A cascade of morphogenic signaling initiated by the meninges controls corpus callosum formation

The corpus callosum is the most prominent commissural connection between the cortical hemispheres, and numerous neurodevelopmental disorders are associated with callosal agenesis. By using mice either with meningeal overgrowth or selective loss of meninges, we have identified a cascade of morphogenic signals initiated by the meninges that regulates corpus callosum development. The meninges produce BMP7, an inhibitor of callosal axon outgrowth. This activity is overcome by the induction of expression of Wnt3 by the callosal pathfinding neurons, which antagonize the inhibitory effects of BMP7. Wnt3 expression in the cingulate callosal pathfinding axons is developmentally regulated by another BMP family member, GDF5, which is produced by the adjacent Cajal-Retzius neurons and turns on before outgrowth of the callosal axons. The effects of GDF5 are in turn under the control of a soluble GDF5 inhibitor, Dan, made by the meninges. Thus, the meninges and medial neocortex use a cascade of signals to regulate corpus callosum development.     

Determination of endotoxin through an aptamer-based impedance biosensor

Lipopolysaccharide (LPS) often referred to endotoxin is an undesirable impurity frequently entrained with various recombinant protein therapeutics and plasmid DNA (pDNA) vaccines of bacterial origin. The inherent toxicities (e.g. fever, hypotension, shock and death) of LPS render its early and sensitive detection essential for several biological assays and/or parenteral administrations of biotherapeutics. In this study, an electrochemical biosensor using an LPS specific single stranded DNA (ssDNA) aptamer as a probe was developed. Amine-terminated aptamer exhibiting high affinity (K(d)=11.9 nM) to LPS was immobilized on a gold electrode using 3-mercaptopropionic acid (MPA) as a linker. Each step of the modification process was characterized by cyclic voltammetry (CV) and electrochemical impendence spectroscopy (EIS). A good linear relationship of the changes in the charge-transfer resistance (ΔR(et)) and the logarithmic value of LPS concentration was demonstrated in a broad dynamic detection range of 0.001-1 ng/ml. Furthermore, the aptasensor showed a high selectivity to LPS despite the presence of pDNA, RNA and bovine serum albumin (BSA) and could be regenerated in low pH condition, offering a promising option for detecting LPS often present in a complex milieu.     

Immobilized cell microchannel bioreactor for evaluating fermentation characteristics of mixed substrate consumption and product formation

An immobilized cell microchannel bioreactor was designed to test continuous fermentation. The fermentation set-up included a bottom hydrophilic quartz channel to immobilize cells using 0.4 wt% polyethyleneimine and a top channel designed to continuously remove metabolically generated carbon dioxide using hydrophobic polypropylene. To evaluate fermentation characteristics of immobilized cells, ethanol fermentation was carried out using Saccharomyces cerevisiae and Pichia stipitis. The immobilized cell microchannel bioreactor was used to identify long-term activity of immobilized S. cerevisiae cells. The continuous flow microchannel bioreactor was operated stably over a period of 1 month. The immobilized cell microchannel bioreactor was used to examine the characteristics cells that consumed mixed substrates. The concentration ratio of glucose to xylose for simultaneous utilization of hemicellulosic sugars was evaluated using the microchannel bioreactor and the results were compared with those obtained by using conventional batch fermentation with P. stipitis.     

Identification of differentially expressed genes from adult cockroach females exhibiting maternal care behavior

Recent challenges in the study of animal behavior are to detect genes related to behavior and how the genes exert their influence on morphological and behavioral plasticity, particularly as related to the mechanism of insect sociability. In this study, we discovered genes related to parental care behavior in social insects. Woodroaches of the genus Cryptocercus provide nutritious materials and symbiotic protists via proctodeal feeding to their young during early developmental stages. Thus, they are a good model species for discovering genes related to parental care behavior. We screened eight differentially expressed genes (DEG1–DEG8) from adult Cryptocercus females exhibiting maternal care behavior. Of the proteins translated from the screened genes, DEG7 showed high homology to apolipophorin-III-like proteins. Analysis of diverse molecular features revealed that DEG7 was a partial clone encoding apoLp-III, which plays essential roles in hemolymph-lipid transport processes in insects. Isolation of full-length cDNAs for the DEGs identified in this study would be very helpful for a functional annotation of the individual genes and further understanding of maternal care behavior at the molecular level in the future.     

Neural model of disinhibitory interactions in the modified Poggendorff illusion

Visual illusions can be strengthened or weakened with the addition of extra visual elements. For example, in the Poggendorff illusion, with an additional bar added, the illusory skew in the perceived angle can be enlarged or reduced. In this paper, we show that a nontrivial interaction between lateral inhibitory processes in the early visual system (i.e., disinhibition) can explain such an enhancement or degradation of the illusory effect. The computational model we derived successfully predicted the perceived angle in the Poggendorff illusion task that was modified to include an extra thick bar. The concept of disinhibition employed in the model is general enough that we expect it can be further extended to account for other classes of geometric illusions.     

Dopamine signalling in mushroom bodies regulates temperature-preference behaviour in Drosophila

The ability to respond to environmental temperature variation is essential for survival in animals. Flies show robust temperature-preference behaviour (TPB) to find optimal temperatures. Recently, we have shown that Drosophila mushroom body (MB) functions as a center controlling TPB. However, neuromodulators that control the TPB in MB remain unknown. To identify the functions of dopamine in TPB, we have conducted various genetic studies in Drosophila. Inhibition of dopamine biosynthesis by genetic mutations or treatment with chemical inhibitors caused flies to prefer temperatures colder than normal. We also found that dopaminergic neurons are involved in TPB regulation, as the targeted inactivation of dopaminergic neurons by expression of a potassium channel (Kir2.1) induced flies with the loss of cold avoidance. Consistently, the mutant flies for dopamine receptor gene (DopR) also showed a cold temperature preference, which was rescued by MB-specific expression of DopR. Based on these results, we concluded that dopamine in MB is a key component in the homeostatic temperature control of Drosophila. The current findings will provide important bases to understand the logic of thermosensation and temperature preference decision in Drosophila.