Homenaje al Dr. Andrés O. M. Stoppani : Su personalidad y trayectoria

Andrés O. M. Stoppani, el Dr. Dr. Dr., tres veces Dr. Andrés Stoppani, como lo denominarían los alemanes, dado que era Dr. en Medicina, Dr. en Química y PhD de Cambridge, fue una persona y un científico que marcó huellas en nuestro país. Hoy estamos aquí reunidos lamentando profundamente y con dolor su desaparición, y al mismo tiempo rindiéndole un sentido y más que merecido homenaje póstumo. Tuve el placer de ser su compañero en la Facultad de Ciencias Exactas, Físicas y Naturales desde 1941 a 1945, y su amigo por siempre aquilatando por ello su personalidad y obra. Así es que me sentí muy honrado y agradecido por poder expresar nuevamente el enorme dolor y la sensación de ausencia que su absurdo fallecimiento me provoca a mí personalmente, a su extraordinaria esposa Antonia, a sus amigos y colegas y a la ciencia argentina.Instituto de Investigaciones Bioquímicas de La Plat

Enfoques de una vida y contribución a la investigación científica de los lípidos

Describir nuestra propia vida, nuestros objetivos y posibles logros científicos, así como nuestra psiquis y elucubraciones mentales puede llevarnos a presentarnos mejor de lo que somos. Por ello es importante incluir en esta descripción también, como nos vieron los demás. Para ello recurro al Dr. Pedro Cattáneo, que reseñó mi labor científica el 7 de Agosto de 1987 en la Asociación Química Argentina (AQA). Hago mías sus palabras retrotrayéndome al 28 de agosto de 1961 en una Sesión de Conferencias del entonces Instituto Argentino de Grasas y Aceites (IAGAL local de IRAM) donde diserté sobre Elaboración de aceites de pescado, tema que entonces señalé con la autoridad resultante de tres factores: profundo conocimiento de la química de esos tipos de grasas, experiencia personal en la industria y la visión e información recogidas en fábricas del viejo mundo que visité en dos oportunidades. Mi segunda experiencia tuvo lugar en el salón Florentino Ameghino de la Sociedad Científica Argentina, el 25 de noviembre de 1974 al recibir el Premio Dr. Enrique Herrero Ducloux 1970-71 de la Academia Nacional de Ciencia Exactas Físicas y Naturales, disertando sobre Algunas contribuciones al estudio de los ácidos grasos no saturados y su biosíntesis.Instituto de Investigaciones Bioquímicas de La Plat

The oxidative desaturation of unsaturated fatty acids in animals

The progress made in the knowledge of the microsomal fatty acid desaturation reaction is described: 1) Studies suggest that different enzymes produce 9, 6, and 5-desaturation. 2) The 6-desaturation of fatty acids would be the principal regulatory step in the biosynthesis of polyunsaturated fatty acids in rat microsomes. 3) The desaturation of fatty acids is quantitatively modified by competitive reactions among acids of the same or different families, and by competition with fatty acid incorporation in the lipids. 4) Dietary components, especially carbohydrates and protein modify quantitatively the fatty acid desaturation. Protein would induce the 6-desaturation reaction. 5) Insulin modifies the 6-desaturation reaction through a dual effect: one modifying glucose metabolism, and the other through enzymatic induction. 6) ATP increases the 6-desaturation of fatty acids 7) By mild extraction of the microsomes with buffered KCl sucrose solution, a “soluble” fraction was separated that was necessary for a full desaturation activity of the microsomes. The nature of this factor is discussed. 8) The main features that characterize the 6-desaturation reaction are discussed and the possible structure of the enzyme outlined.Facultad de Ciencias Médica

Study on the composition-structure relationship of Iipophorins

High density lipophorin (HDLp is the main lipoprotein found in resting insect hemolymph. It has, in general, two molecules of apolipoproteins: apoLp-I (250 kDa) and apoLp-II (80 kDa) and a variable lipid content which ranges from 35% to 59% (w/w). Diacylglycerols (DG), phospholipids (PL), and hydrocarbons (HC) are the main lipid components, whereas cholesterol and triacylglycerols are minor components. DG content varies from 7 to 30%, PL from 11 to 24%, and HC from 0 to 15%. In order to determine the relationship between the lipid composition and the arrangement of lipid and protein components in the lipoprotein particle, a density-composition structural model was designed. The model was established by means of 12 sets of data on lipophorin density-composition relationships, and model validity was determined throughout lipoprotein space- and surface-filling conditions. Despite the differences among the lipid compositions of lipophorins, it is concluded that there are several unifying structural restrictions that govern the molecular organization of lipophorins. Quantitative treatment of the model indicates that lipophorin structure is consistent with the following. 1) Spherical particles with a protein-rich outer layer of approximately 20-21 Å thickness, comprised of proteins, phospholipids, cholesterol, and small amounts of DG, and a lipid-rich core composed of HC, TG, and almost all the lipophorin DG. 2) Apolipophorins have a lipid-embedded localization within the lipoprotein particle. They might represent one of the few examples of proteins containing beta-shift structure, exerting strong hydrophobic interaction and having a lipid-embedded localization. 3) On the lipophorin surface, apoproteins occupy about 31 x 10³ Ų that represents from 62 to 82% of the total lipoprotein surface, depending on the size of lipophorin considered. 4) The content of PL of each lipophorin is closely proportional to the lipoprotein size. 5) Despite the importance of lipophorin as DG carrier, there are only small amounts of this component on the lipophorin surface which could reach a maximal surface lipid concentration of about 10 mol%.Instituto de Investigaciones Bioquímicas de La Plat

