Quantifying Förster Resonance Energy Transfer from Single Perovskite Quantum Dots to Organic Dyes

Colloidal quantum dots (QDs) are promising regenerable photoredox catalysts offering broadly tunable redox potentials along with high absorption coefficients. QDs have thus far been examined for various organic transformations, water splitting, and CO2 reduction. Vast opportunities emerge from coupling QDs with other homogeneous catalysts, such as transition metal complexes or organic dyes, into hybrid nanoassemblies exploiting energy transfer (ET), leveraging a large absorption cross-section of QDs and long-lived triplet states of cocatalysts. However, a thorough understanding and further engineering of the complex operational mechanisms of hybrid nanoassemblies require simultaneously controlling the surface chemistry of the QDs and probing dynamics at sufficient spatiotemporal resolution. Here, we probe the ET from single lead halide perovskite QDs, capped by alkylphospholipid ligands, to organic dye molecules employing single-particle photoluminescence spectroscopy with single-photon resolution. We identify a Förster-type ET by spatial, temporal, and photon-photon correlations in the QD and dye emission. Discrete quenching steps in the acceptor emission reveal stochastic photobleaching events of individual organic dyes, allowing a precise quantification of the transfer efficiency, which is >70% for QD-dye complexes with strong donor-acceptor spectral overlap. Our work explores the processes occurring at the QD/molecule interface and demonstrates the feasibility of sensitizing organic photocatalysts with QDs.

Colloidal Aziridinium Lead Bromide Quantum Dots

The compositional engineering of lead-halide perovskite nanocrystals (NCs) via the A-site cation represents a lever to fine-tune their structural and electronic properties. However, the presently available chemical space remains minimal since, thus far, only three A-site cations have been reported to favor the formation of stable lead-halide perovskite NCs, i.e., Cs+, formamidinium (FA), and methylammonium (MA). Inspired by recent reports on bulk single crystals with aziridinium (AZ) as the A-site cation, we present a facile colloidal synthesis of AZPbBr3 NCs with a narrow size distribution and size tunability down to 4 nm, producing quantum dots (QDs) in the regime of strong quantum confinement. NMR and Raman spectroscopies confirm the stabilization of the AZ cations in the locally distorted cubic structure. AZPbBr3 QDs exhibit bright photoluminescence with quantum efficiencies of up to 80%. Stabilized with cationic and zwitterionic capping ligands, single AZPbBr3 QDs exhibit stable single-photon emission, which is another essential attribute of QDs. In particular, didodecyldimethylammonium bromide and 2-octyldodecyl-phosphoethanolamine ligands afford AZPbBr3 QDs with high spectral stability at both room and cryogenic temperatures, reduced blinking with a characteristic ON fraction larger than 85%, and high single-photon purity (g(2)(0) = 0.1), all comparable to the best-reported values for MAPbBr3 and FAPbBr3 QDs of the same size.

Designer phospholipid capping ligands for soft metal halide nanocrystals

The success of colloidal semiconductor nanocrystals (NCs) in science and optoelectronics is inextricable from their surfaces. The functionalization of lead halide perovskite NCs1-5 poses a formidable challenge because of their structural lability, unlike the well-established covalent ligand capping of conventional semiconductor NCs6,7. We posited that the vast and facile molecular engineering of phospholipids as zwitterionic surfactants can deliver highly customized surface chemistries for metal halide NCs. Molecular dynamics simulations implied that ligand-NC surface affinity is primarily governed by the structure of the zwitterionic head group, particularly by the geometric fitness of the anionic and cationic moieties into the surface lattice sites, as corroborated by the nuclear magnetic resonance and Fourier-transform infrared spectroscopy data. Lattice-matched primary-ammonium phospholipids enhance the structural and colloidal integrity of hybrid organic-inorganic lead halide perovskites (FAPbBr3 and MAPbBr3 (FA, formamidinium; MA, methylammonium)) and lead-free metal halide NCs. The molecular structure of the organic ligand tail governs the long-term colloidal stability and compatibility with solvents of diverse polarity, from hydrocarbons to acetone and alcohols. These NCs exhibit photoluminescence quantum yield of more than 96% in solution and solids and minimal photoluminescence intermittency at the single particle level with an average ON fraction as high as 94%, as well as bright and high-purity (about 95%) single-photon emission.

