Quantitative color Doppler imaging in untreated and irradiated choroidal melanoma.
(17/243)Histological data indicate the importance of tumor vascularization as a determinant of the biological behavior and the response to radiotherapy in choroidal melanoma. Duplex ultrasound and color Doppler imaging, the combination of B-mode ultrasound and pulse-waved Doppler analysis, were used to measure quantitatively neovascular blood flow in 31 patients with choroidal melanoma. Follow-up studies (20 patients) were performed to investigate the change of tumor blood flow in choroidal melanomas after radiotherapy. Blood flow was detected in 30 out of 31 melanomas (size 3.1-17.8 mm) within the tumor and at the tumor base with a mean peak systolic frequency of 1.0 kHz (range 0.3-2.7 kHz), a mean end diastolic frequency of 0.3 kHz (range 0.1-1.0 kHz), and a mean frequency of 0.7 kHz (range 0.2-1.3 kHz). Two and six months after 106Ru/106Rh beta-ray application, 19 patients showed a significant decrease in peak systolic frequency. This occurred with and in advance of the decrease in the tumor size. In one patient, a rising maximum systolic frequency after radiotherapy marked a recurrent tumor growth. Results indicate that the quantitative measurement of tumor blood flow by duplex ultrasound and color Doppler imaging may be a new diagnostic modality for monitoring the effectiveness of radiotherapy in choroidal melanoma. (+info)
An evaluation of the environmental and health effects of vehicle exhaust catalysts in the UK.
(18/243)Since 1993, all new gasoline-engine automobiles in the United Kingdom have been supplied with three-way vehicle exhaust catalytic converters (VECs) containing platinum, palladium, and rhodium, to comply with European Commission Stage I limits on emissions of regulated pollutants: carbon monoxide, hydrocarbons, and oxides of nitrogen. We conducted a physical and economic evaluation of the environmental and health benefits from a reduction in emissions through this mandated environmental technology against the costs, with reference to urban areas in Great Britain. We made both an ex post assessment--based on available data to 1998--and an ex ante assessment--projected to 2005, the year when full penetration of VECs into the fleet is expected. Substantial health benefits in excess of the costs of VECs were indicated: By 1998 the estimated net societal health benefits were approximately 500 million British pounds, and by 2005 they were estimated to rise to as much as 2 billion British pounds. We also found through environmental surveys that although lead in road dust has fallen by 50% in urban areas, platinum accumulations near roads have risen significantly, up to 90-fold higher than natural background levels. This rapid accumulation of platinum suggests further monitoring is warranted, although as yet there is no evidence of adverse health effects. (+info)
New biphenol-based, fine-tunable monodentate phosphoramidite ligands for catalytic asymmetric transformations.
(19/243)Monodentate phosphoramidite ligands have been developed based on enantiopure 6,6'-dimethylbiphenols with axial chirality. These chiral ligands are easy to prepare and flexible for modifications. The fine-tuning capability of these ligands plays a significant role in achieving high enantioselectivity in the asymmetric hydroformylation of allyl cyanide and the conjugate addition of diethylzinc to cycloalkenones. (+info)
Desymmetrization of enone-diones via rhodium-catalyzed diastereo- and enantioselective tandem conjugate addition-aldol cyclization.
(20/243)Catalytic tandem conjugate addition-enolate trapping represents an effective strategy for the design of catalytic transformations that enable formation of multiple C-C bonds. Recently, using enantioselective rhodium-catalyzed conjugate addition methodology, we developed a catalytic tandem conjugate addition-aldol cyclization of keto-enones. Here, we report related desymmetrizations and parallel kinetic resolutions involving the use of diones as terminal electrophiles. The Rh-enolate generated on enone carbometallation effectively discriminates among four diastereotopic pi-faces of the appendant dione, ultimately providing products that embody four contiguous stereocenters, including two adjacent quaternary centers, with quantitative diastereoselection and high levels of enantiomeric excess. This methodology allows concise entry to optically enriched seco-B ring steroids possessing a 14-hydroxy cis-fused C-D ring junction, as found in naturally occurring cardiotonic steroids derived from digitalis. (+info)
Asymmetric hydrogenation of alpha,beta-unsaturated phosphonates with Rh-BisP* and Rh-MiniPHOS catalysts: scope and mechanism of the reaction.
(21/243)Optically active 1,2-bis(alkylmethylphosphino)ethanes and bis(alkylmethylphosphino)methanes are unique diphosphine ligands combining the simple molecular structure and P-stereogenic asymmetric environment. This work shows that these ligands exhibit excellent enantioselectivity in rhodium-catalyzed asymmetric hydrogenation of alpha,beta-unsaturated phosphonic acid derivatives. The enantioselective hydrogenation mechanism elucidated by NMR study is also described. (+info)
Asymmetric hetero-Diels-Alder reaction catalyzed by dirhodium(II) carboxamidates.
