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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Modifying the Genetic Regulation of Bone and Cartilage Cells and Associated Tissue by EMF Stimulation Fields and Uses Thereof

An apparatus and method to modify the genetic regulation of mammalian tissue, bone, or any combination. The method may be comprised of the steps of tuning at least one predetermined profile associated with at least one time-varying stimulation field thereby resulting in at least one tuned time-varying stimulation field comprised of at least one tuned predetermined profile, wherein said at least one tuned predetermined profile is comprised of a plurality of tuned predetermined figures of merit and is controllable through at least one of said plurality of tuned predetermined figures of merit, wherein said plurality of predetermined tuned figures of merit is comprised of a tuned B-Field magnitude, tuned rising slew rate, tuned rise time, tuned falling slew rate, tuned fall time, tuned frequency, tuned wavelength, and tuned duty cycle; and exposing mammalian chondrocytes, osteoblasts, osteocytes, osteoclasts, nucleus pulposus, associated tissue, or any combination to said at least one tuned time-varying stimulation field comprised of said at least one tuned predetermined profile for a predetermined tuned exposure time or plurality of tuned exposure time sequences.

Goodwin, Thomas J.↗
NASA NTRS1988

Immunocytochemical localization of glutamic acid decarboxylase (GAD) and substance P in neural areas mediating motion-induced emesis: Effects of vagal stimulation on GAD immunoreactivity

Immunocytochemical methods were employed to localize the neurotransmitter amino acid gamma-aminobutyric acid (GABA) by means of its biosynthetic enzyme glutamic acid decarboxylase (GAD) and the neuropeptide substance P in the area postrema (AP), area subpostrema (ASP), nucleus of the tractus solitarius (NTS), and gelatinous nucleus (GEL). In addition, electrical stimulation was applied to the night vagus nerve at the cervical level to assess the effects on GAD-immunoreactivity (GAR-IR). GAD-IR terminals and fibers were observed in the AP, ASP, NTS, and GEL. They showed pronounced density at the level of the ASP and gradual decrease towards the solitary complex. Nerve cells were not labelled in our preparations. Ultrastructural studies showed symmetric or asymmetric synaptic contracts between labelled terminals and non-immunoreactive dendrites, axons, or neurons. Some of the labelled terminals contained both clear- and dense-core vesicles. Our preliminary findings, after electrical stimulation of the vagus nerve, revealed a bilateral decrease of GAD-IR that was particularly evident at the level of the ASP. SP-immunoreactive (SP-IR) terminals and fibers showed varying densities in the AP, ASP, NTS, and GEL. In our preparations, the lateral sub-division of the NTS showed the greatest accumulation. The ASP showed medium density of immunoreactive varicosities and terminals and the AP and GEL displayed scattered varicose axon terminals. The electron microscopy revealed that all immunoreactive terminals contained clear-core vesicles which make symmetric or asymmetric synaptic contact with unlabelled dendrites. It is suggested that the GABAergic terminals might correspond to vagal afferent projections and that GAD/GABA and substance P might be co-localized in the same terminal allowing the possibility of a regulated release of the transmitters in relation to demands.

GABA↗
NASA NTRS2001

Stimulated single fiber electromyography in the mouse: techniques and normative data

As the number of new transgenic mouse models of human neuromuscular disease continues to increase, the development of sophisticated electrophysiologic techniques for assessing the peripheral nervous system in these models has become important. Neuromuscular junction (NMJ) dysfunction, in particular, is often not detectable by morphologic or other techniques. To enable sensitive testing of murine NMJ function, we developed and tested a method for stimulated single fiber electromyography (S-SFEMG) in the gastrocnemius muscles of anesthetized mice. Jitter was assessed by measuring the mean consecutive latency difference (MCD) of single fiber responses to sciatic nerve stimulation at 2 HZ. Mean MCD values in normothermic mice were in the range of 6-8 micros for different strains, with no MCD values exceeding 25 micros. Reduced core temperature (to 29 degrees--30 degrees C) resulted in increased jitter, whereas intubation and mechanical ventilation of mice did not alter these values. Intraperitoneal and intravenous injection of vecuronium, however, resulted in progressively increased jitter followed by blocking in continuously monitored fibers. These observations validate the utility of S-SFEMG in mice as an index of NMJ function under a variety of physiologic conditions, and suggest that a high safety factor for neuromuscular transmission exists at mouse NMJs. Copyright 2001 John Wiley & Sons, Inc.

