CM Threshold Research Articles

Joint optimization of condition-based maintenance policy and buffer capacity for a two-component self-repairable serial system

This paper investigates a self-repairable serial system with two components and a buffer. Competitive failure processes are considered due to the internal degradation and external shock processes of components. The system reliability is calculated based on the integration of the internal degradation process and external shock process. When one of the components deteriorates to the PM or CM thresholds, it is restored to an imperfect state under dynamic time limitations based on the previous internal degradation and external shocks. As for the other component, it needs to be repaired or not according to the reliability of the component; it needs to be shut down or not based on the buffer status and the allocation of the component in the system. The optimal initial buffer capacity setting and PM threshold at minimum cost are found by minimizing the system's total cost in a given running cycle. Finally, numerical and case studies are provided to demonstrate the feasibility and superiority of the presented model.

Shift in diagnostic classification of migraine after initiation of preventive treatment with eptinezumab: post hoc analysis of the PROMISE studies

BackgroundMonthly headache frequency directly correlates with personal/societal burden and impacts severity and preventive treatment decisions. This post hoc analysis identified shifts from higher to lower frequency headache categories over 6 months in patients with migraine participating in the PROMISE clinical trials receiving two eptinezumab doses.MethodsHeadache frequency at baseline and over study months 1–6 was categorized into 4 groups: chronic migraine (CM; ≥ 15 monthly headache days [MHDs]), high-frequency episodic migraine (HFEM; 10–14 MHDs), low-frequency episodic migraine (LFEM; 4–9 MHDs), and ≤ 3 MHDs. Outcomes included the percentage of patients within each MHD category, the percentage of patients improving by ≥ 1 MHD category, and the number of months with reduction of ≥ 1 MHD category. Data from patients who received approved eptinezumab doses (100 mg or 300 mg) or placebo were included.ResultsMean headache frequency at baseline in PROMISE-1 was 10 MHDs; most patients were classified as having HFEM (48.6%) or LFEM (43.9%). At Month 1, 62/221 (28.1%), 75/222 (33.8%), and 45/222 (20.3%) patients who received eptinezumab 100 mg, 300 mg, and placebo had ≤ 3 MHDs, with 97/221 (43.9%), 108/222 (48.6%), and 84/222 (37.8%), respectively, falling below the diagnostic EM threshold at Month 6. More than one-third (79/221 [35.7%], 83/222 [37.4%], and 68/222 [30.6%] of patients in the eptinezumab 100 mg, 300 mg, and placebo groups, respectively), had 6 months of reduction of ≥ 1 frequency category. At baseline in PROMISE-2, mean headache frequency was 20.5 MHDs. All patients (100%) in the eptinezumab 100 mg and placebo groups had CM, as did 99.4% of patients receiving eptinezumab 300 mg. At Month 1, 209/356 (58.7%), 216/350 (61.7%), and 167/366 (45.6%) patients treated with eptinezumab 100 mg, 300 mg, and placebo had ≤ 14 MHDs, with 240/356 (67.4%), 249/350 (71.1%), and 221/366 (60.4%), respectively, falling below CM threshold at Month 6. Additionally, 153/356 (43.0%), 169/350 (48.3%), and 116/366 (31.7%) patients in the eptinezumab 100 mg, 300 mg, and placebo groups, respectively, had 6 months of reduction of ≥ 1 frequency category.ConclusionIn the PROMISE studies, episodic and chronic migraine patients treated with eptinezumab were more likely to reduce their headache frequency versus placebo, which directly and in a sustained way improved their diagnostic category classification.Trial registrationClinicalTrials.gov Identifier: NCT02559895, NCT02974153.

