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M Vater

Publications and source records attributed to M Vater.

At least 55 records · Page 3Linked to original sources
PubMed1989

Noradrenaline enhances temporal auditory contrast and neuronal timing precision in the cochlear nucleus of the mustached bat.

In the mustached bat, Pteronotus parnellii, noradrenaline (NA) was applied iontophoretically to single units in the anteroventral cochlear nucleus. NA suppressed tonic components of auditory responses and enhanced phasic onset responses to pure tone stimuli. The enhancement of onset activity was most pronounced in awake bats and was due to a decrease in the latency jitter of the first tone-evoked spikes from 0.55 msec in controls to 0.28 msec during NA application. In addition, NA reduced spontaneous neuronal activity. Noradrenergic antagonists suppressed phasic onset activity and increased the latency jitter of onset spikes. Opposite to the effect of NA, the tonic response component increased during application of the beta-antagonist propranolol but decreased during injection of the alpha 1-antagonist corynanthine. Other putative transmitter substances tested, nonselectively depressed both phasic and tonic response components (GABA, glycine) or increased both components either similarly or had more pronounced effects on the tonic response components (ACh, glutamate). Thus, NA specifically enhances auditory temporal contrast in favor of transients and improves neuronal timing precision, which may be of relevance for auditory tasks like passive sound localization, echolocation, and recognition of temporal patterns.

Acetylcholine↗
PubMed1988

Connections of the superior olivary complex in the rufous horseshoe bat Rhinolophus rouxi.

In the rufous horseshoe bat (Rhinolophus rouxi), the superior olivary complex contains four main divisions. In comparison with other species, the most lateral division is clearly homologous to the lateral superior olive (LSO); the most medial division is homologous to the medial nucleus of the trapezoid body (MNTB). Lying between these landmarks, in approximately the position of the medial superior olive (MSO) of other mammals, are two additional divisions that are cytoarchitecturally distinct from one another yet do not greatly resemble the MSO of nonecholocating mammals such as the cat. We refer to these nuclei as the dorsal medial superior olive (DMSO) and the ventral medial superior olive (VMSO). We examined the afferent and efferent connections of all of these cell groups with retrograde and anterograde transport of WGA-HRP from the superior olivary complex. In the same animals we recorded the binaural response properties of single units in the superior olivary complex. Virtually all units recorded in LSO were excitatory to the ipsilateral ear and inhibitory to the contralateral ear (EI); all of the units sampled in the MNTB and most of those sampled in the VMSO responded only to the contralateral ear (OE). In DMSO the binaural properties of units were varied: the number of units that were inhibitory to the ipsilateral ear and excitatory to the contralateral ear (IE) was about equal to the number of units excitatory to both ears (EE); a few units had OE responses; no units had EI responses. Connectional correlates for these binaural response properties are seen in the patterns of retrograde transport from WGA-HRP injections in the divisions of the superior olive. The LSO receives projections from the ipsilateral cochlear nucleus and MNTB; MNTB receives projections from the contralateral cochlear nucleus. The DMSO and VMSO both receive bilateral projections from the cochlear nuclei. The results of retrograde and anterograde transport suggest that VMSO, in addition, receives projections from the ipsilateral MNTB. The LSO, DMSO, and VMSO all project to the ventral two-thirds of the central nucleus of the inferior colliculus, and their targets are approximately coextensive. However, the LSO projects bilaterally to the inferior colliculus, whereas the medial cell groups project mainly ipsilaterally.

Acoustic Stimulation↗
PubMed1988

Distribution of catecholamine fibers in the cochlear nucleus of horseshoe bats and mustache bats.

The glyoxylic-acid-induced fluorescence technique was applied to demonstrate patterns of catecholaminergic innervation within the auditory brainstem of echolocating bats and the house mouse. In the cochlear nucleus of the rufous horseshoe bat (Rhinolophus rouxi) and the mustache bat (Pteronotus parnellii), species-specific catecholaminergic innervation patterns are found that contrast with the relatively homogeneous innervation in the rodent. In both bats the subnuclei of the cochlear nucleus receive a differentially dense supply of catecholaminergic fibers, and within the subnuclei, the catecholamine innervation densities can be correlated with the tonotopic frequency representation. The areas devoted to the high-frequency echolocation calls are less densely innervated than those regions which are responsive to lower frequencies. Apart from this common scheme, there are noteworthy distinctions between the two bats which correlate with specialized cytoarchitectural features of the cochlear nucleus. The marginal cell group, located medially to the anteroventral cochlear nucleus of Pteronotus, receives the densest supply of catecholaminergic fibers of all auditory nuclei. This plexus is formed by a morphologically distinct population of catecholaminergic fibers.

Animals↗
PubMed1985

Functional organization of the cochlear nucleus of rufous horseshoe bats (Rhinolophus rouxi): frequencies and internal connections are arranged in slabs.

