The backbone of the CIDR is a nylon spine covered by a progesterone (1.38 g) impregnated silicone skin. During the seven days in the vagina the CIDR releases a relatively constant dosage of progesterone. Upon removal of the insert, progesterone is quickly eliminated.
variant. an organism or tissue that is different from the majority of the population but is still sufficiently similar to the common mode to be considered to be one of them, e.g. a variant strain of classical swine fever (hog cholera) virus. 1  Facebook.
Antigenic variation refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters its surface proteins in order to evade a host immune response. It is related to phase variation.ntigenic variation is the expression of various alternative forms of antigen on the cell surface. Whereas phase variation is the phenotypic switch that is usually reversible and is referred to as an ON-OFF switch.