Influence of hemodialysis on total and free malondialdehyde measured by a new HPLC method

Accurate evaluation of oxidative stress is needed for patients on chronic hemodialysis (HD), as cardiovascular risk level seems related to it. Oxidative stress is often evaluated by measuring an end product of lipoperoxidation named malondialdehyde (MDA). However, the most common technique for measuring MDA, the Thio Barbituric Acid Reactive Substances method (TBARS), is known to be sensitive but poorly specific. We measured true total and free plasma MDA in fifty-four unselected patients on long-term HD, before and after HD sessions, by a new, highly specific HPLC method. Total and free MDA were higher before than after dialysis. Essentially, free MDA was decreased by HD but its fractional decrease was lower than that of urea or creatinine. This confirms that, in fact, free MDA is more or less bound to low molecular weight compounds and/or suggests that MDA may be produced mainly during HD sessions. We propose this new tool to further explore the relationship between oxidative stress, HD and true MDA.     

Prospective evaluation of remote, interactive videoconferencing to enhance urology resident education: the genitourinary teleteaching initiative

PURPOSE: Changes in referral patterns and resource allocation into Centers of Excellence affect the educational experience of urology trainees by altering resident exposure to patients and clinicians, especially at sites where subspecialty deficiencies exist. Access to educators at Centers of Excellence using interactive videoconferencing technology may facilitate residency training objectives and enhance trainees' overall educational experience. We prospectively evaluated the implementation of this technology at tertiary care teaching centers to enhance urology resident education. MATERIALS AND METHODS: Using videoconferencing technology, urology residents at the University of Western Ontario (London, Canada) participated in a series of didactic, interactive pediatric urology teleteaching seminars. These were presented by an expert pediatric urologist from the Hospital for Sick Children, Toronto, Canada. Using a 5-point Likert scale (1-strongly disagree, 5-strongly agree), participants responded to statements pertaining to seminar content, technology and ease of use at the completion of each session. The results were subsequently tabulated and evaluated to determine the effectiveness and accessibility of the program in providing expert pediatric urological education to residents at a remote urology training program. RESULTS: The entire urology resident staff from postgraduate year 1 to 5 participated in the seminar program. The overall acceptance of this medium was high (mean score 4.5). The quality of presentation, as well as picture and sound quality, all received mean scores greater than 4. Participants indicated that their ability to interact with the presenter was not inhibited by using this medium. All participants agreed that they would use this technology in the future (mean score 4.5) and that the presentation would not be improved if the presenter were on-site. Due to preexisting technology at both centers, no direct cost was incurred throughout the study. CONCLUSIONS: Our experience suggests that interactive teleteaching using readily available, existing technology, is a cost-effective and accepted method of providing trainees with an appropriate educational experience. In centers where subspecialty deficiencies exist, this medium may provide residents with the necessary education requirements of their respective programs without the need for costly teacher (or student) travel. Continual improvements in technology as well as the addition of multiple sites will increased this medium's impact in the future.     

Hyperammonemia with reduced ornithine, citrulline, arginine and proline: a new inborn error caused by a mutation in the gene encoding delta(1)-pyrroline-5-carboxylate synthase

