Biodiversity of Pyricularia oryzae Cav. in rice-growing regions of the south of Russia using PCR method

Physiology and Molecular Biology of Plants - The purpose of this research by the way of investigating the molecular genetic structure of a highly variable fungal phytopathogen Pyricularia oryzae...     

TFAM knockdown-triggered mtDNA-nucleoid aggregation and a decrease in mtDNA copy number induce the reorganization of nucleoid populations and mitochondria-associated ER-membrane contacts

The correct organization of mitochondrial DNA (mtDNA) in nucleoids and the contacts of mitochondria with the ER play an important role in maintaining the mitochondrial genome distribution within the cell. Mitochondria-associated ER membranes (MAMs) consist of interacting proteins and lipids located in the outer mitochondrial membrane and ER membrane, forming a platform for the mitochondrial inner membrane-associated genome replication factory as well as connecting the nucleoids with the mitochondrial division machinery. We show here that knockdown of a core component of mitochondrial nucleoids, TFAM, causes changes in the mitochondrial nucleoid populations, which subsequently impact ER-mitochondria membrane contacts. Knockdown of TFAM causes a significant decrease in the copy number of mtDNA as well as aggregation of mtDNA nucleoids. At the same time, it causes significant upregulation of the replicative TWNK helicase in the membrane-associated nucleoid fraction. This is accompanied by a transient elevation of MAM proteins, indicating a rearrangement of the linkage between ER and mitochondria triggered by changes in mitochondrial nucleoids. Reciprocal knockdown of the mitochondrial replicative helicase TWNK causes a decrease in mtDNA copy number and modifies mtDNA membrane association, however, it does not cause nucleoid aggregation and considerable alterations of MAM proteins in the membrane-associated fraction. Our explanation is that the aggregation of mitochondrial nucleoids resulting from TFAM knockdown triggers a compensatory mechanism involving the reorganization of both mitochondrial nucleoids and MAM. These results could provide an important insight into pathological conditions associated with impaired nucleoid organization or defects of mtDNA distribution.     

Involvement of the Rho-mDia1 pathway in the regulation of Golgi complex architecture and dynamics

In mammalian cells, the Golgi apparatus is a ribbon-like, compact structure composed of multiple membrane stacks connected by tubular bridges. Microtubules are known to be important to Golgi integrity, but the role of the actin cytoskeleton in the maintenance of Golgi architecture remains unclear. Here we show that an increase in Rho activity, either by treatment of cells with lysophosphatidic acid or by expression of constitutively active mutants, resulted in pronounced fragmentation of the Golgi complex into ministacks. Golgi dispersion required the involvement of mDia1 formin, a downstream target of Rho and a potent activator of actin polymerization; moreover, constitutively active mDia1, in and of itself, was sufficient for Golgi dispersion. The dispersion process was accompanied by formation of dynamic F-actin patches in the Golgi area. Experiments with cytoskeletal inhibitors (e.g., latrunculin B, blebbistatin, and Taxol) revealed that actin polymerization, myosin-II-driven contractility, and microtubule-based intracellular movement were all involved in the process of Golgi dispersion induced by Rho-mDia1 activation. Live imaging of Golgi recovery revealed that fusion of the small Golgi stacks into larger compartments was repressed in cells with active mDia1. Furthermore, the formation of Rab6-positive transport vesicles derived from the Golgi complex was enhanced upon activation of the Rho-mDia1 pathway. Transient localization of mDia1 to Rab6-positive vesicles was detected in cells expressing active RhoA. Thus, the Rho-mDia1 pathway is involved in regulation of the Golgi structure, affecting remodeling of Golgi membranes.     

Soluble guanylate cyclase stimulation prevents fibrotic tissue remodeling and improves survival in salt-sensitive Dahl rats

Background

A direct pharmacological stimulation of soluble guanylate cyclase (sGC) is an emerging therapeutic approach to the management of various cardiovascular disorders associated with endothelial dysfunction. Novel sGC stimulators, including riociguat (BAY 63-2521), have a dual mode of action: They sensitize sGC to endogenously produced nitric oxide (NO) and also directly stimulate sGC independently of NO. Little is known about their effects on tissue remodeling and degeneration and survival in experimental malignant hypertension.

Methods and Results

Mortality, hemodynamics and biomarkers of tissue remodeling and degeneration were assessed in Dahl salt-sensitive rats maintained on a high salt diet and treated with riociguat (3 or 10 mg/kg/d) for 14 weeks. Riociguat markedly attenuated systemic hypertension, improved systolic heart function and increased survival from 33% to 85%. Histological examination of the heart and kidneys revealed that riociguat significantly ameliorated fibrotic tissue remodeling and degeneration. Correspondingly, mRNA expression of the pro-fibrotic biomarkers osteopontin (OPN), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and plasminogen activator inhibitor-1 (PAI-1) in the myocardium and the renal cortex was attenuated by riociguat. In addition, riociguat reduced plasma and urinary levels of OPN, TIMP-1, and PAI-1.

Conclusions

Stimulation of sGC by riociguat markedly improves survival and attenuates systemic hypertension and systolic dysfunction, as well as fibrotic tissue remodeling in the myocardium and the renal cortex in a rodent model of pressure and volume overload. These findings suggest a therapeutic potential of sGC stimulators in diseases associated with impaired cardiovascular and renal functions.     

