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PubMed2006

[Flexibility of adaptation of vestibule-ocular reflex in human beings].

Vestibulo-ocular reflex (VOR) makes images remain relatively stable on the retina. To keep appropriate performance and minimize image slip throughout life, VOR is subject to long-term adaptive regulation by visual input. It has been reported that adaptive changes in VOR gain (eye velocity/head velocity) are evoked either by fitting subjects with magnifying, miniaturizing, or reversing spectacles during normal behavior or by moving a large visual field in or out of phase relative to the subject's head movement. These feature frequency-selectivity. We studied the flexibility of adaptive gain change in VOR required by a horizontal visual-vestibular mismatch in earth vertical axis rotation (EVAR), including adaptive gain change from EVA to off-vertical axis rotation (OVAR) and other velocities. The visual-vestibular mismatch was made by oscillating subjects in EVAR for 30 minutes at 0.3 Hz with the peak velocity of 30 deg/s and 60 deg/s, synchronized with both in-phase (gain decrease: x 0 experiment) and out-of-phase (gain increase: x 2 experiment) sinusoidal rotation of white-black stripe patterns. Subjects were 19 healthy adult volunteers with no history of neurological symptoms. Horizontal and vertical eye positions were recorded by bitemporal DC-coupled electrooculography. In the x 2 adaptation experiment with 0.3 Hz at the peak velocity of 30 deg/s, the percent change in gain (post-pre/ pre) was 110% at the same stimulation and 100% at 40 deg/s in EVA. In the x 0 adaptation experiment with 0.3 Hz at the peak velocity of 30 deg/s, the percent change in gain was -50% at the same stimulation in EVA. In the x 2 adaptation experiment with 0.3 Hz at the peak velocity of 60 deg/s, the percent change in gain was 66% at the same stimulation in EVA, 30% at the same stimulation in nose-up position, and 74% at the same stimulation in nose-down position. In the x 0 adaptation experiment with 0.3 Hz at the peak velocity of 60 deg/s, the percent change in gain was -34% at the same stimulation in EVA. No change in VOR gain was observed at other peak velocities. These results suggest that VOR adaptation depends frequency and maximum angular head velocity, and this characteristic is observed in OVAR.

Adaptation, Ocular↗
PubMed1999

Behavior of acid-adapted and unadapted Escherichia coli O157:H7 when exposed to reduced pH achieved with various organic acids.

A study was done to determine if various organic acids differ in their inhibitory or lethal activity against acid-adapted and unadapted Escherichia coli O157:H7 cells. E. coli O157:H7 strain EO139, isolated from venison jerky, was grown in tryptic soy broth (TSB) and in TSB supplemented with 1% glucose (TSBG) for 18 h at 37 degrees C, then plated on tryptic soy agar (TSA) acidified with malic, citric, lactic, or acetic acid at pH 5.4, 5.1, 4.8, 4.5, 4.2, and 3.9. Regardless of whether cells were grown in TSB or TSBG, visible colonies were not formed when plated on TSA acidified with acetic, lactic, malic, or citric acids at pH values of < or =5.4, < or =4.5, < or =4.2, or < or =4.2, respectively. Cells not adapted to reduced pH did not form colonies on TSA acidified with lactic acid (pH 3.9) or acetic acid (pH 3.9 and 4.2); however, a portion of acid-adapted cells remained viable on TSA containing lactic acid (pH 3.9) or acetic acid (pH 4.2) and could be recovered in TSB. Inactivation of acid-adapted cells was less than that of unadapted cells in TSB acidified at pH 3.9 with citric, lactic, or acetic acid and at pH 3.4 with malic acid. Significantly (P< or =0.05) higher numbers of acid-adapted cells, compared with unadapted cells, were detected 12 h after inoculation of TSB acidified with acetic acid at pH 3.9; in TSB containing lactic acid (pH 3.9), the number of acid-adapted cells was higher than the number of unadapted cells after 5 h. In TSB acidified at pH 3.9 with citric acid or pH 3.4 with malic acid, significantly higher numbers of acid-adapted cells survived. This study shows that organic acids differ in their inhibitory or lethal activity against acid-adapted and unadapted E. coli O157:H7 cells, and acid-adapted cells are more tolerant than unadapted cells when subsequently exposed to reduced pH caused by these acids.

Adaptation, Physiological↗
PubMed2002

Influence of acid adaptation on the tolerance of Escherichia coli O157:H7 to some subsequent stresses.

