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PubMed1978

[High-performance liquid chromatography in the determination of organic acids in wine].

We shall distinguish the case of non aromatic organic acids from that one of phenolic acids. In the first one, we have applied to wines a method used for fruit-juices by Palmer and List, 1973. After contact of the wine with a strong acid resin, its is injected on anion exchange resin Aminex A 25 precolumn (formiate form) which retains all the organic acids. The precolumn is washed with water to eliminate neutral components, then connected with the chromatographic column which contains the same resin. The different acids are eluted with a solution of natrium formiate at 70 degrees C. They are detected by differential refractometry (galacturonic, lactic, malic, succinic, tartric acids) and by ultraviolet at 254 nm (shikimic acid). Beside these compounds which are identified by their retention volumes, others not yet attributed peaks are detected. The limits of detection are 2 mg/l for shikimic acid, 30 mg/l for tartric acid and 15 mg/l for the others. Analysis time is about one hour. In the case of phenolic acids, we extract them from wine by diethyl ether after saturation with NaCl or by demixtion. The determination of phenolic acids is done on the ether extract or on the organic layer of the demixtion. Chromatography is obtained on octadecylsilanised column (RP 18) with solvent gradient (from 10% methanol in KH2PO4O,1 M pH 2,1 to 60% methanol in the same buffer) and detection in ultraviolet at 254 nm. The knowledge of recovery of acids by diethyl ether or by demixtion permits to obtain their concentrations in wine. The different so determinated phenolic acids are: gallic, 4 hydroxybenzoic, cafeic, vanillic, syringic and para coumaric acids. We have applied these methods to 32 wines for phenolic acids and 80 wines for non aromatic acids. Some results are presented in the case of 24 wines issued from Gamay and 8 wines from Pinot and it appears that tartric and shikimic acids have more important average concentrations in the former than in the latter.

Acetates↗
PubMed1994

Regulation of heme oxygenase activity in Cyanidium caldarium by light, glucose, and phycobilin precursors.

Cyanobacteria, red algae, and cryptophytes contain phycobiliproteins which function as photosynthetic light-harvesting pigments. The chromophores of phycobiliproteins are phycobilins, open-chain tetrapyrroles that are synthesized from protoheme. The first step of phycobilin formation is the conversion of protoheme to biliverdin IX alpha in a reaction that is catalyzed by heme oxygenase. In the unicellular red alga, Cyanidium caldarium, light is required for the accumulation of phycobiliproteins. It has been reported previously that the synthesis of the apoprotein components of allophycocyanin and phycocyanin is induced by light in C. caldarium, that the phycobilin precursors, delta-aminolevulinic acid (ALA), protoporphyrin IX, and protoheme can substitute for light, and that the regulation is exerted at the level of mRNA synthesis. We have determined that a key enzyme of phycobilin formation is induced by light in C. caldarium. Extractable heme oxygenase activity is low in dark-grown cells, and it increases approximately 6-fold during the first 24 h after the cells are illuminated. After 24 h, the activity decreases to a level approximately equal to the initial activity. Heme oxygenase is induced in unilluminated cells by administration of ALA. D-Glucose, which is known to inhibit phycocyanin accumulation in C. caldarium, inhibits the induction of heme oxygenase by light or ALA. Induction of heme oxygenase by light or ALA is blocked by cycloheximide, an inhibitor of cytoplasmic protein synthesis, but not by chloramphenicol, an inhibitor of chloroplast protein synthesis. Rifampicin, an inhibitor of algal chloroplast RNA synthesis, and gabaculine, a competitive inhibitor of ALA biosynthesis, block the induction of heme oxygenase by light but not by ALA. These results indicate that heme oxygenase in C. caldarium is induced by phycobilin precursors. The induction by light and the repression of the induction by D-glucose are probably indirect effects mediated by the effects of light and D-glucose on phycobilin precursor formation. The results also indicate that heme oxygenase is encoded by a nuclear gene and is synthesized on cytoplasmic ribosomes.

