- Email: [email protected]
The Influence of Castration and Methimazole on Deoxyribonucleic Acid Content of the Pituitary and Thyroid Glands of White Leghorn Cockerels1,2
The Influence of Castration and Methimazole on Deoxyribonucleic Acid Content of the Pituitary and Thyroid Glands of White Leghorn Cockerels1'2 ROBERT B. CHIASSON Department of Veterinary Science, University of Arizona, Tucson, Arizona 85721 (Received for publication January 14, 1985)
1986 Poultry Science 65:380-383
INTRODUCTION Prolonged hypothyroidism produces a marked increase in pituitary size a n d deoxyribonucleic acid ( D N A ) c o n t e n t in rats (Surks a n d DeFesi, 1 9 7 7 ; Vilchez-Martinez, 1 9 7 3 ) . T h e pituitary gland of cockerels does n o t increase in size after goitrogen feeding (Chiasson et al, 1 9 7 9 ) and t h e duck pituitary gland weighs less t h a n c o n t r o l in m e t h i m a z o l e (goitrogen)-fed birds and increases in size w i t h castrat i o n (Tixier-Vidal et al, 1 9 7 2 ; Sharp et al, 1979). Whether t h e increase in size following castration is d u e t o hyperplasia or h y p e r t r o p h y has n o t y e t been determined, b u t t h e r e are several indications t h a t cellular hyperplasia occurs a t a very low rate in t h e avian pituitary. T y p e I and T y p e II cyclic adenosine m o n o p h o s p h a t e (cAMP)-dependent p r o t e i n kinases undergo selective changes during various stages of growth or differentiation (Costa et al, 1 9 7 8 ; Fuller et al, 1 9 7 8 ; H a d d o x et al, 1 9 7 9 ) , and T y p e I is selectively activated in response t o mitogenic stimuli (Byus et al, 1977). These selected changes in T y p e I and T y p e II cyclic
1 Arizona Agricultural Experiment Station Contribution #4057. 2 Deoxyribonucleic acid and protein assays were performed by Bruce L. Carr and Zia-ur-Rahman.
AMP-dependent p r o t e i n kinases d o n o t occur in t h e pituitary of goitrogen-fed chickens (Combest et al, 1 9 8 0 ) . Thus, m i t o t i c activity in t h e avian pituitary is t h o u g h t t o be very limited and does not account for t h e observed concent r a t i o n of t h y r o t r o p h i c cells after goitrogen feeding (Chiasson et al, 1980). T h e present s t u d y examines t h e D N A and protein c o n t e n t of t h e pituitary of castrated or goitrogent r e a t e d cockerels. MATERIALS AND METHODS T w e n t y White Leghorn cockerels were selected from a larger h a t c h and t e n of these were castrated at 5 w e e k s of age and allowed 2 weeks t o recover from castration surgery. A t 7 weeks of age, all cockerels were placed in individual cages in an environmental c h a m b e r at 2 4 ± 1 C and a lighting schedule of 14 hr light a n d 10 hr darkness. T h e s e conditions were m a i n t a i n e d for 10 weeks (to 17 weeks of age) w h e n all birds w e r e killed. A c o n t r o l group (five birds) and a castrated group (five birds) were fed a standard University of Arizona growing mash t h r o u g h the entire period. A second castrated group (five birds) and an otherwise u n t r e a t e d g r o u p (five birds) were fed a standard University of A r i z o n a growing mash containing . 0 1 % m e t h i m a z o l e (Sigma Chemical Co.). All birds were provided w a t e r ad libitum,
380
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
ABSTRACT The pituitary gland of birds is known to increase in weight with castration and decreases with chemical thyroidectomy. Whether these changes are due to alterations in mitotic activity or to cell size changes has been examined by measurement of deoxyribonucleic acid (DNA) and protein content of these glands. The DNA content of the enlarged pituitary of castrated cockerels is the same as that in the pituitary of normal cockerels. The pituitary size increase may be due to an increase in gonadotrope size including any part of the gonadotrope population which may be obtained by recruitment of other basophils. The retardation in pituitary size and DNA content with methimazole treatment is probably due, at least in part, to growth retardation but may also be due, in part, to the conversion of larger basophils to smaller thyrotropes. (Key words.- thyrotrophs, gonadotrophs, deoxyribonucleic acid, castration, goitrogen)
PITUITARY CHANGES IN CASTRATED COCKERELS
RESULTS
Castrated cockerels had adenohypophyses nearly twice as heavy as those of untreated birds, and the pituitaries of methimazole-fed cockerels were significantly smaller than those of control birds (Table 1). The pituitaries of castrated cockerels fed methimazole weighed the same as controls, which were lighter than those of castrates and heavier than the pituitaries of the methimazole-fed group. The thyroid glands of untreated and castrated cockerels were similar in weight, while the thyroid glands of methimazole-fed cockerels (whether castrated or not) were significantly larger than those of controls. Untreated and castrated cockerels had similar concentrations of pituitary DNA and protein, but methimazole-fed birds (whether castrated or not) had approximately one-half the pituitary DNA content of the other groups (Table 2). The protein content of pituitaries from methimazole-fed castrates was one-third less than that of the other three groups.
