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At least 1,405 records · Page 78Linked to original sources
PubMed2006

Optimization of white matter tractography for pre-surgical planning and image-guided surgery.

Accurate localization of white matter fiber tracts in relation to brain tumors is a goal of critical importance to the neurosurgical community. White matter fiber tractography by means of diffusion tensor magnetic resonance imaging (DTI) is the only non-invasive method that can provide estimates of brain connectivity. However, conventional tractography methods are based on data acquisition techniques that suffer from image distortions and artifacts. Thus, a large percentage of white matter fiber bundles are distorted, and/or terminated early, while others are completely undetected. This severely limits the potential of fiber tractography in pre-surgical planning and image-guided surgery. In contrast, Turboprop-DTI is a technique that provides images with significantly fewer distortions and artifacts than conventional DTI data acquisition methods. The purpose of this study was to evaluate fiber tracking results obtained from Turboprop-DTI data. It was demonstrated that Turboprop may be a more appropriate DTI data acquisition technique for tracing white matter fibers than conventional DTI methods, especially in applications such as pre-surgical planning and image-guided surgery.

Artifacts↗
PubMed1991

White matter disorders.

Magnetic resonance imaging (MRI) has a leading role in the diagnosis of white matter disorders because of its superior sensitivity. It also allows a detailed analysis of white matter disorders, improving the specificity of the diagnoses. There is an increasing knowledge about MRI patterns, in particular in hereditary metabolic disorders. Although these patterns are not always pathognomonic, they often serve as a guide for further diagnostic steps. In the non-hereditary white matter disorders, MRI has an increasing role in the diagnoses, follow-up, and monitoring of clinical trials. In inflammatory disorders, gadolinium-diethylenetriamine-penta-acetic acid (Gd-DTPA) appears to be helpful in analyzing the 'natural' course of the disease. Magnetic resonance spectroscopy (MRS) is gradually also finding a niche in the diagnosis of white matter disorders, both as a marker of neuronal loss and as an indicator of the age and activity of a lesion. New magnetic resonance techniques, such as diffusion and magnetic transfer imaging, will probably provide more information about the involvement of myelin sheaths.

Central Nervous System Diseases↗
PubMed1999

Molecular heterogeneity of oligodendrocytes in chicken white matter.

The classical studies by Del Rio Hortega (Mem. Real. Soc. Espan. Hist. Nat. 14:40-122, 1928) suggest that the oligodendrocyte population includes four morphological subtypes. Recent data from the cat and the rat show that the anatomy of oligodendrocytes related to early myelinating prospective large fibers differs from that of oligodendrocytes related to late myelinating prospective small fibers. After application of a polyclonal antiserum to cryostat sections from the chicken CNS, we noted that glial cells in the spinal cord white matter had become labeled. Analysis of the occurrence and cellular localization of this immunoreactivity--the T4-O immunoreactivity--in the CNS of the adult chicken showed that T4-O immunoreactive cells are enriched in the ventral funiculus and superficially in the lateral funiculus of the spinal cord, where they are co-localized with large fibers. Double staining with T4-O antiserum and anti-GFAP or the lectin BSI-B4 revealed that T4-O immunoreactive cells are not astrocytes or microglia. Staining with anti-HSP108, a general marker for avian oligodendrocytes, showed that T4-O immunoreactivity defines an oligodendroglial subpopulation. A search for T4-O immunoreactivity in spinal cord white matter of some other vertebrates revealed that T4-O immunoreactive cells are not present in sections from fish, frog, turtle, rat, and rabbit spinal cord white matter. These results suggest the presence of a fiber size-related molecular heterogeneity among chicken white matter oligodendrocytes.

Animals↗
PubMedDate not supplied

Role of white matter lesions in cognitive impairment of vascular origin.

White matter changes are detected with high frequency by neuroimaging techniques in aged subjects with cerebrovascular risk factors or diseases and in cognitively impaired patients. Their direct role in causing cognitive deterioration has not been established, although their frequency is higher in demented subjects than in normal controls, and they are associated with specific cognitive deficits, particularly those related to impairment of frontal lobe functions. The aim of this paper is to critically review the existing knowledge about the role of white matter lesions in cognitive impairment of vascular origin. After reviewing the scarce evidence and the numerous clues suggesting a possible role of white matter lesions in causing mental decline, proposals are advanced about elements that could be a basis for revised criteria for vascular dementia for clinical trials. Finally, some items requiring future joint investigations in the fields of age-related white matter lesions are identified.

