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AGE CHANGES IN THE RAT’S EXORBITAL LACRIMAL GLAND
ROLAND WALKER Biological Laboratory, Rensselaer Polytechnic Institute,
Troy, New Pork
TWELVE FIGURES
INTRODUCTION
Histologically, the rat’s exorbital lacrimal gland shows great discrepancies in nuclear size, with apparently valid size classes corresponding to steps in ploidy; and an age metamorphosis of histological types has been described, but has not previously been followed in any close sequence of ages, nor into extreme old age. This study was undertaken as part of the Wistar project on aging in rats, primarily on account of a personal interest in the nuclear size discrepan- cies. The excellent work of Teir ( ’44) answered many of the original questions ; however, this Wistar series, extending to old age, gave a much clearer picture of the course of senile changes in this gland. There were also some unexpected dif- ferences in aging betx-een males and females, and between al- binos and gray rats.
The exorbital lacrimal gland (= estraorbital, outer orbital, Loewenthal’s gland), in spite of its peculiar position at the
1 This study is part of a cooperative investigation of the aging process in rats, supported by the Samuel S. Fels Fund. It is a pleasure to acknowledge the opportunity offered by this project, whose successful progress was due in large part of the planning of Dr. E. J. Farris, Executive Director of the Wistar Institute, helped by Dr. Eleanor Yeakel and other staff members of the Wistar Institute. I want to thank Dr. Hope Hibbard for taking care of one series of tissues during the wartime diaspora; and especially my wife, Dr. Vivian Trombetta Walker, for the care of another series of tissues, for many measure- ments, and for help with the photography.
49
50 ROLAND WALKER
base of the ear (Greene, '35), is very similar to the intraor- bital (= infraorbital) gland. Both these sero-acinar glands differ markedly from the Harderian glands. Mayer (1894), though he confused this exorbital gland with part of the paro- tid, recognized the irregular presence of giant nuclei and binucleation. Loewenthal (1894, '00) described the nuclear relations of both lacrimal glands, and the presence of alveoli resembling Harderian tissue in the intraorbital gland. That he found no such Harderian alveoli in the exorbital gland may have been due to a limited age series (see the present data).
The less striking discrepancies in nuclear size in the rat liver have been extensively studied. For instance, Jacobj ('25) converted measurements of nuclear diameters to vol- umes with mode a t ratios of 1 : 2 : 4: 8. Beams and King ( '42) and Wilson and Leduc ('48) discussed the origin of this situation. For the rat's exorbital gland Collin and Florentin ( '30a and b) recognized similar volume modes of 1: 2: 4 : 8 ; and double nuclear volumes of 2 : 4 : 8: 16 for the binucleate cells. They found many still larger nuclei, but with shapes too irregular for safe measurement. Binucleate cells gen- erally had nuclei closely matched in size, though often strik- ingly different from those of adjacent cells. Collin and Grujic ('32) found that in vesicular (i.e., Harderian alveolar) parts of the gland there was a single mode of 113 p3 (ca. 6 p diam.) corresponding to the minimal or diploid volume class of the acinar portion.
Teir ('44) extended this study of nuclear size classes in white rats up to 18 months of age. (He calculated nuclear volume as the cube of the diameter instead of by the spheroid formula; but his diameter classes are close to those of Collin et al.) Up to 4 months there was an increasing proportion of nuclei in the upper size classes ; and mitotic activity decreased to rarity after 4 months. He found no evidence for amitosis or cell fusion, interpreting polyploid and binucleate cells as being due to ana- and telophase chromosomal bridges, and
AGING O F RAT LACRIMAL GLAND 51
to apolar pro- or metaphase reconstruction. I n 1949 Teir got similar results on the intraorbital gland. Jarvi and Teir ( ’51) reported no sex difference in nuclear size classes, up to 12 months. They, and Teir ( ’51a, ’51b, ’53), Teir and Sundell ( ’53) , Teir and Pyorala ( ’53), and Helweg-Larsen (mouse liver, ’49) attempted experimental analysis of the develop- ment of size classes, but these experiments were not obviously related to old age, nor to tissue metaplasia.
Likewise, the few studies on physiology are of only oblique interest in the present context. Reports by Loreti and Perron- cito (’38) on the effect of pilocarpine on the exorbital gland (“parotid”), and of Denz (’51) on parathion poisoning, are not concerned with age metaplasia. Derrien and Turchini (,24) noted that when the red-fluorescent Harderian glands mere ablated from young rats (only up to two months old) there was increased red fluorescence of the exorbital gland. Figge (’44) and his coworkers have studied this porphyrin fluorescence of Harderian glands in relation to carcinogenesis, but there are no studies of age-altered exorbital tissues for porphyrin fluorescence o r for other than histological evidence of their Harderian nature.
