Ultrastructural Analysis of Thalamus Damages in a Mouse Model of Osmotic-Induced Demyelination.

A murine model used to investigate the osmotic demyelination syndrome (ODS) demonstrated ultrastructural damages in thalamus nuclei. Following chronic hyponatremia, significant myelinolysis was merely detected 48 h after the rapid reinstatement of normonatremia (ODS 48 h). In ODS samples, oligodendrocytes and astrocytes revealed injurious changes associated with a few cell deaths while both cell types seemed to endure a sort of survival strategy: (a) ODS 12 h oligodendrocytes displayed nucleoplasm with huge heterochromatic compaction, mitochondria hypertrophy, and most reclaimed an active NN cell aspect at ODS 48 h. (b) Astrocytes responded to the osmotic stress by overall cell shrinkage with clasmatodendrosis, these changes accompanied nucleus wrinkling, compacted and segregated nucleolus, destabilization of astrocyte-oligodendrocyte junctions, loss of typical GFAP filaments, and detection of round to oblong woolly, proteinaceous aggregates. ODS 48 h astrocytes regained an active nucleus aspect, without restituting GFAP filaments and still contained cytoplasmic proteinaceous deposits. (c) Sustaining minor shrinking defects at ODS 12 h, neurons showed slight axonal injury. At ODS 48 h, neuron cell bodies emerged again with deeply indented nucleus and, owing nucleolus translational activation, huge amounts of polysomes along with secretory-like activities. (d) In ODS, activated microglial cells got stuffed with huge lysosome bodies out of captures cell damages, leaving voids in interfascicular and sub-vascular neuropil. Following chronic hyponatremia, the murine thalamus restoration showed macroglial cells acutely turned off transcriptional and translational activities during ODS and progressively recovered activities, unless severely damaged cells underwent cell death, leading to neuropil disruption and demyelination.

[Effect of Electroacupuncture on Ultrastructure of Oligodendrocytes and Expression of the Related Marker Proteins in the Marginal Zone of Cerebral Ischemia Locus in Rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on changes of ultrastructure of oligodendrocytes in the marginal zone of the cerebral ischemia (CI) locus in rats with cerebral infarction so as to reveal its mechanism underlying improving ischemic cerebral diseases. METHODS: Ninety male SD rats were randomized into sham operation, model and electroacupuncture (EA) groups which were further divided into five subgroups: 1 h, 1 d, 3 d, 7 d, and 21 d after CI (n = 6 in each subgroup). The CI model was established by occlusion of the middle cerebral artery. EA (1 - 3 mA) was applied to "Baihui" (GV 20) and "Dazhui" (GV 14) for 30 min, once a day for 1 h, 1 d, 3 d, 7 d and 21 d, respectively. The ultrastructural changes of oligodendrocytes in the marginal zone of the ischemic cerebral tissue were observed by transmission electron microscope. The immunoactivity levels of A2B5, O4 and 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase) for labeling the oligodendrocyte precursor cells, immature oligodendrocytes, and mature oligodendrocytes respectively were detected by immunohistochemistry. RESULTS: The oligodendrocytes were swelling in structure and increased in number after cerebral ischemia. Compared with the model group, the degree of swelling of oligodendrocytes was obviously decreased and new oligodendrocyte proliferation was found in the EA group. In comparison with the sham group, the immunoactivity levels of cerebral A2B5 and CNPase proteins on day 3 and 7 were significantly higher in the model group (P<0. 05), while those of O4 on day 1, 3, 7 and 21 were obviously lower in the model group (P<0. 01). Following EA intervention, the immunoactivity levels of cerebral A2B5, O4 and CNPase proteins were significantly up-regulated in the EA group in comparison with the model group (P<0. 0 1 , P<0. 05). CONCLUSION: EA intervention may reduce the structural damage of oligodendrocytes in CI rats, which may be associated with its effects in promoting the expression of cerebral A2B5, O4 and CNPase proteins, suggesting an involvement of glial cells in the protective effect of EA.

