Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “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 1,423 records · Page 79Linked to original sources
PubMed2025

Molecular signatures of adaptive introgression and selection in contact zones of closely related pine species (Pinus genus).

BACKGROUND: Natural hybridization plays a key role in shaping genetic diversity, local adaptation, and the dynamics of speciation through interspecific gene flow. Hybrid zones serve as valuable natural systems for studying these processes. In this research, we used genotypic data at thousands of nuclear SNPs to investigate genomic outcomes of hybridization and selection across three contact zones of closely related pine species including Scots pine (Pinus sylvestris L.) and dwarf mountain pine (P. mugo T.). Reference allopatric stands of parental species were used to assess introgression dynamics. RESULTS: Individuals from the hybrid zones showed distinct genetic ancestry patterns and were assigned to groups including putative pure species, first-generation hybrids, and advanced backcrosses. Genotypes of the majority of hybrids were shifted towards P. mugo ancestry. Most outlier loci were shared across all sympatric populations, although some were specific to individual contact zones. The identified outliers were mainly associated with regulatory biological processes related to phosphorylation, proteolysis, and transmembrane transport. Signatures of local adaptation varied in different genetic classes in contact zones and they were strongest in pure P. sylvestris and hybrids with a majority of P. sylvestris ancestry. The pattern suggests that it may be driven by adaptation to peat bog habitats situated outside the species’ core ecological niche. CONCLUSIONS: Our findings indicate strong selective pressure acting on multiple genes in groups of hybrids and pure Pinus sylvestris individuals across all studied hybrid zones. In contrast, the weaker signal of selection observed in individuals with P. mugo ancestry suggests that relict populations of this species, which historically spread across postglacial peat bogs, were pre-adapted to such environments. While several outlier loci were shared across different contact zones, others were unique for one of them, indicating that local environmental pressures and adaptive introgression shape the genomic composition of the populations. These results highlight the role of hybridization in generating adaptive diversity and emphasize the evolutionary significance of hybrid zones in pines.

Hybridization, Genetic↗
PubMed1975

Adaptation to novel environments by the rat: effects of age, stimulus intensity, group testing, and temperature.

Adaptation of operant bar pressing in a dark 2-bar test box was determined during 2-hr tests for singly tested rats 16-18, 24-32, and 750-800 days old. Rats 16-18 days old failed to adapt during the test, although all other age groups did. Adaptation occurred more slowly for the 120-150 day-old group than for the remaining 2 age groups. Experiments with the 2 youngest groups showed that bright light lowered response levels of both age groups, compared with controls, but failed to alter the course of adaptation. In contrast, group testing resulted in lowered response levels and faster adaptation for 16-18 day-old rats, but higher response levels for 24-32 day-old rats compared with singly tested controls. High temperature (32.5 degrees C) resulted in adaptation for the 2 younger groups. The failure of 16-18 day-old rats to adapt may have been due to lower body temperature while in the test chamber than while in the home cage nest area.

Aging↗
PubMed1991

Adaptation to 5-fluorouracil of the heterogeneous human colon tumor cell line HT-29 results in the selection of cells committed to differentiation.

