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Observations on the ultimobranchial body of adult newt Triturus v. viridescens

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Anutoinical Laboratory, P a l e U w h e r s i t y School of Xedicine and t h e Osborn
Zoological Laboratory, Y a l e University, New Raven, Connecticut
Various experiments involving the removal of the thyroid
gland, the pituitary body or both from the adult newt, Triturzis
r. ciridescens (Stone aiid Steinitz, ' 5 3 ) gave us a n opportunity t o study the histological status of the ultimobraiichial body
in this salamander. A survey of tlie literature indicates that
the microscopic anatomy of this body has also been studied
extensively by others and that among the students in this
field a fair degree of coiiseiisus prevails regarding its developmeiit and gross anatomy. However, the possible functional
importance of this organ is a highly controversial question.
Since several of our findings concern themselves with a fuiictional interpretation of certain structures i n the ultimobranchial body they a r e recorded here f o r the first time in tlie
following report.
The adult aquatic Triturus v. c i r i d e s c e m studied for the
purpose of this paper were collected from various poiids in
Connecticut, Uassachusetts and Vermont. Altogether there
lAided by grants froin the James Hudson Brown Memorial Fund of t h e Yale
University School of Medicine.
' J. L. Magnes Fellowship of the Hebrew University-Hadassah Medical School,
Jerusalem, f o r 1951-52. George H. Knight Memorial Research Fellowship of
the Yale University School of Medicine f o r 1952-53.
were 105 animals. The majority of them were from the various groups of experiments mentioned above, involving animals deprived of endocrine glands. The details of the operations have already been described by the authors (Stone and
Steinitz, ’ 5 3 ) . There were 27 animals from which the thyroids
were removed, 25 animals from which the hypophysis was
removed and 23 animals with both thyroids and hypophysis
excised. There were also 4 normal unoperated newts studied
as controls. I n addition the various morphological features
of the normal ultimobranchial body were examined in 26
animals which had received thyroid grafts.
All newts were fixed in Zeriker ’s, many of the gland-deprived
animals being preserved between the second and 6th week
after operation. I n 80% alcohol the lower jaw, including the
“neck” region, was separated from the head, decalcified and
by the usual methods prepared in serial sections 12 p in
thickness which were stained in Ehrlich’s hematoxplin and
erythrosin. With the exception of two cases from which the
thyroids were removed, the serial sections were considered
complete through the essential regions in all specimens.
I n the 105 aiiinials examined the ultimobranchial body was
found in the topographic position described in detail and depicted by Vilder ( ’29). I n 104 animals the ultimobranchial
body was present on the left side only which is a condition
commonly seen in urodeles. I n the remaining case, a normal
control, there were two equally normal ultimobranchial bodies
located symmetrically one on either side, in the same relative
position as observed on the left side in other animals.
The specific tissue of the organ is represented not only by
rounded clusters of epithelial cells and branching cords of
similar cells frequently interconnected, but also quite often
by the presence of follicles of different shape and size (figs.
3 and i ) . In a minority of animals no follicles could be discovered in the ultimobraiicliial body.
\Vhile the cords and clusters are made up of one kind of
cells, two types of cells are observed in the wall of the follicles.
One of the two types appears to be identical with that forming
the solid bars of the organ. This is illustrated by the two
larger follicles in figure 3 and the follicles in figure 7. Following the fixation and staining employed in this study the cells
exhibit very dark staining, tall, often pear-shaped, roughedged nuclei surrounded by very little cytoplasm. Lateral
cell borders are not visible. The cells seem to be arranged in
a very crowded pseudostratified epithelium.
However, there is a very different type of cell which lines
another kind of follicle found in a few ultimobranchial bodies
(fig. 3, indicated by arrow). These are cuboidal cells, lower
and broader than the former ones. The nuclei are light staining, rounded, high or broadly elliptical and generally have a
smooth border. They are nearly central and are surrounded
by a fair amount of light staining eosinophilic cytoplasm.
Follicles with cells of this type are usually larger than the
other kind (figs. 4 and 6) but in a few instances very small
ones were found (fig. 8). There were rare examples where
one segment of the wall of a follicle contained only one cell
type and the remainder was made up of the other type of
cells. The two types were distinct with no transitional zones.
The follicles lined by the cuboidal cells are filled with a
secretion (figs. 3, 4, 6 and 8) which in its appearance in our
preparations is no different from the colloid of the thyroid
gland (figs. 2, 5 and 9). Also the cells lining these follicles
have the appearance of typical thyroid cells. The impression
is therefore that accessory thyroid follicles occur within the
ultimobranchial body of this newt. However they do not occur often. They were detected in only 7 out of 105 animals.
