We have studied a murine tumor previously classified as a poorly differentiated chondrosarcoma. Although the cells in this tumor are surrounded by large quantities of extracellular matrix material, the matrix fails to react with stains specific for the sulfated glycosaminoglycans present in normal cartilage. Here we show at the ultrastructural level that the tumor matrix is a homogeneous, nonfibrillar material, resembling basement membrane. Neither the proteoglycan matrix granules nor collagen fibrils characteristic of cartilage are present in the tumor matrix. Amino acid analyses of whole tumor tissue, enzyme-solubilized tumor components, and the protein extracted from lathyritic tumors confirmed that the tumor matrix is a basement membrane collagen. The collagenous protein extracted from the tumor by nonenzymatic means contains three unique polypeptides larger than the alpha-chain components of the other types of collagen. These studies indicate that the tumor is not a type of chondrosarcoma but a basement membrane producing tumor.

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Sonic hedgehog (Shh) is expressed in the ectoderm of the forming hair follicle and feather bud during normal development. However, inappropriate activation of the Shh signal transduction cascade in human epidermis can cause basal cell carcinoma. Here we show that during normal development of avian skin, Shh is first expressed only after the responsiveness to this protein has been suppressed in most of the surrounding ectodermal cells. Forced expression of Shh in avian skin prior to this time causes a disorganized ectodermal proliferation. However, as skin begins to differentiate, the forced expression of Shh causes feather bud formation. Subsequently, expression of Shh in interfollicular epidermis has little or no morphological effect. Restricted responsiveness to Shh in developing skin has functional consequences for morphogenesis and may have important implications for cutaneous pathologies as well.

Hyaluronate degradation was examined in cultures of vascular wall cells (bovine aortic endothelial cells, rat aortic smooth muscle cells) and in nonvascular cells (chick embryo fibroblasts). The three cell types examined all produced hyaluronidase activity in culture which had a strict acidic pH requirement for activity. This suggested that the enzyme was active only within an acidic intracellular compartment and therefore that hyaluronate degradation occurred at an intracellular site. This was supported by the observation that the presence of hyaluronidase activity alone was not sufficient to ensure degradation of extracellular hyaluronate. Rather, the key limiting factor in this process appeared to be hyaluronate internalization, and this was found to be hyaluronate size-dependent and to a degree, cell-specific. The relationship of these results to morphogenesis and tissue remodeling is discussed.

The VSD makes it possible to approximate, in vitro, those forces encountered by vascular wall cells, in vivo and therefore may make it possible to determine whether specific combinations of mechanical and hemodynamic forces are causally associated with specific vascular diseases.

These data support the hypothesis of a fibrinolytic shift after altered ambient O2 tensions exposure in endothelium and demonstrate that HSVEC are more sensitive to altered O2 tension than HUVEC. Altered O2 tensions depress EC fibrinolysis in this model.

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Abstract-Monolayers of human umbilical vein endothelial cells were activated with 50 U/mL interleukin-1␣ (IL-1␣) for 3 hours and simultaneously conditioned with shear stresses of 0, 0.68, or 13.2 dyne/cm 2 in a parallel-plate flow chamber. In the presence of an inflow buffer containing 100 nmol/L factor X and 10 nmol/L factor VII, production of factor Xa, a measure of functional tissue factor (TF), was determined as the product of outflow concentration of factor Xa (chromogenic assay performed under quasi-static flow conditions after the shear period) and flow rate. Similarly, production of TF pathway inhibitor (TFPI) was estimated as the product of antigenic TFPI (by enzyme-linked immunosorbent assay) in the supernatant and flow rate. In parallel experiments, total RNA was isolated for determination of amplification products of TF mRNA by reverse transcription-polymerase chain reaction. We found that shear stress reduced factor Xa production (meanϮSE; nϭnumber of experiments) from 13.33Ϯ1.14 (nϭ16) fmol/minϫcm 2 at 0 shear stress to 5.70Ϯ2.51 (nϭ5) and 0.54Ϯ0.54 (nϭ4) fmol/minϫcm 2 at shear stresses of 0.68 and 13.2 dyne/cm 2 , respectively. At the same time, immunogold labeling showed that TF antigen on the endothelial surface increased Ͼ5-fold with shear stress, whereas TFPI antigen on the surface increased 2-fold. The secretion of TFPI (appearance of new supernatant TFPI) rose from 7.4Ϯ2.4 (nϭ12) ϫ10 Ϫ3 fmol/minϫcm 2 at 0 shear stress to 23.7Ϯ7.3 (nϭ9) and 50.2Ϯ14.3 (nϭ4) ϫ10 Ϫ3 fmol/minϫcm 2 at 0.68 and 13.2 dyne/cm 2 , respectively. TF mRNA amplification products were not markedly changed by shear stress. We conclude that acute application of shear stress reduces functional, but not antigenic, expression of TF by intact, activated endothelial cell monolayers in a manner associated with shear stress-augmented endothelial cell secretion of TFPI. Key Words: tissue factor Ⅲ endothelial cells Ⅲ shear stress Ⅲ tissue factor pathway inhibitor T issue factor (TF) is the membrane-bound glycoprotein that serves as the nonenzymatic cofactor for factor VII/VIIa in the initiation of blood coagulation, whereas TF pathway inhibitor (TFPI), its principal inhibitor, binds to both activated factor X and the ternary complex formed by TF, factor VIIa, and factor Xa. Both TF and TFPI are synthesized by endothelial cells (ECs), the former usually only after cell activation. 1 With regard to increasing shear stress, functional TF has been shown to increase over a wide range of shear stress for a noncellular system of lipid bilayers, to which has been added exogenous TF that has been immobilized on the inner surface of a glass tube. 2 A similar increase has been demonstrated for monolayers of human fibroblasts, 3 which express TF in the absence of cytokine activation. With respect to monolayers of activated human ECs, however, the dependence on shear stress is more complex, passing through a maximum with respect to shear stress under 1 set of conditions 3 or decreasing monotonically with shear stress under another. 4 Prior work h...