The HT-29 cell line contains a small proportion of differentiated polarized, enterocytic and mucus-secreting cell types (less than 95%) which can be selected under various pressure conditions, e.g., glucose deprivation or methotrexate. The purpose of the present work was to investigate whether this also applies to 5-fluorouracil (FUra). Stepwise adaptation of exponentially growing cells to 1, 5, 10 and 20 microM FUra results, after a phase of high mortality, in the emergence of adapted sub-populations with stable growth rates and curves, and IC50 6, 18, 37, and 110 times higher than in untreated cells respectively. FUra-adapted cells are all differentiated, according to 2 phenotypes: (I) polarized dome-forming cells which express carcinoembryonic antigen at their apical surface and (2) goblet cells which secrete a mucus of colonic immunoreactivity. These phenotypes are present in the parental population and are different from those selected e.g., by glucose deprivation or methotrexate. This differentiation pattern is maintained when the cells are subcultured in drug-free medium. Resistance to FUra is acquired through gene amplification as substantiated by a 4- to 6-fold increase of thymidylate synthase gene copies in cells stably adapted to the drug. Whether the same mechanism or others are responsible for the first steps of resistance to FUra remains to be elucidated. Altogether, these results support the hypothesis that some of the cells which are present in the parental line and are committed to differentiation possess advantages which allow them to immediately resist and secondarily adapt to FUra. Comparison of the differentiation characteristics of FUra-adapted cells with those from cells selected under other pressure conditions suggests that resistance and adaptation to either type of pressure may depend on the differentiated phenotype to which the cells are committed.

Blotting, Northern↗
PubMed1992

Habituation and adaptation of the vestibuloocular reflex: a model of differential control by the vestibulocerebellum.

We habituated the dominant time constant of the horizontal vestibuloocular reflex (VOR) of rhesus and cynomolgus monkeys by repeated testing with steps of velocity about a vertical axis and adapted the gain of the VOR by altering visual input with magnifying and reducing lenses. After baseline values were established, the nodulus and ventral uvula of the vestibulocerebellum were ablated in two monkeys, and the effects of nodulouvulectomy and flocculectomy on VOR gain adaptation and habituation were compared. The VOR time constant decreased with repeated testing, rapidly at first and more slowly thereafter. The gain of the VOR was unaffected. Massed trials were more effective than distributed trials in producing habituation. Regardless of the schedule of testing, the VOR time constant never fell below the time constant of the semicircular canals (approximately 5 s). This finding indicates that only the slow component of the vestibular response, the component produced by velocity storage, was habituated. In agreement with this, the time constant of optokinetic after-nystagmus (OKAN) was habituated concurrently with the VOR. Average values for VOR habituation were obtained on a per session basis for six animals. The VOR gain was adapted by natural head movements in partially habituated monkeys while they wore x 2.2 magnifying or x 0.5 reducing lenses. Adaptation occurred rapidly and reached about +/- 30%, similar to values obtained using forced rotation. VOR gain adaptation did not cause additional habituation of the time constant. When the VOR gain was reduced in animals with a long VOR time constant, there were overshoots in eye velocity that peaked at about 6-8 s after the onset or end of constant-velocity rotation. These overshoots occurred at times when the velocity storage integrator would have been maximally activated by semicircular canal input. Since the activity generated in the canals is not altered by visual adaptation, this finding indicates that the gain element that controls rapid changes in eye velocity in the VOR is separate from that which couples afferent input to velocity storage. Nodulouvulectomy caused a prompt and permanent loss of habituation, returning VOR time constants to initial values. VOR gain adaptation, which is lost after flocculectomy, was unaffected by nodulouvulectomy. Flocculectomy did not alter habituation of the VOR or of OKAN. Using a simplified model of the VOR, the decrease in the duration of vestibular nystagmus due to habituation was related to a decrement in the dominant time constant of the velocity storage integrator (1/h0).(ABSTRACT TRUNCATED AT 400 WORDS)

Acclimatization↗
PubMed1991

Adaptive plasticity in the gaze stabilizing synergy of slow and saccadic eye movements.

