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At least 109 records · Page 6Linked to original sources
PubMed1994

Quantitation of grey matter, white matter, and cerebrospinal fluid from spin-echo magnetic resonance images using an artificial neural network technique.

An operator independent technique has been developed to quantitate the volume of white matter (WM), grey matter (GM), and cerebrospinal fluid (CSF) using spin-echo magnetic resonance images. Using skull stripped spin-echo images, CSF was removed using an automated thresholding technique. The bimodal histogram of the remaining images was used to train a perceptron and a single hidden layer neural network to output the percentage of GM and WM in the image. The output values were compared with those of a semiautomated technique employing a least square fitting technique [graduated nonconvexity algorithm (GNC)] applied to the bimodal histogram. This semiautomated technique allowed for intervention by the radiologist. Fourteen normal volunteers with eight contiguous slices each were analyzed. The individual percentages of WM, GM, and CSF of 40 slices from five subjects not used in the training set as well as the total percentages of GM, WM, and CSF in each individual were predicted using the two artificial network architectures. GM, WM, and CSF percentages were predicted within 7% for individual slices while total percentages of WM, GM, and CSF were computed accurately with an absolute error of less than 5% when compared to the semiautomated technique involving a trained neuroradiologist.

Adult↗
PubMed1998

Selective measurement of white matter and gray matter diffusion trace values in normal human brain.

The trace of the diffusion tensor (or simply the trace) is diagnostically valuable for detecting acute ischemic lesions. A number of studies indicate that the trace of human gray matter (GM) and white matter (WM) are quite similar. This is somewhat surprising considering the different cellular environments of GM and WM. It is possible that partial volume averaging (PVA) effects between GM and WM, inherent in many of the ultrafast imaging sequences used for diffusion measurements, are responsible for this observation. In order to minimize PVA effects, the trace values of GM and WM have been selectively measured by implementing double inversion recovery (DIR) echo planar imaging (EPI) pulse sequences. Results on six normal volunteers indicate that the trace values of WM and GM are not statistically different.

Adult↗
PubMedDate not supplied

[Volumetric analysis of gray matter, white matter and cerebrospinal fluid space in schizophrenia].

Schizophrenia is characterized by diffuse brain abnormalities, some of them involving volumes of three intracranial compartments: gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF). Novel methods, such as Statistical Parametrical Mapping, provide an automated means of comparing structural features across high quality MRI scans and the measurement based on the principles of voxel based morphometry. For the purposes of the present study, we selected sex balanced group of young adults with recent onset illness to assess the effects of the illness on the volumes of compartments and also to minimize the effects of chronicity, medication, sex and aging. Sixty-four subjects were selected from a larger sample (inclusion criteria: age range 18-31). Thirty-one had DSM IV diagnosis of schizophrenia or schizoaffective disorder, 33 were controls. T1 weighted MRI images were acquired on two scanners (1.5T both): a) fast gradient echo sequence, FLASH, 40 msec repetition time, 5 ms echo time, 40 degree flip angle and b) turbo gradient echo, 12 msec repetition time, 4 msec echo time, 20 degree flip angle, 1 excitation). The resulting data set consisted of: a) 128 consecutive slices with 1.17 mm thickness and 256 x 256 pixels per slice and b) 160 consecutive slices of 1 mm thickness and 256 x 256 pixels per slice. All 64 images were processed by ANALZYE, and normalized and segmented by SPM99. Following the automatic segmentation of the images into the three intracranial compartments, volumetry was performed based on the principles of voxel analysis. Results were expressed relative to whole brain volume, and MANOVA analyses were performed to correct the confounding effects of MRI acquisition center differences and age difference between diagnostic groups. Young adults with recent onset schizophrenia had 6% reduction in GM volume and 14% increase in the volume of CSF, after all confounders were included into analyses (MANCOVA: p = 0.006 and 0.0002, respectively). No significant changes in WM volume were evident. In comparison to a few similar studies published recently, all results yielded similar scores regarding effects of recent onset illness and young adult population, thus confirming the reliability of the procedure. In conclusion, global neuropil reduction was discussed as a consequence of the cortical neurodevelopmental disgenesis. It was suggested that neuropil reduction i.e. synaptic and dendritic changes were to induce functional abnormalities and the expression of schizophrenia.

