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PubMed1996

Role of cytoplasmic calcium concentration in the bleaching adaptation of salamander cone photoreceptors.

1. In order to study the possible involvement of Ca2+ in the bleaching adaptation of cones isolated from the retina of the salamander Ambystoma tigrinum, changes in cytoplasmic calcium concentration ([Ca2+]i were opposed by exposing the outer segment to a low-Ca(2+)-O Na+ solution designed to minimize Ca2+ fluxes across the outer segment membrane. 2. When a cone was exposed in normal Ringer solution to bright light bleaching a significant fraction of the photopigment, the circulating current was initially suppressed completely and then recovered to a maintained value less than the value in darkness before the bleach. When the outer segment of the cone was stepped to low-Ca(2+)-O Na+ solution before the bleach was delivered, the circulating current recovered more slowly or (for large bleaches) remained completely suppressed for the duration of the solution exposure. 3. If, during the period for which the current was suppressed in low-Ca(2+)-O Na+ solution, the cone outer segment was exposed to the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), the circulating current was restored. The dim flash response recorded under these conditions exhibited kinetics and integration times similar to those recorded in low-Ca(2+)-O Na+ solution in darkness before the bleach. If, instead, the outer segment was returned to Ringer solution after the bleach, thereby allowing [Ca2+]i to fall from its dark-adapted level to the appropriate bleach-adapted level, the kinetics of the response in low-Ca(2+)-O Na+ solution were greatly accelerated, and the integration time considerably reduced. This was true regardless of whether or not the low-Ca(2+)-O Na+ solution included IBMX. 4. The role of Ca2+ in bleaching adaptation appeared to resemble its role in background adaptation, since in both cases exposure to low-Ca(2+)-O Na+ solution suppressed the acceleration of response kinetics. Responses recorded from cones in low-Ca(2+)-O Na+ solution were nearly identical in waveform and sensitivity during background light or after bleaches, provided that IBMX was used to restore sufficient photocurrent so that responses to flashes could be recorded, and sensitivity was corrected for loss in quantum catch. 5. These results indicate that the fall in [Ca2+]i in cones after a bleach is necessary both for the acceleration of the flash response and the adaptational decrease in sensitivity, as is the case for adaptation by background light.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Chronic insomnia in workers poisoned by inorganic mercury: psychological and adaptive aspects.

Insomnia is one of the symptoms of inorganic mercury poisoning (IMP). The objective of this study is to analyze the chief psychological aspects in the adjustment of workers with chronic insomnia associated with IMP. For this purpose the Preventive Clinical Interview and the Ryad Simon Operational Adaptive Diagnostic Scale (Escala Diagnóstica Adaptativa Operacionalizada-EDAO) were utilized. Fifteen subjects with mean age of 40 years (10 males and 5 females) were studied. Nine were diagnosed with High Adaptive Inefficacy, five with Moderate Inefficient Adaptation and only one with Mild Inefficient Adaptation. Impairment occurred in four adaptive sectors: affective relationship, social-cultural, productivity and organic. Adaptive efficiency indicated that in all the 15 subjects studied the adaptive solutions were frustrating and led to psychic suffering and/or environmental conflict confirming the severity of the involvement in chronic IMP.

Adaptation, Physiological↗
PubMed2026

Adaptations to breath-hold diving: from traditional divers to elite athletes.

Breath-hold diving exposes humans to repeated episodes of profound hypoxia and hypercapnia, eliciting physiological adaptations that enable prolonged underwater performance. This article summarises current knowledge on chronic adaptations in elite breath-hold athletes and traditional diving populations, including the Bajau sea nomads of Southeast Asia and the Korean Haenyeo divers. Evidence indicates that repeated apnoea induces adaptations across multiple physiological systems. Haematological changes include increased spleen size and enhanced splenic contraction, augmenting circulating haemoglobin and oxygen stores during apnoea. In elite divers, structured training can increase resting spleen volume, whereas the Bajau exhibit genetically associated splenic enlargement linked to variants near the PDE10A gene. Cardiopulmonary adaptations include modified pulmonary vascular responses to hypoxia, improved oxygen conservation, and metabolic shifts favoring efficient mitochondrial energy production. Molecular adaptations involve enhanced antioxidant defenses and activation of hypoxia-responsive pathways that may mitigate oxidative stress associated with repeated hypoxia-reoxygenation cycles. Emerging evidence also suggests neural plasticity and possible structural brain adaptations, although the long-term neurological consequences of chronic intermittent hypoxia exposure remain uncertain. Studies of traditional diving populations indicate that both phenotypic plasticity and genetic selection contribute to diving capacity, highlighting interactions between training and evolution. Despite these benefits, breath-hold diving also carries risks, including hypoxic blackout, decompression sickness, and potential neurological injury. Understanding the mechanisms underlying human tolerance to extreme hypoxia may have implications beyond diving physiology, including applications in cardiovascular medicine, hypoxic diseases, and rehabilitation. Further longitudinal, genomic, and mechanistic studies are needed to clarify the limits, benefits, and clinical relevance of these adaptations.

