Hypoxia ameliorates brain hyperoxia and NAD+ deficiency in a murine model of Leigh syndrome.

Leigh syndrome is a severe mitochondrial neurodegenerative disease with no effective treatment. In the Ndufs4-/- mouse model of Leigh syndrome, continuously breathing 11% O2 (hypoxia) prevents neurodegeneration and leads to a dramatic extension (~5-fold) in lifespan. We investigated the effect of hypoxia on the brain metabolism of Ndufs4-/- mice by studying blood gas tensions and metabolite levels in simultaneously sampled arterial and cerebral internal jugular venous (IJV) blood. Relatively healthy Ndufs4-/- and wildtype (WT) mice breathing air until postnatal age ~38 d were compared to Ndufs4-/- and WT mice breathing air until ~38 days old followed by 4-weeks of breathing 11% O2. Compared to WT control mice, Ndufs4-/- mice breathing air have reduced brain O2 consumption as evidenced by an elevated partial pressure of O2 in IJV blood (PijvO2) despite a normal PO2 in arterial blood, and higher lactate/pyruvate (L/P) ratios in IJV plasma revealed by metabolic profiling. In Ndufs4-/- mice, hypoxia treatment normalized the cerebral venous PijvO2 and L/P ratios, and decreased levels of nicotinate in IJV plasma. Brain concentrations of nicotinamide adenine dinucleotide (NAD+) were lower in Ndufs4-/- mice breathing air than in WT mice, but preserved at WT levels with hypoxia treatment. Although mild hypoxia (17% O2) has been shown to be an ineffective therapy for Ndufs4-/- mice, we find that when combined with nicotinic acid supplementation it provides a modest improvement in neurodegeneration and lifespan. Therapies targeting both brain hyperoxia and NAD+ deficiency may hold promise for treating Leigh syndrome.

Respiratory deficiency in yeast mevalonate kinase deficient may explain MKD-associate metabolic disorder in humans.

Mevalonate kinase deficiency (MKD) an orphan drug rare disease affecting humans with different clinical presentations, is still lacking information about its pathogenesis; no animal or cell model mimicking the genetic defect, mutations at MVK gene, and its consequences on the mevalonate pathway is available. Trying to clarify the effects of MVK gene impairment on the mevalonate pathway we used a yeast model, the erg12-d mutant strain Saccharomyces cerevisiae (orthologous of MKV) retaining only 10% of mevalonate kinase (MK) activity, to describe the effects of reduced MK activity on the mevalonate pathway. Since shortage of isoprenoids has been described in MKD, we checked this observation using a physiologic approach: while normally growing on glucose, erg12-d showed growth deficiency in glycerol, a respirable carbon source, that was not rescued by supplementation with non-sterol isoprenoids, such as farnesol, geraniol nor geranylgeraniol, produced by the mevalonate pathway. Erg12-d whole genome expression analysis revealed specific downregulation of RSF2 gene encoding general transcription factor for respiratory genes, explaining the absence of growth on glycerol. Moreover, we observed the upregulation of genes involved in sulphur amino acids biosynthesis that coincided with the increasing in the amount of proteins containing sulfhydryl groups; upregulation of ubiquinone biosynthesis genes was also detected. Our findings demonstrated that the shortage of isoprenoids is not the main mechanism involved in the respiratory deficit and mitochondrial malfunctioning of MK-defective cells, while the scarcity of ubiquinone plays an important role, as already observed in MKD patients.

Atrofia muscular espinal y fracaso respiratorio. ¿Cómo actúan los pediatras de atención primaria en un escenario simulado? / Spinal muscular atrophy and respiratory failure. How do primary care pediatricians act in a simulated scenario?

Introducción: La atrofia muscular espinal tipo 1 (AME-1) suele ser mortal en el primer año de vida sin soporte ventilatorio. La decisión de iniciar dicho soporte o no supone un conflicto ético para los profesionales sanitarios. Material y métodos: Se incluyó un escenario de fracaso respiratorio agudo en un lactante con AME-1 en un programa de formación mediante simulación avanzada para pediatras de atención primaria (PAP). Se analizaron de forma sistemática las actuaciones de 34 grupos de 4 pediatras que participaron en 17 cursos. Se valoraron los aspectos clínicos, éticos y de comunicación con los padres. Resultados: La asistencia técnica inicial (administración de oxígeno y soporte ventilatorio inmediato) fue realizada correctamente por el 94% de los equipos. Sin embargo, los PAP tuvieron problemas al abordar los aspectos éticos del caso. Del 85% de los equipos que plantearon el conflicto ético a los padres, lo hizo por iniciativa propia el 29%, el 23% los excluyó de forma activa y solo el 6% los implicaron y tuvieron en cuenta su opinión en la toma de decisiones. Solo el 11,7% preguntó por la calidad de vida del niño y el 12% por su conocimiento del pronóstico de la enfermedad. Ninguno les explicó las alternativas de tratamiento ni trató de contactar con el pediatra de referencia. Conclusiones: Ante un caso simulado de AME-1, los PAP tienen dificultades para interactuar con la familia e implicarla en la toma de decisiones. La formación práctica de todos los pediatras debería incluir problemas de ética clínica (AU)

