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PubMed2005

Evolution of specialization and ecological character displacement of herbivores along a gradient of plant quality.

We study the combined evolutionary dynamics of herbivore specialization and ecological character displacement, taking into account foraging behavior of the herbivores, and a quality gradient of plant types. Herbivores can adapt by changing two adaptive traits: their level of specialization in feeding efficiency and their point of maximum feeding efficiency along the plant gradient. The number of herbivore phenotypes, their levels of specialization, and the amount of character displacement among them are the result of the evolutionary dynamics, which is driven by the underlying population dynamics, which in turn is driven by the underlying foraging behavior. Our analysis demonstrates broad conditions for the diversification of a herbivore population into many specialized phenotypes, for basically any foraging behavior focusing use on highest gains while also including errors. Our model predicts two characteristic phases in the adaptation of herbivore phenotypes: a fast character-displacement phase and a slow coevolutionary niche-shift phase. This two-phase pattern is expected to be of wide relevance in various consumer-resource systems. Bringing together ecological character displacement and the evolution of specialization in a single model, our study suggests that the foraging behavior of herbivorous arthropods is a key factor promoting specialist radiation.

Adaptation, Biological↗
PubMed2006

Modeling gravity-dependent plasticity of the angular vestibuloocular reflex with a physiologically based neural network.

A neural network model was developed to explain the gravity-dependent properties of gain adaptation of the angular vestibuloocular reflex (aVOR). Gain changes are maximal at the head orientation where the gain is adapted and decrease as the head is tilted away from that position and can be described by the sum of gravity-independent and gravity-dependent components. The adaptation process was modeled by modifying the weights and bias values of a three-dimensional physiologically based neural network of canal-otolith-convergent neurons that drive the aVOR. Model parameters were trained using experimental vertical aVOR gain values. The learning rule aimed to reduce the error between eye velocities obtained from experimental gain values and model output in the position of adaptation. Although the model was trained only at specific head positions, the model predicted the experimental data at all head positions in three dimensions. Altering the relative learning rates of the weights and bias improved the model-data fits. Model predictions in three dimensions compared favorably with those of a double-sinusoid function, which is a fit that minimized the mean square error at every head position and served as the standard by which we compared the model predictions. The model supports the hypothesis that gravity-dependent adaptation of the aVOR is realized in three dimensions by a direct otolith input to canal-otolith neurons, whose canal sensitivities are adapted by the visual-vestibular mismatch. The adaptation is tuned by how the weights from otolith input to the canal-otolith-convergent neurons are adapted for a given head orientation.

Adaptation, Physiological↗
PubMed2006

Learning MHC I--peptide binding.

MOTIVATION AND RESULTS: Motivated by the ability of a simple threading approach to predict MHC I--peptide binding, we developed a new and improved structure-based model for which parameters can be estimated from additional sources of data about MHC-peptide binding. In addition to the known 3D structures of a small number of MHC-peptide complexes that were used in the original threading approach, we included three other sources of information on peptide-MHC binding: (1) MHC class I sequences; (2) known binding energies for a large number of MHC-peptide complexes; and (3) an even larger binary dataset that contains information about strong binders (epitopes) and non-binders (peptides that have a low affinity for a particular MHC molecule). Our model significantly outperforms the standard threading approach in binding energy prediction. In our approach, which we call adaptive double threading, the parameters of the threading model are learnable, and both MHC and peptide sequences can be threaded onto structures of other alleles. These two properties make our model appropriate for predicting binding for alleles for which very little data (if any) is available beyond just their sequence, including prediction for alleles for which 3D structures are not available. The ability of our model to generalize beyond the MHC types for which training data is available also separates our approach from epitope prediction methods which treat MHC alleles as symbolic types, rather than biological sequences. We used the trained binding energy predictor to study viral infections in 246 HIV patients from the West Australian cohort, and over 1000 sequences in HIV clade B from Los Alamos National Laboratory database, capturing the course of HIV evolution over the last 20 years. Finally, we illustrate short-, medium-, and long-term adaptation of HIV to the human immune system. AVAILABILITY: http://www.research.microsoft.com/~jojic/hlaBinding.html.

Algorithms↗
PubMed2005

Stability of the replicator equation for a single species with a multi-dimensional continuous trait space.

