Friday, November 21, 2014

Telling Tales

Upon receipt of the bit of writing below, my French professor wrote in the margin (in French) "You could write French stories." I'm preening, that's for sure--that's quite a complement from Madame M. who is extraordinarily exacting about our grammar. The assignment: write a story about two animals using the three main past tenses (I ate, I was eating/did eat, and I had eaten [before something else happened]). Obviously we have the same three tenses in English but we don't make quite the same big deal about them as the French do.

I chose to retell the fable of the frog and the scorpion (it's antecedent could be this Aesop's fable). You probably know it. Sometimes the frog is a fox or another animal. The frog carries the scorpion on its back across a river, and halfway across, the scorpion stings it. As they are both drowning, the frog asks the scorpion why he did that, and the scorpion replies "I had no choice, it's in my nature." Grim, yes, but I thought it was an appropriate tale since in the novel by Sartre that we are reading for class, everything that happens is predestined.

To puff it up to a length somewhere between 250 and 300 words, I had to embellish the story with background details that aren't usually in the fable. But that's the very nature of storytelling, isn't it? 

L'histoire de la grenouille et le scorpion
Il était une fois un scorpion qui vivait dans un tas de feuilles séchées qui étaient tombées des arbres à l’automne dernier. Près de les des arbres il y avait une grande rivière. Elle s’étendait si loin que le scorpion ne pouvait pas voir l’autre rive. Au bord de la rivière dans les joncs où l’eau était plus tranquille vivait une grenouille verte.

Un jour, le scorpion est allé à la rivière. Il a découvert la grenouille qui était en train d’attraper des mouches et de s’admirer dans l’eau. Le scorpion s’est présenté avec beaucoup de politesse. La grenouille a retourné la salutation.

Il a dit à la grenouille qu’il voulait lui demander de l’aider. Il avait besoin de traverser la rivière parce que le jour précédent il avait reçu une lettre de son frère qui vivait sur l’autre rive. Il était très important pour lui de traverser la rivière pour voir sa famille.

La grenouille réfléchissait à sa proposition. Pour traverser la rivière, le scorpion devait être sur son dos. Elle lui a dit que s’il la piquait, elle mourrait. Et le scorpion, il noierait.

Le scorpion a protesté. Il ne pourrait jamais faire mal à son amie ! Il a insisté. Il a supplié. Il a même pleuré quelques larmes.

Avec un soupir, la grenouille a accepté. Le scorpion est monté sur son dos et la grenouille a commencé à nager.

Au milieu de la rivière, le scorpion l’a piquée. Comme ils se noyaient, la grenouille lui a demandé pourquoi il avait fait cette chose-là. Le scorpion lui a répondu qu'il n'avait pas de choix, c’était dans sa nature.

Tuesday, November 18, 2014

Super Powers and Poisonous Frogs

I think I've mentioned before that the students taking animal science classes are overwhelmingly female. There is nothing inherently wrong with that but it's always nice to have a balance. So I was quite pleased to find out at the beginning of the term that the grad students taking the biostatistics course come from departments all over campus. The class is comprised of about 30% men--still skewed but reasonable. Students in public health, social sciences, and some of the other physical sciences are required to take the class so it has a pretty large enrollment every fall term, around 70 or so total.

We meet twice a week for lecture and once a week for a lab which is taught by a TA (teaching assistant, a grad student hopefully familiar with the course content). In lab, we learn how to use a specialized computer program to calculate various statistics. The lab content generally runs a lecture or two ahead of the lecture content. But for most labs, the TA gives us a quick crash course to introduce just enough of the new concepts so we can run the program and do that week's lab assignment.

Totally by chance, in my lab section, there is only one guy. He's memorable by that fact alone but there is something else that really sets this guy apart. He has a super power the likes of which I've never seen before.

He sucks the intelligence out of your very marrow if you sit within six feet of him. Sit right next to him and you are doomed. 

He's also a whiner. This serves as a convenient warning flag rather like the brilliant coloration of poisonous rainforest frogs

He complains vocally, loudly, petulantly, about everything he doesn't understand, which is everything. If you aren't paying attention to the warning flag and you happen to sit near him, or even worse, choose to do so, you get what you deserve: all your intelligence will disappear in a matter of minutes.

Today he compared reading the textbook to reading a "user's manual for an electric toothbrush in Cantonese". His exact words. I suspect that he believes himself to be clever and amusing but I find him embarrassing. I want to tell him to grow up, shut up, and listen. But I'm afraid to get too close. 

Sunday, November 16, 2014

What I Learned Today: Four Ways to Make Chicken Meat Taste Fishy

I'm stealing this idea for a blog post theme from a friend. I think it will make a good umbrella under which I can occasionally post about odd and intriguing things that I learn about.

Today I want to write a bit about four different mechanisms for making poultry meat smell fishy. This is certainly not a desired experimental outcome--chicken tenders that smell like fish? That's gross. But this very outcome has been reported by some researchers conducting broiler and layer feeding trials. How this can happen was a matter of some debate during my thesis committee meeting last week. It wasn't heated in the sense of being antagonistic but it certainly was intense. Since it seemed to be a topic of interest, I thought it would be time well spent to read some papers and try to figure out why this happens. What I found out is kind of interesting so I thought I'd write about it here too.

We first have to start with the larger issue: why do fish smell fishy. Living fish and fresh fish don't smell fishy. The fishy odor develops in marine products after they have been harvested. The smell is mainly caused by the formation of a molecule called a trimethylamine (although several dozen other kinds of molecules are also involved in creating the fishy odor).

