Tunneled Hemodialysis Catheter-associated Right Atrial Thrombus Presenting with Septic Pulmonary Embolism.

Tunneled hemodialysis (HD) catheter-associated right atrial thrombus (CRAT) is an uncommon complication with significant morbidity. We report the case of a patient undergoing HD through tunneled venous catheter who presented with catheter dysfunction and sepsis and was diagnosed to have CRAT with septic embolism. CRAT formation has a significant association with catheter-related infection. The need for early diagnosis and various treatment options for this entity are highlighted.

Hidden in Plain Sight: An Unusual Cause of Rapidly Progressive Renal Failure.

Hyperoxaluria and resultant oxalate nephropathy are infrequently reported causes of irreversible renal failure. A rapid decline in renal function in an otherwise insidiously progressive oxalate nephropathy may be triggered by various superimposed insults like the use of nephrotoxic drugs. We present the case of a patient with rapidly progressive renal failure due to oxalate nephropathy that lead to a retrospective diagnosis of chronic pancreatitis. This case highlights the importance of timely assessment for enteric hyperoxaluria in patients with unexplained renal failure of tubulointerstitial nature.

Laser in situ Keratomileusis for Anisometropic Amblyopia.

PURPOSE: To evaluate the efficacy and benefit of laser in situ keratomileusis (LASIK) for correction of anisometropic amblyopia. METHODS: LASER was performed in 21 eyes of 21 anisometropic amblyopes with a mean age of 27.71 ± 12.24 years. Three patients were less than 18 years of age. LASIK was performed in the more myopic and amblyopic eye using the Chiron Automated Corneal Shaper microkeratome and the Nidek EC-5000 excimer laser system. RESULTS: Results of 3-month follow-up are presented. Preoperative mean manifest spherical equivalent refraction was -13.20 ± 3.84 D (range, -5.25 to -20.00 D). Mean attempted correction was -12.28 ± 3.47 D. Mean postoperative refraction at 3 months was -0.78 ± 1.63 D. Postoperative uncorrected visual acuity improved by 2 or more lines in all patients and was the same or better than preoperative best spectacle-corrected visual acuity in 95.2% of eyes. Best spectacle-corrected visual acuity improved by 1 or more lines in 61.9% of eyes. The 12-year-old child had a gain of more than 4 lines of uncorrected visual acuity. CONCLUSION: LASIK was a good alternative to contact lenses in adults for anisometropia and resulted in a gain of best spectacle-corrected visual acuity. In children it may be an alternative method of treatment for amblyopia. [J Refract Surg 2000;16(suppl):S264-S267].

Differential methylation of genes and retrotransposons facilitates shotgun sequencing of the maize genome.

The genomes of higher plants and animals are highly differentiated, and are composed of a relatively small number of genes and a large fraction of repetitive DNA. The bulk of this repetitive DNA constitutes transposable, and especially retrotransposable, elements. It has been hypothesized that most of these elements are heavily methylated relative to genes, but the evidence for this is controversial. We show here that repeat sequences in maize are largely excluded from genomic shotgun libraries by the selection of an appropriate host strain because of their sensitivity to bacterial restriction-modification systems. In contrast, unmethylated genic regions are preserved in these genetically filtered libraries if the insert size is less than the average size of genes. The representation of unique maize sequences not found in plant reference genomes is also greatly enriched. This demonstrates that repeats, and not genes, are the primary targets of methylation in maize. The use of restrictive libraries in genome shotgun sequencing in plant genomes should allow significant representation of genes, reducing the number of reactions required.

Kaleidaseq: a Web-based tool to monitor data flow in a high throughput sequencing facility.

