Ageing of enteric neurons: oxidative stress, neurotrophic factors and antioxidant enzymes

ABSTRACT: BACKGROUND: Ageing is associated with gastrointestinal dysfunction, which can have a major impact on quality of life of the elderly. A number of changes in the innervation of the gut during ageing have been reported, including neuronal loss and degenerative changes. Evidence indicates that reactive oxygen species (ROS) are elevated in ageing enteric neurons, but that neurotrophic factors may reduce generation of neuronal ROS. Two such factors, glial cell line derived neurotrophic factor (GDNF) and neurotrophin-3 (NT-3) have also been found to protect enteric neurons against oxidative stress induced cell death of enteric ganglion cells in vitro. We have investigated the possible roles of neurotrophic factors further, by examining their expression in the gut during ageing, and by analysing their effects on antioxidant enzyme production in cultures of enteric ganglion cells. RESULTS: Analysis of the expression of GDNF and its receptors c-Ret and GFR alpha 1in rat gut by RTPCR showed that expression continues throughout life and into ageing, in both ad libitum(AL) and calorically-restricted (CR) animals. Levels of expression of GDNF and GFR alpha 1 were elevated in 24 month AL animals compared to 24 month CR animals, and to 24 CR and 6 month control animals respectively.The related factor Neurturin and its receptorGFR alpha 2 were also expressed throughout life, the levels of the GFR - alpha-2B isoform were reduced in 24 m AL animals. Immunolabelling showed that c-Ret and GFR alpha 1 proteins were expressed by myenteric neurons in ageing animals. GDNF, but not NT-3, was found to increase expression of Cu/Zn superoxide dismutase and catalase by cultured enteric ganglion cells. CONCLUSIONS: The neurotrophic factors GDNF and neurturin and their receptors continue to be expressed in the ageing gut. Changes in the levels of expression of GDNF , GFR alpha-1 and GFR alpha-2b isoform occurred in 24 m AL animals. GDNF, but not NT-3, increased the levels of antioxidant enzymes in cultured enteric ganglion cells, indicating a possible mechanism for the reported protective effect of GDNF against menadione-induced neuronal apoptosis in the ageing gut. Together these data suggest that GDNF family members may play a protective role in the gut throughout life, and support the suggestion that dysregulation of neurotrophic factor support could contribute to neuronal ageing in the gut.     

Brown diamonds from an eclogite xenolith from Udachnaya kimberlite, Yakutia, Russia

We have performed petrographic and spectroscopic studies of brown diamonds from an eclogite xenolith from the Udachnaya pipe (Yakutia, Russia). Brown diamonds are randomly intermixed with colorless ones in the rock and often located at the grain boundaries of clinopyroxene and garnet. Brown diamonds can be characterized by a set of defects (H4, N2D and a line at 490.7 nm) which are absent in colorless diamonds. This set of defects is typical for plastically deformed diamonds and indicates that diamonds were likely annealed for a relatively short period after deformation had occurred. Excitation of brown colored zones with a 632.8 nm He-Ne laser produced the typical diamond band plus two additional bands at 1730 cm(-1) and 3350 cm(-1). These spectral features are not genuine Raman bands, and can be attributed to photoluminescence at ～710 nm (1.75 eV) and ～802 nm (1.54 eV). No Raman peak corresponding to graphite was observed in regions of brown coloration. Comparison with previous reports of brown diamonds from eclogites showed our eclogitic sample to have a typical structure without signs of apparent deformation. Two mechanisms with regard to diamond deformation are proposed: deformation of eclogite by external forces followed by subsequent recrystallization of silicates or, alternatively, deformation by local stress arising due to decompression and expansion of silicates during ascent of the xenolith to surface conditions.     

