title: Giardia lamblia: autoradiographic analysis of nuclear replication.
abstract: Giardia lamblia trophozoites, grown in axenic culture, were labeled for various periods of time with [3H]thymidine. After autoradiography, grains were counted over each of the two nuclei in each trophozoite. Analysis of the fraction of trophozoites labeled for each time period resulted in an estimate of a generation time of 15 hr. The DNA synthetic or S phase for a trophozoite in culture was calculated to be 1.8 hr. G1 and G2 periods were determined to be 8.5 and 3 hr, respectively. A comparison of the labeling density between the two nuclei indicated that replication takes place simultaneously in both nuclei for at least 70% of S period. The fraction of asymmetrically labeled trophozoites is consistent with a model in which the nuclei replicate out of phase by 15-30 min, but, due to the small diameter of the nuclei relative to the grain size, the possibility that replication takes place simultaneously in both nuclei of a trophozoite throughout the S phase cannot be ruled out.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002467:Cell Nucleus / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis; D005872:Giardia / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure*; D007399:Interphase; D007700:Kinetics; D008938:Mitosis
chemical_list: D004247:DNA