Three stains of Escherichia coli O157:H7, including ATCC 43889, ATCC 43895, and 933, were first subjected to acid adaptation at a pH of 5.0 for 4 h. Thermal tolerance at 52 degrees C and survival of the acid-adapted as well as the nonadapted cells of E. coli O157:H7 in the presence of 10% sodium chloride, 0.85% bile salt, or 15.0% ethanol were investigated. Results showed that the effect of acid adaptation on the survival of E. coli O157:H7 varied with the strains and types of subsequent stress. Acid adaptation caused an increase in the thermal tolerance of E. coli O157:H7 ATCC 43889 and ATCC 43895, but no significant difference in the thermal tolerance was noted between acid-adapted and nonadapted cells of E. coli O157:H7 933. Although the magnitude of increase varied with strains of test organisms, acid adaptation generally led to an increase in the tolerance of E. coli O157:H7 to sodium chloride. On the other hand, the susceptibility of acid-adapted cells of the three strains of E. coli O157:H7 tested did not show a significant difference from that of their nonadapted counterparts when stressed with bile salt. The acid-adapted cells of E. coli O157:H7 ATCC 43889 and ATCC 43895 were less tolerant than the nonadapted cells to ethanol, whereas the tolerance of adapted and nonadapted cells of E. coli O157:H7 933 showed no significant differences.

Adaptation, Physiological↗
PubMed2001

Adaptation to temporal contrast in primate and salamander retina.

Visual adaptation to temporal contrast (intensity modulation of a spatially uniform, randomly flickering stimulus) was examined in simultaneously recorded ensembles of retinal ganglion cells (RGCs) in tiger salamander and macaque monkey retina. Slow contrast adaptation similar to that recently discovered in salamander and rabbit retina was observed in monkey retina. A novel method was developed to quantify the effect of temporal contrast on steady-state sensitivity and kinetics of light responses, separately from nonlinearities that would otherwise significantly contaminate estimates of sensitivity. Increases in stimulus contrast progressively and reversibly attenuated and sped light responses in both salamander and monkey RGCs, indicating that a portion of the contrast adaptation observed in visual cortex originates in the retina. The effect of adaptation on sensitivity and kinetics differed in simultaneously recorded populations of ON and OFF cells. In salamander, adaptation affected the sensitivity of OFF cells more than ON cells. In monkey, adaptation affected the sensitivity of ON cells more than OFF cells. In both species, adaptation sped the light responses of OFF cells more than ON cells. Functionally defined subclasses of ON and OFF cells also exhibited asymmetric adaptation. These findings indicate that contrast adaptation differs in parallel retinal circuits that convey distinct visual signals to the brain.

Action Potentials↗
PubMed2003

[Application of suppression subtractive hybridization technique in the investigation of heat adaptation mechanism].

OBJECTIVE: To understand whether there are genes differentially expressed in association with heat adaptation in resting heat-adapted rats at normal temperature, and to evaluate the feasibility of investigating heat adaptation mechanism in light of gene differential expression. METHODS: The mRNAs were extracted from rat liver tissues and reverse transcripted into double-strand cDNAs. Suppression subtractive hybridization (SSH) was applied to compare the gene expression profiles between heat adaptation group and normal temperature control group, and cDNA subtraction libraries of the differentially expressed genes were constructed. PCR-selective differential screening technique was used to identify the differentially expressed genes. RESULTS: Six cDNA fragments were identified in the preliminary experiment to be differentially expressed. CONCLUSIONS: There are genes differentially expressed in the liver of resting heat-adapted rats in association with heat adaptation at normal temperature, and these genes may be involved in maintaining heat adaptation. This study also indicates the feasibility of investigating heat adaptation mechanism by isolating differentially expressed genes associated with heat adaptation.

Adaptation, Physiological↗
PubMed2003

Adaptation to rotating artificial gravity environments.

A series of pioneering experiments on adaptation to rotating artificial gravity environments was conducted in the 1960s. The results of these experiments led to the general belief that humans with normal vestibular function would not be able to adapt to rotating environments with angular velocities above 3 or 4 rpm. By contrast, our recent work has shown that sensory-motor adaptation to 10 rpm can be achieved relatively easily and quickly if subjects make the same movement repeatedly. This repetition allows the nervous system to gauge how the Coriolis forces generated by movements in a rotating reference frame are deflecting movement paths and endpoints and to institute corrective adaptations. Independent mechanisms appear to underlie restoration of straight movement paths and of accurate movement endpoints. Control of head movements involves adaptation of vestibulo-collic and vestibulo-spinal mechanisms as well as adaptation to motor control of the head as an inertial mass. The vestibular adaptation has a long time constant and the motor adaptation a short one. Surprisingly, Coriolis forces generated by natural turning and reaching movements in our normal environment are typically larger than those elicited in rotating artificial gravity environments. They are not recognized as such because self-generated Coriolis forces during voluntary trunk rotation are perceptually transparent. After adaptation to a rotating environment is complete, the Coriolis forces generated by movements within it also become transparent and are not felt although they are still present.

