Characterization of Angiotensin Ii Receptor Subtypes in the Brain

The present studies explore binding, distribution, and function of angiotensin II (AII) receptors (AT\sb1 and AT\sb2) in the brain. The discovery that sulfhydryl reducing agents masked some but not all AII receptors in the brain prompts an evaluation of commonly used binding assay buffer constituents. EDTA enhances binding (40%) at both AT\sb1 and AT\sb2 nuclei, while bacitracin did not alter binding at either receptor subtype. Phenanthroline and BSA differentially altered binding at AT1 (220% of control) and AT\sb2 (118% of control) receptors. The results indicate that phenanthroline and BSA would be poor buffer constituents for studies comparing binding at AT\sb1 and AT\sb2 receptors. All receptors were mapped in normotensive and genetically hypertensive hamster brains and the subtype composition estimated for a number of brain nuclei and the pituitary. Binding in the hamster was similar to that previously observed in the rat brain with exceptions: (1) additional binding in the medial habenula and interpeduncular nuclei, (2) absence of binding in the inferior olive, suprachiasmatic nucleus, medial amygdala, piriform cortex, and subthalamic nucleus and (3) quantitative differences in the dorsomotor nucleus of the vagus, striatum, hippocampus and anterior pituitary. Unlike studies of the normotensive and spontaneously hypertensive rat, we found no significant differences in binding distribution, density or subtype composition when comparing normal and genetically hypertensive hamsters. Finally, the effects of brain angiotensin II (AII) on central catecholamine utilization were determined. We found no significant differences in norepinephrine, epinephrine or dopamine utilization in rat brain homogenates following intracerebroventricular injection of AII. Although there is evidence that AII alters catecholamine utilization in some brain nuclei, these alterations appear limited (anatomically and/or quantitatively) to a relatively small portion of the brain catecholaminergic system. The results indicate that the selection of buffer constituents is an important consideration for AII binding studies, that there are minor species differences in the distribution of AII receptors in the brain and that despite substantial functional and anatomical overlap, only a relatively small portion of the brain catecholaminergic system is modulated by angiotensin II

Synthesis , Characterization and Reactivity of Dual Function of Antioxidants

A deterioração oxidativa de alimentos é o fator determinante na qualidade sensorial e nutricional do produto, podendo ocorrer em alimentos complexos tanto na fase contínua como na fase dispersa. Em geral, a formação de radicais e espécies reativas de oxigênio e nitrogênio é o evento primário que ocorre priori ao progresso da oxidação de componentes e estruturas sensíveis e está comumente associado a eventos na fase aquosa. A oxidação de lipídeos é frequentemente investigada em alimentos e em meio biológico separadamente dos eventos no meio aquoso e a proteção antioxidante somente avaliada na fase dispersa. Entretanto, a oxidação de proteínas e eventos na fase contínua vêm despertando considerável interesse e aparentemente antioxidantes eficientes na fase dispersa não protegem de forma eficaz as proteínas e os componentes na fase contínua. Um futuro progresso na proteção antioxidante de alimentos e sistemas biológicos origina de uma abordagem holística dos processos redox envolvidos em ambas as fases dispersa e contínua, bem como o uso combinado de espécies antioxidantes e antiredutoras para um superior efeito antiradical global. Neste sentido, foram preparados três novos compostos antiradicais de dupla função (antioxidante e antiredutor) com adequado balanço hidrofílico-lipofílico e aprimorada propriedade antiradical global. Os antiradicais diferulato de astaxantina, retinoato de quercetina e retinoato de epicatequina se mostraram melhores antioxidantes e antiredutores do que seus precursores isoladamente ou em misturas, apresentando superior eficiência na desativação do oxigênio singlete excitado, captação do radical 1-hidroxietila, menor efeito pró-oxidante em sistemas de oxidação catalisados por íons de ferro, e eficiência na redução do reativo estado triplete da safranina (E1/2 = 1,48 V vs. NHE).The oxidative deterioration of foods is the determining factor in the sensory and nutritional quality of the product, which may occur in complex food both at the continuous and the dispersed phases. In general, the formation of radicals and reactive oxygen and nitrogen species is the primary event that occurs prior to the progress of oxidation of components and sensitive structures and is commonly associated with events in the aqueous phase. The oxidation of lipids is often investigated in food and biological media separately from the events in the aqueous phase and the measurement of the antioxidant protection is only evaluated in the dispersed phase. However, the oxidation of proteins and the events in the continuous phase have attracted considerable interest and apparently, efficient antioxidants in dispersed phase do not effectively protect proteins and components in the continuous phase. A further progress in the antioxidant protection of food and biological systems arise from a holistic approach of the redox processes involved in both the dispersed and continuous phases as well as the combined use of antioxidant and antireductant species for a superior overall antiradical effect. In this sense three new antiradical compounds with dual function (antioxidant and antireductant) were prepared with proper hydrophilic-lipophilic balance and global antiradical properties. The antiradicals astaxanthin diferulate, epicatechin retinoate, and quercetin retinoate are shown to be better antioxidant and antireductant than their precursors, isolated or in mixture, exhibiting enhanced singlet excited oxygen deactivation, 1-hydroxyethyl radical scavenging, lower pro-oxidative effect in the oxidative system catalysed by iron ions and an efficient reduction of the reactive triplet state of safranine (E1 / 2 = 1.48 V vs. NHE)

