RESUMEN
Industrial waste streams may contain contaminants that are valuable like Pd(II) and/or toxic and mutagenic like Cr(VI). Using Serratia sp. biofilm the former was biomineralized to produce a supported nanocrystalline Pd(0) catalyst, and this biofilm-Pd heterogeneous catalyst was then used to reduce Cr(VI) to less dangerous Cr(III) at room temperature, with formate as the electron donor. Cr(VI)((aq)) is non-paramagnetic while Cr(III)((aq)) is paramagnetic, which enabled spatial mapping of Cr species concentrations within the reactor cell using non-invasive magnetic resonance (MR) imaging experiments. Spatial reactivity heterogeneities were thus examined. In batch reactions, these could be attributed primarily to heterogeneity of Pd(0) distribution and to the development of gas bubbles within the reactor. In continuous flow reactions, spatial reactivity heterogeneities resulted primarily from heterogeneity of Cr(VI) delivery.
Asunto(s)
Biopelículas/crecimiento & desarrollo , Cromo/química , Cromo/metabolismo , Imagen por Resonancia Magnética/métodos , Paladio/química , Serratia/citología , Serratia/metabolismo , Catálisis , Cromo/aislamiento & purificación , Oxidación-Reducción , Microbiología del Agua , Purificación del Agua/métodosRESUMEN
Phase contrast magnetic resonance velocity imaging is a powerful technique for quantitative in vivo blood flow measurement. Current practice normally involves restricting the sensitivity of the technique so as to avoid the problem of the measured phase being 'wrapped' onto the range -pi to +pi. However, as a result, dynamic range and signal-to-noise ratio are sacrificed. Alternatively, the true phase values can be estimated by a phase unwrapping process which consists of adding integral multiples of 2pi to the measured wrapped phase values. In the presence of noise and data undersampling, the phase unwrapping problem becomes non-trivial. In this paper, we investigate the performance of three different phase unwrapping algorithms when applied to three-dimensional (two spatial axes and one time axis) phase contrast datasets. A simple one-dimensional temporal unwrapping algorithm, a more complex and robust three-dimensional unwrapping algorithm and a novel velocity encoding unwrapping algorithm which involves unwrapping along a fourth dimension (the 'velocity encoding' direction) are discussed, and results from the three are presented and compared. It is shown that compared to the traditional approach, both dynamic range and signal-to-noise ratio can be increased by a factor of up to five times, which demonstrates considerable promise for a possible eventual clinical implementation. The results are also of direct relevance to users of any other technique delivering time-varying two-dimensional phase images, such as dynamic speckle interferometry and synthetic aperture radar.
Asunto(s)
Algoritmos , Velocidad del Flujo Sanguíneo , Imagen por Resonancia Magnética/métodos , Aorta/anatomía & histología , Aorta/fisiología , Humanos , Microscopía de Contraste de Fase/métodosRESUMEN
Dynamic contrast agent-enhanced magnetic resonance imaging measurements of the perfusion of an immunogenic murine tumour showed that immune rejection was preceded by an increase in the apparent vascular volume of the tumour. This increase in vascularity, which has been observed previously in other tumours undergoing immune rejection, was confirmed by histological analysis of tumour sections obtained postmortem. Magnetic resonance imaging measurements similar to this could be used in the clinic to monitor the early responses of tumours to immunotherapy, before there is any change in tumour growth rate or volume.
Asunto(s)
Rechazo de Injerto , Imagen por Resonancia Magnética , Neoplasias Experimentales/irrigación sanguínea , Animales , Factores de Crecimiento Endotelial/sangre , Inmunoterapia , Péptidos y Proteínas de Señalización Intercelular/sangre , Linfocinas/sangre , Ratones , Ratones Endogámicos C57BL , Trasplante de Neoplasias , Neoplasias Experimentales/inmunología , Neoplasias Experimentales/patología , Células Tumorales Cultivadas , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial VascularRESUMEN
The C2 domain of synaptotagmin I, which binds to anionic phospholipids in cell membranes, was shown to bind to the plasma membrane of apoptotic cells by both flow cytometry and confocal microscopy. Conjugation of the protein to superparamagnetic iron oxide nanoparticles allowed detection of this binding using magnetic resonance imaging. Detection of apoptotic cells, using this novel contrast agent, was demonstrated both in vitro, with isolated apoptotic tumor cells, and in vivo, in a tumor treated with chemotherapeutic drugs.