There seem to be no previous studies on senescence in lacrimal apparatus (two figures from the present work were borrowed by Andrew, ’52). I n Andrew’s (’49) study of parotid glands from this same series of rats, the senile changes at 700 to 1100 days included fatty degeneration of the paren- chyma, the presence of “oncocytes, ” infiltration of the inter- lobular tissue by mast cells, and of the duct tissue by lymphocytes. These are not closely parallel to the senescent changes in exorbital glands.
MATERIALS AND METHODS
From 1941 to 1944 the staff of the Wistar Institute in Phila- tlclphia raised several series of albino rats (Wistar strain) and of gray Norway rats under as favorable conditions as
52 BOLASD WhLKER
possible. These were f o r a cooperative study of age changes, up to extreme old age. Groups of rats were sacrificed at intervals from 21 days (weaning) to 1000 or 1100 days. By the old rule-of-thumb (a day for a rat equivalent to a month for a man) these oldest rats should have been as senile as humaiis a t 84 to 90 years; and the kinds and degree of path- ology observed are in accord with this.
The staff of the Wistar Institute undertook the planning and care of the series of rats, the dissection (after pento- barbital anesthesia), weighing, and fixing of organs. The organs were distributed to various collaborators, who also received duplicated records of autopsy notes and all weight data. 9 forthcoming paper by E. J. Farris will give a fuller statement of procedure at the Wistar Institute.
For the exorbital lacrimal glands, both right and left glands were weighed separately. However, this study is based on the histology of only one gland from each rat (sometimes right, sometimes lef t ) fixed in Bouin’s fluid. After paraffin sectioning at 10 p, duplicate slides were stained with heniat- osylin and eosin, and with Cajal’s trichrome stain (magenta and picro-indigocarmine). Each slide had from 4 to 8 sections from at least two parts of the ribbon. This incomplete sam- pling seemed of no consequence in the younger and middle stages. I n older male albinos, the random distribution of alterations would have left doubt as to the exact proportions in any sampling other than a closely spaced series.
Of the exorbital glands from 123 rats, 96 were from Wistar albinos, both males and females, from 21 days to 1000 days of age. The 27 glands from gray Norway rats included no young ones ; two were from 650-day males, and there were both males and females from 800 to 1100 days. Lacrimal glands mere not saved from 75, 150, or 200-day albinos, nor from 600-day males.
Generally the whole series of hematoxylin-stained sections was studied for each major criterion considered. For mitosis, a mechanical stage was used to search the total area of all the hematoxylin-stained sections. Mitotic counts (from late
AGING O F RAT LACRINAL GLASD 53
prophase to early telophase) were calculated to mitoses per square millimeter after planimeter measurements of 20x pro- jections.
OBSERVATIONS
Growth a.nd mitosis Both body weights and exorbital lacrimal gland weights are
quite variable, the gland weights also varying considcrably between right and left sides. However, the average figures given in table 1 clearly indicate a trend for the albinos (the two 600-day females should be discounted because of path- ology; see below). Whereas the male albinos reach a plateau of body weight before 300 days, the more slowly growing fe- males continue to increase in weight up to 900 days. Seither males nor females shorn a decline in body weight until between 900 and 1000 days.
Tlic exorbital lacrimal glands (table 1) grow only about half as fast as body weight, from 21 days to 100 days, n single gland (left) starting a t about 0.5 mg per gram of body weidit , and ending s t about 0.25 mg/gm. It will be seen, horn-ever, that in both malcs and females the gland weight has about reached its plateau by 100 days, well before the time of maximal body weight. The females maintain this gland weight into cstrenie old age, while in the senile male albinos (700-1000 d a p ) gland weight drops from 64 mg to about 50 mg. It may be noted that this group of males corresponds to those with R consider- able proportion of Harderian alteration in the exorbi tal glands (histological type '' C,
It is probably unsafe to generalize about the gray Sorvay rats, as to body o r gland weight, in view of the small numbers and greater variability.
Though the distribution of mitotic figures in the albinos is also quite variable, it is obvious froin the table that there is much mitotic activity a t 21 days; that it has fallen off sharply by 50 days, and is rare thereafter. The differences between males and females are of doubtful significance ; but i t looks a s though mitosis declines faster in the females. For the senile
right hand column in table 1).
