Showing papers on "Cell growth published in 1974"

Localisation of a fibroblast growth factor and its effect alone and with hydrocortisone on 3T3 cell growth

Abstract: FGF, a polypeptide found in brain and pituitary, provokes the initiation of DNA synthesis by resting ST3 cells. When glucocorticoids are present FGF stimulates DNA synthesis as effectively as serum.

Development and proliferative capacity of cardiac muscle cells.

Abstract: In this article the cytological features of cardiac enlargement are reviewed. During the embryonic development of the myocardium, both undifferentiated cells and cells containing myofibrillar proteins divide. As the heart grows and approaches maturity, its muscle cells progressively lose their mitotic activity, and hypertrophy of myocytes becomes the principal process of cardiac enlargement. Cytological features of cardiac enlargement secondary to work overloading depend on the stage of heart development. In the early postnatal heart increased work load results in enlargement characterized by an increase in both the number and size of myocardial cells. The adult heart enlarges only by hypertrophy of its myocytes. Morphometric studies of diseased human hearts enlarged in excess of 500 g indicate an increased number of muscle cells. Some of the control mechanisms regulating mitotic activity in myocytes are discussed: (1) Critical mitosis theory: it has been suggested that synthesis of DNA and of cell specific proteins are mutually exclusive processes. A block of DNA synthesis then occurs during differentiation of myoblasts as a conseqence of a specific mitosis leading to a new phenotype cell. (2) ''Critical mass'' theory: it is postulated that the gradually accumulating cell specific structures present a hindrance to mitotic division ofmore » nucleus. After a critical mass has been reached, no more mitoses are possible. (3) Repression of DNA synthesis: synthesis of DNA in developing myocytes declines with maturation. Nevertheless, under rare conditions DNA synthesis can be reactivated, suggesting a repression rather than an irreversible block of DNA synthesis.« less

Characterization of a unique muscle cell line

Abstract: A clonal cell line derived from a mouse neoplasm is described which shares many properties with smooth muscle. The cells have electrically excitable membranes capable of generating overshooting action potentials, and they contract both spontaneously and with electrical stimulation. They respond to the iontophoretic application of acetylcholine with a depolarizing response, and to norepinephrine with a hyperpolarizing response. Electron microscopy reveals that the cells have a morphology similar in many, but not all, respects to that of smooth muscle cells in vivo. The cells secrete soluble collagen-like molecules in addition to several proteins of undefined function. Finally, there is an increase in the specific activities of creatine phosphokinase and myokinase associated with increased cell density and the cessation of cell division.

The splenic suppressor cell. I. Activity of thymus-dependent adherent cells: changes with age and stress.

Abstract: The present study confirms and extends the finding that DA rat spleen cells include a subpopulation of adherent cells which act at high doses of phytohemagglutinin (PHA) or concanavalin H (ConA) to suppress DNA synthesis by other cells. Suppressor activity is lacking in spleens of doubly thymus-deprived rats. Mitomycin C treatment does not reduce the suppressor activity of normal whole spleen. It is inferred that the suppressor cell is a T lymphocyte or depends for its action on the presence of T lymphocytes and that its action does not require cell proliferation. DNA synthesis is much more affected by suppression at high mitogen levels than RNA or protein synthesis. A parallel is drawn between the separate regulation of DNA synthesis and other macromolecular synthesis in lymphocytes and so-called “pleiotypic” effects in other types of cells. Spleen cells of young rats give a relatively low response ( 3 H-thymidine uptake) to optimal or supraoptimal doses of PHA, which is markedly increased by removal of adherent cells on glass wool and is not affected by addition of purified macrophages. In contrast spleen cells of older animals give a high response, which falls when adherent cells are removed but is restored to the original level by addition of macrophages. It is concluded that older animals9 spleens differ from those of younger rats by a variable loss of suppressor cells and an increasing macrophage dependence of PHA-responsive cells. The former may account for the reported increase in autoantibody formation with age. Reactivity of cells of a given age was not affected by culturing them in young or old rat serum pools, respectively. Stress or injection of hydrocortisone acetate result in loss of suppressor cell adhesiveness to glass wool and increased macrophage dependence of PHA-responsive cells at 5 days. At 2 to 3 weeks there is a return to normal levels of adhesiveness and macrophage dependence, accompanied by a marked increase of suppressor activity. The 5-day changes are thought to reflect direct effects of steroid on the properties of T lymphocyte membranes, and the later changes altered levels of thymus hormone or possibly a surge of “post-thymic cells” into the peripheral lymphoid organs.

