We investigated the effects of incline on cardiopulmonary function in five trained 2-year-old Thoroughbred horses during exercise on a high-speed treadmill. The horses began exercise at 1.5 m/s for 2 min followed by 1 min step increments at 4.0, 7.0, 8.0, 9.2, and 10.4 m/s. Each horse performed the exercise test on separate days with at least 2 days interval at four different inclines (0, 3, 6 and 10%). The sequence of exercise test was randomized. The major findings were: 1) Oxygen uptake (Vo2), carbon dioxide production (Vco2), minute ventilation (VE), tidal volume (VT), heart rate (HR), cardiac output (Qt), and % O2 extraction increased linearly with speed and incline, however the regression estimates of the change in Vo2/change in speed (ΔVo2/ΔSp) increased with increasing incline. 2) VE increased linearly with speed and was a function of increased VT and respiratory frequency (f), however the linear increase in VE with incline was solely due to increased VT as f was unchanged. 3) The VE/Vo2 slope for 0% incline was greater than the slope 3%, 6%, 10% incline. 4) The increase in arterio-mixed venous oxygen content difference (Ca-vDO2) with speed and incline was mainly due to the decrease in CvO2, whereas CaO2 increased only slightly with incline and speed. 5) The increased Qt with speed and incline was due to increases in HR, as stroke volume was unchanged with speed and incline.
To clarify the effects of free amino acid types on the change in the physiological character of equine erythrocytes with in vivo aging, the cell density, mean cell haemoglobin concentration (MCHC), acetylcholinesterase activity, osmotic fragility, alanine influx and reduced glutathione (GSH) content of the erythrocytes which were fractionated by the method of Murphy were compared among three types of horses which were classified according to the basic amino acid -positive (BA+) and -negative (BA-), and GSH -low (GSH.L) and -high (GSH.H): type [BA+ :GSH.L] (I), [BA+ :GSH.H] (II) and [BA-:GSH.H] (III) of erythrocytes. Except two of the type III animals, the cell density, MCHC, acetylcholinesterase activily and osmotic fragility of each cell population which was separated into six fractions based on density did not differ significantly among the three cell types. The increase in cell density was associated with a progressive increase in MCHC, and with the decrease in acetylcholinesterase activity and osmotic fragility. The osmotic fragilities of the above two type III were much higher than those of other horses, and did not differ among the six cell fractions. The alanine influx and GSH content of each fractionated cell showed significant differences among the three cell types. The ranking for alanine influx was type I < II < III, and that for GSH content was type I < II =(nearly equal) III. Increase in cell density was associated with a progressive decrease in the alanine influx of both types II and III, but not type I, and a decrease in GSH content in all three types of cells. These experimental results suggest that an increase in equine erythroid density is a function of their in vivo aging, regardless of the three cell types defined by BA and GSH systems. Moreover, the variation in alanine influx and GSH content in erythrocytes among the three cell types might take place before the release of mature red cells from the bone marrow into the circulation.
Equus is one of the most successful plays written by Peter Shaffer, a contemporary British dramatist. Equus is the name of a deity in the myth that Alan, a teenager protagonist, made. Alan, however, ended up in blinding horses as the result of his worship of this deity. Why did Alan blind horses? I found some possible reasons for his blinding horses: his ambivalence to the god, Equus; or the embodiment of his super-ego; or the denial of adult society. I suggest, more importantly, the fear of Eros. Some critics agree only that the horses’ sight interrupted Alan’s sex, but I propose Eros has a more important role for Alan than the physical look. Shaffer’s horses on the stage symbolize Alan’s problem effectively.