The Experts below are selected from a list of 61110 Experts worldwide ranked by ideXlab platform
Ashok Agarwal - One of the best experts on this subject based on the ideXlab platform.
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Spindle and Chromosomal Alterations in Metaphase II Oocytes
Reproductive Sciences, 2013Co-Authors: Rakesh K. Sharma, Abdullahil Azeem, Ashok AgarwalAbstract:The spindle apparatus is a vital structure and must be structurally intact for proper segregation of the oocyte's genetic material during metaphase II. Endometriosis, oxidative stress, and cryopreservation can all adversely affect the structural integrity of the spindle, potentially resulting in aneuploidy and spontaneous abortion of the embryo. Advances in spindle imagery have made it possible to visualize the effects of environmental stresses on spindle structure. Deviation from an oocyte's normal environment can seriously impair the positioning and integrity of the spindle. Oocytes cryopreservation causes Depolymerization and repolymerization of the spindle. Oocytes can also be preserved in an immature state for later in vitro maturation. A comprehensive understanding of the spindle behavior is paramount for the effective manipulation of oocytes in an assisted reproductive setting.
Rakesh K. Sharma - One of the best experts on this subject based on the ideXlab platform.
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Spindle and Chromosomal Alterations in Metaphase II Oocytes
Reproductive Sciences, 2013Co-Authors: Rakesh K. Sharma, Abdullahil Azeem, Ashok AgarwalAbstract:The spindle apparatus is a vital structure and must be structurally intact for proper segregation of the oocyte's genetic material during metaphase II. Endometriosis, oxidative stress, and cryopreservation can all adversely affect the structural integrity of the spindle, potentially resulting in aneuploidy and spontaneous abortion of the embryo. Advances in spindle imagery have made it possible to visualize the effects of environmental stresses on spindle structure. Deviation from an oocyte's normal environment can seriously impair the positioning and integrity of the spindle. Oocytes cryopreservation causes Depolymerization and repolymerization of the spindle. Oocytes can also be preserved in an immature state for later in vitro maturation. A comprehensive understanding of the spindle behavior is paramount for the effective manipulation of oocytes in an assisted reproductive setting.
Helder Maiato - One of the best experts on this subject based on the ideXlab platform.
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establishment and mitotic characterization of new drosophila acentriolar cell lines from dsas 4 mutant
Biology Open, 2013Co-Authors: Nicolas Lecland, Alain Debec, Audrey Delmas, Sara Moutinhopereira, Nicolas Malmanche, Anais Bouissou, Clemence Dupre, Aimie Jourdan, Brigitte Raynaudmessina, Helder MaiatoAbstract:In animal cells the centrosome is commonly viewed as the main cellular structure driving microtubule (MT) assembly into the mitotic spindle apparatus. However, additional pathways, such as those mediated by chromatin and augmin, are involved in the establishment of functional spindles. The molecular mechanisms involved in these pathways remain poorly understood, mostly due to limitations inherent to current experimental systems available. To overcome these limitations we have developed six new Drosophila cell lines derived from Drosophila homozygous mutants for DSas-4, a protein essential for centriole biogenesis. These cells lack detectable centrosomal structures, astral MT, with dispersed pericentriolar proteins D-PLP, Centrosomin and γ-tubulin. They show poorly focused spindle poles that reach the plasma membrane. Despite being compromised for functional centrosome, these cells could successfully undergo mitosis. Live-cell imaging analysis of acentriolar spindle assembly revealed that nascent MTs are nucleated from multiple points in the vicinity of chromosomes. These nascent MTs then grow away from kinetochores allowing the expansion of fibers that will be part of the future acentriolar spindle. MT repolymerization assays illustrate that acentriolar spindle assembly occurs “inside-out” from the chromosomes. Colchicine-mediated Depolymerization of MTs further revealed the presence of a functional Spindle Assembly Checkpoint (SAC) in the acentriolar cells. Finally, pilot RNAi experiments open the potential use of these cell lines for the molecular dissection of anastral pathways in spindle and centrosome assembly.
Emiel Emiel Hensen - One of the best experts on this subject based on the ideXlab platform.
