Today I want to write about something that has bothered me for a while, but which has intensified since I became pregnant. And I know that I run the risk of jumping into a rat’s nest of controversy, as there are many people who passionately believe in one side or another of this controversy. But hey, science is sometimes controversial, so I’ll just take a deep breath and plunge right in.
I want to talk about childhood vaccinations.
You might have heard a lot of stories on the news or in the papers in the last few years about the controversy over vaccinations. Do kids really need them, should they get them, or (and this is really the favorite topic in the media) is the increase in the rate of vaccinations connected with the increased rate of autism in today’s children?
I consider myself very well educated on these topics, and let me just put my position out there. I do not believe there to be any credible scientific backing behind the purported link between vaccinations and autism. I think any “scientific” evidence supporting it is spurious at best. I understand that autism is on the rise among today’s children, my heart breaks for those families with autistic children, and I easily understand how they might want an answer for what has caused the condition. But the science just does not support their claim that it is due to vaccinations.
That’s all I want to say about the recent controversy over vaccines. The main focus of what I want to say about the decision of whether to have your children vaccinated or not is not simply, as I have heard it said, a personal decision. Yes,, it is personal. But it is also a social decision as well. Here’s what I mean.
Rubella, or German measles, is not a very common disease these days (at least in the US). That’s because vaccinations against rubella have been going on for years – it’s a part of the MMR vaccine, and it’s very effective. Some may argue that it’s silly to vaccinate against rubella. Actually, compared to regular measles, rubella is usually pretty mild. You might have a rash, low grade fever, swollen glands, headaches and body aches. Or you might not ever really notice that you have it at all. But here’s the sticky thing. While rubella might not be all that dangerous for children or adults, it is devastating to pregnant women and their unborn children. A pregnant woman who contracts rubella within the first 20 weeks of her pregnancy has a significantly increased risk of spontaneous miscarriage. And even if disease doesn’t kill her child, it is at high risk for congenital rubella syndrome. This syndrome includes a host of birth defects, including heart malformations, deafness, mental retardation, eye defects, low birth weight, or problems with the spleen, liver or bone marrow. These problem can plague a child for the rest of his life.
The easiest way for mothers to protect their unborn children against congenital rubella syndrome is to be vaccinated themselves. That way, even if they encounter someone with rubella, they and their baby will be protected. But here’s what I worry about: I’m sure there are plenty of women who don’t know of the dangers that rubella poses. And so their vaccinations are not up-to-date. What if they come into contact with someone else carrying rubella because they believe that “whether or not I get vaccinated is strictly a personal decision that doesn’t affect anyone else”? I hope that you clearly see that suddenly this is not simply a personal decision. The unvaccinated individual has significantly increased the risk of someone else being born with a serious birth defect – or perhaps even caused the baby to not be born at all. That’s not personal. That’s social.
I realize that I’m not going to sway anyone’s opinion on whether or not they or their children should be vaccinated. (Especially if their belief is based on religious reasons.) However, I just want to make people aware. This really is not just a personal question, and it makes my blood boil, both as a scientist and an expectant mother, when people suggest that it is.
Incidentally, for everyone who’s reading this – have you been vaccinated against MMR?
Tuesday, May 27, 2008
Friday, May 23, 2008
The intelligent octopus
I wrote about giant squid recently, which prompted thoughts on a related topic in my head. I’ve read before that octopus are really intelligent creatures. But I’ve never actually investigated that claim very closely; I’ve just taken it at face value. So I wondered – is it true? How smart are octopus, anyways? And how do we know how smart they are? Is there a little octopus IQ test given to all eight-legged water-dwellers currently residing in aquariums around the world?
Remember, an octopus is a kind of cephalopod. Cephalopods are classified by bilateral body symmetry, prominent heads, and a variation on a mollusk foot called a muscular hydrostat – aka arms or tentacles. (FYI, a muscular hydrostat is a piece of anatomy found in any animal that has muscle but no skeletal support and that is used to move stuff – such as food – around. Your tongue is a perfect example of one.) There are two major types of cephalopods – those with a mollusk shell (like the nautilus) and those without (like squid and octopus). The octopus takes being shell-less even one step further than many of its relatives, however, because it has no skeletal support at all. It doesn’t even have any vestiges of an internal shell or bones, unlike cuttlefish or squid. Its body is entirely soft.
