112 research outputs found
Measurement of hepcidin isoforms in human serum by liquid chromatography with high resolution mass spectrometry
Aim: Hepcidin-25 is the master regulator of iron homeostasis. N-truncated isoforms of hepcidin-25 have been identified (hepcidin-20, -22, -24), although data on the concentrations of these isoforms are sparse. Materials & methods: Serum was mixed with aqueous formic acid, and the supernatant loaded onto a 96-well-SPE-plate. Eluted analytes were analyzed using LC–HR-MS. Forty-seven paired dipotassium-EDTA human plasma and serum samples were analyzed. Results: The LLOQ was 1 μg/l (all analytes). Accuracy and precision were acceptable. There was a good correlation (R2 >0.90, all analytes) between matrices. The median (range) serum hepcidin-20, -22, -24 and -25 concentrations measured were 4 (1–40), 8 (2–20), 8 (1–50) and 39 (1–334) μg/l, respectively. Conclusion: LC–HR-MS is widely applicable to the measurement of hepcidin-25, and truncated isoforms. </jats:p
Sex differences in plasma clozapine and norclozapine concentrations in clinical practice and in relation to body mass index and plasma glucose concentrations: a retrospective survey
Background
Clozapine is widely prescribed and, although effective, can cause weight gain and dysglycemia. The dysmetabolic effects of clozapine are thought to be more prevalent in women with this gender on average attaining 17Â % higher plasma clozapine concentrations than men.
Methods
We investigated the relationship between dose, body mass index (BMI), plasma glucose concentration, and plasma clozapine and N-desmethylclozapine (norclozapine) concentrations in 100 individuals with a severe enduring mental illness.
Results
Mean (10th/90th percentile) plasma clozapine concentrations were higher for women [0.49 (0.27–0.79) mg/L] compared with men [0.44 (0.26–0.70) mg/L] (F = 2.2; p = 0.035). There was no significant gender difference in the prescribed clozapine dose. BMI was significantly higher in women [mean (95 % CI) = 34.5 (26.0–45.3)] for females compared with 32.5 (25.2–41.0) for males. Overall, BMI increased by 0.7 kg/m 2 over a mean follow-up period of 210 days. A lower proportion, 41 % of women had a fasting blood glucose ≤6.0 mmol/L (<6.0 mmol/L is defined by the International Diabetes Federation as normal glucose handling), compared with 88 % of men (χ2  = 18.6, p < 0.0001).
Conclusions
We have shown that mean BMI and blood glucose concentrations are higher in women prescribed clozapine than in men. Women also tended to attain higher plasma clozapine concentrations than men. The higher BMI and blood glucose in women may relate to higher tissue exposure to clozapine, as a consequence of sex differences in drug metabolism
Changes in smoking status, mental state and plasma clozapine concentration: retrospective cohort evaluation
Aims and method. To investigate the percentage of patients who commenced smoking after transferring out of a non-smoking forensic psychiatric unit, the corresponding clozapine dose adjustments, the effects on plasma clozapine/norclozapine concentrations and observed changes in mental state. We reviewed the notes and plasma clozapine/norclozapine concentrations of 46 patients transferred to medium secure units between July 2008 and December 2013. Results. Thirty-five patients commenced smoking. Their median clozapine dose was increased by 50 mg/d. In the non-smokers, the median clozapine dose remained unchanged. Plasma clozapine/norclozapine concentrations were significantly reduced in smokers despite dosage adjustment. Eighteen patients experienced deterioration in mental state after transfer; almost all these patients were smokers. Clinical implications. Approximately three-quarters of patients who were non-smokers by virtue of being in a secure non-smoking environment commenced smoking after transfer. Monitoring of clozapine serum levels and assessment of mental state in the immediate period after a change in smoking status is indicated
Utilization of data below the analytical limit of quantitation in pharmacokinetic analysis and modeling: promoting interdisciplinary debate
Traditionally, bioanalytical laboratories do not report actual concentrations for samples with results below the LOQ (BLQ) in pharmacokinetic studies. BLQ values are outside the method calibration range established during validation and no data are available to support the reliability of these values. However, ignoring BLQ data can contribute to bias and imprecision in model-based pharmacokinetic analyses. From this perspective, routine use of BLQ data would be advantageous. We would like to initiate an interdisciplinary debate on this important topic by summarizing the current concepts and use of BLQ data by regulators, pharmacometricians and bioanalysts. Through introducing the limit of detection and evaluating its variability, BLQ data could be released and utilized appropriately for pharmacokinetic research
