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Gamma Glutamyl Transferase
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The physiological functions of gamma
glutamyl transferase (GGT) are thought to be glutathione metabolism, amino
acid membrane transport, and foreign compound detoxification. Concentrations
of GGT are found in the kidneys, pancreas, liver, gallbladder, and intestines.
The highest concentrations of GGT are found in the kidneys and pancreas;
however, GGT in the blood is believed to be primarily from the liver.
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| Globulin
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In the late nineteenth century, it was
discovered that there were two different proteins in serum. These proteins
were named albumin and globulin. Since then the use of electrophoresis has
aided in the identification of over 22 individual plasma proteins, many of
which are subsets of globulin. As a result of the pre-dominance of these two
protein types among total protein, an approximation of the globulin
concentration can be easily determined by subtracting the albumin
concentration from the total protein concentration.
Globulin synthesis occurs in plasma cells,
lymphocytes, and the liver. The major fractions of globulin are termed alpha,
beta, and gamma. Alpha and beta globulins mainly carry various lipids,
lipid-soluble hormones and vitamins, and other lipid-like substances in the
plasma. Two other alpha globulins, ceruloplasmin and haptoglobin, are carriers
of copper and hemoglobin, respectively. A beta globulin, transferrin, is an
iron carrier. The gamma globulins consist primarily of the immunoglobulins.
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| Glucose
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Glucose is normally the only sugar found in
the blood. Blood glucose concentrations are kept within a relatively narrow
range by such factors as hepatic and renal uptake and release, glucose removal
by peripheral tissues, hormone influences on uptake and release, and
intestinal absorption. The only endogenous sources of glucose are the liver
and kidneys which convert glucose-6-phosphate to glucose. Insulin is the main
hormone that affects glucose blood levels.
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| Granulocytes
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Granulocytes are WBCs that contain
cytoplasmic granules. These include neutrophils, eosinophils and basophils.
These cells are produced in the bone marrow. When we count granulocytes we
mainly estimate the neutrophil numbers and assume that an increased
granulocyte count indicates a neutrophilia and a decreased count indicates a
neutropenia.
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| HDL Cholesterol |
HDL is one of the classes of lipoproteins
that carry cholesterol in the blood. HDL is considered to be beneficial
because it removes excess cholesterol and disposes of it. Hence HDL
cholesterol is often termed "good" cholesterol. The test for HDL measures the
amount of HDL-cholesterol in blood.
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| Hematocrit
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The Hematocrit (HCT) and the Packed Cell
Volume (PCV) indicate the percent of red blood cells in a unit of whole blood.
They are equivalent measurements. The VetScan HMT calculates the HCT. It is
equivalent to the manual centrifuge packing of red cells called the packed
cell volume (PCV). When a blood sample is centrifuged (Spun Hematocrit), it
separates into 3 layers: an upper layer of plasma; a middle layer of WBCs and
thrombocytes (buffy coat); and a bottom layer of packed RBCs. Technically, the
hematocrit is a measure of all the cellular elements of blood (WBCs,
thrombocytes, RBCs). By common usage, however, it has become synonymous with
packed cell volume (PCV). See also Packed Cell Volume.
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| Hemoglobin |
Hemoglobin (Hb) is the oxygen-carrying
pigment formed by developing RBCs in the bone marrow. The hemoglobin value of
a blood sample is approximately one-third of the PCV. Variations from this
indicate a laboratory error, hemolysis or abnormalities, such as Heinz bodies
or lipemia. Altered hemoglobin may form Heinz bodies or crystals.
Determination of hemoglobin provides no clinical advantage over measurement of
the PCV other than allowing the determination of Mean Corpuscular Hemoglobin (MCH)
and Mean Corpuscular Hemoglobin Concentration (MCHC).
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| Immature RBC
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Immature RBCs include reticulocytes and
nucleated red blood cells. Reticulocytes are indicated on the VetScan HMT by a
high MCV and a high RDW. Occasionally immature cells retain their nuclei and
are counted by the VetScan HMT as WBCs.
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| Left Shift |
The term left shift indicates increased
numbers of circulating immature neutrophils (band cells, metamyelocytes,
myelocytes). These cells cannot be differentiated by automatic cell counters.
A regenerative left shift is characterized by band cells and increased numbers
of mature neutrophils. The number of immature neutrophils does not exceed 10%
of the mature neutrophils, and no young cells, such as metamyelocytes, are
present.
A degenerative left shift is characterized
by circulating band cells that exceed 10% of the segmented neutrophils, in
conjunction with decreased numbers of neutrophils or the presence of very
young cells, such as metamyelocytes or myelocytes. In a degenerative left
shift, the total WBC count may vary from below normal to slightly elevated. A
degenerative left shift is an unfavorable prognostic sign.
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| Leukocytes |
Leukocytes are synonymous with "white blood
cells" and may be classified as one of the following: neutrophils, eosinophils,
monocytes,lymphocytes or basophils. These include both the granulocytes and
the mononuclear cells of the lymphoid system. A total WBC count is the sum of
all leukocytes.
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| Leukocytosis
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Leukocytosis is an increased number of WBCs.
It is usually caused by an increase in the number of circulating neutrophils (neutrophilia),
though lymphocytosis (especially with leukemia) occasionally produces
leukocytosis. Absolute values of individual WBC types provide much more
diagnostic specificity than a simple WBC count. Exercise, fear and digestion
cause physiologic leukocytosis. Infection, rapidly growing neoplasms, acute
hemolysis, hemorrhage, intoxication, leukemia and trauma cause pathologic
leukocytosis.
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| Leukopenia |
Leukopenia indicates a decreased total WBC
count. It is usually characterized by decreased numbers of circulating
neutrophils. The most common causes of leukopenia are excessive consumption in
an inflammatory process and primary bone marrow disease. Persistent leukopenia
is a poor prognostic sign.
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| Leukemia |
Leukemia implies neoplastic cells in the
peripheral blood. It may occur in myeloproliferative and lymphoproliferative
diseases. In myeloproliferative diseases immature precursers of red blood
cells, granulocytes, are seen on stained blood smears. In lymphoproliferative
diseases, large numbers of immature lymphocytes are present in peripheral
blood smears.
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| Lymphocytes |
Lymphocytes in the blood are a mixed
population of B-cells and T-cells. They are the major cellular component of
immunity in the body. B-lymphocytes synthesize antibodies that are responsible
for humoral immunity. T-lymphocytes are the principal component of cellular
immunity. Lymphocytes also participate in immune regulation and surveillance,
and some are cytotoxic.
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| Lymphocytosis
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Lymphocytosis indicates increased numbers of
circulating lymphocytes. Pathologic lymphocytosis occurs in chronic
inflammation, recovery from acute infection, lymphocytic leukemia, and
hypoadrenocorticism. Lymphocytosis usually indicates a strong immune stimulus
of some chronic duration from a bacterial infection, viremia or
immune-mediated disease. Lymphocytic leukemia may or may not be accompanied by
lymphocytosis. Lymphocytosis not associated with disease occurs with
physiologic leukocytosis, in healthy cats from excitement, immature
age-related responses in young puppies and kittens, and sometimes following
vaccination.
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| Lymphopenia |
Lymphopenia indicates decreased numbers of circulating
lymphocytes. It may occur with acute severe disease, some viral diseases
(canine distemper, hepatitis, parvovirus and coronavirus infections, feline
panleukopenia, FeLV infection), stress-related corticosteroid response, and
loss of lymph into the gut (chylothorax, lymphangiectasia).
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