Effects of treadmill exercise on osmotic fragility of circulating erythrocytes in jugular venous blood were investigated before and after splenectomy in 3 control and 3 splenectomized thoroughbreds. Both before and after the operation, the fragility of circulating erythrocytes significantly decreased with warming-up, but significantly increased with incremental exercise, and again significantly decreased with cooling down. The fragility of circulating erythrocytes was lower than that of the autologous splenic red cells, and it gradually decreased after the splenectomy. These result suggest that: 1) frequent accumulation in the spleen accelerates the fragility of erythrocytes; and 2) heavy exercise increases fragility, but light exercise decreases it, regardless of the release of red cells from the spleen into the circulation.
Changes in cell density and osmotic fragility of erythrocytes during exercise were determined in 3 control (Group C) and 3 splenectomized (Group S) horses that performed an incremental exercise test on a treadmill until the point of fatigue. Venous blood samples were drawn before the start of the treadmill program, and immediately after the warm-up and the incremental exercise test. After the incremental exercise in Group C, red cells in both groups were swelled by washing with PBS regardless of exercise. Warm-up did not change the density of fractionated red cells that were separated by the method of Murphy in both groups of horses. In contrast, incremental exercise significantly increased the density of cells in Group C but not in Group S. The osmotic fragility of fractionated red cells was significantly lower in Group S than in Group C horses regardless of exercise. Warm-up significantly decreased the fragility, but incremental exercise significantly increased it in all fractionated erythrocytes from both groups. There are two possible explanations for the above phenomena: 1) Erythrocytes which are released from the spleen by strong contraction during heavy exercise show a stronger tendency to regulatory volume decrease which shows osmotic sensitivity, but not during light exercise; and/or 2) The sensitivity of the regulatory volume decreases and membrane fragility versus exercise stress increases with the repeated accumulation of erythrocytes in the spleen.
Pulsed-field gel electrophoresis (PFGE) analysis was used to type 98 strains of Staphylococcus aureus isolated from horses. Fifty-three metritis strains in the Hidaka district of Hokkaido between 1985 and 1991 produced 12 different patterns (A-L). Various genotypes of S. aureus have been found to be involved in metritis, but the same few genotypes of S. aureus were isolated repeatedly from metritis in that period. Ten dermatosis strains in Ibaraki Prefecture between 1985 and 1988 produced 2 patterns (D and G1). The 2 patterns were also found in isolates from metritis. Thirty-five strains obtained from the penis swabs of 7 stallions (5 strains/horse) at one stud farm in the Hidaka district in 1998 belonged to a very closely related group; these strains appear to have originated in a common source. Interestingly, the PFGE patterns of the penis strains were similar to the pattern D observed in both metritis and dermatosis. These results demonstrated the usefulness of the PFGE method for epidemiological investigations of S. aureus.