Green pus, or green nasal mucus, is caused by iron-‐containing myelo-‐peroxidases and other oxidases and peroxidases used by polymorphonuclear (PMN) granulocytes (neutrophils).
These short-‐lived phagocytising leucocytes avidly ingest all sorts of bacteria and inactivate them by oxidative processes, involving the iron containing enzymes. The resulting breakdown product, comprising dead PMNs, digested bacteria and used enzymes, pus, contains significant amounts of iron, which gives it its greenish colour.
At the start of a URTI
Nasal mucus produced at the beginning is clear and is produced in response to tissue damage caused by the invading rhinovirus. It only turns green a few days into the infection as neutrophils respond to clear away the cellular debris and secondary bacterial infection sets in.
Polymorphonuclear leucocytes are equipped with a number of enzymes, the most potent of which is peroxidase.
This same peroxidase is also found in horseradish, giving it a distinctive green color and a sharp bite, as anyone who has tried Japanese wasabi paste can confirm.
When sputum turns green, sputum has stagnated inside the respiratory system long enough for the myeloperoxidase to act. It also implies bacterial superinfection.
Wasabe anyone!?
61) on Iron studies Dear Yin Ling,
My students are frequently confused by iron studies when I ask them to interprete it as part of the work up for anaemia.
Serum Iron
Iron contained in blood serum is normally bound to the protein transferrin. It cannot be floating around by itself! Iron is toxic!
Each molecule of transferrin can transport two molecules of iron to areas of the body that need this element. Think of it as a small lorry, the pasar malam type.
Most of the body’s iron (about 60%) is contained in hemoglobin. Another 30% is stored in ferritin, and a few percent in myoglobin. When body iron stores increase above these relatively normal ratios, proportionally greater amounts of iron are stored in ferritin or a complex called hemosiderin.
Generally men have higher levels of serum iron than women. When laboratories test for Se Iron, they are testing iron contained in plasma that is generally bound to transferrin.
In most people, ONLY about 25 – 35% of the transferrin contained in the serum is used to bind iron for transport. SO THERE ARE SPARE LORRIES. When laboratories measure serum iron they also measure transferrin and calculate the percentage of transferrin molecules that are used to bind iron.
Total Iron Binding Capacity (TIBC) and Transferrin Saturation % (TS%)
Total iron binding capacity: This measurement indicates the TOTAL potential
capacity of transferrin molecules to bind with serum iron, its telling you how much load your entire fleet of lorries can carry.
When TIBC is at or below the low end of a laboratory range, it is an indication that there is limited capacity for transferrin molecules to accept additional iron. If that occurs in combination with a relatively high measure of serum iron, it is likely that the ability of transferrin to safely bind serum iron is impaired. Your toxic products are going to spill on the road!
Iron in the plasma that is not bound to transferrin is called non-‐transferrin bound iron (NTBI). This is a potentially toxic form of iron that can damage body systems.
Generally, when 40% or less of transferrin molecules are used, iron is considered safely bound. Much above that, transferrin becomes saturated and it binding
capacity drops to a point where it will no longer can efficiently harbor NTBI. Some of the iron will then bind to other molecules that does not have transferrin’s ability to protect you. This causes oxidative stress, a process that if not countered by the body’s antioxidant defenses, will over time result in cell, tissue and DNA damage.
Transferrin saturation percentage (TS %) is calculated by dividing serum iron by TIBC, then multiplying by 100. The resulting number is referred to as transferrin saturation percentage (TS %). In people with undiagnosed hemochromatosis, this number is often above 50%, and sometimes even as high as 100%. The normal range of TS % is generally between 25–35%. When the percentage is calculated to be less than 17%
or higher than 45%, a condition of either iron deficiency or iron overload is possible.
Either too little goods or too much goods for your lorries! In either case, further investigation is warranted including ferritin testing. Very low or very high ferritin in
combination with low or high TS % can help a physician confirm a diagnosis of either iron deficiency or iron overload.
Serum Ferritin (SF)
Ferritin is a protein that is mainly utilized to store iron for future use. The body requires iron to make hemoglobin for blood and myoglobin for muscles. Iron in excess of daily needs is stored in ferritin molecules, huge storehouses which hold up to 4,500 iron atoms each!
Normally, dietary intake offsets daily loss iron loss (only about 1 to 1.5 milligrams per day). Therefore, ONLY A MINISCURE one gram of storage iron (1,000 milligrams) is adequate to meet all foreseeable needs. The body routinely loose iron as a result of trauma, blood loss or through menstruation.
However, more than one gram of storage iron can stress the body’s ability to
provide a safe harbor for this potentially toxic metal. With a few exceptions, including events of inflammation (ferritin RISES IN INFLAMMATION eg think of Dengue crisis) or anemia of chronic disease, a blood test measuring SF can provide an accurate surrogate measure of iron stored in the body.
Only a very small fraction of the body’s stored iron is actually stored in transferrin or ferritin molecules circulating in the bloodstream. However, in healthy individuals, the relative amount of ferritin found in serum is an accurate surrogate measure for iron stored in body organs.
Ferritin can be elevated even when both serum iron and transferrin saturation percentages are at low-‐normal levels or below.
High ferritin under these circumstances might not signal iron overload, but can result from a defense mechanism, an acute phase reaction. This is seen in anemia of chronic disease, or inflammatory anemia.
62) on Renal function