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Aging, why do we get old?
Good morning honorable judges, teachers and fellow students. Our human lives are short and people tend to only live for a certain amount of time. Why do we live such short lives while animals such as tubeworms, clams or tortoises can outlive several generations of humans? Well scientists have started to study these organisms and their process of aging, and we are beginning to understand how they achieve such old age and how we might be able to do so as well. I am not talking about how you can eat better and exercise everyday to live longer, but how it works at a cellular level. Aging has to do with why our cells die, how they do it, why our genes make us age and what behavior influences our aging. The human body, as complexed and amazing as it is, is only made up of collections of cells. They exist together as a form of life and try to live long enough reproduce. The cells in our body continue to replicate and live until it gets too difficult for our cells to do that, then we die. This happens to everyone and all animals, everything dies eventually. The process of which this happens is called senescence. In short it is when an organism stops growing or reaches sexual maturity and starts to slowly fall apart. In humans this means, losing the ability to fight diseases, and basically for the body to slowly fail at maintaining its best functions. In organisms that age this way such as humans, no one really dies of old age everyone dies of something. If you want to blame something for your death you can blame your stupid cells. It turns out your cells have their own deaths programmed into them. As you probably know your cells are always dividing and making copies of itself. Most of your cells do this throughout your whole life. But the cells can only do this a certain amount of times. This is called the HAYFLICK LIMIT and Leonard Hayflick discovered it in the 1960’s. He observed that fetal human cells have a limit to how many times they could divide and when they got to that number they just stopped and died. This magic number is what controls the life of the cells and ultimately the lifespan of us. This magical number differs from animal to animal some animals have a low Hayflick number such as a mouse with an average of 22 and a tortoise has a limit of about 130. As the organism get older the Hayflick limit gets smaller until they die, this explains why some animals live longer than others. You may be asking why don’t you just find a way to extend the Hayflick limit? Well the answer lies it what causes the Hayflick limit. When cells divide they replicate their telomeres, non-coding genetic material that protects the DNA from being damaged or errors in copying. With each divide the telomeres on the ends of the cells get smaller and smaller until they disappear and the cell is unable to function. These telomeres were created when we were still inside our mother’s womb when we were just made up of several cells, but afterwards each replication shortens the telomeres more and more. I can hear what you’re asking right now if you haven’t fallen asleep yet. Why can’t scientist just give our cells more telomeres and they can divide forever? The answer is that we already have cells that can do that they are called cancer cells. A cancer cell can replicate indefinitely because it can recreate its own telomeres, but it tends to also create tumors and kill us. So unfortunately it seems that our cells have evolved telomeres to control our cell growth so that our cells don’t go crazy and replicate like cancer cells. Another player that controls our process aging is our genes. In the university of San Francisco in 1993 a scientist named Cynthia Kenyon discovered what is called the Daf-2 gene. At the time her team and herself were studying roundworms called Caenorhabditis elegans. These nifty little creatures live in soil and are transparent they also don’t have that many genes and only live for about 14 days. When she found the gene that controlled ageing she was surprised that only one gene was making the worms grow old. When this gene, Daf-2, was suppressed the worms started to have twice the life span up to 28 days, and they seems to have the same amount of energy and health until they died. They also came across another gene that had the exact opposite job of Daf-2, instead of ageing this gene kept the worms young and healthy, the gene is called Daf-16. Daf-2 and Daf-16 interact with each other when Daf-2 suppresses Daf-16 and that’s why the worms were aging and dying. A similar gene has been found in humans, it is called IGF-1, this gene regulates growth hormones and when suppressed in mice. There is less cell and organ damage caused by oxidation, the mice were fighting off more diseases, and the cancer was much less of a problem for the mice. This made the mice live up to 33% longer then before. Even though this works on mice it may not work on humans, and this growth hormone leads to one more cause of aging, Calories. We have long known that people who take in less calories live longer lives, but until now no one has made the connection that calorie intake simulates IGF-1. Since IGF-1 works to change energy to age your body when it is supplied with energy such as calories it simulates the aging process. Unfortunately we need calories to live so we can’t just stop eating and not simulate IGF-1 gene. When we take in fewer calories our metabolism is forced to direct the energy toward maintaining our current body state and not growing and getting bigger. Now I’m not telling you that you need to stop eating those 1000-calorie burritos and only drink water and eat vegetables, even though your organs will thank you for that. This has only proven to work on mice, so no one has yet to prove these things work on humans even though mice share 99% of our genes. We have come to the conclusion that so far we have manage to figure out what causes aging and how we can make mice and worms live longer, but unfortunately not humans. Hopefully scientist will continue to work on a way to make us live longer, but until then you just have to keep up with your daily heath needs or hope you don’t get hit by a bus for you to live longer. THANK YOU |
TIMOTHYOther Blogs (not mine) Archives
October 2013
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