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PubMed2002

Induction of adaptive response by low-dose radiation in RIF cells transfected with Hspb1 (Hsp25) or inducible Hspa (Hsp70).

An adaptive response results in a reduced effect of a high challenging dose of a stressor after a smaller, inducing dose has been applied a few hours earlier. Radiation-induced fibrosarcoma (RIF) cells did not show an adaptive response, i.e. a reduced effect from a high challenging dose (2 Gy) of a radiation after a priming dose (1 cGy) had been applied 4 or 7 h earlier, but cells of a thermoresistant clone (TR) derived from RIF cells did. Since the expression of inducible Hspa (also known as Hsp70) and Hspb1 (also known as Hsp25) was different in these two cell lines, the role of inducible Hspa and Hspb1 in the adaptive response was examined. When RIF cells were transfected with inducible Hspa or Hspb1, both radioresistance measured by clonogenic assays and a reduction of apoptosis were detected. The adaptive response was also acquired by these two cell lines. The inducible Hspa transfectant showed a more pronounced adaptive response than the Hspb1 transfectant. Based on these results, it appears that inducible Hspa and Hspb1 are at least partly responsible for the induction of the adaptive response in these cells. Moreover, when inducible Hspa or Hspb1 was transfected into RIF cells, co-regulation of the two genes was detected. Heat-shock factor (Hsf) was found to be at least partially responsible for the induction of the adaptive response in these cells.

Adaptation, Physiological↗
PubMed1988

Aldosterone in colonic potassium adaptation in rats.

The influence of adrenalectomy and administration of aldosterone on potassium secretion by colonic epithelium was studied in vivo in rats, particularly in relation to potassium adaptation (induced by feeding a potassium-rich diet) and the response to acute i.v. administration of a potassium load. Adrenalectomy (rats maintained on dexamethasone and saline) impaired the development of potassium adaptation or considerably reduced it if the rats had been previously adapted. The partial adaptation observed in the adrenalectomized rats may be related to the increased plasma potassium concentration developed when these rats received the potassium-rich diet. Within 2 h of acute aldosterone administration, the response of the potassium secretion rate to acute potassium loading in adrenalectomized rats was significantly improved. When aldosterone (2 micrograms/day per 100 g body weight, given by osmotic minipump) was added to the replacement treatment, the plasma concentration of potassium was similar to that of the intact rats, and both potassium adaptation and the response to the acute potassium load were completely restored. Transepithelial potential difference and sodium transport were not stimulated, being similar to the values in intact rats. Considerable changes in potassium secretion induced by acute potassium loading did not significantly affect sodium transport. The findings suggest that the sodium and potassium epithelial pathways are, to a large extent, independently influenced by aldosterone. Aldosterone appears to be essential for complete adaptation and, in a relatively low dose, can completely restore potassium adaptation and the response to acute potassium loads in adrenalectomized rats.

Adaptation, Physiological↗
PubMed2005

Interrelationships among whole-body coordination, functional potentiality, and environmental adaptability.

The term "adaptability" or "capacity of adaptation" is the central concept in the general advancement and promotion of research in physiological anthropology. Throughout the history of Homo sapiens, mankind has adapted itself to environmental stress. As a result, numerous physiological polymorphisms in humans are present in our planet-wide distribution. Totally regulated physiological function by integration and coordination is referred to as whole-body coordination and is associated with a high degree of adaptability in humans. Functional potentiality also affects environmental adaptability. Thus, whole-body coordination and functional potentiality are necessary for adaptation to environmental changes. There is an interrelationship among functional potentiality, whole-body coordination, physiological polymorphisms, and environmental adaptability.

Adaptation, Physiological↗
PubMed2000

Adaptation to a fat-rich diet: effects on endurance performance in humans.

