Exogenous microglia pass through the blood-brain barrier and migrate to ischemic hippocampal lesions when injected into the circulation. We investigated the effect of exogenous microglia on ischemic CA1 pyramidal neurons. Microglia were isolated from neonatal mixed brain cultures, labeled with the fluorescent dye PKH26, and injected into the subclavian artery of Mongolian gerbils subjected to ischemia reperfusion neuronal injury. PKH26-labeled microglia migrated to the ischemic hippocampal lesion, resulting in increased numbers of surviving neurons compared with control animals, even when injected 24 h after ischemia. Interferon-c stimulation of isolated microglia enhanced the neuroprotective effect. Administration of exogenous microglia resulted in normal performance in a passive avoidance-learning task. Additionally, administration of exogenous microglia increased the expression of brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor in the ischemic hippocampus, and thus might have induced neurotrophin-dependent protective activity in damaged neurons. Peripherally injected microglia exhibited a specific affinity for ischemic brain lesions, and protected against ischemic neuronal injury in vivo. It is possible that administration of exogenous microglia can be developed as a potential candidate therapy for central nervous system repair after transitory global ischemia.

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Crystal structures are reported for the following complexes [Fe 3 O(OOCCMe 3 ) 6 (py) 3 ]ClO 4 ‚0.5py, 1; [Mn 3 O-(OOCCMe 3 ) 6 (py) 3 ]ClO 4 ‚MeCN, 2; [Mn 3 O(OOCCMe 3 ) 6 (py) 3 ], 4; [Fe 3 O(OOCCMe 3 ) 6 (py) 3 ], 5. Crystal data are as follows: 1, system monoclinic, space group P2 1 /n, a ) 11.658(5) Å, b ) 35.450(5) Å, c ) 14.084(5) Å, β )In 1 and 2, the triangular metal ion clusters are close to equilateral geometry, but the coordination polyhedra of the metal ions are significantly different. Those of the fully oxidized triiron(III) cluster are close to the ideal tetragonal symmetry. Those of the trimanganese(III) cluster show strong Jahn-Teller distortions, the four Mn-carboxylate bonds defining a long and a short O-Mn-O axis and these axes around the three Mn centers being correlated so as to define an approximate 3-fold screw axis for the whole cluster. In the mixed-valence trimanganese complex 4 the coordination implies localized valence states close to (2Mn 3+ + Mn 2+ ) but in the triiron complex 5 the bond distances are close to those expected for a partially averaged state (2Fe 2.5+ + Fe 3+ ). Mo ¨ssbauer spectra of the mixed-valence iron complex indicate a phase transition to a localized (2Fe 3+ + Fe 2+ ) state below T ) 96 K. In the high-temperature phase, IR spectra support a model in which the electron transfer takes place between two adjacent iron centers at a rate which remains lower than that of the infrared time scale up to room temperature.

An interesting temperature dependence of the valence state was observed in the Mössbauer spectra of the mixed-valence salts of 1′,1'″-dialkylbiferrocenes, measured at various temperatures from 4.2 K to 300 K. A mechanistic consideration of the temperature dependence has been carried out assuming a conformational change of the monocation salts induced both by the variation in the temperature and by the kind of counter anion.

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A mixed-valence trinuclear iron cyanoacetate complex, [Fe(3)O(O(2)CCH(2)CN)(6)(H(2)O)(3)] (1), was prepared, and the nature of the electron-detrapping phase transition was studied by a multitemperature single-crystal X-ray structure determination (296, 135, and 100 K) and calorimetry by comparison with an isostructural mixed-metal complex, [CoFe(2)O(O(2)CCH(2)CN)(6)(H(2)O)(3)] (2). The mixed-valence states at various temperatures were also determined by (57)Fe Mössbauer spectroscopy. The Mössbauer spectrum of 1 showed a valence-detrapped state at room temperature. With decreasing temperature the spectrum was abruptly transformed into a valence-trapped state around 129 K, well corresponding to the heat-capacity anomaly due to the phase transition (T(trs) = 128.2 K) observed in the calorimetry. The single-crystal X-ray structure determination revealed that 1 has an equilateral structure at 296 and 135 K, and that the structure changes into an isosceles one at 100 K due to the electron trapping. The crystal system of 1 at 296 K is rhombohedral, space group R&thremacr; with Z = 6 and a = 20.026(1) Å, c = 12.292(2) Å; at 135 K, a = 19.965(3) Å, c = 12.145(4) Å; and at 100 K, the crystal system changes into triclinic system, space group P&onemacr;, with Z = 2 and a = 12.094(2) Å, b = 12.182(3) Å, c = 12.208(3) Å, alpha = 110.04(2) degrees, beta = 108.71(2) degrees, gamma = 109.59(2) degrees. The X-ray structure determination at 100 K suggests that the electronically trapped phase of 1 at low temperature is an antiferroelectrically ordered phase, because the distorted Fe(3)O molecules, which are expected to possess a nonzero electronic dipole moment, oriented alternatively in the opposite direction with respect to the center of symmetry. On the other hand, no heat-capacity anomaly was observed in 2 between 7 and 300 K, and X-ray structure determination indicated that 2 shows no structure change when the temperature is decreased from 296 K down to 102 K. The crystal system of 2 at 296 K is rhombohedral, space group R&thremacr; with Z = 6 and a = 19.999(1) Å, c = 12.259(1) Å; at 102 K, a = 19.915(2) Å, c = 12.061(1) Å. Even at 102 K the CoFe(2)O complex still has a C(3) axis, and the three metal ion sites are crystallographically equivalent because of a static positional disorder of two Fe(III) ions and one Co(II) ion. The activation energy of intramolecular electron transfer of 1 in the high-temperature disordered phase was estimated to be 3.99 kJ mol(-)(1) from the temperature dependence of the Mössbauer spectra with the aid of the spectral simulation including the relaxation effect of intramolecular electron transfer. Finally the phase-transition mechanism of 1 was discussed in connection with the intermolecular dielectric interaction.

The operative microscope-integrated ICG video angiography as a new intraoperative method for detecting vascular flow, was found to be quick, reliable, cost-effective and possibly a substitute or adjunct for Doppler ultrasonography or intraoperative DSA, which is presently the gold standard. The simplicity of the method, the speed with which the investigation can be performed, the quality of the images, and the outcome of surgical procedures have all reduced the need for angiography. This technique may be useful during routine aneurysm surgery as an independent form of angiography and/or as an adjunct to intraoperative or postoperative DSA.