Tropical tree ectomycorrhiza are distributed independently of soil nutrients

Mycorrhizae, a form of plant-fungal symbioses, mediate vegetation impacts on ecosystem functioning. Climatic effects on decomposition and soil quality are suggested to drive mycorrhizal distributions, with arbuscular mycorrhizal plants prevailing in low-latitude/high-soil-quality areas and ectomycorrhizal (EcM) plants in high-latitude/low-soil-quality areas. However, these generalizations, based on coarse-resolution data, obscure finer-scale variations and result in high uncertainties in the predicted distributions of mycorrhizal types and their drivers. Using data from 31 lowland tropical forests, both at a coarse scale (mean-plot-level data) and fine scale (20 × 20 metres from a subset of 16 sites), we demonstrate that the distribution and abundance of EcM-associated trees are independent of soil quality. Resource exchange differences among mycorrhizal partners, stemming from diverse evolutionary origins of mycorrhizal fungi, may decouple soil fertility from the advantage provided by mycorrhizal associations. Additionally, distinct historical biogeographies and diversification patterns have led to differences in forest composition and nutrient-acquisition strategies across three major tropical regions. Notably, Africa and Asia's lowland tropical forests have abundant EcM trees, whereas they are relatively scarce in lowland neotropical forests. A greater understanding of the functional biology of mycorrhizal symbiosis is required, especially in the lowland tropics, to overcome biases from assuming similarity to temperate and boreal regions.

Distribution of biomass dynamics in relation to tree size in forests across the world

Tree size shapes forest carbon dynamics and determines how trees interact with their environment, including a changing climate. Here, we conduct the first global analysis of among-site differences in how aboveground biomass stocks and fluxes are distributed with tree size. We analyzed repeat tree censuses from 25 large-scale (4-52 ha) forest plots spanning a broad climatic range over five continents to characterize how aboveground biomass, woody productivity, and woody mortality vary with tree diameter. We examined how the median, dispersion, and skewness of these size-related distributions vary with mean annual temperature and precipitation. In warmer forests, aboveground biomass, woody productivity, and woody mortality were more broadly distributed with respect to tree size. In warmer and wetter forests, aboveground biomass and woody productivity were more right skewed, with a long tail towards large trees. Small trees (1-10 cm diameter) contributed more to productivity and mortality than to biomass, highlighting the importance of including these trees in analyses of forest dynamics. Our findings provide an improved characterization of climate-driven forest differences in the size structure of aboveground biomass and dynamics of that biomass, as well as refined benchmarks for capturing climate influences in vegetation demographic models.

Geochemistry and pH control of seepage from Ni-Cu rich mine tailings at Selebi Phikwe, Botswana

Acid mine drainage from mine tailings at Selebi Phikwe, eastern Botswana, has been investigated using a combination of total decomposition, sequential extraction, X-ray diffraction, Mössbauer spectroscopy, and SEM analyses of solid phase samples, water analyses, isotopic analyses, and geochemical modeling. The principal ferric phases in the seepage stream sediments are jarosite and goethite, which incorporate Ni and Cu. The Mössbauer spectroscopy (MS) indicated exclusively 3+ oxidation state of iron with typical features of ferric hydroxides/sulfates. A fraction of dissolved sulfate is also sequestered in gypsum which precipitates further downstream. Significant portions of Fe, Ni, and Cu are transported in suspension. Values of pH decreased downstream due to H⁺ generated by the precipitation of jarosite. Values of δ²H and δ¹⁸O indicate evaporation of pore water in the mine tailings before seepage. Values of δ³⁴S(SO₄) are consistent with the oxidation of sulfides, but sample from the seepage face is affected by dissolution of gypsum. No minerals of Ni and Cu were detected and the principal attenuation processes seem to be adsorption and co-precipitation with jarosite. Higher contents of Cu are sequestered in solid phases compared to Ni, in spite of much higher dissolved Ni concentrations. Based on the speciation calculations, seepage water is undersaturated with respect to all Ni and Cu phases and adsorption and co-precipitation with jarosite seems to be the principal attenuation processes. Direct geochemical modeling was able to reproduce downstream pH trends, thus confirming the precipitation of jarosite as the principal pH-controlling process.

