bluuebunny/crossref_metadata_2025 huggingface dataset:
Partitioning of total pulmonary resistance in horses
Authors: Lavoie J. P. , Pascoe J. R. , Kupershoek C. J.
Published: January 2024

The partitioning of total pulmonary resistance (Rl) into upper airway resistance and lower airway resistance (Rl) was studied in 8 Thoroughbred geldings. In addition, the phase shift and amplitude distortion of 3 catheters used for pressure measurements in this study were evaluated under static and dynamic conditions.

Flow rate was obtained from a heated pneumotachograph attached to a tight-fitting mask placed over the nose. Electronic integration of the flow signal gave tidal volume. Transpulmonary pressure (Pl) was obtained from calculation of the difference between the esophageal balloon catheter pressure and mask pressure. Lateral tracheal pressure was measured from a polyethylene catheter placed percutaneously in the middle portion of the trachea. Lower airway pressure (Pl) was calculated as the difference between esophageal pressure and lateral tracheal pressure. Similarly, upper airway pressure was defined as the difference between lateral tracheal pressure and mask pressure. Pressures are reported as the difference between the maximal and the minimal pressures recorded during a respiratory cycle. Airway resistance was calculated, using the isovolume method, at 50% of tidal volume.

There were individual and group variations in Pl and Pl/Pl, although Pl accounted for more than 60% of Pl in all horses. In 6 horses, RI was more than 50% of Rl whereas in 2 horses, Rl was only 30 and 34% of Rl.

Amplitude distortion was minimal for the 3 catheters under static conditions in the in vitro study. Under dynamic conditions, amplitude distortion varied according to the catheter studied, the frequency, and the resistance of the system. There were no phase differences under static conditions at low frequency. However, phase discrepancy, which was variable through the cycle, was observed for some catheters at high frequency under static and dynamic conditions. It was concluded that, until measuring techniques are standardized in horses, variations in the partitioning of Rl are likely to be obtained between studies and between animals within studies.
Definition of chemiluminescence and superoxide production responses of bovine neutrophils to selected soluble and particulate stimulants, and comparisons with the responses to Pasteurella haemolytica
Authors: Watson G. L. , Slocombe R. F. , Robinson N. E. , Sleight S. D.
Published: January 2024

We defined methods for use of luminol-dependent chemiluminescence (ldcl) and superoxide anion (O2-) production as parameters of the oxidative metabolism of neutrophils isolated from 1.5- to 5-week-old neonatal calves. We determined how variations in blood sample handling, agonist preparation, individual variability, and age of calves influenced the ldcl and O2- responses to certain agonists, and defined concentrations of soluble and particulate agonists that maximally stimulated the oxidative metabolism of bovine neutrophils. Oxidative responses, particularly ldcl, were characterized by marked day-to-day variability, differed greatly within and between calves, were partially age-dependent, and were partially dependent on the individual agonist. Superoxide anion production had substantially less variability.

We compared the in vitro oxidative (ldcl and O2-) responses of neutrophils isolated from neonatal calves stimulated by defined concentrations of the agonists–latex, phorbol myristate acetate, calcium ionophore, and opsonized zymosan–with responses to formylated oligopeptides and zymosan-activated serum, and to live, dead, live opsonized, and dead opsonized Pasteurella haemolytica organisms. Opsonization of particulates, pathogenic or nonpathogenic, enhanced the ldcl and O2- responses of stimulated neutrophils although P haemolytica was a less potent stimulant of oxidative functions than were nonbiological agonists.

We conclude that the generation of reactive oxygen species by bovine neutrophils in response to P haemolytica is highly dependent on the presence of opsonins and is greatly enhanced in live vs killed bacteria. Furthermore, the in vitro generation of reactive oxygen species, including O2- by stimulated neutrophils, may be of biologic importance if similar events occur in vivo, and could have a major role in the pathogenesis of the acute lung injury associated with pneumonic pasteurellosis.
Effects of various risk factors on plasma protein and serum immunoglobulin concentrations of calves at postpartum hours 10 and 24
Authors: Perino Louis J. , Wittum Thomas E. , Ross Gary S.
Published: January 2024

In an attempt to identify important predictors of failure of passive immunoglobulin transfer (< 800 mg of IgG/dl), identify calves with failure of passive immunoglobulin transfer, and determine the effects of a colostrum supplement, blood samples were collected from 263 calves at postpartum hours 10 and 24. Calves of dams diagnosed with mastitis had lower mean plasma protein and IgG concentrations at 10 (P < 0.05) and 24 (P < 0.01) hours. Plasma protein and IgG concentrations were similar for single and twin calves at 10 hours, but IgG concentration at 24 hours was higher (P < 0.01) in twin calves. Calves born to dams that had dystocia had numerically lower mean plasma protein and IgG concentrations than did calves born to dams that had normal delivery. However, observed differences were small and, after adjustment for other important factors, these differences were not significant. Age of dam was associated with plasma protein (P < 0.05) and IgG (P < 0.10) concentrations at 10 hours, but had no effect at 24 hours. Plasma protein and IgG concentrations decreased as calves were born later in the calving season, although the association of birth date with IgG concentration at 24 hours was marginal (P = 0.07). Calf sex, dam body condition score, and birth weight were not related to plasma protein or IgG values. The sensitivity and specificity of a cutoff value of 4.8 g of protein/dl of plasma, measured at 10 hours, for diagnosing failure of passive immunoglobulin transfer at 10 hours were 78 and 94%, and for diagnosing failure of passive immunoglobulin transfer at 24 hours were 88 and 73%, respectively. A colostrum supplement administered to calves with low plasma protein concentration at 10 hours had no effect on plasma protein or IgG values at 24 hours or on pre-weaning morbidity and mortality.
Ventilatory and arterial blood gas tension adjustments to strenuous exercise in Standardbreds
Authors: Art Tatiana , Lekeux P.
Published: January 2024

