Phosphorus availability and microbial respiration across different tundra vegetation types

Phosphorus (P) is an important nutrient in tundra ecosystems that co-limits or in some cases limits primary production. The availability of P is largely driven by soil characteristics, e.g., pH, organic carbon, and abundance of P-sorbing elements such as aluminium (Al) or iron (Fe). We tested how vegetation and soil properties relate to P availability across different tundra vegetation types. The different soil P fractions in the organic horizon were measured and plant foliar nitrogen (N) to P ratio and a plant bioassay was used as indicators of plant nutrient status. Microbial bioassays were used to study microbial respiration kinetics and in response to carbon, N, and P amendments. The distribution of P fractions differed significantly across vegetation types; labile fractions of P were less abundant in meadow sites compared to heath sites. Calcium-phosphates seemed to be an important P-fraction in meadows, but were only found in lower concentrations in the heath. There were only small differences in NaOH–extractable P between the vegetation types and this correlated with the distribution of oxalate-extractable Al. Plant N:P ratios and the plant bioassay indicated decreasing P availability from dry heath to mesic heath to mesic meadow. The microbial bioassay suggests that the heterotrophic microbial community is C-limited with N as a secondary limiting nutrient although there were indications that microbial P availability was lower in the meadow sites. Overall, we suggest that the observed variations in soil P across vegetation types are affecting both plant and microbial function although the differences seem to be relatively small.     

A high-throughput method for measuring growth and loss rates in microalgal cultures

A miniaturized and low-cost assay for algal growth and loss rates, and estimation of compensation light was developed and optimized. Microalgal cultures were grown in white 96-well microplates to estimate specific growth rates at six temperatures, five salinities and eight light levels. Data from black 24-well microplates at six temperatures, five salinities and five light conditions were used in addition to estimate loss rates and compensation light. Absorption and reflection of light were different in the white and black microplates. Growth rates were estimated from daily in vivo fluorescence (IVF) measurements using a microplate reader fitted with a fluorometer. To validate the microplate algal growth assay, IVF was compared with cell counting by flow cytometry. Maximal growth rate for the test alga Pseudochattonella farcimen (Heterokonta) was estimated to 0.52?±?0.05 day^?1 at optimal temperatures ranging from 9 to 14°C and salinities 18–26 psu. Lowest value of compensation light as photosynthetic photon flux density (PPFD) was 4.2?±?1.2 μmol photons m^?2 s^?1, and lowest saturation light, 34.1?±?3.7 μmol photons m^?2 s^?1, was observed in the temperature range 5–11°C and salinity range 23–28 psu. Minimum loss rate was obtained at temperatures 5–8°C and salinities 26–31 psu. Blooms of P. farcimen have been recorded in nature under conditions similar to those minimizing loss rates rather than maximizing growth rates in this study. The microalgal assay described here allows for a large number of conditions to be tested, and accurate optimal conditions for growth and loss rates to be obtained.     

Insights into type IV pilus biogenesis and dynamics from genetic analysis of a C-terminally tagged pilin: a role for O-linked glycosylation

Type IV pili are surface organelles essential for pathogenicity of many Gram-negative bacteria. In Neisseria gonorrhoeae, the major subunit of type IV pili, PilE, is a target of its general O-linked glycosylation system. This system modifies a diverse set of periplasmic and extracellular gonococcal proteins with a variable set of glycans. Here we show that expression of a particular hexa-histidine-tagged PilE was associated with growth arrest. By studying intra- and extragenic suppressors, we found that this phenotype was dependent on pilus assembly and retraction. Based on these results, we developed a sensitive tool to identify factors with subtle effects on pilus dynamics. Using this approach, we found that glycan chain length has differential effects on the growth arrest that appears to be mediated at the level of pilin subunit-subunit interactions and bidirectional remodelling of pilin between its membrane-associated and assembled states. Gonococcal pilin glycosylation thus plays both an intracellular role in pilus dynamics and potential extracellular roles mediated through type IV pili. In addition to demonstrating the effect of glycosylation on pilus dynamics, the study provides a new way of identifying factors with less dramatic effects on processes involved in type IV pilus biogenesis.     

Human urinary excretion and metabolism of (82)Se-enriched selenite and selenate determined by LC-ICP-MS

Urinary excretion of selenium after ingestion of isotope labeled selenite and selenate was studied in seven healthy volunteers, 4 men and 3 women (age 28-50 years). An aqueous solution containing 330 μL (82)Se-selenate (corresponding to 74.3 μg (82)Se) was given orally and urine samples were subsequently collected during the following 24 hours. The scheme was repeated four weeks later with a 280 μL (82)Se-selenite solution (corresponding to 74.4 μg (82)Se). The amount of total Se in the urine samples was determined by inductively coupled mass spectrometry. The mean total urinary excretion of (82)Se following (82)Se-selenate administration was 33.7% (range 15.6-42.5%) while the mean total excretion of (82)Se after (82)Se-selenite administration was 3.2% (range 2.8-3.9%) of the ingested amount. LC-ICPMS analysis of the urine samples showed that the majority of the selenium excreted after selenate ingestion was unchanged selenate for 6 of the individuals while one individual had metabolized a fraction (approx. 20%) of the selenate to selenosugar. Ingestion of 10 times larger doses of selenite in two individuals resulted in 13-23% excretion primarily excreted as selenosugar. These results show that the human metabolic pathways of selenite and selenate are different and indicate that not all selenate, although well absorbed, may be available for the beneficial health effects.     

