Glucocorticoid effects on gastric peroxidase activity

The peroxidase activity in rat gastric mucosa is inhibited after administration of glucocorticoids. The synthetic steroid dexamethasone is more potent than the naturally occurring steroids, such as cortisone or corticosterone. Almost complete inhibition of the enzyme occurs after 24 h with a single dose of 100 μg dexamethasone/120 g body weight. Other mitochondrial enzyme activities, like monoamine oxidase, succinic dehydrogenase and Mg²⁺-ATPase, remain unaltered under the same experimental condition. Submaxillary peroxidase and thyroid peroxidase activity are not inhibited by dexamethasone. Gastric peroxidase activity is increased 200–250% on the 6th day after adrenalectomy. This effect is blocked by the administration of dexamethasone. In fact, the enzyme becomes more sensitive to dexamethasone after adrenalectomy, since it is inhibited by more than 90% at the dose of 25 μg/120 g body weight. The inhibition by dexamethasone in normal animals is reversible. The enzyme is also inhibited after the administration of a single dose of ACTH. The apparent K_m of the enzyme for H₂O₂ is not altered after dexamethasone treatment or after adrenalectomy. The increase in enzyme activity following adrenalectomy is not blocked by actinomycin D or by α-amanitin, but is prevented by puromycin or cycloheximide. After administration of dexamethasone, the iodide concentration process in the gastric mucosa is not affected, but the organification of iodide is significantly diminished.     

Alterations of urinary perchlorate levels in euthyroid postpubertal children with autism spectrum disorder

BackgroundPerchlorates ClO₄(⁻) are known environmental and food contaminants that act as inhibitors of iodine uptake by the thyroid gland; however, information concerning their possible association with the development of autism spectrum disorder (ASD) is still missing. The current study is first presenting the alterations in perchlorate urine levels in euthyroid children with ASD.ObjectivesTo examine urinary perchlorates and iodides in euthyroid children diagnosed with ASD, compared to age-, and BMI-matched neurotypical controls, and to verify the association between these two ions in ASD.MethodsIons were determined in 24 h urine samples determined by ion chromatography–conductivity cell detection (IC-CD) and ion chromatography–pulsed amperometric detection (IC-PAD) techniques, respectively, in a total of 130 postpubertal euthyroid children with normal BMI (the mean age 14.46 years, SD = 1.32; the mean BMI 20.6, SD = 1.37), divided into age- and BMI-matched groups of ASD patients and neurotypical, healthy children (control).ResultsThe ASD group presented with significantly higher perchlorate urine levels than the controls (median = 1.05 μg/L, interquartile range(IQR) = 1.5 versus median = 0.09 μg/L, IQR = 0.097, respectively), as well as lower iodide urine levels (median = 100.2 μg/L, IQR = 37 versus median = 156.95 μg/L, IQR = 26.11, respectively). The ASD group presented significantly lower TSH and higher free thyroid hormone (fT4, fT3) levels than the controls. In regression analyses, perchlorate urine levels showed significant positive relationships with normal BMI values and serum TSH, and inverse relationships with serum fT4. Urinary iodide levels showed significant inverse relationships with BMI values. The absence of ASD was associated with decreased odds of perchlorate urine levels (OR = 0.012, 95 % confidence interval [CI] 0.0002−0.76), and increased odds of iodide urine levels (OR = 1.15, 95 %CI 1.05–1.27).ConclusionsASD may have an independent and significant impact on perchlorate as well as iodide levels in urine of euthyroid lean postpubertal children. Perchlorate levels do not appear to be directly associated with iodide levels in euthyroid children.     

Synthesis of the tetrasaccharide alpha-D-Glcp-(1-->3)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp recognized by calreticulin/calnexin

The title compound as its methyl glycoside was efficiently synthesized using a block synthesis approach. Halide-assisted glycosidations between 6-O-acetyl-2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl iodide and ethyl 2-O-acetyl-4,6-di-O-benzyl-1-thio-alpha-D-mannopyranoside using triphenylphosphine oxide as promoter yielded, with complete alpha-selectivity, a disaccharide building block in high yield. The perbenzylated derivative of this proved to be an excellent donor affording 88% of the protected target tetrasaccharide in an NIS/AgOTf-promoted coupling to a known methyl dimannoside acceptor. Deprotection through catalytic hydrogenolysis then gave the target compound in 47% overall yield.     

