1
|
Hildebrand C, Waxman SG. Regional node-like membrane specializations in non-myelinated axons of rat retinal nerve fiber layer. Brain Res 2013; 258:23-32. [PMID: 24010160 DOI: 10.1016/0006-8993(83)91222-2] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The axons in the nerve fiber layer (NFL) of the adult rat retina were examined by transmission electron microscopy. NFL axons range in size from 0.12 to about 2.0 microm, with a peak at 0.3-0.4 microm. In addition to conventional small mitochondria in the NFL axons contain some large ones, which are similar to astrocytic gliosomes. Two types of regional axon membrane specialization are found in the NFL. One of these represents portions of the initial axon segments of retinal ganglion cells. Apart from features typical for initial axon segments in general, a corona of lamelliform, villous or blunt glial processes is always present. The glial processes originate from MUller cells. The other regional axon membrane specialization consists of patches of an electron-dense subaxolemmal undercoating with associated tufts of Miller cell processes. These patches cover a varying but always limited proportion of the axon circumference and their longitudinal extent varies between 0.5 and 5.0 microm. They are clearly distinct from the initial axon segment and from the initial heminode in the optic nerve. Similar undercoated patches in the optic disc axons are apposed by astrocytic processes. It is concluded that rat NFL axons represent an example of central non-myelinated axons with distinct regional membrane specializations, which have some structural characteristics in common with nodes of Ranvier.
Collapse
Affiliation(s)
- C Hildebrand
- Department of Anatomy, Karolinska Institutet, 104 01 Stockholm, Sweden
| | | |
Collapse
|
2
|
Nilsson Remahl AIM, Masterman T, Risling M. Re-utilization of Schwann cells during ingrowth of ventral root afferents in perinatal kittens. J Anat 2010; 213:194-201. [PMID: 18537848 DOI: 10.1111/j.1469-7580.2008.00922.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Ventral roots in all mammalian species, including humans, contain significant numbers of unmyelinated axons, many of them afferents transmitting nociceptive signals from receptive fields in skin, viscera, muscles and joints. Observations in cats indicate that these afferents do not enter the spinal cord via the ventral root, but rather turn distally and enter the dorsal root. Some unmyelinated axons are postganglionic autonomic efferents that innervate blood vessels of the root and the pia mater. In the feline L7 segment, a substantial proportion of unmyelinated axons are not detectable until late in perinatal development. The mechanisms inducing this late ingrowth, and the recruitment of Schwann cells (indispensable, at this stage, for axonal survival and sustenance), are unknown. We have counted axons and Schwann cells in both ends of the L7 ventral root in young kittens and made the following observations. (1) The total number of axons detectable in the root increased throughout the range of investigated ages. (2) The number of myelinated axons was similar in the root's proximal and distal ends. The increased number of unmyelinated axons with age is thus due to increased numbers of small unmyelinated axons. (3) The number of separated large probably promyelin axons was about the same in the proximal and distal ends of the root. (4) Schwann cells appeared to undergo redistribution, from myelinated to unmyelinated axons. (5) During redistribution of Schwann cells they first appear as aberrant Schwann cells and then become endoneurial X-cells temporarily free of axonal contact. We hypothesize that unmyelinated axons invade the ventral root from its distal end, that this ingrowth is particularly intense during the first postnatal month and that disengaged Schwann cells, eliminated from myelinated motoneuron axons, provide the ingrowing axons with structural and trophic support.
Collapse
Affiliation(s)
- A Ingela M Nilsson Remahl
- Department of Clinical Neuroscience, Division of Neurology, Karolinska Institute, Karolinska University Hospital Huddinge, Stockholm, Sweden.
| | | | | |
Collapse
|
3
|
Wilhelmsson U, Li L, Pekna M, Berthold CH, Blom S, Eliasson C, Renner O, Bushong E, Ellisman M, Morgan TE, Pekny M. Absence of glial fibrillary acidic protein and vimentin prevents hypertrophy of astrocytic processes and improves post-traumatic regeneration. J Neurosci 2005; 24:5016-21. [PMID: 15163694 PMCID: PMC6729371 DOI: 10.1523/jneurosci.0820-04.2004] [Citation(s) in RCA: 334] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The regenerative capacity of the CNS is extremely limited. The reason for this is unclear, but glial cell involvement has been suspected, and oligodendrocytes have been implicated as inhibitors of neuroregeneration (Chen et al., 2000, GrandPre et al., 2000; Fournier et al., 2001). The role of astrocytes in this process was proposed but remains incompletely understood (Silver and Miller, 2004). Astrocyte activation (reactive gliosis) accompanies neurotrauma, stroke, neurodegenerative diseases, or tumors. Two prominent hallmarks of reactive gliosis are hypertrophy of astrocytic processes and upregulation of intermediate filaments. Using the entorhinal cortex lesion model in mice, we found that reactive astrocytes devoid of the intermediate filament proteins glial fibrillary acidic protein and vimentin (GFAP-/-Vim-/-), and consequently lacking intermediate filaments (Colucci-Guyon et al., 1994; Pekny et al., 1995; Eliasson et al., 1999), showed only a limited hypertrophy of cell processes. Instead, many processes were shorter and not straight, albeit the volume of neuropil reached by a single astrocyte was the same as in wild-type mice. This was accompanied by remarkable synaptic regeneration in the hippocampus. On a molecular level, GFAP-/-Vim-/- reactive astrocytes could not upregulate endothelin B receptors, suggesting that the upregulation is intermediate filament dependent. These findings show a novel role for intermediate filaments in astrocytes and implicate reactive astrocytes as potent inhibitors of neuroregeneration.
