Showing papers on "Cellular differentiation published in 1976"
TL;DR: A single cell clonal line which responds reversibly to nerve growth factor (NGF) has been established from a transplantable rat adrenal pheochromocytoma and should be a useful model system for neurobiological and neurochemical studies.
Abstract: A single cell clonal line which responds reversibly to nerve growth factor (NGF) has been established from a transplantable rat adrenal pheochromocytoma. This line, designated PC12, has a homogeneous and near-diploid chromosome number of 40. By 1 week's exposure to NGF, PC12 cells cease to multiply and begin to extend branching varicose processes similar to those produced by sympathetic neurons in primary cell culture. By several weeks of exposure to NGF, the PC12 processes reach 500-1000 mum in length. Removal of NGF is followed by degeneration of processes within 24 hr and by resumption of cell multiplication within 72 hr. PC12 cells grown with or without NGF contain dense core chromaffin-like granules up to 350 nm in diameter. The NGF-treated cells also contain small vesicles which accumulate in process varicosities and endings. PC12 cells synthesize and store the catecholamine neurotransmitters dopamine and norepinephrine. The levels (per mg of protein) of catecholamines and of the their synthetic enzymes in PC12 cells are comparable to or higher than those found in rat adrenals. NGF-treatment of PC12 cells results in no change in the levels of catecholamines or of their synthetic enzymes when expressed on a per cell basis, but does result in a 4- to 6-fold decrease in levels when expressed on a per mg of protein basis. PC12 cells do not synthesize epinephrine and cannot be induced to do so by treatment with dexamethasone. The PC12 cell line should be a useful model system for neurobiological and neurochemical studies.
5,409 citations
TL;DR: Starting with a clone converting to adipose cells with a vary low frequency, it has been possible, by serial selection, to generate subclones which convert with a high frequency, due to spontaneous heritable changes affecting susceptibility to the adipose conversion.
798 citations
TL;DR: The results are consistent with the concept, deveolped from work on other cell types, that plasminogen activator may represent a generalized mechanism for tissue remodeling and cell migration.
569 citations
TL;DR: A definitive test for developmental totipotency of mouse malignant teratocarcinoma cells was conducted by cloning singly injected cells in genetically marked blastocysts, indicating that a near-normal chromosome complement is sufficient for total restoration of orderly gene expression in a normal embryonic environment.
Abstract: A definitive test for developmental totipotency of mouse malignant teratocarcinoma cells was conducted by cloning singly injected cells in genetically marked blastocysts. Totipotency was conclusively shown in an adult mosaic female whose tumor-strain cells had made substantial contributions to all of the wide range of its somatic tissues analyzed; the clonally propagated cell lineage had therefore differentiated in numerous normal directions. The test cells were from "cores" of embryoid bodies of a euploid, chromosomally male (X/Y), ascites tumor grown only in vivo by transplantation for 8 years. The capacity of cells from the same source to differentiate, in a phenotypic male, into reproductively functional sperms, has been shown in our previous experiments [(1975) Proc. Nat. Acad. Sci. USA 72, 3585-3589]. Cells from this transplant line therefore provide material suitable for projected somatic and germ-line genetic analyses of mammalian differentiation based on "cycling" of mutation-carrying tumor cells through developing embryos. In some animals obtained from single-cell injections tumor-derived cells were sporadically distributed in developmentally unrelated tissues. These cases can be accounted for by delayed and haphazard cellular integration, and by a marked degree of sustained cellular developmental flexibility in early mammalian development, irrespective of certain classical "germ-layer" designations. All mosaic mice obtained have thus far been free of teratomas. In one case, the injected stem cell contributed only to the pancreas and gave rise to a malignancy resembling pancreatic adenocarcinoma. The high modal frequency of euploidy in these individually tested cells thus tends to indicate that a near-normal chromosome complement is sufficient for total restoration of orderly gene expression in a normal embryonic environment; it may also be necessary for teratoma stem-cell proliferation to be terminated there.
455 citations
TL;DR: A group of compounds, polymethylene bisacetamides (acetylated diamines), which are potent inducers of erythroid differentiation in murine eryTHroleukemia cells are identified and introduced through varying numbers of methylenes substantially increased the effectiveness of these compounds.
