Entorhinal cortex lesioning promotes neurogenesis in the hippocampus of adult mice

Hippocampal neurogenesis in adult mammals is influenced by many factors. Lesioning of the entorhinal cortex is a standard model used to study injury and repair in the hippocampus. Here we use bromodeoxyuridine (BrdU) labeling combined with immunohistochemical identification using cell type specific markers to follow the fate of neural progenitors in the hippocampus following entorhinal cortex lesioning in mice. We show that unilateral entorhinal cortex lesioning does not alter the rate of neural progenitor proliferation in the ipsilateral dentate gyrus during the first 3 days after lesioning. However it enhances cell survival at 42 days post-lesioning leading to an increased number of beta-III tubulin and calbindin-immunoreactive neurons being produced. By contrast, when BrdU was administered 21 days post-lesioning, the number of surviving cells 21 days later was similar on the lesioned and non-lesioned sides. Thus, acutely entorhinal cortex lesioning promotes neurogenesis by enhancing survival of either neural progenitors or their progeny. However, this stimulus to neurogenesis is not sustained into the recovery period.     

Ischemia-related changes of adrenocorticotropic hormone immunoreactivity and its protective effect in the gerbil hippocampus after transient forebrain ischemia

In the present study, the temporal and spatial alterations of adrenocorticotropic hormone (ACTH) immunoreactivity in the gerbil hippocampus after 5 min transient forebrain ischemia were investigated as followed up 7 days after ischemic insult, and the effects of ACTH after ischemic insult were also investigated 4 days after ischemic insult. The ectopic expression of ACTH (1-24 fragments) immunoreactive neurons in the cornus ammonis 1 (CA1) region of hippocampus and hilar region of the dentate gyrus 1 day after the ischemic insult was observed. Judging from the double immunofluorescence study, these neurons contain GABA. Four days after ischemic insult, the ACTH immunoreactivity was localized in CA1 pyramidal cells and glia near the stratum pyramidale, which normally do not express ACTH. In addition, in the saline-treated groups, the percentage of the detected Cresyl Violet positive neurons was 11.2% compared with the sham-operated group 4 and 7 days after ischemic insult. In these groups, the OX-42 immunoreactive microglia were detected in the strata pyramidale, oriens and radiatum. However, in the Org2766 (analog of ACTH)-treated group, 57.8% neurons compared with the sham-operated group were stained with Cresyl Violet 4 and 7 days after ischemic insult. In these groups, the OX-42 immunoreactive microglia were significantly reduced in the stratum pyramidale. These results suggest that transient forebrain ischemia may provoke selective ectopic and enhanced expression of ACTH in the hippocampus, and further suggest that ACTH plays an important role in reducing the ischemic damage.     

NF-kappa B binding activity and cyclooxygenase-2 expression in persistent CCl(4)-treated rat liver injury

The involvement of NF-kappa B binding activity is known to be important in the mechanism of acute liver injury and in the induction of cyclooxygenase (COX-2). This study was performed to evaluate NF-kappa B binding activity and the expression of COX-2 in chronic liver injury induced by carbon tetrachloride (CCl(4)). Liver tissues from Sprague-Dawley rats were collected at 1, 3, 5, and 7th week after intraperitoneal injection of 0.1 mL of CCl(4)/100 g body weight twice a week. Reactive oxy-gen species (ROS) were measured in the postmitochondrial fraction by dichlorofluorescein formation with a fluorescent probe. An electrophoretic mobility shift assay was performed for NF-kappa B binding activity. Western blot was performed to measure the level of COX-1, COX-2, p65, p50, and I B proteins. ROS and NF-kappa B activity increased during the CCl4-induced chronic liver injury. The expression of nuclear p65 protein and p50 protein increased compared with that of the control, while the cytoplasmic I B protein decreased as the inflammation persisted. The expression of COX-2 in CCl(4)-treated rat liver increased compared with that of the control. It could be suggested that ROS produced by CCl(4) treatment increased NF-kappa B binding activity and thereby COX-2 expression, and these might be implicated in the progress of chronic liver damage.     

Postischemic alterations in ultrastructural cytochemistry of neuronal Golgi apparatus

Functional activity of the Golgi apparatus in postischemic neurons was evaluated by using thiamine pyrophosphatase (TPPase) activity as an histochemical marker for the trans cisternae. Ischemia was produced in rats by permanent occlusion of vertebral arteries and 30-minute occlusion of the carotid arteries. This insult produces irreversible ischemic injury to neurons in the striatum and CA1 zone of hippocampus but only reversible injury to neurons in the paramedian cortex and CA3 hippocampus. The number of neurons with TPPase activity in controls correlated in part with neuronal size and was found in greater than 90% of neurons in cortex and CA3 hippocampus, 70% in CA1 hippocampus, and 40% in striatum. Ischemia plus recirculation for 30 minutes resulted in a decrease in the number of neurons with TPPase activity by 50% in CA1 hippocampus and by 80% in the three other areas. Resistant neurons in cortex and CA3 hippocampus showed partial recovery of TPPase activity by 2 hours after ischemia although the number of neurons was still less than that in controls (55% and 72%, respectively; p less than 0.01). At 24 and 48 hours, TPPase activity in cortical and CA3 neurons was similar to controls. In contrast, irreversibly injured neurons in striatum and CA1 hippocampus showed a persistent loss of TPPase activity during the entire postischemic period. Furthermore, TPPase activity remained significantly decreased in CA1 hippocampus even though previous studies in our laboratory indicated partial recovery of Golgi cisternae before subsequent cell death at 48 to 72 hours. Since TPPase activity has been correlated with functional activity within the Golgi apparatus these results suggest that glycosylation of glycoproteins and glycolipids may be markedly impaired in neurons after cerebral ischemia. The persistent abnormalities in Golgi function may contribute to the development of irreversible injury by interfering with the normal maintenance of plasma membranes and axonal transport.