Dictyostelium amoebae can differentiate into spores without cell-to-cell contact

Development ◽  
1981 ◽  
Vol 62 (1) ◽  
pp. 369-378
Author(s):  
Robert R. Kay ◽  
David J. Trevan
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Time Lapse ◽  
Cell Types ◽  
Spore Formation ◽  
Cellular Interaction ◽  
Cell Contact ◽  
Direct Cell ◽  
Petri Dishes ◽  
Intermediate Density

Amoebae of sporogenous mutants of Dictyostelium discoideum can differentiate into stalk cells and spores in the absence of normal morphogenesis when spread on agar containing cyclic-AMP. The efficiency of differentiation is improved when the amoebae are incubated as submerged monolayers in plastic petri dishes. Under these conditions spore formation is density dependent and hence requires some form of cellular interaction. To determine whether this interaction involves direct cell—cell contact we have made time-lapse films of cells differentiating at intermediate density. These films show that amoebae can develop into spores without making contact with any other cells. In addition, although some cells do divide during incubation, division is not necessary for spore formation. At higher densities small aggregates form which give rise to mixtures of stalk cells and spores. There is no detectable patterning of the two cell types within such aggregates.

Measurements of intracellular pH and its relevance to cell differentiation in Dictyostelium discoideum

1985 ◽  
Vol 76 (1) ◽  
pp. 235-245 ◽  
Author(s):  
K. Inouye
Keyword(s):  
Cell Differentiation ◽  
Dictyostelium Discoideum ◽  
Intracellular Ph ◽  
Spore Formation ◽  
Cell Contact ◽  
Weak Acids ◽  
Alternative Pathways ◽  
Monolayer Cultures ◽  
Fluorescence Dye ◽  
Good Accordance

A method was developed in this study to measure the intracellular pH (pHi) of Dictyostelium discoideum cells with a pH-sensitive fluorescence dye, carboxyfluorescein dibutyrate, and the pHi values of cells on the stalk and spore pathways were compared. The pHi of prestalk cells was lower than that of prespore cells by approximately 0.3 pH unit. In monolayer cultures of sporogenous mutants, which can differentiate into stalk cells and spores without cell contact, the pHi of the amoebae depended on the medium: media in which the majority of cells eventually become stalk cells reduced the pHi while conditions favouring spore formation increased the pHi. Addition of weak acids lowered the pHi. These results are in good accordance with the model presented by Gross and coworkers, which proposes that the choice between alternative pathways of cell differentiation is regulated via pHi and that low pHi favours stalk differentiation whereas high pHi favours spore formation.

Dictyostelium discoideum lipids modulate cell-cell cohesion and cyclic AMP signaling

1991 ◽  
Vol 11 (1) ◽  
pp. 468-475
Author(s):  
D R Fontana ◽  
C S Luo ◽  
J C Phillips
Keyword(s):  
Cyclic Amp ◽  
Adenylyl Cyclase ◽  
Dictyostelium Discoideum ◽  
Membrane Lipids ◽  
Camp Signaling ◽  
Cell Contact ◽  
Complete Elimination ◽  
Cyclase Activation ◽  
Independent Events ◽  
Cell Cell

