orientation and are also important in establishing tissue organization and
flexibility(answer a).Electrostatic interactions (answer c)do not play a
significant role in maintenance of collagen tensile strength. Lysine, along
with hydroxylysine, is the substrate for lysyl oxidase that catalyzes the for-
mation of cross-links (answer e).
98.The answer is e.(Alberts, pp 1081–1088, 1107–1108, Junqueira, pp 67,
91, 115–116.)Laminin is a glycoprotein and a major component of all
basement membranes that is involved in cell adherence to the basal lam-
ina. Laminin in the lamina rara (lucida) of the basal lamina binds to the
laminin receptor (integrin) on the epithelial cell (answer a).Cell-cell
interactions(answer b)are modulated by the cell adhesion molecules
[e.g., the Ca^2 +-dependent cadherins and selectins and the Ca^2 +-independent
CAMs, such as the neural cell adhesion molecule (N-CAM)]. Laminin con-
tains RGD and YIGSR cell-binding sites as well as binding sites for colla-
gen, entactin, and heparan sulfate proteoglycan. Type IV collagen forms
the insoluble scaffolding of the basal lamina (answer c).The highly
charged glycosaminoglycans are responsible for the filtration characteris-
tics(answer d)of the basement membrane (e.g., renal glomerular base-
ment membrane).
99.The answer is e.(Kasper, pp 228, 1953–1954. Junqueira, pp 97–99,
101–103.)Mastocytosis is a disease in which there is excessive produc-
tion of mast cells by the bone marrow. The cells in the biopsy are mast
cells that stain metachromatically (change color of the stain from blue to
purple). Like basophils, they synthesize and secrete heparin and hista-
mine. The result of mastocytosis is an excessive release of the bioactive
products contained in mast cell granules: histamine, heparin, eosinophil
chemotactic factor of anaphylaxis (ECF-A), slow-reacting substance of
anaphylaxis (SRS-A), and leukotrienes. Mastocytosis induces urticaria
pigmentosa (the skin condition from which the patient in the scenario suf-
fers), including edema (caused by the increased vascular permeability
induced by histamine and SRS-A). In mastocytosis, there is infiltration of
eosinophils (attracted by ECF-A), which causes itching. Excessive pro-
duction of acid by the parietal cells of the stomach (answer a)occurs
because of the overstimulation of histamine receptors on these cells. This
can result in peptic ulcers and gastritis. Lower GI tract symptoms include
188 Anatomy, Histology, and Cell Biology