Tracking data flow in high throughput sequencing is important in maintaining a consistent number of successfully sequenced samples, making decisions on scheduling the flow of sequencing steps, resolving problems at various steps and tracking the status of different projects. This is especially critical when the laboratory is handling a multitude of projects. We have built a Web-based data flow tracking package, called Kaleidaseq, which allows us to monitor the flow and quality of sequencing samples through the steps of preparation of library plates, plaque-picking, preparation of templates, conducting sequencing reactions, loading of samples on gels, base-calling the traces, and calculating the quality of the sequenced samples. Kaleidaseq's suite of displays allows for outstanding monitoring of the production sequencing process. The online display of current information that Kaleidaseq provides on both project status and process queues sorted by project enables accurate real-time assessment of the necessary samples that must be processed to complete the project. This information allows the process manager to allocate future resources optimally and schedule tasks according to scientific priorities. Quality of the sequenced samples can be tracked on a daily basis, which allows the sequencing laboratory to maintain a steady performance level and quickly resolve dips in quality. Kaleidaseq has a simple easy-to-use interface that allows access to all major functions and process queues from one Web page. This software package is modular and designed to allow additional processing steps and new monitoring variables to be added and tracked with ease. Access to the underlying relational database is through the Perl DBI interface, which allows for the use of different relational databases. Kaleidaseq is available for free use by the academic community from http://www.cshl.org/kaleidaseq.

Design of expression systems for metabolic engineering: coordinated synthesis and degradation of glycogen.

In metabolic engineering, systems which allow coordinated control of two metabolic pathways can be useful. We designed two expression systems and demonstrated their application by coordinating glycogen synthesis and degradation. The first expression vector pMSW2 expressed the glycogen synthesis genes in one operon and the glycogen degradation gene in a separate, coordinately regulated operon. The plasmid was designed to switch off expression of the first operon and activate expression of the second operon on addition of IPTG. As an alternative means to control glycogen synthesis and degradation pathways, we constructed expression vector pGTSD100, which contains the native Escherichia coli glycogen synthesis and degradation operon under control of the tac promoter. Both expression vectors work successfully to control the net synthesis and degradation of glycogen. In cultures of the E. coli strain TA3476 carrying the plasmid pMSW2, before the addition of IPTG, glycogen continued to accumulate in the culture. About three hours after IPTG was added, glycogen levels began to decrease. When no IPTG was added to cultures of TA3476:pMSW2, glycogen accumulated in the cells as before but the rate of degradation of glycogen was much lower. When IPTG was added to TA3476:pMSW2, the total cell protein at the end of batch cultivation was approximately 15% higher compared to cultures without IPTG addition. The extra biomass was formed during the glycogen degradation phase. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 419-426, 1997.

Improvement in recombinant protein production in ppGpp-deficient Escherichia coli.

Maintaining a metabolically productive state for recombinant Escherichia coli remains a central problem for a wide variety of growth-dependent biosynthesis. This problem becomes particularly acute under conditions of minimal cell growth such as fed-batch fermentations. In this, we investigated the possibility of manipulating the protein synthesis machinery of E. coli whereby synthesis of foreign proteins might be decoupled from cell growth. In particular, the effects of eliminating intracellular ppGpp on the synthesis of foreign proteins were studied in both batch and fed-batch operations. A significant increase in CAT production was observed from the ppGpp-deficient strain during both exponential and fed-batch phases. The increase in CAT production during exponential growth was accompanied by a simultaneous increase in CAT mRNA levels. Interestingly, CAT production was increased five-fold, while the level of CAT-specific mRNA increased only three-fold. Thus, eliminating intracellular ppGpp appears to have increase the production of recombinant protein by increasing not only the pool sizes of CAT mRNA but also possible alternations in the post-transcriptional processes. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 379-386, 1997.

Overproduction of glycogen in Escherichia coli blocked in the acetate pathway improves cell growth.

