MOULTING in hens is normally accompanied

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1 Histological Observations on the Anterior Lobe of the Pituitary Gland in Moulting and Laying Hens M. PEREK: AND B. ECKSTEIN The Department of Poultry Husbandry and Animal Hygiene, Faculty of Agriculture, Hebrew University, Rehovot, Israel MOULTING in hens is normally accompanied by cessation of laying but the hormonal mechanism is poorly understood. Although the puzzle of hormonal initiation of moult seems to be unsolved, there is some knowledge of the hormonal mechanism during the moulting period. Zawadowsky (1927, 1932), Zawadowsky and Rochlin (1928), Greenwood (1936) and Van der Meulen (1939) have established the fact that the thyroid hormone, and the thyrotropic hormone (TSH) have a marked effect on moult. The data of Perek and Sulman (1945) seem to support this view, since they demonstrated that the metabolism of hens during moult is higher than that of laying hens. On the basis of these findings, a theory has been advanced that a close relationship exists between the periodical phenomena of egg-laying and moulting in the fowl. Both phenomena are based on the alternate regulation of the secretion of gonadotrophins and TSH by the anterior pituitary gland. This theory has been elaborated by Greenwood (1936). Histological examination of the thyroid of the wild duck during moult by Hoehn (1949) demonstrated high activity of the gland. These data support the assumption that the thyroid markedly influences the moulting processes in the fowl. The assumption, that the anterior pituitary AND H. SOBEL Department of Zoology, Hebrew University, Jerusalem (Received for publication February 20, 1957) gland may exert a regulatory influence on moult and egg-laying probably more basic than that of the thyroid still lacks histological support. This is a report of histological investigation of the cells of the anterior pituitary gland of the hen in relation to laying and moulting. 954 MATERIALS AND METHODS Four laying, and four moulting White Leghorn hens were used. After the removal of the pituitary glands from the surrounding bone, all glands were fixed, and stained in the same way. Zenkerformol was used as fixative, and the blocks were cut serially. The sections from different cuts were stained with Delafield's hematoxylin-eosin, and azan for the general observation of cells. Some sections were stained according to the Mac- Manus-Hotchkiss (1946) periodic acidleucofuchsin procedure for the visualization of mucopolysaccharide material in the 8-cells. Other sections, Ay., and 6/x. thin, serially cut from various regions of the gland, were stained according to a modification of the periodic acid Schiff procedure described by Purves and Griesbach (1951). This staining procedure permits differentiation between the thyrotropic and the gonadotropic /3-cells. In order to examine the influence of estrogens on the gonadotropic cells in the pituitary gland, 15 ten-week old broilers,

2 HISTOLOGY OF ANTERIOR PITUITARY 955 and 15 pullets of the same age were implanted with diethylstilbestrol pellets, each containing 15 mg. of diethylstilbestrol. After one month, the birds were autopsied, and their pituitary glands were prepared and stained according to the method of Purves and Griesbach. HISTOLOGY In the anterior lobe of the pituitary from laying hens, the a-cells are the most common cell type. In the sections stained with azan, they are seen to be uniformly distributed throughout the lobe, and are conspicuous due to their orange-red staining of their coarse granules. At the same time, only few chromophobe cells are seen, and the /3-cells are also relatively scarce. The vascularization of the gland is very rich, since numerous and wide capillaries surround the lobules of the cells. The anterior pituitaries of the moulting hens present a different appearance. The /3-cells, rather than the a-cells are the predominant cell type at this time. The a- cells are sparsely scattered in the center of the gland, and are more numerous at the periphery. The /3-cells which are abundant in the central area of the lobe, are enlarged and contain fine, blue staining secretory granules and vacuoles. Blue stained "colloid" material is also present in the central lumina of the lobules as well as in the intercellular spaces. Moreover, similar blue droplets were observed in the posterior lobe of the pituitary in all sections of all moulting hens. The interpretation of this observation is rather difficult. It seems that these blue stained droplets originate in the posterior lobe itself, since their transfer from the anterior lobe would encounter a barrier of thick, connective tissue-strand situated characterisitcally between the two lobes of the avian pituitary. With the staining of our different sections by the staining procedure described by Purves and Griesbach (1951), it permitted us to make the differentiation between the gonadotropic, and the thyrotropic /S-cells. In the sections of the lobe of the laying hens, the /3-cells were comparatively scarce. The central site of the lobe is characteristically devoid of these cells, those present being scattered at the periphery of the gland. Two types of /3-cells can be distinguished; some of them are large and polygonal, while the others are smaller, regular in their outline and usually line the border of the glandular lobes, touching the capillaries with their bases (Figure 1). In the rat pituitary, the former type of cells has been shown by Purves and Griesbach to be the thyrotropic cells. In the rat, these cells are also distinguished by the smaller size of their secretory granules. According to our observations, there were no marked differences in Jhe size of granules between both types of cells, in the fowl's pituitary. According to Purves and Griesbach (1951), the gonadotropic /8-cells in the rat are undergoing changes during the reproductive cycle, and also responded to sex hormone treatment. In order to see the response of the latter type of cells towards estrogen treatment, the sections of the anterior pituitaries of 30 young chickens previously treated with stilbestrol implants were examined thoroughly. This examination revealed that the pituitary of chickens responds to estrogenic treatment in a similar manner to that of the rat, described by Purves and Griesbach (1951). In both the male and the female pituitaries, the smaller and regularly shaped /3-cells, i.e. gonadotropic cells, almost disappeared, while the large thyrotropic cells were present. The aspect of the sections of the moulting hens was quite different to those of the laying hens. The central part of the gland was occupied by numerous /3-cells

