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The heart remembers : observations of cardiac memory in the Dorper sheep heart Texto completo
2003
J. Ker | E.C. Webb | J.A. Ker | P.A. Bekker
The heart remembers : observations of cardiac memory in the Dorper sheep heart Texto completo
2003
J. Ker | E.C. Webb | J.A. Ker | P.A. Bekker
Memory is a property common to a diverse range of tissues. Cardiac memory has been demonstrated in the human, dog, rat and rabbit. This is a peculiar phenomenon, reflected in the T wave of the electrocardiogram. The heart is able to remember periods of alterations in the sequence of ventricular activation and once there is a return to a normal sequence of ventricular activation the T waves may manifest memory. Cardiac memory is noted when the T wave during normal ventricular activation retains the vector of the previous abnormal QRS complex, caused by a period of altered ventricular activation. Possible mechanisms of memory in the heart are alterations of the transient outward potassium current (Ito) in ventricular myocytes and new protein synthesis inside myocytes. These two mechanisms operate in short- and long-term cardiac memory respectively. Currently, it is unknown whether memory may have adverse structural consequences in the heart. We were able to demonstrate memory in the hearts of Dorper wethers and this is the first report of cardiac memory in Dorper sheep.
Mostrar más [+] Menos [-]The heart remembers : observations of cardiac memory in the Dorper sheep heart Texto completo
2003
Ker, J. | Webb, E.C. | Ker, J.A. | Bekker, P.A.
Memory is a property common to a diverse range of tissues. Cardiac memory has been demonstrated in the human, dog, rat and rabbit. This is a peculiar phenomenon, reflected in the T wave of the electrocardiogram. The heart is able to remember periods of alterations in the sequence of ventricular activation and once there is a return to a normal sequence of ventricular activation the T waves may manifest memory. Cardiac memory is noted when the T wave during normal ventricular activation retains the vector of the previous abnormal QRS complex, caused by a period of altered ventricular activation. Possible mechanisms of memory in the heart are alterations of the transient outward potassium current (Ito) in ventricular myocytes and new protein synthesis inside myocytes. These two mechanisms operate in short- and long-term cardiac memory respectively. Currently, it is unknown whether memory may have adverse structural consequences in the heart. We were able to demonstrate memory in the hearts of Dorper wethers and this is the first report of cardiac memory in Dorper sheep.
Mostrar más [+] Menos [-]Comparison of electroacupuncture and butorphanol on respiratory and cardiovascular effects and rectal pain threshold after controlled rectal distention in mares Texto completo
2003
Skarda, Roman T. | Muir, William W III
Objective-To compare effects of electroacupuncture and butorphanol on hemodynamic and respiratory variables and rectal analgesia in mares after controlled rectal distention. Animals-8 healthy mares. Procedure-Each horse received saline (0.9% NaCl) solution (0.01 mL/kg, IV; control treatment), butorphanol tartrate (0.1 mg/kg, IV), or 2 hours of electroacupuncture (EA) at acupoints Bladder 21, 25, and 27 on both sides of the vertebral column, Bai hui, and Stomach 36 (right side only). Order of treatments in each mare was randomized. At least 7 days elapsed between treatments. A balloon was inserted in the rectum of each mare, and controlled distention of the balloon (pressures of ≤ 220 mm Hg) was used to measure nociceptive rectal pain threshold. Rectal temperature and cardiovascular and respiratory variables were measured before (baseline) and 5, 15, 30, 60, 90, and 120 minutes after onset of each treatment. Results-Butorphanol produced greater increases in rectal pain threshold, compared with EA (mean +/- SD, 214 +/- 24 vs 174 +/- 35 mm Hg of balloon pressure). Electroacupuncture produced minimal cardiovascular and respiratory changes. Although clinically not important, butorphanol produced moderate significant increases in heart and respiratory rates, arterial blood pressure, and rectal temperature and decreases in arterial oxygen tension. Arterial pH, carbon dioxide tension, bicarbonate concentrations, base excess, Hct, and concentration of total solids were not significantly different from baseline values after EA, butorphanol, and control treatments. Conclusions and Clinical Relevance-Electroacupuncture and butorphanol (0.1 mg/kg, IV) may provide useful rectal analgesia in horses.
