Coral growth on three reefs: development of recovery benchmarks using a space for time approach

This 14-year study (1989–2003) develops recovery benchmarks based on a period of very strong coral recovery in Acropora-dominated assemblages on the Great Barrier Reef (GBR) following major setbacks from the predatory sea-star Acanthaster planci in the early 1980s. A space for time approach was used in developing the benchmarks, made possible by the choice of three study reefs (Green Island, Feather Reef and Rib Reef), spread along 3 degrees of latitude (300 km) of the GBR. The sea-star outbreaks progressed north to south, causing death of corals that reached maximum levels in the years 1980 (Green), 1982 (Feather) and 1984 (Rib). The reefs were initially surveyed in 1989, 1990, 1993 and 1994, which represent recovery years 5–14 in the space for time protocol. Benchmark trajectories for coral abundance, colony sizes, coral cover and diversity were plotted against nominal recovery time (years 5–14) and defined as non-linear functions. A single survey of the same three reefs was conducted in 2003, when the reefs were nominally 1, 3 and 5 years into a second recovery period, following further Acanthaster impacts and coincident coral bleaching events around the turn of the century. The 2003 coral cover was marginally above the benchmark trajectory, but colony density (colonies.m⁻²) was an order of magnitude lower than the benchmark, and size structure was biased toward larger colonies that survived the turn of the century disturbances. The under-representation of small size classes in 2003 suggests that mass recruitment of corals had been suppressed, reflecting low regional coral abundance and depression of coral fecundity by recent bleaching events. The marginally higher cover and large colonies of 2003 were thus indicative of a depleted and aging assemblage not yet rejuvenated by a strong cohort of recruits.     

Calcium Additions and Microbial Nitrogen Cycle Processes in a Northern Hardwood Forest

Evaluating, and possibly ameliorating, the effects of base cation depletion in forest soils caused by acid deposition is an important topic in the northeastern United States. We added 850 kg Ca ha⁻¹ as wollastonite (CaSiO₃) to an 11.8-ha watershed at the Hubbard Brook Experimental Forest (HBEF), a northern hardwood forest in New Hampshire, USA, in fall 1999 to replace calcium (Ca) leached from the ecosystem by acid deposition over the past 6 decades. Soil microbial biomass carbon (C) and nitrogen (N) concentrations, gross and potential net N mineralization and nitrification rates, soil solution and stream chemistry, soil:atmosphere trace gas (CO₂, N₂O, CH₄) fluxes, and foliar N concentrations have been monitored in the treated watershed and in reference areas at the HBEF before and since the Ca addition. We expected that rates of microbial C and N cycle processes would increase in response to the treatment. By 2000, soil pH was increased by a full unit in the Oie soil horizon, and by 2002 it was increased by nearly 0.5 units in the Oa soil horizon. However, there were declines in the N content of the microbial biomass, potential net and gross N mineralization rates, and soil inorganic N pools in the Oie horizon of the treated watershed. Stream, soil solution, and foliar concentrations of N showed no response to treatment. The lack of stimulation of N cycling by Ca addition suggests that microbes may not be stimulated by increased pH and Ca levels in the naturally acidic soils at the HBEF, or that other factors (for example, phosphorus, or Ca binding of labile organic matter) may constrain the capacity of microbes to respond to increased pH in the treated watershed. Possible fates for the approximately 10 kg N ha⁻¹ decline in microbial and soil inorganic pools include components of the plant community that we did not measure (for example, seedlings, understory shrubs), increased fluxes of N₂ and/or N storage in soil organic matter. These results raise questions about the factors regulating microbial biomass and activity in northern hardwood forests that should be considered in the context of proposals to mitigate the depletion of nutrient cations in soil.     

