Immunochemical and morphometric features of astrocyte reactivity vs. plaque location in Alzheimer's disease

The quantitative relationship between glial fibrillary acidic protein (GFAP) hyper-reactivity and -amyloid protein (AP) deposition was investigated by double immunoperoxidase labeling of hippocampal and entorhinal cortex sections from five Alzheimer´s disease (AD) cases and five age-matched controls. AP plaques, which were absent in controls, were found in all AD samples, without significant differences in number or perimeter according to their location among the regions studied. In contrast, the mean number of GFAP (+) cells was significantly greater in the hippocampus than in the entorhinal cortex from AD cases (49 vs.39). Although at lower values (30 vs. 20), predominance of astrocyte hyperplasia in hippocampus as compared with entorhinal cortex was also found in control samples. Concomitant astrocyte hypertrophy, as defined by surface density (Sv) values of GFAP-immunoreactive material exceeding those of control means, affected a similar proportion of cells in the hippocampus (73%) and the entorhinal cortex (74%) from AD cases. Since an increased number of GFAP (+) cells in the hippocampus was not accompanied by an increased number and/or perimeter of neighbouring plaques, such differential hyper-reactivity in samples from AD patients, as well as in those with normal aging, seems to depend partially on the regional location of the involved astrocyte.

Theiler virus-GDVII strain (TMEV-GDVII) infection of cultured astrocytes. An image analysis of its effects on cell activation

Our original aim was to determine whether dBcAMP-induced activation of cultured astrocytes affected the course of subsequent viral infection. After 2 h exposure of 2-day-old first subculture of mouse astrocytes to dBcAMP 1 mM, cell monolayers grown in glass coverslips of Leighton tubes were inoculated with 10(3) PFU of Theiler virus-GDVII strain (TMEV-GDVII). At 9 days post-infection (pi), viral infectivity persisted in supernatants from dBcAMP-treated cultures, but was no longer detectable in non-stimulated controls. The relatively spared astroglial monolayer at day 1 pi, hardly affected by progressive viral cytolytic effect, was chosen for immunolabeled cell count, whether by viral antigen or GFAP. To this end, 20 fields for each coverslip were digitalized at 250x final magnification. In dBcAMP treated cultures, viral antigen(+) cells were fewer and lower in percentage versus infected cultures lacking stimulation. As regards GFAP staining, stimulation or infection per se induced a greater number and percentage of labeled astrocytes. According to morphometric characterization, such increase was due to a greater number of process-bearing astrocytes. It may be concluded that, regardless of previous dBcAMP treatment, early TMEV-GDVII infection enhanced immunocytochemical and morphological differentiation in cultured astrocytes.

Histometric demonstration of periastrocytic fibronectin loss during herpes simplex virus infection

Since Herpes simplex virus-type 1 (HSV-1) is liable to induce modifications and/or loss of immunoreactive fibronectin (FN) in cultured cells, our present goal was to determine whether such loss is attributable to FN binding impairment rather than cell detachment secondary to viral cytopathic effect. For this purpose, we resorted herein to an histometric approach for statistical evaluation of FN pattern in the course of HSV-1 infection of astroglial cell monolayers. The length of FN positive fibers was calculated by means of their tracing on a digitizer tablet; in the same field, cell nucleus count was performed. Recorded data allowed the calculation of an index as the ratio of the length of FN positive fibers over cell nucleus number. On comparing the indices between infected and control cultures, matricial FN loss was found in the former at 48 h post-inoculation, accompanied by cell fusion and retraction, though without cell detachment. A significant loss of FN was thus demonstrated as an event prior to severe cytopathic effect induced by viral infection.