Imaging performance of phase-contrast breast computed tomography with synchrotron radiation and a CdTe photon-counting detector

PurposeWithin the SYRMA-CT collaboration based at the ELETTRA synchrotron radiation (SR) facility the authors investigated the imaging performance of the phase-contrast computed tomography (CT) system dedicated to monochromatic in vivo 3D imaging of the female breast, for breast cancer diagnosis.MethodsTest objects were imaged at 38 keV using monochromatic SR and a high-resolution CdTe photon-counting detector. Signal and noise performance were evaluated using modulation transfer function (MTF) and noise power spectrum. The analysis was performed on the images obtained with the application of a phase retrieval algorithm as well as on those obtained without phase retrieval. The contrast to noise ratio (CNR) and the capability of detecting test microcalcification clusters and soft masses were investigated.ResultsFor a voxel size of (60 μm)³, images without phase retrieval showed higher spatial resolution (6.7 mm⁻¹ at 10% MTF) than corresponding images with phase retrieval (2.5 mm⁻¹). Phase retrieval produced a reduction of the noise level and an increase of the CNR by more than one order of magnitude, compared to raw phase-contrast images. Microcalcifications with a diameter down to 130 μm could be detected in both types of images.ConclusionsThe investigation on test objects indicates that breast CT with a monochromatic SR source is technically feasible in terms of spatial resolution, image noise and contrast, for in vivo 3D imaging with a dose comparable to that of two-view mammography. Images obtained with the phase retrieval algorithm showed the best performance in the trade-off between spatial resolution and image noise.     

Effect of high tannin grain sorghum on gastrointestinal parasite fecal egg counts in goats

The objective of three experiments was to determine the influence of high condensed tannin (CT) grain sorghum on gastrointestinal parasite fecal egg counts (FEC). Sixteen naturally infected Boer crossbred mixed-sex goats were used. Animals that were supplemented with grain daily were removed from pasture and placed in individual pens and fed treatment diets for 21 or 14 days (Experiment 3). Goats were allowed ad libitum access to water and diets containing high or low CT cracked grain sorghum. On day 0 and every 7 days thereafter, PCV, FEC and FAMACHA^® eyelid color scores (EYE; Experiment 1 only) were recorded. For Experiment 1, percentage of animals dewormed, PCV and EYE were not influenced by treatment and averaged 13.6 ± 4.5% per treatment period, 23.4 ± 0.8% and 3.2 ± 0.12, respectively, for all animals. The FEC increased after day 0 for control but not high tannin grain sorghum fed goats (treatment by day interaction, P < 0.02). As expected, EYE and PCV were negatively related (r = −0.45; P < 0.0005). For Experiment 2, there was no influence of diet on PCV or FEC, but there was an effect of day on FEC (P < 0.002) in which all goats had higher FEC on day 0 (1956 ± 219 eggs/g) than any other sampling day. For Experiment 3, there was no effect of feeding high CT grain sorghum on FEC (2992 ± 591 eggs/g) or PCV (25.1 ± 0.5%). In these studies, high CT grain sorghum did not consistently influence FEC and did not impact PCV or number of animals requiring chemical anthelmintic treatment.     

Effects of the cooling mode on the structure and strength of porous scaffolds made of chitosan,alginate, and carboxymethyl cellulose by the freeze-gelation method

A freeze-gelation method was utilized to prepare porous scaffolds made of chitosan, alginate, and carboxymethyl cellulose because of their usefulness in tissue engineering applications. These polysaccharide solutions were cooled down to freezing using either a fast-cooling (FC) mode (>20 °C/min) or a slow-cooling (SC) mode (0.83 °C/min). Then the frozen polysaccharide solutions were immersed in their respective non-solvents to form porous scaffolds. Based on the SEM and optical microscope images of the scaffolds, the FC mode induced non-simultaneous nucleation and generated directional pore structures. In contrast, simultaneous nucleation and uniform and isotropic pore structures (mean pore size: 60–100 μm) were obtained by using the SC mode. Moreover, the tensile strength of the scaffolds prepared by the SC mode (about 60 N/g) was three times higher than that of scaffolds prepared by the FC mode (about 20 N/g). This study reveals that when using the freeze-gelation method, the cooling rate (mode) is a crucial factor which controls the pore structure and strength of porous scaffolds. Therefore, our results suggest that polysaccharide scaffolds with pore structures suitable for tissue engineering applications can be obtained via an appropriate cooling mode.     

