Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “preadaptation”

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 163 records · Page 9Linked to original sources

Binocular rivalry suppression disrupts recovery from motion adaptation.

The motion aftereffect (MAE) lasts longer when the test period does not immediately follow adaptation, a phenomenon called storage. Does storage of the MAE occur if the test target is present but rendered phenomenally invisible owing to the presence of a rival target presented to the other eye during the storage period? Our experiment addressed this question. Following adaptation to a drifting grating, an intervening period preceded testing with a stationary grating. During this period, the adapted eye either viewed the test target immediately or was occluded, and the unadapted eye either viewed a high-contrast rival target or was occluded. Thus four conditions were employed. The duration of the residual MAE was found to be longer for the rivalry condition (grating and rival target viewed) than for the normal MAE condition (grating viewed), and comparable to that in the stored MAE condition (both eyes occluded). Thus, the MAE is stored when the test target is rendered invisible due to binocular rivalry, indicating that a suppressed target is ineffective at promoting decay of the MAE. So while suppression does not prevent information about the adapting grating from reaching the site of generation of the MAE (Lehmkuhle & Fox, 1975), it can prevent information about the test target from reaching the site of the stored MAE. Current models attribute the MAE to reduced responsiveness of direction-selective cortical neurons (Sutherland, 1961; Barlow & Hill, 1963). Thus, storage should reflect a differential return of these adapted cells to preadapted response levels, dependent on postadaptation stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Ocular↗

An ankryin-like protein in ascidian eggs and its role in the evolution of direct development.

An erythrocyte anti-ankryin antibody was used to investigate the presence and distribution of ankryin in eggs and embryos of ascidian species with different modes of development. In eggs of the indirect developer Ascidia ceratodes, anti-ankryin reacted with a 210 kDa polypeptide which has an electrophoretic mobility similar to the vertebrate ankryins. Immunofluorescence microscopy showed that the ankryin-like protein is co-distributed with the myoplasm throughout development. It is restricted to a thin layer under the plasma membrane in unfertilised eggs, undergoes ooplasmic segregation to the posterior pole of the zygote after fertilisation, and is distributed to the tail muscle cells during cleavage and embryogenesis. After gastrulation and neurulation, lower levels of the ankryin-like protein, presumably of zygotic origin, were observed in brain cells and in the apical margin of epidermal cells. The ankryin-like protein was also localised in the myoplasm in eggs and embryos of another indirect developing species, Halocynthia roretzi. The ankryin-like protein may link the cytoskeleton with the plasma membrane in ascidian eggs, as it does in vertebrate erythrocytes. In contrast to A. ceratodes and H. roretzi, which are members of the families Ascidiidae and Pyuridae respectively, the pattern of ankryin-like protein expression was changed in five species in the family Molgulidae. These molgulid ascidians exhibit either indirect or direct development, and eggs of the direct developing species have lost or modified the myoplasm. The ankryin-like protein was present in young oocytes but failed to persist during oogenesis and disappeared in mature eggs and embryos of these molgulid species. The change in ankryin-like protein expression may be a preadaptation for loss of the myoplasm and the evolution of direct development.

Animals↗

On the origin and evolution of major morphological characters.

Although the mathematical principles underpinning population-level evolution are now well studied, the origin and evolution of morphological novelties has received far less attention. Here, a broad but general theory for how this sort of change takes place is outlined, relying on functional continuity, least-constrained components of morphology, redundancy and preadaptation. At least four distinct sorts of redundancy are identified: (i) redundancy arising through duplication (amplification); (ii) redundancy arising through regionalisation (parcellation); (iii) redundancy arising through functional convergence; and (iv) redundancy arising from shared function (functional degeneracy). Although organisms are here recognised to be functionally constrained ("burdened", in Riedl's terminology), these constraints can be overcome through the combination of the four principles given above. Contrary to its common treatment, functional constraint is neither an ever-increasing restriction on the scope of evolution, nor does it require drastic events to overcome or "break" it. Rather, it is an evolutionary quantity, subject to selection at some level. The rules that govern morphological evolution are the primary controls on what is allowed to happen in the evolution of the overall genotype-phenotype system, suggesting strong controls on the sorts of developmental changes that might be associated with macroevolution. This model, then, sees organism functionality as the primary control on evolvability, with exact genetic make-up being of secondary importance. It should prove possible to recast traditional notions of body-plan evolution into the formulations of complex system analysis, which in the future may prove a unifying discipline for fields as disparate as palaeontology and gene regulatory networks. In particular, understanding how morphology can evolve may provide the critical link between the ecological and morphological networks that are currently the intense focus of evolutionary investigations.

