A haplotype of the dopamine transporter gene modulates regional homogeneity, gray matter volume, and visual memory in children with attention-deficit/hyperactivity disorder

BACKGROUND

The dopamine transporter gene (DAT1) and visual memory deficits have been consistently reported to be associated with attention-deficit/hyperactivity disorder (ADHD). This study aimed to examine whether a DAT1 haplotype affected functional and structural brain alterations in children with ADHD and whether those alterations were associated with visual memory.

METHOD

We recruited a total of 37 drug-naïve children with ADHD (17 with the DAT1 rs27048 (C)/rs429699 (T) haplotype and 20 without the CT haplotype) and 37 typically developing children (17 with the CT haplotype and 20 without the CT haplotype). Visual memory was assessed by the pattern recognition memory (PRM) and spatial recognition memory (SRM) tasks. We analyzed functional and structural brain architecture with regional homogeneity (ReHo) and gray matter volume (GMV).

RESULTS

The CT haplotype was associated with decreased ReHo in the left superior occipital gyrus, cuneus, and precuneus; and decreased GMV in the left superior occipital gyrus, cuneus, and precuneus, and in the right angular gyrus. Significant interactions of ADHD and the CT haplotype were found in the right postcentral gyrus for ReHo and in the right supplementary motor area for GMV. For the ADHD-CT group, we found negative correlations of total correct responses in PRM and SRM and positive correlations of mean latency of correct responses in PRM with the GMV in the left superior occipital gyrus, cuneus, and precuneus.

CONCLUSIONS

Our findings suggest that the DAT1-related GMV alterations in the posterior cortical regions may contribute to visual memory performance in children with ADHD.

Automatic concentration and reformulation of PET tracers via microfluidic membrane distillation

Short-lived radiolabeled tracers for positron emission tomography (PET) must be rapidly synthesized, purified, and formulated into injectable solution just prior to imaging. Current radiosynthesizers are generally designed for clinical use, and the HPLC purification and SPE formulation processes often result in a final volume that is too large for preclinical and emerging in vitro applications. Conventional technologies and techniques for reducing this volume tend to be slow, resulting in radioactive decay of the product, and often require manual handling of the radioactive materials. We present a fully-automated microfluidic system based on sweeping gas membrane distillation to rapidly perform the concentration and formulation process. After detailed characterization of the system, we demonstrate fast and efficient concentration and formulation of several PET tracers, evaluate residual solvent content to establish the safety of the formulated tracers for injection, and show that the formulated tracer can be used for in vivo imaging.

Differential effects of methylphenidate and atomoxetine on intrinsic brain activity in children with attention deficit hyperactivity disorder

BACKGROUND

Methylphenidate and atomoxetine are commonly prescribed for treating attention deficit hyperactivity disorder (ADHD). However, their therapeutic neural mechanisms remain unclear.

METHOD

After baseline evaluation including cognitive testing of the Cambridge Neuropsychological Test Automated Battery (CANTAB), drug-naive children with ADHD (n = 46), aged 7-17 years, were randomly assigned to a 12-week treatment with methylphenidate (n = 22) or atomoxetine (n = 24). Intrinsic brain activity, including the fractional amplitude of low-frequency fluctuations (fALFF) and regional homogeneity (ReHo), was quantified via resting-state functional magnetic resonance imaging at baseline and week 12.

RESULTS

Reductions in inattentive symptoms were related to increased fALFF in the left superior temporal gyrus and left inferior parietal lobule for ADHD children treated with methylphenidate, and in the left lingual gyrus and left inferior occipital gyrus for ADHD children treated with atomoxetine. Hyperactivity/impulsivity symptom reductions were differentially related to increased fALFF in the methylphenidate group and to decreased fALFF in the atomoxetine group in bilateral precentral and postcentral gyri. Prediction analyses in the atomoxetine group revealed negative correlations between pre-treatment CANTAB simple reaction time and fALFF change in the left lingual gyrus and left inferior occipital gyrus, and positive correlations between pre-treatment CANTAB simple movement time and fALFF change in bilateral precentral and postcentral gyri and left precuneus, with a negative correlation between movement time and the fALFF change in the left lingual gyrus and the inferior occipital gyrus.