Aminolevulinic Acid↗
PubMed1978

Treatment of subarachnoid hemorrhage from ruptured intracranial aneurysm with tranexamic acid: a double-blind clinical trial.

A double-blind clinical trial of tranexamic acid was carried out on 39 patients with fresh subarachnoid hemorrhage from a ruptured aneurysm. Twenty patients received tranexamic acid, 6 gm daily for 14 to 21 days, while 19 patients received conventional therapy of bedrest and dexamethasone when cerebral edema developed, plus isotonic saline. Rebleeding and mortality were reduced by one-fourth and one-fifth, respectively (p less than 0.001). No side-effects were observed. Tranexamic acid is valuable in the treatment of subarachnoid hemorrhage caused by ruptured intracranial aneurysms.

Adult↗
PubMed2006

Raman and surface-enhanced Raman spectroscopy investigation of vasopressin analogues containing 1-aminocyclohexane-1-carboxylic acid residue.

In this work, Raman spectroscopy (RS) was employed to characterize molecular structures of [Arg8]vasopressin (AVP) and its [Acc2,D-Arg8]AVP, [Acc3]AVP, and [Cpa1, Acc3]AVP analogues. The RS band assignments have been proposed. To determine the mechanism of adsorption of the above-mentioned compounds adsorbed on a colloidal silver surface, surface-enhanced Raman spectra (SERS) were measured. The SERS spectra were used to determine relative proximity of the adsorbed functional groups of [corrected] investigated peptides and their orientation on the silver surface. The AVP and [Acc3]AVP SERS spectra (Acc: 1-aminocyclohexane-1-carboxylic acid) show that the L-tyrosine (Tyr) lies far from the metal surface, whereas the [Cpa1,Acc3]AVP spectrum (Cpa: 1-mercaptocyclohexaneacetic acid) provides evidence that Tyr interacts with the silver surface. These results suggest that [corrected] the binding of the Tyr-ionized phenolic group might be responsible for the selectivity of the analogues. We show that the aromatic ring of L-phenylalanine (Phe) of AVP and [Acc2,D-Arg8]AVP interacts with the silver surface. The strength of this interaction is considerably weaker for [Acc2,D-Arg8]AVP than for AVP. This might be due either to a longer distance between the Phe ring and the silver surface, or to the almost perpendicular orientation of the Phe ring towards the surface. The carbonyl group of the L-glutamine [corrected] (Gln) or L-asparagine [corrected](Asn) of AVP, [Acc2,D-Arg8]AVP, and [Acc3]AVP is strongly bound to the silver surface. We have also found that all peptides adsorb on the silver surface via sulfur atoms of the disulfide bridge, adopting a "GGG" conformation, except [Cpa1,Acc3]AVP, which accepts a "TGG" geometry.

Amino Acids, Cyclic↗
PubMed1994

Measurement of GABA following GABA-transaminase inhibition by gabaculine: a 1H and 31P NMR spectroscopic study of rat brain in vivo.

A selective 1H NMR spin-echo editing method was used to detect the 4-CH2 of GABA in rat brain in vivo before and after intravenous administration of the highly selective GABA transaminase inhibitor, gabaculine (3-amino-2,3-dihydrobenzoic acid-HCl; 100 mg/kg, intravenously). The effects of the inhibitor on high energy phosphates and pHi were determined by 31P NMR. GABA levels increased approximately linearly (r = 0.81 to 0.94; P < 0.0005) from 1.9 +/- 0.4 mumol/g (pre-gabaculine; mean +/- SD) to between 6 and 8 mumol/g after 4 hr at rates of accumulation of 1.1 to 2.9 mumol/hr/g. 1H NMR spectroscopic measurements of cerebral GABA and its rate of turnover offers a new approach in the study of GABA-mediated processes in vivo.

4-Aminobutyrate Transaminase↗