Cerebrovascular Disorders↗
PubMed2000

Quantitative pathological evidence for axonal loss in normal appearing white matter in multiple sclerosis.

We assessed axonal loss in the normal appearing white matter of the corpus callosum in postmortem brains of patients with multiple sclerosis, using quantitative measures of both axonal density and white matter atrophy. The calculated total number of axons was reduced significantly (mean +/- SD, 5.4 x 10(7) +/- 3.1 x 10(7)) compared with normal controls (11.6 x 10(7) +/- 2.2 x 10(7), p = 0.001) with a reduction both in axonal density (median, 34%; range, 16-56%; p = 0.004) and area (mean +/- SD: multiple sclerosis, 584 +/- 170 mm2; controls, 871 +/- 163 mm2; p = 0.004). These results confirm substantial axonal loss in the normal appearing white matter and demonstrate that measures of both axonal density and white matter volume are necessary to appreciate the full extent of axonal loss.

Adult↗
PubMed2000

Proton MR spectroscopy to assess axonal damage in multiple sclerosis and other white matter disorders.

Proton MR spectroscopy allows in vivo measurement of N-acetylaspartate in white matter, providing a biochemical index of axonal integrity. Several recent studies of patients with multiple sclerosis and other white matter disorders have shown both transient and sustained decreases in N-acetylaspartate in white matter lesions and in brain regions appearing normal on conventional MRI. These data have emphasised that a substantial amount of axonal damage or loss (presumably secondary to myelin pathology) is consistently present in most of these disorders. Recent post-mortem studies support these results. In contrast to changes seen with conventional MR imaging, decreases in N-acetylaspartate have shown a close correlation with changes in neurological status. This suggests that axonal damage may be more relevant than demyelination for determining chronic functional impairments in primary white matter diseases. Thus, serial measurement of brain N-acetylaspartate with proton MR spectroscopy can provide a reliable and clinically-relevant monitor of disease evolution. As pathological changes responsible for long-term morbidity are logically important targets for therapeutic agents, early treatment directed at axonal protection should be useful in these disorders.

Axons↗
PubMedDate not supplied

Particulate matter determination in LVPs produced in Dutch hospital pharmacies. Part 2: Overview of the results.

The Laboratory of Dutch Pharmacists determines LVP particulate matter contamination of LVPs produced in Dutch hospital pharmacies. The investigated LVPs must conform to the NVZA/LNA criteria, which prescribes eight samples and sets limits for particles > or = 2 microns, > or = 5 microns, > or = 10 microns, and > or = 25 microns for both mean and mean + 2x standard deviation. LVPs produced in 500 mL glass containers or plastic containers mostly met the NVZA/LNA criteria, but LVPs produced in 100 mL glass containers showed higher levels of particulate matter contamination. The composition of the LVP significantly affected the extent of particulate matter contamination, but the effect was relatively small when compared to the influence of the type of container. LVPs produced in Dutch hospital pharmacies and LVPs obtained from pharmaceutical industries showed comparable amounts of particulate matter contamination.

Drug Contamination↗
PubMed2001

Ampa/kainate receptor activation mediates hypoxic oligodendrocyte death and axonal injury in cerebral white matter.

We developed an in situ model to investigate the hypothesis that AMPA/kainate (AMPA/KA) receptor activation contributes to hypoxic-ischemic white matter injury in the adult brain. Acute coronal brain slices, including corpus callosum, were prepared from adult mice. After exposure to transient oxygen and glucose deprivation (OGD), white matter injury was assessed by electrophysiology and immunofluorescence for oligodendrocytes and axonal neurofilaments. White matter cellular components and the stimulus-evoked compound action potential (CAP) remained stable for 12 hr after preparation. OGD for 30 min resulted in an irreversible loss of the CAP as well as structural disruption of axons and subsequent loss of neurofilament immunofluorescence. OGD also caused widespread oligodendrocyte death, demonstrated by the loss of APC labeling and the gain of pyknotic nuclear morphology and propidium iodide labeling. Blockade of AMPA/KA receptors with 30 microm NBQX or the AMPA-selective antagonist 30 microm GYKI 52466 prevented OGD-induced oligodendrocyte death. Oligodendrocytes also were preserved by the removal of Ca(2+), but not by a blockade of voltage-gated Na(+) channels. The protective action of NBQX was still present in isolated corpus callosum slices. CAP areas and axonal structure were preserved by Ca(2+) removal and partially protected by a blockade of voltage-gated Na(+) channels. NBQX prevented OGD-induced CAP loss and preserved axonal structure. These observations highlight convergent pathways leading to hypoxic-ischemic damage of cerebral white matter. In accordance with previous suggestions, the activation of voltage-gated Na(+) channels contributes to axonal damage. Overactivation of glial AMPA/KA receptors leads to oligodendrocyte death and also plays an important role in structural and functional disruption of axons.

