Catestatin (chromogranin A344-364) is a novel cardiosuppressive agent: inhibition of isoproterenol and endothelin signaling in the frog heart

The catecholamine release-inhibitory catestatin [Cts; human chromogranin (Cg) A(352-372), bovine CgA(344-364)] is a vasoreactive and anti-hypertensive peptide derived from CgA. Using the isolated avascular frog heart as a bioassay, in which the interactions between the endocardial endothelium and the subjacent myocardium can be studied without the confounding effects of the vascular endothelium, we tested the direct cardiotropic effects of bovine Cts and its interaction with beta-adrenergic (isoproterenol, ISO) and endothelin-1 (ET-1) signaling. Cts dose-dependently decreased stroke volume and stroke work, with a threshold concentration of 11 nM, approaching the in vivo level of the peptide. Cts reduced contractility by inhibiting phosphorylation of phospholamban (PLN). Furthermore, the Cts effect was abolished by pretreatment with either nitric oxide synthase (N(G)-monomethyl-l-arginine) or guanylate cyclase (ODQ) inhibitors, or an ET(B) receptor (ET(BR)) antagonist (BQ-788). Cts also noncompetitively inhibited the positive inotropic action of ISO. In addition, Cts inhibited the positive inotropic effect of ET-1, mediated by ET(A) receptors, and did not alter the negative inotropic ET-1 influence mediated by ET(BR). Cts action through ET(BR) was further suggested when, in the presence of BQ-788, Cts failed to inhibit the positive inotropism of both ISO and ET-1 stimulation and PLN phosphorylation. We concluded that the cardiotropic actions of Cts, including the beta-adrenergic and ET-1 antagonistic effects, support a novel role of this peptide as an autocrine-paracrine modulator of cardiac function, particularly when the stressed heart becomes a preferential target of both adrenergic and ET-1 stimuli.     

NaCl-stress induced alteration in glutamine synthetase activity in excised senescing leaves of a salt-sensitive and a salt-tolerant rice cultivar in light and darkness

Alteration in glutamine synthetase activity was studied in excisedsenescing leaves of rice (Oryza sativa L.) of asalt-sensitive (Ratna) and a salt-tolerant (Getu) cultivar subjected toNaCl-stress. Glutamine synthetase activity declined during senescence indarkness, but increased initially and then decreased under light treatment,which is correlated with the degree of leaf senescence. In NaCl-stressed leavesthe declining trend of this enzyme activity was accelerated in the fastersenescing cv. Ratna in both light or darkness. However, it was partiallyretarded in the dark and fully in the light in the slower senescing cv. Getu.This probably indicates that the control mechanism of enzyme activities isdifferent in the sensitive and the tolerant cultivar under saline condition. Thehigher activity of glutamine synthetase and consequently higher syntheticactivity in the tolerant cultivar may be a biochemical adaptation for salttolerance in rice.     

An RNA-binding respiratory component mediates import of type II tRNAs into Leishmania mitochondria

Transport of tRNAs across the inner mitochondrial membrane of the kinetoplastid protozoon Leishmania requires interactions with specific binding proteins (receptors) in a multi-subunit complex. The allosteric model of import regulation proposes cooperative and antagonistic interactions between two or more receptors with binding specificities for distinct tRNA families (types I and II, respectively). To identify the type II receptor, the gene encoding RIC8A, a subunit of the complex, was cloned. The C-terminal region of RIC8A is homologous to subunit 6b of ubiquinol cytochrome c reductase (respiratory complex III), while the N-terminal region has intrinsic affinity for type II, but not for type I, tRNAs. RIC8A is shared by the import complex and complex III, indicating its bi-functionality, but is assembled differently in the two complexes. Knockdown of RIC8A in Leishmania lowered the mitochondrial content of type II tRNAs but raised that of type I tRNAs, with downstream effects on mitochondrial translation and respiration, and cell death. In RIC8A knockdown cells, a subcomplex was formed that interacted with type I tRNA, but the negative regulation by type II tRNA was lost. Mitochondrial extracts from these cells were defective for type II, but not type I, import; import and regulation were restored by purified RIC8A. These results provide evidence for the relevance of allosteric regulation in vivo and indicate that acquisition of new tRNA-binding domains by ancient respiratory components have played a key role in the evolution of mitochondrial tRNA import.     

