Gadoxetate disodium (Gd-EOB-DTPA) contrast-enhanced magnetic resonance imaging for differentiation between benign and malignant splenic lesions in dogs.

Malignant splenic lesions in dogs are common, with hemangiosarcoma diagnosed most frequently, and there have been no consistent clinicopathologic, gross, or imaging characteristics identified that differentiate malignant from benign splenic lesions. Histopathology is required for definitive diagnosis, and given the poor long-term prognosis of malignant splenic lesions, a noninvasive tool to aid in diagnosis would be valuable. This prospective cohort study utilized gadoxetate disodium, a liver-specific contrast agent (Gd-EOB-DPTA; Eovist), to identify the general lesion and pre- and postcontrast signal characteristics of benign and malignant splenic and hepatic lesions in dogs with naturally occurring disease. Twenty-five dogs were enrolled, Eovist-enhanced MRI was performed, and dogs were taken to surgery for splenectomy and other organ biopsy. All histopathology and MRI studies were evaluated by a single pathologist and a single radiologist, respectively. The associations between the tumor type and numerous variables defined on MRI were evaluated using Fisher's exact tests, and the significance was identified at a P-value of .05. Malignant splenic masses were identified in 11/25 (44%) dogs, and 5/11 malignancies represented hemangiosarcoma. The presence of abdominal effusion (P = .017) and the presence of hepatic nodules on MRI (P = .009) were associated with splenic malignancy. There were no benign T2 hyperintense and no malignant T2 hypointense lesions (P = .021). Utilization of the T2 W MRI sequence may aid in the identification of malignant splenic lesions, particularly when accompanied by abdominal effusion and hepatic lesions.

Retrospective comparison of modified percutaneous cystolithotomy (PCCLm) and traditional open cystotomy (OC) in dogs: 218 cases (2010-2019).

OBJECTIVE: To compare short- and long-term clinical variables between dogs undergoing a modified percutaneous cystolithotomy (PCCLm) and open cystotomy (OC) and evaluate for risk factors associated with complications and outcomes within the groups. STUDY DESIGN: Retrospective study. ANIMALS: A total of 218 dogs. METHODS: Records were reviewed for dogs that underwent PCCLm or OC between January 2010 and December 2019. Signalment; history and diagnostic findings; procedural, anesthetic, and hospitalized care data; complications; urolith recurrence; and follow-up were recorded. Logistic regression analysis was used to evaluate effects of clinical variables on outcomes within PCCLm and OC groups and to identify significant categorical variables between PCCLm and OC groups. Two sample t-tests were used to identify significant numerical variables between PCCLm and OC groups. RESULTS: A total of 60.1% (131/218) of dogs underwent the PCCLm procedure and 39.9% (87/218) of dogs underwent the OC procedure. Anesthesia time (p < .001) was significantly longer in the OC group. No significant difference in incomplete urolith removal was noted between groups. Although surgical site infection and inflammation rates were not significantly different between OC and PCCLm groups, incisional infections were significantly associated with complications occurring during PCCLm (p = .027). Significantly reduced postoperative lower urinary tract signs (p = .022) were noted in the PCCLm group. CONCLUSION: The PCCLm may result in reduced lower urinary tract signs postoperatively compared to OC, but other clear advantages of the PCCLm were not identified in this study. CLINICAL SIGNIFICANCE: PCCLm procedures are an effective alternative to OC for urolith removal in dogs.

The effect of remifentanil infusion on sevoflurane minimum alveolar concentration-no movement (MACNM) and bispectral index in dogs.

