Embryonic cerebrospinal fluid influence in the subependymal neurogenic niche in adult mouse hippocampus.

The adult mouse hippocampal neurogenic niche is a complex structure which is not completely understood. It has mainly been related to the Subgranular layer of the dentate gyrus; however, as a result of differential neural stem cell populations reported in the subventricular zone of the lateral ventricle and associated with the hippocampus, the possibility remains of a multifocal niche reproducing developmental stages. Here, using a set of molecular markers for neural precursors, we describe in the adult mouse brain hippocampus the existence of a disperse population of neural precursors in the Subependymal Zone, the Dentate Migratory Stream and the hilus; these display dynamic behaviour compatible with neurogenesis. This supports the idea that the adult hippocampal niche cannot be restricted to the dentate gyrus subgranular layer. In other neurogenic niches such as the Subventricular Zone, a functional periventricular dependence has been shown due to the ability to respond to embryonic cerebro-spinal fluid. In this study, we demonstrate that neural precursors from the three areas studied (Sub-ependymal Zone, Dentate Migratory Stream and hilus) are able to modify their behaviour by increasing neurogenesis in a locally differential manner. Our results are compatible with the persistence in the adult mouse hippocampus of a neurogenic niche with the same spatial structure as that seen during development and early postnatal stages.

Neurogenesis: A process ontogenically linked to brain cavities and their content, CSF.

Neurogenesis is the process underlying the development of the highly evolved central nervous system (CNS) in vertebrates. Neurogenesis takes place by differentiation of specific Neural Precursor Cells in the neurogenic niche. The main objective of this review is to highlight the specific relationship between the brain cavities, and neurogenesis from neural precursors. Brain cavities and their content, Cerebrospinal Fluid (CSF), establish a key relation with the neurogenic "niche" because of the presence in this fluid of neurogenic signals able to control neural precursor cell behaviour, inducing precursor proliferation and neuronal differentiation. This influence seems to be ontogenically preserved, despite the temporal and spatial variations that occur throughout life. In order to better understand this concept, we consider three main life periods in the CSF-Neurogenesis interaction: The "Embryonic" period, which take place at the Neural Tube stage and extends from the isolation of the neural tube at the end of "neurulation" to the beginning of Choroid Plexus activity; the "Fetal" period, which includes the remaining developmental and the early postnatal stages; and the "Adult" period, which continues for the rest of adult life. Each period has specific characteristics in respect of CSF synthesis and composition, and the location, extension and neurogenic activity of the neurogenic niche. However, CSF interaction with the neurogenic niche is a common factor, which should be taken into account to better understand the ontogeny of neuron formation and replacement, as well as its potential role in the success or failure of therapies for the ageing, injured or diseased brain.

FGF2/EGF contributes to brain neuroepithelial precursor proliferation and neurogenesis in rat embryos: the involvement of embryonic cerebrospinal fluid.

BACKGROUND: At the earliest stages of brain development, the neuroepithelium works as an interdependent functional entity together with cerebrospinal fluid, which plays a key regulatory role in neuroepithelial cell survival, replication and neurogenesis; however, the underlying mechanism remains unknown in mammals. RESULTS: We show the presence of fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF), in 13.5-day rat embryo cerebrospinal fluid (eCSF). Immunohistochemical detection of FGF2 expression localized this factor inside neuroepithelial precursors close to the neuroepithelial-CSF interface, suggesting that FGF2 from eCSF could originate in the neuroepithelium by apical secretion. The colocalization of FGFR1 and FGF2 in some neuroepithelial cells close to the ventricular surface suggests they are target cells for eCSF FGF2. Brain neuroepithelium EGF expression was negative. By using a neuroepithelial organotypic culture, we demonstrate that FGF2 and EGF from eCSF plays a specific role in triggering the self-renewal and are involved in neurogenetic induction of mesencephalic neuroepithelial precursor cells during rat development. CONCLUSIONS: We propose eCSF as an intercommunication medium for neuroepithelial precursor behavior control during early rat brain development, and the neuroepithelial regulation of FGF2 and EGF presence in eCSF, as a regulative mechanism controlling precursor proliferation and neurogenesis.

