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At least 631 records · Page 35Linked to original sources
PubMed1997

Binding of malignant lymphoid cells to the white matter of the human central nervous system: role of different CD44 isoforms, beta 1, beta 2 and beta 7 integrins, and L-selectin.

Spreading of reactive and malignant lymphoid cells into the brain parenchyma requires regulated adhesion of the lymphoid cells to the parenchymal cells and/or extracellular matrix of the central nervous system. A multifunctional adhesion molecule CD44 partially mediates binding of lymphocytes to the white matter by interacting with hyaluronate. To analyze which forms of CD44 and what other adhesion molecules mediate this binding. Namalwa cells were transfected to express either standard (CD44st) or variant isoforms of CD44 containing exons v6-v10, v7-v10, and v8-v10. The binding of CD44st and CD44v6-v10 transfectants to human cerebellar white matter was tested and it was about 1.7- and 2-fold greater without and with PMA activation, respectively, compared with vector-transfected control cells. Hyaluronidase digestion of tissue sections decreased binding of CD44 expressing cells to the level of vector-transfected cells. Hermes-1, a monoclonal antibody recognizing the hyaluronate binding site of CD44, inhibited white matter adhesion of CD44v6-v10 and activated CD44st cells and binding of soluble hyaluronate to the CD44 transfectants. Transfectants also expressed beta 1, beta 2 and beta 7 integrins and L-selectin, but antibodies against these molecules did not inhibit adhesion to the white matter. These results suggest: (a) Addition of exons v6-v10 to the membrane proximal region of CD44 does not affect lymphoid cell adhesion to the white matter. (b) The only ligand of CD44 in the central nervous system (CNS) white matter is hyaluronate. (c) Additional adhesion mechanisms other than the ones analyzed above must exist.

Burkitt Lymphoma↗
PubMed2002

Experimental identification of nonpointlike dark-matter candidates.

We show that direct dark-matter detection experiments can distinguish between pointlike and nonpointlike dark-matter candidates. The shape of the nuclear recoil-energy spectrum from pointlike dark-matter particles, e.g., neutralinos, is determined by the velocity distribution of dark matter in the galactic halo and by nuclear form factors. Typical cross sections of nonpointlike dark matter, for example, Q-balls, have a new form factor, which decreases rapidly with the recoil energy. A signal from nonpointlike dark matter is expected to peak near the experimental threshold and to fall off rapidly at higher energies.

Journal Article↗
PubMed2005

Describing oscillations of high energy neutrinos in matter precisely.

We present a formalism for precise description of oscillation phenomena in matter at high energies or high densities, V > Delta m(2)/2E, where V is the matter-induced potential of neutrinos. The accuracy of the approximation is determined by the quantity, where is the mixing angle in matter and is a typical change of the potential over the oscillation length (). We derive simple and physically transparent formulas for the oscillation probabilities, which are valid for arbitrary matter density profiles. They can be applied to oscillations of high-energy accelerator, atmospheric, and cosmic neutrinos in the matter of the Earth, substantially simplifying numerical calculations and providing an insight into the physics of neutrino oscillations in matter. The effect of parametric enhancement of the oscillations of high-energy neutrinos is considered.

Journal Article↗
PubMed1990

White matter changes in dementia of Alzheimer's type: the difference in vulnerability between cell compartments.

Structural white matter changes were found to be common in dementia of Alzheimer's type. A neuropathological investigation was undertaken in order to characterize and quantify these white matter changes. The tissue changes were compared with those in white matter in normal control cases and in complete white matter infarcts. Our results support the hypothesis that the white matter lesion seen in dementia of Alzheimer's type is due to incomplete infarction involving both axons and myelin and is a result of mild ischaemia. In mild ischaemia, the myelin compartment appears to be the most vulnerable. We have termed the lesion selective incomplete white matter infarction.

Aged↗
PubMed2004

Abnormal frontal white matter tracts in bipolar disorder: a diffusion tensor imaging study.

