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The demonstration that the “dedifferentiation” of cells commonly observed in the early days of tissue culture was due to selective overgrowth of fibroblasts led to enrichment culture techniques (alternate animal and culture passage) designed to give a selective advantage to functionally differentiated tumor cells. These experiments resulted in the derivation of a large number of functionally differentiated clonal strains of a range of cell types. These results gave rise to the hypothesis that cells in culture accurately represent cells in vivo but without the complex in vivo environment. This concept has been strengthened with the development of hormonally defined culture media in combination with functionally differentiated clonal cell lines, which have augmented the potential of tissue culture studies. The use of hormonally defined media in place of serum-supplemented media demonstrates that hormonal responses and dependencies can be discovered in culture. Discoveries of hormonal dependencies of cancer cells has led to therapies targeting intracellular signaling pathways while discoveries of hormonal responses of pluripotent cells are helping to identify the potential application of stem cells. In these and other ways tissue culture technology will continue to contribute to solving problems of human health.

About 700,000 mangroves, chiefly Avicennia marina, were grown in the tree-less mud flats of Eritrea by a newly developed technology that provides required nitrogen, phosphorus, and iron. A method of fertilization was devised that eliminates the possibility of fertilizer runoff. Novel methods have been developed for planting seeds at the final site and protecting seedlings from uprooting by wave action and encircling wrasse. Methods were developed for preserving mangrove seeds by sun-drying, which results in a stable grain-like product. However, dried mangrove seeds and foliage are insufficient for supporting good growth of sheep, which was a desired outcome. Supplementation of mangrove material with small quantities of a stress food for sheep, consisting of fat-soluble vitamins and minerals renders the mangroves an adequate food. Together, these findings are capable of forming a profitable sea water agriculture and relieving hunger and poverty in many regions of the world.

Selection techniques are described for the isolation of differentiated mammalian cell lines in culture. Use of the techniques in isolating auxotrophic mutant cell lines and functionally dependent endocrine tumor cell lines is discussed.

The MCF-7 line of human mammary carcinoma cells is a well characterised line1 which has retained a number of the properties expressed by breast epithelium in vivo, making it a good model for the in vitro study of normal and neoplastic mammary cells. MCF-7 cells have been reported to possess receptors for oestrogen, androgen, progesterone, glucocorticoid2, insulin3 and L-3, 3′, 5-triiodothyronine (T3)4. These cells also show responses to prolactin5, and dome formation1. This line, like most cells in culture, requires the addition of a serum supplement to the medium for growth. The complex and undefined nature of serum adds a complicating aspect to the design and interpretation of any experiments aimed at understanding the interactions of hormones or drugs with mammary epithelium. Our laboratory has shown that it is possible to replace the serum requirement for a number of cell lines with mixtures of hormones and purified serum factors6–8. We now report that MCF-7 cells may be grown, without a lag or adaptation phase, in a serum-free medium supplemented with physiological levels of insulin, transferrin, epidermal growth factor (EGF), prostaglandin F2α (PGF2α) and cold-insoluble globulin (CIg). This medium will support a growth rate identical to that of cells in medium supplemented with an optimal concentration of fetal calf serum. The further addition of the α-1 serum protein first purified by Holmes9 results in a morphology identical to that of cells in 10% serum. Turkington has previously shown EGF effects on mouse mammary expiant cultures10, and mouse EGF has been reported to be stimulatory for human mammary tumour cells . Insulin and transferrin have been shown to be required for the continuous serum-free growth of the ZR-75-1 human mammary tumour cell line12. We believe that this is the first report of the effects of transferrin, PGF2α, Clg, EGF or the α-1 protein on the MCF-7 line.