Phase-dependent Effects Research Articles

Entrainment of the locust central flight oscillator by wing stretch receptor stimulation

1. Experiments were designed to examine phase-dependent influences of the wing stretch receptor (SR) afferents on the central oscillator in the flight system of the locust. Reasons were also sought for the failure of earlier workers to find phase-dependent influences of SR activity on the flight oscillator. 2. In preparations with the hindwing sensory nerves left intact, electrical stimulation of the two forewing SRs caused an immediate increase in oscillator frequency reaching a maximum of 16–20 Hz as described by Pearson et al. (1983). After cutting the hindwing sensory nerves, the same stimulation increased the frequency from 6–8 Hz to 12–14 Hz. The absolute reduction in cycle period caused by the stimulation was reduced from 15–25 ms to 10–15 ms as a result of cutting the hindwing sensory nerves. 3. Stimulation of two forewing SRs in completely deafferented preparations in bursts occurring at a constant rate could entrain the flight oscillator. During entrainment, depressor spikes occurred close to the time of the stimulus. The flight oscillator could follow changes in the entrainment frequency, usually only up to 1 Hz (10% cycle period) compared to 4–6 Hz (40–50% cycle period) seen by Pearson et al. (1983). Entrainment could still be elicited when the chordotonal organ afferents were co-stimulated. 4. Bilateral stimulation of the hindwing SRs could also entrain the central flight oscillator over a similar range of frequencies as was observed for forewing SR stimulation. 5. Stimulation of a lateral pair of SRs (one forewing and the ipsilateral hindwing SR) was observed to produce 1∶1 entrainment in only one out of fifteen animals. However, a phase-dependent influence on the oscillator rhythm could be demonstrated by stimulation time-locked to the oscillator output (depressor EMG). SR stimulation close to the time of the depressor spike increased the oscillator frequency and prolonged the duration of rhythmic activity. Stimulation occurring approximately midway between depressor bursts had no obvious effect on the frequency or duration of the oscillator rhythm. 6. The only conditions under which a slow increase in oscillator frequency could be produced by stimulation of a lateral pair of SRs was when the SR stimulus frequency was set much higher than the central oscillator frequency. It is concluded that the failure of earlier workers to observe phase-dependent effects of SR stimulation on the oscillator frequency was due to stimulation of a lateral rather than segmental pair of SRs and the method they used in their attempt to demonstrate phase-dependence. Their observation of a slow phase-independent increase in flight frequency possibly resulted from the high SR stimulus frequencies employed.

Interaction of airborne and structure-borne noise radiated by plates

Analytical and experimental studies were undertaken in order to further the understanding of the interaction of airborne and structure-borne noise radiated by aircraft structures. The results of several measurements and computer simulations of the noise radiated by thin, isotropic, rectangular aluminum plates due to fully coherent combined acoustic and vibrational inputs is presented. The most significant finding of the study was the extremely large influence that the relative phase between the inputs has on the combined noise radiation of the plates. It is shown that phase dependent effects manifest themselves as cross terms in both the dynamic and acoustic portions of the analysis. The results show that these cross terms can radically alter the combined sound power radiated by plates constructed of aircraft-type materials. The results of the study suggest that airborne-structure-borne interactive effects could be responsible for a significant portion of the overall noise radiated by aircraft-type structures in the low frequency regime. These interactive effects have been neglected in the analyses of previous analytical and experimental studies of the interior noise of propeller driven aircraft.

Effects of sympathetic tone on vagally induced phasic changes in heart rate and atrioventricular node conduction in the anesthetized dog.

We examined the effects of stellate ganglia stimulation on the phase-dependent chronotropic and dromotropic responses to brief vagal bursts in open-chest anesthetized dogs. Stellate stimulation affected the phasic vagal effects on heart rate by shortening the latent period, shifting the phase at which maximum decrease in heart rate occurred to earlier phases, and reducing the maximum decrease in heart rate. These effects were due primarily to an increase in the basic heart rate. No significant sympathetic-parasympathetic interaction occurred for heart rate, indicating that accentuated antagonism did not occur with brief vagal bursts. Stellate stimulation primarily decreased the amplitude of the phasic vagal effects on atrioventricular nodal conduction, regardless of the underlying heart rate, and a significant sympathetic-parasympathetic interaction was associated with this effect. The peak of the phase-dependent vagal effects on heart rate and atrioventricular nodal conduction were phase-shifted with one another. From these findings, we postulate the small changes in sympathetic tone might shift the predominant phase-dependent vagal effect from one on heart rate to one on atrioventricular nodal conduction. Furthermore, our results suggest that dynamic vagal control of heart rate and atrioventricular node conduction involves both phase-dependent and phase-independent factors. Sympathetic activity appears to affect only the phase-independent factor(s) in the control of heart rate, whereas it affects both phase-dependent and phase-independent factors in the control of atrioventricular node conduction.

