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D K Mason

Publications and source records attributed to D K Mason.

At least 37 records · Page 2Linked to original sources
PubMed1987

Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. V. Microscopic observations.

Lungs from 19 Thoroughbred racehorses with a history of exercise-induced pulmonary haemorrhage (EIPH) were studied using several forms of microscopy. Light microscopy of paraffin sections revealed three lesions in the caudodorsal region of the lungs from each horse. These correspond with the location of blue to brown stains seen at necropsy. These lesions include sequelae of bronchiolitis, hemosiderophages and increased connective tissue. Much of each of the lungs appeared normal, especially the more cranial or ventral portions. Foci of eosinophil infiltration were found in seven of the 19 lungs examined. With two exceptions, these eosinophilic foci had a different distribution to the three lesions. In areas of severe bronchiolar changes and fibrosis, vascular lesions typical of hypertension were found occasionally. Transmission electron microscopy was used to confirm cell types seen by light microscopy and to examine arterioles for changes characteristic of neovascularisation. Areas of enlarged airspaces from the vascular injected right lungs were examined by scanning electron microscopy. The balance of fibrosis and destruction varied in these areas, but none were as extensive as those seen in chronic obstructive pulmonary disease. The authors hypothesise that bronchiolitis and related neovascularisation are essential components of the aetiology of EIPH.

Animals↗
PubMed1987

Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. VI. Radiological/pathological correlations.

This study was initiated to determine if the extent and intensity of lung lesions associated with exercise-induced pulmonary haemorrhage (EIPH) in horses could be predicted from thoracic radiographs. Sets of thoracic radiographs from 24 horses with varied histories of EIPH were subjectively coded for radiographic quality, and perceived extent and intensity of diffuse interstitial opacity by three radiologists who had no knowledge of the corresponding autopsy results. Codes assigned from radiographs for the chosen parameters were compared with coded estimates of lung surface staining assigned at post mortem and volume measurements of haemosiderin deposits and bronchial arterial neovascularisation recorded from lung slices in separate studies. The non-parametric Spearman rank correlation test was used to test for statistical significance. All radiographically coded estimates of lesion severity were positively correlated with post mortem measurements of actual lesion involvement, but only the correlation between coded estimates of lesion opacity versus haemosiderin deposits and bronchial artery neovascularisation were statistically significant (P less than 0.05). Correlations between radiographic codes for lesion extent versus haemosiderin deposits and neovascularisation were just beyond the level of significance (P greater than 0.05 less than 0.1). These findings indicate that there are graded, radiographically discernible increases in interstitial opacity related to actual lesion severity. However, under the conditions of the study, accurate prediction of lung pathology in individual cases based on radiographic criteria was precluded by the wide variance of the coded values. The authors believe that with good radiographic technique and careful criteria selection, satisfactory prediction of lesion severity in EIPH cases could be achieved.

Animals↗
PubMed1987

Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. VIII. Conclusions and implications.

This paper reviews a series of clinical, post mortem and imaging studies on exercise-induced pulmonary haemorrhage (EIPH) performed on 26 Thoroughbred racehorses. Post mortem techniques included routine gross, subgross and histological examination; coloured latex perfusions of pulmonary and bronchial circulations; and microradiography and computerised tomography scans of lungs with contrast injected vasculature. The major lesions were multiple, separate and coalescing foci of moderately proliferative small airway disease accompanied by intense neovascularisation of the bronchial circulation. As a result of bronchial artery angiogenesis, the systemic circulation dominated the vascular supply of the air exchange structures in affected areas, producing an apparent left to right shunt. Extensive areas of sequestered haemosiderophages indicated previous haemorrhage from vessels apparently supplied by the bronchial arteries. Diffuse and focal parenchymal destruction and connective tissue reactions in affected areas were considered to be secondary to localised haemorrhage and macrophage-induced damage. The aetiology of EIPH was not determined, but the multifocal, small airway-centred lesions indicated that low grade bronchiolitis, possibly of viral origin, was a factor. Gravitational effects also appear to contribute to dorsal distribution of the lesions. The mild focal and subclinical lesions confined to secondary lobules are thought to evolve into the serious lung pathology observed in EIPH cases through the effects of localised hypoxia induced by maximal exercise and partial airway obstruction. Once initiated, a vicious cycle of increasing inflammatory damage and further local bleeding is set in motion.

