A new interpretation of flux ratio exponents using statistical rate theory

By viewing permeation as a three-step process (movements between the bulk intracellular medium and the channel, within the channel, and between the channel and the extracellular bulk medium), and describing each step in the process with a statistical rate theory (SRT) approach, we can envisage different permeation scenarios which consider whether movements across certain interfaces can be approximated to be at equilibrium. A new interpretation of the flux ratio exponent is presented and its value can be used to predict whether the rate-limiting region occurs within the channel or at the interface. By considering saturation profiles, estimates for SRT exchange rates can be obtained, and a comparison with the more well-known Eyring rate theory is provided. Received: 27 May 1998 / Revised version: 9 December 1998 / Accepted: 9 December 1998     

The maturation divisions of the parthenogenetic stick insect Carausius morosus Br. (Orthoptera,Phasmidae)

The meiotic stages in the maturation of the egg of the parthenogenetic stick insect Carausius morosus Br. is described. The meiosis consists of two equational divisions and parthenogenesis is thus apomictic. The first prometaphase is formed between 5.8–5.5 days before oviposition; the first metaphase lasts until oviposition; the meiosis ends between 14 and 24 hours after oviposition. An extra chromosome doubling occurs before first anaphase, causing the first metaphase chromosomes to resemble bivalents and requiring that meiosis consists of two divisions instead of one. A terminal affinity between the daughter chromosomes influences chromosome movement during first and second metaphase and anaphase. The first and second polar bodies degenerate. The first polar body divides amitotically during pycnosis. Meiosis takes place ventrally in the egg, the germ anlage development dorsally. The pronucleus divides mitotically in the ventral part of the egg during its migration from ventral to dorsal, enabling blastoderm development to take place both ventrally and dorsally.     

A systems-mathematical interpretation of psychoanalytic theory

By assigning time-varying coordinates to all environmental stimuli, it has been possible to axiomatize psychoanalytic theory on the five principles of multiple causation, growth-aging influence, genetic influence, historic influence and conscious-unconscious activity. The theorems of summation of response and the inevitability of conscious-unconscious conflict with their corollaries follow directly from the axiomatic foundations, as does the existence of an adaptation-defense mechanism. The interpretation of the defense mechanism in terms of an ego-id feedback system provides the basis for the structural existence of conscious-conscious and unconscious-unconscious conflict.     

A new interpretation of plasmodesmatal ultrastructure

Summary It is shown that simple, unbranched, plasmodesmata between young xylem ray cells of willow have no direct intercellular continuity apart from the plasmalemma which limits the cytoplasm and lines the plasmodesmatal canal. Each plasmodesma is traversed by a 200 Å diameter tubule (the desmotubule) which has a wall with probably 11 subunits arranged around a central cavity through which runs a 40 Å diameter rod. This rod is connected to the inside of the tubule wall, by fine filaments. At the ends of each plasmodesma the plasmalemma and cell wall are closely appressed to the tubule, thus precluding direct continuity between the cytoplasm of adjacent cells. Through the central part of the plasmodesmata the tubule is separated from the plasmalemma by a 90–100 Å wide gap. Cytoplasmic microtubules in the same tissue have a diameter of approximately 250 Å and a wall probably composed of 13 subunits: both desmotubules and cytoplasmic microtubules therefore have a centre-to-centre subunit spacing of about 47 Å. It is suggested that the desmotubules are not microtubules but may be nuclear spindle fibres which become trapped in the wall during cell plate formation. The endoplasmic reticulum, while closely approaching the plasmodesmata, is not continuous across them. It is thought most unlikely that the endoplasmic reticulum traverses plasmodesmata, as the dimensions of the central tubule — found here as well as by other workers — are smaller than those which would be expected to allow a stable molecular configuration in a unit membrane. The plasmalemma, where it lines the plasmodesmatal canal, appears to have particulate subunits in the outer opaque layers and the presence of these subunits may be attributable to the need for stability in membranes arranged about so small a radius.     

A new interpretation of thalamocortical circuitry

Almost all the information that is needed to specify thalamocortical and neocortical wiring derives from patterned electrical activity induced by the environment. Wiring accuracy must be limited by the anatomical specificity of the cascade of events triggered by neural activity and culminating in synaptogenesis. We present a simple model of learning in the presence of plasticity errors. One way to achieve learning specificity is to build better synapses. We discuss an alternative, circuit-based, approach that only allows plasticity at connections that support highly selective correlations. This circuit resembles some of the more puzzling aspects of thalamocorticothalamic circuitry.     