3 956 M. PEREK, B. ECKSTEIN AND H. SOBEL FIG. 1. Central site of anterior pituitary lobe of the laying hen. (Stained with P.A.S. procedure modification by Purves and Griesbach.) Jfk «;. * FIG. 2. Central site of the anterior pituitary lobe of a moulting hen. (Staining procedure: The same as in Fig. 1.) % % v 3*

4 HISTOLOGY or ANTERIOR PITUITARY 957 of the thyrotropic type, whereas the gonadotropic cells were only few (Figure 2). At the periphery, both types of /3-cells were equally distributed. DISCUSSION In view of the theory of the moult mechanism explained by Zawadowsky (1932), Greenwood (1936), and others, mainly the /?-cells of the pituitary gland should be considered, since the secretion of the thyrotropic and gonadotropic hormones is generally attributed to these cells. The question has been raised, whether the changes, if any, occurring in this cell type, could serve as a clue to the interpretation of the hormonal mechanism of the moult. In order to clarify it, the authors applied the modified staining method of Purves and Griesbach (1951) to the anterior pituitary lobes from both laying and moulting hens. According to Purves and Griesbach (1951), two types of /3-cells exist in the rat pituitary, differing in size, shape, and form of their secretory granules (gonadotropic and thyrotropic cells). The present observations on the pituitary of the hen are in general agreement with the above, except as to the size of the secretory granules. In both types of the /3-cells in the fowl's pituitary, the granules are of similar appearance. On the basis of their different histological appearance, and of the response induced in them by experimental estrogenic treatment of rats, one type of the /Q-cells have been considered by Purves and Griesbach (1951) to be the gonadotropic ones (relatively smaller, regular in outline, lining, the blood capillaries and distributed mostly in the peripheral areas of the lobe) and the other type seen as the thyrotropic cells (large, polygonal, more remote from the capillaries and occupying most of the central areas of the lobe). The results of our experiments with male and female growing chickens treated with diethylstilbestrol support the findings of Purves and Griesbach. The disappearance of only the small, regularly shaped /J-cells in our sections, whereas the large 8-cells of polygonal shape remain unaffected, strongly supports the theory of distinction between two separate types of /3-cells, the former as gonadotropic, and the latter as thyrotropic cells. The present observations point towards the active participation of the anterior lobe cells in the two physiological states of laying and moulting in hens. During the laying period, the status between the three main types of the cells in the anterior lobe of the hen is similar to that described in the pituitary of the lizards (Sobel, 1950) during the short period of the descent of eggs through the oviduct. In the laying state of the hens, the a-type cells predominated, while of the 0-cells, the gonadotropic cells were mostly present. During the moulting period, the cell appearance of the anterior lobe is drastically changed; the /3-cells are very abundant, especially in the central area of the lobe, whereas the number of a-cells is relatively small. The aspect of the anterior lobe at the moulting stage points towards an increased secretion of TSH, which precedes the hormonal activities of the thyroid gland. These findings support the histological observations on the thyroid by Hoehn (1949), and the experimental data on this gland by Zawadowsky (1927, 1932), Lektorsky and Kusmina (1935), Woitkewich (1940), Glazener and Jull (1946), Sulman and Perek (1947). SUMMARY The anterior pituitary glands of adult