Single-photon superradiance in individual caesium lead halide quantum dots

The brightness of an emitter is ultimately described by Fermi's golden rule, with a radiative rate proportional to its oscillator strength times the local density of photonic states. As the oscillator strength is an intrinsic material property, the quest for ever brighter emission has relied on the local density of photonic states engineering, using dielectric or plasmonic resonators1,2. By contrast, a much less explored avenue is to boost the oscillator strength, and hence the emission rate, using a collective behaviour termed superradiance. Recently, it was proposed3 that the latter can be realized using the giant oscillator-strength transitions of a weakly confined exciton in a quantum well when its coherent motion extends over many unit cells. Here we demonstrate single-photon superradiance in perovskite quantum dots with a sub-100 picosecond radiative decay time, almost as short as the reported exciton coherence time4. The characteristic dependence of radiative rates on the size, composition and temperature of the quantum dot suggests the formation of giant transition dipoles, as confirmed by effective-mass calculations. The results aid in the development of ultrabright, coherent quantum light sources and attest that quantum effects, for example, single-photon emission, persist in nanoparticles ten times larger than the exciton Bohr radius.

Limited evaluation of microscopic hematuria in pediatrics

OBJECTIVE

The purpose was to determine the value of the standard laboratory and radiologic evaluation of microscopic hematuria in children, and to determine the prevalence of idiopathic hypercalciuria in those children referred for evaluation of unexplained microscopic hematuria.

METHODS

This was a retrospective study of 325 children referred from 1985 to 1994 for the evaluation of asymptomatic microscopic hematuria. The diagnostic studies reviewed included serum creatinine, blood urea nitrogen, serum electrolyte studies, serum complement concentration, antinuclear antibody, urinalysis, urine calcium to creatinine ratios, urinary protein to creatinine ratio and/or 24-hour urinary protein excretion, renal ultrasounds, intravenous pyelograms, voiding cystourethrograms, and historical information.

RESULTS

All creatinine and electrolyte values were normal for age, and none of the biochemical tests obtained in the children with hypercalciuria was abnormal. Of the 325 patients with idiopathic microscopic hematuria, only 18 had abnormal renal ultrasound examinations and 9 voiding cystourethrograms showed low-grade reflux. Hypercalciuria was found in 29 patients. The family history was positive for urolithiasis in 16% of patients without hypercalciuria compared with 14% of patients with hypercalciuria. A positive family history of hematuria was reported in 25% of patients; 62 patients did not have hypercalciuria and 4 of the patients had hypercalciuria. Microscopic hematuria in children is a benign finding in the vast majority of children.

CONCLUSIONS

Our data demonstrate that a renal ultrasound, voiding cystourethrogram, cystoscopy, and renal biopsy are not indicated in the work-up of microscopic hematuria, and microhematuria in the otherwise healthy child is a minimal health threat, rarely indicative of serious illness.

Special topics in pediatric hypertension

This review emphasizes four major areas of pediatric hypertension. Because hypertension is the most common reason student athletes fail the sports pre-participation examinations, we have attempted to provide a rationale approach to the decision process to permit a hypertensive child to partake in leisure and competitive sports. Without question, obesity is a major reason for referral for hypertension to a pediatric nephrologist. The work-up should be directed to diet control and an exercise program to achieve sustained weight reduction. Hypertension associated with chronic renal failure and renal disease secondary to insulin-dependent diabetes mellitus is a major problem in pediatric and adult nephrology. With adequate control of systemic blood pressure, progressive decline in renal function may be delayed. By understanding these common areas of associated pediatric hypertension, a more systematic approach to the evaluation and treatment can be achieved.

