systemic pathology chapter 1

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CHAPTER 1 : INTRODUCTION TO SYSTEMIC PATHOLOGY

WHAT IS AGING?

The study of aging - gerontology- is a relatively new sciencethat has made incredible progress over the last 30 years. In the past,scientists looked for a single theory that explained aging. There are

two main groups of aging theories. The first groupstates that aging is natural and programmed into the body, while thesecond group of aging theories says that aging is a result of damagewhich is accumulated over time. In the end, aging is a complexinteraction of genetics, chemistry, physiology and behavior.

OTHERS DEFINITION ABOUT AGING

Complex biological process in which changes at

molecular, cellular, and organ levels resultin a progressive, inevitable, and inescapable decrease inthe bodys ability to respond appropriately to internaland/or external stressors.

Aging is an enigma of the role of senescence innature.

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AGING AND TELOMERE?????

A chromosome is a long strand of DNA. At the end of achromosome is a telomere, which acts like a bookend.Telomeres keep chomosomes protected and prevent them fromfusing into rings or binding with other DNA. Telomeres play animportant role in cell division.

What Happens When a Cell Divides?

Each time a cell divides, the DNA unwraps and the information in theDNA is copied. The process does not copy all of the DNA information- the telomeres are not copied. When the cell is finished dividing, theDNA comes back together. The telomeres lose a little bit of lengtheach time this happens.

TELOMERE, CELL DEATH AND CANCER..

Cancer

Cancer is a condition in which certain cells in your body stop dying.Every system in your body is carefully balanced to allow for cellsreplicating and dying. If cells stop dying and keep replicating, thebalance is disrupted and there are too many of one kind of cell.Groups of these cells form tumors. Researchers believe that cancercells are creating an enzyme called telomerase, which preventstelomere shortening.

Where Does Telomerase Come From?

Every cell in your body has the genetic code to make telomerase, butonly certain cells need to produce this enzyme. White blood cells andsperm cells, for example, need to have telomere shortening switchedoff in order to make copies of themselves through your lifetime. In

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advanced cancer, the cancer cells also seem to be producingtelomerase, which allows them to continue to replicate without dying.

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PROGRAMMED AGING THEORY:

Assert that the human body is designed to age and there is a certainbiological timeline that our bodies follow.

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These theories assert that aging is an essential and innate part of the

biology of people, and that aging is programmed into our bodysystems. The three main systems that are connected with aging are

the endocrine (hormonal) system, the immunesystem and ourgenes. These systems change over time.These changes cause the symptoms and signs of aging.

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What happen to our endocrine system as we age?

The hormone or endocrine theory of aging asserts that the mostimportant factors in aging are the changes brought about in the body

by the endocrine system. The complex endocrine system of our bodycontrols the hormones that regulate many bodyprocesses. As we age, these systems become less efficient,leading to changes in our bodies such as menopause. The hormonetheory of aging believes that these changes eventually cause theeffects of aging.

How our immune systems contribute in aging?

The immune system theory of aging is that the rate of aging is largelycontrolled by the immune system. As we age, the numbers of criticalcells in the immune system decrease and become less functional.Starting before age 20, the thymus (which produced certain immunecells) begins to shrink.

GENE

The genetic theory of aging believes that lifespan is largelydetermined by the genes we inherit. According to the theory, ourpotential age is primarily determined at the moment of conception.

The Evidence behind the Theory:

There is some evidence to support this theory. People with parents

who have lived long lives are more likely to live long themselves(though this could be partially explained by learned behaviors, suchas food preferences). Also, identical twins (who have the exact samegenes) have closer lifespans than siblings.

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How Genes Impact Lifespan:

Some genes are beneficial and enhance longevity -- a gene that

helps a person metabolize cholesterol would reduce a person's risk ofheart disease, for example. But some genes are harmful, like thosethat increase the risk cancer. Some gene mutations are inherited, too,and may shorten lifespan. (Mutations also can happen after birth,since exposure to toxins, free radicals and radiation can cause genechanges.)

GENE THEORYAND GENE MUTATION THEORY

What is the function of DNA and RNA?