The effects of vortex breakdown bubbles on the mixing environment inside a base driven bioreactor

The bubble-type vortex breakdown inside a cylinder with flow driven by rotation of the base, has applications in mixing. We investigate this phenomena and its effect on the environment inside an open cylinder, with potential application as a tissue-engineering bioreactor, with tissue-scaffolds of two different geometries immersed in the fluid. Addition of scaffolds induces a blockage effect, hindering the flow in the central vortex core returning to the rotating base. This promotes early onset of vortex breakdown and alters the final shape of vortex breakdown bubbles. Placement of the scaffolds centrally on the cylinder axis yields almost identical levels and distributions of shear stress between the upper and lower surfaces of scaffolds. A change from a disk shaped to an ellipsoidal scaffold, of the same size, reduces the intensity of the maximum shear stresses at the scaffold surface by up to 50%. There is a range of Reynolds numbers where increasing Reynolds number, and hence possibly increasing mixing efficiency, leads to a decrease in the maximum levels of fluid forces at the scaffold surfaces. This is an important conclusion for scaffold based tissue engineering where improved mixing is sought, but often sacrificed in favor of minimizing fluid forces.     

Holistic visualisation of the multimodal transport and fate of twelve pharmaceuticals in biosolid enriched topsoils

The use of municipal biosolids as agricultural fertilisers has raised significant concerns in recent years. As part of this, the presence of complex mixtures of pharmaceutical residues and their effects on soil ecosystems remains particularly under-researched. This study focuses on the transfer of a selection of pharmaceutical residues from municipal sewage sludge to agricultural topsoils and their fate therein after an accelerated 6-month rainfall event. Twelve pharmaceuticals encompassing antibiotics, analgesics, anti-inflammatories, beta-blockers, hyperlipidaemics and stimulants were invesigated by employing a combination of extraction techniques and liquid chromatography-tandem mass spectrometry. Both liquid- and solid-phase pharmaceutical contents were analysed and pharmaceutical and personal care products quantified at defined timepoints to elucidate transport behaviour and transformation potential. Results show the distribution and separation of pharmaceuticals over a 100-mm soil depth following typical biosolid enrichment. Using experimentally determined solid–water partition coefficients (K _d) and hydrophobicity distribution ratios (D _ow), mobility and modes of interaction under dynamic conditions are discussed. Finally, a brief study into the susceptibility of soil microbes is also presented. To our knowledge, this is the first investigation of pharmaceutical and personal care products release from amended biosolids to soils to include the factors and mechanisms governing their distribution and transformation even over relatively shallow depths. It applies multicompartmental and mass-balanced chemical analyses as well as microbiological approaches for a holistic view of these complex processes.      

Fddd network phase in ABA triblock copolymer melts

Using self‐consistent field theory, we investigate the stability of the orthorhombic Fddd network phase (O⁷⁰) in ABA triblock copolymer melt systems. Consistent with previous findings, we observe that the gross topology of phase behavior is unchanged with varying chain asymmetry. However, the mean field critical point is displaced from the diblock copolymer value of f_A = 0.5 (f_A is the A segment volume fraction) to larger values as the triblock copolymer symmetry is broken with unequal A block lengths. This deviation significantly shifts the order‐order phase boundaries, resulting in an appreciable region of O⁷⁰ stability in the phase diagram of asymmetric ABA triblock copolymers. More importantly, the stability of the O⁷⁰ phase extends to the intermediate segregation regime for select chain asymmetries. Both features are desirable for achieving a synthetic realization of the phase in binary AB block copolymer systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1112–1117     

A comparative study of the processes of generation of singlet oxygen upon irradiation of aqueous preparations on the basis of chlorin e6 and coproporphyrin III

The photosensitizing ability of an agent based on chlorin e6 (Photoditazin), which is used for photodynamic diagnosis and therapy, is compared with that of a new preparation on the basis of coproporphyrin III in the environment of a phosphate buffer and a simulated biological environment (albumin solution). The efficiency of singlet-oxygen production was estimated by EPR spectroscopy and spectroscopy in the UV and visible ranges with the use of “chemical traps” of singlet oxygen. By irradiating drugs with LED emission centered at λ_max = 520 nm, we determined the quantum yield of singlet-oxygen production in a buffer solution; the obtained values are 0.60 and 0.37 for chlorine and coproporphyrin, respectively. The steady-state concentration of singlet oxygen upon irradiation of solutions of the studied photosensitizers with concentrations of 12–43 μМ and the density of radiation power within the 6–96 W/cm² region was found to be in the region of 10¹⁰–10¹¹ molecules/cm³. It is shown that the introduction into the solution of egg albumin (0.1%) reduces the sensitizing properties of the two drugs by two to three times, while the efficiencies of the preparations with respect to singlet-oxygen production become almost identical (0.19 and 0.17).