Cadaver donation: structural integrity of pulmonary homografts harvested 48 h post mortem in the juvenile ovine model.

Cryopreserved pulmonary homograft (CPH) implantation remains the gold standard for reconstruction of the right ventricular outflow tract (RVOT). Harvesting homografts < 24-h post mortem is the international norm, thereby largely excluding cadaveric donors. This study examines the structural integrity and stability of ovine pulmonary homografts harvested after a 48-h post mortem period, cryopreserved and then implanted for up to 180 days. Fifteen ovine pulmonary homografts were harvested 48-h post mortem and cryopreserved. Five CPH served as a control group (group 1; n = 5). CPH were implanted in the RVOT of juvenile sheep and explanted after 14 days (group 2; n = 5) and 180 days (group 3; n = 5). Leaflet integrity was evaluated by strength analysis, using tensile strength (TS), Young's modulus (YM) and thermal denaturation temperature (Td), and morphology, including haematoxylin and eosin (H&E), Picrosirius red staining, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and von Kossa stains. Echocardiography confirmed normal function in all implants. In explants, no reduction in TS, YM or Td could be demonstrated and H&E showed mostly acellular leaflet tissue with no difference on Picrosirius red. TEM demonstrated consistent collagen disruption after cryopreservation in all three groups, with no morphological deterioration during the study period. von Kossa stains showed mild calcification in group 3. No deterioration of structural integrity could be demonstrated using strength or morphological evaluations between the controls and implant groups over the study period. Extending the post mortem harvesting time of homografts beyond 24 h did not appear to negatively affect the long-term performance of such transplanted valves in this study.

Anastomotic Urethroplasty with Double Layer Continuous Running Suture Re-Anastomosis Versus Interrupted Suture Re-Anastomosis for Infective Bulbar Urethral Strictures: A Prospective Randomised Trial.

INTRODUCTION: The objective of this study was to compare a double-layer running suture re-anastomosis urethral stricture repair with early catheter removal to the conventional interrupted suture re-anastomosis after excision of a bulbar urethral stricture. METHODS: A consecutive series of patients with bulbar urethral stricture were enrolled in the study. The patients were randomized into two groups according to an odd/even serial number distribution. Patients' medical records were analyzed for demographics, stricture characteristics, and lower urinary tract obstructive symptoms. The outcomes were based on the presence/absence of obstructive voiding symptoms, and retrograde urethrography (RGU) performed on the first post-operative day in Group 1 and in both groups (Groups 1 and 2) at six weeks after surgery. Flexible urethroscopy was only performed on specific cases where RGU was unclear both pre- and post-operatively or when clinical recurrence was suspected. The minimum follow-up (FU) was 18 months. Success was defined as no need for subsequent dilatation, direct vision internal urethrotomy (DVIU), or urethroplasty. RESULTS: A total of thirty-six patients with a mean age of 45 years (range 20 to 69 years) with bulbar urethral stricture were included in this study. Group 1 and Group 2 included 19 and 17 patients, respectively. Two patients were lost during randomization and subsequently to FU. The average stricture lengths were comparable between the two groups according to the retrograde urethrogram: 1.20 cm (range 0.6 to 2) in Group 1 and 1.27 cm (range 0.5 to 2.4) in Group 2, respectively (p = 0.631). The success rate for Group 1 was 90% after a mean follow-up of thirty-six months (range 20 to 40), which was clinically significant compared to the 71% in Group 2 after a mean FU of thirty-three months (range 19 to 40; p = 0.0218; 95% CI: 0.462-41.5766). CONCLUSIONS: Anastomotic urethroplasty (AR) performed with a double layer re-anastomosis had a cure rate comparable to the conventional anastomosis with interrupted sutures after a follow-up of eighteen months and longer. The urethral catheter can be safely removed within twenty-four hours after the excision of stricture and double-layer re-anastomosis.

Hemostatic effect of activated factor VII without promotion of thrombus growth in melagatran-anticoagulated primates.

