Effects of salinity on metabolism and life history characteristics of Daphnia magna

In the Baltic Sea area, the cladoceran Daphnia magna is commonly found in brackish water rockpools and it has been suggested that salinity is one of the niche dimensions that affects the distribution of the species. The salinity tolerance of D. magna was studied both in physiological and life history experiments. The experimental salinities were freshwater, 4S and 8S. The highest respiration and ammonium excretion rates were measured in the freshwater treatment with decreasing respiration and ammonium excretion rates at higher salinities. The lowest O/N ratio (oxygen consumption to ammonium excretion), describing the metabolic status of an organism, was obtained at 8S, although the only significant differences were detected when comparing to 4S treatments. Individual growth rate, reproductive output and population growth rate were highest at 4S. At 8S growth and reproduction were reduced as compared to freshwater and 4S. The life history parameters in the performed experiments indicated higher fitness (expressed as r) as well as more favourable conditions for growth and reproduction at 4S, whereas the O/N ratio was more difficult to interpret and, in this case, gave a less clear picture of the salinity influence.     

Colocalisation of the protein tyrosine phosphatases PTP-SL and PTPBR7 with beta4-adaptin in neuronal cells

The mouse gene Ptprr encodes the neuronal protein tyrosine phosphatases PTP-SL and PTPBR7. These proteins differ in their N-terminal domains, with PTP-SL being a cytosolic, membrane-associated phosphatase and PTPBR7 a type I transmembrane protein. In this study, we further explored the nature of the PTP-SL-associated vesicles in neuronal cells using a panel of organelle markers and noted a comparable subcellular distribution for PTP-SL and the beta4-adaptin subunit of the AP4 complex. PTP-SL, PTPBR7 and beta4-adaptin are localised at the Golgi apparatus and at vesicles throughout the cytoplasm. Immunohistochemical analysis demonstrated that PTP-SL, PTPBR7 and beta4-adaptin are all endogenously expressed in brain. Interestingly, coexpression of PTP-SL and beta4-adaptin leads to an altered subcellular localisation for PTP-SL. Instead of the Golgi and vesicle-type staining pattern, still observable for beta4-adaptin, PTP-SL is now distributed throughout the cytoplasm. Although beta4-adaptin was found to interact with the phosphatase domain of PTP-SL and PTPBR7 in the yeast two-hybrid system, it failed to do so in transfected neuronal cells. Our data suggest that the tyrosine phosphatases PTP-SL and PTPBR7 may be involved in the formation and transport of AP4-coated vesicles or in the dephosphorylation of their transmembrane cargo molecules at or near the Golgi apparatus.     

Use of pheromone chemistry to identify Grapholita lobarzewskii as an occasional pest of apple and plum

As shown by chemical analysis and field trapping, the sex pheromone of Grapholita lobarzewskii consists of a blend of (E)-8-dodecenyl acetate and (Z)-8-dodecenyl acetate. Maximum attractiveness was found at 80–95%. Dodecyl acetate and tetradecyl acetate, both present in the female gland, did not affect trap catch. G. lobarzewskii has recently gained importance as a pest of apple and plum, but has so far been referred to as Grapholita janthinana. The latter is attracted to the same two compounds, but in reversed portions (20% E).

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Zusammenfassung Chemische Analysen und Feldversuche zeigen, dass das Sexualpheromon des Kleinen Fruchtwicklers, G. lobarzewskii aus (E)-8-Dodecenylacetat (Z8-12:Ac) und (Z)-8-Dodecenylacetat (Z8-12:Ac) besteht. Die grösste Lockwirkung wurde mit einem Gemisch der beiden Substanzen bei einem E-Anteil von 80–95% erzielt. Dodecylacetat (12:Ac) und Tetradecylacetat (14:Ac) wurden ebenfalls in den weiblichen Pheromondrüsen nachgewiesen, hatten aber im Freiland keinen Einfluss auf die Lockwirkung. G. lobarzewskii tritt seit einiger Zeit in der Schweiz als Schädling von Apfel und Zwetschge auf und ist an ihrem charakteristischem Frassgang leicht erkennbar. Die Art wurde bisher irrtümlich als G. janthinana bezeichnet. G. janthinana lebt auf Rosaceen, und wird vom gleichen Substanzpaar angelockt, allerdings bei umgekehrtem Mischungsverhältnis (20% E).

     

Patterns of rapd markers and heavy metal concentrations in Perna viridis (L.), collected from metal-contaminated and uncontaminated coastal waters: are they correlated with each other?

Genetic variation due to heavy metal contamination has always been an interesting topic of study. Because of the numerous contaminants being found in coastal and intertidal waters, there is always much discussion and argument as to which contaminant(s) caused the variations in the genetic structures of biomonitors. This study used a Single Primer Amplification Reaction (SPAR) technique namely Random Amplified Polymorphic DNA (RAPD) to determine the genetic diversity of the populations of the green-lipped mussel Perna viridis collected from a metal-contaminated site at Kg. Pasir Puteh and those from four relatively' uncontaminated sites (reference sites). Heavy metal levels (Cd, Cu, Pb and Zn) were also measured in the soft tissues and byssus of the mussels from all the sites. Cluster analyses employing UPGMA done based on the RAPD makers grouped the populations into two major clusters; the Bagan Tiang, Pantai Lido, Pontian and Kg. Pasir Puteh populations were in one cluster, while the Sg. Belungkor population clustered by itself. This indicated that the genetic diversity based on bands resulting from the use of all four RAPD primers on P. viridis did not indicate its potential use as a biomarker of heavy metal pollution in coastal waters. However, based on a correlation analysis between a particular metal and a band resulting from a specific RAPD primer revealed some significant (P < 0.01) correlations between the primers and the heavy metal concentrations in the byssus and soft tissues. Thus, the correlation between a particular metal and the bands resulting from the use of a specific RAPD primer on P. viridis could be used as biomonitoring tool of heavy metal pollution.     