Nitric oxide metabolism following unilateral renal ischemia/reperfusion injury in rats

Renal ischemia/reperfusion (I/R) injury results in decreased glomerular filtration and renal blood flow (RBF) and increased urine output, characterized by natriuresis and impaired concentrating ability. We studied unilateral I/R in rats to assess renal handling of nitric oxide (NO). Prior to I/ R, we measured urine flow rate (V), inulin clearance (C[IN]), para-aminohippuric acid clearance (C[PAH]), NO clearance (C[NOx] determined from metabolites NO2 and NO3), tubular transport of NOx (T[NOx], filtered load +/- urinary excretion), urine sodium and potassium excretion (U[Na]V, U[K]V), fractional excretion of sodium (FENa), and fractional excretion of NOx (FENOx) in each kidney. The left renal artery was then ligated for 30 min, followed by 30 min of reperfusion, and all measurements were repeated. C(IN) and C(PAH) were decreased in I/R kidneys compared with the contralateral kidney or pre-ischemia controls. V, FENa, and U(K)V were all significantly increased in I/R kidneys. Plasma NOx concentration was lower after injury in all animals (23.3 +/- 2.8 post injury vs. 30.4 +/- 7.7 microM pre injury, P < 0.05). C(NOx) was significantly higher in I/R kidneys (0.14 +/- 0.05 ml/min per g kidney weight) than in pre-injury kidneys (0.03 +/- 0.02 right, 0.04 +/- 0.30 left) or the contralateral controls (0.04 +/- 0.02) (P < 0.05 for all three controls). T(NOx) showed net tubular reabsorption of NOx in all kidneys (11 +/- 6 in post-ischemic left kidneys vs. 25 +/- 20 in left pre-ischemia, 33 +/- 13 in right pre-ischemia, and 21 +/- 4 right post-ischemia, nM/min per g kidney weight, P = NS). FENOx was higher in injured kidneys (28% +/- 18) than in pre-injury (3% +/- 0.6, 5% +/- 3) or contralateral controls (6% +/- 3) (P < 0.05 for all three controls). Renal NOx excretion and clearance are increased despite decreased plasma levels of NO metabolites after I/R injury. This increased excretion is not dependent on RBF or glomerular filtration, but may be related to impaired tubular reabsorption of NOx combined with increased intra-renal NO production.

Nitric oxide-inhibitory effect of aminoguanidine on renal function in rats

Inhibition of nitric oxide (NO) synthesis by structural analogues of L-arginine reduces glomerular filtration, renal blood flow, sodium excretion, and urine output. N(G)-nitro-L-arginine methyl ester (L-NAME) inhibits constitutive and inducible isoforms of NO synthase, while aminoguanidine (AG) selectively inhibits inducible isoforms of NO synthase. We assessed the NO-inhibitory activity of AG on renal function. Rats were treated with aminoguanidine 50 mg/kg daily for 2 months, followed by L-NAME (25 mg/kg/day) for 1 week to inhibit all NO synthase isoforms. After treatment with L-NAME, we performed baseline renal function measurements, then infused L-arginine (2.5 mg/100 g BW x min) to reverse NO inhibition and assessed whether AG exerted NO-inhibitory activity independently of L-NAME. Prior to L-arginine infusion, AG-treated rats did not differ from controls with respect to body weight, kidney weight, systolic blood pressure, urine flow rate, urinary protein or albumin excretion, or urinary excretion of NO metabolites. After L-arginine infusion, all animals showed a 10-15% decrease in mean arterial blood pressure. L-Arginine-induced increases in urine flow, inulin clearance, PAH clearance, sodium excretion, and NO metabolite excretion were blunted in aminoguanidine-treated animals. To assess long-term effects of aminoguanidine, rats were treated for 12 months. Urinary excretion of NO metabolites was lower than controls. Inulin clearance was higher than controls. Aminoguanidine blunts the effect of L-ariginine on renal hemodynamics independently of the nitric oxide synthase inhibitor, L-NAME. However, the use of aminoguanidine for 12 months in rats did not adversely affect renal function.

Screening dipstick urinalysis: a time to change

OBJECTIVE

This study attempted to determine the minimal cost of screening dipstick urinalyses in a hypothetical cohort of 2000 asymptomatic pediatric patients in a primary care setting.

METHODOLOGY

The minimal cost utilizing a private practitioner in an urban or suburban group pediatric setting was calculated. Costs were determined by using current charges for supplies ordered to perform tests in the office, charges for tests performed by a commercial laboratory, and the cost of an initial evaluation by a pediatric nephrologist. Data from published studies were also utilized.