Introduction: Spinal muscular atrophy type 1 (SMA-1) tends to be fatal in the first year of life if there is no ventilatory support. The decision whether to start such support is an ethical conflict for healthcare professionals. Material and methods: A scenario of acute respiratory failure in an infant with SMA-1 has been included in a training program using advanced simulation for Primary Care pediatricians (PCP). The performances of 34 groups of 4 pediatricians, who participated in 17 courses, were systematically analyzed. Clinical, ethical and communication aspects with parents were evaluated. Results: The initial technical assistance (Administration of oxygen and immediate ventilatory support) was correctly performed by 94% of the teams. However, the PCP had problems in dealing with the ethical aspects of the case. Of the 85% of the teams that raised the ethical conflict with parents, 29% did so on their own initiative, 23% actively excluded them, and only 6% involved them and took their opinion into account in making decisions. Only 11.7% asked about the quality of life of children and 12% for their knowledge of the prognosis of the disease. None explained treatment alternatives, nor tried to contact the pediatrician responsible for the child. Conclusions: When faced with a simulated SMA-1 infant with respiratory failure, PCP have difficulties in interacting with the family, and to involve it in the decision making process. Practical training of all pediatricians should include case scenarios with an ethical clinical problema (AU)

Evaluación de la capacidad cardiorrespiratoria en niños de edad preescolar: adaptación del test de 20m de ida y vuelta / Assessment of cardiorspiratory fitness in preschool children: adaptation of the 20 metres shuttle run test

La capacidad cardiorrespiratoria es un potente indicador de salud presente y futura en niños y adolescentes, sin embargo se desconoce si también lo es para niños de edad reescolar, de 3 a 5 años. En el presente estudio, describimos la adaptación a preescolares del test original de 20m de ida y vuelta, su viabilidad y asimilación en niños de 3 a 5 años, así como su maximalidad y fiabilidad. Un total de 130 alumnos (4,91 ± 0,89 años; 77 niños), realizaron el test dos veces, con dos semanas de separación. La adaptación del test consistió principalmente en reducir la velocidad inicial de 8,5 km/h a 6,5 km/h. El test fue viable y tuvo una buena asimilación tanto en niños como en niñas y en los tres grupos de edad, 3, 4 y 5 años. La frecuencia cardíaca máxima (FCmáx) alcanzada para la muestra completa fue de 199,4 ± 12,5 latidos/minuto, equivalente a un 97% de la FCmáx teórica estimada, y sin diferencias significativas por sexo o edad. La diferencia de medias test-retest (error sistemático) en el número de vueltas alcanzado fue de 2 vueltas, sin diferencias por sexo o edad. No hubo evidencia de heterocedasticidad. Nuestros resultados sugieren que el test es máximo y fiable en este grupo de edad. Futuros estudios de intervención o longitudinales que utilicen este test deberían tener en cuenta que cambios en el rendimiento en el test de 2 vueltas podrían deberse a la propia variabilidad de la medida, mientras que cambios de mayor magnitud podrían ser atribuibles a la intervención o cambios asociados a la edad (AU)

Cardiorespiratory fitness is a strong indicator of present and future health in children and adolescents, however it is unknown whether it is for pre-schoolers, from 3 to 5 years. In the present study, we described the adaptation of the original 20m shuttle run test, it feasibility and acceptance in children from 3 to 5 years and its maximality and reliability. A total of 130 students (4.91 ± 0.89 years; 77 boys) performed the test twice, two weeks apart. The test adaptation consisted mainly in reducing the initial speed of 8.5 km/h to 6.5 km/h. The test was feasible and was well accepted in both boys and girls and the three age groups, 3, 4 and 5 years. The maximum heart rate (MHR) achieved for the entire sample was 199.4 ± 12.5 beats/min, equivalent to 97% of the estimated theoretical MHR, and no significant differences by gender or age. Mean test-retest difference (systematic error) in the number of laps achieved was 2 laps, with no significant differences between sex or age. There was no evidence of heteroscedasticity. Our results suggest the test is maximum and reliable in this age group. Future longitudinal or intervention studies using this test should take into account that changes in the test performance of 2 laps may be due to the variability of the measure, while wider changes would be attributable to the intervention or changes associated with age (AU)

Coenzyme Q supplementation or over-expression of the yeast Coq8 putative kinase stabilizes multi-subunit Coq polypeptide complexes in yeast coq null mutants.

