Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 4.667
Filtrar
1.
Adv Exp Med Biol ; 1190: 65-83, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31760639

RESUMO

Propagation of action potentials along axons is optimized through interactions between neurons and myelinating glial cells. Myelination drives division of the axons into distinct molecular domains including nodes of Ranvier. The high density of voltage-gated sodium channels at nodes generates action potentials allowing for rapid and efficient saltatory nerve conduction. At paranodes flanking both sides of the nodes, myelinating glial cells interact with axons, forming junctions that are essential for node formation and maintenance. Recent studies indicate that the disruption of these specialized axonal domains is involved in the pathophysiology of various neurological diseases. Loss of paranodal axoglial junctions due to genetic mutations or autoimmune attack against the paranodal proteins leads to nerve conduction failure and neurological symptoms. Breakdown of nodal and paranodal proteins by calpains, the calcium-dependent cysteine proteases, may be a common mechanism involved in various nervous system diseases and injuries. This chapter reviews recent progress in neurobiology and pathophysiology of specialized axonal domains along myelinated nerve fibers.


Assuntos
Axônios/fisiologia , Fibras Nervosas Mielinizadas/fisiologia , Condução Nervosa , Axônios/patologia , Humanos , Fibras Nervosas Mielinizadas/patologia , Neuroglia/patologia , Neuroglia/fisiologia
2.
J Pediatr Ophthalmol Strabismus ; 56: e57-e59, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31622478

RESUMO

Few anecdotal reports have documented new onset and progression of myelination of the retinal nerve fiber layer. The authors report the unusual onset and progression of acquired myelination of the retinal nerve fiber layer in two children, following the diagnosis of presumed idiopathic intracranial hypertension. The nosologic relationship between myelination of the retinal nerve fiber layer and idiopathic intracranial hypertension is unclear and requires elucidation by further studies. [J Pediatr Ophthalmol Strabismus. 2019;56:e57-e59.].


Assuntos
Fibras Nervosas Mielinizadas/patologia , Pseudotumor Cerebral/complicações , Doenças Retinianas/diagnóstico , Células Ganglionares da Retina/patologia , Criança , Humanos , Lactente , Masculino , Nervo Óptico/patologia , Pseudotumor Cerebral/diagnóstico , Doenças Retinianas/etiologia , Tomografia de Coerência Óptica
3.
Muscle Nerve ; 60(6): 762-768, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31498901

RESUMO

INTRODUCTION: Equine recurrent laryngeal neuropathy (RLN) is a naturally occurring model of length-dependent axonopathy characterized by asymmetrical degeneration of recurrent laryngeal nerve axons (RLn). Distal RLn degeneration is marked, but it is unclear whether degeneration extends to include cell bodies (consistent with a neuronopathy). METHODS: With examiners blinded to RLN severity, brainstem location, and side, we examined correlations between RLN severity (assessed using left distal RLn myelinated axon count) and histopathological features (including chromatolysis and glial responses) in the nucleus ambiguus cell bodies, and myelinated axon count of the right distal RLn of 16 horses. RESULTS: RLN severity was not associated with RLn cell body number (P > .05), or degeneration. A positive correlation between the left and right distal RLn myelinated axon counts was identified (R2 = 0.57, P < .05). DISCUSSION: We confirm that RLN, a length-dependent distal axonopathy, occurs in the absence of detectable neuronopathy.


Assuntos
Corpo Celular/patologia , Bulbo/patologia , Fibras Nervosas Mielinizadas/patologia , Neurônios/patologia , Nervo Laríngeo Recorrente/patologia , Paralisia das Pregas Vocais/patologia , Animais , Atrofia , Contagem de Células , Cavalos , Nervo Laríngeo Recorrente/fisiopatologia , Paralisia das Pregas Vocais/fisiopatologia
6.
Bull Exp Biol Med ; 166(6): 793-796, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31028587

RESUMO

One of the most common models of sporadic form of Alzheimer's disease is injection of streptozotocin into the lateral ventricles of rat brain. In 3 months after this injection, an increase in the expression of astroglia in the corpus callosum and a decrease in the thickness of the corpus callosum and intensity of its staining with luxol fast blue were observed. This can reflect a decrease in the content of myelinated fibers. In layer V of the sensorimotor cortex, intensive degeneration of neurons was revealed. The lateral ventricles were significantly enlarged and the expression of PSA-NCAM protein, a marker of immature neurons, was reduced in subventricular zone, which can be associated with disturbed neurogenesi.


