A unifying model of the cell proliferation emphasizing plasma membrane fluxes.

The regulation of cellular growth and proliferation is perhaps the most investigated and elusive problem in cell biology and seems to be possible to solve from almost any angle of study chosen. Among the non-systemic factors that have been discussed are genetic damage, genomic control, regulation by stimulatory and inhibitory peptide factors such as EGF, chalones, and fibronectin, protein kinase activation with tyrosine phosphorylation, adenylylcyclase and cAMP, cGMP, membrane perturbations and specifically in tumours the failure of the Pasteur effect in control of glycolysis, excessive membrane ATPase activity, and excessive hydrolytic and proteolytic activities at the cell surface. This article focuses on the central role of fluxes within the plasma membrane and re-examines the possibility that changes of flux of metabolites, ions, and reducing equivalents may be the common denominator regulating cellular proliferation.

Metabolic iteration, evolution and cognition in cellular proliferation.

A model for cellular proliferation is described according to which proliferation ensues when metabolism evolves towards commitment to DNA synthesis, and inhibition of proliferation occurs when enzymic interactions are iterated within a few metabolic pathways, another limiting factor being the supply of metabolites. The model successfully describes cellular growth and division as a 'cognitive process' based on interaction within enzymic elements and the genome, and affords an explanation in these terms of some empirical phenomena which have previously been understood only as isolated observations.

A mathematical approach to cognitive processes.

A mathematical formalization of cognitive processes based on concepts previously given in Experientia is presented. Cognitive processes are described as a set of exponentially decaying interaction probabilities determined by previous interactions between different elements and an association parameter, the inverse of the cognitive stability. The interactions occur in a 'cognitive string' surrounded by a 'cognitive plasma' which carries the contextual information.

Facilitation of actin polymerization by interfilamentous factors.

The polymerization of actin in low ionic strength buffer at 0 degrees C in the presence of 0.25 mM Mg2+ was studied by viscometry, turbidity and absorbance at 232 nm. Under these conditions, significant polymerization occurred only in the viscometer and not in isotropic mixtures.

Validity of Hill's equation in an artificial actomyosin streaming system.

The rotation of an actomyosin motor, assembled from blades, one side onto which F-actin of uniform polarity was attached, suspended in a solution of heavy meromyosin (HMM), was modelled as due to sliding of HMM over the margins of the blades, whereby the work resulting from ATPase activity is used for pushing bulk fluid containing HMM from the leading surface of the blade over the force-generating filaments to the back surface, which leads to increased sliding velocity. The amount of HMM contributing to force-generation is divided into one component perpendicular to the filaments, which is diffusion-limited and regulated by a component parallel to the filaments, represented by the movement of the bulk fluid, the supply of new HMM and the observable velocity of rotation of the blade. Using Hill's equation which essentially states that the product of a virtual force and a virtual velocity is constant within the range of observable forces and velocities, the force can be expressed as velocity, giving a simple first order differential equation.