Five healthy, fit Standardbreds (mean ± sem, 490.4 ± 15.0 kg, 4.0 ± 0.5 years) were studied during a standardized test carried out on a treadmill. The test consisted of an 8-minute warm-up and a 9-minute exercise period (1 minute at 1.7, 4, 7, 8, 9, and 10 m/s; 2 minutes at 4 m/s; and a 1-minute walk at a 6% slope). Respiratory airflow, tidal volume (Vt), and respiratory frequency (f) were continuously recorded, using 2 ultrasonic pneumotachographs connected to a face mask and mass spectrometer. Oxygen uptake, carbon dioxide output, and expired minute volume (V˙e) were obtained on a breath-by-breath basis. Arterial blood was tested at the end of each step for O2 and CO2 partial pressures. Heart rate was continuously recorded, using a heart rate recording system. Stride frequency was measured at each step, and the stride frequency-to-f ratio was calculated. Venous blood was tested for plasma lactate concentration before and 2 minutes after completion of the test.

Some horses had a locomotion-respiration coupling (lrc), but this coupling was occasional and intermittent. The f was lower and Vt was higher than values reported for Thoroughbreds working under similar experimental conditions. Nevertheless, maximal V˙e did not overshoot maximal V˙e reported in Thoroughbreds. All horses were hypoxemic and hypercapnic, but there was wide variability between subjects. The horses with the highest oxygen uptake and the lowest plasma lactate concentration were more hypoxemic and hypercapnic.

The Standardbreds, studied under our laboratory conditions, did not have constant lrc and had lower f with higher Vt than did Thoroughbreds under similar experimental conditions. Despite these differences in breathing strategy, the Standardbreds did not have higher V˙e than did Thoroughbreds, and they were hypoxemic and hypercapnic. The fact that these Standardbreds, which obviously freely selected their breathing strategy, were unable or unwilling to adopt compensatory hyperventilation reinforces the hypothesis that, in strenuous exercising horses, there could be a physiologic limit to ventilation, most probably related to mechanical factors, but independent of any lrc.
Evaluation of oncofetal protein-related mRNA transport activity as a potential early cancer marker in dogs with malignant neoplasms
Authors: Stromberg Paul C. , Schumm Dorothy E. , Webb Thomas E. , Ward Heidi , Couto C. Guillermo
Published: January 2024

A 55-kd protein with mRNA transport activity found in fetal rat liver cells and plasma from mice, rats, and human beings with malignant neoplasms has been designated oncofetal protein 55 (ofp55). Monoclonal antibody produced to rat ofp55 cross-reacts with human ofp55. Using this monoclonal antibody in a bioassay measuring mRNA transport stimulated by ofp55, we tested the plasma from 19 dogs with a variety of malignant neoplasms, including carcinomas, sarcomas, lymphomas, and melanomas, and compared the results with plasma from 20 clinically normal dogs without evidence of neoplasia. The mean mRNA transport activity from the group of dogs with malignant neoplasms was 0.43 ± 0.28%/mg of protein. Mean transport activity from the group of control dogs was 0.04 ± 0.02%/mg of protein. These means were significantly different (P < 0.0001). The degree of overlap between these 2 groups in their ofp55-related mRNA transport activity was minimal, and measurement of this protein appears to have potential for the early detection of malignant neoplasms in dogs.
Gross and histologic evaluation of hepatogastric ligaments in clinically normal dogs and dogs with gastric dilatation-volvulus
Authors: Hall Jean A. , Willer Randy L. , Seim Howard B. , Powers Barbara E.
Published: January 2024

Objective

To investigate any potential structural differences in hepatogastric ligaments between clinically normal dogs and dogs with gastric dilatation-volvulus (gdv).

Design

Case-control study.

Animals

Hepatogastric ligaments were examined in 13 large-breed control dogs and in 13 large-breed dogs referred for surgical treatment of gdv.

Procedure

Measurements and biopsies of hepatogastric ligaments were performed at the time of surgery, circumcostal gastropexy, for correction of gdv. Serial sections from each ligament were stained with H&E, Masson's trichrome, and elastin stains to assess morphology, including smooth muscle, collagen, and elastic fiber contents.

Results

There were no differences observed by light microscopy in incidence or degree of histopathologic alterations between the 2 groups of dogs. The lengths of hepatogastric ligaments in gdv-affected dogs, however, were significantly longer than those of control dogs (gdv-affected dogs, 7.0 [5.0 to 9.5] cm median [range]; control dogs, 5.0 [3.0 to 7.5] cm median [range]; P = 0.01).

Conclusions

Causality can not be inferred from this study. It is not known whether the ligaments were lengthened as a result of gdv or whether the lengthened ligaments predisposed dogs to gdv.

