Assessment of intravenous pbi-shRNA PDX1 nanoparticle (OFHIRNA-PDX1) in yucatan swine.

PDX1 (pancreatic and duodenal homeobox 1) is overexpressed in pancreatic cancer, and its reduction results in tumor regression. Bi-functional pbi-shRNA PDX1 nanoparticle (OFHIRNA-PDX1) utilizes the endogenous micro-RNA biogenesis pathway to effect cleavage- and non-cleavage-dependent degradation of PDX1 mRNA. We have shown that OFHIRNA-PDX1 reduces pancreatic tumor volume in xenograft models. Thus, we are now exploring biorelevant large animal safety of OFHIRNA-PDX1. Mini pigs were chosen as the biorelevant species based on the similarity of human and pig PDX1 target sequence. In the initial study, animals developed fever, lethargy, hyporexia and cutaneous hyperemia following administration of OFHIRNA-PDX1. Twenty-one days later, the same animals demonstrated less toxicity with a second OFHIRNA-PDX1 infusion in conjunction with a prophylactic regimen involving dexamethasone, diphenhydramine, Indocin and ranitidine. In a new group of animals, PDX1 protein (31 kDa) expression in the pancreas was significantly repressed at 48 and 72 h (85%, P=0.018 and 88%, P=0.013; respectively) following a single infusion of OFHIRNA-PDX1 but recovered to normal state within 7 days. In conclusion, a single intravenous infusion of OFHIRNA-PDX1 in conjunction with premedication in pigs was well tolerated and demonstrated significant PDX1 knockdown.

Multilayer vascular grafts based on collagen-mimetic proteins.

A major roadblock in the development of an off-the-shelf, small-caliber vascular graft is achieving rapid endothelialization of the conduit while minimizing the risk of thrombosis, intimal hyperplasia, and mechanical failure. To address this need, a collagen-mimetic protein derived from group A Streptococcus, Scl2.28 (Scl2), was conjugated into a poly(ethylene glycol) (PEG) hydrogel to generate bioactive hydrogels that bind to endothelial cells (ECs) and resist platelet adhesion. The PEG-Scl2 hydrogel was then reinforced with an electrospun polyurethane mesh to achieve suitable biomechanical properties. In the current study, initial evaluation of this multilayer design as a potential off-the-shelf graft was conducted. First, electrospinning parameters were varied to achieve composite burst pressure, compliance, and suture retention strength that matched reported values of saphenous vein autografts. Composite stability following drying, sterilization, and physiological conditioning under pulsatile flow was then demonstrated. Scl2 bioactivity was also maintained after drying and sterilization as indicated by EC adhesion and spreading. Evaluation of platelet adhesion, aggregation, and activation indicated that PEG-Scl2 hydrogels had minimal platelet interactions and thus appear to provide a thromboresistant blood contacting layer. Finally, evaluation of EC migration speed demonstrated that PEG-Scl2 hydrogels promoted higher migration speeds than PEG-collagen analogs and that migration speed was readily tuned by altering protein concentration. Collectively, these results indicate that this multilayer design warrants further investigation and may have the potential to improve on current synthetic options.

Biomechanics of the porcine basilar artery in hypertension.

Hypertension is a significant risk factor for diverse cerebrovascular diseases ranging from stroke to arteriovenous malformations and saccular aneurysms. Our increasing understanding of vascular mechanobiology reveals that changes in mechanical stimuli, such as increased blood pressure, alter basic cellular functions including the production and degradation of extracellular matrix as well as proliferation, migration, and apoptosis. Understanding changes in the biomechanical properties of the vascular wall is fundamental to correlating mechanobiological responses with the altered loads. In this paper, we present the first biomechanical data on a large cerebral artery in terms of the time of development of hypertension in maturity. Specifically, we report rapid changes in both the structural and the material stiffness of the passive basilar artery in a novel aortic-coarctation model of hypertension in the mini-pig. Histological measurements reveal associated increases in fibrillar collagens in the media and adventitia as well as increased smooth muscle in the media. That such dramatic changes occur within 2 weeks of the initiation of hypertension in maturity necessitates a detailed study of the early changes as well as the potential to reverse these changes at later times.

