Please quote Nature Biotechnology as the source of these items.

The November 2005 issue of Nature Biotechnology is available online.

Nature Biotechnology pp 1414 - 1417

Researchers have found a reliable way of rapidly identifying sterile male mosquitoes for use in pest eradication programs for controlling malaria. In the November issue of Nature Biotechnology, Andrea Crisanti and colleagues establish a genetic approach for identifying male larvae of the malaria vector mosquito Anopheles stephensi through the specific expression of a green fluorescent protein in their gonads. By releasing an overabundance of these sterile males in the field, wild male mosquitoes would be unable to mate with females, leading to rapid decline in fertile eggs and the eventual eradication of the mosquito population in the area of release.

The sexing strategy described by Crisanti and colleagues solves the longstanding problem of how to differentiate female sterile mosquitoes, which remain vectors for parasites of the genus Plasmodium that cause malaria and are thus unsuitable for use in pest control from sterile males that do not transmit the parasites. Previously, the precise sorting of males from females among the sterilized larvae was practically impossible. By ensuring that expression of the fluorescent protein occurs only when male gonads appear in mosquito larvae, the authors are able to sort the translucent larvae into female and male on the basis of their fluorescence using existing cell sorting technologies. The sexing of the malaria vector A. stephensi brings this type of mosquito control several steps closer to practical implementation.

Nature Biotechnology pp 1407 - 1413

Scientists have succeeded in using magnetic resonance imaging (MRI) to visualize therapeutic cells transplanted into patients. The technique, described in November’s Nature Biotechnology, should be useful for improving numerous experimental therapies based on transplanting various types of cells, such as immune cells and stem cells.

'Dendritic cells' are specialized immune cells that are being investigated as a means of fighting cancer. To understand why clinical trials using dendritic cells have been less successful than scientists had hoped, Figdor and colleagues wished to determine what happens to the cells after they are transplanted. Adapting an approach that has been demonstrated in animals, they coaxed cultured dendritic cells to take up tiny magnetic particles made of iron oxide. The iron-containing cells were then injected into the lymph nodes of melanoma patients. Imaging with MRI gave a clearer picture of the cells compared with an X-ray method and revealed that, in half the patients, the injection had missed the lymph node altogether, explaining the lack of clinical efficacy. Because the success of any cell therapy depends on getting the cells to the correct site in the body and assuring their survival, the ability to image transplanted cells with MRI will likely facilitate the optimization of many such therapies.

Nature Biotechnology

Researchers have turned human embryonic stem (hES) cells into a cell type found in human embryos that ultimately forms the pancreas, liver, lungs, and other organs. The ability to generate this primitive cell type - definitive endoderm - is a critical step in the effort to transform hES cells into certain mature cell types that scientists hope will serve as 'replacement cells' to treat various diseases, such as type 1 diabetes or liver failure. The study, by Baetge and colleagues, appears in December's Nature Biotechnology. HES cells have the potential to become any specialized cell type in the body. This process happens naturally during development, but reproducing it in the lab - for example, deciphering the complex set of signals that tells a hES cell to become an insulin-producing pancreatic beta cell - is an enormous scientific challenge. Definitive endoderm is one of the three principal (germ) layers of cells in an embryo (in addition to ectoderm and mesoderm), which arise at the very early stage of development known as gastrulation. Understanding how to make definitive endoderm should pave the way to complete differentiation of hES cells to mature endodermal cell types, such as pancreatic beta cells or liver cells.