Cultured bovine capillary endothelial (BCE) cells produce low levels of collagenolytic activity and significant amounts of the serine protease plasminogen activator (PA). When grown in the presence of nanomolar quantities of the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA), BCE cells produced 5-15 times more collagenolytic activity and 2-10 times more PA than untreated cells. The enhanced production of these enzymes was dependent on the dose of TPA used, with maximal response at 10 -~ to 10 -8 M. Phorbol didecanoate (PDD), an analog of TPA which is an active tumor promoter, also increased protease production. 4-O-methyI-TPA and 4c~-PDD, two analogs of TPA which are inactive as tumor promoters, had no effect on protease production. Increased PA and collagenase activities were detected within 7.5 and 19 h, respectively, after the addition of TPA. The TPA-stimulated BCE cells synthesized a urokinase-type PA and a typical vertebrate collagenase.BCE cells were compared with bovine aortic endothelial (BAE) cells and bovine embryonic skin (BES) fibroblasts with respect to their production of protease in response to TPA. Under normal growth conditions, low levels of collagenolytic activity were detected in the culture fluids from BCE, BAE, and BES cells. BCE cells produced 5-13 times the basal levels of collagenolytic activity in response to TPA, whereas BAE cells and BES fibroblasts showed a minimal response to TPA. Both BCE and BAE cells exhibited relatively high basal levels of PA, the production of which was stimulated approximately threefold by the addition of TPA. The observation that BCE cells and not BAE cells produced high levels of both PA and collagenase activities in response to TPA demonstrates a significant difference between these two types of endothelial cells and suggests that the enhanced detectable activities are a property unique to bovine capillary and microvessel endothelial cells.Capillary proliferation in vivo is marked by fragmentation of the capillary basal lamina and subsequent migration and proliferation of distinct endothelial cell populations in response to stimuli (2). New blood vessel formation, or angiogenesis, can be studied in a number of systems (9, 10), and is promoted by angiogenic factors derived from both normal tissues (4, 11), and tumors (2, 9). Since the formation of capillaries is marked by both the destruction of the basal lamina and the invasion of cells through interstitial tissue, capillary formation may require the elaboration of proteases to degrade the proteins of the basal lamina and interstitial stroma. Therefore, we have proposed (20) that angiogenesis requires the secretion of proteases and have initiated experiments to characterize the pro-974 teases produced by endothelial cells in response to various stimuli.Previous work has shown that endothelial ceils derived from large vessels of several tissues and species synthesize at least two extracellular proteases: the serine protease plasminogen activator (PA) and vertebrate interstitial collage...

Human A431 epidermoid carcinoma cells in culture exhibit epidermal growth factor (EGF)-induced "down-regulation" of cell-surface and total cellular (Triton X-100 extractable) EGF receptors caused entirely by an enhanced rate (4-fold) of receptor inactivation [Krupp, M. N., Connolly, D. T. & Lane, M. D. (1982) J. Biol. Chem. 257, 11489-11496]. The following observations show that this enhanced rate of EGF receptor inactivation is closely correlated with an increased cellular activity of plasminogen activator (PA), a serine protease. First, EGF-induced down-regulation of cell-surface and total cellular EGF receptors and the concomitant increase in cellular PA activity occur with identical kinetics, the tl/2 for both processes being 3-3.5 hr.Second, the EGF dose-response curves for down-regulation of total cellular EGF receptor and increased PA activity are similar. The EGF concentrations for half-maximal responses of both processes are 10-15 nM and 20 nM, respectively. Third, the removal of EGF from previously down-regulated cells results in the recovery of total cellular EGF binding activity with a concurrent loss of cellular PA activity. Fourth, blocking PA synthesis or activity with cycloheximide or dexamethasone prevents down-regulation of the EGF receptor. Fifth, the addition of leupeptin, an inhibitor of PA and plasmin action, blocks EGF-induced receptor downregulation as well as the increase of PA activity. That EGF receptor down-regulation is independent of plasminogen per se in the culture medium suggests that PA-mediated events may initiate the rapid inactivation of the EGF receptor that occurs during downregulation.The interaction of epidermal growth factor (EGF), a polypeptide hormone, with specific cell-surface receptors initiates numerous biochemical events (1) in target cells, most notably mitogenesis (2). Such factors as the period of exposure to EGF, the concentration of EGF, and the level of functional receptors at the plasma membrane affect the magnitude of ligand-receptor interactions and, thus, the cellular response to EGF (3-5). It has been established that cells can modulate their level of surface EGF receptors in response to EGF and thereby alter the biological response to this potent mitogen (3-5).Like other receptors for polypeptide hormones (6), the EGF receptor exhibits ligand-induced "down-regulation" of cell-surface EGF binding capacity (3-5). This negative modulation of EGF receptor level in vitro is rapid, EGF concentration dependent, and EGF specific and occurs in many cell types (1, 3, 5). Reduced EGF binding capacity is the result of a lowered EGF receptor level rather than an altered affinity of the EGF receptor for its ligand (3,5 Although the mechanism by which ligand-induced downregulation promotes EGF receptor inactivation is unknown, there is some evidence with another cell-surface receptor that proteolysis modulates receptor metabolism. When proteolysis in chicken myogenic cultures is induced by chemical or viral transformation, both the steady-state concentratio...

compared with sitagliptin for patients with type 2 diabetes who do not have adequate glycemic control with metformin plus sulfonylurea: a 52-week randomized trial. Diabetes Care 2013;36:2508-2515 In the print version of the article listed above, the fasting plasma glucose (FPG) data in conventional units (mg/dL) are not correct in Fig. 2C. The FPG data in SI units are correct; therefore, the conclusions do not change. The corrected Fig. 2C appears below. The online version reflects these changes. 4172DIABETES CARE, VOLUME 36, DECEMBER 2013 care.diabetesjournals.org

Red blood cells (RBC) of children with terminal renal insufficiency show a reduction of the apparent ⁵¹Cr RBC half-life (16.5 ± 5.5 days). The enzymatic activities of phosphofructokinase (PFK) and glucose 6-phosphate dehydrogenase (G6PD) in the RBC of these patients do not differ from those in healthy persons. The RBC of uraemic and healthy children were separated by density gradient centrifugation in dextran medium according to maturity and age. RET count, mean cellular Hb concentration (MCHC), PFK and G6PD activities were determined in the separated cell populations. MCHC increases with increasing cell density, while the number of RET decreases. There is a distinct decrease in the G6PD activity of low-density cells compared to high-density cells. The extent of the decrease in enzymatic activity is about the same for healthy persons as for uraemic patients. A more rapid decrease in G6PD activity per unit of time can be assumed when the enzymatic activity is plotted against the distinctly shortened life span of the RBC of the uraemic children. There is a possible relationship between G6PD activity in old RBC and the premature destruction of these cells. PFK activity apparently does not decrease with increasing cell age.

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