Ronald P. Wilson

Ceramide-Coated Balloon Catheters Limit Neointimal Hyperplasia After Stretch Injury in Carotid Arteries

Neointimal hyperplasia at the site of surgical intervention is a common and deleterious complication of surgery for cardiovascular diseases. We hypothesized that direct delivery of a cell-permeable growth-arresting lipid via the balloon tip of an embolectomy catheter would limit neointimal hyperplasia after stretch injury. We have previously demonstrated that sphingolipid-derived ceramide arrested the growth of smooth muscle cell pericytes in vitro. Here, we show that ceramide-coated balloon catheters significantly reduced neointimal hyperplasia induced by balloon angioplasty in rabbit carotid arteries in vivo. This ceramide treatment decreased the number of vascular smooth muscle cells entering the cell cycle without inducing apoptosis. In situ autoradiographic studies demonstrated that inflating the balloon catheter forced cell-permeable ceramide into the intimal and medial layers of the artery. Intercalation of ceramide into vascular smooth muscle cells correlated with rapid inhibition of trauma-associated phosphorylation of extracellular signal–regulated kinase and protein kinase B. These studies demonstrate the utility of cell-permeable ceramide as a novel therapy for reducing neointimal hyperplasia after balloon angioplasty.

The laboratory rabbit, guinea pig, hamster, and other rodents

The Laboratory Rabbit, Guinea Pig, Hamster, and Other Rodents is a single volume, comprehensive book sanctioned by the American College of Laboratory Animal Medicine (ACLAM), covering the rabbit, guinea pig, hamster, gerbil and other rodents often used in research. This well-illustrated reference won a 2012 PROSE Award for Best Single Volume Reference in Science from the Association of American Publishers. The book includes basic biology, anatomy, physiology, behavior, infectious and noninfectious diseases, husbandry and breeding, common experimental methods, and use of the species as a research model. With many expert contributors, this will be an extremely valuable publication for biomedical researchers, laboratory animal veterinarians and other professionals engaged in laboratory animal science. 2012 PROSE Award winner for Best Single Volume Reference in Science from the Association of American Publishers. It offers one-stop resource for advancements in the humane and responsible care of: rabbit, guinea pig, hamster, gerbil, chinchilla, deer mouse, kangaroo rat, cotton rat, sand rat, and degu. It includes up-to-date, common experimental methods. It is organized by species for easy access during bench research.

Methionine restriction affects oxidative stress and glutathione-related redox pathways in the rat

Lifelong dietary methionine restriction (MR) is associated with increased longevity and decreased incidence of age-related disorders and diseases in rats and mice. A reduction in the levels of oxidative stress may be a contributing mechanistic factor for the beneficial effects of MR. To examine this, we determined the effects of an 80% dietary restriction of Met on different biomarkers of oxidative stress and antioxidant pathways in blood, liver, kidney and brain in the rat. Male F-344 rats were fed control (0.86% methionine) or MR (0.17% methionine) diets for up to six months. Blood and tissues were analyzed for glutathione (GSH) concentrations, related enzyme activities and biomarkers of oxidative stress. MR was associated with reductions in oxidative stress biomarkers including plasma 8-hydoxydeoxyguanosine (8-OHdG) and 8-isoprostane and erythrocyte protein-bound glutathione after one month with levels remaining low for at least six months (P < 0.05). Levels of free GSH in blood were increased after 1–6 months of MR feeding whereas liver GSH levels were reduced over this time (P < 0.05). In MR rats, GSH peroxidase activity was decreased in liver and increased in kidney compared with controls. No changes in the activities of GSH reductase in liver and kidney and superoxide dismutase in liver were observed as a result of MR feeding. Altogether, these findings indicate that oxidative stress is reduced by MR feeding in rats, but this effect cannot be explained by changes in the activity of antioxidant enzymes.

Anticoagulation of juvenile sheep and goats with heparin, warfarin, and clopidogrel.

Little data exist on anticoagulation of young sheep and goats. We tested the effect of heparin, warfarin, and clopidogrel in two sheep and two goats weighing 17–35 kg. Each animal received heparin boluses of 80, 100, and 200 units/kg; goats also received 300, 350, and 400 units/kg. All animals received continuous heparin 40, 60, and 80 units/kg/hour; oral warfarin 0.3, 0.6, and 0.9 mg/kg/day; and oral clopidogrel 75 and 150 mg/day (2.8–3.4 and 5.6–6.9 mg/kg/day). Results were in the form of complete blood counts, activated clotting times (ACT), partial thromboplastin times, prothrombin times, thromboelastograms, and whole-blood lumiaggregometry. After heparin boluses of 200 units/kg, sheep and goats reached mean peak ACTs over 400 seconds. After continuous infusions of 40, 60 and 80 units/kg/hour, sheep and goats exceeded our therapeutic range for ACTs (195–215 seconds for sheep, 155–175 seconds for goats). For warfarin therapy, both sheep and goats required treatment with >0.6 mg/kg/day to achieve INRs over 2.5. Clopidogrel treatment, after 14–17 days of 75–150 mg/day, inhibited sheep platelets by 25–36% and goat platelets by 35–46%. We conclude that young sheep and goats can be safely and effectively anticoagulated with heparin and warfarin, and can also show a modest antiplatelet response to clopidogrel. Doses for each drug were generally higher than those used for humans, and warfarin therapy in sheep may be unpredictable. These results should be useful for developing anticoagulation protocols to test pediatric mechanical circulatory support devices.

