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The effects of simulated increases in body weight for 60 days on robusticity and mineral content of limb bones of hypophysectomized rats.

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THE ANATOMICAL RECORD 210:333-341(1984)
The Effects of Simulated Increases in Body Weight for
60 Days on Robusticity and Mineral Content of Limb
Bones of Hypophysectomized Rats
MARK R. SIMON, KENNETH R. HOLMES, AND AART M. OLSEN
Departments of Veterinary Bwsciences (M.R.S., K. R. H., A.M. 0.)and
Bioengineering (M.R.S., K. R.H.), University of Illinois, Urbana, IL 61801
ABSTRACT
The purpose of this investigation was to subject separate male
and female groups of weanling hypophysectomized rats each to a specific 10%
simulated increase in body weight using constant centrifugation, ranging from
1.1G to 2.OG, to study changes in bone robusticity and bone mineral content.
(In this paper, “G” is the acceleration due to gravity.) After 60 days of centrifugation at 24 rpm, the rats were killed and the humerus, radius, ulna, femur,
and tibia were removed, cleared of soft tissues, weighed, measured, decalcified
with EDTA, and reweighed. Bone robusticity was determined using the ponderal index: P.I. = bone length + 3Jbone weight; and bone mineral content
(BMC) was determined using the formula: BMC = [(W, - Wd) + Wu] x 100.
Tukey’s Studentized Multiple Range T Test was used. The data suggest that,
for both male and female hypophysectomized rats, bone robusticity is decreased with simulated increases in body weight; also, for males, a bimodal
curve describing the relationship between BMC and simulated increases in
body weight is suggested.
In a series of investigations in this laboratory, groups of rats were each subjected to a
specific 10% simulated increase in body
weight (“G” is acceleration due to gravity)
(one group a t l.lG, a second group at 12G,
etc.) ranging from 1.1G to 2.OG to study the
effects of low levels of quantified, increased,
intermittent, compressive forces on limb bone
length, bone robusticity, and bone mineral
content (Simon et al., 1984a-0. Constant centrifugation was used.
When normal male weanling rats were
used, the data suggested that the value of G
and the duration of centrifugation are both
significant factors in the positive effect of
simulated increases in body weight on limb
bone length. When bone robusticity was calculated, the data revealed no single pattern
which would apply to all limb bones measured. When bone mineral content (BMC)
was calculated, the data suggested that centrifugation for 60 days, within the range
1.1G-2.OG, enhances BMC in male weanling
rats, and suggested a bimodal curve to describe the relationship between BMC and
simulated increases in body weight between
1.1G and 2 . O G there were significant (P <
0 1984 ALAN R. LISS, INC.
.05) increases in BMC at l.lG-1.2G and
1.6G-1.7G compared to the controls.
The purpose of the present study was to
investigate whether a 60-day period of simulated increases in body weight would affect
bone robusticity and BMC in hypophysectomized rats in a manner similar to that
observed for normal male weanling rats.
MATERIALS AND METHODS
The following procedures were performed
first on male, then on female, hypophysectomized rats.
The Centrifuge
Details describing the centrifuge construction and operation have been reported elsewhere (Simon et al., 1984a,e). The construction allowed the placement of 60 hanging rat
cages, with six centrifuge cages for each 0.1G
increase from 1.1G to 2.OG, plus six cages
Received December 28, 1983; accepted April 2, 1984.
Address reprint requests t o Dr. Mark R. Simon, Veterinary
Biosciences, College of Veterinary Medicine, University of Ilk
nois, 2001 South Lincoln Avenue, Urbana, IL 61801.
334
M.R. SIMON, K.R. HOLMES, AND A.M. OLSEN
placed on the floor next to the centrifuge for
control rats.
The daily lighting cycle was 12 hours on,
12 hours off.
The Animals
Twenty-one-day-old, hypophysectomized,
Sprague-Dawley rats purchased from the
Hormone Assay Lab, Chicago, IL,were used.
Hypophysectomy produces atrophy of the
adrenal glands. Preliminary results demonstrated that hypophysectomized rats could
not survive the stress imposed by centrifugation without receiving daily supplementary maintenance doses of glucocorticoids and
mineralocorticoids. The animals were, therefore, given a maintenance dosage of SoluCortef (1m g k g of body weightlday, assuming a daily consumption of 10-15 cm3 of water
per rat per day) in the drinking water.
Initially, four rats were placed in each cage.