Perceptual organization deficits in traumatic brain injury patients

Traumatic brain injury (TBI) is a prevalent condition and there is limited visual perception research with this population. Here, we investigated perceptual organization changes in a rather homogeneous sample of closed head TBI outpatients with diffuse axonal injury only and no other known comorbidities. Patients had normal or corrected visual acuity. Perceptual organization was measured with the Leuven Perceptual Organization Screening Test (L-POST), a coherent motion task (CM) and the Leuven Embedded Figures Test (L-EFT). These tests were chosen to screen for deficits in different aspects of perceptual organization (L-POST), to evaluate local and global processing (L-EFT) and grouping in a dynamic set of stimuli (CM). TBI patients were significantly impaired compared to controls in all measures for both response time and accuracy, except for CM thresholds and object recognition subtests. The TBI group was similarly affected in all aspects of the L-EFT. TBI was also similarly affected in all perceptual factors of the L-POST. No significant correlations were found between scores and time post-injury, except for CM thresholds (rs=−0.74), which might explain the lack of group-level differences. The only score significantly correlated to IQ was L-EFT response time (rs=−0.67). These findings demonstrate that perceptual organization is diffusely affected in TBI and this effect has no substantial correlations with IQ. As many of the neuropsychological tests used to measure different cognitive functions involve some level of visual discrimination and perceptual organization demands, these results must be taken into account in the general neuropsychological evaluation of TBI patients.

Sound location modulation of electrocochleographic responses in chinchilla with single-sided deafness and fitted with an osseointegrated bone-conducting hearing prosthesis.

Bone-anchored hearing systems (BAHSs) provide sound location-dependent input to the normal ear for reducing the head shadow effect in the case of single-sided deafness (SSD). Patients with SSD can be fit with a BAHS positioned on the impaired side. Despite successful outcomes and some reports of spatial hearing capabilities, little data are available regarding the physiologic performance of BAHSs in response to free-field sounds. Cochlear microphonics (CMs) were recorded from five chinchillas before and after destruction of one cochlea. A BAHS (Cochlear Baha) was fitted on the deafened side. CM measurements were made in response to tones, with and without the BAHS, to free-field sounds presented ipsilateral to the SSD, on the side of the normal ear, and along the midline. Stimuli were also presented directly through the BAHS and an earphone to generate sounds with interaural time and level differences approximating free-field sounds. With the BAHS, CM thresholds were decreased (re: no BAHS) by approximately 10 dB for sources ipsilateral to the SSD, approximately 14 dB for midline sources, and approximately 5 dB for sources contralateral to the SSD. Changes in CM amplitudes and thresholds were sound location dependent. CM amplitudes were modulated by interaural time and level differences generated by the linear interaction of BAHS and acoustic signals. This study suggests that BAHS can provide input to the normal ear that is modulated by sound location, which serves to reduce the head shadow effect and may also offer cues to sound location.

Origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures.

Nanorod solar cells have been attracting a lot of attention recently, as they have been shown to exhibit a lower carrier multiplication onset and a higher quantum efficiency than quantum dots with similar bandgaps. The underpinning theory for this phenomenon is not yet completely understood, and is still the subject of ongoing study. Here we conduct a theoretical investigation into CM efficiency in elongated semiconductor nanostructures with square cross section made of different materials (GaAs, GaSb, InAs, InP, InSb, CdSe, Ge, Si and PbSe), using a single-band effective mass model. Following Luo, Franceschetti and Zunger we adopt the CM figure of merit (the ratio between biexciton and single-exciton density of states) as a measure of CM efficiency and investigate its dependence on the aspect ratio for both (a) constant cross section (i.e. varying the volume) and (b) constant volume (i.e., varying the cross section), by decoupling electronic structure effects from surface-related effects, increased absorption and Coulomb coupling effects. The results show that in both (a) and (b) cases elongation causes an increase in both single- and bi-exciton density of states, with the latter, however, growing much faster with increasing energy. This leads to the availability of more bi-exciton states than single-exciton states for photon energies just above the bi-exciton ground state and therefore suggests a higher probability of CM at these energies for elongated structures. Our results therefore show that the origin of the observed decrease of the CM threshold in elongated structures can be attributed purely to electronic structure effects, paving the way to the implementation of CM-efficiency-boosting strategies in nanostructures based on the lowering of the CM onset.

