Interspecific differences in milkweeds alter predator density and the strength of trophic cascades

Trophic cascades occur when predators benefit plants by consuming herbivores, but the overall strength of a trophic cascade depends upon the way species interactions propagate through a system. For example, plant resistance to, or tolerance of, herbivores reduces the potential magnitude of a trophic cascade. At the same time, plants can also affect predator foraging or consumption in ways that either increase or decrease the strength of trophic cascades. In this study, we investigated the effects of plant variation on cascade strength by manipulating predator access to aphid populations on two species of milkweed: the slower-growing, putatively more-defended Asclepias syriaca and the faster-growing, putatively less-defended Asclepias incarnata. Predatory insects increased plant growth and survival for both species, but the strength of these trophic cascades was greater on A. incarnata, which supported more aphid growth early in the season than did A. syriaca. More predators were observed per aphid on A. incarnata, and cage treatments generated significant patterns consistent with predator aggregation on A. incarnata, but not A. syriaca. Although predators strongly affected aphids, this effect did not differ consistently between milkweed species. Plant tolerance to herbivory may therefore be the primary driver of the difference in trophic cascade strength observed. Importantly, we observed that the timing of predator exclusion affected plant growth and survival differently, indicating that measures of “cascade strength” may change with phenology and plant physiological responses. Together, our results suggest a mechanism by which differences in resource allocation patterns could explain differences in growth, phenology, and cascade strength between species.     

Mortality and Morbidity of Urban Road Traffic Crashes in Africa: Capture-Recapture Estimates in Bamako,Mali, 2012

Background

Low- and middle-income countries are currently facing the massive public health challenge of road traffic injuries. The lack of effective surveillance systems hinders proper assessment of epidemiologic status and intervention priorities. The objective of our study was to estimate the mortality and morbidity attributable to road crashes in Bamako, Mali using the capture-recapture method.

Methods

During the 1 January, 2012–31 April, 2012 period, we collected data on road traffic crashes from the road accident registers of the police forces of Bamako, Mali on the one hand, and from a register kept by health facilities in the same area. An automatic, then manual matching procedure was performed to find pairs of records related to the same crash victims. The number of victims and the number of fatalities were estimated by the capture-recapture method using the Chapman estimator.

Results

The health facility and the police registries included 3587 and 1432 records, respectively. The matching procedure identified 603 common records, 31 of which were fatalities. The annual incidence estimate for road victims was 1038 in 100 000 and the annual incidence estimate for road fatalities was 12 in 100 000. Victims from both sources were more likely to be male, in the 15–34 age group, and almost half of all injured road users and two in three fatalities were using motorized two-wheelers. One victim out of five was a pedestrian.

Conclusion

Our estimates are in line with available literature data from low-income countries. While more cases were reported by health facilities than by police forces, we believe that an effective surveillance system should not be based solely on medical reports as much would be missing as regards the crash circumstances and characteristics.     

OX133, a monoclonal antibody recognizing protein-bound N-ethylmaleimide for the identification of reduced disulfide bonds in proteins

In vivo, enzymatic reduction of some protein disulfide bonds, allosteric disulfide bonds, provides an important level of structural and functional regulation. The free cysteine residues generated can be labeled by maleimide reagents, including biotin derivatives, allowing the reduced protein to be detected or purified. During the screening of monoclonal antibodies for those specific for the reduced forms of proteins, we isolated OX133, a unique antibody that recognizes polypeptide resident, N-ethylmaleimide (NEM)-modified cysteine residues in a sequence-independent manner. OX133 offers an alternative to biotin-maleimide reagents for labeling reduced/alkylated antigens and capturing reduced/alkylated proteins with the advantage that NEM-modified proteins are more easily detected in mass spectrometry, and may be more easily recovered than is the case following capture with biotin based reagents.     

