Proton re-uptake partitioning between uncoupling protein and ATP synthase during benzohydroxamic acid-resistant state 3 respiration in tomato fruit mitochondria

The yield of oxidative phosphorylation in isolated tomato fruit mitochondria depleted of free fatty acids remains constant when respiratory rates are decreased by a factor of 3 by the addition of n-butyl malonate. This constancy makes the determination of the contribution of the linoleic acid-induced energy-dissipating pathway by the ADP/O method possible. No decrease in membrane potential is observed in state 3 respiration with increasing concentration of n-butyl malonate, indicating that the rate of ATP synthesis is steeply dependent on membrane potential. Linoleic acid decreases the yield of oxidative phosphorylation in a concentration-dependent manner by a pure protonophoric process like that in the presence of FCCP. ADP/O measurements allow calculation of the part of respiration leading to ATP synthesis and the part of respiration sustained by the dissipative H(+) re-uptake induced by linoleic acid. Respiration sustained by this energy-dissipating process remains constant at a given LA concentration until more than 50% inhibition of state 3 respiration by n-butyl malonate is achieved. The energy dissipative contribution to oxygen consumption is proposed to be equal to the protonophoric activity of plant uncoupling protein divided by the intrinsic H(+)/O of the cytochrome pathway. It increases with linoleic acid concentration, taking place at the expense of ADP phosphorylation without an increase in the respiration.     

Effects of 4,4'-diisothyocyanatostilbene-2,2'-disulfonic acid on Trypanosoma cruzi proliferation and Ca(2+) homeostasis

Cell viability requires the perfect functioning of the processes controlling ATP and Ca(2+) homeostasis. It is known that cell death caused by a variety of toxins or pathological conditions is associated with a disruption of ATP and Ca(2+) homeostasis. This study shows that 4,4'-diisothyocyanatostilbene-2,2'-disulfonic acid (DIDS) inhibits Trypanosoma cruzi epimastigote cell growth. This thiol-reagent thiocyanate derivative was able to inhibit two ecto-enzymes present in this parasite. The ecto-ATPase and ecto-phosphatase activities were inhibited in a dose-dependent manner (K(i)=47.7 and 472.5 microM, respectively), but the 5'nucleotidase and 3'nucleotidase activities were not. DIDS uptake was approached by fluorescence microscopy. Pulse-chase experiments revealed the DIDS accumulation in compartments, presumably endocytic, in the posterior region of epimastigotes. In addition, we show that the T. cruzi mitochondria studied in permeabilized cells are able to accumulate and retain medium Ca(2+) in the absence of DIDS. However, in the presence of increasing concentrations of DIDS (50-200 microM), Ca(2+) transport was inhibited in a dose-dependent manner. DIDS also caused a disruption of the mitochondrial membrane potential, in the same concentration range, thus explaining its effect on Ca(2+) uptake. The presence of EGTA prevented the elimination of the mitochondrial membrane potential (DeltaPsi), supporting previous data suggesting that the binding of Ca(2+) to the mitochondrial membrane exposes buried thiols to react with DIDS. This thiocyanate derivative was also able to inhibit Ca(2+) uptake by the endoplasmic reticulum in a dose-dependent manner. Taken together, the data presented here provide further insights into the mechanisms underlying the antiproliferative actions of DIDS in T. cruzi.     

Bias and Sampling Error of the Estimated Proportion of Genotypic Variance Explained by Quantitative Trait Loci Determined From Experimental Data in Maize Using Cross Validation and Validation With Independent Samples.

