Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MATTER”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMedDate not supplied

The parenchymal CT myelogram: in vivo imaging of the gray matter of the spinal cord.

Past attempts to visualize the internal structure of the spinal cord in vivo have been hampered by many factors, including the small size of the cord, the dense bony investiture of the spine, and the similarities of tissue densities from one region to another within the cord. Delayed CT is the imaging technique currently being used at our institution as an adjunct to iopamidol myelography to visualize the deep gray matter of the cord. This visualization is achieved by a poorly understood differential gray/white-matter enhancement, possibly due to either a shielding effect of the white matter as it envelops the gray matter, a differential absorption rate between gray and white matter, or a greater rate of reabsorption of contrast by the more highly vascularized gray matter. This method is not being advocated as a primary diagnostic technique due to the lack of reliability in providing successful results from section to section, from patient to patient, and from one time period of delay to the next. Instead, it is an initial attempt to image the basic, intrinsic structure of the spinal cord in vivo, which may herald a valuable advance in imaging methodology.

Atrophy↗
PubMed1983

[Experimental studies of brain edema by infusion edema model-- biophysical changes of edema fluid in white matter of the brain].

The important changes in the area of brain edema are the accumulation and the spreading of edema fluid through the extracellular space in white matter of the brain. In this study, we described the changes of tissue resistance and compliance as the increment of accumulated volume of fluid produced by the slow infusion of normal saline or plasma into white matter of the cat brain. Adult cats (22) were tracheotomized, paralyzed with Galamine (2 mg/kg) and maintained normocapnic, normotensive under nitrous oxide anesthesia. Normal saline or plasma of their own was infused slowly through 25 gauge needle implanted into left frontal white matter by stereotaxic technique. A low compliance pressure gauge transducer was connected to the line for the measurement of inflow pressure. Tissue resistance and compliance for the movement of infused fluid into white matter were delivered from the changes of inflow pressure by adding the 3 microlitter per minutes on top of the resting steady state pressure. Values of tissue resistance in normal white matter, determined at the accumulated volume of 0.05 ml was very high (normal saline infusion: 6.42 +/- 0.61 X 10(3) mmHg/ml/min, plasma infusion: 5.47 +/- 1.43 X 10(3) mmHg/ml/min). But it decreased rapidly followed by more gradual decrease of tissue resistance became more edematous, reaching a plateau of one sixth of initial value at an infused volume of 0.5 ml. Tissue compliance changed by an opposite pattern of rapid increase and plateau to the changes of tissue resistance.

Animals↗
PubMed1994

[Diffusion anisotropy in cerebral white matter lesion].

Diffusion MRI studies were performed on 14 patients with diffuse high-signal lesions of the cerebral white matter on T2-weighted MR images. There were two patients with adrenoleukodystrophy, four with dentato-rubro-pallido-luysian atrophy, three with familial spastic paraplegia, two with myotonic dystrophy and three with dementia of unknown origin. In addition, a patient with of Sanfilippo disease and one of the three patients who exhibited dementia of unknown origin were also found to be low-signal in the cerebral cortex T2-weighted MR images. In every case except the last two, diffusion-weighted MR images yielded significantly higher apparent diffusion coefficients perpendicular to nerve fibers in the frontal white matter and the corpus callosum than in the normal controls. The lesions displayed increased diffusion anisotropy, calculated as the ratio of the diffusion coefficient perpendicular to the nerve fibers to the diffusion coefficient parallel to the nerve fibers, i.e., diffusion anisotropy was lost in the white matter, suggesting a demyelinating process in the lesion. In the last two cases, on the other hand, the diffusion coefficient and diffusion anisotropy were within normal range. The white matter lesions in these cases were thought to represent degeneration secondary to the cortical involvement. Thus, it was confirmed that diffusion-weighted MR images, unlike T2-weighted MR images, were confirmed to allow differentiation between at least two types of white matter lesions.

Adrenoleukodystrophy↗
PubMedDate not supplied

MR and proton spectroscopy of white matter disease induced by high-dose chemotherapy with bone marrow transplant in advanced breast carcinoma.

