Per Sarah Jones's comments about the call for large cassettes. Been there,
done that same as she has done, for big blocks other than megacassette
size.  However, megacassettes ARE in demand, if they weren't, I don't think
every cassette vendor would sell them.  
 
An ill designed, poor fitting megacassette has no place on the market or in
our labs, especially when you need the depth of a megacassette to hold an
eye or thicker sample for processing.  It is counterproductive, expensive
and time consuming to use another regular cassette back to replace these
expensive little gold nugget megamonsters in order to get a proper fit in a
clamp!  

They sell DEEP metal molds for thick samples and megacassettes. However, in
my estimation, there is a failure in the system - the infamous
megacassette!  Seems to me, after previous discussions and complaints on
Histonet and this tirade, someone would get it right - hasn't happened yet! 

Did some measurements.  Regular, everyday cassettes for 3 mm thick samples
(on clamping side) measure 3.75 cm x 2.8 cm.  One megacassette measured 3.5
cm x 2.8 cm, and when inserted horizontally into clamp left a 4 mm gap
between corner of clamp and cassette corner.  This mega freely slid back
and forth while clamped and fell out of clamp when reoriented in vertical
position!   The other megacassette (same mfr as the regular cassette)
measured 3.7 cm to outside of a little lid tab x 2.85 cm, but left a 3 mm
gap, a tidge sturdier, but not 100%.  Both megas did not provide stability
for sectioning.  I think that is obvious from other commentary.

Me thinks megacassette design is/was based on a "traditional" regular
cassette design with slanted edge for ease of slipping block into a clamp.
IF you are working with a deeper block -  you can actually grasp the block
face and shove it straight back INTO clamp if the cassette back is squared
to fit into the clamp. I would opt for writing surface on side of cassette
- same as routine, small cassettes.  

Had a discussion about megacassette problem with one technical product
advisor from a well known manufacturer/vendor YEARS AGO (time frame
obviously doesn't apply now) and his comment was -  "There is little demand
for megacassettes and not worth expense (hmmmm, bother?) to change how they
are manufactured".  This meant changing the plastic press mold.  Well -
putting it mildly, PHOOEY! That way of thinking doesn't hold water anymore!
If one sells a flawed, ill-designed product, then it should be corrected.
I see megacassettes (with the same basic look/design/dimensions) sold by
cassette vendors - labs are using megacassettes more now than they did 15 -
20 years ago.  I truly appreciate vendor samples to try for comparison and
ALL megacassettes have failed miserably after comparison! Sorry, folks!     

I don't think the mega problem has ever been carefully thought out and
hopefully some vendors in contact with their manufacturers will take it to
heart and redesign megas for cutting stability and correct FIT INTO CLAMP!
The microtomes/clamps are updated, modernized, designed improved
use/sectioning while megacassettes reside in the dark ages.  

Hello out there??? Is anyone who makes megacassettes - listening?   I
CHALLENGE you! NO! DOUBLE DARE you to be the first to redesign a
megacassette useful sans "the bad language syndrome". Our lab will be the
first to buy these with glowing recommendations to others.  

Enough, but looking forward to a new, improved megacassette ----

 

  

  



Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

email: gcallis@montana.edu