Habitat specificity and diversity of tree species in an African wet tropical forest

Niche differentiation with respect to habitat has been hypothesized to shape patterns of diversity and species distributions in plant communities. African forests have been reported to be relatively less diverse compared to highly diversed regions of the Amazonian or Southeast Asian forests, and might be expected to have less niche differentiation. We examined patterns of structural and floristic differences among five topographically defined habitats for 494 species with stems ≥1 cm dbh in a 50-ha plot in Korup National Park, Cameroon. In addition, we tested for species–habitat associations for 272 species (with more than 50 individuals in the plot) using Torus translation randomization tests. Tree density and basal area were lowest in areas with negative convexity, which contained streams or were inundated during rainy periods and highest in moist well-drained habitats. Species composition and diversity varied along the topographical gradient from low flat to ridge top habitats. The low depression and low flat habitats were characterized by high diversity and similar species composition, relative to slopes, high gullies and ridge tops. Sixty-three percent of the species evaluated showed significant positive associations with at least one of the five habitat types. The majority of associations were with low depressions (75 species) and the fewest with ridge tops (8 species). The large number of species–habitat associations and the pronounced contrast between low (valley) and elevated (ridgetop) habitats in the Korup plot shows that niche differentiation with respect to edaphic variables (e.g., soil moisture, nutrients) contributes to local scale tree species distributions and to the maintenance of diversity in African forests.     

Quality control in homograft valve processing: when to screen for microbiological contamination?

Human donor heart valves remain essential for many reconstructive heart procedures. Heart valve donations are a scarce resource which must be used efficiently and safely. Infection transmission remains a potential risk with homograft valve use. Early experience with homograft valves identified high rates of microbial contamination at collection and initiated the practise of immersion in an antibiotic cocktail. Many centres rely on the microbiology screening after exposure to the antibiotic cocktail. We in our centre accept or reject valves on the basis of the microbiology screening at the time of collection prior to immersion in antibiotic solution. We wanted to compare our rate of valve discard and the rate of microbial contamination at implant with other centres. Valves are collected for the Irish Heart Valve Tissue Bank through partnership between the National Centre for Cardiothoracic Surgery and the Irish Blood Transfusion Service. Valves are collected in a surgical theatre setting and processed in dedicated section of the Irish Blood Transfusion Board. Tissues are screening for microbiology at collection and also at implantation. A total of 564 human heart valves and valve conduits were processed through the service during the study period. 167 (29.6%) were discarded during the processing and storage stages. The major reason for this in 117 cases was unsatisfactory microbiology on initial tissue screening. Repeat screening of accepted valves at the time of implantation identified positive cultures in only 0.9%. Optimal use of these limited resources is clearly important. However recipient safety remains paramount. One-fifth of collected valves are discarded at the processing stage due to positive microbiology screening. This is a higher rate of discard then other centres which reject 5.6–10% due to positive microbiology. However our rate of contamination at time of implant is lower then the 3% rate reported elsewhere. We are satisfied that our current discard rate, although significant, reflects rigorous quality control and the optimal balance between valve availability and patient safety.     

Plant traits and extinction in urban areas: a meta‐analysis of 11 cities

Aim Urban environments around the world share many features in common, including the local extinction of native plant species. We tested the hypothesis that similarity in environmental conditions among urban areas should select for plant species with a particular suite of traits suited to those conditions, and lead to the selective extinction of species lacking those traits. Location Eleven cities with data on the plant species that persisted and those that went locally extinct within at least the last 100 years following urbanization. Methods We compiled data on 11 plant traits for 8269 native species in the 11 cities and used hierarchical logistic regression models to identify the degree to which traits could distinguish species that persisted from those that went locally extinct in each city. The trait effects from each city were then combined in a meta‐analysis. Results The cities fell into two groups: those with relatively low rates of extinction (less than 0.05% species per year – Adelaide, Hong Kong, Los Angeles, San Diego and San Francisco), for which no traits reliably predicted the pattern of extinction, and those with higher rates of extinction (> 0.08% species per year – Auckland, Chicago, Melbourne, New York, Singapore and Worcester, MA), where short‐statured, small‐seeded plants were more likely to go extinct. Main conclusions Our analysis reveals patterns in trait selectivity consistent with local studies, suggesting some consistency in trait selection by urbanization. Overall, however, few traits reliably predicted the pattern of plant extinction across cities, making it difficult to identify a priori the extinction‐prone species most likely to be affected by urban expansion.     

