Síndrome de realimentación en niña con parálisis cerebral / Refeeding syndrome in a girl with cerebral palsy

El síndrome de realimentación es una complicacióngrave y potencialmente mortal asociada a la terapianutricional por vía oral, enteral o parenteral. Afecta apacientes con desnutrición severa o en riesgo de desnutrición, como aquellos con parálisis cerebral infantil. Presentamos el caso de una paciente de ocho añoscon parálisis cerebral que ingresó por hipoglucemiasevera y que, tras iniciar la alimentación enteral porsonda nasogástrica, desarrolló un síndrome de realimentación. En niños con parálisis cerebral es fundamental valorar la presencia de factores de riesgo paradesarrollar un síndrome de realimentación, iniciar laalimentación de manera progresiva y monitorizar losiones séricos.(AU)

Refeeding syndrome is a serious and life-threateningcomplication associated with oral, enteral and parenteral nutritional therapy. It appears in severely malnourished patients or in those at risk of malnutrition,such as persons with cerebral palsy. We present the case of an 8-year-old girl with cerebral palsy who was admitted with severe hypoglycemia.After starting enteral nutrition by nasogastric tube, shedeveloped refeeding syndrome. In children with cere-bral palsy, it is essential to assess the presence of riskfactors for refeeding syndrome before starting any nutritional support, and then start feeding progressivelyand monitor serum electrolytes.(AU)

[Refeeding syndrome in a girl with cerebral palsy].

Refeeding syndrome is a serious and life-threatening complication associated with oral, enteral and parenteral nutritional therapy. It appears in severely malnourished patients or in those at risk of malnutrition, such as persons with cerebral palsy. We present the case of an 8-year-old girl with cerebral palsy who was admitted with severe hypoglycemia. After starting enteral nutrition by nasogastric tube, she developed refeeding syndrome. In children with cerebral palsy, it is essential to assess the presence of risk factors for refeeding syndrome before starting any nutritional support, and then start feeding progressively and monitor serum electrolytes.

Single-Molecule Approaches for the Characterization of Riboswitch Folding Mechanisms.

Riboswitches are highly structured RNA molecules that control genetic expression by altering their structure as a function of metabolite binding. Accumulating evidence suggests that riboswitch structures are highly dynamic and perform conformational exchange between structural states that are important for the outcome of genetic regulation. To understand how ligand binding influences the folding of riboswitches, it is important to monitor in real time the riboswitch folding pathway as a function of experimental conditions. Single-molecule FRET (sm-FRET) is unique among biophysical techniques to study riboswitch conformational changes as it allows to both monitor steady-state populations of riboswitch conformers and associated interconversion dynamics. Since FRET fluorophores can be attached to virtually any nucleotide position, FRET assays can be adapted to monitor specific conformational changes, thus enabling to deduce complex riboswitch folding pathways. Herein, we show how to employ sm-FRET to study the folding pathway of the S-adenosylmethionine (SAM) and how this can be used to understand very specific conformational changes that are at the heart of riboswitch regulation mechanism.

Biological removal of p-cresol, phenol, p-hydroxybenzoate and ammonium using a nitrifying continuous-flow reactor.

Phenolic compounds biodegradation and its effect on the nitrification process were studied. A continuous stirrer tank reactor was operated in four stages, and phenolic compounds were fed as sequential way. In the first stage, at loading rate of 220 mg NH(4)(+)-N/Ld, the consumption efficiency was of 91%, being the product, nitrate. After that, p-cresol was fed at 53 mg C/Ld, reaching removal efficiencies for both substrates higher than 90%. In the third stage, p-hydroxybenzoate was fed at 56 mg C/Ld, and the removal efficiencies for all substrates remained high. In the last stage, the reactor was fed at 54 mg C/Ld of phenol, and it caused a diminishing on the ammonium removal efficiency; however, all phenolic compounds were efficiently removed. Kinetic results showed that the presence of each phenolic compound improved the ammonium oxidizing activity, but the nitrite oxidizing activity was not affected.

[Detection of novel sounds. Multiple manifestations of the same phenomenon?]. / Detección de sonidos nuevos. Existen múltiples manifestaciones de un mismo fenómeno?

INTRODUCTION: Detection of novel sounds must be a basic function of the auditory system, but the underlying neuronal mechanisms are largely unknown. DEVELOPMENT: During repetitive stimulation or a monotonous auditory scene, many auditory neurons show a decrease in their response, presumably due to adaptation. However, these neurons are able to recover and respond again any time there is a change in the stimuli. This process is known as stimulus-specific adaptation (SSA), and could be the basis of the neuronal mechanism for change detection. Neurons showing SSA have been reported both in auditory cortex and subcortical regions, such as the inferior colliculus. Neurons that experience SSA at all levels could be involved in a change detection circuit, but the relationship between neurons in different areas is still unclear. SSA, as found in these neurons, shares a number of characteristics with mismatch negativity (MMN), a component of evoked potentials related to the detection of context novelty, and linked to some processes that involve memory and attention. CONCLUSIONS: The responses to changes in sounds can be observed in multiple ways, ranging from the activity of single neurons to evoked potential recordings. The phenomena observed using these different approaches appear to be manifestations of the same underlying sensory process, which would involve both cortical and subcortical auditory nuclei, and could have its basis in stimulus-specific neuronal adaptation.

Detección de sonidos nuevos. ¿Existen múltiples manifestaciones de un mismo fenómeno? / Detection of novel sounds multiple manifestations of the same phenomenon?