Cirugía mínimamente invasiva: implante inmediato con carga inmediata / Minimally invasive surgery: immediate implant with immediate load

El presente trabajo tiene como objetivo el remplazo de piezas dentarias con indicación de extracción por implantes dentales de titanio, con la finalidad de devolver función y estética en forma inmediata respetando los tejidos periodontales y adaptando al máximo la clínica a las necesidades y requerimientos del paciente (AU)

Thermal transport in epitaxial Si1-x Ge x alloy nanowires with varying composition and morphology.

We report on structural, compositional, and thermal characterization of self-assembled in-plane epitaxial Si1-x Ge x alloy nanowires grown by molecular beam epitaxy on Si (001) substrates. The thermal properties were studied by means of scanning thermal microscopy (SThM), while the microstructural characteristics, the spatial distribution of the elemental composition of the alloy nanowires and the sample surface were investigated by transmission electron microscopy and energy dispersive x-ray microanalysis. We provide new insights regarding the morphology of the in-plane nanostructures, their size-dependent gradient chemical composition, and the formation of a 5 nm thick wetting layer on the Si substrate surface. In addition, we directly probe heat transfer between a heated scanning probe sensor and Si1-x Ge x alloy nanowires of different morphological characteristics and we quantify their thermal resistance variations. We correlate the variations of the thermal signal to the dependence of the heat spreading with the cross-sectional geometry of the nanowires using finite element method simulations. With this method we determine the thermal conductivity of the nanowires with values in the range of 2-3 W m-1 K-1. These results provide valuable information in growth processes and show the great capability of the SThM technique in ambient environment for nanoscale thermal studies, otherwise not possible using conventional techniques.

End-tidal desflurane concentration for tracheal extubation in adults. / Concentración al final de la espiración de desflurano requerida para la extubación en el paciente adulto.

OBJECTIVE: To determine the end-tidal desflurane concentration required for tracheal extubation in anaesthetised adults. MATERIAL AND METHODS: After hospital Ethics Committee approval, eighteen ASA I-II adult patients (19-65 years of age), who had been scheduled for elective ambulatory surgery were included in the study. Anaesthesia was induced with propofol 2.5mg.kg-1, fentanyl 2µg.kg-1, and rocuronium 0.6mg.kg-1 for intubation. Maintenance of anaesthesia was provided by desflurane in oxygen and air (40:60), and remifentanil at 0.05-0.25µg.kg-1.min1. Neuromuscular function was monitored with train-of-four (TOF) nerve stimulation and acceleromyography. At the end of the surgery neuromuscular blockade was reversed with sugammadex 2-4mg.kg-1 in accordance with the TOF ratio. The concentration of desflurane at which extubation was attempted was determined by using Dixon's up-and-down method with 0.5% as a step size. Smooth extubation was defined as one without coughing, teeth clenching, gross purposeful movements, and no breath-holding or laryngospasm within 1min of tracheal extubation. RESULTS: It was found that the end-tidal concentration of desflurane was 3.17±0.18% (95% CI: 3%-3.35%) for successful extubation in 50% of adults. CONCLUSION: Extubation in patients receiving desflurane may be feasible at 0.62 minimum alveolar concentration.

Basic interventional radiology in the abdomen. / Intervencionismo básico en abdomen.

This article describes the different basic nonvascular interventional techniques in the abdomen that all general radiologists should be familiar with. It explains the indications and approaches for the different procedures (punctures, biopsies, drainage of collections, cholecystostomies, and nephrostomies). It also discusses the advantages and disadvantages of the different imaging techniques that can be used to guide these procedures (ultrasound, CT, and fluoroscopy) as well as the possible complications that can develop from each procedure. Finally, it shows the importance of following up patients clinically and of taking care of catheters.

Is Microarray Analysis Really Useful and Sufficient to Diagnose Nut Allergy in the Mediterranean Area?

