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Endocrine influences upon the growth of the rudimentary gonad of fowl.

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ENDOCRINE INFLUENCES UPON T H E GROWTH
O F T H E RUDIAIENTARY GONAD O F FOWL1
WALTER R O R N F E L D
Department of Plzysiology and Pharmacology, School of Veterinary Medicine,
University of Georgia, A t h e n s , Georgia
I n domestic fowl the right female gonad ceases to grow
about the ninth day of incubation. At that time cortical development may or may not have occurred. The gonadal rudiment can subsequently be induced to proliferate by removal
of the ovary, and Domm ('27) suggested that the extent of
embryonic differentiation determines whether the rudiment
develops into a testis-like compensatory gonad, an ovotestis,
or an ovary.
Because the rudimentary gonad always hypertrophies following sinistral ovariectomy, it is obvious that the ovary must
exert an inhibitory function even in the immature bird. The
mechanism of inhibition is not known.
Kornfeld and Nalbandov ('54) have shown that estrogen
acts as an inhibitor in. vivo. They demonstrated estrogenic
activity in the blood of female chicks 16 to 20 days old and
succeeded in preventing the hypertrophy of the right gonad
of immature poulards with physiological amounts of an estrogen. Hypophysectomy depressed the established testicular
compensatory gonad of poulards and prolactin depressed
rudiment hypertrophy. Kornfeld ('57) found no effect of
sinistral ovariectomy upon adrenal and thyroid growth when
seasonal variations were not considered.
I wish t o thank Dr. J. L. Carmon f o r his help with the statistical analysis, Dr.
J. Davidson (Upjohn Company) f o r estradiol cyclopentylpropionate, testosterone
eyelopentylpropionate, and gonadotropic hormone of pregnant mare serum, and Dr.
N. L. Heminway (Schering Corporation) f o r progesterone.
619
T H E ALNATOMICAb RECORD, VOL.
APRIG 1958
130, N O . 4
620
WALTER KORKFELD
Evidence for the presence of androgens in female fowl is
only indirect (Breneman, ?55). Kornfeld and Nalbandov ( '54)
and Taber and Salley ('54) inhibited the rudimentary gonad
of poulards with massive doses of an androgen. There is no
evidence for the presence of progesterone in very young birds
and since the right gonad is inhibited from the start, it is
doubtful that this hormone plays a role in the development of
this gland in vivo.
The purpose of this paper is to elucidate further endocrine
interrelations affecting the rudimentary gonad of female
domestic fowl.
MATERIALS AXTD METHODS
Female White Leghorn chicks of the same commercial stock
were used. The battery-brooded birds were randomly assigned
to treatments and to compartinents of finishing batteries; a
commercial ration, which contained neither a hormonal nor a
coccidiostatic supplement, was fed throughout. Unless otherwise stated, sinistral ovariectomies were performed 1 2 to 21
days after hatching. Intact pullets, selected at random before
ovariectomies were performed, were also kept. Corn oil
(hfazola) was used a s diluent for the injection of steroids. A11
other substances were made u p in distilled water. Injection
site was alternately right and left pcctoral and right and left
gluteal region. Doses of steroids will refer to v,g per 100 gm
of body weight per bird per day. Dosages were adjusted at
10-day intervals to the mean body weight of each group and
injected subcutaneously once daily. When only steroids were
administered, the total volume injected was the same for all
birds. In the experiment involving the injection of fat and
water soluble hormones (table 5), controls were not injected
during the last 20 days, but all birds were handled similarly.
Pituitaries used for injection were collected locally from
2,100 unsexed broilers (New Hampshires and White Rocks)
approximately 10 weeks old. The fresh glands were stored as
rapidly as possible in acetone following Breneman's ('45)
procedure. Before use the pituitaries were dried over calcium
H O R M O N E CONTROL O F GON A D A L R U D I M E N T
621
chloride, and the weight was oLtained of each group of 100
glands (146.85 mg with a standard deviation of the mean of
15.44). The glands were finely ground and suspended in water
just prior to administration. One group of randomly chosen
pituitaries was assayed according to Breneman’s (’45) technic which determines primarily FSH potency by its effect
upon testis weight. The activity was found to be 2.4 chick
units per pituitary. The equivalent of 2.5 pituitaries per bird
was made u p to 0.25 em3 in distilled water twice daily and
injected. Other groups received a total of 5 Cartland-Nelson
units of pregnant mares’ seruni gonadotropin ( P M S ) per bird
per day i n a n analogous manner.
