Whales and the contradictions of cancer research

I love Carl Zimmer.  I think he’s one of those people who just really get it… and not only does he get it, but he explains things in a way that makes other people get it.

Recently, he published an article on the Loom discussing whales and cancer, based around a recent review published in Trends in Ecology and Evolution.  The basic premise of cancer works like this:

• Over time, cells make mistakes in DNA replication
• Mistakes accumulate and eventually, mistakes will affect some vital process
• This causes cancer

This stands to reason then, that the more cells you have and the longer you live, the more mistakes you will have, and the higher likelihood that you will have cancer.

But if you looked at blue whales, they’re HUGE.  They have a lot of cells and they can live a long time.  Indeed, according to calculations, half of all blue whales should have colorectal cancer.  By the time they reach middle age, ALL of them should be cancer-ridden.  And that’s only one type of cancer!

However, this is not the case.  Indeed, across all studied species, including humans with our often-poor health choices, cancer occurs at a rate of about 30%.  So mice, with their rapid metabolism and short life spans, get cancer at the same rate as whales, with their much slower metabolism and longer life spans.

This suggests that larger animals have evolved mechanisms against cancer that have held it at the approximately 30% mark – regardless of cell number, age or size, which is contradictory to the current paradigms of cancer as a statistical inevitability.  And if that is so, we would be better off studying how larger animals cope with cancer rather than looking at cancer in mice.

That is not to say that we should suddenly be breeding captive whales for laboratory-style research – but so little is known about the health of these animals in the first place, despite the popularity of sea mammals as aquarium entertainment.  A well sequenced genome would be the first informative step – The authors suggest studying the genome to look at differences in cancer defenses among related species with a wide range of sizes, such as whales and dolphins.  Learning more about their health and biology of these animals may yield interesting new avenues in both human health research and animal veterinary medicine.

Zimmer ends his article eloquently:

“But such an undertaking would have to overcome a lot of inertia in the world of cancer research. Cancer biologists don’t look to big animals as models to study–which is one reason there’s not a single fully-sequenced genome of a whale or a dolphin for scientists to look at. For most cancer researchers, mice are the animals of choice.

But if we want to find inspiration for cancer-fighting medicines, mice are the last animal we’d want to consider. It’s like learning how to play baseball from a bench-cooler at a Little League game, when Willie Mays is waiting to dispense his wisdom.”

Again, find the original article at The Loom.

Read Full Post »

Rodent anesthesia Part 1

This post turned out a bit longer than I expected, so I broke it up into two parts.  Excuse my science-y jargon and please do leave comments if anything is unclear!

*****

Rodent anesthesia falls into two main types: Chemical or Inhalant.

Chemical anesthesia involves the administration of a drug or several drugs via subcutaneous injection.  The most common drug of choice is a combination of ketamine and xylazine.

Xylazine is an alpha-2-adrenergic agonist sedative with short lived analgesia. As a sedative, the drug depresses, or slows down, the respiratory and cardiovascular system and relaxes the muscles.  Too much “slowing down” can be dangerous, especially in mice, where surgeries are generally conducted be a single technician and changes in respiration and cardiovascular function are usually monitored only by visual inspection.  If a person is occupied with the technical aspects of the surgery, slight changes may be easy to miss.  When the respiratory or cardiovascular systems become over-depressed, this is an overdose and death can result.

Ketamine is a “dissociative anesthetic” which renders animals unable to move.  Lubrication of the eyes is absolutely required because the eyes remain open while the animal is in this dissociative state.  Failing to lubricate the eyes during surgery can result in blindness due to drying of the cornea.  Recovery from ketamine can take up to several hours and during this time, the animal must be monitored closely.

By combining the two drugs, you are able to produce a sedate animal which is unable to move.  This is suitable for short surgeries.  However, the recovery period is often rough.  Animals often appear “groggy” and may not resume normal activities for some time after.

Ketamine-xylazine is favoured because it is relatively cheap and non-technical, requiring only the drugs and needles with which to administer the injection.  As well, there are no wastes produced from these chemicals which may be dangerous to the animal or the handler.

However, it is not suitable for long or invasive surgeries and comes with a few complications:

Ketamine-xylazine injection also does not produce lasting analgesia, or pain relief.  Additional painkillers are generally recommended before and after the surgery.

Many animals react differently to ketamine-xylazine injection.  A dosage which works well in one strain of mice may not work well in another.  As well, individual mice may metabolize the drug at slightly different rates, such that a dose that results in 1 hour of anesthesia in one mouse may only give 45 minutes in its cagemate.  This can be disastrous if a surgery is predicated to take 50 minutes to complete.  As such, the appropriate dosage must always be tested for each new strain of mice and for each new experiment, and allowing plenty of time for unexpected results.  The technician should also always have extra drug ready, should the animal show signs of waking up.

