Russell Thomas Woodburne

No abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35054/1/1097_ftp.pd

Comparison of static incubation versus physiologic perfusion techniques for quantitation of luminal release of prostacyclin and thromboxane in canine arteries and veins

Intraluminal release of 6-keto-PGF1[alpha] and TxB2 in ex vivo canine arteries and veins was assessed during five consecutive 15-min periods using static incubation and physiologic perfusion techniques. Arterial segments were perfused with 90 ml/min pulsatile flow at 100 mm Hg and vein segments with 90 ml/min nonpulsatile flow at 7 mm Hg. During the final 15-min period vessels were stimulated with arachidonic acid (AAS). Perfusion of vein segments caused a higher release of 6-keto-PGF1[alpha] during the first 30 min (P P 1[alpha] for 45 min (P P 2 release was higher during the entire observation period in perfused arteries and veins compared to incubated vessels (P and 1[alpha] or TxB2 released when comparing values obtained by one technique to values obtained by the other (P> 0.1). These data suggest that flow related shear stress alters vascular prostanoid production, and that such should be accounted for when interpreting results of studies on prostacyclin and thromboxane release from intact vessels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27222/1/0000226.pd

Effects of thromboxane synthetase inhibition on patency and anastomotic hyperplasia of vascular grafts

The efficacy of a thromboxane synthetase inhibitor (U-63,557A, Upjohn) in promoting early patency and inhibiting anastomotic intimal hyperplasia in ePTFE grafts was compared to that of acetylsalicylic acid (ASA) in a canine model. Animals were started on ASA 5 gr po qd (Group I, n = 12) or U-63,557A 10 mg/kg po bid (Group II, n = 12) 1 day before placement of bilateral 5-mm-i.d., 13- to 16.5-cm-long ePTFE aortoiliac grafts and continued on the medication for the 16-week study. Six dogs in each group received autologous endothelial cell-seeded grafts, while the other six received unseeded grafts. Patency was determined weekly by assessment of femoral pulses. At the conclusion of the study anastomotic intimal hyperplasia was measured on serial sections through the distal anastomosis using a computer-linked digitizer. In Group I the patencies of seeded and unseeded grafts were not significantly different, being 100 and 83%, respectively. Furthermore, luminal narrowing due to intimal hyperplasia was not significantly different being 9.1 +/- 7.6% (x +/- SD) in seeded grafts and 8.8 +/- 8.1% in unseeded grafts. On the other hand, in Group II the seeded grafts had significantly improved patency when compared to the unseeded grafts (83% vs 33%, P P P P < 0.01).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27929/1/0000353.pd

Enhanced endothelialization of dacron grafts by external vein wrapping

The efficacy of external vein wrapping of vascular grafts in promoting the development of a luminal endothelial surface was assessed in 12 dogs who underwent thoracoabdominal bypasses with 26-29 cm x 6-mm i.d. double-velour knitted Dacron grafts. In group I (n = 6) 6-cm segments of the grafts were wrapped with autologous jugular vein with its endothelial surface applied against the outside of the graft. In group II (n = 6) the wrap procedure was performed using abdominal wall fascia. The degree and character of graft incorporation was quantitated in all prostheses at 28 days postimplantation. Group I vein wrap prostheses demonstrated uniform endothelial surface coverage in the vein wrap area () that was significantly greater (P P < 0.04). No significant differences existed in endothelial coverage of unwrapped regions of group I and II grafts. This investigation documented that wrapping knitted Dacron grafts with vein enhanced endothelialization of their luminal surface.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25688/1/0000242.pd

Nuclide imaging of vascular graft-platelet interactions: Comparison of indium excess and technetium subtraction techniques

Indium-111-labeled platelet adherence to ePTFE thoracoabdominal vascular prostheses in a canine model (n = 10) was quantitated by (1) an indium-111 excess technique, contrasting graft radioactivity to that in a reference region, and (2) a technetium-99m subtraction technique, with radioactivity of circulating platelets eliminated by discounting background blood activity. Variation in graft thrombogenicity was provided by seeding six prostheses with enzymatically derived autologous endothelial cells, and implanting four prostheses without seeding. Grafts were imaged at 1, 4, and 6 weeks postimplantation, with platelet labeling using indium-111-oxine and red blood cell labeling using technetium-99m. At 7 weeks grafts were excised and gamma activity was measured in proximal, middle, and distal segments. Luminal generation of TxB2 and 6-keto-PGF1[alpha] from midportions of grafts was assayed. Indium-111 excess ratios at 6 weeks correlated with actual gamma activity of excised grafts (proximal r = 0.80, P r = 0.73, P r = 0.48, ns) but such a correlation did not exist for the technetium-99m subtraction technique (r = -0.05, -0.25, and 0.16, in the three segments, respectively, all ns). The ratio of graft to aortic TxB2 production revealed a positive correlation with graft gamma activity (r = 0.87, P 1[alpha] to TxB2 production also correlated with gamma counts (r = -0.64, P = 0.05). In this experimental setting technetium-99m subtraction analysis was an imprecise method of detecting graft platelet accumulation, whereas indium-111 excess ratios proved to be a more accurate method of quantitating vascular prosthetic thrombogenicity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26220/1/0000300.pd

