The effect of essential fatty acid deficiency on the adrenergic activation of glycogenolysis in rat hepatocytes

The fatty acid composition of total lipids and the adrenoceptor-mediated activation of glycogenolysis were studied in isolated hepatocytes from rats maintained on a control diet or on an essential fatty acid (EFA)-free diet. In cells from rats on the EFA-free diet there was a marked reduction in linoleic and arachidonic acid (AA) contents and an increase in eicosatrienoic, oleic, and palmitoleic acid contents compared to controls. In freshly isolated cells from both groups, phosphorylase a activity was increased by phenylephrine or epinephrine but not by isoproterenol, and the effect of epinephrine was inhibited by phenoxybenzamine but not by propranolol. When control cells were preincubated in a serum-free buffer for 4 h before testing, the effect of phenylephrine on phosphorylase a activity was reduced, isoproterenol became a potent agonist and the effect of epinephrine was partially inhibited either by phenoxybenzamine or by propranolol. The emerging beta-adrenergic response in 4-h cells was associated with a marked potentiation of isoproterenol-induced cAMP accumulation. A similar 4-h preincubation of EFA-deficient cells resulted in a reduced response to phenylephrine while isoproterenol remained ineffective for increasing either phosphorylase a activity or cAMP production. The response of these 4-h cells to isoproterenol could be restored by in vivo replacement of the EFA-deficient diet with control diet for the last 4 weeks prior to the experiment, but not by the in vitro exposure of the EFA-deficient cells to 10 microM AA throughout the 4-h incubation period. Extending previous observations (Refs. (6-8)), the present results suggest that the time-dependent emergence of beta-adrenergic glycogenolysis, but not the parallel reduction of the alpha-adrenergic response, is mediated by AA or its metabolite(s), which probably act by facilitating the G-protein-dependent coupling of beta-receptors.     

Effect of different rootstocks on PAL activity and phenolic compounds in flowers, leaves, hulls and kernels of three pistachio (Pistacia vera L.) cultivars

Phenylalanine ammonia-lyase (PAL) is a biochemical marker of environmental stress and plays a pivotal role in phenolic synthesis. Lower ROS levels and oxidative damage were observed in grafted plants; moreover, the rootstocks have a profound influence on the biochemical composition, especially of phenolic compounds. Regarding the importance of the effect rootstocks have on scion in pistachio trees, this study was carried out to assess and compare three pistachio cultivars (Ahmadaghaii, Ohadi and Kallehghuchi) on four rootstocks (Mutica, Ahli, Sarakhs and Atlantica). PAL activity, phenolic compounds, and flavonoid and anthocyanin contents in leaves, flowers and fruits were measured for the selection of the most suitable and compatible rootstock/scion resistant to environmental stresses. The results showed that PAL activity was different among the cultivars and organs. A positive correlation was observed between PAL activity and phenolic compounds in the leaves and flowers of Mutica-Ahmadaghaii, suggesting that it was more resistant than the others to environmental stresses. PAL activity and total phenolics in pistachio fruits suffered a decrease when the maturation processes began. The hulls of the pistachio fruits contained high levels of phenolic compounds, especially in Mutica-Ahmadaghaii, suggesting its function as a protective layer and a defense chemical against ultraviolet radiation and pathogens. Our results indicated the presence of a number of bioactive compounds in kernels with the highest amount belonging to Mutica-Ahmadaghaii. Therefore, we concluded that pistachio rootstocks mighy affect the antioxidant compounds in kernels.     

Crystal structure of homoserine transacetylase from Haemophilus influenzae reveals a new family of alpha/beta-hydrolases

Homoserine transacetylase catalyzes one of the required steps in the biosynthesis of methionine in fungi and several bacteria. We have determined the crystal structure of homoserine transacetylase from Haemophilus influenzae to a resolution of 1.65 A. The structure identifies this enzyme to be a member of the alpha/beta-hydrolase structural superfamily. The active site of the enzyme is located near the end of a deep tunnel formed by the juxtaposition of two domains and incorporates a catalytic triad involving Ser143, His337, and Asp304. A structural basis is given for the observed double displacement kinetic mechanism of homoserine transacetylase. Furthermore, the properties of the tunnel provide a rationale for how homoserine transacetylase catalyzes a transferase reaction vs hydrolysis, despite extensive similarity in active site architecture to hydrolytic enzymes.     