OBJECTIVE: To determine the effect of remifentanil infusion on the minimum alveolar concentration of sevoflurane preventing movement (SEVOMACNM) and bispectral index (BIS) in dogs. STUDY DESIGN: Prospective, unmasked study. ANIMALS: A total of 10 adult Beagle dogs weighing 9.0 ± 1.1 kg. METHODS: Dogs were anesthetized with sevoflurane and baseline SEVOMACNM was determined. Remifentanil was infused at 5, 10 and 20 µg kg-1 hour-1, in sequence, with 20 minutes washout between infusions. Variables monitored throughout anesthesia included heart rate (HR), oscillometric blood pressure, end-tidal partial pressure of carbon dioxide, end-tidal sevoflurane concentration (Fe'Sevo) and BIS. SEVOMACNM after remifentanil infusion (SEVOMACNM-REMI) determination started 20 minutes after the start of each infusion. Venous blood samples were collected for plasma remifentanil concentration determination at baseline, SEVOMACNM-REMI determination time points, and 20 minutes after each infusion was stopped. A mixed model analysis was used to determine the effect of remifentanil infusion on response variables. The relationships between BIS and Fe'Sevo, plasma remifentanil concentrations and the percentage decrease in baseline SEVOMACNM were evaluated (p < 0.05). RESULTS: The overall SEVOMACNM at baseline was 2.47 ± 0.11%. Addition of remifentanil at all infusion rates significantly decreased SEVOMACNM, but the medium and high doses resulted in significantly greater decreases in SEVOMACNM than the lower dose. There was no difference in SEVOMACNM percentage change between infusions 10 and 20 µg kg-1 hour-1. Plasma remifentanil concentrations were significantly different in all infusion rates. Baseline BIS value was 70 ± 1 and was lower than the BIS values recorded during all remifentanil infusions. BIS values were not significantly different among infusion rates. HR was lower and mean arterial pressure was higher during remifentanil infusions than at baseline. CONCLUSIONS AND CLINICAL RELEVANCE: All remifentanil infusions decreased SEVOMACNM in dogs. Remifentanil infusion at any rate studied did not reduce BIS values.

Endometrial hyperplasia and pyometra in captive lions (Panthera leo) and tigers (Panthera tigris).

Endometrial hyperplasia (EH) is a pathologic condition of the uterus with increased endometrial gland to stroma ratio compared to normal cyclic uterine proliferation. In domestic animals, EH often involves cystic distension of proliferating endometrial glands and may be concurrent with pyometra. In large captive nondomestic felids, an association between EH and pyometra is common; however, detailed species differences between the histological uterine findings in lions (Panthera leo) and tigers (Panthera tigris) and clinical manifestations have yet to be described. Uterine sections from 14 lions and 24 tigers with EH and/or pyometra were scored for several histological parameters and clinical histories were recorded. The percentage of endometrium affected by hyperplasia, endometrial gland to stroma ratio, and adenomyosis were significantly (P = .0385, P = .0008, and P = .0463, respectively) more severe in lions compared to tigers as univariate analytes. Although tubular complexity was not statistically significant (P = .3254), when combined as a proposed EH grading scheme, these 4 features confirmed lions had significantly (P = .0068) more severe EH compared to tigers. Endometrial hyperplasia severity significantly correlated with inflammation/pyometra severity when controlling for species (P = .0203). A significant correlation exists between pyometra-associated clinical sign severity and the presence of pyometra in tigers, (P = .0026) but not in lions (P = .1144). There was no statistical difference in the severity of clinical signs associated with pyometra between these species (P = .1986). This proposed grading scheme may have clinical utility in providing a more consistent and objective evaluation of EH in large captive felids.

Effect of topical florfenicol, terbinafine and mometasone furoate ear drops on adrenocortical function in healthy small breed dogs with bilateral otitis externa.

BACKGROUND: Testing for hyperadrenocorticism is commonly pursued in adult dogs with dermatological disease, and adrenocortical suppression has been well-documented following the use of topical corticosteroids in otic preparations. An otic suspension that contains florfenicol, terbinafine and mometasone furoate, and lasts for 30 days after a single application, frequently is used to treat canine otitis externa (OE). This medication was shown to cause adrenocortical suppression on Day (D)2 postadministration and two weeks after two applications two weeks apart. HYPOTHESIS/OBJECTIVES: The objective of this study was to determine if topical florfenicol/terbinafine/mometasone furoate causes adrenocortical suppression in healthy, small-breed dogs with bilateral OE at D28 postapplication. ANIMAL: Seven client-owned dogs weighing <10 kg diagnosed with non-Pseudomonas bilateral OE. MATERIALS AND METHODS: Cortisol was measured pre- and post-adrenocorticotropic (ACTH) stimulation on D0. Topical florfenicol/terbinafine/mometasone furoate was applied in both ears. Dogs were reassessed on D28, and cortisol was measured pre- and post-ACTH stimulation. RESULTS: The median pre- and post-ACTH cortisol concentrations on D28 were 2.5 µg/dL (range 2.0-5.0 µg/dL) and 14.3 µg/dL (range 11.5-23.1 µg/dL), respectively. There was no significant difference (P = 0.85) between post-ACTH cortisol concentrations from D0 to D28. CONCLUSIONS AND CLINICAL RELEVANCE: Results demonstrated no evidence of adrenocortical suppression, suggesting that there is no need to delay adrenocortical function testing in dogs treated with topical florfenicol/terbinafine/mometasone furoate when applied as per the manufacturer's recommendations.