Non-NASA Center↗
NASA NTRS2000

Primate translational vestibuloocular reflexes. III. Effects of bilateral labyrinthine electrical stimulation

The effects of functional, reversible ablation and potential recruitment of the most irregular otolith afferents on the dynamics and sensitivity of the translational vestibuloocular reflexes (trVORs) were investigated in rhesus monkeys trained to fixate near and far targets. Translational motion stimuli consisted of either steady-state lateral and fore-aft sinusoidal oscillations or short-lasting transient lateral head displacements. Short-duration (usually <2 s) anodal (inhibitory) and cathodal (excitatory) currents (50-100 microA) were delivered bilaterally during motion. In the presence of anodal labyrinthine stimulation, trVOR sensitivity and its dependence on viewing distance were significantly decreased. In addition, anodal currents significantly increased phase lags. During transient motion, anodal stimulation resulted in significantly lower initial eye acceleration and more sluggish responses. Cathodal currents tended to have opposite effects. The main characteristics of these results were simulated by a simple model where both regularly and irregularly discharging afferents contribute to the trVORs. Anodal labyrinthine currents also were found to decrease eye velocity during long-duration, constant velocity rotations, although results were generally more variable compared with those during translational motion.

NASA Program Biomedical Research and Countermeasur↗
NASA NTRS1999

The timing of galvanic vestibular stimulation affects responses to platform translation

We compared the effects of galvanic vestibular stimulation applied at 0, 0.5, 1.5 and 2.5 s prior to a backward platform translation on postural responses. The effect of the galvanic stimulation was largest on the final equilibrium position of the center of pressure (CoP). The largest effects occurred for the 0.5 and 0-s pre-period, when the dynamic CoP pressure changes in response to both the galvanic stimulus and the platform translation coincided. The shift in the final equilibrium position was also larger than the sum of the shifts for the galvanic stimulus and the platform translation alone for the 0.5 and 0-s pre-periods. The initial rate of change of the CoP response to the platform translation was not significantly affected in any condition. Changes in the peak CoP position could be accounted for by local interaction of CoP velocity changes induced by the galvanic and translation responses alone, but the changes in final equilibrium position could only be accounted for by a change in global body orientation. These findings suggest that the contribution of vestibulospinal information is greatest during the dynamic phase of the postural response, and that the vestibular system contributes most to the later components of the postural response, particularly to the final equilibrium position. These findings suggest that a nonlinear interaction between the vestibular signal induced by the galvanic current and the sensory stimuli produced by the platform translation occurs when the two stimuli are presented within 1 s, during the dynamic phase of the postural response to the galvanic stimulus. When presented at greater separations in time, the stimuli appear to be treated as independent events, such that no interaction occurs. Copyright 1999 Elsevier Science B.V.

Non-NASA Center↗
NASA NTRS1998

Arabidopsis thaliana responses to mechanical stimulation do not require ETR1 or EIN2

Plants exposed to repetitive touch or wind are generally shorter and stockier than sheltered plants. These mechanostimulus-induced developmental changes are termed thigmomorphogenesis and may confer resistance to subsequent stresses. An early response of Arabidopsis thaliana to touch or wind is the up-regulation of TCH (touch) gene expression. The signal transduction pathway that leads to mechanostimulus responses is not well defined. A role for ethylene has been proposed based on the observation that mechanostimulation of plants leads to ethylene evolution and exogenous ethylene leads to thigmomorphogenetic-like changes. To determine whether ethylene has a role in plant responses to mechanostimulation, we assessed the ability of two ethylene-insensitive mutants, etr1-3 and ein2-1, to undergo thigmomorphogenesis and TCH gene up-regulation of expression. The ethylene-insensitive mutants responded to wind similarly to the wild type, with a delay in flowering, decrease in inflorescence elongation rate, shorter mature primary inflorescences, more rosette paraclades, and appropriate TCH gene expression changes. Also, wild-type and mutant Arabidopsis responded to vibrational stimulation, with an increase in hypocotyl elongation and up-regulation of TCH gene expression. We conclude that the ETR1 and EIN2 protein functions are not required for the developmental and molecular responses to mechanical stimulation.

