Scanning electron microscopy of variations in human metaphase chromosome structure revealed by Giemsa banding

Trypsinization, used as a pretreatment for Giemsa banding human chromosomes, produced a progressive degradation of metaphase chromosome structure. Over the visible range of G-banding in the light microscope various levels of chromosome structure were revealed in the scanning electron microscope.

High-resolution scanning electron microscopy of human metaphase chromosomes

Human metaphase chromosomes, prepared for light microscopy were examined by scanning electron microscopy. Use of an osmium impregnation technique eliminated the need for sputter-coating and allowed high-resolution visualization of uncoated specimens. Chromosomes were of three-dimensional cylindrical profile, with well-defined chromatids and centromeres. Prior to Giemsa-banding a smooth surface morphology was observed. Relaxation of chromosome integrity by Giemsa-banding pretreatment allowed resolution of several orders of chromosome structure not previously demonstrated by scanning electron microscopy. The observed organization of the chromatin fibres allowed parallels to be drawn with the radial loop model of chromosome construction as described by Marsden and Laemmli.

Cell migration through three-dimensional gels of native collagen fibres: collagenolytic activity is not required for the migration of two permanent cell lines

Three dimensional gels of native type I collagen fibres have been used as a substratum for the growth and migration of Chinese hamster ovary cells (fibroblastoid cell line) and RPMI-3460 melanoma cells (tumorigenic cell line from Syrian hamster). Quantitative data concerning the migration of these cells from the gel surface into the 3-dimensional collagen gel matrix have been obtained. The migration of both cell types into the collagen gel matrix is not accompanied by the degradation of collagen fibres. The possible implications of these observations for tumour cell invasion in vivo are discussed.

Changes in surface morphology associated with ageing and carcinogen treatment of Chinese hamster lung cells

The relationship between ageing and transformation has been investigated by a serial study of the changes in cell-surface morphology as normal and carcinogen-treated cells progressed in culture. A progressive increase in the density of cell surface microvilli occurred in association with the adoption of a more rounded profile and concomitant increase in the rate of cell detachment. These changes occurred earlier after carcinogen treatment, which appeared to indicate a carcinogen-induced acceleration of ageing. The alterations have also been described as characteristic of the transformed state. The observations suggest that the expression of in vitro transformation may be the result of continuous selection from a population with genetic instability and variable morphology.