Endostatin inhibits bradykinin-induced cardiac contraction

.Endogenous fragments of extracellular matrix are known to possess various biological effects. Levels of endostatin, a fragment of collagen type XVIII, increase in certain cardiac diseases, such as cardiac hypertrophy and myocardial infarction. However, the influence of endostatin on cardiac contraction has not been clarified. In the present study, we investigated the effects of endostatin on bradykinin-induced atrial contraction. Isometric contractile force of mouse isolated left atria induced by electrical current pulse was measured. Voltage-dependent calcium current of guinea pig ventricular myocytes was measured by a whole-cell patch-clamp technique. Endostatin (100–1,000 ng/ml) alone treatment had no influence on left atrial contraction. On the other hand, pretreatment with endostatin (300 ng/ml) significantly inhibited bradykinin (1 µM)-induced contraction and voltage-dependent calcium current. These data suggest that endostatin may decrease bradykinin-induced cardiac contraction perhaps through the inhibition of voltage-dependent calcium channel.     

Evaluation of novel sulfonylurea derivatives with a fused heterocyclic moiety as paddy herbicides that control sulfonylurea‐resistant weeds

Herbicidal activity and acetolactate synthase (ALS) inhibition of sulfonylurea derivatives with a fused heterocyclic moiety bonded to a sulfonyl group were investigated. Some compounds that had an imidazo[1,2‐b]pyridazine moiety substituted at the 2‐position by chlorine or methyl controlled sulfonylurea‐resistant (SU‐R) weeds and showed inhibitory activity to ALS prepared from SU‐R Schoenoplectus juncoides shoot. There was a correlation between in vitro and whole‐plant herbicidal activity of the compounds mentioned above against SU‐R Schoenoplectus juncoides. Among them 1‐(2‐chloro‐6‐propylimidazo[1,2‐b]pyridazin‐3‐ylsulfonyl)‐3‐(4,6‐dimethoxypyrimidin‐2‐yl)urea, propyrisulfuron, was selected for further evaluation. Propyrisulfuron effectively controlled paddy weeds at doses of 70 and 140 g a.i. ha^?1 with good rice selectivity in a field trial.     

Antioxidative enzymes response to NaCl stress in salt-tolerant Sesbania rostrata

Sesbania rostrata Brem. & Oberm. has been used as a promising halophytic plant to improve saline soil in north-east Thailand. Our previous study suggested that the salt tolerance of this plant was associated with its ability to translocate Na⁺ and Cl⁻ ions from roots to shoots and trap them in the shoot cells. The present study further investigated the effect of NaCl on the activity of antioxidative enzymes and the tolerance to an active oxygen species generator, paraquat in S. rostrata leaves. Higher constitutive levels of antioxidative enzyme activities, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), as well as higher levels of induced CAT and SOD activities with salinity stress were found in salt-tolerant S. rostrata than salt-sensitive Phaseolus vulgaris L. cv. Meal. Tolerance of S. rostrata to paraquat determined by the chlorophyll content in leaf disks increased with NaCl treatment. These findings indicate that S. rostrata exhibits better protection against the oxidative damage caused by NaCl, at least partly due to a higher constitutive and induced activities of antioxidative enzymes.     

Crude extract of the cyanobacterium, Hapalosiphon sp., causes a cessation of root elongation and cell division in several plant species

The phytotoxic activities of the crude extract from the cyanobacterium, Hapalosiphon sp., on the initial growth and root cell division of several plant species were investigated. Although the germination percentages of the plants were not affected by the extract, their root and shoot growth were remarkably suppressed, depending on the extract concentrations. Roots were more sensitive to the extract than shoots and the sensitivity, determined by the I₅₀ concentrations between the susceptible and tolerant species, differed by 5 and 11 times in dicotyledonous and monocotyledonous plants, respectively. The mitotic index for wheat ( Triticum aestivum L. cv. Norin 61) root cells was not affected, but the mitotic index for onion ( Allium cepa L. cv. Raputa II) was reduced with the increasing concentration of the extract. In the onion root meristem, the number of cells in prophase, metaphase, anaphase, and telophase were decreased significantly with 6 g DW L⁻¹ (g dry weight of algae L⁻¹). This suggests that the extract might inhibit the processes regulating the entry of cells into mitosis.     

Characterization of reactive oxygen species-involved oxidative damage in Hapalosiphon species crude extract-treated wheat and onion roots

Crude extract-induced oxidative damage using the cyanobacterium, Hapalosiphon sp., was investigated in wheat seedlings ( Triticum aestivum L. cv. Norin 61) and onion seedlings ( Allium cepa L. cv. Raputa II). The analysis of root cell viability or cell death using Evans blue uptake showed that the root-tip cells of wheat and onion lost viability after 24 h and 48 h treatment with 3 g dry weight (DW) L⁻¹ of the crude extract, respectively. Lipid peroxidation was induced in the roots of both species and the shoots of onion, whereas no increase in lipid peroxide formation was observed in the wheat shoots. In onion, the degree of random DNA fragmentation increased with the increasing concentration of the extract and laddering of the DNA was observed with 6 g DW L⁻¹ of the extract, but no apparent DNA ladder formation occurred in the wheat. Pretreatment for 1 h with the NADPH oxidase inhibitors, diphenyleneidonium or imidazole, reduced the crude extract-induced root cell death in both species. From the results, we suggest that the Hapalosiphon sp. crude extract might enhance reactive oxygen species (ROS) production, which causes membrane lipid damage and fragmentation of the DNA of plant cells, resulting in cell death and growth inhibition. The crude extract-mediated phytotoxic damage might be caused by ROS, triggered by NADPH oxidase.