Investigation of microbiologically influenced corrosion inhibition of 304 stainless steel by D-cysteine in the presence of Pseudomonas aeruginosa.

The influence of D-cysteine (D-cys) on the microbiologically influenced corrosion (MIC) of 304 stainless steel caused by Pseudomonas aeruginosa was investigated in this work. Immersion tests in the sterile and P. aeruginosa-inoculated culture media with different D-cys concentrations were carried out. The results showed that the addition of D-cys inhibited the formation of P. aeruginosa biofilms on stainless steel surfaces. D-cys itself did not affect the corrosion of stainless steel but could decrease the corrosion rate of MIC of stainless steel caused by P. aeruginosa. X-ray photoelectron spectroscopy (XPS) analysis and scanning electrochemical microscopy (SECM) analysis indicated that the biofilm inhibition effect of D-cys greatly reduced the destructive effect of the adhered P. aeruginosa cells on the passive film of the stainless steel, thus inhibiting the MIC of the stainless steel.

The Forkhead box transcription factor FOXM1 is required for the maintenance of cell proliferation and protection against oxidative stress in human embryonic stem cells.

Human embryonic stem cells (hESCs) exhibit unique cell cycle structure, self-renewal and pluripotency. The Forkhead box transcription factor M1 (FOXM1) is critically required for the maintenance of pluripotency in mouse embryonic stem cells and mouse embryonal carcinoma cells, but its role in hESCs remains unclear. Here, we show that FOXM1 expression was enriched in undifferentiated hESCs and was regulated in a cell cycle-dependent manner with peak levels detected at the G2/M phase. Expression of FOXM1 did not correlate with OCT4 and NANOG during in vitro differentiation of hESCs. Importantly, knockdown of FOXM1 expression led to aberrant cell cycle distribution with impairment in mitotic progression but showed no profound effect on the undifferentiated state. Interestingly, FOXM1 depletion sensitized hESCs to oxidative stress. Moreover, genome-wide analysis of FOXM1 targets by ChIP-seq identified genes important for M phase including CCNB1 and CDK1, which were subsequently confirmed by ChIP and RNA interference analyses. Further peak set comparison against a differentiating hESC line and a cancer cell line revealed a substantial difference in the genomic binding profile of FOXM1 in hESCs. Taken together, our findings provide the first evidence to support FOXM1 as an important regulator of cell cycle progression and defense against oxidative stress in hESCs.

Identification of new cases of early-onset colorectal cancer with an MLH1 epimutation in an ethnically diverse South African cohort.

Lynch syndrome, characterized by young-onset microsatellite unstable colorectal, endometrial and other cancers, is caused by germline mutations of the mismatch repair genes, most commonly MLH1, MSH2 and MSH6. Constitutional MLH1 epimutations, which manifest as soma-wide methylation and transcriptional silencing of a single allele, have been identified in a subset of patients with a Lynch syndrome phenotype in the absence of a mismatch repair mutation. This study aimed to determine if MLH1 epimutations predispose to the development of young-onset colorectal cancer in an ethnically diverse population of South African subjects. A total of 122 index cases with a diagnosis of colorectal cancer below 50 years of age, who had tested negative for a definitive pathogenic mutation of the key mismatch repair genes, were screened for constitutional MLH1 methylation in their leukocyte DNA. Monoallelic MLH1 epimutations were identified in two sporadic cases (1.6%): a male of black African descent and an Asian Indian female. Few alleles were affected by methylation in the female, indicating mosaicism. These cases provide further evidence of the aetiological role for MLH1 epimutations in cancer development and the requirement for sensitive molecular screening techniques to identify mosaic epimutations. Furthermore, while this mechanism is rare, it affects patients of multiple ethnic origins.

Inactivation of acyl-CoA:cholesterol acyltransferase by ATP+Mg2+ in rat liver microsomes.

The molecular modulation of acyl-CoA:cholesterol acyltransferase (EC 2.3.2.26) was studied in the microsomes of rat liver. Acyl-CoA: cholesterol acyltransferase was specifically inactivated by ATP and ADP, requiring Mg2+ as a cofactor. The inactivation was not due to substrate diminution nor to inhibition by the activity of acyl-CoA hydrolase, which was not affected by Mg2+ or ATP+Mg2+. Enhancement of inactivation of acyl-CoA: cholesterol acyltransferase by ATP+Mg2+, NaF and a heat-labile cytosolic factor (or factors) is consistent with a protein-kinase catalyzed phosphorylation being involved in the short term regulation of this enzyme.

Regulation of rat liver microsomal cholesterol 7 alpha-hydroxylase by MgATP: effect of pH.

