Minerva: April 2003
Rabbit sperm will always swim towards the heat in a laboratory mock up of a fallopian tube. The Israeli scientists who discovered this think that human sperm might do the same, guided to their target like small, heat seeking missiles (Nature Medicine 2003;9:149-50). Thermotaxis, they say, has the potential to guide sperm over longer distances than chemotaxis, which probably only works for the last few millimetres.
The next stage of reproduction—implantation of an embryo in the uterine wall—has always been something of a mystery. Laboratory research on human endometrium now suggests that embryos stick to endometrium in the same way as leukocytes sometimes stick to vascular endothelium, by covering themselves in proteins called selectins. When receptive, endometrial cells express oligosaccharide receptors that interlock with selectins, capturing the embryo as it floats by (Science 2003;299:405-8).
A survey of primary school children in England and Sweden confirms what many parents already know—that