Susceptibility to abnormal (kinetotic) swimming fish correlates with inner ear carbonic anhydrase-reactivity.

Larval cichlid fish (Oreochromis mossambicus) were kept at hypergravity (hg; centrifuge) for 6 h. Following the transfer to 1 g (i.e. stopping the centrifuge), animals were separated into normally and abnormally (kinetotic) swimming individuals (the latter were swimming kinetotically, i.e. performing spinning movements). Subsequently, carbonic anhydrase- (CA-) reactivity was histochemically demonstrated and densitometrically determined in inner ear maculae. It was found that both the total macular CA-reactivity as well as the difference in reactivates between left and right maculae were significantly lower in normally swimming hg-animals as compared to the kinetotically behaving hg-fish (P<0.0001). This result is in complete agreement with closely related studies carried out on the calcium incorporation of inner ear otoliths and indicates that a regulatory mechanism, which adjusts otolithic calcium carbonate incorporation towards the gravity vector, acts via activation/deactivation of macular CA.

Histology of the utricle in kinetotically swimming fish: a parabolic aircraft flight study.

OBJECTIVES: Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness, which is a form of kinetosis. As it has been repeatedly shown that some fish in a given batch also reveal kinetotic behaviour (especially so-called spinning movements and looping responses) during PAFs, and as a result of the homology of the vestibular apparatus of all vertebrates, fish can be used as model systems to investigate the origin of susceptibility to motion sickness. Therefore. we were prompted to examine the utricular maculae, which are responsible for the internalization of gravity in teleosteans of fish swimming kinetotically in microgravity (microg) in comparison with those of animals from the same batch who swam normally. MATERIAL AND METHODS: Larval cichlid fish (Oreochromis mossambicus) were subjected to PAFs. Post-flight, animals which had behaved normally or kinetotically during the microg phases were examined histologically The sizes of the inner ear utricular maculae as well as the numbers of sensory and supporting cells were determined. RESULTS: The total numbers of both sensory and supporting cells of the utricular maculae did not differ between kinetotic and normally swimming fish. Cell density (number of sensory and supporting cells/100 microm2) was, however, reduced in kinetotic animals (p < 0.0001), which seemed to be due to the presence of malformed epithelial cells of increased size in the kinetotic specimens. CONCLUSION: These results indicate that susceptibility to kinetosis may originate from genetically predisposed malformed sensory epithelia.

On the origin of susceptibility to kinetotic swimming behaviour in fish: a parabolic aircraft flight study.

Humans taking part in parabolic aircraft flights (PAFs) may suffer from motion sickness (SMS, a kinetosis; it comprises a dynamic and a static component). It has been argued that the so-called static variety of SMS during PAFs might be based on asymmetric statoliths (i.e., differently weighed statoliths on the right and the left side of the head), with asymmetric inputs to the brain being disclosed in microgravity. Since it has been repeatedly shown earlier that some fish of a given batch reveal a kinetotic behaviour during PAFs (especially so-called spinning movements and looping responses), we investigated whether fish swimming kinetotically in microgravity have a pronounced inner ear otolith asymmetry. Therefore, the swimming behaviour of larval cichlid fish was video-recorded during PAFs and subsequently, size and asymmetry (size difference between the left and the right side) of inner ear otoliths were determined. The asymmetry of utricular otoliths of kinetotic samples was found to be significantly higher than that of normally behaving experimental specimens. Regarding the asymmetry of saccular otoliths of the two groups, statistically different results were not obtained. The findings strongly support the earlier theoretical concept, according to which otolith asymmetry causes (static) SMS.

[Neuraminic acid content of fish eggs during early ontogenesis]. / Neuraminsäure-Gehalt in Fischeiern verschiedener Entwicklungsstadien.

The content of neuraminic acid (NA) of different developmental stages of trout eggs was determined. 1. The total NA increases from about 13 µg NA per egg (6-8 weeks before spawning) to 50 µg directly before spawning until hatching. 2. In freshly hatched fish larvae the NA-content is decreased to about 40 per cent as compared with stages before hatching. 3. The ratio of bound to free NA decreases from values of about 13.5 (6-8 weeks before spawning) to 0.85-1.2 at the hatching-stage. 4. The bound NA is almost entirely bound to sialo-glycoproteins.

Quantitative morphogenetic investigations on fine structural changes in the optic tectum of the rainbow trout (Salmo gairdneri) during ontogenesis.

The morphogenetic differentiation of synapses of the optic tectum of the rainbow trout was investigated at different stages of development (from hatching to adult) and compared with the improvement in visual discrimination (minimum separable). (1) The main phase of synaptogenesis (increase in number of synapses, length of contact zone and number of vesicles) begins about one week after hatching and continues up to the age of one month, when the larvae start swimming freely. (2) Myelination begins 26 days after hatching and induces the end of the synaptogenesis period. (3) The visual discrimination (minimum separable) of trout larvae improves from 30 degrees of arc on the 10th day after hatching to 1 degree on day 30, then to about 14 to 18 min of arc in the adult. The results are discussed with special reference to previous biochemical investigations on changes in the ganglioside composition of the trout brain during comparable periods of development.

Hypergravity decreases carbonic anhydrase-reactivity in inner ear maculae of fish.

Previous investigations revealed that fish inner ear otolith growth depends on the amplitude and the direction of gravity. Both otolith total size, otolith bilateral size-asymmetry and the total and bilateral calcium-incorporation are also affected by gravity. Hypergravity, e.g., slows down otolith growth and diminishes bilateral otolith asymmetry as compared to 1 g control specimens raised in parallel. Since the enzyme carbonic anhydrase (CA) plays a prominent role in otolithic calcification, the reactivity of inner ear CA during otolith growth under hypergravity was investigated. CA-reactivity was demonstrated histochemically and densitometrically on sections of inner ear maculae of larval cichlid fish (Oreochromis mossambicus), that were kept for 6 hrs in a 3 g hypergravity centrifuge. The total unilateral macular CA-reactivity and the bilateral difference in CA between the left and the right maculae were significantly lower in 3 g animals than in 1g controls. The result is in complete agreement with previous studies indicating that a regulatory mechanism, which adjusts otolith size and asymmetry towards the gravity vector, acts via activation/deactivation of macular CA.

Developmental profiles of gangliosides in mouse and rat cerebral cortex.

Developmental profiles of 11 gangliosides, concentration of lipid- and glycoprotein-bound sialic acid, and activity of AChE of the rat and mouse cerebral cortex were followed from the 7th day of gestation to the 21st postnatal day.There are three main changes in ganglioside concentration, which are similar in both species. The first occurs from gestation day 10 until birth: parallel to decreased proliferation, cell migration, and neuroblast differentiation, GM3 and GD3 in mouse cortex and GD3 in the rat's decreases in favor of GQ1b, GT1b, and GD1a.The second occurs from birth until the first postnatal week: Parallel to increased growth and arborization of dendrites and axons as well as synaptogenesis in rats and mice, there is a two-fold rise of GD1a, whereas GQ1b and GT1b remain on a nearly constant level. Concomitantly, GM3 and GD3 decreases. The third period of ganglioside changes starts in the second postnatal week, parallel to onset of myelination, and is characterized by an increase of GM1 in parallel with a decrease of the polysialogangliosides GT1b and GQ1b.