A common celiacomesenteric trunk is a rare anatomic variant in dogs.

With the increasing use of CT and MRI for diagnostic imaging and planning of interventional procedures, it is important for veterinary radiologists to be familiar with variations in normal vascular anatomy and not mistake them for pathology. The arterial blood supply to the cranial abdominal viscera is provided by the celiac and the cranial mesenteric arteries. A common celiacomesenteric trunk (CMT) has been reported as a rare anatomical variant in dogs. The goals of this retrospective, observational, cross-sectional prevalence study were to determine the prevalence of a CMT in dogs with non-abdominal disease and compare it to the prevalence in dogs with portosystemic shunts (PSS). Magnetic resonance imaging studies of the thoracolumbar and lumbosacral spine in dogs that included the origin of the celiac and cranial mesenteric arteries and dual-phase CT angiography studies of the abdomen in dogs with portosystemic shunts were retrospectively reviewed by a veterinary student and a board-certified veterinary radiologist. The prevalence of a CMT was determined as the proportion of dogs diagnosed with this vascular anomaly in the MRI and CT group, respectively. Fisher's exact test was used to determine any association of a CMT with the concurrent presence of a PSS, sex, and breed size. A CMT was identified in seven of 606 (1.2%) MRI studies and in none of 47 abdominal CT studies. There was no association between the presence of a CMT and PSS (P = 1.000), sex (P = .4694), or breed size (P = 1.000). A CMT is a rare incidental finding in dogs.

Pharmacokinetics of midazolam in sevoflurane-anesthetized cats.

OBJECTIVE: To estimate the pharmacokinetics of midazolam and 1-hydroxymidazolam after midazolam administration as an intravenous bolus in sevoflurane-anesthetized cats. STUDY DESIGN: Prospective pharmacokinetic study. ANIMALS: A group of six healthy adult, female domestic cats. METHODS: Anesthesia was induced and maintained with sevoflurane. After 30 minutes of anesthetic equilibration, cats were administered midazolam (0.3 mg kg-1) over 15 seconds. Venous blood was collected at 0, 1, 2, 4, 8, 15, 30, 45, 90, 180 and 360 minutes after administration. Plasma concentrations for midazolam and 1-hydroxymidazolam were measured using high-pressure liquid chromatography. The heart rate (HR), respiratory rate (fR), rectal temperature, noninvasive mean arterial pressure (MAP) and end-tidal carbon dioxide (Pe'CO2) were recorded at 5 minute intervals. Population compartment models were fitted to the time-plasma midazolam and 1-hydroxymidazolam concentrations using nonlinear mixed effect modeling. RESULTS: The pharmacokinetic model was fitted to the data from five cats, as 1-hydroxymidazolam was not detected in one cat. A five-compartment model best fitted the data. Typical values (% interindividual variability where estimated) for the volumes of distribution for midazolam (three compartments) and hydroxymidazolam (two compartments) were 117 (14), 286 (10), 705 (14), 53 (36) and 334 mL kg-1, respectively. Midazolam clearance to 1-hydroxymidazolam, midazolam fast and slow intercompartmental clearances, 1-hydroxymidazolam clearance and 1-hydroxymidazolam intercompartment clearance were 18.3, 63.5 (15), 22.1 (8), 1.7 (67) and 3.8 mL minute-1 kg-1, respectively. No significant changes in HR, MAP, fR or Pe'CO2 were observed following midazolam administration. CONCLUSION AND CLINICAL RELEVANCE: In sevoflurane-anesthetized cats, a five-compartment model best fitted the midazolam pharamacokinetic profile. There was a high interindividual variability in the plasma 1-hydroxymidazolam concentrations, and this metabolite had a low clearance and persisted in the plasma for longer than the parent drug. Midazolam administration did not result in clinically significant changes in physiologic variables.

Differential heliothine susceptibility to Cry1Ac associated with gut proteolytic activity.

