Arteriogenese

The remodeling of pre-existing arterioles into functional collateral vessels after occlusion of an artery is termed arteriogenesis. Understanding the molecular mechanisms of collateral growth provides an opportunity for therapeutic stimulation of this natural process and is the aim of arteriogenesis research. This beneficial vascular remodeling is associated with the proliferation of smooth muscle cells (SMC), which leads to an increase of the vascular lumen as well as wall thickness. In animal studies, a ligature of the femoral artery induces arteriogenesis. Subsequent tissue isolation of the collateral arteries allows molecular investigations in order to find the initial trigger of arteriogenesis. Differentially expressed genes, which have been identified in a genome-wide screening of growing collaterals, can be analyzed in terms of significance by targeted gene knock out. To further specify genetic modifications to the vascular wall, gene-targeting strategies that knock out target genes exclusively in a desired tissue while others remain unaffected have been established.     

Improving care for patients with chronic heart failure in the community: the importance of a disease management program

STUDY OBJECTIVE: Utilizing a comparison group of patients with congestive heart failure (CHF) discharged to their primary care physicians, we sought to determine if disease management in a short-term, aggressive-intervention heart failure clinic (HFC) following hospital discharge is associated with improved outcomes. DESIGN: Chart review. SETTING: An integrated health-care center serving a tristate area. PATIENTS: Inclusion criteria were discharge from the hospital with a primary diagnosis of CHF, outpatient follow-up within the hospital system, and the presence of left ventricular systolic dysfunction as the basis for CHF. Patients were categorized into group 1 if they were referred to the HFC after hospital discharge, and into group 2 if follow-up care was provided by their primary care physician. MEASUREMENTS AND RESULTS: There were 38 patients in group 1 and 63 patients in group 2. There was a trend toward a shorter time to the first outpatient visit following discharge (11 days vs 15 days, p = 0.09), more outpatient visits within 90 days (10 visits vs 2 visits, p < 0.001), and more patient-initiated contacts (four contacts vs one contact, p = < 0.001) in group 1 compared to group 2, respectively. The combined hospital readmission and mortality rate at 90 days (10% vs 30%, p < 0.018) and 1 year (21% vs 43%, p < 0.02) was lower in group 1. There was a 77% relative risk reduction for 30-day hospital readmission in favor of group 1, and a statistically lower rate of readmissions at 90 days and 1 year. Utilization and maintenance of standardized CHF medications were significantly higher in patients who attended the HFC. CONCLUSIONS: A comprehensive disease management program for patients discharged with a diagnosis of CHF resulted in fewer rehospitalizations and improved event-free survival compared to patients followed up by their primary care physicians.     

Decreased expression of phospholipase C-beta 2 isozyme in human platelets with impaired function

Platelets from a patient with a mild inherited bleeding disorder and abnormal platelet aggregation and secretion show reduced generation of inositol 1,4,5-trisphosphate, mobilization of intracellular Ca2+, and phosphorylation of pleckstrin in response to several G protein mediated agonists, suggesting a possible defect at the level of phospholipase C (PLC) activation (see accompanying report). A procedure was developed that allows quantitation of platelet PLC isozymes. After fractionation of platelet extracts by high-performance liquid chromatography, 7 out of 10 known PLC isoforms were detected by immunoblot analysis. The amount of these isoforms in normal platelets decreased in the order PLC- gamma 2 > PLC-beta 2 > PLC-beta 3 > PLC-beta 1 > PLC-gamma 1 > PLC- delta 1 > PLC-beta 4. Compared with normal platelets, platelets from the patient contained approximately one-third the amount of PLC-beta 2, whereas PLC-beta 4 was increased threefold. These results suggest that the impaired platelet function in the patient in response to multiple G protein mediated agonists is attributable to a deficiency of PLC-beta 2. They document for the first time a specific PLC isozyme deficiency in human platelets and provide an unique opportunity to understand the role of different PLC isozymes in normal platelet function.     

Human platelet signaling defect characterized by impaired production of inositol-1,4,5-triphosphate and phosphatidic acid and diminished Pleckstrin phosphorylation: evidence for defective phospholipase C activation

