Condensin-Dependent Chromatin Compaction Represses Transcription Globally during Quiescence

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Calpain II induced insolubilization of lens β-crystallin polypeptides may induce cataract

Addition of calpain II (EC 3.4.22.17) to soluble proteins from 10-day-old rat lens caused an increase in turbidity and production of water-insoluble protein. The insolubilization increased with higher concentrations of both lens protein and calpain II, it could be prevented by the cysteine protease inhibitor E-64; it required at least 0.5 mM Ca²⁺, it was limited to 6% of the soluble protein present and resulted from precipitation β-crystallin polypeptides. When compared by two-dimensional electrophoresis, the insoluble β-crystallin polypeptides produced by calpain II were similar to insoluble β-crystallin polypeptides found incataractous lenses. Trypsin also caused insolubilization of β-crystallin polypeptides, but these polypeptides were unlike polypeptides produced during cataract formation. These data suggested that the loss of solubility was due to a specific removal of N/or C-terminal extensions from β-crystallin polypeptides by calpain II, and that a similar process may occur in vivo during cataract formation. It is hypothesized that the insoluble protein produced by calpain II causes cataract by increasing light scatter in the lens.     

A comparative study of EPR spin trapping and cytochrome c reduction techniques for the measurement of superoxide anions

Superoxide anions (O₂^.−) generated by the reaction of xanthine with xanthine oxidase were measured by the reduction of cytochrome c and by electron paramagnetic resonance (EPR) spectroscopy using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Studies were performed to determine the relative sensitivities of these two techniques for the measurement of O₂^.−. Mixtures of xanthine, xanthine oxidase, DMPO generated two adducts, a transient DMPO-OOH and a smaller but longer-lived DMPO-OH. Both adducts were inhibited by superoxide dismutase (SOD), demonstrating they originated from O₂^.−, and were also significantly decreased when the experiments were performed using unchelated buffers, suggesting that metal ion impurities in unchelated buffers alter the formation or degradation of DMPO-adducts. O₂^.−, generated by concentrations of xanthine as low as 0.05 μM, were detectable using EPR spin trapping. In contrast, mixtures of xanthine, xanthine oxidase, and cytochrome c measured spectrophotometrically at 550 nm demonstrated that concentrations of xanthine above 1 μM were required to produce measurable levels of reduced cytochrome c. These studies demonstrate that spin trapping using DMPO was at least 20-fold more sensitive than the reduction of cytochrome c for the measurement of superoxide anions. However, at levels of superoxide generation where cytochrome c provides a linear measurement of production, EPR spin trapping may underestimate radical production, probably due to degradation of DMPO radical adducts.     

Can floral nectars reduce transmission of Leishmania?

BackgroundInsect-vectored Leishmania are responsible for loss of more disability-adjusted life years than any parasite besides malaria. Elucidation of the environmental factors that affect parasite transmission by vectors is essential to develop sustainable methods of parasite control that do not have off-target effects on beneficial insects or environmental health. Many phytochemicals that inhibit growth of sand fly-vectored Leishmania—which have been exhaustively studied in the search for phytochemical-based drugs—are abundant in nectars, which provide sugar-based meals to infected sand flies.Principle findingsIn a quantitative meta-analysis, we compare inhibitory phytochemical concentrations for Leishmania to concentrations present in floral nectar and pollen. We show that nectar concentrations of several flowering plant species exceed those that inhibit growth of Leishmania cell cultures, suggesting an unexplored, landscape ecology-based approach to reduce Leishmania transmission.SignificanceIf nectar compounds are as effective against parasites in the sand fly gut as predicted from experiments in vitro, strategic planting of antiparasitic phytochemical-rich floral resources or phytochemically enriched baits could reduce Leishmania loads in vectors. Such interventions could provide an environmentally friendly complement to existing means of disease control.     

Essai chimiosystématique sur la tribu des Lotées

A survey of the leaves and flowers of 62 representatives of the tribe Loteae (Leguminosae) showed the presence of several classes of flavonoids: flavonol 7-methyl ethers (rhamnocitrin, rhamnetin), 8-O-substituted flavonols (gossypetin, limocitrin, sexangularetin, corniculatusin), 3′,4′,5′-tri-O-substituted flavonols (myricetin, mearnsetin, syringetin, laricitrin), proanthocyanidins and flavone-C-glycosides. The trisubstitution of the B-ring and the 8-O-substitution of the A-ring allow the definition of a major group including the genera Dorycnium, Bonjeania, Lotus and Tetragonolobus. The presence of proanthocyanidins and 7-O-methylation determine a second group consisting of the genus Anthyllis. Finally, Securigera, on the basis of its flavonoid chemistry, appears to be rather remote from other members of the tribe.     

Fluorescent adducts of wheat calmodulin implicate the amino-terminal region in the activation of skeletal muscle myosin light chain kinase

Considerable attention is being directed toward defining a binding site in the central region of calmodulin that forms a high affinity interaction with certain enzymes and amphiphilic peptides. However, other regions of calmodulin are also known to be involved in the activation of enzymes such as myosin light chain kinase, regions which may not be directly involved in the binding of small peptides, e.g. mastoparan X. We investigated the properties of wheat calmodulin fluorescent derivatives, which were modified chemically in the first calcium binding site at Cys-27, in the activation of rabbit fast skeletal muscle myosin light chain kinase. Unmodified wheat calmodulin stimulated myosin light chain kinase to a greater maximal velocity than wheat calmodulin that was modified at Cys-27 by any of four fluorescent compounds, IAANS (2-[4'-iodoacetamidoanilino]naphthalene-6-sulfonic acid), 5-[2'-[[iodoacetyl]amino]ethyl]aminonaphthalene]-1-sulfonic acid, 5-iodoacetamidofluorescein, and 7-diethylamino-3-[4'-maleimidylphenyl]-4-methylcoumarin; the midpoints for activation of myosin light chain kinase were not significantly different for unmodified wheat calmodulin and three of the four wheat calmodulin derivatives. Myosin light chain kinase, but not mastoparan X, enhanced the fluorescence emission intensity of wheat calmodulin-IAANS. Mastoparan X reversed, in a dose-dependent manner, the changes in fluorescence intensity of a preformed complex of myosin light chain kinase and wheat calmodulin-IANNS. Thus, we propose that the region vicinal to Cys-27 participates in the activation but not the high affinity association of myosin light chain kinase. Lastly, a comparison of mammalian and plant calmodulin showed that the Vmax for the stimulation of myosin light chain kinase was 1.6-fold greater for bovine than wheat calmodulin. The difference between the two calmodulins was more pronounced at lower Ca2+ because less Ca2+ was needed to saturate the kinase rate when stimulated by bovine calmodulin.