Nutritional Secondary Hyperparathyroidism in the Horse

14 ’I’he Anatomy of the Parathyroid Glands in the Horsc
The ligh chief cells predominated in horses of all ages. The cells
were arranged in small lobuli, often in a “rosette” configuration
(Figs. 5 and 8) with a capillary in the center. The cells were almost
circular in outline, sometimes polyhedric or, more rarely, rectangular.
The cell margins were variable, sometimes being poorly defined and
other times standing out well. The cytoplasm was faintly acidophilic
with hematoxylin and eosin, but the tinctorial properties varied con-
siderably. With, basic dyes the cytoplasm was diffusely and rather
faintly blue. Tiny spherical, more deeply basophilic structures, the
so-called juxtanuclear bodies, were seen occasionally. They were not
always confined to the immediate vicinity of the nucleus. The nucleus
was well defined and most often located in the center. However, in the
above-mentioned rosettes a peripheral location was more common.
One or two nucleoli were present. The size of the light chief cell and
its nucleus is given in Table I1 and in Charts 3 and 4 (for analysis, see
Appendix, Table 11).
Scarlet red stain revealed fat in the cytoplasm of the light chief
cells to the degree and frequency shown in Table I. In all positive
cases but one, small sudanophilic droplets were present in rather small,
rather well-circumscribed areas of light chief cells. The fat accumula-
tion was never great enough to give a negative image on the embedded
section. In one case, that of a male 8-year-old horse, there was a
diffuse, moderate fatty metamorphosis of practically all light chief cells
in the section. As may be seen from Table I, parenchymatous fat was
present mainly in adolescent and young adult horses but was very
rarely recorded in older horses.
Dark chief cells were rare. They did occur in horses of all ages,
however. The size of these cells is given in Table 11. The cell outline
was poorly defined and the cytoplasm was deep purple. The nucleus
was elongated, with the length usually double the width. It was deeply
and homogeneously basophilic and a nucleolus was therefore not
visible. The dark chief cells contained no fat.
Water-clear cells occurred at any age, but they were relatively
rare in the newborn horse in this series. In a few horses less than 1 year
of age they were quite frequent, although the light chief cells pre-
dominated. It cannot be said, however, that water-clear cells increased
with age. In some of the oldest horses they were relatively scarce.
The water-clear cells were slightly larger than the light chief cells
(Table 11). In the fully developed stage the cytoplasm showed no
aHinity with any stain, but the cell outline was much thicker and better
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