Excessive production of acetate is a problem frequently encountered in aerobic high-cell-density fermentations of Escherichia coli. Here, we have examined genetic alterations resulting in glycogen overproduction as a possible means to direct the flux of carbon away from the acetate pool. Glycogen overaccumulation was achieved either by using a regulatory glgQ mutation or by transforming cells with a plasmid containing the glycogen biosynthesis genes glgC (encoding ADPG pyrophosphorylase) and glgA (encoding glycogen synthase) under their native promoter. Both strategies resulted in an approximately five-fold increase in glycogen levels but had no significant effect on acetate excretion. The glgC and glgA genes were then placed under the control of the isopropyl---D-thiogalactopyranoside (IPTG) inducible tac promoter, and this construct was used to stimulate glycogen production in a mutant defective in acetate biosynthesis due to deletion of the ack (acetate kinase) and pta (phosphotransacetylase) genes. If glycogen overproduction in the ack pta strain was induced during the late log phase, biomass production increased by 15 to 20% relative to uninduced controls. Glycogen overaccumulation had a significant influence on carbon partitioning: The output of carbon dioxide peaked earlier than in the control strain, and the levels of an unusual fermentation byproduct, pyruvate, were reduced. Exogenous pyruvate was metabolized more rapidly, suggesting higher activity of gluconeogenesis or the tricarboxylic acid (TCA) cycle as a result of glycogen overproduction. Potential mechanisms of the observed metabolic alterations are discussed. Our results suggest that ack pta mutants over producing glycogen may be a suitable starting point for constructing E. coli strains with improved characteristics in high-cell-density fermentations.

Computerized tomography with and without intraperitoneal contrast for determination of intraabdominal fluid distribution and diagnosis of complications in peritoneal dialysis patients.

Seven computed tomography scans and 19 computed tomograph peritoneography (CTP) studies performed in 20 peritoneal dialysis patients were analyzed retrospectively as to their diagnostic usefulness in peritoneal dialysis related complications. Computed tomographic peritoneography was found to be superior to computed tomography scans in localizing small leak sites. In seven of nine patients with clinically diagnosed dialysate leakage, computed tomographic peritoneography supported the clinical diagnosis and localized the leak site in six patients. All patients with a conspicuous leak site and/or with leaks through hernias had to have surgical treatment. Computed tomographic peritoneography failed to reveal a leak or identify a fluid tract in patients with intermittent, small leaks. Those leaks responded easily to a dialysis regimen with diminished intraabdominal pressure. Normal intraperitoneal fluid distribution was based on 17 studies after intraperitoneal infusion of 2,000 ml of peritoneal dialysis solution in patients without intraabdominal organomegaly and/or any clinical suspicion of fluid maldistribution, with average peritoneal transport characteristics. As appraised in the supine position, approximate fluid contents in the intraperitoneal spaces were pelvis, 30-55%; paracolic gutter, 15-30%; perisplenic and perihepatic, 10-20% each, and lesser sac, 1-3%. Severe fluid maldistribution on computed tomography peritoneography, particularly a small fluid volume in the pelvic space, is a poor prognostic sign as to the feasibility of peritoneal dialysis; neither of our two patients with no fluid in the pelvic space could be maintained on peritoneal dialysis, while patients with no fluid in the lesser sac, perihepatic and perisplenic spaces could be maintained on peritoneal dialysis. No fluid was seen in the peritoneal cavity after drainage in the vertical position.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term increase in peritoneal membrane transport rates following incidental intraperitoneal sodium hypochlorite infusion.

A patient on continuous ambulatory peritoneal dialysis using an "O" set connection system with sodium hypochlorite as a disinfectant incidentally infused the disinfectant intraperitoneally on two occasions. The product of peritoneal membrane permeability and peritoneal membrane surface area increased after both infusions as judged by peritoneal equilibration test results and/or serum chemistries. Elevated peritoneal solute transport rates and reduced ultrafiltration gradually subsided but did not return to preinfusion values. This observation suggests that intraperitoneal sodium hypochlorite infusion may cause significant long-term alteration in peritoneal membrane transport characteristics.

Acute renal failure--a complication of new multidrug regimen for treatment of leprosy.

A leprosy patient who developed acute renal failure on multidrug therapy is reported. The patient had initially received a once-weekly dose of rifampin and after he had stopped taking the drug for a time, was given rifampin on a once-monthly dose schedule. He recovered completely from his acute renal failure. Kidney biopsy showed interstitial nephritis with mononuclear and eosinophilic cellular infiltrates.