The presence of 12β-deoxydecarbamoylsaxitoxin in the Japanese toxic dinoflagellate Alexandrium determined by simultaneous analysis for paralytic shellfish toxins using HILIC-LC–MS/MS

A differential screening study using high-resolution (HR)-hydrophilic interaction chromatography (HILIC)-electrospray ionization (ESI)–quadrupole time-of-flight mass spectrometry (Q-TOF MS) was conducted to identify saxitoxin (STX) analogues in the marine dinoflagellate toxic sub-clone Alexandrium tamarense Axat-2 and the non-toxic sub-clone UAT-014-009 derived from the same Japanese isolate. One unknown compound was identified only in the toxic sub-clone and was found to have the molecular formula C₉H₁₆N₆O₂. This structure differed from that of decarbamoyl STX (dcSTX; C₉H₁₆N₆O₃) by the loss of a single oxygen. A 12-deoxy-dcSTX standard (a mixture of 12α- and β-deoxy-dcSTX) was chemically prepared from dcSTX by reduction with sodium borohydride. The unknown compound in the toxic strain of A. tamarense was identified as 12β-deoxy-dcSTX by comparison of its HR-HILIC-LC–MS retention time and HR–MS/MS spectrum with those of the chemically prepared standard, and the identification was confirmed by high-sensitivity HPLC analysis with post-column fluorescent derivatization. Moreover, two Japanese isolates of A. catenella showing toxin profiles different from that of A. tamarense were also found to contain 12β-deoxy-dcSTX. Previously, 12β-deoxy-dcSTX was isolated from the freshwater cyanobacterium Lyngbya wollei, which produces a unique set of STX analogues. This study is the first evidence of the presence of 12β-deoxy-dcSTX in marine dinoflagellates.     

Low rates of iridoid glycoside hydrolysis in two Longitarsus leaf beetles with different feeding specialization confer tolerance to iridoid glycoside containing host plants

Iridoid glycosides are plant defence compounds that are deterrent and/or toxic for unadapted herbivores but are readily sequestered by dietary specialists of different insect orders. Hydrolysis of iridoid glycosides by β‐glucosidase leads to protein denaturation. Insect digestive β‐glucosidases thus have the potential to mediate plant–insect interactions. In the present study, mechanisms associated with iridoid glycoside tolerance are investigated in two closely‐related leaf beetle species (Coleoptera: Chrysomelidae) that feed on iridoid glycoside containing host plants. The polyphagous Longitarsus luridus Scopoli does not sequester iridoid glycosides, whereas the specialist Longitarsus tabidus Fabricius sequesters these compounds from its host plants. To study whether the biochemical properties of their β‐glucosidases correspond to the differences in feeding specialization, the number of β‐glucosidase isoforms and their kinetic properties are compared between the two beetle species. To examine the impact of iridoid glycosides on the β‐glucosidase activity of the generalist, L. luridus beetles are kept on host plants with or without iridoid glycosides. Furthermore, β‐glucosidase activities of both species are examined using an artificial β‐glucosidase substrate and the iridoid glycoside aucubin present in their host plants. Both species have one or two β‐glucosidases with different substrate affinities. Interestingly, host plant use does not influence the specific β‐glucosidase activities of the generalist. Both species hydrolyse aucubin with a much lower affinity than the standard substrate. The neutral pH reduces the β‐glucosidase activity of the specialist beetles by approximately 60% relative to its pH optimum. These low rates of aucubin hydrolysis suggest that the ability to sequester iridoid glycosides has evolved as a key to potentially preventing iridoid glycoside hydrolysis by plant‐derived β‐glucosidases.     

Getting to the heart of the matter: CCN2 plays a role in cardiomyocyte hypertrophy

Connective tissue growth factor (CTGF/CCN2) is overexpressed in diabetes. Diabetic rats possess myocardial and cardiomyocyte hypertrophy. In a recent report, Wang and colleagues (Am J Physiol Cell Physiol. 2009 Jul 22. [Epub ahead of print]) show that CCN2 directly mediates cardiomyocyte hypertrophy as well as that induced by high glucose and fatty acid. CCN2 acted via the TrkA receptor. These data are the subject of this commentary, and emphasize that CCN2 may be an excellent target for therapy in diabetes.     

Morphology,phylogeny and novel chemical compounds from Coolia malayensis (Dinophyceae) from Okinawa,Japan

Marine benthic dinoflagellates within the genus Coolia have been reported to produce natural products, some of which are known to be toxic (i.e., cooliatoxin). To date, five species of Coolia have been reported in tropical and temperate waters around the world; however, very few studies have combined detailed morphological and molecular data with chemical analyses. In this study, a clonal culture of Coolia malayensis was isolated and mass cultivated from a coral reef on the island of Okinawa, Japan. Analysis of the thecal plate morphology and molecular phylogeny from 28S rDNA strongly supported the close relationship between this new isolate of C. malayensis from Okinawa and other isolates of C. malayensis from around the world. Following methanol extraction of 250 L of mass culture, chemical analyses using NanoLiquid chromatography mass spectrometry revealed the mass profiles of water-soluble and ethyl acetate-soluble parts. High-resolution mass spectrometry derived the molecular formulas of three novel disulphated polyether analogs of yessotoxin (C₅₆H₇₈O₁₈S₂ 1102.4 (Compound 1), C₅₇H₈₀O₁₈S₂ 1116.4 (Compound 2), and C₅₇H₇₈O₁₉S₂ 1130.4 (Compound 3)); two potential homologous compounds (Compounds 4 and 5) were also observed on the high-resolution mass, albeit with low signal intensity. The five compounds in the C. malayensis from Okinawa are composed of less oxygen, compared to cooliatoxin and other analogs of yessotoxin, suggesting the metabolites produced by C. malayensis are unique to those previously reported from other strains of Coolia.     