Collapse
Affiliation(s)
- Ulrika Wilhelmsson
- Department of Medical Biochemistry, Sahlgrenska Academy at Göteborg University, SE-405 30 Göteborg, Sweden
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Skoglund TS, Pascher R, Berthold CH. Aspects of the organization of neurons and dendritic bundles in primary somatosensory cortex of the rat. Neurosci Res 2004; 50:189-98. [PMID: 15380326 DOI: 10.1016/j.neures.2004.06.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2004] [Accepted: 06/25/2004] [Indexed: 11/19/2022]
Abstract
In order to analyze some aspects of the spatial organization in the primary somatosensory cortex of the rat, we have reconstructed the positions of bundles of apical dendrites and neurons in a cortical prisms measuring 0.5 mm x 0.4 mm x cortical thickness, with special reference to a hypothetical columnar organization. Complete series of semithin (0.65 microm) sections were cut, tangentially from the pial surface down to the white matter, stained and digitizalized into a computer and represented as a stack of 2D images. The mean neuron density (N(V)-value) was (60 x 10(3) +/- 15 x 10(3)) neurons/mm3. The mean number of neurons beneath 1 mm2 of cortical surface (NC-value) was (113 x 10(3) +/- 8 x 10(3)) neurons/mm2. Well-defined bundles of apical dendrites emanating from layer V pyramidal cells were observed. The bundles consisted of 3-12 (mean 5 +/- 2) dendrites. The dendrites within a bundle converged while ascending towards the pial surface and reached a maximal close packing in layer IV. Superficially, the packing density decreased again. The mutual positions of the dendrites within the bundles shifted only slightly along their course towards the pial surface. The occurrence of bundles in tangential sections through layer IV was about 190 bundles/mm2 and the average number of neurons per bundle was estimated at approximately 600. However, when calculating Voronoi-diagrams, the number of neurons, which with this mathematical technique, is ascribed to each of the reconstructed dendritic bundles, varied between 200 and 1000. The possibility that the dendritic bundles are centers in cortical cell modules is discussed.
Collapse
Affiliation(s)
- T S Skoglund
- Institute of Anatomy and Cell Biology and MEDNET-laboratory, Göteborg University, Box 420, S-405 30 Göteborg, Sweden.
| | | | | |
Collapse
|
5
|
Dolapchieva S. Computer-assisted morphometric study on the postnatal growth of axon size and myelin thickness in the ventral and dorsal roots of the rabbit. Ann Anat 2004; 186:61-8. [PMID: 14994913 DOI: 10.1016/s0940-9602(04)80125-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The morphometric analysis of the myelinated fibers is of great value in developmental, experimental, and pathological studies. The present study was performed on the ventral and dorsal spinal roots (L7) of new-born, 10-, 15-, 20-, 30-, 60-, 120- and 240-day-old rabbits. Semi-thin cross-sections were investigated by OLYMPUS Video image analyser. The average axonal diameter was measured as an average length of Feret's diameters and the specific width of the myelin sheaths as a total width of the myelin sheath. In the ventral roots, the increase of the axon size is more intensive than the increase of the myelin thickness. In adult rabbits, the mean axonal diameter for the ventral root is approximately 15% greater than the mean axonal diameter for the dorsal root, whereas the mean myelin thickness values are practically equal for both roots. For the period newborn-adult (240-day-old) rabbits, a full correlation was found in respect to the increase of the dorsal root mean axonal diameter and mean myelin thickness (380% and 380%). In the ventral roots, the mean axonal diameter increased 420% whereas the mean myelin thickness increased 350%. It is intriguing whether the greater axonal size of the ventral roots might compensate their relatively thin myelin sheaths in comparison to the dorsal roots. Our findings of essential increase (16%) of the mean myelin thickness in the last (120-240 days) period in both, ventral and dorsal roots, points to a protracted period of myelinization in the rabbit.
Collapse
Affiliation(s)
- Sabina Dolapchieva
- Department of Anatomy and Histology, Medical University Sofia, Zdrave-Str. 2, BG-1431 Sofia, Bulgaria.
