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At least 289 records · Page 16Linked to original sources
PubMed1992

The NMDA-receptor antagonist CPP abolishes neurogenic 'wind-up pain' after intrathecal administration in humans.

Involvement of the NMDA receptor system in the transmission of nociceptive information, including the development of central sensitization and a wind-up phenomenon, has increased interest in NMDA-receptor antagonists as antinociceptive drugs. This case report describes the use of an NMDA receptor antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) in a carefully selected patient with severe and intractable neurogenic pain in her left leg. The pain syndrome had components of a continuous deep pain, an allodynia, and a wind-up-like component, including afterdischarge and spread of painful sensations outside the territory of the injured nerve. After intrathecal (i.t.) administration of 200 nmol of CPP the continuous deep pain component and allodynia were unchanged, but the following 'wind-up' phenomenon with afterdischarge and spread of the pain sensation in the left half of the body was completely abolished. Another 500 nmol of CPP administered over 2 h did not improve pain relief. Pain thresholds for heat and cold stimulation, measured with a Marstock thermostimulator, did not change. There was no effect on blood pressure, heart rate, sensitivity, reflexes, coordination or motor performance. Psychotomimetic ketamine-like side effects developed 4 h after the last injection of CPP and were probably due to rostral spread of CPP. These early experiences with i.t. administration of NMDA-receptor antagonists to humans indicate that the NMDA-receptor system plays an important role in neurogenic pain and that antagonizing this system may be a useful way to obtain better pain control although psychotomimetic side effects due to rostral spread may be a problem.

Cold Temperature↗
PubMed2005

Unilateral subcutaneous bee venom but not formalin injection causes contralateral hypersensitized wind-up and after-discharge of the spinal withdrawal reflex in anesthetized spinal rats.

This study aimed to investigate the effect of tonic nociception on spinal withdrawal reflexes including (1) long lasting spontaneous responses elicited by subcutaneous (s.c.) administration of formalin (2.5%, 50 microl) and bee venom (BV, 0.2 mg/50 microl) into the hind paw and (2) corresponding ipsilateral (primary) and contralateral (secondary) hypersensitivity to noxious pinch and repetitive supra-threshold (1.5 x T) electrical stimuli at different frequencies (3 Hz: wind-up; 20 Hz: after-discharge) in anesthetized spinal rats. Spinal withdrawal reflexes were studied by simultaneously assessing single motor units (SMUs) electromyographic (EMG) activities from the bilateral medial gastrocnemius (MG) muscles. Subcutaneous formalin-induced persistent spontaneous SMU EMG responses were in typical biphasic manner with an apparent silent period (about 13-18 min), but in contrast, BV elicited monophasic long lasting (about 1 h) SMU EMG responses without any resting state. The mechanically and electrically evoked responsiveness of SMUs were enhanced significantly by ipsilateral BV injection, whereas enhanced electrically, but not mechanically, evoked responses (including wind-up and after-discharge) were found at the non-injection site of the contralateral hind paw. However, s.c. administration of formalin was only able to establish ipsilateral hypersensitivity of the SMUs to repeated electrical, not mechanical, stimulation. Neither mechanically nor electrically evoked contralateral hypersensitivity of the SMUs was found during the ipsilateral formalin-induced nociception. For pharmacological intervention, intrathecal administration of the non-N-methyl-d-aspartate (non-NMDA) receptor antagonist CNQX (40 nmol/10 microl), but not the non-competitive NMDA receptor antagonist MK-801 (40 nmol/10 microl), significantly depressed BV-induced contralateral hypersensitivity of the SMUs to repeated 3 Hz (wind-up) and 20 Hz (after-discharge) frequencies of electrical stimulation. Using the extracellular SMU recording technique, we found that s.c. administration of formalin and BV shows a significant difference in long lasting spontaneous firing of SMUs. This is consistent with previous observations in animal behavioral studies. Additionally, contralateral electrically evoked hypersensitivity of the SMUs was found only following BV injection, not in the formalin test. The maintenance and development of BV-induced contralateral hypersensitivity of the spinal withdrawal reflex to noxious electrical stimulation indeed depend on different central pharmacological receptors. The spinal non-NMDA, but not the NMDA, receptors may play important role in BV-induced contralateral central hyperexcitability and sensitization.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2003

Simultaneous recordings of wind-up of paired spinal dorsal horn nociceptive neuron and nociceptive flexion reflex in rats.