The Cry1Ac protein is the most active insecticidal toxin from the bacterium Bacillus thuringiensis (Bt) to members of the heliothinae subfamily in Lepidoptera, which includes some of the most devastating pests of corn and cotton worldwide. However, there are wide discrepancies in susceptibility among members of this subfamily in the US. Specifically, susceptibility to Cry1Ac in Helicoverpa zea (Hz) is >100-fold lower when compared to Heliothis virescens (Hv) larvae. The biochemical properties and Cry1Ac protoxin processing activity of gut digestive fluids from larvae of Hz and Hv were compared to test their role in differential susceptibility to Cry1Ac. Comparatively lower protease activity, associated with slower Cry1Ac proteolytic processing, was detected in digestive fluids of Hz compared to Hv. Moreover, Cry1Ac toxin processed by Hz digestive fluids displayed significantly lower toxicity in vitro against cultured insect cells compared to toxin activated by Hv proteases. These data support a contributing role for gut proteases in differential susceptibility to Cry1Ac in heliothine larvae.

Evaluation of the sedative effects and pharmacokinetics of detomidine gel administered intravaginally to horses.

OBJECTIVES: To determine the sedative effects and pharmacokinetic profile of detomidine when administered intravaginally as a gel formulation to horses. STUDY DESIGN: Randomized, crossover, masked experimental design. ANIMALS: A group of six healthy adult mares (494 ± 56 kg). METHODS: Mares were studied on two occasions and were administered either detomidine hydrochloride (10 µg kg-1) intravenously (treatment IV) or detomidine gel (40 µg kg-1) intravaginally (treatment IVG), separated by 1 week. Sedation, ataxia, muzzle-floor distance and heart rate (HR) were evaluated every 15 minutes for 240 minutes. Venous blood samples were collected at 15, 30, 45, 60, 90, 120, 150, 180, 240, 300 and 360 minutes postadministration and were analyzed for detomidine and metabolites using liquid chromatography-tandem mass spectrometry. Measured variables were compared over time and between treatments using mixed model analysis. Correlation between drug plasma concentrations and muzzle-floor distance, and sedation and ataxia scores was determined using the Spearman correlation coefficient. Data are presented as mean ± standard error of the mean and p value was set at <0.05. RESULTS: Sedation was shorter with IV (119 ± 16 minutes) than with IVG (188 ± 22 minutes). Ataxia scores remained greater than baseline for 90 and 135 minutes for treatments IV and IVG, respectively. HR was lower than baseline for 45 and 30 minutes for IV and IVG, respectively, but did not differ between treatments. The mean maximum plasma concentration of detomidine, time to maximum concentration and bioavailability for treatment IVG was 8.57 ng mL-1, 0.37 hour and 25%, respectively. There was a significant correlation (r = 0.68) between plasma detomidine concentrations and sedation score. CONCLUSIONS AND CLINICAL RELEVANCE: Detomidine gel administered intravaginally resulted in clinically important sedation and is a viable method for detomidine gel delivery in mares.

Effect of fentanyl on the induction dose and minimum infusion rate of alfaxalone preventing movement in dogs.

OBJECTIVE: To determine the effect of fentanyl on the induction dose and minimum infusion rate of alfaxalone required to prevent movement in response to a noxious stimulus (MIRNM) in dogs. STUDY DESIGN: Experimental crossover design. ANIMALS: A group of six healthy, adult, intact female mixed-breed dogs, weighing 19.7 ± 1.3 kg. METHODS: Dogs were randomly administered one of three treatments at weekly intervals: premedication with 0.9% saline (treatment A), fentanyl 5 µg kg-1 (treatment ALF) or fentanyl 10 µg kg-1 (treatment AHF), administered intravenously over 5 minutes. Anesthesia was induced 5 minutes later with incremental doses of alfaxalone to achieve intubation and was maintained for 90 minutes in A with alfaxalone (0.12 mg kg-1 minute-1), in ALF with alfaxalone (0.09 mg kg-1 minute-1) and fentanyl (0.1 µg kg-1 minute-1) and in AHF with alfaxalone (0.06 mg kg-1 minute-1) and fentanyl (0.2 µg kg-1 minute-1). The alfaxalone infusion was increased or decreased by 0.006 mg kg-1 minute-1 based on positive or negative response to antebrachium stimulation (50 V, 50 Hz, 10 ms). Data were analyzed using a mixed-model anova and presented as least squares means ± standard error. RESULTS: Alfaxalone induction doses were 3.50 ± 0.13 (A), 2.17 ± 0.10 (ALF) and 1.67 ± 0.10 mg kg-1 (AHF) and differed among treatments (p < 0.05). Alfaxalone MIRNM was 0.17 ± 0.01 (A), 0.10 ± 0.01 (ALF) and 0.07 ± 0.01 mg kg-1 minute-1 (AHF) and differed among treatments. ALF and AHF decreased the MIRNM by 44 ± 8% and 62 ± 5%, respectively (p < 0.05). Plasma alfaxalone concentrations at MIRNM were 5.82 ± 0.48 (A), 4.40 ± 0.34 (ALF) and 2.28 ± 0.09 µg mL-1 (AHF). CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl, at the doses studied, significantly decreased the alfaxalone induction dose and MIRNM.