Abstract: This report identifies a group of compounds, polymethylene bisacetamides (acetylated diamines), which are potent inducers of erythroid differentiation in murine erythroleukemia cells. A known inducing agent, N-methylacetamide, was dimerized through varying numbers of methylenes in an attempt to increase the local effective concentration at adjacent target sites. The simple dimer was no more effective than N-methylacetamide alone; introduction of five to eight methylenes between acetamide groups substantially increased the effectiveness of these compounds. The hexamethylene bisacetamide was active between 0.5 mM and 5 mM; the percentage of cells induced and the rate at which they were recruited to differentiation was dependent upon the concentration of inducer within this range. At 5 mM hexamethylene bisacetamide essentially the entire population (greater than 99%) was induced to a pathway of erythroid differentiation which was greater differentiation of the cultured cells than with any inducer yet tested.
351 citations
TL;DR: 3T3-L1 fibroblasts differentiate in culture into cells having adipocyte character and the elevated acetyl-CoA carboxylase activity is the product of an increased cellular enzyme level.
300 citations
TL;DR: It is found that stalk-cell induction by cyclic AMP is markedly dependent on cell density, and evidence for the involvement of a low molecular weight diffusible factor in this process is presented.
Abstract: To understand pattern formation in an organism one needs to know what factors control the differentiation of each cell type and what elements are responsible for the spatial arrangement of these cell types. In the cellular slime mould Dictyostelium discoideum, the problem is relatively simple since the mature fruiting body consists of two basic cell types—stalk cells and spores. The stalk cells of the mature fruiting body are derived from the anterior cells of the multicellular masses formed by aggregation, whereas the spores are derived from the posterior cells1. Cells that are plated at a density too low for aggregation, or are allowed to aggregate under water do not normally differentiate into stalk or spore cells. In many of our experiments we have made use of the fact that cells plated on agar at any density fail to undergo development beyond the stage of aggregation if they are covered by a thin layer of Cellophane. In this paper we present observations on cell differentiation which derive from the original report of Bonner2 of stalk-cell induction by cyclic AMP in isolated cells. We have found that stalk-cell induction by cyclic AMP is markedly dependent on cell density, and present evidence for the involvement of a low molecular weight diffusible factor in this process. We also describe the isolation of a mutant which gives rise to spore cells under cellophane.
293 citations
TL;DR: In this article, a nonspecific polyclonal activator of T lymphocytes, called Canavalin A, was shown to activate Lyl and Ly23 subclasses to the same degree.
Abstract: Concanavalin A, a nonspecific polyclonal activator of T lymphocytes, activates Lyl and Ly23 subclasses to the same degree. After activation, the Ly23 subclass, but not the Lyl subclass, has the following properties: (a) Suppression of the antibody response to sheep erythrocytes (SRBC) in vitro. (b) Production of a soluble factor that suppresses the anti-SRBC response in vitro. (c) Suppression of the generation of cell-mediated cytotoxicity to H-2 target cells in vitro. Con A-activated cells of the Lyl subclass, but not the Ly23 subclass, express helper function in the anti-SRBC response in vitro. Because the intact Con A-stimulated T-cell population contains both cell types, these cells do not exert detectable helper effects in an anti-SRBC system in vitro, because the helper effect of Lyl cells is masked by the suppressor effect of the Ly23 cells. Each function is revealed by eliminating one or the other population with the relevant Ly antiserum. The resting T-cell population, before activation by Con A, also contains already programmed Lyl and Ly23 cells with similar helper and suppressor potentials, respectively. This is revealed by experiments with Ly subclasses which have been separated from the resting T-cell population and then stimulated by Con A. Thus helper and suppressor functions, as expressed in these systems, are manifestations of separate T-cell-differentiative pathways and do not depend upon stimulation of the cells by antigen.
256 citations
TL;DR: These results show that pluripotency in embryonal carcinoma cells need not to be abolished by the introduction of a complete diploid genome from a differentiated cell.