The amount of cardiovascular and respiratory depression is also dangerous, as I mentioned, and this danger increases during longer or more complicated surgeries.  Every time you have to administer a bit of extra drug to keep the animal unconscious, you risk administrating an overdose.

Luckily, there are other methods for producing a surgical level of anesthesia, which I will discuss in the next post.

[Photo by Dale Tidy]

Read Full Post »

Euthanasia of laboratory rodents

During the course of research, rodents are commonly euthanized for tissue collection, to end suffering or to terminate surplus animals.  Several methods of euthanasia are possible, and out of these, CO2 euthanasia is most preferred.

An overview of the types of euthanasia available:

Cervical dislocation describes a method in which the head is separated from the spine.  If performed correctly, it can be a quick death.  However, it is technically demanding and any errors would result in suffering by the rodent.  Due to it’s technical nature and the potential for error, it is not a commonly used technique.

Decapitation describes the physical separation of the head from the body.  Some investigators may pursue this method of euthanasia because it does not contaminate the blood or the tissues, which may be of importance in some studies.  While the death itself is quick, again, it relies on the skill of the technician to perform the euthanasia quickly and flawlessly.  Additionally, the handling and restraint required to decapitate a rodent may cause unnecessary stress prior to death.

Chemical methods of euthanasia are generally brought about through the use of lethal injections, typically barbituates. These are generally administered through a subQ injection.  Chemical euthanasia does not require a lot of handling nor technical skill, but some chemicals may be controlled substances or be considered too costly and time consuming to use on large numbers of animals.

Finally, CO2 euthanasia is a form of gaseous euthanasia.  It is the most common form used in laboratory animal science.  It is cheap, requires little to no technical skills, and has some anesthetic properties.  In this form of euthanasia, carbon dioxide is allowed to gradually fill a chamber containing one or more rodents.  As the oxygen levels decline, the animals are rendered unconscious, followed by death from asphyxiation.

While CO2 euthanasia has been the go-to method in recent years, a 2006 thesis by a UBC Animal Welfare Program grad suggests that CO2 euthanasia may cause distress* in rodents due to the dyspnea (the sensation of “breathlessness”) that precedes unconsciousness.   The idea that CO2 euthanasia causes distress in rodents has been explored in other studies as well.

I will note that the UBC Animal Welfare Program does not harm animals used in it’s research nor does it breed animals for the purposes of research.  All animals used are “surplus” from other labs which would have otherwise been euthanized. I will also note that all information provided here is freely available from the above mentioned papers, Wikipedia, and other online sites.

References:
KM Conlee, ML Stephens, AN Rowan and LA King (2005) Carbon dioxide for euthanasia: concerns regarding pain and distress, with special reference to mice and rats. Lab Anim 39:137-161.

Lee Niel Ph.D. (2006) “Assessment of distress associated with carbon dioxide euthanasia of laboratory rats” (thesis)

***********

* “Distress” is one of those nebulous, poorly defined words used in animal research.  Much like “ethics”.  😉  For the purposes of this post, I use “distress” as defined by the author: “… an umbrella term that encompasses negative affect associated with more specific negative states such as pain, discomfort and fear”.

Read Full Post »

More on Metacam

I think there may have been some confusion over my Metacam post the other week, possibly do to my own initial ill-mannered rantings.  I’ve disabled the previous post (I will make it public again once I’ve edited it) and think that this new post will clarify my thoughts.  I want to make it clear that my issue with Metacam is not it’s use in general, but with the lack of information related to it’s use in laboratory animals, specifically rodents .

Of course it is better to use some sort of pain relief than not at all and it’s great that a simple, easy to use drug such as Metacam is readily available.  My first issue is that there does not seem to be the appropriate tests or reassurances in place regarding the safe use of this drug in small rodents.  My second issue is that researchers, students and technicians need to be made (more) aware of the differences between NSAIDs like Metacam and opiods, like buprenorphine.

Regarding the first point:  The recently published book Small Animal Clinical Pharmacology(2nd.Ed. 2008) lists Metacam as a drug used for the management of soft tissue or musculoskeletal pain, or for peri-operative pain in dogs undergoing orthopedic or soft tissue surgery (p.301).  It also lists that it has recently been approved for short term use in cats and in Europe, for use in horses.  Rodents are not listed at all.

