I was really considering going into pathology until i read more about the carcinogenic effect of long term exposure to formalin. I'll also add the fact that im a hypochondriac. Is there anyone else here worried about it?
tldr;
The time it takes for formalin to penetrate into is exponential for every millimeter increase in tissue(2mm takes 1.6 hours and 4mm takes 6.8 hours). It takes 24 hours for the fixative to actually begin to fix the tissue once it penetrates to the center. Gross large pieces of tissue as soon as possible to 3-4mm pieces so that they can be adequately and evenly fixed.
As a histology lab tech, it seems that the standardization of anything involving histology has been a widely debated. At the moment, student researchers that are visiting our lab have no clue on how to preserve their tissues. I have decided to browse as many primary studies I can in order to fundamentally understand how fixation in formalin works. Here's what I found.
There are several modes of action when immersing a tissue in a fixative like formalin but to simplify things I will use only two: Penetration rate and fixation rate.
According to Baker, experiments involving a gelatin and albumin mixture show that the rate of penetration for formalin and other coagulating fixatives follow the equation: d = k√t
d is distance of penetration in mm
k is the diffusion coefficient
t is the time in hours
The equation can also be rearranged to this: t = (d/k)^2
What this equation means is that it takes an exponential amount of time for every mm increase in thickness of tissue. You can use this equation to calculate how long it would take for the fixative to penetrate into the center of a sample of tissue.
The most conservative estimate for the k value that experimented on real tissue, specifically rabbit livers, is 0.78 from Tellyesnicsky's experiment on 10% NBF. So the equation now looks like this:
t = (d/0.78)^2
With this in mind, we can make a table on how long it would take for fixatives to penetrate in tissue.
| Total thickness(mm) | d(mm) | Penetration time(hrs) | Total fixation binding time(+24 hours) |
|---|---|---|---|
| 2 | 1 | 1.6 | 25.6 |
| 4 | 2 | 6.8 | 30.8 |
| 6 | 3 | 14.7 | 38.7 |
| 8 | 4 | 26.3 | 50.3 |
| 10 | 5 | 41.1 | 65.1 |
Due note the penetration time is how long it takes for the fixative to penetrate all the way into the center of the tissue. We have to add the rate of fixation on top of that time.
In Fox's experiments, 16um thick sections of tissue were immersed in a radioactive carbon containing formaldehyde and the amount of radiation was measured until the radiation levels have reached equilibrium or when the fixative has completely bound with the tissue. The fixed sections are so t
... keep reading on reddit ➡Can I use only formalin for stick insects? Can I use Ethyl Alcohol instead of Isopropyl Alcohol? Should I Fill the insect with the liquid?
I read somewhere that it is alright if used as a fixative. Will it work if I use it on smaller specimens before moving them to a 70% solution? Formalin is practically unobtainable where I live
So I’d been doing some dissections last week and sculpting mini bases using Green Stuff this week.
I opened a fresh pack of the stuff and it immediately struck me that the unmixed putty smells just like formalin.
Anyone else notice this?
It’s extremely hard to get, so far I only have 70% ethyl alcohol, will that be sufficient for smaller creatures?
Can anyone explain the chemistry behind formalin fixation of tissues? Especially in regards to the formaldehyde & methylene glycol reaction with the tissue.
Hello :) I've been preserving and pinning arthropods for about a year now, but am entirely new to vertebrate taxidermy. I also have this relatively small American toad that I placed in the freezer and have had there for... IDK, under three months. My question is, is there any way to preserve and pose the animal without formalin? I have 70% isopropyl (and I assume that isn't good enough). If not, no worries - I'm pretty into the idea of having the bones by themselves. However, I'm unsure how to clean them and store them properly. If you have any tips on either, please let me know. Thank you!
Trying to figure out how much formalin I need to use to fully form the imine when doing a reductive amination on tryptamine. So the formula of the compound would be helpful in trying to figure it out. I can’t find the formula anywhere on hive :/
I started my first week of PathA school this week and we're diving right into the cadaver lab. Working with the formalin doesn't really bother me but the smell is really getting into my hair and doesn't come out until I wash it. Are you guys able to get the smell out without washing, or do you just wash your hair every day? Before school started, I would only wash my hair 1-2 times per week to keep it healthy, so I don't really want to have to wash it every day for the rest of my working career if I don't have to.
In my undergraduate research project in marine biology, I collected 11k individuals belonging to 45 species and stored them all in jars with 10% formaldehyde. Would it be possible to extract DNA from these species? How might the formaldehyde have affected the DNA?
Thanks in advance.
I am aware of the fragmentation issues formalin causes in formalin fixed tissues, however, I was wondering if the damage continues and/or increases if the tissues remains in formalin after being fixed.
For example, if I fix a section of colon in 10%NBF for 8 hours, and it’s completely fixed prior to processing and FFPE sectioning, would the potential for DNA/RNA damage be greater if the tissue was fixed for 24 hours (i.e., 16 hours in addition to when it was considered “fixed,” for the purposes of processing for permanent sections)?
What do you think? What is missing in this skin or is the implementation really bad? FOR RATE
https://preview.redd.it/089fi25ek3t71.jpg?width=3840&format=pjpg&auto=webp&s=b172cc8a295b1cddca90448f9e2486c1c6e76882
https://preview.redd.it/ejelx9qbk3t71.jpg?width=1920&format=pjpg&auto=webp&s=1cd8f7e2308e2d5370b157e932871ee61f98864f
https://preview.redd.it/7zcyq9qbk3t71.jpg?width=1920&format=pjpg&auto=webp&s=f25b8dc8a3529aa56a28ec3c0b15f00d1e1cfa8f
If I have 40% formaldehyde if I add 3 x the amount of distilled water to turn it to 10% would that be ok for wet specimens?
I found two baby bull heads I wanted to create a wet specimens out of.
the most dangerous thing is formalin because its strongly cancerous
but im ignorant so tell me how much safe is your job
another question, since youre an assistant, does your pathologist treats you like if hes your boss
Can I use only formalin for stick insects? Can I use Ethyl Alcohol instead of Isopropyl Alcohol? Should I Fill the insect with the liquid?
In my undergraduate research project in marine biology, I collected 11k individuals belonging to 45 species and stored them all in jars with 10% formaldehyde. Would it be possible to extract DNA from these species? How might the formaldehyde have affected the DNA?
Thanks in advance.
In my undergraduate research project in marine biology, I collected 11k individuals belonging to 45 species and stored them all in jars with 10% formaldehyde. Would it be possible to extract DNA from these species? How might the formaldehyde have affected the DNA?
Thanks in advance.
