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Biomedical subjects

J R Pascoe

Publications and source records attributed to J R Pascoe.

At least 37 records · Page 2Linked to original sources
PubMed1995

Partitioning of total pulmonary resistance in horses.

The partitioning of total pulmonary resistance (RL) into upper airway resistance and lower airway resistance (RI) 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 (PI) 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 Pi and Pl/PL, although Pi accounted for more than 60% of PL in all horses. In 6 horses, Rl 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1995

Microvascular permeability and endothelial cell morphology associated with low-flow ischemia/reperfusion injury in the equine jejunum.

Microvascular permeability of the jejunum of clinically normal equids and microvascular permeability associated with 60 minutes of ischemia (25% baseline blood flow) and subsequent reperfusion were investigated. Eight adult horses were randomly allotted to 2 equal groups: normal and ischemic/reperfusion injury. Lymphatic flow rates, mesenteric blood flow, and lymph and plasma protein concentrations were determined at 15-minute intervals throughout the study. Microvascular permeability was determined by estimates of the osmotic reflection coefficient, which was determined when the ratio of lymphatic protein to plasma protein concentration reached a constant minimal value as lymph flow rate increased (filtration-independent lymph flow rate), which occurred at venous pressure of 30 mm of Hg. Full-thickness jejunal biopsy specimens were obtained at the beginning and end of each experiment, and were prepared for light microscopy to estimate tissue volume (edema) and for transmission electron microscopy to evaluate capillary endothelial cell morphology. The osmotic reflection coefficient for normal equine jejunum was 0.19 +/- 0.06, and increased significantly (P < or = 0.0001) to 0.48 +/- 0.05 after the ischemia/reperfusion period. Microscopic evaluation revealed a significant increase (P < or = 0.0001) in submucosal and serosal volume and capillary endothelial cell damage in horses that underwent ischemia/reperfusion injury. Results indicate that ischemia/reperfusion of the equine jejunum caused a significant increase in microvascular permeability.

Analysis of Variance↗
PubMed1995

Morphologic and morphometric characterization of lung collagen content in clinically normal adult thoroughbreds in race training.

Interstitial and bronchointerstitial pulmonary patterns are commonly observed in thoracic radiographs of Thoroughbreds. Prominent interstitial and bronchointerstitial pulmonary patterns are observed in clinically normal horses, and in horses with respiratory tract disease. Until recently, the relevance of these pulmonary patterns was not known. Previous studies indicated that bronchiolitis, bronchiolar epithelial hyperplasia, epithelial metaplasia, and bronchial arteriolar recruitment correlated strongly with the prominence of the interstitial and bronchointerstitial pulmonary patterns observed radiographically. We examined the content and distribution of collagen in the lungs of 7 clinically normal Thoroughbreds in race training. After standardized fixation, lung tissue was treated with a compound that selectively stains collagen. Standard morphometric techniques were used to determine the volume density of parenchymal tissue and parenchymal airspace, mean linear intercept (estimate of alveolar size), alveolar surface area-to-volume ratio, percentage of parenchyma composed of collagen, percentage of airway wall composed of collagen, and airway wall thickness. These values were compared with radiographic and histopathologic scores obtained from the same horses. The volume density of parenchymal tissue and small airway wall thickness correlated strongly with the prominence of the bronchial and bronchointerstitial pulmonary patterns observed radiographically. Small airway thickness was also highly correlated with the perceived prominence of the interstitial pulmonary patterns observed radiographically, and morphometric estimates of parenchymal tissue and parenchymal collagen. There were also strong correlations between the volume density of parenchymal tissue, the percentage of parenchymal collagen, peribronchiolar mononuclear cell infiltrates, and bronchiolar mucosal plication estimates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Laparoscopic anatomy of the equine abdomen.

Laparoscopy was performed on 6 horses (2 mares, 2 geldings, 2 stallions) to determine the normal laparoscopic anatomy of the equine abdomen. After withholding feed for 36 hours, horses were examined from the left and right paralumbar fossae, and the visceral anatomic structures were recorded by videotape and photography. One mare developed emphysema located subcutaneously at the primary laparoscopic portal; otherwise, there were no complications. The anatomic structures of diagnostic importance that were observed in the left half of the abdomen were the hepatic duct; left lateral and quadrate lobes of the liver; stomach; spleen; left kidney with the associated nephrosplenic ligament; segments of jejunum, descending colon, and ascending colon; left side of the male and female reproductive tracts; urinary bladder; vaginal ring; and mesorchium. Important structures observed in the right side of the abdomen were portions of the common hepatic duct; left lateral, quadrate, and right lobes of the liver; caudate process of the liver; stomach; duodenum; right dorsal colon, epiploic foramen; omental bursa; right kidney; base of the cecum; segments of jejunum, descending colon, and ascending colon; urinary bladder; right half of the male and female reproductive tracts; and rectum.

