Effect of salinity on valves morphology in freshwater diatoms

Increased salt concentration is one of the most widespread problems affecting freshwater worldwide. Aquatic communities, and in particular periphytic diatoms, react to this alteration in water quality by modifying their structural parameters and physiology at the individual level, which is commonly manifested by the appearance of teratological forms. The present work presents the results of an experimental laboratory study in which a biofilm grown on artificial substrates was subjected to a gradient of water conductivities for 4 weeks. The results show an increase in the number of deformed valves over time proportionally to the increase in conductivity for each experimental treatment. These effects are also verified by analyzing the concentration of chlorophyll-a in the experimental biofilms, which demonstrate a metabolic response to the induced osmotic stress. No changes were recorded; however, in species richness or diversity of taxa present in the treatments. Our results, therefore, confirm at the experimental level numerous previous field observations about the harmful effect of salinity on periphytic diatoms, and also their ability to reintegrate with the new stress conditions.

Cynthichlorine: a bioactive alkaloid from the tunicate Cynthia savignyi

From ether extracts of the tunicate Cynthia savignyi, collected in Morocco, a new alkaloid-cynthichlorine-has been isolated. The structure of cynthichlorine has been characterized by extensive 2D-NMR data. Cynthichlorine possesses antifungal activity against two tomato pathogenic fungi: Botrytis cinerea and Verticillium albo atrum and antibacterial activity against Agrobacterium radiobacter, Escherichia coli and Pseudomonas aeruginosa and cytotoxicity against Artemia salina larvae.

[In vitro evaluation of antileishmania activity of Artemisia herba alba Asso]

Aqueous extract and essential oil of Artemisia herba-alba Asso were tested for their antileshmanial activity again Leishmania tropica and Leishmania major. The strongest leishmanicidal activity was observed with the essential oil at 2 micrograms/ml as versus the other two strains tested. The aqueous extract showed an antileshmanial activity at 4 micrograms/ml.

Isolation and bioactivities of epidioxysterol from the tunicate Cynthia savignyi

From a hexane extract of the tunicate Cynthia savignyi, collected in Morocco, epidioxysterol or 5,8-alpha-epidioxy-5alpha-cholest-6-en-3beta-ol has been isolated. This is the first example of epidioxysterol found in the tunicate C. savignyi. The structure of epidioxysterol has been characterised by NMR data (1H, 13C and 2D). Epidioxysterol possesses antifungal activity against three tomato pathogenic fungi: Botrytis cinerea, Fusarium oxysporum and Verticillium albo atrum and antibacterial activity against Agrobacterium tumefaciens, Escherichia coli, Staphylococcusfaecalis, Staphylococcus aureus and Pseudomonas aeruginosa and cytotoxicity against Artemia salina larvae.

Investigation of bioactivity of extracts from Moroccan solitary tunicate Cynthia savignyi

Extracts of the tunicate Cynthia savignyi from the Moroccan Atlantic sea have been investigated in five bioassays. The first is an antibacterial test against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Agrobacterium tumefaciens; the second is an antifungal test against three tomato pathogenic fungi, Botrytis cinerea, Fusarium oxysporum and Verticillium albo-atrum; the third is a test based to the ability to reduce DNA peak size in procedures using an HPLC system for detection of antitumour agents; the fourth is a toxicity test using larva of Artemia salina; and the last is an enzymatic inhibitory test against papain and trypsin. For all the bioassays, extracts of C. savignyi were found to be bioactive. This result suggests that this tunicate is able to produce biologically active agents required for an overall defence against their predators.

Methoxybifurcarenone: an antifungal and antibacterial meroditerpenoid from the brown alga Cystoseira tamariscifolia

A meroditerpenoid metabolite has been isolated from the brown alga Cystoseira tamariscifolia and characterized as methoxybifurcarenone, by spectral analysis. Methoxybifurcarenone possesses antifungal activity against three tomato pathogenic fungi: Botrytis cinerea, Fusarium oxysporum sp. mycopersici and Verticillium alboatrum and antibacterial activity against Agrobacterium tumefaciens and Escherichia coli.

Study of nonspecific cation channel coupled to P2z purinergic receptors using an acid load technique

The intracellular pH (pHi) of rat submandibular cells was measured by 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The cells recovered from ammonium (30 mM) prepulse to their resting pHi within 10 min. Ethylisopropylamiloride (EIPA), an inhibitor of the Na+/H+ exchanger, slows the rate of pHi recovery. ATP (1 mM), in the presence of EIPA, increases the rate of recovery 3.7-fold in the absence or presence of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The recovery was blocked by the addition of 5 mM Mg2+ or 10 microM Coomassie blue. The response was elicited by 2'- and 3'-O-(4-benzoylbenzoyl)-adenosine 5'-triphosphate but not by ADP, UTP, adenyl (beta-gamma-methylene)-diphosphonate, 2-methylthioadenosine 5'-triphosphate, or muscarinic or beta-adrenergic agonists. The purinergic response was also observed when the cells were acidified by sodium propionate and could not be mimicked by the depolarization of the plasma membrane. Aluminum fluoride did not reproduce the response to ATP, suggesting that the observed response does not involve a high-molecular-weight GTP-binding protein. It is concluded that the activation of P2z receptors, probably by the opening of nonspecific cation channels, increases the permeability to protons in rat submandibular glands.

Low affinity purinergic receptor modulates the response of rat submandibular glands to carbachol and substance P

The effect of extracellular ATP on the intracellular calcium concentration ([Ca2+]i) in rat submandibular glands was tested. The dose-response curve for ATP was biphasic with a first increase in the 1-30 microM concentration range and a further increase at concentrations higher than 100 microM. Among ATP analogs, only benzoyl-ATP stimulated the low affinity component. ATP tau S blocked this response. All the other analogs tested reproduced the high-affinity low capacity response. Magnesium and Coomassie blue selectively blocked the low affinity component. High concentrations of ATP blocked the increase of the intracellular calcium concentration [Ca2+]i in response to 100 microM carbachol. By itself, substance P (100 pM-1 microM) increased the [Ca2+]i. One mM ATP potentiated the response to concentrations of substance P higher than 10 nM. This potentiation was reversed by extracellular magnesium. Carbachol 100 microM and substance P (100 pM-1 microM) increased the release of inositol trisphosphate (IP3) from polyphosphoinositides (polyPI). Activation of the low affinity ATP receptors did not activate the polyPI-specific phospholipase C but inhibited its activation by 100 microM carbachol (-50%) and by 100 nM substance P (-60% at 1 nM substance P and -40% at 100 nM substance P). Substance P induced a strong homologous desensitization: a preincubation with 1 nM substance P nearly completely abolished the response to 1 microM substance P. When the cells were exposed to ATP before the second addition of substance P, the purinergic agonist partially restored the response to the tachykinin without totally reversing the desensitization. It is concluded that two types of purinergic receptors coexist in rat submandibular glands; a high-affinity, low capacity receptor which remains pharmacologically and functionally undefined and a low affinity site, high capacity receptor of the P2z type coupled to a non-selective cation channel. The occupancy of these low affinity sites blocks the increase of the [Ca2+]i in response to a muscarinic agonist and the activation of polyPI-specific phospholipase C by carbachol and substance P. It potentiates the effect of high concentrations of substance P on the [Ca2+]i.