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PubMed2006

Rapid adaptive divergence of life-history traits in response to abiotic stress within a natural population of a parthenogenetic nematode.

Sexual reproduction is acknowledged to facilitate adaptation to novel environments while asexual eukaryotes are often regarded as having low adaptive potential. This view has been challenged in a number of studies, but the adaptive potential of asexual populations in the field is poorly documented. We investigated the response of natural populations of the parthenogenetic nematode Acrobeloides nanus to imposed divergent selective pressures. For this purpose, we employed a replicated evolution experiment in the field. After 20 years of evolution under abiotic stress and control conditions, life-history traits were assessed in reaction norm- and reciprocal transplant experiments. Both these experiments indicated adaptive divergence within the population of A. nanus. Namely, the transplant experiment demonstrated that in the stressed soil environment, body growth rate was more reduced in the nematodes originating from the control treatment. In the reaction norm experiment, survival and reproduction were higher under test conditions corresponding to the native environment of the nematodes. The differences in the analysed traits are discussed in the context of life-history theory. Overall, our results strongly support high adaptive potential of A. nanus and suggest that population structure and distribution of asexual species is shaped by local adaptation events.

Adaptation, Physiological↗
PubMed2000

Light-adaptive role of nitric oxide in the outer retina of lower vertebrates: a brief review.

The role of nitric oxide (NO) as a novel neurochemical mechanism controlling light adaptation of the outer retina is discussed by considering mainly published results. The emphasis is on the retinae of fishes and amphibia, but some data from the mammalian (rabbit) retinae have also been included for completeness. In the fish retina, application of NO donors in the dark caused light-adaptive photomechanical movements of cones. The normal effect of light adaptation in inducing cone contractions was suppressed by pretreatment of retinae with an NO scavenger. NO donors modulated horizontal cell activity by uncoupling the cells' lateral gap junctional interconnections and enhancing negative feedback to cones, again consistent with a light-adaptive role of NO. Direct evidence for light adaptation-induced release of NO has been obtained in fish (carp) and rabbit retinae. The results strongly suggest that control of retinal light adaptation is, under multiple neurochemical control, with NO and dopamine having an interactive role.

Adaptation, Physiological↗
PubMed2000

Comparative analyses for adaptive radiations.

Biologists generally agree that most morphological variation between closely related species is adaptive. The most common method of comparative analysis to test for co-evolved character variation is based on a Brownian-motion model of character evolution. If we are to test for the evolution of character-covariation, and we believe that characters have evolved adaptively to fill niches during an adaptive radiation, then it is appropriate to employ appropriate models for character evolution. We show here that under several models of adaptive character evolution and coevolution during an adaptive radiation, which result in closely related species being more similar to each other than to more distantly related species, cross-species analyses are statistically more appropriate than contrast analyses. If the evolution of some traits fits the Brownian-motion model, while others evolve to fill niches during an adaptive radiation, it might be necessary to identify the number of relevant niche dimensions and the modes of character evolution before deciding on appropriate statistical procedures. Alternatively, maximum-likelihood procedures might be used to determine appropriate transformations of phylogenetic branch lengths that accord with particular models of character evolution.

Adaptation, Physiological↗
PubMedDate not supplied

Rapid adaptation to auditory-visual spatial disparity.

The so-called ventriloquism aftereffect is a remarkable example of rapid adaptative changes in spatial localization caused by visual stimuli. After exposure to a consistent spatial disparity of auditory and visual stimuli, localization of sound sources is systematically shifted to correct for the deviation of the sound from visual positions during the previous adaptation period. In the present study, this aftereffect was induced by presenting, within 17 min, 1800 repetitive noise or pure-tone bursts in combination with synchronized, and 20 degrees disparate flashing light spots, in total darkness. Post-adaptive sound localization, measured by a method of manual pointing, was significantly shifted 2.4 degrees (noise), 3.1 degrees (1 kHz tones), or 5.8 degrees (4 kHz tones) compared with the pre-adaptation condition. There was no transfer across frequencies; that is, shifts in localization were insignificant when the frequencies used for adaptation and the post-adaptation localization test were different. It is hypothesized that these aftereffects may rely on shifts in neural representations of auditory space with respect to those of visual space, induced by intersensory spatial disparity, and may thus reflect a phenomenon of neural short-term plasticity.