Adaptation, Physiological↗
PubMed2005

Experimental studies of adaptation in Clarkia xantiana. II. Fitness variation across a subspecies border.

Because the range boundary is the locale beyond which a taxon fails to persist, it provides a unique opportunity for studying the limits on adaptive evolution. Adaptive constraints on range expansion are perplexing in view of widespread ecotypic differentiation by habitat and region within a species' range (regional adaptation) and rapid evolutionary response to novel environments. In this study of two parapatric subspecies, Clarkia xantiana ssp. xantiana and C. x. ssp. parviflora, we compared the fitness of population transplants within their native region, in a non-native region within the native range, and in the non-native range to assess whether range expansion might be limited by a greater intensity of selection on colonists of a new range versus a new region within the range. The combined range of the two subspecies spans a west-to-east gradient of declining precipitation in the Sierra Nevada of California, with ssp. xantiana in the west being replaced by ssp. parviflora in the east. Both subspecies had significantly higher fitness in the native range (range adaptation), whereas regional adaptation was weak and was found only in the predominantly outcrossing ssp. xantiana but was absent in the inbreeding ssp. parvifilora. Because selection intensity on transplants was much stronger in the non-native range relative to non-native regions, there is a larger adaptive barrier to range versus regional expansion. Three of five sequential fitness components accounted for regional and range adaptation, but only one of them, survivorship from germination to flowering, contributed to both. Flower number contributed to regional adaptation in ssp. xantiana and fruit set (number of fruits per flower) to range adaptation. Differential survivorship of the two taxa or regional populations of ssp. xantiana in non-native environments was attributable, in part, to biotic interactions, including competition, herbivory, and pollination. For example, low fruit set in ssp. xantiana in the east was likely due to the absence of its principal specialist bee pollinators in ssp. parviflora's range. Thus, convergence on self-fertilization may be necessary for ssp. xantiana to invade ssp. parviflora's range, but the evolution of outcrossing would not be required for ssp. parviflora to invade ssp. xantiana's range.

Adaptation, Biological↗
PubMed1979

[A report on studies on the child's adaptation to school and family environment after neoplastic disease].

The objective of this study was to learn the course of child's adaptation process to school and family environment following the neoplastic disease. The study also aimed select the environment and personality factors influencing adaptation effect. The study pertains to the child's personality and how it works at home and at school. It also tries to get to know the child's environment. 65 children of different social environment were studied. Motor functions of these children were limited as the result of tumour disease. Special scale of adaptation was prepared when the research was over. By means of this sale two groups of children were distinguished: those who were well adapted to the environment and those who were not. Statistical analysis was used to compare the groups on account of the following factors: health factors including: a kind of tumour, duration of the disease, prevalence of pain, manipulation and locomotive abilities, visibility of handicap; sociological factors including: age and sex of studied persons, the place of residence and education of parent's, living standard of the family, a degree of family participation in cultural life of the society, mother's attitude towards the insane child. These factors allow to formulate the following dependences: The more a level of the child's locomotive functions, following neoplastic disease approaches to the standard, the more favourable course takes the process of child's adaptation to the family and peers. If a neoplastic disease leaves permanent and always visible handicap then child's adaptation effect to the environment is not favourable. An active participation of the family in socially life is beneficial for regular adaptation of a child. Personality development as the result of participation in cultural life allows socially accepted defence mechanism to work in stress situations connected with the disease. Parent's rational attitude towards an insane child correlates with a beneficial child's adaptation to an environment. Other factors did not differentiate the two groups statistically. During clinicalontgenetic analysis concerning particular studied cases, 3 models of nonfunctional adaptation were distinguished: maladjustment of aggressive type prevailing among the children with permanent physical handicap coming of families characteristic for socially nonaccepted standard of behaviour; maladjustment of neurotic type prevailing among the children coming of compliant families whose adult members manifest neurotic vegetative reactions in difficult situations.(ABSTRACT TRUNCATED AT 400 WORDS)

Activities of Daily Living↗
PubMed2006

Neglect and prism adaptation: a new therapeutic tool for spatial cognition disorders.

