Science Frontiers

The free radical theory of aging

2005-07-13T04:20:00.000-07:00

Free radicals are atoms with unpaired electrons. According to the free radical theory, radicals damage cells in an organism, causing aging. Mitochondria, regions of the cell that manufacture chemical energy, produce free radicals and are the primary sites for free radical damage. By eliminating free radicals from cells through genetic means and dietary restriction, laboratories have extended the maximum age of laboratory animals. The administration of antioxidants, which eliminate radicals, to laboratory animals fails to increase maximum lifespan.

The nucleus of an atom is surrounded by a cloud of electrons. These electrons surround the nucleus in pairs, but, occasionally, an atom loses an electron, leaving the atom with an unpaired electron. The atom is then called a "free radical," or sometimes just a "radical," and is very reactive. When cells in the body encounter a radical, the reactive radical may cause destruction in the cell. According to the free radical theory of aging, cells continuously produce free radicals, and constant radical damage eventually kills the cell. When radicals kill or damage enough cells in an organism, the organism ages.¹

The production of radical oxygen, the most common radical in biological systems, occurs mostly within the mitochondria of a cell. Mitochondria are small membrane-enclosed regions of a cell that produce the chemicals a cell uses for energy. Mitochondria accomplish this task through a mechanism called the "electron transport chain." In this mechanism, electrons are passed between different molecules, with each pass producing useful chemical energy. Oxygen occupies the final position in the electron transport chain. Occasionally, the passed electron incorrectly interacts with oxygen, producing oxygen in radical form.²

The primary site of radical oxygen damage is mitochondrial DNA (mtDNA). Every cell contains an enormous set of molecules called DNA which provide chemical instructions for a cell to function. This DNA is found in the nucleus of the cell, which serves as the "command center" of the cell, as well as in the mitochondria. The cell fixes much of the damage done to nuclear DNA. However, mitochondrial DNA (mtDNA) cannot be readily fixed. Therefore, extensive mtDNA damage accumulates over time and shuts down mitochondria, causing cells to die and the organism to age.⁴

Protection of mtDNA from radicals slows aging in laboratory animals. Some laboratories have produced fruit flies that live one-third longer than normal fruit flies. These labs genetically altered the fruit flies to produce more natural antioxidants. Antioxidants are molecules that eliminate radicals, so elevated levels of antioxidants prevent much of the mtDNA damage done by radicals.³ Other labs severely restricted the food intake of laboratory rats, causing a 50% increase in maximum lifespan compared to rats allowed to eat freely.² The mitochondria of starved rats are not provided with enough material to function at full capacity. Therefore, the electron transport chains in mitochondria of the starved rats pass fewer electrons. With fewer electrons passed, fewer oxygen radicals are produced, so aging slows.

One main problem with the free radical theory is the failure of antioxidants administered as dietary supplements, like vitamins E and C, to significantly increase maximum lifespan. Proponents of the radical theory believe that dietary antioxidants, unlike natural antioxidants produced by cells, do not reach mitochondrial DNA, leaving this site susceptible to radical attack. Interestingly, even though supplemental antioxidants fail to increase maximum lifespan, they do increase the chances of living to the maximum lifespan. This may be due to antioxidant protection of other parts of the cell, like cellular proteins and membranes, from radical damage.²

The goal of all research on the free radical theory is to slow aging and increase maximum lifespan. The achievements so far are astounding; increasing the lifespan of fruit flies and rats is an impressive feat. Despite such success, no practical applications of the theory have been perfected. Genetic alteration is both controversial and difficult for humans. Starvation, while lengthening lifespan, is an unappealing alternative. Dietary antioxidants fail to increase maximum lifespan. However, the production of radicals and their role in aging is well understood. Further research may apply this knowledge in the development of a practical method to prevent or repair mtDNA radical damage.

Origins of Life

2005-06-03T21:39:00.000-07:00

Earth began to form over 4.5 billion years ago from the same cloud of gas (mostly hydrogen and helium) and interstellar dust that formed our sun, the rest of the solar system and even our galaxy. In fact, Earth is still forming and cooling from the galactic implosion that created the other stars and planetary systems in our galaxy, a process which began about 16 billion years ago as the Milky Way began to form.

As our solar system began to come together some 6-7 billion years ago, the sun formed within a cloud of dust and gas that continued to shrink upon itself by its own gravitational forces. This caused it to undergo thefusion process and give off light, heat and other radiation. During this process, the remaining clouds of gas and dust that surrounded the sun began to form into smaller lumps called planetisimals,which eventually formed into the planets we know today.

The Earth went through a period of catastrophic and intense formation during its earliest beginnings about 4.5 - 4.6 billion years ago. By 3.8 to 4.1 billion years ago, Earth had become a planet with an atmosphere (not like our atmosphere today!) and an ocean. This period of time of Earth's formation is referred to as the pre-Cambrian Period. The pre-Cambrian is divided into three parts: the Hadean, Archean and Proterozoic Periods.

