. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. f-ER. Figure 1. Ultrastrncnire of upper eleur ;one in centrifugally stratified Arhacia egg. A. Unfertilized: B. fixed uhoitt 5 win after fertilization. After centrifiigalion on a Percoll-seawater density gradient for about 30 min {A), and after an additional 5 inin centrifugation following fertilization (B}. the eggs were fixed in 2% glularaldehyde phosphate Imfter made up in 700-inM sucrose solution. After confirming, with sections of the unfertilized eggs, that the negative birefringence in the upper part of the clea
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. f-ER. Figure 1. Ultrastrncnire of upper eleur ;one in centrifugally stratified Arhacia egg. A. Unfertilized: B. fixed uhoitt 5 win after fertilization. After centrifiigalion on a Percoll-seawater density gradient for about 30 min {A), and after an additional 5 inin centrifugation following fertilization (B}. the eggs were fixed in 2% glularaldehyde phosphate Imfter made up in 700-inM sucrose solution. After confirming, with sections of the unfertilized eggs, that the negative birefringence in the upper part of the clear zone remained intact, the cells were post fixed with osmium, dehydrated, embedded in Epon. and sectioned for electron \. In A. the upper region of the clear zone contains a dense stack of ER, oriented more or less in the direction of the centrifugal force (long arrow t. In B. onl\ small pieces of ER remain, consistent with the (transient) loss of the negative birefringence, at: annulate lamellae. ER: endoplasmic reticiilum. f-ER: fragmented ER. ne: nuclear envelope. Scale bars urn. fringence. Because the birefringence of activated live eggs does return in the upper half of the clear zone after about 10 min, albeit with less ordered alignment of the birefringence axes, the EM of cells fixed at that stage would be expected to again show stacks of large ER membrane sheets, but with the stacks ori- ented along less uniform axes. These observations suggest that the birefringence observed in live eggs with the CPM is a good indicator of membrane aniso- tropy, distribution, and especially their dynamic changes. In addi- tion, centrifugally fragmented mini-cells could well prove to be a useful source for several isolated membrane components of the cells. We thank Hamamatsu Photonics KK, Olympus Optical Com- pany, Kyoto University, and the Marine Biological Laboratory for support of this project. We also thank Louis Kerr and Christina Stamper of the MBL Central Microscop
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
