Scaling-Up Microwave-Assisted Synthesis of Highly Defective Pd@UiO-66-NH2 Catalysts for Selective Olefin Hydrogenation under Ambient Conditions

The need to develop green and cost-effective industrial catalytic processes has led to growing interest in preparing more robust, efficient, and selective heterogeneous catalysts at a large scale. In this regard, microwave-assisted synthesis is a fast method for fabricating heterogeneous catalysts (including metal oxides, zeolites, metal-organic frameworks, and supported metal nanoparticles) with enhanced catalytic properties, enabling synthesis scale-up. Herein, the synthesis of nanosized UiO-66-NH2 was optimized via a microwave-assisted hydrothermal method to obtain defective matrices essential for the stabilization of metal nanoparticles, promoting catalytically active sites for hydrogenation reactions (760 kg·m-3·day-1 space time yield, STY). Then, this protocol was scaled up in a multimodal microwave reactor, reaching 86% yield (ca. 1 g, 1450 kg·m-3·day-1 STY) in only 30 min. Afterward, Pd nanoparticles were formed in situ decorating the nanoMOF by an effective and fast microwave-assisted hydrothermal method, resulting in the formation of Pd@UiO-66-NH2 composites. Both the localization and oxidation states of Pd nanoparticles (NPs) in the MOF were achieved using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively. The optimal composite, loaded with 1.7 wt % Pd, exhibited an extraordinary catalytic activity (>95% yield, 100% selectivity) under mild conditions (1 bar H2, 25 °C, 1 h reaction time), not only in the selective hydrogenation of a variety of single alkenes (1-hexene, 1-octene, 1-tridecene, cyclohexene, and tetraphenyl ethylene) but also in the conversion of a complex mixture of alkenes (i.e., 1-hexene, 1-tridecene, and anethole). The results showed a powerful interaction and synergy between the active phase (Pd NPs) and the catalytic porous scaffold (UiO-66-NH2), which are essential for the selectivity and recyclability.

An electroencephalogram microdisplay to visualize neuronal activity on the brain surface

Functional mapping during brain surgery is applied to define brain areas that control critical functions and cannot be removed. Currently, these procedures rely on verbal interactions between the neurosurgeon and electrophysiologist, which can be time-consuming. In addition, the electrode grids that are used to measure brain activity and to identify the boundaries of pathological versus functional brain regions have low resolution and limited conformity to the brain surface. Here, we present the development of an intracranial electroencephalogram (iEEG)-microdisplay that consists of freestanding arrays of 2048 GaN light-emitting diodes laminated on the back of micro-electrocorticography electrode grids. With a series of proof-of-concept experiments in rats and pigs, we demonstrate that these iEEG-microdisplays allowed us to perform real-time iEEG recordings and display cortical activities by spatially corresponding light patterns on the surface of the brain in the surgical field. Furthermore, iEEG-microdisplays allowed us to identify and display cortical landmarks and pathological activities from rat and pig models. Using a dual-color iEEG-microdisplay, we demonstrated coregistration of the functional cortical boundaries with one color and displayed the evolution of electrical potentials associated with epileptiform activity with another color. The iEEG-microdisplay holds promise to facilitate monitoring of pathological brain activity in clinical settings.

Simultaneous removal of brominated and chlorinated species during the production of oils by e-waste plastics catalytic hydropyrolysis

The production of added-value chemicals via pyrolysis of plastic wastes, such as those from electrical and electronic equipment (WEEE), needs addressing their usual contamination with halogens (mainly Br and Cl). This work compares the conversion via pyrolysis and hydropyrolysis of a real WEEE plastic, having a complex composition, in two different reactor configurations: down-flow (DF) and up-flow (UF). Likewise, the effects of incorporating a Pd/Al2O3 catalyst and using two different pressures (1 and 6 bar) have been assessed. With the DF mode, pyrolysis at 1 bar leads to an oil yield above 80 wt% and a total halogen content of about 600 ppm (vs 1600 ppm in the water-washed WEEE plastic). Under DF catalytic hydropyrolysis at 6 bar, this high oil yield is maintained while its dehalogenation degree is improved (142 ppm). Operating with the up-flow configuration, under 6 bar and H2 presence, leads to some reduction in the oil yield (about 70 wt%) but significantly decreases the oil halogen content (55 ppm Cl and total elimination of Br). These results have been related to the slower pyrolysis and longer residence time in the thermal zone of the UF configuration, which favours the halogen-trapping effect of the char fraction, and the pressure-enhanced hydrodehalogenation activity of the catalyst. This study highlights the environmental benefits of the proposed process, emphasizing the lower halogen content in the resulting oils and promoting a more sustainable approach to plastic waste valorisation.