Acoustic Stimulation↗
PubMed1989

Post-transcriptional control of plastid mRNA accumulation during adaptation of chloroplasts to different light quality environments.

The adaptation of germinating spinach seedlings to yellow and red light was studied and compared with plants grown in white light. Spinach chloroplasts isolated from cotyledons and leaves of yellow and white light-grown plants showed similar membrane structures and compositions, while chloroplasts from plants grown in red light have significant adaptive changes. Based on an equal amount of chlorophyll, these changes include a reduction in the number of photosystem I complexes, an increase of photosystem II antenna size, and an increased ratio of stacked to unstacked membranes in red light-adapted chloroplasts. The decrease in the number of photosystem I complexes per unit of chlorophyll in these chloroplasts was qualitatively correlated with an approximately 10-fold decrease in the level of the psaA mRNA encoding the photosystem I 65-kilodalton to 70-kilodalton chlorophyll apoprotein, as well as with a differential decrease in mRNA levels of other photosynthetic proteins. Light quality adaptations do not significantly affect the plastid to nuclear DNA ratio or the overall chloroplast transcription activity. The relative transcriptional activities of 10 plastid genes, as determined by run-on transcription assays, are similar in chloroplasts from cotyledons and leaves of plants grown under the three light qualities. Only the psaA gene shows a 30% to 40% decrease in transcription activity in chloroplasts of plants adapted to red light. This decrease in psaA transcription activity, however, cannot fully account for the decrease of its mRNA level. We conclude, therefore, that post-transcriptional mechanisms are primarily responsible for the control of differential chloroplast mRNA accumulation in light quality adaptations.

Adaptation, Physiological↗
PubMed2000

Local adaptation, resistance, and virulence in a hemiparasitic plant-host plant interaction.

Coevolution may lead to local adaptation of parasites to their sympatric hosts. Locally adapted parasites are, on average, more infectious to sympatric hosts than to allopatric hosts of the same species or their fitness on the sympatric hosts is superior to that on allopatric hosts. We tested local adaptation of a hemiparasitic plant, Rhinanthus serotinus (Scrophulariaceae), to its host plant, the grass Agrostis capillaris. Using a reciprocal cross-infection experiment, we exposed host plants from four sites to hemiparasites originating from the same four sites in a common environment. The parasites were equally able to establish haustorial connections to sympatric and allopatric hosts, and their performance was similar on both host types. Therefore, these results do not indicate local adaptation of the parasites to their sympatric hosts. However, the parasite populations differed in average biomass and number of flowers per plant and in their effect on host biomass. These results indicate that the virulence of the parasite varied among populations, suggesting genetic variation. Theoretical models suggest that local adaptation is likely to be detected if the host and the parasite have different evolutionary potentials, different migration rates, and the parasite is highly virulent. In the interaction between R. serotinus and A. capillaris all the theoretical prerequisites for local adaptation may not be fulfilled.

Adaptation, Physiological↗
PubMed2004

Evolution of niche width and adaptive diversification.

Theoretical models suggest that resource competition can lead to the adaptive splitting of consumer populations into diverging lineages, that is, to adaptive diversification. In general, diversification is likely if consumers use only a narrow range of resources and thus have a small niche width. Here we use analytical and numerical methods to study the consequences for diversification if the niche width itself evolves. We found that the evolutionary outcome depends on the inherent costs or benefits of widening the niche. If widening the niche did not have costs in terms of overall resource uptake, then the consumer evolved a niche that was wide enough for disruptive selection on the niche position to vanish; adaptive diversification was no longer observed. However, if widening the niche was costly, then the niche widths remained relatively narrow, allowing for adaptive diversification in niche position. Adaptive diversification and speciation resulting from competition for a broadly distributed resource is thus likely if the niche width is fixed and relatively narrow or free to evolve but subject to costs. These results refine the conditions for adaptive diversification due to competition and formulate them in a way that might be more amenable for experimental investigations.

