Yuko Yasuda

Relationship between S100β and GFAP expression in astrocytes during infarction and glial scar formation after mild transient ischemia

The expression of astrocyte marker proteins (S100beta and GFAP) during infarction and glial scar formation after transient middle cerebral artery (MCA) occlusion was examined using double immunostaining. S100beta immunoreactivity markedly decreased in the core of the injured area when observed immediately after reperfusion and did not increase again. In the periphery, however, S100beta expression increased, showing that S100beta synthesis was up-regulated. S100beta+/iNOS+ astrocytes in the periphery were observed from day 1, when small infarct areas were detectable, up to day 5, when infarct expansion had almost ended. TUNEL+ cells in the periphery were present from days 1 to 5. S100beta+/TUNEL+ cells were observed centrally and around the periphery of the injured area, predicting that cell death contributes to the increase of S100beta concentration in the injured area. Our results suggest that (1) higher concentration of S100beta in the extracellular space due to S100beta leakage from damaged astrocytes leads to up-regulation of S100beta synthesis and induction of inducible nitric oxide synthase (iNOS) synthesis in astrocytes, contributing to infarct expansion that results in DNA damage or cell death via NO and ROS production, and (2) GFAP, but not S100beta, is a main contributor to glial scar formation. On day 1 postreperfusion, the microdiascopic images of the injured areas from the unstained thick sections or the areas detected by S100beta immunoreactivity were larger than those of the infarct areas detected by hematoxylin--eosin (HE)-staining. The difference between these sizes might be useful to predict infarct expansion.

Long-lasting reactive changes observed in microglia in the striatal and substantia nigral of mice after 1 -methyl -4 -phenyl-1,2,3,6 -tetrahydropyridine

Parkinsons disease (PD) is an age-related movement disorder that progresses over a period of 10 to 20 years. The existence of microglia in a long-lasting activated state, expressing MHC II, has been thought to play an important role in the progression of PD. PD mouse models, induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), exhibit only transient PD-like movement dysfunction in contrast to MPTP-intoxicated monkeys which show progressive and permanent movement dysfunction. To understand the reasons why the progression does not occur in MPTP-treated mice, we used immunohistochemical analyses to study whether activated microglia in the striatum and/or substantia nigra persist long after MPTP treatment. Microglial changes in the striatum and substantia nigra of mice at 2 days and 6 months after MPTP treatment (four intraperitoneal injections of 20 mg/kg MPTP at two hour intervals) were examined. C57BL/6 mice (which are highly sensitive to MPTP) displayed transient movement dysfunction and highly activated microglia were observed at day two. In contrast, BALB/c mice (which are less sensitive to MPTP) exhibited no movement dysfunction and only slightly activated microglia were observed at day two. After 6 months, the microglia in the striatum and substantia nigra pars compacta of the treated C57BL/6 mice were still more hypertrophic compared with the control, although less hypertrophic than those observed at day two. In the treated BALB/c mice, the microglia were also hypertrophic compared with the control after 6 months. MHC II-positive microglia were undetectable at any time after MPTP treatment in both mice. These data show that MPTP administration results in the existence of persistent activated microglia that are not MHC II-positive, and is independent of the MPTP sensitivity of the mouse strain. These results suggest that long lasting MHC II-positive microglia might be required for PD progression. In MPTP-intoxicated mice, the absence of MHC II-positive microglia might explain why there is no progression of PD-like dysfunctional symptoms.

Acute morphological changes of palisade cells ofSaintpaulia leaves induced by a rapid temperature drop

Early changes in fine structures of intracellular organelles ofSaintpaulia leaves exhibiting chilling-induced degeneration of photosynthetic activities were investigated by electron microscopy. As early as 3 min after exposure to 10C water, thylakoid lamellae in the palisade cells showed extensive disarrangement, especially in intergrana lamellae. Simultaneously, other organelles showed drastic morphological changes, including the condensation of chromatin in the nucleus.

Degradation of photosynthetic activity of saintpaulia leaf by sudden temperature drop

Abstract On contact with 5°C water for 3 s, photosynthesis of Saintpaulia leaf stopped with concomitant drop of delayed luminescence, followed by the decrease in chlorophyll (Chl) fluorescence to the F 0 level within 20 s. In the chloroplasts isolated from chill-treated leaves, the PS I activity became hardly detectable within 3 min while the PS II activity stayed less affected for several hours after chilling. Neither the photosynthetic activity of oxygen evolution nor the variable fluorescence (F v ) was any more restored in the chill-treated leaves. Chill-induced decay in Chl fluorescence occurred in anaerobiosis, in darkness and even in the presence of DCMU. The decay was also seen with the Chl fluorescence at 77K. Disintegration of intergrana lamellae occurred within 10 s, followed by a disarrangement of the grana lamellae. These results suggest that primary event is degradation of the membrane structures leading to loss of the ΔpH and the cessation of electron flow between the two photosystems. Chill-injured leaves of this plant were found to show an abundant oxygen absorption which ceased in a few minutes after the chilling, but the decrease in Chl fluorescence in anaerobiosis indicates that the oxygen absorption is another event induced by the injured organelles other than the chloroplasts.

Temporal profile of cytokines and glial activation after transient global ischemia in rats

P3-e32 Neurosteroid synthesis and synaptocrinology in the hippocampal synapses Yasushi Hojo1,2, Shimpei Higo1,2, Toshihiro Kominami1,2, Hideo Mukai1,2, Takeshi Yamazaki3, Nobuhiro Harada4, Seijiro Honma5, Tetsuya Kimoto1,2, Suguru Kawato1,2 1 The University of Tokyo, Japan; 2 JST, BIRD, Japan; 3 Grad. Sch. of Integrated Arts and Sci., Hiroshima University, Japan; 4 Department of Biochem., Fujita Health University, Japan; 5 Teikoku Hormone Research Center, Japan