 |
|
| SCIENCE & TECHNOLOGY |
|
|
|
Playing god with science
Are mercury tooth
fillings safe? Emotions and rational thinking
Invisibility cloak
THIS UNIVERSE
Prof Yash
Pal
PROF YASH PAL |
|
|
Playing god with science * Mice used as sperm factories for pigs and goats The successful creation of different inter-species (chimeras) animals with tremendous potential for medical and research applications has thrown us in a dilemma. ..….. Are we allowing the life on earth to evolve to such an extent that one day all the animals on earth would be humanised and would carry human organs in them to be used by us, whenever we need. Pluripotent stem cells, the embryonic or bone-marrow cells that can develop into any kind of cells or tissues, offer the possibility of a renewable source of cells/tissue replacement to treat a myriad of diseases and disabilities including renal and liver failure, Parkinson’s and Alzheimer’s diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis. Therefore, all is well with the stem cell research when scientists are using the stem cells of human or an animal species for research and their application in the same species. The problem arises when they cross the line — when they start injecting the embryonic stem cells of one species into another thus creating the animals that had cells/organs from two or more species — the so-called chimeras. Other parallel and equally controversial development is that the scientists have started fusing cells from different species and then cloning them into embryos that have cells with characteristics of both the species. The first successful creation of chimera came from Evan Balaban, at McGill University in Montreal. He took small sections of brain from developing quails and transplanted them into the developing brains of chickens. The resulting chickens exhibited vocal trills and head bobs unique to quails, proving that the complex behaviours could be transferred across species by making chimeras. Irving Weissman, Stanford University’s Institute of Cancer/Stem Cell Biology and Medicine, developed the first mouse with a nearly complete human immune system — an animal that has proved invaluable for tests of new drugs against the AIDS virus, which does not infect conventional mice. He followed it up creating mice with brains that are about 1 per cent human. He may conduct another experiment where the mice would be injected with human neurons and could have 100 per cent human brains. Weissman said he’s not a mad scientist trying to create a human in an animal body. He hopes the experiment leads to a better understanding of how the brain works, which would be useful in treating diseases like Alzheimer’s or Parkinson’s. These chimeras can also be used to test the response of the AIDS virus to new drugs. Weissman might not be a mad scientist but there could be more than one who can get carried away and allow such mice/animals to live and reproduce. Researchers at the University of Nevada at Reno added human stem cells to sheep foetuses in an attempt to create a reliable source of livers for transplant patients. Similarly, the Mayo Clinic in Minnesota has developed a line of pigs that have pig blood cells, human blood cells and hybrid (pig plus human) blood cells. Humanised animals Such “humanised” animals carrying organs that have human characteristics, could have countless uses. They would almost certainly provide better ways to test a new drug’s efficacy and toxicity. The risk is that some human cells will find their way to the developing testes or ovaries, where they might grow into human sperm and eggs. If two such chimeras, say mice, were to mate, a human embryo might form, trapped in the body of a mouse. As defined above, a chimera is a cell / organ or individual having mixture of two or more species in one body. The word traces its origin to the mythical Greek monster with a lion’s head, goat’s body and serpent’s tail. Not all chimeras are considered controversial: Most twins carry at least a few cells from the sibling with whom they shared a womb, and most mothers carry in their blood at least a few cells from each child they have borne. Faulty human heart valves are routinely replaced with ones taken from cows and pigs, the surgery which makes the recipient a human-animal chimera. Scientists have added human genes to bacteria and farm animals, a whole range of pharmaceutical products (e.g. human Insulin) are routinely manufactured in bacteria by inserting the required genes into the bacterial cells. Chimerism becomes a more sensitive topic when it involves growing entire human organs, especially brain, inside animals. What has caused the uproar is the mixing of human stem cells with embryonic animals to create new species. Many philosophers have been wrestling with the question of why so many people believe it is wrong to breach the species barrier. Does the repugnance reflect an understanding of an important natural law? Or is it just another cultural bias, like the once widespread rejection of interracial marriage? Many turn to the Bible’s repeated invocation that animals should multiply “after their kind” as evidence that such experiments are wrong. Others, however, have concluded that the core problem is not the creation of chimeras but how are we going to treat them. If we did enhance (?) the status of a “chimpanzee” to “humanzee”, the animal is certainly not going to complain. During one recent meeting, scientists disagreed on such basic issues as whether it would be unethical for a human embryo to begin its development in an animal’s womb, and whether a mouse would be better or worse off with a brain made of human neurons. But with no guidelines in place in most of the countries, an awkward question hovers above the work: How human must a chimera be before more stringent research rules should be applied? Human being is the only species in the history of life on earth that is aware of evolution — not only the continuum of evolution but also its characteristics and mechanisms. We are not the only species that has knowledge about evolution, we are the only species that can control, modify and give direction to the forces of evolution. By conducting such research to put more and more human characteristics into the animals, are we trying to push the evolution on a turbo jet plane? Does being the master of the world species not put a great responsibility on being human?
