The effect of partial removal of yolk on the chilling sensitivity of zebrafish (Danio rerio) embryos

In a group of 39 patients with ischemic heart and valvular disease (January 1997 to May 1998), three platelet collection methods were compared in terms of safety and effectiveness. The methods were: (i) collection of autologous platelets over several weeks and freezing them for storage until surgery (frozen group, 12 patients); (ii) collection of autologous platelets on the day before surgery and preserving them without freezing (fresh group, 8 patients); and (iii) collection of autologous platelets intraoperatively (intraoperative group, 9 patients). Ten patients served as controls (control group). Blood pressure was not significantly affected by platelet collection in the frozen and fresh groups, but both systolic (P < 0.01) and diastolic blood pressure (P < 0.05) decreased significantly after collecting platelets in the intraoperative group. Similarly, heart rate was unaffected by platelet collection in the frozen and fresh groups, while it increased significantly in the intraoperative group (P < 0.05). Blood loss after 24 h was significantly smaller in the fresh group than in the frozen group (P < 0.05). Total blood transfusion volume was significantly smaller in the frozen and fresh groups than in the intraoperative and control groups (P < 0.05). Bleeding time 2 h postoperatively, when administration of autologous platelets had been completed, was reduced compared with immediately postoperative values in all three groups receiving autologous platelets (P < 0.05). However, only the frozen and fresh groups showed a significantly shorter bleeding time than the control group (P < 0.05). In all three groups receiving autologous platelets, the platelet count was significantly increased after administration of autologous platelets, but only the fresh group had a platelet count that was significantly greater than the control group (P < 0.05). From these results we conclude that the frozen and fresh groups received safer treatment than the intraoperative group. Although hemostasis improved after all three regimes of autologous platelet transfusion, only the frozen and fresh groups had a reduced need for allogeneic blood transfusion compared with the control group. For this reason we conclude that the frozen and fresh groups were also superior to the intraoperative group in terms of effectiveness. However, the recovery of platelets after frozen storage was low, and to obtain a good effect with the freezing method it is necessary to collect and store large volumes of platelets. In terms of simplicity, safety, and efficacy, the fresh method seems to be the preferred technique.