Object shape dependency of in-plane resolution for iterative reconstruction of computed tomography

The present study aimed to investigate whether the in-plane resolution property of iterative reconstruction (IR) of computed tomography (CT) data is object shape-dependent by testing columnar shapes with diameters of 3, 7, and 10 cm (circular edge method) and a cubic shape with 5-cm side lengths (linear edge method). For each shape, objects were constructed of acrylic (contrast in Hounsfield units [ΔHU] = 120) as well as a soft tissue equivalent material (ΔHU = 50). For each shape, we measured the modulation transfer functions (MTFs) of IR and filtered back projection (FBP) using two multi-slice CT scanners at scan doses of 5 and 10 mGy. In addition, we evaluated a thin metal wire using the conventional method at 10 mGy. For FBP images, the MTF results of the tested objects and the wire method showed substantial agreement, thus demonstrating the validity of our analysis technique. For IR images, the MTF results of different shapes were nearly identical for each object contrast and dose combination, and we did not observe shape-dependent effects of the resolution properties of either tested IR. We conclude that both the circular edge method and linear edge method are equally useful for evaluating the resolution properties of IRs.     

BMIT facility at the Canadian Light Source: Advances in X-ray phase-sensitive imaging

The BioMedical Imaging and Therapy (BMIT) facility [1,2] located at the Canadian Light Source, provides synchrotron-specific imaging and radiation therapy capabilities. There are two separate beamlines used for experiments: the bending magnet (05B1-1) and the insertion device (05ID-2) beamline.The bending magnet beamline provides access to monochromatic beam spanning a spectral range of 15–40 keV, and the beam is 240 mm wide in the POE-2 experimental hutch. Users can also perform experiments with polychromatic (pink) beam.The insertion device beamline was officially opened for general user program in 2015. The source for the ID beamline is a multi-pole, superconducting 4.3 T wiggler. The high field gives a critical energy over 20 keV. The optics hutches prepare a beam that is 220 mm wide in the last experimental hutch SOE-1. The monochromatic spectral range spans 25–150+ keV. Several different X-ray detectors are available for both beamlines, with resolutions ranging from 2 μm to 200 μm.BMIT provides a number of imaging techniques including standard absorption X-ray imaging, K-edge subtraction imaging (KES), in-line phase contrast imaging (also known as propagation based imaging, PBI) and Diffraction Enhanced Imaging/Analyzer Based Imaging (DEI/ABI), all in either projection or CT mode. PBI and DEI/ABI are particularly important tools for BMIT users since these techniques enable visualization of soft tissue and allow for low dose imaging.     

Braking characteristics during cutting and pivoting in female soccer players

Most biomechanical studies into changing direction focus on final contact (FC), whilst limited research has examined penultimate contact (PEN). The aim of this study was to explore the kinematic and kinetic differences between PEN and FC of cutting and pivoting in 22 female soccer players (mean ± SD; age: 21 ± 3.1 years, height: 1.68 ± 0.07 m, mass: 58.9 ± 7.3 kg). Furthermore, the study investigated whether horizontal force–time characteristics during PEN were related to peak knee abduction moments during FC. Three dimensional motion analyses of cutting and pivoting on the right leg were performed using Qualysis ‘Proreflex’ infrared cameras (240 Hz). Ground reaction forces (GRF) were collected from two AMTI force platforms (1200 Hz) to examine PEN and FC. Both manoeuvres involved significantly (P < 0.05) greater knee joint flexion angles, peak horizontal GRF, but lower average horizontal GRF during PEN compared to FC. Average horizontal GRF during PEN (R = −0.569, R² = 32%, P = 0.006) and average horizontal GRF ratio (R = 0.466, R² = 22%, P = 0.029) were significantly related to peak knee abduction moments during the FC of cutting and pivoting, respectively. The results indicate PEN during pre-planned changing direction helps reduce loading on the turning leg where there is greater risk of injuries to knee ligaments.     