Body weight and estimates of comb size (comb length x
comb height) were recorded at the beginning and end of each
experiment. Body weights a r e reported only when significantly affected by treatment.
All experiments were terminated 12 to 24 hours after the
last injection. Pituitaries, thyroids, adrenals, oviducts, and
gonadal tissues were fixed in Bouin’s solution, dried superficially, and weighed on an analytical balance. Trends of
treatment effect upon thyroid and adrenal weight of poulards
were not apparent and data a r e not presented. Adrenal and
thyroid weight of intact and ovariectomized controls was
published (Kornfeld, ’57).
Rudiments and structures suspected of being gonadal regenerations were embedded in paraffin, sectioned a t 7 p,
mounted, and stained with Milligan’s ( ’46) trichrome stain.
Only data from completely ovariectomized birds were analyzed. The term “ovotestis” will refer to gonads containing
follicles a s well as medullary tubules with lumina. Oviduct
growth was used as quantitative index of estrogenic activity.
Oviducts distended with abnormal amounts of fluid were excluded from the data and oviduct weights were transformed
into their logarithms before analysis for reasons discussed
by Kornfeld and Nalbandov ( ’54).
622
WALTER KORNFELD
RESULTS
Inhibition of rudiment growth with estrogen
This experiment was designed to establish the niinimal
dosage for estrogen inhibition of the hypertrophy of the right
gonad in poulards and to compare endocrinologically ponlard
and intact female.
Poulards were given injections of the following graded
doses of the ester estradiol cyclopentylpropionate ( E C P ) :
0, 0.125, 0.25, 0.5, 1, 2, and 4 pg.
A t the start of treatment the birds were 34 days old and
reddening of combs had not occurred. The latter serves as a
sensitive criterion for determining the time of onset of androgen secretion by the coinpensatory gonad. The experiment
was terminated after 60 injections.
Rudiments which had not hypertrophied into macroscopically definite structures were assigned a weight of zero and
discarded.
The pituitary weight of poulards (table 1)was increased by
the three lowest doses of estrogen. The lowest dose (2 p g
E C P ) which inhibited rudiment growth, resulted in oviduct
and pituitary weights which did not differ significantly from
those found in pullets of the same age, but it depressed comb
growth.
Growth of the compensatory gonad
Reddening of the comb of White Leghorn poulards occurs
30 to 50 days after ovariectomy of two- to three-week old
birds. An experiment was designed to determine whether a
latent period of similar duration necessarily precedes endocrine activity (table 2).
Two groups, ovariectomized when 12 to 17 days old, were
injected with 2 p g E C P daily for 15 and 30 days respectivc~ly.
Treatment started at the age of 31 days with the intent of
replacing the ovarian inhibitor with ECP f o r a specified
period. Other groups were ovariectomized at thc age of 45,
60, and 75 days and the compensatory gonad of two poulards
HORMONE CONTROL O F GONADAL RUDIMENT
c;
623
9
2
5 (4)
75
Poulards
No. OF
12-17
16-17
45
60
75
12-17
12-17
12-17
14-17
12-14
12-17
14-17
12-16
AGE ( I N DAYS)
AT TIilIE OF
OVARIECTOMY
24
za
<
0
0
0
0
0
0
0
1.5
3
6
12
0
0
0
0
0
0
0
0
0
1
1
1
1
1
2
ECP
gm'day)
TCP
(M'~OO
DOSE
<
58 2 3 1
30 t 10
5 2 7'
9 f 7
6t 8
I t 3'
4 f 11
5 2 13
2f 48
46 f 20
38 f 19
51 f 32
Rudimentary
gonad
~
4.5 2 0.8
7.2 f 2.8 fl
8.3 f 6.2 '
7.6 k 1.9 '
8.9 & 2.1 '
5.8 t 2.4
7.1 2 1.3fl
6.1 f 1.2
7.021.7'
7.0 f 2.0
5.2 f 1.5 '
5.4 t 1.1
7.0 & 1.3 '
8.7 t 2.0
Pituitary
\VEIGHT O F
129 2 47
68 t 14
8 6 2 0
78 f 18
86 f 31
67 t 11
135 f 40
103 t 24
117 f 8
110 t 23
117 f 20
932 5
932 4
97 f 28
Oviduct
a
<
<
The conipensatory gonad of thcse two birds xvab complctely reinoved 83 days a f t e r hatchling.
