Global soil nitrogen cycle pattern and nitrogen enrichment effects: Tropical versus subtropical forests

Tropical and subtropical forest biomes are a main hotspot for the global nitrogen (N) cycle. Yet, our understanding of global soil N cycle patterns and drivers and their response to N deposition in these biomes remains elusive. By a meta-analysis of 2426-single and 161-paired observations from 89 published ¹⁵ N pool dilution and tracing studies, we found that gross N mineralization (GNM), immobilization of ammonium ($I_{{\mathrm{NH}}_4}$) and nitrate ($I_{{\mathrm{NO}}_3}$), and dissimilatory nitrate reduction to ammonium (DNRA) were significantly higher in tropical forests than in subtropical forests. Soil N cycle was conservative in tropical forests with ratios of gross nitrification (GN) to $I_{{\mathrm{NH}}_4}$ (GN/$I_{{\mathrm{NH}}_4}$) and of soil nitrate to ammonium (NO₃⁻/NH₄⁺) less than one, but was leaky in subtropical forests with GN/$I_{{\mathrm{NH}}_4}$ and NO₃⁻/NH₄⁺ higher than one. Soil NH₄⁺ dynamics were mainly controlled by soil substrate (e.g., total N), but climatic factors (e.g., precipitation and/or temperature) were more important in controlling soil NO₃⁻ dynamics. Soil texture played a role, as GNM and $I_{{\mathrm{NH}}_4}$ were positively correlated with silt and clay contents, while $I_{{\mathrm{NO}}_3}$ and DNRA were positively correlated with sand and clay contents, respectively. The soil N cycle was more sensitive to N deposition in tropical forests than in subtropical forests. Nitrogen deposition leads to a leaky N cycle in tropical forests, as evidenced by the increase in GN/$I_{{\mathrm{NH}}_4}$, NO₃⁻/NH₄⁺, and nitrous oxide emissions and the decrease in $I_{{\mathrm{NO}}_3}$ and DNRA, mainly due to the decrease in soil microbial biomass and pH. Dominant tree species can also influence soil N cycle pattern, which has changed from conservative in deciduous forests to leaky in coniferous forests. We provide global evidence that tropical, but not subtropical, forests are characterized by soil N dynamics sustaining N availability and that N deposition inhibits soil N retention and stimulates N losses in these biomes.     

Possible gastrointestinal disorders for athletes during Ramadan: an overview

Ramadan is considered to be the month of the stomach break. It has been reported that Ramadan has some health benefits. In most Muslims countries, there is a huge modification in the diet during this month. These changes could induce some gastrointestinal (GI) disorders (e.g. diarrhea, cramps, fullness, nausea). The aims of the present overview were to present some challenges that could be observed for athletes during the training sessions or competition and present some practical recommendations to avoid GI disorders during Ramadan. Based on previous studies, we could advance that the prevalence of GI disorders will be more pronounced when athletes travel for international competitions during Ramadan. Besides, GI disorders are more frequent for athletes when there is a huge modification in the training load. Dehydration observed during Ramadan is one of the factors that may induce GI disorders. The latter could be exacerbated by sweat loss during training sessions. Carbohydrate is frequently used by athletes to improve performance and is associated with some GI disorders. Therefore, during Ramadan, coaches and athletes should be advised to maintain the same diet and a good hydration as before the fasting month, and avoid air travel when preparing for competitions.     

Identification of genetic defects underlying FVII deficiency in 10 patients belonging to eight unrelated families of the North provinces from Tunisia

ABSTRACT: Inherited factor VII (FVII) deficiency is a rare disorder characterized by a bleeding phenotype varying from mild to severe. To date, more than 200 mutations have been described along the F7 gene encoding for FVII. The aim of this study was the identification of genetic defects underlying FVII deficiency in 10 patients belonging to eight unrelated families of the North provinces from Tunisia. Mutation detection was performed by sequencing the whole F7 gene coding region, exon-intron boundaries and about 400 bp of the promoter region. We identified 5 mutations in five unrelated families; the novel p.F328Y mutation and the reported mutations: p.R304Q, p.M298I, IVS1aG > A and nt1005C > T. For the remaining 5 patients we didn't identified any mutations using PCR/Sequencing protocol. In conclusion, this study represents the first comprehensive molecular series of FVII deficiency affected patients in Tunisia from the North. We will try in the future to continue the molecular study for Tunisian patients from Center and South provinces in order to have a complete idea about the FVII deficiency mutational profile in our country. Virtual slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1288044089753085.     

