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PubMed1986

Consequences of chemosensory phenomena for leukocyte chemotactic orientation.

The stochastic nature of cell surface receptor-ligand binding is known to limit the accuracy of detection of chemoattractant gradients by leukocytes, thus limiting the orientation ability that is crucial to the chemotactic response in host defense. The probabilistic cell orientation model of Lauffenburger is extended here to assess the consequences of recently discovered receptor phenomena: "down-regulation" of total surface receptor number, spatial asymmetry of surface receptors, and existence of a higher-affinity receptor subpopulation. In general, a reduction in orientation accuracy is predicted by inclusion of these phenomena. An orientation signal based on a simple model of chemosensory adaptation (i.e., a spatial difference in relative receptor occupancy) is found to be functionally different from the signal suggested by an experimental correlation (i.e., a spatial difference in absolute receptor occupancy). However, in the context of receptor "signal noise," the signal based on adaptation yields predictions in better qualitative agreement with the experimental orientation data of Zigmond. From this cell orientation model we can estimate the effective time-averaging period required for noise diminution to a level allowing orientation predictions to match observed levels. This time-averaging period presumably reflects the time constant for receptor signal transduction and locomotory response.

Animals↗
PubMed2002

Gender differences in adapting to a child's chronic illness: a causal model.

This study investigated (1) the differential impact of the child's chronic illness (CI) on 80 fathers and 80 mothers and the psychosocial variables contributing to their adaptation and (2) the suitability of the causal model based on the Double ABCX Model to predict parents' adaptation to the child's illness. Eight questionnaires relating to the variables were used. Path analysis revealed similarities and differences between fathers and mothers. Social support and coping behaviors were the main variables influencing both parents' adaptation. Differences between fathers and mothers are discussed in this article. The Double ABCX Model is fairly effective in conceptualizing the process of parents' adaptation to the child's CI.

Adaptation, Psychological↗
PubMedDate not supplied

Is diet shifting facilitated by modulation of intestinal nutrient uptake? Test of an adaptational hypothesis in yellow-rumped warblers.

Yellow-rumped warblers (Dendroica coronata) are one of many avian species that change their diet seasonally. Using them, we tested the predictions that uptake of D-glucose and the amino acid L-leucine will increase as dietary levels of carbohydrate and protein, respectively, are increased and that mediated uptake capacity of the entire small intestine will match nutrient loads from daily food intake. Birds were fed three semisynthetic diets, formulated from fruit, insects, or seeds, for 7 d. Mediated D-glucose uptake in vitro was affected by diet, but contrary to our a priori prediction, fruit eaters eating the diet highest in carbohydrates had the lowest uptake rate. Na(+)-dependent L-leucine uptake at a low concentration (0.01 mmol L-1) was higher in insect and seed eaters, which is consistent with the prediction of adaptation to dietary protein, though dietary fat may also play a role. Mediated D-glucose uptake summed over small intestine length could explain only a small percentage of the estimated whole-animal absorption rate. We thus reject the predictions for carbohydrate but suggest an alternative interpretation of our results that is consistent with economical design.

Adaptation, Physiological↗
PubMed1984

Early prediction of long-term margin adaptation of dental amalgam restorations.

The present study assessed the predictive value of an indirect metric method for the early detection of margin defects of amalgam restorations, relative to results using a direct clinical method. The material consisted of plaster casts of amalgam restorations taken at 1- and 2-yr examinations of four different amalgam-treatment combinations. The widest margin defect of each restoration was measured in a dissection microscope equipped with a metric scale in the ocular. The ranking order obtained from the metric measurements of the different amalgam-treatment combinations after 1 and 2 yr was compared with that obtained from the direct clinical evaluation after 2 yr. Finally, the rank order of those restorations rated Alfa (no visible evidence, along the margin, of a crevice (ditch) into which an explorer will penetrate) at the 2-yr clinical examination was studied in relation to the 1-yr metric measurements. For the total material, the rank order based on the metric measurements of the margin defects of the four amalgam-treatment combinations agreed with that obtained with the clinical rating. In the 1-yr data, where the metric technique was applied only on the restorations rated Alfa at the 2-yr clinical evaluation, the order of two neighboring combinations was reversed; otherwise the same rank order was obtained. It is recommended that the clinical performance of new brands of amalgam alloy are tested in short-term, small-scale studies using the metric evaluation technique, before more extensive field studies over longer periods are instituted, in order to sort out unsatisfactory materials and treatment techniques at an early stage.