PURPOSE: A large proportion of right-hemisphere stroke patients show unilateral neglect, a neurological deficit of perception, attention, representation, and/or performing actions within their left-sided space, inducing many functional debilitating effects on everyday life, and responsible for poor functional recovery and ability to benefit from treatment. This spatial cognition disorder affects the orientation of behaviour with a shift of proprioceptive representations toward the lesion side. METHODS: This shift can be reduced after a prism adaptation period to a right lateral displacement of visual field (induced by a simple target-pointing task with base-left wedge prisms). The modification of visuo-motor or sensory-motor correspondences induced by prism adaptation involves improvement of different symptoms of neglect. RESULTS: Classical visuo-motor tests could be improved for at least 2h after adaptation, but also non-motor and non-visual tasks. In addition, cross-modal effects have been described (tactile extinction and dichotic listening), mental imagery tasks (geographic map, number bisection) and even visuo-constructive disorders. These cognitive effects are shown to result from indirect bottom-up effects of the deeper, adaptive realignment component of the reaction to prisms. Lesion studies and functional imaging data evoke a cerebello-cortical network in which each structure plays a specific role and not all structures are crucial for adaptation ability. CONCLUSIONS: These cognitive effects of prism adaptation suggest that prism adaptation does not act specifically on the ipsilesional bias characteristic of unilateral neglect but rehabilitates more generally the visuo-spatial functions attributed to the right cortical hemisphere. These results reinforce the idea that the process of prism adaptation may activate brain functions related to multisensory integration and higher spatial representations and show a generalization at a functional level. Prism adaptation therefore appears as a new powerful therapeutic tool for spatial cognition disorders.

Adaptation, Physiological↗
PubMed1991

Spatial restriction of light adaptation and mutation-induced inactivation in fly photoreceptors.

The spatial spread within fly photoreceptors of 2 forms of desensitization by bright light have been investigated: the natural process of light adaptation in normal Musca photoreceptors and a receptor-potential inactivation in the no-steady-state (nss) mutant of the sheep blowfly Lucilia. The suction-electrode method used for recording from vertebrate rods was applied to fly ommatidia. A single ommatidium in vitro was partially sucked into a recording pipette. Illumination of the portion of the ommatidium within the pipette resulted in a flow of current having a wave form similar to that of the receptor potential and polarity consistent with current flow into the illuminated region of the photoreceptors. Two 5-microns slits of light, positioned at right angles to the ommatidial axis, were employed to determine the spread of light adaptation or inactivation along the ommatidium. The intensity of a flash of light delivered to one (adapting) slit was adjusted until it produced a criterion fractional reduction in the response to the other (test) slit. The reciprocal of this intensity of the adapting slit was taken as a measure of the effectiveness of the slit in causing light adaptation or inactivation. The effectiveness of the slit in causing light adaptation in normal Musca ommatidia fell as the adapting and test slits were moved farther apart along the ommatidial axis, declining to half its maximal value at a distance of 13 +/- 2 microns. Similar measurements of the effectiveness of a slit in causing light-induced inactivation in the nss mutant of Lucilia also demonstrated localization, declining to half its maximal value at a distance between the slits of 9 +/- 1 microns. Neither light adaptation nor inactivation by the nss mutation, therefore, appear to be mediated by voltage or by a highly diffusible agent. The results are consistent with the idea that inactivation by the nss mutation replaces adaptation in the mutant photoreceptors.

Adaptation, Physiological↗
PubMed1991

Disconjugate adaptation to long-standing, large-amplitude, spectacle-corrected anisometropia.