Graphene oxide-based electrochemical label-free detection of glycoproteins down to aM level using a lectin biosensor

A label-free ultrasensitive impedimetric biosensor with lectin immobilised on graphene oxide (GO) for the detection of glycoproteins from 1 aM is shown here. This is the first time a functional lectin biosensor with lectin directly immobilised on a graphene-based interface without any polymer modifier has been described. The study also shows that hydrophilic oxidative debris present on GO has a beneficial effect on the sensitivity of (8.46 ± 0.20)% per decade for the lectin biosensor compared to the sensitivity of (4.52 ± 0.23)% per decade for the lectin biosensor built up from GO with the oxidative debris washed out.

Geochemistry of mine tailings and behavior of arsenic at Kombat, northeastern Namibia

The mine tailings at Kombat, in semiarid northeastern Namibia, were investigated by the combination of solid-phase analyses, mineralogical methods, leaching tests, and speciation modeling. Dissolution of the most abundant primary sulfides, chalcopyrite and galena, released copper and lead which were adsorbed onto ferric oxyhydroxides or precipitated in the form of malachite, Cu2CO3(OH)2, and cerussite, PbCO3, respectively. Arsenic released from arsenopyrite was incorporated into ferric oxyhydroxides. Based on sequential extraction and (57)Fe Mössbauer spectroscopy, a large amount of ferric iron is present as low solubility hematite and goethite formed rapidly (<10 years) under warm semiarid climatic conditions, and arsenic in these phases is relatively tightly bound. It seems that Cu and especially Pb in carbonate minerals represent a more serious environmental risk. Immobilization of As in hematite has implications for other mining sites in regions with similar climatic conditions because this process results in long-term immobilization of As.

Electric field gradient in FeTiO3 by nuclear magnetic resonance and ab initio calculations

Temperature dependence of nuclear magnetic resonance (NMR) spectra of (47)Ti and (49)Ti in polycrystalline ilmenite FeTiO(3) was measured in the range from 5 to 300 K under an external magnetic field of 9.401 T. NMR spectra collected between 300 and 77 K exhibit a resolved quadrupole splitting. The electric field gradient (EFG) tensor was evaluated for Ti nuclei and the ratio of (47)Ti and (49)Ti nuclear quadrupole moments was refined during the fitting procedure. Below 77 K, the fine structure of quadrupole splitting disappears due to the enormous increase of anisotropy. As a counterpart, ab initio calculations were performed using full potential augmented plane waves + local orbitals. The calculated EFG tensors for Ti and Fe were compared to the experimental ones evaluated from NMR and the Mössbauer spectroscopy experiments.

Patient preferences for cardiac rehabilitation and desired program elements

BACKGROUND

Data evaluating the efficacy of traditional cardiac rehabilitation programs to meet patient needs are limited. The authors studied patient-perceived preferences in cardiac rehabilitation programs and desired program elements to evaluate differences by gender or age.

METHODS

The authors surveyed 199 patients (136 men, 60.0 +/- 11.6 years; 63 women, 63.7 +/- 12.7 years; P = 0.045) discharged from a tertiary referral hospital with acute myocardial infarction. Participants completed a standardized questionnaire regarding enrollment in rehabilitation and preferences for six program types on a 10-point scale (1 = little or no agreement, 10 = strongly agree).