The Brain Electroencephalogram Microdisplay for Precision Neurosurgery

Brain surgeries are among the most delicate clinical procedures and must be performed with the most technologically robust and advanced tools. When such surgical procedures are performed in functionally critical regions of the brain, functional mapping is applied as a standard practice that involves direct coordinated interactions between the neurosurgeon and the clinical neurology electrophysiology team. However, information flow during these interactions is commonly verbal as well as time consuming which in turn increases the duration and cost of the surgery, possibly compromising the patient outcomes. Additionally, the grids that measure brain activity and identify the boundaries of pathological versus functional brain regions suffer from low resolution (3-10 mm contact to contact spacing) with limited conformity to the brain surface. Here, we introduce a brain intracranial electroencephalogram microdisplay (Brain-iEEG-microdisplay) which conforms to the brain to measure the brain activity and display changes in near real-time (40 Hz refresh rate) on the surface of the brain in the surgical field. We used scalable engineered gallium nitride (GaN) substrates with 6" diameter to fabricate, encapsulate, and release free-standing arrays of up to 2048 GaN light emitting diodes (μLEDs) in polyimide substrates. We then laminated the μLED arrays on the back of micro-electrocorticography (μECoG) platinum nanorod grids (PtNRGrids) and developed hardware and software to perform near real-time intracranial EEG analysis and activation of light patterns that correspond to specific cortical activities. Using the Brain-iEEG-microdisplay, we precisely ideFSntified and displayed important cortical landmarks and pharmacologically induced pathological activities. In the rat model, we identified and displayed individual cortical columns corresponding to individual whiskers and the near real-time evolution of epileptic discharges. In the pig animal model, we demonstrated near real-time mapping and display of cortical functional boundaries using somatosensory evoked potentials (SSEP) and display of responses to direct electrical stimulation (DES) from the surface or within the brain tissue. Using a dual-color Brain-iEEG-microdisplay, we demonstrated co-registration of the functional cortical boundaries with one color and displayed the evolution of electrical potentials associated with epileptiform activity with another color. The Brain-iEEG-microdisplay holds the promise of increasing the efficiency of diagnosis and possibly surgical treatment, thereby reducing the cost and improving patient outcomes which would mark a major advancement in neurosurgery. These advances can also be translated to broader applications in neuro-oncology and neurophysiology.

Removal of NO at low concentration from air in urban built environments by activated miscanthus biochar

This work presents an innovative and sustainable approach to remove NO emissions from urban ambient air in confined areas (underground parking areas or tunnels) using low-cost activated carbons obtained from Miscanthus biochar (MSP700) by physical activation (with CO₂ or steam) at temperatures ranging from 800 to 900 °C. The NO removal capacity of the activated biochars was evaluated under different conditions (temperature, humidity and oxygen concentration) and compared against a commercial activated carbon. This last material showed a clear dependence on oxygen concentration and temperature, exhibiting a maximum capacity of 72.6% in air at 20 °C, whilst, its capacity notably decreased at higher temperatures, revealing that physical NO adsorption is the limiting step for the commercial sample that presents limited oxygen surface functionalities. In contrast, MSP700-activated biochars reached nearly complete NO removal (99.9%) at all tested temperatures in air ambient. Those MSP700-derived carbons only required low oxygen concentration (4 vol%) in the gas stream to achieve the full NO removal at 20 °C. Moreover, they also showed an excellent performance in the presence of H₂O, reaching NO removal higher than 96%. This remarkable activity results from the abundance of basic oxygenated surface groups, which act as active sites for NO/O₂ adsorption, along with the presence of a homogeneous microporosity of 6 Å, which enables intimate contact between NO and O₂. These features promote the oxidation of NO to NO₂, which is further retained over the carbon surface. Therefore, the activated biochars studied here could be considered promising materials for the efficient removal of NO at low concentrations from air at moderate temperatures, thus closely approaching real-life conditions in confined spaces.

