Survival of the Sickest: The Surprising Connections Between Disease and Longevity. Jonathan Prince

Чтение книги онлайн.

СКАЧАТЬ core because of constriction in the extremities, the body signals the kidneys to offload some of the extra fluid. But that theory doesn’t fully explain the phenomenon, especially in light of recent studies.

      The U.S. Army Research Institute of Environmental Medicine has conducted more than twenty years of study into human response to extreme heat, cold, depth, and altitude. Their research conclusively demonstrates that even highly cold-acclimated individuals still experience cold diuresis when the temperature dips toward freezing. So the question persists: Why do we need to pee when we’re cold? This certainly isn’t the most pressing question facing medical researchers today – but as you’ll soon discover, the possibilities are intriguing. And the answers may shed light on much bigger issues – like a disease that currently affects 171 million people.

      Let’s put aside the delicate subject of cold diuresis and turn to one much more suitable for the dinner table – ice wine: delicious, prized, and – supposedly – created by accident. Four hundred years ago, a German vintner was hoping to squeak just a few more growing days out of the late autumn when his fields were hit by a sudden frost, or so the story goes. The grapes were curiously shrunken, but, not wanting to let his entire harvest go to waste, he decided to pick the frozen grapes anyway and see what would come of it, hoping for the best. He let the grapes defrost and then pressed the crop as he usually did but was disappointed when it yielded just one-eighth of the juice he was expecting. Since he had nothing to lose, he put his meager yield through the fermentation process.

      And discovered that he had a hit on his hands. The finished wine was insanely sweet. Since its first, semilegendary, certainly accidental harvest, some winemakers have specialized in ice wine, waiting every year for the first frost so they can harvest crops of frozen grapes. Among the many ways wine is rated, graded, and weighted today, it is measured on a “sugar scale.” Typical table wine runs from 0 to 3 on the sugar scale. Ice wine runs from 18 to 28.

      The shrunken nature of the grapes is due to water loss. Chemically speaking, it’s not difficult to guess why grapes might have evolved to offload water at the onset of a freeze – the less water in the grape, the fewer ice crystals there are to damage the delicate membranes of the fruit.

      How about the sharp increase in sugar concentration? That makes sense too. Ice crystals are only made of pure water – but the temperature at which they start to form depends on what else is suspended in the fluid where the water is found. Anything dissolved in water interferes with its ability to form the hexagonal latticework of solid ice crystals. Average seawater, for example, full of salt, freezes at around 28 degrees Fahrenheit instead of the 32 degrees we think of as water’s freezing point. Think about the bottle of vodka some people keep in their freezer. Usually, alcohol is about 40 percent of the liquid volume in the bottle; it does a great job of interfering with the creation of ice – vodka doesn’t freeze until you cool it down to around minus 20 degrees Fahrenheit. Even most water in nature doesn’t freeze at exactly 32 degrees, because it usually contains trace minerals or other impurities that lower the freezing point.

      Like alcohol, sugar is a natural antifreeze. The higher the sugar content in a liquid, the lower the freezing point. (Nobody knows more about sugar and freezing than the food service chemists at 7-Eleven who were in charge of developing a sugar-free Slurpee beverage. In regular Slurpees, the sugar is what helps to keep the frozen treat slurpable – it prevents the liquid from completely freezing. So when they tried to make sugar-free Slurpees, they kept making sugar-free blocks of ice. According to a company press release, it took two decades for researchers to develop a diet Slurpee by combining artificial sweeteners with undigestible sugar alcohols.) So when the grape dumps water at the first sign of frost, it’s actually protecting itself in two ways – first, by reducing water volume; and second, by raising the sugar concentration of the water that remains. And that allows the grape to withstand colder temperature without freezing.

      Eliminating water to deal with the cold? That sounds an awful lot like cold diuresis – peeing when you’re cold. And higher levels of sugar? Well, we know where we’ve heard that; but before we get back to diabetes, let’s make one more stop: the animal kingdom.

      Many animals thrive in the cold. Some amphibians, like the bullfrog, spend the winter in the frigid but unfrozen water at the bottom of lakes and rivers. The mammoth Antarctic cod happily swims beneath the Antarctic ice; its blood contains an antifreeze protein that sticks to ice crystals and prevents them from growing. On the Antarctic surface, the woolly bear caterpillar lives through temperatures as low as minus 60 degrees Fahrenheit for fourteen years, until it turns into a moth and flies off into the sunset for a few short weeks.

      But of all the adaptations to cold under the sun – or hidden from it – none is as remarkable as the little wood frog’s.

      The wood frog, Rana sylvatica, is a cute little critter about two inches long, with a dark mask across its eyes like Zorro’s, that lives across North America, from northern Georgia all the way up to Alaska, including north of the Arctic Circle. On early spring nights you can hear its mating call – a “brack, brack” that sounds something like a baby duck’s. But until winter ends, you won’t hear the wood frog at all. Like some animals, the wood frog spends the entire winter unconscious. But unlike hibernating mammals that go into a deep sleep, kept warm and nourished by a thick layer of insulating fat, the wood frog gives in to the cold entirely. It buries itself under an inch or two of twigs and leaves and then pulls a trick that – despite Ted Williams’s possible hopes and Alcor’s best efforts – seems to come straight out of a science fiction movie.

      It freezes solid.

      If you were on a winter hike and accidentally kicked one of these frogsicles out into the open, you’d undoubtedly assume it was dead. When completely frozen, it might as well be in suspended animation – it has no heartbeat, no breathing, and no measurable brain activity. Its eyes are open, rigid, and unnervingly white.

      But if you pitched a tent and waited for spring, you’d eventually discover that little old Rana sylvatica has a few tricks up its frog sleeves. Just a few minutes after rising temperatures thaw the frog, its heartbeat miraculously sparks into gear and it gulps for air. It will blink a few times as color returns to its eyes, stretch its legs, and pull itself up into a sitting position. Not long after that, it will hop off, none the worse for wear, and join the chorus of defrosted frogs looking for a mate.

      Nobody knows the wood frog better than the brilliant and irrepressible Ken Storey, a biochemist from Ottawa, Canada, who, along with his wife, Janet, has been studying them since the early 1980s. Storey had been studying insects with the ability to tolerate freezing when a colleague told him about the wood frog’s remarkable ability. His colleague had been collecting frogs for study and accidentally left them in the trunk of his car. Overnight, there was an unexpected frost and he awoke to discover a bag of frozen frogs. Imagine his surprise later that day when they thawed out on his lab table and started jumping around!

      Storey was immediately intrigued. He was interested in cryopreservation – freezing living tissue to preserve it. Despite the bad rap it gets for its association with high-priced attempts to freeze the rich and eccentric for future cures, cryopreservation is a critical area of medical research that has the potential to yield many important advances. It has already revolutionized reproductive medicine by giving people the opportunity to freeze and preserve eggs and sperm.

      The next step – the ability to extend the viability of large human organs for transplants – would be a huge breakthrough that could save thousands of lives every year. Today, a human kidney can be preserved for just two days outside the human body, while a heart can last only a few hours. As a result, organ transplants are always a race against the clock, with very little time to find the best match and get the patient, organ, and surgeon into the same operating room. Every day in the United States, a dozen people die because the organ they need hasn’t become available in time. If donated organs could be frozen and “banked” СКАЧАТЬ