Myosin isoform transitions during development of extra-ocular and masticatory muscles in the fetal rat

Abstract

The late fetal development of rat extra-ocular and masticatory muscles was examined by myosin immunohistochemistry. The pattern of slow and neonatal myosin isoform expression in primary and secondary myotubes in these muscles was generally similar to that seen by others in limb muscles. We observed a consistent difference between the Sprague-Dawley and Wistar rats in the degree of maturity reached by all muscles studied at a particular age. In both strains, extra-ocular muscles were also about one day in advance of the masticatory muscles. Thus, secondary myotubes were first seen at E17 in Wistar extraocular muscles, at E18 in Sprague-Dawley extra-ocular muscles and Wistar masticatory muscles, and at E19 in Sprague-Dawley masticatory muscles. There was a strikingly early and complete type differentiation of primary myotubes in extraocular muscles, and tonic myosin first appeared before birth in presumptive extrafusal tonic fibres in the orbital layer of the oculorotatory muscles. Throughout the late fetal period, retractor bulbi was composed of fast myotubes only, but these myotubes were not arranged in classical clusters. In the masticatory muscles at E17/E18 some slow primary myotubes started to express tonic myosin, and these presumptive spindle bag2 fibres were located only in regions of the muscles known to contain spindles in the adult. Presumptive bag1 fibres appeared about a day later (initially without tonic myosin), and in the region of the spindle cluster in anterior deep masseter extrafusal secondary myotube production appeared to be suppressed.

Fast fibres in a large animal: fibre types, contractile properties and myosin expression in pig skeletal muscles

“…Previous studies had shown that in many animal species retractor bulbi is a completely fast muscle (Sartore et al, 1987;Mascarello and Rowlerson, 1992): in porcine retractor bulbi (Fig.·1B) RT-PCR revealed the expression of all three fast MHC isoforms and SDS-PAGE showed two bands corresponding to MHC-2X and MHC-2B and an additional band corresponding to MHC-Eo or extraocular. The band corresponding to MHC-2A was undetectable due to the low amount of this isoform: some single fibres containing MHC-2A were, however, identified (not shown).…”

Expression of eight distinct MHC isoforms in bovine striated muscles:evidence for MHC-2B presence only in extraocular muscles

“…Serial sections (10·m) were cut in a cryostat and stained according to the protocol described by with the following antibodies: monoclonal BF-F3, which is specific for MHC-2B in rat and in pig (Lefaucheur et al, 2002;Toniolo et al, 2004), polyclonal anti-MHC-Eo (Sartore et al, 1987) and polyclonal anti-MHC-Neo (Mascarello and Rowlerson, 1992). The procedures to assess the specificity of the reactions were described in Maccatrozzo et al (2004).…”

Specialized Cranial Muscles: How Different Are They from Limb and Abdominal Muscles?

“…Immunohistochemical staining is conducted using an indirect immunoperoxidase method after incubation of tissue sections in MyHCspecific antibodies. The following MyHC-specific antibodies were used: anti-type I monoclonal (slow skeletal MyHC -Sigma Aldrich clone NOQ7), antifast monoclonal (fast skeletal IIA, IIB and IIX MyHC -Sigma Aldrich clone MY-32), anti-IIA monoclonal (fast IIA -American Type Culture Collection clone SC-71), anti-IIB (American Type Culture Collection clone BF-F3), antineonatal polyclonal [Scapolo et al, 1991], antitonic polyclonal [Mascarello and Rowlerson, 1992], anticardiac monoclonal (cardiac ·MHC -Sera Lab clone MAS-366 and BAG5; American Type Culture Collection Clone BA-G5), and anti-IIM polyclonal . Subsequent to staining serial sections with a panel of antibodies and a series of histochemical stains after various acid and alkali preincubations, biopsies are characterized for the proportions, size and types of fibers present.…”