Competitive kinetics in free radical reactions of cinnamic acid derivatives. Influence of phenoxyl radicals reactions

Relative rates of consumption of caffeic, ferulic and sinapic acids by 2,2'-azobis(2-amidine propane) derived peroxyl radicals has been measured in parallel experiments employing a single substrate and in competitive experiments. Rates of consumption measured in independent experiments at low substrate concentrations (first order limit) follow the order: sinapic > ferulic > caffeic. In agreement with this, in competitive experiments employing simultaneously sinapic and caffeic acid the former compound is consumed considerably faster. On the other hand, in competitive experiments employing ferulic and caffeic acids over a wide range of experimental conditions, caffeic acid is consumed considerably faster than ferulic acid, a result that contrasts with that obtained when both compounds are reacted independently. These apparently anomalous results are interpreted in terms of secondary reactions of the phenol-derived radicals. In particular, hydrogen transfer among phenoxyl radicals and the phenols and fast reactions (disproportionation) of caffeic acid derived radicals could explain these discrepancies.     

Mangrove leaf litter decomposition under mangrove forest stands with different levels of pollution in the Niger River Delta,Nigeria

Nutrient cycling often moves between litter fall and decomposition. It is hypothesized that hydrocarbon pollution will slow down mangrove litter decomposition because of the reduction in microbial activities. We studied decomposition rates at different levels of pollution (i.e. high and low) and amongst different mangrove species (i.e. red, white and black). For the first experiment, fresh leaves of Rhizophora racemosa were collected, sealed in a litter bag and placed on the mangrove floor for 1.24 years at which all the leaves had completely decomposed to humus and were oven‐dried and weighed to calculate the decomposition rate constant (k) of mass loss. Although there was no significant difference in the rate of decomposition (P > 0.05), leaves at the highly polluted plot had lower rate of decomposition (6.58 × 10^?4) when compared to leaves at the lowly polluted plot (1.75 × 10^?3). In the second experiment, there was a significant difference in decomposition rates amongst species (P < 0.05). Red mangrove leaves (0.41) decomposed more than white (0.28) and black (0.28) mangrove leaves. This implies that hydrocarbon pollution slowed, but did not stop the decomposition of mangrove leaves.     

Elucidating multi-input processing 3-node gene regulatory network topologies capable of generating striped gene expression patterns

A central problem in developmental and synthetic biology is understanding the mechanisms by which cells in a tissue or a Petri dish process external cues and transform such information into a coherent response, e.g., a terminal differentiation state. It was long believed that this type of positional information could be entirely attributed to a gradient of concentration of a specific signaling molecule (i.e., a morphogen). However, advances in experimental methodologies and computer modeling have demonstrated the crucial role of the dynamics of a cell’s gene regulatory network (GRN) in decoding the information carried by the morphogen, which is eventually translated into a spatial pattern. This morphogen interpretation mechanism has gained much attention in systems biology as a tractable system to investigate the emergent properties of complex genotype-phenotype maps. In this study, we apply a Markov chain Monte Carlo (MCMC)-like algorithm to probe the design space of three-node GRNs with the ability to generate a band-like expression pattern (target phenotype) in the middle of an arrangement of 30 cells, which resemble a simple (1-D) morphogenetic field in a developing embryo. Unlike most modeling studies published so far, here we explore the space of GRN topologies with nodes having the potential to perceive the same input signal differently. This allows for a lot more flexibility during the search space process, and thus enables us to identify a larger set of potentially interesting and realizable morphogen interpretation mechanisms. Out of 2061 GRNs selected using the search space algorithm, we found 714 classes of network topologies that could correctly interpret the morphogen. Notably, the main network motif that generated the target phenotype in response to the input signal was the type 3 Incoherent Feed-Forward Loop (I3-FFL), which agrees with previous theoretical expectations and experimental observations. Particularly, compared to a previously reported pattern forming GRN topologies, we have uncovered a great variety of novel network designs, some of which might be worth inquiring through synthetic biology methodologies to test for the ability of network design with minimal regulatory complexity to interpret a developmental cue robustly.     

In vivo assessment of mechanical properties during axolotl development and regeneration using confocal Brillouin microscopy

In processes such as development and regeneration, where large cellular and tissue rearrangements occur, cell fate and behaviour are strongly influenced by tissue mechanics. While most well-established tools probing mechanical properties require an invasive sample preparation, confocal Brillouin microscopy captures mechanical parameters optically with high resolution in a contact-free and label-free fashion. In this work, we took advantage of this tool and the transparency of the highly regenerative axolotl to probe its mechanical properties in vivo for the first time. We mapped the Brillouin frequency shift with high resolution in developing limbs and regenerating digits, the most studied structures in the axolotl. We detected a gradual increase in the cartilage Brillouin frequency shift, suggesting decreasing tissue compressibility during both development and regeneration. Moreover, we were able to correlate such an increase with the regeneration stage, which was undetected with fluorescence microscopy imaging. The present work evidences the potential of Brillouin microscopy to unravel the mechanical changes occurring in vivo in axolotls, setting the basis to apply this technique in the growing field of epimorphic regeneration.     

Uterine infusion of conceptus fragments changes the protein profile from cyclic mares

This experiment aimed to compare at day seven after ovulation, the protein profile of uterine fluid in cyclic mares with mares infused two days before with Day 13 conceptus fragments. Experimental animals were ten healthy cyclic mares, examined daily to detect ovulation (Day 0) as soon as estrus was confirmed. On day seven, after ovulation, uterine fluid was collected, constituting the Cyclic group (n = 10). The same mares were examined in the second cycle until ovulation was detected. On day five, after ovulation, fragments from a previously collected concepti were infused into each mare''s uterus. Two days after infusion, uterine fluid was collected, constituting the Fragment group (n = 10). Two-dimensional electrophoresis technique processed uterine fluid samples. A total of 373 spots were detected. MALDI-TOF/TOF and NanoUHPLC-QTOF mass spectrometry identified twenty spots with differences in abundance between the Cyclic and Fragment group. Thirteen proteins were identified, with different abundance between groups. Identified proteins may be related to embryo-maternal communication, which involves adhesion, nutrition, endothelial cell proliferation, transport, and immunological tolerance. In conclusion, conceptus fragments signalized changes in the protein profile of uterine fluid seven days after ovulation in comparison to the observed at Day 7 in the same cyclic mares.