223 citations
TL;DR: Leukocytes from patients with several forms of immunodeficiency characterized by apparently differing defects in B-lymphocyte maturation produced few or no plasmacytoid cells in vitro, and were capable of suppressing the generation of plasma cells in co-culture with cells of normal persons, in the presence of pokeweed mitogen.
Abstract: Leukocytes from patients with several forms of immunodeficiency characterized by apparently differing defects in B-lymphocyte maturation produced few or no plasmacytoid cells in vitro, and were capable of suppressing the generation of plasma cells in co-culture with cells of normal persons, in the presence of pokeweed mitogen. Such inhibition was commonly observed in cultures which included cells from patients with primary immunoglobulin deficiency, but was not seen to a significant degree in identical co-cultures of cells from normals. The suppression observed was not dependent upon mixed leukocyte culture reactivity. Both sheep erythrocyte-rosetting lymphocytes and adherent cells appeared to participate in these effects in some patients. In one patient with common variable immunodeficiency, but not in several others, removal of suppressing cells permitted the patient's remaining cells to differentiate into plasma cells in vitro. Because of the diverse syndromes in which suppression was observed, it is likely that, in at least some hypogammaglobulinemic patients, the suppression is secondary to the disease process rather than being the primary pathogenic mechanism.
202 citations
TL;DR: The results indicate that this cell line might offer a system for studying the regulation of a type of cellular differentiation, and appears to be mediated by increases in intracellular cyclic AMP levels.
Abstract: Green and Kehinde [(1974) cell 1, 113-116] have isolated clones of Swiss 3T3 fibriblasts that are able to convert to adipose cells. In this paper we report on two chemicals (prostaglandin F2alpha, 0.1 mug ml, and 1-methyl-3-isobutyl xanthine, 0.5 mM) that are able to rapidly and irreversibly program the fibroblasts to differentiate into adipose cells. Confluent cultures treated with prostaglandin F2alpha and insulin for 3-5 days, followed by insulin alone for 7-48 hr, yield numerous adipocyte colonies compared to control dishes and dishes treated with insulin alone. Cells treated with prostaglandin F2alpha or 1-methyl-3-isobutyl xanthine alone, rinsed, and then exposed to insulin gave similar results, indicating that the continuous presence of the triggering agent is not required to elicit the conversion of the fibroblasts to adipocytes. Agents that raise intracellular levels of 3':5'-cyclic AMP. 1.0 mM; 8-bromo-cyclic AMP,0.5 mM; and prostaglandin E1, 0.1 mug/ml) do not trigger the conversion process, suggesting that cyclic AMP may not be the mediator of differentiation in these cells. 8-Bromo-cyclic AMP, however, does induce thase; 3':5'-nucleotidohydrolase; EC 3.1.4.17) in these cells; the induction appears to be mediated by increases in intracellular cyclic AMP levels. These results indicate that this cell line might offer a system for studying the regulation of a type of cellular differentiation.
TL;DR: Examination of extensive micrococcal nuclease digests suggests that the chromatin subunits of all of the higher eukaryotic cells the authors have studied contain a core with approximately 140 base pairs of DNA.
Abstract: Biochemical evidence is presented which confirms that the DNA repeat length in micrococcal nuclease (spleen endonuclease, nucleate 3'-oligonucleotidohydrolase, EC 3-1-4-7) digests of Chinese hamster ovary chromatin is shorter than that of rat liver chromatin [J.L. Compton, R. Hancock, P. Oudet, and P. Chambon (1976) Eur. J. Biochem., in press]. A survey of available cells has shown that the DNA repeat length of the chromatin of higher eukaryotes varies widely. A value of 196 base pairs was found for cells of all mature tissues, regardless of the source of the tissue, whereas smaller values were found for cells of actively dividing tissues and larger values were found for a genetically inactive cell. Although the DNA repeat length of the chromatin of cells in culture was usually shorter than 196 base pairs, there was no general correlation between the size of the chromatin DNA repeat length and the rate of cell division or the functional state of the cell in culture. Examination of extensive micrococcal nuclease digests suggests that the chromatin subunits of all of the higher eukaryotic cells we have studied contain a core with approximately 140 base pairs of DNA.
