Cell senescence is dependent on the arrest in cell cycle. Here we studied the role of mitochondrial retrograde response signaling in yeast cell survival under a prolonged arrest. We have found that, ...unlike G1, long-term arrest in mitosis or S phase results in a loss of colony-forming abilities. Consistent with previous observations, loss of mitochondrial DNA significantly increased the survival of arrested cells. We found that this was because the loss increases the duration of G1 phase. Unexpectedly, retrograde signaling, which is typically triggered by a variety of mitochondrial dysfunctions, was found to be a negative regulator of the survival after the release from S-phase arrest induced by the telomere replication defect. Deletion of retrograde response genes decreased the arrest-induced death in such cells, whereas deletion of negative regulator of retrograde signaling MKS1 had the opposite effect. We provide evidence that these effects are due to alleviation of the strength of the S-phase arrest.
The increase in the cost of fuel and energy resource and the deterioration of the environment from the combustion of traditional fossil fuel, have led to a great interest in energy-saving technology ...by using secondary energy resources in the thermal energy of industrial, housing and communal services using heat pump units in Russia and abroad. This paper analyzes the well-known two-stage heat pump units, and reveals their advantages in comparison with single-stage. The modeling of a highly efficient multistage vapor compression heat pump unit is proposed. Moreover, a method for calculating a multistage heat pump unit with a high coefficient of performance is presented. In addition, an example of calculating the thermodynamic cycle of a four-stage heat pump unit is presented. The influence of the number of stages on the increase in coefficient of performance in relation to a single-stage heat pump unit, the effect of the temperature difference between the temperature of the high-potential heat source and the temperature of the low-potential heat source on the coefficient of performance were analyzed. In addition, the influence of the initial value of the temperature of the high-potential heat source before heating during the course in the heat pump unit on the value of coefficient of performance for a different number of stages is analyzed under the condition of a constant difference between the heating temperature of the high-potential heat source at the outlet of the heat pump unit and the temperature of the low-potential heat source.
This work is devoted to the study of magnetic Fe
O
nanoparticles doubly coated with carbon. First, Fe
O
@C nanoparticles were synthesized by thermal decomposition. Then these synthesized ...nanoparticles, 20-30 nm in size were processed in a solution of glucose at 200 °C during 12 h, which led to an unexpected phenomenon-the nanoparticles self-assembled into large conglomerates of a regular shape of about 300 nm in size. The morphology and features of the magnetic properties of the obtained hybrid nanoparticles were characterized by transmission electron microscopy, differential thermo-gravimetric analysis, vibrating sample magnetometer, magnetic circular dichroism and Mössbauer spectroscopy. It was shown that the magnetic core of Fe
O
@C nanoparticles was nano-crystalline, corresponding to the Fe
O
phase. The Fe
O
@C@C nanoparticles presumably contain Fe
O
phase (80%) with admixture of maghemite (20%), the thickness of the carbon shell in the first case was of about 2-4 nm. The formation of very large nanoparticle conglomerates with a linear size up to 300 nm and of the same regular shape is a remarkable peculiarity of the Fe
O
@C@C nanoparticles. Adsorption of organic dyes from water by the studied nanoparticles was also studied. The best candidates for the removal of dyes were Fe
O
@C@C nanoparticles. The kinetic data showed that the adsorption processes were associated with the pseudo-second order mechanism for cationic dye methylene blue (MB) and anionic dye Congo red (CR). The equilibrium data were more consistent with the Langmuir isotherm and were perfectly described by the Langmuir-Freundlich model.
Abstract
Yeasts growing limited for nitrogen source or treated with fusel alcohols form elongated cells – pseudohyphae. Absence of mitochondrial DNA or anaerobic conditions inhibits this process, but ...the precise role of mitochondria is not clear. We found that a significant percentage of pseudohyphal cells contained mitochondria with different levels of membrane potential within one cell. An uncoupler carbonyl cyanide p (trifluoromethoxy) phenylhydrazone (FCCP), but not the ATP synthase inhibitor oligomycin D, prevented pseudohyphal growth. Interestingly, repression of the MIH1 gene encoding phosphatase activator of the G2/M transition partially restores the ability of yeast to form pseudohyphal cells in the presence of FCCP or in the absence of mitochondrial DNA. At the same time, retrograde signaling (the one triggered by dysfunctional mitochondria) appeared to be a positive regulator of butanol induced pseudohyphae formation: the deletion of any of the retrograde signaling genes (RTG1, RTG2, or RTG3) partially suppressed pseudohyphal growth. Together, our data suggest that two subpopulations of mitochondria are required for filamentous growth: one with high and another with low transmembrane potential. These mitochondria activated signaling pathways appear to converge at Mih1p level.
