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PubMed1963

FINE STRUCTURE OF CHLORIDE CELLS FROM THREE SPECIES OF FUNDULUS.

A MORPHOLOGICAL BASIS FOR OSMOREGULATION IN THE TELEOSTS WAS STUDIED BY COMPARING THE FINE STRUCTURE OF CHLORIDE CELLS FOUND IN EPITHELIA OF THE GILLS OF THREE SPECIES OF FISH: Fundulus heteroclitus which can survive in a wide range of salinities, and F. similis and F. chrysotus which are usually restricted to salt water and fresh water environments, respectively. Gills were removed from F. heteroclitus which had been laboratory adapted to either sea water or pond water. For a comparison, gills were also removed from the marine F. similis and the fresh water F. chrysotus which had been adapted to their natural environments. Gill-filaments were fixed in Millonig's phosphate buffered (pH 7.4), 1 per cent osmium tetroxide and were embedded in Epon. Thin sections of filaments were stained with lead hydroxide. The cytoplasm of chloride cells of all three species of Fundulus is heavily populated with mitochondria and is filled with tubules of the agranular endoplasmic reticulum (ER). An orderly secretory cycle was indicated for chloride cells of salt water adapted F. heteroclitus and the marine F. similis. An amorphous material is observed in the agranular ER. Its density increases towards the apical end of the cell. In the apical cytoplasm, tubules of the agranular ER appear to converge and to discharge the amorphous material into an apical cavity. Except for the actual opening of the apical cavity, the distal end of salt water adapted chloride cells is characteristically shielded from the hypertonic environment by thin cytoplasmic flanges projecting from the neighboring epithelial cells. Chloride cells of the fresh water F. chrysotus resemble chloride cells of pond water adapted F. heteroclitus, in that these cells do not have apical cavities with the functional appearance of those in the sea water adapted forms. The distal end of fresh water adapted chloride cells is typically exposed to the free surface of the gill-filament. The possible function of the cell type is discussed.

Adaptation, Biological↗
PubMed1999

Computational nature of human adaptive control during learning of reaching movements in force fields.

Learning to make reaching movements in force fields was used as a paradigm to explore the system architecture of the biological adaptive controller. We compared the performance of a number of candidate control systems that acted on a model of the neuromuscular system of the human arm and asked how well the dynamics of the candidate system compared with the movement characteristics of 16 subjects. We found that control via a supra-spinal system that utilized an adaptive inverse model resulted in dynamics that were similar to that observed in our subjects, but lacked essential characteristics. These characteristics pointed to a different architecture where descending commands were influenced by an adaptive forward model. However, we found that control via a forward model alone also resulted in dynamics that did not match the behavior of the human arm. We considered a third control architecture where a forward model was used in conjunction with an inverse model and found that the resulting dynamics were remarkably similar to that observed in the experimental data. The essential property of this control architecture was that it predicted a complex pattern of near-discontinuities in hand trajectory in the novel force field. A nearly identical pattern was observed in our subjects, suggesting that generation of descending motor commands was likely through a control system architecture that included both adaptive forward and inverse models. We found that as subjects learned to make reaching movements, adaptation rates for the forward and inverse models could be independently estimated and the resulting changes in performance of subjects from movement to movement could be accurately accounted for. Results suggested that the adaptation of the forward model played a dominant role in the motor learning of subjects. After a period of consolidation, the rates of adaptation in the internal models were significantly larger than those observed before the memory had consolidated. This suggested that consolidation of motor memory coincided with freeing of certain computational resources for subsequent learning.

Adaptation, Physiological↗
PubMed2004

Evaluating evidence of psychological adaptation: how do we know one when we see one?

Evolutionary psychologists argue that human nature contains many discrete psychological adaptations. Each adaptation is theorized to have been functional in humans' ancestral past, and empirical evidence that an attribute is an adaptation can come from showing it possesses complexity, efficiency, universality, and other features of special design. In this article, we present a tutorial review of the evidentiary forms that evolutionary psychologists commonly use to document the existence of human adaptations. We also present a heuristic framework for integrating and evaluating cross-disciplinary evidence of adaptation. Pregnancy sickness, incest avoidance, men's desires for multiple sex partners, and an easily learned fear of snakes are evaluated as possible human adaptations using this framework. We conclude that future research and teaching in evolutionary psychology would benefit from more fully utilizing cross-disciplinary frameworks to evaluate evidence of human adaptation.

