William S. Varade

Patterns of Complement Activation in Idiopathic Membranoproliferative Glomerulonephritis, Types I, II, and III

Complement profiles on 22 hypocomplementemic patients with membranoproliferative glomerulonephritis (MPGN) type I, on 11 with MPGN II, and on 16 with MPGN III, gave evidence that the nephritic factor of the amplification loop (NFa) is responsible for the hypocomplementemia in MPGN II and the nephritic factor of the terminal pathway (NFt) for the hypocomplementemia in MPGN III. In contrast, in MPGN I, there was evidence for three complement-activating modalities, NFa, NFt, and immune complexes. As a result, four different patterns of complement activation were seen. NFa, found in MPGN II, produces a complement profile characterized mainly by C3 depression. In addition, four of seven (57%) severely hypocomplementemic MPGN II patients (C3 less than 30 mg/dL) had slightly depressed levels of factor B, and one of seven (14%) of properdin, but in all the C5 concentration was normal. In contrast, all eight severely hypocomplementemic patients with MPGN II had depressed C5 and properdin levels, and six of eight (75%) depressed levels of C6, C7, and/or C9. Of eight MPGN III patients with moderate hypocomplementemia, 50% had depressed C5 and properdin levels and the remainder, depressed C3 only. This spectrum of profiles is most likely produced by varying concentrations of NFt. In MPGN I, nine of 23 (39%) had a profile indicating only classical pathway activation; seven of 23 (39%), a pattern compatible with NFt alone; four of 23 (9%), evidence for both classical pathway activation and NFt; and three of 23 (13%), a pattern compatible with NFa. The unique multifactorial origin of the hypocomplementemia in MPGN I, often giving evidence of classical pathway activation, together with previously reported differences in glomerular morphology and clinical features at onset, makes it distinct from MPGN III. Depressed C8 levels were found to some extent in all hypocomplementemic states. The levels were uncommonly depressed in patients with NFa, most markedly depressed with NFt, and moderately reduced with classical pathway activation. The cause is not known. Diagnostically, profiles showing classical pathway activation and low levels of C6, C7, and/or C9 are specific for MPGN I. Those showing only classical activation are likewise diagnostic of MPGN I if systemic lupus erythematosus (SLE) and chronic bacteremia are ruled out.

Role of urinary supersaturation in the evaluation of children with urolithiasis

Timed urine collections are a standard part of the evaluation for predisposition to stone formation in children with urolithiasis. Supersaturation is defined as the ratio of the concentration of dissolved salt to its solubility in urine. The purpose of the present study was to determine if adding supersaturation to the standard timed urine collection increased the ability to detect a metabolic predisposition to stone formation. Thirty-two children with urolithiasis had 24-hour urine measurements of calcium, oxalate, citrate, uric acid, and cystine (the “traditional” evaluation), as well as supersaturation for calcium oxalate, calcium phosphate, and uric acid, on the same urine sample. Nine (28%) of the 32 were hypercalciuric, 2 (6%) hyperoxaluric, and 4 (12%) hypocitraturic. In total, 14 (44%) had a metabolic predisposition that was detected by the traditional evaluation. Supersaturation was elevated in 18 (56%), including nine who did not have metabolic predisposition detected by traditional evaluation. Urine volume was low in 17 (53%) of 32 children, including eight of nine children with abnormal supersaturation but normal traditional evaluation. Only one child with normal traditional evaluation and normal urine volume had elevated supersaturation. These results show that the benefit of adding supersaturation to the traditional evaluation was largely negated by consideration of urine volume.

Discordance Between Resident and Faculty Perceptions of Resident Autonomy: Can Self-determination Theory Help Interpret Differences and Guide Strategies for Bridging the Divide?

