We analyzed optical coherence tomographic (OCT) characteristics of different types of coronary thrombi that had been confirmed at postmortem histologic examination. We examined 108 coronary arterial segments of 40 consecutive human cadavers. OCT images of red and white thrombi were obtained and the intensity property of these thrombi was analyzed. Red and white thrombi were found in 16 (17%) and 19 (18%) of the 108 arterial segments, respectively. Red thrombi were identified as high-backscattering protrusions inside the lumen of the artery, with signal-free shadowing in the OCT image. White thrombi were identified as low-backscattering projections in the OCT image. There were no significant differences in peak intensity of OCT signal between red and white thrombi (130+/-18 vs 145+/-34, p=0.12). However, the 1/2 attenuation width of the signal intensity curve, which was defined as the distance from peak intensity to its 1/2 intensity, was significantly different between red and white thrombi (324+/-50 vs 183+/- 42 microm, p<0.0001). A cut-off value of 250 microm in the 1/2 width of signal intensity attenuation can differentiate white from red thrombi with a sensitivity of 90% and specificity of 88%. We present the first detailed description of the characteristics of different types of coronary thrombi in OCT images. Optical coherence tomography may allow us not only to estimate plaque morphology but also to distinguish red from white thrombi.

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Sphingosine 1-phosphate (Sph-1-P), the initial product of Sph degradation by Sph kinase, was shown to be a strong inhibitor of cell motility and phagokinesis of B16 melanoma and other types ofcells at 10-100 nM concentration. It also inhibited "chemoinvasion' of tumor cells through a thick layer of Matrigel on a filter membrane. Such inhibitory effects were produced minimally or not at all by Sph, N-methyl derivatives of Sph, or other related sphingolipids and phospholipids. Sph-1-P did not inhibit cell proliferation or protein kinase C (PKC) activity, in contrast to Sph and N-methyl-Sph, which inhibit PKC activity and cell growth in general. of mouse 3T3 cells through a protein kinase C (PKC)-independent pathway (5); they subsequently attributed this growth-stimulatory effect to formation of Sph-1-P (6). Sph or its catabolites may enhance cytoplasmic Ca2+ release (7); this was also attributed to Sph-1-P (6), in analogy to the effect of inositol 1,4,5-trisphosphate on Ca2+ movement (8). Although Sph-1-P was assumed to induce proliferation in 3T3 cells, particularly in synergy with epidermal growth factor and insulin (6), the physiological role of this endogenous product of Sph metabolism in cells remains unknown. We now report that Sph-1-P, either in chemically synthesized form or rapidly converted from exogenous Sph, strongly and specifically inhibits chemotactic motility and invasiveness of tumor cells at very low (nanomolar) concentration but does not affect cell proliferation or PKC activity even at much higher concentrations. These findings suggest that Sph-1-P controls motility of normal cells and invasiveness of tumor cells, without affecting cell proliferation, via changes in transmembrane signaling independent of the PKC pathway. In contrast, N-methyl derivatives of Sph are known to inhibit cell proliferation, via blocking of the PKC pathway or some unknown mechanism (9, 10).* Preparation of Sph Derivatives and Other Lipids. Sph-1-P was prepared both enzymatically and chemically. Enzymatic preparation was by hydrolysis of sphingosylphosphocholine by Streptomyces chromofuscus phospholipase D as described (11) (both reagents were obtained from Sigma).Sph-1-P was chemically synthesized [Weiss (12) succeeded in synthesizing sphinganine 1-phosphate, but failed to synthesize sphingenin 1-phosphate] from 1-0-and N-protected Sph by acylating 3-OH with pivaloyl chloride. Then 2-N-t-Boc-3-O-pivaloyl-D-erythro-Sph was prepared by selective deprotection of the primary OH group with p-toluenesulfonic acid (tosyl) chloride, followed by phosphorylation of the C1 primary OH group. Deprotection of the C3 allytic OH group and primary NH2 gave the desired Sph-1-P. The enzymatically synthesized product was a mixture of L-threo and D-erythro isomers, whereas the chemically synthesized product consisted only of D-erythro isomer, according to NMR data (27). Enzymatically and chemically synthesized Sph-1-P showed identical mass spectra and indistinguishable biological properties. In this study, therefore, we used enzy...

SummaryErythroblastic islands are anatomical units consisting of a central macrophage surrounded by erythroblasts. We studied the adhesion molecules involved in the formation of these structures. Central macrophages of erythroblastic islands isolated from the spleens of phlebotomized mice were dearly stained for vascular cell adhesion molecule 1 (VCAM-1). The surrounding erythroblasts of the erythroblastic islands strongly expressed the a4 integrin of very late activation antigen 4 (VLA-4:a4B1 integrin), the counter receptor of VCAM-1, whereas most reticulocytes and erythrocytes did not. Both monoclonal antibodies (mAbs) against oe4 integrin and VCAM-1 disrupted the erythroblastic islands cultured in the presence of erythropoietin. Moreover, adhesion of splenic erythroblasts to tumor necrosis factor a-stimulated mouse splenic endothelial cells, which showed high expression of VCAM-1 but not intercellular adhesion molecule 1, was inhibited by the anti-VCAM-1 and anti-a4 mAbs. These findings suggest that VLA-4-VCAM-1 interaction plays a crucial role in the formation of erythroblastic islands. Bone marrow resident macrophages (MCFs) establish stroma by extending long cytoplasmic processes and attaching to developing erythroid and myeloid cells (1, 2). These cells are both phenotypica[ly and functionally different from peritoneal M4's and monocytes (3, 4). In long-term bone marrow culture by which hematopoietic stem cells are maintained, immature myelomonocytic cells are attached to and proliferate on the M~s defined by the mAb F4/80 (5). The addition of erythropoietin to these cultures alternatively induces erythropoietic activity on the M~s, which form erythroblastic islands (EI) composed of central M~s and surrounding erythroblasts (Ebs) (6, 7). These lines of evidence suggest that erythropoietin-responsive erythroid precursors adhere to the M~s, where they are induced to proliferate and differentiate into erythrocytes by maintaining contact with the central M~s. To gain insight to the possible function of the M~s in erythropoiesis, we have considered it a priority to identify specific adhesion molecules involved in El formation (8).Recently, Morris et al. (9) characterized the nature of the adhesion using El isolated from fetal liver and found that the adhesion required divalent cations. Soligo et al. (10) demonstrated that a divalent cation-dependent adhesion molecule, very late activation antigen 4 (VLA-4) (a4B1) integrin, was present on Ebs, and that this molecule was localized at sites of intercellular contact between Ebs and M~s in human marrow, suggesting that VLA-4 might be involved in the adhesive interaction. The ligand of VLA-4 for cell-cell interaction is vascular cell adhesion molecule I (VCAM-1), which was first identified on TNF-ce-stimulated human umbilical endothelial cells (11,12). Using the bone marrow stromal cell culture system, VCAM-1 has been shown to be constitutively expressed in stromal cells, and to be involved in B lymphocyte-stromal cell (13) and hematopoietic stem cell-stromal cell i...