The focus of this review is on studies where dietary fat content was manipulated to investigate the potential ergogenic effect of fat loading on endurance exercise performance. Adaptation to a fat-rich diet is influenced by several factors, of which the duration of the adaptation period, the exercise intensity of the performance test and the content of fat and carbohydrate in the experimental diet are the most important. Evidence is presented that short term adaptation, < 6 days, to a fat-rich diet is detrimental to exercise performance. When adaptation to a fat-rich diet was performed over longer periods, studies where performance was tested at moderate intensity, 60 to 80% of maximal oxygen uptake, demonstrate either no difference or an attenuated performance after consumption of a fat-rich compared with a carbohydrate-rich diet. When performance was measured at high intensity after a longer period of adaptation, it was at best maintained, but in most cases attenuated, compared with consuming a carbohydrate-rich diet. Furthermore, evidence is presented that adaptation to a fat-rich diet leads to an increased capacity of the fat oxidative system and an enhancement of the fat supply and subsequently the amount of fat oxidised during exercise. However, in most cases muscle glycogen storage is compromised, and although muscle glycogen breakdown is diminished to a certain extent, this is probably part of the explanation for the lack of performance enhancement after adaptation to a fat-rich diet.

Adaptation, Physiological↗
PubMed1998

Family environment, glycemic control, and the psychosocial adaptation of adults with diabetes.

OBJECTIVE: To evaluate whether the family system variables of adults with diabetes relate to the adequacy of metabolic control or the psychosocial adaptation to the illness. RESEARCH DESIGN AND METHODS: A total of 150 insulin-requiring adults were assessed on a single occasion. They completed two family system measures (the Family Environment Scale [FES] and the Diabetes Family Behavior Checklist [DFBC]), two quality-of-life measures (the Diabetes Quality of Life Scale and the Medical Outcomes Study Health Survey-36), and one measure of cognitive appraisal (the Appraisal of Diabetes Scale). Glycemic control was assessed using HbA1c results. Demographic data (age, sex, diabetes type, duration of diabetes, and number of diabetes-related medical complications) were gathered from the patients' charts. RESULTS: Concerning glycemic control, none of the family system measures were significant predictors of HbA1c. Older age and longer duration of diabetes predicted higher HbA1c values. For psychosocial adaptation, when family members behaved in ways that supported the diabetes care regimen (measured by the DFBC), the individual with diabetes was more satisfied with his or her adaptation to the illness and reported less interference in role function due to emotional problems. Family cohesion (measured by the FES) also related to better physical function. Women reported higher levels of diabetes satisfaction. The Appraisal of Diabetes Scale predicted glycemic control and psychosocial adaptation. CONCLUSIONS: For insulin-treated adults with diabetes, family system variables do not relate to glycemic control, but they do relate to psychosocial adaptation. Future work should explore the impact of family-centered interventions on adaptation, sex differences in adaptation, and the use of the Appraisal of Diabetes Scale as a first-line clinical screening tool.

Adaptation, Psychological↗
PubMed2002

Muscular, skeletal, and neural adaptations following spinal cord injury.

Spinal cord injury is associated with adaptations to the muscular, skeletal, and spinal systems. Experimental data are lacking regarding the extent to which rehabilitative methods may influence these adaptations. An understanding of the plasticity of the muscular, skeletal, and spinal systems after paralysis may be important as new rehabilitative technologies emerge in the 21st century. Moreover, individuals injured today may become poor candidates for future scientific advancements (cure) if their neuromusculoskeletal systems are irreversibly impaired. The primary purpose of this paper is to explore the physiological properties of skeletal muscle as a result of spinal cord injury; secondarily, to consider associated changes at the skeletal and spinal levels. Muscular adaptations include a transformation to faster myosin, increased contractile speeds, shift to the right on the torque-frequency curve, increased fatigue, and enhanced doublet potentiation. These muscular adaptations may be prevented in individuals with acute paralysis and partially reversed in individuals with chronic paralysis. Moreover, the muscular changes may be coordinated with motor unit and spinal circuitry adaptations. Concurrently, skeletal adaptations, as measured by bone mineral density, show extensive loss within the first six months after paralysis. The underlying science governing neuromusculoskeletal adaptations after paralysis will help guide professionals as new rehabilitation strategies evolve in the future.

