8 research outputs found
A regulatable transgene expression system for cultured Plasmodium falciparum parasites
<p>Abstract</p> <p>Background</p> <p>The ability to transfect and create transgenic cultured malaria parasites has transformed the study of <it>Plasmodium falciparum </it>over the last decade. With the completion of the annotated genome sequence, the process of gene discovery now routinely includes gene knockouts, over-expression and complementation analysis. However, while this technology has proven extremely valuable, significant limitations exist. In particular, <it>P. falciparum </it>DNA is often unstable and difficult to clone because of its AT-rich, repetitive nature. As a result, transgene expression constructs can be difficult to assemble due to the need to include two expression cassettes on a single plasmid, one to drive expression of the transgene of interest and a second for expression of the selectable marker. In addition, transgene expression levels are usually not regulatable, making it difficult to assess phenotypes that are sensitive to the amount of protein expressed.</p> <p>Results</p> <p>A plasmid based system for transgene expression is described that uses a single, bidirectional promoter to drive expression of both the transgene and the selectable marker, thus greatly reducing the size of the construct and enhancing stability. Further, by altering the concentration of drug used for selection, it is possible to modulate the copy number of the concatameric episomes and thereby regulate the expression level of the transgene through a range greater than 10 fold.</p> <p>Conclusion</p> <p>The transgene expression system described here should prove useful for both routine protein over-expression and complementation experiments as well as for experiments in which precisely manipulating the expression level of candidate proteins is desirable. This should provide an additional level of precision to the tools used to study the molecular biology of malaria parasites.</p
Recent Advances in the Science of Burst Wave Lithotripsy and Ultrasonic Propulsion
Nephrolithiasis is a common, painful condition that requires surgery in many patients whose stones do not pass spontaneously. Recent technologic advances have enabled the use of ultrasonic propulsion to reposition stones within the urinary tract, either to relieve symptoms or facilitate treatment. Burst wave lithotripsy (BWL) has emerged as a noninvasive technique to fragment stones in awake patients without significant pain or renal injury. We review the preclinical and human studies that have explored the use of these two technologies. We envision that BWL will fill an unmet need for the noninvasive treatment of patients with nephrolithiasis
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Multi-Institutional Variation in Performance of Low-Dose Computed Tomography for the Evaluation of Suspected Nephrolithiasis.
Introduction and Objective: Guidelines from the American Urological Association (AUA) and American College of Radiology (ACR) recommend that patients with suspected nephrolithiasis undergo low-dose CT of the kidney, ureter, and bladder (LD CT KUB) as opposed to higher dose conventional imaging. We hypothesized that even at institutions with established LD protocols, higher dose imaging is common. Materials and Methods: We identified four academic medical centers where LD CT KUB protocols were implemented to yield an effective dose (EDose) consistent with national guidelines. Fifty consecutive adult patients who underwent CT KUB specifically for the evaluation of nephrolithiasis were retrospectively reviewed at each site. Patient age, sex, body mass index (BMI), imaging location, and EDose (millisieverts [mSv]) were recorded. Results: Two hundred patients with a mean age of 54 years were identified. Forty-six patients (23%) underwent CT KUB with an EDose ≤4 mSv, accounting for 10% to 48% of each institution's cohort. One hundred sixteen patients had a BMI <30, and would have been expected to receive LD CTs by the AUA criteria for LD CT KUB. Within this subset, only 37 patients (32%) actually underwent LD CT KUB. The highest dose CT KUB at each institution resulted in an EDose of 33.8 to 44.6 mSv, exceeding the recommended exposure of LD CT KUB by 10-fold. Conclusions: At academic institutions where LD CT KUB was implemented for the evaluation of nephrolithiasis, a minority of patients with BMI <30 received guideline-concordant imaging. Differences in patient BMI did not account for the variation in radiation exposure. Further research is necessary to elucidate barriers to LD CT implementation