I got many replies to my request for information regarding microinjection of zebrafish embryos -- thanks to all who took the time to bestow knowledge upon me! Several people asked that I summarize the information I received, so here goes:
I asked about the volume that could be injected, and I got several responses in the 100-200 pl/egg range, as high as 500 pl/egg, but this apparently produces higher toxicity.
As far as concentration to inject, I'm injecting DNA, and I'm told that full-length DNA can be injected up to 100 ug/ml (more than that is again toxic) Oligos are reportedly more toxic, and RNA much less toxic than DNA.
Everyone who responded told me not to bother dchorionating the eggs -- that they can be injected through (though the chorion does tend to blunt the needle). I'm advised to use phenol red in the DNA, so I can see where it's going, but the phenol red needs to be spun down because it tends to clog the needle.
Some of those who responded inject blastomeres individually, others report that the blastomeres are connected by cytoplasmic bridges, and that diffusible vehicles can diffuse among blastomeres if only one in injected.
I understand that up to 200-300 embryos can be injected by the 8-cell stage if embryos are not dechorionated.
Many people gave me hints on holders to use for microinjection, I have made one that is described in the Zebrafish Book (version 2.1, page 5.29). This was easy and quick to make, and seems to work fine.
Many people referred me to Stuart, GW, McMurray, JV, and Westerfield, M: Replication, integration, and stable germ-line transmission of foreign sequences injected into early zebrafish embryos. Development 103 403-412 1988
I hope this information is helpful to others.
Lisa Cunningham