Differential effects of age on neuromuscular transmission in partially denervated mouse muscle

Jacob, Jane M.; Robbins, Norman N.

doi:10.1523/jneurosci.10-05-01522.1990

Cited by 42 publications

(25 citation statements)

References 21 publications

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“…These results, confirmed with immunofluorescent stains for myelin basic protein and neurofilaments, account for many of the physiological findings (Jacob and Robbins, 1990). Motor unit size expanded 2.5 times in young and 2 times in old muscle at 60 d after partial denervation.…”

supporting

confidence: 70%

“…Functionalfibersper motor unit. The average number of fibers per motor unit before and 60 d after partial denervation could be estimated by combining the above morphological data with corresponding physiological data (Jacob and Robbins, 1990) at 60 d after partial denervation. In young and old muscle, respectively, 100% and 78% of junctions were innervated (Table 1) and reinnervation was not associated with multiple endplate sites on single muscle fibers (results of cholinesterase staining).…”

Section: Resultsmentioning

confidence: 99%

“…In young and old muscle, respectively, 100% and 78% of junctions were innervated (Table 1) and reinnervation was not associated with multiple endplate sites on single muscle fibers (results of cholinesterase staining). Hence, the average number of fibers per motor unit could be derived from the total number of morphologically innervated fibers (total fiber number per muscle x fraction innervated) divided by the mean number of motor units determined by physiological methods (Jacob and Robbins, 1990). In control muscles, there was an average of 49 and 44 fibers per motor unit in young and old muscle, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…70,8B). Since approximately 70% of these unselected terminals must have been reinnervated by collateral sprouts (Jacob and Robbins, 1990), reinnervation was primarily by means of nodal rather than ultraterminal sprouts. In old muscle 60 dafter partial denervation, axons often arrived at the terminals by a tortuous and indirect path.…”

Section: Resultsmentioning

confidence: 99%

“…The aims of this study were 2-fold: first, to determine the morphological parameters that were different after partial denervation in old vs young mice in order to specify those parameters most sensitive to age changes, presumably those with the least safety factor of maintenance (see Jacob and Robbins, 1990); and second, to ascertain the morphological basis for the different physiological findings in young vs old partially denervated muscle (Jacob and Robbins, 1990). Therefore, morphological techniques were used to indicate whether age differences in reinnervation after partial denervation involved deficits in sprouting (Pestronk et al, 1980), pathfinding or recognition of denervated endplates, myelination of sprouted axons, or restoration or maintenance of nerve terminal size after expansion of the motor unit.…”

mentioning

confidence: 99%

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Jacob

Robbins

1990

J. Neurosci.

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supporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Jacob

Robbins

1990

J. Neurosci.

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The spatiotemporal relationship among schwann cells, axons and postsynaptic acetylcholine receptor regions during muscle reinnervation in aged rats

et al. 2001

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To morphologically define the aging-related features during muscle reinnervation the spatiotemporal relationships among the major components of the neuromuscular junctions (NMJs) were investigated. A total of 64 rats, 30 adults (4 months old) and 34 aged adults (24 months old), were used. Between 1 and 12 weeks after sciatic nerve-crushing injury, cryosections of skeletal muscle were single or double labeled for S100, a marker of Schwann cells (SCs), for protein gene product 9.5, a neuronal marker, and for ␣-bungarotoxin (␣-BT), a marker of the acetylcholine receptor site (AChR site), and then observed by confocal laser microscopy. The most obvious age changes were noted: (1) the regenerating SCs and axons were delayed in their arrival at the NMJ, (2) the dimensions of terminal SCs and AChR sites displayed a drastic and long-lasting drop (for terminal SCs, during 1-8 weeks; for AChR sites, during 1-12 weeks); (3) the degree of spatial overlap between AChR sites and terminal SCs was markedly low until 8 weeks post-crush; (4) damage and poor formation in the SCs, terminal axons and AChR sites, together with poor process extension from the terminal SC or terminal axon, were pronounced; (5) persistent aberrant changes, such as multiple innervation and terminal axon sprouting, together with poorly formed collateral innervation, nerve bundles, and NMJs, more frequently occurred in the later reinnervation period. Thus, with aging, regeneration is impaired during the period in which regenerating SC strands and axons extend into NMJs and the subsequent establishment of nerve-muscle contact is in progress. A complex set of morphological abnormalities between or among the TSCs, terminal axons, and AChR sites may be important in slowing of regeneration and reinnervation in aged motor endplates. Anat Rec 264: [183][184][185][186][187][188][189][190][191][192][193][194][195][196][197][198][199][200][201][202] 2001.

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Myelinated fiber regeneration after crush injury is retarded in sciatic nerves of aging mice

Tanaka

Webster

1991

J of Comparative Neurology

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To compare nerve regeneration in young adult and aging mice, the right sciatic nerves of 6- and 24-month-old mice were crushed at the sciatic notch. Two weeks later, both groups of mice were perfused with an aldehyde solution, and, after additional fixation, the sciatic nerves were processed so that the transverse sections of each nerve subsequently studied by light and electron microscopy included the entire posterior tibial fascicle 5 mm distal to the crush site. The same level was sectioned in unoperated contralateral nerves; these nerves served as controls. Electron micrographs and the Bioquant Image Analysis System IV were used to measure areas of posterior tibial fascicles and count the number of myelinated axons, the number of unmyelinated axons, and their frequency in Schwann cell units. In aging mice, the total number of regenerating myelinated axons was significantly reduced, but totals of regenerating unmyelinated axons in aging and young adults did not differ significantly. In aging mice, the frequency of Schwann cells that contained a single unmyelinated axon was greater, suggesting that before myelination began, Schwann cell ensheathment of axons also was slowed. After axotomy by a crush injury, the area of the posterior tibial fascicle was less than that in young adults and the distal disintegration of myelin sheath remnants also appeared to be retarded. The results indicate that responses of neurons, axons, and Schwann cells could be important in slowing the regeneration of myelinated fibers found in sciatic nerves from aging mice.

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Differential effects of age on neuromuscular transmission in partially denervated mouse muscle

Cited by 42 publications

References 21 publications

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The spatiotemporal relationship among schwann cells, axons and postsynaptic acetylcholine receptor regions during muscle reinnervation in aged rats

Myelinated fiber regeneration after crush injury is retarded in sciatic nerves of aging mice

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