A 12-yr-old anisometropic patient had worn corrective eyeglasses (right eye, -0.50 +1.50 x 125; LE, -9.75 +2.50 x 60) for 7 yr, and then changed to contact lenses. Eye movements were recorded before and after the change to contact lenses using binocular search coils. In habitual spectacle viewing, the patient showed disconjugate adaptation. During monocular viewing, for example, ocular alignment changed by as much as 4 degrees during a 20 degrees saccade. Also, during monocular viewing, with either eye, placing the spectacle lens in front of the eye caused an increase in the disconjugate adaptive response compared with viewing without lenses. This finding emphasizes the context specificity of adaptive responses. After switching to contact lenses, the patient still wore his spectacles for 20-40 min each day. Although there was little residual disconjugate adaptation for vertical saccades, he showed considerable adaptation for horizontal saccades, especially for gaze changes that required divergence. The persistence of a partial state of disconjugate adaptation allowed the patient to use immediate, disparity-induced, horizontal vergence to aid ocular alignment in either the contact-lens-viewing or the spectacle-viewing condition. A more complete reversion to conjugacy occurred after nine days of exclusive use of his contact lenses. Then, in a short-term experiment, two minutes of binocular viewing through the eyeglasses induced a considerable reversion toward the previous state of disconjugate adaptation (up to 1.25 degrees of vergence change during monocular viewing). Finally, the waveform of the adapted (to spectacles) intrasaccadic vergence change with monocular viewing was similar to the waveform of the unadapted intrasaccadic vergence change during binocular refixations between targets that required a combined saccade and vergence. This finding suggests a common mechanism for adaptation to spectacle-corrected anisometropia and for normal binocular vergence-saccade interactions.

Adaptation, Ocular↗
PubMed1986

The role of calcium in the rapid adaptation of an insect mechanoreceptor.

The femoral tactile spine of the cockroach is a rapidly adapting mechanoreceptor in which the response to a step displacement is a burst of action potentials lasting about 1 sec. This adaptation seems to occur during the encoding of action potentials from receptor current, since there is no evidence of adaptation in the receptor potential, and the adaptation can be demonstrated by direct electrical stimulation of the single sensory neuron in the spine. We have recently presented evidence for a calcium-activated potassium conductance in the tactile spine receptor neuron, although it was not directly linked to adaptation. Since this conductance could be involved in the rapid adaptation of the tactile spine neuron, we sought an association between adaptation and the entry of calcium ions into the cell. Adaptation in the tactile spine neuron was examined by direct electrical stimulation using a randomly fluctuating current followed by frequency-response analysis. The dynamic behavior was studied as a function of the concentration of calcium ions in the bathing solution, the presence of calcium channel blocking agents, or the divalent cation ionophore antibiotic A23187. No evidence could be found that entry of calcium ions into the cell has a major role in the sensory adaptation.

Adaptation, Physiological↗
PubMed1985

[Effect of preliminary adaptation to short-term stress exposure on the resistance of the spontaneously contracting myocardium to a lipid peroxidation inducer].

Contractile function of the isolated right atrium was studied in male Wistar rats adapted to short-term stressor exposures at varying times after adaptation was completed. Adaptation to short-term stressor exposures induced a limited decrease in myocardial contractility immediately after adaptation was over. On the 3d day an additional reduction in the characteristics of contractile function was still observed. However, by the 5th day the characteristics recovered to the control level. At the same time adaptation completely prevented the derangement of myocardial contractility, induced by exposure to a prolonged stress. That protective effect was observed as early as adaptation was completed, on days 3 and 5 after adaptation, and became lessened on the 10th day. It is assumed that on the 5th day after adaptation the animals are in a postadaptation state where the untoward effect of adaptation disappears whereas the protective effect is demonstrable to a full extent. As a result all the characteristics of myocardial contractility following a prolonged stress on the 5th day after completion of short-term stressor exposures differed in no way from the control parameters.

Adaptation, Physiological↗
PubMed1974

Light adaptation in the ventral photoreceptor of Limulus.

Light adaptation in both the ventral photoreceptor and the lateral eye photoreceptor is a complex process consisting of at least two phases. One phase, which we call the rapid phase of adaptation, occurs whenever there is temporal overlap of the discrete waves that compose a light response. The recovery from the rapid phase of adaptation follows an exponential time-course with a time constant of approximately 75 ms at 21 degrees C. The rapid phase of adaptation occurs at light intensities barely above discrete wave threshold as well as at substantially higher light intensities with the same recovery time-course at all intensities. It occurs in voltage-clamped and unclamped photoreceptors. The kinetics of the rapid phase of adaptation is closely correlated to the photocurrent which appears to initiate it after a short delay. The rapid phase of adaptation is probably identical to what is called the "adapting bump" process. At light intensities greater than about 10 times discrete wave threshold another phase of light adaptation occurs. It develops slowly over a period of (1/2) s or so, and decays even more slowly over a period of several seconds. It is graded with light intensity and occurs in both voltage-clamped and unclamped photoreceptors. We call this the slow phase of light adaptation.

Adaptation, Ocular↗
PubMed1981

[Contribution to problems of the adaptation concept in pathology using the heart as an example (author's transl)].