Child↗
PubMed1984

Mathematical modeling and numerical solutions for functionally dependent bone remodeling.

The phenomenon of bone remodeling is a complex biological process which is dependent on genetic, hormonal, metabolic, and age-related factors as well as functional requirements. The possibility of successfully developing a mathematical model to describe and predict the adaptive response of bone to load will be significantly increased after identification of the nature of the transducer(s) which senses functional requirements and provides signals for the cellular processes responsible for bone synthesis and bone removal. In spite of the present limitations in knowledge about the functional dependence of bone remodeling, a phenomenological model has been developed that assumes that the output signal from the (as yet unspecified) transducer is a remodeling potential that can be modulated by genetic, hormonal, and metabolic factors. An attempt has been made to cast the mathematical model in such a form that the constants and variables appearing in the equations are not mere abstractions, but can be related to biological parameters. In order to use the adaptive hypothesis with specific structural model examples, a numerical procedure has been developed to determine the strain distribution, predict the remodeling (assuming that the remodeling rate is related to the strain history), and update the model by changing the geometry and material properties in response to the remodeling. This numerical procedure is repeatedly iterated to determine the structural architecture at subsequent times. The numerical approach allows use of the remodeling concepts with models of irregular geometry, inhomogeneous material distribution, and anisotropic material properties.

Adaptation, Physiological↗
PubMed2004

An adaptation of Charlson comorbidity index predicted subsequent mortality in a health survey.

OBJECTIVE: The Catalan Health Interview Survey Follow-up Study analyzed survival differences according to comorbidity, using an adaptation of the Charlson's index. STUDY DESIGN AND SETTING: Vital status was ascertained by record linkage with death certificates 5 years after interview. Three thousand one hundred five men and 3,536 women aged 40-84 years old were included in the analysis. Proportional hazards models with age as time scale were used to calculate relative risk (RR) and 95% confidence interval adjusted for potential confounders. RESULTS: The adjusted RR of death in men was 1.02 (0.73-1.41) for a comorbidity index of 1-2; the RR was 1.51 (1-2.30) for an index of 3-4, and 2.64 (1.43-4.89) for an index of >4 composed to an index of 0. In women, for the same comorbidity index categorization, the RR of death were 0.83 (0.55-1.24), 1.71 (1.09-2.72) and 2.65 (1.47-4.77). CONCLUSION: This result confirms the relation between comorbidity and the risk of death based on a comorbidity index that takes into account severity and number of self-declared chronic diseases with mortality.

Adult↗
PubMed1976

Systematic observation of classroom behavior of retarded and autistic preschool children.

Two groups of 6 children, previously diagnosed as autistic and mentally retarded, were observed for seven 20-minute sessions. The following environmental parameters were manipulated: teacher-to-child ratio, presence of food reinforcement, and skill area being presented. Behavior under observation fell into 3 classes: (a) adaptive performance (percentage response and percentage correct), (b) attention, and (c) maladaptive behavior. Results suggested that (a) food reinforcement and the 1:1 teacher-to-child ratio may not generally enhance adaptive performance but may have an effect upon attention and tantrum behavior; (b) attention to task is more predictive of adaptive behavior than attention to teacher; and (c) interactions were generally lacking between the above parameters and diagnostic group, while level of functioning did show such interactions. The present results support the practice of individual behavioral assessment of autistic and retarded children. The present procedure, coupled with statistical analysis for individual subjects, may provide educational prescriptions for individual children.

Aptitude↗
PubMed2026

Cross-Device Adaptation of Mirai for Mammography-Based Breast Cancer Risk Prediction.

