Efficient photochromism from the network of chemical reactions of 7,4'-dihydroxyflavylium in CTAB micelles.

Differently from water, efficient photochromism with a strong colour contrast has been observed for the multistate compound 7,4'-dihydroxyflavylium in the presence of cetyl trimethylammonium bromide (CTAB) micelles. Two states are responsible for the photochromism: trans-chalcone (inside the micelle) in the dark, and flavylium cation, AH(+), (in bulk water) upon irradiation. The kinetics of the system was characterized by flash photolysis and pH jumps. Evidence that the photochemical process leading to AH(+) occurs in the micelle was achieved. The best colour contrast is obtained at pH = 1.5, from a solution practically colourless in the dark, to an intense yellow upon irradiation (quantum yield 0.4). The system is completely reversible with a lifetime of 38 min at room temperature, and exhibits a reasonable stability. A kinetic model capable of fitting the data from thermal entrance of the compound into the micelle, its ejection to bulk water upon irradiation and quantum yields of the photochemical process is proposed.     

Molecule-based magnets with TC above room temperature: Improved synthesis of vanadium–chromium Prussian blue analogues with inserted alkali cations

We report the synthesis of several new vanadium–chromium Prussian blue analogues with a Curie temperature above room temperature. A catalytic amount of vanadium(III) during the synthesis allows to get improved magnetic properties, stable Curie temperatures (T_C) and a magnetisation at saturation in satisfying agreement with the stoichiometry. The insertion of alkali cations (potassium, rubidium, caesium) allows to reach a V:Cr stoichiometry close to 6:5, hence to enhance the number of magnetic neighbours compared to the usual V:Cr 3:2 stoichiometry and to increase accordingly the Curie temperature. For the same stoichiometry, the ferrimagnetic ordering temperature varies slightly with the nature of the inserted alkali cation (T_C/K = 360, 346 and 340 K for the potassium, rubidium and caesium derivatives, respectively). X-ray absorption spectroscopy allows to characterise the local surroundings of the chromium and vanadium ions and to propose an explanation of the magnetic properties.     

Seasonal differences in rainfall,food availability,and the foraging behavior of Tropical Kingbirds in the southern Amazon Basin

ABSTRACT Little is known about the relationship between seasonal food availability and the foraging strategies of insectivorous Neotropical birds. We studied a population of Tropical Kingbirds (Tyrannus melancholicus), a primarily insectivorous species, in eastern Bolivia to examine relationships between rainfall, food availability, and foraging strategies throughout the year. Our study site in the southern Amazon Basin was characterized by strong seasonal variation in the abundance of the kingbird's main insect prey (coleopterans and hymenopterans), with reduced abundance during the nonbreeding season which largely overlaps the dry season. Overall, mean search times for insect prey by Tropical Kingbirds during the breeding (96.9 ± 85.6 [SD] sec) and nonbreeding (83.7 ± 91.2 sec) seasons did not differ (P= 0.23). However, during the nonbreeding season, kingbird search times were negatively, but nonsignificantly, correlated with coleopteran abundance (r²= 0.43, P= 0.16) and significantly and negatively correlated with hymenopteran abundance (r²= 0.72, P= 0.03). Although insect abundance differed seasonally, kingbird search times did not, perhaps because kingbirds forage on a greater variety of insects during the nonbreeding season or, during the breeding season, kingbird search times may be influenced by the need to monitor and defend nests as well as constraints on the types of prey that can be fed to nestlings. However, the reduced abundance of their primary insect prey and negative relationships between the abundance of those prey and search times during the dry, nonbreeding season suggest that Tropical Kingbirds in southern Amazonia may be food limited, potentially explaining why some migrate and spend that season elsewhere.     

Enzymatic activities and protein profile of latex from Calotropis procera.

The laticifer fluid of Calotropis procera is rich in proteins and there is evidence that they are involved in the pharmacological properties of the latex. However, not much is known about how the latex-containing proteins are produced or their functions. In this study, laticifer proteins of C. procera were pooled and examined by 1D and 2D electrophoresis, masses spectrometry (MALDI-TOF) and characterized in respect of proteolytic activity and oxidative enzymes. Soluble laticifer proteins were predominantly composed of basic proteins (PI>6.0) with molecular masses varying between 5 and 95 kDa. Proteins with a molecular mass of approximately 26,000 Da were more evident. Strong anti-oxidative activity of superoxide dismutase (EC 1.15.1.1) (1007.74+/-91.89 Ug(-1)DM) and, to a lesser extent ascorbate peroxidase (EC 1.11.1.1) (0.117(d)+/-0.013 microMol H(2)O(2)g(-1)min(-1)), were detected. However, catalase (EC 1.11.1.6) was absent. The strong proteolytic activities of laticifer proteins from C. procera were shown to be shared by at least four distinct cysteine proteinases (EC 3.4.22.16) that were isolated by gel filtration chromatography. Serine and metaloproteinases were not detected and aspartic proteinase activities were barely visible. Chitinases (EC 3.2.1.14) were also isolated in a chitin column and their activities quantified. The presence of these enzymatic activities in latex from C. procera may confirm their involvement in resistance to phytopathogens and insects, mainly in its leaves where the latex circulates abundantly.     

