Hz Intervals Research Articles

Acoustic analysis of a mechanical circulatory support.

Mechanical circulatory support technology is continually improving. However, adverse complications do occur with devastating consequences, for example, pump thrombosis that may develop in several parts of the pump system. The aim of this study was to design an experimental clot/thrombosis model to register and analyze acoustic signals from the left ventricular assist device (LVAD) HeartMate II (HMII) (Thoratec Corporation, Inc., Pleasanton, CA, USA) and detect changes in sound signals correlating to clots in the inflow, outflow, and pump housing. Using modern telecom techniques, it was possible to register and analyze the HMII pump-specific acoustic fingerprint in an experimental model of LVAD support using a mock loop. Increase in pump speed significantly (P < 0.005) changed the acoustic fingerprint at certain frequency (0–23 000 Hz) intervals (regions: R1–3 and peaks: P1,3–4). When the ball valves connected to the tubing were narrowed sequentially by ∼50% of the inner diameter (to mimic clot in the out- and inflow tubing), the frequency spectrum changed significantly (P < 0.005) in P1 and P2 and R1 when the outflow tubing was narrowed. This change was not seen to the same extent when the lumen of the ball valve connected to the inflow tube was narrowed by ∼50%. More significant (P < 0.005) acoustic changes were detected in P1 and P2 and R1 and R3, with the largest dB figs. in the lower frequency ranges in R1 and P2, when artificial clots and blood clots passed through the pump system. At higher frequencies, a significant change in dB figs. in R3 and P4 was detected when clots passed through the pump system. Acoustic monitoring of pump sounds may become a valuable tool in LVAD surveillance.

Object Characterization Based on Multispectral Acoustic Imaging

In previous studies, acoustic imaging was conducted using a single frequency or a limited number of frequencies that were not sufficient to clearly describe and explain the object characteristics. In this study, multispectral acoustic imaging (MSAI) is proposed to reveal rich information of object characteristics. An experimental study on object surfaces is conducted to verify the validity of the technique. Acoustic imaging of object surfaces is performed on the basis of a significant number of spectra over a wide frequency range. Using the frequency-swept irradiation from 1 to 20 kHz at 30 Hz intervals, we demonstrate the visualization of the following three different object surfaces: a rigid surface with small holes with and without a piece of thin paper covering the surface, and a boundary between wood and rubber plates. The distributions of sound pressure reconstructed at each frequency by a near-field acoustic holography (NAH) technique are shown. In multispectral acoustic imaging, frequency dependence provides us rich information about the surface shape and material properties of the objects; thus, the characteristics of the surfaces are successfully visualized.

Evaluation of the Influence of Shaking Frequency and Duration in Mechanical Harvesting of Sweet Cherry

<abstract><title><italic>Abstract. </italic></title> Almost all fresh-market sweet cherry is currently hand-picked. A decreasing labor supply and rising harvesting costs have caused producers to begin moving toward mechanical harvesting. This study focused on studying different combinations of shaking frequency and duration for a hydraulically-powered mechanical shaking end-effector for effectively harvesting fresh-market sweet cherry from “Y” trellis trees. Shaking frequencies of 14 and 18 Hz, combined with shaking durations of 2 and 5 s, were evaluated in an orchard environment. Dislodged fruit was captured on a sheet laid under the tree, collected and weighed after each shaking interval. This procedure was repeated 4 or 10 times based on two different shaking durations used in the study to reach a cumulative shaking time of 20 s. Each combination was replicated on three trees. Results indicated that the first 2-s interval of 14 Hz shaking removed 29% of total fruit on average from the test trees, and the first 5-s interval of 18 Hz shaking removed 38% on average. Multiple shaking intervals with a total of 20 s shaking duration removed 81%, 73%, 62% and 59% of total fruit on average from four 5-s 18 Hz intervals, ten 2-s 14 Hz intervals, four 5-s 14 Hz intervals and ten 2-s 18 Hz intervals respectively, indicating that both frequency and duration have effects on fruit removal efficiency of a mechanical cherry harvesting system. Based on visual observation, over 60% of remaining fruit were growing on long and slender twigs. This result suggested that a proper pruning of cherry trees to minimize the number and/or length of small and long twigs could contribute substantially to the improvement of the overall fruit removal efficiency of the shaking-based mechanical harvesting system.

