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PubMedDate not supplied

Shear bond strengths of resin adhesive cements to dentin and Ni-Cr-Be alloy.

Two adhesives, Super Bond and Panavia, were evaluated for shear bond strength to dentin. Twenty human teeth were used for each adhesive. Bonding sites were prepared in dentin (600 grit) and the adhesives applied according to the manufacturers' instructions. Bond strengths were determined with an Instron testing machine at 24 hours. Super Bond developed the strongest bond of 21.59 +/- 3.91 MPa. Panavia produced a lower bond strength of 2.68 +/- 1.45 MPa. Statistically, Super Bond was found to have a stronger bond than Panavia. The same two adhesives were applied to Ni-Cr-Be specimens and compared to Comspan. Twenty Rexillium III specimens were used for each adhesive at 24 hours and 20 for thermocycling. The metal specimens were ground flat (600 grit) and then air abraded with 50-micron aluminous oxide. The adhesives were applied to the metal surface in accordance with the manufacturers' instructions. One group was tested at 24 hours while the second group was tested after thermocycling (2,500 cycles at 6 degrees C to 60 degrees C). At 24 hours, Super Bond had a significantly stronger bond than the other materials. Comparison of the 24-hour to thermocycled bond strengths found Comspan had a significant increase in bond strength, Panavia had no significant change and Super Bond had a significant decrease in bond strength. After 2,500 thermocycles, Comspan, Panavia, and Super Bond were not significantly different in bond strength.

Boron Compounds↗
PubMed1992

Bonding Ni-Cr alloy to tooth structure with adhesive resin cements.

This study was to determine the shear bond strengths of Ni-Cr alloy to Ni-Cr alloy (Group I), Ni-Cr alloy to enamel (Group II), and Ni-Cr alloy to dentin (Group III) using Imperva Dual, DC Metabond, All-Bond, Geristore, and Panavia. All bonded specimens were thermocycled 2000 x (5 degrees C-55 degrees C) after 24 hours and subjected to shear bond testing on a Universal Instron Testing Machine. In all groups of the study, Imperva Dual and CB Metabond had significantly (p < .05) higher bond values than Panavia.

Analysis of Variance↗
PubMed1989

Factors determining gastrointestinal transit time of several markers in the domestic fowl.

The aim of this study was to find out how marker characteristics could affect digestive transit time in Gallus gallus. One soluble marker, Cr-EDTA, and two insoluble markers, Cr2O3 and chromium-mordanted plant cells of two sizes, were used. Three- to six-week-old chickens were killed in series after the oral administration of the markers at intervals of 0, 0.5, 1, 2, 3, 5, 7, and 9 h. The amount of chromium in each digestive segment was determined by atomic absorption. There were some differences in the initial distribution of markers; whereas almost the total amount of the chromium-mordanted rice husk of the largest size was found in the crop at time 0, less than half of the Cr-EDTA was found. Marker emptying out of the crop was fast and not related to either the type or size. In contrast, the emptying rate of the gizzard depended on marker particle size. As far as the caeca were concerned, the ileocaecal junction allowed the passage of soluble Cr-EDTA whereas solid markers were impeded (Cr2O3) or not allowed to pass through at all (vegetable fibre of any size). It can be concluded that marker selection is of major importance to transit time studies in chickens, since its characteristics can determine transit time in an absolute way.

Animals↗
PubMed2004

Hydrocarbons in hydrothermal vent fluids: the role of chromium-bearing catalysts.

Fischer-Tropsch type (FTT) synthesis has long been proposed to account for the existence of hydrocarbons in hydrothermal fluids. We show that iron- and chromium-bearing minerals catalyze the abiotic formation of hydrocarbons. In addition to production of methane (CH4aq), we report abiotic generation of ethane (C2H6aq) and propane (C3H8aq) by mineral-catalyzed hydrothermal reactions at 390 degrees C and 400 bars. Results suggest that the chromium component in ultramafic rocks could be an important factor for FTT synthesis during water-rock interaction in mid-ocean ridge hydrothermal systems. This in turn could help to support microbial communities now recognized in the subsurface at deep-sea vents.

Archaea↗
PubMed1981

Astatine-211--tellurium radiocolloid cures experimental malignant ascites.

An investigation of the efficacy of astatine-211--tellurium colloid for the treatment of experimental malignant ascites in mice reveals that this alpha-emitting radiocolloid can be curative without causing undue toxicity to normal tissue. By comparison, negatron-emitting phosphorus-32 as colloidal chromic phosphate had no antineoplastic activity. The most compelling explanation for this striking difference is the dense ionization and short range of action associated with alpha-emission. These results have important implications for the development and use of alpha-emitters as radiocolloid therapy for the treatment of human tumors.