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Gene theory and gene mutation theory both offer explanations foraging at the level of DNA. Gene theory suggests that genes aresomehow altered over time, such that they naturally cause aging.Gene mutation theory is based on the observation that mutationsaccumulate over time, and it is mutations that cause aging anddisease.

This view is supported by the fact that samples of cells fromolder people do generally have more genetic mutations thancells taken from younger people.

In addition, some diseases associated with age result from geneticmutations. Canceris often the result of multiple mutations and somemutations reveal underlying genetic weaknesses, which causedisease in some people. Gene mutation theory also notes that formutations to accumulate, normal DNA-repair mechanisms must haveweakened. All cells have inherent repair mechanisms that routinely fixDNA errors. For these errors to accumulate, the repair system musthave gone awry, and DNA-repair failure is thought to be a factor incancer.

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Cross-link theory:

When you heat onions or toast bread, the sugar molecules bond toprotein molecules. This bonding, which in cooking is called

carmalization, is a result of the sugar molecules attaching to proteinmolecules. When this happens, a series of reactions occur (called

glycation) that result in protein molecules bonding to each other.

The process is slow and complicated, but over time more and moreprotein molecules are cross-linked. These cross-linked moleculesdon't function properly. When enough cross-linked moleculesaccumulate in a specific tissue (such as cartilage, lungs, arteries andtendons), there can be a change in function.

What Changes With Cross-Linking?

Basically, things become stiffer. When tissues stiffen, they do notfunction as efficiently. Many of the symptoms of aging have to do withthe stiffening of tissues. Cataracts, for example, are a stiffening ofyour eyes' lenses.

Researchers believe that if the concentration of sugar in the blood ishigh, then more cross-linking occurs. Everyone could benefit fromkeeping their blood sugar from spiking. Foods with a high glycemicindex, such as sugary sodas and juices, release sugar into the body

quickly. These foods have been associated with cardiovascular

disease.

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FREE RADICAL THEORY:

Free radicals are a byproduct of normal cell function. When cells

create energy, they also produce unstable oxygenmolecules. These molecules, called free radicals, have a freeelectron. This electron makes the molecule highly unstable. The freeradical bonds to other molecules in the body - causing proteins andother essential molecules to not function as they should. Luckily,antioxidants can minimize free radical damage.

Antioxidants - the Free Radical Sponge

This theory asserts that many of the changes that occur as ourbodies age are caused by free radicals. Damage to DNA, proteincross-linking and other changes have been attributed to free radicals.Over time, this damage accumulates and causes us to experienceaging.

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The Evidence:

There is some evidence. Studies have shown that increasing theamount of antioxidants in the diets of mice and other animals can

slow the effects of aging. This theory does not fully explain all thechanges that occur during aging. It is likely that free radicals are onlyone part in the aging equation.

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ACCUMULATE OF ERROR THEORY:

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WEAR AND TEAR THEORY:

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The wear and tear theory of aging believes that the effects of agingare caused by damage done to cells and body systems over time .Essentially, these systems "wear out" due to use. Once they wearout, they can no longer function correctly.

Causes of Damage:

A range of things can damage body systems. Exposure to radiation,toxins and ultraviolet light can damage our genes. The effects ofour body's own functioning can also cause damage. When the bodymetabolizes oxygen, free radicals are produced that can causedamage to cells and tissues.

The Evidence:

Not much. While the theory makes some sense if you think of thebody as a machine, it doesn't really work when you realize thecapacity of the body to repair damage. Of course, not all damage canbe repaired fully, and mistakes in repairs may accumulate over time.

A more likely explanation is that the decrease of functioning that isseen as "tear" in the "wear and tear" theory is really the result, not thecause, of aging.

AUTOIMMUME THEORY:

The immune system is the most important line of defense against foreignsubstances that enter the body. With age the system's ability to producenecessary antibodies that fight disease declines, as does its ability to distinguishbetween antibodies and proteins. In a sense the immune system becomes self-destructive and reacts against itself. Examples of autoimmune disease are lupus,scleroderma and adult-onset diabetes.

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systemic pathology chapter 1

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