Biomedical subjects

S A McKane

Publications and source records attributed to S A McKane.

6 recordsLinked to original sources

PubMed2002

Alveolar fibrosis and changes in equine lung morphometry in response to intrapulmonary blood.

Necropsy studies of horses suffering exercise-induced pulmonary haemorrhage (EIPH) have identified mild inflammatory lesions with evidence of alveolar fibrosis and bronchiolitis. These lesions were thought to be the result of viral infections that predisposed the affected regions of the lung to EIPH. We have shown previously that during erythrophagocytosis in the alveolar space, there is a prolonged period of macrophage influx and activation. This present study used morphometric analysis to quantify the effects of macrophage activity during erythrophagocytosis, on the alveolar cell population and physical structure of the alveolar walls. Segments of the bronchial tree were inoculated with either autologous whole blood or serum, at 15, 8, 3 days, 24 h and 30 min prior to euthanasia. Blood inoculation produced many significant changes in the alveolar morphometry including, increased numbers of alveolar macrophages, increased septal thickness, and a markedly increased percentage of collagen in the alveolar walls. Signs of chronic inflammation including increased macrophage activity and erythrophagocytosis coincided with increased alveolar macrophage numbers (10,688 +/- 1708 cells/mm3 to 30,957 +/- 6831 cells/mm3), septal thickness (4.1 +/- 0.4 microm to 6.1 +/- 0.5 microm) and alveolar septal collagen content (6.6 +/- 0.5% to 27.5 +/- 3.3%). The results suggest that intrapulmonary blood induces a macrophage dominated inflammatory response, septal thickening and the development of alveolar fibrosis. These changes are the probable cause of the observed alveolar fibrosis and bronchiolitis that was once suspected to be the originating cause of EIPH.

Animals↗

PubMed2001

Effects of exogenous insulin on glucose tolerance in alpacas.

OBJECTIVE: To evaluate the effects of exogenous insulin on clearance of exogenous glucose in alpacas. ANIMALS: 7 adult castrated male alpacas. PROCEDURE: Prior to each of 2 trials, food was withheld for 8 hours. Glucose (0.5 g/kg of body weight) was then administered by rapid IV infusion. During 1 of the trials, regular insulin (0.2 U/kg, IV) was also administered 15 minutes later. Blood was collected immediately before (0 minutes) and 15, 20, 25, 30, 45, 60, 90, 120, 180, and 240 minutes after glucose administration. Plasma concentrations of glucose and lactate were determined, and glucose fractional turnover rate and plasma half-life were calculated. RESULTS: Insulin treatment caused a significant increase in fractional turnover rate of glucose and plasma lactate concentration. Plasma glucose concentrations were less in insulin-treated alpacas from 30 minutes after glucose administration (15 minutes after insulin administration) until the conclusion of each trial, compared with nontreated alpacas. In addition, plasma glucose concentration in insulin-treated alpacas returned to baseline values 1 hour sooner than in the nontreated group. CONCLUSIONS AND CLINICAL RELEVANCE: Glucose uptake in alpacas improves after insulin treatment, suggesting that administration of exogenous insulin will increase the therapeutic and decrease the pathologic effects of exogenous glucose administered to hypoglycemic alpacas. However, alpacas and other New World camelids should be monitored carefully during treatment with glucose or insulin, because these species appear to be partially insulin resistant.

Animals↗

PubMed1999

Functional and compositional changes in pulmonary surfactant in response to exercise.

Pulmonary surfactant from bronchoalveolar lavages was obtained from 2 groups of horses. A control group consisting of 6 healthy racehorses that were paddock-rested and lavaged weekly for 6 consecutive weeks were compared with an experimental group of 10 healthy racehorses, lavaged weekly the same period, consisting of a 5 week incremental-intensity treadmill training programme and one week post training paddock rest. Phospholipid content of lavage fluid was determined indirectly by phosphorus assay, and surfactant functional activity was determined by bubble surfactometry. Total cell counts and differential cell percentages of lavage fluid were adjusted to reflect the dilution of alveolar epithelial lining fluid (ELF) using the lavage/serum urea ratio, and data were analysed per volume of ELF. There was no change in phospholipid content for either group, but some horses had consistently greater amounts than did others, ranging from 17.2-64.4 micrograms/microliter. From the exercised group ELF had both increased nucleated cell numbers due to increased macrophage numbers, and increased numbers of erythrocytes. Surface tension increased significantly over the exercise protocol, but not in controls. Functional activity of surfactant varied between horses, independent of phospholipid content, with average values for individuals ranging 10.5-29.5 mN/m. We conclude that exercise of sufficient intensity to induce intrapulmonary haemorrhage also leads to functional decrease in surfactant activity, without affecting phospholipid content. This study also indicates that functional differences in surfactant exist between horses and may be a risk factor for development of exercise-induced pulmonary haemorrhage.

