Changes in morphology and cell proliferation during vitamin A-induced mucous metaplasia of developing chick scale cultured in vitro

Methods of successive multiparametric cytochemistry and microfluorometry on identical cells with special reference to cell cycle phases in a chick embryo

The study of cell cycle kinetics in relation to regulatory mechanisms in embryonic development is considered quite important, but many technical difficulties still remain owing to the complexity of embryonic systems. To facilitate such study, a novel method of multiparametric microfluorometry was developed and is presented here. In many other multiparametric methods, various cytochemistries and fluorometries are conducted at the same time, whereas in our system only one type of cytochemistry and its microfluorometry are performed first and then other types subsequently. Our system is composed of two parts, a method for combining various types of quantitative cytochemistries to be performed in succession on identical cells and a method that permits the implementation of cytochemistries and microfluorometries in succession using in combination a microfluorometer, TV camera, video recorder, digital Telopper, and microcomputers. A method for the evaluation and normalization of microfluorometric data on DNA content is described. The cell cycle phases of each cell can be accurately distinguished on the basis of DNA content and BrdU uptake, using a statistical method. A cell cycle traverse study using embryonic avian scale dermal cells was carried out in which the four parameters of DNA content, double labeling with BrdU and [3H]AdR, and time lapse between the two labelings were included. As an example of its application to molecular cytochemistry, in situ nick translation was conducted on developing scale dermal cells. The special features and scope of application of the present system are discussed.

Hyaluronate accumulation in human epidermis treated with retinoic acid in skin organ culture

Retinoic acid (RA) has been shown to retard the differentiation of epidermal keratinocytes by several morphologic and biochemical criteria. In this study, the epidermal content and localization of hyaluronate (HA), as well as its synthesis and disappearance in human skin organ culture, were characterized to test the idea that some of the RA influences on epidermal differentiation are associated with keratinocyte HA metabolism. RA stimulated the incorporation of 3H-glucosamine into HA by up to 60% at concentrations between 50 nM and 5 microM, while pulse-chase experiments revealed little change in its disappearance rate from epidermis. After 5 d in culture, the chemically quantified HA was more than doubled in the treated epidermis. The accumulation of HA was substantiated by light and electron microscopy with a specific probe prepared from the HA binding region of cartilage proteoglycan. The staining was particularly enhanced between the upper spinous cell layers, where the terminal differentiation into corneocytes normally takes place. A patchy, discontinuous staining was also seen in stratum granulosum and corneum layers, which are not stained at all in control cultures. The present study demonstrates that RA leads to an accumulation of HA in the superficial layers of epidermis by stimulating its synthesis in keratinocytes. This may account for the delay in terminal differentiation, and the weakened cohesion of the keratinocytes previously observed both in vivo and vitro.