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Structural and morphological studies were carried out on cerium- and gadolinium-doped sol−gel silica glasses intended for scintillator applications, to deepen the understanding of rare earth ion incorporation into the glass matrix. Several compositions, ranging from 0 to 5 mol % Ce and from 0 to 8 mol % Gd, were studied by Raman spectroscopy. The vibrational response was compared to that of pure silica glasses:  for cerium doping higher than 0.5 mol %, the F2g Raman mode, characteristic of CeO2, was observed. The presence of CeO2 nanocrystalline clusters, whose size depends on cerium concentration and thermal treatment, was confirmed also by X-ray powder diffraction (XRD) patterns and transmission electron microscopy (TEM) analyses. On the contrary, gadolinium-doped sol−gel silica glasses exhibited Raman spectra similar to those of pure silica glasses, at least for the investigated concentrations up to 8 mol %, and no crystalline particles were detected within the amorphous matrix.

Several alkali germanate glasses of molar composition (100 − x)GeO2·xM2O (M = Na, with 0  x  35, or M = Cs, with 0  x  30) were prepared by melting, and their XPS spectra were recorded and analysed as a function of the alkali content. The simultaneous presence of bridging oxygen (BO) and non-bridging oxygen (NBO) atoms was evaluated in both glass systems. In order to clarify the role of the alkali ions on the formation of NBO species, a series of different alkali germanate glasses were analysed (M = Na, K, Rb, Cs) for a particular glass composition 70GeO2·30M2O. This comparison revealed that the percentage of NBO atoms increased upon insertion of the heavier alkali ions. Some explanations are proposed to account for the ways in which the different alkali ions modify the structure of these germanate glasses, in connection with the so-called germanate anomaly. Copyright © 2002 John Wiley & Sons, Ltd.

A peculiar human cell line (GI-ME-N) derived from the metastatic bone marrow of a 2-yr-old patient with stage IV neuroblastoma (NB) was extensively characterized. Cell-type-specific markers, tumorigenicity in nude mice, morphology, cytogenetics, and amplificationexpression of the N-myc gene were evaluated. All metaphases presented the typical 1p deletion. Surface markers specific for NB cells, vimentin, and neurofilament proteins were all clearly detectable with immunofluorescence andor western blot procedures. Moreover, it was found that GI-ME-N cells did not express N-myc oncogene or HLA class 1 antigens, and were not classified as peripheral neuroectodermal tumor cells. However, extremely short latency and survival times, comparable to peripheral neuroectodermal tumor cells, were observed in nude mice grafted with GI-ME-N. In addition, no correlations were. observed in tumorigenicity of N-myc amplified (IMR32) versusunamplified (SK-N-SH GI-ME-N) human NB cell lines in nude mice. We conclude that N-myc amplification expression do not correlate with the aggressiveness of human NB in athymic animals, which is not always explained by the peripheral neuroectodermal tumor cell nature of the malignant cells, either.

The dipeptidase activity toward L-glutaminyl-L-proline and glycyl-L-proline has been studied in the small intestinal mucosa of human fetuses and newborns between 14 and 36 weeks of fetal age.

Extract: The dipeptidase activity toward L-glutaminyl-L-proline and glycyl-L-proline has been studied in the small intestinal mucosa of human fetuses and newborns between 14 and 36 weeks of fetal age.The small intestine was removed within 15 minutes of death. It was immediately frozen and used for enzymatic studies within 2 to 30 days. The activity of both enzymes was stable for as long a period as three months at a temperature of -20°. Mucosal scrapings were homogenized in 0.01 M Tris-HCl buffer, pH 7, and then centrifuged at 1500 × g for 10 minutes. The supernatant, which contained more than 95% of the enzyme activity, was used for assay; it was incubated in 20 mM substrate, at optimum pH, under conditions permitting calculation of initial velocity. Free proline was measured at the end of the incubation period. By the 14th to 16th week of age, levels of activity of both enzymes were comparable with those of the adult (fig. 1).In order to investigate the distribution of dipeptidase activity, the small bowel from fetuses between 22 and 34 weeks of age was examined. Each sample was homogenized separately before studying. Uniformly high levels of dipeptidase activity were found throughout the proximal six-tenths of the small bowel, while lower values were observed in the terminal ileum (fig. 2). A significant difference in the activity of both enzymes was found between the proximal and the distal third of the small bowel when calculated according to Student's t-test, p < 0.02 (table I). The activity ratios were constant throughout the length of the intestine during the entire age span studied.After centrifugation of the homogenate of intestine at 105,000 × g for one hour, gel filtration on Sephadex G 200 of the supernatant resulted in the partial purification of the enzyme, as indicated by a 4.5- to 6.5-fold increase in specific activity.The enzymes of the crude and the partially purified extracts were studied to determine the influence on enzyme activity of pH, Co++and Mn++ions, heat treatment, substrate concentrations. Co++and Mn++ions clearly activated hydrolysis of glycyl-L-proline, but did not affect that of L-glutaminyl-L-proline. Heating at 40° in a solution of 0.002 M Mn++resulted in an increase of activity of glycyl-L-proline dipeptidase and the nearly complete disappearance of that of L-glutaminyl-L-proline dipeptidase (fig. 5); however, the activity of both enzymes was not separated by gel filtration, ammonium sulphate precipitation, or DEAE cellulose chromatography. Further studies are necessary to determine if a specific enzyme (s) of the small bowel mucosa, other than glycyl-L-proline dipeptidase (EC.3.4.3.7), causes hydrolysis of L-glutaminyl-L-proline.Glycyl-L-proline dipeptidase activity did not change during the age period studied; however, L-glutaminyl-L-proline dipeptidase activity of 14- to 24-week-old fetuses displayed a pH dependence and a kinetic versus substrate concentration not observed in fetuses from 26 to 36 weeks of age (fig.4). These results may suggest that a qualitative change of L-glutaminyl-L-proline dipeptidase had occurred with maturation.Speculation: This study suggests that in the small intestine of the human fetus, L-glutaminyl-L-proline dipeptidase in early stages of life differs qualitatively from that of older fetuses. Further studies on pure enzymes may elucidate the basic mechanism that underlies qualitative changes of some enzyme molecules during growth.

Luminescence and vibrational spectroscopies were used to characterize Gd-enriched phosphate glasses. In particular, the emission spectrum shows, besides the characteristic 3.98 eV band, an additional band at 3.83 eV, assigned to a vibronic transition. To further support this assignment, Raman spectroscopy measurements were carried out to examine the vibrational response of these glasses. A symmetric stretching of a non-bridging oxygen on a Q2 tetrahedron (PO2) was detected at 1190 cm⁻¹, close to the energy separation between the maxima of 3.98 eV and 3.83 eV bands in the emission spectrum. The emission band at 3.83 eV in Gd-enriched phosphate glasses could be thus intepreted as a vibronic band of the 3.98 eV emission of Gd³⁺ due to interaction with the (PO2) stretching mode. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The thermoluminescence properties of Lu3Al5O12:1000 ppm Ce crystals codoped with Zr ions in the range 50–400 ppm have been investigated, both after irradiation at low temperatures (10 K) and at room temperature. The trap depths of glow peaks at around 82, 270 and 352 °C have been evaluated by the “initial rise” method. The role of Zr ions in electron trapping is discussed.