You’d probably agree that an octopus does, indeed, have a noticeably large head. And housed within that head is a very large and complex brain. In terms of brain size relative to body mass, octopus brains rank higher than those of reptiles and fish. And while their brains are organized very differently from that of vertebrates, there is no denying that it is highly differentiated and organized into different sensory processing centers. So that brings us to the question of how intelligent these creatures are. If they have such large brains relative to their body size, it would make sense that they would be intelligent, right?
The answer is – maybe. It depends on whom you ask. Some scientists believe that the size of the octopus brain is not a sign of intelligence at all, but merely an indication that their entire brains are not built very efficiently. And there may be some backing for that. In fact, octopus have been discovered with spines lodged in their brains, from where a meal that they were eating went the wrong way through their system and got wedged in their heads. That’s a pretty good indication that there is something a little screwy about the way their digestive and nervous systems intersect.
However, others believe that octopus have large brains because they are intelligent. When they say “intelligent,” what they really mean is capable of highly complex behaviors above and beyond simple survival skills. Here are some examples of the evidence that scientists falling in to this camp cite as backing for their belief.
1. Captive octopi are extremely good escape artists. Lids of tanks must be heavily weight shut, or the creatures will use their arms to push their way out. Even then, the areas around octopi tanks are frequently carpeted instead of tiled. That’s because octopi can manage to squeeze through incredibly small spaces (remember, they have no bones). So even with a heavily weighted lid, they still sneak out. But they can’t crawl across a carpeted floor, so they have nowhere to go but back where they came from. When they do manage to escape, where do they go, you might wonder? Usually, they are found in neighboring tanks, snacking on whatever tasty treats they find there.
2. Octopi are highly adept at changing their appearance. They can change the color and texture of their skin at will to match their surroundings. Their appearance can change from solid colors to lightly speckled to dramatically striped very rapidly during hunting, courtship, male-to-male aggression and in response to a threat. They accomplish this through the stretching of chromatophores, which are multicelled organs consisting of pigment sacs and various colors. When their muscles fibers contract and expand, the chromatophores change within seconds, making the octopus much faster at changing appearance than any land-based camouflage artist.
3. Researchers have trained octopi to recognize shapes, colors and textures in much the same way that they would teach vertebrates like rats. In the 1950s and 1960s, scientists at the University of Cambridge taught young octopi how to recognize small and large squares, horizontal and vertical stripes, and black and white circles. And the octopi were quick learners, too, though it seems like their maximum level of knowledge is ultimately below that achieved by rats.
4. Octopi are highly skilled navigators underwater, and have been trained to run through mazes just like mice and rats. When presented with a new underwater terrain filled with holes, an octopus can quickly learn to navigate through the correct holes to get to its den (and a treat). And once it’s figured the route out, it is much faster at navigating it the second time through.
5. Octopi have been shown to be able to solve the “food in a container” challenge. If given a closed jar with a crab inside (crabs being a very tasty octopus snack), most octopi will figure out how to open the jar and get their treat, even if they’ve never seen such a jar before. Incidentally, this is a classic test of problem-solving ability in vertebrates such as non-human primates.)
6. There was even one study in 1992 claiming to show that octopi could learn by observing other octopi. According to the study, an octopus was allowed to observe another octopus being trained to prefer one color ball (red) to another (white). Later, the observer octopus showed a preference for red balls, even though he had not received the training himself. This study has been met with much skepticism, however, and it is generally agreed that it must be rigorously repeated before it can be taken at face value. To date, no one else has been able to reproduce the results under more rigorously controlled conditions, so the jury is still out on that question.
This debate rages on even now, as scientists try to come up with the perfect experimental set-up to test whether the octopus is really intelligent, or simply very good at navigating in its surroundings. Regardless, I love watching octopi at aquariums. Whether or not they are as smart as some claim, they are fascinating creatures nonetheless. I’ve never seen one in the wild, though I’ve often looked (while scuba diving). Who knows – maybe some day I’ll get lucky enough to see one in the ocean!
Remember, an octopus is a kind of cephalopod. Cephalopods are classified by bilateral body symmetry, prominent heads, and a variation on a mollusk foot called a muscular hydrostat – aka arms or tentacles. (FYI, a muscular hydrostat is a piece of anatomy found in any animal that has muscle but no skeletal support and that is used to move stuff – such as food – around. Your tongue is a perfect example of one.) There are two major types of cephalopods – those with a mollusk shell (like the nautilus) and those without (like squid and octopus). The octopus takes being shell-less even one step further than many of its relatives, however, because it has no skeletal support at all. It doesn’t even have any vestiges of an internal shell or bones, unlike cuttlefish or squid. Its body is entirely soft.
