SEARCH · Search PubMed

Results for “predictability of adaptation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,711 records · Page 95Linked to original sources

PubMed2002

When feeling is more important than seeing in sensorimotor adaptation.

Perception and action are based on information from multiple sensory modalities. For instance, both vision and proprioception provide information about hand position, and this information is integrated to generate a single estimate of where the hand is in space. Classically, vision has been thought to dominate this process, with the estimate of hand position relying more on vision than on proprioception. However, an optimal integration model that takes into account the precision of vision and proprioception predicts that the weighting of the two senses varies with direction and that the classical result should only hold for specific spatial directions. Using an adaptation paradigm, we show that, as predicted by this model, the visual-proprioceptive integration varies with direction. Variation with direction was so strong that, in the depth direction, the classical result was reversed: the estimate relies more on proprioception than on vision. These results provide evidence for statistically optimal integration of information from multiple modalities.

Adaptation, Physiological↗

PubMed2003

Situational insomnia: consistency, predictors, and outcomes.

STUDY OBJECTIVES: The purpose of this study was to determine the consistency of situational insomnia across several stressful conditions, including the first night in the sleep laboratory, phase advance of sleep time by 3 hours, phase advance of sleep time by 6 hours, and administration of 400 mg of caffeine. The impact of situational insomnia on alertness, metabolic rate, and cardiac measures on the following day was also measured. DESIGN AND SETTING: Subjects spent 5 to 7 nights and the following days in the laboratory. Standard polysomnographic recordings were made on each night. On each day, subjects had a Multiple Sleep Latency Test, performance testing, and metabolic and heart-rate observation periods. PARTICIPANTS: Fifty adult normal sleepers. INTERVENTIONS: Subjects had 1 night with their sleep phase advanced by 3 hours, 1 night with sleep phase advanced by 6 hours, and 1 night with the administration of 400 mg of caffeine 30 minutes prior to lights out. MEASUREMENT AND RESULTS: Sleep efficiency was reduced and variability was increased in each of the stressful conditions, as predicted. Those subjects with the greatest sleep efficiency on the adaptation night (top 25%) were compared with those subjects with the lowest sleep efficiency on the adaptation night (bottom 25%). Those subjects with the poorest sleep on the adaptation night (situational insomnia) had normal sleep on the baseline night that followed but had significantly reduced sleep efficiency when their sleep was advanced or they were given caffeine. Those same subjects had a significant decrease on their Multiple Sleep Latency Test on the day following the 6-hour advance and a significant increase in their Multiple Sleep Latency Test on the day following caffeine administration. The good sleepers had no significant change in their Multiple Sleep Latency Test during any of the study conditions. In terms of demographic variables, the situational insomnia group used less alcohol and tended to include a higher percentage of men. The situational insomnia group also had an elevated heart rate and increased low-frequency and decreased high-frequency electrocardiographic spectral power compared to the good sleepers. Significant differences were not found on personality or historical reports of poor sleep. CONCLUSIONS: Normal young adults have a consistent response to various types of situational stress. Those individuals who respond with poor sleep may display increased sleepiness associated with their poor sleep but may also be more sensitive to the effects of caffeine. These individuals have cardiac changes consistent with sympathetic nervous system activation, and they may be at risk for developing insomnia and other associated disorders.

Adult↗

PubMed2004

Multicellular simulation predicts microvascular patterning and in silico tissue assembly.

Remodeling of microvascular networks in mammals is critical for physiological adaptations and therapeutic revascularization. Cellular behaviors such as proliferation, differentiation, and migration are coordinated in these remodeling events via combinations of biochemical and biomechanical signals. We developed a cellular automata (CA) computational simulation that integrates epigenetic stimuli, molecular signals, and cellular behaviors to predict microvascular network patterning events. Over 50 rules obtained from published experimental data govern independent behaviors (including proliferation, differentiation, and migration) of thousands of interacting cells and diffusible growth factors in their tissue environment. From initial network patterns of in vivo blood vessel networks, the model predicts emergent patterning responses to two stimuli: 1) network-wide changes in hemodynamic mechanical stresses, and 2) exogenous focal delivery of an angiogenic growth factor. The CA model predicts comparable increases in vascular density (370+/-29 mm/mm3) 14 days after treatment with exogenous growth factor to that in vivo (480+/-41 mm/mm3) and approximately a twofold increase in contractile vessel lengths 5-10 days after 10% increase in circumferential wall strain, consistent with in vivo results. The CA simulation was thus able to identify a functional patterning module capable of quantitatively predicting vessel network remodeling in response to two important epigenetic stimuli.

