We're back. In this issue, as you munch on festival sweets and cakes, biologists bring you new insights into a scary aspect of diet: cholesterol. You can read the actual article here: http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=16100574.
There's a lot of bad hype about cholesterol: it can cause heart problems, you want to keep your numbers low, and it can lead to a bigger gut (along with its ugly cousin, fat). But cholesterol can be good for you, too.
We all need a little bit of cholesterol to keep our cells working properly. Cholesterol is a small molecule that slips into the outer wall (the cell membrane) of the components of our bodies, our cells. In there, it helps keep the cell membrane fluid and smooth, not rigid and impenetrable. If you have too little cholesterol, your liver will actually start to make it!
The problems start when you have too much. Too much cholesterol can combine with fat to clog up arteries.
So it's important that your liver stops making cholesterol. How does your body know that there's too much cholesterol and to stop making it? That's something scientists have puzzled over, until now.
Recent studies have shown that when you have too much cholesterol, two genes in your DNA get turned on. They make two proteins called the "Insigs." What are insigs and what do they do? The Insig proteins are special in one particular way: they prevent cholesterol from being made by binding to one of the parts of the cholesterol-making machine.
Imagine: you eat a particularly high cholesterol diet (a large fast-food lunch, or several slices of pizza with lots of cheese). You get a lot of cholesterol into your cells. In the meantime, your body has already been making cholesterol! That's cholesterol you don't need. A machine in your cell is chugging away, making cholesterol, with cholesterol-making proteins.
Now, your insigs spring into action. They go over to the cholesterol-making protein (called SREBPs), and they grab on to it. They glom on and trap it inside the cell so that it can't make more cholesterol-making proteins and more cholesterol. Ta da - you stop making cholesterol. Of course, now you have to do something with the cholesterol you already have.
What happens when your insigs stop working? The scientists removed the insig genes from some mice. When those mice ate a lot of cholesterol-rich food (mmm, cheese!), they got fat. Of course. But not only that! They continued to make cholesterol even when their livers would normally stop.
The cool thing about this study is that if you could treat people who normally make too much cholesterol with something that activates their insigs, they would make less. Then you could someday even increase your insigs to prevent from getting fatty!
Monday, August 29, 2005
Tuesday, July 26, 2005
Biology news 3: Cats don't have a sweet tooth
The third in the series might surprise you: it turns out that cats can't taste sweetness! Anyone who's ever tasted cat food knows it certainly isn't sweet. If you want to read details, see here: http://genetics.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pgen.0010003.
It turns out that most ordinary (that is, tame pet) cats have normal taste, but they can't taste sweetness. This is not true of humans of course, but most other mammals, including dogs, mice, horses, etc. can all tell when something is sweet. Cats can't! And scientists have wondered why for a long time.
How do you know what tastes sweet? Your tastebuds on your tongue detect sugar or sweet compounds (in honey, nutrasweet, splenda) and send a signal to your brain that says, "Hey, that's sweet!" The tastebuds have little proteins on them called receptors that actually attach to sugar molecules and then get turned on to send the message to your brain. When your tongue is burnt, you can't taste anything, because those receptors on your tongue are temporarily missing!
So why can't cats taste the sweet? It turns out their DNA for the sweetness receptor is ok. The sweetness receptor is actually a pair of proteins called "taste receptor 2" and "taste receptor 3." Taste receptor 3 is fine in cats, but taste receptor 2 isn't. Even though the DNA is there, there are changes in it (called mutations) that mess it up so that it never makes it to the cat's tongue. This kind of gene for taste receptor 2, which is actually there but not turned on, is called a pseudogene. With only half of a sweetness detector, the cats can't tell what's sweet and what isn't.
Amazingly, domestic cats aren't the only ones with the problem. Lions, cheetahs, jaguars and tigers can't taste sweet either. Somewhere along in evolution, one ancient cat lost the ability to taste sweetness, and so all its descendants did, too.
What does this mean for cats? Well, there's no point tempting them with sugar in their milk, for one thing. But also, it might explain why cats are carnivores. Since fruit and veggies don't taste good to them, they might prefer the flavor of meat. Or it could be the other way around: maybe because they started eating meat, they lost their sweet tooth.
In any case, it's a mystery, and makes taste even more interesting. In fact, even among humans, only some of us can taste certain types of bitterness (like phenylthiocarbamide, PTC, which is in cigarettes). With lots of taste receptors on our tongues, some people really do have "good taste."
rani
It turns out that most ordinary (that is, tame pet) cats have normal taste, but they can't taste sweetness. This is not true of humans of course, but most other mammals, including dogs, mice, horses, etc. can all tell when something is sweet. Cats can't! And scientists have wondered why for a long time.
How do you know what tastes sweet? Your tastebuds on your tongue detect sugar or sweet compounds (in honey, nutrasweet, splenda) and send a signal to your brain that says, "Hey, that's sweet!" The tastebuds have little proteins on them called receptors that actually attach to sugar molecules and then get turned on to send the message to your brain. When your tongue is burnt, you can't taste anything, because those receptors on your tongue are temporarily missing!
