Plasticity and acclimation to light reflected in temporal and spatial changes of small-scale macroalgal distribution in a stream

The small-scale distribution pattern of macroalgae in the river Ilm, in Germany was monitored. These patterns were then related to abiotic factors and tested to discover whether the distribution of the common macroalgae, Cladophora glomerata (L.) Kütz. and Vaucheria sp., was linked to differences in their photosynthetic plasticity. Cladophora glomerata revealed higher maximum photosynthetic electron transport rates after acclimation to high light (HL) compared with low light (LL) acclimated samples. By contrast, Vaucheria sp. did not acclimate to different growth light conditions. The photosynthetic performance of both algae also varied according to diurnal conditions. High light caused a reversible decrease of the dark-adapted quantum yield (F(v)/F(m)) in C. glomerata and a concomitant reversible decrease of the light-adapted quantum yield (DeltaF/F'(m)). In Vaucheria sp., F(v)/F(m) remained mostly unchanged over the day, whereas DeltaF/F'(m) decreased during the morning at low light. Photosynthetic pigments confirmed acclimational differences between the species. HL C. glomerata showed increased chlorophyll a:chlorophyll b ratios, and higher amounts of xanthophyll-cycle pigments compared with LL samples, whereas Vaucheria sp. did not reveal differences between the light treatments. While preferences for substrate size, water velocity, and depth are similar for C. glomerata and Vaucheria sp., the physiological responses to light conditions are different. It is concluded that light conditions significantly affect the small-scale spatial distribution of macroalgae and that fitness is enhanced in species with a higher plasticity in photosynthetic acclimation in unstable environments.     

Determination of retinoids by reversed-phase capillary liquid chromatography with amperometric electrochemical detection

A method for separating and detecting retinoids by reversed-phase capillary liquid chromatography with amperometric electrochemical detection is described. Packed columns with an inner diameter of 180 μm were employed for the separation using a C₁₈ stationary phase and a mobile phase containing acetonitrile-water-methanol (65:32.5:2.5, v/v/v) with 1% tetrabutylammonium perchlorate and 0.174 M acetate buffered at pH 5. The detection cell consisted of a carbon fiber barrel electrode held at 0.9 V versus an Ag/AgCl reference. Injection volumes of 2 μl produced detection limits of 2.73, 0.472, 0.428, and 0.267 fmol (or 410, 64.1, 60.9, and 38.2 pg ml⁻¹) for 13-cis-retinoic acid, all-trans-retinoic acid, retinaldehyde, and retinol, respectively. This represents an improvement in detection limits of at least three orders of magnitude for similar analyses using liquid chromatography and UV absorbance detection. The detector signal was linear over two orders of magnitude of analyte concentration. Retinoid concentrations in bovine serum were determined and found to be in good agreement with previously reported values.     

Identification of the novel evolutionary conserved obstructor multigene family in invertebrates

Insects have evolved chitin-containing structures such as the cuticle or peritrophic membranes that serve to protect their bodies against the hostile environment. The specific mechanisms by which these structures are produced, are mostly unknown. We have identified a novel multigene family, the obstructor family, which encodes ten putatively secreted chitin-binding proteins that are characterized by a stereotype arrangement of a N-terminal signaling peptide and 3 chitin-binding-domains. Gene expression studies in Drosophila melanogaster embryos demonstrate that obstructor family members are expressed in cuticle forming tissues. Using computational and phylogenetic analysis, we show that obstructor genes represent an evolutionary conserved multigene family in invertebrates.     

V beta profiles in African children with acute cerebral or uncomplicated malaria: very focused changes among a remarkable global stability

T cells are thought to play a critical role in cerebral malaria pathogenesis. However, available evidences are restricted to rodent models in which V beta specific T cell expansion has been associated with neurological syndrome suggesting involvement of superantigens or dominant antigens. Using flow cytometry, we studied the peripheral V beta T cell repertoire of Ghanaian children with cerebral malaria, uncomplicated malaria and asymptomatic control children, to look for either expansion or deletion of specific V beta associated with cerebral malaria. At admission, the general pattern of the repertoire of the patients was very similar, with no major distortion compared to the control group a part a significant increase of the frequency of the V beta 21.3 subset correlating with disease severity and attributed to the CD4 subset. During convalescence very limited fluctuations were observed including a significant decrease of the V beta 21.3 subset and increase of the V beta 20 subset, a subset not detected at admission. The remarkable stability of the V beta repertoire observed in acute malaria either cerebral or uncomplicated argues against the idea that cerebral malaria would result from a T cell-mediated inflammatory shock syndrome driven by some dominant super-antigenic activity(ies). The significance of the reproducible increase of the CD4+V beta 21.3T cell subset deserves further investigations.     

Changes in DNA secondary structure afterγ-irradiation

Native calf thymus DNA was gamma-irradiated at 500 mug/ml in 0.01 M NaCl in the presence or absence of oxygen. By irradiation, an increasing amount of DNA becomes reactive with a water-soluble carbodiimide-derivative (CMEC). In the DNA sections reactive with CMEC the nucleotide strands are separated, a phenomenon previously described as radiation-induced denaturation. The dose-effect curve for the formation of denatured DNA shows an upward-bent form; a distinct oxygen effect of about 2 is observed. By a comparative study with DNA samples, degraded partially with DNAse I, it was shown that a minor part of the radiation-induced denaturation results from the formation of the radiation-induced single strand breaks, whereas the major part is a local denaturation independent of the strand breaks. In these locally denatured regions 20 to 50 nucleotide pairs are separated.     

Synthesis and structure-activity studies of novel benzocycloheptanone oxazolidinone antibacterial agents

We describe a novel class of benzocycloheptanone derived oxazolidinone antibacterial agents. The synthesis and antibacterial activities with structure variation is discussed.     

Vascular redox imbalance in rats submitted to chronic exercise

Exercise training has been used for treatment/prevention of many cardiovascular diseases, but the mechanisms need to be clarified. Thus, our aim was to compare oxidative stress parameters between rats submitted to a swimming training and sedentary rats (control). Twelve male rats were divided into two groups: control and exercise training. The exercise training had daily 1 h swimming sessions for 8 weeks and a load (5% of its body mass) was placed in rat's tail. Thereafter the animals were killed, aorta and heart were surgically removed and blood was collected. Body mass gain, thiobarbituric acid reactive species (TBARS), carbonyl content, total reactive antioxidant potential (TRAP), total antioxidant reactivity (TAR), superoxide dismutase (SOD) activity and catalase (CAT) activity were evaluted. The trained rats showed a lower body mass gain and no modifications on heart. An increased SOD activity was observed on aorta after the training, but no changes were seen for CAT activity, which led to an increased SOD/CAT ratio. The arterial TBARS was also increased for trained rats. The decrease in TRAP in exercise training was the single modification on plasma. Our findings suggest that the increased SOD activity could play a role in vascular adaptations to exercise training. Copyright © 2010 John Wiley & Sons, Ltd.