Elongation of (omega-14C)oleic acid and (omega-14C)nervonic acid.

During feeding experiments with [omega-14C]oleic acid and [omega-14c]nervonic acid to adult rats, 14C-labelled C26, C28 and C30 fatty acids were recovered from the intestinal mucosa, liver, plasma, kidney and stools. The structures of these fatty acids were determined by g.l.c., radio-g.l.c. and mass spectrometry. The Schmidt and Ginger degradation methods indicated that most of the 14C found in these extra-long fatty acids remained in the omega position. These radioactive extra-long fatty acids were found mainly in the polar lipids of rats killed 3 or 15 h after being fed on labelled oleic acid or nervonic acid. Rats killed 63 h later yielded only traces of these extra-long fatty acids. When the rats were given antibiotics or received the same radioactive fatty acids by intravenous injection, the labelled extra-long fatty acids could not be detected in any of the tissues. We conclude that they were probably synthesized by elongation of oleic acid and nervonic acid by intestinal micro-organisms (probably yeasts) and then absorbed by the intestinal mucosa.     

Practical, asymmetric synthesis of 16-hydroxyeicosa-5(Z),8(Z), 11(Z),14(Z)-tetraenoic acid (16-HETE), an endogenous inhibitor of neutrophil activity

An asymmetric synthesis of 16-HETE, an endogenous inhibitor of neutrophil activity, was achieved in six steps from R-(-)-glycidyl benzyl ether in 28% overall yield.     

Synthesis of tetracontapeptide--a hypothetical evolutionary precursor of calcium-binding proteins. I. Synthesis of (1-9), (10-14), (15-20), (21-26), (29-33), (34-40) fragments

Fragments (1-9), (10-14), (15-20), (21-26), (29-33) and (34-40) of a tetracontapeptide hypothetical ancestor of calcium-binding proteins were synthesised with the use of pentafluorophenyl esters. Formation of a succinimide derivative was detected during synthesis of fragment (15-20) containing Asp(OBzl)-Gly sequence. To avoid this side process, tert-butylprotecting group was used instead of benzyl group. alpha-Carboxyls of C-terminal amino acids were protected by phenacyl group.     

Potential bile acid metabolites. 14. Hyocholic and muricholic acid stereoisomers

The complete set of the eight theoretically possible stereoisomeric 3,6,7-trihydroxy-5 beta-cholanic acids, four of which are new, related to hyocholic and muricholic acids were prepared from chenodeoxycholic acid. The principal reactions used were 1) cis-dihydroxylation of delta 6-compounds with osmium tetroxide/N-methylmorpholine N-oxide; 2) trans-dihydroxylation of 6 alpha, 7 alpha-epoxy compounds with boron trifluoride etherate in N,N-dimethyl-formamide; 3) inversion of equatorial 3 alpha-hydroxylated compounds to the corresponding 3 beta-epimers with diethyl azodicarboxylate/triphenylphosphine/formic acid; and 4) stereoselective reduction of 7-keto derivatives with zinc borohydride (or sodium borohydride) and by metallic potassium/tert-amyl alcohol.     

Mechanism and signal transduction of 14 (R), 15 (S)-epoxyeicosatrienoic acid (14,15-EET) binding in guinea pig monocytes

14(R), 15(S)-epoxyeicosatrienoic acid (14,15-EET) is a cytochrome P-450 monooxygenase (epoxygenase) metabolite of arachidonic acid (AA). In this study, we have identified a population of specific high affinity binding sites for 14,15-EET in the guinea pig mononuclear (GPM) cells. The results of competition studies showed that 14(R), 15(S)-EET was an effective competing ligand with a Ki of 226.3 nM followed by 11(R), 12(S)-EET, 14(S), 15(R)-EET, 14,15 thia(S)-ET, and 14,15-aza(N)-ET. The binding was sensitive to various protease treatments suggesting that the binding site is protein in nature. Cholera toxin (CT) and dibutyryl cAMP attenuated 14,15-EET binding in GPM cells. Mean binding site density (Bmax), decreased 32.0% and 19.1% by the pretreatment with cholera toxin (200 micrograms/ml) and dibutyryl cAMP (100 nM), respectively, without changing the dissociation constant. A specific protein kinase A (PKA) inhibitor, H-89, but not the PKC inhibitor K252a reversed the down regulation of 14,15-EET receptor binding caused by dibutyryl cAMP in GPM cells. Thus, the results sug-gest that the specific binding site of 14,15-EET in GPM cells be associated with a receptor that could be down regulated through an increase in intracellular cAMP and activation of a PKA signal trans-duction. We propose that the signal transduction mechanism begins with the binding of 14,15-EET to its receptor that leads to increase intracellular cAMP levels and the activation of PKA, and finally, with the down regulation of 14,15-EET receptor binding.     