Dr Rajinder Chawla is Professor of Biochemistry, Black Lion Hospital, Addis Ababa, Ethiopia. Dr Neena Chawla is Biochemist, Punjab Agricultural University. Ludhiana. |
|
Are mercury tooth
fillings safe? The safety of widely used silver fillings made with mercury will get another look this week in light of persistent complaints that they may cause health problems. Dozens of studies have found no evidence that the fillings are dangerous, except for rare cases of allergic reactions, U.S. health officials say. The Food and Drug Administration will ask a panel of outside experts on Wednesday and Thursday if it agrees with that conclusion or sees reason to worry. Mercury is known to be toxic to the brain and kidneys, but health officials say the mercury vapors emitted from fillings during brushing and chewing are too small to cause harm. Also called dental amalgams, the silver fillings are about half mercury and half a combination of other metals. Makers include Dentsply and Danaher Corp. unit Kerr. The FDA analysed research since 1997, when the U.S. Public Health Service issued a report saying data did not support claims that silver fillings caused serious health problems in humans. A review of 34 studies produced nothing to contradict that finding, the FDA said in a draft report prepared for the advisory panel meeting. “The weight of evidence ... does not support the hypothesis that exposure to mercury via dental amalgam restorations causes adverse biological outcomes,” the agency said. Tens of millions of Americans get silver fillings each year, although dentists today often repair cavities with newer materials that are close to tooth colour. The American Dental Association, on its website, said the silver fillings remain a valuable option because they are durable, easy to use and relatively inexpensive. The FDA lists silver fillings with fish consumption and vaccines as the major sources of mercury exposure in the United States. Studies have found people with more silver fillings have higher levels of the substance in their blood and urine, but health officials say the amounts remain below what is hazardous. Some consumers, however, believe using mercury in dentistry is unnecessary and dangerous given the consensus that other types of mercury exposure can be harmful. Opponents of mercury fillings plan to file a petition today asking the FDA to immediately ban them for pregnant women. Some countries advise dentists not to use silver fillings in women who are expecting. If the FDA does not act, “we are going to still continue to use it in pregnant women and children even though we know mercury causes brain damage. It’s morally and legally unacceptable,” said Charles Brown, counsel for Consumers for Dental Choice.
— Reuters |
|
Emotions and rational thinking Daily life’s problems put people into several situations that require them to cope with distracting emotions, which when interfere with mental functioning may possibly hamper a person’s ability to take rational decisions. But, researchers at American universities have now discovered that the brain is able to prevent emotions from interfering with mental functioning by having a specific “executive processing” area of the cortex inhibit activity of the emotion-processing region. The findings also offer insight into how sufferers of post- traumatic stress disorder (PTSD) or depression are unable to control emotional intrusion into their thoughts, said the researchers, Amit Etkin, Joy Hirsch, and colleagues, who reported the discovery. They published their findings in the September 21, 2006, issue of the journal Neuron, published by Cell Press. The studies were based on previous findings that specific parts of an area of the brain called the anterior cingulate cortex (ACC) — a centre for so-called “executive” control of neural processing — are connected to the amygdala. The amygdala is the brain’s major center for processing emotional events. The experimental challenge for Etkin, Hirsch, and colleagues was to determine whether this region of the ACC was responsible merely for “monitoring” conflict between cognitive and emotional processing or for actively “resolving” that conflict. To distinguish the two processes, Etkin and colleagues designed experiments in which volunteer subjects were asked to indicate by pressing a button whether a face image was happy or fearful. The subjects were instructed to ignore labels of “fear” or “happy” written across each face. These labels might be either “congruent” (e.g., happy face, “happy” word) or “incongruent” (e.g., happy face, “fear” word) with the image. Incongruent face-word combinations constituted a response conflict between emotional and cognitive stimuli. The researchers found that subjects could “resolve” this conflict more readily if an incongruent image was preceded by another incongruent image. This resolution represented an anticipation by the subjects’ brains from the first image that they could resolve the conflict depicted in the second image As the researchers scanned the subjects’ brains with functional magnetic resonance imaging (fMRI), they presented the subjects with a series of such images designed to reveal what parts of the brain were active during such conflict resolution. The technique of fMRI involves using harmless magnetic fields and radio waves to measure blood flow in brain regions, which reflects brain activity.
