Henri Pacheco

The Regional Concentrations of S‐Adenosyl‐l‐Methionine, S‐Adenosyl‐l‐Homocysteine, and Adenosine in Rat Brain

Abstract: The concentrations of S‐adenosyl‐l‐methionine (SAM), S‐adenosyl‐l‐homocysteine (SAH), and adenosine (Ado) were determined in whole brain and rat brain regions by HPLC. The whole brain contains, respectively, 22 nmol, 1 nmol, and 64 nmol of SAM, SAH, and Ado per g of wet tissue. Their distribution indicated that SAM and SAH levels are highest in brainstem, whereas the Ado level is highest in cortex. With aging the SAM concentrations decrease in whole brain, brainstem, and hypothalamus (–25%) and SAH levels increase by 90% in striatum and by 160% in cerebellum, while Ado levels are increased in all regions by 100–180%.

In Vitro and In Vivo Binding of S‐Adenosyl‐L‐Homocysteine to Membranes from Rat Cerebral Cortex

Membranes from rat cerebral cortex are able to bind S‐adenosyl‐L‐homocysteine (SAH) with a KD of 5. 10‐7 M and n of 170 pmol/g fresh tissue (i.e. 20 mg protein). The binding is enhanced by Mg2+ and Ca2‐ but not K+ and Na+, γ‐Aminobutyric acid, diazepine, noradrenaline and a antagonists are without any effect; S‐adenosyl‐L‐methionine, adenosine and adenosine triphosphate inhibit SAH binding. Linkage with an adenosine receptor has not been expressly demonstrated by our method. SAH binding proteins are more abundant in the crude synaptosomal pellet (P2). A similar fixation seems to occur on brain membranes after [3H]SAH administration to rat. The binding might be linked to a methylase activity or an adenosine receptor.

In Vivo Elevation of Mouse Brain S-Adenosyl-L-Homocysteine after Treatment with L-Homocysteine

Intraperitoneal coadministration of adenosine and L‐homocysteine markedly increased S‐adenosyl‐l‐homocysteine in whole mouse brain, but further investigations showed that this elevation could also be produced following administration of l‐homocysteine alone. The noted increase was maximal (+1325%) 10 min after treatment, remaining at about this level for 30‐40 min before returning to control values after 180 min. Cerebral adenosine levels were decreased after treatment with l‐homocysteine, adenosine, or these two substances in combination.

Phospholipid Methylation and Noradrenaline Exchanges in a Synaptosomal Preparation from the Rat Brain

Abstract: When synaptosomes from rat brain were incubated with S‐adenosylmethionine (10−3M), noradrenaline uptake and KCI‐stimulated release were decreased. These effects were dependent on MgCl2, temperature, and incubation time. We have investigated the enzymatic methylation of phosphatidylethanolamine to give phosphatidylcholine.

Activation by S-adenosylhomocysteine of norepinephrine and serotonin in vitro uptake in synaptosomal preparations from rat brain.

S-Adenosylhomocysteine (10−7−10−5 M) activated norepinephrine (NE) and serotonin (5HT) in vitro uptake in synaptosomal preparations from rat brain, but did not affect dopamine (DA) uptake. When administered to rats (7 mg/kg i.p.), it had the same effect on in vitro NE and 5HT uptake. It did not affect NE and 5HT release.

Synthese D'Azotures et de Benzoates de Glycosyle a Partir de Sulfites Cycliques Enc C-1, C-2

Abstract The reaction of sugars bearing a cyclic sulfite group on C-1, C-2 with azide or benzoate ions, is strereoselective and gives trans- 1,2 glycosyl azides or glycosyl benzoates with a free hydroxyle at C-2. The reaction is performed under mild conditions and gives excellent yields of glycosyl derivatives.