Coenzyme Q biosynthesis in yeast requires a multi-subunit Coq polypeptide complex. Deletion of any one of the COQ genes leads to respiratory deficiency and decreased levels of the Coq4, Coq6, Coq7, and Coq9 polypeptides, suggesting that their association in a high molecular mass complex is required for stability. Over-expression of the putative Coq8 kinase in certain coq null mutants restores steady-state levels of the sensitive Coq polypeptides and promotes the synthesis of late-stage Q-intermediates. Here we show that over-expression of Coq8 in yeast coq null mutants profoundly affects the association of several of the Coq polypeptides in high molecular mass complexes, as assayed by separation of digitonin extracts of mitochondria by two-dimensional blue-native/SDS PAGE. The Coq4 polypeptide persists at high molecular mass with over-expression of Coq8 in coq3, coq5, coq6, coq7, coq9, and coq10 mutants, indicating that Coq4 is a central organizer of the Coq complex. Supplementation with exogenous Q6 increased the steady-state levels of Coq4, Coq7, and Coq9, and several other mitochondrial polypeptides in select coq null mutants, and also promoted the formation of late-stage Q-intermediates. Q supplementation may stabilize this complex by interacting with one or more of the Coq polypeptides. The stabilizing effects of exogenously added Q6 or over-expression of Coq8 depend on Coq1 and Coq2 production of a polyisoprenyl intermediate. Based on the observed interdependence of the Coq polypeptides, the effect of exogenous Q6, and the requirement for an endogenously produced polyisoprenyl intermediate, we propose a new model for the Q-biosynthetic complex, termed the CoQ-synthome.

Acid sensing ion channel 1 in lateral hypothalamus contributes to breathing control.

Acid-sensing ion channels (ASICs) are present in neurons and may contribute to chemoreception. Among six subunits of ASICs, ASIC1 is mainly expressed in the central nervous system. Recently, multiple sites in the brain including the lateral hypothalamus (LH) have been found to be sensitive to extracellular acidification. Since LH contains orexin neurons and innervates the medulla respiratory center, we hypothesize that ASIC1 is expressed on the orexin neuron and contributes to acid-induced increase in respiratory drive. To test this hypothesis, we used double immunofluorescence to determine whether ASIC1 is expressed on orexin neurons in the LH, and assessed integrated phrenic nerve discharge (iPND) in intact rats in response to acidification of the LH. We found that ASIC1 was co-localized with orexinA in the LH. Microinjection of acidified artificial cerebrospinal fluid increased the amplitude of iPND by 70% (pH 7.4 v.s. pH 6.5:1.05±0.12 v.s. 1.70±0.10, n = 6, P<0.001) and increased the respiratory drive (peak amplitude of iPND/inspiratory time, PA/Ti) by 40% (1.10±0.23 v.s. 1.50±0.38, P<0.05). This stimulatory effect was abolished by blocking ASIC1 with a nonselective inhibitor (amiloride 10 mM), a selective inhibitor (PcTX1, 10 nM) or by damaging orexin neurons in the LH. Current results support our hypothesis that the orexin neuron in the LH can exert an excitation on respiration via ASIC1 during local acidosis. Since central acidification is involved in breathing dysfunction in a variety of pulmonary diseases, understanding its underlying mechanism may improve patient management.

Hypothalamic orexins/hypocretins as regulators of breathing.

It was suggested half a century ago that electrical impulses from the lateral hypothalamic area stimulate breathing. It is now emerging that these effects may be mediated, at least in part, by neurons containing orexin neuropeptides (also known as hypocretins). These cells promote wakefulness and consciousness, and their loss results in narcolepsy. Recent data also show that orexin neurons directly project to respiratory centres in the brainstem, which express orexin receptors, and where injection of orexin stimulates breathing. Because orexin neurons receive inputs that signal metabolic, sleep/wake and emotional states, it is tempting to speculate that they may regulate breathing according to these parameters. Knockout of the orexin gene in mice reduces CO2-induced increases in breathing by approximately 50% and increases the frequency of spontaneous sleep apneas. The relationship between orexins and breathing may be bidirectional: the rate of breathing controls acid and CO2 levels, and these signals alter the electrical activity of orexin neurons in vitro. Overall, these findings suggest that orexins are important for the regulation of breathing and may potentially play a role in the pathophysiology and medical treatment of respiratory disorders.