Adaptation, Physiological↗

Enhancement of orimulsion biodegradation through the addition of natural marine carbon substrates.

Orimulsion is a bitumen-based heavy fuel that is a less expensive alternative to traditional fuel oils. However, because its density is intermediate between that of freshwater and seawater, in the event of a spill, the fuel could strand in the sediments. Previous work indicated that only 0.6-2.7% of the bitumen would degrade in long incubations of marine sediments. We added various natural carbon substrates to stimulate the degradation of bitumen by native populations of benthic bacteria. The concentration and carbon isotopic signature of the respired carbon dioxide was measured to partition the substrates that supported bacterial respiration. We found that the addition of seagrass and pinfish stimulated the degradation of bitumen by as much as 2-9-fold relative to incubations without these substrates. Biodegradation of bitumen may be enhanced by the addition of natural marine carbon substrates and may be a useful approach for bioremediation. Preadaptation of the bacteria to bitumen did not significantly enhance their ability to degrade it.

Animals↗

Recording the photopic electroretinogram from conscious adult Yucatan micropigs.

The micropig is viewed by many as one of the best animal models of human system physiology. The purpose of this study was to develop a simple, rapid and reliable method to record clinical electroretinograms from conscious adult Yucatan micropigs. Photopic ERGs were recorded from 18 conscious animals following a 3-h period of preadaptation to a moderate photopic environment. Rectal temperature and blood pressure were monitored throughout the experiment. In order to test the reproducibility of our procedure, the same protocol was repeated (n=6 micropigs) on three different recording sessions each separated by a 48-h period. Our results indicate that the recording of reproducible ERGs, in the conscious Yucatan micropig, is feasible provided that an adequate experimental approach is used. We believe that our method will enable investigators to perform retinal physiology experiments using an approach which is compatible with that used in a human clinical setup thus facilitating the transposition of experimental data from animal to human.

Adaptation, Ocular↗

The effect of time of day and repeat reliability on the fast flicker multifocal ERG.

PURPOSE: To investigate the possible influence of different times of the day on multifocal ERG recordings in normals. METHODS: 10 healthy volunteers underwent multifocal ERG recordings (VERIS 3.1.1.) 3 times a day, at 10:30 am, 1:30 pm and 4:30 pm using a fast flicker stimulus of 103 hexagons. Additional night-time recordings were performed in 2 subjects. The first-order and dominant part of the second order response component were analyzed. RESULTS: Neither peak latencies nor peak-to-peak amplitudes showed significant changes during the day (p >0.05). Comparison between night and day time recordings did also not reveal an influence of a circadian rhythm on the MF-ERG. CONCLUSIONS: No significant influence of the time of the day suggestive of a circadian rhythm could be observed. Light adaptation due to preadaptation and the flicker sequence used could be a possible cause for these results.

Adaptation, Ocular↗

Formaldehyde and methanol biodegradation with the methylotrophic yeast Hansenula polymorpha. An application to real wastewater treatment.

