The mitochondrial enzyme involved in the metabolism of clopidogrel and proton pump inhibitors is:

 # The mitochondrial enzyme involved in the metabolism of clopidogrel and proton pump inhibitors is:

a. CYP 2A

b. CYP 2B

c. CYP 2C19

d. CYP 2C20

The correct answer is C. CYP 2C19.

Like ticlopidine, clopidogrel is also a prodrug. About 50% of the ingested dose is absorbed, and

only a fraction of this is slowly activated in liver by CYP2C19, while the rest is inactivated by other enzymes. It is a slow acting drug; antiplatelet action takes about 4 hours to start and develops over days. Since CYP2C19, exhibits genetic polymorphism, the activation of clopidogrel and consequently its antiplatelet action shows high interindividual variability. Some patients are nonresponsive. Omeprazole, an inhibitor of CYP2C19, reduces metabolic activation of clopidogrel and its antiplatelet action. However, like ticlopidine, the action of clopidogrel lasts 5–7 days due to irreversible blockade of platelet P2Y12 receptors. 

Reference: KD Tripathi's Essentials of Medical Pharmacology

Tooth affected with dentinogenesis imperfecta are generally of which shape

 # Tooth affected with dentinogenesis imperfecta are generally of which shape?

A. Tulip

B. Conical

C. Shell

D. Ovoid

The correct answer is A. Tulip.

Aberration in chromosome 4 (loci4q21.3) is associated with Dentinogenesis imperfecta. It encodes dentin specific sialophospho protein (DSPP) gene. Deficiency of sialoprotein is also suggested as a causative factor for Dentinogenesis imperfecta. Tooth affected with dentinogenesis imperfecta are generally tulip shaped. 

Brittle bone syndrome is caused by:

 # Brittle bone syndrome is caused by:

A. Improper synthesis of procollagen 

B. Polymerisation of collagen 

C. Increase osteoclastic activity 

D Increase fibroblastic activity 

The correct answer is A. Improper synthesis of procollagen.

Osteogenesis imperfecta, also known as Brittle Bone Disease, or 'Lobstein syndrome' is disorder of congenital bone fragility caused by mutations in the genes that codify for type I procollagen. This deficiency arises from an amino acid substitution of glycine to bulkier amino acids in the collagen triple helix structure. If the body does not destroy the improper collagen, the relationship between the collagen fibrils and hydroxyapatite crystals to form bone is altered causing brittleness. The following 4 types of osteogenesis imperfecta have been reported. Type I -mild form, type II -extremely severe, type III -severe, type IV -undefined. These partly depend on the genetic subtype. Type I and IV are the most common forms of osteogenesis imperfecta. 

Goldenhar syndrome is:

 Goldenhar syndrome is:

A. Facial deformity, auricular abnormalities and vertebral deformity 

B. Facial deformity, auricular abnormalities, vertebral deformity and genital lesion 

C. Facial and auricular abnormalities only 

D. Auricular abnormalities only 

The correct answer is A. Facial deformity, auricular abnormalities and vertebral deformity.

Goldenhar syndrome or oculoauriculovertebral dysplasia is caused by abnormality in the vascular supply of the head. Hemifacial microsomia is second most common craniofacial anomaly, causing reduced growth and development of one half of the face. The mandible, maxilla, zygoma, external & middle ear, hyoid bone, parotid gland, 5th & 7th nerves, musculature and other soft tissues. When hemifacial microsomia is associated with vertebral abnormalities and epibulbar dermoids, it is known as Goldenhar syndrome.