Mostrar más [+] Menos [-]Pharmacokinetics and plasma concentrations of acetylsalicylic acid after intravenous, rectal, and intragastric administration to horses Texto completo
2003
Broome, Ted A. | Brown, Murray P. | Gronwall, Ronald R. | Casey, Matthew F. | Meritt, Kelly A.
Six healthy adult horses (5 mares and 1 stallion) were given a single dose of acetylsalicylic acid (ASA), 20 mg/kg of body weight, by intravenous (IV), rectal, and intragastric (IG) routes. Serial blood samples were collected via jugular venipuncture over a 36-h period, and plasma ASA and salicylic acid (SA) concentrations were determined by high-performance liquid chromatography. After IV administration, the mean elimination rate constant of ASA (+/- the standard error of the mean) was 1.32 +/- 0.09 h−l, the mean elimination half-life was 0.53 +/- 0.04 h, the area under the plasma concentration-versus-time curve (AUC) was 2555 +/- 98 μg · min/mL, the plasma clearance was 472 +/- 18.9 mL/h/kg, and the volume of distribution at steady state was 0.22 +/- 0.01 L/kg. After rectal administration, the plasma concentration of ASA peaked at 5.05 +/- 0.80 μg/mL at 0.33 h, then decreased to undetectable levels by 4 h; the plasma concentration of SA peaked at 17.39 +/- 5.46 μg/mL at 2 h, then decreased to 1.92 +/- 0.25 μg/mL by 36 h. After rectal administration, the AUC for ASA was 439.4 +/- 94.55 μg · min/mL and the bioavailability was 0.17 +/- 0.037. After IG administration, the plasma concentration of ASA peaked at 1.26 +/- 0.10 μg/mL at 0.67 h, then declined to 0.37 +/- 0.37 μg/mL by 36 h; the plasma concentration of SA peaked at 23.90 +/- 4.94 μg/mL at 4 h and decreased to 0.85 +/- 0.31 μg/mL by 36 h. After IG administration, the AUC for ASA was 146.70 +/- 24.90 μg · min/mL and the bioavailability was 0.059 +/- 0.013. Administration of a single rectal dose of ASA of 20 mg/kg to horses results in higher peak plasma ASA concentrations and greater bioavailability than the same dose given IG. Plasma ASA concentrations after rectal administration should be sufficient to inhibit platelet thromboxane production, and doses lower than those suggested for IG administration may be adequate.
Mostrar más [+] Menos [-]Levels of nicotinamide adenine dinucleotide in extracellular body fluids of pigs may be growth-limiting for Actinobacillus pleuropneumoniae and Haemophilus parasuis Texto completo
2003
O'Reilly, Terrence | Niven, Donald F.
During infection, nutrient deprivation can alter bacterial phenotype. This, in turn, may have implications for pathogenesis and prophylaxis. Actinobacillus pleuropneumoniae (biotype 1) and Haemophilus parasuis, respiratory tract pathogens of swine, are both V-factor-dependent. The concentrations of V factor in the extracellular fluids of pigs are unknown and may limit the growth of these bacteria in vivo. The aim of this study was to determine the concentrations of nicotinamide adenine dinucleotide (NAD) in select porcine body fluids and to compare the availability of NAD in vivo with the affinities of the organisms for this compound. Levels in plasma, tissue fluids (peritoneal, pleural, synovial, and cerebrospinal), and laryngeal, tracheal, and lung washings were determined with an enzymatic cycling assay. We concluded that, although the NAD supply in the respiratory tract is probably not growth-limiting, it may become limiting if the organisms are disseminated.
