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PubMed2001

Bioaccumulation of copper(II) and nickel(II) by the non-adapted and adapted growing Candida sp.

The effect of copper(II) and nickel(II) ions on the growth and bioaccumulation properties of non-adapted and adapted growing cells of a non-pathogenic Candida sp. has been tested under laboratory conditions as a function of initial pH and initial metal ion concentration. Optimum pH value for maximum metal ion accumulation was determined as 4.0 for both the metal ions. Although the copper(II) adapted Candida sp. was capable of removing of copper(II) with the maximum specific uptake capacity of 36.9 mg g-1 at 783.6 mg dm-3 initial copper(II) concentration, non-adapted Candida was only capable of bioaccumulating copper(II) with 23.1 mg g-1 maximum uptake capacity from aqueous solution at 578.7 mg dm-3 initial copper(II) concentration. The non-adapted and nickel(II) adapted Candida cells also showed the highest nickel(II) uptake capacities (46.8 and 30.8 mg g-1, respectively) at 321.5 and 300.6 mg dm-3 initial nickel(II) concentrations, respectively. For both the non-adapted and nickel(II) adapted Candida sp., the growth of cells was totally inhibited by 500 mg dm-3 of nickel(II) ions. The results also indicated that copper(II) adapted Candida sp. has been found to be more efficient to accumulate larger amounts of copper(II) than that of nickel(II) bioaccumulated by nickel(II) adapted Candida at higher initial metal ion concentrations without loosing its biological activity.

Adaptation, Physiological↗
PubMed2003

Adaptive and cross-adaptive responses of persistent and non-persistent Listeria monocytogenes strains to disinfectants.

Persistent and non-persistent Listeria monocytogenes strains were tested for initial resistance and adaptive and cross-adaptive responses towards two quaternary ammonium compounds, alkyl-benzyl-dimethyl ammonium chloride and n-alkyldimethyl ethylbenzyl ammonium chloride, one tertiary alkylamine, 1,3-propanediamine-N-(3-aminopropyl)N-dodecyl, sodium hypochlorite and potassium persulphate. The initial resistance of two persistent and two non-persistent L. monocytogenes strains was observed to differ. Both types of strains adapted after a 2-h sublethal exposure to the quaternary ammonium compounds and the tertiary alkylamine, the highest increase in the minimum inhibitory concentration (MIC) being 3-fold. Progressively increasing disinfecting concentrations at 10 and 37 degrees C resulted in adaptation of L. monocytogenes to all disinfectants except potassium sulphate. The highest observed increase in MIC was over 15-fold, from 0.63 to 10 microg/ml of n-alkyldimethyl ethylbenzyl ammonium chloride. All strains reached approximately similar MICs. Stability of the increased resistance was tested by measuring MICs every seventh day for 28 days. The increased resistance to sodium hypochlorite disappeared in 1 week, but the quaternary ammonium compounds and the tertiary alkylamine showed increased resistance for 28 days. These results suggest that cellular changes due to adaptive responses continue to have an effect on the resistance some time after the exposure. All disinfectants were shown to cause cross-adaptation of L. monocytogenes, the highest increase in MIC being almost 8-fold. The only agent that L. monocytogenes could not be shown to cross-adapt to was potassium persulphate which did, however, cause cross-adaptation to the other disinfectants. The mechanism behind these adaptive responses seemed to be non-specific as cross-adaptation was observed not only between related but also unrelated disinfectants. These findings suggest that sustaining high disinfectant effectiveness may be unsuccessful by rotation, even when using agents with different mechanisms of action.

Adaptation, Physiological↗
PubMedDate not supplied

[Change in adaptability and kinetics of T-lymphocyte adaptation to hypotonia in pathological states of mammals].

