Phytochrome regulation of greening in wild type and long-hypocotyl mutants ofArabidopsis thaliana

A brief pulse of red light (R) given to darkgrown seedlings ofArabidopsis thaliana (L.) Heyn. potentiates rapid synthesis of chlorophyll upon transfer to continuous white light. The time course for potentiation of rapid greening shows that a R pulse in the LF (low fluence) range has maximal effect within a few hours, and that there is a small VLF (very low fluence) component as well. Partial reversal of the effect of R by far-red light (FR) indicates that the pulse acts through phytochrome. As it does in the wild-type (WT), a pulse of R accelerates greening of long-hypocotyl (hy) mutants. The extent of induction by the R pulse was about the same in the WT and in allhy mutants studied. Reversibility by FR was greatly decreased in thehy-1 andhy-2 strains. It is possible that these mutants contain a species of phytochrome with defective phototransformation kinetics. If there is such a defective phytochrome species, it nevertheless appears to be active in the potentiation of rapid greening. Dedicated to Professor Hans Mohr on the occasion of his 60th birthday     

High urine flow rate increases prostaglandin E excretion in the conscious dog

Although previous studies from this and other laboratories have shown that urinary prostaglandin E excretion (U_PGEV) can vary independent of urine flow rate, recent studies during water diuresis in the conscious dog have suggested that high urine flow rate per se may increase U_PGEV. To examine the effect of urine flow rate on U_PGEV we administered either mannitol, chlorothiazide or Ringer's solution to mongrel dogs and measured U_PGEV. During anesthesia neither mannitol or chlorothiazide increased U_PGEV. There was, however, a consistent increase with all three agents in awake animals. This increase in U_PGEV was independent of alterations in glomerular filtration rate. There was a consistent increase in urinary sodium excretion and decrease in urinary osmolality with all three agents. The changes in PGE, however, were similar to those found during water diuresis when no increase in sodium excretion was found. It is not presently clear whether these findings reflect a true increase in renal PGE synthesis due to some change in flow or pressure within the renal medulla or rather represent unchanged PGE synthesis by renal tubular cells, the high tubule fluid flow rate causing increased entry into the tubular lumen in contrast to the renal interstitium.     

Leptin modulates lymphocytes' adherence to hepatic stellate cells is associated with oxidative status alterations

We investigated leptin effects on lymphocyte interactions with hepatic-stellate-cells (HSCs). Leptin showed pro-fibrotic effects on HSCs with oxidative status imbalance.In co-cultures, leptin activates HSCs and consequently adhered HCV-lymphocytes more than healthy ones. Leptin also increased healthy and HCV lymphocyte proliferations; increased their reactive-oxygen-species; decreased antioxidants (reduced-glutathione) levels while inhibited apoptosis only of HCV-lymphocytes. The leptin-treated HCV-lymphocytes activated HSCs, increase interleukin-4 while decreased their apoptosis.Leptin-receptor-deficient (db–db)-HSCs did not adhere lymphocytes. db/db-lymphocytes however showed fewer adherences to HSCs when compared to WT-counterparts.This study presents immune and oxidative modulatory effects of leptin on lymphocytes and their consequent interaction with HSCs.     

Vitreous TIMP-1 levels associate with neovascularization and TGF-β2 levels but not with fibrosis in the clinical course of proliferative diabetic retinopathy

In proliferative diabetic retinopathy (PDR), vascular endothelial growth factor (VEGF) and CCN2 (connective tissue growth factor; CTGF) cause blindness by neovascularization and subsequent fibrosis. This angio-fibrotic switch is associated with a shift in the balance between vitreous levels of CCN2 and VEGF in the eye. Here, we investigated the possible involvement of other important mediators of fibrosis, tissue inhibitor of metalloproteinases (TIMP)-1 and transforming growth factor (TGF)-β2, and of the matrix metalloproteinases (MMP)-2 and MMP-9, in the natural course of PDR. TIMP-1, activated TGF-β2, CCN2 and VEGF levels were measured by ELISA in 78 vitreous samples of patients with PDR (n = 28), diabetic patients without PDR (n = 24), and patients with the diabetes-unrelated retinal conditions macular hole (n = 10) or macular pucker (n = 16), and were related to MMP-2 and MMP-9 activity on zymograms and to clinical data, including degree of intra-ocular neovascularization and fibrosis. TIMP-1, CCN2 and VEGF levels, but not activated TGF-β2 levels, were significantly increased in the vitreous of diabetic patients, with the highest levels in PDR patients. CCN2 and the CCN2/VEGF ratio were the strongest predictors of degree of fibrosis. In diabetic patients with or without PDR, activated TGF-β2 levels correlated with TIMP-1 levels, whereas in PDR patients, TIMP-1 levels, MMP-2 and proMMP-9 were associated with degree of neovascularization, like VEGF levels, but not with fibrosis. We confirm here our previous findings that retinal fibrosis in PDR patients is significantly correlated with vitreous CCN2 levels and the CCN2/VEGF ratio. In contrast, TIMP-1, MMP-2 and MMP-9 appear to have a role in the angiogenic phase rather than in the fibrotic phase of PDR.     

