Table Of ContentTHE METABOLISM OF NORMAL AND THYROXIN-STIMULATED
RANA PIPIENS SKIN
by
Stephanie Henoch Barch
Chairman
Professor Jerry J. Kollros
A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of
Philosophy, in the Department of Zoology
in the Graduate College of the
State University of Iowa
August, 1952
ACKNOWLEDGMENTS
The writer wishes to express her deep
appreciation to Professor Jerry Kollros for the
formulation of the problem and for advice and
assistance during the course of this investigation.
Thanks go to Professor Gordon Marsh who
contributed generously of his time in the solution
of apparatus difficulties.
A grant by the Graduate College for the
purchase of necessary additional equipment is also
acknowledged here.
Finally, the writer wishes to thank her
husband, Abram Barch, for statistical advice.
ii
TABLE OF CONTENTS
page
Introduction ................ 1
Material and Methods .................. 11
Series I ....... 16
Results ...................... 16
Discussion.................. . 17
Series II .......................... 24
Results ...................... 2k
Discussion ................. 25
Series III ........................... 29
Results .......................... 29
Discussion.................... 30
General Discussion .................... 34
Summary ......................... 36
Appendix........................ 38
Bibliography ........................... 42
iii
TABLE OF TABLES
Table page
I Analysis of Variance of Log (10 x
Q,02) for the Grouped Normal Skins 21
II Group Means of QO2 and Log (10 x
0,03) of the Normal Skins ......... 22
III Values of t for the Comparison of
Log (10 x ^02) of Individual Groups
of Normal Skins ..... 23
IV Analysis of Variance of Q02 for
Normal and Thyroxin Treated Animals
for Stages IX Through X I V ....... 27
V Mean QP2 f°r Normal and Thyroxin
Treated Animals for Stages IX
Through XIV ................ 28
VI QP2 of the Skin of the Right Experi
mental Side and of the Left Control
Side of Animals Which Had Received
Pellet Implantations. Two Animals
Pooled in Each Calculation ....... 33
iv
Table of Figures
Figure page
1 Mean 0_ consumption for the various
stages of development of normal and
thyroxin treated Rana pipiens skin 20
v
1
INTRODUCTION
Metamorphosis of amphibian larvae has been
shown to be dependent upon the thyroid hormone in the
circulating body fluids. The beginning of rapid meta-
morphic change is correlated with an increase in the
initially low hormone level. The hormonal control of
metamorphosis and the morphological changes occurring in
metamorphosis have been reviewed by Allen (1929, 1938) and
by Lynn and Wachowski (1951).
Another important function of the thyroid
secretion is the regulation of the basal metabolism. It
has been shown in mammals that a quantitative change in
the secretion of the thyroid hormone is accompanied by a
corresponding change of the basal metabolic level. Since
the hormonal level in the body of the amphibian rises
during metamorphosis, an accompanying rise in the meta
bolism might also be expected.
One of the changes which the larvae undergo
during metamorphosis is a loss of weight. In a great
measure this weight loss is due to a reduction of the
water content. Etkin (1932), studying the water loss in
2
Rana palustis, found a slow dehydration during the period
of rapid leg growth, the preclimax period. During this
period the dry weight increases from 9% of the total body
weight to 14% of the total body weight. When the fore
limbs emerge this percentage increases to 16%. At
met amorphic climax the dry weight rises to 18-22% of the
body weight to give a water loss during this period of
between 2 and 6% of the body weight. Altogether the dry
weight - total body weight ratio doubles from the onset
of rapid leg growth to the end of metamorphosis. In Rana
pipiens the dry weight also rises from about 6.2% of the
body weight at the beginning of rapid leg growth (approxi
mately stage VIII of Taylor and Kollros, 1946) to 14.4% at
the end of metamorphosis (stage XXV). The climax changes
agree with those reported by Nagel (1927)* in his study
of three axolotls. He found that the dry weight of the
control animal was 14.3% of its body weight. The two
animals which were stimulated and carried through meta
morphosis showed a dry weight increase to 19.3% and 19*7%
of the total body weight. The weight loss attributable to
water loss was about 5% in both cases. Nagel did not take
into consideration any water loss prior to the beginning
of metamorphic climax.
3
Several investigators have studied the metabolio
changes during metamorphosis of the entire animal, using
02 consumption or CO output as a measure of the metabolic
rate. Their results are not consistent. Drastich (1923,
1923) studied the growth and development of well fed
Salamandra larvae under different oxygen tensions. He
observed that the animals raised under high oxygen tension
resemble those collected in nature with respect to growth
rate and feeding habits. He used a differential micro-
respirometer and showed an increase in the 02 consumption
and C02 output during premetamorphic development. Meta
morphosis was marked by a sharp decrease in metabolism and
weight. On a unit body weight basis, however, all the
animals showed a slowly decreasing rate of metabolism during
the larval period. The animals which underwent metamorphosis
showed no change in the decreasing rate, although the results
were extremely variable.
Etkin (1934) studied the 02 consumption during
natural metamorphosis of well fed, unanesthetized Rana
catesbeiana by the Winkler titration method. His studies
terminated when the tail was but one-half resorbed. Beyond
that developmental stage the animals would have drowned in
the experimental vessels. During the period of rapid hind
4
leg growth, the 02 consumption increased until stage XX,
the beginning of metamorphic climax. After stage XX,
there was a sharp drop in the 02 consumption which
continued until the experiment had to be terminated about
7 days later. During the preclimax period, the rate of
weight increase and the rate of metabolism increased
proportionally. Therefore, the 02 consumption per unit
of body weight remained approximately constant. During
metamorphic climax, the weight and metabolism decreased.
The loss in body weight began prior to the decrease in 02
consumption. Even before the occurrence of the weight loss
there was some water loss. Although the 02 consumption per
unit of body weight remained constant or even increased
slightly, the ratio of dry weight to total body weight
increased during the period of rapid hind leg growth. This
meant that the respiration per unit of dry weight had
increased during all of this time. By the time of climax
this decrease amounted to 30% of the original rate. This
decreasing metabolic rate continued during metamorphosis.
Groebbels (1922) studied the effect of nutrition
and thyroid administration on the 02 consumption of well
fed Rana temporaria larvae* When animals with well
developed hind legs were given thyroid extract, the 02
5
consumption increased, both with respect to unit weight
of animal and with respect to the animal as a whole. No
abrupt metabolic changes could be seen during normal or
Induced metamorphosis. These results are difficult to
evaluate, because Groebbels did not classify his animals
as to stages in their development, nor did he keep a
running protocol.
Belehradek and Huxley (1927) studied the 02
consumption during thyroxin-induced metamorphosis in the
axolotl in a Haldane apparatus. The animals were starved
or minimally fed, and lightly anesthetized. The anesthesia
depressed the metabolic rate. The induced metamorphosis
was accompanied by an increased metabolism which came very
late in the sequence of morphological changes, after
ecdysis had been initiated. Increased 02 consumption was
not evident until after 8 to 14 days of treatment.
Helff (1923, 1926) studied the 02 consumption
of the thyroid- and di-iodotyrosine-induced metamorphosis
of Rana pipiens by the Winkler titration method. When the
animal's hind legs were 5 mm. long (about stage VIII of
Taylor and Kollros), the respiratory studies were begun. .
Unanesthetized larvae were starved for 24 hours before
the first trial. They were fed dried thyroid gland and
