Division Distribution Research Articles

The comparative cell cycle and metabolic effects of chemical treatments on root tip meristems. II. Propham, chlorpropham, and 2,4-dinitrophenol.

The effects of three chemicals, propham (Isopropyl carbanilate), chlorpropham (Isopropyl m-chloro-carbanilate), and DNP (2, 4-dinitrophenol) on oxygen uptake, ATP synthesis, cell division and cell cycle distribution in root tips of pea (Pisum sativum L.) ‘Alaska’ are reported. At the lowest concentration tested for each chemical (chlorpropham, 4.1×10-7 M; DNP, 1×10-6 M; and propham, 1.2×10-6 M) a reduction in the number of cells able to enter into mitosis was observed. DNP and propham induced a small number of abnormal mitoses, but chlorpropham caused a significant percentage of aberrancies (50%). At the higher range of concentrations tested, chlorpropham (4.1×10-4M) induced a similar mitotic inhibition response, but DNP and propham showed differences. Propham (1.2×10-3 M) caused a rapid decrease in number of mitoses so that by 6 hrs less than 1% of the total cells were dividing and all of them were abnormal, by 24 hrs this level was reduced to about 0.2%. DNP (1×10-3 M) caused an initial reduction in the number of mitotic figures followed by severe inhibition of entry into mitosis; division figures were abnormal from 3 hrs onward. DNP at 1×10-3 M caused the complete inhibition of oxygen uptake and ATP synthesis and inhibited mitotic entry and exit after 3 hrs. This study shows that although DNP (an uncoupler of respiration) and propham (a protein synthesis inhibitor) have different modes of action, both have severe and rapid mitotic inhibitory effects. It also reiterates with mitotic kinetic evidence that chlorpropham is a direct mitotic poison.

Indepencence of plasmid incompatibility and replication control functions in Staphylococcus aureus.

THERE are two basic requirements for the stable maintenance of an autonomous plasmid replicon, namely replication at a constant rate with respect to the cell division cycle and distribution of replicas to daughter cells.

Cellular division and cellular volume distribution in the presence of 2-phenyl-ethanol and some of its derivatives.

AGENTS that inhibit DNA synthesis in cells of higher animals are comparatively rare. Following on our earlier work1, we have tested mouse lymphoma cells in order to determine the rate of division and change in volume brought about by the presence of various concentrations of 2-phenyl-ethanol (PEA) and some of its derivatives.

Grit Unbalance in Sewage Flow Division

When sewage flows from a single inlet conduit to multiple grit chambers, large unbalances in liquid-grit distribution may occur. The slower moving bottom water that carries most of the grit is more easily diverted and will tend to concentrate in side channels at asymmetric bifurcations. Model tests support the proposed method of analysis of flow division distribution and show the complexities of the problem. Several arrangements for correcting unbalance are tested: (1) A vertical wall to advance the point of division and to reduce the effect of lace of symmetry; (2) top vanes that deflect top water into the side channel and force bottom water to move straight ahead; and (3) spiral motion that orients grit in the inlet conduit and alters flow division patterns. None of the tested systems cures all cases of unbalance, but all are effective for appropriate uses.