[Histonet] Re: Genetics anyone?

From:Todd Sherman

On Thu, 06 Nov 2003 10:35:00 -0600, 

Hello Cheryl,

'Ploidy' is the numeric state of the chromosomes, so to speak:
If n = species specific number of chromosomes in a given somatic cell, then
Haploid    -  n ; single set of unpaired chromosomes
Diploid    - 2n ; two of each chromosome (a pair of chromosomes) and the 
standard state of a typical, "resting" cell
Triploid   - 3n
Tetraploid - 4n

So, in Homo sapiens, haploid(23), diploid(46), triploid(69), 
tetraploid(92) are the amounts of chromosomal material - ie. number of 
chromosomes specifically and amount of chromatin generically.

I do not know about the stain to which the researcher alludes but I 
suspect it is able to differentiate between the cell's nuclear condition 
by the amount of chromatin that is visualized after staining. Having said 
that, unless the differences are dramatic and obvious, the use of the word 
"intensity" scares me.

My expertise, such that it is, was in immunohistochemistry... determining 
intensity was often an error-prone exercise. Unless you are able to stain 
a monolayer and incorporate the entire nucleus of the cells in your 
evaluations, this relative intensity stuff is going to be difficult. If 
you section a tissue block and include the entire nucleus of a diploid 
cell and half the nucleus of a tetraploid cell, the amount of nuclear 
chromatin will be the same. Unless there is some other differentiating 
feature between cell stages to help you in your analysis, these relative 
comparisons will be hard... and I just pointed out the most extreme case. 
What if you have 1/3 of one cell's nucleus and 2/3 of another cell's 
nucleus? And what if the first cell is tetraploid (1/3 x 4n = 4/3n) and 
the second is triploid (2/3 x 3n = 6/3n)? In this case, the triploid cell 
would appear to have more chromatin than the tetraploid cell. Moreover, 
how would you know which cell had the higher ploidy if only part of the 
nucleus is visible?

Now, if you are looking at entire tissues at low magnification rather than 
specific cells, then the alluded stain might be appropriate. That is 
because the ploidy is likely uniform/homogeneous throughout the tissue and 
localized aberrations are insignicant or absent. This example would occur 
in an experiment where Tissue A (normal diploid) and Tissue B (abnormal 
n-ploid) were compared. If Tissue B stained twice as intensely as tissue 
A, you might "conclude" that Tissue B had its nuclear material changed to 
tetraploid during experimentation.

The researcher should probably give you more specifics about his study and 
the stain if possible. I probably gave you more info than you wanted but I 
do not think these concerns can be overlooked.

Good luck,

Todd Sherman
HistoSoft Corporation

>   21. Genetics anyone? (Cheryl Crowder)
> --__--__--
> Message: 21
> Date: Thu, 06 Nov 2003 07:47:29 -0600
> From: "Cheryl Crowder" 
> To: "Histonet" 
> Subject: [Histonet] Genetics anyone?
> Good morning - This questions was put to me yesterday and, knowing
> little about genetics, I'm stumped.  Can any of you help me.  This
> researcher is collecting samples which he says are either diploid,
> triploid or tetraploid.  He states that someone told him there is a
> stain techniques that "would distinguish the 'ploidy' by the intensity
> of the stained tissue".
> Have any of you heard of such a thing or know someone I can contact for
> this "unusual" question?  Thank you, in advance.  Cheryl
> Cheryl Crowder, BA, HTL(ASCP)
> Chief Technologist
> Anatomic Pathology
> Department of Pathobiological Sciences
> School of Veterinary Medicine
> Louisiana State University
> Skip Bertman Drive
> Baton Rouge, LA  70803
> 225-578-9734
> FAX:  225-578-9720
> --__--__--

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