The replicator equation model for the evolution of individual behaviors in a single species with a multi-dimensional continuous trait space is developed as a dynamics on the set of probability measures. Stability of monomorphisms in this model using the weak topology is compared to more traditional methods of adaptive dynamics. For quadratic fitness functions and initial normal trait distributions, it is shown that the multi-dimensional continuously stable strategy (CSS) of adaptive dynamics is often relevant for predicting stability of the measure-theoretic model but may be too strong in general. For general fitness functions and trait distributions, the CSS is related to dominance solvability which can be used to characterize local stability for a large class of trait distributions that have no gaps in their supports whereas the stronger neighborhood invader strategy (NIS) concept is needed if the supports are arbitrary.

Adaptation, Physiological↗
PubMed2006

Cyanobacterial ecotypes in the microbial mat community of Mushroom Spring (Yellowstone National Park, Wyoming) as species-like units linking microbial community composition, structure and function.

We have investigated microbial mats of alkaline siliceous hot springs in Yellowstone National Park as natural model communities to learn how microbial populations group into species-like fundamental units. Here, we bring together empirical patterns of the distribution of molecular variation in predominant mat cyanobacterial populations, theory-based modelling of how to demarcate phylogenetic clusters that correspond to ecological species and the dynamic patterns of the physical and chemical microenvironments these populations inhabit and towards which they have evolved adaptations. We show that putative ecotypes predicted by the theory-based model correspond well with distribution patterns, suggesting populations with distinct ecologies, as expected of ecological species. Further, we show that increased molecular resolution enhances our ability to detect ecotypes in this way, though yet higher molecular resolution is probably needed to detect all ecotypes in this microbial community.

Adaptation, Biological↗
PubMed2001

Abnormal Doppler velocimetry and blood flow volume in the middle cerebral artery in very severe intrauterine growth restriction: is the occurence of reversal of compensatory flow too late?

OBJECTIVES: To determine the time course of quantified volumetric flow and pulsatility index changes in the middle cerebral arteries of severe intrauterine growth restricted fetuses with absent or reversed end diastolic flow velocities (AREDFV) on umbilical artery Doppler with a view to defining the threshold for early intervention before the onset of reversal of adaptation. SETTING: Fetal growth clinic of a large UK teaching hospital. SAMPLE: Seventeen severe intrauterine growth restricted (AC < third centile for gestation and gender) fetuses with abnormal umbilical artery Doppler velocimetry and oligohydramnios (amniotic fluid index <third centile for gestation). METHODS: One to three daily Doppler velocimetry and quantified volume flow of the middle cerebral artery Doppler velocimetry of the umbilical arteries and daily cardiotocography. RESULTS: Reversal of adaptation occurred in eight fetuses, four of which ended as stillbirths and four as neonatal deaths. In two of these fetuses, this had already occurred before the diagnosis of intrauterine growth restriction. In the others, the onset was rapid and difficult to predict. Volume flow in the middle cerebral arteries decreased in those fetuses exhibiting reversal of adaptation but rose in the nine in which compensatory Doppler indices persisted. The decrease in volume flow occurred before the onset of reversal of adaptation in the pulsatility index. In the fetuses exhibiting reversal of adaptation, the rise in the pulsatility index was consistent over 48 hours compared with the physiological fluctuations in pulsatility index in some fetuses where the rise was only for 24 hours followed by a fall. Quantified volume flow fell in the fetuses before reversal of adaptation set-in. The umbilical artery Doppler indices fluctuated between absent and reversed end diastolic velocities within the same fetus irrespective of the changes in the middle cerebral artery Doppler indices. CONCLUSION: Reversal of adaptation is of sudden onset and is associated with poor prognosis. Predicting its occurrence on Doppler indices is difficult as the changes may be very rapid. However, volume flow changes appear to be slower and of earlier onset than the pulsatility index changes. This may therefore be a more useful tool in predicting imminent reversal of adaptation and therefore early delivery.

Adult↗
PubMed1992

Therapeutic drug monitoring and pharmacokinetic dose prediction methods.

Therapeutic drug monitoring is recommended in suspected drug overdosage, in cases of therapeutic failure, in the establishment of regimens in patients with altered pharmacokinetics and in patients with unknown previous medications. Pharmacokinetic dose prediction methods have been developed allowing individual dosage adaptation. As examples, the three-point method of Sawchuk and the Bayesian technique are described. Drug concentrations could be predicted with sufficient accuracy by use of the three-point method in critically ill patients treated with aminoglycosides or flucytosine. Bayesian forecasting proved to be useful in predicting the nocturnal concentration curves in patients with asthma treated with a sustained-release preparation of theophylline for once-daily dosage. The efficiency of drug treatment can be considerably improved by monitoring serum drug concentrations and individualizing dosage using pharmacokinetic methods.

