Inducibility of the response of yeast cells to peroxide stress.

Exponential phase cells of the yeast, Saccharomyces cerevisiae when treated with a non-lethal concentration of hydrogen peroxide (H2O2; 0.2mM) for 60 min adapted to become resistant to the lethal effects of a higher dose of H2O2 (2mM). From studies using cycloheximide to inhibit protein synthesis it appears that protein synthesis is required for maximal induction of resistance but that some degree of protection from the lethal effects of peroxide can be acquired in the absence of protein synthesis. Treatment of cells with 50 micrograms cycloheximide ml-1 alone lead to them acquiring some protection from peroxide. Cells subjected to heat shock became more resistant to 2mM-H2O2; however, peroxide pretreatment did not confer thermotolerance. L-[35S]Methionine labelling of cells subjected to 0.2 mM-H2O2 stress showed that synthesis of at least ten polypeptides was induced by peroxide treatment. Some of these were also induced in cells subjected to heat shock (23 to 37 degrees C shift) but the synthesis of at least four polypeptides (45, 39.5, 38 and 24 kDa) was unique to peroxide-stressed cells. Resistance to peroxide was also inducible in an isogenic petite and an isogenic strain with a mutation in the HAP1 gene, indicating that the adaptive response does not require functional mitochondria.     

Time-resolved magnetic circular dichroism spectroscopy of photolyzed carbonmonoxy cytochrome c oxidase (cytochrome aa3).

Nanosecond time-resolved magnetic circular dichroism (TRMCD) and time-resolved natural circular dichroism (TRCD) measurements of photolysis products of the CO complex of eukaryotic cytochrome c oxidase (CcO-CO) are presented. TRMCD spectra obtained at 100 ns and 10 microseconds after photolysis are diagnostic of pentacoordinate cytochrome a3Fe2+, as would be expected for simple photodissociation. Other time-resolved spectroscopies (UV-visible and resonance Raman), however, show evidence for unusual Fea3(2+) coordination after CO photolysis (Woodruff, W. H., O. Einarsdóttir, R. B. Dyer, K. A. Bagley, G. Palmer, S. J. Atherton, R. A. Goldbeck, T. D. Dawes, and D. S. Kliger. 1991. Proc. Nat. Acad. Sci. U.S.A. 88:2588-2592). Furthermore, time-resolved IR experiments have shown that photodissociated CO binds to CuB+ prior to recombining with Fea3(2+) (Dyer, R. B., O. Einarsdóttir, P. M. Killough, J. J. López-Garriga, and W. H. Woodruff. 1989. J. Am. Chem. Soc. 111:7657-7659). A model of the CcO-CO photolysis cycle which is consistent with all of the spectroscopic results is presented. A novel feature of this model is the coordination of a ligand endogenous to the protein to the Fe axial site vacated by the photolyzed CO and the simultaneous breaking of the Fe-imidazole(histidine) bond.     

Warming Induces Significant Reprogramming of Beige,but Not Brown,Adipocyte Cellular Identity

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Efficacy of different interaction devices using non-immersive virtual tasks in individuals with Amyotrophic Lateral Sclerosis: a cross-sectional randomized trial

Background

Amyotrophic Lateral Sclerosis (ALS) is a rapid progressive neurodegenerative disease, characterized by a selective loss of motor neurons, brain stem and spinal cord which leads to deterioration of motor abilities. Devices that promote interaction with tasks on computers can enhance performance and lead to greater independence and utilization of technology.

Objective

To evaluate performance on a computer task in individuals with ALS using three different commonly used non-immersive devices.

Method

Thirty individuals with ALS (18 men and 12 women, mean age 59?years, range 44–74?years) with a mean score of 26, (minimum score of 14 and maximum 41) on the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) and 30 healthy controls matched for age and gender, participated. All participants were randomly divided into three groups, each using a different device system (motion tracking, finger motion control or touchscreen) to perform three task phases (acquisition, retention and transfer).

