Bicarbonate protects the water-oxidizing complex of photosystem II against thermoinactivation in intact <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> cells

Currently available data about bicarbonate (BC) action on the Mn-containing water-oxidizing complex (WOC) of the photosystem II (PSII) were obtained almost solely in vitro, e.g. on subchloroplast membrane fragments enriched with PSII. To investigate the in vivo BC effect on the PSII donor side, we used the method of dark thermoinactivation of intact Chlamydomonas reinhardtii cells. Photosynthetic activity of PSII was measured as photoinduced changes in the PSII chlorophyll fluorescence yield and as the rate of photosynthetic oxygen evolution. To exclude a “direct” effect of the absence of BC on the PSII activity, before measurements of the photosynthetic activity, the concentration of BC in all samples was equalized by addition of NaHCO₃ to each of them (except for those that contained 5 mM of NaHCO₃ during thermoinactivation) to reach the final concentration of 5 mM. This allowed registering only so-called “irreversible” (i.e., not reversible by subsequent addition of BC) effect of the absence of BC during thermoinactivation. It was shown that, if 5 mM NaHCO₃ was added to the medium before thermoinactivation, the rate of inactivation of the PSII donor side was lower than in BC-depleted medium 1.5-to 2-fold. The obtained results are interpreted as an indication that BC protects the donor side of PSII against thermoinactivation in vivo, in intact C. reinhardtii cells. This proves the correctness of the earlier proposition that BC is an integral constituent of the Mn-containing water-oxidizing complex of PSII. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 3, pp. 342–349. The article was translated by the authors.     

Serum levels of immunoglobulins, allergen-specific IgE antibodies, and interleukin-4 in cosmonauts before and after short flights on the International Space Station

Serum levels of immunoglobulins G, A, M, and E (IgG, IgA, IgM, and IgE, respectively); allergenspecific IgE antibodies; and interleukin-4 (IL-4) were measured in ten cosmonauts before and after flights of 7–11 days on the International Space Station. These relatively short spaceflights did not cause any significant changes in the parameters tested. No linear correlation was found between the serum levels of total IgE and IL-4 for either the pre-or the postflight period.     

Delayed termination of nuclear histone doubling after premeiotic DNA synthesis inTriturus vulgaris male meiosis

It has been shown by means of double wavelength cytophotometry of DNA (Feulgen reaction) and histone (fast green, pH 8.2) inTriturus vulgaris spermatocytes that the doubling of DNA content in nuclei terminates at the end of preleptotene to beginning of leptotene whereas the doubling of histone content begun at premeiotic interphase is delayed and proceeds till the end of leptotene to beginning of zygotene. As a result preleptotene spermatocytes contain approximately 4C DNA and only 3C histone. Histone content in leptotene amounts to 93% of 4C, and in zygotene, pachytene and metaphase I both DNA and histone contents equal 4C. Thus, the temporal pattern of nucleo-histone doubling in meiotic chromosomes ofT. vulgaris differs from the synchronous DNA and histone doubling in mitotic chromosomes of all previously studied species. The delay of histone doubling inT. vulgaris meiocytes is less pronounced than in the previously studied insectsAcheta domestica andPyrrhocoris apterus where the histone content amounts to 3C in leptotene—zygotene and the equal histone/DNA ratio is restored only in pachytene.—Responsibilities for this phenomenon and its biolgoical sinnificance are discussed in connection with recent hypotheses concerning mechanisms of homologous chromosome pairing.     

Photodynamic injury to heated leaves

Summary The leaves of Tradescantia fluminensis Vell, were kept in light and darkness after short-term heating (5 min and 10 min) at different temperatures. In light temperature causing injury was 10° lower than in darkness. A considerable destruction of chlorophyll occurred when the heated leaves were kept in light. If the light intensity was 4,000 lux or even lower the damage to cells was not accompanied by bleaching of chlorophyll. Light produced no effect on unheated leaves. In variegated white-green leaves of Chlorophytum elatum R. Br. light injured only green parts of leaf blades. The minimal light intensity which brought about injury of Tradescantia leaves in experimental conditions was 1,000 lux. Light of the same intensity accelerated death of heated isolated leaves of Cucumis sativus L.Light damage to Tradescantia leaves occurred when the action of light was accompanied by that of high temperature.In an atmosphere of nitrogen the injurious effect of light sharply decreased.It is suggested that the injury of heated leaves in light is caused by photooxydation which is sensitized by chlorophyll and occurs at the expense of photochemical energy which is not used in photosynthesis. Photosynthesis itself is repressed by heating.     

