Nutritional Secondary Hyperparathyroidism in the Horse

Discussion 27
Table VZZ. Nuclear size and cytoplasm/nucleus ratio of parathyroid cells in man
and horse
Ma,, Horse
Nuclear size C/N Nuclear size C/N
planimeter ratio sq. ,LL ratio
units
Dark chief cells 9.9-1 3.5 1.69 10-12 2.5
Light chief cells 13.7-1 7.3 2.44 18.66 5.28
Small water-clear cells 12.7-1 7.1 2.88 -
Large water-clear cells 16.3-21.9 5.76 14.02 7.81
Dark oxyphil cells 11.2-18.0 4.05 -
Pale oxyphil cells 9.2-14.6 8.56 19.71 10
It should be noted that EGER and VAN LESSEN gave the size of the
nuclei in planimeter units. Their figures are therefore not directly
comparable with those for the horse, which are given in conventional
measures.
Because of the changing nuclear size and the cytoplasm to
nucleus ratio in the different cells, EGER and VAN LESSEN (1954) felt
that the functional capacity increased from the resting dark chief cell
through the small water-clear cell and then gradually decreased to no
activity in the pale oxyphil cell. TRIER (1958), however, showed in
electron micrographs, that the typical granulation of the oxyphil cells
was due to accumulations of mitochondria. He thus established that
the oxyphil cells are highly active metabolically. He was confirmed in
1961 by independent investigations by BALOGH and COI-IEN and by
TREMBLAY and CARTIER which showed that the highest enzymatic
activity was present in the oxyphil cells.
Although the size of the cytoplasm and, consequently, the cytoplasm
to nucleus ratio of all parathyroid cells are considerably greater
in the horse than in man, the tinctorial properties of these cells
justifj the use of the same nomenclature in the two species.
It is difficult to make an evaluation of the parathyroid activity as a
function of individual horses, sex, and age from our material. With the
great variations in the parenchyma to interstitiurn ratio and with the
high incidence of embryologic rudiments in the parathyroids, weight
as such is of little or no importance in the evaluation of the functional
state. The regression line of the relative weight of the upper parathyroids
as a function of age showed a slight but insignificant decrease.
There were no differences between the sexes, but the variation between
horses was remarkable. The parenchyma to interstitium ratio, the
3 Krook/Lowe
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