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PubMed1988

A simulation model of psychobiosocial theory of human food-intake controls.

Over 15 years ago, a psychobiosocial theory of appetite was formulated in the light of experimental evidence from rats and people that appetite was suppressed by the flow of energy to lean body mass and that much ingestion was a learned response to integrated dietary, somatic and social cues. Enough was known in 1973 about these influences on food intake and about rates of flow of energy-yielding substrates around the body of the rat to program a computer simulation which had no loose parameters. This rat model successfully predicted feeding patterns under a variety of normal and abnormal conditions, including the day-night meal rhythm, the overeating and obesity following ventromedial hypothalamic lesions, and the suppression of appetite by fenfluramine via slowed gastric emptying. In 1976, its parameter values were adjusted to those expected for an adult person having food freely available and a sedentary lifestyle. The output of this human model was remarkably realistic in meal pattern: culture appears to adapt to the physiological average. The predicted effect on appetite of energy released from adipose in proportion to the energy stored was relatively minute but very persistent. These old results are no less relevant now to improvement of our understanding of human food-intake controls and to more effective reduction and prevention of unhealthy overweight.

Appetite↗
PubMed1996

Identification of sequence changes responsible for the attenuation of highly virulent infectious bursal disease virus.

The genetic changes responsible for the attenuation of infectious bursal disease virus (IBDV) have not been defined at the molecular level, although passage of the virus in cell culture results in the loss of virulence. To understand the molecular basis of IBDV virulence and attenuation, the IBDV genome segment encoding the precursor polyprotein (NH2-VP2-VP4-VP3-COOH) of a cell culture-adapted OKYMT strain derived from highly virulent OKYM was cloned as cDNA, and the nucleotide sequence was determined. Comparison of the identified nucleotide and deduced amino acid sequences of the attenuated strain with the parental virulent OKYM strain revealed only five amino acid differences: four in the VP2 variable domain and one in the VP3. Two amino acid substitutions at positions 279 (Asp-->Asn) and 284 (Ala-->Thr) in the VP2 variable domain were commonly predicted in another cell culture-adapted strain. These two amino acid changes resulted in reduced hydrophila of this region and deletion of the alpha-helix which might alter the conformation of the virion surface structures. These results may imply that the amino acid residues at position 279 and 284 in VP2 variable domain contribute to virulence of IBDV.

Animals↗
PubMed2003

Role of feedforward control of movement stability in reducing slip-related balance loss and falls among older adults.

Human upright posture is inherently unstable. To counter the mechanical effect of a large-scale perturbation such as a slip, the CNS can make adaptive adjustments in advance to improve the stability of the body center-of-mass (COM) state (i.e., its velocity and position). Such feedforward control relies on an accurate internal representation of stability limits, which must be a function of anatomical, physiological, and environmental constraints and thus should be computationally deducible based on physical laws of motion. We combined an empirical approach with mathematical modeling to verify the hypothesis that an adaptive improvement in feedforward control of COM stability correlated with a subsequent reduction in balance loss. Forty-one older adults experienced a slip during a sit-to-stand task in a block of slip trials, followed by a block of nonslip trials and a re-slip trial. Their feedforward control of COM stability was quantified as the shortest distance between its state measured at seat-off (slip onset) and the mathematically predicted feasible stability region boundary. With adaptation to repeated slips, older adults were able to exponentially reduce their incidence of falls and backward balance loss, attributable significantly to their improvement in feedforward control of stability. With exposure to slip and nonslip conditions, subjects began to select "optimal" movements that improved stability under both conditions, reducing the reliance on prior knowledge of forthcoming perturbations. These results can be fully accounted for when we assume that an internal representation of the COM stability limits guides the adaptive improvements in the feedforward control of stability.

Adaptation, Physiological↗
PubMed2001

Hybridization and adaptive mate choice in flycatchers.

Hybridization in natural populations is strongly selected against when hybrid offspring have reduced fitness. Here we show that, paradoxically, pairing with another species may offer the best fitness return for an individual, despite reduced fitness of hybrid offspring. Two mechanisms reduce the costs to female collared flycatchers of pairing with male pied flycatchers. A large proportion of young are sired by conspecific male collared flycatchers through extra-pair copulations, and there is a bias in favour of male offspring (which, unlike females, are fertile) within hybrid pairs. In combination with temporal variation in breeding success, these cost-reducing mechanisms yield quantitative predictions about when female collared flycatchers should accept a male pied flycatcher as a mate; empirical data agree with these predictions. Apparent hybridization may thus represent adaptive mate choice under some circumstances.