Measurement of Diurnal Body Tilt Angle Distributions of Threeline Grunt Parapristipoma trilineatum Using Micro-Acceleration Data Loggers

The body tilt angle of a fish has a large effect on the acoustic target strength. For an accurate estimation of fish abundance using acoustic methods, it is necessary to measure body tilt angles in free-ranging fish. We measured diurnal body tilt angle distributions of threeline grunt (Parapristipoma trilineatum) while swimming in schools in a fish cage. Micro-acceleration data loggers were used to record (for 3 days) swaying and surging accelerations (at 16 Hz intervals) of 10 individuals among 20 forming a school in a fish cage. Time series analysis of 1-h mean body tilt angles revealed significant differences in body tilt angles between day (−7.9 ± 3.28°) and night (0.8 ± 5.89°), which must be taken into account when conducting acoustic surveys. These results will be useful for calculating the average dorsal aspect target strength (TS) of threeline grunt for accurate estimations of fish abundance.

Corticomuscular coherence revealed during treadmill walking: further evidence of supraspinal control in human locomotion

Corticomuscular coherence revealed during treadmill walking: further evidence of supraspinal control in human locomotion

Dental Pulp Blood Flow and Its Oscillations in Women with Different Estrogen Status

IntroductionThe skin microcirculation is significantly affected by serum estrogen levels. The objective of this study was to investigate the effects of estrogen serum level changes associated with the menstrual cycle and postmenopause on dental pulp blood flow (PBF) as well as its dynamics. MethodsYoung women at the menstrual phase (low serum estrogen levels) and in the mid-cycle phase of the menstrual cycle (high serum estrogen levels) and postmenopausal women were enrolled in the study. PBF and its oscillations were measured by laser Doppler flowmetry and analyzed by using wavelet transform. Serum levels of estradiol-17β were measured by immunoassay. ResultsPBFs of young women in the menstrual phase and postmenopausal women were mutually similar and significantly lower than those of young women in the mid-cycle period. With respect to the mid-cycle phase, relative amplitude and power were significantly increased in the interval 0.0095–0.02 Hz and decreased in the intervals 0.02–0.06 and 0.06–0.2 Hz in the menstrual phase. A significant decrease in 0.0095–0.02 Hz and increase in 0.02–0.06, 0.06–0.2, 0.2–0.6, and 0.6–1.6 Hz intervals were observed in postmenopause. ConclusionsThe study has shown that the menstrual phase of the menstrual cycle and postmenopause have similar PBF decrease, but PBF oscillations are differently affected in the mid-cycle phase.

731 Acoustic Analysis of a Mechanical Circulatory Support

Mechanical circulatory support technology is continually improving. However, adverse complications do occur with devastating consequences, for example, pump thrombosis that may develop in several parts of the pump system. The aim of this study was to design an experimental clot/thrombosis model to register and analyze acoustic signals from the left ventricular assist device (LVAD) HeartMate II (HMII) (Thoratec Corporation, Inc., Pleasanton, CA, USA) and detect changes in sound signals correlating to clots in the inflow, outflow, and pump housing. Using modern telecom techniques, it was possible to register and analyze the HMII pump-specific acoustic fingerprint in an experimental model of LVAD support using a mock loop. Increase in pump speed significantly (P<0.005) changed the acoustic fingerprint at certain frequency (0-23,000 Hz) intervals (regions: R1-3 and peaks: P1,3-4). When the ball valves connected to the tubing were narrowed sequentially by ∼50% of the inner diameter (to mimic clot in the out- and inflow tubing), the frequency spectrum changed significantly (P<0.005) in P1 and P2 and R1 when the outflow tubing was narrowed. This change was not seen to the same extent when the lumen of the ball valve connected to the inflow tube was narrowed by ∼50%. More significant (P<0.005) acoustic changes were detected in P1 and P2 and R1 and R3, with the largest dB figs. in the lower frequency ranges in R1 and P2, when artificial clots and blood clots passed through the pump system. At higher frequencies, a significant change in dB figs. in R3 and P4 was detected when clots passed through the pump system. Acoustic monitoring of pump sounds may become a valuable tool in LVAD surveillance.