Removal of NO at low concentrations from polluted air in semi-closed environments by activated biochars from renewables feedstocks

Efficient measures are urgently required in large cities for nitric oxide (NO) elimination from air in urban semi-closed environments (parking lots and tunnels), characterized by low NO concentrations (<10 ppmv) and temperatures. One of the most promising abatement alternatives is the NO oxidation to NO₂, which can be further easily captured in an alkali solution or over a porous solid. However, most of the research devoted to this topic is focused on the elimination of NO from fuel exhaust gases, with high NO concentrations (400-2000 ppmv). In this work, sustainable and low-cost activated biochars of different origin and having very different ash contents were employed in NO removal at very low concentrations. Thus, low ash content forestry (oak woodchips, OAK) and high ash content from agriculture (oilseed rape straw, OSR) biochars were subjected to physical activation with CO₂ at 900 °C (OAK550-A900CO₂ and OSR700-A900CO₂, respectively). The NO removal performance tests of such activated carbons were carried out at different experimental conditions: i.e., temperature, relative humidity (0-50 vol% RH), NO-containing gas (N₂ or air), amount of activated carbon, and NO concentration, to assess how the activated biochar properties influence their NO removal capacity. The sample OSR700-A900CO₂ contained a higher population of oxygen surface functionalities, which might play an important role in the NO removal efficiency in dry conditions since they could assist NO oxidation on carbon active sites when used above room temperature (50-75 °C). However, at room temperature (25 °C), the presence of narrow micropore size distribution at 6 Å became a more relevant property, since it facilitates an intimate contact between NO and O₂. Accordingly, the activated biochar from OAK was much more efficient, achieving complete removal of NO from air flow (dry or with 50 vol% RH) at 25 °C during 400 min of testing, making it an ideal candidate as biofilter for purifying air streams of semi-closed spaces contaminated with low concentrations of NO.

Determining the Role of Fe-Doping on Promoting the Thermochemical Energy Storage Performance of (Mn1- x Fex )3 O4 Spinels

Mn oxides are promising materials for thermochemical heat store, but slow reoxidation of Mn₃ O₄ to Mn₂ O₃ limits efficiency. In contrast, (Mn_{1- x} Fe_x )₃ O₄ oxides show an enhanced transformation rate, but fundamental understanding of the role played by Fe cations is lacking. Here, nanoscale characterization of Fe-doped Mn oxides is performed to elucidate how Fe incorporation influences solid-state transformations. X-ray diffraction reveals the presence of two distinct spinel phases, cubic jacobsite and tetragonal hausmannite for samples with more than 10% of Fe. Chemical mapping exposes wide variation of Fe content between grains, but an even distribution within crystallites. Due to the similarities of spinels structures, high-resolution scanning transmission electron microscopy cannot discriminate unambiguously between them, but Fe-enriched crystallites likely correspond to jacobsite. In situ X-ray absorption spectroscopy confirms that increasing Fe content up to 20% boosts the reoxidation rate, leading to the transformation of Mn²⁺  in the spinel phase to Mn³⁺ in bixbyite. Extended X-ray absorption fine structure shows that FeO length is larger than MnO, but both electron energy loss spectroscopy and X-ray absorption near edge structure indicate that iron is always present as Fe³⁺  in octahedral sites. These structural modifications may facilitate ionic diffusion during bixbyite formation.