During the first 2 weeks of centrifugation, a
number of animals displayed signs of nonacclimation (ataxia, inanition, etc.) and were
removed from the experiment. Additionally,
any rats that appeared obviously oversized
compared to the other rats of that group were
removed from the study; a n oversized rat
would indicate that hypophysectomy had
been incomplete. A Sprague-Dawley rat, hypophysectomized at 21 days of age, will have
a body weight of approximately 80-100 gm
at 90 days of age, whereas a normal SpragueDawley rat would weigh approximately 250
gm for females and 350 gm for males. If hypophysectomy is incomplete, the effect on
general body growth is minimal, such that
by 30 days of centrifugation, those rats which
had received a n incomplete hypophysectomy
were almost double the size of a typically
hypophysectomized rat.
The humerus, radius, ulna, femur, and tibia were carefully cleared of muscle and connective tissues. The fixed limb bones were
blotter-dried and weighed on a Mettler analytic balance with a n accuracy of 0.1 mg.
Bone lengths were measured on Helios calipers with a n accuracy of 0.05 mm.
Index of Robusticity
Bone robusticity was determined using a n
index proposed by Riesenfeld (1972, 1974a,b,
1977, 1978): Ponderal index (P.1.) = bone
lengthJ3Jbone weight, in which the length of
a bone is related to the cube root of its weight.
A lower index represents a greater bone
robusticity.
Determination of Bone Mineral Content
(BMC)
For the purposes of our research program,
it was necessary to ascertain BMC and still
preserve the integrity of the bone so that it
could be processed for histologic study. The
disadvantage to ashing (Jankovich, 1971;
Nielsen et al., 1980; Trotter and Peterson,
1962; Trotter and Hixon, 1976) and flame
atomic absorption (Calvo et al., 1982) is the
loss of the bone as a n anatomical entity. Photon absorptiometry (Cameron et al., 1968;
Fisher et al., 1974) measures BMC along a
transverse line which may not be indicative
of BMC for the bone as a whole.
We decided to try a technique which would
preserve the integrity of the bone and give
results which would be indicative of BMC for
the entire bone: After the fixed limb bones
had been weighed, they were decalcified in
EDTA, at neutral pH and 36”C, instead of
the more traditional acidic decalcifiers. When
examination by radiographs indicated that
the bones were completely decalcified, the
bones were blotter-dried and reweighed. BMC
could then be calculated from the formula
BMC
=
w u
-
W,
Wd
x 100
where W, is the undecalcified weight and Wd
is the decalcified weight.
EDTA is a relatively slow decalcifying
agent, but it preserves the structural integrity of the tissue. Although acid decalcifying
agents are more rapid in their action on the
tissue, they cause distortion because they will
also attack collagen and other components of
the organic matrix. Overdecalcifying in a n
acidic agent results, therefore, in loss of cellular detail. EDTA, on the other hand, does
not attack the organic matrix. It works at
neutral pH and acts as a chelating agent
binding 1 mole of calcium per 1 mole of
EDTA. Once the chelate is formed, calcium
disodium edate is considered a stable calcium
complex. The target of EDTA is the hydroxyapatite crystal or a deficient one (Charman
and Reid, 1972; Eggert and Germain, 1979).
Since EDTA is a chelating agent, not a n
acidic decalcifier, one cannot overdecalcify;
i.e., EDTA will stop its action when it has
exhausted the inorganic matrix (Charman
and Reid, 1972).
This technique was utilized in our previous
study on centrifugation and BMC (Simon et
335
BONE ROBUSTICITY AND MINERAL CONTENT
al., 19848, and our results for BMC of control male rat femur agreed favorably with
those from another study (Jankovich, 1971)
utilizing ashing.
are a part of the set having the lowest mean
values for ponderal index for all bones measured except for male tibia, in which group
1.2G constituted the set.
Statistical Analysis
Preliminary analysis showed no statistically significant differences between the left
and right limb bones for the animals; therefore, the ponderal indices reported reflect the
average of the left and right limb bones for
each animal. Analysis of variance was performed to determine if there was a n overall
response of weight-specific 1) bone robusticity and 2) BMC to G among the entire range
of control and centrifuged groups (Table 1).
Because the sample size differed among the
experimental groups, Tukey's Studentized
Multiple Range Test was performed to identify aggregations or sets of G groups between
which there are significant (P < .05) differences; however, between the groups comprising a set there is no significant (P > .05)
difference. This test is the appropriate multiple range test to use when sample sizes
differ (Miller, 1966).
