La localisation microsomale de la synthese des acides gras dans le foie de la souris vivante

Mice were given glucose-U-¹⁴C and the radioactivity of triglyceride and phospholipid glycerol and fatty acids was measured 30 sec, 3 or 30 min after the i.v. administration in liver microsomes and supernatant. After the acetate administration the radioactivity of palmitic and stearic acids and that of their carboxyl carbons was also measured. The repartition of the radioactivity was discussed in relation with the localization of fatty acid synthesis. In agreement with our previous results it was suggested that the endoplasmic reticulum is the main site of this synthesis.     

Cycle interne de l'azote et du soufre dans les horizons humiferes forestiers des sols bruns acides

Resume Dans le cas du soufre, on observe une minéralisation nette négligeable ou nulle tant en incubation au laboratoire que sur le terrain pour une longue période. Cela pose le problème du mécanisme de la mobilisation du soufre organique.La vitesse d'échange unique entre les phases minérales et organiques actives peut être évaluée, sans devoir ajouter du saccharose au substrat.Le soufre de la phase organique active ne représente alors que 2 à 3 pourcent du soufre total, chiffre qui paraît plus plausible que les 10–15 pour-cent obtenus pour l'azote organique actif par la méthode des marquages croisés.Le calcul des énergies apparentes d'activation montre que le renouvellement du soufre dans l'horizon holorganique est moins affecté par les variations de température que ce renouvellement dans les horizons hémorganiques.

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Summary In the case of sulphur, the net mineralization observed can be neglected or is nil, when incubation is carried out under laboratory conditions or in the field for a long period. Hence the question arises how organic sulphur is mobilized.The single exchange rate between mineral and active organic phases can be measured without addition of sucrose to the substrate.Active organic phase sulphur does not amount to more than 2 to 3 per cent of total sulphur, an amount which seems nearer the truth than the 10 to 15 per cent obtained for the active organic nitrogen by cross tagged incubation technique.Estimation of apparent activation energies shows that sulphur turnover in the holorganic horizon is less influenced by temperature change than in hemiorganic horizons.

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Centre subsidié par l'Institut pour l'Encouragement de la Recherche Scientifique dans l'Industrie et l'Agriculture (I.R.S.I.A.). Directeur: Prof. G. Manil.     

Orientation nouvelle du métabolisme des acides hydroxycinnamiques dans les fruits de tomates blessés (Lycopersicon esculentum)

A change in the metabolism of hydroxycinnamic acids in wounded tomato fruits (Lycopersicon esculentum) .
Healing of lesions in tomato fruits (Lycopersicon esculentum Mill. var. cerasiforme ) is partly due to lignification of cells bordering the wounded zones. The pericarp of healthy fruits contains a high level of hydroxycinnamic derivatives but never shows lignification. Thus, the reaction of the fruit to wounding seems to be a change in the metabolism, leading to the formation of monomeric units of which lignins are constituted. Hydroxycinnamate:CoA ligase (EC 6.2.1.12; CL) and O-methyltransferase (EC 2.1.1.6; OMT) appear to play an important role in this change. In wounded fruits CL acts preferentially on p-coumarate and ferulate as compared to caffeate, and OMT is particularly active with 5-OH ferulate as substrate. These changes lead to the formation of p-coumaroyl CoA, feruloyl CoA and sinapate, which are incorporated into lignin. Phenylalanine ammonialyase (EC 4.3.1.5) and glucosyltransferase activities increase greatly after wounding, whereas the activity of hydroxycinnamoyl-CoA:quinate hydroxycinnamoyl transferase decreases. These data complement those previously reported on peroxidases and suggest that, after the increase of enzyme activities, monomeric units are formed and then polymerized by some peroxidases specific for lignification.     