CONCLUSIONS

Our findings suggest differential neurophysiological mechanisms for the treatment effects of methylphenidate and atomoxetine in children with ADHD.

Compact microfluidic device for rapid concentration of PET tracers

HPLC purification and reformulation of positron emission tomography (PET) tracers can lead to significant dilution of the final product, making it difficult to produce a sufficiently high radioactivity concentration for some applications (e.g. small animal imaging, in vitro assays, and labelling of proteins with prosthetic groups). This is especially true for molecules with lengthy or low-yield syntheses. Starting the synthesis with more radioactivity increases the final radioactivity concentration but increases hazards and complexity of handling. An alternative is to concentrate the final product by a process such as rotary evaporation prior to downstream use. Because a rotovap requires significant space within a hot cell that could be put to more productive use, we developed a compact microfluidic system for concentration of PET tracers. This system also provides advantages in terms of repeatability, interfacing and potential for automation. We present here the design and performance characterization of the system, and demonstrate the concentration of several tracers in aqueous-based HPLC mobile phases.

A microreactor with phase-change microvalves for batch chemical synthesis at high temperatures and pressures

We present a simple microreactor with dimethyl sulfoxide (DMSO) phase-change valves suitable for performing batch organic chemistry under high temperature and pressure conditions. As a proof of principle, we demonstrate a radiofluorination reaction important in the synthesis of [(18)F]FAC, a new positron emission tomography biomarker for immune system monitoring and prediction of chemotherapy response. We achieved high radioactivity recovery (97 ± 1%, n = 3) and conversion efficiency (83 ± 1%, n = 3), comparable to that achieved with macroscale systems, but with a volume 30× smaller. This platform overcomes the limitations of previously reported phase-change valves in terms of compatibility with organic chemistry, and extends the range of reaction conditions for carrying out harsh batch chemistry at the microscale.

Disturbed microstructural integrity of the frontostriatal fiber pathways and executive dysfunction in children with attention deficit hyperactivity disorder

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is recognized as an early-onset neuropsychiatric disorder with executive dysfunctions and neurobiological deficits. The authors compared executive functions and microstructural integrity of the frontostriatal circuit in children with ADHD and typically developing children. Method We assessed 25 children with ADHD and 25 age-, sex-, handedness- and intelligence-matched typically developing children by using psychiatric interviews, the Wechsler Intelligence Scale for Children - third edition, and the tasks involving executive functions in the Cambridge Neuropsychological Test Automated Battery. The frontostriatal tracts were reconstructed by diffusion spectrum imaging tractography and were subdivided into four functionally distinct segments, including dorsolateral, medial prefrontal, orbitofrontal and ventrolateral tracts. Tract-specific and matched case-control analyses were used and generalized fractional anisotropy values were computed.

RESULTS

Children with ADHD had lower generalized fractional anisotropy of all the bilateral frontostriatal fiber tracts and poorer performance in verbal and spatial working memory, set-shifting, sustained attention, cognitive inhibition and visuospatial planning. The symptom severity of ADHD and the executive functioning performance significantly correlated with integrity of the frontostriatal tracts, particularly the left orbitofrontal and ventrolateral tracts. Children with ADHD also demonstrated loss of the leftward asymmetry in the dorsolateral and medial prefrontal tracts that was present in typically developing children.

CONCLUSIONS

Our findings demonstrate disturbed structural connectivity of the frontostriatal circuitry in children with ADHD and add new evidence of associations between integrity of the frontostriatal tracts and measures of core symptoms of ADHD and a wide range of executive dysfunctions in both groups.

