Motor And Sensory Innervation Of Muscle-spindles In The Neonatal Rat
Anatomy & Morphology; Developmental Biology
Kucera J; Walro J M; Reichler J
Anatomy and Embryology
1988
1988
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00304740" target="_blank" rel="noreferrer noopener">10.1007/bf00304740</a>
Differential-effects Of Neonatal Denervation On Intrafusal Muscle-fibers In The Rat
afferents; Anatomy & Morphology; denervation; Developmental Biology; expression; heavy-chain isoforms; innervation; intrafusal muscle fiber; motor denervation; muscle spindles; myosin heavy chains; neonatal rat; nerve dependence; nerve growth-factor; spindle development; spindles
The response of developing muscle spindles to denervation was studied by sectioning the nerve to the medial gastrocnemius muscle of rats at birth. The denervated spindles were examined daily throughout the first postnatal week for changes in ultrastructure and expression of several isoforms of myosin heavy chain (MHC). Each of the three different types of intrafusal muscle fiber exhibited a different response to denervation. Within 5 days after the nerve section nuclear bag, fibers degenerated completely; nuclear bag1 fibers persisted, but ceased to express the 'spindle-specific' slow-tonic MHC isoform and thereby could not be differentiated from extrafusal fibers; nuclear chain fibers did not form. The capsules of spindles disassembled, hence spindles or their remnants could no longer be identified 1 week after denervation. Neonatal deefferentation has little effect on these features of developing spindles, so removal of afferent innervation is presumably the factor that induces the loss of spindles in denervated muscles. Degeneration of the bag2 fiber, but not bag1 or extrafusal fibers, reflects a greater dependence of the bag2 fiber than the bag1 fiber on afferent innervation for maintenance of its structural integrity. This difference in response of the two types of immature bag fiber to denervation might reflect an origin of the bag2 fibers from a lineage of myogenic cells distinct from that giving rise to bag1 or extrafusal fibers, or a difference in the length of contact with afferents between the two types of bag fiber prior to nerve section.
Kucera J; Walro J M; Reichler J
Anatomy and Embryology
1993
1993-04
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00185898" target="_blank" rel="noreferrer noopener">10.1007/bf00185898</a>
Transient Expression Of A Slow-tonic Mhc Isoform By Extrafusal Fibers In The Developing Rat
Anatomy & Morphology; denervation; Developmental Biology; diversity; extrafusal fibers; intrafusal fibers; intrafusal muscle-fibers; monoclonal-antibody; motor innervation; muscle; myosin heavy-chain; neonatal rats; skeletal-muscle; slow-tonic myosin; spindles
ALD 19, a monoclonal antibody that recognizes the slow-tonic myosin heavy chain (MHC) isoform, has been used extensively as a marker for nuclear bag intrafusal fibers of muscle spindles in developing and adult rats. Extrafusal fibers of adult rat hindlimb muscles do not express slow-tonic MHC. However, while using ALD 19 to trace the fate of intrafusal fibers following neonatal denervation, we noted that some extrafusal fibers of neonates also bound this antibody. The immunolabeled extrafusal fibers were a subset of slow fibers located in the deep axial regions of crural muscles. The same fiber subset transiently displayed a weak affinity for ALD 19 during the first postnatal week in normal muscles. Denervation at birth increased the intensity of ALD 19 immunolabelling by these extrafusal fibers and extended the duration of the slow-tonic immunoreactivity into the 2nd postnatal week, after which expression diminished or ceased. Demonstration that some developing extrafusal fibers have a nerve-independent capacity for transiently expressing slow-tonic MHC, an MHC previously thought to be expressed only by intrafusal fibers, raises the possibility that both types of fiber originate from a subset of bipotential slow primary myotubes in rat hindlimbs.