When a normal human subject is briefly turned in total darkness while trying to "look" at a spatially fixed target, the vestibulo-ocular reflex (VOR) produces slow-phase compensatory eye movements tending to hold the eyes on target. However, slow-phase compensation per se is generally inadequate in these circumstances. Nevertheless it has recently been found, that even in the dark, this inadequacy tends to be corrected by supplementary saccades usually acting in the compensatory direction. The present study further investigates this phenomenon by measuring the respective contributions of saccadic, slow-phase and overall net compensation in 9 subjects tested before and after 30% adaptive attenuation of VOR slow-phase gain. In each test series, subjects attempted to stabilize their gaze on a previously seen target during each of 40 brief (approximately 0.5 s) whole body rotations (40 degrees/s, 20 degrees amp) conducted in complete darkness. The adaptive experience comprised 2 h of full-field visual suppression of the VOR during sinusoidal rotation of subject and surround at 1/6 Hz and 40 degrees/s velocity amplitude. Before adaptation, the cumulative slow-phase and cumulative saccadic components produced on average 78% and 14% respectively of the ideal (100%) compensation, thus yielding an overall net compensation which was 92% of the desired value. After adaptation, the corresponding values in the same population were 53%, 18% and 71% respectively. Thus after adaptation, the combined saccadic-slow-phase response brought the final gaze position to a point in space that was systematically shifted in the direction of head rotation (i.e. undercompensation). Subjects re-exposed to 30 min of normal visual-vestibular interaction displayed a variety of recovery patterns using different combinations of slow and saccadic eye movements. However, there was a consistent "synergistic" tendency for saccadic eye movements to improve slow-phase performance, regardless of the subject's adaptive state. In one subject, compensatory saccadic eye movements corrected a consistent directional asymmetry in the slow-phase response. It is suggested that a conscious vestibular percept of self-rotation might underlie the combined saccadic-slow-phase response, and that the net under performance after adaptation might reflect attenuation of this percept relative to the actual rotational stimulus.

Acclimatization↗
PubMed1982

Oculomotor response to rapid head oscillation (0.5-5.0 Hz) after prolonged adaptation to vision-reversal. "Simple" and "complex" effects.

This study examined long-term (up to 27 days) effects of maintained vision reversal on (i) smooth visual tracking with head still, (ii) oculomotor response to actively, generated head oscillation and (iii) "spontaneous" saccades. Dove prism goggles produced horizontal, but not vertical (sagittal plane), vision reversal. Eye movements were recorded by EOG; head movements by an electro-magnetic search coil. Both visual tracking and saccade dynamics remained unchanged throughout. In contrast, both the ocular response to active head oscillations (goggles off and subject looking at a stationary target) and associated retinal image blur showed substantial and retained adaptive changes, akin to those previously found in the vestibulo-ocular reflex as tested in darkness at 0.17 Hz. However, several addition unexpected results emerged. First, in the fully adapted state smooth eye movements tended to be of reversed phase in the range 0.5-1.0 Hz (in spite of normal vision during tests), but of normal phase from about 2 Hz and above (in spite of negligible visual tracking in this upper range). Second, after permanent removal of the inverting goggles, this peculiar frequency response of the fully adapted state quickly (36 h) reverted to a dynamically simpler condition manifest as retained (2-3 weeks) attenuation of gain (eye vel./head vel.) which, as in control conditions, was monotonically related to frequency. From these two findings it is inferred that the fully adapted state may have comprised two separate components: (i) A "simple element of monotonic and long-lasting gain attenuation and (ii) a "complex", frequency labile, element which could be quickly rejected. Dynamic characteristics of the putative "complex" element were estimated by vectorial subtraction of the "simple" one from that of the fully adapted condition. The outcome suggests that the inferred "complex" condition might represent a predictive element. Two further findings are reported: (i) Substantially different vectors of the adapted response were obtained with normal and reversed vision at 3.0 Hz head oscillation, indicating a novel visual tracking. (ii) During head oscillation in the vesicle sagittal plane (in which vision was not reversed) there was never any image blur, indicating high geometric specificity in the adaptive process.

Acoustic Stimulation↗
PubMed1996

Hypothermic general cold adaptation induced by local cold acclimation.

