell differentiation markers, we found that a subpopulation of NG2-immunopositive cells co-expressing doublecortin (DCX), an immature neuron marker, ubiquitously reside in the adult rat neocortex. Furthermore, these cells are the major population of proliferating cells in the region. The DCX(+)/NG2(+) cells reproduced the same daughter cells, or differentiated into DCX(+)/NG2(,) (approximately 1%) or DCX(,)/NG2(+) (approximately 10%) cells within 2 weeks after cell division. The DCX(+)/NG2(,) cells were also immunopositive for TUC-4, a neuronal linage marker, suggesting that these cells were committed to neuronal cell differentiation, whereas the DCX(,)/NG2(+) cells showed faint immunoreactivity for glutathione S-transferase (GST)-pi, an oligodendrocyte lineage marker, in the cytoplasm, suggesting glial cell lineage, and thereafter the cells differentiated into NG2(,)/GST-pi(+) mature oligodendrocytes after a further 2 weeks. These findings indicate that DCX(+)/NG2(+) cells ubiquitously exist as ,multipotent progenitor cells' in the neocortex of adult rats. [source] Role of intracellular Ca2+ and calmodulin/MAP kinase kinase/extracellular signal-regulated protein kinase signalling pathway in the mitogenic and antimitogenic effect of nitric oxide in glia- and neurone-derived cell linesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2006Antonella Meini Abstract To elucidate the mechanism of cell growth regulation by nitric oxide (NO) and the role played in it by Ca2+, we studied the relationship among intracellular Ca2+ concentration ([Ca2+]i), mitogen-activated protein kinases [extracellular signal-regulated protein kinase (ERK)] and proliferation in cell lines exposed to different levels of NO. Data showed that NO released by low [(z)-1-[2-aminiethyl]-N-[2-ammonioethyl]amino]diazen-1-ium-1,2diolate (DETA/NO) concentrations (10 µm) determined a gradual, moderate elevation in [Ca2+]i (46.8 ± 7.2% over controls) which paralleled activation of ERK and potentiation of cell division. Functionally blocking Ca2+ or inhibiting calmodulin or MAP kinase kinase activities prevented ERK activation and antagonized the mitogenic effect of NO. Experimental conditions favouring Ca2+ entry into cells led to increased [Ca2+]i (189.5 ± 4.8%), ERK activation and cell division. NO potentiated the Ca2+ elevation (358 ± 16.8%) and ERK activation leading to expression of p21Cip1 and inhibition of cell proliferation. Furthermore, functionally blocking Ca2+ down-regulated ERK activation and reversed the antiproliferative effect of NO. Both the mitogenic and antimitogenic responses induced by NO were mimicked by a cGMP analogue whereas they were completely antagonized by selective cGMP inhibitors. These results demonstrate for the first time that regulation of cell proliferation by low NO levels is cGMP dependent and occurs via the Ca2+/calmodulin/MAP kinase kinase/ERK pathway. In this effect the amplitude of Ca2+ signalling determines the specificity of the proliferative response to NO possibly by modulating the strength of ERK activation. In contrast to the low level, the high levels (50,300 µm) of DETA/NO negatively regulated cell proliferation via a Ca2+ -independent mechanism. [source] The corticoid environment: a determining factor for neural progenitors' survival in the adult hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2004Edmund Y. H. Wong New neurons continue to be generated in the adult dentate gyrus of the hippocampus. Corticosterone (CORT), a steroid secreted by the adrenal glands, had been shown to regulate progenitor proliferation. High levels of CORT suppress proliferation while low levels of the steroid stimulate it. Here we present an investigation into the regulation of survival by corticoids, with emphasis on the differential effects of the pre-mitotic and post-mitotic corticoid environments. Post-mitotic adrenalectomy increased subsequent survival of progenitors at 28 days, while additional CORT administered during the post-mitotic period decreased survival. In contrast, a corticoid-free environment prior to progenitor division resulted in a reduced survival rate of new cells and, similarly, high levels of CORT before proliferation reduced subsequent survival. In addition, phased treatment with CORT during a 27-day post-mitotic interval showed that newly formed cells lose their sensitivity to administered CORT after about 18 days. These results are the first to show that the corticoid environment both before and after cell division regulates survival. [source] | ||||||||||||||||||||||||||||||||||||||||||||||