Cucurbitacins and aromatic compounds from Crinodendron hookerianum

Cucurbitacins-D, -F, -H, and the new member 23,24-dihydrocucurbitacin F have been isolated from Crinodendron hookeranium. This is the first report of cucurbitacins in the Elaeocarpaceae. Other components isolated included gallic and ellagic acids, methyl 3-O-methylgallate and an ellagitannin.     

Somatostatin binding sites in cytosolic fractions of parietal and non-parietal cells from rabbit fundic mucosa

Specific binding sites for somatostatin have been found in the cytosolic fractions of both parietal and non-parietal cells from rabbit gastric fundic mucosa. The stoichiometric data suggested the presence of two classes of binding sites in both types of ceils. The number of low-affinity binding sites was significantly higher in parietal cells than in non-parietal cells. The reverse was true for the high-affinity binding sites. However, the affinity of each class of binding sites was similar in the cytosolic fractions of both parietal and non-parietal ceils. It thus appears that low-affinity somatostatin binding sites are mainly located in the parietal ceils whereas the high-affinity sites occur principally in the non-parietal cells.     

Moonstruck Primates: Owl Monkeys (Aotus) Need Moonlight for Nocturnal Activity in Their Natural Environment

Primates show activity patterns ranging from nocturnality to diurnality, with a few species showing activity both during day and night. Among anthropoids (monkeys, apes and humans), nocturnality is only present in the Central and South American owl monkey genus Aotus. Unlike other tropical Aotus species, the Azara''s owl monkeys (A. azarai) of the subtropics have switched their activity pattern from strict nocturnality to one that also includes regular diurnal activity. Harsher climate, food availability, and the lack of predators or diurnal competitors, have all been proposed as factors favoring evolutionary switches in primate activity patterns. However, the observational nature of most field studies has limited an understanding of the mechanisms responsible for this switch in activity patterns. The goal of our study was to evaluate the hypothesis that masking, namely the stimulatory and/or inhibitory/disinhibitory effects of environmental factors on synchronized circadian locomotor activity, is a key determinant of the unusual activity pattern of Azara''s owl monkeys. We use continuous long-term (6–18 months) 5-min-binned activity records obtained with actimeter collars fitted to wild owl monkeys (n = 10 individuals) to show that this different pattern results from strong masking of activity by the inhibiting and enhancing effects of ambient luminance and temperature. Conclusive evidence for the direct masking effect of light is provided by data showing that locomotor activity was almost completely inhibited when moonlight was shadowed during three lunar eclipses. Temperature also negatively masked locomotor activity, and this masking was manifested even under optimal light conditions. Our results highlight the importance of the masking of circadian rhythmicity as a determinant of nocturnality in wild owl monkeys and suggest that the stimulatory effects of dim light in nocturnal primates may have been selected as an adaptive response to moonlight. Furthermore, our data indicate that changes in sensitivity to specific environmental stimuli may have been an essential key for evolutionary switches between diurnal and nocturnal habits in primates.     

The Role of Protein Denaturation Energetics and Molecular Chaperones in the Aggregation and Mistargeting of Mutants Causing Primary Hyperoxaluria Type I

Primary hyperoxaluria type I (PH1) is a conformational disease which result in the loss of alanine:glyoxylate aminotransferase (AGT) function. The study of AGT has important implications for protein folding and trafficking because PH1 mutants may cause protein aggregation and mitochondrial mistargeting. We herein describe a multidisciplinary study aimed to understand the molecular basis of protein aggregation and mistargeting in PH1 by studying twelve AGT variants. Expression studies in cell cultures reveal strong protein folding defects in PH1 causing mutants leading to enhanced aggregation, and in two cases, mitochondrial mistargeting. Immunoprecipitation studies in a cell-free system reveal that most mutants enhance the interactions with Hsc70 chaperones along their folding process, while in vitro binding experiments show no changes in the interaction of folded AGT dimers with the peroxisomal receptor Pex5p. Thermal denaturation studies by calorimetry support that PH1 causing mutants often kinetically destabilize the folded apo-protein through significant changes in the denaturation free energy barrier, whereas coenzyme binding overcomes this destabilization. Modeling of the mutations on a 1.9 Å crystal structure suggests that PH1 causing mutants perturb locally the native structure. Our work support that a misbalance between denaturation energetics and interactions with chaperones underlie aggregation and mistargeting in PH1, suggesting that native state stabilizers and protein homeostasis modulators are potential drugs to restore the complex and delicate balance of AGT protein homeostasis in PH1.     

