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PubMed1997

Mammalian skeletal muscle fiber type transitions.

Mammalian skeletal muscle is an extremely heterogeneous tissue, composed of a large variety of fiber types. These fibers, however, are not fixed units but represent highly versatile entities capable of responding to altered functional demands and a variety of signals by changing their phenotypic profiles. This adaptive responsiveness is the basis of fiber type transitions. The fiber population of a given muscle is in a dynamic state, constantly adjusting to the current conditions. The full range of adaptive ability spans fast to slow characteristics. However, it is now clear that fiber type transitions do not proceed in immediate jumps from one extreme to the other, but occur in a graded and orderly sequential manner. At the molecular level, the best examples of these stepwise transitions are myofibrillar protein isoform exchanges. For the myosin heavy chain, this entails a sequence going from the fastest (MHCIIb) to the slowest (MHCI) isoform, and vice-versa. Depending on the basal protein isoform profile and hence the position within the fast-slow spectrum, the adaptive ranges of different fibers vary. A simple transition scheme has emerged from the multitude of data collected on fiber type conversions under a variety of conditions.

Animals↗
PubMed2005

Testing a middle-range theoretical model of adaptation to chronic pain.

The purpose of this cross-sectional, correlational study was to test a middle-range theory of adaptation to chronic pain that was deduced from the Roy adaptation model using structural equation modeling. The sample consisted of 200 community-dwelling older adults with a mean age of 76. The Roy adaptation model theoretical framework provided an adequate fit to the data and supported the majority of the hypothesized relationships and findings from prior research. Significant direct effects, however, were found between both focal and contextual stimuli, suggesting that contextual stimuli need to be considered when developing a plan of care for older adults experiencing chronic pain.

Adaptation, Psychological↗
PubMed1974

The response of laryngeal afferent fibres to mechanical and chemical stimuli.

1. We have recorded afferent activity from ;single fibres' dissected from the superior laryngeal nerve of anaesthetized cats.2. Units which responded to gentle mechanical stimulation of the larynx epithelium were chosen for study.3. Receptors with myelinated fibres were grouped according to their spontaneous activity. Group 1 fibres had little or no spontaneous activity: group 2 fibres had constant and continuous spontaneous activity.4. Group 1 fibres had a wide range of adaptation rates. Their conduction velocities lay between 3.0 and 30 m/sec. The receptors were generally stimulated by ammonia and distilled water and often by CS riot control agent, 5 and 10% CO(2), 200 ppm SO(2), and cigarette smoke. Histamine, phenyl diguanide, graphite dust, 100 ppm SO(2) and saline drops did not generally excite the fibres.5. Group 2 fibres were slowly adapting. Their conduction velocities ranged between 8.0 and 26.5 m/sec. Ammonia usually, and distilled water sometimes, excited these fibres while 5 and 10% CO(2) mixtures inhibited them. A minority of group 2 fibres were pH sensitive, inhibited by acids and stimulated by alkaline buffers. Cigarette smoke had complex actions, either excitation, inhibition or, at different times, both. Histamine, P.d.g., CS, SO(2), saline drops and dust had no action on these fibres.6. Recordings were made from one unmyelinated fibre (conduction velocity 1.9 m/sec) which responded to stroking of the epithelium with a thread and to histamine, P.d.g. and ammonia vapour applied to the epithelium.7. We consider the site, method of excitation and reflex actions of the different receptors described.

Action Potentials↗
PubMed1989

The structure of physiologically located periodontal ligament mechanoreceptors of the cat canine tooth.

