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First published online May 2, 2008
Journal of Experimental Biology 211, 1521-1523 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.011783
JEB Classics |
IN VIVO BLOOD AND GUTS PHYSIOLOGY IN FISHES
University of Prince Edward Island
dstevens{at}upei.ca
|
Previous studies on respiration in fish had focussed on how much oxygen was
removed from the water and how it changed with fish species, environmental
conditions (e.g. temperature and salinity) and, especially, how it changed
with the animal's level of activity. These studies conducted in the 1940s were
the focus of much of the work of Fred Fry in the 1960s at the University of
Toronto and by his students, Roly Brett, Bill Beamish, Madan Rao and Narayan
Kutty (Fry, 1971
). Brett
published an intensive and extensive study of the cost of swimming in salmon
using a swim tube that he designed specifically for the study
(Brett, 1964). In addition,
much had been learned about the oxygen binding properties of fish blood in
vitro, especially through the work of Edgar Black and R. W. Root, and the
functional anatomy of fish gills, especially by George Hughes. Thus, in the
early 1960s, quite a bit was known about factors affecting gas exchange of
fishes and about in vitro properties of blood. However, little was
known about actual cardiovascular and blood gas parameters in fish while the
fish was swimming until Randall published his series of five classic papers in
1967.
Randall, fresh from doing a PhD with Graham Shelton at the University of
Southampton, had just come to University of British Columbia (UBC) in
Vancouver. His PhD on the control of respiration during hypoxia in fish had
led to the question of the functional significance of the decrease in heart
rate observed when fish are exposed to hypoxic water. Randall realized that
one way to tackle the problem would be to measure gas partial pressures of
gases in both media and on both sides of the exchanger – that is, in the
blood going into and coming out of the gills and in the water coming into and
after passing over the gills. Roly Brett had just published his classic paper
on oxygen uptake in salmon based on his work at the Pacific Biological Station
at Nanaimo – a short ferry ride away from UBC – and a visit with
Roly was very fruitful for two reasons. First, because Brett invited Randall's
group, which included myself and George Holeton, to come to his lab at Nanaimo
and use his fish swimming tubes. And, second, while there, Randall learned of
the methods that Gordon Bell, also at the Nanaimo lab working with Lynwood
Smith, had modified to cannulate the dorsal aorta of salmon based on the
preliminary efforts of Randall and Brett. Smith and Bell had used their
technique to inject radio-opaque dyes into the vasculature of fish and to make
preliminary measurements of blood volume in salmonids
(Smith and Bell, 1964).
Randall was very encouraged by this development; he recognized that it would
allow sampling blood after it had passed through the gas exchanger. At the
invitation of Brett, Randall joined the Nanaimo group and showed that it was
also possible to measure blood pressure in intact, unanesthetized,
unrestrained but confined fish (Randall et
al., 1965).
Several other factors played important roles for our studies. Ken Wolf had
just developed a saline solution suitable for use in salmonids, so-called
Courtland saline, which approximated the ionic constituents in trout blood
(Wolf, 1963); in the Smith and
Bell blood volume study (Smith and Bell,
1964) 1% sodium chloride had been used. Leland Clark had developed
the polarographic oxygen electrode in 1956
(Clark, 1956) and John
Severinghaus and Freeman Bradley had gone on to develop small versions
suitable for measuring oxygen and carbon dioxide partial pressures and pH in
small blood samples (Severinghaus and
Bradley, 1958). Just as we were embarking on our studies,
commercial versions of these electrodes became available from Beckman (Beckman
model 160 physiological blood gas analyser), and the Fisheries Research Board,
through Brett, came up with the money to purchase this equipment. Another
factor facilitating the research was that in the mid '60s, the national
granting agency (called the National Research Council of Canada at that time)
had received huge increases in funds that became available for university
laboratories so that Randall could fund the work. Thus, Randall had the ideas,
the equipment was on the market, and the funds were available to buy the
equipment. George Holeton from Calgary and myself from Edgar Black's lab in
the medical school at UBC joined Randall's lab in the fall of 1965 and thus we
were in the right place at the right time to make the ground-breaking move
into physiological measurements in unrestrained, intact unanesthetized
fish.
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Despite the decades that have elapsed, several aspects of these studies
have stood the test of time. For example, the following observations are all
still valid: the increases in ventilation and cardiac output during moderate
exercise or hypoxia are due more to changes in volume per beat than to changes
in respiration rate or heart rate (Holeton
and Randall, 1967b; Stevens
and Randall, 1967b); moderate exercise or hypoxia results in
increases in blood pressure on both sides of the gills
(Holeton and Randall, 1967a;
Stevens and Randall, 1967a);
effectiveness of oxygen uptake by the blood approaches 100%, does not change
much during moderate exercise, but is decreased markedly during severe hypoxia
(Randall et al., 1967).