Preferences for Very Low and Very High Voice Pitch in Humans

Manipulations of voice pitch have been shown to alter attractiveness ratings, but whether preferences extend to very low or very high voice pitch is unknown. Here, we manipulated voice pitch in averaged men's and women's voices by 2 Hz intervals to create a range of male and female voices speaking monopthong vowel sounds and spanning a range of frequencies from normal to very low and very high pitch. With these voices, we used the method of constant stimuli to measure preferences for voice. Nineteen university students (ages: 20–25) participated in three experiments. On average, men preferred high-pitched women's voices to low-pitched women's voices across all frequencies tested. On average, women preferred men's voices lowered in pitch, but did not prefer very low men's voices. The results of this study may reflect selection pressures for men's and women's voices, and shed light on a perceptual link between voice pitch and vocal attractiveness.

Differential effects of strain, circadian cycle, and stimulation pattern on LTP and concurrent LTD in the dentate gyrus of freely moving rats

Because long-term potentiation (LTP) and long-term depression (LTD) are thought to be involved in learning and memory, it is important to delineate factors that modulate their induction and persistence, especially as studied in freely moving animals. Here, we investigated the effects of rat strain, circadian cycle, and high-frequency stimulation (HFS) pattern on LTP and concurrently induced LTD in the dentate gyrus (DG). Comparison of two commonly used rat strains revealed that medial perforant path field EPSP-population spike (E-S) coupling and LTP were greater in Long-Evans than Sprague-Dawley rats. Circadian cycle experiments conducted in Long-Evans rats revealed greater E-S coupling and enhanced LTP during the dark phase. Interestingly, concurrent LTD in the lateral perforant path did not significantly differ across strains or circadian cycle. Testing HFS protocols during the dark phase revealed that theta burst stimulation (100 Hz bursts at 5 Hz intervals) was ineffective in eliciting either LTP or concurrent LTD in DG, whereas 400 Hz bursts delivered at theta (5 Hz) or delta (1 Hz) frequencies produced substantial LTP and concurrent LTD. Thus, these natural and experimental factors regulate granule cell excitability, and differentially affect LTP and concurrent LTD in the DG of freely moving rats. © 2011 Wiley Periodicals, Inc.

Maturation of EEG power spectra in early adolescence: a longitudinal study

This study investigated the fine-grained development of the EEG power spectra in early adolescence, and the extent to which it is reflected in changes in peak frequency. It also sought to determine whether sex differences in the EEG power spectra reflect differential patterns of maturation. A group of 56 adolescents were tested at age 10 years and then at two further time-points approximately 18 months apart. The EEG was recorded during both eyes-closed and eyes-open conditions and Fourier transformed to provide estimates of absolute and relative spectral power at 0.5 Hz intervals from 0.5 to 40 Hz. The peak alpha frequency for each individual at each time-point was also determined for relative spectral power. Partial Least Squares (PLS) analysis was used to determine the combination of electrodes and frequencies that showed developmental change, or differed between the sexes. As a function of age, absolute delta and theta frequencies power decreased, and relative alpha2 and beta frequencies increased, replicating the standard findings of a decrease in lower, and increase in higher, frequencies with age. A small but significant increase in peak alpha frequency with age was detected. Moreover PLS analysis performed with individual alpha frequencies aligned to 10 Hz suggested that the age-related increase seen in alpha2 relative power was driven by changes in the peak frequency. Although males demonstrated higher alpha power than females, there were no sex differences in peak frequency, suggesting that there may be more to sex differences in EEG power than simply different rates of maturation between the two sexes.