Differences in sucrose metabolism relative to accumulation of bird-deterrent sucrose levels in fruits of wild and domestic Vaccinium species

We examined variability in sucrose levels and metabolism in ripe fruits of wild and domestic Vaccinium species and in developing fruits of cultivated blueberry (V. ashei and V. corymbosum). The objective was to determine if sufficient variability for fruit sucrose accumulation was present in existing populations to warrant attempts to breed for high-sucrose fruit, which potentially would be less subject to bird predation. Threefold differences in fruit sucrose concentration were found among Vaccinium species, ranging from 19 to 24 mg (g fresh weight)^?1 in V. stamineum and V. arboreum to approximately 7 mg (g fresh weight)^?1 in cultivated blueberry (V. ashei and V. corymbosum) and V. darrowi. Hexose levels were similar among species, ranging from 90 to 110 mg (g fresh weight)^–1, and glucose and fructose were present in equal amounts. Soluble acid invertase (EC 3.2.1.26) activity was negatively correlated with fruit sucrose concentration. There was no apparent correlation between fruit sugar concentration and either sucrose synthase (EC 2.4.1.13) or sucrose phosphate synthase (EC 2.4.1.14) activities, both of which were low for all species studied. Developmental increases in fruit sugar levels of cultivated blueberry followed a pattern similar to that observed in fruit fresh weight accumulation. Hexose concentrations ranged from 6 to 30 mg (g fresh weight)^?1 during the first 60 days after anthesis. Between 60 days and fruit ripening (80 days), hexose levels rose from 30 to 80 mg (g fresh weight)^?1. Sucrose was not detected in fruits until ripening, when low levels were found. Insoluble acid invertase activity was relatively high early in fruit development, decreasing as soluble acid invertase activity increased. Between 60 days and fruit ripening, soluble acid invertase activity increased from 3 to 55 μmol (g fresh weight)^–1 h^–1. Both sucrose synthase and sucrose phosphate synthase activities were low throughout development. The extent of sucrose accumulation in fruits and the degree of variability for this trait among Vaccinium species support the feasibility of developing high sucrose fruits, which would be a potentially valuable addition to current strategies of minimizing crop losses to birds.     

Toll-Like Receptor 4 Upregulation by Angiotensin II Contributes to Hypertension and Vascular Dysfunction through Reactive Oxygen Species Production

Hypertension is considered as a low-grade inflammatory disease, with adaptive immunity being an important mediator of this pathology. TLR4 may have a role in the development of several cardiovascular diseases; however, little is known about its participation in hypertension. We aimed to investigate whether TLR4 activation due to increased activity of the renin-angiotensin system (RAS) contributes to hypertension and its associated endothelial dysfunction. For this, we used aortic segments from Wistar rats treated with a non-specific IgG (1 µg/day) and SHRs treated with losartan (15 mg/kg·day), the non-specific IgG or the neutralizing antibody anti-TLR4 (1 µg/day), as well as cultured vascular smooth muscle cells (VSMC) from Wistar and SHRs. TLR4 mRNA levels were greater in the VSMC and aortas from SHRs compared with Wistar rats; losartan treatment reduced those levels in the SHRs. Treatment of the SHRs with the anti-TLR4 antibody: 1) reduced the increased blood pressure, heart rate and phenylephrine-induced contraction while it improved the impaired acetylcholine-induced relaxation; 2) increased the potentiation of phenylephrine contraction after endothelium removal; and 3) abolished the inhibitory effects of tiron, apocynin and catalase on the phenylephrine-induced response as well as its enhancing effect of acetylcholine-induced relaxation. In SHR VSMCs, angiotensin II increased TLR4 mRNA levels, and losartan reduced that increase. CLI-095, a TLR4 inhibitor, mitigated the increases in NAD(P)H oxidase activity, superoxide anion production, migration and proliferation that were induced by angiotensin II. In conclusion, TLR4 pathway activation due to increased RAS activity is involved in hypertension, and by inducing oxidative stress, this pathway contributes to the endothelial dysfunction associated with this pathology. These results suggest that TLR4 and innate immunity may play a role in hypertension and its associated end-organ damage.     

Entamoeba histolytica: Differential gene expression during programmed cell death and identification of early pro- and anti-apoptotic signals

We have demonstrated that programmed cell death (PCD) in Entamoeba histolytica is induced in vitro by G418 aminoglycoside antibiotic. To ascertain if biochemical and morphological changes previously observed are paired to molecular changes that reflect a genetic program, we looked here for early differential gene expression during the induction of PCD.Using cDNA-amplified fragment length polymorphisms (AFLPs) and in silico derived analysis we showed in E. histolytica a differential gene expression during PCD induced by G418. The genes identified encoded for proteins homologous to Glutaminyl-tRNA synthase, Ribosomal Subunit Proteins 40S and 18S, Saposin-like, Silent Information Regulator-2 (Sir-2), and Grainins 1 and 2. Using real-time quantitative PCR (RT Q-PCR), we found that glutaminyl-tRNA synthetase, sir-2, grainins and saposin-like genes were strongly overexpressed after 30 min of PCD induction, while its expression dramatically decreased up to 60 min. On the other hand, overexpression of ribosomal genes increased only 7-fold of basal expression, showing a progressive down-regulation up to 90 min. glutaminyl-tRNA synthetase, sir-2 and grainins could act as negative regulators of PCD, trying to control the biochemical changes related to PCD activation. Overexpression of saposin-like gene could act as up-regulator of some cell death pathways. Our results give evidence of the first genes identified during the early stage of PCD in E. histolytica that could be implicated in regulation of apoptotic pathways.