Publication: Aging affects different human muscles in various ways. An image analysis of the histomorphometric characteristics of fiber types in human masseter and vastus lateralis
muscles from young adults and the very old
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Date
2000
Authors
Kirkeby, S. ; Garbarsch, C.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
This study is an attempt to objectively
evaluate age-related changes in human muscles by use of
histomorphometric methods. Aging in humans induces
dramatic transformations in the skeletal muscles but
little is known as to whether or not the aging processes
per se may affect all muscles equally. In this study aging
of two human muscles with different functions, origin
and nerve supply is compared.
Sections were cut from masseter and vastus lateralis
muscles obtained from young adults aged 18-24 years
and from the very old aged 90-102 years. Muscle fiber
types were classified with the traditional myofibrillar
ATPase staining. Various histomorphometric parameters
of the different fiber types in human masseter and vastus
lateralis muscle sections were obtained by image
analyses to evaluate the age-related changes in the
muscle fibers. The following variables were calculated:
the number of each fiber type per photographed area; the
area of each fiber and two indicators for the shape of the
muscle fibers. In the aging muscles there was no relative
preferential loss of a fiber type. High numbers of
intermediate ATPase-stained fibers (IM fibers) were
found in some old vastus muscles but were only sporadic
in young vastus muscles. However, there was no change
in the percentage distribution of intermediate ATPasestained
fibers when young and very old human masseter muscles were compared. Incubation of the sections with
antimyosin antibodies showed that the IM fibers in old
masseter and old vastus contained different myosin
heavy chains. Thus ATPase activity and anti-myosin
staining displayed a somewhat different pattern of fiber
type distribution. The main changes in the shape and area indicated that type I fibers in the masseter became
more circular while in the vastus they decreased
significantly in size. The type I1 fibers in the vastus
became very small and deviated significantly from
circularity whereas the type I1 fibers in the masseter only
exhibited a decrease in the size of the fibers. Histomorphometric
measurements show that aging affects
different human muscles in various ways.
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