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Biomedical subjects

R F Slocombe

Publications and source records attributed to R F Slocombe.

At least 91 records · Page 5Linked to original sources
PubMed1982

Ovalbumin-induced lung disease in the pony: role of vagal mechanisms.

In awake sensitized ponies, we studied the effect of aerosol ovalbumin challenge on ventilation, pulmonary mechanics, lung volume, and gas exchange before and after vagal blockade. We also challenged the left lung and measured respiratory rate (f) and right and left respiratory system resistance (RrsR, RrsL) before and after both left and bilateral vagal section. Bilateral ovalbumin aerosol challenge increased f, minute ventilation (VE), total respiratory system resistance (Rrs), and minimal volume, decreased dynamic compliance, total lung capacity, and arterial oxygen tension, and was without effect on tidal volume (VT), functional residual capacity, quasi-static lung compliance, and arterial carbon dioxide tension. Vagal blockade reversed the increase in f, VE, and Rrs and increased VT. Challenge of the left lung increased f and RrsL but did not alter RrsR. Bilateral vagal section reversed the tachypnea but unilateral section did not. Histopathologic lesions included acute fibrinopurulent obstructive bronchiolitis, bronchitis, edema, and alveolar distension. We conclude that local mechanisms are of critical importance in the pathogenesis of ovalbumin-induced airway obstruction in ponies, that increased sensitivity of airway smooth muscle to normal vagal tone may also play a role, and that tachypnea following challenge is caused by activity of pulmonary receptors with vagal afferent fibers.

Aerosols↗
PubMed1982

Influence of beta-adrenergic antagonism on the response of bovine neonatal lungs to intravenous histamine.

The effects of IV histamine infusion and beta-adrenergic blockade on pulmonary function were studied in neonatal Holstein calves, beta-Adrenergic blockade with IV propranolol increased total pulmonary resistance, but was without effect on lung compliance, lung volumes, and gas exchange. beta-Adrenergic blockade enhanced the histamine-induced increase in total pulmonary resistance and the decrease in dynamic and quasistatic compliance, lung volumes, and arterial oxygen tension. These data indicate that beta-adrenergic receptors may be present in the large and small airways of cattle and they modulate the effects of bronchoconstrictor agents as in other species.

Adrenergic beta-Antagonists↗
PubMed1982

Quantitative ultrastructural anatomy of esophagus in different regions in the horse: effects of alternate methods of tissue processing.

A qualitative and quantitative study was made of 2 adult horses to determine the effect of specimen preparation and the influence of anatomically separate regions on the microscopic structure of the esophagus. The effects of 3 fixative solutions (formalin, Bouin's fixative and Karnovsky's fixative) and 4 histologic staining procedures (hematoxylin and eosin, Gomori's trichrome, Laidlow's reticulum, and orcein-elastin) were compared. Density-dependent image analysis was used to compare the relative contributions of elastic and reticular fibers in esophageal connective tissue for each region. Cross-sectional dimensions of the tissue layers which comprise the esophageal wall were obtained by light microscopic measurement and were compared for each region. The mucosal surface structure was examined by scanning electron microscopy. Our results indicate that specimen preparation has significant effects on the structural integrity of esophageal tissues. Bouin's fixative was inferior to the other fixatives in this regard. Furthermore, there are extensive regional differences in esophageal microstructure. Formalin-fixed tissues stained with either hematoxylin and eosin or Gomori's trichrome appear the most suitable for routine quantitative morphologic studies of the equine esophagus.

Acetates↗
PubMed1982

Pulmonary function tests in standing ponies: reproducibility and effect of vagal blockade.

