Because of the fact that they do contain genetic material, and that they are responsible for the production of energy that help power the cell's life processes, any defect in their make-up, or the way they interacted with the rest of the cell, could result in a number of serious diseases, such as fatal liver failure, blindness, mental retardation with intractable epilepsy, muscle weakness, diabetes and deafness.

The article brought to light a major problem regarding the creation of human-animal cytoplasmic hybrids (or cybrids) for research that the Bioethics Advisory Committee (BAC) is considering legalising in Singapore.

In this area of scientific research, scientists take the nucleus of a body cell (such as the skin) taken from a human individual and insert it into the egg of an animal (such as a cow) whose own nucleus has been removed.

This new one-cell being (with 99 per cent human genes and 1 per cent animal genes) is then given a 'spark' to stimulate it to grow as an embryo.

Later in its development (at the blastocyst stage), stem cells from the inner cell mass are taken from this embryo, which is destroyed in the process. It is hoped that these stem cells can be used to develop cell lines that can then be used to treat diseases such as Parkinson's Disease, diabetes and stroke.

Dr Ho's article has, to my mind, now raised more questions about whether such research should at all be allowed to take place in the first place.

There are various problems associated with such research:

>>The material from the animal egg cell may contain virions or retroviruses that can cause previously unknown animal diseases to pass over to the human race. An example of such infectious material can be found in the virion that causes 'mad cow disease', which may not be apparent or detected till years later.

>>Animal related mitochondrial disease can be transmitted to the human genome, whether of themselves or through their interaction with human genes.

>>The creation of cybrids is essentially a form of cloning, but in this case using material from two different species (for example, a human and a cow). Cloned animals have been shown to exhibit many defects, some even grotesque. This suggests that the technique used can and does result in abnormalities in the cells produced, a problem of cloning that scientists have not been able to surmount, despite many years of research on animal models. Even pioneers of such cloning techniques such as Dr Ian Wilmut (creator of Dolly the sheep) has abandoned this procedure for others that seem to be more promising and less ethically problematic.

>>Because the stem cells obtained from such a cybrid are essentially of embryonic origin, they are highly prone to developing tumours. This has been the case with the use of embryonic stem cells in the past, and one that scientists are unlikely to overcome in the foreseeable future.

>>The idea of mixing animal with the human genome does naturally give rise to a sense of repugnance to many, and understandably so. As Leon Kass, former chairman of the US President's Council on Bioethics, once said: 'In crucial cases.... repugnance is the emotional expression of deep wisdom, beyond reason's power fully to articulate it... Shallow are the souls that have forgotten how to shudder.'

>>In view of these problems, it is unlikely that they will attain commercial viability, despite the huge amounts of funds that might be needed for such research.

We should encourage research that can lead to the development of new cures for human diseases. But we must do so prudently, channelling funds not only to those that are more likely to be commercially viable, but also ethical and more likely to be safe for the human race.

One example is found in that of adult stem cells obtained from sources such as bone marrow, umbilical cord and the placenta. This area of research has indeed brought about many treatments for disease such as leukaemia and other blood disorders. Recent developments have even shown them to hold exciting promise in the area of regenerating nerve and heart cells.

Hui Keem Peng John (Dr)