Electrocochleography in children with auditory synaptopathy/neuropathy: Diagnostic findings and characteristic parameters

IntroductionThe early diagnosis of AS/AN in children remains challenging because it exclusively relies on the detection of OAE and/or CM, while ABR are pathologically changed or missing.The aim of our study was to ensure the diagnosis of AS/AN, demarcate it to an outer hair cell damage and possibly differentiate between pre- and postsynaptic pathologies. MethodsWe retrospectively evaluated the transtympanic ECochG results of ten children with AS/AN and compared them to a matched group with SNHL and without any signs of AS/AN. We analyzed the thresholds, latencies and – as a new parameter – the amplitude ratio between CAP and SP. ResultsCM and SP thresholds were significantly lower than CAP thresholds in AS/AN patients and significantly lower than SP and CM thresholds in SNHL patients with comparable CAP thresholds. The CAP/SP ratio of amplitudes in SNHL children was more than three times (significantly) higher than in AS/AN children. The cutoff value was set at 1.0 in order to differentiate between both groups with a 80–90% sensitivity and specifity.It was not possible to differentiate between a pre- and postsynaptic type of AS/AN in our collective. Summary and conclusionThe ECochG can add valuable information for a precise differential diagnosis of AS/AN, especially in babyhood. We identified the CAP/SP ratio as a new parameter for differentiation between AS/AN and SNHL. When the CAP/SP ratio falls below 1.0, patients can be diagnosed AS/AN with high specificity and sensitivity. Significantly smaller SPL are needed to evoke SP and CM in the AS/AN group, thus showing the preserved hair cell function.

Thresholds of irradiance for seagrass Posidonia oceanica meadow metabolism

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 466:69-79 (2012) - DOI: https://doi.org/10.3354/meps09928 Thresholds of irradiance for seagrass Posidonia oceanica meadow metabolism E. Gacia1,*, N. Marbà2, J. Cebrián3,4, R. Vaquer-Sunyer2, N. Garcias-Bonet2, C. M. Duarte2,5 1Biogeodynamics and Biodiversity Group, Centre d’Estudis Avançats de Blanes, Consejo Superior de Investigaciones Cientificas (CEAB-CSIC), Blanes 17300, Spain 2Department of Global Change Research, Mediterranean Institute for Advanced Studies (IMEDEA; UIB-CSIC), Miquel Marqués 21, Esporles 07190, Spain 3Dauphin Island Sea Lab, 101 Bienville Blvd, Dauphin Island, Alabama 36528, USA 4Department of Marine Sciences, University of South Alabama, Mobile, Alabama 36688, USA 5The UWA Oceans Institute, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia *Email: gacia@ceab.csic.es ABSTRACT: Meadows of the endemic seagrass Posidonia oceanica are threatened in the Mediterranean due to a general deterioration of the light environment that becomes critical when light irradiance is insufficient to meet the carbon requirements of the system. Here, we conduct a 3 wk, in situ shading experiment (8 levels plus controls) to determine the threshold of irradiance for balanced metabolism in a shallow P. oceanica meadow and further assess the recovery of the system 1 wk later. Reduced light irradiance decreased the net community production of the meadow, which may turn negative (i.e. respiration exceeded gross community primary production) under 338 µE m−2 s−1. Shading throughout the experiment did not appear to cause sustained physiological damage to the system since values of net community production after the cessation of shading were similar to pre-experimental, ambient levels. Sediment acid volatile sulfide pools ranged between 0.002 and 0.058 mol m−2 across shading treatments, and the highest pools were observed in the most shaded sediments. At high light impairment, meristematic cell divisions were low, and carbohydrate content in young rhizomes decreased throughout the experiment. Eight days after the cessation of shading, reduced rhizome carbohydrate stores and elevated sediment sulfide levels still persisted in the previously intensively shaded areas. The present study provides evidence of resistance and resilience of the seagrass Posidonia oceanica to light impairment for short (3 wk) periods of time. Although the compensation irradiance of the system varied by ~2-fold, it provides a quantitative estimate of the irradiance threshold at which seagrass meadows may shift from being coastal carbon sinks to CO2 sources. KEY WORDS: Seagrass · Ecosystem · Production · Respiration · Compensation Irradiance · Mediterranean Full text in pdf format Supplementary material PreviousNextCite this article as: Gacia E, Marbà N, Cebrián J, Vaquer-Sunyer R, Garcias-Bonet N, Duarte CM (2012) Thresholds of irradiance for seagrass Posidonia oceanica meadow metabolism. Mar Ecol Prog Ser 466:69-79. https://doi.org/10.3354/meps09928 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 466. Online publication date: October 15, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Electrocochleographic and mechanical assessment of round window stimulation with an active middle ear prosthesis