Cholesterol 7 alpha-hydroxylase when assayed under conditions that favour phosphorylation can be activated or inactivated by MgATP, depending on ATP concentration and the pH of the incubation medium. Maximum stimulation of 7 alpha-hydroxylase was obtained with 0.5 mM ATP in both acidic and alkaline pH. At a pH lower than 7.4, 7 alpha-hydroxylase was inactivated by 2.0 and 3.0 mM MgATP. The inactivation by 3 mM MgATP was significantly greater at pH 6.7 than pH 7.4. Protein kinases enhanced these effects, suggesting covalent modification of the enzyme by phosphorylation. These findings are consistent with a protein kinase catalyzed phosphorylation, and suggest that MgATP may have a dual role in the activation and inactivation of 7 alpha-hydroxylase in vivo.

Regulation of rat liver microsomal cholesterol 7 alpha-hydroxylase: reversible inactivation by ATP + Mg2+ and a cytosolic activator.

Modulation of cholesterol 7 alpha-hydroxylase catalytic activity by adenine nucleotides was studied in rat liver microsomal preparations. Inactivation of cholesterol 7 alpha-hydroxylase showed specific requirements of ATP and ADP. AMP and cyclic AMP were stimulatory and cyclic AMP had no effect in the ATP inactivation. The inactivation reactions by ATP were dependent on Mg2+ ions, a cytosolic factor, and time. Ca2+ ions were less effective whereas Mn2+ ions were highly inhibitory to hydroxylase activity. The inactivation could be reversed in a time-dependent reaction requiring a cytosolic activator that was precipitable by ammonium sulphate of saturation up to 65%. The current data suggest that cholesterol 7 alpha-hydroxylase can exist in two catalytic forms that are reversible.

Regulation of rat liver microsomal cholesterol 7 alpha-hydroxylase: presence of a cytosolic activator.

Microsomal cholesterol 7 alpha-hydroxylase (EC 1.14.13.7) in rat liver was assayed by a single-isotope-incorporation method, and factors influencing its activity were studied. Crude cytosol contained a non-catalytic activator which was heat-stable and on-dialyzable. This activator enhanced cholesterol 7 alpha-hydroxylase catalytic activity. The stimulatory property of this cytosolic activator was not altered by cholestyramine feeding, and was retained after fractionation by ammonium sulfate of saturation up to 65%. 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) stimulated hydroxylase activity at concentrations up to 90 micro M. ATP at concentration greater than 1.2 mM inhibited hydroxylase activity. NaF was stimulatory at concentrations up to 50 mM with a maximum stimulatory effect at 10 mM, and was antagonistic in effect to ATP. HMG-CoA and ATP at the above inhibitory concentrations and higher abolished the activating effect of the cytosolic factor.

Phospholipid composition and metabolism in mouse muscular dystrophy.

1. The composition and metabolism of phospholipids were studied in various tissues from both normal and dystrophic mice of the 129 ReJ strain. Phospholipids extracted from forebrain, spinal cord, sciatic nerve and plasma were fractionated by t.l.c. and measured. 2. Very significant alterations were found in the choline phospholipids from these tissues, except forebrain. Plasma phosphatidylcholine in the dystrophic mouse was increased by 38%. There was a 2-fold increase in lysophosphatidylcholine in the spinal cord of dystrophic mice. The sciatic nerve showed a marked decrease in sphingomyelin content, which is approximately half of that in the controls. 3. Five enzymes involved in phosphatidylcholine metabolism [namely cholinephosphotransferase (EC 2.7.8.2); phospholipases A (EC 3.1.1.4, EC 3.1.1.32); lysophospholipase (EC 3.1.1.5); lysophosphatidylcholine acyltransferase (EC 2.3.1.23); phospholipase C (EC 3.1.4.3)] were studied in tissue preparations from forebrain, spinal cord, sciatic nerves, gastrocnemius muscles and liver. 4. Activities of phospholipases A and C were significantly increased, about 5-fold and 60% respectively, in gastrocnemius muscle of dystrophic mice compared with controls. Phospholipases A also showed 50% higher activity in the sciatic nerves of dystrophic than of normal mice. Lysophosphatidylcholine acyltransferase activities were significantly increased in the sciatic nerves and spinal cord, by 50-100% over that of the controls. The forebrain and spinal cord from dystrophic mice, however, had only 60% of lysophospholipase activities of that of the normal control. Cholinephosphotransferase activity was unchanged in these tissues from both normal and dystrophic mice. 5. It is suggested that are number of features of mouse muscular dystrophy related to altered membrane structure and function can be rationalized in terms of changes in lipid composition and metabolism.