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PubMed2001

The population ecology of contemporary adaptations: what empirical studies reveal about the conditions that promote adaptive evolution.

Under what conditions might organisms be capable of rapid adaptive evolution? We reviewed published studies documenting contemporary adaptations in natural populations and looked for general patterns in the population ecological causes. We found that studies of contemporary adaptation fall into two general settings: (1) colonization of new environments that established newly adapted populations, and (2) local adaptations within the context of a heterogeneous environments and metapopulation structure. Local ecological processes associated with colonizations and introductions included exposure to: (1) a novel host or food resource; (2) a new biophysical environment; (3) a new predator community; and (4) a new coexisting competitor. The new environments that were colonized often had depauperate communities, sometimes because of anthropogenic disturbance. Local adaptation in heterogeneous environments was also often associated with recent anthropogenic changes, such as insecticide and herbicide resistance, or industrial melanism. A common feature of many examples is the combination of directional selection with at least a short-term opportunity for population growth. We suggest that such opportunities for population growth may be a key factor that promotes rapid evolution, since directional selection might otherwise be expected to cause population decline and create the potential for local extinction, which is an ever-present alternative to local adaptation. We also address the large discrepancy between the rate of evolution observed in contemporary studies and the apparent rate of evolution seen in the fossil record.

Adaptation, Biological↗

PubMed1985

Photoconversion from the light-adapted to the dark-adapted state of bacteriorhodopsin.

Dark and light adaptation of bacteriorhodopsin in purple membrane multilayers at less than 100% relative humidity differs from that seen in suspensions. Equilibrium between the two bacteriorhodopsin isomers (bR cis 550 and bR trans 570) in the light-adapted state becomes dependent on the wavelength of actinic light. Excitation at the red edge of the visible absorption band causes dark adaptation in a light-adapted sample. Using polarized actinic and measuring light, we show that acceleration of the dark adaptation through heating by actinic light cannot explain this observation. A light-driven bR trans 570 to bR cis 550 reaction that competes with the well-known 13 cis-to-all-trans light adaptation reaction must exist under our experimental conditions. Trans-to-cis conversion is a one-photon process distinct from the two photon process observed by others in purple membrane suspensions (Sperling, W., C. N. Rafferty, K. D. Kohl, and N. A. Dencher, 1978, FEBS (Fed. Eur. Biochem. Soc.) Lett. 97:129-132). Its quantum efficiency increases monotonously on reducing the hydration level, and is paralleled by an increase in the lifetime of the M410 intermediate of the trans photocycle. We suggest that at this point a branch leads from the all-trans into the 13-cis photocycle. It is probably the same reaction that causes the reduced light adaptation in monomeric bacteriorhodopsin (Casadio, R., H. Gutowitz, P. Mowery, M. Taylor, and W. Stoeckenius, 1980, Biochim. Biophys. Acta. 590:13-23; Casadio, R., and W. Stoeckenius, 1980, Biochemistry. 19:3374-3381).

Bacteriorhodopsins↗

PubMed2003

Base compositions of genes encoding alpha-actin and lactate dehydrogenase-A from differently adapted vertebrates show no temperature-adaptive variation in G + C content.

There is a long-standing debate in molecular evolution concerning the putative importance of GC content in adapting the thermal stabilities of DNA and RNA. Most studies of this relationship have examined broad-scale compositional patterns, for example, total GC percentages in genomes and occurrence of GC-rich isochores. Few studies have systematically examined the GC contents of individual orthologous genes from differently thermally adapted species. When this has been done, the emphasis has been on comparing large numbers of genes in only a few species. We have approached the GC-adaptation temperature hypothesis in a different manner by examining patterns of base composition of genes encoding lactate dehydrogenase-A (ldh-a) and alpha-actin (alpha-actin) from 51 species of vertebrates whose adaptation temperatures ranged from -1.86 degrees C (Antarctic fishes) to approximately 45 degrees C (desert reptile). No significant positive correlation was found between any index of GC content (GC content of the entire sequence, GC content of the third codon position [GC(3)], and GC content at fourfold degenerate sites [GC(4)]) and any index of adaptation temperature (maximal, mean, or minimal body temperature). For alpha-actin, slopes of regression lines for all comparisons did not differ significantly from zero. For ldh-a, negative correlations between adaptation temperature and total GC content, GC(3), and GC(4) were observed but were shown to be due entirely to phylogenetic influences (as revealed by independent contrast analyses). This comparison of GC content across a wide range of ectothermic ("cold-blooded") and endothermic ("warm-blooded") vertebrates revealed that frogs of the genus Xenopus, which have commonly been used as a representative cold-blooded species, in fact are outliers among ectotherms for the alpha-actin analyses, raising concern about the appropriateness of choosing these amphibians as representative of ectothermic vertebrates in general. Our study indicates that, whereas GC contents of isochores may show variation among different classes of vertebrates, there is no consistent relationship between adaptation temperature and the percentage of thermal stability-enhancing G + C base pairs in protein-coding genes.

