Evaluation of vacuum infiltration vitrification and cryo-mesh cryopreservation techniques with Arabidopsis thaliana shoot tips.

BACKGROUND: Novel cryo-techniques are continuously being developed that may better improve cryogenic survival in plants, with the aim of reducing exposure times to otherwise toxic cryoprotective agents whilst maximising regeneration rates. OBJECTIVE: This study used cryo-mesh and vacuum infiltration vitrification with two vitrification solutions (PVS2 and PVS3) to develop an optimised cryopreservation protocol for Arabidopsis thaliana. MATERIALS AND METHODS: Shoot tips from 10-day old seedlings of wild type A. thaliana were cryopreserved using either vacuum infiltration vitrification or the cryo-mesh technique. Shoot tips were treated for up to 60 min in increments of 10 min with PVS2 and PVS3, and for an additional 180 and 300 min incubation for cryo-mesh prior to exposure to liquid nitrogen. RESULTS: Both methods resulted in very high regeneration rates, but which decreased after longer exposure to the vitrification solutions. The highest regeneration rate for vacuum-infiltration vitrification was attained after only 30 min incubation in PVS2 (92.5%) and 50 min incubation in PVS3 (93.6%). In the case of cryo-mesh the highest regeneration was observed after 180 min incubation in either PVS2 (100%) or PVS3 (92.2%). CONCLUSION: Vacuum-infiltration vitrification is more effective than cryo-mesh by reducing exposure times to cryoprotective solutions whilst achieving very high regeneration rates of shoot tips of A. thaliana. https://doi.org/10.54680/fr22610110712.

A 3'-UTR KRAS-variant is associated with cisplatin resistance in patients with recurrent and/or metastatic head and neck squamous cell carcinoma.

BACKGROUND: A germline mutation in the 3'-untranslated region of KRAS (rs61764370, KRAS-variant: TG/GG) has previously been associated with altered patient outcome and drug resistance/sensitivity in various cancers. We examined the prognostic and predictive significance of this variant in recurrent/metastatic (R/M) head and neck squamous cell carcinoma (HNSCC). PATIENTS AND METHODS: We conducted a retrospective study of 103 HNSCCs collected from three completed clinical trials. KRAS-variant genotyping was conducted for these samples and 8 HNSCC cell lines. p16 expression was determined in a subset of 26 oropharynx tumors by immunohistochemistry. Microarray analysis was also utilized to elucidate differentially expressed genes between KRAS-variant and non-variant tumors. Drug sensitivity in cell lines was evaluated to confirm clinical findings. RESULTS: KRAS-variant status was determined in 95/103 (92%) of the HNSCC tumor samples and the allelic frequency of TG/GG was 32% (30/95). Three of the HNSCC cell lines (3/8) studied had the KRAS-variant. No association between KRAS-variant status and p16 expression was observed in the oropharynx subset (Fisher's exact test, P = 1.0). With respect to patient outcome, patients with the KRAS-variant had poor progression-free survival when treated with cisplatin (log-rank P = 0.002). Conversely, KRAS-variant patients appeared to experience some improvement in disease control when cetuximab was added to their platinum-based regimen (log-rank P = 0.04). CONCLUSIONS: The TG/GG rs61764370 KRAS-variant is a potential predictive biomarker for poor platinum response in R/M HNSCC patients. CLINICAL TRIAL REGISTRATION NUMBERS: NCT00503997, NCT00425750, NCT00003809.

Medicine, economics and agenda-setting.

The filtering of potential policy issues from a large range of possibilities to a relatively small list of agenda items allows the organisation of power and influence within a policy sector to be examined. This study investigated power and influence in health policy agenda-setting in one State of Australia (Victoria) in the years 1991, 1992 and 1993. The actors seen as influential were predominantly medically trained and working in academia, health bureaucracies and public teaching hospitals. This research supports an elite model of health policy agenda-setting, in which outcomes are dependent on the structured interests within the policy field. However, while the corporate elite of the profession is influential, the frontline service providers are not, as indicated by the location of influentials in large and prestigious organisations. Politicians and professional associations and unions are less well represented, and consumer and community groups are virtually absent. In 1993 there was a sharp increase in economists being nominated as influentials, with a subsequent decrease in influentials with medical training. This relates to a (perceived or real) shift in influence from the medical profession to senior health bureaucrats. Economic concerns appear to be shaping the visible health policy agenda, through an increased number of influentials with economics training, but also through an apparent ability to shape the issues that other influentials are adding as agenda items. The corporate elite of medicine remains powerful, but their range of concerns has been effectively limited to cost containment or cost reduction, better planning and efficiency. This limiting of concerns occurs within an international policy context, where the general trends of globalisation and an emphasis on neo-liberal economics impact on the direction of health policy in individual countries.

The expression of alternative oxidase and uncoupling protein during fruit ripening in mango.

The expression of alternative oxidase (Aox) and uncoupling proteins (Ucp) was investigated during ripening in mango (Mangifera indica) and compared with the expression of peroxisomal thiolase, a previously described ripening marker in mango. The multigene family for the Aox in mango was expressed differentially during ripening. Abundance of Aox message and protein both peaked at the ripe stage. Expression of the single gene for the Ucp peaked at the turning stage and the protein abundance peaked at the ripe stage. Proteins of the cytochrome chain peaked at the mature stage of ripening. The pattern of protein accumulation suggested that increases in cytochrome chain components played an important role in facilitating the climacteric burst of respiration and that the Aox and Ucp may play a role in post-climacteric senescent processes. Because both message and protein for the Aox and Ucp increased in a similar pattern, it suggests that their expression is not controlled in a reciprocal manner but may be active simultaneously.

Unraveling the role of mitochondria during oxidative stress in plants.

The sedentary habit of plants means that they must stand and fight environmental stresses that their mobile animal cousins can avoid. A range of these abiotic stresses initiate the production in plant cells of reactive oxygen and nitrogen species that ultimately lead to oxidative damage affecting the yield and quality of plant products. A complex network of enzyme systems, producing and quenching these reactive species operate in different organelles. It is the integration of these compartmented defense systems that coordinates an effective response to the various stresses. Future attempts to improve plant growth or yield must consider the complexity of inter-organelle signaling and protein targeting if they are to be successful in producing plants with resistance to a broad range of stresses. Here we highlight the role of pre-oxidant, antioxidant, and post-oxidant defense systems in plant mitochondria and the potential role of proteins targeted to both mitochondria and chloroplasts, in an integrated defense against oxidative damage in plants.