The kinetics of adaptation of the volume of T-lymphocytes and their membrane potential in a hypotonic medium is investigated. It is shown to have a quasiperiodic character. The shortest adaptation period T = 2 min characterizes the adaptation of T-lymphocytes test animals, the most complete adaptation of the volume and the membrane potential in hypotonic medium. Upon adaptation their values are only 6% higher than respective values in an isotonic medium. If an aseptic inflammatory process develops in a mammalian organism, the adaptation period increases to T = 2.5 min, while the volume and the membrane potential remains 28% higher than in an isotonic medium. In the course of development of induced cancerogenesis, 10 min after the cells have been placed in a hypotonic medium, their size is equal to that at the point of maximal swelling, while the membrane potential is 20% lower than that in an isotonic medium. The reason for the varying adaptability of T-lymphocytes is, in our opinion, that, as the inflammation develops, the concentration of corticosteroids increases, the concentration of intracellular K+ decreases, the concentration of macromolecules increases and the potential of the plasmatic membrane of the cell rises, thus leading to the slowing down of the process of adaptation and its decreased extent. The lack of regulation of the volume by T-lymphocytes of mammals in the organisms of which cancerogenesis develops, testifies to the fact that, in such a case, cells lose their adaptability to changing external conditions. Therefore, the disappearance of adaptability of T-lymphocytes on the third day of development of cancerogenesis represents an early test of the process.

Adaptation, Physiological↗
PubMed1982

The acute regulation of mitochondrial proton conductance in cells and mitochondria from the brown fat of cold-adapted and warm-adapted guinea pigs.

Cells and mitochondria were prepared from the brown adipose tissue of adult guinea-pigs adapted to either 4-7 degrees C or 22-25 degrees C. The cold-adapted cells displayed noradrenaline-stimulated, propranolol-sensitive respiration, but noradrenaline failed to increase the respiration of the warm-adapted cells. Purine-nucleotide-sensitive proton conductance was greater in cold-adapted mitochondria than in warm-adapted controls. At the same time cold-adapted mitochondria were extremely sensitive to the uncoupling effect of endogenous and infused fatty acids, and resembled the mitochondria from the brown adipose tissue of cold-adapted hamsters. Warm-adapted mitochondria were ninefold less sensitive, and resembled liver mitochondria. With cold-adapted, but not warm-adapted mitochondria, respiration increased proportionately to the rate of fatty acid infusion. It is concluded that the presence of the 32000-Mr proton conductance pathway is necessary for the expression of a high sensitivity to fatty acid uncoupling, suggesting that the fatty acids interact directly with this protein to modulate the proton conductance during the acute regulation of thermogenesis.

Acclimatization↗
PubMed1995

Light adaptation of the human photopic oscillatory potentials: influence of the length of the dark adaptation period.

Photopic electroretinograms recorded immediately after a period of dark adaptation show a regular increase in amplitude with time spent in light. The retinal mechanisms at the origin of this light adaptation effect remain obscure. The purpose of this study was to investigate the duration of the dark adaptation period needed to produce an optimal light adaptation effect as demonstrated by photopic oscillatory potential recordings. Our results indicate that the light adaptation effect can be separated into two distinct processes. The first one, activated early in the dark adaptation process, reduces the amplitude of the fourth oscillatory potential to 32% of control after less than 5 min of dark adaptation, while the second process, activated after more than 10 min of dark adaptation, appears to impact solely the amplitude of the earlier oscillatory potentials 2 and 3. Our results suggest that the light adaptation effect is mediated by two distinct retinal pathways or mechanisms.

Adaptation, Ocular↗
PubMed1994

Understanding adaptive processes in a developmental context. A reappraisal of Hartmann's problem of adaptation.

Hartmann's theory of adaptation introduced the metapsychology of ego as an agent of adaptation to external reality as well as a defense against internal conflict. His notions of autonomous ego functions serving adaptation and of the child's biological preparedness for adaptation made a significant contribution to psychoanalytic developmental theory. However, the study of children developing in the midst of environmental discord and violence who enter such environments with or without an adequate endowment encourages a reappraisal of three issues in Hartmann's view of adaptation: (1) the developmental vicissitudes of adaptation, (2) the notion of an average expectable environment; and (3) the distinction between adaptation as state and as process. These issues are reviewed to outline factors that may preserve and foster adaptation for children in the face of adversity and chronic trauma. It is suggested that adaptation is better understood as the individual's reaching a relative state of autonomy vis-à-vis deviations from average expectable endowment, experience, or environment and as one that occurs not in spite of but in the context of adversity.

Adaptation, Psychological↗
PubMed1981

Adaptation problems with nursing home application for elderly persons: an application of the Roy adaptation nursing model.

