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Photosynthetic light reactions--an adjustable hub in basic production and plant immunity signaling.
Kangasjärvi, S, Tikkanen, M, Durian, G, Aro, EM
Plant physiology and biochemistry : PPB. 2014;:128-34
Abstract
Photosynthetic efficiency is a key trait that influences the sustainable utilization of plants for energy and nutrition. By now, extensive research on photosynthetic processes has underscored important structural and functional relationships among photosynthetic thylakoid membrane protein complexes, and their roles in determining the productivity and stress resistance of plants. Photosystem II photoinhibition-repair cycle, for example, has arisen vital in protecting also Photosystem I against light-induced damage. Availability of highly sophisticated genetic, biochemical and biophysical tools has greatly expanded the catalog of components that carry out photoprotective functions in plants. On thylakoid membranes, these components encompass a network of overlapping systems that allow delicate regulation of linear and cyclic electron transfer pathways, balancing of excitation energy distribution between the two photosystems and dissipation of excess light energy in the antenna system as heat. An increasing number of reports indicate that the above mentioned mechanisms also mediate important functions in the regulation of biotic stress responses in plants. Particularly the handling of excitation energy in the light harvesting II antenna complexes appears central to plant immunity signaling. Comprehensive understanding of the underlying mechanisms and regulatory cross-talk, however, still remain elusive. This review highlights the current understanding of components that regulate the function of photosynthetic light reactions and directly or indirectly also modulate disease resistance in higher plants.
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Transcriptional regulation of bacterial virulence gene expression by molecular oxygen and nitric oxide.
Green, J, Rolfe, MD, Smith, LJ
Virulence. 2014;(8):794-809
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Abstract
Molecular oxygen (O2) and nitric oxide (NO) are diatomic gases that play major roles in infection. The host innate immune system generates reactive oxygen species and NO as bacteriocidal agents and both require O2 for their production. Furthermore, the ability to adapt to changes in O2 availability is crucial for many bacterial pathogens, as many niches within a host are hypoxic. Pathogenic bacteria have evolved transcriptional regulatory systems that perceive these gases and respond by reprogramming gene expression. Direct sensors possess iron-containing co-factors (iron-sulfur clusters, mononuclear iron, heme) or reactive cysteine thiols that react with O2 and/or NO. Indirect sensors perceive the physiological effects of O2 starvation. Thus, O2 and NO act as environmental cues that trigger the coordinated expression of virulence genes and metabolic adaptations necessary for survival within a host. Here, the mechanisms of signal perception by key O2- and NO-responsive bacterial transcription factors and the effects on virulence gene expression are reviewed, followed by consideration of these aspects of gene regulation in two major pathogens, Staphylococcus aureus and Mycobacterium tuberculosis.
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Modeling phenotypic metabolic adaptations of Mycobacterium tuberculosis H37Rv under hypoxia.
Fang, X, Wallqvist, A, Reifman, J
PLoS computational biology. 2012;(9):e1002688
Abstract
The ability to adapt to different conditions is key for Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), to successfully infect human hosts. Adaptations allow the organism to evade the host immune responses during acute infections and persist for an extended period of time during the latent infectious stage. In latently infected individuals, estimated to include one-third of the human population, the organism exists in a variety of metabolic states, which impedes the development of a simple strategy for controlling or eradicating this disease. Direct knowledge of the metabolic states of M. tuberculosis in patients would aid in the management of the disease as well as in forming the basis for developing new drugs and designing more efficacious drug cocktails. Here, we propose an in silico approach to create state-specific models based on readily available gene expression data. The coupling of differential gene expression data with a metabolic network model allowed us to characterize the metabolic adaptations of M. tuberculosis H37Rv to hypoxia. Given the microarray data for the alterations in gene expression, our model predicted reduced oxygen uptake, ATP production changes, and a global change from an oxidative to a reductive tricarboxylic acid (TCA) program. Alterations in the biomass composition indicated an increase in the cell wall metabolites required for cell-wall growth, as well as heightened accumulation of triacylglycerol in preparation for a low-nutrient, low metabolic activity life style. In contrast, the gene expression program in the deletion mutant of dosR, which encodes the immediate hypoxic response regulator, failed to adapt to low-oxygen stress. Our predictions were compatible with recent experimental observations of M. tuberculosis activity under hypoxic and anaerobic conditions. Importantly, alterations in the flow and accumulation of a particular metabolite were not necessarily directly linked to differential gene expression of the enzymes catalyzing the related metabolic reactions.
