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At least 1,081 records · Page 60Linked to original sources
PubMed1990

Leukotriene C4 decreases the activity of respiratory cilia in vitro.

In the present study we assessed the effect of leukotriene C4 on ciliary beat frequency in vitro. Chicken tracheas were sliced into thin rings and ciliary activity was viewed microscopically. Ciliary beat frequency was measured through an optical fibre by a fast Fourier transformer analyser and recorded on an oscilloscope. Ciliary beat frequency was measured at one fixed point during 30 min at room temperature in RPMI-HEPES medium alone and in medium containing leukotriene C4 at a range of concentrations (10(-6)-10(-9) M). Our results demonstrate that leukotriene C4 (10(-7) and 10(-8) M) caused a significant decrease in ciliary beat frequency in all tracheal rings tested (mean decrease of 24%). The specificity and Ca2(+)-dependency of leukotriene C4 activity was elucidated by the ability of FPL 55712 (SRS-A specific antagonist), Ca2(+)-free medium, calcium channel blockers (nifedipine and verapamil) and the calmodulin inhibitor trifluroperazine to abrogate its effect on ciliary beating.

Adenosine Triphosphate↗
PubMed1992

Activation of ATPase activity of 14S dynein from Tetrahymena cilia by microtubules.

The ATPase activity of 14S dynein was activated by the presence of microtubule-associated-protein-free microtubules. The activation was 2.5-3.5 fold at 10 mg microtubule/ml, and the activity increased further with increasing microtubule concentration. The microtubule-14S-dynein complex, microtubule bundles with 14S dynein, was treated with a zero-length chemical cross-linker, 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). The ATPase activity of the complex responded to EDC in a biphasic, concentration-dependent manner and, at most, it was enhanced 5-10 fold. The complex treated with EDC was no longer unbundled by addition of ATP, as revealed by electron-microscopic observation. Several ATP analogues, which support in vitro microtubule translocation mediated by 14S dynein, were turned over faster by this mechanochemical enzyme in the presence of microtubules than in their absence. However, some ATP analogues which do not support the translocation were also turned over faster in the presence of microtubules. Thus, microtubule-dynein motility and substrate-turnover activation are not tightly coupled, which indicates that all three major motor systems, actin- heavy-meromyosin, microtubule-kinesin [Shimizu, T., Furusawa, K., Ohashi, S., Toyoshima, Y. Y., Okuno, M., Malik, F. & Vale, R. D. (1991) J. Cell Biol. 112, 1189-1197] and microtubule-dynein, have this characteristic property in common.

Adenosine Triphosphatases↗
PubMed1992

Purification, characterization and structure of protein phosphatase 1 from the cilia of Paramecium tetraurelia.

A type 1 serine/threonine protein phosphatase (PP1) which is mostly localized in the excitable ciliary membranes from the protozoan Paramecium, was purified to homogeneity. Approximately 4 micrograms enzyme of 37 kDa was isolated from 100 l axenic culture. The enzymic properties were characterized using phosphorylase a from rabbit skeletal muscle as a substrate and several known effectors of mammalian PP1. The protozoan PP1 was enzymically indistinguishable from its mammalian congener. The amino acid sequence of the Paramecium PP1 was deduced from its cDNA. The full-length clone was obtained in several steps starting with a pair of degenerate primers made according to the two most conserved peptides of rabbit PP1 and PP2A. The gene encodes a protein of 36,392 Da. The identity of the cloned gene and the isolated ciliary PP1 was unequivocally established by microsequencing of four tryptic and cyanogen-bromide peptides which were generated from the purified protein. Paramecium PP1 shows 75% amino-acid-sequence identity with rabbit PP1 alpha. Areas of major differences are the C-termini and N-termini and a sequence between residues 219-242.

Amino Acid Sequence↗
PubMed1979

Effect of trichloroethylene on cilia activity in rabbit trachea.

The ciliotoxicity of trichloroethylene was studied in terms of the time required for ciliostasis in specimens of trachea from 35 male rabbits following exposure of the specimens to different vapour concentrations. The highest vapour concentration was linked with the most rapid ciliostasis but even in the lowest concentration tested, 5.000 p.p.m. (26 g/m3), hastened ciliostasis. Specimens from the upper region of the trachea underwent ciliostasis more slowly than did those from the lower region. The absolute uptake of trichloroethylene was lower in the former than in the latter specimen. The difference in uptake could not be explained by a difference in weight or in lipid content. That ciliostasis occurred at different times depending upon the region of the trachea, favours the theory of a critical tissue concentration for trichloroethylene.

Animals↗
PubMed1966

Reversal response elicited in nonbeating cilia of paramecium by membrane depolarizatin.

Ciliary reversal occurs in response to electrical and chemical stimuli in specimens of Paramecium caudatum in which ciliary beat has been completely inhibited by external application of nickel ions. The mechanism underlying ciliary reversal appears, therefore, to differ from that of ciliary beat. The cessation of ciliary beat has no effect on the intracellular potential of Paramecium. However, depolarizing action potentials are associated with ciliary reversals in paramecia, treated with nickel, without ciliary beat. Thus, membrane depolarization in this species seems specifically concerned with the ciliary reversal, and not with ciliary beat.

Animals↗