Interaction of metal ions with humic-like models. Part VII. Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of 2,5-dihydroxybenzoic acid

Complexes of formula M(2,5-DHB)₂4H₂O (M = Mn, Co, Ni, Zn, Cu and Cd; 2,5-DHB = 2,5-dihydroxybenzoate) were prepared and characterized by means of infrared and electronic spectroscopy, and by electron spin resonance. For the Zn complex the crystal and molecular structure was also determined by single-crystal X-ray diffraction analysis. The crystal is orthorhombic, space group Pbca (No. 61), with a = 18.503(4), b = 13.536(3), c = 6.900(2) Å, and Z = 4. The final refinement used 877 reflections and gave a residual R value of 0.041. The complex has slightly compressed octahedral coordination, with the zinc atom bound to two monodentate carboxylate groups lying in trans positions and four water molecules. X-ray data and infrared spectra show the Mn, Co, Ni, Zn and Cd complexes to be isostructural with the Zn compound. The electronic, infrared and ESR spectra of the copper(II) complex are consistent with a CuO_4? based chromophore involving two water molecules and two monodentate carboxylate groups in the metal plane, and long axial contacts.     

The mechanism underlying the hypolipemic effect of perfluorooctanoic acid (PFOA), perfluorooctane sulphonic acid (PFOSA) and clofibric acid.

The influence of the peroxisomal proliferators perfluorooctanoic acid (PFOA), perfluorooctane sulphonic acid (PFOSA) and clofibric acid on lipid metabolism in rats was studied. Dietary treatment of male Wistar rats with these three compounds resulted in rapid and pronounced reduction in both cholesterol and triacylglycerols in serum. The concentration of liver triacylglycerols was increased by about 300% by PFOSA. Free cholesterol was increased by both perfluoro compounds. Cholesteryl ester was reduced to 50% by PFOSA as well by clofibrate. In hepatocytes from fed rats, all the compounds resulted in reduced cholesterol synthesis from acetate, pyruvate and hydroxymethyl glutarate, but there was no reduction of synthesis from mevalonic acid. The oxidation of palmitate was also increased in all groups. The perfluoro compounds, but not clofibrate, caused some reduction in fatty acid synthesis. The activity of liver HMG-CoA reductase was reduced to 50% or less in all treatment groups and all three compounds led to lower activity of acyl-CoA:cholesterol acyltransferase (ACAT). Changes in other enzymes related to lipid metabolism were inconsistent. The present data suggest that the hypolipemic effect of these compounds may, at least partly, be mediated via a common mechanism; impaired production of lipoprotein particles due to reduced synthesis and esterification of cholesterol together with enhanced oxidation of fatty acids in the liver.     

Immunological evidence for structural homology between Drosophila melanogaster (S14), rabbit liver (S12), Saccharomyces cerevisiae (S25), Bacillus subtilis (S6), and Escherichia coli (S6) ribosomal proteins.

Specific antibodies directed against Drosophila melanogaster acidic ribosomal protein S14 were used in a comparative study of eucaryotic and procaryotic ribosomes by immunoblotting and enzyme-linked immunosorbent assays. Common antigenic determinants and, thus, structural homology were found between D. melanogaster, Saccharomyces cerevisiae (S25), rabbit liver (S12), Bacillus subtilis (S6), and Escherichia coli (S6) ribosomes.     

Biosynthesis of ergosta-4,6,8(14),22-tetraen-3-one. A novel oxygenative pathway

Specifically (tritium) labeled precursors (VIII, X, XIV, XV, and XVI), upon feeding to Penicillium rubrum, are incorporated into ergosta-4,6,8(14),22-tetraen-3-one (IV) to the extent of 14.2, 4.5, 11.4, 16.3, and 5.5% respectively. Proof that the ergostane skeleton was incorporated intact was afforded by a chemical-biosynthetic cycle, the latter stages of which entailed reduction of isolated (IV) to ergosterone (VIII), followed by removal of the label through base-catalyzed exchange. A search of the growth medium of P. rubrum revealed the presence of nonartefactual ergosterol epidioxide (XIII) and ergosta-6,22-dien-3β,5α,8α-triol (XVIII). The incorporation data are consistent with a set of multiple pathways with no unique biosynthetic sequence apparent.     

Iron(III) reduction by D-galacturonic acid. Part II. Influence of uranyl(VI), lead(II), nickel(II), and cadmium(II) complexes formation

As a part of our study on iron reduction-mobilization in biological systems, in particular at root-soil interface, the effect of the addition of different metal ions to the iron(III)-D-galacturonic acid system has been investigated. The ions which are found to form particularly stable complexes with the galacturonate ligand strongly increase the yield of the reduction of iron(III) to iron(II). These findings are in agreement with the capability of some metal ions to form stable complexes through interaction both with the carboxylate group and with the ring oxygen atom of the sugar molecule, inducing opening of the ring and formation of a free aldehydic group. The importance of these processes in availability of iron to plant roots is emphasized.