Adolescent↗
PubMed1987

Influence of supplemental nitrogen source on digestion of nitrogen, dry matter and organic matter and on in vivo rate of ruminal protein degradation.

Seven Holstein steers (340 kg) fitted with ruminal, duodenal and ileal cannulae were used to measure the influence of supplemental N source on digestion of dietary crude protein (CP) and on ruminal rates of protein degradation. Diets used were corn-based (isonitrogenous, 12% CP on a dry matter basis, and isocaloric, 80% total digestible nutrients) with urea, soybean meal (SBM), linseed meal (LSM) or corn gluten meal (CGM) as supplemental N. Ruminal ammonia N concentrations were higher (P less than .05) in steers fed LSM than in those fed CGM, but did not differ from those in steers fed urea or SBM (11.7, 6.7, 9.1 and 9.2 mg/100 ml, respectively). Due to the high degradability of urea, ruminal digestion of dietary CP was greater (P less than .05) in steers fed urea than in those fed CGM, but intermediate in steers fed SBM and LSM (58.4, 48.8, 53.1 and 53.9%, respectively). Flow of bacterial nonammonia N to the duodenum was highest (P less than .05) in steers fed SBM or LSM, intermediate (P less than .05) for urea and lowest (P less than .05) for CGM (86.8, 86.1, 76.3 and 65.9 g/d, respectively). Efficiency of bacterial protein synthesis was lowest in steers fed CGM and differed (P less than .05) from SBM (15.6 vs 21.8 g N/kg organic matter truly digested, respectively). Rate of ruminal digestion for SBM-CP differed (P less than .05) from that of CGM-CP but not from that of LSM-CP (17.70, 5.20 and 10.13%/h, respectively). The slow rate of ruminal degradability of CGM resulted in increased amounts of dietary protein reaching the intestinal tract but lower amounts of bacterial protein, thus intestinal protein supply was not appreciably altered.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Age-related total gray matter and white matter changes in normal adult brain. Part I: volumetric MR imaging analysis.

BACKGROUND AND PURPOSE: A technique of segmenting total gray matter (GM) and total white matter (WM) in human brain is now available. We investigated the effects of age and sex on total fractional GM (%GM) and total fractional WM (%WM) volumes by using volumetric MR imaging in healthy adults. METHODS: Fifty-four healthy volunteers (22 men, 32 women) aged 20-86 years underwent dual-echo fast spin-echo MR imaging. Total GM, total WM, and intracranial space volumes were segmented by using MR image-based computerized semiautomated software. Volumes were normalized as a percentage of intracranial volume (%GM and %WM) to adjust for variations in head size. Age and sex effects were then assessed. RESULTS: Both %GM and %WM in the intracranial space were significantly less in older subjects (> or =50 years) than in younger subjects (<50 years) (P <.0001 and P =.02, respectively). Consistently, %GM decreased linearly with age, beginning in the youngest subjects. %WM decreased in a quadratic fashion, with a greater rate beginning only in adult midlife. Although larger GM volumes were observed in men before adjustments for cranium size, no significant differences in %GM or %WM were observed between the sexes. CONCLUSION: GM volume loss appears to be a constant, linear function of age throughout adult life, whereas WM volume loss seems to be delayed until middle adult life. Both appear to be independent of sex. Quantitative analysis of %GM and %WM volumes can improve our understanding of brain atrophy due to normal aging; this knowledge may be valuable in distinguishing atrophy of disease patterns from characteristics of the normal aging process.