During Dictyostelium discoideum development, cell-cell communication is mediated through cyclic AMP (cAMP)-induced cAMP synthesis and secretion (cAMP signaling) and cell-cell contact. Cell-cell contact elicits cAMP secretion and modulates the magnitude of a subsequent cAMP signaling response (D. R. Fontana and P. L. Price, Differentiation 41:184-192, 1989), demonstrating that cell-cell contact and cAMP signaling are not independent events. To identify components involved in the contact-mediated modulation of cAMP signaling, amoebal membranes were added to aggregation-competent amoebae in suspension. The membranes from aggregation-competent amoebae inhibited cAMP signaling at all concentrations tested, while the membranes from vegetative amoebae exhibited a concentration-dependent enhancement or inhibition of cAMP signaling. Membrane lipids inhibited cAMP signaling at all concentrations tested. The lipids abolished cAMP signaling by blocking cAMP-induced adenylyl cyclase activation. The membrane lipids also inhibited amoeba-amoeba cohesion at concentrations comparable to those which inhibited cAMP signaling. The phospholipids and neutral lipids decreased cohesion and inhibited the cAMP signaling response. The glycolipid/sulfolipid fraction enhanced cohesion and cAMP signaling. Caffeine, a known inhibitor of cAMP-induced adenylyl cyclase activation, inhibited amoeba-amoeba cohesion. These studies demonstrate that endogenous lipids are capable of modulating amoeba-amoeba cohesion and cAMP-induced activation of the adenylyl cyclase. These results suggest that cohesion may modulate cAMP-induced adenylyl cyclase activation. Because the complete elimination of cohesion is accompanied by the complete elimination of cAMP signaling, these results further suggest that cohesion may be necessary for cAMP-induced adenylyl cyclase activation in D. discoideum.

scholarly journals Cell behavior in Dictyostelium discoideum: preaggregation response to localized cyclic AMP pulses.

1982 ◽  
Vol 92 (3) ◽  
pp. 807-821 ◽  
Author(s):  
R P Futrelle ◽  
J Traut ◽  
W G McKee
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
System Analysis ◽  
Natural Populations ◽  
Time Lapse ◽  
Cell Behavior ◽  
Motion Data ◽  
Oriented Movement ◽  
Scattering Response ◽  
Cell Motion

The motion of cells in the aggregation phase of Dictyostelium discoideum development is complex. To probe its mechanisms we applied precisely timed (+/- 1 s) and positioned (+/-2 micrometers) pulses of cyclic AMP to fields of cells of moderate density using a micropipette. We recorded cell behavior by time lapse microcinematography and extracted cell motion data from the film with our Galatea computer system. Analysis of these data reveals: (a) Chemotaxis lasts only about as long as the cyclic AMP signal; in particular, brief pulses (approximately 5 s) do not induce chemotaxis. (b) Chemotactic competence increases gradually from within an hour after the initiation of development (starvation) to full competence at approximately 15 h when aggregation begins under our conditions. (c) Cell motion reverses rapidly (within 20 s) when the external gradient is reversed. There is no refractory period for motion. We present a new description of the process of aggregation consistent with our result and other recent findings. (d) The behavioral response to cyclic AMP includes a phenomenon we call "cringing." In a prototypical cringe the cell speed drops within 3 s after a brief cyclic AMP stimulus, and the cell stops and rounds and then resumes motion after 25 s. (e) The development of the speed response in cringing as the cells age closely parallels the development of the cyclic AMP-induced light-scattering response of cells in suspension. (f) Cringing occurs in natural populations during weak oriented movement. The computerized analysis of cell behavior proves to be a powerful technique which can reveal significant phenomena that are not apparent to the eye even after repeated examination of the film.

scholarly journals Monocytes increase human cardiac myofibroblast-mediated extracellular matrix remodeling through TGF-β1

2016 ◽  
Vol 310 (6) ◽  
pp. H716-H724 ◽  
Author(s):  
Holly E. M. Mewhort ◽  
Brodie D. Lipon ◽  
Daniyil A. Svystonyuk ◽  
Guoqi Teng ◽  
David G. Guzzardi ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Peripheral Blood ◽  
Cellular Interaction ◽  
Cell Contact ◽  
Blood Monocytes ◽  
Paracrine Factors ◽  
Peripheral Blood Monocytes ◽  
Direct Cell ◽  
Cardiac Myofibroblasts ◽  
Cell Cell