Adaptation, Physiological↗
PubMed1992

Adaptation of the gastric mucosa to stress. Role of prostaglandin and epidermal growth factor.

This study was designed to determine whether repeated exposures to stress lead to the adaptation of the gastric mucosa to stress ulcerogenesis. Wistar rats with intact or resected salivary glands were exposed to a standard period (3.5 h) of water-immersion and restraint stress every other day up to 8 days. The significant reduction in the severity of gastric lesions was first noticed after the second exposure to stress and was maximal after 6-day exposures to stress. This tolerance to stress ulcerogenesis disappeared after a 6-day rest during which animals were not exposed to stress. Histologically, the hemorrhages and edema seen after a single stress were less frequent during adaptation; instead the mucosa regenerated in spite of continuation of exposure to stress. During adaptation, the mucosal blood flow (MBF) and mucosal biosynthesis of PG were markedly increased. Administration of indomethacin (5 mg/kg i.p.) completely abolished gastric adaptation to stress and this was accompanied by about 85% reduction in mucosal generation of PG and significant decrease in the MBF. Salivectomy, which significantly reduced the luminal contents of epidermal growth factor (EGF) in the stomach, delayed and reduced the adaptation. We conclude that the stomach has the ability to adapt to repeated exposures to stress and that this adaptation is mediated, at least in part, by endogenous PG and EGF.

Adaptation, Physiological↗
PubMed1984

Binaural phase differences and binaural auditory adaptation.

In order to determine the relationship between binaural phase localization and auditory adaptation, subjects were asked to perform a series of phase-based localization tasks, as well as an SDLB adaptation task. A binaurally presented 400 Hz tone was used for midplane localization tasks, and adaptation balances. The tone was presented monaurally during adaptation after binaural localization and the SDLB pre-test. Following 7 min exposure, subjects readjusted phase to centre the binaural stimulus in the midline, and then adjusted intensity to determine dB of adaptation. No consistent or statistically significant change in phase settings occurred. There was a significant decline in the balance intensity as a function of adaptation. A further re-establishment of the midline by phase manipulation also showed no localization effect. For the stimulus values used in the present study, there was no inter-effect of binaural phase localization, and SDLB auditory adaptation.

Adaptation, Physiological↗
PubMed1983

Quantitative studies of stimulus coding in first-order vibrissa afferents of rats. 2. Adaptation and coding of stimulus parameters.

Mechanosensory neurons are often classified as either rapidly adapting or slowly adapting. We examined response decay (adaptation) during constant deflection of the vibrissae with quantitative, repeatable, ad hoc measures. We found that first-order vibrissa-activated neurons of the fifth ganglion exhibit a variety of adaptation rates that appear to be distributed continuously between the rapidly and slowly adapting extremes. Also, adaptation rate is influenced markedly by stimulus magnitude. We found no evidence for a dichotomy within the more slowly adapting neurons on the basis of discharge regularity. Threshold tuning curves were used to evaluate vibration sensitivity. Both the best frequencies and 1:1 discharge thresholds for sinusoidal stimulation ranged over two orders of magnitude and were continuously distributed. First-order vibrissa-activated afferents exhibit a broad variety of response patterns to constant-velocity stimulation. The pattern of discharge varied both as a function of time during constant-velocity (ramp) deflection and as a function of stimulus velocity. Although information about the parameters of a stimulus may be conveyed by any of several features of the response pattern, it appears that few if any neurons function as "pure" encoders of any particular stimulus parameter. We examined quantitatively the relationship between discharge rate and both velocity and amplitude of vibrissa deflection with the aid of a computer-based curve-fitting procedure. We found that about half the observed rate-level functions were best described by a power function; the remainder were best fit by a logarithmic function. The parameters of the best-fitting functions varied widely and continuously, emphasizing further the diversity of coding properties of the rat's vibrissa afferents. Rate-level curves for stimulus magnitude generally exhibited saturation; some were nonmonotonic. None were described adequately by either a logarithmic function or a power function.