Arterial blood gas tensions, pulmonary mechanics, and lung volumes were measured in 4 sedated ponies every hour for 6 hours and in 5 ponies 4 times at 2-month intervals to assess the short- and long-term reproducibility of pulmonary function measurements. Variability in blood gas tensions was small over the short- and long-term measurement periods, whereas the variability in total respiratory resistance and functional residual capacity was small over the short term but larger over the long term. The variability in tidal volume, minute ventilation, respiratory rate, and dynamic and quasistatic compliance was relatively large over the short and long term. When data from 5 ponies were pooled, significant change did not occur in any of the variables over a 6-month period. Vagal blockade increased tidal volume and decreased respiratory rate and total respiratory resistance, but arterial blood gas tensions, minute ventilation, dynamic compliance, quasistatic compliance, functional residual capacity, and lung and thoracic cage pressure-volume curves were unaffected. Total respiratory resistance decreased with increasing lung volume, with the vagus intact. After vagal blockade, the decrease in total respiratory resistance with lung volume was minimal. Dynamic compliance was frequency independent over a range of 15 to 60 breaths/min-1, suggesting that measurable inhomogeneity of peripheral time constants did not exist in our clinically normal ponies.

Animals↗
PubMed1982

3-methylindole-induced pulmonary toxicosis in ponies.

In unanesthetized ponies, arterial blood gas tensions, pulmonary mechanics, and lung volumes were determined before and 24 to 48 hours after oral administration of 500 ml of corn oil or 100 mg of 3-methylindole (3MI)/kg of body weight in 500 ml of corn oil. In the latter group, variables were also measured after bilateral cervical vagotomy. Respiratory rate and minute ventilation were increased by 3MI treatment and decreased after vagotomy, suggesting that the tachypnea induced by 3MI was vagally mediated. The arterial O2 tension (PaO2) was unaffected but arterial CO2 tension (PaCO2) decreased below base line after 3 MI and vagotomy. Specific respiratory conductance and dynamic compliance wee decreased by 3MI. Specific conductance increased again after vagotomy. Functional residual capacity, which increased after 3MI, was unaffected by vagotomy. Total lung capacity and quasistatic compliance were unaffected by either treatment. Minimal volume was larger in 3MI-treated ponies than in untreated ponies. Decreased dynamic compliance and specific respiratory conductance and increased functional residual capacity and minimal volume are all compatible with small airway obstruction produced by the necrotizing bronchiolitis and bronchiolar obstruction observed histologically in 3MI-treated ponies.

Animals↗
PubMed1982

Effect of vagotomy on respiratory mechanics and gas exchange in the neonatal calf.

The effect of vagotomy on the mechanical and gas exchange properties of the respiratory system was determined in 7 healthy, anesthetized neonatal Holstein calves. A pressure-compensated volume displacement plethysmograph measured the quasi-static pressure-volume (PV) characteristics of the lungs and thoracic cage. Functional residual capacity (FRC) was determined by He equilibration. Lung and chest wall compliances per kilogram of body weight were 2.25 +/- 0.19 ml/cm of H2O/kg and 8.85 +/- 2.44 ml/cm of H2O/kg, respectively. Total lung capacity (TLC) averaged 78.3 +/- 13 ml/kg and FRC was 51 +/- 5% of TLC. The lung PV curve deviated from single exponential behavior below 75% of TLC, indicating airway closure at large lung volumes. Residual volume, which averaged 28.1 +/- 6.0% of TLC, appeared to be determined by airway closure because the thoracic cage was compliant between FRC and residual volume. Vagotomy had no effect on the lung and thoracic cage PV curves, lung volumes, or the alveolar-arterial oxygen difference, but it decreased pulmonary resistance and increased respiratory system conductance and the dead space/tidal volume ratio, indicating dilation of large conducting airways. The calf appears similar to other neonates, in that the thoracic cage is compliant and airway closure occurs at large lung volumes. Both of these factors may predispose the calf to atelectasis.

Animals↗
PubMed1982

Acute toxicosis of budgerigars (Melopsittacus undulatus) caused by pyrolysis products from heated polytetrafluoroethylene: clinical study.

