Assessment of trace elements in human brain using inductively coupled plasma mass spectrometry

Recent brain research reveals a major role of trace elements in various diseases such as multiple sclerosis, Alzheimer's and Wilson's disease. The majority of published tissue concentrations dates back decades, and was assessed with various methods. Little is known about hemispherical differences, the correlation of trace elements or age-dependent changes in the human brain. Thus, the aim of this study was to examine trace element concentrations in different human brain regions after whole brain formalin fixation.549 samples of 13 brain regions were investigated in 11 deceased subjects without known history of brain pathology. Regional wet-to-dry mass ratios and concentrations of iron, copper, magnesium, manganese, calcium and zinc were determined using inductively coupled plasma mass spectrometry.Cortical gray matter revealed higher water content (wet-to-dry mass ratios 5.84–6.40) than white matter regions (wet-to-dry mass ratios 2.95–3.05). Element concentrations displayed specific regional differences. Good linear correlation of concentrations between elements was found for iron/copper as well as for manganese/magnesium (Spearman's rank correlation coefficient 0.74 and 0.65, respectively). Significant inter-hemispherical differences were found for copper in occipital white matter, for magnesium and calcium in putamen and for iron and copper in temporal white matter. An age dependent increase was seen in cortical gray matter for calcium, for magnesium in all regions except in cortical gray matter, for copper in substantia nigra and for zinc in occipital cortex.The presented trace element concentrations can serve as a fundamental basis for further brain research. Wet-to-dry mass ratios allow a comparison with reference data from other studies.     

Regional distribution of adenosine deaminase in the human neuraxis

Adenosine deaminase was determined in 28 different areas of the human neuraxis in 5 adult male cadavers, with no known disease of the nervous system, using a very sensitive colorimetric method. The enzyme was highest in the frontal lobe white matter, and lowest in the medulla and all levels of the spinal cord. Enzyme content was about twice as great in the white matter of the frontal and temporal lobes and cerebellum as it was in the cortical gray matter of these areas, but only slightly higher in the white matter of the parietal and occipital lobes as compared to gray. Average values of the enzyme were found in the remaining areas of the brain, with the exception of the pons and cerebellar white matter, where a higher than average value was noted.     

利用激光显微切割与microarray 技术对恒河猴脑中白质与 灰质基因表达的差异性的研究

目的:利用激光显微切割技术和microarray技术比较恒河猴脑组织中前额叶皮质(prefontal cortex,PFC)与小脑皮质(cere-bellar cortex,CBC)的灰质与白质基因表达的差异。方法:利用激光显微切割技术(laser capture dissection,LCM)与microarray技术的有效结合,提取恒河猴PFC与CBC的白质与灰质,分别提取RNA,合成cDNA文库。最后利用GeneChip 1.0 ST芯片技术,分析得出大脑与小脑中灰质与白质的表达差异性。结果:无论是灰质还是白质,在PFC中的高表达基因都要远远多于在CBC中的高表达基因。结论:使用LCM可以提取单一的细胞群,从而用于要求更为精确的实验当中。     

Regional distribution of potassium,calcium, and six trace elements in normal human brain

Eight elements (i.e. K, Ca, Mn, Fe, Cu, Zn, Se, and Rb) were measured in 50 different regions of 12 normal human brains by particle-induced X-ray emission (PIXE) analysis. The dry weight concentrations of K, Fe, Cu, Zn, Se, and Rb were consistently higher for gray than for white matter areas. The K, Zn and Se concentrations for the regions of mixed composition and, to some extent, also the Rb concentrations, were intermediate between the gray and white matter values, and they tended to decrease with decreasing neuron density. The mean dry weight concentrations of K, Ca, Zn, Se, and Rb in the various brain regions were highly correlated with the mean wet-to-dry weight ratios of these regions. For Mn, Fe, and Cu, however, such a correlation was not observed, and these elements exhibited elevated levels in several structures of the basal ganglia. For K, Fe, and Se the concentrations seemed to change with age. A hierarchical cluster analysis indicated that the structures clustered into two large groups, one comprising gray and mixed matter regions, the other white and mixed matter areas. Brain structures involved in the same physiological function or morphologically similar regions often conglomerated in a single subcluster.     

