Expression and properties of the mitochondrial and cytosolic forms of fumarase in germinating maize seeds

Fumarase (EC 4.2.1.2) catalyzes reversible interconversion of malate and fumarate. It is usually associated with the tricarboxylic acid cycle in mitochondria, although the cytosolic form has also been detected. We investigated the expression of two fumarase genes and activities of the mitochondrial and cytosolic isoforms of fumarase in maize (Zea mays) scutellum during germination. Both isoforms were purified to electrophoretic homogeneity. The cytosolic form had low optimum pH (6.5) and high affinity to malate (K_m 5 μM) when compared with the mitochondrial form (optimum pH 7.0, K_m 50 μM). The cytosolic form was strongly activated by Mg²⁺ and even more by Mn²⁺, whereas the mitochondrial form was moderately activated by Mg²⁺ and Mn²⁺ was less effective. The highest fumarase activity in scutellum and a high expression of the gene encoding the cytosolic form were observed during the maximal activity of the glyoxylate cycle. In leaves, the localization of fumarase is only mitochondrial and only one fumarase gene is expressed. It is concluded that the function of cytosolic fumarase in maize scutellum can be related to metabolism of succinate formed in the glyoxylate cycle.     

Lysophosphatidic acid activates lipogenic pathways and de novo lipid synthesis in ovarian cancer cells

One of the most common molecular changes in cancer is the increased endogenous lipid synthesis, mediated primarily by overexpression and/or hyperactivity of fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC). The changes in these key lipogenic enzymes are critical for the development and maintenance of the malignant phenotype. Previous efforts to control oncogenic lipogenesis have been focused on pharmacological inhibitors of FAS and ACC. Although they show anti-tumor effects in culture and in mouse models, these inhibitors are nonselective blockers of lipid synthesis in both normal and cancer cells. To target lipid anabolism in tumor cells specifically, it is important to identify the mechanism governing hyperactive lipogenesis in malignant cells. In this study, we demonstrate that lysophosphatidic acid (LPA), a growth factor-like mediator present at high levels in ascites of ovarian cancer patients, regulates the sterol regulatory element binding protein-FAS and AMP-activated protein kinase-ACC pathways in ovarian cancer cells but not in normal or immortalized ovarian epithelial cells. Activation of these lipogenic pathways is linked to increased de novo lipid synthesis. The pro-lipogenic action of LPA is mediated through LPA(2), an LPA receptor subtype overexpressed in ovarian cancer and other malignancies. Downstream of LPA(2), the G(12/13) and G(q) signaling cascades mediate LPA-dependent sterol regulatory element-binding protein activation and AMP-activated protein kinase inhibition, respectively. Moreover, inhibition of de novo lipid synthesis dramatically attenuated LPA-induced cell proliferation. These results demonstrate that LPA signaling is causally linked to the hyperactive lipogenesis in ovarian cancer cells, which can be exploited for development of new anti-cancer therapies.     

Role of LPA4/p2y9/GPR23 in negative regulation of cell motility

Lysophosphatidic acid (LPA) is a ligand of multiple G protein–coupled receptors. The LPA_1–3 receptors are members of the endothelial cell differentiation gene (Edg) family. LPA₄/p2y9/GPR23, a member of the purinergic receptor family, and recently identified LPA₅/GPR92 and p2y5 are structurally distant from the canonical Edg LPA receptors. Here we report targeted disruption of lpa₄ in mice. Although LPA₄-deficient mice displayed no apparent abnormalities, LPA₄-deficient mouse embryonic fibroblasts (MEFs) were hypersensitive to LPA-induced cell migration. Consistent with negative modulation of the phosphatidylinositol 3 kinase pathway by LPA₄, LPA₄ deficiency potentiated Akt and Rac but decreased Rho activation induced by LPA. Reconstitution of LPA₄ converted LPA₄-negative cells into a less motile phenotype. In support of the biological relevance of these observations, ectopic expression of LPA₄ strongly inhibited migration and invasion of human cancer cells. When coexpressed with LPA₁ in B103 neuroblastoma cells devoid of endogenous LPA receptors, LPA₄ attenuated LPA₁-driven migration and invasion, indicating functional antagonism between the two subtypes of LPA receptors. These results provide genetic and biochemical evidence that LPA₄ is a suppressor of LPA-dependent cell migration and invasion in contrast to the motility-stimulating Edg LPA receptors.     

Tricyclic azepine derivatives as selective brain penetrant 5-HT6 receptor antagonists

Starting from a benzazepine sulfonamide 5-HT(6) receptor antagonist lead with limited brain penetration, application of a strategy of conformational constraint and reduction of hydrogen bond donor count led to a novel series of tricyclic derivatives with high 5-HT(6) receptor affinity and excellent brain:blood ratios.     

Objective patterns in the evolving network of non-equivalent observers

The world's objective pattern is formed through consistent histories of quantum measurements originating as different branches of the same wave function. When we come close to the limits of measurement (either by approaching the speed of light or the values of the Planck's quantum), the relational effects come into place and the objectivity of world's pattern melts down. But when we are positioned far from these limits, we live in a comfortable area of the world common to all beings and approximating the objective environment (classical spacetime). Living systems are based on reflective cycles that can interact with relative predictability. Being quantum mechanical observers having different clocks, they generate perpetually evolving fitness landscape. I discuss how the perception of the objective is formed by the generation of same limits of iteration for the processes performed by non-equivalent observers and how the uniform time appears from its counting through these objective processes.     

