Gas-liquid chromotographic determination of perazine, thioridazine and thioridazine metabolites in human plasma.

A gas-liquid chromatographic method for the detection of perazine, thioridazine and its major metabolites in human plasma is presented. Repeated extraction, an internal standard and a temperature program with flame ionization detection make possible accurate and reproducible results with patients on therapeutic doses of these drugs. Examples of chromatograms after extraction of plasma are given.     

Kinetics of ferrocenoylacetonato substitution from (1,5-cyclooctadiene)(ferrocenoylacetonato)rhodium(I) with 2,2′-dipyridyl and derivatives of 1,10-phenanthroline

Treatment of MeOH solutions of [Rh(cod)(fca)] (cod = 1,5-cyclooctadiene, fca = ferrocenoylacetonato) with seven derivatives of 1,10-phenanthroline (N,N), as well as with the (N,N) ligand 2,2-dipyridyl, gave [Rh(cod)(N,N)]⁺. The kinetics of these reactions follow the rate law: Rate = k[Rh(cod)(fca)[N,N] The temperature dependence of all the studied substitutions resulted in activation entropies, S , more negative than –100 J K^–1 mol^–1 which is indicative of associative mechanisms. The pK _a's of the incoming phenanthroline derivatives were between 3.03 and 6.31 but did not influence the reaction rate to any significant extent. This implies that the rate determining step during the substitution involves Rh—O bond breaking and not Rh—N bond formation. Substitution of fca with 2,2-dipyridyl was slightly faster (k = 118 dm³ mol^–1 s^–1) than with the 1,10-phenanthroline derivatives (k _average = 14.2 dm³ mol^–1 s^–1) and may be attributed to the free rotation capability of the two pyridyl rings about the 1-1 carbon–carbon axis in 2,2-dipyridyl. 1,10-Phenanthroline cannot rotate about the corresponding carbon axis.     

High-resolution MALDI imaging mass spectrometry allows localization of peptide distributions at cellular length scales in pituitary tissue sections

Matrix assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) has been used to determine peptide distributions directly from rat, mouse and human pituitary tissue sections. Since these organs are small (10²–10³ μm) the spatial resolution of IMS is a key issue in molecular imaging of pituitary tissue sections. Here we show that high-resolution IMS allows localization of neuropeptide distributions within different cell clusters of a single organ of a pituitary tissue section. The sample preparation protocol does not result in analyte redistribution and is therefore applicable to IMS experiments at cellular length scales. The stigmatic imaging mass spectrometer used in this study produces selected-ion-count images with pixel sizes of 500 nm and a resolving power of 4 μm, yielding superior spatial detail compared to images obtained in microprobe imaging experiments. Furthermore, we show that with imaging mass spectrometry a distinction can be made between different mammalian tissue sections based on differences in the amino acid sequence of neuropeptides with the same function. This example demonstrates the power of IMS for label-free molecular imaging at relevant biological length scales.     

Strategies for kinome profiling in cancer and potential clinical applications: chemical proteomics and array-based methods

Kinases are key enzymes involved in deregulated signal transduction associated with cancer development and progression. The advent of personalized medicine drives the development of new diagnostic tools for patient stratification and therapy selection Ginsburg and Willard (Transl Res 154:277-287, 2009). Since deregulation of kinase-mediated signal transduction is implied in tumorigenesis, the analysis of all kinases (the kinome) active in a particular tumor may yield tumor-specific information on aberrant cell signalling pathways. Tumor tissue kinase activity profiles may correlate with response to therapy and therefore may be used for future therapy selection. In this Trend paper we describe peptide array and mass spectrometry-based technologies and new developments for kinome profiling, and we present an outlook towards future implementation of therapy selection based on kinome profiling in clinical practice.     

13C NMR spectra of 3-substituted phlorophenone compounds

The ¹³C NMR spectra of a series of 3-allyl-, 3-prenyl- and 3-benzyl-phlorophenone compounds are reported. Relative substituent effects are discussed.     

