Monday 2 November 2015

21 seconds to empty

. . . the bladder.  The Ig Nobel awards have been running for 25 years now.  They were set up by the team from the Annals of Improbable Research [not to be confused with The Journal of Irreproducible Results]to give tribs to scientific papers that "Make you laugh . . . and then make you think".  We've had Benoit Mandelbrot giving a talk at the award ceremony previously.  When you consider that serious science is full of sleepers that are never heard from again (45% of scientific papers are never cited), then the hit rate is far higher at the quirky end of the spectrum.  If your reaction is WTF would anyone want to spend time over such a problem, or even harrrumph!: waste of tax-payers money. then you're quite possibly wrong.  We know not where the next inspiration and the next great leap forward will come from.  It is almost certainly not going to come from science funded by government agencies that are trying too hard to get short-term results.

One of the 2015 awards that caused a brief flurry in the press several weeks ago was the finding that all mammals that are bigger than a breadbox [3kg to 3000kg aNNyway] take the same time to empty their bladders.  Much of the coverage was a perfectly dreadful soup of coyness, archness and cheap jokes. Livescience was one of the better takes on the reportage. It seems that David Hu of Georgia Tech was changing a particularly brimful diaper and wondered about the bladder-capacity of an elephant. Whatever the reasons for starting the investigations, the results are definitely counter-intuitive.  Lots of things scale up as dimensions increase and not always in a linear fashion.  For example, a newborn baby weighs about 3kg and is about 0.5m long. Over the next 18 years, the length will increase by 4x but the weight by 20x (or more if obesity is at issue).  But the size of the cells doesn't change: a red blood cell is 8µm across from cradle to grave.  Indeed r.b.cs are the same size across the whole range of mammals.  It's because the physical chemistry of gaseous exchange between the rbc and the walls of capillaries [which are also 8µm across) is so clever, intricate and complex that it hasn't been invented twice; it's just been increased in network size.  Same for cells-in-general, they are an average of 30µm across, so mice have fewer cells than we do rather than the same number of smaller cells.

It's a different constraint in the neck.  All mammals have seven (7) cervical vertebrae: all of us from pygmy shrews Sorex minutus to hump-back whales Megaptera novaeangliae have the same neck-bone count. It is these cross-species similarities and scalings that allowed Georges Cuvier, the father of comparative anatomy to say that he could reconstruct the whole animal from a single bone.  The humerus of an elephant is built like a tree trunk because they both have to support enormous weights; a bat's humerus not so much.

Most of us would think that an elephant's bladder, at full 18 lt capacity, would take a considerable time to void and a cat's rather less. That's working on the assumption that the urethra [the tube between bladder and out; not to be confused with the ureter the tube between kidney and bladder] would be, like a capillary, be about the same size in all species. But Professor's Hu's team has shown that this is not so: urethras are all in a length to width ratio of 18:1 regardless of absolute size. They are vessel-emptying devices.  For mammals smaller than a bread-box, the rule doesn't hold: at small sizes the physics of water, including surface tension, comes to the fore and, although rats and mice have bladders, they tended to be dribbly.

Last month at Wexford Science Café we discussed a cunning plan by the Irish Times to carry out a massive crowd-sourcing project like their scheme earlier in the year to gather genetic data about domestic cats.  That persuaded more than 10,000 people to share these data about their cats, without any of them paw-signing an informed consent form. If you're in the science zone, it shouldn't be hard to think of a question that can be addressed scientifically without needing any expensive kit or hours of time. The sample size being beefed up, and the scientific value thereby enhanced, by multiple participants. With 21-seconds-to-pee somewhere near the fore-front of my mind, I'd spent the previous several days counting "1 battleship, 2 battleship, 3 battleship ..." - but not necessarily aloud - every time I took a leak and was accumulating data. The headlines about the Georgia Tech study have all been about the average length of time it takes to empty bladders of all sizes. But biology is at least as much about variability as it is about the mean and the central tendency. Indeed it is the variability that makes life so interesting. This will strike those who know me as far far too much information TMI but I'm quicker than most - about 16 seconds.  In a week you could get a sample of 20 emptyings each with a time-of-day.  10,000 people, male and female, young and old, diabetic and post-partum could generate a dataset worthy of analysis.  Who's with me?

It would be a poor show if we allowed the talk of passing water to pass without recording a hilarious example of Dublin street wit. In 1966, to celebrate the 50th anniversary of the Easter Rising, Dublin City commissioned a statute of patriot Thomas Davis [R] incorporating a fountain representing the heralds of the Four Provinces showering the country with the good news of national identity. The installation was instantly christened Urination Once Again.  On a more serious note, if you're a young chap you will not need instructions about how to empty your bladder but this link will explain that not everyone can take this essential life-skill for granted.

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