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The hormonal basis for pubertal maturation of hair in the albino rat.

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The Hormonal Basis for Pubertal Maturation of
Hair in the Albino Rat‘
EDWARD G. RENNELS AND WILLIAM P. CALLAHAN2
Department of Anatomy, University of Texas, Medical Branch,
Galveston, Texas
In the classical paper by P. E. Smith
(’30) on the effects of hypophysectomy
and replacement therapy in the rat, it was
pointed out that hypophysectomy of young
animals results in a retention of the
“puppy” or infantile type hair. He also
observed that replacement therapy by
means of daily pituitary implants was an
effective means of bringing about a maturation of the coat to the adult type. Since
that time many studies have been made of
the biology of hair growth in the rat, but
such studies do not yet include a careful
analysis of the hair maturation process
and the factors which influence it. This is
the subject of the present communication.
The coat of the adult rat contains two
types of hair; fine underhairs of small
caliber and large, coarse, overhairs or
guard hairs. When animals are hypophysectomized prior to puberty, they retain
the infantile type hair which becomes long,
fine and silky. In such animals most of
the hairs are of very small diameter and
the guard hairs typical of the normal adult
animal are much reduced in number; those
which are present are much smaller than
in the normal coat. An additional feature
characteristic of the hair of the hypophysectomized rat is the higher density of the
hair per unit area of skin surface. These
features make it easy to distinguish infantile from adult hair. Since, in the normal
animal, the transition in hair texture occurs at about the time of puberty we have
referred to this process as pubertal hair
maturation (Rennels, Sanders and Callahan, ’58; Rennels, ’58, ’59). This term
seems appropriate but it should be emphasized that the phenomenon is in no way
dependent on the presence of the gonads.
This fact was shown a number of years
ago by Butcher (’35) who also described
the essential features of the cyclical nature
of hair growth in the rat. A few facts concerning the normal hair cycle in the rat
will aid in understanding the presentation
which follows.
According to Fraser (’28) the first coat
of hair begins to be visible during the
second day after birth when the hair erupts
uniformly over the entire body. Each cycle
consists of a growing period which is followed by a resting period of approximately
equal duration. During the resting period
the hair is retained in the follicle as a
“club” hair. According to Butcher (’35)
each complete cycle in the rat lasts for
about 35 days. The second and later cycles
differ from the first in that they occur as
waves of hair growth which begin ventrally
and spread to the dorsal midline in accordance with a definite pattern. Such patterns
have been studied by Haddow and Rudall
(’45) by the injection of an alloxazine
derivative which is taken up by the growing hair and dyes them yellow. More recently they have been studied in great detail by Johnson (’58) who analyzed not
only the patterns of growth but a number
of other parameters of hair growth in rats.
Suffice it to say that an adequate description of hair growth has already been made.
In addition, there is an extensive literature
dealing with the effects of various hormones on hair growth which has recently
been reviewed (Mohn, ’58). Many factors
have been shown to alter hair growth and
it seems probable that the normal control
of this total process is conditioned by multiple hormonal, nutritional, genetic and
environmental factors. We wish to con1 This study was supported by research grant
RG-4723 from the U. S. Public Health Service.
2 Present address:
Department of Anatomy,
Hahnemann Medical College.
21
22
EDWARD G. RENNELS AND WILLIAM P. CALLAHAN
sider at this time only those factors which
have to do with the pubertal maturation of
hair in the rat. As will be demonstrated,
this change in the texture of the coat appears to have a simple hormonal basis and
to be directly dependent on the presence
of a sufficient level of pituitary luteotrophin.