The functional organization of the cochlear nucleus (CN) was studied with physiological recording and anatomical tracing techniques. Recordings were made from single CN neurons to examine their temporal firing patterns to tone burst stimuli and their frequency tuning characteristics. Recording loci of individual neurons were carefully monitored in order to understand how the functional properties of a cell relate to its location within the CN. We found that tonal frequencies were systematically represented in each of the three CN divisions (anteroventral, AVCN; posteroventral, PVCN; dorsal, DCN). Eight temporal response patterns were observed in CN neurons when stimulated at units' best excitatory frequencies (BF). With a few exceptions, neurons in each CN division could generate all eight firing patterns with different distributions for the three division. A focal injection of horseradish peroxidase (HRP), at the end of the physiological study, to a group of neurons possessing a similar BF in one CN division resulted in anterograde labeling of nerve terminals in the other two divisions at precisely the areas where the same frequency band was processed in these divisions. Labeled terminals in each division were closely congregated in the form of a thin slab. The slab orientation was division specific whereas its location was frequency specific, which could be predicted on the basis of physiological data. HRP injections into the DCN also resulted in retrograde labeling of somata in the AVCN and PVCN. On the other hand, only DCN neurons were retrogradely labeled when HRP was injected into the AVCN or the PVCN. These data showed how the three CN divisions are internally connected. Furthermore, retrogradely labeled cells occupied the same slabs where we found anterogradely labeled nerve terminals. Additionally, in a group of bats, HRP was injected into various functionally (i.e., BF) identified regions of the central nucleus of the inferior coliculus (IC) to clarify the type and location of CN projecting neurons. Retrogradely labeled cells in individual CN divisions likewise were arranged in slabs whose locations in the CN nuclei depended on the BFs of neurons at the injection site in the IC. These results show that slabs represent units of functional organization (i.e., tonal frequency, local connection and central projection) in the CN.

Animals↗
PubMed1985

A comparative study of the physiological properties of the inner ear in Doppler shift compensating bats (Rhinolophus rouxi and Pteronotus parnellii).

Cochlear microphonic (CM) and evoked neural (N-1) potentials were studied in two species of Doppler shift compensating bats with the aid of electrodes chronically implanted in the scala tympani. Potentials were recorded from animals fully recovered from the effects of anesthesia and surgery. In Pteronotus p. parnellii and Rhinolophus rouxi the CM amplitude showed a narrow band, high amplitude peak at a frequency about 200 Hz above the resting frequency of each species. In Pteronotus the peak was 25-35 dB higher in amplitude than the general CM level below or above the frequency of the amplitude peak. In Rhinolophus the amplitude peak was only a few dB above the general CM level but it was prominent because of a sharp null in a narrow band of frequencies just below the peak. The amplitude peak and the null were markedly affected by body temperature and anesthesia. In Pteronotus high amplitude CM potentials were produced by resonance, and stimulated cochlear emissions were prominent in Pteronotus but they were not observed in Rhinolophus. In Pteronotus the resonance was indicated by a CM afterpotential that occurred after brief tone pulses. The resonance was not affected by the addition of a terminal FM to the stimulus and when the ear was stimulated with broadband noise it resulted in a continual state of resonance. Rapid, 180 degree phase shifts in the CM were observed when the stimulus frequency swept through the frequency of the CM amplitude peak in Pteronotus and the frequency of the CM null in Rhinolophus. These data indicate marked differences in the physiological properties of the cochlea and in the mechanisms responsible for sharp tuning in these two species of bats.

Anesthesia, General↗
PubMed1985

An HRP-study of the frequency-place map of the horseshoe bat cochlea: morphological correlates of the sharp tuning to a narrow frequency band.

The frequency-place map of the horseshoe bat cochlea was studied with the horseradish peroxidase (HRP) technique involving focal injections into various, physiologically defined regions of cochlear nucleus (CN). The locations of labeled spiral ganglion cells and their termination sites on inner hair cells of the organ of Corti from injections into CN-regions responsive to different frequencies were analyzed in three dimensional reconstructions of the cochlea. Horseshoe bats from different geographical populations were investigated. They emit orientation cells with constant frequency (CF) components around 77 kHz (Rhinolophus rouxi from Ceylon) and 84 kHz (Rhinolophus rouxi from India) and their auditory systems are sharply tuned to the respective CF-components. The HRP-map shows that in both populations: the frequency range around the CF-component of the echolocation signal is processed in the second half-turn of the cochlea, where basilar membrane (BM) is not thickened, secondary spiral lamina (LSS) is still present and innervation density is maximal; frequencies more than 5 kHz above the CF-component are processed in the first half-turn, where the thickened BM is accompanied by LSS and innervation density is low; frequencies below the spectral content of the orientation call are represented in apical turns showing no morphological specializations. The data demonstrate that the cochlea of horseshoe bats is normalized to the frequency of the individual specific CF-component of the echolocation call. The HRP-map can account for the overrepresentation of neurons sharply tuned to the CF-signal found in the central auditory system. A comparison of the HRP-map with a map derived with the 'swollen nuclei technique' following loud sound exposure (Bruns 1976b) reveals that the latter is shifted towards cochlear base by about 4 mm. This discrepancy warrants a new interpretation of the functional role of specialized morphological structures of the cochlea within the mechanisms giving rise to the exceptionally high frequency selectivity of the auditory system.