This study sought to identify adaptation problems on the part of elderly persons and significant others that were associated with nursing home applications for elderly persons. Within the framework of the Roy Adaptation Nursing Model, an ex post facto research design was utilized to identify these adaptation problems. The four adaptive modes in this model are: physiological, self-concept, role function, and interdependence. The study group (n = 22) and a control group of elderly persons living in Calgary, as well as their significant others, were administered a structured questionnaire. Five hypotheses relating to overall adaptation problems, powerlessness, role reversal, guilt, and knowledge and utilization of services were formulated and tested. Only the hypothesis indicating role reversal on the part of the significant others was accepted. Adaptation problems encountered by the elderly which were associated with nursing home applications occurred in the self-concept and interdependence adaptive modes. The adaptation problems perceived by the significant others, which were associated with nursing home applications for their elderly, occurred in the self-concept, role function, and interdependence modes. Adaptation problems from the significant others' perception rather than from the elderly persons' perception appear to be more significantly associated with nursing home applications.

Adaptation, Psychological↗
PubMed1983

Light adaptation in cells of macaque lateral geniculate nucleus and its relation to human light adaptation.

Responses of macaque lateral geniculate nucleus (LGN) cells to stimuli of different incremental intensities and wavelength compositions were studied at different levels of light adaptation from scotopic to low photopic levels. Stimuli were large in comparison with receptive-field size. Human increment thresholds were measured for comparison. The strength of responses grew in many cells from threshold up to a saturation level as a logarithmic function of incremental intensity. More complex intensity-response functions were also obtained, particularly from parvocellular layer (PCL) cells, but the shape and slope of the intensity-response function changed as a function of adaptation level only with chromatic backgrounds. As a function of adaptation level, the intensity-response functions shifted along the logarithmic abscissa but not sufficiently for a complete contrast constancy. Thus responses to any constant contrast became smaller when adaptation level decreased. The change from cone to rod responses, when possible, took place without noticeable change in shape of intensity-response functions, and much of the adaptive shift of the functions could be attributed to the change-over between rods and cones. Differences between different cells in light adaptation and dark-adapted sensitivity were large, mostly because of variation in the strength of rod input. The strongest excitatory rod inputs were found in PCL cells activated by short-wavelength light, so that the highest sensitivity at low levels of illumination occurred in blue- and blue-green-sensitive cells. The lowest increment thresholds based on cones matched the thresholds of macaque cone late receptor potentials recorded by Boynton and Whitten (3). They were also similar to human cone thresholds measured psychophysically but only for small stimulus sizes that may approximate the size of the receptive-field centers. Human sensitivity was much higher when measured with large stimulus sizes, indicating integration at post-geniculate neural levels. Light adaptation, as evaluated with respect to contrast constancy and Weber law behavior, was similarly incomplete in monkey single cells and human perception. A few cat LGN cells were studied in a control experiment; results agreed with previous findings. The light adaptation of cat cels was more complete and sensitivity higher than those observed under comparable conditions in macaque single cells and human. The maintained activity level of cells was little affected by the intensity of steady backgrounds. Thus, the steady-state hyper-polarisation of receptors was not transmitted to LGN cells.

Adaptation, Ocular↗
PubMed1998

Pre-adaptation, adaptation and de-adaptation to high altitude in humans: hormonal and biochemical changes at sea level.

