The study of the decomposition of hair over time

[Rosemary]

ok, so I now know the independent and dependent variables for my experiment, however, do I need a control? If I had one, would it be the hair out of a live rat? Or does my project not require one? Im not sure.

[heatherL]

ok, so I now know the independent and dependent variables for my experiment, however, do I need a control? If I had one, would it be the hair out of a live rat? Or does my project not require one? Im not sure.

That's a great question! Let's take a moment to think about what a "control" is. A control is something that does not undergo the treatment. In your case, the "treatment" is death, followed by natural decay. Your idea of pulling hairs from a live rat is a great idea! Just make sure that you take the necessary precautions (so you don't get bitten), and that this is something you can do without permits. (As researchers, we have to get permits to work with live vertebrate animals, especially if we might cause them even momentary pain.)

Here are a few things you should keep in mind:

1) You will want to measure more than a single hair at each time point, since not every hair will begin at the same size. This includes your control hairs (from the live rat).

2) You actually have two potential controls:
a) Hairs from a live rat (no death).
b) Hairs at the time of death, if possible. This would establish a baseline value for you. However, since it's not likely that you will be able to pull hairs at the exact time of death, your live rat hairs can serve as your baseline.

3) It would be helpful if you can ask the lab or facility from which you obtain your rat(s) to note the exact time(s) of death for you.

You're doing great!

Cheers,
Heather

[geoffbruton]

Hi Rosemary,

I'm very excited to hear that you're almost ready to start the experimental stage of your project!

With regards to your last question and Heather's excellent response, I would like to ask if you ever went back and looked up the stages of hair growth? (I had suggested this in previous posts a couple of times.) Since hair goes through a growth cycle, you will need to take this into consideration when monitoring your controlled variable.

However, in discussion with your project with my colleagues here at the crime lab, it looks as though you will not want to limit your examination and observations to just the hair root. The state of the decomposition of the root over time is certainly worthy of investigation (so please don't even think about changing your project!); however, your review of the relevant scientific literature should also have indicated the potential for decomposition "bands". Observation of these bands is actually quite rare - and for some reason is only observed in one of the growth stages of hair. When located, these bands are visible *above* the hair root. This is most likely due to the decomposition products of the surrounding soft tissue staining the hair shaft - but why it occurs in only one stage of hair growth is unknown. Consequently, I think this would be an excellent study to incorporate into your project!

My colleagues were good enough to provide me with a file on microscopic postmortem hair changes. Depending on what you have found already, these three papers would definitely be of value to you:

Petraco, N., Fraas, C., Callery, F.X. and De Forest, P.R., "The morphology and evidential significance of human hair roots," J Forensic Sci 1988; 33(1): 68-76.

Linch, C.A. and Prahlow, J.A., "Postmortem microscopic changes observed at the human head hair proximal end," J Forensic Sci 2001; 46(1): 15-20.

Tafaro, J.T., "The use of microscopic postmortem changes in anagen hair roots to associate questioned hairs with known hairs and reconstruct events in two murder cases," J Forensic Sci 2000; 45(2): 495-499.

Hope this helps and good luck!
Geoff.

[Rosemary]

I looked up the stages of hair growth and found that anagen hairs are most likely to show signes of deterioration. I think I have found a source to give me dead mice, however, Im not sure how I will be able to get a hair from the mouse at the time of death or while it is still alive. Does freezing the mouse and thawing it out again act in the same manner as natural decompositon? If so, how do I know when the mouse is thawed out enough to look at the roots? Also, the articles that Geoff Bruton gave me, I can only find the abstracts, where are the articles at? Thanks again.
Oh and one more thing, Im thinking of buying a trinocular head for a microscope so I can take pictures of the root. Do you have any suggestions?

[geoffbruton]

Hi Rosemary,

You're absolutely right! Research indicates that the anagen (or growth) phase of the hair does appear to provide the greatest indicator as to time since death. Great work!

Re: the dead mouse / live mouse issue. What is your source? If you were able to obtain one from a laboratory that uses them as part of their work, they should be able to assist you in acquiring a sample of hair from a live mouse. (I know we sound like a broken record, but please be sure that you have all the necessary paperwork and approval for doing this work.)

Your question about the freeze/thaw effect on dead bodies is a very interesting one. I'm going to look into this, but my initial thoughts are that this will not correlate with "natural decomposition" (unless this process were to actually occur, such as at high altitude). Keep in mind that the rate of decomposition is highly variable and is entirely dependent upon the environment in which the body is situated. In your proposed method, the process of freezing will most likely cause the cells to rupture - thereby accelerating the rate of decomposition. However, the rate of decomposition is also going to be slowed during the time that the rodent is frozen. So, you have two processes that are acting against one another... Is there any reason why you won't be able to pull the hairs from the dead rodent on a regular basis, whilst maintaining a controlled (and consistent) environment? Oh, and whilst I'm on this subject, please make sure that you record all of the environmental data during your experiment - including temperature and humidity (if possible).