Animals↗
PubMed1985

The cochlear frequency map of the mustache bat, Pteronotus parnellii.

The frequency-place map of the cochlea of mustache bats was constructed by the analysis of HRP-transport patterns in spiral ganglion cells following iontophoretic tracer injections into cochlear nucleus regions responsive to different frequencies. The cochlea consists of 5 half turns (total length 14.3 mm) and the representation of certain frequency bands can be assigned to specific cochlear regions: The broad high frequency range between 70 and 111 kHz is represented in the most basal half turn within only 3.2 mm. This region is terminated apically by a distinct narrowing of the scala vestibuli that coincides with a pronounced increase in basilar membrane (BM) thickness. The narrow intermediate frequency range between 54 and 70 kHz is expanded onto 50% of cochlear length between 4.0 and 11.1 mm distance from apex. The frequency range around 60 kHz, where the tuning characteristics of the auditory system are exceptionally sharp, is located in the center of this expanded BM-region in the second half turn within a maximum of innervation density. These data can account for the vast overrepresentation of neurons sharply tuned to about 60 kHz at central stations of the auditory pathway. In the cochlear region just basal to the innervation maximum, where label from injections at 66 and 70 kHz was found, a number of morphological specializations coincide: the BM is maximally thickened, innervation density is low, the spiral ligament is locally enlarged, and the 'thick lining', a dense covering of the scala tympani throughout the basal halfturn, suddenly disappears. Low frequencies up to 54 kHz are represented within the apical half turns over a 4 mm span of the basilar membrane. The data are compared to the cochlea of horseshoe bats and the possible functional role of the morphological discontinuities for sharp tuning and the generation of otoacoustic emissions is discussed.

Animals↗
PubMed1985

Evoked acoustic emissions and cochlear microphonics in the mustache bat, Pteronotus parnellii.

In the echolocating bat, Pteronotus parnellii, otoacoustic responses at a frequency of 62 kHz are measurable in the external ear canal during continuous and after transient acoustic stimulation. These responses are interpreted to represent emissions from the cochlea. They can reach an amplitude as large as 70 dB SPL and occur in the frequency range most important for echolocation, namely on the average about 700 Hz above the constant frequency component of the orientation calls. A sharp maximum of the amplitude of cochlear microphonic potentials at about 62 kHz could be correlated with the emission frequency. In one bat an evoked otoacoustic response changed to a spontaneous otoacoustic emission. The frequency and amplitude of the evoked otoacoustic responses reversibly decreased after exposure for 1 min to continuous sounds of more than 85 dB SPL with frequencies of about 2.5-7.5 kHz above the emission frequency. Similar effects occurred during anaesthesia or cooling. A possible relation between the existence of otoacoustic emissions and morphological specializations of the cochlea is discussed.

Acoustic Impedance Tests↗
PubMed1985

Caudal or dorsal nerve block? A comparison of two local anaesthetic techniques for postoperative analgesia following day case circumcision.

Fifty boys presenting for day case circumcision were allocated randomly to receive either caudal analgesia or dorsal nerve block (DNB) to provide postoperative pain relief. Analgesia was assessed by a single, unbiased observer utilising a three-point scale. Subsequently, parents completed a simple questionnaire. Subjects in the DNB group micturated earlier (P less than 0.05) and stood unaided earlier (P less than 0.025) than patients in the caudal group. The incidence of vomiting was significantly lower in the DNB group (P less than 0.05). There was no significant difference in the duration of analgesia, although that produced in the DNB group tended to wane sooner. It is concluded that DNB provides satisfactory analgesia following circumcision and has specific advantages when compared with caudal analgesia.

Adolescent↗
PubMed1984

Pharmacokinetics of single-dose i.v. morphine in normal volunteers and patients with end-stage renal failure.