OBJECTIVES: Prefrontal white matter has been hypothesized to be integral to the pathophysiology of bipolar disorder. Recent morphometric studies however, have not observed changes in white matter in bipolar patients. We hypothesized that changes in prefrontal function in bipolar disorder, widely reported in the literature, may be related to a loss of white matter tract integrity with a resultant dysconnectivity syndrome. In this study we utilized diffusion tensor imaging (DTI) to examine prefrontal white matter in patients with bipolar disorder. METHODS: Nine patients with bipolar disorder and nine healthy controls were recruited. DTI and localizing anatomic data were acquired, and regions of interest (ROIs) identified in the prefrontal white matter at 15, 20, 25, and 30 mm superior to the anterior commissure (AC). Fractional anisotropy (FA) and trace apparent diffusion coefficient (TADC) were compared by ROI between study groups. RESULTS: The FA of ROIs 25 and 30 mm above the AC was significantly reduced in patients with bipolar disorder; FA of all ROIs showed high-medium to large effect sizes. No significant group differences were identified in TADC. CONCLUSIONS: Our findings suggest that a loss of bundle coherence is present in prefrontal white matter. This loss of coherence may contribute to prefrontal cortical pathology in patients with bipolar disorder.

Adult↗
PubMed1995

Pathogenesis of lacuna-like cyst formation and diffuse degeneration of the white matter in the brain of stroke-prone spontaneously hypertensive rats.

1. In an attempt to clarify the developmental mechanisms of lacuna and diffuse degeneration of the white matter in the brain in chronic hypertension, we investigated histologically the cerebral changes and histochemically, as well as biochemically, the lysosomal enzymes in the brain of stroke-prone spontaneously hypertensive rats (SHRSP). 2. The most prominent advanced lesions observed in SHRSP were cyst formation in the cortex and subcortical white matter, and diffuse degeneration of the white matter. On the other hand, the early cerebral changes were all related to blood-brain barrier dysfunction. The localization of cystic lesions and degeneration of the white matter corresponded very well with the extent of brain oedema demonstrated by immunostaining for leaked fibrinogen. All lysosomal enzyme activities in the adult SHRSP, both in the cortex and white matter, were higher than those in the controls. Histochemical investigation showed that SHRSP had an increased number of cells, reactive astrocytes and microglial cells, with positive reaction to lysosomal enzymes in the oedematous portion. 3. These findings suggest that chronic oedema due to blood-brain barrier dysfunction causes cystic changes as well as diffuse degeneration of the white matter, and that activated lysosomal enzymes in the reactive astrocytes and microglia play an important role in the development of such hypertensive lesions.

Animals↗
PubMed2006

Pathological and biochemical studies on a case of Pick disease with severe white matter atrophy.

We report on a male patient with Pick disease who had shown severe white matter atrophy and dilatation of the lateral ventricle in the frontal lobe from an early stage. Upon admission to our hospital 2 years after disease onset, the patient showed apathy, and MRI revealed severe atrophy of the cortex and white matter of the frontal lobe. He died at age 74, 11 years after disease onset. Autopsy revealed severe atrophy of the frontal and temporal lobes, severe loss of white matter in the frontal lobe, dilatation of the lateral ventricles, and cortical thinning. Histopathological examination showed severe loss of myelinated fibers in the frontal white matter and severe neuronal loss with gliosis in the frontal and temporal cortices. Many Pick bodies were seen. Our patient had a rare case of Pick disease predominantly affecting the frontal lobe with severe involvement of the white matter from an early stage. This case suggests that myelinated fibers in the white matter as well as cerebral neurons are primarily affected in Pick disease.

Aged↗
PubMedDate not supplied

The influence of white matter lesions on neuropsychological functioning in demented and non-demented 85-year-olds.

White matter lesions on computed tomography of the head were studied in relation to neuropsychological functioning in subjects from a representative sample of non-demented (n = 134) and demented (n = 98) 85-year-olds. Non-demented subjects with white matter lesions (n = 46) scored significantly lower in tests of verbal ability (Synonyms), spatial ability (Block Design, Clock Test), perceptual speed (Identical forms), secondary memory (Thurstone Picture Memory), basic arithmetic (Coin Test) and the global cognitive screening test Mini-Mental State Examination than non-demented subjects without white matter lesions (n = 88). Demented subjects with white matter lesions (n = 67) scored significantly lower in tests of spatial ability (Block Design and Clock Test) and secondary memory (free recall in the MIR memory test, Ten-word memory test I and II) and in the Mini-Mental State Examination than demented subjects without white matter lesions (n = 31). It is concluded that white matter lesions contribute to cognitive decline in both non-demented and demented elderly subjects.

