Clinical Chemistry : Lipids, Lipoproteins, And Other Cardiac Markers

Explanation
All values are important in assessing cardiac function, but what gives physicians the clearest prediction of possible artherosclerotic and cardiac risk is the Low-Density Lipoprotein. Troponin I and Potassium, among other cardiac markers, gives physicians the sign that cardiac damage is happening.

Explanation
Arteriosclerosis is often interchanged with atherosclerosis but there is a difference between the two.

Arteriosclerosis is an umbrella term (meaning, a general term) for any number of diseases which cause the artery walls to thicken and narrow. There are three types of arteriosclerosis which includes atherosclerosis (the others being Moenckeberg Medial Calcific Sclerosis and Arteriolosclerosis).

Atherosclerosis is the name given to the build up of fats inside the artery walls which causes these to narrow and eventually restrict blood flow.

The pathogenesis is explained as follows:
 
The narrower your arteries, the harder your heart has to work to pump blood through them. This further increases the pressure of the blood flow which causes your blood pressure to rise even more.


The danger here is if an artery narrows to the extent that it becomes blocked which then prevents blood from flowing through. The part of the body which is nourished by this blood flow (and receives oxygen and vital nutrients) then dies which can have serious consequences.
 

If this happens near the brain then a stroke occurs.
 

If it happens near the heart then a heart attack occurs.

Explanation
Both equations are otherwise known are the Friedewald Formula. Both yield the same results, because 0.20 = 1/5.

Explanation
The colored product for the LB Reaction is green, whereas that for the Salkowski Reaction (also known as the Zak Reaction) is red.

On an additional note for non-enzymatic cholesterol measurement:

One-Step Method
/ Colorimetry

Pearson-Stern-MacGavack Method
Zlatkis-Zak-Boyle Method
Ferro-Ham Method
Wybenga Method


Two-Step Method
/ Colorimetry + Extraction


Carr-Drekter Method (extraction is done by Zeolite)
Bloors Method (extraction is done by the Bloors Reagent / 3:1 Ethanol-Ether)


Three-Step Method
/ Colorimetry + Extraction + Saponification


Abell-Kendall Method (former CDC reference method)


Four-Step Method
/ Colorimetry + Extraction + Saponification + Precipitation


Schoenheimer-Sperry and Parekh-Jung Method (former CDC reference method)
Sperry-Webb Method


Take special note that the sequence for all four reactions will always start with the additional step (if there is any) and will always end with colorimetry (D U H). Therefore:
One-Step : Colorimetry
Two-Step : Extraction --> Colorimetry
Three-Step : Saponification --> Extraction --> Colorimetry
Four-Step : Precipitation --> Saponification --> Extraction --> Colorimetry

The methods of choice nowadays are nevertheless the enzymatic methods:

The Cholesterol Oxidase Method is the most commonly used method for cholesterol in laboratories. The chromogen measured is a quinoneimine dye.

The Modified Abell-Kendall / Abell-Levy-Brodie Method is considered the current CDC Reference Method. This employs the typical three-step method but neither the Bloors nor Zeolite Reagent is used, and it is rather hexane. The color reagent utilized is the Liebermann-Burchardt, thus resulting in a green chromogen measured with an absorbance of 410 nm.

Explanation
Apo A-IV is the correct answer because it is known to be the cofactor for LCAT (lecithin-cholesterol acyltransferase). LCAT is an enzyme involved in the metabolism of lipoproteins, specifically in the esterification of cholesterol. Apo A-IV helps activate LCAT, allowing it to carry out its function effectively. Apo A-II, Apo A-I, and Apo A-III are other apolipoproteins but they do not serve as cofactors for LCAT.

Explanation
Both Type 1 and 2b, and other lipoproteinemias (Types 3, 4, and 5) exhibit high triglyceride levels.

Explanation
Xanthelasmas are yellow plaques that occur most commonly near the inner canthus (corner) of the eyelid, more often on the upper lid than the lower lid.

Arcus Juvenilis is a lipid-rich corneal arcus and a predominantly extracellular deposit that forms at the corneoscleral limbus.

Acanthosis nigricans is a skin disorder characterized by darkening (hyperpigmentation) and thickening (hyperkeratosis) of the skin, occurring mainly in the folds of the skin, back of the neck, the axilla and/or groin.

All of these, among others, are cutaneous markers for Coronary Artery Disease.

Explanation
Basser-Kornzweig Syndrome are the same thing.

XK gene mutation is the disorder of McLeod Syndrome, and is characterized by the presence of acanthocytes, as well.

Explanation
This also aids in the identification of rare familial disorders such as Types I, III, and V Hyperlipidemia.

GC-MS specifically measures cholesterol.

Polyanion Precipitation is most commonly and reasonably specific for HDL.

Ultracentrifugation is for estimative fractionation of lipoprotein classes.

Explanation
The function of the precipitant in this assay is to remove LDL.

The function of ultracentrifugation is to remove VLDL.

Therefore, only HDL will be detected.

(Chylomicrons have a short span in the bloodstream, and is extinguished after the hours desired for lipid profile fasting.)

Explanation
The correct answer is 340 nm because the question states that products for all enzymatic methods of triglycerides have an absorbance measured at this wavelength. This suggests that 340 nm is the specific wavelength at which the enzymatic methods used for measuring triglycerides produce a detectable change in absorbance, indicating the presence or concentration of triglycerides.

Explanation
Immunonephelometry is for apolipoprotein measurement.

Explanation
These are all troponin subunits. Troponin C binds calcium, Troponin I inhibits troponin T, which is the tropomyosin-binding component. These, together with actin, are the contractile proteins of the cardiac myofibril.

Explanation
B-type Natriuretic Peptide is a hormone secreted by the heart in response to increased pressure and volume in the cardiac chambers. It acts as a vasodilator and promotes diuresis to regulate blood pressure and fluid balance. This hormone is released into the bloodstream, affecting distant organs and tissues, which indicates an endocrine function of the heart. Therefore, the correct answer is "Endocrine".

Explanation
Concentrations of CRP (as detected by hs-CRP) below those seen in infection but nevertheless above healthy values can be a marker of atherosclerosis.