You’d probably agree that an octopus does, indeed, have a noticeably large head. And housed within that head is a very large and complex brain. In terms of brain size relative to body mass, octopus brains rank higher than those of reptiles and fish. And while their brains are organized very differently from that of vertebrates, there is no denying that it is highly differentiated and organized into different sensory processing centers. So that brings us to the question of how intelligent these creatures are. If they have such large brains relative to their body size, it would make sense that they would be intelligent, right?
The answer is – maybe. It depends on whom you ask. Some scientists believe that the size of the octopus brain is not a sign of intelligence at all, but merely an indication that their entire brains are not built very efficiently. And there may be some backing for that. In fact, octopus have been discovered with spines lodged in their brains, from where a meal that they were eating went the wrong way through their system and got wedged in their heads. That’s a pretty good indication that there is something a little screwy about the way their digestive and nervous systems intersect.
However, others believe that octopus have large brains because they are intelligent. When they say “intelligent,” what they really mean is capable of highly complex behaviors above and beyond simple survival skills. Here are some examples of the evidence that scientists falling in to this camp cite as backing for their belief.
1. Captive octopi are extremely good escape artists. Lids of tanks must be heavily weight shut, or the creatures will use their arms to push their way out. Even then, the areas around octopi tanks are frequently carpeted instead of tiled. That’s because octopi can manage to squeeze through incredibly small spaces (remember, they have no bones). So even with a heavily weighted lid, they still sneak out. But they can’t crawl across a carpeted floor, so they have nowhere to go but back where they came from. When they do manage to escape, where do they go, you might wonder? Usually, they are found in neighboring tanks, snacking on whatever tasty treats they find there.
2. Octopi are highly adept at changing their appearance. They can change the color and texture of their skin at will to match their surroundings. Their appearance can change from solid colors to lightly speckled to dramatically striped very rapidly during hunting, courtship, male-to-male aggression and in response to a threat. They accomplish this through the stretching of chromatophores, which are multicelled organs consisting of pigment sacs and various colors. When their muscles fibers contract and expand, the chromatophores change within seconds, making the octopus much faster at changing appearance than any land-based camouflage artist.
3. Researchers have trained octopi to recognize shapes, colors and textures in much the same way that they would teach vertebrates like rats. In the 1950s and 1960s, scientists at the University of Cambridge taught young octopi how to recognize small and large squares, horizontal and vertical stripes, and black and white circles. And the octopi were quick learners, too, though it seems like their maximum level of knowledge is ultimately below that achieved by rats.
4. Octopi are highly skilled navigators underwater, and have been trained to run through mazes just like mice and rats. When presented with a new underwater terrain filled with holes, an octopus can quickly learn to navigate through the correct holes to get to its den (and a treat). And once it’s figured the route out, it is much faster at navigating it the second time through.
5. Octopi have been shown to be able to solve the “food in a container” challenge. If given a closed jar with a crab inside (crabs being a very tasty octopus snack), most octopi will figure out how to open the jar and get their treat, even if they’ve never seen such a jar before. Incidentally, this is a classic test of problem-solving ability in vertebrates such as non-human primates.)
6. There was even one study in 1992 claiming to show that octopi could learn by observing other octopi. According to the study, an octopus was allowed to observe another octopus being trained to prefer one color ball (red) to another (white). Later, the observer octopus showed a preference for red balls, even though he had not received the training himself. This study has been met with much skepticism, however, and it is generally agreed that it must be rigorously repeated before it can be taken at face value. To date, no one else has been able to reproduce the results under more rigorously controlled conditions, so the jury is still out on that question.
This debate rages on even now, as scientists try to come up with the perfect experimental set-up to test whether the octopus is really intelligent, or simply very good at navigating in its surroundings. Regardless, I love watching octopi at aquariums. Whether or not they are as smart as some claim, they are fascinating creatures nonetheless. I’ve never seen one in the wild, though I’ve often looked (while scuba diving). Who knows – maybe some day I’ll get lucky enough to see one in the ocean!
Wednesday, May 21, 2008
Why don’t they go bad?
This post is for anyone who’s ever ordered coffee at a restaurant and wondered about the little cups of creamer that they bring with it. These creamers hold maybe a tablespoon full of cream that tastes actually tastes pretty decent in your average cup of coffee, but they also have an inherent mystery about them that has always puzzled me a bit. You see, unlike regular milk or cream, these little things do not need to be refrigerated. Says so right on the lid – no refrigeration necessary. And yet, if you look at the ingredients, there is actual milk in there. So why doesn’t it go bad?
