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P E Stopp

Publications and source records attributed to P E Stopp.

17 recordsLinked to original sources
PubMed1990

The problem of obtaining reproducible quantitative data of the olivocochlear pathway as exemplified in the guinea pig.

We have tried to quantify the number of efferent neurons comprising the olivocochlear bundle in the guinea pig by using the retrogradely transported fluorescent dye, true blue. The dye was injected into numerous regions of the cochlea for various distances. The data from 14 complete experiments have been evaluated. The majority of the labelled cells were found ipsilaterally, with the lateral superior olive containing 59.2% and showing cochleotopicity. Of the 28.9% found contralaterally, the nucleus of the ventral lateral lemniscus had 16.9%, and the trapezoid body nucleus 8.0%, differing significantly from the other nuclei of the superior olivary complex. Although the distribution of the labelling was consistent, there was great variability in actual numbers. Calculations based on cell density showed no differences along the length of the basilar membrane, and resulted in a total of around 2500 efferent neurones. This figure agrees closely with the maximum counts found by other workers. However, the cause of the individual variability remains unanswered.

Animals↗
PubMed1983

Effects on guinea pig cochlea from exposure to moderately intense broad-band noise.

Guinea pigs, which were either anesthetized (A) or conscious (U), were exposed to four 2 h sessions of broad-band noise of 96 dB SPL. Cochlear microphonics and N1 thresholds were measured prior to killing from 1 to 13 days later. The cochleas were examined by SEM and by section. The U series suffered less N1 threshold loss and recovered within 10-13 days, while the large initial loss in the A series did not completely reverse within the period of study. Initially, the IHC stereocilia in the basal half of the cochlea showed marked bending, the affected area being somewhat more extensive in the A group. These hairs gradually recovered, although not progressively. On the other hand, the disturbance to OHC stereocilia, which appeared to be less pronounced early on and was more apically centered, developed over time into marked permanent damage. The outermost row consistently showed the greatest effect with hairs becoming elongated or fused, and occasionally lost altogether. Susceptibility to noise varied between individuals of both groups. The recovery of N1 threshold was concomitant with the recovery of the erectness of the IHC hairs.

Animals↗
PubMed1979

The effect of raising the scala tympani potassium concentration on the tone-induced cochlear responses of the guinea pig.

Scala tympani (ST) in guinea pig was perfused with modified Ringer's solutions containing 5--50 mM potassium; tone-induced cochlear responses from the basal turn of ST were compared before, during and after perfusions. The compound nerve action potential (N1) and afterpotential (a/p) amplitudes were reduced, especially above 20 mM; the summating potential (SP) was variable, but its onset shape changed consistently with 13--20 mM levels. However, the cochlear microphonic amplitude (CM) remained substantially unchanged even at the 35 mM level. K+ concentration was monitored in ST with ion-sensitive pipettes. Stable levels were reached within 2 min, but N1 responses continued to fall beyond this time. Recovery to normal K+ levels took place spontaneously and the concentration curve which resulted showed a 2-slope characteristic. These experiments question whether elevated potassium concentration in scala tympani depolarizes the hair cells, and if it does, whether the hear cell resting potential is involved in the generation of the CM.

Acoustic Stimulation↗
PubMed1979

Relationship of centrifugal fibres to 'supporting' cells.

We have described cholinergic fibres which cross the tunnel to three levels of the cells on the opposite side--from the level of the efferent network to the base of a plaque at the level of the nucleus of the first Deiters cell. These fibres are dependent upon the OCB being intact. The same is true for those fibres seen within the Hensen cell region. However, the cholinesterase-staining fine fibres travelling along the floor of the tunnel to the base of the plaque are independent of the integrity of the OCB.

Acetylcholinesterase↗
PubMed1979

The effect of cerebrospinal fluid pressure on perilymphatic flow in the opened cochlea.

Scala tympani of guinea pigs was perfused with elevated potassium solutions whose concentraus recovery, the concentration curve showed a 'break' approximately 3 min after perfusion ceased. When the CSF pressure was released by opening the cisterna magna, cochlear flow was markedly reduced, and the recovery curve became smoothly exponential, following a much slower return to control levels. This finding lends support to the idea proposed by Moscovitch, Gannon & Laszlo (1973) that longitudinal flow of CSF contributes to perilymph efflux in the patent cochlea.

Animals↗
PubMed1970

The characteristics of the cochlear after-potential studied in the guinea-pig by perfusion and stimulation.

1. An after-potential which comprises three components can be recorded from scala tympani or scala vestibuli following the termination of a tone burst of more than 20-30 msec duration. The major component is of opposite polarity to the negative summating potential (SP) when recorded from scala tympani (ST) and of the same polarity as the SP when recorded from scala vestibuli.2. The size of this after-potential is dependent on the duration and strength of the tonal stimulus but not on the stimulus frequency or its rate of turn-off.3. A single short tone-pip (10 msec) produces no visible after-potential, but an after-potential is seen following the end of a train of such pips separated by intervals of similar duration.4. Replacement of the perilymph in ST by Ringer solution has a negligible effect on the cochlear responses. However, replacing the sodium ion in Ringer solution by lithium or adding DNP to the perfusate abolishes the after-potential just as in the case of a neuronal after-potential. The latter manoeuvre affects also the N(1), CM and SP, while the former does not.5. It is suggested that there exists an active membrane mechanism at the hair cell/nerve junction, which is responsible for the after-potential and which can be influenced by perfusion of ST. It is further suggested that this neural mechanism makes a contribution to the recorded SP over and above the SP component due to non-linear factors.

Animals↗
PubMed1969

The transient electric responses of the cochlea.

1. DC responses were recorded from the cochleae of pigeons, cats and guinea-pigs. In addition to the known summating potential, transients of the same polarity were observed at the onset and termination of the tonal stimulus.2. These transients were most noticeable in the pigeon, being least in the guinea-pig responses.3. They could be modified by changing the rate of rise and fall of the stimulus envelope, but not by cutting the middle ear muscles.4. Comparable effects were seen when the ear was directly driven by a mechanical stimulus.5. With stimuli of long duration the off-transient was usually masked by a slow potential of opposite polarity. This deflexion appears to be an afterpotential, rather than a mechanical transient, since it is dependent on the duration of the preceding stimulus.

Animals↗