Spindle organization

Only the major features of spindle organization as now known will be considered here. Spindle chemistry, kinetochore structure, and some details of spindle organization will be discussed in the sections which follow on chromosome movement and distribution. 

Yuan J, Li M, Wei L, Yin S, Xiong B, Li S, Lin SL, Schatten H, Sun QY. 2009. Astrin regulates meiotic spindle organization, spindle pole tethering and cell cycle progression in mouse oocytes. Cell Cycle 8(20) 3384-3395. 

Centrosomes, also called the microtubule organizing centre, are protein complexes that contain two cen-trioles (ringlike structures) and y- tubulin. They serve as nucleation points for microtubular polymerization and constrain the lattice structure of a microtubule to 13 protofilaments. They are responsible for organizing the mitotic spindle during mitosis. 

Whereas in children internal organ involvement (systemic mastocytosis, SM) is unusual, MPCM in adults is associated with SM in the majority of cases [10]. WHO criteria for SM consist of the major criterion of multifocal mast cell infiltrates in the bone marrow or other extracutaneous organ(s) and four minor criteria (table 2) [21] 25% or more of mast cells in non-cutaneous biopsy sections with spindle-shaped or abnormal morphology, or... 

Mailer Why do you say that the first spindle poles are made of PCM Is there some reason to think that PCM is needed without a centrosome In Nenopus, I have never heard anyone argue that there is PCM organizing the meiotic spindles. If you look at the /-tubulin staining pattern, it is totally different in a meiotic spindle than in a mitotic spindle. 

The chromatid separation process has also remained mysterious. It is an autonomous process that does not direcdy depend on the mitotic spindle (Wilson 1925, Mazia 1961). This is most vividly seen in cells whose spindles have been destroyed by spindle poisons such as colchicine. In many organisms, in particular in plant cells, the cell cycle delay induced by colchicine is only transient and chromatids eventually split apart in the complete absence of a mitotic spindle (Mole-Bajer 1958, Rieder Palazzo 1992) (Fig. 2). Mitosis in the presence of colchicine or colcemid (known as c-mitosis) leads to the production of daughter cells with twice the normal complement of chromosomes. This process is routinely used for manipulating plant genomes and may contribute to the therapeutic effects of taxol in treating breast cancer. 

Hunt Normally cyclin A goes away very early in mitosis—almost as soon as the nuclear envelope breaks down. If it doesn t go away, what seems to happen is that the spindle doesn t organize itself properly, yet it goes through anaphase. It is peculiar the spindles look horrible. These are spindles with both cyclin A and cyclin B. The cyclin A seems to be necessary to get it up to that point, but then you need to get rid of it in order for the cyclin B to take over. 

In the same way that muscle spindles are responsible for the maintenance of muscle length, Golgi tendon organs are responsible for maintenance of muscle tension. 

Ge Z, Liu C, Bjorkholm M, Gruber A, Xu D (2006) Mitogen-activated protein kinase cascade-mediated histone H3 phosphorylation is critical for telomerase reverse transcriptase expression/telomerase activation induced by proliferation. Mol Cell Biol 26(l) 230-237 Giet R, Glover DM (2001) Drosophila aurora B kinase is required for histone H3 phosphorylation and condensin recruitment during chromosome condensation and to organize the central spindle during cytokinesis. J Cell Biol 152(4) 669-682... 

Kinesins and other molecular motors. Before considering further how the myosin motor may work, we should look briefly at the kinesins, a different group of motor molecules,1683 which transport various cellular materials along microtubule "rails." They also participate in organization of the mitotic spindle and other microtubule-dependent activities.168a/b/C See Section C,2 for further discussion. More than 90 members of the family have been identified. Kinesin heads have much shorter necks than do the myosin heads. 

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