delta(1)-pyrroline-5-carboxylate synthase (P5CS), a bifunctional ATP- and NADPH-dependent mitochondrial enzyme, catalyzes the reduction of glutamate to delta(1)-pyrroline-5-carboxylate, a critical step in the biosynthesis of proline, ornithine and arginine. Recently, we reported the cloning and expression of human and murine P5CS cDNAs. Previously, we showed that mammalian P5CS undergoes alternative splicing to generate two isoforms differing only by a 2 amino acid insert at the N-terminus of the gamma-glutamyl kinase active site. The short isoform has high activity in the gut, where it participates in arginine biosynthesis and is inhibited by ornithine. The long isoform, expressed in multiple tissues, is necessary for the synthesis of proline from glutamate and is insensitive to ornithine. Here, we describe a newly recognized inborn error due to the deficiency of P5CS in two siblings with progressive neurodegeneration, joint laxity, skin hyperelasticity and bilateral subcapsular cataracts. Their metabolic phenotype includes hyperammonemia, hypoornithinemia, hypocitrullinemia, hypoargininemia and hypoprolinemia. Both are homozygous for the missense mutation, R84Q, which alters a conserved residue in the P5CS gamma-glutamyl kinase domain. R84Q is not present in 194 control chromosomes and dramatically reduces the activity of both P5CS isoforms when expressed in mammalian cells. Additionally, R84Q appears to destabilize the long isoform. This is the first documented report of an inborn error of P5CS and suggests that this disorder should be considered in the differential diagnosis in patients with neurodegeneration and/or cataracts and connective tissue disease.     

The Effects of Lansoprazole on the Disposition of Antipyrine and Indocyanine Green in Normal Human Subjects

This study was designed to evaluate the potential effects of acute and chronic daily oral doses of lansoprazole (60 mg) on the disposition of antipyrine, an almost completely metabolized low hepatic extraction compound, and indocyanine green, a hepatically secreted compound with high extraction ratio. The study utilized a randomized, placebo-controlled, double-blind, two-period crossover design. Sixteen of 18 subjects completed all phases of the study. Both antipyrine (10 mg kg(minus sign1)) and indocyanine green (0.5 mg kg(minus sign1)) were administered as single intravenous bolus doses on Days 1 and 7 of lansoprazole or placebo dosing. Acute exposure to lansoprazole had no statistically significant effects on the plasma pharmacokinetics of indocyanine green or antipyrine. After the seventh dose, there was a small but statistically significant reductions in indocyanine green total body clearance (CL), and elimination rate constant of 10.6% and 8%, respectively. Additionally, a small statistically significant reduction (8.6%) in antipyrine volume of distribution was detected. No other plasma antipyrine pharmacokinetic parameters were changed with concomitant lansoprazole administration. About a 12% increase in the recovery of one of the major antipyrine urine metabolites (NORA) was detected. Overall, this study demonstrates little or no effect of lansoprazole on the pharmacokinetics of antipyrine and indocyanine green.     

Abnormal α-aminoadipic acid excretion in a newborn with a defect in platelet aggregation and antenatal cerebral haemorrhage

Summary -Aminoadipic acid (AA) is an intermediate in lysine metabolism. We report a new case with AA excess in urine and plasma, without -ketoadipic acid, in a full-term male child born to unrelated parents; he presented at 24h of life with seizures that failed to respond to phenobarbital, clonazepam, and Vigabatrin and death occurred on the 38th day of life. Brain imaging suggested antenatal haemorrhage. Small quantities of AA were also detected in the blood and urine of both parents and a healthy brother, all three of whom exhibited the same defect in platelet aggregation as the deceased child. Both parents had decreased levels of plasma neopterin, a finding that might be related to the immunodeficiency described in other cases.     

Neurosarcoidosis--the great mimicker

INTRODUCTION: Neurosarcoidosis is rare and difficult to diagnose especially in the absence of systemic involvement. CASE REPORT: A 22-year-old African-American man presented with inability to gaze laterally. He underwent magnetic resonance imaging (MRI) the day before that revealed "a 5-mm enhancing mass with surrounding edema in the pons anterior to the fourth ventricle most likely compatible with pontine glioma." CT angiography of the brain was negative. Two days later, the patient developed right facial droop. During craniotomy, a small lesion of rubbery consistency was identified at the mid-portion of the floor of the fourth ventricle. Frozen-section study came suggestive of lymphoma. Further pathological examination revealed sarcoidosis. The patient was discharged on prednisone, and he recovered quickly and completely. CONCLUSION: Neurosarcoidosis can mimic common neurosurgical entities. It is important to keep neurosarcoidosis in mind when making the diagnosis, which often requires biopsy.