Nonlinear coupling of Alfvén and magnetoacoustic waves in partially ionized plasmas: the effect of thermal misbalance on propagating waves.

Partially ionized plasmas constitute an essential ingredient of the solar atmosphere, and ground- and space-based observations have pointed out the presence of oscillations in partially ionized solar plasmas such as chromosphere, photosphere, prominences or spicules, which have been interpreted in terms of magnetohydrodynamic waves. Our aim is to study the spatial behaviour of propagating weakly and fully nonlinear Alfvén waves, and the subsequent excitation of field-aligned motions and perturbations, when dissipative mechanisms, such as ambipolar diffusion and radiative losses, together with parametrized heating mechanisms, are taken into account. When only ambipolar diffusion is taken into account, first-order Alfvén waves as well as ponderomotive-driven perturbations are spatially damped, while field-aligned motions and perturbations representing propagating slow waves are undamped. These perturbations are damped when thermal effects are also considered and their damping lengths can be longer or shorter than those of ponderomotive-driven perturbations. Therefore, after the initial excitation, Alfvén waves and ponderomotive-driven perturbations could be quickly damped while slow waves still remain in the plasma, and vice versa. This article is part of the theme issue 'Partially ionized plasma of the solar atmosphere: recent advances and future pathways'.

Large scale coherent magnetohydrodynamic oscillations in a sunspot.

Although theoretically predicted, the simultaneous excitation of several resonant modes in sunspots has not been observed. Like any harmonic oscillator, a solar magnetic flux tube can support a variety of resonances, which constitute the natural response of the system to external forcing. Apart from a few single low order eigenmodes in small scale magnetic structures, several simultaneous resonant modes were not found in extremely large sunspots. Here we report the detection of the largest-scale coherent oscillations observed in a sunspot, with a spectrum significantly different from the Sun's global acoustic oscillations, incorporating a superposition of many resonant wave modes. Magnetohydrodynamic numerical modeling agrees with the observations. Our findings not only demonstrate the possible excitation of coherent oscillations over spatial scales as large as 30-40 Mm in extreme magnetic flux regions in the solar atmosphere, but also paves the way for their diagnostic applications in other astrophysical contexts.

Woody plant richness and NDVI response to drought events in Catalonian (northeastern Spain) forests.

The role of species diversity on ecosystem resistance in the face of strong environmental fluctuations has been addressed from both theoretical and experimental viewpoints to reveal a variety of positive and negative relationships. Here we explore empirically the relationship between the richness of forest woody species and canopy resistance to extreme drought episodes. We compare richness data from an extensive forest inventory to a temporal series of satellite imagery that estimated drought impact on forest canopy as NDVI (normalized difference vegetation index) anomalies of the dry summer in 2003 in relation to records of previous years. We considered five different types of forests that are representative of the main climatic and altitudinal gradients of the region, ranging from lowland Mediterranean to mountain boreal-temperate climates. The observed relationship differed among forest types and interacted with the climate, summarised by the Thorntwaite index. In Mediterranean Pinus halepensis forests, NDVI decreased during the drought. This decrease was stronger in forests with lower richness. In Mediterranean evergreen forests of Quercus ilex, drought did not result in an overall NDVI loss, but lower NDVI values were observed in drier localities with lower richness, and in more moist localities with higher number of species. In mountain Pinus sylvestris forests NDVI decreased, mostly due to the drought impact on drier localities, while no relation to species richness was observed. In moist Fagus sylvatica forests, NDVI only decreased in plots with high richness. No effect of drought was observed in the high mountain Pinus uncinata forests. Our results show that a shift on the diversity-stability relationship appears across the regional, climatic gradient. A positive relationship appears in drier localities, supporting a null model where the probability of finding a species able to cope with drier conditions increases with the number of species. However, in more moist localities we hypothesize that the proportion of drought-sensitive species would increase in richer localities, due to a higher likelihood of co-occurrence of species that share moist climatic requirements. The study points to the convenience of considering the causes of disturbance in relation to current environmental gradients and historical environmental constraints on the community.