BMC
The data in Table 4 are summarized in
Table 5 , in which the groups comprising a
set are listed and, in which, for each bone,
the mean values for BMC of set 1 > set 2 >
set 3 > set 4 > set 5 , the differences between
sets being statistically (P < .05) significant.
The data suggest a pattern which is, however, not present for all bones. The pattern
consists of a first set containing two groups,
one group between 1.2G-1.4G and 1.9G; a
second set which contains the controls (l.OG);
a fourth set which contains group 2.OG; and
for the females, a fifth set composed of only
group 1.3G. For tibia, males and females,
and for femur, for females, there is a third
set between the second and fourth sets. For
ulna, for males, there was a large set which
contained both the controls and group 2.OG.
It is so indicated by listing both groups as a
combined set 3.
RESULTS
DISCUSSION
Bone Robusticity
The data in Table 2 are summarized in
Table 3. The data reveal that the controls
(1.OG)for both male and female constitute or
The results suggest that simulated increases in body weight, within the range
l.lG-2.OG, produce a decrease in bone robusticity, for both male and female weanling
TABLE 1. Analysis of variance
Bone
Bone robusticity
Humerus
Sex
F1
PR2
F
5.34
2.80
5.45
3.69
9.00
2.90
18.14
3.58
1.98
2.85
,0001
.0037
.0001
.0002
.0001
.0027
,0001
.0003
,0414
,0031
25.49
5.66
26.47
7.18
24.65
3.17
40.66
12.92
47.28
12.04
,0001
.0001
,0001
,0001
,0001
,0014
.0001
,0001
.0001
,0001
M
-~
Radius
Ulna
Femur
Tibia
Bone mineral content
Humerus
F
M
F
M
F
M
F
M
F
M
F
~~
Radius
Ulna
Femur
Tibia
M
F
M
F
M
F
M
'The F value indicates a significant effect due to G in the presence of weight as a covariate.
'PR, level of probability.
Body weight (gm)
89.8
86.4
84.8
85.6
85.9
81.2
80.4
81.4
85.1
86.3
82.4
Humerus (P.I.)
4.174
4.134
4.100
4.094
4.068
4.065
4.059
4.058
4.040
3.968
3.776
Radius (P.1.)
5.703
5.655
5.632
5.583
5.558
5.509
5.500
5.465
5.463
5.449
5.373
Ulna (P.1.)
6.359
6.307
6.283
6.282
6.270
6.214
X
-
2.0
1.1
1.5
1.6
1.8
1.7
1.3
1.4
1.9
1.2
1.0
2.0
1.1
1.5
1.8
1.6
1.7
0.142
0.254
0.166
0.148
0.160
0.138
0.323
0.206
0.092
0.167
0.123
0.155
0.245
0.237
0.141
0.124
0.141
2.0
1.5
1.6
1.1
1.4
1.7
1.8
1.3
1.2
15
11
5.6
6.7
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
G
0.108
0.103
0.081
0.147
0.083
0.078
0.088
0.103
0.064
0.063
0.684
10
13
12
10
12
n
6.6
5.5
4.7
7.5
6.7
a
Hypophysectomized male rats
I
1.6
2.0
1.5
1.7
1.9
1.8
1.2
1.4
1.3
1.1
1.0
1.6
1.5
2.0
1.9
1.7
1.8
1.2
1.3
1.4
1.1
1.0
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
1.9
1.7
1.6
j 14
I
1
I
G
12
11
6
11
13
14
6.424
6.329
6.303
6.292
6.255
6.236
5.634
5.618
5.611
5.585
5.575
5.539
5.531
5.530
5.474
5.432
5.257
4.116
4.113
4.110
4.109
4.102
4.095
4.072
4.056
4.047
3.975
3.922
82.5
84.6
81.4
87.5
81.3
84.1
Hypophysectomized female rats
n
X
TABLE 2. Tukey’s Studentized Multiple Range Test for body weight; and for bone robusticity, body weight as cowariatel
0.133
0.156
0.129
0.170
0.205
0.166
0.125
0.157
0.118
0.166
0.144
0.117
0.174
0.146
0.122
0.133
0.255
0.068
0.052
0.086
0.115
0.092
0.087
0.080
0.093
0.088
0.105
0.124
8.3
8.4
6.3
8.2
8.9
7.9
7.0
8.5
7.5
10.5
10.3
a
5
*
k
5
3:
“Z
w
Q,
w
w
6.189
6.144
6.069
5.989
5.825
Femur (P.1.)