In vitro inhibition of tumour cell growth and DNA synthesis by peritoneal and lung macrophages from mice injected with corynebacterium parvum

Abstract: Peritoneal and lung macrophages from CBA mice injected with Corynebacterium parvum were tested for in vitro inhibition of growth and DNA synthesis of syngeneic tumour cells. Peritoneal macrophages inhibited the growth of RI leukaemia cells, and the DNA synthesis of RI leukaemia and T3 fibrosarcoma cells. Maximum inhibition of DNA synthesis was at 5 days after C. parvum injection. Inhibition was most effective when contact between macrophages and target cells was allowed, since medium from macrophage cultures was only slightly inhibitory. Macrophages maintained alone in culture for 48 h lost their ability to inhibit RI cell DNA synthesis. Lung macrophages inhibited the DNA synthesis of RI cells most effectively 14 days after C. parvum injection.

Evidence that mitogenic lectins induce changes in lymphocyte membrane fluidity

Abstract: MITOGENIC plant lectins, such as phytohaemagglutinin (PHA) and concanavalin A (con A), are useful tools to study the control of cell proliferation in lymphocytes. Recent evidence suggests that these mitogenic lectins trigger mitogenesis at the cell membrane1,2. It is likely that an understanding of the mechanisms by which these lectins stimulate lymphocytes will provide important clues to more general problems of the regulation of proliferation in eukaryotic cells.

Activation of guanyl cyclase and intracellular cyclic GMP by fibroblast growth factor

Abstract: THE induction of cell growth by animal serum in quiescent cultured fibroblasts is preceded by a sequence of regulated steps1. These steps include stimulation of cellular transport systems1, protein synthesis1, ribosomal and tRNA synthesis2 and eventually the induction of DNA synthesis followed by cell division3,4. Two of the earliest changes observed after growth induction by serum are a transient increase in intracellular cyclic GMP5 (10-fold) and a decrease in cyclic AMP (two-to-threefold)5,6,7. It has been suggested that cyclic GMP acts as a positive intracellular signal for cell growth since intracellular cyclic GMP concentrations showed an early transient increase upon growth induction by phytohaemagglutinin whereas no changes were observed in cyclic AMP concentrations8, and additions of high, non-physiological (10−6 to 10−4 M) concentrations of cyclic GMP can induce substantial increases in DNA synthesis in resting fibroblasts5. Recently a new polypeptide hormone, fibroblast growth factor (FGF), was isolated from bovine pituitary glands9. FGF in combination with the glucocorticoid, hydrocortisone, and a nonspecific carrier protein, bovine serum albumin (BSA), can completely replace exogenously added serum in bringing about all the steps leading to the initiation of DNA synthesis and cell division in some lines of BALB/c 3T3 cells10. Hydrocortisone, as it fails to initiate DNA synthesis alone in the absence of serum11 is considered to potentiate the action of FGF9 (permissive effect).

Growth control in cultured mouse fibroblasts: induction of the pleiotypic and mitogenic responses by a purified growth factor.

Abstract: Addition of serum to quiescent mouse fibroblasts induces a series of macromolecular changes (a pleiotypic response) followed by DNA synthesis and cell division. A new pituitary hormone, fibroblast growth factor, and hydrocortisone acting at physiological concentrations can completely replace exogenously added serum for the induction of these events in lines of BALB/c 3T3 cells. The induction of cell growth is specific for cultured fibroblasts; no stimulation is observed for mouse epithelial cells or virally transformed fibroblasts.

