neurilemma

[cmungall]

Current representation of neurilemma is vague and confused

Attempt to group Drosophila with mammal/vertebrate structure results in incoherency, since we follow various defs that state neurilemma is made of Schwann cells, and FBbt classifies as acellular. No def in FBbt (@dosumis, any suggestions?)

This is blocking release, so as a quick fix classify as multi-cell-part structure (which is part of a Schwann cell in verts) but should do a more comprehensive analysis later

[dosumis]

From memory - neurilemma in insects is acellular - secreted by the 'glial cells' that wrap nerves (note - not individual axons). There may be some functional reasons for the shared name. So, need distinct foundry unique name for each. @mmc46 - can you confirm details?

[mmc46]

All except one paper that I've found define neurilemma as acellular (a layer of finely granular and fibrillar material). Defined for insects in general. I'll add a definition to the term.

For the record, 2 confusing issues: a few papers use neurolemma instead of neurilemma. And neurilemma cell is used as a synonym for the thecogen or eo glial cell of an external sensory organ (tbc). I'll be adding these synonyms as well.

[RDruzinsky]

In vertebrates or chordates, the term neurolemma or neurilemma is not used much these days. I found this footnote in a classic textbook of histology:

"Originally the word neurilemma, as employed by European workers early in the twentieth century, meant the connective tissue tunic, continuous with the pia mater, known today as the endoneurium. English-speaking authors, however, used the term to designate the clear layer of Schwann membranes defined above in the text. A related term, axolemma, originally referred to the inner membrane of the Schwann cell, but it is now commonly used to signify the plasmalemma of the axon" (Bloom and Fawcett 1975 A Textbook of Histology, 10th ed., pg. 352).

Some contemporary authors (e.g., Moore, Dalley, Agur 2010 Clinically Oriented Anatomy, sixth ed., pg. 1079) seem to treat neurolemma and the entire layer of Schwann cells of peripheral axons as synonyms, which is consistent with the footnote above. However, many contemporary anatomy and histology texts do not even mention these terms.

Robert E. Druzinsky, Ph.D. Clinical Associate Professor Dept. of Oral Biology College of Dentistry University of Illinois at Chicago 801 S. Paulina Chicago, IL 60612 druzinsk@uic.edu

Office: 312-996-0406 Lab: 312-996-0629 Website: www.peerj.com/RobertDruzinsky

On Mon, Feb 23, 2015 at 9:43 AM, mmc46 notifications@github.com wrote:

All except one paper that I've found define neurilemma as acellular (a layer of finely granular and fibrillar material). Defined for insects in general. I'll add a definition to the term.

For the record, 2 confusing issues: a few papers use neurolemma instead of neurilemma. And neurilemma cell is used as a synonym for thecogen cell of an external sensory organ.

— Reply to this email directly or view it on GitHub https://github.com/obophenotype/uberon/issues/646#issuecomment-75567527.

[cmungall]

Thanks RObert, this is v helpful.

Looks like all these classes need a bit of work

[mmc46]

FBbt also has a 'neural lamella' term (FBbt:00007088). def: "Acellular sheath which forms the outermost layer of the central nervous system. It consists, in part, of a matrix of 'collagen-like' fibers and is invaded by tracheoles." [FlyBase:FBrf0058936, ISBN:978-0-7204-7136-6]

The only difference with 'neurilemma' being that 'neural lamella' is part of the CNS, whereas the former is part of the nervous system. Though I have not seen this clear distinction in the literature. Many papers use 'neural lamella' as a synonym for neurilemma, others for the outer layer of the neurilemma, when the latter encompasses the acellular and cellular layer (perineurium).

Does 'neural lamella' exist in vertebrates?

In locusts (Ashhurst, 1959, Quarterly Journal of Microscopical Science, 3-51, 401-412): "Several different terms have been used for the two layers of the sheath. The outer, non-cellular layer has most commonly been called the neural lamella (Schneider, 1902; Scharrer, 1939; Wigglesworth, 1950; Hoyle, 1952; Imms, 1957; Hess, 1958), but it has also been referred to as the perilemma (Wigglesworth, 1956; Smith and Wigglesworth, 1959) and the 'guaina neurale' (Baccetti, 1955). A similar situation exists for the underlying cells, since they have been called either the perineurium (Schneider, 1902; Scharrer, 1939; Wigglesworth, 1950, 1956; Baccetti, 1955), the epineurium (Imms, 1957), or the perilemma (Hoyle, 1952; Hess, 1958). The two layers together have been called the perilemma (Scharrer, 1939; Baccetti, 1955) and the epineurium (Imms, 1925), while the developing sheath has been called the neurilemma (Eastham, 1930; Roonwal, 1937; Johannsen and Butt, 1941). In this paper it is proposed to use the term 'neural lamella' for the outer, non-cellular layer. The underlying layer of cells will be referred to simply as the sheath-cells. It is suggested that the terms 'perineurium' and 'epineurium', which are used for different connective tissue layers in vertebrate nerves, should not be used, since the insect nerve-sheath is not homologous with that found in vertebrates."

[gouttegd]

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