This paper investigates how openness to international goods markets affects pollution concentrations. We develop a theoretical model to divide trade's impact on pollution into scale, technique, and composition effects and then examine this theory using data on sulfur dioxide concentrations. We find international trade creates relatively small changes in pollution concentrations when it alters the composition of national output. Estimates of the trade-induced technique and scale effects imply a net reduction in pollution from these sources. Combining our estimates of all three effects yields a somewhat surprising conclusion: freer trade appears to be good for the environment.

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Summary: Microvascular integrity is lost during focal cere bral ischemia. The degradation of the basal lamina and extra cellular matrix are, in part, responsible for the loss of vascular integrity. Matrix metalloproteinases (MMPs) may play a pri mary role in basal lamina degradation. By using a sensitive modification of gelatin zymography, the authors investigated the activity of MMP-2 and MMP-9 in frozen lO-f.Lm sections of ischemic and nonischemic basal ganglia and plasma samples of 27 non-human primates after middle cerebral artery occlusion/ reperfusion (MCAO/R) for various periods. The gelatinolytic activities were compared with parallel cell dUTP incorporation in the ischemic zones of adjacent sections. In the brain, the integrated density of MMP-2 increased significantly by 1 hour 624after MCAO and was persistently elevated thereafter. Matrix metalJoproteinase-2 expression was highly correlated with the extent of neuron injury and the number of injured neurons (r = 0.9763, SE = 0.004, 2P < 0.0008). Matrix metalloproteinase-9 expression only was significantly increased in subjects with hemor rhagic transformation. In plasma, only MMP-9 increased transiently at 2 hours of MCAO. These findings highlight the early potential role of MMP-2 in the degradation of basal lamina leading to neuronal injury, and an association of MMP-9 with hemorrhagic transformation after focal cerebral ischemia. Key Words: Matrix metalloproteinase-Cerebral ischemia-Zymography-Neuron injury-Hemorrhagic trans formation-Basal lamina.

This essay reviews what we currently know about the environmental consequences of economic growth and international trade. Using a unified framework, we critically review both theory and empirical evidence on issues such as the Environmental Kuznets Curve, the pollution haven hypothesis, and the effects of environmental policy differences on trade and investment flows. We consider how this evidence can help us evaluate ongoing policy debates, and we discuss directions for further research.

Background and Purpose: Microvascular perfusion defects may accompany sustained occlusion and subsequent reperfusion of the middle cerebral artery; however, the nature of such "no-reflow" defects remains unclear.Methods: In the absence of antithrombotic pretreatment, we documented lenticulostriatal microvascular flow integrity following 3-hour middle cerebral artery occlusion and 1-hour reperfusion in a baboon occlusion/reperfusion model by two methods identifying 1) microvascular occlusion and 2) microvascular patency.Results: Microvascular "no-reflow" involved capillaries (vessels of 4.0-7.5 /un diameter) of the lenticulostriatal territory. Capillary reflow included 27-39% of all capillaries in two subjects, indicating a significant reduction of perfusion from normal (2p=0.045). In identical experimental preparations, single polymorphonuclear leukocytes completely occluded 4.7% of microvessels of capillary diameter in randomly selected fields, partially occluded 33% of postcapillary venules, and occluded 40% (four of 10) of capillaries in linear reconstruction along a 110 /*m length. Circumferential contact between polymorphonuclear leukocytes and the luminal endothelial cell membranes was documented, with an intercellular gap of, at most, 160 nm. Fibrin was found with degranulated platelets when the latter were associated with granulocytes, but not with polymorphonuclear leukocytes alone.Conclusions: The rinding of capillary-obstructing polymorphonuclear leukocytes in the microvascular bed following middle cerebral artery reperfusion in focal ischemia in this model satisfies an essential requirement for postulating their role in early microvascular injury and the "no-reflow" phenomenon. {Stroke 1991 ;22:1276-1283)

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For the last ten years environmentalists and the trade policy community have engaged in a heated debate over the environmental consequences of liberalized trade. The debate was originally fueled by negotiations over the North American Free Trade Agreement and the Uruguay round of GATT negotiations, both of which occurred at a time when concerns over global warming, species extinction and industrial pollution were rising. Recently it has been intensified by the creation of the World Trade Organization (WTO) and proposals for future rounds of trade negotiations. The debate has often been unproductive. It has been hampered by the lack of a common language and also suffered from little recourse to economic theory and empirical evidence. The purpose of this essay is set out what we currently know about the environmental consequences of economic growth and international trade. We critically review both theory and empirical work to answer three basic questions. What do we know about the relationship between international trade, economic growth and the environment? How can this evidence help us evaluate ongoing policy debates? Where do we go from here?

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