Effects of Neonatal Undernutrition on the Lipid Composition of Gray Matter and White Matter in Rat Brain

Abstract: Separate analyses were made of gray matter and white matter from rat brain after neonatal undernutrition. Newborn rats were redistributed into control, large-litter, and protein-deficient groups. Large litters had 16 rather than 8 pups with a dam. Protein-deficient dams were fed a 4%, instead of a 24%, casein diet. For controls at 21 days of age, the 2',3'-cyclic nucleotide-3'-phosphohydrolase activity was more than fivefold greater in white matter than in gray matter. Severe undernutrition (protein-deficient) gave 2',3'-cyclic nucleotide-3'-phosphohydrolase activities that were 36% lower in gray matter and 56% lower in white matter. Lipid galactose concentrations were 17% less than control in both gray matter and white matter. In protein-deficient white matter, phospholipid concentrations were 15% lower than control. Ethanolamine plasmalogens and phosphatidyl serine were affected most. Moderate undernutrition (large litter) had no effect on 2',3'-cyclic nucleotide-3'-phosphohydrolase activity. A 14% deficit of galactolipids was the only difference from controls in large-litter white matter. In large-litter gray matter, phospholipid concentrations were 16% higher than controls. Nearly all glycerophos-pholipids, including plasmalogens, were affected. With the exception of the myelination markers, 2',3'-cyclic nucleotide-3'-phosphohydrolase and lipid galactose, the development of lipids in gray matter is almost completely spared from the effects of undernutrition. The primary effect of undernutrition is on myelination, especially in white matter.     

Membrane Lipids, Selectively Diminished in Alzheimer Brains, Suggest Synapse Loss as a Primary Event in Early-Onset Form (Type I) and Demyelination in Late-Onset Form (Type II)

Abstract: Major membrane lipids were quantified in frontal (Brodmann area 9) and temporal (Brodmann areas 21 and 22) cortices, caudate nucleus, hippocampus, and frontal white matter of 12 cases with Alzheimer's disease (AD) type I (early onset), 21 cases with AD type II (late onset), and 20 age-matched controls. The concentration of gangliosides—a marker for axodendritic arborization—was reduced to 58–70% of the control concentration in all four gray areas (p < 0.0001) and to 81 % in frontal white matter (p < 0.01) of AD type I cases, whereas it was only significantly reduced in temporal cortex (p < 0.01), hippocampus (p < 0.05), and frontal white matter (p < 0.05) in AD type II cases. The concentration of phospholipids was also significantly reduced (p < 0.01–0.0001) in all four gray areas of AD type I cases but in no area of AD type II cases. The loss of cholesterol was only 50% of the corresponding phospholipid diminution in AD type I. These results suggested a pronounced loss of nerve endings in AD type 1. The characteristic membrane lipid disturbance in AD type II was a loss of myelin lipids. This is the first time a fundamental biochemical difference has been shown between the two major forms of AD.     

Implementation of X-ray Fluorescence Microscopy for Investigation of Elemental Abnormalities in Amyotrophic Lateral Sclerosis

The abnormalities of metallochemical reactions may contribute to the pathogenesis of Amyotrophic Lateral Sclerosis (ALS). In the present work, an investigation of the elemental composition of the gray matter, nerve cells and white matter from spinal cord tissues representing three ALS cases and five non-ALS controls was performed. This was done with the use of the synchrotron microbeam X-ray fluorescence technique (micro-SRXRF). The following elements were detected in the tissue sections: P, S, Cl, K, Ca, Fe, Cu, Zn and Br. A higher accumulation of Cl, K, Ca, Zn and Br was observed in the nerve cell bodies than in the surrounding tissue. Contrary to all other elements, Zn accumulation was lower in the white matter areas than in the gray matter ones. The results of quantitative analysis showed that there were no general abnormalities in the elemental accumulation between the ALS and the control group. However, for individual ALS cases such abnormalities were observed for the nerve cells. We also demonstrated differences in the elemental accumulation between the analyzed ALS cases.     