Context‐dependent outcomes in a reproductive mutualism between two freshwater fish species

1. The development of encompassing general models of ecology is precluded by underrepresentation of certain taxa and systems. Models predicting context‐dependent outcomes of biotic interactions have been tested using plants and bacteria, but their applicability to higher taxa is largely unknown.
2. We examined context dependency in a reproductive mutualism between two stream fish species: mound nest‐building bluehead chub Nocomis leptocephalus and mountain redbelly dace Chrosomus oreas, which often uses N. leptocephalus nests for spawning. We hypothesized that increased predator density and decreased substrate availability would increase the propensity of C. oreas to associate with N. leptocephalus and decrease reproductive success of both species.
3. In a large‐scale in situ experiment, we manipulated egg predator density and presence of both symbionts (biotic context), and replicated the experiment in habitats containing high‐ and low‐quality spawning substrate (abiotic context).
4. Contradictory to our first hypothesis, we observed that C. oreas did not spawn without its host. The interaction outcome switched from commensalistic to mutualistic with changing abiotic and biotic contexts, although the net outcome was mutualistic.
5. The results of this study yielded novel insight into how context dependency operates in vertebrate mutualisms. Although the dilution effect provided by C. oreas positively influenced reproductive success of N. leptocephalus, it was not enough to overcome both egg predation and poor spawning habitat quality. Outcomes of the interaction may be ultimately determined by associate density. Studies of context dependency in vertebrate systems require detailed knowledge of species life‐history traits.

     

Metabolic Tumour Burden Measured by 18F-FDG PET/CT Predicts Malignant Transformation in Patients with Neurofibromatosis Type-1

Background

To investigate the diagnostic and prognostic performances of ¹⁸F-FDG PET/CT measures of metabolic tumour burden in patients with neurofibromatosis type-1 (NF1), suspect of malignant transformation.

Methods

This retrospective study included 49 patients (15–60 years old, 30 women) with a diagnosis of NF1, followed in our Reference Centre for Rare Neuromuscular Diseases, who presented clinical signs of tumour progression (pain, neurological deficit, tumour growth). Quantitative metabolic parameters were measured on 149 tumoral targets, using semi-automatic software and the best cut off values to predict transformation was assessed by Receiver Operating Characteristics (ROC) analysis. Prognostic value of PET/CT metabolic parameters was assessed by Kaplan-Meier estimates of overall survival.

Results

Lesions were histologically documented in 40 patients: a sarcomatous transformation was found in 16, a dysplastic neurofibroma (NF) in 7, and a benign NF in 17; in the remaining 9 patients, a minimal follow-up of 12 mo (median 59 mo) confirmed the absence of transformation. The optimal cut off values for detection of malignant transformation were, in decreasing order of area under the ROC curves, a tumour-to-liver (T/L) ratio >2.5, SUV_max > 4.5, total lesion glycolysis (TLG) > 377, total metabolic tumour volume (TMTV) > 88 cm³, and heterogeneity index (HI_suv) > 1.69. The best prognostic marker was the TLG: the 4-y estimates of survival were 97% [95% CI, 90% - 100%] in patients with TLG ≤ 377 vs. 27% [95% CI, 5% - 49%] in patients with TLG > 377 (P < 0.0001; χ² 27.85; hazard ratio 13.27 [95% CI, 3.72–47.35]). T/L ratio, SUV_max and TMTV demonstrated slightly lower performance to predict survival, with χ² ranging 14.41–19.12. The HI_suv index was not predictive of survival.

Conclusion

Our study demonstrates that TLG and TMTV, as PET/CT measures of metabolic tumour burden, may be used clinically to identify sarcomatous transformation in patients with NF1 and predict overall survival, with a higher specificity for the TLG. Conventional measures such as the SUV_max, and T/L ratio also demonstrate high prognostic value.     

Cholestasis Reveals Severe Cortisol Deficiency in Neonatal Pituitary Stalk Interruption Syndrome

Objectives

Cholestasis has been reported during the course of congenital hypothalamic-pituitary deficiency, but crucial information is lacking regarding both its origin and prognosis. We aimed to characterize the course of cholestasis and factors contributing to it in patients with deficiency due to pituitary stalk interruption syndrome (PSIS).

Methods

We conducted a retrospective single-center, case-cohort study including 16 patients with PSIS diagnosed before one year of age. We collected clinical and biological parameters from medical records and compared the characteristics of the endocrine syndrome in PSIS patients with and without cholestasis.