Endurance Training Per Se Increases Metabolic Health in Young,Moderately Overweight Men

Health benefits of physical activity may depend on a concomitant weight loss. In a randomized, controlled trial, we compared the effects of endurance training with or without weight loss to the effect of weight loss induced by an energy‐reduced diet in 48 sedentary, moderately overweight men who completed a 12‐week intervention program of training (T), energy‐reduced diet (D), training and increased diet (T‐iD), or control (C). An energy deficit of 600 kcal/day was induced by endurance training or diet in T and D and a similar training regimen plus an increased dietary intake of 600 kcal/day defined the T‐iD group. Primary end point was insulin sensitivity as evaluated by HOMA‐IR (mainly reflecting hepatic insulin sensitivity) and hyperinsulinemic, isoglycemic clamps (primarily reflecting peripheral insulin sensitivity). Body mass decreased in T and D by 5.9 ± 0.7 and 5.3 ± 0.7 kg, respectively, whereas T‐iD and C remained weight stable. Total and abdominal fat mass were reduced in an additive manner in the T‐iD, D, and T groups by 1.9 ± 0.3/0.2 ± 0.1, 4.4 ± 0.7/0.5 ± 0.1, and 7.7 ± 0.8/0.9 ± 0.1 kg, respectively. HOMA‐IR was improved in T, D, and T‐iD, whereas insulin‐stimulated glucose clearance and suppression of plasma nonesterified fatty acids (NEFAs) were increased only in the two training groups. Thus, loss of fat mass (diet or training induced) improves hepatic insulin sensitivity, whereas peripheral insulin sensitivity in skeletal muscle and adipose tissue is increased by endurance training only. This demonstrates that endurance training per se increases various metabolic health parameters and that endurance training should preferably always be included in any intervention regimen for improving metabolic health in moderately overweight men.     

ZNF385B and VEGFA Are Strongly Differentially Expressed in Serous Ovarian Carcinomas and Correlate with Survival

Background

The oncogenesis of ovarian cancer is poorly understood. The aim of this study was to identify mRNAs differentially expressed between moderately and poorly differentiated (MD/PD) serous ovarian carcinomas (SC), serous ovarian borderline tumours (SBOT) and superficial scrapings from normal ovaries (SNO), and to correlate these mRNAs with clinical parameters including survival.

Methods

Differences in mRNA expression between MD/PD SC, SBOT and SNO were analyzed by global gene expression profiling (n = 23), validated by RT-qPCR (n = 41) and correlated with clinical parameters.

Results

Thirty mRNAs differentially expressed between MD/PD SC, SBOT and SNO were selected from the global gene expression analyses, and 21 were verified (p<0.01) by RT-qPCR. Of these, 13 mRNAs were differentially expressed in MD/PD SC compared with SNO (p<0.01) and were correlated with clinical parameters. ZNF385B was downregulated (FC = −130.5, p = 1.2×10⁻⁷) and correlated with overall survival (p = 0.03). VEGFA was upregulated (FC = 6.1, p = 6.0×10⁻⁶) and correlated with progression-free survival (p = 0.037). Increased levels of TPX2 and FOXM1 mRNAs (FC = 28.5, p = 2.7×10⁻¹⁰ and FC = 46.2, p = 5.6×10⁻⁴, respectively) correlated with normalization of CA125 (p = 0.03 and p = 0.044, respectively). Furthermore, we present a molecular pathway for MD/PD SC, including VEGFA, FOXM1, TPX2, BIRC5 and TOP2A, all significantly upregulated and directly interacting with TP53.

Conclusions

We have identified 21 mRNAs differentially expressed (p<0.01) between MD/PD SC, SBOT and SNO. Thirteen were differentially expressed in MD/PD SC, including ZNF385B and VEGFA correlating with survival, and FOXM1 and TPX2 with normalization of CA125. We also present a molecular pathway for MD/PD SC.     

Cognitive Functions in Middle Aged Individuals Are Related to Metabolic Disturbances and Aerobic Capacity: A Cross-Sectional Study

Aims

Metabolic disturbances may contribute to cognitive dysfunction in patients with type 2 diabetes. We investigated the relation between cognitive impairment and metabolic deteriorations, low physical fitness, low-grade inflammation and abdominal obesity in middle aged individuals.