Mechanical stimulation of the round window (RW) with an active middle ear prosthesis (AMEP) has shown functional benefit in clinical reports in patients with mixed hearing loss (MHL). Further objective physiological data on the efficacy of RW stimulation is needed, however, to demonstrate that RW stimulation with an AMEP can generate input to the inner ear comparable to acoustic input.Cochlear microphonic (CM) and mechanical (stapes velocity) responses to sinusoidal stimuli were measured by electrode and laser Doppler vibrometry in eight chinchillas in response to normal acoustic stimulation via sealed calibrated insert earphones and to AMEP stimulation (Otologics MET, Boulder, CO, USA) of the RW with and without lateral ossicular chain disarticulation.CM thresholds for acoustic stimulation were frequency dependent and ranged from 16 to 50dB SPL. CM thresholds measured with RW stimulation ranged from −14 to 35dBmV with an intact middle ear chain and from −7 to 36dBmV after lateral ossicular chain disarticulation. Acoustically, stapes velocity maxima was observed at ∼700Hz and minima at ∼2.65kHz. With application of the AMEP to the RW, peak stapes velocity was observed at 2–3kHz. The equivalent ear canal sound pressure level (LEmaxdB SPL) evoked by RW stimulation with the AMEP was 60–105dB SPL for the intact middle ear and 70–100dB SPL after ossicular chain disarticulation.Stimulating the inner ear through the RW with an AMEP produces evoked responses (CM) comparable to normal acoustic input. When adjusted for threshold (due to unit differences, dB SPL or dB mV), the sensitivity of the CM (slope) for acoustic was comparable to sensitivities obtained by AMEP stimulation of the RW. Mechanical stimulation of the RW with an AMEP produces cochlear responses (CMs) and stapes velocities that are functionally equivalent to acoustic stimulation.

Design of self-checking fully differential circuits and boards

A design methodology for on-line testing analog linear fully differential (FD) circuits is presented in this work. The test strategy is based on concurrently monitoring via an analog checker the common mode (Chi) at the inputs of all amplifiers, The totally self-checking (TSC) goal is achieved for linear FD implementations provided that the checker CM threshold is small enough with respect to the specified margins of erroneous behavior in the circuit outputs. The design methodology is illustrated for a switched-capacitor biquadratic filter and the self-checking properties evaluated for a hard/soft-fault model. A large checker threshold of 100 mV of CM is chosen since the filter implementation does not minimize nonidealities (e.g., amplifier offsets or clock feedthrough) which result in significant CM components. The circuit outputs are accepted to deviate within a 10% band. With the implemented checker, the TSC goal is not achieved for some faults in narrow regions of the frequency band. For the worst case, a hard fault which results in a 31% deviation is undetected in only a narrow band of approximately 310 Hz. The circuit can be made TSC with a checker threshold of 40 mV and an accepted output deviation of 15%. This is, however, more demanding on the checker (which currently takes less than 3% of the total area and about 7.6% of the total power) and requires an improved filter implementation to reduce CM components. Our solution consists of relaxing a bit the TSC property of the functional block and applying a periodical off-line test to make the checker strongly code disjoint (SCD). This is easy to implement since an off-line test is also required for the checker. The checker outputs a double-rail error indication which ensures compatibility with digital checkers and makes the design of self-checking mixed signal circuits straightforward. The circuit-level mixed-signal approach is extended to the board level by means of the IEEE Std. 1149.1 digital test bus.

