Towards a molecular understanding of symbiont function: Identification of a fungal gene for the degradation of xylan in the fungus gardens of leaf-cutting ants

<p>Abstract</p> <p>Background</p> <p>Leaf-cutting ants live in symbiosis with a fungus that they rear for food by providing it with live plant material. Until recently the fungus' main inferred function was to make otherwise inaccessible cell wall degradation products available to the ants, but new studies have shed doubt on this idea. To provide evidence for the cell wall degrading capacity of the attine ant symbiont, we designed PCR primers from conserved regions of known xylanase genes, to be used in PCR with genomic DNA from the symbiont as template. We also measured xylanase, cellulase and proteinase activities in the fungus gardens in order to investigate the dynamics of degradation activities.</p> <p>Results</p> <p>We cloned a xylanase gene from the mutualistic fungus of <it>Acromyrmex echinatior</it>, determined its protein sequence, and inserted it in a yeast expression vector to confirm its substrate specificity. Our results show that the fungus has a functional xylanase gene. We also show by lab experiments <it>in vivo </it>that the activity of fungal xylanase and cellulase is not evenly distributed, but concentrated in the lower layer of fungus gardens, with only modest activity in the middle layer where gongylidia are produced and intermediate activity in the newly established top layer. This vertical distribution appears to be negatively correlated with the concentration of glucose, which indicates a directly regulating role of glucose, as has been found in other fungi and has been previously suggested for the ant fungal symbiont.</p> <p>Conclusion</p> <p>The mutualistic fungus of <it>Acromyrmex echinatior </it>has a functional xylanase gene and is thus presumably able to at least partially degrade the cell walls of leaves. This finding supports a saprotrophic origin of the fungal symbiont. The observed distribution of enzyme activity leads us to propose that leaf-substrate degradation in fungus gardens is a multi-step process comparable to normal biodegradation of organic matter in soil ecosystems, but with the crucial difference that a single fungal symbiont realizes most of the steps that are normally provided by a series of microorganisms that colonize fallen leaves in a distinct succession.</p

Characterisation of Water Uptake and swelling Force of pharmaceutical Tablets

Tablets are the most common dosage form in the pharmaceutical industry. Rapid drug release is ensured by quick tablet disintegration which is caused by the absorption of water into the tablet. Therefore, water uptake and subsequent volume expansion are necessary requirements for tablet disintegration. In this work, binary mixtures of excipients were compacted to tablets with varying structural and mechanical properties to determine the influence of formulation and process parameters on water uptake and resulting swelling force of tablets. Results showed strong influences of disintegrant concentration as well as tablet porosity on both absorbed amount of water and acting swelling force. Obtained results revealed that water uptake and swelling force measurements are useful tools for an improved understanding of tablet disintegration

Superconducting order of Sr2RuO4\mathrm{Sr}_2\mathrm{RuO}_4 from a three-dimensional microscopic model

We compute and compare even- and odd-parity superconducting order parameters of strontium ruthenate ($\mathrm{Sr}_2\mathrm{RuO}_4$) in the limit of weak interactions, resulting from a fully microscopic three-dimensional model including spin-orbit coupling. We find that odd-parity helical and even-parity $d$-wave order are favored for smaller and larger values of the Hund's coupling parameter $J$, respectively. Both orders are found compatible with specific heat data and the recently-reported nuclear magnetic resonance (NMR) Knight shift drop [A. Pustogow et al. Nature 574, 72 (2019)]. The chiral $p$-wave order, numerically very competitive with helical order, sharply conflicts with the NMR experiment.Comment: 11 pages, 8 figure

Chronic obstructive pulmonary disease and cancer risk: A Danish nationwide cohort study

SummaryIntroductionLittle is known about the risk of cancer in patients with chronic obstructive pulmonary disease (COPD), including which cancer sites are most affected. We examined the short- and long-term risk of lung and extrapulmonary cancer in a nationwide cohort of COPD patients.MethodsWe linked the Danish National Registry of Patients and the nationwide cancer registry, and examined the incidence of various cancers in 236,494 individuals with a first incident hospital contact with COPD during 1980–2008. The observed cancer incidence in this cohort was compared with the expected incidence in the general population on the basis of national age-, sex-, and site-specific incidence rates.ResultsMedian follow-up was 3.5 years. During the first year of follow-up, 9434 cancers were diagnosed in COPD patients [standardized incidence ratio (SIR) = 3.1; 95% CI 3.0 to 3.2]. The 1-year SIR was 8.5 (8.2–8.9) for lung cancer, 5.1 (5.0–5.2) for all tobacco-related cancers, and 1.9 (1.9–2.0) for other cancers. In the following years, cancer incidence was increased 1.4-fold (1.4–1.5) in COPD patients. These patients had an increased risk of developing tobacco-related cancers (SIR = 2.1; 95% CI 2.0–2.1), including cancers of the lung, larynx, tongue, oral cavity, pharynx, esophagus, stomach, liver, pancreas, cervix uteri, and urinary tract (with SIRs ranging between 1.3 and 2.8).ConclusionsPatients with first-time hospital-diagnosed COPD are at considerably increased risk of developing both lung cancer and extrapulmonary cancers. Physicians should be aware of cancer in COPD patients