Scaling-Up of Bio-Oil Upgrading during Biomass Pyrolysis over ZrO2 /ZSM-5-Attapulgite

Ex situ catalytic biomass pyrolysis was investigated at both laboratory and bench scale by using a zeolite ZSM-5-based catalyst for selectively upgrading the bio-oil vapors. The catalyst consisted of nanocrystalline ZSM-5, modified by incorporation of ZrO₂ and agglomerated with attapulgite (ZrO₂ /n-ZSM-5-ATP). Characterization of this material by means of different techniques, including CO₂ and NH₃ temperature-programmed desorption (TPD), NMR spectroscopy, UV/Vis microspectroscopy, and fluorescence microscopy, showed that it possessed the right combination of accessibility and acid-base properties for promoting the conversion of the bulky molecules formed by lignocellulose pyrolysis and their subsequent deoxygenation to upgraded liquid organic fractions (bio-oil). The results obtained at the laboratory scale by varying the catalyst-to-biomass ratio (C/B) indicated that the ZrO₂ /n-ZSM-5-ATP catalyst was more efficient for bio-oil deoxygenation than the parent zeolite n-ZSM-5, producing upgraded bio-oils with better combinations of mass and energy yields with respect to the oxygen content. The excellent performance of the ZrO₂ /n-ZSM-5-ATP system was confirmed by working with a continuous bench-scale plant. The scale-up of the process, even with different raw biomasses as the feedstock, reaction conditions, and operation modes, was in line with the laboratory-scale results, leading to deoxygenation degrees of approximately 60 % with energy yields of approximately 70 % with respect to those of the thermal bio-oil.

Transitando hacia el ejercicio de autonomía y liderazgo: … «para el posicionamiento hay que luchar»

Introducción: En Chile, las enfermeras/os tienen respaldo legal para gestionar el cuidado, esto facilita el desarrollo de competencias para ejercer autonomía y liderazgo. Actualmente persisten barreras para transitar hacia un reconocimiento real de la independencia profesional. Objetivo: Develar la experiencia vivida de enfermeras con cargos en niveles de jefatura respecto al propio desarrollo para lograr el liderazgo y autonomía profesional. Metodología: Estudio cualitativo descriptivo-interpretativo, desde la trayectoria fenomenológica de Edmund Husserl. Muestreo selectivo de caso homogéneo de tres enfermeras que desempeñaban rol de jefatura en instituciones de salud, región Valparaíso, Chile. Participación consentida. Entrevista no estructurada. Análisis del discurso utilizando el modelo de liderazgo integral de Ken Wilber. Resultados: Categorías: Conciencia del líder «ser inquieta...intelectualmente». Construyendo competencias «el liderazgo se aprende». Transitando hacia el ejercicio de la autonomía y el liderazgo, “para el posicionamiento hay que luchar”. El peso de las estructuras organizacionales «tu rol es parte de un hospital». Interpretación: El eEjercicio del liderazgo y la autonomía se fundamenta en competencias actitudinales por sobre las cognitivas y técnicas. Existe mayor apoyo y reconocimiento a nivel institucional, que al interior del equipo de salud. Persisten limitaciones para lograr máxima expresión del liderazgo y autonomía, por persistencia de modelos institucionales hegemónicos, centrados en decisiones médicas y desconocimiento del rol integrado. Conclusión: El líder se mueve en un escenario dual, entre un menor reconocimiento del equipo y un creciente empoderamiento del rol autónomo y visibilidad a nivel directivo institucional.

The crucial role of clay binders in the performance of ZSM-5 based materials for biomass catalytic pyrolysis

The effect of agglomerating ZrO₂/n-ZSM-5 catalyst with different clays on biomass catalytic pyrolysis is evaluated.

From 3D to 2D zeolite catalytic materials

Research activities and recent developments in the area of three-dimensional zeolites and their two-dimensional analogues are reviewed. Zeolites are the most important industrial heterogeneous catalysts with numerous applications. However, they suffer from limited pore sizes not allowing penetration of sterically demanding molecules to their channel systems and to active sites. We briefly highlight here the synthesis, properties and catalytic potential of three-dimensional zeolites followed by a discussion of hierarchical zeolites combining micro- and mesoporosity. The final part is devoted to two-dimensional analogues developed recently. Novel bottom-up and top-down synthetic approaches for two-dimensional zeolites, their properties, and catalytic performances are thoroughly discussed in this review.

