Evaluation of pacing site in dogs with naturally occurring complete heart block

Objective

To compare left ventricular synchronization and systolic performance with transvenous pacing of the right ventricular apex (RVA), left ventricular free wall (LVF) or simultaneous pacing of the RVA and LVF (BiV).

Animals, materials and methods

Seven canine patients with complete heart block. Prospective study evaluating effect of pacing site. Twenty four hours following implantation of transvenous BiV pacing systems, electrocardiograms and echocardiograms were assessed during pacing from the: (1) Right Atrial Appendage/RVA (RAA/RVA), (2) RAA/LVF, and (3) RAA/BiV.

Results

QRS duration was significantly shorter with BiV pacing versus LVF pacing (p < 0.001), or RVA pacing (p < 0.001). Echocardiographic indices of systolic performance fractional shortening (FS), ejection fraction (EF), cardiac output (CO) were significantly higher with BiV pacing than with pacing from the RVA (P = 0.023, 0.006, and 0.002 respectively). Cardiac output, measured by the biplane Simpson's method, was higher with LVF versus RVA pacing (P = 0.036). There was no difference in FS or EF when comparing LVF to RVA pacing. Tissue Doppler measurements of synchronization and systolic performance did not show any difference between pacing mode, but a significantly increased number of segments were seen to contract following aortic valve closure during LVF pacing (P = 0.0268) and RVA pacing (P = 0.0197) as compared to BiV pacing.

Conclusions

Findings suggest that BiV pacing improves cardiac output and systolic performance versus RVA pacing. This improvement however, is not reflected in tissue Doppler indices of synchronization and systolic performance.     

Immunohistological distributions of fibronectin, tenascin, type I, III and IV collagens, and laminin during tooth development and degeneration in fetuses of minke whale, Balaenoptera acutorostrata.

The immunohistological distributions of fibronectin, tenascin, type I, III and IV collagens, and laminin were observed in the tooth buds of fetuses of minke whale, Balaenoptera acutorostrata. Distributions of extracellular matrices (ECMs) examined in this study except for tenascin were generally similar to those of terrestrial mammalian species during development of the tooth bud. Tenascin in the fetuses of minke whale showed characteristic distributions in the dental lamina and the enamel organ in the early tooth developmental stage. In the physiological degeneration stage of tooth bud development, immunoreactivity of the ECMs were very weakly and limitedly detected in the dental papilla and the surrounding mesenchyme. Immunoreactivity of tenascin and type I and III collagens were positively detected in the developing baleen plate germ which was associated with the degenerating tooth bud. These findings suggested that expressions of the ECMs were related to the formation of the tooth bud and baleen plate germ, and that the lack of the ECMs was related to the degeneration of the tooth bud in the fetal minke whale.     

Conservation of nitrogen in cattle feedlot waste with urease inhibitors.

Feedlot cattle normally retain less than 20% of their dietary nitrogen intake. Sixty to 80% of the nitrogen excreted is normally lost through volatilization of ammonia, which is primarily generated from urea. This loss of ammonia nitrogen pollutes the environment and creates an unfavorable ratio of nitrogen to phosphorous (N:P) in the waste for crop growth. Two urease inhibitors, cyclohexylphosphoric triamide (CHPT) and N-(n-butyl) thiophosphoric triamide (NBPT) were evaluated for their ability to reduce the rate of urea hydrolysis in beef cattle feedlot pens. Initially, a total of six pens were used, two pens per treatment, with approximately 70 cattle per pen, and a single topical application of CHPT or NBPT at 20 mg/kg of manure. Essentially no urea was found in untreated pens. However, with CHPT treatment, 2 g of urea/kg of dry manure accumulated by d 4, and all gradually disappeared by d 11; NBPT conserved 3 and 3.5 g of urea/kg by d 4 and 9, respectively, and it had disappeared by d 14 (treatment [trt] x day, P = .003). A second study involved application of NBPT weekly for 6 wk. This caused urea to accumulate to a peak concentration of 17 g/kg of manure by d 30 (trt x day2, P = .001). Once the treatment was stopped the urea concentration began to decrease. When the NBPT was applied weekly, the concentration of ammonia in the waste was less for the treated pens (trt x day, P = .01), the total nitrogen was greater (trt x day, P = .04), pH tended to be lower (trt x day, P = .10), and the total volatile acids were not different (trt x day, P = .51) from untreated pens. We concluded that urease inhibitors could be used to control ammonia emissions from animal wastes, prevent environmental damage, and produce a more balanced (N:P) fertilizer from manure.     