Action Potentials↗
PubMed2001

[Cerebral white matter lesions in the elderly: vascular risk factors and cognitive consequences].

With the advent of sensitive brain imaging techniques, white matter lesions are commonly observed in healthy as well as in demented elderly people. Primarily vascular risk factors have been related to the presence of white matter lesions, such as hypertension, atherosclerosis and atrial fibrillation. Subcortical white matter lesions are mainly associated with depression in the elderly, while periventricular lesions are clearly associated with cognitive dysfunction. Current evidence on the relation between vascular risk factors, white matter lesions and cognition is based on cross-sectional studies. Prospective studies are needed to confirm causality and to study the efficacy of treatment of vascular risk factors.

Aged↗
PubMed2000

[Soil nitrogen and organic matter losses under water erosion].

The results of artificial water-scoured experiment show that with the increase of water-scoured intensity, the losses of nitrate and ammonium in runoff, and those of organic matter and total N in sediment increased greatly, while the enrichment ratios of organic matter and total N in sediment reduced correspondingly. When the soils in gully-hilly loess region were fertilized with same amount of NH4NO3, the ammonium and nitrate loss in runoff was respectively 0.9-3.5% and 8.2-19.7% of the application amount. Nitrate mainly lossed in runoff, not in sediment. The correlation coefficient of soil erosion module, organic matter and total N loss with > 20 microns soil aggregates was -0.8935, -0.7928 and -0.8151, respectively. The content of > 20 microns soil aggregates could be used as an index to differentiate the soil organic matter and total N loss.

Fertilizers↗
PubMed2002

[Spacial distribution characteristics of soil organic matter and nitrogen in the natural floodplain wetland].

The spatial distribution characteristics of soil organic matter and nitrogen in the natural floodplain wetland were studied in this paper. The results showed that the vertical distributions of nutrients in floodplain wetland were very similar, and the horizontal distribution of them in surface soil were distinctly different. The highest concentration of nutrients was not in the frequently-flooded floodplain wetland where the concentrations of soil organic matter and total nitrogen were 2.36% and 2605.4 mg/kg, but in the floodplain with a certain flood frequency. The concentrations of soil organic matter in the one-year floodplain wetland and five-year floodplain wetland were 3.70% and 3.92%, respectively; and the concentrations of total nitrogen were 3666.4 mg/kg and 3125.6 mg/kg, respectively. The ratios of carbon and nitrogen were relatively low. All the factors such as cycling of dry and wet, underground underset, vegetation growth and pH values etc. influenced the distribution of soil organic matter and nitrogen in wetland.

Hydrogen-Ion Concentration↗
PubMed2002

Structural gray matter differences between first-episode schizophrenics and normal controls using voxel-based morphometry.

The aim of this study was to compare the gray matter segments from T1 structural MR images of the brain in first-episode schizophrenic subjects (n = 34) and normal control subjects (n = 36) using automated voxel-based morphometry (VBM). This study is novel in that few studies have examined subjects in their first episode of schizophrenia. The subjects were recruited for the Edinburgh High Risk project and regional brain volumes were previously measured using a semi-automated volumetric region of interest (ROI) method of analysis. The primary interest was to compare the results from the compatible parts of the ROI study and the primary VBM approach. Our secondary interest was to compare the results of a study-specific template that was constructed from the control group to those using the generic T1 template (152 Montreal Neurological Institute brains) supplied with SPM99 (statistical parametric mapping). The images were processed and statistically analyzed using the SPM99 program. VBM analysis identified significant decreases in gray matter in the schizophrenics relative to the normal control group at the corrected voxel level (P < 0.05) in the right anterior cingulate, right medial frontal lobe, left middle temporal gyrus, left postcentral gyrus, and the left limbic lobe. There were no increases in gray matter in the schizophrenics relative to the control group. The construction of a customized template appeared to improve the detection of structural abnormalities. The analyses were subsequently restricted to voxels within the amygdala-hippocampal complex using the SPM small-volume correction. This identified gray matter decreases in the schizophrenics, at the corrected voxel level (P < 0.05), in the left and right uncus and parahippocampal gyri and the right amygdala. These results are compatible with and extend the relevant findings of the previous volumetric ROI analysis, when allowing for the differences between the methods and interpretation of their results.

