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HIV - Human Immunodeficiency Virus

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What is HIV?

HIV stands for Human Immunodeficiency Virus.  A virus can only survive by living in the cells of another organism. HIV is a type of virus called a retrovirus: It incorporates itself into the genetic material of cells called 'CD4 white blood cells', which are part of  the immune system.  This process is called 'reverse transcription', and it enables HIV to replicate.  This leads to destruction of the CD4 cells and damages the immune system.

What is AIDS?

AIDS stands for Acquired Immune Deficiency Syndrome.  A syndrome is a set of signs and symptoms that occur together, as a result of a specific cause.  The syndrome of AIDS is caused by HIV.  However a person infected with HIV may not necessarily progress to having AIDS.

HIV/AIDS Virus
HIV causes AIDS by damaging the immune system and making the body vulnerable to 'opportunistic infections'.  These are called ‘opportunistic’ because the weakened immune system gives them the ‘opportunity’ to take hold. These infections can cause death in people were severely weakened immune system.

AIDS was first diagnosed in 1981. Since then HIV and AIDS have spread rapidly and cases have been reported in more than 150 countries.  At the beginning of 2004 it was estimated that nearly 42,000,000 people were living with HIV and AIDS.

In Australia at the beginning of 2004, more than 20,000 people have been diagnosed with HIV infection. Over 8000 of these have been diagnosed with AIDS, and nearly 6000 people have died from AIDS related illnesses.

Different Stages if HIV/ AIDS

HIV infects cells in the immune system and the central nervous system. The main cell HIV infects is called a T helper lymphocyte. The T helper cell is a crucial cell in the immune system. It co-ordinates all other immune cells so any damage or loss of the T helper cell seriously affects the immune system.

HIV/AIDS Virus
HIV infects the T Helper cell because it has the protein CD4 on its surface. HIV needs to use CD4 to enter cells it infects. This is why the T helper cell is referred to as a CD4 lymphocyte. Once inside a T helper cell, HIV takes over the cell and the virus then replicates. In this process (which takes around a couple of days) the infected cell dies. New virus then seeks out new T helper cells to infect.

However, battling against this the immune system is rapidly killing HIV and HIV-infected cells, and replacing the T helper cells that have been lost.
HIV progression can generally be broken down into four distinct stages:

  • Primary infection
  • Clinically asymptomatic stage
  • Symptomatic HIV infection
  • Progression from HIV to AIDS.

Breast Cancer

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Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas.
Breast CancerPrognosis and survival rate varies greatly depending on cancer type and staging. Computerized models are available to predict survival.  With best treatment and dependent on staging, 10-year disease-free survival varies from 98% to 10%. Treatment includes surgery, drugs (hormonal therapy and chemotherapy), and radiation.

Worldwide, breast cancer comprises 10.4% of all cancer incidence among women, making it the most common type of non-skin cancer in women and the fifth most common cause of cancer death.  In 2004, breast cancer caused 519,000 deaths worldwide (7% of cancer deaths; almost 1% of all deaths).  Breast cancer is about 100 times more common in women than in men, although males tend to have poorer outcomes due to delays in diagnosis.

Some breast cancers are sensitive to hormones such as estrogen and/or progesterone which makes it possible to treat them by blocking the effects of this hormones in the target tissues. These have better prognosis and require less aggressive treatment than hormone negative cancers.

Breast cancers without hormone receptors, or which have spread to the lymph nodes in the armpits, or which express certain genetic characteristics, are higher-risk, and are treated more aggressively. One standard regimen, popular in the U.S., is cyclophosphamide plus doxorubicin (Adriamycin), known as CA; these drugs damage DNA in the cancer, but also in fast-growing normal cells where they cause serious side effects.

Sometimes a taxane drug, such as docetaxel, is added, and the regime is then known as CAT; taxane attacks the microtubules in cancer cells. An equivalent treatment, popular in Europe, is cyclophosphamide,  methotrexate, and fluorouracil (CMF).  Monoclonal antibodies, such as trastuzumab  (Herceptin), are used for cancer cells that have the HER2 mutation.

Radiation is usually added to the surgical bed to control cancer cells that were missed by the surgery, which usually extends survival, although radiation exposure to the heart may cause damage and heart failure in the following years.

Causes of Breast Cancer

  • You're over 50 There's nothing strange about this – cancers are caused by cell mutation, and the older you are, the more chance there is of a cell mutation occurring.
  • Someone in your family has had breast cancer This slightly increases your risk. In most cases there's no family association. But scientists have identified certain genes that are responsible for some cases of breast cancer, and these can be transmitted to offspring. In these cases the cancer tends to occur at a younger age.

 

Breast Cancer

  • The big ONo, not the late Roy Orbison, we're talking about the hormone oestrogen. High levels of oestrogen for long periods of time increase the likelihood of breast cancer. So do early puberty, late menopause, having your first child at a later age (over 35), not breast feeding, and never having children at all. The oral contraceptive pill is thought to increase the risk slightly, as does hormone replacement therapy (HRT) if taken for more than five years.

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