ROS-dependent signaling pathways in plants and algae exposed to high light: Comparisons with other eukaryotes

Abstract Like all aerobic organisms, plants and algae co-opt reactive oxygen species (ROS) as signaling molecules to drive cellular responses to changes in their environment. In this respect, there is considerable commonality between all eukaryotes imposed by the constraints of ROS chemistry, similar metabolism in many subcellular compartments, the requirement for a high degree of signal specificity and the deployment of thiol peroxidases as transducers of oxidizing equivalents to regulatory proteins. Nevertheless, plants and algae carry out specialised signaling arising from oxygenic photosynthesis in chloroplasts and photoautotropism, which often induce an imbalance between absorption of light energy and the capacity to use it productively. A key means of responding to this imbalance is through communication of chloroplasts with the nucleus to adjust cellular metabolism. Two ROS, singlet oxygen (1O2) and hydrogen peroxide (H2O2), initiate distinct signaling pathways when photosynthesis is perturbed. 1O2, because of its potent reactivity means that it initiates but does not transduce signaling. In contrast, the lower reactivity of H2O2 means that it can also be a mobile messenger in a spatially-defined signaling pathway. How plants translate a H2O2 message to bring about changes in gene expression is unknown and therefore, we draw on information from other eukaryotes to propose a working hypothesis. The role of these ROS generated in other subcellular compartments of plant cells in response to HL is critically considered alongside other eukaryotes. Finally, the responses of animal cells to oxidative stress upon high irradiance exposure is considered for new comparisons between plant and animal cells

Role of the trauma nurse coordinator in Hong Kong

Background: Trauma is one of the leading causes of death for all ages in Hong Kong. In 2003, the Hospital Authority designated five hospitals as trauma centres. Five Trauma Nurse Coordinators (TNCs) were employed to facilitate multidisciplinary care and to coordinate all aspects of quality improvement for injured patients. The present paper investigates the characteristics and roles of TNCs in Hong Kong. Methods: A questionnaire was developed and sent to all TNCs in HK to ascertain information about demographic characteristics, education, job training, roles and the TNCs’ position within the organizational structure. Results: The TNCs were 30–40 years of age (four females); are experienced registered graduate nurses; hold post-registration certificates or diplomas in emergency/critical care; and have 11–18 years nursing experience. All TNCs have pursued masters degrees, with two completed. Four of the TNCs had received formal training on computerized data management, abbreviated injury scale coding and trauma nurse coordination. TNCs averaged 2.5 years experience in their post. TNCs manage the trauma registry, are involved in clinical patient management, quality assurance activities, professional and public education and research. Conclusion: TNCs play an important role in trauma management in Hong Kong

Activation and Inhibition of Histone Deacetylase 8 by Monovalent Cations*

The metal-dependent histone deacetylases (HDACs) catalyze hydrolysis of acetyl groups from acetyllysine side chains and are targets of cancer therapeutics. Two bound monovalent cations (MVCs) of unknown function have been previously observed in crystal structures of HDAC8; site 1 is near the active site, whereas site 2 is located >20 Å from the catalytic metal ion. Here we demonstrate that one bound MVC activates catalytic activity (K1/2 = 3.4 mm for K+), whereas the second, weaker-binding MVC (K1/2 = 26 mm for K+) decreases catalytic activity by 11-fold. The weaker binding MVC also enhances the affinity of the HDAC inhibitor suberoylanilide hydroxamic acid by 5-fold. The site 1 MVC is coordinated by the side chain of Asp-176 that also forms a hydrogen bond with His-142, one of two histidines important for catalytic activity. The D176A and H142A mutants each increase the K1/2 for potassium inhibition by ≥40-fold, demonstrating that the inhibitory cation binds to site 1. Furthermore, the MVC inhibition is mediated by His-142, suggesting that this residue is protonated for maximal HDAC8 activity. Therefore, His-142 functions either as an electrostatic catalyst or a general acid. The activating MVC binds in the distal site and causes a time-dependent increase in activity, suggesting that the site 2 MVC stabilizes an active conformation of the enzyme. Sodium binds more weakly to both sites and activates HDAC8 to a lesser extent than potassium. Therefore, it is likely that potassium is the predominant MVC bound to HDAC8 in vivo