| |
Collapse
|
6
|
Dolapchieva S, Eggers R, Kühnel W. Automatic image analysis of the postnatal growth of axons and myelin sheaths in the tibial and peroneal nerves of the rabbit. Ann Anat 2000; 182:133-42. [PMID: 10755180 DOI: 10.1016/s0940-9602(00)80072-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The numerous morphometric studies on the myelinated fibers in the peripheral nerves have presented varying results. Only a few studies deal with the peripheral nerves from rabbits. In this work, a morphometric study was carried out on the tibial and peroneal nerves of new-born, 10-, 15-, 20-, 30-, 60-, 90- and 240-day-old rabbits. The bilateral proximal segments of both nerves were investigated. Negatives of semi-thin cross sections were used for myelinated fiber morphometric analysis, carried out by an OLYMPUS Video image analyser. Two morphometric parameters, the average axon diameter (AD) (the average length of Feret's diameters) and the specific width of the myelin sheaths (SWMS) (specifying the total width of the myelin sheath), were evaluated for every age group. In the tibial and peroneal nerves a bimodal distribution of the average AD appeared on the 20th day, and of the SWMS on the 10th day postnatum. A tight correlation was obtained when comparing mean AD (mAD) and mean SWMS (mSWMS) in new-born and 240-day-old rabbits. From birth to adulthood the mAD increased in both nerves by about 270% and the mSWMS by about 280%. The mAD/mSWMS ratio in both new-born and 8-month-old rabbits was found to be 4 in the tibial and 5 in the peroneal nerves. According to the available data, an approach to the measurement of AD as an average length of Feret's diameters and the measurement of the myelin thickness as a SWMS has not yet been employed. An extension of this methodological approach could help to understand the growth and myelinization of peripheral nerve fibers.
Collapse
Affiliation(s)
- S Dolapchieva
- Department of Anatomy and Histology, Medical University Sofia, Bulgaria
| | | | | |
Collapse
|
7
|
Skoglund TS, Pascher R, Berthold CH. Aspects of the quantitative analysis of neurons in the cerebral cortex. J Neurosci Methods 1996; 70:201-10. [PMID: 9007760 DOI: 10.1016/s0165-0270(96)00119-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We address three problems concerning the quantitative analysis of nerve cell distribution in the cerebral cortex: (i) preparatory tissue deformation (shrinkage); (ii) difficulties in differentiating between small neurons and astroglia; and (iii) the bias introduced by the counting method. We found that staining with Richardson's solution led to no shrinkage in Vibratome-cut sections of aldehyde-fixed rat brains, but did result in staining of the neurons and left the glial cells unstained. This was in striking contrast to Nissl staining which introduced a linear shrinkage of 20-30% and stained all kinds of cortical cells indiscriminately. A computer-based unbiased counting method was implemented by taking advantage of the stereological procedure referred to as the 'optical disector' (Gundersen, H.J.G. (1986) Stereology of arbitrary particles, J. Microsc., 143: 3-45).
Collapse
Affiliation(s)
- T S Skoglund
- Institute of Anatomy and Cell Biology, University of Göteborg, Sweden.
| | | | | |
Collapse
|
8
|
Bjartmar C. Oligodendroglial sheath lengths in developing rat ventral funiculus and corpus callosum. Neurosci Lett 1996; 216:85-8. [PMID: 8904789 DOI: 10.1016/0304-3940(96)12990-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The lengths of uncompacted and partly compacted oligodendroglial sheaths in the developing rat spinal cord (SC) ventral funiculus (ages F19 and F21) and corpus callosum (CC; ages P12 and P17) were studied by serial section electron microscopy. The average newly formed uncompacted sheath is 21 and 33 microns long in the SC (F19) and CC (P12), respectively, many being less than 10 microns. In these early series, approximately 2/3 of the analysed axon length is unensheathed. The average partly compacted sheath is 102 and 69 microns long in the SC (F21) and CC (P17), respectively. Here, about 1/3 of the examined axon length is unensheathed. These results suggest that oligodendroglial sheaths initially are very short, and that they elongate actively before and during compaction. The limited unensheathed space along these axons indicate that some early sheaths must be eliminated.
Collapse
Affiliation(s)
- C Bjartmar
- Department of Cell Biology, Faculty of Health Sciences, University of Linköping, Sweden.
| |
Collapse
|
9
|
Hildebrand C, Loeliger S, Bjartmar C, Karlsson M. Sheath lengths of large motor axons in the ventral root L5 of neonatal and adult rats. Neurosci Lett 1996; 202:173-76. [PMID: 8848259 DOI: 10.1016/0304-3940(95)12242-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
This study examines the developmental sheath elongation in the rat ventral root L5. Electron microscopic analysis of serial transverse sections through roots from newborn rats shows an average internuclear distance (IND) of 66 microns (calculated fresh length 73 microns). Light microscopic analysis of teased adult roots shows that the largest fibers have an average internodal length of some 1250 microns at 5 months. Hence, large fibers exhibit a developmental sheath elongation of 17 times. The ventral root L5 elongates 11 times only. This mismatch necessitates a myelin sheath remodelling.
Collapse
Affiliation(s)
- C Hildebrand
- Department of Cell Biology, University of Linköping, Sweden
| | | | | | | |
Collapse
|
10
|
Jansson T, Gustavsson T, Rydmark M, Berthold CH, Pascher R, Skoglund T. Automated correction of linear deformation due to sectioning in serial micrographs. J Microsc 1995; 177:119-27. [PMID: 7714891 DOI: 10.1111/j.1365-2818.1995.tb03542.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This paper describes an objective and automatic method for detection and correction of sectioning deformations in digitized micrographs, as well as an evaluation of the method applied to light and electron microscopic images of semi-thin and ultra-thin serial sections from brain cortex. The detection is based on matching of image subregions and the deformation model is bi-linear, i.e. two first-order polynomials are used for modelling compression/expansion in perpendicular directions. The procedure is applicable to prealigned serial two-dimensional sections and is primarily aimed at three-dimensional reconstruction of tissue samples consisting of a large number of cells with random distribution and morphology.