Humans↗
PubMed2004

[Significance of adaptive response to study of traditional Chinese medicine].

Adaptive response is a topic of general interest in medical research. Utilization of adaptive response has become a new treatment strategy for some diseases, the core of which is to stimulate the mechanisms of body internal protection, to improve the adaptive and anti-injury capability, and to maintain the homeostasis of the body. The existence of adaptive response indicates that the body internal protection can be induced and its key mechanism is the inducement of internal protective factors (internal protective proteins). In this article, some connections between adaptive response and the theory of traditional Chinese medicine (TCM) were discussed, which indicated that adaptive response is much beneficial for explaining some theories of TCM such as correspondence between human and nature, strengthening healthy qi to consolidate constitution, acupuncture theory, adaptogen herbs, and treating disease before its onset, etc. Thus the adaptive response is of great significance for explaining scientifically the connotative meaning of the theories of TCM and for promoting the integration of TCM and western medicine.

Acupuncture Therapy↗
PubMedDate not supplied

Adaptation to hand injury: an evolving experience.

OBJECTIVES: Objectives of this study were to examine similarities and differences in physical recovery and psychosocial adaptation, engagement in occupations and relationships, perceived outcomes and expectations, and adaptive issues and strategies of 5 participants from an ongoing longitudinal study of adaptation to hand injury. METHODS: Participants were tracked for 12 months using quantitative measures of physical recovery and psychosocial adaptation, and qualitative adaptation interviews focused on the impact of an injury experience in clients' daily lives. A computerized graphic format documented changes over time in key quantitative and qualitative indicators in individual Adaptation Trajectories. RESULTS: Findings included the importance of motivating occupations and relationships, changes over time in expectations for the future, and differences between independent and interdependent adaptive strategies following hand injury. DISCUSSION: Connections between the International Classification of Functioning and Disability domains of body systems, activity capabilities, and social participation were examined. Findings support the value of individualized, occupation-based therapy that addresses the mind and spirit as well as physical recovery in occupational therapy practice with hand injury clients.

Adaptation, Physiological↗
PubMed1978

Excitation and adaptation in the vertebrate rod photoreceptor.

The excitatory processes and the reactions of the rhodopsin photoproducts in vertebrate rods are summarized, and an adaptation model of the rod is outlined. The transmitter factor Q describes the ability of the discs to release a transmitter carrying the signal from the site of light adaptation to the plasma membrane of the receptor. If Q decreases appropriately when the background light intensity increases, the response range of the rod is preserved and the rod obeys Weber's law. This kind of receptor adaptation is experimentally observed in several species. A photoisomerization in a disc apparently affects the release of a transmitter also in neighbouring discs. The background light also affects the neuronal network of the retina, preserving the response range of the ganglion cell. After an exposure bleaching an appreciable fraction of rhodopsin the sensitivity of the rod returns in two phases: a fast intermediate adaptation and a slow opsin adaptation. After a rather small bleach the photoresponse is fairly well preserved (mainly Q-adaptation), but large bleaches cause a strong reduction in the response range. Different experimental methods utilized when correlating rhodopsin photoproducts and intermediate adaptation are discussed.

Adaptation, Ocular↗
PubMed1999

Longitudinal assessment of adaptive and maladaptive behaviors in fragile X males: growth, development, and profiles.