RESULTS

Nine percent (179/2000) of patients were calculated to have an initial abnormal urinalysis. Upon retesting only 1.5% (29/2000) of patients were calculated to have a persistent abnormality. The calculated rate of a false positive/transient abnormality for all patients in the hypothetical cohort of 2000 asymptomatic pediatric patients was 84% (150/179). The calculated minimal cost for the outpatient evaluation of 2000 asymptomatic pediatric patients by dipstick urinalyses ranged between $5022 to $6475. The range depends on whether 50% versus 100% of patients with a repeat abnormal dipstick urinalysis were referred to a pediatric nephrologist for further evaluation. The calculated cost was $1290 to initially screen all 2000 patients with a dipstick urinalysis or 65 cents per patient. The calculated cost to evaluate the 29 patients with any persistent abnormality on repeat dipstick urinalysis was $3732 to $5185 or $129 to $179 per patient. This is the calculated cost for a single screening of 2000 asymptomatic pediatric patients. The calculated cost for four multiple screening urinalyses as currently recommended is $20 088 to $25 900. Additionally, these are only minimal initial calculated costs. Costs of any renal imagining or function studies ordered by the pediatric nephrologist or the pediatrician pursuing a further evaluation on his/her own were not included.

CONCLUSION

Multiple screening dipstick urinalyses in asymptomatic pediatric patients are costly and should be discontinued. In their place, we propose that a single screening dipstick urinalysis be obtained at school entry age, between 5 and 6 years old, in all asymptomatic children. The sample should be a first morning void.

Renal transplantation in children from 1987-1996: the 1996 Annual Report of the North American Pediatric Renal Transplant Cooperative Study

The 1996 Annual Report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) summarizes data voluntarily collected from 130 centers on 4329 children and adolescent patients who received renal transplants on or after January 1, 1987. This report updates information on transplants; data on dialysis and chronic renal insufficiency have, for the first time, been reported separately (in submission). The NAPRTCS registry shows that the majority of pediatric renal transplants are performed in children above 6 years of age (73%). The most frequent diagnoses include obstructive uropathy (16%), aplastic/hypoplastic/dysplastic kidneys (16%), and focal segmental glomerulosclerosis (12%). Pre-emptive transplantation was performed in 24% of patients. Triple drug maintenance therapy with prednisone, cyclosporine and azathioprine was used by >70% of all transplant recipients throughout 7 years of follow-up. Fifty-six per cent of transplant recipients were rehospitalized during months 1-5 (51% live donor (LD), 62% cadaver donor (CD)), with rejection and infection as the main causes. In the period 30-35 months post-transplant, 19-22% of patients (163 LD, 185 CD) were rehospitalized. The median time to the first rejection was 46 days for CD transplants and 377 days for LD grafts (p<.001). Six-year graft survival rates were 73% and 56% for LD grafts and CD grafts, respectively (p<.001). The overall growth deficit was constant over a period of 60 months. However, children transplanted under 5 years of age reduce their height deficit by about one-third compared to an increase in height deficit of up to 22% for older children. The NAPRTCS data analysis also demonstrates a delay in first rejection episodes in LD compared to CD transplants, and a steady improvement in CD graft survival over the past 5 years in pediatric transplant recipients.

Enalapril and renal function in hypertensive rats transgenic for mouse renin gene

We examined the effect of long-term enalapril treatment on renal function and histology in the monogenetically hypertensive TGR(mRen2)27 rat strain. Untreated transgenic rats had significantly (P<.01) higher blood pressures than treated transgenic and control animals throughout the study. Urinary nitric oxide metabolite excretion was significantly lower in young transgenic rats and rose with enalapril, suggesting abnormal TGR nitric oxide production and its correction by enalapril. Converting enzyme inhibition produced preferential preglomerular vasodilatation and increased renal blood flow (6.5 +/- 0.5 versus 9.0 +/- 0.7 mL/min per gram kidney weight, P<.05) without altering whole-kidney and single-nephron glomerular filtration rates in TGR(mRen2)27. Glomerular capillary pressure fell modestly in treated transgenic animals (54 +/- 1 versus 50 +/- 1 mm Hg, P<.05). These hemodynamic changes were associated with reductions in albuminuria (59 +/- 6 versus 9 +/- 2 mg/d, P<.01) and glomerulosclerosis in TGR. However, urinary albumin excretion (15 +/- 3 versus 3 +/- 1 mg/d, P<.05) and glomerulosclerosis also declined in treated control animals in the absence of significant alterations in glomerular hemodynamics. The mechanism of the beneficial effect of enalapril on the TGR(mRen2)27 kidney is unclear but could involve either control of hypertension or suppression of the intrarenal renin-angiotensin system.

