6. Changes of metabolic parameteres Flashcards
The total protein content of the plasma (serum) is dependent on:
- the intake
- synthesis
- transformation
- catabolism
- hydration status (dehydration, hyperhydration).
Which measurments are used to find the TP?
Measurements can be performed by:
-chromatography
- electrophoresis
- refractometry
What is TP?
The total protein concentration in the blood.
What are the detection range of the refractometry?
20-100 g/l
What is the average TP conc of plasma?
60-80 g/l
where are the smaller TP concentrations?
Smaller TP concentrations:
- urine
- cerebrospinal fluid
- body cavity fluids
- tissue homogenates.
How do we measure the smaller concentrations?
- Lowry method in which the Folin-phenol reagent is used
- or by the so called Ultrasensitive TP method in which proteins are bound directly to stain molecules.
Biuret test reagent
Reagent contains: KNaSCN, CuSO4, KI and NaOH.
Ultrasensitive total protein analysis:
What happens?
How is it measured?
What is the sensitivty and standards?
Na-molibdate, and pirogallol-red reagent forms a complex molecule by binding proteins.
- Measured on 600 nm wave length.
- Sensitivity is 0.2 g/l - 4g/l.
- Standards are: 0.25, 0.5, 1. 2 g/l.
Teory behind Refractometry:
- Light is refracted when reaching the border of media with different specific gravity, which light refraction is dependent on.
- The total protein content in blood plasma or serum influences its specific gravity.
- In the refractometer the specific gravity of one media is given (glass), so the changes in light refraction depend on the quality of plasma/serum.
- Specific gravity is also dependent on temperature.
How do we do refractometry?
After calibration (distilled water) 1 droplet of plasma/serum is placed on the glass, the cover is closed and looking in the visor the result is read: the horizontal line intercepting the scale of serum/plasma total protein.
The procedure should be performed in room temperature.
What is good about refractometry?
The method is quick and easy, but less precise than spectrophotometry.
Can be used in the range of 25-95 g/l, may give uncorrect result in haemolysis or lipaemia.
TP concentration of blood plasma depends not only on the protein metabolism but ….
also on the water balance. During dehydration TP increases, or hyperhydration TP decreases.
What are some major fractions of proteins?
albumin, globulin and fibrinogen.
How do we measure albumin? (method 1)
Spectrophotometry! Bromocresol green is used as a reagent. It binds to albumin on pH 4.2 and forms a blue-green complex. Measured on 578 nm wave length.
How do we measure albumin? (method 2)
Serum electrophoresis used in combination with TP is a reliable method. The cost is higher, but it is used when protein fraction analysis is the basic aim. This method provides albumin as %, thats why we need to knoe the TP concentration.
Decreased albumin conc:
- Decreased intake of proteins
- decreased absorption (maldigestion, malabsorption)
- Decreased synthesis
- liver failure, acute inflammation (it is a negative acute phase protein)
- Increased utilisation
- physiologic conditions cause mild changes: pregnancy, work, exercise, production (milk, egg etc.) and chronic diseases (chronic inflammation, neoplasm)
-Increased loss :
via the kidneys (protein loosing nephropathy - PLN), gastrointestinal tract (protein loosing enteropathy- PLE),
skin (burn),
whole blood loss,
sequestration into body cavities
-Other (relative decrease): hyperhydration (may be iatrogen)
Increased albumin conc:
dehydration
How do we calculate globulins? (method 1)
Globulin concentration is calculated roughly by the difference of TP and albumin concentration of serum.
How do we calculate globulins? (method 2)
Serum electrophoresis is used if protein fraction analysis is the basic aim. This method provides percentage values, so objective concentration (g/L) has to be calculated knowing the TP concentration.
Explain the Alb/Glob ratio
The decrease of albumin/globulin ration is most frequently caused by the increase of globulin concentration e.g inflammatory processes or processes related to neoplasia. This inflammatory reaction can be evaluated using the RBC sedimentation test and the glutaric-aldehyde test The other cause for the decrease of alb/glob ratio is the decrease of albumin concentration.
Theory of Electrophoresis:
Electrophoresis based on the fact that the proteins have amphoteric character (acidic amino acids - Asp, Glu go to the + pole (charge) alkaline amino acids go to the - pole.) Electrophoresis is a laboratory technique where the blood serum is placed on special paper treated with agarose gel and exposed to an electric current to separate the serum protein components into five classifications by size and electrical charge, those being serum albumin, alpha-1-globulins, alpha-2-globulins, beta globulins, and gamma globulins.
What is SPEP?
Serum protein electrophoresis (SPEP) is a laboratory test that examines specific proteins in the blood called globulins.
What is blood serum?
blood serum is the fluid portion of the blood after the blood has clot.
Explain the separation of ions by electrophoresis:
Electrophoresis is the process whereby ions move through a medium in response to an applied electric field. Separation of ions by electrophoresis exploits the fact that the rate of motion of charged particles in any particular applied electric field is directly proportional to their charge and inversely proportional to their size and the viscosity of the medium.
Which molecules will move in a greater distance in electrophoresis?
Small and highly charged molecules will move a greater distance than will large and lower charged molecules in the same period of time.
The efficiency of electrophoretic separation of ions is determined by….
.. by the relative charge densities (charge per unit volume) of the ions in the mixture.
Which gel is used in gel electrophoresis?
In gel electrophoresis the medium is typically polyacrylamide or agarose, a viscous media that is required to minimize diffusion of the constituent ions.
What are the most used electrophoresis methods?
- sodium docecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)
- isoelectric focusing (IEF).
When is the proteins denatured? What happens to them?
Protein samples are first denatured by heating in SDS. Denaturation in SDS results in the coating of the polypeptides with negatively charged SDS molecules, rendering each protein highly negatively charged. The denatured proteins are then applied to one end of a slab of polyacrylamide. Electrodes are then attached to opposite ends of the slab with the cathode (-) at the end where the denatured protein was applied and the anode (+) to the other end.
What happens if you apply voltage across the gel ?
Application of voltage across the gel forces the negatively charged proteins to migrate towards the anode. In the highly viscous polyacrylamide, larger denatured proteins will experience greater frictional drag than smaller denatured proteins and move through the gel matrix at a much slower rate.
When do you stain during electrophoresis?
After a predetermined period of time, the electrodes are removed and the gel slab is stained with dye to show the locations of proteins in the gel. The smaller proteins are found closer to the anode than the larger ones. An inverse log-linear relationship of protein molecular weight to the distance traveled is typically observed.
What happens after staining in electrophoresis?
After staining separated protein fractions the densitometer can detect the results. The square below the curve depends on the concentration of the protein fraction. Serum contains 60% of albumin, 40 % of globulin Plasma contains 50% of albumin, 30% of globulin, 20% of fibrinogen
Which types of globulins do we have?
a1, a2, b1, b2, gamma1, gamma2. alfa globulins are acute phase proteins, beta globulins are imunoglobulins (IgA, IgM), and some other proteins i.e. LDL, gamma globulins are immunglobulins, too (IgG).
Proteins, especially immunglobulins are derived from:
special lymphoid cells (plasma cells). One cell group of the same origin is a clone, produces the same proteins.