BACKGROUND: Component-based diagnosis on multiplex platforms is widely used in food allergy but its clinical performance has not been evaluated in nut allergy. OBJECTIVE: To assess the diagnostic performance of a commercial protein microarray in the determination of specific IgE (sIgE) in peanut, hazelnut, and walnut allergy. METHODS: sIgE was measured in 36 peanut-allergic, 36 hazelnut-allergic, and 44 walnut-allergic patients by ISAC 112, and subsequently, sIgE against available components was determined by ImmunoCAP in patients with negative ISAC results. ImmunoCAP was also used to measure sIgE to Ara h 9, Cora 8, and Jug r 3 in a subgroup of lipid transfer protein (LTP)-sensitized nut-allergic patients (positive skin prick test to LTP-enriched extract). sIgE levels by ImmunoCAP were compared with ISAC ranges. RESULTS: Most peanut-, hazelnut-, and walnut-allergic patients were sensitized to the corresponding nut LTP (Ara h 9, 66.7%; Cor a 8, 80.5%; Jug r 3, 84% respectively). However, ISAC did not detect sIgE in 33.3% of peanut-allergic patients, 13.9% of hazelnut-allergic patients, or 13.6% of walnut-allergic patients. sIgE determination by ImmunoCAP detected sensitization to Ara h 9, Cor a 8, and Jug r 3 in, respectively, 61.5% of peanut-allergic patients, 60% of hazelnut-allergic patients, and 88.3% of walnut-allergic patients with negative ISAC results. In the subgroup of peach LTP-sensitized patients, Ara h 9 sIgE was detected in more cases by ImmunoCAP than by ISAC (94.4% vs 72.2%, P < .05). Similar rates of Cora 8 and Jug r 3 sensitization were detected by both techniques. CONCLUSIONS: The diagnostic performance of ISAC was adequate for hazelnut and walnut allergy but not for peanut allergy. sIgE sensitivity against Ara h 9 in ISAC needs to be improved.

Estabilidad cardiovascular en la microcirugía laríngea y recuperación postoperatoria precoz: comparación entre remifentanilo-sevoflurano vs. remifentanilo-propofol / Cardiovascular and emergence characteristics between sevofluraneremifentanil and propofol-remifentanil in microlaryngeal surgery

Introducción: La microcirugía laríngea es un proceso de corta duración que se asocia con un importante estímulo adrenérgico y frecuentemente realizada en cirugía de día. Diferentes técnicas anestésicas han sido empleadas para el control hemodinámico. Sin embargo, ningún estudio previo ha comparado la eficacia de la combinación sevoflurano y remifentanilo frente a propofol y remifentanilo en el control de la respuesta hemodinámica y parámetros de recuperación. Material y métodos: 37 pacientes ASA I-III con edades comprendidas entre 23-77 años y programados para microcirugía laríngea fueron incluidos en el estudio. Los pacientes fueron randomizados en dos grupos: grupo S-R (sevoflurano y remifentanilo); grupo P-R (propofol y remifentanilo). La infusión de remifentanilo se ajustó para mantener los valores hemodinámicos alrededor de un 20 % de los valores basales (dosis de 0,2 a 0,6 µg/kg/min). Se registraron los parámetros hemodinámicos cada 3 minutos desde la inducción y durante la inserción del laringoscopio rígido. Se compararon los tiempos de extubación, de orientación y de dolor postoperatorio entre ambos grupos. Resultados: No hubo diferencias entre ambos grupos en los parámetros basales. No hubo diferencias entre ambos grupos en la evolución de los valores hemodinámicos tras la inducción y durante la inserción (..) (AU)

Introduction: Laryngeal microsurgery is a short procedure associated with a huge adrenergic response. Different anaesthetics techniques and drugs have been used to try blunting these haemodynamic changes. No previous investigation has directly compared the combination of sevoflurane and remifentanil with that propofol and remifentanil in laryngeal microsurgery. We aimed to compare the haemodynamic responses and emergence characteristics between this two anaesthetic combinations. Material and methods: 37 patients, ASA status I-III, age 23-77 years, scheduled for elective laryngeal microsurgery were included in the study. They were randomly allocated in two groups: Group S-R (sevoflurane-remifentanil) and group P-R (propofol-remifentanil). Remifentanil infusion was adjusted to maintain haemodynamic values around 20 % of baseline. (From 0.2-0.6 µg.kg-1.min-1). Haemodynamic data were measured every 3 minutes from induction and during insertion of the operating laryngoscope. Extubation times, orientation and pain after surgery were recorded. Results: There were no significant differences during baseline. The haemodynamic parameters were similar between the two groups at induction and during insertion of the operating laryngoscope. Thee were no differences in remifentanil requirements between both groups, and the extubation time was similar. More patients had an Aldrete score of 10 at five minutes after extubation in SR group vs. PR group (100 vs. 67 %, p = 0.018). In PACU a higher (..) (AU)

¿Es necesaria la biopsia de la arteria temporal para el diagnóstico de arteritis de la temporal? / Is temporal artery biopsy necessary for the diagnosis of temporal arteritis?