To answer this question, let’s first look at how regular milk is processed for sale in the US. Milk (as well milk-related products like cream and non-dairy products like juice) undergoes a process called pasteurization before it is put on the market. Pasteurization is a process by which any liquid is heated to destroy any microorganisms in it, such as bacteria and mold. It’s named after Louis Pasteur, a famous French scientist who accomplished many things over the course of his life, including advancing the idea that diseases are caused by germs and for developing a vaccine for rabies. He also figured out that heating liquids to a temperature below their boiling point would significantly extend their shelf life (the amount of time before the liquid spoils). There are 2 major methods for pasteurization in use today – High Temperature/Short Time (HTST) and Extended Shelf Life (ESL) treatments. These different methods just use different machinery to achieve the same end. Pasteurization is different from sterilization, in that it is not designed to kill all of the microorganisms within the liquid. Instead, it results in a logarithmic reduction in their levels, reducing them to a point where they are unlikely to cause disease as long as the product is refrigerated. However, as anyone who has ever left a carton of milk in the fridge for too long knows, even a pasteurized product will go bad eventually. That’s because there are still some microorganisms left in the liquid that will cause it to curdle, sour, or otherwise go bad after enough time. If you were to leave the milk out at room temperature, the residual bacteria would spoil the milk even faster – even as fast as overnight.
So if they contain real dairy, why don’t those little creamer packages go bad when left out overnight, too? Well, it turns out that those things undergo a slightly different process called ultrapasteurization. This is also known as ultrahigh-temperature pasteurization, or UHT. Ultrapasteurization is really a process of sterilization instead of pasteurization. When a product is ultrapasteurized, it is heated hotter than in regular pasteurization. This results in the killing of all microorganisms within it – they simply can’t survive the heat. And without any microorganisms, the liquid simply won’t go bad – at least not for a very long time. You can keep ultrapasteurized dairy at room temperature for months if it has not been opened, and it will still be as good when you open it as when it was first produced. Of course, once it is opened, then you need to refrigerate it. That’s because there are numerous bacteria and mold spores floating around in the air, covering your skin, and on every surface in the world. So when that package is opened, those little beasties can get inside and work their destructive magic.
So there you have it. You don’t need to refrigerate little packets of creamer because they have been sterilized. Just another example of science making a difference in little aspects of life you may never have realized!
To answer this question, let’s first look at how regular milk is processed for sale in the US. Milk (as well milk-related products like cream and non-dairy products like juice) undergoes a process called pasteurization before it is put on the market. Pasteurization is a process by which any liquid is heated to destroy any microorganisms in it, such as bacteria and mold. It’s named after Louis Pasteur, a famous French scientist who accomplished many things over the course of his life, including advancing the idea that diseases are caused by germs and for developing a vaccine for rabies. He also figured out that heating liquids to a temperature below their boiling point would significantly extend their shelf life (the amount of time before the liquid spoils). There are 2 major methods for pasteurization in use today – High Temperature/Short Time (HTST) and Extended Shelf Life (ESL) treatments. These different methods just use different machinery to achieve the same end. Pasteurization is different from sterilization, in that it is not designed to kill all of the microorganisms within the liquid. Instead, it results in a logarithmic reduction in their levels, reducing them to a point where they are unlikely to cause disease as long as the product is refrigerated. However, as anyone who has ever left a carton of milk in the fridge for too long knows, even a pasteurized product will go bad eventually. That’s because there are still some microorganisms left in the liquid that will cause it to curdle, sour, or otherwise go bad after enough time. If you were to leave the milk out at room temperature, the residual bacteria would spoil the milk even faster – even as fast as overnight.
So if they contain real dairy, why don’t those little creamer packages go bad when left out overnight, too? Well, it turns out that those things undergo a slightly different process called ultrapasteurization. This is also known as ultrahigh-temperature pasteurization, or UHT. Ultrapasteurization is really a process of sterilization instead of pasteurization. When a product is ultrapasteurized, it is heated hotter than in regular pasteurization. This results in the killing of all microorganisms within it – they simply can’t survive the heat. And without any microorganisms, the liquid simply won’t go bad – at least not for a very long time. You can keep ultrapasteurized dairy at room temperature for months if it has not been opened, and it will still be as good when you open it as when it was first produced. Of course, once it is opened, then you need to refrigerate it. That’s because there are numerous bacteria and mold spores floating around in the air, covering your skin, and on every surface in the world. So when that package is opened, those little beasties can get inside and work their destructive magic.
So there you have it. You don’t need to refrigerate little packets of creamer because they have been sterilized. Just another example of science making a difference in little aspects of life you may never have realized!