Non-NASA Center↗
NASA NTRS1997

The effect of optokinetic stimulation on daytime sleepiness

This study examined the effect of optokinetic stimulation on objective sleepiness, as measured by the Multiple Sleep Latency Test (MSLT). The Nightcap, a portable sleep monitor, was used in a novel way to perform MSLTs, as well as record sleep in the home. Subjects wore the Nightcap for seven consecutive nights. On days 3 and 5 of the protocol, subjects came into the lab for an MSLT. On the experimental day, subjects underwent 10 minutes optokinetic stimulation (OKS), resulting in moderate motion sickness prior to each MSLT trial. Although subjects in the OKS condition reported significantly more drowsiness than controls, this did not result in significantly reduced sleep latencies.

NASA Discipline Neuroscience↗
NASA NTRS1993

Potentiation by choline of basal and electrically evoked acetylcholine release, as studied using a novel device which both stimulates and perfuses rat corpus striatum

We examined the release of acetylcholine (ACh) and dopamine (DA) using a novel probe through which striatal neurons could be both superfused and stimulated electrically in both anesthetized and freely moving awake animals. Optimal stimulation parameters for eliciting ACh release from cholinergic neurons differed from those required for eliciting DA release from dopaminergic terminals: at 0.6 ms pulse duration, 20 Hz and 200 microA, ACh release increased to 357 +/- 30% (P < 0.01) of baseline and was blocked by the addition of tetrodotoxin (TTX). Pulse durations of 2.0 ms or greater were required to increase DA release. Unlike ACh release, DA release showed no frequency dependence above 5 Hz. The maximal evoked releases of ACh and DA were 556 +/- 94% (P < 0.01) and 254 +/- 38% (P < 0.05) of baseline, respectively. Peripheral administration of choline (Ch) chloride (30-120 mg/kg) to anesthetized animals caused dose-related (r = 0.994, P < 0.01) increases in ACh release; basal release rose from 117 +/- 7% to 141 +/- 5% of initial baseline levels (P < 0.05) and electrically evoked ACh release rose from 386 +/- 38% to 600 +/- 34% (P < 0.01) in rats given 120 mg/kg. However, Ch failed to affect basal or evoked DA release although neostigmine (10 microM) significantly elevated basal DA release (from 36.7 fmol/10 min to 71.5 fmol/10 min; P < 0.05). In awake animals, Ch (120 mg/kg) also elevated both basal (from 106 +/- 7% to 154 +/- 17%; P < 0.05) and electrically evoked (from 146 +/- 13 to 262 +/- 16%; P < 0.01) ACh release.(ABSTRACT TRUNCATED AT 250 WORDS).

NASA Program Space Physiology and Countermeasures↗
NASA NTRS1981

Eye-head coordination during optokinetic stimulation in squirrel monkeys

Head and eye movements in the yaw plane were recorded during and after optokinetic stimulation in squirrel monkeys. 1) Phasic or tonic head deviations to the side of the ocular quick phase occurred in 94% of total recordings (n = 50) during the perstimulus period, and in 75% of recordings (n = 49) during the poststimulus period. Magnitude of mean head deviation was significantly different between perstimulus and poststimulus periods. 2) Head nystagmus associated with eye nystagmus was consistently observed in seven of nine squirrel monkeys during optokinetic stimulation. Squirrel monkeys are thereby less prone to display head nystagmus than either guinea pigs, pigeons or chickens. 3) Slow phase speeds of coupled head and eye nystagmus were subjected to statistical analysis. A highly significant negative correlation was found between slow phase head and eye speeds. The correlation coefficient was - 0.81 at 60 degrees / sec stimulus (n = 119) and -0.72 at 100 degrees / sec stimulus (n = 131). The gaze speed, calculated by summing the head and eye speeds, was 59.1 plus or minus 6.8 / sec at 60 degrees / sec and 92.2 plus or minus 11.4 at 100 degrees / sec stimulus. There was no significant difference between the gaze speed in a free head condition and the eye speed when the head was fixed.

