PIPES-buffered glutaraldehyde has been used for subsequent electron
micr= oscopy since the early 1970s but it has been shown to cause
artifacts - = intracellular vesicles and myelin figures
- when used for perfu= sion fixation of the brain. See
Schultz RL= & Wagner DO (1986)
Membrane alterations in cerebral cortex when= using PIPES buffer.
J. Neurocytol. 1= 5:
461-469. The authors attributed these art= ifacts,
which potentially could be mistaken for pathological changes,= to
the low toxicity of PIPES. Apparently cacodylate or phosphate buff er prevented the metabolic changes that caused the artifacts during
the = early phase of fixation, but PIPES allowed the changes to
occur. <= BR> The reason for using cacodylate
buffer rather tha= n phosphate is that it doesn't precipitate with
calcium ions. A Ca s= alt in the fixative improves the
immobilization of phospholipids in cell membranes. John Kiernan Anatomy,
UW= O London, Canada = = = ----- Original
Messa= ge ----- From: Robert Richmond
<RSRICHMOND@aol.com&= gt; Date: Sunday,
November 16, 2008 14:13 Subjec= t: [Histonet] Re:
Buffer. To: histonet@lists.utso uthwestern.edu
> About the potential toxicity
of= arsenic-containing cacodylate buffers: >
>= A Histonetter who prefers to remain anonymous notes
>>The= arsenic > discussion comes up on
the Microscopy Listserve= r every once in while, >
usually because someone is eith= er pregnant & concerned about
exposure > or has sa= fety officers who freak out over
the stuff. It was used in &g= t; the early days because
phosphate buffers can interact with some <= BR>> of
the > fixative combinations and leave pre= cipitates.
Also, I'd suspect, > cacodylate is less= prone to
beasties growing in stock solutions over > time.= The
"modern" zwitterionic buffers are used a lot these &g t; days - > PIPES & that crowd - if you want
to = avoid cacodylate & >
phosphate.<<= > Those zwitterionic
buffers are often referred to as Goo= d's > buffers
or > Good buffers, since = they were introduced by
Norman Good in the 1960's. > S= ee >
http://en.wikipedia.org/wiki/Good's_buffers > > I don't know why they aren't
commo= nly used as buffers for > histologic
fixatives. = > > Bob
Richmond > Samurai Pathologi= st >
Knoxville TN > > ___ _______________________ 5F ____________________ =2
6g= t; Histonet mailing list >
Histonet@lists.utsouthwes= tern.edu >
http://lists.utsouthwestern.edu/mailman= /listinfo/histonet
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