Etude comparee des lipides et de la fixation passive du calcium dans les racines et les fractions subcellulaires du Lupinus luteus et de la Vicia faba

In both lupin and broad bean, the root lipids contain paraffins, triglycerides, diglycerides, free fatty acids and polar lipids (phospholipids and galactolipids). The polar lipids and the triglycerides are the more abundant classes. The root galactolipids are mono- and di-galactosyldiglycerides; two steryl glycosides are also present. The phospholipids in both species are: phosphatidylinositol, phosphatidylcholine, phosphatidylglycerol, phosphatidylserine, phosphatidylethanolamine, diphosphatidylglycerol and phosphatidic acid. This last phospholipid represents 8·3% of total lipid phosphorus in Lupinus against 2·3% in Vicia. The other acidic phospholipids represent 30·4% in Lupinus against 20·9% in Vicia. The lipids of Lupinus are rich in linolenic acid whereas those found in Vicia are richer in linoleic acid. The various subcellular fractions prepared from the roots of both species have an homogeneous lipid composition, reflecting exactly that of entire cells. The calcium passive fixation capacity in microsomes and mitochondria of Lupinus roots is more important than that in the same organelles of Vicia faba roots. Thus a relationship is suggested between the amount of phospholipids in membranes and the passive fixation of calcium.     

Quelques aspects du métabolisme des acides gras à longue chaîne par les cellules bathmotropes de cœur de rat en culture

As a preliminary to the study of the metabolism of erucic acid by beating heart cells of post natal rats in culture, the activity of lipoprotein lipase and the oxidation of palmitic acid have been studied. The results have led us to use 14 day cultures as the material of choice for experiments on the incorporation of erucic acid into cardiac cells, and on its subsequent distribution into different classes of lipid. Work on fatty acid oxidation has been carried out on 5–8 day cultures.We have shown that erucic acid enters cardiac muscle cells, but that the cells are not capable of oxidizing it directly.We have suggested two independent mechanisms by which this is done, namely shortening of the chain followed by the complete utilization of this smaller molecules by β-oxidation. The delay which this implies would explain the accumulation of erucic acid in the heart cells.We have also proposed that the accumulation of large quantities of erucic acid in phospholipids and esters of cholesterol may modify the structure of cellular and mitochondrial membranes, thus explaining the pathological effects of erucic acid.     

Modalites de passage des lamelles aux fibres dans la muraillede Tabules (Micheliniidae) du Devonien et du Permien

A layer of minute lunulae is intercalated between the undukate lamellae and the embossed fibres. This lunular layer has a precise localisation in the corallum. Attention is focused on the importance of the relations between the various types of microstructure for the Tabulata systematics.     

Relations floristiques entre les groupements prairiaux du Triseto-Polygonion et les megaphorbiaies (Adenostylion) dans les Alpes occidentales

Résumé L'application de l'analyse factorielle des correspondances à un ensemble de données floristiques relatives aux prairies grasses d'altitude (Triseto-Polygonion) et aux mégaphorbiaies (Adenostylion) permet d'éclaircir la conception phytosociologique de ces groupements dans les Alpes occidentales. Elle conduit à l'éclatement du Trisetetum flavescentis des auteurs suisses en deux associations bien individualisées, Triseto-Meetum localisé aux massifs sud-occidentaux et Triseto-Agrostidetum propre aux chaînes plus septentrionales. Par contre, elle entraîne le rattachement des divers groupements de mégaphorbiaie décrits au seul Adenostylo-Cicerbitetum, association qui se différencie secondairement, selon les secteurs de son aire, en trois sous-unités distinctes. Cette synthèse aboutit, d'autre part, à la mise en évidence d'espèces communes aux deux types de groupements mais qui en fait, sous une apparence morphologique semblable, représentent vraisemblablement des taxons distincts. Dans une seconde phase, l'étude caryologique et l'analyse chimiotaxonomique devraient permenttre de saisir les différences de constitution génotypique existant entre les populations issues des mégaphorbiaies et celles développées dans les groupements du Triseto-Polygonion.     

