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Shortly before his death my father confessed to me that we had narrowly missed being killed by a V2. A few months after my birth in 1944, he had been [...]

The role of [Beta]-carotene in chemoprevention of cancers and other chronic diseases generated controversy when sub-populations taking [Beta]-carotene supplements showed increased mortality in clinical trails. Determination of the dynamics of [Beta]-carotene in individual human subjects has emerged as a high priority. Stable isotope labeled [Beta]-carotene tracers can be employed to determine rates of conversion to retinol (vitamin A), but tracer doses must be small to minimize perturbation of endogenous retinoid and carotenoid pools. In such cases, ratios of labeled tracer/endogenous retinol are often low, and quantitative analysis at enrichments of

An investigation has been carried out on three modes of resonant excitation in the development of an analytical protocol for the determination of polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs) by ion trap tandem mass spectrometry. The resonant excitation modes investigated are single-frequency irradiation (SFI), secular frequency modulation (SFM), and multifrequency irradiation (MFI) of isolated molecular ion species. Each excitation mode was examined for fragmentation channel selectivity so as to optimize instrument sensitivity. Collision-activated dissociation mass spectra obtained with each excitation mode are compared with those obtained by triple-stage quadrupole mass spectrometry (TSQMS). While the same reaction channels (corresponding to losses of Cl*, COCl*, and 2COCl* for PCDDs and Cl*, COCl*, and CO[Cl.sub.2] and CO[Cl.sub.3]* for PCDFs) were observed for each excitation mode, the fragment ion relative abundances differed among the resonant excitation modes and showed that internal energy deposition in the precursor ion was in the order MFI [greater than] SFI [greater than] SFM. In each resonant excitation mode, the observed conversion efficiency for loss of COCl* exceeded that observed with TSQMS. The procedure of tuning SFI to ion secular frequencies was laborious, while the required duration of irradiation with SFM was excessively long compared to the gas chromatographic time scale. The tuning requirements of MFI using 1 and 2 kHz bandwidth pulses were less rigorous than those for SFI, and the duration of irradiation was compatible with the gas chromatographic time scale.

James Neil Graham Ritchie entered the world, as he left it, in Edinburgh, and the city always held a very special place in both his intellectual and physical affection. His [...]

This volume comprises 18 papers focusing upon current research in the early prehistory of Northern Britain, many of which had their origins in a conference, The Stone Age in Scotland, [...]

Epigenetic mechanisms, such as histone modifications, regulate responsiveness to drugs of abuse, such as cocaine, but relatively little is known about the regulation of addictive-like behaviors by DNA methylation. To investigate the influence of DNA methylation on the locomotor-activating effects of cocaine and on drug-seeking behavior, rats receiving methyl supplementation via chronic L-methionine (MET) underwent either a sensitization regimen of intermittent cocaine injections or intravenous self-administration of cocaine, followed by cue-induced and drug-primed reinstatement. MET blocked sensitization to the locomotor-activating effects of cocaine and attenuated drug-primed reinstatement, with no effect on cue-induced reinstatement or sucrose self-administration and reinstatement. Furthermore, upregulation of DNA methyltransferase 3a and 3b and global DNA hypomethylation were observed in the nucleus accumbens core (NAc), but not in the medial prefrontal cortex (mPFC), of cocaine-pretreated rats. Glutamatergic projections from the mPFC to the NAc are critically involved in the regulation of cocaine-primed reinstatement, and activation of both brain regions is seen in human addicts when reexposed to the drug. When compared with vehicle-pretreated rats, the immediate early gene c-Fos (a marker of neuronal activation) was upregulated in the NAc and mPFC of cocaine-pretreated rats after cocaine-primed reinstatement, and chronic MET treatment blocked its induction in both regions. Cocaine-induced c-Fos expression in the NAc was associated with reduced methylation at CpG dinucleotides in the c-Fos gene promoter, effects reversed by MET treatment. Overall, these data suggest that drug-seeking behaviors are, in part, attributable to a DNA methylation-dependent process, likely occurring at specific gene loci (e.g., c-Fos) in the reward pathway. [ABSTRACT FROM AUTHOR]

This is an important book that seeks, and to a very considerable extent achieves, a re-balancing of the wheels of prehistory, and its interpretation, on either side of the Irish [...]

The charge inversion mass spectra of C1 to C3 alkoxide ions have been obtained using He, N2 and O2 as collision gases. The three collision gases show similar efficiencies for collisional charge inversion and produce similar mass spectra, although fewer high-energy oxenium ions are formed when O2 and N2 are used as collision gases. Using two collision cells and an intermediate deflector electrode the alkoxide ions have been neutralized in the first collision cell and the fast neutrals ionized in the second cell. The neutralization-reionization mass spectra obtained are similar to the direct charge-inversion mass spectra indicating that mainly alkoxyl radicals are produced, although, depending on the neutralization collision gas and the alkoxide ion studied, other neutrals are formed in small yields. Deuterium isotopic labelling has been used to show that the main fragmentation reactions of the unstable oxenium ions formed involve 1,1-elimination of H2 or an alkane. [ABSTRACT FROM AUTHOR]

The 70 e V-electron impact mass spectra of the C7-C10 n-alkynes have been determined as well as the metastable ion spectra of the molecular ions and the [CS2]+ and [N2O]+ charge exchange mass spectra of the C7-C9 n-alkynes. The metastable ion mass spectra provide only a limited opportunity to distinguish between isomers; however, the 70-eV EI mass spectra of isomeric compounds permit a ready distinction between isomers. The [CS2]+ charge exchange mass spectra of isomeric compounds also show substantial differences. The [N2O]+ charge exchange mass spectra do not show the enhancement of β-fission fragments observed in field ionization experiments, despite representing ions of similar internal energy, and it is concluded that field dissociation is responsible for the β-fission fragments in the field ionization experiments. [ABSTRACT FROM AUTHOR]