Cerebellar edema. A metabolic and cellstatistical analysis

SUR1-TRPM4 and AQP4 form a heteromultimeric complex that amplifies ion/water osmotic coupling and drives astrocyte swelling

Astrocyte swelling occurs after central nervous system injury and contributes to brain swelling, which can increase mortality. Mechanisms proffered to explain astrocyte swelling emphasize the importance of either aquaporin-4 (AQP4), an astrocyte water channel, or of Na⁺ -permeable channels, which mediate cellular osmolyte influx. However, the spatio-temporal functional interactions between AQP4 and Na⁺ -permeable channels that drive swelling are poorly understood. We hypothesized that astrocyte swelling after injury is linked to an interaction between AQP4 and Na⁺ -permeable channels that are newly upregulated. Here, using co-immunoprecipitation and Förster resonance energy transfer, we report that AQP4 physically co-assembles with the sulfonylurea receptor 1-transient receptor potential melastatin 4 (SUR1-TRPM4) monovalent cation channel to form a novel heteromultimeric water/ion channel complex. In vitro cell-swelling studies using calcein fluorescence imaging of COS-7 cells expressing various combinations of AQP4, SUR1, and TRPM4 showed that the full tripartite complex, comprised of SUR1-TRPM4-AQP4, was required for fast, high-capacity transmembrane water transport that drives cell swelling, with these findings corroborated in cultured primary astrocytes. In a murine model of brain edema involving cold-injury to the cerebellum, we found that astrocytes newly upregulate SUR1-TRPM4, that AQP4 co-associates with SUR1-TRPM4, and that genetic inactivation of the solute pore of the SUR1-TRPM4-AQP4 complex blocked in vivo astrocyte swelling measured by diolistic labeling, thereby corroborating our in vitro functional studies. Together, these findings demonstrate a novel molecular mechanism involving the SUR1-TRPM4-AQP4 complex to account for bulk water influx during astrocyte swelling. These findings have broad implications for the understanding and treatment of AQP4-mediated pathological conditions.

The contribution of Wernicke's encephalopathy to alcohol-related cerebellar damage

Mid-sagittal histological sections of the cerebellar vermis were prepared for light microscopy from six patients with Wernicke's encephalopathy, 13 alcoholics and 16 normal controls. From Nissl stained sections, the Wernicke's encephalopathy group was found to have a significant 29% lower Purkinje cell count relative to controls, while the alcoholic group had a non-significant 10% lower cell count. The degree of shrinkage of the molecular layer paralleled the degree of Purkinje cell loss. Damage to the medullary layer in the form of shrinkage in Nissl sections and torpedo formation in silver sections did not correlate as well with Purkinje cell loss. Thiamine deficiency would seem to be a significant contributing factor to the neuropathology of cerebellar damage seen in alcoholism. The presence or absence of cirrhosis of the liver was also found to influence the degree of Purkinje cell loss.

Focal appearance of cerebellar torpedoes associated with discrete lesions in the cerebellar white matter

Cerebellar torpedoes, unique fusiform swellings of Purkinje cell axons within the granular layer, have been known to occur sparsely associated with diffuse cerebellar changes. This report describes, in three human autopsy cases with focal necrotic lesions in the cerebellar white matter, torpedoes which were essentially confined to the cerebellar cortex overlying the lesions. Purkinje cells in the same region showed no recognizable change, but were obviously decreased in number. The location of the necrotic lesions was such that they may well have severed Purkinje cell axons projecting into the deeply located cerebellar nuclei from the torpedo-carrying cortex. These findings indicate that damage to Purkinje cell axons, even if it occurs far away from the cell bodies, may have a critical influence upon the metabolism of Purkinje cells and play an important role in the formation of torpedoes.

A quantitative study of the composition of cerebellar cortical dysplasias

The areas of molecular and granular layers in four large cerebellar cortical dysplasias were measured with the planimeter and the Purkinje cells were counted. There was a relative deficit of molecular layer and a still greater deficit of Purkinje cells in three of the four dysplasias. The fourth one had normal numbers of Purkinje cells per molecular layer and a relative deficit of granular layer. These abnormal proportions in the composition of a dysplasia may relate to the timing of its origin.

Non-neoplastic expanding lesions of the vermis cerebelli

✓ This report describes the clinical, roentgenological, and histopathological findings in 13 patients in whom the preoperative roentgen diagnosis was tumor of the vermis cerebelli but in whom no neoplasm was found at operation nor suggested by postoperative course. There was a striking clinical conformity; the majority of the patients were between 50 and 70 years of age, had a history of rheumatoid arthritis and/or cardiovascular disease, and a histological picture characterized by small cavernous-capillary hemangiomas and spongiosis indicating perifocal edema. The pathogenesis and clinical significance of the lesions are discussed.

AN ATAXIC FORM OF SUBACUTE PRESENILE POLIOENCEPHALOPATHY (CREUTZFELDT-JAKOB DISEASE)

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