INTRODUCTION: Pharmacological enhancement of coagulation using activated prothrombin complex concentrate (APCC) or activated factor VII (FVIIa) might be useful hemostatic approaches to bleeding emergencies during anticoagulant therapy. However, any such intervention should not increase thrombotic risk. We therefore investigated their hemostatic and prothrombotic potential during propagation of large arterial-type thrombin in anticoagulated baboons. MATERIALS AND METHODS: High dose melagatran, a competitive inhibitor of thrombin (0.6 mg/kg/h), or inactivated FVIIa (FVIIai), a competitive inhibitor of FVIIa (2 mg/kg) were used for anticoagulation. APCC or FVIIa were administered to melagatran-anticoagulated animals only. Primary hemostasis was assessed as template bleeding time (BT). Thrombus formation was quantified as fibrin deposition (FD) and platelet deposition (PLD) in synthetic vascular grafts that were deployed for 40 min into arteriovenous shunts. RESULTS: Melagatran (n=11) prolonged BT to 279% (95% CI +/-140%; P<0.019), reduced FD to 33% [+/-8%; P<0.001]; and PLD to 39% [+/-11%; P<0.001] of untreated controls. FVIIai (n=3) prolonged BT (222% [+/-51%; P<0.010]) without inhibiting thrombus propagation. APCC (n=10) reduced the antithrombotic effect of melagatran (FD 52% [+/-9%; P<0.002], PLD 61% [+/-17%; P=0.028] versus melagatran alone) at a dose (250 U/kg) that had no effect on the BT (327% [+/-150%; P=0.607]. Meanwhile, FVIIa (n=12) normalized the BT to 115% (+/-32%; P<0.05) at a dose (270 microg/kg) that was not yet prothrombotic (FD 26% [+/-4%; P<0.001], PLD 39% [+/-9%; P=0.970]). CONCLUSION: Administration of FVIIa during antithrombotic treatment with direct thrombin inhibitors might support hemostasis before promoting the intraluminal expansion of thrombi.

A radiological evaluation of alveolar bone regeneration between the left and right mandibles and maxillae of the Chacma baboon.

There is a lack of information in comparing the healing rate between the left and right sides of the maxilla and mandible. Osteogenesis of alveolar bone was evaluated with digital radiology by comparing differences in bone density (BD) at different time points within the left and right maxilla and mandible. Alveolar bone defects were created in five healthy Chacma baboons. Standardised x-ray images were acquired over time and the densities of the selected trauma areas were measured pre-operatively, post-operatively and at 3 and 6 weeks post-operatively. Differences in densities were statistically tested. There was no significant difference when the grey scale averages of the combined first and fourth quadrants (right side) and combined second and third quadrants (left side) were compared pre-operatively (t = 0.70), immediately post-operatively (t = 0.34), 3 weeks post-operatively (t = 0.40) and 6 weeks post-operatively (t = 0.66). There was also no significant difference between the values for the first and second quadrants (maxilla) pre-operatively (t = 0.37), immediately post-operatively (t = 0.30), 3 weeks post-operatively (t = 0.30) and 6 weeks post-operatively (t = 0.38); the third and fourth quadrants (mandible) were also not significantly different pre-operatively (t = 0.29), immediately post-operatively (t = 0.69), 3 weeks post-operatively (t = 0.07) and 6 weeks postoperatively (t = 0.06). However, the results showed an increased predisposition of the right side to regenerate faster than the left side and indicated sufficient information to investigate the effect of laterality and preferred side of mastication on the rate of healing and alveolar BD in the maxilla and mandible.

In vivo platelet redistribution and acute transient thrombocytopenia after eptifibatide injection in baboons.

