Cellular Aging: Telomeres | Cellular Aging: Telomeres Information | HighBeam Research - FREE Trial

 

CELLULAR AGING: TELOMERES

Aging is a complex process that occurs on multiple levels. The end result of aging is that life span is limited in multicellular organisms. The cells that make up multicellular organisms also have limited life spans. The limitation on cellular life span is comprised of two parts: (1) cells become unable to continue dividing but remain metabolically active, and (2) at some future time cell death occurs. Many cells in the human body are continually undergoing cellular division. Cellular division is a normal condition of certain tissues; examples include hair growth, the sloughing off of skin every several days, and the complete turnover and replacement of the cells of the immune systems every few months. In some instances, cellular division occurs in order to heal damaged tissues. Thus, having a limited number of cellular divisions available could contribute to aging by slowing down processes such as wound healing, as well as affecting general tissue maintenance.

In the 1960s, Leonard Hayflick first noted that human cells undergo a limited number of divisions when placed in culture. Furthermore, he noted that the number of divisions cells undergo is related to the number of prior divisions undergone by the cells. This observation suggested the existence of an intracellular clock that marked the division history of each cell. In addition, it suggested that once a predetermined number of divisions has occurred, a signal (or signals) is generated that prevents the cell from undergoing further divisions. The timing mechanisms underlying and regulating this process remained elusive until the end of the twentieth century. The first of these clocks to be identified and characterized, the telomere, is active in several human cell types.

Telomeres are chromosome caps

Telomeres are specialized structures present at the end of liner chromosomes; they serve the essential function of protecting and stabilizing chromosome ends. The telomere was first defined in the 1930s following observations that naturally occurring chromosome ends behave differently than chromosome breaks induced by damaging agents such as ionizing radiation. Both structures are ends of double-stranded DNA molecules. However, chromosome ends are stable, allowing accurate transmission of chromosomes from generation to generation without loss of genetic material, whereas induced breaks are very unstable, reacting with other chromosomes in the cell to create rearrangements and chromosome fusions. In addition, broken ends of DNA trigger cellular protective responses. These responses act either to allow the DNA damage to be repaired, or to remove the cell from the population by cellular suicide, called apoptosis. Even though telomeres are the physical end of a DNA molecule, they do not trigger these protective responses. These observations indicated that there is something special about naturally occurring chromosome ends.

Telomere structure

Telomeres are made up of short tandem repeats of a simple DNA sequence and associated proteins. In humans, and all other vertebrates, the telomeric DNA sequence is 5'(TTAGGG)3', oriented towards the end of one DNA strand, with the complimentary sequence 5'(CCCTAA)3' oriented towards the interior of the chromosome. The duplexed telomeric repeats are arranged in tandem and are present in more than a thousand copies at the end of each human chromosome. At the very end of the chromosome there is a single-stranded protrusion of the G-rich strand that extends for twenty or more repeats.

Cellular Aging: Telomeres | Cellular Aging: Telomeres Information | HighBeam Research - FREE Trial

Study provides direct evidence of the role of telomeres in disease development. - Cancer Weekly | HighBeam Research - FREE trial

 

Study provides direct evidence of the role of telomeres in disease development. - Cancer Weekly | HighBeam Research - FREE trial

Telomere shortening may be early marker of cancer activity. - Biotech Week | HighBeam Research - FREE trial

 

Telomere shortening may be early marker of cancer activity. - Biotech Week | HighBeam Research - FREE trial

ARE TELOMERES THE KEY TO AGING AND CANCER?

Inside the center or nucleus of a cell, our genes are located on twisted, double-stranded molecules of DNA called chromosomes. At the ends of the chromosomes are stretches of DNA called telomeres, which protect our genetic data, make it possible for cells to divide and hold some secrets to how we age and get cancer.

Telomeres have been compared with the plastic tips on shoelaces because they prevent chromosome ends from fraying and sticking to each other, which would scramble an organism's genetic information to cause cancer, other diseases or death. Yet, each time a cell divides, the telomeres get shorter. When they get too short, the cell no longer can divide and becomes inactive or "senescent" or dies. This process is associated with aging, cancer and a higher risk of death. So telomeres also have been compared with a bomb fuse.

What are telomeres?

Like the rest of a chromosome and its genes, telomeres are sequences of DNA - chains of chemical code. Like other DNA, they are made of four nucleic acid bases: G for guanine, A for adenine, T for thymine and C for cytosine. Telomeres are made of repeating sequences of TTAGGG on one strand of DNA bound to AATCCC on the other strand. Thus, one section of telomere is a "repeat" made of six "base pairs."

In human blood cells, the length of telomeres ranges from 8,000 base pairs at birth to 3,000 base pairs as people age and as low as 1,500 in elderly people. (An entire chromosome has about 150 million base pairs.) Each time a cell divides, an average person loses 30 to 200 base pairs from the ends of that cell's telomeres.

Cells normally can divide only about 50 to 70 times, with telomeres getting progressively shorter until the cells become senescent, die or sustain genetic damage that can cause cancer. Telomeres do not shorten with age in tissues such as heart muscle in which cells do not continually divide.

Why do chromosomes have telomeres?

Without telomeres, the main part of the chromosome - the part containing genes essential for life - would get shorter each time a cell divides. So telomeres allow cells to divide without losing genes. Cell division is needed so we can grow new skin, blood, bone and other cells when needed.

