RAT WHOLE-EMBRYO CULTURE SYSTEM AS A TOOL TO INVESTIGATE DEVELOPMENTAL MECHANISMS OF LEFT RIGHT BODY AXIS/

The rat whole embryo culture (WEC) system is a suitable experimental t ool for the study of the mechanisms of development of the left/right b ody axis (L/R axis) because embryos can be cultured from before and du ring the development of several asymmetric structures including the he art. This paper reviews the development of asymmetric structures in ra t embryos during the culture period and the literature on abnormal dev elopment of the L/R axis studied using the WEC system. In addition, th e author suggests the following guideline for investigators who use th is system to study the development of the L/R axis. (1) Precisely stag e the embryos according to a modified Theiler's system. (2) Examine th e sidedness of three asymmetric structures whose sidedness is controll ed by different mechanisms [i.e. the heart, chorioallantoic placenta a nd the lower part of the embryo (the so-called 'tail')]. (3) Establish the background incidences of inversion of the above structures in con trol groups cultured from different stages. (4) Perform dose-response studies if testing a chemical. (5) Examine antagonists or inactive iso forms to confirm the pharmacological effects of the test chemical.