High altitude residence is known to modify body biochemistry and hormone status. However, the effects of such a sojourn on these status observed at sea level both immediately and later after return are not as well established as are the effects of an intermittent acclimation. The aim of this study was therefore to investigate these changes. To achieve our objectives, nine subjects received intermittent acclimation at low pressure in a barometric chamber (8 h daily for 5 days, day 1 at 4500 m, day 5 at 8500 m) before an expedition to the Himalayas. Hormonal and biochemical changes were studied using samples of venous blood taken at sea level before and after acclimation, after return from the expedition and 1 and 2 months after descent. Concentrations of thyroid hormones, adrenaline, noradrenaline (NA), hormones of hydromineral metabolism (aldosterone, renin, arginine vasopressin, atrial natriuretic peptide) as well as prolactin, cortisol, insulin and endothelin 1 were measured. Biochemical measurements made were plasma osmolality, and concentrations of glucose, total cholesterol, total proteins, pre-albumin, transferrin, complement 3C, apolipoproteins A1 and B and serum iron. Acclimation induced no alteration in hormone (except for NA with increases of about 1.5, fold P < 0.05) and biochemistry data. After the expedition, hormone responses were characterized by a higher total triidothyronine concentration (+18%, P < 0.05) while other hormones did not vary. A linear relationship was found between thyroid-stimulating-hormone and body mass changes after the expedition (r = 0.67, P < 0.05). The observed increased concentrations of plasma proteins and total cholesterol (P < 0.05) could be related to the restoration of lean body mass. At 1 and 2 months after return, no changes in hormones were observed but a significant decrease in transferrin concentration was noticed. The higher serum iron concentration reported after 1 month (P < 0.05) could have been the result of a physiological haemolysis. It was concluded that both acclimation and the expedition in the Himalayas affected hormone status and body biochemistry status even though the observed changes were slight and rapidly reversed.

Adaptation, Physiological↗
PubMed1993

Interactions between short-term vertical phoria adaptation and nonconjugate adaptation of vertical pursuits.

We have demonstrated that short-term vertical position-specific phoria adaptation contributes to nonconjugate adaptation of vertical pursuits, but not to nonconjugate adaptation of vertical saccades. Binocular adaptation to multiple stationary vertical disparities resulted in both nonconjugate pursuits and phoria aftereffects but had little effect on the early step component of vertical saccades. Similarly, binocular nonconjugate adaptation of vertical pursuits produced both nonconjugate pursuits and fixation phoria aftereffects. Position-specific adaptation of nonconjugate pursuit was demonstrated by adapting to disparate motion in the upper field which resulted in nonconjugate pursuit aftereffects that were greater in the upper than the lower hemifield. These nonconjugate pursuits were accompanied by position-specific phoria aftereffects, indicating that common mechanisms underlie adaptation of vertical phoria and nonconjugate pursuits.

Adaptation, Ocular↗
PubMedDate not supplied

Adaptation aftereffects in single neurons of cat visual cortex: response timing is retarded by adapting.

Extracellular single-unit recordings were made from simple cells in area 17 of anesthetized cats. Cells were tested with drifting gratings under control and adapted conditions. Response amplitude and phase were measured as a function of either contrast or temporal frequency. Adapting not only reduces amplitude, but also retards phase. Adaptation alters the responses of simple cells in a particular way: the onset of the response to each cycle of a sinusoidally modulate stimulus is delayed. Once cells start to respond during each cycle, however, they generally recover to control levels, and the offset of the response is unaffected by adapting. The timing aftereffects are independent of the amplitude aftereffects. Timing aftereffects are tuned around the adapting temporal frequency, with a bias toward lower temporal frequencies. Adaptation thus modifies cortical responses even more specifically then previously thought. Firing rates are depressed primarily at response onset, even after several stimulus cycles have occurred following the end of adapting. Because all cells appear to adapt in this way, the data offer an opportunity to theorize about cortical connectivity. One implication is that inhibition onto a simple cell arises from other simple cells with similar response properties that fire a half-cycle out of phase with the target cell.

Adaptation, Ocular↗
PubMed2002

Sensorimotor adaptation of speech I: Compensation and adaptation.

When motor actions (e.g., reaching with your hand) adapt to altered sensory feedback (e.g., viewing a shifted image of your hand through a prism), the phenomenon is called sensorimotor adaptation (SA). In the study reported here, SA was observed in speech. In two 2-hour experiments (adaptation and control), participants whispered a variety of CVC words. For those words containing the vowel /E/, participants heard auditory feedback of their whispering. A DSP-based vocoder processed the participants' auditory feedback in real time, allowing the formant frequencies of participants' auditory speech feedback to be shifted. In the adaptation experiment, formants were shifted along one edge of the vowel triangle. For half the participants, formants were shifted so participants heard /a/ when they produced /E/; for the other half, the shift made participants hear /i/ when they produced /E/. During the adaptation experiment, participants altered their production of /E/ to compensate for the altered feedback, and these production changes were retained when participants whispered with auditory feedback blocked by masking noise. In a control experiment, in which the formants were not shifted, participants' production changes were small and inconsistent. Participants exhibited a range of adaptations in response to the altered feedback, with some participants adapting almost completely, and other participants showing very little or no adaptation.