Following myocardial infarction (MI), cardiac myofibroblasts remodel the extracellular matrix (ECM), preventing mechanical complications. However, prolonged myofibroblast activity leads to dysregulation of the ECM, maladaptive remodeling, fibrosis, and heart failure (HF). Chronic inflammation is believed to drive persistent myofibroblast activity; however, the mechanisms are unclear. We assessed the influence of peripheral blood monocytes on human cardiac myofibroblast activity in a three-dimensional (3D) ECM microenvironment. Human cardiac myofibroblasts isolated from surgical biopsies of the right atrium and left ventricle were seeded into 3D collagen matrices. Peripheral blood monocytes were isolated from healthy human donors and cocultured with myofibroblasts. Monocytes increased myofibroblast activity measured by collagen gel contraction (baseline: 57.6 ± 5.9% vs. coculture: 65.2 ± 7.1% contraction; P < 0.01) and increased local ECM remodeling quantified by confocal microscopy. Under coculture conditions that allow indirect cellular interaction via paracrine factors but prevent direct cell-cell contact, monocytes had minimal effects on myofibroblast activity (17.9 ± 11.1% vs. 6.4 ± 7.0% increase, respectively; P < 0.01). When cells were cultured under direct contact conditions, multiplex analysis of the coculture media revealed an increase in the paracrine factors TGF-β1 and matrix metalloproteinase 9 compared with baseline (122.9 ± 10.1 pg/ml and 3,496.0 ± 190.4 pg/ml, respectively, vs. 21.5 ± 16.3 pg/ml and 183.3 ± 43.9 pg/ml; P < 0.001). TGF-β blockade abolished the monocyte-induced increase in cardiac myofibroblast activity. These data suggest that direct cell-cell interaction between monocytes and cardiac myofibroblasts stimulates TGF-β-mediated myofibroblast activity and increases remodeling of local matrix. Peripheral blood monocyte interaction with human cardiac myofibroblasts stimulates myofibroblast activity through release of TGF-β1. These data implicate inflammation as a potential driver of cardiac fibrosis.

scholarly journals Stalk cell formation in monolayers from isolated prestalk and prespore cells of Dictyostelium discoideum: evidence for two populations of prestalk cells

Development ◽  
1988 ◽  
Vol 104 (1) ◽  
pp. 121-127 ◽  
Author(s):  
L. Kwong ◽  
A. Sobolewski ◽  
L. Atkinson ◽  
G. Weeks
Keyword(s):  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Cell Population ◽  
Cell Formation ◽  
Cell Types ◽  
Stalk Cell ◽  
Cell Populations ◽  
Anterior Portion ◽  
Percoll Gradients ◽  
Two Populations

Cells from the pseudoplasmodial stage of Dictyostelium discoideum differentiation were dispersed and separated on Percoll gradients into prestalk and prespore cells. The requirements for stalk cell formation in low-density monolayers from the two cell types were determined. The isolated prespore cells required both the Differentiation Inducing Factor (DIF) and cyclic AMP for stalk cell formation. In contrast, only part of the isolated prestalk cell population required both cyclic AMP and DIF, the remainder requiring DIF alone, suggesting the possibility that there were two populations of prestalk cells, one independent of cyclic AMP and one dependent on cyclic AMP for stalk cell formation. The finding that part of the prestalk cell population required only a brief incubation in the presence of DIF to induce stalk cell formation, whilst the remainder required a considerably longer incubation in the presence of both DIF and cyclic AMP was consistent with this idea. In addition, stalk cell formation from cyclic-AMP-dependent prestalk cells was relatively more sensitive to caffeine inhibition than stalk cell formation from cyclic-AMP-independent prestalk cells. The latter cells were enriched in the most anterior portion of the migrating pseudoplasmodium, indicating that there is spatial segregation of the two prestalk cell populations. The conversion of prespore cells to stalk cells took longer and was more sensitive to caffeine when compared to stalk cell formation from cyclic-AMP-dependent prestalk cells.