Indomethacin Enhances Brown Fat Activity.

Indomethacin, a nonsteroidal anti-inflammatory drug, has been shown to induce white adipocyte differentiation; however, its roles in brown adipocyte differentiation and activation in brown adipose tissue (BAT) and obesity are unknown. To address this issue, we treated mouse brown preadipocytes with different doses of indomethacin, and delivered indomethacin to interscapular BAT (iBAT) of obese mice using implanted osmotic pumps. Indomethacin dose dependently increased brown preadipocyte differentiation and upregulated both mRNA and protein expression of uncoupling protein 1 (UCP1) and peroxisome proliferator-activated receptor (PPAR) γ coactivator 1-alpha. The mechanistic study showed that indomethacin significantly activated the reporter driven by the PPAR response element, indicating that indomethacin may work as a PPARγ agonist in this cell line. Consistently, indomethacin significantly decreased iBAT mass and fasting blood glucose levels in high-fat diet-induced obesity (DIO) mice. Histologic analysis showed that brown adipocytes of indomethacin-treated mice contained smaller lipid droplets compared with control mice, suggesting that indomethacin alleviated the whitening of BAT induced by the high-fat diet. Moreover, indomethacin significantly increased UCP1 mRNA expression in iBAT. Taken together, this study indicates that indomethacin can promote mouse brown adipocyte differentiation, and might increase brown fat and glucose oxidation capacity in DIO mice.

Seasonally Relevant Cool Temperatures Interact with N Chemistry to Increase Microcystins Produced in Lab Cultures of Microcystis aeruginosa NIES-843.

Freshwater cyanobacterial blooms are regularly formed by Microcystis spp., which are well-known producers of the hepatotoxin microcystin. The environmental factors that regulate microcystin synthesis remain unclear. We used reverse transcription-quantitative PCR (RT-qPCR), metabolomics, and toxin profiling (both by LC-MS) to measure the response of Microcystis aeruginosa NIES-843 to nitrogen (N) concentration, N chemistry (nitrate versus urea), and a range of seasonally relevant temperatures. Growth rates at lower temperatures were slower but resulted in increased cellular microcystin content (quota), and at these lower temperatures, N concentration had no effect on toxin production. In contrast, at warmer temperatures, reduction in N concentration increased toxin production, especially when urea was supplied as the nitrogen source. Our culture results demonstrate how temperature may lead to physiological responses ranging from slow growing yet very toxic cells at cool temperatures, to faster growing but less-toxic cells at warmer temperatures. This response represents a key interaction in bloom dynamics. Capturing this phenomenon as a temperature-driven toxin phenotype incorporated into models might improve the ability to predict microcystin biosynthesis during cyanobacterial blooms.

Investigation of parameters predicting the need for diagnostic imaging beyond computed tomography in the evaluation of dogs with thoracolumbar myelopathy: Retrospective evaluation of 555 dogs.