Actins↗

PubMed1998

Adapting to supernormal auditory localization cues. II. Constraints on adaptation of mean response.

A series of experiments was performed in which subjects were trained to interpret auditory localization cues arising from locations different from their normal spatial positions. The exact pattern of mean response to these alterations (as a function of time) was examined in order to begin to develop a quantitative model of adaptation. Mean responses were roughly proportional to the normal position associated with the localization cues presented. As subjects adapted, the best-fit slope (relating mean response and normal position) changed roughly exponentially with time. The exponential rate and adaptation asymptote were found for each subject in each experiment, as well as the rate and asymptote of readaptation to normal cues. The rate of adaptation does not show any statistical dependence on experimental conditions; however, the asymptote of the best-fit slope varied with the strength of the transformation used in each experiment. This result is consistent with the hypothesis that subjects cannot adapt to a nonlinear transformation of auditory localization cues, but instead adapt to a linear approximation of the transformation. Over time, performance changes exponentially towards the best-fit linear approximation for the transformation used in a particular experiment, and the rate of this adaptation does not depend upon the transformation employed.

Auditory Perception↗

PubMed2001

Background light adaptation of the retinal neuronal adaptive system. I. Effect of background light intensity.

The behaviour of the neuronal adaptive retinal mechanisms to environmental light exposures was studied by measuring the oscillatory potentials (OPs) of the electroretinogram. Dark adapted rats were exposed to four levels of background light (BG), starting at a 'low scotopic' level of 1.43x 10(6) cd/m2, increased by steps of two log units, through 'high scotopic' -, 'low mesopic' - and finally the 'high mesopic' BG of 1.43x 10(0) cd/m2. The summed oscillatory response significantly increased as the BG intensity was raised, except at the 'high mesopic' level. The amplitudes of the a- and b-waves reduced as the BG light increased above the 'high scotopic' level. Each OP responded individually to the different BGs. O1 and O2, significantly enhanced at the 'low scotopic' BG. The amplitudes of the three later OPs increased significantly at the 'low mesopic' BG. The adaptational behaviour of the retinal oscillatory response to BG illumination was different to that of the a- and b- waves. The results indicate that the adaptational neuronal system, as reflected by the OPs, seems to be relatively robust and is separate from the slower photochemical adaptive process in the distal retina. The tentative corollary suggests the oscillatory system to play a vision-preserving role, possibly as an alert against undue depletion of the slowly regenerating visual pigment. The enhancement of the oscillatory response at the 'mesopic' illumination levels indicate both scotopic and photopic processes to contribute to neuronal adaptive activity of the retina.

Adaptation, Ocular↗

PubMed1980

Relation of brightness to threshold for light-adapted and dark-adapted rods and cones: effects of retinal eccentricity and target size.

'Equal-brightness' functions of retinal eccentricity and target diameter were measured by a matching procedure, and compared with the corresponding threshold functions for four different adaptation conditions: light-adapted cones (LAC), dark-adapted cones (DAC), light-adapted rods (LAR) and dark-adapted rods (DAR). The separation between log brightness matches and log thresholds decreased with eccentricity and increased with target size for all adaptation conditions, but overall separation was substantially greater for the DAR condition than for the other three. A two-channel model of achromatic brightness is proposed to explain the results. The model assumes 'strong' and 'weak' channels, which contribute unequally to brightness. These channels are tentatively identified with tonic and phasic classes of retinal ganglion cells.

Adaptation, Ocular↗

PubMed2025

Adaptive Evolution for Freshwater Adaptation in Coilia nasus by Directional Selection on Osmoregulation Genes.