Clinical Relevance

This finding may reflect increased laxity of the supporting hepatogastric ligament in the right quadrant of the abdomen. An elongated ligament may permit increased stomach mobility and predispose dogs to partial or complete gastric volvulus.
Abnormalities in oxygenation, coagulation, and fibrinolysis in colonic blood of horses with experimentally induced strangulation obstruction
Authors: Kawcak C. E. , Baxter G. M. , Getzy D. M. , Stashak T. S. , Chapman P. L.
Published: January 2024

Objective

To measure arterial and venous blood gas, coagulation, and fibrinolysis variables in blood from isolated segments of control and ischemic large colons for the purpose of identifying variables for rapid, indirect assessment of colonic mucosal injury.

Design

Variables were determined at specific intervals during the 4-hour study (3 hours of ischemia and 1 hour of reperfusion).

Animals

Seven clinically normal horses between 2 and 15 years old.

Procedure

Horses underwent laparotomy and occlusion of the lumen and vasculature of the mid-portion of the pelvic flexure of the large colon. During ischemia of 1 randomly-chosen colonic segment, variables were measured to determine colonic mucosal damage and were compared with histologic scores of colonic biopsy specimens.

Results

Significant (P < 0.05) differences from control values were observed over time for venous pH, Pco2, Po2, oxygen saturation, oxygen content, arteriovenous oxygen difference, and lactate and glucose concentrations. Mean histologic scores of biopsy specimens obtained from ischemic colons were significantly (P < 0.05) greater (indicating greater damage) than those from control colons, and increased significantly (P < 0.05) with duration of ischemia.

Conclusions

Venous lactate, oxygen saturation, and Po2 values were the most significant predictors of the severity of histologic damage within the ischemic colons (R2 = 0.661).

Clinical Relevance

Venous blood gas and lactate values in the large colon are good predictors of the amount of intestinal damage incurred during 3 hours of ischemia, and may be clinically useful for the rapid determination of colonic viability.
Kinematic evaluation of gait in dogs with cranial cruciate ligament rupture
Authors: DeCamp Charles E. , Riggs Craig M. , Olivier N. Bari , Hauptman Joe G. , Hottinger Heidi A. , Soutas-Little Robert W.
Published: January 2024

Objective

Noninvasive, computer-assisted, three-dimensional kinematic gait analysis was used to describe lameness in a chronic model of cranial cruciate ligament rupture (CCLR) in dogs.

Design

Hind limb lameness was evaluated prior to and at 1, 3, and 6 months after transection of the cranial cruciate ligament.

Animals

Seven clinically normal large dogs.

Procedure

Dynamic flexion and extension angles and angular velocities were calculated for the coxofemoral, femorotibial, and tarsal joints. Distance and temporal variables were determined. Essential Fourier coefficients were used to develop mean flexion extension curves for all joints and to compare changes in movement that developed with CCLR over time.

Results

Each joint had a characteristic pattern of flexion and extension movement that changed with CCLR. The femorotibial joint angle was more flexed throughout stance and early swing phase of stride and failed to extend in late stance. Angular velocity of the femorotibial joint was damped throughout stance phase, with extension velocity almost negligible. The coxofemoral and tarsal joint angles, in contrast to the femorotibial joint angle, were extended more during stance phase. These changes were documented as differences noted in the essential Fourier coefficients. Stride length and frequency also varied significantly after CCLR.

Conclusions

Cranial cruciate ligament rupture affects movement of the coxofemoral and tarsal joints, as well as the femorotibial joint, in gait. A pattern of joint movement may be discerned in which the coxofemoral and tarsal joints compensate for the dysfunction of the femorotibial joint.

Clinical Relevance

Methods were developed that will improve objective evaluation of CCLR and its treatment in dogs. (Am J Vet Res 1996;57:120-126)
Effects of subject velocity on ground reaction force measurements and stance times in clinically normal horses at the walk and trot
Authors: McLaughlin Ron M. , Gaughan Earl M. , Roush James K. , Skaggs Chad L.
Published: January 2024

Objective

The objective of the study reported here was to evaluate the effects of changing velocity on stance time and ground reaction force (GRF) measurements in horses at the walk and trot.

Design

Force plate gait analysis was used to evaluate clinically normal horses at variable velocities. Ground reaction force measurements and stance times were recorded and compared.

Animals

12 adult horses.

Procedure

Data were obtained from 192 valid trials at the walk and 162 valid trials at the trot. Vertical, braking, and propulsive peak forces and impulses were measured. Pearson’s correlation coefficients were determined for velocity and stance time and all measured forces and impulses in the forelimbs and hind limbs. Trials were divided into distinct velocity ranges. Trials obtained at velocities within the established ranges were analyzed to evaluate changes in vertical, braking, and propulsive peak forces and impulses at differing speeds within the walk and trot gaits.

Results

At the walk and trot, a significant negative correlation was found between velocity and forelimb and hind limb stance times. Velocity and stance time were significantly correlated with many of the GRF and impulse measurements. Velocity was significantly correlated with vertical and braking forces in the hind limbs at the walk, with vertical force in the forelimbs at the trot, and with braking force in the forelimbs and hind limbs at the trot. Velocity and stance time correlated significantly with forelimb and hind limb vertical impulses. Forelimb and hind limb stance times decreased significantly as velocity increased. Hind limb braking force increased and forelimb and hind limb vertical impulses decreased significantly as walk velocity increased. Forelimb braking force increased significantly between velocity ranges at the trot.