Three of the animals were hypophysectomized, three were
thyroidectomized and one possessed a thyroid graft. None
was found in the ultimobranchial bodies of the 4 normal
The other more common type of ultimobranchial follicles
shows a variety of seemingly different secretions even within
the same gland. The secretion may have a coarse and heterogeneous appearance ; at other times it is homogeneous.
It stains deep red or light blue and sometimes simulates the
colloid of the thyroid follicle even though the cells are not
like those of the thyroid.
I n an earlier paper (Stone and Steinitz, '53) we have assumed a functional identity of the rarer type of the ultimobranchial follicles of Triturus uiridescens with those in the
thyroid gland and classified them as accessory thyroid follicles
along with other thyroid follicles, single or grouped, observed
in various places between the muscles of the lower jaw. The
reason for doing so was not only the histological identity of
the follicles in question with those of the thyroid gland but
also the characteristic reaction they exhibited subsequent to
the removal of the hypophysis. We had in our experiment
three hypophysectomized animals possessing thyroid-like follicles in the ultimobranchial body which demonstrate the
striking reaction.
One newt fixed 15 days after complete pituitary removal
showed the skin condition described in detail by Adams, Kuder
and Richards ( '32) as significant after this operation. Figure
9 illustrates the regressed thyroid gland of this animal with
a low epithelium lining the follicles. A comparison with a
normal thyroid (fig. 2) emphasises the extent of the changes
caused by hypophysectomy (see Adams, '33, and Adams and
Grey, '36). One section (fig. 7) through the ultimobranchial
body in this animal shows the common type of follicles lined
by high cells with dark staining nuclei. They are not different from those usually found in the normal ultimobranchial
body. Another section of the same gland (fig. 8) shows two
types of follicles. The one indicated by the arrow was indistinguishable from the follicles of the thyroid of the same
animal (fig. 9) and like them showed the unmistakable involution of the epithelial cells.
Snother animal preserved 21 days after complete hypophysectomy showed the typical skin reaction and the marked
response of the epithelium lining the thyroid follicles (fig.
5). The thyroid-like follicle found in the ultimobranchial
body of this animal (fig. 6, indicated by arrow) also shows
the same response to hypophysectomy.
A third animal, fixed 19 days after pituitary removal,
showed the typical effects upon the skin and thyroid follicles.
I n the ultimobranchial body there were, among many normal
follicles of the common type, two of the thyroid-like follicles
showing the characteristic signs of the hypophyseoprivous
condition. Serial sections of the pituitary region of the head
in this case indicated that a remnant of the pituitary was
left behind containing adenohypophyseal as well as neurohypophyseal tissue. However, the conditions found in this
animal demonstrate that the remnant was functionally insignificant.
It can be concluded then, that the response of certain
thyroid-like follicles in the ultimobranchial body appears to
be related to the absence of thyrotropic hormone resulting
from the removal of the hypophysis. On the other hand if
the thyroids were removed and the hypophysis were left
intact the latter organ might be expected to increase secretion of the thyrotropic hormone. For such a test we had
available a series of 25 animals, in 23 of which the serial
sections were complete for determining the success of thyroid
removal and an examination of the follicles in the ultimobranchial body. An examination was made for evidence of
the presence or absence of pronounced stimulation, such as
general hypertrophy, proliferation, increased cell size, increased amount of secretion or comparable effects. A brief
description of 4 cases will illustrate the general findings.
An examination of one specimen fixed 37 days after thyroidectomy showed no remnants of thyroid glands and no
intermuscular accessory thyroid follicles. The typical thyreoprivous skin condition had been developed. This was
presumably a good test of any possible effects upon the ultimobranchial body. However, the latter was quite normal in
appearance. There were a few small follicles of the common
type among the epithelial strands and one thyroid type fol-
licle was present. Nowhere in the organ were there signs of
hypersecretion, proliferation or enlargement.
Another animal with the typical skin conditions was preserved 47 days after tliyroidectomy. The serial sections
showed as in the previous case no thyroid remnants and no
accessory follicles among the jaw muscles. The ultimobrans
chial body was conspicuously small. The tissue ~ 7 a organized
in solid strands and various size follicles lined only by epithelium of the common type. There was a colloid-like secretion
present but no sign of hyperfunction.
The conditioiis found in the ultimobranchial bodies of two
other cases were somewhat different. They were likewise
good tests of the experiment, for serial sections showed no thyroid remnants and no accessory intermuscular follicles. The
animals possessed the characteristic skin reaction. I n one case
preserved 38 days after thyroidectomy the ultimobranchial
body contained an unusual number of epithelium-lined cavities
and very little solid epithelial structures. Figure 3 shows in
this case not only small follicles but two large ones of the common type with secretory material. Between these follicles is
the well defined thyroid type follicle found in this gland. It is
indicated by an arrow. It contains the typical colloid material
unlike the contents of the other follicles.