Sumher of observations of oviduct weight (distentions omitted).
ECP was discontinued after 15 injections when the birds were 45 days old.
' ECP was discontinued after 30 iiijections when the birds were 60 days old.
One compensatory gonad was lost.
Highly significant difference from intact controls (P 0.01).
' Sigiiificaiit difference from intact controls (P 0.05).
' Highly significant diffcreiice from ovariectomized controls (P 0.01).
Significant difference froin ovariectomized controls (P
0.05).
10
Pullets
'8'
'3'
'3'
'8'
2
1
0
0
0
0
1
1
0
0
0
1
1
0
1
0
0
0
1
0
1
1
2
3
1
0
0
1
5
6
1
5
4
0
0
Ovary
9
Testis Ovotestis
T Y P E O F HYPERTROPHIED R U D I M E N T :
3 7 2 2 93
505 t 253
202 2 2 0 1
225 f 67'1'
277 k 87'
218 2 26
251 2 92'*'
264 f 63
4 1 8 2 79
780 % 147
1633 f 268
183 k 55'3'
332 -t 162 '
2 8 8 f 70'
GROWTH
CoMR
(Mean organ and tissue weights in mg 2 S D ; comb growth as % increase in comb area f SD)
T h e estrogen-androgen synergism u p o n rudiment inhibition and data on the znduction period of rudiment Ikypertrophy following sinistral
ovariectomy a t daferent ages
TABLE 2
H O R M O N E CONTROL O F GONADAL R U D I M E N T
625
was removed 83 days after hatching. Each comb was inspected a t 10-day intervals and the onset of reddening was
recorded. All birds were terminated at 100 days of age.
Neither estrogen treatment to the age of 45 and 60 days, nor
ovariectomy at the age of 45 days had a significant effect
upon gonad size, but the weight of the compensatory gonad
was depressed i n the birds which had been ovariectomized
when 60 and 75 days old. There was no significant treatment
effect on log oviduct and pituitary weights.
Because reddening of some combs occurred during E C P
treatment and because combs of the birds which were ovariectomized at 75 days of age never lost their color completely,
observations of these groups could not be interpreted. F o r
the three remaining treatments data a r e listed in the following
sequence from left to right: Age (in days) at the time of
ovariectomy ; days elapsed between ovariectomy and first observation of comb reddening; days elapsed between ovariectomy and the time when combs of the majority of birds had
begun to turn red.
12-17
45
60
34
14
19
53
34
19
The figures suggest that the interval from ovariectomy to
onset of androgen secretion by the compensatory gonad is
greatest when the ovary is removed from the very young.
Regardless of treatment effect upon rudiment hypertrophy
and pituitary size, comb growth f or the entire experimental
period was significantly less than that of intact pullets in all
groups except the one ovariectomized at 60 days of age. Comb
growth of two bilaterally ovariectomized birds was similar to
that observed after sinistral ovariectomy at the age of 7 5
days. Comb area (in em2) increased during the 17 days after
the removal of the compensatory gonad from 5.64 to 5.99 and
from 5.39 to 5.45 respectively. No gonadal tissue was found.
Estrogen-androgen synergisna in t h e inhibition of
r u d i m e n t growth
Because E C P doses of 1 p g and above depressed comb
growth of poulards below that of the intact controls, the possi-
626
WALTER KORNFELD
bility of a n androgen-estrogen synergism in the pullet’s inhibitory mechanism had to be considered. This hypothesis was
tested by treating poulards with a dose of estrogen xhich is
subminimal for the inhibition of rudiment growth and with
combinations of this dose with graded amounts of androgen.
Intact and ovariectomized controls were kept as well as a
control group of poulards receiving the inhibitory dose of 2 p g
E CP. Poulards were treated with 1 p g E C P alone and in
combination with the followiiig amounts of testosterone cyclopentylpropionate ( T C P ) : 1.5, 3, 6, and 12 pg. Treatment was
started when the birds were 31 days old and before gonadal
androgen had begun to stimulate the comb visibly. The esperinient was terminated after 70 injections.
