Development of Transverse Tubular Systems (T-Tubules) in the Hamster {Mesocricetus Auratus) Myocardium.
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Date
2003-01
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University of Ghana
Abstract
With the aid of an electron microscope the development of
transverse tubules (T-tubules or system) was studied in pre- and
post-natal hamsters (Mesocricetus auratus) labelled with horse
radish peroxidase (HRP). Thin sections (70-90 nm) and semi-thin
sections (800-1000 nm) were cut using an ultramicrotome and
examined under an electron microscope. No evidence of T-tubules
was observed during the pre-natal and first week in neonatal stages
of development when myocytes were characterised by large
cytoplasmic spaces with few and partially developed but
functioning myofibrils. Between seven and fourteen days of postnatal
life, myofibrils developed rapidly and the A-and I-bands
became more distinct. By the seventh day, shallow indentations of
the sarcolemma at the Z-line regions appeared, representing the
early beginnings of the T-system. Wide T-tubule invaginations of
the sarcolemma with cross-sectional diameter of 200-205 nm
began to appear in right and left ventricular myocytes by the
twenty-first day of post-natal life in some Z-line regions of
myofibrils. At this stage also, myofibrils had adopted adult forms,
with well organised cross-striations. Mitochondria were also well
developed, occupying the spaces between rows of myofibrils.
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This study supports the view that T-tubules are primarily
adapted for homeostatic functions of the mammalian cardiac
myocytes, improving efficiency of transport of metabolic
substrates and products, and that they are not for excitationcontraction
coupling as presumed by some workers. It also shows
that the wide T-system observed in the studies of myocytes of an
adult hamster is pre-determined, as this feature is noticeable as
early as the third week of post-natal development, coinciding with
maturation of the myofibrils for active adult life.
Description
Thesis (MPhil) - University of Ghana, 2003