Fig. 2. Hair growth defects and lack of exocrine glands in c^IBN mice. (A) Only an intermediate type of hair is seen in c^IBN mice: monotrich/awl. In wild-type animals, all four types are found: Au, auchenes; Aw, awl; M, monotrich; Z, zigzag. Pictures were taken on a dark field using a Leica DC100 camera. (B) Strongly reduced numbers of hair follicles in newborn c^IBN pups compared with wild-type littermates, shown in plastic sections of back skin (upper panels). No hair follicle anlagen are seen in the tail of newborn c^IBN pups (middle panel, right), although they are readily detected in wild-type littermates (black arrows, left). Lower panels, dorsal skin sections of adult (P30) wild-type and c^IBN littermates. Owing to the decreased number of hair follicles in the adult c^IBN animal, the skin appears thinner. (C) Development of sweat glands in the foot pads is severely impaired. Compared with wild-type littermates, only very small residual glands can be detected in adult c^IBN mice (black arrows). (D) Meibomian glands in the eyelid of a control littermate (left panel, right arrow) are absent in a 1-month-old c^IBN mouse (right panel). The lid epidermis in wild-type animals (upper left panel, left arrow) is much thinner than in c^IBN mice (right panels). The lower two panels show a magnified view of the part of the lid displaying the mucous membrane and the Meibomian glands (left panel, arrow), which are absent in c^IBN mice (right). Connective tissue and the thickened epidermis of the lid margin (right panel, arrows) and a hair follicle (arrowhead) are indicated.