MATERIAL AND METHODS
All of the animals studied were rats of
the Holtzman strain. The normal pubertal
maturation process was investigated in
more detail in the female, in which preparations were obtained from two animals
at each of the following ages: 30, 60, 90,
120, 150 and 180 days. It was observed
that the maturation process was completed
between the ages of 30 and 90 days. Subsequently, a large number of hypophysectomized animals were observed during a
treatment period which extended from the
6th to the 12th or in some experiments to
the 14th week of life. Much of this experimental material was especially designed
for an analysis of the hormonal factors
affecting sebaceous glands and many of
the details of the experiments not considered relevant to the subject of hair
maturation will be omitted from this presentation. The hormones injected, either
singly or in various combinations, during
this period of time were as follows : Luteotrophin (Squibb Luteotrophin and Armour
Panlitar Lactogenic Hormone3), ACTH
(Armour ACTHAR), Growth Hormone
(Armour Somar,3 Armour Growth Hormone lot no. R285128 and Parke Davis
Antuitrin Growth), Estradiol, ProgesterTestosterone Propionate and Cortisone.
In addition to the hypophysectomized,
hormone-treated series, observations were
also made on hypophysectomized animals
bearing pituitary autografts or homografts
in the renal capsule. Again, these animals
were operated on at 6 weeks of age and
observed for a 6 or 8-week period following
the operation. Our initial interest in this
problem was aroused when it was observed
that young hypophysectomized animals
bearing pituitary autografts developed the
typical adult type pelage in a normal manner. We then studied a small number of
animals of both sexes in which the pitui-
tary was left intact but from which the
thyroid, adrenal glands and gonads were
extirpated.
All of the animals were maintained in
air-conditioned quarters and fed a diet of
laboratory chow. Hypophysectomized animals were given 5% sucrose solution to
drink and their diet was supplemented with
lettuce and carrots. The hypophysectomies
were performed in our laboratory under
ether anesthesia and by the standard parapharyngeal approach. When the anterior
lobe of the pituitary was transplanted to
the kidney it was placed briefly in sterile
saline after being removed by suction from
its location in the sella turcica. In doing
the pituitary homograft operations littermate animals were used and they were
operated on by pairs with the anterior
lobes being reciprocally exchanged.
Previous studies of pituitary grafts
(Sanders and Rennels, '57, '59) formed a
basis for our evaluation of the completeness of all hypophysectomies and viability
of the pituitary autografts and homografts.
In any case where pituitary tissue was
found in the sella at autopsy this tissue was
fixed and studied cytologically. This information was then correlated with the
body growth curve, weight of endocrines
and condition of the animal's hair. In all
experiments the animals were weighed and
observed at weekly intervals and at autopsy
all endocrine glands known to reflect pituitary function were weighed. In some cases
these organs were also examined histologically.
During the course of this study, weekly
observations were made on the texture of
the hair. In certain cases one of us, or a
third party, would evaluate the hair texture
of the animals without knowledge of the
group to which the various animals belonged. In such cases it was usually easy
to classify the hair as belonging to one of
three categories : ( 1 ) very fine or infantile,
( 2 ) coarse of adult, or ( 3 ) intermediate.
In some experiments a small sample of
hair from the mid-sacral region of each
3These preparations were gifts from the
Endocrinology Study Section, National Institutes
of Health.
Crystalline progesterone was kindly supplied
by Dr. D. A. McGinty of the Research Department
of Parke Davis and C o .
HAIR MATURATION IN T H E RAT
23
animal which is of small caliber but stays
relatively short.
Besides these differences which concern
the nature of the hair follicles there are
other factors which may modify the subjective “feel” of an animal‘s coat. Differences in the density and thickness of the
dermis as well as differences in tonus of
the underlying musculature may modify
one’s subjective evaluation of what we call
hair texture. In this connection it has been
our consistent observation that the dermis
of the hypophysectomized animal is reduced in thickness and collagen content
and that the muscular tonus of such animals is poor. It should be mentioned that
certain of the hormone treatments not only
affected the hair follicles but also caused
changes in the dermis and body musculature.