Abdomen↗
PubMed1994

Perioperative intratumoral administration of cisplatin for treatment of cutaneous tumors in equidae.

Twenty-seven horses (and 1 mule) with 32 histologically confirmed cutaneous tumors were studied to evaluate the effects of intratumoral injection of cisplatin initiated at the time of surgery. As a result of surgery, 9 of the wounds were closed primarily (5 sarcoids, 4 carcinomas) and 23 were left open to granulate (16 sarcoids, 6 carcinomas, 1 hamartoma). Chemotherapy consisted of 4 treatment sessions of intratumoral injection of cisplatin in purified sesame oil at 2-week intervals. The first treatment session was administered intraoperatively. A controlled-release formulation of cisplatin in sesame oil was used to limit drug egress from the injection site. Dosage was 1 mg of cisplatin/cm3 of tissue. The mean relapse-free interval was 41 +/- 3.7 months. The estimates of overall relapse-free survival rates were 92 +/- 5% at 1 year and 77 +/- 11% at 4 years. Cisplatin-related local toxicosis was minimal and wound healing was not compromised. Intratumoral injection of cisplatin appears safe and effective when administered in the perioperative period for selected tumors in equidae.

Animals↗
PubMed1994

Surface oximetry for intraoperative assessment of colonic viability in horses.

Surface oximetry was used to evaluate viability of the ascending colon in 60 horses with naturally occurring colonic volvulus or displacement. Tissue surface oxygen tension (PsO2) was measured on the serosal surface of the pelvic flexure after anatomic correction of the colonic obstruction. Horses with PsO2 > 20 mm of Hg were predicted to have viable colon; whereas, horses with PsO2 < or = 20 mm of Hg were predicted to have nonviable colon. Results of surface oximetry were compared with final outcome. For surface oximetry, sensitivity (ability to accurately identify colon that was nonviable) was 53%, but specificity (ability to accurately identify bowel that was viable) was 100%. Negative predictive value (probability that a horse with PsO2 < or = 20 mm of Hg truly had nonviable bowel) was 87%, and positive predictive value (probability that a horse with PsO2 < or = 20 mm of Hg truly had nonviable bowel) was 100%. The overall accuracy was 88%. Of the 45 horses that had a colonic PsO2 > 20 mm of Hg and survived, 7 had been given, on the basis of subjective assessment of visual criteria, a good prognosis, 28 had been given a guarded prognosis, and 10 had been given a poor prognosis. Of the horses that had a colonic PsO2 > 20 mm of Hg but died after surgery because of further colonic infarction, confirmed at necropsy, 4 had been given a poor prognosis, and 3 had been given a guarded prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Endoscopic anatomy and map of the equine bronchial tree.

To develop a bronchoscopic map of the equine respiratory tree, the major airways of the lungs of 6 healthy Thoroughbred horses were systematically explored with a flexible fibreoptic endoscope through a tracheostomy while the horses were sedated in stocks. With the carina as the reference point, measurements were made of distances to the branches of the major airways using markers on the shaft of the endoscope. All branches were explored until the narrowing of their diameters prevented further advancement of the endoscope. Positions of origins of branches from the parent bronchus were recorded in relation to a 12 h clock. Branching patterns of the right and left lungs were similar. Seventeen branches of the principal and caudal lobar bronchi of the left lung, and 18 branches of the principal and caudal lobar bronchi of the right lung were identified. Mean explorable distances from the carina to the ends of the right and left caudal lobar bronchi were 34.0 +/- 3.5 (sd) and 34.5 +/- 3.0 cm, respectively. Generally, smaller horses had shorter explorable bronchial lengths. Branching patterns of the parent bronchi were fairly consistent among horses, particularly the branches closest to the carina. After endoscopy and euthanasia, the lungs were removed, and dried with pressurised air flowing through them for 7-10 days. Attempts to explore the airways of the dried lungs endoscopically were relatively unsuccessful, because airways were much smaller in the dried lungs, and many of the branches were distorted when compared with their antemortem appearances. However, having a dried lung specimen as a reference during the bronchoscopic procedure was useful for maintaining orientation in the lungs. Radiographs were used to estimate the location of the origin and destination of each airway branch in relation to the nearest intercostal space. This makes the airway map useful when lesions identified radiographically are to be lavaged.

Animals↗
PubMed1994

Body position and direction preferences in horses during road transport.