Animals↗
PubMed1987

Heterogeneity of amino acid transport in horse erythrocytes: a detailed kinetic analysis of inherited transport variation.

1. Thoroughbred horses were divisible into five distinct amino acid transport subgroups on the basis of their erythrocyte permeability to L-alanine, measured uptake rates ranging from 5 to 625 mumol l cells-1 h-1 (0.2 mM-extracellular L-alanine, 37 degrees C). 2. Erythrocytes from animals belonging to the lowest L-alanine permeability subgroup (5-15 mumol l cells-1 h-1) (transport-deficient type) exhibited slow nonsaturable transport of this amino acid. In contrast, cells from horses of the four transport-positive subgroups possessed additional high-affinity (apparent L-alanine Km (Michaelis constant) congruent to 0.3 mM) and/or low-affinity (apparent L-alanine Km congruent to 13 mM) Na+-independent transport routes selective for L-neutral amino acids of intermediate size. The two transporters, designated systems asc1 and asc2, respectively, also possessed a significant affinity for dibasic amino acids. 3. Amino acid transport activity in horse erythrocytes behaved as if controlled by three co-dominant alleles (s, h and l), where s is a silent allele, and h and l code for the functional presence of systems asc1 and asc2, respectively. 4. At physiological temperature, system asc1 operated preferentially in an exchange mode. In contrast, system asc2 did not participate in exchange reactions at 37 degrees C, but did exhibit significant trans-acceleration at 25 degrees C. 5. Reduction of the incubation temperature also resulted in dramatic decreases in apparent Km and Vmax for L-alanine uptake by system asc2, whereas the effects of temperature on system asc1 were much less marked. At 5 degrees C the two transporters exhibited equivalent kinetic constants for L-alanine influx. L-Alanine uptake by transport-deficient cells was relatively insensitive to temperature. Influx by this route may represent the ground-state permeability of the lipid bilayer. 6. The effects of low temperature on system asc2 suggest a preferential impairment of the mobility of the unloaded carrier relative to that of the loaded transporter. Similarly, the different kinetic properties of systems asc1 and asc2 at physiological temperature are attributed to a difference in the mobilities of the empty carriers, this difference being minimized at 5 degrees C.

Alanine↗
PubMed1986

Gastric ulceration in mature thoroughbred horses.

Routine post mortem examination of 195 Thoroughbreds in Hong Kong revealed that 66 per cent suffered from gastric ulceration. Racehorses killed straight out of training suffered a significantly greater incidence of ulceration (80 per cent) than those having been retired for a month or more (52 per cent). The macroscopic findings post mortem enabled a classification of equine gastric ulceration to be suggested (Types 1, 2, 3), according to severity. Severe lesions (Types 2 and 3) were present in 45 per cent of horses put down from training and 5 per cent of retired horses. This difference was significant. Lesions appeared to be chronically progressive during training, but to regress during retirement. The observed difference of gastric ulceration between the two groups of horses was similar for different age groups.

Animals↗
PubMed1985

Characterization of a novel Na+-independent amino acid transporter in horse erythrocytes.

Horse erythrocytes are polymorphic with respect to L-alanine permeability. The present investigation compared the specificity, kinetics and cation-dependence of erythrocyte amino acid transport in two groups of thoroughbred horses, those with erythrocyte L-alanine permeabilities in the range 5-15 mumol/h per litre of cells (0.2 mM extracellular L-alanine, 37 degrees C) (transport-negative type) and those with L-alanine permeabilities in the range 450-700 mumol/h per litre of cells (transport-positive type). Transport-positive cells are shown to possess a novel high-affinity, stereospecific, Na+-independent transporter selective for neutral amino acids of intermediate size. This carrier system (provisional designation asc) operates preferentially in an exchange mode and is functionally absent from erythrocytes of transport-negative-type horses.

Alanine↗
PubMed1985

Ultrastructural variations in the sweat glands of anhidrotic horses.

The ultrastructure of sweat glands from the skin of free sweating horses was compared with that of glands from anhidrotic cases. Evidence of atrophied and abnormal sweat glands in the anhidrotic horses indicates that the condition involves progressive failure of the glandular mechanism of sweat production.

Animals↗
PubMed1985

Breed and species comparison of amino acid transport variation in equine erythrocytes.

