Pathological Effects
43
higher percentage of total leucocytes in Belews Lake fish, but
hemoblasts were less numerous than in reference fish (Sorensen et a1.
1984). These shifts in hematological parameters reflect important
changes in the overall health of fish. Reductions in hematocrit values
are associated with anemia and lowered mean corpuscular hemoglobin concentrations (MCHC) (Lemly 1993b). Reduced MCHC causes impaired respiratory capacity because selenium can bind to hemoglobin,
rendering it incapable of carrying oxygen. A decrease in respiratory
capacity can quickly lead to metabolic stress because the fish must
expend more energy to meet respiratory demands (Lemly 1993b). Lower
numbers of hemoblasts reflect reduced erythropoiesis and delayed replacement of aging red cells in circulation, which also contribute to
reduced respiratory capacity and metabolic stress (Lemly 1993b). An
elevation in lymphocytes signals a generalized immune response, triggered by physiological stress, and a reduced state of health.
Liver
The structural features of liver tissue from normal green sunfish consist of bilaminar arrays of hepatocytes (liver plates) separated by small
blood sinusoids. Blood enters the liver from the hepatic artery and
hepatic portal vein, moves between the liver plates in the sinusoids,
and ultimately collects in central veins which empty into the hepatic
vein. Parenchymal hepatocytes typically contain numerous mitochondria, abundant rough endoplasmic reticulum, well developed nucleoli,
and both central and peripheral chromatin islands (Sorensen 1986).
Kupffer cells, (phagocytic tissue histocytes) are rarely present in healthy
individuals, and lymphocytes are not numerous. Green sunfish from
Belews Lake exhibited several histopathological differences from normal liver tissue. Lymphocyte infiltration was apparent along with extensive vacuolization of parenchymal hepatocytes around central veins.
Increased numbers of Kupffer cells were present, and the central veins
were distended and swollen due to loss of surrounding parenchymal
cells. Cell nuclei were often deformed and pleomorphic, and numerous peri sinusoidal lipid droplets (unmetabolized residues) were present
(Sorensen et a1. 1984). Collectively, these ultrastructural changes reflect a degeneration of tissue structure that is sufficient to significantly
alter liver function. This liver pathology syndrome is characteristic of
chronic selenosis in fish and other vertebrates (Sorensen 1986).
Kidney
At the ultrastructure level, the kidney of a normal fish is quite similar
to that of a human. It is made up of glomeruli, mesangial cells,
43
higher percentage of total leucocytes in Belews Lake fish, but
hemoblasts were less numerous than in reference fish (Sorensen et a1.
1984). These shifts in hematological parameters reflect important
changes in the overall health of fish. Reductions in hematocrit values
are associated with anemia and lowered mean corpuscular hemoglobin concentrations (MCHC) (Lemly 1993b). Reduced MCHC causes impaired respiratory capacity because selenium can bind to hemoglobin,
rendering it incapable of carrying oxygen. A decrease in respiratory
capacity can quickly lead to metabolic stress because the fish must
expend more energy to meet respiratory demands (Lemly 1993b). Lower
numbers of hemoblasts reflect reduced erythropoiesis and delayed replacement of aging red cells in circulation, which also contribute to
reduced respiratory capacity and metabolic stress (Lemly 1993b). An
elevation in lymphocytes signals a generalized immune response, triggered by physiological stress, and a reduced state of health.
Liver
The structural features of liver tissue from normal green sunfish consist of bilaminar arrays of hepatocytes (liver plates) separated by small
blood sinusoids. Blood enters the liver from the hepatic artery and
hepatic portal vein, moves between the liver plates in the sinusoids,
and ultimately collects in central veins which empty into the hepatic
vein. Parenchymal hepatocytes typically contain numerous mitochondria, abundant rough endoplasmic reticulum, well developed nucleoli,
and both central and peripheral chromatin islands (Sorensen 1986).
Kupffer cells, (phagocytic tissue histocytes) are rarely present in healthy
individuals, and lymphocytes are not numerous. Green sunfish from
Belews Lake exhibited several histopathological differences from normal liver tissue. Lymphocyte infiltration was apparent along with extensive vacuolization of parenchymal hepatocytes around central veins.
Increased numbers of Kupffer cells were present, and the central veins
were distended and swollen due to loss of surrounding parenchymal
cells. Cell nuclei were often deformed and pleomorphic, and numerous peri sinusoidal lipid droplets (unmetabolized residues) were present
(Sorensen et a1. 1984). Collectively, these ultrastructural changes reflect a degeneration of tissue structure that is sufficient to significantly
alter liver function. This liver pathology syndrome is characteristic of
chronic selenosis in fish and other vertebrates (Sorensen 1986).
Kidney
At the ultrastructure level, the kidney of a normal fish is quite similar
to that of a human. It is made up of glomeruli, mesangial cells,