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Ethanol as capping agent and formaldehyde scavenger for efficient Depolymerization of lignin to aromatics
Green Chemistry, 2015Co-Authors: Xiaoming Huang, Michael Boot, Tamas I Koranyi, Emiel Emiel HensenAbstract:Obtaining renewable fuels and chemicals from lignin presents an important challenge to the use of lignocellulosic biomass to meet sustainability and energy goals. We report on a thermocatalytic process for the Depolymerization of lignin in supercritical ethanol over a CuMgAlOx catalyst. Ethanol as solvent results in much higher monomer yields than methanol. In contrast to methanol, ethanol acts as a scavenger of formaldehyde derived from lignin decomposition. Studies with phenol and alkylated phenols evidence the critical role of the phenolic –OH groups and formaldehyde in undesired repolymerization reactions. O-alkylation and C-alkylation capping reactions with ethanol hinder repolymerization of the phenolic monomers formed during lignin disassembly. After reaction in ethanol at 380 °C for 8 h, this process delivers high yields of mainly alkylated mono-aromatics (60–86 wt%, depending on the lignin used) with a significant degree of deoxygenation. The oxygen-free aromatics can be used to replace reformate or can serve as base aromatic chemicals; the oxygenated aromatics can be used as low-sooting diesel fuel additives and as building blocks for polymers.
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catalytic Depolymerization of lignin in supercritical ethanol
Chemsuschem, 2014Co-Authors: Xiaoming Huang, Michael Boot, Tamas I Koranyi, Emiel Emiel HensenAbstract:One-step valorization of soda lignin in supercritical ethanol using a CuMgAlOx catalyst results in high monomer yield (23 wt?%) without char formation. Aromatics are the main products. The catalyst combines excellent deoxygenation with low ring-hydrogenation activity. Almost half of the monomer fraction is free from oxygen. Elemental analysis of the THF-soluble lignin residue after 8 h reaction showed a 68?% reduction in O/C and 24?% increase in H/C atomic ratios as compared to the starting Protobind P1000 lignin. Prolonged reaction times enhanced lignin Depolymerization and reduced the amount of repolymerized products. Phenolic hydroxyl groups were found to be the main actors in repolymerization and char formation. 2D HSQC NMR analysis evidenced that ethanol reacts by alkylation and esterification with lignin fragments. Alkylation was found to play an important role in suppressing repolymerization. Ethanol acts as a capping agent, stabilizing the highly reactive phenolic intermediates by O-alkylating the hydroxyl groups and by C-alkylating the aromatic rings. The use of ethanol is significantly more effective in producing monomers and avoiding char than the use of methanol. A possible reaction network of the reactions between the ethanol and lignin fragments is discussed.
R. W. Briehly - One of the best experts on this subject based on the ideXlab platform.
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Fiber Depolymerization
Biophysical Journal, 2006Co-Authors: M S Turner, F. A. Ferrone, G. Agarwal, C W Jones, Sam Kwong, J C Wang, Robert Josephs, R. W. BriehlyAbstract:Depolymerization is, by definition, a crucial process in the reversible assembly of various biopolymers. It may also be an important factor in the pathology of sickle cell disease. If sickle hemoglobin fibers fail to depolymerize fully during passage through the lungs then they will reintroduce aggregates into the systemic circulation and eliminate or shorten the protective delay (nucleation) time for the subsequent growth of fibers. We study how Depolymerization depends on the rates of end- and side-Depolymerization, kendand kside, which are, respectively, the rates at which fiber length is lost at each end and the rate at which new breaks appear per unit fiber length. We present both an analytic mean field theory and supporting simulations showing that the characteristic fiber Depolymerization time τ = 1√kendksidedepends on both rates, but not on the fiber length L, in a large intermediate regime 1 ≪ ksideL2/kend≪ (L/d)2, with d the fiber diameter. We present new experimental data which confirms that both mechanisms are important and shows how the rate of side Depolymerization depends strongly on the concentration of CO, acting as a proxy for oxygen. Our theory remains rather general and could be applied to the Depolymerization of an entire class of linear aggregates, not just sickle hemoglobin fibers. © 2006 by the Biophysical Society.