Leigh syndrome associated with the T9176C mutation in the ATPase 6 gene of mitochondrial DNA.

A child with clinical and neuroradiologic evidence of Leigh syndrome (LS) had the T-to-C transition at nt 9176 in the ATPase 6 gene of mtDNA. The mutation was homoplasmic in muscle and maternally inherited. The proband's mother had ataxia and harbored 93% of mutant genomes in blood, whereas three clinically unaffected maternal relatives had varying degrees of heteroplasmy in blood. These data confirm the association of the T9176C mutation with LS and extend the clinical heterogeneity of mutations in the ATPase 6 gene.

Conduction velocity along muscle fibers in situ in healthy infants.

The muscle fibers of the biceps brachii were stimulated distally with low voltages by means of two monopolar needles in twenty-two infants aged 2 to 14 years. The electrical activity was recorded proximally by means of a SFEMG electrode. Conduction velocity of the muscle fibers (MFCV) in situ calculated with this method had a bimodal distribution in the youngest individuals of less than 4 years, and a Gaussian distribution in children aged 5 to 14 years. Propagation velocity along muscle fibers increases with children's age and is significantly slower than in adults, in good correlation with the shorter limb perimeter and with the significantly smaller fiber diameter found in muscle biopsies in infancy. The latency of the evoked potentials was linearly related with the distance between stimulating and recording points, and muscle activity and propagation velocities were the same before and after curarization, that is consistent with the reliability of the method in infancy.

Motor unit remodelling in Duchenne muscular dystrophy. Electrophysiological assessment.

Conventional EMG, motor and sensory conduction velocities, averaging analysis of MUPs, SFEMG, and muscle fiber conduction velocity in situ were performed in 14 boys with Duchenne muscular dystrophy (DD) aged 5 to 11 years. MUPs parameters study showed a striking increment of long duration MUPs followed by satellites and increase of polyphasic potentials of variable duration. The main findings in SFEMG examination were increment in fiber density of the motor unit, large MISI and presence of complex potentials of long duration in all patients. Muscle fiber conduction velocity in situ was significantly slower than in controls, with significant decrease in minimum conduction and increased variability (large SD) in propagation velocity values. Low conduction velocity of muscle fibers, long duration of polyphasics and MUPs followed by satellites, and large MISI were significantly related. These findings support the hypotheses which have suggested that the motor unit remodelling in DD is mainly myogenic. The abnormalities in muscle fiber conduction velocity in situ reflect an increased diameter variation of muscle fibers consistent with splitting fibers, small groups of regenerating and necrotic fibers, and fiber diameter variation found in histological studies. Thus, increased variability in fiber diameter may be the cause of complex and long duration MUPs in DD.

[Epilepsy as a symptom]. / La epilepsia como síntoma.

Epilepsy and seizures are often misinterpreted as identical phenomenon and treatment of seizures confused with treatment of epilepsy. In this paper the concept of both epilepsy and seizures are revised and also the more new etiopathogenics hypothesis, stressing the importance of etiological diagnosis for a suitable therapy and prognosis, which depends more of the etiology than the morphology of seizures.

[Introduction to the study of peroxisomal disorders]. / Introducción al estudio de las enfermedades peroxisomales.

The peroxisome is an organelle found in all nucleated cells of mammalian. Its name is due to H2O2 formation as result of cell respiration catalyzed by oxidases and catalases and play and important role on myelination and neuronal migration. Peroxisomes are formed by assembling of membrane proteins (structural, receptors and transporters) into peroxisomal membrane. Peroxisomal proteins are encoded by nuclear genes, synthesized on cytosol ribosomes and imported into peroxisomal matrix, mediated by receptors and transporters membrane proteins. There are two main categories of peroxisomal disorders: disorder of peroxisome biogenesis exemplified by Zellweger syndrome, where multiple peroxisomal protein, functions are deficient and disorders which involves a single peroxisomal protein, exemplified by X-adrenoleukodystrophy, where the organelle is apparently intact.

[Evolutive neuroradiological alterations in Sandhoff's disease]. / Alteraciones neurorradiológicas evolutivas en la enfermedad de Sandhoff.

