Search PubMed⌕ Search

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.

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

At least 1,243 records · Page 69Linked to original sources
PubMed1999

Testing alternative hypotheses for variation in amphipod behaviour and life history in relation to parasitism.

We tested two hypotheses concerning changes in investment in current reproduction for parasitised hosts, using amphipods (Corophium volutator) which act as second intermediate hosts for trematodes (Gynaecoyla aduncta). One hypothesis requires that parasites exert control over their hosts (parasite manipulation), whereas the other predicts that hosts control decisions over investment (adaptive host response). Although these hypotheses are viewed as mutually exclusive, our various results support both hypotheses. For example, female amphipods infected by late-stage larvae were often found crawling at times when predation by sandpipers (Calidris pusilla), which are the final hosts for trematodes, was likely, while uninfected females typically remained in their burrows. Furthermore, old females that were newly-infected by trematodes often aborted and ate their young. Both of these responses seem inconsistent with female investment in current reproduction, but can be interpreted as adaptive parasite manipulation. In contrast, young non-ovigerous females that were newly-infected hastened the onset of their parturial moult and thus, time to becoming receptive. This response can be explained as a host adaptation to minimise the cost of parasites. We contend that differences between parasitised and unparasitised hosts in behaviour or investment can be explained as both parasite and host adaptations, expressed at different times in the host's life history. Such compromise will help explain the persistence of parasite-host associations in nature.

Adaptation, Physiological↗
PubMed1983

Physical conditioning of children.

Exercise-induced changes in muscular and cardiovascular function in pre- and postpubescent children are explained in terms of a "Trigger Hypothesis." This hypothesis predicts that, prepubertally, there will be only small training-induced biological alterations because of the lack of hormonal control. It is suggested, therefore, that emphasis be placed on skill acquisition rather than physiological conditioning during prepuberty. Postpubertal exercise-induced changes are well documented and follow predictable patterns. The principles that govern physiological adaptations to exercise are discussed in terms of energy transfer and the factors that affect training. Duration, intensity, and frequency of performance are detailed. It is recommended that emphasis be placed on these factors when designing a physiologically sound physical training program.

Adaptation, Physiological↗
PubMed2000

Reversible associative depression and nonassociative potentiation at a parallel fiber synapse.

The electrosensory lobe (ELL) of mormyrid electric fish is one of several cerebellum-like sensory structures in fish that remove predictable features of the sensory inflow. This adaptive process obeys anti-Hebbian rules and appears to be mediated by associative depression at the synapses between parallel fibers and Purkinje-like cells of ELL. We show here that there is also a nonassociative potentiation at this synapse that depends only on the repeated occurrence of the EPSP. The depression can be reversed by the potentiation and vice versa. Finally, we show that the associative depression requires NMDA receptor activation, changes in postsynaptic calcium, and the occurrence of a postsynaptic dendritic spike within a few milliseconds following EPSP onset.

2-Amino-5-phosphonovalerate↗
PubMed2006

Profiling the near field of a plasmonic nanoparticle with Raman-based molecular rulers.

The enhanced local optical fields at the surface of illuminated metallic nanoparticles and nanostructures are of intense fundamental and technological interest. Here we report a self-consistent measurement of the spatial extent of the fringing field above a plasmonic nanoparticle surface. Bifunctional DNA-based adsorbate molecules are used as nanoscale optical rulers, providing two distinct surface enhanced Raman scattering signals that vary independently in intensity as a function of distance from the nanoparticle surface. While the measurement technique is calibrated on gold nanoshell surfaces with controlled and predictable electromagnetic nanoenvironments, this approach is broadly adaptable to a wide range of plasmonic geometries.

DNA↗
PubMed2006

Comparative evolutionary psychology of sperm competition.