TL;DR: It is speculated that direct heterotypic cell contacts, which occur prior to the cessation of preameloblast cell division and precede the secretion of enamel proteins, may be instructive in the induction ofEnamel protein biosynthesis.
01 Jan 1976
TL;DR: Although morphogenesis and differentiation are not exact or discrete terms (they both involve metabolic, cytological, and behavioral changes), it is the behavioral aspects that are emphasize when morphogenesis is spoken of and the metabolic and cytological changes that are emphasized when differentiation is spokenOf.
Abstract: Morphogenesis of an organ or tissue is a complex and specific series of events leading to a unique, functional organization of cellular and extracellular elements. Underlying these events are several types of cell behavior such as cell movement, recognition and adhesion, shape changes, mitosis, and death. Morphogenesis is usually accompanied by and necessary for cellular differentiation, in which the component cells undergo a series of distinctive metabolic and cytological changes that result in the synthesis or secretion of characteristic and functional cell products. Although morphogenesis and differentiation are not exact or discrete terms (they both involve metabolic, cytological, and behavioral changes), it is the behavioral aspects that are emphasized when morphogenesis is spoken of and the metabolic and cytological changes that are emphasized when differentiation is spoken of.
TL;DR: The results of this study indicate that the morphogenetic factors and mechanisms that govern so precisely growth, cellular differentiation, and organogenesis during the normal course of development can completely suppress the tumorous state, leading to the formation of cells, tissues, and organs that appear normal in every respect but are, in fact, inherently neoplastic.
Abstract: The neoplastic state in cells of tissues and organs that develop from cloned lines of crown gall teratomas of tobacco may be completely but reversibly suppressed. Stems and leaves found on teratoma shoots may appear morphologically normal and such organs contain all of the specialized cell types and are histologically and functionally indistinguishable from those found in normal tobacco shoots of comparable age. When however, specialized cells of several different kinds that are present in stems and leaves of the teratomas are excised from the plant and grown on a basic culture medium they again assume their neoplastic properties. The results of this study indicate that the morphogenetic factors and mechanisms that govern so precisely growth, cellular differentiation, and organogenesis during the normal course of development can completely suppress the tumorous state, leading to the formation of cells, tissues, and organs that appear normal in every respect but are, in fact, inherently neoplastic. Whether the normal or tumor phenotype is expressed appears to depend on the activation or repression of select biosynthetic systems, one of which, the auxin sytems, has been identified here.
TL;DR: The experiments on the activation of DNA synthesis and thymidine kinase F activity suggest that genes determining cell cycle proteins are readily accessible to transcription and translation in essentially all nucleated cells.
Abstract: A resume has been presented of some recent investigations which show that DNA synthesis can be initiated in many types of quiescent animal cells by external stimuli, by introducing a quiescent nucleus into the cytoplasm of a proliferating cell, or by a virus infection. The components of the DNA replication apparatus are described. It is shown that deoxyribonucleoside triphosphate pools increase substantially in animal cells at the time DNA synthesis is initiated due to the enhanced activities of enzymes functioning in nucleotide synthesis. Especially striking is the increase of thymidine kinase activity, indicating that this enzyme may be a useful marker of the shift from the quiescent to the replicative state. The thymidine kinase isozymes of vertebrate cells have been characterized. Thymidine kinase F, which is found principally in the cytosol, is the isozyme that increases when G1(Go) phase cells are stimulated or infected with oncogenic viruses. Chick cytosol thymidine kinase F can also be reactivated by introducing differentiated chick erythrocyte nuclei into the cytoplasm of enzyme-deficient LM(TK−) mouse cells. Furthermore, herpesviruses code for distinctive, virus-specific thymidine kinase isozymes, so that another way to transform thymidine kinase-deficient LM(TK−) cells to kinase-positive cells is by infecting them with UV-irradiated herpes simplex viruses. The experiments on the activation of DNA synthesis and thymidine kinase F activity have been discussed in the context of the proliferative activityin vivo and the immortalization in culture of neoplastic cells. These experiments suggest that genes determining cell cycle proteins are readily accessible to transcription and translation in essentially all nucleated cells. The tendency of transformed cells to become multinucleated after cytochaliasin B treatment also suggests that one important difference between malignant cells and most normal cells may be the ability of malignant cells to ‘stockpile’ the proteins (and/or their messenger RNAs) of the DNA replicative apparatus and to maintain the ‘stockpiles’ in progeny cells.
