Interaction of epithelial cells with the edges of fluid and solid lipid films

Capping of Concanavalin A (Con A) on the surface of epithelial cells near the cell-cell contacts has been compared with that in the regions of cell contacts with the edges of lipid films. If the lipids are in "fluid" state, Con A is capped likely as on the free edges of epithelial sheets, while contacts with the edge of solid lipid film inhibit capping of Con A as do cell-cell contacts. The same is true for capping of liposomes adsorbed on the surface of epithelial cells. We suppose that solid rather than fluid domains in plasma membranes may play a significant role in establishing cell-cell contacts.     

Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections

A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusabler ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A.V. Somlyo, and A.P. Somlyo. 1976. Ultramicros. 1:317-339.) of freeze-dried ultrathin cryto sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of CI in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition if striated muscle. There was no evidence of sequestered CI in the terminal cisternae of resting muscles, although calcium (66mmol/kg dry wt +/- 4.6 SE) was detected. The values of [C1](i) determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial Ci ratio of 2.4 +/- 0.88 SD. The elemental concentrations (mmol/kg dry wt +/- SD) of muscle fibers measured with 0.5-9-μm diameter electron probes in normal frog striated muscle were: P, 302 +/- 4.3; S, 189 +/- 2.9;C1, 24 +/- 1.1;K, 404 +/- 4.3, and Mg, 39 +/- 2.1. It is concluded that: (a) in normal muscle the "excess CI" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic C1 in low [K](0) solutions exceeds that predicted by a passive electrochemical distribution. Hypertonic 2.2 X NaCl, 2.5 X sucrose, or 2.2 X Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P = approximately (6 Ca + 1 Mg)/6P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules.     

Plant virus infection development as affected by heavy metal stress

The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants.     

Genetic divergence in the tribe Electronini (Myctophidae)

To reveal evolutionary relationships and the rate of divergence of lanternfishes in the tribe Electronini (Myctophidae), analysis of sequence of cox 1 mtDNA fragment in three genera (12 species) of the tribe and in a closely related genus Myctophum (9 species) was performed. The results support the tribe monophyly; however, the divergence within it appeared to be not profound: genetic distances between genera and subgenera are smaller than between species within Myctophum and other genera of myctophids. In subgenera of Protomyctophum, species formation has obviously not completed since interspecies distances in them (0.5–4.7%) are comparable to estimates of intraspecific variation in other lanternfishes. Minimal genetic differences were found between species P. (Hierops) arcticum and P. (H.) subparallelum, whose ranges at the present time are isolated in the northern and southern hemispheres. After calibration of the molecular clock, the time of isolation of these two species can be dated to the Middle Pleistocene. Weak tribe diversification indicates its evolutionary youth, which can be related to the absence of efficient hydrographic barriers for isolation. The data obtained do not permit to consider tribe members as the most primitive in the family Myctophidae.     

A novel feeder-free system for human embryonic stem cells and characterization of their sublines with autogenic and allogenic cultivation

We developed a feeder-free system for human embryonic stem cells (ESCs) based on extracellular matrix protein (ECM) as the substrate. ECM was synthesized by mesenchymal stem cells (SC5-MSC) derived from an original ESC line, SC5. The ECM proteins fibronectin and laminin facilitate ESC growth in the feeder-free system. An important component of this system is a conditioned medium from SC5-MSC cells. Two ESC sublines were obtained: SC5-FF cells were cultured in an autogenic, and SC7-FF in an allogenic, feeder-free system. SC5-FF and SC7-FF underwent more than 300 and 115 population doublings, respectively, and retain a normal diploid karyotype. Histochemical and immunofluorescence assays showed that both sublines express undifferentiated ESC markers—alkaline phosphatase, Oct-4, SSEA-4, and TRA-1-81—as well as multidrug resistance transporter ABCG2. PCR assay revealed that undifferentiated SC5-FF cells, like the original SC5 line, maintained on feeder cells express OCT4 and NANOG genes common for somatic cells and DPPA3/STELLA and DAZL genes common for germ line cells. Expression of these genes was gradually diminished during differentiation of embryoid bodies, whereas expression of genes specific for early differentiated cells increased: GATA4, AFP (extraembryonic and embryonic endoderm), PAX6 (neuroectoderm), and BRY (mesoderm). ESC properties (karyotype structure, average time of population doubling, undifferentiated cell number in population) of the SC5 and SC7 and SC5-FF and SC7-FF sublines derived from original ESCs were not altered. It shows that the feeder-free systems, which are more stable than any feeder systems, maintain key ESC properties and may be recommended for fundamental, biomedical, and pharmacological studies performed with human ESCs.     

Reproductive Strategies and the Origin of Parapatric and Sympatric Forms of Arctic Charr Salvelinus alpinus (Salmonidae) in the System of Lakes Bol’shoe Leprindo and Maloe Leprindo (Northern Transbaikalia)

Journal of Ichthyology - In the system of lakes Bol’shoe Leprindo and Maloe Leprindo (Lena basin, Transbaikalia), spawning of two isolated populations of the dwarf form of Arctic charr...     

Population Genetic Diversity of Arctic Cod (Boreogadus saida) of Russian Arctic Seas

Journal of Ichthyology - We present the data on genetic variation of Arctic cod Boreogadus saida assessed using seven microsatellite loci in four samples collected in the Kara, Laptev, and...     

Bioenergetics of <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> Cells Grown at Alkaline Conditions

Energy status of the novel alkalitolerant Yarrowia lipolytica yeast strain grown at alkaline conditions (pH 9.7) was examined. Cells grown under such severe conditions were found to preserve high respiratory activity. The oxidative phosphorylation system dominated in the energy budget of the cell. A procedure was specially design to isolate tightly coupled mitochondria from yeast cells grown at alkaline conditions. The isolated mitochondrial preparations met known criteria of physiological intactness, as inferred from their ability to maintain distinctive state 4–3 respiration transition upon addition of ADP, high respiratory rates, good respiratory control values, and ADP/O ratios close to the theoretically expected maxima for the substrates used.     

Cross-Talk between Reactive Oxygen Species and Calcium in Living Cells

The results of many investigations have shown that calcium is essential for production of reactive oxygen species (ROS). Elevation of intracellular calcium level is responsible for activation of ROS-generating enzymes and formation of free radicals by the mitochondria respiratory chain. On the other hand, an increase in intracellular calcium concentration may be stimulated by ROS. H₂O₂ has been recently shown to accelerate the overall channel opening process in voltage-dependent calcium channels in plant and animal cells. The 1,4,5-inositol-triphosphate-receptors as well as the ryanodine receptors of sarcoplasmic reticulum have also been demonstrated to be redox-regulated. Activity of Ca²⁺-ATPases and Na²⁺/Ca²⁺ exchangers of animal cells are modulated by the intracellular redox state. Simultaneously, Ca²⁺ may activate antioxidant enzymes, such as plant catalase and glutathione reductase, and increase the level of superoxide dismutase in animal cells. Reviewed data support the speculation that Ca²⁺ and ROS are two cross-talking messengers in various cellular processes.