Adaptation, Physiological↗
PubMed1991

Changes in colour appearance following post-receptoral adaptation.

Current models of colour vision assume that colour is represented by activity in three independent post-receptoral channels: two encoding chromatic information and one encoding luminance. An important feature of these models is that variations in certain directions in colour space modulate the response of only one of the channels. We have tested whether such models can predict how colour appearance is altered by adaptation-induced changes in post-receptoral sensitivity. In contrast to the changes predicted by three independent channels, colour appearance is always distorted away from the direction in colour space to which the observer has adapted. This suggests that at the level at which the adaptation effects occur, there is no colour direction that invariably isolates only a single post-receptoral channel.

Adaptation, Physiological↗
PubMed2000

Impression formation from intellectual and social traits: evidence for behavioural adaptation and cognitive processing.

Judgments of intellectual and social attractiveness of a target were taken from a pair of moderate and extreme intellectual or social traits. Weights of the traits given were identified from the pattern in their two-way interaction effect. Responses to a control condition of no-trait information provided the estimates of the person positivity bias in the participants, and the relative effects of the negative and positive traits were determined relative to such bias values. Consistent with the cognitive hypothesis, positive intellectual and negative social traits received more weight in the intellectual and social attraction responses, respectively. However, negative and moderate traits carried more weight in social attraction as predicted by the hypothesis of behavioural adaptation. Despite the asymmetric weighting of intellectual traits in intellectual attraction and of social traits in social attraction, the negativity effect was stronger than the positivity effect. Evidently, mechanisms postulated by both the hypotheses co-exist but they are detectable by only the operationalization employed in the two research paradigms.

Adolescent↗
PubMed2003

The adaptive dynamics of altruism in spatially heterogeneous populations.

We study the spatial adaptive dynamics of a continuous trait that measures individual investment in altruism. Our study is based on an ecological model of a spatially heterogeneous population from which we derive an appropriate measure of fitness. The analysis of this fitness measure uncovers three different selective processes controlling the evolution of altruism: the direct physiological cost, the indirect genetic benefits of cooperative interactions, and the indirect genetic costs of competition for space. In our model, habitat structure and a continuous life cycle makes the cost of competing for space with relatives negligible. Our study yields a classification of adaptive patterns of altruism according to the shape of the costs of altruism (with decelerating, linear, or accelerating dependence on the investment in altruism). The invasion of altruism occurs readily in species with accelerating costs, but large mutations are critical for altruism to evolve in selfish species with decelerating costs. Strict selfishness is maintained by natural selection only under very restricted conditions. In species with rapidly accelerating costs, adaptation leads to an evolutionarily stable rate of investment in altruism that decreases smoothly with the level of mobility. A rather different adaptive pattern emerges in species with slowly accelerating costs: high altruism evolves at low mobility, whereas a quasi-selfish state is promoted in more mobile species. The high adaptive level of altruism can be predicted solely from habitat connectedness and physiological parameters that characterize the pattern of cost. We also show that environmental changes that cause increased mobility in those highly altruistic species can beget selection-driven self-extinction, which may contribute to the rarity of social species.

Adaptation, Physiological↗
PubMed2004

Structural remodeling of mouse gracilis artery after chronic alteration in blood supply.

The goals of this study were to determine the time course and spatial dependence of structural diameter changes in the mouse gracilis artery after a redistribution of blood flow and to compare the observations with predictions of computational models for structural adaptation. Diameters were measured 1, 2, 7, 14, 21, 28, and 56 days after resection of one of the two blood supplies to the artery. Overall average diameter, normalized with respect to diameters in untreated vessels, increased slightly during the first 7 days, then increased more rapidly, reaching a peak around day 21, and then decreased. This transient increase in diameter was spatially nonuniform, being largest toward the point of resection. A previously developed theoretical model, in which diameter varies in response to stimuli derived from local metabolic and hemodynamic conditions, was extended to include effects of time-delayed remodeling stimuli in regions of reduced perfusion. Predictions of this model were consistent with observed diameter changes, including the transient increase in diameters near the point of resection, when a remodeling stimulus with a time delay of approximately 7 days was included. The results suggest that delayed stimuli significantly influence the dynamic characteristics of vascular remodeling resulting from reduced blood supply.