Adaptation, Physiological↗
PubMed2005

Study of blue and red flash in dark-adapted electroretinogram.

PURPOSE: To investigate the characteristics of the waveform generated by blue and red light stimulations in a dark-adapted electroretinogram (ERG) and those of cone responses in the dark-adapted condition. METHODS: The study subjects were 52 persons (88 eyes) with no previous medical history. The author recorded b-waves (rod response) with red light stimulation and the x-waves (dark-adapted cone response) that appeared before the b-waves. The author also recorded b-waves with blue light stimulation, which had the same amplitude as the b-waves from the red light stimulation. The differences with respect to age and gender were studied. Waveforms of the dark-adapted cone ERGs were recorded by using a digital subtraction technique. RESULTS: The x-wave always appeared before the b-wave with 0 dB (2.4 cd.s/m2) red stimulation. With blue stimulation, a b-wave equivalent to the b-wave stimulated with the red light of 0 dB intensity appeared at an average of -14.57 dB. The implicit time for the b-wave was delayed significantly for the male group. There were no significant differences between different age groups. The dark-adapted cone ERG demonstrated the waveform of a negative response followed by a series of oscillatory potentials (OPs) and a positive response. CONCLUSIONS: The cone responses were followed by the rod responses with red light stimulation of 0 dB in the dark-adapted ERG. The waveforms of the cone ERGs were obtained in dark adaptation with red and blue light stimulation.

Adolescent↗
PubMed1994

Adaptive response to ionizing radiation induced by low dose of gamma ray in human hepatoma cell lines.

When cells are exposed to a low dose of a mutagenic or clastogenic agent, they often become less sensitive to the effects of a higher dose administered subsequently. Such adaptive responses were first described in Escherichia coli. Studies on mammalian cells have been limited to human lymphocytes exposed to low doses of an alkylating agent. In this study, the adaptive response to 1 cGy of gamma rays was investigated in human tumor cells using two human hepatoma cell lines, Hep G2 and Hep 3B. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results of this study indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher doses (50 cGy). The time necessary for the expression of the adaptive response was determined by varying the time interval between the two doses from 1 hour to 72 hours. In G2 chromatids, the adaptive response was observed both at short time intervals, as early as 1 hour, and at long time intervals. In S chromatids, however, the adaptive response was shown only at long time intervals. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the experimental groups. Therefore, it is suggested that the adaptive response can be observed in human hepatoma cell lines, which is first documented through this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1992

Spatial-frequency-contingent color aftereffects: adaptation with two-dimensional stimulus patterns.

The spatial-frequency theory of vision has been supported by adaptation studies using checkerboards in which contingent color aftereffects (CAEs) were produced at fundamental frequencies oriented at 45 degrees to the edges. A replication of this study failed to produce CAEs at the orientation of either the edges or the fundamentals. Using a computer-generated display, no CAEs were produced by adaptation of a square or an oblique checkerboard. But when one type of checkerboard (4 cpd) was adapted alone, CAEs were produced on the adapted checkerboard and on sine-wave gratings aligned with the fundamental and third harmonics of the checkerboard spectrum. Adaptation of a coarser checkerboard (0.80 cpd) produced CAEs aligned with both the edges and the harmonic frequencies. With checkerboards of both frequencies, CAEs were also found on the other type of checkerboard that had not been adapted. This observation raises problems for any edge-detector theory of vision, because there was no adaptation to edges. It was concluded that spatial-frequency mechanisms are operating at both low- and high-spatial frequencies and that an edge mechanism is operative at lower frequencies. The implications of these results are assessed for other theories of spatial vision.

Adaptation, Ocular↗
PubMed2004

[Family resiliency factors for the adaptation of family who have a congenital heart disease].

