88.A pregnant 29-year-old woman diagnosed with type I diabetes 2
decades ago, taking Humulin three times per day, is referred to the oph-
thalmology clinic. She is complaining of “floaters” and difficulty with
night-time driving. Dilated indirect ophthalmoscopy coupled with biomi-
croscopy and fundus photography detect the presence of proliferative dia-
betic retinopathy with leaky retinal vessels indicative of increased vascular
permeability, growth of new, fragile vessels on the retina and posterior sur-
face of the vitreous and macular edema. Overexpression of fibronectin is a
histological marker of diabetic microangiopathy. Which of the following is
the primary function of fibronectin in the basement membrane?
a. Elasticity
b. Cell attachment and adhesion
c. Binding to selectins
d. Binding to cadherins
e. Binding to actin filaments
89.A 36-year-old man is referred by his family medicine physician to the
pulmonary clinic. He complains of shortness of breath following physical
activity and a decreased capacity for exercise. He says that strenuous exercise
including yard work is impossible without sitting down and resting every few
minutes. After he takes several deep breaths during the physical exam he
begins to wheeze. He is not a smoker and as an office worker he is not exposed
to dust, fumes or other irritants at work. He appears slightly jaundiced. Serum
alpha-1 antitrypsin (AAT) concentration is below normal and is followed up
with alpha-1 antitrypsin phenotype and DNA testing indicating one copy
of S and one of Z (SZ) mutations and 40% abnormal AAT protein produc-
tion. Desmosineand isodesmosine are elevated in the urine. Desmosine and
isodesmosine contribute to the elasticity of the lung by:
a. Cross-linking fibrillin
b. Cross-linking tropoelastin
c. Activating elastase
d. Inactivating AAT
e. Binding type IV collagen to elastin
172 Anatomy, Histology, and Cell Biology