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PubMed2006

A role for genetic accommodation in evolution?

Whether evolutionary change can occur by genetic assimilation, or more generally by genetic accommodation, remains controversial. Here we examine some of the experimental evidence for both phenomena. Several experiments in Drosophila suggest that assimilation is possible, and a new paper shows that a color polyphenism in the tobacco hornworm, Manduca sexta, can evolve by genetic accommodation. We argue that genetic accommodation, including assimilation, is a plausible mechanism in evolution; however, more work is required to test how this mechanism acts and how often it is involved in evolutionary change.

Animals↗
PubMed2003

Adaptive branching in evolution and epigenesis.

We describe one of the simplest models that exhibit an adaptive branching behaviour. It is analysed both experimentally and formally, and its successive bifurcations provide a good model of what R. Thom called 'generalized catastrophes'. Two theorems on the stochastic adaptivity of the algorithm to very general shapes of target are given. The model further displays the phenomenon of abortive branching: each macroscopic branching appears after a burst of microscopic branchings that stop growing after a very short time. The mathematical analysis of the model explains why and how this behaviour occurs. Possible applications of these models to Evolution (natural and artificial) and Epigenesis are briefly mentioned, and a higher dimensional version is applied to growing a tree in a space of shapes in the context of a database of medical images.

Adaptation, Physiological↗
PubMed2004

Plenty more fish in the sea: comparative and functional genomics using teleost models.

Biology has collaborated with evolution to create an enormous repertoire of animal variation. This in turn has provided experimental biologists with models that can be used in the lab to simulate more complex systems. Amongst the organisms that have been used in this way are fish, where a large number of species have been utilised in a variety of different ways. Fish possess the smallest genomes of any vertebrate, making them ideal as models for genome analysis and gene discovery. Fish are also easy to maintain in a laboratory environment and can be bred easily. Fish often have well-defined physiology and respond well to many experimental procedures. Finally, fish are of great economic importance in their own right, as one of the world's largest sources of protein. In this review, the relationship between fish species is examined along with the role of different fish models in a wide range of biological disciplines.

Animals↗
PubMed1985

The temporal evolution of hypoglycemic brain damage. III. Light and electron microscopic findings in the rat caudoputamen.

The caudate nucleus and putamen belong to the selectively vulnerable brain regions which incur neuronal damage in clinical and experimental settings of both hypoglycemia and ischemia. We have previously documented the density and distribution of the hypoglycemic damage in rat caudoputamen, but the evolution of the injury, i.e., the sequence of structural changes, has not been assessed. Therefore, in the present study we analyze the light and electron microscopic alterations in the caudoputamen of rats exposed to standardized, pure insults of severe hypoglycemia with isoelectric EEG for 10-60 min, or in rats which, following insults of 30 or 60 min, were allowed to recover for periods from 5 min to 6 months. The hypoglycemic insult produced severe nerve cell injury in the dorsolateral caudoputamen. Immediately after the insult abnormal light neurons with clearing of the peripheral cytoplasm were present. These cells disappeared early in the recovery period, as they do in the cerebral cortex. Dark neurons were also present, but unlike those in the cerebral cortex they did not appear until recovery was instituted. Their number increased for a couple of hours and they became acidophilic within 4-6 h. At this stage, electron microscopy revealed severe clumping of the nuclear chromatin and cytoplasm as well as incipient fragmentation of cell membranes, all these changes indicating an irreversible injury. Within 24 h flocculent densities appeared in the mitochondria and by day 2-3 of recovery the great majority of the medium-sized neurons had undergone karyorrhexis and cytorrhexis, their remnants being subsequently removed by macrophages. After some weeks only large and a few medium-sized neurons remained amidst reactive astrocytes and numerous macrophages. The delay in the appearance of dark, lethally injured medium-sized neurons until the recovery was instituted suggests an effect that does not become apparent until the substrate supply and energy production are restored. Furthermore, it points out again the selectivity of the hypoglycemic nerve cell injury with respect to the type (metabolic characteristics?) and topographic location of the neurons.

Animals↗
PubMed2005

Evolution of extraordinary female-biased sex ratios: the optimal schedule of sex ratio in local mate competition.