The various experimental groups which
OBSERVATIONS
will now be considered are summarized in
The difference between the hair coat of table 1. For purposes of simplification only
an intact animal and one which has been those experimental groups given pituitary
hypophysectomized prior to puberty is in- hormone preparations or bearing pituitary
deed striking. This distinction is very grafts are listed. In other preliminary exmarked by the 6th post-operative week periments groups of hypophysectomized
when hypophysectomy is performed on animals were given adrenal or gonadal
6-week-old animals. Consequently, we hormones and the possibility of any of
may say that the pubertal maturation these steroid hormones being responsible
process involves primarily the second for hair maturation was eliminated. Both
wave of hair growth which forms the estrogens and androgens cause some alterthird coat. According to Johnson (’58) ation in hair texture and do, in fact, acthis growth wave begins at about 8Y2 count for the familiar sex difference; the
weeks in male and at about 9 weeks hair of males being normally somewhat
in female rats. This is similar to our coarser than that of females. This gonadal
own observations made by clipping the influence is superimposed on and comentire dorsal surface of the body during pletely unrelated to the pubertal maturathe resting phase of the second cycle. The tion process. It need not, therefore, condifference between infantile and adult type cern us further at this time.
In studies of pituitary autografts to the
hair can be demonstrated readily by reference to sections of skin cut parallel to the renal capsule we first noted that a pituitary
surface (figs. 3 , 4). It is much less appar- graft was capable of bringing about a norent when the more usual type preparation mal pubertal maturation of hair in both
of skin sections are examined (figs. 1, 2). male and female rats (fig. 5). Our evaluaDifferences in the diameter and density of tion of the cytology and functional capacity
the hairs are quite striking as well as the of such grafts (Sanders and Rennels, ’57,
differences in the prominence of guard ’59) confirmed the earlier studies of
hairs. Another factor which contributes to Desclin (’50) and Everett (’54) to the
the difference between infantile and adult effect that such grafts are capable of the
type hair is that of hair length. The hair secretion of appreciable amounts of luteoof the hypophysectomized animal grows to trophin. We found no evidence for the
a greater length than that of the intact ani- secretion of follicle stimulating hormone
mal. In this respect it differs also from (FSH), luteinizing hormone (LH) or thythat of the infantile hair of the prepubertal roid stimulating hormone (TSH) in ani-
animal was plucked at weekly intervals
and mounted whole on a glass slide.
At the termination of the several experiments, the animals were killed by decapitation. The hair over the dorsum was
closely clipped and a rectangular piece of
skin about 1%” X 3” was removed, attached to an index card to prevent shrinkage, and fixed in 10% formalin. Whole
mount preparations in which the sebum
within the sebaceous glands was stained
with oil blue N were prepared from this
material. In addition, areas of skin were
embedded in paraffin and cut serially for
routine hematoxylin and eosin preparations. Usually these sections were cut in a
plane parallel to the long axis of the hair
follicles, but in certain cases serial sections
were also prepared in the plane parallel to
the skin surface.
24
EDWARD G. RENNELS AND WILLIAM P. CALLAHAN
TABLE 1
Type animal
Hormone treatment
No.
Sex
Hair texture
Intact control
Intact control
Hypex. control
Hypex. control
Hypex. autograft
Hypex. autograft
Hypex. homograft
Hypex. homograft
Hypex.
None
None
None
None
None
None
None
None
5 I.U.LTH'
14
5
F
M
F
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
Hypex.
25 I.U. LTH'
40 I.U. LTHZ
50 I.U. LTH3
50 I.U. LTH3 -I- 1 R.U. STH4
50 I.U. LTH3 4 I.U. ACTH5
50 I.U. LTH3 f 1 R.U. STH4
4 I.U. ACTH5
0.5 m e STH7
0.5 mg STH7
1 R.U.STH4
1 R.U.STH4
1mg STH6
4 T.U. ACTH5
Mature
Mature
Infantile
Infantile
Mature
Mature
Mature
Mature
Intermediate
to mature
Mature
Mature
Mature
Mature
Mature
~~
+
+
+
+
23
9
10
13
9
9
7
+
+
M
F
M
F
M
F
7
4
5
4
4
F
F
F
F
F
5
5
5
5
5
5
5
F
F
M
M
F
F
F
Mature
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Infantile
1 Some of the animals in this group received Squibb Luteotrophin, the
others Armour Panlitar
Lactogenic Hormone.