El eco-Doppler color (ED) se ha empleado en el diagnóstico de la arteritis de la temporal (AT), describiendo un halo hipoecoico perivascular (HHP). El objetivo de este estudio es valorar la utilidad del ED en el diagnóstico de AT. Material y método: Estudio prospectivo en 32 pacientes con sospecha de AT. Se realizó ED evaluando la presencia de HHP. Posteriormente se practicó biopsia de arteria temporal, analizando la presencia de células gigantes multinucleadas. Se compararon los resultados obtenidos, valorando sensibilidad, especificidad, valor predictivo positivo (VPP) y valor predictivo negativo (VPN).Resultados: La presentación clínica fue: 40,6% (13) cefalea, 12,5% (4) clínica visual, 21,9%(7) dolor de la arteria temporal, 9,4% (3) AIT, 15,6% (5) polimialgia, 9,4% (3) claudicación mandibular, y 87,5% (28) elevación de VSG. Se visualizó HHP en el ED en 6 casos (18,8%). El resultado anatomopatológico de AT fue positivo en 3 casos (9,4%). Al comparar los resultados se obtiene una sensibilidad, especificidad, VPP y VPN del 66, 86, 33 y 96%, respectivamente. Conclusión: El ED es una prueba útil en el diagnóstico de AT, dejando la biopsia de la arteria temporal para casos seleccionados (AU)

Duplex ultrasound (DU) has been used in the diagnosis of temporal arteritis (TA), showing a hypoechoic perivascular halo (HPH). The aim of this study is to assess the usefulness of DU in the diagnosis of TA. Materials and method: A prospective study was conducted on 32 patients with suspected TA. DU was performed to detect the presence of HPH. A temporal artery biopsy was subsequently to analyse the presence of multinucleated giant cells. The results were compared by evaluating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Results: The clinical presentation was: 40.6% (13) headache, 12.5% (4) visual clinical signs,21.9% (7) temporal artery pain, 9.4% (3) TIA, 15.6% (5) polymyalgia, 9.4% (3) jaw claudication, and 87.5% (28) elevated ESR.HPH was visualized in the DU in 6 cases (18.8%). The pathology of TA was positive in 3 patients (9.4%). On analysing the results, the sensitivity, specificity, PPV and NPV was 66%, 86%, 33%, and 96%, respectively. Conclusion: DU is a useful screening test in diagnosis of TA, leaving temporal artery biopsy for selected cases (AU)

Probing local strain and composition in Ge nanowires by means of tip-enhanced Raman scattering.

Local strain and Ge content distribution in self-assembled, in-plane Ge/Si nanowires grown by combining molecular beam epitaxy and the metal-catalyst assisted-growth method were investigated by tip-enhanced Raman scattering. We show that this technique is essential to study variations of physical properties of single wires at the nanoscale, a task which cannot be achieved with conventional micro-Raman scattering. As two major findings, we report that (i) the Ge distribution in the (001) crystallographic direction is inhomogeneous, displaying a gradient with a higher Ge content close to the top surface, and (ii) in contrast, the (uncapped) wires exhibit essentially the same small residual compressive strain everywhere along the wire.

Embryonic cerebrospinal fluid activates neurogenesis of neural precursors within the subventricular zone of the adult mouse brain.

INTRODUCTION: There is a nondeveloped neurogenic potential in the adult mammalian brain, which could be the basis for neuroregenerative strategies. Many research efforts have been made to understand the control mechanisms which regulate the transition from a neural precursor to a neuron in the adult brain. Embryonic cerebrospinal fluid (CSF) is a complex fluid which has been shown to play a key role in neural precursor behavior during development, working as a powerful neurogenic inductor. We tested if the neurogenic properties of embryonic CSF are able to increase the neurogenic activity of neuronal precursors from the subventricular zone (SVZ) in the brains of adult mice. RESULTS: Our results show that mouse embryonic CSF significantly increases the neurogenic activity in precursor cells from adult brain SVZ. This intense neurogenic effect was specific for embryonic CSF and was not induced by adult CSF. CONCLUSIONS: Embryonic CSF is a powerful neurogenesis inductor in homologous neuronal precursors in the adult brain. This property of embryonic CSF could be a useful tool in neuroregeneration strategies.

