In vivo assessment of blood-spinal cord barrier permeability: serial dynamic contrast enhanced MRI of spinal cord injury

Serial in vivo dynamic contrast enhanced (DCE) MRI studies were performed on spinal cord injured rats on post-injury Days 0, 10, 20 and 30 to determine the distribution of gadopentetate-dimeglumine (Gd) concentration in injured cord tissue. A two-compartment pharmacokinetic model was fitted to the time course of the concentration data at the epicenter of injury for each post-injury day. From these fits, the rates of the Gd transport between plasma and injured cord tissue were determined as a measure of blood-spinal cord barrier (BSCB) permeability. The results indicated that Gd transport rates decrease steadily with a concomitant improvement in motor functions of the rats with post-injury time. Specifically, the rates of Gd accumulation in injured SC tissue and its clearance correlated with the neurobehavioral scores with correlation coefficients of rho = -0.96 and -0.79, respectively, suggesting a significant link between the neurobehavioral function and the restoration of BSCB integrity as a result of the ongoing repair and recovery processes within the injured cords.     

In vivo interactions of magnetic nanoparticles with the blood-brain barrier

Targeted drug delivery to the brain parenchyma, i.e., in brain tumor patients, by means of magnetically supported carrier delivery through the tight vascular endothelium of the blood-brain barrier is of critical biomedical importance. We were interested in delineating the first steps in successful brain drug delivery, which focuses on the interactions between magnetically guided yet freely blood circulating nanoparticles and the blood-brain barrier. We employed an in vivo model to quantitatively determine changes in cerebrovascular flow rate and volume during magnetically guided exposure of circulating nanoparticles.     

In vivo fluorescent imaging of the mouse retina using adaptive optics

In vivo imaging of the mouse retina using visible and near infrared wavelengths does not achieve diffraction-limited resolution due to wavefront aberrations induced by the eye. Considering the pupil size and axial dimension of the eye, it is expected that unaberrated imaging of the retina would have a transverse resolution of 2 microm. Higher-order aberrations in retinal imaging of human can be compensated for by using adaptive optics. We demonstrate an adaptive optics system for in vivo imaging of fluorescent structures in the retina of a mouse, using a microelectromechanical system membrane mirror and a Shack-Hartmann wavefront sensor that detects fluorescent wavefront.     

In vivo assessment of human skin aging by multiphoton laser scanning tomography

Changes of dermal collagen and elastin content are characteristic for skin aging as well as for pathological skin conditions. To evaluate these changes, we used in vivo multiphoton laser tomography to measure two-photon excited autofluorescence (AF) and second harmonic generation (SHG). We tested 18 patients of all ages and calculated the SHG-to-AF aging index of dermis (SAAID). We observed a negative relationship between the SAAID and age, which was accelerated for the female (n=7) subgroup. The current findings are the first in vivo demonstration of this relationship, and they show that specific characteristics of aged skin such as the ratio of extracellular matrix components collagen and elastin can be evaluated by in vivo AF and SHG measurements using near-IR femtosecond laser pulses.     

Surface barrier and magnetic hysteresis of ac permeability in YBaCuO single crystal

The nature of hysteretic behavior of the flux line lattice (FLL) contribution to ac magnetic permeability (μ_v) is analyzed for the case of YBa₂Cu₃O_x single crystal (at applied magnetic field Hc axis). It is shown that hysteresis loops μ_v(H) corresponding to different temperatures (T=70–84 K) are scaled to a universal curve in normalized coordinates. Such a behavior is interpreted in terms of the FLL interaction with the crystal surface. The explicit relationship between μ_v and magnetic induction B is found for the near-surface region of the superconductor. It is shown that the μ_v(H) loops are closely related to the hysteresis of B at cycling of applied magnetic field. The latter hysteresis stems from the Bean–Livingston surface barrier. The estimates demonstrate strong suppression of the surface barrier in YBa₂Cu₃O_x crystal in comparison to that expected for the ideal surface. As a result, the lower branch of the hysteresis loop corresponding to the increasing field is very close to the equilibrium μ_v(H) curve and the surface barrier appreciably affects only the upper branch when magnetic flux leaves the sample. The comparison of theoretical predictions and experimental data provides an opportunity to refine the actual range of stability H_max(B)–H_min(B) for the FLL at fixed B for YBa₂Cu₃O_x crystal in the case of Hc.     