2 Armour Panlitar Lactogenic Hormone.
3 Squibb Luteotrophin.
4 Parke Davis and Co. Antuitrin Growth.
Armour ACTHAR.
6Armour Lot no. R285128.
7 Armour Somar Somatotropin Lot no. R50109.
mals which were operated on just prior to
puberty. The fact that luteotrophin is the
chief secretory product of such grafts led
us to suspect that this hormone might be
involved in the production of pubertal hair
maturation. The possibility that small
amounts of growth hormone or somatotrophin (STH) and adrenocorticotrophin
(ACTH) might also be involved was considered. The fact that hair maturation in
intact animals or in animals bearing pituitary autografts did not depend on the presence of adrenals, gonads or thyroid was
established by appropriate extirpation experiments (Rennels, Sanders and Callahan, '57). In view of these facts it became
clear that hair maturation was the direct
result of some pituitary hormone or hormones which were produced by either the
intact or transplanted gland.
We have found in experiments with
hypophysectomized rats that if hair
maturation occurs there is invariably
some remnant of anterior lobe tissue
present in the sella at autopsy. In
some cases hair maturation has been
observed in animals which failed to
grow over a period of several weeks
after hypophysectomy. Always in such
cases a pituitary fragment has been found,
although in some instances the fragments
have been extremely small. A skin section
from one such animal is shown in figure 6.
In such cases we must assume that the
pituitary fragment is incapable of secreting
somatotrophin at a level necessary for promoting body growth, although it is still
capable of effecting hair maturation.
In the series of animals in which pituitary exchange homografts were made it
was found in all cases that a normal maturation of the hair occurred. It should be
pointed out again that littermate pairs
were used in all of these operations. The
growth of these animals following the
operation was comparable to that of the
animals bearing pituitary autografts. Furthermore, the sex of the donor animal did
not appear to have any effect on the capacity of the pituitary graft to induce hair
maturation. As shown in table 1, all animals bearing either pituitary autografts or
HAIR MATURATION IN TH E RAT
homografts developed adult type hair
which could not be distinguished from that
of the animals with an intact pituitary
gland.
In the hormone-injected series of hypophysectomized animals it was found that
only luteotrophin was effective in producing a complete hair maturation (figs. 7
and 8). This effect could be seen in some
animals at dose levels as low at 5 I.U. per
day when the treatment was extended over
a 6-week period (fig. 7). In most animals
at this dosage however, the maturation
was incomplete and the hair was evaluated
as intermediate in type. At this dosage
level of the Amour Panlitar preparation
the estimated content of somatotrophin in
the daily dose would be approximately
0.3 clg of a highly purified bovine growth
hormone standard. While it is not possible
to give a comparable estimate of the contamination of Luteotrophin Squibb with
growth hormone it can be stated that
no evidence of any growth hormone
contamination was seen in the hypophysectomized animals which received
our highest dose level (50 I.U./day)
of this preparation. In contrast, the
Armour preparation did cause a sigmficant growth of the animals at a daily dosage of 25 and 40 I.U.
In the series of hypophysectomized female rats which were given combinations
of luteotrophin, adrenocorticotrophin and
somatotrophin (table 1) it will be observed that the only hormone treatment
common to all groups was luteotrophin.
All of these animals showed a mature type
hair beginning at about 4 or 5 weeks following the start of the injections. No
evidence of any inhibitory or potentiating
effects due to simultaneous injection of
ACTH or growth hormone along with luteotrophin was detected.