Rudiments which had not visibly hypertrophied were again
assigned a weight of zero. Several additional experimental
groups of poulards which were run with these same controls
(table 2) have already been discussed.
Estrogen, singly and in combination with androgen, depressed rudiment weight and reduced the number of proliferating compensatory gonads. Analysis of variance which
showed no significant effect of this treatment 011 log oviduct
weight, showed a highly significant treatment effect on pituit a r y w i g h t . The mean pituitary weight of intact controls was
lovrer than ihat of any treated group.
Only the comb growth produced by the estrogen-androgen
combination of 1 p g E C P plus 3 p g T C P did not differ significantly from that of intact and ovariectomized controls.
Regression coefficients of comb a r ea on age were calcnlated
(table 3). The three regression coefficients did not differ significantly from each other and a linear regression fitted the
data significantly better than a quadratic. The fact that comb
growth of pullet and poulard controls does not differ significantly, indicates that endogpilous androgen secretion alone
does not prevent rudiment hypertrophy. This proves, according to the experimental design, that the estrogen-androgen
effect represents a synergism.
1.40
1.50
Ovariectomized controls
Poulards on estrogen and
androgen
9
2.26
2.20
2.69
3.20
2.98
3.42
1 pg ECP plus 3 fig TCP per 100 gm of body weight per day.
10
1.66
49
Dqs
39
Days
29
1);~)s
Intact controls (pullets)
TREATICENT
10
NO. O F
BIRDS
4.24
3.81
4.07
5.41
4.60
4.81
At
of
59 the age69
Days
Days
(CM’)
6.55
5.52
5.72
79
Days
7.30
6.51
6.58
7.62
7.96
7.69
99
Days
89
Days
physiological” estrogen-androgen dose
X P 4 N COMB AREA
Comb growth of controls and of poulards receiving a
TABLE 3
0.008
0.094 & 0.005
0.095
0.083 k 0.006
(Comb area
on age)
REGRESSION
COEFFICIENT
z
z
H
z
m
L
2
H
d
w
P
6*
0
0
0
H
Q
0
2
0
628
WALTER I i O R N F E L D
The number of hypertrophied right gonads was also maximally reduced by the synergistic dose of 1p g ECP plus 3 pg
TCP. Only one of 10 rudiments appeared to have hypertrophied and even its weight (9 mg) is in line with that of the
rudiment weight of intact pullets (tables 4 and 5).
TABLE 4
E f f e c t s of a “physiological” estrogen-androgen dose zcpon immature poulards at
t w o different intervals a f t e r ovariectomy at 14-17 days of age
(Mean organ and tissue weights in mg f SD; comb growth
as % increase i n comb area
SD)
+
AGE A T T I X E OF TERMINATION
100 days
60 days
Pullets
No. of birds
Rudimentary gonad
weight
Pituitary weight
Oviduct weight
Comb growth
Type of rudiment:
Testis
Ovotestis
Ovary
Poulards
*
Pullets
Poulards
7
3 (2)
7+3
8-r-7
4.4 -r- 1.0
8
6+2
10
+6
3.4 k 0.7
4.0
+ 1.2
3.8 % 0.6
52 f 9
57
+- 5
511
+ 635
106 % 40
157 2 19
414 % 213
5
3
5
0
6
0
2
0
0
121
a
+ 26
557 k 174
3
0
0
~_____
~
(1,ug ECP plus 3 fig TCP per 100 gm of body weight per day.)
* 30 injections. Treatment was terminate? when the poulards were 59 days old.
40 injections. Treatment was terminated when the poulards were 99 days old.
observations of oviduct weight (distentions omitted).
Significant difference from pullets ( P
0.05).
‘ Number of
<
Additional information regarding the “physiological” dose
of 1 p g ECP plus 3 p g TCP is presented in table 4. Two
groups of poulards receiving a total of 30 and 40 daily injections were compared with pullet controls. The birds were
killed at the ages of 60 and 100 days. All rudiments were
weighed and sectioned. Data were analyzed by appropriate
use of “student’s’’ t-test.
1165
1170
1104
1134 '
?C
28
1051
1096
75
1197
1145'
35 & 34
Final body weight adjusted f o r weight differences at the ape of 80 days.
Final body weight
(in Em)
7f 4
46 rtr: 13
Last 20 days of
exper.