A correlative morphological study was carried out on physiologically located periodontal mechanoreceptors in anaesthetised cats. Three periodontal mechanoreceptors were electrophysiologically identified from functionally single fibres teased from the inferior alveolar nerve. One receptor was studied by recording in the mesencephalic nucleus. The four receptors were located by punctate stimuli in the labial aspect of the periodontal ligament of the left mandibular canine tooth in three cats. The receptors were within the intermediate to rapidly adapting part of the range of adaptation rates with conduction velocities of 39.6 ms-1 +/- 4.7 ms-1 and were typical of those recorded in previous studies. The receptor loci were marked and these regions were studied in silver-stained sections and ultrastructurally. Under each ink-marked region Ruffini terminals and smaller terminals resembling free nerve endings were observed. The Ruffini terminals were unencapsulated and the majority had diameters of 2-3 microns. The terminals were observed near the junction of the inner (cemental) and middle zones of the periodontal ligament with the axons running from the alveolar aspect. The results support the view that periodontal mechanoreceptors, even those with more rapidly adapting properties, are Ruffini terminals.

Action Potentials↗
PubMed2002

Host range and local parasite adaptation.

Parasites may be expected to become locally adapted to their hosts. However, while many empirical studies have demonstrated local parasite adaptation, others have failed to demonstrate it, or have shown local parasite maladaptation. Researchers have suggested that gene flow can swamp local parasite-host dynamics and produce local adaptation only at certain geographical scales; others have argued that evolutionary lags can account for both null and maladaptive results. In this paper, we use item response theory (IRT) to test whether host range influences the likelihood of parasites locally adapting to their hosts. We collated 32 independent experiments testing for local adaptation, where parasites could be assigned as having either broad or narrow host ranges (BHR and NHR, respectively). Twenty-five tests based on BHR parasites had a significantly lower average effect size than seven NHR tests, indicating that studies based on BHR parasites are less likely to demonstrate local parasite adaptation. We argue that this may relate to evolutionary lags during diffuse coevolution of BHR parasites with their hosts, rather than differences in experimental approaches or other confounds between BHR and NHR studies.

Adaptation, Physiological↗
PubMed2006

Limits to evolution at range margins: when and why does adaptation fail?

What stops populations expanding into new territory beyond the edge of a range margin? Recent models addressing this problem have brought together population genetics and population ecology, and some have included interactions among species at range edges. Here, we review these models of adaptation at environmental or parapatric margins, and discuss the contrasting effects of migration in either swamping local adaptation, or supplying the genetic variation that is necessary for adaptation to continue. We illustrate how studying adaptation at range margins (both with and without hybridization) can provide insight into the genetic and ecological factors that limit evolution more generally, especially in response to current rates of environmental change.

Adaptation, Biological↗
PubMed1992

Acuity-sensitivity trade-offs of X and Y cells in the cat lateral geniculate complex: role of the medial interlaminar nucleus in scotopic vision.

1. The cat medial interlaminar nucleus (MIN) receives inputs almost exclusively from tapetal retina, suggesting that the MIN has a special role in dim-light vision. In this study we compared the sensitivities of cells in the MIN with those in layers A and magnocellular C of the lateral geniculate nucleus (LGNd), using drifting sinusoidal gratings to determine contrast thresholds as a function of spatial frequency and retinal adaptation level over the entire scotopic range. 2. About one-half of the cells recorded in the MIN and layer A had brisk responses that could be nulled by properly positioned, counterphased sinusoidal gratings, and were classified as X cells. The rest of the cells in the MIN and layer A, as well as all cells recorded in layer C, were Y cells. 3. MIN cells had higher contrast sensitivity than layer A cells for low spatial frequencies (0.15 cycles/deg and below) over a wide range of adaptation levels, both overall and for separate comparisons within X or Y cells. Layer C Y cells were intermediate in sensitivity between MIN and layer A Y cells. For low spatial frequencies, Y cells as a group were more sensitive than X cells, whereas the reverse was true for high spatial frequencies. 4. These data enable one to determine the lowest adaptation level at which stimuli of a given contrast can be detected for a given structure. At the lowest spatial frequencies, the MIN can function at adaptation levels approximately 1 log unit below layer A, averaged over all stimulus contrasts. In contrast, the tapetum lowers luminance threshold by at most 0.16 log unit. 5. For scotopic conditions and eccentricities within 15 degrees of the area centralis, contrast sensitivity decreases with eccentricity for low spatial frequencies and remains flat or slightly increases for high spatial frequencies. This relationship, which is opposite to that found for photopic vision, is strongest for MIN Y cells. 6. These data support the hypothesis that the retinal conflict between sensitivity and acuity is ameliorated in the CNS through separate thalamic relays with different degrees of afferent convergence. MIN cells have higher luminance sensitivity than layer A cells, but at the expense of acuity. Layer C appears to occupy an intermediate position in this trade-off.