Alpha Particles↗
PubMed2000

Dissimilatory metal reduction by the facultative anaerobe Pantoea agglomerans SP1.

Anaerobic enrichments with acetate as the electron donor and Fe(III) as the terminal electron acceptor were obtained from sediments of Salt Pond, a coastal marine basin near Woods Hole, Mass. A pure culture of a facultatively anaerobic Fe(III) reducer was isolated, and 16S rRNA analysis demonstrated that this organism was most closely related to Pantoea (formerly Enterobacter) agglomerans, a member of the family Enterobacteriaceae within the gamma subdivision of the Proteobacteria. This organism, designated strain SP1, can grow by coupling the oxidation of acetate or H(2) to the reduction of a variety of electron acceptors, including Fe(III), Mn(IV), Cr(VI), and the humic substance analog 2,6-anthraquinone disulfonate, but not sulfate. To our knowledge, this is the first mesophilic facultative anaerobe reported to couple acetate oxidation to dissimilatory metal reduction.

Acetates↗
PubMed1985

Intestinal permeability to 51Cr-EDTA in rats with experimentally induced enteropathy.

Intestinal permeability has been investigated in the normal rat by measuring the five hour urine excretion of 51Cr-EDTA after intragastric administration. Twelve control animals excreted 2.06% +/- 0.22 (mean +/- SE) of the administered dose. Prolonged intestinal transit times with atropine had no significant effect on the apparent permeability with a urine excretion 2.31% +/- 0.36. The concomitant administration of a hypertonic, but rapidly absorbed glycerol solution, was accompanied by increased urinary excretion (3.05% +/- 0.33) while the administration of a poorly absorbed sugar, lactulose, significantly decreased the apparent permeability (urine excretion 0.61% +/- 0.14) showing that passive intestinal permeability estimations are affected by test dose composition. Enteropathy was induced by ethanol, cetrimide, or methotrexate and each was associated with increased permeability, with urine excretions of 4.19% +/- 0.47, 4.20% +/- 0.66 and 3.97% +/- 0.49 respectively. It is thus suggested that the normal rat mucosa is maximally resistant to the absorption of foreign compounds such as 51Cr-EDTA and intestinal damage will disrupt this barrier.

Animals↗
PubMed1996

Respiratory health of workers exposed to low levels of chromium in stainless steel production.

OBJECTIVES: To determine whether occupational exposure to chromite, trivalent chromium, or hexavalent chromium causes respiratory diseases, an excess of respiratory symptoms, a decrease in pulmonary function, or signs of pneumoconiosis among workers in an integrated chain of stainless steel production. METHODS: This cross sectional study was carried out in 1993 and the inclusion criterion was a minimum of eight years of employment in the same production department. A self administered questionnaire was collected, and spirometry, measurement of diffusing capacity, chest radiography, and laboratory tests were carried out by a mobile research unit. RESULTS: There were 221 workers in the exposure groups and 95 in the control group. The average duration of employment was 18 years. No significant differences in the odds ratios (ORs) of the symptoms were found between the exposure and the control groups. In a logistic regression analysis age and smoking significantly explained the occurrence of most of the respiratory symptoms. The smokers in the chromite group had significantly lower forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and diffusing capacity than the corresponding values of the control group. The analysis of variance between study groups, smoking, and exposure time, without modelling for interactions, showed that the chromite group had lower values for FVC, FEV1, and diffusing capacity than the other groups. The occurrence of small opacities was more frequent on the chest radiographs of the workers in the chromite group. CONCLUSIONS: An average exposure time of 18 years in ferrochromium and stainless steel production and exposure to dusts containing low concentrations of hexavalent or trivalent chromium do not lead to any respiratory changes detectable by lung function tests or radiography nor to any increase in symptoms of respiratory diseases. The lung function values were lower and the occurrence of radiological findings was more frequent among the workers from the chromite mine than among the controls. The difference was partly caused by differences in age and smoking habits, but evidently also partly by higher exposures more than two decades ago or by the fibrous components of the dust.

Adult↗
PubMed1997

Mortality in a cohort of tannery workers.