Fine-tuning can adapt pretrained medical imaging models to new clinical datasets, but device-specific domain shifts may limit generalizability. We evaluated Mirai, a mammography-based deep learning model for breast cancer risk prediction, in a large screening cohort containing Hologic and General Electric (GE) full-field digital mammography systems, including GE Premium View (GE PV) and Tissue Equalization (GE TE) post-processing software. Native Mirai showed lower performance on TE images than on Hologic or PV images. Fine-tuning on TE images improved TE performance, particularly for short-term risk prediction, but substantially reduced performance on Hologic images, consistent with catastrophic forgetting. To mitigate this effect, we developed a device-invariant model using interleaved multi-device sampling and conditional adversarial training. This approach largely restored Hologic performance while maintaining improved TE performance, providing better robustness across heterogeneous imaging platforms. Comparison of cumulative and annual risk AUCs over a five-year time horizon further showed that performance gains were driven mainly by short- and intermediate-term predictions. These findings highlight both the value and dangers of device-specific fine-tuning and support balanced domain-adaptation strategies for deploying mammography-based risk models across diverse clinical imaging environments.

Journal Article↗
PubMed1998

Sex and the evolution of intrahost competition in RNA virus phi6.

Sex allows beneficial mutations that occur in separate lineages to be fixed in the same genome. For this reason, the Fisher-Muller model predicts that adaptation to the environment is more rapid in a large sexual population than in an equally large asexual population. Sexual reproduction occurs in populations of the RNA virus phi6 when multiple bacteriophages coinfect the same host cell. Here, we tested the model's predictions by determining whether sex favors more rapid adaptation of phi6 to a bacterial host, Pseudomonas phaseolicola. Replicate populations of phi6 were allowed to evolve in either the presence or absence of sex for 250 generations. All experimental populations showed a significant increase in fitness relative to the ancestor, but sex did not increase the rate of adaptation. Rather, we found that the sexual and asexual treatments also differ because intense intrahost competition between viruses occurs during coinfection. Results showed that the derived sexual viruses were selectively favored only when coinfection is common, indicating that within-host competition detracts from the ability of viruses to exploit the host. Thus, sex was not advantageous because the cost created by intrahost competition was too strong. Our findings indicate that high levels of coinfection exceed an optimum where sex may be beneficial to populations of phi6, and suggest that genetic conflicts can evolve in RNA viruses.

Adaptation, Physiological↗
PubMed1998

Negative life events and the adjustment of school-age children: testing protective models.

Investigated the association between negative life events and protective factors in predicting the adaptive, emotional, and behavioral functioning of school-age children. Three possible models of this relation were tested using hierarchical analyses: the compensatory model, the challenge model, and the immunity/vulnerability model. Participants were 140 children between the ages of 8 to 13.6 years. Inconsistent with all 3 models, negative life events were not associated with adaptive or internalizing behavior. However, consistent with the compensatory model, both negative life events and protective factors contributed independently to the prediction of externalizing behavior. Also, a significant interaction was found in predicting internalizing behavior for the female-only sample showing girls with significant negative life events and social support demonstrating less internalizing behavior.

Adaptation, Psychological↗
PubMed2005

Constructing a prospective model of psychosocial adaptation in young adolescents with spina bifida: an application of optimal data analysis.

OBJECTIVE: To examine how individual- and family-level predictors in late childhood and preadolescence relate to psychosocial adaptation (i.e., scholastic success, social acceptance, and positive self-worth) in early adolescence. METHOD: This prospective longitudinal study includes 68 families of children with spina bifida and 68 comparison families of healthy children. Multimethod, multiinformant data were evaluated via optimal data analysis (ODA) and classification tree analysis (CTA) techniques. RESULTS: Factors best predicting psychosocial adaptation in early adolescence included (a) intrinsic motivation, (b) estimated verbal IQ, (c) behavioral conduct, (d) coping style, and (e) physical appearance. There were no significant group (spina bifida vs. able-bodied) effects. CONCLUSIONS: The final classification model correctly classified 77.8% of the total sample, indicating that this model had significant predictive capabilities. Results suggested that processes leading to psychosocial adaptation may be similar for youth with and without chronic illness.