Thoracolumbar myelopathy encompasses a number of disease processes such as intervertebral disc disease, discospondylitis, trauma, congenital malformations, neoplasia, and intramedullary spinal cord disease. Compressive disc herniations are most common in dogs and require imaging procedures such as myelography, computed tomography (CT), and/or magnetic resonance imaging (MRI) to determine the need and location for decompressive surgery. The purposes of this retrospective, cross-sectional study were to evaluate all dogs undergoing thoracolumbar CT imaging as the initial diagnostic step between 2010 and 2015 and determine whether any of the imaging characteristics could be used to predict the need for additional imaging in the form of myelography, CT myelography, and/or MRI. A total of 555 dogs were identified in this time frame which underwent CT imaging for myelopathy of the thoracolumbar region. Various parameters including age, gender, sexual status, breed, chronicity, site of lesion, time of study, and contrast administration were evaluated. Findings indicated that 7.6% of dogs needed additional imaging after CT. Dachshunds were less likely to need additional imaging (P = 0.0111) as were patients scanned during normal business hours (P = 0.0075). Increasing age of the patient increased the likelihood of additional imaging (P = 0.0107). Dogs which did not have additional imaging performed were 21.89 times more likely to require surgery than those which did have additional imaging (P < 0.0001). Findings supported the use of CT as a first-line imaging modality for dogs presenting with thoracolumbar myelopathy.

Effect of dexmedetomidine on the minimum infusion rate of propofol preventing movement in dogs.

OBJECTIVE: To determine the effect of dexmedetomidine on induction dose and minimum infusion rate of propofol preventing movement (MIRNM). STUDY DESIGN: Randomized crossover, unmasked, experimental design. ANIMALS: Three male and three female healthy Beagle dogs weighing 10.2 ± 2.8 kg. METHODS: Dogs were studied on three occasions at weekly intervals. Premedications were 0.9% saline (treatment P) or dexmedetomidine (1 µg kg-1, treatment PLD; 2 µg kg-1, treatment PHD) intravenously. Anesthesia was induced with propofol (2 mg kg-1 and then 1 mg kg-1 every 15 seconds) until intubation. Anesthesia was maintained for 90 minutes in P with propofol (0.5 mg kg-1 minute-1) and saline, in PLD with propofol (0.35 mg kg-1 minute-1) and dexmedetomidine (1 µg kg-1 hour-1), and in PHD with propofol (0.3 mg kg-1 minute-1) and dexmedetomidine (2 µg kg-1 hour-1). The stimulus (50 V, 50 Hz, 10 ms) was applied to the antebrachium, and propofol infusion was increased or decreased by 0.025 mg kg-1 minute-1 based on a positive or negative response, respectively. Data were analyzed using a mixed-model anova and presented as mean ± standard error. RESULTS: Propofol induction doses were 8.68 ± 0.57 (P), 6.13 ± 0.67 (PLD) and 4.78 ± 0.39 (PHD) mg kg-1 and differed among treatments (p < 0.05). Propofol MIRNM values were 0.68 ± 0.13, 0.49 ± 0.16 and 0.26 ± 0.05 mg kg-1 minute-1 for P, PLD and PHD, respectively. Propofol MIRNM decreased 59% in PHD (p < 0.05). Plasma propofol concentrations were 14.04 ± 2.30 (P), 11.30 ± 4.30 (PLD) and 7.96 ± 0.72 (PHD) µg mL-1 and dexmedetomidine concentrations were 0.68 ± 0.12 (PLD) and 0.89 ± 0.08 (PHD) ng mL-1 at MIRNM determination. CONCLUSIONS AND CLINICAL RELEVANCE: Dexmedetomidine (1 and 2 µg kg-1) decreased propofol induction dose. Dexmedetomidine (2 µg kg-1 hour-1) resulted in a significant decrease in propofol MIRNM.

Effect of fentanyl on the induction dose and minimum infusion rate of propofol preventing movement in dogs.

OBJECTIVE: To determine the effect of fentanyl on the induction dose of propofol and minimum infusion rate required to prevent movement in response to noxious stimulation (MIRNM) in dogs. STUDY DESIGN: Crossover experimental design. ANIMALS: Six healthy, adult intact male Beagle dogs, mean±standard deviation 12.6±0.4 kg. METHODS: Dogs were administered 0.9% saline (treatment P), fentanyl (5 µg kg-1) (treatment PLDF) or fentanyl (10 µg kg-1) (treatment PHDF) intravenously over 5 minutes. Five minutes later, anesthesia was induced with propofol (2 mg kg-1, followed by 1 mg kg-1 every 15 seconds to achieve intubation) and maintained for 90 minutes by constant rate infusions (CRIs) of propofol alone or with fentanyl: P, propofol (0.5 mg kg-1 minute-1); PLDF, propofol (0.35 mg kg-1 minute-1) and fentanyl (0.1 µg kg-1 minute-1); PHDF, propofol (0.3 mg kg-1 minute-1) and fentanyl (0.2 µg kg-1 minute-1). Propofol CRI was increased or decreased based on the response to stimulation (50 V, 50 Hz, 10 mA), with 20 minutes between adjustments. Data were analyzed using a mixed-model anova and presented as mean±standard error. RESULTS: ropofol induction doses were 6.16±0.31, 3.67±0.21 and 3.33±0.42 mg kg-1 for P, PLDF and PHDF, respectively. Doses for PLDF and PHDF were significantly decreased from P (p<0.05) but not different between treatments. Propofol MIRNM was 0.60±0.04, 0.29±0.02 and 0.22±0.02 mg kg-1 minute-1 for P, PLDF and PHDF, respectively. MIRNM in PLDF and PHDF was significantly decreased from P. MIRNM in PLDF and PHDF were not different, but their respective percent decreases of 51±3 and 63±2% differed (p=0.035). CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl, at the doses studied, caused statistically significant and clinically important decreases in the propofol induction dose and MIRNM.