Cell Differentiation↗

PubMed2006

Modelling external bone adaptation using evolutionary structural optimisation.

External remodelling is significant in the bone healing process, and it is essential to predict the bone external shape in the design of artificial bone grafts. This paper demonstrates the effectiveness of the evolutionary structural optimisation (ESO) method for the simulation of bone morphology. A two-dimensional ESO strategy is developed which is capable of finding the modified bone topology beginning with any geometry under any loading conditions. The morphology of bone structure is described by the quantitative bone adaptation theory, which is integrated with the finite element method. The evolutionary topology optimisation process is introduced to find the bone shape. A rectangle, which occupies a larger space than the external shape of the bone structure, is specified as a design domain; the evolutionary process iteratively eliminates and redistributes material throughout the domain to obtain an optimum arrangement of bone materials. The technique has been tested on a wide range of examples. In this paper, the formation of trabecular bone architecture around an implant is studied; as another example, the growth of the coronal section of a vertebral body is predicted. The examples support the assertion that the external shape of bone structure can be successfully predicted by the proposed ESO procedure.

Adaptation, Physiological↗

PubMed2004

Experimental evaluation of lesion prediction modelling in the presence of cavitation bubbles: intended for high-intensity focused ultrasound prostate treatment.

The accuracy of high-intensity focused ultrasound (HIFU) lesion prediction modelling was evaluated for a truncated spherical transducer designed for prostate cancer treatment The modelling adapted the bio heat transfer equation (BHTE) to take into account the activity of cavitation bubbles generated during HIFU exposure. This modelling was used to predict the lesions produced by three different transducer geometries: fixed-focus, concentric-ring and 1.5D phased-array. Lesions were predicted for different ultrasound exposure conditions close to those used in prostate cancer treatment. Twenty-one in vitro and nine in vitro experiments were performed on pig liver to validate the accuracy of the predictions. A good match was found between the predicted and experimental lesion shapes. Lesion dimensions (maximum depth and length, area at the centre of the lesion or central surface area) were measured on experimental and predicted lesions. The central surface area was predicted by the model with a range of error of 0.15-6.5% for in vitro tests and 0.97-9% in vivo. For comparison, BHTE without bubbles had a range of error of 0.4-55.5% (in vitro) and 9-25.5% (in vivo). The model should be accurate enough to predict HIFU lesions under ultrasound exposure conditions used in prostate cancer treatment.

Acoustics↗

PubMed1997

Determinants of regular source of care among homeless adults in Los Angeles.

OBJECTIVES: The authors explore the determinants of having a regular source of care in a community-based probability sample of homeless adults in Los Angeles. Results from this study should be more representative than those from previous studies of the homeless that are clinic- or shelter-based. In addition to those factors found to be barriers to regular sources of care in the general population, we hypothesized that psychosocial characteristics of the homeless and the homeless lifestyle would negatively impact their likelihood of having a regular source of care. METHODS: The authors conducted a multiple logistic regression to predict regular source of care among the homeless, using an adaptation of the Behavioral Model of health services utilization as an analytic framework. RESULTS: Fifty-seven percent of the sample reported that they had a regular source of care. Of those with a source of care, 30% reported a hospital outpatient department; 25% reported a community or homeless clinic; 23% reported a hospital emergency room; 14% reported a government clinic; and 9% reported a private physician's office as their source of care. Some factors found to be barriers to having a regular source of care in the general population (male, Hispanic, young age) also were barriers among homeless adults. Additional barriers in this sample included homelessness-related characteristics such as competing needs, long-term homelessness, and social isolation. Chronic mental illness and chronic substance dependence were not related to having a source of care among the homeless. Characteristics that increased the likelihood of having a regular source of care in the general population (poor health status, Medicaid) were not related to having a regular source of care among the homeless. CONCLUSIONS: In a context of limited resources, the distribution of regular source of care among the homeless appears to be highly inequitable. Although some of the characteristics identifying those with a regular source of care suggest differential patterns of behavior across subgroups, others suggest differential advantage in access to care and a lack of fit between the needs of the homeless and the organization of health services.

