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Biomedical subjects

H R Powell

Publications and source records attributed to H R Powell.

At least 19 recordsLinked to original sources
PubMed2002

Automation of the collection and processing of X-ray diffraction data -- a generic approach.

With modern detectors and synchrotron sources, it is now routine to collect complete data sets in 10-30 min. To make the most efficient use of these resources, it is desirable to automate the collection and processing of the diffraction data, ideally to a level at which multiple data sets can be acquired without any intervention. A scheme is described to allow fully automated data collection and processing. The design is modular, so that it can easily be interfaced with different beamline-control programs and different data-processing programs. An expert system provides a communication path between the data-processing software and the beamline-control software and takes decisions about the data collection based on project information provided by the user and experimental data provided by the data-processing program.

Algorithms↗
PubMed2002

Factors influencing growth and final height after renal transplantation.

Growth retardation occurs commonly in children and adolescents with chronic renal insufficiency. While some children exhibit catch-up growth following renal transplantation, for many children growth remains sub-optimal. The aim of the current study was to review the factors influencing growth and final height following renal transplantation. Data from all children who had a renal transplant performed between 1985 and 1998 at the Royal Melbourne and Royal Children's Hospitals, Melbourne (n = 85), were examined retrospectively. Two children who died in the first year post-transplant and one patient lost to follow-up within 6 months of their transplant were excluded. Children with multiple grafts had only growth following their most recent graft analyzed. The mean height standard deviation score (Ht-SDS) at the time of transplantation was -2.11 (range: -5.05 to 0.27), improving to -1.50 (range: -3.67 to 1.27) at 7 yr post-transplant. On univariate analysis, the dose of cyclosporin at 6 months and at 1 and 3 yr, and the graft function at 1 yr, had a significant positive correlation with the change in Ht-SDS (DeltaHt-SDS) at each of those time-points post-transplant. At all time-points there was a strong correlation between pretransplant height and subsequent growth. A sub-group of children who were 16 yr of age or older at December 1999, and who were considered to have reached their final height, were examined to determine predictors of final height. Multiple regression analysis of clinical and laboratory parameters from the sub-group of patients > or = 16 yr of age showed that height at the time of transplant, age at the time of transplant, and final glomerular filtration rate, were significant independent predictors of growth (r2 = 0.82, p = 0.01). In addition, the immunosuppressive regimen at 1, 3, and 5 yr post-transplant had a significant effect on growth. This study confirms the importance of each of these factors for post-transplant growth.

Adolescent↗
PubMed2001

Clinical spectrum of Denys-Drash and Frasier syndrome.

Denys-Drash syndrome (DDS) and Frasier syndrome (FS) are two related conditions caused by mutations of the Wilms tumor gene, WT1. Both syndromes are characterized by male pseudohermaphroditism, a progressive glomerulopathy, and the development of genitourinary tumors. DDS and FS have previously been distinguished by differences in nephropathy, with DDS patients demonstrating diffuse mesangial sclerosis (DMS) in contrast to focal and segmental glomerulosclerosis (FSGS) in FS patients. The clinicopathological features and genotype analysis of two patients with WT1 mutations are presented in this report. Genotype analysis of the first patient revealed a previously undescribed mutation in exon 8 of the WT1 gene. The second patient presented with a rapidly progressive nephropathy characterized histologically by DMS, but was found to have the genetic mutation seen in FS patients. A summary of all reported patients with the characteristic mutation associated with FS demonstrates the clinical overlap of this syndrome with DDS. This suggests that both these conditions should be considered as part of the spectrum of disease due to WT1 gene mutations rather than as separate diseases. Clinical classification remains important for prognosis, as the underlying renal disease appears to predict the progression of nephropathy independently of the genetic abnormality.

Base Sequence↗
PubMed2000

Evaluation and long-term outcome of pediatric renovascular hypertension.

Seventeen children with renovascular hypertension were managed at the Royal Children's Hospital, Melbourne, over the 20-year period from 1975 to 1996. The age at presentation ranged from 10 days to 18 years. All children presented with severe hypertension with mean systolic blood pressure 7 standard deviations above age-matched averages and mean diastolic blood pressure 5.5 standard deviations above age-matched averages. Neurofibromatosis was the most common etiology (58% of patients) and there were no cases of Takayasu's arteritis. Patients underwent a variety of biochemical and imaging investigations but in all cases renal angiography was necessary for definitive diagnosis and for planning therapy. Ten of the 17 patients had surgical procedures performed. Percutaneous transluminal angioplasty was performed in four patients but led to cure in only one patient following thrombosis of the affected artery producing segmental renal infarction. Other vascular reconstructive procedures, including the use of autologous or synthetic bypass grafts and autotransplantation, produced cure of hypertension in 50% of children with improvement in a further 30%. The long-term outlook for children treated with surgical reconstructive procedures was excellent. One patient underwent surgery for avulsion of an arterial graft following a pubertal growth spurt. No other patient originally cured by surgery has required reoperation with no cases of restenosis at a mean follow-up of 11 years 3 months.

