Ralf H. Anken

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The amounts of calcium and strontium were measured by inductively coupled plasma mass spectrometry (ICP-MS) in saccular and utricular inner ear otoliths (sagittae and lapilli, respectively) of developing cichlid fish. These fish had been maintained for 22 days at 3-g hypergravity conditions within a centrifuge. During this time-span, the animals completed(More)
Research in microgravity is indispensable to disclose the impact of gravity on biological processes and organisms. However, research in the near-Earth orbit is severely constrained by the limited number of flight opportunities. Ground-based simulators of microgravity are valuable tools for preparing spaceflight experiments, but they also facilitate(More)
1. The functional properties of biological membranes depend on their molecular composition. In regard to this, charged glycosphingolipids play an outstanding role in the functional adaptation of membranes to different temperatures. 2. In order to shed some light on the respective functional properties of complex membraneous glycosphingolipids, the effects(More)
Inner ear otolith formation in fish is supposed to be performed by the molecular release of proteinacious precursor material from the sensory epithelia, followed by an undirected and diffuse precipitation of calcium carbonate (which is mainly responsible for the functionally important weight of otoliths). The pathway of calcium into the endolymph, however,(More)
The distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (or -dehydrogenase, NADPHDH, a marker for nitric oxide synthase, NOS) positive neurons was demonstrated histochemically in the central nervous system of the swordtail fish Xiphophorus helleri, a highly derived telost of the atherinomorph outgroup. All nuclei of the swordtail fish,(More)
Previous investigations revealed that the growth of fish inner ear otoliths depends on the amplitude and the direction of gravity, thus suggesting the existence of a (negative) feedback mechanism. In the course of these experiments, it was shown that altered gravity both affected otolith size (and thus the provision of the proteinacious matrix) as well as(More)
The presence of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHDH) in fixed tissue was histochemically demonstrated in the Mauthner cells of the teleost fish Xiphophorus helleri. This is the first detection of the enzyme in these giant neurons (which are restricted to fishes and amphibians) of a gnathostomate vertebrate. NADPHDH reactivity in(More)
Stato- or otoliths are calcified structures in the organ of balance and equilibrium of vertebrates, the inner ear, where they enhance its sensitivity to gravity. The compact otoliths of fish are composed of the calcium carbonate polymorph aragonite and a small fraction of organic molecules. The latter form a protein skeleton which determines the morphology(More)
Size and asymmetry (size difference between the left and right sides) of inner ear otoliths of larval cichlid fish were determined after a long-term stay in moderate hypergravity conditions (3g; centrifuge), in the course of which the animals completed their ontogenetic development from hatch to freely swimming. Neither the normal morphogenetic development(More)
Synapse counts were undertaken by conventional electron microscopy in primary vestibular integration centers, (i.e. nucleus descendens and nucleus magnocellularis of the brainstem area octavolateralis) and in the diencephalic visual nucleus corticalis of spaceflown neonate swordtail fish Xiphophorus helleri as well as in 1 g control siblings. Spaceflight(More)