Aged↗
PubMed1999

Visual hallucinations, white matter lesions and disease severity in Parkinson's disease.

OBJECTIVES: To determine if visual hallucinations in patients with Parkinson's disease are associated with an increased prevalence of white matter lesions. PATIENTS AND METHODS: Fifteen patients with (group 1) and 15 patients without (group 2) a history of visual hallucinations were studied. Both groups were matched for age. Magnetic resonance imaging was performed in all patients using standard T2 weighted Fast-Spin-Echo sequences. Assessment of cerebral white matter changes was performed using a modification of established criteria, with semiquantitative evaluation of periventricular and deep white matter changes. RESULTS: There was no significant group difference with regard to the total amount of white matter changes, nor was a group difference found between the amount or extent of periventricular hyperintensities or deep white matter lesions. Group 1 was significantly (P = 0.001) more disabled as evaluated by Hoehn/Yahr stage controlling for age and duration of disease. Mean increases in Hoehn/Yahr stage were not significantly greater in group 1 compared with group 2 at a 2-year follow-up examination (0.6 vs. 0.3, P = 0.166). CONCLUSION: Our data suggest that visual hallucinations are an indicator of a more aggressive course of the disease, but are not associated with a higher prevalence of global or occipital white matter lesions.

Aged↗
PubMed2002

Cognitive associations of subcortical white matter lesions in older people.

Hyperintense lesions (HL), as visualized on T2-weighted or FLAIR MRI, are a common finding in older people, but their clinical significance and influence on cognitive function remain to be clarified. We investigated the relationship between HL in deep white and gray matter structures and cognition in older subjects. We recruited 154 nondemented (Mini-Mental State Examination > 24) subjects (79 males) over the age of 70 from primary care (103 subjects with mild hypertension and 51 normotensive subjects). All subjects underwent FLAIR and proton density and T2-weighted axial 1.5-tesla MRI scans (slice thickness: 5 mm). The scans were rated for the presence and distribution of HL in the subcortical gray matter (caudate, putamen, globus pallidus, thalamus) and associated white matter tracts (internal/external capsule). Subjects (n = 149) underwent a comprehensive cognitive assessment involving tests of attention, processing speed, episodic memory, working memory, and executive function. Partial correlations (correcting for age, systolic blood pressure, and New Adult Reading Test [NART] score) were performed to investigate the relationship between cognition and white matter change. HL were found in 49% of subjects. HL in both the gray (thalamus and caudate) and white matter were significantly associated with impaired cognitive function in tasks involving processing speed and/or executive function, but showed no associations with episodic or working memory. HL in both subcortical gray matter structures and associated fiber tracts correlate with impairments in attention, executive function and processing, and memory retrieval speed in nondemented older community-dwelling subjects. Such lesions may be an important cause of age-related attentional and executive dysfunction in the elderly, as well as temporal lobe and hippocampal changes that have previously been reported to be associated with impairments to the ability to actually store and retrieve information from memory.

Aged↗
PubMed2002

Delayed white matter injury in a murine model of shaken baby syndrome.

Shaken baby syndrome, a rotational acceleration injury, is most common between 3 and 6 months of age and causes death in about 10 to 40% of cases and permanent neurological abnormalities in survivors. We developed a mouse model of shaken baby syndrome to investigate the pathophysiological mechanisms underlying the brain damage. Eight-day-old mouse pups were shaken for 15 seconds on a rotating shaker. Animals were sacrificed at different ages after shaking and brains were processed for histology. In 31-day-old pups, mortality was 27%, and 75% of survivors had focal brain lesions consisting of hemorrhagic or cystic lesions of the periventricular white matter, corpus callosum, and brainstem and cerebellar white matter. Hemorrhagic lesions were evident from postnatal day 13, and cysts developed gradually between days 15 and 31. All shaken animals, with or without focal lesions, had thinning of the hemispheric white matter, which was significant on day 31 but not earlier. Fragmented DNA labeling revealed a significant increase in cell death in the periventricular white matter, on days 9 and 13. White matter damage was reduced by pre-treatment with the NMDA receptor antagonist MK-801. This study showed that shaking immature mice produced white matter injury mimicking several aspects of human shaken baby syndrome and provided evidence that excess release of glutamate plays a role in the pathophysiology of the lesions.

Animals↗
PubMed2004

Gestational hypoxia induces white matter damage in neonatal rats: a new model of periventricular leukomalacia.