Virion and Tumor Cell Antigens of C-Type RNA Tumor Viruses

Abstract: Publisher Summary This chapter reviews the structure, function, and immunological properties of C-type virus-directed macromolecules that are immunologically active, and therefore approachable by immunological techniques. Antigen is used to designate such molecules, essentially because the chemical constitution of many of them is not yet known. The mechanism of virus assembly by a budding process suggests that the virus may contain many host cell constituents that are not essential to the virus structure, but rather represent virus-associated “contaminant.” It also seems feasible that as a result of virus-induced changes in cell physiology new antigenic determinants appear either by the exposure of hidden antigenic macromolecules or through the synthesis of new antigens as a result of the derepression of cellular genes that are inactive in a normal cell. The chapter focuses on C-type viruses of different species, which are closely related with respect to fundamental properties. They mature by budding from the cell membrane, are similar in the morphology, size, and constitution of nucleic acid, proteins, lipids, and enzymes, and require similar cell growth conditions for infection.

Cyclic GMP and cyclic AMP levels in normal and transformed fibroblasts

Abstract: THE 3′–5′ cyclic nucleotides, cyclic AMP and cyclic GMP have been implicated in the control of the growth of cultured fibroblasts in that early, transient decreases in intracellular cyclic AMP1–3 and increases in cyclic GMP4 are observed on reinitiation of the growth of quiescent mouse fibroblasts by serum. Moreover additions of high, nonphysiological concentrations (10−5 M to 10−3 M) of either cyclic AMP or cyclic GMP (or their butyrated analogues) either suppress the induction of DNA synthesis after serum addition5 or initiate substantial increases in DNA synthesis respectively4 in quiescent mouse fibroblasts. Cyclic nucleotide concentrations in asynchronously-growing cell cultures are an average over the entire cell cycle and depend for cyclic AMP on the proportion of cells in a particular phase. The average cyclic AMP level is often correlated with growth rate6, although this may not be such a reliable parameter for cell growth as the relative proportions of G1, S, G2 and M vary with cell type and the culture conditions7. The larger changes in cyclic GMP are correlated directly with the initiation of fibroblast growth when cells are moving out of the G0 state or by passage through the M and G1 boundary and are not exhibited during the remainder of the cell cycle (W. S., and P. S. R., unpublished). Thus cyclic GMP concentrations and the ratios of cyclic AMP to cyclic GMP may be more sensitive and reliable indicators of the growth state of a cell.

Growth stimulation of human diploid fibro‐blasts by the tumor promoter, 12‐0‐tetradecanoyl‐phorbol‐13‐acetate

Abstract: When the tumor promoter, 12-0-tetradecanoyl-phorbol-13-acetate (TPA), was added to freshly seeded cultures of human diploid fibroblasts, cell growth was inhibited for 24–48 h and then proceeded at the same rate as in controls. After the control cultures had become confluent, cell division and the incorporation of tritiated thymidine continued in treated cultures, and the cell yield after 9–11 days was increased by as much as 50% compared to untreated cultures. TPA induced striking morphological changes including a decrease in cell size, suggesting that it may enhance cell division by increasing the number of cells per unit area required for cell-to-cell contact and confluence to be attained. TPA produced similar effects when added to growing cultures of NIH Swiss 3T3 mouse embryo and chick embryo fibroblasts. Continuous cultivation of human fibroblasts in the presence of TPA increased the cell yield for approximately five successive passages but did not increase the total number of population doublings over the entire life-span of the cultures.

Mechanisms by which activated normal macrophages destroy syngeneic rat tumour cells in vitro. Cytokinetics, non-involvement of T lymphocytes, and effect of metabolic inhibitors.

