Radio source counts from the Ohio survey

The Ohio survey shows a decrease in the number of faint sources relative to the number which would be expected for a uniform, Euclidean universe. This confirms the results of the Cambridge 5C2 survey at 408 MHz, but the decrease is sharper for the Ohio counts at 1415 MHz.     

Flares from a candidate Galactic magnetar suggest a missing link to dim isolated neutron stars

Magnetars are young neutron stars with very strong magnetic fields of the order of 10(14)-10(15) G. They are detected in our Galaxy either as soft gamma-ray repeaters or anomalous X-ray pulsars. Soft gamma-ray repeaters are a rare type of gamma-ray transient sources that are occasionally detected as bursters in the high-energy sky. No optical counterpart to the gamma-ray flares or the quiescent source has yet been identified. Here we report multi-wavelength observations of a puzzling source, SWIFT J195509+261406. We detected more than 40 flaring episodes in the optical band over a time span of three days, and a faint infrared flare 11 days later, after which the source returned to quiescence. Our radio observations confirm a Galactic nature and establish a lower distance limit of approximately 3.7 kpc. We suggest that SWIFT J195509+261406 could be an isolated magnetar whose bursting activity has been detected at optical wavelengths, and for which the long-term X-ray emission is short-lived. In this case, a new manifestation of magnetar activity has been recorded and we can consider SWIFT J195509+261406 to be a link between the 'persistent' soft gamma-ray repeaters/anomalous X-ray pulsars and dim isolated neutron stars.     

Mitochondrial aspartyl-tRNA synthetase deficiency causes leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation

Leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation (LBSL) has recently been defined based on a highly characteristic constellation of abnormalities observed by magnetic resonance imaging and spectroscopy. LBSL is an autosomal recessive disease, most often manifesting in early childhood. Affected individuals develop slowly progressive cerebellar ataxia, spasticity and dorsal column dysfunction, sometimes with a mild cognitive deficit or decline. We performed linkage mapping with microsatellite markers in LBSL families and found a candidate region on chromosome 1, which we narrowed by means of shared haplotypes. Sequencing of genes in this candidate region uncovered mutations in DARS2, which encodes mitochondrial aspartyl-tRNA synthetase, in affected individuals from all 30 families. Enzyme activities of mutant proteins were decreased. We were surprised to find that activities of mitochondrial complexes from fibroblasts and lymphoblasts derived from affected individuals were normal, as determined by different assays.     

Helminths of 13 species of microhylid frogs (Anura: Microhylidae) from Papua New Guinea

In an attempt to better document the invertebrate biodiversity of the threatened fauna of Papua New Guinea (PNG), 208 microhylid frogs representing 13 species collected in 2009 and 2010 in PNG were examined for endoparasitic helminths. This study found mature individuals of one species of Digenea (Opisthioglyphe cophixali), adults of two species of Cestoda (Nematotaenia hylae, Cylindrotaenia sp.) and cysticerci of an unidentified cestode species; adults of nine species of Nematoda (Aplectana krausi, Bakeria bakeri, Cosmocerca novaeguineae, Cosmocercella phrynomantisi, Falcaustra papuensis, Icosiella papuensis, Ochtoterenella papuensis, Parathelandros allisoni, Parathelandros andersoni), and one species of Acanthocephala (cystacanths in the family Centrorhynchidae). There was a high degree of endemism among the helminth species infecting the microhylids, with 83% of the species known only from PNG. Yet the helminth fauna infecting Papuan microhylids are generalists with direct life cycles (no intermediate host) that also infect other anuran species. We thus conclude infection is more dependent upon habitat conditions than diet. Twenty-nine new host records are reported.     

Depression by morphine of various descending inhibitory controls modulating the transmission of nociceptive information at the spinal level in the rat

Recording from convergent neurones--i. e. those responding to both non-noxious and noxious cutaneous stimuli--in the dorsal horn of the intact anaesthetized Rat, two distinct effects are seen after application of noxious stimuli: there is an activation of units of the segmental pool, along with a very powerful inhibition of the remaining neuronal population (diffuse noxious inhibitory controls, DNIC). Morphine at doses inadequate to directly depress the activity of these units specifically blocks the inhibition. Since DNIC is dependent upon supraspinal mechanisms, these observations show that morphine is capable of depressing certain descending inhibitory controls, at least when these are induced by noxious peripheral stimuli.     

Judgmental extrapolation and the salience of change

People may often forecast using cognitive procedures that resemble formal time-series extrapolation models. A model of judgmental extrapolation based on exponential smoothing is proposed in which the setting of the trend parameter is hypothesized to depend upon the relative salience of the successive changes. The salience hypothesis was first tested with exponential series by the use of a framing manipulation. As predicted, focusing the subjects' attention on the changes led to more accurate forecasts. In two investment simulation studies, the salience hypothesis was further examined by varying the statistical properties of the price changes. As predicted, subjects were more likely to sell as prices fell and to buy as prices rose (1) as the sample size of similar changes increased; (2) when the variance of the changes was low; and (3) when the absolute value of the mean change was high. Conditions that may influence judgmental forecasting processes are discussed.     

Structure of a Na+/H+ antiporter and insights into mechanism of action and regulation by pH

The control by Na+/H+ antiporters of sodium/proton concentration and cell volume is crucial for the viability of all cells. Adaptation to high salinity and/or extreme pH in plants and bacteria or in human heart muscles requires the action of Na+/H+ antiporters. Their activity is tightly controlled by pH. Here we present the crystal structure of pH-downregulated NhaA, the main antiporter of Escherichia coli and many enterobacteria. A negatively charged ion funnel opens to the cytoplasm and ends in the middle of the membrane at the putative ion-binding site. There, a unique assembly of two pairs of short helices connected by crossed, extended chains creates a balanced electrostatic environment. We propose that the binding of charged substrates causes an electric imbalance, inducing movements, that permit a rapid alternating-access mechanism. This ion-exchange machinery is regulated by a conformational change elicited by a pH signal perceived at the entry to the cytoplasmic funnel.     

Isoniazid and 4-aminobenzoic acid in the treatment of murine tuberculosis

Zusammenfassung Bei der Mäusetuberkulose war die kombinierte Therapie von Isoniazid mit 4-Aminobenzoesäure (PABA) (3 mg/Tag/Tier) wirksamer als diejenige von Isoniazid allein. Bei niedrigerer PABA-Dosis wurde der Synergismus nicht nachgewiesen.PABA allein verkürzt die mittlere Überlebenszeit bei tuberkulösen Mäusen.

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Part of these experiments was performed in the Institute of Microbiology, University of Brno.