ISSN:
0886-1544
Keywords:
divalent metal ions
;
lanthanide ions
;
calcium contraction
;
spasmoneme
;
Vorticella
;
stalk
;
contractile regulation
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
The glycerinated stalks of the peritrich ciliate, Vorticella, can contract helically and reversibly on the addition of not only Ca2+ but also other divalent or trivalent cations having ionic radii not far from 1 Å. In order to investigate the stalk contraction quantitatively in the absence of Ca2+-chelators, we developed a method to eliminate contaminating Ca2+ and other metal ions in KC1 and pHbuffer solutions by using a Ca2+-and heavy metal ion-specific ion exchange resin (Eporas MX-2) Thus, it was possible to measure the relationship between the fractional stalk length of Vorticella and the free concentration of alkaline earth metal, transition metal, and lanthanide ions in the 0.1 M KC1 and buffer (pH 6.8) solutions. Among these ions, Ca2+, Nd3+, and Eu3+ (having ionic radii of about 1 Å) had the highest affinity for the contractile element in the spasmoneme. As the concentration of lanthanide ions (except Nd3+ and Eu3+) is increased, the Vorticella stalk contracts abruptly at a threshold level; this means that the Hill's parameter is very high, probably more than 6. The results of these experiments and of the co-mixtures of Ca2+ and Tb3+ suggest that a contractile element in the spasmoneme contains both contractile Ca2+-binding and regulatory Ca2+-binding sites.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cm.970070106
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