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Effect of inanition upon the growth of the brain of the albino rat.

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EE'FECT O F INANITION UPON THE GlZOWTH O F
THE BRAIN OF THE ALHINO BAT'
DAVID XUDIN
Department of Aiiafont:y, Uniwrszty of MtnnesotcL
T W O FIGURES
That the brain of the newborn and very young animal has n
remarkable capacity lo resist the ravages of inanition has
been shown by various investigators (Hatai, '04, '08 ; Jackson,
'15 a and h, '25, '29, '32; Sicmart, '16, '18 a, '19; Sugita, '17,
'18, '19). Altliough the methods employcd in thesc experiments have differed, the results uniformly show lhat tho
brain as well as certain otiier tissues (testes, suprareiials,
skeleton) eoiitinues to grow while the rcst of the body remains
at a standstill or diminislies. This leads t o a marlrcd disproportion in size of various members of the boclp.
Within the brain proper the various componeiits show a
differential giwm-th rate. Stewart ( '18 b ) has arrxiged ilie
various portions of the brain in order of growth capacity ils
follows: 1) cerebclium; 2) olfactory bulbs; 3) cerebrum; 4)
brain stem. Sugita ('17, '18, '19) paid particular attention
to thc cerebral cortex iii normal development and during
inanition, the latter beginning imiiiediatcly after birth. His
results also showed tliat the cerchrnl cortex grows t o a considerable extent regardless of the inanition. Efc computed -the
volume of the cortex by meails of n formula (Magita, '17, '18)
bawd 011 the sagittal aiid frontal diameters of the cwcbral
hemispheres and thc thickness of the cortex, rather than by
tlic more direct method employed here. 'l'hrough the kindness of Doctor Jacksoii, who has receiitly restudied the problem of inanition iii the newborii albino rat (Jackson, '3%),a
175
T f l E ANATOhfICdL PECOEU, VOI..
G3, NO. 2
176
DAVID RUDIN
larger series of brains has been made available than before.
In addition, this material registers the effect of a more severe
inanition than has ever been imposed on such young animals.
Finally observations have been extended to include the effect
of inanition upon the growth of the cerebellar cortex and
Purkinje cells.
MATERIALS AND METHODS
The material consisted of 48 r a t brains comprisl'ng 15
brains from newborn litter mate controls, desig.nated as 'initial controls'; 16 brains from experimental or test rats maintained at birth weight from 1 2 to 16 days ; and 17 brains from
rats 12 to 16 days old that had been allowed to feed normally,
the so-called ' age controls. ' The maintenance at birth weight
was effected by diminished nursing periods. These induced
a severe degree of inanition which held the weight within
1 gm. plus or minus of the birth weight. The brains were
obtained from the chloroformed animals within half an hour
after death. I n order to prevent evaporation the fresh tissues
were weighed in a moist chamber. They were then fixed in 10
per cent formalin; dehydrated for 24 hours each in 50, 60, 70,
80, 90, 95 per cent, and absolute alcohol; cleared in chloroform; passed through a mixture of chloroform and paraffin
and through soft paraffin; blocked in harder paraffin (54")
and cut at 10 v. Every tenth section was mounted, carefully
spread, and stained with hematoxylin and eosin. Each stained
section was projected onto paper of uiiiform thickness a t a
magnification of 20 diameters (a surface area X 400). The
entire brain and the outer shell of gray matter, including the
olfactory bulbs, were carefully traced with a hard pencil.
Wherever the cerebellar cortex was perfectly preserved it
was also traced, but unfortunately many sections had minor
defects which, while not sufficient to modify the brain weight
as a whole, were serious enough to affect the estimated
volume of the cerebellar cortex itself, due t o the small size
of this part. The cerebral and cerebellar cortical areas were
then cut out with scissors and both parts weighed in order
I N A N I T I O N A N D G R O W T H O F RAT BRAIN
177
to ascertain the ratio of the volume of the cortex to that of
the entire brain. Knowing the fresh weight of the brain the
absolute weight of the cortex could then be calculated.
By means of a camera lucida 100 large ganglion cells from
the cortical ganglionic layer of the cerebral cortex were projected and drawn as closely togcther as possible onto strips
100 Cells from Cerebral Cortex of Normal Rat Two Wecks Old
Area = 123 0 sq c m
Area = 1010 sq c n
100 Cells from
Newborn Rat
Fig. I Rnniple area occupied by 100 ganglion ceIIs i n each of the three groups
of animals. Where the differences are rather pronounced such illustrations
give at a glance a fair idea of relative size, but of course not accurate volumes.
of paper 5 em. wide. Oiily sections at right angles to the
surface were selected arid thc locations from which the cells
were taken were similar in all cases. The magnification was
x 800 throughout. In selecting cells, all the large ganglion
cells that were cut through the largest diameters and contained the nucleolus were drawn until 100 cells had been
outlined. The area they occupied was then calculated.
