Light scattering in the eye of the blowfly chalky mutant: the effect on spectral sensitivity of photoreceptors R1-6.

In non-pigmented insect eyes, stray light causes the narrowing of the spectral sensitivity functions of the visual cells, and this effect is shown to be a sensitive tool for estimation of the stray light absorption by a photoreceptor. Spectral sensitivity functions of single cells of Calliphora chalky mutants were obtained in three sets of experiments with different contribution of stray light in total light absorption by a visual cell, and the relative parasitic absorption due to stray light appeared to be as high as 70% of total absorption even with a point light source. The effect of light scattering may be of some functional significance in non-pigmented parts of the wild type eyes as, for instance, in the dorsal rim area of the crickets.

Electroantennogram of the American cockroach: effect of oxygen and an electrical model.

1. With a view to clarifying the role of oxygen in the olfactory reception of insects, the intact antenna of the male American cockroach (Periplaneta americana) was studied under normal conditions and during reversible anoxia, external or tracheal, using an electroantennogram (EAG) elicited by a sex pheromone stimulation. As a first step, the anatomical and electrical characteristics of the antenna were investigated. 2. Based on the microanatomical study, a cockroach antenna was characterized by structural parameters reflecting the haemolymph and gas exchange in the antenna. Valves in the wall of a haemolymphatic vessel were discovered. 3. The resting DC background voltage (DCBV) and the EAG were continuously recorded and proved to be more strongly affected by tracheal anoxia than by anoxia from the outside. 4. A minimal electrical model of the antenna based on the Thurm-Kaissling-De Kramer equivalent circuit of a sensillum was shown to be valid to explain the origin of the DCBV and EAG as well as their changes after oxygen cutoff and resumption. 5. Two formal opposing processes, excitation and desensitization, probably related to the receptor mechanisms, have been used to interpret the kinetics of the EAG and the effect of anoxia on EAG parameters. The desensitization is thought to be more sensitive to oxygen lack than the excitation.

[Changes in the functional characteristics of the compound eye of the honeybee after mutations interfering with the metabolism of tryptophan]. / Izmenenie funktsional'nykh kharakteristik slozhnogo glaza medonosnoi pchely vsledstvie mutatsii, narushaiushchikh obmen triptofana.

The compound eye of worker honeybees with a genetic interruption of the ommochrome synthesis from tryptophan (mutations snow an laranja) showed a sharp increase in light sensitivity, more than 100-fold in snow and more than 10-fold in laranja with respect to the wild bee eye. Peaks of the spectral sensitivity curves recorded using ERG were shifted to 530 nm in snow and 550 nm in laranja while in the wild type it was at 545 nm. An unusual shape of the ERG in the both mutants was shown to result from an additional component of the receptor potential, the spike, which has been never observed in the normal bee eye. Since the pigment granules of ommatidium in both snow and laranja were strongly defective or immature due to blocking a normal process of ommochrome formation, It is suggested that the ommochrome granules, apart of their light protective functions, can be involved in biochemical process underlying the electrical passivity of the photoreceptor membrane.

[Peculiarities of transmission of the receptor signal in photoreceptors]. / Osobennosti peredachi retseptornogo signala v fotaretseptorakh.

These ability of photoreceptors to respond to single photons by single electrical events was shown to underlie an astonishing combination of electrotonic transmission of the receptor signal with the impulse principle of its coding. During functional evolution of photoreceptors, the discrete nature of the light itself made it unnecessary for photoreceptors to evolve the spike generating mechanism inherent in other primary sensitive receptors.

The structural and functional organization of the vestibular apparatus of rats exposed to weightlessness for 20 days on board the Sputnik "Kosmos-782".

This investigation of the vestibular apparatus of rats exposed for 20 days to weightlessness on board an earth satellite and to acceleration during take-off and landing has revealed a set of changes in the structural and functional organization, such as adjoinment of the otolith to the utricle receptor surface and peripheral localization of the nucleoli inside the receptor cells' nuclei. Destruction of some receptor cells, apparently due to increased swelling of the vestibular apparatus tissue and alteration of the shape and structure of the otoconia were observed. In the horizontal crista, detachment of the cupula took place.

[Polarization and spectral sensitivity of individual house cricket photoreceptors]. / Poliarizatsionnaia i spektral'naia chuvstvitel'nost' odinochnykh fotoretseptorov domovogo sverchka.

Polarization and spectral sensitivities of single photoreceptors of a house-cricket were measured. Morphologically, the cricket rhabdom is a symmetric model in which the polarization sensitivity of a single photoreceptor is equal to the dichroic ratio of a single microvillus. The spectral sensitivity curves of all the photoreceptors measured (24 cells) appeared to be similar and showed the main peak of sensitivity at 500 nm and the secondary peak at 360 nm--the situation reminding properties of vertebrate rhodopsin. The polarization sensitivity measured was equal to 2.28 +/- 0.85 (mean for 70 cells +/- standard deviation). This value is in favour of small preferential orientation of the dipole moments of the pigment molecules along the microvillar axes.

The role of gravity in the phylogeny of structure and function in animal sensors of spatial orientation, and their predicted action in weightlessness.

The evolution of the structural, functional and cytochemical organization of the gravity receptor which determines a body position in the gravitational field of the earth by means of muscular regulation was traced both invertebrates and vertebrates, using electron microscopic and histochemical methods. In the course of evolution of vertebrates, the specialized gravity receptor-statocyst which, as a rule, consists of primary sensory cells and supplies otoliths, is formed. In vertebrates, there exists a vestibular apparatus made up of secondary sensory cells and also having otoliths. The receptor cells, both of statocysts and the vestibular apparatus, are supplied with special antennas (kinocilia and stereocilia). Deviation of the antennas stimulated by displacement of the otoliths resulting from locomotor activity of animals leads to excitation of the receptor cells. When exposed to a modified gravitational field (linear accelerations of 10 g, for 3 min), the receptor cells of the vestibular apparatus, in all classes of vertebrates, show progressive changes in RNA content and protein synthesis (increase followed by decrease) which return to normal only after 12 days. Thus, immediate transfer of animals and man from acceleration to weightlessness appears to be a reason for movement disease. The above consideration showed the need for an experiment in which an animal (with its vestibular apparatus) which had not undergone previous accelerations, would be exposed to weightlessness. Frog embryos, Rana temporaria, at the stage preceding the organogenesis, when the vestibular apparatus and other organs were lacking, were chosen as a suitable subject. Frog embryos at the stage of an early gastrula were placed in a special container Emkon aboard the Soyuz 10 spacecraft. After short accelerations, they were exposed to weightlessness for 44 hours. The embryos were allowed to continue to develop to the stage of early tail bud. The experimental embryos showed normally developed acoustic vesicles and vestibular ganglia. Clear differentiation of the receptor cells with antennas (kinocilia and stereocilia) was found in the acoustic vesicles. Thus, in weightlessness, vestibular apparatus develops just as well as in the gravitational field of the earth. However, only a much longer stay in weightlessness conditions will indicate whether there are any changes in the structural, cytochemical and functional organization of vestibular apparatus. The similarity in the structural, functional and cytochemical organization of the gravity receptor in vertebrates and invertebrates appears to allow the prediction of the behaviour of the gravity receptor as a whole, and of its receptor elements, both in normal and changed gravitational fields. The first attempts were carried out only on the vestibular apparatus of vertebrates.