Effect of annealing temperature and dopant concentration on the thermoluminescence sensitivity in LiF:Mg,Cu,Ag material

LiF:Mg,Cu,Ag is a new dosimetry material that is similar to LiF:Mg,Cu,P in terms of dosimetric properties. The effect of the annealing temperature in the range of 200 to 350°C on the thermoluminescence (TL) sensitivity and the glow curve structure of this material at different concentrations of silver (Ag) was investigated. It has been demonstrated that the optimum values of the annealing temperature and the Ag concentration are 240°C and 0.1 mol% for better sensitivity, respectively. The TL intensity decreases at annealing temperatures lower than 240°C or higher than 240°C, reaching a minimum at 300°C and then again increases for various Ag concentrations. It was observed that the glow curve structure altered and the area under the low temperature peak as well as the area under the main dosimetric peak decreased with increasing annealing temperature. The position of the main dosimetric peak moved in the direction of higher temperatures, but at 320 and 350°C annealing temperatures, it shifted to lower temperatures. It was also observed that the TL sensitivity could partially be recovered by a combined annealing procedure.     

Hyperosmotic stress contributes to mouse colonic inflammation through the methylation of protein phosphatase 2A

There are several reports suggesting hyperosmotic contents in the feces of patients suffering from inflammatory bowel disease (IBD). Previous works have documented that hyperosmolarity can cause inflammation attributable to methylation of the catalytic subunit of protein phosphatase 2A (PP2A) and subsequent NF-kappaB activation resulting in cytokine secretion. In this study, we demonstrate that dextran sulfate sodium (DSS) induces colitis due to hyperosmolarity and subsequent PP2A activation. Mice were randomized and fed with increased concentrations of DSS (0 mOsm, 175 mOsm, 300 mOsm, and 627 mOsm) for a duration of 3 wk or with hyperosmotic concentrations of DSS (627 mOsm) or mannitol (450 mOsm) for a duration of 12 wk. Long-term oral administration of hyposmotic DSS or mannitol had no demonstrable effect. Hyperosmotic DSS or mannitol produced a significant increase in colonic inflammation, as well as an increase in the weight of sacral lymph nodes and in serum amyloid A protein levels. Similar results were obtained through the ingestion of comparable osmolarities of mannitol. Hyperosmolarity induces the methylation of PP2A, nuclear p65 NF-kappaB activation. and cytokine secretion. The rectal instillation of okadaic acid, a well-known PP2A inhibitor, reverses the IBD. Short inhibiting RNAs (siRNAs) targeted toward PP2Ac reverse the effect of hyperosmotic DSS. The present study strongly suggests that DSS-induced chronic colitis is a consequence of the methylation of PP2Ac induced by hyperosmolarity.     

Co-composting of oil-based drilling cuttings by bagasse

Bioprocess and Biosystems Engineering - The feasibility of using a locally abundant bulking material (sugarcane bagasse) in Khuzestan province, Iran, to remove petroleum hydrocarbons from oil-based...     

Resistance of peripheral and sub-cortical somatosensory pathway to electrical noise

The somatosensory system is vulnerable to large amounts of noise distortion. But how does the central nervous system distinguish the peripheral inputs which carry information to the brain from that which does not possess information? To address this question we studied the effect of electrical stimulation of the median nerve on tactile spatial frequency perception in healthy subjects and Parkinson's disease (PD) patients. Subjects were categorized in two groups (healthy and PD patients) and were asked to report if a test tactile frequency pattern (TFP) was the same as the reference TFP given to the other hand. In each case stimulation was either present or absent on the median nerve of the hand holding the test pattern. We observed no impairment of tactile performance in the presence of electrical stimulation of the median nerve. This result together with previous work on direct stimulation of the somatosensory relay nucleus of the thalamus (Abbassian et al., Stereotact Funct Neurosurg 76: 19–28, 2001) in which the same result of no impairment of the tactile discrimination task was observed suggest a high degree of noise tolerance exists in the somatosensory pathway.     

Decreased vitamin B12 availability induces ER stress through impaired SIRT1-deacetylation of HSF1

Vitamin B12 (cobalamin) is a key determinant of S-adenosyl methionine (SAM)-dependent epigenomic cellular regulations related to methylation/acetylation and its deficiency produces neurodegenerative disorders by elusive mechanisms. Sirtuin 1 deacetylase (SIRT1) triggers cell response to nutritional stress through endoplasmic reticulum (ER) stress. Recently, we have established a N1E115 dopaminergic cell model by stable expression of a transcobalamin–oleosin chimera (TO), which impairs cellular availability of vitamin B12, decreases methionine synthase activity and SAM level, and reduces cell proliferation. In contrast, oleosin-transcobalamin chimera (OT) does not modify the phenotype of transfected cells. Presently, the impaired cellular availability of vitamin B12 in TO cells activated irreversible ER stress pathways, with increased P-eIF-2α, P-PERK, P-IRE1α, ATF6, ATF4, decreased chaperon proteins and increased pro-apoptotic markers, CHOP and cleaved caspase 3, through reduced SIRT1 expression and consequently greater acetylation of heat-shock factor protein 1 (HSF1). Adding either B12, SIRT1, or HSF1 activators as well as overexpressing SIRT1 or HSF1 dramatically reduced the activation of ER stress pathways in TO cells. Conversely, impairing SIRT1 and HSF1 by siRNA, expressing a dominant negative form of HSF1, or adding a SIRT1 inhibitor led to B12-dependent ER stress in OT cells. Addition of B12 abolished the activation of stress transducers and apoptosis, and increased the expression of protein chaperons in OT cells subjected to thapsigargin, a strong ER stress stimulator. AdoX, an inhibitor of methyltransferase activities, produced similar effects than decreased B12 availability on SIRT1 and ER stress by a mechanism related to increased expression of hypermethylated in cancer 1 (HIC1). Taken together, these data show that cellular vitamin B12 has a strong modulating influence on ER stress in N1E115 dopaminergic cells. The impaired cellular availability in vitamin B12 induces irreversible ER stress by greater acetylation of HSF1 through decreased SIRT1 expression, whereas adding vitamin B12 produces protective effects in cells subjected to ER stress stimulation.     