In Silico Evaluation of a Self-powered Venous Ejector Pump for Fontan Patients

Purpose The Fontan circulation carries a dismal prognosis in the long term due to its peculiar physiology and lack of a subpulmonic ventricle. Although it is multifactorial, elevated IVC pressure is accepted to be the primary cause of Fontan's high mortality and morbidity. This study presents a self-powered venous ejector pump (VEP) that can be used to lower the high IVC venous pressure in single-ventricle patients. Methods A self-powered venous assist device that exploits the high-energy aortic flow to lower IVC pressure is designed. The proposed design is clinically feasible, simple in structure, and is powered intracorporeally. The device's performance in reducing IVC pressure is assessed by conducting comprehensive computational fluid dynamics simulations in idealized total cavopulmonary connections with different offsets. The device was finally applied to complex 3D reconstructed patient-specific TCPC models to validate its performance. Results The assist device provided a significant IVC pressure drop of more than 3.2 mm Hg in both idealized and patient-specific geometries, while maintaining a high systemic oxygen saturation of more than 90%. The simulations revealed no significant caval pressure rise ( 84%) in the event of device failure, demonstrating its fail-safe feature. Conclusions A self-powered venous assist with promising in silico performance in improving Fontan hemodynamics is proposed. Due to its passive nature, the device has the potential to provide palliation for the growing population of patients with failing Fontan.publishedVersio

Is there evidence of fetal-maternal heart rate synchronization?

BACKGROUND: The prenatal condition offers a unique possibility of examining physiological interaction between individuals. Goal of this work was to look for evidence of coordination between fetal and maternal cardiac systems. METHODS: 177 magnetocardiograms were recorded in 62 pregnancies (16(th)–42(nd )week of gestation). Fetal and maternal RR interval time series were constructed and the phases, i.e. the timing of the R peaks of one time series in relation to each RR interval of the other were determined. The distributions of these phases were examined and synchrograms were constructed for real and surrogate pairs of fetal and maternal data sets. Synchronization epochs were determined for defined n:m coupling ratios. RESULTS: Differences between real and surrogate data could not be found with respect to number of synchronization epochs found (712 vs. 741), gestational age, subject, recording or n:m combination. There was however a preference for the occurrence of synchronization epochs in specific phases in real data not apparent in the surrogate for some n:m combinations. CONCLUSION: The results suggest that occasional coupling between fetal and maternal cardiac systems does occur

Influence of Prior Imaging Information on Diagnostic Accuracy for Focal Skeletal Processes-A Retrospective Analysis of the Consistency between Biopsy-Verified Imaging Diagnoses

Introduction: Comparing imaging examinations with those previously obtained is considered mandatory in imaging guidelines. To our knowledge, no studies are available on neither the influence, nor the sequence, of prior imaging and reports on diagnostic accuracy using biopsy as the reference standard. Such data are important to minimize diagnostic errors and to improve the preparation of diagnostic imaging guidelines. The aim of our study was to provide such data. Materials and methods: A retrospective cohort of 216 consecutive skeletal biopsies from patients with at least 2 different imaging modalities (X-ray, CT and MRI) performed within 6 months of biopsy was identified. The diagnostic accuracy of the individual imaging modality was assessed. Finally, the possible influence of the sequence of imaging modalities was investigated. Results: No significant difference in the accuracy of the imaging modalities was shown, being preceded by another imaging modality or not. However, the sequence analyses indicate sequential biases, particularly if MRI was the first imaging modality. Conclusion: The sequence of the imaging modalities seems to influence the diagnostic accuracy against a pathology reference standard. Further studies are needed to establish evidence-based guidelines for the strategy of using previous imaging and reports to improve diagnostic accuracy