The development and evaluation of a conducting matrix for the electrochemical regeneration of the immobilised co-factor NAD(H) under continuous flow.

Through the preparation of a novel controlled pore glass-poly(pyrrole) material we have developed a conducting support that is not only suitable for the co-immobilisation of enzymes and co-factors, but also enables the facile electrochemical regeneration of the co-factor during a reaction. Employing the selective reduction of (rac)-2-phenylpropionaldehyde to (S)-phenyl-1-propanol as a model, we have demonstrated the successful co-immobilisation of the HLADH enzyme and co-factor NAD(H); with incorporation of the material into a continuous flow reactor facilitating the in situ electrochemical regeneration of NAD(H) for in excess of 100 h. Using this approach we have developed a reagent-less, atom efficient system applicable to the cost-effective, continuous biosynthesis of chiral compounds.

Immobilization of thermophilic enzymes in miniaturized flow reactors.

The exploitation of enzymes for biotransformation reactions for the production of new and safer drug intermediates has been the focus of much research. While a number of enzymes are commercially available, their use in an industrial setting is often limited to reactions that are cost-effective and they are rarely investigated further. However, the development of miniaturized flow reactor technology has meant that the cost of such research, once considered cost- and time-inefficient, would be much less prohibitive. The use of miniaturized flow reactors for enzyme screening offers a number of advantages over batch enzyme assay systems. Since the assay is performed on a miniaturized scale, enzyme, substrate and cofactor quantities are significantly reduced, thus reducing the cost of laboratory-scale investigations. Since flow reactors use microfluidic systems, where the substrate and products flow out of the system, the problems of substrate inhibition and product inhibition encountered by some enzymes are avoided. Quite often, enzymes fulfil a single-use function in biotransformation processes; however, enzyme immobilization allows enzyme reuse and often helps to increase enzyme stability. We have used an aminoacylase enzyme with potential use for industrial biotransformation reactions and have successfully immobilized it in miniaturized flow reactors. This L-aminoacylase is from the thermophilic archaeon Thermococcus litoralis. Two approaches to enzyme immobilization have been examined, both involving enzyme cross-linking. The first reactor type has used monoliths, to which the enzyme was attached, and the second contained previously cross-linked enzyme trapped using frits, in the microfluidic channels. Two different microreactor designs were used in the investigation: microreactor chips for the monoliths and capillary flow reactors for the cross-linked enzyme. These systems allowed passage of the substrate and product through the system while retaining the aminoacylase enzyme performing the catalytic conversion. The enzyme has been successfully immobilized and used to produce stable biocatalytic microreactors that can be used repeatedly over a period of several months.

A new short form individual quality of life measure (SEIQoL-DW): application in a cohort of individuals with HIV/AIDS.

Quality of life is an increasingly important outcome measure in medicine and health care. Many measures of quality of life present patients with predetermined lists of questions that may or may not be relevant to the individual patient. This paper describes a brief measure, the SEIQoL-DW, which is derived from the schedule for evaluation of individual quality of life (SEIQoL). The measure allows respondents to nominate the areas of life which are most important, rate their level of functioning or satisfaction with each, and indicate the relative importance of each to their overall quality of life. Given its practicality and brevity, the measure should prove particularly useful in clinical situations where patient generated data on quality of life is important. This article describes the first clinical application of the measure, assessing the quality of life of a cohort of patients with HIV/AIDS managed in general practice.

Detection of malignant bone tumors: MR imaging vs scintigraphy.

One hundred six patients with a known or suspected diagnosis of bone cancer (11 patients with biopsy-proved primary tumors, 95 patients with metastatic disease) were evaluated with scintigraphy and MR imaging to determine the relative sensitivity of each technique in the detection of bone disease. MR imaging was performed at 0.5 T as part of the entry evaluation into Intramural Research Board protocols (30%), for evaluation of cord compression, or because of an equivocal scintigram. MR was performed with T1-weighted (e.g., 300-500/10-20 [TR/TE]), T2-weighted (e.g., 2000/80) spin-echo (SE), and a short-TI inversion recovery (STIR) pulse sequence. Scintigrams were performed with 99mTc-methylene diphosphonate. A retrospective analysis showed that in 30 (28%) of 106 patients, MR imaging performed over a limited region of interest revealed a focal abnormality consistent with tumor that was not observed on scintigraphy. Only one patient had an abnormality on scintigraphy, caused by a metastasis, that was not found on MR images. In 73 (69%) of the 106 patients, the results of MR imaging and scintigraphy were equivalent; in 41 cases results of both techniques were normal. A McNemar analysis of the discordant cases showed MR imaging to be more sensitive than scintigraphy was (p less than .001). Our results suggest that although MR imaging has a greater sensitivity in detecting focal disease, scintigraphy is still the most useful screening test for evaluating the entire skeleton. MR imaging should be reserved for clarification of scintigraphic findings when suspicion is high for tumor.

Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging.

Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.

Pituitary adenomas in patients with Cushing disease: initial experience with Gd-DTPA-enhanced MR imaging.

To assess the role of magnetic resonance imaging in the evaluation of adrenocorticotropic-hormone (ACTH)-producing pituitary adenomas, and the effect of intravenously administered gadolinium-diethylenetriaminepentaacetic acid (DTPA) on lesion/pituitary contrast, imaging was performed in 13 patients with clinical and chemical evidence of Cushing disease. Images were obtained at 0.5 T before and after the injection of Gd-DTPA (0.1 mmol/kg). Lesions were identified in eight of 12 precontrast and ten of 12 postcontrast studies. In these 12 patients adenomas were found at transsphenoidal surgery. The other patient, with normal images, was found to have an ectopic source of ACTH. Coronal images corresponded remarkably well with the neurosurgeon's intraoperative findings. Serial T1-weighted images disclosed early enhancement of the pituitary gland and delayed enhancement of the cystic adenomas. The discrepancy in times to peak enhancement accounted for improved lesion/pituitary contrast in some early images and for reversal or diminution of lesion/pituitary contrast in later images.