Showing papers on "Cell growth published in 1976"

Genetic control of the cell division cycle in the fission yeast Schizosaccharomyces pombe

Abstract: Twenty seven recessive temperature sensitive mutants have been isolated in Schizosaccharomyces pombe which are unable to complete the cell division cycle at the restrictive temperature. These mutants define 14 unlinked genes which are involved in DNA synthesis, nuclear division and cell plate formation. The products from most of these genes complete their function just before the cell cycle event in which they are involved. Physiological characterisation of the mutants has shown that DNA synthesis and nuclear division form a cycle of mutually dependent events which can operate in the absence of cell plate formation. Cell plate formation itself is usually dependent upon the completion of nuclear division.

Platelet factors stimulate fibroblasts and smooth muscle cells quiescent in plasma serum to proliferate

Abstract: Whole blood serum is widely recognized as essential for the growth of diploid cells in culture. Dermal fibroblasts and arterial smooth muscle cells fail to proliferate in culture in the presence of serum derived from platelet-poor plasma. Platelet-poor plasma serum is capable of maintaining monkey arterial smooth muscle cells quiescent in culture at either low (1.5 x 10(3)) or high (2.0 x 10(4)) population densities. The proportion of cell traversing the cell cycle under these conditions was approximately 3%. Equal numbers of quiescent smooth muscle cells initiated DNA synthesis and cell division when treated with whole blood serum or with an equivalent quantity of platelet-poor plasma serum supplemented with a factor(s) derived from a supernate obtained after exposure of human platelets to purified thrombin in vitro.

Aerobic glycolysis during lymphocyte proliferation

Abstract: GLYCOLYSIS, for most mammalian cells, is only a prelude to the complete respiratory oxidation of glucose. Lactate production is usually barely, if at all, detectable in aerobic conditions1. Consequently, when Warburg2,3 observed that various tumours showed active aerobic glycolysis, he postulated that defective tumour cell respiration was the reason and was, moreover, the basic difference between normal and cancer cells. Although aerobic glycolysis by tumour tissue has been confirmed many times, defective respiration in cancer cells has not been established4. The failure to uncover a respiratory defect in cancer cells has led to other explanations. It has been suggested, for example, that aerobic glycolysis is linked to cell growth rather than to malignancy5, and for several hepatomas a correlation could be made between the amount of lactate produced and the cell doubling time6,7. It follows that if aerobic glycolysis is related to cell growth, it might be possible as much in normal as malignant cells. There is some evidence for this. Aerobic glycolysis has been noted in proliferating fibroblasts during the period of maximum increase in cell numbers8,9. Human lymphocytes have shown an increase in respiration and also produced lactate when stimulated by the mitogen phytohaemagglutinin10,11. In chick embryo and skeletal muscle fibroblasts12,13, glycolysis increased during log phase growth, but several factors seemed to influence lactate production. Medium composition, aggregation state of cells, culture pH and cell density were all considered more important in determining glycolytic activity than growth rate. It should be noted, however, that these factors are also important to the proliferative rate of these cells. We believe that the important question is not whether culture conditions can influence lactate production, but rather whether glycolysis is linked to cell division. So far no systematic study of the relationship of the appearance of aerobic glycolysis to cell proliferation or the phases of the cell cycle has been reported. This report presents evidence in normal lymphocytes that aerobic glycolysis not only is associated with cellular proliferation, but more specifically is temporally related to DNA synthesis.

Presence of diadenosine 5',5''' -P1, P4-tetraphosphate (Ap4A) in mamalian cells in levels varying widely with proliferative activity of the tissue: a possible positive "pleiotypic activator"