Collateral circulation in experimental coarctation of the aorta in minipigs: a possible association with hypertrophied vasa vasorum.

Experimental coarctation of the thoracic aorta was produced in 13 adult Yucatan minipigs by placing a gradually expanding "C-shaped" occluder around the aorta. The aortic constriction was standardized by measuring the blood pressure above the coarctation, with a mean arterial pressure of 165-170mmHg as the target. The pigs were humanely killed after 8 weeks of hypertension. No deaths were associated with constriction of the aorta, and neither rear limb weakness nor neurological dysfunction was noted. The lack of clinical signs in these animals suggested the development of an extensive collateral circulation. Collateral vessels, which were verified angiographically, included intercostal arteries, muscular intercostal arteries, and the internal thoracic artery. In two of the animals in which the thoracic aorta was completely occluded, revascularization also occurred via small arterial channels. Histologically, there was a marked increase in the number of vessels as well as significant hyperplasia and hypertrophy of smooth muscle of adventitial vasa vasorum. These findings support the hypothesis that collateralization of occluded thoracic aortas may be aided by hypertrophy of the vasa vasorum. To our knowledge, these vessels have not previously been shown convincingly by histopathological methods to revascularize occluded large arteries such as the aorta.

Complications common to ventricular assist device support are rare with 90 days of DeBakey VAD support in calves.

The DeBakey VAD is a miniaturized, electromagnetically driven axial flow pump intended for long-term ventricular assist. Safety and performance data from six calves implanted with the complete DeBakey VAD system are reported elsewhere; here we describe complications and necropsy findings for these same six animals, all of which survived 90 days. The study was conducted according to a uniform protocol, which included anticoagulation and antibiotic prophylaxis. Clinical complications tracked included bleeding, cardiovascular abnormalities (e.g., arrhythmias, tachycardia unrelated to pain, bradycardia), hemolysis, hepatic dysfunction, renal dysfunction, thromboembolism (neurologic or peripheral), or infection. Each adverse event was retrospectively categorized with regard to severity (mild, moderate, severe) and relationship to device. Clinical findings were confirmed by necropsy. There was no evidence of systemic infection, thromboembolism, hemolysis, or renal or hepatic dysfunction in these six animals during the study period. A single adverse event was noted in each of two of the calves. Both events were considered mild according to the predefined criteria. Bleeding related to the surgical implantation procedure and requiring reoperation occurred in one animal. The other animal had evidence of a superficial infection at the exit site of the cables on the left lateral thoracic wall; the infection did not extend into the thoracic cavity. Chronic, healed small renal infarct scars were present in several animals. Mild valvular endocardiosis was observed in two calves and mild fibroelastosis was present in the endocardium at the site of the inflow cannula in three calves; however, these lesions were not considered clinically significant. No other gross or histologic abnormalities were noted at necropsy. In conclusion, calves implanted with the complete DeBakey VAD for 90 days demonstrated few complications and had no significant necropsy findings. Complications common to ventricular assist device (VAD) support (i.e., hemolysis, infection, bleeding, thromboembolism) were rare during long-term support (90 days) with the DeBakey VAD.

Chylothorax in cats: is there a role for surgery?