Conclusions

Results of this study confirm that a significant negative linear correlation exists between subject velocity and stance times in clinically normal horses at the walk and trot. Significant correlations were also identified between velocity and many GRF measurements, indicating that subject velocity does influence the generation of GRF measurements in horses. Variation in subject velocity should be minimized when performing force-plate analysis in horses. (Am J Vet Res 1996;57:7-11)
Effects of topical administration of 0.5% apraclonidine on intraocular pressure, pupil size, and heart rate in clinically normal dogs
Authors: Miller Paul E. , Nelson Marie J. , Rhaesa Suzanne L.
Published: January 2024

Objective

To evaluate the effect of 0.5% apraclonidine on intraocular pressure (IOP), pupil size, and heart rate in clinically normal dogs.

Design

Randomized masked saline-controlled case study.

Animals

Nine clinically normal conditioned adult dogs of either sex.

Procedure

Normal diurnal variation in IOP, pupil size, and resting heart rate were determined from 7 AM to 7 PM (day 1). These measurements were repeated on day 2 after topical application of 60 μl of 0.5% apraclonidine to 1 randomly chosen eye of each dog. The contralateral eye received saline solution.

Results

Compared with the saline-treated fellow eye, mean IOP in the apraclonidine-treated eye was significantly reduced (3.0 mm of Hg, 16%) 8 hours after treatment. Because of mild day-to-day variations in IOP, however, IOP in the apraclonidine-treated eye on day 2 was not significantly different from day-1 baseline values obtained from the same eye. Significant mydriasis (2.1 mm, 29.7%), persisting for up to 8 hours, occurred in apraclonidine-treated eyes. Although apraclonidine did not significantly alter heart rate when all 9 dogs were viewed as a group, 4 dogs experienced a 9 to 19.5% reduction in heart rate 2 hours after treatment. Mild blanching of the conjunctiva occurred in apraclonidine-treated eyes.

Conclusions

Apraclonidine lowered IOP and, in contrast to cats where it causes miosis, induced mydriasis in dogs. Although heart rate generally is unchanged, it may be reduced in select individuals.

Clinical Relevance

Topically applied 0.5% apraclonidine may be a useful adjunct to other antiglaucoma treatment modalities in dogs, but is unlikely to be effective as the sole agent in most forms of canine glaucoma. (Am J Vet Res 1996;57:79-82)
Effects of topical administration of 0.5% apraclonidine on intraocular pressure, pupil size, and heart rate in clinically normal cats
Authors: Miller Paul E. , Rhaesa Suzanne L.
Published: January 2024

Objective

To evaluate the effect of a topical α2-agonist, 0.5% apraclonidine, on intraocular pressure (IOP), pupil size, and heart rate in clinically normal cats.

Design

Randomized masked saline-controlled case study.

Animals

Nine clinically normal conditioned adult cats of either sex.

Procedure

Normal diurnal variation in IOP, pupil size, and resting heart rate was determined from 7 AM to 7 PM (day 1). On day 2, the same measurements were made after the topical application of 30 μl of 0.5% apraclonidine to 1 randomly chosen eye of each cat. The contralateral eye received saline solution.

Results

Apraclonidine lowered IOP a mean of 4.8 mm of Hg (24.0%) when compared with IOP in the fellow saline-treated eye 6 hours after treatment. Unilateral administration of the drug also may have reduced IOP in both eyes. Pupil size was reduced a mean 46% in only the apraclonidine-treated eye, and miosis persisted for up to 24 hours. Heart rate was significantly lower (11.8%) at 3 hours, and 8 of 9 cats vomited after topical administration of the drug. Mild blanching of the conjunctiva occurred in all apraclonidine-treated eyes.

Conclusions

Apraclonidine reduced IOP, pupil size, and resting heart rate in clinically normal cats, but also induced undesirable systemic side-effects. In contrast to dogs where the drug induced mydriasis, apraclonidine caused miosis in cats.

Clinical Relevance

The current commercially available formulation of topical 0.5% apraclonidine is too toxic for clinical use in cats. Reformulation, or identification of a less toxic congener, may result in a clinically useful antiglaucoma preparation for cats. (Am J Vet Res 1996;57:83-86)
Scotopic threshold response of the electroretinogram of dogs
Authors: Yanase Jun , Ogawa Hiroyuki , Ohtsuka Hiromitsu
Published: January 2024

Objective

To study characteristics of the scotopic threshold response (STR) in dogs.

Design

We recorded the electroretinogram (ERG) in anesthetized Beagles under several recording conditions to examine characteristics of the STR.

Animals

Seven clinically normal Beagles.

Procedure

Beagles were paralyzed by continuous IV administration of muscle relaxant and were artificially ventilated with a gas mixture of nitrous oxide and oxygen during experiments. Corneal ERG were recorded, using full-field white stimuli, under several recording conditions.

Results

The canine STR was a simple corneal negative response elicited by dim stimuli below the b-wave threshold. Maximal amplitude of the canine STR was approximately 50 to 120 µV, much larger than those of other animal species, such as human beings, monkeys, and cats. Peak latency of the maximal STR was approximately 75 to 96 milliseconds. The spectral sensitivity of the canine STR corresponded to that of the canine rod visual pigment. The canine STR was completely eliminated by dim background light, which had no suppressive effect on the a- and b-waves. By using such dim background light, we could record the photoreceptor-derived a-wave in the ERG intensity series.

