Biomedical subjects

Brian C Cooley

Publications and source records attributed to Brian C Cooley.

11 recordsLinked to original sources

PubMed2006

Posterolateral intertransverse lumbar fusion in a mouse model: surgical anatomy and operative technique.

BACKGROUND CONTEXT: Animal models are frequently used for studying the effect of bone graft substitutes or allogeneic materials on osterolateral lumbar fusion. Transgenic technology in the mouse provides a unique opportunity to further understand the biology of spine fusion. PURPOSE: To describe pertinent lumbar spine anatomy and formulate a surgical protocol for posterolateral fusion in the mouse model. STUDY DESIGN: Diagnostic model: development of an animal model for biologic evaluation of posterolateral spine fusion. METHOD: Ten mice were killed to study relevant lumbar spine anatomy and develop a protocol for lumbar spine fusion. The L4-L6 fusion protocol was validated in 46 mice for ease of exposure, preparation of the posterolateral fusion bed, introduction of bone inductive agents, and perioperative care. RESULTS: Anatomy and surgical technique for posterolateral intertransverse lumbar fusion in the mouse model are described. A paraspinal approach allows exposure of the transverse processes, decortication, and graft placement at the L4-L6 intertransverse fusion site. Decortication alone did not result in fusion, whereas the use of bone graft resulted in satisfactory fusion rates. Perioperative morbidity and mortality rates were low. CONCLUSION: The mouse posterolateral lumbar spine fusion model is reproducible, inexpensive, and has low complication rates. Knowledge of the relevant anatomy and adherence to a well-defined surgical protocol provides a reliable and reproducible experimental spine fusion model.

Animals↗

PubMed2006

Increased venous versus arterial thrombosis in the Factor V Leiden mouse.

BACKGROUND: Deep vein thrombosis (DVT) occurs with high prevalence in association with the Factor V Leiden (R506Q) mutation, whereas most evidence suggests no correlation with clinical arterial thrombosis. OBJECTIVE: This study compared arterial to venous thrombosis in the mutationally analogous Factor V Leiden mouse. METHODS: Three separate vascular thrombosis models were evaluated in Fv(+/+) (wild-type), Fv(Q/+) (heterozygous) and Fv(Q/Q) (homozygous) Factor V Leiden mice. RESULTS: In a FeCl(3)-induced arterial thrombosis model, no statistical differences among the three genotypes were found in the time to thrombotic occlusion. In contrast, Fv(Q/+) and Fv(Q/Q) mice demonstrated larger femoral vein thrombi at 30 and 60 min compared to wild-types, with Fv(Q/Q) mice having statistically larger thrombi than both wild-type and Fv(Q/+) mice at 10 and 60 min and 24 h (p<0.05). In a model of thrombotic occlusion following arterial and venous anastomotic repair, both Fv(Q/+) and Fv(Q/Q) mice had higher rates of venous thrombosis than wild-types, but only Fv(Q/Q) homozygotes showed a statistically greater arterial occlusion rate than wild-types. CONCLUSION: The Factor V Leiden mouse demonstrated a greater propensity for venous vs. arterial thrombosis, paralleling clinical epidemiologic findings and supporting its use for research on deep vein thrombosis.

Amino Acid Substitution↗

PubMed2006

Factor VIII ectopically targeted to platelets is therapeutic in hemophilia A with high-titer inhibitory antibodies.

Inhibitory immune response to exogenously infused factor VIII (FVIII) is a major complication in the treatment of hemophilia A. Generation of such inhibitors has the potential to disrupt gene therapy for hemophilia A. We explore what we believe to be a novel approach to overcome this shortcoming. Human B-domain-deleted FVIII (hBDDFVIII) was expressed under the control of the platelet-specific alphaIIb promoter in platelets of hemophilic (FVIIInull) mice to create 2bF8trans mice. The FVIII transgene product was stored in platelets and released at the site of platelet activation. In spite of the lack of FVIII in the plasma of 2bF8trans mice, the bleeding phenotype of FVIIInull mice was corrected. More importantly, the bleeding phenotype was corrected in the presence of high inhibitory antibody titers introduced into the mice by infusion or by spleen cell transfer from recombinant hBDDFVIII-immunized mice. Our results demonstrate that this approach to the targeted expression of FVIII in platelets has the potential to correct hemophilia A, even in the presence of inhibitory immune responses to infused FVIII.

Animals↗

PubMed2005

Long-term BMP-2-induced bone formation in rat island and free flaps.

