On Sat, 24 Jul 1999, Elizabeth Wenig wrote:

> Thanks for your response! Could you try to address some other issues on
> the subject,eg: the effect/wear of the salts on the VIPs, the
> processing quality of certain tissues,etc.
> In appreciation,
> Elizabeth
                                               25/7/1999
    Dear Elizabeth,

    It's nice to be appreciated, but:-

    I'm not sure what you mean. An alcoholic formaldehyde fixative
    usually does not contain any salts: typically it's alcohol,
    formalin, acetic acid and water, with many variations in the
    concentrations. I would advise against buying a commercial
    mixture unless its exact composition is declared and you
    intend to use it all in the near future. These mixtures
    change with time: ethyl acetate is slowly formed by reaction
    of ethanol and acetic acid. (I know at least one paper that
    provides evidence of improved fixation because of chemical
    changes in older solutions. In that case the fixative also
    contained picric acid.) If you mix a formal-acetic-alcohol
    (FAA) combination shortly before using, you know it will be
    The same every time. If you are not satisfied with the result
    you can vary concentrations one at a time.

    As for "VIP," to me this is vasoactive intestinal polypeptide.
    I have immunostained for it in material fixed in neutral
    buffered formaldehyde and in neutral formaldehyde with picrate,
    and so have many others. I do not know if it is preserved by FAA. 
    I cannot think of a reason why its antigenicity should not be 
    well preserved, but the only way to know is by trying it out with
    a known positive control such as a sensory ganglion or (more
    difficult) small intestine or skin. VIP is present in the smaller
    neurons of sensory ganglia. 

    The easiest sensory ganglion to find is the trigeminal ganglion 
    of the rat, which is conspicuous after removing the brain, lying
    lateral and posterior to the pituitary gland. To get it out, you
    need a sharp-pointed scalpel blade (#11) to cut through the
    overlying dura. This is a much easier job than finding and
    removing a spinal ganglion or any of the other cranial nerve
    ganglia.

      This presumption about VIP may be wrong; you actually said
      "VIPs" in your message. If you really mean very important
      persons, an alcoholic cocktail is certainly the one
      of choice, if they do not arrive already pickled. Yeltsin's
      fixative, said to be about 45% ethanol, is well known to
      be very effective if a large volume is provided.
    
   You replied to my reply after a 10 day delay, so if you have a
   further question please be more prompt, because for 4 weeks
   starting 28th July I will be globe trotting and completely
   unsubscribed, unscribed, unsusribed and utherwize unobtainable
   on HistoNet (if I can get the spellings right).
                                                   J.A.K.
 
> --- "J. A. Kiernan" <jkiernan@julian.uwo.ca> wrote:
> > On Thu, 15 Jul 1999, Elizabeth Wenig wrote:
> > 
> > > Can I please have some pros and cons concerning
> > the use of
> > > comercialized, pre-made 10% formalin verses a
> > scratch measured recipe
> > > of 37% formaldahyde, absolute alcohol and h2o? I
> > have a few of my own,
> > > but need some more! 
> > 
> >   If you have the recipe, the ingredients, a
> > graduated
> >   cylinder and a bottle, why would you even think of
> > 
> >   paying extra to buy the stuff pre-mixed?
> >                                            John Kiernan
> >                                            London, Canada
> > 
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