Chylothorax is a complex disease with many identified underlying causes including cardiac disease, mediastinal masses, heartworm disease and trauma. Management of this disease should be directed at identifying the cause, if possible, and treating the underlying disorder. In cats with idiopathic chylothorax, medical management is recommended initially because the condition may resolve spontaneously. Owners should be made aware of the potential development of fibrosing pleuritis in affected cats. When medical management is impractical or unsuccessful, surgical intervention should be considered. Surgical options include mesenteric lymphangiography and thoracic duct ligation, pericardiectomy, omentalisation, passive pleuroperitoneal shunting, active pleuroperitoneal or pleurovenous shunting, and pleurodesis. Of these, only thoracic duct ligation and pericardiectomy are preferred by the author because, if successful, the result is complete resolution of the chylothorax, thereby reducing the risk of developing fibrosing pleuritis. Omentalisation may be beneficial in some animals as adjuvant therapy, but this procedure may still allow fibrosing pleuritis to occur. Until the aetiology of the effusion in cats with idiopathic chylothorax is understood, the treatment success rate will be less than ideal. Future research needs to be directed at determining the pathophysiologic mechanisms underlying this disease in cats.

Cooled-tip diode laser catheter for improved catheter ablation of ventricular tachycardia.

Catheter ablation for the treatment of arrhythmias has evolved dramatically over the past two decades. Researchers have investigated alternative energy sources and catheter constructs to improve the efficacy and safety of catheter ablation. This study tested the hypothesis that a new prototype cooled-tip laser catheter used with a low-power diode laser would improve catheter ablation of ventricular tachycardias. Four mongrel dogs underwent a median sternotomy. The cooled-tip laser catheter was advanced into the left ventricle via the left carotid artery and positioned adjacent to the endocardium. Laser powers of 3 and 4 W were delivered at four exposure times to select areas of the endocardium. During application of laser energy, room-temperature saline was circulated through the catheter. At necropsy the hearts were examined and fixed in formalin for histologic examination. Gross examination of the endocardial surfaces showed no indication of crater or thrombus formation. Cross-section of the lesions revealed sharply demarcated, circular-shaped areas of coagulative necrosis extending into the mid-myocardium. Areas of coagulative necrosis were identified within the myocardium extending into the mid-myocardium and occasionally the subepicardium. A sharp line of demarcation was observed between the lesions and the surrounding normal myocardium. The results of this study showed that we could use surface cooling during slow laser heating to create large subsurface lesions with characteristics appropriate for treatment of ventricular tachycardia and little to no surface damage. We believe our catheter system addresses many of the previous issues with laser-based approaches.

Long-term outcome of gonadectomy performed at an early age or traditional age in cats.

OBJECTIVE: To determine long-term results and complications of gonadectomy performed at an early age (prepubertal) or at the traditional age in cats. DESIGN: Cohort study. ANIMALS: 263 cats from animal shelters. PROCEDURE: Cats that underwent gonadectomy were allotted to 2 groups on the basis of estimated age at surgery (traditional age, > or = 24 weeks old; prepubertal, < 24 weeks old). Adoptive owner information was obtained from shelter records, and telephone interviews were conducted with owners to determine physical or behavioral problems observed in the cats after adoption. Follow-up information was obtained from attending veterinarians for cats with complex problems or when owners were uncertain regarding the exact nature of their cat's problem. RESULTS: Compared with traditional-age gonadectomy, prepubertal gonadectomy did not result in an increased incidence of infectious disease, behavioral problems, or problems associated with any body system during a median follow-up period of 37 months. Additionally, the rate of retention in the original adoptive household was the same for cats that underwent prepubertal gonadectomy as those that underwent traditional-age gonadectomy. CONCLUSIONS AND CLINICAL RELEVANCE: Prepubertal gonadectomy may be performed safely in cats without concern for increased incidence of physical or behavioral problems for at least a 3-year period after gonadectomy.

Tracheal collapse in a young boxer.

A four-month-old, female boxer developed severe inspiratory dyspnea three days after elective ear crop surgery. Radiographs confirmed the diagnosis of collapse of the distal cervical trachea. The puppy was treated with oxygen, aminophylline, and ampicillin, but required emergency tracheostomy to stent the collapsed region. Clinical signs resolved following application of five polypropylene total-ring prostheses, and the puppy continued to do well despite significant growth to maturity.