The paper represents a contribution to the problems associated with the adaptation concept used in biology and medicine for which there does not yet exist an exact and generally accepted definition. Several aspects of the adaptation concept as it is applied in pathology (adaptation and disease, adaptation on the cellular level, adaptation and and optimation, systemic and local adaptation) are illustrated by means of the adaption of the heart to physiological and pathological condition, with particular attention being paid to questions of cellular adaptation. Finally, it is emphasized that knowledge of the structural and functional changes underlying the adaptation of the organism is of great importance to the prevention of diseases.

Adaptation, Physiological↗
PubMed1995

[Glare adaptation for inhomogeneous glare distribution with respect to the dynamic components of the vision task].

Basic investigations in the field of adaptation luminance were carried out using Holladay's visual threshold criterion. The connection between adaptation luminance LA, illumination at the spot in the eye EB1 and the angle of glare theta is LA = 9.2 x EB1 x theta -2 LA in cd/m2, Eb1 in 1x, theta in degrees. In most cases the investigations of adaptation luminance were also carried out under conditions of fixed view and static visual tasks. It is however, important to take into account the dynamic visual task and the adaptation process by determining the adaptation luminance, but very few measurements have been carried out under these conditions. For the results represented here the visual threshold was replaced by the readaptation time necessary for perception of movement direction of a striped pattern (dynamic) and with the idea of also comparing the perception of the slot location in a ring in the Landolt rings (static). The method of investigations was as follows: The subject adapts to the inhomogeneous field of luminance for which the adaptation luminance must be determined. Then in a dark surrounding field for comparison, the visual task is offered, and the readaptation time necessary for the fulfillment of the visual task is measured. This procedure is repeated with a homogeneous field of luminance. The luminance of a homogeneous field is equal to the adaptation luminance. If the readaptation times are equal, the inhomogeneous distribution of luminance has the adaptation luminance LA. The important difference in comparison to previous investigations is the inclusion of dynamic components (readaptation time and dynamic visual task).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Ocular↗
PubMed1996

[Effects of gastric mucosal blood flow (GMBF) on the role of adaptive cytoprotection of rat gastric mucosa].

By the use of hydrogen gas clearance technique, we have investigated the role of GMBF in the adaptive cytoprotection induced by intragastric perfusion with low concentration prior to high concentration of HCl plus ethanol. The results were as follows: (1) intragastric perfusion with low concentration prior to high concentration of HCl plus ethanol led to an adaptive cytoprotection, i.e., the gross and the deep damage were decreased by 47.09% and 44.57% respectively, as compared with those caused by high concentration of HCl plus ethanol alone; correspondingly, GMBF also showed an adaptive hyperemic response, i.e., GMBF was increased by 28.02% as compared with that due to high concentration alone; (2) close arterial infusion of vasopressin blocked the adaptive hyperemic response and abolished the adaptive cytoprotection; (3) intravenous indomethacin reduced the basal GMBF, and abolished both the adaptive hyperemic response and cytoprotection; furthermore, the gross and deep damage were aggravated compared with that caused by high concentration alone. The results showed that the adaptive hyperemic response of gastric mucosa was involved in the adaptive cytoprotection and suggested that the adaptive cytoprotection of endogenous prostaglandin might be partially related to the increase of GMBF.

Adaptation, Physiological↗
PubMedDate not supplied

[Nitric oxide as a factor in the antihypoxic effect of adaptation to physical loading].

It is known that adaptation to exercise enhances the organism resistance to acute hypoxia. However the mechanism of this cross protective effect have been insufficiently studied. The analysis of literature suggests that NO may play a role in the development of the antihypoxic effect of adaptation to exercise. The aim of the present study was to test this hypothesis: first, by evaluating the influence of NO donor and NO-synthase inhibitor on the antihypoxic effect of adaptation to exercise and, second, by evaluating the changes of NO production in acute hypoxia and after a course of adaptation to exercise. It was shown that the NO donor could both reproduce and considerably (three times) potentiate the antihypoxic effect of adaptation to exercise. At the same time, the NO-synthase inhibitor completely suppressed the development of the protective antihypoxic effect of adaptation. After adaptation to exercise, the cerebral NO production was unchanged, while the hepatic NO production doubled. Acute hypoxia induced a biphase change in tissue NO production; initial increase (twofold in the brain) preceded a decrease (by 25% in liver and 37% in the brain as compared to the control). Therefore, the increased NO production following adaptation to exercise can underlie the antihypoxic effect of such an adaptation.

Acute Disease↗