Aminoglycosides↗
PubMedDate not supplied

Predictors of a health-promoting life-style among well adult clients in a nursing practice.

The self-reported health-promoting life-style (HPL) of 130 well adults in a primary care clinical population was examined in relation to the cognitive/perceptual and sociodemographic factors hypothesized in Pender's Health Promotion Model (1987) to predict this behavior. Subjects were randomly drawn from the clients of a group nurse practitioner practice emphasizing health maintenance. Data were collected by mailed survey (response rate, 59%) with one telephone prompt. The mean age of the subjects was 39.7 years; 72.3% were female; 51.2% were married; 47.7% had college degrees; and 67.4% were white. Blacks were underrepresented in the sample compared to the practice population (chi = 7.56, p = .006). Using multiple regression, the definition of health, importance of health, health locus of control, age, gender, marital status, race, education, income, and rural/urban residence were studied to determine their effects on health-promoting behavior. Results generally supported the Pender Model. Defining health eudiamonistically, that is, as exuberant well-being (rather than adaptive, functional, or absence of disease), predicted HPL. Ranking health above other values such as achievement and harmony had no effect; chance health locus of control had a negative relationship. In the final regression model, predictors of HPL were eudiamonistic conception of health and college education (p = .0001, R2 = 17). Based on this data, considerations of a clients' health conception when framing health-promotion messages is warranted in this population.

Adult↗
PubMed2026

AI-Driven Precision Medicine in Alzheimer's Disease: Drug Repurposing, Digital Therapeutics and Clinical Decision Support.

Alzheimer's Disease (AD) is a neurodegenerative disease that causes significant clinical, social, and economic burden worldwide. Despite improvements in understanding its multifaceted pathogenesis, current treatments are mostly symptomatic and ineffective across varied patient populations. To overcome these constraints, AI-driven precision medicine allows tailored risk assessment, treatment selection, and disease monitoring. This review covers AI's role in AD precision medicine, focusing on drug repurposing, digital therapies and clinical decision support systems. Machine and deep learning models are used to predict medication response, integrate heterogeneous data sources such as genomics, transcriptomics, neuroimaging and electronic health records, and uncover pharmacogenomic treatment success factors. The paper covers AIenabled precision pharmacology, including tailored dosing algorithms, adaptive therapeutic monitoring, and adverse drug reaction prediction. Bioinformatics-based target identification, network pharmacology, graphbased AI models, virtual screening, and real-world and clinical data validation are emphasized in AI-driven medication repurposing. AI-powered digital treatments like personalized cognitive training platforms, wearable- derived digital biomarkers, virtual and mixed reality interventions, adherence monitoring, and digital twins for therapy optimization have been discussed. AI-based clinical decision support systems are also thoroughly assessed for clinical value, accuracy, and explainability in disease subtyping, trajectory prediction, and risk stratification in preclinical and prodromal AD. Despite these promises, data heterogeneity, algorithmic bias, legal barriers, and privacy concerns exist. Federated learning enables safe multi-center collaboration and hybrid AI-human approaches, and it represents the future. AI's ability to alter AD care opens the door to precision medicine paradigms that use repurposed medications, digital tools and intelligent decision-making to improve patient outcomes.

Alzheimer&#x2019;s disease↗
PubMed2005

Qualitative differences between naïve and scientific theories of evolution.

Philosophers of biology have long argued that Darwin's theory of evolution was qualitatively different from all earlier theories of evolution. Whereas Darwin's predecessors and contemporaries explained adaptation as the transformation of a species' "essence," Darwin explained adaptation as the selective propagation of randomly occurring mutations within a population. The present study explored the possibility of a parallel between early "transformational" theories of evolution and modern naïve theories. Forty-two high school and college students and three evolutionary biologists were tested on their understanding of six evolutionary phenomena: variation, inheritance, adaptation, domestication, speciation, and extinction. As predicted, a plurality of participants demonstrated transformational reasoning inconsistent with natural selection. Correlational analyses revealed that participants who demonstrated transformational reasoning were as internally consistent as participants who demonstrated an understanding of natural selection, with the exception of one group of participants who appeared to have assimilated two heuristics--"survival of the fittest" and "acquired traits are not inherited"--into an otherwise transformational framework. These findings suggest that the widespread and early-developing tendency to essentialize biological kinds precludes students from conceptualizing species as populations of individuals differentially affected by the environment.