Effect of seed inoculation,mycorrhizal infection and organic amendment on wheat growth

Summary The effect of seed inoculation withAzotobacter spp. orAzospirillum spp., and garbage amendment (0.5%), on the growth of wheat was studied in a field experiment under sub-tropical conditions. Two levels of N fertilizer were applied, the usual field rate (150 kg N ha^–1) and half this amount. Tillering of plants, dry matter contents and nitrogenase activity were determined 30, 60 and 90 days after sowing. At the end of the experimental period, spore numbers and percentage of mycorrhizal infection were observed in the rhizosphere and root systems of plants. Straw and grain yields were also determined. The results of this study showed that seed inoculation and/or organic amendment stimulated plant growth, nitrogenase activity and mycorrhizal infection. This was more noticeable withAzotobacter than withAzospirillum. Inoculation withAzotobacter together with 1/2 N dose and organic amendment was the most effective application (19.75 and 10.70 t ha^–1 were recorded for straw and grain yield, respectively).     

Eye Movements in Ephedrone-Induced Parkinsonism

Patients with ephedrone parkinsonism (EP) show a complex, rapidly progressive, irreversible, and levodopa non-responsive parkinsonian and dystonic syndrome due to manganese intoxication. Eye movements may help to differentiate parkinsonian syndromes providing insights into which brain networks are affected in the underlying disease, but they have never been systematically studied in EP. Horizontal and vertical eye movements were recorded in 28 EP and compared to 21 Parkinson''s disease (PD) patients, and 27 age- and gender-matched healthy subjects using standardized oculomotor tasks with infrared videooculography. EP patients showed slow and hypometric horizontal saccades, an increased occurrence of square wave jerks, long latencies of vertical antisaccades, a high error rate in the horizontal antisaccade task, and made more errors than controls when pro- and antisaccades were mixed. Based on oculomotor performance, a direct differentiation between EP and PD was possible only by the velocity of horizontal saccades. All remaining metrics were similar between both patient groups. EP patients present extensive oculomotor disturbances probably due to manganese-induced damage to the basal ganglia, reflecting their role in oculomotor system.     

Catalytic mechanism of fungal homoserine transacetylase

Homoserine transacetylase is a required catalyst in the biochemical pathway that metabolizes Asp to Met in fungi. The enzyme from the yeast Schizosaccharomyces pombe activates the hydroxyl group of L-homoserine by acetylation from acetyl coenzyme A. This enzyme is unique to fungi and some bacteria and presents an important new target for drug discovery. Steady-state kinetic parameters provide evidence that this enzyme follows a ping-pong mechanism. Proton inventory was consistent with a single-proton transfer, and pH studies suggested the participation of at least one residue with a pKa value of 6.4-6.6, possibly a His or Asp/Glu in catalysis. Protein sequence alignments indicate that this enzyme belongs to the alpha/beta-hydrolase fold superfamily of enzymes, indicating the involvement of an active-site nucleophile and possibly a canonical catalytic triad. We constructed site-specific mutants and identified Ser163, Asp403, and His432 as the likely active-site residues of a catalytic triad based on steady-state kinetics and genetic complementation of a yeast null mutant. Moreover, unlike the wild-type enzyme, inactive site mutants were not capable of producing an acetyl-enzyme intermediate. Homoserine transacetylase therefore catalyzes the acetylation of L-homoserine via a covalent acyl-enzyme intermediate through an active-site Ser. These results form the basis of future exploitation of this enzyme as an antimicrobial target.     

Endocannabinoids as cardiovascular modulators

Cannabinoids, the bioactive constituents of the marijuana plant and their synthetic and endogenous analogs cause not only neurobehavioral, but also cardiovascular effects. The most important component of these effects is a profound decrease in blood pressure and heart rate. Although multiple lines of evidence indicate that the hypotensive and bradycardic effects of anandamide and other cannabinoids are mediated by peripherally located CB1 cannabinoid receptors, anandamide can also elicit vasodilation in certain vascular beds, which is independent of CB1 or CB2 receptors. Possible cellular mechanisms underlying these effects and the cellular sources of vasoactive anandamide are discussed.