Motility cycle

Lasek, R. J. and Brady, S. T. Adenylyl imidodiphosphate (AMPPNP), a nonhydrolyzable analogue of ATP, produces a stable intermediate in the motility cycle of fast axonal transport. Biol. Bull. 167 503,1984. 

Figure 2. Amoeboid motility cycle. (1) A resting cell is stimulated by an external signal (possibly a gradient of chemoattractant). (2) The cell protrudes a lamellipod towards the source of the stimulus. (3) New focal contacts are formed under the extended lamellipod. (4) The cell exerts force on the cytoskeleton via contraction. [5] The old focal contacts detach under the exerted force, resulting in net translocation of the cell. Taken with permission from Condeelis et al. [43],...

Wessels, D., Vawter-Hugart, H., Murray, J. et al. (1994). Three-dimensional dynamics of pseudopod formation and the regulation of turning during the motility cycle of Dictyostelium. Cell MotU. Cytoskeleton 27, 1-12. 

Murray, J., Vawter-Hugart, H., Voss, E. and Soil, D.R. (1992). Three-dimensional motility cycle in leukocytes. Cell MotH. Cytoskeleton 22, 211-223. 

Monomeric actin binds ATP very tightly with an association constant Ka of 1 O M in low ionic strength buffers in the presence of Ca ions. A polymerization cycle involves addition of the ATP-monomer to the polymer end, hydrolysis of ATP on the incorporated subunit, liberation of Pi in solution, and dissociation of the ADP-monomer. Exchange of ATP for bound ADP occurs on the monomer only, and precedes its involvement in another polymerization cycle. Therefore, monomer-polymer exchange reactions are linked to the expenditure of energy exactly one mol of ATP per mol of actin is incorporated into actin filaments. As a result, up to 40% of the ATP consumed in motile cells is used to maintain the dynamic state of actin. Thus, it is important to understand how the free energy of nucleotide hydrolysis is utilized in cytoskeleton assembly. 

Lassing, I Lindberg, U. (1988). Evidence that the phosphatidyl-inositol cycle is linked to cell motility. Expt. Cell Res. 174, 1-15. 

Oestradiol and progesterone regulate the structural and functional changes in oviducts, uterus, cervix and vagina that occur during the menstrual cycle. They provide conditions in the oviduct for the upward motility of sperm, and the downward movement of ova, and also conditions favourable for fertilisation in the oviduct and implantation in the uterus. Another effect is to stimulate vaginal secretions. 

Nevertheless, the process of encystment dictates when a substantial fraction of a Gonyaulax population leaves the water column, regardless of the ability of motile cells to persist for extended periods. The encystment/excystment cycle can thus define the temporal limits of some blooms. More work is needed to evaluate the importance of this process relative to bloom termination from factors such as grazing or advection that decrease the numbers of motile cells. 

Testicular atrophy was reported in rats exposed to 19 mg cobalt/m (as cobalt sulfate) for 16 days." Male mice exposed for 13 weeks at 1.14 mg cobalt/m had a decrease in sperm motility, and at 11.4 mg cobalt/m there was testicular atrophy at the high dose female mice had a significant increase in length of the estrous cycle."... 

Valouev lA, Kushnirov VV, Ter-Avanesyan MD (2002) Yeast polypeptide chain release factors eREl and eRE3 are involved in cytoskeleton organization and cell cycle regulation. Cell Motil Cytoskelet 52 161-... 

Thirty mice of an inbred colony were used to study the effect of di(2-ethylhexyl) phthalate on reproductive function (Jain Joshi, 1991). Fifteen mice were dosed orally with 1000 mg/kg bw di(2-ethylhexyl) phthalate [purity not specified] in 0.1 mL olive oil for one week. The fertility (evaluated by the ability of the motile spermatozoa to fertilize normal cycling females) was reduced from 90 to 75%. Sperm density and sperm motility were also significantly reduced. 

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