Changes with Age in the Number and Size of Myelinated Axons in the Rat L&lt;sub&gt;4&lt;/sub&gt; Dorsal Spinal Root

Rao, Rupanagudi S.; Krinke, G.

doi:10.1159/000145786

Cited by 31 publications

(25 citation statements)

References 8 publications

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“…The findings implicate that cell loss itself cannot account for the sensory deficits seen in elderly individuals. Furthermore, our results are consistent with studies of dorsal roots that have described only small or no loss of (myelinated) fibers with advancing age (Mitsumori et al, 1981;Rao and Krinke, 1983;Knox et al, 1989). The present findings, moreover, add to the growing body of studies showing that aging is not accompanied by a substantial loss of neurons (see e.g., Satorre et al, 1985;Ahmad and Spear, 1993;Madeira et al, 1995; for reviews, see Coleman and Flood, 1987;Wickelgren, 1996).…”

Section: Number Of Drg Neurons and Loss Of Neurons During Agingsupporting

confidence: 92%

Loss of primary sensory neurons in the very old rat: Neuron number estimates using the disector method and confocal optical sectioning

Bergman

Ulfhake

1998

J. Comp. Neurol.

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Loss of neurons has been considered to be a prime cause of nervous disturbances that occur with advancing age. However, the notion of a constitutive aging-related loss of neurons has been challenged recently in several studies that used up-to-date methods for counting neurons. In this study, we have applied stereological techniques with the objective of obtaining quantitative data on total neuron numbers and the distribution of neuron cross-sectional areas in the fifth cervical (C5) and fourth lumbar (L4) dorsal root ganglion (DRG) of 3- and 30-month-old Sprague-Dawley rats. Tissue data were recorded on a confocal laser-scanning microscope with the use of the optical-disector technique and random, systematic sampling. Aged rats of both sexes disclosed only a small decrease (approximately 12%) in the number of cervical and lumbar DRG neurons. Furthermore, there was no significant correlation between the degree of neuron loss and the extent of behavioral deficits among the aged individuals. The DRG neurons of aged rats had a smaller mean cross-sectional area (approximately 15%; P < 0.001) at both DRG levels. Further analysis of the male cohorts was carried out by using isolectin B4 and neurofilament subunit (phosphorylated 200 kDa; RT97) immunoreactivity (IR) as selective markers for unmyelinated and myelinated axons, respectively, and disclosed no significant change in the relative frequencies of immunoreactive neuron profiles in the old rats. However, RT97-IR DRG neurons of the aged rats had significantly smaller cross-sectional areas (approximately 9% in C5; approximately 16% in L4; P < 0.001) than the young adult rats, indicating a selective cell body atrophy among myelinated primary afferents during aging. The results indicate that loss of primary sensory neurons cannot exclusively explain the functional deficits in sensory perception among senescent individuals. It seems likely that other factors at the subcellular level and/or target interaction(s) contribute substantially to the sensory impairments observed with advancing age.

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Section: Number Of Drg Neurons and Loss Of Neurons During Agingsupporting

confidence: 92%

Loss of primary sensory neurons in the very old rat: Neuron number estimates using the disector method and confocal optical sectioning

Bergman

Ulfhake

1998

J. Comp. Neurol.

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“…Observations in humans that conduction velocity, which is inversely related to fiber diameter, is also in versely related to height [ 16] and forearm length [ 17] support this notion. Age-related shrinkage has been de scribed in myelinated axons of the rat dorsal spinal root [18], but it does not occur before the third year of life, and cannot easily explain our findings in mature animals of about 4 months. More likely, our observations repre sent a technical artifact reflecting the swelling of the tissue from younger animals during fixation.…”

Section: Discussioncontrasting

confidence: 65%

Myelination in the Chorda Tympani of the Postnatal Rat: A Quantitative Electron Microscope Study

Ferrell¹,

Tsuetaki²,

Chole³

1985

Cells Tissues Organs

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We determined the course of myelination of the chorda tympani in rats aged from 4- to 30-days-old, the interval of the most rapid developmental changes in neurophysiological taste responses and behavioral discrimination among chemical stimuli. The overall number of axons in rats aged from 16- to 30-days-old and in mature 120-day-old animals were the same and averaged 1,500. By 30 days, rats had 80% of the total number of myelinated axons observed in adults, but the average thickness of the myelin sheath per neuron and the proportion of the total cross-sectional area that were only about 60% of adult values. Observed increases in myelination closely parallel decreasing response latencies of single chorda tympani fibers to tongue stimulation with salts.