5 958 M. PEREK, B. ECKSTEIN AND H. SOBEL hens have been studied by means of histochemical methods. Histological changes occurring in the anterior hypophysis during the laying and moulting periods have been described. Diethylstilbestrol has been administered to young chickens. The results of these experiments point clearly towards the existence of two types of ;3-cells, i.e. the gonadotropic, and the thyrotropic cell type. The histological findings support the assumption that a hormonal regulation by the pituitary gland is involved in the processes of laying and moulting. In the anterior pituitary increased activity of j8-cells occurs during the moult, and of a-cells during the laying period. REFERENCES Glazener, E. W., and M. A. Jull, Effect of thiouracil on naturally occurring molt in the hen. Poultry Sci. 25: Greenwood, A. W., Physiology of the molt in the fowl. Weltgefluegelkundekonferenz, 1: 265. Hoehn, E. 0., Seasonal changes in the thyroid gland and effect of thyroidectomy in the mallard in relation to molt. Amer. J. Physiol. 153: Lektorsky, I. N., and N. A. Kusmina, Das Verhalten des thyroidektomierten Vogels. Biol. LARRO NOTES A new 1,160 acre research farm, four miles east of Indianola, Iowa, was officially opened by Larro Feed Division of General Mills in May. Dr. H. E. Bechtel is Director of Research. The company had operated a research farm near Detroit, Michigan, since PENNSYLVANIA NOTES Professor E. W. Callenbach, Head of the Department of Poultry Husbandry, Pennsylvania State University, will retire on October 1st with Emeritus rank, and will be succeeded by Dr. A. J. G. Maw now Professor of Poultry Husbandry. NEWS AND NOTES (Continued from page 939) (Continued Zbl. 55: McManus, J. F. A., Histological demonstration of mucin after periodic acid. Nature, 158: 202. Perek, M., and F. Sulman, 1945: The basic metabolic rate in molting and laying hens. Endocrinology, 36: Purves, H. D., and W. E. Griesbach, The site of TSH and gonadotrophins production in the rat pituitary studied by the McManus-Hotchkiss staining for glycogen. Endocrinology, 49: Sobel, H., Anatomical and histological studies of the hypophysis in lizards. Thesis, Hebrew University, Jerusalen, Israel. Sulman, F., and M. Perek, Influence of thiouracil on the basal metabolic rate and on moulting in hens. Endocrinology, 41: Van der Meulen, J. B., Hormonal regulation of molt and ovulation. Proc. Seventh World Poultry Congress: 109. Woitkewich, A. A., Comp. Rend. Acad. Sci. Moscow, 26: 511. Zawadowsky, B. M., Zur Frage der Wechselbeziehungen zwischen Schilddruese und Geschlechtsdruese bei Huehnern. Roux Arch. 110: Zawadowsky, B. M., Hormone und das Gefieder der Voegel. Endokrinologie, 10: Zawadowsky B. M., and M. Rochlin Zur Frage nach dem Einfluss der Hyperthyroidisierung auf die Faerbung und Geschlechtsstruktur des Huehnergefieders. Arch, fuer Entwicklungsmech, 113: Callenbach was born in New York in 1901 and obtained a B.S. degree at the University of Wisconsin in He did post graduate work at Rutgers University in , and obtained a M.S. degree at Pennsylvania State College in In 1925 he was appointed Instructor in Poultry Husbandry at the Pennsylvania State College, now Pennsylvania State University, becoming Assistant Professor in 1928, Associate Professor in 1931, Professor in 1939, and becoming Head of the Department in During his years on the faculty, he conducted extensive research in poultry 'breeding; poultry brooding systems; propagation and nutrition of ringnecked pheasants and bobwhite quail; nutrition of chickens and turkeys with emphasis on vitamins, on page 966)