In Vivo Hemodynamic Performance Evaluation of Novel Electrocardiogram-Synchronized Pulsatile and Nonpulsatile Extracorporeal Life Support Systems in an Adult Swine Model

The primary objective of this study was to evaluate a novel electrocardiogram (ECG)-synchronized pulsatile extracorporeal life support (ECLS) system for adult partial mechanical circulatory support for adequate quality of pulsatility and enhanced hemodynamic energy generation in an in vivo animal model. The secondary aim was to assess end-organ protection during nonpulsatile versus synchronized pulsatile flow mode. Ten adult swine were randomly divided into a nonpulsatile group (NP, n = 5) and pulsatile group (P, n = 5), and placed on ECLS for 24 h using an i-cor system consisting of an i-cor diagonal pump, an iLA membrane ventilator, an 18 Fr femoral arterial cannula and a 23/25 Fr femoral venous cannula. Trials were conducted at a flow rate of 2.5 L/min using nonpulsatile or pulsatile mode (with assist ratio 1:1). Real-time pressure and flow data were recorded using a custom-based data acquisition system. To the best of our knowledge, the oxygenator and circuit pressure drops were the lowest for any available system in both groups. The ECG-synchronized i-cor ECLS system was able to trigger pulsatile flow in the porcine model. After 24-h ECLS, energy equivalent pressure, surplus hemodynamic energy, and total hemodynamic energy at preoxygenator and prearterial cannula sites were significantly higher in the P group than those in the NP group (P < 0.05). Urine output was higher in P versus NP (3379 ± 443 mL vs. NP, 2598 ± 1012 mL), and the P group seemed to require less inotropic support, but both did not reach statistical significances (P > 0.05). The novel i-cor system performed well in the nonpulsatile and ECG-synchronized pulsatile mode in an adult animal ECLS model. The iLA membrane oxygenator had an extremely lower transmembrane pressure gradient and excellent gas exchange capability. Our findings suggest that ECG-triggered pulsatile ECLS provides superior end-organ protection with improved renal function and systemic vascular tone.

The opioid growth factor, [Met5]‐enkephalin, inhibits DNA synthesis during recornification of mouse tail skin

Opioid peptides serve as tonically active negative growth regulators in renewing and regenerating epithelia. To examine the involvement of opioids in renewal of the stratum corneum after tape stripping of tail skin, C57BL/6 J mice were given systemic injections of the potent opioid antagonist, naltrexone (NTX, 20 mg/kg i.p.) following injury. Blockade of opioidreceptor interaction by NTX for 4 h resulted in an elevation of 36–;66% in basal cell DNA synthesis measured 24 h after injury. Injection of the endogenous opioid peptide, [Met5]‐enkephalin (OGF, 10 mg/kg i.p.) 4 h before termination, suppressed radiolabelled thymidine incorporation in the basal cell layer by 37–46%at 24 h after wounding. The magnitude of the effects on DNA synthesis of OGF, but not NTX, depended on the timing of administration with respect to injury. OGF maximally depressed basal cell labelling (72%) when given 16 h after tape stripping. Concomitant administration of naloxone (10 mg/kg) with OGF blocked the inhibition of DNA synthesis; naloxone alone at the dosage utilized had no effect on cell labelling. Both OGF and its receptor, OGFr, were detected by immunocytochemistry in the basal and suprabasal cell layers, but not the cornified layer of tape stripped and uninjured tail skin. These results indicate: (a) a native opioid peptide and its receptor are expressed in epidermal cells of injured and uninjured mouse tail skin; (b) removal of the stratum corneum by tape stripping does not disrupt the function of the endogenous opioid growth system; (c) the proliferative response to wounding of the tail is tonically inhibited by the receptor‐mediated action of an endogenous opioid peptide; and (d) DNA synthesis by basal cells can be elevated by disrupting opioid peptidereceptor interactions.