Adolescent↗
PubMed1999

Determination by MAD-DM of the structure of the DNA duplex d[ACGTACG(5-BrU)]2 at 1.46 A and 100 K.

A four-wavelength MAD experiment on a new brominated octanucleotide is reported here. d[ACGTACG(5-BrU)], C77H81BrN30O32P7, Mr (DNA) = 2235, tetragonal, P43212 (No. 96), a = 43.597, c = 26.268 A, V = 49927.5 A3, Z = 8, T = 100 K, R = 10.91% for 4312 reflections between 15.0 and 1.46 A resolution. The self-complementary brominated octanucleotide d[ACGTACG(5-BrU)]2 has been crystallized and data measured to 1.45 A at both 293 K and a second crystal flash frozen at 100 K. The latter data collection was carried out to the same resolution at the four wavelengths 0.9344, 0.9216, 0.9208 and 0.9003 A, around the Br K edge at 0.92 A and the structure determined from a map derived from a MAD data analysis using pseudo-MIR methodology, as implemented in the program MLPHARE. This is one of the first successful MAD phasing experiments carried out at Sincrotrone Elettra in Trieste, Italy. The structure was refined using the data measured at 0.9003 A, anisotropic temperature factors and the restrained least-squares refinement implemented in the program SHELX96, and the helical parameters are compared with those previously determined for the isomorphous d(ACGTACGT)2 analogue. The asymmetric unit consists of a single strand of octamer with 96 water molecules. No countercations were located. The A-DNA helix geometry obtained has been analysed using the CURVES program.

Carbohydrate Conformation↗
PubMed1999

The Rossmann Fourier autoindexing algorithm in MOSFLM.

The fast Fourier transform (FFT) autoindexing routines written by the Rossmann group at Purdue University have been incorporated in MOSFLM, providing a rapid and reliable method of indexing oscillation images. This is a procedure which extracts direct-space information about the unit cell from the FFT. The method and its implementation in MOSFLM are discussed.

Algorithms↗
PubMed1997

The bi-loop, a new general four-stranded DNA motif.

The crystal structure of the cyclic octanucleotide d contains two independent molecules that form a novel quadruplex by means of intermolecular Watson-Crick A.T pairs and base stacking. A virtually identical quadruplex composed of G.C pairs was found by earlier x-ray analysis of the linear heptamer d(GCATGCT), when the DNA was looped in the crystal. The close correspondence between these two structures of markedly dissimilar oligonucleotides suggests that they are both examples of a previously unrecognized motif. Their nucleotide sequences have little in common except for two separated 5'-purine-pyrimidine dinucleotides forming the quadruplex, and by implication these so-called "bi-loops" could occur widely in natural DNA. Such structures provide a mechanism for noncovalent linking of polynucleotides in vivo. Their capacity to associate by base stacking, demonstrated in the crystal structure of d(GCATGCT), creates a compact molecular framework made up of four DNA chains within which strand exchange could take place.

Base Composition↗
PubMed1996

An extreme example of the neonatal form of Bartter's syndrome.

A male infant is described who had polyuria over the 4 months of his life with urine volumes exceeding 1,000 ml/kg per day, severe serum electrolyte losses, metabolic alkalosis and increased plasma renin activity (56 ng/ml per hour). He had a normal blood pressure and glomerular filtration rate when fluid replete. The urine flow rate was about 25% of the glomerular filtration rate. Renal histology showed hyperplasia of the juxtaglomerular apparatus and abnormalities of the proximal tubules. The features of this case suggest an extreme form of Bartter's syndrome presenting from the first days of life.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

Left ventricular abnormalities in children, adolescents and young adults with renal disease.