Cytokine secretion from monocytes persists differentially after activator removal-One mechanism of long-term biological response to implants

Biomedical implants significantly improve the quality of life in an ever-increasing number of patients. However, inflammation of tissues around implants remains a long-term, post-placement sequelae that may contribute to implant failure. Infection-mediated failure is partly a consequence of inappropriate host response and chronic inflammation, and is mediated primarily by the secretory products of monocytes and macrophages. Although the secretion of inflammatory mediators from activated monocytes is well characterized, the resolution of mediator levels post-activation is relatively unstudied. The current study defines the time course of cytokine secretion by activated human monocytes after the activator has been removed. THP1 human monocytes were activated by LPS, and cytokine secretion was monitored over time after LPS removal using enzyme-linked immunosorbent assays (TNFalpha or IL8) or a cytokine array. The release of cytokines was compared with conditions without LPS removal. As expected, secretion of nearly all cytokines was reduced when LPS was removed, but the amount of the reduction was highly cytokine-dependent. Furthermore, levels of cytokines were stable in medium alone but not in cell-culture, suggesting an active process to either degrade or internalize secreted cytokines. Our results are consistent with clinical experience that inflammation resolves rapidly after treatment to remove bacteria or inflamed tissue. However, the differential cytokine regulation indicates a sophisticated coordination of cytokine levels probably associated with management of the wound healing response after removal of the bacterial insult. This wound healing response is one critical component of the long-term success of biomedical implants.

Alternating droplet generation and controlled dynamic droplet fusion in microfluidic device for CdS nanoparticle synthesis

A multifunctional and high-efficiency microfluidic device for droplet generation and fusion is presented. Through unique design of the micro-channels, the device is able to alternately generate droplets, generating droplet ratios ranging from 1 ratio 5 to 5 ratio 1, and fuse droplets, enabling precise chemical reactions in several picoliters on a single chip. The controlled fusion is managed by passive control based on the channel geometry and liquid phase flow. The synthesis of CdS nanoparticles utilizing each fused droplet as a microreactor for rapid and efficient mixing of reagents is demonstrated in this paper. Following alternating droplet generation, the channel geometry allows the exclusive fusion of alternate droplets with concomitant rapid mixing and produces supersaturated solution of Cd2+ and S2- ions to form CdS nanoparticles in each fused droplet. The spectroscopic properties of the CdS nanoparticles produced by this method are compared with CdS prepared by bulk mixing.

Anti-rheumatic gold compounds as sublethal modulators of monocytic LPS-induced cytokine secretion

The objective of this study was to quantify the ability of sublethal concentrations of several gold compounds to differentially modulate the monocytic secretion of key cytokines that are important in the etiology of rheumatic diseases. Human THP1 monocytic cells were exposed to the anti-rheumatic drugs auranofin (AF), gold sodium thiomalate (GSTM) or HAuCl4 (Au(III)) for 24-72 h. Succinate dehydrogenase (SDH) activity of the monocytes was used to determine sublethal concentrations. Monocytes were then exposed to sublethal concentrations of gold compounds for 72 h, and the activator lipopolysaccharide (LPS) was added (or not) to cultures for the last 6h. The secretion of IL6, IL8, IL10, and TNFalpha were measured in cell supernatants using ELISA. Cytokine secretion was compared among concentrations and gold compounds. SDH experiments established a sublethal concentration range of 0-75 microM for GSTM and Au(III) and 0-0.5 microM for AF. In cytokine experiments, none of the compounds alone activated secretion of any of the cytokines, but all differentially (50-440%, p<0.05) increased LPS-induced secretion of IL6 and IL8 over TNFalpha and IL10. In conclusion, sublethal concentrations of AF, GSTM, and Au(III) all may differentially modulate activation of monocytic cells, and this differential modulation may be important in the mechanisms of action of these compounds.