Adult↗
PubMed2003

The fate, distribution, and toxicity of lindane in tests with Chironomus riparius: effects of bioturbation and sediment organic matter content.

In this laboratory study, we address the effect of Chironomus bioturbation (0, 2,000, 6,000, and 18,000 ind/m2) and sediment organic matter content (10, 20, and 40%) on the fate, distribution, and bioavailability of 14C-lindane under standardized conditions in toxicity tests with artificial sediment. The results show that both Chironomus burrowing activity and sediment organic matter strongly modify test conditions. Larval mortality and development were inversely related with Chironomus densities and lindane concentration. Sediment organic matter content affected larval development rates but not mortality. Partitioning of lindane between the sediment, overlying water, and interstitial water was affected negatively by Chironomus larval densities: however, sediment partitioning was positively affected by sediment organic matter content. Bioturbation by Chironomus resulted in a remobilization of particle-associated lindane to the interstitial and overlying water, implying an increase in the bioavailability of the test compound. Strong positive relationships were found between Chironomus densities and lindane concentrations in interstitial water. The presence of Chironomus also resulted in lower label recovery. Label recovery on sediment particles ranged from 49 to 61% of initially added label in microcosms without Chironomus, from 41 to 56% at low larval densities, and from 15 to 50% at high larval densities. These results show that large discrepancies may exist between nominal test concentrations (from test compound additions) and true exposure concentrations even under standardized test conditions, which can introduce a relatively large error term in risk assessments. Calculations show that volatilization may be a quantitatively important sink for test compounds.

Animals↗
PubMed2001

Growth, CO2 exchange rate and dry matter partitioning in mungbean (Vigna radiata L.) grown under elevated CO2.

This study was conducted to determine the effects of anticipated future level of CO2 on growth and dry matter partitioning of mungbean (Vigna radiata). Plants were grown from seedlings to maturity inside the open top chamber under amhient CO2 (350 +/- 25 microL L(-1)) and elevated CO2 (600 +/- 50 microL L(-1)) at Indian Agricultural Research Institute, New Delhi (India). Plants were harvested at 20, 35 and 50 days after germination. Mungbean plants grown under elevated CO2 concentration resulted in greater photosynthetic rate on a leaflet area basis and no acclimation in photosynthesis was recorded due to high CO2. Plants grown under CO, enrichmcnt were taller and attained greater leaf area along with more dry matter than ambient CO2 grown plants at all growth stages. Response to high CO, depends upon the growth stage of the plant and it was more at early growth stages compared to maturity stages. The high CO2 grown mungbean plants also exhibited increased root growth along with stem and leaves. There was a substantial increase in pod number and seed number/plant under elevated CO2 conditions. The increase in dry matter and growth of root, stem and leaves proved that CO2 enrichment of the atmosphere can stimulate photosynthetic rate which can ultimately lead to an increase in dry matter and growth.

Carbon Dioxide↗
PubMed2002

[Study on dry matter accumulations of Houttuynia cordata on heavy loam].

In this paper the characteristics of dry matter accumulation of Houttuynia cordata cultivated on three kinds of heavy loams were studied. The results showed that the accumulated curves of whole plant dry matter were somewhat different. During testing period, the accumulated curves of dry matter of Houttuynia cordata grown on clay silt loam and silt sand loam presented logistic ones, but those grown on sandy silt loam were still in line growth period. It was concluded that the harvest period of Houttuynia cordata on the sandy silt loam could be properly put off while only considered the yielding. The experiment on heavy loam also showed that the sandy field should be the better selection than others, but organic fertilizer should be enhanced as base fertilizer, with proper nitrogen as top application. This paper also discussed the dry matter accumulations of different organs of Houttuynia cordata.

Drugs, Chinese Herbal↗
PubMedDate not supplied

Description of the carbonaceous particulate matter evolution in an urban area.

