Effect of postweaning protein deficiency on the content and lipid composition of gray and white matter in neonatally undernourished rat brain

The effects of neonatal undernutrition and postweaning protein deficiency on the content and lipid composition of gray and white matter of 63 days old rat brain have been studied. The concentrations of different lipids remain the same, but the relative proportion of gray and white matter changes thus reflecting the differences in the concentration of whole brain lipids.     

Substantial sulfatide deficiency and ceramide elevation in very early Alzheimer's disease: potential role in disease pathogenesis

In addition to pathology in the gray matter, there are also abnormalities in the white matter in Alzheimer's disease (AD). Sulfatide species are a class of myelin-specific sphingolipids and are involved in certain diseases of the central nervous system. To assess whether sulfatide content in gray and white matter in human subjects is associated with both the presence of Alzheimer's disease (AD) pathology as well as the stage of dementia, we analyzed the sulfatide content of brain tissue lipid extracts by electrospray ionization mass spectrometry from 22 subjects whose cognitive status at time of death varied from no dementia to very severe dementia. All subjects with dementia had AD pathology. The results demonstrate that: (i) sulfatides were depleted up to 93% in gray matter and up to 58% in white matter from all examined brain regions from AD subjects with very mild dementia, whereas all other major classes of lipid (except plasmalogen) in these subjects were not altered in comparison to those from age-matched subjects with no dementia; (ii) there was no apparent deficiency in the biosynthesis of sulfatides in very mild AD subjects as characterized by the examination of galactocerebroside sulfotransferase activities in post-mortem brain tissues; (iii) the content of ceramides (a class of potential degradation products of sulfatides) was elevated more than three-fold in white matter and peaked at the stage of very mild dementia. The findings demonstrate that a marked decrease in sulfatides is associated with AD pathology even in subjects with very mild dementia and that these changes may be linked with early events in the pathological process of AD.     

High throughput lipidomic profiling of schizophrenia and bipolar disorder brain tissue reveals alterations of free fatty acids, phosphatidylcholines, and ceramides

A mass spectrometry based high throughput approach was employed to profile white and gray matter lipid levels in the prefrontal cortex (Brodmann area 9) of 45 subjects including 15 schizophrenia and 15 bipolar disorder patients as well as 15 controls samples. We found statistically significant alterations in levels of free fatty acids and phosphatidylcholine in gray and white matter of both schizophrenia and bipolar disorder samples compared to controls. Also, ceramides were identified to be significantly increased in white matter of both neuropsychiatric disorders as compared to control levels. The patient cohort investigated in this study includes a number of drug naive as well as untreated patients, allowing the assessment of drug effects on lipid levels. Our findings indicate that while gray matter phosphatidylcholine levels were influenced by antipsychotic medication, this was not the case for phosphatidylcholine levels in white matter. Changes in free fatty acids or ceramides in either white or gray matter also did not appear to be influenced by antipsychotic treatment. To assess lipid profiles in the living patient, we also profiled lipids of 40 red blood cell samples, including 7 samples from drug naive first onset patients. We found significant alterations in the concentrations of free fatty acids as well as ceramide. Overall, our findings suggest that lipid abnormalities may be a disease intrinsic feature of both schizophrenia and bipolar disorder reflected by significant changes in the central nervous system as well as peripheral tissues.     

Membrane redistribution of gangliosides and glycosylphosphatidylinositol-anchored proteins in brain tissue sections under conditions of lipid raft isolation

Sphingolipids, glycosylphosphatidylinositol (GPI)-anchored proteins, and certain signaling molecules segregate from bulk membrane lipids into lateral domains termed lipid rafts, which are often isolated based on their insolubility in cold nonionic detergents. During immunohistological studies of gangliosides, major sphingolipids of the brain, we found that cold Triton X-100 solubility is bidirectional, leading to histological redistribution from gray to white matter. When brain sections were treated with > or =0.25% Triton X-100 at 4 degrees C, ganglioside GD1a, which is normally enriched in gray matter and depleted in white matter, redistributed into white matter tracts. Incubation of brain sections from knockout mice lacking GD1a with wild-type sections in the presence of cold Triton X-100 resulted in GD1a redistribution from wild-type gray matter to knockout white matter. GM1, which is normally enriched in white matter, remained in white matter after cold detergent treatment and did not migrate to knockout mouse brain sections. However, when gray matter gangliosides were enzymatically converted into GM1 in situ, the newly formed GM1 transmigrated to knockout mouse brain sections in the presence of cold detergent. When purified GD1a was added to knockout mouse brain sections in the presence of cold Triton X-100, it preferentially incorporated into white matter tracts. These data demonstrate that brain white matter is a sink for gangliosides, which redistribute from gray matter in the presence of low concentrations of cold Triton X-100. A GPI-anchored protein, Thy-1, also transmigrated from wild-type to Thy-1 knockout mouse brain sections in the presence of detergent at 4 degrees C, although less efficiently than did gangliosides. These data raise technical challenges for using nonionic detergents in certain histological protocols and for isolation of lipid rafts from brain tissue.     

