Variation in the cortical area map of C57BL/6J and DBA/2J inbred mice predicts strain identity

BACKGROUND: Recent discoveries suggest that arealization of the mammalian cortical sheet develops in a manner consonant with principles established for embryonic patterning of the body. Signaling centers release morphogens that determine regional growth and tissue identity by regulating regional expression of transcription factors. Research on mouse cortex has identified several candidate morphogens that affect anteroposterior or mediolateral cortical regionalization as well as mitogenesis. Inbred strains of laboratory mice can be exploited to study cortical area map formation if there are significant phenotypic differences with which to correlate gene polymorphism or expression data. Here we describe differences in the cortical area map of two commonly used inbred strains of laboratory mice, C57BL/6J and DBA/2J. Complete cortical hemispheres from adult mice were dissected and stained for the cytochrome oxidase enzyme in order to measure histochemically defined cortical areas. RESULTS: C57BL/6J has the larger neocortex, relatively larger primary visual cortex (V1), but relatively smaller posterior medial barrel subfield of the primary somatosensory cortex (PMBSF). The sample of C57BL/6J and DBA/2J mice can be discriminated with 90% accuracy on the basis of these three size dimensions. CONCLUSION: C57BL/6J and DBA/2J have markedly different cortical area maps, suggesting that inbred strains harbor enough phenotypic variation to encourage a forward genetic approach to understanding cortical development, complementing other approaches

Influence of Incubation Temperature on 9,10-Anthraquinone-2-Sulfonate (AQS)-Mediated Extracellular Electron Transfer

The electron shuttling process has been recognized as an important microbial respiration process. Because the incubation temperature can influence both the reactivity of electron mediators and cell growth, it may also affect the electron-shuttle-mediated extracellular electron transfer (EET) process. Here, the effect of incubation temperature (22–38°C) was investigated in a bioelectrochemical system (BES) using Shewanella oneidensis MR-1 and 50 μM of 9,10-anthraquinone-2-sulfonate (AQS). We found that current generation increased as the temperature was increased from 22 to 34°C and then decreased sharply at 38°C. The biofilm biomass, as indicated by the total protein extracted from the electrode, increased as the temperature increased from 22 to 34°C and then decreased at 38°C, mirroring the current generation results. These results were further confirmed by increasing the temperature slowly, step-by-step, in a single BES with a constant biofilm biomass, suggesting that the EET rates could be substantially influenced by temperature, even with the same biofilm. The effects of temperature on the AQS bioreduction rate, c-type cytochrome (c-Cyts)-bound-cofactor-mediated EET, the AQS mid-point potential, and the AQS diffusion coefficient were studied. From these results, we were able to conclude that temperature influenced the EET rates by changing the c-Cyts-bound-cofactor-mediated EET process and the AQS bioreduction rate, and that the change in biofilm formation was a dominant factor influencing the overall EET rates. These findings should contribute to the fundamental understanding of EET processes. Moreover, optimization of the operating parameters for current generation will be helpful for the practical application of bioelectrochemical techniques

Geometric morphometrics defines shape differences in the cortical area map of C57BL/6J and DBA/2J inbred mice

BACKGROUND: We previously described planar areal differences in adult mouse visual, somatosensory, and neocortex that collectively discriminated C57BL/6J and DBA/2J inbred strain identity. Here we use a novel application of established methods of two-dimensional geometric morphometrics to examine shape differences in the cortical area maps of these inbred strains. RESULTS: We used Procrustes superimposition to align a reliable set of landmarks in the plane of the cortical sheet from tangential sections stained for the cytochrome oxidase enzyme. Procrustes superimposition translates landmark configurations to a common origin, scales them to a common size, and rotates them to minimize an estimate of error. Remaining variation represents shape differences. We compared the variation in shape between C57BL/6J and DBA/2J relative to that within each strain using a permutation test of Goodall's F statistic. Significant differences in shape in the posterior medial barrel subfield (PMBSF), as well as differences in shape across primary sensory areas, characterize the cortical area maps of these common inbred, isogenic strains. CONCLUSION: C57BL/6J and DBA/2J have markedly different cortical area maps, in both size and shape. These differences suggest polymorphism in genetic factors underlying cortical specification, even between common isogenic strains. Comparing cortical phenotypes between normally varying inbred mice or between genetically modified mice can identify genetic contributions to cortical specification. Geometric morphometric analysis of shape represents an additional quantitative tool for the study of cortical development, regardless of whether it is studied from phenotype to gene or gene to phenotype

