Table 4.

Microglial ultrastructure in both layers of the dorsal hippocampus CA1

Parameters		Number per cell (mean ± SEM)
		Stratum radiatum		Stratum lacunosum-moleculare
		Day 0	Day 7 p.i.	Day 0	Day 7 p.i.
Organelles of phagolysosomal pathway within microglia
Lysosomes	Immatures	0.031 ± 0.031	0.406 ± 0.126*	0.313 ± 0.123	0.306 ± 0.087
	Matures	0.094 ± 0.052	0.250 ± 0.078	0.344 ± 0.124	0.333 ± 0.089
	Total	0.125 ± 0.059	0.656 ± 0.159*	0.656 ± 0.159	0.639 ± 0.139
Endosomes	Empty	0.094 ± 0.052	0.188 ± 0.105	0.063 ± 0.043	0.222 ± 0.081
	With content	0.531 ± 0.180	0.281 ± 0.112	0.719 ± 0.175	0.472 ± 0.116
	Total	0.625 ± 0.178	0.469 ± 0.201	0.781 ± 0.189	0.694 ± 0.178
Lipidic inclusions		0.156 ± 0.079	0.250 ± 0.089	0.250 ± 0.100	0.417 ± 0.108
Altered organelles within microglia
ER/Golgi	Dilation	0.875 ± 0.059	0.781 ± 0.074	0.906 ± 0.052	0.944 ± 0.039
Mitochondria	Elongated	0.188 ± 0.095	0.438 ± 0.134	0.594 ± 0.173	0.417 ± 0.128
	Holy	0.094 ± 0.052	0.094 ± 0.069	0.094 ± 0.052	0.139 ± 0.058
	Donut-shaped	0.031 ± 0.031	0 ± 0	0.031 ± 0.031	0.055 ± 0.039
	Abnormal	0.281 ± 0.103	0.375 ± 0.117	0.688 ± 0.182	0.611 ± 0.175
	Total (normal + altered)	2.188 ± 0.319	3.531 ± 0.741	3.531 ± 0.552	3.833 ± 0.531
Contacts of microglia with microenvironment
Synaptic elements   (neurons)	Pre-synaptic	4.406 ± 0.638	3.375 ± 0.451	5.813 ± 0.595	4.944 ± 0.569
	Post-synaptic	1.875 ± 0.361	2.094 ± 0.352	3.219 ± 0.380	2.389 ± 0.439*
Myelin   (neurons)	Myelinated axons	0.344 ± 0.115	0.313 ± 0.138	0.625 ± 0.290	0.333 ± 0.098
	Degraded myelin	0.469 ± 0.149	0.969 ± 0.260	1.250 ± 0.220	0.778 ± 0.200 (P= 0.05)
Brain cells or vasculature	Neuronal cell bodies	0.189 ± 0.095	0.063 ± 0.043	0.031 ± 0.031	0.083 ± 0.047
	Astrocytic cell bodies	0.031 ± 0.031	0.031 ± 0.031	0.219 ± 0.087	0.306 ± 0.078
	Blood vessels	0.156 ± 0.065	0.094 ± 0.052	0.156 ± 0.079	0.139 ± 0.058
Myelin debris		0.500 ± 0.135	0.594 ± 0.184	0.906 ± 0.217	0.722 ± 0.181
Extracellular space		3.935 ± 0.510	2.625 ± 0.399	3.531 ± 0.557	2.750 ± 0.517
Extracellular digestion		0.438 ± 0.174	1.194 ± 0.199**	0.281 ± 0.121	0.639 ± 0.121*

ER/Golgi, endoplasmic reticulum and Golgi apparatus cisterna; p.i., post-infection; SEM, standard error of the mean

Results are the mean ± SEM of 32–33 microglia per time point (6–10 microglia per animal for a total of 4 mice per time point) in the stratum radiatum and of 32–36 microglia per time point (7–10 microglia per animal for a total of 4 mice per time point) in the stratum lacunosum-moleculare

Statistical analyses were performed using a nonparametric Mann-Whitney comparison test. Results that are statistically different compared to day 0 (noninfected mice) are presented as follows: * P < 0.05; ** P < 0.01 and are indicated in bold