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.     

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.     

Phospholipids and acyl groups in subcellular fractions from human cerebral cortex

Subcellular fractionation of human brain cortex obtained at autopsy yielded microsomal and synaptosome-rich fractions from the gray matter and microsomal and purified myelin fractions from the white matter. The phospholipids of myelin were high in plasmalogens, and the molar ratio of alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 4. The acyl groups of the myelin phosphoglycerides were enriched in monoenes (mainly 18:1 and 20:1) and a tetraene, 22:4(n - 6). The phospholipids in the synaptosome-rich fraction were high in diacyl sn-glycero-3-phosphorylcholine, and the molar ratio of the alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 0.88. The acyl groups of synaptosomal ethanolamine phosphoglycerides were rich in 22:6(n - 3) but contained a very low amount of 20:1. The lipid composition of microsomes from the gray matter was different from that of microsomes from the white matter but was nearly identical with that of the synaptosome-rich fraction. Except for a slightly lower proportion of alkenyl acyl sn-glycero-3-phosphorylethanolamine and sphingomyelin, the lipid composition of microsomes from the white matter was also similar to that of the myelin. There were also species-related differences between the brain lipid composition of human and subhuman primates and that of the rodents. Furthermore, the brain lipid composition in normal human subjects is rather constant and does not seem to be affected much by individual variations.     

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。     

Plasmalogen deficiency in early Alzheimer's disease subjects and in animal models: molecular characterization using electrospray ionization mass spectrometry

To explore the hypothesis that alterations in ethanolamine plasmalogen may be directly related to the severity of dementia in Alzheimer's disease (AD), we performed a systematic examination of plasmalogen content in cellular membranes of gray and white matter from different regions of human subjects with a spectrum of AD clinical dementia ratings (CDR) using electrospray ionization mass spectrometry (ESI/MS). The results demonstrate: (1) a dramatic decrease in plasmalogen content (up to 40 mol% of total plasmalogen) in white matter at a very early stage of AD (i.e. CDR 0.5); (2) a correlation of the deficiency in gray matter plasmalogen content with the AD CDR (i.e. approximately 10 mol% of deficiency at CDR 0.5 (very mild dementia) to approximately 30 mol% of deficiency at CDR 3 (severe dementia); (3) an absence of alterations of plasmalogen content and molecular species in cerebellar gray matter at any CDR despite dramatic alterations of plasmalogen content in cerebellar white matter. Alterations of ethanolamine plasmalogen content in two mouse models of AD, APP(V717F) and APPsw, were also examined by ESI/MS. A plasmalogen deficiency was present (up to 10 mol% of total plasmalogen at the age of 18 months) in cerebral cortices, but was absent in cerebella from both animal models. These results suggest plasmalogen deficiency may play an important role in the AD pathogenesis, particularly in the white matter, and suggest that altered plasmalogen content may contribute to neurodegeneration, synapse loss and synaptic dysfunction in AD.     

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.     

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.     

Distinct spatio-temporal expression of ABCA and ABCG transporters in the developing and adult mouse brain

Using in situ hybridization for the mouse brain, we analyzed developmental changes in gene expression for the ATP-binding cassette (ABC) transporter subfamilies ABCA1-4 and 7, and ABCG1, 2, 4, 5 and 8. In the embryonic brains, ABCA1 and A7 were highly expressed in the ventricular (or germinal) zone, whereas ABCA2, A3 and G4 were enriched in the mantle (or differentiating) zone. At the postnatal stages, ABCA1 was detected in both the gray and white matter and in the choroid plexus. On the other hand, ABCA2, A3 and A7 were distributed in the gray matter. In addition, marked up-regulation of ABCA2 occurred in the white matter at 14 days-of-age when various myelin protein genes are known to be up-regulated. In marked contrast, ABCA4 was selective to the choroid plexus throughout development. ABCG1 was expressed in both the gray and white matters, whereas ABCG4 was confined to the gray matter. ABCG2 was diffusely and weakly detected throughout the brain at all stages examined. Immunohistochemistry of ABCG2 showed its preferential expression on the luminal membrane of brain capillaries. Expression signals for ABCG5 and G8 were barely detected at any stages. The distinct spatio-temporal expressions of individual ABCA and G transporters may reflect their distinct cellular expressions in the developing and adult brains, presumably, to regulate and maintain lipid homeostasis in the brain.     

d-Aspartate in Human Brain

The presence of the biologically uncommon D-aspartic acid (D-aspartate) in human brain white matter has been previously reported. The earlier study has now been expanded to include D/L-aspartate ratios from 67 normal brains. The data show that the D-aspartate content increases rapidly from 1 year to approximately 35 years of age, levels off in middle age, and then appears to decrease somewhat. The D-aspartate content in gray matter remains at a consistently low level (half of that found in white matter) throughout the human life span. Within the limitations of current analytical methods, there was no detectable difference in D/L-aspartate ratios in white and gray matter of brains with Alzheimer's disease and several other pathologies when compared with brains of normal subjects. However, the presence of a significant D-aspartate level in white matter during the adult life span may lead to changes in protein configuration related to dysfunctions associated with the aging brain.     

