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At least 37 records · Page 2Linked to original sources
PubMed1977

Impulse dependent adaptation in Helix pomatia neurones: demonstration of the adaptation conductance.

By conventional voltage clamp methods an increase in membrane conductance after a depolarizing pulse is demonstrated in neurones of Helix pomatia. This increase decays exponentially with a time constant in the range of 5--20 s. The rise of the conductance during the depolarization can be represented by 3 exponentials with time constants from 12 ms to 1 s. The steady state value of the conductance depends on the membrane potential in a sigmoid manner. The conductance gives rise to an outward current, which appears to be carried by potassium ions. The firing pattern of the cell is governed by the conductance. A short, rectangular potential change, a pulse clamp, is used to disturb the firing pattern of the freely firing cell. The effect on the firing pattern depends on the height and duration of the clamp pulse in the same manner as the conductance increase. The normal firing produces similar changes in the membrane conductance.

Adaptation, Physiological↗
PubMed1976

The effect of parathyroidectomy and large doses of cholecalciferol on the ability of rats to adapt to changes in dietary intake of calcium.

1. Adaptation to different dietary levels of calcium was produced by feeding a low (0-2%) calcium diet or one of two high (1-6 or 0-8%) calcium diets for 4 or 6 weeks. Adaptive changes in true and apparent absorption of calcium, apparent absorption of phosphate and urinary excretion of calcium, were observed. 2. Parathyroidectomy performed prior to adaptation did not greatly impair the ability of rats to adapt to different levels of calcium in the diet. The response of the rats to parathyroidectomy was affected by their subsequent dietary history. 3. Six weeks after parathyroidectomy the plasma calcium was significantly higher than it had been immediately post-operatively. This rise in plasma calcium was seen in the rats adapted to the 1-6% calcium diet but not in those adapted to the 0-2% calcium diet. 4. Parathyroidectomy performed after adaptation had taken place did not abolish the adaptive changes. The response of rats to parathyroidectomy was affected by their previous dietary history. 5. Large doses of cholecalciferol given for 8 days after adaptation had taken place increased the absorption of calcium in rats adapted to the 0-8% calcium diet thereby abolishing or reducing the adaptive differences in absorption between these rats and rats adapted to the 0-2% calcium diet. The cholecalciferol increased urinary calcium excretion but did not abolish adaptive differences in urinary excretion of calcium between rats adapted to diets with different calcium levels. 6. It is concluded that parathyroid hormone does not play a major role in mediating adaptation to different dietary intakes of calcium. The possible role of 1-25 dihydroxycholecalciferol is discussed.

Adaptation, Physiological↗
PubMed2026

Cerebellar iTBS enhances gait adaptation by modulating cortical sensorimotor network dynamics: a randomized controlled trial.

Gait adaptation enables individuals to maintain locomotor stability under persistent perturbations. Although the cerebellum is critical for sensory prediction error-based (SPE) adaptation, how cerebellar neuromodulation reshapes cortical sensorimotor networks to enhance gait adaptation remains unclear. This study investigated the behavioral effects and underlying cortical neurodynamic mechanisms of cerebellar intermittent theta-burst stimulation (iTBS) on gait adaptation. Thirty-two healthy adults received either active or sham cerebellar iTBS. Participants performed a split-belt treadmill adaptation task before and after intervention. Cortical responsiveness was evaluated using TMS-evoked EEG over primary motor cortex (M1), while resting-state EEG was analyzed to assess spectral power and directional functional connectivity. Compared to sham, cerebellar iTBS significantly enhanced gait adaptation, evidenced by a faster adaptation rate (p = 0.035) and enhanced Early Adaptation SLS (p = 0.011), without altering initial perturbation responses or post-adaptation outcomes. The iTBS increased TMS-evoked α (p = 0.031) and γ (p = 0.022) power in M1, while the α power was correlated with faster adaptation (r = 0.526, p = 0.002). Furthermore, iTBS strengthened PPC-to-M1 directed connectivity in the β (p = 0.025) and γ (p = 0.013) bands. Enhanced parieto-motor directionality were positively associated with adaptation rate (β: r = 0.515, p = 0.003; γ: r = 0.463, p = 0.009). These findings suggest that cerebellar iTBS facilitates gait adaptation by modulating cortical responsiveness and directional sensorimotor network connectivity, providing multi-level neurodynamic evidence for the cerebello-cortical modulation during gait adaptation and offering a strong physiological rationale for targeted neuromodulation in gait rehabilitation strategies.