Due to differences in pituitary gland sizes, the DNA/mg gland and protein/mg gland values were lower in castrated cockerels and higher in methimazole-fed birds than in the controls. Only the protein/mg gland value of methimazole-fed cockerels was significantly higher than that of control birds (Table 2). The two methimazole-fed groups had enlarged thyroid glands (Table 1), increased thyroid DNA, and reduced total thyroid protein compared to either untreated or castrated cockerels (Table 2). DISCUSSION
The retarding effect of methimazole feeding is evident in the lower DNA levels and smaller size of the pituitaries of methimazole-fed cockerels. The smaller pituitary of methimazole-fed birds may be partly due to the direct inhibition of pituitary growth by methimazole and indirectly to the lack of thyroid hormone which is required for normal growth (May et al., 1973). Castrated birds have pituitaries that are nearly twice as large as those of controls but with an equal amount of DNA. These values indicate that castrated cockerels increase pituitary size by cellular hypertrophy and with no increase in cell number. It is also suggested that a portion of the population of the "cells of castration" are recruited from cells that had not previously served as gonadotrophs. The gonadotroph population alone would need to quadruple or more in size in order to double the size of the pituitary. Sharp et al. (1979) found a lesser population of thyrotrophs in the pituitary of the castrated drake than that of the control or methimazole-fed duck. This suggests that "castration cells" may be recruited in part from thyrotrophs. Castrated birds fed methimazole have pituitaries equal in size to control
TABLE 1. Body, pituitary, and thyroid weights (X ± SEM) of 17-week-old cockerels maintained at 24 C for 10 weeks following castration or methimazole treatment
Body weight
Treatment
(g) Control Castrate Castrate and methimazole Methimazole
6 5 4 5
1769 1634 869 891
±47a ± 58 a + 38 b + 60b
Thyroid weight
Pituitary weight
(mg) 9.3 18.9 10.1 6.8
+ ± ± ±
.6 a 1.2 b .8a .4 C
' Means in columns with different superscripts are significantly different (P<.05).
93 86 243 256
+ 3a + 7a ±41b ± 68b
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
Wet weights of all tissues were determined on a torsion balance (Roller-Smith). Protein and DNA were determined by absorbance changes measured on a spectrophotometer (Beckman DU-2). Protein was assessed by the Coomassie Blue G 250 method described by Bradford (1976), in which bovine serum albumin is used as a standard. Pituitary and thyroid DNA values were determined by the modified diphenylamine method described by Giles and Myers (1965), in which calf thymus DNA (Sigma) serves as a standard. All data were analyzed by a one-way analysis of variance with Fisher's protected LSD test used for estimating significant differences among means (Steel and Torrie, 1960).
