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At least 1,063 records · Page 59Linked to original sources
PubMed1980

Interactions of dynein arms with b subfibers of Tetrahymena cilia: quantitation of the effects of magnesium and adenosine triphosphate.

Tetrahymena 30S dynein was extracted with 0.5 M KCl and tested for retention of several functional properties associated wtih its in situ force-generating capacity. The dynein fraction will rebind to extracted outer doublets in the presence of Mg2+ to restore dynein arms. The arms attach at one end to the A subfiber and form bridges at the other end to the B subfiber of an adjacent doublet. Recombined arms retain an ATPase activity that remains coupled to potential generation of interdoublet sliding forces. To examine important aspects of the dynein-tubulin interaction that we presume are directly related to the dynein force-generating cross-bridge cycle, a simple and quantitative spectrophotometric assay was devised for monitoring the associations between isolated 30S dynein and the B subfiber. Utilizing this assay, the binding of dynein to B subfibers was found to be dependent upon divalent cations, saturating at 3 mM Mg2+. Micromolar concentrations of MgATP2- cause the release of dynein from the B subfiber; however, not all of the dynein bound under these conditions is released by ATP. ATP-insensitive dynein binding results from dynein interactions with non-B-tubule sites on outer-doublet and central-pair microtubules and from ATP-insensitive binding to sites on the B subfiber. Vanadate over a wide concentration range (10(-6)-10(-3) M) has no effect on the Mg2+-induced binding of dynein or its release by MgATP2-, and was used to inhibit secondary doublet disintegration in the suspensions. In the presence of 10 microM vanadate, dynein is maximally dissociated by MgATP2- concentrations greater than or equal to 1 microM with half-maximal release at 0.2 microM. These binding properties of isolated dynein arms closely resemble the cross-bridging behavior of in situ dynein arms reported previously, suggesting that quantitative studies such as those presented here may yield reliable information concerning the mechanism of force generation in dynein-microtubule motile systems. The results also suggest that vanadate may interact with an enzyme-product complex that has a low affinity for tubulin.

Adenosine Triphosphatases↗
PubMed2006

The reproductive significance of human Fallopian tube cilia.

Effective tubal transport of ova, sperm and embryos is a prerequisite for successful spontaneous pregnancy. Although there is much yet to be discovered about the mechanisms involved, it is evident that tubal transit is a far more complicated process than initially thought. Propulsion of gametes and embryos is achieved by complex interaction between muscle contractions, ciliary activity and the flow of tubal secretions. Evidence is accumulating of the important and possibly pre-eminent role of ciliary motion in this process; and this review describes current knowledge about ciliary activity and its physiological regulation. There is also a description of the effects on ciliary function of cigarette smoking and various pathological states, including endometriosis and microbial infection, with consideration given as to how altered ciliary activity may impact upon fertility.

Chlamydia↗
PubMed1977

Effects of adenosine triphosphate on N-ethylmaleimide-induced modification of 30S dynein from Tetrahymena cilia.

Ciliary 30S dynein of Tetrahymena was investigated with regard to modification of the ATPase activity with N-ethylmaleimide (NEM) in the presence of ATP. The elevation of enzyme activity due to the modification was largely repressed by addition of ATP at a concentration of 1 mM or more during preincubation of 20 h at 0 degrees C. The repression was highly specific for ATP, though ADP and AMPPNP showed slight repressive effects. After complete hydrolysis of ATP added to the preincubation mixture, however, elevation of 30S dynein ATPase activity occurred. It is suggested that the repression by ATP of NEM-induced elevation of 30S dynein ATPase activity is simply due to a protecting effect of ATP on certain SH group(s) (probably SH1-type group(s)) around the active center of 30S dynein. When 30S dynein was maximally activated by modification with NEM, ATP or ADP did not significantly promote the inactivation of the modified enzyme upon further treatment with NEM, indicating that 30S dynein lacks the characteristics of SH2-type groups. On the other hand, ATP also showed a protective effect against inhibition of native 30S dynein by high concentrations of NEM. High concentrations of ADP and AMPPNP were inhibitory to 30S dynein ATPase activity but inorganic phosphate did not inhibit 14S or 30S dynein ATPase activities at all.

Adenosine Diphosphate↗
PubMed2005

Cigarette smoke inhibits hamster oocyte pickup by increasing adhesion between the oocyte cumulus complex and oviductal cilia.

Previous research has shown that oocyte cumulus complex (OCC) pickup rate is inhibited in hamsters when oviducts and OCCs are simultaneously exposed to cigarette smoke solutions, independent of any effect on ciliary beat frequency. The purpose of this research was to determine whether smoke solutions caused a change in adhesion between the OCC and infundibulum of the oviduct and to determine whether a change in adhesion could account for decreased OCC pickup rate. OCC pickup rate and adhesion were measured before and after infundibula or OCCs recovered from acute in vitro exposures to mainstream and sidestream whole, gas, or particulate smoke solutions. Ciliary beat frequency was also measured on infundibula. Overall, smoke solutions decreased oocyte pickup rate 40% to 80% below control levels and increased adhesion 52% to 91% above control levels when infundibula were pretreated. A change in adhesion was observed in cases for which decreased OCC pickup rate could not be explained by a change in ciliary beat frequency. OCC pickup rate decreased 20% to 35% below control levels and adhesion increased 39% to 54% above control levels when OCCs were pretreated. These data show not only that cigarette smoke causes an increase in OCC adhesion to the oviduct, but also that there is a correlation between increased adhesion and decreased OCC pickup rate. The results also show that the both the OCC and oviduct are targets of cigarette smoke. The oviduct is more sensitive to the adverse effects of smoke; however, this may be caused by a combined impact on mechanisms involved in both adhesion and ciliary function.

Animals↗
PubMed1987

SRS-A leukotrienes decrease the activity of human respiratory cilia.

We have studied the effects of the slow reacting substance of anaphylaxis (SRS-A) constituents leukotrienes (LT) C4 and D4 on the ciliary activity of human respiratory cells. The ciliary beat frequency on human nasal cells harvested by cell scraping from the inferior turbinate was measured in a blind design by a microphoto-oscillographic technique. A total of 740 ciliated cells from seventy-four cell scrapings were studied. Mean baseline of ciliary beat frequency was 10.2 Hz. The ciliary beat frequency exhibited a pronounced variability in the spontaneous changes between the cell scrapings, yet less so within cell samples from the cell scrapings. We, therefore, evaluated the effect of the test solutions relative to the spontaneous decrease found during simultaneous perfusion with control solution of samples from the same cell scrapings. LTC4, 3-300 nmol/l, caused a highly significantly dose-related decrease in the ciliary beat frequency by up to approximately 20% as compared to the corresponding control solution. The effect of LTC4 was significantly inhibited by the SRS-A receptor antagonist FPL 55712 (10 mumol/l), but not by indomethacin (10 mumol/l). LTD4, 300 nmol/l, also decreased the ciliary beat frequency. LTB4, which is a leukotriene, although without the sulphidopeptide side chain of the SRS-A leukotrienes, did not affect the ciliary beat frequency in a concentration of 100 nmol/l. This would seem to confirm the structure specificity of the elucidated effect of the SRS-A leukotrienes. Histamine (100 mumol/l) did not affect the ciliary beat frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromones↗