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PubMed2002

Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability.

PURPOSE: Five days of a high-fat diet produce metabolic adaptations that increase the rate of fat oxidation during prolonged exercise. We investigated whether enhanced rates of fat oxidation during submaximal exercise after 5 d of a high-fat diet would persist in the face of increased carbohydrate (CHO) availability before and during exercise. METHODS: Eight well-trained subjects consumed either a high-CHO (9.3 g x kg(-1) x d(-1) CHO, 1.1 g x kg(-1) x d(-1) fat; HCHO) or an isoenergetic high-fat diet (2.5 g x kg(-1) x d(-1) CHO, 4.3 g x kg(-1) x d(-1) fat; FAT-adapt) for 5 d followed by a high-CHO diet and rest on day 6. On day 7, performance testing (2 h steady-state (SS) cycling at 70% peak O(2) uptake [VO(2peak)] + time trial [TT]) of 7 kJ x kg(-1)) was undertaken after a CHO breakfast (CHO 2 g x kg(-1)) and intake of CHO during cycling (0.8 g x kg(-1) x h(-1)). RESULTS: FAT-adapt reduced respiratory exchange ratio (RER) values before and during cycling at 70% VO(2peak); RER was restored by 1 d CHO and CHO intake during cycling (0.90 +/- 0.01, 0.80 +/- 0.01, 0.91 +/- 0.01, for days 1, 6, and 7, respectively). RER values were higher with HCHO (0.90 +/- 0.01, 0.88 +/- 0.01 (HCHO > FAT-adapt, P < 0.05), 0.95 +/- 0.01 (HCHO > FAT-adapt, P < 0.05)). On day 7, fat oxidation remained elevated (73 +/- 4 g vs 45 +/- 3 g, P < 0.05), whereas CHO oxidation was reduced (354 +/- 11 g vs 419 +/- 13 g, P < 0.05) throughout SS in FAT-adapt versus HCHO. TT performance was similar for both trials (25.53 +/- 0.67 min vs 25.45 +/- 0.96 min, NS). CONCLUSION: Adaptations to a short-term high-fat diet persisted in the face of high CHO availability before and during exercise, but failed to confer a performance advantage during a TT lasting approximately 25 min undertaken after 2 h of submaximal cycling.

Adaptation, Physiological↗
PubMed1981

Adaptation and heterochromatic matching.

This study is a follow-up of a previous study of the effect of adaptation on heterochromatic matching by flicker photometry and direct comparison. In flicker photometry, two patches of color are applied alternately to a region of the retina adapted to a mixture of the two colors. In direct comparison, the two halves of the pattern are usually applied to regions of the retina adapted to the separate colors. Two additional methods of equalizing the state of adaptation in the two halves of the retina in direct comparison matching have been tested. In both cases, equalizing the states of adaptation reduces the discrepancy between flicker photometry and direct comparison for two of the three subjects tested. For the third subject, the discrepancies are small but one can still demonstrate effects produced by equalizing the states of adaptation. Further study is needed to delineate the specific mechanisms of adaptation involved.

Adaptation, Ocular↗
PubMed1984

Adaptive changes with prolonged effect of comitant and incomitant vergence disparities.

When comitant and incomitant vergence disparities are induced for prolonged periods of time, the adaptive state becomes more stable. When the change is complete, the adaptive ability of the oculomotor system to a further disparity should be the same as that before any induced effect. Comitant change was investigated in five subjects who wore a 2 delta base-up Fresnel prism for prolonged periods of time (1 to 3 days). Adaptation was periodically monitored with a further 2 delta base-up prism. In three subjects the rate of adaptation to the additional prism approached that which occurred before the experiment. In two subjects, both of whom suffered asthenopic symptoms with the initial disparity, adaptation to the additional prism remained slow and incomplete. Incomitant change was investigated in two subjects who wore a -3.00 contact lens-spectacle lens (CL-SL) system for 2 to 3 days. Adaptation was monitored with a further -1.50 CL-SL system at the start and the end of the prolonged wear. Both these subjects had a much faster rate of adaptation at the end of the prolonged period than they had at the beginning.

Adaptation, Ocular↗
PubMed1994

Vergence adaptation and senescence.