Stochastic simulation of the FDA centrifugal blood pump benchmark

Biomechanics and Modeling in Mechanobiology - In the present study, the effect of physical and operational uncertainties on the hydrodynamic and hemocompatibility characteristics of a centrifugal...     

Cloning and Characterization of Uronate Dehydrogenases from Two Pseudomonads and Agrobacterium tumefaciens Strain C58

Uronate dehydrogenase has been cloned from Pseudomonas syringae pv. tomato strain DC3000, Pseudomonas putida KT2440, and Agrobacterium tumefaciens strain C58. The genes were identified by using a novel complementation assay employing an Escherichia coli mutant incapable of consuming glucuronate as the sole carbon source but capable of growth on glucarate. A shotgun library of P. syringae was screened in the mutant E. coli by growing transformed cells on minimal medium containing glucuronic acid. Colonies that survived were evaluated for uronate dehydrogenase, which is capable of converting glucuronic acid to glucaric acid. In this manner, a 0.8-kb open reading frame was identified and subsequently verified to be udh. Homologous enzymes in P. putida and A. tumefaciens were identified based on a similarity search of the sequenced genomes. Recombinant proteins from each of the three organisms expressed in E. coli were purified and characterized. For all three enzymes, the turnover number (k_cat) with glucuronate as a substrate was higher than that with galacturonate; however, the Michaelis constant (K_m) for galacturonate was lower than that for glucuronate. The A. tumefaciens enzyme was found to have the highest rate constant (k_cat = 1.9 × 10² s⁻¹ on glucuronate), which was more than twofold higher than those of both of the pseudomonad enzymes.Aldohexuronate catabolism in bacteria is reported to involve two different pathways, one initiating with an isomerization step and the other with an oxidation step. In the isomerization pathway, aldohexuronate (glucuronate and galacturonate) is isomerized to ketohexuronate by uronate isomerase and ultimately degraded to pyruvate and 3-phosphoglyceraldehyde. The isomerization pathway has been previously reported to occur in bacteria, including Escherichia coli (7), Erwinia carotovora (18), Erwinia chrysanthemi (15), Klebsiella pneumoniae (9, 23), and Serratia marcescens (28). In the oxidation pathway, aldohexuronate is oxidized to aldohexarate by uronate dehydrogenase (Udh) and further catabolized to pyruvate (2, 5, 7, 9, 18, 19, 24). Uronate dehydrogenase, the key enzyme of this pathway, has been investigated in two plant pathogen bacteria, Pseudomonas syringae and Agrobacterium tumefaciens. To date, only limited studies pertaining to the properties of Udh have been reported in the literature (3, 6, 38, 43), and no sequence has yet been identified. Udh is classified as an NAD-linked oxidoreductase (EC 1.1.1.203), with a total molecular weight of about 60,000. It is a homodimer composed of two subunits with molecular weights of about 30,000 each (38). Udh is a thermally unstable, reversible enzyme, with an optimum pH of about 8.0 (3, 6, 38).In E. coli MG1655 that has the isomerization pathway for aldohexuronate catabolism, glucuronate is transported by an aldohexuronate transporter encoded by exuT and converted to fructuronate by uronate isomerase, encoded by uxaC (22, 30) (Fig. ​(Fig.1).1). Fructuronate is transferred to the Entner-Doudoroff pathway to be utilized as an energy source via 2-keto-3-deoxy-6-phospho-gluconate (7, 27, 31, 32). Therefore, E. coli MG1655 with a uxaC deletion cannot use glucuronate as a carbon source. In this strain, glucarate is converted to 5-keto-4-deoxy-d-glucarate by d-glucarate dehydratase, encoded by gudD, and then transferred to glycolysis via pyruvate or 2-phosphoglycerate (27, 33). Recently, a number of bacterial genome sequences have been published, including those of the Udh-containing P. syringae pv. tomato strain DC3000 and A. tumefaciens strain C58 (4, 10). A shotgun library of P. syringae was constructed to identify the gene encoding Udh. Screening for Udh was conducted in E. coli MG1655 ΔuxaC. Since uronate dehydrogenase converts glucuronate to glucarate, uxaC deletion strains of E. coli harboring the shotgun library of P. syringae that can grow in a minimal medium containing glucuronate as a sole carbon source may carry the gene encoding Udh (Fig. ​(Fig.1).1). Once an initial Udh is identified from P. syringae, a BLAST homology search may lead to the identification of Udhs from other bacteria.Open in a separate windowFIG. 1.Catabolism of glucuronate and glucarate in bacteria. Glucuronate consumption is prevented by knockout of the uxaC gene. The presence of uronate dehydrogenase in a uxaC knockout enables growth of E. coli on glucuronate.