To study relationships between local cold adaptation of the lower limbs and general cold adaptation, eight subjects were submitted both to a cold foot test (CFT, 5 degrees C water immersion, 5 min) and to a whole-body standard cold air test (SCAT, 1 degree C, 2 h, nude at rest) before and after a local cold acclimation (LCA) of the lower limbs effected by repeated cold water immersions. The LCA induced a local cold adaptation confirmed by higher skin temperatures of the lower limbs during CFT and a hypothermic insulative general cold adaptation (decreased rectal temperature and mean skin temperature P < 0.05) without a change either in metabolic heat production or in lower limb skin temperatures during SCAT after LCA. It was concluded that local cold adaptation was related to the habituation process confirmed by decreased plasma concentrations of noradrenaline (NA) during LCA (P < 0.05). However, the hypothermic insulative general cold adaptation was unrelated either to local cold adaptation or to the habituation process, because an increased NA during SCAT after LCA (P < 0.05) was observed but was rather related to a "T3 polar syndrome" occurring during LCA.

Acclimatization↗
PubMed1994

Recursive running DCT algorithm and its application in adaptive filtering of surface electrical recording of small intestine.

A rhythmic electrical signal is present in the human small intestine and can be recorded using surface electrodes. Surface electrical recordings of the small intestine contain severe interference that obscures the electrical signal of the small intestine. An adaptive system is proposed in the paper for the enhancement of the small-intestinal signal. To obtain better performance, adaptive signal enhancement is performed in the transform domain using a discrete cosine transform (DCT). A fast recursive algorithm is developed for the calculation of running DCT. The computational complexity of the proposed recursive algorithm is only 2/N (N = length of the adaptive filter) of the direct calculation of the running DCT. A series of simulations are conducted to investigate the performance of the proposed transform-domain adaptive filtering using DCT in comparison with time-domain adaptive filtering and with transform-domain adaptive filtering using a discrete Fourier transform (DFT). The parameters of the proposed adaptive system are optimised, and their effects on system performance are investigated. The application of the proposed method for the enhancement of the small-intestinal signal is presented and discussed.

Algorithms↗
PubMed2005

Slow adaptation in spider mechanoreceptor neurons.

Slow adaptation of action potential firing is a common but poorly understood property of sensory neurons. We quantified slow adaptation in a cuticular mechanoreceptor organ of the spider, Cupiennius salei, by stimulating with continuous pseudorandom mechanical displacements while recording action potentials intracellularly from the cell bodies. Firing rate declined over a period of several minutes before reaching a steady level at about half the initial rate. This slow adaptation was fitted by an exponential decay with mean time constant of 18.5 s. Recovery from slow adaptation was also fitted by an exponential process, but with a longer time constant of 167 s. The receptor potential produced by the same stimulation protocol did not change its amplitude or dynamics, showing that slow adaptation occurs during action potential encoding from the receptor potential. Experiments with chemical blockers of calcium entry or the known potassium currents failed to reduce the slow adaptation. The Na+/K+ pump blocker Ouabain decreased the time constant of slow adaptation, suggesting that ion accumulation is involved. In some experiments, a second class of small action potentials were observed, which were tentatively attributed to failed conduction from the sensory dendrite through the soma to the axon.

Acclimatization↗
PubMed2025

Social Responsiveness as a Mediator in Adapted Cognitive Behavioral Therapy for Autistic Youth with Maladaptive and Interfering Anxiety.