Adolescent↗

PubMed2000

Developments of the Price equation and natural selection under uncertainty.

Many approaches to the study of adaptation, following Darwin, centre on the number of offspring of individuals. Population genetics theory makes clear that predicting gene frequency changes requires more detailed knowledge, for example of linkage and linkage disequilibrium and mating systems. Because gene frequency changes underlie adaptation, this can lead to a suspicion that approaches ignoring these sophistications are approximate or tentative or wrong. Stochastic environments and sexual selection are two topics in which there are widespread views that focusing on number of offspring of individuals is not enough, and that proper treatments require the introduction of further details, namely variability in offspring number and linkage disequilibrium, respectively. However, the bulk of empirical research on adaptation and a great deal of theoretical work continue to employ these approaches. Here, a new theoretical development arising from the Price equation provides a formal justification in very general circumstances for focusing on the arithmetic average of the relative number of offspring of individuals.

Adaptation, Biological↗

PubMed1989

A study of behavioural responses to an industrial disaster.

Based upon 7 response variables we categorized the impact behaviour of 123 industrial employees who had been exposed to a disastrous factory explosion and had survived without suffering severe injuries. The subjects were personally examined and the data controlled by cross-interviews shortly after the disaster. In the analysis the subjects were divided into a high stress (n = 64) and a medium stress exposure group (n = 59) based upon their closeness to the explosion centre. The 7 variables were cognitive function, inadequate behaviour, help received, leadership, cooperative activity, absolute and relative rescue efforts. While about 50% of the total number reported some disturbance in their cognitive control, and 34% of the high stress exposure group experienced a near total loss of cognitive control, severe inadequate behaviour did not occur. Modelling and corrective social interactions may have played an important role in this. Still, 20% of the high stress exposure group had some behavioural response that increased the risk to their life or that of others. The 7 scores were added to an index and cut-off points established to separate 3 different groups of behavioural responses: 29% of the high stress group displayed Maladaptive Disaster Behaviour; inhibited behaviour and uncontrolled flight behaviour dominated in this group. Adaptive Disaster Behaviour was rated in 34% and Optimal Disaster Behaviour in 37%. The following background variables correlated strongly to Optimal Disaster Behaviour: high level of disaster training/experience, male sex, age above 40, maritime occupational background, above average intellectual ability, a life history without mental health problems. A discriminant analysis with 8 variables predicted correctly whether the response would be Optimal or less than that in 84% of the 121 subjects tested in the analysis. A high level of disaster training/experience yielded an overall correct prediction rate of 63.6%, and a sensitivity of 81%, specificity of 85.9% and positive predictive power of 70.7% in predicting Optimal Disaster Behaviour.

Accidents, Occupational↗

PubMed1998

Role of neurosympathetic pathways in the vascular response to sepsis.