381
382
CHIASSON TABLE 2. Deoxyribonucleic acid and protein levels in the pituitary and thyroid glands of castrated or goitrogen-treated cockerels (X ± SEM)
Treatment
n
DNA/gland
DNA/ gland
(Mg)
Protein/gland
Protein/ gland
(fjg/ing/
6 5 4 5
62.8 ± 65.6 ± 36.0 ± 37.6 ±
2.7a 4.6 a 3.2 b 1.9b
5.83 3.53 4.60 6.00
+ .5a ±.2b ± . 3b ± .7a
Control Castrate Castrate and nlethimazole Methimazole
6 5 4 5
232.8 ± 357.4 + 409.5 ± 673.2 ±
40a 21 ab 80b 12ic
2.33 3.78 1.69 2.63
±.2a ±.6a ± .4a + .7a
340 + 388 ± 220 + 368 +
19 a 24 a 23b 24 a
7017 ± 714 a 5450 ± 833 a 2930 ± 316 b 4817 ±
32.1 21.6 28.1 53.8
±2a ± 2b ±4ab ± 5C
68.8 ± 5.8 a 56.6 ± 5.9 b 12.1 ± 2.8 C 17.8+ . 3 C
a,b,c Means for each gland in columns with different superscripts are significantly different (P<.05).
birds but with the same DNA content as pituitaries of noncastrated methimazole-fed cockerels. The larger size of the pituitary of the castrated cockerel fed methimazole, compared to that of the intact methimazole-fed bird, might be explained by the possibility that methimazole feeding recruits a population of "thyrodectomy cells" that cannot be converted by castration. Castration, in turn, enlarges those available cells to provide a gland significantly larger than that of noncastrated cockerels fed methimazole. Sharp et al. (1979) found castration has no effect on thyroid weight but may increase plasma thyroxine and decreases the number of pituitary thyrotrophs of the domestic drake. Similarly, there were no substantial differences in weights between the thyroids of untreated and castrated cockerels. Although castration appears to have a moderating effect on growth stimulation of the thyroid gland by methimazole treatment, the route by which this mechanism operates is unknown. Chiasson and Carr (1985) have suggested an inhibitory role for testosterone on both the pituitary and thyroid glands. Castration removes the inhibition and may permit some increase in normal thyroid function which counteracts the hypertrophy effect of methimazole. The thyroid glands of methimazole-fed birds have elevated DNA levels with cellular hyperplasia (Handa and Chiasson, 1981). Thyroids of castrated, methimazole-fed cockerels have
lower DNA levels than do intact, methimazolefed cockerels. REFERENCES Bradford, M. M., 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein dye binding. Anal. Biochem. 72:248-254. Byus, C. V„ G. R. Klimpel, D. O. Lucas, and D. H. Russell, 1977. Type I and type II cyclic AMPdependent protein kinase as opposite effectors of lymphocyte mitogenesis. Nature 268:63—64. Chiasson, R. B., and B. L. Carr, 1985. Some effects of photoperiod on the pituitary/thyroid axis of castrated cockerels. Poultry Sci. 64:1205-1209. Chiasson, R. B., W. L. Combest, and D. H. Russell, 1980. Cyclic AMP-dependent protein kinase activity in the avian pituitary and thyroid glands following goitrogen treatments. Advances in Physiological Science, Vol. 33. Recent Advances of Avian Endocrinology. Akademiai Kiado/Pergamon Press, Budapest/New York. Chiasson, R. B., P. J. Sharp, H. Klandorf, C. G. Scanes, and S. Harvey, 1979. The effect of rapeseed meal and methimazole on levels of plasma hormones in growing broiler cockerels. Poultry Sci. 58:1575— 1583. Combest, W. L., R. B. Chiasson, and D. H. Russell, 1980. Alterations in type I and type II protein kinases in the thyroid and adenohypophysis in response to a dietary goitrogen. Gen. Comp. Endocrinol. 40:494-502. Costa, M., E. W. Gerner, and D. H. Russell, 1978. Cyclic AMP levels and types I and II cyclic AMPdependent protein kinase activity in synchronized cells and in quiescent cultures stimulated to proliferate. Biochem. Biophys. Acta 5 3 8 : 1 10. Fuller, D.J.B., C. V. Byus, and D. H. Russell, 1978. Specific regulation by steroid hormones of the
