Search

Three-dimensional Lagrangian particle model, listed with tunnel experiment diffusion data, is used to compute the emitted tracer concentration in the base region of a two-dimensional hill. The results are used in a mass-consistent model to compute mean concentration fields and to interpolate the turbulence structure. The concentration fields depict topographical data on the flow structures in turbulence system.

The possibility of increasing n-3 and n-6 long-chain polyunsaturated fatty acids ( PUFA) content in microalgal mixtures used to feed Tapes philippinarum larvae was explored by lowering culture temperature from 26 to 14 °C. Although fatty acid composition of different microalgal species has a genetic basis, the algal cultures grown at 14 °C significantly increased the content of long-chain n-3 PUFA in Isocrysis galbana and in Thalassiosira pseudonana, while in Tetraselmis tetrathelo, the PUFA increase only involved shorter chain PUFA, namely 16:4n-3 and 18:4n-3. However, larvae fed on the PUFA enriched microalgal mixture did not show improvements in growth and survival performances with respect to the control group fed the microalgal mixture grown at 26 °C. From a biochemical perspective, two key aspects emerged from the results: (i) clam larvae have adequate biotransformation and selection skills to adjust fatty acid profile to their requirements as they can even modulate the incorporation of essential long-chain PUFA as 20:5n-3 and 22:6n-3 when the dietary supply exceeds the physiological requirements; (ii) bivalve can biosynthesize non-methylene-interrupted dienoic ( NMID) fatty acids as confirmed by the constancy of relative proportion with larvae growth in spite of the NMID fatty acid absence in the diet. [ABSTRACT FROM AUTHOR]

Abstract: A primary goal in antimicrobial drug design is to find molecules which inhibit key proteins in bacteria without affecting mammalian homologues. To this aim, structural differences between eukaryotic and prokaryotic enzyme proteins involved in life processes are widely exploited. The membrane-bound enzyme complex ATP synthase synthesizes the energy currency molecule of the cell. Due to its bioenergetic role, it represents “the enzyme of life” of all living beings. The enzyme complex has the unique bi-functional property of exploiting either the electrochemical transmembrane gradient to make ATP or, conversely, the free energy of ATP hydrolysis to build an electrochemical gradient across the membrane. The catalytic mechanism of ATP synthesis/hydrolysis, based on the coupling between the two rotary sectors FO and F1 is shared by eukaryotes and prokaryotes. However slight structural differences distinguish prokaryotic ATP synthases, embedded in cell membrane, from eukaryotic ones localized in the mitochondrial inner membrane. In spite of its fundamental task in living organisms, up to now the ATP synthase has been poorly exploited as target in antibacterial therapy, mainly due to harmful effects on patients. Recent advances shoulder the use of drugs targeting the ATP synthase to fight mycobacteria and treat human tuberculosis. Macrolide antibiotics and other antimicrobial drugs specifically bind to the c-ring of the membrane-embedded FO domain, thus blocking ion translocation through FO which is essential for both ATP synthesis and ATP hydrolysis. Our findings show that, once bound to the ATP synthase, probably through different binding sites on a common binding region on FO, the macrolide antibiotics oligomycin, venturicidin and bafilomycin behave as enzyme inhibitors. Interestingly, the c subunits of mitochondrial ATP synthase contain conserved cysteine residues which are absent in bacteria. We pointed out that when these crucial cysteine thiols are oxidized, the common drug binding site of the enzyme is somehow destabilized, thus weakening the enzyme–drug interactions and making the ATP synthase insensitive to drug inhibition. On these bases we hypothesize that the selective oxidation of these cysteine thiols can be exploited to desensitize the mitochondrial ATP synthase to drugs which target FO and maintain their inhibitory potency on bacterial ATP synthases. According to our hypothesis, this strategy could represent an intriguing tool to prevent adverse effects of antimicrobial drugs in mammals, thus enhancing the number of natural and synthetic compounds which can be used in therapy. To this aim studies should be addressed to the identification and formulation of compounds and/or treatments able to selectively oxidize the crucial cysteine thiols of c-subunits without affecting the overall functionality of the mitochondrial ATP synthase and other thiol containing proteins. [Copyright &y& Elsevier]

Rainbow trout Oncorhynchus mykiss Walbaum were fed a pelleted diet (14.3% wet weight lipid) containing 9 p.p.m. 3, 5, 3′-triiodo-l-thyronine (T[sub 3]) for 1 month and then transferred from fresh water to brackish water (average 22 p.p.t. salinity), where they were maintained untreated for 22 days. Trout fed a control diet were subjected to the same protocol. For both treated and control trout, liver lipid and fatty acid composition, mitochondrial respiratory activity and oxidative phosphorylation and (Na[sup +] + K[sup +])-ATPase activity were monitored in fish sampled periodically throughout the trial. No differences between treated and control trout occurred in liver total lipid, phospholipid and cholesterol content or fatty acid composition. Conversely, irrespective of T[sub 3] administration, the trout from the two habitats showed adaptive changes to salinity, differing in phospholipids and in the fatty acid composition of total and neutral lipids and selected phospholipids. Liver membrane permeability and mitochondrial respiratory activity were affected by both T[sub 3] treatment and salinity transfer. The latter was apparently greater than the former in affecting mitochondrial respiratory activity. The higher (Na[sup +] + K[sup +])-ATPase activity in T[sub 3]-treated trout after 22 days in brackish water may reflect long-term effects of the hormone linked to salinity adaptation. [ABSTRACT FROM AUTHOR]