Sum
mar
y of
wei
ghts
, m
itot
ic a
ctiv
ity,
and
his
tolo
gica
l ty
pes
of l
acri
mal
gla
nds
of
all
rats
stu
died
(d
ata
for
the
two
600-
da
y fe
mal
es a
re s
uspe
ct:
one
had
a la
rge
tum
or,
and
path
olog
y w
as n
oted
in
the
lacr
imal
gla
nds
of b
oth)
. S
eria
l nu
mbe
rs a
re n
ot
iefe
rred
to
in
the
tex
t,
but
are
incl
uded
for
tho
se w
ho m
ay w
ish
to c
onsu
lt d
ata
avai
labl
e at
th
e W
ista
r In
stit
ute
on o
ther
org
ans
of
thes
e ra
ts,
or o
n th
e co
ndit
ions
at
auto
psy.
L
acri
mal
gla
nd w
eigh
ts a
re t
he a
vera
ge f
or
the
left
gla
nds
of
the
grou
p re
pres
ente
d.
Mit
oses
wer
e co
unte
d in
the
who
le
of o
ne s
lide
(us
uall
y 4
sect
ions
) fo
r on
e gl
and
(rig
ht o
r le
ft),
an
d di
vide
d by
the
tot
al a
rea
of
thes
e se
ctio
ns.
The
fig
ures
Cod
e fo
r hi
stol
ogic
al
type
s:
A,
the
char
acte
rist
ic
acin
ar
pare
nchy
ma,
whe
ther
im
mat
ure
or w
ith
hete
roge
neou
s nu
clea
r po
pula
tion
; B
, ar
eas
conv
erte
d to
sm
all-
nucl
eate
, di
sorg
aniz
ed
acin
ar,
or t
o ep
ithe
lioi
d ti
ssue
, b
ut
stil
l m
ildl
y ba
soph
ilic
(f
igs.
4,
5) ;
C, ‘
Har
deri
an ’ ’
alve
oli-
smal
l-nu
clea
te,
acid
ophi
l, fi
nely
va
cuol
ate
(fig
s. 8
, 11) ; b
and
c,
tiss
ues
like
B o
r C
are
pres
ent,
bu
t ex
cept
iona
l. F
or t
he l
ast
colu
mn,
‘‘%
T
ype
C (H
arde
rian
),”
no d
irec
t m
easu
rem
ents
wer
e m
ade,
bu
t fo
r ea
ch g
land
the
who
le a
rea
of t
he s
ecti
ons
was
ins
pect
ed,
and
the
perc
enta
ge o
f th
e ar
ea
occu
picd
by
Har
deri
an a
lveo
li w
as c
aref
ully
est
imat
ed b
y tw
o in
depe
nden
t ob
serv
ers.
T
he f
igur
es g
iven
are
the
rang
e of
est
i-
m + $ c’ $ 2
give
n ar
e th
e av
erag
es f
or a
11 r
ats
of e
ach
grou
p.
mat
es f
or
the
indi
vidu
als
of
each
gro
up.
__
F
LEFT E
XO
RB
.
WT. MG
MF
UC
R.
GL
AK
D
hi w
os
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/mn
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DY
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-
AG
E
WT. G
M
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I.41
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F
IS l
J.\Y
S M
F
Mal
e Fe
mal
e
% TYPEC
( HA
RD
ER
IAN
~
w 141
F
Alb
inos
35
14
8.
5 A
0
33
16
12.2
A
0
350
671
351
672
21
379
690
380
691
692
693
695
696
119
38
1.4
A
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1
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Ac
0-
1
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A
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204
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A
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1
320
323
50
163
167
100
349
325
240
232
~
364
63
29
A
bc
0-
5 24
8 70
.0
4 A
0-
1
13
221
16
222
300
24
257
26
303
2G6
304
301
313 98
60
0 in
9
(264
) -0
1 A
b 0
51
.07
AB
C
10-5
0 29
4 68
.0
6 A
c 0-
5
126
736
17
794
700
361
129
737
141
795
392
828
405
832
396
829
406
833
399
830
407
834
400
831
435
835
836
3 76
52
.05
AB
C
318
70
.03
Ac
60
410
10
955
900
90
426
97
956
10-8
0 0- 1
373
453
127
958
398
896
337
977
954
387
978
390
979
443
980
444
991
473
551
166
478
1000
262
47
.01
AB
C
0-70
k-
513
561
204
987
248
67
.02
Abc
0-
5
2 2 51
4 99
9 23
0 10
09
0
Y
rn
Gra
y ra
ts
9036
91
06
650
423
80
.05
Abc
1
F
U
b 43
6 64
.o
Ac
0-
1
Q
340
69
.01
(A)
OR
or
.03
AC
0-
70
2
IOOO
G 49
G
1003
G
1000
404
75
1002
G
9936
10
046
270
63
.01
Abc
0-
5
tJ
8676
86
90
800
8686
89
56
1007
G
656
9946
90
0 40
9 48
.o
AB
0
15 0
F +-
78
.001
(A
) 71
G
995G
29
1 lO
OGG
9966
9980
10
05G
lO
OlG
10
086
52
.o A
BC
0-
50
274
100
.05
Ac
5-10
1
76
5
0
1100
31
4 60
G
40
6
56 ROLAND WALKER
group it should be noted that though mitosis is rare (absent in 11 of 27 males and in 16 of 35 females) it is still present at all ages. Some of these mitotic figures in old rats were clearly polyploid, and a few were tri- or tetrapolar. Mitotic status in the group of senile gray Norway rats is generally similar to that in the senile albinos.