Toll-Like Receptors in Peripheral Blood Cells of Cosmonauts after Long-term Missions on Board the International Space Station

Studies of Toll-like receptors (TLR) in 20 cosmonauts, members of long-term (124- to 199-day) missions on board the International Space Station showed changes in the relative and absolute counts of peripheral blood monocytes with TLR2, TLR4, and TLR6 on their surface, expression of genes TLR2 and TLR6, as well as genes of molecules involved in the TLR signaling pathway and TLR-related NF-κB-, JNK/p38- and IRF pathways on the day of return to Earth. The observed changes displayed individual variability.     

Bone Mineral Density and Molecular Genetic Markers of Bone Remodeling in Blood of Cosmonauts after Long-term Missions on Board the International Space Station

The results of the investigation of the bone system of 24 Russian cosmonauts after long-term (124–199 days) missions on board the International space station (ISS) are presented. Functional adaptation of the bone system involves some complex changes in the metabolic activity of osteoblasts and osteoclasts, such as alterations of the serum concentrations of osteocalcin, tartrate-resistant acid phosphatase (TRAP), osteoprotegerin, and the activator ligand of the receptor of nuclear factor kappa-B (RANKL); in addition, in peripheral blood leucocytes, there are changes in the expression of genes regulating the development of skeletal system and bone mineral metabolism. Significant variability in the mineral density of femoral neck and molecular genetic markers studied after long-term space flights indicates individual variability of the balance of the processes of bone remodeling, bone formation and resorption. Significant bone mass losses in the femoral bone of cosmonauts are associated with more pronounced changes in the markers of metabolic activity of osteoclasts.     

The activation processes of the immune system during low intensity exercise without relaxation

The activation processes of T-, B- and NK-cells were studied during 8-week low intensity strength training without relaxation. After the long-term training, no changes occurred in the peripheral blood contents of the main subpopulations of immunocompetent cells (CD3+, CD4+, CD8+, CD19+ and CD16+/CD56+ lymphocytes) and serum levels of immunoglobulin A, M, and G. At the same time, training was accompanied by positive activation of the immunocompetent cells which was evident from increased percentage of CD3+, CD19+ and /CD56+ cells expressing CD69 after activation (PHA, PW and II.2, respectively). The final period of the training course was also associated with a decrease in the level of lymphocyte apoptosis and increase of proliferative responses of lymphocytes.     

Effect of water activity and relative air humidity on the growth of Penicillium chrysogenum thom, Aspergillus repens (Corda) Sacc., and Trichoderma viride Pers. isolated from living spaces

Original data on the growth parameters of the fungi Penicillium chrysogenum Thom, Aspergillus repens (Corda) Sacc., and Trichoderma viride Pers. isolated from living spaces in Moscow are presented. Spore germination, fungal growth, and the radial growth rate of the colonies were investigated upon cultivation on agarized nutrient media with different water activity (a_w) values. Spore germination and fungal growth were studied in house dust under laboratory conditions at different relative air humidity (RH). It was shown that, at decreased a_w and RH, the spore germination time increased, as did the period from germination to mycelium and conidia formation, while the radial growth rate of colonies decreased. House dust was found to be a suitable growth substrate for A. repens and P. chrysogenum, supporting their complete life cycle. It was suggested that house dust is unsuitable as a substrate for the growth of T. viride. The a_w and RH ranges for development of these micromycetes were determined. On this basis, the A. repens, P. chrysogenum, and T. viride strains isolated from living spaces were identified as xerophilic, xerotolerant, and hygrophilic ones, respectively.