Abstracts: 6th NASA Symposium on The Role of the Vestibular Organs in the Exploration of Space

2002 Journal of Vestibular Research-Equilibrium & Orientation  
Alterations in sensory and motor function occur during and following exposure to microgravity. Vestibular abnormalities may include postural illusions, sensations of rotation, nystagmus, dizziness, and vertigo. Adaptation to the microgravity environment usually occurs within one week, and a subsequent re-adaptation period is often required upon return to Earth. During this re-adaptation period, recurrences of dizziness, nausea and vomiting, and disturbances in postural equilibrium in the
more » ... of vision may occur. The present study was conducted to identify the ultrastructural alterations in adult rat cerebellar cortex that correlate with short-term adaptation to spaceflight and re-adaptation to Earth. Hindbrain tissue was obtained from adult rats flown on the Neurolab shuttle mission (STS-90) as part of an IACUC-approved experiment. Tissue for the present report was obtained from four rats sacrificed on orbit during flight day 2 (FD2) and five animals sacrificed on Earth 24 hr after shuttle return (R+1). Following decapitation, hindbrains were immersion-fixed in aldehydes for 18 days, and then the cerebellum was dissected away from the ventral portion of the brainstem by severing the cerebellar peduncles. The entire cerebellum of each rat was Vibratome-sectioned parasagittally. These sections were collected serially, processed for electron microscopy, and embedded as tissue wafers in resin. Complete reconstructions of the nodulus from each animal were performed and used to identify the midsagittal tissue wafer. Using this as the zero point, the wafers from the otolithrecipient parasagittal zones were identified and examined using electron microscopy. Cisterns of smooth endoplasmic reticulum that are normally present in Purkinje cells were substantially enlarged in tissue from the nodulus of FD2 and R+1 flight animals. The increased complexity of these cisterns resulted in the formation of lamellar bodies that were observed throughout entire Purkinje cells, including the somata, dendrites, thorns, and axon terminals. Profoundly enlarged mitochondria were also apparent in some nodular Purkinje cells from FD2 and R+1 animals, as well as electron-dense degeneration in Purkinje cell dendrites.
doi:10.3233/ves-2002-113-514 fatcat:mszwuktpjvfpzmh2ptapi2ux7i