ACYL AND ALK-1'-ENYL GROUP COMPOSITION OF ETHANOLAMINE PHOSPHOGLYCERIDES OF HUMAN BRAIN

Ethanolamine phosphogylcerides (EPG) of human brain gray and white matter were analyzed for their alk-1′-enyl group and fatty acid compositions in sn-glycerol positions 1 and 2. Gray matter contained more 18:0 (54%) and less 18:1 (24.5%) alk-1′-enyl residues than white matter (16% and 57%. Sixty per cent of alk-1′-enyl 18.1 in gray matter was the (n-7), against 71%, in white matter. Both gray and white matter contained small amounts of 18:1 (n-5) and (n-3) isomers. The fatty acids in position I of the phosphatidylethanolamines were more saturated than the corresponding alk-1′-enyl groups of the plasmalogens. The ratios of monoenoic fatty acid isomers in position 1 were markedly different from those of the corresponding alk-1′-enyl groups in gray matter. The fatty acid patterns in position 2 of plasmalogen and phosphatidylethanolamines of white matter were similar except for 22:4(n-6) which was concentrated in the plasmalogen (16% against 10%, in the phosphatidyl ethanolamine). In gray matter, the same trend was noted. The data suggest that alk-1′-enyl residues and the fatty acids in position 1 as well as the fatty acids in position 2 of alk-1′-enyl acyl and diacyl type EPG in both gray and white matter are, at least in part, of different provenance.     

Prolonged Gray Matter Disease without Demyelination Caused by Theiler's Murine Encephalomyelitis Virus with a Mutation in VP2 Puff B

Theiler's murine encephalomyelitis virus (TMEV) is divided into two subgroups based on neurovirulence. During the acute phase, DA virus infects cells in the gray matter of the central nervous system (CNS). Throughout the chronic phase, DA virus infects glial cells in the white matter, causing demyelinating disease. Although GDVII virus also infects neurons in the gray matter, infected mice developed a severe polioencephalomyelitis, and no virus is detected in the white matter or other areas in the CNS in rare survivors. Several sequence differences between the two viruses are located in VP2 puff B and VP1 loop II, which are located near each other, close to the proposed receptor binding site. We constructed a DA virus mutant, DApBL2M, which has the VP1 loop II of GDVII virus and a mutation at position 171 in VP2 puff B. While DApBL2M virus replicated less efficiently than DA virus during the acute phase, DApBL2M-induced acute polioencephalitis was comparable to that in DA virus infection. Interestingly, during the chronic phase, DApBL2M caused prolonged gray matter disease in the brain without white matter involvement in the spinal cord. This is opposite what is observed during wild-type DA virus infection. Our study is the first to demonstrate that conformational differences via interaction of VP2 puff B and VP1 loop II between GDVII and DA viruses can play an important role in making the transition of infection from the gray matter in the brain to the spinal cord white matter during TMEV infection.     

Phosphoethanolamine and phosphocholine transferases in gray matter and white matter from developing rat brain

We have studied the activities of 2′,3′-cyclic nucleotide 3′-phosphohydrolase, 1,2-diacylglycerol: CDPethanolamine phosphoethanolamine transferase (EC 2.7.8.1), and 1,2-diacylglycerol: CDPcholine phosphocholine transferase (EC 2.7.8.2) in developing rat brain gray matter and white matter. The specific activity of cyclic nucleotide phosphohydrolase was 5–8 fold higher in white matter than in gray matter at all ages. No significant changes were observed during development. The specific activity of phosphocholine transferase was 2 to 3 fold higher than phosphoethanolamine transferase at all ages both in gray and white matter. Both phosphocholine transferase and phosphoethanolamine transferase increased more than 2 fold in specific activity between 14 and 90 days of age. The total activity of phosphocholine transferase also showed an increase during development. The apparentK _m values for nucleotides and dicaprin were similar in gray matter and white matter. Except for lowK _m values for nucleotides at 14 days of age, no significant changes were observed during development. Changes in rates of glycerophospholipid synthesis may be partly due to the specific activities of these enzymes but are also determined by the quantities of substrates and inhibitors and by affinities for the substrates. Special Issue dedicated to Dr. Eugene Kreps.     

