When young suckle, they are rewarded intermittently with a let-down of milk that results from reflex secretion of the hormone oxytocin. Oxytocin is a neuropeptide made by specialised neurons in the hypothalamus, and is secreted from nerve endings in the pituitary gland. During suckling, every 5 min or so, each of these neurons discharges a brief, intense burst of action potentials; these are propagated down the axons, and release a pulse of oxytocin into the circulation. Here, we have built a computational model to understand how these bursts arise and how they are synchronized. In our model, bursting is an emergent behaviour of a complex system, involving both positive and negative feedbacks, between many, sparsely connected cells. The oxytocin cells are regulated by independent afferent inputs, but they interact by local release of oxytocin and endocannabinoids. Oxytocin released from the dendrites of these cells has a positive-feedback effect, while endocannabinoids have an inhibitory effect by suppressing the afferent input to the cells. Many neurons make peptides that act as messengers within the brain, and many of these are also released from dendrites, so this model may reflect a common pattern-generating mechanism in the brain.
Fundamental research goals for scientists interested in social evolution are to determine the numbers and types of genes that directly regulate individual social behaviors as well as to understand how the social environment indirectly influences the expression of socially relevant traits. The fire ant Solenopsis invicta features a remarkable form of social variation in which the occurrence of two distinct social types that differ in colony queen number is associated with genetic differences at a genomic region marked by the gene Gp-9. Our analyses of gene expression profiles in fire ant workers revealed that differences in Gp-9 genotype are associated with the differential expression of an unexpectedly small number of genes, many of which are predicted to function in chemical communication relevant to the regulation of colony queen number. Surprisingly, worker gene expression profiles are more strongly influenced by indirect effects associated with the social environment within their colony than by the direct effect of their own Gp-9 genotype. These results suggest a complex genetic architecture underlying the control of colony queen number in fire ants, with a single Mendelian factor directly regulating, and the social environment indirectly influencing, the expression of the individual behaviors that, in aggregate, yield an emergent colony social organization.
The prospects confronting a “new-born” schistosome cercaria are formidable. That some of these microscopic helminths successfully negotiate the tortuous route from snail to human vasculature is a truly remarkable feature of adaptive biology. After escaping the birth pore of its parental sporocyst, a cercaria (at least we infer from studies of other digeneans ) swims and crawls through the snail body cavity before it burrows through a pre-formed escape tunnel to the aquatic environment. Once in that milieu, a cyclical suite of swimming behaviours positions the cercaria for its potential assault on the skin of an available host, should one appear. Upon skin penetration, the larva (now called a schistosomulum) sits within the skin for up to 72 hours before tracking to the lung, whereupon it re-enters a second static phase. This journey takes the organism through three distinct environments (five if we include the solid integuments of snail and human hosts), incorporates a wholesale remodelling of the surface membrane, and includes two poorly understood periods of relative immobility in the skin and the lung. Further development in the liver is required before the adults reach their ultimate destination in the vasculature of the intestine or bladder. How the juvenile stages of schistosomes negotiate these environments is of intense interest, not the least because protective immunity in schistosome infections, when it occurs, appears to be directed against the early intra-host stages, with the principal target being the lung stage schistosomulum
Whole-genome sequencing has revealed that organisms exhibit extreme variability in chromosome structure. One common type of chromosome structure variation is genome arrangement variation: changes in the ordering of genes on the chromosome. Not only do we find differences in genome arrangement across species, but in some organisms, members of the same species have radically different genome arrangements. We studied the evolution of genome arrangement in pathogenic bacteria from the genus Yersinia. The Yersinia exhibit substantial variation in genome arrangement both within and across species. We reconstructed the history of genome rearrangement by inversion in a group of eight Yersinia, and we statistically quantified the forces shaping their genome arrangement evolution. In particular, we discovered an excess of rearrangement activity near the origin of chromosomal replication and found evidence for a preferred configuration for the relative orientations of the origin and terminus of replication. We also found real inversions to be significantly shorter than expected. Finally, we discovered that no single reconstruction of inversion history is parsimonious with respect to the total number of inversion mutations, but on average, reconstructed genome arrangements favor “balanced” genomes–where the replication origin is positioned opposite the terminus on the circular chromosome.
Innovation in computational biology research is predicated on the availability of published methods and computational resources. These resources facilitate the generation of new hypotheses and observations both on the part of the creators and the scientists who use them. These methods and resources include Web servers, databases, and software, both complex and simple, that implement a specific procedure or algorithm. Usually, a resource is maintained by the laboratory in which it was initially developed. We would assert that there is a growing level of frustration among scientists who attempt to use many of these resources and find that they no longer exist or are not properly maintained. Whether you agree or disagree with this statement and the evidence that follows, we welcome your thoughts and invite you to add a Comment to this article to share your own experiences and perspectives.