15 (Table 2) (Gundersen et al., 1999). The estimation of DG microglia mean body cell volume, microglia mean body cell number, and DG volume, was assisted by Stereologer™ software (Stereology Resource Center, Chester, MD). The software was installed on a Dell Optiplex tower computer and connected to a Nikon Eclipse E600 microscope

(Nikon, Melville, NY) fitted with an X–Y–Z motorized stage controller (Prior Scientific, Rockland, MA), linear encoder microcator (z-axis gauge) (Heidenhain, Schaumburg, IL), high resolution color video camera (IMI Tech, Inc., Encinitas, CA) selleck products and .50 C-mount (Nikon, Melville, NY). DG volume was estimated at 4× (Nikon Plan 4× 0.10); PI3K inhibitor DG microglia mean cell volume and mean cell number were estimated at 60× (Nikon Plan APO 1.40 Oil). The camera image was processed with a high resolution video card and displayed on a 21 in. high resolution Dell monitor. One experimenter (C.S.) collected all of the stereological data without knowledge of the blood Pb level of each subject;

the experimenter was not blind to treatment group. An unbiased estimate of the number of microglia in the DG was obtained using the optical fractionator method (West et al., 1991) as reported previously for quantification of total number of microglia in mouse models of aging and neuropathology (Mouton et al., 2002). For each section the software randomly sampled virtual 3-D counting frames (disector) at 60× magnification with a 2 μm guard area. Using thin-focal

plane optical scanning, microglia were counted when they fell within the central depth of the counting frame and/or touched the inclusion lines. The total number of microglia was estimated with the following Thymidylate synthase formula: Nobj = ΣQ− × 1/SSF × 1/ASF × 1/TSF; where ΣQ− = sum of the objects sampled; SSF = sampling interval; ASF = total area sampled/total area on all sampled sections; and TSF = the height of the sample/total section thickness. For each frame, mean cell volume was quantified on microglia counted with the disector probe. The dentate gyrus reference volume (V(ref)) was determined at 4× magnification using the Cavalieri-point counting approach ( Gundersen and Jensen, 1987): V(ref) = ([k × t] × ∑P × [a(p)/M2]); where: k = sampling interval; t = post-processing section average thickness; and thus [k × t] = distance between planes; ∑P = sum of points counted; [a(p)/M2] = test grid area per point (μm2) divided by the magnification factor squared. Examples of microglia images are provided in Fig. 4. SAS Version 9.2 statistical software was used for all analyses. All data were entered and checked for accuracy and distribution properties prior to analysis. No extreme outliers were identified, and all data were included for analysis.