Role of intravenous urogram in investigation of urinary tract infection: an observational study.

OBJECTIVES: To examine the value of an intravenous urogram (i.v.U) in patients with abnormal differential (99m)Tc dimercaptosuccinic acid (DMSA) uptake without scarring or ultrasound abnormality. STUDY DESIGN: Forty patients (age 0-19 years) were identified over a two year period in whom the differential renal uptake was >10%, who had smooth renal outlines, and had no evidence of scarring. All patients had an ultrasound examination. Two had marked urological abnormalities on ultrasound and eight had a duplex system in the kidney with greater DMSA uptake. In 18 patients where no explanation was apparent for the discrepant DMSA uptake, an i.v.U was performed. RESULTS: Eight patients had a normal i.v.U. In the remaining 10 patients, six had duplex systems without scarring and four had appearances of scarring in the kidney with reduced DMSA uptake. CONCLUSIONS: In this small selected group an i.v.U will identify a significant number of patients with normal kidneys, unrecognised simple duplex systems, or scarring where the DMSA scan has been inconclusive. This will help in planning long term follow up.

C-terminal peptide of thrombospondin-1 induces platelet aggregation through the Fc receptor gamma-chain-associated signaling pathway and by agglutination.

A peptide from the C-terminal domain of thrombospondin-1 (Arg-Phe-Tyr-Val-Val-Met-Trp-Lys; known as 4N1-1) has been reported to induce platelet aggregation and to bind to the integrin-associated protein (IAP), which is also known as CD47. In this study, it was discovered that 4N1-1 or its derivative peptide, 4N1K, induces rapid phosphorylation of the Fc receptor (FcR) gamma chain, Syk, SLP-76, and phospholipase C gamma2 in human platelets. A specific inhibitor of Src family kinases, 4-amino-4-(4-methylphenyl)-7-(t-butyl) pyrazola[3,4-d]pyrimidine, prevented phosphorylation of these proteins, abolished platelet secretion, and reduced aggregation by approximately 50%. A similar inhibition of aggregation to 4N1-1 was obtained in the presence of Arg-Gly-Asp-Ser in mouse platelets deficient in FcR gamma chain or SLP-76 and in patients with type I Glanzmann thrombasthenia. These results show that 4N1-1 signals through a pathway similar to that used by the collagen receptor glycoprotein (GP) VI. The alphaIIbbeta3-independent aggregation induced by 4N1-1 was also observed in fixed platelets and platelets from patients with Bernard-Soulier syndrome, which are deficient in GPIbalpha. Surprisingly, the ability of 4N1-1 to stimulate aggregation and tyrosine phosphorylation was not altered in platelets pretreated with anti-IAP antibodies and in IAP-deficient mice. These results show that the C-terminal peptide of thrombospondin induces platelet aggregation through the FcR gamma-chain signaling pathway and through agglutination. The latter pathway is independent of signaling events and does not use GPIbalpha or alphaIIbbeta3. Neither of these pathways is mediated by IAP.

The role of the adapter molecule SLP-76 in platelet function.

Following vascular injury, one of the most critical initial events is activation of platelets followed by formation of a hemostatic plug. Platelets are capable of responding to a diverse array of agonists resulting in adhesion and granule release. The biochemical events underlying platelet activation are just beginning to be understood. One class of molecules shown to play important roles in this process is adapters. Adapter molecules contain distinct modular domains which mediate protein-protein or protein-lipid interactions giving these proteins the ability to nucleate signal transduction complexes. In this review we will discuss the function of the hematopoietic cell specific adapter molecule, SLP-76 in both platelet activation and hemostasis. Because many parallels exist between signal transduction pathways in platelets and lymphocytes, we will also review the function of SLP-76 in coordinating signal transduction pathways following antigen bind to the T cell receptor.

Hypercalciuria in ex-preterm children, aged 7-8 years.