PURPOSE: To determine whether the MR-detectable white matter changes associated with high-dose chemotherapy and bone marrow transplant in patients with advanced breast carcinoma are accompanied by neurochemical disturbances detectable by proton MR spectroscopy. METHODS: MR studies were obtained in 13 patients, and single-voxel proton MR spectra were acquired in vivo in 12 of these 13 for comparison with 13 age- and sex-matched control subjects. RESULTS: Considerable white matter change determined with MR was found in 10 of 13 patients with volume white matter change ranging from 1 to 153 cm3 (mean, 49 cm3; SD, 50 cm3). Single-voxel spectra successfully acquired in 12 patients revealed no significant difference in patients compared with control subjects for the spectral ratios N-acetyl aspartate to creatine or N-acetyl aspartate to choline at either short or long echo times (30 and 136 milliseconds). CONCLUSION: Extensive, late-stage white matter change induced by high-dose chemotherapy is not accompanied by measurable disturbances in the putative neuronal marker N-acetyl aspartate, suggesting that chemotherapy-induced white matter disease is predominantly a water space and possibly an extraneuronal process rather than a primary neuronal (axonal) disease. The MR spectroscopic examination, accomplished at the time of the MR imaging examination, complements the MR imaging study by increasing the specificity of the MR-based clinical evaluation.

Adult↗
PubMedDate not supplied

Cranial MR in Wilson disease: abnormal white matter in extrapyramidal and pyramidal tracts.

PURPOSE: To describe abnormal white matter in the brain on MR in Wilson disease and to compare with anatomic location of white matter tracts. METHODS: Forty-six patients with Wilson disease were examined. Axial T1-weighted inversion-recovery, axial T2-weighted spin-echo, and coronal T2*-weighted gradient-echo MR images were performed. Imaging studies were compared with clinical data. RESULTS: Seventeen patients showed abnormalities in the region coinciding with the following white matter tracts: corticospinal tract (24%, n = 11), dentatorubrothalamic tract (24%, n = 11), and pontocerebellar tract (17%, n = 8). CONCLUSION: Abnormal extrapyramidal and pyramidal white matter tracts are part of the neuroimaging spectrum of Wilson disease. No significant correlation was found with neurologic groups and individual white matter tracts affected.

Basal Ganglia Diseases↗
PubMed1997

Alteration of white matter MR signal intensity in frontotemporal dementia.

PURPOSE: To determine the diagnostic potential of MR imaging to show white matter involvement in frontotemporal dementia. METHODS: We evaluated MR signal intensity in cerebral white matter by visually inspecting and by quantitatively measuring signal intensity on MR images in 22 patients with frontotemporal dementia. The findings were compared with those in 22 age- and sex-matched patients who had had Alzheimer disease for the same length of time and with 16 age- and sex-matched healthy control subjects. RESULTS: Patients with frontotemporal dementia had a significant increase in white matter signal intensity in the frontal and/or temporal lobes on T2- and proton density-weighted images. Visual inspection of regular proton density-weighted images and measurements made on the T2- and proton density-weighted images were sensitive to changes in white matter signal. CONCLUSION: Increased MR signal intensity in the frontotemporal white matter on T2- and proton density-weighted MR images is a useful diagnostic sign of frontotemporal dementia and distinguishes this condition from Alzheimer disease.

Aged↗
PubMed1997

[Age-related changes of diffusional anisotropy in the cerebral white matter in normal subjects].

To investigate age-related changes of diffusional anisotropy in the cerebral white matter, we performed diffusion-weighted MRI studies in 21 normal subjects aged 25 to 96 years. The anisotropic rations (ARs), defined as the apparent diffusion coefficients perpendicular to the nerve fibers to those parallel to the nerve fibers, were significantly higher in elderly than in young subjects in the anterior and posterior white matter surrounding the lateral ventricle. Moreover, significant correlation between age and AR was found in the anterior white matter. The ventricular index (VI) measured on MRI, as a quantitative indicator of brain atrophy, was significantly higher in elderly than younger subjects, and significantly correlated with AR in the anterior white matter. Multiple regression analysis demonstrated that the VI showed the highest correlation for AR. On the other hand, there was no significant correlations between ARs in the corpus callosum and age. These results suggest that morphological changes in the myelin and axon in the white matter occur in elderly normal subjects, probably due to neuronal loss with aging.