Figure 1is a reproduction of a sample of 100 cells from each
175
DAVID RUDIX
of the three Froups of animals. The Purkinje cells mere
treated in a simiIar manner. Since such a cell column consists of a single layer of cclls, the average magnified space oc)3.
cupied by one cell was calculated by the formula (
This affords a rough comparison OP the average volume of a
cell with changcs in t,he weight of the brain and it,s parts.
4tot$F
RESUL'L'S
A comparison of the figures in table 1shows that, while the
esperimcntal animals havc the samc body weight as that of
thc newborn (initial coiitrols), their brain exceeds that of the
ne1~7bor11aboizt 3.5 times and their cortex about 3.5 times. The
cortex has grown from 32.44 per cent of tlie whole brain in the
iiornial ncwhorn to 44.6 per cent of the brain in the tcst auimals. Thc area of 100 gaiigliou cells shows also an increase.
If the cells are reduced to three dimensional equivalents by
the above formula, thc increasc is about 4.7 timcs.
Thc ct.1~ebellarcortex shows a more pronounced increase
in size, bearing o u t the conclusions of Stewart ('18 a). This
orgmi shows a sixfold increase in weight. The Pnrkinjc cells
show an increase of 3.1 times. In short, the brain as a whole,
the cortex mith its ganglion cells, and the cerebellar cortex
with its Purkinje cells, all show a marlcetl tendency to grow
under this type of inanition.
However, wheii group 3 (age controls) are compared with
thc test animals the fact is revealed that wliilei the brains of
the experimental animals grew nevcrtheless they were retarded as compared with brains of normal rats of the same
age. In other words, brains of the starved rats did not reach
tlie normal sizc f o r thcir age. Thc whole brain oE the expcrimcntd animal represcnts only 49.6 per ccnt of the weight
of the brain of the normal rat of the same agc, i.e., it failed
in its growth by 50.4 per ccnt. The cerebral cortex in the
test brain represcnts only 43.3 per cent of the cerebral cortex
of the age-control brain-a retardation in growth of 56.7 per
ccnt. Even in relation to the brain as a whole, the cortex has
a deficiency of 6 per cent. The average volume of a ganglion
INANITION AND GROWTH O F EAT BRAIN
179
cell in the cliperiincntal brains is only 74.5 per cent of the cell
volume of the age controls-a growth deficiency of 25.5 per
cent. The cerebellar cortex of the experimental brain exhibits a 53.5 per cent shortage of growth, since it amounts to
TABLE 1
Compnvison of bram weights in test animals a?,cl controls
~
AQE.
DAYS
BODY
FlCESH
WEIGHT,
RR-4MS
WEIOHT
CORTEX
BKAlb
Per cent
of brain
Weight,
prams
Area of
100 cells
( a ) Cerebral covtex (iacluding olfactory bu2bs)
1
Initial
control
15
0-1
Averagc
Average
Avcrage
5.9
0.243
32.44
Rangc
Range
Range.
Average.
0.080
Range
0.208-0.287
24.52-36.8
0.062-0.097
A{ wage
Avrragc
Arerage
0.613
44.6
0.271
5.O-6.7
Average
2
Experimental
16
12-16
6.4
Range
4.7-7.9
Average
3
Age
17
12-16
control
IZange
Range
Range
0.310-0.783 37.78-51.27 0.135-0.376
Average
Average
Averagc
Arerage
41
Range
24-54
Average
115
Range
95-145
A\rerage
29.2
1.035
50.6
0.627
120.4
Range
Range
Rangc
R,ange
R,angc
22-42
1.062-1.45
43.5-54.4
0.494-0.1393
107-139
Average
( 6 ) Cerebellar corlrz
1
Initial
control
3
0-1
Average
Average
Average
6.5
0.258
3.8
Range
Range
Range
Average
0.010
Range
0.251-0.285
3.36-4.17
0.008-0.011
43-45
Average
Average
Average
Avera.ge
6.2-6.7
2
Experimcntrtl
Average
3
12-14
3
Age
control
17
12-16
44
Range
7.3
0.754
8.57
0.064
95
Range
Range
Range
Range
Range
6.6-7.8
0.710-0.783
8.12-9.36
1.058-0.073
87-104
Average
Average
Average
Average
Average
20.3
1.235
11.2
0.140
128
Range
Range
Range
Range
Range
22.0-42.0
1.057-1.450
7.7-14.2
7.oxa-o.18o
101-171
only 46.5 per cent of the cerebellar cortex of the age control.
The average volume of a Purlrinje cell, similarly, amounts i o
only 63.3 per cent of the Purkinjc cell volume of the control.
Again, there is a growth failure of 36.7 per cent. The results
180
DAVID RUDIN
in general agree with those of Sugita (’18) although lie used
an entirely different technique and a lesser degree of inanition.