The cardiac abnormalities that complicate chronic renal failure and renal replacement therapy are not well characterized in young people. These abnormalities are becoming more important because successful renal transplantation has resulted in children with end-stage renal failure living longer. Echocardiographic abnormalities of cardiac function and structure were studied in children and young adults (< 27 years old) with chronic renal failure (CRF, N = 32), end-stage renal failure treated with chronic peritoneal dialysis (CPD, N = 10) or renal transplantation (N = 30) or controls (N = 60). Left ventricular mass indexed for height (LVM/Ht and LVM/Ht2.7) and body surface area (LVM/SA), fractional shortening, measurement of left ventricular diastolic function (peak E and A wave velocities and the EA ratio) and structural (such as valvular) abnormalities were determined by echocardiography. The median (and range) of LVM/Ht in the groups were control 51.8 (23.1 to 119.8), CRF 60.2 (22.2 to 135.8), CPD 80.2 (14.5 to 100.9) and transplant group 97.8 (51.2 to 182.1) g/m. The increases in LVM/Ht, LVM/Ht2.7 and LVM/SA in the transplant group were significant (P < 0.01). The CRF group had significantly increased LVM/Ht2.7 and LVM/SA (P < 0.01). Systolic function was not significantly different between the groups. A significant correlation between creatinine and LVM indexed for height was found in the CRF group. Systolic or diastolic blood pressure could not be correlated with LVM indices in the transplant group. Changes in diastolic function were found (increased peak A wave velocity and decreased E/A ratios in the CRF and CPD groups, and increased peak E wave velocity in the transplant group). The study demonstrated that left ventricular hypertrophy is a frequent and often severe finding in children with chronic renal failure and those treated with renal replacement therapy. Factors other than hypertension and anaemia are important, and evidence was found for a link between serum creatinine and increased left ventricular mass prior to end-stage renal failure.

Adolescent↗
PubMed1995

Familial hypomagnesaemia--hypercalciuria leading to end-stage renal failure.

Several disorders of hypomagnesaemia of hetary renal origin are now recognised. The cases of two sisters from a consanguineous marriage with the syndrome of renal magnesium wasting, hypercalciuria and nephrocalcinosis are presented. Pathological examination of the heterozygous parental kidneys revealed mild focal interstitial fibrosis. This condition is a previously unreported cause of end-stage renal failure in childhood, and this report suggests that transplantation from heterozygous parental donors can be successfully undertaken without recurrence of the syndrome.

Calcium↗
PubMed1995

Renal transplantation in young children.

AIMS: To review the outcome of renal transplantation in small children treated with triple immunosuppression at a single Australian centre. METHODS: The medical records of all children under the age of five years undergoing renal transplantation from 1988 were reviewed. The duration of follow-up was 30 months (range 18-36). RESULTS: Six children received seven renal allografts (five living-related [LR] and two cadaveric [CD]). They had a median age of 3.75 years (range 1.5-4.9) and weight of 11.6 kg (9.1-14.5) at the time of transplantation. All patients received an immunosuppressive regime involving cyclosporin A, azathioprine and prednisolone. There were no deaths. The only graft lost was a CD graft (severe acute rejection within one week of transplantation). Hypertension occurred in all recipients and usually required more than one antihypertensive drug for treatment. Renal function measured by serum median creatinine concentration (range) was 0.05 mmol/L (0.03-0.11) at three months (n = 6) and 0.10 mmol/L (0.07-0.22) at 30 months (n = 4). Growth estimated from median (range) height standard deviation scores was -1.97 (-1.36-(-4.04)) at three months (n = 6) and -1.90 (-1.74-2.50) at 30 months (n = 4). No patient was entirely weaned from prednisolone. Cyclosporin A side effects included hirsutism (five patients), gingival hyperplasia (six patients) and nephrotoxicity (three patients). CONCLUSIONS: Satisfactory patient and graft survival can be accomplished in this recipient age group. The results compare with other international experience and accumulating Australian experience. Hypertension and poor skeletal growth were consistent observations. The long-term outcome of renal function using triple immunosuppression remains to be determined.

Azathioprine↗
PubMed1995

Sonographic measurement of renal enlargement in children with acute pyelonephritis and time needed for resolution: implications for renal growth assessment.