In a previous study, 8 of 28 ex-preterm infants, aged 4-5 years, had increased urinary calcium excretion. The aim of this study was to confirm this finding and to determine if raised urinary calcium excretion is associated with reduced bone mineralisation. Forty-six ex-preterm children, aged 7-9 years, and 40 age- and sex-matched controls were recruited. The calcium excretion measured from 3 separate 24-h urine collections was recorded and a dietary assessment made from a diary record. Data were retrieved from the neonatal case notes and included aminoglycoside usage. Dual energy X-ray absorptiometry was used to measure bone mineral content and bone mineral density (BMD) in all children. The mean maximum 24-h urinary calcium was significantly higher in the preterm group than the term group (P=0.01). Increased calcium excretion was associated with raised neonatal aminoglycoside levels (P=0.0013). Height standard deviation score and hip BMD were significantly lower in the 21 preterm children with a 24-h urinary calcium above 4 mg/kg per day than term controls (P=0.04 and P=0.004, respectively). Urinary calcium excretion had a negative relationship with hip BMD in the preterm group (P=0.004). This difference in BMD was not observed in the 25 preterm children with normocalciuria. In the 10 preterm girls with hypercalciuria, hip BMD was lower than in control females (P=0.01). This difference in hip BMD between the 11 preterm boys with hypercalciuria and term boys was not significant (P=0.05). In conclusion, preterm children are shorter and have a lower hip BMD than those with normocalciuria. Further prospective studies are required to assess this risk and its influence on subsequent impaired bone mineralisation.

The molecular adapter SLP-76 relays signals from platelet integrin alphaIIbbeta3 to the actin cytoskeleton.

Platelet adhesion to fibrinogen through integrin alpha(IIb)beta(3) triggers actin rearrangements and cell spreading. Mice deficient in the SLP-76 adapter molecule bleed excessively, and their platelets spread poorly on fibrinogen. Here we used human platelets and a Chinese hamster ovary (CHO) cell expression system to better define the role of SLP-76 in alpha(IIb)beta(3) signaling. CHO cell adhesion to fibrinogen required alpha(IIb)beta(3) and stimulated tyrosine phosphorylation of SLP-76. SLP-76 phosphorylation required coexpression of Syk tyrosine kinase and stimulated association of SLP-76 with the adapter, Nck, and with the Rac exchange factor, Vav1. SLP-76 expression increased lamellipodia formation induced by Syk and Vav1 in adherent CHO cells (p < 0.001). Although lamellipodia formation requires Rac, SLP-76 functioned downstream of Rac by potentiating adhesion-dependent activation of PAK kinase (p < 0.001), a Rac effector that associates with Nck. In platelets, adhesion to fibrinogen stimulated the association of SLP-76 with the SLAP-130 adapter and with VASP, a SLAP-130 binding partner implicated in actin reorganization. Furthermore, SLAP-130 colocalized with VASP at the periphery of spread platelets. Thus, SLP-76 functions to relay signals from alpha(IIb)beta(3) to effectors of cytoskeletal reorganization. Therefore, deficient recruitment of specific adapters and effectors to sites of adhesion may explain the integrin phenotype of SLP-76(-/-) platelets.

Differential requirement for SLP-76 domains in T cell development and function.

The hematopoietic cell-specific adaptor protein, SLP-76, is critical for T cell development and mature T cell receptor (TCR) signaling; however, the structural requirements of SLP-76 for mediating thymopoiesis and mature T cell function remain largely unknown. In this study, transgenic mice were generated to examine the requirements for specific domains of SLP-76 in thymocytes and peripheral T cells in vivo. Examination of mice expressing various mutants of SLP-76 on the null background demonstrates a differential requirement for specific domains of SLP-76 in thymocytes and T cells and provides new insight into the molecular mechanisms underlying SLP-76 function.

Hematopoietic reconstitution of SLP-76 corrects hemostasis and platelet signaling through alpha IIb beta 3 and collagen receptors.