Results

Both the ALS and control group (CG) showed better performance on the computer task when using the touchscreen device, but there was limited transfer of performance onto the task performed on the Finger Motion control or motion tracking. However, we found that using the motion tracking device led to transfer of performance to the touchscreen.

Conclusion

This study presents novel and important findings when selecting interaction devices for individuals with ALS to access technology by demonstrating immediate performance benefits of using a touchscreen device, such as improvement of motor skills. There were possible transferable skills obtained when using virtual systems which may allow flexibility and enable individuals to maintain performance overtime.

Trial registration

Registration name: Virtual Task in Amyotrophic Lateral Sclerosis; Registration number: NCT03113630; retrospectively registered on 04/13/2017. Date of enrolment of the first participant to the trial: 02/02/2016.

     

Glutathione synthetase is dispensable for growth under both normal and oxidative stress conditions in the yeast Saccharomyces cerevisiae due to an accumulation of the dipeptide gamma-glutamylcysteine.

Glutathione (GSH) synthetase (Gsh2) catalyzes the ATP-dependent synthesis of GSH from gamma-glutamylcysteine (gamma-Glu-Cys) and glycine. GSH2, encoding the Saccharomyces cerevisiae enzyme, was isolated and used to construct strains that either lack or overproduce Gsh2. The identity of GSH2 was confirmed by the following criteria: 1) the predicted Gsh2 protein shared 37-39% identity and 58-60% similarity with GSH synthetases from other eukaryotes, 2) increased gene dosage of GSH2 resulted in elevated Gsh2 enzyme activity, 3) a strain deleted for GSH2 was dependent on exogenous GSH for wild-type growth rates, and 4) the gsh2 mutant lacked GSH and accumulated the dipeptide gamma-Glu-Cys intermediate in GSH biosynthesis. Overexpression of GSH2 had no effect on cellular GSH levels, whereas overexpression of GSH1, encoding the enzyme for the first step in GSH biosynthesis, lead to an approximately twofold increase in GSH levels, consistent with Gsh1 catalyzing the rate-limiting step in GSH biosynthesis. In contrast to a strain deleted for GSH1, which lacks both GSH and gamma-Glu-Cys, the strain deleted for GSH2 was found to be unaffected in mitochondrial function as well as resistance to oxidative stress induced by hydrogen peroxide, tert-butyl hydroperoxide, and the superoxide anion. Furthermore, gamma-Glu-Cys was at least as good as GSH in protecting yeast cells against an oxidant challenge, providing the first evidence that gamma-Glu-Cys can act as an antioxidant and substitute for GSH in a eukaryotic cell. However, the dipeptide could not fully substitute for the essential function of GSH in the cell as shown by the poor growth of the gsh2 mutant on minimal medium. We suggest that this function may be the detoxification of harmful intermediates that are generated during normal cellular metabolism.     

IN SITU UPTAKE KINETICS OF AMMONIUM AND PHOSPHATE AND CHEMICAL COMPOSITION OF THE RED SEAWEED GRACILARIA TIKVAHIAE1

The uptake kinetics of ammonium and phosphate by Gracilaria tikvahiae McLachlan were studied under field conditions. Seaweeds, pulse fed once a week for 6 h over a 4-week period, had maximum uptake rates of 19 μmol·g fwt^?1·h^?1 for ammonium and 0.28 μmol·g fwt^?1·h^?1 for phosphate. For both nutrients there was a positive linear correlation between uptake rate (v) and concentration (S) over the entire range of concentration tested. In a nutrient depletion experiment, the phosphate uptake curve determined over a wide range of concentrations consisted of two stages of saturation at low concentrations, and a linear phase at high concentrations. Ash free dry weight, chlorophyll a, phycoerythrin, and protein content were higher in pulse fed plants than in control plants receiving no nutrient additions, while the reverse held true for carbohydrate contents and the C/N ratios. The C/N ratio inversely correlated with ammonium and phosphate uptake rate as well as protein and phycoerythrin content, and positively with carbohydrate content.