PubMed Health⌕ Search

Biomedical subjects

E F Pate

Publications and source records attributed to E F Pate.

5 recordsLinked to original sources
PubMed1986

Differentiation, cell sorting and proportion regulation in the slug stage of Dictyostelium discoideum.

Recent experimental work suggests that under normal conditions cell sorting plays an important part in maintaining and re-establishing the axial pattern of cell types in the slug stage of the cellular slime mold Dictyostelium discoideum. Following removal of the anterior zone of the slug, anterior-like cells that are normally distributed throughout the posterior of the slug rapidly migrate to the anterior end of the transected slug, and new anterior-like cells appear in the posterior portion. These results provide evidence that the direct linkage between spatial location and differentiation hypothesized in positional information models of spatial pattern formation is not universal. In this paper we develop and analyze a class of mathematical models of the slug in which cell determination can be less rigidly tied to spatial location, and which involve chemotactic cell sorting to re-establish and maintain the spatial pattern of cell types. We show that these models can reproduce the qualitative aspects of the experimental observations and that sorting takes place on the observed time scale when reasonable values of the parameters are used.

Cell Differentiation↗
PubMed1985

Resolution of the competitive inhibitory effects of lithium and AMPPNP on the beat frequency of ATP-reactivated, demembranated, sea urchin sperm flagella.

About half of the inhibitory effect on the beat frequency of sea urchin spermatozoa flagella by beta, gamma-imido-adenosine-5'-triphosphate (AMPPNP) previously reported by Okuno & Brokaw (1981) was actually the result of inhibition by lithium resulting from the use of a tetralithium salt of AMPPNP. Li+ (or LiATP3-) acts as a competitive inhibitor of beat frequency, with a Ki for Li+ of about 30 mM. Under improved reactivation conditions which reduce the Km for beat frequency to about 0.1 mM, the Ki for lithium-free MgAMPPNP2- is about 2.3 mM, and magnesium pyrophosphate (MgPPi-), which may be an equivalent ligand, gives a Ki of 3.4 mM.

Adenosine Triphosphate↗
PubMed1980

Cross-bridge behavior in rigor muscle.

Properties of the rigor state in muscle can be explained by a simple cross-bridge model, of the type which has been suggested for active muscle, in which detachment of cross-bridges by ATP is excluded. Two attached cross-bridge states, with distinct force vs. distortion relationships, are required, in addition to a detached state, but the attached cross-bridge states in rigor muscle appear to differ significantly from the attached cross-bridge states in active muscle. The stability of the rigor force maintained in muscle under isometric conditions does not require exceptional stability of the attached cross-bridges, if the positions in which attachment of cross-bridges is allowed are limited so that the attachment of cross-bridges in positions which have minimum free energy is excluded. This explanation of the stability of the rigor state may also be applicable to the maintenance of stable rigor waves on flagella.

Adenosine Triphosphate↗
PubMed1980

Effect of shape on pressure-volume relationships of ellipsoidal shells.

Previous theoretical procedures for determining the slope and intercept of the stiffness-stress relationship of the passive myocardium from diastolic pressure-volume (P-V) data assume that the eccentricity of the left ventricle (LV) is invariant. In this study a mathematical model for an ellipsoidal membrane was developed that does not contain that constraint. The model predicts a small (less than 10%) but significant decrease in eccentricity as transmural pressure increases. This result was confirmed by the use of a thick-wall finite element model. The implications of this result are as follows. 1) The slope and intercept of the stiffness-stress relationship of unconstrained ellipsodial shells can be determined by fitting a spherical model to the P-V relationships exhibited by the shells. 2) An ellipsoidal model that assumes that the eccentricity of such shells is invariant for all pressures would predict erroneous intercepts. 3) If the eccentricity of the diastolic LV initially decreases relative to its value at zero transmural pressure, then a thick-wall spherical model may be adequate for determining the slope and intercept of the myocardial stiffness-stress relationship.

Compliance↗