Assuntos
Doença de Alzheimer/patologia , Astrócitos/patologia , Corpo Caloso/patologia , Ventrículos Laterais/patologia , Fibras Nervosas Mielinizadas/patologia , Córtex Sensório-Motor/patologia , Doença de Alzheimer/induzido quimicamente , Doença de Alzheimer/metabolismo , Animais , Astrócitos/metabolismo , Biomarcadores/metabolismo , Corpo Caloso/metabolismo , Modelos Animais de Doenças , Expressão Gênica , Indóis , Injeções Intraventriculares , Ventrículos Laterais/metabolismo , Masculino , Fibras Nervosas Mielinizadas/metabolismo , Molécula L1 de Adesão de Célula Nervosa/genética , Molécula L1 de Adesão de Célula Nervosa/metabolismo , Neurônios/metabolismo , Neurônios/patologia , Ratos , Ratos Wistar , Córtex Sensório-Motor/metabolismo , Ácidos Siálicos/genética , Ácidos Siálicos/metabolismo , Técnicas Estereotáxicas , Estreptozocina/administração & dosagem
7.
World Neurosurg ; 127: e542-e547, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30928592

RESUMO

OBJECTIVE: We evaluated the spinal cord injury range in patients with tethered cord syndrome (TCS) who had urinary incontinence. METHODS: We included 30 subjects in the present study, 15 with tethered cord syndrome and urinary incontinence and 15 normal volunteers. All 30 subjects underwent magnetic resonance diffusion tensor imaging (DTI). Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were calculated from a region of interest). All the patients and volunteers were measured 4 segments above the conus medullaris. RESULTS: All the FA values and ADC values could be measured from the DTI scans in the normal volunteers and patients. The average ADC value was 1.244 ± 0.061 in the control group and 1.052 ± 0.045 in the TCS group. The difference was statistically significant (P < 0.05). The average FA value was 0.866 ± 0.030 in the control group and 1.079 ± 0.049 in the TCS group, with a statistically significant difference (P < 0.05). The differences in the ADC values in each segment were statistically significant in the 2 groups, although only the difference in the FA value of the fourth segment above the conus medullaris was statistically significant in the 2 groups. CONCLUSION: DTI can detect the spinal cord damage range in patients with TCS. In the patients with urinary incontinence, the spinal cord damage was widespread, and the most severe lesion was at the fourth segment above the conus medullaris. This might indicate that decompression of the spinal cord should at least include the fourth segment above the conus medullaris.


Assuntos
Imagem de Tensor de Difusão , Fibras Nervosas Mielinizadas/patologia , Compressão da Medula Espinal/patologia , Traumatismos da Medula Espinal/patologia , Adolescente , Adulto , Criança , Descompressão Cirúrgica/métodos , Imagem de Tensor de Difusão/métodos , Feminino , Humanos , Masculino , Defeitos do Tubo Neural/patologia , Procedimentos Neurocirúrgicos/métodos , Medula Espinal/patologia , Adulto Jovem
8.
World Neurosurg ; 125: e620-e638, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30716486

RESUMO

OBJECTIVE: White fiber dissection using a gyrus-based approach was performed to study the various associations, commissural, and projection fiber bundles of the brain. METHODS: Ten previously frozen and formalin-fixed cadaveric human brains were included. The fiber dissection techniques described by Klingler were used. The primary dissection tools were thin handmade wooden spatulas and curved metallic spatulas with tips of various sizes. The fibers were studied by the naked eye and with the use of magnification. The various fiber bundles were studied using a gyrus-based approach. The dissection was performed through each named gyrus, and the fiber tracts encountered during dissection were identified, and their relationship to other adjacent fiber bundles was studied. RESULTS: From our dissections, the white fibers of the brain were divided architecturally into 5 groups-4 horizontal groups and 1 vertical group. The 4 horizontal groups were the superficial, middle, deep, and central groups. The association fibers constituted the superficial, middle, and deep groups. The commissural fibers formed the central group, and the projection fibers formed the vertical group. The course of the fiber bundles and their functional co-relationship were determined. CONCLUSIONS: When planning the surgical trajectory, knowledge of the location of white matter tracts is essential to help minimize the occurrence of postoperative deficits. Fiber dissection using the Klingler technique is useful in gaining an understanding of the complex 3-dimensional nature of these white matter tracts and can provide a valuable resource in neurosurgical training.