The ground concentrations of particulate matter, total carbon, elemental carbon and organic carbon were measured in a monitoring station located inner a park in downtown Rome. The description of the evolution of the boundary layer is given by radon concentration measurements. The results show that the particulate matter of Rome contains about 30% of carbonaceous matter. The elemental and organic carbon behaviours show that elemental carbon is essentially a primary pollutant emitted directly from vehicular traffic and organic carbon behaviour instead can be primary (combustion and biogenic emission) and secondary. A chemical fine particulate matter mass balance is given; an organic carbon investigation has been carried out in order to determine n-alkanes, n-alkanoic acids and polycyclic aromatic hydrocarbons.

Air Pollutants↗
PubMed2003

[Three cases of non-differentiated leukodystrophy with involvement of cerebral hemisphere's white matter and cerebellum and specific lesions of cerebral pathways. Neuroimaging and clinico-biochemical characteristics].

We presented three cases of the non-differentiated White Matter's disease. There are clinical resemblance and the similar MRI patterns including MR spectroscopy in all patients. They are outpatients: girl (K), 7 years old, boy (N), 13 yrs and young men (N), 24 yrs without any family relationship, and were investigated in Burdenko Neurosurgical Institute, in 2002 year. The cerebral MRI examinations all of that patients have shown extensive abnormalities in the hemispheric's white matter of cerebrum and cerebellum. Meanwhile there are some specific lesions of the brain stem's tracts (the posterior limb of the internal capsule, the splenium of the corpus callosum, the medial lemniscus and the mesencephalic trigeminal tracts). Step by step progression of suffer ness with unknown time of beginning, mild mnestic reduction and hemyparesis and moderate cerebellar disorder without loss of sensitivity were characteristic for all patients. The results of the biochemical markers for leucodistrophy testing are negative. A proton spectrum of the abnormal white matter showed elevated lactate in one case (girl, 7 yrs). In our opinion clinical diagnosis in all three cases is the new pathology that some body named as "WMDL" (White matter disease with lactate). It should be differentiated with adrenoleucodistrophy, Refsum disease and NARP syndrome (neuropathy, ataxia, pigmentive retinitis).

Adolescent↗
PubMed1992

Ionic mechanisms of anoxic injury in mammalian CNS white matter: role of Na+ channels and Na(+)-Ca2+ exchanger.

White matter of the mammalian CNS suffers irreversible injury when subjected to anoxia/ischemia. However, the mechanisms of anoxic injury in central myelinated tracts are not well understood. Although white matter injury depends on the presence of extracellular Ca2+, the mode of entry of Ca2+ into cells has not been fully characterized. We studied the mechanisms of anoxic injury using the in vitro rat optic nerve, a representative central white matter tract. Functional integrity of the nerves was monitored electrophysiologically by quantitatively measuring the area under the compound action potential, which recovered to 33.5 +/- 9.3% of control after a standard 60 min anoxic insult. Reducing Na+ influx through voltage-gated Na+ channels during anoxia by applying Na+ channel blockers (TTX, saxitoxin) substantially improved recovery; TTX was protective even at concentrations that had little effect on the control compound action potential. Conversely, increasing Na+ channel permeability during anoxia with veratridine resulted in greater injury. Manipulating the transmembrane Na+ gradient at various times before or during anoxia greatly affected the degree of resulting injury; applying zero-Na+ solution (choline or Li+ substituted) before anoxia significantly improved recovery; paradoxically, the same solution applied after the start of anoxia resulted in more injury than control. Thus, ionic conditions that favored reversal of the normal transmembrane Na+ gradient during anoxia promoted injury, suggesting that Ca2+ loading might occur via reverse operation of the Na+)-Ca2+ exchanger. Na(+)-Ca2+ exchanger blockers (bepridil, benzamil, dichlorobenzamil) significantly protected the optic nerve from anoxic injury. Together, these results suggest the following sequence of events leading to anoxic injury in the rat optic nerve: anoxia causes rapid depletion of ATP and membrane depolarization leading to Na+ influx through incompletely inactivated Na+ channels. The resulting rise in the intracellular [Na+], coupled with membrane depolarization, causes damaging levels of Ca2+ to be admitted into the intracellular compartment through reverse operation of the Na(+)-Ca2+ exchanger. These observations emphasize that differences in the pathophysiology of gray and white matter anoxic injury are likely to necessitate multiple strategies for optimal CNS protection.

Amiloride↗