RESULTS

In this study, 54.3% of subjects enrolled in cardiac rehabilitation. Older patients (> or = 65 years) were more likely to enroll in home-based programs compared with younger patients (< 65 years) (11.8% versus 1.4%, P = 0.02). Younger patients preferred a short-term rehabilitation facility more than older patients (7.4 +/- 3.5 versus 5.1 +/- 4.1 units on the 10-point scale, P = 0.001), and rated the following more favorably than older patients: local health club programs (6.2 +/- 3.7 versus 4.5 +/- 4.0, P = 0.01), long-term programs (6.5 +/- 3.8 versus 4.9 +/- 4.2, P = 0.02), and comprehensive programs (6.6 +/- 3.7 versus 4.9 +/- 2.2, P = 0.02). Younger patients rated the following program elements more favorably compared with older patients: stress management (7.0 +/- 3.5 versus 5.7 +/- 4.1, P = 0.04), vocational counseling (5.1 +/- 3.9 versus 1.9 +/- 2.4, P = 0.001), and smoking cessation (4.9 +/- 4.4 versus 2.7 +/- 3.4, P = 0.001).

CONCLUSIONS

Program preferences differed significantly by age, but not gender. Older patients enrolled in home-based programs over clinic-based programs. Younger patients rated stress management, vocational counseling, and smoking cessation more favorably than older patients. Strategies to enhance patient participation in cardiac rehabilitation should incorporate patient age and preferences for program types and elements.

Acrylonitrile metabolism in the rat

Acrylonitrile (AN) is metabolized by an oxidative pathway via glycidonitrile and glycolaldehyde cyanohydrin to cyanide (CN-), which is transformed to thiocyanate. The major route of AN metabolism (more than 2/3), however, proceeds via cyanoethylation of glutathione, to N-acetyl-S-(2-cyanoethyl)cysteine (AN-mercapturic acid) as a final product.

[Acute toxic liver lesion through industrial noxious substances and drugs in higher than therapeutic doses]

From the accessible material an attempt was made to estimate the frequency of acute toxic disturbances of liver and its relation to all intoxications together with special regard to the composition of noxious substances on the conditions of this country. From 3700 cases of all acute intoxications or serious attempts of intoxication 54 cases were discovered to have marked hepatic disturbance (about 1.5%). The noxious substance causing hepatic disturbance in the overwhelming majority of cases was tetrachlormethan (and chemically related substances) or new herbicide drugs of the dipyridine compounds. The last mentioned group is highly lethal and the more important as it is a relatively new substance to which health control and practice is less accustomed as to a potential hepatotoxic drug than to tetrachlormethan. It is pointed further to a less frequent potential intoxication by phenylbutazone and its derivatives especially in children and to the acute intoxication by INH when high single doses of this drug are used.

Ammonia and uric acid formation after rapid intravenous fructose administration to healthy subjects and patients with compensated cirrhosis of the liver

To seven healthy volunteers, 12 and 24 g i.v. fructose were administered in the form of 20% solution at a rate of 4 g/min. After both doses, during the 10th min after the completed intravenous administration, a statistically significant increase of serum ammonia and serum uric acid occurred. After 24 g, the rise of the uric acid level remains significant during the 40th min after administration, while ammonia values return to the basal level. Increments of ammonia and uric acid are higher after a larger fructose dose. Under the same set-up and at the same rate, 24 g fructose were administered to eight patients with compensated cirrhosis of the liver. The rise of uric acid was practically the same as in healthy subjects similar to the rise of the ammonia level during the 10th min after administration. 40 min after administration, however, the ammonia level in cirrhotic patients remained significantly raised, as compared with the initial level.

The metabolism of isocytidine in Escherichia coli

Intact cells and cell-free extracts of E. coli convert isocytidine to isocytosine and uracil. The radioactive label of 5-[(3)H]isocytidine is incorporated into RNA and, DNA of growing bacteria at a rate equal to about 1.4% of that of cytidine under similar conditions; the radioactivity is found in uridylic, cytidylic and 2'-deoxythymidylic acids, while less than 0.4% of incorporated radioactive material might be due to possible incorporation of intact isocytidine. Uridine phosphorylase and cytidine deaminase apparently do not participate in the metabolic conversion of isocytidine.5-[(3)H]isocytidine was prepared by platinum-catalyzed dehalogenation of 5-bromoisocytidine in the presence of tritium. The 5-bromo derivative was obtained from 2',3'-0- -isopropylideneisocytidine by N-bromsuccinimide bromination followed by acidic hydrolysis.