Adaptation, Physiological↗
PubMed1993

Cloning and overexpression of the triosephosphate isomerase genes from psychrophilic and thermophilic bacteria. Structural comparison of the predicted protein sequences.

We focused on the temperature adaptation of triosephosphate isomerase (TIM; E.C. 5.3.1.1.) by comparing the structure of TIMs isolated from bacterial organisms living in either cold or hot environments. The TIM gene from psychrophilic bacteria Moraxella sp. TA137 was cloned and its nucleotide sequence determined. Its deduced amino acid sequence revealed 34% identity with the thermophilic bacteria Bacillus stearothermophilus TIM. Expression vectors were constructed and recombinant Moraxella TA137 and Bacillus stearothermophilus TIMs were overproduced and purified to homogeneity. Recombinant TIM inactivation constants (Ki), measured at various temperatures, compared to those of the mesophilic Escherichia coli recombinant TIM clearly show that Moraxella TA137 and B. stearothermophilus TIMs have respectively psychrophilic and thermophilic characteristics. To try to elucidate the structure-thermolability and structure-thermostability relationship, factors affecting the overall stability of these two TIMs were examined, based on the alignment with the mesophilic chicken TIM, the three-dimensional structure of which is already known. From this comparison, it appears that the adaptability of TIM to high temperature is favored by better stabilizing residues for the helix dipole as well as better helix-forming residues whereas the adaptability of TIM to low temperature seems to reside in the nature of helix-capping residues.

Amino Acid Sequence↗
PubMed2006

Motor adaptation to a small force field superimposed on a large background force.

The human motor system adapts to novel force field perturbations during reaching by forming an internal model of the external dynamics and by modulating arm impedance. We studied whether it uses similar strategies when the perturbation is superimposed on a much larger background force. Consistent with the Weber-Fechner law for force perception, subjects had greater difficulty consciously perceiving the force field perturbation when it was superimposed on the large background force. However, they still adapted to the perturbation, decreasing trajectory distortion with repeated reaching and demonstrating kinematic after effects when the perturbation was unexpectedly removed. They also adapted by increasing their arm impedance when the background force was not present, but did not vary the arm impedance when the background force was present. The identified parameters of a previously proposed mathematical model of motor adaptation changed significantly with the presence of the background force. These results indicate that the motor system maintains its sensitivity for internal model formation even when there are large background forces that mask perception. Further, the motor system modulates arm impedance differently in response to the same perturbation depending on the background force onto which that perturbation is superimposed. Finally, these results suggest that computational models of motor adaptation will likely need to include force-dependent parameters to accurately predict errors.

Adaptation, Physiological↗
PubMed2004

Theoretical study of the structures, stability and vibrational spectra of the nitrous acid complexes with CH4.

The structures, stability and vibrational spectra of the binary complexes CH4...HONO-trans and CH4...HONO-cis have been investigated using ab initio calculations at the SCF and MP2 levels with 6-311++G(d,p) basis set and B3LYP calculations with 6-31G(d,p) and 6-31+G(d,p) basis sets. Full geometry optimization was made for the complexes studied. It was established that the complex CH4...HONO-trans is more stable by 0.41 kcal mol(-1) than the complex CH4...HONO-cis. The accuracy of the ab initio calculations have been estimated by comparison between the predicted values of the vibrational characteristics (vibrational frequencies and infrared intensities) and the available experimental data. It was established, that the methods, used in this study are well adapted to the problem under examination. The predicted values with the B3LYP calculations are very near to the results, obtained with 6-311++G(d,p)/MP2. The changes in the vibrational characteristics of methane and trans-, cis-nitrous acid upon formation of the hydrogen bond show that the complexes CH4...HONO-trans and CH4...HONO-cis have geometry in which the OH group interacts with a methane molecule forming a single hydrogen bond. This fact is confirmed by relatively strong perturbation of the OH stretching vibration to lower frequencies and an increase of the infrared intensity of this vibration up to three times upon hydrogen bonding.

