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.
Subject(s)
Calcium Signaling/physiology , Calcium/metabolism , Cell Movement/physiology , Cell Nucleus/metabolism , Cytoplasm/metabolism , Euplotes/metabolism , Animals , Calcium/pharmacology , Cell Cycle/drug effects , Cell Cycle/physiology , Cell Movement/drug effects , Cell Nucleus/drug effects , Cell Nucleus/ultrastructure , Cell Size/drug effects , Cell Size/physiology , Chelating Agents/pharmacology , Cilia/physiology , Cytoplasm/drug effects , Cytoplasm/ultrastructure , Dose-Response Relationship, Drug , Eukaryotic Cells/metabolism , Euplotes/cytology , Euplotes/drug effects , HeLa Cells/cytology , HeLa Cells/drug effects , HeLa Cells/metabolism , Humans , Nuclear Envelope/drug effects , Nuclear Envelope/metabolism , Paramecium/cytology , Paramecium/drug effects , Paramecium/metabolismABSTRACT
A 24-year-old woman was diagnosed as having hereditary elliptocytosis and post-transfusion hepatitis. On admission, a marked delay in indocyanine green (ICG) plasma clearance was noted while bromsulphalein excretion was almost normal. Even when her levels of serum bilirubin and transaminases were decreased to the normal ranges and a liver biopsy revealed no evidence of any liver cirrhosis or active hepatitis, ICG excretion still remained abnormal. These findings were compatible to those of constitutional ICG excretory defect.