PURPOSE: The characteristics of prism adaptation have been evaluated by many previous studies but most have been performed on young subjects (typically 18 to 35 years of age). Because little information is available regarding the effect of age on vergence adaptation, we assessed prism adaptation on 25 visually normal subjects across a wide age range (19 to 85 years) for both convergent and divergent induced disparities. METHODS: A "flashed" (125 ms) Maddox rod procedure was used for distance fixation (5 m) over a 3.5 min adaptation period and a 2.5 min recovery period. Stimulus presentation and occlusion time were controlled with an Apple lle microcomputer through a ClL Microsystems interface. RESULTS: Prism adaptation was shown to be present in all age groups, with convergence showing a greater amplitude than divergence. However, the magnitude of adaptation declined significantly as a function of increasing age at a rate of approximately 0.6% per year. CONCLUSION: An adaptation mechanism is present in all subjects but it operates with reduced gain in older subjects. The finding may explain the clinical observation that older patients readily accept prismatic correction to control oculomotor imbalance.

Adaptation, Ocular↗
PubMed1991

Contrast adaptation and contrast masking in human vision.

After a preliminary study of visual evoked potentials (VEPS) to a test grating seen in the presence of masks at different orientations, psychophysical data are presented showing the effects of adaptation and of masking on thresholds for detecting the same test grating. The test is a vertical grating of spatial frequency 2 cycles per degree; adapting and masking gratings differ from the test either in orientation or in spatial frequency. The effects of adaptation and masking are explained by a single mechanism model that assumes: (i) adaptation and masking both alter the contrast response (or transducer) function of the mechanism that detects the test; (ii) masks, but not adaptors, stimulate the mechanism that detects the test; and (iii) a test is detectable when it raises response level by a constant amount. The model incorporates two distinct tuning functions, a broad adaptive contrast function and a narrow effective contrast function. It accounts adequately for all the data, including the location and size of the facilitative dip found in some masking functions, the constant slopes of the threshold elevation segments of adaptation functions and the varying slopes of masking functions. It also predicts the sometimes surprising joint effects of adaptation followed by masking and of two masks operating simultaneously.

Adaptation, Ocular↗
PubMed2002

Basal metabolic rate and the evolution of the adaptive immune system.

Vertebrates have evolved an adaptive immune system in addition to the ancestral innate immune system. It is often assumed that a trade-off between costs and benefits of defence governs the evolution of immunological defence, but the costs and benefits specific to the adaptive immune system are poorly known. We used genetically engineered mice lacking lymphocytes (i.e. mice without adaptive, but with innate, immunity) as a model of the ancestral state in the evolution of the vertebrate immune system. To investigate if the magnitude of adaptive defence is constrained by the energetic costs of producing lymphocytes etc., we compared the basal metabolic rate of normal and lymphocyte-deficient mice. We found that lymphocyte-deficient mice had a higher basal metabolic rate than normal mice with both innate and adaptive immune defence. This suggests that the evolution of the adaptive immune system has not been constrained by energetic costs. Rather, it should have been favoured by the energy savings associated with a combination of innate and adaptive immune defence.

Adaptation, Physiological↗
PubMed1994

Adaptive acid tolerance response (ATR) in Aeromonas hydrophila.

Aeromonas hydrophila, a gastrointestinal pathogen of humans, was shown to exhibit a significant adaptive acid tolerance response (ATR) capable of protecting cells from severe acid at a pH of 3.5. The ATR was induced by exposure to a relatively mild pH level of 5.0 for 20 min. Adaptation required protein synthesis since treatment with chloramphenicol during adaptation to pH 5.0 prevented the development of acid tolerance. The adaptation to acid environment was found to be a non-transient phenomenon. Also, iron was not required for acid adaptation in A. hydrophila. Two-dimensional protein analyses revealed an increased production of 28 proteins and decreased synthesis of 10 following pH shifts from 7.2 to 5.0. The mild pH treatment must act as a signal to A. hydrophila to adapt and survive in acid environments by producing 'protective' proteins. The adaptation and survival of this pathogen in low pH may provide valuable information about its ability to withstand acid environments in nature and in the human gastrointestinal tract.

Acids↗
PubMedDate not supplied

Visuomotor adaptation in normal aging.