A study of aminolevulinic acid-induced protoporphyrin IX fluorescence kinetics in the canine oral cavity.

BACKGROUND AND OBJECTIVE: 5-Aminolevulinic acid-induced protoporphyrin IX is a promising photosensitizer that could enhance the spectroscopic contrast between normal and diseased oral tissues. Knowledge of the pharmacokinetics and effects on tissue type are important for diagnostic and therapeutic procedures. STUDY DESIGN/MATERIALS AND METHODS: Dogs randomly were administered five doses of 5-aminolevulinic acid: 5, 25, 50, 75, and 100 mg/kg. The fluorescence was recorded from buccal mucosa, gums, tongue, and facial skin using a fiberoptic probe connected to an optical multichannel analyzer. Blood samples were collected for hematologic and serum biochemical analysis. Pharmacokinetic parameters of interest were estimated using a compartmental model. RESULTS: Protoporphyrin fluorescence at all sites reached a peak in 2-6 hours, and returned to baseline in 24-31 hours, depending on the dose. Plasma protoporphyrin peaked earlier than oral tissues. CONCLUSION: The rate of synthesis of protoporphyrin, and its conversion to heme products are dose dependent. Different tissues have different pharmacokinetic response.

Thrombosis of the caudal vena cava presenting as an unusual cause of an abdominal mass and thrombocytopenia in a dog.

Thrombosis of the caudal vena cava in a dog secondary to metastatic neoplasia is described. The dog had a palpable abdominal mass and persistent thrombocytopenia due to a thrombosed caudal vena cava that was surgically removed. A few days after its removal, the dog died and neoplastic cells of neural crest origin were identified at the edge of the thrombus. Massive thrombosis can be an unusual cause of platelet consumption, leading to thrombocytopenia and disseminated intravascular coagulation. Deep vein thrombosis of the vena cava can occur in dogs and may mimic an abdominal mass. Multiple mechanisms may be involved in the development of venous thrombosis, including endothelial damage by neoplastic cells and the presence of a hypercoagulable state secondary to neoplasia. Extensive collateral circulation may allow removal of diseased vena cava.

The efficacy of mechanical abrasion and talc slurry as methods of pleurodesis in normal dogs.

OBJECTIVE: To determine the efficacy of mechanical abrasion and talc slurry as methods for pleurodesis in normal dogs. STUDY DESIGN: Experimental study. ANIMALS OR SAMPLE POPULATION: Ten normal beagle dogs. METHODS: Group I dogs had mechanical abrasion (MA) of the pulmonary and costal pleurae performed in one hemithorax with a dry gauze sponge with a median sternotomy approach. Group II dogs had 100 mL of a 1 g talc slurry (TS) administered into one hemithorax through a tube thoracostomy. Administration of the TS was visualized by using video thoracoscopy. All dogs were evaluated at 2, 10, 20, and 30 days postoperatively by means of thoracic radiography and ultrasonographic thoracic wall measurement. The dogs were euthanatized 30 days postoperatively and a gross necropsy was performed. Hemithoraces were assigned a pleurodesis score (0-4) and an obliteration grade (0-6). Tissues were collected for histopathologic examination of pulmonary pleura, costal pleura, and pleural adhesions. Pulmonary and costal pleurae were graded for the degree of fibrosis (0-4). RESULTS: Obliteration grade and costal pleural fibrosis score were significantly higher for the treated sides in the MA dogs compared with the TS dogs. MA Dogs: Mechanical abrasion dogs had pleurodesis, obliteration, and pleural fibrosis scores that were greater on the treated side than the untreated side, however, the differences were not statistically significant. Only two MA dogs had firm adhesion of the pulmonary pleura to the costal pleura in portions of the cranial and middle lung lobes in the treated hemithorax. Thoracic wall surface area covered with adhesions was 15% and 21% in each of these two dogs. The median pulmonary pleural fibrosis score of all MA dogs for the treated hemithorax was 3 compared to 0 on the untreated side. TS Dogs: There was no statistical difference for pleurodesis scores and obliteration grades between the treated and untreated sides. No dogs showed evidence of pulmonary to costal pleural adhesions. Histopathology showed talc crossover into the untreated side in all five dogs. Median pulmonary fibrosis score of the treated hemithorax was 1 compared with 0 on the untreated side. CONCLUSIONS: Neither method of pleurodesis produced sufficient pleural adhesions to obliterate the pleural space. It is possible that the degree of pulmonary pleural fibrosis present in MA dogs may be sufficient to limit air leakage from pulmonary blebs and bullae resulting in successful treatment of spontaneous pneumothorax.