Kucera J; Walro J M
Anatomy and Embryology
1993
1993-10
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00185950" target="_blank" rel="noreferrer noopener">10.1007/bf00185950</a>
Superfluousness Of Motor Innervation For The Formation Of Muscle-spindles In Neonatal Rats
afferents; Anatomy & Morphology; Developmental Biology; efferents; expression; fibers; intrafusal muscle fiber; muscle differentiation; neonatal rat; nerve dependence; nerve lesion; spindle development
Muscle spindles form de novo in reinnervated muscles of neonatal rats treated with nerve growth factor. Whether the spindles can also form in muscle reinnervated only by afferents was investigated by removing the lumbosacral segment of the spinal cord immediately after crushing the nerve to the medial gastrocnemius muscle at birth, and administering nerve growth factor for 10 days afterwards. As predicted, the medial gastrocnemius muscles were reinnervated by afferents, but not efferents. No motor endplates were visible on any muscle fibers, and extrafusal fibers were atrophied. The reinnervated muscles contained spindle-like encapsulations of one to four fibers at 5, 7, 9 and 30 days after the nerve crush. The number of spindles as well as encapsulated fibers exceeded that of normal medial gastrocnemius muscles. The encapsulated fibers resembled typical intrafusal fibers. They had normal sensory-muscle contacts, but no motor endings. The fibers displayed equatorial clusters of myonuclei and expressed the spindle-specific slow-tonic myosin heavy chain isoform at postnatal day 30. Thus, efferents are not essential for the formation and differentiation of muscle spindles in reinnervated muscles of neonatal rats.
Kucera J; Walro J M
Anatomy and Embryology
1992
1992-09
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00185978" target="_blank" rel="noreferrer noopener">10.1007/bf00185978</a>
Sequences Of Intrafusal Fiber Formation Are Muscle-dependent In Rat Hindlimbs
Anatomy & Morphology; cat; development; Developmental Biology; embryonic-development; expression; innervation; intrafusal fibers; motor; muscle; muscle spindles; myosin heavy chains; myosin heavy-chain; neonatal rats; skeletal-muscle; slow myosin; spindles; tenuissimus muscles
A rat muscle spindle typically contains four intrafusal fibers - one nuclear bag(2), one nuclear bag, and two nuclear chain fibers. We compared the sequence of formation of the three intrafusal fiber types among the tibialis anterior (TA), soleus (SOL) and medial gastrocnemius (RIG) muscles using immunocytochemistry of spindle-specific myosin heavy chain isoforms. Spindles of the TA began to differentiate earlier and acquired the full complement of intrafusal fibers sooner than spindles of the SOL or MG muscles. At the onset of spindle assembly, the intrafusal myotubes expressed myosin heavy chains similar to those expressed by extrafusal myotubes. The first intrafusal myotube then differentiated into the bag, fiber regardless of the muscle. However, the fate of the second-forming intrafusal myotube varied among the muscles studied. It usually differentiated into a chain fiber in the TA, into a bag(1) fiber in the SOL, and into either a bag(1) or a chain in the MG. The fate of the third-forminge was reciprocal to that of the second; i.e. in those spindles in which the bag(1) fiber was second to form, a chain was third, and vice versa. The fourth and last intrafusal myotube gave rise to a chain fiber. The inter- and intramuscular variability in the fate of intrafusal myotubes of the second and third generation argues against the existence of a program intrinsic to the myotubes that would mandate their differentiation along specific paths. Rather, an extrinsic regulatory factor, probably associated with the primary afferent neuron, may govern differentiation of pluripotential myotubes into particular types of intrafusal fiber. The fate of the intrafusal myotubes might then depend on the timing of the regulatory effect of afferents relative to the stage of development of the intrafusal bundle.
Kucera J; Walro J M
Anatomy and Embryology
1994
1994-09
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00234305" target="_blank" rel="noreferrer noopener">10.1007/bf00234305</a>
Postnatal Expression Of Myosin Heavy-chains In Muscle-spindles Of The Rat
Anatomy & Morphology; Developmental Biology
Kucera J; Walro J M
Anatomy and Embryology
1989
1989
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00305063" target="_blank" rel="noreferrer noopener">10.1007/bf00305063</a>
Postnatal Maturation Of Spindles In Deafferented Rat Soleus Muscles
Anatomy & Morphology; Developmental Biology
Kucera J; Walro J M
Anatomy and Embryology
1987
1987
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00310086" target="_blank" rel="noreferrer noopener">10.1007/bf00310086</a>
Origin Of Intrafusal Fibers From A Subset Of Primary Myotubes In The Rat
afferents; Anatomy & Morphology; development; Developmental Biology; developmental myosins; expression; intrafusal fibers; isoforms; muscle; muscle spindles; muscle spindles; myosin heavy chains; myosin heavy-chain
S46, a monoclonal antibody (mAb) specific for the SM-1 and SM-2 isoforms of avian slow myosin heavy chains (MHC), was used to study the earliest stages of development of intrafusal fibers in muscle spindles of the rat hindlimb. Spindles formed only in the regions of fetal muscles that contained primary myotubes reactive to mAb S46, such as the axial region of the tibialis anterior muscle. The first intrafusal fiber to form, the nuclear bag, fiber, originated from within the population of S46-reactive primary myotubes. Binding of mAb S46 by myotubes giving rise to the bag, fibers preceded the appearance of encapsulated spindles in the muscles by electron microscopy. However, reactivity to S46 intensified in the myotubes transforming into bag, fibers after the innervation of the fibers by afferents, and dissipated in myotubes differentiating into slow-twitch (type I) extrafusal fibers. Thus, afferents may enhance intrafusal expression of the MHC isoform reactive to mAb S46. The pattern of S46 binding to nuclear bag and chain intrafusal fibers in both developing and adult spindles was the same as that reported for the mAb ALD19, suggesting that both antibodies bind to the same MHC isoform. This isoform is probably a developmental form of slow myosin, because it was transiently expressed during the development of type I extrafusal fibers. The origin of bag, intrafusal and type I extrafusal fibers from a bipotential subpopulation of primary myotubes reactive to mAb S46 correlates with the location of muscle spindles in the slow regions of muscles in adult rat hindlimbs.