4.024
3.986
3.978
3.958
3.952
3.942
3.934
3.920
3.918
3.868
3.775
Tibia (P.I.)
4.988
4.983
4.928
4.913
4.910
4.908
4.902
4.853
4.851
4.842
Sex
M
F
M
F
M
F
M
F
M
F
Humerus
Tibia
Femur
Ulna
Radius
I
I
1.6
1.5
1.3
1.8
1.2
2.0
1.4
1.9
1.7
1.1
2.0
1.5
1.6
1.7
1.9
1.8
1.4
1.2
1.3
1.1
1.0
1.2
1.4
1.3
1.1
1.0
1.0, 1.2-1.4, 1.7, 1.9
1.0
1.0
1.0, 1.1
1.2
1.0
1.0
1.o
1.0
1.9, 1.0, 1.2
Set having lowest mean
values for ponderal index
TABLE 3. Summary of Tukey's Test for bone robusticity
2.0
1.5
1.4
1.3
1.1
1.6
1.0
1.9
1.7
1.8
Bone
0.120
0.085
0.091
0.112
0.176
0.122
0.110
0.100
0.136
0.149
1.1
1.0
2.0
1.6
1.5
1.2
1.9
1.8
1.4
1.7
1.3
0.114
0.085
0.130
0.270
0.063
0.124
0.074
0.061
0.135
0.107
0.077
I
1.9
1.4
1.3
1.0
1.2
0.093
0.203
0.401
0.233
0.883
5.000
4.958
4.956
4.950
4.950
4.949
4.927
4.926
4.907
4.861
4.047
4.044
4.022
4.016
4.015
4.010
3.962
3.944
3.923
3.802
3.678
6.200
6.188
6.078
6.020
5.782
0.098
0.104
0.071
0.123
0.093
0.094
0.086
0.107
0.189
0.116
0.091
0.069
0.079
0.096
0.097
0.091
0.086
0.089
0.103
0.090
0.086
0.254
0.136
0.251
0.211
0.275
w
w
-3
338
M.R. SIMON, K.R. HOLMES, AND A.M. OLSEN
TABLE 4. Tukey's Studentized Multiple Range Test for bone mineral content, body weight as couariate'
X
-
Hypophysectomized female rats
Hypophysectomized male rats
Humerus (%BMC)
67.54
67.16
64.70
64.37
63.59
63.32
62.17
61.42
60.38
60.27
59.16
Radius (%BMC)
68.27
67.64
67.26
65.12
65.00
64.08
64.06
62.40
62.19
61.94
60.33
Ulna (%BMC)
70.35
69.93
69.09
68.40
68.10
67.18
67.08
65.90
65.40
65.36
63.60
Femur (%BMC)
62.42
60.38
59.25
58.78
58.63
58.30
55.91
55.05
54.44
53.93
53.91
Tibia (%BMC)
61.62
60.56
60.18
60.12
59.72
59.20
57.14
56.43
56.28
55.90
54.64
G
ll
10.25
2.48
3.15
0.81
2.11
2.33
1.12
2.16
3.43
2.19
2.55
G
I :::
1.3
1.6
1.5
1.0
1.8
1.1
1.7
1.4
2.0
-
X
ll
69.00
68.95
67.49
66.93
66.21
65.93
63.68
63.50
62.41
62.13
59.33
1.58
1.66
2.27
2.57
1.44
1.21
1.93
1.97
0.91
1.61
3.16
1.2
69.98
69.27
68.91
67.28
67.03
1.5
1.6
2.0
I 1.3
59.38
2.76
1.66
1.95
1.66
2.75
2.27
1.82
2.12
1.72
1.60
2.22
1.7
1.9
1.4
1.8
1.1
1.2
1.0
1.6
1.5
2.0
1.3
72.82
72.28
71.80
69.92
69.69
69.61
69.21
67.64
66.84
66.25
62.25
2.00
2.02
1.69
2.50
1.52
2.32
1.53
0.86
1.87
2.17
2.68
I
1.4
1.9
1.7
1.o
1.2
1.1
1.3
I
5.40
3.84
2.22
1.61
1.36
1.85
1.27
5.89
1.25
3.44
2.10
1.3
1.0
1.9
1.8
1.2
1.5
1.6
1.7
1.4
2.0
1.1
1.81
8.67
5.54
2.39
1.13
2.30
1.62
4.76
1.77
1.61
3.41
1.9
1.2
1.3
1.0
1.6
1.8
1.5
1.7
1.4
1.1
2.0
2.42
1.97
3.66
1.64
2.83
2.85
3.56
1.48
2.81
1.81
2.65
1.9
1.2
1.3
1.6
1.5
1.0
1.1
1.8
2.0
1.4
1.7
1.4
1.9
1.7
1.0
1.1
1.2
1.8
1.5
2.0
1.6
1.3
64.25
63.51
62.61
62.59
61.64
60.74
58.47
55.88
55.12
54.99
52.51
1.92
1.90
1.60
3.17
1.35
1.50
1.93
1.23
2.89
1.62
2.72
1.78
2.15
2.53
1.49
1.43
1.9
1.0
1.3
1.2
I .I0
1.5
1.1
1.8
2.0
1.4
1.7
1.4
1.9
1.0
1.2
1.1
1.7
1.8
1.6
1.5
2.0
1.3
64.60
64.39
63.94
62.65
62.30
62.17
59.63
57.54
57.22
57.09
54.12
1.71
2.15
1.88
1.33
1.37
1.62
1.88
1.12
2.04
0.84
1.73
3.02
1.42
2.99
1.28
3.13
I
1.9
1.7
I
1.6
~~
1
1
I
I
'Mean values for body weight are in grams. Mean values for bone mineral content are in percentages. Groups are listed in
descending order of % BMC. Groups comprising a set are joined by vertical lines on either side of the group number.