Remaniement des nannofossiles calcaires maastrichtiens dans les sédiments du Danien basal de Bidart (France) : arguments isotopiques (carbone et oxygène)

The sediments at the Cretaceous-Tertiary boundary record a major crisis of pelagic carbonate producers (calcareous nannofossils and planktonic foraminifera). Nevertheless, Maastrichtian-like nannofossils are found in lowermost Danian sediments. Their origin (reworked vs. survivors) is still under debate. A recently developed protocol leading to separation of the various calcareous components included in the lowermost Danian sediments allows evaluation of the nannofossil isotopic signatures across the Cretaceous-Paleocene boundary. Maastrichtian-like nannofossils found in Danian sediments record isotopic ratios (carbon and oxygen) similar to the Cretaceous ones. These results provide evidence that Maastrichtian-like nannofossils are mostly reworked at Bidart.     

Incorporation du desmosterol-3-(3)h dans les sterols du tabac nicotiana tabacum

The propionate of 3-(3)H desmosterol has been applied to the leaves of the tobacco Nicotiana tabacum Wisconsin. Radioactivity is incorporated into cholesterol and campesterol with a yield of about 0.5%; the C(29) sterols are not labelled in this experiment.     

Empreintes de pas de reptiles au Pic des Merveilles dans le Permien du massif du Mont-Bego (Alpes-Maritimes)

The Permian formations outcropping on the southern side of the Mercantour massif (Barrot dome; Mont-Bego and the Vallée des Merveilles) have not, up until now, yielded vertebrate footprints, unlike other southern French regions (Lodévois, Provence). However, this has now changed. Discoveries have been made, first on loose blocks and then in stratigraphy (upper part of the Meraviglie or Merveilles formation), during a geological survey in the national Mercantour Park. These footprints belong to the same ichnite type, Varanopus curvidactylus Monodi, 1929. Nonetheless, this attribution needs to be confirmed by subsequent footprint discoveries. Despite unfavourable outcropping conditions and often intense tectonic deformation (fracturation, beginning of schistosity, network of quartzous vein, occasionally with epidote), the traces and the associated sedimentary features (current ripples, mudcracks, raindrop imprints, cyanobacterial mats, annelid bioturbations) allow us to correlate the depositional environment of the upper Meraviglie terrigenous formation with a deltaic lower flood plain of a lakeshore.     

Sur la presence de lipides (phospholipides et sterides) dans les vacuoles de certaines cellules vegetales

Sans résumé     

Les relations isopedine - tissu osseux dans le post-temporal et les ecailJes de la ligne laterale de Latimeria chalumnae (Smith)

The scaly part of the posttemporal bone and the lateral-line scales have the same structure as other scales. However, the lateral line with its bony canal induces some local transformations in both structures. The posttemporal bone can be interpreted as a lateral-line scale whose dermo-component is extensively developed. With its composite structure, both osseous and scaly, the posttemporal bone affords an instance peculiarly well suited for studying the relationships between isopedine and bone. The observations demonstrate that isopedine whose superposed collagen layers make a double-twisted plywood, is a specialized structure which evolved from a bony tissue. The fibrous basal plate of a Latimeria scale is homologous to the osseous basal plate of a cosmoid scale.     

Metabolism of 2-hydroxy(4-14C)estradiol by rat liver microsomes

The metabolism of ¹⁴C-labeled estradiol and 2-hydroxyestradiol by rat liver microsomes has been compared under a variety of experimental conditions. An active liver microsomal system as well as NADPH was required to obtain high percentage yields of water-soluble metabolites from both steroids. Spermine stimulated the formation of polar products in both cases but the sex-difference in metabolism observed with estradiol was less marked with 2-hydroxyestradiol as substrate.     

Les associations des calpionelles du Berriasien et du Valanginien inférieur de la Tunisie septentrionale. Comparaison avec les associations du Rif externe (Maroc)

The study of ten thin sections from outcrops from Lower Cretaceous deposits and several thin sections obtained from three petroleum wells, allow us to better characterize the associations of calpionellid zones and subzones of the Berriasian and Lower Valanginian in northern Tunisia. The B and C zones, respectively, show three and two levels with calpionellid associations corresponding to B1, B2, B3 and C1, C2 subzones. In the D zone, associations of the D1 and D2 subzones were identified. The E zone has been characterized for the first time in Tunisia and in southern-Tethyan margin of North Africa, on the basis of its index specie and associated species.