Chromosome 21 mosaicism. A review

Despite the great efforts contributed to studies on the trisomy 21 etiology, basic mechanisms of nondisjunction are still poorly understood. Even less is known about mosaic variant of trisonomy 21. In this paper, some problems of masaicism are considered: (1) estimation of the prevalence of mosaicism in patients affected with Down syndrome, (2) determination of population rate of parental mosaicism, (3) evaluation of the role of ovarian mosaicism in etiology of Down syndrome, (4) origin of the extra chromosome, (5) mechanisms of production of mosaic lines, (6) phenomenon of skewed sex ratio (female predominance, in fetuses particularly), (7) effect of maternal age.     

The AtC-VPS protein complex is localized to the tonoplast and the prevacuolar compartment in arabidopsis

Plant cells contain several types of vacuoles with specialized functions. Although the biogenesis of these organelles is well understood at the morphological level, the machinery involved in plant vacuole formation is largely unknown. We have recently identified an Arabidopsis mutant, vcl1, that is deficient in vacuolar formation. VCL1 is homologous to a protein that regulates membrane fusion at the tonoplast in yeast. On the basis of these observations, VCL1 is predicted to play a direct role in vacuolar biogenesis and vesicular trafficking to the vacuole in plants. In this work, we show that VCL1 forms a complex with AtVPS11 and AtVPS33 in vivo. These two proteins are homologues of proteins that have a well-characterized role in membrane fusion at the tonoplast in yeast. VCL1, AtVPS11, and AtVPS33 are membrane-associated and cofractionate with tonoplast and denser endomembrane markers in subcellular fractionation experiments. Consistent with this, VCL1, AtVPS11, and AtVPS33 are found on the tonoplast and the prevacuolar compartment (PVC) by immunoelectron microscopy. We also show that a VCL1-containing complex includes SYP2-type syntaxins and is most likely involved in membrane fusion on both the PVC and tonoplast in vivo. VCL1, AtVPS11, and AtVPS33 are the first components of the vacuolar biogenesis machinery to be identified in plants.     

On the effect of cholesterol on the fate of CYP11A1 imported into yeast mitochondria in vivo

It has earlier been shown that CYP11A1 (cytochrome P450scc precursor), synthesized in yeast cells, is imported into yeast mitochondria. However, in large part the foreign protein undergoes degradation or aggregates. In this work, we tried to prevent aggregation of CYP11A1 and stimulate its insertion into the mitochondrial inner membrane by substituting cholesterol (a substrate for cytochrome P450scc) for ergosterol in yeast cells. To this end, an ergosterol-deficient Saccharomyces cerevisiae mutant, growing in the presence of cholesterol and expressing a modified bovine CYP11A1 gene, was used. Under defined conditions, the mitochondrial respiratory system developed in this yeast and CYP11A1 with the CoxIV targeting presequence was imported into the mitochondria, being then proteolytically processed. However, substitution of cholesterol for ergosterol did not result in lowered aggregation of the imported CYP11A1 and its increased content in the SMP fraction. Hence, the presence of cholesterol is not instrumental in proper intramitochondrial compartmentalization and folding of CYP11A1.     

Induction of permeability of the inner membrane of yeast mitochondria

The current view on apoptosis is given, with a special emphasis placed on apoptosis in yeasts. Induction of a non-specific permeability transition pore (mPTP) in mammalian and yeast mitochondria is described, particularly in mitochon-dria from Yarrowia lipolytica and Dipodascus (Endomyces) magnusii yeasts, which are aerobes possessing the fully competent respiratory chain with all three points of energy conservation and well-structured mitochondria. They were examined for their ability to induce an elevated permeability transition of the inner mitochondrial membrane, being subjected to virtually all conditions known to induce the mPTP in animal mitochondria. Yeast mitochondria do not form Ca²⁺-dependent pores, neither the classical Ca²⁺/P_i-dependent, cyclosporin A-sensitive pore even under deenergization of mitochondria or depletion of the intramitochondrial nucleotide pools, nor a pore induced in mammalian mitochondria upon concerted action of moderate Ca²⁺ concentrations (in the presence of the Ca²⁺ ionophore ETH129) and saturated fatty acids. No pore formation was found in yeast mitochondria in the presence of elevated phosphate concentrations at acidic pH values. It is concluded that the permeability transition in yeast mitochondria is not coupled with Ca²⁺ uptake and is differently regulated compared to the mPTP of animal mitochondria.     

Description of rearrangement of distraction reclaim in the extension of the lower extremities and elimination of their deformity in patients with various etiology of shortening

The data of X-ray and computed tomographic studies of a long tube distraction reclaim were analyzed in 80 patients who had limb shortening and deformity of varying etiology. The analysis has shown that during distraction there is a positive correlation between the increase in the connective-tissue interlayer area of a distraction reclaim and the overall increase in the area of the distraction reclaim (their ratio is not greater than 30% under the optimal elongation conditions). During fixation there is a decrease in the ratio of the area of a growth zone to the total area of a reclaim and in its total density with a parallel increase in the density of cortical laminae of a newly formed bone. Complete organotypic rearrangement comes to the end in the range of 1-3 years depending on the magnitude of pathomorphological and biomechanical changes and limb function.     

Effect of Chitosan as Part of Biologically Active Feeding BiHit on Economically Useful Features of Bees

Applied Biochemistry and Microbiology - Currently biostimulants based on chitosan and its derivatives are increasingly used in veterinary medicine. Chitosan and its modifications have many...     

Psychophysiological Indicators of Postural Control. Contribution of the Russian Scientific School. Part I

Human Physiology - This article aimed to systematically review the published results of studies of psychophysiological mechanisms of posture maintenance and identify the key factors that influence...     

Ethylene synthesis in petunia stigma tissues governs the growth of pollen tubes in progamic phase of fertilization

In the pollen-pistil system of petunia (Petunia hybrida L.) self-compatible and self-incompatible clones within 7 h after self-pollination, we determined the content of ACC (1-aminocyclopropane-1-carboxylic acid), the activity of two enzymes (ACC synthase and ACC oxidase), and the rate of ethylene production. Depending on the type of pollination, germination of pollen on the stigma surface and the pollen tube growth in the tissues of style were accompanied by different levels of ACC and ethylene release. The pollen-pistil system of the self-compatible clone contained twice more ACC than in the self-incompatible clone, whereas the pollen-pistil system in the self-incompatible clone produced 4–5 times more ethylene than in the self-compatible clone. For both types of pollination, ACC and ethylene were predominantly produced in the stigma tissues. The rate of ethylene production therein was 50 times greater than in the styles and ovaries, and the content of ACC was 100 times higher than in the styles and ovaries. Germination of male gametophyte after both types of pollination was accompanied by elevated ACC synthase activity (especially in the case of compatible pollination), whereas notable increase in ACC oxidase activity was manifested in growing pollen tubes after self-incompatible pollination