Assuntos
Encéfalo/patologia , Fibras Nervosas Mielinizadas/patologia , Vias Neurais/fisiologia , Substância Branca/patologia , Mapeamento Encefálico , Dissecação/métodos , Humanos , Substância Branca/cirurgia
9.
Neurology ; 92(9): e933-e943, 2019 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-30700595

RESUMO

OBJECTIVE: We sought to determine the underlying mechanism for altered white matter diffusion tensor imaging (DTI) measures at the histopathologic level in patients with cerebral amyloid angiopathy (CAA). METHODS: Formalin-fixed intact hemispheres from 9 CAA cases and 2 elderly controls were scanned at 3-tesla MRI, including a diffusion-weighted sequence. DTI measures (i.e., fractional anisotropy [FA] and mean diffusivity [MD]) and histopathology measures were obtained from 2 tracts: the anterior thalamic radiation and inferior longitudinal fasciculus. RESULTS: FA was reduced in both tracts and MD was increased in cases with CAA compared to controls. Regional FA was significantly correlated with tissue rarefaction, myelin density, axonal density, and white matter microinfarcts. MD correlated significantly with tissue rarefaction, myelin density, and white matter microinfarcts, but not axonal density. FA and MD did not correlate with oligodendrocytes, astrocytes, or gliosis. Multivariate analysis revealed that tissue rarefaction (ß = -0.32 ± 0.12, p = 0.009) and axonal density (ß = 0.25 ± 0.12, p = 0.04) were both independently associated with FA, whereas myelin density was independently associated with MD (ß = -0.32 ± 0.12, p = 0.013). Finally, we found an association between increased MD in the frontal white matter and CAA severity in the frontal cortex (p = 0.035). CONCLUSIONS: These results suggest that overall tissue loss, and in particular axonal and myelin loss, are major components underlying CAA-related alterations in DTI properties observed in living patients. The findings allow for a more mechanistic interpretation of DTI parameters in small vessel disease and for mechanism-based selection of candidate treatments to prevent vascular cognitive impairment.


Assuntos
Axônios/patologia , Angiopatia Amiloide Cerebral/patologia , Infarto Cerebral/patologia , Fibras Nervosas Mielinizadas/patologia , Substância Branca/patologia , Idoso , Idoso de 80 Anos ou mais , Anisotropia , Estudos de Casos e Controles , Angiopatia Amiloide Cerebral/diagnóstico por imagem , Infarto Cerebral/diagnóstico por imagem , Imagem de Tensor de Difusão , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Substância Branca/diagnóstico por imagem
10.
Int J Neurosci ; 129(4): 320-324, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30260726

RESUMO

AIM OF THE STUDY: Cognitive decline due to aging is most probably the result of changes in the white matter in the central nervous system (CNS) and/or demyelination. MATERIAL AND METHODS: We used electron microscopic analysis of the morphological changes in aging rats' optic nerves as an easily accessible part of the CNS. RESULTS: Several age changes were observed in aging rats (36 months) vs. young adult rats (6 months), namely degeneration of axons, decreased packing density and morphological alterations of myelination, including the ballooning of some myelin sheaths, separation of myelin lamellae and degenerative changes in the oligodendrocytes population. CONCLUSION: Cognitive decline related to aging may occur in part due to the disturbed myelination of axons in CNS white matter.


Assuntos
Envelhecimento/patologia , Axônios/patologia , Bainha de Mielina/patologia , Degeneração Neural/patologia , Fibras Nervosas Mielinizadas/patologia , Nervo Óptico/patologia , Fatores Etários , Animais , Masculino , Microscopia Eletrônica , Nervo Óptico/diagnóstico por imagem , Ratos , Ratos Sprague-Dawley
11.
Am J Dermatopathol ; 41(1): 65-67, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29894359

RESUMO

Cutaneous nerve hyperplasia is characterized by the presence of increased and hypertrophic myelinated and unmyelinated nerve fibers in the dermis. We report a case of periadnexal nerve hyperplasia as an asymptomatic and infrequent reactive histopathological change, with no associated risk of malignancy that can be seen in scars, in patients with no syndromic stigmata.