Mostrar más [+] Menos [-]Effect of velocity on ground reaction forces in dogs with lameness attributable to tearing of the cranial cruciate ligament Texto completo
2003
Evans, Richard | Gordon, Wanda | Conzemius, Mike
Objective-To ascertain the effectiveness of evaluating ground reaction forces (GRFs) at velocities during walking and trotting in dogs with naturally occurring lameness and determine whether walking would provide sufficient motion to adequately characterize GRFs with respect to trotting. Animals-29 dogs with a naturally occurring tear of the cranial cruciate ligament. Procedure-Dogs were walked and trotted over a force platform, and GRFs were recorded during the stance phase. Correlation was used to assess the agreement between walking and trotting for GRF. The coefficient of variation was calculated to assess the relative variation of outcome variables among the gaits. Group means for walking GRF were compared between dogs that trotted and that failed to trot. Results-GRFs during walking and trotting were highly correlated. The coefficient of variation was smaller for GRFs during walking than during trotting. Dogs that failed to trot had significantly smaller mean values of peak vertical force and vertical impulse during walking, compared with values for dogs that were able to trot. Conclusions and Clinical Relevance-Either velocity is acceptable for GRF evaluation in dogs. Mean GRF during walking was significantly different between dogs that could and could not trot, principally because dogs with the most severe lameness failed to trot. These dogs would be eliminated from a clinical study, and thus, that study would become biased toward dogs that were less lame. In that situation, differences between interventions may be less pronounced, because they would be evaluated on dogs with less lameness.
Mostrar más [+] Menos [-]Identification of geographic factors associated with early spread of foot-and-mouth disease Texto completo
2003
Rivas, Ariel L. | Smith, Stephen D. | Sullivan, Patrick J. | Gardner, Beth | Aparicio, Juan P. | Hoogesteijn, Almira L. | Castillo-Chávez, Carlos
Objective-To explore whether early analysis of spatial data may result in identification of variables associated with epidemic spread of foot and mouth disease. Sample Population-37 farms with infected cattle (ie, case farms) reported within the first 6 days of the 2001 Uruguayan foot-and-mouth disease epidemic. Procedure-A georeferenced database was created and retrospective analysis was performed on case farm location in relation to farm density, cattle density, farm type (ie, beef vs dairy cattle production), road density, case farm distance to the nearest road, farm size, farm ownership, and day of infection. Mean or median results of 1 to 3 day versus 4 to 6 day spatial data were compared. Spatial-temporal associations were investigated by correlation analysis. Results-Comparison of mean or median values between the first 3 days and days 4 to 6 of the epidemic and results of correlation analysis indicated a significant increase in road density, cattle density, and dairy cattle production and a significant decrease in farm size and case farm distance to the nearest road that developed over time. A route that linked most case farms by the shortest possible distance and also considered significantly associated variables was created. It included 86.1% of all case farms reported by 60 days into the epidemic. Conclusions and Clinical Relevance-Epidemic direction can be assessed on the basis of road density and other spatial variables as early as 6 days into an epidemic. Epidemic control areas may be more effectively identified if local and regional georeferenced data are considered.
Mostrar más [+] Menos [-]Sample collection factors affect the sensitivity of the diagnostic test for Tritrichomonas foetus in bulls Texto completo
2003
Parker, Sarah | Campbell, John | Ribble, Carl | Gajadhar, Alvin
The current diagnostic test for Tritrichomonas foetus involves the culture of collected preputial or vaginal samples. In an earlier study, which evaluated sampling tools for use with bulls, it was observed that the sensitivity of the diagnostic test was higher for 2nd samples collected from the right side of the prepuce than it was for samples collected 1st from the left side. The study described in this paper was conducted to evaluate which of these factors was responsible for the effect on diagnostic sensitivity. Twenty-nine bulls infected with T. foetus were repeatedly sampled in a 2-factor cross-over design. Samples taken from the right side of the prepuce were 4 times as likely to be positive as samples taken from the left side (P = 0.03). Other factors did not have a significant effect on the outcome of the diagnostic test. Unexpected factors may affect the sensitivity of the diagnostic test for T. foetus.
Mostrar más [+] Menos [-]Results of epidemic simulation modeling to evaluate strategies to control an outbreak of foot-and-mouth disease Texto completo
2003
Bates, Thomas W. | Thurmond, Mark C. | Carpenter, Tim E.