OBJECTIVE: Failure of a kidney to grow satisfactorily in childhood is evidence of renal disease. Because kidneys may enlarge during an episode of acute pyelonephritis, concomitant renal length measurements cannot be used as baselines for growth assessment. This study was designed to determine the degree of renal enlargement in children with acute pyelonephritis and the time the enlargement takes to resolve after treatment is started to find the optimum time for obtaining baseline measurements. SUBJECTS AND METHODS: In a cohort study, 180 children younger than 5 years old with their first proven acute urinary tract infection, with or without pyelonephritis, had renal scintigraphy and sonography within 15 days of starting treatment. The presence of cortical defects on scintigrams indicated pyelonephritis. The lengths of kidneys with and without scintigraphic defects (i.e., with and without pyelonephritis) were compared, adjusting for age and sex, and the length of kidneys with defects was related to time elapsed between the start of treatment and sonography. RESULTS: Ninety-nine kidneys (28%) in 77 children (43%) had scintigraphic defects. Kidneys with defects were an average of 3.2 mm longer than kidneys without defects. Length and time interval between treatment and sonography in kidneys with defects correlated negatively, with mean length approaching that of kidneys without defects by 10-11 days. CONCLUSION: Kidneys with acute pyelonephritis initially increase in length but return to normal on average by the 11th day of treatment. If poor renal growth is used as an indication of renal disease, sonography should be delayed or repeated at least 2 weeks after the start of treatment to determine the length of the uninflamed kidney.

Acute Disease↗
PubMed1994

Triple immunosuppression with subsequent prednisolone withdrawal: 6 years' experience in paediatric renal allograft recipients.

Thirty-four children (< or = 15 years of age) with end-stage renal failure received 39 renal allografts between 1985 and 1991 and were treated with cyclosporin A (CyA), azathioprine and low-dose prednisolone (PNL). We aimed to withdraw PNL by 6 months after transplantation. Median duration of follow-up was 2 years 4 months (range 0.1 month to 6 years 4 months). There were no deaths. Crude graft survival for living-related grafts (n = 9) was 100%, although only 1 patient has been followed for > 2 years. For cadaveric grafts (n = 30), 1- and 5-year actuarial graft survivals were 90% and 79% respectively. At 12 months posttransplant, the median (range) glomerular filtration rate for all patients was 63 (19-109) ml/min per 1.73 m2 (n = 25) and at 5 years was 48 (17-64) ml/min per 1.73 m2 (n = 9). Complications observed included rejection episodes which occurred after discontinuation of PNL. Long-term (after 12 months), 28% of patients remain on PNL. Hypertension was present in more than 50% of patients. Severe CyA nephrotoxicity was not seen. Catch-up growth as determined by the change (delta) in mean height standard deviation score (Ht-SDS) was noted at 1 year [delta SDS/year = +0.60; P < 0.001 (n = 18)] and at 2 years [delta SDS/year = +0.27; P < 0.01 (n = 16)] in pre-pubertal patients. The median Ht-SDS at 2 years for pre-pubertal children was -0.71 SD and growth velocity did not improve thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1994

Tamm-Horsfall protein: are serum levels a marker for urinary tract obstruction?

Tamm-Horsfall protein (THP) has been found in the renal interstitium in patients with obstructive uropathy. The aim of this study was to investigate whether serum concentrations of THP could serve as a screening test for urinary tract obstruction. The presence of THP in normal human serum was confirmed by sodium dodecyl sulphate polyacrylamide gel electrophoresis and Western blotting. A specific enzyme immunoassay was then used to measure the serum concentration of THP. Serum THP concentrations were estimated in a cross-sectional study of a group of 23 patients who had technetium-99m-diethylene-triaminepenta-acetic acid (DTPA) nuclear urinary excretion studies to define urinary tract obstruction, and in longitudinal studies in 2 patients who developed acute bilateral ureteric obstruction following operations for ureteric reimplantation. The subjects with DTPA-proven urinary tract obstruction had higher concentrations of serum THP (n = 10, median = 43.9 ng/ml, range 10.4-152.1 ng/ml) than those who did not have obstruction (n = 13, median = 9.6 ng/ml, range 1.26-61.9 ng/ml). While this difference was significant (P < 0.01, Mann-Whitney U test), 6 of the 10 patients with obstruction had serum THP concentrations within the range of those patients without obstruction. The patients who developed acute bilateral ureteric obstruction both had increases in serum THP concentrations with obstruction and decreases in serum THP concentrations following relief of obstruction. These changes paralleled those in serum creatinine. The studies indicate that urinary tract obstruction results in increases in serum THP concentrations but these changes are not sufficient in magnitude to allow screening of children for urinary tract obstruction.

Adolescent↗
PubMed1994

The effect of growth hormone on growth and blood urea levels in children with chronic renal failure.