Local capsaicin application to the stellate ganglion and stellatectomy attenuate neurogenic inflammation in rat bronchi

The present study investigated the contributions of vagal and nonvagal sensory nerve fibers on neurogenic inflammation in rat bronchial airways. A surgical procedure was developed via the rat mediastinum ventral intercostal space to prepare an intercostal opening without causing pneumothorax for performing stellate ganglionectomy alone, thoracic vagus nerve section alone, and stellatectomy plus thoracic vagotomy, and for injecting capsaicin (2 microl, 10 mg/ml) and 6-hydroxydopamine (2 microl, 50 mg/ml) into the ganglion. One week later in our procedure, we investigated if neurogenic inflammation induced by an intravenous injection of capsaicin (300 nmol/ml/kg) and innervation density of substance P-immunoreactive sensory axons could be decreased after chronic denervation in the rat lower airways. The major findings were that surgical removal of the right stellate ganglion and local capsaicin application resulted in a significant attenuation of neurogenic plasma extravasation in the right bronchial tree evoked by systemic capsaicin application. Reduction of neurogenic plasma extravasation was totally abolished by combined stellatectomy and thoracic vagotomy. The number of substance P-containing axons was also greatly decreased following these surgical and capsaicin treatments. It is concluded that sensory nerve fibers from both vagal source and nonvagal (spinal) source, which associated with the stellate ganglion, contributed significantly to neurogenic inflammation in the bronchial airways with a slightly higher contribution from the vagus nerve.

Validation of diffusion tensor magnetic resonance axonal fiber imaging with registered manganese-enhanced optic tracts

Noninvasive mapping of white matter tracts using diffusion tensor magnetic resonance imaging (DTMRI) is potentially useful in revealing anatomical connectivity in the human brain. However, a gold standard for validating DTMRI in defining axonal fiber orientation is still lacking. This study presents the first validation of the principal eigenvector of the diffusion tensor in defining axonal fiber orientation by superimposing DTMRI with manganese-enhanced MRI of optic tracts. A rat model was developed in which optic tracts were enhanced by manganese ions. Manganese ion (Mn(2+)) is a potent T1-shortening agent and can be uptaken and transported actively along the axon. Based on this property, we obtained enhanced optic tracts with a T1-weighted spin-echo sequence 10 h after intravitreal injection of Mn(2+). The images were compared with DTMRI acquired with exact spatial registration. Deviation angles between tangential vectors of the enhanced tracts and the principal eigenvectors of the diffusion tensor were then computed pixel by pixel. We found that under signal-to-noise (SNR) of 30, the variance of deviation angles was (13.27 degrees). In addition, the dependence of this variance on SNR obeys stochastic behavior if SNR is greater than 10. Based on this relation, we estimated that an rms deviation of less than 10 degrees could be achieved with DTMRI when SNR is 40 or greater. In conclusion, our method bypasses technical difficulties in conventional histological approach and provides an in vivo gold standard for validating DTMRI in mapping white matter tracts.

The effect of curing light intensity on the cytotoxicity of a dentin-bonding agent

Various dentin-bonding agents (DBAs) have been widely used to improve the bonding strength of dental resins and to prevent microleakage at the resin-dentin interface, although DBA may exert potentially detrimental effects upon dental pulp. In this study, a DBA (Scotchbond Multi-purpose) cured at different light intensities (100, 200 and 300-mW/cm2) for 10 seconds was extracted with Dulbecco's modified Eagle's medium (DMEM) for 24 hours. Thereafter, pulp cells (1 x 10(4) cells/well) were exposed to DMEM with or without DBA extract for 12 hours, 24 hours and five days. Pulp-cell cytotoxicity was measured with a modified 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. No significant cytotoxicity of DBA eluents on pulp cells was found for the 12-hour exposure group. Following 24-hour exposure of cells to DBA cured at 100-mW/cm2, pulp cells became rounder, more retracted and lost some cellular processes as compared to controls. Five-day exposure of pulp cells to DBA extract cured by light at levels of 100, 200 and 300 mW/cm2, respectively, led to a growth retardation of 26%, 48% and 70% as analyzed by the inhibition of mitochondrial dehydrogenase activity. These results indicate that DBA may exert some cytotoxic effects upon dental pulp, especially when DBA-curing is insufficiently complete, as may occur at a low light intensity.