Mascarilla Laríngea Supreme en colecistectomía laparoscópica y cirugía de mama / Supreme laryngeal mask in laparoscopic cholecystectomy and breast surgery

Introducción: la Mascarilla Laríngea Supreme TM (MLS) es un dispositivo supraglótico desechable nuevo, provisto de canal gástrico y con características en el diseño del manguito que permiten presiones de sellado superior a las de la mascarilla laríngea clásica. El objetivo del presente estudio es valorar la eficacia de la MLS en dos procedimientos de cirugía ambulatoria: en la colecistectomía laparoscópica y en la cirugía de mama. Material y métodos: estudio prospectivo, observacional, realizado en 100 pacientes en régimen ambulatorio, programados para colecistectomía laparoscópica y de mama, bajo anestesia general y empleo de la MLS. El objetivo del estudio fue valorar la eficacia y seguridad de la MLS en ambos procedimientos. Resultados: de los 100 pacientes, 65 fueron intervenidos de colecistectomía laparoscópica y 35 de cirugía de mama. La inserción de la MLS fue posible en todos los pacientes y en un 86% de los casos en el primer intento. La presión de sellado media fue de 30,02 ± 1,92 cm de H2O. No se objetivaron efectos adversos durante la ventilación ni con los cambios de posición del paciente. No fue preciso cambiar la MLS por otro dispositivo y ningún paciente requirió intubación orotraqueal. Conclusiones: la MLS es un dispositivo seguro y eficaz en el manejo de la vía aérea en pacientes intervenidos de colecistectomía laparoscópica y cirugía de mama, en régimen ambulatorio (AU)

Introduction: supreme laryngeal mask (MLS) is a new disposable supraglottic device, and gastric channel provided with design features which allow the sleeve sealing pressures higher than those of the classic laryngeal mask. The aim of this study is to assess the effectiveness of the MLS in two ambulatory surgical procedures: in laparoscopic cholecystectomy and breast surgery. Material and methods: prospective, observational study conducted in 100 patients undergoing ambulatory surgery, scheduled laparoscopy cholecystectomy and breast surgery, under general anesthesia with laryngeal mask. The aim of the present study was to evaluate the effectiveness and safety of the MLS in both procedures. Results: one hundred patients were included in the study, laparoscopic cholecystectomy (N = 65) and breast surgery (N = 35). In all patients the insertion of the LMS was accomplished and was inserted at the first attempt in 86% of cases. The average airway sealing pressure was 30.02 ± 1.92 cm H2O. No adverse effects were observed during ventilation or with changes in patient position. There was no need to change the MLS by another device and no patient required intubation. Conclusions: the MLS its safe and effective supraglottic device in the management of the airway in outpatient scheduled laparoscopic cholecystectomy and breast surgery (AU)

¿Es útil el eco-Doppler portátil en el diagnóstico de enfermedad arterial periférica? Estudio de validación / Usefulness of a portable duplex scanning device in the diagnosis of peripheral arterial disease. A validation study

Objetivos: Validar el eco-Doppler portátil (EDP) para el diagnóstico de enfermedad arterial periférica (EAP) y analizar la influencia del tipo de lesión arterial en el resultado. Material y método: Estudio prospectivo: 60 extremidades (45 pacientes), edad media 68 años, 33 hombres/12 mujeres, 30% diabéticos, 37% dislipémicos, 58% hipertensos, 27% cardiópatas. Realizamos un EDP siguiendo las guías de diagnóstico vascular no invasivo del sector femoropoplíteo (8 segmentos), comparándolo con la arteriografía. Clasificamos como estenosis < 50%, > 50% y trombosis. Calculamos sensibilidad (S), especificidad (E), VPP, VPN e índice de acuerdo kappa. Las lesiones arteriales se clasifican en únicas o múltiples y se comparan con el grado de acierto del EDP (test chi cuadrado). Resultados: En el sector supragenicular el índice de acuerdo es bueno para diagnóstico de trombosis (K=0,779, S=86%, E=95%, VPP=79%, VPN=96%) y de estenosis > 50% (K=0,651, S=82%, E=85%, VPP=70% y VPN=92%).En el sector infragenicular el grado de acuerdo es bueno para diagnóstico de trombosis (K=0,610, S=72%, E=87%, VPP=77%, VPN 84%), pero moderado en estenosis > 50% (K=0,472, S=68%, E=78%, VPP=70% y VPN=76%).El EDP identifica correctamente 94% de trombosis en lesiones únicas frente 85% en estenosis múltiples (p=0,008) y 86% de estenosis > 50% en lesiones únicas frente 79% en múltiples (p=0,070). Conclusiones: La sensibilidad, especificidad, VPP y VPN del EDP son buenos en diagnóstico de EAP siendo más sensible para diagnóstico de trombosis que estenosis.- El EDP ofrece mayor fiabilidad en diagnóstico de EAP en sector supragenicular frente al infragenicular.- Las lesiones arteriales múltiples disminuyen la fiabilidad del EDP en el diagnóstico de trombosis(AU)

