Lecture 10 - B12

Question 1

B12 and Folate?

Answer 1

B12 cleaves methane from inactive folate to activate it, both folate and B12 coenzyme active and available to donate methane for DNA synthesis

Question 2

Requirements to absorb B12?

Answer 2

Acid to release food-bound cobalamin, intrinsic factors released from parietal cells, pancreatic secretions, normal ileal absorption

Question 3

Conservation of B12?

Answer 3

Enterohepatic circulation, liver stores

Question 4

Megaloblastic Anaemia?

Answer 4

B12 deficiency, blood cells larger and irregularly shaped

Question 5

R-Binders?

Answer 5

Secreted in saliva and stomahc, can bind to B12, pancreatic enzymes cleave this so B12 can bind to intrinsic factor

Question 6

B12 Stomach problem?

Answer 6

Percinious anaemia: autoimmune disease against intrinsic factor

Question 7

Testing for Pernicious Anaemia?

Answer 7

Antibodies to either parietal cells or intrinsic factor, autoimmune gastritus in biopsy, raised plasma gastrin indicating low acid output, evidence of other autoimmune

Question 8

Treating Pernicious Anaemia?

Answer 8

1000 micrograms weekly for 4-6 then every 4 months, intramuscular as poor GI absorption

Question 9

Monitoring response to B12 replacement?

Answer 9

Check B12 levels, increase in haemoglobin/reticulocyte response, resolution of neurological symptoms

Question 10

Low B12 following partial Gastrectomy?

Answer 10

No antrum means no G cells and low gastrin, no pylorus means bile reflux to stomach causing atrophic gastritus (loss of parietal cells releasing intrinsic factor)