Architecture of the trypanosome RNA editing accessory complex, MRB1

Trypanosoma brucei undergoes an essential process of mitochondrial uridine insertion and deletion RNA editing catalyzed by a 20S editosome. The multiprotein mitochondrial RNA-binding complex 1 (MRB1) is emerging as an equally essential component of the trypanosome RNA editing machinery, with additional functions in gRNA and mRNA stabilization. The distinct and overlapping protein compositions of reported MRB1 complexes and diverse MRB1 functions suggest that the complex is composed of subcomplexes with RNA-dependent and independent interactions. To determine the architecture of the MRB1 complex, we performed a comprehensive yeast two-hybrid analysis of 31 reported MRB1 proteins. We also used in vivo analyses of tagged MRB1 components to confirm direct and RNA-mediated interactions. Here, we show that MRB1 contains a core complex comprised of six proteins and maintained by numerous direct interactions. The MRB1 core associates with multiple subcomplexes and proteins through RNA-enhanced or RNA-dependent interactions. These findings provide a framework for interpretation of previous functional studies and suggest that MRB1 is a dynamic complex that coordinates various aspects of mitochondrial gene regulation.     

Biology of the Greenland shark Somniosus microcephalus

Greenland shark Somniosus microcephalus is a potentially important yet poorly studied cold-water species inhabiting the North Atlantic and Arctic Oceans. Broad-scale changes in the Arctic ecosystem as a consequence of climate change have led to increased attention on trophic dynamics and the role of potential apex predators such as S. microcephalus in the structure of Arctic marine food webs. Although Nordic and Inuit populations have caught S. microcephalus for centuries, the species is of limited commercial interest among modern industrial fisheries. Here, the limited historical information available on S. microcephalus occurrence and ecology is reviewed and new catch, biological and life-history information from the Arctic and North Atlantic Ocean region is provided. Given the considerable by-catch rates in high North Atlantic Ocean latitudes it is suggested that S. microcephalus is an abundant predator that plays an important, yet unrecognized, role in Arctic marine ecosystems. Slow growth and large pup sizes, however, may make S. microcephalus vulnerable to increased fishing pressure in a warming Arctic environment.     

Thoracic empyema: a 12-year study from a UK tertiary cardiothoracic referral centre

Background

Empyema is an increasingly frequent clinical problem worldwide, and has substantial morbidity and mortality. Our objectives were to identify the clinical, surgical and microbiological features, and management outcomes, of empyema.

Methods

A retrospective observational study over 12 years (1999–2010) was carried out at The Heart Hospital, London, United Kingdom. Patients with empyema were identified by screening the hospital electronic ‘Clinical Data Repository’. Demographics, clinical and microbiological characteristics, underlying risk factors, peri-operative blood tests, treatment and outcomes were identified. Univariable and multivariable statistical analyses were performed.

Results

Patients (n = 406) were predominantly male (74.1%); median age = 53 years (IQR = 37–69). Most empyema were community-acquired (87.4%) and right-sided (57.4%). Microbiological diagnosis was obtained in 229 (56.4%) patients, and included streptococci (16.3%), staphylococci (15.5%), Gram-negative organisms (8.9%), anaerobes (5.7%), pseudomonads (4.4%) and mycobacteria (9.1%); 8.4% were polymicrobial. Most (68%) cases were managed by open thoracotomy and decortication. Video-assisted thoracoscopic surgery (VATS) reduced hospitalisation from 10 to seven days (P = 0.0005). All-cause complication rate was 25.1%, and 28 day mortality 5.7%. Predictors of early mortality included: older age (P = 0.006), major co-morbidity (P = 0.01), malnutrition (P = 0.001), elevated red cell distribution width (RDW, P<0.001) and serum alkaline phosphatase (P = 0.004), and reduced serum albumin (P = 0.01) and haemoglobin (P = 0.04).

Conclusions

Empyema remains an important cause of morbidity and hospital admissions. Microbiological diagnosis was only achieved in just over 50% of cases, and tuberculosis is a notable causative organism. Treatment of empyema with VATS may reduce duration of hospital stay. Raised RDW appears to associate with early mortality.     