Cardiovascular and respiratory effects of tiletamine-zolazepam

The combination of tiletamine and zolazepam is an important dissociative anesthetic-tranquilizer. However, little is known about the effects of this combination on the heart and respiration in rats. Adult, male rats anesthetized with tiletamine-zolazepam alone or tiletamine-zolazepam combined with xylazine or butorphanol were evaluated for changes in heart rate, mean arterial blood pressure, arterial blood pH, and blood gases during a 75-min period of anesthesia. Rats anesthetized with tiletamine-zolazepam had increased mean arterial blood pressure and less respiratory depression than did rats anesthetized with sodium pentobarbital. Tiletamine-zolazepam combined with xylazine at either dose produced bradycardia and a marked hypotension that persisted throughout the 75-min period. This combination produced respiratory depression comparable to tiletamine-zolazepam alone. The addition of butorphanol to tiletamine-zolazepam caused a transient hypotension and bradycardia. Tiletamine-zolazepam plus butorphanol produced a mild to severe respiratory depression that was dose and time dependent. These results demonstrate that: a) Tiletamine-zolazepam is cardiostimulatory, a property consistent with the known cardiovascular effects of other dissociative anesthetics; b) xylazine plus tiletamine-zolazepam is a potent cardiovascular depressant combination; and c) tiletamine-zolazepam plus butorphanol at specific doses is an anesthetic-analgesic combination with minimal effects on cardiovascular and respiratory function.

Midazolam enhances the analgesic properties of dexmedetomidine in the rat

OBJECTIVE To investigate the analgesic properties of different dose combinations of midazolam and dexmedetomidine administered intraperitoneally (IP) in the rat. STUDY DESIGN Prospective experimental trial. ANIMALS Seventy adult male Sprague Dawley rats weighing 250-300 g. METHODS Dexmedetomidine (D) 0.03, 0.06, 0.09, 0.12, 0.15, 0.18, 0.21 mg kg(-1) and midazolam (M) 5, 10, 25, 50 mg kg(-1) were administered IP, alone then in combinations ranging from 0.03 D:5 M to 0.18 D:30 M mg kg(-1). Analgesia was evaluated using the tail-flick test at time 0 (before injection), 15, 30, 45, 60 and 75 minutes. RESULTS Midazolam at all doses administered (5-50 mg kg(-1)) did not significantly change tail-flick latencies from baseline values whereas D showed clear dose-dependent increases in tail-flick latency for doses administered in the range of 0.03-0.18 mg kg(-1). Tail-flick latencies in rats administered D+M combinations were significantly greater than D alone (p<0.05). CONCLUSIONS A dose-related analgesic effect was demonstrated for D in the rat, which was enhanced by co-administration of M. CLINICAL RELEVANCE The combination of D+M administered IP to rats at doses of 0.12:20 and 0.09:15 mg kg(-1) was shown to be a good combination to provide sedation/analgesia with a duration of action greater than 60 minutes. The onset of sedation was rapid (1-3 minutes), and onset of profound analgesia was reached within 5-10 minutes.

Animal Model Development for the Penn State Pediatric Ventricular Assist Device

In March 2004, the National Heart, Lung, and Blood Institute awarded five contracts to develop devices providing circulatory support for infants and small children with congenital and acquired cardiac disease. Since 2004, the team at Penn State College of Medicine has developed a pneumatically actuated ventricular assist device (VAD) with mechanical tilting disk valves. To date, hemodynamic performance, thrombogenesis, and hemolysis have been chronically evaluated in 16 animals, including 4 pygmy goats and 12 sheep. Major complications, mainly respiratory failure, have been encountered and resolved by a multi-disciplinary team. Multi-modal analgesia, appropriate antibiotic therapy, and attentive animal care have contributed to successful outcomes. Time after implant has ranged from 0 to 40 days. Most recently, a sheep implanted with Version 3 Infant VAD was electively terminated at 35 days postimplant, with no major adverse events. This report describes a successful in vivo model for evaluating a pediatric VAD.

Antinociceptive properties of tiletamine-zolazepam improved by addition of xylazine or butorphanol

A combination of tiletamine HCl and zolazepam HCl is frequently used as an anesthetic, but little is known about the antinociceptive properties of tiletamine-zolazepam. The antinociceptive properties of tiletamine-zolazepam alone or combined with xylazine or butorphanol were determined in the adult male rate using the tail-flick test. Changes in tail-flick latency were determined at 15, 45, and 75 min after IP drug administration of sterile water, sodium pentobarbital, morphine, tiletamine-zolazepam, xylazine, butorphanol, and tiletamine-zolazepam plus xylazine or butorphanol. Tail-flick latency approximated 100% maximum possible effect (MPE) at 15-75 min postinjection in morphine-treated rats. Tiletamine-zolazepam, xylazine, and butorphanol alone, at any dose utilized, produced less than 50% MPE. However, the combination of tiletamine-zolazepam with butorphanol or xylazine increased tail-flick latency approximately three times greater than tiletamine-zolazepam alone. These results demonstrate that: a) consonant with earlier findings, analgesia and anesthesia are independent states; b) tiletamine-zolazepam is not an effective combination with respect to analgesia; but c) in concert with appropriate drugs, it can exhibit potent antinociceptive properties.