Hematuria. An integrated medical and surgical approach

The need to perform a detailed work-up of microscopic hematuria is based on the following set of questions: Does the history or physical examination findings suggest systemic or renal disease? Is the patient able to acidify and concentrate urine? Is proteinuria present? Do other family members have hematuria or other renal problems? Does the microscopic analysis show casts, crystals, or WBCs? Are the RBCs eumorphic or dysmorphic? Using this scheme of questions, most children do not require laboratory tests or radiographic studies. In the case of gross or macroscopic hematuria, the initial evaluation may require only a urine culture, urine calcium-to-creatinine ratio, and renal and bladder sonography or a very detailed evaluation for renal parenchymal disease, stones, tumors, or anatomic abnormalities. In these instances, consultation with a pediatric nephrologist, urologist, or both is necessary.

Laboratory predictors of fluid deficit in acutely dehydrated children

To determine which laboratory studies are most predictive of the fluid deficit in acutely dehydrated children, we studied a convenience sample of 40 children requiring intravenous fluid resuscitation. Nine laboratory studies (serum BUN/cr, total serum CO2, serum uric acid, serum anion gap, urine anion gap, venous pH, venous base deficit, urine specific gravity, and fractional excretion of sodium) were individually assessed in simple linear regression models with fluid deficit as the dependent variable. Only the serum BUN/cr and serum uric acid were significantly associated with increasing fluid deficit (r = 0.52, P = 0.0005 and r = 0.35, P = 0.03, respectively). The sensitivities and specificities of these two laboratory studies for the detection of > 5% fluid deficit were poor. Conventional laboratory studies used to assess dehydration in children are poorly predictive of fluid deficits.

Decreased urinary excretion of nitric oxide in acute rejection episodes in pediatric renal allograft recipients

Acute renal allograft rejection continues to have a negative effect on graft survival despite a better understanding of the molecular basis of renal allograft rejection. Nitric oxide (NO) has important biological functions in cell defense and injury and some evidence exists that it may act as an immunomodulator in allograft transplantation. To determine if NO has any role in acute renal allograft rejection in pediatric patients, acute rejection episodes in pediatric renal transplant recipients were evaluated. Four out of eleven patients who received a renal allograft in 1995 at Children's Kidney Center at The Children's Hospital of Buffalo had eight episodes of acute rejection. One patient received a living-related and three received cadaveric grafts. Stable metabolites of NO (NO-2 + NO-3 = NOx) were measured in the serum and urine samples of the patients daily. Serum levels of NO did not change significantly during acute rejection episodes. Urinary NOx levels decreased by 73+/-9% of the baseline values during episodes of acute rejection: mean +/-SE urinary nitric oxide/creatinine ratio (NOx/Cr) of 0.17+/-0.05 at baseline vs. 0.05+/-0.01 during rejection (P=0.02). Successful treatment of acute rejection by administration of high dose i.v. steroids or OKT-3 induced acute rises in the urinary NO levels to baseline values: NO/Cr = 0.17+/-0.04 (mean +/-SE). We conclude that urinary NO excretion decreases significantly during acute renal allograft rejection and that NOx concentration in the urine increases in response to successful antirejection therapy.

Nutritional intake in children with renal insufficiency: a report of the growth failure in children with renal diseases study

OBJECTIVE

This study was designed to assess sequentially the nutrient intake in children with chronic renal insufficiency and its relationship to body size, the level of renal failure, and growth velocity.

