[Histonet] Iron demonstration in smears

[Monfils, Paul]

In reference to the previously posted comment about fungal growth on stored
slides ...

This problem is almost always the result of refrigeration. There is a
natural tendency to expect better preservation under refrigeration than at
room temperature, and this is certainly true for tubes of blood, whole
tissue specimens, lunch meat and cheese. But slides - either cut sections or
smears - are a different story.

Fungi have four basic requirements for optimal growth - a nutrient source,
warmth, darkness, and moisture.  Moist materials like those mentioned above
have to be refrigerated.  On the other hand, while slides stored in a slide
box at room temperature in a drawer or on a shelf may provide nutrients,
warmth and darkness, they are in a dessicated state, and without moisture
fungi won't grow. (Of course this might not apply if you work in a very
humid climate and don't have air conditioning in the lab).  The problem with
refrigeration is that it provides the additional growth requirement -
moisture; and while the relatively low temperature of a refrigerator will
slow the growth of fungi, it won't stop such growth, as anyone realizes who
has thrown out a moldy piece of lunch meat or cheese.  To stop fungal growth
thermally you need sub-freezing temperatures.  Therefore the best long-term
preservation of dry fixed specimens is at room temperature.

Methanol fixation is good, as already stated by another poster, and several
types of cytology spray fixatives also work very well.