As for the articles, I would suggest that you try getting in touch with a local college or university library. Depending upon the courses offered at the institute, they may already subscribe to JFS. If not, they should be able to get you a copy of the article(s) at a relatively low cost (as part of the inter-library loan process). When I was in grad' school, our library was able to provide us with copies of articles for the equivalent of a dollar or so - but that may be dependent upon if you are a registered student at that place of learning. A few inquiries should help.

Finally, the trinocular head for the microscope: what sort of camera do you have? Depending upon the type of photomicrograph (that is, a photograph taken through a microscope) that we need to take, we will either mount a camera on to a trinoc' head or simply hold the camera lens up to the eyepiece of the microscope and take it that way. For this latter process, we use a relatively inexpensive digital camera with an auto-focus capability. The lens of the camera takes the place of your eye, and auto-focusing will ensure that the image you are photographing is in focus (obviously!). There is also no need to use the flash. These are quick and easy to do, and if the camera is digital, you can check to see how the photomicrograph came out right away. You will most likely see the image contained within a ring, with the rest of the photo' being black. Don't worry about this, it's perfectly normal. It also has the added feature of illustrating that the photo' was taken through the microscope - kind of like those movies where you see two intersected circles pretending to show the viewer looking through binoculars! Since this is easy to see if it works, try it out - you may be very pleased with the results.

Anyway, apologies for the long-winded answer! If I find any more on the freeze/thaw cycle, I will let you know.

Please post back with any questions, and good luck!
Geoff.

[geoffbruton]

Hi again, Rosemary,

Okay, I did some digging and if you haven't gotten around to getting to the library yet, here is more literature that you may find useful:

Micozzi, M.S. (1997). "Frozen environments and soft tissue preservation" in Forensic Taphonomy: The Postmortem Fate of Human Remains; Haglund, W.D. and Sorg, M.H. (eds.). CRC Press, Inc.; Boca Raton, Florida.

Also,

Micozzi, M.S. (1986). "Experimental study of postmortem change under field conditions: Effects of freezing, thawing and mechanical injury." Journal of Forensic Sciences 1986; 31:953-961.

Basically, the effect of a freeze-thaw cycle on tissue will affect the rate of decomposition. I would recommend against using this technique.

Any questions, please just let us know.

Good luck!
Geoff.

[Rosemary]

I used a digital camera to take pictures through the lens and it worked!!! Now I am not sure how to measure the hair on my computer. I could count the pixels and convert that to millimeters, but Im not sure of that relationship. I could use a micrometer to put on the slide and measure the hair, but Im not sure where to find one. Do you have any suggestions on how to measure the hair once the digital image is on the computer? thanks

[geoffbruton]

Hi Rosemary,

Great to hear back from you, and I am delighted to hear that your photomicrography worked!

With regards to measuring small objects, there are a couple of options:

Depending upon the level of accuracy that you require, the easiest thing to do is to take a photomicrograph of the hair with a scale in the same field of view. For example, if you can align a suitable scale (preferably one with individual millimeters) beside the hair on the slide, you would be able to estimate the approximate size (width, length, etc.), based on this scale. If you are relatively skilled with some of the imaging computer software that is available, you could then calculate the measurement you need, based on a known quantity (that is, your scale, which is in the same photomicrograph). When you use the scale, please make sure that it is in the same plane (at the same relative height) as your hair. Otherwise your measurements will be off, or either the hair or the scale will be out of focus. If you do not understand this process, please just let me know, and I will try and expand upon my description.

Please keep in mind that classroom rulers and so forth are not designed to measure this accurately. I would recommend talking to either your science teacher or someone who worked in the lab you were using and see what they suggest. Here in our lab (for non-critical measurements), we use a paper scale that has an adhesive backing - allowing you to simply stick your ruler on to the slide (or the object itself, if it is not fragile). Because the scale is printed on paper, depth is not a problem at low-power magnification.

If you do decide to go this route, please make sure that you measure from a specific location on one millimeter graduation to the same location on the next graduation. Do *not* measure from the 'inside' edge of one graduation to the 'inside' edge of the adjacent graduation. This will give you a lower value than the 'real' one. (This is because the width of the graduation physically occupies a space and one millimeter is actually the distance from the middle of one graduation to the middle of the next - does that make sense? I tried drawing it, but it didn't work on the preview.)

Another alternative that can also be used in an ocular scale - though again, this would depend upon what you have available. Basically, the lens of the eyepiece has a "built in" scale. Depending upon the level of magnification used, this can then be used to measure what is being viewed through the microscope. It simply requires the viewing of an object of a standard size (like a ruler!), and determining what each graduation on the eyepiece is equal to.

If you do find a micrometer, I would be hesitant to use it. Hair can be crushed quite easily, and so you could find that your measurements are off quite a bit. If you can lay your hands on one and have someone who know's how to use it, then that is also an option.

Anyway, I hope this helps and please let us know if you have any more questions. We can't wait to hear your results!

Good luck!
Geoff.

[heatherL]

Hi Kelly,

Congratulations on getting your photomicrography to work! (I have struggled with that process myself. )

Geoff gave you some really great advice. For my study (measuring hair diameters), I used an ocular scale like the one Geoff described. It has little tick marks in the actual eyepiece of the microscope. I had to calibrate the scale first, at the different magnifications. As Geoff said, you should be able to ask your science teacher or a lab scientist to help you with this.

