Herman de Jong

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The relation between prolonged hypergravity and structural adaptation of otoconia was studied in hamsters (n = 56). Three groups of hamsters (n = 27), were conceived and born in a centrifuge: group 1 (n = 10) 1 month under 2.5 G, group 2 (n = 9) 5 months under 2.5 G and 4 months under 1 G, group 3 (n = 8) 1 month under 2.5 G and 8 months under 1 G. Control(More)
One group of rats were bred and kept under hypergravity (HG) conditions (2.5 g) in a centrifuge. Another group were bred and kept under normal gravity conditions (1 g). Rats from both groups were dropped from a supine position into a water basin under infrared illumination leaving only gravity (1 g for both groups) for orientation. The airrighting reflex(More)
We studied vestibular function in 37 hamsters (1 month old) conceived and born in either hypergravity (n = 21) or normal gravity (n = 16). Four groups were made: (1) HL group: 20 weeks in 2.5 G and 14 weeks in 1 G; (2) HS group: 4 weeks in 2.5 G and 30 weeks in 1 G; (3) CON group: 34 weeks in 1 G; and (4) ROT group: 4 weeks in 1 G, 16 weeks in rotation in 1(More)
Gravity represents a stable reference for the nervous system. When the individual is increasing in size and weight, gravity may influence several aspects of the sensory and motor developments. To clarify this role, we studied age-dependent modifications of several exteroceptive and proprioceptive reflexes in five groups of rats conceived, born and reared in(More)
Rats were exposed to a hypergravity (HG) level of 2.5 x g from conception until the age of 14 weeks. The vestibular epithelia of four of these animals and four control animals were immunohistochemically labeled for actin and tubulin. The apical cross-sectional area of epithelial cells of HG exposed rats appeared to be larger in all end organs. Area increase(More)
The vertebrate vestibular system detects linear (otolith organs) and angular (semicircular canals) acceleration. The function of the otolith system is twofold, 1: perception of linear acceleration of the head, and 2: assessment of the spatial orientation of the head relative to the vector of gravity. Because of the latter function, a change of gravity will(More)
We studied the functional adaptation process in 40 hamsters subjected to either prolonged hypergravity to normal gravity. Subadult golden hamsters (n = 20) exposed to a hypergravity condition of 2.5 G for 6 months were tested to investigate the effect of hyper gravity on the perceptive motor skills and compared with control hamsters (n = 20). The motor(More)
Golden hamsters were exposed to conditions of 2.5 times normal gravity (hypergravity, HG) for 4 months. During this period, tests were carried out to study equilibrium maintenance, swimming behaviour and open-field behaviour of these HG hamsters and of control hamsters living in a normal-gravity environment. The tests proved to be useful devices for(More)
We investigated the effect of prolonged hypergravity on the otoconial layer of the maculae utriculi and the maculae sacculi in hamsters. The animals were placed in a centrifuge under conditions of 2.5 G, and remained there for 6 months. We then determined the calcium contents of the otoconia with energy dispersive X-ray element analysis, and recorded the(More)
BACKGROUND Birds and fish show tumbling and spinning movements when subjected to short periods of weightlessness during parabolic flight. The reason for this behavior is not clear. HYPOTHESIS The semicircular canal system is a rotation-detecting device; however, it seems that linear accelerations have an influence, too. Microgravity induces rotatory(More)