Lesion Site in Sudden Deafness: Study with Electrocochleography and Transiently Evoked Otoacoustic Emission

We examined electrocochleogram (ECochG) and transiently evoked otoacoustic emission (TEOAE) on five cases of sudden sensorineural hearing loss which had no abnormalities detected on diagnostic imagings and showed complete recovery of hearing. At the initial examination, three cases showed a broadened wave I with prolonged latency in the auditory brainstem response (ABR) at 90 dB HL. The ECochG AP showed a broad waveform, low amplitude, and high threshold. CM threshold, although increased, was relatively well preserved compared with hearing threshold measured with conventional pure-tone audiometry. The thresholds in TEOAE examination were similar to those for CM and preserved better when compared with pure-tone audiometric thresholds. These findings suggest that the location of the disorder in these three cases involved not only the cochlea but also the retrocochlear auditory pathway. The other two cases showed normal ABR waveforms at 90 dB HL at the initial examinations. ECochG examination showed that a normal AP in one case and a smaller amplitude AP, an elevated threshold, and normal waveform of AP in the other ear. CM thresholds coincided with the conventional audiometry thresholds. These findings suggest that hearing loss in these two cases involved primarily the sensory hair cells.

Changes with aging in ECochG

The present study was designed to determine the standard values of AP, adapted AP and CM (0.5, 1, 2, and 4kHz) of the electrocochleogram using subjects with normal hearing (20 ears, mean subject age 30.4 years). The input-output function, the latency and the threshold were measured in AP, whereas only an input-output curve was made for the adapted AP and the input-output function and the threshold were measused in CM. The CM threshold had the highest positive correlation with the threshold of the conventional pure tone audiometry at 1kHz. These standard curves will be very useful for analysing clinical data. In order to discuss the aging changes affecting electrocochleograms, the test subjects were divided into two groups, i.e. one group was composed of subjects under 30 years of age (mean: 19.7 y/o, 10 ears) and the other of those 30 years old or over (mean: 41.1y/o, 10 ears). There were no differences in hearing threshold or the threshold of the electrocochleogram between the two groups. The CM threshold exhibited the highest positive correlation with the threshold of conventional audiometry at 1kHz in both groups. AP and adapted AP showed no difference in any item between the two groups. Although there was no difference in the CM threshold, there was an obvious difference in the CM input-output curves between these two groups at high stimulus intensities of 2 and 4kHz. It is known that the EP decrement makes CM smaller. However, it is unlikely that this decreased CM response in the older group was due to EP suppression, since this phenomenon was only observed in response to high intensity stimulo and there was no difference in responses to low intensity stimulo. Another possible explanation for this phenomenon is aging changes in the basilar membrane, tectorial membrane and hair cells. Further studies are necessary to elucidate the etiology of the CM suppression revealed in the present study.