Conclusions

In Beagles, the STR strongly influences the ERG waveforms recorded under the dark-adapted condition. Special attention may be necessary in using the dark-adapted ERG to assess the retinal photoreceptor function. Canine STR is expected to be a good indicator of assessment of the proximal retinal function in dogs, and Beagles might be a good experimental animal for the study of the STR.(Am J Vet Res 1996;57:361-366)
Enzyme-linked immunosorbent assay for thrombin-antithrombin III complexes in horses
Authors: Topper Michael J. , Prasse Keith W. , Morris Michael J. , Duncan Alexander , Crowe Natalie A.
Published: January 2024

Objectives

To adapt and characterize a human ELISA kit to quantify thrombin-antithrombin III (TAT) complexes in horses, and to evaluate TAT as a marker for hypercoagulation in horses.

Animals

29 clinically normal horses used as controls, and 4 ill horses used to evaluate assay for known causes of hypercoagulation.

Procedure

A commercially available human sandwich-type ELISA kit with 2 antibodies against human thrombin and antithrombin III that bind selectively to their corresponding TAT antigenic sites was used. Equine TAT standards were made from purified equine thrombin and antithrombin III. Proteins diluted in a phosphate-buffered saline solution containing 0.1 % Tween and 1 U of heparin/ml were used to establish standard curves. Reference intervals for TAT concentration in citrated equine plasma, and intra- and interassay coefficients of variation were determined.

Results

Mean ± SD values were 3.95 ± 1.93 µg/L, with median of 3.18 µg/L and range of 1.95 to 9.03 µg/L. One horse with cecal perforation had TAT concentration of 174.30 µg/L, and a horse infused IV with endotoxin had TAT concentration of 62.98 µg/L 12 hours after infusion.

Conclusions

The data suggest that human TAT ELISA kits can be used to measure TAT concentration in citrated equine plasma, and that TAT is a marker for hypercoagulation in horses.

Clinical Relevance

Assays for equine TAT many help to further characterize the hypercoagulable state in horses. (Am J Vet Res 1996;57:427–431)
In vitro effect of ketones and hyperglycemia on feline hemoglobin oxidation and D- and L-lactate production
Authors: Fallin Carol W. , Christopher Mary M.
Published: January 2024

Objectives

To investigate in vitro effects of ketosis and hyperglycemia on feline erythrocyte Heinz body formation, reduced glutathione (GSH) concentration, and D-and L-lactate production, and to identify potential metabolic mechanisms of oxidative stress in diabetic cats.

Design

Washed feline erythrocytes suspended in buffers containing normal or high glucose concentration were incubated with various concentrations of ketone bodies and tested at defined time intervals for Heinz bodies, GSH concentration, and D- and L-lactate production.

Animals

Three healthy female domestic cats.

Procedure

Erythrocytes were washed, suspended in buffers containing 5 mM glucose (simulates euglycemia) or 25 mM glucose (simulates hyperglycemia), and incubated with acetone (5 and 10 mM), acetoacetate (5 and 10 mM), or β-hydroxybutyrate (5 and 25 mM) for 24 hours at 37 C. Aliquots were stained with new methylene blue for Heinz bodies, and assayed spectrophotometrically for GSH and D- and L-lactate concentrations. Experiments were done in triplicate. Data were analyzed, using ANOVA with repeated measures.

Results

Neither high glucose concentration nor ketosis had direct effects on Heinz body formation or GSH values. Glutathione decreased to 89% of initial values over the 24-hour period in all samples. High glucose concentration also had no effect on erythrocyte D-lactate production; however, the rate of D-lactate production was slightly increased in samples containing 25 mM β-hydroxybutyrate. Linear L-lactate production confirmed metabolic viability of the erythrocyte suspensions. Samples in high glucose concentration produced L-lactate at a slightly higher (1.2×) rate than did samples in normal glucose concentration.

Conclusions

High glucose concentration and ketosis do not account directly for oxidative damage and glyoxalase induction in feline erythrocytes in vitro, although high concentrations of β-hydroxybutyrate may stimulate D-lactate formation. (Am J Vet Res 1996;57:463–467)
Alterations in colonic smooth muscle function in cats with idiopathic megacolon
Authors: Washabau Robert J. , Stalls Ilse H.
Published: January 2024

Objective

To determine whether colonic smooth muscle dysfunction is involved in the pathogenesis of idiopathic megacolon in cats.

Design

In vitro smooth muscle mechanical measurements.

Animals

Colon from healthy cats and cats with idiopathic megacolon.

Procedure

Colonic smooth muscle strips were suspended in physiologic buffer solution, attached to isometric force transducers, and contracted with acetylcholine (ACh; 10−9 to 10−4M), substance P (SP; 10−10 to W−6M), cholecystokinin (CCK; 10−11 to 10−6M), potassium chloride (KCI; 10 to 80 mM), or electrical field stimulation (EFS; 25 V, 1 to 30 Hz, 0.5-millisecond duration). Isometric stress responses were compared with those obtained from healthy controls. Colonic smooth muscle strips were also evaluated histologically for neuronal and smooth muscle cell morphology.

Results

Passive isometric stress was not altered, but the active isometric stress responses of megacolon smooth muscle to ACh, SP, CCK, KCI, and EFS were significantly (P < 0.05) diminished, compared with healthy controls. Differences were observed in longitudinal and circular smooth muscle from proximal and distal portions of the colon. Histologic evaluation revealed few abnormalities of smooth muscle cells or of myenteric or submucosal plexus neurons. The contractile response of megacolon smooth muscle to EFS, and the inhibition of this response by tetrodotoxin, suggest that myenteric and submucosal plexus neurons in megacolon smooth muscle are functional.