Without telomeres, chromosome ends could fuse together and degrade the cell's genetic blueprint, making the cell malfunction, become cancerous or die. Because broken DNA is dangerous, a cell has the ability to sense and repair chromosome damage. Without telomeres, the ends of chromosomes would look like broken DNA, and the cell would try to fix something that wasn't broken. That also would make them stop dividing and eventually die.

Why do telomeres get shorter each time a cell divides?

Before a cell can divide, the chromosomes within it are duplicated so that each of the two new cells contains identical genetic material. A chromosome's two strands of DNA must unwind and separate. An enzyme (DNA polymerase) then starts to make two new strands of DNA to match each of the two unwound strands. It does this with the help of short pieces of RNA. When each new matching strand is completed, it is a bit shorter than the original strand because of the room needed at the end by this small piece of RNA. It is like someone who paints himself into a corner and cannot paint the corner.

Does anything counteract telomere shortening?

An enzyme named telomerase adds bases to the ends of telomeres. In young cells, telomerase keeps telomeres from wearing down too much. But as cells divide repeatedly, there is not enough telomerase, so the telomeres grow shorter and the cells age.

Telomerase remains active in sperm and eggs, which are passed from one generation to the next. If reproductive cells did not have telomerase to maintain the length of their telomeres, any organism with such cells soon would go extinct.

What role do telomeres play in cancer?

As a cell begins to become cancerous, it divides more often, and its telomeres become very short. If its telomeres get too short, the cell may die. It can escape this fate by becoming a cancer cell and activating an enzyme called telomerase, which prevents the telomeres from getting even shorter.

Studies have found shortened telomeres in many cancers, including pancreatic, bone, prostate, bladder, lung, kidney, and head and neck.

Measuring telomerase may be a new way to detect cancer. If scientists can learn how to stop telomerase, they might be able to fight cancer by making cancer cells age and die. In one experiment, researchers blocked telomerase activity in human breast and prostate cancer cells growing in the laboratory, prompting the tumor cells to die. But there are risks. Blocking telomerase could impair fertility, wound healing, and production of blood cells and immune system cells.

What about telomeres and aging?

Geneticist Richard Cawthon and colleagues at the University of Utah found shorter telomeres are associated with shorter lives. Among people older than 60, those with shorter telomeres were three times more likely to die from heart disease and eight times more likely to die from infectious disease.

Rest of artickle here: http://learn.genetics.utah.edu/content/begin/traits/telomeres/

What YOUR Brain can do

Your Brain's Potential

In the brain there are 1,000,000,000,000 (a million million) individual neurons or nerve cells.

If each neuron can interact with anywhere between 1 and 100,000 other neurons then the brain's potential for pattern forming (the number of possible permutations) is a massive number that even in normal text would require 10.5 million kilometres of space to write one after the other!

That means that your brain has an almost infinite capacity for storing information.

What are you going to learn today to start realising your potential?

Prominence eruption from sun is seen

A prominence eruption from the sun is seen in this image taken by the Solar Dynamics Observatory (SDO) on March 30, 2010. NASA released the first publicimages from the SDO on April 21, 2010.

Source: http://news.yahoo.com/nphotos/NASA-releases-images-sun/ss/events/sc/042210nasasun#photoViewer=/100422/ids_photos_wl/r938069384.jpg

Best Camera Prices in South Africa

Highly Recommended: Looking for the best value and service for cameras in South Africa?

One sees cameras advertised all over. If you are a beginner photographer looking for start-up or a Pro looking for an upgrade, there is really only one place we can recommend with all good faith. In stead of providing a link to the main website (which will require you to register and go through a lengty process) we will give you the shortcut. Send a mail to the link below and provide your requirements and they will mail you back with exact details on how to get hold of what you really need.

In the first place, we have bought many cameras from the company without ever having a single hitch in order nor delivery. Their cameras are sources internationally as well as having an international warrenty. We had one camera that had a simple problem and the money was refunded even before the camera was returned to them (then I may add we have a long relationship with the dealer so there were mutual trust) and neither have they ever received any complaints on their service from buyers to the best of our knowledge.

One of the big electronic stores in SA which are advertising low prices has a few catches which you are not told about: 1) Their products are Grey Market and  2) there is no exchange policy (which is why it is Gray Market). Meaning, if you bought the camera today, get home, find a problem and take it back the following day, they do not replace or refund you, they send it in for repairs and you can wait up to six weeks to get the repair back, if it has been fully repaired.

So with years of experience in the photographic field we recommend this one single dealer in SA and if you now or ever require a camera of any model or photographic equipment, we recommend sending an email and you will in all likelyhood get what you want at the best price you can pay anywhere. All equipment are sent via overnight courier so you have to wait just one day.

We do not publish the name of the dealer since they advertise in other media and it could constitute a conflict of their agreement with their normal sales channels to be listed somewhere else and we would not want that. At 2012survivornet.com we aim to help people in all communities and countries and thus this is a service we offer our subscribers and readers.

eMail address: sales@eezeehost.com

Note: We have no affiliation of any nature with the seller neither do we receive any compensation for this recommendation. In fact we have not contacted the seller beforehand advising that we will publish this post.

If you are a dealer of any type of commodities that benefit the community and help the person on the street, you are welcome to mail us for consideration of including your service or product in future posts.