Collapse
Affiliation(s)
- T Jansson
- Department of Applied Electronics, Chalmers University of Technology, Göteborg, Sweden
| | | | | | | | | | | |
Collapse
|
11
|
Skoglund T, Pascher R, Berthold CH, Rydmark M, Jansson T, Gustavsson T. 3D reconstruction of biological objects from sequential image planes--applied on cerebral cortex from cat. Comput Med Imaging Graph 1993; 17:165-74. [PMID: 8402523 DOI: 10.1016/0895-6111(93)90040-t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A prism of cat cerebral cortex was reconstructed with a method for three-dimensional (3D) representation of biological objects. A series of 918 semithin sections were digitized into an image analysis system. The images were aligned and analyzed, and a data base with the coordinates and a classification of the cells was created. The data base (i.e., the cortical prism) was visualized in a 3D graphic terminal, and parameters such as columnar and lamellar organization, clustering, and cell density were analyzed. A neuronal perikaryon and its neurites was reconstructed and shown together with the cortical prism.
Collapse
Affiliation(s)
- T Skoglund
- Department of Anatomy, Medical Faculty, Göteborg University, Sweden
| | | | | | | | | | | |
Collapse
|
12
|
Rydmark M, Jansson T, Berthold CH, Gustavsson T. Computer-assisted realignment of light micrograph images from consecutive section series of cat cerebral cortex. J Microsc 1992; 165:29-47. [PMID: 1552572 DOI: 10.1111/j.1365-2818.1992.tb04303.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two computer- and image-analysis-based procedures for realignment of images of consecutive light micrographs of nerve tissue (cat motor cortex) have been developed. One procedure (CENT) was interactive, employing the subjective overall 'best fit' of two images to each other and the other (AUTOCENT) was based on an automatic comparison of two images (image thresholding and binary comparison). Images of light micrographs of several hundred consecutive sections were realigned using the interactive and the automatic methods. The interactive procedure was easy to use; realignment of an image took only a few minutes in the hands of an experienced operator and should be easy to implement on commercially available smaller computers like PCs and workstations, but the realignment was possibly disturbed by the operator's subjective expectancy of regular forms. The automatic procedure realigned 1-4 images per hour, might be implemented on smaller computers if the programming is made more efficient, was probably objective and restored the 'true position of images'.
Collapse
Affiliation(s)
- M Rydmark
- MEDNET, Computer Laboratory of the Medical Faculty, Göteborg University, Gothenburg, Sweden
| | | | | | | |
Collapse
|
13
|
Ramírez V, Ulfhake B. Postnatal development of cat hind limb motoneurons supplying the intrinsic muscles of the foot sole. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1991; 62:189-202. [PMID: 1769098 DOI: 10.1016/0165-3806(91)90166-g] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The postnatal development of dendrite anatomy in alpha-motoneurons intracellularly labeled with horseradish peroxidase (HRP), innervating the intrinsic muscles of the sole of the foot (IFS MNs) in the cat, was investigated. The number of dendrites per neuron was about 11 and did not change from birth to adult. The number of branches per dendrite decreased during the same period by 20-25%. The net elimination of dendritic branches appeared to occur at distal branching points, as revealed by topological analysis. The dendritic branching pattern tended to be asymmetric at birth and the net decrease in dendritic branching postnatally did not alter this pattern. The length of preterminal branches (PTB) increased by a factor of 2, while terminal branch (TB) length increased by a factor of 3.3 postnatally. The large increase in TB length was attributed to both longitudinal growth and an apparent lengthening caused by resorption of distal branches during development. Dendritic length in the transverse spinal cord plane increased in parallel with the overall growth of the parent spinal cord segment, while dendritic growth along the rostro-caudal axis exceeded, by about one order of magnitude, dendritic growth in the transverse plane. Average branch diameter doubled from birth to adult. The decrease in branch diameter across branching points did not obey satisfactorily to the 'power rule' of Rall. However, the 1.5 power ratio of daughters-to-parents branch dropped from 1.18 to 1.08 between 3 weeks of age and adult. Tapering was evident in both PTBs and TBs. The rate of taper did not change postnatally. From birth onwards, 'local' branch diameter correlated closely with amount of membrane area and combined length of the dendritic branches located distal to the 'supporting' parent branch. These relations were similar in all age groups and are suggested to be properties intrinsic to the IFS MNs. The local branch diameter also co-varied with the number of distal dendritic branches, but in this case there was a systematic shift in the relationship with increasing postnatal age. It appears that the local diameter in IFS MN dendrites is a key indicator of the size of the distal dendritic arborization.
