Cultivation of Arabidopsis cell cultures in a stirred bioreactor at variable oxygen levels: Influence on tocopherol production

Abstract

In plants, an increased production of toxic oxygen species is commonly observed under low oxygen stress, but cellular responses still have to be fully investigated. Plant cell cultures can be a valuable tool to study plant metabolic responses to various environmental stresses including low oxygen condition. Arabidopsis suspension cultures growing in shake flasks were subjected to hypoxia by stopping shaking for different intervals, showing an increase of the antioxidant metabolite α‐tocopherol. In order to obtain a more controlled condition, cultivation of Arabidopsis suspension cultures was established in a 5‐l stirred bioreactor. A constant aeration of 20% dissolved oxygen was found to be the most suitable for cell growth. A 4‐h anoxic shock was induced by suspending the aeration and flushing into the vessel with nitrogen. During the anoxic stress, tocopherol levels resulted increased at the end of the treatment, indicating that the complete oxygen deprivation, indeed, induced a defence response involving antioxidant metabolism. The presence of an oxidative stress as a consequence of anoxic condition was also confirmed by the increased levels of H₂O₂. Overall, these results indicate that Arabidopsis suspension cultures grown in a stirred bioreactor can be a useful in vitro system for investigating low oxygen stress.     

Cost-utility of cognitive behavioral therapy versus U.S. Food and Drug Administration recommended drugs and usual care in the treatment of patients with fibromyalgia: an economic evaluation alongside a 6-month randomized controlled trial

Introduction

Cognitive behavioral therapy (CBT) and U.S. Food and Drug Administration (FDA)-recommended pharmacologic treatments (RPTs; pregabalin, duloxetine, and milnacipran) are effective treatment options for fibromyalgia (FM) syndrome and are currently recommended by clinical guidelines. We compared the cost-utility from the healthcare and societal perspectives of CBT versus RPT (combination of pregabalin + duloxetine) and usual care (TAU) groups in the treatment of FM.

Methods

The economic evaluation was conducted alongside a 6-month, multicenter, randomized, blinded, parallel group, controlled trial. In total, 168 FM patients from 41 general practices in Zaragoza (Spain) were randomized to CBT (n = 57), RPT (n = 56), or TAU (n = 55). The main outcome measures were Quality-Adjusted Life Years (QALYs, assessed by using the EuroQoL-5D questionnaire) and improvements in health-related quality of life (HRQoL, assessed by using EuroQoL-5D visual analogue scale, EQ-VAS). The costs of healthcare use were estimated from patient self-reports (Client Service Receipt Inventory). Cost-utility was assessed by using the net-benefit approach and cost-effectiveness acceptability curves (CEACs).

Results

On average, the total costs per patient in the CBT group (1,847€) were significantly lower than those in patients receiving RPT (3,664€) or TAU (3,124€). Patients receiving CBT reported a higher quality of life (QALYs and EQ-VAS scores); the differences between groups were significant only for EQ-VAS. From a complete case-analysis approach (base case), the point estimates of the cost-effectiveness ratios resulted in dominance for the CBT group in all of the comparisons performed, by using both QALYs and EQ-VAS as outcomes. These findings were confirmed by bootstrap analyses, net-benefit curves, and CEACs. Two additional sensitivity analyses (intention-to-treat analysis and per-protocol analysis) indicated that the results were robust. The comparison of RPT with TAU yielded no clear preference for either treatment when using QALYs, although RPT was determined to be more cost-effective than TAU when evaluating EQ-VAS.

Conclusions

Because of lower costs, CBT is the most cost-effective treatment for adult FM patients. Implementation in routine medical care would require policymakers to develop more-widespread public access to trained and experienced therapists in group-based forms of CBT.

Trial registration

Current Controlled Trials ISRCTN10804772. Registered 29 September 2008.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0451-y) contains supplementary material, which is available to authorized users.     

Cold-Adapted Enzymes from Marine Antarctic Microorganisms

The Antarctic marine environment is characterized by challenging conditions for the survival of native microorganisms. Indeed, next to the temperature effect represented by the Arrhenius law, the viscosity of the medium, which is also significantly enhanced by low temperatures, contributes to slow down reaction rates. This review analyses the different challenges and focuses on a key element of life at low temperatures: cold-adapted enzymes. The molecular characteristics of these enzymes are discussed as well as the adaptation strategies which can be inferred from the comparison of their properties and three-dimensional structures with those of their mesophilic counterparts. As these enzymes display a high specific activity at low and moderate temperatures associated with a relatively high thermosensitivity, the interest in these properties is discussed with regard to their current and possible applications in biotechnology.     

Methylation damage response in hematopoietic progenitor cells

The cellular response to methylation DNA damage was compared in multipotent CD34(+) hematopoietic stem cells and mature CD34(-) cells isolated from cord blood of the same donor. Cytofluorimetric analysis of freshly isolated cord blood cells indicated that both cell types were in the G0/G1 phase of the cell cycle. Quantitative RT-PCR identified a general trend towards high expression of several DNA repair genes in CD34(+) cells compared to their terminally differentiated CD34(-) counterparts. The overexpressed genes included members of the mismatch repair (MMR) (MSH2, MSH6, MLH1, PMS2), base excision repair (AAG, APEX), DNA damage reversal (O(6)-methylguanine DNA methyltransferase) (MGMT), and DNA double strand breaks repair pathways. These differences in gene expression were not apparent in CD34(+) and CD34(-) cells obtained following expansion of CD34(+) cells in a medium containing early acting cytokines. Early progenitor CD34(+) and early precursor CD34(-) cells form the two populations isolated under these experimental conditions, and both contain a significant proportion of cycling cells. The methylating agent N-methyl-N-nitrosourea (MNU) induced similar levels of apoptosis in these cycling CD34(+) and CD34(-) cells. Cytotoxicity required the presence of the MGMT inhibitor O(6)-benzylguanine and the timing of MNU cell death (48 and 72h) was similar in CD34(+) and CD34(-) cells. These data indicate that cycling CD34(+) and CD34(-) cells are equally sensitive to methylation damage. MGMT provides significant protection against MNU toxicity and MGMT and MMR play the expected roles in the MNU sensitivity of these cells.