Rapid and recoverable in vivo magnetic resonance imaging of the adult zebrafish at 7T

Increasing scientific interest in the zebrafish as a model organism across a range of biomedical and biological research areas raises the need for the development of in vivo imaging tools appropriate to this subject. Development of the embryonic and early stage forms of the subject can currently be assessed using optical based techniques due to the transparent nature of the species at these early stages. However this is not an option during the juvenile and adult stages when the subjects become opaque. Magnetic resonance imaging (MRI) techniques would allow for the longitudinal and non-invasive assessment of development and health in these later life stages. However, the small size of the zebrafish and its aquatic environment represent considerable challenges for the technique. We have developed a suitable flow cell system that incorporates a dedicated MRI imaging coil to solve these challenges. The system maintains and monitors a zebrafish during a scan and allows for it to be fully recovered. The imaging properties of this system compare well with those of other preclinical MRI coils used in rodent models. This enables the rapid acquisition of MRI data which are comparable in terms of quality and acquisition time. This would allow the many unique opportunities of the zebrafish as a model organism to be combined with the benefits of non-invasive MRI.     

Synthesis of 2,3-dimorpholino-6-aminoquinoxaline derivatives and application to a new intramolecular fluorescent probe

Two fluorescent monomers having a quinoxaline skeleton, N-(2,3-dimorpholinoquinoxalin-6-yl)acrylamide (QxA) and N-(1-(2,3-dimorpholinoquinoxalin-6-ylamino)prop-2-yl)methacrylamide (QxAlaMA), were synthesized. Thermo-responsive copolymers of N-isopropylacrylamide (NIPAM) and a small amount of a fluorescent monomer were synthesized and their fluorescence properties investigated. The fluorescent monomers showed intense solvatochromism in their fluorescence. The wavelength at the maximum fluorescence intensity of the QxAlaMA-labeled PNIPAM dramatically blue-shifted and the fluorescence intensity of the QxA-labeled PNIPAM significantly increased around the transition temperature. It was found that these fluorescent dyes can sense and report the thermo-responsive behavior of the PNIPAM in water. Both QxAlaMA and QxA were demonstrated to be applicable to new intramolecular fluorescent probes.     

多重全内反射红外光谱原位研究混凝土渗透性

将多重全内反射傅里叶变换红外光谱(FTIR-MIR)技术应用于混凝土渗透性研究.考察了水灰比和养护龄期与混凝土微孔结构之间的关系及其对混凝土渗透性的影响.简要分析了水和硫酸根离子在混凝土中传输规律.原位FTIR-MIR研究表明,水在混凝土中的传输主要依靠混凝土内部孔隙两端的毛细势能梯度.SO2-4离子的传输过程则要考虑对流和浓度差引起的扩散两种方式以及SO2-4与混凝土中水化产物的反应.混凝土抗渗性能与其微观孔结构有着密切的关系,随着水灰比降低或养护龄期延长,混凝土孔隙率减小,孔的连通性下降,混凝土抗渗性能提高.     

MRI measurement of blood-brain barrier permeability following spontaneous reperfusion in the starch microsphere model of ischemia

Quantification of the acute increases in blood-brain barrier (BBB) permeability that occur subsequent to experimental ischemic injury has been limited to single time-point, invasive methodologies. Although permeability can be qualitatively assessed to visualise regional changes during sequential studies on the same animal using contrast-enhanced magnetic resonance imaging (MRI), quantitative information on the magnitude of change is required to compare barrier function during sequential studies on the same animal or between different animals. Recently, improvements in MRI tracer kinetic models and in MR hardware design mean that an estimate of permeability in vivo can now be obtained with acceptable accuracy and precision. We report here the use of such methods to study acute changes following spontaneous reperfusion in an animal model of ischemia. We have obtained estimates of BBB permeability following spontaneous reperfusion, subsequent to forebrain ischemia by unilateral carotid injection of starch microspheres in the rat. T2*-weighted and diffusion-trace imaging were used to monitor the initial reduction in CBF and the time-course of ischemia, respectively. Following reperfusion, an intraveneous bolus of dimeglumine gadopentetate (Gd-DTPA) and horseradish peroxidase (HRP) was given during a continuous acquisition of T1 maps with a 48 s temporal resolution. Permeability maps were constructed using a 4-compartment model; K(trans), the permeability-surface area product of the capillary walls was estimated to be 9.2 +/- 0.6 x 10(-4) min(-1) in the cortex. Visualisation of the regional extent of HRP extravasation on histological sections following termination of the experiment demonstrated very little correspondence to the region of Gd-DTPA leakage. Quantitative MRI assessment of BBB permeability following ischemia-reperfusion is consistent with published values obtained by invasive methods. Differences between Gd-DTPA-enhancement and HRP may reflect differences in the molecular size of the tracers.     