Age- and area-dependent distinct effects of ethanol on Bax and Bcl-2 expression in prenatal rat brain

Cell proliferation and differentiation are critical processes in a developing fetal rat brain, during which programmed cell death (PCD) also plays an important role. One of the decisive factors for PCD is Bcl-2 family proteins, where Bax induces cell death, whereas Bcl-2 acts as an inhibitor of PCD. As maternal drinking is known to cause fetal alcohol syndrome (FAS) or malformation of the fetal brain during pregnancy, the objective of the present study was to investigate whether maternal ethanol exposure alters the PCD-related Bax and Bcl-2 protein expression during fetal brain development. Pregnant female rats were orally treated with 10% ethanol and the subsequent expressions of the Bax and Bcl-2 proteins examined in the fetal brain, including the forebrain, midbrain, and hindbrain, from gestational day (GD) 15.5 to GD 19.5, using Western blots, in situ hybridization, and immunohistochemistry. With regard to the ratio of Bcl-2 to Bax proteins (Bcl-2/Bax), the Bax protein was dominant in the forebrain and midbrain of the control GD 15.5 fetuses, except for the hindbrain, when compared with the respective ethanol-treated groups. Moreover, Bcl-2 became dominant in the midbrain of the control GD 17.5 fetuses when compared with the ethanoltreated group, representing an alternation of the natural PCD process by ethanol. Furthermore, a differential expression of the Bcl-2 and Bax proteins was found in the differentiating and migrating zones of the cortex, hippocampus, thalamus, and cerebellum. Thus, when taken together, the present results suggest that ethanol affects PCD in the cell differentiation and migration zones of the prenatal rat brain by modulating Bax and Bcl-2 expression in an age- and area-dependent manner. Therefore, this is the first evidence that ethanol may alter FAS-associated embryonic brain development through the alteration of Bax and Bcl-2 expression.     

Effect of steroid hormones on serotonin,norepinephrine and epinephrine contents in the pineal-paraphyseal complex of the soft-shelled turtle (Lissemys punctata punctata)

Summary Steroids (testosterone, oestrogen, progesterone, corticosterone, dexamethasone and deoxycorticosterone) were administered intramuscularly (0.1 mg · 100 g bw^-1) on seven consecutive days to juvenile male soft-shelled turtles. Serotonin, norepinephrine and epinephrine contents of the pineal-paraphyseal complex were measured spectrofluorometrically 24 h after the last injection. Testosterone and oestrogen decreased serotonin, norepinephrine and epinephrine levels. Progesterone treatment resulted in an increase of serotonin level and a fall in norepinephrine and epinephrine levels. Corticosterone treatment caused an increase of serotonin level and a decrease of norepinephrine and epinephrine levels. Dexamethasone failed to alter serotonin content, increased norepinephrine and decreased epinephrine levels. Deoxycorticosterone decreased serotonin and elevated epinephrine content.Abbreviations 5-HIAA 5-hydroxyindole-acetic acid - 5-MTOH 5-methoxytryptophol - ANOVA analysis of variance; bw body weight - COMT catecholamine-o-methyl transferase - E epinephrine - HIOMT hydroxyindole-o-methyl transferase - MAO monoamine oxidase - MS mean sum of squares - NAT N-acetyltransferase - NE norepinephrine - SR synaptic ribbon - SS sum of squares - SV source of variation     

Chromosomal aberrations in arsenic-exposed human populations: a review with special reference to a comprehensive study in West Bengal, India

For centuries arsenic has played an important role in science, technology, and medicine. Arsenic for its environmental pervasiveness has gained unexpected entrance to the human body through food, water and air, thereby posing a great threat to public health due to its toxic effect and carcinogenicity. Thus, in modern scenario arsenic is synonymous with "toxic" and is documented as a paradoxical human carcinogen, although its mechanism of induction of neoplasia remains elusive. To assess the risk from environmental and occupational exposure of arsenic, in vivo cytogenetic assays have been conducted in arseniasis-endemic areas of the world using chromosomal aberrations (CA) and sister chromatid exchanges (SCE) as biomarkers in peripheral blood lymphocytes. The primary aim of this report is to critically review and update the existing in vivo cytogenetic studies performed on arsenic-exposed populations around the world and compare the results on CA and SCE from our own study, conducted in arsenic-endemic villages of North 24 Parganas (district) of West Bengal, India from 1999 to 2003. Based on a structured questionnaire, 165 symptomatic (having arsenic induced skin lesions) subjects were selected as the exposed cases consuming water having a mean arsenic content of 214.96 microg/l. For comparison 155 age-sex matched control subjects from an unaffected district (Midnapur) of West Bengal were recruited. Similar to other arsenic exposed populations our population also showed a significant difference (P < 0.01) in the frequencies of CA and SCE between the cases and control group. Presence of substantial chromosome damage in lymphocytes in the exposed population predicts an increased future carcinogenic risk by this metalloid.     