See, animals that live in the ocean have a bit of a problem. They live in a saline solution but their cells also contain saline solutions. The concentration of sodium and potassium ions inside and outside of cells is delicately balanced. If those ions are out of balance, cells can't make energy and things generally go downhill from there. A very large number of biochemical processes depend on this balance being kept just so. So back to fish. They have developed some special biochemical mechanisms to keep the sodium and potassium ion concentrations in the correct balance. One of these depends on a molecule called trimethyl oxide. When a fish is killed, these molecules are slowly and inexorably converted to the insanely stinky trimethylamines.

You might take fish oil supplements. I don't take them myself but I give them to the dogs. I learned that the fish oil in those capsules has been subjected to an amazingly complicated purification process which includes a deodorization step to remove the trimethylamines.

So the first way we can make poultry meat smell fishy is to feed chickens diets that contain fish meal or fish oil that has not been purified to levels acceptable for human-grade consumption. Chickens consume the trimethylamines and their eggs and meat will smell fishy.

It also turns out that some chickens and some people have a genetic mutation in their DNA so that they don't make working copies of a particular enzyme that breaks down trimethylamine. We need this enzyme because our gut bacteria naturally make trimethylamines as part of their life cycles. If we don't have the mutation, no problem. The enzyme breaks down the molecules in our gut. But if you or a chicken has this mutation, then you can still smell fishy even if you never consume any fish product of any kind because the trimethylamine that is made by your gut bacteria is never broken down. So the second way for (some) poultry meat to smell fishy is to have strains of chickens with the mutated gene. People with the mutated gene have a disease called trimethylaminuria and they smell fishy too.

However, our gut bacteria have plenty of tricks up their tiny sleeves. They can make trimethlyamines out of choline. Choline is an essential nutrient which means that we must consume it in our diets; it is essential for chickens too. Diets deficient in choline can cause disease. However, if we feed chickens diets that contain large amounts of choline, we overwhelm the ability of their systems to break down all the resulting trimethylamines...and their meat and eggs can smell fishy. This third mechanism is not well quantified (how much choline is "too much", does it depend on age or type of chicken, does it depend on other dietary elements) but we know it happens.

And finally, the fourth mechanism for making poultry meat smell fishy has nothing at all to do with fish or bacteria. When you are trying to create a consumer product that is "enriched in omega-3 fatty acids" you are trying to increase the concentration of long-chain polyunsaturated omega-3 fatty acids in the parts of the chicken that we eat. I know, that's a mouthful. We generally abbreviate that mess to LC n-3 PUFA. Long-chain means the carbon backbone of the fat molecule contains between 18 and 22 carbons linked together. Polyunsaturated means that some of the carbons are linked with special molecular bonds called double bonds. You should already know that diets high in saturated fatty acids, fats with no double bonds at all, are strongly correlated to increased risk of heart attack and stroke; to be healthy we are supposed to consume fewer saturated fats and more unsaturated fats. Some of the omega-3 fatty acids can have up to six double bonds. We are trying to put more of these kinds of fatty acids into chicken meat and eggs. But there is a problem.

When a fatty acid has lots of double bonds, it is more susceptible to peroxidation than the unhealthy fatty acid that lacks all those double bonds. Peroxidation refers to a specific process by which a chain reaction breaks the unsaturated fats apart at their double bonds. Not only does lipid peroxidation form free radicals (very, very bad things to have floating around your cells) but the fatty acid fragments are converted into other molecules such as aldehydes and ketones. And most of these are quite stinky. 

When this happens, the meat tissues can change color, will taste bad (rancid), and will develop an off-flavor that is often described as "fishy" even though it isn't caused by the same molecules as fishy odors in fish. This is not an immediate process in general. Normal, every-day chicken meat will undergo peroxidation given enough time but it will happen sooner in "enriched" chicken meat.

So that's the fourth mechanism to make poultry meat taste fishy: enrich that meat with long-chain polyunsaturated fats and fail to protect the fats from peroxidation by lax handling, storage, and/or lack of antioxidants in the meat or diet.

It turns out this animal nutrition business is rather complicated. And there is no way to avoid the related issue of human nutrition and health--we and chickens are what we eat.

Thursday, November 06, 2014

Back to School, the Continuing Saga

You'd think that since I'm only taking two courses this term, I would have lots of free time. French is not that difficult but I spend a lot of time outside of class working on the many assignments. It seems like a major one is due every other day. No, my mistake, it seems that way because it is that way. 

My other class is biostatistics. That very word may cause some of you to get glassy-eyed, but not only am I enjoying the material, I'm learning new skills that I am applying to my own research. The class has a heavy focus on applied analyses with just enough theory to confuse and confound. Most of the examples are based on human health studies but nutrition is nutrition. Substitute "broiler birds" for "males aged 20 to 49 years of age who don't smoke" and you've got a winner!

At the end of each week, I return to the statistical analyses of my experiments and understand them just a little bit better. The math is easy, trivially so. But the intellectual leaps we need to make every week--ah, well, it takes quite a few re-readings of the lecture notes and text and homework problems to get those down. 

Progress on the thesis must continue too. I at last feel like I have a handle on that. Even though the feeding trials are long over, it's only been in the past three or four weeks that I could clearly articulate my hypothesis and describe the two experiments in less than a billion stumbling words. I've always found it ironic that being succinct requires far more time and effort than being verbose.

I'll get the chance to practice my succinctness next week when I give a short departmental seminar, about half an hour, to introduce my project and dangle a couple of preliminary results. Two days after that will be my first committee meeting. I hope that the next time I see the committee gathered is the last time they need to gather, at my thesis defense in June. 

I've got a title for my project now too: Enzyme supplementation of poultry diets as a tool to enhance n-3 fatty acids in human diets. Sexy, isn't it?