A TEN YEAR OLD STRAIN OF FIBROBLASTS
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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...Keywords:
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1. When various types of protoplasm are treated with dilute solutions of ammonium salts, there is an increase in the free fat or lipid.2. This effect is due to an alkalinization of the protoplasm.
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ABSTRACT A technique for measuring the elastic value of living protoplasm is described. An elastic value of the cortical layer of the protoplasm of the Echinarachnius egg is given. The presence of an elastic property in protoplasm is incompatible with the emulsion hypothesis of protoplasmic structure.
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1. The bathing of the protoplasm of slime molds in various salts and acids, or the injection of these into protoplasm, brings about the formation of rhythmic bands through the precipitation of protoplasmic proteins.2. Both the hydrogen ion and the ions of heavy metals produce banded precipitates in protoplasm. 3. The periodic precipitation of concentric rings in protoplasm bears a striking resemblance to the Liesegang phenomenon.4. The more rapid entrance of solutes at certain restricted and isolated points of the plasmodium indicates pronounced differentiation in the permeability of the surface.
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Protoplasm separated from disrupted cells of gram-negative bacteria was extracted with hot phenol-water or was precipitated with ethyl alcohol after digestion with Pronase. These methods recovered about 10 times more endotoxin than was detectable in the untreated protoplasm. Inactivation of endotoxin by protoplasm also occurred in vitro when the endotoxin was first dissociated into subunits before reaction with protoplasm. Despite this increased yield from another source, the major proportion of endotoxin was still found in the cell walls.
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When Escherichia coli 15T- cells growing exponentially at 70- to 80-min doubling times are subjected to a nutritional shift-up via glucose addition, cell division continues at the preshift rate for about 70 min (rate maintenance). The same cells growing at doubling times of 120 min or longer, however, begin to divide at a new faster rate immediately upon glucose addition. In both the rate maintenance and immediate division situations, cell mass, as measured by optical density (OD), begins to increase immediately upon shift-up. Consequently, the OD/cell pattern differs in the two growth-rate transitions. During rate maintenance, the OD/cell ratio increases dramatically for 60 to 70 min, and then slows appreciably and approaches the OD/cell characteristic of the new medium. During immediate division situations, the OD/cell increases only slightly for the first 180 +/- min; then the rate of increase accelerates but does not stop at the OD/cell characteristic of the new medium. Immediate division upon nutritional shift-up apparently depends upon initial doubling times in excess of 115 to 120 min and provision of a readily metabolized carbon source supporting doubling times of about 40 min. Similar immediate division occurs in E. coli B/r and K-12.
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Abstract Skin fibroblast cultures from six patients with Down's syndrome (Trisomy 21) were compared with four in vitro age‐matched normal fibroblast cultures. Growth rates were calculated from increases in cell number and total protein during exponential growth, early in culture lifetime (less than 20 doublings). The Down's syndrome (D.S.) cultures had an average population doubling time of 35.6 ± 1.1 hours and average mass doubling time of 38.6 ± 3.2 hours, significantly lower (p<0.005) than the corresponding normal culture values of 23.0 ± 0.7 hours, and 23.3 ± 1.9 hours. D. S. Cells also contained 4.46 ± 0.19 ± 10 −4 μg protein/cell as compared to 3.06 ± 0.13 × 10 −4 μg/cell (p<0.001) for normal fibroblasts. Similar in vitro observations of increased doubling time and protein content have been reported in normal fibroblasts from older donors, and from individuals with premature aging syndromes, as well as in normal fibroblasts near the end of their in vitro lifetime. The present results, obtained from cultures young in vitro, may therefore suggest that D.S. fibroblast cultures age prematurely. This hypothesis is consistent with clinical manifestations of premature aging in D.S. patients and points to a defect in growth regulation, both in vivo and in vitro, resulting from an extra copy of chromosome 21.
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The development of the placental tissue of the tomato fruit has been investigated and it has been found that the protoplasm of cells of this tissue separates into organized units of protoplasm as the fruit matures and ripens. Similar organized protoplasmic units have been detected in other fruits at a comparable stage of development. A study has been made of the structure and stability of these organized units, and it has been deduced that these organized units of protoplasm are in fact compartments of the protoplasm of the cell which have become separated from one another. Each organized protoplasmic unit is able to exist independently of the cell for several days, and is apparently surrounded by a membrane of the endoplasmic reticulum. The possible significance of these new findings is discussed in relation to the structural and biochemical organization of the plant cell.
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