The molecular mechanisms underlying the adaptation to freshwater habitats in fish of marine origin remain unclear. Grenadier anchovies, such as Coilia nasus, originate from marine environments and include both anadromous and freshwater-resident conspecifics, making them ideal for studying adaptive evolution from marine to freshwater habitats. We conducted a comparative population genomic and transcriptome analysis of two distinct C. nasus lineages, one anadromous and the other freshwater-resident, collected from mainstream and estuarine regions of the Yangtze River, China. By genome-wide genotyping of the anadromous and the freshwater-resident populations, we observed significant divergence in osmoregulation, energy metabolism, and immune response pathways associated with ecological adaptation and energy expenditure for migration. Some ion transport genes such as CAMK1, ATP1α3, KCNJ1 and SLC30A2 were identified that may contribute to freshwater adaptation. Notably, numerous mineralocorticoid signalling genes (e.g., NR3C2, SGK1, ATP1α3, KCNJ1) exhibit dynamic change between the anadromous and freshwater populations, suggesting an important role for the hormone cortisol in regulating salinity acclimation in euryhaline fish. Among these genes, the ion channel ATP1α3 experienced adaptive amino acid substitutions (Val317Ile and Thr329Ser), which appear to be evolutionary hotspots across migratory species based on ortholog comparisons. These variants may facilitate sodium/potassium transport and highlight salinity tolerance as a key driver of divergence in anadromous fish transitioning to freshwater. These results enhance our understanding of the genetic basis underlying freshwater adaptation for an anadromous fish across osmotic boundaries.

Animals↗

PubMed1992

Adaptation and recovery from adaptation of the auditory nerve neurophonic (ANN) using long duration tones.

The time course of the interaction between adaptation and the recovery from adaptation of the auditory nerve neurophonic (ANN) responses was examined. The interaction between the process of recovery and the adaptation process of long probe tones which follow a masker, the so called whole tone recovery, was determined for the ANN response for different silent intervals between masker offset and probe onset. The auditory nerve neurophonic (ANN) reflects the ensemble response of phase-locked firing in single auditory nerve fibers to sustained signals. Consequently, neural response properties such as adaptation and recovery from adaptation of these coherent, time-locked responses can be studied. Recovery from adaptation was determined by recording the response of a 290 ms duration probe tone following a 100 ms masker tone, equal in frequency to the probe, ranging from -5 to 20 dB relative to the probe amplitude. Two different time patterns of the whole tone recovery were observed. If short silent intervals and/or loud maskers were used, the time course of the probe tone can be described as an exponential increase in amplitude toward a steady state expressed by the equation: A(tp) = Ass-Yr e(-tp/tau Rr)-Ys e(-tp/tau Rs) ('ascending exponential'). For longer silent intervals and/or fainter maskers, the time course of the probe tone can be described by an exponential decrease expressed by the equation: A(tp) = Yr e(-tp/tau Rr) +Ys e(-tp/tau Rs) +A(ss) ('declining exponential').

Acoustic Stimulation↗

PubMed1997

Microtubule assembly in cold-adapted organisms: functional properties and structural adaptations of tubulins from antarctic fishes.

Fishes native to the coastal waters of the Antarctic have adapted to habitat and body temperatures in the range -1.8 to +2 degrees C. Their cytoplasmic microtubules, unlike those of mammals and temperate poikilotherms, have evolved to assemble efficiently at these low temperatures. To learn about the underlying molecular adaptations, my laboratory is studying microtubule proteins [tubulin alpha beta dimers and microtubule-associated proteins (MAPs)] and tubulin genes from several Antarctic fishes, including the rockcods Notothenia coriiceps and Gobionotothen gibberifrons. We find that the assembly-enhancing adaptations of the fish microtubule proteins are intrinsic to the tubulin subunits themselves. Furthermore, microtubule formation by Antarctic fish tubulins is strongly entropy driven, due in part to an increased reliance, relative to tubulins from other species, on hydrophobic interactions. Based on analyses of tubulin polypeptides and cDNAs, we suggest that the structural adaptations of Antarctic fish tubulins most likely involve alterations in the primary sequences of tubulin isotypes. With respect to neural beta tubulins from other vertebrates, for example, the class II beta-tubulin isotype of N. coriiceps brain contains seven unique amino acid substitutions and one novel insertion in its 446-residue primary sequence. Most of these changes are located in a structural domain that forms contacts between tubulin dimers during microtubule assembly and would be expected to enhance polypeptide flexibility, thereby facilitating addition of tubulin to microtubule ends. The acidic carboxy-terminal tails of the alpha and beta tubulins, by contrast, appear not to be sites of cold adaptation of polymerization. We have also found that brain and egg tubulins from Antarctic fishes differ strikingly in their polymerization efficiencies, which demonstrates, in agreement with the multitubulin hypothesis, that tissue-specific tubulin isoforms can possess distinct functional properties. Thus, study of microtubule proteins from organisms, such as the Antarctic fishes, that have adapted to extreme thermal regimes should contribute significantly to an understanding of the quaternary interactions that control microtubule assembly in all eukaryotes.

