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| Human stem cells: key to healing Dr Rajeev Goel The recent advances in biomedical research have provided new fundamental insights not only into various diseases and disorders but also into medical diagnostics and therapies.
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Human stem cells: key to healing
Types of stem cells The embryonic stem cells are the cells of the embryo in its very early stage of development. These embryos can either be developed in uterus or in test tube as in fertility clinics. The various tissues like heart, brain, muscle etc in the developing fetus are formed from the embryonic stem cells. The adult stem cells reside in various adult tissues/organs like bone marrow, muscle, brain, where they generate replacement for cells that are lost through normal wear and tear, injury or diseases. It has been observed in the lab that the adult stem cells may not only produce the type of tissue in which they reside but can sometime also form altogether a different tissue. That is to say that under certain experimental conditions, stem cells of blood can give rise to muscle tissue and neurons. Scientists are still not clear about the sources of adult stem cells in the body. Are they “left over” embryonic stem cells during the process of development or do they arise in some other way is still unknown? Besides the embryonic and adult stem cells, the stem cells can also be obtained from aborted fetus and umbilical cord (placenta) blood. The specific factors and conditions that allow stem cells to form a particular tissue are of great interest to scientists. The researchers do now know that turning the genes on and off is central to this process. The medical scientists have already developed methods for developing these cells into more than 110 types of human cells/tissues such as bones, blood, brain, heart etc which can be used for organ transplantation. The tissues and organs developed form stem cells may also be used to study the effects of new drugs and toxins thereby minimising the human clinical trials and animal studies. Knowing the mechanism how stem cells develop into tissues/organs has also provided insight to understand the process of abnormal growth and development (such as cancers and birth defects) which in turn will also lead to the discovery of new ways and drugs to prevent cancer and birth defects.
Properties The embryonic and adult stem cells have different characteristics and functions. Embryonic stem cells are easier to grow and can divide for longer periods of time in the lab to produce more stem cells. Unfortunately, embryonic stem cells are risky to transplant as they may develop into tumors when transplanted. The adult stem cells grow slower and are less robust compared to embryonic stem cells. The stem cells in adult tissue are often present in minute quantities and their number may decrease with age besides being difficult to isolate and purify. The biggest drawback so far regarding adult stem cells is their inability to get transformed into all the types of cells in the body as the embryonic stem cells could. The scientists, therefore, would like to use embryos to harvest the embryonic stem cells having wider characteristics. However, only adult stem cells are currently being tried for clinical trials. The embryonic stem cells are only used to have information about how stem cells grow and develop into a tissue or an organ.
Stem cells in
medicine Stem cell research holds the promise of hope for the million of people living with incurable diseases like diabetes, Alzheimer,
Parkinson's, leukemia, spinal cord injury, hepatitis, multiple sclerosis, stroke, osteo-arthritis, incomplete bladder control, heart diseases etc. It is really amazing to know that stem cells grafted in the spinal cord of a paralysed mice restored its movements. Stem cells transformed into insulin producing cells could treat the diabetes in mice. Stem cells of the bone marrow are precursors of all blood cells that could be clinically used for restoring the blood system after certain cancer treatments. This novel possibility of using cell-based therapies to treat diseases is often referred to as regenerative or reparative medicine. Researchers have also been able to coax the embryonic stem cells into heart muscle cells which when implanted into the heart of mice successfully repopulated the heart tissue. This as the potential to help people suffering from myocardial ischemia. Embryonic stem cells could also treat
Parkinson's like disease in rats. It is rather thought that the
Parkinson's may be the first disease to be amenable to treatment using stem cell transplantation. The physicians might also be able to use the blood stem cells to generate the immune cells, which are killed or destroyed by HIV invasion.
Human cloning Cloning and embryonic stem cell researches bear few points of similarity. Cloning is to create a twin human and the goal of the embryonic stem cell research is to create an embryo to get the embryonic stem cells. Embryonic stem cell research is sometimes called as “therapeutic cloning”. The embryo is destroyed after getting the embryonic stem cells whereas in cloning the embryo is allowed to develop further to produce a clone of an individual. The opponents of the embryonic stem cells research argue that creating and growing the embryo exclusively for extraction of stem cells and destroying it afterwards amounts to murdering a human being. They call the embryonic stem cells research methodology as “pro-abortive” research methodology.
