Intragenic duplication and divergence in the spectrin superfamily of proteins

Many structural, signaling, and adhesion molecules contain tandemly repeated amino acid motifs. The alpha-actinin/spectrin/dystrophin superfamily of F-actin-crosslinking proteins contains an array of triple alpha-helical motifs (spectrin repeats). We present here the complete sequence of the novel beta-spectrin isoform beta(Heavy)- spectrin (beta H). The sequence of beta H supports the origin of alpha- and beta-spectrins from a common ancestor, and we present a novel model for the origin of the spectrins from a homodimeric actin-crosslinking precursor. The pattern of similarity between the spectrin repeat units indicates that they have evolved by a series of nested, nonuniform duplications. Furthermore, the spectrins and dystrophins clearly have common ancestry, yet the repeat unit is of a different length in each family. Together, these observations suggest a dynamic period of increase in repeat number accompanied by homogenization within each array by concerted evolution. However, today, there is greater similarity of homologous repeats between species than there is across repeats within species, suggesting that concerted evolution ceased some time before the arthropod/vertebrate split. We propose a two-phase model for the evolution of the spectrin repeat arrays in which an initial phase of concerted evolution is subsequently retarded as each new protein becomes constrained to a specific length and the repeats diverge at the DNA level. This evolutionary model has general applicability to the origins of the many other proteins that have tandemly repeated motifs.      

Effects of root herbivory by an insect on a foliar-feeding species,mediated through changes in the host plant

Summary The effects of root herbivory by larvae of the scarabaeid, Phyllopertha horticola, on the growth of Capsella bursa-pastoris were examined. Individuals of Aphis fabae were reared on the leaves to determine what effect, if any, root feeding has on the performance of this insect. The experiment was conducted under two watering regimes (low and high). Low watering and root feeding caused water stress in the plants and this was reflected in a reduction in vegetative biomass and an increase in the proportion of material allocated to reproduction. Supplying plants with ample water in the high treatment enabled the water stress caused by root herbivory to be offset, but not completely overcome. Low watering and root feeding caused an increase in aphid weight and growth rate, while root feeding also increased fecundity and adult longevity. These effects are attributed to an improvement in food quality, measured by total soluble nitrogen, and caused by amino acid mobilization due to the water stress. The implications of these results in agricultural and ecological situations are discussed.     

Meta-analysis of the literature on diagnostic accuracy of SPECT in parkinsonian syndromes

Background  

Parkinson's disease (PD) is the second most common neurodegenerative disorder. One of the most widely used techniques to diagnose PD is a Single Photon Emission Computer Tomography (SPECT) scan to visualise the integrity of the dopaminergic pathways in the brain. Despite this there remains some discussion on the value of SPECT in the differential diagnosis of PD. We did a meta-analysis of all the existing literature on the diagnostic accuracy of both pre- and post-synaptic SPECT imaging in the differential diagnosis of PD.     

Characterising alternative recycled waste materials for use as green roof growing media in the U.K.

We characterised four recycled materials that have been manufactured into useful substrates for use on extensive green roofs. These were a crushed red brick (the U.K. industry standard substrate base and therefore used as a control) and three alternative pellets made from: clay and sewage sludge (waste clay from excavations, fly ash and sewage sludge), paper ash (from recycled newspapers) and carbonated limestone (from quarry fines). Investigations into optimal organic content – conifer-bark compost for plant nutrients – and characterisations such as pH, particle size distribution, loose bulk density, particle density, XRF and leachate analyses were performed. Greenhouse experiments showed significant interactions between the four aggregates and the amount of added organic material, meaning that organic addition did not have the same effect on plant growth in each aggregate. The addition of organics also significantly reduced the pH of the recycled aggregates, making growing conditions for plants more favourable in these substrates. Particle density and loose bulk density results have shown all substrates to be classed as lightweight aggregates and leaching analysis has confirmed that all substrates perform within legal leachate limits for drinking water. As all the aggregates are commercially available at similar costs to the crushed red brick control, we believe that the alternative substrates have great potential in the green roof market and as they can be locally sourced we would also suggest that they are as good, if not better, than the industry standard, both economically and environmentally.     

Continuous-time modeling of cell fate determination in Arabidopsis flowers

Background  

The genetic control of floral organ specification is currently being investigated by various approaches, both experimentally and through modeling. Models and simulations have mostly involved boolean or related methods, and so far a quantitative, continuous-time approach has not been explored.     

The foliar endophytic fungal community composition in Cirsium arvense is affected by mycorrhizal colonization and soil nutrient content

Foliar fungal endophytes are ubiquitous, but understudied symbionts of most plant species; relatively little is known about the factors affecting their occurrence, diversity and abundance. We tested the effects of soil nutrient content and arbuscular mycorrhizal (AM) colonization on the occurrence of foliar endophytic fungi in Cirsium arvense in two field studies. In the first study, we assessed relationships between soil moisture, organic matter, carbon and nitrogen content and plant water, nitrogen and carbon content and AM colonization and the occurrence of foliar endophytic fungal species. In the second study, we manipulated soil nutrient content and AM colonization of potted seedlings and identified differences in endophytic fungal species composition of the leaves and stems. The results reveal that endophytes can occur either more or less frequently, depending on soil nutrient and plant water content and AM colonization. We propose that these patterns were the result of differences in fungal growth responses to nutrient availability in the leaves, which can be affected by resources obtained from the soil or symbiotic fungi in the roots.     

Clinical Reactivations of Herpes Simplex Virus Type 2 Infection and Human Immunodeficiency Virus Disease Progression Markers

Background

The natural history of HSV-2 infection and role of HSV-2 reactivations in HIV disease progression are unclear.

Methods

Clinical symptoms of active HSV-2 infection were used to classify 1,938 HIV/HSV-2 co-infected participants of the Women''s Interagency HIV Study (WIHS) into groups of varying degree of HSV-2 clinical activity. Differences in plasma HIV RNA and CD4+ T cell counts between groups were explored longitudinally across three study visits and cross-sectionally at the last study visit.

Results

A dose dependent association between markers of HIV disease progression and degree of HSV-2 clinical activity was observed. In multivariate analyses after adjusting for baseline CD4+ T cell levels, active HSV-2 infection with frequent symptomatic reactivations was associated with 21% to 32% increase in the probability of detectable plasma HIV RNA (trend p = 0.004), an average of 0.27 to 0.29 log10 copies/ml higher plasma HIV RNA on a continuous scale (trend p<0.001) and 51 to 101 reduced CD4+ T cells/mm³ over time compared to asymptomatic HSV-2 infection (trend p<0.001).

Conclusions

HIV induced CD4+ T cell loss was associated with frequent symptomatic HSV-2 reactivations. However, effect of HSV-2 reactivations on HIV disease progression markers in this population was modest and appears to be dependent on the frequency and severity of reactivations. Further studies will be necessary to determine whether HSV-2 reactivations contribute to acceleration of HIV disease progression.     

Targeted cDNA differential display (TcDD)

Targeted cDNA differential display (TcDD) was developed to study expression of a different selected gene families especially those at low copy numbers per cell. This method is an adaptation of our previously described targeted genomic differential display method (TGDD). In TcDD, the expression of genes containing target sequences such as CAG repeating sequences or genes encoding for zinc-finger binding proteins were followed in an experimental rat model with salt-induced hypertension. DNA sequencing experiments demonstrated that the effectiveness of targeting was greater than 99%.