Ectopic osteoinduction by exogenous bone morphogenetic proteins (BMPs) is rapid but heretofore characterized as transient. A rat model of carrier-free recombinant human BMP-2 intramuscular implantation was used, followed by creation of either an island flap or transplantation of a free flap. BMP-2 injection into an unaltered gastrocnemius, thigh adductor, or cutaneous trunci (thoracic wall) muscle site led to bone resorption at 4 weeks. In contrast, creation of an island or free flap of the muscle/injection site caused the newly formed ossicle to maintain its bony composition with active osteoblastic presence, from 3-8 weeks. Muscle denervation or sectioning of the Achilles tendon (for gastrocnemius injections) did not prevent bone resorption at 4 weeks. There was little osteoclastic activity within de novo bone sites of island- and free flap-injected muscles at 4 and 8 weeks. These data demonstrate that simple injection of BMP-2 into a surgically isolated flap site results in the prolonged presence of de novo bone. These findings suggest that BMP-injected island or free muscle flaps may be used to generate new bone for reconstruction of a bony defect.

Animals↗

PubMed2005

Model of murine interpositional vein grafting.

A new murine model is presented for interpositional vein grafting into an artery. In ICR (outbred) mice, the femoral vein or a branch of the jugular vein was harvested and placed into a femoral artery defect, using standard microvascular techniques to achieve end-to-end anastomoses with 11-0 nylon suture. The technique requires a high level of microsurgical experience and competence. Success rates (vessel patency) were higher with moderate systemic heparinization (200 units/kg body weight, single i.v. bolus). Vein grafts were successfully transplanted between syngenic C57Bl/6J mice, with patency demonstrated from 1 day to 3 months postoperatively. The model is applicable to studies of vein graft stenosis using murine transgenic/knockout models.

Anastomosis, Surgical↗

PubMed2005

A prothrombotic phenotype in the Copenhagen rat strain.

INTRODUCTION: Experimental and epidemiologic studies have identified several potential genetic components for increased thrombotic risk. Studies of thrombosis often use rat models without considering the effect of strain differences on thrombotic propensity. MATERIALS AND METHODS: A comparison of in vivo thrombotic occlusion after small-vessel anastomosis was made between age/weight-matched male Copenhagen and Lewis rats. RESULTS: One-day thrombotic occlusion rates were significantly higher in Copenhagen arteries (67%) and veins (100%) compared to Lewis arteries (8%) and veins (50%), respectively. Single-bolus intravenous heparin (150 units/kg body weight) had a slight effect on reducing occlusion rates in Copenhagen rats (50% and 67% for arteries and veins, respectively), while occlusion was totally prevented by heparin in both vessel types of Lewis rats (0% occlusion). In vitro assays for platelet aggregation and coagulation revealed no apparent differences between these two rats strains, although AT-III levels were slightly higher in Copenhagen rats, contrary to the prothrombotic state. CONCLUSIONS: These findings indicate a profound prothrombotic tendency in the Copenhagen rat strain and support a broader investigation of the genetic basis of this thrombotic potential.

Anastomosis, Surgical↗

PubMed2005

A murine model of deep vein thrombosis: characterization and validation in transgenic mice.

Deep vein thrombosis (DVT) occurs with high prevalence in association with a number of risk factors, including major surgery, trauma, obesity, bed rest (> 5 days), cancer, a previous history of DVT, and several predisposing prothrombotic mutations. A novel murine model of DVT was developed for applications to preclinical studies of transgenically constructed prothrombotic lines and evaluation of new antithrombotic therapies.A transient direct-current electrical injury was induced in the common femoral vein of adult C57BI/6 mice. A non-occlusive thrombus grew, peaking in size at 30 min, and regressing by 60 min, as revealed by histomorphometric volume reconstruction of the clot. Pre-heparinization greatly reduced clot formation at 10, 30, and 60 min (p < 0.01 versus non-heparinized). Homozygous FactorV Leiden mice (analogous to the clinical FactorV Leiden prothrombotic mutation) on a C57Bl/6 background had clot volumes more than twice those of wild-types at 30 min (0.121 +/- 0.018 mm3 vs. 0.052 +/- 0.008 mm3, respectively; p < 0.01). Scanning electron microscopy revealed a clot surface dominated by fibrin strands, in contrast to arterial thrombi which showed a platelet-dominated structure. This new model of DVT presents a quantifiable approach for evaluating thrombosis-related murine transgenic lines and for comparatively evaluating new pharmacologic approaches for prevention of DVT.

