Anatomical inferences on aerial bud protection of three Eugenia shrub species from the Cerrado

• Location and degree of protection of aerial buds are important functional traits in disturbance- or stress-prone environments since aerial buds ensure the development of new organs under favourable growing conditions. This study was carried out in a Brazilian Cerrado area under regeneration after long-term Pinus cultivation, where the trees were clear-cut in 2012 and the remaining material was burned in 2014.
• After the fire treatment, several species resprouted from belowground organs and their aboveground organs were directly exposed to full sunlight. We collected 15 terminal branches with fully expanded leaves from three individuals of each of three Eugenia species to investigate if those with well-developed belowground organs invest in bark for aboveground bud protection. The samples were analysed using light and electron microscopy.
• In addition to terminal and axillary buds, all species presented accessory buds, and the number varied according to the node analysed. None of the aerial buds were protected by bark, but all were well protected by cataphylls and densely pubescent leaf primordia. There were also inter- and intra-petiolar colleters that released a mucilaginous protein exudate. The distance between the shoot apical meristem and the outer surface was longer in the terminal bud than in axillary buds. The bud leaf primordia covering the shoot apical meristem had a thick cuticle, unicellular non-glandular trichomes that accumulate phenolic and lipophilic compounds, and secretory cavities.
• Our study shows that all three Eugenia species studied here had highly protected aerial buds allocated from belowground organs. These morphological traits may improve the chances of the species' persistence in areas subjected to frost events, low relative humidity, high irradiance and harmful UV levels.

     

Outdoor supplementation systems for studies of the effects of increased UV-B radiation

Studies of the effects of increases in ultraviolet-B (UV-B) radiation on plants and terrestrial ecosystems have been undertaken using a variety of methods including: controlled-environment cabinets, glasshouses, outdoor filtration and outdoor supplementation using fluorescent UV-B lamps. Outdoor supplementation systems provide a method of study which creates only small alterations to the microclimate and the number of such studies has increased during the past 3 years. These supplementation systems differ in their methods of operation, equipment, UV-B exposure regime and experimental design. This essay surveys the systems currently developed, considers problems associated with their use and discusses these in relation to the interpretation of biological effects.     

A radiobiological comparison of hypo-fractionation versus conventional fractionation for breast cancer 3D-conformal radiation therapy

BackgroundThe present research was aimed to compare the toxicity and effectiveness of conventional fractionated radiotherapy versus hypo-fractionated radiotherapy in breast cancer utilizing a radiobiological model.Materials and methodsThirty-five left-sided breast cancer patients without involvement of the supraclavicular and axillary lymph nodes (with the nodal stage of N0) that had been treated with conventional or hypo-fractionated were incorporated in this study. A radiobiological model was performed to foretell normal tissue complication probability (NTCP) and tumor control probability (TCP).ResultsThe data represented that TCP values for conventional and hypo-fractionated regimens were 99.16 ± 0.09 and 95.96 ± 0.48, respectively (p = 0.00). Moreover, the NTCP values of the lung for conventional and hypo-fractionated treatment were 0.024 versus 0.13 (p = 0.035), respectively. Also, NTCP values of the heart were equal to zero for both regimens.ConclusionIn summary, hypo-fractionated regimens had comparable efficacy to conventional fraction radiation therapy in the case of dosimetry parameters for patients who had left breast cancer. But, utilizing the radiobiological model, conventional fractionated regimens presented better results compared to hypo-fractionated regimens.     

The water channel of cytochrome c oxidase: inferences from inhibitor studies.

Cytochrome c oxidase couples electron transfer to proton transfer from inside the mitochondrion to the cytosol. Protons pass through a channel; it is closed except when protons are pumped. Electron transfer is also coupled to a water cycle. Water moves into and out of the oxidase during electron transfer, presumably through a channel. The three processes are coupled because of the common dependence on electron transfer. If water and protons had to pass through the same channel for the proton to pass, it might be possible to block the pore by entraining small molecules in the flow. The data in this report indicate that there is a correlation between the ability of a compound to inhibit the oxidase and its size. Formamide and formaldehyde are potent inhibitors. Larger and smaller molecules are poor inhibitors. Formamide introduces an internal block in electron transfer. It is a slow-onset, reversible inhibitor, dependent on turnover to manifest its effects. Vesicular oxidase is less influenced by formamide than is soluble oxidase; formamide must pass a permeability barrier to act. The data are consistent with a proton channel with constrictions at both ends that open to yield a pore of approximately 4 A.     

The phylogenetic placement of Chondrichthyes: inferences from analysis of multiple genes and implications for comparative studies

Elasmobranch fishes (sharks and rays) have proven valuable for inferring general and specific properties of molecular evolution through comparative studies with crown group vertebrates because they are the most ancient group of gnathostomes. Recent studies have questioned the conventional phylogenetic placement of sharks in the vertebrate tree, however. In this paper I review the importance of the basal position of Chondrichthyes for comparative biology and compile evidence from multiple, independent genes to evaluate the phylogenetic placement of sharks. The results suggests that alternative phylogenetic hypotheses of the relationships among the Chondrichthyes, Actinopterygii and Sarcopterygii can not be refuted with available data, implying that the assumption of the basal placement of sharks in the vertebrate tree is suspect. Resolving the phylogeny of basal vertebrates is important for testing hypotheses about the evolution of vertebrates, and the current lack of a robust phylogeny limits evolutionary inferences that can be gained from comparative studies that include sharks and rays.