Oxidative addition of methyl iodide to [Rh(CO)2I]2: synthesis, structure and reactivity of neutral rhodium acetyl complexes, [Rh(CO)(NCR)(COMe)I2]2

Reaction of [Rh(CO)₂I]₂ (1) with MeI in nitrile solvents gives the neutral acetyl complexes, [Rh(CO)(NCR)(COMe)I₂]₂ (R=Me, 3a; ^tBu, 3b; vinyl, 3c; allyl, 3d). Dimeric, iodide-bridged structures have been confirmed by X-ray crystallography for 3a and 3b. The complexes are centrosymmetric with approximate octahedral geometry about each Rh centre. The iodide bridges are asymmetric, with Rh-(μ-I) trans to acetyl longer than Rh-(μ-I) trans to terminal iodide. In coordinating solvents, 3a forms mononuclear complexes, [Rh(CO)(sol)₂(COMe)I₂] (sol=MeCN, MeOH). Complex 3a reacts with pyridine to give [Rh(CO)(py)(COMe)I₂]₂ and [Rh(CO)(py)₂(COMe)I₂] and with chelating diphosphines to give [Rh(Ph₂P(CH₂)_nPPh₂)(COMe)I₂] (n=2, 3, 4). Addition of MeI to [Ir(CO)₂(NCMe)I] is two orders of magnitude slower than to [Ir(CO)₂I₂]⁻. A mechanism for the reaction of 1 with MeI in MeCN is proposed, involving initial bridge cleavage by solvent to give [Rh(CO)₂(NCMe)I] and participation of the anion [Rh(CO)₂I₂]⁻ as a reactive intermediate. The possible role of neutral Rh(III) species in the mechanism of Rh-catalysed methanol carbonylation is discussed.     

Uptakes of iodide and chloride by primary cultures of mouse astrocytes and neurons

Primary cultures of both mouse astrocytes and neurons accumulate more¹²⁵I^– than³⁶Cl^– from the medium. The average cell/medium ratio of¹²⁵I^– of astrocytes (1.01) is greater than that of neurons (0.74), whereas the ratio of³⁶Cl^– of neurons (0.47) is greater than that of astrocytes (0.25). The equilibrium potentials of both¹²⁵I^– and³⁶Cl^– calculated from the cell/medium ratios in astrocytes and neurons are significantly lower than their corresponding resting transmembrane potentials which suggest that both iodide and chloride are actively transported into both cell types. With respect to different transport inhibitors, thiocyanate is more effective in inhibiting¹²⁵I^– uptake whereas furosemide is more effective in inhibiting³⁶Cl^– uptake. Radioiodide uptake by mouse astrocytes was directly proportional to the [Na⁺]_o but was not significantly affected by changes of [Cl^–]_o or [HCO ₃ ^– ]_o, except that it is low in bicarbonate-free medium. Radiochloride uptake by astrocytes was inversely related to [Cl^–]_o and [HCO ₃ ^– ]_o and was not affected [Na⁺]_o, except that it was low in sodium-free medium. Radioiodide uptake by neurons was directly related to [Na⁺]_o between 60 and 140 mM and inversely related to [HCO ₃ ^– ]_o between 10 and 40 mM, but it was not affected by [Cl^–]_o. Radiochloride uptake by neurons was directly related to [Cl^–]_o and to [Na⁺]_o between 60 and 140 mM and was not affected by [HCO ₃ ^– ]_o. However, in sodium-free medium both¹²⁵I^– and³⁶Cl^– uptakes into neurons were higher than those in [Na⁺]_o between 5 and 60 mM. These results indicate that uptake of¹²⁵I^– and³⁶Cl^– into astrocytes and neurons are different in their ion dependence and that they are under separate regulation.Special issue dedicated to Dr. Paola S. Timiras     

Availability of iodide and iodate to spinach (Spinacia oleracea L.) in relation to total iodine in soil solution

A greenhouse pot experiment was carried out to investigate the availability of iodide and iodate to soil-grown spinach (Spinacia oleracea L.) in relation to total iodine concentration in soil solution. Four iodine concentrations (0, 0.5, 1, 2 mg kg⁻¹) for iodide (I⁻) and iodate (IO₃⁻) were used. Results showed that the biomass productions of spinach were not significantly affected by the addition of iodate and iodide to the soil, and that iodine concentrations in spinach plants on the basis of fresh weights increased with increasing addition of iodine. Iodine concentrations in tissues were much greater for plants grown with iodate than with iodide. In contrast to the iodide treatments, in iodate treatment leaves accounted for a larger fraction of the total plant iodine. The soil-to-leaf transfer factors (TF_leaf) for plants grown with iodate were about tenfold higher than those grown with iodide. Iodine concentrations in soil solution increased with increasing iodine additions to the soil irrespective of iodine species. However, total iodine in soil solution was generally higher for iodate treatments than iodide both in pots with and without spinach. According to these results, iodate can be considered as potential iodine fertilizer to increase iodine content in vegetables.     

