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16 Cards in this Set
- Front
- Back
What is diagnostic enzymology?
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a means of locating where tissue injury or stimulation of increased production has occurred
serum enzyme activities are helpful in understanding the disease process and in making a diagnosis |
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How are enzymes measured?
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by their activities
enzymes catalyze biochemical reactions by converting a substrate into a product activity is measure by either disappearance of substrate or formation of product enzyme activity reported in international units/liter |
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What are leakage enzymes?
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maybe in cytosol, organelles or both
enzymes escape from the cell as a result of injury to cell membranes or organelles injury may be as severe as cell death or maybe as mild as increased cell membrane permeability examples: AST,ALT CK (seen with muscle damage) |
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What are induced enzymes?
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usually attached to membranes, rarely increased due to cell injury
increases are usually due to increased production |
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What happens to enzymes when the are released from tissue?
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enzymes are degraded or excreted from the body
they may persist, but they lose their activity over time the rate of degradation or loss is quite variable depending on the enzyme |
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What are some considerations when look at enzymes?
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the presence or absence of an enzyme in a specific tissue
the concentration of enzyme in the tissue where the enzyme does after leakage or secretion the half life of the enzyme isoenzymes (same catalytic activity, but other properties differ) |
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ALP has the longest half life in what organ? Shortest?
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Liver- 3 days
Intestine, placenta, kidney- 6 minutes |
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Does magnitude of ALT increase equal the severity of injury?
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no,needs to be 2-3 times RI
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What lab values indicate muscle injury?
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AST, CK, Urine Mb
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Where is creatine kinase found at highest concentration?
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free in the cytoplasm of muscle cells
-skeletal -cardiac -smooth muscle -CNS injury does not raise serum serum CK but may increase in cerebral spinal fluidQ |
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Where is apartate aminotransferase found in highest concentration?
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cytoplasmic associated with organelles
highest activity -skeletal muscle and cardiac mucles -hepatocytes ***not muscle specific** |
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What can causes increases in serum creatine kinase?
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skeletal muscle injury due to:
-necrosis -IM injectious -trauma -strenuous exercise Cardiac muscle injury muscle breakdown -severely anorexic cats |
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How long does it take for CK to show up and then return to normal after being elevated?
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Increases rapidly after injury 6-12 hours
very short half life can return to normal within 48 hours after an acute injury |
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What is ALT?
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liver specific enzyme in dogs and cats
can be increased with severe muscle damage |
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What is myoglobin?
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released from dead/dying muscle
-generally severe, acute injury low molecular weight not protein blood in blood -passes glomerulus readily and excreted in urine |
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How do you distinguish hemoglobin vs myoglobin?
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supporting laboratory data
anemia suggestes hemoglobin increased CK suggest myoglobin Myoglobin is rapidly cleared so serum usual not discolored can distinguish the two with ammonium sulfate precipitation test (precipitates hemoglobin not myoglobin) dipstick is + if it is myoglobin extreme hemoglobinuria may not all precipitate = false positive |