Adult↗
PubMed2002

Age-related total gray matter and white matter changes in normal adult brain. Part II: quantitative magnetization transfer ratio histogram analysis.

BACKGROUND AND PURPOSE: The magnetization transfer ratio (MTR) is a sensitive and quantitative identifier of underlying structural changes in the brain. We quantitatively evaluated age- and sex-related MTR changes in global gray matter (GM) and global white matter (WM) in healthy adults. METHODS: Fifty-two healthy volunteers (21 men, 31 women) aged 20-86 years underwent dual-echo fast spin-echo and magnetization transfer imaging performed with and then without a saturation pulse. GM and WM were distinguished by using a computer-assisted semiautomated segmentation technique. MTR histograms were generated for each segmented tissue in each subject and compared among age and sex groups. RESULTS: The mean, median, first quartile, and peak height of the MTR histogram were significantly lower in the older group (> or =50 years) than those in the younger group (<50 years) for both GM and WM. The age dependency of these values can be expressed in a quadratic fashion over the entire span of adulthood. The MTRs started to decline only after the age of approximately 40 years in both tissues. No statistically significant differences in MTR histogram measurements between the sexes were observed. CONCLUSION: The different MTR values for both GM and WM in the two age groups suggest that notable microscopic changes occur in GM and WM with advancing age, yet no significant sex-related variations in MTR measurements were found in these neurologically healthy adults. Such normative data based on the inherent contrast in MTRs are essential in studies of specific disorders of aging, and they may have implications for our understanding of the gross structural changes in both GM and WM in the aging brain.

Adult↗
PubMed2004

Method for combining information from white matter fiber tracking and gray matter parcellation.

We introduce a method for combining fiber tracking from diffusion-tensor (DT) imaging with cortical gray matter parcellation from structural high-spatial-resolution 3D spoiled gradient-recalled acquisition in the steady state images. We applied this method to a tumor case to determine the impact of the tumor on white matter architecture. We conclude that this new method for combining structural and DT imaging data is useful for understanding cortical connectivity and the localization of fiber tracts and their relationship with cortical anatomy and brain abnormalities.

Adult↗
PubMedDate not supplied

Mutagenic activity of non-volatile organic matter associated with suspended matter in urban air.

Extracts of atmospheric suspended matter showed a direct mutagenic effect in the Ames test. This effect was increased by metabolic activation. These extracts were separated into an aliphatic, an aromatic and a polar fraction. The aliphatic fraction had no effect, with or without activation; the aromatic fraction showed the greatest mutagenicity with and without activation; the polar fraction was also mutagenic, but its metabolic activation did not enhance the effect. The active compounds in this last fraction could be represented in a significant part by oxygenated derivatives of polycyclic aromatic hydrocarbons.

Air↗
PubMed2001

Fractionation and characterization of dissolved organic matter in a shallow eutrophic lake, its inflowing rivers, and other organic matter sources.

Dissolved organic matter (DOM) in water from eutrophic Lake Kasumigaura, its inflowing rivers, and several other DOM sources in the lake catchment area was fractionated using resin adsorbents into five classes: aquatic humic substances (AHS), hydrophobic neutrals (HoN), hydrophilic acids (HiA), bases (BaS), and hydrophilic neutrals (HiN). The DOM-fraction distribution pattern and the ultraviolet absorbance to dissolved organic carbon ratio (UV/DOC ratio) were found remarkably effective for evaluating the characteristics of DOM in water. DOM-fraction distribution patterns were significantly different depending on the origin of the sample. AHS and HiA were found to be the dominant fractions in DOM in all samples studied. HiA prevailed over AHS in the lake water, whereas AHS were slightly more abundant than HiA in the river waters. AHS were in the great majority in forest streams and plowed-field percolates. HiA abounded in paddy-field outflow, domestic sewage, and sewage-treatment-plant effluent. Only domestic sewage contained a significant amount of HoN. The UV/DOC ratio also varied depending on the origin of the sample: the ratios in total DOM, AHS, and HiA were greater in river waters than in the lake water. The greatest ratio of AHS was found in paddy-field outflow and the lowest in domestic sewage. The UV/DOC ratios in the sewage-treatment-plant effluent were very similar to those in the lake water.

