Grafts In Dogs Research Articles

Characterization of host cells involved in resistance to marrow grafts in dogs transplanted from unrelated DLA-nonidentical donors

A canine model of marrow transplantation was used to further define the host cells mediating resistance to marrow engraftment. Recipient dogs were given 9.2 Gy of total body irradiation followed by marrow infusion from unrelated DLA-nonidentical donors. No postgrafting immunosuppression was given. At three and ten days posttransplantation recipient marrow and peripheral blood cells were obtained and characterized by the following in vitro studies: morphologic analysis; phenotypic analysis with monoclonal antibodies; assays for natural killer cell (NK) activity; and cocultures with donor marrow to study the effect on donor CFU-GM growth. Daily differential cell counts revealed a proliferation of peripheral blood mononuclear cells approximately eight days posttransplant. By day 10 surviving host cells were uniformly large granular lymphocytes which were phenotypically of T cell lineage, had NK activity, and were capable of suppressing donor marrow CFU-GM growth. Mononuclear cells from dogs given total body irradiation only and no marrow infusion (radiation control group), did not suppress CFU-GM growth when cocultured with marrow from unrelated DLA-mismatched dogs. These results suggest that radioresistant host cells with the morphology of large granular lymphocytes and NK activity and which proliferate in response to the infused donor marrow cells mediate resistance to DLA-nonidentical marrow grafts. It remains to be determined, however, whether in vitro functional studies reflect the mechanisms involved in vivo.

Characterization of Host Cells Involved in Resistance to Marrow Grafts in Dogs Transplanted From Unrelated DLA-Nonidentical Donors

A canine model of marrow transplantation was used to further define the host cells mediating resistance to marrow engraftment. Recipient dogs were given 9.2 Gy of total body irradiation followed by marrow infusion from unrelated DLA-nonidentical donors. No postgrafting immunosuppression was given. At three and ten days posttransplantation recipient marrow and peripheral blood cells were obtained and characterized by the following in vitro studies: morphologic analysis; phenotypic analysis with monoclonal antibodies; assays for natural killer cell (NK) activity; and cocultures with donor marrow to study the effect on donor CFU-GM growth. Daily differential cell counts revealed a proliferation of peripheral blood mononuclear cells approximately eight days posttransplant. By day 10 surviving host cells were uniformly large granular lymphocytes which were phenotypically of T cell lineage, had NK activity, and were capable of suppressing donor marrow CFU-GM growth. Mononuclear cells from dogs given total body irradiation only and no marrow infusion (radiation control group), did not suppress CFU-GM growth when cocultured with marrow from unrelated DLA-mismatched dogs. These results suggest that radioresistant host cells with the morphology of large granular lymphocytes and NK activity and which proliferate in response to the infused donor marrow cells mediate resistance to DLA-nonidentical marrow grafts. It remains to be determined, however, whether in vitro functional studies reflect the mechanisms involved in vivo.

A new model for hetero-orthotopic heart-lung transplantation in the dog

A method of hetero-orthotopic heart-lung transplantation is described in the dog. The model was developed to study patterns of rejection in the transplanted heart and lung, since the dog will not survive bilateral pneumonectomy and loss of the Hering-Breuer reflex. After removal of the recipient's left lung the donor heart and left lung are explanted en bloc. End-to-end connection is made of both left main bronchi, and the donor aorta is joined end-to-side with the recipient's descending aorta. An atrio-atrial anastomosis is performed between the recipient's left and the donor's right atrium. Four experiments were done to develop the surgical technique and 10 long-term studies were performed to investigate rejection patterns. The average survival rate of these animals was 28.5 ± 8.3 days, ranging from 5 to 53 days. Causes of death were not due to operative complications. Heterotopic heart-lung transplantation is an uncomplicated surgical method which does not require cardiopulmonary bypass or anticoagulation and allows the investigator to study heart and lung grafts in dogs for long-term periods after surgery. Bronchoscopy, bronchoalveolar lavage, and heart and lung biopsies of both donor and recipient organs can be performed.