Comparison of Odiosoft-Rhino and rhinomanometry in evaluation of nasal patency

To conduct a preliminary study testing the validity of the Odiosoft-Rhino (OR) in the evaluation of nasal patency in patients with nasal septal deviation and compare the results with visual analogue score (VAS) of nasal obstruction and rhinomanometry (RMM). OR and RMM were performed on 68 patients with nasal septal deviation and 61 healthy controls. VAS, nasal resistance values and nasal sound analysis were noted for the left and right nasal cavities. There are statistically significant differences between VAS, RMM and nasal endoscopic findings between the patient and the control group. The OR results at expiratory and inspiratory 2000 - 4000 Hz and 4000 - 6000 Hz intervals for both nasal cavities show a statistically significant difference between the patient and control groups. Nasal endoscopic findings, RMM, OR results of the deviated sides in the 2000 - 4000 Hz interval correlate well with VAS. OR may be a practical test in assessment of nasal patency. OR at the 2000 - 4000 Hz interval shows a correlation with VAS. However, showing a correlation between a test and a variable is not the same as proving that it is a useful diagnostic test. Therefore, more studies with larger series are needed.

CYCLICAL CHANGES IN THE TIMING RESIDUALS FROM THE PULSAR B0919+06

We report the detection of a large glitch in the pulsar B0919+06 (J0922+0638). The glitch occurred in 2009 November 5 (MJD 55140) and was characterized by a fractional increase in the rotation frequency of Deltanu/nu=1.3x10^{-6}. A large glitch happens in the pulsar whose rotation has unstable character. We present the results of the analysis of the rotation behavior of this pulsar over the 30-year time span from 1979 to 2009. These results show that the pulsar's rotation frequency underwent continuous, slow oscillations which look like glitch-like events. During the 1991-2009 interval, the pulsar experienced a continuous sequence of 12 slow glitches with a fractional increase in the rotation frequency Deltanu/nu=1.5x10^{-9}. All the slow glitches observed have a similar signature related to a slow increase in the rotation frequency during 200 days and the subsequent relaxation back to the pre-glitch value during 400 days. We show that a continuous sequence of such slow glitches is characterized by practically identical amplitudes equal to Deltanu=3.5x10^{-9} Hz and identical time intervals between glitches of about 600 days and is well described by a periodic sawtooth-like function. The detection of two different phenomena, such as a large glitch and a sequence of slow glitches, indicates the presence of two types of discontinuities in the rotation frequency of the pulsar B0919+06. These discontinuities can be classified as normal and slow glitches.

Dynamic Cerebral Autoregulation in the Old Using a Repeated Sit-Stand Maneuver

The aim of this study was to assess the feasibility and reproducibility of a simple and nonobtrusive repeated sit-stand maneuver to assess cerebral autoregulation (CA) in healthy old subjects >70 years. In 27 subjects aged 76 (SD 4) years, we continuously measured blood pressure using photoplethysmography and cerebral blood flow velocity in the middle cerebral artery (transcranial Doppler ultrasonography) during 5 min of sitting rest and again during repeated sit-stand maneuvers at 10 s (0.05 Hz) and 5 s (0.1 Hz) intervals. In 11 randomly selected subjects, these measurements were repeated after 3 months. Both maneuvers induced substantial periodic oscillations in pressure and flow. For example, the maneuvers at 0.05 Hz increased the power spectral density (magnitude) of blood pressure and cerebral blood flow velocity oscillations with 16.3 (mm Hg) 2 and 14.5 (cm/s) 2, respectively ( p < 0.001). These larger oscillations led to an increase in transfer function coherence compared with spontaneous oscillations from 0.46 to 0.60 for 0.05 Hz maneuvers and from 0.56 to 0.76 for 0.1 Hz maneuvers ( p < 0.01), allowing for more confident assessment of CA through transfer function phase and gain. This increased coherence was not associated with improved reproducibility however. In conclusion, we were able to investigate CA in old patients using these repeated sit-stand maneuvers, which, compared with spontaneous oscillations, produced a stronger and more clinically relevant hemodynamic challenge for CA. (E-mail: j.claassen@ger.umcn.nl)