OBJECTIVES: To evaluate the mortality of a group of tannery workers. METHODS: The cohort consisted of 1244 workers (870 men and 374 women) employed at a chrome tannery between 1955 and 1988. A total of 36414 person-years of follow up was calculated (369 people had died). National and regional mortalities were used to estimate the expected numbers. RESULTS: All cause mortality was similar to that of the general population. The most remarkable excess was for bladder cancer (observed 10, standardised mortality ratio (SMR) 242, 95% confidence interval (95% CI) 116 to 446). An excess of colorectal cancer (observed 17, SMR 180, 95% CI 105 to 288) was also found, based on an increased risk of both colon (SMR 166) and rectal cancer (SMR 206). No recognisable patterns emerged from the analyses by years since first employment, calendar year of hire, or lagging exposures. CONCLUSIONS: The increased mortality from bladder cancer is likely due to exposure to benzidine based leather dyes. If the apparent excess of colorectal cancer is real, its causes are as yet unknown.

Adolescent↗
PubMed1994

Effects of a chromated-copper-arsenate wood preservative on the bacterial degradation of pentachlorophenol.

The effect of a chromated-copper-arsenate wood preservative on the degradation of pentachlorophenol by Flavobacterium sp. strain ATCC 53874 was examined in liquid culture. Both a commercially available and a laboratory-prepared formulation were tested. Each increased the lag time required for measurable pentachlorophenol degradation and the time required for complete degradation to nondetectable levels. This response was noted at all pentachlorophenol concentrations examined (10, 25, 50, 75, and 100 micrograms.mL-1). The commercial formulation of chromated-copper-arsenate had the more significant impact on pentachlorophenol degradation. Inhibitory effects were evident at chromated-copper-arsenate component metal concentrations 0.1-0.5 mg.L-1. These levels are thousands of times below those used commercially.

Arsenates↗
PubMed1982

Chromium trioxide oxidation of acetylated 3-amino-3,6-dideoxy-L-hexosides.

Glycosides of the fully acetylated 3-amino-3,6-dideoxy-L-hexosides in the gluco, galacto, manno, and talo configurations have been treated with chromium trioxide in acetic acid. The alpha-L-methyl glycosides, which exist in the more stable chair conformation 1C4, with an axially oriented aglycon, are resistant to this oxidation, whereas the beta-L-linked glycoside having the gluco configuration (1C4 conformation) and the alpha-L-methyl glycoside having the talo configuration (4C1 conformation), both with equatorially oriented aglycons, are oxidized to the corresponding 5-adulosonates.

Acetylation↗
PubMed1983

Structural elucidation of the capsular polysaccharide of Streptococcus pneumoniae type 9N.

The specific capsular polysaccharide of Streptococcus pneumoniae type 9N (American type 9) contains D-glucose, D-glucuronic acid, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-mannose in the molar ratio of 2:1:1:1. Accumulated data from spectroscopic (13C and 1H nuclear magnetic resonance) and methylation analyses of the native and specifically degraded polysaccharide indicated that it was linear and composed of the following pentasaccharide repeating unit; -4)-alpha-D-GlcpA-(1 leads to 3)-alpha-D-Glcp-(1 leads to 3)-beta-D-ManpNAc-(1 leads to 4)-alpha-D-Glcp-(1 leads to 4)-beta-D -GlcpNAc(1 leads to. Structural regions in the type 9N polysaccharide common to those of types 9A, 9L, and 9V have been identified which account for the cross-reactivity of this groups of polysaccharides.

Amino Acid Sequence↗
PubMed1981

Effects of injection volume on the tissue dose, dose rate, and therapeutic potential intraperitoneal 32p.

Increasing the injection volume had no significant long-term effect on the distribution or tissue dose of intraperitoneal 32P in New Zealand white rabbits. Further, the range of doses and dose rates observed in the rabbit had little effect in vitro against either a human ovarian cancer line or an established Chinese hamster cell line. Demonstrable kill of human ovarian cancer cells was achieved, however, for initial 32P dose rates of 11 and 22 rad/h (0.11 and 0.22 Gy/h). From these results, it is estimated that administered 32P activities ranging from about 75-150 mCi (2.8-5.6 GBq) would be required for significant tumoricidal effects in ovarian cancer patients.

Animals↗
PubMed1983

Observations on the intraperitoneal distribution of chromic phosphate (32P) suspension for intraperitoneal therapy.

Seven patients received intraperitoneal chromic phosphate (32P) suspension in a 3-ml bolus with a saline flush, and another ten patients were given the suspension in a 500-ml infusion of normal saline. During the first six hours after administration, most 32P activity redistributed to the gravity-dependent portion of the peritoneal cavity. From 24 hours up to seven weeks after administration, activity distributions were fixed. Dispersions were heterogeneous in every patient, but the most marked examples of localized activity occurred in patients who had received bolus injections. We concluded that large-volume infusions and frequent changes in patient position for several hours following the infusion, contribute to improved dispersion of 32P suspension.

Chromium↗