Abstract: An accurate assay of diadenosine 5',5'''- P1,P4-tetraphosphate [A(5') pppp(5')A], which was shown to be formed in vitro in the backreaction of the amino acid activation step, has been developed in various cell lines in culture and in normal mouse liver or hepatoma in vivo. Use of radioactive labeling of acid-soluble nucleotides to high specific activity followed by chromatographic separation techniques yielded levels of Ap4A varying from 5 to 0.05 muM (from 30 pmol/mg of protein to 0.15 pmol), depending on the doubling time of the cell line or the proliferative state of the cells. The levels of Ap4A incells is inversely related to their doubling time, varying from 0.1 X 10(-4) of the cellular ATP levels in slowly growing cells to 20 X 10(-4) of the ATP levels of cells with rapid doubling times. The steady-state levels of ATP of different cell lines, although showing some fluctuations, are not related to the doubling time of the cells. Arrest of cellular proliferation by serum deprivation or amino acid starvation, which does not alter the cellular ATP levels more than 2-fold, does nevertheless cause a decrease of 30 to 50-fold in the Ap4A levels. Inhibition of protein synthesis by pactamycin or puromycin, or inhibition of DNA synthesis by hydroxyurea, leads to a more dramatic decrease of 50 to 100-fold in intracellular Ap4A levels. The metabolic lability of Ap4A is also demonstrated by its rapid depletion after decreases in the ATP/ADP ratio. The possibility of Ap4A being a metabolic "signal nucleotide" that is formed at the onset of protein synthesis and is active in positive growth regulation (positive pleiotypic activation) is discussed.

Cell length, cell growth and cell division.

Abstract: When cells of E. coli reach a certain critical length, which is constant in all growth conditions and eqqal to twice the minimum cell length, they abruptly increase their rate of elongation and divide about 20 min later. Chromosome replication terminates at about this same cell length but is not the signal for the change in rate of cell elongation.

Alpha-methyl ornithine, a potent competitive inhibitor of ornithine decarboxylase, blocks proliferation of rat hepatoma cells in culture

Abstract: A biphasic increase of putrescine concentration occurs in rat hepatoma tissue culture cells induced to proliferate. DL-alpha-Methyl ornithine, a competitive inhibitor of ornithine decarboxylase ( L-ornithine carboxylyase, EC 4.1.1.7) of hepatoma tissue culture cells, blocks the usual increases of putrescine and spermidine concentrations in these cells, and causes a rapid fall in the levels of putrescine which is followed by a striking decrease of spermidine.In parallel with the depletion of these amines, incorporation of [3H]thymidine into DNA and cell proliferation are inhibited. Addition of putrescine, spermidine, or spermine results in an immediate resumption of cell proliferation. Cell proliferation is also restored by L-ornithine presumably due to in situ competitive inhibition of ornithine decarboxylase. These findings of hepatoma tissue culture cells support the concept that polyamines play an essential function in the cell division processes.

Clustering of replicating cells in aortic endothelium.

Abstract: Cell division in the aortic endothelium of the rat is not randomly distributed. Maps of the aortic surface show focal areas where the daily rate of replication may be in excess of 50%. This implies the existence of focal areas of rapid cell growth or rapid cell turnover and other areas where growth or turnover is largely absent.

Chapter 8 – CELL PROLIFERATION AND EXPERIMENTAL LIVER CANCER

Abstract: The concept that cell replication plays an essential role in the initiation of liver cell cancer is suggested by several lines of evidence. A single treatment of an adult animal with a hepatocarcinogen rarely induces liver cell cancer; the rate of cell replication in adult liver is very low. However, a single treatment does induce liver cell cancer in situations where the rate of cell replication is high, as in newborn animals, or in adult animals in which restorative hyperplasia of the liver has been induced by partial hepatectomy or by treatment with certain hepatotoxins. To produce liver cell cancer in the absence of an independent stimulus for mitosis, chronic administration of the carcinogen is usually necessary. This chronic administration can lead to progressive liver cell damage and hence to restorative hyperplasia, so that the carcinogen is in fact injuring cells which are replicating. The explanation of the increased sensitivity of replicating cells is by no means certain, and may vary in different situations. However, there is evidence in a number of cases that cell replication alters neither the metabolism of the carcinogen, nor the nature, extent or persistence of the binding of the activated carcinogen to macromolecules. For cell replication, however, there must be replication of DNA, at least some of which has been damaged by the carcinogen. Thus the initiation of the carcinogenic process may result from the replication of DNA which takes place before the damage has been repaired by DNA repair systems of the cell. This aberrant replication may be essential to ‘fix’ a change in DNA, such as mispairing of bases at replication. Such mispairing may convert the transitory occurrence of abnormal bases formed by the reaction of the carcinogen into a stable inheritable form such as a change in base sequence. It is possible that an informational change of this kind in the genetic material could be an essential event in the initiation of cancer.