Histological chamges i n male albigzos
One of the most striking results of this study was a recog- nition of clear sex differences, and of differences between albinos and gray Norway rats. Since the pecularities of the exorbital lacrimal gland emphasized in the literature are clear- est in the male albinos, and since the picture of senile change is also clearest in them, it seems well to base the main story on them, and to make comparisons later.
At 21 days the exorbital gland of the male albino (fig. 1) is like many other immature serous tubulo-acinar glands. The acini are small and close-packed. The nuclei are round or oval, small and relatively uniform in size (ca 5-7 p diam., cor- responding to the minimal size class, presumably diploid). The cells are small enough so that the nuclei seem close- packed; thus the general impression of basophilia in the gland is greater than is justified by the mildly basophilic cyto- plasm (i.e., there is still a high K/P ratio). The nuclei are basal in position, though the smallness of the cells makes this less obvious. The 50-day stage is intermediate in character- istics between the 21-day and 100-day stages.
At 100 days the gland has approached maturity and looks quite uniform in acinar structure (figs. 7, 2). The acini have greatly increased in size without any notable increase in cell number. An apparent decrease in nuclear number is due to the smaller proportion of the thickness of an acinus included within the 10 section. There is a good indication of differ- entiation within the cytoplasm. The proximal end is basophilic, and occasionally endoplasmic reticulum (lamellar ergasto- plasm) is visible. The nuclei, though larger, occupy a smaller proportion of the cells; they are now definitely unequal in
AGING OF RAT LACRIMAL GLAND 57
size, and arranged less neatly with respect to the acinus than a t 21 days. There is a great tendency for the nuclei to occur in pairs of matched size; the members of a pair may be in a single binucleate cell (though this is hard to see), or in adja- cent cells. There is a random distribution of nuclei o r of pairs of nuclei of at least three size classes, presumably including octoploids, with a few still larger nuclei.
In 300-day male albinos (fig. 3) the acini have not changed greatly in size, but irregularities have increased. Besides the obvious differences in nuclear size, there are irregularities of nuclear shape. At 100 days almost all the nuclei were round or smoothly oval; now those of the larger size classes may be irregular, lobulated, or occasionally pycnotic. Nuclear vacu- oles or inclusions are commoner than before. The cytoplasm too is less homogeneous, and small vacuoles are not uncommon. Shrinkage of the acinar cells from the stroma, and occasion- ally from each other, is presumably a fixation artifact, but it is characteristic of this age group for the first time. There seems to be a little more cellular infiltration of the connective tissue. In the senile group of male albinos there is much variability
of pattern within a section, and from individual to individual; but no histological criterion has been found to distinguish among the 700-day, 900-day, and 1000-day groups, so they will be considered together. The most striking changes in this group are a greater heterogeneity of histological pattern (fig. 8) and disorganization of acinar structure (figs. 4, 5).
For purposes of classification (table 1) three tissue types have been designated A, B, and C. I n figure 8 the left area, though distorted, is recognizably derivative from the acinar structure of the younger stages, and this principal type is called A. Here the irregularities of nuclei and cytoplasm, noted before, are exaggerated (fig. 4). Giant nuclei may reach 20 p in diameter and there are more and larger nuclear inclu- sions, and nuclear and cytoplasmic vacuoles. The acinar pattern is much deranged.
Both types B and C involve nuclear reversion to the minimal or diploid size, but the cytoplasmic and topographic relations
58 ROLAND WALKER
are different. I n type B (figs. 4, 5) there are segregated patches of close-packed small nuclei in slightly basophilic cyto- plasm ; neither nuclei nor cytoplasm are recognizably different from those of the ducts (which may get included in this classi- fication), but often there is no obvious tubular nor acinar pat- tern-rather the tissue is epithelioid. Small patches of this tissue may be seen among the type A acini in figure 8, but often type B occupies somewhat larger areas of the section. The round nuclei of type B should be easily distinguished from the cellular infiltration of the connective tissue which is common in these senile males (figs. 4, 8).