Adult↗
PubMed1997

Cystlike white matter lesions in tuberous sclerosis.

PURPOSE: To investigate the presence of small cystlike structures in the cerebral hemispheric white matter on MR images of patients with tuberous sclerosis. METHODS: The MR images of 18 consecutive patients with tuberous sclerosis were reviewed retrospectively. RESULTS: Eight of the 18 patients were found to have cystlike structures in the cerebral white matter. The signal intensity of these lesions was isointense with cerebrospinal fluid on T1-, proton density-, and T2-weighted images. Four patients were imaged with a fluid-attenuated inversion recovery sequence, which in each case also showed fluid-type signal in these areas. Three of the patients had CT for correlation, and these scans supported the diagnosis of cystic lesions. Cysts ranged in number from one to 12 per patient and were usually smaller than 1 cm. The most common location was adjacent to the occipital horn or trigone of the lateral ventricle (six of eight patients). Less frequent sites were near the frontal horns, in the corpus callosum, and in the deep white matter near the body of the lateral ventricle. Cysts in five patients were either immediately adjacent to a cortical tuber or in the center of a white matter dysplastic lesion. A cyst in one patient had septa, and none of the cysts enhanced. CONCLUSIONS: Cystlike structures in the cerebral hemispheric white matter were seen on the MR images of 44% of 18 patients with tuberous sclerosis. Whether these findings represent cystic degeneration of dysplastic tissue or are unrelated to the disease process of tuberous sclerosis is unknown. More than one pathogenesis may exist.

Adult↗
PubMed1997

Scaling of cortical neuron density and white matter volume in mammals.

A prior scaling model, based on repeating cortical units, whose number and size increase with brain size, gave discrete exponents for cortical thickness (1/9), outer (visible) surface area (2/3), folded cortical surface area (8/9) and cortical volume (1), each as a function of brain volume. These exponents are in reasonable agreement with a diversity of empirical data (Prothero, 1997). Rockel et al. (1980) reported that neuron number, assayed in a narrow column across cortex (pia to white matter) is invariant over several differing brain regions and species. Since cortical thickness scales, empirically, as about the 1/9 power of brain volume, their data imply that neuron line density (across cortex) scales with an exponent of about -1/9. Rockel et al. (1980) also urged that cortical neuron surface density is invariant. This extrapolation implies that neuron volume density scales, like line density, as the -1/9 power of brain volume, in marked disparity with the data of Haug (1987) and Tower (1954). The present model assumes an invariant number of neurons per repeating unit. Thus neuron number, assayed across cortical thickness, is independent of brain size, in accord with Rockel et al. (1980). The model predicts that neuron line density (in any direction) scales as the -1/9 power of brain volume. Now neuron volume density scales as the -1/3 power of brain volume, in reasonable agreement with the results of Haug (1987) and Tower (1954). For white matter, I assume that mean axon length scales with brain diameter (exponent of 1/3). The number of white matter axons scales in proportion to the number of repeating units (exponent of 2/3). Given an invariant size distribution of white matter axons, white matter volume thus scales with an exponent of one, in reasonable accord with Haug (1970).

Animals↗
PubMed1998

[Delineation of the white and gray matter of the normal human cervical spinal cord using diffusion-weighted echo planar imaging].