339
BONE ROBUSTICITY AND MINERAL CONTENT
TABLE 5. Summary of Tukey's Multiple Range Test for BMC for male and female weanling hypophysectomized
rats'
Bone
Humerus
Radius
Ulna
Femur
Tibia
Humerus
Radius
Ulna
Femur
Tibia
Sex
F
F
F
F
F
M
M
M
M
M
Set 1
1.4
Set 2
1.9
1.9
1.7, 1.9
1.4
1.2
1.9
1.2, 1.3, 1.9
1.2
1.9
. . .1.0. . .
. . .1.0. . .
. . .1.0. . .
. . .1.0. . .
.. .LO. . .
. . .1.0. . .
. . .LO. . .
. . .1.0. . .
. . .1.0. . .
Set 3
Set 4
Set 5
1.8
1.8
. . .2.0. . .
. . .2.0. . .
. . .2.0. . .
. . .2.0. . .
. . .2.0. . .
. . .2.0. . .
. . .2.0. . .
1.3
1.3
1.3
1.3
1.3
. . .1.0,2.0...
1.1. 1.2. 1.5. 1.6
1.1
. . .2.0. . .
. . .2.0. . .
'The G groups comprising each set are listed. That other groups also comprise sets 2 and 4 is indicated by three periods on both
sides of groups 1.0 and 2.0. For ulna, male, set 3 included the groups otherwise found in sets 2 and 4.
hypophysectomized rats. In a previous study nificant factors in the reaction of bone to
(Simon et al., 1984d) normal male weanlings simulated increases in body weight (Simon
were subjected to 60 days of simulated in- et al., 1984a).
creases in body weight to investigate changes
In a previous study (Simon et al., 1984d)
in bone robusticity. The results of that study BMC was determined for normal weanling
revealed no set pattern which would account male rats subjected to simulated increases in
for all bones measured. However, there were body weight (l.lG-2.OG) for 60 days. When
no instances in which the controls consti- the results of that study are compared to
tuted a set for greater bone robusticity.
those from the male hypophysectomized rats,
In a n earlier study (Simon et al., 1984b)the both similarities and differences are manieffects of simulated increases in body weight fest. For the normal male rats, simulated
on limb bone length in hypophysectomized increases in body weight enhanced BMC; for
rats were investigated. The results of that humerus, femur, and tibia, the control anistudy revealed that whereas both male and mals had the lowest mean value for BMC.
female control groups had significantly For the hypophysectomized male rats, most
higher mean values for body weight, the ex- of the mean values for BMC were lower than
perimental groups had significantly higher those of the control animals. Whereas the
mean values for limb bone length, for abso- general pattern for the normal male rats was
lute values. When bone length was standard- an initial increase in BMC at l.lG, for the
ized by the cube root of the body weight, the hypophysectomized male rats, group 1.1G
controls formed a set for lowest mean value had a lower mean value for BMC than did
for bone length, for all bones measured ex- the controls, for all bones measured. For the
cept for male tibia and female femur. There normal male rats, the data suggested a biwas no instance in which group 1.3G, for modal curve, with peaks at l.lG-1.2G and
female rats, constituted a set.