It should be made clear at this time
that we have made no attempt to study
the effects which the various hormone
treatments may have in modifying the
hair cycle. In many cases it became
obvious that the hair cycle was disturbed by the hormones injected. It
should be kept in mind that the cycle is
profoundly altered by hypophysectomy
alone and many hormones are known to
affect it in various ways (Mohn, '58). At
25
the same time it seems certain that the
disturbance in cyclical growth which follows hypophysectomy is not the direct
cause of the retention of the infantile type
hair in such animals. We have observed
that hypophysectomy performed after the
animal has a mature coat does not result
in a regression of the hair to the infantile
type. This indicates that hair maturation
is dependent not only on the proper endocrine state but that age factors are also
important. It also indicates that once the
maturation process is completed the mature coat will be retained in the absence of
all pituitary hormones and even in the
presence of a disturbance in the cyclical
growth of hair.
The injections of ACTH failed to bring
about hair maturation in the hypophysectomized animals (fig. 9). The adrenal
glands of these animals were markedly
stimulated and one must assume that increased adrenocortical secretion would produce inhibitory effects on hair growth.
Such effects of ACTH on the growth of
hair in hypophysectomized rats have been
demonstrated by Houssay, Penhos and
Foglia ('55). In view of such recognized
effects of adrenal hormones on hair growth
it is especially noteworthy that the ACTHtreated animals all possessed hair of the
infantile type. This again emphasizes the
point that many factors which influence
hair growth are completely without effect
on the pubertal maturation process.
Finally, we observed that growth hormone produces a definite change in the
quality of the hair but that it seems incapable of bringing about a complete maturation to adult type (fig. 10). We have used
three different preparations of growth hormone and while they have all caused a
considerable coarsening of the hair we feel
that this is a reflection of the general or
non-specific growth promoting effects of
the hormone. It seems doubtful that the
similar effects of these three preparations
on hair size is due to a contamination with
luteotrophin although this possibility
should be kept in mind. At the dosage
used of the Amour Somar preparation the
estimated level of contamination with
luteotrophin would be less than 0.1 I.U.
per day. On the basis of our experiments
with a daily dose of 5 I.U. of luteotrophin
26
EDWARD G. RENNELS AND WILLIAM P. CALLAHAN
we would not anticipate an effect from a ently based on a very limited experience
dose of less than 0.1 I.U. It is also worth with a low dosage of the hormone given
noting that in all cases the dosage of to intact animals. Aside from these ingrowth hormone administered was suffi- conclusive experiments, it appears that no
cient to produce a body weight gain com- other study of the action of luteotrophin on
parable to that of intact animals. Conse- the pelage has been made.
All of our findings point to the fact that
quently, if growth hormone were primarily
responsible for hair maturation one might pituitary luteotrophin is directly responsexpect such a dosage over a 6-week period ible for the pubertal maturation of hair in
to produce a fully mature type hair and the rat. This can be demonstrated by
means of pituitary grafts when endogenous
this was never seen.
hormone is responsible. In this case it is
DISCUSSION AND CONCLUSIONS
not possible to eliminate the involvement
Only a few investigators have made any of growth hormone since such animals
attempt to determine which pituitary hor- show a limited growth for a period of
mone is responsible for hair maturation in about three weeks following the operation.
the rat. An early report by Thompson and However, hair maturation can be comGaiser ( ’ 3 2 ) that a “growth extract” caused pleted in hypophysectomized rats in the
the hypophysectomized rat to develop a absence of body growth by the daily innormal coat should probably by discounted jection of highly purified preparations of
since the preparation they used was un- luteotrophin. The possibility that ACTH
doubtedly very crude as judged by present might also be involved was eliminated by
day standards. In another early study the demonstration that ACTH given to hySnow and Whitehead (’35) used male rats pophysectomized animals fails to cause
and compared untreated, hypophysecto- a maturation of hair. Also, it was found
mized animals with others which were in- that purified preparations of growth horjected with a growth hormone extract mone caused a definite enlargement of the
(phyone) for 51 days. Although they hair follicles without producing a fully
tested no other hormones they suggested mature type coat. Companion studies of
that this preparation caused a ‘‘specific the sebaceous glands (Callahan, ’58) instimulation of the hair follicles.” Unfortu- dicate that luteotrophin is also involved in
nately, we have no information concern- the control of these associated glands.
