Temperature acclimation in the channel catfish, Ictalurus punctatus: Seasonal variation and cellular mechanisms
Seddon, William Lannon
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https://hdl.handle.net/2142/23731
Description
Title
Temperature acclimation in the channel catfish, Ictalurus punctatus: Seasonal variation and cellular mechanisms
Author(s)
Seddon, William Lannon
Issue Date
1994
Doctoral Committee Chair(s)
Prosser, C. Ladd
Department of Study
Biology, Animal Physiology
Discipline
Biology, Animal Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Language
eng
Abstract
Seasonal variations were seen in liver composition and activities of liver enzymes of channel catfish acclimated to $7\sp\circ\rm C,$ $15\sp\circ\rm C,$ or $25\sp\circ\rm C.$ Fall and winter catfish exhibited positive acclimation for total liver protein and DNA, hepatosomatic index, and activity of pentose phosphate shunt enzymes, while spring and summer fish showed little or inverse compensation. LDH showed little compensation or seasonal variation in either liver or muscle. Cytox showed seasonal variation in muscle but no seasonal variation in liver.
Liver and muscle of channel catfish acclimated to $7\sp\circ\rm C,$ $15\sp\circ\rm C,$ or $25\sp\circ\rm C$ showed no differences in isozymal expression of G6PDH, 6PGDH, LDH, MDH, or IDH. Concentration of G6PDH was higher in cold-acclimated fish when compared to warm-acclimated fish. G6PDH concentration paralleled differences in G6PDH activity for the three temperature groups. LDH did not demonstrate any consistent trends with respect to acclimation temperature and measured concentrations of LDH agreed poorly with activity measurements.
Hepatocytes were isolated from $15\sp\circ\rm C$ acclimated channel catfish using an EDTA-based collagenase-free perfusion system. Yields were superior to previously used collagenase-based systems and hepatocyte viability was comparable. Isolated hepatocytes generally did not acclimate as in vivo. But, when cultured in pH and osmotically corrected medium at $7\sp\circ\rm C,$ $15\sp\circ\rm C,$ or $25\sp\circ\rm C$ with added serum from catfish acclimated to the same temperatures, the cells more closely resemble liver in vivo.
PCR using degenerate oligonucleotide primers was used in several attempts to amplify cDNA copies of G6PDH and LDH mRNA. A partial sequence (153 nucleotides) encoding LDH was amplified and sequenced. The channel catfish sequence was 91.5% similar to the LDH-B sequence for F. heteroclitus. Three different pairs of degenerate oligonucleotide primers were used in attempts to amplify cDNA encoding G6PDH, but no G6PDH sequence was obtained.
A $5\sp\prime$-end-labeled degenerate oligonucleotide probe was designed and constructed to quantitate G6PDH mRNA in livers of thermally-acclimated channel catfish. No G6PDH mRNA was detected using Northern blot analysis. The failure of the PCR and $5\sp\prime$-end-labeled oligonucleotide probe experiments can be attributed to the relative scarcity of G6PDH mRNA.
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