Isolation and amino acid sequence of a novel 6.8-kDa mitochondrial proteolipid from beef heart. Use of FAB-MS for molecular mass determination

We have isolated a 6.8 kDa proteolipid from an acidic chloroform/methanol extract of bovine cardiac muscle. The molecular mass of the polypeptide was measured by fast atom bombardment-mass spectrometry (FAB-MS) (m/z6834.1). Its amino acid sequence was partly determined by direct sequencing and completed by characterization of cyanogen bromide and tryptic fragments (sequencing, FAB-MS and amino acid analysis). The polypeptide consists of 60 amino acid residues. Polyclonal antibodies raised in rabbit allowed its localization by electroimmunoblotting in mitochondria.     

Hypolipidaemic Effects of (24R)-4α-methyl-5α-stigmasta-7,22-dien-3β-ol Derived from Aurantiochytrium mangrovei BT3 in the HEPG2 Cell Line

Applied Biochemistry and Microbiology - Aurantiochytrium mangrovei BT3, a heterotrophic marine microalga, has the ability to produce high amounts of polyunsaturated fatty acids and bioactive...     

Categorical judgments do not modify sensory representations in working memory

Categorical judgments can systematically bias the perceptual interpretation of stimulus features. However, it remained unclear whether categorical judgments directly modify working memory representations or, alternatively, generate these biases via an inference process down-stream from working memory. To address this question we ran two novel psychophysical experiments in which human subjects had to reverse their categorical judgments about a stimulus feature, if incorrect, before providing an estimate of the feature. If categorical judgments indeed directly altered sensory representations in working memory, subjects’ estimates should reflect some aspects of their initial (incorrect) categorical judgment in those trials. We found no traces of the initial categorical judgment. Rather, subjects seemed to be able to flexibly switch their categorical judgment if needed and use the correct corresponding categorical prior to properly perform feature inference. A cross-validated model comparison also revealed that feedback may lead to selective memory recall such that only memory samples that are consistent with the categorical judgment are accepted for the inference process. Our results suggest that categorical judgments do not modify sensory information in working memory but rather act as top-down expectations in the subsequent sensory recall and inference process.     

Loss of endothelial cell-specific autophagy-related protein 7 exacerbates doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is an effective, broad-spectrum antineoplastic agent with serious cardiotoxic side effects, which may lead to the development of heart failure. Current strategies to diagnose, prevent, and treat DOX-induced cardiotoxicity (DIC) are inadequate. Recent evidence has linked the dysregulation and destruction of the vascular endothelium to the development of DIC. Autophagy is a conserved pro-survival mechanism that recycles and removes damaged sub-cellular components. Autophagy-related protein 7 (ATG7) catalyzes autophagosome formation, a critical step in autophagy. In this study, we used endothelial cell-specific Atg7 knockout (EC-Atg7^?/?) mice to characterize the role of endothelial cell-specific autophagy in DIC. DOX-treated EC-Atg7^?/? mice showed reduced survival and a greater decline in cardiac function compared to wild-type controls. Histological assessments revealed increased cardiac fibrosis in DOX-treated EC-Atg7^?/? mice. Furthermore, DOX-treated EC-Atg7^?/? mice had elevated serum levels of creatine kinase-myocardial band, a biomarker for cardiac damage. Thus, the lack of EC-specific autophagy exacerbated DIC. Future studies on the relationship between EC-specific autophagy and DIC could establish the importance of endothelium protection in preventing DIC.     

The terminal enzymes of cholesterol synthesis,DHCR24 and DHCR7, interact physically and functionally

Cholesterol is essential to human health, and its levels are tightly regulated by a balance of synthesis, uptake, and efflux. Cholesterol synthesis requires the actions of more than twenty enzymes to reach the final product, through two alternate pathways. Here we describe a physical and functional interaction between the two terminal enzymes. 24-Dehydrocholesterol reductase (DHCR24) and 7-dehydrocholesterol reductase (DHCR7) coimmunoprecipitate, and when the DHCR24 gene is knocked down by siRNA, DHCR7 activity is also ablated. Conversely, overexpression of DHCR24 enhances DHCR7 activity, but only when a functional form of DHCR24 is used. DHCR7 is important for both cholesterol and vitamin D synthesis, and we have identified a novel layer of regulation, whereby its activity is controlled by DHCR24. This suggests the existence of a cholesterol “metabolon”, where enzymes from the same metabolic pathway interact with each other to provide a substrate channeling benefit. We predict that other enzymes in cholesterol synthesis may similarly interact, and this should be explored in future studies.     

