Heterogeneity in the accessory olfactory system

The mammalian accessory olfactory bulb (AOB) is chemoarchitecturally heterogeneous in that it stains differentially with a number of markers; the receptor cells that project to the AOB are similarly heterogeneous. What is the significance of this heterogeneity? We have found that the AOB of the gray, short-tailed opossum, Monodelphis domestica, stains differentially with a number of 'markers': antibodies to olfactory marker protein (OMP) and the alpha subunit of the G protein Gi2, the lectin of Vicia villosa and NADPH-diaphorase. These markers stain the rostral AOB more strongly than the caudal AOB whereas, the G protein subunit G(o) alpha is located predominantly in the posterior subdivision of the AOB. This heterogeneity in the chemoarchitecture of the AOB may reflect a fundamental organizational dichotomy within the vomeronasal system that corresponds to a functional dichotomy. The vomeronasal sensory epithelium also exhibits a chemoarchitectural heterogeneity: receptor cells in the basal third are G(o) alpha-immunoreactive whereas the cells in the middle third are Gi2 alpha-immunoreactive. Tracing studies using WGA-HRP demonstrate that the neurons in the middle third of the vomeronasal sensory epithelium project their axons to the anterior AOB whereas those in the basal third appear to project to the posterior AOB.      

The Minds of the West: Ethnocultural Evolution in the Rural Middle West, 1830-1917

The Minds of the West: Ethnocultural Evolution in the Rural Middle West, 1830-1917. Jon Gjerde. Chapel Hill: University of North Carolina Press, 1997. 426 pp.     

A new subclass of nucleoporins that functionally interact with nuclear pore protein NSP1.

NSP1 is a nuclear pore protein (nucleoporin) essential for cell growth. To identify the components that functionally interact with NSP1 in the living cell, we developed a genetic screen for mutants that are lethal in a genetic background of mutated, but not wild type NSP1. Fourteen synthetic lethal mutants were obtained, belonging to at least four different complementation groups. The genes of two complementation groups, NSP116 and NSP49, were cloned. Like the previously described nucleoporins, these genes encode proteins with many repeat sequences. NSP116 and NSP49, however, contain a new repetitive sequence motif 'GLFG', which classifies them as a subclass of nucleoporins. NSP116 and NSP49, tagged with the IgG binding domain of protein A and expressed in yeast, are located at the nuclear envelope. These data provide in vivo evidence that distinct subclasses of nucleoporins physically interact or share overlapping function in nuclear pore complexes.     

Mating behaviour in the endangered Sonoran topminnow: speciation in action

Two species of the endangered Sonoran topminnow, Poeciliopsis occidentalis and P. sonoriensis, occur in two isolated drainage systems in southeast Arizona, U.S.A., and are allopatric throughout their range. Although these two taxa are morphologically very similar, and have been previously described as the same species or subspecies, several molecular studies have since indicated that they differ more than their morphology suggests. To determine whether the behaviours of the two species function as premating barriers to reproduction, we investigated their mating preferences and behavioural patterns in a laboratory setting. Results from no-choice mating observations showed that the mating behaviours of the two species differ. Observations conducted during multiple-choice mating trials provided evidence of assortative mating, suggesting an early stage of premating reproductive isolation.