Monday, May 12, 2008
How to see the inner man (or woman)
There is a major event happening in the life of my family right now, and I haven’t written about it yet but have been waiting for the opportunity. My husband and I are expecting our first child! There are so many things that I’ve thought about writing with respect to the science of pregnancy – what causes morning sickness, how amazing the pattern of development of the human body really is, how statistically unlikely it was that we would have twins (though lots and lots of people teased us about the possibility), and how much I hope our child grows up loving science as much as we do. But I held off, waiting for the perfect topic. And today, I think I’ve found it – I want to write about ultrasounds.
Actually, I’d like to write about some of the various ways that medicine has come up with to look at what’s going on inside the human body – short of surgery, that is. Three big techniques come to my mind, and I’d like to take a few minutes to discuss what each one does, how they are different from each other, and what their advantages are. These three are ultrasounds, x-rays, and MRIs.
I’ll start with the ultrasound (particularly near and dear to us at the moment). The word “ultrasound” actually means sound waves that are above the range of human hearing (20,000 hertz), so when we talk about ultrasounds in a medical sense, we are actually talking about ultrasonography. Ultrasonography has been around for about 50 years, and is extremely widely used in diagnostic procedures to visualize soft tissues, muscles, tendons, and some internal organs (including the heart, liver, gallbladder, kidneys and bladder). It is also commonly used to look at a developing fetus within a mother’s uterus. During the process, ultrasound waves are produced by a small wand, or transducer, which radiate out into the body to focus at the specified depth. This sound wave is partially reflected from the layers between different tissues – specifically, where there is a change in tissue density. The sound waves that get bounced back towards the transducer are detected by a sensitive microphone, which are then translated into an image on a computer screen. There are several big advantages to using sonography as a diagnostic tool. For one thing, it does not use ionizing radiation (as do x-rays), making it safe to use for developing babies. For another, it is relatively cheap compared to its high-power brothers like the MRI. However, it is limited in its ability to see certain structures within the body – it is not good at visualizing bones or the brain, for example.
So let’s go now to the next imaging technique on my list – the x-ray. The medical use of x-rays manipulates the physical properties of – you got it – x-rays. (Clever, huh?) An x-ray is a high energy type of light wave. The energy of a light wave can be measured by its wavelength – the shorter the wavelength, the higher the energy the wave has. In the visible spectrum, red light has lower energy (and longer wavelengths) and blue light has higher energy (and shorter wavelengths). Past the visible spectrum comes ultraviolet light, followed by x-rays. While visible light does not have enough energy to pass through your skin, x-rays have considerably more energy, and thus can pass right through your skin and muscle. However, they are not strong enough to pass through bone. So when you undergo a medical x-ray (for example, to see whether you’ve broken a bone or when you are at the dentist), the doctor will put you in front of an x-ray emitter, which sends x-rays through your body and picked up by a detector (usually a piece of film) on the other side of you. Places of your body where the x-rays pass through (eg muscles and soft tissue) show up as black, while pieces of your body where the x-rays were absorbed (eg bone and teeth) show up white. The film is developed, and the doctor can tell whether your bones are all as they should be – whole and unbroken (hopefully). X-rays are more powerful than sonograms, especially for diagnosing problems specific to the skeleton. However, their major drawback is that they use ionizing radiation in the process. Too much ionizing radiation can cause all kinds of problems for your cells and tissues; however, the exposure any of us will be likely to receive from medical x-rays over the course of our lives is minimal and of low risk.
What about the fancier techniques, like MRI? MRI stands for magnetic resonance imaging, and it uses an entirely different basic principle to visualize the interior of the human body. Instead of sonography (which uses sound) or x-rays (which uses high-energy light), MRIs use magnetic fields. When a person is subjected to an MRI, their body is immersed in a strong magnetic field, which has an effect on the hydrogen atoms throughout their body. The human body can be upwards of 75% water; in each molecule of water, there are 2 hydrogen atoms. Thus, the amount of hydrogen in your body from water alone is really high. And these hydrogen ions will all align with the magnetic field when you are in the MRI machine. So you sit there, with all your hydrogens aligned, and then your body is pulsed with a radio wave. This pushes some of the hydrogen atoms out of alignment with the magnetic field. The radio wave stops, and the hydrogens all slowly snap back into alignment. However, depending on what tissue they happen to be sitting in, they will snap back into place at different speeds. And the speed at which the hydrogens align themselves with is detected by the machine, then calculated to determine what tissue is what. An MRI is a very powerful technique, and can be used to diagnose a number of different medical conditions, including multiple sclerosis, brain tumors, torn ligaments, spinal hernias, tendonitis, and even strokes in the early stages. Another advantage is that they, like sonograms, do not use any form of ionizing radiation. And yet another advantage is that MRIs can be used to look at any plane of the human body – sideways, top-to-bottom, or any other way you can think of. There are some disadvantages, though. Certain people cannot receive MRIs, because the strong magnetic field would be dangerous for them (for example, people with pacemakers). MRIs take a very long time to do, as well, and they are extremely expensive – much more so than either x-rays or a sonogram.
