Initial brain lesion size affects the extent of subsequent pathophysiological responses.

The severity of an ischemic stroke is variable in patients, because the occlusion position on the artery and the territory of distal vessels are individual. However, the relationship between the extent of initial brain lesion and the subsequent pathophysiological responses is poorly understood. Here, we studied the effects of the initial brain lesion size on the subsequent pathophysiological responses by using a photochemically induced thrombotic brain damage (PIT-BD) model, in which the brain lesion size can be well-reproducibly controlled than that induced by a middle cerebral artery occlusion (MCA-O) model. In the PIT-BD model, a large lesion, which comprised 4.9% of the whole brain on day 3, showed a 56% reduction until day 7. However, a small lesion, which comprised 1.3% of the whole brain, showed a 30% reduction. In addition, on day 5, the activation of both microglia and astrocytes was lesser in mice with small lesions than in mice with large lesions. Furthermore, we found that, smaller lesions in mice lacking gene of urokinase-receptor (uPAR(-/-)) than wild type (uPAR(+/+)) mice on day 3 showed less reduction until day 7 in MCA-O model, whereas lesions with comparable size in uPAR(-/-) mice showed comparable reduction with uPAR(+/+) mice in PIT-BD model. Thus it was indicated that the less reduction of the lesions in uPAR(-/-) mice in the MCA-O model did not result from the deficient gene but the difference of the initial lesion size. These findings suggested that the more severe the brain damage, the stronger the subsequent pathophysiological responses.

Enhancement of fibrinolytic activity in vascular endothelial cells by heterologous expression of adenine nucleotide translocase-1.

The fibrinolytic activity of blood is regulated by expressing tissue-type plasminogen activator (t-PA) and its specific inhibitor, type-1 plasminogen activator inhibitor (PAI-1), from vascular endothelial cells. Since t-PA is a major plasminogen activator in blood, it is considered that the binding protein for t-PA, which exists on endothelial cell membrane, immobilizes t-PA on the surface of endothelial cells and enhances their antithrombotic property. Recently, we have found a new t-PA binding protein in endothelial cells. Its amino acid sequence has matched that of human adenine nucleotide translocase-1 (ANT1). The aims of this study are to confirm the binding of t-PA to ANT1, and to clarify the effect of ANT1 on fibrinolytic activity around endothelial cells. ANT1 is prepared from recombinant glutathione S-transferase (GST)-ANT1 fusion protein, and reveals t-PA binding activity in a ligand blot assay. In addition, ANT1 is exclusively expressed on endothelial cell membrane by using pDisplay vector. Interaction of t-PA with ANT1, which is expressed on the surface of endothelial cells, is confirmed by IAsys binding analysis and chromogenic assay. The heterologous expression of ANT1 on endothelial cell membrane enhances the t-PA binding ability of endothelial cells and the effect of ANT1 expression on fibrinolytic activity is demonstrated by increasing t-PA-catalyzed plasminogen activation. These results suggest that a novel t-PA-binding protein, ANT1, may concentrate t-PA on the surface of cells and enhance fibrinolytic properties around endothelial cells; therefore, ANT1 can be a powerful tool for regulating the plasminogen activation system in the vessel.

A new pollination system: brood-site pollination by flower bugs in Macaranga (Euphorbiaceae).

BACKGROUND AND AIMS: Macaranga (Euphorbiaceae) is a large genus of dioecious trees with approx. 260 species. To date, only one pollination study of the genus has reported brood-site pollination by thrips in M. hullettii. In this study, the pollination system of Macaranga tanarius is reported. METHODS: The study was conducted on Okinawa and Amami Islands, Japan. Flower visitors on M. tanarius were collected and their pollen load and behaviour on the flowers examined, as well as inflorescence structure and reward for the pollinators. KEY RESULTS: The most abundant flower visitors found on the male and female inflorescences were Orius atratus (Anthocoridae, Hemiptera), followed by Decomioides schneirlai (Miridae, Hemiptera). Pollen load on O. atratus from flowering pistillate inflorescences was detected as well as from staminate flowers. Orius atratus and D. schneirlai are likely to use the enclosed chambers formed by floral bracts as breeding sites before and during flower anthesis, and feed on nectar on the adaxial surface of flower bracts. The extrafloral nectary has a ball-shaped structure and the contained nectar is not exposed; the hemipterans pierce the ball to suck out the nectar. CONCLUSIONS: The results indicate that the plant is pollinated by flower bugs breeding on the inflorescences. This study may be the first report of pollination systems in which flower bugs are the main pollinators. Similarity of pollination systems between M. hullettii and M. tanarius indicates that the two brood-site pollination systems have the same origin. The pollinator species belongs to a predacious group, whose major prey includes thrips. The pollination system might represent a unique example of evolution from predatory flower visitors feeding on the pollinators (thrips) to the main pollinators.

Urokinase-type plasminogen activator receptor (uPAR) augments brain damage in a murine model of ischemic stroke.

Urokinase-type plasminogen activator receptor (uPAR) is a key component of the plasminogen activation system at the cell surface. Recent studies showed that uPAR is expressed in the ischemic damaged brain, suggesting its involvement in brain damage. In this study, we evaluated the role of uPAR in ischemic brain damage induced by permanent middle cerebral artery (MCA) occlusion in mice with genetic deficiency of uPAR (uPAR(-/-)) or of uPA (uPA(-/-)). Brain damage at 3 days was smaller in uPAR(-/-) mice (4.5+/-1.0mm(3)) than in littermate wild-type mice (uPAR(+/+)) (9.1+/-1.8mm(3), p<0.05), whereas it was comparable in uPA(-/-) (8.0+/-4.1mm(3)) and uPA(+/+) (6.9+/-2.6mm(3)) mice. uPAR expression was upregulated in the ipsilateral cerebral cortex within 12h, and remained elevated for up to 3 days. At 1 or 2 days after MCA occlusion, uPAR expression was selectively localized in vessels at the border of the damaged area. These findings suggest that uPAR expressed by endothelial cells augments the ischemic brain damage via a uPA-independent mechanism.