The other case, sacrificed 43 days after thyroidectomy possessed an ultimobranchial body with a variety of follicles
most of which were of the common type. However, a few were
lined with epithelial cells characteristic of the two types of
follicles. A t the same time there were several follicles of the
purely thyroid type. One of them (fig. 4) was very large,
representing apparently a system of confluent follicles filled
with the typical colloid. The cells are slightly more crowded
than usual and although mitoses were not found the situation
may be indicative of proliferation having occurred. This is
the largest follicle of the thyroid type we have observed.
From our observations on the ultimobrancliial body of the
newt, Tritirrrts v. riridcscens: two different kinds of cells werc
found which distinguish the type of follicles in the gland.
There was an occasional thyroid-like follicle sharply defined
from the common dark staining type (fig. 3 ) . There were even
rare cases in which a follicle contained both kinds of cells
with areas distinctly marked from each other. Our experiments show that when the pituitary of this newt is removed
the two types react differently. While the thyroid-like type
responds with marked regression just as the thyroid gland
itself, the other type, making up the bulk of the ultimobranchial body does not react visibly. From this we conclude that
the ultimobranchial body may occasionally contain thyroid
follicles and, like the accessory thyroid follicles situated betmeen the jaw muscles, these structures should be considered
as part of the thyroid system that is controlled by the thyrotropic hormone of the hypophysis.
K i t h regard to the pituitary control of the ultimobranchial
body in other cold blooded animals the opinion of Schaefer
('38, working on the fish and lizard) and Eggert ('38a and
'38b, working on salamanders) may be of interest at this point.
Schaefer studied the development of the ultimobranchial
body in Triturus vulgaris and l'. alpestris. He noted that
the epithelial outgrowth from the pharynx soon developed
small follicles in which later cell proliferation obliterated the
lumina. At the end of metamorphosis the cells were smaller
and the nuclei were crowded, but when the newts took on
terrestrial life the cells became larger, their nuclei stained
darker and very small lumina reappeared containing colloicl
secretion. The whole gland, however, did not grow. This investigator also thyroidectomized recently metamorphosed
newts which he followed for 48 days. He reports that the
formerly stratified epithelium receded to one layer, the cells
enlarged, nuclei became prominent and less darkly stained,
the follicles increased in size and possessed more colloid secretion while in some activated follicles there were patches
of apparently untransformed cells with dark staining nuclei.
He considers that the ultimobranchial body, having been
checked by the thyroid now takes over the role of the thyroid.
I t is not clear whether he believes the thyroid control is
direct or by way of the pituitary.
I n the 23 thyroidectomized adult Triturus v. viridescem
which we preserved from 11 to 47 days after operation we
found no evidence of a progressive increase in the number
of thyroid-like follicles in the ultimobranchial body. I n fact
there were only a few of this type in the three animals already
described which were preserved 37, 38, and 43 days after thyroidectomy. I n the oldest of these there was a suggestion of
possible proliferation. I n many other experiments terminating during this period as well as all other animals preserved
earlier, no thyroid-like follicles were found. While our experiments are not numerous and were done on another species
they do not support the conclusions of Schaefer.
The hypophysectomized newts of Schaefer are not directly
comparable to ours. He operated on larval stages which
stabilized the larval condition of the ultimobranchial body for
4 months after operation. He also hypophysectomized animals when the first indication of metamorphosis became apparent. He claimed that the follicular elements in the ultimobranchial body hypertrophied but not the solid epithelial
bands. This he thought was due to the regression of the
thyroid now unable to check the ultimobranchial body. However, further consideration of the possible part the pituitary
is playing here should be given in an attempt to confirm his
Eggert did demonstrate influence on the ultimobranchial
body in Xiphophorus ( '38a) and Lacerta agilis ('38b) with
injections of thyrotropic hormone. He showed in the fish,
for example, that disintegration of the organ was taking place
after long administration of the hormone. But why there was
no activation of the thyroid-like structures still remains unanswered. One might well ask whether or not the colloid
material in the thyroid-like follicles of the ultimobranchial
body is identical with that found in the thyroid. Eggert's
('3%) experiments attempt to answer this question but they
are still not conclusive. He implanted the lizard ultimobran-
chial body, which resembles the thyroid in many respects,
into the body cavity of Triturus alpestris larvae but failed
to accelerate metamorphosis. His conclusion from this was
that the secretion in the ultimobranchial body is not comparable to the thyroid.