Polytetrafluoroethylene (PTFE), a synthetic polymer widely used as a nonstick surface in cookware, releases toxic pyrolysis products when exposed to excessive heat. Thirty-two budgerigars (Melopsittacus undulatus) were exposed to pyrolysis products of either heated PTFE cookware or plain aluminum cookware in a specially designed exposure chamber for given periods. Clinical signs were recorded and necropsies were done on all birds at the termination of each exposure period. The PTFE products caused acute respiratory distress and rapid death in many of the exposed birds. At necropsy, lesions were seen only in the respiratory tract--extensive pulmonary hemorrhage and congestion.

Acute Disease↗
PubMed1982

Acute toxicosis of budgerigars (Melopsittacus undulatus) caused by pyrolysis products from heated polytetrafluoroethylene: microscopic study.

An ultrastructural study was performed on the respiratory system of budgerigars (including 6 controls) which were acutely affected by inhalation of toxic fumes from heated polytetrafluoroethylene (PTFE pyrolysis products) or had survived fro 24 hours after a sublethal exposure. The controls were exposed to fumes from heated plan aluminum (ie, not coated with PTFE). The microanatomy of lungs of the controls was described and compared with that of lungs of the birds exposed to PTFE pyrolysates. The PTFE pyrolysates caused extensive, severe necrotizing and hemorrhagic pneumonitis. These lesions were associated with amorphous elongate conglomerates of particles which were similar to those isolated on membrane filters from fumes generated from heated PTFE--this supporting the hypothesis that the toxic principle in PTFE pyrolysates is at least, in part, related to generated particulates.

Acute Disease↗
PubMed1982

Pulmonary effects of intravenous histamine in the conscious pony: dose-response relationships and reproducibility.

In standing sedated ponies, we measured dynamic lung compliance (Cdyn) and pulmonary resistance (RL) during IV infusion of various doses of histamine; this was done in a given pony 3 times at 1-week intervals between experiments. Histamine doses causing a decrease in Cdyn of 50% and 75% and an increase in RL of 300% and 600% (ED50Cdyn, ED75Cdyn, ED300RL and ED600RL, respectively) were interpolated from the histamine dose-response curves. We also measured respiratory frequency, tidal volume, minute ventilation, functional residual capacity, arterial oxygen tension, arterial carbon dioxide tension, arterial oxygen tension, arterial blood pressure before and after infusion of histamine sufficient to cause a decrease in Cdyn of at least 75% and at least a 600% increase in RL. Histamine decreased arterial oxygen tension and functional residual capacity, but did not alter arterial carbon dioxide tension, pH, respiratory frequency, tidal volume, minute ventilation, and mean arterial blood pressure. There was at least a 6-fold variability in ED50Cdyn, ED75Cdyn, ED300RL, and ED600RL between ponies, but these values were very reproducible for each individual. The ED50Cdyn, ED75Cdyn, ED300RL, and ED600RL all decreased with increasing age.

Airway Resistance↗
PubMed1982

Pulmonary response of neonatal calves to intravenous and aerosol bradykinin.

The effect of IV and aerosol bradykinin on the lung quasistatic pressure volume curves, dynamic compliance, total pulmonary resistance, alveolar-arterial oxygen difference, and blood gas tensions was determined in anesthetized, ventilated neonatal calves. Bradykinin given by either route had no effect on these measures. Intravenous bradykinin caused pulmonary and systemic hypotension, but no change in hematocrit or total solids. Aerosol bradykinin had no cardiovascular effects.

Aerosols↗
PubMed1981

Histamine H1, H2 receptor effects on mechanics of ventilation and gas exchange in neonatal calves.

The effect of histamine infusion (IV) on pulmonary mechanical and gas exchange properties of healthy neonatal Holstein-Friesian calves was determined. Histamine increased pulmonary resistance and static pressure-volume hysteresis and decreased dynamic compliance, but failed to change static compliance; changes were compatible with constriction of both large and small airways without a change in lung elasticity. Histamine decreased arterial oxygen tension by increasing the alveolar-arterial oxygen difference, probably because ventilation-perfusion inequalities resulted from small airway constriction. The pulmonary mechanical and gas exchange effects of histamine were prevented by pretreatment with the H1 receptor antagonist, tripelennamine, but not with the H2 receptor antagonist, metiamide. The histamine-induced changes in static pressure-volume hysteresis and dynamic compliance were reversed by sighing, and histamine effects on the lung were eliminated by 15 minutes after cessation of histamine infusion.