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.     

EFFECT OF OLIGEMIA ON REGIONAL METABOLITE LEVELS IN CAT BRAIN

Abstract— Incomplete cerebral ischemia (oligemia) was produced in cat by carotid occlusion combined with arterial hypotension. Lowering arterial pressure to 50–60 Torr for 20 min caused marked alterations of the ATP, phosphocreatine, and lactate content of subcortical white matter. In contrast, metabolite levels in cerebral cortex and caudate nucleus were only moderately perturbed from control values. More severe oligemia resulted when arterial pressure was lowered to 30 Torr for 20 min following carotid occlusion. Metabolite levels in cortex, caudate nucleus, and white matter were greatly altered from control. In the gray matter there was regional heterogeneity of metabolic alteration, as evidenced from the pattern of NADH tissue fluorescence. The cortex contained micro-patches (0.1mm) of increased NADH, which frequently exhibited a columnar orientation.
These findings demonstrate two distinct types of cerebral inhomogeneity of metabolic failure with reduced blood flow; white matter fails before gray matter, and there is micro-heterogeneity of metabolic failure in the gray matter.     

Concentration and fatty acid composition of cerebrosides and sulfatides in mature and immature human brain

The fatty acid composition of cerebrosides and sulfatides from frontal lobe gray and white matter was determined for five fresh and four formalinized adult brains and for eight infants. Fatty acid patterns were unaffected by formalinization, but varied considerably from one another in the proportion of saturated to unsaturated fatty acids. The percentages of 24:0 and 24:1 increased with age. Cerebrosides obtained from areas such as the brainstem and cerebellum, where myelination was more advanced, tended to have a larger proportion of long-chain fatty acids than samples extracted from frontal or parietal lobe white matter. Hydroxy fatty acids showed an adult pattern in all instances in which amounts sufficient for accurate quantification could be isolated. Lipid hexose, cerebroside + sulfatide hexose, and methanoleluted hexose were measured in the brains of 12 infants ranging in age from a 4 month fetus to 2 yr. In the most immature, the majority of lipid hexose was in the form of glycolipids more polar than cerebrosides and sulfatides. These have tentatively been identified as hematosides and globosides. With maturation, cerebrosides and sulfatides increased progressively, but the amounts of the more polar glycolipids remained constant in relation to the total lipid content of tissue.     

Lipid Compositions of Different Regions of the Human Brain During Aging

The neutral and phospholipid compositions of various regions of the human brain were analyzed using autopsy material covering the life period between 33 and 92 years of age. The protein content was also measured and, on a weight basis, this content is unchanged in the cerebellum, pons, and medulla oblongata, whereas in the 90-year-old group it decreases in the hippocampus, gray matter, and nucleus caudatus. In white matter, the protein content decreases continuously with age. The phospholipid composition is characteristic of the region investigated, but remains unchanged during aging. The total phospholipid content exhibits only a 5-10% decrease in the oldest age group. The content of dolichol and its polyisoprenoid pattern are also characteristic of the region analyzed. Between 33 and 92 years of age, the amount of dolichol in all portions of the brain increases three- to fourfold, but the isoprenoid pattern remains constant. The level of dolichyl-P varies between different regions, but only a moderate increase is seen with age. Ubiquinone content is highest in the nucleus caudatus, gray matter, and hippocampus, and in all areas this content is decreased to a great extent in the oldest age groups. All regions of the human brain are rich in cholesterol, but alterations in the amount of this lipid are highly variable during aging, ranging from no change to a 40% decrease.     

The regional distribution of manganese in the normal human brain

The concentration of manganese per gram dry tissue weight was determined in samples from 39 areas of 8 normal human brains. Manganese was shown to be unevenly distributed with the largest concentrations in the pineal gland and the olfactory bulb. The gray matter yielded a higher content of manganese than the white matter. Significant differences between individuals were found for identical areas of the gray and white matter of the cerebral cortex. Higher levels of manganese were demonstrated in the tail of the caudate nucleus than in the body and the head of the same structure. No significant correlation was shown between the amount of manganese in brain and age.     

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.     

Effect of exogenous dolichyl monophosphate on a developmental change in mannosylphosphoryldolichol biosynthesis

The initial rate of mannosylphosphoryldolichol formation by pig brain white matter is 2.9 to 3.3-fold higher in membranes from actively myelinating animals as compared to similar preparations from adults. Exogenous dolichyl monophosphate stimulated mannolipid synthesis in both preparations indicating that the level of the acceptor lipid was rate-limiting. The relative enhancement, however, was higher in membranes from adult animals reducing the ratio of initial rates for young/adult. Exogenous dolichyl monophosphate also stimulated the labeling of a mannosylated oligosaccharide lipid and mannoproteins, including a polypeptide (apparent molecular weight of 100,000) not labeled by gray matter membranes.