A comparative evolutionary psychological perspective predicts that species that recurrently faced similar adaptive problems may have evolved similar psychological mechanisms to solve these problems. Sperm competition provides an arena in which to assess the heuristic value of such a comparative evolutionary perspective. The sperm competition that results from female infidelity and polyandry presents a similar class of adaptive problems for individuals across many species. The authors first describe mechanisms of sperm competition in insects and in birds. They suggest that the adaptive problems and evolved solutions in these species provide insight into human anatomy, physiology, psychology, and behavior. The authors then review recent theoretical and empirical arguments for the existence of sperm competition in humans and discuss proposed adaptations in humans that have analogs in insects or birds. The authors conclude by highlighting the heuristic value of a comparative evolutionary psychological approach in this field.

Animals↗
PubMed2006

Dyslexia and the failure to form a perceptual anchor.

In a large subgroup of dyslexic individuals (D-LDs), reading difficulties are part of a broader learning and language disability. Recent studies indicate that D-LDs perform poorly in many psychoacoustic tasks compared with individuals with normal reading ability. We found that D-LDs perform as well as normal readers in speech perception in noise and in a difficult tone comparison task. However, their performance did not improve when these same tasks were performed with a smaller stimulus set. In contrast to normal readers, they did not benefit from stimulus-specific repetitions, suggesting that they have difficulties forming perceptual anchors. These findings are inconsistent with previously suggested static models of dyslexia. Instead, we propose that D-LDs' core deficit is a general difficulty in dynamically constructing stimulus-specific predictions, deriving from deficient stimulus-specific adaptation mechanisms. This hypothesis provides a direct link between D-LDs' high-level difficulties and mechanisms at the level of specific neuronal circuits.

Adaptation, Psychological↗
PubMed2003

Cortical coordination dynamics and the disorganization syndrome in schizophrenia.

There has been a long history of investigation in the fields of neuropsychology and cognitive psychology into the question of functional integration in the brain. Each of the several dominant themes in that history can be interpreted as representing an important feature of a unitary general mechanism that integrates distributed processes in the cerebral cortex. This mechanism must allow local areas to function within the large-scale anatomical structure of the cortex so as to satisfy competing requirements for stability and flexibility. Each specialized cortical area must perform a unique role by expressing its own form of information, yet must have its performance constrained by interactions with other areas to which it is connected. In order to generate adaptive behavior within changing and not fully predictable environments, the cortex as a whole must be able to rapidly coordinate the activities of variable assemblages of areas that can collectively express consensual information that is appropriate for the functional requirements engendered by each successive stage of behavioral performance. This paper proposes that the phase synchronization of neuronal population activity from different cortical areas may serve a role in large-scale coordination. Theoretical studies suggest that the cortex normally operates in a metastable dynamic regime in which groups of areas are able to coordinate rapidly and reversibly their activities through changes in their degree of phase synchronization. A disruption of phase synchronization, leading to an excess of local information expression by cortical areas, is proposed as a contributing factor to the disorganization syndrome in schizophrenia.

Animals↗
PubMed2003

Evolution of the human hand: the role of throwing and clubbing.

It has been proposed that the hominid lineage began when a group of chimpanzee-like apes began to throw rocks and swing clubs at adversaries, and that this behaviour yielded reproductive advantages for millions of years, driving natural selection for improved throwing and clubbing prowess. This assertion leads to the prediction that the human hand should be adapted for throwing and clubbing, a topic that is explored in the following report. It is shown that the two fundamental human handgrips, first identified by J. R. Napier, and named by him the 'precision grip' and 'power grip', represent a throwing grip and a clubbing grip, thereby providing an evolutionary explanation for the two unique grips, and the extensive anatomical remodelling of the hand that made them possible. These results are supported by palaeoanthropological evidence.

Adaptation, Physiological↗
PubMed2002

Chromatographic isolation of methionine-containing peptides for gel-free proteome analysis: identification of more than 800 Escherichia coli proteins.

A novel gel-free proteomic technology was used to identify more than 800 proteins from 50 million Escherichia coli K12 cells in a single analysis. A peptide mixture is first obtained from a total unfractionated cell lysate, and only the methionine-containing peptides are isolated and identified by mass spectrometry and database searching. The sorting procedure is based on the concept of diagonal chromatography but adapted for highly complex mixtures. Statistical analysis predicts that we have identified more than 40% of the expressed proteome, including soluble and membrane-bound proteins. Next to highly abundant proteins, we also detected low copy number components such as the E. coli lactose operon repressor, illustrating the high dynamic range. The method is about 100 times more sensitive than two-dimensional gel-based methods and is fully automated. The strongest point, however, is the flexibility in the peptide sorting chemistry, which may target the technique toward quantitative proteomics of virtually every class of peptides containing modifiable amino acids, such as phosphopeptides, amino-terminal peptides, etc., adding a new dimension to future proteome research.

