Growth hormone cells

Feedback on entries received in 2012

We know that the entrants were just two terms into year 12 and that they had no significant experience of essay writing of this kind. Nonetheless, we were impressed with their often bold and thoughtful attempts to make sense of difficult subjects. Most had correctly prepared bibliographies; some indicating prodigious efforts of research. Many had a sound structure, a logical narrative and a clear focus with not too much misuse of words. The participants gave every indication of having enjoyed their research.

What can we learn from the lives of identical twins?

Registers of twins have been kept since the mid-19th century in Scandinavia because scientists thought important conclusions could be drawn about the relative importance of nature and nurture.

The essay that reached the final round showed a clear appreciation of the potential useful medical insights that could emerge from monozygotic twins if only one of a pair suffered ill health. The author realised that an important process must be overruling the normal pattern of gene expression and that this probably involved modifications of the genome, that we now call epigenetic. Such changes are likely to be in response to an environmental trigger. An example or two - rheumatism or arthritis and the effect of chronic inflammation - would have improved this essay. There is now a substantial amount of evidence showing that as identical twins get older substantial differences in the epigenome emerge reflecting differences in life experiences. Other notable findings from this approach that could have been mentioned from this approach include the observation that only about 30% of the variation in human lifespan is inherited and only about 10% of the prevalence of most cancers is genetic.

Is vaccination really necessary?

Some people think the dangers of vaccination exceed the risks posed by the diseases we want to suppress.

Disappointingly none of the essays on this topic got through to the final round. Although many essays were nicely written they lacked a sharp focus. What was needed was to show with vivid examples that vaccination campaigns have made the world a much safer place with only few ill effects. Furthermore, this result could not have been achieved by any other route. One cannot really argue against the importance of the world-wide smallpox campaign as the disease has been eradicated forever and diseases like diphtheria, whooping cough, polio and yellow fever are becoming much less prevalent. There was little awareness of the significance of “herd immunity” - the idea that 80-90 % of a population must be vaccinated to break the chain of transmission in the community. In this context it is important to show how bad publicity can sabotage a vaccination campaign. Many entries commented on Andrew Wakefield and his discredited notion that the MMR vaccine caused autism. However, quite a few missed an important consequence: the surge in cases of measles following the mass refusal of parents to authorise vaccination. Another example was the upsurge in diphtheria after the break up of the USSR; their previously excellent vaccination system broke down so that within 10 years of the break-up the disease was causing many deaths.

We wondered how effectively this subject is being taught as none of the 21 entries really seemed to show much appreciation that vaccination was of enormous importance.

What makes cancer cells different to other cells?

Ever since cancer cells were first grown in tissue culture, scientists have known they were fundamentally different from the cells present in normal tissues.

Three of the finalists wrote on this topic, providing a great deal of information about what makes cancer cells different to normal cells. They noted the ability of cancer cells to divide uncontrollably, thereby forming tumours, and then being able to invade other parts of the body. They all recognised the importance of a succession of genetic changes to make cells malignant. Two of the finalist had a lively appreciation that normal cells can only make a finite number of cell divisions - the Hayflick limit - and that cancer cells ignore this restraint. They described how this is governed by a kind of molecular clock called the telomere, found at the tips of chromosomes, that loses its repeating units at each division until they reach the limit. Properly regulated telomeres are a key defence against cancer. The steps that make a cell cancerous include: loss of control of cell division, loss of contact with neighbours, production of growth factors that make them grow faster, a breakdown of genomic organisation, creation of a new blood supply to the tumour, secretion of “offensive” proteins that upset local and whole-body physiology. Crucially cancer cells evade programmed cell death and all the defences one might hope the body could marshal against “irregular cellular behaviour”.

Each of the finalists explored metaphorical ways of explaining the peculiar behaviour of cancer cells. We especially liked the one that wrote as though the author was a cancer cell with human characteristics of deviousness, spitefulness and an out-of control rumbustiousness.

Why has type-2 diabetes become a world-wide epidemic in the 20th century?

The origins of type-2 diabetes are mysterious; what kind of widespread life experiences might contribute to the failure to keep blood glucose to optimal levels.

The best entries on this topic were very clear that type-2 diabetes occurs when cells become unresponsive to insulin and the pancreas stops making insulin, and that obesity was an important contributory factor. There was some confusion about the indirect causes, particularly in recognising that obesity is chiefly a consequence of a mismatch between exercise and food intake. The finalists knew of the extreme vulnerability of some populations (the Pima Indians and the Nauruans), who eighty years ago were lean and fit but with the arrival of abundant food, and a decline in physical effort, this changed. One finalist realised that these individuals were probably more susceptible to type-2 diabetes because they were well adapted to a feast-and-famine existence. They could store energy as fat during periods of plenty and “mobilise” it during periods of famine but during periods of prolonged abundance they became obese and developed the disease. Europeans may be more resistant to type-2 diabetes than other ethnicities but probably the same principle is involved.

Are we too clean for our own good?

The hygiene hypothesis suggests that childhood exposure to chemicals or microbes would make us less susceptible to allergies and autoimmune diseases.

The two entries in the final on this topic both recognised the strange recent increase in autoimmune disease in the developed world, while it remains relatively rare in the developing world. Both were aware of the two parts of the T cell response to microbes (Th1 and Th2) and correctly attributed the increasing prevalence of autoimmunity to lack of experience of the Th1 response in childhood that may make individuals susceptible to inappropriate immunological responses to harmless antigens generated by the Th2 system. Both made a cogent case for the “hygiene hypothesis”, which suggests that lack of exposure to microbes during childhood may be responsible, but it is a major undertaking for students to disentangle the massive web of data. They did very well to see the significance of parasite infections, immunisation, use of antibiotics in the first year of life, being brought up on farms, exposure to raw milk and being brought up in a large family. One essayist wondered if the real problem was the loss of friendly microbes that could protect without doing harm and suggested “doctors will be back in business, recreating the diseases they had abolished, in popular easy-to-use forms” (a quotation from The hitch-hiker’s guide to the galaxy).

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