Exogenous Electron Shuttle-Mediated Extracellular Electron Transfer of <i>Shewanella putrefaciens</i> 200: Electrochemical Parameters and Thermodynamics

Despite the importance of exogenous electron shuttles (ESs) in extracellular electron transfer (EET), a lack of understanding of the key properties of ESs is a concern given their different influences on EET processes. Here, the ES-mediated EET capacity of <i>Shewanella putrefaciens</i> 200 (SP200) was evaluated by examining the electricity generated in a microbial fuel cell. The results indicated that all the ESs substantially accelerated the current generation compared to only SP200. The current and polarization parameters were linearly correlated with both the standard redox potential (<i>E</i>_ES⁰) and the electron accepting capacity (EAC) of the ESs. A thermodynamic analysis of the electron transfer from the electron donor to the electrode suggested that the EET from <i>c</i>-type cytochromes (<i>c</i>-Cyts) to ESs is a crucial step causing the differences in EET capacities among various ESs. Based on the derived equations, both <i>E</i>_ES⁰ and EAC can quantitatively determine potential losses (Δ<i>E</i>) that reflect the potential loss of the ES-mediated EET. In situ spectral kinetic analysis of ES reduction by <i>c</i>-Cyts in a living SP200 suspension was first investigated with the <i>E</i>_ES, <i>E</i>_{<i>c</i>‑Cyt}, and Δ<i>E</i> values being calculated. This study can provide a comprehensive understanding of the role of ESs in EET

Biological and chemical processes of microbially mediated nitrate-reducing Fe(II) oxidation by Pseudogulbenkiania sp strain 2002

In the microbially mediated nitrate-reducing Fe(II) oxidation system, it is recognized that chemical oxidation of Fe(II) by nitrite, which is a bioreduction intermediate of nitrate, can occur under anoxic conditions (chemo-denitrification), but it is still difficult to quantitatively evaluate the contributions of biological Fe(II) oxidation and chemodenitrification. Here, nitrate reduction coupled with Fe(II) oxidation by a suggested lithoautotro phic nitrate-reducing Fe(II)-oxidizing bacterium, Pseudogulbenkiania sp. strain 2002, was investigated in PIPES buffered medium without any organic cosubstrate through reaction kinetics, nitrogen isotope fractionation, and secondary mineral characterization. Substantial Fe(II) oxidation was observed in the presence of cells and nitrate, and nitrite (0.59 mM) was able to quickly oxidize Fe(II). Stored carbon in strain 2002 harvested during pre-incubation can serve as carbon source for nitrate reduction. Furthermore, the N isotopic composition (delta N-15) of N2O in Cell + NO3- + Fe(II) was much more negative than those in Cell + NO3-/ NO2-, Cell + NO2- + Fe (II), and NO2- + Fe(II), implying that Fe(II) affects N fractionation associated with the reduction of nitrate to nitrite. Goethite was formed in Fe(II)+ NO2-, while lepidocrocite was the main mineral phase in Cell + Fe(II) + NO3-. The morphology and cell-mineral interactions determined by electron microscopy showed that secondary minerals were formed outside of cells in Cell + NO2- + Fe(II), while cell encrustation was observed in the periplasmic space of cells in Cell + NO3- + Fe(II). The secondary minerals present in the different treatments further illustrated the co-occurrence of biological, chemical, and coupling processes in the microbially mediated nitrate-reducing Fe(II) oxidation system. This study highlights the involvements of the biological Fe(II) oxidation and chemical Fe(II) oxidation by nitrite in microbially mediated nitrate-reducing Fe(II) oxidation