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At least 19 recordsLinked to original sources
PubMed2025

The Relationship Among Range Adaptation, Social Anhedonia, and Social Functioning: A Combined Magnetic Resonance Spectroscopy and Resting-State fMRI Study.

BACKGROUND AND HYPOTHESIS: Social anhedonia is a core feature of schizotypy and correlates significantly with social functioning and range adaptation. Range adaptation refers to representing a stimulus value based on its relative position in the range of pre-experienced values. This study aimed to examine the resting-state neural correlates of range adaptation and its associations with social anhedonia and social functioning. STUDY DESIGN: In study 1, 60 participants completed resting-state magnetic resonance spectroscopy and fMRI scans. Range adaptation was assessed by a valid effort-based decision-making paradigm. Self-reported questionnaires was used to measure social anhedonia and social functioning. Study 2 utilized 26 pairs of participants with high (HSoA) and low levels of social anhedonia (LSoA) to examine the group difference in range adaptation's neural correlates and its relationship with social anhedonia and social functioning. An independent sample of 40 pairs of HSoA and LSoA was used to verify the findings. STUDY RESULTS: Study 1 showed that range adaptation correlated with excitation-inhibition balance (EIB) and ventral prefrontal cortex (vPFC) functional connectivity, which in turn correlating positively with social functioning. Range adaptation was specifically determined by the EIB via mediation of ventral-medial prefrontal cortex functional connectivities. Study 2 found HSoA and LSoA participants exhibiting comparable EIB and vPFC connectivities. However, EIB and vPFC connectivities were negatively correlated with social anhedonia and social functioning in HSoA participants. CONCLUSIONS: EIB and vPFC functional connectivity is putative neural correlates for range adaptation. Such neural correlates are associated with social anhedonia and social functioning.

Humans↗
PubMed1988

Control of contractile properties within adaptive ranges by patterns of impulse activity in the rat.

These experiments explore the relationship between patterned impulse activity and contractile properties of skeletal muscles. Soleus (SOL) and extensor digitorum longus (EDL) muscles of adult rats were denervated and stimulated directly from 4 to 15 weeks with the same number of pulse trains at different intratrain pulse frequencies (1-500 Hz), with different numbers of pulse trains (864-4,320,000 pulses/d) at the same intratrain pulse frequencies, or with different combinations of pulse trains at 10 and 100 Hz. Chronic stimulation of the denervated SOL resulted in twitch times-to-peak and half-relaxation times that varied in a graded manner between values longer than those in the normal SOL to values as fast as those in the normal EDL, depending upon the pattern used. Increasing pulse frequencies (constant number) resulted in faster twitches, lower twitch/tetanus ratios, increasing post-tetanic potentiations, and larger tetanic tensions. Increasing pulse numbers (constant frequencies) resulted in slower twitches, lower twitch/tetanus ratios, post-tetanic depressions, and higher fatigue indices. The effect of varying the pulse number on twitch parameters was greater at low frequencies (10-20 Hz) than at high frequencies (100 Hz). SOL muscles receiving pulse trains at both 10 and 100 Hz became much faster than muscles receiving pulse trains at 10 Hz only, even in the experiments where the stimulation pattern contained 9 times as many pulses at 10 as at 100 Hz. Chronic stimulation of both the denervated and the innervated EDL with large numbers of pulses at 10 or 15 Hz resulted in twitches that were only half as slow as those induced in the SOL by the same "slow" patterns. In addition, these patterns led to a marked decrease in maximum tetanic tension and a marked increase in twitch/tetanus ratio. During stimulation with a small number of pulses at 150 Hz, on the other hand, twitch speed, twitch/tetanus ratio, and maximum tetanic tension remained normal or almost normal. We conclude that the isometric twitch and related properties of the rat SOL muscle can be graded within wide "adaptive ranges" by varying either the number or the frequency of pulses. In the EDL, the corresponding adaptive ranges appear much narrower, suggesting that the EDL and the SOL contain intrinsically different muscle fibers.

