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PubMed2006

Enhanced wear and fatigue properties of Ti-6Al-4V alloy modified by plasma carburizing/CrN coating.

In this study, a newly developed duplex coating method incorporating plasma carburization and CrN coating was applied to Ti-6Al-4V and its effects on the wear resistance and fatigue life were investigated. The carburized layer with approximately150 microm in depth and CrN coating film with 7.5 microm in thickness were formed after duplex coating. Hard carbide particles such as TiC And V(4)C(3) were formed in the carburized layer. XRD diffraction pattern analysis revealed that CrN film had predominant [111] and [200] textures. The hardness (Hv) was significantly improved up to about 1,960 after duplex coating while the hardness value of original Ti-6Al-4V was 402. The threshold load for the modification and/or failure of CrN coating was measured to be 32 N using the acoustic emission technique. The wear resistance and fatigue life of duplex-coated Ti-6Al-4V improved significantly compared to those of un-treated specimen. The enhanced wear resistance can be attributed to the excellent adhesion and improved hardness of CrN coating film for the duplex-coated Ti-6Al-4V. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the surface, resulting in the enhanced fatigue life.

Alloys↗
PubMed2006

Conformational and structural analysis of bovine beta lactoglobulin-A upon interaction with Cr+3.

Thermodynamic studies have been made on the effect of Cr(+3) on the conformation and structure of bovine beta lactoglobulin-A, (Blg-A) in 50 mM sodium chloride solution at 27 degrees C using isothermal titration calorimetry (ITC), circular dichroism (CD) and fluorescence spectroscopy. There is a set of six identical and independent binding sites for Cr(+3) by a dissociation binding constant of 124 microM and the molar enthalpy of binding -17.8 kJ/mol. Circular dichroism studies do not show any significant change in the secondary structure of the protein after the binding of chromium ion on the Blg-A. Fluorescence spectroscopy studies do not show any considerable change in the tertiary structure of Blg-A due to the increasing of Cr(+3) in low concentration. However, occupation of fourth and fifth binding sites for chromium ions induce partially unfolding in the tertiary structure of the protein resulted from solvent - exposed hydrophobic patches on BLG-A.

Animals↗
PubMed2005

Non-enzymatic phosphorylation of bovine serum albumin by Cr(V) complexes: role in Cr(VI)-induced phosphorylation and toxicity.

Evidence for the non-enzymatic phosphorylation of bovine serum albumin (BSA) by sodium bis(2-ethyl-2-hydroxybutyrato)oxochromate(V), Na[CrVO(ehba)2], 1, sodium bis(2-hydroxy-2-methylbutyrato)oxochromate(V), Na[CrVO(hmba)2], 2 and potassium dichromate, K2Cr2O7, 3 in the presence of labeled adenosine-5'-triphosphate (ATP) under conditions of physiological pH is presented. Aggregation and extent of phosphorylation of BSA mediated by 1, 2 or 3 seems to increase with the concentration and time of incubation of the reaction mixture containing all the reactants. The [gamma-32P] label in ATP is incorporated into aggregates of BSA in the in vitro reaction of the protein with ATP in the presence of 1, 2 or 3. Phosphorylation of BSA by ATP in the absence of 1, 2 or 3 is negligible. Addition of EDTA reverses aggregation of protein and liberates partially the incorporated phosphate label. The stoichiometry of phosphorylation is found to be the highest and is equal to 12.25 mol PO4(3-)/mol BSA in the presence of 500 microM of 1, which decreases to 10.56 mol PO4(3-)/mol BSA after EDTA treatment. Resistance to the removal of phosphate label by EDTA increases with increase in time of incubation. Dialysis of phosphorylated BSA reverses the incorporated [gamma-(32)P] label only partially, indicating the formation of covalent links of phosphate groups to BSA. Evidence for the site of phosphorylation in the reaction mediated by 1, 2 or 3 being hydroxyl side groups of tyrosine and serine/threonine residues has been gained. Based on the results, a possibility that 1, 2 and 3 mimic the function of tyrosine and serine/threonine kinases has been invoked.

Adenosine Triphosphate↗
PubMed2005

Differential impact of ionic and coordinate covalent chromium (Cr)-DNA binding on DNA replication.

