Two-dimensional minimum free energy spectral estimation

1995 ◽  
Vol 142 (3) ◽  
pp. 169 ◽  
Author(s):  
P. Kiernan
Keyword(s):  
Free Energy ◽  
Spectral Estimation ◽  
Minimum Free Energy ◽  
Two Dimensional

Polarity and gradients in lepidopteran wing epidermis

Development ◽  
1976 ◽  
Vol 36 (3) ◽  
pp. 489-512
Author(s):  
James B. Nardi ◽  
Fotis C. Kafatos
Keyword(s):  
Free Energy ◽  
Minimum Free Energy ◽  
Alternative Interpretation ◽  
Original Position ◽  
Cell Contact ◽  
Two Dimensional ◽  
Free Energies ◽  
Minimal Cell ◽  
Final Size ◽  
Cell Densities

For explaining the Manduca wing gradient (Nardi & Kafatos, 1976) a model which postulates a proximo-distal gradient in cellular adhesiveness is considered. The model is based on Steinberg's (1963) differential adhesiveness hypothesis. Rosette formation in certain trans-posed and/or reoriented grafts can be adequately explained by this model. Several predictions, formulated by using the concept of surface free energy as a thermodynamic measure of adhesiveness, have been tested and proven correct. (1) Transposed grafts tend to assume circular forms, which are configurations of minimum free energy. (2) Because of the pressure difference expected across the interface of two cell populations with different surface free energies, cell densities increase in both distally and proximally transposed grafts. As a corollary to this rule, final size of a graft is a function of its distance from the original position.(3) Histological sections of host-graft boundaries suggest minimal cell contact at the interface. In proximal grafts placed in distal regions, cell density is far lower near the host-graft inter face, as compared to the high interior density; the peripheries of distal grafts do not show this effect. (4) Juxtaposition of three different wing regions in all possible arrangements yields the expected two-dimensional configurations. (5) Differences in adhesiveness can be demonstrated by allowing two different wing grafts to interact in an essentially neutral environment (i.e. at a leg or antenna site). As the distance between two given graft regions increases, the extent of their final contact decreases. When applied to other insect systems, the model not only offers an alternative interpretation for results currently explained by diffusible substance models, but also accounts for certain features that were unexplained by other models.

Sign in / Sign up

Export Citation Format

Share Document