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
Control Castrate Castrate and nnethimazole Methimazole
PITUITARY CHANGES IN CASTRATED COCKERELS
Sharp, P. J., R. B. Chiasson, M. M. El Tounsy, H. Klandorf, and W. J. Radke, 1979. Localization of cells producing thyroid stimulating hormone in the pituitary gland of the domestic drake. Cell Tissue Res. 198:53-63. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. A Biometrical Approach. McGraw-Hill Book Co., Inc., New York, NY. Surks, M. I., and C. R. DeFesi, 1977. Determination of the cell number of each cell type in the anterior pituitary of euthyroid and hypothyroid rats. Endocrinology 101:946-958. Tixier-Vidal, A., A. Chandola, and F. Franquelin, 1972. "Cellules de thyroidectomie" et "cellues de castration" chez la caille japonaise, Cotumix coturnix japonica. Z. Zellforsch. 125:506—531. Vilchez-Martinez, J. A., 1973. Study of the pituitarytesticular axis in hypothyroid adult male rats. J. Reprod. Fertil. 35:123-126.
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
amount of type I cyclic AMP-dependent protein kinase holoenzyme. Proc. Natl. Acad. Sci. 75: 223-227. Giles, K. W., and A. Myers, 1965. An improved diphenylamine method for the estimation of deoxyribonucleic acid. Nature 206:93. Haddox, M. K„ W. R. Roeske, and D. H. Russell, 1979. Specific regulation by steroid hormones of the amount of cyclic AMP-dependent protein kinase holoenzyme. Proc. Natl. Acad. Sci. 75: 223-227. Handa, R. J., and R. B. Chiasson, 1981. Comparative effects of three goitrogenic treatments of White Leghorn chickens. Avian Dis. 24:916—929. May, J. D., L. R. Kubena, J. W. Deaton, and F. N. Reece, 1973. Thyroid metabolism of chickens. 1. Estimation of hormone concentration by the thyroxine binding globulin technique. Poultry Sci. 52:688-692.
383
1986 Poultry Science 65:380-383
INTRODUCTION Prolonged hypothyroidism produces a marked increase in pituitary size a n d deoxyribonucleic acid ( D N A ) c o n t e n t in rats (Surks a n d DeFesi, 1 9 7 7 ; Vilchez-Martinez, 1 9 7 3 ) . T h e pituitary gland of cockerels does n o t increase in size after goitrogen feeding (Chiasson et al, 1 9 7 9 ) and t h e duck pituitary gland weighs less t h a n c o n t r o l in m e t h i m a z o l e (goitrogen)-fed birds and increases in size w i t h castrat i o n (Tixier-Vidal et al, 1 9 7 2 ; Sharp et al, 1979). Whether t h e increase in size following castration is d u e t o hyperplasia or h y p e r t r o p h y has n o t y e t been determined, b u t t h e r e are several indications t h a t cellular hyperplasia occurs a t a very low rate in t h e avian pituitary. T y p e I and T y p e II cyclic adenosine m o n o p h o s p h a t e (cAMP)-dependent p r o t e i n kinases undergo selective changes during various stages of growth or differentiation (Costa et al, 1 9 7 8 ; Fuller et al, 1 9 7 8 ; H a d d o x et al, 1 9 7 9 ) , and T y p e I is selectively activated in response t o mitogenic stimuli (Byus et al, 1977). These selected changes in T y p e I and T y p e II cyclic
1 Arizona Agricultural Experiment Station Contribution #4057. 2 Deoxyribonucleic acid and protein assays were performed by Bruce L. Carr and Zia-ur-Rahman.
