Optimal systems: II. The vascular system

A refinement of a model of the vascular system (Cohn, 1954) is discussed. We now consider that the major vessels arise from the aorta as secondary branching vessels rather than by successive dichotomies of the aorta as previously considered. It is shown that this change does not affect calculated values of flow, the number of branchings, or the relative radii of vessels at a branching. A comparison is made of theoretical predictions with experimental data and good greement is found. The method of analysis of this paper is used to extend the treatments of the previous paper to a more general case. It is shown that the results previously obtained are valid.     

Optimal systems: III. Muscle

The optimal systems approach to the muscular system leads to difficulties since the properties of the muscular system are determined to a great extent by the nature of the contractile unit or molecule. This unit has determined the morphology and dynamic characteristics of muscle, and only smaller order alterations are then possible to adapt muscle to its several functions. A model of the contractile unit is developed that shows agreement with experimental findings with respect to the velocity-load relation, heat effects, and several aspects of knowledge of the structure of the contractile proteins.     

Polymorphisms of the main genes of neurotransmitter systems: I. The dopaminergic system

The review is focused on the molecular and genetic bases of human personality traits useful for predicting individual performance in sports. Dopamine receptor gene polymorphisms have been found to be associated with novelty seeking, reward dependence, persistence, etc. These facts demonstrate the importance of studies on the contributions of different gene variants characteristic of the dopamine system to the formation of the predisposition of an athlete to success in sports.     

Bimolecular systems: I. Linear systems of complexes

A vast number of biologically important processes are based upon bimolecular systems. In these systems intermediate complexes are formed. Bimolecular systems in which no complex-complex interactions occur are called linear systems of complexes. A definition and some characteristic properties of these systems are given here. There may exist a contradiction of Onsager's principle of detailed balancing in these systems; however, no principal differences are found between the steady state behavior of an open system and that of a closed system. It is shown that the steady state behavior of a linear system of complexes of arbitrary complexity has some similarities with the steady state behavior of a simple bimolecular system, e.g., Michaelis-Menten enzymatic reaction. Multiplicity of action of the substances participating in biomolecular processes may produce some qualitative differences in the steady state behavior of the system.     

Determination of equilibrium constants and maximum binding capacities in complexIn vitro systems: I. The mammillary system

It is shown that in a system containingn types of mutually noninteracting binding sites, the association constants are then roots of annth order polynomial while the maximum binding capacities can be evaluated by solving a set ofn simultaneous linear equations. Thenth order polynomial and the system ofn linear equations are defined in terms of 2n intermediate coefficients, the coefficients being themselves evaluated by substituting 2n sets of appropriate experimental data into an auxiliary system of 2n linear equations. The existence and uniqueness of the solutions are established.     

Optimal foraging in an amphibious mammal. I. The aqualung effect

The marginal value theorem of Charnov is extended to a simple model covering the case of mammalian carnivores hunting underwater, in which situation their total search time and pursuit effort is constrained by the limited oxygen capacity of their lungs. In the mink Mustela vison hunting rudd in an experimental tank the duration of dives, of giving-up times, and of the pursuit phase of underwater hunts, as well as the frequency of dives, were consistent with the usual marginal value predictions. Giving-up times were also essentially constant within bouts, as expected. An interaction between foraging economics and oxygen reserves derived from the extended model was confirmed experimentally.     

Evolution of macromolecules: I. Dual coding systems

The evolution of proteins determined by two independently mutable coding mechanisms (e.g., one in which nucleic acids operate with unit coding ratio) has been analyzed kinetically in two ways. The first presumes a system of mutating and reproducing proteins; the dependent variables are the numbers of the various kinds of proteins—wild types, and mutants obtained by mutations in one or another of the two coding mechanisms. The second approach deals with kinds rather than numbers of proteins; the reproductive element in the evolving system is dealt with by assuming a specific rate of extinction for members of each protein class, due to the occurrence of lethal mutations in the proteins themselves or in other proteins in the organisms that carry them. If the two kinds of mutants occur at different rates, it is shown in both treatments that time will not necessarily extinguish the initial advantage of one of them—that is, the notion that the slower class will eventually occur often enough to produce a random distribution of the two classes after long periods of evolution is not in general true. The effects of mutation rate, reproduction rate, and extinction rate on the distribution of the various protein classes are analyzed. Contribution No. 666 from the Division of Basic Health Sciences.     