Smith (’34) reports the volume of the ncocortes in the
albino rat at 17.11 per cent of the whole brain in the newborn,
and 24.93 per cent in the normal animals 21 days old. A
comparison of our results on normal animals with his data
10 0
%
75
50
15
0
Newborn
L___
control mts Experimntai rats Cohtrol rats
Author’s colo!uJ
Suqitak colony
Fig.2 The percentage of cerebral cortex in t h e three groups of animals and
comparison with Sugita’s figures, which are based on less severe aiid less uniform inanition.
h e Indaqs 12 hl
cannot be made because he deals with the neocortex only,
which does not include the olfactory bulbs and the olfactory
cortex medial to the rhinal fissure.
The percentage of the cerebral cortex in all three groups of
animals is shown graphically in figure 2, where a comparison
is also made with Sugita’s values. Tlie results are surprisingly similar in spite of the differences in severity of the
inanition and method of obtaining the volumes of the cortex.
INANITION A N D GROWTH O F RAT BRAIN
181
SUMMARY
1. This study represents a quantitative appraisal of the
brains of a series of albino rats that have been subjected to
diminished nursing periods from birth to 2 weeks of age, as
a result of which the body weight has been held at approximately that of the newborn animal.
2. Comparisoii has been made mith normal newborn rats
and with animals of the same age as that of the expcrimeiital
rats.
3. The brain unlike the body as a whole, does not stop growing in response to inanition, but increases in weight about
2.5 times, although it fails to attain its normal age weight by
50 per cent.
4. The cerebral cortex continues to grow at a more rapid
rate than the brain as a whole, but fails t o attain the size of
the cortex of the normal age control by about 57 per cent.
5 . The percentage of the cerebral cortex in relation to the
brain as a whole increase relatively as wcll as absolutely, but
fails to attain the weight of the cortex of a normal age control
animal hy about 6 per cent.
6. The ganglion cells of the cerebral cortex increase in
volume, but fail t o reach the cell volume of a normal age control by about 25 per cent.
7. The cerebellar cortex also continues to grow very
rapidly, but fails to attain the normal weight for its age by
about 53 per cent.
8. The percentage of the cerebellar cortex in relation to
the brain as a ~vholeincreases relatively as well as absolutely, but here again it fails to reach its normal percentage
weight for its age by about 25 per cent.
9. The Purkinje cells also exhibit rapid growth, but fail to
attain the normal volume for their age by 37 per cent,
It is a pleasure and a privilege to acltnowledgc indebtedness t o Dr. A. T. Rasmussen for his generous assistance and
constant guidance during the1 course of this work and to Dr.
C . hf. Jackson for the materials and facilities which made
this investigation possible.
DAVID RUDIN
LITERATURE CITED
HATAI,S. 1904 The effect of partial starvation on t h e brain of the white rat.
Am. J. Physiol., vol. 12, pp. 116-127.
1908 Preliminary note on the size and condition of the central
nervous system in albino rats experinientally stunted. J. Comp.
Neur., vol. 18, pp. 151-153.
JACKSON,
C. M. 1915 a Effects of acute and chronic inanition upon tlic relativc weights of the various oigaris and s p t e i n s of the adult albino
rat. Am. J. Anat., vol. 18, pp. 75-116.
1515 b Changes in thc relative weights of the various parts,
systems and organs of young albino rats held a t constant body weight
by underfeeding for various periods. J. E r p . Zool., vol. 19, pp.
5 9-15 6.
1925 The effects of inallition and malnutrition upon growth and
structure. Blakiston’s Son & Co., Phlladclphia.
1929 Recent work on effects of ilianition and malnutrition on
growth and structure. Arch. Path., vol. 7, pp. 1042-1078; vol. 8,
pp. 81-122, 273-315.
____
1932 Structural changcs rvhen growth is suppressed by undernourishment in albino rats. -4m.J. h a t . , vol. 51, pi). 347-279.
SUITII, C. G. 1934 The volume of the neocortex of the albino r a t and the
changes its undergoes after birth. J. Coinp. Neur., voL GO, pp.
319-347.
STEWART,
C. A. 1016 Growth of the body and of various organs of youiig
albino rats after inanition for various periods. Biol. Bull., vol. 31,
pp. 16-51.
1 9 1 8 s Weights of various parts of the brain in normal and
underfed albino rats at different ages. J, Comp. Neur., vol. 29, pp.
511-528.
___1918 b Changes in weight of rarious parts, systems, and organs
in albiiio rats kept a t birth wcighl by underfeeding for various
periods. Am. J. Physiol., vol. 48, pp. 67-78.
SUGITA,
NAOKI 1917 Comparative studies on the growth of cerebral cortcx.
T I . On the illcrease in t h e thickness of the cerebral cortex during tlic
post-natal growth of the brain. Albino rat. J. Comp. Neur., vol. 28,
pp. 511-591.
1918 Comparative studies on the growth of the (webra1 cortex.
V. On the area of the cortex and on the number of cell in a unit
volume, etc. J. Comp. Neur., 101. 29, pp. 61-117.
1919 Comparative studies on the growth of cerebral cortex.
VII. On the influcnec of starvatiolt at an early age upon the devclopnlerit of the cerebral cortex. Albino rat. J. Comp. Neur., vol. 29,
pp. 177-240.
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