Density dependence and interspecific interactions between arbuscular mycorrhizal fungi mediated plant growth, glomalin production, and sporulation

Functional differences between the arbuscular mycorrhizal fungi Glomus intraradices Schenk and Smith and Scutellospora heterogama Nicolson and Gerdemann as they affect Persea americana Mill. growth, glomalin, and fungal sporulation were examined by varying the composition and relative density of the two fungi over a gradient of available phosphorus (P). The plant benefit provided by these mycorrhizal fungi together was not a simple sum of the benefits pro-vided by each fungus in monoculture at its respective density. Glomus intraradices and S. heterogama interacted to reduce plant growth rates and uptake of P, zinc (Zn), and iron (Fe) relative to plants inoculated with G. intraradices alone. Thus, for plant growth and nutrition, no evidence for functional complementarity was detected. Instead, interspecific interactions between mycorrhizal fungi resulted in a negative feedback on plants. Under high available P, fungal functional differences were reduced, whereas the overall difference between mycorrhizal and nonmycorrhizal plants was greatest. Overall, S. heterogama produced more glomalin than did G. intraradices. In a mixture, sporulation of the inferior mutualist, S. heterogama, was lower than that of the superior mutualist, G. intraradices, but interspecific fungal interactions increased the sporulation of both fungi. Despite the negative impact of interspecific interactions on plants, supporting multiple arbuscular mycorrhizal fungi was of greater benefit than being nonmycorrhizal. © 2007 NRC

Wikipedia Information Flow Analysis Reveals the Scale-Free Architecture of the Semantic Space

In this paper we extract the topology of the semantic space in its encyclopedic acception, measuring the semantic flow between the different entries of the largest modern encyclopedia, Wikipedia, and thus creating a directed complex network of semantic flows. Notably at the percolation threshold the semantic space is characterised by scale-free behaviour at different levels of complexity and this relates the semantic space to a wide range of biological, social and linguistics phenomena. In particular we find that the cluster size distribution, representing the size of different semantic areas, is scale-free. Moreover the topology of the resulting semantic space is scale-free in the connectivity distribution and displays small-world properties. However its statistical properties do not allow a classical interpretation via a generative model based on a simple multiplicative process. After giving a detailed description and interpretation of the topological properties of the semantic space, we introduce a stochastic model of content-based network, based on a copy and mutation algorithm and on the Heaps' law, that is able to capture the main statistical properties of the analysed semantic space, including the Zipf's law for the word frequency distribution

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods This study comprised an analysis of GlobalSurg-1 and -2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle- and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 per cent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P < 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P < 0·001) in low- compared with middle- and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P < 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P < 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P < 0·001). Conclusion Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone

Density dependence and interspecific interactions between arbuscular mycorrhizal fungi mediated plant growth, glomalin production, and sporulation

Functional differences between the arbuscular mycorrhizal fungi Glomus intraradices Schenk and Smith and Scutellospora heterogama Nicolson and Gerdemann as they affect Persea americana Mill. growth, glomalin, and fungal sporulation were examined by varying the composition and relative density of the two fungi over a gradient of available phosphorus (P). The plant benefit provided by these mycorrhizal fungi together was not a simple sum of the benefits pro-vided by each fungus in monoculture at its respective density. Glomus intraradices and S. heterogama interacted to reduce plant growth rates and uptake of P, zinc (Zn), and iron (Fe) relative to plants inoculated with G. intraradices alone. Thus, for plant growth and nutrition, no evidence for functional complementarity was detected. Instead, interspecific interactions between mycorrhizal fungi resulted in a negative feedback on plants. Under high available P, fungal functional differences were reduced, whereas the overall difference between mycorrhizal and nonmycorrhizal plants was greatest. Overall, S. heterogama produced more glomalin than did G. intraradices. In a mixture, sporulation of the inferior mutualist, S. heterogama, was lower than that of the superior mutualist, G. intraradices, but interspecific fungal interactions increased the sporulation of both fungi. Despite the negative impact of interspecific interactions on plants, supporting multiple arbuscular mycorrhizal fungi was of greater benefit than being nonmycorrhizal. © 2007 NRC

Relatedness among arbuscular mycorrhizal fungi drives plant growth and intraspecific fungal coexistence.

Arbuscular mycorrhizal fungi (AMF) form symbioses with most plant species. They are ecologically important determinants of plant growth and diversity. Considerable genetic variation occurs in AMF populations. Thus, plants are exposed to AMF of varying relatedness to each other. Very little is known about either the effects of coexisting AMF on plant growth or which factors influence intraspecific AMF coexistence within roots. No studies have addressed whether the genetics of coexisting AMF, and more specifically their relatedness, influences plant growth and AMF coexistence. Relatedness is expected to influence coexistence between individuals, and it has been suggested that decreasing ability of symbionts to coexist can have negative effects on the growth of the host. We tested the effect of a gradient of AMF genetic relatedness on the growth of two plant species. Increasing relatedness between AMFs lead to markedly greater plant growth (27% biomass increase with closely related compared to distantly related AMF). In one plant species, closely related AMF coexisted in fairly equal proportions but decreasing relatedness lead to a very strong disequilibrium between AMF in roots, indicating much stronger competition. Given the strength of the effects with such a shallow relatedness gradient and the fact that in the field plants are exposed to a steeper gradient, we consider that AMF relatedness can have a strong role in plant growth and the ability of AMF to coexist. We conclude that AMF relatedness is a driver of plant growth and that relatedness is also a strong driver of intraspecific coexistence of these ecologically important symbionts

Early increase of NOX2-derived oxidative stress in children: relationship with age

BACKGROUND: Studies conducted in the prepubertal period showed that biomarkers of oxidative stress decreased with increasing age in normocholesterolemic children (NC), and, conversely, they are persistently high in hypercholesterolemic children (HC). Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is the most important cellular source of reactive oxygen species. No data have been reported concerning the behavior of age-related oxidative stress generated by NOX2, the catalytic subunit of NADPH oxidase, in children. METHODS: We performed a cross-sectional study comparing oxidized low-density lipoprotein (ox-LDL), as a marker of oxidative stress, and NOX2 activity, as assessed by blood levels of soluble NOX2-derived peptide (sNOX2-dp), in a population of 250 children, induding 125 NC and 125 HC. RESULTS: HC had higher sNOX2-dp (25.8 +/- 16.1 pg/ml) and ox-LDL (23.6 +/- 14.4 U/I) levels as compared with NC (15.4 +/- 10.1 and 11.6 +/- 6.4 pg/ml, respectively; P < 0.001). Multiple linear regression analysis showed that ox-LDL and total cholesterol were the only independent predictive variables associated with sNOX2-dp. In NC, ox-LDL and sNOX2-dp significantly decreased from the first to the second quintile of age. In HC, ox-LDL and sNOX2-dp levels did not show significant differences among quintiles of age. CONCLUSION: This study suggests that NOX2 contributes to generating ox-LDL during the early phase of life in NC and to the persistent high oxidative stress in the prepubertal period of HC