148 
Monitoring Stem Cell Research 
Endoderm: Lower layer of a group of cells derived from the inner cell 
mass of the blastocyst; it gives rise to lungs and digestive organs. 
(NIH) 
Endometrium: The mucous membranes lining the uterus. 
Endothelicd: relating to a flat layer of cells lining the heart, for exam- 
ple, or blood vessels. (SMD) 
Epidermal growth factor: A cell messenger protein that has effects 
including stimulation of epidermal development, in newborn animals 
it hastens eyelid-opening and tooth-eruption (SMD) 
Ex vivo: Outside the body, frequently the equivalent of “in vitro." 
Fate (of cell progeny): The normal outcome of differentiation of a 
cell’s progeny. 
Feeder layer: Cells used in co-culture to maintain pluripotent stem 
cells. Cells usually consist of mouse embryonic fibroblasts. (NIH) 
Fertilization: The process whereby male and female gametes unite. 
(NIH) 
Fetus: A developing human from usually two months after concep- 
tion to birth. (NIH) 
Fibroblast: A stellate (star-shaped) or spindle-shaped cell with cyto- 
plasmic processes present in connective tissue, capable of forming 
collagen fibers. (SMD) 
Gamete: A reproductive cell (egg or sperm). (CR) 
Gamma-interferon: A type of small protein with antiviral activity, 
made by T lymphocytes. 
Gastrulation: The process whereby the cells of the blastocyst are 
translocated to establish three germ layers. Also sometimes used to 
mark the end of the blastocyst stage and the beginning of the next 
stage of embryonic development. (Based on SMD) 
PRE-PUBLICATION VERSION 