Absorption↗
PubMed2002

Amorphous and condensed organic matter domains: the effect of persulfate oxidation on the composition of soil/sediment organic matter.

The composition of amorphous and condensed soil/sediment organic matter (SOM) domains was investigated for one soil sample and four sediment samples. These samples were oxidized with persulfate to remove amorphous SOM, before and after which the composition of SOM was studied by thermogravimetric analysis, pyrolysis-GC/MS, and cross polarization magic angle spinning 13C-NMR. Comparison of the SOM composition before and after oxidation showed that condensed SOM was more thermostable and less polar than amorphous SOM. Condensed SOM was relatively low in O-alkyl C and carboxyl C and it was likely to contain only small amounts of labile organic components (carbohydrates, peptides, fatty acids). Apart from these general characteristics, the composition of the condensed and amorphous domains appeared to be highly dependent on the origin and nature of the SOM investigated. Condensed domains in relatively undecomposed SOM were enriched in aliphatic C, whereas condensed domains in relatively weathered SOM were enriched in aromatic C. Altogether, the compositional changes upon persulfate oxidation were similar to the compositional changes upon humification, which supports the idea that weathered SOM is more condensed than the original material.

Carbon Isotopes↗
PubMed1999

Asperger syndrome: a simple matter of white matter?

Asperger syndrome, one of the Pervasive Developmental Disorders, is formally diagnosed on the basis of a cluster of cognitive, social and motor signs. It is also associated with poor visuo-spatial skills, good verbal performance, gauche social behaviour and clumsiness. Many of the difficulties evident in those with Asperger syndrome are closely associated with right-hemisphere dysfunction. In this respect they also resemble signs used to diagnose what has been labelled Nonverbal Learning Disorder. Here, these are treated as being the same or closely-related disorders with a possible common underlying aetiology; that is, a neurodevelopmental abnormality affecting white matter. This review examines the ability of this approach to account for a wide range of characteristics of the Asperger syndrome, and contrasts this with a theory-of-mind approach, which, although able to account for the primary features of Asperger syndrome, is less successful at explaining some of its secondary features.

Journal Article↗
PubMed2005

Adsorption of organic matter at mineral/water interfaces: 5. Effects of adsorbed natural organic matter analogues on mineral dissolution.

The effects of the adsorption of pyromellitate, an analogue for natural organic matter, on the dissolution behavior of corundum (alpha-Al2O3) have been examined over a wide range of pyromellitate concentrations (0-2.5 mM) and pH conditions (2-10). The adsorption modes of pyromellitate on corundum have first been examined using in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and are shown to be dominated by a fully deprotonated, outer-sphere pyromellitate species ([triple bond]AlOH2+. . .Pyr4-) at pH >/= 5.0. At lower pH conditions, however, an additional protonated outer-sphere species ([triple bond]AlOH2+. . .H2Pyr2-) and an inner-sphere species are also evident. In accordance with the ATR-FTIR findings, modeling of macroscopic pyromellitate adsorption data using an extended constant capacitance treatment was possible using two outer-sphere ([triple bond]AlOH2+. . .Pyr4- and [triple bond]AlOH2+. . .H2Pyr2-) and one inner-sphere ([triple bond]AlPyr3-) adsorbed pyromellitate species. The presence of adsorbed pyromellitate strongly inhibited the dissolution of corundum under acidic (pH < 5) conditions, consistent with a mechanism previously proposed by Johnson et al. whereby outer-spherically adsorbed Pyr4- species sterically protect dissolution-active surface sites from attack by dissolution-promoting species such as protons. A reduction in the protolytic dissolution rate of corundum results. A reference Suwannee River fulvic acid, which also adsorbs to aluminum (oxyhydr)oxide surfaces in a predominantly outer-sphere manner, was similarly shown to strongly inhibit the dissolution of corundum at pH = 3.