As young fully mutated fragile X [fra(X)] males age, cognitive levels (IQ scores) and adaptive behavior levels (DQ scores) decline. Given the variable behavioral profiles reported previously, we wondered whether changes in specific attributes of adaptive behavior are related to declines in composite adaptive behavior levels. We also examined maladaptive behavior to determine if changes are related to age. Therefore, we evaluated three areas of adaptive behavior, as well as maladaptive behavior, in 28 fully mutated fra(X) males, ages 4-14 years. To develop a profile of adaptive behavior, we analyzed nine subscale scores from the Vine-land Adaptive Behavior Scale (VABS). To assess maladaptive behavior, we graded part I of the VABS Maladaptive Behavior Scale. Subjects were sorted into three age cohorts, according to their initial test age: younger than 6 years; 6 to 9 years; older than 9 years. Results indicate that, in all age groups, the communications domain is the most severely impacted compared with either the socialization domain or daily living skills and that, in all age groups, the socialization domain is a relative strength compared with either the communications domain or daily living skills. The youngest cohort manifested significant increases in age-equivalent community living skills. Significant differences in age-equivalent scores between cohorts were observed in written language and play skills. Maladaptive behavior scores were available from cross-sectional data only. Twenty males (74%) showed significantly higher maladaptive scores than expected from other children their age. Our data analysis also revealed a moderate and significant negative correlation between maladaptive behavior levels and age (r = -0.54; P < 0.01). Curiously, adaptive and maladaptive behaviors did not correlate with each other.

Adaptation, Psychological↗
PubMed1998

Transient studies of light-adapted cultures of hairy roots of Catharanthus roseus: growth and indole alkaloid accumulation.

Cultures of C. roseus transgenic ("hairy") root clones LBE-6-1 and LBE-4-2 were adapted with periodic daily illumination to investigate the effect of light on growth and nutrient utilization, and the accumulation of the indole alkaloids. Light-adapted roots appeared green and had radially thickened morphology compared with dark-grown controls. Their growth rates were higher than dark-grown controls, with 45% lower doubling times: LBE-6-1, 3.6 days; LBE-4-2, 2.8 days. Relative to dark-grown controls, light-adapted growth increased the biomass (DW) of LBE-6-1 by 25%, but had no effect on the DW of LBE-4-2. The macronutrients NH4+, NO3-, Pi, and sugars, were depleted completely by light-adapted root cultures in that order. The specific and total levels of the indole alkaloid serpentine was enhanced and of tabersonine was lowered in both root clones, while the overall trends of growth and non-growth association of tabersonine and serpentine, respectively, remained unaltered by light adaptation. Ajmalicine accumulation was enhanced in LBE-6-1, but lowered in LBE-4-2; its accumulation was growth-associated in dark-grown LBE-6-1, but appeared non-growth associated in light-adapted cultures. The accumulation of tabersonine-related compounds, lochnericine, and hörhammericine exhibited growth-associated trends, and were either negatively affected or unaffected by light adaptation of LBE-6-1. Neither vindoline nor its precursor, deacetylvindoline, was detected.

Adaptation, Physiological↗
PubMed1999

The adaptiveness of mothers' working models of caregiving through the first year: infant and mother contributions.

How a mother's working model of caregiving develops through an infant's first post-term year has implications for the infant's health. Change in the adaptiveness of the working model of caregiving through the first year and influencing conditions (mother and infant) were examined for 33 premature infants and 44 full-term infants. Adaptiveness was coded from the transcription of a video-assisted interview at 1, 4, 8 and 12 months postterm age. Mother conditions included years of education, symptoms of depression, and evaluation of caregiving. Infant conditions included status at birth, birth weight, weight-for-age, and amenability of temperament. Hierarchical fixed occasions repeated measures analysis showed significant change in working-model adaptiveness with time. The highest adaptiveness scores were at 4 months and the lowest scores were at 8 months. At 8 months, mother's education had a significant positive effect on adaptiveness, mother's symptoms of depression had a negative effect, and infant weight-for-age had a positive effect. Further research is needed to learn what features of a mother's education enhance working model adaptiveness and to identify mechanisms that explain the effects of the infant's weight-for-age on adaptiveness.

Adaptation, Psychological↗
PubMed2001

Differentiating primary pathophysiologic from secondary adaptational processes.

