The effect of the antiepileptic drug valproic acid (VPA) on mitochondrial oxidative phosphorylation (OXPHOS) was investigated in vitro. Two experimental approaches were used, in the presence of selected respiratory-chain substrates: (1) formation of ATP in digitonin permeabilized rat hepatocytes and (2) measurement of the rate of oxygen consumption by polarography in rat liver mitochondria. VPA (0.1-1.0 mM) was found to inhibit oxygen consumption and ATP synthesis under state 3 conditions with glutamate and 2-oxoglutarate as respiratory substrates. No inhibitory effect on OXPHOS was observed when succinate (plus rotenone) was used as substrate. We tested the hypothesis that dihydrolipoyl dehydrogenase (DLDH) might be a direct target of VPA, especially its acyl-CoA intermediates. Valproyl-CoA (0.5-1.0 mM) and valproyl-dephosphoCoA (0.5-1.0 mM) both inhibited the DLDH activity, acting apparently by different mechanisms. The decreased activity of DLDH induced by VPA metabolites may, at least in part, account for the impaired rate of oxygen consumption and ATP synthesis in mitochondria if 2-oxoglutarate or glutamate were used as respiratory substrates, thus limiting the flux of these substrates through the citric acid cycle. 相似文献
All tailed bacteriophages follow the same general scheme of infection: they bind to their specific host receptor and then transfer their genome into the bacterium. DNA translocation is thought to be initiated by the strong pressure due to DNA packing inside the capsid. However, the exact mechanism by which each phage controls its DNA ejection remains unknown. Using light scattering, we analyzed the kinetics of in vitro DNA release from phages SPP1 and λ (Siphoviridae family) and found a simple exponential decay. The ejection characteristic time was studied as a function of the temperature and found to follow an Arrhenius law, allowing us to determine the activation energy that governs DNA ejection. A value of 25-30 kcal/mol is obtained for SPP1 and λ, comparable to the one measured in vitro for T5 (Siphoviridae) and in vivo for T7 (Podoviridae). This suggests similar mechanisms of DNA ejection control. In all tailed phages, the opening of the connector-tail channel is needed for DNA release and could constitute the limiting step. The common value of the activation energy likely reflects the existence for all phages of an optimum value, ensuring a compromise between efficient DNA delivery and high stability of the virus. 相似文献
Dolichoura has two species, D. spiritusanctensis and D. kollmannii, the latter described here. The genus can be recognized within the tribe Merianieae by 6-or 7-merous flowers, purple petals,
stamens with a dorsal, spiraled appendage at the base of the connective, and seeds with narrow, lateral wings. The new species
can be recognized by the suffruticose habit, 4-winged branches, coriaceous leaves with very small petioles and bullate adaxial
surfaces, and by the 6-merous flowers. 相似文献
We investigated responses toward novel foods and novel objects by wild capuchins that routinely exploit visitors' foods in Brasília National Park. Given the capuchins' daily exposure to human foods and objects, we expected them to be more explorative toward novel foods and objects compared to capuchins that are not habituated to visitors. However, since the safety and palatability of potential foods have to be learned, we also expected the capuchins to be cautious about eating novel foods, as has been reported for wild and captive capuchins. Stimuli were presented on a platform in four experimental conditions: familiar food (FF), novel food (NF), familiar food plus novel object (FF+O), and novel food plus novel object (NF+O). Latencies to approach and contact the platform, and to approach and to ingest food did not differ across conditions. Nevertheless, the capuchins were significantly more responsive (measured in terms of interest, manipulation, etc.) toward familiar foods than novel foods, and ate significantly more of the former. In other words, their explorative response toward novel foods led to little consumption. Our results do not support the "readiness to eat" hypothesis, according to which a lower readiness to eat and food neophobia are the consequences of the presence of a distracting novel object. The finding that capuchins explore novel stimuli but remain cautious about eating novel foods supports the view that neophilia and neophobia are motivationally independent responses. 相似文献
The antifungal activity of 10 dehydroabietic acid derivatives with different configuration in A and B rings (cis/trans A/B junction) and different substituents and/or functionalities was evaluated in bioassays in vitro and in situ (pine wood blocks).
The test compounds dissolved in acetone were assayed at several concentrations w/w (test compound/culture medium) against the fungi. The Relative Inhibition (RI) was determined by measuring the radial growth of colonies of the fungi treated with the test compounds by comparison with those of control cultures; the results are expressed as EC50.
The results of bioassays in vitro have shown that hydroxyl and aldehyde functions are required for antifungal activity in this group of compounds and deisopropylation can increase the activity. Our assay of antifungal activity in situ (in pine wood blocks) provides a means to investigate the preservative activities of these antifungal compounds under actual conditions of use.
The dehydroabietic acid derivative cis-deisopropyldehydroabietanol (10) inhibited the growth of several of the fungi tested, in vitro and in situ.
The results obtained in situ with the test compound (10) at 6% and 8% were not significantly different from the reference products and a good level of protection of the wood against the organisms tested was achieved.
The results in wood bioassays present new possibilities in the search for natural new compounds in the wood protection, as an alternative to conventional fungicides. 相似文献
Amino Acids - Interventions that can modulate subcutaneous white adipose tissue (scWAT) function, such as exercise training and nutritional components, like taurine, modulate the inflammatory... 相似文献
Melipona capixaba, popularly known as “uruçu preta”, is a stingless bee restricted to the mountainous Atlantic Rainforest areas of Espírito Santo State, Brazil. Due to the endemism and small population size, this species discovered in 1994 is now considered “vulnerable to extinction”. Using ISSR, PCR–RFLP and microsatellites markers, we studied the genetic variability and structure of M. capixaba from 88 colonies collected throughout the distribution area of the species within Espírito Santo State. The microsatellite, ISSR and mitochondrial haplotype analyses showed that M. capixaba has low genetic variability compared to other insect species. The molecular analyses also indicated a high genetic similarity among the M. capixaba samples, with no clear pattern of structuring. The analyses of molecular variance results indicated that most of the total genetic variation in M. capixaba was explained by the genetic diversity within local populations. Results suggest that the analyzed samples could be treated as a single population for preservation purposes. Thus, given its endemism, local adaptation and low number of natural colonies, efforts for the conservation of M. capixaba should focus on preservation and increasing the number of colonies in the wild, so that M. capixaba can support constant captures and the effects of habitat deforestation in Espírito Santo State. 相似文献