AMP-dependent p r o t e i n kinases d o n o t occur in t h e pituitary of goitrogen-fed chickens (Combest et al, 1 9 8 0 ) . Thus, m i t o t i c activity in t h e avian pituitary is t h o u g h t t o be very limited and does not account for t h e observed concent r a t i o n of t h y r o t r o p h i c cells after goitrogen feeding (Chiasson et al, 1980). T h e present s t u d y examines t h e D N A and protein c o n t e n t of t h e pituitary of castrated or goitrogent r e a t e d cockerels. MATERIALS AND METHODS T w e n t y White Leghorn cockerels were selected from a larger h a t c h and t e n of these were castrated at 5 w e e k s of age and allowed 2 weeks t o recover from castration surgery. A t 7 weeks of age, all cockerels were placed in individual cages in an environmental c h a m b e r at 2 4 ± 1 C and a lighting schedule of 14 hr light a n d 10 hr darkness. T h e s e conditions were m a i n t a i n e d for 10 weeks (to 17 weeks of age) w h e n all birds w e r e killed. A c o n t r o l group (five birds) and a castrated group (five birds) were fed a standard University of Arizona growing mash t h r o u g h the entire period. A second castrated group (five birds) and an otherwise u n t r e a t e d g r o u p (five birds) were fed a standard University of A r i z o n a growing mash containing . 0 1 % m e t h i m a z o l e (Sigma Chemical Co.). All birds were provided w a t e r ad libitum,
380
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
ABSTRACT The pituitary gland of birds is known to increase in weight with castration and decreases with chemical thyroidectomy. Whether these changes are due to alterations in mitotic activity or to cell size changes has been examined by measurement of deoxyribonucleic acid (DNA) and protein content of these glands. The DNA content of the enlarged pituitary of castrated cockerels is the same as that in the pituitary of normal cockerels. The pituitary size increase may be due to an increase in gonadotrope size including any part of the gonadotrope population which may be obtained by recruitment of other basophils. The retardation in pituitary size and DNA content with methimazole treatment is probably due, at least in part, to growth retardation but may also be due, in part, to the conversion of larger basophils to smaller thyrotropes. (Key words.- thyrotrophs, gonadotrophs, deoxyribonucleic acid, castration, goitrogen)
PITUITARY CHANGES IN CASTRATED COCKERELS
RESULTS
Castrated cockerels had adenohypophyses nearly twice as heavy as those of untreated birds, and the pituitaries of methimazole-fed cockerels were significantly smaller than those of control birds (Table 1). The pituitaries of castrated cockerels fed methimazole weighed the same as controls, which were lighter than those of castrates and heavier than the pituitaries of the methimazole-fed group. The thyroid glands of untreated and castrated cockerels were similar in weight, while the thyroid glands of methimazole-fed cockerels (whether castrated or not) were significantly larger than those of controls. Untreated and castrated cockerels had similar concentrations of pituitary DNA and protein, but methimazole-fed birds (whether castrated or not) had approximately one-half the pituitary DNA content of the other groups (Table 2). The protein content of pituitaries from methimazole-fed castrates was one-third less than that of the other three groups.
Due to differences in pituitary gland sizes, the DNA/mg gland and protein/mg gland values were lower in castrated cockerels and higher in methimazole-fed birds than in the controls. Only the protein/mg gland value of methimazole-fed cockerels was significantly higher than that of control birds (Table 2). The two methimazole-fed groups had enlarged thyroid glands (Table 1), increased thyroid DNA, and reduced total thyroid protein compared to either untreated or castrated cockerels (Table 2). DISCUSSION
The retarding effect of methimazole feeding is evident in the lower DNA levels and smaller size of the pituitaries of methimazole-fed cockerels. The smaller pituitary of methimazole-fed birds may be partly due to the direct inhibition of pituitary growth by methimazole and indirectly to the lack of thyroid hormone which is required for normal growth (May et al., 1973). Castrated birds have pituitaries that are nearly twice as large as those of controls but with an equal amount of DNA. These values indicate that castrated cockerels increase pituitary size by cellular hypertrophy and with no increase in cell number. It is also suggested that a portion of the population of the "cells of castration" are recruited from cells that had not previously served as gonadotrophs. The gonadotroph population alone would need to quadruple or more in size in order to double the size of the pituitary. Sharp et al. (1979) found a lesser population of thyrotrophs in the pituitary of the castrated drake than that of the control or methimazole-fed duck. This suggests that "castration cells" may be recruited in part from thyrotrophs. Castrated birds fed methimazole have pituitaries equal in size to control
TABLE 1. Body, pituitary, and thyroid weights (X ± SEM) of 17-week-old cockerels maintained at 24 C for 10 weeks following castration or methimazole treatment
Body weight
Treatment
(g) Control Castrate Castrate and methimazole Methimazole
6 5 4 5
1769 1634 869 891
±47a ± 58 a + 38 b + 60b
Thyroid weight
Pituitary weight
(mg) 9.3 18.9 10.1 6.8
+ ± ± ±
.6 a 1.2 b .8a .4 C
' Means in columns with different superscripts are significantly different (P<.05).