Cross validation (CV) was used to analyze the effects of different environments and different genotypic samples on estimates of the proportion of genotypic variance explained by QTL (p). Testcrosses of 344 F(3) maize lines grown in four environments were evaluated for a number of agronomic traits. In each of 200 replicated CV runs, this data set was subdivided into an estimation set (ES) and various test sets (TS). ES were used to map QTL and estimate p for each run (p(ES)) and its median (p(ES)) across all runs. The bias of these estimates was assessed by comparison with the median (p(TS.ES)) obtained from TS. We also used two independent validation samples derived from the same cross for further comparison. The median p(ES) showed a large upward bias compared to p(TS.ES). Environmental sampling generally had a smaller effect on the bias of p(ES) than genotypic sampling or both factors simultaneously. In independent validation, p(TS.ES) was on average only 50% of p(ES). A wide range among p(ES) reflected a large sampling error of these estimates. QTL frequency distributions and comparison of estimated QTL effects indicated a low precision of QTL localization and an upward bias in the absolute values of estimated QTL effects from ES. CV with data from three QTL studies reported in the literature yielded similar results as those obtained with maize testcrosses. We therefore recommend CV for obtaining asymptotically unbiased estimates of p and consequently a realistic assessment of the prospects of MAS.     

Mitochondria generated nitric oxide protects against permeability transition via formation of membrane protein S-nitrosothiols

Mitochondria generated nitric oxide (NO) regulates several cell functions including energy metabolism, cell cycling, and cell death. Here we report that the NO synthase inhibitors (L-NAME, L-NNA and L-NMMA) administered either in vitro or in vivo induce Ca²⁺-dependent mitochondrial permeability transition (MPT) in rat liver mitochondria via a mechanism independent on changes in the energy state of the organelle. MPT was determined by the occurrence of cyclosporin A sensitive mitochondrial membrane potential disruption followed by mitochondrial swelling and Ca²⁺ release. In in vitro experiments, the effect of NOS inhibitors was dose-dependent (1 to 50 µM). In addition to cyclosporin A, L-NAME-induced MPT was sensitive to Mg²⁺ plus ATP, EGTA, and to a lower degree, to catalase and dithiothreitol. In contrast to L-NAME, its isomer D-NAME did not induce MPT. L-NAME-induced MPT was associated with a significant decrease in both the rate of NO generation and the content of mitochondrial S-nitrosothiol. Acute and chronic in vivo treatment with L-NAME also promoted MPT and decreased the content of mitochondrial S-nitrosothiol. SNAP (a NO donor) prevented L-NAME mediated MPT and reversed the decrease in the rate of NO generation and in the content of S-nitrosothiol. We propose that S-nitrosylation of critical membrane protein thiols by NO protects against MPT.     

Inhibition of specific electron transport pathways leads to oxidative stress and decreased Candida albicans proliferation

Candida parapsilosis mitochondria contain three respiratory chains: the classical respiratory chain (CRC), a secondary parallel chain (PAR) and an “alternative” oxidative pathway (AOX). We report here the existence of similar pathways in C. albicans. To observe the capacity of each pathway to sustain yeast growth, C. albicans cells were cultured in the presence of inhibitors of these pathways. Antimycin A and KCN totally abrogated yeast growth, while rotenone did not prevent proliferation. Furthermore, rotenone promoted only partial respiratory inhibition. Lower concentrations of KCN that promote partial inhibition of respiration did not inhibit yeast growth, while partial inhibition of respiration with antimycin A did. Similarly, AOX inhibitor BHAM decreased O₂ consumption slightly but completely stunted cell growth. Reactive oxygen species production and oxidized glutathione levels were enhanced in cells treated with antimycin A or BHAM, but not rotenone or KCN. These findings suggest that oxidative stress prevents C. albicans growth.     