Animals↗

PubMed2004

Murine model of neointimal formation and stenosis in vein grafts.

OBJECTIVE: Previous studies have suggested that neointimal formation, a central cause of vein graft stenosis, has several potential cell sources. It was hypothesized that neointimal cells arise primarily from the cells of the vein graft. METHODS AND RESULTS: This study investigated vein graft neointimal cell origins using a model of vein-to-artery cross-transplantation between transgenic Rosa26 mice (constitutive expression of bacterial beta-galactosidase marker gene) and wild-type mice. Vein-originating cells survived and make a major contribution to neointimal formation within the vein graft, mostly adjacent to the lumen/endothelium, suggesting an intimate association with endothelial cells. Cross-transplantation of veins from thrombomodulin promoter-driven beta-galactosidase reporter transgenic mice to wild-type arteries demonstrated survival of vein graft endothelial cells. Neointimal thickening was greater at the proximal and, to a lesser extent, distal ends, in comparison to the middle of the graft. By contrast, arterial grafts had almost no neointimal formation throughout the graft. The relative neointimal wall thickness is much greater in this model compared with other murine and larger-species vein graft models, even showing near-occlusive stenosis of the perianastomotic region. CONCLUSIONS: Vein graft neointimal cells arise predominantly from vein-derived cells, suggesting clinical relevance of stenosis-inhibiting therapies directed at the vein graft.

Animals↗

PubMed2003

Cause-effect relation between hyperfibrinogenemia and vascular disease.

Elevated plasma levels of fibrinogen are associated with the presence of cardiovascular disease, but it is controversial whether elevated fibrinogen causally imparts an increased risk, and as such is a true modifier of cardiovascular disease, or is merely associated with disease. By investigating a transgenic mouse model of hyperfibrinogenemia, we show that elevated plasma fibrinogen concentration (1) elicits augmented fibrin deposition in specific organs, (2) interacts with an independent modifier of hemostatic activity to regulate fibrin turnover/deposition, (3) exacerbates neointimal hyperplasia in an experimental model of stasis-induced vascular remodeling, yet (4) may suppress thrombin generation in response to a procoagulant challenge. These findings provide direct experimental evidence that hyperfibrinogenemia is more than a by-product of cardiovascular disease and may function independently or interactively to modulate the severity and/or progression of vascular disease.

Animals↗

PubMed2003

Effect of exercise on microsurgical hand tremor.

This study investigated the effects of upper-body and aerobic/lower-body-only (nonupper-body) exercise on microsurgical hand tremor. Subjects were given a task of holding a microsurgical needle tip over a small target, with video-microscopic documentation immediately before and 0, 2, 4, 8, and 24 h after either upper-body or nonupper-body (aerobic) exercise. Tremor was quantified by the amount of time the needle was maintained within a 100 x 100-microm target zone and the number of times the needle extruded from the zone. Both upper-body and aerobic-only exercise groups had significant increases in tremor immediately after exercise (P < 0.02), with a return to baseline tremor 2 h after exercise in the aerobic group and only a slightly prolonged return to baseline (by 4 h) in the majority of upper-body exercise subjects. These findings demonstrate that microsurgical hand tremor increases following exercise, but returns to baseline within 4 h in the majority of individuals, particularly after aerobic-only workouts.

Exercise↗

PubMed2003

Genetic mapping and characterization of the bleeding disorder in the fawn-hooded hypertensive rat.

Release of platelet dense granule contents occurs in response to vascular injury, playing an important role in platelet aggregation and primary hemostasis. Abnormalities of the platelet dense granules results in a bleeding disorder of variable severity termed "storage pool defect" (SPD). We have examined the fawn-hooded hypertensive (FHH) rat as a model of SPD in order to genetically map the locus (Bd) responsible for prolonged bleeding. Platelet function assays of the FHH rat confirmed the presence of a platelet dense granule SPD. However electron microscopy and lysosomal enzyme assays indicated differences between the FHH rat and other rodent models of SPD. Genetic mapping through the use of congenic FHH rats localized the Bd locus to an approximately 1 cM region on rat chromosome 1. Through the use of comparative mapping between species and analysis of the initial draft of the rat genome assembly, six known and thirty-four putative genes were identified in the Bd locus. None of these genes have been previously implicated in platelet function. Therefore positional cloning of the gene responsible for the bleeding disorder in the FHH rat will lead to new insights in platelet physiology, with implications for diagnosis and management of hemostatic and thrombotic disorders.

Animals↗