Search Results

You are looking at 21 - 28 of 28 items for

  • Author or Editor: Frederik J. Derksen x
  • Refine by Access: All Content x
Clear All Modify Search

Summary

Respiratory syncytial virus (rsv) infection causes severe lower respiratory tract disease in infants and calves. Neonatal respiratory tract infection in children often produces persistent changes in lung function. The specific objective of this study was to determine whether neonatal calves have transient or persistent alterations in pulmonary function and airway reactivity following rsv infection. Six 2- to 3-day-old Holstein bull calves were inoculated with 10 ml of bovine respiratory syncytial virus (brsv) inoculum (102.7 to 103.8 cell culture infective doses/ml) intranasally and 10 ml of brsv inoculum (104.8 to 105.9 cell culture infective doses/ml) intratracheally for 4 consecutive days, and 5 other calves were sham-inoculated. Prior to inoculation (day 0) and on days 4, 14, and 30 after the last inoculation, body weight (kg), dynamic compliance (Cdyn), pulmonary resistance (RL), and 2 indices of airway reactivity (effective dose [ed] 65Cdyn and ed 200RL) were measured. Control calves gained weight progressively throughout the study, whereas rsv-inoculated calves failed to gain weight for 14 days, but equaled control calf weight by 30 days after inoculation. The Cdyn of control calves increased significantly by 30 days, but did not in the rsv-infected calves. Pulmonary resistance was increased significantly at 4, 14, and 30 days, but was unaffected by sham inoculation. The ed 65Cdyn and ed 200RL indicated an age-dependent increase in reactivity to histamine and an increase in responsiveness in the infected group beginning at 14 days and persisting until the end of the study. The data indicate that brsv causes airway obstruction and hyperreactivity in neonatal calves, which persists for at least 30 days following viral exposure.

Free access
in American Journal of Veterinary Research

Summary

A nerve muscle pedicle (nmp) graft was placed in the cricoarytenoideus dorsalis (cad) muscle of 6 horses with induced left laryngeal hemiplegia. The nmp graft was created by use of the first cervical nerve and omohyoideus muscle. In 1 horse (control), the first cervical nerve was transected after placement of the nmp graft. One year after the surgical procedure, horses were examined endoscopically and then anesthetized. While the larynx was observed endoscopically, the first cervical nerve was stimulated. Horses were subsequently euthanatized, and the larynx was harvested.

Prior to anesthesia, the endoscopic appearance of the larynx of all horses was typical of laryngeal hemiplegia. During anesthesia, stimulation of the first cervical nerve produced vigorous abduction of the left aiytenoid in principal horses but not in the control horse. The right cricoarytenoideus lateralis and cad muscles were grossly and histologically normal. Also, the left cricoarytenoideus lateralis was atrophic in all horses as was the left cad muscle of the control horse. In contrast, the left cad muscle harvested from principal horses had evidence of reinnervation with type 1 or type 2 fiber grouping. One year after the nmp graft procedure, horses with left laryngeal hemiplegia had reinnervation of the left cad muscle. In another study, reinnervation was sufficient to allow normal laryngeal function during exercise. Combined, these data suggest that the nmp graft procedure is a viable technique for the treatment of left laryngeal hemiplegia in horses.

Free access
in American Journal of Veterinary Research

SUMMARY

Upper airway flow mechanics and arterial blood gas measurements were used to assess the efficacy of subtotal arytenoidectomy for treatment of induced left laryngeal hemiplegia in horses. Measurements were collected with the horses at rest, and trotting or pacing on a treadmill (6.38° incline) at speeds of 4.2 and 7.0 m/s. Experimental protocols were performed after right common carotid artery exteriorization (baseline), after left recurrent laryngeal neurectomy (lrln), and after left subtotal arytenoidectomy.

At baseline, increasing treadmill speed progressively increased peak inspiratory and expiratory flow (Vi max and Ve max respectively), peak inspiratory and expiratory transupper airway pressure (PuI and PuE, respectively), respiratory frequency (f), tidal volume (VT), minute volume (VE), and heart rate. Inspiratory and expiratory times (TI and TE, respectively) and arterial oxygen tension (Pao2) decreased with increased treadmill speed; inspiratory and expiratory impedance (ZI and ZE, respectively) did not change.

After lrln, Vi max, f, and Pao 2 significantly (P < 0.05) decreased at exercise, whereas PuI, TI, and ZI significantly increased. Minute volume decreased at exercise after lrln, but the changes were not significant; lrln had no effect on Ve max PuE, ZE, heart rate, arterial carbon dioxide tension (Paco 2), or VT.