Numerous adaptations to interventions have been included in cognitive behavioral therapy (CBT) for autistic youth. This study examines the degree to which CBT adapted to the social needs of autistic youth confers significant benefit by promoting social responsiveness. A secondary analysis was conducted on a multisite randomized clinical trial (Wood et al. in JAMA Psychiatry 77:474-483, 2020) comparing adapted CBT with standard-of-practice CBT and treatment-as-usual (TA). Autistic youth (N&#x2009;=&#x2009;167; aged 7-13) with maladaptive and interfering anxiety participated. The adapted CBT (BIACA) uses a modular format, with an emphasis on supplementing common CBT practice elements (reframing and graded exposure) with social skill supports. The primary outcome measure was the Pediatric Anxiety Rating Scale. Social responsiveness was assessed with the Social Responsiveness Scale, Second Edition. Participants' general mental health was assessed as a secondary outcome using the Brief Problem Checklist. Mediation was tested using the SPSS PROCESS macro. Analyses suggested that the effect of adapted CBT on anxiety was mediated by its effects on social responsiveness, with a statistically significant indirect effect. Youth randomly assigned to adapted CBT exhibited better overall mental health at posttreatment compared to those randomized to the other conditions, and this effect was also mediated by improved social responsiveness. CBT adapted to address some of the social needs of autistic youth may enhance mental health outcomes by supporting social responsiveness, perhaps increasing the ease and effectiveness with which some youth can navigate potentially stressful situations such as entering and participating in group activities.

Humans↗
PubMed1983

Modification of liver mitochondrial lipids and of adenine nucleotide translocase and oxidative phosphorylation by cold adaptation.

The decrease in respiration rate following thyroidectomy is preceded by changes in the lipid composition of the mitochondrial membrane (Hoch, F.L., Subramanian, C., Dhopeshwarkar, G.A. and Mead, J.F. (1981) Lipids 16, 328-334) and in concert, changes in the kinetic parameters of the adenine nucleotide translocase (Mak, I.T., Shrago, E. and Elson, C.E. (1981) Fed. Proc. 40, 398). To demonstrate that physiological adaptation also involves this sequence of events, rats were housed at 8 degrees C for 3-4 weeks. Cold adaptation resulted in a modest (5%) increase in the unsaturation index for the mitochondrial fatty acids comprised of a significant increase in arachidonic acid and a reciprocal decrease in linoleic acid. Phospholipid analysis indicated that cold adaptation increased the mitochondrial phosphatidylethanolamine and reciprocally decreased the phosphatidylcholine content. Concomitantly, cold adaptation resulted in 25-30% increases in rat liver mitochondrial respiratory activities without changing the respiratory control or ADP/O ratios. The kinetic parameters of the adenine nucleotide translocase were determined by the back-exchange method (Pfaff, E. and Klingenberg, M. (1968) Eur. J. Biochem. 6, 66-79). At 0-4 and 10 degrees C, the Vmax and Km of the cold-adapted rat liver adenine nucleotide translocase were not distinguishable from the control values. The Ki values determined by Dixon plot studies for atractylate and palmitoyl-CoA were also comparable between the two groups. However, at 25 and 37 degrees C, cold-adapted rat liver adenine nucleotide translocase exhibited a 20% increase in Vmax and a 20% decrease in Km for external ADP. The results suggest that one adaption to a cold environment involves hormone-mediated changes in the lipid composition in the mitochondrial membranes which in turn modulate the adenine nucleotide translocase and subsequent respiratory activities.

Acclimatization↗
PubMed1993

Adaptation in short-bowel syndrome: reassessing old limits.

The improving survival of patients with severe short-bowel syndrome along with the advent of successful intestinal transplantation have accentuated the need to answer two questions. (1) Is there an intestinal length below which adaptation to full enteral nutrition can not be expected to occur? (2) How much time is necessary to complete intestinal adaptation? We reviewed the outcome of 21 infants with less than 50 cm of small intestine to answer these questions. Patients were divided into three groups based on intestinal length, regardless of ileocecal valve status: group I, < 10 cm (n = 3); group II, 10 to 30 cm (n = 11); and group III, 30 to 50 cm (n = 7). Data were collected to assess survival, incidence of adaptation, time to adaptation, and causes of mortality. Infants in group I did not achieve intestinal adaptation to full enteral nutrition. One survived and 2 died, one from varicella pneumonia and the other after intestinal transplantation. Eight of the 11 (73%) patients in group II survived and 5 of 8 (63%) survivors achieved full intestinal adaptation after a mean interval of 320 days (range, 148 to 506 days) on parenteral nutrition. Six of the seven patients (86%) in group III survived and all survivors (100%) achieved complete enteral adaptation after an average of 376 days (range, 58 to 727 days). The overall survival was 71% (15/21), but survival in patients with > 10 cm was 78%.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization, Central Venous↗
PubMed1987

Potent induction of the adaptive response by a weak mutagen, methyl iodide, in Escherichia coli.