Adaptation, Physiological↗

PubMed1996

Phosphate analogs block adaptation in hair cells by inhibiting adaptation-motor force production.

To ensure optimal sensitivity for mechanoelectrical transduction, hair cells adapt to prolonged stimuli using active motors. Adaptation motors are thought to employ myosin molecules as their force-producing components. We find that beryllium fluoride, vanadate, and sulfate, phosphate analogs that inhibit the ATPase activity of myosin, inhibit adaptation by abolishing motor force production. Phosphate analogs interact with a 120-kDa bundle protein, most likely myosin 1 beta, in a manner that coincides with their effects on adaptation. Features of transduction following inhibition of motor force production suggest that the gating and extent springs of the hair cell orient in parallel at rest and that the negative limit of adaptation arises when force in the stretched extent spring matches the force output of the adaptation motor.

Adaptation, Physiological↗

PubMed2001

SOS mutator DNA polymerase IV functions in adaptive mutation and not adaptive amplification.

Adaptive point mutation and amplification are induced responses to environmental stress, promoting genetic changes that can enhance survival. A specialized adaptive mutation mechanism has been documented in one Escherichia coli assay, but its enzymatic basis remained unclear. We report that the SOS-inducible, error-prone DNA polymerase (pol) IV, encoded by dinB, is required for adaptive point mutation in the E. coli lac operon. A nonpolar dinB mutation reduces adaptive mutation frequencies by 85% but does not affect adaptive amplification, growth-dependent mutation, or survival after oxidative or UV damage. We show that pol IV, together with the major replicase, pol III, can account for all adaptive point mutations at lac. The results identify a role for pol IV in inducible genetic change.

Adaptation, Physiological↗

PubMed2005

Adaptation mechanism of the aspartate receptor: electrostatics of the adaptation subdomain play a key role in modulating kinase activity.

The aspartate receptor of the Escherichia coli and Salmonella typhimurium chemotaxis pathway generates a transmembrane signal that regulates the activity of the cytoplasmic kinase CheA. Previous studies have identified a region of the cytoplasmic domain that is critical to receptor adaptation and kinase regulation. This region, termed the adaptation subdomain, contains a high density of acidic residues, including specific glutamate residues that serve as receptor adaptation sites. However, the mechanism of signal propagation through this region remains poorly understood. This study uses site-directed mutagenesis to neutralize each acidic residue within the subdomain to probe the hypothesis that electrostatics in this region play a significant role in the mechanism of kinase activation and modulation. Each point mutant was tested for its ability to regulate chemotaxis in vivo and kinase activity in vitro. Four point mutants (D273N, E281Q, D288N, and E477Q) were found to superactivate the kinase relative to the wild-type receptor, and all four of these kinase-activating substitutions are located along the same intersubunit interface as the adaptation sites. These activating substitutions retained the wild-type ability of the attractant-occupied receptor to inhibit kinase activity. When combined in a quadruple mutant (D273N/E281Q/D288N/E477Q), the four charge-neutralizing substitutions locked the receptor in a kinase-superactivating state that could not be fully inactivated by the attractant. Similar lock-on character was observed for a charge reversal substitution, D273R. Together, these results implicate the electrostatic interactions at the intersubunit interface as a major player in signal transduction and kinase regulation. The negative charge in this region destabilizes the local structure in a way that enhances conformational dynamics, as detected by disulfide trapping, and this effect is reversed by charge neutralization of the adaptation sites. Finally, two substitutions (E308Q and E463Q) preserved normal kinase activation in vitro but blocked cellular chemotaxis in vivo, suggesting that these sites lie within the docking site of an adaptation enzyme, CheR or CheB. Overall, this study highlights the importance of electrostatics in signal transduction and regulation of kinase activity by the cytoplasmic domain of the aspartate receptor.

Adaptation, Physiological↗

PubMed1999

Bright light treatment used for adaptation to night work and re-adaptation back to day life. A field study at an oil platform in the North Sea.

