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Stromal changes in the pars distalis of the rat following thyroidectomy demonstrated by silver impregnation.

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Stromal Changes in the Pars Distalis of the R a t
Following Thyroidectomy Demonstrated by
Silver Impregnation
Department of Anatomy, Boston University School of Medicine,
Bas ton, Mnssac huse tts
Morphological, chemical and cytochemical studies of the anterior hypophysis under varied experimental conditions are
numerous throughout the literature. The
large majority of these investigations concern the parenchyma of the gland and few
included the stroma. Recent studies employing the electron microscope have reported on the structure of the sinusoidal
wall and the presence of a perisinusoidal
space in which cells of phagocytic ability
are found (Rinehart and Farquhar, '58).
These cells may be stimulated to engulf
foreign material such as trypan blue. It
was further reported that thyroidectomy
would produce morphological changes in
the perisinusoidal space. An investigation
of the stromal modifications found in the
anterior hypophysis in the thyroidectomized animal is reported in this paper.
Twenty male albino rats of the Wistar
strain, weighing approximately 150 gm,
were employed in this investigation. Ten
animals were surgically thyroidectomized
30 days before they were killed; 10 animals
served as controls. The hypophyses were
fixed in 10% buffered formalin, embedded
in paraffin, and sectioned at 6 w. The modification of Marshall's ('56) ammoniacal
silver technique as employed by Black and
Speer ('58) was used to impregnate the
cytoplasm of the macrophages. Control
sections of normal spleen were included in
each group of slides to check the ability of
the stain to demonstrate metallophilic
cells. Sections were also stained with
Halmi's method ('50) preceded by one
hour mordanting in Bouin's solution at
37"C, as well as the PAS orange G technique (Pearse, '50).
The anterior hypophysis of the normal
rat contains few metallophilic cells when
stained with ammoniacal silver. An occasional spindle-shaped cell can be identified
among the epithelial elements of the gland
and a group of rounded, metallophilic cells
is generally present between the pars distalis and the pars intermedia (fig. 1 ) .
Following thyroidectomy there is an increase in the size and metallophilia of
these cells. Figure 2 shows the metallophilic cells of the rat's anterior hypophysis
after 30 days of thyroidectomy. The cells
have become increased in size and are
multiprocessed, extending between the adjacent parenchymal cells. Sections of the
same gland stained with PAS fail to demonstrate this cell type. In Halmi-stained
sections an occasional small, darkly
stained, processed cell can be seen lying
between the parenchymal elements or adjacent to a sinusoid. The cytoplasm of
these cells is stained with the green
counterstain of the Halmi technique
(fig. 3 ) .
Cells similar to those found in the thyroidectomized animal are rare in the anterior hypophysis of the normal animal except in the region between the pars distalis
and the pars intermedia. In this region a
layer of rounded, metallophilic cells separates these two areas of the gland (fig. 4).
In Halnii stained preparations these cells
stained green or are unstained. In PASstained preparations their cytoplasm is
colored pale orange or colorless. These
cells may be found extending into the pars
intermedia as trabeculae and a few are
found at the junction of the intermedia
and the pars nervosa.
Investigations of morphological changes
occurring in the anterior hypophysis have
centered on the epithelial cells and neglected the stromal cellular components,
The studies of Reinhart and Farquhar
( ’ 5 5 ) , using the electron microscope, have
shown that the sinusoidal region of the
gland is highly specialized and associated
with three cellular types : ( a ) endothelium,
( b ) perisinusoidal reticular cells, ( c ) cells
with clear cytoplasm and long processes
extending between the epithelial cells of
the glandular parenchyma. These authors
reported, moreover, that following thyroidectomy, definite morphological changes
took place in the sinusoidal area. Such
alterations have not been reported by the
use of standard staining techniques and
the light microscope.
The ability to impregnate the cells of the
reticuloendothelial system with silver was
first reported by Del Rio-Hortega in 1927.
The ammoniacal silver method as employed by Marshall (’56) is able to demonstrate cells with phagocytic ability.