Structural and ultrastructural analysis of cerebral cortex, cerebellum, and hypothalamus from diabetic rats.

Autonomic and peripheral neuropathies are well-described complications in diabetes. Diabetes mellitus is also associated to central nervous system damage. This little-known complication is characterized by impairment of brain functions and electrophysiological changes associated with neurochemical and structural abnormalities. The purpose of this study was to investigate brain structural and ultrastructural changes in rats with streptozotocin-induced diabetes. Cerebral cortex, hypothalamus, and cerebellum were obtained from controls and 8 weeks diabetic rats. Light and electron microscope studies showed degenerative changes of neurons and glia, perivascular and mitochondrial swelling, disarrangement of myelin sheath, increased area of myelinated axons, presynaptic vesicle dispersion in swollen axonal boutoms, fragmentation of neurofilaments, and oligodendrocyte abnormalities. In addition, depressive mood was observed in diabetic animals. The brain morphological alterations observed in diabetic animals could be related to brain pathologic process leading to abnormal function, cellular death, and depressive behavioral.

Ultrastructural study of the effects of cyclosporine in the brainstem of Wistar rats submitted to the ethidium bromide demyelinating model.

The ethidium bromide-demyelinating model (EB) was used to study remyelination in the brainstem under the use of cyclosporine (CsA). Wistar rats were submitted to intracisternal injection of 0.1% EB or 0.9% saline solution, and others were taken as histologic controls (group I). Within those injected with EB, some have not received immunosuppressive treatment (II); some were treated by intraperitonial route with CsA (III.E-10 mg/kg/day). Rats from group III.C were injected with saline solution and treated with CsA. The animals were perfused from 15 to 31 days post-injection collecting brainstem sections for light and transmission electron microscopy studies. After EB injection it was noted the presence of macrophages and non-degraded myelin debris, demyelinated axons, oligodendrocyte or Schwann cell remyelinated axons, groups of infiltrating pial cells, hypertrophic astrocytes and few lymphocytes. Tissue repair of EB-induced lesions in group III.E was similar to that of group II, but with the presence of a higher density of oligodendrocytes near remyelinating areas.

Ultrastructural study of the effects of cyclosporine in the brainstem of Wistar rats submitted to the ethidium bromide demyelinating model / Estudo ultra-estrutural dos efeitos da ciclosporina no tronco encefálico de ratos Wistar submetidos ao modelo desmielinizante do brometo de etídio

The ethidium bromide-demyelinating model (EB) was used to study remyelination in the brainstem under the use of cyclosporine (CsA). Wistar rats were submitted to intracisternal injection of 0.1 percent EB or 0.9 percent saline solution, and others were taken as histologic controls (group I). Within those injected with EB, some have not received immunosuppressive treatment (II); some were treated by intraperitonial route with CsA (III.E - 10 mg/kg/day). Rats from group III.C were injected with saline solution and treated with CsA. The animals were perfused from 15 to 31 days post-injection collecting brainstem sections for light and transmission electron microscopy studies. After EB injection it was noted the presence of macrophages and non-degraded myelin debris, demyelinated axons, oligodendrocyte or Schwann cell remyelinated axons, groups of infiltrating pial cells, hypertrophic astrocytes and few lymphocytes. Tissue repair of EB-induced lesions in group III.E was similar to that of group II, but with the presence of a higher density of oligodendrocytes near remyelinating areas.

Empregou-se o modelo desmielinizante do brometo de etídio (BE) com o objetivo de estudar a remielinização no tronco encefálico frente ao uso de ciclosporina (CsA). Foram utilizados ratos Wistar, submetidos à injeção de BE a 0,1 por cento ou de solução salina na cisterna pontina, assim como controles histológicos (grupo I). Dos animais injetados com BE, alguns não receberam tratamento imunossupressor (II); outros foram tratados por via intraperitoneal com CsA (III.E - 10 mg/kg/dia). O grupo III.C incluiu animais injetados com salina e tratados com CsA. Os animais foram perfundidos dos 15 aos 31 dias pós-injeção, com colheita de material do tronco encefálico para estudos de microscopia de luz e eletrônica de transmissão. Após injeção de BE, foram observados macrófagos e restos de mielina não-degradada, axônios desmielinizados ou remielinizados por oligodendrócitos e por células de Schwann, grupos de células piais infiltrantes, astrócitos hipertróficos e poucos linfócitos. O processo de reparo das lesões no grupo III.E apresentou-se similar ao do grupo II, porém com maior densidade de oligodendrócitos próximos às áreas de remielinização.