Effects of extracellular pH on PGI2 and TxA2 release from perfused canine veins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28426/1/0000209.pd

Alternative techniques of seeding cultured endothelial cells to ePTFE grafts of different diameters, porosities, and surfaces

Attachment of 111 Indium-oxine labeled cultured canine venous endothelial cells to expanded polytetrafluorethylene (ePTFE) grafts was evaluated in vitro . Three alternative seeding techniques were studied in grafts having different diameters, porosities, and surfaces, including: (I) manual milking of blood contiaining endothelial cells within the graft; (II) a two-step procedure of incubating grafts initially with blood and then with an endothelial cell suspension; and (III) mechanical spinning of grafts filled with blood containing endothelium. Method II had significantly higher cell attachment to the graft (11.6%) than did Method I (1.5%) or III (4.7%). A somewhat higher seeding efficiency was noted in 10-mm-I. D. grafts (11.6%) compared to 6-mm-I. D. grafts (6.3%). Different graft porosity, created by altering internodal distances, did not cause significant changes in cell attachment (10 Mm, 13.4%, 30 Mm, 6.3%; 90 M, 16.0%). Fibronectin-coated surfaces, which should have enhanced cell adhesion, demonstrated a 6.0% cell attachment, a lower efficiency than the 11.6% observed with a blood coating alone. Acetone-soaked surfaces, which should have predictably exhibited less hydrophobicity, produced quite variable attachments (range 3.4 to 59.7%, mean 23.4%). In the present investigation the best seeding technique was method II, the two-step incubation procedure. Consistant differences were not noted with various ePTFE graft configurations or surfaces.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37997/1/820210807_ftp.pd

Sequential studies of healing in endothelial seeded vascular prostheses: Histologic and ultrastructure characteristics of graft incorporation

Chronological events leading to incorporation of endothelial cell seeded prosthetic vascular grafts were documented in this investigation. Forty-one adult dogs underwent thoracoabdominal bypass using double-velour Dacron grafts. Experimental grafts were preclotted with blood containing enzymatically derived endothelium immediately after derivation, or after 14 days of cultivation. Control grafts were preclotted without addition of endothelial cells. Grafts were studied grossly as well as by light, scanning electron, transmission electron, and fluorescence microscopy, 1 to 28 days postimplantation. Control graft healing proceeded from pannus and perigraft ingrowth. Experimental grafts healed from seeded cells as well. Platelets covered all grafts by Days 1 and 2. Thrombus accumulations on control grafts, first evident on Day 4, became maximal by Day 14. Seeded grafts appeared relatively thrombus free with patches of endothelial cells noted by 4 days. These cells were initially separated by gaps, often containing leukocytes. Endothelium became densely packed with cellular migration and proliferation. Subendothelial tissues were composed of fibrin and smooth muscle. Control and experimental grafts were approximately 10 and 80% endothelialized, respectively, by Day 28. Smooth muscle dominated subintimal tissue in experimental grafts. These cells initially appeared fibroblastoid. Endothelial seeding enhances both pseudointimal development and rapid graft incorporation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24409/1/0000679.pd

Transplantation of lac-Z-Transduced Microvascular Endothelial Cells into the Skeletal Muscle Capillary Bed of the Rat Hindlimb Occurs Independent of the Duration of Fernoral Artery Occlusion after Injection of Cells

The skeletal muscle capillary bed may be an ideal recipient site for transplantation of genetically modified autologous endothelial cells and thus provide a basis for a technique of somatic gene therapy that would be applicable to a variety of acquired and inherited human diseases. The purpose of this study was to test the hypothesis that adhesion of lac-Z -transduced microvascular endothelial cells (MVEC) in the skeletal muscle capillary bed in vivo is dependent on the duration of arterial occlusion after injection of the transduced MVEC. MVEC derived from the abdominal fat pad of syngeneic rats (Wistar F-455) were transfected with the BAG vector, a replication-incompetent retroviral vector containing the lac-Z gene for [beta]-galactosidase and the Tn5 gene for selection of the transduced cells by the neomycin analogue, G418. lac-Z-transduced MVEC were radiolabeled with 125I-PKH-95, and, after the femoral artery was occluded for 10 min, these cells (1 to 2 x 106) were injected intraarterially into the rat hindlimb. In the experimental groups the femoral artery clamp was removed at 0, 60, or 120 min after injection. A control group without pre- or postinjection femoral arterial occlusion was also studied. Adhesion of MVEC in the skeletal muscle capillary bed (mean percentage of injected 125I activity) was determined in groups of 4 rats at 1 day, 1 week, and 1 month after injection. Adhesion of the transduced MVEC did not increase as the duration of femoral artery occlusion after injection was increased. The highest rate was found in the group subjected to only a 10-min preclamp (32% at 1 day, 17% at 1 week, and 15% at 1 month). These results indicate that mechanical forces such as capillary shear rate and perfusion pressure may not be important determinants of adhesion and incorporation of transduced MVEC into skeletal muscle capillaries. Nevertheless, these results document significant adhesion and persistence of genetically modified MVEC transplanted into the capillary bed of the skeletal muscle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31167/1/0000066.pd