Junctional transfer in cultured vascular endothelium: I. Electrical coupling

Vascular endothelial cultures are composed of flat, polygonal monolayer cells which retain many of the growth, metabolic and physiological characteristics of the intimal endothelium. However, intercellular gap and tight junctions, which are thought to perform important roles in normal intimal physiology, are reduced in complexity and extent in culture. We have used electrophysiological techniques to test confluent (3- to 5-day) primary cultures of calf aortic (BAEC) and umbilical cord vein (BVEC) endothelium for junctional transfer of small ions. Both cell types are extensively electrically coupled. The passive electrical properties of the cultured cells were calculated from the decrease in induced membrane potential deflections with distance from an intracellular, hyperpolarizing electrode. Data analyses were based on a thin-sheet model for current flow (Bessel function). The generalized space constants (lambda) were 208.6 microns (BAEC) and 288.9 microns (BVEC). The nonjunctional (6.14 and 8.72 X 10(8) omega) and junctional (3.67 and 3.60 X 10(6) omega) resistances were similar for the BAEC and BVEC, respectively. We detected no statistically significant differences in the resistance estimates for the two cell types. In vivo ultrastructural studies have suggested that aortic endothelium has more extensive gap junctions than venous endothelium. We have found that these ultrastructural differences are reduced in culture. The lack of any significant difference in electrical coupling capability suggests that cultured BAEC and BVEC have functionally similar junctional characteristics.     

Limiting-laws of polyelectrolyte solutions. Ionic distribution in mixed-valency counterions systems. I: The model

An extension of the counterion-condensation (CC) theory of linear polyelectrolytes has been developed for the case of a system containing a mixture of counterions of different valency, i and j. The main assumption in the derivation of the model is that the relative amount of the condensed counterions of the type i and j is strongly correlated and it is determined by the overall physical bounds of the system. The results predicted by the model are consistent, in the limiting cases of single species component, with those of the original CC theory. The most striking results are obtained for the cases of low charge density and excess of counterion species: in particular, an apparent positive "binding" cooperativity of divalent ions is revealed for small, increasing additions of M2+ ions to a solution containing a swamping amount of monovalent salt and a polyelectrolyte of low charge density. Apparent "competitive binding" of mono- and divalent ions derives as a bare consequence of the electrostatic interactions. Theoretical calculations of experimentally accessible quantities, namely single-(counter) ion activity coefficients, confirm the surprising predictions at low charge density, which qualitatively agree with the measured quantities.     

Optimal rates of dispersal I. Haploid populations

The problem of how an individual should divide its progeny into dispersed and non-dispersed descendants is investigated for a number of haploid models. In each model, a unique optimal ratio of dispersed to non-dispersed has been found, where the type with this optimal strategy has a selective advantage over all other types. Although the survival ability of a dispersed offspring is reduced (compared to that of a non-dispersed offspring), the optimal strategy implies that a substantial part of the progeny will be dispersed.     

The parametric pump mechanism in separation of components in heterogeneous systems. I. Macroscopic distributed systems.

A dynamic method is proposed for the separation of the electrolyte components using a parametric pump with an ion exchange column. It was studied experimentally and described mathematically. The parametric separation of mixtures is based on interactions of two oscillating fields with a heterogeneous system containing two phases, a liquid and a solid one, the components of the mixture being able to redistribute between the phases. The field of mechanical force is responsible for cyclic relative displacement of the phases, and synchronously changing temperature causes redistribution of the components between them. This results in sodium and potassium fluxes opposite in direction which in turn leads to accumulation of sodium and potassium in opposite end cells.