Open vegetation formations (grasslands and savannahs) support a higher diversity of Cetoniidae (Insecta: Coleoptera) than forest formations in the brazilian Cerrado

Brazil has 22 genera and 75 species of Cetoniidae, with the Cerrado hosting the greatest diversity among Brazilian biomes. However, the diversity of groups among the different phytophysiognomies of the biome is not known. The objectives of this study are to assess Cetoniidae diversity and to verify the seasonality of these beetles in three Cerrado phytophysiognomies (gallery forest, cerrado sensu stricto, and campo sujo) located in three conservation units in Brasilia, Distrito Federal, Brazil. We collected adults monthly (October/2016 to September/2018) using 180 traps baited with bananas fermented with sugarcane juice, totaling 1,574 specimens, 8 genera, and 17 species. Cetoniidae diversity was higher in the phytophysiognomies with lower tree density (campo sujo and cerrado sensu stricto) than in gallery forests (forest formation), confirming our hypothesis that more open areas favor the dispersal of these insects due to their diurnal long-flying behavior. The seasonality of Cetoniidae was directly related to the precipitation, with higher numbers of individuals and species in the rainy season. However, the distribution varies among the phytophysiognomies, with aggregated distribution in campo sujo and gallery forest and dispersed in cerrado sensu stricto. Our results suggest that the Cetoniidae take advantage of the open Cerrado physiognomies to locate resources faster and with less energy expenditure, presenting higher diversity in these environments, despite the more ephemeral and dispersed food resources.

     

The dynamic cycle of bacterial translation initiation factor IF3

Initiation factor IF3 is an essential protein that enhances the fidelity and speed of bacterial mRNA translation initiation. Here, we describe the dynamic interplay between IF3 domains and their alternative binding sites using pre-steady state kinetics combined with molecular modelling of available structures of initiation complexes. Our results show that IF3 accommodates its domains at velocities ranging over two orders of magnitude, responding to the binding of each 30S ligand. IF1 and IF2 promote IF3 compaction and the movement of the C-terminal domain (IF3C) towards the P site. Concomitantly, the N-terminal domain (IF3N) creates a pocket ready to accept the initiator tRNA. Selection of the initiator tRNA is accompanied by a transient accommodation of IF3N towards the 30S platform. Decoding of the mRNA start codon displaces IF3C away from the P site and rate limits translation initiation. 70S initiation complex formation brings IF3 domains in close proximity to each other prior to dissociation and recycling of the factor for a new round of translation initiation. Altogether, our results describe the kinetic spectrum of IF3 movements and highlight functional transitions of the factor that ensure accurate mRNA translation initiation.     

Biotransformation of Colchicinoids into Their Corresponding 3-O-Glucosyl Derivatives by Selected Strains of Bacillus megaterium

Natural colchicinoids and their semisynthetic derivatives are important active ingredients for pharmaceutical applications. Thiocolchicoside (3-demethoxy-3-glucosyloxythiocolchicine) is used in several countries as standard therapy for the treatment of diseases of the muscle–skeletal system, due to its potent antiinflammatory and myorelaxant properties. Manufacturing of thiocolchicoside requires a key step, the regioselective demethylation and glucosylation of chemically derivative thiocolchicine. High selectivity and efficiency of this transformation cannot be achieved in a satisfactory way with a chemical approach. In particular, the chemical demethylation, a part from requiring toxic and aggressive reagents, generates a complex mixture of products with no industrial usefulness. We report herein an efficient, direct and green biotransformation of thiocolchicine into thiocolchicoside, performed by a specific strain of Bacillus megaterium. The same process, with minor modifications, can be used to convert the by-product 3-O-demethyl-thiocolchicine into thiocolchicoside. In addition, we describe the B. megaterium strain selection process and the best conditions for this effective double biotransformation. The final product has a pharmaceutical quality, and the process has been industrialised.     

Evaluation of the mutagenicity and antimutagenicity of Ziziphus joazeiro Mart. bark in the micronucleus assay

The aim of this study was to evaluate the mutagenicity (clastogenicity/aneugenicity) of a glycolic extract of Ziziphus joazeiro bark (GEZJ) by the micronucleus assay in mice bone marrow. Antimutagenic activity was also assessed using treatments associated with GEZJ and doxorubicin (DXR). Mice were evaluated 24–48 h after exposure to positive (N-nitroso-N-ethylurea, NEU - 50 mg.kg⁻¹ and DXR - 5 mg.kg⁻¹) and negative (150 mM NaCl) controls, as well as treatment with GEZJ (0.5–2 g.kg⁻¹), GEZJ (2 g.kg⁻¹) + NEU and GEZJ (2 g.kg⁻¹) + DXR. There were no significant differences in the frequencies of micronucleated polychromatic erythrocytes in mice treated with GEJZ and GEJZ + DXR compared to the negative controls, indicating that GEZJ was not mutagenic. Analysis of the polychromatic:normochromatic erythrocyte ratio revealed significant differences in the responses to doses of 0.5 g.kg⁻¹ and 1–2 g.kg⁻¹ and the positive control (NEU). These results indicated no systemic toxicity and moderate toxicity at lower and higher doses of GEZJ. The lack of mutagenicity and systemic toxicity in the antimutagenic assays, especially for treatment with GEZJ + DXR, suggested that phytochemical compounds in Z. joazeiro bark attenuated DXR-induced mutagenicity and the moderate systemic toxicity of a high dose of Z. joazeiro bark (2 g.kg⁻¹). Further studies on the genotoxicity of Z. joazeiro extracts are necessary to establish the possible health risk in humans and to determine the potential as a chemopreventive agent for therapeutic use.     

In vitro drug permeation from chitosan pellets

The purpose of this study was to prepare and characterize coated pellets for controlled drug delivery. The influence of chitosan (CS) in pellets was evaluated by swelling, in vitro drug release and intestinal permeation assays. Pellets were coated with an enteric polymer, Kollicoat^® MAE 30 DP, in a fluidized-bed apparatus and the coating formulations were based on a factorial design. Metronidazole (MT) released from coated and uncoated pellets were assessed by dissolution method using Apparatus I. Intestinal permeation was evaluated by everted intestinal sac model in rats, used to study the absorption of MT from coated pellets containing CS or not through the intestinal tissue. Although the film coating avoided drug dissolution in gastric medium, the overall drug release and intestinal permeation were dependent on the presence of CS. Thus, pellets containing CS show potential as a system for controlled drug delivery.     

Formin leaky cap allows elongation in the presence of tight capping proteins

Formins, characterized by formin homology domains FH1 and FH2, are required to assemble certain F-actin structures including actin cables, stress fibers, and the contractile ring. FH1FH2 in a recombinant fragment from a yeast formin (Bni1p) nucleates actin filaments in vitro. It also binds to the filament barbed end where it appears to act as a "leaky" capper, slowing both polymerization and depolymerization by approximately 50%. We now find that FH1FH2 competes with tight capping proteins (including gelsolin and heterodimeric capping protein) for the barbed end. We also find that FH1FH2 forms a tetramer. The observation that this formin protects an end from capping but still allows elongation confirms that it is a leaky capper. This is significant because a nucleator that protects a new barbed end from tight cappers will increase the duration of elongation and thus the total amount of F-actin. The ability of FH1FH2 to dimerize probably allows the formin to walk processively with the barbed end as the filament elongates.