(22/243)Chiral dirhodium(II) carboxamidates are highly efficient catalysts for reactions between a variety of aldehydes and activated dienes. Catalyst loadings as low at 0.01 mol % have been realized with enantioselectivities up to 97%. Kinetic investigations reveal a pronounced electronic influence on the rate of the hetero-Diels-Alder reaction with a Hammett rho value of +1.9 (versus sigma(+)). Inhibition of the catalyst by reactant aldehyde is apparent, but reactions show first-order dependence on aldehyde and diene, and there is a variable dependence on catalyst. (+info)
Cytotoxicity and cell death pathways invoked by two new rhodium-ferrocene complexes in benign and malignant prostatic cell lines.
(23/243)BACKGROUND: Apoptotic propensity is currently viewed as an important parameter in drug-induced toxicity. But other cell death pathways exist e.g. micronucleation, intermitotic cell death, abnormal nuclear morphology and necrosis. This investigation explores the onset of apoptosis and abnormal morphology in response to 3 drugs i.e. Cisplatin, a novel Ferrocene (fctfa) and a novel Rhodium-Ferrocene [Rh(fctfa)(cod)] complex. MATERIALS AND METHODS: A pair of prostate cell lines from normal human prostate epithelium (1542N) and malignant human prostate epithelium (1542T) were exposed to increasing concentrations of the drugs for 24 hours, double-stained with FITC-Annexin V and with Propidium Iodide and analysed by dual parameter flow cytometry to quantitate viable cells in quadrant I, early apoptotic cells in quadrant IV and late apoptotic/necrotic cells in quadrant III. Apoptosis was also scored by microscopy after Acridine Orange staining, by Western blots for caspase 3 induction and for caspase 8 induction using a colorimetric assay. RESULTS: The toxicity of Cisplatin and the Ferrocene and Rhodium-Ferrocene complexes was found to be 0.9-1.3 microM; 4.1-4.5 microM and 10.1-13.2 microM, respectively. Apoptotic propensity scored after 24 hours was found to be dose-dependent and in the range of 7-19% for Cisplatin and 1-4.1% for the Ferrocene and Rhodium-Ferrocene complexes. Cisplatin produces a distinct apoptotic response followed by a necrotic response, whereas the Ferrocene and the Rhodium-Ferrocene complexes produce a massive necrotic reaction in the region of 3-19% and very little if any apoptosis. Absence of apoptosis was corroborated by lack of caspase 3 activation, absence of typical apoptotic morphology and by lack of caspase 8 activation. CONCLUSION: The 3 drugs Cisplatin, the novel Ferrocene and the novel Rhodium-Ferrocene complexes show similar toxicities in the 1-10 micro-molar range in prostate cell lines. However the drugs differ significantly in the activation of death pathways. While Cisplatin predominantly induces apoptosis documented by morphology, Annexin V staining and caspase 8 activation, the Ferrocene and Rhodium-Ferrocene complexes induce late necrosis and abnormal nuclear morphology. Unlike Cisplatin-treated cells which enter apoptosis and necrosis sequentially, the 2 Ferrocene drugs invoke direct entry of cells into late necrosis without first entering the early apoptotic compartment. (+info)
Identification of intrinsic high-level resistance to rare-earth oxides and oxyanions in members of the class Proteobacteria: characterization of tellurite, selenite, and rhodium sesquioxide reduction in Rhodobacter sphaeroides.
(24/243)We have identified intrinsic high-level resistance (HLR) to tellurite, selenite, and at least 15 other rare-earth oxides and oxyanions in the facultative photoheterotroph Rhodobacter sphaeroides grown either chemoheterotrophically or photoheterotrophically. Other members of the class Proteobacteria, including members of the alpha-2 and alpha-3 phylogenetic subgroups, were also shown to effect the reduction of many of these compounds, although genera from the alpha-1, beta-1, and gamma-3 subgroups did not express HLR to the oxyanions examined. Detailed analyses employing R. sphaeroides have shown that HLR to at least one class of these oxyanions, the tellurite class (e.g., tellurate, tellurite, selenate, selenite, and rhodium sesquioxide), occurred via intracellular oxyanion reduction and resulted in deposition of metal in the cytoplasmic membrane. The concomitant evolution of hydrogen gas from cells grown photoheterotrophically in the presence of these oxyanions was also observed. HLR to tellurite class oxyanions in R. sphaeroides was not affected by exogenous methionine or phosphate but was reduced 40-fold by the addition of cysteine to growth media. In contrast HLR to the periodate class oxyanions (e.g., periodate, siliconate, and siliconite) was inhibited by extracellular PO4(3-) but did not result in metal deposition or gas evolution. Finally, we observed that HLR to arsenate class oxyanions (e.g., arsenate, molybdate, and tungstate) occurred by a third, distinct mechanism, as evidenced by the lack of intracellular metal deposition and hydrogen gas evolution and an insensitivity to extracellular PO4(3-) or cysteine. Examination of a number of R. sphaeroides mutants has determined the obligate requirement for an intact CO2 fixation pathway and the presence of a functional photosynthetic electron transport chain to effect HLR to K2TeO3 under photosynthetic growth conditions, whereas functional cytochromes bc1 and c2 were required under aerobic growth conditions to facilitate HLR. Finally, a purification scheme to recover metals from intact bacterial cells was developed. (+info)