Biophysical interpretation of membrane fluidity by catastrophe theory

Topological approach of Jungian psychology

In this work, we compare two global approaches which are usually considered as completely unconnected one with the other. The former is Thom's topology and the latter is Jung's psychology. More precisely, it seemed to us interesting to adapt some morphologies of Thom's catastrophe theory to some Jung's notions. Thus, we showed that the swallowtail, which is one of these morphologies, was able to describe geometrically the structural organisation of the psyche according to Jung, with its collective unconscious, personal unconscious and conscious. Moreover, we have correlated this morphology with Jung's evolutive processes like individualization and individuation. These comparisons incited us to think that some morphologies of Thom's catastrophe theory are the geometrical dealing of Jung's archetypes.

Generalised biological function

A physiological function can be described as a cycle based on a cusp bifurcation set in catastrophe theory. This cycle involves four phases that are successively developed along a functional potential, which is used to perform a given physiological act. The work we present is firstly based on a detailed study of the global function of vision, which covers a vast field extending from the molecular to cerebral scale. We then present other examples of generalised functions by expanding the frame of reference, from the scale of an organ to the scale of a whole organism with predation function, and to the scale of a social group with crisis management. We observed that the criteria remain the same, whether the function is considered on the scale of a cell membrane or a group of individuals organised into a cohort. Moreover, a so-called generalised function can be broken down into simpler sub-functions, each phase of the initial function containing the physiological act of each sub-function. It seems thus that a fractal extension may characterise the four-cusp spiral. This spiral is increasingly large as the types of sub-functions are multiplied. In functions relative to sociological science, such as crisis management, which are not natural but built and designed by humans, close attention must be paid to following the rules of these generalised biological functions.

Simultaneous changes in lipid composition, fluidity and enzyme activity in piglet intestinal brush border membrane as affected by dietary polyunsaturated fatty acid deficiency

The effects of dietary polyunsaturated fatty acid (PUFA) deficiency on intestinal brush border membrane (BBM) fluidity, lipid composition and 5'-nucleotidase activity were examined in piglets. Cholesterol/phospholipid and sphingomyelin (SM)/phosphatidylcholine (PC) ratios were unaffected. However, fluidity was decreased in the external regions and also tended to decrease in the core of the PUFA-deficient pig membrane lipid bilayer. Therefore, the change in the membrane physical properties seemed to be due to the large diet-induced alteration in the phospholipid (PL) fatty acid composition and to the concomitant decrease in PC and increase in phosphatidylserine levels. In the membrane total PL, the arachidonic acid level was slightly lowered, while linoleic, eicosapentaenoic and docosahexaenoic acid levels markedly decreased. PC was mainly concerned by the altered distribution of unsaturated fatty acids, but not SM. However, a significant decrease in (n-6)/(n-3) ratio occurred in the latter. These structural changes were associated with a higher 5'-nucleotidase activity in the intestinal BBM of PUFA-deficient as compared to control piglets.

[The Catastrophe theory and membrane physiological functions]

This communication is based on a preliminary work which emphasized a topological model of biomembranes from Thom's Catastrophe Theory. In this model called swallowtail bifurcation set, the structural state of a biomembrane was within the control of two structural attractors. Then, the physiological act of this biomembrane resulted in a sudden transfer of weight from the hydrophilic attractor to the hydrophobic attractor. In this consecutive work, the physiological act appears to be one of the four stages which permit to describe the larger notion of cyclic membrane function. Two of these stages unfold in the structural axis of the swallowtail model. They prepare the two others (physiological act and refractory stages) which expand in the functional direction. This conceiving of cyclic membrane function is applied to physiological examples such as the action potential and the endocytosis. Then, changes in this function are discussed on the basis of pathological data.

Membrane properties of the sarcolemma and sarcoplasmic reticulum of pigs susceptible to malignant hyperthermia. Action of halothane

The role of sarcolemma and sarcoplasmic reticulum in malignant hyperthermia was studied by the esr technique using the trapezius muscle membrane of both normal and genetically susceptible pigs. Normal and malignant hyperthermia membranes from sarcolemma as well as from sarcoplasmic reticulum did not show significant differences near the polar heads of the phospholipidic bilayer. In contrast, the fluidity and activation energy of normal membranes differed from those in malignant hyperthermia; in both sarcolemma and sarcoplasmic reticulum the mobility of the label was greater than the controls. The presence of halothane was examined, by inducing this disease anesthetically. The drug effect confirmed the above results, i.e. the disease affects mainly the hydrophobic core of the lipid bilayer of both sarcolemma and sarcoplasmic reticulum membranes.