METHODS

The nutrient intake from 401 4-day food records obtained from 120 children with renal insufficiency over a 6-month observation period was analyzed. The height and weight were measured at the beginning and end of the observation period. The glomerular filtration rate was estimated from the height and serum creatinine.

RESULTS

The mean caloric intake in these children was 80 +/- 23% (mean +/- SD) of the Recommended Dietary Allowance (RDA) for age. Fifty-six percent of the food records obtained from these children revealed a caloric intake that was less than 80% of the RDA. Caloric intake expressed as the %RDA for age decreased with increasing age. However, the mean caloric intake when factored by body weight was in the normal range. There was no correlation between caloric intake and height velocity. The mean protein intake in these children was 153 +/- 53% of the RDA. Further, 45% of the food records indicated a protein intake greater than 150% of the RDA. There was no relationship between the degree of renal insufficiency and caloric or protein intake. Calcium, vitamin, and zinc intakes were also low.

CONCLUSIONS

Children with chronic renal failure consume less calories than their age matched peers, but the majority of these children appear to ingest adequate amounts for their body mass. This reduction in caloric intake occurs early in renal insufficiency. They also ingest inadequate amounts of calcium, zinc, vitamin B6, and folate.

Hypertensive encephalopathy and reversible magnetic resonance imaging changes in a renal transplant patient

An 18-year-old renal transplant patient presented with sudden onset of seizures almost 2 years after she received the graft. Diagnostic work-up was unrevealing except for magnetic resonance imaging abnormalities of the brain that resolved spontaneously 4 weeks later. In this brief report, we discuss the etiology of the seizures and neurological abnormalities in renal transplant patients in light of the findings of our patient.

Prolonged hypocomplementemia in poststreptococcal acute glomerulonephritis

Complement levels conventionally return to normal in eight weeks in patients with poststreptococcal acute glomerulonephritis (PSAGN). The objective of this study was to determine the significance of prolonged hypocomplementemia (> 8 weeks) in this group of patients. Between April 1993 and January 1995, 20 patients were followed prospectively for a mean of 6 months (range 3-20 months after the episode of PSAGN. Serum C3 concentrations were measured at diagnosis and at regular intervals. Five patients (26%) had prolonged hypocomplementemia. Percutaneous renal biopsies were performed in three patients which revealed findings consistent with the clinical diagnosis of PSAGN. All of these patients showed gradual improvement of their symptoms; some have persistent microscopic hematuria without proteinuria. Kidney function is normal in all despite hypocomplementemia. We conclude that hypocomplementemia (> 8 weeks) with resolving features of acute glomerulonephritis does not exclude the diagnosis of PSAGN, and a renal biopsy may be deferred if there is clinical improvement.

Spectrum of glomerulocystic kidneys: a case report and review of the literature

An 8-year-old boy developed end-stage renal disease 7 years after the in utero diagnosis of bilateral cystic kidneys. There was no history of cystic renal disease in the family. Initial ultrasonographic screening of the parents failed to reveal cysts in the kidneys. Pathological evaluation of the kidney biopsy findings was consistent with the glomerulocystic kidney disease. He had bilateral nephrectomies in preparation for a living related renal transplant at 7 years of age. At that time, a repeated renal ultrasound examination of the mother showed bilateral cystic kidneys. Pathological evaluation of the nephrectomy specimens confirmed the diagnosis of autosomal dominant polycystic kidney disease. In this report, a discussion of the differential diagnosis of glomerular cysts and the relationship of glomerulocystic kidney disease and autosomal dominant polycystic kidney disease is provided.