Evidence for a hydrogen-sink mechanism of (+)catechin-mediated emission reduction of the ruminant greenhouse gas methane

Methane formation in the rumen is a major cause of greenhouse gas emission. Plant secondary compounds in ruminant diets, such as essential oils, saponins and tannins, are known to affect methane production. However, their methane-lowering properties have generally been associated with undesired side effects such as impaired feed digestibility. Here we show that microbial methane formation in diluted and buffered rumen fluid was significantly lowered in the presence of (+)-catechin, a natural polyphenol. This flavan-3-ol, a tannin precursor, decreased the production of methane in a dose-dependent manner, where 1.0 mol catechin prevented the emission of 1.2 mol methane. During methane mitigation, (+)-catechin was step-wise degraded via C- and A-ring cleavage and reductive dehydroxylation reactions, as indicated by LC-QToF-MS based metabolomic profiling and NMR-based metabolite identification. This accounted for the acceptance of six hydrogen atoms per catechin molecule. Consequently, catechin functions as an extensive hydrogen sink, thereby competing with methane production by rumen methanogens (TeX). Catechin therefore acts as an antireductant under the anaerobic test conditions, in contrast to its well-known antioxidant role during oxidative stress. The reductive degradation of catechin had no impact on the formation of ruminal fermentation products such as short-chain fatty acids in this model system. These results highlight the potential of plant secondary compounds to replace methane precursors as hydrogen sinks, and justify future scientific screening programs for similar, potentially more effective organic compound

Impairment of mixed melanin-based pigmentation in parrots

Parrots and allies (Order Psittaciformes) have evolved an exclusive capacity to synthesize polyene pigments called psittacofulvins at feather follicles, which allows them to produce a striking diversity of pigmentation phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been investigated. Given the color redundancy, and physiological limitations associated with pheomelanin synthesis, we hypothesized that the latter would be avoided by psittaciform birds. Here, we tested this using Raman spectroscopy to identify pigments in feathers exhibiting colors suspected of being produced by pheomelanin (i.e. dull red, yellow, greyish-brown and greenish-brown) in 26 species from the three main lineages of Psittaciformes. We detected the non-sulphurated melanin form (eumelanin) in black, grey and brown plumage patches, and psittacofulvins in red, yellow and green patches, but there was no evidence of pheomelanin. As natural melanins are assumed to be composed of eumelanin and pheomelanin in varying ratios, our results represent the first report of impairment of mixed melanin-based pigmentation in animals. Given that psittaciforms also avoid the uptake of circulating carotenoid pigments, these birds seem to have evolved a capacity to avoid functional redundancy between pigments, likely by regulating follicular gene expression. Our study provides the first vibrational characterization of different psittacofulvin-based colors and thus helps to determine the relative polyene chain length in these pigments, which is related to their antireductant protection activity

Evidence for a hydrogen-sink mechanism of (+)catechin-mediated emission reduction of the ruminant greenhouse gas methane

Methane formation in the rumen is a major cause of greenhouse gas emission. Plant secondary compounds in ruminant diets, such as essential oils, saponins and tannins, are known to affect methane production. However, their methane-lowering properties have generally been associated with undesired side effects such as impaired feed digestibility. Here we show that microbial methane formation in diluted and buffered rumen fluid was significantly lowered in the presence of (+)-catechin, a natural polyphenol. This flavan-3-ol, a tannin precursor, decreased the production of methane in a dose-dependent manner, where 1.0 mol catechin prevented the emission of 1.2 mol methane. During methane mitigation, (+)-catechin was step-wise degraded via C- and A-ring cleavage and reductive dehydroxylation reactions, as indicated by LC-QToF-MS based metabolomic profiling and NMR-based metabolite identification. This accounted for the acceptance of six hydrogen atoms per catechin molecule. Consequently, catechin functions as an extensive hydrogen sink, thereby competing with methane production by rumen methanogens (TeX). Catechin therefore acts as an antireductant under the anaerobic test conditions, in contrast to its well-known antioxidant role during oxidative stress. The reductive degradation of catechin had no impact on the formation of ruminal fermentation products such as short-chain fatty acids in this model system. These results highlight the potential of plant secondary compounds to replace methane precursors as hydrogen sinks, and justify future scientific screening programs for similar, potentially more effective organic compound