Cerebral aneurysm blood flow simulations are sensitive to basic solver settings

Computational modeling of peri-aneurysmal hemodynamics is typically carried out with commercial software without knowledge of the sensitivity of the model to variation in input values. For three aneurysm models, we carried out a formal sensitivity analysis and optimization strategy focused on variation in timestep duration and model residual error values and their impact on hemodynamic outputs. We examined the solution sensitivity to timestep sizes of 10⁻³ s, 10⁻⁴ s, and 10⁻⁵ s while using model residual error values of 10⁻⁴, 10⁻⁵, and 10⁻⁶ using ANSYS Fluent to observe compounding errors and to optimize solver settings for computational efficiency while preserving solution accuracy. Simulations were compared qualitatively and quantitatively against the most rigorous combination of timestep and residual parameters, 10⁻⁵ s and 10⁻⁶, respectively. A case using 10⁻⁴ s timesteps, with 10⁻⁵ residual errors proved to be a converged solution for all three models with mean velocity and WSS difference RMS errors less than <1% compared with baseline, and was computationally efficient with a simulation time of 62 h per cardiac cycle compared to 392 h for baseline for the model with the most complex flow simulation. The worst case of our analysis, using 10⁻³ s timesteps and 10⁻⁴ residual errors, was still able to predict the dominant vortex in the aneurysm, but its velocity and WSS RMS errors reached 20%. Even with an appealing simulation time of 11 h per cycle for the model with the most complex flow, the worst case analysis solution exhibited compounding errors from large timesteps and residual errors. To resolve time-dependent flow characteristics, CFD simulations of cerebral aneurysms require sufficiently small timestep size and residual error. Simulations with both insufficient timestep and residual resolution are vulnerable to compounding errors.     

Gender Determines Serum Free Cortisol: Higher Levels in Men

Objective: Because only the free fraction of serum cortisol can readily access glucocorticoid receptors, we investigated whether or not a gender-related difference in serum free cortisol (FC) exists in the basal and adrenocorticotropic hormone (ACTH)-stimulated state.Methods: Serum total cortisol (TC) and FC were measured in 323 subjects (175 men; 148 women). Additionally, the low-dose 1-μg ACTH test was performed in 56 subjects (30 women, 26 men). Subjects were healthy volunteers, recruited in a preventive medicine screening program and an outpatient clinic.Results: Overall, basal serum TC and FC level were ~18 and ~33%, respectively, higher in men than in women (TC, 14.5 ± 0.33 μg/dL vs. 12.3 ± 0.33 μg/dL; P<.0001; FC, 0.68 ± 0.02 μg/dL vs. 0.51 ± 0.02 μg/dL; P<.0001). The higher FC in men relative to women was apparent across a wide age range (17 to 86 years) and persisted after adjustment for age and body mass index. The FC fraction (%FC, out of TC) was concordantly higher in men (5.4 ± 0.09% vs. 4.8 ± 0.3%; P = .046). FC was not related to the estimated menopausal status (women age below and above 47, 50, or 53 years). ACTH-stimulated FC levels were significantly higher in men compared to women, as reflected by the area under the response curve (49.4 ± 3.4 μg × min vs. 39.6 ± 2.2 μg × min; P = .0014).Conclusion: Gender is an unrecognized determinant of serum FC in humans. The possibility of lifelong exposure to the higher bioactive fraction of cortisol under basal conditions or daily stress involving ACTH stimulation should be further investigated in the context of gender-related phenotypic features such as “android” (visceral) fat deposition and longevity.Abbreviations:ACTH = adrenocorticotropic hormoneBMI = body mass indexCBG = cortisol-binding globulinFC = free cortisolHPA = hypothalamic-pituitary-adrenalTC = total cortisol     

Chemical bioimaging for the subcellular localization of trace elements by high contrast TEM,TEM/X-EDS,and NanoSIMS

Chemical bioimaging offers an important contribution to the investigation of biochemical functions, biosorption and bioaccumulation processes of trace elements via their localization at the cellular and even at the subcellular level. This paper describes the combined use of high contrast transmission electron microscopy (HC-TEM), energy dispersive X-ray spectroscopy (X-EDS), and nano secondary ion mass spectrometry (NanoSIMS) applied to a model organism, the unicellular green algae Chlamydomonas reinhardtii. HC-TEM providing a lateral resolution of 1 nm was used for imaging the ultrastructure of algae cells which have diameters of 5–10 μm. TEM coupled to X-EDS (TEM/X-EDS) combined textural (morphology and size) analysis with detection of Ca, P, K, Mg, Fe, and Zn in selected subcellular granules using an X-EDS probe size of approx. 1 μm. However, instrumental sensitivity was at the limit for trace element detection. NanoSIMS allowed chemical imaging of macro and trace elements with subcellular resolution (element mapping). Ca, Mg, and P as well as the trace elements Fe, Cu, and Zn present at basal levels were detected in pyrenoids, contractile vacuoles, and granules. Some metals were even localized in small vesicles of about 200 nm size. Sensitive subcellular localization of trace metals was possible by the application of a recently developed RF plasma oxygen primary ion source on NanoSIMS which has shown good improvements in terms of lateral resolution (below 50 nm), sensitivity, and stability. Furthermore correlative single cell imaging was developed combining the advantages of TEM and NanoSIMS. An advanced sample preparation protocol provided adjacent ultramicrotome sections for parallel TEM and NanoSIMS analyses of the same cell. Thus, the C. reinhardtii cellular ultrastructure could be directly related to the spatial distribution of metals in different cell organelles such as vacuoles and chloroplast.     