Sex chromosomes do not influence renal injury in borderline hypertensive rats

The present study was undertaken to investigate whether the development of proteinuria in the borderline hypertensive rat (BHR) is influenced by the Y chromosome and to determine if the onset of proteinuria in the BHR is delayed when blood pressure is lowered with enalapril, an angiotensin I converting enzyme inhibitor. Male F1, rats were the first-generation offspring of the mating of spontaneously hypertensive (SHR) females and Wistar-Kyoto (WKY) males and the mating of SHR males and WKY females. At 20 weeks of age, enalapril (125 mg/l) was added to the drinking water. Untreated BHR and enalapril-treated BHR (BHRE) were followed to 90-100 weeks of age. Urine was collected every 10-20 weeks for determination of protein, albumin, and nitric oxide (NO2/NO3) metabolite excretion. Indirect blood pressure in BHR from both crosses was approximately 175 mm Hg from 20 to 90-100 weeks of age. Enalapril lowered blood pressure by about 30 mm Hg, but was ineffective in reducing urinary protein or albumin excretion rates at any age. Urinary excretion of nitric oxide metabolites was similar in all groups at all time periods. There were significant differences in the percent of glomerulosclerosis between the two matings. Based on these results, renal injury in the BHR is not associated with the Y chromosome and can be dissociated from hypertension. Further studies using congenic and transgenic technology will be necessary to identify functions of genes and associations with hypertension in order to understand the kidney disease in this model of hypertension.

Resistance to glomerular injury in the diabetic biobreeding rat

This study was designed to determine whether the diabetic BioBreeding rat develops significant renal injury following long-term moderate to severe hyperglycaemia. Diabetic and control rats were followed from the onset of diabetes (2-4 months) to 18 months of age. Frank proteinuria and/or albuminuria were always absent. Glomerular filtration rate, measured by inulin clearance (ml min-1 (100 g body weight)-1), was significantly higher in diabetic rats than in controls at 10, 12 and 18 months of age. Advanced glycosylation end-product cross-links assessed by percentage solubility of tail tendon collagen were moderately increased in diabetic compared with control animals. Urinary excretion of advanced glycosylation end-products in unfractionated urine and in urine fractionated for low molecular mass peptides (< 10 kDa) was 11-fold greater in the diabetic rats than in the control group. Urinary excretion of nitric oxide metabolites (nmol NO2- and NO3- (24 h)-1) were significantly (P < 0.05) greater in diabetic rats than in controls after 8 months of age. Mild histopathology resembling human diabetic nephropathy, including increased mesangial volume and glomerular basement membrane thickness, was detected at 18 months of age. The findings of hyperfiltration and mild glomerular morphological changes in diabetic BioBreeding rats are similar to the abnormalities seen in stage 2 human diabetic nephropathy. We hypothesize that two factors which may contribute to the resistance or tolerance to renal injury in the BioBreeding diabetic rat are increased nitric oxide production and the decreased accumulation of advanced glycosylation end-products.

Hematuria in children and adolescents with insulin-dependent diabetes mellitus

Hematuria is not described as a common finding in diabetic nephropathy, and may suggest nondiabetic renal disease. We reviewed the records of 59 children and adolescents with insulin-dependent diabetes mellitus referred to the Children's Kidney Center from 1983 to 1992. Fifty-two patients had clinical and/or biopsy evidence of diabetic nephropathy; 18/52 (35%) had microscopic hematuria at the time of referral. Patients with hematuria on presentation were referred for: hypertension (61%), proteinuria (61%), and decreased glomerular filtration rate (GFR) (11%). For patients without hematuria on presentation, reasons for referral included hypertension (79%), proteinuria (56%), and decreased GFR (3%). When comparing patients with and without hematuria, those with hematuria had a significantly longer duration of diabetes (12.8 +/- 3.1 versus 10.8 +/- 3.7 years, p < 0.05). The groups did not differ significantly with regard to age (18.3 +/- 1.8 versus 17.1 +/- 2.9 years), height (162.2 +/- 10.4 versus 159.3 +/- 11.3 cm), weight (63.9 +/- 10.9 versus 59.4 +/- 14.8 kg), systolic blood pressure (137.2 +/- 11.9 versus 133.2 +/- 13.2 mm Hg), diastolic blood pressure (85.6 +/- 7.6 versus 83.9 +/- 13.4 mm Hg), serum creatinine (1.0 +/- 0.18 versus 1.0 +/- 0.43 mg/dL), blood urea nitrogen (15 +/- 5 versus 13 +/- 4 mg/dL), glomerular filtration rate (117 +/- 34 versus 117 +/- 46 mL/min/1.73 m2), 24-h urine protein (2311 +/- 3862 versus 570 +/- 476 mg/day), or microalbuminuria (75 +/- 41 versus 34 +/- 35 micrograms/min). We detected a significant association between retinopathy and microscopic hematuria (sensitivity 47%, specificity 82%, p < 0.05), but no association between labstix proteinuria or sex and hematuria.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between calcium, phosphorus, and sodium intake, race, and blood pressure in children with renal insufficiency: a report of the Growth Failure in Children with Renal Diseases (GFRD) Study