The reactive species produced by the reduction of Cr(VI), particularly Cr(III), can form both ionic and coordinate covalent complexes with DNA. These Cr(III)-DNA interactions consist of Cr-DNA monoadducts, Cr-DNA ternary adducts, and Cr-DNA interstrand cross-links (Cr-ICLs), the latter of which are DNA polymerase arresting lesions (PALs). We sought to determine the impact of Cr-DNA interactions on the formation of replication blocking lesions in S. cerevisiae using a PCR-based method. We found that target sequence (TS) amplification using DNA isolated from Cr(VI)-treated yeast actually increased as a function of Cr(VI) concentration. Moreover, the enhanced TS amplification was reproduced in vitro using Cr(III)-treated DNA. In contrast, PCR amplification of TS from DNA isolated from yeast exposed to equitoxic doses of the inorganic DNA cross-linking agent cisplatin (CDDP), was decreased in a concentration-dependent manner. This paradox suggested that a specific Cr-DNA interaction, such as an ionic Cr-DNA complex, was responsible for the enhanced TS amplification, thereby masking the replication-blocking effect of certain ternary Cr-DNA adducts (i.e. interstrand cross-links). To test this possibility, we removed ionically associated Cr from the DNA using salt extraction prior to PCR analysis. This procedure obviated the increased amplification and revealed a dose-dependent decrease in TS amplification and an increase in Cr-PALs. These data from DNA analyzed ex vivo after treatment of intact cells indicate that ionic interactions of Cr with DNA result in increased DNA amplification whereas coordinate-covalent Cr-DNA complexes lead to formation of Cr-PALs. Thus, these results suggest that treatment of living cells with Cr(VI) leads to two modes of Cr-binding, which may have conflicting effects on DNA replication.

Carcinogens↗
PubMed1982

Intraperitoneal chromic phosphate in peritoneoscopically confirmed stage I ovarian adenocarcinoma.

From December 15, 1975 to June 16, 1980, 20 evaluable patients with International Federation of Gynaecology and Obstetrics Stage I invasive adenocarcinoma of the ovary were entered into a prospective study, including pretherapy restaging peritoneoscopy followed by treatment with intraperitoneal chromic phosphate if there was no evidence of residual macroscopic tumor. During a follow-up of 1 1/2 to 6 years (median, 3 years and 1 month), the survival rate without evidence of recurrent ovarian carcinoma was 95%. Moreover, there was a total absence of complications with the use of the sequential steps of pretherapy peritoneoscopy, a normal preinjection peritoneogram, injection of chromic phosphate in large volumes of solution, frequent change of position of the patient after injection, and abdominal scans after injection. This method appears to be safe and is associated with a significantly high survival rate.

Adenocarcinoma↗
PubMed1985

Intraperitoneal chromic phosphate P 32 suspension therapy of malignant peritoneal cytology in endometrial carcinoma.

Malignant peritoneal cytology in patients with endometrial carcinoma is a poor prognostic feature, identifying patients at high risk for early intra-abdominal recurrence. Between 1977 and January, 1983, 65 women with endometrial carcinoma who had malignant peritoneal cytology were treated with adjuvant intraperitoneal radioactive chromic phosphate P 32 suspension. Fifty-three patients (80%) were clinical Stage I, nine (14%) were Stage II, and three (7%) were clinical Stage III. Life-table estimates of disease-free survival were 89% for clinical Stage I patients and 94% for surgical Stage I patients beyond 24 months. One patient developed an intraperitoneal recurrence, four had simultaneous intraperitoneal and extraperitoneal recurrences, and six developed recurrences outside of the peritoneal cavity. Few significant acute complications occurred after therapy with radioactive chromic phosphate P 32 suspension. Chronic intestinal morbidity that required surgical correction was encountered in five of 17 patients (29%) who received adjuvant pelvic radiation, compared to none of the 48 patients (0%) who received only radioactive chromic phosphate P 32 suspension (p less than 0.001). Intraperitoneal instillation of radioactive chromic phosphate P 32 suspension is effective therapy for patients with malignant peritoneal cytology from endometrial carcinoma. Caution should be exercised when radioactive chromic phosphate P 32 suspension and external radiation therapy are combined.

Adenocarcinoma↗
PubMed1987

Intraperitoneal chromic phosphate P 32 as salvage therapy for persistent carcinoma of the ovary after surgical restaging.

From 1977 through 1984, 23 patients with persistent epithelial carcinomas of the ovary received intraperitoneal instillation with chromic phosphate P 32 suspension as salvage therapy after second- or third-look laparotomy. Patients received a median 10 cycles of chemotherapy before chromic phosphate P 32. Disease consisted of microscopic residual only in 10 patients (43%), macroscopic residual that was completely resected in eight (35%), and macroscopic residual disease in which the largest diameter was less than 0.5 cm in five patients (22%). Ten patients are free of disease at 13 to 94 months after chromic phosphate P 32 salvage therapy. Life table survival is 75% at 2 years and 57% at 4 years, with a disease-free survival rate of 54% at 2 years and 27% at 4 years. Patients with no gross residual disease had median disease-free survival of 27 months versus 9 months for patients with macroscopic residual disease (p greater than 0.1). Only three patients (13%) developed surgical bowel complications related to chromic phosphate P 32. Compared with previous studies, intraperitoneal chromic phosphate P 32 as salvage therapy for patients with minimal residual ovarian carcinoma defined at secondary surgical evaluation results in comparable survival and fewer complications than does salvage abdominopelvic irradiation and should be considered as an option to further chemotherapy in selected patients.

