Effects of Pt dispersion on electronic and oxide ionic conductivity in Pr1.90Ni0.71Cu0.24Ga0.05O4.

The effects of dispersing Pt particles in bulk Pr1.90Ni0.71Cu0.21Ga0.05O(4+δ) (PNCG) on the electrical conductivity and oxygen permeability of the material were studied. The different thermal expansion coefficients of PNCG and Pt generated a mechanical compressive strain in the PNCG. This may cause the electrical conductivity to decrease in samples containing Pt. In contrast, the oxide ion conductivity estimated from the oxygen permeability increased upon dispersion of Pt. These variations appear to be related to the electron hole and interstitial oxygen concentrations. Moreover, the present study suggests that the mechanical strain induces a chemical strain via the introduction of oxygen defects as well as changes in cation valences.

Adenovirus-mediated overexpression of a gene prevents hearing loss and progressive inner hair cell loss after transient cochlear ischemia in gerbils.

The use of adenoviral vectors has recently provided a novel strategy for direct gene transfer into the cochlea. In this study, we assessed the utility of an adenoviral vector expressing glial-cell-derived neurotrophic factor (GDNF) in ischemia-reperfusion injury of the gerbil cochlea. The vector was injected through the round window 4 days before ischemic insult. The distribution of a reporter transgene was confirmed throughout the cochlea from the basal to the apical turn and Western blot analysis indicated significant upregulation of GDNF protein 11 days following virus inoculation. Hearing ability was assessed by sequentially recording compound action potentials (CAP), and the degree of hair cell loss in the organ of Corti was evaluated in specimens stained with rhodamine-phalloidin and Hoechst 33342. On the seventh day of ischemia, the CAP threshold shift and inner hair cell loss were remarkably suppressed in the Ad-GDNF group compared with the control group. These results suggest that adenovirus-mediated overexpression of GDNF is useful for protection against hair cell damage, which otherwise eventually occurs after transient ischemia of the cochlea.

Hypothermia reduces glutamate efflux in perilymph following transient cochlear ischemia.

The effect of hypothermia on ischemic injury of the cochlea in gerbils was studied with particular regard to glutamate efflux in the perilymph. Under normothermic conditions interruption of the blood supply to the cochlea for 15 min caused a remarkable elevation of the compound action potential (CAP) threshold, and an increase in perilymphatic glutamate. The CAP threshold recovered to some extent with reperfusion, but not to preischemic levels. CAP thresholds, under hypothermic conditions and with reperfusion, recovered promptly to near pre-ischemic levels, while glutamate concentration did not change. These results, together with electron microscopy studies, suggest that hypothermia prevents hearing loss primarily through reduction of glutamate efflux at the synopses between inner hair cells and primary afferent auditory neurons.

The CaMKII UNC-43 activates the MAPKKK NSY-1 to execute a lateral signaling decision required for asymmetric olfactory neuron fates.

A stochastic cell fate decision mediated by axon contact and calcium signaling causes one of the two bilaterally symmetric AWC neurons, either AWCL or AWCR, to express the candidate olfactory receptor str-2. nsy-1 mutants express str-2 in both neurons, disrupting AWC asymmetry. nsy-1 encodes a homolog of the human MAP kinase kinase kinase (MAPKKK) ASK1, an activator of JNK and p38 kinases. Based on genetic epistasis analysis, nsy-1 appears to act downstream of the CaMKII unc-43, and NSY-1 associates with UNC-43, suggesting that UNC-43/CaMKII activates the NSY-1 MAP kinase cassette. Mosaic analysis demonstrates that UNC-43 and NSY-1 act primarily in a cell-autonomous execution step that represses str-2 expression in one AWC cell, downstream of the initial lateral signaling pathway that coordinates the fates of the two cells.

Inhibition of Wnt signaling by ICAT, a novel beta-catenin-interacting protein.

Wnt signaling has an important role in both embryonic development and tumorigenesis. beta-Catenin, a key component of the Wnt signaling pathway, interacts with the TCF/LEF family of transcription factors and activates transcription of Wnt target genes. Here, we identify a novel beta-catenin-interacting protein, ICAT, that was found to inhibit the interaction of beta-catenin with TCF-4 and represses beta-catenin-TCF-4-mediated transactivation. Furthermore, ICAT inhibited Xenopus axis formation by interfering with Wnt signaling. These results suggest that ICAT negatively regulates Wnt signaling via inhibition of the interaction between beta-catenin and TCF and is integral in development and cell proliferation.

Lactate attenuates neuron specific enolase elevation in newborn rats.

This study was undertaken to investigate the protective role of lactate on the hypoxic brain in newborn rats. A total of 107 7-day-old Wistar rats were divided into three groups. The lactate accumulation group was given 5% oxygen and 95% nitrogen for 30 minutes. The lactate elimination group was given 5% oxygen, a concentration of 7.5% carbon dioxide, and 87.5% nitrogen for 30 minutes. The control rats were placed in room air. Lactate levels in the brain tissue were higher in the lactate accumulation group than in those of the control group (control: 1.78 +/- 0.91, lactate accumulation: 11.42 +/- 1.64 mmol/kg) and significantly decreased in the lactate elimination group (4.10 +/- 1.73 mmol/kg). Blood pH remained at the same levels in the two groups. Neuron specific enolase in the cerebrospinal fluid, which is the initial neurocyte damage marker, was significantly elevated in the lactate elimination group (control: 18.3 +/- 7.5, lactate accumulation: 18.8 +/- 7.9, lactate elimination: 63.1 +/- 61.3 ng/mL). Brain adenosine 5'-triphosphate levels were significantly decreased in the lactate elimination group. Histologic findings of the brain at 72 hours after the load revealed no abnormal changes in any of the groups examined. The authors conclude that lactate accumulation plays a protective role on the hypoxic brain in newborn rats.

Nitric oxide modulates premature renal circulation in hypoxic newborn piglets.

We studied the role of nitric oxide (NO) on the regulation of blood flow in the immature kidney during hypoxia, resuscitation and the recovery period using the NO inhibitor N(omega)-nitro-L-arginine (L-NNA) in a newborn piglet model, and the possibility of urinary cGMP as an index of renal function. After administration of L-NNA, the blood flow in both the cortex and medulla significantly decreased, indicating that NO is constantly released to maintain renal circulation. During hypoxia, the renal blood flow fell remarkably, and there were no differences between the control and L-NNA groups. During the post-resuscitation period, the recovery of renal blood flow was significantly suppressed in L-NNA administration, and it was speculated that NO might be an important factor for recovery of circulation from vasoconstriction due to hypoxemia. Urinary cGMP/cr was significantly increased on recovery from hypoxemia and was suppressed by L-NNA administration. This result suggested that the change in cGMP/cr represents renal blood flow change. We conclude that NO may play an important role in maintaining basal hemodynamics, and may also be a crucial factor for recovery from post-hypoxic vasoconstriction in premature kidneys. Urinary cGMP/cr might serve as one of the indices for assessment of premature renal circulation.