Acute moderate hyponatraemia and its rapid correction: effects on striatal and pontine ultrastructure in an animal model of the TURP syndrome.

BACKGROUND AND OBJECTIVE: To investigate the effects of moderate hyponatraemia, induced by intravenous application of an electrolyte-free irrigation fluid, as a model of the human transurethral prostate resection syndrome and of its rapid correction by hypertonic saline infusion in rats. METHODS: Experimental animals received irrigation fluid (Purisole SM) 20 mL kg(-1) body weight, intravenously. In one group, hyponatraemia was subsequently rapidly corrected by infusion of hypertonic saline (NaCl 5.85%), while rats of group two were 'sham-corrected' by infusion of a balanced salt crystalloid solution. Plasma sodium concentrations were analysed during and at the end of the experiments. After 10 days, experimental and untreated control animals were killed humanely, fixed by perfusion and the brains were prepared for electron microscopic investigation of myelin sheets and glial cell numbers in the striatum and pons. RESULTS: The myelin appearance was unaltered in experimental groups compared to controls, but glial cell numbers were distinctly altered in the pons but not in the striatum. In the pons, oligodendrocytes were significantly reduced in number upon rapid correction of hyponatraemia, while astrocyte numbers were increased in rats with uncorrected hyponatraemia. CONCLUSIONS: Our electron microscopic data demonstrate that the effects of hyponatraemia and of its rapid correction are multifarious in animals. This may also apply for human patients during transurethral prostate resection.

The human NTERA2 neural cell line generates neurons on growth under neural stem cell conditions and exhibits characteristics of radial glial cells.

NTERA2 cells are a human neural cell line generating neurons after exposure to retinoic acid and, as such, are widely used as a model of neurogenesis. We report that these cells form spheres when grown in serum-free medium supplemented with basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). These spheres were found to express markers of radial glial cells such as, Pax6, glutamate transporter (GLAST), tenascin C, brain lipid-binding protein (BLBP), and the 3CB2 antigen. On plating on an adhesive substrate, NTERA2 spheres generate a large percentage of immature neurons (30-50%) together with a minority of cells of the oligodendrocyte lineage. Thus NTERA2 cells share properties with neural stem cells. However, at variance with the latter, we found that they produce their own bFGF implicated in an autocrine or paracrine proliferative loop and that they do not generate astrocytes after differentiation. These results provide an interesting model to study radial glial cells and their role in human neurogenesis.

Distribution of various types of oligodendrocytes and cellular localisation of iron in the frontal cortex of the adult rat.

Oligodendrocytes, called oligodendroglia, are present in the white and grey substance of the CNS. They constitute a heterogeneous group, in which 3 types of these cells have been distinguished: those of light, medium and dark cytoplasm. They locate themselves at the neurones and blood vessels. The number of light oligodendrocytes decrease with age, while the number of dark oligodendrocytes increase. In histochemical studies the product of the reaction located itself in the body and processes, indicating the participation of these cells in the metabolism of iron.

Eliprodil stimulates CNS myelination: new prospects for multiple sclerosis?