— ANI |
|
It might not seem like much compared with Harry Potter’s magic garment, but the first functional invisibility cloak has emerged from a North Carolina laboratory. The disk of concentric fiberglass-and-copper bands—about the size of a cocktail coaster—bends a narrow-frequency range of microwaves around a protected zone at its center. By then reorienting those electromagnetic rays so that they exit the disk on their original paths, as if undisturbed, the shield renders itself and whatever is in its protected zone almost invisible to a microwave detector downstream. A team with members from Duke University in Durham, N.C., the Imperial College London, and the San Diego–based company SensorMetrix created the new device. Several of the scientists last spring proposed how to make such invisibility shields. In the latest experiments, the researchers placed a copper hoop in the path of microwaves and took readings with and without the novel cloak around the hoop. The measurements showed that the cloak eliminated nearly all the microwave disturbances that a naked hoop would cause. The structure is “doing two things, not perfectly, [that] are the essence of cloaking” says Duke physicist David Schurig, who designed the device. “One is to reduce reflection, and the other is to reduce shadow.” He and his colleagues describe the work in a report released Oct. 19 online by Science. Physicist Oskar J. Painter of the California Institute of Technology in Pasadena calls the shield “a clear breakthrough that will have a ripple effect throughout the research-and-development community.” It’s “a very big splash in the field,” agrees mechanical engineer Xiang Zhang of the University of California, Berkeley. “Cloaking has been a dream for many years for many physicists and technologists.” Still, there was a noticeable shadow, notes theoretical physicist Costas M. Soukoulis of Iowa State University in Ames. “I was expecting the device to perform better,” he says. |
|
|
A new Hubble image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. As the two galaxies smash together, billions of stars are born, mostly in groups and clusters of stars. The brightest and most compact of these are called super star
clusters. The universe is an all-action arena for some of the largest, most slowly evolving dramas known to mankind. A new picture taken by the Advanced Camera for Surveys (ACS), onboard the NASA/ESA Hubble Space Telescope, shows the “best ever” view of the Antennae galaxies - seemingly a violent clash between a pair of once isolated galaxies, but in reality a fertile marriage. As the two galaxies interact, billions of stars are born, mostly in groups and clusters of stars. The brightest and most compact of these are called super star
clusters. The two spiral galaxies started to fuse together about 500 million years ago making the Antenna galaxies the nearest and youngest example of a pair of colliding galaxies. Nearly half of the faint objects in the Antennae are young clusters containing tens of thousands of stars. The orange blobs to the left and right of image centre are the two cores of the original galaxies and consist mainly of old stars criss-crossed by filaments of dark
brown dust. The two galaxies are dotted with brilliant blue star-forming regions surrounded by pink hydrogen gas. The image allows astronomers to better distinguish between the stars and super star clusters created in the collision of two spiral galaxies. The observations show that only about 10% of the newly formed super star clusters in the Antennae will live to see their ten millionth birthday. The vast majority of the super star clusters formed during this interaction will disperse, with the individual stars becoming part of the smooth background of the galaxy. It is, however, believed that about a hundred of the most massive clusters will survive to form regular globular clusters, similar to the globular clusters found in our own Milky Way galaxy. |
|
|
THIS UNIVERSE
If the Moon revolves around the Earth and also rotates around its axis then why are we not able to
see its backside? The reason is that Moon’s period of revolution around the earth is exactly the same as the period of its rotation around its axis. It almost seems like a deliberate, crafty thing that the moon does to hide its backside from our view! As if it was ashamed of its badly scarred look on that side! But science cannot be satisfied with such reasoning. So one has to do some deep thinking and the observation you have made becomes inevitable. The reasoning goes somewhat like this: The
Moon was most probably produced in some sort of collision with the
Earth itself. It might have been even closer to us than it is now. The tidal forces between the moon and the earth would have also been stronger than now. Such forces cause a bulge on the
Earth in the direction of the Moon - that we know very well. But these forces are also acting on the
Moon, causing a similar bulge on it. This bulge would be highest at the point nearest the earth. Force between the
Earth and the Moon would also be highest at that location. As the moon rotates, this force would act as a braking torque trying to slow its turning. Such continuous braking over a long time would lead to a synchronisation of rotation and revolution movements of the moon. That is the reason we would see only one face of the
Moon, unless we travel out to space to look at its backside. This has been done and by now the backside of the
Moon has been photographed by spacecraft. Kindly tell me why a fish dies quickly when taken out of water
but whales do not. All these creatures need oxygen for their metabolism. Whales have large lungs and they can stay under water much longer without breathing. Normal fish does not breathe like us. It has no apparatus like our lungs through which oxygen could be sucked and mixed with its blood. But fish has the capability to extract oxygen dissolved in water through its gills. Sometimes I feel it would have been wonderful for us to have an arrangement with lungs and gills both, along with a capability to switch between the two modes of oxygenation. That way we could have lived in water or on solid earth, as we liked! But I suppose that sort of complicated system was not developed because it would have been subject to frequent malfunction. If we try to push a proton towards another proton, it will not budge No matter how small the force the proton you are attacking will be disturbed if it were free. It would be pushed away. If the target proton is bound to a nucleus or some other way then its motion might be restricted, even to the point that it does not move at all. In that case the proton you were pushing would, on being released, bounce back with the energy you expended in pushing it. Think of the force of repulsion as a spring you are trying to compress. You were distorting the electrostatic field while trying to press your proton into a bound proton and your energy is stored in that field, very much like the way it would in a spring you try to compress. |
The most radical experiment, still not conducted, would be to inject human stem cells into an animal embryo and then transfer that chimeric embryo into an animal’s womb. Scientists suspect the proliferating human cells would spread throughout the animal embryo as it matured into a foetus and integrate themselves into every organ.