INVESTIGATION OF ENROFLOXACIN-ASSOCIATED RETINAL TOXICITY IN NONDOMESTIC FELIDS.

Enrofloxacin is known to cause retinal toxicity in domestic cats. The hallmark lesion of enrofloxacin-associated retinal toxicity in domestic cats is thinning of the outer nuclear layer of the retina. Enrofloxacin is commonly used to treat bacterial infections in nondomestic felids because of its action against a wide spectrum of bacteria and the ability for it to be given orally. No previous studies have investigated the potential retinal toxicity of enrofloxacin in nondomestic felids. This retrospective study evaluated 81 eyes from 14 lions ( Panthera leo ) and 33 tigers ( Panthera tigris ) that had been enucleated or collected postmortem. The thickness of the outer nuclear retina was assessed in two separate sites in each eye by counting the rows of nuclei and by using digital image analysis software to determine the area of the nuclei at each site. Medical records were reviewed to determine the enrofloxacin dose for each cat. Cats that had not received enrofloxacin (n = 11) were compared with treated animals (n = 36). The outer nuclear layer thickness or area in treated versus untreated cats was not significantly different. Additionally, no clinical blindness was reported in any of the cats. This study showed no evidence of enrofloxacin-associated thinning of the outer nuclear layer in the lions and tigers evaluated, suggesting that enrofloxacin can be used safely in these animals.

Magnetic resonance imaging subtraction vs. pre- and post-contrast 3D gradient recalled echo fat suppressed imaging for evaluation of the canine and feline brain.

Subtraction magnetic resonance imaging (MRI) has been reported to increase accuracy in the diagnosis of meningeal and inflammatory brain diseases in small animals. 3D T1W gradient recalled echo (GRE) techniques have been proposed as a suitable alternative to conventional spin echo sequences in imaging the canine brain. The aim of this study was to compare subtraction images and paired pre- and post-contrast 3D T1W GRE fat suppressed (FS) images in canine and feline MRI studies using clinical diagnosis as the gold standard. Paired pre- and post-contrast T1W 3D FS GRE images and individual subtraction images of 100 small animal patients were randomized and independently evaluated by 2 blinded observers. Diagnosis categories were "normal," "inflammatory," "neoplastic," and "other." Clinical diagnosis was made in the same categories and served as the gold standard. Image interpretation results were compared to the clinical diagnosis. Interobserver agreement was determined. Clinically, 41 studies were categorized as "normal," 18 as "inflammatory," 28 as "neoplastic," and 13 as "other." The agreement of the pre- and post-contrast GRE images with the gold standard was significantly higher than that of the subtraction images (k = 0.7491 vs. k = 0.5924; p = 0.0075). The largest sources of error were misinterpretation of "other" as "normal" and "normal" as "inflammatory." There was no significant difference between the two observers (p = 0.8820). Based on this study, subtraction images do not provide an advantage to paired pre- and post-contrast FS GRE images when evaluating the canine and feline brain.

Replacement of tibialis cranialis tendon with polyester, silicone-coated artificial tendon preserves biomechanical function in rabbits compared to tendon excision only.