Adaptation, Biological↗
PubMed2002

Psychopathology or adaptation? Genetic and evolutionary perspectives on individual differences and psychopathology.

A greater understanding of psychopathology will be found in the integration of genetic and evolutionary perspectives on adaptation and function. Evolutionary theory proposes that adaptive traits are reproduced more successfully than maladaptive ones. However, some traits, while contributing to fitness in the ancestral environment, may contribute to fitness no longer. This is known as mismatch theory. Evolutionarily informed research into various "pathologies" has yielded interesting results, some based on this theory. This paper serves to distinguish between genetic and evolutionary perspectives on psychopathology as well as to examine some recent research on the selective forces that may be implicated in psychopathy, anorexic behavior, and ADHD. We suggest that research into psychopathy in general would benefit from an evolutionary perspective and an examination of the assumptions behind past research.

Adaptation, Biological↗
PubMedDate not supplied

The macro-ethics of genomics to health: the physiome project.

Advances in pharmacology and genomics, and their intervention in human biology are beyond our abilities to understand their consequences. Therapeutic intervention in highly complex, non-linear, adaptive biological systems results in some unforeseen and undesirable consequences. To do the most good with the least harm, the information on biological systems should be gathered into databases, and into comprehensive quantitative models that can help to predict the long-range effects of proposed interventions. This is a societal or professional macro-ethical imperative. The Physiome Project helps to meet this imperative via databasing and creating models and tools for large-scale integration.

Computational Biology↗
PubMed1980

Enamel remineralization as a factor in the pathogenesis of dental caries.

This paper described an investigation of local resistance acquired in response to cariogenic attacks and remineralization periods from environmental fluids. Surfaces from extracted human teeth with yellow and brown areas indicative of consolidated carious lesions were exposed to acid buffers. Subsurface lesions were developed on areas of sound enamel adjacent to, but not in areas of, consolidated lesions. The development of higher tooth resistance to acid through demineralization and remineralization was demonstrated experimentally on bovine enamel presoftened in acid, treated with fluoride, exposed to the oral environment, and finally exposed to acid buffers for development of subsurface lesions. These results are interpreted as an extension of theory of tissue adaptation to an injurious challenge, in that the tooth surface is primed by the challenge for possible remineralization and the development of higher resistance. This, cariogenic challenges can result in either local adaptation of the enamel to the challenge through lesion consolidation or to open cavitation. As in any biological adaptation, the determining factors for the final outcome are: (a) the frequency and duration of the challenge, (b) the frequency and duration of remineralizing conditions, and (c) the composition of the remineralizing fluid. The implications of the theory in the pathogenesis of caries are discussed in the light of clinical and laboratory investigations.

Animals↗
PubMed1987

Compulsive eating and dietary restraint.

The phenomenology of compulsive eating has encouraged comparisons with addictive behaviours and this has suggested that similar underlying processes might be at work. In this paper it is argued that craving for food, preoccupation with eating and loss of control over food intake represent a natural psychobiological adaptation to sub-optimal weight and food deprivation. Compulsive eating is therefore best understood in terms of a conflict between a biologically derived drive for food and a culturally derived drive for thinness. Both of these processes have their parallels in the maintenance of dependency disorders. The crucial difference however is that the urge to eat is biologically adaptive, and recovery from compulsive eating depends upon relaxing restraint.

Appetite↗
PubMed1997

[Treatment of venous thrombosis with low molecular weight heparin. Progress and outlook].

Low molecular weight heparins are in European countries the standard of treatment for deep venous thrombosis. Initially the use of low molecular weight heparins was derived of the use of unfractionated heparin: two daily subcutaneous injections with a biological adaptation on anti-Xa activity. However, rapidly, the safety of a fixed dose based on the weight was demonstrated and the biological control is no more recommended. A new low molecular weight heparin, tinzaparin, has proved its efficiency in once a day injection, several published trials have demonstrated similar results with others low molecular weight heparins. Thus the treatment of patients with deep venous thrombosis as out patients is actually a major alternative. In the future long term treatment of venous thrombosis with low molecular weight heparins could be an alternative to the oral anticoagulation. Trials in pregnant women is an emergency, low molecular weight heparins are theoretically the ideal approach for treatment of deep venous thrombosis during pregnancy. Finally low molecular weight heparins are different but the clinical implications of theses differences is still an open question.