Toxicidad pulmonar asociada al empleo de oxígeno hiperbárico: procedimientos de cálculo / Pulmonary toxicity is associated with the hyperbaric oxygen: methods of calculation

OBJETIVOS: Estudiar si una exposición hiperbárica de larga duración motivada por la aparición de una enfermedad descompresiva bajo presión, presenta alteraciones espirométricas y si éstas están acompañadas de sintomatología clínica pulmonar compatible con toxicidad pulmonar por oxígeno. PACIENTES Y MÉTODO: 3 buceadores profesionales que durante una inmersión a 100 metros de profundidad, uno de ellos presenta, antes de terminar la inmersión una patología descompresiva que requiere aumentar los tiempos de respiración de oxígeno, se realizan espirometrías pre- y post-inmersión midiendo: FVC, FEV1, PEF, FEV1/FVC, FEF25-75, FEF 75-85, FEF 25, FEF 50, FEF 75. RESULTADOS: Los resultados post-inmersión demuestran un descenso global de todos los parámetros estudiados destacando el descenso de PEF (12.8%), FEF 50 (9,3%) y FEV1 (8.8%), de forma individual 2 buceadores mostraron descenso de todos los parámetros mientras que un buceador de los nueve parámetros estudiados solo experimentó descenso en cinco. Estos resultados no estuvieron acompañados de sintomatología pulmonar y carecieron de significado estadístico. CONCLUSIONES: Tras esta exposición hiperbárica se alteró el flujo y la capacidad sin la presencia de sintomatología clínica pulmonar y papel importante de la susceptibilidad individual. Los estudios de función pulmonar se deberían extender a colectivos sometidos a: cambios constantes de presión y a la respiración de oxígeno, gas con efectos tóxicos agudos y a largo plazo (AU)

INTRODUCTION: We studied if one hyperbaric exposition in the long term with decompression sickness under pressure causes disturbances in the pulmonary functions and if they are related with clinical manifestations which are compatibles with pulmonary oxygen toxicity. PATIENTS AND METHOD.-Three professional divers carried out one immersion at 100 meters of deep, only one person displayed, before the immersion was finished, one decompression pathology which need increase the times breathing of oxygen, we valued the pulmonary functions pre and post immersion so we measured: FVC, FEV1, PEF, FEV1/FVC, FEF25-75, FEF 75-85, FEF 25, FEF 50 and FEF 75. RESULTS: The post immersion results showed one total decline of all studied parameters showed the decrease of PEF (12.8%), FEF 50 (9.3%) and FEV1 (8.8%), two divers showed one decline of all parameters meanwhile that one diver registered decrease only in five parameters. These results are not accompanied of pulmonary symptoms and of significant statistic. CONCLUSIONS: After this hyperbaric exposure, the flow and the capacity were disturbed but they did not show neither clinic pulmonary symptoms nor had one important role in the personal susceptibility. The studies of pulmonary function should include group with constant pressure changes and the breathing of oxygen, this gas have acute toxic effects in the long term (AU)

Organization and chromosomal localization of the human ECEL1 (XCE) gene encoding a zinc metallopeptidase involved in the nervous control of respiration.

ECEL1 (endothelin-converting enzyme-like 1; previously known as XCE) is a putative zinc metalloprotease that was identified recently on the basis of its strong identity with endothelin-converting enzyme. Although the physiological function of ECEL1 is unknown, inactivation of the corresponding gene in mice points to a critical role of this protein in the nervous control of respiration. In the present study we have characterized the human ECEL1 gene. It was located to region q36-q37 of chromosome 2 and shown to be composed of 18 exons spanning approx. 8 kb. The structure of the ECEL1 gene displays some striking similarities with those of genes of related metallopeptidases, supporting the hypothesis that they are all derived from a common ancestor. A short phylogenetic study describing the relationship between the various members of this gene family is also presented.

Breathing patterns of monozygous twins during behavioural tasks.

To better understand behavioural and genetic influences upon breathing, the breathing patterns of 8 pairs of monozygous (MZ) twins were measured under 4 behavioural conditions; relaxed without standardisation; eyes closed; eyes open; and reading. Breathing was quantified by inspiratory and expiratory durations (TI, TE), tidal volume (VT) and derived variables. Airflow shape was normalised and quantified using 8 dimensions. Reading caused breathing to increase by > 500 ml/min compared to the other four conditions. Differences in breathing between combinations of two conditions were compared by testing whether the differences within an individual were smaller than the differences between random pairs of individuals from the same 16 subjects. For almost all respiratory variables, and whatever the behavioural condition, there were highly significant similarities within an individual (p < 0.00025 on 32/80 comparisons). Under each condition, the differences within MZ twin-pairs were compared to the differences within random-pairs from the same subject population. There were highly significant similarities within twin-pairs for the airflow shape across all conditions. However, TI, TE and VT failed to consistently show significant similarities within twin pairs. Hence, an individual's airflow shape appears to be a fundamental characteristic which is conserved when behavioural condition and level of ventilation changes. Further, MZ twins have similar airflow shapes--whatever the behavioural situation. Hence, behavioural influences upon airflow shape act upon monozygous twin pairs in similar ways, or such influences were negligible under the conditions of the present study.