Unusual patterns in 15N blood values after a diet switch in red knot shorebirds

When a diet switch results in a change in dietary isotopic values, isotope ratios of the consumer's tissues will change until a new equilibrium is reached. This change is generally best described by an exponential decay curve. Indeed, after a diet switch in captive red knot shorebirds (Calidris canutus islandica), the depletion of ¹³C in both blood cells and plasma followed an exponential decay curve. Surprisingly, the diet switch with a dietary ¹⁵N/¹⁴N ratio (δ¹⁵N) change from 11.4 to 8.8 ‰ had little effect on δ¹⁵N in the same tissues. The diet-plasma and diet-cellular discrimination factors of ¹⁵N with the initial diet were very low (0.5 and 0.2 ‰, respectively). δ¹⁵N in blood cells and plasma decreased linearly with increasing body mass, explaining about 40 % of the variation in δ¹⁵N. δ¹⁵N in plasma also decreased with increasing body-mass change (r ²=.07). This suggests that the unusual variation in δ¹⁵N with time after the diet switch was due to interferences with simultaneous changes in body-protein turnover.     

Assessment of the amount of body water in the Red Knot (Calidris canutus): an evaluation of the principle of isotope dilution with 2H, (17)O, and (18)O as measured with laser spectrometry and isotope ratio mass spectrometry

We have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (Red Knot, Calidris canutus) through an assessment of the amount of body water in it. Birds were quantitatively injected with a dose of water with elevated concentrations of 2H, (17)O, and (18)O. Thereafter, blood samples were taken and distilled. The resulting water samples were analysed using an isotope ratio mass spectrometry (for 2H and (18)O only) and a stable isotope ratio infrared laser spectrometry (2H, (17)O, and (18)O) to yield estimates of the amount of body water in the birds, which in turn could be correlated to the amount of body fat. Here, we validate laser spectrometry against mass spectrometry and show that all three isotopes may be used for body water determinations. This opens the way to the extension of the doubly labelled water method, used for the determination of energy expenditure, to a triply labelled water method, incorporating an evaporative water loss correction on a subject-by-subject basis or, alternatively, the reduction of the analytical errors by statistically combining the (17)O and (18)O measurements.     

Subcellular imaging mass spectrometry of brain tissue

Imaging mass spectrometry provides both chemical information and the spatial distribution of each analyte detected. Here it is demonstrated how imaging mass spectrometry of tissue at subcellular resolution can be achieved by combining the high spatial resolution of secondary ion mass spectrometry (SIMS) with the sample preparation protocols of matrix-assisted laser desorption/ionization (MALDI). Despite mechanistic differences and sampling 10(5) times less material, matrix-enhanced (ME)-SIMS of tissue samples yields similar results to MALDI (up to m/z 2500), in agreement with previous studies on standard compounds. In this regard ME-SIMS represents an attractive alternative to polyatomic primary ions for increasing the molecular ion yield. ME-SIMS of whole organs and thin sections of the cerebral ganglia of Lymnaea stagnalis demonstrate the advantages of ME-SIMS for chemical imaging mass spectrometry. Subcellular distributions of cellular analytes are clearly obtained, and the matrix provides an in situ height map of the tissue, allowing the user to identify rapidly regions prone to topographical artifacts and to deconvolute topographical losses in mass resolution and signal-to-noise ratio.     

Estimating Parameters of a Microsimulation Model for Breast Cancer Screening Using the Score Function Method

In developing decision-making models for the evaluation of medical procedures, the model parameters can be estimated by fitting the model to data observed in (randomized) trials. For complex models that are implemented by discrete event simulation (microsimulation) of individual life histories, the Score Function (SF) method can potentially be an appropriate approach for such estimation exercises. We test this approach for a microsimulation model for breast cancer screening that is fitted to data from the HIP randomized trial for early detection of breast cancer. Comparison of the parameter values estimated using the SF method and the analytical solution shows that method performs well on this simple model. The precision of the estimated parameter values depends (as expected) on the size of the sample of simulated life histories, and on the number of parameters estimated. Using analytical representations for parts of the microsimulation model can increase the precision of the estimated parameter values. Compared to the Nelder and Mead Simplex method which is often used in stochastic simulation because of its ease of implementation, the SF method is clearly more efficient (ratio computer time: precision of estimates). The additional analytical investment needed to implement the SF method in an (existing) simulation model may well be worth the effort.