Asunto(s)
Apoptosis , Proteínas de Unión al Calcio , Imagen por Resonancia Magnética/métodos , Animales , Antineoplásicos Fitogénicos/uso terapéutico , Membrana Celular/metabolismo , Medios de Contraste , Etopósido/uso terapéutico , Compuestos Férricos , Citometría de Flujo , Técnicas In Vitro , Magnetismo , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Microscopía Confocal , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/patología , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/metabolismo , Unión Proteica , Estructura Terciaria de Proteína , Ratas , Sinaptotagmina I , SinaptotagminasRESUMEN
The requirement for tumour vascularisation to permit the expansion of solid tumours beyond a threshold size of approximately 1 mm diameter has focussed attention on anti-vascular and anti-angiogenic agents for cancer therapy. Combretastatin-A4 (cis CA-4P) is a tubulin-binding agent that is cytotoxic for proliferating endothelial cells in vitro and causes anti-vascular effects in the established tumour vessels of some primary tumours. Preliminary data from Phase I clinical trials indicate that cis CA-4 may also be effective in targeting the vasculature of human tumours. As metastatic disease is the principal cause of mortality in cancer, we have investigated the effects of cis CA-4 on metastatic development using an in vivo model. We show that bolus or continuous administration of cis CA-4P results in potent inhibition of metastases derived from ectopic primary Lewis lung carcinomas in mice whereas the trans CA-4 isomer is without effect. These data further characterise the activity of CA-4 in vivo and suggest that the drug should be evaluated clinically as an anti-metastatic agent.
Asunto(s)
Antineoplásicos Fitogénicos/uso terapéutico , Carcinoma Pulmonar de Lewis/tratamiento farmacológico , Neoplasias Pulmonares/tratamiento farmacológico , Estilbenos/uso terapéutico , Animales , Carcinoma Pulmonar de Lewis/metabolismo , Carcinoma Pulmonar de Lewis/secundario , Técnicas para Inmunoenzimas , Pulmón/fisiología , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Neovascularización Patológica/prevención & control , Factor de von Willebrand/metabolismoRESUMEN
The acute effects of the antivascular drug, combretastatin A4 phosphate, on tumor energy status and perfusion were assessed using magnetic resonance imaging (MRI) and spectroscopy. Localized (31)P magnetic resonance spectroscopy showed that LoVo and RIF-1 tumors responded well to drug treatment, with significant increases in the P(i)/nucleoside triphosphate ratio within 3 h, whereas SaS, SaF, and HT29 tumors did not respond to the same extent. This variable response was also seen in MRI experiments in which tumor perfusion was assessed by monitoring the kinetics of inflow of the contrast agent, gadolinium diethylenetriaminepentaacetate. These data were analyzed to give the initial rate and time constant for inflow of contrast agent and the integral under the inflow curve. The differential susceptibility of the tumors to combretastatin A4 phosphate showed a positive correlation with prior MRI measurements of tumor vascular permeability, which was determined by measuring the inflow of a macromolecular contrast agent, BSA-gadolinium diethylenetriaminepentaacetate.
Asunto(s)
Antineoplásicos Fitogénicos/farmacología , Neoplasias Experimentales/irrigación sanguínea , Estilbenos/farmacología , Albúminas/farmacocinética , Animales , Permeabilidad Capilar/fisiología , Medios de Contraste/farmacocinética , Femenino , Gadolinio DTPA/farmacocinética , Humanos , Angiografía por Resonancia Magnética , Espectroscopía de Resonancia Magnética/métodos , Ratones , Ratones Endogámicos CBA , Ratones SCID , Neoplasias Experimentales/tratamiento farmacológico , Neovascularización Patológica/tratamiento farmacológico , Neovascularización Patológica/fisiopatología , Fósforo , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The effects of combretastatin A4 prodrug on perfusion and the levels of 31P metabolites in an implanted murine tumour were investigated for 3 h after drug treatment using nuclear magnetic resonance imaging (MRI) and spectroscopy (MRS). The area of regions of low signal intensity in spin-echo images of tumours increased slightly after treatment with the drug. These regions of low signal intensity corresponded to necrosis seen in histological sections, whereas the expanding regions surrounding them corresponded to haemorrhage. Tumour perfusion was assessed before and 160 min after drug treatment using dynamic MRI measurements of gadolinium diethylenetriaminepentaacetate (GdDTPA) uptake and washout. Perfusion decreased significantly in central regions of the tumour after treatment. This was attributed to disruption of the vasculature and was consistent with the haemorrhage seen in histological sections. The mean apparent diffusion coefficient of water within the tumour did not change, indicating that there was no expansion of necrotic regions during the 3 h after drug treatment. Localized 31P-MRS showed that there was decline in cellular energy status in the tumour after treatment with the drug. The concentrations of nucleoside triphosphates within the tumour fell, the inorganic phosphate concentration increased and there was a significant decrease in tumour pH for 80 min after drug treatment. The rapid, selective and extensive damage caused to these tumours by combretastatin A4 prodrug has highlighted the potential of the agent as a novel cancer chemotherapeutic agent. We have shown that the response of tumours to treatment with the drug may be monitored non-invasively using MRI and MRS experiments that are appropriate for use in a clinical setting.
