ANNUAL MEETING
OF THE BIOLOGICAL STAIN COMMISSION
FRIDAY
JUNE 6, 2008
MANCHESTER GRAND
HYATT HOTEL
SAN DIEGO,
CALIFORNIA
SYMPOSIUM:
A SEMINAR ON DYES AND STAINING
Introduction to the
seminar.
Co-chairmen:
Dr Richard W. Dapson
Vice President, Biological Stain
Commission
Dr Richard W. Horobin
Associate Editor, Biotechnic & Histochemistry
Staining of
macromolecules: possible mechanisms, examples, and strategies for
investigation
Dr Poul Prento
Zoological
Institutes, University of Copenhagen, Denmark (retired)
Staining a tissue section from an aqueous dye solution is a 2-step
process. In Step 1, ion exchange builds up the concentration of
appropriately charged dye ions in the immediate neighbourhood of the
charged macromolecule. In Step 2, the actual intermolecular binding
process occurs, where bonds, predominantly non-polar, are formed
between macromolecule and dye. Step 2 follows the same principle as the
processes which establish the tertiary structures of most proteins and
nucleic acids. In this step the solvent (water) participates actively
in the dye-binding process, which may be termed hydrophobic interaction
and occurs concomitant with the formation of ordered systems of
intramolecular hydrogen bonds. As fixation and processing do not lead
to extensive protein unfolding, hydrogen bonding plays a minor or no
role in the staining of most globular proteins, but can be important
when staining extended protein structures such as collagens, elastin
and amyloid. Staining of mucins and connective tissue
glucosaminoglycans may also be by ion exchange followed by hydrophobic
interactions as demonstrated by the phenomenon of metachromasia.
However, if the dye ion is highly charged, only Step 1 (ion exchange)
may happen. The latter is exemplified by staining with Alcian blue and
possibly also by staining with colloidal iron. This attempt to explain
staining from “the macromolecular point of view”
will be further elaborated and exemplified, and some of the
experimental strategies used in the investigations will be discussed.
Characterization of
hematoxylin-based stain for use in the ThinPrep Imaging System
Wendy Stanick, Matthew McCormack, Steven
Guertin, Kellie Forrestall and Michael Hopkins
Hologic
Inc.
The ThinPrep® Imaging System is a technique of staining and
imaging human cervical cells to aid in the diagnosis of cervical cancer
and its precursors. The system utilizes a hematoxylin-based stain
(Nuclear Stain) designed to be approximately stoichiometric. It stains
the nucleus in contrast with the cytoplasm providing the ability to
identify potentially abnormal cells for subsequent CT review. The
success of this system depends upon consistent and reproducible slide
preparation and staining. Meeting these strict requirements dictated
that we investigate various measurements and analytical tests such as
UV, HPLC and LC/MS to further characterize ThinPrep Nuclear Stain.
These experiments have improved our ability to predict the
stain’s functional performance over time. Additionally, we
have investigated the effect of stain age, specimen quality and storage
conditions.
Historic dyes and how to
identify them
Chris
Cooksey MSc CChem MRSC
Watford, England, UK
This presentation will cover the identification of historic dyes and
pigments on ancient and not so ancient artefacts using a variety of
physical and chemical techniques. Up to the mid-20th century,
analytical tools were too blunt to resolve many of the identification
problems. Since then advances in chromatographic and spectroscopic
methods have yielded a wealth of data about the identity of colorants.
This allows us, for example, to determine which species of madder
(alizarin and purpurin) was used in dyeing and consequently, sometimes,
to determine the geographic origin of the plant. In the same way
cochineal (carmine) from Polish insects can be distinguished from that
of American origin.
Roundtable discussion:
Modern challenges with dyes and staining.
Drs
Dapson and Horobin, Moderators.
PRESIDENT'S FORUM
The hematoxylin shortage
of 2008 (John Kiernan, BSC Trustee)
Reports of BSC committees
Project and research
reports from members
Informal open discussion
of topics of interest