Revisiting the HPLC-FLD Method to Quantify Paralytic Shellfish Toxins: C3,4 Quantification and the First Steps towards Validation

Paralytic shellfish toxins (PSTs) are a large group of biotoxins that cause paralytic shellfish poisoning. Their appearance in natural waters and their ingestion by aquatic species have a huge socio-economic impact, whereby their monitoring is of the upmost relevance to minimize the consequences. For earlier detection and faster response/action by stakeholders, validation of adjusted analytical methods, particularly for lower concentration levels, is important. This work proposes a derived High-Performance Liquid Chromatography method, with fluorescence detection (HPLC-FLD). The main differences from the official method are the size of the HPLC column and the gradient elution conditions. It covers the current eleven certified reference materials (CRM) available on the market, including the most recent—C3,4. This first calibration report for C3,4 suggests limits of detection (LOD) and limits of quantification (LOQ) of 6 nM and 19 nM (~5 µg STX.2HCl eqv./kg and 17 µg STX.2HCl eqv./kg), respectively. For the remaining CRM, LODs ranged between 3 and 28 nM (~0.9 and 127 µg STX.2HCl eqv./kg), while LOQs varied between 11 and 94 nM (~3 and 409 µg STX.2HCl eqv./kg, considering toxicity equivalency factors (TEFs) reported by EFSA).     

Evaluation of masticatory activity during unilateral single tooth clenching using muscle functional magnetic resonance imaging

Masticatory muscle activity during teeth clenching is affected by occlusal pattern. However, few studies have performed simultaneous evaluation of all masticatory activities during teeth clenching under various occlusal conditions. The aim of this study was to use muscle functional magnetic resonance imaging (mfMRI) to evaluate the effects of changes in occlusal point on masticatory activity during single tooth clenching. Changes in mean proton transverse relaxation time (?T2) as an index of activity in all masticatory muscles during left unilateral clenching at the first molar or first premolar for 1 min were examined in nine healthy volunteers. Bite force was maintained at 40% of the maximum voluntary clenching force. The ?T2 values of the masseter and lateral pterygoid muscles were analysed separately for superficial and deep layers, and for superior and inferior heads. The ?T2 values for the ipsilateral deep masseter were significantly lower, and for the superior head of the ipsilateral lateral pterygoid muscles were significantly higher, after left first premolar clenching compared to left first molar clenching. These results quantitatively demonstrate a significant increase in activity of the superior head of the ipsilateral lateral pterygoid muscle and a significant decrease in activity of the ipsilateral deep masseter muscle with forward displacement of the occlusal contact point during unilateral tooth clenching.     

Assessing the variability of 23Na MRI in skeletal muscle tissue: Reproducibility and repeatability of tissue sodium concentration measurements in the lower leg at 3 T

The goal of this study was to evaluate the reproducibility and repeatability of tissue sodium concentration (TSC) measurements using ²³Na MRI in skeletal muscle tissue. ²³Na MRI was performed at 3 T on the right lower leg of eight healthy volunteers (aged 28 ± 4 years). The examinations were repeated at the same site after ~ 22 weeks to assess the variability over a medium‐term period. Additionally, they were scanned at a second site shortly before or shortly after the first visit (within 3 weeks) to evaluate the inter‐site reproducibility. Moreover, we analysed the effect of B₀ correction on the variability. Coefficients of variations (CVs) from mean TSC values as well as Bland–Altman plots were used to assess intra‐site repeatability and inter‐site reproducibility. In phantom measurements, the B₀ correction improved the quantitative accuracy. We observed differences of up to 4.9 mmol/L between the first and second visit and a difference of up to 3.7 mmol/L between the two different sites. The CV for the medium‐term repeatability was 15% and the reproducibility CV was 9%. The Bland–Altman plots indicated high agreement between the visits in all muscle regions. The systematic bias of ?0.68 mmol/L between site X and Y (P = 0.03) was slightly reduced to ?0.64 mmol/L after B₀ correction (P = 0.04). This work shows that TSC measurements in healthy skeletal muscle tissue can be performed with good repeatability and reproducibility, which is of importance for future longitudinal or multicentre studies.     

Cortical circumferential profile of SPECT cerebral perfusion in Alzheimer''s disease

We developed a semiautomatic method termed “cortical circumferential profiling” for objective analysis of cerebral cortex function in emission tomographic neuroimaging studies. This method treats cortex as a continuous ring near the outer brain edge. A computer algorithm samples the cortex at 60 contiguous, equiangular locations, using 1-cm² samples. These values are plotted as a function of cortical angle to produce the cortical circumferential profile. This method was used in a study of regional cerebral perfusion in 15 patients with Alzheimer's disease and 8 elderly control subjects using N-isopropyl [I-123]-iodoamphetamine. Cortical circumferential profiling decreases variability, examines the entire cortex within slices at preselected levels above the orbital-meatal line, and facilitates intrasubject and intersubject comparisons.     

