Mandible is the common site for Ameloblastoma due to:

 # Mandible is the common site for Ameloblastoma due to:

a. SMO mutation

b. BRAF mutation

c. p53 mutation

d. SH3BP2 mutation

The correct answer is B. BRAF mutation.

Mutations in the oncogenes BRAF (kinase signaling pathway) in mandibular tumors and SMO (hedgehog signaling pathway) in maxillary tumors have been discovered in a large proportion of

ameloblastomas. Drugs developed to inhibit the mutated proteins of these genes may have a role in the future treatment of ameloblastomas. Mutations of the p53 gene do not appear to play a role in the development and growth of ameloblastoma; a role for ameloblastin protein has been identified, although it is not specific to ameloblastoma.

Addison's disease is due to:

 # Addison's disease is due to:

a. Chronic insufficiency of adrenal cortex

b. Chronic insufficiency of adrenal medulla

c. Insufficiency of pancreas

d. Hypofunction of thyroid gland

The correct answer is A. Chronic insufficiency of adrenal cortex.

Addison's disease, also known as primary adrenal insufficiency, is a rare long-term endocrine disorder characterized by inadequate production of the steroid hormones cortisol and aldosterone by the two outer layers of the cells of the adrenal glands (adrenal cortex), causing adrenal insufficiency. Symptoms generally come on slowly and insidiously and may include abdominal pain and gastrointestinal abnormalities, weakness, and weight loss. Darkening of the skin in certain areas may also occur. Under certain circumstances, an adrenal crisis may occur with low blood pressure, vomiting, lower back pain, and loss of consciousness. Mood changes may also occur. Rapid onset of symptoms indicates acute adrenal failure which is a serious and emergent condition. An adrenal crisis can be triggered by stress, such as from an injury, surgery, or infection. 

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.