BACKGROUND: Artificial tendons may be an effective alternative to autologous and allogenic tendon grafts for repairing critically sized tendon defects. The goal of this study was to quantify the in vivo hindlimb biomechanics (ground contact pressure and sagittal-plane motion) during hopping gait of rabbits having a critically sized tendon defect of the tibialis cranialis and either with or without repair using an artificial tendon. METHODS: In five rabbits, the tibialis cranialis tendon of the left hindlimb was surgically replaced with a polyester, silicone-coated artificial tendon (PET-SI); five operated control rabbits underwent complete surgical excision of the biological tibialis cranialis tendon in the left hindlimb with no replacement (TE). RESULTS: At 8 weeks post-surgery, peak vertical ground contact force in the left hindlimb was statistically significantly less compared to baseline for the TE group (p = 0.0215). Statistical parametric mapping (SPM) analysis showed that, compared to baseline, the knee was significantly more extended during stance at 2 weeks post-surgery and during the swing phase of stride at 2 and 8 weeks post-surgery for the TE group (p < 0.05). Also, the ankle was significantly more plantarflexed during swing at 2 and 8 weeks postoperative for the TE group (p < 0.05). In contrast, there were no significant differences in the SPM analysis among timepoints in the PET-SI group for the knee or ankle. CONCLUSIONS: Our findings suggest that the artificial tibialis cranialis tendon effectively replaced the biomechanical function of the native tendon. Future studies should investigate (1) effects of artificial tendons on other (e.g., neuromuscular) tissues and systems and (2) biomechanical outcomes when there is a delay between tendon injury and artificial tendon implantation.

Changes in tibial cortical dimensions and density associated with long-term locking plate fixation in goats.

PURPOSE: Cortical porosis, secondary to either vascular injury or stress-shielding, is a comorbidity of fracture fixation using compression bone plating. Locking plate constructs have unique mechanics of load transmission and lack of reliance on contact pressures for fixation stability, so secondary cortical porosis adjacent to the plate has not been widely investigated. Therefore, this study aimed to assess the effects of long-term locking plate fixation on cortical dimensions and density in a caprine tibial segmental ostectomy model. METHODS: Data was acquired from a population of goats enrolled in ongoing orthopedic research which utilized locking plate fixation of 2 cm tibial diaphyseal segmental defects to evaluate bone healing over periods of 3, 6, 9, and 12 months. Quantitative data included tibial cortical width measurements and three-dimensionally reconstructed slab density measurements, both assessed using computed tomographic examinations performed at the time of plate removal. Additional surgical and demographic variables were analyzed for effect on cortical widths and density, and all cis-cortex measurements were compared to both the trans-cortex and to the contralateral limbs. RESULTS: The tibial cis-cortex was significantly wider and more irregular than the trans-cortex at the same level. This width asymmetry differed in both magnitude and direction from the contralateral limb. The bone underlying the plate was significantly less dense than the trans-cortex, and this cortical density difference was significantly greater than that of the contralateral limb. These cortical changes were independent of both duration of fixation and degree of ostectomy bone healing. CONCLUSIONS: This study provides evidence that cortical bone loss consistent with cortical porosity is a comorbidity of locking plate fixation in a caprine tibial ostectomy model. Further research is necessary to identify risk factors for locking-plate-associated bone loss and to inform clinical decisions in cases necessitating long-term locking plate fixation.

Exposure to Cry1 Toxins Increases Long Flight Tendency in Susceptible but Not in Cry1F-Resistant Female Spodoptera frugiperda (Lepidoptera: Noctuidae).

The fall armyworm (JE Smith) (Spodoptera frugiperda) is a polyphagous pest targeted by selected Cry and Vip3A insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) that are produced in transgenic Bt corn and cotton. Available evidence suggests that sublethal larval exposure to Cry1Ac increases flight activity in adult Spodoptera spp. However, it is not known whether this effect is also observed in survivors from generally lethal exposure to Cry1Ac. Moreover, while multiple cases of field-evolved resistance to Bt proteins have been described in the native range of S. frugiperda, the effect of resistance on flight behavior has not been examined. Long-distance migratory flight capacity of S. frugiperda is of concern given its ongoing global spread and the possibility that migrants may be carrying resistance alleles against pesticides and Bt crops. In this study, we used rotational flight mills to test the effects of generally lethal exposure to Cry1Ac in susceptible and sublethal exposure in Cry1F-resistant S. frugiperda strains. The results detected altered pupal weight after larval feeding on diet containing Cry proteins, which only translated in significantly increased tendency for longer flights in female moths from the susceptible strain. This information has relevant implications when considering current models and assumptions for resistance management of Bt crops.