The following manuscript is mainly conceptual in nature. It should be read with reservation since the relevance of its suggestions have yet to be proven. Basically it proposes two rules for the differentiation between primary illness-related pathophysiological vs. secondary adaptational processes. These rules may guide hypotheses generation for further research that is aimed at understanding psychiatric disorders and their shared and unshared mechanisms. For example, in the case of anxiety disorders and depression, it may be of interest to learn if their shared properties are of primary pathophysiological or secondary adaptational significance. We first present some historical observations on the development of the concept of "secondary adaptational processes." We assume such adaptational processes are generated by the organism in order to compensate for primary pathophysiological malfunction or impairment. Next, we propose rules that may enable the dissection of secondary adaptational from primary pathophysiological processes. We also discuss the possible implications of designing studies to sort out these processes, suggesting that the understanding of adaptational processes, may explain the effects of "placebo treatment." Finally we illustrate the application of these rules by two examples: a) amygdala activation, a biological alteration shared by anxiety disorders and major depression and b) elevated plasma soluble interleukin 2 receptor, an unshared property by anxiety disorders and major depression. Also, the first example relates to a biological perturbation associated with a primary pathophysiological mechanism, while the second represents a biological alteration associated with secondary adaptational processes.

Adaptation, Psychological↗
PubMed1995

Biochemical adaptations in the mesolimbic dopamine system in response to heroin self-administration.

Previous studies have shown that chronic, forced exposure to opiates produces specific biochemical adaptations in the ventral tegmental area (VTA) and nucleus accumbens (NAc). The functional consequences of these adaptations have been hypothesized to contribute to certain motivational aspects of drug addiction. In this study, the possibility that similar adaptations could occur in response to intermittent heroin self-administration was tested by comparing homogenates of VTA and NAc from rats self-administering heroin, rats receiving yoked injections of heroin, and rats receiving yoked injections of saline (controls). Tyrosine hydroxylase (TH) immunoreactivity was increased (31-38%) in the VTA and decreased (11%) in the NAc of heroin-exposed rats relative to controls. Heroin exposure also increased cAMP-dependent protein kinase (PKA) activity in both particulate (19-27%) and soluble (17-20%) fractions of the NAc, and decreased (16-17%) the level of Gi alpha immunoreactivity in this brain region. In contrast, no significant biochemical changes were found in the substantia nigra or caudate-putamen, indicating a selective effect on the mesolimbic dopamine system. Overall, adaptations in the VTA and NAc of heroin-exposed rats were similar to, but generally smaller in magnitude than, adaptations produced by chronic morphine administration. However, in contrast to morphine-treated animals, heroin-exposed animals failed to display overt signs of opiate physical dependence, suggesting that adaptations in motivational systems may occur more readily than adaptations in brain regions associated with physical dependence.

Adaptation, Physiological↗
PubMed1993

Selective adaptation of internally triggered saccades made to visual targets.

We examined whether internally triggered saccades made to a nonjumping target (I-saccades) could be adapted independently from externally triggered saccades induced by a jumping target (E-saccades). Five subjects made I-saccades between two fixed targets, one placed straight ahead and the other one positioned at an eccentricity of 17.5 degrees. The peripheral target was displaced to an eccentricity of 8.75 degrees during the saccadic movements toward this target. Amplitudes of the I-saccades made from the central to the peripheral target before and after adaptation were compared with each other. Saccadic amplitudes after adaptation were between 10% and 42% smaller than those before adaptation. E-saccades induced by a single target which jumped from straight ahead to the same peripheral target position as was used for the I-saccades were also measured before and after the adaptation of I-saccades. Amplitudes of E-saccades before and after adaptation were hardly different from each other except in one subject. The mean decreases in amplitude of the two types of saccades, averaged over all subjects, were 21% for I-saccades and 5% for E-saccades. These results show that I-saccades can be adapted to changed visual conditions while E-saccades remain unadapted. We conclude from this finding that I-saccades and E-saccades are generated by at least partially different neural mechanisms.

Adaptation, Physiological↗
PubMed1996

On the short-term adaptation of eye saccades and its transfer to head movements.

