Motility polar

Intracellular motility is also of vital importance in the lives of cells and the organisms they form. Material and organelles are transported within cells along microtubules and microfilaments an extreme example of this are the axons of nerve cells which transport materials to the synapses where they are secreted—another motile event. Other examples of intracellular motility include phagocytosis, pino-cytosis, the separating of chromosomes and cells in cell division, and maintenance of cell polarity. 

The processes of meiosis and mitosis involve many motile events, from the separation of the daughter chromosomes to the final act of cell separation at cytokinesis (Wadsworth, 1993). DNA replication itself may be considered as a motile event, because the polymerase complex moves along the linear DNA. One of the most obvious motile events is the separation of the chromosomes along the mitotic spindle at anaphase. Details of the structure and polarity of microtubules in the spindle apparatus in meiosis and mitosis are known through electron and light microscopy, but it is not yet clear whether the chromosomes are pushed, pulled or... 

Shimonaka M, Katagiri K, Nakayama T, et al. Rapl translates chemokine signals to integrin activation, cell polarization, and motility across vascular endothelium under flow. J Cell Biol 2003 161 (2) 417 427. 

It is an aerobic, gram-negative, nonsporing, rod-shaped bacterium. It is motile with a single polar flagellum. 

Breast milk neutrophils are also present in an activated form, as evidenced by increased levels of CDllb/CD18 and lower expression of L-selecfin (Goldman et al., 1998). Flowever, these neutrophils may have a limited functional capacity once secreted into milk as they demonstrate lower adherence, polarity, and motility when in the activated state (Thorpe et al, 1986). Little is known about the impact of milk neufrophils on immune development in the mfant, but most researchers suggest that the main role is maternal protection as they have limited functional capacity once they are secreted into milk. 

Taurine (2-aminoethanesulfonic acid 4.235) is an inhibitory neurochemical that probably acts primarily as a neuromodulator rather than a neurotransmitter. It is formed from cysteine, and its accumulation can be prevented by the cardiac glycoside ouabain. Although receptor sites and specific actions cannot be elucidated without an antagonist, taurine has been implicated in epilepsy and, potentially, in heart disease. There are a large number of physiological effects attributed to taurine, among them cardiovascular (antiarrythmic), central (anticonvulsant, excitability modulation), muscle (membrane stabilizer), and reproductive (sperm motility factor) activity. Analogs of taurine, phthalimino-taurinamide (4.236) and its iV-alkyl derivatives, are less polar than taurine and are potent anticonvulsant molecules. 

The cortical region of many cells is enriched in actin and associated actin-binding proteins, which function in motility, cell shape maintenance, and membrane protein distribution in polarized cells. In some cases, discrete structures anchor actin to the membrane, as is the case for intercellular adherens junctions and cell-substrate focal contacts. In certain special cell types, the fundamental blueprint for an adherens junction is taken to a new structural level, serving as scaffolding for cell-type specific complexes, such as the dystrophin-associated protein complex (DPC) in striated muscle. Although for years morphological studies have described a close association with IF with the actin-rich cortex, recent advances in methods to study protein-protein interactions have provided new insight into the intimate structural and functional relationship between IFs and these membrane domains. 

The most striking difference between MSP and actin, from the standpoint of the mechanism of motility, lies in the polarity of the filaments... 

The principles of the push-pull model probably apply generally to amoeboid cell motility. Indeed, a consensus is developing that in both sperm and actin-based crawling cells the force for protrusion is derived from localized cytoskeletal assembly (reviewed by Pollard and Borisy, 2003). However, as applied to nematode sperm locomotion, the model envisions that lamellipod extension and cell body retraction are linked reciprocally to the polymerization state of the cytoskeleton. The lack of structural polarity of MSP filaments, the precise localization of cytoskeletal polymerization and depolymerization at opposite ends of the fiber complexes, and insights gained from reconstitution of cytoskeletal dynamics and motility in vitro and in vivo all support the conclusion that nematode sperm move without using motor proteins and that, instead, they rely on... 

Rlecent advances. . . suggest that these organelles may have served multiple roles in early eukaryotic cells... we speculate that protocilia were the primary determinants of cell polarity and directed motility in early eukaryotes. .. we believe that addition of an asymmetric central apparatus. .. provided refined directional control.. . . This paper presents hypothesized steps in this evolutionary process, and examples to support these hypotheses.24... 

Wang, F., Herzmark, P., Weiner, O. D., Srinivasan, S., Servant, G., and Bourne, H. R. (2002). Lipid products of PI(3)Ks maintain persistent cell polarity and directed motility in neutrophils. Nat. Cell Biol 4, 513-518. 

Family III.—Spirillaceae.—Cells curved or spirally bent, generally motile through polar flagella. 

Meads T, Schroer TA. 1995. Polarity and nucleation of microtubules in polarized epithelial cells. Cell Motil. Cytoskelet. 32 273-88... 

The actin cytoskeleton is important in cell shape changes, polarization, motility, chemotaxis, metastasis and ceU division, and Rho family proteins play critical roles in these effects. The involvement of PLD in changes in the actin cytoskeleton was first suggested by the effects of exogenous PLD and PA, which induced actin stress fiber formation and also increased the F-actin content of fibroblasts [172, 173]. Another study utilizing endotheUal ceUs also showed that PA that was free of LPA induced actin stress fiber formation [174]. Furthermore, the effects of LPA to induce this change in the actin cytoskeleton and also PA formation were blocked by butan-l-ol, but not butan-2-ol [174] (Fig. 4.6). 

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