Re: MGP (long answer)

From:"J. A. Kiernan" wrote:
> I have a question about the MGP stain.  Does it stain all RNA/DNA?

If by MGP you mean methyl green-pyronine, then:
  (a) The technique, correctly done, stains nuclear DNA
      and ribosomal and nucleolar RNA red. 
  (b) Dyes sold under the name methyl green have really been a
      related dye, ethyl green, for probably more than 25 years.
      Ethyl green is a better dye in this technique (lots of
      reasons, but they would make this reply too long; it's all
      in the literature, books and journals). Vendors sell ethyl
      green as "methyl green" because users (that's us) don't
      keep up to date. This has gone on for too long. We should
      have been talking EGP rather than MGP back in the 1970s.
      Let's get our act together. Our worthy suppliers will
      continue to provide high quality ethyl green, proudly and
      correctly named. 

> ...  We are looking at the possibility of using this stain to see 
> if RNA is present in the tissue verses doing ISH.  Is this a 
> cost-effective alternative?

It isn't an alternative at all. In situ hybridization detects
a messenger RNA for an individual gene or the DNA of an
individual gene.
(For "gene" allow for less specificity, such as groups of similar
nucleotide sequences etc.) 

The nucleotide sequence of DNA or mRNA for a single gene (and the 
protein it encodes) is a tiny fraction of the total DNA or RNA 
present in a cell, and it cannot be expected to contribute
to the intensity of staining of a section by a method that shows 
all the DNA and all the RNA, albeit in different colours.

In the 1960s it was the fashion to associate increased
basophilia (much of which is ribosomal RNA) with known increased
activity of secretory cells.  There were microspectrophotometric
studies that correlated more RNA with more protein synthesis.
was important work back then, and an impressive technical 
accomplishment in its day, and it confirmed previously tentative
identification of cell-types that produced particular proteins.
Examples are insulin from pancreatic islet B-cells and 
vasopressin from neurons in the supraoptic nucleus of the

Nowadays, staining for total DNA & RNA by the EGP method provides
easy recognition of cells that have particularly large amounts
of ribosomal RNA. These are neurons (not just in the CNS; also in
enteric ganglia) and plasma cells (which manufacture
in lymphoid tissue. 

EGP and in situ hybridization are techniques for answering
questions. Advise your boss to buy a book (there are lots) and
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1

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