The Acrasina

Shaffer, Blake

doi:10.1016/b978-1-4831-9949-8.50007-9

Cited by 173 publications

(39 citation statements)

References 92 publications

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“…The all-ornone response becomes graded when the steady state lies further apart from A; the triangles in fig.2 then represent quasi-threshold [ 11 ] values given by the inflection points of the dose-response curves. Besides accounting for the existence of a threshold for relay [19], the phase-plane analysis provides an explanation for the fact that D. discoideum cells are refractory, during a period which lasts several minutes, after relay of a cAMP signal [17][18][19]. Here, we should draw the distinction, as in the study of the nerve membrane [ 11], between an absolute and a relative refractory period.…”

Section: Resultsmentioning

confidence: 99%

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Excitability in the adenylate cyclase reaction in Dictyostelium discoideum

Goldbeter

Erneux

1978

FEBS Letters

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Section: Resultsmentioning

confidence: 99%

“…These properties account, on molecular grounds, for several observations made on the wavelike aggregation of D. discoideum amoebae [17][18][19], and substantiate the description of the aggregation fields as excitable media [20].…”

Section: Introductionmentioning

confidence: 99%

Excitability in the adenylate cyclase reaction in Dictyostelium discoideum

Goldbeter

Erneux

1978

FEBS Letters

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“…However it is likely that different-sized slugs will have different signaling properties and thus different proportions of actively moving cells. In fact, in early experiments by Francis (quoted in Shaffer, 1964) the tip of a slug was replaced by a smaller one and the resulting slug moved more slowly, and larger tips grafted onto a slug resulted in faster migration. This might be due to the cAMP produced by the tip, which would cause a smaller or larger proportion of cells to move actively.…”

Section: Article In Pressmentioning

confidence: 99%

How cellular movement determines the collective force generated by the Dictyostelium discoideum slug

Dallon

Othmer

2004

Journal of Theoretical Biology

106

134

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How the collective motion of cells in a biological tissue originates in the behavior of a collection of individuals, each of which responds to the chemical and mechanical signals it receives from neighbors, is still poorly understood. Here we study this question for a particular system, the slug stage of the cellular slime mold Dictyostelium discoideum (Dd). We investigate how cells in the interior of a migrating slug can effectively transmit stress to the substrate and thereby contribute to the overall motive force. Theoretical analysis suggests necessary conditions on the behavior of individual cells, and computational results shed light on experimental results concerning the total force exerted by a migrating slug. The model predicts that only cells in contact with the substrate contribute to the translational motion of the slug. Since the model is not based specifically on the mechanical properties of Dd cells, the results suggest that this behavior will be found in many developing systems. r

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“…The other cells respond to attractant stimulation by moving towards its source and by relaying the signal (4)(5)(6)(7)(8). In addition to their role as chemotactic signals, periodic pulses of cAMP stimulate amoeboid differentiation (9,10).…”

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confidence: 99%

Unified mechanism for relay and oscillation of cyclic AMP in Dictyostelium discoideum.

Goldbeter¹,

Segel²

1977

Proc. Natl. Acad. Sci. U.S.A.

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A modified version of an allosteric model for adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] previously analyzed for sustained oscillations of adenosine 3':5'-cyclic monophosphate (cAMP) in Dictyostelium discoideum [Goldbeter, A. (1975) The cellular slime mold Dictyostelium discoideum is a major model for the study of development (1, 2). When deprived of nutrients, amoebae of this species aggregate around centers by a chemotactic response to adenosine 3':5'-cyclic monophosphate (cAMP), and further develop into multicellular fruiting bodies (3). The process of aggregation has a periodicity of several minutes. Successive "steps" of inward amoeboid movement appear to propagate outward from the center toward the periphery of the aggregation territory. It has long been suggested that aggregation centers autonomously release the attractant in periodic fashion. The other cells respond to attractant stimulation by moving towards its source and by relaying the signal (4-8). In addition to their role as chemotactic signals, periodic pulses of cAMP stimulate amoeboid differentiation (9, 10).Both the relay (11, 12) and the autonomous oscillation (13, 14) of cAMP have been demonstrated experimentally in suspensions of D. discoideum cells. We show here that oscillation and relay can be explained by a unified model based on regulatory mechanisms reported in the literature, the two different qualitative behaviors corresponding to two different parameter regimes. Our work can be regarded as extending Goldbeter's demonstration (15) that oscillation can be generated by the intracellular regulation (16) of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]. Here, we consider a compartmental model in which control of intracellular cAMP synthesis by external cAMP is analyzed explicitly.The unified mechanism for relay and oscillation of cAMP suggests an explanation for the emergence of aggregation centers and for a temporal sequence of developmental events observed during interphase in D. discoideum. RESULTSIn an attempt to capture the essential biochemical mechanisms responsible for oscillation and relay, let us consider the activating effect of extracellular cAMP on adenylate cyclase (17). This activation follows the binding of cAMP to a receptor that might be specific for relay (18). The simplest assumption one can make is that the cAMP receptor on the cell surface is a regulatory part of adenylate cyclase; such an assumption is consistent with the finding that the catalytic site of this membrane-bound enzyme faces the interior of the cell (19). We thus consider the following three concentration variables in a basic compartmental model (see Fig. 1):a, intracellular ATP; fB intracellular cAMP; -y, extracellular cAMP.[1] Here the actual concentrations are normalized by dividing them respectively by Ks, Kp, and Kp, where Ks and Kp are the Michaelis constant of adenylate cyclase for ATP and the dissociation constant of complexes formed by the enzyme with cAMP at the regulatory (receptor) ...

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The Acrasina

Cited by 173 publications

References 92 publications

Excitability in the adenylate cyclase reaction in Dictyostelium discoideum

Excitability in the adenylate cyclase reaction in Dictyostelium discoideum

How cellular movement determines the collective force generated by the Dictyostelium discoideum slug

Unified mechanism for relay and oscillation of cyclic AMP in Dictyostelium discoideum.

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