Assuntos
Carcinoma Basocelular/cirurgia , Cicatriz/patologia , Achados Incidentais , Fibras Nervosas Mielinizadas/patologia , Fibras Nervosas Amielínicas/patologia , Neoplasias Cutâneas/cirurgia , Pele/inervação , Idoso , Biópsia , Carcinoma Basocelular/patologia , Humanos , Hiperplasia , Imuno-Histoquímica , Masculino , Neoplasias Cutâneas/patologia
12.
Int Ophthalmol ; 39(5): 987-990, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-29594794

RESUMO

PURPOSE: To record the coexistence of polypoidal choroidal vasculopathy (PCV) with other rare fundus diseases in a Chinese population. METHOD: In this retrospective hospital-based study, a chart review of 861 patients with newly diagnosed PCV was performed. The clinical features of rare fundus comorbidities of PCV were recorded. RESULTS: Five eyes of 5 patients aged 63.4 ± 11.22 years (0.58%) had PCV coexisting with other fundus diseases in the same eye. Of the 5 PCV patients, 2 (0.23%) had myelinated nerve fiber, 2 (0.23%) had branch retinal vein occlusion, and 1 (0.12%) had retinal angiomatous proliferation. CONCLUSION: We reported rare fundus comorbidities of PCV in a large Chinese cohort. These comorbidities included myelinated nerve fiber, branch retinal vein occlusion and retinal angiomatous proliferation. The combination might constitute an accidental occurrence.


Assuntos
Doenças da Coroide/diagnóstico , Corioide/irrigação sanguínea , Degeneração Macular/epidemiologia , Fibras Nervosas Mielinizadas/patologia , Pólipos/diagnóstico , Oclusão da Veia Retiniana/epidemiologia , Acuidade Visual , Idoso , Idoso de 80 Anos ou mais , China/epidemiologia , Doenças da Coroide/epidemiologia , Comorbidade , Feminino , Angiofluoresceinografia , Fundo de Olho , Humanos , Macula Lutea/patologia , Degeneração Macular/diagnóstico , Masculino , Pessoa de Meia-Idade , Oftalmoscopia , Pólipos/epidemiologia , Doenças Raras , Células Ganglionares da Retina/patologia , Oclusão da Veia Retiniana/diagnóstico , Estudos Retrospectivos , Tomografia de Coerência Óptica
13.
Glia ; 67(2): 376-392, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30450647

RESUMO

The tightly controlled processes of myelination and remyelination require the participation of the cytoskeleton. The reorganization of the cytoskeleton is controlled by small GTPases of the RhoA family. Here, we report that Vav3, a Rho GTPase regulating guanine nucleotide exchange factor (GEF) is involved in oligodendrocyte maturation, myelination and remyelination. When Vav3 was eliminated by genetic recombination, oligodendrocyte precursor cell (OPC) differentiation toward mature oligodendrocytes was accelerated. In contrast, Vav3-deficient oligodendrocytes displayed a reduced capacity to myelinate synthetic microfibers in vitro. Furthermore, remyelination was impaired in Vav3 knockout cerebellar slice cultures that were demyelinated by the addition of lysolecithin. In agreement with these observations, remyelination was compromised when the cuprizone model of myelin lesion was performed in Vav3-deficient mice. When Vav3-deficient oligodendrocytes were examined with Förster resonance energy transfer (FRET)-based biosensors, an altered activation profile of RhoA GTPases was revealed on the cellular level, which could be responsible for an impaired remyelination. Taken together, this study highlights Vav3 as a novel regulator of oligodendrocyte maturation and remyelination, suggesting that manipulation of the Vav3-dependent signaling pathway could help to improve myelin repair.


Assuntos
Diferenciação Celular/genética , Leucoencefalopatias/patologia , Células Precursoras de Oligodendrócitos/fisiologia , Proteínas Proto-Oncogênicas c-vav/metabolismo , Remielinização/genética , Animais , Caspase 3/metabolismo , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Quelantes/toxicidade , Cuprizona/toxicidade , Modelos Animais de Doenças , GTP Fosfo-Hidrolases/metabolismo , Antígeno Ki-67/metabolismo , Leucoencefalopatias/induzido quimicamente , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína Básica da Mielina/metabolismo , Fibras Nervosas Mielinizadas/patologia , Células Precursoras de Oligodendrócitos/patologia , Técnicas de Cultura de Órgãos , Proteínas Proto-Oncogênicas c-vav/genética , Remielinização/efeitos dos fármacos , Proteína rhoA de Ligação ao GTP/metabolismo
14.
Neurotoxicology ; 70: 161-179, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30471306