During a sequence of eye saccades toward a target that is systematically displaced during initiation of the saccade, the oculomotor system adjusts saccadic amplitude and direction in less than 100 trials to directly reach the second target position. The goal of the present work was to test whether and under which conditions these short-term, adaptive modifications in eye movements are transferred from horizontal eye saccades to horizontal head-pointing movements. In the first series of experiments subjects had to execute head yaw rotations to an extent defined by verbal command (assessed movements). These head movements were not part of visually elicited gaze shifts. They were recorded before and after a period of saccadic adaptation. Saccades were adapted to reduced amplitudes by using target displacements from 30 to 20 degrees and from 40 to 30 degrees. After 40-50 trials per target displacement, the amount of eye saccade adaptation was 79% (30-20 degrees) and 97% (40-30 degrees) of the displacement amplitude. In the second series of experiments, visually triggered head movements to briefly illuminated targets (100 ms) were measured before and after adaptation. The data obtained from both series did not reveal a functionally significant transfer of saccadic adaptation to head movements. The amount of possible transfer given as a percentage of the amount of achieved adaptation was: assessed head movements, 40 degrees, 1.9%, 20 degrees, -8.6%; visually triggered movements, 40 degrees, 5.1%, 20 degrees, 10.0%. No values significantly deviated from zero.

Adaptation, Physiological↗
PubMed1991

Differential effects of GABA and bicuculline on rapidly- and slowly-adapting neurons in primary somatosensory cortex of primates.

In cortical area 3b of monkeys, responses of 71 single neurons to controlled indentations of glabrous skin were recorded before and during iontophoretic application of GABA and bicuculline methiodide (BMI), a GABA receptor antagonist. Constant amplitude indentations were applied to selected sites within the receptive fields of neurons representing the glabrous skin on the digits and palm. Profiles of response magnitudes across stimulation sites were used to quantify receptive field dimensions before and during antagonism of GABAergic inhibition. During administration of BMI, the receptive fields of 26 rapidly-adapting neurons were increased by 3-4 times their original size. Response latencies were substantially longer in the region of expansion than in the original receptive field, suggesting that expansion might be mediated by intracortical connections. The expansion of RFs onto adjacent digits after blockade of GABAergic inhibition suggests that somatotopic reorganization following digit amputations may be subserved by existing excitatory connections. The responses of slowly-adapting neurons were separated into two components, a "dynamic" response corresponding to activity elicited by the initial indenting ramp and a "static" response produced by the sustained indentation. Among 8 slowly-adapting neurons tested with BMI, the receptive fields of the dynamic response component increased to an extent that was similar to the change produced in rapidly-adapting neurons. By contrast, the static response component was rarely altered by BMI. Comparison of the responses to administration of GABA revealed that only 12 of 27 slowly-adapting neurons were inhibited in a dose-dependent manner, whereas 37 of 44 rapidly-adapting neurons exhibited significant reduction of responses in the presence of GABA. Hypotheses are proposed to explain the differential effect of BMI and GABA on slowly- and rapidly-adapting cortical neurons.

Adaptation, Physiological↗
PubMed1987

Ultrastructure of hepatocytes in golden ide (Leuciscus idus melanotus L.; Cyprinidae: Teleostei) during thermal adaptation.

The morphological alterations of hepatocytes of golden ide, Leuciscus idus melanotus, following adaptation to low and high temperatures (14 and 28 degrees C) were investigated by means of light and electron microscopy. The temperature-dependent behaviour of peroxisomes was visualized cytochemically with the alkaline diaminobenzidine medium; the morphological studies were supplemented by the biochemical determination of catalase activity. Cold adaptation of ide hepatocytes is manifested by proliferation and stacking of endoplasmic reticulum, an enhanced secretory activity of Golgi fields and a higher number of peroxisomes as compared with the warm-adapted animals. The latter organelles are characterized by a marked heterogeneity in size, shape and catalase activity, and by a more intimate association with mitochondria and endoplasmic reticulum. The occurrence of small peroxisomal profiles is restricted to lower temperature. Catalase activity can be shown both cytochemically and biochemically to increase during cold adaptation. Whereas the number of mitochondria seems to be unaffected by thermal adaptation, stacking of mitochondria as well as the formation of intramitochondrial membrane piles indicate cold-adaptive processes. A feature typical of warm-adaptation is the formation of membrane-glycogen complexes, which may represent the morphological expression of enhanced carbohydrate metabolism documented in a decreased storage of glycogen at 28 degrees C. At 28 degrees C lipid is the predominant storage product. These findings indicate that fish liver is well-suited to serve as a model for the analysis of the interaction of environmental temperature conditions and hepatic morphology.