Animals↗
PubMed1980

Case report: cystic dilatation of the parotid duct of a goat.

Cystic dilatation of the parotid duct of a goat was diagnosed by exploratory surgery and analysis of cyst contents. The cyst and its associated salivary gland were surgically removed. This case is compared with the more common salivary mucocele.

Animals↗
PubMedDate not supplied

Airflow mechanics in models of equine obstructive airway disease under conditions simulating exercise.

Effects of respiratory tract obstructions on ventilatory mechanics in horses exercising at high speeds were tested with a fibreglass replica of the airways (nares to mainstem bronchi) of an adult horse. Segmental pressures were recorded at six sites along the model at four different unidirectional flows (1300-4100 litre min-1), and the respective resistances (R) to airflow were calculated. The external nares and the larynx made the greatest contributions to the total resistance (RTOT) when no obstruction was present. Modifying the model to simulate severe pharyngeal lymphoid hyperplasia (PLH) had no effect on R at the larynx or at any point in the trachea under these flow conditions. Two 16 litre anaesthetic rebreathing bags were attached to the bronchial end of the model, and tidal ventilation generated by a piston pump. Upper (nares to pharynx) and lower tract R (RU and RL) and RTOT, and dynamic compliance were determined for pump volumes (Vp) of six and 12 litres, at pumping frequencies (fp) of 20-100 min-1 while the airway was clear, and after modifying it to simulate either PLH or partial bronchial obstruction. Model condition had no effect on RU. However, RL and RTOT were higher in the PLH simulated condition when fp > or = 90 and Vp = 12 litres (P < 0.05). This suggested that severe PLH may significantly interfere with airflow distal to the site of the lesions during high frequency high volume ventilation of the type seen in galloping horses. With partial bronchial obstruction RL and RTOT were increased when fp > 34 with each Vp. The applicability of the model was verified by comparing results from the unobstructed state with those from normal horses exercising on a treadmill.

Animals↗
PubMedDate not supplied

Experimental hendra virus infectionin pregnant guinea-pigs and fruit Bats (Pteropus poliocephalus).

Antibodies to Hendra virus (HeV) have been found in a high percentage of fruit bats (Pteropus spp.) in Australia, indicating a possible reservoir for the virus. The aim of the experiments reported here was to investigate transplacental infection as a possible mode of transmission of the virus in fruit bats and other animals. In a first experiment, 18 pregnant guinea-pigs in the mid-stage of gestation were inoculated with HeV, as an experimental model in a conventional laboratory animal. Nine developed HeV disease as confirmed by viral isolation, histopathology and immunohistochemistry. In five of the nine clinically affected guinea-pigs there was necrosis and strong positive immunostaining in the placentas in an indirect immunoperoxidase (IPX) test for HeV antigen. One of these five guinea-pigs aborted and HeV was isolated from its three fetuses, one of which was also positive to the IPX test. In three other sick guinea-pig dams, virus was isolated from fetuses, and there was positive immunostaining in two of the latter. In a second experiment, four fruit bats were inoculated with a similar dose of HeV. (A further four guinea-pigs inoculated at the same time developed severe disease, indicating adequate virulence.) Two bats were killed at 10 days post-inoculation and two were killed at 21 days. In these bats, no overt clinical disease was observed, but subclinical disease occurred, as indicated by viral isolation, seroconversion, vascular lesions and positive immunostaining. Transplacental transmission was indicated by positive immunostaining in two placentas and confirmed by isolation of virus from one of the associated fetuses.

Animals↗
PubMedDate not supplied

Interaction of saddle girth construction and tension on respiratory mechanics and gas exchange during supramaximal treadmill exercise in horses.