OBJECTIVE: To examine the potential of eliprodil-a neuroprotective agent with a high affinity for sigma-receptors-to promote myelination in neuron-oligodendrocytes cocultures. BACKGROUND: Remyelination is one of the major therapeutic issues in MS. Because neuronal integrity is required for CNS myelination, the authors postulated that neuroprotective molecules might favor myelination. METHODS: Two experimental culture conditions were compared: standard medium Bottenstein and Sato ([B-S] medium) and a medium depleted of both thyroid hormones and progesterone (depleted [D] medium). Myelination was quantified by counting the number of myelinated internodes, identified immunocytochemically with an antimyelin basic protein (anti-MBP) antibody. RESULTS: The authors first confirmed that in D medium myelination was reduced by a factor of 3.5 compared with cultures maintained in B-S medium. Under both culture conditions, addition of 10(-6) M eliprodil did not modify significantly the total number of either microtubule associated protein-2-positive neurons or MBP-positive oligodendrocytes. However, eliprodil induced a twofold (p < 0.01) increase in myelination when added to B-S medium, and a 4.7-fold (p < 0.0001) increase when added to D medium. CONCLUSION: Although the molecular mechanism mediating the effect of the sigma-receptor agonist on myelination remains to be elucidated, these results strongly suggest that neuroprotective molecules may be of therapeutic interest in demyelinating diseases such as MS.

Familial dysmyelination in a Long Evans rat mutant.

Tremors were observed in 15 Long Evans rats beginning at 10 to 12 days of age. These were followed by progressively worsening ataxia, hind limb paresis, episodes of immobility, and seizures by 5 to 14 weeks. Gross lesions were not observed at necropsy in rats euthanized and perfused at 4 to 16 weeks of age. Neurohistologic examination revealed dysmyelination in the central nervous system. Astrogliosis in the white matter with marked increase of expression of the glial fibrillary acid protein marker was accompanied by diffuse microgliosis. Scattered glial cells, interpreted to be oligodendrocytes, contained minute periodic acid-Schiff-positive cytoplasmic granules. Large mineralized periodic acid-Schiff-positive and laminated structures were observed in the cerebellar white matter, midbrain, and thalamus of rats over 6 weeks old. Neuronal degeneration and loss was evident in the cortex, hippocampus, and midbrain. Large axonal spheroids were found in the ventral and lateral funiculi of the spinal cord. An ultrastructural study of four affected rats revealed an almost complete absence of myelinated axons and normal sheaths, and degeneration and necrosis of oligodendrocytes. The Long Evans shaker rat represents a novel myelin mutant with a remarkable survival period and appears to have an autosomal recessive mode of inheritance.

[Effect of supplementation of culture media with polyunsaturated fatty acids on the morphology and composition of cell cultures of fetal mouse brain]. / Influence de la supplémentation en acides gras polyinsaturés de milieux de culture sur la morphologie et la composition des cultures de cellules foetales de cerveau de souris.

Dissociated cell cultures were grown from fetal Mouse Cerebral hemisphere taken on the 16th day of gestation. Cells grown in chemically defined medium (MCD) for 8 days contain half the polyunsaturated fatty acids (PUFA) (in %) found at day 0. Cells contain n-9 trienes demonstrating that they are grown under conditions of essential fatty acid deficiency. The reduced amount of PUFA in MCD cells is balanced by an increase in monounsaturated fatty acids. The satured fatty acids are not affected. The PUFA present in the starting cells are partly preserved and reutilized (70%). Adding fatty acids of the n-6 series increases the content of n-6 fatty acids in the cells, but also provokes an increase in the n-3 fatty acids. Among several combinations of fatty acids, only the mixture of 20:4 and 22:6, added to the culture restores a fatty acid profile similar to controls (i.e. in vivo tissue taken at post-natal day 5). The concentrations were respectively 1 microgram 20:4/25 micrograms albumin/ml and 0,5 microgram/12,5 micrograms albumin/ml. Adding PUFA stimulates the proliferation of small dense cells by more than 200% of the control, as quantified by autoradiography of 3H-thymidine. These cells are not neurons, but possibly oligodendrocytes.

Fine needle aspiration biopsy of deep cerebrum. A comparison of normal and neoplastic morphology.