Parathyroid hormone-responsive adenylate cyclase in induced transplantable osteogenic rat sarcoma.

Abstract: AN apparent paradox prevents accurate assessment of the role of cyclic AMP in the development and maintenance of tumours. Although cell culture experiments indicate that malignant transformation is associated with decreased adenylate cyclase activity and intracellular cyclic AMP levels1,2, the same is not true of in vivo studies with tumours, in which a range of results have been obtained, from low3 to normal4 and elevated5 tumour cell cyclic AMP levels. We report here the development of a transplantable osteogenic sarcoma which has retained through many generations a parathyroid hormone-responsive adenylate cyclase, providing a system which can be used to evaluate the significance of hormone-responsive adenylate cyclase for tumour cell growth and differentiation.

Growth and characterization of human skin epithelial cell cultures.

Abstract: In 129 of 140 attempts, human skin cells were successfully cultured on the dermal collagen bed of sterile, dead pigskin. Diploid epithelial cells grew selectively on the collagen bed; fibroblasts grew on the glass surfaces of the culture dishes. The cultures could be subdivided physically up to six times at a 1:2 split ratio, but at least 24 to 48 cell generations were produced over the months the cells could be carried. Much of the cell multiplication resulted in maturation into distinct basal, squamous, granular, and keratinized cell layers. The cultured cells were considered epithelial because of their shape, possession of intercellular bridges, desmosomes and tonofibrils, and because they formed maturating epithelium in vitro and upon transplantation back to the original human donor. As the cells grew they digested the pigskin collagen, thus producing clear zones that could be used to monitor and quantitate cell growth. Multiplication of epithelial cells, rather than migration, was indicated by mitotic figures in colchicine-treated cultures and by DNA synthesis.

Relationship of Cell Growth Behavior in Vitro to Tumorigenicity in Athymic Nude Mice

Abstract: The serum requirements, anchorage requirements, saturation densities, and contact inhibition responses of a variety of mammalian cell lines were determined under uniform conditions. The serum requirement of both transformed and normal cells was a sensitive function of initial plating density. Cloning efficiency on irradiated mouse monolayers was found to be an invalid indicator of contact inhibition of growth, since most cell lines that failed to form visible colonies on cell monolayers nonetheless proliferated on these monolayers. When normal and neoplastic cells from a variety of sources were examined, none of the growth parameters that serve to define the transformed state in vitro correlated consistently with cellular tumorigenicity in athymic nude mice. It is concluded that the most reliable and physiologically meaningful assay for malignant transformation is, at present, cellular tumorigenicity in athymic nude mice.

Effect of adriamycin on the cell cycle traverse and kinetics of cultured human lymphoblasts.

Abstract: Exposure of cultured human lymphoblasts to adriamycin (ADM) (0.1 μg/ml for 24 hr or 0.5 μg/ml for 1 hr) leads to an accumulation of cells with the DNA content of late S and G2. Higher concentrations of ADM (0.5 to 10 μg/ml) inhibit cell cycle traverse. Effect of ADM on cell cycle traverse, cell growth, and incorporation of labeled precursors into DNA is dependent on drug concentration and length of exposure to ADM. Synchronized cells in G1 or G2 part of the cell cycle are less sensitive to ADM than cells in S phase. Similarly, plateau-phase cells are less sensitive to ADM than cells from log-phase cultures.

Induction of human fibroblast proliferation by epidermal growth factor (EGF): enhancement by an EGF-binding arginine esterase and by ascorbate.