Eye Movements↗
NASA NTRS1978

Influence of central venous pressure upon sinus node responses to arterial baroreflex stimulation in man

Measurements were made of sinus node responses to arterial baroreceptor stimulation with phenylephrine injection or neck suction, before and during changes of central venous pressure provoked by lower body negative pressure or leg and lower truck elevation. Variations of central venous pressure between 1.1 and 9.0 mm Hg did not influence arterial baroreflex mediated bradycardia. Baroreflex sinus node responses were augmented by intravenous propranolol, but the level of responses after propranolol was comparable during the control state, lower body negative pressure, and leg and trunk elevation. Sinus node responses to very brief baroreceptor stimuli applied during the transitions of central venous pressure also were comparable in the three states. The authors conclude that physiological variations of central venous pressure do not influence sinus node responses to arterial baroreceptor stimulation in man.

Mark, A. L.↗
NASA NTRS1977

Stimulated-emission cross section at 1064 and 1342 nm in Nd:YVO4

The stimulated-emission cross sections at 1064 and 1342 nm in Nd:YVO4 were determined by measurement of laser thresholds as a function of output mirror reflectivity. Small samples of Nd:YVO4 and Nd:YAG were end pumped at room temperature with a CW 514.5-nm argon ion laser in an almost identical geometrical arrangement which permitted comparative values to be obtained. Assuming that the pumping quantum efficiency of Nd:YVO is similar to that of Nd:YAG, the stimulated-emission cross sections obtained for the 1064- and 1342-nm transitions were respectively 12 x 10 to the -19th and 6.0 x 10 to the -19th/sq cm.

Tucker, A. W.↗
NASA NTRS1979

A study of scattering, production, and stimulated emission of sound by vortex flows

The basic theory of aeroacoustics of homentropic fluid media is applied to the problems of sound scattering, production, and stimulated emission. A general theory of scattering from low speed three-dimensional vortex flows is presented. Specific results are given for the horseshoe vortex and vortex ring. The noise of an elementary corotating vortex pair in various flows is calculated. It is shown that a potential flow and shear flow can substantially increase the basic pair noise. Small reverse shears can annihilate vortex pairs and eliminate the pair noise mechanism. The pair results are used to explain qualitatively the operation of noise suppression devices. The stimulated emission of a single vortex pair and four and six vortex arrays is demonstrated. The results for six vortices illustrate how external pure tones can amplify the broadband noise of a jet in agreement with recent experimental evidence.

Yates, J. E.↗
NASA NTRS1979

Laser-stimulated migration of adsorbed atoms on solid surfaces

This paper presents a unified theory of the coherent, multiple-photon excitation and laser-stimulated migration of atoms adsorbed on solid surfaces. We show that under steady-state excitation the migration of the adsorbed atom on the surface is diffusional, with diffusion constant dependent upon field intensity, surface temperature, relaxation constants, dipole moment strength, laser frequency, and the vibrational frequency of the adsorbed atom. In particular, it is shown that the rate of diffusion is proportional to the field intensity. Finally, we discuss the utility of laser-stimulated migration in the enhancement of surface chemical reactions, as well as in the analysis of surface relaxational processes.

Slutsky, M. S.↗
NASA NTRS1980

Bioelectrical activity of limb muscles during cold shivering of stimulation of the vestibular apparatus

The effects of caloric and electric stimulation of the vestibular receptors on the EMG activity of limb muslces in anesthetized cats during cold induced shivering involved flexor muscles alone. Both types of stimulation suppressed bioelectrical activity more effectively in the ipsilateral muscles. The suppression of shivering activity seems to be due to the increased inhibitory effect of descending labyrinth pathways on the function of flexor motoneurons.

Kuzmina, G. I.↗
NASA NTRS1981

The stimulation of auroral kilometric radiation by type III solar radio bursts

It has been found that the onset of auroral kilometric radiation (AKR) frequently coincides with the arrival of type III solar radio bursts. Although the AKR onsets are usually abrupt and appear to be spontaneous, they sometimes develop from a discrete frequency near the leading edge of a type III burst or sometimes occur at progressively lower frequencies following that edge. From this, and the absence of the related solar electrons in specific cases, it was concluded that the incoming type III waves were sometimes responsible for stimulating auroral kilometric radiation. It was estimated that intense, isolated type III bursts were capable of stimulating AKR roughly one third of the time, and that at least ten percent of the observed AKR onsets could be attributed to these and weaker bursts, including some barely detectable by the ISEE plasma wave receivers.

Calvert, W.↗