Ticlopidine versus aspirin and dipyridamole: Influence on platelet deposition and three-month patency of polytetrafluoroethylene grafts

In an attempt to establish a specific drug regimen that would retard neointimal fibrous thickening (NFT) and promote patency of small arterial grafts, we studied acute platelet accumulation and 3-month patency of 4 mm polytetrafluoroethylene (PTFE) grafts in dogs treated with oral aspirin (2 mg/kg/day) in combination with dipyridamole (5 mg/kg/day) (ASA/D) or ticlopidine (25 mg/kg/day) (T). After 3 days of treatment, 15 dogs were given indium 111-labeled autologous platelets and then had bilateral femoral artery grafts placed (control, 10 grafts; each drug group, 10 grafts). The calculated graft radioactivity expressed as average counts per 10 minutes ± standard error of the mean (SEM) was as follows: control = 542,003 ± 63,991; ASA/D = 135,163 ± 14,443 (p < 0.001, Student's t test); T = 104,650 ± 14,004 (p < 0.001). Bilateral femoral artery and carotid artery grafts were placed in 15 other dogs (control, 20 grafts; each drug group, 20 grafts). Three months later the 60 grafts were excised and their patency recorded: control = 20% (4 of 20 grafts); ASA/D = 70% (12 of 17 grafts) (p < 0.01, chi-square analysis); T = 30% (6 of 20 grafts) (p > 0.05). Mean anastomotic NFT ± SEM of each graft was measured with an ocular micrometer: control = 1.6 ± 0.2 mm; ASA/D = 0.7 ± 0.2 mm (p < 0.001, Student's t test); T = 1.3 ± 0.2 mm (p > 0.1). These data demonstrate significant and equivalent decreases in radioactive platelet deposition with ASA/D or T, but only animals receiving ASA/D had a significant decrease in NFT and an improvement in 3-month patency. Mechanisms in addition to platelet adhesion and aggregation may contribute to NFT in small arterial grafts.

Xenograft seeding of dacron grafts in dogs

The benefit of autologous endothelial cell seeding in dogs has been widely accepted. This experiment seeks to determine if a similar effect accompanies the use of xenograft (porcine) endothelial cells in dogs. Thirty-two mongrel dogs underwent thoracoabdominal aortic bypass with 25- to 30-cm segments of double velour Dacron 8-mm grafts. Endothelial cell seeding was performed with whole blood suspensions of either autologous endothelial cells (Group I) or heterologous endothelial cells from pigs (Group II). Cell-free culture medium was added to whole blood for preclotting in unseeded control animals (Group III). Ten animals in each group were sacrificed at 30 days and all grafts were patent. Thrombus-free surface areas were Group I = 61.7 (±6.4%, SEM); Group II = 53.2 (±6.8%, SEM); and Group III 42.2 (±8.0%, SEM). There was a significant difference between autologous-seeded and unseeded grafts ( P < 0.04). Endothelialization was confirmed by scanning and transmission electron microscopy in all groups but was better in both seeded groups: Group I— 9 10 grafts, Group II— 8 10 grafts, and Group III— 4 10 grafts. Factor VIII immunofluorescent staining confirmed the presence of endothelium on selected grafts in each group. These results raise questions concerning the proposed mechanism of endothelial seeding since xenograft cells seem to facilitate healing in the canine model. If heterograft cells can be effective, it may not be necessary to harvest cells from the recipient in order to achieve the benefits of seeding.

Quantification of deposition of neutrophilic granulocytes on vascular grafts in dogs with 111In-labeled granulocytes: Dewanjee MK, Solis E, Mackey ST, et al. Mayo Clin Proc 1983;60:173–179

Quantification of deposition of neutrophilic granulocytes on vascular grafts in dogs with 111In-labeled granulocytes: Dewanjee MK, Solis E, Mackey ST, et al. Mayo Clin Proc 1983;60:173–179

Effects of antiplatelet agents in combination with endothelial cell seeding on small-diameter Dacron vascular graft performance in the canine carotid artery model