To study the sensory-motor interaction of spinal processing underlying the neuronal mechanisms of the nociceptive flexion reflex (NFR) and its temporal facilitation, 16 spinal dorsal horn (DH) wide-dynamic-range (WDR) neurons and paired 16 single motor units (SMU) from the gastrocnemius soleus muscle (GS) were simultaneously recorded using extracellular single unit and electromyographic techniques in spinal, halothane-anesthetized rats. The paired DH WDR neuron and GS SMU showed a parallel increase in the firing rate and duration of spike responses to noxious pinch stimuli applied to their common cutaneous receptive field (cRF) on the ipsilateral hind paw skin. Innocuous brush or pressure evoked no, or less, firing in the SMU but evoked a graded increase in spike responses in the simultaneously-recorded WDR neuron. Moreover, both pressure and noxious pinch stimuli evoked a short-lasting after-discharge (for several min) in the WDR neuron but without any after-discharge in the simultaneously-recorded SMU. The paired WDR neuron and SMU also showed a parallel basal response (termed as early and late components according to latency), after-discharge and wind-up of the late response to repetitively applied supra-threshold electrical stimulation (intensity: >1.5 T, duration: 1 ms and frequency: 1 Hz for 15 s). Linear regression and cross-correlation histogram analyses showed that the DH WDR neuron had a significant correlation with the simultaneously-recorded SMU and they were functionally located in the spinally-organized NFR circuitry via polysynaptic connections. Systemic administration of fentanyl, an opioid receptor agonist, resulted in a parallel, naloxone-reversible suppression of both basal late response component and wind-up response in both WDR neuron and SMU paired; however, fentanyl suppressed only the early response of the SMU without any effect on that of the DH WDR neuron. The present results provide new direct evidence showing an essential role of spinal DH WDR neurons in the mediation of spinally-organized NFR as well as its temporal facilitation (wind-up). Based on these data, the spinal DH WDR neuron seems to function as a signal discriminator or frequency encoder of multireceptive primary afferent impulses that may determine excitable level of motor output and the occurrence of a behavioral NFR via polysynaptic connections. Consequently, the spinal WDR neuron-mediated NFR and its temporal facilitation are likely to be modulated by spinal endogenous opioid peptides via opioid receptors on the nociceptive sensory components of the spinally-organized NFR circuitry.

Analgesics, Opioid↗
PubMed2003

Interleukin-1beta increases spinal cord wind-up activity in normal but not in monoarthritic rats.

Cytokines produced by spinal cord glia after peripheral inflammation, infection or trauma have a relevant role in the maintenance of pain states. The effect of intrathecally administered interleukin-1beta (IL-1beta) on spinal cord nociceptive transmission was studied in normal and monoarthritic rats by assessing wind-up activity in a C-fiber-mediated reflex paradigm evoked by repetitive (1 Hz) electric stimulation. Low i.t. doses of IL-1beta (0.03, 0.12, 0.5 and 2.0 ng) dose-dependently enhanced wind-up activity in normal rats, while higher doses (8.0 ng) only produced a marginal unsignificant effect. IL-1beta administration to monoarthritic rats did not significantly change wind-up scores at any dose. Adaptive changes developed in the spinal cord during chronic pain may underlie the ineffectiveness of exogenous IL-1beta to up-regulate nociceptive transmission.

Animals↗
PubMed2003

Dynamical coupling of wind and ocean waves through wave-induced air flow.