330 & 154
184t31
322 C 1 7 6
390 k 1 3 0
7.5 t 2.4
117 t 55
3.5 k 0.4
4.1 t 0.6
768 t 175 1074 1
:224
4.2 t 0.4
338 & 445
Oviduct weight
Comb growth :
Duration of
entire exper.
38 C 12
6
37 & 21
36 C 25
1228
1328
1 1 t 3
1 1 t 3
6 t 2
6 C 2
9
7
3
0
1
0
4
10
5
3
0
0
3
Controls
+
Progest.
(last 20
days) PMS
4
0
1
5
Progest.
Pituitary weight
Type of gonadal
rudiment:
Testis
Ovotestis
Ovary
Rudimentary gonad
weight:
All rudiments
Testicular rudiments
Non-testicular
rudiments
No. of birds
Controls
PULLETS
1098
1156
49 t 16
396 & 9 9
1136
11401
41 rt 14
366 5 8 8
96t21
4.7 t 1.0
6.1 t 1.7
98t20
15
l l t 5
1 1 t 5
9
1
0
10
PMS
1087
1101
58 2 2 6
468 2 1 6 6
89t23
7.5 t 1.8
49
17-C-12
1 3 t l
8
1
0
9
0
91
29
7.0 rt 2.1
1203
1167'
21C16
1176
1157'
26t25
312 & 1 1 7
1079
1095 '
1 7 ~ 2 1
308 & 186
414
8.0 2 1.6
206
-+ 1.6
85 2 2 7
7.5
27 2 35
18 18
1 4 t 6
7
3
0
10
Avian Pit.
48 t 2 9
25 t 24
1 2 t 5
25 +- 1 2
22t10
33 2 14
7
3
1
11
PMS
+ A to age 80 day8
+ (last 20 days)
7
3
0
10
E
286 t 9 4
POULARDS
Avian Pit.
+ A to age 100 days
+ (last 20 days)
76
20218
1 5 t 5
11
0
1
12
0
E
T h e e f f e c t of gonadotropins u p o n the steroid-inhibited rudimentary gonad
(Mean organ and tissue weights in mg t SD; comb growth as % increase in comb area f SD. For details about treatment Bee text)
TABLE 5
630
WALTER K O R N F E L D
Of the 7 poulards killed at 60 days of age, two had ovarian
rudiments. They were larger (15 and 22 mg) than the remainder of testicular structures. The rudiments of the poulards in the older group were all testicular and their growth
was inhibited even though treatment had been started about 45
days after the removal of the left gonad.
Poulard treatment with a hormone dosage calculated on the
basis of body weight, resulted in pullet-like growth of pituitary, rudiment, and oviduct a t the ages of 60 and 100 days. At
the age of 60 days, but not at 100 days, comb growth of the
treated poulards was significantly greater than that of the intact controls and it appears possible that the rate of pullets’
comb growth increases with age. However, in another experiment (table 3) analysis of analogous comb growth data failed
to show a significant difference at the age of 59 days.
T h e effect of gonadoti-opins upovt, the inhibited rudiment
To determine the possible effect of the pituitary upon the
development of the compensatory gonad, crude avian pituitary
powder or PMS were administered to poulards either concurrently with the injection of an inhibitory dose of sex hormones, or under the waning influence of residual sex hormones.
This approach allowed f o r the possibility that the compensatory gonad of untreated poulards might already he maximally
stimulated by endogenous gonadotropins o r that it might
only respond to avian gonadotropins.
TTeatment with the synergistic dose of 1 p g ECP plus 3 p g
TCP per 100 gni of body weight per day was started on 30
day old poulards. Of three groups which were treated with
estrogen ( E ) plus androgen ( A ) for 70 days, two groups
were injected in addition with 5 CNU of PMS o r the equivalent of five avian pituitaries p3cr day during the last 20 days
of the experiment. Three other groups were treated in an
analogous manner, except that the injection of E plus A was
discontinued the day before the administration of €’>‘IS or
pituitaries was begun. Intact and ovariectomizcd controls
HORMONE CONTROL O F GONADAL R U D I M E N T
631
were maintained and two groups of intact pullets were injected f o r 70 days with 0.5 mg of progesterone per 100 g m of
body weight per day with or without the addition of 5 CNU
of PAIS during the last 20 days of the experiment. The age
selected for the start of gonadotropin injection was 80 days
because the compensatory gonads of ovariectomized controls
are large enough then to permit an accurate interpretation of
differences in size due to treatment. Twenty days was considered adequate for a weight response. All rudiments were
weighed and sectioned. Rudiment weights mere converted into
logs f o r statistical analysis because of unequal variances.