Algorithms↗
PubMed2001

Empirical links between achievement goal theory and self-determination theory in sport.

The aim of this study was to examine the empirical links between achievement goal theory and self-determination theory in sport. Addressing theoretical and methodological limitations of previous research, the study tested the independent and interactive effects of goal orientations and perceived competence on seven motivational variables with different degrees of self-determination. Regression analyses of data collected from 247 British university students showed that task orientation predicted motivational variables with high self-determination. In contrast, ego orientation predicted motivational variables with low self-determination. Perceived competence predicted both high self-determined and low self-determined motivational variables. A significant interaction emerged between task and ego orientations in predicting external regulation. The results suggest the adaptive role of task orientation in facilitating self-determined motivation in sport. However, the findings are not conclusive, as the variance explained in most analyses was relatively small. Suggestions are offered for a more comprehensive empirical testing of the links between the two theories.

Achievement↗
PubMed2006

Evaluation of a dual-arm Archimedean spiral array for microwave hyperthermia.

PURPOSE: This effort describes a third-party performance evaluation of a novel, commercial, dual-armed Archimedean spiral array hyperthermia applicator. The applicator is analysed for its ability to couple efficiently into muscle equivalent phantom loads, operate over a broad bandwidth to help accommodate variable tissue properties and generate predictable and repeatable SAR contours that are adaptable to clinically probable disease shapes. MATERIALS AND METHODS: Characterization of the applicator includes E-field and return-loss measurements in liquid muscle tissue-equivalent phantom, as well as comparison of 'treatment-planning' simulations of several possible array SAR patterns with measured SAR from non-coherently driven spiral array antennae. RESULTS: The applicator demonstrates a reasonably low return loss over a large bandwidth and the ability to generate a very uniform heating pattern. Ability to adjust SAR contours spatially to fit specific shapes is also demonstrated. CONCLUSIONS: This device should prove a welcome addition to a currently limited set of superficial heating applicators to provide controllable heating of superficial tissue disease.

Equipment Design↗
PubMed2000

Seed Germination in Desert Annuals: An Empirical Test of Adaptive Bet Hedging.

Temporal variability in survivorship and reproduction is predicted to affect the evolution of life-history characters. Desert annual plants experience temporal variation in reproductive success that is largely caused by precipitation variability. We studied several populations of the desert annual Plantago insularis along a precipitation gradient. Whereas models of bet hedging in unpredictable environments generally predict one optimal germination fraction for a population, empirical studies have shown that environmental conditions during germination can cause a range of germination fractions to be expressed. In a 4-yr field study, we found that populations in historically more xeric environments had lower mean germination fractions, as is predicted by bet-hedging models. However, populations exhibited significant variation in germination among years. Two experimental studies measuring germination under several environment conditions were conducted to elucidate the source of this in situ variation. Germination fractions exhibited phenotypic plasticity in response to water availability and date within the season. Populations differed in their norms of reaction such that seeds from more xeric populations germinated under less restrictive conditions. A pattern of delayed germination consistent with among-year bet-hedging predictions arose in the field through the interaction of seed germinability and the distribution of environmental conditions during germination.

bet hedging↗
PubMed2005

Frontal and temporal morphometric findings on MRI in children after moderate to severe traumatic brain injury.