Journal Article↗
PubMedDate not supplied

The 1998 Baltimore Particulate Matter Epidemiology-Exposure Study: part 1. Comparison of ambient, residential outdoor, indoor and apartment particulate matter monitoring.

A combined epidemiological exposure panel study was conducted during the summer of 1998 in Baltimore, Maryland. The objectives of the exposure analysis component of the 28-day study were to investigate the statistical relationships between particulate matter (PM) and related co-pollutants from numerous spatial boundaries associated with an elderly population, provide daily mass concentrations needed for the epidemiological assessment, and perform an extensive personal exposure assessment. Repeated 24-h integrated PM2.5 (n=394) and PM10 (n=170) data collections corresponding to stationary residential central indoor, individual apartment, residential outdoor and ambient monitoring were obtained using the same sampling methodology. An additional 325 PM2.5 personal air samples were collected from a pool of 21 elderly (65+ years of age) subjects. These subjects were residents of the 18-story retirement facility where residential monitoring was conducted. Mean daily central indoor and residential apartment concentrations were approximately 10 microg/m3. Outdoor and ambient PM2.5 concentrations averaged 22 microg/m3 with a daily range of 6.7-59.3 microg/m3. The slope of the central indoor/outdoor PM2.5 mass relationship was 0.38. The average daily ratio of PM2.5/PM10 mass concentrations across the measurement sites ranged from 0.73 to 0.92. Both the central indoor and mean apartment PM2.5 mass concentrations were highly correlated with the outdoor variables (r>0.94). The lack of traditionally recognized indoor sources of PM present within the facility might have accounted for the high degree of correlation observed between the variables. Results associated with the personal monitoring effort are discussed in depth in Part 2 of this article.

Aged↗
PubMed2006

[Adsorption of dissolved organic matter in soil and dissolved organic matter effect on the copper precipitation in high pH range].

Batch experiments were performed to study the dissolved organic matter (DOM) derived from green manure and pig manure sorption in acidic and calcareous soils and the effect of DOM derived from green manure and pig manure compost on the precipitation of copper at different pH in solution. The results showed that there was a significant net release of dissolved organic carbon (DOC) in soil (33.58 mg x L(-1) for calcareous soil and 17.17 mg x L(-1) for acidic soil) when a DOC-free solution was added. As the amount of added DOC increased, the release of DOC from soils decreased. This indicates that parts of the added DOC were sorbed by thesoil material and this effect was influenced by DOM's properties and soil properties. In this experiment the initial mass (IM) isotherm was used to describe the DOM sorption in soil which has been shown to be a useful tool for describing the sorption of DOC insoils because it takes into consideration the release of indigenous DOM from soil. As compared to green manure DOM, pig manure DOM had high m and Kd values, which indicated that it had a higher affinity with soil. As compared to that of green manure DOM, the m and Kd values are 0.4241, 2.946 in acidic soil and 0.2846, 1.58 in calcareous soil, respectively. What's more, the results also indicated that the acidic soil with higher Fe-oxide and Al-oxide content exhibited much higher DOC adsorption ability than calcareous soil rich in 2:1 minerals. In this experiment, green manure and pig manure compost DOM were selected to investigate the effects of DOM on the precipitation-dissolution behavior of copper at different pH. It can be found that DOM can inhibit the copper precipitation especially at high pH range because of the formation of DOM-Cu complex. From pH 6 to pH 10, as compared to the control treatment with no DOM added, the precipitation rate average decreased by 43.6% for the treatment with green manure DOM added and 22.65% for the treatment with pig manure compost DOM.

Adsorption↗