Sandhoff's disease is a severe form of gangliosidosis GM2 which presents in the first year of life, basically as progressive psychomotor retardation and/or a macular red cherry spot. Our patient presented the clinical picture characteristic of the disease. Diagnosis was confirmed by determining the activity of hexosaminidases A and B in serum and of beta-N-acetil hexosaminases in fibroblast culture. In view of the fatal prognosis of the disease, in 1991 a transplant of alogenic bone marrow (TMO) was carried out to try to replace the enzymes. This required exhaustive radiological follow-up to determine the possible neuro-radiological changes seen in this storage disease. Although treatment was not successful, the neuro-radiological findings may be of interest as perhaps being characteristic of the GM2 gangliosidosis: 1. Bilateral thalamic hyperecogenity in the cerebral ecography. 2. Differences between the thalamo-putamen densities due to bilateral homogeneous thalamic hyperdensity on the CT scan. 3. Thalamic hypointensity both on T2 sequences and in proton density on MR with the cerebral white matter being progressively affected. In conclusion, we suggest that bilateral symmetrical thalamic changes are an early finding which is probably specific to the GM2 gangliosidoses and may be useful from the point of view of carrying out more specific investigations in infants suspected of having a degenerative neurological disorder.

Community structures of N2 -fixing bacteria associated with the phyllosphere of a Holm oak forest and their response to drought.

Biological nitrogen (N) fixation is a key pathway in terrestrial ecosystems and is therefore critical for understanding the responses of ecosystems to global environmental changes. The free-living diazotrophic community is distributed along the canopy-to-soil profile, but the ecological significance of epiphyllic N2 fixers, despite their functional relevance, on plant foliar surfaces remains very poorly understood compared with the N2 -fixing community in forest litter and soils. We assessed the community structure of N2 fixers and overall bacteria by genetic fingerprinting (t-RFLP) to explore the seasonal successional patterns of the microbial community in the natural phyllosphere of a Holm oak (Quercus ilex) forest submitted to 12-year field experiment of rain exclusion mimicking the conditions of drought projected for the coming decades. Leaves of Holm oak were analysed in different seasons over a period of 1.5 years. The bacterial community of the phyllosphere did not correspond to the surrounding soil biome in the same area. These analyses provided field evidence for the presence of free-living diazotrophs associated with the tissues of leaves of Holm oak, the dominant tree species of many Mediterranean forests. The results also revealed that the community composition is affected seasonally and inter-annually by the environment, and that the composition shifts in response to climate change. Drought treatment increased the richness of the epiphyllic microbial community, especially during the summer. These changes were associated with higher C:N ratios of leaves observed in response to drought in semiarid areas. This epiphyllic microbiota that can potentially fix N2 extends the capacity of plants to adapt to the environment.

Summer season and long-term drought increase the richness of bacteria and fungi in the foliar phyllosphere of Quercus ilex in a mixed Mediterranean forest.

We explored the changes in richness, diversity and evenness of epiphytic (on the leaf surface) and endophytic (within leaf tissues) bacteria and fungi in the foliar phyllosphere of Quercus ilex, the dominant tree species of Mediterranean forests. Bacteria and fungi were assessed during ontogenic development of the leaves, from the wet spring to the dry summer season in control plots and in plots subjected to drought conditions mimicking those projected for future decades. Our aim was to monitor succession in microbiota during the colonisation of plant leaves and its response to climate change. Ontogeny and seasonality exerted a strong influence on richness and diversity of the microbial phyllosphere community, which decreased in summer in the whole leaf and increased in summer in the epiphytic phyllosphere. Drought precluded the decrease in whole leaf phyllosphere diversity and increased the rise in the epiphytic phyllosphere. Both whole leaf bacterial and fungal richness decreased with the decrease in physiological activity and productivity of the summer season in control trees. As expected, the richness of epiphytic bacteria and fungi increased in summer after increasing time of colonisation. Under summer dry conditions, there was a positive relationship between TRF (terminal restriction fragments) richness and drought, both for whole leaf and epiphytic phyllosphere, and especially for fungal communities. These results demonstrate that changes in climate are likely to significantly alter microbial abundance and composition of the phyllosphere. Given the diverse functions and large number of phyllospheric microbes, the potential functional implications of such community shifts warrant exploration.

Water relations, gas exchange and growth of dominant and suppressed shoots of Arbutus unedo L.

Basal shoots produced by Arbutus unedo L. after cutting at ground level vary in size and growth rate, and are classified accordingly as dominant or suppressed. The suppressed shoots eventually cease growth and die. In this study, we investigated the role of light and water in the competition among shoots of A. unedo. Dominant and suppressed shoots of A. unedo showed similar leaf water potentials and tissue water relations over the year, suggesting that water status is not responsible for the lack of flushing in suppressed shoots. Although suppressed shoots did not flush under low light, they showed many characteristics of shade-tolerant plants. Leaves of suppressed shoots had lower leaf conductance and light-saturated photosynthetic rate, and higher specific leaf area than leaves of dominant shoots. We conclude that light was the main resource determining competition among shoots and the death of suppressed shoots.

Conduction velocity along muscle fibers in situ in Duchenne muscular dystrophy.

The muscle fibers of the biceps brachii muscle were stimulated distally with low voltage by means of two monopolar needles in 14 boys with Duchenne muscular dystrophy (DD). The electric activity was recorded proximally by means of a SFEMG electrode. The mean conduction velocity of 508 muscle fibers in situ (MFCV) calculated with this method shows that MFCV in DD patients (2.38 +/- .94 m/sec) is significantly slower than in 20 control children of the same age (3.24 +/- .53 m/sec). The distribution frequency of MFCV in all fibers tested in healthy children shows a Gaussian distribution (mode = 3.2 m/sec). In DD patients the distribution frequency is bimodal with spikes at 1.2 and 2.4 m/sec. Significant decrease in minimum propagation velocity and increased SD values were other striking results in patients with DD. Slowing and large variation in MFCV were significantly correlated with some findings in a coaxial needle electromyogram, such as long polyphasics and motor unit potentials followed by satellites. Satellites might arise from atrophic muscle fibers with slow conduction velocity. The results of MFCV were supported by the pathologic findings in DD subjects. The reported method for MFCV in situ is reliable and easy to apply in children, has merit for testing the size and function of muscle fiber, and helps to explain some electropathologic features in DD patients.

[Duchenne muscular dystrophy. Review of 37 cases]. / Distrofia muscular de Duchenne. Revisión de 37 casos.

Clinical, analytical, histological and electromyographical findings observed in 37 males with Duchenne's Muscular Dystrophy are presented. Ages were between 14 months and 10 years. Follow-up of 18 patients was made. Motor development retardation is very often the first sign of the disease. 32% of the children did not get the sitting position before 8 months old. 86% walked after 14 months. Clinical alterations are similar to that reported in the literature. Serum muscular enzymes levels don't decrease with age during the first ten years of life, and they aren't in proportion with the severity of clinical disturbances. The most frequent findings in EMG were increase of polyphasia and presence of late components in Motor Unit Potentials (MUP). Decrease of duration of MUP was found only in 50% of studied children. Mothers and other females belonging to families of 17 children were studied; EMG alterations in 97% of females studied were observed. Healthy people controls with EMG were not made. Analytical and EMG findings in these relatives are commented.

Late components of motor unit potentials in central core disease.

Electromyographic studies in five patients suffering from central core disease are presented. A variable amount of late components of motor unit potentials were found in all of them, as others have found in Duchenne muscular dystrophy. This suggests the existence of collateral innervation of the resultant fragments of the muscular fibre splitting present in this disorder.

[Facial asymmetry with crying: a neurophysiological study and clinical account of this entity]. / Asimetría facial con el llanto: estudio neurofisiológico y recuerdo clínico de esta entidad.