In vivo MRI volumetric analysis enables investigators to evaluate the extent of tissue loss following traumatic brain injury (TBI). However, volumetric studies of pediatric TBI are sparse, and there have been no volumetric studies to date in children examining specific subregions of the prefrontal and temporal lobes. In this study, MRI volumetry was used to evaluate brain volume differences in the whole brain, and prefrontal, temporal, and posterior regions of children following moderate to severe TBI as compared to uninjured children of similar age and demographic characteristics. The TBI group had significantly reduced whole brain, and prefrontal and temporal regional tissue volumes as well as increased cerebrospinal fluid (CSF). Confidence interval testing further revealed group differences on gray matter (GM) and white matter (WM) in the superior medial and ventromedial prefrontal regions, WM in the lateral frontal region, and GM, WM, and CSF in the temporal region. Whole brain volume and total brain GM were reduced, and total ventricular volume, total CSF volume, and ventricle-to-brain ratio (VBR) were increased in the TBI group. Additional analyses comparing volumetric data from typically developing children and subgroups of TBI patients with and without regional focal lesions suggested that GM loss in the frontal areas was primarily attributable to focal injury, while WM loss in the frontal and temporal lobes was related to both diffuse and focal injury. Finally, volumetric measures of preserved frontotemporal tissue were related to functional recovery as measured by the Glasgow Outcome Scale (adapted for children) with greater tissue preservation predicting better recovery.

Adolescent↗
PubMed2026

Identification and Classification of Expressed Orphan Genes, Spurious Orphan Genes, and Conserved Genes in the Human Gut Microbiome.

Orphan genes (OGs)-genes lacking detectable homologs outside a species-are widespread in microbial genomes and are thought to contribute to their adaptation and molecular innovation. However, not all predicted OGs may represent novel functional coding sequences. False positive OGs, also called spurious OGs, can arise from gene prediction errors. We reason that OGs lacking detectable expression are more likely to be spurious. To test this, we combined large-scale metatranscriptomic profiling of the human gut microbiome with machine learning to distinguish expressed OGs from spurious ones and compare them with conserved genes (CGs) found in multiple species. Using nearly 5,000 metatranscriptome libraries, we identified ∼218,000 OGs supported by expression evidence, while ∼330,000 predicted OGs lacked detectable expression and were classified as spurious. We extracted 154 features for sequence, structural, and evolutionary properties for each gene and trained XGBoost classifiers while accounting for genomic representation. The models achieved an area under the receiver operating characteristic curve (AUC) of 0.82 in distinguishing expressed OGs from spurious OGs and an AUC of 0.93 in distinguishing expressed OGs from CGs. Interpretation based on SHAP (SHapley Additive exPlanations) revealed clear biological signals. Particularly, expressed orphans were present in more genomes than spurious ones, and expressed OGs were shorter than CGs. This work improves OG discovery and suggests that expressed OGs differ systematically from CGs and spurious OGs in sequence composition, structural constraints, and evolutionary signals.

Humans↗
PubMed1996

Recent advances regarding attention deficit-hyperactivity disorder in adolescence.

This paper reviews recent studies of attention deficit-hyperactivity disorder, focusing on research with implications for adolescents. Only 10 of the 31 recent investigations discussed employed an exclusively adolescent sample, necessitating considerable extrapolation from studies of children or adults or mixed samples with a wide range of ages. Significant advances include increased accuracy of predicting negative outcomes and the identification of adaptive skill dysfunction. Further information has become available on the long-term impact of attention deficit-hyperactivity disorder, and additional data have been reported on risk factors. Other reports have described typical services provided by pediatric and family medicine practices for attention deficit-hyperactivity disorder; beneficial effects of combined behavioral and pharmacologic treatment; absence of adverse effects of methylphenidate on cognitive constriction or tics; and disappointing results for nonstimulant pharmacotherapy. A National Institute of Mental Health multisite treatment study has recently been initiated.

Adolescent↗
PubMed2006

Triplet ultrasound growth parameters.

