An ultrastructural investigation of the surface microbiota present on the leaves and reproductive structures of the resurrection plant Myrothamnus flabellifolia

The leaves, flower and stems of the southern African angiosperm resurrection plant Myrothamnus flabellifolia were investigated at the ultrastructural level to determine the source of previously reported fungal contamination. Fungal mycelia and hyphae of the genera Aspergillus and Penicillium were found localized to the hydathodes of the leaves and stigmatic surfaces of the female flowers in both desiccated and hydrated specimens. A waxy bacterium of the genus Bacillus was found to colonise the waxy epidermal surfaces of the leaves and flowers which was also where fungal cells were found to be absent. It is suggested that the wax like deposits within the leaves and stems as well as over the epidermal surface prevent the growth of the fungal organisms. These fungi opportunistically invade moist surfaces, such as the floral stigmas, during periods of moisture availability and may thus negatively impact plant development

Insights into the cellular mechanisms of desiccation tolerance among angiosperm resurrection plant species

ABSTRACT Water is a major limiting factor in growth and reproduction in plants. The ability of tissues to survive desiccation is commonly found in seeds or pollen but rarely present in vegetative tissues. Resurrection plants are remarkable as they can tolerate almost complete water loss from their vegetative tissues such as leaves and roots. Metabolism is shut down as they dehydrate and the plants become apparently lifeless. Upon rehydration these plants recover full metabolic competence and 'resurrect'. In order to cope with desiccation, resurrection plants have to overcome a number of stresses as water is lost from the cells, among them oxidative stress, destabilization or loss of membrane integrity and mechanical stress. This review will mainly focus on the effect of dehydration in angiosperm resurrection plants and some of the strategies developed by these plants to tolerate desiccation. Resurrection plants are important experimental models and understanding the physiological and molecular aspects of their desiccation tolerance is of great interest for developing drought-tolerant crop species adapted to semi-arid areas

Synapse Type-Dependent Expression of Calcium-Permeable AMPA Receptors

Calcium-permeable (CP) AMPA-type glutamate receptors (AMPARs) are known to mediate synaptic plasticity in several different interneuron (IN) types. Recent evidence suggests that CP-AMPARs are synapse-specifically expressed at excitatory connections onto a subset of IN types in hippocampus and neocortex. For example, CP-AMPARs are found at connections from pyramidal cells (PCs) to basket cells (BCs), but not to Martinotti cells (MCs). This synapse type-specific expression of CP-AMPARs suggests that synaptic dynamics as well as learning rules are differentially implemented in local circuits and has important implications not just in health but also in disease states such as epilepsy

Synapse-specific expression of calcium-permeable AMPA receptors in neocortical layer 5

In the hippocampus, calcium‐permeable AMPA receptors have been found in a restricted subset of neuronal types that inhibit other neurons, although their localization in the neocortex is less well understood. In the present study, we looked for calcium‐permeable AMPA receptors in two distinct populations of neocortical inhibitory neurons: basket cells and Martinotti cells. We found them in the former but not in the latter. Furthermore, in basket cells, these receptors were associated with particularly fast responses. Computer modelling predicted (and experiments verified) that fast calcium‐permeable AMPA receptors enable basket cells to respond rapidly, such that they promptly inhibit neighbouring cells and shut down activity. The results obtained in the present study help our understanding of pathologies such as stroke and epilepsy that have been associated with disordered regulation of calcium‐permeable AMPA receptors

Scaling in high-temperature superconductors

A Hartree approximation is used to study the interplay of two kinds of scaling which arise in high-temperature superconductors, namely critical-point scaling and that due to the confinement of electron pairs to their lowest Landau level in the presence of an applied magnetic field. In the neighbourhood of the zero-field critical point, thermodynamic functions scale with the scaling variable $(T-T_{c2}(B))/B^{1/2\nu}$, which differs from the variable $(T - T_c(0))/B^{1/2\nu}$ suggested by the gaussian approximation. Lowest-Landau-level (LLL) scaling occurs in a region of high field surrounding the upper critical field line but not in the vicinity of the zero-field transition. For YBaCuO in particular, a field of at least 10 T is needed to observe LLL scaling. These results are consistent with a range of recent experimental measurements of the magnetization, transport properties and, especially, the specific heat of high-$T_c$ materials.Comment: 22 pages + 1 figure appended as postscript fil

Recognition memory, self-other source memory, and theory-of-mind in children with autism spectrum disorder.

