Biomedical subjects

J S Erulkar

Publications and source records attributed to J S Erulkar.

3 recordsLinked to original sources

PubMed2000

Biomechanical evaluation of the New Zealand white rabbit lumbar spine: a physiologic characterization.

Physiologic motions of the human, sheep, and calf lumbar spines have been well characterized. The size, cost, and ease of care all make the rabbit an attractive alternative choice for an animal lumbar spine model. However, comparisons of normal biomechanical characteristics of the rabbit lumbar spine have not been made to the spines of larger species. The purpose of this study was to establish baseline physiologic kinematic data for the rabbit lumbar spine. Ten skeletally mature New Zealand white rabbit osteoligamentous spines were obtained. L4-L7 spine segments were harvested and mounted. Multi-directional flexibility testing was performed by applying pure moments up to 0.27 Nm. Resulting rotations were measured using an Optotrak system. Data were analyzed for each intervertebral level in the three planes of rotation. The three levels tested had roughly similar range of motion (ROM). The mean (SD) angular ROMs in flexion for L4-L5, L5-L6, L6-L7 were 12.10 degrees (2.59 degrees), 12.38 degrees (2.70 degrees), and 15.17 degrees (3.22 degrees), respectively. The ROMs in extension were 5.86 degrees (1.21 degrees), 5.58 degrees (1.48 degrees), and 6.13 degrees (2.03 degrees). Lateral bending and axial rotation were roughly symmetric due to the symmetric nature of the spine. For right lateral bending, the ROMs were 8.25 degrees (2.44 degrees), 4.96 degrees (1.70 degrees ), and 4.25 degrees (1.20 degrees). For left axial rotation, the ROMs were 1.23 degrees (1.16 degrees), 0.35 degrees (0.61 degrees), 0.87 degrees (0.64 degrees ). Neutral zone (NZ) was on average 60% (29%) of ROM for the motions studied. The physiologic ROM of the New Zealand white rabbit lumbar spine was found to be similar between the rabbit and human. This relatively conserved physiologic flexibility supports the use of the rabbit as a model of the lumbar spine for kinematic studies. However, the overall NZ was found to be a greater percentage of ROM in the rabbit than the corresponding percentage in the human (60% as compared to 25%). This suggested that the rabbit lumbar spine has a greater laxity than that of the human.

Animals↗

PubMed1996

Functional changes in the aging mouse middle ear.

Laser interferometry was used to measure sound-induced umbo velocity in the aging mouse middle ear. Velocity reductions of as much as 8 dB were seen as the mice aged. These functional differences suggest a variety of structural changes that may occur in the aging middle ear.

Acoustic Stimulation↗

PubMed1996

Hair bundle morphology on surviving hair cells of the chick basilar papilla exposed to intense sound.

Exposure to intense sound produces a well-defined "patch" lesion on the chick basilar papilla in which 30-35% of the short hair cells are lost. The present study compares various aspects of sensory hair bundle morphology on surviving hair cells in the patch lesion with hair bundles from matched locations on nonexposed control papilla immediately after removal from the exposure and 12-days post exposure. The height and thickness of the hairs, the total number of hairs in the bundle, the width of the bundle, and the area and perimeter of the apical surface of the hair cell were quantified from scanning electron microscope photomicrographs. An attempt was also made to determine if there was a consistent microstructure to the pattern of hair cell loss within the lesion area. Similar observations in 12-day recovered ears are also presented. The results indicated that stereocilia height increased and width decreased on surviving hair cells in the exposed ear. The width of the hair bundle, the hair cell surface area, and perimeter also decreased. However, the number of hairs per cell remained unchanged, and there was no evidence of any consistent organization to the hair cell loss within the patch across a number of specimens. These observations indicated that the hair bundles on short hair cells underwent changes as a consequence of intense sound exposure. The results after 12 days of recovery were complicated by developmental changes on the papilla and incomplete maturation of the newly regenerated hair cells. It remains to be seen whether these changes were the result of cell sampling in the sound-damaged ear or were due to true structural alterations within the sensory hairs themselves.

Animals↗