The so-called Harderian alveoli (type C, right side of fig. 8) are part of the classical description of the exorbital gland of the rat. The rather pale-staining nuclei are of the minimal size class, and the cytoplasm has lost all basophilia. Though eosinophil, the cytoplasm loolis pale because of the finely vacuolar texture. The cells are generally cuboidal, and there is a considerable alveolar lumen, often with cellular debris indicating apocrine or even holocrine activity. The largest type-C alveoli of fig. 8 are exceptional; figure 11 is a more characteristic picture of the Harderian tissue, though it hap- pens to be from a gray rat.
Though the Harderian alveoli are very prominent in these senile males, they are only sparsely distributed in younger stages. I n only two (both 1000-day) of the 27 senile males was there doubt of the presence of Harderian tissue; other- wise it constituted from 10 to 80% of the area (table 1). Such tissue was never observed in 21- or 50-day males; in one 100-day male it was about 1% of the area; and in four of the six 300-day males it was from 1 to 5%. I t should be remarked that in the autopsy notes by dissectors, who were probably not familiar with the expected histological criteria in this gland, there were frequent annotations on the lacrimals of senile male albinos, such as “small, pale;” “very pale, granular ;” “atrophic, granular;” “small, pale tannish;” etc. No such comments were recorded for younger males, nor for any of the albino females (except for one 600-day female; different
AGING O F RAT LACRIMAL GLAND 59
comment-"pathologica17'). Table 1 also shows a definite weight reduction in the exorbital glands of the senile males, which is probably related to this Harderian metaplasia.
Female albinos
As mentioned above, the females grow more gradually, but their exorbital lacrimal glands reach maximum weight by 100 days, and this weight is maintained throughout life. IVlitosis has probably become negligible in effect before 100 days.
At 21 days and 50 days the young exorbital glands are in- distinguishable from those of the males. At 100 days they are still essentially similar to those of males: uniform and well- formed acini of the mature type, with proximal basophilia, and with distinct nuclear size classes.
From here on, the story contrasts sharply with that of the male albinos in the relative absence of old-age changes. At 300 days, the exorbital glands are essentially like those of 100-day females, without exaggeration of the upper size classes, or distortion of nuclear shape, or pycnosis, or fixation shrinkage of the acini. Alterations in the lacrimal glands of the two 600-day females, such as heavy vacuolation (fatty degeneration?) are discounted because of the autopsy notes of general pathological involvement.
Even in the "senile" group of 700 to 1000 days there is remarkably 'little histological indication of senility (figs. 6, 9). I n histological pattern and in nuclear size classes, the closest match in the male series would still be at 100 days. In these old females there is generally little change to types B and C ; Harderian tissue was found in only 4 of 33 rats, and then only to the extent of 14% of the area. (Also at 100 and 300 days individuals were found with minute patches of Harderian tissue.) Perhaps in these old females the acini are not as regularly arranged as at 100 days, and the apical cyto- plasm may be less smooth-textured and somewhat more vacuo- lated. I n a few glands there are moderate patches of strongly vacuolated cells ; or ill-defined areas somewhat resembling type
60 ROLAND WALKER
B ; or greater cellular infiltration of the connective tissue than appears in figures 6 and 9. However, these are exceptional.
The presence of a yellow-brown pigment in some of the parenchymal cells is the one positive, though inconspicuous, characteristic of this group of old females. This pigment is in sharply-defined homogeneous spots : a granule, fleck, or sphe- roid; usually one in a cell, rarely two or more; in any position in the cytoplasm, though most commonly near the nucleus on the apical side. Even a t 1000 days usually not more than 1% of the cells are affected; at 900 days some glands show as few as one to five pigmented cells per 10 fields searched (440 X ) ; and a t 700 days, in 4 of 13 glands pigment was not found in 10 fields. None of this pigment was found in any male albinos, nor in females from 21 to 300 days.
Gray Norway Rats No young gray rats were included in this series. At the
ages represented the lacrimal glands of both male and female gray rats differ markedly from those of the male albinos, and resemble each other (figs. 10, 12) almost more than they resemble those of the old female albinos. In both males and females, the standard acinar tissue is minimally distorted ; cytoplasmic vacuolation, and nuclear vacuolation OF pycnosis are much less common than in even the females of the old albino series. The discrepancies in nuclear volume are less than in 300-day male albinos; also less than in most old female albinos (fig. 6 shows a little less nuclear size discrepancy than the average f o r senile female albinos).