Mice deficient in the hematopoietic cell-specific adapter protein SLP-76 demonstrate a failure of T cell development and fetal hemorrhage. Although SLP-76-deficient platelets manifest defective collagen receptor signaling, this alone may not explain the observed bleeding diathesis. Because alpha IIb beta 3, the platelet fibrinogen receptor, is required for normal hemostasis, we explored a potential role for SLP-76 in alpha IIb beta 3 signaling. Interaction of soluble or immobilized fibrinogen with normal human or murine platelets triggers rapid tyrosine phosphorylation of SLP-76. Moreover, platelet adhesion to fibrinogen stimulates actin rearrangements, filopodial and lamellipodial extension, and localization of tyrosine phosphorylated proteins to the cell periphery. In contrast, SLP-76-deficient murine platelets bind fibrinogen normally, but spread poorly and exhibit reduced levels of phosphotyrosine. The in vivo bleeding diathesis as well as the defects in platelet responses to fibrinogen and collagen are reversed by retroviral transduction of SLP-76 into bone marrow derived from SLP-76-deficient mice. These studies establish that SLP-76 functions downstream of alpha IIb beta 3 and collagen receptors in platelets. Furthermore, expression of SLP-76 in hematopoietic cells, including platelets, plays a necessary role in hemostasis.

Functional association between SLAP-130 and SLP-76 in Jurkat T cells.

T cell antigen receptor (TCR) engagement results in protein-tyrosine kinase activation which initiates signaling cascades leading to induction of the interleukin-2 gene. Previous studies identified two substrates of the TCR-induced protein-tyrosine kinases, SH2 domain-containing leukocyte specific protein of 76 kDa (SLP-76) and SLP-76-associated phosphoprotein of 130 kDa (SLAP-130). While SLP-76 appears to couple the TCR with downstream signals, SLAP-130 may play a negative regulatory role in T cell activation. In this study, we demonstrate that consistent with its ability to abrogate the SLP-76 augmentation of TCR-induced activation of the NFAT/AP1 region of the interleukin-2 promoter, overexpression of SLAP-130 also interferes with the rescue of signaling in SLP-76-deficient Jurkat cells in co-transfection experiments. The effect of SLAP-130 on SLP-76 function is specific for regulating TCR-induced ERK activation, but not phospholipase Cgamma 1 phosphorylation. By generating both deletion and point mutants of SLAP-130, we identified tyrosine 559 as critical for the interaction between SLP-76 and SLAP-130. We show that mutation of this residue in context of full-length SLAP-130 diminishes the ability of SLAP-130 to abrogate SLP-76 function. These data suggest that the SLAP-130/SLP-76 association is important for the negative regulatory role that SLAP-130 appears to play in T cell signaling.

Immunisation against varicella in end stage and pre-end stage renal failure. Trans-Pennine Paediatric Nephrology Study Group.

OBJECTIVES: To investigate the seroconversion rate and duration of persistence of protective antibody titres after varicella immunisation in children with renal failure. DESIGN: 32 children (25 end stage and 7 pre-end stage renal failure) were immunised using 2 x 2,000 plaque forming unit doses of varicella vaccine 3 months apart. Varicella antibody titres were measured by enzyme linked immunosorbent assay. RESULTS: All children initially seroconverted after immunisation. At a mean follow up of 20.3 months, 23 of 28 had protective antibody titres, 4 children having died of unrelated causes. Two children required a third booster dose. 11 children underwent renal transplantation; 10 had protective titres at the time of transplantation and, at a mean of 23.4 months after immunisation, 6 currently have protective titres. Minor side effects occurred after 11 vaccine doses in 9 children. No child developed varicella, despite 10 clear episodes of exposure to the wild-type virus. CONCLUSIONS: Varicella immunisation in children with end stage and pre-end stage renal failure results in a high rate of seroconversion and persistence of protective antibody titres. More widespread use of the vaccine before renal transplantation is recommended.

Antigen specific T lymphocyte activation.