Magnetoencephalography reveals thalamocortical dysrhythmia in children born very preterm

Event Abstract Back to Event Magnetoencephalography reveals thalamocortical dysrhythmia in children born very preterm Sam Doesburg1*, Urs Ribary2, Anthony Herdman2, Alexander Moiseev3, Teresa Cheung2, Steven Miller1, Hal Weinberg2 and Ruth Grunau1 1 University of British Columbia, Canada 2 Simon Fraser University, Canada 3 Down Syndrome Research Foundation, Canada Very preterm children without major intellectual impairment, at school age often show selective deficits in executive function, memory, and problem solving. Little is known about what differences in brain activity underlie such cognitive problems. Reduced thalamic volume and white matter abnormalities revealed by MRI suggest that thalamocortical dynamics may be altered in children born very preterm. Thalamocortical dysrhythmia (TCD), characterized by altered oscillatory network activity related to thalamocortical connectivity, has been previously identified in several neurological and neuropsychiatric conditions. To examine whether altered oscillatory brain dynamics in children born very preterm indicate the presence of TCD, we recorded resting MEG from 11 children born ≤32 weeks gestation (mean 30.3, sd 2.4), and 11 age-matched full-term controls at age 7.5 years. No child had significant brain injury or intellectual impairment. Data from each of 151 MEG sensors was narrowly bandpass filtered at 1 Hz intervals from 4 – 50 Hz to determine spectral power. Preterm children, relative to controls, exhibited a number of alterations in resting MEG consistent with TCD (p < 0.05): a) reduced alpha-band power b) a shift in the peak of oscillatory power from the alpha range toward the lower-frequency theta-band which was maximal over bilateral frontal cortex; c) increased cross-frequency coupling over bilateral frontal cortex. In addition, there were trends toward increased theta oscillations at the frontal peak of this frequency shift and widespread increases in gamma-band power. In a group of children born very preterm but without intellectual impairment, specific changes in resting MEG activity indicate slight-to-moderate thalamocortical dysrhythmia. The concentration of oscillatory slowing in bilateral frontal cortex suggests that altered thalamocortical dynamics may underlie specific cognitive problems commonly diagnosed in this population. Funding: NIH grant HD039783-06A2 to REG. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: MEG: Clinical applications Citation: Doesburg S, Ribary U, Herdman A, Moiseev A, Cheung T, Miller S, Weinberg H and Grunau R (2010). Magnetoencephalography reveals thalamocortical dysrhythmia in children born very preterm. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00305 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Apr 2010; Published Online: 05 Apr 2010. * Correspondence: Sam Doesburg, University of British Columbia, Vancouver, Canada, sam.doesburg@sickkids.ca Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sam Doesburg Urs Ribary Anthony Herdman Alexander Moiseev Teresa Cheung Steven Miller Hal Weinberg Ruth Grunau Google Sam Doesburg Urs Ribary Anthony Herdman Alexander Moiseev Teresa Cheung Steven Miller Hal Weinberg Ruth Grunau Google Scholar Sam Doesburg Urs Ribary Anthony Herdman Alexander Moiseev Teresa Cheung Steven Miller Hal Weinberg Ruth Grunau PubMed Sam Doesburg Urs Ribary Anthony Herdman Alexander Moiseev Teresa Cheung Steven Miller Hal Weinberg Ruth Grunau Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Investigation of the modulation between EEG alpha waves and slow/fast delta waves in children in different depths of Desflurane anesthesia