ing the state of purity of the preparation Such a role for luteotrophin is not surpristhey used. It is quite possible that it was ing in view of its recognized action in
contaminated with luteotrophin to an ex- stimulating the mammary glands, specialtent that would affect the hair. On the ized glands of the skin. Thus, while many
other hand, there is no denying that the hormones have been shown capable of
three preparations of growth hormone modifying the process of hair growth it
which we used all caused a considerable now appears clear that pituitary luteotroenlargement of the hair follicIes. How- phin is chiefly, if not entirely, responsible
ever, we see no reason to attribute this for bringing about the transition from ineffect to a specific “pilotrophic” action, in- fantile to adult type hair.
asmuch as this hormone results in a genSUMMARY
eralized growth of the whole animal.
In
the
rat,
maturation
of the hair to the
In his recent review of the effects of
hormones on hair growth Mohn (’58) con- adult type is under pituitary control. Excludes that growth hormone is responsible periments are described which demonstrate
for changing the hair to the adult type. that this effect is not mediated through any
His basis for this conclusion is certainly of the dependent endocrine glands. Pituinot clear since he seems not to have given tary autografts or homografts to the kidthis hormone to prepubertal, hypophysec- ney capsule are capable of effecting hair
tomized animals. He also states that the maturation. Such grafts are known to
quality of the pelage is not affected by in- secrete luteotrophin but may also secrete
jections of luteotrophin. This statement small amounts of growth hormone and
also seems unwarranted since it is appar- ACTH.
HAIR MATURATION IN THE RAT
Purified preparations of luteotrophin,
growth hormone and ACTH were given
daily for a 6-8 week period to animals
which were hypophysectomized at 6 weeks
of age. In such animals without treatment
the hair remains infantile in type. The
results show that only luteotrophin is capable of effecting a complete maturation of
hair in the hypophysectomized animal.
Growth hormone exerts definite stimulatory effects on the hair follicles but these
appear to be non-specific in nature. No
effect of ACTH on the maturation process
could be detected. It appears, therefore,
that pituitary luteotrophin is the hormone
chiefly responsible for pubertal hair maturation in the rat.
LITERATURE CITED
Butcher, E. 0. 1935 The hair cycles in the
albino rat. Anat. Rec., 61: 5-20.
Callahan, W. P. 1958 The morphology of
sebaceous glands of the rat as influenced by
certain hormonal factors. Ph.D. Diss., University of Texas Medical Branch.
Desclin, L. 1950 A propos du mechanisme
d'action des oestrogbes sur le lobe antbrieur
de l'hypophyse chez le rat. Ann. Endocrinol.,
11: 656-659.
Everett, J. W. 1954 Luteotrophic function of
autografts of the rat hypophysis. Endocrinology, 54: 685-690.
Fraser, D. A. 1928 The development of the skin
of the back of the albino rat until the eruption
of the first hairs. Anat. Rec., 38: 203-223.
27
Haddow, A., and K. M. Rudall 1945 Artificial
coat coloration and the growth of hair. Endeavor, 4: 141-147.
Houssay, A. G., J. C. Penhos and V. G. Foglia
1955 Hipofisis y crecimiento del pel0 en la
rata blanca. Rev. SOC.Argent. Biol., 32: 7-21.
Johnson, E. 1958 Quantitative studies of hair
growth in the albino rat. I. Normal males and
females. J. Endocrinol., 16: 337-350.
Mohn, M. P. 1958 The effects of different
hormonal states on the growth of hair in rats.
In: The Biology of Hair Growth. Academic
Press, Inc., New York.
