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The effect of total thyroidectomy on the structure of the pituitary gland in the rabbit.

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THE E F F E C T O F TOTAL THYROIDECTOMY ON THE
STRUCTURE O F THE PITUITARY GLAND
I N THE RABBIT
ARTHUR R. BRYANT
Hull Laboratory of Anatomy, The University of Chicago
OSE COLORED PLATE (TWO FIGURES)
INTRODUCTION
Practically all observers are agreed that thyroidectomy
affects the pituitary body and that the latter increases in
size after this operation. All but Herring ('08) agree that
the chief change is in the anterior lobe. While some think
that it is chiefly in the chromophobe cells, others (Satwornitzkaja, '26) regard the hasophiles as the cells chiefly affected,
and Cimoroni ( '07) considers that the eosinophile cells are
markedly increased.
The reason for these disagreements is undoubtedly to be
found in the fact that, notwithstanding much iiivestigation
of the most searching cytological sort, the functional composition of the glandular portions of the pituitary body is
still impcrfectly understood.
Since the work of Lothringer ('86)' Flesch ('86)' and
Rogowitsch ('89) it has been known that the anterior lobe
contains at least two types of cells. To these Schonemann
('92) added a third in the so-called hasophile (cyanophile)
cell, and the work of Tihey ('14) and Atwell ('26) set aside
the pars tuberalis as different from the anterior lobe, while
the observations of Maurer and Lewis ('22) and of Rasmussen ( '21) recognized special characteristics in certain
cells of the pars intermedia of the pig and woodchuck.
131
TIIE ANATOXICAL RECORD, VOL. 47, NO. 2
NOVEMBER, 1930
133
ARTLICI: t:.
BRYANT
Only one of these cells, however, has been clearly recognized as a dif'f'erentiated cellular type constant in its occurrence throughout vertebrates. That is the so-called eosinophilc cell of Schoncmann, better termed alpha cell, a s
proposed by Bailey ( '28). This cell is among the earliest t o be
differentiated from the common cell mass in the embryo, has
lwei1 recognized in every pituitary body which has been examined, and is easily recognized by perfectly definite structural and tinctorial characteristics.
The basophile cell, or beta cell, however, while constituting
in the hnman pituitary body and in that of the pig, dog, ox,
and .Ir-oodchuck a clcarly defined cellular tvpe, has been
frequently identified by vague tinctorial characters which
neither establish it as a distinct cell type in other species
nor separate it definitely from certain cells belonging to tlic
cliromophobe series. I n the species mentioned above this
cell is characterized by the presence in its cytoplasm of discrete granules which stain with the less disperse dyes such
as the aniline blue of the Mallorp stain, acid violet of the
Maurer and Lewis techniques, or the kresofuchsin of Rraus
('12). It is apparent from a perusal of the literature that
cclls have been identified as basophile cells wlicn their protoplasm took up these stains in a diffuse way with no suggestion
of special granules. Otlier characters often ascribed to the
basophile o r beta cells are possessed in some degree by all
other components of the anterior lobe. This statement refers
to the presence of vacuoles in the cytoplasm, to the presence
of a cytocentrum (rnacula) associated with a vacuonie or
Golgi apparatus, and to mitochondria1 and nuclear characters.
The special cells of the pars intermedia described by
Maurer and Lewis ( '22) in the pig and by Rasmussen ( '21)
in the woodchuck liavc not been generally recognized by other
observers, but have, in the species just mentioned, a character wliieh should make their recognition easy if suitable
technical precautions are observed. Tliese cells are of large
size and contain a variahlc amount of a finely granular cell
product mliicli occupies definite compartmeii ts in the cell
CHANGES IX HYPOPHYSIS AFTER TIIYI:OIDECTOJZY
133
heparated by cytoplasmic partitions. This suljstance hfaurer
and Lewis showed to be extremcly labile, dissolving out of
4he cell when fixation was delayed. These cells also show a
quality which is not exclusive to them, but forms one of their
conspicuous characteristics, namely, a large mass of cytoplasm near the nucleus, rich in mitochondria, containing the
vacuome and the cytocentrnm.