Conclusions

Idiopathic megacolon is a generalized dysfunction of colonic smooth muscle in cats. The diminished isometric stress responses to receptor occupancy (ACh, SP, and CCK) and membrane depolarization (KCI) further suggest that the disorder involves disturbance in the activation of smooth muscle myofilaments. (Am J Vet Res 1996;57:580-587)
Protection of BALB/c mice against homologous and heterologous species of Brucella by rough strain vaccines derived from Brucella melitensis and Brucella suis biovar 4
Authors: Winter Alexander J. , Schurig Gerhardt G. , Boyle Stephen M. , Sriranganathan Nammalwar , Bevins Julia S. , Enright Fred M. , Elzer Philip H. , Kopec John D.
Published: January 2024

Objective

To evaluate stable rough mutants derived from Brucella melitensis 16M and B suis 2579 (biovar 4) as vaccines against homologous and heterologous Brucella spp in the BALB/c mouse model.

Design, Animals, and Procedure

Rough mutants VTRM1 and VTRS1 were obtained from B melitensis 16M and B suis 2579, respectively, by allelic exchange of the rfbU gene encoding mannosyltransferase with a Tn5-disrupted rfbU gene. Mice were vaccinated with VTRM1 or VTRS1 and challenge exposed 8 weeks later.

Results

VTRM1 and VTRS1 replicated extensively in the spleen during the first 3 weeks of infection, then decreased rapidly. Antibodies specific for the O polysaccharide were not detected in sera of mice inoculated with either rough strain. Vaccination with VTRM1 or VTRS1 induced protection against virulent strains of B abortus (2308), B melitensis (16M), B suis biovar 1 (750), and B suis biovar 4 (2579). VTRM1 also protected against B ovis (PA) and against 4 field isolates of B abortus from bison or elk. VTRS1 conferred protection against 4 field isolates of B suis biovar 4 from reindeer. Vaccines prepared from live VTRM1 or VTRS1 provided significantly greater protection than that afforded by vaccines of killed cells in QS- 21 adjuvant. Vaccination with VTRM1 containing VTRS1 gave minimal protection against the antigenically unrelated Listeria monocytogenes, thus demonstrating the immunologic specificity of protection against Brucella spp.

Conclusions and Clinical Relevance

Results encourage evaluation, in primary host species, of VTRM1 and VTRS1, along with RB51, as alternative vaccines to strain 19, Rev 1, or other smooth phase vaccines. (Am J Vet Res 1996; 57:677–683)
Influence of adrenergic and cholinergic mediators on the equine jejunum in vitro
Authors: Malone E. D. , Brown D. R. , Trent A. M. , Turner T. A.
Published: January 2024

Objective

To characterize the response of equine jejunal smooth muscle to adrenergic and cholinergic mediators.

Design

Evaluation of myogenic responses, using an in vitro model.

Sample Population

Intestinal tissues were obtained from horses without gastrointestinal tract disorders or systemic disease.

Procedure

Baseline myogenic tone and amplitude and frequency of contraction were determined for suspended jejunal muscle strips. The level of adrenergic and cholinergic regulation was assessed, using atropine and adrenoceptor antagonists. The response of the muscles to norepinephrine was characterized, using adrenergic blockade and α- and β-agonists.

Results

Adrenergic and cholinergic blockade had minimal effect on baseline myogenic activity. However, α1- and β2-agonists induced significant (P < 0.05) decreases in the amplitude and frequency of contraction. Surprisingly, α2-agonists caused an increase in the contraction amplitude of longitudinal muscle fibers (neurogenic in origin). Change in circular muscle activity was not induced by α2-agonists. Norepinephrine induced a similar selective response and was inhibited by yohimbine.

Conclusions

Baseline jejunal activity appears to be myogenic in origin and can function independently of sympathetic and parasympathetic input. However, intestinal smooth muscle can be affected by adrenergic agonists and potentially by increased concentrations of circulating catecholamines. Norepinephrine may act by altering the activity of other neurotransmitters. Differing responses between circular and longitudinal muscle fibers indicates a need to evaluate both components.

Clinical Relevance

Selective α2-agonists may be potentially useful for motility modification of the equine jejunum. Therapeutic use of adrenergic blockade will be effective only in cases of increased adrenergic stimulation. (Am J Vet Res 1996;57:884–890)
Use of detergent to prevent initial responses to endotoxin in horses
Authors: Longworth Kim E. , Smith Barbara L. , Staub Norman C. , Steffey Eugene P. , Serikov Vladimir B.
Published: January 2024

Objective

To determine whether a detergent can prevent most of the early effects of IV infusion with Escherichia coli endotoxin (< 100 ng/kg of body weight) in horses: marked pulmonary hypertension, acute leukopenia, and fever.

Animals

8 healthy adult horses (4 male, 4 female), 415 to 615 kg.

Design and Procedure

Control and detergent experiments were performed in each horse while it was awake but sedated. In control experiments, 10 to 100 ng of E coli endotoxin/kg was given. In detergent experiments, 100 mg of detergent/kg was given 1 hour before injecting endotoxin, similar to the control experiments.

