Osteoblasts Subjected To Spaceflight And Simulated Space Shuttle Launch Conditions
acceleration; bone cells; bone-formation; Cell Biology; cells; Developmental Biology; differentiation; flight; gene-expression; growing rats; in-vitro; messenger-rna expression; microgravity; vibration; weightlessness
To understand further the effects of spaceflight on osteoblast-enriched cultures, normal chicken calvarial osteoblasts were flown aboard shuttle flight STS-77, and the total number of attached cells was determined. Spaceflight and control cultures were chemically fixed 3 h and 3 d after launch. These fixed cultures were processed for scanning electron microscopy (SEM). The SEM analysis showed that with just 3 d of exposure to spaceflight, coverslip cultures contained 300 +/- 100 cells/mm(2), whereas 1G control samples contained a confluent monolayer of cells (2400 +/- 200 cells/mm(2)). Although the cultures flown in space experienced a drastic decline in cell number in just 3 d, without further experimentation it was impossible to determine whether the decline was a result of microgravity, the harsh launch environment, or some combination of these factors. Therefore, this research attempted to address the effect of launch by subjecting osteoblasts to conditions simulating shuttle launch accelerations, noise, and vibrations. No differences, compared with controls, were seen in the number of total or viable cells after exposure to these various launch conditions. Taken together, these data indicate that the magnitude of gravitational loading (3G maximum) and vibration (7.83G rms maximum) resulting from launch does not adversely affect osteoblasts in terms of total or viable cell number immediately, but launch conditions, or the microgravity environment itself, may start a cascade of events that over several d contributes to cell loss.
Kacena M A; Todd P; Landis W J
In Vitro Cellular & Developmental Biology-Animal
2003
2003-11
Journal Article or Conference Abstract Publication
n/a
Frequency sensitivity range of the saccule to bone-conducted stimuli measured by vestibular evoked myogenic potentials
Audiology & Speech-Language Pathology; bone conduction; frequency sensitivity range; myogenic potential; nerve; neurons; Neurosciences & Neurology; Otorhinolaryngology; repetition rate; responses; saccule; sound; squirrel-monkey; vestibular; vestibular evoked myogenic potential; vibration
Vestibular evoked myogenic potentials (VEMPs) occurring in cervical muscles after intense sound stimulation conducted by air or bone are thought to be a polysynaptic response of otolith-vestibular nerve origin. We report the results of an experiment to investigate whether acoustic stimulation of the saccule by bone conduction produces VEMPs in which response amplitudes are somewhat sensitive to stimulus frequency, as appears, to be the case with air-conducted stimuli. Prior to this we investigated the effect of stimulation repetition rate on bone-conducted VEMPs (B-VEMPs) at stimulus frequencies of 200 and 400 Hz with five different repetition rates (5, 10, 20, 40, and 80 Hz). B-VEMPs were recorded from 12 normal hearing subjects in response to bone-conducted 70 dB (normal hearing level), 10-ms tone bursts (rise/fall time = 1 ms and plateau time = 8 ms) at frequencies of 100, 200, 400, 800, 1600 and 3200 Hz. Our study showed that B-VEMP amplitudes were highest at 10 Hz but decreased as the repetition rate increased. B-VEMP response amplitudes were found to be maximal for stimulus frequencies from 200 to 400 Hz. This response may contribute to the perception of loud sounds. (C) 2001 Elsevier Science B.V. All rights reserved.
Sheykholeslami K; Kermany M H; Kaga K
Hearing Research
2001
2001-10
Journal Article
<a href="http://doi.org/10.1016/s0378-5955(01)00333-1" target="_blank" rel="noreferrer noopener">10.1016/s0378-5955(01)00333-1</a>