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Oxygen carriers: a selected review.
Inayat, MS, Bernard, AC, Gallicchio, VS, Garvy, BA, Elford, HL, Oakley, OR
Transfusion and apheresis science : official journal of the World Apheresis Association : official journal of the European Society for Haemapheresis. 2006;(1):25-32
Abstract
The most common and widely transplanted tissue world wide is blood, which in 2000 resulted in the transfusion of 12.5 million units of blood in the US alone [Goodnough LT, Shander A, Brecher ME. Transfusion medicine: looking to the future. Lancet 2003;361:161-9]. The current use of donated blood products is relatively safe; however, there are inherent problems with allogeneic blood transfusions. The wide spread use of blood in procedures results in problems involving inadequate supply exacerbated in times of war and disasters and by the limited storage life of blood donations (30-42 days). Blood contamination due to patient pre-disposition, poor collection, sterilization, or storage is the second most common cause of death from transfusion in the US [Hillyer CD, Josephson CD, Blajchman MA, Vostal JG, Epstein JS, Goodman JL. Bacterial contamination of blood components: risks, strategies, and regulation: joint ASH and AABB educational session in transfusion medicine. Hematology (Am Soc Hematol Educ Program) 2003:575-89]. Blood is a complex tissue involved in a plethora of homeostatic roles, including immunity, wound healing and the transport of nourishment, electrolytes, hormones, vitamins, heat, oxygen and the removal of metabolic waste products. However, by far the principle role of blood transfusions is the replacement of red cell volume and the maintenance of oxygen levels within the circulation. Creation of investigational new drugs (INDs) which would function as oxygen carriers and prolong shelf life is now a very active arena of scientific research. Several such IND products are now in clinical trials. This article gives an easy to follow concise evaluation of major areas of focus and current testing for each type of blood substitution molecule.
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The influence of oxygenated water on the immune status, liver enzymes, and the generation of oxygen radicals: a prospective, randomised, blinded clinical study.
Gruber, R, Axmann, S, Schoenberg, MH
Clinical nutrition (Edinburgh, Scotland). 2005;(3):407-14
Abstract
BACKGROUND & AIMS Oxygenated water with an oxygen concentration of 30-120 mg/l water is believed to improve the immune status, without any toxicological effects. The purpose of this clinical study was to assess the effects of long-term drinking of oxygenated water on the immune status. METHODS In this prospective, double-blinded, randomised study 24 volunteers of either sex (age 18-63 years) drank daily 3 times 500 ml either oxygenated (Verum-group: n=12) or normal mineral water (Placebo-group: n=12) for 28 days. On day 1 and day 28 standard laboratory tests, IgG, IgA and IgM, lymphocyte subpopulations and functional analysis of T-cells by flow cytometry, were done. Furthermore, the oxygen radicals were determined by the detection of the ascorbyl radicals. RESULTS Drinking of normal or oxygenated water had no effect on whole blood count or the liver enzymes. Interestingly the volunteers in the Verum-group showed a significant increase in ascorbyl radicals after drinking oxygenated water for 14 and 21 days. CD4+ and CD4+CD45RA+ lymphocytes as well as lymphocyte activation marker (CD69) and soluble IL-2 receptor increased in both groups, in contrast T-helper2 cells and IgG decreased during the study. The only differences between the two groups were a significant decrease of NK-cells form 13.42%+ or -5.04 to 10.83%+ or -4.82 (P<.002) and an increase of the Th1/Th2-ratio from 2.77%+ or -1.07 to 6.68%+ or -5.33 (P<.03) in the Verum-group. CONCLUSION Long-term consumption of oxygenated water has no apparent harmful effect on the liver, blood and the immune system. Moreover it leads to a transient moderate increase of oxygen radicals in the blood. An interesting observation is the increase of the Th1/Th2-ratio in the Verum group, whereas in both groups T-cell activation after mitogen stimulation, the soluble IL-2 receptor, the CD4+ and the naive CD4+CD45RA+ cells increased.