Writing and Using Learning Objectives.

Learning objectives (LOs) are used to communicate the purpose of instruction. Done well, they convey the expectations that the instructor-and by extension, the academic field-has in terms of what students should know and be able to do after completing a course of study. As a result, they help students better understand course activities and increase student performance on assessments. LOs also serve as the foundation of course design, as they help structure classroom practices and define the focus of assessments. Understanding the research can improve and refine instructor and student use of LOs. This essay describes an online, evidence-based teaching guide published by CBE-Life Sciences Education (LSE) at http://lse.ascb.org/learning-objectives. The guide contains condensed summaries of key research findings organized by recommendations for writing and using LOs, summaries of and links to research articles and other resources, and actionable advice in the form of a checklist for instructors. In addition to describing key features of the guide, we also identify areas that warrant further empirical studies.

Ultrasound imaging of acute cardiac transplant rejection with microbubbles targeted to intercellular adhesion molecule-1.

BACKGROUND: Noninvasive techniques for detecting acute cardiac transplant rejection are limited. We hypothesized that ultrasound contrast microbubbles targeted to the endothelial cell (EC) inflammatory marker intercellular adhesion molecule-1 (ICAM-1) would selectively bind to rejecting versus nonrejecting myocardium and that myocardial contrast echocardiography can therefore detect acute rejection. METHODS AND RESULTS: Lipid-based microbubbles were conjugated to anti-rat ICAM-1 (MBICAM) or isotype control antibody (MBControl). In vitro MBICAM adhesion to cultured rat ECs, as assessed in a parallel plate flow apparatus, was greater to inflammatory versus normal ECs (11+/-3 versus 3+/-2 microbubbles/EC, P<0.005). In vivo abdominal heterotopic heart transplantation was performed in rats (rejection group: Brown Norway to Lewis strain; control group: Lewis to Lewis or Brown Norway to Brown Norway). Triggered myocardial contrast echocardiography was performed during intravenous MBICAM or MBControl (2.5x10(6)) injection on postoperative day 5. Myocardial videointensity from adhered MBICAM was significantly higher in rejecting (n=8) versus control (n=7) rats (10+/-4 versus 1+/-4 U, P=0.01). Postmortem histology showed normal myocardium in control rats, whereas allograft myocardium demonstrated grade III to IV rejection and strong immunohistochemical ICAM-1 staining. CONCLUSIONS: Preferential adherence of ICAM-1-targeted microbubbles to rejecting versus nonrejecting rat cardiac transplant myocardium can be detected ultrasonically. Targeted microbubbles may thus offer a noninvasive ultrasound imaging technique for the detection of acute cardiac transplant rejection and other processes characterized by endothelial dysfunction.

Myocardial contrast echocardiography can be used to assess the microvascular response to vascular endothelial growth factor-121.

BACKGROUND: Therapeutic angiogenesis is a new approach to treating ischemic heart disease, and the optimal method for assessing its efficacy is unclear. We used myocardial contrast echocardiography (MCE) to evaluate the therapeutic response to the angiogenic agent, vascular endothelial growth factor-121 (VEGF121). METHODS AND RESULTS: After placement of an ameroid constrictor (day 0) around the left anterior descending artery (LAD), dogs were given intracoronary VEGF121 protein (108 microg, n=6) or placebo (n=6) on days 7 and 21, and subcutaneous VEGF121 (1 mg) or placebo on days 8 to 20 and 22 to 27. On day 48, MCE was performed during rest and dobutamine stress. Videointensity (y) and pulsing interval (t) were fit to an exponential model (y=A[1-e(-beta(t))]) used to derive indices of red cell velocity (beta) and capillary area (A), and parameters were compared with radiolabeled microsphere flow data. VEGF(121) treatment resulted in higher resting left anterior descending artery/left circumflex flow ratio compared with placebo (P<0.03) and improved collateral flow reserve. Beta was 0.94+/-0.37 in VEGF121 dogs versus 0.38+/-0.31 in controls (P<0.02), with the greatest difference in the endocardium. The parameter A was comparable in both groups, suggesting that microvascular changes did not alter capillary cross-sectional area, and histology indicated a trend toward higher arteriolar density in VEGF121-treated animals. CONCLUSIONS: VEGF121 protein improves collateral flow and reserve. MCE can evaluate the transmural location and structural and functional responses of the microvasculature to angiogenic interventions.

Targeted in vivo labeling of receptors for vascular endothelial growth factor: approach to identification of ischemic tissue.

BACKGROUND: A method for identifying tissue experiencing hypoxic stress due to atherosclerotic vascular disease would be clinically useful. Vascular endothelial growth factor-121 (VEGF121) is an angiogenic protein secreted in response to hypoxia that binds to VEGF receptors overexpressed by ischemic microvasculature. We tested the hypothesis that VEGF receptors could serve as markers for ischemic tissue and hence provide a target for imaging such tissue with radiolabeled human VEGF121. METHODS AND RESULTS: A rabbit model of unilateral hindlimb ischemia was created by femoral artery excision (n=14). Control rabbits (n=5) underwent identical surgery without femoral excision. On postoperative day 10, rabbits were intravenously administered 100 microCi of 111In-labeled recombinant human VEGF121, and biodistribution studies and planar imaging were conducted at 3, 24, and 48 hours. On postmortem gamma counting, there was greater accumulation of 111In-labeled VEGF121 in ischemic than in control tissue (P<0.02). Differential uptake of isotope by ischemic muscle was not seen in rabbits injected with 125I-labeled human serum albumin (n=6). Radioactivity imaged in hindlimb regions of interest was significantly higher in ischemic muscle than in sham-operated and contralateral nonoperated hindlimb at 3 hours (P<0.02). Immunohistochemical staining confirmed upregulation of VEGF receptors in ischemic skeletal muscle. CONCLUSIONS: Identification of the ischemic state via targeted radiolabeling of hypoxia-induced angiogenic receptors is possible. This approach could be useful for monitoring the efficacy of revascularization strategies such as therapeutic angiogenesis.

A novel hydrodynamic approach to the treatment of coronary artery disease.

AIMS: During severe coronary stenosis, capillary resistance increases. Drag-reducing polymers (DRPs) are blood-soluble macromolecules that reduce vascular resistance, possibly by altering blood hydrodynamics and rheology. Thus, we hypothesized that DRPs would enhance myocardial perfusion distal to a severe coronary stenosis. METHODS AND RESULTS: A flow-limiting left anterior descending (LAD) coronary artery stenosis was created in 12 open chest dogs. Coronary driving pressure, flow, trans-stenotic gradient, and radiolabelled microsphere myocardial perfusion were measured. Myocardial contrast echocardiography was performed and videointensity vs. pulsing interval data in the LAD and left circumflex beds were used to derive red cell velocity and capillary volume. Relative to baseline, the stenosis decreased LAD bed capillary volume (P = 0.019) and red blood cell velocity (P = 0.010). Intravenous DRP (polyethylene oxide, 2.5 ppm) decreased LAD microvascular resistance (P = 0.003) and increased microsphere flow (P = 0.009), capillary volume (P = 0.0006), and red cell velocity (P = 0.007) despite the presence of a severe stenosis. DRP did not alter blood viscosity. CONCLUSIONS: DRPs improve perfusion to myocardium subserved by a flow-limiting coronary stenosis by decreasing microvascular resistance through an increase in capillary volume. Primary modulation of blood hydrodynamics and rheology to reduce microvascular resistance offers a novel approach to the treatment of ischaemic coronary syndromes.