The role of salicylic acid in the glutathione-mediated protection against photooxidative stress in rice

Salicylic acid (SA) is known to be an essential component responsible for disease resistance in dicotyledonous plants. In rice, however, tissue contains extremely high endogenous levels of SA that do not increase after pathogen infection, suggesting that the SA has other major functions in healthy leaves. Although involvement of SA in oxidative-stress response is known in some dicotyledonous plants, antioxidative role of SA in rice is obscure. In this study, we examined the involvement of SA in the protection against oxidative stress in rice, using transgenic plants expressing the bacterial nahG gene that encodes salicylate hydroxylase, an SA-degrading enzyme. In SA-deficient NahG rice, the glutathione pool size was constitutively diminished as compared with control plants. NahG seedlings showed a delayed development phenotype, an increased susceptibility to oxidative stress and they developed light-induced lesions in their leaves without pathogen infection. Conversely, treatment with an activator of the SA-mediated defense-signaling pathway, probenazole, increased the glutathione pool size and suppressed lesion formation. These results suggest that in rice, SA has an important role in the response to high-light-induced oxidative stress, through its regulatory effects on glutathione homeostasis.     

Involvement of endogenously synthesized interleukin (IL)-18 in the protective effects of IL-12 against pulmonary infection with Cryptococcus neoformans in mice

We previously demonstrated that interleukin (IL)-12 protected mice against fatal pulmonary infection with a highly virulent strain of Cryptococcus neoformans, which correlated well with the production of interferon (IFN)-gamma as well as IL-18 in the primary infected site. In the present study, we examined the role of endogenously synthesized IL-18 in IL-12-induced host resistance to this pathogen. There was little or no production of IFN-gamma and IL-18 both at mRNA and protein levels in lungs of mice infected with C. neoformans, while treatment with IL-12 induced a marked production of these cytokines. Caspase-1 mRNA was expressed in infected mice even without IL-12 treatment. Administration of neutralizing anti-IFN-gamma monoclonal antibody (mAb) clearly inhibited production of IFN-gamma and IL-18 induced by IL-12, while control IgG did not show such an effect. However, administration of IFN-gamma did not induce the production of both cytokines in infected mice, although tumor necrosis factor (TNF)-alpha and IFN-gamma-inducible protein (IP)-10 were synthesized by the same treatment. Finally, neutralizing anti-IL-18 antibody (Ab) significantly interfered with the production of IFN-gamma and elimination of the microorganism from the lung induced by IL-12 treatment. Furthermore, both IFN-gamma synthesis and host protection caused by IL-12 were profoundly diminished in IL-18 gene-disrupted mice. Considered collectively, our results indicated that host protection against C. neoformans induced by IL-12 involved endogenously synthesized IL-18 and that the production of IL-18 was mediated at least in part by endogenous IFN-gamma.     

Comparative study of reserve lipid accumulation during somatic and zygotic <Emphasis Type="Italic">Acca sellowiana</Emphasis> (O. Berg.) Burret embryogenesis

Somatic embryogenesis is an in vitro morphogenetic route in which isolated cells or a small group of somatic cells give rise to bipolar structures resembling zygotic embryos. Lipids, carbohydrates, and proteins are major compounds in plant and animal metabolism. Comparative analysis along different developmental stages of Acca sellowiana (Myrtaceae) zygotic and somatic embryos, revealed a progressive increase in levels of total lipids. A high degree of similarity could be found in the total lipids composition between A. sellowiana somatic and zygotic embryos. High lipid levels were found in zygotic embryos in the torpedo and cotyledonary stages, and these levels increased according to the progression in the developmental stages. Somatic embryos obtained through direct embryogenesis route showed higher levels of lipids than in indirect somatic embryogenesis. The compounds most frequently were linoleic acid (C18:2), palmitic (C16:0) and oleic (C18:1). These results indicate a high similarity degree of accumulation of total lipids, regardless of zygotic or somatic embryogenesis.     

Caspar-like gene depletion reduces Leishmania infection in sand fly host Lutzomyia longipalpis

Female phlebotomine sand flies Lutzomyia longipalpis naturally harbor populations of the medically important Leishmania infantum (syn. Leishmania chagasi) parasite in the gut, but the extent to which the parasite interacts with the immune system of the insect vector is unknown. To investigate the sand fly immune response and its interaction with the Leishmania parasite, we identified a homologue for caspar, a negative regulator of immune deficiency signaling pathway. We found that feeding antibiotics to adult female L. longipalpis resulted in an up-regulation of caspar expression relative to controls. caspar was differentially expressed when females were fed on gram-negative and gram-positive bacterial species. caspar expression was significantly down-regulated in females between 3 and 6 days after a blood feed containing Leishmania mexicana amastigotes. RNA interference was used to deplete caspar expression in female L. longipalpis, which were subsequently fed with Leishmania in a blood meal. Sand fly gut populations of both L. mexicana and L. infantum were significantly reduced in caspar-depleted females. The prevalence of L. infantum infection in the females fell from 85 to 45%. Our results provide the first insight into the operation of immune homeostasis in phlebotomine sand flies during the growth of bacterial and Leishmania populations in the digestive tract. We have demonstrated that the activation of the sand fly immune system, via depletion of a single gene, can lead to the abortion of Leishmania development and the disruption of transmission by the phlebotomine sand fly.     