This study investigated semantic and episodic memory in autism spectrum disorder (ASD), using a task which assessed recognition and self-other source memory. Children with ASD showed undiminished recognition memory but significantly diminished source memory, relative to age- and verbal ability-matched comparison children. Both children with and without ASD showed an “enactment effect”, demonstrating significantly better recognition and source memory for self-performed actions than other-person-performed actions. Within the comparison group, theory-of-mind (ToM) task performance was significantly correlated with source memory, specifically for other-person-performed actions (after statistically controlling for verbal ability). Within the ASD group, ToM task performance was not significantly correlated with source memory (after controlling for verbal ability). Possible explanations for these relations between source memory and ToM are considered

Establishing and Prioritising Research Questions for the Treatment of Alopecia Areata: The Alopecia Areata Priority Setting Partnership

BACKGROUND: Alopecia areata is a common hair loss disorder that results in patchy to complete hair loss. Many uncertainties exist around the most effective treatments for this condition. OBJECTIVES: To identify uncertainties in alopecia areata management and treatment that are important to both service users (people with hair loss, carers and relatives) and healthcare professionals. METHODS: An alopecia areata priority setting partnership was established between patients, their carers and relatives, and healthcare professionals to identify the most important uncertainties in alopecia areata. The methodology of the James Lind Alliance was followed to ensure a balanced, inclusive and transparent process. RESULTS: In total 2747 treatment uncertainties were submitted by 912 participants, of which 1012 uncertainties relating to alopecia areata (and variants) were analyzed. Questions were combined into "indicative uncertainties" following a structured format. A series of ranking exercises further reduced this list to a top 25 that were taken to a final prioritization workshop where the top 10 priorities were agreed. CONCLUSIONS: We present the top 10 research priorities for alopecia areata to guide researchers and funding bodies to support studies important to both patients and clinicians. This article is protected by copyright. All rights reserved

Fluctuation Study of the Specific Heat of MgB2

The specific heat of polycrystalline Mg$^{11}$B$_{2}$ has been measured with high resolution ac calorimetry from 5 to 45 K at constant magnetic fields. The excess specific heat above T$_{c}$ is discussed in terms of Gaussian fluctuations and suggests that Mg$^{11}$B$_{2}$ is a bulk superconductor with Ginzburg-Landau coherence length $\xi_{0}=26$ \AA . The transition-width broadening in field is treated in terms of lowest-Landau-level (LLL) fluctuations. That analysis requires that $\xi_{0}=20$ \AA . The underestimate of the coherence length in field, along with deviations from 3D LLL predictions, suggest that there is an influence from the anisotropy of B$_{c2}$ between the c-axis and the a-b plane.Comment: Phys. Rev. B 66, 134515 (2002

Numerical studies of the phase diagram of layered type II superconductors in a magnetic field

We report on simulations of layered superconductors using the Lawrence-Doniach model in the framework of the lowest Landau level approximation. We find a first order phase transition with a $B(T)$ dependence which agrees very well with the experimental ``melting'' line in YBaCuO. The transition is not associated with vortex lattice melting, but separates two vortex liquid states characterised by different degrees of short-range crystalline order and different length scales of correlations between vortices in different layers. The transition line ends at a critical end-point at low fields. We find the magnetization discontinuity and the location of the lower critical magnetic field to be in good agreement with experiments in YBaCuO. Length scales of order parameter correlations parallel and perpendicular to the magnetic field increase exponentially as 1/T at low temperatures. The dominant relaxation time scales grow roughly exponentially with these correlation lengths. We find that the first order phase transition persists in the presence of weak random point disorder but can be suppressed entirely by strong disorder. No vortex glass or Bragg glass state is found in the presence of disorder. The consistency of our numerical results with various experimental features in YBaCuO, including the dependence on anisotropy, and the temperature dependence of the structure factor at the Bragg peaks in neutron scattering experiments is demonstrated.Comment: 25 pages (revtex), 19 figures included, submitted to PR