BACKGROUND: The occurrence of thrombocytopenia has been reported during clinical eptifibatide (Integrilin) therapy, but the exact mechanism is not yet established to explain the varied duration and severity of thrombocytopenia associated with glycoprotein (GP) IIb/IIIa inhibitors. We assessed the redistribution of platelets in juvenile baboons during acute transient thrombocytopenia that was observed after eptifibatide injection. METHODS: Eptifibatide was administered intravenously to eight baboons by infusion at 20 microg/kg/min or a bolus injection of 10 mg. Platelet distribution was measured with a gamma scintillation camera using 111In-labeled autologous platelets. Platelet function and GP IIb/IIIa receptor inhibition were evaluated using the Plateletworks system. The effects of pretreatment with abciximab (0.4 mg/kg) or human immunoglobulin concentrate (0.75 g/kg) were also investigated. RESULTS: Eptifibatide, administered as an infusion or a bolus, caused transient thrombocytopenia with uptake of platelets predominantly by the liver. The recovery of platelet aggregation was associated with the re-entry of platelets from the liver into the systemic circulation. Pretreatment with either abciximab (0.4 mg/kg) or human intravenous immunoglobulin (IVIG, 0.75 g/kg) attenuated eptifibatide-induced thrombocytopenia and the hepatic uptake of radiolabeled platelets. CONCLUSION: Acute thrombocytopenia after eptifibatide injection was caused by the transient redistribution of platelets to the liver. Attenuation of the decrease in platelet count and hepatic sequestration by abciximab and IVIG suggests that thrombocytopenia may have been caused by ligand-induced binding site antigen induction and recognition by the reticuloendothelial system.

Inhibition of platelet glycoprotein Ib, glycoprotein IIb/IIIa, or both by monoclonal antibodies prevents arterial thrombosis in baboons.

The antithrombotic efficacy of the monoclonal antibodies 6B4-Fab and MA-16N7C2 against platelet glycoprotein (GP) Ib and GP IIb/IIIa, respectively, on acute platelet-mediated thrombosis was evaluated in a baboon model of femoral artery stenosis, which is a modification of the original Folts model: platelet thrombi form on the injured stenosed artery, producing cyclic flow reductions (CFRs). A dose of 0.6 mg/kg 6B4-Fab significantly reduced the CFRs by 59 +/- 15%, whereas 2 mg/kg 6B4-Fab completely abolished the CFRs without prolongation of the bleeding time. MA-16N7C2 inhibited CFRs by 43 +/- 8% at a dose of 0.1 mg/kg and abolished the CFRs at a dose of 0.3 mg/kg but with a significant prolongation of the bleeding time. Finally, the combination of 0.6 mg/kg 6B4-Fab and 0.1 mg/kg MA-16N7C2 fully prevented the CFRs without prolongation of the bleeding time. The present study demonstrates that the inhibition of platelet GP Ib function by 6B4-Fab is a powerful intervention to prevent platelet thrombus formation in injured arteries without prolongation of the bleeding time; the latter is in contrast to the result after the inhibition of GP IIb/IIIa. Moreover, we demonstrate that combining a GP Ib blocker with a GP IIb/IIIa blocker can achieve a strong antithrombotic effect without increasing the bleeding time. This provides new information that will be beneficial in designing clinical therapeutic approaches.

In vitro effect of a thrombin inhibition peptide selected by phage display technology.

A repeated selection of phages from a cyclic heptapeptide phage display library resulted in the enrichment of phages that bind to human alpha-thrombin. One clone of the binding phages that competed with PPACK for binding to thrombin and that had the best binding characteristics was chosen. The amino acid sequence of the peptide displayed on this phage was determined and a peptide with the sequence, Cys-Asn-Arg-Pro-Phe-Ile-Pro-Thr-Cys was synthesised. This peptide, thrombin-inhibiting peptide (TIP), is a full competitive inhibitor of thrombin with an inhibition constant (K(i)) of 0.4974 mM. It lengthened the thrombin time and inhibited thrombin-induced platelet activation and the platelet release reaction, both in a dose-dependent manner. It also reduced platelet adhesion onto a human microvascular endothelial matrix in the parallel plate flow chamber under both arterial and venous shear conditions. Thus, we have selected and synthesised a cyclic heptapeptide that competes with PPACK to bind to thrombin and that can be developed as a direct antithrombin.

Ozone treatment of alveolar bone in the cape chacma baboon does not enhance healing following trauma.

