THE EFFECT OF ATHYROIDISM ON THE RATE O F CELL DMSION

ALFREDTAYLOR Department of Zoology, Oregon Sta te College, CorvaUia

I n a previous study (Taylor, '36) it was found that tissues subject to relatively rapid replacement by cell division in the adult salamander are especially affected by the athyroid state. Such tissues as the epidermal and glandular portions of the skin, the epithelial lining of the digestive tract, and the spleen manifest definite structural abnormalities in association with the thyroidless condition. There seems to be a tendency for these tissues to become adversely affected before tissues the cells of which divide at a slower rate or not a t all. I n addition it is well known that young growing animals are much more seriously affected by thyroidectomy than mature animals.

The question arose as to whether there might not be a relation between the degree of disturbance to a tissue by reason of lack of the thyroid principle and the rate of mitosis of the component cells. If, as would naturally be assumed, the rate of cell division tended to be less in thyroidectomized animals, then it would be understandable why a tissue such as the epidermis is adversely affected among all the forms investigated. It would mean that worn out cells are not replaced by cell division in the basal layer rapidly enough to keep this tissue in a normal condition.

Accordingly, the present investigation was undertaken with the object of determining what changes, if any, occur in the rate of cell division of tissues whose normal rate is relatively high in association with the athyroid state.

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240 ALFRED TAYLOR

MATERIAL8 AND METHOD8

Adult salamanders (Triturus torosus) all of about the same size were utilized. The operative procedure and the care of the animals were as previously described (Taylor, ’36).

Experimental animals were killed 20, 30, 50, 60, 90, 140 and 180 days after the removal of the thyroid gland. Integument from the mid-dorsal area between the suprascapulas, intestinal mucosa from the duodenal region, and the spleen were fixed with Bouin’s fluid. Sections from these tissues were stained with iron hematoxylin.

Ten experimental animals for each of the time groups given above were utilized. The tissues from fifteen normal salamanders served as controls.

The rate of cell division for the epidermis was based on the number of mitoses per linear centimeter and the rates of cell division for the intestine and the spleen were based on the number of mitoses per equivalent cross section.

EXPERIMENTAL RESULTS

Cells undergoing division in the tissues of the various ex- perimental groups were first examined from the standpoint of possible abnormalities in the mechanics of mitosis. No difference in this respect was noted as between the thyroidless animals and the normal controls. Also the new cells produced appeared to be normal at least up to and including the 90-day group. For example, the cells of the basal layer of the epi- dermis were indistinguishable from the same cells of the con- trols. The cells above the basal layer tended to be abnormal in varying degrees. There seemed to be a premature aging and tendency toward disintegration in these cells especially in the later time groups.

The same effects were noted in the epithelial portion of the small intestine. Both cytoplasm and nuclei of the cells lining the lumen of the intestine were structurally abnormal.

The disturbance to the rate of cell division varied with the time the animal had been thyroidless. Data for the tissues considered are summarized in table 1. It will be noted that

ATHYROIDISM AND CELL DIVISION 241

the epidermis has a slightly depressed mitotic rate in the 20- and 30-day groups. Unexpectedly this tissue tended toward an abnormally high rate of cell division in the 50-, 60- and 90-day groups. The small intestine follows almost the same trend as the epidermis. In this instance, however, the above- normal period extends over an additional time group, the 30-day group. It will be observed that all three of the tissues investigated have a lower than normal mitotic rate in the 140- and 180-day groups.

TABLE 1 The rate of cell division of the epidermis, intestinal mucosa, a d spleen in normal

salanucnders and salam&rs thyraidless for varying perioda of time. Normal group fifteen animals, experimental groups ten animals each

Normal 20-day 30-day 50-day 60-day

140-day 180-day

go-day

3.0 f 0.72 1.3 f 0.40 1.5 f 1.1 5.2 2 1.1

14.0 f 2.2 7.0 f 3.0 1.7 f 0.60 0.57 f 0.40

Intestinal mucma

5.6 2 2.6 2.5 & 1.3

10.0 -+: 2.2 8.0 -+: 2.0

12.0 f 2.8 5.4 f 1.7 4.7 & 1.2 3.2 f 1.1

Spleen

7.0 f 3.0 44.0 f 14.0 97.0 f 26.0

8.0 f 4.0 6.0 2 2.0 7.0 f 3.0 4.0 f 1.5 2.0 f 0.75

The spleen, as table 1 records, shows a very definite dis- turbance to the mitotic rate of its cells as a result of thyroid- ectomy. Some individual salamanders from the early time groups had spleens exhibiting an amazing rate of mitosis. I n some instances the number of mitoses were so numerous as to be practically uncountable.

The mitotic rate of all three of the tissues studied was sub- ject to considerable individual variation. This was especially so in the instance of the time groups in which the cell division rate was high. Such differences are to be expected since the syndrome associated with the athyroid state may appear at slightly different periods after thyroidectomy in individual salamanders.