So why can't cats taste the sweet? It turns out their DNA for the sweetness receptor is ok. The sweetness receptor is actually a pair of proteins called "taste receptor 2" and "taste receptor 3." Taste receptor 3 is fine in cats, but taste receptor 2 isn't. Even though the DNA is there, there are changes in it (called mutations) that mess it up so that it never makes it to the cat's tongue. This kind of gene for taste receptor 2, which is actually there but not turned on, is called a pseudogene. With only half of a sweetness detector, the cats can't tell what's sweet and what isn't.
Amazingly, domestic cats aren't the only ones with the problem. Lions, cheetahs, jaguars and tigers can't taste sweet either. Somewhere along in evolution, one ancient cat lost the ability to taste sweetness, and so all its descendants did, too.
What does this mean for cats? Well, there's no point tempting them with sugar in their milk, for one thing. But also, it might explain why cats are carnivores. Since fruit and veggies don't taste good to them, they might prefer the flavor of meat. Or it could be the other way around: maybe because they started eating meat, they lost their sweet tooth.
In any case, it's a mystery, and makes taste even more interesting. In fact, even among humans, only some of us can taste certain types of bitterness (like phenylthiocarbamide, PTC, which is in cigarettes). With lots of taste receptors on our tongues, some people really do have "good taste."
rani
Thursday, June 09, 2005
Biology news 2: Male and female dinosaurs
The second in the series is an interesting one: now you can tell which dinosaurs are male and which are female. The story is here: http://www.sciencemag.org/cgi/content/abstract/308/5727/1456
So, how can you tell a girl dinosaur apart from a boy? If you had a whole dinosaur, it would be easier: you could look at reproductive organs, which ones laid eggs, who raises the kids, who wears lipstick, etc. But scientists don't have the luxury of observing whole, live dinosaurs. They don't even have whole, dead ones. All they have is fossilized bones!
So, we have to use something else to tell which one is male and which is female. The typical methods used relative size to tell if an animal was male, and it was usually not very reliable (so, that huge, scary T rex you saw at the museum might have been a mommy or a daddy!).
Now, scientists have found a Tyrannosaurus rex in the Rockies that they know for sure is a female. A fertile female. One who was laying eggs.
How do they know? Well, it turns out that when female dinosaurs are laying eggs, they change the inside of the bones in their back legs. The coolest thing about this is that birds do the same thing!
In current-day birds (especially ostriches and emus), when the girl birds start to make eggs, their hormones (like estrogen) go up, and they make this lining on the inside of their bones. The lining has calcium in it that helps them make eggshells. Amazingly, only birds do this.
So what does this mean? Well, for one it means that any dinosaur that has this special type of bone lining is definitely a female. It means the female was laying eggs.
And it also means something else: it means that dinosaurs are related to birds, especially ostriches and emus! So next time you see an ostrich at the zoo, remember: its great-great-great-great-great-great... grandmother could have been a T rex!
rani
So, how can you tell a girl dinosaur apart from a boy? If you had a whole dinosaur, it would be easier: you could look at reproductive organs, which ones laid eggs, who raises the kids, who wears lipstick, etc. But scientists don't have the luxury of observing whole, live dinosaurs. They don't even have whole, dead ones. All they have is fossilized bones!
So, we have to use something else to tell which one is male and which is female. The typical methods used relative size to tell if an animal was male, and it was usually not very reliable (so, that huge, scary T rex you saw at the museum might have been a mommy or a daddy!).
Now, scientists have found a Tyrannosaurus rex in the Rockies that they know for sure is a female. A fertile female. One who was laying eggs.
How do they know? Well, it turns out that when female dinosaurs are laying eggs, they change the inside of the bones in their back legs. The coolest thing about this is that birds do the same thing!
In current-day birds (especially ostriches and emus), when the girl birds start to make eggs, their hormones (like estrogen) go up, and they make this lining on the inside of their bones. The lining has calcium in it that helps them make eggshells. Amazingly, only birds do this.
So what does this mean? Well, for one it means that any dinosaur that has this special type of bone lining is definitely a female. It means the female was laying eggs.
And it also means something else: it means that dinosaurs are related to birds, especially ostriches and emus! So next time you see an ostrich at the zoo, remember: its great-great-great-great-great-great... grandmother could have been a T rex!
rani
Tuesday, May 17, 2005
Biology news 1: Antibodies protect against HIV
Hi everyone,
As a biologist, I feel I need to educate people about biology and what the latest news is. We'll start with a simple discovery: that certain antibodies can protect against HIV infection. A full description is here: http://www.nature.com/news/2005/050509/full/050509-2.html
What is HIV? Well, it is the virus that causes AIDS (no doubt about that). In AIDS, the cells in your body that kill the bad things (viruses, bacteria, worms) are themselves killed by the virus. So when you have AIDS you get really sick because your own internal army is destroyed and you're not strong enough to fight off other infections.
