Biomedical subjects

L C Shaddock

Publications and source records attributed to L C Shaddock.

6 recordsLinked to original sources

PubMed1985

A morphometric technique for analysis of cochlear vessels.

A computer based system was developed for morphometric analysis of the cochlear lateral wall vasculature. Variables measured were vascular density, RBC density, vessel width, aggregation density, lumen compression count, WBC count and pigment density. Vessels were divided into three systems based on the lateral wall structures that they supplied. The results indicated that these three vessel systems were morphologically distinct in terms of their vascular density, RBC density, and vessel width. How these differences relate to functional needs of the lateral wall is discussed.

Animals↗

PubMed1985

A morphometric study of microvascular pathology following experimental rupture of Reissner's membrane.

In a previous paper (this volume) we described a method for evaluating the cochlear microvasculature. This method was applied to the analysis of lateral wall tissue from chinchillas sacrificed 1 h, 24 h, 1 week and 3 weeks after surgical rupture of Reissner's membrane. The degree, direction, and time course of pathological changes seen in the microvessels were different for the system of stria vascularis vessels, the system of spiral ligament vessels, and the system of spiral prominence vessels. These results indicate that it is important to evaluate all of the lateral wall vessels rather than just the stria vascularis, and emphasize the importance of dividing the microvasculature into three independent systems, in order to obtain a clearer perspective on microvascular changes which occur following cochlear trauma.

Animals↗

PubMed1983

Tympanostomy tubes and otic drops.

Otic drops have been proposed as a form of prophylaxis against the otitis media which follows middle ear contamination by water in patients with tympanostomy tubes. The potential adverse effects of this form of therapy were studied in chinchillas with tympanostomy tubes; 31 chinchillas underwent bilateral tympanostomy tube insertion. Seven animals had a mixture of green dye and Cortisporin otic suspension placed in both external auditory canals 24 hours following the placement of tympanostomy tubes and were sacrificed 30 minutes later for gross examination; 3 of these animals had previous eustachian tube obstruction with Silastic sponge. Twenty-one animals had Cortisporin otic suspension placed in the right external auditory canal on postoperative days 3, 4, 5, 6 and 7. No otic drops were placed in the left ear. Ten of these 20 animals had VIIIth nerve action potentials measured on postoperative day 17 and the other 11 animals had VIIIth nerve action potentials measured on postoperative day 42 followed by immediate sacrifice for histological examination and scanning electronmicroscopy. The remaining 3 animals had VIIIth nerve action potentials measured 21 days following tympanostomy tube insertion and served as electrophysiological controls. The 8 ears receiving Cortisporin otic drops mixed with green dye from animals with normal eustachian tubes showed staining of the round window membrane at sacrifice, while the 6 ears receiving Cortisporin otic suspension and green dye from animals with eustachian tube obstruction demonstrated no dye in the middle ear. All animals receiving Cortisporin otic drops in the right ear showed an intra-aural difference in action potentials with the right ear being attenuated by an average of 10.3 dB at 2,000 Hz, 12 dB at 4,000 Hz, 21 dB and 8,000 Hz, and 26 dB at 12,000 Hz. Morphological study revealed hair cell loss in the hook portion of the cochlea in those animals receiving Cortisporin otic drops. It was concluded from this study that, in patients with patent tympanostomy tubes in place, potentially ototoxic topical agents should be used with caution.

Action Potentials↗

PubMedDate not supplied

Cochlear vascular and sensory cell changes induced by elevated temperature and noise.

The vascular anatomy of the chinchilla cochlea was quantitatively analyzed and compared in animals exposed to 155- or 160-dB impulse noise at normal (37 degrees C) and elevated (40 degrees C) body temperatures. Vascular changes persisted 45 days after noise exposure in all experimental animals. Six variables were most susceptible to change in one or more of the vessels studied: 1) irregularities in the vessel lumen, 2) plasma spaces between red blood cells (RBCs) and the vessel wall, 3) columns of RBCs, 4) variability in density of RBCs, 5) pigment clumps in the stria vascularis, and 6) perivascular cells compressing the vessel lumen. These vascular changes, which indicate a reduction in blood flow, were present throughout the length of the cochlea, with a tendency toward maximum change in areas of maximum hair cell loss. There was no evidence in the vascular results to support an interaction between noise and increased body temperature. However, the cochleograms from the experimental animals indicate that at the 160-dB exposure level the noise and high temperature may have interacted to increase hair cell loss.

Animals↗

PubMedDate not supplied

Effect of high intensity impulse noise on the vascular system of the chinchilla cochlea.

Changes in the vasculature of the chinchilla cochlea were quantitatively assessed 45 days after impulse noise exposure of either 155- or 160-dB peak sound pressure level. The condition of the vessels in the lateral wall and spiral lamina of each cochlea was evaluated in terms of 20 morphological parameters. Multivariate statistical analysis identified the parameters that were significantly affected by the noise exposure. Evaluation of these significant parameters indicated a net reduction in blood flow to the cochlea. All of the noise-exposed cochleas showed vascular changes when compared to controls, and the magnitude of these changes was related to the amount of hair cell loss. The vascular changes are presumed to be permanent.

Animals↗

PubMedDate not supplied

An experimental study of inner ear pathology due to NaCl on the round window.

An animal experiment was performed to evaluate structural and ultrastructural changes to the inner ear as a result of placing 3-4 crystals of reagent grade sodium chloride (NaCl) on the round window membrane. Chinchillas were sacrificed at 8 and 24 hours after treatment and the cochlear and vestibular tissues were examined by light microscopy and scanning electron microscopy. Inner ear pathology consisted of destruction of both sensory and supporting cells in the basal turn of the organ of Corti, atrophy of the stria vascularis and alterations to the otoconia and the maculae and ampullae of the vestibular system. This study demonstrates that NaCl in the middle ear does not provide a model for Meniere's disease as previously suggested by Arslan. It may, however, be utilized in the destructive treatment of selected inner ear disorders.

Animals↗