Night-time atmospheric fate of acrolein and crotonaldehyde.

The absolute rate coefficients for the gas-phase reaction of the NO3 radical with acrolein and crotonaldehyde have been measured overthe temperature range 249-330 K, using a discharge flow system and monitoring the NO3 radical by laser induced fluorescence (LIF). The obtained rate coefficients at 298 K for NO3 reactions with acrolein and crotonaldehyde were (3.30 +/- 0.39) x 10(-15) cm3 molecule(-1) s(-1) for acrolein and (1.35 +/- 0.04) x 10(-14) cm3 molecule(-1) s(-1) for crotonaldehyde, and the proposed Arrhenius expressions are k(T) = (1.72 +/- 0.5) x 10(-13) exp[(-1190 +/- 43)/T] and k(T) = (5.02 +/- 0.7) x 10(-13) exp[(-1076 +/- 47)/T], respectively, in units of cm3 molecule(-1) s(-1). In addition, the products and mechanisms were investigated using an environmental chamber/FTIR absorption system. Formaldehyde, CO, and acryloylperoxy nitrate were identified as the main products for the acrolein reaction with molar yields of 31.6 +/- 2.0, 20.9 +/- 1.9, and 47 +/- 3, respectively. In the crotonaldehyde reaction the main products detected were crotonylperoxy nitrate and CO with yields of 93.6 +/- 4.3 and 8.3 +/- 1.1, respectively. On the basis of the rate constant measured, the activation energy calculated, and the identified products, abstraction of the aldehydic H seems to be the main degradation pathway at room temperature for the reaction of acrolein with NO3. For crotonaldehyde, the mechanism is unclear on the basis of the experimental results. The atmospheric implications of the reactions in question are also discussed.

Acetylated low-density lipoproteins promote the release and metabolism of arachidonic acid by murine macrophages.

We studied the effect of acetyl-LDL on the synthesis of eicosanoids by primary cultures of mouse-resident peritoneal macrophages. A dosis of 150 micrograms of acetyl-LDL proteins promotes a maximal release of arachidonic acid metabolites into extracellular medium. This process is very rapid and reaches the maximal value about ten minutes after stimulation. The pattern of arachidonic acid metabolites released is different from that obtained when the cells are stimulated with a phagocytosable particle like zymosan or calcium ionophore A23187. The data show that the metabolism of arachidonic acid by cycloxigenase is diminished. In an unusual way the amounts of prostaglandin PGE2, 6-keto-prostaglandin PGF1 alpha and thromboxane TXB2 synthesized are similar.

[Lipoprotein Lp(a): a risk factor for atherosclerosis]. / Lipoproteína Lp(a): factor de riesgo para la aterosclerosis.

To evaluate whether lipoprotein Lp(a) favors the development of coronary atherosclerosis and may be considered as a risk factor for acute myocardial infarction, we studied 185 patients with this conditions who where compared with a control group. Total cholesterol and cholesterol bound to the several lipoprotein fractions were simultaneously evaluated. Comparisons were carried out, the subjects being subdivided into age groups of 40-49, 50-59 and more than 60 years; they were also subdivided depending on the level of Lp(a) cholesterol (lower than 25 mg/dl, between 25 and 50 mg/dl and higher than 50 mg/dl). Lp(a) appeared as indicative of a vascular risk in the younger groups. The incidence of myocardial infarction was higher when Lp(a) level was greater than 50 mg/dl.