Genetic regulation of the ompX porin of Salmonella Typhimurium in response to hydrogen peroxide stress.

BACKGROUND: Salmonella Typhimurium is a Gram-negative pathogen that causes a systemic disease in mice resembling typhoid fever. During its infective cycle, S. Typhimurium is phagocytized by macrophages and proliferates inside a Salmonella-containing vacuole where Salmonella is exposed and survives oxidative stress induced by H2O2 through modulation of gene expression. After exposure of Salmonella to H2O2, the expression of the porin-encoding gene ompX increases, as previously shown by microarray analysis. Expression of ompX mRNA is regulated at a post-transcriptional level by MicA and CyaR sRNAs in aerobiosis. In addition, sequence analysis predicts a site for OxyS sRNA in ompX mRNA. RESULTS: In this work we sought to evaluate the transcriptional and post-transcriptional regulation of ompX under H2O2 stress. We demonstrate that ompX expression is induced at the transcriptional level in S. Typhimurium under such conditions. Unexpectedly, an increase in ompX gene transcript and promoter activity after challenges with H2O2 does not translate into increased protein levels in the wild-type strain, suggesting that ompX mRNA is also regulated at a post-transcriptional level, at least under oxidative stress. In silico gene sequence analysis predicted that sRNAs CyaR, MicA, and OxyS could regulate ompX mRNA levels. Using rifampicin to inhibit mRNA expression, we show that the sRNAs (MicA, CyaR and OxyS) and the sRNA:mRNA chaperone Hfq positively modulate ompX mRNA levels under H2O2-induced stress in Salmonella during the exponential growth phase in Lennox broth. CONCLUSIONS: Our results demonstrate that ompX mRNA is regulated in response to H2O2 by the sRNAs CyaR, MicA and OxyS is Salmonella Typhimurium.

Update on the utility of en face optical coherence tomography in the assessment of vitreoretinal diseases.

En face optical coherence tomography (EF-OCT) is a rapid, non-invasive, high-resolution imaging technique that has evolved in recent years to be a routine examination for the assessment and follow-up of various vitreoretinal diseases. With the introduction of swept-source OCT (SS-OCT), which can achieve up to 100,000 A-scans per second and better-quality imaging of deeper structures using a longer wavelength (1050nm), EF-OCT reconstruction can produce high-resolution frontal images of the retina and choroid (C-Scans) that give an overview of disease extent. These images allow a more accurate study of vitreoretinal interface pathologies such as epiretinal membranes, macular holes, and vitreomacular traction. They also provide key information in the study of various retinal vascular diseases and the differential diagnosis of cystic macular edema. EF-OCT provides valuable information about the severity of vitreoretinal interface alterations and precisely assesses the choriocapillaris and choroidal vasculature in pachychoroid disorders. Finally, this technique provides valuable information about atrophic and neovascular age-related macular degeneration and various uveitic entities. This review aims to describe the current clinical applications of EF-OCT in various vitreoretinal diseases as well as the latest findings and future perspectives.

Bilateral solar maculopathy in a patient with bipolar disorder.

A case of solar maculopathy is described in a 36-year-old man with a history of bipolar disorder. The patient reported directly looking at the sun for several hours in the setting of a bipolar disorder decompensation. The visual acuity was 0.3 in both eyes (BE). Intraocular pressure and anterior segment were normal. In the fundus exam, a peri-macular halo with loss of the foveolar reflex was observed in BE. The macular optical coherence tomography revealed a disruption of the ellipsoid line and the retinal pigment epithelium. Bilateral central defects were seen in the Humphrey 24-2 visual field. After 6 months of follow-up, the visual clinical picture remains stable with the same degree of visual acuity. Solar maculopathy is a disorder due to the phototoxic effects of radiation, which cause a decrease in visual acuity by disrupting the retinal photoreceptor layer.

Bilateral solar maculopathy in a patient with bipolar disorder. / Maculopatía solar bilateral en un paciente con trastorno bipolar.

A case of solar maculopathy is described in a 36-year-old man with a history of bipolar disorder. The patient reported directly looking at the sun for several hours in the setting of a bipolar disorder decompensation. The visual acuity was 0.3 in both eyes (BE). Intraocular pressure and anterior segment were normal. In the fundus exam, a peri-macular halo with loss of the foveolar reflex was observed in BE. The macular optical coherence tomography revealed a disruption of the ellipsoid line and the retinal pigment epithelium. Bilateral central defects were seen in the Humphrey 24-2 visual field. After 6 months of follow-up, the visual clinical picture remains stable with the same degree of visual acuity. Solar maculopathy is a disorder due to the phototoxic effects of radiation, which cause a decrease in visual acuity by disrupting the retinal photoreceptor layer.

Genetic regulation of the ompX porin of Salmonella Typhimurium in response to hydrogen peroxide stress

BACKGROUND: Salmonella Typhimurium is a Gram negative pathogen that causes a systemic disease in mice resembling typhoid fever. During its infective cycle, S. Typhimurium is phagocytized by macrophages and proliferates inside a Salmonella containing vacuole where Salmonella is exposed and survives oxidative stress induced by H2O2 through modulation of gene expression. After exposure of Salmonella to H2O2, the expression of the porin encoding gene ompX increases, as previously shown by microarray analysis. Expression of ompX mRNA is regulated at a post transcriptional level by MicA and CyaR sRNAs in aerobiosis. In addition, sequence analysis predicts a site for OxyS sRNA in ompX mRNA. RESULTS: In this work we sought to evaluate the transcriptional and post transcriptional regulation of ompX under H2O2 stress. We demonstrate that ompX expression is induced at the transcriptional level in S . Typhimurium under such conditions. Unexpectedly, an increase in ompX gene transcript and promoter activity after challenges with H2O2 does not translate into increased protein levels in the wild type strain, suggesting that ompX mRNA is also regulated at a post transcriptional level, at least under oxidative stress. In silico gene sequence analysis predicted that sRNAs CyaR, MicA, and OxyS could regulate ompX mRNA levels. Using rifampicin to inhibit mRNA expression, we show that the sRNAs (MicA, CyaR and OxyS) and the sRNA:mRNA chaperone Hfq positively modulate ompX mRNA levels under H2O2 induced stress in Salmonella during the exponential growth phase in Lennox broth. CONCLUSIONS: Our results demonstrate that ompX mRNA is regulated in response to H2O2 by the sRNAs CyaR, MicA and OxyS is Salmonella Typhimurium.