Chronic survival of calves implanted with the DeBakey ventricular assist device.

The DeBakey ventricular assist device (VAD) is a miniaturized, electromagnetically driven axial flow pump capable of generating in excess of 10 L/min output. The VAD was evaluated in 19 calves during experiments designed to test iterative modifications in the system and to determine the safety of the DeBakey VAD for intermediate to long-term implant. Five of the animals died or were euthanized during the perioperative period (i.e., Days 1-5) due to complications associated with bleeding (n = 3), sudden cardiac arrest (n = 1), or pump occlusion due to a muscle remnant associated with coring (n = 1). The remaining 14 animals survived from 7-145 days. Ten of the 14 animals survived 30 or more days, and 2 animals survived 93 and 145 days before elective euthanasia. Pump function was evaluated in the 14 calves that survived beyond the perioperative period. Pump output at implantation averaged 3 L/min while output at 100 days (n = 2) averaged 4.22 L/min. The electrical current did not change across time during the study, indicating normal operation of the bearings. Pumps consumed less than 10.5 W of power for all support durations. Hemolysis did not occur; the average daily plasma free hemoglobin varied from 2.0 to 8.0 mg/dl. Evaluation of serum biochemical data showed that implantation of the DeBakey VAD in calves with normal hearts did not impair end organ function; BUN, creatinine, and total bilirubin varied minimally within the normal range. The white blood cell count of implanted animals remained within the normal range throughout the study.

Lymphangiosarcoma in a dog presenting with massive head and neck swelling.

A three-year-old, neutered male Chesapeake Bay retriever was presented for acute onset of severe, progressive swelling of the head, neck, and cranial trunk. Diffuse lymphangiosarcoma involving the superficial and deep dermis and subcutaneous tissue was observed on skin biopsies. Lymphangiosarcoma is a rarely reported tumor of the lymphatic system in dogs and cats. The importance of obtaining skin biopsies in animals with acute edema of unknown etiology is emphasized. Additionally, neoplasia should be considered as a potential diagnosis in a dog with an acute onset of edema.

Successful treatment of uterine torsion and fetal retention in a postparturient Great Pyrenees bitch with septic peritonitis and prothrombotic complications.

The treatment and favorable outcome of a bitch with uterine torsion and two retained fetuses are described. The condition was corrected surgically by ovariohysterectomy. Complications (i.e., septic shock, peritonitis, and hemostatic abnormalities) were managed with aggressive medical therapy. Torsion of the gravid uterus in dogs is a life-threatening condition which can have a successful outcome if medical complications encountered in the pre- and postoperative periods are treated quickly and effectively.

Evaluation of the Palmaz stent in the trachea and mainstem bronchi of normal dogs.