Preferential Secretion of Thymic Stromal Lymphopoietin (TSLP) by Terminally Differentiated Esophageal Epithelial Cells: Relevance to Eosinophilic Esophagitis (EoE)

Eosinophilic esophagitis (EoE) is a chronic Th2 and food antigen-mediated disease characterized by esophageal eosinophilic infiltration. Thymic stromal lymphopoetin (TSLP), an epithelial derived cytokine which bridges innate and Th2-type adaptive immune responses in other allergic conditions, is overexpressed in esophageal biopsies of EoE subjects. However, the triggers of TSLP expression in the esophageal epithelium are unknown. The objective of the current study was to characterize TSLP expression in human esophageal epithelium in EoE in vivo and to determine the role of food antigens upon epithelial TSLP expression in vitro. Using immunohistochemistry (IHC), we localized TSLP in esophageal biopsies of active EoE (≥15 eos/hpf), inactive EoE (<15 eos/hpf) and non-EoE control subjects, and found that TSLP expression was restricted to the differentiated suprabasal layer of the epithelium in actively inflamed EoE biopsies. Consistent with these results in vivo, inducible TSLP protein secretion was higher in CaCl₂ differentiated telomerase-immortalized esophageal epithelial cells (EPC2-hTERT) compared to undifferentiated cells of the basal phenotype, following stimulation with the TLR3 ligand poly(I:C). To determine whether food antigens could directly induce epithelial TSLP secretion, differentiated and undifferentiated primary esophageal epithelial cells from EoE and non-EoE subjects were challenged with food antigens clinically relevant to EoE: Chicken egg ovalbumin (OVA), wheat, and milk proteins beta-lactoglobulin (blg) and beta-casein. Food antigens failed to induce TSLP secretion by undifferentiated cells; in contrast, only OVA induced TSLP secretion in differentiated epithelial cells from both EoE and control cell lines, an effect abolished by budesonide and NF-κb inhibition. Together, our study shows that specific food antigens can trigger innate immune mediated esophageal TSLP secretion, suggesting that esophageal epithelial cells at the barrier surface may play a significant role in the pathogenesis of EoE by regulating TSLP expression.     

The pp60c-Src inhibitor PP1 is non-competitive against ATP

The C7-cyclitol 2-epi-5-epi-valiolone is the first precursor of the cyclitol moiety of the -glucosidase inhibitor acarbose in Actinoplanes sp. SE50. The 2-epi-5-epi-valiolone becomes phosphorylated at C7 by the ATP dependent kinase AcbM prior to the next modifications. Preliminary data gave evidences that the AcbO protein could catalyse the first modification step of 2-epi-5-epi-valiolone-7-phosphate. Therefore, the AcbO protein, the encoding gene of which is also part of the acbKMLNOC operon, was overproduced and purified. Indeed the purified protein catalysed the 2-epimerisation of 2-epi-5-epi-valiolone-7-phosphate. The chemical structure of the purified reaction product was proven by nuclear magnetic resonance spectroscopy to be 5-epi-valiolone-7-phosphate.     

Stress and the developing hippocampus: a double-edged sword?

The mechanisms that regulate neuronal function are a sum of genetically determined programs and experience. The effect of experience on neuronal function is particularly important during development, because early-life positive and adverse experience (stress) may influence the still “plastic” nervous system long-term. Specifically, for hippocampal-mediated learning and memory processes, acute stress may enhance synaptic efficacy and overall learning ability, and conversely, chronic or severe stress has been shown to be detrimental. The mechanisms that enable stress to act as this “double-edged sword” are unclear. Here, we discuss the molecular mediators of the stress response in the hippocampus with an emphasis on novel findings regarding the role of the neuropeptide known as corticotropin-releasing hormone (CRH). We highlight the physiological and pathological roles of this peptide in the developing hippocampus, and their relevance to the long-term effects of early-life experience on cognitive function during adulthood.