Contents Volume 93 (1982)

A thymidine kinase heterozygote was isolated from a diploid human lymphoblast line which forms colonies with high efficiency in microtiter dishes. We show that this cell line, called TK6, can be mutated from a tK^+/? to TK^?/? state by diverse mutagens, including ethyl methanesulfonate, butyl methanesulfonate, nitrosomethylurea, UV light, ICR-191, 4-nitroquinoline oxide, fluorodeoxyuridine, benzo[a]pyrene and aflatoxin B₁. We report here the experiments required to demonstrate the applicability of this new line in quantitative assays of mutation in human cells.Mitotic recombination between the centromere and the tk locus could not be induced by either dimethylsulfoxide or phorbol-12-myristate-13-acetate.     

The seasonal distribution of the marine diatom genus Chaetoceros Ehr. in Narragansett Bay, Rhode Island (1981-1982)

The seasonal dynamics of the diatom genus Chaetoceros Ehrenbergwere investigated in Narragansett Bay, Rhode Island. Whole watersamples were collected weekly from July 1981 to October 1982at four locations in the lower Bay and were preserved, concentratedby settling and enumerated. Chaetoceros were most abundant inlate winter–early spring; a second peak occurred in thefall. As in many other temperate neritic areas, C. debilis,C. compressus and C. didymus were major components of die Chaetocerospopulation and could be found throughout the year. Species compositionand dynamics were quite similar at the Jerusalem, GSO Pier andWickford Harbor stations, but were markedly different in PettaquamscuttRiver, a reduced salinity tidal estuary.