OBJECTIVE: To create ultrasound growth curves for normal growth of fetal triplets using statistical methodology that properly accounts for similarities of growth of fetuses within a mother as well as repeated measurements over time for each fetus. METHODS: In this longitudinal study, all triplet pregnancies managed at a single tertiary center from 1992-2004 were reviewed. Fetuses with major anomalies, prior selective reduction, or fetal demise were excluded. Data from early and late gestation in which there were fewer than 30 fetal measurements available for analysis were excluded. We used multilevel models to account for variation in growth within a single fetus over time, variations in growth between multiple fetuses within a single mother, and variations in fetal growth between mothers. Medians (50th), 10th, and 90th percentiles were estimated by the creation of multiple quadratic growth models from bootstrap samples adapting a previously published method to compute prediction intervals. Estimated fetal weight was derived from Hadlock's formula. RESULTS: One hundred fifty triplet pregnancies were identified. Twenty-seven pregnancies were excluded for the following reasons: missing records (23), fetal demise (3), and fetal anomaly (1). The study group consisted of 123 pregnancies. The gestational age range was restricted to 14-34 weeks. Figures and tables were developed showing medians, 10th and 90th percentiles for estimated fetal weight, femur length, biparietal diameter, abdominal circumference, and head circumference. CONCLUSION: Growth curves for triplet pregnancies were derived. These may be useful for identification of abnormal growth in triplet fetuses. LEVEL OF EVIDENCE: III.

Anthropometry↗
PubMed1980

Effects of Chromatic Adaptation on the Photochemical Apparatus of Photosynthesis in Porphyridium cruentum.

Cells of Porphyridium cruentum were grown in different colors of light which would be absorbed primarily by chlorophyll (Chl) (red and blue light) or by the phycobilisomes (green or two intensities of cool-white fluorescent light), and samples of these cells were frozen to -196 C for measurements of absorption and fluorescence emission spectra. Cells grown in the high intensity white light had least of all of the photosynthetic pigments, a higher ratio of carotenoid/Chl, but essentially the same ratio of phycobilin to Chl as cells grown in the low intensity white light. The ratio of photosystem II (PSII) to photosystem I (PSI) pigments was affected by light quality; the ratios of phycobilin to Chl and of short wavelength (PSII) Chl to long wavelength (PSI) Chl were both greater in the cells grown in red or blue light.Light quality also exerted a strong influence on the structural and functional organization of the photochemical apparatus. Data on the relative optical cross-sections of PSI and PSII as a function of excitation wavelength indicate that cells grown in light absorbed primarily by the phycobilisomes package a large fraction of their Chl into PSI (PSI Chl/PSII Chl approximately 20), whereas cells grown in light absorbed by Chl distribute their Chl much more equitably (PSI Chl/PSII Chl approximately 1.5). In both types of cells the phycobilisomes transfer their excitation energy predominantly to PSII Chl with little or no direct energy transfer to PSI, but the yield of energy transfer from PSII to PSI is approximately twice as large for cells grown in the phycobilin wavelengths of light. These differences in functional organization and energy distribution account for the physiological expressions of chromatic adaptation. The effects of chromatic adaptation on O(2) evolution can be predicted from our calculations of energy distribution between PSI and PSII for cells grown in the different colors of light.

Journal Article↗
PubMed2004

Ecological and life history characteristics predict population genetic divergence of two salmonids in the same landscape.

Ecological and life history characteristics such as population size, dispersal pattern, and mating system mediate the influence of genetic drift and gene flow on population subdivision. Bull trout (Salvelinus confluentus) and mountain whitefish (Prosopium williamsoni) differ markedly in spawning location, population size and mating system. Based on these differences, we predicted that bull trout would have reduced genetic variation within and greater differentiation among populations compared with mountain whitefish. To test this hypothesis, we used microsatellite markers to determine patterns of genetic divergence for each species in the Clark Fork River, Montana, USA. As predicted, bull trout had a much greater proportion of genetic variation partitioned among populations than mountain whitefish. Among all sites, FST was seven times greater for bull trout (FST = 0.304 for bull trout, 0.042 for mountain whitefish. After removing genetically differentiated high mountain lake sites for each species FST, was 10 times greater for bull trout (FST = 0.176 for bull trout; FST = 0.018 for mountain whitefish). The same characteristics that affect dispersal patterns in these species also lead to predictions about the amount and scale of adaptive divergence among populations. We provide a theoretical framework that incorporates variation in ecological and life history factors, neutral divergence, and adaptive divergence to interpret how neutral and adaptive divergence might be correlates of ecological and life history factors.

Animals↗