93 86 243 256
+ 3a + 7a ±41b ± 68b
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
Wet weights of all tissues were determined on a torsion balance (Roller-Smith). Protein and DNA were determined by absorbance changes measured on a spectrophotometer (Beckman DU-2). Protein was assessed by the Coomassie Blue G 250 method described by Bradford (1976), in which bovine serum albumin is used as a standard. Pituitary and thyroid DNA values were determined by the modified diphenylamine method described by Giles and Myers (1965), in which calf thymus DNA (Sigma) serves as a standard. All data were analyzed by a one-way analysis of variance with Fisher's protected LSD test used for estimating significant differences among means (Steel and Torrie, 1960).
381
382
CHIASSON TABLE 2. Deoxyribonucleic acid and protein levels in the pituitary and thyroid glands of castrated or goitrogen-treated cockerels (X ± SEM)
Treatment
n
DNA/gland
DNA/ gland
(Mg)
Protein/gland
Protein/ gland
(fjg/ing/
6 5 4 5
62.8 ± 65.6 ± 36.0 ± 37.6 ±
2.7a 4.6 a 3.2 b 1.9b
5.83 3.53 4.60 6.00
+ .5a ±.2b ± . 3b ± .7a
Control Castrate Castrate and nlethimazole Methimazole
6 5 4 5
232.8 ± 357.4 + 409.5 ± 673.2 ±
40a 21 ab 80b 12ic
2.33 3.78 1.69 2.63
±.2a ±.6a ± .4a + .7a
340 + 388 ± 220 + 368 +
19 a 24 a 23b 24 a
7017 ± 714 a 5450 ± 833 a 2930 ± 316 b 4817 ±
32.1 21.6 28.1 53.8
±2a ± 2b ±4ab ± 5C
68.8 ± 5.8 a 56.6 ± 5.9 b 12.1 ± 2.8 C 17.8+ . 3 C
a,b,c Means for each gland in columns with different superscripts are significantly different (P<.05).