Adaptation, Physiological↗
PubMed1988

Reversion of neurovirulence and in vitro phenotype of neural cell-adapted canine distemper virus after passage in non-neural cells.

The stability of neurovirulence and in vitro phenotypes of canine distemper viruses adapted to neural cells was examined. Neurovirulence was estimated by the morbidity, mortality, and histopathological changes in the central nervous system of mice. After a single passage of the adapted viruses in Vero cells in which the unadapted virus had been passed, the neurovirulence of glioblastoma-adapted and oligodendroglioma-adapted viruses reverted completely to that of the unadapted virus. However, the neurovirulence of a neuroblastoma-adapted virus reverted partially. In vitro phenotypes such as the two-dimensional electrophoretic patterns of viral proteins and the cross-neutralization patterns also reverted to those of the unadapted virus. However, plaque sizes remained similar to those of the viruses adapted to neural cells.

Adaptation, Physiological↗
PubMed1982

A conceptual model of children's cognitive adaptation to physical disability.

Increasing numbers of children are being required to adapt to lifelong illness and disability. While numerous studies exist on theories of adaptation, reaction to illness, and children's concepts of self and of illness, an integrated view of children's ability to conceptualize themselves, their disabilities and possible adaptations has not been formulated. In this article an attempt has been made to integrate models of adaptation to disability and knowledge about children's cognitive development using Piagetian theory of cognitive development and Crate's stages of adaptation to chronic illness. This conceptually integrated model can be used as a departure point for studies to validate the applicability of Piaget's theory to the development of the physically disabled child and to clinically assess the adaptational stages available to the child at various developmental stages.

Adaptation, Psychological↗
PubMed2006

PBP3 inhibition elicits adaptive responses in Pseudomonas aeruginosa.

Adaptive evolution depends on both the genetic variability in a population of organisms and the selection of the better adapted genotypes. However, for the fittest variants to be selected they must survive over a sufficient period under the new conditions. Bacteria are often exposed to different types of stress in nature, including antibiotics. We analysed the global expression profiles of the opportunistic pathogen Pseudomonas aeruginosa in response to ceftazidime, a PBP3 inhibitor, at different concentrations and times. PBP3 inhibition exerts a global impact on the transcription of a large number of genes. From an adaptive perspective, it is noteworthy the induction of several SOS genes, as well as adaptation, protection and antibiotic resistance genes. Intriguingly, transcription of pyocin genes, previously described as SOS-regulated, was repressed upon PBP3 inhibition. Ciprofloxacin, an SOS inducer, produced transcriptional induction of pyocins. Our results indicate that: (i) the SOS responses resulting from treatments with these two antibiotics cause only partially overlapping transcription profiles; (ii) PBP3 and DNA-gyrase inhibition produce opposite effects on transcription of pyocin genes. Consequently, ceftazidime decreases ciprofloxacin toxicity; (iii) error-prone DNA-polymerase DinB is induced by PBP3 inhibition but not by DNA-gyrase inhibition; (iv) PBP3 inhibition causes induced mutagenesis; (v) ceftazidime upregulates several antibiotic-resistance and adaptation genes; and (vi) ceftazidime concentrations thought previously to be lethal are not, as most cells treated with ceftazidime remain alive and recover their capacity to form colonies. Thus, transcriptional changes demonstrated in this work are likely to be adaptively relevant to cells that survive.

Adaptation, Physiological↗
PubMed2005

Stress and adaptation in conservation genetics.

Stress, adaptation and evolution are major concerns in conservation biology. Stresses from pollution, climatic changes, disease etc. may affect population persistence. Further, stress typically occurs when species are placed in captivity. Threatened species are usually managed to conserve their ability to adapt to environmental changes, whilst species in captivity undergo adaptations that are deleterious upon reintroduction into the wild. In model studies using Drosophila melanogaster, we have found that; (a) inbreeding and loss of genetic variation reduced resistance to the stress of disease, (b) extinction rates under inbreeding are elevated by stress, (c) adaptive evolutionary potential in an increasingly stressful environment is reduced in small population, (d) rates of inbreeding are elevated under stressful conditions, (e) genetic adaptation to captivity reduces fitness when populations are reintroduced into the 'wild', and (f) the deleterious effects of adaptation on reintroduction success can be reduced by population fragmentation.