Actuarial Analysis↗
PubMed1986

Specific tritium labeling of glucosyl- and galactosylceramides at the 6-position of the carbohydrate moiety using CrO3-graphite.

A new procedure for introducing tritium into the carbohydrate portions of glucosyl- and galactosylceramides was developed using a new catalyst, CrO3-graphite, which specifically oxidizes the primary alcohol group to the aldehyde. About 10% of the glycolipid was converted to the aldehyde and the aldehyde produced was then reduced back to the original form with KB3H4. After methanolysis, more than 96.7% of the radioactivities of [3H]glucosyl- and [3H]galactosylceramides were found to be located in the carbohydrate portions, and the specific activities of the [3H]galactosyl- and [3H]glucosylceramides were 2.08 to 4.30 X 10(4) cpm/nmol, which could be increased greatly by purifying the aldehydes and reducing them with KB3H4. In addition, beta-galactosidase activity was successfully determined with [3H]galactosylceramide as the enzyme substrate; the Km was 18.73 mM and the Vmax was 11.63 nmol/mg/h, indicating that no significant structural modification occurs during the oxidation.

Animals↗
PubMed1989

Enhancement of colloid uptake by tumor cell surface electrical charge modification.

Colloidal [51Cr]chromic phosphate uptake is considerably increased by preincubation of P388 ascites leukemia cells with poly(DL-lysine). The uptake increase is in direct relationship with the concentration and the degree of polymerization of poly(DL-lysine). The probable implication of cell surface electrical charge modification in these phenomena is discussed.

Animals↗
PubMed1990

Structure of an exocellular polysaccharide produced by Streptococcus thermophilus.

Streptococcus thermophilus strains grown on skimmed milk produced a viscosifying, exocellular, and water-soluble polysaccharide which contains D-glucose, D-galactose, and N-acetyl-D-galactosamine in the ratio of 1:2:1. Methylation analysis identified the glycosidic linkages in the tetrasaccharidic repeating-unit, and Smith degradation and nitrous deamination after N-deacetylation gave the sequence of monosaccharides in the repeating-unit. The anomeric configurations of the sugar residues were determined by oxidation of the peracetylated polysaccharide with chromium trioxide and by 1H- and 13C-n.m.r. spectroscopy. The following structure was assigned to the repeating unit of the polysaccharide,----3)-beta-D-Galp-(1----3)-[alpha-D-Galp-(1----6)]-beta- D- Glcp-(1----3)-alpha-D-GalpNAc-(1----.

Acetylation↗
PubMed1984

Rat liver microsomal cholesterol biosynthesis and drug oxidase activity are affected by chromium ions (Cr3+) in vitro.

Chromium ions (Cr3+)evoked a biphasic curve of changes of rat liver microsomal cholesterol biosynthesis using [14C]acetate and/or [14C]mevalonate as precursors. While for the lower range of Cr3+ concentrations the rate of cholesterol biosynthesis rises, at concentrations above 8 X 10(-6) M they evoke a decrease in the cholesterol biosynthesis, up to 50% down on its control value at a concentration of 8 X 10(-4) M. Differences were more pronounced when using [14C]mevalonate instead of [14C]acetate as precursor. The activity of the microsomal enzyme biphenyl-4-hydroxylase showed an equally intense rise to that of cholesterol biosynthesis up to a 8 X 10(-6) M Cr3+ concentration. Above this concentration, however, the activity of the enzyme starts to drop. NADPH-cytochrome c reductase and NADPH-oxidase were decreased at all Cr3+ concentrations used, which cover a 100-fold range. Lineweaver-Burk plots of the cytoplasmic glucose-6-phosphate dehydrogenase demonstrated an uncompetitive mechanism of inhibition by Cr3+ ions. The results are discussed in terms of the possible significance of the Cr3+ concentration-dependent effects on cholesterol biosynthesis, with the observed atherosclerosis in Cr-deficient humans.

Acetates↗
PubMed1980

Measure of rheumatoid factor in human sera by passive haemagglutination of human erythrocytes carrying immunoglobulin linked by chromic chloride.

Serum rheumatoid factor in sero-positive patients with rheumatoid arthritis may be measured by passive haemagglutination of trypsin-treated human red cells linked with heat-aggregated human IgG by chromic chloride. The results show excellent correlation with those obtained with the classical Rose-Waaler test. The sera may be tested unheated and do not require preliminary absorption with red cells. By this test procedure it should also be possible to analyse the species, allotypic and conformational specificity of different rheumatoid factors.

Animals↗