Drug Stability↗
PubMed2005

Vibrational frequencies and infrared intensities of the hydrogen-bonded complexes of nitrous acid with ethers: ab initio and DFT studies.

The vibrational spectra of the binary complexes formed by HONO-trans and HONO-cis with dimethyl and diethyl ethers have been investigated using ab initio calculations at the SCF and MP2 levels with 6-311++G(d,p) basis set and B3LYP calculations with 6-31G(d,p) and 6-31+G(d,p) basis sets. Full geometry optimisation was made for the complexes studied. The accuracy of the ab initio calculations have been estimated by comparison between the predicted values of the vibrational characteristics (vibrational frequencies and infrared intensities) and the available experimental data. It was established, that the methods, used in this study are well adapted to the problem under examination. The predicted values with the B3LYP calculations are very near to the results, obtained with 6-311++G(d,p)/MP2. The ab initio and DFT calculations show that the changes in the vibrational characteristics (vibrational frequencies and infrared intensities) upon hydrogen bonding for the hydrogen-bonded complex (CH3)2O...HONO-trans are larger than for the complex (CH3)2O...HONO-cis.

Ethers↗
PubMed1997

Adaptation of retinal processing to image contrast and spatial scale.

Owing to the limited dynamic range of a neuron's output, neural circuits are faced with a trade-off between encoding the full range of their inputs and resolving gradations among those inputs. For example, the ambient light level varies daily over more than nine orders of magnitude, whereas the firing rate of optic nerve fibres spans less than two. This discrepancy is alleviated by light adaptation: as the mean intensity increases, the retina becomes proportionately less sensitive. However, image statistics other than the mean intensity also vary drastically during routine visual processing. Theory predicts that an efficient visual encoder should adapt its strategy not only to the mean, but to the full shape of the intensity distribution. Here we report that retinal ganglion cells, the output neurons of the retina, adapt to both image contrast-the range of light intensities-and to spatial correlations within the scene, even at constant mean intensity. The adaptation occurs on a scale of seconds, one hundred times more slowly than the immediate light response, and involves 2-5-fold changes in the firing rate. It is mediated within the retinal network: two independent sites of modulation after the photoreceptor cells appear to be involved. Our results demonstrate a remarkable plasticity in retinal processing that may contribute to the contrast adaptation of human vision.

Action Potentials↗
PubMed1995

Aminoglycoside pharmacokinetics and -dynamics: a nonlinear approach.

A model which correctly describes the pharmacokinetic-pharmacodynamic relationship is necessary to perform a rational pharmacotherapy. This model could predict the effects under variable conditions. The prediction will provide a basis for adapting therapy to individuals. A nonlinear model should be most appropriate for describing drug effects. A new model, containing nonlinear pharmacokinetics and pharmacodynamics, is presented to describe effects of aminoglycosides on bacterial growth and accumulation in kidney tissue.

Amikacin↗
PubMed2006

Operon prediction in Pyrococcus furiosus.

Identification of operons in the hyperthermophilic archaeon Pyrococcus furiosus represents an important step to understanding the regulatory mechanisms that enable the organism to adapt and thrive in extreme environments. We have predicted operons in P.furiosus by combining the results from three existing algorithms using a neural network (NN). These algorithms use intergenic distances, phylogenetic profiles, functional categories and gene-order conservation in their operon prediction. Our method takes as inputs the confidence scores of the three programs, and outputs a prediction of whether adjacent genes on the same strand belong to the same operon. In addition, we have applied Gene Ontology (GO) and KEGG pathway information to improve the accuracy of our algorithm. The parameters of this NN predictor are trained on a subset of all experimentally verified operon gene pairs of Bacillus subtilis. It subsequently achieved 86.5% prediction accuracy when applied to a subset of gene pairs for Escherichia coli, which is substantially better than any of the three prediction programs. Using this new algorithm, we predicted 470 operons in the P.furiosus genome. Of these, 349 were validated using DNA microarray data.

Algorithms↗
PubMedDate not supplied

Cognitive styles and personality characteristics strongly influence the decision to have photorefractive keratectomy.