The amino acid permeability of red blood cells from Equus caballus (thoroughbred, Arab, shire and pony), E przewalskii (Przewalski's horse), E asinus (donkey and mule) and E burchelli (common or plains zebra) was measured. Individual animals exhibited stable but widely differing rates of L-[U-14C]alanine uptake in the range 5 to 1554 mumol (litre cells)-1 h-1 (0.2 mM extracellular L-alanine, 37 degrees C). Of the thoroughbreds tested, 30 per cent had red blood cells which were essentially impermeable to L-alanine (5 to 10 mumol (litre cells)-1 h-1, giving transport rates similar to those found previously in amino acid transport-deficient sheep erythrocytes. In contrast, only 3 per cent of the ponies tested had red blood cells impermeable to L-alanine. No cases of erythrocyte amino acid transport deficiency were found in the other horse breeds and species tested.

Alanine↗
PubMed1984

Effect of bedding on the incidence of exercise induced pulmonary haemorrhage in racehorses in Hong Kong.

An investigation into the incidence of exercise induced pulmonary haemorrhage (EIPH) in thoroughbreds in Hong Kong was carried out between the 1981 and 1983 racing seasons. A total of 1039 post race endoscopic examinations were performed in 1982-1983 and the results indicated that 46.8 per cent of runners had EIPH. This was not statistically different from the percentage of horses showing EIPH during 1981-82 (46.9 per cent). As it had been postulated that dust, especially from straw, could be implicated in lung haemorrhage a proportion of horses were bedded on paper in the 1982-83 season. No significant differences could be demonstrated in the incidence of EIPH resulting from the use of paper bedding in preference to straw.

Animals↗
PubMed1983

Haematological response to racing and training exercise in Thoroughbred horses, with particular reference to the leucocyte response.

The haematological response to racing and to fast and slow training exercise was investigated in studies involving two populations of horses which differed widely in geographical location, climatic factors and management (Newmarket and Hong Kong). The well documented elevations in erythrocyte parameters were demonstrated and changing responses in leucocyte parameters, resulting in variations in the neutrophil to lymphocyte (N/L) ratio were described. It was shown that the immediate response to the anticipation or stress of exercise was a decrease in N/L ratio in association with an increase in lymphocyte numbers. The magnitude of the lymphocyte increases was similar in the two populations of horses producing a reversal of the N/L ratio (lymphocytes predominating) in the British but not the Hong Kong horses, owing to the higher resting ratio of the latter population. At 3 and 4 h after exercise, an increase in N/L ratio occurred in association with an increase in neutrophils and decrease in lymphocytes. All parameters had returned to resting level by 6 h following exercise. Those and the many other factors associated with alterations in equine N/L ratios are discussed in terms of the need for care when interpreting the results of haematological examinations.

Animals↗
PubMed1979

Dry mouth.

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Adult↗
PubMed1977

Nutritional deficiency in oral candidosis.

A retrospective study of 108 patients was carried out to investigate the possible relationship between infection of the mouth with Candida albicans and blood levels of iron, folic acid and vitamin B12. The patients were separated into two groups--those with hyperplastic and those with atrophic candidal lesions--and compared with separate control groups. Twenty-one patients had chronic hyperplastic candidosis and seven were iron deficient. Comparison with an age- and sex-matched control group showed the differences to be significant only at the p less than 0.1 level. Seven of the patients with hyperplastic lesions had folic acid deficiency and the difference between patients and controls was statistically significant (less than 0.05). However, no significant differences in iron or folic acid deficiency were noted between 87 patients with atrophic candidosis and 65 conttrols, and vitamin B12 deficiency was not statistically significant for either the hyperplastic or the atrophic group. It is concluded that deficiency of iron, folic acid or vitamin B12 alone does not promote growth of Candida albicans on the oral mucous membrane but that in some susceptible individuals, iron or folic deficiency may facilitate epithelial invasion by hyphae of Candida albicans.

Atrophy↗
PubMed1977

Some haematological and biochemical parameters in race horses in Hong Kong.

Haematological and biochemical values were determined in 2 groups of flat-race horses, which were trained on the same track in Hong Kong. The first group comprised 217 horses (435 blood samples) from various training strings. The second group, 66 horses (309 blood samples) were from one string kept under similar managemental conditions, but given salts by stomach tube 8 hours before blood sampling. Both groups were sub-divided to show the efs, thus confirming work by other authors. The lower haematological values in the group of horses given salts were discussed and the effect of water retention as a possible explanation was considered.

Age Factors↗