Phosphoinositide-3-kinase inhibition elevates ferritin level resulting depletion of labile iron pool and blocking of glioma cell proliferation

Background

Elevated endogenous phosphoinositide-3-kinase (PI3K) activity is critical for cell proliferation in gliomas. Iron availability is one of the essential factors for cell growth and proliferation. However, any relation between PI3K and cellular iron homeostasis has not been understood so far.

Colorimetric endpoint assay for enzyme-catalyzed iodide ion release for high-throughput screening in microtiter plates

Efforts are being made to engineer enzymes with enhanced activities against haloalkanes, a toxicologically important class of compounds widely used and frequently occurring in the environment. Here we describe a facile, inexpensive, and robust method for the screening of libraries of mutated enzymes with iodoalkane substrates. Iodide formed in the enzymatic reaction is oxidized to iodine, which in the presence of starch gives blue color that can be measured at 610nm or scored with the human eye. The assay can be performed with enzymes in crude cell lysates in 96-wells microtiter plates. Expression clones of several glutathione transferases showed diverse activities with different iodoalkanes, and a mutant library of human glutathione transferase A1-1 expressed variants with enhanced substrate selectivities.     

Acute and chronic leptin effect upon in vivo and in vitro rat thyroid iodide uptake

Leptin has stimulatory effects on the hypothalamic-pituitary-thyroid axis and on deiodinases activities. Here, we evaluated the effect of leptin injection upon in vivo and in vitro thyroid 125I uptake (RAIU). We designed two experiments: acute leptin (LepA) with a single dose of leptin (8 microg/100 g BW/sc), and chronic leptin (LepC), injected with the same dose of LepA, once a day, for 6 days. In parallel, control groups were saline-injected. For in vivo study, part of the animals were injected with 125I (3700 Bq) and killed after 15 or 120 min. In vivo thyroid RAIU was not changed in LepA animals. However, LepC animals showed higher in vivo thyroid RAIU (15 min:+130% and 120 min:+72%; p<0.05). For in vitro study, the other animals were killed and their thyroids were incubated with 125I. Thyroids explants from LepA and LepC groups presented lower thyroid 125I content (-32% and -29% p<0.05, respectively). The amount of our data suggest that, in vitro, leptin causes a direct inhibition of the rat thyroid RAIU, but in vivo, the effect of leptin was different according to the treatment period, which indicates that other indirect mechanisms are involved in the in vivo leptin chronic stimulation of the thyroid gland.     

Protein repertoire impact of Ubiquitin-Proteasome System impairment: insight into the protective role of beta-estradiol

The Ubiquitin-Proteasome System (UPS) and the Autophagy-Lysosome Pathways (ALP) are key mechanisms for cellular homeostasis sustenance and protein clearance. A wide number of Neurodegenerative Diseases (NDs) are tied with UPS impairment and have been also described as proteinopathies caused by aggregate-prone proteins, not efficiently removed by proteasome. Despite the large knowledge on proteasome biological role, molecular mechanisms associated with its impairment are still blur. We have pursued a comprehensive proteomic investigation to evaluate the phenotypic rearrangements in protein repertoires associated with a UPS blockage. Different functional proteomic approaches have been employed to tackle UPS impairment impact on human NeuroBlastoma (NB) cell lines responsive to proteasome inhibition by Epoxomicin. 2-Dimensional Electrophoresis (2-DE) separation combined with Mass Spectrometry and Shotgun Proteomics experiments have been employed to design a thorough picture of protein profile. Unsupervised meta-analysis of the collected proteomic data revealed that all the identified proteins relate each other in a functional network centered on beta-estradiol. Moreover we showed that treatment of cells with beta-estradiol resulted in aggregate removal and increased cell survival due to activation of the autophagic pathway. Our data may provide the molecular basis for the use of beta-estradiol in neurodegenerative disorders by induction of protein aggregate removal.