Contrast enhancement of speckle patterns from blood in synchrotron X-ray imaging

Hemodynamics has been a very important factor in understanding and diagnosing various vascular diseases. Recently, the X-ray particle image velocimetry (X-ray PIV) method using speckle patterns of blood has been introduced as a new quantitative visualization method for blood flows without any seeding tracer or contrast agents. In this study, the peculiar optical characteristics of blood on the synchrotron X-ray imaging method, which were not presented in previous studies, were investigated in depth and systematically. The experimental conditions required for X-ray PIV application were found to be the distance between the sample and the scintillator (～40 cm), the thickening of the blood sample (>0.3 mm), and hematocrit (20.0–80.0%). In addition, we verified that the X-ray PIV method is reliable as an advanced flow velocimetry by comparing the flow rate evaluated from the X-ray PIV result and the input flow rate supplied from a syringe pump with an error of less than 1%. Through this study, based on the understanding of contrast enhancement mechanisms of speckle patterns from blood, we could establish a trustworthy flow visualization method that can be used effectively in hemodynamic studies.     

Développement clinique de l’IRM du tenseur de diffusion de la moelle épinière dans un contexte de lésion médullaire

Magnetic resonance diffusion tensor imaging of the spinal cord is challenging because of the cord's thin structure and the presence of physiological and susceptibility artifacts. To circumvent these issues, we developed a methodology for imaging the thoraco-lumbar spinal cord of cats at 3 T using single-shot spin-echo echo planar imaging. The presented method could potentially be applied to humans since it was developed on a clinical scanner with a standard spine coil. Results provide (1) suggestions for optimal slice orientation and phase encoding direction; (2) an assessment of the benefits of parallel imaging to reduce geometric distortions; (3) the feasibility of acquiring quality diffusion weighted data in 13 min at a resolution of 1.1 mm³ and (4) the determination of axonal disruption, in two cats with complete spinal cord transection, using tractography.     

Determination of half value layers of X-ray equipment using computed radiography imaging plates

A method for determining half value layers (HVLs) of inverter-type X-ray equipment using a computed radiography (CR) systems was developed. This method is similar to the traditional method, where the air kerma (K) is measured using an ionization based dosimeter and increasing aluminum (Al) absorber thickness, but utilized an imaging plate (IP) and the sensitivity index (S number) of the CR system as the dosimeter and the dosimeter reading, respectively. The IP and the S number were calibrated using an ionization chamber having traceability to the National Standard Ionization Chamber. A modified version of the S number definition equation $K=a\times S^{?b}$ was used to translate the S number to K values for X-ray beams produced using tube voltages ranging from 50 to 120 kV and additional Al filtration up to 2.5 mm. The coefficient ‘a’ varied depending on the beam quality, while the coefficient ‘b’ showed a constant value of 0.991. The HVLs in the range from 1.8 to 5.5 mm Al that were obtained with this method were in good agreement with those obtained with the traditional method, as uncertainties were between ?7 and 4%. This method can be used to determine the HVLs of inverter-type X-ray equipment within an acceptable accuracy.     