Adaptation, Physiological↗
PubMed2025

Eco-Evolutionary Genomics Reveal Mountain Range-Specific Adaptation and Intraspecific Variation in Vulnerability to Climate Change of Alpine Endemics.

Alpine plants restricted to rocky habitats exhibit intraspecific diversification due to range fragmentation during Holocene warming, complicating predictions of their climate vulnerability. A lack of understanding of eco-evolutionary mechanisms driving their response to climate change results in ineffective conservation efforts. To uncover the genomic basis of their diversification and explain spatial patterns of their vulnerability, we combine landscape genomics and species distribution modelling. Our model, the Campanula lehmanniana complex, occurs in three distinct central Asian mountain ranges, considered both a biodiversity hotspot and a vascular plant diversity darkspot. Genome-environment association confirmed the adaptive basis of intraspecific diversification, driven by numerous loci of small effect. Genomic and ecological data indicate mountain range-specific climate sensitivity driven by altitude, temperature and precipitation. The cold-dry adapted group from Zeravshan-Hissar Mts will face niche decline but show a higher degree of preadaptation to future climate, while the temperate-humid group from Tian Shan shows an opposite response, with a higher risk of maladaptation despite predicted niche expansion. Maladapted populations at northern margins may require an influx of adaptive variation to cope with predicted changes. However, limited landscape connectivity between island-like habitats, combined with long migration distances required to minimise genotype-environment disruption, highlights the role of human-assisted migration in enabling evolutionary rescue. These results underscore the need to facilitate gene flow from pre- to maladapted populations and the importance of population-specific approaches to inform effective conservation strategies in heterogeneous mountain ecosystems. The results may be relevant to numerous Central Asian mountain species that show similar phylogeographic patterns.

Climate Change↗
PubMed1989

Genome structure of adenovirus 12 host range mutants adapted to growth in simian Vero cells.

Mutants of adenovirus type 12 adapted to growth in Vero cells were studied by restriction enzyme and sequence analysis. Plaque-purified mutants were isolated either after long-term passage of the virus in Vero cells (CS-1, CL-1) or from Vero cells transfected with viral DNA (11-g, 12-k). The plaque-forming activity of these mutants was equal or even slightly higher in Vero cells than in HeLa cells, whereas the activity of wild-type virus in HeLa cells exceeded that in Vero cells by about one to two orders of magnitude. All mutants tested had an insertion of variable length consisting of adenoviral sequences at the right end of the viral genome. Sizes of the insertions were determined to be 294 bp (CS-1, 12-k), 560 (11-g), or 180 bp (CL-1). Additional insertions of multiple size and less than equimolar amount were detected and seem to exist in some of the viral particles. Furthermore, all four mutants tested showed an identical 69-bp deletion in the first exon of the E1a gene.

Adenoviridae↗
PubMed1986

Adaptation of tonic accommodation reduces accommodative lag and is masked in darkness.

Tonic aftereffects of accommodation were investigated under three open loop conditions; Maxwellian view (pin hole pupil), empty field, and darkness. Duration of accommodative aftereffects, following 5 sec of adaptation, ranged within several seconds for all three open loop conditions. After adapting for 1 min to a 2-D stimulus, the duration of accommodative aftereffects increased by approximately an order of magnitude for the Maxwellian view and empty field conditions; however, they increased modestly for the dark condition. Tonic aftereffects of accommodation were also stimulated by convergence with base out prism or divergence with base in prism while the accommodative loop was opened. The ratio of open-loop aftereffect amplitude/closed-loop accommodative response to lenses ranged from 0.95 to 0.48, and it became smaller when the accommodative stimulus approached the amplitude of accommodation. The rapid decay of tonic aftereffects of accommodation in darkness was reversable when a visible stimulus was presented while the accommodative loop was opened by Maxwellian view or empty field. Hence, darkness only masked aftereffects that were manifest primarily when there was light stimulation of the retina. The amplitudes of accommodative aftereffects were reciprocally related to the amplitude of the lag of accommodation. During a 2-min adaptation period, accommodative response increased gradually for 30-60 sec as it approached the amplitude of the accommodative stimulus. This resulted in a reduction of accommodative error or lag. Opening the accommodative loop before or after the lag was reduced resulted in a small or large aftereffect of accommodation respectively. Accommodative aftereffects appear to be related to accommodative lag as prism adaptation is related to fixation disparity.