Gray and White Matter Distribution in Dyslexia: A VBM Study of Superior Temporal Gyrus Asymmetry

In the present study, we investigated brain morphological signatures of dyslexia by using a voxel-based asymmetry analysis. Dyslexia is a developmental disorder that affects the acquisition of reading and spelling abilities and is associated with a phonological deficit. Speech perception disabilities have been associated with this deficit, particularly when listening conditions are challenging, such as in noisy environments. These deficits are associated with known neurophysiological correlates, such as a reduction in the functional activation or a modification of functional asymmetry in the cortical regions involved in speech processing, such as the bilateral superior temporal areas. These functional deficits have been associated with macroscopic morphological abnormalities, which potentially include a reduction in gray and white matter volumes, combined with modifications of the leftward asymmetry along the perisylvian areas. The purpose of this study was to investigate gray/white matter distribution asymmetries in dyslexic adults using automated image processing derived from the voxel-based morphometry technique. Correlations with speech-in-noise perception abilities were also investigated. The results confirmed the presence of gray matter distribution abnormalities in the superior temporal gyrus (STG) and the superior temporal Sulcus (STS) in individuals with dyslexia. Specifically, the gray matter of adults with dyslexia was symmetrically distributed over one particular region of the STS, the temporal voice area, whereas normal readers showed a clear rightward gray matter asymmetry in this area. We also identified a region in the left posterior STG in which the white matter distribution asymmetry was correlated to speech-in-noise comprehension abilities in dyslexic adults. These results provide further information concerning the morphological alterations observed in dyslexia, revealing the presence of both gray and white matter distribution anomalies and the potential involvement of these defects in speech-in-noise deficits.     

High-affinity glycine and glutamate transport in pig forebrain white and gray matter: a quantitative study

High-affinity uptake of glycine and glutamate modulates glutamatergic neurotransmission in gray matter. N-Methyl-D-aspartate (NMDA) receptors were recently described on white matter oligodendrocytes, therefore uptake of glutamate and glycine in white matter may also modulate NMDA receptor function. We found that glycine uptake in white structures of pig forebrain (corpus callosum, fimbria, subcortical pyramidal tracts, and occipital subcortical white matter) was similar to that in gray structures (frontal and temporal cortices and hippocampus), and that it was sensitive to sarcosine, a GLYT1 inhibitor (IC(50) 15 microM). Glutamate uptake in white matter was approximately 10% of that in gray; it was sensitive to dihydrokainate, an EAAT2 inhibitor. The levels of glycine and its precursor serine were similar in white and gray matter: approximately 2 and 1 nmol/mg tissue, respectively. The white matter level of glutamate was approximately 7.6 nmol/mg tissue, or approximately 74% of gray matter levels. The activity of serine hydroxymethyl transferase, which converts serine into glycine, was similar in white and gray matter (11-18 pmol/(mg tissue)min), whereas the white matter activity of phosphate-activated glutaminase, which converts glutamine into glutamate, was approximately 100 pmol/(mg tissue)min, or approximately 34% of gray matter activity. The white matter activity of glutamine synthetase, the glial enzyme that converts glutamate into glutamine, was 20-40 nmol/(mg tissue)min in neocortex and 5-6 nmol/(mg tissue)min in white matter. The data show that forebrain white matter is equipped to regulate extracellular levels of glycine and glutamate, functions that may modulate white matter NMDA receptor function.     