RESUMO

During the mammalian brain development, oligodendrocyte progenitor cells (OPCs) are generated from neuroepithelium and migrate throughout the brain. Myelination is a tightly regulated process which involves time framed sequential events of OPCs proliferation, migration, differentiation and interaction with axons for functional insulated sheath formation. Myelin is essential for efficient and rapid conduction of electric impulses and its loss in the hippocampus of the brain may result in impaired memory and long-term neurological deficits. Carbofuran, a carbamate pesticide is known to cause inhibition of hippocampal neurogenesis and memory dysfunctions in rats. Nonetheless, the effects of carbofuran on OPCs proliferation, fate determination, maturation/differentiation and myelination potential in the hippocampus of the rat brain are still completely elusive. Herein, we investigated the effects of sub-chronic exposure of carbofuran during two different time periods including prenatal and adult brain development in rats. We observed carbofuran hampers OPCs proliferation (BrdU incorporation) and oligodendroglial differentiation in vitro. Similar effects of carbofuran were also observed in the hippocampus region of the brain at both the time points. Carbofuran exposure resulted in reduced expression of key genes and proteins involved in the regulation of oligodendrocyte development and functional myelination. It also affects the survival of oligodendrocytes by inducing apoptotic cell death. The ultrastructural analysis of myelin architecture clearly depicted carbofuran-mediated negative effects on myelin compaction and g-ratio alteration. Conclusively, our study demonstrated that carbofuran alters myelination potential in the hippocampus, which leads to cognitive deficits in rats.


Assuntos
Carbofurano/toxicidade , Hipocampo/efeitos dos fármacos , Inseticidas/toxicidade , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Oligodendroglia/efeitos dos fármacos , Efeitos Tardios da Exposição Pré-Natal/induzido quimicamente , Fatores Etários , Animais , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/fisiologia , Técnicas de Cocultura , Relação Dose-Resposta a Droga , Feminino , Hipocampo/patologia , Hipocampo/ultraestrutura , Masculino , Fibras Nervosas Mielinizadas/patologia , Fibras Nervosas Mielinizadas/ultraestrutura , Neurogênese/efeitos dos fármacos , Neurogênese/fisiologia , Oligodendroglia/patologia , Oligodendroglia/ultraestrutura , Gravidez , Efeitos Tardios da Exposição Pré-Natal/patologia , Ratos , Ratos Wistar
15.
Zh Nevrol Psikhiatr Im S S Korsakova ; 119(10. Vyp. 2): 28-34, 2019.
Artigo em Russo | MEDLINE | ID: mdl-31934986

RESUMO

Biogenic amines are key mediators of neuroimmune interaction and may influence on multiple sclerosis (MS) pathogenesis and MS course. At the same time, the role of biogenic amines in immunoregulation of early stages of demyelination, in particular clinically isolated syndrome (CIS) and radiologically isolated syndrome (RIS) is still unclear. This literature review addresses a role of norepinephrine in the regulation of neuroimmune interactions in the early stages of the demyelination. Neuropsychological disorders, immunological characteristics, gut-brain axis as well as the role of norepinephrine in these interactions in patients with CIS, RIS and early MS are discussed.


Assuntos
Microbioma Gastrointestinal , Esclerose Múltipla/microbiologia , Esclerose Múltipla/patologia , Fibras Nervosas Mielinizadas/patologia , Norepinefrina/metabolismo , Encéfalo/patologia , Encéfalo/fisiopatologia , Humanos , Esclerose Múltipla/imunologia , Esclerose Múltipla/metabolismo
16.
PLoS One ; 13(12): e0208985, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30540822

RESUMO

Elucidating whether there is a correlation between biomechanical functions and histomorphometric data in the rat sciatic nerve crush injury model would contribute to an accurate evaluation of the regeneration state without sacrificing animals. The gold standard for functional evaluation is the sciatic functional index (SFI) despite there being intrinsic shortcomings. Kinematic analysis is considered a reliable and sensitive approach for functional evaluation, most commonly assessed as ankle angle at various phases of a gait cycle. Studies utilizing the toe angle for functional evaluation are scarce, and changes in the toe angle following surgery remain unknown. The present study assessed correlations of ankle angle, toe angle and SFI with histomorphometric data, aiming to determine which parameters most accurately reflect changes in histomorphometric data over time. Six Lewis rats were designated as the control group. 30 animals received surgery, six of them were randomly selected on the first, second, third, fourth, and sixth week after surgery for measurements of ankle and toe angles in the "toe-off" phase, and for evaluation of SFI. Histomorphometric analysis were also performed, to determine the number of myelinated nerve fibers, diameters of myelinated nerve fibers, axon diameters, and myelin sheath thicknesses. Furthermore, we investigated changes in ankle angle, toe angle, SFI, and histomorphometric data over time, as well as correlations between ankle angle, toe angle, and SFI with histomorphometric data. The results revealed that changes in SFI, ankle angle, and toe angle highly correlate with histomorphometric data in the rat sciatic nerve crush injury model. Toe angle reflected changes in histomorphometric data with time more precisely than ankle angle or SFI did, and ankle angle was a better prognostic parameter than SFI.


