High phosphate level directly stimulates parathyroid hormone secretion and synthesis by human parathyroid tissue in vitro

Phosphate retention plays an important role in the pathogenesis of secondary hyperparathyroidism in patients with renal failure. In in vitro studies, high extracellular phosphate levels directly stimulate PTH secretion in rat and bovine parathyroid tissue. The present study evaluates the effect of high phosphate levels on the secretion of PTH and the production of prepro PTH mRNA in human hyperplastic parathyroid glands. The study includes parathyroid glands obtained from patients with primary adenomas and from hemodialysis and kidney-transplant patients with diffuse and nodular secondary hyperplasia. The experiments were performed in vitro using small pieces of parathyroid tissue. The ability of high calcium levels to decrease PTH secretion was less in adenomas than in secondary hyperplasia; among the secondary hyperplasia, nodular was less responsive to an increase in calcium than diffuse hyperplasia. In diffuse hyperplasia, PTH secretion was increased in response to 3 and 4 mM phosphate compared with 2 mM phosphate, despite a high calcium concentration in the medium; prepro PTH mRNA levels increased after incubation in 4 mM phosphate. Similar results were obtained with nodular hyperplasia, except that the elevation of PTH secretion in response to 3 mM phosphate did not attain statistical significance. In adenomas, high calcium concentrations (1.5 mM) did not result in inhibition of PTH secretion, independent of the phosphate concentration, and the prepro PTH mRNA was not significantly increased by high phosphate levels. In conclusion, first, the PTH secretory response to an increase in calcium concentration is less in nodular than diffuse hyperplasia; second, high phosphate levels directly affect PTH secretion and gene expression in patients with advanced secondary hyperparathyroidism.     

Identification of Novel α-Methoxylated Phospholipid Fatty Acids in the Caribbean Sponge <Emphasis Type="Italic">Erylus goffrilleri</Emphasis>

The phospholipid fatty acid composition of the Caribbean sponge Erylus goffrilleri is described for the first time. A total of 70 fatty acids with chain lengths between 13 and 29 carbons were identified in the sponge. Methyl-branched fatty acids predominated in E. goffrilleri suggesting the presence of a considerable number of bacterial symbionts. The novel fatty acids (5Z,9Z)-2-methoxy-5,9-hexadecadienoic acid, (5Z,9Z)-2-methoxy-5,9-octadecadienoic acid, (5Z,9Z)-2-methoxy-5,9-nonadecadienoic acid, and (5Z,9Z)-2-methoxy-5,9-eicosadienoic acid are described for the first time in the literature. In addition, the iso-methyl-branched fatty acids (9Z)-2-methoxy-15-methyl-9-hexadecenoic acid and (5Z,9Z)-2-methoxy-15-methyl-5,9-hexadecadienoic acid, also identified in E. goffrilleri, were identified for the first time in nature. Based on the identified metabolites it is proposed that the unprecedented biosynthetic sequence: i-17:1Δ9 → 2-OMe-i-17:1Δ9 → 2-OMe-i-17:2Δ5,9 might be responsible for the biosynthesis of the novel iso-α-methoxylated fatty acids in E. goffrilleri.     

Nutritional evaluation of meat–soya bean protein product blends

The nutritive value of protein of blends consisting of meat and soya bean protein products, which replaced either 20 or 40 % of protein of meat, were determined in rat feeding experiments. Protein efficiency ratio (PER) and net protein utilisation (NPU) were significantly lower (P<0.05) in blends containing either 20% protein from soya isolate or 40% protein from soya concentrate or soya flakes than blends containing sirloin only. However, there were no significant differences in PER and NPU when model meat (consisting of 70 and 30% protein from sirloin and connective tissue, respectively) was replaced by up to 20% protein from soya isolate or up to 40% protein from soya concentrate.     

Comparison of various modeling methods for analysis of powder compaction in roller press

Recently used models relating basic properties of the feed material, roller press design and its operating parameters are reviewed. In particular, we discuss the rolling theory for granular solids proposed by J.R. Johanson in the 1960s, later trials utilizing slab method and newly developed final element models. These methods are compared in terms of efficiency and accuracy of predicting the course of basic process variables like nip angle, pressure distribution in roll nip region, neutral angle, roll torque and roll force.

The finite element method offers the most versatile approach because it incorporates adequate information about powder behavior, geometry and frictional conditions. This enables to perform realistic computer experiments minimizing costs, time and resources needed for process and equipment optimization.     