Afferent perturbations during "monopodal" swimming movements in the turtle: phase-dependent cutaneous modulation and proprioceptive resetting of the locomotor rhythm

Locomotion consists of a repeating series of movement cycles (locomotor rhythm) with an orderly activation of musculature during each movement cycle (intracycle motor pattern). The effects of sensory stimulation, on both the intracycle motor pattern and the locomotor rhythm, were examined during electrically elicited swimming movements of a single turtle hindlimb. The resulting "monopodal" swimming was not subject to movement-related reflexes from other limbs or postural constraints, and provided a sensitive system for analyzing the effects of transient sensory perturbations. During "monopodal" swimming, cutaneous and extensor muscle-nerve stimulation (single 0.1- to 0.3-msec electrical pulse) had similar phase-dependent effects on the swim cycle in progress. Stimuli delivered during the powerstroke (limb retracting) shortened the period of the cycle. Stimulation during the returnstroke prolonged the cycle. Changes in cycle period were accompanied by in-phase adjustments of the EMG burst duration or interburst interval which was being expressed at the time of stimulus delivery. The in-phase adjustment of each muscle served to maintain the timing relationships between muscles, and resulted in the preservation of the intracycle motor pattern. Cutaneous and muscle-nerve stimulation had dramatically different effects on the locomotor rhythm. Cutaneous nerve stimulation produced period changes in poststimulus cycles which led to a temporary phase shift of the swimming rhythm. This temporary modulation suggests that cutaneous afferents do not have direct access to the timing circuitry of the central nervous system locomotor network. Muscle-nerve stimulation only altered the period of the cycle in progress at the time of stimulus delivery, and thus permanently reset the locomotor rhythm. This permanent phase shift suggests that muscle afferents have direct access to a central timing network which controls the locomotor rhythm.

The effect of current passage on N-methyl- d-aspartate-induced, tetrodotoxin-resistant membrane potential oscillations in lamprey neurons active during locomotion

In lamprey spinal cord neurons, N-methyl-aspartate (NMA) can elicit tetrodotoxin (TTX)-resistant membrane potential oscillations (10–25 mV), that are of similar frequency to those recorded during NMA-induced fictive locomotion before TTX. The frequency of the oscillations was progressively reduced when increasing the amount of hyperpolarizing DC current. Brief de- or hyperpolarizing pulses gave phase-dependent effects on the duration of the oscillation cycle and rhythm resetting. Periodic stimuli could entrain the oscillatory activity. Under normal conditions, these oscillations will be influenced by synaptic activity, leading to an adequate coordination between neurons active during locomotion.

Spectral variability in early-type binary X-ray systems

Theoretical models for the ionization of trace elements in a strong stellar wind by a compact binary X-ray source and for the resulting orbital phase dependence of the emergent soft X-ray spectra and the profiles of ultraviolet resonance lines are presented. Model results agree qualitatively with the X-ray and ultraviolet spectra of the system 4U 0900-40/HD 77581 and explain the suppression of the absorption profiles of the Si IV upsilon 1394 and C IV upsilon 1548 lines when the X-ray sources is in front of the star. The model predicts that the absorption profiles of the N V upsilon 1239 and O VI upsilon 1032 lines will be enhanced rather than suppressed during this orbital phase. We predict phase-dependent linear polarization in the resonance lines profiles. Future observations of these phase dependent effects in early-type binary X-ray systems may be used to investigate the dynamics of stellar winds and their interactions with the X-ray source.

Remote and autogenic articulatory adaptation to jaw perturbations during speech: More on functional synergies

The present research is a continuation of a program devoted to understanding the cooperative behavior among neuromuscular elements during speech. In an earlier study, we found functionally specific electomyographic and kinematic evidence of compensation in remote articulators (upper lip and tongue) to perturbations of the jaw [J. A. S. Kelso, B. Tuller and C. A. Fowler, J. Acoust. Soc. Am. Suppl. 1 72, S103 (1982)]. Here we extend the earlier work to include additional subjects and phonetic contrasts and to test for phase dependent perturbation effects on the extent and style of compensation. We observe in this case that compensation in perturbed productions of /bæb/ and /bæp/ is primarily autogenic, that is local to the perturbed structure itself, the lower lip-jaw complex. We also find that contrasts not involving different articulators, e.g., between final /b/ and /p/, differ only in the degree to which compensation is achieved; the paterns are kinematically similar. The phase at which the jaw cycle is perturbed does not seem to affect either the position to which the system recovers following perturbation or the style of compensation. There are, however, phase dependent acoustic differences which suggest that compensation of a largely autogenic kind is not sufficient for complete compensation. [Work supported by NINCDS and ONR.]

