Abstract

It has been concluded from this study that nerve fibers in the superior laryngeal nerves have an influence on the development of C-cells in the mouse thyroid. This conclusion is based on the results of two types of investigation. The first is an analysis of the effect of age on the number of C-cells and the second is an investigation of the influence of denervation and hemithyroid-parathyroidectomy on the age related changes in C-cells numbers.

I. The distribution and c011centraticn of C-cells in mouse thyroid at various ages.

Serial 6 µm sections of thyroid glands from Swjss Webster mice at one day, two weeks, four weeks and eight weeks of age were studied, using an immunoperoxidase method ( an adaptation of the unlabeled antibody enzyme method of Sternberger et al., 1970). The number of C-cell nuclei were counted in every sixth section and totaled for both left and right lobes. Each age group consisted of four animals, two males and two females, except for the one-day old mice in which C-cells could be demonstrated in only two male mice.

Several histological observations were made. Autonomic ganglia, sometimes with closely associated C-cells, were regularly observed in the superior poles.

C-cells in the mouse thyroid at all ages studied were concentrated in the middle one-third of the gland. They were in intra - and parafollicular locations and occurred singly and in groups. Ultimobranchial follicles were present in the same region. Mitoses of C-cells were observed in animals which were one day, two weeks and four weeks old, but not in the eight-week old mice.

In both one-day and two-week old mice, it was very difficult to demonstrate the calcitonin granules in the C-cells. In the one-day old mice stainable C-cells could be demonstrated in only two specimens out of a total of 45, and in two week-old mice, four specimens out of a total of 15 specimens. The number of stainable C-cells in the thyroid gland of eight-week old animals was about 18 fold greater than the number in the one-day old mice, about 5.5 fold greater than the two-week old and about 2.5 fold greater than the four-week old animals. But the concentration of C-cells (number of C-cells per mm3) was highest in the four-week old animals.

The volume of the thyroid glands in the eight-week old animals compared with the one-day, two-week and four-week old mice was respectively 14, 4 and 3 fold greater.

It is concluded that C-cells increase in numbers during growth partly by mitosis. In addition there is no doubt an increase in the calcitonin content of the C-cells. This would also increase the number of stainable C-cells.

II. Influence of denervation and hemitbyroid-paratbyroidectomy on the age related increase in C-cells.

In each of four experiments both experimental and sham-operated animals from the same litter were used. Surgeries took place at about four weeks of age and animals were sacrificed at eight weeks of age. Tissues were prepared and studied following the same method used in the first study.

  1. Bilateral superior laryngeal neurectomy. Four male mice were used for the experimental. and four for the sham-operated animals. The number of C-cells in the thyroid glands in the denervated animals was markedly less than the number in the sham operated animals. The mean number of C-cells found in the experimental animals was 68% of the number found in the sham-operated animals (P-value of the Student's t-test was < 0.05). There was no significant difference in the volume of the glands. The concentration of C-cells was also significantly less (P-value

  2. Right partial thyroidectomy and superior laryngeal neurectomy. Four male mice were in the experimental group and three in the sham group. Because two animals of the experimental mice were abnormal, the results were inconclusive.

  3. Right unilateral superior and inferior laryngeal neurectomy. Five male mice were used for the experimental and five for the sham-operated animals. No effect on the number of C-cells was observed. The significance of this finding is discussed.

  4. Right hemithyroid-parathyroidectomy. Six female mice were in the experimental and six were in the sham-operated group.

The volume of the remaining lobe in the experimental animals markedly increased when compared with the left lobe of the sham-operated animals. The P-value of the volume difference was <0.002.

The number of C-cells found in the remaining left lobe of the experimental animals was unchanged when compared with the number in the left lobe of the sham group. But the concentration of C-cells in the experimental group when compared. with the sham group was obviously less. The P-value of the difference was <0.02.

LLU Discipline

Anatomy

Department

Anatomy

School

Graduate School

First Advisor

Arthur E. Dalegleish

Second Advisor

Paul J. McMillan

Third Advisor

Walter H. B. Roberts

Fourth Advisor

Paul C. Engen

Fifth Advisor

Donald D. Rafuse

Sixth Advisor

Carrol S. Small

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

1978

Date (Title Page)

6-1978

Language

English

Library of Congress/MESH Subject Headings

Calcitonin; Thyroid Gland

Type

Dissertation

Page Count

vii; 103;4

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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