摘要:

AbstractSkin 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 ± 10−4μg protein/cell as compared to 3.06 ± 0.13 × 10−4μg/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 o

ISSN:0021-9541    

DOI:10.1002/jcp.1040830112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractStrong evidence is given that a nucleoside diphosphate kinase is present to some extent on the surface of intact neoplastic cells in culture. Experiments could be performed with cells cultured in a few plates to which an incubation medium was added. The cells were firmly attached to the supporting medium and remained viable during the incubation procedure.Determinations of lactate dehydrogenase were carried out to rule out any possible contamination from the culturing medium as well as from the cell interior. From these analyses, a procedure was developed which easily removed the last traces of the culturing medium and which showed that there was no leakage of intracellular lactate dehydrogenase during the incubation procedure. There was a rather insignificant diffusion of nucleoside diphosphate kinase into the incubation medium. In common with other nucleoside diphosphate kinases, the glioma cell surface enzyme seemed to be nonspecific with regard to nucleotide substrates.

ISSN:0021-9541    

DOI:10.1002/jcp.1040830113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractColchicine resistant (CHR) lines of stable phenotype have been isolated from cultured Chinese hamster (CHO) cells. Successive single‐step selections for increasing resistance were performed by isolating resistant colonies at each step. Two complementary assays involving [3H] colchicine uptake by whole cells and binding of [3H] colchicine by cytoplasmic extracts were developed to test for altered permeability and altered intracellular target protein, respectively. All clones isolated appeared to have decreased permeability to the drug while their colchicine‐binding ability was not reduced. The amount of reduction in colchicine uptake correlated strongly with cellular resistance. The CHRlines were also cross resistant to other drugs such as actinomycin D, vinblastine and Colcemid; furthermore, the degree of cross resistance was positively correlated with the degree of colchicine resistance. The non‐ionic detergent Tween 80 potentiated the cytotoxic action of colchicine on mutant cells as well as its rate of uptake into whole

ISSN:0021-9541    

DOI:10.1002/jcp.1040830114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractA perfusion technique is described for the study of melanosome response in ventral tailfin melanophores ofXenopus laevistadpoles. The melanosomes remain aggregated (punctate melanophores) in Ringer's. Theophylline (15 mM) and caffeine (30 mM) cause a reversible dispersion (stellate melanophores) of melanosomes which is partly blocked by cytochalasin B (10 μg/ml). When added with theophylline or caffeine to stellate cells, cytochalasin B causes a disrupted distribution of pigment granules, characterized by a melanosome free central region. C‐AMP (20 mM) and dibutyryl c‐AMP (1 mM) cause a reversible dispersion of melanosomes which is partly inhibited by cytochalasin. When cytochalasin plus a nucleotide are added to stellate cells, some show the disrupted distribution of melanosomes. Colchicine (5 mM) causes irreversible, while griseofulvin (0.2 mM) causes a slight, but reversible dispersion of melanosomes, and cytochalasin has little effect on these reactions. Perfused tailfin melanophores remain capable of responding to reversible reagents for at least 12 hours and are unresponsive to changes in illumina

ISSN:0021-9541    

DOI:10.1002/jcp.1040830115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractHigh density L cell suspension cultures were previously shown to remain viable for indefinite periods of time and to exhibit marked inhibition of DNA synthesis and mitosis while the fraction of total protein synthesis represented by collagen is increased. The present study demonstrates that regulation in this system extends to the activity of acetylcholinesterase found to be approximately 100‐fold greater in the high density populations than in low density exponentially growing cultures. Kinetic studies of the increase of the activity, its fluctuation over an extended period of time and its decrease upon resumption of exponential growth after dilution of the cultures were performed. The data obtained indicate that the enzyme does not accumulate in high density populations merely as a result of the absence of net protein synthesis and cell division but that changes of its rates of synthesis and possibly degradation are involved. The expression of regulated acetylcholinesterase activity in a cell line of connective tissue origin is considered in relation to phenotype reprogramming and to cell membrane associated growth control mechanism

ISSN:0021-9541    

DOI:10.1002/jcp.1040830116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractA clonal strain of epithelial cells has been established from the transplantable Morris hepatoma 7800 and is designated 7800C1. The cells grow with a population doubling time of about three days in serum‐supplemented synthetic medium. Cells of the 7800C1strain have maintained measurable activities of all the enzymes of the urea cycle during 17 months in continuous culture. The activity of argininosuccinate lyase is approximately that found in normal rat liver, while argininosuccinate synthetase, carbamoyl phosphate synthetase, arginase and ornithine carbamoyl transferase activities are, respectively, 40%, 28%, 6%. and 1% of normal values. Treatment of 7800C1cells with glucagon, dibutyryl 3′,5′‐cyclic adenosine monophosphate or hydrocortisone did not increase the activity of any of the five

ISSN:0021-9541    

DOI:10.1002/jcp.1040830117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThe attraction of fern spermatozoids by secretions from the female reproductive structures, and by salts of malic acid, has long been known as a classic example of precise chemotactic orientation by motile cells. Spermatozoids of the bracken fern are attracted by the partially ionized form of malic acid, bimalate ion, and also by calcium ions. Both calcium and bimalate ions must be present for chemotactic response and for response to voltage gradients, Spermatozoids swimming up a bimalate concentration gradient swim in helical paths of abnormally small radius; if they accidentally swim down the concentration gradient the radii of their path helices become abnormally large.These observations suggest that changes in the direction of flagellar beating in response to the rate of change of bimalate ion concentration with time may be the basis for chemotactic orientation. A “coupled diffusion” hypothesis for chemo‐reception is presented, which postulates a membrane carrier which can only circulate freely in the membrane if it binds both bimalate and calcium ions. This hypothesis could explain time‐differentiation of the stimulus, the coupling of a specific stimulus — bimalate ions — to a general mediator of intracellular response — calcium ions — and the quantitative relationship between response of the spermatozoids and the chemical potential of “

ISSN:0021-9541    

DOI:10.1002/jcp.1040830118

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

ISSN:0021-9541    

DOI:10.1002/jcp.1040830119

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

ISSN:0021-9541    

DOI:10.1002/jcp.1040830101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY