The cornea consists of cells (nuclei with plenty of cytoplasmic protein) and
parallel bundles (lamellae) of collagen fibres, also protein. It is wonderful
that the normal cornea is transparent.
Doesn't any fixative make the cornea opaque?
Davidson's (=Hartmann's) fixative contains plenty of formaldehyde (to add to
and slowly crosslink all protein molecules, including collagen fibrils) but
perhaps not quite enough ethanol to rapidly coagulate soluble proteins in
cytoplasm.
(Davidson's 22.2% v/v EtOH is slightly more than in sherry, madeira or
vermouth; about half of that in whisky, gin etc.) The acetic acid (about 10%)
can be expected to make nuclear DNA molecules and their associated proteins
shrink into the patterns we see as typical of different cell-types.
Most of the many formalin-acetic-alcohol fixatives contain enough ethanol to
bring about protein coagulation before the more slowly reacting formaldehyde
does its stuff. As Tony points out, more research is needed.
John Kiernan
https://www.schulich.uwo.ca/anatomy//people/faculty/emeriti/kiernan_john.html
= = =
From: Tony Henwood via Histonet
Sent: June 27, 2024 7:17 PM
To: histonet@lists.utsouthwestern.edu ;
Davoli, Katherine A
Subject: Re: [Histonet] cloudy cornea after Hartman's fix
Hartman's (also known as Davidson's) fixative is sometimes used to reveal lymph
nodes in resections where they appear opaque - white. It is not surprising that
the tissues of the eye would react the same.
I assume that the alcohol causes the bleaching of the tissue (or is it the
acetic acid?) - more research needed.
Regards,
Tony Henwood MSc, BAppSc, GradDipSysAnalys, CT(ASC), FFSc(RCPA) (Retired)
Principal Scientist, the Children’s Hospital at Westmead (Retired)
Adjunct Fellow, School of Medicine, University of Western Sydney.
From: Davoli, Katherine A via Histonet
Sent: 28 June 2024 04:12
To: histonet@lists.utsouthwestern.edu
Subject: [Histonet] cloudy cornea after Hartman's fix
Anyone know why the cornea of my pig eye got white/cloudy on dropping it in to
Hartman's fixative? I'm used to working with mice where, if this happens I
didn't notice.
Katherine Davoli, MDiv, HTL(ASCP)cm(they/them/theirs)
Lab Manager, Tissue Culture & Histology Cores, U. Pitt Dept of Ophthalmology
7.373 UPMC Mercy Pavilion1622 Locust St., Pittsburgh PA 15219
(412) 624-8508 this number cannot receive texts
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