Cognition in children does not suffer from very low lead exposure.

We studied the relationship between exposure to lead and memory and attention in children. Participants were 313 boys aged 9 to 12 years who attended special education schools in the Netherlands. Children whose possible attentional or memory problems were obviously due to causes other than lead contamination were excluded from the study.

Impulsivity and negative priming: evidence for diminished cognitive inhibition in impulsive children.

This study addresses the relationship between impulsivity and lack of inhibition. Inhibition was measured both by the interference score and by the negative priming effect in a Stroop colour-word paradigm. The negative priming effect in this paradigm is defined by slower naming of a target colour if this colour was the distractor in the immediately preceding trial.

Exposure to lead and specific attentional problems in schoolchildren.

A pilot study was carried out to investigate the relationship between exposure to lead and attention in children. The participants were 43 boys, 8 to 12 years of age, attending special schools for children with educational and/or learning problems (so called LOM schools). Children with probable causes of attentional or memory problems other than lead contamination were excluded from the study.

Involvement of microbodies in penicillin biosynthesis.

Penicillium chrysogenum strains were constructed which express a mutant acyltransferase lacking the putative targeting signal for microbody proteins. The mutated enzyme was located in vacuoles and in neighbouring cytoplasm. Although acyltransferase was expressed in vivo and was active in vitro, the mutants did not produce penicillin.

A preparation method of specimens of the fungus Penicillium chrysogenum for ultrastructural and immuno-electron microscopical studies.

A combination of cryofixation without pre-treatment, freeze-substitution and low-temperature embedding was used to prepare specimens of Penicillium chrysogenum for electron microscopy. To produce specimens which are thin enough for appropriate cryofixation, the P.chrysogenum colonies were grown between dissected-dialysis tubing on an agar plate, which in addition allowed longitudinal sectioning.

Localization of the pathway of the penicillin biosynthesis in Penicillium chrysogenum.

The localization of the enzymes involved in penicillin biosynthesis in Penicillium chrysogenum hyphae has been studied by immunological detection methods in combination with electron microscopy and cell fractionation. The results suggest a complicated pathway involving different intracellular locations. The enzyme delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase was found to be associated with membranes or small organelles.

Cloning and characterization of the acyl-coenzyme A: 6-aminopenicillanic-acid-acyltransferase gene of Penicillium chrysogenum.

A gene, aat, encoding acyl-CoA: 6-aminopenicillanic acid acyltransferase (AAT), the last enzyme of the penicillin (Pn) biosynthetic pathway, has been cloned from the genome of Penicillium chrysogenum AS-P-78. The gene contains three introns in the 5'-region and encodes a protein of 357 amino acids with an Mr of 39,943. It complements mutants of P.

2H-NMR, 31P-NMR and DSC characterization of a novel lipid organization in calcium-dioleoylphosphatidate membranes. Implications for the mechanism of the phosphatidate calcium transmembrane shuttle.

2H-NMR, 31P-NMR and DSC investigations are presented on the structure and dynamics of the Ca2+-dioleoylphosphatidate complex which is formed upon addition of calcium to dispersions of pure dioleoylphosphatidate or of dioleoylphosphatidate in mixtures with dioleoylphosphatidylcholine (DOPC). It is concluded that the phosphate region in the polar headgroup of dioleoylphosphatidate is immobilized, while the oleate chains remain liquid and have increased disorder. In mixtures of dioleoylphosphatidate and DOPC in the presence of calcium a dioleoylphosphatidate-rich phase is segregated, in which the molecular behaviour of phosphatidate is rather similar to that of the pure Ca2+-dioleoylphosphatidate complex.

Calcium-induced changes in permeability of dioleoylphosphatidylcholine model membranes containing bovine heart cardiolipin.

At calcium concentrations up to about 4 mM a selective permeability increase of cardiolipin/dioleoylphosphatidylcholine (50:50, mol%) membranes for calcium and its chelator arsenazo III is observed. Under these conditions calcium does not occupy all the binding sites of cardiolipin at the membrane interface and no vesicle-vesicle interactions are found. Lowering of the cardiolipin content of the vesicles to 20 mol% extends the calcium concentration range in which a selective permeability for calcium and arsenazo III is appearing up to about 12 mM.

Consequences of the interaction of calcium with dioleoylphosphatidate-containing model membranes: calcium-membrane and membrane-membrane interactions.

Calcium binds to dioleoylphosphatidate/dioleoylphosphatidylcholine (DOPA/DOPC) (20:80, mol%) multilamellar vesicles in the presence of a calcium ionophore with stoichiometry of about 0.6 nmol calcium per nmol phosphatidate and an apparent dissociation constant of about 1.7 mM.

Ethylene glycol causes acyl chain disordering in liquid-crystalline, unsaturated phospholipid model membranes, as measured by 2H NMR.

2H NMR has been used to probe the effects of ethylene glycol at the level of the acyl chains in liposomes prepared from dioleoylphosphatidic acid or dioleoylphosphatidylcholine, labeled with 2H at the 11-position of both oleic acid chains. Increasing concentrations of ethylene glycol lead to a proportional and substantial decrease in the quadrupolar splittings, measured from the 2H NMR spectra of both liposomal systems, indicative of acyl chain disordering.

Consequences of the interaction of calcium with dioleoylphosphatidate-containing model membranes: changes in membrane permeability.

The permeability behaviour of dioleoylphosphatidate/dioleoylphosphatidylcholine (20:80, mol%) large unilamellar vesicles at low millimolar calcium concentrations is different for various solutes. Between 0.5 mM and 2.

Essential adaptation of the calcium influx assay into liposomes with entrapped arsenazo III for studies on the possible calcium translocating properties of acidic phospholipids.

An adapted version of the Ca2+-influx assay of Weissmann et al. (Weissmann, G., Anderson, P.

Isolation and purification of cardiolipin from beef heart.

A simple and efficient procedure is described for the preparation of cardiolipin sodium salt from beef heart. A crude phospholipid fraction is isolated by chloroform-methanol extraction of the homogenized tissue, followed by acetone precipitation and reprecipitation in 4% aqueous CaCl2-methanol. Cardiolipin is separated from the calcium salts of the acidic phospholipids by partition column chromatography on silica gel (Polygosil 60-63100) using 2-propanol-cyclohexane-water 50:43:7 (v/v/v) as eluent.

Relationship between SCR, heart rate and information processing.

This study was designed to investigate the relationship between the amount of information processing in concept learning (CL) and autonomic physiological activity as measured by skin conductance response (SCR). Heart rate (HR) was also measured. Two conceptual rules were used: a conjunctive and an inclusive disjunctive concept.