Summary
To observe the very early changes in platelets during hemostasis, exposed carotid
arteries of 3 rabbits were punctured with a needle, immediately fixed by 0.5% glutaraldehyde
solution and their inner surface examined with a scanning electron microscope (SEM).
Many platelets adhered in each case to the inner surface of the artery around the
wound and all of them, whether solitary or aggregated, showed a spheroidal form with
several pseudopodia.
Platelets in shed blood from the incised ear vein of 3 control and 3 heparinized rabbits
were fixed by glutaraldehyde and observed by SEM. The percentage of aggregated platelets
was 60.9% in the control and 84.1 % in the heparinized rabbits immediately after the
incision. The difference was statistically significant (P < 0.01). Sixty seconds after
the incision, the percentages of aggregated platelets in the samples from the control
and heparinized rabbits were 78.8% and 62.2% respectively. The difference was significant
(P < 0.01). In accordance with this phenomenon, the percentage of the number of flat
platelets decreased and that of altered platelets increased in the control rabbits.
In the heparinized rabbits, far fewer flat platelets and larger numbers of altered
platelets were observed in the samples than in those of the control rabbits immediately
after the bleeding. However, 15 or 30 seconds later, the platelets of the heparinized
rabbits showed fewer changes than those of the control.
