The mixture of bensulfuron-methyl and acetochlor (MBA) has been widely applied as a rice herbicide in China, but the mixture toxicity of MBA to aquatic organisms is largely unknown. The current study aims to investigate the acute effects of MBA to juvenile red swamp crayfish, Procambarus clarkii. Firstly, a 96 h semi-static exposure was conducted to determine the Lethal Concentration 50 (LC50) values at 24, 48, 72 and 96 h, as well as to assess the behavioral and morphological effects. A second 96 h exposure was conducted at an MBA concentration of 50% of the 96 h LC50 (72.62 mg/L) to assess the histological changes in the gill, perigastric organ, muscle, heart, stomach, and midgut. The results showed that MBA exhibited low acute toxicity with the 24, 48, 72 and 96 h LC50 values of 191.25 (179.37–215.75), 166.81 (159.49–176.55), 154.30 (148.36–160.59) and 145.24 (138.94–151.27) mg/L, respectively. MBA-exposed crayfish showed body jerk, belly arch, equilibrium loss, body and appendage sway, and lethargy; and the dead crayfish showed dark gray or grayish-white body color and separated cephalothorax and abdomen. At 72.62 mg/L, MBA exposure caused significant histopathological alterations, mainly including the cuticular and epithelial degeneration of all the gills; atrophy of tubule lumina and cellular vacuolation of the perigastric organs (61.15 ± 9.90% of the tubules showed lesions); epithelial hyperplasia (48.40 ± 9.00%), myocardial fibers and epithelial cell lysis (17.30 ± 2.01%), and hemocytic infiltration of the hearts; cuticular swelling (15.82 ± 2.98%) and vacuolate connective tissue (11.30 ± 2.47%) of the stomachs; atrophied bladder cell and fragmented longitudinal muscles (95.23 ± 4.77%) of the midguts; and slight myofibers fragmentation and lysis (7.37 ± 0.53%) of the abdominal muscles. Our results indicate that MBA can cause behavioral, morphological and histopathological effects on juvenile P. clarkii at relatively high concentrations, but its acute toxicity is low compared with many other common herbicides.
1,4-Dicarbonyl compounds are intriguing motifs and versatile precursors in numerous pharmaceutical molecules and bioactive natural compounds.D irect incorporation of two carbonyl groups into ad ouble bond at both ends is straightforward, but also challenging.Represented herein is the first example of 1,2-dicarbonylation of alkenes by photocatalysis.K ey to success is that N(n-Bu) 4+ not only associates with the alkylanion to avoid protonation, but also activates the a-keto acid to undergo electrophilic addition. The a-keto acid is employed both for acyl generation and electrophilic addition. By tuning the reductive and electrophilic ability of the acyl precursor,u nsymmetric 1,4-dicarbonylation is achieved for the first time.T his metal-free,r edox-neutral and regioselective 1,2-dicarbonylation of alkenes is executed by ap hotocatalyst for versatile substrates under extremely mild conditions and shows great potential in biomolecular and drug molecular derivatization.
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