Animals↗
PubMed1995

Color appearance under chromatic adaptation varied along theoretically significant axes in color space.

Changes in color appearance caused by chromatic adaptation were measured with a wide range of adapting fields. Observers viewed a 39'-55' annular test field composed of an admixture of lights from the red phosphor and the green phosphor of a CRT. The annular mixture field was centered and superimposed upon a 4.7 degrees steady, circular background field. After the observer was completely adapted to the background, the luminance of the red phosphor in the test was held fixed while the observer adjusted the luminance of the green phosphor until the test appeared neither reddish nor greenish. Twenty-two equiluminant backgrounds (4.5 cd/m2, approximately 50 Td) were systematically selected along two axes in Judd chromaticity space. One axis was along tritanopic confusion lines, with middle-wavelength-sensitive- (M-) and long-wavelength-sensitive- (L-) cone stimulation held constant. The other axis maintained constant short-wavelength-sensitive- (S-) cone stimulation. The results show that adapting backgrounds that were varied along tritanopic confusion lines do not have a differential effect on color appearance at high test levels (well above the adapting level). At lower test levels there is a systematic change in color appearance of the test light, which is quantitatively described by additive redness. Along constant S-cone-stimulation lines, adapting backgrounds differentially affect color appearance in a systematic way, reflecting changes in receptoral gain and the additive contribution. The measurements taken with adapting fields throughout color space are described by the two-process model of chromatic adaptation.

Adaptation, Ocular↗
PubMed2004

Necessary conditions for a minimal model of receptor to show adaptive response over a wide range of levels of stimulus.

Sensory systems respond to temporal changes in the stimulus and adapt to the new level when it persists, this pattern of response being maintained in a wide range of levels of stimulus. Here we use a simple model of adaptation developed by Segel et al. (J. Theor. Biol. 120 (1986) 151-179) and extended by Hauri and Ross (Biophys. J. 68 (1995) 708-722) to study the conditions in which it shows wide range of response. The model consists of a receptor that switches between a variable number of states, either by mass action law or by covalent modification. Using a global optimization procedure, we have optimized the adaptive response of the alternatives of the model with different number of states. We find that it is impossible to obtain a wide range of response if the receptor switches between states following mass-action laws, irrespective of the number of states. Instead, a wide range (of five orders of magnitude of ligand concentration) can be obtained if the receptor switches between several states by irreversible covalent modification, in agreement with previous models. Therefore, in this model, expenditure of energy to maintain a large number of covalent modification cycles operating outside equilibrium is necessary to achieve a wide range of response. The optimal values of the parameters present similar patterns to those reported for specific receptors, but there is no quantitative agreement. For instance, ligand affinity varies several orders of magnitude between the different states of the receptor, what is unlikely to be fulfilled by real systems. To see if the minimal model can show adaptive response and range with quantitatively plausible parameter values a sub-optimal receptor was studied, finding that adaptive response of high intensity can still be obtained in at least three orders of magnitude.

Adaptation, Physiological↗
PubMed2005

Adaptively merging large-scale range data with reflectance properties.

