Decreased fibrinolytic capacity has been sug-

SUMMARY1. Stable N-methyl-D-aspartic acid (NMDA) receptor-mediated currents in cultured mouse hippocampal neurones were evoked by 20 ms pressure pulse applications of L-aspartate, repeatedly applied at 30 or 40 s intervals, to the cell body region of the neurone. We have characterized the voltage-and use-dependent blockade of the currents by three dissociative anaesthetics: ketamine, phencyclidine (PCP) and MK-801 in mouse hippocampal neurones grown in dissociated tissue culture.2. We have used a simple model of the blockade, based on the 'guarded receptor hypothesis' to interpret our data. The model assumes that receptors are maximally activated at the peak of the response with an open probability (PO) approaching 1, that there is no desensitization and that the blocking drug only associates with, or dissociates from, receptor channels which have been activated by agonist (e.g. open channels).3. The model allows us to estimate forward and reverse rate constants for binding of the blockers to open channels from measurements of the steady-state level of blockade and the rate of change of the current amplitude per pulse during onset and offset of blockade. As predicted by the model, the estimated reverse rate was independent of blocker concentration while the forward rate increased with concentration. Changing the level of positively charged ketamine (pKa 7 5) tenfold by changing pH from 6-5 to 8-5 caused a corresponding change in the forward rate while having no effect on the reverse rate. Most of the voltage dependence of the blockade could be accounted for by reduction of the reverse rate by depolarization.4. Estimated forward rate constants for ketamine, PCP and MK-801 were similar to one another when measured under similar conditions and were 3 x 104-3 x 105 M-1 s-1. Most of the differences in potency of the three blockers could be accounted for by differences in the reverse rate constants which were approximately 0-2, 0 03 and 0 003 s-1 for ketamine, PCP and MK-801, respectively.The estimated rate constants actually are the product of the rate constants and 1/PO. I 843616-2 J. F. MAcDONALD AND OTHERS Suggestions that maximum P. is much less than 1 for NMDA channels imply that both forward and reverse rate constants of blockade may in fact be larger than we have calculated. However, their magnitudes, relative to one another, are unaffected by this consideration. 5. The reverse rate constant of blockade increased at positive potentials. This increase was prevented when the neurone was loaded with N-methyl-D-glucamine, an impermeant cation which prevented outward currents. This observation suggests that the voltage-dependent blockade by dissociative anaesthetics is in fact current dependent and reflects displacement of anaesthetic molecules, bound to the vicinity of the outer mouth of the channel, by intracellular cations that move out of the cell via the channel at positive potentials. This suggestion is supported by the observation that the voltage dependence of the blockade by the neutral PCP analogue, 1-(1-...

Expansion of atherosclerotic abdominal aortic aneurysm (AAA) has been attributed to remodeling of the extracellular matrix by active proteolysis. We used in situ hybridization to analyze the expression of fibrinolytic genes in aneurysm wall from eight AAA patients. All specimens exhibited specific areas of inflammatory infiltrates with macrophagelike cells expressing urokinase-type plasminogen activator (u-PA) and tissue-type PA (t-PA) mRNA. Type 1 PA inhibitor (PAM-) mRNA was expressed at the base of the necrotic atheroma of all specimens and also within some of the inflammatory infiltrates where it frequently colocalized in regions contining u-PA and t-PA mRNA expressing cells.However, in these areas, the cellular distribution of the transcripts for t-PA and u-PA extended far beyond the areas of PAT-i expression. These observations suggest a local ongoing proteolytic process, one which is only partially counteracted by the more restricted expression of PAT-i mRNA. An abundance of capillaries was also obvious in all inflammatory infiltrates and may reflect local angiogenesis in response to active pericellular fibrinolysis. The increased fibrinolytic capacity in AAA wall may promote angiogenesis and contribute to local proteolytic degradation of the aortic wall leading to physical weakening and active expansion of the aneurysm. (J. Clin. Invest. 1995. 96:639-645.)

There is a significant association between intrapulmonary right-to-left shunt and migraine.

Background-␤ 2 -Glycoprotein I (␤2GPI) is a major antigenic target of antiphospholipid antibodies, which possesses natural anticoagulant properties. The aim of the present study was to determine its presence and localization within human atherosclerotic plaques and to study its association with endothelial cells and monocyte macrophages in vitro. Methods and Results-Human atherosclerotic lesions were obtained after carotid endarterectomies and studied immunohistochemically with anti-␤2GPI as well as antibodies to CD4/CD8, macrophages, and adhesion molecules. In vitro, human umbilical vein endothelial cells (HUVECs) and U937 (myelomonocytic cell line) cells were investigated for their ability to associate with radiolabeled ␤2GPI. We found ␤2GPI to be abundantly expressed within the subendothelial regions and intimal-medial borders of human atherosclerotic plaques and to colocalize with CD4-positive lymphocytes. This observation was confirmed by Western blot applied on homogenates of atherosclerotic lesions with anti-␤2GPI antibodies. Both HUVECs and U937 cells bound labeled ␤2GPI, and the process was inhibited by oxidized LDL and not by native LDL. Conclusions-The abundant presence of human ␤2GPI within the lesions, its association with endothelial cells and macrophages, and its colocalization with CD4-positive lymphocytes suggests that it may serve as a target for an immune-mediated reaction that can influence lesion progression. (Circulation. 1999;99:2227-2230.)

The self-contained intravascular MRI catheter successfully identified TCFA and may prove to be an important diagnostic approach to determining the presence of lesions with increased risk of causing death or myocardial infarction.

SummaryTissue factor (TF), the principal procoagulant of human brain, resides in specific regions of the non-human primate central nervous system. Immunohistochemical studies employing murine anti-human TF monoclonal antibodies (MoAbs) detected TF antigen in the cortex, basal ganglia, cerebellum, and cervical spinal cord in three normal baboon subjects. Although significantly less prominent than human cortical gray matter, a distinct partition of TF in gray matter >white matter was noted. The gray matter predilection of TF was confirmed in primate temporal and parietal lobe cortex by both sandwich ELISA and one-stage coagulation assay. Variation in the relative quantity of TF antigen was observed by ELISA among the three subjects studied. Procoagulant activity followed the pattern of TF antigen (cortical gray matter >basal ganglia ≥cerebellum >cortical white matter), and was 96.5–98.5% inhibitable by a function inhibiting anti-human TF MoAb combination. TF antigen was associated with the microvasculature of all cerebral tissues studied, and spared capillaries most selectively in the cerebral cortex, basal ganglia, and cerebellum. These findings suggest a highly specific ordering of TF antigen and related procoagulant activity in the central nervous system of the baboon, confined primarily to gray matter parenchyma, and to the non-capillary microvasculature.

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