PURPOSE: The purpose of this study was to explore the relationships of family strain, perceived social support, family hardiness, and family adaptation and identify the family resiliency factors for the adaptation of families who have a child with congenital heart disease. METHOD: The sample consisted of 90 families who had a child diagnosed with congenital heart disease and completed surgical treatment. Data was collected from parents using a questionnaire. RESULTS: Results from path analyses revealed that family strain had a direct effect on both perceived social support and family hardiness, and an indirect effect on family adaptation. Also, the findings revealed that perceived social support had a direct effect on both family hardiness and family adaptation, and family hardiness had a direct effect on family adaptation. Thus, these results indicated that perceived social support and family hardiness had a mediating effect on family strain. CONCLUSION: Findings provide the evidence for the theoretical and empirical significance of perceived social support and family hardiness as family resiliency factors for family adaptation. Clinical implications of these findings might be discussed in terms of family-centered nursing interventions for the families who have a child with congenital heart disease based on an understanding of family resiliency for adaptation.

Adaptation, Psychological↗
PubMed1999

Acid adaptation of Listeria monocytogenes strains does not offer cross-protection against an activated lactoperoxidase system.

Listeria monocytogenes has been implicated in foodborne illness outbreaks involving several types of cheeses made from acidified milk. Acid shock response (ASR) and acid tolerance response (ATR) could be possible reasons for its survival. The ASR and ATR of three strains of L. monocytogenes (V7, V37, and CA) in skim milk acidified to pH 4.0 and 3.5 with lactic acid and held at 32 degrees C were studied. Studies were also done to determine if acid adaptation of the organism enhanced survival in the presence of an activated lactoperoxidase system. The cells were directly shocked at pH 4.0 and 3.5 in skim milk to study the ASR. To study the ATR, cells were initially adapted in skim milk at a mild pH of 5.5 for the equivalent of one generation before being shocked at pH 4.0 and 3.5 in skim milk. Cells adapted at pH 5.5 in tryptic soy broth without dextrose and nonadapted cells were challenged at pH 4.5 in skim milk with or without an activated lactoperoxidase system. In all cases, viability and pH were measured 24 or 48 h after challenge. In pH 4.0 skim milk, for all three strains, the adapted cell population survived better (0.5 to 1.0 log higher) than that of nonadapted cells for 24 h. In pH 3.5 skim milk, the acid-adapted populations of all three strains were 3 to 4 logs greater than those of nonadapted cells at 6 h. The acid adapted cells of all three strains had survival rates similar to those of the nonadapted cells at pH 4.5 both in the presence and absence of an activated lactoperoxidase system. It was also evident that these strains do not exhibit an adaptive ATR at pH 4.5, although they do at lower pH levels (pH 4.0 and 3.5). Survival due to the ATR was better seen at pH 3.5 than at pH 4.0.

Adaptation, Physiological↗
PubMed1990

Small firm adaptation: responses of physicians' organizations to regulatory and competitive uncertainty.

This study addressed the pattern of small organizations' adaptation responses to uncertainty in the regulatory and competitive sectors of their environment using data from physicians in solo practice. An existing general model of adaptation was modified to reflect small-firm work processes. The result is a four-cell model that distinguishes adaptive strategies in terms of their functional orientations and how firms pursue them--whether alone or in collaboration with other firms. Data analyses supported the propositions that adaptation in small firms is a multicomponent construct and that regulatory and competitive uncertainty differentially influence the adaptation process. Although individual relationships found among the sets of adaptation activities supported the contention that adaptation choices follow a hierarchical cost pattern, the overall fit of the model suggests modification of the theory in subsequent research efforts.

Adaptation, Psychological↗
PubMed1999

Liu-Jun-Zi-Tang, a kampo medicine, promotes adaptive relaxation in isolated guinea pig stomachs.