In this paper, we tackle the problem of geometric and photometric modeling of large intricately shaped objects. Typical target objects we consider are cultural heritage objects. When constructing models of such objects, we are faced with several important issues that have not been addressed in the past-issues that mainly arise due to the large amount of data that has to be handled. We propose two novel approaches to efficiently handle such large amounts of data: A highly adaptive algorithm for merging range images and an adaptive nearest-neighbor search to be used with the algorithm. We construct an integrated mesh model of the target object in adaptive resolution, taking into account the geometric and/or photometric attributes associated with the range images. We use surface curvature for the geometric attributes and (laser) reflectance values for the photometric attributes. This adaptive merging framework leads to a significant reduction in the necessary amount of computational resources. Furthermore, the resulting adaptive mesh models can be of great use for applications such as texture mapping, as we will briefly demonstrate. Additionally, we propose an additional test for the k-d tree nearest-neighbor search algorithm. Our approach successfully omits back-tracking, which is controlled adaptively depending on the distance to the nearest neighbor. Since the main consumption of computational cost lies in the nearest-neighbor search, the proposed algorithm leads to a significant speed-up of the whole merging process. In this paper, we present the theories and algorithms of our approaches with pseudo code and apply them to several real objects, including large-scale cultural assets.

Algorithms↗
PubMed2004

Individual differences in emotional complexity: their psychological implications.

Two studies explored the nature and psychological implications of individual differences in emotional complexity, defined as having emotional experiences that are broad in range and well differentiated. Emotional complexity was predicted to be associated with private self-consciousness, openness to experience, empathic tendencies, cognitive complexity, ability to differentiate among named emotions, range of emotions experienced daily, and interpersonal adaptability. The Range and Differentiation of Emotional Experience Scale (RDEES) was developed to test these hypotheses. In Study 1 (N=1,129) students completed questionnaire packets containing the RDEES and various outcome measures. Study 2 (N=95) included the RDEES and non-self-report measures such as peer reports, complexity of representations of the emotion domain, and level of ego development measured by a sentence completion test. Results supported all of the hypotheses, providing extensive evidence for the RDEES's construct validity. Findings were discussed in terms of the role of emotional complexity in ego maturity and interpersonal adaptability.

Adaptation, Psychological↗
PubMed1999

The G-factor as a tool to learn more about bone structure and function.

In normal life on earth, the locomotor system is exposed to two types of stimulation: gravity (passive stimulation) and motion (active stimulation). Both permanently combine, and the interactions between locomotion and gravity induce an overall recruitment which is repeated daily and maintains the bone tissue structure within the range of constraints to which it is adapted. This range is one of the basic hypotheses underlying the mechanical concepts of bone structure control, and it has been considered as logical to assume that weightlessness of spaceflight should produce bone loss since astronauts are outside of the terrestrial gravitational field of forces, no longer relying on muscular work to change positions or move. But, thirty years after the first changes in phospho-calcium metabolism were observed in astronauts after spaceflight, current knowledge does not provide a full understanding of this pathogeny, and prove the G-factor is now considered as an essential component of the experimental tools available to study bone physiology. The study of the physiology of bone tissue usually consists in the investigation of its two fundamental roles, i.e. reservoir of inorganic elements (calcium, phosphorus, magnesium) and mechanical support for soft tissues. Together with the combined action of muscles, tendons, and ligaments, this support permits motion and locomotion. These two functions rely on a sophisticated bone tissue architecture, and on the adaptability of this structure, with modeling and remodeling processes, themselves associated with the coupled activity of specialized bone cell populations.

Animals↗
PubMed2000

Sleep-related behavioural adaptations in free-ranging anthropoid primates.

Several aspects of behaviour relating to sleep in monkeys and apes are reviewed, including sleeping site selection, approach to and departure from sleeping sites, social behaviour at the sites, and nocturnal activities. Illustrative examples are given for each topic. Good sleeping sites for primates give protection from predators and/or some physical comfort from the elements and other sources of disturbance. Availability of sleeping sites may determine ranging patterns and whether an area is exploited or not. Times of retiring and resumption of daytime activities are influenced by foraging and ranging requirements. Social relationships and their influencing factors continue during the night, including dominance, kinship, affiliation and sex. Social partners may be used for thermoregulation and for increasing postural stability. Primates show a range of solutions to the problems surrounding sleep, and similarities and differences between monkeys and the large-bodied, nest-building great apes are described. Knowledge of natural sleep-related phenomena in non-human primates can provide valuable insights for human sleep research, and vice-versa.

Journal Article↗
PubMed2003

Reverberation of rapid and slow trills: implications for signal adaptations to long-range communication.

