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This study demonstrates that a CD34–, vascular endothelial cadherin– (VE-cadherin–), AC133+, and fetal liver kinase+ (Flk1+) multipotent adult progenitor cell (MAPC) that copurifies with mesenchymal stem cells from postnatal human bone marrow (BM) is a progenitor for angioblasts. In vitro, MAPCs cultured with VEGF differentiate into CD34+, VE-cadherin+, Flk1+ cells — a phenotype that would be expected for angioblasts. They subsequently differentiate into cells that express endothelial markers, function in vitro as mature endothelial cells, and contribute to neoangiogenesis in vivo during tumor angiogenesis and wound healing. This in vitro model of preangioblast-to-endothelium differentiation should prove very useful in studying commitment to the angioblast and beyond. In vivo, MAPCs can differentiate in response to local cues into endothelial cells that contribute to neoangiogenesis in tumors. Because MAPCs can be expanded in culture without obvious senescence for more than 80 population doublings, they may be an important source of endothelial cells for cellular pro- or anti-angiogenic therapies

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Background: Platelet-derived microparticles (MPs) are believed to play an important role in coagulation and inflammatory disorders. Unfortunately, MP size renders them difficult to study and analyze by conventional flow cytometry. Methods: We analyzed and characterized platelet-derived MPs, using antibodies against the major surface glycoproteins (GP), the platelet activation antigen P-selectin (CD62P), and a marker of procoagulant activity (phosphatidylserine exposure). MPs were generated by exposure of platelets to thrombin receptor activating peptide (TRAP) or ionophore. Both agonists induced significant microvesiculation of platelets, and the resulting MPs were analyzed by a new digital flow cytometer: Becton-Dickinson FACSAria TM . Results: Membrane GPs were equally well represented in MPs generated by either reagent. In contrast, P-selectin

Sickle cell anemia is characterized by painful vaso-occlusive crises. It is hypothesized that monocytes are activated in sickle cell disease and can enhance vaso-occlusion by activating endothelium. To test this hypothesis, human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (MVEC) with sickle and normal mononuclear leukocytes were incubated, and endothelial activation was measured. Endothelial cells incubated with sickle mononuclear leukocytes were more activated than those incubated with normal mononuclear leukocytes, as judged by the increased endothelial expression of adhesion molecules and tissue factor and the adhesion of polymorphonuclear leukocytes (PMNL). Monocytes, not lymphocytes or platelets, were the mononuclear cells responsible for activating endothelial cells. Sickle monocytes triggered endothelial nuclear factor-kappa B (NF-κB) nuclear translocation. Cell-to-cell contact of monocytes and endothelium enhanced, but was not required for, activation. Antibodies to tumor necrosis factor-alpha (TNF-α) and interleukin-1-beta (IL-1β) blocked activation of the endothelium by monocytes. Peripheral blood monocytes from patients with sickle cell disease had 34% more IL-1β (P = .002) and 139% more TNF-α (P = .002) per cell than normal monocytes. Sixty percent of sickle monocytes expressed the adhesion molecule ligand CD11b on their surfaces compared with only 20% of normal monocytes (P = .002). Serum C-reactive protein, a marker of systemic inflammation, was increased 12-fold in sickle serum than in normal serum (P = .003). These results demonstrate that sickle monocytes are activated and can, in turn, activate endothelial cells. It is speculated that vascular inflammation, marked by activated monocytes and endothelium, plays a significant role in the pathophysiology of vaso-occlusion in sickle cell anemia.

Sickle cell anemia is characterized by painful vaso-occlusive crises. It is hypothesized that monocytes are activated in sickle cell disease and can enhance vaso-occlusion by activating endothelium. To test this hypothesis, human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (MVEC) with sickle and normal mononuclear leukocytes were incubated, and endothelial activation was measured. Endothelial cells incubated with sickle mononuclear leukocytes were more activated than those incubated with normal mononuclear leukocytes, as judged by the increased endothelial expression of adhesion molecules and tissue factor and the adhesion of polymorphonuclear leukocytes (PMNL). Monocytes, not lymphocytes or platelets, were the mononuclear cells responsible for activating endothelial cells. Sickle monocytes triggered endothelial nuclear factor-kappa B (NF-κB) nuclear translocation. Cell-to-cell contact of monocytes and endothelium enhanced, but was not required for, activation. Antibodies to tumor necrosis factor-alpha (TNF-α) and interleukin-1-beta (IL-1β) blocked activation of the endothelium by monocytes. Peripheral blood monocytes from patients with sickle cell disease had 34% more IL-1β (P = .002) and 139% more TNF-α (P = .002) per cell than normal monocytes. Sixty percent of sickle monocytes expressed the adhesion molecule ligand CD11b on their surfaces compared with only 20% of normal monocytes (P = .002). Serum C-reactive protein, a marker of systemic inflammation, was increased 12-fold in sickle serum than in normal serum (P = .003). These results demonstrate that sickle monocytes are activated and can, in turn, activate endothelial cells. It is speculated that vascular inflammation, marked by activated monocytes and endothelium, plays a significant role in the pathophysiology of vaso-occlusion in sickle cell anemia.