Abstract: The effect of mouse epidermal growth factor (mEGF) and an mEGF-binding arginine esterase on the growth of cultured human fibroblasts has been studied Physiological concentrations (10(-9)-10(-10) M) of the growth factor were found to stimulate DNA replication and cell proliferation in quiescent cultures, and the arginine esterase, which is normally associated with mEGF in vivo, was shown to enhance this growth effect synergistically The cellular response to mEGF was dependent upon a low, growth-limiting concentration of serum in the extracellular medium Ascorbic acid, which alone exhibited no growth-promoting effect, could partially replace this requirement, and was found to elicit a rapid and marked increase in proline hydroxylation Quiescent cultures in serum-free medium containing ascorbic acid were stimulated by the combination of mEGF and the esterase in a manner comparable to that achieved with serum shift-up The possible requirement of a collagen-containing extracellular matrix for the growth response to mEGF is discussed

Mutagenesis and transformation of normal cells by chemical carcinogens.

Abstract: TREATMENT of normal cells1–6 or some established cell lines7 in culture with chemical carcinogens can result in cell transformation and malignancy. Cells which have an oriented pattern of cell growth, a limited life span in vitro and are not tumorogenic in vivo, are then converted into cells with a hereditary random pattern of cell growth, an ability to grow continuously in culture and to form tumours in vivo. Studies with a variety of polycyclic hydrocarbons and other chemicals have shown a correlation between the frequency of colonies with a hereditary random pattern of cell growth (transformed colonies) and the degree of carcinogenicity in animals2,6,7.

Antiviral and cell growth inhibitory activities reside in the same glycoprotein of human fibroblast interferon.

Abstract: IT has been shown repeatedly that preparations of mouse interferon inhibit the growth of mouse cells in vitro1–4 In addition to inducing the antiviral state and inhibiting cell growth, preparations of mouse interferon stimulate interferon production by priming5, enhance phagocytic activity6, and potentiate in cells the toxic effect of double-strand ed RNA7. All attempts with preparations of mouse interferon to separate the antiviral activity from the non-antiviral activities have been unsuccessful3,5,8. With human interferon few experiments have been reported, although the data available indicate inhibition of growth by preparations of human leukocyte interferon9–11. It has been claimed that the antiviral and cell growth inhibitory activities of human leukocyte interferon reside in different molecules and can be separated from each other by certain methods of fractionation12. In a more recent report13, however, separation of the two activities could not be demonstrated even in drastic denaturing conditions. I have shown that both the antiviral and the cell growth inhibitory activity of human fibroblast interferon reside in the same glycoprotein.

The pathology of experimental liver cell cancer

Abstract: SUMMARY Liver cell cancer can be induced in animals by a diverse group of chemicals. The majority of these require metabolic conversion to a reactive derivative in order to initiate carcinogenesis. Many different acute effects are induced in virtually every part of the liver cell and in every macromolecule, many of which appear to be reversible. One of the most striking effects is an inhibition of DNA synthesis or of cell proliferation. The liver cell cancers induced by many different chemical carcinogens are remarkably similar in the spectrum of their appearance and behaviour. Virtually every such carcinoma shows an immature arrangement of hepatocytes, with multiple cell-thick plates being common. Associated with this altered organization is the expression of foetal and other non-adult phenotypic properties. Although such deviations are common, no two carcinomas appear to show the same patterns, indicating the probability of each being unique. The liver shows the appearance of new cell populations during most of the time period between initiation and the appearance of liver cell cancer. These new hepatocyte populations show many common and distinctive structural and biochemical properties, even when induced by one of many different carcinogens. These populations also show an arrangement of hepatocytes different from that in mature liver. When early, such populations show differentiation or maturation to apparently normal-appearing liver. This maturation is absent or takes place much more slowly in late putative pre-malignant lesions. In addition to a variety of negative markers (decrease or loss of activity), the presumptive precursor populations show at least two positive markers - alpha-fetoprotein and pre-neoplastic (PN) antigen. A major problem in carcinogenesis is the growth of hepatocytes in a carcinogen-induced environment in which normal cell proliferation is inhibited. This and other data suggest that the altered new cell populations have acquired a resistance to the cytotoxic action of carcinogens and that this resistance may be a key characteristic in the selection of putative pre-neoplastic or pre-malignant hepatocytes. Consistent with this hypothesis are the findings of a large decrease in the activities of one or more of the constituents of the microsome monooxygenase or mixed function oxidase systems in pre-malignant hepatocytes. These observations lead to a working hypothesis of liver carcinogenesis in which mutation, altered differentiation and selective resistance to cytotoxicity each play a role as pathogenetic mechanisms in encouraging the cellular evolution to liver cell cancer.