TL;DR: The existence of messenger-specific nuclear post-transcriptional control mechanisms which do not use poly(A) as a signal, and which allow the cytoplasmic accumulation of globin mRNA only in erythroid tissues, suggests the existence of messages coding for alpha- and beta-globin may nonetheless be transcribed at very low levels in all mouse cells.
TL;DR: Studies with cell lines capable of undergoing erythroid differentiation in culture have made possible a comparison of normal and leukaemic erythropoiesis, by the combined approaches of cell biology, molecular biology and somatic cell genetics.
Abstract: Recent work has clarified how different erythroid functions may be regulated during normal erythropoiesis, and have helped to define the role of the hormone erythropoietin. Studies with cell lines (Friend cells) capable of undergoing erythroid differentiation in culture have made possible a comparison of normal and leukaemic erythropoiesis, by the combined approaches of cell biology, molecular biology and somatic cell genetics.
TL;DR: It is found that an elimination after induction with the thymic polypeptide removes a substantial amount of terminal transferase from the bone marrow cell population, suggesting that at least one-half of the marrow cells bearing this enzyme are related to those found in theThymus.
Abstract: Terminal deoxynucleotidyl transferase is an enzyme which has the unique property of polymerizing polydeoxynucleotides onto a primer in the absence of a template (1,2). This enzyme is found both in the thymus and the bone marrow of birds, rodents, and humans (3-7). Whether the marrow cells that contain terminal transferase are related to thymocytes, or are on a separate pathway of differentiation, is not yet known (7,8). To determine the lineage of the murine bone marrow cells that have terminal transferase, we have investigated whether these cells have the antigen Thy-1 induced on the cells by treatment with thymopoietin (9). Thymopoietin is known to induce a set of characteristic T-cell markers including the Thy-1 alloantigen on the surface of a subpopulation of bone marrow cells committed to T-cell differentiation (prothymocytes) (10). Destruction of Thy- 1-positive cells after exposure to thymopoietin allows elimination of a substantial fraction of those bone marrow cells that can repopulate an irradiated thymus (11). We find that such an elimination after induction with the thymic polypeptide removes a substantial amount of terminal transferase from the bone marrow cell population, suggesting that at least one-half of the marrow cells bearing this enzyme are related to those found in the thymus.
TL;DR: Cell lines with B- and T-characteristics from patients with lymphoproliferative diseases had much lower activities than those of B-cell lines derived from normal subjects, and the highest activity was in a human myeloma line active in synthesis of an immunoglobulin light chain.
Abstract: gamma-Glutamyl transpeptidase, an enzyme that catalyzes gamma-glutamyl transfer from gamma-glutamyl compounds to amino acid and peptide acceptors, and which is known to be localized in the membranes of many epithelial cells, was found in a variety of lymphoid cells. The lymphoid cell enzyme is located on the cell surface, and exhibits substantially the same substrate specificity as the enzyme found in epithelial cells. Human and rat (but not mouse) lymphocyte gamma-glutamyl transpeptidase was stimulated by treatment of the cells with mitogens. Normal human peripheral B-cells were more active than T-cells, but the reverse relationship of activities was found in chronic lymphocytic leukemia lymphocytes. Human lymphoblastic lines vary markedly in activity. In general, cell lines with B- and T-characteristics from patients with lymphoproliferative diseases had much lower activities than those of B-cell lines derived from normal subjects. The highest activity found was in a human myeloma line active in synthesis of an immunoglobulin light chain. The data indicate that gamma-glutamyl transpeptidase is a surface marker reflecting differentiation in normal and neoplastic cells.
Journal Article•
TL;DR: Maximal inhibition of LPS-induced differentiation was associated with increased cellular proliferation as measured by incorporation of 3H-thymidine, whereas treatment with anti-mu alone over a wide dosage range did not stimulate cellular proliferation.