Objectives Investigation of the amplitude modulation of alpha-band EEG oscillations (i.e., grouping of alpha-band activities) by delta-band EEG activities in various depths of anesthesia (DOA). Methods This modulation, which is a sort of phase dependent amplitude modulation, is studied in 10 children in various depths of Desflurane anesthesia. Two parameters are defined to quantify the modulation: strength of modulation (SOM) and phase of modulation (POM). SOM indicates to what extent delta and alpha activities are related to each other, and POM is the delta phase in which the alpha amplitude is maximal. These parameters are analyzed in different DOA for various formations of delta sub-bands. Results The ability of POM and SOM were explored to characterize mechanisms contributing to delta activities and their correlation with the level of anesthesia. These parameters are influenced by DOA and frequency intervals of delta sub-bands. SOM takes higher values around certain frequency ranges of delta band. According to this, delta band comprises three main sub-bands in various unconsciousness levels. Although boundaries of these sub-bands change with DOA, they are almost in [0.1–0.5] Hz (very slow delta), [0.7–1.7] Hz (slow delta) and [2–4] Hz (fast delta) intervals. POMs relating to slow and fast delta bands increase with consciousness level. This is an indication that delta waves differently modulate alpha EEG activities (in terms of phase lag) in different DOA. In deep anesthesia, POM relating to fast delta correlates with DOA better than POM relating to slow delta does. In light anesthesia this correlation is inversed. Investigation regarding to different formations of delta sub-bands shows that POM relating to [1.8–4] Hz is a proper choice for distinguishing deep, moderate and light anesthesia. Conclusion SOM allows separating mechanisms underlying delta band activities, and POM can be seen as a complementary neurophysiologic-based parameter for quantifying DOA.

The rule of 1 s for padding kinematic data prior to digital filtering: Influence of sampling and filter cutoff frequencies

The influence of signal sampling frequency and the low-pass digital filter cutoff frequency on the minimum number of padding points when applied to kinematic data are factors often absent in data processing descriptions. This investigation determined a relationship between the number of padding points and the ratio of filter cutoff to signal sampling frequencies ( f c/ f s). Two kinematic recordings were used which represented signals with high and low deterministic variation magnitudes at the signals’ beginning. Signal sampling rates (40–128 Hz) were generated at intervals of 1 Hz. Filter cutoff frequency was iterated from 2 to 10 Hz at 0.5 Hz intervals. Data extrapolation was performed using three different techniques (first order polynomial, third order polynomial, and data reflection). A maximum of 2 s of padding points were added to the beginning of each test signal which was then dual-pass filtered using a second order Butterworth filter. For each successive increase in the number of padding points, the filtered test signal was compared to a criterion signal and the root mean square difference (RMSD) over the first second was calculated. The number of padding points required to attain a constant RMSD was recorded as the minimum number of padding points needed for that ratio of filter cutoff to sampling frequency. As f c/ f s increased, the number of padding points decreased non-linearly. More padding points were required for the signal with higher deterministic variation at the beginning than the signal with lower deterministic variation. Additional padding points (beyond the determined minimum) did not further reduce the RMSD. The largest temporal extrapolation determined by the algorithm to produce a stable RMSD was 1 s. It is suggested that a minimum of 1 s of extraneous data be used when using a low-pass recursive digital filter to remove noise from kinematic data.

Expiratory nasal sound analysis as a new method for evaluation of nasal obstruction in patients with nasal septal deviation: comparison of expiratory nasal sounds from both deviated and normal nasal cavity

The reliability of nasal obstruction measurements could be improved, and several new techniques are being developed. Our objective was to investigate the use of a new software program, Odiosoft-Rhino, in the assessment of nasal obstruction via analysis of the sounds of nasal expiration. We compared the nasal symptom scores and Odiosoft-Rhino and acoustic rhinometry test results for 61 patients with known nasal septal deviation. We found a significant difference, and a correlation, between Odiosoft-Rhino results at 2000-4000 Hz and 4000-6000 Hz intervals, and the minimal cross-sectional area 2.2 cm from the nostril, in the right nasal cavity in patients with right-sided deviations. Similar results were observed for the left nasal cavity in patients with left-sided deviations. The Odiosoft-Rhino software test is noninvasive, requires minimal cooperation and experience, and provides results that can be saved as digital data. Additionally, data from the Odiosoft-Rhino test are strongly correlated with acoustic rhinometry results and visual analogue scores of nasal obstruction. It seems that sound intensity within the 2000-4000 Hz and 4000-6000 Hz intervals is more sensitive than other sound intensity intervals. Thus, we speculate that Odiosoft-Rhino testing could be used as a new diagnostic method in order to evaluate nasal airflow in clinical practice.