The application of methylotrophic yeast Hansenula polymorpha to the treatment of methanol and formaldehydecontaining wastewater was experimentally verified. A variety of real wastewater samples originating from chemical industry effluent were examined. The yeast cell culture could grow in the wastewater environment, revealing low trophic requirements and a very high adaptation potential to poor cultivation conditions. The proliferation of cells was accompanied by a concomitant xenobiotic biodegradation. Grown, preadapted cellular suspension at a density of about 1 x 10(7) cells/ml proved to be able to utilize formaldehyde present in wastewater at concentrations up to 1750 mg/l, levels toxic to most microorganisms. The biological waste treatment method presented shows the enhanced potential by means of specific enzymatic activities of monocarbonic compound oxidations through methylotrophic pathway reactions. The need to obtain mutants highly resistant to formaldehyde has also been rationalized.

Biodegradation, Environmental↗

Adaptation to heat limits stress-induced activation of caspases in the thymus.

We demonstrated selective activation of caspases in the thymus during heat shock, i.e. primary activation of initiator caspase 9 (but not caspase 8) and effector caspase 3 (but not caspase 6). Preadaptation to heat improved animal survival after heat shock and reduced heat shock-induced activation of both initiator and effector caspases. Hence, adaptation to heat produced an antiapoptotic effect, which was not selective towards receptor-dependent or mitochondrial pathway of the caspase cascade activation.

Adaptation, Physiological↗

Adaptation to stress improves resistance to gastric damage during acute stress in Wistar rats and decreases resistance in August rats: role of serotonin.

In August rats more resistant to acute stress-induced gastric damage than Wistar rats, preadaptation to nondamaging stress exposure did not prevent damage and even potentiated these damages. By contrast, in Wistar rats such adaptation decreased gastric damage caused by acute stress. Higher initial resistance of August rats to stress damage was associated with higher serotonin level and lower norepinephrine/serotonin ratio in the gastric mucosa than in Wistar rats. The negative effect of adaptation in August rats was associated with decreased serotonin level and increased norepinephrine/serotonin ratio in the stomach during stress. In Wistar rats exposed to stress the protective effect of adaptation was associated with an increase of serotonin content and a decrease of the norepinephrine/serotonin ratio in the stomach. Hence, the degree of resistance to stress-induced gastric damage can be due to genetically determined serotonin level and norepinephrine/serotonin ratio in the stomach.

Adaptation, Physiological↗

Parental investment by skin feeding in a caecilian amphibian.

Although the initial growth and development of most multicellular animals depends on the provision of yolk, there are many varied contrivances by which animals provide additional or alternative investment in their offspring. Providing offspring with additional nutrition should be favoured by natural selection when the consequent increased fitness of the young offsets any corresponding reduction in fecundity. Alternative forms of nutrition may allow parents to delay and potentially redirect their investment. Here we report a remarkable form of parental care and mechanism of parent-offspring nutrient transfer in a caecilian amphibian. Boulengerula taitanus is a direct-developing, oviparous caecilian, the skin of which is transformed in brooding females to provide a rich supply of nutrients for the developing offspring. Young animals are equipped with a specialized dentition, which they use to peel and eat the outer layer of their mother's modified skin. This new form of parental care provides a plausible intermediate stage in the evolution of viviparity in caecilians. At independence, offspring of viviparous and of oviparous dermatotrophic caecilians are relatively large despite being provided with relatively little yolk. The specialized dentition of skin-feeding (dermatophagous) caecilians may constitute a preadaptation to the fetal feeding on the oviduct lining of viviparous caecilians.

Amphibians↗

An adaptive radiation model for the origin of new gene functions.

Current models for the evolution of new gene functions after gene duplication presume that the duplication events themselves have no effect on fitness. But those duplications that result in new gene functions are likely to be positively selected from their inception. The evolution of new function may start with the amplification of an existing gene with some level of preadaptation for that function, followed by a period of competitive evolution among the gene copies, resulting in the preservation of the most effective variant and the 'pseudogenization' and eventual loss of the rest.

Adaptation, Physiological↗

Adequate intake values for dietary fibre based on faecal bulking indexes of 66 foods.