Humans↗
PubMed2026

Pathogen local adaptation shapes Pierce's disease of grapevines outcomes under field conditions.

Climate change is broadly expected to increase the range of many plant diseases, yet the current status of local thermal adaptation in many pathogens is poorly understood. Xylella fastidiosa (Xf) is a global bacterial plant pathogen that causes Pierce's disease (PD) of grapevines and infects over 700 other host plant species, impacting both agricultural and natural ecosystems. In a common garden experiment with 477 vines in the field, we compared PD outcomes from a local (colder climate in CA) vs non-local (warmer climate in CA) bacterial strain in 13 Mediterranean grapevine varieties over 3 years. Relative to the local strain, there was 77% lower overwinter survival in the non-local strain from a warmer climate, strongly indicating local adaptation in these CA Xf populations. Host genotype also had a significant effect on pathogen winter survival, and grapevine varieties differed in PD susceptibility. Additionally, we assessed in planta evolution of the two pathogen strains over 3 years by whole-genome sequencing 58 field-derived isolates. There were convergent loss-of-function mutations in genes encoding minor Type IV pilin (T4P) proteins, which control twitching motility and other virulence phenotypes, suggesting rapid adaptive evolution. Our results suggest local adaptation to cold temperatures in a bacterial plant pathogen and a possible role for minor Type IV pilins in thermal adaptation. These findings demonstrate the urgent need to incorporate X. fastidiosa evolution and local thermal adaptation into global models of PD spread. Differentiating pathotypes with distinct thermal adaptations will improve disease forecasting and inform quarantine decisions.IMPORTANCEForecasting the movement of plant pathogens is a critical issue under global warming to effectively manage future plant disease outbreaks. Yet, current plant pathogen local thermal adaptation is often unaccounted for, especially in bacterial pathogens. Our study examines local adaptation to temperature in a bacterial plant pathogen, Xylella fastidiosa, that causes disease in grapevines in addition to infecting 700 other plant species. In a large-scale field experiment across 13 grapevine varieties, we demonstrate local adaptation in pathogen winter survival in distinct Xylella fastidiosa strains. Additionally, we found evidence of adaptive evolution in just 3 years, as we observed convergent mutations after resequencing strains that evolved in the field. Our results suggest that X. fastidiosa populations-even within a small geographic area-have distinct adaptations to winter temperatures and may exhibit differential responses to warming winters.

Type IV pili↗
PubMed1979

Dark-adaptation in frog rods: changes in the stimulus-response function.

1. Aspartate-isolated photoresponses of the frog's rods to weak and strong flashes have been recorded during dark-adaptation after bleaching a fraction of rhodopsin (generally 4--30%). Stimulus--response functions were measured before the bleach and in the steady state after dark-adaptation. 2. The movements of the operating curve, i.e. the stimulus--response function plotted in a log-log diagram, are interpreted in terms of a model of outer segment adaptation, where the adaptation processes are associated with the transmitter release (Q-adaptation), the number of active sodium channels and leakage channels in the plasma membrane of the outer segment (M-adaptation), and the transmitter background (c1-adaptation). 3. A small bleach in a fully dark-adapted, non-bleached retina brings about a displacement of the operating curve predominantly to the right. The shift back to the left is approximately exponential, typical time constants being 6--12 min. 4. A strong exposure (bleaching 15--30% of rhodopsin) in a previously partially bleached retina brings about a nearly vertical displacement of the operating curve: after the bleach the maximum photoresponse is strongly reduced, and during intermediate adaptation the operating curve returns mainly upwards. 5. Cumulatively increasing permanent displacements of the operating curve are observed in the steady states after successive dark-adaptation transients. The permanent displacements are predominantly to the right and they increase with increasing temperature. 6. The experimental results, as interpreted according to the model, indicate that the Q-adaptation process is dominant in physiological conditions (small or moderate bleaches), whereas the M-adaptation becomes important only after rather large bleaches and especially after several successive bleaches in an isolated retina.

Animals↗