Methyl iodide (MeI), a weakly mutagenic and highly chemoselective chemical, was tested for its abilities to induce the adaptive and SOS responses in E. coli CSH26/pMCP1000 (alkA'-lacZ') and CSH26/pSK1002 (umuC'-lacZ'). MeI induced the adaptive response effectively but gave a very weak SOS response. Its potent ability in inducing the adaptive response was also demonstrated by adaptation to both the mutagenic and killing effects of N-methyl-N-nitrosourea (MNU) in E. coli WP2 cells. Simultaneous treatment with MeI in a non-growth medium slightly increased the mutagenicity of MNU, probably as a result of depletion of the repair enzyme, O6-methylguanine-DNA methyltransferase, which is constitutively present in the cells. As MeI itself proved to be only weakly mutagenic, a small part of the adaptive response which we have observed may involve indirect methylation of the repair enzyme by methyl transfer from MeI-induced O6-methylguanine residues in DNA. But the extent of the induced adaptive response seems to be much higher than would be expected from the observed weak mutagenicity of MeI. It is therefore suggested that the mechanism of induction of the adaptive response may involve direct methylation of the O6-methylguanine-DNA methyltransferase itself.

Enzyme Induction↗
PubMed1995

Central processes in gustatory adaptation.

In two experiments the adapting stimuli at the periphery of the taste system were of a constant objective intensity but, using mixture suppression and spatial summation, their perceived intensity was varied. The results have shown that, in spite of the constancy in stimulus concentration, the adaptation degree changed with the perceived intensity of the stimulus. The adaptation to the compounds when in binary mixtures proved to be significantly less effective than the adaptation to the same equimolar compounds when unmixed. Similarly, the adaptation effects of solutions of a constant concentration, when applied to a small tongue area, were significantly smaller than when applied to a larger area. This adaptation dependence upon the taste sensation intensity suggests that in the gustatory adaptation, peripheral as well as central processes take part.

Attention↗
PubMed1994

Adaptation of sweeteners in water and in tannic acid solutions.

Repeated exposure to a tastant often leads to a decrease in magnitude of the perceived intensity; this phenomenon is termed adaptation. The purpose of this study was to determine the degree of adaptation of the sweet response for a variety of sweeteners in water and in the presence of two levels of tannic acid. Sweetness intensity ratings were given by a trained panel for 14 sweeteners: three sugars (fructose, glucose, sucrose), two polyhydric alcohols (mannitol, sorbitol), two terpenoid glycosides (rebaudioside-A, stevioside), two dipeptide derivatives (alitame, aspartame), one sulfamate (sodium cyclamate), one protein (thaumatin), two N-sulfonyl amides (acesulfame-K, sodium saccharin), and one dihydrochalcone (neohesperidin dihydrochalcone). Panelists were given four isointense concentrations of each sweetener by itself and in the presence of two concentrations of tannic acid. Each sweetener concentration was tasted and rated four consecutive times with a 30 s interval between each taste and a 2 min interval between each concentration. Within a taste session, a series of concentrations of a given sweetener was presented in ascending order of magnitude. Adaptation was calculated as the decrease in intensity from the first to the fourth sample. The greatest adaptation in water solutions was found for acesulfame-K, Na saccharin, rebaudioside-A, and stevioside. This was followed by the dipeptide sweeteners, alitame and aspartame. The least adaptation occurred with the sugars, polyhydric alcohols, and neohesperidin dihydrochalcone. Adaptation was greater in tannic acid solutions than in water for six sweeteners. Adaptation of sweet taste may result from the desensitization of sweetener receptors analogous to the homologous desensitization found in the beta adrenergic system.