Genetic susceptibility to chronic Chagas disease: an overview of single nucleotide polymorphisms of cytokine genes

Chagas disease is a parasitic infection that is a significant public health problem in Latin America. The mechanisms responsible for susceptibility to the infection and the mechanisms involved in the development of cardiac and digestive forms of chronic Chagas disease remain poorly understood. However, there is growing evidence that differences in susceptibility in endemic areas may be attributable to host genetic factors. The aim of this overview was to analyze the genetic susceptibility to human Chagas disease, particularly that of single nucleotide polymorphisms of cytokine genes. A review of the literature was conducted on the following databases: PubMed/MEDLINE and Scopus. The search strategy included using the following terms: "Cytokines", "Single Nucleotide Polymorphisms" and "Chagas Disease". After screening 25 citations from the databases, 19 studies were selected for the overview. A critical analysis of the data presented in the articles suggests that genetic susceptibility to Chagas disease and chronic Chagas cardiomyopathy is highly influenced by the complexity of the immune response of the host. Follow-up studies based on other populations where Chagas disease is endemic (with distinct ethnic and genetic backgrounds) need to be conducted. These should use a large sample population so as to establish what cytokine genes are involved in susceptibility to and/or progression of the disease.     

Hyperbaric oxygen prevents early death caused by experimental cerebral malaria

Background

Cerebral malaria (CM) is a syndrome characterized by neurological signs, seizures and coma. Despite the fact that CM presents similarities with cerebral stroke, few studies have focused on new supportive therapies for the disease. Hyperbaric oxygen (HBO) therapy has been successfully used in patients with numerous brain disorders such as stroke, migraine and atherosclerosis.

Methodology/Principal Findings

C57BL/6 mice infected with Plasmodium berghei ANKA (PbA) were exposed to daily doses of HBO (100% O₂, 3.0 ATA, 1–2 h per day) in conditions well-tolerated by humans and animals, before or after parasite establishment. Cumulative survival analyses demonstrated that HBO therapy protected 50% of PbA-infected mice and delayed CM-specific neurological signs when administrated after patent parasitemia. Pressurized oxygen therapy reduced peripheral parasitemia, expression of TNF-α, IFN-γ and IL-10 mRNA levels and percentage of γδ and αβ CD4⁺ and CD8⁺ T lymphocytes sequestered in mice brains, thus resulting in a reduction of blood-brain barrier (BBB) dysfunction and hypothermia.

Conclusions/Significance

The data presented here is the first indication that HBO treatment could be used as supportive therapy, perhaps in association with neuroprotective drugs, to prevent CM clinical outcomes, including death.     

Detection of Legionella pneumophila serogroup 1 antigen in respiratory samples using an immunochromatographic membrane test

The immunochromatographic membrane test (ICT) efficacy of Legionella antigen detection (Binax Now Legionella®) was evaluated using respiratory samples, including bronchial washings (44 cases) and sputum (128 cases), from suspected Legionella pneumonia patients. The ICT results using respiratory samples agreed well with isolation of L. pneumophila SG1 and ICT using urines.     

Compositional Discrimination of Decompression and Decomposition Gas Bubbles in Bycaught Seals and Dolphins

Gas bubbles in marine mammals entangled and drowned in gillnets have been previously described by computed tomography, gross examination and histopathology. The absence of bacteria or autolytic changes in the tissues of those animals suggested that the gas was produced peri- or post-mortem by a fast decompression, probably by quickly hauling animals entangled in the net at depth to the surface. Gas composition analysis and gas scoring are two new diagnostic tools available to distinguish gas embolisms from putrefaction gases. With this goal, these methods have been successfully applied to pathological studies of marine mammals. In this study, we characterized the flux and composition of the gas bubbles from bycaught marine mammals in anchored sink gillnets and bottom otter trawls. We compared these data with marine mammals stranded on Cape Cod, MA, USA. Fresh animals or with moderate decomposition (decomposition scores of 2 and 3) were prioritized. Results showed that bycaught animals presented with significantly higher gas scores than stranded animals. Gas composition analyses indicate that gas was formed by decompression, confirming the decompression hypothesis.