[Study of the structure of receptor organs of the vestibular apparatus of rats after space flight on "Kosmos-1667"]. / Issledovanie struktury retseptornykh organov vestibuliarnogo apparata krys posle poleta na biosputnike "Kosmos-1667".

The receptor organs of the vestibular apparatus of rats flown for 7 days on Cosmos-1667 were examined. Serial sections were examined by light microscopy, some utriculus sections by electron microscopy, and otolith membranes by scanning electron microscopy. The fixation method used revealed a distinct structural heterogeneity of the receptor epithelium. In the striola area of the utriculus and sacculus as well as in the central apical area of cristae there are receptor cells surrounded by enlarged cup-like nerve endings. The nerve endings occupy over 70% of the cup-receptor cell complex. The area incorporating the enlarged nerve endings differs in size from animal to animal and from left to right ear in the same animal. The flown rat that was the first to be killed after recovery showed a very well pronounced asymmetry: in the right ear enlarged cups were seen all over the epithelium while in the left ear they were located in distinct spots. Since such changes were not identified in the remaining flown and control rats, it is concluded that they were produced by space flight effects but remained reversible and disappeared after recovery. This paper describes the causes responsible of the changes and their structural and functional relevances as well as other structural modifications that should be considered during vestibular studies.

[Changes in the otolithic apparatus of rats and fish after long-term rotation with increased acceleration]. / Izmeneniia v otolitovom apparate krys i ryb posle dlitel'nogo vrashcheniia pri povyshennoi sile tiazhesti.

Otolith membranes of the utriculus and sacculus of rats exposed to 2 g during a month showed a typical size-related distribution of otoconia, which had optic activity. The length (L) and diameter (D) of utricular otoconia were linearly correlated as follows: D = 0.4 + + 0.4 L (microns). During chronic acceleration the mean size of utricular otoconia tended to diminish. Guppy fish were rotated at 1.8-2.2 g for 4 months and showed an absolute and a relative increase of the saccular mass when compared to the mass of the utricular or lagenar otolith. During chronic centrifugation the microrelief of the auditory sulcus of the saccular otolith changed. It can be concluded that prolonged centrifugation causes structural changes in the otolith apparatus of terrestrial and water animals which are probably of adaptive character.

[Scanning electron microscope study of the labyrinth of Macaca mulatta under hypokinetic conditions]. / Issledovanie s pomoshch'iu skaniruiushchego mikroskopa labirinta makak Macaca mulatta, nakhodivshikhsia v usloviiakh gipokinezii.

Rhesus monkeys have been kept in horizontal position under klinostatic or antiorthostatic hypokinetic conditions for 7 and 19 days. Using scanning electron microscope, studies were made of the otolithic membrane of the utricle, the receptor surface of the utricle, crista ampullaris of the lateral semicircular canals, the organ of Corti, the stria vascularis and spiral ligament. No significant differences were found between control and experimental animals.

[Receptor surface of Corti's organ in guinea pig embryos]. / Issledovanie retseptornoi poverkhnosti kortieva organa émbrionov morskoi svinki.

Using scanning electron microscope, studies have been made of the structure of the receptive surface of the organ of Corti in 48- and 57-day old embryos of the guinea pig. It was found that some structural modifications take place in this period: the size and the number of microvilli in the supporting cells decrease, the width of the organ of Corti increases, the number of ball-like cytoplasmic protrusions from the cellular surface decreases, the number of kinocilia in the receptor cells is reduced. These processes are associated presumably with the development of Nuel's space, Corti's tunnel, the origin of flexible connection between the tectorial membrane and the receptive surface, as well as with maturation of the ionic composition of the inner ear fluid.

[The utricular otolith membrane in the guinea pig]. / Issledovanie otolitovoi membrany utrikuliusa morskoi svinki.

Several types of otoconia are present in the otolithic membrane of the utricle of fetal, young and adult guinea pigs. These include smooth, transitional and rough otoconia, and a few rhombohedrons. The smooth otoconia are nearly the same numeric fraction in all the specimens. The mean size of otoconia increases only during the course of gestation. Our measurements indicate that the diameter (d) and the length (l) of otoconia are related linearly as: d = 0.4l + 0.4. The smooth otoconia seem to be independent morphological form which is not derived from more "primitive", rough or transitional ones. The otoconia consist mainly of CaCO3 and contain Na, Mg and trace amount of K. The chemical composition of otoconia is similar in fetal, young and adult guinea pigs.

[Ultrastructural changes in the ovaries of chickens following exposure to x-rays]. / Ul'trastrukturnye izmeneniia v iaichnikakh tsypliat posle vozdeistviia rentgenovskimi luchami.

Changes in the ovaries of chicken embryos (17th day of incubation) and in 2-day-old chickens at different terms (2, 24, 72 h) were studied by light and electron microscopic methods after x-ray irradiation in the doses of 606 and 1200 rad. In oocytes of 17 embryos x-ray irradiation acts as an additional factor, enhancing and increasing the degree of chromatin condensation and producing earlier appearance of pachynema stage. In the ovarian oocytes, at diplonema stage, in 2-day-old chickens after irradiation, condensation of chromosomal substance is observed; in this case, irradiation produces a reverse action to that of normal despiralization. Ultrastructural changes in cellular organelles, in nuclear membrane, in particular, depend on the degree of oocyte differentiation and the irradiation dose applied. Within the terms of investigation, x-ray irradiation does not produce any considerable ultrastructural changes in the oocytes, but its disturbes the contacts between them and follicular cells, which is supposed to be the cause of oocyte destruction.