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242 ALFRED TAYLOR

It was interesting to note that cell division may be pro- ceeding at a higher rate than normal a t a time when the tissue itself manifests to a high degree the abnormalities character- istic of the athyroid state. Gastric epithelium of one sala- mander thyroidless 150 days contained many times more mitoses than was seen in this tissue from normal animals. At the same time it was so structurally disorganized as to be scarcely recognizable.

DISCUSSION

From the data presented, it appears that the pathological changes observed in the skin, the intestinal mucosa, and the spleen which develop as a result of lack of the thyroid principle are not mediated through a depression of the rate of cell division. The rate of cell division may be abnormally high in tissues which are seriously affected by the athyroid condition.

The stimulus to the increased mitotic rate which tends to obtain in the early weeks after thyroidectomy probably re- sults from the accumulation of autolyzed tissue. Disintegrat- ing cells are characteristic of tissues such as those considered in the present study in association with the thyroidless condi- tion. Chambers and Scott ('25) found that malignant tumor cells upon autolyzing produce a substance which accelerates the growth of tumor tissue in vitro. Dustin ('21) concluded from his researches that mitosis was induced by the liberation of material from degenerating cells and Gutherz ('25) came to the same coaclusion.

The results of the present investigation also appear to render still more untenable the assumption that the thyroid principle is directly and primarily concerned with the oxida- tions of the individual cells. Loeb (1895) reported that cells deprived of oxygen will not divide and Mathews ( '07) found that cold, quinine, and anesthetics which are known to reduce oxidations will also depress cell division. These data have been generally substantiated even though Gray ('25) reported that during active mitosis cells have the same respiratory level as cells in which the nuclear membrane persists. Also

ATHYROIDISM AND CELL DIVISION 243

Meyerhof ( '11) could find no appreciable changes in heat pro- duction as a result of cell division. The evidence indicates, then, that though no extra oxidative activity as a result of mitosis can be detected, cells not freely supplied with utilizable oxygen will divide less frequently or not at all. The fact, as here reported, of cells undergoing mitosis at a higher rate than normal at periods when the athyroid symptoms were acute indicates there is no interference with oxygen utilization under these conditions and that lessened use of oxygen by thyroidless animals is a secondary effect of the lack of the thyroid principle.

SUMMARY

The rate of cell division of the epidermis tends to be higher than normal in salamanders that have been thyroidless 50 to 90 days. The mucosa of the intestine follows the same general trend except that the above-normal mitotic period begins 30 days after thyroidectomy. The rates of cell divi- sion of the spleen are sharply above normal in salamanders thyroidless 20 to 30 days. The epidermis, intestinal mucosa, and spleen all show a depressed rate of mitosis in salamanders thyroidless 140 to 180 days.

These data make it improbable that the pathological effects induced in the tissues considered by lack of the thyroid principle are mediated by interference with the frequency of cell division. The results obtained also are against the hypothesis that the thyroid principle is directly concerned with the oxidations of the individual cells.

244 ALFRED TAYLOR

LITERATURE CITED

Cmmnw, H. rn G. S m 1925 On a growth promoting factor in tumor tissue, Brit. J. Exp. Path., vol. 7, p. 33.

DUSTIN, A. P. DBclenchement experimental d’une onde einbtique par in- jection intrapMton6aIe de sbrum. 1921 L’onde de ciiieses e t l’onde de pycnoses dans le thymus de la

souris apr& injection intrapbritoneale de serum Btranger. C. R. SOC. Biol., T. 85, p. 260.

GRAY, J. 1925 The mechanism of cell-division. 11. Oxygen Consumption during cleavage. Proc. Camb. Philos. 800. Biol., Series 1, p. 225.

GUTHERZ, €3. 1925 a e r vorzeitige Chromatinreifung an physiologisch de- generierenden Skugeroozyten des frfihen Wachstumsperiode. Zeit. f. mikr. Anat. Forsch., Bd. 2, S. 1.

LOEB, J. 1895 Untersuchungen iiber die physiologischen Wirkungen des Sauer- stoffmangels. Arch. f. ges. Physiol., Bd. 62, S. 249.

MATHEWS, A. P. 1907 A contribution to the chemistry of cell division, matura- tion, and fertilization. Am. J. Physiol., vol. 18, p. 87.

M~YEBBOF, 0. 1911 Untersuchungen uber die Warmetonung der vitalen o-xyda- tionsvorgange im Seeigelei. Biochem. Zeit., Bd. 35, S. 246.

TAYLOR, ALFRED 1936 Athyroidism in the salamander Triturus torosus, Rathke. J. Exp. Zool., vol. 73, p. 153.

1921 C. R. SOC. Biol., T. 85, p. 23.