ABSTRACT
Microalgae are considered promising sustainable sources of natural bioactive compounds to be used in biotechnological sectors. In recent years, attention is increasingly given to the search of microalgae-derived compounds with antioxidant and anti-inflammatory properties for nutraceutical or pharmacological issues. In this context, attention is usually focused on the composition and bioactivity of algae or their extracts, while less interest is driven to their biological features, for example, those related to morphology and cultivation conditions. In addition, specific studies on the antioxidant and anti-inflammatory properties of microalgae mainly concern Chlorella or Spirulina. The present work was focused on the characterization of the Chlorophyta Neochloris oleoabundans under two combinations of cultivation modes: autotrophy and glucose-induced mixotrophy, each followed by starvation. Biomass for morphological and biochemical characterization, as well as for extract preparation, was harvested at the end of each cultivation phase. Analyses indicated a different content of the most important classes of bioactive compounds with antioxidant/anti-inflammatory properties (lipids, exo-polysaccharides, pigments, total phenolics, and proteins). In particular, the most promising condition able to prompt the production of antioxidant algal biomass with anti-inflammatory properties was the mixotrophic one. Under mixotrophy, beside an elevated algal biomass production, a strong photosynthetic metabolism with high appression of thylakoid membranes and characteristics of high photo-protection from oxidative damage was observed and linked to the overproduction of exo-polysaccharides and lipids rather than pigments. Overall, mixotrophy appears a good choice to produce natural bioactive extracts, potentially well tolerated by human metabolism and environmentally sustainable.
ABSTRACT
The synaptic connection between the commissural portion of the nucleus tractus solitarius (ComNTS) and the dorsal motor nucleus of the vagus (DMV) was studied in rat brain stem slices, using the patch-clamp technique. The excitatory postsynaptic currents (EPSC) evoked by stimulation of the ComNTS were blocked by kynurenic acid (1 mM) and, in Mg2+-free solution, were sensitive to both the N-methyl-D-aspartic acid (NMDA) receptor blocker 3-[(RS)-2-carboxypiperazine-4-yl] -propyl-1-phosphonic acid (20 microM) and the non-NMDA receptor blocker 2,3-dihydro-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (5 microM). Norepinephrine (NE, 1-100 microM) inhibited the EPSC, and the inhibition was attenuated by the alpha2-adrenoceptor antagonists idazoxan (1 microM) and yohimbine (10 microM) but not by the beta-adrenoceptor antagonist nadolol (50 microM). The NE-releasing agent tyramine (100 microM) reduced the EPSC, and the inhibition was attenuated by 1 microM idazoxan. NE (30 microM) did not affect the membrane input resistance but reduced the paired-pulse depression, demonstrating that NE acts on presynaptic alpha2-adrenoceptors. The results indicate the existence of a glutamatergic pathway from the ComNTS to the DMV neurons modulated by presynaptic NE receptors. This pathway might be a component of the vagovagal reflex regulating gastrointestinal function.