In the premature infant, periventricular leukomalacia, usually related to hypoxicischemic white matter damage, is the main cause of neurological impairment. We hypothesized that protracted prenatal hypoxia might induce white matter damage during the perinatal period. Pregnant Sprague-Dawley rats were placed in a chamber supplied with hypoxic gas (10% O2-90% N2) from embryonic day 5 (E5) to E20. Neonatal rat brains were investigated by histology, immunocytochemistry, western blotting, in situ hybridization, DNA fragmentation analysis, and in vivo magnetic resonance imaging (MRI). Body weight of pups subjected to prenatal hypoxia was 10 to 30% lower from P0 to P14 than in controls. Specific white matter cysts were detected between P0 and P7 in pups subjected to prenatal hypoxia, in addition to abnormal extra-cellular matrix, increased lipid peroxidation, white matter cell death detected by TUNEL, and increased activated macrophage counts in white matter. Subsequently, gliotic scars and delayed myelination primarily involving immature oligodendrocytes were seen. In vivo MRI with T1, T2, and diffusion sequences disclosed similar findings immediately after birth, showing strong correlations with histological abnormalities. We speculate that protracted prenatal hypoxia in rat induces white matter damage occurring through local inflammatory response and oxidative stress linked to re-oxygenation during the perinatal period.

Animals↗
PubMed1999

Phase-coherent amplification of matter waves

Phase-coherent matter-wave amplification was demonstrated using Bose- Einstein-condensed rubidium-87 atoms. A small seed matter wave was created with coherent optical Bragg diffraction. Amplification of this seed matter wave was achieved by using the initial condensate as a gain medium through the superradiance effect. The coherence properties of the amplified matter wave, studied with a matter-wave interferometer, were shown to be locked to those of the initial seed wave. The active matter-wave device demonstrated here has great potential in the fields of atom optics, atom lithography, and precision measurements.

Journal Article↗
PubMed1961

Determination, by spodography, of the intracellular distribution of mineral matter throughout the life history of Bacillus cereus.

Knaysi, Georges (Cornell University, Ithaca, N. Y.). Determination, by spodography, of the intracellular distribution of mineral matter throughout the life history of Bacillus cereus. J. Bacteriol. 82:556-563. 1961.-The intracellular distribution of mineral matter throughout the life history of Bacillus cereus strain C(3) was investigated by microincineration for which the term spodography is suggested. The organism was grown in microcultures on collodion membranes supported by agar media. At various stages of development, microcultures were floated on distilled water, picked onto cover glasses, air-dried, and incinerated at 500 to 525 C. The mineral residue is deposited in situ and shows the distribution of mineral matter in the cells. Study of the spodograms thus obtained shows that in the spore mineral matter is concentrated in a peripheral layer surrounding a minerally poor core. As soon as the spore begins to germinate, often before one notes any change in its optical properties, the minerally rich layer increases in thickness while the core becomes gradually smaller and finally disappears. The germ cell appears nearly homogeneous, with evidence of mineral aggregation into discrete granules more readily seen in subsequent generations. The nuclei of the vegetative cells are sites of mineral accumulation. In the compound nuclei, minerals seem to be concentrated in a superficial ring around a minerally poor center. In the young forespore, mineral matter is homogeneously distributed. As the spore stage is approached, however, the mineral matter tends to occupy a peripheral position as in the completed spore. The results indicate that the calcium dipicolinate of the spore is principally in the minerally rich, peripheral layer. The relation of this layer to the other peripheral structures of the spore has not been determined. Observation was made with a phase microscope in dark contrast and using a dry objective.

Animals↗
PubMed2006

Frontal white matter anisotropy and symptom severity of late-life depression: a magnetic resonance diffusion tensor imaging study.

OBJECTIVES: To investigate the disruption of neural circuits in the frontal lobes and limbic structures in late-life depressed patients compared with healthy controls, and to examine the correlation between the degree of microstructural abnormalities of white matter and clinical symptom severity in late-life depression. METHODS: Thirteen patients with late-life depression and matched control subjects underwent diffusion tensor imaging. Fractional anisotropy (FA), an index of the integrity of white matter tracts, was determined in the white matter of frontal, temporal, and occipital brain regions and the corpus callosum. RESULTS: A significant reduction was found in white matter FA values of widespread regions of the frontal and temporal lobes of depressed patients. Also, there was some evidence suggesting that white matter FA values of the inferior frontal brain region are inversely related to severity of depression. CONCLUSIONS: These results suggest the possible loss of integrity within frontal and temporal white matter fibre tracts and implicate the orbitofrontal circuit in symptom severity in late-life depression.