The cells which are commonly termed chromophobe, those
cells of the pars intermedia which do not belong to the
category just described, and the cells of the pars tuberalis
constitute a group of cellular elements containing no one
knows how many functional types, since up to Ihe present it
has not been possible t o define them with sufficient accuracy
so that an observer can recognize them from one another
when he sees them. Rogowitsch and all subsequent observers
recognized that some were large and some small, and Maurer
Lewis demonstrated a special kind of chromophobe cell in the
anterior end of the anterior lohe of the pig’s pituitary, but,
in general, while there is much prolixity of description,
neither mitochondria, nor Golgi apparatus, nor secretory
content has sufficiently defined any one of these cell types
so that an experimenter can distinguish it with certainty from
other similar cells or trace its changes under experimental
conditions. Moreover, the relations of the cells constituting
the chromophobe series t o the chromophile cells of both types
remain obscure. Whether the latter reproduce their kind,
are recruited from the chromophobe group, or are transformable one into another is unknown.
The irregular distribution of the various chromophile cells
in the anterior lobe is also undoubtedly a source of much
confusion where the work is not controlled by the serialsection method o r by careful quantitative study like that
of Basmussen on the woodchuck. It is not difficult to be
misled by the comparison of sections from an experimental
and a control gland which are not taken from the same part
niid the same plane of the gland.
134
hRTHUR R. BRYANT
In spite of these handicaps which still remain, I have
endeavored to ascertain by experiment in the rabbit whether
removal of the thyroid gland produces changes in the
pituitary body and the cells that are involved in this change.
After a preliminary series of experiments on the adult animals which yielded positive results, it was decided to use for
the experiment young males, reserving their male litter mates
for controls. I n the experimental animals both lobes and
the isthmus of the thyroid gland were removed under ether
anaesthesia in the usual way, leaving the external parathyroids in situ to avoid postoperative tetany. The experimental animals were then kept in the same cages with their
male litter mates under the same conditions as regards food,
etc., until a sufficient time had elapsed The animals were
then killed by heart puncture, the calvarium removed, the
pituitary body carefully extracted from the sella, placed in
r? weighing tube and carefully weighed, then fixed in IZegaud’s
fluid. The animal was then carefully inspected to be sure
that the thyroidectomy had been complete. With this end
in view, the animals were perfused from the aorta with a
1-40,000 solution of Meldola’s naphtol blue, which has the
property of staining thyroid tissue intensely blue. All suspected tissue was then removed, fixed, embedded, and sectioned to see if it contained thyroid tissue. Tn one case only
was this found.
The pituitary bodies after embedding were sectioned in
complete series in the sagittal plane and stained by the anilin
acid-fuchsin methyl-green method of Rensley usually
employed f o r mitochondria1 stain.
For the study of the normal gland and glands From adult
Cretins, the pituitary glands of these indiriduals fixed in
Bensley ’s f ormalin-Zenker solution or Regaud’s f ormalinlnichromate solution were stained in a modification of the
kfallory method f o r connective tissue, using a 10 per cent
solution of acid fuclisin in anilin water instead of the usual
fuchsin solution. The iron-haematoxylin and the anilin acidfuchsin methyl-green methods wcre also employed. The modi-
CHANGES IN HYPOPHYSIS
135
AFTER THYKOIDECTOMY
fied Mallory method when used on the human pituitary gland
o r on that of the pig o r dog is particularly useful in differentiating very clearly the alpha cells, the granules of which
stain red or yellow, the beta cells, the granules of which stain
blue, and the chromophobe cells, which contain no specific
granules, but stain in different intensities of blue corresponding to a variable content of a non-granular secretory product.
Either this method or the anilin acid-fuchsin methyl-green
method serves well to define the characteristics of the special
cell of the pars intermedia as described by Maurer and Lewis
and by Rasmussen.
TIIE EFFECT O F TIIYROIDECTOMY ON T H E SIZE O F THE PITUITARY
GLAND I N RABBITS
Our results obtained by comparison of weights of the
pituitary gland of thyroidectomized animals with those of
their litter mates of the same sex confirm the earlier quantitative results of Stieda ( '90) and the impressions of numerous
other investigators that thyroid deficiency results in an
increased size of the pituitary body.
TABLE 1
ANIMAL AND
SERIES NO.
~
.
.
INITIAL
WEIGHT
MAXIMUM
I
WEIGHT
~
__
~-
Series 1:
Rabbit P
Control
Series 2 :
Rabbit 8
Rabbit T
Control
Series 3 :
Rabbit U
(female
Control
Series 4 :
Rabhit X
Control
Control
FINAL
WEIQHT
410
Nottaken
550
550
530
1
1140
1570
960
1420
81
I
I
1230
1300
1340
1230
1270
1220
110
79
640
500
64
1020
1020
830
550
820
920
I
I
'
320
460
400
360
340
~
I
s20
920
1
'
I
'
0.022
0.0188
0.0246
0.0185'
0.0193
I
0.0225
I
90
j
1
0.0198
0.022
0.016
0.015
~
'Rabbit T was found, on reoperation on the seventy-eighth day, t o have some
residual thyroid tissue. This was removed, but the animal died tho following
day, and the weight of the hypophysis showed that t h e condition of the latter
was as in a normal animal.