Perhaps a more fruitful approach to the problem would
be through the use of radioactive iodine such as Gorbman
('47) has applied in the mouse to demonstrate that part of
the lateral thyroid lobe is derived from the ultimobranchial
body. This close association is known in many mammals
where, during development, the ultimobranchial body becomes
incorporated in the thyroid and then lost. It has been suggested without experimental proof that the assimilation is
induced by the thyroid. However, if thyroid-like follicles
found in the ultimobranchial body of newts prove to be identical with those in the thyroid gland the induction hypothesis
could hardly apply here. It may be that a hormonal balance
on the basis of an original capacity of the organ a d a g e is
playing a certain role as indicated by Schaefer's embryological investigations. The question is still open to further
1. Observations were made on the ultimobranchial body
of 105 adult Triturus zi. viridescens under normal and various
experimental conditions involving the thyroid and pituitary
2. The ultimobranchial body of this adult newt contains
one or two different kinds of cells and follicles. The specific
ultimobranchial type of cells forms solid structures, follicles,
or se,gments of follicles. The second type is observed only in
follicles; it forms segments only, or all of the follicular walls.
Because of its structural properties this type is called the
thyroid-like cell and/or follicle. This type is rare.
3. After hypophysectomy regression of the thyroid-like
follicles of the ultimobranchial body is observed to be equal
to that of the thyroid gland under the same conditions. The
specific ultimobranchial tissue does not react visiblF.
4. After thyroidectomy (pituitary gland left intact) no
clear signs of activation or hypertrophy of either part of
the ultirnobranchial body was observed.
5. The structural features and response after hypophpsectoniy are considered proof of the thyroid character of the
second type of ultimobranchial tissue.
6. Various theories of other authors concerning the hormonal dependence and control of the ultimobranchial body
are discussed in the light of the observations reported.
ADAXS, A. 1.:. 1933 The effects of hypophysectoniy and anterior lobe administration on the skin and thyroid of Triton cristatw. J. Exp. Biol.,
10: 247-255.
ADANS, A . E., A X D B. GRAY 1936 A comparative study of the thyroid glands
of I~ypophysectomized newts after treatment with anterior pituitary,
thyroid, and iodine. Anat. Rec., 65: 69-81.
1932 The endocrine glands and
molting i n l'riturus viridescens. J. Exp. Zool., 63: 1-55.
B. 1938a Der ultimobranchiale KBrper der Knochenfische. Zsclir. Zellf.
mikr. Anat., 27: 754-763.
193813 Der ultimobranchiale Karper. Endocrinologie, 80: 1-7.
GORBMAN, A. 1947 Functional and morphological properties i n the thyroid
gland, utimobranchial body, and persisting ductus pharyngiobranchialis
IV. of a n adult mouse. Anat. Rec., 98: 93-101.
RrHmFm, K. 1938 Morphologische und physiologische Untersuchungen am
ultimobranchialen KSrper von T'ritumcs vulgaris und Trit. alpestris.
Z. wiss. Zool., 151: 22-38.
STONE,L. S., AKD H. STEINITZ1953 Effects of hypophysectomy and thproidectomy on lens and retina regeneration in the adult newt T'riturzts
T. ciridescens. J. Exp. Zool., 164: 464-504.
WILDER,M. C. 1929 The significance of the ultimobranchial body (postbranchial
body, suprapencardial body) : a comparative study of its occurrence
in nrodelos. a. Morph., 473 283-333.
1 Ultimobraiicliial body of normal control adult newt to show epithelial strands
and ordinary type of follicles with same kind of cells. X 130.
Thyroid gland of normal control newt. X 130.
3 Thyroid-like follicle, indicated by arrom-, between tiTo ordinary types of
u1tiniobranchi;il folliclre, 38 days after thyroidectomy. X 130.
4 Largest thyroid-like follicle observed in an ultimobranchial body. Below i t
are several ordinary type follicles. X 130.
5 Xarlied regression of epithelimn in thyroid gland of newt 41 days after
hypophyseetomy. X 130.
6 Marked regression of epithelium in thyroid-like follicle, indieated by arrow,
and lack of reaction in ordinary type follicles and cells in ultimobranchial
bod?. Same case as in figure 5. X 130.
7, 8, 9 Showing in the same animal, 15 days after hypophyseetomy, no visible
reaction of ordinary type ultimobraiichial follicles (fig. 7 ) but marked regression of epithelium in thyroid-like follicle (indicated by arrow) in nltimobranchial body (fig. 8 ) and in follicles of the thyroid gland (fig. 9). X 130.
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adults, observations, newt, viridescens, body, ultimobranchial, triturus
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