Lipoxygenase- and cyclooxygenase-reaction products and incorporation into glycerolipids of radiolabeled arachidonic acid in the bovine retina

The metabolism of radiolabeled arachidonic acid (AA) by the intact bovine retina has been studied. Synthesis of prostaglandins (PGs) and hydroxyeicosatetraenoic acids (HETEs), and incorporation of AA into glycerolipids has been measured by reverse-phase and straight-phase high performance liquid chromatography with flow scintillation detection, and by thin-layer chromatography. AA was actively acylated into glycerolipids, particularly triglycerides, phosphatidylcholine and phosphatidylinositol. AA was also converted to the major PGs, PGF_2α, PGE₂, PGD₂, 6-keto-PGF_1α and TXB₂, and to the lipoxygenase reaction products, 12-HETE, 5-HETE, and other monohydroxy isomers. Approximately 6% of the radiolabeled AA was converted to eicosanoids. The synthesis of HETEs was inhibited in a concentration-dependent manner (IC₅₀ = 8.3 NM) by nordihydroguaiaretic acid (NDGA). PG synthesis was inhibited by aspirin (10 μM), indomethacin (1 μM) and NDGA (IC₅₀ = 380 nM). Metabolism of AA via lipoxygenase, cyclooxygenase and activation-acylation was inhibited by boiling retinal tissue prior to incubation. These studies demonstrate an active system for the uptake and utilization of AA in the bovine retina, and provide the first evidence of lipoxygenase-mediated metabolism of AA, resulting in the synthesis of mono-hydroxyeicosatetraenoic acids, in the retina.     

Nonsense RNA: a tool for specifically inhibiting the expression of a gene in vivo

We describe a general technique to inhibit gene expression in eukaryotic cells. The gene we chose to inhibit was the E. coli LacZ gene (encoding beta-galactosidase), which has previously been cloned into a eukaryotic expression vector [1]. This plasmid is called pCH110. We constructed a variant of pCH110 in which we flipped a 2566 base pair 5' fragment of the LacZ gene into the antiparallel orientation. The plasmid containing this mutated LacZ gene is called pNSLacZ (NS signifies non-sense coding sequence). When equal amounts of pCH110 and pNSLacZ are co-transfected into 3T6 mouse fibroblasts, the beta-galactosidase activity is decreased by approximately a factor of ten. Increasing the ratio of pNSLacZ to pCH110 above 1:1 does not appreciably increase the level of inhibition. Next, we prove the specificity of the inhibition by adding a third gene to the transfection mixture. For this purpose, we used pSVneo beta, a plasmid which expresses a phosphotransferase. We found that even when the beta-galactosidase activity was diminished by a factor of 10, the phosphotransferase activity was unaffected. Therefore, we have demonstrated that: the presence of an antiparallel copy of the LacZ gene results in a significant and specific diminution of the LacZ gene's expression; only a fraction of the LacZ gene needs to be in the antiparallel orientation in order to observe this effect. These results suggest that this technique can serve as a tool to decrease the level of gene expression in order to study the function of specific genes, or as a therapeutic manoeuvre in the treatment of disorders of abnormal gene expression.     

Interaction of peanut agglutinin,a lectin specific for nonreducing terminal d-galactosyl residues,with embryonal carcinoma cells

Peanut agglutinin (PNA), a lectin specific for terminal d-galactosyl residues, was found to react with embryonal carcinoma cells, but not with their differentiated derivatives. Receptors for PNA were detectable at the surface of all cells of the quasinullipotent F9 line and on only 50% of the multipotent PCC3/A/1 line. The fraction of the PCC3/A/1 population which expresses the F9 antigen was found to be included in the subpopulation carrying the PNA receptors. PNA⁺ and PNA^? subpopulations of PCC3/A/1 were separated by a PNA-mediated reversible agglutination of PNA⁺ cells with rabbit erythrocytes. These subpopulations were essentially F9⁺ and F9^?, respectively.     