Kucera J; Walro J M
Anatomy and Embryology
1995
1995-08
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00186003" target="_blank" rel="noreferrer noopener">10.1007/bf00186003</a>
An Immunocytochemical Marker For Early-type-i Muscle-fibers In The Developing Rat Hindlimb
Anatomy & Morphology; Developmental Biology; expression; extrafusal; fibers; isoforms; mhc isoforms; muscle development; myosin heavy-chain; myotubes; skeletal-muscle; slow myosin; slow myosins; type i fibers
Muscle fibers develop sequentially from several generations of myotubes that express specific isoforms of myosin heavy chain (MHC). We observed that the chicken-derived monoclonal antibody (mAb) S46 binds to myotubes of the fetal rat hindlimb in a specific temporal and spatial pattern. To determine the type and fate of the S46-reactive myotubes, we immunoreacted sections of fetal, neonatal and postnatal hindlimb muscles to this antibody. The mAb S46 bound to a subpopulation of primary myotubes in the tibialis anterior, and to all primary and slow/fast secondary myotubes in the soleus muscle. The S46-reactive primary myotubes represented the oldest set of myotubes in the muscles. Reactivity to S46 was present from the earliest stages of muscle development, peaked in the late fetal period, and dissipated in the first postnatal week, suggesting that mAb S46 binds to a developmental form of slow myosin. The regional distribution of myotubes that bound S46 in fetal muscles was identical to the distribution of type I (slow-twitch) fibers in the adult, indicating that S46-reactive myotubes ultimately develop into type I extrafusal fibers. Thus, mAb S46 can be used as a marker for prospective type I extrafusal fibers in the rat hindlimb.
Kucera J; Walro J M
Anatomy and Embryology
1995
1995-08
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1007/bf00186002" target="_blank" rel="noreferrer noopener">10.1007/bf00186002</a>
Ultrastructural aspects of atrium development: demonstration of endocardial discontinuities and immunolabeling of atrial natriuretic factor in the Syrian hamster.
Animals; Immunohistochemistry; Cricetinae; Microscopy; Atrial Natriuretic Factor/*analysis; Endocardium/analysis/*embryology/ultrastructure; Endothelium/analysis/embryology/ultrastructure; Heart Atria/analysis/embryology/ultrastructure; Electron
The endocardium ultrastructure of 13 embryonic day old hamsters was examined, especially in relationship with the atrial myocytes. The endothelial morphology was described, including the junctional attachments and their relationships with subjacent atrial myocytes. Characteristic atrial myocytes organelles were identified: myofibrils, atrial granules, lipidic inclusions, and polysomes. Immunogold labeling demonstrated that atrial natriuretic factor (ANF)-containing granules were already present in the differentiating cardiomyocytes, even before the myofibrils were completely organized. At this stage of development, while the endothelium was a narrow barrier between the blood and the cardiomyocytes, it displayed fenestrations, but also epithelial discontinuities. In addition it also contains immunoreactive-ANF products. In light of the current knowledge about ANF processing it was proposed that the endocardium lining could be an obligated passageway for transport or activating proANF into ANF before its release into the blood stream. In addition the endocardial gaps could suggest that, until about 13 to 14 days of fetal development, heart atrial tissue could be more susceptible to the effects of pathogenetic compounds than in a later state of development.
Gilloteaux J
Anatomy and embryology
1989
1989
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1007/bf00326587" target="_blank" rel="noreferrer noopener">10.1007/bf00326587</a>