When I walk into London underground stations I am frequently confronted with the stark contrast between the Christian mindset and the world's desires. Sex appeal is used to sell designer clothes and beach holidays. Posters advertising the latest films, albums and gadgets to spend money on, pander to our self-interest. Their brashness makes it easier to spot their influence on us. We are often tempted to conform to the world's servitude of money, sex and power.

The apostle Paul contrasts this self-orientated obsession with a God-orientated Christian mindset. He instructs us, in Romans 12:1,2, to honour God with both our bodies and minds in response to his grace: 'Do not conform any longer to the pattern of this world, but be transformed by the renewing of your mind' (Rom 12:2 (a)). We may be alert to temptation on the tube. But how careful are we to guard our minds from the world's influence in the realm of medical ethics? Why should we bother with approaching ethics from a Christian perspective? Helen Barratt, a former Nucleus editor, answers the question in her article (pp35-39).

Human embryos are under fierce assault and our view of them sets the tone for how we respond to most issues that impact on early human life. Their destruction through abortion, embryonic stem cell research, and post-coital contraception is happening because the world sees them as less than human. Peter Saunders defends the embryo from a biblical perspective in The Moral Status of the Embryo (pp17-26). What then about 'different' embryos like parthenotes and chimeras? Jacky Engel considers the implications of the cutting edge of embryonic biology (pp27-34).

In the remainder of Romans 12, Paul explains how our experience of grace should impact our relationships with other people. Medical students need to consider how best to witness to Christ in every situation. This issue's ethical enigma offers a Christian response in a scenario where physician assisted suicide is legalised. But praise God that the UK recently took a step away from that reality. Mark Pickering updates us on the work of the Care Not Killing Alliance in securing the rejection of the Joffe bill at the House of Lords in May (pp4,5).

We may yet neglect our personal walk with Jesus even as we consider a Christian approach to ethics. How can we 'offer up our bodies as living sacrifices…(our) spiritual act of worship' (Rom 12:1)? The double book review of Every (Young) Man's Battle makes it clear that the quest for sexual purity involves breaking some sweat (p42).

I would like to say a personal hello to Nucleus readers as I take over from Gavin Ling as student editor. Make my day by writing in to nucleus@cmf.org.uk on anything in this issue. Your letter could be published next time!