Objectives: The aim of this study is investigate the agreement between a portable duplex scanner (PDS and angiography in the diagnosis of peripheral arterial disease (PAD) and analyse the influence of the type of lesion on the result. Material and methods: A prospective study was conducted on 60 limbs (45 patients) with a mean age of 68 years, 33 males/12 females, 30% diabetes mellitus, 37% dyslipidaemias, 58% arterial hypertension, and 27% heart diseases. A PDS was made following the guidelines for the non-invasive diagnosis of femoral-popliteal sector (8 segments) and comparing it with the angiography. The stenosis were classified as <50%, and thrombosis as >50%. The sensitivity (Se), specificity (Sp), Positive Predictive Value (PPV), Negative Predictive Value (NPV) and Kappa (K) index of agreement was calculated. The arterial lesions were classified in singles or multiples, and were compared with the level of accuracy of the PDS (chi-squared test). Results: In the above-knee segment, the level of agreement was good for the diagnosis of thrombosis (K=0.779, Sp=86%, Se=95%, PPV=79%, NPV=96%) and stenosis >50% (K=0.651, Se=82%, Se=85%, PPV=70% and NPV=92%).In the below-knee segment, the index of agreement was good for the diagnosis of thrombosis (K=0.610, Sp=72%, Se=87%, PPV=77%, PNV=84%), and moderate in stenosis >50% (K=0.472, Sp=68%, Se=78%, PPV=70% and NPV=76%).The PDS correctly identified 94% of thrombosis in single lesions compared to 85% in the multiple lesions (P=.008) and 86% in stenosis >50% in single lesions compared to 79% in multiple lesions (P=.070)(AU)

Conclusions: The sensitivity, specificity, PPV, NPV and Kappa index are good in the diagnosis of PAD, being more sensitive for the diagnosis of thrombosis than for the diagnosis of stenosis.- The was more reliable for the diagnosis of PAD in above-knee segments than below-knee segments.- Multiple arterial lesions decrease the reliability of PDS in the diagnosis of thrombosis(AU)

Modified Stranski-Krastanov growth in Ge/Si heterostructures via nanostenciled pulsed laser deposition.

The combination of nanostenciling with pulsed laser deposition (PLD) provides a flexible, fast approach for patterning the growth of Ge on Si. Within each stencilled site, the morphological evolution of the Ge structures with deposition follows a modified Stranski-Krastanov (SK) growth mode. By systematically varying the PLD parameters (laser repetition rate and number of pulses) on two different substrate orientations (111 and 100), we have observed corresponding changes in growth morphology, strain and elemental composition using scanning electron microscopy, atomic force microscopy and µ-Raman spectroscopy. The growth behaviour is well predicted within a classical SK scheme, although the Si(100) growth exhibits significant relaxation and ripening with increasing coverage. Other novel aspects of the growth include the increased thickness of the wetting layer and the kinetic control of Si/Ge intermixing via the PLD repetition rate.

Effects of pulsed laser radiation on epitaxial self-assembled Ge quantum dots grown on Si substrates.

Laser irradiation of Ge quantum dots (QDs) grown on Si(100) substrates by solid-source molecular beam epitaxy has been performed using a Nd:YAG laser (532 nm wavelength, 5 ns pulse duration) in a vacuum. The evolution of the Ge QD morphology, strain and composition with the number of laser pulses incident on the same part of the surface, have been studied using atomic force microscopy, scanning electron microscopy and Raman spectroscopy. The observed changes in the topographical and structural properties of the QDs are discussed in terms of Ge-Si diffusion processes. Numerical simulations have been developed for the investigation of the temperature evolution of the QDs during laser irradiation. The obtained results indicate that the thermal behaviour and structural variation of the nanostructures differ from conventional thermal annealing treatments and can be controlled by the laser parameters. Moreover, an unusual island motion has been observed under the action of subsequent laser pulses.

