Biomaterial Database

Freeze-fracture electron microscopy of preexisting and nascent cell membrane in cleaving eggs of Xenopus laevis. 1976

J G Bluemink, and L G Tertoolen, and P H Ververgaert, and A J Verkleij

During cell division in the Xenopus egg (diameter 1.25 mm) new cell membrane is formed in the furrow region (rate of growth approx 4-10(4) mum2/min). Freeze-fracture electron microscopy has produced the following data. Preexisting plasma membrane faces show a reversed polarity with respect to particle distribution, i.e. more particles are attached to the E-face (density 1600-2200 particles/mum2) than to the P-face (300 particles/mum2). A frequency histogram of 2331 measured intramembranous particles does not show a continuous range of sizes. The following sizes were very obvious: 95 A (12%), 125 A (30%) and 180 A (6%). At the tips of surface protrusions both the E- and the P- face are particle-free. Nascent cell membrane fracture faces are more difficult to obtain. The particle density is low (E-face 300-500 particles/mum2). Lowering the ambient temperature to 5 degrees C for approx. 5 mins does not change the normal particle pattern, but it improves the output in nascent membrane fracture faces. The fact that in the Xenopus egg preexisting and nascent membrane regions are continuous but nevertheless maintain their highly different particle densities is noteworthy. The freeze-fracture data are discussed in relation to, among other things, the known values of the specific resistances of these membrane regions.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D010063	Ovum	A mature haploid female germ cell extruded from the OVARY at OVULATION.	Egg,Egg, Unfertilized,Ova,Eggs, Unfertilized,Unfertilized Egg,Unfertilized Eggs
D002455	Cell Division	The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.	M Phase,Cell Division Phase,Cell Divisions,Division Phase, Cell,Division, Cell,Divisions, Cell,M Phases,Phase, Cell Division,Phase, M,Phases, M
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D003572	Cytochalasins	11- to 14-membered macrocyclic lactones with a fused isoindolone. Members with INDOLES attached at the C10 position are called chaetoglobosins. They are produced by various fungi. Some members interact with ACTIN and inhibit CYTOKINESIS.
D005260	Female		Females
D005614	Freeze Fracturing	Preparation for electron microscopy of minute replicas of exposed surfaces of the cell which have been ruptured in the frozen state. The specimen is frozen, then cleaved under high vacuum at the same temperature. The exposed surface is shadowed with carbon and platinum and coated with carbon to obtain a carbon replica.	Fracturing, Freeze,Fracturings, Freeze,Freeze Fracturings
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014981	Xenopus	An aquatic genus of the family, Pipidae, occurring in Africa and distinguished by having black horny claws on three inner hind toes.