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Introduction: The epidemiological distribution of extended-spectrum beta-lactamase (ESBL) types in Escherichia coli and Klebsiella pneumoniae was evaluated in various hospitals in Spain and compared with previous studies., Methods: A total of 11 Spanish hospitals participated in this study. Each center collected the first 15 isolates of E. coli and the first 5 of K. pneumoniae suspected of being ESBL-producers and isolated during the first quarter of 2004. Clonal study was done by PFGE after total DNA digestion with XbaI and by ERIC-PCR (Enterobacterial Repetitive Intergenic Consensus Sequences-Polymerase Chain Reaction), typing. ESBL-producers were characterized by isoelectric focusing (IEF), PCR and sequencing., Results: A total of 124 strains were collected. PFGE restriction patterns showed considerable diversity among E. coli strains; 4 clusters of 2 strains each were detected. ESBL characterization of 92 E. coli strains showed a predominance of CTX-M-14 (45.7%), CTX-M-9 (20.6%) and SHV-12 (21.7%). Clonal diversity among the 32 K. pneumoniae strains was less pronounced than in E. coli; 3 clusters included 53.1% of strains. The ESBL detected in these strains included a CTX-M type in 20 cases (62.5%) (CTX-M-1, CTX-M-9, CTX-M-14 and CTX-M-15); a SHV type in 11 (34.4%) (SHV-12 and SHV-5) and TEM-4 (3.1%) in 1 case., Conclusion: The E. coli and K. pneumoniae strains analyzed in this period displayed a greater diversity of ESBL than has been observed in previous epidemiological studies. Analysis of clonal relationships revealed a greater diversity in E. coli than in K. pneumoniae.

Neurons that participate in the olfactory system arise in different areas of the developing mouse telencephalon. The generation of these different cell populations and their tangential migration into the olfactory cortex (OC) was tracked by tracer injection and in toto embryo culture. Cells originating in the dorsal lateral ganglionic eminence (LGE) migrate tangentially along the anteroposterior axis to settle in the piriform cortex (PC). Those originating in the ventral domain of this structure occupy the thickness of the olfactory tubercle (OT), whereas cells from the rostral LGE migrate tangentially into the most anterior telencephalon, at the level of the prospective olfactory bulb (pOB). Neurons from the dorsal telencephalon migrate ventrally, bordering the PC, toward olfactory structures. Two cell populations migrate tangentially from the rostromedial telencephalic wall to the OT and the PC, passing through the ventromedial and dorsolateral face of the telencephalon. Some cells from the germinative area of the rostral telencephalon, at the level of the septoeminential sulcus, migrate rostrally to the pOB or caudally to the OC. Thus, we demonstrate multiple telencephalic origins for the first olfactory neurons and each population following different migratory routes to colonize the OC according to an accurate topographic map.

The first layer that appears in the cortical neuroepithelium, the preplate, forms in the upper part of the cortex immediately below the pial surface. In mice, this layer exists between embryonic days (E) 10 and 13, and it hosts different cell populations. Here, we have studied the first cell population generated in the preplate, the Cajal-Retzius cells. There is considerable confusion regarding these cells with respect to both their site of generation and the migratory routes that they follow. This perhaps is due largely to the different opinions that exist regarding their characterization. We have studied the site of origin of these cells, their migratory routes, and the molecular markers that may distinguish them by injecting tracers into early embryos, culturing them in toto for 24 hours, and then performing immunohistochemistry. We found that the Cajal-Retzius cells are most likely generated in the cortical hem by comparing with other cortical or extracortical origins. These cells are generated mainly at E10 and E11, and they subsequently migrate tangentially to cover the whole cortical mantle in 24 hours. From their site of origin in the medial wall of the telencephalon, they spread in a caudorostral direction, following an oblique migratory path toward the lateral part of the neuroepithelium. Prior to the splitting of the preplate, a percentage of the Cajal-Retzius cells that can be distinguished by the expression of reelin do not contain calretinin. Furthermore, there were no early-migrating neurons that expressed calbindin., (Copyright 2006 Wiley-Liss, Inc.)

We have established previously that, although the olfactory epithelium is absent in the homozygous Pax-6 mutant mouse, an olfactory bulb-like structure (OBLS) does develop. Moreover, this OBLS contains cells that correspond to mitral cells, the primary projection neurons in the olfactory bulb. The current study aimed to address whether the dendrites of mitral cells in the olfactory bulb or in the OBLS mitral-like cells, exhibit a change in orientation in the presence of the olfactory epithelium. The underlying hypothesis is that the olfactory epithelium imparts a trophic signal on mitral and mitral-like cell that influences the growth of their primary dendrites, orientating them toward the surface of the olfactory bulb. Hence, we cultured hemibrains from wild-type and Pax 6 mutant mice from two different embryonic stages (embryonic days 14 and 15) either alone or in coculture with normal olfactory epithelial explants or control tissue (cerebellum). Our results indicate that the final dendritic orientation of mitral and mitral-like cells is directly influenced both by age and indeed by the presence of the olfactory epithelium., (Copyright 2004 Wiley-Liss, Inc.)