Abstract: Lipopolysaccharide-(LPS) induced differentiation of mouse B lymphocytes to cells synthesizing large amounts of cytoplasmic IgM and IgG2 could be suppressed by antibodies to mu-chains. Maximal inhibition of LPS-induced differentiation was associated with increased cellular proliferation as measured by incorporation of 3H-thymidine, whereas treatment with anti-mu alone over a wide dosage range did not stimulate cellular proliferation. Spleen cells from newborn mice were suppressed by concentrations of anti-mu several hundred-fold lower than required for adult spleen cells; the adult pattern of susceptibility to suppression was acquired by 1 week of age. No significant differences in susceptibility to anti-mu were found in comparisons of adult spleen, lymph node, bone marrow, and Peyer's patch lymphocytes.
TL;DR: Two main morphological patterns are significant for the organization of the retina during neurogenesis: the cell to cell contacts of migrating cells and the spatial arrangement of Müller cells which could provide guidelines for migration of neuronal elements.
Abstract: Fixed retinae of chick embryos and chicks of the first week after hatching were fractured and examined with the scanning electron microscope. The matrix cells of the retina proliferate up to the beginning of the second week. The migrating cells are oriented in cell cords. This columnar organizaion prevails up to the development of the plexiform layers formed as a consequence of the outgrowth of the dendritic and axonal cell processes. Special attention was paid to the differentiation of the ganglion, bipolar and receptor cells, and the radial fibers (Muller cells). Two main morphological patterns are significant for the organization of the retina during neurogenesis: a)the cell to cell contacts of migrating cells and b)the spatial arrangement of Muller cells which could provide guidelines for migration of neuronal elements.
TL;DR: The hypothesis that the differentiation of B lymphocytes proceeds through at least four distinct stages characterized by the following phenotypes is proposed: Ig-Ia-CR- leads to Ig+Ia+CR- leading to Ig+.
Abstract: Among bone-marrow-derived (B) lymphocytes exist subpopulations of cells that can be induced to express the markers: surface immunoglobulin (Ig), the antigen associated with the immune response gene (Ia), and the receptor for the third complement component (CR). Inducible cells for the first two markers are found in bone marrow, and inducible cells for all three are in spleen. Experiments were designed to determine whether induction involves a single precursor cell population that on triggering with lipopolysaccharide expresses all three surface markers, or three separate precursor cell populations each of which expresses a single marker. Specific B cell subpopulations were eliminated by treatment with anti-Ig or anti-Ia and complement, or by rosette formation with erythrocytes-antibody-complement followed by differential centrifugation, and surviving cells were subsequently tested for inducibility of the three B cell markers. After anti-Ig cytolysis only Ig, but not Ia and CR, could be induced, implying that the Ia- and the CR-inducible cells are Ig+. Similarly, after anti-Ia cytolysis Ig and Ia but not CR could be induced. Thus, CR-inducible cells must have the Ig+Ia+ phenotype. Elimination of CR+ cells did not affect the induction of Ig, Ia, or CR from their precursors. None of the three elimination experiments affected the conversion of prothymocytes (Thy-1-) to thymocytes (Thy-1+). From these results we propose the hypothesis that the differentiation of B lymphocytes proceeds through at least four distinct stages characterized by the following phenotypes: Ig-Ia-CR- leads to Ig+Ia-CR- leads to Ig+Ia+CR- leads to Ig+Ia+CR+.
TL;DR: The experiments with emission anisotropy represent the first analyses and separations of single cells on the basis of fluorescence polarization and indicated the feasibility of obtaining homogeneous classes of cell types in a viable state.