Visuomotor adaptation to a gradual or sudden screen cursor rotation was investigated in healthy young and elderly subjects. Both age groups were equally divided into two subgroups; one subgroup was exposed to 11.25 degrees step increments of visual feedback rotation, every 45 trials (up to a total of 90 degrees), whereas a second subgroup was subjected to 90 degrees rotation from the onset of exposure. Participants performed discrete, horizontal hand movements to virtual targets in four randomized directions. Targets appeared on a computer screen in front of them, and a board prevented vision of the hand at all times. Differential effects of aging on visuomotor adaptation were found, depending on the time course of the visual distortion. In both age groups, early exposure to the sudden visual feedback distortion resulted in typical spiral-like trajectories, which became straighter by late exposure. However, the final adaptation level was reduced in the aged group, although the aftereffects were similar. When subjects were exposed to the gradual distortion, no statistically significant differences in measures of adaptation with advancing age were found. In this case, both age groups appeared to adapt equally. However, after removal of the distortion, elderly subjects showed reduced aftereffects as compared with the young group. These findings suggest differential effects of aging on adaptation to gradual versus sudden visual feedback distortions, and may help to explain the conflicting results obtained in previous visuomotor adaptation studies.

Adaptation, Physiological↗
PubMed1996

A cross-coupling model of vertical vergence adaptation.

Vertical disparity vergence aligns the two eyes in response to vertical misalignment (disparity) of the two ocular images. An adaptive response to vertical disparity vergence is demonstrated by the continuation of vertical vergence when one eye is occluded. The adaptive response is quantified by vertical phoria, the eye alignment error during monocular viewing. Vertical phoria can be differentially adapted to vertical disparities of opposite sign located at two positions along the horizontal or vertical head-referenced axes. Vertical phoria aftereffects vary in amplitude as the eyes move from one adapted direction of gaze to another along the adaptation axis. A cross-coupling model was developed to account for the spatial variations of vertical phoria aftereffects. The model is constrained according to both single cell recordings of eye position sensitive neurons, and eye position measurements during and following adaptation. The vertical phoria is computed by scaling the activities of eye position sensitive neurons and converting the scaled activities into a vertical vergence signal. The three components of the model are: neural activities associated with conjugate eye position, cross-coupling weights to scale the activities, and vertical vergence transducers to convert the weighted activities to vertical vergence. The model provides a biologically plausible mechanism for vertical vergence adaptation.

Adaptation, Physiological↗
PubMed2000

Adaptation and the cost of complexity.

Adaptation is characterized by the movement of a population toward a many-character optimum, movement that results in an increase in fitness. Here I calculate the rate at which fitness increases during adaptation and describe the curve giving fitness versus time as a population approaches an optimum in Fisher's model of adaptation. The results identify several factors affecting the speed of adaptation. One of the most important is organismal complexity--complex organisms adapt more slowly than simple ones when using mutations of the same phenotypic size. Thus, as Fisher foresaw, organisms pay a kind of cost of complexity. However, the magnitude of this cost is considerably larger than Fisher's analysis suggested. Indeed the rate of adaptation declines at least as fast as n-1, where n is the number of independent characters or dimensions comprising an organism. The present results also suggest that one can define an effective number of dimensions characterizing an adapting species.

Adaptation, Physiological↗
PubMed2003

Fitness and adaptation in a novel environment: effect of inbreeding, prior environment, and lineage.

The ability of populations to undergo adaptive evolution depends on the presence of genetic variation for ecologically important traits. The maintenance of genetic variation may be influenced by many variables, particularly long-term effective population size and the strength and form of selection. The roles of these factors are controversial and there is very little information on their impacts for quantitative characters. The aims of this study were to determine the impacts of population size and variable versus constant prior environmental conditions on fitness and the magnitude of response to selection. Outbred and inbred populations of Drosophila melanogaster were maintained under benign, constant stressful, and variably stressful conditions for seven generations, and then forced to adapt to a novel stress for seven generations. Fitness and adaptability were assayed in each replicate population. Our findings are that: (1) populations inbred in a variable environment were more adaptable than those inbred in a constant environment; (2) populations adapted to a prior stressful environment had greater fitness when reared in a novel stress than those less adapted to stress; (3) inbred populations had lower fitness and were less adaptable than the outbred population they were derived from; and (4) strong lineage effects were detectable across environments in the inbred populations.

Adaptation, Biological↗
PubMed1988

Characterization of canine distemper viruses adapted to human neural cells.

