Clinical Pathology - Specific Proteins

Front 1

total protein is measured using serum, which lacks ___

Back 1

fibrinogen, as does the SPEP sample

Front 2

cathode vs anode

Back 2

cathode(negative pole, attracts cations)

anode(positive pole, attracts anions)

Front 3

column separation: gel filtration using beads rated by pore size; larger molecules move __ through column

Back 3

fastest, because they move through interstices of the column and do not enter the pores of the beads

Front 4

anion exchange vs cation exchange chromatography

Back 4

anion:
- alkaline pH
- proteins are negatively charged and exchanged with anions from salt buffer

cation:
- acid pH
- proteins are positively charged
- displaced by cations from salt buffer

Front 5

affinity chromatography is used for __

Back 5

quantitating glycosylated hemoglobin

- use antibodies fixed to a solid support medium w/in a column

Front 6

proteins in soln absorb UV light at what wavelength? what about nucleic acids?

Back 6

proteins: 280 nm; mostly due to tryptophan content

nucleic acid: 260 nm

If using spectrophotometric assays to quantitate protein, must correct for nucleic acid content

protein conc (mg/mL)= 1.55 A(280) - 0.76A(260)

Front 7

Specific gravity can be used to estimate protein content; it uses __

Back 7

copper sulfate
- drop of blood or serum added to a graded series of copper sulfate solns
- the drop can remain stationary, drop, or float to top
- protein conc is estimated from the specific gravity of the copper sulfate soln in which the drop remained stationary

- commonly used for Hb screening (what the drop to drop to bottom)

Front 8

Biuret method

Back 8

- extensively used for protein quant, esp in automated analyzers (see below Lowry method)
- specific for proteins
- in alkaline soln, copper salts form a complex with molecules with two or more peptide bonds (biuret complex)
- biuret complex absorbs UV light at 540-560nm

- reliable down to 10-15mg/dL

Lowry method: uses the biuret method followed by phenol reagent, which greatly enhances the color reaction
-

Front 9

Albumin can be quantitated in samples contain other protein by virtue of its __

Back 9

specific binding to certain dyes
- commonly used dye is BCG(bromcresol green); extensively used in automated analyzers
- often measure albumin in parallel with total protein by the biuret method
- BCG-alb absorb at slightly different wavelength

Front 10

Nephelometry

Back 10

detects turbidity produced by precipitation of reagent antibody with its target protein
- specific
-

Front 11

prealbumin

Back 11

AKA: transthyretin (TTR)
- faster than albumin (anodal to albumin)
- small protein
- binds little thyroxine (TBG has a 100-fold higher affinity for thyroxine)
- plays significant role in vitA metabolism; TTR binds retinol bindind protein which binds vitA to transport it thorughout body
- TTR-RBP complex keeps the small RBP from being rapidly clear through the kidney
- TTR-RBP-retinal complex is formed in the ER of hepatocytes

Front 12

Type I familial amyloidotic polyneuropathy

Back 12

- due to mutation in prealbumin, which makes it susceptible to proteolysis and the release of beta-structured fragments thah lead to amyloid deposits in nerve fibers

Front 13

Prealbumin has a relatively __ half-life

Back 13

2 days
- its synthesis rate is very sensitive to adequate nutrition and changes in liver function
- serum prealbumin levels - useful marker for nutritional status

Front 14

prealbumin can cross into the __

Back 14

CSF! due to its small size
- CSF electrophoresis (concentrated of course) shows a distinct preablumin band, not seen in SPEP or UPEP
- normal CSF electrophoresis pattern: prealbumin, albumin, and small transferrin bands

Front 15

What could lead to the presence of a "pseudo prealbumin" band on SPEP

Back 15

- patients given heparin
- heparin activates lipoprotein lipase in vivo, which alters the triglyceride content of lipoproteins and thus their electrophoretic mobility
- RESULT: see a band in the prealbumin area due to altered beta-lipoproteins
- this is an in vivo effect that does not occur if heparin is added to an already collected samples

Front 16

congenital analbuminemia is characterized by a __

Back 16

compensated hydrostatic pressure, with no major fluid abnormalities

Front 17

Many albumin variants exist; most cause ___

Back 17

No clinically significant abnormality
- Bisalbuminemia: 2 albumin bands on SPEP

- Exception: one variant has a high affinity for thyroxine, leading to elevated T3, but normal FT3 and a euthyroid state

Front 18

half-life of circulating albumin is __

Back 18

17 days

Front 19

Fructosamine (aka___) can be useful for monitoring diabetic control in patients with ____; in place of glycosylated hemoglobin

Back 19

aka: glycosylated albumin
- useful in patients with hemolytic anemias (sickle cell dz, AIHA, thalassemias) in whom glycosylated Hb is unreliable