Platelet interaction with vascular smooth muscle in synthesis of prostacyclin

1991 ◽  
Vol 260 (5) ◽  
pp. H1544-H1551
Author(s):  
D. H. Hechtman ◽  
M. H. Kroll ◽  
M. A. Gimbrone ◽  
A. I. Schafer
Keyword(s):  
Smooth Muscle ◽  
Platelet Aggregation ◽  
Vascular Smooth Muscle ◽  
Cell Types ◽  
Arterial Injury ◽  
Rat Aorta ◽  
Cell Contact ◽  
Ionophore A23187 ◽  
Inhibit Platelet Aggregation ◽  
Direct Cell

Because vascular smooth muscle cells (SMC) can be exposed to platelets at sites of significant arterial injury, we studied whether cultured rat aorta SMC can utilize platelet-derived arachidonate and prostaglandin (PG) endoperoxides (PGG2/PGH2) in the synthesis of prostacyclin (PGI2). SMC converted exogenous PGH2 to PGI2, measured by radioimmunoassay (RIA) of 6-keto-PGF1 alpha, despite cyclooxygenase inhibition or PGH2-receptor blockade. SMC produced increasing amounts of PGI2 in the presence of an increasing number of platelets when the two cell types were coincubated with arachidonate. Furthermore, aspirin-pretreated SMC produced PGI2 in response to arachidonate, ionophore A23187, or thrombin in the presence of platelets but not in their absence. SMC, by themselves unresponsive to thrombin, produced PGI2 during coincubation with thrombin-stimulated aspirin-pretreated platelets. Separation of the SMC monolayer and platelets with a filter did not prevent platelet-dependent PGI2 formation by the SMC. Finally, aspirin-pretreated SMC, in cosuspension with platelets, inhibited platelet aggregation in association with PGI2 production. These data indicate that 1) SMC can synthesize PGI2 from exogenously added PGH2 and from platelet-derived arachidonate or endoperoxides, 2) direct cell-cell contact is not required for intercellular endoperoxide transfer, and 3) SMC can inhibit platelet aggregation possibly through PGI2 production from platelet-derived endoperoxides.

The mechanism of T cell mediated cytotoxicity II. morphological studies of cell death by time-lapse microcinematography

1976 ◽  
Vol 192 (1107) ◽  
pp. 241-255 ◽  
Keyword(s):  
Cell Death ◽  
T Cell ◽  
Morphological Changes ◽  
Time Lapse ◽  
Cell Types ◽  
Cell Contact ◽  
Target Cells ◽  
Spherical Form ◽  
Morphological Studies ◽  
Natural Cell

The morphological changes in mastocytoma cell death by complement, T cell mediated cytotoxicity and in natural cell death as seen by time-lapse microcinematography are recorded. In complement lysis, progressive changes leading to a final swelling of the cell occur in the absence of cell membrane activity. This is in marked contrast to the T-cell lysis in which violent zeiosis (boiling) of the cytoplasm is a constant feature. Similar changes are seen in natural cell death and the possibility that a similar mechanism is involved in both cases is discussed. Analysis of the data showed that there was no fixed time relation between T cell contact and zeiosis. Target cells were sometimes killed rapidly after contact, but in some cases periods of up to 200 min were observed between contact and killing. After contact and up to the onset of zeiosis target cells retain normal morphology and movement, suggesting that contact itself does not damage the target cell. This is consistent with the data showing that the release of both small and large cytoplasmic markers have similar kinetics. An analysis of the relation between cell volume and time between T cell contact and zeiosis suggested that mastocytoma cells may be more susceptible to c. m. c. during G 1 phase. Studies with peritoneal exudate cells as target cells have allowed the morphological changes to be seen in a variety of other cell types. Macrophages rapidly retract to a spherical form immediately before zeiosis, indicating a change preceding zeiosis. The phase of zeiosis varies with different cell types.