To delineate the white and gray matter of the normal human cervical spinal cord, diffusion-weighted echo planar imaging (DW-EPI) was performed in 11 healthy volunteers. Three axial (X-, Y- and Z-axis) anisotrophic diffusion-weighted images were obtained on a 1.5T superconducting clinical unit using a single-shot DW-EPI sequence. On X- and Y-axis DWIs the white and gray matter could be well differentiated: the former showed high intensity and the latter low intensity. Anterior columns were clearly visible, whereas posterior columns were not. On Z-axis DWI the white and gray matter could not be differentiated at all, because both showed low intensity. In conclusion, DW-EPI can clearly delineate the white and gray matter of the cervical spinal cord, and this technique will be useful to evaluate white matter disorders such as ischemic or demyelinating disease.

Echo-Planar Imaging↗
PubMed2024

Sex and APOE ε4 allele differences in longitudinal white matter microstructure in multiple cohorts of aging and Alzheimer's disease.

INTRODUCTION: The effects of sex and apolipoprotein E (APOE)-Alzheimer's disease (AD) risk factors-on white matter microstructure are not well characterized. METHODS: Diffusion magnetic resonance imaging data from nine well-established longitudinal cohorts of aging were free water (FW)-corrected and harmonized. This dataset included 4741 participants (age = 73.06 ± 9.75) with 9671 imaging sessions over time. FW and FW-corrected fractional anisotropy (FAFWcorr) were used to assess differences in white matter microstructure by sex and APOE ε4 carrier status. RESULTS: Sex differences in FAFWcorr in projection tracts and APOE ε4 differences in FW limbic and occipital transcallosal tracts were most pronounced. DISCUSSION: There are prominent differences in white matter microstructure by sex and APOE ε4 carrier status. This work adds to our understanding of disparities in AD. Additional work to understand the etiology of these differences is warranted. HIGHLIGHTS: Sex and apolipoprotein E (APOE) ε4 carrier status relate to white matter microstructural integrity. Females generally have lower free water-corrected fractional anisotropy compared to males. APOE ε4 carriers tended to have higher free water than non-carriers.

Humans↗
PubMed2026

Effect of cognitive enhancement therapy for early course schizophrenia on gray matter volume: A confirmatory multisite randomized clinical trial.

BACKGROUND: Cognitive Enhancement Therapy (CET) is an evidence-based cognitive remediation intervention for early course schizophrenia with established benefits for cognition. CET may protect against broad temporolimbic gray matter volume loss associated with cognitive improvement, but this finding has yet to be replicated. This research reexamined if CET protects against temporolimbic gray matter volume loss in an independent and larger multisite early course sample, and if this neuroprotective effect predicts cognitive and social adjustment improvement. METHODS: Ninety-nine participants with early course schizophrenia completed MRI, cognitive, and social adjustment assessments at baseline, 9 (mid-treatment), and 18 (end of treatment) months. Linear mixed-effects models examined the differential impact of CET (n = 56) compared to Enriched Supportive Therapy (n = 43) on temporolimbic gray matter volume in regions-of-interest (ROIs) that previously demonstrated CET-related neuroprotection (primary ROIs), as well as frontotemporal ROIs outlined in the first trial (secondary ROIs). RESULTS: The right rostral anterior cingulate was the only primary ROI to demonstrate a significant group × time interaction, but was unrelated to cognitive and social adjustment change. No secondary ROIs exhibited a differential treatment effect. CONCLUSION: This confirmatory trial did not recapitulate the observed broad pattern of CET-related temporolimbic gray matter volume neuroprotection. Consistent with the larger literature demonstrating limited evidence of cognitive remediation effects on the brain in schizophrenia, these findings underscore the need for continued investigation of CET-related changes with other neuroimaging modalities, especially given its established cognitive benefits. Such information is critical for cognitive remediation optimization based on validated therapeutic mechanisms.

Humans↗
PubMed2026

Exposure to size-specific particulate matter accelerates DNA methylation aging in people with HIV.

