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Auditory and vestibular pathology of seizure-prone chicks
Insights
The paroxysmal (px) gene mutation in chickens causes seizures and degeneration of auditory and vestibular systems. This degeneration begins early and progresses, leading to chick mortality.
Area of Science:
- Neuroscience
- Genetics
- Animal Science
Background:
- The sex-linked lethal recessive px gene in White Leghorn chicks causes spontaneous seizures.
- Seizures begin around day 8 post-hatching and are triggered by auditory stimuli.
- Affected chicks exhibit decreased food intake, leading to mortality within 4-10 weeks.
Purpose of the Study:
- To investigate the histological changes in the brains of px chicks.
- To determine the onset and progression of neural degeneration associated with the px mutation.
- To assess the impact of ambient noise on degeneration and seizure onset.
Main Methods:
- Histological examination of chick brains using a modified cupric-silver staining technique.
- Comparison of brains from px chicks and non-px siblings at various ages (pre-seizure and post-seizure onset).
- Assessment of degeneration in auditory and vestibular systems, including cerebellar nuclei.
Main Results:
- Extensive degeneration was observed in the nuclei and fiber tracts of the auditory and vestibular systems in px chicks.
- Degeneration was evident as early as 5 days of age, primarily affecting deep cerebellar nuclei.
- Degeneration progressed over time, maximally affecting sensory systems by 20 days of age; ambient noise had no significant effect.
Conclusions:
- The px gene mutation leads to progressive degeneration of the auditory and vestibular systems in chickens.
- Neural degeneration precedes seizure onset and is a significant factor in the pathology.
- The findings provide insights into the genetic basis of neurological disorders and sensory system degeneration.
Abstract:
The mutant sex-linked lethal recessive px (paroxysmal) gene, expressed in White Leghorn chicks (Gallus domesticus) causes seizures beginning on approximately day 8 post-hatching. Seizures are spontaneous and inducible by auditory but not by photic stimulation. Prior to seizure onset px chicks are indistinguishable from non-px siblings. With seizure onset is a decrease in food intake which causes deterioration and death by 4-10 weeks of age. In a preliminary histological study conducted on 22-day-old seizure-prone chicks, brains were perfused and sections treated according to a modified cupric-silver staining technique. Nuclei and fiber tracts of px auditory and vestibular systems were extensively degenerated; control brains showed essentially no degeneration. A second experiment was conducted with preseizure chicks to determine whether and to what extent degeneration occurs prior to seizure onset. Deep nuclei of px cerebellum appeared to be the first seriously affected (5 days of age). Extent of degeneration progressed steadily over time through 20 days of age, by which time all components of the two sensory systems were maximally affected. Ambient noise did not affect onset or extent of degeneration, nor did it affect onset of seizures.