Subtotal arytenoidectomy did not improve upper airway flow mechanics or blood gas measurements impaired by laryngeal hemiplegia.

Free access
in American Journal of Veterinary Research

SUMMARY

The role of endotoxin in the pathogenesis of acute pneumonic pasteurellosis is uncertain. Recently, we reported that Escherichia coli -derived endotoxin given by airway inoculation fails to induce lung injury in calves. Because Pasteurella haemolytica-derived endotoxin may differ substantially from E coli in its pathogenicity, we repeated these studies with Pasteurella endotoxin. Intratracheal inoculation of P haemolytica endotoxin caused hypoxemia and increased the alveolar-arterial oxygen differences without causing hypercarbia or changes in lung mechanical properties and volumes. In contrast, iv inoculation of endotoxin caused systemic hypotension, leukopenia, gas exchange impairment, increased total pulmonary resistance, and decreased dynamic compliance. Both routes of inoculation increased serum endotoxin concentrations and were associated with areas of pulmonary hemorrhage, edema, and acute inflammation. We concluded that P haemolytica-derived endotoxin is pathogenic by iv and airway routes of inoculation, and therefore differs from E coli endotoxin in its ability to induce lung lesions in calves.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To investigate relationships between cough frequency and mucus accumulation, airway obstruction, and airway inflammation and to determine effects of dexamethasone on coughing and mucus score.

Animals—13 horses with recurrent airway obstruction( RAO and 6 control horses.

Procedure—6 RAO-affected and 6 control horses were stabled for 3 days. Coughing was counted for 4 hours before and on each day horses were stabled. Before and on day 3 of stabling, tracheal mucus accumulation was scored, airway obstruction was assessed via maximal change in pleural pressure (ΔPplmax), and airway inflammation was evaluated by use of cytologic examination of bronchoalveolar lavage fluid (BALF). Effects of dexamethasone (0.1 mg/kg, IV, q 24 h for 7 days) were determined in 12 RAO-affected horses.

Results—To assess frequency, coughing had to be counted for 1 hour. In RAO-affected horses, stabling was associated with increases in cough frequency, mucus score, and ΔPplmax. Control horses coughed transiently when first stabled. In RAO-affected horses, coughing was correlated with ΔPplmax, mucus score, and airway inflammation and was a sensitive and specific indicator of ΔPplmax > 6 cm H2O, mucus score > 1.0, and > 100 neutrophils/µL and > 20% neutrophils in BALF. Dexamethasone reduced cough frequency, mucus score, and ΔPplmax, but BALF neutrophil count remained increased.

Conclusions and Clinical Relevance—Because of its sporadic nature, coughing cannot be assessed accurately by counting during brief periods. In RAO-affected horses, coughing is an indicator of airway inflammation and obstruction. Corticosteroid treatment reduces cough frequency concurrently with reductions in ΔPplmax and mucus accumulation in RAO-affected horses. ( Am J Vet Res 2003;64:550–557)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of 2 weeks of intense exercise on expression of markers of pulmonary venous remodeling in the caudodorsal and cranioventral regions of the lungs of horses.

Animals—6 horses.

Procedures—Tissue samples of the caudodorsal and cranioventral regions of lungs were obtained before and after conditioning and 2 weeks of intense exercise. Pulmonary veins were isolated, and a quantitative real-time PCR assay was used to determine mRNA expression of matrix metalloproteinase-2 and −9, tissue inhibitor of metalloproteinase-1 and −2, collagen type I, tenascin-C, endothelin-1, platelet-derived growth factor, transforming growth factor (TGF)-β, and vascular endothelial growth factor (VEGF). Protein expression of collagen (via morphometric analysis) and tenascin-C, TGF-β, and VEGF (via immunohistochemistry) was determined.

Results—Exercise-induced pulmonary hemorrhage was detected in 2 horses after exercise. The mRNA expression of matrix metalloproteinase-2 and −9, tissue inhibitor of metalloproteinase-2, TGF-β, and VEGF was significantly lower in pulmonary veins obtained after exercise versus those obtained before exercise for both the caudodorsal and cranioventral regions of the lungs. Collagen content was significantly higher in tissue samples obtained from the caudodorsal regions of the lungs versus content in samples obtained from the cranioventral regions of the lungs both before and after exercise. Exercise did not alter protein expression of tenascin-C, TGF-β, or VEGF.

Conclusions and Clinical Relevance—Results of this study indicated 2 weeks of intense exercise did not alter expression of marker genes in a manner expected to favor venous remodeling. Pulmonary venous remodeling is complex, and > 2 weeks of intense exercise may be required to induce such remodeling.

Full access
in American Journal of Veterinary Research