However, the ability to analyze the micrographs on your computer is exciting! The computer program that I use to analyze my photomicrographs is ImageJ, which you can download for free from NIH (the National Institute of Health): http://rsb.info.nih.gov/ij/download.html

If all of your photomicrographs were taken at the same magnification, you should be able to compare them using this program. I am not an expert on ImageJ, but they do have some information on their web site to help you get started: http://rsb.info.nih.gov/ij/docs/index.html

Good luck, and let us know if you have any more questions!

Cheers,
Heather

[Rosemary]

Okay, so Ive been doing my project for a week now. I have taken samples of hair from a dead mouse every 12 hours to determine how long it takes for the hair roots to change. I havent analyzed my data yet, but Im not noticing too much change, if any at all. How long does it usually take hair roots to decompose while still in the body?

[geoffbruton]

Hi Rosemary,

Great to hear from you! I was very pleased to hear that your experimental stage is well under way. With regards to your question concerning the decomposition rate of hair - well, that's what we're all interested in finding out!

As I mentioned in an earlier post (and I'm sure you know from your own research), the rate of decomposition of any tissue is highly-dependent upon the environment. Consequently, it will depend upon the environment in which you are performing this experiment. In addition, there is limited data available specifically concerning the decomposition of hair - which is why your science fair project is such an excellent idea!

What decompositional changes have you observed in the mouse? Does it appear to be drying out (dessicating), swelling, or is it oozing liquid? Is the carcass infested with insects or maggots? Were precautions taken to prevent / allow this? Are the hairs easier to remove as time passes? As you know, on a gross scale (meaning large, not unpleasant - though this could be considered "gross" by some!), there are defined stages of decomposition. Even if you are not observing any changes in the anagen hair / root, you should still be able to see the stages of decomposition as the carcass passes through them. If you keep a detailed log of your observations, this would be able to tie neatly in with your hair observations over time - therefore allowing you to state the particular stage at which such hair damage occurs during decomposition.

Did the research articles you read give any indication as to the time at which the researchers observed these changes in the hair? If your environmental conditions are similar, this may be a good indicator as to when you may begin to see them; however, if your work is well thought out (which I know it is) and if your data is meticulously recorded (which I'm sure it is), you should still be able to draw some valid conclusions from your work, even if it is not in complete agreement with the published articles.

Please don't feel discouraged. It has only been a week since you started the experiment, and depending upon the level of decay, there are probably at least several more weeks of study to be done. (Sorry, this isn't a quick experiment!) On top of that, this phenomenon is not always observed - but your research is still valid!

Please keep us informed of your progress, and good luck!
Geoff.

[Rosemary]

I have recently finished my experiment and got some weird results. I noticed that after 24 hours, the hair root swelled to over double its size from the first hair root I pulled. This was definelty something I didnt expect, and Im not sure why that happened. Other than during that time period, nothing happened. Im guessing that it may be due to a loss of blood or water in the root, but i dont know for sure. Do you have any ideas on what may have happened? I need to say something about it in my report. Thanks.

[MelissaB]

Rosemary,

I'm afraid I don't know enough about decomposition to provide a valid explanation. However, I do know that many cells use energy to concentrate solutes (such as potassium and calcium) inside them. Perhaps when the cells die the pumps keeping intracellular fluid concentrated break down and water from the environment enters the cell by osmosis because the solution inside the cells is so concentrated? I'm afraid that's more of a guess than an hypothesis. Hopefully one of the other experts will chime in.

[geoffbruton]

Hi Rosemary,

Sorry for the delay in getting back to you. Your results DO sound interesting - and I am pleased to hear that you recorded such observations.

As for what caused this swelling - I'm afraid I am at a loss to explain it, too. My initial thought was that the swelling was somehow related to cellular trauma, since swelling is something that is normally observed when an area of tissue is damaged. However, since the mouse died, rather than suffered some sort of trauma in that location, I don't think that is quite right... Ordinarily, when a cell is damaged, the cell begins to take in water and nutrients in anticipation of repairing / replacing the damaged cell(s). This is why you feel a lump if ever you've bumped into something. Due to increased blood flow, the area can also feel warmer. Now, in your case, there was no blood flow and with the cells dead I find it unlikely that cellular intake of nutrients would explain the swelling. The cell pump failure sounds much more likely - I think MelissaB may be right on the money!

What has your research uncovered with regards to what happens during decomposition on a cellular level? Perhaps that may shed some light on what is happening.

I will check with some of my colleagues here at the lab and let you know if they have any suggestions.

Thanks,
Geoff.

[Rosemary]

I have asked another expert and he said that the swelling may be caused as the outer layer is loosened from the inner layer, which is where the keratin has just hardened. how does that explanation sound to you? I just want a second opinion to make sure that my hypothesis is correct. Let me know if you come up with any more ideas, and thanks again. Also, i didnt notice anything on the cellular level, but I did notice root banding.