Accuracies in Po-210 determination for lead-210 dating

Various laboratory techniques have been utilized worldwide for measuring lead-210 in sub-recent deposits through its grand-daughter product polonium-210. Isotope dilution alpha spectrometry proved a suitable tool for absolute determination of lead-210 for the dating of aquatic deposits. Moreover, isotope dilution alpha spectrometry along with speciation experiments can be used to resolve depositional anomalies arising from supported lead-210/Ra-226 disequilibrium levels and unsupported lead-210 mobile fractions. Isotope dilution alpha spectrometry of sub-recent sediment and peat deposits has been critically evaluated for more than ten years. Our results show that type, size and composition of deposits analyzed as well as radiochemical procedures used, together with alpha counting techniques, are important factors influencing lead-210 determinations and tailing corrections using its granddaughter product polonium-210. Optimization of these parameters is of prime importance to achieve economic and accurate analyses, especially at low lead-210 concentrations and small sample sizes.     

Ammonium photo-production by heterocytous cyanobacteria: potentials and constraints

Over the last decades, production of microalgae and cyanobacteria has been developed for several applications, including novel foods, cosmetic ingredients and more recently biofuel. The sustainability of these promising developments can be hindered by some constraints, such as water and nutrient footprints. This review surveys data on N₂-fixing cyanobacteria for biomass production and ways to induce and improve the excretion of ammonium within cultures under aerobic conditions. The nitrogenase complex is oxygen sensitive. Nevertheless, nitrogen fixation occurs under oxic conditions due to cyanobacteria-specific characteristics. For instance, in some cyanobacteria, the vegetative cell differentiation in heterocyts provides a well-adapted anaerobic microenvironment for nitrogenase protection. Therefore, cell cultures of oxygenic cyanobacteria have been grown in laboratory and pilot photobioreactors (Dasgupta et al., 2010; Fontes et al., 1987; Moreno et al., 2003; Nayak & Das, 2013). Biomass production under diazotrophic conditions has been shown to be controlled by environmental factors such as light intensity, temperature, aeration rate, and inorganic carbon concentration, also, more specifically, by the concentration of dissolved oxygen in the culture medium. Currently, there is little information regarding the production of extracellular ammonium by heterocytous cyanobacteria. This review compares the available data on maximum ammonium concentrations and analyses the specific rate production in cultures grown as free or immobilized filamentous cyanobacteria. Extracellular production of ammonium could be coupled, as suggested by recent research on non-diazotrophic cyanobacteria, to that of other high value metabolites. There is little information available regarding the possibility for using diazotrophic cyanobacteria as cellular factories may be in regard of the constraints due to nitrogen fixation.     

The protective effects of MSC‐EXO against pulmonary hypertension through regulating Wnt5a/BMP signalling pathway

The aim of the study was to explore the mechanism of mesenchymal stem cell‐derived exosomes (MSC‐EXO) to protect against experimentally induced pulmonary hypertension (PH). Monocrotaline (MCT)‐induced rat model of PH was successfully established by a single intraperitoneal injection of 50 mg/kg MCT, 3 weeks later the animals were treated with MSC‐EXO via tail vein injection. Post‐operation, our results showed that MSC‐EXO could significantly reduce right ventricular systolic pressure (RVSP) and the right ventricular hypertrophy index, attenuate pulmonary vascular remodelling and lung fibrosis in vivo. In vitro experiment, the hypoxia models of pulmonary artery endothelial cell (PAEC) and pulmonary vascular smooth muscle cell (PASMC) were used. We found that the expression levels of Wnt5a, Wnt11, BMPR2, BMP4 and BMP9 were increased, but β‐catenin, cyclin D1 and TGF‐β1 were decreased in MSC‐EXO group as compared with MCT or hypoxia group in vivo or vitro. However, these increased could be blocked when cells were transfected with Wnt5a siRNA in vitro. Taken together, these results suggested that the mechanism of MSC‐EXO to prevent PH vascular remodelling may be via regulation of Wnt5a/BMP signalling pathway.     

Quercetin-induced yeast apoptosis through mitochondrial dysfunction under the accumulation of magnesium in Candida albicans

Latterly, the upsurge in use of antifungal drugs has brought about the emergence of several drug-resistance strains, making it skeptical to continue relying on current therapeutic regime. In the necessity of resistance-free antifungal agent, flavonoids presented possibilities of replacing existing drugs, displaying antifungal activity against pathogenic fungi. Among them, quercetin, one of the most representative flavonoids, exhibited antifungal activity against Candida albicans. To inspect the further understanding regarding quercetin, the antifungal mode of action of quercetin was investigated. In the initial step, the apoptosis was monitored after quercetin treatment. Moreover, intracellular levels of Mg²⁺ was assessed and was determined that Mg²⁺ increase occurred under the influence of quercetin. In addition, several features of mitochondrial dysfunction were monitored. Mitochondrial dysfunction triggers decrease in mitochondrial redox levels and leads to disruption in mitochondrial antioxidant system. Increased intracellular ROS and decreased intracellular redox levels were also displayed, indicating the occurrence of overall disruption in antioxidant systems. Sequentially, DNA fragmentation was observed and this DNA damage in turn induces apoptosis. In analyses, hexaamminecobalt(III) chloride (Cohex) was applied to inhibit Mg²⁺ transport between cytosol and mitochondria. Cohex attenuated the effects induced by quercetin, which demonstrates that the presence of Mg²⁺ is essential in quercetin-induced apoptosis.