assumptions about technologicaldevelopment. Dynamic modelling is just asvulnerable to implicit error in this regard. William E. ReesSchool of Community and Regional Planning,University of British Columbia, 6333 Memorial Road, Vancouver, British Columbia V6T 1Z2, Canada

Xenotransplantation’sbenefits outweigh risksSir — Your News item “Diabetes trial stirsdebate on safety of xenotransplants” (Nature419, 5; 2002), discussing our clinical trialof pancreatic islet xenotransplantation,states: “Mexico has no published guidelineson clinical trials in xenotransplantation.”This is untrue. Mexico has a general healthlaw that regulates the conduct of all experi-mental investigation in human beings; italso regulates organ and tissue transplan-tation, and xenotransplantation, whichwas added recently. The protocol for ourclinical trial was approved by the research,ethics and biosafety committees of ourinstitution and of the National AutonomousUniversity of Mexico Medical School.

Your article did not mention theexistence of other published studies onporcine–human islet xenotransplantation,although these studies are admittedlysmall, use different methods from ours anddo not show significant benefit to patients.With regard to your reporter’s commentabout the need to test “any proposedapproach” on non-human primates, thereare many examples in the fields of bothtransplantation and diabetes where experi-mental studies in humans are performedfollowing evidence of benefit derived onlyfrom other mammalian models. Indeed,one of the problems we faced was that thereis no appropriate model for auto-immunediabetes in non-human primates.

You report our critics’ views that weshould have undertaken preclinical studiesbefore proceeding, but vast amounts ofpreclinical data on animal models alreadyexist, both on efficacy of islet xenotrans-plantation and the protective effects ofSertoli cells, including our own publishedwork. We have not published some of ourwork, to protect patents. But we considerthe available literature sufficient to justifyour trials on young diabetic patients, thepopulation that stands to benefit most.

You report our critics as stating that our work was on patients too young to giveproper informed consent. We recruitedadolescent and high-school studentsbecause they had had diabetes type 1 formore than four years, so that spontaneousremission would not occur, yet there wereno diabetic complications typical of adult

patients. It is our strong contention thatthey were old enough to understand fullythe potential risks and responsibilities. Wehad several meetings with the patients andtheir parents to explain in detail theprocedure. After time for reflection, theysigned extensive informed consent formsconforming to international requirements,for example the Helsinki declaration.

Type 1 diabetes causes the death ofmore than 40% of patients before theyreach the age of 40, and is a leading causeof terminal renal insufficiency andblindness, among other devastatingcomplications. We believe that the benefitsof better metabolic control, and insulinand immunosuppression independence,offered by pancreatic islet xenotransplan-tation far outweigh the risks.Rafael Valdes GonzalezHospital Infantil de México “Federico Gomez”,Laboratorio de Xenotrasplantes, Edificio Mundet 4° Piso, Calle Dr Marquez 162, Col. Doctores, CP 06720, México D.F.

UK government closesits eyes to medical needsSir — Readers of Nature may get theimpression that funding for basic researchin the United Kingdom is in good health(“Calling for entrepreneurs: London”Naturejobs 19 September, 4–5; 2002). We wish to put the record straight.

The UK government uses the periodicResearch Assessment Exercise (RAE) todetermine levels of funding for universitydepartments and institutes. Following thelatest RAE, funding for hospital-basedclinical subjects, which underpins the coreof translational research in medical schoolsacross the United Kingdom, was severelycut. Despite having received, for the thirdconsecutive time, the highest possiblerating (5*), the Institute of Ophthalmologyin London faces a 19.7% cut in its predictedannual budget because the government hasfailed to honour its pre-RAE fiscal commit-ments. The problem is even greater forthose who received a rating of 5 and whonow face a massive 38% cut.

This takes £970,000 (US$1.5 million) ayear out of our operating budget. We areunable to appoint even a single technicalpost that we require to run newly commis-sioned laboratories, which puts extra stresson academic staff. The cuts also exacerbatethe financial difficulties faced by ourparent body, University College London,after years of underfunding.

The reason UK medical schools arehaving problems is self-evident, and thecrisis extends across the country. In thelonger term our institute, together withothers in hospital-based clinical subjects,

will be less able to fulfil its mission, whichis to deliver the translational research thatenables laboratory science to be developedinto clinical trials and ultimately intobenefits to patients.

The message appears to be that, withregard to translational medical research,the government is not only blind to theachievements of 5* departments andinstitutes, it has also, incomprehensibly,decided to slash the support they receive.We also suspect that the cuts are due atleast in part to inept planning andmuddled thinking. Institutes such as ours have to budget, recruit and develop a coherent research strategy within theconstraints of government policy. It istherefore essential that the governmentkeeps its promises. This it has not done. In the United Kingdom the phrase ‘sciencepolicy’ has become an oxymoron.

If, as I. B. Holland suggests (Nature 419,248; 2002), underfunding is less acute herethan in other European countries, then theprospects for our continent of beleagueredresearchers must be bleak. Governmentsare often short-sighted when it comes topolicy development, but in this case we areconfronted by a total lack of vision. And aswe are only too well aware at this institute,myopia may be corrected but blindnessremains virtually untreatable.Stephen E. Moss, Gary Rubin, John Greenwood, Adam SillitoInstitute of Ophthalmology, University CollegeLondon, 11–43 Bath Street, London EC1V 9EL, UK

Mother knows bestSir — In his otherwise excellent News andViews “The grand assault” (Nature 419,493–494; 2002), Russell F. Doolittle writes:“Eukaryotes can be loosely defined asorganisms whose cells have nuclei andcytoskeletons, distinguishing them from the Bacteria and the Archaea, neither of which has introns in theircoding sequences.”

Bacteria and the phage that infect themdo contain introns in their genomes. Thefirst example of an intron in a bacterialsystem was found in the thymidylatesynthase gene of bacteriophage T4 (F. K. Chu, G. F. Maley, F. Maley and M. Belfort Proc. Natl Acad. Sci. USA 81,3049–3053; 1984) — the last author beingmy mother. Since then, hundreds ofintrons have been found in archaea,bacteria and their phage.

It has been a long time since I utteredthese words, but I couldn’t be more proudto say: “Mommy told me so.”Gabriel M. BelfortDepartment of Biochemistry, K-building,Boston University School of Medicine, 715 AlbanyStreet, Boston, Massachusetts 02118, USA

correspondence

268 NATURE | VOL 420 | 21 NOVEMBER 2002 | www.nature.com/nature© 2002 Nature Publishing Group© 2002 Nature Publishing Group