- normally up to 8% of albumin is glycosylated

Front 20

elevated serum albumin is due to __

Back 20

- uncommon
- dehydration
- prolonged used of tourniquet

Front 21

albumin is a negative acute phase reactant

Back 21

decreased in many conditions (non-specific)
- malnutrition
- protein-losing enteropathy
- nephropathy
- liver disease

Front 22

decreased albumin can be associated with a decrease in what two common cations

Back 22

Mg2+ and Ca2+

Front 23

nephrotic syndrome with loss of albumin; can see a compensatory rise in ___ in order to maintain oncotic pressure

Back 23

alpha-2-macroglobulin (alpha-2 band)
- some increased production
- also selective retention due to large molecular size

Front 24

In cirrhosis, a loss of albumin synthesis can be associated with a compensatory rise in __ in order to maintain oncotic pressure

Back 24

gamma-globulin fraction

Front 25

Vast majority of people are ___ for the fully active __ allele of alpha-1-antitrypsin (AAT)

Back 25

homozygous
fully active M allele
PiMM

- 10% are heterozygous for PiM(other); 2% of these are PiMZ

Front 26

In AAT def, Pi__ is associated with ___ and ___ disease

Back 26

homozygous PiZZ
- hepatic and pulmonary disease
-

Front 27

Can screen for AAT def using __

Back 27

SPEP

nephelometry (serum AAT levels)

- must be confirmed by more specific assay, give the vast number of potential mutations (75 different alleles exist!)

Front 28

AAT deficiency, therapy is useful for __, but not __

Back 28

- useful for treatment of pulmonary emphysema; IV AAT replacement
- prevention of pulmonary emphysema; inhaled AAT

- AAT replacement is does not improve cirrhosis that develops in children

Front 29

Cirrhosis secondary to AAT develops in __ and is treated with __

Back 29

children (PiZZ)
- liver transplant
- recipient takes on the donor's AAT phenotype!! (liver synthesizes AAT)

Front 30

The largest major non-immunoglobulin serum protein is __

Back 30

alpha-2-macroglobulin (AMG)
- rises 10-fold in nephrotic syndrome due to selective retention due to size, while albumin is lost
- may also be increased synthesis (absolute increase)
- maintains oncotic pressure

Front 31

haptoglobin migrates in the __ region on SPEP

Back 31

alpha-2 region along with AMG

Front 32

serum haptoglobin can help evaluation a positive urine dipstick test for blood in the absence of intact RBCs

Back 32

- the dipstick test actually test for pseudoperoxidase activity of heme, found in both Hb and myoglobin

- if serum haptoglobin is low, this suggest hemolysis with hemoglobinuria
- if serum haptoglobin is high, this suggest myoglobinuria
- also LDH1 is alos a/w hemolysis, while CK is released in rhabdomyolysis

Front 33

The major beta-globulin is __

Back 33

transferrin

Front 34

transferrin transport iron in the ___ state

Back 34

ferric (Fe3+)

Front 35

transferrin mRNA sythesis is increased in the __ in response to __

Back 35

liver!!
- response to low serum iron and hepatocyte iron

Front 36

transferrin can produce a pseudoparaprotein on SPEP in cases of __

Back 36

severe iron deficiency

Front 37

chonic transferrin saturation occurs in ___

Back 37

idiopathic hemochromatosis and transfusion-related hemosiderosis

- almost no U(unsaturated)IBC

Front 38

screening for hemochromatosis can be accomplished by __

Back 38

measure:
- serum iron
- transferrin (TIBC)
calculate:
- percent saturation

Front 39

Hereditary Hemochromatosis results in __

Back 39

cirrhosis
diabetes
cardiomyopathy
arthritis
other endocrine d/o

toxic effects of excess free iron deposition

- tx w/ phlebotomy and/or chelation therapy

Front 40

Variants of transferrin can be seen; produce a __ on SPEP

Back 40

doublet bands for transferrin
(heterozygotes)

Front 41

Transferrin is produced by the liver; it is a glycoprotein, in which various sugar molecules are added to newly synthesized proteins

In contrast, in the CSF there is ___

Back 41

In the CSF there is a variant of transferrin that lacks sialic acid residues (asialotransferrin)

Front 42

Asialotransferrin (aka___) is found in __ and is useful in __

Back 42

aka: tau protein or beta-2-transferrin

CSF (also vitreous and endolymph)

- it has slightly less negativity, thus is located slightly more cathodal to transferrin

CSF contains both transferrina and asialotransferrin

Plasma contain ONLY transferrin

If question is whether or not clear fluid leakage from a fistula or skull injury represents CSF - protein electrophoresis can help
- if two beta bands (transferrin and asialotransferrin) are present, it is presumptive evidence of CSF
- if only one beta band (transferrin only) it is not CSF

IMPORTANT: Must do serum (SPEP) in conjunction, two rule out the posibility of a transferrin variant in the serum; thus also given two beta bands, mimicking CSF findings