It has been hypothesised that horses have a preference for facing backward in a trailer during road transport in order to minimise shifts of body weight due to accelerations and decelerations. To determine if horses have preferences for facing forward vs. backward in a horse trailer, the authors analysed the percentages of time horses spent in different body positions and directions while standing in a moving or parked horse trailer. Body positions and directions of 8 Thoroughbred geldings were videotaped while horses were transported singly and untethered in a 4-horse stock trailer over a 32 km route of country roads; or while the same horses were untethered in the same trailer stationary in a parking lot. Analysis of the logit-transformed percentages of time horses spent in different directions indicated that they spent significantly more time facing backward when the trailer was in motion, but not when it was parked. Several horses displayed strong individual preferences for the directions they faced during road transport.

Animals↗
PubMed1994

Effect of body direction on heart rate in trailered horses.

To determine whether body direction in a trailer affects the degree to which a horse is excited (and presumably stressed) during transport, heart rates were measured in 8 Thoroughbred geldings transported over a 32-km route of county roads while tethered facing forward or backward in a 4-horse stock trailer. Heart rates also were measured on the horses while they were tethered facing forward or backward in the same trailer while it was parked. Heart rates decreased during the first 10 minutes for both groups, and remained stable after the first 15 minutes. Heart rates were not significantly different between horses facing forward or backward during transport or while parked. Heart rates were significantly (P < 0.05) higher for horses during transport, compared with those of horses in a parked trailer whether facing forward or backward.

Animals↗
PubMed1994

Evaluation of a technique for detection of pulmonary hemorrhage in horses, using carbon monoxide uptake.

The diffusing capacity for carbon monoxide (DLCO) and the functional residual capacity (FRC) of the lung were measured in 5 healthy Thoroughbreds before and after instillation of autologous blood into their lungs, in an attempt to develop a method to quantitate extravascular blood in the lungs of horses with exercise-induced pulmonary hemorrhage. Mean (+/- SD) baseline values of DLCO and FRC were 333.8 +/- 61.9 ml/min/mm of Hg and 21.464 +/- 4.156 L, respectively. Blood instillation resulted in decreases in DLCO and FRC. The paradoxic decrease in DLCO (we were expecting to find an increase owing to blood in the airspaces, as has been reported in people) appears to be associated with the bronchoscopic procedure and with presence of blood in the airways. We concluded that rebreathing DLCO measurements were not effective for detecting blood introduced bronchoscopically into the lungs of horses.

Animals↗
PubMed1993

Intratumoral chemotherapy with cisplatin in oily emulsion in horses.

Twenty horses with 30 lesions were studied to evaluate the effects of intratumoral chemotherapy with cisplatin in sesame oil on equine sarcoids (n = 19), squamous cell carcinomas (n = 7), and squamous cell papillomas (n = 4). Treatment consisted of 4 sessions of intratumoral cisplatin chemotherapy at 2-week intervals. A controlled-release formulation of cisplatin in sesame oil was used to limit drug egress from the injection site. Mean dosage per session was 0.97 (+/- 0.17, SEM) mg of cisplatin/cm3 of tumor tissue treated for tumor volumes ranging from 10 to 20 cm3. Dosage tended to be slightly higher for smaller tumors and slightly lower for larger tumors. Tumor regression was observed in all horses. Complete response was observed in 18 of the sarcoids, 5 of the squamous cell carcinomas, and 4 of the squamous cell papillomas. The mean relapse-free interval was 21.6 and 14 months in horses with sarcoid and carcinoma/papilloma, respectively. The 1-year relapse-free rates were 87 and 65% for equine sarcoid and carcinoma/papilloma, respectively. In horses with relapse, 70% had tumor recurrence outside the treated field. Cisplatin-related local toxicosis was minimal. Intratumoral cisplatin chemotherapy was found to be a practical and effective treatment of sarcoid and squamous cell carcinoma/papilloma in horses.

Animals↗
PubMed1993

Radiographic and microscopic correlation of diffuse interstitial and bronchointerstitial pulmonary patterns in the caudodorsal lung of adult thoroughbred horses in race training.

Complete thoracic radiographic examinations were performed on 7 horses ranging in age from 24 to 60 months, followed by in-situ lung fixation. Radiographs were examined by 3 radiologists for the presence, degree and distribution of generalised pulmonary patterns within a region of interest in the caudodorsal lung. Pulmonary tissue was obtained from 12 sites within a designated volume of interest in the caudodorsal lung, corresponding to the area of interest evaluated radiographically, and examined for the presence, character and severity of microscopic lesions. Radiographic findings within the volume of interest consisted of mild to moderate bronchial, bronchointerstitial, or interstitial pulmonary patterns. Interstitial and bronchointerstitial radiographic findings were related to severity of peribronchiolar mononuclear cell infiltrates, the degree of bronchiolar mucosal plication, and alveolar capillary and peribronchial blood vessel erythrocyte content. The severity of the interstitial radiographic pattern was inversely associated with the perceived diagnostic quality of the radiographic examinations. There was no evidence of spatial variation in the severity of the microscopic changes examined in this limited pulmonary region. Inter-rater reliability between radiologists was good in the assessment of diagnostic quality of the radiographic examinations but poor in assessing severity of the primary generalised pulmonary patterns within the radiographic region of interest.