Regression of atherosclerosis is characterized by broad changes in the plaque macrophage transcriptome

We have developed a mouse model of atherosclerotic plaque regression in which an atherosclerotic aortic arch from a hyperlipidemic donor is transplanted into a normolipidemic recipient, resulting in rapid elimination of cholesterol and monocyte-derived macrophage cells (CD68+) from transplanted vessel walls. To gain a comprehensive view of the differences in gene expression patterns in macrophages associated with regressing compared with progressing atherosclerotic plaque, we compared mRNA expression patterns in CD68+ macrophages extracted from plaque in aortic aches transplanted into normolipidemic or into hyperlipidemic recipients. In CD68+ cells from regressing plaque we observed that genes associated with the contractile apparatus responsible for cellular movement (e.g. actin and myosin) were up-regulated whereas genes related to cell adhesion (e.g. cadherins, vinculin) were down-regulated. In addition, CD68+ cells from regressing plaque were characterized by enhanced expression of genes associated with an anti-inflammatory M2 macrophage phenotype, including arginase I, CD163 and the C-lectin receptor. Our analysis suggests that in regressing plaque CD68+ cells preferentially express genes that reduce cellular adhesion, enhance cellular motility, and overall act to suppress inflammation.     

Oxirapentyns B–D produced by a marine sediment-derived fungus Isaria felina (DC.) Fr

Three new highly oxygenated chromene derivatives, oxirapentyns B–D (1–3) and one known oxirapentyn A (4) were isolated from the lipophilic extract of the marine-derived fungus Isaria felina KMM 4639. The structures of compounds 1–3 were determined based on spectroscopic methods. The absolute configuration of oxirapentyn B (1) as 2R, 4S, 5S, 6S, 7R, 8S, 9S was established by a combination of modified Mosher's method, X-ray analysis, and NOESY data. Oxirapentyn A (4) showed weak cytotoxicity against SK-Mel-5, SK-Mel-28 human malignant melanoma, and T-47D human breast cancer cell lines.     

Treatment with interferon alpha prior to discontinuation of imatinib in patients with chronic myeloid leukemia

Imatinib (IM) is the current first line treatment for chronic myeloid leukemia (CML). However, the disease will progress in the majority of patients pausing IM. IFN-α may intensify the response and increase the percentage of patients maintaining remission after IM cessation. Eleven patients with stable (≥ 2 years) complete cytogenetic responses (CCyR) on IM therapy were recruited to the study. They were administered Peg-IFN-α for 9 months before and for 3 months following IM discontinuation. During the 12 months of Peg-IFN-α therapy the remission status improved in five (45%) of the patients. Six (55%) of the patients experienced cytogenetic relapses at a median period of 8 months (range 2-33) after IM withdrawal. All six patients regained CCyR following IM restart. With a median follow up of 47 months (range 35-50), five (45%) out of the 11 studied patients maintain cytogenetic response off IM therapy. The role of Peg-IFN-α in patients pausing IM is to be further evaluated.     

Symmetry Breaking in a Model of Antigenic Variation with Immune Delay

Effects of immune delay on symmetric dynamics are investigated within a model of antigenic variation in malaria. Using isotypic decomposition of the phase space, stability problem is reduced to the analysis of a cubic transcendental equation for the eigenvalues. This allows one to identify periodic solutions with different symmetries arising at a Hopf bifurcation. In the case of small immune delay, the boundary of the Hopf bifurcation is found in a closed form in terms of system parameters. For arbitrary values of the time delay, general expressions for the critical time delay are found, which indicate bifurcation to an odd or even periodic solution. Numerical simulations of the full system are performed to illustrate different types of dynamical behaviour. The results of this analysis are quite generic and can be used to study within-host dynamics of many infectious diseases.     

Conformational epitopes at cadherin calcium-binding sites and p120-catenin phosphorylation regulate cell adhesion

We investigated changes in cadherin structure at the cell surface that regulate its adhesive activity. Colo 205 cells are nonadhesive cells with a full but inactive complement of E-cadherin-catenin complexes at the cell surface, but they can be triggered to adhere and form monolayers. We were able to distinguish the inactive and active states of E-cadherin at the cell surface by using a special set of monoclonal antibodies (mAbs). Another set of mAbs binds E-cadherin and strongly activates adhesion. In other epithelial cell types these activating mAbs inhibit growth factor-induced down-regulation of adhesion and epithelial morphogenesis, indicating that these phenomena are also controlled by E-cadherin activity at the cell surface. Both types of mAbs recognize conformational epitopes at different interfaces between extracellular cadherin repeat domains (ECs), especially near calcium-binding sites. Activation also induces p120-catenin dephosphorylation, as well as changes in the cadherin cytoplasmic domain. Moreover, phospho-site mutations indicate that dephosphorylation of specific Ser/Thr residues in the N-terminal domain of p120-catenin mediate adhesion activation. Thus physiological regulation of the adhesive state of E-cadherin involves physical and/or conformational changes in the EC interface regions of the ectodomain at the cell surface that are mediated by catenin-associated changes across the membrane.