Vitamin A--a probe in the study of growth, differentiation and morphogenesis]

Scientific work on vitamin A research has started more than one hundred years ago. The information accumulated thus far has already been published in thousands of original papers, review articles, monographic series and books. The overall result of these investigations can be concentrated in the title of the present review. Vitamin A and its analogues, the retinoids, participate directly in several physiological functions, such as vision, growth, development and differentiation. These compounds have also found useful application in the cure of several serious dermatological diseases and in cancer therapy. Their activities are also widely exploited to study embryogenesis, teratogenesis and carcinogenesis. Recent advances ascribe to retinoic acid properties, which render it a putative candidate for the first vertebrate morphogen. These developments, in combination with progress made in the study of homeo box genes, open new ways towards elucidating the mode of action of retinoids at the molecular level. It is tempting to speculate that, understanding enough about the basic biology of retinoid action, might be beneficially exploited for the betterment of the mankind.     

Factors controlling the DNA-synthesis in 3T3 and EAT cells

Beta globulins, (Cohn Fr. III), are a major source of molecules affecting the DNA-synthesis of 3T3 and EAT cells. Growth inhibitors for both cell types, chromatograph at the same position, corresponding to a mol. wt of about 50,000. A very basic, (pI 10.1), factor is isolated by gel electrofocusing, which stimulates the DNA-synthesis of 3T3 and EAT cells. Because of its extremely high cationic charge and its adsorption on gels, the estimation of the exact molecular weight and its preparative isolation, becomes very difficult. Some of the above mentioned molecules are heat-stable and express their action even after boiling for 10 min at pH 3.     

Influence of vitamin A palmitate on the growth of regenerating Triturus alpestris forelimbs

The objective of this investigation was to analyse the effects of vitamin A palmitate orally administered to young postmetamorphic Triturus alpestris on the growth of regenerates. Vitamin A was administered for 4, 7, 11 and 14 days after amputation at the middle of the right zeugopod. Growth of regenerates was evaluated on the basis of external size measurements and blastema cell proliferation. Calculation of the percentages of cells in each cell-cycle phase and estimation of mitotic indices during the period of drug administration were performed by microdensitometric scanning of Feulgen-stained nuclei and counting of chromosome configurations, respectively. Vitamin A was found to induce polyploidism, to enhance transition from G1- to S-phase cell nuceli, to prolong the duration of G2-phase to the detriment of S-phase and to promote mitotic activity in the mesenchyme cells. In accordance with the above, an acceleration in the growth rates of treated blastemas with respect to controls was observed.