The biochemical characteristics of canine distemper virus (CDV) adapted to three human neural cells (glioblastoma, oligodendroglioma, and neuroblastoma cells) were compared with those of the unadapted original virus. The specific gravity of the virions and nucleocapsids of the original and the three adapted viruses were not different. The molecular weights of genomic RNA and messenger RNAs encoding H, F, P, and NP proteins of the adapted viruses as estimated by Northern blot hybridization were similar to those of the original virus. By T1-resistant oligonucleotide analysis of the genomic RNA, the glioblastoma- and the neuroblastoma-adapted viruses gave two more spots than the original virus; the oligodendroglioma-adapted virus had a pattern identical to that of the original virus. By two-dimensional gel electrophoresis of virion proteins, we found a difference in the isoelectric point of the viral envelope proteins H and F between the original and the adapted viruses. These results suggest that viral genomic changes occurred during adaptation, resulting in the alteration of viral envelope proteins.

Adaptation, Physiological↗
PubMed2005

Neural circuit-dependent odor adaptation in C. elegans is regulated by the Ras-MAPK pathway.

The molecular machinery that mediates odor adaptation in the olfactory neurons is well documented in various animal species. However, types of adaptation that depend on neural circuits are mostly unexplored. We report here that the Ras-MAPK pathway is essential for such a type of odor adaptation, called early adaptation, in C. elegans. Early adaptation requires a pair of AIY interneurons, which receive synaptic inputs from olfactory neurons. Mutants of the Ras-MAPK pathway show defects in early adaptation. Continued exposure to an odorant causes activation of MAP kinase not only in the olfactory neurons, but also in the AIY interneurons. While activity of the Ras-MAPK pathway in the olfactory neurons is important for odor perception, its activity in the AIY interneurons is important for odor adaptation. Our results thus reveal a dual role of the Ras-MAPK pathway in sensory processing in the nervous system of C. elegans.

Adaptation, Physiological↗
PubMed2006

Relative number of generations of hosts and parasites does not influence parasite local adaptation in coevolving populations of bacteria and phages.

A potential consequence of host-parasite coevolution in spatially structured populations is parasite local adaptation: local parasites perform better than foreign parasites on their local host populations. It has been suggested that the generally shorter generation times of parasites compared with their hosts contributes to parasites, rather than hosts, being locally adapted. We tested the hypothesis that relative generation times of hosts and parasites affect local adaptation of hosts and parasites, using the bacterium Pseudomonas fluorescens and a lytic phage as host and parasite, respectively. Generation times were not directly manipulated, but instead one of the coevolving partners was regularly removed and replaced with a population from an earlier time point. Thus, one partner underwent more generations than the other. Manipulations were carried out at both early and later periods of coevolutionary interactions. At early stages of coevolution, host and parasites that underwent relatively more generations displayed higher levels of resistance and infectivity, respectively. However, the relative number of generations that bacteria and phages underwent did not change the level of local adaptation relative to control populations. This is likely because generalist hosts and parasites are favoured during early stages of coevolution, preventing local adaptation. By contrast, at later stages manipulations had no effect on either average levels of resistance or infectivity, or alter the level of local adaptation relative to the controls, possibly because traits other than resistance and infectivity were under strong selection. Taken together, these data suggest that the relative generation times of hosts and parasites may not be an important determinant of local adaptation in this system.

Adaptation, Biological↗
PubMed1996

Adaptation of the gastric epithelium to injury is maintained in vitro and is associated with increased TGF-alpha expression.

Adaptation is the name given to the progressive decrease in gastric mucosal damage following repeated dosing with damaging agents. This study aimed to determine whether adaptation is an intrinsic property of the gastric epithelium and the role in the development of this process of TGF alpha. Rats were given either one or six daily doses of 10 mg/kg diclofenac or six daily doses of vehicle only (1% methylcellulose). On the 7th day, antral mucosa was taken for organ culture and loaded with [51Cr]. Explants were challenged with ethanol and damage quantified by [51Cr] release. In a separate experiment, rats were dosed as above and the gastric mucosa was extracted and TGF alpha quantified by RIA. The rate of [51Cr] release was significantly lower after ethanol injury in explants from rats previously adapted to diclofenac (9.2 +/- 2.5%) compared with those exposed to a single damaging dose of diclofenac (25.9 +/- 3.5%) or vehicle only (26.4 +/- 3.3%; P < 0.01; ANOVA). The concentration of TGF alpha was significantly higher in the gastric epithelium of rats adapted to diclofenac than other groups (P < 0.05; t-test). Cross adaptation of the gastric mucosa to injury has therefore been demonstrated in antral mucosal explants in organ culture while TGF alpha peptide expression is elevated in the adapted gastric mucosa. These findings suggest that adaptation is an inherent property of the gastric epithelium and it is likely that TGF alpha may play a role in its maintenance.