後迷路性難聴症例の評価 か電図および誘発耳音響放射から

Using electrocochleography the evoked otoacoustic emission, we examined a patient with retrocochlear deafness which had been diagnosed by conventional audiometry.We used a transtympanic method to record AP (100 ms of 1ST), adapted AP (4 ms of 1ST) and CM. A needle electrode TN-92004 (Co. Unique Medical) was used to record the electrocochleogram and a probe N-1 (Co. Cortitone) to record the evoked otoacoustic emission.The patient was a 49-year-old female with bilateral sensori-neural hearing loss starting at age 13.Plain X-ray films did not show any abnormality. It was shown by the pure tone audiometry that 500 Hz dip and aging change without laterality. The SISI test, self-recording audiometry and speech discrimination tests showed retrocochlear deafness. The ABR recorded no response and there was no canal paresis or no other abnormal findings on ENG.The CM threshold was better than that obtained by conventional audiometry, and the CM amplitude was within normal limits. The AP threshold was much higher and the AP amplitude much lower than in normal subjects. The adapted AP amplitude was within normal limits.The best frequency of the evoked otoacoustic emission was 1kHz in both ears. The echo of otoacoustic emission was detected at-5 dBnHL in the right ear and at-10 dBnHL in the left ear. The evoked otoacoustic emission was normal.These results show that the region of her sensori-neural hearing loss is the spiral ganglion and/or cochlear nerve and that the organon spirale is intact.The electrocochleogram and the evoked otoacoustic emission were very useful in determining the region of sensori-neural hearing loss.

Contributions of the middle ear to the development of function in the cochlea

The contribution of middle ear immaturities to the development of cochlear microphonic potential (CM) responses was studied throughout the ontogeny of auditory function in the Mongolian gerbil. CM produced by direct mechanical stimulation of the stapes was compared with CM generated by acoustic stimulation of the intact ear at various postnatal ages. The results indicated that during development acoustically generated CM reflects middle ear as well as inner ear maturational factors. With direct stapes driving, CM was first elicited at 10 days after birth (DAB), two days earlier than with acoustic stimulation. Controlling for the contributions of middle ear immaturity, maturation of the inner ear accounted for approximately a 75 dB improvement in CM thresholds between 10 and 18 DAB. Comparisons between the results obtained with the acoustic and stapes driving stimulation protocols suggested that the major maturational changes in the middle ear conduction apparatus occurred between 14 and 16 DAB. This period was associated with the final stages of resorption of middle ear mesenchyme and ossicular ossification. Before 16 DAB, acoustically evoked CM thresholds reflect approximately a 25 dB loss in sensitivity due to middle ear immaturity.

Effect of perilymphatic pressure on the CM threshold in hydropic ears of guinea pigs

The effect of perilymphatic pressure on the CM threshold was examined in 30 guinea pigs with endolymphatic hydrops. When a pressure of 300 mmH2O was applied to the scala tympani of the basal turn, the 500 Hz CM threshold shift in hydropic ears was significantly smaller in the early stage than in normal ears, and it returned gradually to normal. The findings in the present study may be similar to the time course of the scala media pressure in hydropic ears; i.e. an initial increase, followed by a gradual decline towards normal.

The effect of perilymphatic pressure upon the CM threshold in hydropic ear of the guinea pig

The effect of perilymphatic pressure upon the CM threshold in hydropic ear of the guinea pig

Electrophysiological studies on the hydropic animals with special analysis as an animal model of Meniere's disease

The endolymphatic hydrops was made by the obliteration of the endolymphatic sac in 62 albino guinea pigs. AP, CM and SP were examined at the 1st, 2nd, 4th and 12th postoperative weeks and the results obtained were analysed in comparison with the audiological and electrocochleographical findings in Meniere's disease. Although abnormal SP was frequently found in the both groups, its appearance rates as a function of the time elapsed after the surgery or the first attack of Meniere's disease were different in these two groups. The AP and CM thresholds in the ani-mal were elevated with the similar time course as the progressive loss of hearing in Meniere's disease. The AP latency was prolonged in some of 12 weeks animals. This result was in accordance with that of Meniere's disease in which its prolongation was observed only in patients with long history.

Effect of hypothermia on the cochlear potentials.

