Evidence against AMPA receptor-lacking glutamatergic synapses in the superficial dorsal horn of the rat spinal cord

Pure NMDA receptor (NMDAr)-mediated EPSCs, thought to correspond to "silent" glutamatergic synapses that lack AMPA receptors (AMPArs), have been observed in superficial spinal dorsal horn of neonatal but not adult rats. Recent anatomical studies suggest that AMPArs are present at virtually all glutamatergic synapses in this region in adults. We used antigen retrieval to examine colocalization of AMPArs and PSD-95 (a marker for glutamatergic synapses) in laminae I–II of neonatal and adult rats. We found a high degree of colocalization in all cases, which suggests that AMPArs are present in the great majority of glutamatergic synapses even in neonatal animals. We therefore reexamined evidence for silent synapses by performing blind whole-cell recordings from superficial dorsal horn neurons in slices from neonatal or adult rats, with focal stimulation to activate glutamatergic synapses. On some occasions in both neonatal (10 of 109, 9%) and adult (9 of 77, 12%) slices, NMDAr-mediated EPSCs were observed when the holding potential was raised to +50 mV at a stimulus strength that had failed to evoke AMPAr-mediated EPSCs. However, in all cases tested, AMPAr-mediated EPSCs were then observed when the cell was returned to –70 mV; this and other properties of the EPSCs suggest that they do not represent genuine silent synapses. When compared with previous findings, our results indicate that the appearance of silent synapses depends on experimental protocol. This suggests that pure NMDAr-mediated EPSCs seen in previous studies do not correspond to AMPAr-lacking synapses but result from another mechanism, for example, loss of labile AMPArs from recently formed synapses

Feasibility study of spatial-phase-locked focused-ion-beam lithography

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995.Includes bibliographical references (leaves 66-68).by Anto Yasaka.M.S

Preparation of ZnO-SrO-B2O3 Glass Systems Doped with Dy2O3 for the White Light Emission Material Application

ZnO-SrO-B2O3 glasses doped with Dy3+ ions were prepared by a conventional melt quenching technique. The molar volume density and refractive index tends to increase with increasing of Dy2O3 concentration. The absorption bands show energy levels transition from 6H15/2 ground state to excited states such as 781 nm (6F3/2), 801 nm (6F5/2), 895 nm (6F7/2), 1083 nm (6F9/2), 1254 nm (6F11/2) and 1661 nm (6H11/2), and the intensity of the peak at 1254 nm is the highest. The excitation spectra of the 7 peaks glass sample were found in the wavelength range of 320-470 nm with the highest intensity peak at 386 nm. The emission spectra represent four emission bands, and all emission bands are over the visible range. The peak at 575 nm is the highest intensity peak. The CIE chromaticity (x,y) coordinates fall in the white light region of the CIE chromaticity diagram. The experimental decay time (τexp) of 6H13/2 transition of Dy3+ ions obtained from the measurement tends to increase with increasing of Dy2O3 concentration. These results show the potential for use in white LED applications