Understanding the physical mechanisms behind the generation of ocean waves by wind has been a longstanding challenge. Previous studies have assumed that ocean waves induce fluctuations in velocity and pressure of the overlying air that are synchronized with the waves, and numerical models have supported this assumption. In a complex feedback, these fluctuations provide the energy for wave generation. The spatial and temporal structure of the wave-induced airflow therefore holds the key to the physics of wind-wave coupling, but detailed observations have proved difficult. Here we present an analysis of wind velocities and ocean surface elevations observed over the open ocean. We use a linear filter to identify the wave-induced air flow from the measurements and find that its structure is in agreement with 'critical-layer' theory. Considering that the wave-induced momentum flux is then controlled by the wave spectrum and that it varies considerably in vertical direction, a simple parameterization of the total air-sea momentum flux is unlikely to exist.

Journal Article↗
PubMed2003

Voyager 1 exited the solar wind at a distance of approximately 85 Au from the Sun.

The outer limit of the Solar System is often considered to be at the distance from the Sun where the solar wind changes from supersonic to subsonic flow. Theory predicts that a termination shock marks this boundary, with locations ranging from a few to over 100 au (1 Au approximately 1.5 x 10(8) km, the distance from Earth to the Sun). 'Pick-up ions' that originate as interstellar neutral atoms should be accelerated to tens of MeV at the termination shock, generating anomalous cosmic rays. Here we report a large increase in the intensity of energetic particles in the outer heliosphere, as measured by an instrument on the Voyager 1 spacecraft. We argue that the spacecraft exited the supersonic solar wind and passed into the subsonic region (possibly beyond the termination shock) on about 1 August 2002 at a distance of approximately 85 Au (heliolatitude approximately 34 degrees N), then re-entered the supersonic solar wind about 200 days later at approximately 87 au from the Sun. We show that the composition of the ions accelerated at the putative termination shock is that of anomalous cosmic rays and of interstellar pick-up ions.

Journal Article↗
PubMed2003

Reproducibility of a laboratory-based 40-km cycle time-trial on a stationary wind-trainer in highly trained cyclists.

The purpose of the present study was to examine the reproducibility of laboratory-based 40-km cycle time-trial performance on a stationary wind-trainer. Each week, for three consecutive weeks, and on different days, forty-three highly trained male cyclists (x +/- SD; age = 25 +/- 6 y; mass = 75 +/- 7 kg; peak oxygen uptake [VO (2)peak] = 64.8 +/- 5.2 ml x kg (-1) x min (-1)) performed: 1) a VO (2)peak test, and 2) a 40-km time-trial on their own racing bicycle mounted to a stationary wind-trainer (Cateye - Cyclosimulator). Data from all tests were compared using a one-way analysis of variance. Performance on the second and third 40-km time-trials were highly related (r = 0.96; p < 0.001), not significantly different (57 : 21 +/- 2 : 57 vs. 57 : 12 +/- 3 : 14 min:s), and displayed a low coefficient of variation (CV) = 0.9 +/- 0.7 %. Although the first 40-km time-trial (58 : 43 +/- 3 : 17 min:s) was not significantly different from the second and third tests (p = 0.06), inclusion of the first test in the assessment of reliability increased within-subject CV to 3.0 +/- 2.9 %. 40-km time-trial speed (km x h (-1)) was significantly (p < 0.001) related to peak power output (W; r = 0.75), VO (2)peak (l x min (-1); r = 0.53), and the second ventilatory turnpoint (l x min (-1); r = 0.68) measured during the progressive exercise tests. These data demonstrate that the assessment of 40-km cycle time-trial performance in well-trained endurance cyclists on a stationary wind-trainer is reproducible, provided the athletes perform a familiarization trial.

Adult↗
PubMed2005

Shoot circumnutation and winding movements require gravisensing cells.