Adaptation, Physiological↗
PubMed1983

The effect of furosemide on luminal sodium, chloride and potassium transport in the early distal tubule of Amphiuma kidney. Effects of potassium adaptation.

Previous experiments in the early distal tubule of the doubly perfused kidney of Amphiuma demonstrated net reabsorption of potassium (K) which is reversed to net K secretion after K adaptation. Furthermore, it is known that this particular segment exhibits extensive chloride (Cl) net reabsorption which depends on the presence of sodium (Na) and which is inhibited by furosemide. In order to test for a possible interrelationship between NaCl and K transport, K activity in lumen and cell, transepithelial electrical potential difference, peritubular cell membrane potentials and volume reabsorption were measured in control animals and after K adaptation, in presence and absence of furosemide. In control animals the direction of net K transport is reversed from reabsorption to secretion upon addition of furosemide or following the removal of Cl from the tubular lumen. Volume reabsorption is inhibited by some 80%. In K adapted animals a similar inhibition of volume reabsorption is observed, however K secretion is not further enhanced. In control as well as in K-adapted animals intracellular K activities are still above electrochemical equilibrium after furosemide. The data suggest that a common transport system for Na, Cl and K is present in the luminal cell membrane which is inhibited by furosemide. K secretion observed in controls after furosemide and in K-adapted animals is driven by the cell to lumen electrochemical gradient for K across the K permeable luminal cell membrane. The shift of the luminal pump-leak system towards K secretion following K adaptation may be explained by an increase of the luminal K conductance and/or by a reduction of the activity of the luminal cotransport system. However, other mechanisms may also contribute to the observed phenomenon of K adaptation and cannot be ruled out at present.

Adaptation, Physiological↗
PubMed1993

Trajectory of adaptive behavior in males with fragile X syndrome.

Adaptive behavior in males with fragile X syndrome was longitudinally examined in 17 subjects, ages 1 to 17. Subjects received adaptive behavior evaluations on two occasions within one of three age periods. All domains of the Vineland Adaptive Behavior Scales increased from youngest to oldest age groups, yet older subjects (ages 10 to 17) showed significant declines in their adaptive behavior scores from first to second testing. A relative strength in Daily Living Skills and weakness in Socialization emerged only among older subjects. There was a significant relationship between adaptive behavior and mental age scores in all subjects. Discussion emphasized the parallels between declines in IQ and adaptive behavior as well as the need for further research on adaptive skills in young adults with fragile X syndrome.

Activities of Daily Living↗
PubMed1995

Effects of prolonged uniocular dark adaptation on the direct-current electroretinogram of pigmented and albino rabbits.

The direct-current electroretinogram of seven pigmented and seven albino rabbits was recorded from both eyes for almost 4 h in response to repeated identical light stimuli. Stimulus duration was 10 s, light intensity was 6.8 x 10(2) lux, and the interval between the beginning of succeeding light stimuli was 3 min. The dark-adaptation period preceding light stimulation was 30 min for one of the eyes ('unoccluded eye') and 150 min for the contralateral eye ('occluded eye'), which was patched during the first part (117 min) of the experiment. In pigmented animals, the b- and c-wave amplitudes of the unoccluded eye slowly increased during the first part of the experiment but not significantly during the second. The a-wave amplitude was not significantly changed. After removal of the cover, the a- and b-wave amplitudes of the occluded eye immediately attained but not exceed the level of those in the unoccluded eye, irrespective of the light adaptation induced by the stimulus flashes previously presented to the unoccluded eye. (Control experiments on six pigmented rabbits confirmed that stimuli identical to those used in the main part of the study caused a light adaptation, since a decrease in a- and b-wave amplitudes occurred after the first light stimulus following an initial dark-adaptation period of 2 h for both eyes). In albino rabbits, electroretinogram responses were clearly discernible in the occluded eye also during the first part of the experiment, probably because of transillumination of the head. In other respects, the results were essentially similar to those of pigmented animals. The observation that occluded eyes did not dark adapt better, as judged by the electroretinogram responses, than contralateral eyes given repeated light adaptive stimuli may indicate the presence of a mechanism for transfer of adaptation information between the eyes.

Albinism, Ocular↗