Singleton K, Woodruff R I
Department of Biology, West Chester University, Pennsylvania 19383.
Dev Biol. 1994 Jan;161(1):154-67. doi: 10.1006/dbio.1994.1017.
In ovarian follicles of Drosophila, changes in external osmolarity affect the steady-state potentials of oocytes more than those of nurse cells. Thus the osmolarity of the incubation medium affects the occurrence and the direction of an electrical gradient across the connecting intercellular bridges. At 255 mOsm nurse cell Em averaged 2.5 mV negative to oocyte Em (P < 0.001). At 275 and at 300 mOsm there was no significant difference between oocyte and nurse cell. At 400 mOsm nurse cell Em averaged 1.1 mV positive to oocyte Em (P = 0.007). The osmolarity of adult Drosophila hemolymph was measured by a variation of freezing point depression and averaged 251 +/- 9 (SE) mOsm. The measured osmolarity and measured ionic concentrations of adult Drosophila hemolymph were used to develop an incubation medium, which was used to incubate developing ovarian follicles. Electrical measurements made in this saline, which mimics in vivo conditions, confirmed reports of a nurse cell-oocyte electrical gradient, with nurse cell Em significantly more negative than oocyte Em. Microinjections of the negatively charged dye Lucifer yellow CH showed that this charged molecule accumulated in the oocyte at the in vivo osmolarity, and in the nurse cells at highly elevated osmotic levels.
在果蝇的卵巢卵泡中，外部渗透压的变化对卵母细胞稳态电位的影响大于对滋养细胞的影响。因此，孵育培养基的渗透压会影响跨细胞间连接桥的电势梯度的出现和方向。在255毫渗量浓度时，滋养细胞的膜电位（Em）平均比卵母细胞的Em负2.5毫伏（P < 0.001）。在275和300毫渗量浓度时，卵母细胞和滋养细胞之间没有显著差异。在400毫渗量浓度时，滋养细胞的Em平均比卵母细胞的Em正1.1毫伏（P = 0.007）。通过冰点降低法的一种变体测量了成年果蝇血淋巴的渗透压，其平均值为251±9（标准误）毫渗量浓度。利用所测量的成年果蝇血淋巴的渗透压和离子浓度来配制一种孵育培养基，并用其孵育发育中的卵巢卵泡。在这种模拟体内条件的盐溶液中进行的电测量，证实了关于滋养细胞 - 卵母细胞电势梯度的报道，即滋养细胞的Em明显比卵母细胞的Em更负。对带负电荷的染料路西法黄CH进行显微注射显示，这种带电荷的分子在体内渗透压下在卵母细胞中积累，而在高渗透压水平下在滋养细胞中积累。