A new way of tracking motion, shape, and divisions

The process of detecting and tracking biological features such as bacteria and nuclei is complicated by the fact that they constantly change their shape. Shape changes happen both continuously as the biological features grow and discontinuously as they divide or die. In this paper I present a new method of tracking such features for the case that they can be reasonably approximated by a relatively simple mathematical shape such as a cylinder or an ellipse. Using contour plots with multiple levels to detect the features and their shapes, rather than the commonly used single contour detection technique, this method can efficiently detect multiple features even if they have large differences in brightness, as well as reliably track divisions when both brightness and size drop dramatically.     

The organization of the octavolateralis area in actinopterygian fishes: A new interpretation

The octavolateralis area of actinopterygian fishes can be subdivided into a dorsal lateralis area composed of first-order lateral line nuclei, and a ventral octavus area composed of nuclei receiving first-order input from the eighth nerve. Three patterns of organization of the lateralis area are recognized in the present study. The organization of this area in polypteriforms and chondrosteans is similar to that in chondrichthyans. On the basis of recent studies in chondrichthyans (McCready and Boord, '76; Boord and Campbell, '77; Bodznick and Northcutt, '80), it is hypothesized that this pattern reflects the subdivision of the lateral line system into mechanoreceptive and electroreceptive portions. As petromyzontid agnathans also share this pattern of organization, it is hypothesized that they are elecroreceptive. The lateralis area of holosteans and nonelectroreceptive teleosts exhibits a second organizational pattern that is hypothesized to reflect the loss of the electroreceptive portion of the lateral line system; it is suggested that electroreception was lost sometime between the chondrostean and teleostean radiations. Each group of electroreceptive teleosts is believed to have evolved electroreception independently (Bullock, '74), a situation that is reflected centrally by a third organizational pattern within the lateralis area, which is distinctly different from that of early radiations of electroreceptive fishes. The octavus area of actinopterygians exhibits two patterns of organization–that of polypteriforms, chondrosteans, and holosteans, and that of teleosts. The functional significance of these patterns has yet to be elucidated.     

The theory of phyllotaxis. II. Crystallographic interpretation of the interrelation between lower and superior phyllotaxis forms

Cross-opposite phyllotaxis forms are defined as superior with respect to the alternate ones and verticillate phyllotaxis forms as superior with respect to the opposite ones. Different phyllotaxis forms can be interpreted as a result of stretching of crystal-like structures of the embryo formed by dense packing of rudiments. Based on hypothetical concepts of the properties of plant rudiments and embryos, possible mechanisms of the formation of superior phyllotaxis forms from the lower ones have been analyzed. It was shown that the superior phyllotaxis forms can be considered as the results of additive summation of the lower forms. The theoretical conclusions are confirmed by the examples of polymorphic phyllotaxis in conspecific plants and by the facts of accidental splitting of superior phyllotaxis forms into the corresponding lower forms in nature and in experiment. The mechanisms underlying the formation of multiple forms of helical phyllotaxis have been proposed. The concept of a new type of mixed hexagonal-tetragonal phyllotaxis has been formulated and the mechanism of its formation has been considered. The forms of corn grain packaging in the corncob and leaf arrangement on the strawberry tomato stem are given as examples of true hexagonal-tetragonal phyllotaxis in nature.     

A new mathematical continuum theory of axoplasmic transport.

The hypothesis is advanced that successive waves of apparent contraction-relaxation (due perhaps to filament sliding) propagate along the filamentous proteins that pierce axoplasm oriented parallel to the axon length. A mathematical continuum model is developed to characterize the flow that could result in the viscous fluid bathing the moving filamentous proteins. This flow is complicated and oscillatory in time and space, but, on the average, it yields a bi-directional drift of fluid. It would transport various substances riding in the fluid, soluble and particulate, at various distinct speeds both up and down the axon. The model can thus account qualitatively for many observed features of axoplasmic transport.     

270-MHz nuclear-magnetic-resonance study on linear gramicidin A in dimethylsulfoxide. A new interpretation.

On the basis of the finding of two sets of coupling constants (8.8 Hz and 6.7 Hz) in the 270-MHz proton magnetic resonance spectra of linear Gramicidin in dimethylsulfoxide and the comparison of its infrared spectrum with those of known conformations of alternating poly(gamma-benzyl-D-glutamate--gamma-benzyl-L-glutamate), it is proposed that the antibiotic has an LD-ribbon structure.