Revisiting the BaO2/BaO redox cycle for solar thermochemical energy storage

The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.

Assessing biomass catalytic pyrolysis in terms of deoxygenation pathways and energy yields for the efficient production of advanced biofuels

The present work systematically studies the effect of the operation conditions of biomass catalytic pyrolysis on parameters like bio-oil oxygen content and mass yield, but also on additional indicators, such as the distribution of oxygen and chemical energy among the products.

Transition Metal Phosphide Nanoparticles Supported on SBA-15 as Highly Selective Hydrodeoxygenation Catalysts for the Production of Advanced Biofuels

A series of catalysts constituted by nanoparticles of transition metal (M = Fe, Co, Ni and Mo) phosphides (TMP) dispersed on SBA-15 were synthesized by reduction of the corresponding metal phosphate precursors previously impregnated on the mesostructured support. All the samples contained a metal-loading of 20 wt% and with an initial M/P mole ratio of 1, and they were characterized by X-ray diffraction (XRD), N2 sorption, H2-TPR and transmission electron microscopy (TEM). Metal phosphide nanocatalysts were tested in a high pressure continuous flow reactor for the hydrodeoxygenation (HDO) of a methyl ester blend containing methyl oleate (C17H33-COO-CH3) as main component (70%). This mixture constitutes a convenient surrogate of triglycerides present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes. The results of the catalytic assays indicate that Ni2P/SBA-15 catalyst presents the highest ester conversion, whereas the transformation rate is about 20% lower for MoP/SBA-15. In contrast, catalysts based on Fe and Co phosphides show a rather limited activity. Hydrocarbon distribution in the liquid product suggests that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the different catalysts, although MoP/SBA-15 possess a selectivity towards hydrodeoxygenation exceeding 90%. Accordingly, the catalyst based on MoP affords the highest yield of n-octadecane, which is the preferred product in terms of carbon atom economy. Subsequently, in order to conjugate the advantages of both Ni and Mo phosphides, a series of catalysts containing variable proportions of both metals were prepared. The obtained results reveal that the mixed phosphides catalysts present a catalytic behavior intermediate between those of the monometallic phosphides. Accordingly, only marginal enhancement of the yield of n-octadecane is obtained for the catalysts with a Mo/Ni ratio of 3. Nevertheless, owing to this high selectivity for hydrodeoxygenation MoP/SBA-15 appears as a very promising catalyst for the production of advanced biofuels.

[Latent tuberculosis infection screening in healthcare workers in four large hospitals in Santiago, Chile]

BACKGROUND

It is currently unknown which is the prevalence of latent tuberculosis infection in healthcare workers in Chile, but this group has been described as at higher risk of developing active tuberculosis than general population.

OBJECTIVES

To determine the prevalence of latent tuberculosis infection in a sample of healthcare workers from at risk areas.

METHODOLOGY

A cross-sectional, descriptive study, conducted in health care workers from clinical laboratories or respiratory care areas in four hospitals in Santiago. Latent tuberculosis infection detection was determined by Quantiferon® TB Gold In Tube testing (QFT).

RESULTS

QFT resulted positive in 20 of 76 (26.3%) of the individuals tested. Test positivity reached 62.5% among the personnel that reported history of past TB contact in the community, 50% among the personnel who belonged to the national tuberculosis control program and 38% among those doing induced sputum, acid fast smear or mycobacterial cultures. The proportion of individuals with positive QFT was significantly lower in those personnel who had no such risk factors (15.7%, p = 0.03). The proportion of latent tuberculosis infection also increased in direct relation to the age of the subject.

CONCLUSION

Latent tuberculosis infection as detected by QFT testing was highly prevalent in healthcare workers included in the present study. Further exploring the limitations and possible scenarios for this new diagnostic tool is needed, with emphasis on health personnel at higher-risk and younger individuals.