PURPOSE: The aim of this study was to determine the role of sympathetic neural activity in the hemodynamic adaptations to sepsis in pigs with an emphasis on circuit adaptations. A fall in resistance to venous return (RVR) was predicted in contrast to what was previously observed in sympathetically intact animals that had no change in RVR. MATERIALS AND METHODS: We anesthetized and ventilated 13 pigs and gave 5 mg/kg of indomethacin. We measured cardiac output (CO) by thermodilution and measured pulmonary arterial (PAP), pulmonary capillary wedge (Pcw), right atrial pressure (Pra), and arterial pressure (MAP). Intermittent inflation of a 50-mL balloon in the right atrium was used to transiently arrest the circulation for the measurement of mean circulatory filling pressure (MCFP). RVR was calculated from (MCFP - Pra)/CO. Animals were divided into two groups; 6 received 10 mg/kg of the ganglionic blocker, hexamethonium and norepinephrine to maintain MAP; 7 had their spinal cords cut at C-2. After baseline measurements, all animals received 10 microg/kg/h of endotoxin for 2 hours, and hemodynamic measurements were repeated. Plasma samples were obtained for measurements of immunoreactive endothelin-1 (ET-1), which was assayed by a radioimmunoassay. RESULTS: Hexamethonium had no significant effect on hemodynamics except for an increase in heart rate. After endotoxin, MAP and SVR fell, PAP rose, and CO and RVR did not change. Spinal section resulted in an increase in heart rate and small increase in PAP and MCFR After endotoxin, there was a further increase in heart rate, PAP, and MCFP with a marked fall in MAP and CO. RVR increased from 2.1 +/- 0.46 after spinal section to 3.6 +/- 54 mm x min/L (P < .05). ET-1 in the hexamethonium group (n = 2) rose from 2.21 +/- .14 to 11.5 +/- 2.1 pg/ml at 2 hours, and in the spinal group (n = 7) from 2.04 +/- 0.77 to 6.85 +/- 3.9 pg/mL at 45 minutes. CONCLUSION: Spinal section resulted in a more profound fall in blood pressure and less increase in MCFP than in previously studied animals with sympathetic nervous system intact, but there was still an increase in RVR and PAP ET-1 is a possible mediator of the increase in RVR and PAP.

Adaptation, Physiological↗

PubMed1999

Prediction of the risk of bleeding during anticoagulant treatment for venous thromboembolism.

OBJECTIVES: To construct and validate the bleeding risk prediction score, which is based on variables identified in the literature that can be easily obtained before the institution of anticoagulant therapy, in a large independent cohort of patients who were treated with anticoagulant therapy for established venous thromboembolism to allow for quantitative assessment of the risks and benefits of the therapy and to adapt the patient's management accordingly. METHODS: We constructed a bleeding risk prediction score, based on variables and their odds ratios identified in the literature, which can be easily obtained before the institution of anticoagulant therapy (score = [ 1.6 X age] + [1.3 x sex] + [2.2 X malignancy]). Subsequently, we evaluated the score in a test group of 241 patients treated with anticoagulant therapy for venous thromboembolism to determine the optimal cutoff points for the prediction of hemorrhagic complications, using receiver operating characteristic curve analysis. We then validated this score in an independent cohort of 780 patients. A score of 3 or more points, 1 to 3 points, or 0 points represented a high, intermediate, or low bleeding risk, respectively. RESULTS: The score in about one fifth of the patients in the test group was classified as predicting high risk for bleeding complications. The risk of all bleeding complications was 26% in this group and the risk of major bleeding complications was 14%. The area under the curve was 0.75 (95% confidence interval, 0.64-0.84) and 0.82 (95% confidence interval, 0.66-0.98) for all bleeding complications and major bleeding complications, respectively. When validated, there was a moderate loss of predictive power of the score, but the categorization of the patients by the score remained clinically useful; 20% of the patients were classified as high risk, and the bleeding rate was 17% for all bleeding complications and 7% for major bleeding complications compared with 4% and 1%, respectively, in those categorized as low risk. CONCLUSIONS: With the use of 3 easily obtainable, clinical variables in a prediction model, it is possible to identify a subgroup of patients at the start of anticoagulant therapy who have a high risk of developing hemorrhagic complications. Further studies should address whether additional measures to prevent bleeding decrease the bleeding incidence without compromising efficacy.

Anticoagulants↗

PubMed2006

From optimization to adaptation: shifting paradigms in environmental management and their application to remedial decisions.

Current uncertainties in our understanding of ecosystems require shifting from optimization-based management to an adaptive management paradigm. Risk managers routinely make suboptimal decisions because they are forced to predict environmental response to different management policies in the face of complex environmental challenges, changing environmental conditions, and even changing social priorities. Rather than force risk managers to make single suboptimal management choices, adaptive management explicitly acknowledges the uncertainties at the time of the decision, providing mechanisms to design and institute a set of more flexible alternatives that can be monitored to gain information and reduce the uncertainties associated with future management decisions. Although adaptive management concepts were introduced more than 20 y ago, their implementation has often been limited or piecemeal, especially in remedial decision making. We believe that viable tools exist for using adaptive management more fully. In this commentary, we propose that an adaptive management approach combined with multicriteria decision analysis techniques would result in a more efficient management decision-making process as well as more effective environmental management strategies. A preliminary framework combining the 2 concepts is proposed for future testing and discussion.