Kinetics of linoleic and arachidonic acid incorporation and eicosatrienoic depletion in the lipids of fat-deficient rats fed methyl linoleate and arachidonate

Changes induced by dietary methyl linoleate and arachidonate in the fatty acid composition of liver phosphatidyl choline, phosphatidyl ethanolamine, cholesterol esters, and triglycerides were investigated in essential fatty aciddeficient rats. The esters were fed for 0, 24, 50, 96, 192, and 360 hr. The lipids were fractionated by thin-layer chromatography and the fatty acid composition was estimated by gas liquid chromatography. Acids bound to the a'- and 8-carbons of phosphatides were separated by lipolysis with phospholipase A. From the compositions found it was deduced that both dietary linoleate and arachidonate inhibited eicosatrienoate synthesis from oleate but that only arachidonate replaced eicosatrienoate quantitatively in the 8-position of lecithin and cephalin. Both dietary acids displaced some of the &positioned oleate. Monoenoic: saturated acid ratios were also decreased by both esters both in triglycerides and in a'-bound acids in phosphatides. In triglycerides this change preceded any significant incorporation of linoleate or arachidonate. Arachidonate effects seemed to be more rapid and more marked than those of linoleate and although final compositions were similar, because of the conversion of linoleate into arachidonate, a different pattern of reactions led to these results.Facultad de Ciencias Médica

Fatty Acids Synthesized from Hexadecane by <i>Pseudomonas aeruginosa</i>

The lipids extracted from Pseudomonas aeruginosa incubated with hexadecane in a mineral medium were separated into a nonpolar and three polar fractions by thin-layer chromatography. The fatty acid composition of the four cellular fractions and that of the lipids excreted into the medium was studied by gas-liquid chromatography. Saturated fatty acids with 14 to 22 carbons were recognized, together with monoenoic, dienoic, and hydroxylated acids. Hydroxylated fatty acids were principally found in two polar fractions containing rhamnose and glucose; the other polar fraction, containing serine, alanine, ethanolamine, and leucine, was richer in monoenoic fatty acids. Octadecadienoic acid was found in the neutral fraction.Facultad de Ciencias Médica

Protein Factor Involved in Fatty Acid Desaturation of Linoleic Acid

It has been established that the enzyme system involved in stearyl-CoA desaturation reaction has three integral components of the microsomal membrane: the NADH-cytochrome b5 reductase, cytochrome b5 and the desaturase (Gaylor et al, 1970; Holloway et al, 1970; Holloway, 1971; Oshino et al, 1971, Shimakata et al, 1972). All these components have been separated and purified (Strittmatter et al, 1974; Enoch et al, 1976).Facultad de Ciencias Médica

Composition and biosynthesis of fatty acids in Pyramimonas grossii

The green algaPyramimonas grossii orginating in the coastal waters of the Atlantic Ocean Argentina was subcultured until a monoalgal culture was obtained. The fatty acid composition of the alga grown in a mineral medium at 12 C was determined by gas liquid chromatography (GLC) on 2 columns. The major fatty acids were oleic, linoleic, palmitic and α-linolenic acids, but the 20-carbon polyunsaturated acids, 20∶4ω6 and 20∶5ω3, respectively, belonging to the linoleic and α-linolenic series, were also found. Incubation with [14C] oleate, [14C] acetate, [14C] linoleate and [14C] α-linolenate suggests that linoleate is not directly converted to α-linolenate. [14C] Acetate was easily converted to palmitic, palmitoleic and oleic acids. However, after 48 hr of incubation, only traces of radioactivity were detected in linoleic acid and no label was found in α-linolenic acid.Facultad de Ciencias Médica

Seasonal changes in lipid and fatty acid composition of the freshwater mollusk, Diplodom patagonicus

Diplodom patagonicus is a freshwater bivalve mollusk living in lakes of the patagonian Andes mountains in Argentina. Lipid composition and seasonal changes in the mollusk were studied in the natural habitat. In addition to common nonpolar and polar lipids, small amounts of alk-1-enyldiacylglycerol ethers and significant quantities of ceramide aminoethyl phosphonate were present. Total lipid content changed during the year, primarily because of decreased triacylglycerols in winter. The fatty acid composition of the lipids, remarkably different from that of marine bivalves, and even from other fresh water animals, was especially rich in the ω6 fatty acids, linoleic and arachidonic (ca. 25%), and poor in the ω3 acids, 20∶5 and 22∶6. The ω6/ω3 acid ratio was ca. 2, which is very high compared to marine bivalves. The fatty acid composition and the ω6/ω3 acid ratio were constant during the whole year, suggesting a very stable diet, rich in vegetal detritus and poor in diatoms. The influence of environmental temperature fluctuation with season on fatty acid composition also was negible. Modest proportions of 22∶2 nonmethylene-interrupted (NMI) acids were detected and confirmed by mass spectrometry. It was shown that 20∶2 NMI acids were absent.Facultad de Ciencias Médica

Oxidative desaturation of α-linolenic, linoleic, and stearic acids by human liver microsomes

The desaturation of stearic, linoleic, and α-linolenic acids by human liver microsomes were studied. The microsomes were isolated from liver biopsies obtained during operations. It was shown that human liver microsomes are able to desaturate 1-¹⁴C-α-linolenic acid to octadeca-6,9,12,15-tetraenoic acid; 1-¹⁴C-linoleic acid to γ-linolenic acid; and 1-¹⁴C-stearic acid to oleic acid in the same system described in the rat. However, the desaturation activity obtained was low compared to other mammals. This effect was attributed to fasting, premedication, or the anaesthesia.Facultad de Ciencias Exacta