Iron uptake in Pseudomonas aeruginosa mediated by N-(2,3-dihydroxybenzoyl)-L-serine and 2,3-dihydroxybenzoic acid

Abstract Pseudomonas aeruginosa is known to have an inducible uptake system for the enterobacterial siderophore enterobactin. In this work we have examined iron transport mediated by the biosynthetic precursor 2,3-dihydroxybenzoic acid and N -(2,3-dihydroxybenzoyl)- l -serine, a breakdown product of enterobactin. Iron complexed with 2,3-dihydroxybenzoyl-L-serine was transported into P. aeruginosa IA1 via a transport system which is energy-dependent and iron-repressible. The rate of transport was not altered by growing the cells in the presence of either pyoverdin or pyochelin, which have been shown previously to induce transport via that system. Growth of the cells in the presence of enterobactin did cause an increase in the rate of transport, indicating that the complex can be transported by the inducible enterobactin uptake system, but also that a separate system must exist. In contrast, transport of iron complexed with 2,3-dihydroxybenzoic acid was neither iron-repressible nor strongly energy-dependent, from which we conclude that there must be a novel mode of transport not characteristic of iron-siderophore transport systems.     

Model Construction and Analysis of Respiration in Halobacterium salinarum

The archaeon Halobacterium salinarum can produce energy using three different processes, namely photosynthesis, oxidative phosphorylation and fermentation of arginine, and is thus a model organism in bioenergetics. Compared to its bacteriorhodopsin-driven photosynthesis, less attention has been devoted to modeling its respiratory pathway. We created a system of ordinary differential equations that models its oxidative phosphorylation. The model consists of the electron transport chain, the ATP synthase, the potassium uniport and the sodium-proton antiport. By fitting the model parameters to experimental data, we show that the model can explain data on proton motive force generation, ATP production, and the charge balancing of ions between the sodium-proton antiporter and the potassium uniport. We performed sensitivity analysis of the model parameters to determine how the model will respond to perturbations in parameter values. The model and the parameters we derived provide a resource that can be used for analytical studies of the bioenergetics of H. salinarum.     

Deltamethrin-Mediated Toxicity and Cytomorphological Changes in the Midgut and Nervous System of the Mayfly Callibaetis radiatus

Immature instars of mayflies are important constituents of the food web in aquatic ecosystems (especially in Neotropical regions) and they are among the most susceptible arthropods to pyrethroid insecticides. These insecticides have been recognized as important stressors of freshwater ecosystems, but their cellular effects in aquatic insects have been neglected. Here, we assessed the susceptibility to deltamethrin (a typical type II pyrethroid) as well as the deltamethrin-mediated cytomorphological changes in the central nervous system and midgut of the mayfly Callibaetis radiatus. While the deltamethrin LC₅₀ for 24h of exposure was of 0.60 (0.46–0.78) μg of a.i/L, the survival of C. radiatus was significantly reduced in deltamethrin concentrations ≥ 0.25 μg a.i/L at 96h of exposure. Sub-lethal deltamethrin exposure severely affected the cytomorphology of C. radiatus midgut (e.g., muscle layer retraction, cytoplasm vacuolation, nucleus and striated border disorganization) and also induced slight cytomorphological changes in the brain (e.g., presence of pyknotic nuclei) and in the thoracic ganglia (e.g., vacuolation of neurons and presence of pyknotic nuclei) of these insects. However, DNA damage was absent in all of these organs, suggesting that the sublethal cellular stress induced by deltamethrin might disrupt physiological processes (e.g., metabolism or electrical signal transmission) rather than cause cell death (e.g., apoptosis) in C. radiatus. Thus, our findings indicated that deltamethrin actions at cellular levels represent a clear indication of sublethal effects on the C. radiatus survival abilities.