Circumnutation and winding in plants are universal growth movements that allow plants to survive despite their sessile nature. However, the detailed molecular mechanisms controlling these phenomena remain unclear. We previously found that a gravitropic mutant of Japanese morning glory (Pharbitis nil or Ipomoea nil), Shidare-asagao (weeping), is defective not only in circumnutation but also in the winding response. This phenotype is similar to that of the Arabidopsis SCARECROW (SCR) mutant. We therefore investigated whether morning glory SCR (PnSCR) is involved in the weeping phenotype. We found that one amino acid was inserted into the highly conserved VHIID motif in weeping-type PnSCR; this mutation caused abnormal endodermal differentiation. We introduced either the mutant or WT PnSCR into Arabidopsis scr mutants for complementation tests. PnSCR of the WT, but not of weeping, rescued the shoot gravitropism and circumnutation of scr. These results show that both the abnormal gravitropism and the circumnutation defect in weeping are attributable to a loss of PnSCR function. Thus, our data show that gravisensing endodermal cells are indispensable for shoot circumnutation and the winding response and that PnSCR is responsible for the abnormal phenotypes of weeping.

Amino Acid Sequence↗
PubMed2003

Effect of long-term ketamine administration on vocalization to paw pressure and on spinal wind-up activity in monoarthritic rats.

The antinociceptive effect of long-lasting ketamine administration (mini-osmotic pump) was studied in monoarthritic rats by using hindpaw pressure testing and wind-up measurement in a C-fiber reflex paradigm. Chronic ketamine induced antinociception in the monoarthritic paw and significantly suppressed mechanical hyperalgesia during the 14-day treatment period. The treatment also reduced C-reflex wind-up in the monoarthritic hindpaw. After pump removal, vocalization thresholds and spinal wind-up scores from the monoarthritic paw returned to control values, while hyperalgesia developed in the normal paw. Results suggest that ketamine upregulates NMDA receptors upon long-term administration, resulting in hyperalgesic response in the normal paw after drug withdrawal.

Analgesics↗
PubMedDate not supplied

Adaptive growth of tree root systems in response to wind action and site conditions.

Soil-root plate dimensions and structural root architecture were examined on 46-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees that had been mechanically uprooted. Rooting depth was restricted by a water table, and root system morphology had adapted to resist the wind movement associated with shallow rooting. The spread of the root system and the ratio of root mass to shoot mass (root/shoot ratio) were both negatively related to soil-root plate depth. Root systems had more structural root mass on the leeward side than the windward side of the tree relative to the prevailing wind direction. Cross sections of structural roots were obtained at distances of 0.5, 0.75, 1.0, and 1.25 m from the tree center. Buttressed parts of roots had greater lateral and vertical secondary thickening above rather than below the biological center. This uneven growth, which produced a shape similar in cross section to a T-beam, was greater on the leeward side of the tree, and was greatest at 0.5 m from the tree center of shallow rooted trees. Further from the tree, particularly on the windward side, many roots developed eccentric cross-sectional shapes comparable to I-beams, which would efficiently resist vertical flexing. Roots became more ovoid in shape with increasing distance from the tree, especially on deep rooted trees where lateral roots tapered rapidly to a small diameter. We conclude that these forms of adaptive growth in response to wind movement improve the rigidity of the soil-root plate and counteract the increasing vulnerability to windthrow as the tree grows.

Journal Article↗
PubMed2005

Generalized dimensions for fluctuations in the solar wind.

We analyze time series of velocities of the solar wind plasma including the outward-directed component of Alfvénic turbulence within slow wind observed by the Helios 2 spacecraft in the inner heliosphere. We demonstrate that the influence of noise in the data can be efficiently reduced by a singular-value decomposition filter. The resulting generalized dimensions show a multifractal structure of the solar wind attractor in the inner heliosphere. The obtained multifractal spectrum is consistent with that for the multifractal measure on the self-similar weighted baker's map with two parameters describing uniform compression and natural invariant measure on the attractor of the system.

Journal Article↗
PubMed2005

Critical fluctuation of wind reversals in convective turbulence.

