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Observations at the CNS-PNS Border of Ventral Roots Connected to a Neuroma.

Remahl S, Angeria M, Remahl IN, Carlstedt T, Risling M - Front Neurol (2010)

Bottom Line: The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS.It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS.Thus, in this first detailed study on the behavior of recurrent sprouts at the CNS-PNS border.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Karolinska Institutet Stockholm Sweden.

ABSTRACT
Previous studies have shown that numerous sprouts originating from a neuroma, after nerve injury in neonatal animals, can invade spinal nerve roots. However, no study with a focus on how such sprouts behave when they reach the border between the central and peripheral nervous system (CNS-PNS border) has been published. In this study we have in detail examined the CNS-PNS border of ventral roots in kittens with light and electron microscopy after early postnatal sciatic nerve resection. A transient ingrowth of substance P positive axons was observed into the CNS, but no spouts remained 6 weeks after the injury. Using serial sections and electron microscopy it was possible to identify small bundles of unmyelinated axons that penetrated from the root fascicles for a short distance into the CNS. These axons ended blindly, sometimes with a growth cone-like terminal swelling filled with vesicles. The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS. It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS. A maldevelopment of myelin sheaths at the CNS-PNS border of motor axons was observed and it seems possible that this could have consequences for the propagation of action potential across this region after neonatal nerve injury. Thus, in this first detailed study on the behavior of recurrent sprouts at the CNS-PNS border.

No MeSH data available.


Related in: MedlinePlus

Electron micrographs showing a thin section from the CNS–PNS border of a cat, 90 days after sciatic nerve resection. A number of large unmyelinated axons filled with mitochondria and vesicles were observed at the PNS/CNS border (A) and in the pia mater (B–D). The axons shown in (B,C) had a perivascular location. The axon profile in (C) is only invested partly by a basal lamina (white arrowhead). In most cases, the content of vesicles was heterogeneous. The lumen of the blood vessels is indicated by “L.” The axon shown in (D) contained electron lucent vesicles as well as a number of dense cored vesicles (arrows) (magnification in A–C). Scale bars = 0.5 μm.
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Figure 4: Electron micrographs showing a thin section from the CNS–PNS border of a cat, 90 days after sciatic nerve resection. A number of large unmyelinated axons filled with mitochondria and vesicles were observed at the PNS/CNS border (A) and in the pia mater (B–D). The axons shown in (B,C) had a perivascular location. The axon profile in (C) is only invested partly by a basal lamina (white arrowhead). In most cases, the content of vesicles was heterogeneous. The lumen of the blood vessels is indicated by “L.” The axon shown in (D) contained electron lucent vesicles as well as a number of dense cored vesicles (arrows) (magnification in A–C). Scale bars = 0.5 μm.

Mentions: A number of large unmyelinated axon profiles filled with numerous mitochondria and vesicles were observed at the CNS–PNS border (Figure 4A) and adjacent to blood vessels in the pia mater (Figures 4B–D). Some of these axon profiles with a close vascular relation (Figures 4B,C) were only partly invested by a basal lamina. Examination at a higher magnification revealed that both electron lucent and dense cored vesicles were present in this type of axon profiles (Figure 4D). Electron-microscopic examination of LR-White sections incubated with substance SP-antiserum revealed a number axon-like profiles labeled with gold particles (Figure 5A). Labeling was observed only in axon profiles that contained vesicle-like structures, to which the gold-labeled antibody complex preferentially appeared to attach. These gold-labeled axons represented only a fraction of the unmyelinated axons that were present at the CNS–PNS border. A number of unlabeled axons containing vesicles were likewise observed in the vicinity to the CNS–PNS border.


Observations at the CNS-PNS Border of Ventral Roots Connected to a Neuroma.

Remahl S, Angeria M, Remahl IN, Carlstedt T, Risling M - Front Neurol (2010)

Electron micrographs showing a thin section from the CNS–PNS border of a cat, 90 days after sciatic nerve resection. A number of large unmyelinated axons filled with mitochondria and vesicles were observed at the PNS/CNS border (A) and in the pia mater (B–D). The axons shown in (B,C) had a perivascular location. The axon profile in (C) is only invested partly by a basal lamina (white arrowhead). In most cases, the content of vesicles was heterogeneous. The lumen of the blood vessels is indicated by “L.” The axon shown in (D) contained electron lucent vesicles as well as a number of dense cored vesicles (arrows) (magnification in A–C). Scale bars = 0.5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3008941&req=5

Figure 4: Electron micrographs showing a thin section from the CNS–PNS border of a cat, 90 days after sciatic nerve resection. A number of large unmyelinated axons filled with mitochondria and vesicles were observed at the PNS/CNS border (A) and in the pia mater (B–D). The axons shown in (B,C) had a perivascular location. The axon profile in (C) is only invested partly by a basal lamina (white arrowhead). In most cases, the content of vesicles was heterogeneous. The lumen of the blood vessels is indicated by “L.” The axon shown in (D) contained electron lucent vesicles as well as a number of dense cored vesicles (arrows) (magnification in A–C). Scale bars = 0.5 μm.
Mentions: A number of large unmyelinated axon profiles filled with numerous mitochondria and vesicles were observed at the CNS–PNS border (Figure 4A) and adjacent to blood vessels in the pia mater (Figures 4B–D). Some of these axon profiles with a close vascular relation (Figures 4B,C) were only partly invested by a basal lamina. Examination at a higher magnification revealed that both electron lucent and dense cored vesicles were present in this type of axon profiles (Figure 4D). Electron-microscopic examination of LR-White sections incubated with substance SP-antiserum revealed a number axon-like profiles labeled with gold particles (Figure 5A). Labeling was observed only in axon profiles that contained vesicle-like structures, to which the gold-labeled antibody complex preferentially appeared to attach. These gold-labeled axons represented only a fraction of the unmyelinated axons that were present at the CNS–PNS border. A number of unlabeled axons containing vesicles were likewise observed in the vicinity to the CNS–PNS border.

Bottom Line: The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS.It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS.Thus, in this first detailed study on the behavior of recurrent sprouts at the CNS-PNS border.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Karolinska Institutet Stockholm Sweden.

ABSTRACT
Previous studies have shown that numerous sprouts originating from a neuroma, after nerve injury in neonatal animals, can invade spinal nerve roots. However, no study with a focus on how such sprouts behave when they reach the border between the central and peripheral nervous system (CNS-PNS border) has been published. In this study we have in detail examined the CNS-PNS border of ventral roots in kittens with light and electron microscopy after early postnatal sciatic nerve resection. A transient ingrowth of substance P positive axons was observed into the CNS, but no spouts remained 6 weeks after the injury. Using serial sections and electron microscopy it was possible to identify small bundles of unmyelinated axons that penetrated from the root fascicles for a short distance into the CNS. These axons ended blindly, sometimes with a growth cone-like terminal swelling filled with vesicles. The axon bundles were accompanied by p75 positive cells in both the root fascicles and the pia mater, but not in the CNS. It may thus be suggested that neurotrophin presenting p75 positive cells could facilitate axonal growth into the pia mater and that the lack of such cells in the CNS compartment might contribute to the failure of growth into the CNS. A maldevelopment of myelin sheaths at the CNS-PNS border of motor axons was observed and it seems possible that this could have consequences for the propagation of action potential across this region after neonatal nerve injury. Thus, in this first detailed study on the behavior of recurrent sprouts at the CNS-PNS border.

No MeSH data available.


Related in: MedlinePlus