In the international literature, the role of Ozone (O3) in the advancement in alveolar bone healing in the absence of bone pathology was not tested before. The purpose of this study was to evaluate alveolar bone regeneration after a bone defect was created and treated with a single topical administration of O3. Alveolar bone defects were created on five healthy chacma baboons. One side of the maxilla and mandible was topically treated with a single treatment of an O3/O2 mixture (3,5-4 % O3), while the opposite sides were not treated and thus served as control. Regeneration was measured radiologically, using a standardized gray scale, as the increase in bone density in the treatment area at 3 and 6 weeks post-operative and was statistically analyzed using multivariate analysis of variance (MANOVA). There were no significant differences in densities observed between the O3/O2 mixture treatment and the control (p > 0.05). A single O3 treatment did not increase alveolar bone healing over a 3- and 6-week period in the mandible and the maxilla.

A comparison of mandibular and maxillary alveolar osteogenesis over six weeks: a radiological examination.

INTRODUCTION: Insufficient information exists on comparing radiological differences in bone density of the regeneration rate in the alveolar bone of the maxilla and mandible following the creation of similar defects in both. METHODS: Alveolar bone defects were created from five healthy Chacma baboons. Standardized x-ray images were acquired over time and the densities of the selected defect areas were measured pre-operatively, directly post-operatively and at three- and six weeks post-operatively. Differences in densities were statistically tested using ANOVA. RESULTS: The maxilla was significantly more radiologically dense (p = 0.026) than the mandible pre- operatively. No differences were obtained between the maxilla and mandible directly postoperatively and three- and six weeks post-operatively respectively; i.e. densities were not significantly different at the different time points after the defects had been created (three weeks: t = 1.08, p = 0.30; six weeks: t = 1.35, p = 0.19; three to six weeks: t = 1.20, p =0.25). The increase in density in the mandible was 106% (8.9 ± 7.6%/time versus 4.3 ± 2.7%/time) over three weeks, 28% (15.0 ± 8.1%/time versus 11.7 ± 8.0%/time) over six weeks and 56% (12.5 ± 9.7%/time versus 8.0 ± 6.9%/time) over three-to-six weeks and was higher than in the maxilla over the same intervals. CONCLUSIONS: Radiological examination with its standardized gray-scale analysis can be used to determine the difference in bone density of the maxilla and mandible. Although not statistically significant, the mandible healed at a faster rate than the maxilla, especially observed during the first three weeks after the defects were created.

Inhibition of the von Willebrand (VWF)-collagen interaction by an antihuman VWF monoclonal antibody results in abolition of in vivo arterial platelet thrombus formation in baboons.

The interaction between collagen, von Willebrand factor (VWF), and glycoprotein Ib is the first step in hemostasis and thrombosis especially under high shear conditions. We studied the inhibition of the VWF-collagen interaction by using an antihuman VWF monoclonal antibody 82D6A3 to prevent arterial thrombosis in baboons to develop a new kind of antithrombotic strategy and determine for the first time experimental in vivo data concerning the importance of the collagen-VWF interaction. We used a modified Folts model to study the antithrombotic efficacy of 82D6A3, where cyclic flow reductions (CFRs) were measured in the femoral artery. Administering a dose of 100, 300, and 600 microg/kg resulted in a 58.3%, 100%, and 100% reduction in the CFRs, respectively. When 100 microg/kg 82D6A3 was infused into the baboons, 80% of VWF-A3 domain was occupied, corresponding to 30% to 36% ex vivo inhibition of VWF binding to collagen, with no prolongation of the bleeding time. The bleeding time was also not significantly prolonged when the CFRs were abolished at doses of 300 microg/kg and 600 microg/kg. At these doses 100% of VWF was occupied by the antibody and 100% ex vivo inhibition of the VWF-collagen binding was observed. 82D6A3 has a high affinity for VWF; after 48 hours still 68% VWF (300 microg/kg) was occupied with a pharmacologic effect up to 5 hours after administration (80%-100% occupancy). In conclusion, these results clearly indicate that the VWF-collagen interaction is important in vivo in thrombosis under high shear conditions and thus might be a new target for preventing arterial thrombosis.