Persistent abnormality detected in the non-ictal electroencephalogram in primary generalised epilepsy

Objectives: Gamma oscillations (30–100 Hz gamma electroencephalographic (EEG) activity) correlate with high frequency synchronous rhythmic bursting in assemblies of cerebral neurons participating in aspects of consciousness. Previous studies in a...

A comparison of middle ear acoustic admittance in adults and 3-week-old infants based on multifrequency tympanometry

The assessment of newborn hearing requires information on middle ear status yet the interpretation of tympanometry in newborns is unclear. This study aims to further our understanding of acoustic admittance in the newborn middle ear. Multifrequency tympanograms were recorded from sixteen 3-week-old infants (30 ears) and sixteen young normal-hearing adults (30 ears). Tympanometry was conducted using the Virtual 310 middle ear analyzer using 9 probe tone frequencies between 226 and 1000 Hz at roughly 100 Hz intervals. All infants passed a hearing screening using automated ABR (Algo II) shortly after birth (within 24 h) and again at 3-weeks of age. At 226 Hz, admittance tympanograms had a single peak in all adult ears while 60% of infant ears had multiple peaks or irregular patterns. At 1000 Hz admittance tympanograms had a single peak for 74% of infant ears while 78% of adult ears showed multiple peak or irregular patterns. Analyses of tympanometric shape (using the Vanhuyse classification scheme), as well as static admittance, static susceptance, and static conductance also reveal differences in adult and infant middle ear function. Implications for the clinical application of tympanometry in the first month of life will be discussed.

Effects of left ventricular hypertrophy on force and Ca2+ handling in isolated rat myocardium.

To study the effect of left ventricular (LV) hypertrophy on force and Ca2+ handling in isolated rat myocardium, LV hypertrophy was induced in rats by banding of the abdominal aorta. After 16 wk, arterial pressure was assessed by catheterization. LV trabeculae were isolated and loaded with indo 1 salt by iontophoretic injection. Isometric force and intracellular free Ca2+ concentration ([Ca2+]i) were measured at stimulation frequencies between 0.25 and 3 Hz and rest intervals between 2 and 240 s. Sarcoplasmic reticulum (SR) Ca2+ content was also investigated using rapid cooling contractures (RCC). Systolic and diastolic pressure as well as heart weight-to-body weight ratios were significantly elevated in banded compared with control animals (167 vs. 117 mmHg, 108 vs. 83 mmHg, and 4.6 vs. 4.0 mg/g, respectively). At high frequencies, twitch relaxation and [Ca2+]i decline rates were significantly slower in banded compared with control rats, and diastolic [Ca2+]i was higher in the banded rat muscles (at 3 Hz, force half-time = 83 vs. 68 ms; time constant of [Ca2+]i decline = 208 vs. 118 ms; and diastolic [Ca2+]i = 505 vs. 353 nM). These differences could not be ascribed to altered Na+/Ca2+ exchange, since twitch relaxation and Ca2+ handling were not different between groups in the presence of caffeine (or cyclopiazonic acid plus ryanodine), where relaxation depends primarily on Na+/Ca2+ exchange. After long rest intervals (> or = 120 s), control rats showed a significant rest potentiation of force and Ca2+ transients, whereas banded rats did not. In addition, RCC amplitudes increased with rest in control but were unaltered in banded rats. In summary, pressure-overload hypertrophy was associated with slower twitch relaxation and [Ca2+]i decline but also with blunted rest potentiation of twitches and SR Ca2+ content of LV trabeculae. The decrease in SR Ca(2+)-ATPase function in banded rats may contribute to the observed diastolic dysfunction associated with pressure-overload hypertrophy.