Pre-Cambrian Period

The Earth formed under so much heat and pressure that it formed as a molten planet. For nearly the first billion years of its formation -- called the Hadean Period (or "hellish" period) -- Earth was bombarded continuously by the remnants of the dust and debris -- like asteroids, meteors and comets -- until it formed into a solid sphere, fell into an orbit around the sun, and began to cool down.

As Earth began to take solid form, it had no free oxygen in its atmosphere. It was so hot that the water droplets in its atmosphere could not settle to form surface water or ice. Its atmosphere was also so poisonous that nothing would have been able to survive.

Earth's atmosphere was formed mostly from the outgassing of such volatile compounds as water vapor, carbon monoxide, methane, ammonia, nitrogen, carbon dioxide, nitrogen, hydrochloric acid and sulfur produced by the constant volcanic eruptions that besieged the Earth. It had no free oxygen.

About 4.1 billion years ago, the Earth's surface -- or crust -- began to cool and stabilize, creating the solid surface with its rocky terrain. Clouds formed as the Earth began to cool, producing enormous volumes of rain water that formed the oceans. For the next 1.3 billion years (3.8 to 2.5 billion years ago), called the Archean Period, first life began to appear (at least as far as our fossil records tell us... there may have been life before this!) and the world's land masses began to form. Earth's initial life forms were bacteria which could survive in the highly toxic atmosphere that existed during this time. In fact, all life was bacteria during the Archean Period.

Toward the end of the of the Archean Period and at the beginning of the Proterozoic Period, about 2.5 billion years ago, oxygen-forming photosynthesis began to occur. The first fossils, in fact, were a type of blue-green algae that could photosynthesize.

Some of the most exciting events in Earth's history and life occurred during this time which spanned about two billion years until about 550 million years ago. The continents began to form and stabilize, creating the supercontinent Rodinia about 1.1 billion years ago. (Rodinia is widely accepted as the first supercontinent, but there were probably others before it.) Although Rodinia is composed of some of the same land fragments as the more popular supercontinent, Pangea, they are two different supercontinents. Pangea formed some 225 million years ago and would evolve into the seven continents we know today.

Free oxygen began to build up around the middle of the Proterozoic Period -- around 1.8 billion years ago -- and made way for the emergence of life as we know it today. This event, of course, created conditions that would not allow most of the existing life to survive and thus made way for the more oxygen dependent life forms.

By the end of the Proterozoic Period, Earth was well along in its evolutionary processes leading to our current period, the Holocene Period, also known as the Age of Man. Thus, about 550 million years ago, the Cambrian Period began. During this period, life "exploded," developing almost all of the major groups of plants and animals in a relatively short time. It ended with the massive extinction of most of the existing species about 500 million years ago, making room for the future appearance and evolution of new plant and animal species.

Indian Wealth

2005-05-14T11:04:00.000-07:00

India, the land of diversities, has been a home to ancient sages and millions of marvellous products of evolution of life. The green blankets of grass protect the rodents underneath. The gigantic trees support many generations of primates and birds. The ponds and lakes contain an entirely different world of aquatic animals. All was well in this huge home until a new species evolved a million years ago. This being was neither as strong as a lion nor as swift as squirrel. But this being was destined to dominate the world with its intelligence, which would make it the most powerful species. This unique product of evolution was Man.

In ancient India, Man was stimulated by the peculiarity of Nature and was provoked to find the secrets hidden in the caves of Science. Thus, sages and high thinkers flourished here in abundance. Man understood the priceless value of Nature. He learnt to live as part of it. Forests were the most priced possessions of ancient Indians. But this did not last for long.

The population of humans increased dramatically. The need for food and space drove humans to the forest and as a consequence deforestation began to increase.

This is continuing even now. In addition to that, we, in India are polluting Nature4 in every possible way. The flexibility of plastic and its easy availability has further increased soil pollution. The vehicles on the roads are polluting the atmosphere as never before. There are frequent oil spills, which take away the lives of millions of beings. We are inviting our own doom!

India is a developing nation. India is not wealthy in terms of materialistic money, but India is one of the richest nations in terms of natural wealth of wildlife and jungles. The Indians are poor in terms of money and therefore they cannot afford to pay for eco-friendly products. Hence they opt for cheaper synthetic products, which are eco-unfriendly.

I, as a true Indian, have assigned myself the duty of protecting India’s wealth for the benefit and existence of humanity as a whole, and to make India and Indians feel good.

It is my aim to become a scientist in the field of environment sciences and find out new alternatives to eco-unfriendly products. I will devote all my time to promote e4co-friendly activities. This is my plan for the future. At present I am still doing my best to be environment friendly.

It is in the hands of us Indians to save India’s forests, which form the identity of India and are India’s symbol. Every Indian must do his or her best to keep up the identity of our motherland. The future of India is solely in the hands of us Indians. If we protect our natural resources, India Will regain its past glory and rise above all nations. But if we continue to harm natural resources of India, there will be no India at all!

If we want India and the future generations to feel good, then we must protect our environment.

- Sushant Swamy