Abstract: Analysis of the kinetics of the in vitro interaction between nonimmune activated macrophages and syngeneic tumour cells (induced in inbred DA rats by polyoma virus, dimethylbenzanthracene or methylcholanthrene) has shown that a distinctive series of events can be clearly separated. The earliest consequence of interaction detectable by objective means is a marked decrease in tumour cell proliferation as reflected in the reduction of the capacity of tumour cells to incorporate DNA precursors such as [3H]thymidine. By 3—4 hours, the cytostatic effect is strongly marked, and is essentially established after 12 hours of interaction. Shrinkage, agglutination and decrease in the number of tumour cells as examples of the morphological consequences of cytostatic target cell damage accomplished by activated macrophages are rarely perceptible before 10–12 hours although the tumour cells have completely disappeared after 24–48 hours. Under the experimental conditions employed, occasional tumour cells escaped interaction with activated macrophages. The fact that such recovery of targets was fully reversed by adding further activated macrophages indicates that tumour cell revival reflects a decrease in macrophage effector functions during prolonged incubation. The possibility that some tumour cells might be resistant to macrophage effects thus seems excluded. Activated macrophages from normal and from congenitally athymic nude mice are equally effective in reducing tumour cell proliferation. Thus T lymphocytes and/or their soluble mediators are not essential for the macrophage function under investigation. Pretreatment of activated macrophages with an extensive array of metabolic inhibitors and agents known to affect distinct cellular functions yields much data but does not yet permit a simple comprehensive interpretation. However, the findings are compatible with the thesis that macrophage activation is accompanied by the de novo or enhanced synthesis of the cytostatic principle. Once possessed of this mechanism, other basic functional capacities of macrophages, such as membrane activity, movement or endocytosis are no longer essential for the mediation of the cytostatic effects.

Cyclic Nucleotides and Growth Control in Cultured Mouse Cells: Correlation of Changes in Intracellular 3′:5′cGMP Concentration with a Specific Phase of the Cell Cycle

Abstract: The commencement of cell growth following serum addition to quiescent cultures of mouse fibroblasts is preceded by transient changes in intracellular concentrations of cAMP and cGMP. By artificial depletion of the culture medium for different nutrients, cell growth can be reversibly arrested in various phases of the cell cycle. Here it is shown that the major cGMP increases are only observed when cultures which are arrested in the G0 phase are stimulated to grow or when synchronized growing cells pass through the G1 phase. In addition to its concomitant decrease, cAMP exhibits rhythmic changes during the cell cycle. This suggests that the increase in cGMP could act as a specific signal for movement of cells out of the G0 or G1 phase of the cell cycle by activating the pleiotypic and mitogenic program of the cell.

Cytoplasmic glucocorticoid-binding proteins in glucocorticoid-unresponsive human and mouse leukemic cell lines.

Abstract: Cytoplasmic glucocorticoid-binding proteins of high affinity and specificity were identified, quantified, and partially characterized in three steroid-unresponsive tissue culture lines, one derived from an AKR mouse leukemia and two derived from human lymphoblastic leukemia cells. The number of receptors per cell appeared to be comparable to that found in many steroid-responsive cells. Temperature-dependent entry of cytoplasmic receptor into the nucleus did not appear to be abnormal as determined in an in vitro nuclear binding assay. Cell growth, nucleoside and amino acid incorporation into macromolecules, amino acid pools, and glucose uptake were found to be unaffected by added glucocorticoid. The presence of specific cytoplasmic receptor proteins for glucocorticoids in malignant tissue does not appear to guarantee steroid responsiveness.

Multiple control mechanisms underlie initiation of growth in animal cells.

Abstract: THE understanding of the control of cell proliferation and differentiation requires the unravelling of the early events that trigger the initiation of growth. An in vitro system to study the initiation of growth is provided by the mouse 3T3 cell line. These cells exist in two alternative growth states: either reversibly arrested in the G0 phase of the cell cycle or in active proliferation. When resting 3T3 cells are exposed to fresh serum they recommence DNA synthesis and cell division1. Functional membrane changes are among the earliest events associated with the reinitiation of growth2. Within minutes of serum addition, the rate of transport of inorganic phosphate, nucleosides and glucose is increased several fold2–6, while cyclic AMP, which has been implicated in the regulation of growth of cultured fibroblasts, shows an opposite change7–11.