Analysis of the inhibition of mammalian thioredoxin, thioredoxin reductase, and glutaredoxin by cis-diamminedichloroplatinum (II) and its major metabolite, the glutathione-platinum complex.

Several studies have demonstrated a correlation between cellular toxicity of cis-diamminedichloroplatinum (II) (cisplatin, CDDP) and inhibited intracellular activity of the thioredoxin system, i.e., thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH. Conversely, increased cellular activity of the Trx system confers resistance to CDDP. In this study, we have analyzed the interaction of CDDP with Trx and TrxR in order to clarify the mechanism. The inhibition with time-dependent kinetics by CDDP of NADPH-reduced (but not oxidized) TrxR was irreversible, strongly suggesting covalent modification of the reduced selenocysteine-containing active site. Assuming second order kinetics, the rate constant of TrxR inhibition by CDDP was 21 +/- 3 M(-1) x s(-1). Transplatin was found to be an even more efficient inhibitor, with a second order rate constant of 84 +/- 22 M(-1) x s(-1), whereas carboplatin (up to 1 mM) gave no inhibition of the enzyme under the same conditions. Escherichia coli Trx or human or bacterial glutaredoxin (Grx) activities were in comparison only slightly or not at all inhibited by either CDDP, transplatin, or carboplatin. However, glutaredoxins were found to be inhibited by the purified glutathione adduct of cisplatin, bis-(glutathionato)platinum(II) (GS-Platinum complex, GS-Pt), with an IC50 = 350 microM in the standard beta-hydroxyethyl disulfide-coupled assay for human Grx. Also the mammalian Trx system was inhibited by GS-Pt with similar efficiency (IC(50) = 325 microM), whereas neither the E. coli Trx system nor glutathione reductase were inhibited. Formation of GS-Pt is a major route for cellular elimination of CDDP. The fact that GS-Pt inhibits the mammalian Trx as well as Grx systems shows that CDDP may exert effects at several stages of its metabolism, including after conjugation with GSH, which are intimately linked with the cellular disulfide/dithiol redox regulatory systems.     

Reactive oxygen species, antioxidants, and the mammalian thioredoxin system.

Reactive oxygen species (ROS) are known mediators of intracellular signaling cascades. Excessive production of ROS may, however, lead to oxidative stress, loss of cell function, and ultimately apoptosis or necrosis. A balance between oxidant and antioxidant intracellular systems is hence vital for cell function, regulation, and adaptation to diverse growth conditions. Thioredoxin reductase (TrxR) in conjunction with thioredoxin (Trx) is a ubiquitous oxidoreductase system with antioxidant and redox regulatory roles. In mammals, extracellular forms of Trx also have cytokine-like effects. Mammalian TrxR has a highly reactive active site selenocysteine residue resulting in a profound reductive capacity, reducing several substrates in addition to Trx. Due to the reactivity of TrxR, the enzyme is inhibited by many clinically used electrophilic compounds including nitrosoureas, aurothioglucose, platinum compounds, and retinoic acid derivatives. The properties of TrxR in combination with the functions of Trx position this system at the core of cellular thiol redox control and antioxidant defense. In this review, we focus on the reactions of the Trx system with ROS molecules and different cellular antioxidant enzymes. We summarize the TrxR-catalyzed regeneration of several antioxidant compounds, including ascorbic acid (vitamin C), selenium-containing substances, lipoic acid, and ubiquinone (Q10). We also discuss the general cellular effects of TrxR inhibition. Dinitrohalobenzenes constitute a unique class of immunostimulatory TrxR inhibitors and we consider the immunomodulatory effects of dinitrohalobenzene compounds in view of their reactions with the Trx system.     

Self-antigen maintains the innate antibacterial function of self-specific CD8 T cells in vivo

Self-specific CD8 T cells, which are selected by high-affinity interactions with self-Ags, develop into a lineage distinct from conventional CD8 T cells. We have previously shown that these self-specific cells acquire phenotypic and functional similarities to cells of the innate immune system including the expression of functional receptors associated with NK cells. In this study, we show that these self-specific cells have the ability to produce large amounts of IFN-gamma in response to infection with Listeria monocytogenes in a bystander fashion. The rapid production of IFN-gamma is associated with a dramatic reduction in the number of viable bacteria at the peak of infection. Self-specific CD8 T cells provide only marginal innate protection in the absence of self-Ag; however, the presence of self-Ag dramatically increases their protective ability. Exposure to self-Ag is necessary for the maintenance of the memory phenotype and responsiveness to inflammatory cytokines such as IL-15. Significantly, self-specific CD8 T cells are also more efficient in the production of IFN-gamma and TNF-alpha, thus providing more cytokine-dependent protection against bacterial infection when compared with NK cells. These findings illustrate that self-reactive CD8 T cells can play an important innate function in the early defense against bacterial infection.