DLA 15 + Lecture 23-24

Question 1

Cystinuria

Answer 1

tubular reabsorption of cystine is decreased due to deficiency of cystine transporter

cysteine excreted in urine

tends to precipitate in the renal tubules
one of the causes of stones in children

Question 2

Hartnup disease

Answer 2

inherited defect in the transport of tryptophan

decreased absorption and increased excretion

may lead to NAD deficiency (Pellagra)
most are normal
need more niacin and protein

Question 3

symptoms of pellagra

Answer 3

diarrhea
dermatitis
dementia
death

Question 4

alanine metabolism

Answer 4

alanine is converted to pyruvate by ALT (with the help of B6)

alanine can be transferred to alpha-ketoglutarate to form glutamate

Question 5

one of the functions of the glucose-alanine cycle

Answer 5

takes care of the excess nitrogen in the muscle

Question 6

aspartate metabolism

Answer 6

asparagine is converted to aspartate by asparaginase

aspartate is converted to oxaloacetate by AST (B6)

aspartate can be converted back to asparagine by asparagine synthetase

Question 7

clinical importance of asparaginase

Answer 7

can be used to treat some forms of leukemia

reduces asparagine levels; thus inhibits cancer growth

Question 8

glutamate metabolism

Answer 8

glutamine is converted to glutamate by glutaminase

then glutamate is converted to alpha ketoglutarate by glutamate dehydrogenase

glutamate back to glutamine is done by glutamine synthetase

Question 9

reactions of the ammonia cycle: CPS I

Answer 9

activated by NAS (allosteric)
incorporates free ammonia

rate limiting step

Question 10

management of hyperammonemia

Answer 10

dialysis: acute emergency situation

administration of benzoic acid or phenylbutyrate
excreted in urine has hippuric acid (glycine)

low protein intake
prevention of stress

long term: liver transplant

Question 11

administration of phenylbutyrate for hyperammonemia

Answer 11

undergoes beta oxidation to phenylacetate

ends up forming phenylacetylglutamine
this compound is excreted in urine and removes two N atoms per molecule

Question 12

CPS I deficiency or Type I Hyperammonemia

Answer 12

sometimes responds to arginine therapy

arg forms NAG which might stimulate CPS I

seen to have hyperammonemia

Question 13

OCT deficiency or Type II hyperammonemia

Answer 13

Most common UCD
usually seen in males and more severe in males

X linked

elevated serum ammonia
elevated urine and serum orotic acid

Question 14

classic Citrullinemia

Answer 14

Argininosuccinate synthetase deficiency

diagnosis:
hyperammonemia
very high levels of serum citrulline
and citrulline in the urine

Question 15

Argininosuccinic aciduria

Answer 15

Argininosuccinate lyase deficiency

arginiosuccinate elevated in the plasma and CSF
elevated levels of citrulline
arginiosuccinate in urine

Question 16

arginase deficiency or Hyperargininemia

Answer 16

elevated blood ammonia and elevated arginine
ammonia levels not as high as others

treatment includes essential AA’s
but no arginine

adult onset
neurological disorders

Question 17

Acquired hyperammonemia

Answer 17

liver disease due to viral or drug induced hepatitis
alcoholic cirrhosis

in cirrhosis: there is porto-systemic shunting of blood, thus more NH4 in blood
lead to neurotoxicity

Question 18

treatment for Acquired hyperammonemia

Answer 18

low protien / high carb diet

lactulose

neomycin

Question 19

Ammonia Neurotoxicity

Answer 19

brain CT scan will show loss of cortical sulci and gray-white differentiation

cerebral edema

NH4 interferes with many functions such as brain metabolism, neurotransmitters, cell function

Question 20

saliva production and secretion

Answer 20

The acinus produces saliva similar to the plasma; its isotonic (contains Na, K, Cl, HCO3)

ducts modify the salvia (absorb Na, Cl, and excrete K and HCO3) thus hypotonic

Question 21

regulation of saliva secretion

Answer 21

regulated by parasympathetics and sympathetics

Ach, VIP, and Substance P increase Ca and effects volume of excretion

NE elevates cAMP and increases enzyme and mucus content

Question 22

enterogastrones

Answer 22

enteric hormones that inhibit gastric acid secretion

Question 23

H-K ATPase inhibitors

Answer 23

Omeprazole, Lanzoprazole

Question 24

histamine receptor blockers (H2)

Answer 24

cimetidine and ranitidine

Question 25

muscarinic antagonist

Answer 25

atropine

Question 26

gastrin receptor blocker

Answer 26

benzotript

Question 27

The gastric mucosal barrier

Answer 27

HCO3 is secreted and trapped in mucus gel which neutralizes acid in lumen

tight junctions prevent the back flow of H+ to protect the oxyntic cells