Controversies The stem cell research is still in its infancy. Yet individuals, both professional and the general public, have given serious thoughts concerning embryonic stem cells as far as its research, medical, societal, ethical, moral and religious implications are concerned. Embryonic stem cell research is a controversial subject worldwide because of the differing views on when a human life begins. Harvesting of the stem cells from embryo is a very hot political matter all over the world. However, unlike research on embryonic stem cells, there are diminished or minor concerns expressed by most individuals over adult stem cells. The vast majority of dilemma rests on the side of “ embryonic stem cells”. There is nothing wrong in using the discarded embryos from the fertility clinic for the embryonic stem cell research, but the opponents, mainly the “pro-life” advocates, want a complete ban on research and funding of any kind involving human embryonic stem cells as well as a ban on the intentional creation of human life by means of human cloning. They argue that funding could be diverted to other research approaches such as development of pharmaceutical or recombinant protein based alternative therapies. The “pro-life” lobby is of the view that adult stem cells, which have no ethical problems, can do the job of embryonic stem cells. Keeping in view the controversies associated with the stem cell research, it is, therefore, imperative to educate the masses regarding the differences between the embryonic and the adult stem cell research with regard to the science. However, the studies both on adult stem cells as well as embryonic stem cells should go ahead in parallel because what is learnt about one cell type can help progress research into the other. There is still too much to learn from stem cells and there are many hurdles to overcome before we know how useful stem cells therapies will be. To sum up, the stem cells are no doubt one of the most fascinating areas of modern biology today and we must not lose sight of the tremendous life saving possibilities of stem cell research. |
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UNDERSTANDING THE UNIVERSE How do the scientists differentiate between galaxies? Is there any natural differentiation? You know that there are billions of galaxies and each of them has billions of stars. Galaxies are far away extending to distances from which light might take hundreds of million years to come to us. When we look at these objects we are seeing the universe a long time ago. We can estimate their distances by finding out the extent to which the light emitted by their atoms is shifted towards longer wavelengths due to Doppler effect. Actually this measurement gives us only the velocity at which they are receding from us and we use our knowledge about the rate of expansion of the universe to convert this rate into a distance. Morphologically, we find several shapes, the dominant one being that of a spiral. Galaxies are also found in clusters. They all rotate, as does our own galaxy. One has measured the rate of rotation as also the change in the period of rotation as a function of the distance from the centre of the galaxy. Using observations at different wavelengths, including x-rays one, has obtained evidence for existence of black holes at the centers of various galaxies. The cores of these galaxies emit enormous amounts of energy, sometimes out-shining whole of the galaxy. I might be confusing you by giving all these bits of information. The purpose is to communicate that their coordinates, shape, energy emission and many other features can identify galaxies. There are galaxies that have beams of high-energy electrons shooting out from their poles that produce large fans of radio clouds towards North and South poles of the galaxy. It is clear that magnetic fields are important components of the galaxies and shapes of these clouds give them their specific character
Why are planets spherical in shape? As matter accretes its gravitational attraction increases. Continuous accretion leads to an inward gravitational force that can overwhelm the forces that give solid-state structures their integrity. Under a gravitational force that is large enough, even rocks melt and flow. Each particle on the surface of the aggregate wants to get as close to the centre as possible and the shape of the aggregate tends to become spherical — that is what natural equity or democracy would demand. Extremely high mountains — protrusions beyond the spherical surface — are not viable because their weight would make them sink down. When we get to aggregations of planetary levels the height of the highest mountain is inversely proportional to the mass of the planet. Mars has higher mountains and deeper valleys than does the earth because it is less massive than the earth. Even our tiny satellite, the
Moon, outcompetes the Earth whose highest mountain peak sticks out to a height of barely 9 km on a sphere whose diameter is nearly 13,000 km. The spherical shape of heavenly bodies testifies that gravitational force of matter in bulk can overcome all other sustaining forces.
The orbits of electrons in an atom are titled K,L,M,N....why not a,b,c,d......? There is no scientific reason. Historically these were the names given by the pioneers who derived the atomic structure by studying optical and X-ray spectra. No point now to change the names. |