Adaptation, Physiological↗
PubMed1990

On the universality of human nature and the uniqueness of the individual: the role of genetics and adaptation.

The concept of a universal human nature, based on a species-typical collection of complex psychological adaptations, is defended as valid, despite the existence of substantial genetic variation that makes each human genetically and biochemically unique. These apparently contradictory facts can be reconciled by considering that (a) complex adaptations necessarily require many genes to regulate their development, and (b) sexual recombination makes it improbable that all the necessary genes for a complex adaptation would be together at once in the same individual, if genes coding for complex adaptations varied substantially between individuals. Selection, interacting with sexual recombination, tends to impose relative uniformity at the functional level in complex adaptive designs, suggesting that most heritable psychological differences are not themselves likely to be complex psychological adaptations. Instead, they are mostly evolutionary by-products, such as concomitants of parasite-driven selection for biochemical individuality. An evolutionary approach to psychological variation reconceptualizes traits as either the output of species-typical, adaptively designed development and psychological mechanisms, or as the result of genetic noise creating perturbations in these mechanisms.

Adaptation, Psychological↗
PubMed1995

Adaptive skills dysfunction in ADD and ADHD children.

Adaptive functioning was examined in children with Attention Deficit Hyperactivity Disorder (ADHD) or Attention Deficit Disorder (ADD), and a psychiatric comparison group of children with pervasive developmental disorders or mild mental retardation (PDD/MR). As assessed with the Vineland Adaptive Behavior Scales, adaptive functioning was well below average for all three clinic groups. (The PDD/MR group had the lowest adaptive functioning scores, although not statistically different from the other groups). However, the level of adaptive functioning relative to IQ in the areas of Socialization, Communication and Daily Living was significantly lower for the ADD and ADHD groups. These deficits in adaptive functioning that characterize children with ADHD and ADD may help explain the poor long-term prognosis of ADHD, suggesting that increased attention should be paid to the assessment and treatment of adaptive functioning in individuals with ADHD and ADD.

Adaptation, Psychological↗
PubMed2004

Temporal adaptation of tubuloglomerular feedback: effects of COX-2.

BACKGROUND: Reductions in proximal reabsorption cause increases in delivery of sodium chloride to the macula densa (MD), which activates the tubuloglomerular feedback (TGF) mechanism and reduces glomerular filtration rate. TGF undergoes temporal adaptation, permitting filtration rate to rise in spite of elevated MD delivery of NaCl. Inhibitors of nitric oxide synthase I (NOS I) prevent TGF adaptation, but angiotensin-converting enzyme inhibitors have no effect. COX-2 activity moves in parallel with changes in NOS I and intrarenal renin. We examined the impact of COX-2 inhibition on TGF temporal adaptation and effects of inhibition of COX-2 and NOS I on plasma and kidney angiotensin II (Ang II). METHODS: Kidney blood flow (RBF) and glomerular filtration rate (GFR) were measured before and during benzolamide (BNZ) infusion in control Wistar rats and rats concurrently receiving COX-2 inhibitors. Plasma and kidney angiotensin II content was evaluated by radioimmunoassay in control rats, rats after 60 minutes of BNZ, and during COX-2 and NOS-1 inhibition after BNZ. RESULTS: BNZ reduced both RBF and GFR in all groups. During BNZ, RBF and GFR returned to normal control values within 60 minutes. COX-2 inhibitors totally prevented TGF adaptation. Plasma and kidney Ang II did not change after BNZ, and NOS I and COX-2 inhibitors had no effect on plasma or intrarenal Ang II. CONCLUSION: Within 1 hour after BNZ, rats undergo TGF temporal adaptation. Administration of COX-2 inhibitors prevented TGF temporal adaptation, identical to the effect of NOS I inhibition. Changes in intrarenal Ang II cannot explain this prevention of TGF temporal adaptation.

Adaptation, Physiological↗