OBJECTIVE: This study evaluates the efficacy of the Palmaz balloon expandable intraluminal stent in the trachea and mainstem bronchi of normal dogs. STUDY DESIGN: Effects of the stent were evaluated by physical examination, thoracic radiography, respiratory tract fluoroscopy and endoscopy, tracheal diameter measurement, postmortem examination, and airway histomorphometry. ANIMALS OR SAMPLE POPULATION: Ten normal beagle dogs. METHODS: Stent size was estimated from thoracic radiographs in awake dogs. Group I dogs (n = 4) had two stents placed: one in the thoracic trachea (TT) plus a randomly chosen mainstem bronchus (MB). Group II dogs (n = 3) had stents placed in the MB (one stent), TT (one stent), and mid- or proximal cervical trachea (CT) (one or two stents). Three dogs were used as sham-operated controls (group III). Temperature, pulse, respiration, and cough were measured twice daily. Dogs were evaluated at 21 and 49 to 56 days after stent placement, euthanatized, and tissues were collected for histomorphometric analysis of stent integration and epithelial pathology. RESULTS: Mean tracheal diameters of awake (10.5 +/- 1.7 mm) and anesthetized dogs before stent implantation (13.9 +/- 2.0 mm) were significantly different (P < .01). Complications associated with stent placement included acute pulmonary edema (n = 2), stent migration (n = 7), stent collapse (n = 4 CT, 2 TT, and 1 MB), and positive tracheal culture (n = 10). Group II dogs coughed more at rest, exercise, and with tracheal palpation than dogs in other groups (P < .01). Group I dogs coughed more at rest than group III dogs (P < .01). Stent integration ranged from 0 to 91.3%. Squamous metaplasia and epithelial ulceration associated with stents ranged from 0 to 57.5% and 0 to 32.7%, respectively. CONCLUSIONS: Determination of stent size should be based on measurements taken on anesthetized dogs because use of inappropriately sized stents may promote stent migration, squamous metaplasia, and/or ulceration. Epithelialization over stent struts may occur if the stent is closely associated with tracheal epithelium. CLINICAL RELEVANCE: Palmaz stents do not appear to be appropriate for placement in the CT of dogs; however, with technical modifications, application in the TT and MB may be feasible.

Duodenal perforation in a cheetah (Acinonyx jubilatus).

An 11-yr-old female cheetah (Acinonyx jubilatus) from a privately owned breeding center for endangered species was referred for evaluation with a history of vomiting and depression of 10 days' duration. After anesthetic induction with tiletamine and zolazepam and anesthetic maintenance with isoflurane, a complete diagnostic workup was performed, including hematology, serum chemistry, and radiography. The clinical diagnosis was septic suppurative inflammation and hemorrhage in the abdomen, consistent with perforation or rupture of the gastrointestinal tract. An exploratory laparotomy showed a perforated duodenal ulcer, which was resected. Subsequent endoscopy revealed no further evidence of ulceration in the upper gastrointestinal tract. Biopsy of the ulcerated tissue collected from the duodenum revealed Gastrospirillum-like organisms. Histologic examination revealed widespread infiltration of lymphocytes and plasma cells into the lamina propria and submucosa. Intraepithelial leukocytes were present along with attenuation, erosion, and ulceration of the superficial epithelium. Fourteen days after surgery, this cheetah was returned to its breeding compound, and no subsequent vomiting has been observed for 4 yr.

Presumptive, iatrogenic gastric outflow obstruction associated with prior gastric surgery.

Iatrogenic gastric outflow obstruction in two dogs appeared to be caused by prior gastric surgery. The obstructions were believed to be anatomical rather than functional based on endoscopic examinations. Initially, the dogs had been evaluated and each had received two abdominal surgeries because of gastrointestinal bleeding, vomiting, or both. Eventually, both dogs were euthanized due to complications arising after attempted surgical correction of the iatrogenic obstructions. While gastric surgery commonly is performed, it seldom is considered to be a potentially harmful procedure. However, as these cases demonstrate, the decision to perform a gastrotomy must be weighed against possible risks and complications. Iatrogenic gastric outflow obstruction associated with surgery may be prevented by minimizing tissue inversion into the gastric lumen when surgery is performed near the pyloric outflow tract. Additionally, when large lesions near the pylorus are resected surgically, preservation of the continuity of the outflow tract is necessary.