Conservation of Natural Resources↗

PubMed1995

Psychological sex differences. Origins through sexual selection.

Men and women clearly differ in some psychological domains. A. H. Eagly (1995) shows that these differences are not artifactual or unstable. Ideally, the next scientific step is to develop a cogent explanatory framework for understanding why the sexes differ in some psychological domains and not in others and for generating accurate predictions about sex differences as yet undiscovered. This article offers a brief outline of an explanatory framework for psychological sex differences--one that is anchored in the new theoretical paradigm of evolutionary psychology. Men and women differ, in this view, in domains in which they have faced different adaptive problems over human evolutionary history. In all other domains, the sexes are predicted to be psychologically similar. Evolutionary psychology jettisons the false dichotomy between biology and environment and provides a powerful metatheory of why sex differences exist, where they exist, and in what contexts they are expressed (D. M. Buss, 1995).

Adaptation, Psychological↗

PubMed2005

Accelerating perfusion process optimization by scanning non-steady-state responses.

Perfusion processes provide consistent culture conditions, high productivity and low product residence times. However, process development can be slow due to the 1 week or more required to reach each steady state. The objective of this work was to accelerate process development in perfusion cultures by scanning non-steady-state transient responses to qualitatively predict steady-state performance. The method was tested using a shift in temperature every 3 days, scanned down by steps of 2 degrees C from 37 degrees C to 31 degrees C, then scanned up to 37 degrees C. Higher t-PA concentrations were predicted at lower temperatures, confirmed by subsequent pseudo-steady-state results. In most cases, transient values on the 3rd day were in close concordance with pseudo-steady-state values. To further accelerate process development, transient scanning was applied to small-scale, non-instrumented cultures. Similar results were obtained, although quantitative t-PA values were 15-30 times lower than in high cell density perfusion cultures. The method was further explored by investigating 1 day transient shifts in temperature where more variability was observed, suggesting that the cells were still adapting to the new environment. Nonetheless, the overall response again qualitatively predicted the pseudo-steady-state temperature response. Use of transient scanning in conjunction with pseudo-steady-state verification and refinement of optimal results could reduce process development time to a third or less of comparable steady-state-based optimization.

Animals↗

PubMed2004

Local co-adaptation leading to a geographical mosaic of coevolution in a social parasite system.

The geographical mosaic theory of coevolution predicts differences in the advance or trajectory of the coevolutionary process between local communities due to their composition and the strength of ecological selection pressures through competition and resource availability. In this study, we investigate local co-adaptation in different populations of a social parasite. We conducted cross-fostering experiments to test for interpopulational differences in raiding efficiency between various populations of a slave-making ant and the defence abilities of local hosts. Here, we demonstrate that the success of raids strongly depends on the combination of populations of the parasite Harpagoxenus sublaevis and its host Leptothorax acervorum, indicating very localized coevolution. We found no absolute differences between slave-maker populations; the outcome of an encounter depended more on whether the two opponents occur in sympatry or allopatry. Furthermore, this study supports the results of our earlier work, that the unparasitized English L. acervorum population is most aggressive against the parasite.

Adaptation, Biological↗

PubMed1984

Virulence of two strains of Cowdria ruminantium in mice and their use to predict drug activity against heartwater.

A study was made of the infectivity of two mouse-adapted strains of Cowdria ruminantium in mice. The Kwanyanga strain was most virulent in Balb/C mice which died nine days after infection with homogenate of liver from infected mice. CD-1 mice were least susceptible of six strains tested. The du Plessis strain of C. ruminantium was equally virulent in all six mouse strains. The du Plessis strain in CD-1 mice was used as the basis of a drug screen to detect activity against heartwater (C. ruminantium infection) and was highly predictive when active compounds were tested in sheep infected with the Ball 3 strain of C. ruminantium.

