Author:
Greenwood Paul L.,Slepetis Ramona M.,Bell Alan W.,Hermanson John W.
Abstract
Cellular development of muscle was studied in
sheep fetuses at 85 days of gestation. Large and small fetuses were compared
at 100, 115 and 130 days, and an additional group of large 130-day fetuses
were studied following 7 days of maternal undernutrition. Myogenesis in the
peroneus longus muscle was completed between 100 and 115
days of gestation, and myofibre number did not differ between small and large
fetuses. The proportion of myofibre-related nuclei identified as entering
S-phase of the cell cycle was 1.7% per hour in 85-day fetuses. In large
fetuses, subsequent rates were relatively constant (=1.5% h
–1 ), whereas in small fetuses cell cycle activity
declined with age from 1.3 to 0.9% h –1 ,
and was 0.5 % h –1 in 130-day fetuses of
restricted ewes. The constant rate of cell cycle activity in large fetuses was
associated with an increasing estimated rate of muscle growth
(peroneus longus (mg) = 0.831 ¥ 10
(0.024 ¥ age [d]) ,
r 2 = 0.98), which
contrasted with slow and relatively constant muscle accretion in small fetuses
(8.4 mg day –1 ), and slower muscle accretion at
130 days in large fetuses from restricted ewes. Differences in DNA and RNA
content in the semimembranosus muscle increased with
age, large fetuses having 70% more muscle DNA, 108% more muscle
RNA and 104% larger muscles than small fetuses at 130 days (all
P<0.001). The results demonstrate that myonuclei
accumulation, but not myofibre number, is associated with fetal growth in
sheep and, therefore, with fetal nutrition during mid to late gestation.
Subject
Developmental Biology,Endocrinology,Genetics,Molecular Biology,Animal Science and Zoology,Reproductive Medicine,Biotechnology
Cited by
89 articles.
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