However, these experiments also had several shortcomings; for example, blood
oxygen content was estimated rather than actually measured
(Holeton and Randall, 1967b;
Stevens and Randall, 1967b)
and thus the estimates of cardiac output and ventilation volume were crude
estimates rather than exact values. In addition there was wide temperature
variation across experimental trials (ranging from 4 to 19°C) because we
did not have temperature control of the holding tanks, making some of the
comparisons between studies somewhat tenuous. Finally, the hypoxia study was
compromised by the fact that CO2 accumulated as the oxygen was
depleted (Holeton and Randall,
1967a; Holeton and Randall,
1967b) and the exercise study was of short duration and not very
strenuous (Stevens and Randall,
1967a; Stevens and Randall,
1967b).
The real import of these initial studies was that they resulted in, to use
an obnoxious buzzword, a paradigm shift. We had shown to everyone doing
experiments in fish physiology that it was possible to make measurements in
intact, unanesthetized, unrestrained fish
(Fig. 1). It was also clear
from our work that measurements taken from restrained fish may be challenged.
The shortcomings of the initial studies also provided opportunities for later
students (e.g. Kiceniuk and Jones,
1977). Some of the subsequent studies that were stimulated by
these initial studies looked at gas exchange in greater detail and actually
measured rather than estimated gas content (e.g.
Brauner et al., 2000). In
addition, it was realized that the method could be applied to the transfer of
substances other than gases across fish gills. For example, there are a huge
number of studies on ion exchange and acid–base balance, especially by
Chris Wood, Steve Perry, Katie Gilmour, Dave Jones, Gord MacDonald, Norbert
Heisler, Pat Walsh, Bob Boutilier and their students. Ken Olson and his
students have made a career of looking at factors that control peripheral
circulation, whereas Tony Farrell and Kurt Gamperl have focussed more on the
regulation of the heart and measuring blood flow directly with flow probes
under a variety of conditions. Others have used similar techniques to look at
turnover of metabolites in fish (e.g. Jim Cameron, Jim Ballantyne, and
especially Jean-Michel Weber) or changes associated with stress (George
Iwama). Unfortunately, George Holeton was involved in a fatal automobile
accident early in his career and so was not able to share in seeing much of
the impact his work has had on others.
In summary, this series of papers pioneered the approach that set the stage for an explosion of studies in fish physiology, especially in Canada, that dominated much of comparative physiology for the next three decades. It also is noteworthy that much of the subsequent work has some connection with UBC – either done by graduate students, postdoctoral students, or visiting scientists in Randall's laboratory.
Footnotes
Don Stevens writes about the series of five papers from Dave Randall's laboratory published in 1967 on gas exchange in fish. All of the papers are available at http://jeb.biologists.org/content/vol46/issue2.
References
Brauner, C. J., Thorarensen, H., Gallauhger, P., Farrell, A. P. and Randall, D. J. (2000). The interaction between O2 and CO2 exchange in rainbow trout during graded sustained exercise. Respir. Physiol. 119, 83-96.[CrossRef][Medline]
Brett, J. R. (1964). The respiratory metabolism and swimming performance of young sockeye salmon. J. Fish. Res. Bd Canada 21,1183 -1226.
Clark L. C. (1956). Monitor and control of blood and tissue oxygen tensions. Trans. Am. Soc. Artificial Internal Organs 2,41 -48.[Medline]
Fry F. E. J. (1971). The Effect Of Environmental Factors On The Physiology Of Fish, vol.6 . pp. 1-98. New York: Academic Press.
Holeton, G. F. and Randall, D. J. (1967a).
Changes in blood pressure in the rainbow trout during hypoxia. J.
Exp. Biol. 46,297
-305.
Holeton, G. F. and Randall, D. J. (1967b). The
effect of hypoxia upon the partial pressure of gases in the blood and water
afferent and efferent to the gills of rainbow trout. J. Exp.
Biol. 46,317
-327.
Kiceniuk, J. W. and Jones, D. R. (1977). The
oxygen transport system in trout during sustained exercise. J. Exp.
Biol. 69,247
-260.
Randall, D. J., Smith, L. S., and Brett, J. R. (1965). Dorsal aortic blood pressures recorded from the rainbow trout (Salmo gairdneri). Can. J. Zool. 43,863 -872.[Medline]
Randall, D. J., Holeton, G. F. and Stevens, E. D.
(1967). The exchange of oxygen and carbon dioxide across the
gills of rainbow trout. J. Exp. Biol.
46,339
-348.
Severinghaus, J. W. and Bradley, A. F. (1958).
Electrodes for blood PO2 and
PCO2 determination. J. Appl.
Physiol. 13,515
-520.
Smith, L. S. and Bell, G. R. (1964). A technique for prolonged blood sampling in free-swimming salmon. J. Fish. Res. Bd Canada 21,711 -717.
Stevens, E. D. and Randall, D. J. (1967a).
Changes in blood pressure, heart rate and breathing rate during moderate
swimming activity in rainbow trout. J. Exp. Biol.
46,307
-315.
Stevens, E. D. and Randall, D. J. (1967b).
Changes of gas concentrations in blood and water during moderate swimming
activity in rainbow trout. J. Exp. Biol.
46,329
-337.
Wolf, K. (1963). Physiological salines for fresh-water teleosts. Progr. Fish Culturist 25,135 -140.[CrossRef]
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