Cerebrospinal fluid control of neurogenesis induced by retinoic acid during early brain development.

Embryonic-cerebrospinal fluid (E-CSF) plays crucial roles in early brain development including the control of neurogenesis. Although FGF2 and lipoproteins present in the E-CSF have previously been shown to be involved in neurogenesis, the main factor triggering this process remains unknown. E-CSF contains all-trans-retinol and retinol-binding protein involved in the synthesis of retinoic acid (RA), a neurogenesis inducer. In early chick embryo brain, only the mesencephalic-rombencephalic isthmus (IsO) is able to synthesize RA. Here we show that in chick embryo brain development: (1) E-CSF helps to control RA synthesis in the IsO by means of the RBP and all-trans-retinol it contains; (2) E-CSF has retinoic acid activity, which suggests it may act as a diffusion pathway for RA; and (3) the influence of E-CSF on embryonic brain neurogenesis is to a large extent due to its involvement in RA synthesis. These data help to understand neurogenesis from neural progenitor cells.

Early embryonic brain development in rats requires the trophic influence of cerebrospinal fluid.

Cerebrospinal fluid has shown itself to be an essential brain component during development. This is particularly evident at the earliest stages of development where a lot of research, performed mainly in chick embryos, supports the evidence that cerebrospinal fluid is involved in different mechanisms controlling brain growth and morphogenesis, by exerting a trophic effect on neuroepithelial precursor cells (NPC) involved in controlling the behaviour of these cells. Despite it being known that cerebrospinal fluid in mammals is directly involved in corticogenesis at fetal stages, the influence of cerebrospinal fluid on the activity of NPC at the earliest stages of brain development has not been demonstrated. Here, using "in vitro" organotypic cultures of rat embryo brain neuroepithelium in order to expose NPC to or deprive them of cerebrospinal fluid, we show that the neuroepithelium needs the trophic influence of cerebrospinal fluid to undergo normal rates of cell survival, replication and neurogenesis, suggesting that NPC are not self-sufficient to induce their normal activity. This data shows that cerebrospinal fluid is an essential component in chick and rat early brain development, suggesting that its influence could be constant in higher vertebrates.

Crystallisation of amorphous germanium thin films.

By combining cross-sectional transmission and scanning electron microscopy with Raman scattering we have investigated the mechanism of nanocrystal formation in ultrathin amorphous SiO2/Ge/SiO2 trilayers grown by e-beam evaporation as a function of annealing temperature and a-Ge layer thickness. We observe that with decreasing a-Ge thickness the amorphous-to-crystalline (a-to-c) transition occurs at considerably higher temperatures, even avoiding crystallisation for very thin films below 2 nm thickness. Furthermore, we demonstrate that the formation of Ge nanocrystals by annealing at around 900 degrees C takes place driven by a liquid-mediated mechanism. As indicated by the observed microstructure, the metallic liquid film dewets from the surface forming droplets that upon cooling and under the influence of the SiO2 capping layer, solidify into barrel-type nanocrystals.

Chondroitin sulphate-mediated fusion of brain neural folds in rat embryos.

Previous studies have demonstrated that during neural fold fusion in different species, an apical extracellular material rich in glycoconjugates is involved. However, the composition and the biological role of this material remain undetermined. In this paper, we show that this extracellular matrix in rat increases notably prior to contact between the neural folds, suggesting the dynamic behaviour of the secretory process. Immunostaining has allowed us to demonstrate that this extracellular matrix contains chondroitin sulphate proteoglycan (CSPG), with a spatio-temporal distribution pattern, suggesting a direct relationship with the process of adhesion. The degree of CSPG involvement in cephalic neural fold fusion in rat embryos was determined by treatment with specific glycosidases.In vitro rat embryo culture and microinjection techniques were employed to carry out selective digestion, with chondroitinase AC, of the CSPG on the apical surface of the neural folds; this was done immediately prior to the bonding of the cephalic neural folds. In all the treated embryos, cephalic defects of neural fold fusion could be detected. These results show that CSPG plays an important role in the fusion of the cephalic neural folds in rat embryos, which implies that this proteoglycan could be involved in cellular recognition and adhesion.