What are antibodies? Well, they are proteins (like the protein you eat) that are made inside your body, but they are shaped like a Y. The Y shape is useful because these antibodies can attach to other proteins - for example, they could latch on to a bacteria that's infected you (food poisoning), or some poison you accidentally touched (poison ivy), or in this case, a virus. When the antibodies attach to the virus, they can drag the virus away so that your body can kill it. The antibodies are like harpoons and hooks that your body can use to grab on to the viruses and destroy them.
So, it may come as no surprise that antibodies can prevent HIV from growing. But in fact it is, because for the longest time, people have had a hard time finding antibodies that work in people who have AIDS. In fact, most of the antibodies that AIDS patients have don't do anything to the virus! They just sit there floating around, maybe attaching a little, but then the virus changes and the hooks don't attach anymore.
In this study, what the scientists did was give people specific antibodies (particular Y shapes that attach to particular proteins) that would attach to HIV. They found that if you gave the patients the antibodies, the HIV didn't grow as fast as it did when you didn't give the antibodies or if you gave them random Y shapes that attach to something else.
The new study is exciting because it says that some antibodies that we could give to patients might help prevent the virus from growing inside a person. They aren't very strong, and they don't work as well as the other drugs that doctors usually give people with HIV in the US, so they will probably be part of a combined treatment, but it might be another bit of hope for people outside the US who can't get drugs very easily.
Also, the antibodies working might mean that other ways of helping a person make more antibodies might be useful in the fight against AIDS.
rani
As a biologist, I feel I need to educate people about biology and what the latest news is. We'll start with a simple discovery: that certain antibodies can protect against HIV infection. A full description is here: http://www.nature.com/news/2005/050509/full/050509-2.html
What is HIV? Well, it is the virus that causes AIDS (no doubt about that). In AIDS, the cells in your body that kill the bad things (viruses, bacteria, worms) are themselves killed by the virus. So when you have AIDS you get really sick because your own internal army is destroyed and you're not strong enough to fight off other infections.
What are antibodies? Well, they are proteins (like the protein you eat) that are made inside your body, but they are shaped like a Y. The Y shape is useful because these antibodies can attach to other proteins - for example, they could latch on to a bacteria that's infected you (food poisoning), or some poison you accidentally touched (poison ivy), or in this case, a virus. When the antibodies attach to the virus, they can drag the virus away so that your body can kill it. The antibodies are like harpoons and hooks that your body can use to grab on to the viruses and destroy them.
So, it may come as no surprise that antibodies can prevent HIV from growing. But in fact it is, because for the longest time, people have had a hard time finding antibodies that work in people who have AIDS. In fact, most of the antibodies that AIDS patients have don't do anything to the virus! They just sit there floating around, maybe attaching a little, but then the virus changes and the hooks don't attach anymore.
In this study, what the scientists did was give people specific antibodies (particular Y shapes that attach to particular proteins) that would attach to HIV. They found that if you gave the patients the antibodies, the HIV didn't grow as fast as it did when you didn't give the antibodies or if you gave them random Y shapes that attach to something else.
The new study is exciting because it says that some antibodies that we could give to patients might help prevent the virus from growing inside a person. They aren't very strong, and they don't work as well as the other drugs that doctors usually give people with HIV in the US, so they will probably be part of a combined treatment, but it might be another bit of hope for people outside the US who can't get drugs very easily.
Also, the antibodies working might mean that other ways of helping a person make more antibodies might be useful in the fight against AIDS.
rani
Have you tried the RSS feeds on My Yahoo! website?
Now you can customize your My Yahoo pages with RSS feeds for various websites. You can even have different pages for different categories. You can aggregate all the News websites you want in one page, All Tech-related feeds in a second page, Bargains and Deals in the third page and so on. RSS aggregation on My Yahoo! really makes life easy for many of us who do not have visit each website individually to see if there's a content of interest to us. Now you can know that simply by opening your My Yahoo! Page. I strongly suggest you give it a try.
Here's what you need to do to try this out. Go to http://my.yahoo.com and sign in with your Yahoo ID and password. Choose 'Add Content' link on the 'My Yahoo' page and you'll be directed to the page where you add content to your 'My Yahoo' page. Apart from a bunch of tools provided by Yahoo, you're also allowed to choose your own RSS feeds. Type in your search terms in the Text Box next to 'Find Content' to discover news sources. Try adding the following URL in the Text box and try it out: http://tekzon.blogspot.com/atom.xml
--Rajesh
Here's what you need to do to try this out. Go to http://my.yahoo.com and sign in with your Yahoo ID and password. Choose 'Add Content' link on the 'My Yahoo' page and you'll be directed to the page where you add content to your 'My Yahoo' page. Apart from a bunch of tools provided by Yahoo, you're also allowed to choose your own RSS feeds. Type in your search terms in the Text Box next to 'Find Content' to discover news sources. Try adding the following URL in the Text box and try it out: http://tekzon.blogspot.com/atom.xml
--Rajesh
Wednesday, August 04, 2004
Tek corner Blog site
Welcome to my Tekzon. Here you'll find articles and snippets on Tehnology related stuff.
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