Photoperiodic time measurement inSarcophaga argyrostoma: An attempt to use daily temperature cycles to distinguish external from internal coincidence

1. Larvae ofSarcophaga argyrostoma raised in continuous darkness (DD) and in ‘square-wave’ temperature cycles or thermoperiods (Hot:Cold4:20 to20:4, whereH=25 °C and C=15 °C) entered pupal diapause at a rate equivalent to that in DD and a constant temperature equal to the arithmetic mean of the cycle. Therefore, unlike many other insects so tested,S. argyrostoma appears to show no thermoperiodic regulation of diapause induction. 2. A daily low temperature pulse (3 h at 5 °C; =HC21:3), however, had marked phase-dependent effects on diapause incidence when administered with a concomitant light cycle (LD14:10), diapause increasing when the cold pulse fell early in the night, but decreasing when late in the night. This result is interpreted in terms of the phaseresetting effects of the cold pulse on the circadian oscillations making up the clock. 3. These results are considered to be consistent with an ‘external coincidence’ model for the photoperiodic clock and appear to differentiate between the ‘internal’ and ‘external’ alternatives (forS. argyrostoma) by demonstrating an inductive requirement for light in addition to that for entrainment.

Masking by spatially-modulated gratings

Contrast- or quasi-frequency-modulated masker gratings consisting of three high frequency components (8.8, 11 and 13.2 c/deg) affect the detectability of a 2.2 c/deg signal grating, to an extent that is strongly dependent upon the relative phase between signal and masker. Unmodulated high frequency maskers have no such phase-dependent effects. This paper explores the possibility that the visual system's nonlinear response to luminance is responsible for these phenomena. A specific hypothesis is proposed according to which the effects of the spatially modulated maskers are due entirely to a distortion product at 2.2 c/deg caused by the visual nonlinearity. Although some of the predictions of this hypothesis are borne out by the experimental findings, others are contradicted.

Observations of SiO maser emission from R Leo during its summer 1981 maximum

view Abstract Citations (8) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of SiO maser emission from R Leo during its summer 1981 maximum. Clark, F. O. ; Waak, J. A. ; Bologna, J. M. Abstract The 7-mm J = 1→0, υ = 1 and υ = 2 SiO maser emission from the Mira variable R Leo has been closely sampled in time near the summer 1981 optical maximum in order to observe possible phase-dependent effects. A significant broadening of both υ = 1 and υ = 2 emission, accompanied by profile changes, was observed between phases 0.95 and 0.98. If these changes are attributed to the expected passage of the shock front, the line formation region can be inferred to be very close to the photosphere of the star, and the radial extent of the line formation region may be crudely estimated. Publication: The Astronomical Journal Pub Date: December 1982 DOI: 10.1086/113269 Bibcode: 1982AJ.....87.1803C Keywords: Interstellar Masers; M Stars; Silicon Oxides; Spectral Line Width; Stellar Envelopes; Variable Stars; Emission Spectra; Linear Polarization; Astrophysics full text sources ADS | data products SIMBAD (2)

Peripheral control of the cat's step cycle. I. Phase dependent effects of ramp-movements of the hip during "fictive locomotion".

Acute spinal and curarized cats can generate "fictive locomotor activity" after an i.v. injection of Nialamid followed by 4-AP and L-DOPA. The efferent burst activity to flexors and extensors can be recorded in peripheral nerve filaments. Ramp-formed movements were applied in the hip at constant angular velocity in different phases of the spontaneous efferent burst activity. The cycle duration was markedly influenced. A flexion or an extension ramp applied in the early part of the "step-cycle" (during flexor activity) will prolong the cycle duration, but in the later part of the cycle instead a marked shortening effect will occur. The transition from a prolongation to a shortening is very steep for the extensive-ramps, with a subsequent gradual increase from a shortening to a lengthening of the cycle. This type of phase response curve expresses a potent peripheral modulatory effect on the central pattern generator. A ramp movement (flexion or extension) applied in the beginning of the flexor burst will reinforce the flexor activity. In the end of the flexor burst instead there is a directional sensitivity with positive feedback, resulting in an excitation of the flexor activity for flexion ramps, but a depression of the flexor activity for extension-ramps. Extension-ramps also show a position dependent effect which enhances the response in the flexors for more extended hip positions.