The purpose of this study was to assess the success of endothelial cell—seeded and non-seeded small-diameter vascular grafts in dogs medicated with antiplatelet agents. Eighty dogs underwent bilateral carotid artery replacements with 6 cm lengths of 4 mm I.D. double-velour Dacron grafts. In each dog one graft was seeded with enzymatically derived autologous endothelial cells; the contralateral graft was nonseeded. The following antiplatelet medications were administered beginning 4 days preoperatively: aspirin (5 grains every day); dipyridamole (50 mg twice a day); aspirin plus dipyridamole (5 grains each day plus 50 mg twice a day); aspirin (1.25 grains every other day); ibuprofen (10 mg/kg/day); U-53,059, a cyclooxygenase inhibitor (3 mg/kg/day); and U-63557A, a thromboxane synthase inhibitor (10 mg/kg/day). Grafts were harvested 5 weeks postoperatively. Graft success was evaluated by patency, thrombus-free surface area, area endothelialized, and graft production of prostacyclin. None of the medications prevented neoendothelialization of seeded grafts. Mean patencies of endothelial cell-seeded grafts from medicated dogs were significantly greater than mean patencies of endothelial cell-seeded grafts from nonmedicated dogs. The cyclooxygenase inhibitors best maintained patency in non-seeded grafts. Thrombus-free surface areas of endothelial cell-seeded grafts from medicated dogs were significantly greater than from nonseeded control grafts from the medicated dogs. All medications impaired prostacyclin synthesis. We conclude that the combination of endothelial cell seeding plus antiplatelet medication is most efficacious in small-vessel grafting success and that high levels of prostacyclin production by vascular grafts are not necessary to maintain patency in dogs medicated with antiplatelet agents.

Effect of a cyclic hexapeptide analog (L363,586) of somatostatin on the function of pancreas grafts in dogs

Complications related to the exocrine secretions cause some pancreas grafts to fail in the early postoperative period. Somatostatin inhibits exocrine secretion, as well as insulin and glucagon release. L363,586 is a cyclic hexapeptide analog of somatostatin that is 50 to 100 times more potent than the native hormone in inhibiting islet hormone release. In a preliminary experiment in which permanent fistulas were created in two dogs, we demonstrated that L363,586 (0.3 μg/kg/60 min) results in a fourfold decrease in pancreatic exocrine secretion when measured for 210 min following a beef meal. In a separate experiment, five totally pancreatectomized dogs who received segmental pancreas autografts with pancreaticoductocystostomy 10 months previously had L363,586 (0.3 μg/kg/hr) administered by the Alzet osmotic pump subcutaneously for 7 days. Mean (±SE) daily serum amylase activity (IU/dl) during the week before the implant was 78 ± 3, during the week of infusion was 65 ± 2 ( P < 0.001), and during the week afterward was 76 ± 2. In a prospective experiment, 12 totally pancreatectomized dogs received segmental pancreas autografts with anastomosis of the graft vessels to the iliac vessels and of the pancreatic duct to the bladder. L363,586 was administered by osmotic pump for 7 days to seven dogs at a dose of 0.3 μg/kg/hr. Mean (±SE) daily serum amylase levels at 1, 2, and 3 weeks posttransplant were 223 ± 17, 81 ± 3, and 82 ± 5 in the L363,586-treated dogs and 229 ± 18, 108 ± 5, and 90 ± 5 in the five untreated dogs ( P < 0.001 at 2 weeks). K values during intravenous glucose tolerance tests performed at 2 weeks posttransplant were −2.89 ± 0.19 in the L363,586-treated dogs and −1.87 ± 0.35 in the untreated dogs, a significant ( P < 0.05) difference. We conclude that L363,586 inhibits the exocrine secretion of pancreas graft, and may help graft pancreatitis resolve earlier in the immediate postpancreas transplant period, as evidenced by the more rapid decline of amylase in the treated than in the control dogs. The higher K values in the treated animals suggest that reduction of posttransplant pancreatitis by suppression of exocrine function might also help to preserve endocrine function. Thus L363,586 appears to inhibit exocrine function of pancreas grafts without an adverse, and perhaps a salutary effect, on endocrine function.

The effect of electrical current on the healing of mandibular freeze-dried bone allografts in dogs

Low levels of electrical current have been shown to affect the process of osseous repair. This study experimentally evaluated the effect of electrical stimulation on the healing of freeze-dried mandibular allogeneic bone grafts in dogs. Healing of the grafts was monitored by sequential submento-occlusal radiographs and radionuclide bone imaging at two, four, six, and eight weeks after grafting. Results indicated no significant difference in the osseous repair of stimulated and nonstimulated freeze-dried allogeneic bone grafts.