Adaptation, Psychological↗
PubMed2005

Adaptation of teams in response to unforeseen change: effects of goal difficulty and team composition in terms of cognitive ability and goal orientation.

Halfway through a 3-hour experiment in which 64 3-person teams needed to make a series of decisions, a communications channel began to deteriorate, and teams needed to adapt their system of roles in order to perform effectively. Consistent with previous research, team composition with respect to members' cognitive ability was positively associated with adaptation. Adaptation was also influenced by interactions of team goal difficulty and team composition with respect to team members' goal orientation. Teams with difficult goals and staffed with high-performance orientation members were especially unlikely to adapt. Teams with difficult goals and staffed with high-learning orientation members were especially likely to adapt. Supplemental analyses provided insight into the observed effects in that the difficulty of team goals and members' goal orientation predicted interpersonal, transition, and action processes, all of which predicted team adaptation.

Adaptation, Psychological↗
PubMed2006

Learning to predict the future: the cerebellum adapts feedforward movement control.

The role of the cerebellum in motor control and learning has been largely inferred from the effects of cerebellar damage. Recent work shows that cerebellar damage produces greater impairment of movements that require predictive as opposed to reactive control. This dissociation is consistent across many different types of movement. Predictive control is crucial for fast and ballistic movements, but impaired prediction can also affect slow movements, because of increased reliance on time-delayed feedback signals. The new findings are compatible with theories of cerebellar function, but still do not resolve whether the cerebellum operates by predicting the optimal motor commands or future sensory states. Prediction mechanisms must be learned and maintained through comparisons between predicted and observed outcomes. New results show that not all such error information is equivalent in driving cerebellar learning.

Adaptation, Physiological↗
PubMed2004

Numerical analysis of bone adaptation around an oral implant due to overload stress.

A finite element (FE) numerical model of an oral implant was implemented with the theory of bone adaptation to predict the response over time of the bone tissue to the implant and to explain a phenomenon regarding the clinical situation: the bone loss due to an overload stress. An adaptation routine, based on Beaupré theory, was developed to interface with the FE packages. The value of the mechanical stimulus, corresponding to the overload stress, was evaluated by applying the Taylor crack propagation theory. The predictions obtained by the numerical analyses demonstrated that the overload resorption is blocked only with spongy bone of 'good quality'.

Adaptation, Physiological↗
PubMed2003

Patterns of adaptation and personality disorders.

Patterns of adaptation to conflict were explored with the Serial Color-Word Test, and personality disorders were assessed by means of the Coolidge Axis II Inventory in a group of 76 nonpsychotic women volunteers in the age range 18-50 yr. (M=29.1 yr., SD=8.3), who attended a psychiatric outpatients unit. Forward multiple regression analyses were performed to investigate whether patterns of adaptation were associated with personality disorders. 10 out of 13 personality scales, as measured by the Coolidge Axis II Inventory, were significantly predicted by adaptive variables. Some predictors were positive and others were negative. The variable R(AD) was a negative predictor of avoidant and dependent personalities, and a positive predictor of Extraversion, Aggressive personality, and Antisocial personality; this finding suggests that R(AD) may represent the regulative counterpart of a continuum from passive introversion to aggressive extraversion. The results encourage further research on nontrait laboratory correlates of personality disorders.

Adaptation, Psychological↗
PubMed2003

[Coping with acute psychological traumas in childhood].

While there is increasing knowledge about predictors of posttraumatic stress reactions in adults, much less is known in children. Importantly, the theoretical integration of research findings and the development of models of post-trauma adaptation have been neglected. After some introducing remarks on the classification and the prevalence of posttraumatic stress reactions, this paper aims to integrate current research findings within a trauma adaptation model that is based on transactional stress theory. Characteristics of the trauma, the child and the social context are assumed to predict posttraumatic adaptation. The effect of these variables on trauma adaptation may be direct or indirect, i.e. mediated by appraisals and coping processes. Based on the proposed theoretical model current research findings are presented and discussed in detail. Finally, the usefulness of the model for the planning and the development of psychosocial interventions after trauma is shown.