A pesar de que la detección de los sonidos nuevos es una tarea básica del sistema auditivo, todavía sedesconocen en gran medida los procesos neuronales subyacentes. Desarrollo. Durante una estimulación repetitiva o una escena auditiva monótona, muchas neuronas auditivas muestran una reducción de su respuesta, debido a un proceso de adaptación.Este fenómeno, conocido como adaptación específica a los estímulos –stimulus specific adaptation (SSA)–, podría constituir el mecanismo neuronal de la detección de cambios en el entorno acústico. Estudios recientes han descrito la existencia de neuronas que muestran claramente SSA tanto en áreas auditivas corticales como subcorticales (como el colículo inferior) yque podrían formar parte del circuito neuronal de detección de cambios o eventos novedosos. La SSA, como se manifiesta en dichas neuronas, comparte numerosas características con el potencial de disparidad –mismatch negativity (MMN)–, un componentede los potenciales evocados relacionado con la detección de novedad contextual y que puede vincularse a ciertos procesos de memoria y focalización de la atención. A pesar de estos hallazgos, la relación entre SSA y MMN aún no está clara. Conclusiones. Las respuestas neuronales a cambios de sonidos pueden observarse de múltiples formas, desde el registro de neuronas hasta los potenciales evocados. Estas respuestas parecen representar distintas manifestaciones de un mismo procesosensorial subyacente, que involucraría a una serie de áreas auditivas tanto corticales como subcorticales. La base neuronal de este proceso sensorial tendría su origen en alguna forma de adaptación neuronal

Detection of novel sounds must be a basic function of the auditory system, but the underlyingneuronal mechanisms are largely unknown. Development. During repetitive stimulation or a monotonous auditory scene, many auditory neurons show a decrease in their response, presumably due to adaptation. However, these neurons are able to recover and respond again any time there is a change in the stimuli. This process is known as stimulus-specific adaptation (SSA), and could be the basis of the neuronal mechanism for change detection. Neurons showing SSA have been reported bothin auditory cortex and subcortical regions, such as the inferior colliculus. Neurons that experience SSA at all levels could be involved in a change detection circuit, but the relationship between neurons in different areas is still unclear. SSA, as found in these neurons, shares a number of characteristics with mismatch negativity (MMN), a component of evoked potentials relatedto the detection of context novelty, and linked to some processes that involve memory and attention. Conclusions. The responses to changes in sounds can be observed in multiple ways, ranging from the activity of single neurons to evoked potential recordings. The phenomena observed using these different approaches appear to be manifestations of the sameunderlying sensory process, which would involve both cortical and subcortical auditory nuclei, and could have its basis in stimulus-specific neuronal adaptation

Duration selective neurons in the inferior colliculus of the rat: topographic distribution and relation of duration sensitivity to other response properties.

Many animals use duration to help them identify the source and meaning of a sound. Duration-sensitive neurons have been found in the auditory midbrain of mammals and amphibians, where their selectivity seems to correspond to the lengths of species-specific vocalizations. In this study, single neurons in the rat inferior colliculus (IC) were tested for sensitivity to sound duration. About one-half (54%) of the units sampled showed some form of duration selectivity. The majority of these (76%) were long-pass neurons that responded to sounds exceeding some duration threshold (range: 5-60 ms). Band-pass neurons, which only responded to a restricted range of durations, made up 13% of duration-sensitive neurons (best durations: 15-120 ms). Other units displayed short-pass (2%) or mixed (9%) response patterns. The majority of duration-sensitive neurons were localized outside the central nucleus of the IC, especially in the dorsal cortex, where more than one-half of the neurons sampled had long-pass selectivity for duration. Band-pass duration tuned neurons were only found outside the central nucleus. Characteristics of duration-sensitive neurons in the rat support the idea that this filtering arises through an interaction of excitatory and inhibitory inputs that converge in the IC. Band-pass neurons typically responded at sound offset, suggesting that their tuning is created through the same mechanisms that have been described in echolocating bats. The finding that the first-spike latencies of all long-pass neurons were longer than the shortest duration to which they responded supports the idea that they receive transient inhibition before, or simultaneously with, a sustained excitatory input. The ranges of selectivity in rat IC neurons are within the range of durations of rat vocalizations. These data suggest that a population of neurons in the rat IC have evolved to transmit information about behaviorally relevant sound durations using mechanisms that are common to all mammals, with an emphasis on long-pass tuning characteristics.

The inferior colliculus of the rat: a quantitative analysis of monaural frequency response areas.

Frequency response areas (FRAs) were measured for 237 single units in the inferior colliculus (IC) of urethane-anesthetized pigmented rats using monaural pure-tone stimulation. Based on qualitative criteria [J Neurosci 21 (2001) 7303], FRAs were classified as V-shaped in 69% of neurons, non-V-shaped in 29%, and unclassifiable in the remaining 2%. Non-V-shaped FRAs were heterogeneous, comprising a number of subtypes including narrow, closed, low- and high-tilt, multipeaked, U-shaped, mosaic and inhibitory. To complement this subjective classification, we applied quantitative measures used by others (e.g. [J Neurophysiol 84 (2000) 1012]), including the inverse slope of the upper and lower FRA borders, Q-values, and other measures of bandwidth. The results suggest that FRAs in the rat IC are best described as forming a continuous distribution among subtypes, rather than clustering into discrete categories. Moreover, there is a broad range of frequency tuning characteristics and FRA types across the entire frequency spectrum. Within this general pattern, however, there are some frequency-specific differences in FRA type distribution. The relative proportion of V-shaped FRAs was greatest at the high and low ends of the auditory range, with the highest proportion of non-V-shaped FRAs in the mid-range from 6 to 12 kHz. For most neurons with multipeaked FRAs, the peak frequencies were not harmonically related. Frequency tuning in the pigmented rat IC is generally similar to that in other species. Comparison of Q values across auditory nuclei shows little evidence that FRAs are sharpened at levels above the auditory nerve. Rather, there is a broad range of frequency tuning properties at each level.