Methods

We conducted a cross-sectional study including 40 to 65 year-old patients with type 2 diabetes and limited co morbidity (N = 56), age-matched individuals with impaired glucose tolerance (N = 56) as well as age-matched controls with normal glucose tolerance (N = 72). Specific cognitive functions were assessed with focus on verbal memory, processing speed, executive functions, and a composite overall mean score. Oral glucose tolerance test, VO₂max test, systemic inflammation, DXA scanning and abdominal MRI were measured.

Results

Multiple linear regression analyses adjusting for age, gender and verbal intelligence demonstrated that a low score in processing speed, executive functions and overall cognitive function were related to high fasting C-peptide, as well as low insulin sensitivity, beta-cell function and VO₂max. Measurements of blood glucose, obesity and inflammation were not associated with cognitive function.

Conclusion

Low cognitive scores are seen in middle aged individuals with hyperinsulinemia, low insulin sensitivity, beta-cell function and low aerobic capacity. These findings emphasize the importance of appropriate lifestyle and not only blood glucose control in prevention of cognitive disability.     

Ultrastructure and molecular phylogeny of thaumatomonads (Cercozoa) with emphasis on Thaumatomastix salina from Oslofjorden, Norway

A culture of Thaumatomastix was isolated from a sediment sample collected in Oslofjorden and established as a monospecific strain (UIO286). Based on this culture, light and transmission electron microscopy and phylogenetic analyses were carried out. Thaumatomastix species are confined within the order Thaumatomonadida of the class Imbricatea and phylum Cercozoa. They are heterotrophic and their cell bodies are covered with silica scales. Observations of thin sections as well as whole mounts indicate that the morphology and ultrastructure of UIO286 is identical to T. salina, which was initially described from salt pools in Denmark. Detailed examination revealed some new features such as the presence of pseudopodia and silica deposition vesicles producing spine scales. The phylogeny presented here includes ribosomal DNA sequences from both imbricatean cultures and environmental samples. The 18S rDNA phylogenetic tree suggests that (i) Thaumatomastix is paraphyletic within the Thaumatomonadida clade, (ii) there is no close affinity between T. salina and other cultured and sequenced strains, but it is closely related to a sequence obtained from environmental DNA; we propose the present strain to serve as a reference culture of Thaumatomastix species and T. salina. Further, we discuss the distribution, habitats, and evolution of scale formation among euglyphids and thaumatomonads.     

Small angle X-ray studies reveal that Aspergillus niger glucoamylase has a defined extended conformation and can form dimers in solution

The industrially important glucoamylase 1 is an exo-acting glycosidase with substrate preference for alpha-1,4 and alpha-1,6 linkages at non-reducing ends of starch. It consists of a starch binding and a catalytic domain interspersed by a highly glycosylated polypeptide linker. The linker function is poorly understood and structurally undescribed, and data regarding domain organization and intramolecular functional cooperativity are conflicting or non-comprehensive. Here, we report a combined small angle x-ray scattering and calorimetry study of Aspergillus niger glucoamylase 1, glucoamylase 2, which lacks a starch binding domain, and an engineered low-glycosylated variant of glucoamylase 1 with a short linker. Low resolution solution structures show that the linker adopts a compact structure rendering a well defined extended overall conformation to glucoamylase. We demonstrate that binding of a short heterobidentate inhibitor simultaneously directed toward the catalytic and starch binding domains causes dimerization of glucoamylase and not, as suggested previously, an intramolecular conformational rearrangement mediated by linker flexibility. Our results suggest that glucoamylase functions via transient dimer formation during hydrolysis of insoluble substrates and address the question of the cooperative effect of starch binding and hydrolysis.     

Is fertility reduced among men exposed to radiofrequency fields in the Norwegian Navy?

The effects of radiofrequency fields on human health are not well understood, and public concern about negative health effects has been rising. The aim of this study was to examine the relationship between workers exposed to electromagnetic fields and their reproductive health. We obtained data using a questionnaire in a cross-sectional study of naval military men, response rate 63% (n = 1487). We asked the respondents about exposure, lifestyle, reproductive health, previous diseases, work and education. An expert group categorized the work categories related to electromagnetic field exposure. We categorized the work categories "tele/communication," "electronics" and "radar/sonar" as being exposed to electromagnetic fields. Logistic regression adjusted for age, ever smoked, military education, and physical exercise at work showed increased risk of infertility among tele/communication odds ratio (OR = 1.72, 95% confidence interval 1.04-2.85), and radar/sonar odds ratio (OR = 2.28, 95% confidence interval 1.27-4.09). The electronics group had no increased risk. This study shows a possible relationship between exposure to radiofrequency fields during work with radiofrequency equipment and radar and reduced fertility. However, the results must be interpreted with caution.