title: Ca2+-dependent contractility of isolated and demembranated macronuclei in the hypotrichous ciliate Euplotes aediculatus.
abstract: The hypotrichous ciliated protozoan Euplotes aediculatus possesses a characteristic C-shaped somatic nucleus (macronucleus) within the cytoplasm, which shows dynamic shape change during the cell cycle. It is shown that isolated macronuclei possess Ca(2+)-dependent contractility. Macronuclei were isolated, stuck fast on the glass surface, and subjected to different concentrations of Ca(2+) in a Ca(2+)-EGTA buffer. The nuclei became expanded at [Ca(2+)]<10(-7)M, and they contracted on subsequent addition of higher concentrations of Ca(2+). Cycles of expansion and contraction of the nucleus could be repeated many times by alternate addition of EGTA and Ca(2+), indicating that the size of isolated nuclei can be regulated by [Ca(2+)] alone. The nuclear contraction was observed in all phases of the cell cycle, but contractility was less evident around replication bands in the S phase. In addition to the hypotrichous ciliate Euplotes, similar Ca(2+)-dependent nuclear contractility was found to exist in other cell types, including protozoans of different taxa (a heliozoon Actinophrys sol and a peniculine ciliate Paramecium bursaria), and also mammalian culture cells (HeLa cells). Our findings suggest a possibility that Ca(2+)-dependent nuclear contractility may be shared among diverse eukaryotic organisms.
authors.affiliation: Department of Biology, Faculty of Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Arikawa
authors.forename: N
authors.initials: N
authors.lastname: Momokawa
authors.forename: A
authors.initials: A
authors.lastname: Saito
authors.forename: G
authors.initials: G
authors.lastname: Omura
authors.forename: S M M K
authors.initials: SM
authors.lastname: Khan
authors.forename: Y
authors.initials: Y
authors.lastname: Suetomo
authors.forename: S
authors.initials: S
authors.lastname: Kakuta
authors.forename: T
authors.initials: T
authors.lastname: Suzaki
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020013:Calcium Signaling / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D002923:Cilia / Q000502:physiology; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D005057:Eukaryotic Cells / Q000378:metabolism; D016812:Euplotes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006367:HeLa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D009685:Nuclear Envelope / Q000187:drug effects / Q000378:metabolism; D010247:Paramecium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D002118:Calcium