Abstract: The automated high-speed analysis and separation of cells on the basis of spectroscopic parameters has been applied to studies of cellular differentiation in two systems. The temporal changes following induction of differentiation by dimethylsulfoxide in the Friend virus-transformed erythroid cells were quantitated by multiparameter analysis leading to the separation of discrete subpopulations. Thus, following induction, cell size decreased as measured by light scattering, the number of H-2 histocompatibility antigen sites decreased as measured by indirect fluorescent antibody binding, the number of lectin-binding sites per cell increased as measured by fluorescein-labeled concanavalin-A and the microviscosity of the hydrocarbon region of the plasma membrane increased as determined by the fluorescence emission anisotropy of the membrane probe 1,6-diphenyl-1,3,5-hexatriene. Cells were separated on the basis of several of these parameters and analyzed for their hemogloglobin content by benzidine staining. Examination of cells separated according to the anisotropy parameter showed that high anisotropy values were correlated with (a) small cell size, (b) positive staining with benzidine and (c) pronounced reactivity with fluorescent antibody to the erythrocyte protein spectrin. Disaggregated cells from Hydra attenuata were selectively stained with the dyes rhodanile blue, 7-(p-methoxybenzylamino)-4-nitrobenz-2-oxa-1,3-diazole and fluorescamine. Distribution analyses and preliminary separations indicated the feasibility of obtaining homogeneous classes of cell types in a viable state. The experiments with emission anisotropy represent the first analyses and separations of single cells on the basis of fluorescence polarization. Many other uses of this technique are anticipated.
TL;DR: The murine-virus-infected erythroleukemia cell system provides an opportunity to examine regulatory mechanisms controlling cytodifferentiation by isolating a cloned cell line resistant to the erythropoiesis-inducing effect of dimethylsulfoxide (Me2SO).
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.
Journal Article•
TL;DR: It is to be hoped that a careful study of retrodifferentiation in physiological and tumoral models will help to distinguish that which in neoplastic development can be relevant to an adaptive cell behavior from that which might eventually be the result of specific or constitutive alterations.
Abstract: Summary The close relationship at the molecular level between cellular differentiation and neoplasia has been evidenced by the discovery in adult individuals of fetospecific antigens and fetal type isozymes associated with many spontaneous and experimentally induced malignant tumors. One question in relation with this finding is whether cancerous tumors develop from the differentiation of a tissue reserve of stem cells or by a process of retrodifferentiation, i.e., the nucleocytoplasmic stepwise reversion of cells toward stationary states with simplified structure and less information content. The question is not merely academic; elucidation of the nature of the target cells from which neoplastic growth emerges has obvious physiopathological and therapeutic implications. This contribution is an analysis of the nature and the mechanism of cellular retrodifferentiation and a discussion of its possible role in regeneration and metaplasia, as well as in neoplastic development. Throughout living systems, retrodifferentiation appears as a common adaptive process for the maintenance of cell integrity against deleterious agents of varied etiology (physical, chemical, and viral). While preserving the entire information encoded on its genome, cells undergoing retrodifferentiation lose morphological and functional complexity by virtue of a process of self-deletion of cytoplasmic structures and the transition to a more juvenile pattern of gene expression. This results in a progressive uniformization of originally distinct cell phenotypes and to a decrease of responsiveness to regulatory signals operational in adult cells. Retrodifferentiation is normally counterbalanced by a process of reontogeny that tends to restore the terminal phenotypes from where the reversion started. This explains why retrodifferentiation remains invariably associated to cell regeneration and tissue repair. There is an ever growing evidence that neoplastic transformation in vivo and in vitro is frequently preceded and/or accompanied by biochemical, morphological, and behavioral transitions characteristic of a cell undergoing retrodifferentiation. Contrary to what occurs in regenerating tissues, the “unbalanced” character of tumor-associated retrodifferentiation seems to be a property linked to cancer. The question arises why a unique mechanism of cell rejuvenation is in physiological conditions (regeneration), followed by a process of reontogeny, while in neoplasia the process remains incomplete or does not occur and leads to the emergence of a population of persistently dividing cells. It is to be hoped that a careful study of retrodifferentiation in physiological and tumoral models will help to distinguish that which in neoplastic development can be relevant to an adaptive cell behavior from that which might eventually be the result of specific or constitutive alterations.
TL;DR: In this paper, the authors demonstrate that soluble T-cell products can replace the requirement for helper T cells in the generation of T-effector or killer cells, and are as effective as T-helper cells during the differentiation of precursor T cells into killer cells.
