In matrix derivatization combined with LC-MS/MS results in ultra-sensitive quantification of plasma free metanephrines and catecholamines

Plasma-free metanephrines and catecholamines are essential markers in the biochemical diagnosis and follow-up of neuroendocrine tumors and inborn errors of metabolism. However, their low circulating concentrations (in the nanomolar range) and poor fragmentation characteristics hinder facile simultaneous quantification by liquid chromatography and tandem mass spectrometry (LC-MS/MS). Here, we present a sensitive and simple matrix derivatization procedure using propionic anhydride that enables simultaneous quantification of unconjugated l-DOPA, catecholamines, and metanephrines in plasma by LC-MS/MS. Dilution of propionic anhydride 1:4 (v/v) in acetonitrile in combination with 50 μL of plasma resulted in the highest mass spectrometric response. In plasma, derivatization resulted in stable derivatives and increased sensitivity by a factor of 4-30 compared with a previous LC-MS/MS method for measuring plasma metanephrines in our laboratory. Furthermore, propionylation increased specificity, especially for 3-methoxytyramine, by preventing interference from antihypertensive medication (β-blockers). The method was validated according to international guidelines and correlated with a hydrophilic interaction LC-MS/MS method for measuring plasma metanephrines (R2 > 0.99) and high-performance liquid chromatography with an electrochemical detection method for measuring plasma catecholamines (R2 > 0.85). Reference intervals for l-DOPA, catecholamines, and metanephrines in n = 115 healthy individuals were established. Our work shows that analytes in the subnanomolar range in plasma can be derivatized in situ without any preceding sample extraction. The developed method shows improved sensitivity and selectivity over existing methods and enables simultaneous quantification of several classes of amines

Blood sampling for metanephrines comparing venipuncture vs. indwelling intravenous cannula in healthy subjects

Background: To diagnose pheochromocytoma or sympathetic paraganglioma, guidelines recommend blood sampling after at least 30 min of supine rest and using an indwelling intravenous cannula is preferred. Although blood sampling by venipuncture is more convenient and cost-effective, it is unknown whether venipuncture affects plasma concentrations of free metanephrines (MNs). We therefore investigated whether there is a difference in plasma concentrations of free MNs collected by venipuncture or by an intravenous cannula. Methods: We included 22 healthy participants (12 men and 10 women, median age 26 years). We collected blood using an indwelling cannula and venipuncture to determine plasma concentrations of free MNs and catecholamines, and calculated the median of the individually calculated absolute and relative differences. Results: Plasma concentrations of free MN, normetanephrine (NMN) and epinephrine were higher with blood sampling using venipuncture compared to that when using an indwelling cannula. The median (interquartile range [IQR]) difference was MN 0.020 (â'0.004 to 0.040) nmol/L, median percentage difference 20.5% (â'2.4 to 35.2%), NMN 0.019 (â'0.004 to 0.077) nmol/L, median percentage difference 4.6% (â'1.1 to 25.4%) and epinephrine 0.022 (0.007-0.079) nmol/L, median percentage difference 24.9% (7.8-83.3%). When the two sampling conditions were compared, plasma-free 3-methoxytyramine (3-MT), norepinephrine and dopamine concentrations did not differ. Conclusions: Blood sampling by venipuncture resulted in statistically significant higher concentrations of MN, NMN and epinephrine compared to sampling by means of an indwelling cannula. However, differences were small. For most patients it seems justifiable to collect blood via venipuncture

Self-trapped states and the related luminescence in PbCl2_2 crystals

We have comprehensively investigated localized states of photoinduced electron-hole pairs with electron-spin-resonance technique and photoluminescence (PL) in a wide temperature range of 5-200 K. At low temperatures below 70 K, holes localize on Pb$^{2+}$ ions and form self-trapping hole centers of Pb$^{3+}$. The holes transfer to other trapping centers above 70 K. On the other hand, electrons localize on two Pb$^{2+}$ ions at higher than 50 K and form self-trapping electron centers of Pb$_2$$^{3+}$. From the thermal stability of the localized states and PL, we clarify that blue-green PL band at 2.50 eV is closely related to the self-trapped holes.Comment: 8 pages (10 figures), ReVTEX; removal of one figure, Fig. 3 in the version

Towards Response ADAptive Radiotherapy for organ preservation for intermediate-risk rectal cancer (preRADAR): protocol of a phase I dose-escalation trial