GROWTH CONTROL OF DIFFERENTIATED FETAL RAT HEPATOCYTES IN PRIMARY MONOLAYER CULTURE V. Occurrence in Dialyzed Fetal Bovine Serum of Macromolecules Having Both Positive and Negative Growth Regulatory Functions

Abstract: Dialyzed fetal bovine serum contains two distinct growth-controlling macromolecular fractions: one stimulates and the other inhibits proliferation of primary cultured differentiated fetal rat hepatocytes. Both fractions are precipitated by ammonium sulfate (50% saturation, pH 7.4, 4°C). Serum fraction I (SFI, mol wt > 120,000 daltons estimated by gel filtration with Bio-gel P200) appears to contain at least two factors which function, respectively, to initiate DNA synthesis (activity pH 4-10 stable) and to increase the rate at which initiated cells traverse the cell cycle (activity pH 4 and pH 10 labile). Intraperitoneai injections of SFI into adult rats have produced detectable stimulation of hepatic but not renal DNA synthesis. Serum fraction II (SFII, mol wt 40,000-80,000 daltons) suppressesin vitro incorporation of CHs-[SH]thymidine into DNA under conditions which diminish neither cell viability nor cell attachment. Mixing experiments indicate that SFI and SFII mutually antagonize each other with respect to DNA synthesis and cell multiplication. Thus, both the relative and absolute serum levels of multiple factors control in vitro fetal hepatocyte proliferation.

Modulation of cell proliferation by macrophages: a possible function apart from cytotoxic tumour rejection.

Abstract: The in vitro interaction between activated, non-immune macrophages (AM) and a variety of syngeneic, allogeneic or xenogeneic “normal” and “malignant” target cell lines was followed by different parameters such as target cell proliferation, viability or morphology. Proliferation of all rapidly replicating cell lines examined, irrespective of whether they were of syngeneic, allogeneic or xenogeneic origin, or showed normal or neoplastic growth characteristics, was similarly blocked by the presence of AM in an effector/target cell ratio of 10:1. It was only in very slowly proliferating cells that this inhibitory effect was not detectable. A marked diminution in target cell proliferation was also achieved with target cells growing in suspension, where maintenance of close contact between effectors and targets is unlikely, indicating that this macrophage effect may be mediated by a soluble product of AM. The finding of clear differences in the proliferation inhibition of slowly proliferating normal and neoplastic targets suggested that proliferation per se may not fully mirror the consequences of the macrophage/target cell interaction. This was affirmed when viability and morphology were used as parameters: viability was virtually unaffected in normal targets whereas neoplastic cells were killed. Accordingly, it is suggested that activated non-immune macrophages can affect targets in strikingly different ways. Inhibition of proliferation could be an important homoeostatic regulatory function of the macrophage which would affect every replicating cell. Cytocidal killing of targets, on the other hand, is achieved only on neoplastic cells.

Effects of steroid hormones on human fibroblasts in vitro. I. Glucocorticoid action on cell growth and collagen synthesis.

Abstract: Fibroblasts are the predominant cells of connective tissue and their integrity is therefore dependent upon factors which influence the metabolism of these cells. The sensitivity of fibroblasts to anti-inflammatory steroids has been shown by the suppression of collagen and mucopolysaccharide synthesis in vivo (Castor and Baker, 1950; Mancini, Stringa, and Canepa, 1960; Houck, Sharma, Patel, and Gladner, 1968) and in vitro (Castor, 1965), and the inhibition of cell growth in vitro (Grossfeld, 1959; Wellings and Moon, 1961; Berliner and Ruhmann, 1967). During prolonged therapy with anti-inflammatory steroids the inhibition described at a cellular level in vitro is reflected in vivo by an increased susceptibility to skin bruising (West, 1961) and by a decrease in skin thickness (Grahame, 1969). At the site of 'steroid bruising' there is a loss and disorganization of dermal collagen (Scarborough and Shuster, 1960). In order to study the mode of action of antiinflammatory steroids on skin, an in vitro fibroblast culture system has been used, and in this paper the effects of two anti-inflammatory steroids (prednisolone and cortisol) on fibroblast growth and metabolism will be described.

Properties of protein polymers as substratum for cell growth in vitro.

Abstract: The behavior of two established cell lines was found to vary when subcultivated on protein polymers covered with either negatively or positively charged substances. Results indicate that the influence on cell behavior is conditioned by the charge rather than by structural differences or degree of attachment of the substances to the polymer. Furthermore, the substratum seems to have just a physical effect at the cell membrane without any direct influence on cell metabolism. Cells were also seeded on a calf serum polymer and it was found that serum loses its properties on cultivated cells when used as substratum.