Adaptation, Psychological↗
PubMed2006

Impact of small fitness costs on pest adaptation to crop varieties with multiple toxins: a heuristic model.

A deterministic two-locus model was used to examine how small fitness costs to individuals carrying resistance alleles could impact the risk of panmictic insect pest populations adapting to crop varieties that produced two distinct toxins. Parameters examined were (1) level of toxicity of each toxin, (2) initial frequencies of alleles for adaptation to the toxins, (3) percentage of population feeding on nontoxic plants, and (4) level of fitness cost associated with adaptation to each of the two toxins. Resistance to each toxin was assumed to be biochemically independent, controlled by a resistance coding allele at a single locus, and inherited as a partially recessive trait in the field. When plants are extremely toxic to the pest, effective refuge size is 10%, and there is a fitness cost to resistance alleles only when in homozygous form (5%), the pest population is never predicted to adapt to either toxin as long as the initial frequencies of the resistance alleles are below 0.05. Even if the initial frequency of the allele for adapting to one toxin is 0.95 when a two-toxin cultivar completely replaces a one-toxin cultivar, the model predicts that a low equilibrium allelic frequency will develop for both resistance alleles, as long as the frequency of the allele for adapting to the second toxin is initially 0.001 or less. If cultivars with one and two toxins are planted, the model predicts that resistance will develop. Nonrandom mating and stochastic variation within subpopulations also could lead to evolution of resistance.

Adaptation, Physiological↗
PubMedDate not supplied

A neural model of cortico-cerebellar interactions during attentive imitation and predictive learning of sequential handwriting movements.

Much sensory-motor behavior develops through imitation, as during the learning of handwriting by children. Such complex sequential acts are broken down into distinct motor control synergies, or muscle groups, whose activities overlap in time to generate continuous, curved movements that obey an inverse relation between curvature and speed. How are such complex movements learned through attentive imitation? Novel movements may be made as a series of distinct segments, but a practiced movement can be made smoothly, with a continuous, often bell-shaped, velocity profile. How does learning of complex movements transform reactive imitation into predictive, automatic performance? A neural model is developed which suggests how parietal and motor cortical mechanisms, such as difference vector encoding, interact with adaptively timed, predictive cerebellar learning during movement imitation and predictive performance. To initiate movement, visual attention shifts along the shape to be imitated and generates vector movement using motor cortical cells. During such an imitative movement, cerebellar Purkinje cells with a spectrum of delayed response profiles sample and learn the changing directional information and, in turn, send that learned information back to the cortex and eventually to the muscle synergies involved. If the imitative movement deviates from an attentional focus around a shape to be imitated, the visual system shifts attention, and may make an eye movement, back to the shape, thereby providing corrective directional information to the arm movement system. This imitative movement cycle repeats until the cortico-cerebellar system can accurately drive the movement based on memory alone. A cortical working memory buffer transiently stores the cerebellar output and releases it at a variable rate, allowing speed scaling of learned movements which is limited by the rate of cerebellar memory readout. Movements can be learned at variable speeds if the density of the spectrum of delayed cellular responses in the cerebellum varies with speed. Learning at slower speeds facilitates learning at faster speeds. Size can be varied after learning while keeping the movement duration constant (isochrony). Context-effects arise from the overlap of cerebellar memory outputs. The model is used to simulate key psychophysical and neural data about learning to make curved movements, including a decrease in writing time as learning progresses; generation of unimodal, bell-shaped velocity profiles for each movement synergy; size and speed scaling with preservation of the letter shape and the shapes of the velocity profiles; an inverse relation between curvature and tangential velocity; and a Two-Thirds Power Law relation between angular velocity and curvature.

Attention↗