Crop Improvement and Abiotic Stress Tolerance Promoted by Moringa Leaf Extract

Moringa leaf extract (MLE) has been shown to promote beneficial outcomes in animals and plants. It is rich in amino acids, antioxidants, phytohormones, minerals, and many other bioactive compounds with nutritional and growth-promoting potential. Recent reports indicated that MLE improved abiotic stress tolerance in plants. Our understanding of the mechanisms underlying MLE-mediated abiotic stress tolerance remains limited. This review summarizes the existing literature on the role of MLE in promoting plant abiotic stress acclimation processes. MLE is applied to plants in a variety of ways, including foliar spray, rooting media, and seed priming. Exogenous application of MLE promoted crop plant growth, photosynthesis, and yield under both nonstress and abiotic stress conditions. MLE treatment reduced the severity of osmotic and oxidative stress in plants by regulating osmolyte accumulation, antioxidant synthesis, and secondary metabolites. MLE also improves mineral homeostasis in the presence of abiotic stress. Overall, this review describes the potential mechanisms underpinning MLE-mediated stress tolerance.     

Succinate dehydrogenase in Arabidopsis thaliana is regulated by light via phytochrome A

The effect of light on succinate dehydrogenase (SDH) activity and mRNA content was studied in Arabidopsis thaliana plants. The transition from darkness to light caused a short transient increase in the SDH activity followed by a decrease to a half of the original activity. The white or red light were found to be down-regulating factors for the mRNA content of the sdh1-2 and sdh2-3 genes and SDH catalytic activity both in A. thaliana wild-type plants and in the mutant deficient in the phytochrome B gene, but not in the mutant deficient in the phytochrome A gene, while the far-red light of 730 nm reversed the red light effect. It is concluded that phytochrome A participates in the regulation of mitochondrial respiration through effect on SDH expression.     

The internal rotenone‐insensitivae NADPH dehydrogenase contributes to malate oxidation by potato tuber and pea leaf mitochondria

Inside-out submitochondrial particles from both potato (Solanum tuberosum L. cv. Bintje) tubers and pea (Pisum sativum L. cv. Oregon) leaves possess three distinct dehydrogenase activities: Complex I catalyzes the rotenone-sensitive oxidation of deamino-NADH, ND_in(NADPH) catalyzes the rotenone-insensitive and Ca²⁺-dependent oxidation of NADPH and ND_in(NADH) catalyzes the rotenone-insensitive and Ca²⁺-independent oxidation of NADH. Diphenylene iodonium (DPI) inhibits complex I, ND_in(NADPH) and ND_in (NADH) activity with a K_i of 3.7, 0.17 and 63 µM, respectively, and the 400-fold difference in K_i between the two ND_in made possible the use of DPI inhibition to estimate ND_in (NADPH) contribution to malate oxidation by intact mitochondria. The oxidation of malate in the presence of rotenone by intact mitochondria from both species was inhibited by 5 µM DPI. The maximum decrease in rate was 10–20 nmol O₂ mg^?1 min^?1. The reduction level of NAD(P) was manipulated by measuring malate oxidation in state 3 at pH 7.2 and 6.8 and in the presence and absence of an oxaloacetate-removing system. The inhibition by DPI was largest under conditions of high NAD(P) reduction. Control experiments showed that 125 µM DPI had no effect on the activities of malate dehydrogenase (with NADH or NADPH) or malic enzyme (with NAD⁺ or NADP⁺) in a matrix extract from either species. Malate dehydrogenase was unable to use NADP⁺ in the forward reaction. DPI at 125 µM did not have any effect on succinate oxidation by intact mitochondria of either species. We conclude that the inhibition caused by DPI in the presence of rotenone in plant mitochondria oxidizing malate is due to inhibition of ND_in(NADPH) oxidizing NADPH. Thus, NADP turnover contributes to malate oxidation by plant mitochondria.     

Management of disorders of the posterior pelvic floor

INTRODUCTION: Constipation is a relatively common problem affecting 15 percent of adults in the Western world, and over half of these cases are related to pelvic floor disorders. This article reviews the clinical presentation and diagnostic approach to posterior pelvic floor disorders, including how to image and treat them. METHODS: A Pubmed search using keywords "rectal prolapse," "rectocele," "perineal hernia," and "anismus" was performed, and bibliographies of the revealed articles were cross-referenced to obtain a representative cross-section of the literature, both investigational studies and reviews, that are currently available on posterior pelvic floor disorders. DISCUSSION: Pelvic floor disorders can occur with or without concomitant physical anatomical defects, and there are a number of imaging modalities available to detect such abnormalities in order to decide on the appropriate course of treatment. Depending on the nature of the disorder, operative or non-operative therapy may be indicated. CONCLUSION: Correctly diagnosing pelvic floor disorders can be complex and challenging, and the various imaging modalities as well as clinical history and exam must be considered together in order to arrive at a diagnosis.