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Vestibular cytotoxicity in gentamicin-treated frogs: a preliminary report
Tapan K Bhattacharyya1, Arvind Kumar
1Department of Otoalaryngology-Head and Neck Surgery, University of Illinois at Chicago, 60612, USA. tbhatt@uic.edu
Objective:
The aim of this study is to determine the immediate effects of intraperitoneal doses of gentamicin (GM) which would result in variable degrees of destruction of crista ampullary hair cells of frogs. This information will serve as a baseline guide to cell regeneration experiments on the damaged vestibular sense organ.
Study Design:
The American bullfrog was administered daily intraperitoneal doses of 50, 100, 150, and 200 mg/kg of GM for 7 days. Animals were sacrificed 1 day after the final injection for cytomorphic evaluation. Histologically processed posterior semicircular duct cristae were resin-embedded, and tissue samples were subjected to serial cross sectioning of the crista from the periphery to the central zone using glass knives in an ultramicrotome. Stained sections were analyzed in light microscope using ocular grid micrometry. The areal density of nuclear profiles of the vestibular sensory and supporting cells (sensory cells [SNCs] and supporting cells [SPCs], respectively; number per square millimeter) and the nuclear diameter of SNCs were manually determined.
Results:
A 7-day administration of GM produced noticeable quantitative alteration of the posterior crista hair cells and SPCs. Histological analysis revealed a significant decrease in the density of SNCs and a concomitant increase in the density of SPCs (1-way analysis of variance).
Conclusion And Significance:
The cytomorphic data derived from this study show that 4 doses of intraperitoneal gentamicin administered to the bullfrog caused a decline in the areal density of sensory hair cells of the posterior canal crista ampullaris. Also noted was an increase in the density of adjacent SPCs. Although speculative, the increase in SPC population could be a harbinger of regeneration of the vestibular hair cells as suggested by other investigators in different species. The significance of present observations will be helpful to initiate future studies related to recovery of SNCs in a similarly damaged frog ampullary organ. Through a standardized quantitative approach to the study of SNCs and SPCs of the crista organ, the vestibulo-toxicity of newly developed drugs can be assessed.
Insights
Gentamicin (GM) treatment in frogs significantly reduced sensory hair cells (SNCs) in the vestibular organ. This study provides a baseline for understanding hair cell regeneration and assessing drug toxicity.
Area of Science:
- Vestibular system research
- Ototoxicity studies
- Cell regeneration mechanisms
Background:
- The vestibular system's sensory hair cells (SNCs) are crucial for balance.
- Gentamicin (GM) is known to cause ototoxicity.
- Understanding GM's effects is vital for drug development and regenerative medicine.
Purpose of the Study:
- To quantify the immediate impact of intraperitoneal gentamicin (GM) on frog vestibular sensory hair cells (SNCs).
- To establish a baseline for future studies on vestibular organ regeneration.
- To assess the potential of gentamicin-induced damage as a model for studying cell regeneration.
Main Methods:
- American bullfrogs received daily intraperitoneal doses of gentamicin (50-200 mg/kg) for 7 days.
- Posterior semicircular duct cristae were processed for histological analysis.
- Areal density of sensory cells (SNCs) and supporting cells (SPCs) was determined using microscopy and micrometry.
Main Results:
- A 7-day gentamicin administration led to a significant decrease in the density of sensory hair cells (SNCs).
- A corresponding increase in the density of supporting cells (SPCs) was observed.
- Quantitative alterations in vestibular sensory and supporting cells were dose-dependent.
Conclusions:
- Intraperitoneal gentamicin significantly reduces vestibular sensory hair cell density in frogs.
- The observed increase in supporting cells may indicate a regenerative response.
- This study provides a quantitative foundation for investigating vestibular hair cell regeneration and assessing drug-induced vestibulo-toxicity.
