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At least 865 records · Page 48Linked to original sources
PubMed1991

Negative cilia concept for thromboresistance: synergistic effect of PEO and sulfonate groups grafted onto polyurethanes.

In order to investigate the interaction between various sulfonated polyurethanes (PUs) and blood, a commercial PU surface was chemically modified by poly(ethylene oxide) (PEO), dodecanediol(DDO), and propane sultone to give hydrophilic, hydrophobic, and negative sulfonated surfaces, respectively. The blood compatibility of modified PUs was evaluated by an in vitro platelet adhesion test, activated partial thromboplastin time (APTT), and prothrombin time (PT) measurements as well as an ex vivo rabbit A-A shunt method. In the platelet adhesion test, the hydrophilic PEO grafted PUs showed less platelet adhesion than untreated PU and hydrophobic DDO grafted PU. Sulfonated PU-PEO exhibited a lower degree of adhesion and shape change of platelet. The APTT and PT, especially APTT, of the sulfonated PUs were extended, whereas those of PU-PEO and PU-DDO did not show any significant change compared with untreated PU. Meanwhile, in the ex vivo experiment, hydrophilic PEO grafted PUs showed longer occlusion times than untreated PU or hydrophobic DDO grafted PU. In addition, the incorporation of SO3 groups at the end of PU-DDO and PU-PEO, particularly PU-PEO-SO3, exhibited an enormous prolongation in occlusion time, indicating a synergistic effect of the hydrophilic PEO and the negative SO3 groups on thromboresistance. These occlusion times corresponded well to in vitro evaluation results: the less adhesion and shape change of platelet and the longer APTT and PT, the more extended the ex vivo occlusion time.

Animals↗
PubMed2004

Perisynaptic Schwann cells of the vertebrate motor endplate bear modified cilia.

Perisynaptic Schwann cells (PSCs), descendants of the myelinating Schwann cells, cover the axon terminal of the vertebrate motor endplate of the skeletal muscle fiber. PSCs are assumed to support the function of the axon terminal. This function suggests a net material transport in the direction of the axon terminal. Morphologically it is to be expected that these cells have a cytoskeleton aligned to the axon terminal. Investigations clarifying this statement have not yet been undertaken. From previous investigations we know, however, that the PSCs have a microtubule-organizing center, which is a part of this cytoskeleton. The centrioles of the organizing center may also participate in the formation of a modified cilium structure whose function is unknown. In the present investigation, characteristic ultrastructural features of the modified cilium structure and its relationship to the Golgi apparatus and the axon terminal are presented. A function for the modified cilium structure is discussed.

Animals↗
PubMed1979

Effect of thiourea and substituted thioureas on dynein ATPase and on the turbidity response of Tetrahymena cilia.

The effects of thiourea and of several substituted thioureas -- phenylthiourea, alpha-naphtylthiourea, metiamide, and burimamide -- on dynein ATPase have been studied. The substituted thioureas are over 30 times more potent than thiourea in causing enhancement of 30S dynein ATPase activity and inhibition of 14S dynein ATPase activity. The effects of thiourea and phenylthiourea can be prevented by very low concentrations of beta-mercaptoethanol or dithiothreitol. Axonemal ATPase is also enhanced by the thioureas, but the reaction proceeds more slowly than for solubilized 30S dynein. Enhancement of 30S dynein ATPase by metiamide is prevented by low (approximately 1 microM) concentrations of ATP and, less effectively, by AMP-PNP, but not by AMP-PCP even though the latter is a stronger inhibitor of 30S dynein ATPase than is AMP-PNP. The thioureas inhibit the ATP-induced decrease in turbidity (measured as delta A350) of axonemal suspensions. Inhibition of the turbidity response is also prevented by low concentrations of beta-mercaptoethanol, but, in contrast to the irreversible enhancement of ATPase activity, inhibition of the turbidity response is largely reversible. The ability of 30S dynein to rebind onto twice-extracted axonemes is not changed by treatment with phenylthiourea or metiamide. These observations indicate that the thioureas react with at least two sets of SH or S--S groups on axonemes. Reaction with the group(s) on the 30S dynein causes an apparently irreversible enhancement of ATPase activity. Reaction with another group(s) causes a reversible inhibition of the turbidity response.

Adenosine Triphosphatases↗
PubMedDate not supplied

Nicotine increases ciliary beat frequency by a direct effect on respiratory cilia.

We studied the direct effects of nicotine on the ciliary beat frequency (CBF) undisturbed by interference from mucus secretion by using epithelial strips from ferret tracheae which contain no goblet cells and, because the glands were left behind in the submucosa, no gland tissue either. Strips were studied in a chamber perfused with medium M-199 at 37 degrees C at a perfusion rate of 1.6 ml min-1 using a perfusion pump (Braun, Melsungen). CBF was determined photometrically, the signal being subjected to a fast Fourier transformation. We measured CBF continuously for 10 min (5 min with and 5 min without perfusion). Under baseline conditions without nicotine, it decreased from 23.4 +/- 0.8 to 22.2 +/- 0.5 Hz during perfusion and increased from 22.0 +/- 0.8 to 23.3 +/- 0.8 Hz during the subsequent period without perfusion. Nicotine increased CBF transiently, i.e., the effect was demonstrable only during perfusion, being strongest during the first 3 min of perfusion. At 10(-5) M, the increase in CBF was significant only during the 3rd minute, but at 10(-4) and 10(-3) M, CBF was elevated significantly throughout most of the perfusion period compared with control tissues perfused with medium M-199 only. Thus, at 2 min, CBF was 22.8 +/- 0.6 (mean +/- SE) in tissues perfused with medium M-199 only but was 24.3 +/- 0.8 Hz (NS, Student's unpaired t-test), 26.6 +/- 0.5 Hz (P = 0.001), and 26.8 +/- 1.2 Hz (P = 0.01) in tissues perfused with 10(-5), 10(-4), and 10(-3) M nicotine (dissolved in medium M-199), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