From 650 to 900 days the limited male material shows very little Harderian transformation (type C, table 1). At 900 and 1000 days, however, one male of the two at each age shows much of this transformation (fig. ll), while the other shows none. I n the females there is also late and sparse Harderian metaplasia (5-10% at 1100 days). A few females at 800 and 900 days show an unusually fine-grained vacuolation of acinar tissue ; the apical cytoplasm looks almost like that of Harder-
AGING O F RAT LACRIMAL GLAND 61
ian cells, but neither nuclei nor acinar pattern confirm this resemblance.
The flecks of yellow pigment in the cytoplasm, mentioned as characteristic of old albino females, but not males, are present in about half of this series, about equally in males and females; the amount is decidedly less than in the albino females.
DISCUSSION'
The big surprise in this study was the strong sexual di- morphism of the exorbital lacrimal gland, and of its aging process in the albino rats; this has not been hinted before. Almost equally surprising was the much greater histological uniformity, and lack of sexual dimorphism in the gray Norway rats. I n other words, the extremes of nuclear size discrepancy, of cytoplasmic and nuclear vacuolation, of nuclear pycnosis, and of alteration of acinar pattern, are characteristic of the senile male albinos rather than of the female albinos or the gray rats of either sex. This poses many questions, even on the mere distribution of extreme nuclear variability in various strains of rats, and other species of rodents. And if hormonal control is hinted a t (cf. Helweg-Larsen, '49, on mouse liver), it would seem that sex hormones must play some role in the balance of this part of the aging process. Teir and his col- leagues have been pursuing the mechanisms of nuclear size control in this gland, but mostly in the stages of development to maturity, before the sexual differences have become so pronounced.
The histological picture of transformation of acini to Harderian alveoli was described by Collin and Grujic ( '32). However, there is still doubt as to whether the similarity of these alveoli to those of the true Harderian gland really repre- sents a functional equivalence. I n our series the glands were all in Bouin's fixative and lipids were gone before we formu- lated these questions: Are the contents of the vacuoles lipid? And are these altered alveoli responsible for the red fluo- rescence induced by Derrien and Turchini ( '24) ?
62 ROLAND WALKER
SUMMARY
Exorbital lacrimal glands from 96 albino rats, 21 to 1000 days of age, were studied histologically; also glands froin 27 gray Norway rats, from 650 to 1100 days.
I n albinos the gland reaches a weight plateau (ca. 63 mg for one gland) at 100 days, long before the age of maximal body weight. I n males only there is a decline of gland weight to ca. 50 mg in senescence (700-1000 days).
I n the adult male albinos, the classical description of this “gland of Loewenthal” is confirmed: the gland is composed of acini in which there is a great discrepancy of nuclear size ; this implies a range from diploid to a highly polyploid condi- tion, and nuclei tend to occur in pairs of similar size. With aging there is a transformation of many parts of the gland, with reduction in nuclear and cell size. One characteristically altered type of tissue, spottily distributed through the gland, resembles Harderian alveoli with cuboidal epithelium and small (ca. 6 p) pale nuclei, and finely vesicular acidophil cyto- plasm.
The glands of 21-day male albinos are characteristic of young sero-acinar glands. From 50 to 300 days there is a progressive increase of nuclear size, even more of cytoplasmic volume, and increasing discrepancy in nuclear size. There may be some vacuolation of nucleus or cytoplasm, and there may be small patches of Harderian tissue. I n the senile group of male albinos (700-1000 days) all of these characteristics are exaggerated or more wide-spread.
The glands of old female albinos differ essentially from those of the males in the greater uniformity of the cells: few giant nuclei, and sparseness of vacuolated cells or transformed acini. There is a characteristic though sparse deposit of yel- low pigment in both glandular and stromal cells, increasing from 600 to 1000 days; this is not seen in male albinos.
Both male and female series of old gray rats differ strongly from the male albinos in the much lower degree of nuclear size discrepancy, of nuclear and cytoplasmic vacuolation, and of acinar transformation (though two old males did show a high
AGING OF RAT LACRIMAL GLAITD 63
proportion of Harderian tissue). Both males and females have a little of the yellow pigment found in the albino series only in old females.
The general appearance of the exorbital lacrimal tissue of old gray rats of both sexes, and of the old female albinos, is definitely healthier, less “senile” than that of the old male albinos. Likewise, both in maturity and old age the classical description of the gland fits the male albinos better than the other groups of this series.