OBJECTIVE: To determine the effect of girth construction and tension on respiratory mechanics and gas exchange during supramaximal treadmill exercise in horses. METHODS: Six healthy detrained Thoroughbred horses were exercised on a treadmill inclined at 10% at 110% VO2max. Horses were instrumented for respiratory mechanics and gas exchange studies, and data were recorded during incremental exercise tests. The animals were exercised for 2 min at 40% VO2max, and samples and measurements were collected at 1 min 45 sec. After 2 min, speed was increased to that estimated at 110% VO2max and data was collected at 45 sec, 90 sec and every 30 sec thereafter at this speed until the horses fatigued. Horses were run on three occasions with the same racing saddle and saddle packing but using two different girths, either an elastic girth (EG) or a standard canvas girth (SCG) which is nonelastic. A run with 5 kg tension applied to a standard canvas girth was the control for each horse, with additional runs at 15 kg using either the standard canvas girth or using the elastic girth. The runs were randomised and tensions applied were measured at end exhalation whilst at rest. RESULTS: Increasing girth tension was not associated with changes in respiratory mechanical or gas exchange properties. Although girths tightened to 15 kg tension had short run to fatigue times this was not found to be significantly different to girths set at 5 kg resting tension. Girth tensions declined at end exhalation in horses nearing fatigue. CONCLUSIONS: Loss in performance associated with high girth tensions is not due to alteration of respiratory mechanics. Loss in performance may be related to inspiratory muscles working at suboptimal lengths due to thoracic compression or compression of musculature around the chest. However, these changes are not reflected in altered respiratory mechanical or gas exchange properties measured during tidal breathing during supramaximal exercise. Other factors may hasten the onset of fatigue when horses exercise with tight girths and further studies are required to determine why excessively tight girths affect performance.

Abdomen↗
PubMedDate not supplied

Comparison of girth materials, girth tensions and their effects on performance in racehorses.

OBJECTIVE: To compare the effect of girth materials and commonly used girth tensions on athletic performance of race-horses and to test the length tension properties of commercially available girths. PROCEDURE: Seven horses were exercised at speeds to produce 95% of maximal heart rates on 15 occasions using a randomised block design, and girthed with 5 different girths at 3 nominal tensions of 6, 12 or 18 kg. The girths used were a standard elastic race girth, an 'American' elastic race girth, an elastic race girth twice the normal width, a standard canvas race girth and a canvas race girth at twice the normal width. Tension in the girth was recorded continuously using an in-line load cell connected to a physiograph. Horses ran to fatigue on a treadmill inclined at 10% slope. Tensions were measured at peak inhalation (T/inh) and exhalation (T/exh), recorded at rest (rest) and during exercise (ex). An analysis of variance was used to compare the mean run to fatigue times (RTFT) between girth types and tensions, multiple pair-wise comparisons were then carried out using Tukey's test where significant differences were found. The length-tension relationships of five commercially available girths for training and racing of Thoroughbred racehorses were studied by the application of standardized weights in series to multiple samples of each type of girth. Measurements were taken in a controlled environment and analysis of variance was used to compare the means for length-tension of each girth type. RESULTS: The elastic and the 'American' elastic girths produced significantly longer RTFT when compared to the standard canvas girth (P = 0.01 and P = 0.001 respectively). Also girths tensioned at Texhrest 6 kg and Texhrest 12 kg produced significantly longer RTFT than when girthed at Texhrest 18 kg (P = 0.03 and P = 0.08 respectively). There were significant differences between the commercially available girth types at each tension (P < 0.05), but differences were not significant between girths of the same type. Girths with an elastic component reached their peak for maximum extension at 14.5 kg and thereafter their extension declined. CONCLUSION: The type of girth and the tension at which it is applied affects athletic performance. Lower girth tensions and the use of elastic materials in the girth would appear to optimise performance. However according to this study and our previous study, none of the commercially available girths studied would adequately protect against the potentially detrimental effects of overtightening on athletic performance.

Abdomen↗