Female-biased sex ratio in local mate competition has been well studied both theoretically and experimentally. However, some experimental data show more female-biased sex ratios than the theoretical predictions by Hamilton [1967. Science 156, 477-488] and its descendants. Here we consider the following two effects: (1) lethal male-male combat and (2) time-dependent control (or schedule) of sex ratio. The former is denoted by a male mortality being an increasing function of the number of males. The optimal schedule is analytically obtained as an evolutionarily stable strategy (ESS) by using Pontrjagin's maximum principle. As a result, an ESS is a schedule where only males are produced first, then the proportion of females are gradually increased, and finally only females are produced. Total sex ratio (sex ratio averaged over the whole reproduction period) is more female-biased than the Hamilton's result if and only if the two effects work together. The bias is stronger when lethal male combat is severer or a reproduction period is longer. When male-male combat is very severe, the sex ratio can be extraordinary female-biased (less than 5%). The model assumptions and the results generally agree with experimental data on Melittobia wasps in which extraordinary female-biased sex ratio is observed. Our study might provide a new basis for the evolution of female-biased sex ratios in local mate competition.

Aggression↗
PubMed2005

Ankle skeletal injury predictions using anisotropic inelastic constitutive model of cortical bone taking into account damage evolution.

The most severe ankle skeletal injury called pilon fractures can cause long term disability and impairment. Based on previous experimental studies, the pilon fractures are regarded as caused by a high-energy compressive force in the ankle joint and affected by a muscular tension force generated by emergency braking. However, quantitative injury criteria for the pilon fractures are still unknown. More accurate prediction of bone fractures in the distal tibia using a FE model of human lower leg can help us know the quantitative injury criteria. Therefore we newly proposed an anisotropic inelastic constitutive model of cortical bone including damage evolution and then implemented it to a FE code, LS-DYNA. The proposed model successfully reproduced most of anisotropy, strain rate dependency, and asymmetry of tension and compression on material and failure properties of human femoral cortical bone. However, the simplified model using an isotropic elasto-viscoplastic material, which has been used in previous studies, did not reproduce the characteristic features of the cortical bone. Two series of validation on axial impact cadaver tests for the foot and ankle indicate that the proposed model predicts the pilon fractures more accurately than the simplified model. Parametric studies on footwell impacts and pedal impacts for the foot using the proposed model show that the severity of the pilon fractures increases when the foot sustains normal and heel impacts with the impact velocity of 5 m/s and the pedal hits the forefoot with the impact velocity of 3 m/s regardless of the muscular tension force.

Journal Article↗
PubMed2002

Experimental design to optimize preparation of activated carbons for use in water treatment.

A series of seven activated carbons was obtained for use in drinking water treatments by steam-activation of olive-waste cakes. This raw material is an abundant and cheap waste byproduct of oil production, making these activated carbons economically feasible. The activated carbons, prepared by the one step method, were characterized, and the evolution of their characteristics (yield, adsorption capacities, and porosity) was analyzed as a function of the experimental parameters (activation temperature and activation time), using the Doehlert matrix. The Doehlert matrix allows the response surface to be studied with a good quality parameter estimation of the quadratic model. Each response has been described by a second order model that was adequate to predict responses in all experimental regions. The coefficients of the postulated model were calculated from the experimental responses by means of least squares regression, using the NEMROD software. We determined the region in which the optimum values of both activation temperature and activation time were achieved for the preparation of activated carbons suitable for use in water treatments. The "optimal activated carbon" was experimentally obtained, and its characteristic parameters showed a good agreement with those calculated from the model. The results obtained for activated carbons prepared by the one-step method were compared with those for activated carbons prepared by the two-step method. The characteristics of activated carbons obtained by the one-step and two-step methods showed that "one-step" activated carbons have a highly developed porous texture formed mainly of large macropores and micropores, whereas "two-step" activated carbons have a predominance of mesopores and narrow micropores. These activated carbons from olive-waste cakes showed a high capacity to adsorb herbicides (2,4-dichlorophenoxyacetic acid, 2,4-D; and 2-methyl, 4-chlorophenoxyacetic acid, MCPA) from water, with adsorption capacity values higher than those corresponding to a commercial activated carbon used from drinking water treatments.

Adsorption↗
PubMed2001

Changing views of brain evolution.

Although brain studies began in ancient Egypt, speculations on vertebrate brain evolution occurred only much later, after the publication of Darwin's Origin of Species in 1859. Subsequently, views of brain evolution have been shaped by a complex interplay of theory and technique. Darwin's theory allowed the variation in brain size and complexity to be re-interpreted within an evolutionary context, albeit an erroneous pre-Darwinian context based on scala naturae. With the development of histological techniques, research shifted to descriptions of cellular structure, cellular aggregates and their putative interconnections. In spite of these technical advances, brain evolution continued to be viewed within the context of scala naturae. Following the publication of The Comparative Anatomy of the Nervous System of Vertebrates by Ariëns Kappers, Huber, and Crosby in 1936, there followed a period of stasis, after which biological views of evolution were radically altered by the confluence of genetics, paleontology, and systematics, termed the Evolutionary Synthesis. Against this background, the development of new experimental techniques for establishing neural connections resulted in a new flowering of comparative neuroanatomy. While comparative descriptive and experimental studies of brain organization continue, the rapprochement of embryology and genetics is fueling a new renaissance that promises to increase our understanding of brain evolution and its genetic basis.