Data are presented in table 5.
Neither progesterone nor gonadotropins had a significant
effect upon rudiment growth. None of the treatments affected
log oviduct weight significantly. The pituitaries of all pullet
groups and those of the poulards treated with P M S plus E
plus A were lighter than the rest. An analysis of variance for
treatment effect upon comb growth was not significant for the
first 50 days, but was highly significant for the entire experimental period. During the last 20 days of the experiment,
E plus A with or without avian gonadotropin caused comb
growth to exceed ( P < 0.01) that of the ovariectomized controls. PMS which accelerated the comb growth of the progesterone treated pullets temporarily (the birds became refractory after about 15 days of treatment), failed to have even a
transitory effect on the poulards.
Analysis of variance showed a very significant difference in
the final body weights of the experimental groups which was,
however, shown to be due t o differences existing already before the start of gonadotropin injection. The failure of the
gonadotropin to accelerate compensatory gonad growth was,
therefore, apparently not due t o a general growth depressing
effect of the avian pituitary preparation.
Analysis of variance shows that treatment with the synergistic dose of steroids depressed log rudiment weight of
poulards very significantly. It remained, however, very significantly larger than log rudiment weight of the intact pullet
632
WALTER K O R N F E L D
groups. Weights of the testicular rudiments (their variances
were homogeneous) did not differ significantly between the
three intact groups and those of poulards which had been
treated with E plus A throughout the experimental period.
This shows that the synergistic androgen-estrogen dosage
level inhibited only testicular proliferation. Non-testicular
compensatory gonads (18 out of 85) were fairly evenly distributed among treatments and wherever ovarian and ovotesticular types occurred i n the same group, the ovary was larger.
DISCUSSION
Breneman ('55) reported that very small doses of estradiol
increase the gonadotropic potency of the pituitary of pullets
and have no significant effect on piuitary weight. Data presented in this paper show that the pituitary weight of poulards, which is already larger than that of pullets, was further
increased significantly following the administration of low
doses of ECP (0.125 to 0.5 p g ) . A dose of 1 p g ECP was not
consistently effective and pituitary weights of poulards
treated with 2 pg ECP or more did not differ significantly
from those of the intact pullets.
Doses of ECP which were followed by a n increase in pituitary weight did not inhibit the hypertrophy of the right gonad.
All pituitary weights which decreased following estrogen
treatment, approached the value f o r the intact pullet whose
rudiment is also inhibited. This indicates that a depression of
pituitary weight occurs in the presence of physiological
amounts of estrogen. Breneinan's ('55) above mentioned results suggest that the pituitary of the intact pullet is not very
sensitive to additional estrogen after its initial response to
endogenous hormone. I n line with these findings are those of
Kornfeld ('57) who reports a significant difference in pituit a r y and oviduct weight of pullets and poulards as early as a t
45 days of age. While this difference must be attributed to
ovarian secretion, the absence of a significant difference in
comb size between pullets and poulards causes this worker
HORMONE CONTROL O F GONADAL RUDIMENT
633
to discount the importance of a physiological androgen effect
upon the hypertrophy of the right gonad.
The dosage combination of 1 y g E C P (which alone is subminimal for the consistent inhibition of rudiment growth in
the poulard) and 3 p g T C P per 100 gm of body weight per day
definitely depressed the growth of testicular rudiments. On
the basis of its effect upon comb growth, oviduct weight, and
effect on testicular rudiments, i t seeins that this dose approaches the equivalent of the pullet’s endogenous hormone
secretion. The pullet’s actual secretion rate of estrogen must
nevertheless lie above the equivalent of 1 p g ECP. This bclief
is based upon the apparent lack of effect of the above mentioned synergistic androgen-estrogen dose in thc inhibition of
non-testicular compensatory gonads of poulards and upon its
inconsistent effect upon pituitary size.