Adaptation, Physiological↗
PubMed2003

Quantifying generalization from trial-by-trial behavior of adaptive systems that learn with basis functions: theory and experiments in human motor control.

During reaching movements, the brain's internal models map desired limb motion into predicted forces. When the forces in the task change, these models adapt. Adaptation is guided by generalization: errors in one movement influence prediction in other types of movement. If the mapping is accomplished with population coding, combining basis elements that encode different regions of movement space, then generalization can reveal the encoding of the basis elements. We present a theory that relates encoding to generalization using trial-by-trial changes in behavior during adaptation. We consider adaptation during reaching movements in various velocity-dependent force fields and quantify how errors generalize across direction. We find that the measurement of error is critical to the theory. A typical assumption in motor control is that error is the difference between a current trajectory and a desired trajectory (DJ) that does not change during adaptation. Under this assumption, in all force fields that we examined, including one in which force randomly changes from trial to trial, we found a bimodal generalization pattern, perhaps reflecting basis elements that encode direction bimodally. If the DJ was allowed to vary, bimodality was reduced or eliminated, but the generalization function accounted for nearly twice as much variance. We suggest, therefore, that basis elements representing the internal model of dynamics are sensitive to limb velocity with bimodal tuning; however, it is also possible that during adaptation the error metric itself adapts, which affects the implied shape of the basis elements.

Adaptation, Physiological↗
PubMedDate not supplied

Computer assisted mapping in quantitative analysis of cerebral positron emission tomograms.

For quantitative analysis of CT of the brain, an interactive FORTRAN program was developed to provide a time saving mapping procedure with high, largely user-independent reproducibility and flexible adaptation to individual anatomical variations. Program scope and functions are demonstrated, and results obtained in a group of seven normal volunteers are presented for positron emission tomography using the [18F]-2-fluoro-2-deoxy-D-glucose (FDG) method. Basically, the procedure is designed as a two step process: first, a region raw contour is defined geometrically on the basis of local Cartesian or polar coordinates relative to the whole brain contour; second, the final region is delimited within the raw region, in the FDG images according to relative local tissue activity. Although all parameters for mapping a brain slice are stored in a standard parameter file ensuring reproducibility and comparability, interactive control of all steps permits user-guided corrections whenever necessary. Numerical results closely correspond to the data obtained in a previous study of normal subjects with individual manual mapping; discrimination between gray and white matter is in good agreement with theoretical predictions. The program can be easily adapted to other CT techniques.

Brain↗
PubMed2005

Female common lizards (Lacerta vivipara) do not adjust their sex-biased investment in relation to the adult sex ratio.

Sex allocation theory predicts that facultative maternal investment in the rare sex should be favoured by natural selection when breeders experience predictable variation in adult sex ratios (ASRs). We found significant spatial and predictable interannual changes in local ASRs within a natural population of the common lizard where the mean ASR is female-biased, thus validating the key assumptions of adaptive sex ratio models. We tested for facultative maternal investment in the rare sex during and after an experimental perturbation of the ASR by creating populations with female-biased or male-biased ASR. Mothers did not adjust their clutch sex ratio during or after the ASR perturbation, but produced sons with a higher body condition in male-biased populations. However, this differential sex allocation did not result in growth or survival differences in offspring. Our results thus contradict the predictions of adaptive models and challenge the idea that facultative investment in the rare sex might be a mechanism regulating the population sex ratio.

Animals↗
PubMed1986

Open communication as an effective stress management method for breast cancer patients.

The social and emotional adaptation of 51 breast cancer patients was assessed four times during the first year after mastectomy according to Weissman and Paykel's Social Adaptation Scale (SAS) and judges' ratings. Openness of communication was measured by eight indices during the first two interviews. It was predicted that they would correlate positively with successful adaptation as measured at the third and fourth interviews. Most patients were aware of their diagnosis, and their communication about their plight was found to be multifaceted. Successful copers sought information; less successful copers avoided it. However, where emotions and not facts were the issue, palliative measures such as avoidance of speaking about the threat and refusal to accept its further implications were connected with better adjustment. The findings indicate that palliation is a prerequisite to good instrumental adjustment when the emotional reactions are intense and countermeasures are limited. More research is needed for assessing communication with specific others and change over time.

Adaptation, Psychological↗
PubMed2006

Estimating SRS-22 quality of life measures with SF-36: application in idiopathic scoliosis.