A decade of molecular cell biology: achievements and challenges

Nature Reviews Molecular Cell Biology celebrated its 10-year anniversary during this past year with a series of specially commissioned articles. To complement this, here we have asked researchers from across the field for their insights into how molecular cell biology research has evolved during this past decade, the key concepts that have emerged and the most promising interfaces that have developed. Their comments highlight the broad impact that particular advances have had, some of the basic understanding that we still require, and the collaborative approaches that will be essential for driving the field forward.     

Uncovering genomic causes of co-morbidity in epilepsy: gene-driven phenotypic characterization of rare microdeletions

Background

Patients with epilepsy often suffer from other important conditions. The existence of such co-morbidities is frequently not recognized and their relationship with epilepsy usually remains unexplained.

Methodology/Principal Findings

We describe three patients with common, sporadic, non-syndromic epilepsies in whom large genomic microdeletions were found during a study of genetic susceptibility to epilepsy. We performed detailed gene-driven clinical investigations in each patient. Disruption of the function of genes in the deleted regions can explain co-morbidities in these patients.

Conclusions/Significance

Co-morbidities in patients with epilepsy can be part of a genomic abnormality even in the absence of (known) congenital malformations or intellectual disabilities. Gene-driven phenotype examination can also reveal clinically significant unsuspected condition.     

Prevalence and predictors of vitamin D insufficiency in children: a Great Britain population based study

ObjectivesTo evaluate the prevalence and predictors of vitamin D insufficiency (VDI) in children In Great Britain.DesignA nationally representative cross-sectional study survey of children (1102) aged 4–18 years (999 white, 570 male) living in private households (January 1997–1998). Interventions provided information about dietary habits, physical activity, socio-demographics, and blood sample. Outcome measures were vitamin D insufficiency (<50 nmol/L).ResultsVitamin D levels (mean = 62.1 nmol/L, 95%CI 60.4–63.7) were insufficient in 35%, and decreased with age in both sexes (p<0.001). Young People living between 53–59 degrees latitude had lower levels (compared with 50–53 degrees, p = 0.045). Dietary intake and gender had no effect on vitamin D status. A logistic regression model showed increased risk of VDI in the following: adolescents (14–18 years old), odds ratio (OR) = 3.6 (95%CI 1.8–7.2) compared with younger children (4–8 years); non white children (OR = 37 [95%CI 15–90]); blood levels taken December-May (OR = 6.5 [95%CI 4.3–10.1]); on income support (OR = 2.2 [95%CI 1.3–3.9]); not taking vitamin D supplementation (OR = 3.7 [95%CI 1.4–9.8]); being overweight (OR 1.6 [95%CI 1.0–2.5]); <1/2 hour outdoor exercise/day/week (OR = 1.5 [95%CI 1.0–2.3]); watched >2.5 hours of TV/day/week (OR = 1.6[95%CI 1.0–2.4]).ConclusionWe confirm a previously under-recognised risk of VDI in adolescents. The marked higher risk for VDI in non-white children suggests they should be targeted in any preventative strategies. The association of higher risk of VDI among children who exercised less outdoors, watched more TV and were overweight highlights potentially modifiable risk factors. Clearer guidelines and an increased awareness especially in adolescents are needed, as there are no recommendations for vitamin D supplementation in older children.     

A role for endocytic recycling in hyphal growth

Actin plays multiple complex roles in cell growth and cell shape. Recently it was demonstrated that actin patches, which represent sites of endocytosis, are present in a sub-apical collar at growing tips of hyphae and germ tubes of filamentous fungi. It is now clear that this zone of endocytosis is necessary for filamentous growth to proceed. In this review evidence for the role of these endocytic sites in hyphal growth is examined. One possibility if that the role of the sub-apical collar is associated with endocytic recycling of polarized material at the hyphal tip. The 'Apical Recycling Model' accounts for this role and predicts the need for a balance between endocytosis and exocytosis at the hyphal tip to control growth and cell shape. Other cell differentiation events, including appressorium formation and Aspergillus conidiophore development may also be explained by this model.