Shin-ichi Yamagami

Expression of calbindin-D28K by reactive astrocytes in gerbil hippocampus after ischaemia

Calbindin-D28K (calbindin) is a member of the superfamily of calcium-binding proteins that is implicated in the regulation of intracellular calcium. In the adult mammalian brain, calbindin was thought to be present only in neurones, where it is believed to serve a neuroprotective role. We now report the expression of calbindin after ischaemia in reactive astrocytes in the CA1 subfield of the hippocampus. Since other calcium-binding proteins, such as S-100 and calmodulin, which induce transformation or proliferation of glia, occur in astrocytes, it is conceivable that the expression of calbindin after ischaemia might be an important part of the process of gliosis.

The chronic cell death with DNA fragmentation after post-ischaemic hypothermia in the gerbil hippocampus.

Summary The long-term effects of post-ischaemic hypothermia are controversial. The purpose of this study was to examine the long-term effects of post-ischaemic hypothermia on neuronal survival in gerbils in terms of morphology and function. Hypothermia was induced at 32° C for 4 h immediately after ischaemia. Examination was performed at 1 week and at 1 month after ischaemia. Post-ischaemic hypothermia prevented CA1 neuronal damage 1 week after ischaemia. At 1 month after ischaemic insult, however, the degree of the protective effect of post-ischaemic hypothermia was reduced in the lateral and medial CA1 areas. DNA fragmentation was also observed at 1 month. The errors in the 8-arm radial maze trial were increased at 1 month. These data may indicate that cells in the CA1 area are very vulnerable to ischaemia and die after post-ischaemic hypothermia, and that their death is associated with apoptosis.

Suppression of hyperemia after brain ischemia by L-threo-3,4-dihydroxyphenylserine

ALTHOUGH several studies have shown that L-threo-3,4-dihydroxyphenylserine (DOPS) may provide a neuroprotective effect against ischemic brain damage, its protective mechanism is not fully understood. Glutamate release and hippocampal blood flow in ischemia with administration of DOPS were investigated to elucidate the neuroprotective mechanism of DOPS. Pre- (but not post-) ischemic administration of DOPS rescued 73% of hippocampal CA1 neurons (p < 0.001, compared with ischemia only) 1 week after transient global ischemia in gerbils. While glutamate release induced by ischemia was not affected, the increase of hippocampal blood flow during reperfusion was significantly suppressed by DOPS. These results demonstrate that DOPS may prevent reperfusion injury by suppression of hyperemia after ischemia, resulting in neuroprotection.

A chronological study of the expression of glial fibrillary acidic protein and calbindin-D28 k by reactive astrocytes in the electrically lesioned rat brain

Immunoreactivity of neuronal and glial marker proteins of reactive astrocytes around the electrically damaged pyramidal layer and stratum radiatum of the hippocampal CA1 region and corpus callosum was chronologically studied in electrically lesioned rat brains. A monoclonal antibody against calbindin-D28 k (CD28-Ab) and a polyclonal antibody against glial fibrillary acidic protein (GFAP-Ab) were used for immunostaining. Immunoreactivity of CD28 and GFAP in the reactive astrocytes was detected in brains 1-6 weeks post-lesion but not in non-lesioned brains. The number of immunohistochemically stained reactive astrocytes around the electrically damaged areas were counted and then compared with the number of those in the same areas of non-lesioned brains. The number of CD28- and GFAP-immunoreactive astrocytes began to increase around the lesion from 1-3 weeks following lesion in the pyramidal layer of the hippocampal CA1 region and from 1-4 weeks following lesion in the stratum radiatum of the hippocampal CA1 region and corpus callosum. These immunoreactive astrocytes could be observed for 6 weeks (the maximum survival time studies) in all areas of the lesioned brains studied. The increase in the number of reactive astrocytes might have been induced by the stimulatory effects of neurotrophic factors, or growth factors, produced around the lesioned site. The constancy in the number of reactive astrocytes after 3 and 4 weeks in the lesioned areas may have been due to the termination of the initial phase of the repair process, i.e. space-filling. Reactive astrocytes which were stained by GFAP-Ab were separated into two groups, based on the presence of CD28, i.e. CD28-positive and CD28-negative reactive astrocytes. The presence of CD28 might confer certain functions via calcium-mediated mechanisms on CD28-positive astrocytes in addition to the constructive role mediated by GFAP.