The Health Canada Drug Database lists Metacam Oral Suspension 1.5mg/ml as a veterinary product for dogs.  It lists injectable Metacam formulations as being available for dogs, cats and cattle.

There are studies in primary literature regarding the safety and efficacy of Metacam in rabbits (Carpenter et al. 2009, Turner et al. 2006), in dairy cattle (Hirsch and Phillip 2009) and of course dogs (many…), but there have not been published studies of Metacam in mice (that I know of).

Regarding my second point: If I were an investigator, and Metacam was suggested as an analgesic for my mice, would someone be able to tell me how this drug is metabolized, how long it takes to metabolize and what are its known side effects?   These characteristics are known at least in general terms because NSAIDs are a well characterized group of drugs and veterinarians are presumably aware of these characteristics.   So yes, I am sure that for planned experiments, vets will recommend appropriate drugs and labs will follow these guidelines.  But when animals need unexpected treatment (eg. post-surgery complications, opened sutures, deep fight wounds, etc), vets are typically not consulted and these decisions are made in-house.  Is your average tech well-informed such that they are able to recommend the correct treatment?  Will they be able to tell an investigator about potential side effects, modes-of-action and possible interactions with current experimental treatments?

I think it’s important to be aware of the science behind the techniques we use.  Some procedures and conditions are probably managed fine with Metacam while other procedures are probably better managed with opiods or through a combination of drugs.  But underlying the choice of which drugs to use should be knowledge of the drug and its effects on the species you are working with.  This should be true whether you are a post-doc, a student or a tech and it is in that respect that I think that a lot of people are not completely aware of the limitations of Metacam.

References:
James W. Carpenter, Christal G. Pollock, David E. Koch, Robert P. Hunter (2009) Single and Multiple-Dose Pharmacokinetics of Meloxicam After Oral Administration to the Rabbit (Oryctolagus cuniculus). Journal of Zoo and Wildlife Medicine: December 2009, Vol. 40, No. 4, pp. 601-606.

Patricia V. Turner, Cheng H. Chen, Michael W. Taylor (2006) Pharmacokinetics of Meloxicam in Rabbits After Single and Repeat Oral Dosing. Comparative Medicine, Volume 56, Number 1, February 2006 , pp. 63-67(5)

AC Hirsh and H Philipp (2009) Effects of meloxicam on reproduction parameters in dairy cattle. Journal of Veterinary Pharmacology and Therapeutics Volume 32, Issue 6, pages 566–570, December 2009

Read Full Post »

CALAS seminar: Pulse Oximetry

Hi all,
Just a reminder that CALAS-Pacific has finally gotten around to gracing us with another seminar Wednesday Oct 20 and guess what? It’s a webinar! :p Your member dollars at work…

I think this one is at least somewhat interactive, but I’m not sure. The speakers will be discussing a new technique for measuring oxygen content in mice.

It will be held at the BC Cancer Research Centre at 675 West 10th Ave, Vancouver BC tomorrow from 2:30 – 3:30. Enter from the main doors and head to your right to get to the auditorium.

Read Full Post »

Happy mouse, unhappy mouse

Like most rodents, mice are prey animals with a range of predators such as urban owls and cats. As a prey species, mice will attempt to hide any signs of distress or pain. In the wild, this is can be a beneficial behaviour because many predators will choose prey which appear weaker or slower than the rest. However, it can also make it difficult to determine the health of your mouse.

A happy and healthy mouse has a sleek coat that is well groomed and tidy. His eyes are bright and alert and his skin is flush slightly pink. When pinched at the scruff, the skin should be elastic and smooth. His body should be filled out and usually slightly plump. When placed in the cup of your hand, the mouse should be curious and attempt to investigate his new surroundings. A mouse that has been well cared for and well acclimatized to humans should not attempt to bite.

An unhappy or distressed mouse many show many or few symptoms. General signs of stress may present itself as a ruffled, ungroomed appearance. The eyes may be dull. This is when you should start taking a closer look at your mouse.

• She may show other grooming-related symptoms such as an oily coat (eg. diarrhea) or patchy fur (eg. over grooming, ulcerative dermatitis).
• She may have signs of skin irritation, in the form of reddened areas and inflammed skin (eg. ulcerative dermititis)
• She may be isolating herself from cagemates. As mice like to hide their discomfort, when it is obvious that a mouse is acting “differently” from the other mice, it is a definite sign that some thing is wrong. When isolation is accompanied by a lethargic appearance and lack of activity, this often indicates that the mouse is in extreme pain or discomfort and should be taken very, very seriously.