The effects of hypothermia upon the cochlear potentials were studied in 30 guinea pigs. Particular attention was paid to the transient increase in AP amplitude at a moderate temperature. CM and AP were recorded via an Ag-AgCl lead placed on the round window membrane. Although the CM amplitude and threshold, and the AP latency and threshold were both impaired concomitant with the lowering of body temperature, the AP amplitude exhibited a transient increase at the beginning of cooling (peak at 30 degrees C) and a decrease thereafter. Narrow-band analysis of AP revealed that this phenomenon was most prominent in the high-frequency region. When the cochlear efferent fibers (crossed and uncrossed olivocochlear bundle) were cut, this transient increase in AP amplitude disappeared. This phenomenon seems to be due to the difference in sensitivity to hypothermia between the efferent and afferent fiber systems.

ビタミンＤ欠乏によるラットのか牛電位への影響

It has been reported that sensorineural hearing loss is frequently observed in patients with renal failure. This phenomenon has been confirmed in animal experiments by Ikeda et al (1985). It is known that Ca metabolism is disturbed in cases of renal failure. The present study was designed to determine whether disturbance of Ca metabolism have any effect on cochlear function.Cochlear potentials were measured in 19 rats on a vitamin D deficient diet. Serum Ca2+ concentrations were about half of the normal value, and the rats lost weight on this diet.N1 was elicited by click of stimuli and filtered tone bursts of 2, 4, 8 and 12kHz. Narrow-band analysis was performed by low-cut masking, and responses above 8kHz, from 4 to 8kHz 2 to 4kHz were recorded. CM was evoked by filtered tone bursts.As the vitamin D deficient diet continued, N1 latency prolongation, depression of CM amplitude and elevation of CM threshold increased. The latency of narrowband APs was prolonged in most regions of the cochlear partition, but the N1 amplitude and threshold did not change.It is considered that the influence of Ca2+, parathyroid hormone and vitamin D on the cochlea caused these changes in cochlear potentials.

Corrective effects of thyroxine on cochlear abnormalities induced by congenital hypothyroidism in the rat. II. Electrophysiological study

In order to study the corrective effects of thyroxine (T 4) on functional abnormalities induced by congenital hypothyroidism, small doses of T 4 were injected to propylthiouracil-treated (PTU-treated) rat pups for 2 consecutive days on selected periods of development (days 3 and 4, 6 and 7, 9 and 10, 12 and 13, 18 and 19). Some animals also received thyroid replacement therapy from days 12 to 17. The animals were tested electrophysiologically on day 30, by recording the compound action potential and the cochlear microphonic from the round window after click and tone burst stimulation. PTU-treated animals given T 4 for 2 consecutive days demonstrated both AP and CM threshold shifts. On the contrary, PTU-treated animals given T 4 from days 12 to 17 demonstrated a normal CM output of the cochlea, but still showed elevated AP thresholds. These results are discussed with previous data concerning the corrective effects of T 4 on cochlear structures in PTU-treated rats previously described.

ビタミンＤ欠乏ラットにおける外リンパ液Ｃａ｀２＋´濃度

In order to investigate the cause of the changes of the cochlear potentials in vitamin D deficiency rats, namely prolongation of N1 latency, depression of CM amplitude and elevation of CM threshold, Ca2+ concentration in perilymph was measured by Ca2+ selective microelectrode. The result was that Ca2+ concentration in perilymph showed 3.3×10-4M (n=4) in vitamin D deficiency rats and 7.4×10-4M (n=4) in controls and its ratio to serum Ca2+ concentration exhibited 63% and 57%, respectively.The cause of the decrease in perilymphatic Ca2+ concentration in vitamin D deficiency rats was thought to be due to the secondary effect of the decrease in serum Cas2+ concentration. But the gradient of Ca2+ concentration between perilymph and serum was maintained to be normal in vitamin D deficiency rats.It is postulated that this secondary decrease of Ca2+ concentration in perilymph and possibly in endolymph had an effect on the acoustic transduction and the synaptic transmission, by which the alternations of N1 and CM were induced.