Digital breast tomosynthesis: Dose and image quality assessment

The aim of this work was to evaluate how different acquisition geometries and reconstruction parameters affect the performance of four digital breast tomosynthesis (DBT) systems (Senographe Essential – GE, Mammomat Inspiration – Siemens, Selenia Dimensions – Hologic and Amulet Innovality – Fujifilm) on the basis of a physical characterization.Average Glandular Dose (AGD) and image quality parameters such as in-plane/in-depth resolution, signal difference to noise ratio (SDNR) and artefact spread function (ASF) were examined.Measured AGD values resulted below EUREF limits for 2D imaging. A large variability was recorded among the investigated systems: the mean dose ratio DBT/2D ranged between 1.1 and 1.9.In-plane resolution was in the range: 2.2 mm⁻¹–3.8 mm⁻¹ in chest wall-nipple direction. A worse resolution was found for all devices in tube travel direction.In-depth resolution improved with increasing scan angle but was also affected by the choice of reconstruction and post-processing algorithms. The highest z-resolution was provided by Siemens (50°, FWHM = 2.3 mm) followed by GE (25°, FWHM = 2.8 mm), while the Fujifilm HR showed the lowest one, despite its wide scan angle (40°, FWHM = 4.1 mm).The ASF was dependent on scan angle: smaller range systems showed wider ASF curves; however a clear relationship was not found between scan angle and ASF, due to the different post processing and reconstruction algorithms.SDNR analysis, performed on Fujifilm system, demonstrated that pixel binning improves detectability for a fixed dose/projection.In conclusion, we provide a performance comparison among four DBT systems under a clinical acquisition mode.     

Effects of heather and oat supplementation on gastrointestinal nematode infections and performance of grazing Cashmere goats

This work aimed to evaluate the effects of tannin-containing heather (Calluna vulgaris, Erica spp.) and energy (oats, Avena sativa) supplementation, combined or not, on feed intake, gastrointestinal nematode infections and performance of goats grazing mountain grasslands. Two successive experiments were established across one grazing season on four paddocks. The first (late April to early August, Period 1) involved two treatments, i.e., supplementation with heather (+H) vs. non-supplementation (−H), each randomly allocated to two paddocks. The second (mid-August to mid-November, Period 2) consisted on four treatments in a 2 × 2 factorial design, i.e., supplementation with heather and oats (+H+O), only heather (+H−O), only oats (−H+O), and no supplementation (−H−O). Results from Period 1 indicated that faecal nematode egg counts (FEC) were lower in +H goats (50% less in August), achieving more favourable live weight (LW) and body condition changes than −H goats. Total dry matter intake (DMI) in June was similar between treatments, with heather accounting for 0.21 of +H goat diets. Kids FEC and LW gains were not affected by heather supplementation. In Period 2, both heather and oat supplementation reduced FEC (45 and 61%, respectively) and improved goat performance, without an interaction between both factors. Total DMI in October was higher in +H+O compared to other treatments (48 vs. 30 g DM kg LW^−0.75 d⁻¹; P < 0.01). Rumen ammonia concentration was lower (P < 0.001) in +H than in −H goats, and in +O than in −O goats, whereas that of volatile fatty acids (VFA) was not affected by treatments, though the molar proportions of some VFA were modified. It is concluded that the combination of both supplements (tannins and energy) contributes to reduce gastrointestinal nematode parasitism and increases goat performance, allowing a lower dependence on conventional chemotherapy.     

Vascular imaging in small rodents using micro-CT

In vivo animal models of neoplasm, stroke, subarachnoid hemorrhage, and other diseases involving alterations in vessel anatomy and diameter, require a fast and easy-to-use imaging tool that captures anatomical structure and biologic function data. Micro-computed tomography angiography (μCTA) offers high spatial and temporal resolution and is suitable to perform this task. However, conducting μCTA in small rodents, especially in mice, requires a high degree of accuracy and precision. This article describes a setup for in vivo μCTA in mice using both a bolus technique with a conventional contrast agent, as well as, angiography with a blood-pool contrast agent. Our setup in mice is at isotropic resolutions up to 16 μm with scanning times less than 1 min. The described protocol also addresses some of the technical challenges associated with the imaging of vascular structures in mice models.     