Anisotropy↗
PubMed2002

Diffusion-weighted MR imaging in the brain in children: findings in the normal brain and in the brain with white matter diseases.

PURPOSE: To establish quantitative standards for age-related changes in diffusion restriction of cerebral white matter in healthy children and to compare data with results in children with white matter diseases. MATERIALS AND METHODS: Diffusion-weighted magnetic resonance (MR) imaging was performed in 44 children (age range, 7 days to 7.5 years) without brain abnormalities and in 13 children with proved leukodystrophy. Apparent diffusion coefficient (ADC) and apparent anisotropy (AA) were measured in 11 regions of interest within white matter. Age-related changes were analyzed with regression analysis. RESULTS: During normal brain myelination, ADCs in different anatomic regions were high at birth (range, 1.04 x 10(-9) m(2)/sec +/- 0.05 [SD] to 1.64 x 10(-9) m(2)/sec +/- 0.09) and low after brain maturation (range, 0.75 x 10(-9) m(2)/sec +/- 0.02 to 0.92 x 10(-9) m(2)/sec +/- 0.02). AA was low at birth (range, 0.05 +/- 0.01 to 0.52 +/- 0.04) and high after brain maturation (range, 0.25 +/- 0.02 to 0.85 +/- 0.03). Age relationship could be expressed with monoexponential functions for all anatomic regions. Anisotropy preceded the myelination-related changes at MR imaging. ADC and AA in four children with Pelizaeus-Merzbacher disease were identical with results in healthy newborn children and showed no age dependency. In peroxisomal disorders, Krabbe disease, and mitochondriopathy, demyelination on T1- and T2-weighted MR images led to expected findings at diffusion-weighted MR imaging, with high ADC and low AA, whereas in Canavan disease and metachromatic leukodystrophy, the opposite findings were revealed, with low ADC within the demyelinated white matter. CONCLUSION: During early brain myelination, diffusion restriction in normal white matter increases. Anisotropy precedes myelination changes that are visible at MR imaging. Compared with T1- and T2-weighted MR imaging, diffusion-weighted MR imaging in white matter diseases reveals additional information.

Adolescent↗
PubMed1987

White-matter lesions in MR imaging of clinically healthy brains of elderly subjects: possible pathologic basis.

Patchy white-matter lesions occur in the magnetic resonance (MR) imaging brain studies of 20%-30% of neurologically healthy elderly subjects. To determine the frequency of histologically verifiable white-matter lesions at autopsy in such subjects the authors examined serial, microscopic, whole brain sections from 15 clinically healthy subjects aged 52-72 years. Small white-matter lesions were found in 12. In these 12, zones of atrophic perivascular demyelination were present in eight brains. These are not the familiar thrombotic, embolic, or ischemic vascular lesions that produce acute necrosis. This mild vascular insufficiency produces atrophy, which has been recognized in the pathology literature but whose clinical significance remains unknown. Other lesions seen were small vascular malformations in the centrum ovale in four brains, diverticula of the lateral ventricle extending into the white matter in three, and an isolated central white-matter infarction in one. All of these lesions are probably the basis of the patchy white-matter lesions seen on MR imaging studies in the neurologically healthy elderly population.

Aged↗
PubMed1988

Association of heterotopic gray matter with seizures: MR imaging. Work in progress.

Heterotopic gray matter, which previously had been associated with severe congenital malformations of the brain and developmental delay, was found without these associated conditions. The authors found ten cases of heterotopic gray matter on magnetic resonance (MR) images. The lesions had a signal intensity that was isointense compared with that of gray matter on T1, spin-density, and T2-weighted images. Nine of the ten cases were associated with a seizure disorder. The tenth case, discovered during a workup for metastatic lung disease, was confirmed with pathologic studies. Heterotopic gray matter is the presence of cortical neurons in an abnormal location, which may be periventricular (nodular) or within the white matter (laminar). A knowledge of heterotopic gray matter and its association with seizures may prevent the misinterpretation of findings on MR images.

Adolescent↗