Adaptation, Biological↗
PubMedDate not supplied

Adaptation of rat gastric mucosa to repeated doses of non-salicylate non-steroidal anti-inflammatory drugs.

To determine whether gastric mucosal adaptation occurs to the damaging effects of repeated non-steroidal anti-inflammatory drug (NSAID) administration, we compared the extent of gastric damage in rats after single or repeated doses of four non-salicylate NSAID. With daily dosing, adaptation occurred only to repeated doses of the short-acting NSAID ibuprofen and diclofenac but not to indomethacin and naproxen, both of which have considerably longer half-lives. Adaptation to indomethacin was demonstrable if the dosage interval was lengthened and the drug was given on alternate days rather than daily. Histological examination of the gastric mucosa of diclofenac-treated rats showed a similar degree of superficial damage in the single and repeatedly dosed groups. However there was a highly significant reduction in the amount of deeper mucosal damage in the repeatedly dosed rats. Our findings show that under certain conditions of dosage, adaptation to non-salicylate NSAID is demonstrable. The pharmacokinetics of individual NSAID appear to be important in determining whether or not adaptation occurs. Histological examination showed that adaptation to one of the shorter acting NSAID, diclofenac, was characterized by a significant reduction in deeper mucosal damage.

Adaptation, Physiological↗
PubMed2004

Quantification of dark adaptation dynamics in retinitis pigmentosa using non-linear regression analysis.

PURPOSE: Non-linear regression analysis was used to determine dark adaptation indices in people with retinitis pigmentosa and in control subjects. METHODS: Dark adaptation data were collected for 13 people with retinitis pigmentosa and 21 controls using the Goldmann-Weekers Dark Adaptometer. Data were analysed using an exponential non-linear regression model and dark adaptation indices derived. The results were compared to age-related values. RESULTS: The mean cone threshold of the group with RP (4.73 +/- 0.19 log units) was significantly greater than that found in the control group (3.69 +/- 0.12 log units). The rate of cone dark adaptation in the RP group was not significantly different from that of the control group. The a break in the RP group (6.46 +/- 0.70 minutes) was delayed when compared to the control group (4.29 +/- 0.21 minutes) and the rate of rod dark adaptation in the RP group was slower (10 +/- 2 per cent per minute) than that of the control group (15 +/- 1 per cent per minute). CONCLUSIONS: This study has shown that a relatively simple data analysis can provide a more quantitative and intuitive description of dark adaptation rates in people with retinal disease. This technique will enable more effective use of dark adaptometry as a supplement to objective electrophysiology, when monitoring people with retinitis pigmentosa.

Adult↗
PubMed2006

A novel type of cold-sensitive neuron in rat dorsal root ganglia with rapid adaptation to cooling stimuli.

Cold sensing in mammals is heterogeneous and more than one type of receptor molecule is likely to be involved in the transduction process. Most features of innocuous cold receptors have been explained by TRPM8, the cold and menthol receptor, but their fast adaptation to cooling has not yet been reproduced in cellular systems. In this study we have used a newly developed system for applying fast thermal stimuli to dissociated dorsal root ganglia (DRG) neurons from young rats (150-200 g) in primary culture. We describe a novel type of cold-sensitive rat DRG neuron with rapid adaptation to cooling. These cells (4.3% of the total DRG population) do not express either TRPM8 or the other cold-activated TRP channel, TRPA1, and the epithelial sodium channel (ENaC) is not involved in their transduction. Increases in intracellular calcium induced by cooling in rapidly adapting neurons are caused by calcium entry. These neurons express a large and rapidly adapting cold-induced inward current with a time constant of adaptation in the seconds range, and may correspond to the rapidly adapting cold receptors described in vivo.

Adaptation, Physiological↗
PubMed1990

The fate of early experience following developmental change: longitudinal approaches to individual adaptation in childhood.