Synaptic analysis of amacrine cells with neuropeptide Y-like immunoreactivity in turtle retina

Neuropeptide Y-like immunoreactivity has been localized previously within three classes of amacrine cells in the turtle retina. We have used the avidin-biotin with horseradish peroxidase technique to label these neurons for examination at the ultrastructural level to answer the following questions. Where are the synaptic contacts of these neurons made? What types of neurons are involved pre- and postsynaptically? What is the intracellular distribution of the immunoreactivity? Processes with neuropeptide Y-like immunoreactivity were located primarily within three regions of the inner plexiform layer: stratum 1, stratum 3, and at the border between strata 4 and 5. In all three regions the processes with neuropeptide Y-like immunoreactivity received synaptic contacts from both unlabeled amacrine and bipolar cells, but the majority of the synaptic input in all three regions was from unlabeled amacrine cells. Processes with neuropeptide Y-like immunoreactivity were presynaptic to unlabeled amacrine cells in all three regions, but also formed contacts onto unlabeled bipolar cells in the region between strata 4 and 5. The immunoreactivity within these cells gave rise to a diffuse reaction product that was distributed throughout the cytoplasm and within large vesicles. This localization of neuropeptide Y-like immunoreactivity within large vesicles suggests that this peptide may play a neuromodulatory role. Such a role would be consistent with previous studies of neuropeptides in the turtle retina.     

声触诊组织成像量化技术评估正常人群冈上肌腱弹性变化

目的 探讨声触诊组织成像量化技术（VTIQ）评估正常人冈上肌腱弹性变化的价值。方法 对120名健康志愿者行二维超声及VTIQ检查,根据年龄将其分为组1（20~39岁）、组2（40~59岁）及组3（≥ 60岁）。测量冈上肌腱最大厚度及其浅层、深层剪切波速度（SWV）,比较不同性别、年龄组及优势手与非优势手侧冈上肌腱厚度及浅层与深层SWV值的差异。结果 同一性别内优势手侧与非优势手侧、不同性别间非优势手侧及优势手侧冈上肌腱厚度值差异均无统计学意义（P均>0.05）。3组间优势手侧及非优势手侧冈上肌腱厚度值差异均有统计学意义（P均<0.05）;组3优势手侧及非优势手侧冈上肌腱厚度均大于组1及组2（P均<0.05）,组1与组2差异均无统计学意义（P均>0.05）。3组组内优势手侧与非优势手侧冈上肌腱厚度值差异均无统计学意义（P均>0.05）。3组间优势手侧及非优势手侧冈上肌腱浅层、深层SWV值差异均有统计学意义（P均<0.001）;3组组内优势手侧冈上肌腱浅层、深层SWV值与非优势手侧差异均无统计学意义（P均>0.05）,但优势手侧及非优势手侧冈上肌腱深层SWV值大于浅层（P均<0.05）。组3男性冈上肌腱浅层及深层SWV均高于女性（P均<0.05）,其余2组差异均无统计学意义（P均>0.05）。结论 肌腱退行性变时,不仅在形态学上表现为厚度增加,在力学特征上还可表现为肌腱软化。VTIQ可间接评价冈上肌腱弹性变化。     

On the use of R1 and R2* for measurement of contrast agent concentration in isolated perfused rat liver

We present experimental MRI protocols at 4.7 T for quantitative determination of the Dotarem distribution volume in isolated perfused rat liver. The procedures involved either constant contrast agent (CA) concentration or bolus administration conditions. R1 and R2* effects of the CA in liver and perfusate were measured using gradient echo fast imaging (GEFI) experiments by varying either the excitation angle or the echo time. CA concentrations in liver and perfusate were also measured after MRI by inductively coupled plasma atomic emission spectroscopy, in order to determine in situ relaxivities in the perfusate (r1=4.2 +/- 0.1 s(-1) mm(-1), r2*=17 +/- 2 s(-1) mm(-1)) and in the liver (r1=7.2 +/- 0.2 s(-1) mm(-1), r2*=99 +/- 5 s(-1) mm(-1)). When CA concentrations were estimated from R1 measurements and r1, the CA distribution volume estimations in liver resulting from bolus (0.31 +/- 0.01) and stationary (0.32 +/- 0.05) experiments were not significantly different. In contrast, after a bolus, CA concentrations derived from R2* and r2* were overestimated in liver and even more in perfusate. However, with R1 and R2* being measured before CA bolus administration, zero echo time signal intensities computed from multiple TE measurements during multiple boli yielded good estimations of R1 and thus correct CA concentrations in liver and in perfusate. Under these conditions, a single multi-echo GEFI acquisition should be sufficient to determine the concentration-time curves. Consequently, this protocol should be appropriate to rapidly estimate the distribution volume in vivo when multiple boli have to be avoided.