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Abstract

Objective—To determine effects of the angiotensin converting enzyme inhibitor benazepril in cats with induced renal insufficiency.

Animals—32 cats.

Procedure—Renal mass was surgically reduced, and cats were assigned to 1 of 4 eight-cat groups. Group 1 received placebo, whereas groups 2, 3, and 4 received benazepril hydrochloride orally once daily for approximately 6.5 months at the following doses: group 2, 0.25 to 0.50 mg/kg of body weight; group 3, 0.50 to 1.00 mg/kg; and group 4, 1.00 to 2.00 mg/kg. Arterial blood pressures, glomerular filtration rate (GFR), and renal plasma flow were determined before treatment and during the treatment period. Other determinants of renal hemodynamics were measured by use of micropuncture techniques. Renal biopsy specimens were examined microscopically.

Results—Compared with cats that received placebo, mean systolic arterial blood pressure was significantly less and GFR significantly greater in cats that received benazepril. Glomerular capillary pressure and the ratio of efferent to afferent arteriolar vascular resistance were also significantly less in treated cats. However, histologic differences in renal specimens were not detected.

Conclusions and Clinical Relevance—Treatment with benazepril sustained single nephron GFR in remnant nephrons of cats with induced renal insufficiency. Administration of benazepril was also associated with a small but significant reduction in degree of systemic hypertension and an increase in whole kidney GFR. Benazepril may be an effective treatment to slow the rate of progression of renal failure in cats with renal disease. (Am J Vet Res 2001;62:375–383)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate 3 neurokinin-2 (NK2) receptor antagonists on the basis of their ability to block neurokinin A (NKA)-induced contractile responses in various regions of the guinea pig respiratory tract.

Animals—48 clinically normal guinea pigs.

Procedure—After euthanasia, the trachea and lungs were removed en bloc. The spirally cut trachea was divided into lower, middle, and upper portions. The main bronchus was spirally cut. A lung strip was cut from the edge of the lung. Tissue strips were mounted in organ baths containing Tyrode solution at 37°C and attached to force transducers interfaced with a polygraph. Lung strips were set at a tension of 1 g; other tissue strips were set at 2 g. After 45 minutes of equilibration, cumulative concentration-response (CR) relationships to graded concentrations of NKA were determined. In the treatment groups, tissues were incubated (30 minutes) with antagonists (MEN 10376, SR 48968, and SR 144190) at 3 concentrations (10–9, 10–7, and 10–5M) before CR relationships were determined. Effectiveness of SR 48968 against NKA was also tested in vivo.

Results—Lung strips failed to contract, but all others responded in a concentration-dependent manner. Bronchial spirals were most sensitive. SR 48968 had the highest pA2 value and effectively blocked NKA.

Conclusions and Clinical Relevance—The bronchial region where airflow resistance is high was the most sensitive to NKA, suggesting the importance of NKA in bronchoconstriction. Nonpeptide antagonists (SR 48968 and SR 144190) were more potent than the peptide antagonist (MEN 10376), indicating their greater therapeutic potential as antiasthmatic agents. ( Am J Vet Res 2004;65:984–991)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To compare laryngeal impedance, in terms of air flow and pressure, following arytenoid corniculectomy (COR) versus 3 other airway interventions (left-sided laryngoplasty with ipsilateral ventriculocordectomy [LLP], LLP combined with COR [LLPCOR], and partial arytenoidectomy [PA]) performed on cadaveric equine larynges with simulated left recurrent laryngeal neuropathy (RLN) and to determine whether relative laryngeal collapse correlated with the interventions performed.

SAMPLE

28 cadaveric equine larynges.

PROCEDURES

Each larynx in states of simulated left RLN alone and with airway interventions in the order LLP, LLPCOR, COR, and PA was evaluated in a box model construct that replicated upper airway flow mechanics consistent with peak exercise in horses. Results for impedance, calculated from airflow and pressure changes, were compared between states for each larynx. Multivariable mixed-effects analysis controlling for repeated measures within larynx was performed to calculate the predicted mean impedance for each state.

RESULTS

Results indicated that tracheal adapter diameter, individual larynx properties, airway intervention, and relative laryngeal collapse affected laryngeal impedance. The LLP and LLPCOR interventions had the lowest impedance, whereas the COR and PA interventions did not differ substantially from the simulated left RLN state. Residual intraclass correlation of the model was 27.6 %.

CONCLUSIONS AND CLINICAL RELEVANCE

Although impedance was higher for the simulated left RLN with the COR intervention state than with the LLP intervention state, given the clinical success of PA for treating RLN in horses and the similar results for the COR and PA intervention states in the present study, the use of COR warrants further investigation. The residual interclass correlation suggested that individual laryngeal variation affected impedance and may have a clinical effect.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVES

To characterize the 3-D geometry of the equine larynx replicating laryngeal hemiplegia and 4 surgical interventions by use of CT under steady-state airflow conditions. Secondly, to use fluid mechanic principles of flow through a constriction to establish the relationship between measured airflow geometries with impedance for each surgical procedure.

SAMPLE

10 cadaveric horse larynges.

PROCEDURES

While CT scans were performed, inhalation during exercise conditions was replicated for each of the following 5 conditions: laryngeal hemiplegia, left laryngoplasty with ventriculocordectomy, left laryngoplasty with ipsilateral ventriculocordectomy and arytenoid corniculectomy, corniculectomy, and partial arytenoidectomy for each larynx while CT scans were performed. Laryngeal impedance was calculated, and selected cross-sectional areas were measured along each larynx for each test. Measured areas and constriction characteristics were analyzed with respect to impedance using a multilevel, mixed-effects model.

RESULTS

Incident angle, entrance coefficient, outlet coefficient, friction coefficient, orifice thickness, and surgical procedure were significantly associated with upper airway impedance in the bivariable model. The multivariate model showed a significant influence of incident angle, entrance coefficient, and surgical procedure on impedance; however, the orifice thickness became nonsignificant within the model.

CLINICAL RELEVANCE

Laryngeal impedance was significantly associated with the entrance configuration for each procedure. This suggested that the equine upper airway, despite having a highly complex geometry, adheres to fluid dynamic principles applying to constrictions within pipe flow. These underlying flow characteristics may explain the clinical outcomes observed in some patients, and lead to areas of improvement in the treatment of obstructive upper airway disease in horses.

Full access
in American Journal of Veterinary Research