Control of cell type proportions by a secreted factor in Dictyostelium discoideum

Development ◽  
1989 ◽  
Vol 107 (3) ◽  
pp. 605-609
Author(s):  
K. Inouye
Keyword(s):  
Dictyostelium Discoideum ◽  
Suspension Cultures ◽  
Cell Contact ◽  
Cell Type ◽  
Dialysis Membrane ◽  
Direct Cell ◽  
Constant Cell

It has been shown that, in Dictyostelium discoideum, conversion of prestalk cells to prespore cells in suspension cultures is inhibited by coexisting prespore cells. To examine whether the inhibition of conversion requires direct cell contact or is mediated by substances secreted by the cells, prestalk cells and prespore cells were incubated in shaken suspension, separated from each other by a dialysis membrane, and conversion of the prestalk cells to prespore cells scored after 24 h. Prestalk-to-prespore conversion was significantly inhibited if the density of the prespore cells was sufficiently high. In contrast, prestalk cells had little influence on prestalk-to-prespore conversion. Media conditioned by prespore cells, but not by prestalk cells, also inhibited the conversion of prestalk cells. Adenosine, propionate, diethylstilboestrol and differentiation inducing factor (DIF), all of which are known to influence the prestalk/prespore differentiation, were examined for their effects on prestalk-to-prespore conversion. Among these, all except adenosine significantly inhibited the conversion. Based on these results, possible mechanisms for maintenance of the constant cell-type ratio in D. discoideum slugs were discussed.

Incomplete contact site A glycoprotein in HL220, a modB mutant of Dictyostelium discoideum

1985 ◽  
Vol 73 (1) ◽  
pp. 49-68
Author(s):  
G. Gerisch ◽  
U. Weinhart ◽  
G. Bertholdt ◽  
M. Claviez ◽  
J. Stadler
Keyword(s):  
Molecular Weight ◽  
Monoclonal Antibodies ◽  
Cyclic Amp ◽  
Dictyostelium Discoideum ◽  
Apparent Molecular Weight ◽  
Uniform Structure ◽  
Cell Contact ◽  
Wild Type ◽  
Developmentally Regulated ◽  
Contact Formation

HL220, a modB mutant that lacks a modification of certain membrane proteins of Dictyostelium discoideum, has been shown to aggregate and to form EDTA-stable intercellular contacts typical of aggregating wild-type cells. A developmentally regulated glycoprotein of 80 X 10(3) apparent molecular weight has been identified as a target site of adhesion-blocking Fab and thought to be involved in EDTA-stable cell contact formation (Muller & Gerisch, 1978). In the HL220 mutant this glycoprotein is no longer recognized by a modB-specific antibody. Therefore, it has been suggested that the 80 X 10(3) Mr glycoprotein, or a modification on it, is not required for the EDTA-stable cell contact of aggregating cells. We show that HL220 synthesizes an equivalent of the 80 X 10(3) Mr glycoprotein with an apparent molecular weight of 68 X 10(3). The mutant product reacted with certain monoclonal antibodies highly specific for the 80 X 10(3) Mr glycoprotein in the wild type, and was developmentally regulated like the 80 X 10(3) Mr glycoprotein. These results indicate that the 68 X 10(3) Mr protein of the mutant lacks a modification, most likely an oligosaccharide residue, the absence of which causes the substantial shift of the apparent molecular weight from 80 X 10(3) to 68 X 10(3). Monoclonal antibodies that did not react with proteins of the mutant could be classified according to their reactions with different sub-sets of wild-type proteins. These results indicate that the proteins that reacted with either one or the other antibody were not modified by a uniform structure. The modification rather varies from one sub-set of cross-reacting proteins to another, suggesting differences between the glycosyl residues of the partially cross-reacting proteins. HL220 cells showed strongly reduced EDTA-stable contact formation under our conditions. EDTA-sensitive intercellular adhesion was undetectable in the mutant, whereas adhesion of the cells to the substratum appeared to be strengthened. The rear ends of the cells, in particular, were tightly attached to glass or Teflon surfaces. The mutant cells were capable of responding chemotactically. Propagated excitation waves like those known to be based on periodic cyclic AMP production and relay were clearly seen. Extracellular phosphodiesterase induction by cyclic AMP and phosphodiesterase inhibitor production were normal. These results indicate that the generation of chemotactic signals and the cellular responses to cyclic AMP are not severely affected by the mutation.

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