OBJECTIVE: To determine an adequate daily intake value for dietary fibre (AIdf) based on faecal bulking indexes (FBIs) for 66 foods of known total dietary fibre (TDF) content. DESIGN: FBIs of 66 foods were measured and expressed as wheat bran equivalents (WBEfb) per 100 g of food. A daily WBEfb requirement for humans was calculated from faecal bulk generated per gram of wheat bran TDF in humans, using a critical faecal mass of 200 g/day for protection against large bowel disease. TDF content was regressed against WBEfb content for all 66 foods assayed, and an AIdf value obtained by substituting the calculated human WBEfb requirement into the regression equation. METHOD: FBI was measured using a validated rat assay, with eight large (400+/-50 g) rats per group, preadapted to dietary fibre, and fed adequate restricted diets containing test foods at inclusion rates consistent with human intakes. The critical faecal mass was based on epidemiological studies, and the faecal bulk generated per gram of wheat bran TDF was the mean of 27 published values. RESULTS: WBEfb requirements for humans were calculated to be 90 g/day, corresponding to a faecal output of 200 g/day. The regression equation relating WBEfb measured in the FBI assay to TDF in all 66 foods was TDF=0.491WBEfb + 3.19, R2=0.81 Substituting the human WBEfb requirement of 90 g into the regression equation gave an AIdf value of 40.9 g TDF/day. CONCLUSION: The AIdf value of 40.9 g TDF/day based on faecal bulking supports the AIdf of 38 g TDF/day recently set by the Institute of Medicine (USA), for young men, based on protection against heart disease. The AIdf value is obtained from the relation between the effects of foods and their content of mixed function, plant cell wall dietary fibres within the food matrices, and should not be used to guide intakes of extrinsic functional polysaccharides.

Animals↗

Synchronizing the Neurospora crassa circadian clock with the rhythmic environment.

The metronomic predictability of the environment has elicited strong selection pressures for the evolution of endogenous circadian clocks. Circadian clocks drive molecular and behavioural rhythms that approximate the 24 h periodicity of our environment. Found almost ubiquitously among phyla, circadian clocks allow preadaptation to rhythms concomitant with the natural cycles of the Earth. Cycles in light intensity and temperature for example act as important cues that couple circadian clocks to the environment via a process called entrainment. This review summarizes our current understanding of the general and molecular principles of entrainment in the model organism Neurospora crassa, a simple eukaryote that has one of the best-studied circadian systems and light-signalling pathways.

Biological Clocks↗

Colonization history and introduction dynamics of capsella bursa-pastoris (Brassicaceae) in north america: isozymes and quantitative traits

Multilocus isozyme genotypic composition for aspartate aminotransferase (AAT), leucine aminopeptidase (LAP) and glutamate dehydrogenase (GDH) was studied for Capsella in the source continent, Europe (9000 plants from 593 populations), and in the colonized continent, North America (2700 plants from 88 populations). North America was depauperate in the number of genotypes (by approximately 50%), but in terms of frequencies, a few genotypes were common and shared by both continents. Although some, very rare, genotypes were, however, unique for North America, our data provided no evidence to indicate that the introduced gene pools were reconstructed on a multilocus genetic basis after introduction. Instead, they argued for a considerable number of independent introduction events. Geographical distribution patterns of multilocus genotypes in Europe and North America were pronounced and enabled us to trace the colonization history of Californian Capsella back to Spanish ancestral populations and those of temperate North America back to temperate European gene pools. A random-block field experiment with 14 Californian populations from different climatic regions revealed that variation patterns of quantitative traits reflect ecotypic variation, and the ecological amplitude of Capsella in North America is similar to that in Europe, which can be traced back to the introduction of preadapted genotypes. It appears that certain multilocus isozyme genotypes are associated with certain ecotypes. The variable European gene pool of Capsella was essentially introduced into North America without major genetic changes.

Journal Article↗

Slender and stumpy bloodstream forms of Trypanosoma brucei display a differential response to extracellular acidic and proteolytic stress.