Erythroid cell differentiation: murine erythroleukemia cell variant with unique pattern of induction by polar compounds.

Abstract: The murine-virus-infected erythroleukemia cell system provides an opportunity to examine regulatory mechanisms controlling cytodifferentiation. A cloned cell line (DR10c3) resistant to the erythropoiesis-inducing effect of dimethylsulfoxide (Me2SO) was isolated from the Me2SO-sensitive line DS19. DR10c3 is characterized as follows: (1) the uptake of [3H]Me2SO is similar to that in DS19; (2) cell growth with and without Me2SO is similar to that of DS19; (3) resistance is relatively stable; (4) the karyotype of DR10c3 reveals an average loss of five chromosomes per cell, but is otherwise similar to that of DS19; (5) total protein and globin synthesis by cells cultured 4 days with or without Me2SO is similar to these syntheses in DS19 cultured without Me2SO; (6) virtually no globin mRNA is detectable after 3 days in Me2SO, as assayed both by RNA-complementary DNA hybridization and by the heterologous cell-free protein-synthesizing system; (7) other polar compounds, N-methylpyrrolidinone, 1-methyl-2-piperidone, N, N-dimethylacetamide, and N-methylacetamide, induce erythroid differentiation in DR10c3, and the accumulation of alpha- and beta-globin chains is indistinguishable from that in DS19; and (8) the concentration optima for induction of differentiation by all these compounds are identical for DR10c3 and DS19.

OESTRIOL, OESTRADIOL-17β AND THE PROLIFERATION AND DEATH OF UTERINE CELLS

Abstract: It has been suggested that oestriol protects against breast cancer, because in some experiments on uterine growth it is only weakly active, and partially inhibits the effects of oestradiol-17beta When its effects are measured 24 h after a single injection, oestriol behaves as a typical impeded oestrogen with low potency and a flat dose-response line This does not result from failure to stimulate certain critical stages of growth but from failure to sustain the products of growth We found that oestriol induced all phases of uterine growth including DNA synthesis and cell division It was as effective as oestradiol in stimulating early increases in protein synthesis and uterine weight, and half as effective in stimulating epithelial cells to replicate DNA and divide However, epithelial cell numbers did not increase after a single injection of oestriol because cell death rate increased at the same time as mitotic rate, apparently as a result of the more rapid loss of oestriol from the uterus Repeated injections of oestriol prevented premature cell death and produced as much uterine hypertrophy and hyperplasia as oestradiol-17beta These results support the thesis that the oestrogenic potency of a substance is largely determined by the duration of its occupation of receptors Thus in situations of continuous production, (eg pregnancy) oestriol would be as active as oestradiol and unlikely to exert any significant 'buffering' or protective action The findings are also discussed in relation to a new model for the regulation of cell proliferation

Regulation of immunity and inflammation by mediators from macrophages

Abstract: Mononuclear phagocytes secrete a number of materials into the extracellular environment. The materials secreted by phagocytes can be grouped into three categories: a) enzymes affecting extracellular proteins (collagenase, elastase, lysosomal proteases, plasminogen activators), b) materials involved in defense processes (complement proteins, interferons, lysozyme), and c) factors regulating activities of surrounding cells. The latter include lymphostimulatory molecules, a colony-stimulating factor, and inhibitors of cell growth. The conditions for secretion of the materials depend on the activity of the phagocytes. The lymphostimulatory molecules secreted by macrophages exert various effects: 1) an increase in DNA synthesis of lymphocytes, 2) a maturation of early thymocytes to mature T cells, and 3) the differentiation of some B cells to antibody-secreting cells. The mitogenic principle has been partially isolated as a protein of 15,000 to 20,000 daltons. The secretion of lymphostimulatory molecules is increased following uptake of various materials by macrophages or by addition of activated T cells to macrophage cultures.