Effects of diets differing in propensity to promote gastric lesions on defense systems in gastric mucosae.

The objectives were to characterize biochemical changes, focusing on the antioxidant defense system, in stratified squamous and oxyntic mucosae in pigs fed diets with differing propensity to promote gastric lesions. Barrows (n = 24; 48.7+/-1.0 kg BW) housed in individual pens were used in the experiment. Barrows were fed a corn-soybean meal diet. Half of the animals were fed the diet as a coarsely ground meal (CGM; average particle size = 886 microm), and half were fed the diet as a finely ground pelleted (FGP; average particle size = 528 microm) feed. Initiation and termination of the experiment were staggered over a 3-wk period. Diets were fed for 6 wk. Visual evaluation of the stratified squamous mucosa of the proximal stomach showed increased (P<.001) damage in animals fed the FGP diet. These results were supported by histological evaluation. Thiobarbituric acid-reacting substances (TBARS), indicative of peroxide generation, relative to amount of protein were higher (P<.001) in stratified squamous than in oxyntic mucosa, and, per unit of tissue, TBARS were highest in stratified squamous mucosa of animals fed the FGP diet. Glutathione peroxidase activity followed a pattern similar to that of peroxides. Prostaglandin E2 was higher (P<.004) in stratified squamous than in oxyntic mucosa. In contrast, the activity of catalase was higher (P<.001) in oxyntic mucosa and was not affected by diet. The data show differences in the production of peroxides, the antioxidant defense system, and PGE2 between stratified squamous and oxyntic mucosae. Generation of prooxidants and the antioxidant defense system may play a role in the predilection of ulcers for the stratified squamous mucosal region of the pig stomach.     

Development and evaluation of an enzyme-linked immunosorbent assay (ELISA) for the determination of the trypanocidal drug homidium in serum of treated cattle

Two enzyme-linked immunosorbent assays (ELISA) for the determination of homidium in serum of treated cattle have been developed and evaluated. One is a direct competition (Assay 1) and the other an indirect competition assay (Assay 2). Both assays are highly sensitive with a limit of detection of 0.1 ng homidium per mL serum. Homidium levels were measurable in serum of cattle for over 2 months following administration of a single intramuscular (i.m.) dose at 1 mg/kg bodyweight. The level of sensitivity afforded by these assays makes them potentially useful tools in the pharmacokinetic evaluation of homidium and for investigating drug resistance or causes of drug failure. Assay 2 was chosen as being most suitable for further studies.     

Egg production forecasting: Determining efficient modeling approaches

Several mathematical or statistical and artificial intelligence models were developed to compare egg production forecasts in commercial layers. Initial data for these models were collected from a comparative layer trial on commercial strains conducted at the Poultry Research Farms, Auburn University. Simulated data were produced to represent new scenarios by using means and SD of egg production of the 22 commercial strains. From the simulated data, random examples were generated for neural network training and testing for the weekly egg production prediction from wk 22 to 36. Three neural network architectures-back-propagation-3, Ward-5, and the general regression neural network-were compared for their efficiency to forecast egg production, along with other traditional models. The general regression neural network gave the best-fitting line, which almost overlapped with the commercial egg production data, with an R(2) of 0.71. The general regression neural network-predicted curve was compared with original egg production data, the average curves of white-shelled and brown-shelled strains, linear regression predictions, and the Gompertz nonlinear model. The general regression neural network was superior in all these comparisons and may be the model of choice if the initial overprediction is managed efficiently. In general, neural network models are efficient, are easy to use, require fewer data, and are practical under farm management conditions to forecast egg production.     