In vivo observation of oxygen-supersaturated water in the human mouth and stomach

In recent years, a rising number of different table waters supersaturated with oxygen have hit the market with claims of both positive health effects and an increase in athletic performance. A scientific validation of these claims needs additional knowledge on the fate of the oxygen supersaturation in the human digestive tract. Taking advantage of the fact that molecular oxygen is paramagnetic, MRI can be applied to observe the behavior of oxygen-supersaturated water after oral uptake. In this contribution we report results obtained on several healthy volunteers. On the basis of these results we can conclude that oral uptake of oxygen-supersaturated drinking water with a low content in CO(2) leads to a considerable increase in the oxygenation in the lumen of the oral cavity and of the stomach. Comparing the observed contrast changes with those brought about by conventional contrast agents, even the highly oxygen-supersaturated waters still perform rather poorly.     

In vivo MR evaluation of Gd-DTPA conjugated to dextran in normal rabbits.

A dextran-Gd-DTPA compound has been recently synthesized utilizing 70,800 Da molecular weight dextran. This polymeric contrast agent for magnetic resonance imaging has been found chemically to be very stable and to demonstrate in vitro improved relaxivities of 1.5 to 2.3 times that of monomeric Gd-DTPA at 100 MHz. This MR experiment examines the in vivo distribution and relaxivity of the 70,800 Da molecular weight dextran-Gd-DTPA compound in a rabbit model by measuring the change in signal-to-noise ratio of a variety of organs (renal cortex, renal medulla, liver, brain, and torcula herophile) compared to the preinjection state. Results demonstrate prolonged (beyond 60 min) enhancement of the renal cortex, renal medulla, liver and torcula, and no enhancement of brain parenchyma.     

In vivo (31)P-MRS assessment of cytosolic [Mg(2+)] in the human skeletal muscle in different metabolic conditions

Cytosolic free [Mg(2+)] can be assessed in vivo by (31)P-MRS from the chemical shift of beta-ATP. The reliability of in vivo measurements depends on the availability of appropriate in vitro calibration curves obtained by using solutions that mimic the in vivo cytosolic conditions as far as possible. We build a semi-empiric equation that correlates the chemical shift of beta-ATP to free [Mg(2+)] taking into account the amount of Mg(2+) bound to all other ligands in solution. Our experiments resulted in a reliable ten-parameters equation directly usable to assess the cytosolic free [Mg(2+)] of human skeletal muscle at rest, during work and recovery. Our experiments also resulted in a new equation that allows the assessment of cytosolic pH from the chemical shift of Pi taking into account the measured free [Mg(2+)]. To perform simultaneous calculation of free [Mg(2+)] and pH in the skeletal muscle in different metabolic conditions we developed a specific software package available on Internet (http://www.unibo.it/bioclin) together with another program based on the equation previously obtained to calculate cytosolic free [Mg(2+)] in the human brain. The reliability and effectiveness of our equations and software were tested on the calf muscles of healthy volunteers at rest, during work and recovery.     

Quantitative assessment of intracranial tumor response to dexamethasone using diffusion, perfusion and permeability magnetic resonance imaging

There is increasing interest in obtaining quantitative imaging parameters to aid in the assessment of tumor responses to treatment. In this study, the feasibility of performing integrated diffusion, perfusion and permeability magnetic resonance imaging (MRI) for characterizing responses to dexamethasone in intracranial tumors was assessed. Eight patients with glioblastoma, five with meningioma and three with metastatic carcinoma underwent MRI prior to and 48-72 h following dexamethasone administration. The MRI protocol enabled quantification of the volume transfer constant (K(trans)), extracellular space volume fraction (nu(e)), plasma volume fraction (nu(p)), regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), longitudinal relaxation time (T(1)) and mean diffusivity (D(av)). All subjects successfully completed the imaging protocol for the presteroid and poststeroid scans. Significant reductions were observed after the treatment for K(trans), nu(e) and nu(p) in enhancing tumor as well as for T(1) and D(av) in the edematous brain in glioblastoma; on the other hand, for meningioma, significant differences were seen only in edematous brain T(1) and D(av). No significant difference was observed for any parameter in metastatic carcinoma, most likely due to the small sample size. In addition, no significant difference was observed for enhancing tumor rCBF and rCBV in any of the tumor types, although the general trend was for rCBV to be reduced and for rCBF to be more variable. The yielded parameters provide a wealth of physiologic information and contribute to the understanding of dexamethasone actions on different types of intracranial tumors.     