Many acoustic signals in animals include trills, i.e., rapid repetitions of similar elements. Elements within these trills usually are frequency modulated and are degraded by reverberation during long-range transmission. Reverberation primarily affects consecutive elements with the same frequency characteristics and thus imposes a major constraint in the evolution of design and perception of long-range signals containing trills. Here transmission of frequency-unmodulated trills with different element repetition rates was studied. Trills were generated at different frequencies to assess frequency dependence of reverberation and then broadcast under three acoustic conditions--an open field and to assess seasonal changes in transmission properties, a deciduous forest before and after foliage had emerged. Reverberation was quantified at different positions within trills. The results show strong effects of vegetation density (season), transmission distance, frequency, element repetition rate, and element position within the trill on effects of reverberation. The experiments indicate that fast trills transmit less well than slow trills and thus are less effective in long-range communication. They show in particular that selection on trills should not act only on element repetition rate within trills but also on the trill duration as effects of reverberation increased with trill duration.

Acoustics↗
PubMed1981

Simple adaptations to extend the range of flow cytometry five orders of magnitude for the DNA analysis of uni-and multicellular systems.

Procedures and instrumentation are described to extend the capability of a cytometry system to record samples that exhibit a wide range of fluorescence such as multicellular systems. The method employs a log amplifier in combination with a set of neutral density filters that reduces the incident light reaching the photomultiplier tube. With any given filter, signals within an intensity range of 200-fold can be measured; different filters can be used to obtain an extended overall range. Polystyrene fluorescent microspheres and a variety of mithramycin stained biological samples ranging from yeast cells to Paramecium were processed by the system. The relative DNA content of individual multicellular embryos was determined for a heterogeneous population of embryonic stages isolated from the nematode, Caenorhabditis elegans. As part of the evaluation of the procedure, the practical upper limit of range extension was determined. The most intense fluorescent signal was produced when untreated pecan pollen stained with ethidium bromide fluoresced with a factor (8.4 +/- 1.3) X 10(4) more than ethidium bromide stained E. coli cells.

Ambystoma↗
PubMed1998

Aftereffect of high-speed motion.

A visual illusion known as the motion aftereffect is considered to be the perceptual manifestation of motion sensors that are recovering from adaptation. This aftereffect can be obtained for a specific range of adaptation speeds with its magnitude generally peaking for speeds around 3 deg s-1. The classic motion aftereffect is usually measured with a static test pattern. Here, we measured the magnitude of the motion aftereffect for a large range of velocities covering also higher speeds, using both static and dynamic test patterns. The results suggest that at least two (sub)populations of motion-sensitive neurons underlie these motion aftereffects. One population shows itself under static test conditions and is dominant for low adaptation speeds, and the other is prevalent under dynamic test conditions after adaptation to high speeds. The dynamic motion aftereffect can be perceived for adaptation speeds up to three times as fast as the static motion aftereffect. We tested predictions that follow from the hypothesised division in neuronal substrates. We found that for exactly the same adaptation conditions (oppositely directed transparent motion with different speeds), the aftereffect direction differs by 180 degrees depending on the test pattern. The motion aftereffect is opposite to the pattern moving at low speed when the test pattern is static, and opposite to the high-speed pattern for a dynamic test pattern. The determining factor is the combination of adaptation speed and type of test pattern.

Adaptation, Psychological↗
PubMed1995

The effect of contrast adaptation on briefly presented stimuli.

Wilson and Humanski (1993) have recently reported evidence that adapting to low temporal frequency sinewave gratings yields little threshold elevation for briefly presented test stimuli. We postulated that brief stimuli may be detected by a transient channel which would be minimally affected by a low temporal frequency adapting pattern. We therefore measured the effect of adaptation on briefly presented test stimuli for a wider range of adapting temporal frequencies. The results indicate that adaptation may yield threshold elevation for briefly presented stimuli and that threshold elevation is greater for high than low temporal frequency adapting patterns. These results are consistent with the hypothesis that briefly presented stimuli are detected by a transient channel.

Adaptation, Ocular↗