Improving the Thermochemical Energy Storage Performance of the Mn2 O3 /Mn3 O4 Redox Couple by the Incorporation of Iron

Redox cycles of manganese oxides (Mn2 O3 /Mn3 O4 ) are a promising alternative for thermochemical heat storage systems coupled to concentrated solar power plants as manganese oxides are abundant and inexpensive materials. Although their cyclability for such a purpose has been proved, sintering processes, related to the high-temperature conditions at which charge-discharge cycles are performed, generally cause a cycle-to-cycle decrease in the oxidation rate of Mn3 O4 . To guarantee proper operation, both reactions should present stable reaction rates. In this study, it has been demonstrated that the incorporation of Fe, which is also an abundant material, into the manganese oxides improves the redox performance of this system by increasing the heat storage density, narrowing the redox thermal hysteresis, and, above all, stabilizing and enhancing the oxidation rate over long-term operation, which counteracts the negative effects caused by sintering, although its presence is not avoided.

Synthesis strategies in the search for hierarchical zeolites

Great interest has arisen in the past years in the development of hierarchical zeolites, having at least two levels of porosities. Hierarchical zeolites show an enhanced accessibility, leading to improved catalytic activity in reactions suffering from steric and/or diffusional limitations. Moreover, the secondary porosity offers an ideal space for the deposition of additional active phases and for functionalization with organic moieties. However, the secondary surface represents a discontinuity of the crystalline framework, with a low connectivity and a high concentration of silanols. Consequently, hierarchical zeolites exhibit a less "zeolitic behaviour" than conventional ones in terms of acidity, hydrophobic/hydrophilic character, confinement effects, shape-selectivity and hydrothermal stability. Nevertheless, this secondary surface is far from being amorphous, which provides hierarchical zeolites with a set of novel features. A wide variety of innovative strategies have been developed for generating a secondary porosity in zeolites. In the present review, the different synthetic routes leading to hierarchical zeolites have been classified into five categories: removal of framework atoms, surfactant-assisted procedures, hard-templating, zeolitization of preformed solids and organosilane-based methods. Significant advances have been achieved recently in several of these alternatives. These include desilication, due to its versatility, dual templating with polyquaternary ammonium surfactants and framework reorganization by treatment with surfactant-containing basic solutions. In the last two cases, the materials so prepared show both mesoscopic ordering and zeolitic lattice planes. Likewise, interesting results have been obtained with the incorporation of different types of organosilanes into the zeolite crystallization gels, taking advantage of their high affinity for silicate and aluminosilicate species. Crystallization of organofunctionalized species favours the formation of organic-inorganic composites that, upon calcination, are transformed into hierarchical zeolites. However, in spite of this impressive progress in novel strategies for the preparation of hierarchical zeolites, significant challenges are still ahead. The overall one is the development of methods that are versatile in terms of zeolite structures and compositions, capable of tuning the secondary porosity properties, and being scaled up in a cost-effective way. Recent works have demonstrated that it is possible to scale-up easily the synthesis of hierarchical zeolites by desilication. Economic aspects may become a significant bottleneck for the commercial application of hierarchical zeolites since most of the synthesis strategies so far developed imply the use of more expensive procedures and reagents compared to conventional zeolites. Nevertheless, the use of hierarchical zeolites as efficient catalysts for the production of high value-added compounds could greatly compensate these increased manufacturing costs.

Pneumocystis colonization in older adults and diagnostic yield of single versus paired noninvasive respiratory sampling

The presence of Pneumocystis was assessed in oropharyngeal wash specimens from 110 adults (median age, 76 years; age range, 69-95 years), 66 of whom had a paired nasal swab specimen. Pneumocystis jirovecii DNA was detected in 12.8% of oropharyngeal wash specimens, and the frequency increased to 21.5% in paired specimens. Pneumocystis colonization is prevalent in older adults. Double noninvasive sampling increases the diagnostic yield.

Preparation of bimodal micro–mesoporous TiO2with tailored crystalline properties

A new mild crystallization procedure has been applied after a synthesis route in the presence of a non-ionic surfactant, leading to the preparation of bimodal micro-mesoporous TiO2, with remarkable textural properties and pore walls formed by anatase nanocrystals, which exhibit photocatalytic activity.