Animals↗
PubMed1993

Stress failure of pulmonary capillaries in racehorses with exercise-induced pulmonary hemorrhage.

Bleeding into the lungs in thoroughbreds is extremely common; there is evidence that it occurs in essentially all horses in training. However, the mechanism is unknown. We tested the hypothesis that exercise-induced pulmonary hemorrhage (EIPH) is caused by stress failure of pulmonary capillaries. Three thoroughbreds with known EIPH were galloped on a treadmill, and after the horses were killed with intravenous barbiturate the lungs were removed, inflated, and fixed for electron microscopy. Ultrastructural studies showed evidence of stress failure of pulmonary capillaries, including disruptions of the capillary endothelial and alveolar epithelial layers, extensive collections of red blood cells in the alveolar wall interstitium, proteinaceous fluid and red blood cells in the alveolar spaces, interstitial edema, and fluid-filled protrusions of the endothelium into the capillary lumen. The appearances were consistent with the ultrastructural changes we have previously described in rabbit lungs at high capillary transmural pressures. Actual breaks in the endothelium and epithelium were rather difficult to find, and they were frequently associated with platelets and leukocytes that appeared to be plugging the breaks. The paucity of breaks was ascribed to their reversibility when the pressure was lowered and to the fact that 60-70 min elapsed between the gallop and the beginning of lung fixation. Capillary wall stress was calculated from pulmonary vascular pressures measured in a companion study (Jones et al. FASEB J. 6: A2020, 1992) and from measurements of the thickness of the blood-gas barrier and the radius of curvature of the capillaries. The value was as high as 8 x 10(5) dyn/cm2 (8 x 10(4) N/m2), which exceeds the breaking stress of most soft tissues. We conclude that stress failure of pulmonary capillaries is the mechanism of EIPH.

Animals↗
PubMed1993

Modulation of bronchial responsiveness in horses by phenylbutazone and furosemide.

Effects of phenylbutazone (PBZ) and furosemide (FUR) on the respiratory tract of horses were evaluated, focusing on bronchial responsiveness. Four healthy Thoroughbreds were used and data were analyzed by use of a Latin square design. Histamine provocation tests (0.5, 1, 2, and 4 micrograms/min, i.v.) were done: (1) without prior treatment with PBZ or FUR, (2) 30 minutes after administration of PBZ (8 mg/kg, i.v.), (3) 1 hour after administration of FUR (1 mg/kg, i.v.), and (4) after administration of PBZ plus FUR. Pulmonary function tests (dynamic compliance, resistance, respiratory frequency, and tidal volume) and heart rate were monitored throughout the experiments. Phenylbutazone did not influence basal pulmonary function test results, whereas FUR caused a significant (P < 0.05) increase in dynamic compliance and decrease in resistance. Histamine infusion resulted in a dose-dependent decrease in dynamic compliance and a dose-dependent increase in resistance, respiratory frequency, and heart rate. Phenylbutazone administration significantly (P < 0.05) attenuated most of the changes induced by histamine, whereas FUR had less protective action. Administration of PBZ plus FUR before administration of histamine was less effective than administration of PBZ alone.

Airway Resistance↗
PubMed1993

Measurement of pulmonary diffusing capacity for carbon monoxide and functional residual capacity during rebreathing in conscious thoroughbreds.

A rebreathing method for measurement of pulmonary diffusing capacity for carbon monoxide (DLCO) and functional residual capacity (FRC) was evaluated in conscious horses. Horses were manually ventilated through an endotracheal tube, using a custom-made syringe filled with a gas mixture containing 18-carbon monoxide (18CO) and helium (He). The 18CO and He concentrations were continuously monitored by use of a mass spectrometer connected to the rebreathing circuit. Values for DLCO and FRC were calculated from changes in the concentration of these 2 gases. In 11 Thoroughbreds, mean (+/- SD) DLCO was 330.3 +/- 56.9 ml.min-1 x mm of Hg-1, and FRC was 20.21 +/- 3.35 L. Body weight normalization yielded mean (+/- SD) values of 0.652 +/- 0.114 ml.min-1 x mm of Hg-1 x kg-1 for DLCO, and 39.9 +/- 6.4 ml.kg-1 for FRC.

Animals↗