Rennels, E. G. 1958 The dependence of hair
maturation in the rat on luteotrophin. Anat.
Rec., 130: 363 (abstract).
1959 Further evidence concerning the
role of pituitary luteotrophin in the maturation
of hair in the rat. Ibid., 133: 328. (abstract).
Rennels, E. G., A. Sanders and W. P. Callahan
1957 An effect of pituitary autografts o n hair
maturation in the rat. Ibid., 127: 443
(abstract).
Sanders, A,, and E. G. Rennels 1957 The cytology and functional capacity of the rat pituitary
gland after autotransplantation. Ibid., 127:
360 (abstract).
1959 Evidence on the cellular source
of luteotrophin derived from a study of rat
pituitary autografts. Z.Zellforsch, 49: 263-274.
Smith, P. E. 1930 Hypophysectomy and a replacement therapy in the rat. Am. J. Anat.,
45: 205-273.
Snow, J. S., and R. W. Whitehead 1935 Relationship of the hypophysis to hair growth in
the albino rat. Endocrinology, 19: 88-96.
Thompson, K. W., and D. W. Gaiser 1932 The
effect of diet and pituitary growth-hormone on
hypophysectomized rats. Yale J. Biol. Med., 4:
677-690.
PLATE 1
EXPLANATION OF FIGURES
All figures are photomicrographs of 6 p paraffin sections of skin stained with hematoxylin
and eosin.
Skin of normal female rat killed at 12 weeks of age. Note the large guard hairs in the
center of the field. x 37.
Skin of hypophysectomized female rat. This animal was operated on at 6 weeks of age
and killed at an age of 12 weeks. The section is slightly oblique to the long axis of the
hair follicles but the smaller caliber of the hair can be seen. x 37.
This section is from the same block as figure 1 but cut parallel to the skin surface at a
level just deep to the sebaceous glands. Note the regular distribution pattern of the larger
guard hairs. x 55.
Section comparable to figure 3, taken from same block as figure 2. Compare with figure
3 for differences in size and number of hair follicles. X 55.
28
HAIR MATURATION IN THE RAT
Edward G. Rennels and William P. Callahan
PLATE 1
29
PLATE 2
EXPLANATION O F FIGURES
Figures 5-10 represent skin sections cut in the plane parallel to the skin surface at a
comparable level in the dermis. All are at the same magnification.
30
5
Skin section from a 14-week old female rat. At 6 weeks of age the pituitary gland was
removed and placed in the kidney capsule as a n autograft. The hair is of the adult type.
x 55.
6
Skin section from a 14-week-old femaIe rat. This animal was hypophysectomized a t 6
weeks of age but a minute fragment of anterior lobe tissue was found in the sella at
autopsy. The pattern of hair follicles is typical of the adult type. x 55.
7
Skin section from a 12-week-old female rat. Hypophysectomy at 6 weeks was followed
by the daily injection of 5 I.U. of Luteotrophin (Squibb). This caused a complete
maturation of hair. X 55.
8
Skin section from a 12-week-old female rat. Hypophysectomy at 6 weeks was followed
by the daily injection of 40 I.U.Armour Panlitar Lactogenic Hormone. The hair is of
the adult type. x 55.
9
Skin section from a 12-week-old female rat. Hypophysectomy at 6 weeks was followed
by the daily injection of 4 I.U.Armour ACTHAR. The pattern of hair follicles is typical
of infantile type hair. x 55.
10
Skin section from a 12-week-old female rat. Hypophysectomy at 6 weeks was followed
by the daily injection of 1 mg of growth hormone (Armour lot no. 285128). Compare
with sections of skin from animals with infantile (fig. 9) and adult (figs. 5-8) type
hair. This represents hair of intermediate type. x 55.
HAIR MATURATION I N THE RAT
Edward G . Rennels and William P. Callahan
PLATE 2
31
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albina, basic, maturation, hormonal, rat, pubertal, hair
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