All three of these techniques are powerful in their own right. They can be used to look at different parts of the body – soft tissue, organs, bones or ligaments – with different resolutions. Each one uses a different major method of visualization – magnetic fields, sound waves or electromagnetic radiation. Each one has different costs, risks and benefits. And all in all, I’m glad to live in a day and age where all three are used as a part of everyday medicine. Each one is so much safer than having to cut the body open to see what’s going on inside!
Oh, and by the way, we have had our ultrasound to check on our developing baby. All looks good – 2 arms, 2 legs, and all pieces where they should be! Now we just have to wait to see the little one in person!
Actually, I’d like to write about some of the various ways that medicine has come up with to look at what’s going on inside the human body – short of surgery, that is. Three big techniques come to my mind, and I’d like to take a few minutes to discuss what each one does, how they are different from each other, and what their advantages are. These three are ultrasounds, x-rays, and MRIs.
I’ll start with the ultrasound (particularly near and dear to us at the moment). The word “ultrasound” actually means sound waves that are above the range of human hearing (20,000 hertz), so when we talk about ultrasounds in a medical sense, we are actually talking about ultrasonography. Ultrasonography has been around for about 50 years, and is extremely widely used in diagnostic procedures to visualize soft tissues, muscles, tendons, and some internal organs (including the heart, liver, gallbladder, kidneys and bladder). It is also commonly used to look at a developing fetus within a mother’s uterus. During the process, ultrasound waves are produced by a small wand, or transducer, which radiate out into the body to focus at the specified depth. This sound wave is partially reflected from the layers between different tissues – specifically, where there is a change in tissue density. The sound waves that get bounced back towards the transducer are detected by a sensitive microphone, which are then translated into an image on a computer screen. There are several big advantages to using sonography as a diagnostic tool. For one thing, it does not use ionizing radiation (as do x-rays), making it safe to use for developing babies. For another, it is relatively cheap compared to its high-power brothers like the MRI. However, it is limited in its ability to see certain structures within the body – it is not good at visualizing bones or the brain, for example.
So let’s go now to the next imaging technique on my list – the x-ray. The medical use of x-rays manipulates the physical properties of – you got it – x-rays. (Clever, huh?) An x-ray is a high energy type of light wave. The energy of a light wave can be measured by its wavelength – the shorter the wavelength, the higher the energy the wave has. In the visible spectrum, red light has lower energy (and longer wavelengths) and blue light has higher energy (and shorter wavelengths). Past the visible spectrum comes ultraviolet light, followed by x-rays. While visible light does not have enough energy to pass through your skin, x-rays have considerably more energy, and thus can pass right through your skin and muscle. However, they are not strong enough to pass through bone. So when you undergo a medical x-ray (for example, to see whether you’ve broken a bone or when you are at the dentist), the doctor will put you in front of an x-ray emitter, which sends x-rays through your body and picked up by a detector (usually a piece of film) on the other side of you. Places of your body where the x-rays pass through (eg muscles and soft tissue) show up as black, while pieces of your body where the x-rays were absorbed (eg bone and teeth) show up white. The film is developed, and the doctor can tell whether your bones are all as they should be – whole and unbroken (hopefully). X-rays are more powerful than sonograms, especially for diagnosing problems specific to the skeleton. However, their major drawback is that they use ionizing radiation in the process. Too much ionizing radiation can cause all kinds of problems for your cells and tissues; however, the exposure any of us will be likely to receive from medical x-rays over the course of our lives is minimal and of low risk.