Natural infections of mammals with African trypanosomes, such as Trypanosoma brucei, are generally pleomorphic, the population consisting of different forms, termed slender and stumpy forms, that vary in number as the parasitaemia develops. We show that the differentiation of slender into stumpy forms is characterized by the acquisition by the parasite of the ability to regulate its internal pH, even in the face of a large, inwardly directed gradient of H+, as well as a tolerance towards external proteolytic stress. These adaptations effectively abbrogate cellular stress-activated signalling pathways involving adenylate cyclase and glycosylphosphoinositol-specific phospholipase-C mediated release of the surface coat. Although in metabolic terms stumpy forms of the parasite are considered to be preadapted to life in the arthropod vector, these data clearly demonstrate that these forms also possess additional cellular adaptations designed to deal with the immediate and potentially harmful changes in the extracellular environment that occur upon ingestion of a bloodmeal by the tsetse fly vector.

Acid-Base Equilibrium↗

The life-cycle of Leishmania in the sandfly with special reference to the form infective to the vertebrate host.

A review is given of recent advances in studies on the life-cycles of leishmaniae in phlebotomine sandflies including observations on the morphology and attachment of the parasites, putative genetic exchange in Leishmania, newly found factors affecting the development of the parasite in the fly, and the characteristics of metacyclic promastigotes related to their preadaptation for life in the vertebrate host.

Animals↗

Utility of siRNA against Keap1 as a strategy to stimulate a cancer chemopreventive phenotype.

A duplex 21 nucleotide small interfering RNA (siRNA) against human Keap1 is described that represents a unique class of cancer chemopreventive agent. This siRNA can knockdown Keap1 mRNA and thereby relieve negative regulation of nuclear factor erythroid 2 p45-related factor 2 (Nrf2)-mediated gene expression. The siRNA lowered endogenous Keap1 mRNA to <30% of control levels between 24 and 72 h after transfection in human HaCaT keratinocyte cells and was capable of blocking ectopic expression of FLAG-tagged human Keap1 protein but not that of ectopic V5-tagged mouse Keap1 protein. Transfection of human HaCaT cells with Keap1 siRNA markedly enhanced endogenous levels of nuclear factor erythroid 2 p45-related factor 2 (Nrf2) protein and increased transcription of an antioxidant response element-driven reporter gene by 2.3-fold. Furthermore, 48 h after transfection of these cells with Keap1 siRNA, expression of aldo-keto reductase 1C1/2 and the glutamate cysteine ligase catalytic and modifier subunits was elevated between 5- and 14-fold. A modest increase of 3-fold in NAD(P)H:quinone oxidoreductase 1 was also observed. The Keap1 siRNA produced a 1.75-fold increase in intracellular glutathione 48 h after transfection. Thus, antagonism of Keap1 by siRNA can be used to preadapt human cells to oxidative stress without the need to expose them to redox stressors.

Alcohol Oxidoreductases↗

Ancestral reconstruction of the ligand-binding pocket of Family C G protein-coupled receptors.

The metabotropic glutamate receptors (mGluRs) within the Family C subclass of G protein-coupled receptors are crucial modulators of synaptic transmission. However, their closest relatives include a diverse group of sensory receptors whose biological functions are not associated with neurotransmission, raising the question of the evolutionary origin of amino acid-binding Family C receptors. A common feature of most, if not all, functional Family C receptors is the presence of an amino acid-binding site localized within the large extracellular Venus flytrap domain. Here, we used maximum likelihood methods to infer the ancestral state of key residues in the amino acid-binding pocket of a primordial Family C receptor. These residues were reconstructed in the background of the fish 5.24 chemosensory receptor, a broad-spectrum amino acid-activated receptor. Unlike the WT 5.24 receptor, which was not activated by mGluR agonists and displayed low sensitivity toward l-glutamate, the reconstructed ancestral receptor possessed a pharmacological profile characterized by high affinity for both l-glutamate and selective Group I mGluR agonists. This pharmacological phenotype could be largely recapitulated by mutating only two residues in the 5.24 receptor-binding pocket. Our results suggest that this primordial Family C receptor may have arisen early in metazoan evolution and that it already was preadapted as a glutamate receptor for its later use at excitatory synapses in glutamate-mediated neurotransmission.

Animals↗