Autolytic activities of the cell wall in rice coleoptiles. Effects of nojirimycin

Oryza sativa L. var. bahia coleoptile cell walls show sufficient autolytic activity for the release into the surrounding medium of amounts up to 60 μg of sugars per mg of dry weight of cell wall. The products released elute in Bio-gel P.2 as mono- and polysaccharides with glucose as the sole component. The polysaccharide component releases tri- and tetrasaccharides on treatment with a glucanase specific for β (1–3) (1–4) linkages in the same proportion as that of the mixed glucan of the cell wall. This supports the hypothesis that the polysaccharide component originates from the cell wall glucan and that autolysis is therefore related to the processes of the loss of rigidity of the cell wall. Nojirimycin (a specific glucanase inhibitor and inhibitor of auxin-induced elongation) decreases autolytic activity of the cell walls, reducing it to 30% of its normal value. Bio-gel P. 2 elution of the products released in autolysis in the presence of nojirimycin shows that only the monosaccharide fraction was affected.     

Role of pancreatic enzymes in the intraluminal transport and ileal absorption of vitamin B 12 (Cb 1)

The present paper outlines the classical concepts of transport and absorption of vitamin B12 and discusses findings which provide new insight into the important role of pancreatic enzymes in the absorption of the vitamin B12. In vivo experiments with healthy subjects and patients with exocrine pancreatic insufficiency demonstrate that the pancreatic enzymes do not activate "the precursor" intrinsic factor molecule but solely dissociate vitamin from the inactive R type proteins with a consequent coupling to the biologically active intrinsic factor.     

Succession,diversité et amplitude de niche dans les påturages du centre de la péninsule ibérique

Some diversity and niche amplitude parameters were applied to rangeland pastures of the Central Iberian Peninsula and to their succession stages after the periodical ploughing typical of the traditional management of these areas. Four different slopes within a large area of undulating terrain were selected for the monitoring of succession as they contained the characteristical geomorphological pattern of the area (denudation, transport and accumulation sectors).If we consider the total entropy theorem, H (E.P.)=H(E)+H(P/E), the total entropy of the slope H(E.P) and the entropy of species H(E) increase as succession progresses. As the value of the entropy of the sampling plots conditioned by the species H(P/E) is affected by the number of plots utilized, we employed the expression A=H(P/E)/log₂ number of plots, similar to Pielou's index for niche amplitude, W=H(P/E)/H(P).This values decreases with succession, indicating that plant species tend to occupy more definite sectors along the slope. The number of low entropy species H(P/E) _i or specialist species, confined to narrow sectors also increases. When computed separately within the different sectors niche amplitude results in small values for the low slope regions (accumulation sector). This effect becomes more pronounced when succession advances.

Nous remercions le Conseil d'Administration de La Paranza, propriétaire du Castillo de Vañuelas, et particulièrement Mrs. C. Hernandez-Ros et J. A. Léon-Vrquijò, pour les faeilités qu'ils ont données à cette équipe durant la réalisation de ce travail.     

Expression and synthesis of cross-reactive idiotypic antibodies by peripheral blood lymphocytes and their suppression by anti-idiotypes in patients with IgA nephropathy.

We have recently described that patients with IgA nephropathy present high serum levels of anti-BSA idiotypic antibodies that were well correlated with the existence of hematuria. Furthermore, these Id were found in circulating and renal deposited immune complexes. In the present work, we examined the expression of surface idiotypic determinants on PBL by flow cytometry and their in vitro production, using as reagent anti-idiotypic antibodies previously well characterized. The presence of cross-reactive Id-bearing cells was observed in 5 out of 6 patients studied, with frequencies ranging from 3 to 12% of lymphocytes. After 7 days of culture, the spontaneous synthesis of idiotypic antibodies by PBL was found elevated in 6 out of 13 (46%) patients. A major Id cell expression and production was noted in patients with active disease as defined by hematuria. The preincubation of PBL with 20 and 50 micrograms of anti-idiotypic antibodies/2 x 10(6) cells for 3 days induced a significant inhibition of cross-reactive Id production in a dose-dependent fashion, with a degree of suppression between 12 and 50% in five out of six patients studied. In the above assays, as negative controls, we used the anti-Id antibodies previously adsorbed on an Id-Sepharose column. On the whole, these results suggest that patients with IgA nephropathy present dysfunctions in the Id-Anti-Id network that could play an important role in the pathogenesis of this disease.