Case Studies Flashcards
(10 cards)
Which enzyme is deficient in Clumsy Calf 2 (citrullinaemia), and what metabolite accumulates as a result?
Argininosuccinate synthetase is deficient, causing citrulline and ammonia to accumulate.
What neurological consequence results from ammonia build-up in urea cycle disorders?
Ammonia enters the brain, is converted to glutamine, increasing osmotic pressure in astrocytes, leading to cerebral oedema.
Why is BUN decreased in a calf with citrullinaemia?
Urea is not being produced due to a block in the urea cycle, so BUN remains low despite ammonia build-up.
What metabolic changes indicate ovine pregnancy toxaemia?
Low glucose, high NEFA and ketones, low cholesterol
Why do pregnant ewes develop hepatic lipid accumulation in pregnancy toxaemia?
In response to hypoglycaemia, fats are mobilised and processed in the liver, which exceeds its capacity, leading to fat deposition.
What are the key blood findings in MSUD (Bitter Sweet case)?
Elevated leucine, isoleucine, valine and their keto-acids in blood and urine.
What enzyme is defective in MSUD, and what metabolic pathway is blocked?
Branched-chain α-keto acid dehydrogenase; BCAA catabolism is blocked.
What causes myelin oedema in MSUD?
Accumulation of BCAAs and keto-acids draws water into the myelin sheath, disrupting neuronal function.
Why might only some calves from the same parents show signs of citrullinaemia or MSUD?
These are autosomal recessive disorders, so only homozygous offspring (aa) will show symptoms.
How does low α-ketoglutarate due to ammonia toxicity affect cellular energy?
TCA cycle activity drops, ATP production decreases, contributing to neurological dysfunction.