The irregular reversals of wind direction in convective turbulence are found to have fluctuating intervals that can be related, under certain circumstances, to critical behavior. In particular, by focusing on its temporal evolution, the net magnetization of a two-dimensional Ising lattice of finite size is observed to fluctuate in the same way. Detrended fluctuation analysis of the wind reversal time series results in a scaling behavior that agrees remarkably well with that of the Ising problem. The specific properties found here, as well as the lack of an external tuning parameter, also suggest that the wind reversal phenomenon exhibits signs of self-organized criticality.

Journal Article↗
PubMed2002

Kaluza-Klein states versus winding states: can both be above the string scale?

Closed strings in extra compactified dimensions give rise to both Kaluza-Klein states and winding states. Since the masses of these states play a reciprocal role, it is often believed that either the lightest Kaluza-Klein states or the lightest winding states must be at or below the string scale. In this Letter, we demonstrate the contrary, showing that there exist toroidal compactifications for which all Kaluza-Klein states as well as all winding states are heavier than the string scale. Within the context of low-scale string theories, this implies that it may be possible to cross the string scale without detecting any states associated with spacetime compactification.

Journal Article↗
PubMed2005

Compressibility in solar wind plasma turbulence.

Incompressible magnetohydrodynamics is often assumed to describe solar wind turbulence. We use extended self-similarity to reveal scaling in the structure functions of density fluctuations in the solar wind. The obtained scaling is then compared with that found in the inertial range of quantities identified as passive scalars in other turbulent systems. We find that these are not coincident. This implies that either solar wind turbulence is compressible or that straightforward comparison of structure functions does not adequately capture its inertial range properties.

Journal Article↗
PubMed1970

Plant gas exchange at high wind speeds.

High altitude Rhododendron ferrugineum L. and Pinus cembra L. seedlings were exposed to winds at 15 meters per second for 24-hour periods. Wind-sensitive stomata of Rhododendron seedlings immediately initiated a closing response which resulted in decreased photosynthesis and an even greater reduction in transpiration. Stomatal aperture and transpiration rates of P. cembra were only slightly reduced by high speed winds. However, photosynthesis was substantially reduced because of changes in needle display to available irradiation.

Journal Article↗
PubMed1984

Phycomyces: an increase in mechanical extensibility after a humidified wind stimulus.

The mechanical extensibilities of stage IVb Phycomyces were measured before and after a humidified wind stimulus. We find that when the humidity of the wind is greater than that of the ambient air, there is an increase in the mechanical extensibility of the cell wall. We also find that a step decrease in wind humidity results in a decrease in the mechanical extensibility of the cell wall.

Journal Article↗
PubMed2005

Solar wind origin in coronal funnels.

The origin of the solar wind in solar coronal holes has long been unclear. We establish that the solar wind starts flowing out of the corona at heights above the photosphere between 5 megameters and 20 megameters in magnetic funnels. This result is obtained by a correlation of the Doppler-velocity and radiance maps of spectral lines emitted by various ions with the force-free magnetic field as extrapolated from photospheric magnetograms to different altitudes. Specifically, we find that Ne7+ ions mostly radiate around 20 megameters, where they have outflow speeds of about 10 kilometers per second, whereas C3+ ions with no average flow speed mainly radiate around 5 megameters. Based on these results, a model for understanding the solar wind origin is suggested.

Journal Article↗
PubMed2006

Solar wind neon from Genesis: implications for the lunar noble gas record.

Lunar soils have been thought to contain two solar noble gas components with distinct isotopic composition. One has been identified as implanted solar wind, the other as higher-energy solar particles. The latter was puzzling because its relative amounts were much too large compared with present-day fluxes, suggesting periodic, very high solar activity in the past. Here we show that the depth-dependent isotopic composition of neon in a metallic glass exposed on NASA's Genesis mission agrees with the expected depth profile for solar wind neon with uniform isotopic composition. Our results strongly indicate that no extra high-energy component is required and that the solar neon isotope composition of lunar samples can be explained as implantation-fractionated solar wind.

Journal Article↗