[Influence of weak magnetic fields on fish retina photoreceptors].

It has been shown for the first time that retina photoreceptors of the salmon Oncorhynchus masou (masu salmon) fry exposed to a constant magnetic field (80 Gs) in conditions of twilight illumination demonstrated not a twilight reaction, as in the control, but a darkness (scotopic) reaction. The pigment epithelium in this case reacted as to bright light. Under the influence of long wavelength red light, the retinomotor reaction corresponded to partial light adaptation. After the indemnification of the horizontal component (0.1 Gs) of the geomagnetic field, fish retina adapted to complete darkness demonstrated changes that could not be attributed to one of standard conditions of light exposure. Thus, the rods and cones demonstrated a reaction similar to that to twilight, double cones reacted as to complete darkness ("correct" reaction), and PE borrowed a position as at twilight. Apparently, the basic stimuli of the retina reactions were not light but changes of the magnetic field. Based on these results and the results available in literature, the authors offer a new variant of the hypothesis of light-dependent magnetoreception, which is based on the assumption that the liquid crystals of retina pigments are very sensitive receptors of magnetic field and do not require the presence of magnetite crystals. We assume that the layer of retina pigment epithelium participates in the complex process of transformation of a light signal, which takes into account the influence of magnetic field but not simply absorbs light superfluous for photoreceptors. The changes in magnetic field cause a distortion of the liquid crystal line structure of the pigment, which results in the transformation of the light signal acting on the photoreceptors. Monochromatic red light in the same way deforms the response to the native magnetic signal.

[Magnetic field induced structural changes of Oncorhynchus masou retina ]. / Morfologicheskie izmeneniia v setchatke molodi simy Oncorhynchus masou pri éksperimental'nom izmenenii magnitnogo polia.

The work describes the retinomotor response of Oncorhynchus masou young kept at illumination ranging from 1 to 10 lux, exposed to a field of a permanent magnet, and under conditions of geomagnetic field compensation. Retinomotor response in young exposed to magnetic field in darkness corresponds to partial light adaptation. During the exposure to a field of a permanent magnet the pigment was found to concentrate in pigmentocyte processes endings, forming the layer, that subdivided cone outer segments and rod outer segments and ellipsoids. Pigment in an aggregated state poorly shielded rod outer segments. In experiments with geomagnetic field compensation in darkness double and central cones were significantly elongated, the pigment is concentrated in initial parts of the processes and in pigmentocyte bodies. Pigment demonstrates the reaction that is similar to darkness adaptation, while the state of photoreceptors corresponds to a partial light adaptation. The changes of a natural magnetic field were accompanied by unusual retinomotor responses, in which the state of photoreceptors and retinal pigment epithelium did not correspond to photopic, mesopic or scotopic adaptation.

[Morphology of retinomotor response of Oncorhynchus masou fry exposed in magnetic field and red light]. / Morfologicheskie osobennosti retinomotornoi reaktsii u moldi simy (Oncorhynchus masou) v magnitnom pole i krasnom svete.

The retinomotor response of Oncorhynchus masou fry was studied following their experimental exposure to constant magnetic field, red light and their combination. Photoreceptor and pigment epithelium reactions to red light had a mesopic character. The mesopic state of retina after exposure of fishes to magnetic field in darkness differed from that after exposure to red light by the reaction of a pigment epithelium (PE). Exposure to magnetic field after red light resulted in the summation of these two effects. As rods are adapted to twilight, and cones are adapted to light, combined functioning of two perception mechanisms is possible, which is never found in normal conditions. After exposure to red light that followed the action of magnetic field, retinomotor reaction reflected the physiological dysfunction, with no functioning of either rods or cones. PE was actively participating in reactions to changes of magnetic field. The assumption that the cells of PE of fish retina can act as a light-dependent magnetoreceptor, is discussed.

[Ultrastructure of melanocytes from retina and choroid of the Pacific salmon]. / Ul'trastruktura malanotsitov setchatoi i sosudistoi obolochek glaza tikhookeanskikh lososei.

The ultrastructure of the retina and choroid cells in three species of the Pacific salmon, Oncohrynchus gorbuscha, O. keta and O. masou, was studied. The structure of retina pigment cells is similar in all the three species, only a small difference was found in the percentage of lengthened and rounded forms of melanosomes. Melanocytes of the masu salmon differ also in the structure of their nuclei. The pigment cells of choroid differ from those of retina by a more extended form of melanosomes and by the presence of less rounded melanosomes. In the chum salmon retina we found electron lucent "contact vesicles", whose assignment is open to discussion. In retina pigment cells of the masu salmon smolts ready for migration, the activity of Golgi appararus rises, mitochondria and mature melanosomes increase in number. The choroid pigment cells are slightly swollen, their processes more often and deeper penetrate into the walls of vessels, down to the endothelium. Results of the experiment with the application of an artificial magnetic field (AMF) have shown that the retina and choroid pigment cells in the masu salmon fry react to the field of a certain direction. The phenomenon of magnetosensitivity of pigment cells is discussed in addition to their possible involvement in magnetoreception.

[The magnetic susceptibility of the melanin in the eyes of representatives of different vertebrate classes]. / Magnitnaia vospriimchivost' melanina glaz u predstavitelei razlichnykh klassov pozvonochnykh.

The magnetoperceptivity (Chi) and element composition of eye pigment epitelium (EPE) melanin in vertebrate animals were measured. The minimal values of EPE Chi were found in winter-sleeping and anabiotic animals (Ursus arctos, Rana temporaria). The magnetoperception was high in migrating animals (Oncorhynchus keta, 0. gorbuscha, Anas crecca) and in wild gray rats as well, EPE magnetoperceptivity in albino rats wasn't practicaly established. In the majority of cases the quantity of magnetoperceptivity correlates with per-cent content of iron. The evident correlation between melanin magnet properties and the life strategy of the investigated animals allows to propose the participance of eye pigment epithelium in orientation and navigation of the animals.

[The vascular melanocytes of the pia mater and mesentery of the small intestine in the frog: structure and functions]. / Melanotsity sosudov miagkoi mozgovoi obolochki i bryzheiki tonkoi kishki liagushki: struktura i funktsii.

Melanocytes of frog blood vessels were studied by electron transmission, scanning and vital optical microscopy. The melanocyte distribution on the brain envelope and mesenterial vessels was determined. The morphology and ultrastructure of melanocytes in various tissues were studied. On the base of our results and literary data, the problem of functioning of melanocytes in vessels of internal organs is discussed.