The Neuromelanin-related T2* Contrast in Postmortem Human Substantia Nigra with 7T MRI

High field magnetic resonance imaging (MRI)-based delineation of the substantia nigra (SN) and visualization of its inner cellular organization are promising methods for the evaluation of morphological changes associated with neurodegenerative diseases; however, corresponding MR contrasts must be matched and validated with quantitative histological information. Slices from two postmortem SN samples were imaged with a 7 Tesla (7T) MRI with T1 and T2* imaging protocols and then stained with Perl???s Prussian blue, Kluver-Barrera, tyrosine hydroxylase, and calbindin immunohistochemistry in a serial manner. The association between T2* values and quantitative histology was investigated with a co-registration method that accounts for histology slice preparation. The ventral T2* hypointense layers between the SNr and the crus cerebri extended anteriorly to the posterior part of the crus cerebri, which demonstrates the difficulty with an MRI-based delineation of the SN. We found that the paramagnetic hypointense areas within the dorsolateral SN corresponded to clusters of neuromelanin (NM). These NM-rich zones were distinct from the hypointense ventromedial regions with high iron pigments. Nigral T2* imaging at 7T can reflect the density of NM-containing neurons as the metal-bound NM macromolecules may decrease T2* values and cause hypointense signalling in T2* imaging at 7T.ope

Locus coeruleus imaging as a biomarker for noradrenergic dysfunction in neurodegenerative diseases

Pathological alterations to the locus coeruleus, the major source of noradrenaline in the brain, are histologically evident in early stages of neurodegenerative diseases. Novel MRI approaches now provide an opportunity to quantify structural features of the locus coeruleus in vivo during disease progression. In combination with neuropathological biomarkers, in vivo locus coeruleus imaging could help to understand the contribution of locus coeruleus neurodegeneration to clinical and pathological manifestations in Alzheimer’s disease, atypical neurodegenerative dementias and Parkinson’s disease. Moreover, as the functional sensitivity of the noradrenergic system is likely to change with disease progression, in vivo measures of locus coeruleus integrity could provide new pathophysiological insights into cognitive and behavioural symptoms. Locus coeruleus imaging also holds the promise to stratify patients into clinical trials according to noradrenergic dysfunction. In this article, we present a consensus on how non-invasive in vivo assessment of locus coeruleus integrity can be used for clinical research in neurodegenerative diseases. We outline the next steps for in vivo, post-mortem and clinical studies that can lay the groundwork to evaluate the potential of locus coeruleus imaging as a biomarker for neurodegenerative diseases

Induction, purification, and characterization of a laccase isozyme from Pleurotus sajor-caju and the potential in decolorization of textile dyes

Ferulic acid causes a strain of Pleurotus sajor-caju to excrete large amounts of one laccase isozyme, that was purified to homogeneity. Ferulic acid was the best inductor for laccase in this fungal strain. Laccase molecular weight, copper, and sugar content were characterized. Its catalytic activity was studied using a wide range of phenolics and aromatic amines; the purified laccase was found to be able to oxidize catechols, quinols, methoxyphenols, some aromatic amines and their methyl derivatives, and also resorcinol and phloroglucinol. In addition, its thermostability and activity in the presence of some organic solvents were evaluated. The ability of the enzyme to decolorize some textile dyes was studied, also in the presence of the co-oxidizer hydrogen peroxide, and compared to that of some peroxidases. (c) 2010 Elsevier B.V. All rights reserved

Contrast mechanisms associated with neuromelanin-MRI.

Purpose To investigate the physical mechanisms associated with the contrast observed in neuromelanin-MRI. Methods Phantoms having different concentrations of synthetic melanins with different degrees of iron loading were examined on a 3T scanner using relaxometry and quantitative magnetization transfer (MT). Results Concentration-dependent T1- and T2-shortening was most pronounced for the melanin pigment when combined with iron. Metal-free melanin had a negligible effect on the magnetization transfer spectra. On the contrary, the presence of iron-laden melanins resulted in a decreased magnetization transfer ratio. The presence of melanin or iron (or both) did not have a significant effect on the macromolecular content, represented by the pool size ratio. Conclusion The primary mechanism underlying contrast in neuromelanin-MRI seems to be the T1 reduction associated with melanin-iron complexes. The macromolecular content is not significantly influenced by the presence of melanin with or without iron, and thus the MT is not directly affected. However, as T1 plays a role in determining the MT-weighted signal, the magnetization transfer ratio is reduced in the presence of melanin-iron complexes.</p

Contrast mechanisms associated with neuromelanin-MRI.

Purpose To investigate the physical mechanisms associated with the contrast observed in neuromelanin-MRI. Methods Phantoms having different concentrations of synthetic melanins with different degrees of iron loading were examined on a 3T scanner using relaxometry and quantitative magnetization transfer (MT). Results Concentration-dependent T1- and T2-shortening was most pronounced for the melanin pigment when combined with iron. Metal-free melanin had a negligible effect on the magnetization transfer spectra. On the contrary, the presence of iron-laden melanins resulted in a decreased magnetization transfer ratio. The presence of melanin or iron (or both) did not have a significant effect on the macromolecular content, represented by the pool size ratio. Conclusion The primary mechanism underlying contrast in neuromelanin-MRI seems to be the T1 reduction associated with melanin-iron complexes. The macromolecular content is not significantly influenced by the presence of melanin with or without iron, and thus the MT is not directly affected. However, as T1 plays a role in determining the MT-weighted signal, the magnetization transfer ratio is reduced in the presence of melanin-iron complexes.</p