The budding yeast Saccharomyces cerevisiae actively transports adverse factors (e.g. oxidized proteins) from the daughter to mother cells. The transport is believed to ensure that the daughters are ...born "young", thus preventing clonal senescence. Is this the only reason for the existence of such transport? We subjected yeast cells to various stress conditions and compared survival of mother and daughter cells. It was found that replicative age-dependent mortality under our experimental stress conditions was U-shaped: the resistance of both virgin daughters and old mother cells (more than three bud scars) was lower compared to the young mothers. SIR2 mutants were shown to fail to maintain the mother-daughter asymmetry. We showed that sir2 knockout affects the relative stress resistance in favor of the mothers. Thus, daughter cells are more vulnerable to a variety of stresses than the young mothers, and Sir2-dependent transport of the adverse factors acts to equalize the resistance.
Eukaryotic cells contain dynamic mitochondrial filaments: they fuse and divide. Here we summarize data on the protein machinery driving mitochondrial dynamics in yeast and also discuss the factors ...that affect the fusion-fission balance. Fission is a general stress response of cells, and in the case of yeast this response appears to be prosurvival. At the same time, even under normal conditions yeast mitochondria undergo continuous cycles of fusion and fission. This seems to be a futile cycle and also expensive from the energy point of view. Why does it exist? Benefits might be the same as in the case of sexual reproduction. Indeed, mixing and separating of mitochondrial content allows mitochondrial DNA to segregate and recombine randomly, leading to high variation in the numbers of mutations per individual mitochondrion. This opens a possibility for effective purifying selection-elimination of mitochondria highly contaminated by deleterious mutations. The beneficial action presumes a mechanism for removal of defective mitochondria. We argue that selective mitochondrial autophagy or asymmetrical distribution of mitochondria during cell division could be at the core of such mechanism.
Protein aggregation is intimately linked to a number of neurodegenerative diseases. Expansion of the huntingtin polyglutamine-rich domain causes protein aggregation and neuronal degeneration. ...Recently we found that, similar to neurons, yeast expressing the expanded domain show markers of programmed cell death. Here we showed that deletion of yeast metacaspase gene YCA1 partly rescues the toxic effect of the domain overexpression. We also performed genetic screen for other genes deletions alleviating the toxic effect and found ASE1. Ase1 is a substrate of the Cdh1 form of anaphase promoting complex, APC/Cdh1. We tested Cdh1 overexpression and the deletion of CLB2 (mitotic cyclin, substrate of APC/Cdh1) and found that both mutations had a rescuing effect on the expanded polyglutamine toxicity. Our data suggest that the toxic effect of aggregated proteins is partly indirect. We speculate that cellular attempt to degrade the aggregates overloads the proteasome, and this leads to pathological accumulation of APC substrates.
Stressed Saccharomyces cerevisiae cells easily lose respiratory function due to deletions in mitochondrial DNA, and this increases their general stress resistance. Is the loss active? We found that ...erythromycin (an inhibitor of mitochondrial translation) prevents the loss in control cells but not in the ones expressing mitochondrially-encoded protein Var1 in the nucleus. Var1 is a component of mitochondrial ribosomes; it is hydrophilic, positively charged, and prone to aggregation. Addition of DNase altered Var1 content in a preparation of mitochondrial nucleoids. Our data indicate that Var1 physically interacts with mitochondrial DNA and under stress negatively regulates its maintenance.
A sandwich-type rhodium polyoxotungstate with unprecedented tetrarhodium-oxo core Na(12)(Rh(4)(μ(3)-O)(2)(H(2)O)(2))(H(2)W(9)O(33))(2)·38H(2)O (1) was obtained by hydrothermal reaction of rhodium(II) ...acetate and sodium tungstate; crystal structure was determined by X-ray diffractometry and was confirmed by (183)W NMR data; 1 is active in electrocatalytic water oxidation.
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