Linked Life Data

16310856

Source:http://linkedlifedata.com/resource/pubmed/id/16310856

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2006-5-2
pubmed:abstractText
Measurements of drug levels in the fluids of the inner ear are required to establish kinetic parameters and to determine the influence of specific local delivery protocols. For most substances, this requires cochlear fluids samples to be obtained for analysis. When auditory function is of primary interest, the drug level in the perilymph of scala tympani (ST) is most relevant, since drug in this scala has ready access to the auditory sensory cells. In many prior studies, ST perilymph samples have been obtained from the basal turn, either by aspiration through the round window membrane (RWM) or through an opening in the bony wall. A number of studies have demonstrated that such samples are likely to be contaminated with cerebrospinal fluid (CSF). CSF enters the basal turn of ST through the cochlear aqueduct when the bony capsule is perforated or when fluid is aspirated. The degree of sample contamination has, however, not been widely appreciated. Recent studies have shown that perilymph samples taken through the round window membrane are highly contaminated with CSF, with samples greater than 2microL in volume containing more CSF than perilymph. In spite of this knowledge, many groups continue to sample from the base of the cochlea, as it is a well-established method. We have developed an alternative, technically simple method to increase the proportion of ST perilymph in a fluid sample. The sample is taken from the apex of the cochlea, a site that is distant from the cochlear aqueduct. A previous problem with sampling through a perforation in the bone was that the native perilymph rapidly leaked out driven by CSF pressure and was lost to the middle ear space. We therefore developed a procedure to collect all the fluid that emerged from the perforated apex after perforation. We evaluated the method using a marker ion trimethylphenylammonium (TMPA). TMPA was applied to the perilymph of guinea pigs either by RW irrigation or by microinjection into the apical turn. The TMPA concentration of the fluid sample was compared with that measured in perilymph prior to taking the sample using a TMPA-selective microelectrode sealed into ST. Data were interpreted with a finite element model of the cochlear fluids that was used to simulate each aspect of the experiment. The correction of sample concentration back to the perilymph concentration prior to sampling can be performed based on the known ST volume (4.7microL in the guinea pig) and the sample volume. A more precise correction requires some knowledge of the profile of drug distribution along the cochlear prior to sampling. This method of sampling from the apex is technically simple and provides a larger sample volume with a greater proportion of perilymph compared to sampling through the RW.
pubmed:grant
pubmed:commentsCorrections
http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-10399889, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-10522939, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-11201817, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-11423219, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-11568567, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-12372647, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-12701740, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-12943372, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-12948598, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-12948599, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-15474111, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-15474112, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-2606807, http://linkedlifedata.com/resource/pubmed/commentcorrection/16310856-6732610
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0165-0270
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
153
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
121-9
pubmed:dateRevised
2009-11-18
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Perilymph sampling from the cochlear apex: a reliable method to obtain higher purity perilymph samples from scala tympani.
pubmed:affiliation
Department of Otolaryngology, Box 8115, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA. salta@msnotes.wustl.edu
pubmed:publicationType
Journal Article, Evaluation Studies, Research Support, N.I.H., Extramural