Fine needle aspirates of deep white matter, basal ganglia and thalamus from necropsies of three neurologically normal men were compared with two aspirates of cerebral infarcts and with eight aspirates from neoplasms that occurred in the deep cerebrum. Normal white matter contained oligodendroglia with small, dark, round nuclei and astrocytes with larger, bland, oval nuclei and occasional cytoplasmic extensions. Basal ganglia and thalamus contained, in addition, numerous neurons with large nuclei and prominent nucleoli. Recognition of these normal components of the deep cerebral structures is necessary to avoid erroneous diagnoses of neoplasia.

Edematous necrosis in thiamine-deficient encephalopathy of the mouse.

Acute encephalopathy was produced in the adult male Swiss mouse by pyrithiamine injection in conjunction with a thiamine-deficient diet. The condition of some mice was reversed within 24 hours by a treatment of a high dose of thiamine. The lesions occurred selectively in the thalamus, pontine tegmentum, and mammillary body and were manifested by hemorrhage and edematous necrosis consisting of severe edema of astrocytes, myelin sheaths, and neuronal dendrites. Before thiamine treatment, these degenerative changes were not associated with any mesenchymal reaction. At 48 and 96 hours after thiamine treatment, these edematous changes persisted. Fat-laden macrophages appeared in the lesion. Some axons showed Wallerian-type degeneration. After three weeks of thiamine treatment, macrophages became thin and rod-shaped. Wallerian-type degeneration and myelin edema persisted. The oligodendrocytes and astrocytes were hypertrophic. These lesions of thiamine-treated encephalopathy of the mouse closely resembled the non-hemorrhagic lesions of human Wernicke encephalopathy. Mice which were concomitantly-induced with hyperglycemia and encephalopathy showed no significant differences in clinical and morphologic manifestations from the encephalopathic mice with normal blood sugar levels. Vascular permeability to horseradish peroxidase was increased only slightly at the initial stage, but was reversed in the mice which clinically responded quickly to thiamine treatment. Occasionally, persistent increase of permeability was seen in 21-day-old lesions. These findings suggested that, in thiamine-deficient encephalopathy, both nervous and vascular components in the brain were involved and that the morphologic manifestations of the nervous component were far more extensive than those of the blood vessels.

The presence and possible significance of agranular reticulum in paranodal oligodendrocyte cytoplasm and in periglomerular astrocyte processes.

Paranodal glial loops (lateral belt cytoplasm) of myelinated CNS and PNS fibres contain tubules of agranular reticulum, as well as microtubules, wound spirally around the axon. Similar agranular elements run circumferentially in the expanded rims of sheet-like astrocytic processes encapsulating thalamic synaptic glomeruli. A role for agranular reticulum in these sites in control of the ionic composition of adjacent cellular and extracellular compartments is suggested.

Specialized contacts of astrocytes with astrocytes and with other cell types in the hypothalamus of the hamster.

Adult hamsters were used for this electron microscopic study of the hypothalamic region. Specialized contacts between astrocytes and astrocytes, and between astrocytes and other cellular elements, are described and illustrated. The specialized inter-astrocytic junctions occur primarily in perivascular and subpial regions, but also in areas of high synaptic density. The junctions between astrocytic processes are of hemidesmosomal type. Astrocytes are connected to oligodendroglial cells by means of desmosomes, and to neuronal processes by means of zonulae occludens. The functional significance of these arrangements is discussed.

Complex oligodendroglial invaginations within myelinated nerve fibers of the central nervous system during axonal degeneration.

Ultrastructural studies of spinal cord in rats subjected to hyperbaric oxygen exposure and experimental spinal cord trauma have resulted in frequent degeneration of axons. In both experimental situations central nervous system myelinated fibers containing complex cytoplasmic interdigitations of electron lucent, normal appearing cytoplasm, and dense cytoplasm, interpreted as degenerative, were observed. In some of the complex profiles the electron lucent cytoplasm could be traced back to the inner mesaxon, where its relation to the latter indicated a glial origin. Cytochemical evaluation of acid phosphatase activity in the complex cytoplasmic interdigitations revealed that both components contain significant lysosomal activity. The complex structures are interpreted as being sequestrations of degenerating axoplasm by distal adaxonal oligodendroglial processes, possibly representing an unusual form of heterophagocytosis.