Salmonella: Now you see it,now you don't

Diseases caused by Salmonella species are characterized by bacterial invasion of host cells. Salmonella invasion requires a genetic locus (inv) with homology to bacterial systems involved in specific protein export and organelle assembly. Until recently, the actual Salmonella invasion factors exported or assembled by the inv system remained unidentified. It now appears that Salmonella produces novel appendages upon contact with host cells. These appendages are transient, appearing and disappearing rapidly from the bacterial surface. Appendages are altered in strains unable to invade due to mutations within the inv/spa locus. Therefore, a role for the invasion locus has been identified, providing another example of bacterial pathogens responding to signals provided by the host cell surface.     

GPI-anchored proteins: now you see 'em, now you don't.

Many cell surface proteins are attached to membranes via covalent glycosylphosphatidylinositol (GPI) anchors that are posttranslationally linked to the carboxy-terminus of the protein. Removal of the GPI lipid moieties by enzymes such as GPI-specific phospholipases or by chemical treatments generates a soluble form of the protein that no longer associates with lipid bilayers. We have found that the removal of lipid moieties from the anchor can also have a second, unexpected effect on the antigenicity of a variety of GPI-anchored surface molecules, suggesting that they undergo major conformational changes. Several antibodies raised against GPI-anchored proteins from protozoa and mammalian cells were no longer capable of binding the corresponding antigens once the lipid moieties had been removed. Conversely, antibodies raised against soluble (delipidated) forms reacted poorly with intact GPI-anchored proteins, but showed enhanced binding after treatment with phospholipases. In the light of these findings, we have reevaluated a number of publications on GPI-anchored proteins. Many of the results are best explained by lipid-dependent changes in antigenicity, indicating this might be a widespread phenomenon. Since many pathogen surface proteins are GPI-anchored, researchers should be aware that the presence or absence of the GPI lipid moieties may have a major impact on the host immune response to infection or vaccination.     

Now you see him, now you don't: experience, not age, is related to reproduction in kittiwakes

In long-lived species, individuals can skip reproduction. The proportion of breeders affects population growth rate and viability, there is a need to investigate the factors influencing intermittent breeding. The theory predicts that if lack of experience is an important constraint, breeding probabilities should increase with experience for individuals of the same age, whereas under the so-called restraint hypothesis, breeding probabilities should increase with age regardless of experience. However, because the probability of detecting individuals in the wild is generally less than 1, it is difficult to know exactly the number of previous breeding episodes (breeding experience). To cope with this issue, we developed a hidden process model to incorporate experience as a latent state possibly influencing the probability of breeding. Using a 22-year mark-recapture dataset involving 9970 individuals, we analysed simultaneously experience and age effects on breeding probabilities in the kittiwake (Rissa tridactyla). We did not detect an influence of age on adult breeding probabilities. We found that inexperienced birds breed less frequently than experienced birds. Our approach enables us to highlight the key role of experience on adults breeding probabilities and can be used for a wide range of organisms for which detection is less than 1.     

Knowing a nascent synapse when you see it

To understand brain development, we must learn how synapse formation shapes functional neural circuits. At the heart of this process lies the nascent synapse--an enigmatic structure spanning the developmental gap between initial cell-cell contact and the mature synapse. New experimental techniques are beginning to illuminate the processes involved in synaptogenesis, but much remains to be learned, including simply how to recognize the synapse in its nascent form.     

What many transgender activists don't want you to know: and why you should know it anyway

Currently the predominant cultural understanding of male-to-female transsexualism is that all male-to-female (MtF) transsexuals are, essentially, women trapped in men's bodies. This understanding has little scientific basis, however, and is inconsistent with clinical observations. Ray Blanchard has shown that there are two distinct subtypes of MtF transsexuals. Members of one subtype, homosexual transsexuals, are best understood as a type of homosexual male. The other subtype, autogynephilic transsexuals, are motivated by the erotic desire to become women. The persistence of the predominant cultural understanding, while explicable, is damaging to science and to many transsexuals.     

Multisensory integration: what you see is where you hear

Recent studies of multisensory integration compel a redefinition of fundamental sensory processes, including, but not limited to, how visual inputs influence the localization of sounds and suppression of their echoes.