Relationship between multidrug resistance,hypersensitivity to resistance modifiers and cell volume in Chinese hamster ovary cells.

We have previously shown that very high levels of hypersensitivity to several resistance modifiers are correlated with increasing multidrug resistance in a series of Chinese hamster ovary cell lines. We have now selected a new member of the series which is an exception to this correlation in that although it is almost twice as multidrug resistant as the cell line from which it was derived, it shows much less hypersensitivity to resistance modifiers. Level of resistance modifier hypersensitivity correlated with the level of reduction of verapamil accumulation in these cells, and with the density of P-glycoprotein, but since the selection of this cell line has involved a doubling of cell volume, it was not correlated with total amount of P-glycoprotein.     

Control of woolly aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Pemphigidae) on mature apple trees using insecticide soil-root drenches

Abstract Woolly aphid, Eriosoma lanigerum , is an important pest of apples that infests both the aerial and root parts of the tree. Root colonies are protected from the pesticide sprays applied during the growing season and the climatic effects of winter. Consequently, root colonies are a major source of aerial re-infestation in the following spring. Imidacloprid, the first of a new group of insecticides from the chloronicotinyl family, is known to provide excellent control of woolly aphid on trees up to 7-years-old when applied as a root soil drench. This study compared the effects of a single application of chlorpyrifos, imidacloprid, pirimicarb or vamidothion, applied as a root drench over four growing seasons. A soil wetting agent was added to each chemical to improve soil saturation and penetration. Imidacloprid provided excellent control of woolly aphid on the trees that were 17-years-old at the start of the study and continued to do so for four seasons. Pirimicarb appeared to offer some suppression of woolly aphid during the first season but not in subsequent seasons, while chlorpyrifos and vamidothion failed to control woolly aphid in any season. The potential role for imidacloprid in IPM programs is discussed.     

A rapid technique for the analytical and preparative isolation of transfer RNA from reaction mixtures

The isolation of enzymically modified tRNA's from enzyme reaction mixtures is usually achieved by one of two general methods. Amino-acyl synthetase reactions are easily assayed by filter paper techniques (1) in which the tRNA is precipitated on filters of materials such as cellulose ester or glass fiber. After drying, the filters can be counted by several techniques. The limitations of this technique include unknown counting efficiency and loss of the sample. In cases in which recovery of the tRNA is desired the usual procedure involves phenol extraction of the tRNA followed by selective precipitation with salts and/or organic solvents.     

Membrane Attachment of R-Factor Deoxyribonucleic Acid in Compatible and Incompatible Cell Pairs Following Conjugation

Superinfection of an Escherichia coli R(+) strain with a closely related R-factor was associated with the accumulation of replicative intermediates of the superinfecting deoxyribonucleic acid. This deoxyribonucleic acid remains associated with a rapidly sedimenting cell component.