Valentina P. Bozhkova

Mesoderm differentiation in explants of carp embryos.

An analysis of carp blastoderm development was carried out in culture after isolation from the yolk cell and its yolk syncytial layer (YSL). The blastoderms were separated from the YSL at four different stages of embryogenesis: the blastula, early epiboly, early gastrula and late gastrula stages. Absence of the YSL in explants was checked by scanning electron microscopy. From observations of living embryos and histological examination of tissues which were formed in explants from all stages studied it was observed that they contained notochordal, muscle and neural tissue as signs of dorsal types of differentiation. Only in explants from the early and late gastrula stages were histotypical tissues organized in an embryonic-like body pattern. The data indicate that mesoderm differentiation in fish embryos is independent from the YSL, contrary to normal pattern formation which needs the presence of the YSL before the onset of gastrulation.

Spatial-temporal characteristics of intercellular junctions in early zebrafish and loach embryos before and during gastrulation.

Abstract Injections of lucifer yellow and fluorescein dyes into loach (Misgurnus fossilis) and zebrafish (Danio rerio) embryos were used to analyse the intercellular communication via gap junctions (GJs) and their role in morphogenetic processes during the period from early blastula to late gastrula. It is shown that the efficiency of dye transfer between the superficial blastomeres increases by the late blastula stage. Blastomeres of the basal layer, on the other hand, become gradually uncoupled from the yolk cell (YC). This process is spatially uneven and finishes by the late gastrula stage. Prior to it, at the early epiboly stage, a local increase in dye transfer is observed in the circular zone of the blastoderm margin. During gastrulation, GJ communication between blastomeres and the YC in this zone and also in the newly-formed germ ring region (the prospective mesoderm domain) persists for a longer period of time (up to the stage of 60–70% epiboly) than in the remaining part of the basal layer (the prospective ectoderm domain). Taking into account the data on changes in the adhesive properties of blastomeres during normal development and observations on embryos with retarded epiboly, we hypothesize that changes in GJ communication between superficial blastomeres, on one hand, and between basal blastomeres and the YC, on the other, are the consequences of the same, more general morphogenetic process of compaction occurring within the blastoderm, which supports epiboly and is probably responsible for the distinction between mesodermal and ectodermal fates of cells differently located within the forming epithelioid sheet.

Characteristics of smooth pursuit in children and adults in apparent motion tests

The efficiency of smooth pursuit was estimated in healthy young subjects (college and school students) by a contactless method based on stroboscopic stimulation causing an illusion of smooth motion of an object. Stable individual differences in the smooth pursuit efficiency were found in both children and adults. Eleven-to 12-year-old children exhibited, on average, a less smooth pursuit of stimuli moving horizontally at velocities of 6–17 deg/s than young adults did.

Smooth Pursuit In Human Vision And Possibilities Of Its Simulation

Possible advantages of bionic models based on the algorithms of human vision are discussed. Experimentally it was demonstrated that when observing moving objects the human vision system estimates the dynamic characteristics of the object and can program smooth pursuit on the basis of those. The programmed pursuit considerably widens the capabilities of the foveal vision system.

Smooth Pursuit in Elderly Adults Studied With Apparent Motion.

The variability of smooth pursuit eye movements was studied in a group of healthy subjects for horizontal apparent motion by a method that does not require direct measurements of eye movements. It was found that the individual smooth pursuit efficiencies for binocular perception in group of healthy elderly subjects (mean age 61 years) as well as in the group of healthy young adults were distinctly differentiated. Furthermore, we have not detected any age-related decrease in the fraction of subjects showing high smooth pursuit efficiencies. This fact demonstrates that the human oculomotor system is relatively resistant to the effects of aging. At the same time, an appreciable increase of percentage of persons with directional asymmetry of smooth pursuit has been found among elderly adults. A higher smooth pursuit efficiency was noticed reliably more often in the direction from left to right rather than in the opposite direction. Subject eye movements were recorded with i-View XTM Hi-Speed 1250 eye tracking system (SMI Inc.). These records confirmed that the smooth pursuit accuracy of older adults is less than that of young persons, at least in some directions of tracking.

Frequence and the mutation spectrum of GJB2-related hearing loss in children of Dagestan as compared with the central European part of Russia

The sequencing of the entire coding region and the donor site of the splicing of the GJB2 gene has shown that prelingual neurosensory nonsyndromic autosomal recessive deafness/poor hearing in Dagestan Republic is genetically more heterogeneous than in the central European part of Russia. Thus, the number of the revealed mutations in the GJB2 gene in Dagestan was only 28% of the total number of alleles in patients tested. The main mutations in the GJB2 gene in Dagestan were represented by three forms typical for West Asia: 35delG mutation (22% of all mutant alleles), ΔE120 mutation (22%), both in the coding region, and IVS 1+1 G>A (44%) in the donor site of splicing. In addition, a novel mutation, ΔE187, was revealed in the coding region. All mutations were found in a compound heterozygous or a heterozygous state. This result allows one to explain the deafness/poor hearing by pathogenic mutations in the GJB2 gene only in 19% of Dagestan families with neurosensory nonsyndromic autosomal recessive disorders of hearing. We suggest that the origin and maintenance of the allele diversity of inherited deafness/poor hearing in Dagestan can be explained by the national and cultural peculiarities of small populations of nations of North Caucasus.

Comparison of characteristic of smooth pursuit in left-handed and right-handed subjects

In a study on healthy young adults with the use of a stroboscopic stimulation, estimation of the efficiency of smooth pursuit has been performed. The influence of manual function asymmetry on smooth pursuit has been studied. It has been shown that markedly right-handed (“strong right-handed”) persons display a high efficiency of smooth pursuit of stimuli moving horizontally in the rightward and leftward directions with velocities of 20°/s and 25°/s. Left-handed persons track similar stimuli, on average, worse than the “strong right-handed” ones. The influence of manual function asymmetry on the dependence of the smooth pursuit efficiency on the moving stimuli direction (left to right or right to left) has not been observed.

Lateral mobility of plasma membrane proteins in dividing eggs of the loach (Misgurnus fossilis): Regional differences and changes during the cell cycle

Regional differences in lateral diffusion rates of fluorescence-labeled proteins have been studied in the plasma membrane of dividing eggs of the loach (Misgurnus fossilis) by fluorescence recovery after photobleaching (FRAP). Apparent animal-vegetal differences in fluorescence intensity, lateral diffusion coefficients, and fractions of mobile proteins have been found, with all these quantities being higher in the animal pole region than in the yolk region. Cyclic changes in protein diffusion coefficients and mobile fractions during the first few cell cycles have also been recorded. Soon after the end of a cleavage, the diffusion coefficient reaches its minimal value and increases rapidly before the next cleavage.