BACKGROUND: People with HIV (PWH) face accelerated aging and increased health risks, with DNA methylation age (DNAmAge) as a critical senescence biomarker. Particulate matter is linked to DNAmAge acceleration (DNAmAA) in general population, but its impact in PWH remains unstudied. METHODS: Thirty-two PWH from Wuhan, China, were enrolled in a prospective panel study with follow-up, and each participant underwent at least two repeated measurements during the study period. Portable air quality monitor measured PM 1 , PM 2.5 , and PM 10 exposures 72 h preblood sampling. We analyzed genome-wide DNA methylation in peripheral blood and calculated six AA metrics. Linear mixed-effects and weighted quantile sum regression models evaluated associations between particulate matter exposure and DNAmAA. RESULTS: Significant associations between particulate matter exposure and DNAmAA were observed at various lag windows. For every 10 μg/m 3 increase in 24-h average PM 2.5 , Hannum DNAmAA, Pheno DNAmAA, Grim DNAmAA, SkinBlood DNAmAA, and Elastic DNAmAA increased by 0.266 years [95% confidence interval (CI): 0.035-0.480], 0.421 years (95% CI: 0.032-0.701), 0.336 years (95% CI: 0.073-0.546), 0.295 years (95% CI: 0.021-0.495), and 0.254 years (95% CI: 0.034-0.445), respectively. PM 10 contributed most substantially to the cumulative PM effect on epigenetic AA in the lag0-24 h window. CONCLUSION: Short-term particulate matter exposure, particularly PM 10 , significantly accelerates epigenetic aging in PWH, highlighting the need to integrate air quality management into healthy aging strategies for this vulnerable population.

China↗
PubMed2006

Isotopic composition as a tool for assessment of origin and dynamic of organic matter in tropical freshwater.

The isotopic composition (13C and 15N) and C:N ratio of sediment and particulate were investigated to assess the origin and dynamic of the organic matter in two river basins located in the Parana State, Brazil. The main sources of organic matter, plants, litter and soil, were analyzed in the study. This study was carried out during the dry and wet seasons. Although organic matter contribution for the particulate material has been mixed, the main contribution in the two seasons for both rivers was autochthonous characterized by delta13C and C:N ratio values ranging from -31.0 to -21.8 per thousand and from 5.1 to 11.4, respectively. The soil with delta13C values ranging from -25.9 to -20.6 per thousand, and C:N ratio from 10.2 to 15.8, was the main carbon source for the river sediment for the two tributaries in the wet and dry seasons. The sediment delta15N values for both the rivers in the wet season showed an 15N enrichment trend in most of studied sites when compared to the dry season values, suggesting major input of nutrients as dissolved organic nitrogen and sewage nitrate. In the dry season, 14N enriched compounds, could have been used by phytoplankton, causing 15N enrichment. The isotope and C:N ratio data clearly showed that the agricultural activity has been influencing the origin and dynamic of organic matter in the two rivers, with potential biochemical consequences for the lower basin of the major Tibagi river.

Agriculture↗
PubMed2006

Exposure to airborne particulate matter in the ambient, indoor, and occupational environments.

Exposure to airborne particulate matter results in various adverse health effects. Unlike other pollutants, such as ozone, sulfur dioxide, carbon monoxide, and oxides of nitrogen, for which there is significant exposure, particulate matter exposure is much more complex because it is not a single chemical species or even a limited number of chemical species. Particulate matter includes various chemical species in particles having a wide range of diameters and shapes that have widely varying toxicities. People are exposed to particles in the ambient environment, in indoor spaces, and in the occupational environment. This article reviews the information available on the concentrations of particulate matter and its composition in these general environmental categories.

Air Pollutants↗
PubMed2001

Cobalt-55 positron emission tomography in vascular dementia: significance of white matter changes.