Results

In control experiments, pulmonary arterial pressure increased transiently over 40 minutes by 33 ± 8 mm of Hg (mean ± SD; P < 0.001), then returned to baseline. Circulating leukocytes decreased to 47 ± 19% (P < 0.02) of baseline by 1 hour after endotoxin, then increased above baseline by 6 hours. Rectal temperature increased by 0.7 ± 0.4 C (P < 0.01). In detergent experiments, the increase in pulmonary arterial pressure was much less than that in the control experiments (8 ± 7 mm of Hg; P < 0.001). Circulating leukocytes did not decrease, and the increase in rectal temperature after endotoxin was blocked.

Conclusions

This attenuation of the response to endotoxin may occur because the normal steps in the response of pulmonary intravascular macrophages (ie, endocytosis of endotoxin and subsequent release of inflammatory mediators) are altered by the detergent. This low-technology, inexpensive, and safe treatment could be an important new clinical tool for veterinarians in combating endotoxemia. (Am J Vet Res 1996;57:1063–1066)
Ontogeny of epinephrine, norepinephrine, dopamine-β-hydroxylase, and chromogranin A in the adrenal gland of pigs
Authors: Laroche Sabine M. , Pinxteren Jef A. , Van Reempts Patrick J. , De Potter Werner P. , Weyns André A. , Verhofstad Albert A. , Van Acker Karel J.
Published: January 2024

Objective

To obtain data on the ontogeny of catecholamines and other chromaffin vesicle components, which could serve as a basis for the study of their role during fetal life in normal and pathologic conditions.

Design

Epinephrine, norepinephrine, dopamine-β-hydroxylase, and chromogranin A contents were measured in the porcine adrenal gland during various stages of gestation.

Animals

934 porcine fetuses representing 22 gestational ages between 43 and 108 days.

Procedure

Total homogenates of adrenal glands were extracted and contents of different neurochemical markers were measured, using high-performance liquid chromatography, immunoassays, and western blotting. Immunohistochemical studies also were performed.

Results

Epinephrine and norepinephrine contents as a function of gestational age can be represented by a sigmoidal curve. Norepinephrine content rises early in gestation, whereas epinephrine content increases later. Maximal increase was significantly higher for epinephrine content. A progressive appearance of separate epinephrine- and norepinephrine-storing cells was documented. Dopamine-β-hydroxylase content as a function of gestational age can be adequately represented by a parabolic curve. No quantitative changes in chromogranin A concentration were observed, but western blotting revealed qualitative changes with progressing gestational age.

Conclusions

Important changes occur in catecholamine formation around day 60 of gestation. The sharp increase in epinephrine/norepinephrine contents and the appearance of separate epinephrine- and norepinephrine-storing cells may be related to the progressive splanchnic innervation of the adrenal gland. The presence of chromogranin A early in gestation may indicate its necessity for catecholamine storage. (Am J Vet Res 1996;57:1074–1079)
Effect of nasal occlusion on tracheal and pharyngeal pressures in horses
Authors: Holcombe Susan J. , Derksen Frederik J. , Stick John A. , Robinson N. Edward , Boehier Deborah A.
Published: January 2024

Objective

To compare tracheal and pharyngeal inspiratory and expiratory pressures achieved during 60 seconds of nasal occlusion in standing horses with pressures achieved in horses during intense exercise.

Animals

5 Standardbreds.

Procedure

Tracheal and pharyngeal inspiratory and expiratory pressures were obtained from 5 horses during 60 seconds of nasal occlusion and compared with tracheal and pharyngeal pressures achieved during incremental treadmill exercise tests in which horses ran at 50, 75, and 100% of the speed that resulted in maximal heart rate ( HRmax)

Results

Significant difference was not detected between peak tracheal inspiratory pressure during nasal occlusion and peak tracheal inspiratory pressure at HRmax. Peak pharyngeal inspiratory pressure was sig nificantly more negative, and peak tracheal and peak pharyngeal expiratory pressures were sig nificantly more positive during 60 seconds of nasal occlusion than those observed in horses running at HRmax.

Conclusion

During upper airway endoscopy in standing horses, 60-second nasal occlusion induced tracheal and pharyngeal inspiratory pressures that equaled or exceeded pressures achieved during high-intensity exercise.

Clinical Relevance

Nasal occlusion is useful to simulate upper airway pressures achieved during high-intensity exercise. (Am J Vet Res 1996;57:1258–1260)
Respiratory tract disease and mucosal colonization by Pasteurella haemolytica in transported cattle
Authors: Frank Glynn H. , Briggs Robert E. , Loan Raymond W. , Purdy Charles W. , Zehr Emilie S.
Published: January 2024

Objectives

To follow incidence of Pasteurella haemolytica (PH) in the upper respiratory tract of healthy calves at the farm and through the marketing process, and to determine the effect of vaccination on PH colonization of the upper respiratory tract and on the incidence of respiratory tract disease (RTD).

Animals

2- to 5-month-old calves (n = 104) from 4 farms.

Procedure

Calves were vaccinated with a killed PH serotype-1 product. Nasal secretion and tonsil wash specimens were cultured for PH, and serum antibody was measured by indirect hemagglutination. Calves with RTD were treated with tilmicosin phosphate.

Results

At the feedyard, 73 calves had RTD. The incidence of RTD was significantly related to the farm of origin, and was inversely related to the PH serum titer at the farm, but was not influenced by vaccination. Isolations of PH serotype 1 however, were reduced by vaccination. The major serotypes of PH encountered were 1 and 6.