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“…The present age-related histopathologic findings are in close agreement with a previous report [5,8] suggesting that neuropathy in senescent mice is not species specific, but is less severe, even in susceptible B6C3F1 female mice, than neuropathies in rats or guinea pigs. A review of previously reported age-related changes and pressure-induced neuropathies in rats [3,7] suggests a more severe nerve pathology than that seen in elderly mice [5,8].…”

mentioning

confidence: 95%

“…Groups of five were first maintained in plastic cages (22 L × 38 W × 20 H cm) with solid floors covered by a deep (Received 22 September 1999 / Accepted 18 February 2000 Address corresponding: H. Tabata, Safety Research Laboratories , Yamanouchi Pharmaceutical Co., Ltd,[1][2][3][4][5][6][7][8] Japan Neuropathy is a spontaneous complication which often arises during aging. Localized peripheral nerve lesions, including demyelination, Wallerian degeneration and Renaut bodies, are reported to arise in the hindfeet of rats as a result of living in cages with wiregrate flooring [6,12].…”

mentioning

confidence: 99%

Comparison of Age-Related Peripheral Nerve Changes in Mice Housed in Either Plastic Cages with Sawdust-Covered Solid Flooring or Wire-Mesh-Floor Cages.

Tabata¹,

Ikegami²,

Kariya

2000

Exp. Anim.

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A comparative histologic survey was conducted on the dorsal root, sciatic, tibial and medial plantar nerves of 90-and 110-week-old B6C3F1 female mice reared in either solid-floor cages covered in sawdust or wire-mesh-floor cages. Age-related peripheral nerve lesions, characterized by axonal degeneration and remyelination, were present in all nerves surveyed, and were especially prominent in the sciatic and medial plantar nerves at 110 weeks of age but, there were no differences associated with the type of cage floor in clinical signs, grasping power of the fore-and hind-limbs, motor nerve conduction velocity or histopathologic findings at these ages. Key words: cage floor, mice, peripheral nerves, pressure neuropathy in mice [5,8]. There is marked variation between CD-1 and B6C3F1 strains in the incidence of the spontaneous peripheral neuropathy, suggesting increased susceptibility to B6C3F1 strain [5]. In this study, a histologic survey was conducted on the dorsal root, sciatic, tibial and plantar nerves of 90-and 110-week-old B6C3F1 female mice housed in either plastic cages or wiremesh-floor cages to attempt to delineate the clinical and functional disorders which compose this peripheral neuropathy.Eighty 6-week-old female B6C3F1 mice were purchased from Charles River Japan (Kanagawa, Japan) and housed inside a barriered rodent facility. Groups of five were first maintained in plastic cages (22 L × 38 W × 20 H cm) with solid floors covered by a deep (Received 22 September 1999 / Accepted 18 February 2000 Address corresponding: H. Tabata, Safety Research Laboratories , Yamanouchi Pharmaceutical Co., Ltd,[1][2][3][4][5][6][7][8] Japan Neuropathy is a spontaneous complication which often arises during aging. Localized peripheral nerve lesions, including demyelination, Wallerian degeneration and Renaut bodies, are reported to arise in the hindfeet of rats as a result of living in cages with wiregrate flooring [6,12]. Mizisin et al. [6] demonstrated that wire grates rapidly induce hindpaw tactile hyperesthesia and plantar neuropathy in rats, which could complicate or invalidate studies which assess hindlimb function and structure. This effect is not limited to rats; pressure neuropathy also arises in the plantar nerves of guinea pigs kept in cages with wire mesh floors [1,10]. Although spontaneous, age-related, peripheral neuropathy has been studied extensively in rats [2-4, 7, 11], there are few reports concerning this phenomenon

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Changes with Age in the Number and Size of Myelinated Axons in the Rat L<sub>4</sub> Dorsal Spinal Root

Cited by 31 publications

References 8 publications

Loss of primary sensory neurons in the very old rat: Neuron number estimates using the disector method and confocal optical sectioning

Loss of primary sensory neurons in the very old rat: Neuron number estimates using the disector method and confocal optical sectioning

Myelination in the Chorda Tympani of the Postnatal Rat: A Quantitative Electron Microscope Study

Comparison of Age-Related Peripheral Nerve Changes in Mice Housed in Either Plastic Cages with Sawdust-Covered Solid Flooring or Wire-Mesh-Floor Cages.

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