Collapse
Affiliation(s)
- V Ramírez
- Department of Anatomy, Karolinska Institutet, Stockholm, Sweden
| | | |
Collapse
|
14
|
Reles A, Friede RL. Axonal cytoskeleton at the nodes of Ranvier. JOURNAL OF NEUROCYTOLOGY 1991; 20:450-8. [PMID: 1869882 DOI: 10.1007/bf01252273] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The relationship between the degree of nodal narrowing and the changes in the structure of the axonal cytoskeleton was studied in 53 fibres of mouse sciatic nerve. Nodal narrowing increased with increasing fibre calibre to reach about 20% of the internodal area in the thicker fibres. The narrowing corresponded quantitatively to a decreased number of nodal neurofilaments. Nodal microtubule numbers varied greatly, and a majority of fibres had considerably (approximately 55%) more microtubules in their nodal profile than in the internode. Nodal profiles of different calibre showed an increase in the number of filaments and of microtubules with nodal calibre, although at rates different from those in the internode. The degree of observed axon non-circularities had no discernible effect on the restructuring of the axonal cytoskeleton at the node. A transnodal transport of the axonal cytoskeleton can occur with: (1) accelerated transnodal transport of filaments, (2) stationary internodal fraction of filaments, (3) depolymerization of filaments proximal to the node and repolymerization distally, or (4) different nodal and internodal polymerization equilibria.
Collapse
Affiliation(s)
- A Reles
- Department of Neuropathology, University of Göttingen, Federal Republic of Germany
| | | |
Collapse
|
15
|
Gatzinsky KP, Berthold CH, Rydmark M. Axon-Schwann cell networks are regular components of nodal regions in normal large nerve fibres of cat spinal roots. Neurosci Lett 1991; 124:264-8. [PMID: 2067726 DOI: 10.1016/0304-3940(91)90109-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The paranodal occurrence of axon-Schwann cell networks (ASNs), which are entities assumed to take part in the removal of degenerate axonal material, was examined quantitatively by electron microscopical serial section analysis in normal cat ventral and dorsal spinal roots. In nerve fibres greater than or equal to 10 microns in diameter 88% of the nodal regions in the ventral roots and 97% in the dorsal roots showed ASN complexes, which especially in the ventral roots often consisted of many segregated axoplasmic portions. The corresponding frequencies in fibres less than 10 microns were 28% and 62% in the ventral and the dorsal roots, respectively. ASN complexes were rare in fibres less than 5 microns. The results show that the ASN is a part of the normal paranodal architecture in large myelinated nerve fibres. The ASN occurrence seems to differ with neurone type.
Collapse
Affiliation(s)
- K P Gatzinsky
- Department of Anatomy, University of Göteborg, Sweden
| | | | | |
Collapse
|
16
|
Ornung G, Ulfhake B. Changes in size and shape during histochemical preparation for light and electron microscopy of neurons intracellularly labelled with horseradish peroxidase. ACTA PHYSIOLOGICA SCANDINAVICA 1990; 140:501-6. [PMID: 2082712 DOI: 10.1111/j.1748-1716.1990.tb09026.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In this study we show that neurons labelled intracellularly with horseradish peroxidase react differently from surrounding unlabelled neurons in vibratome sections during histological preparations for light and electron microscopy. The diameters and cross-sectional area of the cell bodies of intracellularly horseradish peroxidase-labelled neurons increased by about 6 and 11% respectively, while the surrounding unlabelled neurons decreased by the same amount. Also, the caliber of the proximal dendrites of horseradish peroxidase-labelled neurons increased during the histological preparation while dendritic path lengths remained unchanged. Since the surrounding tissue shrunk, the dendritic path shapes became more tortuous during histological processing. The demonstrated reaction of horseradish peroxidase-labelled neurons is suggested to be caused by the horseradish peroxidase reaction product.
Collapse
Affiliation(s)
- G Ornung
- Department of Anatomy, Karolinska Institutet, Stockholm, Sweden
| | | |
Collapse
|
17
|
Risling M, Lindå H, Cullheim S, Franson P. A persistent defect in the blood-brain barrier after ventral funiculus lesion in adult cats: implications for CNS regeneration? Brain Res 1989; 494:13-21. [PMID: 2765912 DOI: 10.1016/0006-8993(89)90138-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Previous studies have shown that, in adult cats, spinal motoneurons are able to regenerate their axons after lesions in the ventral funiculus of the spinal cord. These axons regrow through a scar tissue composed of glial processes and connective tissue elements before they enter the denervated ventral root. In the present study the integrity of the blood-brain barrier (BBB) in the lesion area was assessed by i.v. injections of horseradish peroxidase (HRP), 3 weeks to 7 months postoperatively. The lesion area in the lumbosacral spinal cord was compared with the intact cervical spinal cord and the area postrema in the light and electron microscope. The results show that the BBB fails after a ventral funiculus lesion. The BBB was not restored during the examined period. The leakage of HRP appears to be the result of a transendothelial vesicular transport. In addition, it was observed that the blood vessels in the lesion area were surrounded by wide and irregular perivascular spaces with broken outer basal laminae. Other studies on traumatic defects in the BBB have indicated that the barrier is reorganized within 4 weeks after the lesion. The possibility that a prolonged defect in the BBB after a ventral spinal cord lesion might be linked with the survival of axonal sprouts is discussed.
Collapse
Affiliation(s)
- M Risling
- Department of Anatomy, Karolinska Institutet, Stockholm, Sweden
| | | | | | | |
Collapse
|
18
|
Torch S, Stoebner P, Usson Y, D'Aubigny GD, Saxod R. There is no simple adequate sampling scheme for estimating the myelinated fibre size distribution in human peripheral nerve: a statistical ultrastructural study. J Neurosci Methods 1989; 27:149-64. [PMID: 2709883 DOI: 10.1016/0165-0270(89)90098-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Morphometric studies of peripheral nerves (PN) usually involve some sampling of the myelinated fibres (MF). In order to scrutinize the statistical properties of the sampling processes in common use and the reliability of the resulting estimates, a quantitative analysis of human superficial peroneal nerves from 8 different normal subjects was undertaken at the ultrastructural level, both in terms of MF spatial distribution and of their size distribution. This study used sampling rates involving more than 10% of the whole myelinated fibre population observed in each nerve fascicle. However, in nearly all the fascicles evaluated, the sampling fluctuations are so high that neither the number of axons nor their diameter distribution can be assessed with enough accuracy. A systematic study of the myelinated fibres shows that the spatial distribution of their size is not uniform. This marked heterogeneity in the MF size distribution imposes measurement of large enough samples (500 or 600 MFs usually represent about one-half or two-thirds of the whole MF population) in a way to secure a reliable enough estimate of the density and size distributions. However, the practical usefulness of sampling schemes requiring more than one-half of the whole MF population in a nerve fascicle, is questionable.
Collapse
Affiliation(s)
- S Torch
- Laboratoire de Biologie Animale, Unité Associée CNRS no 682, Université Joseph Fourier, Grenoble, France
| | | | | | | | | |
Collapse
|
19
|
Ulfhake B, Cullheim S, Franson P. Postnatal development of cat hind limb motoneurons. I: Changes in length, branching structure, and spatial distribution of dendrites of cat triceps surae motoneurons. J Comp Neurol 1988; 278:69-87. [PMID: 3209753 DOI: 10.1002/cne.902780105] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The postnatal development of length, branching structure, and spatial distribution of dendrites of triceps surae motoneurons, intracellularly stained with horseradish peroxidase, was studied from birth up to 44-46 days of postnatal (d.p.n.) age in kittens and compared with corresponding data from adult cats. The number of dendrites of a triceps surae motoneuron was about 12, and the arborization of each dendrite generated an average of 12-15 terminal branches. There was no net change in the number of dendrites of a neuron or in the degree of branching of the dendrites despite the occurrence of both a transient remodeling of the dendritic branching structure and changes of the spatial distribution of the dendritic branches during postnatal development. The perisomatic territory in the transverse plane occupied by the dendritic branches of a motoneuron increased in parallel with the overall growth of the spinal cord. Thus, the relative size of the dendritic territory in this plane was kept almost constant, whereas dendritic branches projecting in the rostrocaudal direction grew much faster than the spinal cord and also became more numerous. At birth the rostro-caudal dendritic span of individual motoneurons bridged 1:6 to 1:5 of the L7 spinal cord segment length; this figure was 1:3 at 22-24 d.p.n. Hence, in this direction, the growing dendritic branches invaded novel dendritic territories. The change in dendritic branch length from birth to 6 weeks of age corresponded to an average growth rate of 2 to 4 microns per dendritic branch and day, which implies that the total increase in length of the dendrites of a neuron could amount to 1 mm/day. The increase in branch length did not occur in a uniform or random manner; instead, it followed a spatiotemporal pattern with three phases: From birth to 22-24 d.p.n., growth was particularly prominent in greater than or equal to 3rd order preterminal and 2nd through 6th order terminal branches. From 22-24 to 44-46 d.p.n., a large increase in branch length confined to terminal branches of greater than or equal to 3rd branch orders was observed. As indicated by topological analysis, this length increase was probably due in part to a resorption of peripheral dendritic branches during this stage of development. From 44-46 d.p.n. to maturity, the increase of dendritic branch length was restricted to preterminal branches of low (less than or equal to 4th) branch order.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- B Ulfhake
- Department of Anatomy, Karolinska Institute, Stockholm, Sweden
| | | | | |
Collapse
|
20
|
Abstract
A quantitative and morphometric study has been done on the effects of age on myelinated nerve fibres of the sciatic nerve of rats ranging from 100 to 824 days of age. Using 1.0 micron semi-thin sections and a particle size analyser (TGA 10, Zeiss) it was found that both myelin sheaths and their associated axons grew in diameter until about 400 days of age, but massive destruction and disappearance of myelinated nerve fibres became manifest only after 700 days of age. In addition, onset, development and distribution of degenerative changes of nerve fibres were studied in spinal roots, lumbar plexus and sciatic nerves. Analysis of the observed data suggests that two independent mechanisms are involved in the degenerative changes of myelinated peripheral nerve fibres with age: one is axonal atrophy or loss and the other is vacuole forming, segmental demyelination and remyelination. The former begins very early in a limited number of nerve fibres and in more distal parts of the nerve, while the latter begins at a significantly later age and from the most proximal (spinal root) region.
Collapse
Affiliation(s)
- H Kazui
- Department of Neuropathology, Tokyo Metropolitan Institute for Neurosciences, Japan
| | | |
Collapse
|
21
|
Abstract
In order to clarify the in situ shape of axons, the entire shape of freeze-substituted axons (FS axons) was compared with that of chemically-fixed axons (CF axons) using the serial semi-thin section method coupled with rapid freezing technique. Mouse saphenous nerves were rapidly frozen by being contacted against a pure copper block cooled to 4 K by liquid helium. At the internode, the FS axons showed a cylindrical outline while the CF axons showed a polygonal contour. At regions near the node of Ranvier, both FS and CF axons showed a cog-wheel contour, and at the node they became circular and highly attenuated. These findings indicated that the axons, at the internode, were artifactually distorted during chemical fixation and that the in situ shape of myelinated axons was characterized by the cylindrical internodal segment, the distorted juxtaparanodal segment and the attenuated nodal segment. The physiological meanings of the entire shape of axons were discussed with special reference to the molecular mechanism of slow axonal transport and membrane excitation.
Collapse
|
22
|
McCartney MD, Dickson DH. Morphometric analysis of circadian variations in the retinal photoreceptor synaptic terminals of the adult and fetal guinea pig. THE AMERICAN JOURNAL OF ANATOMY 1986; 176:1-17. [PMID: 3728342 DOI: 10.1002/aja.1001760102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In order to test whether the alterations in photoreceptor synaptic terminal size and shape reported in lower vertebrates occur in a mammalian visual system, adult and fetal guinea pig retinas were exposed to an LD 12:12 lighting cycle, as well as to long-term light (LL) and long-term dark (DD) regimes. Representative random samples from all retinal quadrants, obtained at various times during these lighting regimes, were processed for electron microscopy. The synaptic terminals of all three photoreceptor cell types in this retina (alpha and paranuclear rods, and cones) were analyzed with computer-assisted morphometrics for changes in their area, perimeter, synaptic vesicle density, and the degree of plasmalemmal infolding. The data showed all three types of adult receptor terminals to have increased area and vesicle density, as well as decreased membrane infolding, during the light period, while both types of rods showed increased perimeter measurements in the dark. Results from adults maintained under extended lighting conditions (LL and DD) showed no difference when compared with sample times during a typical LD 12:12 lighting regimen where clear statistical differences existed. Data from fetal retinas showed no significant sustainable pattern in any of the measured variables. These quantitative findings have led to the conclusion that while alterations in perimeter measurements may be explained by using the vesicle recycling hypothesis, observed changes in terminal size and shape may be controlled by a light-initiated or light-enhanced mechanism and effected through an annular configuration of cross-striated fibrils found within these photoreceptor synaptic terminals.
Collapse
|
23
|
Abstract
The thickness of the myelin sheath of nerve fibers was traditionally assessed solely as a function of axon caliber. Studies concerning the additional effect of variation in internode length are of relatively recent date. Carefully calibrated measurements of sheath thickness and internode geometry were used in this study to define an equation to predict the approximate number of lamellae from axon caliber and internode length, for normal and regenerated peripheral nerve fibers, and for fibers from hypomyelinated murine mutants. The definition of sheath thickness thus obtained was compared with different assumptions on the biophysical nature of myelin sheath resistance. The observed relations between sheath thickness and internode geometry were not compatible with an effective adjustment of sheath thickness to a radial flow of current across the sheath. Conversely, sheath thickness was found to vary in such a way that the resistance of the spiral path between the lamellae was matched precisely to axonal current density. The calculated resistance of the spiral leakage path, furthermore, was equal to measured sheath resistance. This new concept reconciles low sheath resistance with a high resistance of the myelin leaflet, yielding, at the same time, a fine tuning of sheath resistance to variations of internode geometry.
Collapse
|
24
|
Friede RL. Computer editing of morphometric data on nerve fibers. An improved computer program. Acta Neuropathol 1986; 72:74-81. [PMID: 3548204 DOI: 10.1007/bf00687950] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A short guide is given for the planning of nerve fiber morphometry using computer-assisted methods. A new computer program is introduced which allows, among other factors, correction for myelin sheath shrinkage. If myelin shrinkage is not corrected for, there will be false high values for axon caliber and false low values for sheath thickness. The magnitude of the skew produced by this factor is shown on hand from computer editing.
Collapse
|
25
|
Saxod R, Torch S, Vila A, Laurent A, Stoebner P. The density of myelinated fibres is related to the fascicle diameter in human superficial peroneal nerve. Statistical study of 41 normal samples. J Neurol Sci 1985; 71:49-64. [PMID: 4087019 DOI: 10.1016/0022-510x(85)90036-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The density of myelinated fibres in the superficial peroneal nerve was studied in 41 samples from 24 control human subjects. Photographic montages of the whole nerve fascicle were made from semithin and ultrathin transverse sections and used for a statistical analysis of sampling procedures, range of variations and relations between density and other variables. The results indicate that the spatial distribution of myelinated fibres within a nerve is often non-uniform. Therefore, it was not possible to define a statistically valid sampling system. The study of relations between variables shows the lack of any correlation between density and age and a considerable variation in the density. In contrast, there is a strong positive linear correlation between the surface area of the nerve fascicle and its content of myelinated fibres. That is, the fibre density of a given normal nerve is related to its diameter and can be predicted within a narrow range of error. We propose the term "derived density" for this value, and its application as a tool in the diagnosis of peripheral neuropathies is now being studied.
Collapse
|
26
|
Friede RL, Beuche W. Combined scatter diagrams of sheath thickness and fibre calibre in human sural nerves: changes with age and neuropathy. J Neurol Neurosurg Psychiatry 1985; 48:749-56. [PMID: 4031926 PMCID: PMC1028445 DOI: 10.1136/jnnp.48.8.749] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A computer-assisted method permits collection of large numbers of measurements of fibre profiles in electron micrographs of human sural nerve biopsies. The method is based on simultaneous demonstration of fibre calibre and of sheath thickness in terms of the g-ratio (quotient axon diameter/fibre diameter), and on the recalculation of all parameters for circular fibre profiles. The fibres of small and large diameters of human sural nerves were found to form separate populations with distinctly different trends for sheath thickness and also different patterns of maturation. Preliminary data in neuropathy show that this method gives a better distinction of the extent of damage to either of the two populations; it also permits assessment of the number of regenerating or remyelinating fibres.
Collapse
|
27
|
Hodgkiss JP, McIlroy HM. The conduction velocity, number, and diameter of unmyelinated fibers in Remak's nerve. EXPERIENTIA 1985; 41:919-21. [PMID: 4007127 DOI: 10.1007/bf01970012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Remak's nerve in the chicken was examined ultrastructurally and electrophysiologically to determine the characteristics of fibers in the nerve trunk. The ration of unmyelinated fibers to myelinated ones was 111:1. The mean number of unmyelinated fibers was 3555 plus/minus 232 (SEM, n=5) and they had a mean diameter of 0.502 plus/minus 0.034 (SEM) micron. The compound action potential consisted almost entirely of a large diphasic waveform which had a mean peak conduction velocity of 0.62 plus/minus 0.031 (SEM, n=5) m.s-1 at 37 degrees C.
Collapse
|
28
|
Berthold CH, Rydmark M. Electrophysiology and morphology of myelinated nerve fibers. VI. Anatomy of the paranode-node-paranode region in the cat. EXPERIENTIA 1983; 39:964-76. [PMID: 6884495 DOI: 10.1007/bf01989761] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
29
|
Rydmark M, Berthold CH. Electron microscopic serial section analysis of nodes of Ranvier in lumbar spinal roots of the cat: a morphometric study of nodal compartments in fibres of different sizes. JOURNAL OF NEUROCYTOLOGY 1983; 12:537-65. [PMID: 6619904 DOI: 10.1007/bf01181523] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Serially sectioned nodes of Ranvier from nerve fibres 2-20 micron in diameter of feline ventral and dorsal spinal roots were examined electron microscopically, reconstructed to scale and analysed morphometrically. The assumed 'fresh-state' value of several structural variables, considered to be of functional significance, were calculated by the use of compensation factors. The compensated data were plotted against fibre and axon diameters. It was calculated that the membranous area of the 'fresh-state' nodal axon segment increased more or less exponentially from less than 5 micron2 to 30 micron2 with increasing fibre diameter (D). Most variables associated with the nodal gap and the Schwann cell initially increased rapidly with D and then levelled out or even decreased in fibres with a D value greater than 8-12 micron. The area open for communication between the nodal axolemma and the endoneurial space was 30-100 times smaller than the membrane area of the nodal axolemma. The volume of the extracellular space in the nodal gap, outside the nodal axolemma, increased linearly from less than 0.1 micron3 to about 0.6 micron3 with increasing fibre size. The Schwann cell membrane area facing the nodal gap outnumbered the membrane area of the nodal axon by 10-15 times in nerve fibres with a D value between 5 and 15 microns. Some functional implications of the 'fresh-state' nodal model are discussed.
Collapse
|
30
|
Berthold CH, Rydmark M. Electron microscopic serial section analysis of nodes of Ranvier in lumbosacral spinal roots of the cat: ultrastructural organization of nodal compartments in fibres of different sizes. JOURNAL OF NEUROCYTOLOGY 1983; 12:475-505. [PMID: 6875620 DOI: 10.1007/bf01159386] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The general ultrastructural organization of nodes of Ranvier in peripheral nerve fibres from 2 to 20 microns in diameter (D) was investigated in the adult cat using serially sectioned ventral and dorsal spinal roots. The study was performed in order to collect and systematize information considered necessary for a morphometric analysis of the node of Ranvier. In all cases a node of Ranvier could be divided into a central nodal axon segment and a surrounding nodal Schwann cell compartment. The latter included a nodal gap matrix substance, more or less overlapping nodal Schwann cell collars and, as a rule, also a Schwann cell brush-border emanating from the nodal Schwann cell collars and occupying the nodal gap. The relative size and the organization level of the nodal Schwann cell compartment increased with increasing fibre size up to a fibre diameter of 8-10 microns. At this fibre size the nodal gap was of a fairly even height (1 micron) all around the nodal axon and contained a thick brush-border of densely packed, more or less radially arranged Schwann cell microvilli. In very small fibres (D less than 3 microns) the nodal gap was low (less than 0.1 microns) and contained no or few microvilli. In fibres greater than 10 microns in diameter the relative size and the degree of structural order of the nodal Schwann cell compartment decreased with increasing fibre size. Drastic sectorial variations in nodal gap height and local thinning-out of the brush-border became prominent features in the largest fibres. The possible in vivo organization of the nodal Schwann cell compartment is discussed. Preliminary calculations indicate that the extracellular space directly surrounding the nodal axon might be quite small and that the area open for free communication between this extracellular space and the endoneurial space might be very much restricted, measuring as little as 2% of the area of the nodal axolemma. Algorithms for calculating various nodal structural parameters are discussed.
Collapse
|