Introduction Organ preservation is associated with superior functional outcome and quality of life (QoL) compared with total mesorectal excision (TME) for rectal cancer. Only 10% of patients are eligible for organ preservation following short-course radiotherapy (SCRT, 25 Gy in five fractions) and a prolonged interval (4–8 weeks) to response evaluation. The organ preservation rate could potentially be increased by dose-escalated radiotherapy. Online adaptive magnetic resonance-guided radiotherapy (MRgRT) is anticipated to reduce radiation-induced toxicity and enable radiotherapy dose escalation. This trial aims to establish the maximum tolerated dose (MTD) of dose-escalated SCRT using online adaptive MRgRT.Methods and analysis The preRADAR is a multicentre phase I trial with a 6+3 dose-escalation design. Patients with intermediate-risk rectal cancer (cT3c-d(MRF-)N1M0 or cT1-3(MRF-)N1M0) interested in organ preservation are eligible. Patients are treated with a radiotherapy boost of 2×5 Gy (level 0), 3×5 Gy (level 1), 4×5 Gy (level 2) or 5×5 Gy (level 3) on the gross tumour volume in the week following standard SCRT using online adaptive MRgRT. The trial starts on dose level 1. The primary endpoint is the MTD based on the incidence of dose-limiting toxicity (DLT) per dose level. DLT is a composite of maximum one in nine severe radiation-induced toxicities and maximum one in three severe postoperative complications, in patients treated with TME or local excision within 26 weeks following start of treatment. Secondary endpoints include the organ preservation rate, non-DLT, oncological outcomes, patient-reported QoL and functional outcomes up to 2 years following start of treatment. Imaging and laboratory biomarkers are explored for early response prediction.Ethics and dissemination The trial protocol has been approved by the Medical Ethics Committee of the University Medical Centre Utrecht. The primary and secondary trial results will be published in international peer-reviewed journals.Biological, physical and clinical aspects of cancer treatment with ionising radiatio

DEFECTS IN PbFCl

La conductivité ionique de monocristaux de PbFCl pur et dopé a été mesurée. La conductivité perpendiculaire à l'axe c est supérieure à la conductivité parallèle à cet axe d'environ trois puissances de 10 à la température ordinaire. Les nombres de transport ont été déterminés entre 510 et 550 K. Les expériences montrent que tPb est inférieur à 0,03, ce qui signifie que tF + tCl = 1. La conductivité de PbFCl a été comparée a la conductivité de PbC12 (défauts de Schottky) et de β-PbF2 (défauts anioniques de Frenkel). Cette comparaison, la conductivité des cristaux dopés et des considérations de structure sont en faveur d'un désordre thermique de Schottky.The ionic conductivity of undoped and doped PbFCl single crystals has been measured. The conductivity of PbFCl ⊥ c-axis exceeds at room temperature the conductivity || c-axis by about three powers of ten. Transference numbers have been deterrnined in the temperature region 510-550 K. The experiments revealed that tPb is less than 0.03, which means that tF + tCl = 1. The conductivity of PbFCl has been compared to the conductivity of PbCl2 (Schottky defects), and , β-PbF2 (anion Frenkel defects). This comparison, the conductivity of the doped crystals and structural considerations favour a thermal disorder of the Schottky-type

Precision radiotherapy using MR-linac for pancreatic neuroendocrine tumors in MEN1 patients (PRIME): a protocol for a phase I-II trial, and systematic review on available evidence for radiotherapy of pNETs.

BACKGROUND: Surgical resection is the standard of care for the treatment of pancreatic neuro-endocrine tumors (pNETs) in patients with Multiple Endocrine Neoplasia Type 1 (MEN1). However, surgery can cause significant short- and long-term morbidity. Magnetic resonance-guided radiotherapy (MRgRT) is a potential effective treatment with little side effects. With traditional radiotherapy techniques, irradiation of pancreatic tumors to high dose levels was hampered by poor visibility of the tumor during treatment. MRgRT uses onboard MRI to guide the treatment, thereby enabling delivery of ablative irradiation doses to the tumor, while sparing surrounding tissues. In this study, we describe results from a systematic review assessing efficacy of radiotherapy in pNET and present the protocol of the PRIME study. METHODS: PubMed, Embase and Cochrane Library were searched for articles assessing efficacy and side effects of radiotherapy for the treatment of pNETs. Risk of bias was assessed using the ROBINS-I Risk of Bias Tool for observational studies. Descriptive statistics were used to describe results of included trials. RESULTS: Four studies comprising of 33 patients treated by conventional radiotherapy were included. Despite the heterogeneity of studies, radiotherapy appeared to be effective for the treatment of pNETs with most patients responding (45.5%) or stabilizing (42.4%) in tumor size. CONCLUSION AND TRIAL DESIGN: Due to the limited literature available and concerns about damage to surrounding tissue, conventional radiotherapy is currently little used for pNETs. The PRIME study is a phase I-II trial with a single arm prospective cohort study design, investigating the efficacy of MRgRT in MEN1 patients with pNET. MEN1 patients with growing pNETs with a size between 1.0 and 3.0 cm without malignant features are eligible for inclusion. Patients are treated with 40 Gy in 5 fractions on the pNET, using online adaptive MRgRT on a 1.5T MR-linac. The primary endpoint is the change in tumor size at MRI 12 months follow-up. Secondary endpoints include radiotoxicity, quality of life, endocrine and exocrine pancreas function, resection rate, metastatic free and overall survival. When MRgRT is found effective with low radiotoxicity, it could reduce the need for surgery for pNET and preserve quality of life. SYSTEMATIC REVIEW REGISTRATION: PROSPERO https://clinicaltrials.gov/, (CRD42022325542)