Regional differences in astrocyte activation in HIV-associated dementia

Since astrogliosis is a histological marker usually observed in HIV-associated dementia (HIV-D),we decided to investigate the potential relationship between the expression of glial fibrillary acidicprotein (GFAP) and the regional distribution of cells positive (+) for this specific marker of astrocyte activation.Histological sections of brain tissues obtained at necropsy from 5 HIV-D patients and 5 age-matched controlswithout history of neuropsychiatric illness were immunostained with peroxidase. Mean numbers of GFAP(+)astrocytes were significantly increased in entorhinal cortex, hippocampus and subcortical white matter of patients,but values in frontal cortex and basal ganglia were similar to those of controls. In contrast, surface density ofimmunoreactive GFAP was significantly increased in all tested brain areas from all patients, including unusuallyaffected regions such as entorhinal cortex and hippocampus. Therefore, such consistent finding of hypertrophicastrocytes, ranging from highest cell percentajes in subcortical white matter to lowest in basal ganglia indicatesthat quantification of surface density in GFAP (+) cells appears to be a more reliable approach to score gliosisthan the counting of their cell nuclei. Because astrocyte activation involves both protective and detrimental effectson adjacent neuronal subsets, the evidence of regional differences in this reactive potential highlights theimportance of accurately defining their contribution to the neuropathogenesis not only of HIV-D, but of a widerange of neurodegenerative disorders.

Diferencias regionales en la activación astrocitaria en demencia asociada a HIV. Siendo laastrogliosis un signo histológico habitualmente presente en demencia asociada a HIV, se investigóla eventual relación entre expresión de proteína gliofibrilar ácida (GFAP) y localización regional de células positivaspara ese marcador específico de la activación astrocitaria. Por inmunoperoxidasa, se procesaron cortes histológicosde tejidos cerebrales obtenidos por necropsia de 5 pacientes y 5 controles de edades similares pero sin antecedentesneuropsiquiátricos. Según los valores de las medias registrados por conteo de astrocitos GFAP(+) en pacientes,el número fue significativamente mayor en corteza entorrinal, hipocampo y sustancia blanca subcortical, mientrasque en corteza frontal y ganglios basales no se encontraron diferencias con controles. En cambio, la densidad desuperficie del material GFAP inmunorreactivo en pacientes estuvo significativamente aumentada en todas las áreascerebrales analizadas, incluso en regiones inusualmente afectadas, como corteza entorrinal e hipocampo. Entreesos astrocitos hipertróficos, el mayor porcentaje correspondió a sustancia blanca subcortical, y el menor a gangliosbasales. Cabe concluir que el constante hallazgo de agrandamiento astrocitario señala a la medida de la superficieinmuno-reactiva como mejor índice de activación celular que el conteo de núcleos de las células marcadas. Dadoslos reconocidos efectos de la astrogliosis sobre las subpoblaciones neuronales vecinas, la comprobadaregionalización de ese potencial reactivo destaca el interés de precisar su contribución en la neuropatogenia, tantode demencia asociada a HIV como de otras enfermedades neurodegenerativas.

Distant microglial and astroglial activation secondary to experimental spinal cord lesion

This paper analysed whether glial responses following a spinal cord lesion is restricted to a scar formation close to the wound or they might be also related to widespread paracrine trophic events in the entire cord. Spinal cord hemitransection was performed in adult rats at the thoracic level. Seven days and three months later the spinal cords were removed and submitted to immunohistochemistry of glial fibrillary acidic protein (GFAP) and OX42, markers for astrocytes and microglia, as well as of basic fibroblast growth factor (bFGF), an astroglial neurotrophic factor. Computer assisted image analysis was employed in the quantification of the immunoreactivity changes. At the lesion site an increased number of GFAP positive astrocytes and OX42 positive phagocytic cells characterized a dense scar formation by seven days, which was further augmented after three months. Morphometric analysis of the area and microdensitometric analysis of the intensity of the GFAP and OX42 immunoreactivities showed reactive astrocytes and microglia in the entire spinal cord white and gray matters 7 days and 3 months after surgery. Double immunofluorescence demonstrated increased bFGF immunostaining in reactive astrocytes. The results indicated that glial reaction close to an injury site of the spinal cord is related to wounding and repair events. Although gliosis constitutes a barrier to axonal regeneration, glial activation far from the lesion may contribute to neuronal trophism and plasticity in the lesioned spinal cord favoring neuronal maintenance and fiber outgrowth

Retinoblastoma--a histologic and immunohistologic study.

Histopathology and various immunohistochemical markers were studied in 40 cases of human retinoblastoma. In histopathology, tumour type, extent and invasion were studied. In immunohistochemistry, both glial and neural markers were used to know the histogenesis of this tumour. The glial markers, glial fibrillary acidic protein and vimentin, were detected in retinal astrocytes and Muller's cells in normal retina and perivascular glia in retinoblastoma. The neural marker, neurone-specific enolase stained neurones in outer and inner nuclear layers in normal retina, Flexner-Wintersteiner rosettes in retinoblastoma and tumour cells is differentiated retinoblastoma. Another neural marker, neurofilament triplet polypeptide stained neurones in inner nuclear layer of normal retina and Flexner-Wintersteiner rosettes in well-differentiated retinoblastoma. These results support the view that retinoblastoma has predominantly neuronal origin.