Varves form only in fresh or brackish water, because the high levels of salt in normal sea water coagulate the clay into coarse grains. Since the saline waters leave coarse particles all year, it is nearly impossible to distinguish the individual layers in salt waters.
An aspartate aminotransferase (AST) test measures the amount of this enzyme in the blood. AST is normally found in red blood cells, liver, heart, muscle tissue, pancreas, and kidneys. AST formerly was called serum glutamic oxaloacetic transaminase (SGOT). Low levels of AST are normally found in the blood. When body tissue or an organ such as the heart or liver is diseased or damaged, additional AST is released into the bloodstream. The amount of AST in the blood is directly related to the extent of the tissue damage.
AST is an enzyme found mostly in the liver, red blood cells, heart and other muscles. When liver, red blood cells, heart or muscle cells are injured, they release AST into the blood.n the slowly developing variety of liver disease, chronic hepatitis, AST levels are usually not as high, often less than 4 times the highest normal level. In chronic hepatitis, AST often varies between normal and slightly increased, so doctors might request the test regularly to determine the pattern of change.