Accommodation, Ocular↗
PubMed1979

Nonlinear kernels of the human ERG.

In this paper we examine the use of a symmetric binary random stimulus for eliciting the ERG, and for calculating the first-order and second-order kernels of a nonlinear functional expansion of the response. We show that if the stimulus is represented in a non-dimensional form, then the units in which all kernels are measured are the same as the units used to measure the response, microvolts in the case of the ERG; further, contributions from all kernels to the response can be added without scale factors. We present the first-order and second-order kernels measured for a population of 15 normal subjects in a clinical setting. The measurements were made at various levels of adaptation ranging from photopic to scotopic conditions. The second-order kernels illustrate the processes of rapid adaptation (less than 100 ms) in the retina.

Adult↗
PubMed1991

Short-term nonconjugate adaptation of human saccades to anisometropic spectacles.

It has been demonstrated before that the long-term wearing of anisometropic spectacles may induce nonconjugate adaptations of saccades. Saccades then become different in size in the two eyes. We examined the time-course and the limits of such adaptations of horizontal and vertical saccades during the short-term (1-6 hr) wearing of anisometropic spectacles. After only 1 hr of conditioning to 2 D of anisometropia, the nonconjugate size-adaptations were almost complete along the horizontal meridian. For progressively larger anisometropias (up to 8 D) the adaptative nonconjugacies after 1 hr became also systematically larger. An anisometropia larger than 6 D did not further increase the rate of adaptation during the first 6 hr of conditioning, which suggests that about 6 D of difference in spectacle correction, causing size differences of about 12%, may be the upper limit of the nonconjugate adaptive range of the saccadic subsystem. Post-saccadic drift of horizontal saccades was also adequately changed. In addition, nonconjugate adaptations had developed in smooth-pursuit eye movements. All of these plastic changes persisted during monocular viewing, indicating that the basic programming of these eye movements was changed.

Adaptation, Ocular↗
PubMed1987

Chesson strain Plasmodium vivax in Saimiri sciureus boliviensis monkeys.

Nine Saimiri sciureus boliviensis monkeys were inoculated with sporozoites of Plasmodium vivax (Chesson strain) dissected from Anopheles stephensi mosquitoes infected by feeding on blood from infected chimpanzees. The animals were splenectomized 7 days after inoculation. Seven animals developed infections with prepatent periods ranging from 12 to 43 days (mean of 19.6 days). Parasitemias were low during the first 50 days. Maximum parasitemias in 5 animals in which the strain adapted ranged from 10,000 to 46,800 per mm3. Anopheles freeborni mosquitoes were infected by feeding on 4 of the monkeys.

Animals↗
PubMed1986

The spatial organization of retinal receptive fields in light and darkness as revealed by the pattern electroretinogram.

The spatial selectivity of the electroretinogram in response to pattern onset-offset stimuli was studied in man at several levels of adaptation ranging from scotopic to photopic levels. Under conditions of rod function the peak of the spatial selectivity based on amplitude measurements of the pattern-onset response occurs at a low spatial frequency. With increasing light adaptation a gradual shift of the selectivity to higher spatial frequencies occurs. This change in the character of the response can be explained by the assumption that antagonistic center-surround retinal receptive fields contribute to the response, which are larger under scotopic than under photopic levels of stimulation.

Darkness↗
PubMed1988

Predictive value of screening for different areas of development.