Results

5/16 patients had cholestasis, all with a neonatal onset and multiple hypothalamic-pituitary deficiency. Patients with cholestasis presented with lower Apgar score and higher rate of ophthalmic malformations: 3/5 vs 1/11, p = 0.03 and 5/5 vs 4/11, p = 0.02, respectively. The plasma cortisol level was strongly decreased in patients with cholestasis: 12.4 ng/mL (8–15 ng/mL) vs 79.4 ng/mL (10–210 ng/mL), p = 0.04. Cholestasis resolved within 9 months following hormone supplementation. No development of chronic liver disease was observed during a median follow-up of 9.4 years (range, 1.3–13.3 years).

Conclusions

Cholestasis is a frequent symptom at presentation of PSIS during the neonatal period that may help earlier diagnosis and that indicates a profound cortisol deficiency.     

Spatiotemporal Evolution of Ebola Virus Disease at Sub-National Level during the 2014 West Africa Epidemic: Model Scrutiny and Data Meagreness

Background

The Ebola outbreak in West Africa has infected at least 27,443 individuals and killed 11,207, based on data until 24 June, 2015, released by the World Health Organization (WHO). This outbreak has been characterised by extensive geographic spread across the affected countries Guinea, Liberia and Sierra Leone, and by localized hotspots within these countries. The rapid recognition and quantitative assessment of localised areas of higher transmission can inform the optimal deployment of public health resources.

Methods

A variety of mathematical models have been used to estimate the evolution of this epidemic, and some have pointed out the importance of the spatial heterogeneity apparent from incidence maps. However, little is known about the district-level transmission. Given that many response decisions are taken at sub-national level, the current study aimed to investigate the spatial heterogeneity by using a different modelling framework, built on publicly available data at district level. Furthermore, we assessed whether this model could quantify the effect of intervention measures and provide predictions at a local level to guide public health action. We used a two-stage modelling approach: a) a flexible spatiotemporal growth model across all affected districts and b) a deterministic SEIR compartmental model per district whenever deemed appropriate.

Findings

Our estimates show substantial differences in the evolution of the outbreak in the various regions of Guinea, Liberia and Sierra Leone, illustrating the importance of monitoring the outbreak at district level. We also provide an estimate of the time-dependent district-specific effective reproduction number, as a quantitative measure to compare transmission between different districts and give input for informed decisions on control measures and resource allocation. Prediction and assessing the impact of control measures proved to be difficult without more accurate data. In conclusion, this study provides us a useful tool at district level for public health, and illustrates the importance of collecting and sharing data.     

Adolescent Sexual and Reproductive Health Services and Implications for the Provision of Voluntary Medical Male Circumcision: Results of a Systematic Literature Review

Background

Voluntary medical male circumcision (VMMC) is a critical HIV prevention tool. Since 2007, sub-Saharan African countries with the highest prevalence of HIV have been mobilizing resources to make VMMC available. While implementers initially targeted adult men, demand has been highest for boys under age 18. It is important to understand how male adolescents can best be served by quality VMMC services.

Methods and Findings

A systematic literature review was performed to synthesize the evidence on best practices in adolescent health service delivery specific to males in sub-Saharan Africa. PubMed, Scopus, and JSTOR databases were searched for literature published between January 1990 and March 2014. The review revealed a general absence of health services addressing the specific needs of male adolescents, resulting in knowledge gaps that could diminish the benefits of VMMC programming for this population. Articles focused specifically on VMMC contained little information on the adolescent subgroup. The review revealed barriers to and gaps in sexual and reproductive health and VMMC service provision to adolescents, including structural factors, imposed feelings of shame, endorsement of traditional gender roles, negative interactions with providers, violations of privacy, fear of pain associated with the VMMC procedure, and a desire for elements of traditional non-medical circumcision methods to be integrated into medical procedures. Factors linked to effective adolescent-focused services included the engagement of parents and the community, an adolescent-friendly service environment, and VMMC counseling messages sufficiently understood by young males.

Conclusions

VMMC presents an opportune time for early involvement of male adolescents in HIV prevention and sexual and reproductive health programming. However, more research is needed to determine how to align VMMC services with the unique needs of this population.