Synthèse de nucléosides pyrimidiques non protégés en O-2′ à partir de sulfites cycliques en C-1—C-2☆

Abstract Treatment of 3,5,6-tri- O -benzoyl-α- d -glucofuranose 1,2-sulfite with an excess of bis(trimethylsil) uracil, in fusion processes without any catalyst, afforded an excellent yield of 1-(3,5,6-tri- O -benzoyl-2- O -trimethylsilyl-β- d -glucofuranosyl)uracil, which was readily hydrolyzed in slightly acid conditions to give in almost quantitative yield 1-(3,5,6-tri- O -benzoyl-β- d -glucofuranosyl)uracil. This new synthetic method for nucleosides unprotected at O-2′ was also tested in other sugar series. In some cases, only the 1′,2′- trans -nucleosides were obtained, but in others, small yields (3–10%) of 1′,2′- cis -nucleosides were detected. The α-to-β ratio seems to be dependent on the reaction temperature. 2,4-Dimethoxypyrimidine also reacted with sugar 1,2-sulfites and 4- O -methyl-1-(3,5,6-tri- O -benzyl-β- d -glucopyranosyl)-2-pyrimidinone was prepared in 85% yield from 3,5,6-tri- O -benzyl-α- d -glucopyranose 1,2-sulfite.

Purification et propriétés de la diamine: oxygène oxydo-reductase du placenta humain

Summary Histaminase or diamine: oxygen oxydoreductase (E.C.1.4.3.6.) has been purified 9,600 times from human placenta. The major difficulty was to eliminate hemoglobin from the extracts. In addition, the enzyme has to be stabilized by sucrose during the last steps. As fractionation progresses, a latency time up to 3 h 30 mn modifies the enzymatic kinetic. This latency time is annihilated by preincubation without histamine at 37°C. The enzyme requires Mn++ ions and hemoglobin; there is a potentiating effect for these activators. The isoelectric point is near 6.0 and histaminase is unstable at this pH. The optimum pH is 7.4. The optimum temperature is superior to 45°C. Filtration on Biogel reveals 4 active forms whose molecular masses are multiples from 1 to 4 of 125,000 ± 5,000. Apparent Michaelis constants determined for histamine, putrescine and cadaverine are respectively 0.6 × 10−5 M, 3.3 × 10−6 M and 3.3 × 10−6 M. Histaminase is inhibited by excess histamine but other diamines do not entail this result. Monoamines are not altered by the enzyme. Aminoguanidine is the best inhibitor; semicarbazide is much less active. According to several of its physico-chemical characteristics, diamine: oxygen oxydoreductase from human placenta is different from similar enzymes already described.

SAH analogs, modified in the aminoacid region, inhibitors of phosphatidyl-ethanolamine methylase activity and 3H-SAH binding to rat brain membranes

The study of phosphatidylethanolamine methylase inhibition by 10 SAH analogs points out the importance of the L-homocysteine amino and carboxylic groups and the sulfur atom for the activity of SAH. Besides, the inhibition of phosphatidylethanolamine methylase by SAH analogs is correlated with their affinity for the 3H-SAH binding sites on the rat cortical membranes.

Synthèses, structure et réactivité vis-à-vis de nucléophiles du 1,2:3,4-disulfite de β-l-arabinopyranose

Abstract Treatment of l -arabinose, at low temperature, with thionyl chloride in the presence of pyridine afforded, in 93% yield, a mixture of the four diastereoisomeric β- l -arabinopyranose 1,2:3,4-disulfites. Configurations at the sulfur atoms were determined for each isomer by high resolution 1H-n.m.r. spectroscopy. Reaction of these compounds with various nucleophiles, including bis(trimethylsilyluracil), led in high yields to 1,2-trans-glycosides, unprotected at O-2 and having a cyclic 3,4-sulfite group. The latter compound was substituted by azide ion to give, after benzoylation, 1-(3-azido-2,4-di-O-benzoyl-3-deoxy-α- l -lyxopyranosyl)uracil from 1-(O-trimethylsilyl-α- l -arabinopyranosyl 3,4-sulfite)uracil. Hydrolysis of the cyclic sulfite group of 1-(α- l -arabinopyranosyl 3,4-sulfite)uracil afforded 1-(α- l -arabinopyranosyl)uracil in almost quantitative yield. Thus, this nucleoside was synthesized in 77% overall yield from l -arabinose via β- l -arabinopyranose 1,2:3,4-disulfite.