الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Bone is essentially a highly vascular and constantly changing
mineralized connective tissue. These properties are remarkable for
its hardness, resilience and regenerative capacity, as well as its
characteristic growth mechanisms. Microscopically, bone consists
of cells and calcified intercellular matrix. There are many types of
cells such as; osteoprogenitor cells, osteoblasts, osteocytes, bone
lining cells, and osteoclasts.
Growth and skeletal maturity are also closely related to
ovarian, testicular and adrenal cortical endocrine activities.
Meanwhile, balanced endocrine activities are essential for the
maintenance of normal bone maturation and their disturbances may
have profound effects. Moreover, concentration ofthe circulating
estrogen and androgen have been reported to be positively
associated with spinal bone density in adult women.
This work was designed to study; (1) the effect of estrogen
deficiency, (2) the effect of estrogen administration and (3) the
effect of testosterone administration, on the histological structure of
the vertebrae and inter-vertebral discs of the lumbar region in the
normal and ovariectomized female rats at different ages, from birth
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till adult. This study also aimed to clarify the pattern of bone turnover
in the lumbar vertebrae in the normal and ovariectomized
female rats at different ages, from birth till adult.
One hundred and eighty female Wistar rats, from neonatal to
adult periods, were used throughout this work. The rats were
divided according to their ages into three main groups; A, B, C
representing the neonatal period (from birth to 6 weeks), adolescent
period (from 7 to 12 weeks), and adult period (from 12 to 24 weeks)
respectively. Each age group was subdivided into two equal
subgroups; the first was left with intact ovary and the second was
ovariectomized. Each of the normal and ovariectomized groups
were further subdivided into three equal divisions; one was injected
with testosterone, another with estrogen, and the third was used as a
control for this patch. In the ovariectomized rats, injections were
started one week after the operation to ensure osteoporosis due to
ovarian hormone deficiency. Two hormones were used in this study;
(1) 17 p-estradiol (E2) was injected subcutaneously for four weeks
in a daily dose of 100 u/ kg body weight and un Testosterone
propionate was injected subcutaneously over a period of four weeks
in a daily dose ofO.S mg/kg body weight.
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One hundred and eighty stained sections were used for
morphometric analysis; 4-8 fields were chosen at random from each
slide for analysis to estimate; thickness of the cortex, number of
osteocytes, osteoblasts and osteoclasts. Values are presented as
means ± standard error of mean (S.E.M.). Data were analyzed
statistically by one way analysis of variance (ANaVA) using
current SPSS statistical package. Scheffe test for post-hoc pairwise
compansons was performed. The level of significance was
determined to be less than 0.05 throughout the study.
The findings of the present work demonstrates that
ovariectomy in female rats resulted in reduction in the bone mass of
the lumbar vertebrae as evidenced from the decrease in the
thickness of the cortex with rarefaction of the bone spicules. There
was also widening of the bone marrow cavities with increase in their
communications. The number of osteocytes and osteoblasts was
decreased while the number of osteoclasts was increased. These
criteria of bone loss were statistically significant in the adolescent
and adult groups but not significant in the neonatal group. The body
weight of the ovariectomized adolescent and adult rats was
significantly increased at the end of the experiment, but the body
weight of the ovariectomized neonatal rats showed no significant
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change. Moreover, there was no significant change detected in the
microscopical structure of the inter-vertebral discs in all of the
ovariectomized rats.
Estrogen administration had anabolic effect on the lumbar
vertebrae. It stimulated bone formation and inhibited bone
resorption. This was statistically significant in the adolescent and
adult non-ovariectomized and ovariectomized rats but not significant
in the neonatal group. Stimulation of bone formation was evidenced
by increase in the thickness of the cortex and bone spicules with
narrowing of the bone marrow cavities. The number of osteocytes
and osteoblasts was significantlyincreased. The inhibition of bone
resorption was detected by the decrease in the number of
osteoclasts. The estrogen administrationwas found to have no effect
on body weight in the non-ovariectomized rats, but it return the
body weight of the ovariectomized adolescent and adult rats to its
normal level. Estrogen was also found to have no significant effect
on the structure of the inter-vertebral discs of all the experimental
groups.
Testosterone administration in the female rats was found to
have no significant effect on the lumbar vertebrae of the neonatal
non-ovariectomized or the ovariectomized rats. However, in the
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adolescent and adult rats, testosterone injection had a reducing
effect on bone formation with enhancing effect on bone resorption.
This was evidenced by the reduction in the thickness of the cortex
and bone spicules with more widening of the bone marrow cavities
and the increase in their communications.The number of osteocytes
and osteoblasts was significantly decreased with increase in the
number of osteoclasts. It was demonstrated that testosterone
injection have an anabolic effect on the body weight but this was
less than that of the ovariectomy. Meanwhile, testosterone
administration in the adolescent and adult rats, had anabolic effect
on the collagen fibers of the annulus fibrosus of the inter-vertebral
discs. This increase of collagen fibers encroached over the area of
the nucleus pulposus. This criterion was more obvious in the
ovariectomized than the non-ovariectomized rats. The possible
explanation is that testosterone has anabolic effect on the body
tissues, which needs further investigation.