LITERATURE CITED
ANDREW, W. 1949 Age changes in the parotid glands of mistar Institute rats with special reference t o the occurrence of oncocytes in senility. Ani. J. Anat., 85: 157-197. - 1952 Cellular changes with age. Charles C Thomas, Springfield, Ill.
BEAMS, H. W., AND R. L. KING The origin of binucleate and large mono- nucleate cells i n the liver of the rat. Anat. Rec., 83: 281-297.
COLLIN, R., AND P. FLORENTIN 1930a Croissance des noyaux en progression g6oni6trique dans la glande de Loewenthal. Compt. rend. acad. sci. (Paris), 191: 444-446.
Nouvelles recherches caryombtriques sur la glande de Loewen. thal. Compt. rend. soc. biol., 104: 1279-1281.
COLLIN, R., AND M. GRUJIC 1932 Caryombtrie cornparbe des deux portions de la glande de Loewenthal. Ibid., 109 : 472-474.
DENZ, F. A. Poisoning by p-nitrophenyl diethyl thiophosphate (E. 605) ; a contribution to the study of anticholinesterase compounds. J. Pathol. Bacteriol., 63: 81-91.
Sur l’accumulation d’une porphyrine dans la glande de Harder des Rongeurs du genre Mus et sur son mode d’excr6tion. Compt. rend. soc. biol., 91 : 637-639.
FARRIS, E. J. 1958 Weight changes with age in the organs of rats; P a r t One- Albino; Pa r t Two-Gray. Am. Anat. Memoirs, No. 21: in press.
FIGGE, F. H. J. 1944 Fluorescence studies on cancer. I. Porphyrin metabolism, Harderian gland fluorescence, and susceptibility to carcinogenic agents. Cancer Res., 4 : 465-471.
GREENE, E. C. Anatomy of the rat. Trans. Am. Phil. Soc., N. S. 27: 1-370. HELWEG-LARSEN, H. F. 1949 Studies on hereditary dwarfism in mice. IX.
Dependence of the nuclear class formation upon the pituitary hormones. Acta Pathol. Microbiol. Scand., 26 : 609-619.
Uber das rhythmische Wachstum der Zellen durch Verdop- plung ihres Volumens. Wilhelm ROUX’ Arch. Entwicklungsmech. Organ., 206: 124-192.
1942
1930b
1951
DERRIBK, E., AND J. TURCHINI 1924
1935
JACOBJ, W. 1925
64 ROLAND WALKER
JARVI, O., AND H. TEIR 1951 Experimental alterations of cell size and mitotic activity in the outer orbital gland of the white rat. 111. The influence of experimental scar tissue inside and around the gland. Acta Pathol. Microbiol. Scand., 29: 401-415.
LOEWENTHAL, N. 1894 Zur Kenntnis der Glandula infraorbitalis einiger Sauge- tiere. Anat. Anz., 10: 123-130.
1900 Driisenstudien. 11. Die G1. infraorbitalis und eine besondere der Parotis anliegende Driise bei der weissen Ratte. Arch. mikroskop. Anat. u. Entwicklungsmech., 56: 535-552.
Ergastoplasma, caratteri nucleari e nucleo- lari, amitosi e mitosi atipiche in parotidi iperattive de Epimys norvegicus (var. albina), Erxl. Z. Zellforsch. u. niikr. Anat., 25: 12-34.
LORETI, F., AND G. PERRONCITO 1938
MAYER, S. 1894 Adenologische Mitteilungen. Anat. Anz., 10 : 177-191. TEIR, H. 1944 Uber Zcllteilung und Kernklassenbildung in der Glandula orbitalis
externa der Ratte. Acta Pathol. Microbiol. Scand., Suppl. 56: 1-185. 1949 On the sizes of the nuclei in the glaiidula infraorbitalis of
the white rat. Ibid., 86: 620-635. 1951a Experimental alterations of cell size and mitotic activity in
the outer orbital gland of the white rat. I. Patho-physiological investi- gations. SOC. Sci. Fennica, Commentationes Biol., 13, N o . 1: 1-32.
1951b Experimental alterations of cell size and mitotic activity in the outer orbital gland of the white rat. 11. Influence of tissue degen- eration in other organs and tissues. Ibid., 13, N o . 6 : 1-16.
Experimental alterations of cell size and mitotic activity in the outer orbital gland of the white rat. VI. Influence of single dose roentgen irradiation. Acta Pathol. Microbiol. Scand., 32 : 337-347.