Animals↗
PubMed2002

Memory for animal tracks: a possible cognitive artifact of human evolution.

Although many human behaviors are held to have adaptive significance, specific examples of behaviors that represent direct holdovers from the ancient world have been few, particularly in the cognitive realm. In the present research, the authors tested the hypothesis that such cognitive examples might in fact exist and be experimentally verifiable. They suggested that human predispositions to learn basic aspects of hunting with relative ease might be "left over" from human evolution in the pre-agricultural past. This hypothesis was tested in 3 experiments with reference to the learning and recall of animal tracks, an activity of probable high adaptive significance within the area of visual memory. Undergraduate students selected at random learned and recalled animal tracks with significantly greater ease than they recalled other animate and inanimate items. A single exception lay in relatively unfamiliar kitchen implements, which were recalled with greater facility than were animal tracks, consistent with current theoretical considerations. Results indicate that direct behavioral holdovers from the ancient world may exist in the cognitive realm and that these may be accessed experimentally and predictably under appropriate conditions.

Adult↗
PubMed1998

A Particle-Level Model of Irreversible Protein Adsorption with a Postadsorption Transition.

Modeling the kinetics of protein adsorption at solid surfaces is needed to predict protein separations, design biosensors, and determine the body's initial response to foreign objects. We develop, at the particle level, a kinetic model that accounts geometrically for the surface blockage due to adsorption and postadsorption conformational (or orientational) transitions. Proteins are modeled as disk-shaped particles of diameter final sigmaalpha that adsorb irreversibly at random positions onto a surface at a rate kac (c is the concentration of protein in the bulk solution). Adsorption occurs only where the surface is empty. Following adsorption, a particle attempts to spread (symmetrically) to a larger diameter final sigmabeta at a rate ks. Spreading only occurs if no overlap with any previously placed particle would result. A set of equations is developed for determining the time evolution of the adsorbed protein density. These predictions are compared to new experimental data for fibronectin onto silica-titania obtained using optical waveguide lightmode spectroscopy (OWLS). We also discuss the general application of this model to experimental data. Copyright 1998 Academic Press.

Journal Article↗
PubMed2000

Effects of Sodium Salicylate on the Microstructure of an Aqueous Micellar Solution and Its Rheological Responses.

In this article, we consider the effects of sodium salicylate on the microstructure evolution and rheological responses of an aqueous cetyltrimethylammonium bromide (CTAB) solution. The experimental runs covered CTAB solutions ranging from dilute to semidilute, which were far above its critical micelle concentration. Sodium salicylate (NaSal) was used as a structure-forming agent with the molar ratio of NaSal to CTAB ranging from 0.1 to 10.0. The experimental results showed that the rheological responses of the surfactant solution were influenced strongly by both the CTAB concentration and the molar ratio. At low molar ratios, below 0.3, the surfactant solutions behaved like a Newtonian fluid. However, as the molar ratio increased, the deviation from Newtonian behavior became pronounced. Specifically, for 0.05 M CTAB solutions with molar ratios ranging from 1.0 to 5.0, an apparent yield stress developed at low shear rates and a stress plateau was displayed at intermediate shear rates. When the shear rate exceeded a certain threshold value, the shear stress increased, again passing over the plateau value. In addition, viscoelastic response and relaxation behavior were observed. The relaxation behavior after the cessation of flow was strongly dependent on the molar ratio, which was also confirmed by rheo-optical observations. The optical anisotropy measured by rheo-optical methods was closely related to flow-induced stretching and alignment of the wormy micelles and was consistent with the rheological responses. Copyright 2000 Academic Press.

Journal Article↗
PubMed1993

The effect of vitamin A (retinoids) on pattern formation implies a uniformity of developmental mechanisms throughout the animal kingdom.

