Development of Chemical Strategies for Specifically Probing and Identifying Sulfur Carrier Proteins and Vitamin B6-Dependent Enzymes in Bacteria

Activity based protein profiling (ABPP) is a functional proteomic technology that uses chemical probes to detect mechanistically related classes of enzymes. Chemically probing a certain class of proteins helps to understand their biological function as a group, and discover new biosynthetic pathways for drug design. This research describes two activity based proteomic methods that have been developed to probe and identify sulfur carrier proteins and vitamin B6 dependent proteins, respectively. Sulfur carrier proteins are small proteins (<10 kDa) involved in pathways for efficient sulfur delivery. A chemical probe with sulfonyl-azide functional group was designed to label and identify the sulfur carrier proteins through a thioacid-azide reaction. This method identified a new sulfur carrier protein in Streptomyces coelicolor. Further study of its biological function led to the discovery and characterization of a new pathway of homocysteine formation, which is probably another direct sulfurylation of methionine biosynthesis. Vitamin B6 dependent proteins are a class of enzymes that cover a wide range of cellular functions such as transamination, racemization, and decarboxylation. Also, vitamin B6 dependent proteins have a critical role in human disease and the metabolic pathways of pathogens and plants. We used Escherichia coli as a model system to develop both radioactive and nonradioactive based methods to probe and identify vitamin B6 containing proteins in the bacterial proteome. This technique was then used to study how vitamin B6 proteins are regulated in response to cellular stress

Cost-effectiveness of diagnostic imaging work-up and treatment for patients with intermittent claudication in the Netherlands

Objective: to determine the societal cost-effectiveness of various management strategies, including both the diagnostic imaging work-up and treatment, for patients with intermittent claudication in The Netherlands. Methods: a decision-analytic model was used and included probability and quality of life data available from the literature. A cost-analysis was performed in a university setting in The Netherlands. Imaging work-up options included magnetic resonance angiography (MRA), color-guided duplex ultrasound, or intraarterial digital subtraction angiography (DSA) and treatment options were percutaneous transluminal angioplasty with selective stent placement if feasible or bypass surgery. Management strategies were defined as combinations of imaging work-up and treatment options. A conservative strategy with no imaging work-up and walking exercises was considered as reference. Main outcome measures were quality-adjusted life years (QALYs), lifetime costs (is not an element of), and incremental cost-effectiveness (CE) ratios. The base-case analysis evaluated 60-year-old men with severe unilateral intermittent claudication of at least one year duration. Results: the range in QALYs and costs across management strategies that considered angioplasty as only treatment option was small (maximum difference: 0.0033 QALYs and is not an element of451). Similarly, the range was small across management strategies that considered angioplasty if feasible otherwise bypass surgery (maximum difference: 0.0033 QALYs and is not an element of280). MRA in combination With angioplasty (6.1487 QALYs and is not an element of8556) had a CE ratio of is not an element of20 000/QALY relative to the conservative strategy. The most effective strategy was DSA in combination with angioplasty if feasible otherwise bypass surgery (6.2254 QALYs and is not an element of18 583) which had a CE ratio of is not an element of131 000/QALY relative to MRA in combination with angioplasty. Conclusion: the results suggest that the imaging work-up with non-invasive imaging modalities can replace DSA for the work-up of patients with intermittent claudication without a substantial loss in effectiveness and a minimal cost-reduction, Management strategies including angioplasty are cost-effective in the Netherlands but although strategies including bypass surgery are more effective, their incremental costs are very high

Reduction of noise in medullary renograms from dynamic MR images

Dynamic magnetic resonance images of the kidney can be used to acquire separate renograms of the cortex and medulla, A high-quality cortical renogram can be determined directly from a region of interest (ROI) placed in the cortex. Due to partial volume effects, part of the signal from a ROI placed in the medulla is caused by cortical tissue, By subtracting a fraction of the cortical signal from the cortico-medullary signal, a purer medullary renogram can be obtained. A side effect of this subtraction is an increase in noise level. The noise level increases with larger partial volume fractions. Using a matched image filter, it is possible to exclude those areas from the ROI that have a high partial volume content, thus reducing the amount of cortical signal that has to be separated from the medullary signal, Noise reductions of up to 50% have been achieved in the medullary renogram, with an average reduction of 23%. (C) 2000 Wiley-Liss, Inc.</p

Multicenter phase-II trial of safety and efficacy of NC100150 for steady-state contrast-enhanced peripheral magnetic resonance angiography

The aim of this study was to test the safety and efficacy of NC100150 injection for steady-state contrast-enhanced peripheral MR angiography in a multicentre phase-II trial. Thirty-three patients underwent steady-state NC100150 enhanced MR angiography (5 mg Fe/kg body weight) of the aortoiliac and femoropopliteal arteries. Safety assessment consisted of pre- and post-injection (2, 24 and 72 h) monitoring of vital signs, physical examination as well as laboratory and electrocardiographic parameters. To determine sensitivity and specificity for detection of haemodynamically significant stenoses (HSS; >50% reduction of luminal diameter) MR angiograms were compared with intra-arterial digital subtraction angiography (IA DSA), which was considered the standard of reference. In 33 patients a mean of 12.8 ml NC100150 was injected. Eleven patients reported 13 mild and 2 moderate adverse events. Five mild and one moderate adverse event were considered due to NC100150 injection. There were no significant changes in vital signs, laboratory or electrocardiographic parameters. Sensitivity and specificity (in percent) for detection of HSS were 87 and 64, 56 and 76, and 75 and 84, for iliac, femoral and popliteal arteries, respectively. NC100150 high-resolution steady-state MR angiography can be performed safely and is feasible for the detection of peripheral arterial HSS, but is as yet not a clinically useful alternative to conventional gadolinium-enhanced MR angiography

Reduction of noise in medullary renograms from dynamic MR images

Dynamic magnetic resonance images of the kidney can be used to acquire separate renograms of the cortex and medulla, A high-quality cortical renogram can be determined directly from a region of interest (ROI) placed in the cortex. Due to partial volume effects, part of the signal from a ROI placed in the medulla is caused by cortical tissue, By subtracting a fraction of the cortical signal from the cortico-medullary signal, a purer medullary renogram can be obtained. A side effect of this subtraction is an increase in noise level. The noise level increases with larger partial volume fractions. Using a matched image filter, it is possible to exclude those areas from the ROI that have a high partial volume content, thus reducing the amount of cortical signal that has to be separated from the medullary signal, Noise reductions of up to 50% have been achieved in the medullary renogram, with an average reduction of 23%. (C) 2000 Wiley-Liss, Inc

Identifying vulnerable carotid plaques by noninvasive imaging

Stroke results in considerable morbidity and mortality. Prevention is therefore of particular importance. On the basis of large clinical trials, carotid endarterectomy (CEA) is performed in selected patient groups to prevent stroke. Patient symptomatology and degree of carotid stenosis are the main clinical grounds to perform CEA. However, many individual patients undergo surgery with its attendant risks without taking advantage of it, whereas in others CEA is probably incorrectly withheld. There is therefore an urgent need for new adjuncts to identify high-risk subgroups of patients who particularly benefit from potentially hazardous interventions. Multiple noninvasive imaging modalities have shown their potential to differentiate high-risk, vulnerable carotid plaques from stable plaques. The ultimate goal is to implement one or a combination of these imaging modalities in daily clinical practice. This review gives an up-to-date overview of the clinical potential of these imaging modalities in identifying patients with carotid atherosclerosis who are at high risk for developing stroke. Advantages and limitations of each imaging technique are outlined. Additionally, recommendations for future research are presented