The lack of effect of dose 1p g E C P plus 3 p g T C P upon the
growth of non-testicular compensatory gonads was difficult to
prove. Only in one experiment (table 5) were these structures
fairly evenly distributed among treatments. I n the second
experiment (table 2 ) only testicular gonads were found in the
poulards treated with 1 p g E C P alone or in conjunction with
1.5 and 3 pg TCP. Under the influence of 1 p g E C P plus
6 1-19T C P only one gonad hypertrophied, a n ovary (35 mg),
and under the influence of 1 p g E C P plus 1 2 p g T C P two
gonads developed, one ovary (38 mg) and one ovotestis (7 mg).
When the “physiological” dose of 1 p g E C P plus 3 p g T C P
was repeated to the age of 60 days (table 4), the two largest
gonads found (22 mg and 15 mg) were ovaries and only testicular gonads were found in the group which was treated from
the age of 60 to 100 days of age. The effect of the greater
weight of non-testicular rudimentary gonads upon mean gonad
weight was more pronounced in the experiments in which all
rudimentary gonads were actually weighed (tables 4 and 5).
Previously a weight of zero had been assigned t o rudiments
which were too small to be macroscopically definite structures
and which a r e assumed to be maximally inhibited. While the
weight of each gonad must obviously exceed zero, the method
634
WALTER KORNFELD
of weighing minute gonadal structures tends to overestimate
their size somewhat because unrelated tissue is removed with
many of these structures which have poorly defined boundaries. It appears definitely, however, that the inhibitory
threshold for rudiments with cortical development must lie
above that for testicular rudimentary gonads.
Pituitary weights following the daily injection of 1p g E C P
alone (per 100 gm of body weight per day) were significantly
larger than those of intact controls in one experiment (table
a), but not in the other (table l), and the lowest androgenestrogen dose depressed pituitary weight (table 2). The
dosage combination of 1~gECP with 3 p g or 6 p g TCP results
in pituitaries which are very significantly larger than those of
pullets and which fail to differ significantly in size from those
of the ovariectomized controls. The dose of 2 p g E C P without
the addition of androgen, consistently depressed the poulard's
pituitary weight to the point where it no longer differed significantly from that of the intact controls (tables 1 and 2).
This dose also inhibits rudiment proliferation consistently.
Kornfeld ('57) has shown that in birds, ovariectomized at
14 to 17 days of age, the compensatory gonad is not significantly larger a t the age of 45 days than that of pullets of the
same hatch. Hypertrophy of the rudiment in poulards ovariectomixed during the third week of age, becomes apparent
between the ages of 45 and 60 days. Neither estrogen treatment of poulards to the age of 45 days, nor ovariectomy at 45
days had a significant effect upon the rudiment weight a t 100
days. Estrogen administration to poulards to the age of 60
days as well as ovariectomy a t 60 or 75 days of age caused
the weight of the compensatory gonad a t 100 days to fall below
that of controls ovariectomized 12 to 21 days after hatching.
The current data fail t o show whether the latent period is increased or whether the growth rate of the compensatory gonad
is decreased when pullets are ovariectomized during the third
week of age rather than a t 45 days of age. At 100 days of age
the comb size of birds ovariectomized at 45 days was, however,
significantly smaller than that of poulards whose left gonads
H O R M O N E CONTROL O F GONADAL R U D I M E N T
635
had been removed at the age of 12 to 17 days even though the
compensatory gonads showed no significant difference in size
and appearance. This indicates that gonad size and endocrine
activity are not influenced alike by the age at the time of
ovariectomy.
The last experiment of this series (table 5) was designed
to test the effect of gonadotropins upon rudiment growth. Because of the complete lack of response t o avian pituitary and
to PMS under these conditions, a working hypothesis seems
justified now which holds that the inhibition of the right gonad
of domestic fowl is due to a direct inhibitory effect of the
secretion of the ovary. This view is not incompatible with the
observation of Kornfeld and Nalbandov ('54) that the pituitary is necessary for the maintenance of the compensatory
gonad of poulards.
Until the successful acceleration of the growth of the compensatory gonad of fowl is accomplished, the possibility that
a sub-threshold dose of avian gonadotropin was used cannot
be discounted. The prolactin content of the pituitary powder
is not known, but if one puts credence in Huble's ('56) hypothesis that prolactin is the avian growth hormone, it does
not appear likely that the preparation used contained a high
amount of it. It is worth noting that a 10 day treatment of
pullets of similar age and breed with 4 mg of dried pituitary
powder of similar origin, was shown by Das and Nalbandov
('55) to cause a significant increase in comb size and ovarian
weight. I n the experiment which is reported here, about twice
this amount (7.5 mg per day) was administered f o r twice
the length of time.
