2,3-dihydrojaborosalactone A,a withanolide from Acnistus breviflorus

From Acnistus breviflorus the new 27-hydroxy-5β,6β-epoxy-1-oxo-(22R)-witha-24-enolide (2,3-dihydrojaborosalactone A) as well as seven known withanolides, withaferin A, 2,3-dihydrowithaferin A, 6α-chloro-5β-hydroxywithaferin A, 5,6-deoxywithaferin A, jaborosalactone A, jaborosalactone D and jaborosalactone E were isolated and characterized by means of spectroscopic (¹H NMR, ¹³ C NMR and mass spectral) methods. Depending on the extraction solvent (methanol or ethanol), a known artifact (3β-methoxy-2,3-dihydrowithaferin A) and the new 5α-methoxy-4,5-dihydrojaborosalactone B and 5α-ethoxy-4,5-dihydrojaborosalactone B were also isolated and characterized.     

Ent-beyerene and ent-atisene diterpenes from viguiera insignis

The new diterpenes, ent-beyer-15-ene-12α,19-diol and ent-atis-13-en-3β,16α-diol, were isolated as minor constituents from the aerial part of Viguiera insignis. The structures were established by biomimetic transformation, spectroscopic means and comparison with closely related compounds.     

Genetic Characterization of the Phenylacetyl-Coenzyme A Oxygenase from the Aerobic Phenylacetic Acid Degradation Pathway of Escherichia coli

We show here that the paaABCDE genes of the paa cluster responsible for phenylacetate degradation in Escherichia coli W encode a five-component oxygenase that hydroxylates phenylacetyl-coenzyme A (CoA), the first intermediate of the pathway. The primary structure of the subunits of bacterial phenylacetyl-CoA oxygenases revealed that these enzymes constitute the prototype of a new and distinct group of the large bacterial diiron multicomponent oxygenase family.     

Environmental Control of Early Succession on a Large Landslide in a Tropical Dry Ecosystem (Casita Volcano, Nicaragua)

We described the plant communities on a large landslide in a human-dominated area of tropical dry forest landscape (Casita Volcano, Nicaragua) and in the adjacent forest, 3 yr after landslide occurrence. At both sites, we determined the relationships between spatial changes in environmental factors and the spatial distribution of species and plant traits. Subsequently, we tested the hypothesis that the compositional similarity between the landslide and the forest increased with a decrease in the distance from the forest edge and the width of the landslide. In the forest, the spatial distribution of species and plant traits was determined mainly by an elevational gradient that was associated with the amount of bare soil, whereas, on the landslide, there was no such gradient but species distributions were influenced mostly by the presence of residual agricultural and forest soils and human disturbance. We did not find an increase in compositional similarity between the landslide and the forest at the edge or in the narrow zones of the landslide. Compared to other landslides, the recovery process was strongly influenced by the extreme abiotic heterogeneity, climate seasonality, and human use in the area. The study of succession in tropical dry landslides located in densely populated zones should focus on understanding the response of regional ecosystems to a complex disturbance regime in which human-induced disturbances play a major role.     

Cytoskeletal rearrangement and cell death induced by Bothrops alternatus snake venom in cultured Madin-Darby canine kidney cells.

Bothrops snake venoms cause renal damage, with renal failure being the main cause of death in humans bitten by these snakes. In this work, we investigated the cytoskeletal rearrangement and cytotoxicity caused by Bothrops alternatus venom in cultured Madin-Darby canine kidney (MDCK) cells. Incubation with venom (10 and 100 microg/mL) significantly (p <0.05) decreased the cellular uptake of neutral red dye after 1 and 3 h. Venom (100 microg/mL) also markedly decreased the transepithelial electrical resistance (RT) across MDCK monolayers. Staining with rhodamine-conjugated phalloidin revealed disarray of the cytoskeleton that involved the stress fibers at the basal cell surface and focal adhesion-associated F-actin in the cell-matrix contact region. Feulgen staining showed a significant decrease in the number of cells undergoing mitosis and an increase in the frequency of altered nuclei. Scanning electron microscopy revealed a decrease in the number of microvilli and the presence of cells with a fusiform format. Flow cytometry with annexin V and propidium iodide showed that cell death occurred by necrosis, with little apoptosis, a conclusion supported by the lack of DNA fragmentation characteristic of apoptosis. Pretreating the cells with catalase significantly attenuated the venom-induced loss of viability, indicating a possible involvement of H2O2 in the cellular damage; less protection was observed with superoxide dismutase or N omega-nitro-L-arginine methyl ester. These results indicate that Bothrops alternatus venom is cytotoxic to cultured MDCK cells, possibly via the action of reactive oxygen species. This cytotoxicity could contribute to nephrotoxicity after envenoming by this species.     

Peroxisomal manganese superoxide dismutase: Purification and properties of the isozyme from pea leaves

The peroxisomal manganese superoxide dismutase (perMn‐SOD; EC 1.15.1.1) was purified to homogeneity for the first time from peroxisomes of pea ( Pisum sativum L.) leaves. Peroxisomes were isolated from pea leaves by sucrose density‐gradient centrifugation, and then perMn‐SOD was purified from these organelles by two purification steps involving anion‐exchange and gel‐filtration fast protein liquid chromatography. Pure peroxisomal Mn‐SOD had a specific activity of 2 880 units per mg protein and was purified 3 000‐fold, with a yield of about 7 µg enzyme per kg pea leaves. The relative molecular mass determined for perMn‐SOD was 92 000, and it was composed of four equal subunits of 27 kDa. Ultraviolet and visible absorption spectra of the enzyme showed two absorption maxima at 278 and 483 nm, respectively, and two shoulders at 290 and 542 nm. By isoelectric focusing (pH 5‐7), an isoelectric point of 5.53 was determined for perMn‐SOD. In immunoblot assays, purified Mn‐SOD was recognized by a polyclonal antibody against mitochondrial Mn‐SOD (mitMn‐SOD) from pea leaves. The amino acid sequence of the N‐terminal region of the purified peroxisomal enzyme was determined. A 100% identity was found with the mitMn‐SOD from pea leaves, and high identities were also found with Mn‐SODs from other plant species.