VDAC3 regulates centriole assembly by targeting Mps1 to centrosomes

Centrioles are duplicated during S-phase to generate the two centrosomes that serve as mitotic spindle poles during mitosis. The centrosomal pool of the Mps1 kinase is important for centriole assembly, but how Mps1 is delivered to centrosomes is unknown. Here we have identified a centrosome localization domain within Mps1 and identified the mitochondrial porin VDAC3 as a protein that binds to this region of Mps1. Moreover, we show that VDAC3 is present at the mother centriole and modulates centriole assembly by recruiting Mps1 to centrosomes.     

The Effect of Polyhydramnios on Cervical Length in Twins: A Controlled Intervention Study in Complicated Monochorionic Pregnancies

Objective

To test the hypothesis that cervical shortening in polyhydramnios reflects the degree of excess amniotic fluid, and increases with normalisation of amniotic fluid volume.

Study Design

Prospective cohort study of 40 women with monochorionic twins undergoing interventional procedures between 16–26 weeks. Cervical length was assessed via transvaginal sonography pre-procedure, 1 and 24 hours post-procedure, and results compared between amnioreduction and control procedures. Amniotic fluid index (AFI) was measured pre- and post-procedure.

Results

Pre-procedural cervical length correlated with AFI (linear fit = 5.07 -0.04x, R² = 0.17, P = 0.03) in patients with polyhydramnios (n = 28). Drainage of 2000ml fluid (range 700–3500ml), reduced AFI from 42cm to 21cm (P<0.001). Their pre-procedural cervical length did not change at one (mean Δ:−0.1cm, 95%CI, −0.4 to 0.2) or 24 hours (0.2cm, −0.1 to 0.6) after amnioreduction. There was no change in cervical length at control procedures.

Conclusion

Cervical shortening in twins with polyhydramnios does not appear to be an acute process; cervical length can be measured before or after therapeutic procedures.     

Microbial biomass and nitrogen cycling responses to fertilization and litter removal in young northern hardwood forests

The influence of site fertility on soil microbial biomass and activity is not well understood but is likely to be complex because of interactions with plant responses to nutrient availability. We examined the effects of long-term (8 yr) fertilization and litter removal on forest floor microbial biomass and N and C transformations to test the hypothesis that higher soil resource availability stimulates microbial activity. Microbial biomass and respiration decreased by 20–30 % in response to fertilization. Microbial C averaged 3.8 mg C/g soil in fertilized, 5.8 mg C/g in control, and 5.5 mg C/g in litter removal plots. Microbial respiration was 200 µg CO₂-C g^–1 d^–1 in fertilized plots, compared to 270 µg CO₂-C g^–1 d^–1 in controls. Gross N mineralization and N immobilization did not differ among treatments, despite higher litter nutrient concentrations in fertilized plots and the removal of substantial quantities of C and N in litter removal plots. Net N mineralization was significantly reduced by fertilization. Gross nitrification and NO₃ ^– immobilization both were increased by fertilization. Nitrate thus became a more important part of microbial N cycling in fertilized plots even though NH₄ ⁺ availability was not stimulated by fertilization.Soil microorganisms did not mineralize more C or N in response to fertilization and higher litter quality; instead, results suggest a difference in the physiological status of microbial biomass in fertilized plots that influenced N transformations. Respiration quotients (qCO₂, respiration per unit biomass) were higher in fertilized plots (56 µg CO₂-C mg C^–1 d^–1) than control (48 µg CO₂-C mg C^–1 d ^–1) or litter removal (45 µg CO₂-C mg C^–1 d^–1), corresponding to higher microbial growth efficiency, higher proportions of gross mineralization immobilized, and lower net N mineralization in fertilized plots. While microbial biomass is an important labile nutrient pool, patterns of microbial growth and turnover were distinct from this pool and were more important to microbial function in nitrogen cycling.