Circadian Rhythm of Cardiac Output, Peripheral Vascular Resistance, and Related Variables by a Beat-to-Beat Monitoring

This study aimed to explore the 24-h patterns of stroke volume, cardiac output, and peripheral vascular resistance along with other correlated variables, such as left ventricular ejection time, ejection velocity index, thoracic fluid index, heart rate, and blood pressure. The study was performed on 12 clinically healthy subjects by means of a noninvasive beat-to-beat monitoring using the thoracic electric bioimpedance technique associated with the automated sphygmomano-metric recording. Time data series were analyzed by means of chronobiological procedures. The results documented the occurrence of a circadian rhythm for all the variables investigated, giving relevance to the beat-to-beat bioperiodicity of cardiac output and peripheral vascular resistance. Temporal quantification of the investigated variables may be useful for a better insight of the chronophysiology of the cardiovascular apparatus.     

The proteasome regulatory particle subunit Rpn6 is required for Drosophila development and interacts physically with signalosome subunit Alien/CSN2

The eukaryotic 26S proteasome plays a central role in ubiquitin-dependent intracellular protein metabolism. The multimeric holoenzyme is composed of two major subcomplexes, known as the 20S proteolytic core particle and the 19S regulatory particle (RP). The RP can be further dissected into two multisubunit complexes, the lid and the base complex. The lid complex shares striking similarities with another multiprotein complex, the COP9 signalosome. Several subunits of both complexes contain the characteristic PCI domain, a structural motif important for complex assembly. The COP9 signalosome was shown to act as a versatile regulator in numerous pathways. To help define the molecular interactions of the signalosome during Drosophila development, we performed a yeast two-hybrid screen to identify proteins that physically interact with subunit 2 of the complex, namely Alien/CSN2. Here, we report that Drosophila Rpn6, a non-ATPase subunit of the RP lid complex, interacts with Alien/CSN2 via its PCI domain. The temporal and spatial expression patterns of Rpn6 and alien/CSN2 overlap on a large scale during development providing additional evidence for their interaction in vivo. Analyses of an Rpn6 P element insertion mutant and newly generated Rpn6 alleles reveal that Rpn6 is essential for Drosophila development.     

Central Amazon Floodplain Forests: Root Adaptations to Prolonged Flooding

The floodplains of Central Amazonia represent a complex system of inundated river valleys and shallow lakes along the Solimões–Amazonas river, which is subjected to an annual flood-pulse lasting up to 10 months. Such flooding reaching an amplitude of about ten meters causes dramatic changes in the bioavailability of nutrients and oxygen levels and poses extreme constraints for plant survival and reproductivity. Tree species of inundation forests in Central Amazonia had to evolve adaptive mechanisms to both desiccation of soils and partial or full submergence. To adapt to flooded conditions, some trees overcome the flood period by dormancy accompanied by defoliation and formation of annual rings in the wood. Other species maintain metabolism and retain the foliage during the flooding, representing another adaptive mechanism to low oxygen availability. This investigation focused on the root physiology and morphology of six species typical of white-water inundation areas (várzea) led to a preliminary classification of adaptive strategies of trees inhabiting forest communities in floodplains of the Amazon basin.     

Binding of aflatoxins to the 20S proteasome: effects on enzyme functionality and implications for oxidative stress and apoptosis

Aflatoxins (AF) are contaminants of improperly stored foods; they are potent genotoxic and carcinogenic compounds, exerting their effects through damage to DNA. They can also induce mutations that increase oxidative damage. The goal of this study was to evaluate the possibility that a third mechanism could be involved in the carcinogenic action of aflatoxins, namely, direct binding to key enzymes involved in the regulatory pathways of the cell cycle, thereby modulating enzyme functionality. The 20S constitutive and immunoproteasome peptidase and proteolytic activities were assayed in the presence of aflatoxins B1, G1 and M1. All three toxins activated multiple peptidase activities of the proteasome. Aflatoxin (AF) M1 was the most potent activator of proteasome activity, while the constitutive 20S proteasome was specifically stimulated by AFG1. Furthermore, the effects of AFB1 on cultured hepatoma cells were investigated and the various proteasomal activities determined with cell lysates were differently affected. Taking into account the key role of the proteasome in cellular defense against oxidative stress, the carbonyl group content and the activities of antioxidant enzymes in cell lysates were analyzed. The proapoptotic effect of AFB1 was also investigated by measuring caspase-3 activity and cellular levels of p27 and IkappaBalpha.     

Redox regulation of chloroplast enzymes in Galdieria sulphuraria in view of eukaryotic evolution

Redox modulation is a general mechanism for enzyme regulation, particularly for the post-translational regulation of the Calvin cycle in chloroplasts of green plants. Although red algae and photosynthetic protists that harbor plastids of red algal origin contribute greatly to global carbon fixation, relatively little is known about post-translational regulation of chloroplast enzymes in this important group of photosynthetic eukaryotes. To address this question, we used biochemistry, phylogenetics and analysis of recently completed genome sequences. We studied the functionality of the chloroplast enzymes phosphoribulokinase (PRK, EC 2.7.1.19), NADP-dependent glyceraldehyde 3-phosphate dehydrogenase (NADP-GAPDH, GapA, EC 1.2.1.13), fructose 1,6-bisphosphatase (FBPase, EC 3.1.3.11) and glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49), as well as NADP-malate dehydrogenase (NADP-MDH, EC 1.1.1.37) in the unicellular red alga Galdieria sulphuraria (Galdieri) Merola. Despite high sequence similarity of G. sulphuraria proteins to those of other photosynthetic organisms, we found a number of distinct differences. Both PRK and GAPDH co-eluted with CP12 in a high molecular weight complex in the presence of oxidized glutathione, although Galdieria CP12 lacks the two cysteines essential for the formation of the N-terminal peptide loop present in higher plants. However, PRK inactivation upon complex formation turned out to be incomplete. G6PDH was redox modulated, but remained in its tetrameric form; FBPase was poorly redox regulated, despite conservation of the two redox-active cysteines. No indication for the presence of plastidic NADP-MDH (and other components of the malate valve) was found.     

Mecardonia tenella (Plantaginaceae) Attracts Oil-, Perfume-, and Pollen-Gathering Bees in Southern Brazil

Floral characteristics often indicate the pollinators' functional group visiting the plant and the pollination syndromes associated with them. This idea has been challenged in the past decades due to increasing evidence that most plants, including those exhibiting floral syndromes, are visited by large arrays of species that differ in their effectiveness as pollinators. Our study focuses on Mecardonia tenella (Plantaginaceae) from the Araucaria forest of southern Brazil, which exhibits characteristics of the oil flower pollination syndrome. However, it is visited by three types of functional groups of bees: male orchid bees, oil-collecting bees, and pollen-seeking bees. The relative contribution of each functional group to the plant's reproductive success was estimated based on their pollen load, visitation frequency, and morphology. We assessed resources, phenology, and breeding system of M. tenella . Our results indicate that flowers lack nectar, but volatiles, lipids, and pollen are resources that can be gathered by visitors. This combination of floral traits and visitors' assemblage makes M. tenella a challenge to the concept of pollination syndromes. Our findings indicate that the current interactions may not reflect the circumstances under which some floral traits of this plant were selected.