Plasma thyroxine and cortisol profiles and gill and kidney Na+/K+-ATPase and SDH activities during acclimation of the catfish Heteropneustes fossilis (bloch) to higher salinity, with special reference to the effects of exogenous cortisol on hypo-osmoregulatory ability of the catfish

When the stenohaline catfish Heteropneustes fossilis was transferred from fresh water (FW) to 30% seawater (SW), the Na(+)/K(+)-ATPase activity significantly increased in the kidney, while in gills it remained more or less constant. A reverse pattern was observed for succinic dehydrogenase (SDH) activity inasmuch as it significantly increased in gills and remained unchanged in the kidney. Plasma osmolality significantly increased within 3 days of transfer to 30% SW and remained significantly higher throughout the duration of experiment. These results suggest that catfish gills may not be able to reverse their function from salt uptake in FW to salt excretion at higher salinity, and that the elimination of monovalent as well as divalent ions is performed by the kidney but not the gills. The significant decline in plasma cortisol (F) levels following transfer to higher salinity may not be due to reduced production but rather to an enhanced utilization and clearance rate, a conclusion supported by the fact that exogenous administration of cortisol acetate (FA) resulted in significant increases in branchial and renal Na(+)/K(+)-ATPase in FW and 30% SW. FA also improved the plasma osmotic regulatory ability of the catfish, possibly due to a change in branchial function from salt-absorption to salt excretion, as was evident from a significant increase in branchial Na(+)/K(+)-ATPase activity in the fish in 30% SW pretreated with FA for 5 days. Consistently higher levels of plasma thyroxine (T4) following transfer to higher salinity suggest the involvement of this hormone at higher salinity.     

Triacontanol Protects Mentha arvensis L. from Nickel-Instigated Repercussions by Escalating Antioxidant Machinery,Photosynthetic Efficiency and Maintaining Leaf Ultrastructure and Root Morphology

Nickel (Ni), an essential micronutrient and a prime component of the plant enzyme urease, has an indispensable role in plants. Triacontanol (TRIA) is a conspicuous plant growth regulator in agriculture, which proved advantageous in enhancing the overall production of plants. Therefore, an experiment was laid down to understand the effects of Ni toxicity on the menthol mint (Mentha arvensis L.) and its mitigation by exogenously applied TRIA. The different treatments applied to the plants were 0 (control), TRIA (10⁻⁶ M), Ni (60 mg kg⁻¹), Ni (80 mg kg⁻¹), TRIA (10⁻⁶ M) + Ni (60 mg kg⁻¹), and TRIA (10⁻⁶ M) + Ni (80 mg kg⁻¹). This work was evaluated on the basis of various growth, biochemical, physiological, yield and quality parameters. Nickel applied at 80 mg kg⁻¹ of soil exhibited maximum inhibition in the parameters studied. Application of TRIA improved all the growth parameters such as plant height, fresh and dry weights as well as herbage yield under non stress and stressed conditions. The levels of carbonic anhydrase (CA) activity, photosynthetic parameters (chlorophyll and carotenoids), and chlorophyll fluorescence of the plants were also stimulated by TRIA under Ni stress. Exogenous TRIA also displayed positive effects on the cellular antioxidant defense mechanism of Ni-affected plants as it increased the levels of proline (PRO), electrolytic leakage (EL), and activities of antioxidant enzymes, viz. superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX), therefore, restrained the triggering of the oxidative burst (reactive oxygen species) in the plant cells. Moreover, TRIA improved the overall production (in terms of yield and content) of EO in the plants and maintained the leaf ultrastructure and root morphology under Ni treatment. GC–MS analysis revealed that TRIA upregulated the level of menthone and menthyl acetate over their respective controls and under Ni-stressed condition.