Some patients with dysmotility-like functional dyspepsia present impaired reservoir functions such as gastric adaptive relaxation. A traditional Chinese herbal medicine, Liu-Jun-Zi-Tang, has been identified as an effective drug against dyspeptic symptoms and is widely used for therapy in such patients. In this study, we examined the effects of this drug on the gastric adaptive relaxation in isolated guinea pig stomachs. The changes in intragastric volume and pressure were recorded in the presence of atropine and guanethidine. Gastric adaptive relaxation was induced by luminal distention. Liu-Jun-Zi-Tang (100 mg/ml) induced gastric adaptive relaxation at a lower intragastric pressure and increased the % volume of the gastric adaptive relaxation and the absolute intragastric volume. Metoclopramide (2 mg/ml), trimebutine (6 mg/ml) and cisapride (2 mg/ml) did not affect gastric adaptive relaxation. It was inhibited by means of the incubation of the stomach with NG-nitro-L-arginine (100 microM). Liu-Jun-Zi-Tang (100 mg/ml), but not gastroprokinetics overcame the effect of NG-nitro-L-arginine. These results suggested that Liu-Jun-Zi-Tang promoted gastric adaptive relaxation. This effect might, at least in part, contribute to the symptom relief in patients with functional dyspepsia.

Adaptation, Physiological↗
PubMed2000

Cellular mechanisms of long-lasting adaptation in visual cortical neurons in vitro.

The cellular mechanisms of spike-frequency adaptation during prolonged discharges and of the slow afterhyperpolarization (AHP) that follows, as occur in vivo with contrast adaptation, were investigated with intracellular recordings of cortical neurons in slices of ferret primary visual cortex. Intracellular injection of 2 Hz sinusoidal or constant currents for 20 sec resulted in a slow (tau = 1-10 sec) spike-frequency adaptation, the degree of which varied widely among neurons. Reducing either [Ca(2+)](o) or [Na(+)](o) reduced the rate of spike-frequency adaptation. After the prolonged discharge was a slow (12-75 sec) AHP that was associated with an increase in membrane conductance and a rightward shift in the discharge frequency versus injected current relationship. The reversal potential of the slow AHP was sensitive to changes in [K(+)](o), indicating that it was mediated by a K(+) current. Blockade of transmembrane Ca(2+) conductances did not reduce the slow AHP. In contrast, reductions of [Na(+)](o) reduced the slow AHP, even in the presence of pronounced Ca(2+) spikes. We suggest that the activation of Na(+)-activated and Ca(2+)-activated K(+) currents plays an important role in prolonged spike-frequency adaptation and therefore may contribute to contrast adaptation and other forms of adaptation in the visual system in vivo.

Adaptation, Ocular↗
PubMed2000

Effects of adaptation to intermittent high altitude hypoxia on ischemic ventricular arrhythmias in rats.

We compared the effects of adaptation to intermittent high altitude (IHA) hypoxia of various degree and duration on ischemia-induced ventricular arrhythmias in rats. The animals were exposed to either relatively moderate hypoxia of 5000 m (4 or 8 h/day, 2-3 or 5-6 weeks) or severe hypoxia of 7000 m (8 h/day, 5-6 weeks). Ventricular arrhythmias induced by coronary artery occlusion were assessed in isolated buffer-perfused hearts or open-chest animals. In the isolated hearts, both antiarrhythmic and proarrhythmic effects were demonstrated depending on the degree and duration of hypoxic exposure. Whereas the adaptation to 5000 m for 4 h/day decreased the total number of premature ventricular complexes (PVCs), extending the daily exposure to 8 h and/or increasing the altitude to 7000 m led to opposite effects. On the contrary, the open-chest rats adapted to IHA hypoxia exhibited an increased tolerance to arrhythmias that was even more pronounced at the higher altitude. The distribution of PVCs over the ischemic period was not altered by any protocol of adaptation. It may be concluded that adaptation to IHA hypoxia is associated with enhanced tolerance of the rat heart to ischemic arrhythmias unless its severity exceeds a certain upper limit. The opposite effects of moderate and severe hypoxia on the isolated hearts cannot be explained by differences in the occluded zone size, heart rate or degree of myocardial fibrosis. The proarrhythmic effect of severe hypoxia may be related to a moderate left ventricular hypertrophy (27 %), which was present in rats adapted to 7000 m but not in those adapted to 5000 m. This adverse effect can be overcome by an unknown protective mechanism(s) that is absent in the isolated hearts.

Adaptation, Physiological↗