Assuntos
Fenômenos Biomecânicos , Recuperação de Função Fisiológica , Nervo Isquiático/lesões , Animais , Axônios/fisiologia , Modelos Animais de Doenças , Masculino , Bainha de Mielina/patologia , Bainha de Mielina/fisiologia , Fibras Nervosas Mielinizadas/patologia , Fibras Nervosas Mielinizadas/fisiologia , Ratos , Ratos Endogâmicos Lew , Nervo Isquiático/patologia , Tarso Animal/patologia , Tarso Animal/fisiologia , Dedos do Pé/fisiologia
17.
Proc Natl Acad Sci U S A ; 115(43): E10225-E10234, 2018 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-30297414

RESUMO

Repetitive electrical activity produces microstructural alteration in myelinated axons, which may afford the opportunity to noninvasively monitor function of myelinated fibers in peripheral nervous system (PNS)/CNS pathways. Microstructural changes were assessed via two different magnetic-resonance-based approaches: diffusion fMRI and dynamic T2 spectroscopy in the ex vivo perfused bullfrog sciatic nerves. Using this robust, classical model as a platform for testing, we demonstrate that noninvasive diffusion fMRI, based on standard diffusion tensor imaging (DTI), can clearly localize the sites of axonal conduction blockage as might be encountered in neurotrauma or other lesion types. It is also shown that the diffusion fMRI response is graded in proportion to the total number of electrical impulses carried through a given locus. Dynamic T2 spectroscopy of the perfused frog nerves point to an electrical-activity-induced redistribution of tissue water and myelin structural changes. Diffusion basis spectrum imaging (DBSI) reveals a reversible shift of tissue water into a restricted isotropic diffusion signal component. Submyelinic vacuoles are observed in electron-microscopy images of tissue fixed during electrical stimulation. A slowing of the compound action potential conduction velocity accompanies repetitive electrical activity. Correlations between electrophysiology and MRI parameters during and immediately after stimulation are presented. Potential mechanisms and interpretations of these results are discussed.


Assuntos
Axônios/patologia , Bainha de Mielina/patologia , Fibras Nervosas Mielinizadas/patologia , Animais , Anuros , Mapeamento Encefálico/métodos , Difusão , Imagem de Difusão por Ressonância Magnética/métodos , Imagem de Tensor de Difusão/métodos , Processamento de Imagem Assistida por Computador/métodos , Nervo Isquiático/patologia
18.
Neuroradiology ; 60(12): 1335-1341, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30264168

RESUMO

PURPOSE: Cognitive decline in Down syndrome generally shows neurodegenerative aspects similar to what is observed in Alzheimer's disease. Few studies reported information on white matter integrity. The aim of this study was to evaluate white matter alterations in a cohort of young Down subjects, without dementia, by means of DTI technique, compared to a normal control group. METHODS: The study group consisted of 17 right-handed subjects with DS and many control subjects. All individuals participating in this study were examined by MR exam including DTI acquisition (32 non-coplanar directions); image processing and analysis were performed using FMRIB Software Library (FSL version 4.1.9, http://www.fmrib.ox.ac.uk/fsl )) software package. Finally, the diffusion tensor was estimated voxel by voxel and the FA map derived from the tensor. A two-sample t test was performed to assess differences between DS and control subjects. RESULTS: The FA is decreased in DS subjects, compared to control subjects, in the region of the anterior thalamic radiation, the inferior fronto-occipital fasciculum, the inferior longitudinal fasciculum, and the cortico-spinal tract, bilaterally. CONCLUSIONS: The early white matter damage visible in our DS subjects could have great impact in the therapeutic management, in particular in better adapting the timing of therapies to counteract the toxic effect of the deposition of amyloid that leads to oxidative stress.


