MORPHOMETRIC ANALYSIS OF COATED VESICLES IN DEVELOPING RAT MUSCLE-SPINDLES
acetylcholine-receptors; cells; coated vesicles; development; innervation; intrafusal fibers; membrane; morphometry; motor; muscle spindle; Physiology; rat
The incidence of coated vesicles under sarcolemmal surfaces of equatorial, juxtaequatorial and polar regions in developing and adult spindles of the rat soleus muscle was examined by quantitative morphometry of transverse ultrathin sections. Coated vesicles were more numerous: 1) under primary sensory endings than under other types of neuromuscular contacts; 2) under the appositional sarcolemma between neighbouring intrafusal fibres than under free surfaces of the sarcolemma; and 3) in developing than in mature spindles. Factors such as location and age of the animal often interacted to produce an additive effect on the incidence of coated vesicles. Although there was a high incidence of coated vesicles at the postsynaptic surface under sensory terminals of bag2 fibres in 18 and 19 day gestational embryonic rats, it peaked in 4 day postnatal animals. The high incidence of coated vesicles at sensory endings supports the view that coated vesicles mediate neurotrophic interactions between afferents and intrafusal fibres during the critical late gestation and early postnatal time period, as sensory axons first contact their target fibres and exert a maximal directing influence on the differentiation of intrafusal fibre types. In addition, the preferential localization of coated vesicles under appositional rather than free surfaces of developing intrafusal fibres in 0-4 day rats suggests that they play a role in the transport of active substances among intrafusal fibres exhibiting different stages of maturity.
Stephens H; Walro J M; Kucera J
Physiological Research
1992
1992
Journal Article
n/a
NONNEURAL AND NEURAL EXPRESSION OF MYOSIN HEAVY-CHAINS BY REGENERATED INTRAFUSAL FIBERS OF RATS
intrafusal fiber; muscle regeneration; muscle spindle; myosin heavy chain; Neurosciences & Neurology
Expression of myosin heavy chain (MHC) isoforms was studied in rat soleus (SOL) and extensor digitorum longus (EDL) muscles which regenerated in the presence or absence of innervation. Frozen sections of two 5 day denervated SOL and EDL grafts, two 40 day denervated SOL and EDL grafts, and two reinnervated 40 day SOL and EDL grafts were processed for demonstration of motor endplates, sensory endings, myosin adenosine triphosphatase (mATPase) and for expression of 4 MHCs. No qualitative differences in MHC expression were noted between 5 day or 40 day denervated grafts of the SOL and EDL muscles. All regenerated intrafusal and extrafusal myotubes or myofibers reacted to antibodies against neonatal and fast-twitch MHCs, but not to antibodies against slow-twitch and slow-tonic MHCs in these grafts. These data indicate that MHCs expressed by regenerated intrafusal myotubes do not parallel those expressed by myotubes which give rise to the three types of intrafusal fibers during development and that MHC expression by regenerated intrafusal myotubes parallels that of regenerated extrafusal myotubes prior to innervation. However, some regenerated intrafusal fibers in 40 day nerve-intact grafts bound antibodies to slow-twitch and slow-tonic MHCs, thus expressions of these two MHCs are nerve-dependent in regenerated muscle spindles.
Walro J M; Kucera J; Narvy R
Neuroscience Letters
1991
1991-01
Journal Article
<a href="http://doi.org/10.1016/0304-3940(91)90861-m" target="_blank" rel="noreferrer noopener">10.1016/0304-3940(91)90861-m</a>
Development of fusimotor innervation correlates with group Ia afferents but is independent of neurotrophin-3
deficits; Developmental Biology; expression; fusimotor innervation; growth factor; messenger-rna; mice; motor-neurons; muscle spindle; nervous-system; Neurosciences & Neurology; neurotrophin-3; proprioception; rat; transgenic mice
Fusimotor neurons, group Ia afferents and muscle spindles are absent in mutant mice lacking the gene for neurotrophin-3 (NT3). To partition the effect of Ia afferent or spindle absence from that of NT3 deprivation on fusimotor neuron development, we examined the fusimotor system in a mutant mouse (NesPIXpNT3) that lacks Ia afferents and spindles, but has normal or elevated tissue levels of NT3 during embryogenesis. Fusimotor fibers were absent in lumbar ventral spinal roots, and limb muscles were devoid of Ia afferents and spindles in adult NesPIXpNT3 mice. In contrast, no deficiency in motoneuron numbers was observed in the trigeminal nucleus which contains cell bodies of motor axons innervating muscles of mastication. Spindles and Ia afferents were also present in the masticatory muscles. Thus, the development and/or survival of fusimotor neurons correlates with the presence of Ia afferents and/or spindles, and not with the amount of NT3 in the spinal cord or muscle. (C) 1998 Elsevier Science B.V. All rights reserved.
Ringstedt T; Copray S; Walro J; Kucera J
Developmental Brain Research
1998
1998-12
Journal Article
<a href="http://doi.org/10.1016/s0165-3806(98)00146-1" target="_blank" rel="noreferrer noopener">10.1016/s0165-3806(98)00146-1</a>