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Semaphorin-3A (Sema3A), a member of class 3 semaphorins, regulates axon and dendrite guidance in the nervous system. How Sema3A and its receptors plexin-As and neuropilins regulate neuronal guidance is unknown. We observed that in fyn- and cdk5-deficient mice, Sema3A-induced growth cone collapse responses were attenuated compared to their heterologous controls. Cdk5 is associated with plexin-A2 through the active state of Fyn. Sema3A promotes Cdk5 activity through phosphorylation of Tyr15, a phosphorylation site with Fyn. A Cdk5 mutant (Tyr15 to Ala) shows a dominant-negative effect on the Sema3A-induced collapse response. The sema3A gene shows strong interaction with fyn for apical dendrite guidance in the cerebral cortex. We propose a signal transduction pathway in which Fyn and Cdk5 mediate neuronal guidance regulated by Sema3A.

Nickel–yttria-stabilized zirconia (Ni–YSZ) cermet is a conventional anode for use in solid oxide fuel cells, and its composition and microstructure are carefully controlled to achieve high performance and long-term stability. In this study, the performance stability of the electrolyte-supported cell (Ni–YSZ|YSZ|LSM) was examined at 1000°C by feeding humidified fuel, x%normalH2O–(100−x)%normalH2 . The influence of the cermet composition on degradation was also studied. The degradation behavior was significantly dependent on the fuel humidity and cermet composition. In the case of Ni–YSZ with a volume ratio of 50 to 50, peculiar phenomena were observed. When the fuel of 30%normalH2O–70%normalH2 was supplied to the anode at the terminal voltage of 0.7 V, the current density decreased gradually soon after the discharge of up to 69 h, followed by a sudden drop in the current density. After the subsequent open-circuit holding, the performance was partially recovered in the discharge operation. This behavior of the degradation-recovery was reversibly repeated upon the discharge-open-circuit holding operation. Under the 40%normalH2O–60%normalH2 atmosphere, an irreversible performance deterioration was observed accompanied with a drastic decrease in the volume-specific triple-phase boundary (TPB) length. The TPB length of the degraded anode was evaluated to be 1.66–1.68μmμnormalm−3 by a focused ion beam scanning electron microscopy technique, whereas that of the as-prepared anode was 2.49μmμnormalm−3 .

No abstract

Fiber connections of the nucleus ventromedialis thalami (VM) of Schnitzlein (J. Comp. Neurol. 118:225-267, '62) in a teleost (Sebastiscus marmoratus) were examined by means of the horseradish peroxidase (HRP) tracing method. This nucleus receives fibers from the ipsilateral telencephalon (area dorsalis pars centralis), contralateral retina, contralateral VM, ipsilateral optic tectum, ipsilateral torus semicircularis, contralateral corpus cerebelli, contralateral sensory nucleus of the trigeminal nerve, bilateral bulbospinal reticular formation, contralateral obex region, and contralateral dorsal portion of upper spinal segments. In turn, axons arising from VM terminate in the dorsal telencephalic areas (pars centralis, pars dorsalis, and pars medialis) ipsilaterally, ventral telencephalic area (pars supracommissuralis) bilaterally, nucleus prethalamicus of Meader (J. Comp. Neurol. 60:361-407, '34) bilaterally, nucleus dorsomedialis thalami bilaterally, VM contralaterally, optic tectum bilaterally, torus semicircularis bilaterally, and nucleus lateralis valvulae ipsilaterally. Based on the cytoarchitecture and fiber connections, VM is subdivided into rostral and caudal components. The caudal part of VM in Sebastiscus is considered to be a multimodal thalamic complex that contains some cells that constitute the dorsal thalamus in other vertebrate groups.

Material composition and porous structure are important factors in the formation and maturation of newly formed bone and replacement of materials by new bone. Conventional bone graft materials often lack suitability for bone generation because of the complexity of their macroporous structures, which can interfere with the penetration of cells related to bone remodeling and angiogenesis in the materials. In the present study, carbonate apatite (CO3Ap), hydroxyapatite (HAp), and β-tricalcium phosphate (TCP) honeycomb granules (HCGs) with uniformly sized macropores (∼115 μm) were fabricated. These HCG macropores were arranged in a regular fashion and penetrated straight into the granules. They were implanted into a rabbit femur defect for further evaluation. In the CO3Ap HCG implantation group, mature bone formed within CO3Ap HCG macropores by 4 weeks after grafting, and a large portion of CO3Ap HCGs was replaced by new bone at 12 weeks. By contrast, in the β-TCP HCG implantation group, new bone was not always formed in the regions after β-TCP HCG disappearance, and immature bone was present within β-TCP HCG macropores even after 12 weeks. HAp HCGs were not resorbed, and their macropores were filled with immature bone. The area of mature bone in the CO3Ap HCG implantation group was 3.3 and 1.6 times higher at 4 weeks and 2.2 and 1.7 times higher at 12 weeks compared with the HAp and β-TCP HCG implantation groups, respectively. Furthermore, the degrees of bone maturation for CO3Ap, HAp, and β-TCP HCGs were 100, 34, and 64% at 4 weeks, and 100, 54, and 69% at 12 weeks, respectively. Thus, the composition of the HCGs affected bone formation and maturation.