Objective-To assess estimated effectiveness of control and eradication procedures for foot-andmouth disease (FMD) in a region of California. Sample Population-2,238 herds and 5 sale yards in Fresno, Kings, and Tulare counties of California. Procedure-A spatial stochastic model was used to simulate hypothetical epidemics of FMD for specified control scenarios that included a baseline eradication strategy mandated by USDA and supplemental control strategies of slaughter or vaccination of all animals within a specified distance of infected herds, slaughter of only high-risk animals identified by use of a model simulation, and expansion of infected and surveillance zones. Results-Median number of herds affected varied from 1 to 385 (17% of all herds), depending on type of index herd and delay in diagnosis of FMD. Percentage of herds infected decreased from that of the baseline eradication strategy by expanding the designated infected area from 10 to 20 km (48%), vaccinating within a 50-km radius of an infected herd (41%), slaughtering the 10 highest-risk herds for each infected herd (39%), and slaughtering all animals within 5 km of an infected herd (24%). Conclusions and Clinical Relevance-Results for the model provided a means of assessing the relative merits of potential strategies for control and eradication of FMD should it enter the US livestock population. For the study region, preemptive slaughter of highest-risk herds and vaccination of all animals within a specified distance of an infected herd consistently decreased size and duration of an epidemic, compared with the baseline eradication strategy.
Mostrar más [+] Menos [-]Effects of diet formulations containing proteins from different sources on intestinal colonization by Campylobacter jejuni in broiler chickens Texto completo
2003
Udayamputhoor, Roy S. | Hariharan, Harry | Van Lunen, Ted A. | Lewis, P Jeffrey | Heaney, S. (Susan) | Price, Lawrence | Woodward, David
The objective of this study was to compare the effects of 3 diet formulations containing different protein sources (animal, plant, and a combination of animal and plant) on the colonization of Campylobacter jejuni in the gastrointestinal tract of broiler chickens. A freshly isolated strain of C. jejuni (biotype IV, serotype HS O:21, O:29, HL untypable) from a broiler chicken was used to infect 3-day-old chicks that had been free of C. jejuni; 0.5 mL of an inoculum containing 108 colony-forming units was administered orally. Shedding of the organism was studied, and C. jejuni in the ceca, jejuni, and crop were enumerated by quantitative culture. The isolates recovered from the birds during the study period of 35 d were characterized and confirmed as C. jejuni by the use of standard methods and underwent biotyping, serotyping, antimicrobial susceptibility testing by disk diffusion and the E-test, and flagellin gene typing. A cyclical pattern of shedding of C. jejuni was observed in all the birds. Colonization was highest in the ceca. The ceca of birds receiving plant-protein-based feed had significantly less colonization then the ceca of birds receiving the other types of feed, whereas the differences in colonization of the jejuni and crops were not significant. Characterization by biotyping, serotyping, and flagellin gene typing showed that 95% of the recovered isolates were identical to the strain used for infecting the chicks. However, with the Lior-HL typing scheme, 74% of the recovered isolates were HL untypable. Antimicrobial resistance testing did not reveal significant differences between the infecting strain and the recovered isolates among the different feed groups.
Mostrar más [+] Menos [-]Verification by polymerase chain reaction of vertical transmission of Theileria sergenti in cows Texto completo
2003
Baek, Byeong K. | Soo, Kim B. | Kim, Jin H. | Hur, Jin | Lee, Bou O. | Jung, J.M. | Onuma, Misao | Oluoch, Anthony O. | Kim, Chʻang-hyŏn | Kakoma, Ibulaimu
To evaluate the transplacental transfer of Theileria sergenti infection in cattle, we used DNA probes to detect T. sergenti in 6 pregnant cows and their calves. All the animals were monitored by parasitologic, serologic, and polymerase chain reaction (PCR) assays for a predicted 875-base-pair (bp) DNA product and a 684-bp amplicon detected by nested PCR in the blood and spleens of aborted fetuses. An open reading frame (ORF) starting at nucleotide 170 and terminating at position 1021 was shown to code for a polypeptide of 283 amino acid residues. All 6 dams and 5 calves were positive for T. sergenti in all tests. One calf was positive only with nested PCR. We conclude that transplacental transmission of T. sergenti is a significant problem. The relevance of the data in the programmed introduction of new (especially pregnant) animals into established clean herds needs serious consideration with regard to control of theileriosis and other tickborne diseases.
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