Changes of cerebral white matter in patients suffering from Pantothenate Kinase-Associated Neurodegeneration (PKAN): A diffusion tensor imaging (DTI) study

BACKGROUND

To look for microstructural white matter alterations in patients with dystonia due to Pantothenate Kinase-Associated Neurodegeneration.

MATERIAL AND METHODS

We examined 21 genetically confirmed patients and an age-matched group of 21 healthy controls by diffusion tensor imaging. Evaluation of data was performed by tract-based spatial statistics analysis and a voxel-wise comparison of calculated maps of fractional anisotropy. Findings were compared between groups and correlated to the dystonia score of the Burke-Fahn-Marsden Scale (p ≤ 0.05).

RESULTS

Patients showed reductions of fractional anisotropy mainly in the periventricular substance surrounding the third ventricle, in the medial part of both putamina and in the frontal white matter including the anterior limbs of the internal capsules and the corpus callosum. Infratentorially, the cerebellar white matter and dorsal parts of the pons and medulla were affected.

CONCLUSION

In addition to cortical grey matter changes, we now have a second structural finding pointing to a more widespread affection of cerebral tissue in PKAN dystonia than just the lesion and iron accumulation in the globus pallidus.

NAA and NAAG variation in neuronal activation during visual stimulation

N-acetyl-aspartyl-glutamate (NAAG) and its hydrolysis product N-acetyl-aspartate (NAA) are among the most important brain metabolites. NAA is a marker of neuron integrity and viability, while NAAG modulates glutamate release and may have a role in neuroprotection and synaptic plasticity. Investigating on a quantitative basis the role of these metabolites in brain metabolism in vivo by magnetic resonance spectroscopy (MRS) is a major challenge since the main signals of NAA and NAAG largely overlap. This is a preliminary study in which we evaluated NAA and NAAG changes during a visual stimulation experiment using functional MRS. The paradigm used consisted of a rest period (5 min and 20 s), followed by a stimulation period (10 min and 40 s) and another rest period (10 min and 40 s). MRS from 17 healthy subjects were acquired at 3T with TR/TE = 2000/288 ms. Spectra were averaged over subjects and quantified with LCModel. The main outcomes were that NAA concentration decreased by about 20% with the stimulus, while the concentration of NAAG concomitantly increased by about 200%. Such variations fall into models for the energy metabolism underlying neuronal activation that point to NAAG as being responsible for the hyperemic vascular response that causes the BOLD signal. They also agree with the fact that NAAG and NAA are present in the brain at a ratio of about 1:10, and with the fact that the only known metabolic pathway for NAAG synthesis is from NAA and glutamate.

Establishment of a protocol for large-scale gene expression analyses of laser capture microdissected bladder tissue

PURPOSE

Lower urinary tract symptoms (LUTS) can be caused by structural and functional changes in different compartments of the bladder. To enable extensive investigations of individual regions even in small bladder biopsies, we established a combination protocol consisting of three molecular techniques: laser capture microdissection microscopy (LCM), RNA preamplification and quantitative polymerase chain reaction (qPCR).

METHODS

Urinary bladders of ten mice were resected and frozen immediately or after a delay of 15 min. Cryosections were obtained and smooth muscle was isolated using the LCM technique. Then, RNA was extracted, including protocols with and without DNase digestion as well as with and without the addition of carrier RNA. Extracted RNA was either used for reverse transcriptase (RT)-PCR plus qPCR or for a combination of RNA preamplification and qPCR.

RESULTS

Our data showed that with RNA preamplification, 10 μg cDNA can be regularly generated from 2.5 ng RNA. Depending on expression levels, this is sufficient for hundreds of pPCR reactions. The efficiency of preamplification, however, was gene-dependent. DNase digestion before preamplification lead to lower threshold cycles in qPCR. The use of partly degraded RNA for RNA preamplification did not change the results of the following qPCR.

CONCLUSIONS

RNA preamplification strongly enlarges the spectrum of genes to be analyzed in distinct bladder compartments by qPCR. It is an easy and reliable method that can be realized with standard laboratory equipment. Our protocol may lead in near future to a better understanding of the pathomechanisms in LUTS.