N”th the exception of rabbit U, all the animals used in this
study were males, and the members of each serie,c were litter
mates.
These experiments demonstrate that complete thyroidcctomy results in increase in weight of the pituitary gland.
It remains to be seen to \\-hat tissue element of the gland this
iiicrcase is due. T n order to do this, it is necessary first to
consider the structure and cell composition of the normal
gland.
THE N O R J I A L I’ITUITARY G L A N D 01’ THE RABBIT
Tlic normal pitnitarp gland of the rabbit consists, as in
other mammals, of the following parts : pars distalis. or main
glandular lobe ; pars inf undihnlaris, or epithelial portion,
which surrounds the pars nervosa : pars tuberalis, cstelltling
forward on the under surface of the brain ; and pars nerrosa.
Thc pars distalis constitutes the main glandular mass iisually known as anterior lobe. It is partly separated from the
pars infuiidibularis by the residual lumen, a cavity derived
from the original pouch of Rathke, but is continuous vith the
infuiidibular part at the extremities of this cavity. It is
also continuous above with the pars tuberalis.
The cell types found in the anterior lobe are well illustrated
hy figure 1,which is drawn from a normal rabbit gland fixed
in formalin-Zenker and stained with anilin acid fuchsin and
Xallory ’s anilin blue-orange G mixture. The conspicuous
cell type is the alpha cell (eosinophile), which, in this preparation, is stained strovigly with the acid fuchsia. The red
stain is due to the fact that the cytoplasm is closely packed
with minute granules which take the stain, filling the cell so
closely in many cases from the normal gland that the individual granules are difficult to discern. I n the rabbit’s gland,
however, it is not uncommon to find many alpha cells whicli
have their granule content reduced to a mere line of granules
along the edge. Some of the alpha cells contain granules
which stain with the orange component of the dye, and this
is particularly the case with clusters of small alpha cells
which appear to be young elements, or elements just beginning secretion storage.
Tlie alpha cells in the rabbit’s gland a r e present in all parts
of the anterior lobe, but are particularly iiumerous in the
portion of this lobe wliich is adjacent to the residual lumen
and to the p a r s infundibnlaris and on the reiitral and lateral
surfaces of the lobe. Tlie anterior portion of the lohe and
the adjacent central portions contain scattered alpha cells,
but they a r e relatively infrequent. This area constitutes
the so-called triangular area of Rogowitscli. The upper
border of the anterior lobe is also poor in alpha cells and is
directly continuous with the p a r s tnberalis.
Among the deeply stained cells of the anterior lobe of the
rabbit’s gland may be recognized a certain number of cells
which prefer the blue dye and so have tlie general characteristics of tlie hasophile cell of the human gland. In these cells,
however, one does not find the discrete blue-stained granules
of the human gland, but the staining is diffuse. The racuome
with its associated cytocentrum is conspicuous in these cells
a s it is in the human basophiles, but this is merely a result
of the more vivid staining of the cytoplasmic background.
T\lorcover, these cells grade through a whole series of iiitermediate degrees of staining into the palely staining chromophobes of the anterior lobe. It is extremely doubtful whether
these a r e true physiological homologues of tlie hasopliile cell
of man.
The chromophobe cells wliich make up a considerable portion of tlie anterior lobe are, as indicated in the iiitroduction,
palely staiiiiiig cells of indefinite character in wliicli no clearly
tlefined secretory snbstaiicc is discernible. They vary much
in size, howerer, and some a r e more cyanopliilc than others.
The chromopliobe cells of tlie upper arid anterior border of
the glaiid a r e continuous with the peculiar cell cords atid
tubules wliich constitute the p a r s tubcralis. There is no
abrupt change of cell type in passing from p a r s anterior to
pars tubcralis, but the cells of the latter stain less intensely
than the c.hromophoBes of tlie anterior lobe, aiid the cell cords
138
ARTHUR R. BRYART
show a greater tendency to form central lumina-a tendency,
however, which is also displayed in some degree by the
chromophobes of the anterior lobe ; moreover, as the secluel
will show, the cells of the pars tuberalis react less to thTroic1
deficiency.