Increased Cerebral Water Content in Hemodialysis Patients

Little information is available on the impact of hemodialysis on cerebral water homeostasis and its distribution in chronic kidney disease. We used a neuropsychological test battery, structural magnetic resonance imaging (MRI) and a novel technique for quantitative measurement of localized water content using 3T MRI to investigate ten hemodialysis patients (HD) on a dialysis-free day and after hemodialysis (2.4±2.2 hours), and a matched healthy control group with the same time interval. Neuropsychological testing revealed mainly attentional and executive cognitive dysfunction in HD. Voxel-based-morphometry showed only marginal alterations in the right inferior medial temporal lobe white matter in HD compared to controls. Marked increases in global brain water content were found in the white matter, specifically in parietal areas, in HD patients compared to controls. Although the global water content in the gray matter did not differ between the two groups, regional increases of brain water content in particular in parieto-temporal gray matter areas were observed in HD patients. No relevant brain hydration changes were revealed before and after hemodialysis. Whereas longer duration of dialysis vintage was associated with increased water content in parieto-temporal-occipital regions, lower intradialytic weight changes were negatively correlated with brain water content in these areas in HD patients. Worse cognitive performance on an attention task correlated with increased hydration in frontal white matter. In conclusion, long-term HD is associated with altered brain tissue water homeostasis mainly in parietal white matter regions, whereas the attentional domain in the cognitive dysfunction profile in HD could be linked to increased frontal white matter water content.     

Medial Frontal White and Gray Matter Contributions to General Intelligence

The medial orbitofrontal cortex (mOFC) and rostral anterior cingulate cortex (rACC) are part of a wider neural network that plays an important role in general intelligence and executive function. We used structural brain imaging to quantify magnetic resonance gray matter volume and diffusion tensor white matter integrity of the mOFC-rACC network in 26 healthy participants who also completed neuropsychological tests of intellectual abilities and executive function. Stochastic tractography, the most effective Diffusion Tensor Imaging method for examining white matter connections between adjacent gray matter regions, was employed to assess the integrity of mOFC-rACC pathways. Fractional anisotropy (FA), which reflects the integrity of white matter connections, was calculated. Results indicated that higher intelligence correlated with greater gray matter volumes for both mOFC and rACC, as well as with increased FA for left posterior mOFC-rACC connectivity. Hierarchical regression analyses revealed that DTI-derived FA of left posterior mOFC-rACC uniquely accounted for 29%–34% of the variance in IQ, in comparison to 11%–16% uniquely explained by gray matter volume of the left rACC. Together, left rACC gray matter volume and white matter connectivity between left posterior mOFC and rACC accounted for up to 50% of the variance in general intelligence. This study is to our knowledge the first to examine white matter connectivity between OFC and ACC, two gray matter regions of interests that are very close in physical proximity, and underscores the important independent contributions of variations in rACC gray matter volume and mOFC-rACC white matter connectivity to individual differences in general intelligence.     

Bovine brain gray and white matter exhibit differential protein prenyl transferase activity

Protein farnesyl transferase and geranylgeranyl transferase-I activities were determined in gray and white matter from various regions of bovine brain. Farnesyl transferase activity was 3–8 times greater than geranylgeranyl transferase-I activity. However, farnesyl transferase activity was about 2 times greater in the white matter than in the gray matter in all regions of the brain. Mixing experiments indicated lack of farnesyl transferase activators in white matter. This difference in farnesyl transferase activity may be due to enzyme content and may have implications in brain cell function.     

Long-chain acyl CoA synthetase in microsomes from rat brain gray matter and white matter

Long-chain acyl coenzyme A (CoA) synthetase in homogenates and microsomes from rat brain gray and white matter was studied. The formation of the thioesters of CoA was studied upon addition of [1-¹⁴C]-labeled fatty acids. The maximal activities were seen with linoleic acid, followed by arachidonic, palmitic, and docosahexaenoic acids in both gray and white matter homogenates and microsomes. The specific activities in microsomes were 3–5 times higher than in homogenates. The presence of Triton X-100 in the assay system enhanced the activity of long-chain acyl CoA synthetase in homogenates. The effect was more pronounced in palmitic and docosahexaenoic acid activation. The apparentK _m values andV _max values for palmitic and docosahexaenoic acids were much lower than for linoleic and arachidonic acids. The presence of Triton X-100 in the medium caused a definite decrease in the apparentK _m and Vmax values for all the fatty acid except palmitic acid in which case the reverse was true. There were no significant differences observed in the kinetic measurements between gray and white matter microsomes. These findings are similar to those resulting from the known interference of Triton X-100 in the measurement of kinetic variables of long-chain acyl CoA synthetase of liver microsomes. In this work, no correlation was observed between the fatty acid composition of gray and white matter and the capacity of these tissues for the activation of different fatty acids.     