Purpose To identify and interpret differences between resident and faculty perceptions of resident autonomy and of faculty support of resident autonomy. Method Parallel questionnaires were sent to pediatric residents and faculty at the University of Rochester Medical Center in 2011. Items addressed self-determination theory (SDT) constructs (autonomy, competence, relatedness) and asked residents and faculty to rate and/or comment on their own and the other group’s behaviors. Distributions of responses to 17 parallel Likert scale items were compared by Wilcoxon rank-sum tests. Written comments underwent qualitative content analysis. Results Respondents included 62/78 residents (79%) and 71/100 faculty (71%). The groups differed significantly on 15 of 17 parallel items but agreed that faculty sometimes provided too much direction. Written comments suggested that SDT constructs were closely interrelated in residency training. Residents expressed frustration that their care plans were changed without explanation. Faculty reported reluctance to give “passive” residents autonomy in patient care unless stakes were low. Many reported granting more independence to residents who displayed motivation and competence. Some described working to overcome residents’ passivity by clarifying and reinforcing expectations. Conclusions Faculty and residents had discordant perceptions of resident autonomy and of faculty support for resident autonomy. When faculty restrict the independence of “passive” residents whose competence they question, residents may receive fewer opportunities for active learning. Strategies that support autonomy, such as scaffolding, may help residents gain confidence and competence, enhance residents’ relatedness to team members and supervisors, and help programs adapt to accreditation requirements to foster residents’ growth in independence.

Urine-to-blood carbon dioxide tension gradient and maximal depression of urinary pH to distinguish rate-dependent from classic distal renal tubular acidosis in children

We determined the prevalence and clinical features of rate-dependent distal renal tubular acidosis (dRTA) in 31 children examined for possible renal tubular acidosis by measuring the urinary-minus-blood partial pressure of carbon dioxide (U-B PCO2) gradient, minimal urinary pH, and fractional excretion of bicarbonate. Of 20 patients with low U-B PCO2 gradients, nine could not lower urinary pH < or = 5.5, indicating classic dRTA, whereas 11 could lower urinary pH < or = 5.5, as described in rate-dependent dRTA. When patients with rate-dependent dRTA and classic (type I) dRTA were compared, there was no difference in the mean U-B PCO2 gradient or in clinical findings, including age, reason for referral, presence of nephrocalcinosis, or depression of linear growth. We conclude that children with rate-dependent dRTA are susceptible to at least some of the same sequelae as children with classic dRTA. Measurement of minimal urinary pH will not detect this subtle form of dRTA. Determination of the U-B PCO2 gradient should be considered a routine part of evaluation for suspected renal tubular acidosis in a child.

Isolation of germinal centerlike events from human spleen RNA. Somatic hypermutation of a clonally related VH6DJH rearrangement expressed with IgM, IgG, and IgA.

12 rearranged human VH6 immunoglobulin heavy chain genes arising from the same rearrangement were isolated without preselection from the RNA of a fragment of human spleen. The 12 clones were isolated from a pool of 31 unique VH6 clones arising from 18 unique rearrangements. 2 of the 12 related clones were expressed with IgM, 2 with IgG, and 8 with IgA1. All the clones, including those expressing IgM, showed extensive somatic mutation of germline bases (5.6%), which was consistent with antigen-driven activation of these VH6-expressing clones with recruitment into the immune repertoire. On the basis of significant sharing of somatic mutations between the IgM clones and clones expressing the other isotypes (six mutations shared with IgG clones and eight mutations shared with IgA clones), it was apparent that the IgM-expressing precursor in this diversified family had undergone extensive antigen-driven somatic mutation prior to isotype switching. This family of related clones suggests that a germinal centerlike event had been sampled. The highly mutated IgM clones suggest that there may exist memory B cells capable of further somatic mutation and differential isotype-switching depending on the specific antigenic stimulus.

Human splenic IgM immunoglobulin transcripts are mutated at high frequency

Human spleen immunoglobulin gene rearrangements that used the VH6 gene and were expressed with IgM were characterized for their frequency of somatic hypermutation from PCR amplified spleen cDNA. A high frequency of rearrangements that were somatically mutated was demonstrated by restriction endonuclease analysis and sequencing of cloned rearrangements. The 24 rearrangements cloned from three different spleens had an overall mutation frequency of 3.1% mutations/bp sequenced and ranged from 0.4 to 6.0%. These mutations appeared to have been antigenically selected based on both the high frequency and high amino acid replacement to silent (R/S) ratios in the complementarity determining regions. Five clones that arose from two different rearrangements showed evidence of intraclonal diversification with both shared and unique mutations. The mutated clones of one spleen donor were lower in frequency and were not concentrated in the CDR, which suggested these mutations had not been antigenically selected. These findings support the dissociation of somatic mutation and isotype switching and the possibility that IgM-expressing B cells may serve as human memory B cells.

