B-gal is an abbreviation for an enzyme, beta-galactosidase. The gene
sequence that produces this enzyme is very well known (by molecular
biologists) and relatively short. That being the case, this sequence can be
inserted in a vector (typically, a circle of DNA with fixed insertion
sites)upstream or downstream from another gene sequence. This entire vector
can then be inserted into target cells (e.g. mouse bone marrow stromal
cells) by a process called transfection. Transfection can be accomplished by
several techniques, none of which are relevant to this answer.

You're probably thinking, "Great! Ask a simple question and get anything But
a simple answer". I'm getting there.

X-gal is a chemical (5-bromo-4-chloro-3-indolyl B-D-galactopyranoside) that
in the presence of beta-galactosdase (enzyme) will form a permanent
green-blue precipitate. So, for example, if you have a tissue (like the leg
bone of a rat) that you've transfected with a gene sequence for fibroblastic
growth factor (FGF) and you have inserted with this FGF sequence a sequence
for B-gal, you can look for the activity of the B-gal enzyme as a MARKER for
the gene sequence you're really interested in, FGF.

We have recently perfected in situ polymerase chain reaction (IS-PCR)
techniques to look for the gene sequence (like, FGF)of interest without
having to look for a marker sequence (like B-gal). Cutting out the middle
man, so to speak.

Hope this explaination helps. Best wishes, Donna Montague
UAMS Orthopaedic Research
Little ROck, AR

-----Original Message-----
From: lynn_brennan@smtplink.Coh.ORG
[mailto:lynn_brennan@smtplink.Coh.ORG]
Sent: Monday, August 02, 1999 4:28 PM
To: MontagueDonnaC@exchange.uams.edu
Subject: RE:B-GAL stain for paraffin?


Dear Donna:
I work in histology research on neuro so i'm not as familar with all the
terms
used on the histonet.  RE: B-GAL stain for paraffin.  What is B-GAL and
X-gal? 
What does the protocol stain?
Is there a way to access the J.Histo and  cytochem  from the internet?
Thank you 
Lynn Brennan 
City of Hope medical center
lbrennan@coh.org