Adaptation, Physiological↗
PubMed2002

The population genetics of adaptation: the adaptation of DNA sequences.

I describe several patterns characterizing the genetics of adaptation at the DNA level. Following Gillespie (1983, 1984, 1991), I consider a population presently fixed for the ith best allele at a locus and study the sequential substitution of favorable mutations that results in fixation of the fittest DNA sequence locally available. Given a wild type sequence that is less than optimal, I derive the fitness rank of the next allele typically fixed by natural selection as well as the mean and variance of the jump in fitness that results when natural selection drives a substitution. Looking over the whole series of substitutions required to reach the best allele, I show that the mean fitness jumps occurring throughout an adaptive walk are constrained to a twofold window of values, assuming only that adaptation begins from a reasonably fit allele. I also show that the first substitution and the substitution of largest effect account for a large share of the total fitness increase during adaptation. I further show that the distribution of selection coefficients fixed throughout such an adaptive walk is exponential (ignoring mutations of small effect), a finding reminiscent of that seen in Fisher's geometric model of adaptation. Last, I show that adaptation by natural selection behaves in several respects as the average of two idealized forms of adaptation, perfect and random.

Adaptation, Physiological↗
PubMed2000

Role of nitric oxide in adaptation to hypoxia and adaptive defense.

Adaptation to hypoxia is beneficial in cardiovascular pathology related to NO shortage or overproduction. However, the question about the influence of adaptation to hypoxia on NO metabolism has remained open. The present work was aimed at the relationship between processes of NO production and storage during adaptation to hypoxia and the possible protective significance of these processes. Rats were adapted to intermittent hypobaric hypoxia in an altitude chamber. NO production was determined by plasma nitrite/nitrate level. Vascular NO stores were evaluated by relaxation of the isolated aorta to diethyldithiocarbamate. Experimental myocardial infarction was used as a model of NO overproduction; stroke-prone spontaneously hypertensive rats (SHR-SP) were used as a model of NO shortage. During adaptation to hypoxia, the plasma nitrite/nitrate level progressively increased and was correlated with the increase in NO stores. Adaptation to hypoxia prevented the excessive endothelium-dependent relaxation and hypotension characteristic for myocardial infarction. At the same time, the adaptation attenuated the increase in blood pressure and prevented the impairment of endothelium-dependent relaxation in SHR-SP. The data suggest that NO stores induced by adaptation to hypoxia can either bind excessive NO to protect the organism against NO overproduction or provide a NO reserve to be used in NO deficiency.

Adaptation, Physiological↗
PubMed1991

[Studies on the changes of adaptation with children in the dental setting. The relationship between the changes of adaptation and various psychological tests].

The purpose of this study was to discover the changes in the adaptation of children to the Dental setting, and to discover the relationship between the adaptation, and the personality of the child, the personality of the mother, as well as the relationship between the mother and child. The subjects were 60 two to six year old children and their mothers who visited at the Department of Pedodontics, School of Dentistry, Showa University. The results were as follows: 1) The changes of adaptation were classified in groups of four classes. Four groups: Continuous Adaptability (45.0%) Acquired Adaptability (18.3%) Continuous Inadaptability (16.7%) Extreme Inadaptability (20.0%) 2) The inadaptability groups (Continuous Inadaptability and Extreme Inadaptability) of the two to three year old children did not correlate to the change of adaptation and personality of the child, and the relationship between the mother and child. 3) The extreme inadaptability group with the four year old children showed a connection with the change of adaptation and the various Psychological Tests. Concerning personality, the children showed elements of "dependence" "retrogression" and "maladaptation to school (kindergarten)". Concerning the mother child relationship, there were elements of "anxiety" "dotage" "follow blindly" "disagreement". 4) Nobody showed extreme inadaptability in the group of five to six year old children. Continuous Inadaptability group with the five to six year old children showed scarcely any problems. 5) The Personality of mother did not correlate to the change of adaptation of children in the dental setting.

Adaptation, Psychological↗