Adult↗
PubMed1996

Psychophysiology and adaptive automation.

Adaptive automation is an approach to automation design where tasks are dynamically allocated between the human operator and computer systems. Psychophysiology has two complementary roles in research on adaptive automation: first, to provide information about the effects of different forms of automation thus promoting the development of effective adaptive logic; and second, psychophysiology may yield information about the operator that can be integrated with performance measurement and operator modelling to aid in the regulation of automation. This review discusses the basic tenets of adaptive automation and the role of psychophysiological measures in the study of adaptive automation. Empirical results from studies of flight simulation are presented. Psychophysiological measures may prove especially useful in the prevention of performance deterioration in underload conditions that may accompany automation. Individual differences and the potential for learned responses require research to understand their influence on adaptive algorithms. Adaptive automation represents a unique domain for the application of psychophysiology in the work environment.

Arousal↗
PubMed2005

An adaptive window width/center adjustment system with online training capabilities for MR images.

OBJECTIVE: Adaptive and automatic adjustment of the display window parameters for magnetic resonance images under different viewing conditions is a challenging problem in medical image perception. An adaptive hierarchical neural network-based system with online adaptation capabilities is presented to achieve this goal in this paper. METHODOLOGY: The online adaptation capabilities are primarily attributed to the use of the hierarchical neural networks and the development of a new width/center mapping algorithm. The large training image set is hierarchically organized for efficient user interaction and effective re-mapping of the width/center settings. The width/center mapping functions are estimated from the new user-adjusted width/center values of some representative images by using a global spline function for the entire training images as well as a first-order polynomial function for each selected image sequence. The hierarchical neural networks are then re-trained for the new training data set after this mapping process. RESULTS: The proposed automatic display window parameter adjustment system is implemented as a program on a personal computer for testing its adaptation performance. Experimental results show that the proposed system can successfully adapt its parameter adjustment on a variety of MR images after user re-adjustment and re-training of neural networks. CONCLUSION: This demonstrates the effective adaptation capabilities of the proposed system based on the framework of training data mapping and neural network re-training.

Algorithms↗
PubMed2004

Light adaptation of bacteriorhodopsin correlates with dielectric spectral kinetics in purple membrane.

The retinal protein, bacteriorhodopsin (bR), has several potential bioelectronic applications and it is considered as a model for G-protein coupled receptors. Its electrical parameters, therefore, deserve particular attention. Such parameters could be determined by virtue of studying its dielectric spectrum in the low frequency range (20 Hz-1 MHz). The kinetics of dark-light adaptation of bR is reported in terms of electrical parameters of the purple membrane (PM) containing bR. The data have exhibited sudden pronounced increase in the ac-conductivity, upon illuminating the dark-adapted bR (DA-bR), which may be considered in further implications of bR for biotechnological applications. These changes turned out to be composed of, at least, two growing exponential components: one relatively fast followed by slower one. Their lifetime ratio exhibited decreases with increasing the frequency; meanwhile, their amplitude ratio displayed very exciting behavior at significant frequencies. This may correlate the kinetics of light adaptation to relaxations in PM. Moreover, the light adaptation has been observed to cause initial fast and large decreases in dc-conductivity with subsequent slower and smaller decreases. Changing the conductivity during the time of light adaptation reflects changes in the surface charge of the PM. The lifetimes of these events, therefore, help follow the kinetics of the pathway of conformational changes that might be occurring during light adaptation. The dipole moment (permanent and induced) of PM, in addition to, its size showed one exponential growth of comparable lifetime (approximately 7 min) during the light adaptation. The variation in PM size from dark to light state should be in keeping with that diffusion may influence the three-dimensional data storage in data processing based on bR.

Bacteriorhodopsins↗