Using expert knowledge and modeling to define mangrove composition,functioning, and threats and estimate time frame for recovery

Mangroves are threatened worldwide, and their loss or degradation could impact functioning of the ecosystem. Our aim was to investigate three aspects of mangroves at a global scale: (1) their constituents (2) their indispensable ecological functions, and (3) the maintenance of their constituents and functions in degraded mangroves. We focused on answering two questions: “What is a mangrove ecosystem” and “How vulnerable are mangrove ecosystems to different impacts”? We invited 106 mangrove experts globally to participate in a survey based on the Delphi technique and provide inputs on the three aspects. The outputs from the Delphi technique for the third aspect, i.e. maintenance of constituents and functions were incorporated in a modeling approach to simulate the time frame for recovery. Presented here for the first time are the consensus definition of the mangrove ecosystem and the list of mangrove plant species. In this study, experts considered even monospecific (tree) stands to be a mangrove ecosystem as long as there was adequate tidal exchange, propagule dispersal, and faunal interactions. We provide a ranking of the important ecological functions, faunal groups, and impacts on mangroves. Degradation due to development was identified as having the largest impact on mangroves globally in terms of spatial scale, intensity, and time needed for restoration. The results indicate that mangroves are ecologically unique even though they may be species poor (from the vegetation perspective). The consensus list of mangrove species and the ranking of the mangrove ecological functions could be a useful tool for restoration and management of mangroves. While there is ample literature on the destruction of mangroves due to aquaculture in the past decade, this study clearly shows that more attention must go to avoiding and mitigating mangrove loss due to coastal development (such as building of roads, ports, or harbors).     

Thermostable direct hemolysin downregulates human colon carcinoma cell proliferation with the involvement of E-cadherin, and β-catenin/Tcf-4 signaling

Background

Colon cancers are the frequent causes of cancer mortality worldwide. Recently bacterial toxins have received marked attention as promising approaches in the treatment of colon cancer. Thermostable direct hemolysin (TDH) secreted by Vibrio parahaemolyticus causes influx of extracellular calcium with the subsequent rise in intracellular calcium level in intestinal epithelial cells and it is known that calcium has antiproliferative activity against colon cancer.

Key Results

In the present study it has been shown that TDH, a well-known traditional virulent factor inhibits proliferation of human colon carcinoma cells through the involvement of CaSR in its mechanism. TDH treatment does not induce DNA fragmentation, nor causes the release of lactate dehydrogenase. Therefore, apoptosis and cytotoxicity are not contributing to the TDH-mediated reduction of proliferation rate, and hence the reduction appears to be caused by decrease in cell proliferation. The elevation of E-cadherin, a cell adhesion molecule and suppression of β-catenin, a proto-oncogene have been observed in presence of CaSR agonists whereas reverse effect has been seen in presence of CaSR antagonist as well as si-RNA in TDH treated cells. TDH also triggers a significant reduction of Cyclin-D and cdk2, two important cell cycle regulatory proteins along with an up regulation of cell cycle inhibitory protein p27^Kip1 in presence of CaSR agonists.

Conclusion

Therefore TDH can downregulate colonic carcinoma cell proliferation and involves CaSR in its mechanism of action. The downregulation occurs mainly through the involvement of E-cadherin-β-catenin mediated pathway and the inhibition of cell cycle regulators as well as upregulation of cell cycle inhibitors.     

Have mangrove restoration projects worked? An in‐depth study in Sri Lanka

This study investigated the effectiveness of mangrove planting initiatives in Sri Lanka. All the lagoons and estuaries in Sri Lanka were included in the study. We documented all agencies and locations, involved in mangrove planting efforts, along with the major drivers of these planting initiatives, their extents, and the possible causes of the success or failure of planting. An adapted three‐step framework and a field survey consisting of vegetation and soil surveys and questionnaires were used to evaluate the objectives. We found that about 1,000–1,200 ha of mangroves, representing 23 project sites with 67 planting efforts, have been under restoration with the participation of several governmental and nongovernmental organizations. However, about 200–220 ha showed successful mangrove restoration. Nine out of 23 project sites (i.e. 36/67 planting efforts) showed no surviving plants. The level of survival of the restoration project sites ranged from 0 to 78% and only three sites, that is, Kalpitiya, Pambala, and Negombo, showed a level of survival higher than 50%. Survival rates were significantly correlated with post‐care. Planting mangrove seedlings at the incorrect topography often entails inappropriate soil conditions for mangroves. Survival rates showed significant correlations with a range of soil parameters except soil pH. Disturbance and stress caused by cattle trampling, browsing, algal accumulation, and insect attacks, factors that may themselves relate to choosing sites with inappropriate topography and hydrology, were common to most sites. The findings are a stark illustration of the frequent mismatch between the purported aims of restoration initiatives and the realities on the ground.