The objectives of the present study were: 1) to develop a simple and more efficient technique for sperm microinjection than is currently available, using the rabbit as a model, and 2) to evaluate the development of rabbit oocytes fertilized by single or multiple sperm microinjection. Hyperosmotic sucrose in phosphate-buffered saline (SPBS) was employed to dehydrate oocytes to increase the perivitelline space for sperm microinjection and prevent possible injury to the vitellus. In the first experiment, 58% (n = 29) oocytes treated with 0.5 M SPBS developed to morulae following multiple sperm microinjection compared, respectively, to 47% (n = 34) and 60% (n = 15) for control IVF with or without sucrose exposure (P greater than 0.05). Blastocyst development from microinjected oocytes, however, was much lower (P less than 0.05) than that of controls (14% vs. 42% and 40%, respectively). Sham operation by puncturing the zona pellucida of the sucrose-treated oocytes with the microinjection pipette did not increase parthenogenesis (P greater than 0.05). In Experiment 2 a smaller-size injection pipette and shorter sucrose exposure time after sperm microinjection resulted in 41% (n = 42) of the oocytes developing into blastocysts for the microinjection group, whereas only 21% (n = 24) developed to blastocysts in the control IVF group (P less than 0.05). When relatively older oocytes (17 hr post ovulation injection) were used to test if microinjection could reduce the time to fertilization and cleavage (Expt. 3), an average of 27% (n = 63) blastocysts resulted from microinjection vs. 0% (n = 28) for the control IVF group.
Traditional lead brass products pollute the environment and do harm to the human health. Fabrication of the new kind of the brass without lead is an urgent task. Bi-brass is the most popular lead-free easy-cutting brass. However, its mechanical and hot-working properties are not satisfied. In present paper, aluminum element was added into the Bi-brass alloy in order to improve the alloy’s mechanical and hot-working property. Experiment results showed that the aluminum can increase the surface tension of the Bi and change the existing morphology of Bi from film-like into particle-like. Therefore, the ingot’s hot-working property is excellent. Experiment results showed that even the extrusion ration reaches 256, the ingot still can be extruded into rod successfully. Experiment results also indicated that the homogenizing annealing treatment on the ingot and addition of the rare earth La did not improve the mechanical properties or the machinability.
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