Conclusion

Vaccination can reduce the frequency of colonization of the uoper respiratory tract by PH. (Am J Vet Res 1936;57:1317-1320)
Muscle biopsy as a tool for assessing muscular adaptation to training in horses
Authors: Rivero Jose-Luis L.
Published: January 2024

Objective

To describe an applied method for quantitative estimation of training condition in horses.

Animals

17 sedentary adult (5 to 14 years old) stallions of several breeds endurance trained for 3 months.

Procedure

Muscle biopsy specimens from 2 depths (20 and 60 mm) of the gluteus medius muscle were obtained before and after training and were analyzed for fiber type distribution, mean cross-sectional area, relative fiber area, and mean number of capillaries in contact with each fiber type relative to their mean area. Fiber types were designated as types 1, 2A, and 2B (high, low, and moderate myosin ATPase activities at pH 4.5, respectively). Data were subjected to discriminant and principal component analyses.

Results

77% of the observations were correctly discriminated according to training condition of horses by use of discriminant analyses when histochemical and morphometric data from the 2 muscle biopsy specimens were used. Principal component analysis indicated that the most efficient variables describing muscular adaptation to training are fiber area and number of capillaries in contact with type-1 and type-2A fibers, particularly from the deepest sampling site of the muscle.

Conclusion

It is possible to satisfactorily classify an individual horse in a given training category on the basis of a physiologic muscle index.

Clinical Relevance

These methods could become a useful aid for evaluation of the individual horse's response to training. (Am J Vet Res 1996;57:1412-1416)
Nonlinear dynamics stability measurements of locomotion in healthy Greyhounds
Authors: Marghitu Dan B. , Kincaid Steven A. , Rumph Paul F.
Published: January 2024

Objective

To characterize normal locomotion of dogs, using nonlinear dynamic stability measurements to analyze two-dimensional kinematic data.

Animals

5 healthy, orthopedically sound Greyhounds.

Procedure

Data were studied by sequentially constructing phase plane portraits from the angular velocity and displacement data; creating first-return (Poincare) maps from periodically sampled data; and evaluating the dynamic stability of the gait, using Floquet multipliers calculated from the assembled data. Retroreflective markers were placed on the left craniodorsal aspect of the iliac spine, greater trochanter, lateral epicondyle of the femur, lateral malleolus, and fifth metatarsophalangeal joint. Each dog was repeatedly led at a trot along a 10-m runway. Data were collected, using a video-based, two-dimensional motion measurement and analysis system. Dogs were considered a nonlinear system and were represented by the joint angular displacements and velocities. Phase plane portraits and first-return maps were constructed to analyze the smoothed data. The Floquet theory was then used to investigate the local stability of critical points of the discrete map.

Results

The femorotibial joint had the highest angular velocity, ranging from −2.5 to 4.9 radians/s. Tarsal joint velocity ranged from −2.7 to 3.2 radians/s, and the coxofemoral angle had the lowest range of −2.2 to 2.2 radians/s. The points on the first-return maps converged to the 45° diagonal line and were clustered together. The largest Floquet multiplier averaged 0.452, which characterized the stability of this population and will be used to draw a comparison between this and future work.

Conclusions

Nonlinear dynamics can be effectively used to analyze two-dimensional kinematic data from animal models to quantify the dynamic stability of animal locomotion through precise mathematical measurements. The method is general and can be applied to normal or abnormal gaits.

Clinical Relevance

Point mapping and quantitative measurement of joint movement have several advantages associated with the application to animal and human locomotion. The clinician can visually distinguish the normal gait pattern from abnormal patterns to assist in the diagnosis of musculoskeletal abnormalities (diseases). (Am J Vet Res 1996;57:1529–1535)
Bacterial killing by use of once daily gentamicin dosage in guinea pigs with Escherichia coli infection
Authors: Campbell Bonnie G. , Bartholow Steven , Rosin Eberhard
Published: January 2024

Objective

To determine whether the antibacterial activity of 6 mg of gentamicin/kg of body weight given SC once daily, is equivalent to the standard gentamicin dose of 2 mg/kg given SC every 8 hours.

Animals

Guinea pigs with infected thigh wound: 5 in an untreated control group and 12 in 6 and 2 mg/kg gentamicin treatment groups.

Procedure

Guinea pigs were inoculated with 109 Escherichia coli in the thigh muscle. Gentamicin treatment (2 mg/kg, SC, q 8 h or 6 mg/kg, SC, q 24 h) was begun 4 hours after E coli inoculation and continued for 72 hours. Four hours after the last gentamicin treatment, all guinea pigs were euthanatized and the cranial thigh muscle containing the entire inoculum was removed. Colony forming units were counted to determine the E coli concentration in each thigh.

Results

Mean ± SD log10 colony-forming units was 9.293 ± 0.074 in the control group, 8.161 ± 0.478 in the 2 mg/kg treatment group, and 7.796 ± 0.182 in the 6 mg/kg treatment group. One-way ANOVA revealed a significant (P < 0.05) difference between the control group and both treatment groups, and between both treatment groups.

Conclusion

Bacterial killing did not differ between gentamicin given at a dosage of 6 mg/kg once daily, compared with 2 mg/kg every 8 hours in guinea pigs infected with E coli.

Clinical Relevance

Gentamicin dosage regimens with high peak concentration and long dosing interval are as efficacious as divided dosage regimens. These data support the concept that once daily administration of gentamicin for treatment of E coli infection should be investigated clinically. (Am J Vet Res 1996;57:1627–1630)