Cognitive Processing Speed in Older Adults: Relationship with White Matter Integrity

Cognitive processing slows with age. We sought to determine the importance of white matter integrity, assessed by diffusion tensor imaging (DTI), at influencing cognitive processing speed among normal older adults, assessed using a novel battery of computerized, non-verbal, choice reaction time tasks. We studied 131 cognitively normal adults aged 55–87 using a cross-sectional design. Each participant underwent our test battery, as well as MRI with DTI. We carried out cross-subject comparisons using tract-based spatial statistics. As expected, reaction time slowed significantly with age. In diffuse areas of frontal and parietal white matter, especially the anterior corpus callosum, fractional anisotropy values correlated negatively with reaction time. The genu and body of the corpus callosum, superior longitudinal fasciculus, and inferior fronto-occipital fasciculus were among the areas most involved. This relationship was not explained by gray or white matter atrophy or by white matter lesion volume. In a statistical mediation analysis, loss of white matter integrity mediated the relationship between age and cognitive processing speed.     

Gray matter imaging in multiple sclerosis: what have we learned?

At the early onset of the 20^th century, several studies already reported that the gray matter was implicated in the histopathology of multiple sclerosis (MS). However, as white matter pathology long received predominant attention in this disease, and histological staining techniques for detecting myelin in the gray matter were suboptimal, it was not until the beginning of the 21^st century that the true extent and importance of gray matter pathology in MS was finally recognized. Gray matter damage was shown to be frequent and extensive, and more pronounced in the progressive disease phases. Several studies subsequently demonstrated that the histopathology of gray matter lesions differs from that of white matter lesions. Unfortunately, imaging of pathology in gray matter structures proved to be difficult, especially when using conventional magnetic resonance imaging (MRI) techniques. However, with the recent introduction of several more advanced MRI techniques, the detection of cortical and subcortical damage in MS has considerably improved. This has important consequences for studying the clinical correlates of gray matter damage. In this review, we provide an overview of what has been learned about imaging of gray matter damage in MS, and offer a brief perspective with regards to future developments in this field.     

The immune system preferentially clears Theiler's virus from the gray matter of the central nervous system.

Infection of susceptible strains of mice with Daniel's (DA) strains of Theiler's murine encephalomyelitis virus (DAV) results in virus persistence in the central nervous system (CNS) white matter and chronic demyelination similar to that observed in multiple sclerosis. We investigated whether persistence is due to the immune system more efficiently clearing DAV from gray than from white matter of the CNS. Severe combined immunodeficient (SCID) and immunocompetent C.B-17 mice were infected with DAV to determine the kinetics, temporal distribution, and tropism of the virus in CNS. In early disease (6 h to 7 days postinfection), DAV replicated with similar kinetics in the brains and spinal cords of SCID and immunocompetent mice and in gray and white matter. DAV RNA was localized within 48 h in CNS cells of all phenotypes, including neurons, oligodendrocytes, astrocytes, and macrophages/microglia. In late disease (13 to 17 days postinfection), SCID mice became moribund and permitted higher DAV replication in both gray and white matter. In contrast, immunocompetent mice cleared virus from the gray matter but showed replication in the white matter of their brains and spinal cords. Reconstitution of SCID mice with nonimmune splenocytes or anti-DAV antibodies after establishment of infection demonstrated that both cellular and humoral immune responses decreased virus from the gray matter; however, the cellular responses were more effective. SCID mice reconstituted with splenocytes depleted of CD4+ or CD8+ T lymphocytes cleared virus from the gray matter but allowed replication in the white matter. These studies demonstrate that both neurons and glia are infected early following DAV infection but that virus persistence in the white matter is due to preferential clearance of virus from the gray matter by the immune system.