Relationships between admissions requirements and pre-clinical and clinical performance in a distributed veterinary curriculum

The purpose of this study was twofold: first, to assess the relationships between knowledge-based admission requirements and pre-clinical and clinical performance in a distributed model of veterinary education that uses problem-based learning as the main instruction method in the first two years of the curriculum; second, to compare pre-clinical and clinical performance with performance on the Program for the Assessment of Veterinary Education Equivalence (PAVE) exam. Admissions data including overall GPA, prerequisite GPA, Graduate Record Examination (GRE) score on the Analytical, Analytical Writing, Quantitative, and Verbal sections), veterinary school performance data (GPA for pre-clinical and clinical years), and performance PAVE (taken at the end of second year) were analyzed for two classes (N = 155, 85.8% women and 14.2% men). Overall GPA, prerequisite GPA, and GRE Quantitative and Analytical scores were the best predictors for pre-clinical (years 1 and 2) performance (R = 0.49, 23.5% of the variance), GRE Analytical score was the best predictor for year 3 (pre-clinical and clinical) performance (R = 0.25, 6.3% of the variance), GRE Quantitative score was the best predictor for PAVE performance (R = 0.27, 7.5% of the variance), and GRE Analytical score was the best predictor for clinical performance (year 4; R = 0.21, 4.4% of the variance). PAVE scores correlated with GRE Quantitative scores (r = 0.27, p <.01) and veterinary school performance, with higher correlations in the pre-clinical years (rs = 0.67-0.36, p < .01), providing evidence of convergent validity for the PAVE exam.     

Monitoring of antimicrobial resistance in healthy dogs: first report of canine ampicillin-resistant Enterococcus faecium clonal complex 17

National surveillance programs on antimicrobial usage and antimicrobial resistance in animals have been established in various countries but few of them include bacteria from pets. The objectives of this study were to assess the prevalence of antimicrobial resistance in healthy dogs and to search for resistance phenotypes of clinical relevance. Escherichia coli and Enterococcus spp. were isolated from faecal swabs obtained from 127 dogs. Disk diffusion was used to measure antimicrobial susceptibility in 117 Escherichia coli, 10 Enterococcus faecium and 51 Enterococcus faecalis of canine origin. Resistance was relatively low compared with food animal species in Denmark. All Escherichia coli isolates were susceptible to broad-spectrum aminopenicillins, third generation cephalosporins and fluoroquinolones. Despite the low prevalence of resistance, statistical analysis of questionnaire data revealed a significant association (p=0.02) between recent antimicrobial treatment and resistance in Escherichia coli. Interestingly, two dogs were found to shed Enterococcus faecium resistant to ampicillin. Multilocus sequence typing of these isolates indicated that the two isolates belonged to sequence types associated with human nosocomial infections, and one (ST-192) was genetically related to human epidemic clonal complex 17. The detection of ampicillin-resistant Enterococcus faecium warrants further studies on the prevalence of these bacteria in dogs and on the possible implications to both animal and human health. The results suggest that distinct methods for detection and assessment of antimicrobial resistance in animals should be considered depending on the target animal species and the purposes of the study.     

Treatment of canine atopic dermatitis with zafirlukast, a leukotriene-receptor antagonist: a single-blinded, placebo-controlled study

Zafirlukast and placebo were administered orally as individual agents to 20 dogs with atopic dermatitis. The pruritus was effectively reduced by at least 50% in 2/18 (11%) dogs that completed the trial with zafirlukast. Two dogs vomited after administration of the active drug.     

The development of thermal resistance of the feather coat in broilers with different feathering genotypes and feeding regimes

1. This study compared the development of thermal resistance of the feather coat in broilers, with early or late feathering genes, and with or without the naked neck gene, allowed ad libitum or restricted feeding. 2. Male and female broilers of one of the 4 genotypes were reared to 6 weeks of age and allocated to one of the two feeding regimes. The thermal resistance of the back and crop region was measured at weekly intervals. A sample of birds were killed at the same ages and total feather weight, primary and secondary flight feather weight, liver weight and abdominal fat weight were measured. 3. All three main factors, sex, feeding and genotype, had significant effects on feather weight over time. The primary and secondary flight feathers were less affected by feed restriction than the feather coat as a whole. Birds with the naked neck gene showed a greater depression in growth rate than birds with a normal neck under conditions of restricted feeding. 4. The thermal resistance of the feathers on the back was greater in females, increased by early feather growth and decreased by restricted feeding. 5. Relative to metabolic body size, birds on restricted feeding had a greater feather weight and a smaller liver. There was a marked reduction in fat deposition, to almost negligible levels by 6 weeks of age. 6. Broilers given restricted feeding, in preparation for breeding, would benefit by a warmer environment, particularly those with feathering genotypes which confer a lower thermal resistance.