Associations between the results of developmental screening at five ages between 30 weeks and three years and the children's educational and behavioural status in normal primary schools at 6 1/2 to 7 1/2 years were examined in two samples of children living in Dundee and born in 1974 and 1975. In one sample the screening results for 417 children with moderately severe or severe school problems were compared with the screening results for a control group without school problems. Positive associations were found between school problems and motor and adaptive screening test results (from 39-week screening onward), language (from 15 months), preschool behaviour (at 39 weeks and two years) and neurological status (at 39 weeks and three years). In the second sample the questionnaire scores of 570 children known to be suspect on screening were compared with the scores of a control group whose screening results had been considered within the normal range. Adaptive and neurological screening tests provided the best predictors of behaviour problems in school and of educational failure. It is suggested that more thorough developmental and neurological assessments, at less frequent intervals, than is common in most screening programmes would facilitate identification of (and intervention for) preschool neurodevelopmental disability among children at risk of early schooling problems.

Child↗
PubMed1989

The role of sensory adaptation in the retina.

Adaptation, a change in response to a sustained stimulus, is a widespread property of sensory systems, occurring at many stages, from the most peripheral energy-gathering structures to neural networks. Adaptation is also implemented at many levels of biological organization, from the molecule to the organ. Despite adaptation's diversity, it is fruitful to extract some unifying principles by considering well-characterized components of the insect visual system. A major function of adaptation is to increase the amount of sensory information an organism uses. The amount of information available to an organism is ultimately defined by its environment and its size. The amount of information collected depends upon the ways in which an organism samples and transduces signals. The amount of information that is used is further limited by internal losses during transmission and processing. Adaptation can increase information capture and reduce internal losses by minimizing the effects of physical and biophysical constraints. Optical adaptation mechanisms in compound eyes illustrate a common trade-off between energy (quantum catch) and acuity (sensitivity to changes in the distribution of energy). This trade-off can be carefully regulated to maximize the information gathered (i.e. the number of pictures an eye can reconstruct). Similar trade-offs can be performed neurally by area summation mechanisms. Light adaptation in photoreceptors introduces the roles played by cellular constraints in limiting the available information. Adaptation mechanisms prevent saturation and, by trading gain for temporal acuity, increase the rate of information uptake. By minimizing the constraint of nonlinear summation (imposed by membrane conductance mechanisms) a cell's sensitivity follows the Weber-Fechner law. Thus, a computationally advantageous transformation is generated in response to a cellular constraint. The synaptic transfer of signals from photoreceptors to second-order neurones emphasizes that the cellular constraints of nonlinearity, noise and dynamic range limit the transmission of information from cell to cell. Synaptic amplification is increased to reduce the effects of noise but this resurrects the constraint of dynamic range. Adaptation mechanisms, both confined to single synapses and distributed in networks, remove spatially and temporally redundant signal components to help accommodate more information within a single cell. The net effect is a computationally advantageous removal of the background signal. Again, the cellular constraints on information transfer have dictated a computationally advantageous operation.

Adaptation, Physiological↗
PubMed1990

[Stress caused by sports in pregnancy].

The wide adaptation range of the circulatory system, the respiratory system, and the metabolism of the female organism during pregnancy permits utilization of many positive effects of physical exercise for optimal health and wellbeing. Hitherto physically inactive pregnant women should be intensively motivated and advised, while women who are already physically active regularly should be advised to combine planned pregnancies with an optimally step-by-step reduction in training. After an uncomplicated delivery, and dependent on a normal uterus involution and lactation, a gradual adaptation to a renewed training program can be recommended. The advantages of physical exercise during pregnancy were analysed in relation to possibly dangerous complications during intensive training periods. The most important contraindications are described. The authors emphasize the increasing importance of cooperation between the Pregnancy Health Service and the Sports Medicine Service for optimal medical guidance of physically active pregnant women.

Female↗
PubMedDate not supplied

Regulatory aspects of placental iron transfer--a comparative study.