Animals↗

PubMed2003

Constraints on the conformation of the cytoplasmic face of dark-adapted and light-excited rhodopsin inferred from antirhodopsin antibody imprints.

Rhodopsin is the best-understood member of the large G protein-coupled receptor (GPCR) superfamily. The G-protein amplification cascade is triggered by poorly understood light-induced conformational changes in rhodopsin that are homologous to changes caused by agonists in other GPCRs. We have applied the "antibody imprint" method to light-activated rhodopsin in native membranes by using nine monoclonal antibodies (mAbs) against aqueous faces of rhodopsin. Epitopes recognized by these mAbs were found by selection from random peptide libraries displayed on phage. A new computer algorithm, FINDMAP, was used to map the epitopes to discontinuous segments of rhodopsin that are distant in the primary sequence but are in close spatial proximity in the structure. The proximity of a segment of the N-terminal and the loop between helices VI and VIII found by FINDMAP is consistent with the X-ray structure of the dark-adapted rhodopsin. Epitopes to the cytoplasmic face segregated into two classes with different predicted spatial proximities of protein segments that correlate with different preferences of the antibodies for stabilizing the metarhodopsin I or metarhodopsin II conformations of light-excited rhodopsin. Epitopes of antibodies that stabilize metarhodopsin II indicate conformational changes from dark-adapted rhodopsin, including rearrangements of the C-terminal tail and altered exposure of the cytoplasmic end of helix VI, a portion of the C-3 loop, and helix VIII. As additional antibodies are subjected to antibody imprinting, this approach should provide increasingly detailed information on the conformation of light-excited rhodopsin and be applicable to structural studies of other challenging protein targets.

Algorithms↗

PubMed1978

Anticipatory HR deceleration as a function of perceived control and probability of aversive loud noise: a deployment of attention account.

Five groups of 10 undergraduate subjects each participated in an experiment to examine the effects of perceived control over, and the probability of occurrence of, noxious (white-noise) stimulation on anticipatory heart rate (HR) deceleration. All groups performed an arithmetic task, the numbers for which were changed on each of the 20 trials, but three groups were defined as active groups since they were instructed that the occurrence of noxious stimulation was contingent upon their performance on the task. The actual probability of occurrence of noxious stimulation (i.e., either 0.9, 0.5 or 0.1) was manipulated between these three groups. A fourth (passive) group (0.5 probability of occurrence) was instructed as to the non-contingent relationship between performance and the aversive white noise. The last group was a control group which only performed the task, and thus both provided an estimate of the rate of return to baseline following the expected HR acceleration to the task and eliminated the need for a within-subject control period to assess HR deceleration. The results indicated that all active and passive groups produced significant HR decelerations, relative to the control group, prior to the noxious stimulus. However, all active groups (regardless of probability levels) displayed significantly greater, and required more trials to maximally develop, anticipatory deceleration than the passive group. In addition, the results for the active groups revealed a direct relationship between the probability of occurrence of noxious stimulation and the magnitude of anticipatory deceleration. It is argued that the results cannot be adequately accommodated by the preparatory-adaptive-response theory. A deployment-of-attention account is suggested since it appears both to account for the obtained pattern of results completely and to generate additional testable predictions for the future.

Adaptation, Psychological↗

PubMed1996

[Prediction of therapeutic response in depressive states].

Predicting the clinical improvement of patients with antidepressant drugs, at an early stage and in a individualistic manner, allows to choose the product which is most adapted to each case and to avoid leaving patients under an inefficient medication for several weeks. Predictability studies have multiplied. A general review of these studies is made here by examining the clinical, biological, electrophysiological, and finally the pharmacokinetic predictors. Clinical predictors have a practical use as they define certain clinical types of depression which best respond to antidepressants specific to a monoaminergic axis. It has been shown that a complete absence of symptomatic improvement after two weeks of treatment predicts the inefficacy of the treatment. Inversely, to this day, none of the biological predictors lead to a practical application during the treatment of patients, but they allow a better understanding of the antidepressants' mode of action. Finally, the elaboration of pharmacokinetic equations define for each patient the doses that allow to determine the therapeutic zones when these have been recognized.

Antidepressive Agents, Tricyclic↗