1953 Expermiental alterations of cell size and mitotic activity in the outer orbital gland of the white rat. VII. Influence of fractioned roentgen irradiation. Ann. Med. Exptl. et Biol. Fenniae,
Experimental alterations of cell size and mitotic activity in the outer orbital gland of the white rat. VIII. Influence of extirpation and of intra-abdominal implantation of outer orbital gland tissue. Acta Pathol. Microbiol. Scand., 3.3 : 492-499.
WILSON, J. W., AND E. H. LEDUC 1948 The occurrence and formation of bi- nucleate and multinucleate cells and polyploid nuclei in the mouse liver. Am. J. Anat., 82: 353-391.
1953
TEIR, H., .4ND K. PYORXLH
32: 103-110. TEIR, H., AND B. SUNDELL 3953
PLATES
All figures a re of the exorbital lncrimal gland of rat, fixed in Bouiii’s fluid, seetioiled at 10 p, and stained with hernstoxylin and eosiii. Figures 1-6 and 10-12 a r e X 400; 7-9 are X 120.
Figures 1-5 are an age series of male albinos, while figure 6 is from an old fcni:~le. Figures 10-12 are from old gray Norway rats. Figures 2 and 4 1i:rve previously :rppe:trcvl :is figure 24, A and B, of Andrew ( ’ 5 2 ) .
P L A T E 1
ESI’LANA‘l’ION OF FIGURES
1
2 A 100-day male albino, X 400. Cliaracteristic exorbital 1:icrini:iI gI:t~id. Acini are larger, cells have inore proxinial basopliilia, ant1 the nuclei arc of iliffercwt sizes, usually paired as to size in one cell or in :icljaccwt cclls.
A 21-d;iy ni:ilc albiiio, x 400. Cli;ir:ictcristic juvenile aciiiar glnnd.
3 A 300-day ~riale albino, X 400. Es;iggeratecl difference bctwceii iiuclci, atitl Slirilikage of xciiiar cells f rom coiinectivc larger oiitis with irregular sh:tpe.
tissuc is c1i:ir:icteristic of tlic sections ill this group.
A 700-day male albino, X 400. Still further ii.rcgulnrity in iiiwlear size and shape, in aciiiar pattern and aciuar cells; cytop1:isn:ic vaeuole~, :iiirl iiue1c:i~ vacuolcs or inelusioiis. Patelies of small-iiucleatr epitlielioid tissue (typc R).
5 A 100O-d:ty male albino, X 400. Siiiiikir yitterii. The greater proportion of small-iiucleate, type B tissue is not necessarily c1i:iiacte~istic of this age. The 700- to 1000-day mnle albiiios arc alike iii aii irregiilar t1istril)utiou of tliesr types, and of “Harderian” tissue ( type C ; compnrc figs. 8, 11).
A 700-day female albino, X 400. The aciii:ir patterii :iii(l nnclear classes are more nearly comparable to tliosc of :I. 100-il;iy i i i n l c ~ tli:Iii to those of niiy older iii;tle alhiiio group.
4
6
AGING OF RAT LACRIMAL GLAND R O L A N D W A L K E R
PLATE 1
1’LBTE 2
ESPL.%NhTION OF FIGURES
7 A 100-d;iy inale albiiio, X 120. C1i;n:ictc~ristic ni:lttil’c glalid
8 A iOCI-day male albino, X 120. Reside t h e distorted acinnr tissue ( type A ) , witli small scattered p t c h r s of type B, a i d some cellular infi1tr:Ltioli of tlrc’ co~inective tissue, there is a n area of siir;~ll-~iuclcnte, ac~iclopliil, ‘ ‘ Harderian ’ ’ alveoli (type C) . A 900-day feiriale albino, x 120. Kelxtivc uniforniitg of Iiisto1ogic:ll p t t c r n as compared with old male albinos.
9
10 A 1000-day m i l e gray Norway ra t , x 400. Re1:itively uniform histology :IS
coiiipared with old albi~ios.
A 2000-day iiiale gray h-orway rat, x 400. A fivltl sclcxcted to sliow clr:ir:ictcir- istic “ Hartleriaii” alveoli ( type C) . Tlir cytoplasm of type-i2 nciilar crlls is inore vacuolateil than iii fig. 10, bu t these tv.3 are within the raligr of vari:ibility. Type I3 altrratioii is rare in tlic gray rats.
A 1000-d:iy female gray Nor~vny rat, x 400. Not sliarply diffcreiitiablc froii i
old nialr gray (fig. l o ) , nor from old fcnialc allliiio (fig. 1;) ; c>oiitr:~sts strongly witli old iriale albinos (figs. 4, 5).
iYwlc:~r size iliffvre~ices are not, estreinc.
11
12
69