Morphine 0.125 mg kg-1 was administered i.v. to 11 normal subjects and nine patients with chronic renal failure requiring regular haemodialysis. Plasma morphine concentrations were measured using high pressure liquid chromatography (HPLC). Although there was considerable individual variation in both groups, mean plasma concentrations of morphine were significantly higher in the patients with renal failure for 15 min after administration. The decay of plasma concentration fitted a three-compartment mamillary pharmacokinetic model in all subjects. Derived values (mean +/- SEM) of T 1/2 alpha, volume of distribution of the second compartment (V2), total volume of distribution at steady state (Vss) and transfer rate constant from the first to the second compartment (k12), were significantly different between groups. Mean values of terminal elimination half-life (T 1/2 gamma) and total body clearance were similar in the two groups. It was concluded that elimination of unchanged morphine is not impaired significantly in patients with chronic renal failure, although accumulation of morphine-3-glucuronide probably occurs. Although the pharmacological effect of morphine is not related temporally to plasma morphine concentrations, the higher values in patients with renal failure may be implicated in their increased sensitivity to the drug.

Adult↗
PubMed1984

Pharmacokinetics and analgesic effect of slow-release oral morphine sulphate in volunteers.

Sustained-release oral morphine sulphate (MST) 20 mg was administered to 11 healthy volunteers. Mean peak plasma morphine concentration was 14.8 ng ml-1, and occurred at a mean time of 142.5 min after ingestion. Analgesia assessed by an ischaemic forearm pain test increased to a maximum approximately 40 min after the calculated peak plasma concentration of morphine had been achieved, and remained greater than control values as plasma morphine concentration decayed. However, there was not a significant correlation between analgesia and plasma morphine concentration. This may result from delay in brain penetration by morphine. The mean systemic availability of morphine in the first 7 h after administration of MST was 18.3%.

Administration, Oral↗
PubMed1984

Non-parenteral postoperative analgesia. A comparison of sublingual buprenorphine and morphine sulphate (slow release) tablets.

Sixty-nine patients undergoing upper and lower abdominal surgery were studied after operation to compare the analgesic effects of sublingual buprenorphine (0.4 mg) and slow release morphine sulphate tablets (MST, 20 mg) given 6 hourly in a double-blind, double-dummy trial. Both MST and buprenorphine produced satisfactory postoperative analgesia but the linear analogue pain scores were significantly lower on the second post operative day with MST.

Abdomen↗
PubMed1983

Catecholamine responses during anaesthesia for phaeochromocytoma.

Plasma catecholamine concentrations were measured, at frequent intervals, in a 40-yr-old female patient undergoing resection of a phaeochromocytoma under enflurane anaesthesia. Measurements before operation revealed that the tumour secreted predominantly noradrenaline and during surgery the plasma concentration of the hormone increased markedly (180 pmol ml-1; normal range 1.5-3.0 pmol ml-1). Plasma adrenaline concentrations increased markedly only at endotracheal intubation and in the period immediately after operation.

Adrenal Gland Neoplasms↗
PubMed1983

Plasma catecholamine responses to tracheal intubation.

Plasma adrenaline and noradrenaline concentrations were measured in 24 patients during the induction of anaesthesia and the subsequent tracheal intubation. The patients received either suxamethonium 1 mg kg-1 or pancuronium 0.1 mg kg-1 to facilitate tracheal intubation. Mean arterial pressure (MAP) increased in both groups following laryngoscopy and tracheal intubation and there were concomitant increases in the plasma catecholamine concentrations, the changes being more marked in the suxamethonium group. There was a significant correlation between MAP and plasma catecholamine concentrations in the suxamethonium group. Measurement of plasma catecholamine concentrations in samples obtained simultaneously from central venous, peripheral venous and arterial sites were in broad agreement; the greatest changes occurred in central venous samples.

Aged↗
PubMed1983

Quantitative effects of respired helium and oxygen mixtures on gas flow using conventional oxygen masks.

A model lung system with a variable artificial constriction was used to quantify the changes in flow produced by the addition of helium to the gas mixture in the system. The tracheal concentration of helium obtained when administering 79% helium/21% oxygen to the system via conventional, disposable face masks was determined using a resuscitation dummy. The greatest proportion of the increase in flow through the orifice occurred at concentrations of helium up to 40%. A tracheal concentration of 40% helium could be obtained with all oxygen masks at fresh gas flow rates greater than 8 litres/minute. These findings will help to rationalise the administration of 79% helium/21% oxygen to patients with upper respiratory tract obstruction.

Airway Obstruction↗
PubMed1981

Mapping of the auditory area in the cerebellar vermis and hemispheres of the little brown bats, Myotis lucifugus.

Mapping of auditory area in the cerebellar vermis and hemispheres of little brown bats, Myotis lucifugus, shows that a large area of the bat's cerebellum contains units responding to acoustic stimuli. These units had latencies between 4 and 34 msec and best frequencies between 33.0 and 92.5 kHZ. The Q10-dB values of their tuning curves ranged from 2.0 to 19.7. Most of the units studied fired only a few impulses during a stimulus with minimum thresholds between 22 and 90 dB SPL. Units in the cerebellar vermis tend to have higher best frequencies and shorter latencies than those in the cerebellar hemispheres. However, there is no evidence of clear tonotopic organization therein.

Animals↗