Assuntos
Imagem de Tensor de Difusão/métodos , Síndrome de Down/patologia , Fibras Nervosas Mielinizadas/patologia , Substância Branca/patologia , Adolescente , Adulto , Mapeamento Encefálico , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Masculino
19.
Neuroimage Clin ; 20: 594-602, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30186763

RESUMO

Diffusion tensor imaging and its distinct capability to detect micro-structural changes in vivo allows the exploration of white matter (WM) abnormalities in patients who have been diagnosed with schizophrenia; however, the results regarding the anatomical positions and degree of abnormalities are inconsistent. In order to obtain more robust and stable findings, we conducted a multi-level analysis to investigate WM disruption in a relatively large sample size (142 schizophrenia patients and 163 healthy subjects). Specifically, we evaluated the univariate fractional anisotropy (FA) in voxel level; the bivariate pairwise structural connectivity between regions using deterministic tractography as the network node defined by the Human Brainnetome Atlas; and the multivariate network topological properties, including the network hub, efficiency, small-worldness, and strength. Our data demonstrated callosal and subcortical WM alterations in patients with schizophrenia. These disruptions were evident in both voxel and connectivity levels and further supported by associations between FA values and illness duration. Based on the findings regarding topological properties, the structural network showed weaker global integration in patients with schizophrenia than in healthy subjects, while brain network hubs showed decreased functionality. We replicated these findings using an automated anatomical labeling atlas to define the network node. Our study indicates that callosal and subcortical WM disruptions are biomarkers for chronic schizophrenia.


Assuntos
Corpo Caloso/diagnóstico por imagem , Imagem de Tensor de Difusão/métodos , Rede Nervosa/diagnóstico por imagem , Esquizofrenia/diagnóstico por imagem , Substância Branca/diagnóstico por imagem , Adulto , Corpo Caloso/metabolismo , Imagem de Tensor de Difusão/tendências , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fibras Nervosas Mielinizadas/metabolismo , Fibras Nervosas Mielinizadas/patologia , Rede Nervosa/metabolismo , Esquizofrenia/metabolismo , Substância Branca/metabolismo
20.
Neuroimage Clin ; 20: 61-70, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30094157

RESUMO

We performed a longitudinal case-control study on patients with clinically isolated syndrome (CIS) with the aid of quantitative whole-brain myelin imaging. The aim was (1) to parse early myelin decay and to break down its distribution pattern, and (2) to identify an imaging biomarker of the conversion into clinically definite Multiple Sclerosis (MS) based on in vivo measurable changes of myelination. Imaging and clinical data were collected immediately after the onset of first neurological symptoms and follow-up explorations were performed after 3, 6, and, 12 months. The multi-component Driven Equilibrium Single Pulse Observation of T1/T2 (mcDESPOT) was applied to obtain the volume fraction of myelin water (MWF) in different white matter (WM) regions at every time-point. This measure was subjected to further voxel-based analysis with the aid of a comparison of the normal distribution of myelination measures with an age and sex matched healthy control group. Both global and focal relative myelination content measures were retrieved. We found that (1) CIS patients at the first clinical episode suggestive of MS can be discriminated from healthy control WM conditions (p < 0.001) and therewith reproduced our earlier findings in late CIS, (2) that deficient myelination in the CIS group increased in T2 lesion depending on the presence of gadolinium enhancement (p < 0.05), and (3) that independently the CIS T2 lesion relative myelin content provided a risk estimate of the conversion to clinically definite MS (Odds Ratio 2.52). We initially hypothesized that normal appearing WM myelin loss may determine the severity of early disease and the subsequent risk of clinically definite MS development. However, in contrast we found that WM lesion myelin loss was pivotal for MS conversion. Regional myelination measures may thus play an important role in future clinical risk stratification.


Assuntos
Doenças Desmielinizantes/diagnóstico por imagem , Progressão da Doença , Imagem por Ressonância Magnética/tendências , Esclerose Múltipla/diagnóstico por imagem , Fibras Nervosas Mielinizadas/patologia , Adulto , Estudos de Casos e Controles , Estudos de Coortes , Doenças Desmielinizantes/fisiopatologia , Feminino , Humanos , Estudos Longitudinais , Imagem por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Esclerose Múltipla/fisiopatologia , Valor Preditivo dos Testes , Adulto Jovem
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA