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Morphology of early developing oligodendrocytes in the ventrolateral chicken spinal cord
Linköping University, Department of Biomedicine and Surgery, Cell biology. Linköping University, Faculty of Health Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

As observed by Del Rio-Hortega (1928), the oligodendroglial population includes Type I and 11 cells related to several thin axons, Type III cells with a few processes in relation to relatively thick axons and Type IV cells related to a single thick axon. This structural diversity of oligodendrocytes is accompanied by a molecular heterogeneity. In the chicken spinal cord oligodendrocytes have begun to contact axons at embryonic day (E)10 and compact sheaths have appeared by E12. AI the latter stage, most sheath-forming oligodendrocytes contact more than one axon. At E15, however, each sheath-forming cell seems to have developed a Schwann cell-like anatomy, being related to a single axon. Against this background, the present study examines the 3D anatomy of early developing oligodendrocytes in the chicken spinal cord. Examination of slices immunostained with antibodies against the oligodendroglial marker 04 showed that a few positive cells are at hand at E6, after which the occurrence increases with age. At E12 most immunostained cells have two or more processes. At E15 however, dye-injected oligodendrocytes have developed a Type IV structure. Between E12 and E15, mean sheath length increases some 4x, from 50 µm to over 200 flm, while the length of the spinal cord increases 36% only. Hence, early oligodendrocytes in chicken white matter develop a Type IV anatomy between E12 and E15 through an elimination of sheaths.

National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-81479OAI: diva2:552883
Available from: 2012-09-17 Created: 2012-09-17 Last updated: 2012-09-17Bibliographically approved
In thesis
1. The type IV Oligodendrocyte: experimental studies on chicken white matter
Open this publication in new window or tab >>The type IV Oligodendrocyte: experimental studies on chicken white matter
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In mammals, islet amyloid polypeptide (IAPP) is co-produced with insulin in pancreatic ß-cells. In the chicken, the expression of IAPP in the brain is more than 10-fold higher than in the pancreas. We made the fortuitous finding that a polyclonal rabbit antiserum raised against chicken IAPP did not recognise the immunogen, but labelled a subpopulation of oligodendroglia! cells in chicken white matter. The hitherto unknown antigen was called T4-O (Type 4 Oligodendrocyte) since it was localised to the Schwann cell-like Type IV oligodendrocyte of Del Rio-Hortega (1928). This formed a starting point for the present thesis, which is centred on the Type IV oligodendrocyte in chicken white matter.

Biochemical analysis of chicken spinal cord showed that the T4-O molecule is a protein with a molecular weight of approximately 100 kDa and an isoelectric point of about 4. Further characterisation has not yet been possible.

Immunohistochemical studies on frozen sections revealed that the white matter oligodendrocytes exhibit subpopulations expressing T4-O immunoreactivity strongly, weakly or not at all. Strongly T4-O immunoreactive (IR) oligodendrocytes are co-localised with thick myelinated fibres in the ventral (VF) and lateral funiculi of the spinal cord. A corresponding T4-O immunoreactivity is not found in the fish, the frog, the turtle, the rat and the rabbit.

To find out when the T4-0 antigen first appears during development we examined sections from embryonic and post-hatching chicken spinal cords by immunohistochemistry. This showed that the T4-O molecule is first expressed in the VF at embryonic day (E)15, after which the number of IR cells increases with age. Oligodendrocytes cultivated in vitro without or with neurons do not develop a T4-O IR phenotype.

These findings called for a closer analysis of the structural development of chicken VF white matter. Electron microscopic (EM) examination revealed a developmental sequence of events principally similar to the development of mammalian white matter, but with a more rapid time course. As seen in the electron microscope the first compact myelin has appeared by E12, when most oligodendrocytes are multipolar. By E15 it seems that these cells have developed a Type IV phenotype, possibly by eliminating some sheaths.

Histochemical analysis of Vibratome sections showed that Marchi-positive myelinoid bodies are enriched in white matter areas containing many T4-O IR oligodendrocytes and many large myelinated axons.

Examination of the three-dimensional (3D) anatomy of early VF oligodendrocytes in Vibratome slices after 04 labelling or after intracellular injection of a fluorescent dye revealed that these units indeed are Schwann cell-like, with a start length of around 50 µm. We also found that these sheaths expand very rapidly, reaching lengths exceeding 200 µm in three days (E12- E15). The 3D data conformed to our EM evidence that the early oligodendrocytes develop a unipolar Schwann cell-like Type IV anatomy through elimination of some sheaths.

To my knowledge the present observations represent the first evidence for an oligodendroglia! heterogeneity in the chicken spinal cord. Differences among oligodendrocytes might, conceivably, explain why inherited disorders of myelin metabolism such as Krabbe's disease, affect some CNS areas more than others.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2002. 96 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 720
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-25545 (URN)9992 (Local ID)91-7373-162-5 (ISBN)9992 (Archive number)9992 (OAI)
Public defence
2002-03-08, Berzeliussalen, Universitetssjukhuset, Linköping, 13:00 (Swedish)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2012-12-04Bibliographically approved

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