Anticoagulants↗
PubMed2000

The Raymond Pearl memorial lecture, 1997: The quest for medical normalcy-who needs it?

Darwinian natural selection is the only factor in evolution that maintains and improves adaptation. It does so by favoring genes that enhance the genetic success of their bearers under historically prevalent conditions, and need not favor health or happiness or conformity to some universally normal state. It may favor unpleasant departures from medical normalcy if they contribute to long-term genetic success, either directly or as unavoidable costs of features that make such contributions. It is also blind to future consequences of current evolution, so that every evolving lineage accumulates historical legacies that may seriously constrain future adaptation. Examples of adaptive but unpleasant abnormality are found in infectious diseases and other instances of conflict (between the sexes, between parent and offspring, between competitors for limited resources). Examples of unfortunate historical legacies are found in limitations on numbers of parts (limbs, sense organs) and in the tight human birth passage. Adaptation is a more useful medical concept than normalcy, but the purpose of medicine is not to facilitate natural selection or uncritically encourage biological adaptations. Medical intervention may legitimately promote human values by frustrating adaptations (e.g., by anesthesia) or by seeking the grossly abnormal (e.g., birth through the abdomen rather than the vagina). Am. J. Hum. Biol. 12:10-16, 2000. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗
PubMed1997

Finite element models in tissue mechanics and orthopaedic implant design.

This article attempts to review the literature on finite element modelling in three areas of biomechanics: (i) analysis of the skeleton, (ii) analysis and design of orthopaedic devices and (iii) analysis of tissue growth, remodelling and degeneration. It is shown that the method applied to bone and soft tissue has allowed researchers to predict the deformations of musculoskeletal structures and to explore biophysical stimuli within tissues at the cellular level. Next, the contribution of finite element modelling to the scientific understanding of joint replacement is reviewed. Finally, it is shown that, by incorporating finite element models into iterative computer procedures, adaptive biological processes can be simulated opening an exciting field of research by allowing scientists to test proposed 'rules' or 'algorithms' for tissue growth, adaptation and degeneration. These algorithms have been used to explore the mechanical basis of processes such as bone remodelling, fracture healing and osteoporosis. RELEVANCE: With faster computers and more reliable software, computer simulation is becoming an important tool of orthopaedic research. Future research programmes will use computer simulation to reduce the reliance on animal experimentation, and to complement clinical trials.

Journal Article↗
PubMed1993

Cardiac hypertrophy and failure--a disease of adaptation. Modifications in membrane proteins provide a molecular basis for arrhythmogenicity.

Cardiac hypertrophy is the physiological adaptation of the heart to chronic mechanical overload. Cardiac failure indicates the limits of the process. Cardiac hypertrophy is only one example of biological adaptation and results from the induction of several changes in gene expression, mostly of the fetal type, including those coding for the myosin heavy chain or the alpha-subunit of the Na+,K(+)-ATPase. From a thermodynamic point of view, the decrease in Vmax allows the heart to produce a normal tension at a lower cost. This process results from changes both in the sarcomere and in the expression of certain membrane proteins. The decrease in calcium transient is determined by several changes in membrane proteins that result in a rather fragile equilibrium in terms of calcium homeostasis. Any abnormal input in calcium will have exaggerated detrimental consequences on a hypertrophied myocyte and may cause automaticity and arrhythmias or an exaggerated response to anoxia in terms of compliance.

Adaptation, Physiological↗
PubMed1977

The cost of evolution and the imprecision of adaptation.

Comparisons of six hypothetical cases suggest that Haldane overstimated the cost of natural selection by allele substitution. The cost is reduced if recessive alleles are advantageous, if substitutions are large and few, if selection is strong and substitutions are rapid, if substitutions are serial, and if substitutions in small demes are followed by deme-group substitutions. But costs are still so heavy that the adaptations of complex organisms in complex and changing environments are never completed. The rule probably is that most species most of the time are not fully adapted to their environments, but are just a little better than their competitors for the time being.

Adaptation, Biological↗