Magnetic resonance imaging assessment of left ventricular function and wall motion

Assessment of left ventricular (LV) function is essential for the diagnosis and treatment of cardiac patients. A reliable and noninvasive tool for quantifying global and local LV function is needed. Magnetic resonance (MR) imaging has several unique features that are well suited to clinical examinations: it is noninvasive, does not expose the patient to ionizing radiation, and provides images of high spatial resolution and excellent soft tissue contrast without the need for contrast medium injection. In this paper, I review the reported evidence concerning the validity of MR imaging assessment of LV volume, including end-diastolic volume, end-systolic volume, and ejection fraction, and the validity of using MR imaging to monitor LV wall motion. Abundant evidence from phantom, animal, and human studies supports that MR imaging provides accurate and reproducible information that is substantially superior to that from conventional modalities such as angiographic ventriculography, radionuclide scintigraphy, and echocardiography. A fast MR imaging technique, cine MR imaging, further enhances the clinical feasibility of MR imaging by reducing the scanning time to about 20 minutes. Today, cine MR imaging is widely accepted as a reliable clinical tool. It may be considered an in vivo standard for quantification of LV volume and wall motion. Faster MR imaging techniques, such as TurboFLASH and echo-planar imaging, decrease the examination time to several seconds. This allows evaluation of transient functional changes during pharmacologically or physically induced stress tests.

Myocardial fiber shortening in humans: initial results of MR imaging

PURPOSE

To use diffusion-sensitive magnetic resonance (MR) imaging to obtain images of fiber orientation in vivo and to map fiber shortening in humans by means of integrating such data with strain images.

MATERIALS AND METHODS

Images of fiber shortening for midventricular short-axis sections were acquired in eight healthy subjects. Fiber orientation maps obtained by means of diffusion-sensitive MR imaging were coregistered with systolic strain maps obtained by means of velocity-sensitive MR imaging. Fiber shortening was quantified by use of the component of systolic strain in the fiber direction.

RESULTS

The results were reproducible among subjects and were consistent with published values. MR imaging of myocardial fibers showed axisymmetric progression of fiber angles from -90 degrees epicardially to +90 degrees endocardially, with maxima near 0 degrees. Fiber shortening (mean, 0.12 +/- 0.01 [SD]) was more uniform than radial, circumferential, longitudinal, or cross-fiber strain or any principal strain. Fiber orientation coincided with the direction of maximum contraction epicardially, with that of minimum contraction endocardially, and varied between these extremes linearly with wall depth (r = 0.6).

CONCLUSION

Registered diffusion and strain MR imaging can be used quantitatively to map fiber orientation and its relations to myocardial deformation in humans.

Cardiac diffusion tensor MRI in vivo without strain correction

Cardiac diffusion MRI with diffusion encoding that spans a cardiac cycle is complicated by myocardial strains. This paper presents a method to obtain accurate diffusion data without strain correction. Owing to the synchrony of normal cardiac motion, there are time points in the cardiac cycle, "sweet spots," when the cardiac configuration approximates its temporal mean. If the diffusion is encoded then, the net effect of strain on the observed diffusion approximates zero. To test this, MRI diffusion and strain-rate movies are performed on cyclically deformed gel phantoms and in five normal subjects. In phantoms, the sweet spots predicted from the strain time curves agree with the times when the observed diffusion equals the true diffusion. In humans, the strain prediction of the sweet spots and the locations determined by the diffusion trace show a high correlation, r = 0.99. In all subjects, diffusion MRI presents a fiber orientation pattern comparable to that obtained from a stationary specimen. Magn Reson Med 42:393-403, 1999.

