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CC LAB LDH Flashcards

1
Q

What method is used in Lactate dehydrogenase (LDH) Determination?

A

Kinetic Method by Buhl and Jackson, Modified by Wacker

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2
Q

The enzyme lactate dehydrogenase is distributed in _____, ____, ____, and _______

A

Heart, liver,muscle and kidney

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3
Q

Elevated serum levels are observed in?

A

Myocardial infarction, liver disease, certain forms of anemia, malignant diseases, and progressive muscle dystrophy

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4
Q

Lactate to pyruvate method offers a number of advantages such as____?

A

Better reagent stability, elimination of pre incubation in the procedure, rate of reaction being linear over a wide range , and less contamination of NAD with inhibiting products

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5
Q

LDH catalyzes the ___ of lactate to ____ in the presence of NAD, which is subsequently reduced to _____

A

Oxidation, pyruvate, NADH

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6
Q

The rate of NADH formation measured at ______ is ___ to the activity of serum LDH

A

340 nm; directly proportional

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7
Q

L-lactate + NAD <————> pyruvate + NADH + H+

A

LDH (ph 8.3 - 9.8)

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8
Q

True or False: Lactate dehydrogenase does not act on D- lactate

A

True

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9
Q

The pyruvate formed will proceed to the ______ for generation of energy

A

Embden-Meherhoff Pathway

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10
Q

Colorimetric Method based on Wacker

A mixture of ____ and _____ reacts with NADH to produce a ______ compound.

A

Phenazine methosulfate and Nitroblue tetrazolium; blue colored compound

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11
Q

The absorbance of this product is directly proportional to the amount of NADH present which in turn is proportional to the activity of LD in the sample.

A

Colorimetric method based on Wacker

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12
Q

This method involves the conversion of pyruvate to lactate by LDH (pH 7.4-7.8) in the presence of NADH

A

Wroblewski and La Due

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13
Q

True of False: The decrease in the concentration of NADH is measured and is directly proportional to the activity of LD in the sample. (Wroblewski and La due)

A

True

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14
Q

True or False: In Wroblewski and La Due Method, the rate of forward reaction is 3x faster than the reverse reaction, allowing smaller sample volumes and shorter reaction time.

A

False: the rate of reverse reaction is 3 x faster than the forward reaction

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15
Q

What are the methods for separation and quantitation of LDH isoenzymes?

A

Electrophoresis
Column chromatography
Immuno-inhibition
Babson’s Method
Kaplan and Berger
Using alpha-hydrobutyrate as a substrate

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16
Q

True of False: LDH1 migrates the fastest and LDH6 being the lowest

A

True

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17
Q

An LDH bound to immunoglobulin such as _____ and ____ migrate between LDH3 and LDH 4

A

IgA and IgG

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18
Q

This method is employed for isolation of LDH1 and LDH2 for screening of acute myocardial infarction

A

Column Chromatography

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19
Q

This method is used for the isolation of LDH1.

A

Immuno-inhibition

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20
Q

(Immuno inhibition) : An antibody to the _____ of lactate dehydrogenase is assed to a serum sample

A

M sub-unit

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21
Q

True or false: any isoenzyme containing an M-subunit binds to it, rendering the protein actively

A

False: inactive

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22
Q

Which LDH does not contain the M subunit?

A

LDH1

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23
Q

This measures the ratio of LDH1 to LDH5 by using solution of M-lactate to inhibit LDH1 and M-lactate- 1M urea to inhibit LDH5

A

Babson’s method

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24
Q

This method involves determination f LDH1 using the rate of heart production in a batch type of colorimeter

A

Kaplan and Berger

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25
Q

True or False: Using alpha-hydrobutyrate as a substrate; The M subunit has a greater affinity than that of the H subunit

A

False the H subunit has a greater affinity than that of the M subunit

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26
Q

What enzyme is used in the utility for the measurement of LD1 activity

A

Alpha-hydroxybutyrate dehydrogenase

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27
Q

True of false: It is not only specific to LD1 because LD2,3, and 4 also contains varying amount of H subunit

28
Q

True or False: hemolyzed specimen should not be used as red blood cells contain LDH activity 100-150 times that found in serum

29
Q

Sample and Assay considerations in LDH: For accuracy of results, It is advisable to analyze the sample immediately or within ____ hours of collection. In case of delayed processing, LDH is reported to be stable for _____ at room temperature

A

2 hours; 2 to 3 days

30
Q

True or False: The loss of activity occurs more quickly at 25 degrees Celsius than at 4 degrees Celsius

A

False: the lost of activity occurs more quickly at 4 degrees Celsius than at 25 degrees Celsius

31
Q

What isoenzyme is labile at cold temperature and is destroyed if frozen and thawned

32
Q

____ and ____ compete with lactate for its binding site on the enzyme

A

Borate and Oxalate

33
Q

True or False; Heparin inhibit LDH activity by chelating zinc (role as an activator is not fully established )

34
Q

True or False: pyruvate and lactate in excess cause inhibition of activity

35
Q

_____ is not recommended to use since a possible contamination with platelets exists

36
Q

This method is linear up to an LDH activity of _____ IU/L. Samples exceeding this value should be diluted ____ (1:1) with ____, rerun and multiply results by two

A

800 IU/L; two-fold; deionized water

37
Q

What isoenzyme of LDH is measured in this assay?

A

Total lactate dehydrogenase

38
Q

What is the temperature limitation of the assay (LDH)

A

Temperature must be maintained within +/- 0.1 degrees Celsius

39
Q

____ specifically catalyzes the oxydation of lactate to pyruvate with the subsequent reduction of NAD to NADH

40
Q

True or False; the rate which NADH forms is proportional to LD activity

41
Q

The method determines NADH absorbance increase per minute at ______

42
Q

What are the reagent composition of LDH determination

A

L-lithium lactate
NAD
non-reactive stabilizers and fillers
Buffer

43
Q

L- lithium lactate (____)

44
Q

NAD (____)

45
Q

Non-reactive stabilizers and fillers (____)

46
Q

Buffer (_____)

47
Q

What is the choice of specimen in LDH determination

A

Clear, non-hemolyzed serum

48
Q

Serum LDH is reportedly stable at ____

49
Q

These isoenzymes are decreased in frozen samples

A

LD4 and LD5

50
Q

What inhibits the assay for LDH determination

A

Heparin, Oxalate,and Citrate

51
Q

What requires a serum blank in LDH determination

A

Icteric and Lipemic samples

52
Q

Multiplying factor of LDH determination

53
Q

Total Assay Volume (____)

54
Q

Millimolar Absorptivity for NADH (____)

55
Q

Sample volume (____)

56
Q

Light path (_____)

57
Q

37-> 30C is multiplied by

58
Q

30C -> 37 C is multiplies by:

59
Q

Conversion factor

60
Q

Reference value for men at 30 C

A

50-166 U/L

61
Q

Reference value for men at 37 C

A

80-285 U/L

62
Q

Reference value for females at 30 C

A

60-132 U/L

63
Q

Reference value for females at 37 C

A

103-227 U/L

64
Q

Linearity of LDH determination

65
Q

Dry reagent should have a uniform __ or ____ appearance, and is stable at ____ until expiration date. Reconstituted reagent is stable for ___ at 2-8C.

A

White or Off-white appearance; 2-8C; 14 days

66
Q

Reagent absorbance greater than _____ (at 340 nm and 1cm light path) indicates deterioration

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