Night workers complain of sleepiness, reduced performance and disturbed sleep due to lack of adjustment of the circadian rhythm. In simulated night-work experiments scheduled exposure to bright light has been shown to reduce these complaints. Here we studied the effects of bright light treatment on the adaptation to 14 days of consecutive night work at an oil platform in the North Sea, and the subsequent readaptation to day life at home, using the Karolinska sleep/wake diary. Bright light treatment of 30 min per exposure was applied during the first 4 nights of the night-shift period and the first 4 days at home following the shift period. The bright light exposure was scheduled individually to phase delay the circadian rhythm. Bright light treatment modestly facilitated the subjective adaptation to night work, but the positive effect of bright light was especially pronounced during the re-adaptation back to day life following the return home. Sleepiness was reduced and the quality of day was rated better after exposure to bright light. The modest effect of bright light at the platform was, possibly, related to the finding that the workers seemed to adapt to night work within a few days even without bright light. These results suggest that short-term bright light treatment may help the adaptation to an extended night-work period, and especially the subsequent re-adaptation to day life.

Adaptation, Physiological↗

PubMed1999

Mutators, population size, adaptive landscape and the adaptation of asexual populations of bacteria.

Selection of mutator alleles, increasing the mutation rate up to 10, 000-fold, has been observed during in vitro experimental evolution. This spread is ascribed to the hitchhiking of mutator alleles with favorable mutations, as demonstrated by a theoretical model using selective parameters corresponding to such experiments. Observations of unexpectedly high frequencies of mutators in natural isolates suggest that the same phenomenon could occur in the wild. But it remains questionable whether realistic in natura parameter values could also result in selection of mutators. In particular, the main parameters of adaptation, the size of the adapting population and the height and steepness of the adaptive peak characterizing adaptation, are very variable in nature. By simulation approach, we studied the effect of these parameters on the selection of mutators in asexual populations, assuming additive fitness. We show that the larger the population size, the more likely the fixation of mutator alleles. At a large population size, at least four adaptive mutations are needed for mutator fixation; moreover, under stronger selection stronger mutators are selected. We propose a model based on multiple mutations to illustrate how second-order selection can optimize population fitness when few favorable mutations are required for adaptation.

Adaptation, Physiological↗

PubMed1990

Spectral sensitivity and adaptation characteristics of cone mechanisms under white-light adaptation.

Increment-threshold spectral-sensitivity (ITSS) functions and threshold-versus-intensity (tvi) curves were measured under white-light adaptation in rhesus monkeys. The tvi curves showed shape and test wavelength invariance, implying that three cone mechanisms were mediating detection. In general, the results were in agreement with the differential adaptation hypothesis proposed by Stiles that predicted spectral shape invariance of the cone mechanisms but overall changes in the shape of the spectral-sensitivity function with increases in the intensity of the adapting field. The principal changes occurring in the ITSS function as the level of adaptation increased involved a smaller loss in sensitivity of the short-wavelength and the long-wavelength peaks compared with the corresponding loss in sensitivity of the middle-wavelength peak. A three-channel model with an opponent L-M mechanism and a nonopponent L-M mechanism (both with S-cone input) and an independent S-cone mechanism described the ITSS data as well as other increment-threshold and suprathreshold data. The model values for the ITSS functions, along with parameters derived from the transformation of these data to cone-contrast coordinates, permitted the factoring out of first-site adaptation, second-site adaptation, and the relative strengths of contribution of the L and M cones within the opponent and nonopponent L-M channels.

Adaptation, Ocular↗

PubMed1996

Mucosal irritation, adaptive cytoprotection, and adaptation to topical ammonia in the rat stomach.