Measurement of blood flow in arteriovenous malformations before and after embolization using arterial spin labeling

The assessment of shunt reduction after an embolization of an arteriovenous malformation (AVM) or fistula (AVF) from conventional angiography is often difficult and may be subjective. Here we present a completely non-invasive method using magnetic resonance imaging (MRI) to measure shunt reduction. Using pulsed arterial spin labeling (PASL), we determined the relative amount of signal attributed to the shunt over 1.75 s and 6 different slices covering the lesion. This amount of signal from the shunt was related to the total signal from all slices and measured before and after embolization. The method showed a fair agreement between the PASL results and the judgement from conventional angiography. In the case of a total or subtotal shunt occlusion, PASL showed a shunt reduction between 69% and 92%, whereas in minimal shunt reduction as judged by conventional angiography, the ASL result was -6% (indicating slightly increased flow) to 35% in a partially occluded vein of Galen aneurysm. The PASL method proved to be fairly reproducible (up to 2% deviation between three measurements without interventions). On conclusion, PASL is able to reliably measure the amount of shunt reduction achieved by embolization of AVMs and AVFs.

Involvement of globus pallidus and midbrain nuclei in pantothenate kinase-associated neurodegeneration: measurement of T2 and T2* time

PURPOSE

To quantify involvement of globus pallidus and two midbrain nuclei (substantia nigra and red nucleus) in Pantothenate Kinase-Associated Neurodegeneration (PKAN).

MATERIAL AND METHODS

We performed T2 and T2* weighted imaging with calculation of the corresponding relaxation times on a subset of 5 patients from a larger group of 20 patients with PKAN from the southwest part of the Dominican Republic. Examinations were carried out on a 3T scanner and included a multi-echo spin-echo as well as a multi-echo gradient echo sequence. Results were compared to a control group of 19 volunteers.

RESULTS

T2 and T2* weighted sequences showed abnormal signal reduction in the globus pallidus of all patients. On T2* weighted imaging, abnormal signal in the substantia nigra could reliably be detected in 75% of cases, but differentiation from normal was less reliable in T2 weighted scans. Correspondingly, relaxation times differed from normal with very high significance (p < 0.0001) in the globus pallidus, but with with less significance in the substantia nigra (p ≤ 0.03). The red nucleus was not affected.

CONCLUSIONS

Signal reduction in the globus pallidus, which probably is due to abnormal accumulation of iron, is severe in PKAN and can be differentiated from normal with high reliability. The substantia nigra is affected to a lesser degree, and the red nucleus is not involved. The reason for this selective susceptibility of normally iron-rich brain structures for pathological accumulation of iron remains speculative. Our quantitative results might be helpful to assess the value of an iron chelation approach to therapy.

Diffusion tensor imaging in patients with acute onset of neuropsychiatric systemic lupus erythematosus: a prospective study of apparent diffusion coefficient, fractional anisotropy values, and eigenvalues in different regions of the brain

PURPOSE

To investigate whether apparent diffusion coefficient (ADC), fractional anisotropy (FA), and eigenvalues in neuropsychiatric systemic lupus erythematosus (NPSLE) patients differ from those of healthy controls.

MATERIAL AND METHODS

Eight NPSLE patients (aged 23-55 years, mean 42.9 years) and 20 healthy age-matched controls (aged 22-59 years, mean 44.4 years) underwent conventional brain magnetic resonance (MR) and diffusion tensor imaging (DTI). The ADC, FA, principal eigenvalue (lambda parallel), and the corresponding average perpendicular eigenvalue (lambda perpendicular) (=(lambda2+lambda3)/2) were measured in selected regions of normal appearing gray and white matter brain parenchyma. For statistical evaluation of differences between the two groups, a Student's t-test was used. The P value for statistical significance was set to P=0.0025 after Bonferroni correction for multiple measurements.

RESULTS

Significantly increased ADC values were demonstrated in normal-appearing areas in the insular cortex (P<0.001), thalamus (P<0.001), and the parietal and frontal white matter (P<0.001 and P<0.001, respectively) in NPSLE patients. Significantly decreased FA values were demonstrated in normal-appearing thalamus (P<0.001), corpus callosum (P=0.002), and in the parietal and frontal white matter (P<0.001 and P<0.001, respectively) in NPSLE patients compared to healthy controls. The lambda perpendicular was significantly higher in several of these regions in NPSLE patients compared to healthy controls.

CONCLUSION

Our study demonstrates alterations in normal-appearing gray and white matter brain parenchyma of patients with NPSLE by means of abnormal ADC, FA, and eigenvalues. These alterations may be based on loss of tissue integrity in part due to demyelination. It is possible that DTI in the future could assist in the diagnosis of NPSLE and possibly help to further elucidate the pathogenesis of NPSLE.