What about the fancier techniques, like MRI? MRI stands for magnetic resonance imaging, and it uses an entirely different basic principle to visualize the interior of the human body. Instead of sonography (which uses sound) or x-rays (which uses high-energy light), MRIs use magnetic fields. When a person is subjected to an MRI, their body is immersed in a strong magnetic field, which has an effect on the hydrogen atoms throughout their body. The human body can be upwards of 75% water; in each molecule of water, there are 2 hydrogen atoms. Thus, the amount of hydrogen in your body from water alone is really high. And these hydrogen ions will all align with the magnetic field when you are in the MRI machine. So you sit there, with all your hydrogens aligned, and then your body is pulsed with a radio wave. This pushes some of the hydrogen atoms out of alignment with the magnetic field. The radio wave stops, and the hydrogens all slowly snap back into alignment. However, depending on what tissue they happen to be sitting in, they will snap back into place at different speeds. And the speed at which the hydrogens align themselves with is detected by the machine, then calculated to determine what tissue is what. An MRI is a very powerful technique, and can be used to diagnose a number of different medical conditions, including multiple sclerosis, brain tumors, torn ligaments, spinal hernias, tendonitis, and even strokes in the early stages. Another advantage is that they, like sonograms, do not use any form of ionizing radiation. And yet another advantage is that MRIs can be used to look at any plane of the human body – sideways, top-to-bottom, or any other way you can think of. There are some disadvantages, though. Certain people cannot receive MRIs, because the strong magnetic field would be dangerous for them (for example, people with pacemakers). MRIs take a very long time to do, as well, and they are extremely expensive – much more so than either x-rays or a sonogram.
All three of these techniques are powerful in their own right. They can be used to look at different parts of the body – soft tissue, organs, bones or ligaments – with different resolutions. Each one uses a different major method of visualization – magnetic fields, sound waves or electromagnetic radiation. Each one has different costs, risks and benefits. And all in all, I’m glad to live in a day and age where all three are used as a part of everyday medicine. Each one is so much safer than having to cut the body open to see what’s going on inside!
Oh, and by the way, we have had our ultrasound to check on our developing baby. All looks good – 2 arms, 2 legs, and all pieces where they should be! Now we just have to wait to see the little one in person!
Monday, May 5, 2008
The giant of the deep
As you might have guessed from my various postings through the months, I like to write about animals. There are so many things about them that I find interesting – the purring of cats, lizards whose appearance hasn’t changed in a million years, goats that randomly fall over when they are startled, how kangaroos can’t walk backwards, and how, ounce for ounce, bats are one of the longest living mammals on earth. Well, today I’d like to talk about an animal that no one knows very much about, but one that I have found fascinating ever since I first heard about it. This creature is one of the great animal mysteries of the world – we know that it exists, but short of that, we know relatively little about it at all. The animal in question – Architeuthis. The giant squid.
What is a giant squid? Since it is not very creatively named, you’ve probably guessed that it’s simply a really, really big squid. But how big is it? How does it get so big? Where does it live? And why do we know so little about it?
First, let’s discuss squid and octopus in general. Your basic squid has a few standard anatomical features – 8 arms and 2 tentacles, each with hooks and/or suckers, a head (with a very large brain), a mantle (or torso), and 2 fins at the rear of the mantle. Your basic octopus is the same, except that it doesn’t usually have fins, and it’s arms and tentacles only have suckers, not hooks. (There are a few species of octopus with fins, however; they live off the coast of New Zealand and are considered primitive relative to other octopus. That’s why they are referred to as “Dumbo octopus.”) The tentacles of squid are generally much longer than the arms. In fact, there are 2 ways to measure the length of a squid. You can either measure the standard length, which is the length from fins to the end of the arms, or total length, which is the length of the fins to the tentacles. Most squid are quite small, reaching an average total length of almost 2 feet. Of course, that’s the size of most squid – except for the giant squid.
How big a giant squid can get is a matter of debate, since they are so hard to find. The largest reported giant squid ever found washed up in New Zealand in 1887, supposedly at a total length of 55 feet. However, since it was dead, it is likely that its tentacles became stretched like rubber bands once it died and washed up. Based on the length of its mantle, it is now believed to have been only around 30 feet long. Scientists now generally base their estimates of how big a giant squid can get on the remnants of them found in the stomachs of their only known predators, sperm whales. Based on these leftovers, it is now believed that they can reach up to 45 feet in total length. The only invertebrate believed to be larger than the giant squid, actually, is its cousin, the colossal squid (which may be twice as long).
Giant squid live in the depths of every ocean in the world. They are usually found near continental and island slopes of the North Atlantic, the South Atlantic, and New Zealand and Australia, and are rarely seen in tropical waters or near the poles. Unfortunately for scientists, they are often studied after they’ve died, whether they’ve washed up on a beach or are taken out in pieces from a sperm whale’s stomach. In 2004, however, major news was made when scientists off the coast of Japan filmed a live giant squid for the first time ever in its natural habitat. Finding live giant squid in the ocean is notoriously difficult. Scientists usually try to follow sperm whales in the hopes of finding one, but that has proved relatively fruitless. Unless we come up with a better way of finding these elusive giants, they might remain a mystery for some time to come.