Quantification of Deposition of Neutrophilic Granulocytes on Vascular Grafts in Dogs With 111In-Labeled Granulocytes

A new radioisotopic technique has been developed for quantification of deposition of neutrophilic granulocytes on vascular grafts. Nine healthy mongrel dogs underwent bilateral femoral artery resection and reconstruction with grafts of femoral vein and Gore-Tex. Pure granulocytes that had been separated from whole blood by centrifugal elutriation were labeled with 111In-tropolone in plasma. The granulocyte harvesting efficiency was 25 +/- 12%, and the labeling efficiency was 87 +/- 7%. Three hours after injection of labeled granulocytes and 2 hours after reperfusion, the grafts were harvested and cut into several segments for study of areas of anastomoses and midsections. On the basis of the radioactivity in the blood and in anastomotic and graft sections, the area of graft sections, and the neutrophilic granulocyte and differential leukocyte counts, the number of neutrophilic granulocytes adherent to a unit area and the total number of neutrophilic granulocytes on graft sections were calculated. These quantifications of the deposition of neutrophilic granulocytes indicated that the midsections of Gore-Tex grafts retained more neutrophilic granulocytes than did the midsections of vein grafts. Although the anastomotic areas retained more neutrophilic granulocytes than did the midsections of vein grafts, the opposite finding prevailed for the Gore-Tex grafts. A major fraction of neutrophilic granulocytes on Gore-Tex grafts was incorporated into thrombus. Semiquantitative information obtained by scintigraphy of the deposition of neutrophilic granulocytes on vascular grafts also confirmed this observation.

Successful autotransplantation of cryopreserved dispersed pancreatic grafts in dogs.

The University of Newcastle upon Tyne Department of Surgery Royal Victoria Infirmary Newcastle upon Tyne NE1 4LP, England

Quantification of platelet retention in aortocoronary femoral vein bypass graft in dogs treated with dipyridamole and aspirin.

Autologous femoral vein segments were implanted as aortocoronary bypass grafts in 50 dogs, 25 of which were treated with dipyridamole and aspirin to inhibit platelet deposition and 25 that were not. Autologous platelets labeled with indium-111 were injected into some dogs 48 hr before they were killed on the first day after surgery; other dogs were injected 24 hr before they were killed (3, 7, 30, and 90 days after surgery). Radioactivity on the grafts and on control specimens of contralateral femoral veins was converted to quantification of platelets adhering to the vessel wall (platelets/cm2). The treated group had fewer graft platelets per square centimeter than the untreated group on postoperative days 3, 7 (p less than .01), and 30 (p less than .05). Graft and control vein platelets per square centimeter were nearly equal by day 90. Comparison of graft and control specimens by scanning electron microscopy nearly equal by day 90. Comparison of graft and control specimens by scanning electron microscopy revealed deendothelialization at 1 and 7 days after grafting and reendothelialization at 30 and 90 days. The data suggest that indefinite prolongation of therapy to inhibit platelet deposition after bypass grafting may be unnecessary (although other atherosclerotic vessels may benefit from therapy).

Replacement of Segments of Excised Ureters by Omentally Wrapped Partial Thickness Bladder Grafts in Dogs. A Preliminary Report

Replacement of Segments of Excised Ureters by Omentally Wrapped Partial Thickness Bladder Grafts in Dogs. A Preliminary Report

Replacement of segments of excised ureters by omentally wrapped partial thickness bladder grafts in dogs. A preliminary report.

Summary— The development of a 2-stage procedure, using omentally wrapped partial thickness bladder grafts, to replace excised lengths of ureters in dogs is described. The results of morphological and radiological assessments are reported and discussed.

Prostacycin production by arterialized autogenous venous grafts in dogs

Arteries are capable of producing significantly larger quantities of protacyclin than are veins. To test the hypothesis, whether prostacyclin production by the vessel wall is related to blood pressure and flow, we measured the amounts of PGI 2 released and synthesized by venous segments transplanted for 6 weeks into the arterial circulation. These results were compared with the production of prostacyclin by normal veins and arteries. In 20 dogs a segment of jugular vein was interposed into the carotid system; a sham dissection was done on the opposite side. “Arterialized” vein grafts showed prominent intima lined by endothelium, medial smooth muscle cell proliferation and fibrotic proliferation in adventitia. Spontaneous and arachidonic acid- stimulated prostacyclin production (measured by radioimmunoassay for 6-keto-PGF 1α) was not significantly different between arterialized venous autografts and jugular veins. Significantly larger amounts of prostacyclin were synthesized by the carotid artery. Thus, histologic changes and rheologic effects occurring in vein grafts transposed to the arterial site do not affect prostacyclin production.