Serum netrin and VCAM-1 as biomarker for Egyptian patients with type IΙ diabetes mellitus

ObjectiveThis study aimed to evaluate the serum level of netrin and soluble vascular cell adhesion molecule 1 (VCAM-I) in patients with type IΙ diabetes mellitus (T2DM) and evaluate the association of their levels with the development of a diabetic complication.Patients and methodsThis study was carried out on type II diabetic patients with and without complications and healthy individuals served as controls. All subjects were submitted to the estimation of serum lipid profile, serum creatinine, urinary albumin/creatinine ratio (ACR), fasting blood glucose (FBG), glycated hemoglobin (HbA1c), visceral adiposity index (VAI), atherogenic index of plasma (AIP), lipid accumulation product (LAP) and detection of serum level of netrin1 and VCAM1.ResultsDiabetic patients with complications had significantly higher serum levels of creatinine, ACR, cholesterol, Triglyceride, low-density lipoprotein, netrin1, and VCAM1 than diabetic patients without complications. Likewise, the level of VAI and LAP as markers of excessive body fat were significantly higher in diabetic patients with complications than diabetic patients without complications. The netrin1 and VCAM1 were a significant discriminator of T2DM renal complications with a sensitivity of 96%, 90%, and specificity of 82.7%, 91.3% respectively.ConclusionIt can be concluded that serum netrin1 and VCAM1 correlated significantly with markers of excessive body fat, a renal complication in the patient with type 2 diabetes mellitus.     

Sterol methenyl transferase inhibitors alter the ultrastructure and function of the Leishmania amazonensis mitochondrion leading to potent growth inhibition

We describe here the effects of Delta(24(25)) sterol methenyl transferase inhibitors (SMTI) on promastigote and axenic amastigote forms of Leishmania amazonensis. When these cells were exposed to 20-piperidin-2-yl-5alpha-pregnan-3beta-20-diol (22,26-azasterol; AZA), hydrazone-imidazol-2-yl-5alpha-pregnan-3beta-ol (IMI), 20-hydrazone-pyridin-2-yl-5alpha-pregnan-3beta-ol (PYR) or 24(R,S),25-epiiminolanosterol (EIL), a concentration- and time-dependent inhibition of growth was observed, with IC(50) values in the sub-micromolar range. Ultrastructural alterations in treated cells were mainly observed in the mitochondrion, which displayed an intense swelling and a reduction of the electron density of the matrix with remarkable changes in the inner mitochondrial membranes. Mitochondrial transmembrane electric potential (DeltaPsi) was measured using spectrophotometric methods in control and treated promastigotes permeabilized with digitonin. After energization with the substrates for complexes I, II or IV of the respiratory chain, it was possible to detect marked changes of DeltaPsi in promastigotes treated with 1 microM of the SMTI for 48 or 72 h when compared with normal cells, indicating that these compounds led to the loss of the energy-transducing properties of the mitochondrial inner membrane, probably related to the alteration of its lipid composition. The present study confirms these findings, showing that in Leishmania amazonensis the mitochondrial complex appears to be the first organelle affected after treatment with different SMTI.     

Histological and Ultrastructural Studies on the Curative Effects of Mandipropamid on Plasmopara viticola

The mandelic acid amide, mandipropamid, which belongs to the carboxylic acid amide (CAA) fungicides, is active against Plasmopara viticola, the causal agent of grapevine downy mildew. The fungicide primarily inhibits the germination of encysted zoospores, thus preventing the pathogen’s penetration into the host tissues, but it also shows curative effects. In this study, the infection structures of P. viticola in both leaves and berries were investigated to detect the histological and ultrastructural alterations induced by mandipropamid when applied after inoculation. Compared to the untreated samples characterized by a diffuse colonization of the tissues and by a normal ultrastructure of the pathogen, the application of mandipropamid 24 h after inoculation with P. viticola reduced pathogen colonization in leaves and berries. In addition, detachment of the plasmalemma from the hyphal and haustorial walls was observed 72 h after inoculation. In the berries, an abnormal proliferation of the pathogen plasma membrane was observed. Collapsed hyphae and haustoria in treated leaves were surrounded by callose or encapsulated in an amorphous material inside the host cell 72 h after inoculation, while a similar effect was observed in later stages (7 days) in berries. The results confirm that mandipropamid, which acts at the interface between the pathogen plasmalemma and cell wall, has curative activity against P. viticola, appearing more rapidly in leaves than in berries.