Signal transduction on platelet activation involves phosphoinositide- specific phospholipase C (PLC)-mediated hydrolysis of phosphatidylinositides and formation of inositol-1,4,5-triphosphate [I(1,4,5)P3], which mediates Ca2+ mobilization, and diacylglycerol (DG), which activates protein kinase C (PKC) to phosphorylate a 47-kD protein (Pleckstrin). We studied these events in two related patients previously reported (Blood 74:664, 1989) to have abnormal aggregation and 14C-serotonin secretion, and impaired intracellular Ca2+ mobilization in response to several agonists. Thrombin-induced I(1,4,5)P3 and phosphatidic acid formation were diminished. Pleckstrin phosphorylation was impaired on activation with thrombin, platelet- activating factor, and ionophore A23187, but was normal with PKC activator 1,2-dioctonyl-sn-glycerol (DiC8). Ca2+ mobilization induced by guanosine triphosphate (GTP) analog guanosine 5'-0-(3 thiotriphosphate) (GTP gamma S) was diminished. Pretreatment with either A23187 or DiC8 did not correct the impaired adenine diphosphate- induced secretion; however, upon stimulation with A23187 plus DiC8, pleckstrin phosphorylation and secretion were normal, indicating that both PKC activation and Ca2+ mobilization are essential for normal secretion. We conclude that these patients have a unique inherited platelet defect in formation of two key intracellular mediators [I(1,4,5)P3 and DG] and in the responses mediated by them due to a defect in postreceptor mechanisms of PLC activation.     

Recovery of the heart after normothermic ischemia. Part II: Myocardial function during postischemic reperfusion.

Contraction and relaxation of the canine myocardium were examined during normothermic ischemia in an isolated heart model. Decrease in the development of tension depends on the duration of ischemia. Deficient functional recovery was observed after ischemic periods extending beyond 30 minutes, in spite of reperfusion periods of over 1 hour. A decrease in compliance was observed during the anoxic period, but a persistent defect of relaxation occurred only after 60 minutes of ischemia. After this period there was also a disturbance in the autoregulative mechanisms of coronary perfusion and an uncoupling of O2-consumption and mechanical efficiency. A prolonged reperfusion period of the heart beating empty allowed ultrastructural recovery of the damaged myocardium. In contrast, functional recovery of the myocardium, as determined by several parameters of contraction and relaxation, did not correlate with ultrastructural recovery and was not improved by prolonged reperfusion.     

Acquired granular pool defect in stored platelets

Platelets stored as concentrates (PC) for 72 h at 22 degrees C develop a functional defect. Alterations in adenine nucleotides of platelets have been shown to affect platelet function. Adenine nucleotide content of platelets was measured before and after storage and a decrease of 27.1 /+- 1.7% (mean /+- SE) in ATP and 39.1 /+- 2.6% in ADP were found in 34 PC stored with final volume of 50 ml. In 11 PC with 30 ml volume. ATP and ADP decreased by 39.4 /+- 3.2% and 49.4 /+- 2.1%, respectively. The mean ATP to ADP ratio of stored platelets was significantly higher than of fresh platelets in both groups, suggesting a relatively greater decrease in granular than metabolic pool nucleotides. Levels of low affinity platelet factor 4 measured by radioimmunoassay in plasma from 0.86 /+- 0.08 microgram/ml in the fresh PC to 8.59 /+- 0.39 microgram/ml in stored PC, indicating a concomitant alpha-granular secretion. Labeling of metabolic pool with 14C-adenine revealed a mean decrease in the adenylate energy charge of 2.0 /+- 0.4% in 12 of 16 stored PC, with a lower ATP and higher hypoxanthine labeling in stored as compared to fresh platelets. These observations suggest that stored platelets develop an acquired defect in both dense and alpha granules and in their ability to maintain ATP homeostasis.     

Influence of collateral blood flow and of variations in MVO2 on tissue-ATP content in ischemic and infarcted myocardium

The left anterior descending coronary artery was occluded for 22.5, 45, 90, 180, and 360 mins in anesthesized open-chest dogs and pigs and thereafter reperfused for 30 min. Myocardial oxygen consumption was varied in dogs by cholinergic stimulation (bradycardia) and by cutting of the right and left vagus nerve (tachycardia). Regional myocardial blood flow was measured with radioactive tracer microspheres at the end of the occlusion period and 5 and 30 min after reflow. Tissue content of adenine nucleotides and of phosphocreatine were determined in the subendo- and subepicardium of transmural biopsies at the end of reflow. Infarct size was determined with nitrobluetetrazolium and compared with risk region size. Porcine hearts developed infarcts sooner. Those canines with a high MVO2 due to tachycardia had larger infarcts than those with bradycardia and resembled infarct development in the pig. The evolution of infarcts with time depended strongly on collateral flow which was significantly higher in canine hearts. Higher collateral flow and lower MVO2 in one group of canine hearts also resulted in better preserved tissue ATP. The fall in tissue ATP with time after coronary occlusion was compared with the O2-supply via collateral flow during occlusion. Assuming that the oxygen entering ischemic myocardium was used for ADP phosphorylation, we could estimate the degree of ATP-"overspending". Overspending was highest in low-flow ischemia and it correlated well with the speed of infarction. The ATP-data are best explained by the phosphocreatine energy shuttle model and by assuming slow access of cytosolic ATP to the ATP-splitting sites at the myofibrils. In conclusion, we postulate that both collateral flow as well as myocardial oxygen consumption before and during occlusion determine infarct size.