Following recognition of foreign antigens, the T cell antigen receptor (TCR) transduces signals leading to clonal expansion and differentiation into effector cells. Engagement of the TCR results first in the activation of cytosolic protein tyrosine kinases, followed by initiation of multiple signaling cascades. Recently, it has been shown that regulation and integration of these signaling pathways requires formation of multimolecular complexes and the recruitment of these complexes to specific regions within the cell. This review focuses on the events leading to T cell activation including the signaling cascades and the role of adapter molecules in coordination of these pathways. In addition, the mechanism by which TCR ligation can lead to T cell removal following elimination of an antigenic challenge is discussed.

Renal blood flow velocity in acute renal failure following cardiopulmonary bypass surgery.

Diminished renal perfusion is believed to be the main factor precipitating acute renal failure (ARF) following cardiopulmonary bypass surgery (CPB). We aimed to assess renal perfusion in patients following CPB surgery using Doppler ultrasound measurements. The Pulsatility index (PI) of the renal and intrarenal arteries was calculated as an index of renal perfusion. Two groups of patients were studied. Group 1 consisted of children with complex cardiac malformations who developed ARF following CPB. Group 2 consisted of children with atrial septal defects who were studied before and after CPB, but who did not develop ARF. In group 1, there were significant correlations between PI of the renal artery and standard deviation score of systolic blood pressure (SDS) (correlation coefficient = -0.588, p < 0.0001), and PI and urine output (UOP) (correlation coefficient = -0.46, p = 0.001). In the survivors, PI of the renal artery dropped significantly at the onset of recovery from ARF (6.27-2.15, p = 0.007). In group 2, PI of renal and intrarenal arteries remained unchanged on day 1 and day 4 post-CPB surgery in comparison with preoperative values. PI of the renal artery may aid the prediction of onset and recovery from ARF following CPB surgery, and help modify treatment in these critically ill patients.

Renal calcification in preterm infants: follow up at 4-5 years.

AIM: To determine the consequences of renal calcification in preterm infants. METHODS: A cohort of 11 preterm babies was studied at the age of 4 to 5 years. They had had renal calcification as neonates. Seventeen matched controls were also studied. Each child had a renal ultrasound scan, a calcium load test, and a desmopressin test for renal concentrating ability (RCA). The study group also had glomerular filtration rate (GFR) estimated, using the height:creatinine ratio, and tubular phosphate reabsorption, without phosphate load, per glomerular filtration rate (Tp/GFR) calculated, RESULTS: In the study group the median GFR was 61 ml/min/1.73m2 (range 46-79 ml/min/1.73m2) and the median calculated Tp/GFR SD score was -0.94 (range -2.8-0.68). Five children out of the study group had ultrasonic evidence of renal calcification. There was no significant difference between the two groups in renal size, calciuria, before or after calcium load, or RCA. Eight children (three patients, five controls) had an abnormal calcium load test. The RCA of the children in the study and control groups combined was below that of published values, with a median calculated SD score -0.71 (95% CI -1.21 to -0.23). CONCLUSIONS: There was evidence of renal dysfunction in children who had been born preterm. Renal calcification detected in the neonatal period does not seem to be a major predisposing factor for the abnormalities of renal function subsequently observed in these infants.

Focal and segmental glomerulosclerosis in children with reflux nephropathy.

A histological review of 86 pediatric nephrectomy specimens from patients with vesicoureteric reflux (with or without apparent obstruction at the vesicoureteric junction) investigated the relationship between the presence and extent of focal and segmental glomerulosclerosis (FSGS) and coexisting renal hypoplasia and postnatally acquired cortical damage. FSGS was found in 18 patients, 9 of whom were less than 5 years old. There was no significant association between the presence (or grade) or absence of FSGS and age at nephrectomy, gender, presence or absence of obstruction, and severity of hypoplasia and/or postnatally acquired cortical loss. FSGS was absent from 18 hypoplastic kidneys without vesicoureteric reflux (although of relatively young age), 40 normally developed kidneys age-matched with the index population, and 72 nephrectomy specimens without vesicoureteric reflux (except in 2 known cases of focal segmental glomerulonephritis). Within the index population FSGS was significantly (P < .01) associated with hypertension, and hypertension was significantly associated with proteinuria (P < .001) but not with an abnormal contralateral kidney. There was no significant association between FSGS, proteinuria, and an abnormal contralateral kidney. Our results were unexpected when interpreted within a pathogenesis for FSGS of glomerular "hyperfiltration." They may, at least in the pediatric age group, indicate a possible role for other mechanisms in the development of FSGS.