If these signs are not noticed immediately, an unhappy mouse may progress to more serious symptoms. For example, the spine may begin to show itself as the mouse loses weight. When pinched at the scruff, the skin might show a “tented” appearance rather than being elasticky – this is a sign of dehydration.

Keep in mind that mice are very little animals and when things go downhill, they can get bad very quickly. Do your mice a favour and keep an eye on them! Things like dehyration or over-grooming should be treated immediately. Stress and over-grooming can often be prevented through gentle handling and adequate environmental enrichment. Give your mice something to chew on other than each other! And finally, if it looks like a mouse might be in pain, realize that he’s probably been in pain for longer than you realized and euthanize the poor little guy.

(And then go revisit your protocol and ask yourself what you can do to prevent this from happening again!)

Read Full Post »

Revisiting the grimacing mouse

Earlier this month, I wrote about a recent paper which looked at creating a “pain scale” based on the facial expressions of mice. I finally got around to reading the actual published paper.

Here’s the reference: Langford, DJ et al. Nature (2010). Some interesting things I noted:

“Causing headaches in mice”
This one made me blink when I read it in a news release. How can you claim to cause headaches in mice when your study is looking at how to classify pain in mice? Well, apparently, some of the mice used were transgenics which carried a gene linked to familial hemiplegic migraine in humans. These mice seemed to exhibit a baseline level of pain, presumably due to the transgenic gene they carry. I wouldn’t say that’s equivalent to “causing mice headaches” but hey, I don’t write for newspapers.

They measured what?!
When I read the news releases, I was under the impression that lots of fancy imaging software was being used, that microscopic twitches and fine-detail facial expressions were being mapped, and in general, crazy stuff was going on. How wrong I was! The original article included representative images used to rate different levels of mouse pain. For each trait, there were three images. Images set to a scale of 1 to 3 – 1 being “normal” and 3 being “severe pain”. After looking at the pictures, I had a “And this needed to be a scientific study… why?” moment. For example, under “orbital tightening”, there was a normal mouse, a slightly squinty mouse, and a mouse whose eyes were dry and narrowed to slits. Any animal technician would (or at least, should) be able to tell you that the mice in the #3 category were in pain and that the animals in the #2 category were not doing well.

But, to be fair, it is true that recognizing and using something daily is not the same as having a defined, well-studied scale to refer to. If making an official scale helps animal care, I’m all for it. To be honest, I’m a little surprised that a scale as not been officially developed (studied and peer reviewed) before, considering that the majority of animal facilities use some sort of point-scale for rating animal health.

Looking forward to hearing more from this group. Hopefully they’ll go into some more applications next time.

Read Full Post »

Why are nude mice nude?

Personally, I think nude mice are super-cute!

Nude mice, commonly used in research, are instantly identifiable by their hairless, wrinkled pink forms.  Sometimes called “athymic”, due to their lack of a functional thymus, nude mice are also immunodeficient and do not produce T cells.  But how do immunodeficiency and hairlessness relate?

Nude mice have a mutation in a gene called FOXN1.  This gene encodes a transcription factor, which is a protein that is required to activate a gene.  In this case, FOXN1 normally encodes a protein which activates a gene involved in the differentiation of a type of cell called epithelium.

Epithelial cells are cells which form body surfaces, such as skin, and glands, such as the thymus.  Normal development of epithelial cells results in skin with hair and a functional, T cell producing thymus.

The mutation in FOXN1 disrupts the normal development of both skin progenitor cells and thymus progenitor cells.  This results in skin which forms without hair and a non-functional thymus.  And there you go!  A nude, immunodeficient mouse!

Read Full Post »

Albino… mouse?

Albinos are a result of genetic abnormalities, usually the possession of two recessive genes for albinism.  Recessive genes are usually not a problem – chances are, everyone has at least a few.  But, when you happen to inherit two, interesting things can result.  Albinism is one of them.

Albino mice show characteristics typical of albinism in general: lack of pigment and red-tinted eyes.  They’re commonly used in biomedical research in the form of mouse strains such as CD1.  In the wild, many albino animals don’t survive due to their lack of camouflaging pigment.  But, some persist and a notable few have an almost cult-like status.

So why choose a genetic abnormality as the name for a science blog?

Well, science is quirky.  Is there anything normal about spending your day mixing chemicals and cells in a dish and then counting them?  I think not.  There is a very high probability of failure – just ask any grad student.  But when the stars align, the supervisor is happy and the antibody works… interesting things can happen.

And hey, if it works for grad students – Who knows what might happen here.  🙂

[Photo by Dale Tidy]

Read Full Post »