Prediction of ring crack initiation in ceramics and glasses using a stress–energy fracture criterion

Crack initiation in brittle materials upon spherical indentation is associated with the tensile radial stresses during loading. However, location of crack onset often differs (offset) from the site of maximal stress. In addition, experiments reveal a strong dependency of crack initiation forces on geometrical parameters as well as the surface condition of the sample. In this work, a coupled stress–energy fracture criterion is introduced to describe the initiation of ring cracks in brittle materials, which takes into account the geometry of the contact and the inherent strength and fracture toughness of the material. Several experiments reported in literature are evaluated and compared. The criterion can explain the location offset of the ring crack upon loading, as observed in various ceramics and glasses. It also predicts the ring crack initiation force upon contact loading, provided that surface compressive stresses, introduced during grinding or polishing processes, are taken into account. Furthermore, the stress–energy criterion may be employed to estimate the surface residual stress of ceramic parts, based on simple contact damage experiments.     

The peak-shift method for the description of structural relaxation in glassy materials: a critical review

Nowadays, the glass transition kinetics is most commonly described in terms of the Tool–Narayanaswamy–Moynihan (TNM) model. Evaluation of one of the most prominent features of the structural relaxation motions—the relaxation nonlinearity—was traditionally done using the peak-shift (PS) method. This paper introduces, for the first time, extensive testing of the PS method by means of theoretical simulations for all practically observable types of structural relaxation behavior and all types of glassy/amorphous materials (tested range of the glass transition temperatures: −55 to 1000°C; tested range of the relaxation activation energies: 300–1300 kJ⋅mol⁻¹). For the majority of types of structural relaxation behavior, the PS method tends to slightly overestimate the value of the TNM nonlinearity parameter x (by ∼ 0.05–0.10). In the specific cases of the highly linear behavior (↑ x) combined with a broad distribution of relaxation times, the PS method systematically vastly underestimates the value of x. A new, improved temperature program was proposed for the PS method, eliminating the major intrinsic drawback of the originally proposed version of the PS methodology. In addition, based on the comparison between the theoretically simulated and real-life experimental data, a new approach (based on the characteristic PS dependence shape) was introduced to estimate the width of the relaxation times distribution.     

Feasibility study on electrically conductive joining of MoSi2 electrodes for spark plugs

Despite the often outstanding functional as well as (high temperature-) mechanical properties of ceramics, their usage is often limited due to their inherent brittleness. This also compromises the joining with metals, which is often indispensable for engineering applications. In this context, electrically conductive ceramics like MoSi₂ are promising materials for the application as electrodes where high temperatures in harsh environments are present (e.g., in spark plugs for large gas engines). Due to the difficult joining of the respective materials, long-term experiments are thereby often still pending. In this work, adhesive bonding, brazing, tungsten inert gas-, and resistance welding were performed to evaluate their applicability for generating electrically conductive as well as mechanically reliable joints between MoSi₂ and Inconel 600, aiming to utilize MoSi₂ electrodes in spark plugs. Fractographic analyses are performed to understand cracks associated with the high (thermo-) mechanical stresses. Additionally, a finite element model was set up for a deeper understanding of the observed fracture behavior. While adhesive bonding is acceptable for short-term experiments at low temperatures, brazing and resistance welding may qualify for fast and reliable manufacturing of spark plugs with ceramic electrodes.     

Bacterial Dehydrogenases Facilitate Oxidative Inactivation and Bioremediation of Chloramphenicol

Antimicrobial resistance represents a major threat to human health and knowledge of the underlying mechanisms is therefore vital. Here, we report the discovery and characterization of oxidoreductases that inactivate the broad-spectrum antibiotic chloramphenicol via dual oxidation of the C3-hydroxyl group. Accordingly, chloramphenicol oxidation either depends on standalone glucose-methanol-choline (GMC)-type flavoenzymes, or on additional aldehyde dehydrogenases that boost overall turnover. These enzymes also enable the inactivation of the chloramphenicol analogues thiamphenicol and azidamfenicol, but not of the C3-fluorinated florfenicol. Notably, distinct isofunctional enzymes can be found in Gram-positive (e. g., Streptomyces sp.) and Gram-negative (e. g., Sphingobium sp.) bacteria, which presumably evolved their selectivity for chloramphenicol independently based on phylogenetic analyses. Mechanistic and structural studies provide further insights into the catalytic mechanisms of these biotechnologically interesting enzymes, which, in sum, are both a curse and a blessing by contributing to the spread of antibiotic resistance as well as to the bioremediation of chloramphenicol.     

Holistic Analysis of the Tribological Interfaces of an Axial Piston Pump – Focusing on the Pump Efficiency

Research work performed on an axial piston pump is shown in a holistic manner, analyzing each lubricating interface by linking their gap height and temperature behavior to the overall pump efficiency. The temperature field and dynamic fluid film height were measured in two of the three lubricating interfaces. This is the first time that the temperature fields and gap heights were simultaneously measured in two of the main three interfaces of an axial piston machine. For a deeper analysis of the measurement data, all gaps were simulated with a numerical tool which takes solid body deformation due to temperature and pressure loads into account. This unique combination of both extensive measurement data and sophisticated simulation resulted in novel trends that clarify the complex phenomena occurring in these hydrostatic fluid films.