birds but with the same DNA content as pituitaries of noncastrated methimazole-fed cockerels. The larger size of the pituitary of the castrated cockerel fed methimazole, compared to that of the intact methimazole-fed bird, might be explained by the possibility that methimazole feeding recruits a population of "thyrodectomy cells" that cannot be converted by castration. Castration, in turn, enlarges those available cells to provide a gland significantly larger than that of noncastrated cockerels fed methimazole. Sharp et al. (1979) found castration has no effect on thyroid weight but may increase plasma thyroxine and decreases the number of pituitary thyrotrophs of the domestic drake. Similarly, there were no substantial differences in weights between the thyroids of untreated and castrated cockerels. Although castration appears to have a moderating effect on growth stimulation of the thyroid gland by methimazole treatment, the route by which this mechanism operates is unknown. Chiasson and Carr (1985) have suggested an inhibitory role for testosterone on both the pituitary and thyroid glands. Castration removes the inhibition and may permit some increase in normal thyroid function which counteracts the hypertrophy effect of methimazole. The thyroid glands of methimazole-fed birds have elevated DNA levels with cellular hyperplasia (Handa and Chiasson, 1981). Thyroids of castrated, methimazole-fed cockerels have
lower DNA levels than do intact, methimazolefed cockerels. REFERENCES Bradford, M. M., 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein dye binding. Anal. Biochem. 72:248-254. Byus, C. V„ G. R. Klimpel, D. O. Lucas, and D. H. Russell, 1977. Type I and type II cyclic AMPdependent protein kinase as opposite effectors of lymphocyte mitogenesis. Nature 268:63—64. Chiasson, R. B., and B. L. Carr, 1985. Some effects of photoperiod on the pituitary/thyroid axis of castrated cockerels. Poultry Sci. 64:1205-1209. Chiasson, R. B., W. L. Combest, and D. H. Russell, 1980. Cyclic AMP-dependent protein kinase activity in the avian pituitary and thyroid glands following goitrogen treatments. Advances in Physiological Science, Vol. 33. Recent Advances of Avian Endocrinology. Akademiai Kiado/Pergamon Press, Budapest/New York. Chiasson, R. B., P. J. Sharp, H. Klandorf, C. G. Scanes, and S. Harvey, 1979. The effect of rapeseed meal and methimazole on levels of plasma hormones in growing broiler cockerels. Poultry Sci. 58:1575— 1583. Combest, W. L., R. B. Chiasson, and D. H. Russell, 1980. Alterations in type I and type II protein kinases in the thyroid and adenohypophysis in response to a dietary goitrogen. Gen. Comp. Endocrinol. 40:494-502. Costa, M., E. W. Gerner, and D. H. Russell, 1978. Cyclic AMP levels and types I and II cyclic AMPdependent protein kinase activity in synchronized cells and in quiescent cultures stimulated to proliferate. Biochem. Biophys. Acta 5 3 8 : 1 10. Fuller, D.J.B., C. V. Byus, and D. H. Russell, 1978. Specific regulation by steroid hormones of the
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
Control Castrate Castrate and nnethimazole Methimazole
PITUITARY CHANGES IN CASTRATED COCKERELS
Sharp, P. J., R. B. Chiasson, M. M. El Tounsy, H. Klandorf, and W. J. Radke, 1979. Localization of cells producing thyroid stimulating hormone in the pituitary gland of the domestic drake. Cell Tissue Res. 198:53-63. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. A Biometrical Approach. McGraw-Hill Book Co., Inc., New York, NY. Surks, M. I., and C. R. DeFesi, 1977. Determination of the cell number of each cell type in the anterior pituitary of euthyroid and hypothyroid rats. Endocrinology 101:946-958. Tixier-Vidal, A., A. Chandola, and F. Franquelin, 1972. "Cellules de thyroidectomie" et "cellues de castration" chez la caille japonaise, Cotumix coturnix japonica. Z. Zellforsch. 125:506—531. Vilchez-Martinez, J. A., 1973. Study of the pituitarytesticular axis in hypothyroid adult male rats. J. Reprod. Fertil. 35:123-126.
Downloaded from http://ps.oxfordjournals.org/ at University of Pennsylvania Library on May 14, 2015
amount of type I cyclic AMP-dependent protein kinase holoenzyme. Proc. Natl. Acad. Sci. 75: 223-227. Giles, K. W., and A. Myers, 1965. An improved diphenylamine method for the estimation of deoxyribonucleic acid. Nature 206:93. Haddox, M. K„ W. R. Roeske, and D. H. Russell, 1979. Specific regulation by steroid hormones of the amount of cyclic AMP-dependent protein kinase holoenzyme. Proc. Natl. Acad. Sci. 75: 223-227. Handa, R. J., and R. B. Chiasson, 1981. Comparative effects of three goitrogenic treatments of White Leghorn chickens. Avian Dis. 24:916—929. May, J. D., L. R. Kubena, J. W. Deaton, and F. N. Reece, 1973. Thyroid metabolism of chickens. 1. Estimation of hormone concentration by the thyroxine binding globulin technique. Poultry Sci. 52:688-692.
383