2 strategies were used to investigate the continued impact of early experience and adaptation given subsequent experience and/or developmental change in a poverty sample (N = 190). Groups were defined whose adaptation was similar during the preschool years but consistently different earlier; then these 2 groups were compared in elementary school. In addition, a series of regression analyses was performed in which variance accounted for by near-in or contemporary predictors of adaptation in middle childhood was removed before adding earlier adaptation in subsequent steps. Children showing positive adaptation in the infant/toddler period showed greater rebound in the elementary school years, despite poor functioning in the preschool period. Regression analyses revealed some incremental power of early predictors with intermediate predictors removed. The results were interpreted as supporting Bowlby's thesis that adaptation is always a product of both developmental history and current circumstances. While this research cannot resolve such a complicated issue, it does point to the need for complex formulations to guide research on individual development.

Adaptation, Psychological↗
PubMed2004

Adolescents with Turkish background in Norway and Sweden: a comparative study of their psychological adaptation.

Using a questionnaire survey, this study compared psychological adaptation (self-esteem, life satisfaction, and mental health problems) of Turkish adolescents in Norway and Sweden, and examined to what extent ethnic and majority identities, acculturation strategies, and perceived discrimination accounted for adaptation among Turkish adolescents. The samples consisted of 407 Turks (111 in Norway and 296 in Sweden) with a mean age of 15.2 years and 433 host adolescents (207 in Norway, 226 in Sweden) with a mean age of 15.6 years. Turks in Norway reported poorer psychological adaptation than Turks in Sweden. Predictors of good adaptation were Turkish identity and integration, whereas poor adaptation was related to marginalization and perceived discrimination. The results indicated that the poorer adaptation of Turks in Norway compared to that of Turks in Sweden could be due to lower degree of Turkish identity and higher degree of perceived discrimination.

Acculturation↗
PubMed2006

Eye movements and visuoverbal descriptions exhibit heterogeneous and dissociated patterns before and after prismatic adaptation in unilateral spatial neglect.

This prospective study examined the effects of prismatic adaptation on visual exploration strategies in patients with left unilateral spatial neglect (USN). Photo-oculographic gaze recordings were obtained, as the subjects (28 brain-damaged; 15 control) performed a free visual exploration task before and after a session of prismatic adaptation. (i) Before prismatic adaptation, the pattern of visual exploration described two subgroups of patients (symmetrical exploration of hemispaces - similar to the control subjects, deficient exploration of left hemispace). Twelve of 20 patients failed to describe significant elements in the left part of the displayed image. Several visuoverbal patterns were observed, some dissociating visual exploration and verbal description. (ii) Immediately after prismatic adaptation, patients with asymmetrical visual exploration presented a significant increase in the number of point fixations and saccades in the left hemispace. Patients with symmetrical exploration presented the opposite pattern. Improved pattern of visual exploration contrasted with an absence of improved verbal description. Eye movements and visuoverbal descriptions exhibit heterogeneous and dissociated patterns before and after prismatic adaptation. This results demonstrate that prismatic adaptation has no effect in certain patients, suggesting that therapeutic indications and evaluation of prismatic test results should take into consideration the heterogeneous nature of USN.

Adaptation, Physiological↗
PubMed2005

Constraints on the evolution of adaptive phenotypic plasticity in plants.

The high potential fitness benefit of phenotypic plasticity tempts us to expect phenotypic plasticity as a frequent adaptation to environmental heterogeneity. Examples of proven adaptive plasticity in plants, however, are scarce and most plastic responses actually may be 'passive' rather than adaptive. This suggests that frequently requirements for the evolution of adaptive plasticity are not met or that such evolution is impeded by constraints. Here we outline requirements and potential constraints for the evolution of adaptive phenotypic plasticity, identify open questions, and propose new research approaches. Important open questions concern the genetic background of plasticity, genetic variation in plasticity, selection for plasticity in natural habitats, and the nature and occurrence of costs and limits of plasticity. Especially promising tools to address these questions are selection gradient analysis, meta-analysis of studies on genotype-by-environment interactions, QTL analysis, cDNA-microarray scanning and quantitative PCR to quantify gene expression, and two-dimensional gel electrophoresis to quantify protein expression. Studying plasticity along the pathway from gene expression to the phenotype and its relationship with fitness will help us to better understand why adaptive plasticity is not more universal, and to more realistically predict the evolution of plastic responses to environmental change.

Adaptation, Physiological↗