STUDY DESIGN: Comparison of a generic- with a disorder-specific health-related quality of life (HRQL) questionnaire. OBJECTIVES: To determine the association between generic- and disorder-specific questionnaire domains of similar construct. SUMMARY OF BACKGROUND DATA: Short Form-36 (SF-36), a general HRQL questionnaire, has been widely used to evaluate patients with scoliosis and related spine deformity. How it relates to the disorder-specific Scoliosis Research Society-22 (SRS-22) questionnaire is currently unknown. METHODS: Seventy-eight patients, operated at a mean age 14.5 years for idiopathic scoliosis with a mean largest Cobb of 60 degrees , completed both questionnaires at a mean of 9.25 years after surgery. RESULTS: The predictability of the SRS-22 Mental Health domain is excellent using the SF-36 Mental Health domain, from which it was adapted (R2 = 0.81). The SRS-22 Pain domain predictability using the SF-36 Bodily Pain domain is also excellent (R2 = 0.79). The SRS-22 Function domain predictability using the SF-36 Physical Component Summary domain is good (R2 = 0.64). The SRS-22 Self-Image and Management Satisfaction/Dissatisfaction domains are poorly predicted by the SF-36 General Health and Physical Component Summary domains, respectively, R2 = 0.52 and 0.54. CONCLUSION: SRS-22 Mental Health and Pain domain scores can be accurately calculated from correlating SF-36 domain scores. SRS-22 Function scores can be fairly well predicted from correlated SF-36 domain scores. Self-Image and Management Satisfaction/Dissatisfaction domain scores cannot be approximated from SF-36 domain scores.

Adolescent↗
PubMed1996

Orthogonal motion after-effect illusion predicted by a model of cortical motion processing.

The motion after-effect occurs after prolonged viewing of motion; a subsequent stationary scene is perceived as moving in the opposite direction. This illusion is thought to arise because motion is represented by the differential activities of populations of cortical neurons tuned to opposite directions; fatigue in one population leads to an imbalance that favours the opposite direction once the stimulus ceases. Following adaptation to multiple directions of motion, the after-effect is unidirectional, indicating that motion signals are integrated across all directions. Yet humans can perceive several directions of motion simultaneously. The question therefore arises as to how the visual system can perform both sharp segregation and global integration of motion signals. Here we show in computer simulations that this can occur if excitatory interactions between different directions are sharply tuned while inhibitory interactions are broadly tuned. Our model predicts that adaptation to simultaneous motion in opposite directions will lead to an orthogonal motion after-effect. This prediction was confirmed in psychophysical experiments. Thus, broadly tuned inhibitory interactions are likely to be important in the integration and segregation of motion signals. These interactions may occur in the cortical area MT, which contains motion-sensitive neurons with properties similar to those required by our model.

Afterimage↗
PubMed2001

Development and application of a genotypic AZT resistance assay: quantitative assessment of the resistance profile of clinical samples and the relative predictive ability of a resistance index.

OBJECTIVES: To develop and validate a rapid, genotypic, quantitative AZT resistance assay, and to evaluate the predictive ability of a resistance index. METHODS: AZT resistance profiles of paired samples from HIV-infected patients were determined by a ligase chain reaction (LCR) assay. AZT resistance levels and surrogate markers of HIV disease progression (viral load and CD4 counts) were used to compare AZT-naive and AZT-experienced patients. The ability of a "mutant/wild-type HIV-1 quasi-species" index to predict viral load was assessed. RESULTS: AZT resistance, evident at baseline in both AZT-experienced and AZT-naive patients, increased over 6 months of treatment. The resistance profile of AZT-naive patients differed from that of AZT-experienced patients ( p <.05); viral load and CD4 counts were similar. The relative predictive ability (for subsequent viral load) of the resistance index was similar to or higher than that of baseline viral load or CD4 count. CONCLUSIONS: This assay used to detect AZT resistance could be adapted for use with other antiretrovirals. The predictive ability of the proposed resistance index was equal to or surpassed that of viral load and CD4 count, lending further support to the use of resistance assays in selecting drug regimens both before and during antiretroviral therapy.

Anti-HIV Agents↗
PubMed1991

Development and current status of USAF mental health screening.

Early detection and appropriate disposition of non-adaptable military recruits has been a concern of the military for many years. In the 1950s and 1960s, various branches of the military conducted large studies searching for accurate, cost-effective ways to predict which recruits could and could not adapt to military training. In the 1970s, research in this area spawned the development of the Air Force Medical Evaluation Test (AFMET), the three-phase mental health screening process used by the Air Force today. This article briefly reviews the development of AFMET, and presents current data supporting its utility and effectiveness.

Adaptation, Psychological↗