INHERENT PROPERTIES OF SOMATIC HYPERMUTATION AS REVEALED BY HUMAN NON-PRODUCTIVE VH6 IMMUNOGLOBULIN REARRANGEMENTS

To study inherent properties of somatic hypermutation of human immunoglobulin genes in the absence of antigen selection, mutations of human non‐productive VH6 rearrangements enriched by subtractive hybridization were characterized. Ten unique clones arising from nine non‐productive rearrangements were isolated. The frequency of mutation was 3·0%. Analysis of these mutations showed intrinsic bias for transitions and cytosine (C) to guanine (G) and G to C transversions. Bias for the strand of DNA targeted by mutation was not evident. Replacement mutations in the complementarity‐determining region (CDR) occurred more frequently than expected based on the primary DNA sequence. This targeting of replacement mutations to the CDR may explain the conservation of the VH6 sequence in primates.

Development of a Novel Curriculum to Enhance the Autonomy and Motivation of Residents

Teaching hospitals nationwide have experienced intense pressures on patient care systems that in the past provided a nurturing home for resident education. Increased regulatory burdens and the drive to increase revenues, among other changes, have placed severe constraints on resident and faculty time for education. In our pediatric residency program at the University of Rochester Medical Center, a symptom of these changes has been a perceived erosion of resident autonomy. Faculty have reported that residents are reticent to generate their own patient care plans, whereas residents have stated that faculty are overly directive and do not always take the time to listen to their assessment and plan. Recently, a resident “delegation” brought to our faculty a proposed educational contract, the purpose of which was to increase resident responsibilities for initiation of patient care plans and clarify the responsibility of the faculty to provide timely and constructive feedback on these plans. This contract has been received with enthusiasm by the faculty. It provides an ideal opportunity for introduction of our new curriculum to enhance resident autonomy, which will be implemented and tested over the next several years. We believe that the competency domain of practice-based learning and improvement, which is often challenging for residents, may be enriched by the application of self-determination theory (SDT), a body of knowledge and tools that has proven effective in business, education, athletics, and health care to enhance motivation.1,–,5 SDT was developed by 2 University of Rochester psychologists: Professors Edward Deci and Richard Ryan. It teaches that people who cultivate intrinsic motives to pursue goals are higher achievers than those who are prodded to perform by extrinsic rewards and punishments. The theory posits that human motivation is driven by psychological need fulfillment in 3 areas: autonomy (the need to … Address correspondence to William S. Varade, MD, University of Rochester Medical Center, 601 Elmwood Ave, Box 777R, Rochester, NY 14642. E-mail: william_varade{at}urmc.rochester.edu

Prolonged reversible renal failure with nephrotic syndrome.

Steroid nonresponsive nephrotic syndrome in a 15-year-old girl with reversible renal failure required dialysis and aggressive nutritional therapy for 1 year. Severe interstitial edema and foot process fusion were the only processes identified to explain the renal failure. Diabetes-like alterations of the glomerular capillary wall basement membrane may have been an outcome of the intense alimentation.

Acute Kidney Injury

Acute renal failure, now termed acute kidney injury (AKI), is a common occurrence in the pediatric intensive care unit. It impacts the management decisions and outcomes of critically ill patients. This chapter will review the factors involved in measuring renal function in children and recognizing abnormal renal function. The major clinical subtypes of AKI and how to distinguish between them will be addressed as well as some of the more common causes within each subtype. Management of AKI will be reviewed, including the indications for renal replacement therapy. The impact of impairment of renal function on the overall management and outcome of the critically ill pediatric patient will be discussed.