1. Strains of epithelium and fibroblasts cultivated side by side in the same medium keep their individual characteristics. When sectioned and stained by the Van Gieson method, the cultures show the epithelium stained greenish yellow and the fibroblasts and their fibrillæ pink. 2. There are no transition forms between the epithelial cells and fibroblasts. 3. The epithelial cells belonging to an older strain are still able to form primitive structures of winding tubules, with typical glandular epithelium. 4. Under the conditions of the experiments, no dedifferentiation takes place.
A strain of fibroblasts, obtained from the heart of a chick embryo on January 17, 1912, has completed the tenth year of its life in vitro. On April 19, 1922, our incubators contained about 60 cultures which represented the 1906th generation of the connective tissue cells. Their growth is as rapid as during the past years, each fragment generally doubling its volume in 48 hours. In 10 years, more than 30,000 cultures have been derived from a fragment of heart less than 1 cubic millimeter in size. This demonstrates first, that the cells transform the food stuffs in their medium into protoplasm. Second, under the conditions of the experiments, the cells are no longer subject to the influence of time, as they are when living within the organism, and demonstrate that they are potentially immortal. The cells have now exceeded the average life of chickens, which disposes of criticisms on this point.Pure cultures of cells are important in studying biological problems. The strain responds readily to changes in the...
1. Pure strains of mononuclear leucocytes were isolated from the blood of adult chickens and keptin active condition for nearly 3 months. 2. The cultures were composed of large mononuclear leucocytes which migrated and proliferated in vitro at a slower rate than fibroblasts. The cells had no tendency to form a tissue, as do fibroblasts and epithelial cells. They were much less resistant than fibroblasts. 3. Differentiation of the large mononuclears into cells assuming the appearance of fibroblasts took place under certain conditions. 4. The activity of the large mononuclears was increased by embryonic tissue juice and inhibited by homologous serum.
1. A pure strain of fibroblasts has been isolated from the Jensen rat sarcoma. The cells give rise to tumors on transplantation into animals and during several months of life in vitro have maintained their malignancy unchanged. 2. The malignant cells are generally coarser and more refringent than normal cells. They possess the cytological characteristics of fibroblasts without showing any morphological abnormality. They can be considered as healthy cells. The texture of their colonies is looser than that of normal fibroblasts and Sarcoma No. 10 fibroblasts. Their residual activity does not differ markedly from the normal. They proliferate unlimitedly in a nutrient medium. 3. They liquefy the fibrin of rat plasma and turn phenol red golden yellow. They do not liquefy the fibrin of chicken plasma. 4. They multiply in chick embryo juice, calf liver digest, and also in rat serum. Their growth activity is increased by the presence of bone marrow. 5. The unlimited growth of Jensen sarcoma within the body may possibly be attributed to the ability of the fibroblasts to maintain themselves upon the substances present in rat serum. This property itself probably depends upon the increased enzyme activity of the cells.
IT MAY BE CONCLUDED THAT, UNDER THE CONDITIONS OF THE EXPERIMENTS: 1. The inhibiting action on homologous fibroblasts of the heated serum of a young animal increases relatively more than that of an old animal. After it has been heated, the inhibiting action of the serum of the old animal is still greater than that of the young animal. 2. The CO(2) precipitate obtained from the serum of a young animal definitely increases the proliferative activity of homologous fibroblasts, while the CO(2) precipitate of the serum of an old animal has practically no activating power. After the removal of the CO(2) precipitate, the inhibiting action of the serum of young animals is increased, while that of old animals is not modified. 3. The increased inhibiting action of serum on homologous fibroblasts in old age is partly due to the disappearance of the growth-activating substances and to the enhanced activity of the growth-inhibiting principle.
Under the conditions of these experiments, fibroblasts from a 24-year-old strain tolerate glucose concentrations of 390, 650, and 1,150 mg. % over a period of 7 days. There is no evidence of an inhibiting or toxic effect. The higher concentrations, namely, 2,090 and 3,200 mg. %, have an inhibiting effect from the very beginning and are ultimately toxic.
Abstract Photomicrographs have been made of grasshopper spermatocytes using ultraviolet light of several wave lengths. For studying chromosomes this wave length should be between ca 2800 A and ca 2500 A. With higher frequencies the entire cell becomes strongly absorbing and relatively little detail is to be seen. All cell structures, including the chromosomes, are as transparent to λ = 3500 A and to longer ultraviolet waves as they are to visible light. The present experiments do not indicate the exact point between λ = 3500 A and λ = 2800 A at which the selective chromatin absorption commences.
The importance of developing artificial media, which can be used in place of serum for maintaining the life of organs and tissues outside the body, hardly needs to be emphasized. Many of the studies for which the organ-culture technic was invented, as well as others that can be carried out by the simpler methods of tissue-culture, depend for their success on the creation of suitable artificial media. These media are needed to reduce the cost of experimentation, to make possible extensive work with human organs and those of small animals from which serum in large quantity cannot be obtained, and for all studies in which the production of serum and other protein substances is to be investigated. For cultivating organs and for all work with tissues in which function rather than growth is the subject of study, it is important that these media maintain the cells without causing proliferation. All the artificial media previously reported have been designed to promote growth. The media to be described in this paper were designed for maintenance. One of them is serumless. In the others, a very small amount of serum has been incorporated. The results obtained when these media were used to maintain a pure strain of fibroblasts in tissue-culture are described below. Experiments in which they were used for cultivating organs will be reported in another communication. To bring the vitamin A into solution, it was necessary to dissolve it at high concentration in serum and then use a small amount of this serum in the medium The concentration required proved to be only 0.07%
Abstract This paper describes ultraviolet (λ = 2750 A) photomicrographs of resting and dividing chicken macrophages and fibroblasts and of erythrocytes and lymphocytes. The structures found in these photographs are compared with the ones brought out in fixed material by Feulgen staining and found to be essentially similar in appearance. A preliminary series of ultraviolet pictures is also shown of a single fibroblast passing through several of its stages of division.
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