Oct 25, 2008

The Neural Network

Traditionally when we speak of neural network it refers to network or circuit of biological neurons. But in this modern age it refers to artificial neural networks (ANN),also called simulating neural networks (SNN) ,which is made of artificial neurons or nodes. These nodes are highly interconnected working together to solve specific problem by mimicking somehow like brain neural network. Of course brain neural network are much more complex than artificial neural networks. Neural network is used in artificial intelligence and cognitive modeling.

Thanks to neural network that it is now possible to recognize speech, analysis of image, and production of autonomous robots which can learn by own, no need to over burden a robot with huge software till its nervous break down occurs.

Neural network take a different approach to deal with problem where as conventional computer make use of algorithmic approach i.e. a sequence of instructions to solve a problem. We can say that neural network are non linear statistical data modeling or decision making tool. Neural network learn by example like our brain does. They are not been programmed to do a definite work.

Neural networks are built in by simulating the way that signals or impulses are carried by neurons in our nervous system or brain. As much is unknown about how the brain processes information the neural network model are only gross idealizations of real networks of brain.

So it's really important to understand completely the mechanism of nerve conduction. In recent year much of investigation in done in studying about neuromodulators such as dopamine, acetylcholine, and serotonin on behavior and learning. Biophysics model such as BCM theory has proved important to decipher the mechanism of neuron plasticity i.e. ability to change the strength of connection between two neurons.

May 29, 2008


Ever taste a shape, or smell a color?
ATLANTA, Georgia (CNN) -- Imagine a world in which the senses fuse together; where sounds are seen and words and aromas have color; where the number 10 can be smelt, and fuchsia has flavor. That's the world of synesthesia -- loosely defined as a difficulty in distinguishing between different sensory inputs.
Synesthesia means "joined sensation," and is an automatic physical experience in which one sense triggers off an additional perception in a different sense or senses. For example, a synestheste not only sees the color red, but might "smell" it, too.
Neurologist Richard Cytowic, author of "The Man who Tasted Shapes," said a synestheste's experience forms the building blocks of perception. "They get a sampling of perception at an earlier stage before it becomes separated -- before, that was a sound, this is a color, a texture..." he explained.
The phenomenon varies in impact. It could be a disorder in some, and a perceptual curiosity in others. It is rare however, occurring in roughly one in 25,000 individuals.
But people who experience the phenomenon, the ringing of a doorbell could resemble a series of triangles, or a dog bark could seem like a circle with dots around it. For a more tangible peek into this enigma, synesthestes recommend Walt Disney's "Fantasia," an animated film that attempts to visualize music.

Artist Carol Steen, who is part of the tiny world of synesthestes, says she possesses a "wonderful gift." The shapes and colors she experiences through music and acupuncture, she said, inspire her paintings and sculptures. "I use the colors I see. I use the shapes that I see," she says. "It's like an additional form of consciousness."
Cytowic attempts to provide some insight into the enigma using a black and white placard printed with the word "weary." That same placard, he said, would appear flush with different colors for a synestheste. "For us, the touch, taste and smell, they are all separate," he said. "But for synesthestes, it is not."
For Cytowic, who has spent more than a decade studying synesthesia, it is more than just an unusual phenomenon. He thinks of synesthestes as "cognitive fossils," and believes a search to understand the condition will eventually lead to a new model of the mind.

Mar 11, 2008

Fight to HIV

Engineered cells against HIV

Engineered Immune cells can know be used to kill HIV infected cells before they become HIV virus producing factories. Researchers at Albert Einstein College of Medicine made a breakthrough in fight against HIV by transforming genetically engineered immune cells into potent weapons against the disease.

A subgroup of immune cells known as CD8 cytotoxic T lymphocytes or CTLs, recognize cells infected with HIV and kill them before they become HIV-producing factories. This CTL activity initially keeps the infection in check.

However, CTLs may not bind tightly enough to the infected cells or because HIV mutates so rapidly, the virus subdues the immune system, thus boosting the virus in the absence of drug therapy and resulting in AIDS.


The idea……

Certain of the CTLs of elite controllers may be genetically equipped to bind tightly to HIV-infected cells and destroy them and thereby suppress the infection indefinitely.

The idea was first to identify the elite controllers "super" CTLs and to isolate the genes that enable these cells to bind tightly to HIV-infected cells and kill them efficiently; then this gene
would be
transfer into CTLs that do not recognize HIV- infected cells and convert them into potent killers of those cells.

The breakthrough…….

CTLs T-cell receptor(TCR) has two chains- alpha and beta, that the researchers isolated the genes that code for each of the two "chains" from potent HIV-specific CTL.

The genes were combined and packaged inside a special type of virus, called a lentivirus. The lentiviruses the inserted these genes into chromosomes of naive CTLs obtained from a naïve donor's (not infected by HIV) blood and reprogrammed them into potent HIV-specific CTLs.

During the study, the researchers injected mice with both HIV infected human cells and with reprogrammed naïve CTLs into which the HIV recognizing T-cell receptor genes had been inserted using the lentiviral delivery system.

The findings revealed that after on week the infected cells had virtually been eliminated. Researchers found that these genetically reprogrammed CTLs have very strong activity in terms of killing HIV-infected cells in both test-tubes and an animal model. Researchers believe that the novel strategy could lead to and entirely new approach for combating AIDS and other viral diseases.


Mar 6, 2008



Upps Enzyme Antibody Abzymes confuses me….

The binding of an antibody to its antigen is similar in many ways to the binding of an enzyme to its substrate. In both cases the binding involves weak, noncovalent interactions and exhibits high specificity and often high affinity. What distinguishes an antibody-antigen interaction from an enzyme-substrate interaction is that the antibody does not alter the antigen, whereas the enzyme catalyzes a chemical change in its substrate. However, like enzymes, antibodies of appropriate specificity can stabilize the transition state of a bound substrate, thus reducing the activation energy for chemical modification of the substrate.


The similarities between antigen-antibody interactions and enzyme-substrate interactions raised the question of whether some antibodies could behave like enzymes and catalyze chemical reactions. To investigate this possibility, a hapten-carrier complex was synthesized in which the hapten structurally resembled the transition state of an ester undergoing hydrolysis. Spleen cells from mice immunized with this transition state analogue were fused with myeloma cells to generate monoclonal antihapten monoclonal antibodies. When these monoclonal antibodies were incubated with an ester substrate, some of them accelerated hydrolysis by about 1000-fold; that is, they acted like the enzyme that normally catalyzes the substrate’s hydrolysis. The catalytic activity of these antibodies was highly specific; that is, they hydrolyzed only esters whose transition-state structure closely resembled the transition state analogue used as a hapten in the immunizing conjugate. These catalytic antibodies have been called abzymes in reference to their dual role as antibody and enzyme.

What’s in Research??

A central goal of catalytic antibody research is the derivation of a battery of abzymes that cut peptide bonds at specific amino acid residues, much as restriction enzymes cut DNA at specific sites. Such abzymes would be invaluable tools in the structural and functional analysis of proteins. Additionally, it may be possible to generate abzymes with the ability to dissolve blood clots or to cleave viral glycoproteins at specific sites, thus blocking viral infectivity. Unfortunately, catalytic antibodies that cleave the peptide bonds of proteins have been exceedingly difficult to derive. Much of the research currently being pursued in this field is devoted to the solution of this important but difficult problem.