Animals↗

PubMed1999

Sequential changes in bronchoalveolar cytology after autologous blood inoculation.

Six horses, free of recent exercise-induced pulmonary haemorrhage (EIPH), each had 8 bronchial segments inoculated with 40 ml of autologous blood lavaged on Days 3, 5, 7, 10, 14 and 21 after inoculation. The bronchoalveolar lavage (BAL) fluid samples were analysed, and total leucocyte counts and differential cell percentages determined. Statistical analysis of the differences between the 8 post inoculation and 1 pre-inoculation (control) lavage sites demonstrated an early neutrophilic response, rising from < 5% of alveolar leucocytes to 10% by 24-48 h post inoculation. As this response waned, macrophage numbers increased and persisted at mildly elevated levels for the remainder of the experiment. Small numbers of erythrophagocytes were observed prior to 3 days post inoculation, but their numbers increased 10-fold by Day 10. In the first 3 days, blood was observed endoscopically streaming from inoculated lung regions, suggesting that mucociliary clearance is a major mechanism of early erythrocyte clearance. However, both free and phagocytosed whole erythrocytes were recovered in lavages 14 days after inoculation with small numbers of erythrocytes still present at 21 days. We conclude that intrapulmonary blood provokes a mild, but prolonged inflammatory reaction and that the removal of alveolar haemorrhage is dependent on a combination of mucociliary clearance and phagocytic mechanisms. Erythrophagocytosis is slow to commence and the removal of blood prolonged, suggesting that horses in fast work, sufficient to induce EIPH, are unlikely to recover fully if intervals between strenuous work are less than 14 days.

Animals↗

PubMed1995

Comparison of bronchoalveolar lavage findings and measurements of gas exchange during exercise in horses with poor racing performance.

Twenty-four Thoroughbred and twelve Standardbred racehorses aged between 2 and 6 years, presented for reported poor racing performance, underwent clinical exercise testing. During the last 10 s of exercise at each speed throughout an incremental speed exercise test on a treadmill inclined at a 10% slope, samples of arterial blood and expired gases were collected. Maximum oxygen uptake and the partial pressures of oxygen and carbon dioxide in arterial blood were determined. These values were compared between the two breeds of horses and also with reference to cytological findings of bronchoalveolar lavage samples, including neutrophil, erythrocyte and haemosiderophage percentage and the total nucleated cell concentration. The results revealed an inverse relationship (Spearman R = -0.45, p < 0.05) between the total nucleated cell count in bronchoalveolar lavage samples and arterial oxygen partial pressure during exercise at 11 m.s(-1). This result suggests that subclinical pulmonary disease may be a more important cause of poor racing performance than previously thought. Also of note was a positive correlation (Spearman R = 0.50, p < 0.05) between maximum oxygen uptake and the percentage of erythrocytes.

Journal Article↗

PubMed1993

Equine bronchoalveolar lavage cytology: survey of thoroughbred racehorses in training.

Sixty-two Thoroughbred horses aged between 1 and 7 years in training in Sydney had bronchoalveolar lavage (BAL) samples collected for cytological examination. All horses, except the yearlings and those with a cough, had raced at the time of the examination and the trainers reported satisfactory performance. Free erythrocytes were found in 73% of samples and haemosiderophages in 90% of the samples, indicating immediate or past occurrences of exercise-induced pulmonary haemorrhage (EIPH). Bronchoalveolar fluid from the yearlings contained significantly less (P < 0.05) erythrocytes and haemosiderophages than samples from horses in other age groups. In the older horses, there was also more haemosiderin within the macrophages. No differences in BAL cytology could be attributed to gender, and there was no relationship between BAL cytology and racing performance. The main cytological findings were (mean +/- sd): total nucleated cells--832 +/- 578/microL with the main cell types being: macrophages--59 +/- 10% (haemosiderophages--20 +/- 24%); neutrophils--9 +/- 6%; lymphocytes--31 +/- 9%. The erythrocyte count was 10.3 +/- 17.7% of the total cell count. Horses with chronic coughing had a higher proportion of macrophages and a lower proportion of lymphocytes in the leucocytes obtained from BAL. There was a higher occurrence of EIPH detected in BAL findings than that previously reported when endoscopic examination has been used to diagnose EIPH. The occurrence and severity of EIPH as indicated by the BAL findings was found to be related to exercise intensity. The cytological findings were similar to those reported in horses in the northern hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)

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