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.

A complete molecular-orbital energy-level diagram for Ti02 is empirically deduced from the combined T&L 1~1, TiK, and OK x-ray emission and absorption band spectra. All of the occupied and vacant orbitals within 25 eV of E& are located on a relative energy scale. The titanium 3d, 4s, and 4p states and the oxygen 2s and 2p states all play important roles in the chemical bonding and all have specific influences on the x-ray bands. The deduced energylevel diagram is also shown to be compatible with the optical-absorption, photoconductivity, optical-reflectivity, and ultraviolet photoemission spectra.

Background— A method for identifying tissue experiencing hypoxic stress due to atherosclerotic vascular disease would be clinically useful. Vascular endothelial growth factor-121 (VEGF 121 ) 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 VEGF 121 . 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 μCi of 111 In-labeled recombinant human VEGF 121 , and biodistribution studies and planar imaging were conducted at 3, 24, and 48 hours. On postmortem gamma counting, there was greater accumulation of 111 In-labeled VEGF 121 in ischemic than in control tissue ( P <0.02). Differential uptake of isotope by ischemic muscle was not seen in rabbits injected with 125 I-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.