Abstract-The role that the central sympathetic nervous system plays in the development of obesity hypertension and insulin was evaluated by feeding dogs a high fat diet with or without clonidine treatment. Thirteen adult mongrel dogs were chronically instrumented and randomly assigned to receive either a high fat diet and no clonidine (nϭ6) or a high fat diet plus clonidine (nϭ7), 0.3 mg BID. Blood pressure, heart rate, plasma insulin, and electrolytes were measured daily. Insulin resistance was assessed with a multiple-dose euglycemic clamp (1, 2, and 30 mU ⅐ kg Ϫ1 ⅐ min Ϫ1 ) before and after 1, 3, and 6 weeks of the high fat diet. Clonidine prevented the hypertension, tachycardia, and insulin resistance associated with feeding dogs the high fat diet but did not affect weight gain. The present study suggests that the central sympathetic nervous system plays a critical role in the development of both insulin resistance and hypertension associated with feeding dogs a high fat diet. Key Words Ⅲ hypertension, arterial Ⅲ obesity Ⅲ insulin resistance Ⅲ clonidine Ⅲ sympathetic nervous system Ⅲ cardiac output T he mechanism involved in the pathogenesis of the increased blood pressure in obesity is incompletely understood. Studies in our laboratory 1,2 and by others 3 suggest that insulin resistance may be the link between obesity and hypertension. However, other observations suggest that the relation between insulin and obesity-induced hypertension is not so straightforward. The San Antonio Heart Study showed that hyperinsulinemia is more common in Mexican Americans than in white non-Hispanics, yet the prevalence of hypertension is high in the latter group. 4 Hall et al 5 failed to observe an increase in blood pressure when normal dogs were given a chronic infusion of insulin with or without norepinephrine.We believe that an alternate hypothesis to explain the pathogenesis of obesity-induced hypertension is that chronic central sympathetic nervous system activation links insulin resistance and hypertension. Sowers et al 6 observed that borderline hypertensive obese subjects had higher norepinephrine levels than did nonobese normotensive control subjects, that their blood pressure correlated with norepinephrine levels, and that weight loss was accompanied by a fall in blood pressure that correlated with a decrease in serum norepinephrine. Hall et al 7 suggested that combined ␣-and ␤-adrenergic blockade reduced arterial pressure to a much greater extent in obese than in normal dogs. Fasting or caloric deprivation reduces sympathetic activity and overfeeding stimulates sympathetic activity. 8 Diebert and DeFronzo 9 demonstrated that impairs both peripheral and hepatic resistance to the action of insulin.Jamerson et al 10 demonstrated that a reflex increase in sympathetic tone in normotensive individuals can lead to acute insulin resistance in the forearm.Thus, it is possible that central activation of the sympathetic nervous system is the physiological link that connects excess dietary intake to insulin resistance and hyp...

The current study evaluated both the time course of insulin resistance associated with feeding dogs a high-fat diet and the relationship between the development of insulin resistance and the increase in blood pressure that also occurs. Twelve adult mongrel dogs were chronically instrumented and randomly assigned to either a control diet group (n = 4) or a high-fat diet group (n = 8). Insulin resistance was assessed by a weekly, single-dose (2 mU.kg-1.min-1) euglycemic-hyperinsulinemic clamp on all dogs. Feeding dogs a high-fat diet was associated with a 3.7 +/- 0.5 kg increase in body weight, a 20 +/- 4 mmHg increase in mean blood pressure, a reduction in insulin-mediated glucose uptake [(in mumol-kg-1.min-1) decreasing from 72 +/- 6 before to 49 +/- 7 at 1 wk, 29 +/- 3 at 3 wk, and 30 +/- 2 at 6 wk of the high-fat diet, P < 0.01]. and a reduced insulin-mediated increase in cardiac output. In eight dogs (4 high fat and 4 control), the dose-response relationship of insulin-induced glucose uptake also was studied. The whole body glucose uptake dose-response curve was shifted to the right, and the rate of maximal whole body glucose uptake was significantly decreased (P < 0.001). Finally, we observed a direct relationship between the high-fat diet-induced weekly increase in mean arterial pressure and the degree to which insulin resistance developed. In summary, the current study documents that feeding dogs a high-fat diet causes the rapid development of insulin resistance that is the result of both a reduced sensitivity and a reduced responsiveness to insulin.