1.6G-1.7G for radius BMC, there was a sigThe results from this study also suggest nificant increase in BMC only at 1.2G. For
some commonalities between male and fe- the hypophysectomized male rats, the patmale hypophysectomized, weanling rats in tern is nascent. It is not as evident as was
the effects of simulated increases in body the consistent pattern for the normal male
weight (l.lG-2.OG) on BMC. For both sexes, rats; however, there are three groups for
certain simulated increases in body weight males (1.2G, 1.3G, 1.9G) and for females
enhanced BMC for humerus, ulna, and fe- (1.4G, 1.7G, 1.9G)in which BMC is enhanced.
mur, and not for tibia.
For males, two groups have diminished BMC
For females, for humerus and femur, group (l.lG, 2.OG) compared to the controls. For
1.4G was included in the set having the high- both sexes, only one group (1.9G) showed enest mean values for BMC. However, for all hanced BMC and only one group (2.OG)
limb bones measured, group 1.3G consis- showed diminished BMC. When, however,
tently constituted the set having the lowest the data for the males are considered sepamean values for BMC. That contiguous G rately, a bimodal curve is suggested for hugroups can show opposing reactions lends merus, ulna, and femur. Significant (P < .05)
support to our hypothesis that the specific G increases in BMC occurred at 12G, 1.3G, and
and duration of centrifugation are both sig- 1.9G, the ends of each curve indicating no
340
M.R. SIMON, K.R. HOLMES, AND A.M. OLSEN
TABLE 6. Comparison of Tukey’s Test for bone mineral content
Bone
Humerus
Radius
Ulna
Femur
Tibia
Groups comprising the set having the higher mean values
Hypophysectomized male rats
60-day rats
1.2G. 1.9G
12G, 1.3G, 1.9G
1.2G, 1.9G
significant (P > .05) difference, compared to
the controls, or diminished BMC. There is,
therefore, a similarity in effect of simulated
increases in body weight on BMC between
normal and hypophysectomized male weanlings (Table 6). This similarity is not as apparent for female hypophysectomized
weanlings.
The results suggest that the phenomena of
bone growth and bone mineral content are
not directly related in hypophysectomized
rats.
This may be explained, in part, by the fact
that in hypophysectomy there is a resultant
atrophy of the thyroid gland. Secretion of
thyroxin is almost nil. In addition to the disturbance to general metabolism, a condition
of delayed ossification will ensue (Nocenti,
1968).
It is our conclusion, then, that the data
suggest no single pattern to describe the relationship between BMC and simulated increases in body weight, and limb bone length
and simulated increases in body weight
which would be valid for rats, whether or not
they had been subjected previously to a n experimentally induced condition known to disturb normal bone growth. One would have to
ascertain first the optimal G and time to
enhance bone growth for the clinical-experimental condition under investigation.
Additionally, the effects of simulated increases in body weight (l.lG-2.OG) on limb
bone growth may be dissimilar for male and
female rats for the clinical-experimental conditions under investigation.
That there are dissimilar patterns to describe changes in bone mineraI content and
bone robusticity is most significant in view
of the generalized use of the term “osteoporosis.” The term has come to be accepted as
meaning any reduction in bone mass. Specifically, osteoporosis refers to a loss of bone
matrix. Under histologic examination, large
“porosities” are visible. Osteomalacia is a
condition of undermineralized bone. Since
bone is routinely decalcified in histologic
LlG, 1 2 G , 1.6G, 1.7G
1.2G
l.lG-1.3G, 1.6G, 1.7G
l.lG, 1.2G, 1.6G, 1.7G
1.1G, 1.2G, 1.6G, 1.7G
preparation, it is impossible to tell from a
histologic section if a bone is osteomalacic.
Therefore, the almost immediate reduction
in bone calcium reported for astronauts
should not be labelled as a problem of osteoporosis. Since the inorganic matrix of bone is
embedded within the organic matrix, osteoporosis will involve loss of bone mineral as
well as organic matrix. Radiographic examination of a piece of bone would have a similar
appearance for both osteomalacia and osteoporosis since unmineralized organic matrix
will appear as a soft tissue density and be
hardly visible. Of course, both phenomena
can occur concurrently. The use of the ponderal index (Riesenfeld, 1972) to determine
bone robusticity and the index we have proposed for bone mineral content (Simon et al.,
19848 have allowed the two phenomena to
be distinguished and investigated separately.
ACKNOWLEDGMENTS
This study was supported, in part, by N M
grant No. PHS R01 AM26810.
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