. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 114 G. R. WINKEL AND R. NUCCITELLI BWJIEM '1 100% 21/21 520 8191 17/21 1007, 21/21 "'-. 76% 16/21 -221 90% 19/21 -478 Figure 3. Diagramatic display of results from studies of 21 postim- plantation mouse embryos. The numbers (I -7) along the inner margin of the embryo represent the probe recording positions. At each position the length of the arrow represents the average current vector (MA/cnr) of all of the embryos. The numbers beneath each vector show the num- ber and percent of embryos exhibiting current with thi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 114 G. R. WINKEL AND R. NUCCITELLI BWJIEM '1 100% 21/21 520 8191 17/21 1007, 21/21 "'-. 76% 16/21 -221 90% 19/21 -478 Figure 3. Diagramatic display of results from studies of 21 postim- plantation mouse embryos. The numbers (I -7) along the inner margin of the embryo represent the probe recording positions. At each position the length of the arrow represents the average current vector (MA/cnr) of all of the embryos. The numbers beneath each vector show the num- ber and percent of embryos exhibiting current with this polarity. In a few embryos the detected current polarity was opposite to the average orientation. Note that at the embryonic/extraembryonic junction the inward current was more variable and likewise the average inward/out- ward magnitude was reduced. The point of maximum outward current was observed to be over the developing foregut, while the maximal in- ward current was over the extraembryonic yolk sac nearest the ectopla- cental cone. To further characterize the nature of these currents, we tested whether an artificially created leak, such as in puncture of the embryonic epithelium by a micropipet, would result in an outward current greater than that ob- served with an intact epithelium. This is indeed the case and in an embryo exhibiting a typical outward foregut current of ^A/cm2, we recorded currents of , , and ^A/cm2 at 2, 4, and 6 min after puncture with a micropipet. The larger value recorded initially supports the interpretation that the outward current is a passive leakage current. After a short interval of time this current stabilized to a value similar to that before injury, suggesting that the leak was repaired after a few minutes. This observation supports the hypothesis that outward current at the primitive streak is a passive leak due to the reduced junctional resistance along the embryonic midline (Jaffe and Stern. 1979). The above experime
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