Evolution of a Focal Brain Lesion Produced by Interlaced Microplanar X-Rays

Stereotactic radiosurgery has led to advances in the treatment of central nervous system disease. It relies upon the principle of delivering relatively high dose irradiation to a precise target, while exposing surrounding tissues to extremely low doses. We describe a novel radiosurgical approach using interlaced microplanar X-rays which we have termed "microradiosurgery." The use of microbeams allows for 1,000-times greater precision than current clinically employed techniques. As a demonstration of this new method, we produced a approximately 3.8 mm (3) lesion in the rat brain. The lesion was followed over a period of 216 days using 9.4 Tesla magnetic resonance imaging. Our results show a gradually developing lesion at the site of the interlaced beams. The lesion began as a high T2 signal only, but advanced to include a central area of low T1 and mixed T2 signal within 2 months. No lesion was observed in the other side of the brain which was exposed to non-interlaced microbeams only. Interlaced microbeams is an effective method to create focal brain microlesions. This technique may allow the future treatment of pathology not accessible by surgical or more traditional radiosurgical means.

Functional changes of human quadriceps muscle injured by eccentric exercise

The present study evaluated functional changes of quadriceps muscle after injury induced by eccentric exercise. Maximal isometric torque of quadriceps and the surface electromyography (root mean square, RMS, and median frequency, MDF) of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles were examined before, immediately after and during the first 7 days after injury. Serum creatine kinase (CK) levels and magnetic resonance imaging (MRI) were used to identify muscle injury. The subject was used as her own control and percent refers to pre-injury data. Experiments were carried out with a sedentary 23-year-old female. Injury was induced by 4 bouts of 15 maximal isokinetic eccentric contractions (angular velocity of 5 /s; range of motion from 40 to 110 of knee flexion). The isometric torque of the quadriceps (knee at 90 flexion) decreased 52% immediately after eccentric exercise and recovered on the 5th day. The highest reduction of RMS occurred on the 2nd day after injury in both VL (63%) and VMO (66%) and only VL recovered to the pre-injury level on the 7th day. Immediately after injury, the MDF decreased by 5 and 3% (VMO and VL, respectively) and recovered one day later. Serum CK levels increased by 109% on the 2nd day and were still increased by 32% on the 7th day. MRI showed large areas of injury especially in the deep region of quadriceps. In conclusion, eccentric exercise decreased the isometric torque and electromyographic signals of quadriceps muscle, which were recovered in one week, despite the muscle regeneration signals.

Asymmetrical gradient coil for head imaging

This work presents a novel approach to develop dedicated transverse gradient coils for head imaging. The proposed coil design is based on the stochastic optimization of an asymmetrical stream function and improves the matching between the region-of-interest and the homogeneous gradient volume. Additionally, the electric field produced by these asymmetrical coils is 30% lower than that produced by standard symmetrical designs, which minimizes the risk of magnetostimulation of nerves in fast imaging techniques. A prototype of the asymmetrical gradient coil was built to test the method and magnetic field produced by the prototype was measured. Magnetic field measurements and electrical parameters of coils are in good agreement with theoretical calculations.

Fast optimization of a biplanar gradient coil set

This work presents an approach for fast optimization of gradient coils, using the simulated annealing method. The shielding condition derived from a target field method and the analytical evaluation of the fields produced by simple geometries were used to reduce the computing time. This method is applied to the optimization of a shielded biplanar gradient coil set. Efficiency, inductance, and homogeneity of the gradient fields produced by the optimized geometries were studied as a function of the number of wires, for the longitudinal and transverse gradient coils. A prototype of the gradient set was made to test the proposed design method. The resulting experimental values of coil efficiency, inductance, field linearity, and shielding performance exhibit good agreement between theory and experiment.