Abstract: IMMUNOLOGICAL responses to histoincompatible tissues and to tumour cells are mediated by thymus-derived (T) lymphocytes. The cells that effect these responses have been termed cytotoxic T-killer cells and are derived from T-precursor cells that have become programmed (committed) to recognise specific antigenic determinants. The generation of T-effector or killer cells involves the collaboration of two distinct subpopulations of T cells. Helper T cells interact with specific precursor T cells when stimulated by antigen and, during the resultant differentiation processes, the precursor clones mature into specific killer cells1–3. The nature or mechanisms of the collaboration between the precursor and helper T cells has been obscure until now. The data presented here demonstrate that soluble T-cell products can replace the requirement for helper T cells in the generation of T-killer cells. The active substances are produced on antigenic stimulation and are as effective as T-helper cells during the differentiation of precursor T cells into killer cells.
TL;DR: The detection of a cell marker which is produced in situ in the earliest stages of differentiation, and one which is detectable by highly sensitive techniques would circumvent both of these problems.
Abstract: THE primary observable event of differentiation in the mammalian embryo is the formation of the trophectoderm and the inner cell mass (ICM). Differentiation first becomes evident in the mouse embryo during early blastulation and is clear and apparently irreversible by the 60-cell blastocyst stage. The 45 or so trophectoderm cells surround a blasto-coelic cavity containing the ICM, they pump fluid, are phagocytic, are interconnected through junctional complexes and can elicit an implantation response in the uterus1. The trophectoderm gives rise to the ectoplacental trophoblast, primary and secondary trophoblastic giant cells and probably also to extra-embryonic ectoderm1,2. The cells of the ICM are less evidently differentiated, being rounded, sticky cells somewhat like cleavage stage blasto-meres, but having lost the capacity to form trophoblast3,4. The ICM gives rise to embryonic ectoderm, and to both extra-embryonic and embryonic endoderm1,2,5. Although the fully differentiated cells of the blastocyst are distinguishable by structural and functional criteria, adequate markers of differentiation are not available for the morula stage, when the determinative events leading to differentiation are presumed to occur. Thus, attempts to detect blastomeres with a commitment to one or the other differentiated cell type have relied for an index of commitment on the subsequent behaviour of genetically or physically marked blastomeres combined in various spatial relations with other distinguishable blastomeres. This experimental approach is open to criticism. Frequently, many cell divisions must elapse before suitable genetic markers can be detected with sufficient sensitivity, and the procedures involve artificial manipulation and therefore possibly modification of blastomeres to test their potency2,6. The detection of a cell marker which is produced in situ in the earliest stages of differentiation, and one which is detectable by highly sensitive techniques would circumvent both of these problems. We describe here the detection of tissue specific markers which may prove to fulfil these criteria.
TL;DR: By applying Pontryagin's maximum principle to a set of mathematical models of lymphocyte populations and their antibody production, it is found that the optimal strategy of bang-bang control appears robust.
Abstract: The optimal strategy available to the immune system for responding to a non-replicating thymus-independent antigen is examined. By applying Pontryagin's maximum principle to a set of mathematical models of lymphocyte populations and their antibody production, it is found that the optimal strategy of bang-bang control appears robust. In a variety of structurely related biological models, similar behaviour is observed. The models that we consider assume that antigen triggers a population of B-lymphocytes. These triggered lymphocytes can either proliferate and secrete modest amounts of antibody or differentiate into nondividing plasma cells which secrete large amounts of antibody. For biologically reasonable parameter values it is found that for low doses of antigen, immediate differentiation into plasma cells is optimal, while for high antigen doses a proliferative state followed by differentiation is the best strategy.
01 Jan 1976
TL;DR: The alteration of gene expression during development is of cardinal importance in cell differentiation and the molecular basis of the progressive appearance of diverse phenotypes from cells with the same genotype is explained.
Abstract: Cell differentiation is one of the central problems of contemporary biology and medicine. How does the fertilized egg develop into an adult organism with a myriad of cell types? It is common knowledge that all cells in a multicellular organism possess the same genetic information, hence an identical genotype. What is the molecular basis of the progressive appearance of diverse phenotypes from cells with the same genotype? The alteration of gene expression during development is of cardinal importance in cell differentiation.