Effect of serum on the growth of balb 3t3 a31 mouse fibroblasts and an sv40-transformed derivative.

Abstract: The effect of serum on the growth properties of non-transformed Balb 3T3 A31 and SV40-transformed Balb 3T3 A31 was studied. The concentration of serum in the growth medium of non-transformed cells had little effect on the initial population doubling time, but did regulate the cell density at which the population became quiescent in G/sub 1/. The doubling time of transformed cells, however, was increased significantly as the concentration of serum was decreased below 4 percent. This effect on the growth of transformed cells was seen at serum concentrations so low that non-transformed cells did not complete one population doubling. Flow microfluorometric analysis of these populations indicated that the primary effect of different serum concentrations on the non-transformed cells was to modulate the average residence time in G/sub 1/, whereas, all the cell cycle phases of the transformed cells were affected by serum. At saturation densities, the non-transformed cells became quiescent in G/sub 1/, but the transformed cells still traversed the cell cycle and their saturation density appeared to be a balance between cell production and cell death occurring primarily in the G/sub 1/ phase of the cell cycle.

Mast cell activation and tissue cell proliferation.

Abstract: The effect of mast cell activation and degranulation on the proliferation in the intact mesentery was studied in Sprague-Dawley rats. Mast cell activation was achieved by a single intraperitoneal injection of Compound 48/80. The proliferation was studied using three independent methods for estimation of cell production and DNA synthesis: 1. the mitotic index, 2. the relative number of cells having a DNA content in the S and G2 regions, by Feulgen photometric measurement in individual cells, and 3. the specific DNA activity, employing a method which combines a liquid scintillation technique after an intravenous injection of 3H-thymidine and Feulgen photometric determination of the DNA content per membrane preparation. It was found that the proliferation of the normal mesenchymal cells adjacent to the activated and degranulated mast cells in the mesentery was significantly increased within 24 and 32 h, the maximum increase being more than 20-fold compared to untreated controls. The results suggest that the common type of mast cell may have a pathophysiological function related to stimulation of local cell proliferation.

Cell-mediated immune response in vitro. I. The development of suppressor cells and cytotoxic lymphocytes in mixed lymphocyte cultures.

Abstract: During the in vitro development of cytotoxic lymphocytes (CL), suppressor cells also develop. Spleen cells or lymph node cells harvested from mixed lymphocyte cultures (MLC) on day 2 (day-2 MLC) and added to a fresh MLC suppressed the development of CL. This suppressive effect was sensitive to treatment with anti-θ and C. The suppressive effect of day-2 MLC was not due to cytotoxic effects nor to altered kinetics of the development of CL. Thymidine hot pulse experiments showed that cell proliferation is necessary for the development of both suppressor cells and CL. Although CL develop from hydrocortisone-treated spleen cells, day-2 MLC of hydrocortisone-treated spleen cells did not suppress the development of CL. These studies suggest that suppressor cells and CL are derived from different T cell subpopulations.

Effects of interferon on cell and virus growth in transformed human cell lines.

Abstract: The anticellular and antiviral effects of human leukocyte interferons were studied in vitro in the transformed human embryonic cell lines. RSa and RSb. The growth of these cells was inhibited and they began to deteriorate about 48 h after treatment with 500 units/ml of interferon. When interferon was washed out within 48 h, their growth recovered gradually. The effects of interferon on cell growth depended on the amount of interferon added per cell. A subline, named IFr, was isolated which grows in the presence of 2000 units/ml of interferon, whereas growth of vesicular stomatitis virus in these cells is suppressed by 10 units/ml of interferon, just as in the parent cells. The anticellular and antiviral effects of interferon on IFr cells are discussed in relation to cell surface receptors.