Microfabricated structures for integrated DNA analysis

Photolithographic micromachining of silicon is a candidate technology for the construction of high-throughput DNA analysis devices. However, the development of complex silicon microfabricated systems has been hindered in part by the lack of a simple, versatile pumping method for integrating individual components. Here we describe a surface-tension-based pump able to move discrete nanoliter drops through enclosed channels using only local heating. This thermocapillary pump can accurately mix, measure, and divide drops by simple electronic control. In addition, we have constructed thermal-cycling chambers, gel electrophoresis channels, and radiolabeled DNA detectors that are compatible with the fabrication of thermocapillary pump channels. Since all of the components are made by conventional photolithographic techniques, they can be assembled into more complex integrated systems. The combination of pump and components into self-contained miniaturized devices may provide significant improvements in DNA analysis speed, portability, and cost. The potential of microfabricated systems lies in the low unit cost of silicon-based construction and in the efficient sample handling afforded by component integration.

Improved method for the concentration and purification of faecal cysts of Entamoeba histolytica for use as antigen

Human stool samples are the most widely used source of E. histolytica cysts for diagnosis and research. Cysts concentrated from faecal samples are contaminated with faecal debris and bacteria and are unsuitable for use as antigens. Other gradient purification and sedimentation procedures result in considerable cyst losses. We present an effective and simple purification procedure using varying densities of Percoll that yields an adequate cyst concentration from a moderate cyst load in a single stool sample.

Complement resistance of pathogenic Entamoeba histolytica mediated by trypsin-sensitive surface component(s)

Pathogenic forms of the protozoan parasite Entamoeba histolytica were reported previously to resist the cytolytic effect of the alternative complement pathway (AP) only temporarily during exposure to complement. In contrast, nonpathogenic forms of E. histolytica had been found to show AP resistance as a stable property. We studied the mechanisms of AP resistance of the two forms. Upon exposure to AP activity, resistant pathogenic or nonpathogenic forms bound significantly less C3 products than complement-sensitive pathogenic amebae, indicating that the two resistant forms both inhibited AP amplification. Various enzymatic treatments and inhibition of membrane mobility by cytochalasin B and glutaraldehyde fixation showed that the mechanisms of AP inhibition differed between pathogenic and nonpathogenic forms; in contrast to nonpathogenic forms, pathogenic amebae required intact membrane mobility and a trypsin-sensitive surface component(s) to inhibit AP activation.

Induction of complement resistance in cloned pathogenic Entamoeba histolytica

The lytic effect of complement activated through the alternative pathway (AP) was studied on pathogenic and nonpathogenic Entamoeba histolytica recently isolated from stool samples. Recent nonpathogenic isolates were nearly unaffected by exposure to AP whereas recent pathogenic stool isolates were highly susceptible to AP dependent complement-mediated lysis. Complement susceptible pathogenic stool isolates developed complement resistance in vivo during hamster liver passage and in vitro during cultivation in the presence of increasing concentrations of normal human serum (NHS). Since a clone of pathogenic HM-1:IMSS which initially was highly susceptible also acquired complement resistance during cultivation in the presence of NHS, it is concluded that complement resistance was caused by induction rather than by selection alone. Because cultivation in the presence of heat-inactivated NHS did not affect complement susceptibility of the cloned HM-1:IMSS, complement activation itself might induce complement resistance in pathogenic E. histolytica.

Lysis of pathogenic and nonpathogenic Entamoeba histolytica by human complement: methodological analysis

The effect of nonimmune human serum on Entamoeba histolytica trophozoites was studied: (a) using whole serum in the presence of Ca and Mg ions allowing complement activation via both the alternative and classical pathways or in the presence of MgEGTA permitting alternative pathway activation only; (b) using different E. histolytica isolates; (c) varying serum and trophozoite concentrations and the time of incubation; and (d) using three different methods to quantify lysis, i.e., microscopic inspection, flow cytometry and 111In release. All three methods yielded similar results, with flow cytometry being most sensitive in identifying membrane damage and 111In release being most valid in determining cell death. Microscopic analysis was reliable only when a chamber was used to calculate the number of complement treated cells in relation to the initial cell count. E. histolytica isolates were classified into three groups according to their susceptibility to lysis by complement: (i) pathogenic isolates after long term cultivation in vitro were susceptible; (ii) pathogenic isolates after recent in vivo passage were less susceptible; and (iii) nonpathogenic isolates were nearly unaffected by exposure to the alternative pathway alone. The extent of lysis of the various isolates correlated with the degree of complement consumption in the serum samples, suggesting that unlysed isolates did not activate complement under the conditions employed. In general, lysis of susceptible trophozoites increased with the serum concentration and with the time of incubation. However, when the trophozoite concentration was 10(6)/ml or higher, lysis no longer reflected complement susceptibility because of exhaustion of the complement supply.