Routes of entry of Piscirickettsia salmonis in rainbow trout Oncorhynchus mykiss

Since 1989, Piscirickettsia salmonis, the causal agent of piscirickettsiosis, has killed millions of farmed salmonids each year in southern Chile. The portal of entry for the pathogen was investigated by use of selected experimental infections in juvenile rainbow trout (12 g). The methods used were intraperitoneal injection, subcutaneous injection, patch contact on skin, patch contact on gills, intestinal intubation and gastric intubation. Cumulative mortalities at Day 33 post-inoculation were 98, 100, 52, 24, 24, and 2%, respectively. It was shown that intact skin and gills could be penetrated by P. salmonis. The high mortality obtained in subcutaneously injected fish indicated that skin injuries could facilitate the invasion of this pathogen. Results suggested that the main entry sites are through the skin and gills and that the oral route may not be the normal method by which P. salmonis initiates infection of salmonids.

Bilateral alterations in local cerebral glucose utilization following intranigral application of the GABAergic agonist muscimol

Rates of cerebral glucose utilization were measured by means of the autoradiographic 2-deoxy-D-[1-14C] glucose technique in 70 anatomically discrete central nervous structures in conscious awake rats following unilateral intranigral application of the GABAergic agonist muscimol. Intranigral injection of 1.3 microliters 1 microM muscimol (0.15 ng) induced increases in glucose consumption locally in the substantia nigra reticulata (by 87%), distally in the contralateral reticulata, red nucleus, nucleus accumbens, and prefrontal cortex, and bilaterally in the pyriform cortex, as compared to values in control animals. Intranigral injection of 1.3 microliters 1 mM muscimol (150 ng) effected a local metabolic activation in the substantia nigra reticulata (by 111% compared to the control group) and in compacta (by 18%), as well as a distal activation in the contralateral reticulata (by 39%) and contralateral compacta (by 29%). Beyond the structures affected by the lower dose, the higher dose of muscimol elicited widespread bilateral increases in glucose metabolism in the rat brain. Among the principal nigral reticulata efferent projections, the deep superior colliculi displayed ipsilateral metabolic activation (by 30%), whereas the parafascicular, mediodorsal, and ventromedial thalamic projecting areas, as well as the pedunculopontine nucleus, displayed bilateral activations compared to the control animals. The ventromedial and ventrolateral thalamic nuclei contralateral to the injected substantia nigra reticulata were 20% activated compared to the ipsilateral homologous structures and 30% activated compared to the control rats. The areas that send afferent projections to the reticulata (globus pallidus, entopeduncular and subthalamic nuclei) were mainly activated contralateral to the injected reticulata compared to values for control animals. In general, following intranigral muscimol (1 mM) injection, glucose metabolism was activated to a larger extent on the side contralateral to the injection than on the ipsilateral side. It is suggested that the present findings are due to a presynaptic nigral effect of muscimol on the GABAergic autoreceptors of the striatonigral terminals and to a consequent disinhibition of the reticulata GABAergic output.

Deoxyglucose analysis of the specific topographic functional interrelations between substantia nigra and globus pallidus

The response of the ipsilateral globus pallidus (GP) to unilateral electrical stimulation of the substantia nigra reticulata (SNr) was studied in the rat, by the autoradiographic [14C]-deoxyglucose method. Different compartments within the GP were metabolically activated, depending on the localization of the electrically stimulated subregions within the SNr. Computer generated, quantified colour coded glucograms were used for the analysis of specific topographic organization of the pallido-nigral functional system. Stimulation of the medial or lateral segments within the SNr induced activation in the medial or lateral compartments of the GP, respectively. Stimulation of the dorsal or ventral subregions within the SNr elicited activation in the ventral or dorsal compartments of the GP, respectively. Activation of the medial or lateral GP compartments was independent of stimulation in the dorsal or ventral SNr segments and vice versa. These results suggest that the topographic interrelations between the substantia nigra and the globus pallidus are characterized by preservation of the mediolateral and inversion of the dorsoventral functional correspondence. The neuronal territory involved into this topographic organization is suggested to consist of the subthalamic and striatal nerve cells projecting collateral axons to both the SNr and the GP.