Quantitative determination of nitroglycerin in human plasma by capillary gas chromatography with electron-capture detection

A sensitive method for the selective determination of nitroglycerin at concentrations down to 50 pg/ml in human plasma is described. After the addition to plasma of a known amount of butane-1,2,4-triol trinitrate as internal standard, both compounds are extracted into hexane. Nitroglycerin is then quantitated by capillary gas chromatography with electron-capture detection.     

Quantitative determination of norethisterone acetate in human plasma by capillary gas chromatography with mass-selective detection

An analytical method for the determination of norethisterone acetate (NETA) in human plasma by capillary gas chromatography-mass-selective detection (GC-MS), with testosterone acetate as internal standard, was developed and validated. After addition of the internal standard, the compounds were extracted from plasma at basic pH into diethyl ether-dichloromethane (3:2 v/v), which was then evaporated to dryness. The compounds were converted into their pentafluoropropionyl derivatives which were determined by gas chromatography using a mass selective detector at m/z 486 for NETA and m/z 476 for the internal standard. Intra-day and inter-day accuracy and precision were found suitable over the range of concentrations between 0.10 to 10 ng/ml. The method was applied to clinical samples.     

Etude comparative de l'alkylation des tetraphenylporphyrines de l'etain et de leurs formes reduites par les reactifs de grignard

A comparative study of alkylation by Grignard reagents of PSn(OH)₂ (P = tetraphenylporphyrin (TPP), tetraphenylchlorine (TPC), tetraphenylisobacteriochlorine (TPiBC)) shows that dialkylstannylisobacteriochlorines are the most easily obtained. The presence of transition metals in the magnesium crystals directs the reaction towards reduction of the macrocycle instead of alkylation on tin. This is supplementary proof for the intervention of a single electron transfer mechanism (SET) in alkylation of a macrocycle by Grignard reagents.These results fit very well with earlier electrochemical experiments and the measurements of the reduction potentials of the Group IVB metalloporphyrins and their reduced forms.     

Heritability of Stroop and flanker performance in 12-year old children

Background  

There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks.     

The contribution of high frequencies to human brain activity underlying horizontal localization of natural spatial sounds

Background  

In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization. A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information. Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening experiment.