Gore-Tex (polytetrafluoroethylene) in canine coronary artery bypass

Because of the occasional need for a prosthesis in coronary artery operations, we investigated the potential use of microporous polytetrofluoroethylene (PTFE) with and without antiplatelet drugs as an aorta-coronary bypass graft in 43 dogs. In 13 animals without antiplatelet drugs, no grafts were patent at 1 month. When antiplatelet drugs were used (25 dogs), the 1 month patency rate increased to 64%. The addition of antibiotic treatment 1 month patency rate to 80%. The 6 month patency rate in dogs treated with antiplatelet drugs, preoperative bowel preparation, and systemic antibiotics was 60%. Our data indicate that microporous PTFE grafts used as coronary artery bypass grafts in dogs can be maintained patent for at least 6 months when the animals are treated with antiplatelet drugs.

Effects of autogenous cancellous bone on healing of homogenous cortical bone grafts.

ABSTRACTA comparative clinical and histological study was made of the effects of autogenous cancellous grafts on the rate of healing of homogenous cortical bone grafts in dogs: their right foreleg received homogenous bone grafts and their left foreleg received pre‐drilled homogenous bone grafts filled with autogenous cancellous bone. Histologically, the use of homogenous cortical grafts with pre‐drilled holes and autogenous cancellous bone appeared to accelerate reorganization and development of these grafts. This was seen particularly 1–2 months post‐operatively and at nine months when the graft in the left leg was made up of spongy bone marrow; whereas the right leg graft still contained compact dead bone and the marrow was filled with fibrous tissue.

Platelet serotonin changes in dogs with prosthetic aortic grafts

The purpose of this study was to elucidate the mechanisms underlying the striking reduction in platelet serotonin found after placement of prosthetic aortic grafts in dogs. Changes in platelet serotonin paralleled changes in platelet survival time. Both were reduced after graft placement, remained depressed for up to a year, and then returned to normal. In vivo release of serotonin was assessed by labeling autologous platelets with 51Cr (a nonreleasable, cytoplasmic label) and 14C-serotonin (a releasable, storage granule label). In dogs with grafts, 14C-serotonin persisted in the circulation beyond the life span of 51Cr-labeled platelets. The ratio of platelet 14C/ 51Cr activity over 5 days following infusion of double-labeled platelets markedly increased. These data indicated in vivo release and reutilization of labeled serotonin. In vitro platelet uptake of 14C-serotonin was assessed in separate experiments and was found to be depressed following graft placement. We conclude that the reduction in platelet serotonin stems from platelet interaction with aortic prostheses. Platelets adhere to the prosthetic surface, release serotonin, and recirculate. Reutilization of released serotonin occurs but may be limited by depressed platelet uptake. The net effect is a reduction in platelet serotonin. These findings support our view that platelet interaction with prosthetic surfaces is, in large measure, a reversible phenomenon, with platelets reentering the circulation in an altered state.

Noninvasive radioisotopic technique for detection of platelet deposition in coronary artery bypass grafts in dogs and its reduction with platelet inhibitors.

At 8 and 32 hours after saphenous vein bypass graft surgery in six dogs, in vivo images of the graft were obtained with a gamma camera after intravenous injection, 2 hours postoperatively of autologous platelets labeled with indium-111. Platelet deposition in the grafts could be imaged in vivo from the scintiphotos. In vitro images of the excised heart showed saphenous vein graft uptake confirming the in vivo image. In vitro determination of radioactivity in the graft averaged 17 +/- 14 times greater than in blood and 33 +/- 26 times greater than in the lung. Under identical conditions, in eight dogs treated with dipyridamole (55 mg/day) plus aspirin (325 mg/day), the grafts appeared to have considerably less platelet deposition as estimated by imaging. In vitro determination of radioactivity in the graft averaged 5 +/- 2 times greater than in blood and 8 +/- 4 times greater than in the lung (p less than 0.01). This noninvasive technique may be a promising tool for a better understanding of the role played by platelets in the process of occlusion of saphenous vein bypass grafts in man and its prevention with platelet inhibotors.

Velocity distribution and intimal proliferation in autologous vein grafts in dogs.

Velocity distribution and intimal proliferation in autologous vein grafts in dogs.