Cycle-Dependent Anticancer Drug Cytotoxicity in Mammalian Cells Synchronized by Centrifugal Elutriation<xref ref-type="fn" rid="FN2">2</xref>

The cycle-dependent cytotoxicity of seven chemotherapy agents was compared with the use of subpopulations of Chinese hamster ovary cells separated into the various phases of the cell cycle by centrifugal elutriation. The proportion of cells killed by either beta-cytosine arabinoside or hydroxyurea agreed well with the proportion of S-phase cells in the treated subpopulations. Cell-cycle survival patterns were also determined for bleomycin (BLM), adriamycin (ADR), cis-diamminedichloroplatinum (II) (cis-DDP), Asaley, and Yoshi 864. Three of the agents (cis-DDP, Asaley, and Yoshi 864) had similar cell-cycle survival patterns in that they all preferentially killed cells in the G1 phase. In contrast, BLM preferentially killed cells in G2+M phase, whereas ADR was most cytotoxic to cells in middle to late S-phase. This investigation demonstrated that separation of cultured mammalian cells into the various cell-cycle phases by centrifugal elutriation allows the rapid determination of the phase-dependent cytotoxic effects exerted by chemotherapy agents.

Circadian Phase-Dependent Stimulatory Effects of Epidermal Growth Factor on Deoxyribonucleic Acid Synthesis in the Tongue, Esophagus, and Stomach of the Adult Male Mouse*

Epidermal growth factor (EGF) previously isolated from the submandibular gland of mice was injected ip at different circadian phases into separate subgroups of adult male CD2F1 mice. Subsequent to each of the five time points of injection (0900, 1500, 1800, 2100, and 0300 h for animals standardized to 12 h of light alternating with 12 h of darkness), five animals were killed, 4, 8, and 12 h after the injection of EGF; comparable control groups were injected only with the carrier substance. Thirty minutes before sacrifice, each mouse was injected ip with 24 muCi [3H]thymidine. Incorporation of [3H]-thymidine into the DNA of the tongue, esophagus, and stomach was determined. The results demonstrate for the first time that EGF has a strong in vivo stimulatory effect on DNA synthesis in the tongue, esophagus, and stomach (studies on other areas of the gut have not yet been completed). Under the conditions of the study, stimulatory effects occurred as soon as 4 h subsequent to injection; however, maximal stimulation occurred for all three tissues 8 h after injection. Twelve hours after injection, the levels of DNA synthesis in all tissues were generally returning to normal levels found in the control animals. The results suggest circadian variation in susceptibility to EGF in the different tissues.

Circadian phase-dependent prolactin mechanisms in hepatic lipogenesis of a teleost.

In the teleost, Fundulus grandis, injections of prolactin early in the light phase cause an immediate 50% depression in the rate of hepatic lipogenesis ([14C]acetate incorporation); 10 h later, that rate has returned to levels not different from controls. Injections of prolactin late in the light phase cause an even more dramatic immediate depression of lipogenesis (79%) followed by a gradual increase in lipogenic rate which is 2.6 times higher than the control rate after 24 h. The stimulation of lipogenesis by prolactin is blocked by simultaneous treatment with indomethacin, an inhibitor of prostaglandin synthesis. These circadian phase-dependent effects of prolactin on hepatic lipogenesis are discussed with reference to possible mechanisms of action exerted by endogenous prolactin rhythms.

Reversal of sign of long spinal reflexes dependent on the phase of the step cycle in the high decerebrate cat

Reversal of the sign of long ascending and descending spinal reflexes dependent on the phase of the step cycle has been shown in the high decerebrate cat. Electrical stimuli were applied to the skin over the dorsum of the metacarpals and metatarsals and the effects were recorded in the corresponding hindlimb or forelimb of the same side. Stimulation generally evoked an increase in activity of flexor or extensor muscles shortly before, and during, activity of the muscle. Inhibition of a muscle occurred when its activity overlapped with the activity of an antagonist muscle. From the latencies it was concluded that at least the early components of the long reflex responses are due to spinal mechanisms. In the stimulated limb the activity of flexor and extensor muscles was also modulated in a phase dependent manner. No consistent long spinal responses to skin stimulation were obtained in high spinal cats during stepping. Electrical stimulation of cutaneous nerve trunks in decerebrate preparations during stepping gave variable though phase dependent long spinal reflex effects.

STROBOSCOPIC HOLOGRAPHIC INTERFEROMETRY

An experimental evaluation of a stroboscopic technique as applied to holographic interferometry is described. This technique is applicable in the analysis of vibrations with high amplitudes and complex wave forms and in the investigation of phase-dependent and nonsymmetrical effects.