The efferent and afferent pathways of the carp torus longitudinalis were studied by means of degeneration and retrograde HRP methods. Efferent projections were only seen in the most superficial layer of the ipsilateral optic tectum (stratum fibrosum marginale). Afferent pathways to the torus longitudinalis were found to originate mainly in the valvula cerebelli. Degenerating fibers course in the tractus mesencephalocerebellaris posterior within the valvula, and join the tractus mesencephalocerebellaris anterior in the tegmentum. The fibers which ascend in the tract gradually invade the optic tectum through which they are distributed to the torus longitudinalis. The remaining fibers pass through the posterior commissure and terminate in the torus longitudinalis at the rostral end of the tract. Degenerating terminals were also seen in the torus longitudinalis when lesions were made in the optic tectum, tectal commissure, torus semicircularis, and in the area between the valvula and the corpus cerebelli. The possibility of projections from these areas is discussed depending upon the results of the retrograde HRP method.

Reoxidation of a nickel catalyst in anode generally leads to deterioration of cell performance for solid oxide fuel cells ͑SOFCs͒. The aim of this study is to clarify the correlation between microstructural and electrochemical characteristics during reductionoxidation ͑redox͒ cycles of a Ni-yttria-stabilized zirconia ͑YSZ͒ anode. Cell performance was deteriorated after the first redox cycle because of the increase in the polarization resistance of the anode. Ohmic loss of the anode also increased after the thermal cycle in pure oxygen. For the Ni-YSZ anode after the redox cycles, the increase in surface area of the nickel phase was observed by focused ion beam-scanning electron microscopy, which indicated that the nickel particles became finer and more complicated in shape. The lengths of triple phase boundary ͑TPB͒ derived from three-dimensional-reconstructed images of the Ni-YSZ anodes were 2.39 and 2.11 m/m 3 after the first and fourth redox cycles, respectively, which were smaller than that before the redox treatment with a TPB length of 2.49 m/m 3 . Large cracks were produced on the Ni-YSZ anode after the thermal cycle, which led to the increase in the ohmic loss of the anode. The increase in the polarization resistance was caused by the decrease in the length of TPB during the early stage of the redox cycles for the Ni-YSZ anode.Solid oxide fuel cells ͑SOFCs͒ are expected to be power generation systems with high energy conversion efficiency. SOFCs are generally operated at high temperature ϳ973 to 1173 K, which enable to generate power without expensive noble catalysts such as platinum. A cermet of nickel-yttria-stabilized zirconia ͑Ni-YSZ͒ is widely used as an anode of SOFCs. The nickel catalyst demonstrates high activity for electrochemical oxidation of hydrogen and reforming of hydrocarbon fuels. However, the nickel catalyst is deactivated by oxidation at high oxygen partial pressures. For instance, the performance of the Ni-YSZ anode deteriorated with an elapse of time under a high steam content of 40% H 2 O-60% H 2 due to the partial oxidation of nickel catalyst. 1 The nickel catalyst was also oxidized electrochemically under current loading in a fuel shortage condition. 2-4 Furthermore, air leakage from the cathode side to the anode side is anticipated at the crack on the electrolyte or sealant and at the end of the fuel path. 5 The oxidation of nickel causes not only the deactivation of the catalyst but also the change in microstructure. The nickel particle shrinks by reduction from oxide to metal. However, the nickel particle expands irreversibly by reoxidation. It was reported to observe the growth of finer nickel oxide grains on original particles by reoxidation. 6,7 The anomalous dimensional expansion of the Ni-YSZ anode substrate induced the breakage of an electrolyte thin film by tensile stress or anode-supported cells. [8][9][10][11] The effects of microstructural changes of nickel particles by reoxidation on mechanical properties were evaluated by many researchers. However, few studies dealt ...