     

Some aspects of osmoregulation in a stenohaline freshwater catfish, Heteropneustes fossilis (Bloch), in different salinities

Transfer of the catfish, Heteropneustes fossilis , to 10% sea water (101 mosmol l⁻¹) or to 0·4% NaCl (140 mosmol l⁻¹) does not evoke any change in plasma osmolarity from the normal freshwater values. There is, however, a reduction in urine flow rate (UFR) and increase in urine osmolarity without any change in the rate of osmolar clearance. In isosmotic (25% sea water or 0·7% NaCl) and in hyperosmotic (30% sea water or 1·1% NaCl) media there is a significant increase in plasma osmolarity accompanied by marked reduction in glomerular filtration rate (GFR), UFR and free water clearance. The results suggest that the catfish cannot effectively osmoregulate in isosmotic or hyperosmotic media and that the inability of the renal tubules to increase reabsorption of water and to reduce free water clearance may account for the restricted range of salinity tolerance of this catfish. Also, in the hyperosmotic media, plasma levels of cortisol are lowered while in the proximal pars distalis the corticotrophs appear active, suggesting increased utilization and clearance of cortisol. Prolactin-secreting cells, however, are degranulated and chromophobic in catfish maintained in hyperosmotic environment.     

Impaired ion channel function related to a common KCNQ1 mutation — Implications for risk stratification in long QT syndrome 1

Long QT syndrome (LQTS) 1 is the most common type of inherited LQTS and is linked to mutations in the KCNQ1 gene. We identified a KCNQ1 missense mutation, KCNQ1 G325R, in an asymptomatic patient presenting with significant QT prolongation (QTc, 448–600 ms). Prior clinical reports revealed phenotypic variability ranging from the absence of symptoms to syncope among KCNQ1 G325R mutation carriers. The present study was designed to determine the G325R ion channel phenotype and its association with the clinical LQTS presentation. Electrophysiological testing was performed using the Xenopus oocyte expression system. KCNQ1 G325R channels were non-functional and suppressed wild type (WT) currents by 71.1%. In the presence of the native cardiac regulatory ß-subunit, KCNE1, currents conducted by G325R and WT KCNQ1 were reduced by 52.9%. Co-expression of G325R and WT KCNQ1 with KCNE1 shifted the voltage-dependence of I_Ks activation by 12.0 mV, indicating co-assembly of mutant and WT subunits. The dysfunctional biophysical phenotype validates the pathogenicity of the KCNQ1 G325R mutation and corresponds well with the severe clinical presentation revealed in some reports. However, the index patient and other mutation carriers were asymptomatic, highlighting potential limitations of risk assessment schemes based on ion channel data.     

Neutral-lipid analysis reveals elevation of acylglycerols and lack of cholesterol esters in Plasmodium falciparum-infected erythrocytes

Here we show that blood-stage Plasmodium falciparum organisms accumulate a high mass of triacylglycerol and diacylglycerol. However, we failed to detect cholesterol esters, a second neutral lipid species reported to be important for a related apicomplexan, Toxoplasma gondii. Evidence for P. falciparum and T. gondii homologues of acyl coenzyme A:diacylglycerol acyltransferase suggests that acylglycerols may be the conserved neutral lipids in apicomplexans.     

CD90 Expression on human primary cells and elimination of contaminating fibroblasts from cell cultures

Cluster Differentiation 90 (CD90) is a cell surface glycoprotein originally identified on mouse thymocytes. Although CD90 has been identified on a variety of stem cells and at varying levels in non-lymphoid tissues such as on fibroblasts, brain cells, and activated endothelial cells, the knowledge about the levels of CD90 expression on different cell types, including human primary cells, is limited. The goal of this study was to identify CD90 as a human primary cell biomarker and to develop an efficient and reliable method for eliminating unwanted or contaminating fibroblasts from human primary cell cultures suitable for research pursuant to cell based therapy technologies.     

Esterification of cholesterol by a type III secretion effector during intracellular Salmonella infection

Survival of Salmonella typhimurium within a vacuole in host cells depends on secreted virulence factors encoded by the Salmonella pathogenicity island 2 (SPI-2). High levels of cholesterol are detected at the Salmonella -containing vacuole (SCV). Here we show that the SPI-2 effector SseJ esterifies cholesterol in vitro , in cells and during infection. Intracellular infections with wild-type as compared with Δ sseJ bacteria led to higher levels of cholesterol ester production in HeLa cells and RAW macrophages and were shown to increase levels of lipid droplets (structures enriched in cholesterol esters). Ectopic expression of SseJ reduced cholesterol levels in cellular membranes and antagonized a major membrane activity of a second bacterial effector known to be important to the stability of the SCV. Previous studies in mouse models of infection have established a virulence defect in Δ sseJ bacteria and have suggested a role for SseJ in regulating SCV dynamics. Our data indicating the molecular activity of SseJ suggest that cholesterol and its esterification at the SCV are functionally important for intracellular bacterial survival.