Piecewise Whittle estimator for trabecular bone radiograph characterization

Osteoporosis is a disease in which low bone mass and microarchitectural deterioration of bone tissue lead to increased bone fragility and a consequent increase in fracture risk. The objective of this paper is to develop and validate a new method to assess bone microarchitecture on radiographs. Taking into account the piecewise fractal nature of bone radiograph images, an appropriate fractal model (piecewise fractional Brownian motion) is used to characterize the trabecular bone network. Based on the Whittle estimator, a new method for calculating the Hurst exponent H is developed to better consider the piecewise fractal nature of the data. Different estimators are used and compared to the proposed method to discriminate two populations composed of healthy controls and osteoporotic patients. Our findings demonstrate that the new estimator proposed here provides effective results in terms of discrimination of the subjects and is better adapted to bone radiograph image analysis.     

Mitochondrial DNA structure in the Arabian Peninsula

Background  

Two potential migratory routes followed by modern humans to colonize Eurasia from Africa have been proposed. These are the two natural passageways that connect both continents: the northern route through the Sinai Peninsula and the southern route across the Bab al Mandab strait. Recent archaeological and genetic evidence have favored a unique southern coastal route. Under this scenario, the study of the population genetic structure of the Arabian Peninsula, the first step out of Africa, to search for primary genetic links between Africa and Eurasia, is crucial. The haploid and maternally inherited mitochondrial DNA (mtDNA) molecule has been the most used genetic marker to identify and to relate lineages with clear geographic origins, as the African Ls and the Eurasian M and N that have a common root with the Africans L3.     

The genetic structure of the Kuwaiti population

Summary Frequency estimates were determined on seventeen blood group, serum protein, and red-cell enzyme markers on random samples of 193 individuals from two Bedouin tribes in addition to the general population in Kuwait. Genetic heterogeneity between the three communities is evident from the significant differences in allelic distribution of the polymorphic markers.Genetic distance measurements were used to compare the results with the oral history of descent of the two tribal communities. Results were in agreement with tribal history.     

Effects of L-carnitine loading on the aerobic and anaerobic performance of endurance athletes

L-Carnitine (L-C), a well known physiological carrier across the inner mitochondrial membrane of activated long chain fatty acids and acceptor of acyl groups from acyl-CoA, has been recently synthesised industrially. This has made it possible to study the effects of L-C loading (4 g X d(-1) by mouth over a period of 2 weeks) on the aerobic and anaerobic performance of 6 long distance competitive walkers. As a result of the treatment: 1) mean total, free and esterified serum L-C both at rest and shortly after completing a 120 min walk at about 65% of the individual maximal aerobic power (VO2max) were significantly increased; 2) VO2max increased 6%, from 54.5 +/- 3.7 (S.D.) to 57.8 +/- 4.7 m1O2 X kg(-1) X min(-1) (P less than 0.02); 3) blood lactate concentration (Lab) as a consequence of short bouts repeated exercise (series of 10, 15 and 20 jumps off both feet on a force platform) was unchanged; 4) heart rate, pulmonary ventilation, oxygen consumption, and respiratory quotient in the same conditions as for 1) were unchanged. It is concluded that, in trained athletes, as a consequence of L-C loading VO2max is slightly but significantly raised, probably as a result of an activation of substrate flow through the TCA cycle, whereas the lipid contribution to metabolism in prolonged submaximal exercise remains unchanged.     

Heterogeneity of bile salts resistance in the Lactobacillus isolates of a probiotic consortium

The effect of bile salts was tested on a collection of 38 strains of Lactobacillus isolated from a probiotic bacterial consortium Half of the strains were slightly affected by 0.3% bile salts showing a delay of growth below 1 h, to reach an absorbance of 0.3 at 600 nm in MRS broth, compared to a reference curve without bile salts. According to the heterogencity of sensitivity, the resistance to bile salts should be checked for the selection of probiotic strains of Lactobacillus.     

Experimental sensitivity analysis of a trickle bed bioreactor for lignin peroxidases production by P. chrysosporium

A systematic experimental analysis of the parameters affecting the behaviour of a Trickle Bed Reactor (TBR) was performed. Lignin peroxidases (LiPs) were produced in the reactor by Phanerochaete chrysosporium entrapped in a Ca-alginate film covering ceramic supports (Berl saddles). Gas and liquid velocity, liquid flow regime, and thickness of encapsulating matrix were experimentally investigated. Reactor productivity and biological activity were considered as representative of reactor performance and evaluated by six probe parameters to take into account different process system configurations, i.e. single LiP extraction, multiple LiP extraction every 24 h and in vivo applications. Liquid fluid dynamics were the critical phenomena affecting LiPs production; the ranges of gas and liquid superficial velocity influencing the reactor performance were also identified. Alginate film thickness was shown to influence specific biomass activity but a limited impact on reactor productivity was verified.