BACKGROUND: Vascular dementia (VaD) is still used as a covering term to indicate the relationship between cerebrovascular disease and the progressive cognitive disorder. The contribution of white matter changes (WMCs), seen with computed tomography (CT) and magnetic resonance imaging (MRI) of the brain, to dementia had not been fully elucidated. Cobalt-55 (55Co) positron emission tomography (PET) allows us to distinguish between recent and old infarcts. PURPOSE: The present study investigates whether 55Co PET can detect the lesions responsible for the progression of the cognitive disorder in VaD patients. PATIENTS AND METHODS: 20 consecutive patients with a previous history of repeated strokes occurring more than 6 months before and with multiple cortical infarcts, lacunes and WMCs on CT and 5 age-matched controls were investigated with 55Co PET. The stroke patients were divided in two groups: 8 with and 12 without VaD. Average 55Co counts in cerebral cortex, deep gray nuclei and white matter were compared to the value in the cerebellum used as reference. RESULTS: In the control group, the 55Co uptake was identical in the cerebral cortex and in the cerebellum, but lower in the deep gray nuclei and the cerebral white matter. When comparing the stroke groups with the control, the 55Co uptake was similar for the cerebral cortex and deep gray nuclei, but significantly increased in the cerebral white matter. The 55Co uptake was also more increased in the stroke group with VaD compared to the non-demented group. CONCLUSION: 55Co PET shows that the WMCs are due to the ongoing damage of probably ischaemic origin which is more prominent in stroke patients with progressive cognitive decline.

Adult↗
PubMed1988

Disproportionate atrophy of cerebral white matter in chronic alcoholics.

Morphometric analysis of postmortem brains from chronic ethyl alcohol abusers and controls was performed to determine the regional distribution and extent of atrophy in the cerebral hemispheres of alcoholics. This study was performed by digitizing photographs of coronal slices of the brains to compute the cross-sectional area of the cerebrum, cerebral cortex, subcortical nuclei, cerebral white matter, and the ventricular system at five standardized levels. Although the alcoholics and controls had similar demographic features and mean brain weights, brains from the alcoholic group showed mild but consistent atrophy of the cerebral cortex (2.5% to 4.2% reductions in cross-sectional area at all five levels), moderate atrophy of cerebral white matter (6.1% to 17.5% reductions), and enlargement of the ventricular system (31.8% to 71.9% increases). There were no differences in the sizes of subcortical nuclei. The absolute increase in the size of the ventricles in the alcoholic group was roughly equal to the amount of tissue lost in cerebral white matter, thereby representing hydrocephalus ex vacuo. The disproportionate loss of cerebral white matter relative to cerebral cortex suggests that a major neurotoxic effect of chronic alcohol intoxication in the central nervous system is axonal degeneration.

Adult↗
PubMed1995

White matter hyperintensities in Parkinson's disease. Clinical correlations.

OBJECTIVES: To verify recent preliminary data indicating that white matter hyperintensities on magnetic resonance imaging are more abundant in patients with Parkinson's disease (PD) than in healthy subjects and to examine possible correlation between these abnormalities and clinical features of PD. DESIGN: Magnetic resonance imaging data on patients with PD and normal subjects were compared as to frequency, extent, and topographic location of white matter hyperintensities; moreover, in the PD group, we studied the possible correlation of white matter hyperintensities with clinical features such as severity, disease duration, and therapy. SETTING: The outpatient clinic of the Institute of Clinical Neurology and the Neuroradiology Unit of the University of Pisa (Italy). PATIENTS: We studied 102 nondemented patients with idiopathic PD and 68 sex- and age-matched healthy controls, all screened for absence of cerebrovascular risk factors. OUTCOME MEASURES: White matter hyperintensities were classified as periventricular hyperintensities and deep hyperintensities. Frequency, extent, and topographic location of both periventricular and deep hyperintensities were evaluated. The clinical parameters examined were disease duration, treatment type, and disease severity (using Hoehn and Yahr staging and the Unified Parkinson's Disease Rating Scale), as well as disease progression index (ratio between Hoehn and Yahr stage and disease duration). RESULTS: The frequency and the extent of periventricular hyperintensities were significantly higher in patients with PD than in healthy subjects. Moreover, within the PD group, the patients who had periventricular hyperintensities had significantly shorter disease duration and greater disease severity, ie, a higher disease progression index, than those who did not. CONCLUSION: These data suggest that periventricular hyperintensities may represent a marker for a clinical subtype of PD characterized by a more rapid neurodegenerative process.

Aged↗