519. Delta waves of electroencephalogram have frequency of:

1. More than 14 cycles per second. 
2. Between 8 and 13 cycles per second. 
3. Less than 3.5 cycles per second. 
4. Between 4 and 7 cycles per second.

518. Which of the following cell types show abnormal function when there is a history in a young adult of multiple arm and leg fractures following minor falls, with a slight weakness of facial muscles on the left, mild anemia, and with generalized bony widening with partial obliteration of marrow spaces?

 A.  Granulocytic stem cells 
 B.  Megakaryocytes 
 C.  Plasma cells 
 D.  Osteoblasts 
 E.  Osteoclasts

517. A 5-year-old child has blue-tinged sclera, hearing loss, and small, slightly blue, misshapen teeth. Radiologic studies confirm the presence of numerous fractures of various ages. No significant degree of bruising is seen over sites of recent fracture. The disease this child most likely has is related to abnormal metabolism involving which of the following substances?

 A.  Collagen 
 B.  Glycogen 
 C.  Mucopolysaccharides 
 D. Purines 
 E.  Tyrosine