Of course, just because we don’t know a lot about them scientifically hasn’t stopped us from using our imaginations to envision them. Giant squid have been a source of legend for thousands of years. Tales of them have been around among mariners since ancient times. In fact, it is believed that the giant squid probably gave rise to the legend of the kraken - a giant sea monster off the coast of Norway and Iceland that was capable of engulfing entire ships (and one that you might remember from the recent Hollywood blockbuster “Pirates of the Caribbean 2: Dead Man’s Chest").
I don’t know why I find these creatures so intriguing, to be honest. Perhaps it’s simply because of their mystery. Imagine – an enormous creature, swimming in the depths of the ocean, so well adapted to its environment that we can’t even find it. Something so large that it only has one predator it needs to fear. And something that, unlike sharks, has not successfully been made into the villain of a Hollywood movie plot such that we feel the need to hunt it down and kill it. Maybe someday we’ll know more about this giant animal. Until then, I must say that I kind of like the uncertainty.
What is a giant squid? Since it is not very creatively named, you’ve probably guessed that it’s simply a really, really big squid. But how big is it? How does it get so big? Where does it live? And why do we know so little about it?
First, let’s discuss squid and octopus in general. Your basic squid has a few standard anatomical features – 8 arms and 2 tentacles, each with hooks and/or suckers, a head (with a very large brain), a mantle (or torso), and 2 fins at the rear of the mantle. Your basic octopus is the same, except that it doesn’t usually have fins, and it’s arms and tentacles only have suckers, not hooks. (There are a few species of octopus with fins, however; they live off the coast of New Zealand and are considered primitive relative to other octopus. That’s why they are referred to as “Dumbo octopus.”) The tentacles of squid are generally much longer than the arms. In fact, there are 2 ways to measure the length of a squid. You can either measure the standard length, which is the length from fins to the end of the arms, or total length, which is the length of the fins to the tentacles. Most squid are quite small, reaching an average total length of almost 2 feet. Of course, that’s the size of most squid – except for the giant squid.
How big a giant squid can get is a matter of debate, since they are so hard to find. The largest reported giant squid ever found washed up in New Zealand in 1887, supposedly at a total length of 55 feet. However, since it was dead, it is likely that its tentacles became stretched like rubber bands once it died and washed up. Based on the length of its mantle, it is now believed to have been only around 30 feet long. Scientists now generally base their estimates of how big a giant squid can get on the remnants of them found in the stomachs of their only known predators, sperm whales. Based on these leftovers, it is now believed that they can reach up to 45 feet in total length. The only invertebrate believed to be larger than the giant squid, actually, is its cousin, the colossal squid (which may be twice as long).
Giant squid live in the depths of every ocean in the world. They are usually found near continental and island slopes of the North Atlantic, the South Atlantic, and New Zealand and Australia, and are rarely seen in tropical waters or near the poles. Unfortunately for scientists, they are often studied after they’ve died, whether they’ve washed up on a beach or are taken out in pieces from a sperm whale’s stomach. In 2004, however, major news was made when scientists off the coast of Japan filmed a live giant squid for the first time ever in its natural habitat. Finding live giant squid in the ocean is notoriously difficult. Scientists usually try to follow sperm whales in the hopes of finding one, but that has proved relatively fruitless. Unless we come up with a better way of finding these elusive giants, they might remain a mystery for some time to come.
Of course, just because we don’t know a lot about them scientifically hasn’t stopped us from using our imaginations to envision them. Giant squid have been a source of legend for thousands of years. Tales of them have been around among mariners since ancient times. In fact, it is believed that the giant squid probably gave rise to the legend of the kraken - a giant sea monster off the coast of Norway and Iceland that was capable of engulfing entire ships (and one that you might remember from the recent Hollywood blockbuster “Pirates of the Caribbean 2: Dead Man’s Chest").
I don’t know why I find these creatures so intriguing, to be honest. Perhaps it’s simply because of their mystery. Imagine – an enormous creature, swimming in the depths of the ocean, so well adapted to its environment that we can’t even find it. Something so large that it only has one predator it needs to fear. And something that, unlike sharks, has not successfully been made into the villain of a Hollywood movie plot such that we feel the need to hunt it down and kill it. Maybe someday we’ll know more about this giant animal. Until then, I must say that I kind of like the uncertainty.
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