An autoradiographic study of the binding of 3-H-chlorambucil to cells of a drug-sensitive and drug-resistant strain of the Yoshida ascites sarcoma.

The binding of chlorambucil to drug-sensitive and drug-resistant. Yoshida sarcoma cells has been investigated by an autoradiographic technique. The cells were treated with the drug at various concentrations both in vitro and in vivo. Using both light and electron microscope techniques, and by counting grains on various areas of the cell, the following conclusions were reached. (1) At all drug concentrations there was general cytoplasmic and nuclear uptake by both cell lines. There was no evidence of a specific localization in one site only or for specific exclusion of any one site. (2) At high dose levels (equivalent to 2 mM) the binding was approximately equal in both cell lines, although a few damaged cells bound much greater amounts of drug. (3) At low dose levels (equivalent to 3 mu-M) there was a higher uptake by the nucleus of the sensitive cells compared with the nucleus of the resistant cells; the cytoplasmic binding was similar.     

Handling and staining epoxy resin sections for light microscopy.

Epoxy resin sections 0 1-1.0 mum thick of specimens embedded for electron microscopy, were collected from the ultramicrotome using strips of cover slip, and, after drying on a hot plate, were bulk stained in specially made troughs. After treatment with periodic acid, the sections were stained first in basic fuchsin at 70 degrees C and then in alkaline methylene blue at room temperature. The handling technique allows accurate collection of serial sections without interrupting the sectioning process, and the stain combination is suitable for different specimens in different epoxy resins and is unaffected by storage for more than 1 year.     

Quantitative evaluation of autoradiographs by X-ray spectroscopy.

Measurements of mass of developed silver in autoradiograms have been made using X-ray microanalysis. This procedure has been applied to a scanning electron microscopic study of protease-induced cell stimulation in 3H-thymidine-labelled bladder tissues in vitro. Differences in silver concentrations over individual nuclei were demonstrated by X-ray analysis and quantitative data was obtained showing an increased rate of 3H-thymidine incorporation in protease-treated cultures. The initial evidence indicates that X-ray microanalysis could provide a potentially useful quantitative procedure for autoradiography.     

The role of adiabatic shear in solid particle erosion

A comparison is made of the deformation produced when titanium and mild steel target specimens are impacted obliquely by flat-ended cylindrical projectiles. The impact process is studied by high speed photography; it is shown that whereas in mild steel material is not removed from the surface but merely displaced, in titanium, the displaced material detaches by a process involving the formation of adiabatic shear bands. Attention is drawn to the influence of susceptibility to adiabatic shear on resistance to solid particle erosion.     

Relationship between the coefficient of friction and the wear rate of metals

A very approximate mathematical analysis is given for the relationship between the coefficient of friction and the wear factor of metals for the case of sliding wear. The analysis is based on the delamination theory of wear, the empirically determined plastic strain field near the surface at the onset of delamination of a wear sheet and a constitutive relation which takes into account the effect of cyclic softening. An energy argument is used. The agreement between experimentally observed values and theoretically predicted values is good.     

An analysis of stick-slip motion

A theory for stick-slip motion for the case of constant static and constant dynamic coefficients of friction has been derived. The theory was checked using a specimen of rubber and the experimentally observed results were in very good agreement with the results predicted by the theory.