Breneman ( '55), working with immature Leghorn pullets,
has shown that the combination of sex hormones with PMS
produces marked growth and secretory activity of the ovary.
This response occurs along with a decrease of pituitary gonadotropic potency, but not of pituitary weight. There is no
indication that the right gonad of fowl responds similarly. I n
the absence of any gonadal response, the combined administra-
636
WALTER KORNEELD
tion of sex hormones and PMS caused a significant depression
of the pituitary weight of poulards (table 5).
CONCLUSION
The minimal dose of estrogen which prevented the hypertrophy of the rudimentary right gonad of poulards, ovariectomized 12 to 21 days after hatching, lies above 1 p g and may
be as high as 2 p g ECP (estradiol cyclopentylpropionate)
per 100 gm of body weight per day. The minimal inhibitory
dose of estrogen had no effect upon either pituitary or oviduct
weight.
Pituitaries of poulards were heavier than those of pullets.
The poulards’ pituitary weight was further increased by very
small doses of ECP (0.5 p g or less). Doses of 1 ug E C P and
above decreased the weight of the poulards’ pituitaries t o a
level which did not differ significantly from that of the pullets’.
A definite synergism between androgen and estrogen for the
inhibition of the growth of testicular compensatory gonads of
poulards was shown. The synergistic androgen-estrogen dose
of 1p g E C P plus 3 pg T C P (testosterone cyclopentylpropionate) per 100 gm of body weight per day, failed t o inhibit nontesticular compensatory gonads completely even in the early
stages of proliferation found in poulards killed at 60 days of
age. The inhibitory effect of a physiological dose of estrogen ( 2 p g ECP per day f o r 30 days and discontinued at the
age of 60 days) upon rudiment growth is completely overcome
by the age of 100 days. It was also shown that the size of the
rudiment at 100 days of age is no larger m-hen pullets are
ovariectomized during the third week after hatching than
when the operation i s pcriormed on 45 day old birds. Ovariectomies performed on birds 60 or 75 days of age resulted in
smaller compensatory gonads at the age of 100 days. Regardless of the size of the rudiment at the termination of the experiment, comb growth was greater among untreated poulards
which had been ovariectomized during the third week of life
than in any of the other groups.
H O R M O N E CONTROL O F GOiSADAL EUDIMENT
637
Evidence is presented which suggests that the latent period
from ovariectomy until the onset of androgen secretion by
the compensatory gonad is greatest when the ovary is removed
from the very young bird.
Attempts to stimulate growth of the steroid inhibited rudiincntary gonad of poulards with PMS o r avian pituitary
gonadotropin have failed.
L I T E R A T U R E CITED
BRENEXAN,
W. R.
3945 The gonadotropic activity o f the anterior pituitary of
cockerels. Endocrinology, 36 :190-190.
1955 Reproduction in binls: the female. Mem. Soc. Endocrinology,
4 :94-1 7 0.
DAS, B. C., AND A. V. NALRANDOV1935 Responses of ovaries of immature
chickens to avian and niammaliaii gonadotropins. Endocrinology, 57 :
705-710.
DOMN, L. V. 1927 New experiments on orariotomy and the problem of sex
inversion in the fowl. J. Exp. Zool., 48: 31-173.
H U B L ~J., 1956 Gonadal and hypophyseal interactions on the chondrogencsis in
young fowl. Acta Endocrin., d.3: 101-104.
MILLIGAN,M. 1946 Trichrome stain for formalin fixed tissue. Am. J. Clin. Path.,
10: 184-185.
1954 Endocrine influences on the dcvelopKORNFELD,
W., AND A. V. NALBANDOV
ment of the rudimentary gonad of fowl. Endocrinology, 55: 751-761.
1957 Gonadal effects upon the growth o f pituitary, adrenals, thyroids, oviduct, and comb of immature fowl. Anat. Rec., 128: 419.
TABER,E., AND K. W. SaLLEY 1954 The effects of sex hormones on the development of the right gonad in female fowl. Endocrinology, 54: 415-424.
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