Effective dose and image quality for intraoperative imaging with a cone-beam CT and a mobile multi-slice CT in spinal surgery: A phantom study

PurposeTo compare the effective dose (ED) and image quality (IQ) of O-arm cone-beam CT (Medtronic, Minneapolis, MN, USA) and Airo multi-slice CT (Brainlab AG, Munich, Germany) for intraoperative-CT (i-CT) in spinal surgery.MethodsThe manufacturer-defined protocols available in the O-arm and Airo systems for three-dimensional lumbar spine imaging were compared.Organ dose was measured both with thermo-luminescent dosimeters and GafChromic films in the Alderson Radiation Therapy anthropomorphic phantom.A subjective analysis was performed by neurosurgeons to compare the clinical IQ of the anthropomorphic phantom images acquired with the different i-CT systems and imaging protocols.Image uniformity, noise, contrast-to-noise-ratio (CNR), and spatial resolution were additionally assessed with the Catphan 504 phantom.ResultsO-arm i-CT caused 56% larger ED than Airo due to the high definition (HD) imaging protocol.The noise was larger for O-arm images leading to a lower CNR than that measured for Airo. Moreover, scattering and beam hardening effects were observed in the O-arm images. Better spatial resolution was measured for the O-arm system (9 lp/cm) than for Airo (4 lp/cm).For all the investigated protocols, O-arm was found to be better for identifying anatomical features important for accurate pedicle screw positioning.ConclusionsAccording to phantom measurements, the HD protocol of O-arm offered better clinical IQ than Airo but larger ED. The larger noise of O-arm images did not compromise the clinical IQ while the superior spatial resolution of this system allowed a better visibility of anatomical features important for pedicle screw positioning in the lumbar region.     

Do indicators of maternal iron status reflect placental iron status at delivery?

Indicators of maternal iron (Fe) status were studied in relation to placental Fe (Pl-Fe) status. Placental (Pl) and maternal (M) venous blood samples were obtained from primiparous women ($n=38$), with normal delivery at Paroissien Hospital, Argentina. Maternal hemoglobin (M Hb), soluble transferrin receptor (M sTfR) (ELISA) and serum ferritin (M S-Ft) were studied in relation to Pl-Fe, ferritin (Pl-Ft) and transferrin receptor (Pl-TfR). Pl-TfR was measured by dot blot assay, Pl-Ft and M S-Ft by immunoassay (IRMA) and Pl-Fe by atomic absorption spectrometry. Fe status indicators were, respectively, (mean±SD): M Hb 113±16 g/L; M S-Ft 36±42 μg/L; M sTfR 6.3±3.1 mg/L; Pl-Fe 170±56 μg/g placenta; Pl-Ft 33±18 μg/g placenta; Pl-TfR 18±18 (range 0–58) μg/g placenta. Pl-Fe, Pl-Ft and Pl-TfR did not correlate to M Hb, M S-Ft and M sTfR. Women with Pl- Fe, Pl-Ft and Pl-TfR above or below the corresponding median values did not show any statistical significant difference in M Hb, M sTfR or M S-Ft values. Pl-Ft concentration was lower in women with Hb<110 g/L than in women with normal values: 26±13 vs. 38±20 μg/g, respectively ($p=0.021$). When Pl-TfR, Pl-Ft and Pl-Fe were compared in women with M S-Ft above or below the cut-off point of 10 or 20 μg/L, no significant difference was found for Pl-TfR neither for Pl-Ft nor Pl-Fe. These results suggest that maternal indicators of Fe status, particularly M sTfR and M S-Ft, do not reflect Fe status of the placenta at delivery.     

Differential changes of neuroactive amino acids in samples obtained from discrete rat brain regions after systemic administration of saxitoxin

Aspartic acid, glutamic acid, γ-amino-n-butyric acid (GABA) and 2-aminoethanesulfonic acid are neuroactive amino acids. They are found in the central rat nervous system. Here, we have studied if a relationship exists between the presence of saxitoxin (STX) a paralytic poisoning shellfish (PSP) and the neuroactive amino acids. Samples of striatum (S), hypothalamus (H), mid brain (MB), frontal cortex (FC), brain stem (BS), right hemisphere (RH) and left hemisphere (LH) of rat brain were collected and analyzed for neuroactive amino acids (AAn_t) by Aswad method (1984). Experiments, consisting of intraperitoneal injection of SXT (5 and 10 μg kg^?1 body weight) to young male rats, evoked significant changes in AAn_t above basal values. Aspartic and glutamic acid significantly increased for RH and LH (after 30 min the increased was 116% and 210%, P ≤ 0.001 over basal values, respectively). On the other hand, aspartic, glutamic, taurine and GABA significantly decreased for S (after 30 min the decreased was 77.4%; 84%; 93.8% and 95.3%, P ≤ 0.001 over basal values, respectively). These results suggest that STX alters AAn_t. It is produced at least in part, because STX blocks voltage-gated sodium channels and this blockade could decrease AAn_t release by exocytotic dependent mechanism of depolarization.