Oxidatively Modified Plasma Phospholipids Containing Reactive Carbonyl Functions Measured by HPLC: Evidence for Phosphatidylcholine-Bound Aldehydes in Plasma of Burn Patients

A HPLC method has been developed to measure phosphatidylcholine (PC) containing reactive carbonyl functions in the sn-acyl residue in order to study processes in which such reactive carbonyls can be formed due to e.g. oxidative fragmentation. The method has been applied to determine PC-bound carbonyls as 2, 4-dinitrophenylhydrazones (DNPH) in plasma of burn patients. Plasma from healthy volunteers served as controls. Additionally, in vitro oxidation experiments (A: plasma, buffer diluted; B: plasma + iron-EDTA complex and C: plasma + iron-EDTA complex + H₂O₂) have been performed to obtain and to identify 2, 4-dinitrophenylhydrazine derivatizable carbonyl functions in plasma PC. Both, the PC-aldehydes and PC-aldehyde DNPH derivatives were cleavable with phospholipase C. Quantification was based on thin-layer chromatography purified soybean phosphatidylcholine, which was identically oxidized and derivatized as the plasma lipids in vitro.     

Chemical synthesis of a 7 kDa insect gonadotropic neurohormone

An original insect neurohormone of 65 residues was synthesized by the solid-phase methodology using t-Boc strategy and Boc-Val-PAM–resin. The purification, conducted by several steps of liquid chromatography having mass, polarity or charge as separative criteria, yielded the product with the correct molecular weight of 6922 Da determined by mass spectrometry. The synthetic peptide had both the same affinity for the antinative neurohormone serum and the same biological activity as the native neurohormone.     

Effects of T3 and rearing temperature on growth and skeletal myosin heavy chain isoform transition during early development in the salmonid Salvelinus alpinus (L.)

Rearing of 1-year-old Arctic charr (Salvelinus alpinus) at 12°C, as well as the administration of 50 or 75 mgT₃/kg feed, accelerated the neonatal to adult fast myosin heavy chain transition, but the effect of temperature was more dramatic than the effect of T₃ administration. The endogenous plasma levels of T₃ in charrs reared at 12°C were higher than those of analogous groups reared at natural temperature, which in the period under study was between 0.5 and 12°C. As in other species, T₃ seemed to play a role in the regulation of the neonatal to adult fast myosin isoform transition by down-regulating the levels of the neonatal and increasing the levels of an adult fast myosin heavy chain. Temperature seemed to accelerate this transition at least, but not only, by inducing an increase in the endogenous levels of T₃ in the Arctic charr.     

The yeast protein encoded by PUB1 binds T-rich single stranded DNA.

We have characterized binding activities in yeast which recognise the T-rich strand of the yeast ARS consensus element and have purified two of these to homogeneity. One (ACBP-60) is detectable in both nuclear and whole cell extracts, while the other (ACBP-67) is apparent only after fractionation of extracts by heparin-sepharose chromatography. The major binding activity detected in nuclear extracts was purified on a sequence-specific DNA affinity column as a single polypeptide with apparent mobility of 60kDa (ACBP-60). This protein co-fractionates with nuclei, is present at several thousand copies per cell and has a Kd for the T-rich single strand of the ARS consensus between 10(-9) and 10(-10) M. Competition studies with simple nucleic acid polymers show that ACBP-60 has marginally higher affinity for poly dT30 than for a 30 nt oligomer containing the T-rich strand of ARS 307, and approximately 10 fold higher affinity for poly rU. Internal sequence information of purified p60 reveals identity with the open reading frames of genes PUB1 and RNP1 which encode polyuridylate binding protein(s). The second binding activity, ACBP-67, also binds specifically to the T-rich single strand of the ARS consensus, but with considerably lower affinity than ACBP-60. Peptide sequence reveals that the 67kDa protein is identical to the major polyA binding protein in yeast, PAB1.     

Partial Purification and Immunocytocharacterization of the Plasma Membrane ATPase of Jerusalem artichoke (Helianthus tuberosus L.) Tubers in Relation to Dormancy

Plasmalemma ATPase from Jerusalem artichoke tubers was studiedin relation to the dormancy of tubers. After partial purification,one peptide of 110 kDa appeared on SDS PAGE electrophoresisfrom dormant and non-dormant materials. ATPase specific activitywas twice higher on dormant material in the crude and solubilizedfractions, but was the same in both materials after partialpurification. Immunolabeling of this enzyme was made using aspecific antibody raised against the C terminal portion of theH⁺-ATPase from Arabidopsis thaliana. Immunolabeling was morepronounced in dormant material, in vitro and in situ. Severalworks had shown that the C terminal part of the enzyme couldbe involved in its regulation. The results presented are discussedin relation to the hypothesis according to which an internaleffector could modulated the plasmalemma ATPase activity, duringdormancy breaking. (Received October 25, 1993; Accepted September 6, 1994)     

Effect of exogeneous methyl oleate on the time course of some parameters of Streptomyces hygroscopicus NRRL B-1865 culture

Addition of methyl oleate to a Streptomyces hygroscopicus NRRL B-1865 culture modified the metabolic properties of this strain. This addition decreased the pH of the medium, increased the valine uptake of the cells and reduced their consumption of glucose until the beginning of antibiotic biosynthesis, which was delayed. At the same time, an increase in growth (× 1.8) and a marked improvement in antibiotic production (× 20) could be observed. The use of labelled methyl oleate showed that methyl oleate was not a precursor of antibiotics produced by S. hygroscopicus NRRL B-1865. It is suggested that methyl oleate addition may cause some alteration in membrane permeability, inducing an increase in H⁺ extrusion and stimulating the accumulation of branched amino acids, known to be direct precursors of polyether antibiotics. Correspondence to: L. David     

The loss of culturability by Escherichia coli cells in seawater depends on availability of phosphate ions and phosphate transport systems

Using strains with or without the PhoE porin or different components of the phosphate regulon, we determined that maintenance of the culturability of Escherichia coli in seawater depended significantly on the presence of structures allowing access of phosphate ions to the periplasm, then to the cytoplasm of cells. Cells totally deprived of the two main phosphate transport systems (Pit, Pst) exhibited the highest loss of culturability. Most of this effect resulted from the loss of the high-affinity Pst system, and more specifically that of the periplasmic phosphate-binding protein PhoS. Survival was enhanced in seawater supplemented with phosphate (0.5 mm), whether or not these structures were present. From an ecological point of view, it is assumed that the presence of phosphate ions, even at low concentrations, can influence the behavior of E. coli cells in seawater. Offprint requests to: M.J. Gauthier     

Volatile sensation: The chemical ecology of the earthy odorant geosmin

Geosmin may be the most familiar volatile compound, as it lends the earthy smell to soil. The compound is a member of the largest family of natural products, the terpenoids. The broad distribution of geosmin among bacteria in both terrestrial and aquatic environments suggests that this compound has an important ecological function, for example, as a signal (attractant or repellent) or as a protective specialized metabolite against biotic and abiotic stresses. While geosmin is part of our everyday life, scientists still do not understand the exact biological function of this omnipresent natural product. This minireview summarizes the current general observations regarding geosmin in prokaryotes and introduces new insights into its biosynthesis and regulation, as well as its biological roles in terrestrial and aquatic environments.