Retinoids are low molecular weight, lipophilic derivatives of vitamin A which have a profound effect upon the development of a diverse array of animals. Here, I review these effects on Invertebrates: a colonial hydroid, a colonial ascidian, and Vertebrates: the regenerating amphibian limb, the developing chick limb bud, the regenerating amphibian tail, the anteroposterior axis of the early embryo, the developing chick embryo skin. There is a striking uniformity of effect of retinoids on pattern formation when applied to these diverse organisms. The majority react by being posteriorized in their development, although additional effects can also be seen. Several hypotheses which can explain these results are discussed along with the deduction that they lead to: retinoids may be components of a universal developmental mechanism or they may simply act in a similar way to alter a universal developmental mechanism. In either case the experimental analysis of retinoid effects on development has important implications for the evolution of developmental mechanisms.

Animals↗
PubMed1984

The evolution of prebiological self-organization: probable colloid-chemical evolution of first prokaryotic cells.

This is an attempt to analyse the mechanisms of self-assembly in the course of the origin and early evolution of life on the Earth. A special attention is paid to the investigation of transient stages between the physico-chemical and biological bases of self-assembly, including experimental models and paleontological results. The theory of coacervate-in-coacervate is discussed from the point of view of evolution of first procaryotic cells. Many of the high developed structures of the contemporary cells, such as ribosomes, chromosomes, lipid membranes, some other organelles etc., are claimed to posses a rudimentary polyionic coacervate character.

Biological Evolution↗
PubMed2005

Application of a mathematical model and Differential Evolution algorithm approach to optimization of bacteriocin production by Lactococcus lactis C7.

The effect of pH and temperature on cell growth and bacteriocin production in Lactococcus lactis C7 was investigated in order to optimize the production of bacteriocin. The study showed that the bacteriocin production was growth-associated, but declined after reaching the maximum titer. The decrease of bacteriocin was caused by a cell-bound protease. Maximum bacteriocin titer was obtained at pH 5.5 and at 22 degrees C. In order to obtain a global optimized solution for production of bacteriocin, the optimal temperature for bacteriocin production was further studied. Mathematical models were developed for cell growth, substrate consumption, lactic acid production and bacteriocin production. A Differential Evolution algorithm was used both to estimate the model parameters from the experimental data and to compute a temperature profile for maximizing the final bacteriocin titer and bacteriocin productivity. This simulation showed that maximum bacteriocin production was obtained at the optimal temperature profile, starting at 30 degrees C and terminating at 22 degrees C, which was validated by experiment. This temperature profile yielded 20% higher maximum bacteriocin productivity than that obtained at a constant temperature of 22 degrees C, although the total amount of bacteriocin obtained was slightly decreased.

Algorithms↗
PubMed2005

Reasonable partiality and animal ethics.

Moral psychology is often ignored in ethical theory, making applied ethics difficult to achieve in practice. This is particularly true in the new field of animal ethics. One key feature of moral psychology is recognition of the moral primacy of those with whom we enjoy relationships of love and friendship--philia in Aristotle's term. Although a radically new ethic for animal treatment is emerging in society, its full expression is severely limited by our exploitative uses of animals. At this historical moment, only the animals with whom we enjoy philia--companion animals--can be treated with unrestricted moral concern. This ought to be accomplished, both for its own sake and as an ideal model for future evolution of animal ethics.

Animal Experimentation↗
PubMedDate not supplied

Protein protease inhibitors in insects and comparison with mammalian inhibitors.

1. Studies on insect protein protease inhibitors are summarized. Biochemical, genetic and physiological investigations of the silkworm are performed. 2. In addition, the properties and characteristics of fungal protease inhibitors from the silkworm (Bombyx mori) are described and their importance as defensive functions is emphasized. 3. This review also concerns comparative and evolutionary studies of protease inhibitors from various sources. 4. The biological significance of inhibitors is discussed in view of the extensive experimental results.

Amino Acids↗
PubMed2003

Direct observation of lipid domains in free standing bilayers: from simple to complex lipid mixtures.

The direct observation of temperature-dependent lipid phase equilibria, using two-photon excitation fluorescence microscopy on giant unilamellar vesicles (GUVs) composed of different lipid mixtures, provides novel information about the physical characteristics of lipid domain coexistence. Physical characteristics such as shape, size, and time evolution of different lipid domains are not directly accessible from the traditional experimental approaches that employ either small and large unilamellar vesicles or multilamellar vesicles. In this short presentation, I will address the most relevant findings reported from our laboratory, regarding the direct observation of lipid domain coexistence at the level of single vesicles in artificial and natural lipid mixtures. In addition, key points concerning our experimental approach will be discussed. The unique advantages of the fluorescent probe 6-dodecanoyl-2-dimethylamino-naphthalene (LAURDAN) under the two-photon excitation fluorescence microscopy will be particularly addressed, especially, the possibility to obtain information about the phase-state of different lipid domains directly from the fluorescent images.

2-Naphthylamine↗