A Novel GLP1 Receptor Interacting Protein ATP6ap2 Regulates Insulin Secretion in Pancreatic Beta Cells

GLP1 activates its receptor, GLP1R, to enhance insulin secretion. The activation and transduction of GLP1R requires complex interactions with a host of accessory proteins, most of which remain largely unknown. In this study, we used membrane-based split ubiquitin yeast two-hybrid assays to identify novel GLP1R interactors in both mouse and human islets. Among these, ATP6ap2 (ATPase H⁺-transporting lysosomal accessory protein 2) was identified in both mouse and human islet screens. ATP6ap2 was shown to be abundant in islets including both alpha and beta cells. When GLP1R and ATP6ap2 were co-expressed in beta cells, GLP1R was shown to directly interact with ATP6ap2, as assessed by co-immunoprecipitation. In INS-1 cells, overexpression of ATP6ap2 did not affect insulin secretion; however, siRNA knockdown decreased both glucose-stimulated and GLP1-induced insulin secretion. Decreases in GLP1-induced insulin secretion were accompanied by attenuated GLP1 stimulated cAMP accumulation. Because ATP6ap2 is a subunit required for V-ATPase assembly of insulin granules, it has been reported to be involved in granule acidification. In accordance with this, we observed impaired insulin granule acidification upon ATP6ap2 knockdown but paradoxically increased proinsulin secretion. Importantly, as a GLP1R interactor, ATP6ap2 was required for GLP1-induced Ca²⁺ influx, in part explaining decreased insulin secretion in ATP6ap2 knockdown cells. Taken together, our findings identify a group of proteins that interact with the GLP1R. We further show that one interactor, ATP6ap2, plays a novel dual role in beta cells, modulating both GLP1R signaling and insulin processing to affect insulin secretion.     

Heteropteran insects as mosquito predators in water jars in southern Vietnam

Residents of Vietnam living in areas with water shortages and/or poor tap water maintain water storage containers, such as jars, in and around their domiciles in order to store water used in daily life. Although these water jars are known to be important breeding sources of the Aedes mosquito, use of chemical larvicides in such containers is legally prohibited in Vietnam. In this study, we identified the dominant mosquito insect predators in water jars in and around residences located in Tan Chanh, Long An, southern Vietnam. Of 3,646 Heteroptera collected from such jars, Corixidae (Micronecta spp.) and Veliidae (Microvelia spp.) were revealed to be the dominant predators. Polymerase chain reaction (PCR) analysis revealed that 40% of Micronecta and 12% of Veliidae had Aedes aegypti‐positive reactions, indicating that these two dominant Heteroptera are important predators of Ae. aegypti. Our results suggest that aquatic Heteroptera may be an important mosquito control agent in addition to the currently used copepods.     

Economic incentive for applying vetiver grass to remediate lead, copper and zinc contaminated soils

The application of vetiver grass (Chrysopogon zizaniodes) for phytoremediation of heavy metal contaminated soils can be promoted by economic return through essential oil production. Four levels of lead (0, 500, 2000, and 8000 mg kg(-1) dry soil), copper (0, 100, 400, and 1600 mg kg(-1) dry soil) and zinc (0, 400, 1600, and 6400 mg kg(-1) dry soil) were used to study their effects on vetiver growth, essential oil composition and yield. This study also investigated the effect of nitrogen concentrations on vetiver oil yield. Vetiver accumulated high concentrations of Pb, Cu and Zn in roots (3246, 754 and 2666 mg kg(-1), respectively) and small amounts of contaminants in shoots (327, 55, and 642 mg kg(-1), respectively). Oil content and yield were not affected at low and moderate concentrations of Cu and Zn. Only the application of Pb had a significant detrimental effect on oil composition. Extraction of vetiver essential oils by hydrodistillation produced heavy metal free products. High level of nitrogen reduced oil yields. Results show that phytoremediation of Cu and Zn contaminated soils by vetiver can generate revenue from the commercialization of oil extracts.     

Effect of calcium on growth performance and essential oil of vetiver grass (Chrysopogon zizanioides) grown on lead contaminated soils

The aim of this study was to investigate effect of calcium on growth, survival, essential oil yield and chemical compositions of vetiver grass grown on lead contaminated soils. Calcium inform of CaCO3 (0, 2000, 4000, 6000 mg Ca kg(-1)) was added to river sand soils containing 4000 mg Pb kg(-1) dry soil. Results showed that, in the absence of calcium treatment, no plants survived after 2 weeks of cultivation, while the rest grew well to the end of the experimental period (42 weeks). Calcium treatments generally resulted in a slight decrease in biomass. Interestingly, an increase in calcium over 2000 mg kg(-1) did not result in a decrease in accumulation of lead in vetiver roots and shoots. The levels of lead in roots and shoots under calcium treatments were around 2000 and 90 mg kg(-1) dry weight, respectively. The addition of CaCO3 did not improve vetiver essential oil yield and chemical composition compared to the control. A level of applied CaCO3 about half of the lead concentration in soils was sufficient to improve vetiver growth and survival, and accumulate high concentrations of lead in the roots. This finding can be applied for re-vegetation of lead contaminated soils using vetiver.