Marshall refers to the impregnated cells as
“metallophils .” Application of this silver
technique to the anterior hypophysis of the
normal rat reveals few metallophilic cells
in the stroma of the gland. Following thyroidectomy, however, the hypophysis was
found to contain numerous, intensely
metallophilic cells which were highly
The application of silver staining techniques to the hypophysis is not new. Many
workers have studied the gland, employing
the argyrophilia of the various cells in both
the anterior and posterior lobe as a staining
characteristic. Knigge (’55) studied argyrophilic cells in the pars distalis of the rat
using Bodian’s method which blackened
the cytoplasmic granules of certain epithelial cells of the gland. Application of
Bodian’s method fails to demonstrate the
“metallophils,” as can be easily demonstrated when the method is applied to
lymph node or spleen tissue. Knigge found
no significant changes in the argyrophilic
cells following thyroidectomy. Silver techniques designed to show nerve fibers have
also been employed to stain the pars
distalis. Such techniques fail to stain the
“metallophil” or reticulo-endothelial cell.
It is therefore apparent, that while several
studies employing silver stains on the hypophysis have been reported, they have failed
to note the stromal argyrophilic cell or the
The layer of metallophilic cells separating the pars intermedia from the pars
distalis has not been previously noted to
the author’s knowledge. Wislocki and King
(’36), while studying the permeability of
the hypophysis to vital dyes, mentioned
cells in this location in the rabbit hypophysis which they classed as macrophages.
In the present investigation it is notable
that these cells were much more intensely
metallophilic in regions where colloid was
present in the residual lumen of Rathke’s
pouch. Figure 4 illustrates the metallophilia of these cells in the region of a small
amount of colloid material.
The results of the present investigation
indicate that removal of the thyroid gland
not only influences the hypophysis through
the increased demand for thyrotrophin, resulting in the so-called thyroidectomy cell,
but also produces morphological changes
of the stromal cells of the gland. These
changes comprise an increase in the size
and metallophilia of the perinsinusoidal
cells. The physiological cause for this
alteration is unknown and may be a reflection of either the peripheral utilization
of thyroid hormone or the result of changes
occurring within the anterior hypophysis
along with the formation of thyroidectomy
cells as a reflection of increased activity on
the part of the gland.
Hypophyseal stromal changes are reported in the thyroidectomized rat. These
consist of an increased metallophilia and
size of the perisinusoidal cells as demonstrated by the ammoniacal silver technique
of Marshall. The results indicate that procedures designed to demonstrate the interrelation between the anterior hypophysis
and the other endocrine glands not only
affect the parenchymal tissue of the hypo,
but also the stromal component.
Black, M. M., and F. D. Speer 1958 AntigenInduced changes i n lymph node metallophilia.
A.M.A. Arch. Path., 66: 754-760.
Del Ria-Hortega, P. 1927 As mentioned i n
McClung’s Handbook of Microscopical Techniques. Ed. R. M. Jones. P. B. Hoeber, Inc.,
New York, 1950, third edition.
Halmi, N. S. 1950 Two types of basophils i n
the anterior pituitary of the rat and their respective cytophysiological significance. Endocrinology, 47: 289-299.
Knigge, K. 1955 Identity of the argyrophilic
cell i n the pars distalis of the rat’s pituitary
gland. Ibid., 57: 719-739.
Marshall, A. H. E. 1956 A n Outline of the
Cytology and Pathology of the Reticular Tissue.
Oliver and Boyd, Ltd., London.
Pearse, A. G . E. 1950 Differential stain for the
human and animal hypophysis. Stain Tech.,
25: 95-102.
Rinehart, J. F., and M. G. Farquhar 1955 The
fine vascular organization of the anterior pituitary gland. Anat. Rec., 121: 207-240.
Wislocki, G. B., and L. S. King 1936 The permeability of the hypophysis and hypothalamus
to vital dyes, with a study of hypophyseal blood
supply. Am. J. Anat., 58: 421-472.
Control. Pars distalis stained with ammoniacal silver. Note the pale, spindle-shaped,
metallophilic cells. x 640.
Thirty days following thyroidectomy. Note the increased size, number and metallophilia
of the multoprocessed “metallophils” demonstrated i n the pars distalis. x 640.
Thirty days following thyroidectomy. Section is stained with Halmi’s method. Arrows
indicate several small, dark green cells which are multiprocessed and appear to be
the “metallophil” in ammoniacal silver stained preparations. x 640.
Control. Area between the pars distalis and pars intermedia. Arrow indicates a small
amount of colloid material i n the residual lumen. Note the layer of meta.llophilic cells
which separates the pars distalis above from the pars intermedia below. x 640.
William F. McNary, Jr.
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silver, change, distalis, following, demonstrated, impregnation, pars, rat, stroma, thyroidectomy
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