OBJECTIVE: The objectives of this study were to determine in our newborn population the frequency of facial asymmetry during crying or congenital hypoplasia of the depressor anguli oris muscle (DAOM) without associated major malformations and to evaluate the contribution of electrophysiological studies in the diagnosis of this anomaly. PATIENTS AND METHODS: We performed a prospective study of the living newborns with facial asymmetry which did not need to be admitted to the hospital and that were delivered without the use of forceps in our hospital during 4 consecutive years. Newborn evaluation included physical examination, facial nerve electroneurography and DAOM electromyography. RESULTS: This anomaly without major malformations was present in 0.348/1,000 newborns. Electrophysiological studies demonstrated a normal latency in the facial nerve electroneurography and an absence or reduced number of motor unit potential without signs of denervation in the electromyography. CONCLUSIONS: Diagnosis of this entity is important to exclude facial nerve palsy. Only a physical examination is necessary for a correct diagnosis.

Confirmation of low genetic diversity and multiple breeding females in a social group of Eurasian badgers from microsatellite and field data.

The Eurasian badger (Meles meles) is a facultatively social carnivore that shows only rudimentary co-operative behaviour and a poorly defined social hierarchy. Behavioural evidence and limited genetic data have suggested that more than one female may breed in a social group. We combine pregnancy detection by ultrasound and microsatellite locus scores from a well-studied badger population from Wytham Woods, Oxfordshire, UK, to demonstrate that multiple females reproduce within a social group. We found that at least three of seven potential mothers reproduced in a group that contained 11 reproductive age females and nine offspring. Twelve primers showed variability across the species range and only five of these were variable in Wytham. The microsatellites showed a reduced repeat number, a significantly higher number of nonperfect repeats, and moderate heterozygosity levels in Wytham. The high frequency of imperfect repeats and demographic phenomena might be responsible for the reduced levels of variability observed in the badger.

[Schwartz-Jampel syndrome. A case report and review of literature (author's transl)]. / Síndrome de Schwartz-Jampel. Aportación de un nuevo caso y revisión de la literatura.

A new case with distinctive features of Schwartz-Jampel syndrome is reported, which makes the patient number 28 after reviewing world literature on the subject. Clinical, genetic, neurophysiological and pathological point of view is studied. The myotonic discharges which the patient presented while resting, did not diminish either with general anesthesia or with curarization, being this the pattern of a true myotonia.

[Sturge-Weber syndrome. Findings in 22 infantile cases (author's transl)]. / Síndrome de Sturge-Weber. Hallazgos en 22 casos infantiles.

Twenty two infants, 13 females and nine males, with Sturge-Weber syndrome are reviewed. Facial "nevus flammeus" is found to be located unilaterally in 13 cases and bilaterally in nine cases. Twenty infants presented seizures with generalized type being most frequent. E.E.G. alterations appeared in 18 cases. The I.Q. was normal in five infants although somewhat lower than the inferior limits of a normal I.Q. range. The major radiological alterations seen were an increased thickness of the skull cap; intracranial calcification (11 cases), unilateral in eight and bilateral in three; cerebral hemiatrophy (10 cases), arterial and venous hypoplasia and tortuosity in the entire extension of the carotid artery. One of the infants died with no apparent cause. This death cannot be attributed to the orignal syndrome. Computerized tomography offers early adequate data concerning the intracranial calcifications and cerebral hemiatrophy. Based on this study there does not seem to be sufficient motives to separate the Sturge-Weber and the Klippel-Trenaunay syndromes into two different entities.

Evaluation of congenital dysautonomia other than Riley-Day syndrome.

We report on four children, from different families, who suffer from a congenital autonomic disorder, presumably inherited. Three of them have a sensory neuropathy but do not fit any described hereditary sensory and autonomic neuropathy. All four were examined along with some of their immediate family members. We assessed the cardiovagal, sympathetic adrenergic and sympathetic cholinergic functions with a battery of non-invasive tests. Results demonstrated that sudomotor and cardiovascular orthostatic regulation exhibited the greatest abnormalities, pointing to a predominant impairment of sympathetic components, both cholinergic and adrenergic. The overall examination showed a heterogeneous group of congenital dysautonomia, exclusive of Riley-Day or other recognized hereditary sensory and autonomic neuropathies. We emphasize the importance of studying whole family groups to diagnose subclinical impairment and to provide correct genetic counselling.