BACKGROUND: A substantial number of patients who elect to undergo photorefractive keratectomy do so without the motivation of occupational uncorrected vision requirements. We hypothesized that information processing preferences for the auditory (versus visual) modality in a global, associative (versus detailed, sensory-oriented) style with adaptability and risk-taking (versus predictability) personality characteristics would predominate in patients electing photorefractive keratectomy. METHOD: Seventy-three prospective photorefractive keratectomy patients attended informational sessions. Sixteen occupationally driven patients and one refusal were excluded from the analysis. The 27 patients electing to proceed with surgery were compared with the 29 declining surgery. Personality characteristics and cognitive styles were determined by the Myers-Briggs Type Indicator: Abbreviated Version and the Modality Strengths Indicator. RESULTS: Subjects electing surgery showed significantly greater preferences for processing information in the auditory modality and in a global, associative style, with adaptability and risk-taking personality characteristics. Combining the attributes statistically differentiated the two groups. CONCLUSIONS: Specific cognitive styles and personality characteristics strongly influence the choice to pursue photorefractive keratectomy when that choice is not occupationally driven.

Adult↗
PubMedDate not supplied

[Adaptivity of social systems: the problem for scientific research].

The notion of adaptive evolution of social systems as of a real process of selection of the properties of such systems implies group selection. But strong evidences of effective group selection seem impossible, at least in vertebrates. However, understanding the origin of social systems adaptivity based on individual selection is difficult, as well, without analyzing the proximal mechanisms of the formation of such systems. I suppose that social systems change due to changes of individual features that underlie the proximal mechanisms of the system formation. These features are the characteristics of neurophysiological and hormonal regulatory mechanisms. They are strongly associated with intrinsic biochemical processes and are coded in the genome. Thus, the evolution of social systems is the evolution of their proximal mechanisms. At the same time, the specificity of neurophysiological and hormonal regulation determines not only social interactions, but also the individual behaviour of animals. The most important characteristics of life history, such as the regime of activity, foraging strategy, etc., are strongly affected by the same regulatory mechanisms. This view is useful for understanding the relations combining many features into an integrated and adaptive species-specific life form. I suppose that such forms emerged as evolutionary consequences of changes in regulatory mechanisms adaptive to specific environment. Thus, we have as substantial reasons to discuss adaptations of social systems to ecological features as to discuss ecological features adapted to particular social systems. The species-specificity of regulatory mechanisms is probably based on different kinds of evolutionary choice between the rapidity and the perfection of adaptation, between flexibility and stability, and between sensibility and resistibility. I think that this choice depends largely on the predictability of the environment. The less predictable it is, the more it increases the selective value of sensibility, flexibility, and rapidity of evolution. On the contrary, stable and predictable environment stimulates less rapid but more perfect adaptations. Such choices consolidate in the genome during evolution as specific features of neurophysiological and hormonal regulation systems. These specific features, in their turn, determine ecological, behavioural, and physiological species-specificity. From this point of view, evolutionary changes in social systems can be readily perceived as consequences of the selection of individuals, promoting optimal properties under particular conditional features of regulation systems. The boundary condition for this model is the absence of specificity of the characteristics of regulation systems to different forms of stress. This condition needs to be considered closely.

Adaptation, Physiological↗
PubMed2005

The application of topology optimization on the quantitative description of the external shape of bone structure.

The aim of this paper was to introduce the idea of topology optimization in engineering to the simulation of bone morphology. The external shape of bone structure was predicted with the quantitative bone functional adaptation theory. The high-order nonlinear equation of bone remodeling proposed by Zhu et al. (J. Biomech. 35(7)(2002)951) combining with the finite element method was adopted to a rectangular design domain, which occupies a larger space than the external shape of bone structure. It was at this point we imported the idea of topology optimization in engineering. The proximal femur was used here as an example, whose external shape and internal density distribution were simultaneously simulated quantitatively to validate that the external shape of bone structure could be successfully predicted in this way. Then the growth of vertebral body from young to old was simulated numerically in its coronal section to discuss the significance of the prediction of external shape. The study in this paper provides computational basis for further studies on osteophyte formation, osteoporosis, osteoarthritis, bone growth and even bone evolution, etc.

Aging↗