Showing papers in "Journal of Theoretical Biology in 1971"

TL;DR: An antithesis to the view that gregarious behaviour is evolved through benefits to the population or species is presented, and simply defined models are used to show that even in non-gregarious species selection is likely to favour individuals who stay close to others.

TL;DR: The chemotactic response of unicellular microscopic organisms is viewed as analogous to Brownian motion, and a macroscopic flux is derived which is proportional to the chemical gradient.

TL;DR: A phenomenological theory of traveling bands is developed starting with partial differential equations which describes the consumption of the critical substrate and the change in bacterial density due to random motion and to chemotaxis and predicts the shapes of the graphs of bacterial density and substrate concentration in the traveling band.

TL;DR: The treatment given here offers wide flexibility in dealing with cell surfaces in the languages of the cell physiologist, biochemist and physical chemist.

TL;DR: It is suggested that the most important advantage of sex arises when two genetically different populations migrate into a new environment, in which the best adapted genotype is a combination of genes from the two invading populations.

TL;DR: A mathematical model is developed of growth and seed production in plants when the growing period is limited which maximizes final seed yield, i.e. the time course of the partition coefficient of photosynthetic products between vegetative and reproductive growth has been worked out.

TL;DR: The present paper assumes that a functional relationship between potential level and mitotic activity does in fact exist and proceeds with the formulation of a basic theory of mitosis control wherein the intracellular ionic conditions associated with various levels of the potential difference act to regulate preparation for DNA synthesis and other essential mitotic preparations.

TL;DR: A powerful new method for analyzing onset of instability in arbitrary networks of compartments or model cells is developed, and network structure is found to influence interaction of intracellular chemical reactions and intercellular transfers, and thereby the stability of uniform stationary states of the network.

TL;DR: A model to account for cases where the predator emerges in the midst of an aggregation of potential prey, and indicates that the most probable dispersion is a tight circular flock of all the prey animals in the vicinity.

TL;DR: This paper introduces explicit minimal anatomies and physiological rules that formally give rise to analogous phenomena of operant conditioning that consider only aspects of positive conditioning.

TL;DR: In this paper, an attempt was made to describe the multifarious form of erect trees by a few parameters: branching angle and relative ratio of the branch lengths, which were well demonstrated to have great effects upon the whole form of the tree-like body.

TL;DR: Theorems were obtained concerning partial characterizations of the class of developmental systems without cellular interactions, and some of the mathematical properties of this class are discussed.

TL;DR: Temperature “breaks” in Arrhenius plots of biological data are real and can be explained as a consequence of a phase change in the system.

TL;DR: The temporal behaviour of a chemical system beyond a non-equilibrium unstable transition is analysed and compared to the behaviour of Volterra-Lotka type systems and certain types of biological rythmic phenomena are discussed.

TL;DR: A modified trophic model incorporating a distinction between organisms ingesting living material and those subsisting on dead organic matter is used to develop a hypothesis explaining how mean densities of first-order biophagus organisms are determined in accordance with life history characteristics of autotrophs in the system.

TL;DR: A detailed theory of the velocity of propagation of the acrasin pulse responsible for the aggregation of some of the cellular slime molds is presented and it is shown that there is a critical density of amebae below which the waves cannot propagate.

TL;DR: It is argued that because the former mechanism is essentially macroscopic in character it cannot, in fact, be used in those biological processes, like muscular contraction or active transport, in which useful molecular work is done and that only the latter may be so used.

TL;DR: The rate of production of the end product at the first stages of the reaction is markedly higher in the immobilized enzyme system than that predicted for a corresponding homogeneous system.

TL;DR: There is a definite logarithmic relation between branch order and lengths and numbers and this definite relation is quantitatively comparable, within limits, among river networks, tree branching systems, and several random-walk models in both two and three dimensions.

TL;DR: Known species of bacteria are arranged in a postulated phylogenetic sequence which begins with the simplest anerobes and progresses through a series of relatively small, discrete steps to the photosynthetic bacteria and the blue-green algae.

TL;DR: An extension of the codon modulation theory of development and aging to a number of areas that were not included in the original versions of this theory, and it appears that early predictions of the model are borne out by recent findings.

TL;DR: A unitary theory of membrane fusion is proposed on the basis of similarities between events in cell fusion and the fusion of subcellular membrane systems, and particular emphasis is placed on the role of Ca2+, ATP and membrane-associated ATPase enzyme systems in regulating the membrane changes responsible for fusion.

TL;DR: A mathematical model of the proposed mechanism gives a satisfactory explanation of the various features of the process of cytodifferentiation such as the requirement for mitotic divisions, the induction phenomena, etc and suggest implications of the model for understanding other biological phenomena, such as carcinogenesis and the emergence of new organic forms for natural selection.

TL;DR: Models and experiments jointly suggest that the normal organism utilizes only a subset of the cell types of which its genome is capable without mutation, thus epigenetic cancer is at least possible.

TL;DR: The effects of changes in various membrane properties on the form and conduction velocity of action potentials have been calculated using the Hodgkin-Huxley plus cable equations and the effect of passive fibres in a nerve trunk on the amplitude of an action potential recorded extracellularly from an active fibre is computed.

TL;DR: The effect of aggregative movement on organizing wave propagation in the cellular slime molds is considered and an appreciable Doppler shift of the apparent frequency of the signal as seen by those amebae having a chemotactic response different from the average is seen.

TL;DR: It is assumed that there exists an initial divergence in genetic activity due to an unequal distribution of egg cytoplasmic regulatory elements among the different cells in early cleavage and that individual cells would differ in their response to external inductive agents arising, for example, in nearby cell layers.

TL;DR: An attempt is made to assess the effects of an increase in body weight and whether increases or decreases in temperature will affect the relation between the cardiac and branchial pumps in limiting oxygen supply to the tissues.

TL;DR: Positive feedback in two equivalent reaction systems is achieved by generalized autocatalysis, respectively, where A ∗ A ∘ and B ∗ B ∘ are pairs of optical antipodes and S is the common optically inactive substrate.

TL;DR: Data in the literature indicate that the transitional region between the kinetosome and the flagellar or ciliary shaft of many Protozoan species is specialized as a breaking point, but only two Metazoan species have been examined from this point of view.