It has been claimed that low protein diets slow deterioration of chronic renal failure (CRF) by reducing renal solute load. The anabolic effect of recombinant human growth hormone (rhGH) also has potential to reduce renal solute load and thereby slow progression of renal failure. The aim of this study was to determine the effect of rhGH on growth, renal solute load and renal function in children with CRF. Seven prepubertal children, aged 2-14 years, with moderately severe CRF (creatinine clearance 7.7-23.4 mL/min per 1.73m2) were treated with daily subcutaneous rhGH, 1 U/kg per week for 10-12 months. As expected, mean height velocity standard deviation scores (SDS) increased, from -2.87 before treatment to +3.39 on rhGH, and mean height increased from -3.1 to -2.4 SDS. Serum urea concentrations decreased in most patients during the first month of growth hormone treatment from a mean of 20.0 +/- 7.7 mmol/L to 14.8 +/- 5.8 mmol/L (P = 0.006). The serum urea then returned to pretreatment levels over the next few months. In the 12 months before treatment with growth hormone, mean creatinine clearance decreased from 19.3 mL/min per 1.73 m2 to 16.7 mL/min per 1.73 m2. In the next 12 months on rhGH mean creatinine clearance decreased further to 13.5 mL/min per 1.73 m2. Therefore the rate of deterioration of renal function was unaffected during treatment with growth hormone. Initial treatment with rhGH is associated with decrease in serum urea concentrations in children with CRF, probably mediated by stimulation of anabolic incorporation of dietary nitrogen into body protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Vesicoureteral reflux: an accurate predictor of acute pyelonephritis in childhood urinary tract infection?

PURPOSE: To determine the association between vesicoureteral reflux (VUR) and the presence of acute pyelonephritis in children with urinary tract infections. MATERIALS AND METHODS: The authors studied 150 consecutive patients less than 5 years of age with their first proved urinary tract infection. All patients underwent renal cortical scintigraphy (with technetium-99m dimercaptosuccinic acid or Tc-99m gluconate) and voiding cystourethrography (VCUG) to identify the presence of cortical defects and VUR, respectively. RESULTS: Of 300 kidneys, 88 (29.3%) had a cortical defect at scintigraphy. Fifty-four of the 88 patients (61%) did not have VUR demonstrated at VCUG. Conversely, 72 of the 300 kidneys (24%) had VUR; of these, 38 (53%) had no cortical defect. The sensitivity of VCUG in helping predict a defect was 38.6%, and the specificity was 82.1%. CONCLUSION: VUR (as shown by VCUG) and renal cortical scintigraphic defects frequently occur independently of each other. Renal cortical scintigraphy may be a more accurate predictor of patients at risk for scarring.

Acute Disease↗
PubMed1994

Risk factors in the development of early renal cortical defects in children with urinary tract infection.

OBJECTIVE: Defects seen on early cortical scintigrams of the renal cortex in children with urinary tract infection may represent acute inflammatory change or established scar. The purpose of this study was to determine the relationship between these defects and age, sex, the presence and grade of vesicoureteral reflux, and infective organism in a cohort of children examined after their first proved urinary tract infection. SUBJECTS AND METHODS: We prospectively examined 193 consecutive patients less than 5 years old who were seen at the ambulatory pediatric department during a 3-year period and had a first proved urinary tract infection. Children with obstructed or solitary kidneys were excluded. All patients were imaged with scintigraphy of the renal cortex and radiographic voiding cystourethrography within 15 days of diagnosis. The association of age, sex, the presence and grade of vesicoureteral reflux, and infective organism with a defect (acute pyelonephritis or a renal scar) seen on a cortical renal scan was studied. RESULTS: The prevalence of cortical defects was greater in the kidneys of patients less than 2 years old (96/290, 33%) than in older children (16/96, 17%) and greater in those with vesicoureteral reflux (41/92, 45%) than in those without it (71/294, 24%). Vesicoureteral reflux was absent in 63% (71/112) of kidneys with a cortical defect. No association with sex or infective organism was established. As well as having a greater prevalence of cortical defects, 145 (75%) of the 193 urinary tract infections included in the study were in children less than 2 years old. The kidneys of these younger patients also had a greater severity and prevalence of vesicoureteral reflux (74/290, 26%) than did those of older children (18/96, 19%). CONCLUSION: Early cortical defects are associated with an age less than 2 years and vesicoureteral reflux. However, the association of early defects with the presence and grade of vesicoureteral reflux is confounded by the declining prevalence and severity of reflux with age. A significant proportion of cortical defects occur in the absence of vesicoureteral reflux, and the contribution of reflux to scar formation might be less than previously considered.

Age Distribution↗