Asunto(s)
Antineoplásicos Fitogénicos/farmacología , Metabolismo Energético/efectos de los fármacos , Neoplasias Experimentales/tratamiento farmacológico , Profármacos/farmacología , Estilbenos/farmacología , Animales , Femenino , Concentración de Iones de Hidrógeno , Imagen por Resonancia Magnética , Espectroscopía de Resonancia Magnética , Ratones , Ratones Endogámicos CBA , Neoplasias Experimentales/irrigación sanguínea , Neoplasias Experimentales/metabolismo , Fosfatos/metabolismoRESUMEN
The association of vancomycin group antibiotics with the growing bacterial cell wall was investigated by using the cell wall precursor analog di-N-acetyl-Lys-D-Ala-D-Ala in competition binding experiments. The affinities of the antibiotics for the -D-Ala-D-Ala-containing cell wall precursors of Bacillus subtilis ATCC 6633 (a model for vancomycin-susceptible gram-positive bacteria) and for the -D-Ala-D-Lac-containing cell wall precursors of Leuconostoc mesenteroides (a model for vancomycin-resistant strains of Enterococcus faecium and Enterococcus faecalis) were determined by a whole-cell assay. The binding of strongly dimerizing antibiotics such as eremomycin to the bacterial surface was thus shown to be enhanced by up to 2 orders of magnitude (relative to the binding in free solution) by the chelate effect, whereas weakly dimerizing antibiotics like vancomycin and antibiotics carrying lipid tails (teicoplanin) benefited less (ca. 1 order of magnitude). The affinity measured in this way correlates well with the MIC of the antibiotic, and a consequence of this is that future design of semisynthetic vancomycin-group antibiotics should attempt to incorporate chelate effect-enhancing structural features.
Asunto(s)
Antibacterianos/metabolismo , Bacillus subtilis/efectos de los fármacos , Leuconostoc/efectos de los fármacos , Vancomicina/metabolismo , Antibacterianos/química , Antibacterianos/farmacología , Unión Competitiva , Membrana Celular/efectos de los fármacos , Farmacorresistencia Microbiana , Enlace de Hidrógeno , Relación Estructura-Actividad , Vancomicina/análogos & derivados , Vancomicina/química , Vancomicina/farmacologíaRESUMEN
The clinically important glycopeptide antibiotic vancomycin binds to bacterial cell wall peptides of Gram-positive bacteria which terminate in -Lys-D-Ala-D-Ala, thereby inhibiting cell wall synthesis resulting in cell death. We have removed the N-terminal leucine residue of vancomycin by an Edman degradation and acylated the exposed amino group of residue 2 with N-Me-Gly, N-Me-D-Ala, acetyl, butyl, and isohexyl groups to generate novel vancomycin analogues. The binding of vancomycin and these vancomycin analogues to the bacterial cell wall analogue di-N-Ac-L-Lys-D-Ala-D-Ala (DALAA) was studied by NMR techniques and UV spectroscopy. The effects that these structural modifications of the carboxylate binding pocket of vancomycin have on the antibiotic-DALAA recognition process show that a cooperative effect between non-polar and ionic forces appears to be partly responsible for the highly efficient sequestering of the DALAA C-terminal carboxylate from aqueous solution.
Asunto(s)
Bacterias/efectos de los fármacos , Pared Celular/efectos de los fármacos , Vancomicina/análogos & derivados , Secuencia de Aminoácidos , Bacterias/metabolismo , Sitios de Unión , Pared Celular/metabolismo , Datos de Secuencia Molecular , Estructura Molecular , Soluciones , Relación Estructura-Actividad , Vancomicina/metabolismo , Vancomicina/farmacologíaRESUMEN
Antibiotics of the vancomycin group are shown to enhance their affinities for the bacterial cell wall by the devices of either dimerization (vancomycin and other glycopeptides which dimerize even more strongly) or use of a membrane anchor (teicoplanin); a chelate mechanism is suggested in both cases, as supported by antagonism experiments with the cell wall analog di-N-acetyl-L-Lys-D-Ala-D-Ala. These results may have implications for other binding processes which occur near membrane surfaces.