The residual lumen is an irregular space interposed between the pars infundibularis and the anterior lobe. It contains a creamy material which resembles thyroid colloid, but
is less homogeneous. The lumen is lined by relatively undifferentiated stomodaeal epithelium, many cells of which bear
cilia. Among these cells on the anterior border of the lumen
a fern alpha cells may intrude, and on the posterior border
occasionally a special pars-inf undibularis cell.
The pars infundibularis is the mass of epithelial cells SUFronnding the pars nervosa. I t consists of a thin layer of
cells covering the posterior aiid lateral aspects of the pars
nervosa and a thick blanket of cells separating the pars
iiervosa from the residual lumen. The latter is the epithelial
portion usually referred to as the pars intermedia.
The pars infundibularis contains cells of several sorts, 0111:one of which is, however, specific for this portion of the
hypophysis. This is the large pars-intermedia cell first
described in detail by Maurer and Lewis ('22) in the pig,
afterward recognized and described by Rasmusseii ( '21) in
the woodchuck. Other observers have been unsuccessful for
the most part in differentiating this cell from the other components of the pars intermedia. The reason for this is that
these cells contain a type of secretion grannle which is estremely labile and rapidly disappears from the cell postmortem, so that unless the pituitary gland is properly and
speedily fixed after death, the characteristic content of these
cells disappears. These cells, which form the maiii mass of
the pars intermedia in the rabbit, are practically identical
with those of the pig, and the description of them by Uaurer
and Lewis applies with full force to the rabbit's gland. The
cells are large in size, and coiitain a variable arnoant of
secretion in the form of vcrp minute granules wliicll staiii
CHANGES I N HYPOPHYSIS AFTER THYKOIDECTOMY
139
blue in the anilin acid-fuchsin Mallory method. The secretion
is contained in rather large spaces in the cytoplasm, separated
from one another by strands of cytoplasm which radiate Erom
the nucleus and from a condensed mass of cytoplasm about
the same size as the nucleus and alongside of the latter. This
condensed mass of cytoplasm contains very numerous small
rod-like mitochondria, and incloses the vacuome and the cytocentrum. The cytoplasmic condensation is so characteristic
that under low powers these cells appear to contain two
nuclei.
Cells of this sort are found only in the pars intermedia.
The latter, however, is continuous with pars distalis at the
ends of and around the residual lumen, and at these points
the pars-intermedia cells may easily be mistaken for accumulations of basophile anterior-lobe cells.
The other cells of the pars intermedia are the folloaing:
1) Indifferent stomodaeal epithelium and ciliated cells forming the posterior boundary of the residual lumen. These
cells also tend to extend through the pars intermedia and
separate the special cells of that part into groups. 2) Cells
of low order of differentiation, of small size and palely staining, scattered among the special cells of the pars intermedia.
Cells of this sort also form vesicles containing a clear colloid
optically similar to that of the thyroid gland. The cells
surrounding these vesicles sometimes contain small intracellular drops of similar colloid, but are most frequently
free from it. Part of the wall of the colloid-containing
vesicles may also be formed by the special pars-intermedia
cells.
The pars nervosa calls for no special description except to
remark that it contains the usual masses called hyaline bodies.
These are not, however, actually hyaline, but have a finely
granular structure and they stain differentially from the colloid of the pars intermedia in Nallory’s connective-tissue
stain, which colors the liyaline bodies red and the colloid
hlue, and in Mallory ’s phosphotungstic acid-haematoxylin,
which stains the colloid pink and the hyaline bodies blue.
(IHAKGES IN THE TlIPROIDECTOMIZEU ANIMALS
I n the thyroidectomized animals the cellixlar compositioii
of the p a r s distalis (anterior lobe) is profoundly chaiiged.
I n the other parts of the pituitary gland-namely,
pars
tuhcralis, p a r s intermedia, and neural lobe-1 can detect no
change. The content of colloid cysts and of hj-aline bodies
in tlio pars intermedia a i d p a r s nervosa, respectively, is
within the normal range of variation, and 1can therefore not
confirm Herring ('08) i n this respect.
Tlic pars anterior, as indicated above, is profouiidl-j- modified. The most striking change on first study is the great
rcduction in the numher of eosinophile cells. I n the longstanding cases this amonnts almost to a disappearance of
eosinophiles from the anterior lobe. The triangular area
of Rogowitscli becomes practically f ree from alpha cells, and
in the posterior portion where they are normally abundant
t h y a r e sparse. This is a progressive change which becomes
more pronounced with the longer duration of athyroidism.
The eosiiiophiles which remain a r e no longer the deeply staiiiing granule-packed cells of the normal gland, but the graiinles
are fewer in number and stain less intensely.
