244
AUSTEN RIGGS
differ substantially at a po2 of 150 mm. The red cells were only 50%
saturated with 0, at an extracellular pH of 7.0, whereas the hemolyzate
was at least 95% saturated at this pH. These results appear to be inconsistent with those of Yoshioka et al. (1968). Although different species
of eel were used in the two studies, this fact still does not explain why
Yoshioka et al. did not observe any difference between the hemolyzate
and the intact cells.
Manwell et al. (1963) have studied the oxygen equilibria of hemolyzates obtained from several hybrid sunfish. They report that these
experiments form a possible molecular basis of “hybrid vigor.” The
primary basis for this conclusion was the oxygen equilibrium of the
hemolyzate from F, hybrids obtained by crossing “warmouth” and
“green” sunfish ( Chaenobyttus gulosus X Lepomis cyanellus). Their
starch gel patterns showed that two new components were present in
addition to those of the parents. They did not determine the proportions
of these components nor did they determine their nature. The data show
that the individual points are slightly displaced from those of the parental hemolyzates. They plotted their data as the log ratio of oxy- to
deoxyhemoglobin vs. log po,. The slope of such a plot gives n, a measure
of cooperativity. The hybrid curve appears slightly steeper, but this
depends primarily on only two points that appear to differ from the
average of points for the parental strains by no more than about 0.5%
oxygenation. The double log plot magnifies this difference. The other
points are very close to one of the parental curves, and any differences
appear to be within experimental error. The conclusion that it has been
“uncontestably established that “larger heme-heme interactions” are
present therefore is unwarranted.
Extensive studies of air-breathing fishes have been camed out by
Johansen, Lenfant, and colleagues. Their study of the obligate air
breather, the electric eel, Electrophorus electricus, is particularly instructive (Johansen et al., 1968). Their studies of lungfishes will be
discussed in the next section. The adult eel utilizes extensive gas exchange in the mouth; the gills are degenerate. The blood of the electric
eel has an enormous Bohr effect ( r = 0.77)--one of the largest found in
any fish. The oxygen affinity of the blood is not unusually high (P,, = 14
mm at pH 7.4), but the oxygen capacity of the blood is quite high.
No studies have yet been carried out on hemoglobin solutions.
The high Bohr effect appears to be an adaptation to deal with the
high CO, tension of Electrophorus blood. Johansen et al. point out that
a high tension of CO, is characteristic of air-breathing fish which utilize
a bimodal gas exchange. The CO, is also elevated because blood passes
directly from the mouth to the venous circulation,
AUSTEN RIGGS
differ substantially at a po2 of 150 mm. The red cells were only 50%
saturated with 0, at an extracellular pH of 7.0, whereas the hemolyzate
was at least 95% saturated at this pH. These results appear to be inconsistent with those of Yoshioka et al. (1968). Although different species
of eel were used in the two studies, this fact still does not explain why
Yoshioka et al. did not observe any difference between the hemolyzate
and the intact cells.
Manwell et al. (1963) have studied the oxygen equilibria of hemolyzates obtained from several hybrid sunfish. They report that these
experiments form a possible molecular basis of “hybrid vigor.” The
primary basis for this conclusion was the oxygen equilibrium of the
hemolyzate from F, hybrids obtained by crossing “warmouth” and
“green” sunfish ( Chaenobyttus gulosus X Lepomis cyanellus). Their
starch gel patterns showed that two new components were present in
addition to those of the parents. They did not determine the proportions
of these components nor did they determine their nature. The data show
that the individual points are slightly displaced from those of the parental hemolyzates. They plotted their data as the log ratio of oxy- to
deoxyhemoglobin vs. log po,. The slope of such a plot gives n, a measure
of cooperativity. The hybrid curve appears slightly steeper, but this
depends primarily on only two points that appear to differ from the
average of points for the parental strains by no more than about 0.5%
oxygenation. The double log plot magnifies this difference. The other
points are very close to one of the parental curves, and any differences
appear to be within experimental error. The conclusion that it has been
“uncontestably established that “larger heme-heme interactions” are
present therefore is unwarranted.
Extensive studies of air-breathing fishes have been camed out by
Johansen, Lenfant, and colleagues. Their study of the obligate air
breather, the electric eel, Electrophorus electricus, is particularly instructive (Johansen et al., 1968). Their studies of lungfishes will be
discussed in the next section. The adult eel utilizes extensive gas exchange in the mouth; the gills are degenerate. The blood of the electric
eel has an enormous Bohr effect ( r = 0.77)--one of the largest found in
any fish. The oxygen affinity of the blood is not unusually high (P,, = 14
mm at pH 7.4), but the oxygen capacity of the blood is quite high.
No studies have yet been carried out on hemoglobin solutions.
The high Bohr effect appears to be an adaptation to deal with the
high CO, tension of Electrophorus blood. Johansen et al. point out that
a high tension of CO, is characteristic of air-breathing fish which utilize
a bimodal gas exchange. The CO, is also elevated because blood passes
directly from the mouth to the venous circulation,