The protein per cell decreases during a 96-hour growth of Chang's and HeLa cells cultivated in suspension. This decrease is very high for the cytoplasmic proteins, while the nuclear proteins appear to be more stable. The content of cell proteins is reestablished during a phase of intensive enrichment which occurs during the first 30-60 min of the newly inoculated culture. The rate of protein labelling in this phase appears to be greater in the nuclei than in the cytoplasm. Both the level of rapid accumulation and the decrease of the protein content with time appear t o be a function of cell density. The rapid protein accumulation occurs when this density in the culture is lowest. With time and increase of the cell density in the culture, the protein content per cell goes down. I n non-synchronized cells this decrease is steady. I n "naturally" synchronized cells it shows itself in an oscillatory fashion. The artificial thymidine synchronization of HeLa suggests that the fluctuating protein production in the "naturally" synchronized cultures of these cells is linked with the periodical doubling of the cell number during the growth cycle which includes, for HeLa, a t least three cell cycles.
It has been found by density transfer and genetic mapping experiments that prophage SPO2 is linked to the antibiotic resistance marker ery-l in Bacillus subtilis 168. A site for the attachment of the prophage bacteriophage SPO2 (4) has been found on the chromosome of Bacillus subtilis 168. From transduction studies with phage PBS1 (7), the site was found to be closely linked to the erythromycin locus, ery-J (3). An approximate physical localization of the SPO2 prophage on the genetic map was first obtained by performing density transfer experiments. These experiments were carried out by transferring light spores of B. subtilis 168 thyA thyB, requiring thymine and lysogenized with SPO2, to a deuterated medium and allowing them to germinate in the manner described by Smith et al. (6). At 30-min intervals, beginning 90
Temperature-sensitive mutants of phage α were obtained by means of various mutagens and assigned to 25 complementation groups. Temperature-sensitive mutants belonging to 21 complementation groups and a mutant giving turbid plaques were used to perform two- and three-factor crosses. Seventeen of the cistrons and the turbid mutant were shown to belong to the same linear linkage group, which showed no signs of circularity. The remaining four unlinked cistrons showed peculiarities in their recombination properties. Genes which are known to be expressed earlier apear to be grouped together in a terminal segment of the linkage group.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.