Renal developmental arrest in sudden infant death syndrome.

Investigations linking sudden infant death syndrome (SIDS) and type II intrauterine growth retardation (IUGR) have thus far failed due in part to technical limitations. Recently developed stereological methods for the unbiased estimation of total nephron number in the human kidney are capable of detecting deviations from normal values of greater than 10%. We compared the total number of nephrons in the kidneys of 24 SIDS victims with those from 16 controls with the same age range. Mean nephron number was significantly (P < 0.001) reduced in ex-IUGR SIDS cases (birthweight under the 10th centile, n = 9, mean number 635,000, range 327,000-1,010,000) in comparison with controls (903,000, 740,000-1,060,000). A similarly significant (P < 0.01) reduction in the "normal birthweight" SIDS group (birthweight over 10th centile, n = 15, 690,000, 361,000-1,040,000) was found. This hitherto unreported renal developmental arrest may be only one manifestation of a general, somatic developmental defect, reflecting adverse intrauterine conditions; other organ systems, similarly critical to homeostasis may be comparably affected. The findings, although not proposed as direct cause of SIDS, may represent a potential explanation for the recognized association of IUGR and SIDS, and provide--we believe--the first quantitative evidence of intrauterine growth retardation in, at least a number of, children of average birthweight.

Compliance with antibiotic prophylaxis in urinary tract infection.

Compliance with antibiotic prophylaxis after urinary tract infection was assessed in 32 children, using a parent questionnaire, and a urine test for antibacterial substances. In 31 (97%) cases, parents reported giving the antibiotics every day but only 22 (69%) of urine tests were positive. Failure to understand the reasons for prophylaxis and non-compliance were significantly associated.

Antidiuretic hormone following surgery in children.

We studied 13 children subjected to elective tonsillectomy, 6 of whom (study patients) received supplemental intravenous isotonic saline during and after operation, and 7 of whom (controls) did not. Clinical and biochemical evidence of hypovolaemia was present in the control but not in the study patients. Plasma antidiuretic hormone (ADH) and urine osmolality were higher in controls (p less than 0.005 and p less than 0.05 respectively). Plasma sodium concentration and osmolality were similar in the two groups. We conclude that hypovolaemia is the principal stimulus to ADH release following surgery and that, in addition to replacement of observed losses of blood and other fluids by fluids of appropriate composition, hypovolaemia should be prevented by the administration of maintenance quantities of isotonic fluid, rather than exacerbated by fluid restriction, in patients in whom oral fluid intake is interrupted for more than a brief period. Hypotonic and sodium free fluids should be avoided because of the risk of hyponatraemia.

Hyponatraemia in premature babies and following surgery in older children.

Hyponatraemia implies water retention in excess of sodium with or without increased loss of sodium from the body; extracellular fluid volume may be increased, normal or reduced. It has many causes which are briefly reviewed. Among these is the rare syndrome of inappropriate secretion of antidiuretic hormone (SIADH). It is suggested that SIADH is often diagnosed incorrectly because the raised ADH levels are appropriate for the volume status of the child. Precision in the diagnosis is important because whilst water restriction is necessary for the treatment of SIADH, other measures including the administration of extra fluid are often required if the raised ADH is appropriate. Hyponatraemia in the newborn may be caused by prerenal failure, renal failure or renal sodium wasting which is common in premature infants. Careful control of sodium intake as well as water intake is vital in this age group. Surgery is associated with water retention, but recent studies suggest that ADH levels are raised post-operatively because of volume depletion and that present recommendations for fluid therapy during and following surgery are inadequate. The use of electrolyte-free dextrose solutions should be abandoned and more liberal use of physiological saline or colloid is recommended.