Changes in Organic Matter of a Ferrallitic Tropical Soil Degraded by Cropping Systems: The Case of Southern Senegal

Understanding of the mechanisms involved in the restoration of degraded soils is necessary in order to assess the sustainability of a cropping system. For this purpose, an 8-year experiment was set up to test the efficiency of four cropping systems involving applications of fertilizer and/or manure and incorporation of crop residues and/or fallows on the regeneration of a Haplic Acrisol degraded by about 90 years of traditional cropping (groundnut-millet rotation without any input). The supply of nitrogen by the soil and particle size and chemical distribution were measured and used to characterize the soil organic matter (SOM) after 2 and 8 years of treatments, and then related to nutrients uptake. Two of the four cropping systems tested that were expected to regenerate soil fertility (Q1 and Q2: 4-year rotations including a plowed-in fallow, incorporation of crop residues, and mineral fertilization) both had a depressive effect on SOM content, although the losses of total C and N observed during the experiment (e.g .,-23% N and -20% N for Q1 and Q2, respectively) were less than that for the control (traditional cropping B, -33% N). Only the multiyear fallow did not result in further degradation of SOM, without, however, enriching the soil. On the other hand, an annual application of 10 Mg dry matter of manure ha -1 , combined with fertilizer, markedly increased the SOM (total N increased by factor 2 after only 2 years), an effect that seemed, however, stabilized at the end of the 8 years. Only a strong (10 Mg dry matter ha -1 ) and annual supply of manure, associated with mineral fertilization, had a positive effect on SOM, but its durability is not established.     

Physicochemical Interpretation of Acid‐Base Abnormalities in 54 Adult Horses with Acute Severe Colitis and Diarrhea

Background

The quantitative effect of strong electrolytes, pCO₂, and plasma protein concentration in determining plasma pH and bicarbonate concentrations can be demonstrated with the physicochemical approach. Plasma anion gap (AG) and strong ion gap (SIG) are used to assess the presence or absence of unmeasured anions.

Hypotheses

The physicochemical approach is useful for detection and explanation of acid‐base disorders in horses with colitis. AG and SIG accurately predict hyperlactatemia in horses with colitis.

Animals

Fifty‐four horses with acute colitis and diarrhea.

Methods

Retrospective study . Physicochemical variables were calculated for each patient. ROC curves were generated to analyze sensitivity and specificity of AG and SIG for predicting hyperlactatemia.

Results

Physicochemical interpretation of acid‐base events indicated that strong ion metabolic acidosis was present in 39 (72%) horses. Mixed strong ion acidosis and decreased weak acid (hypoproteinemia) alkalosis was concomitantly present in 17 (30%) patients. The sensitivity and specificity of AG and SIG to predict hyperlactatemia (L‐lactate > 5 mEq/L) were 100% (95% CI, 66.4–100; P < .0001) and 84.4% (95% CI, 70.5–93.5 P < .0001). Area under the ROC curve for AG and SIG for predicting hyperlactatemia was 0.95 (95% CI, 0.86–0.99) and 0.93 (95% CI, 0.83–0.99), respectively.

Conclusion and Clinical relevance

These results emphasize the importance of strong ions and proteins in the maintenance of the acid‐base equilibria. AG and SIG were considered good predictors of clinically relevant hyperlactatemia.     

High-performance liquid chromatography-mass spectrometry profiling of phenolic compounds for evaluation of olive oil bitterness and pungency

Bitterness and pungency are important parameters for olive oil quality. Therefore, two instrumental methods for evaluation of these taste attributes were developed. The first one is based on the photometric measurement of total phenolic compounds content, whereas the second one is based on the semiquantitative evaluation of hydrophilic compounds by high-performance liquid chromatography-mass spectrometry (HPLC-MS). Evaluation of total phenolic compounds content was performed by a modified method for the determination of the K(225) value using a more specific detection based on the pH value dependency of absorbance coefficients of phenols at λ = 274 nm. The latter method was not suitable for correct prediction, because no significant correlation between bitterness/pungency and total phenolic compounds content could be found. For the second method, areas of 25 peaks detected in 54 olive oil samples by a HPLC-MS profiling method were correlated with the bitterness and pungency by partial least-squares regression. Six compounds (oleuropein aglycon, ligstroside aglycon, decarboxymethyl oleuropein aglycon, decarboxymethyl ligstroside aglycon, elenolic acid, and elenolic acid methyl ester) show high correlations to bitterness and pungency. The computed model using these six compounds was able to predict bitterness and pungency of olive oil in the error margin of the sensory evaluation (±0.5) for most of the samples.     

The influence of fermentation processes and cereal grains in wholegrain bread on reducing phytate content

Wholegrain bread is generally thought of as being more healthy than white bread due to it having a higher content of dietary fibre, vitamins (especially vitamin B and E) and many important minerals. However, wholegrain bread also contains high levels of phytate (myo-inositolhexakisphosphate, InsP-6) which may bind desirable nutrients, preventing their absorption in the gut and thereby reducing the nutritional value of the end product. In order to evaluate factors influencing phytate levels, the effects of fermentation and selected wholemeal flours from rye, oats and wheat were investigated. Phytate levels were assessed using a spectrophotometric assay based on the measurement of iron with 2,2′-bipyridine. Phytate decreased in freshly ground wholegrain flour dough during the fermentation process with time of fermentation being the most important factor. Fermentation temperature was found to make only a small difference to the process of phytate reduction. Since the potential benefits of wholemeal breads incorporating various grains (e.g. oats and rye) are increasingly evident, this research has important implications for human health.     

Structure of a cofactor-deficient nitrogenase MoFe protein

One of the most complex biosynthetic processes in metallobiochemistry is the assembly of nitrogenase, the key enzyme in biological nitrogen fixation. We describe here the crystal structure of an iron-molybdenum cofactor-deficient form of the nitrogenase MoFe protein, into which the cofactor is inserted in the final step of MoFe protein assembly. The MoFe protein folds as a heterotetramer containing two copies each of the homologous alpha and beta subunits. In this structure, one of the three alpha subunit domains exhibits a substantially changed conformation, whereas the rest of the protein remains essentially unchanged. A predominantly positively charged funnel is revealed; this funnel is of sufficient size to accommodate insertion of the negatively charged cofactor.     

The crystal structure of [Fe]-hydrogenase reveals the geometry of the active site

Biological formation and consumption of molecular hydrogen (H2) are catalyzed by hydrogenases, of which three phylogenetically unrelated types are known: [NiFe]-hydrogenases, [FeFe]-hydrogenases, and [Fe]-hydrogenase. We present a crystal structure of [Fe]-hydrogenase at 1.75 angstrom resolution, showing a mononuclear iron coordinated by the sulfur of cysteine 176, two carbon monoxide (CO) molecules, and the sp2-hybridized nitrogen of a 2-pyridinol compound with back-bonding properties similar to those of cyanide. The three-dimensional arrangement of the ligands is similar to that of thiolate, CO, and cyanide ligated to the low-spin iron in binuclear [NiFe]- and [FeFe]-hydrogenases, although the enzymes have evolved independently and the CO and cyanide ligands are not found in any other metalloenzyme. The related iron ligation pattern of hydrogenases exemplifies convergent evolution and presumably plays an essential role in H2 activation. This finding may stimulate the ongoing synthesis of catalysts that could substitute for platinum in applications such as fuel cells.