The question m.lictlier the eosinophiles are diminished b;v
loss of specific granules or by degeneration and cell breakdown is not easy to determine, and I cannot give a final
answer to it. This much is cerlain, that many eosinophiles
show evidences of degeneration in reduction in size and in
granule content mil by a shrniiken pycnotic iiuclens, while
otliers sliow vacuolation, reduction of granule content, and
cliromatolysis. Both a r e midoubtedly degenerating cells and
some of the deficit is t o be accoiiiited for by this process. If
there a r e in addition decliff erentiated eosinophiles, the)- are
not to be distingnished from the profoizndly modified chromoIdlohe cells of tho anterior lobe.
The chomophohe cells of the anterior lohe a r e mainlj.
responsible f o r the illcrease in size and weight of the organ
a f t e r thp-oitlectomy. I n the tliyroidectomy gland Inasophilc
c d l s a r e 110 longer rccogiiizahle, so, if the vagnely defined
CHANGES IR HYPOPHYSIS AFTER T1IYKOII~ECTOMY
141
basophiles of the normal gliji1<1were really spccific cell types,
the)- have lost their diffcrciitial characters or have disappeared. All of the cliromophobes, 011 the other liaiitl, a r c
markedly liypertrophied, a i d this cell lippcrtropli>T is responsible, notwithstanding the fact that there is evidence
of much cell destruction, f o r tlic increase in size aiid weight
of tlic gland. Mitoses a r e quite exceptional.
The liypertroplip of tlie chromophohe c d l s is ivell slioivii
in figure 3, wliich also sliows the extraoidiiiary dimiiintioii of
alpha cells. Whether this increase in size is clue to an ticcumulation of noii-granular secretion in t l i ~ s ecells or to
iiicrcase of cytoplasm T am iiiiablc to say.
bl any evitleiices of clegeiicratioii are found in the liypert rophied cliromophobes of the anterior lobe. rrliese vary
from a moderate vacuolation of the cytoplasm to a complete
brealidowii of tlie cell. The latter is responsible f o r the
presence iii the thj-roitlec,tomy glaiicl of large iiitercellnlar
spaces which h a r e a punched-out appearance. These spaces
eoiitaiii a variable amount of cellular d6hris.
The specific reactioii of tlie cliromophohe cells to thvroitl
tieficieiicy is m o t h e r ei4dciice that these cells i q r e s e i i t oiie
( 9 1 - more types of specific secretoyv elements in the h;r.pophysis,
aiitl are iiot merely i*escrvecells.
I do not find groups of special stroma (>ellsin the rabbit
like those described by Satwornitzkaja (’36) in the dog after
partial thyi*oidectomy.
COR’(’1,l~RIONS
C’omplete removal of the thyroid glaiitl iii llir! mlihit results
RII enlargemciit of tlic pitnitarv hocly.
This increase in
size is exclusively in tlie aiiterior lohe, and is due to a progressive hypertrophy of the chromophohe cells. There is also
a progressive reduction in number of the cosiiiopliile cells.
Also, marip of tlie hypertrophied chromophohe cells degenerate, first 1)ccoming vacnolatccl aiitl tlieii completely breaking
( 1 0 ~ 1 1 ,lwviiig large gaps c~oiitaiiiiiigcellular c16bris.
in
THE; ANATOMICAI, RICORD, YOL. 47, NO.
2
142
ARTHUR R. URYAXT
‘I’lici-t> i h 110 justification for i i i t o i * p i ~ ~ t itlicsc
~ i g ~ * o s ~ i l at hs
iiidicatiiig aii increased swretory acti\*itp of the pituitary
glmd in cases of th>-roiil cleficieiicy-quite tlie contrary. The
cIisal,r,eai.aiice or rcductioii of the alpha cells indicates rather
a tlcprcssioii of the specific secretion of these cells, and the
tciidency of t h c b crilargvd chromoplio1)es to degciicratc is an
iiiciicntioii of the leiitleiicy of fiirictioiially depressed cells i o
corriplet ci their cytomorpliosis a i i d (lihiippear ratliw than to
tlc.(lifforentii~tew ~ l t lrepi*odwc..
Tlio profouiid modification of both alpha cells a i d cliromo~ ) l i o h sniitlcr tlicw cwiiclitioiis snggests tliat somc of tlie
i w u l t s of tliyrvid defi(+iicy may lw p i * o d i ~ w liiidiiwtly
tlirougli deprcssioii of tlre pituitary gland.
144
PLATE 1
145
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