Gravitational Lensing with Three-Dimensional Ray Tracing
High redshift sources suffer from magnification or demagnification due to
weak gravitational lensing by large scale structure. One consequence of this is
that the distance-redshift relation, in wide use for cosmological tests,
suffers lensing-induced scatter which can be quantified by the magnification
probability distribution. Predicting this distribution generally requires a
method for ray-tracing through cosmological N-body simulations. However,
standard methods tend to apply the multiple thin-lens approximation. In an
effort to quantify the accuracy of these methods, we develop an innovative code
that performs ray-tracing without the use of this approximation. The efficiency
and accuracy of this computationally challenging approach can be improved by
careful choices of numerical parameters; therefore, the results are analysed
for the behaviour of the ray-tracing code in the vicinity of Schwarzschild and
Navarro-Frenk-White lenses. Preliminary comparisons are drawn with the multiple
lens-plane ray-bundle method in the context of cosmological mass distributions
for a source redshift of .Comment: 17 pages, 10 figures, 0 tables; Accepted for publication in MNRA
The effect of non--gravitational gas heating in groups and clusters of galaxies
We present a set of gas-dynamical simulations of galaxy groups and clusters
aimed at exploring the effect of non-gravitational heating. We use GASOLINE, a
parallel Tree+SPH code, to simulate the formation of four cosmic halos with
temperature 0.5<T<8 keV. Non-gravitational heating is implemented in two
different ways: (1) by imposing a minimum entropy floor at a given redshift,
1<z<5; (2) by gradually heating gas, proportionally to the SN rate expected
from semi-analytical modeling of galaxy formation. Our main results are the
following. (a) An extra heating energy of about 1 keV per gas particle is
required to reproduce the observed Lx-T relation, independent of whether it is
provided so as to create an entropy floor of 50-100 keV cm^2, or is modulated
in redshift; our SN feedback recipe provides only 1/3 keV/part. (b) The M-T
relation is almost unaffected by non-gravitational heating and follows the M
T^{3/2} scaling, with a normalization ~40% higher than observed, independent of
the heating scheme. The inclusion of cooling in a run of a small group has the
effects of increasing T_ew by ~30%, possibly reconciling simulated and observed
M-T relations, and of decreasing Lx by ~40%. In spite of the inclusion of SN
feedback energy, almost 40% of the gas becomes cold, in excess of current
observational estimates. (abridged)Comment: 18 pages, 15 figures, to appear in MNRAS. Version with high
resolution images available at
http://www.daut.univ.trieste.it/borgani/LT/lt_1.ps.g
Atomic-resolution imaging of surface and core melting in individual size-selected Au nanoclusters on carbon
Experimental and theoretical data sets for the Nature Communications paper "Atomic-resolution imaging of surface and core melting in individual size-selected Au nanoclusters on carbon". Data structure and formats are described in the README.docx file
Bioanalytical Studies of the Assessment of Vitamin D Status
The most widely used and clinically accepted biochemical marker for assessing vitamin D status is the total serum 25-hydroxyvitamin D (25-OHD) concentration. In high-throughput clinical diagnostic laboratories, there is a trend towards the use of fully-automated clinical analysers for such assays. This means that immunoassays are commonly used, despite significant inter-assay variability due to varying concentrations of other related vitamin D metabolites and sample-to-sample matrix differences. It is important for clinicians requesting 25-OHD analyses to understand these issues and limitations, and where necessary to confront laboratories for details of analytical methods used. The availability of reference measurement procedures for 25-OHD based on liquid chromatography and tandem mass spectrometry (LC-MS/MS), whilst not intended for routine clinical sample analysis, should be utilised to improve assay harmonisation and reduce interlaboratory variability. The development of higher-throughput, semi-automated LC-MS/MS methods for routine application is also increasing due to recognition of the pitfalls of immunoassay-based methods for 25-OHD analysis, as well as the opportunity to individually measure multiple vitamin D metabolites. This thesis will discuss the reasons for ongoing 25-OHD assay variability, but will also discuss the novel application of LC-MS/MS to larger molecules related to the assessment vitamin D status. These include the analysis of parathyroid hormone (PTH) and PTH variants, and the three major isoforms of vitamin D binding protein
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