Biomedical subjects

R R Marsh

Publications and source records attributed to R R Marsh.

60 records · Page 4Linked to original sources

PubMedDate not supplied

Drugs affecting clearance of middle ear secretions: a perspective for the management of otitis media with effusion.

Otitis media with effusion (OME) is characterized by the production and accumulation in the middle ear of mucus secretions, whose physicochemical properties are an important feature in the etiology and treatment of the disease. Many types of pharmaceutical agents, including anti-inflammatory agents, antihistamines, antibiotics, and mucolytics, have been used in attempts to improve the clinical status of patients with OME. This study critically reviews the literature from the point of view of possible changes induced by these agents in the physicochemical properties of the secretions and hence their clearance from the middle ear. In vitro studies on mucociliary clearance of respiratory (tracheobronchial) secretions and middle ear effusions are cited as the basis for analyzing the important parameters expected to govern middle ear clearance and to determine the rationale for use (or nonuse) of various classes of drugs. It is expected that this analysis will prove useful in the design of properly controlled trials of such agents.

Animals↗

PubMedDate not supplied

Generators of the frequency-following response in the guinea pig.

Generators of the frequency-following response (FFR) were assessed in 13 guinea pigs by cooling of the whole body and by experimental lesions of the brain stem. In the temperature study, the amplitude-temperature function of the FFR contained a significant cubic component that was absent from that of the cochlear microphonic potential (CM) recorded from the round window. The phase shift of the FFR increased with decreasing body temperature. In experimental lesions of the brain stem, a significant phase shift of the FFR was obtained following contralateral postcollicular section. The FFR amplitude with transection of the auditory nerve was similar to that found before surgical sections of the brain stem. The duration of the FFR after the transection corresponded precisely to that of the round window CM. These results indicate that the origin of the FFR contains both nonneural (ie, cochlea) and neural (ie, involving the inferior colliculus) generators.

Animals↗

PubMedDate not supplied

Brain stem response evoked by electrical stimulation of the round window of the guinea pig.

The wave that is believed to correspond to wave V in man is an appropriate indicator of auditory nerve excitability because it is not contaminated by nonauditory neurogenic responses to electrical stimulation. The responses to direct electrical stimulation of the auditory nerve could be distinguished from the electrophonic response by the steep input-output function and constant latency of the former. Myogenic responses are prominent unless a muscle relaxant is administered.

Acoustic Stimulation↗

PubMedDate not supplied

Effect of site of stimulation on the guinea pig's electrically evoked brain stem response.

Stimulation by a bipolar modiolus electrode yields a wider dynamic range than does monopolar stimulation at the same site. Stimulation via a single electrode in the scala tympani or scala vestibuli is characterized by a precipitous input-output function, but current passing from one scala to the other generates a discontinuous function with a shallow slope at low intensities and a steep slope at high intensities.

Animals↗

PubMedDate not supplied

Development of the paranasal sinuses in children with sinus disease.

In a previous report, the authors defined the normal development of the paranasal sinuses. Landmarks and dimensions relevant to functional endoscopic sinus surgery were measured on the computed-tomography images of 145 children who were free of significant sinusitis. The present study compares those normal values to the same measurements in 235 cases of sinus disease. No significant difference was found between normal and diseased groups in any of the 10 dimensions originally reported or in six derived measures. There appears to be no association between sinus disease and any of these dimensions. The previously reported norms are applicable to cases of pediatric sinus disease.

Adolescent↗

PubMedDate not supplied

Reflex inhibition audiometry. A new objective technique.

The reflexive eyeblink, elicited by a tactile stimulus, is inhibited if an auditory stimulus precedes the eliciting stimulus by 100 msec. With adult subjects the threshold for this effect was found to be sufficiently low to suggest that reflex inhibition may be useful in objective audiometry. A preliminary investigation with infants and children showed that the inhibitory process is present, though variable, in children as young as 6 weeks olds.

Acoustic Stimulation↗