Spectral mechanisms in the retina of the Arctic ground squirrel

1977 ◽  
Vol 55 (9) ◽  
pp. 1454-1460 ◽  
Author(s):  
Gerald H. Jacobs ◽  
R. B. H. Tootell
Keyword(s):  
Spectral Sensitivity ◽  
Dark Adaptation ◽  
Ground Squirrel ◽  
Chromatic Adaptation ◽  
The Arctic ◽  
Arctic Ground Squirrel ◽  
Light Levels ◽  
Ground Squirrel Spermophilus Undulatus ◽  
Spermophilus Undulatus ◽  
Peak Location

The electroretinogram (ERG) was used to investigate the spectral mechanisms present in the retina of the Arctic ground squirrel (Spermophilus undulatus). Under conditions of dark adaptation, the spectral sensitivity of this eye is adequately accounted for by the operation of a typical mammalian rhodopsin (500-nm peak) indicating that, like other ground squirrel species, the Arctic ground squirrel eye probably contains a population of functional rods. When the eye was adapted to lights having a luminance of 0.1 cd/m2 or greater, spectral sensitivity shifted to a new peak location of about 520 nm. Experiments involving chromatic adaptation led to the conclusion that there are at least two spectral mechanisms in this retina which are operative at photopic light levels. These results, along with measurements of preretinal absorbance, indicate that the spectral mechanisms in the retina of the Arctic ground squirrel are very similar to those previously described for several other species of ground-dwelling sciurids.

Transferrin polymorphism among populations of the arctic ground squirrel, Spermophilus undulatus (Pallas)

1969 ◽  
Vol 47 (5) ◽  
pp. 1051-1057 ◽  
Author(s):  
Charles F. Nadler ◽  
Phillip M. Youngman
Keyword(s):  
Gel Electrophoresis ◽  
Ground Squirrel ◽  
Species Complex ◽  
The Arctic ◽  
Starch Gel Electrophoresis ◽  
Genetic Expression ◽  
Ground Squirrel Spermophilus Undulatus ◽  
Spermophilus Undulatus ◽  
Starch Gel ◽  
Transferrin Polymorphism

Starch-gel electrophoresis of sera from Canadian and Alaskan populations of Spermophilus undulatus demonstrates four molecular trausferrins, Tf 5, 6, 7, and 8. Single and double band transferrin patterns reflect homozygous and heterozygous genetic expression respectively.Spermophilus undulatus parryii is characterized by Tf 6 alone or in combination with Tf 7 or Tf 8, S. u. ablusus by Tf 7 alone, and S. u. plesius by Tf 5 alone or in combination with Tf 7.Transferrins offer a means for clarifying the taxonomy of this holarctic species complex, and for investigating the origins and distributions of nearctic populations.

Temperature and the Regulation of Enzyme Activity in the Hibernator. Isoenzymes of Liver Pyruvate Kinase from the Hibernating and Non-hibernating Arctic Ground Squirrel

1974 ◽  
Vol 52 (10) ◽  
pp. 894-902 ◽  
Author(s):  
Hans W. Behrisch
Keyword(s):  
Molecular Weight ◽  
Pyruvate Kinase ◽  
Wide Temperature Range ◽  
Ground Squirrel ◽  
Energy Charge ◽  
High Energy ◽  
Ground Squirrels ◽  
The Arctic ◽  
Arctic Ground Squirrel ◽  
Temperature Range

Liver of the hibernating (H) Arctic ground squirrel (Citellus undulatus) contains a single species of pyruvate kinase (PyK) that is distinct from the single isoenzyme of pyK observed in the non-hibernating (NH) ground squirrel, which has been previously described (Behrisch &Johnson (1974) Can. J. Biochem. 52, 547–559). The H-PyK has a pI value of 5.7 and a molecular weight of 241 000 – 243 000. Affinity of the H-PyK for the substrates phosphoenolpyruvate (PEP) and ADP is not affected by changing temperature. It is argued that this stability of the apparent Km's for substrate over a wide temperature range permits the hibernator to take advantage of the Q10 effect in maintaining a low rate of the PyK reaction. Similarly, affinity of H-PyK for the allosteric activator fructose-1,6-phosphate (FDP) and the inhibitor ATP is also conspicuously independent of temperature, suggesting a fine stoichiometry in the relative concentrations of the regulatory ligands in control of H-PyK over a wide temperature range. Further, affinity of H-PyK for the inhibitor ATP is about three- to fourfold lower than that of the NH-PyK, a condition that would favor the maintenance of a high energy charge in the hibernating liver cell. ATP apparently inhibits PyK by causing a dissociation of the enzyme molecule into two "halves" of about 110 000 molecular weight each. This dissociation is offset and reversed by FDP. Removal of the ATP by dialysis does not of itself result in a reassociation of the PyK "halves"; FDP and/or the substrates are required for the two subunits of PyK to reassociate. As the apparent Ki of H-PyK for ATP is higher than that of NH-PyK, substantially higher concentrations of ATP are required to effect the dissociation of H-PyK. Similarly, elevated concentrations of FDP are required to offset the ATP-caused dissociation of the H-PyK.Hibernating Arctic ground squirrels that are preparing to emerge finally from the hibernating state already possess substantial activities of the NH-PyK isoenzyme. This suggests that the animal "anticipates" its transition from one metabolic state from another. On the basis of these data a formal mechanism is proposed for the regulation of liver PyK in the Arctic ground squirrel in both the non-hibernating and hibernating states.

scholarly journals Resistance to Systemic Inflammation and Multi Organ Damage after Global Ischemia/Reperfusion in the Arctic Ground Squirrel

PLoS ONE ◽  
2014 ◽  
Vol 9 (4) ◽  
pp. e94225 ◽  
Author(s):  
Lori K. Bogren ◽  
Jasmine M. Olson ◽  
JoAnna Carpluk ◽  
Jeanette M. Moore ◽  
Kelly L. Drew
Keyword(s):  
Systemic Inflammation ◽  
Ground Squirrel ◽  
Ischemia Reperfusion ◽  
Organ Damage ◽  
Global Ischemia ◽  
The Arctic ◽  
Arctic Ground Squirrel
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