Receptor-mediated endocytosis is generally assumed to be the process by which the haemochorial placenta takes up iron from transferrin. The involvement of an additional nonendocytic process cannot, however, be excluded. It appears from a study of iron transport mechanisms and of the maturation of the transfer process that placental ferritin is involved in the transfer of iron from mother to fetus. The metabolic relationship between the ferritin pool and the placental transfer pool remains to be elucidated. There is no evidence for short-term regulation of placental transfer capacity in response to changes in the maternal iron supply or to changes in the trophoblastic iron content. This cannot yet be said of fetal feedback control of placental iron uptake because the experiments performed so far do not permit conclusions on this point. The capacity for iron uptake and transfer seems to increase in accordance with the ontogenetically determined placental growth pattern. This does not exclude long-range adaptive modifications of the transfer capacity in response to early maternal or fetal disturbances. The results obtained from studying placental maturation suggest that a possible long-term regulatory interaction between growing placenta and fetus may occur. Clinical evidence so far is inconclusive. The relatively moderate reductions in the fetal iron stores which are generally associated with severe iron-deficient pregnancies might be seen as an argument in favour of long-term placental control. The marked impact of pregnancy on maternal iron metabolism in rodents, as compared to other mammals, is possibly met by means of direct placental control of mucosal iron uptake. In primates, mucosal iron uptake during pregnancy seems to be governed by factors related to systemic iron deficiency only.

Animals↗
PubMed1978

Utility of specific locus systems in higher plants to monitor for mutagens.

Plants possess biological and operational attributes that have encouraged geneticists to use them extensively in the development of fundamental genetic concepts. Attributes such as regenerative plasticity, high fecundity, cultural adaptability, range of ploidy, economics of culture and maintenance of specific populations, and versatility make plant genetic systems prime candidates with which to monitor the environment for mutagens. A specific locus (equivalent to a classical Mendelian gene) controls the development of a phenotypic characteristic. It can also mutate to a new allelic form with a consequentially altered phenotypic characteristic and can be separated by crossing over from adjacent loci that govern other specific phenotypic characteristics. Since various plant species have numerous specific loci, one has a rich array of potential systems from which to select. Specific locus systems in higher plants could be used to assess the mutagenicity of single chemical compounds or combinations of chemical compounds. Depending on the circumstances, seeds and/or seedlings could be used; plants could be grown in situ in either containers or plots to assess the immediate environment for one or more mutagens over an extended period. Since plants are eucaryotes, data from such experiments could serve as one more source of information along with that obtained from a battery of other tests used in the tier system.

Biological Assay↗
PubMed1992

Application of a programmable dual-channel adaptive electrical stimulation system for the control and analysis of gait.

A dual-channel electrical stimulation system with a stimulator and a programmer/stride analyzer was designed for clinical rehabilitation of gait and for subsequent daily use as an orthotic aid. The stimulator, with controls to adjust amplitude only (50 mA), adapts chosen stimulation sequences to the walking rate of a patient. Pulse duration (50-500 microseconds), frequency (5-120 Hz), shape (symmetrical biphasic, monophasic), stimulation sequences (16 stride segments) and their cycle (2-12 sec), and right/left foot-switch choices are selected for each patient and programmed into a separate unit. The programming unit also statistically processes the foot-switch data collected by the stimulator. The device was evaluated with regard to the programmable parameters, effectiveness during gait, and feasibility in clinical use. It was applied to 11 stroke patients and 10 brain injury patients during gait, stimulating 22 combinations of peroneal nerve and hamstring, quadriceps, triceps brachii, and gluteus maximus muscles. Forces on both feet, equinovarus, knee extension and hyperextension, elbow flexion, and hip extension were corrected. Selection of the stimulation sequences, their adaptation, range of pulse duration, and valid statistics were verified. Improved forces and joint angles were recorded together with significant changes in the stride time, length, and velocity by the stimulation.

Adult↗
PubMed1992

Transcriptional regulation of heat shock genes. A paradigm for inducible genomic responses.

The heat shock response offers an ideal paradigm to understand how the cell recognizes and responds to acute and chronic exposures to environmental and physiological stress. Of the numerous inducible genomic responses, the heat shock response has contributed fascinating insights into the molecular and cellular mechanisms of adaptation, ranging from the regulation of heat shock gene expression to the function of stress proteins. The recent cloning of multiple heat shock transcription factor (HSF) genes in higher eukaryotes and studies on the biochemical and cellular properties of HSFs have revealed several novel features of the transcriptional response.

Animals↗
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↗