Reduced capillary perfusion and permeability in human tumour xenografts treated with the VEGF signalling inhibitor ZD4190: an in vivo assessment using dynamic MR imaging and macromolecular contrast media

We describe the use of perfusion-permeability magnetic resonance imaging (ppMRI) to study hemodynamic parameters in human prostate tumor xenografts, following treatment with the vascular endothelial growth factor-A (VEGF) receptor tyrosine kinase inhibitor, ZD4190. Using a macromolecular contrast agent (P792), a fast MR imaging protocol and a compartmental data analysis, we were able to demonstrate a significant simultaneous reduction in tumor vascular permeability, tumor vascular volume and tumor blood flow (43%, 30% and 42%, respectively) following ZD4190 treatment (100 mg/kg orally, 24 h and 2 h prior to imaging). This study indicates that MR imaging can be used to measure multiple hemodynamic parameters in tumors, and that tumor vascular permeability, volume and flow, can change in response to acute treatment with a VEGF signaling inhibitor.     

In vivo imaging of the human rod photoreceptor mosaic

Although single cone receptors have been imaged in vivo, to our knowledge there has been no observation of rods in the living normal eye. Using an adaptive optics ophthalmoscope and post processing, evidence of a rod mosaic was observed at 5° and 10° eccentricities in the horizontal temporal retina. For four normal human subjects, small structures were observed between the larger cones and were observed repeatedly at the same locations on different days, and with varying wavelengths. Image analysis gave spacings that agree well with rod measurements from histological data.     

One injection for one-week controlled release: In vitro and in vivo assessment of ultrasound-triggered drug release from injectable thermoresponsive biocompatible hydrogels

Episodic release of bioactive compounds is often necessary for appropriate biological effects under specific physiological conditions. Here, we aimed to develop an injectable, biocompatible, and thermosensitive hydrogel system for ultrasound (US)-triggered drug release. An mPEG-PLGA-BOX block copolymer hydrogel was synthesized. The viscosity of 15 wt% hydrogel is 0.03 Pa*s at 25 °C (liquid form) and 34.37 Pa*s at 37 °C (gel form). Baseline and US-responsive in vitro release profile of a small molecule (doxorubicin) and that of a large molecule (FITC-dextran), from the hydrogel, was tested. A constant baseline release was observed in vitro for 7 d. When triggered by US (1 MHz, continuous, 0.4 W/cm²), the release rate increased by approximately 70 times. Without US, the release rate returned to baseline. Baseline and US-responsive in vivo release profile of doxorubicin was tested by subcutaneous injection in the back of mice and rats. Following injection into the subcutaneous layer, in vivo results also suggested that the hydrogels remained in situ and provided a steady release for at least 7 d; in the presence of the US-trigger, in vivo release from the hydrogel increased by approximately 10 times. Therefore, the mPEG-PLGA-BOX block copolymer hydrogel may serve as an injectable, biocompatible, and thermosensitive hydrogel system that is applicable for US-triggered drug release.     

Synthesis,spectroscopic characterization,and computed optical analysis of green fluorescent cyclohexenone derivatives

Cyclohexenone containing chalcones core is one important class of materials, which exhibit high nonlinear optical (NLO) responses and good crystallizability. The present study reports the successful development of six new fluorescent cyclohexenone derivatives (CDs) via conventional Robinson annulation method. The molecular structures of these newly synthesized CDs were confirmed by using various analytical techniques such as ¹H NMR, ¹³C NMR, FTIR, EIMS, UV–Vis spectroscopy and single crystal X‐ray diffraction. The crystallographic data revealed that the spatial structure of the representative CD (4BE) belongs to monoclinic, P2₁/c space group. The results from luminescence studies show that the CDs molecules apparently emit intense green light at room temperature in aqueous media. The relative polarity and molecular chemical stability of the CDs molecules were predicted by measuring the molecular electrostatic potential and frontier molecular orbital energy. In addition, the UV–Vis spectra, transition character and electronic structures of these CDs were computed by using quantum chemical methodology. It was interesting to note that the values of computed and experimental electronic transitions (λ_max) were in good agreement and these CDs display high hyperpolarizability (β) values. The present work will be helpful for systematical understanding of the structures and the optical properties of CDs for studying the structure–activity relationship that will suggest their potential application in photonic devices. Copyright © 2015 John Wiley & Sons, Ltd.     

Toxicity of citrate-capped AuNPs: an in vitro and in vivo assessment

In this study, we show that 15 nm citrate-capped AuNPs exert a remarkable toxicity in living systems. The assessment was performed by using well-characterized AuNPs, the combination of in vitro and in vivo models (namely two different cell lines and Drosophila melanogaster), exposure to low dosages of nanoparticles (in the sub-nanomolar concentration range), along with the application of several biological assays to monitor different aspects of the toxic effects, such as viability, genotoxicity, and molecular biomarkers.