BACKGROUND: The urease-ammonia (NH4OH) system has been proposed to play a major role in the pathogenesis of the Helicobacter pylori-associated gastritis, but the mechanism of the mucosal damage has not been fully explained. This study was designed to examine possible adaptive cytoprotection and the adaptation of rat gastric mucosa to the irritant action of NH4OH and urease. METHODS AND RESULTS: Single application of NH4OH alone in various concentrations (15-500 mM) caused concentration-dependent mucosal damage starting with 30 mM and reaching a maximum at 250 mM NH4OH, similar to that obtained with 100% ethanol; it was accompanied by a decrease in gastric blood flow (GBF) to approximately 30% of the normal value. When the mucosa was first exposed to the low, non-damaging concentration (15 mM) of NH4OH and then insulted with 100% ethanol, the extent of ethanol damage was greatly attenuated as compared with that caused by ethanol alone. This adaptive cytoprotection was accompanied by the rise in GBF and reversed, in part, by the pretreatment with indomethacin, an inhibitor of prostaglandin (PG)-cyclooxygenase; with L-NAME, a blocker of NO-synthase; or with capsaicin deactivating the sensory nerves. Damaging concentrations of NH4OH (125 mM) caused widespread mucosal damage after the first application, but with repeated insults with 125 mM NH4OH a gradual reduction in the mucosal lesions, accompanied by enhanced mucosal cell proliferation and over-expression of epidermal growth factor (EGF) (using immunocytochemistry) and mRNA of EGF (using trans-reverse polymerase chain reaction), were observed. CONCLUSIONS: NH4OH alone damages gastric mucosa only at the concentration exceeding that found in H. pylori-infected stomachs, whereas at lower concentrations it acts as 'mild' irritant to induce adaptive cytoprotection. This adaptive cytoprotection appears to be mediated, in part, by endogenous PG, sensory nerves, and an arginine-NO-dependent pathway, and repeated applications of NH4OH induce gastric adaptation, probably mediated by enhanced expression of EGF and its receptors and by an increased cell proliferation.

Adaptation, Physiological↗

PubMed1997

Wheelchair users' experience of non-adapted and adapted clothes during sailing, quad rugby or wheel-walking.

The purpose of the present quasi-experimental post-test-design study was to compare 32 wheelchair users' (mostly para/tetraplegics) experience of wearing specially adapted clothes and non-adapted clothes for sailing, quad rugby or wheel-walking. Four existing assessment instruments were used: the Klein-Bell Activities of Daily Living Scale; a two-part Basic Information Questionnaire eliciting experience of effort, comfort and feeling of physical condition; the Experience Sampling Form for investigating the individuals' attitudes in terms of involvement and affective and activity mood states, and the Occupational Therapy Assessment of Leisure Time interview framework for collecting data about experience of leisure time. The wheelchair users all associated significantly greater comfort with use of the adapted clothes and, particularly the 'sailors', better physical condition. Overall, significantly greater involvement and more positive affect states were associated with the adapted clothes than with conventional garments, and mood state changed for the better. The wheelchair users set a higher priority upon work or leisure activities than upon independence in activities of daily living, and for this reason the Klein-Bell ratings showed great variation between the 'sailors' and the 'quad rugby players' (range 57%-93%), though these groups demonstrated more independence than the 'wheel-walkers'. The results of the study confirm the value of adapting sportswear for handicapped people. Such adaptations should also be of benefit for other activities than those studied.

Adaptation, Physiological↗

PubMed2006

The presentation and organization of adaptive cytoprotection in the rat stomach, duodenum, and colon. Dedicated to André Robert the founder of the concept of cytoprotection and adaptive cytoprotection.

BACKGROUND: Adaptive cytoprotection could be demonstrated in lesion attenuation within the whole gastrointestinal tract, in particular sequences, with onset and duration longer than the initial short-lasting period (i.e. one hour) defined by Robert in the stomach only. MATERIAL/METHODS: Adaptive cytoprotection possibly appeared and lesions were attenuated when the stomach, duodenum or colon, in various combinations and sequences, were challenged with initial (mild) and/or final (strong) irritants over a two-week period. Rats were challenged with the mild or strong irritants 25% or 96% ethanol intragastrically 1 ml/rat (stomach) and cysteamine 40 mg or 400 mg/kg subcutaneously (duodenum), or intrarectally (colon). To postulate the prostaglandin relationship known in Robert's cytoprotection and adaptive cytoprotection, indomethacin (1 mg/kg subcutaneously) was given simultaneously with the second challenge. RESULTS: Administering the mild and strong irritant protocols within the same part of the gastrointestinal tract, adaptive cytoprotection presents in the stomach (1 h to 14 days), duodenum (2 h to 14 days), but not in the colon. With these protocols applied to different parts of the gastrointestinal tract, adaptive cytoprotection cross-reaction was evident in the stomach-duodenum, duodenum-stomach (1 h-14 days and 2 h-14 days), stomach-colon, and duodenum-colon (both 2-24 hours), but not in the colon-stomach or colon-duodenum. This protection was fully antagonized with indomethacin. CONCLUSIONS: As observed for a day and even weeks, stomach-duodenum-colon adaptive cytoprotection is an important new defensive phenomenon.

Adaptation, Physiological↗