NMR study of solid C60(gamma-cyclodextrin)2

A solid complex of C60 with gamma-cyclodextrin (gamma-CyD) was examined with NMR spectroscopic methods in order to understand the dynamics of C60, and the interaction between C60 and gamma-CyD. A 13C solid-state cross-polarization magic angle spinning (CP/MAS) NMR spectra shows C60 resonance at 142.6 ppm. This provides the evidence of interaction between 13C spins in C60 and 1H spins in the gamma-CyD host. Ambient temperature experiments on the 13C CP/MAS NMR, with varying contact time, shows that the water associated with gamma-CyDs plays an important role in the nuclear relaxation processes. The dynamics of C60 in gamma-CyD was investigated using temperature and field-dependent 13C spin-lattice relaxation time measurements. The influence of water on the dynamics of C60 was less significant below 250 K.

Multiplanar gradient recalled images of the knee: comparison of different flip angles and echo times

To determine the most appropriate combination of echo time (TE) and flip angle in gradient echo images of the knee, the authors used different TEs (10, 20 and 30 msec) and flip angles (10, 30, 50, 70, 90, 120 and 150 degrees) to perform a systematic study of MRI on 10 volunteer knees. Contrast-to-noise ratios of cartilage-fat, fluid-cartilage, fluid-fat and fluid-ligament were calculated and compared. Images with a 30-degree flip angle combined with 20 msec of TE were found to have the best contrast-to-noise ratios in both objective data analysis and subjective observation. Hyaline cartilage of the knee was hyperintense and was well delineated on this pulse sequence, appearing distinct in contrast to the intra-articular fluid. It is concluded that this T2-weighted gradient echo pulse sequence is an alternative to conventional spin echo T2-weighted imaging of the knee.

Solid and papillary neoplasm of the pancreas: report of three cases

We report 3 cases of solid and papillary neoplasm of the pancreas, which is a rare pancreatic tumor with distinct clinicopathologic characteristics. Sonographic, computed tomographic (CT) and gross pathologic findings of these 3 patients were obtained and compared. The tumors had a smooth, enhanced capsule and variable internal architecture. Two of the tumors appeared to be of the heterogeneous soft tissue density type, while one of the tumors was of the mixed solid and cystic type. Because the CT appearance of this tumor is subject to variation, it should be differentiated from other pancreatic lesions with variable CT appearances. Several CT features such as soft tissue density of the mass in a precontrast study, a well-enhanced capsule and the absence of pancreatic or biliary duct dilatation, as well as the characteristic young-female predilection, may aid in a correct diagnosis before surgery.

Burkitt's and non-Burkitt's type lymphoma: clinicopathological and radiological manifestations

Nine cases of Burkitt's type and 5 case of non-Burkitt's type small, non-cleaved cell lymphoma were retrospectively studied to evaluate their clinical and radiological manifestations. In the Burkitt's group, the median age of onset was 9 years old; the male to female ratio was 2:1; and the most frequent presentation was abdominal mass. These features conformed to those of non-endemic (or American) type Burkitt's lymphoma. In comparison with the Burkitt's group, less male-predominance (M:F = 2:3) and cervical mass as the most frequent initial symptom were found in the non-Burkitt's group. Plain films and computed tomographies were collected to evaluate the encroachment of the disease into various organs or compartments. There was a statistically significant correlation in site of the main mass between these two types; the Burkitt's type prefers extranodal, whereas the non-Burkitt's type prefers nodal, involvement. Computed tomographic appearance of Burkitt's lymphoma was also analyzed and summarized by the following five aspects: (1) tumor location-predominantly in the abdomen or head/neck region; (2) tumor density-rather homogeneous and slightly less than that of muscle; (3) tumor margin-often well-localized with distinct contrast to adjacent normal tissue; (4) extranodal predilection- the most frequent pattern of involvement; and (5) bony chang-often mild, despite the size of the mass.