The Effect of Gases on the Structural Integrity of Ice that Forms when Water and Cryoprotective Solutions Are Frozen: An Optical-Microscope Study

Biophysics - The effects of air, helium, argon, xenon, and sulfur hexafluoride on the integrity of the ice structure formed when water and a cryoprotective solutions were frozen in the temperature...     

A shift in sensitivity to auxin within development of maize seedlings

The auxin-induced changes in cytosolic concentrations of Ca(2+) and H(+) ions were investigated in protoplasts from maize coleoptile cells at 3rd, 4th and 5th day of development of etiolated seedlings. The shifts in [Ca(2+)](cyt) and [H(+)](cyt) were detected by use of fluorescence microscopy in single protoplasts loaded with the tetra[acetoxymethyl]esters of the fluorescent calcium binding Fura 2, or pH-sensitive carboxyfluorescein, BCECF, respectively. Both the auxin-induced shifts in the ion concentrations were specific to the physiologically active synthetic auxin, naphthalene-1-acetic acid (1-NAA), and not to the non-active naphthalene-2-acetic acid (2-NAA). Regardless of the age of the seedlings, the rise in [Ca(2+)](cyt) was prior to the acidification in all investigated cases. The maximal acidification coincided with the highest amplitude of [Ca(2+)](cyt) change, but not directly depended on the concentration of 1-NAA. Within aging of the seedlings the amplitude of auxin-induced [Ca(2+)](cyt) elevation decreased. The shift in auxin-induced acidification was almost equal at 3rd and 4th day, but largely dropped at 5th day of development. The acidification was related to changes in the plasma membrane H(+)-ATPase activity, detected as phosphate release. The decrement in amplitude of both the tested auxin-triggered reactions well coincided with the end of the physiological function of the coleoptile. Hence the primary auxin-induced increase in [Ca(2+)](cyt), which is supposed to be an important element of hormone signal perception and transduction, can be used as a test for elucidation of plant cell sensitivity to auxin.     

Biosynthesis of phytohormones in algae

Like in the case of higher plants, algal growth and development are controlled by the hormonal regulatory system. Essentially all known phytohormones were identified in various algal taxa, and the range of their physiological activities was confirmed. At the same time, our knowledge of enzymes involved in the phytohormone synthesis in algae is rather limited. Data concerning genes encoding these enzymes are still more fragmentary. Current data about proteomes of some algae allow the revealing of amino acid sequences with homology to those of the higher plant enzymes and their conserved domains.     

Atopically transplanted thymus tissues are capable of distantly changing metabolic status of the organism

It has been demonstrated that an atopic transplantation of the thymus tissue from young animals in different variants decreased the rate of irreversible age-related atrophy of the thymus in a statistically significant manner. This retards an age-dependent degradation of the T-cell component of the immune system.     

Activity of Plasma Membrane H<Superscript>+</Superscript>-ATPase in Coleoptile Cells during Development of Maize Seedlings

Hydrolytic activities of the H⁺-ATPase were compared for plasma membrane fractions isolated from coleoptile cells of 3-, 4-, and 5-day-old etiolated maize seedlings. The membrane preparations obtained by differential centrifugation were additionally purified in the gradient of sucrose density and in the polyethylene glycol-dextran system. The highest level of ATP-hydrolyzing activity was observed in the plasmalemma fraction obtained from 4-day-old seedlings. The pattern of age-dependent changes in H⁺-ATPase activity of the plasma membranes was clearly different from the monotonic deceleration of coleoptile cell elongation in the period examined. It is supposed that changes in ATPase activity reflect different regulatory roles of this principal ion-transporting enzyme of the plasma membrane at the stage of cell elongation and at a later developmental stage when the coleoptile has completed its physiological function.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 566–572.Original Russian Text Copyright © 2005 by Rudashevskaya, Kirpichnikova, Shishova.     

The Effect of Helium on Cryopreservation of HeLa and L929 Cells

The effect of helium on cell survival during cryopreservation was studied using the HeLa and L929 cell lines. Cell suspensions were incubated in an atmosphere of helium, nitrogen, or air and frozen in the presence or absence of glycerol as a cryoprotectant. After thawing, the cell viability was evaluated by the Trypan Blue exclusion test and culture development for 18 h. Helium was found to provide better preservation of cell suspensions compared with nitrogen and air. The positive effect of helium was the greatest in the case of freezing without cryoprotectants (the HeLa cell survival increased by a factor of 1.5–2) and somewhat lower in the case of freezing in the presence of low glycerol concentrations (the L929 cell survival increased by a factor of 1.2–1.5 in the presence of 3% glycerol). Use of helium for cell suspensions may improve cryopreservation methods by making it possible to reduce the concentrations of conventional cryoprotectants, which are generally highly toxic and undesirable to use for cryopreservation of biological material for medical applications.     

Metabolomic and physiological changes of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> (Chlorophyceae,Chlorophyta) during batch culture development

During mixotrophic batch culturing, the microalga Chlamydomonas reinhardtii goes through S-shaped growth kinetics and cells consistently transit from division to death. Photosynthesis and respiration had two simultaneous maxima at the first half of the exponential growth phase and at the border of the stationary phase. GC-MS analysis detected about 300 compounds of which about 100 were identified. Differences in metabolite profiles were observed between cells sampled at different time points of the growth curve. Several data mining methods clearly indicated that metabolomes tended to group together in a time-dependent manner. Clustering analysis revealed three major groups of metabolites varied in concentration dynamic. The alterations in lipophilic compounds and carbohydrates took place even within the same phase of culture growth, which indicated complex rearrangements in cell biochemistry and physiology. Special attention was paid to alterations in the ratios between metabolite groups. The most significant ratio changes were discovered for pools of amino and fatty acids.     

Age- and Organ-Specific Differences of Potato (<Emphasis Type="Italic">Solanum phureja</Emphasis>) Plants Metabolome

Potato Solanum phureja Juz. & Bukasov crop species' metobolome at the flowering stage includes 234 compounds, 117 of which were identified. The most represented group among them contains sugars and their derivatives that are in accordance with intensive carbohydrate exchange of potato tissues and organs. Young leaves and developing reproductive organs are characterized by a wide spectrum of organic and amino acids, nitrogen-containing compounds, and lipids as well as compounds of secondary metabolism that may indicate the intensity of metabolic processes and the formation of defense mechanisms. Depletion of metabolites’ profile in senescent leaves agrees with the idea of weakening synthetic processes in them and the onset of metabolites’ outflow to new forming attracting potato organs. Specificity of metabolic profiles, which corresponds to age and physiological status of potato organ or tissue, was revealed.