Nutritional data compiled during the Growth Failure in Children with Renal Diseases Clinical Trial were analyzed to determine the relationship between the dietary intake of divalent minerals and sodium, nutritional status, and serum calcium, phosphorus, and parathyroid hormone (PTH) concentrations and blood pressure in black versus white children. One hundred eighteen patients are included in this report; 25 were black (21%) and 93 were white (79%). Although more of the blacks were male, the age distribution, midarm circumference, midarm muscle circumference, blood pressure, and serum calcium, phosphorus, and PTH concentrations were comparable in the two groups. Phosphorus intake was within the recommended daily allowance in both groups; in contrast, calcium intake was inadequate in all patients: 81% of the recommended daily allowance in whites, and 74% in blacks. Sixteen children were noted to be hypertensive during the observation period; six patients were receiving a variety of antihypertensive medications, including diuretics in two children. Linear regression analysis revealed that systolic and diastolic blood pressures were directly related to calcium and phosphorus intake in black patients. In white children, only dietary phosphorus intake and diastolic blood pressure were directly related. There was no relationship between sodium intake or GFR and blood pressure in the white or black children. PTH levels were directly correlated with systolic and diastolic blood pressure in all children. The correlations between PTH and blood pressure were stronger in white versus black patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Single nephron hemodynamics in spontaneously hypertensive rats

This study was designed to determine whether glomerular hypertension develops as a function of age in the spontaneously hypertensive rat (SHR). Male SHR and age-matched Wistar-Kyoto (WKY) normotensive controls were divided into three groups for measurements of whole kidney and single nephron hemodynamics at 5, 10, and 15 months of age. As reported previously, SHR developed significant proteinuria which was predominantly an albuminuria, after 5 months of age. There were no differences in whole kidney or single nephron glomerular filtration rates between SHR and WKY. Afferent glomerular capillary hydraulic pressure (PGC) was slightly increased in SHR compared with WKY at 10 months of age. At 15 months of age, PGC in SHR was significantly lower than WKY. Our studies indicate that increased capillary pressure is not a major factor in the development and progression of renal injury in the spontaneously hypertensive rat.

Dietary cholesterol supplementation in the spontaneously diabetic rat

Dietary cholesterol supplementation was used to increase serum cholesterol concentration in diabetic and non-diabetic rats. With the use of numerous dietary formulations, extremely elevated serum cholesterol concentrations and gastrointestinal intolerance were found. We conclude that there are unacceptable side effects with a vast number of exogenous cholesterol supplemented diets which preclude standard and long-term usage.

Microalbuminuria in an adolescent cohort with insulin-dependent diabetes mellitus

To document the incidence of microalbuminuria in children and adolescents with longstanding insulin-dependent diabetes mellitus (IDDM) and to compare the clinical characteristics and determinant risk factors of those with and without microalbuminuria, 135 adolescent patients with IDDM for 5 years or longer were evaluated. The study population was divided on the basis of microalbumin excretion into normal (< 20 micrograms/min), incipient (20-200 micrograms/min), and overt (> 200 micrograms/min) nephropathy groups. There were 106 patients in the normal group, 24 patients in the incipient group, and five in the overt nephropathy group. Glycosylated hemoglobin, cholesterol concentration, and glomerular filtration rate (GFR) were analyzed. The incidence of incipient and overt nephropathy was 17.8% and 3.7%, respectively. Mean cholesterol concentration in the incipient and overt nephropathy groups (208 +/- 39 mg/dL [5.4 +/- 1.0 mmol/L]) and 227 +/- 49 mg/dL [5.9 +/- 1.3 mmol/L], respectively) was significantly higher than the normal group (186 +/- 37 mg/dL [4.8 +/- 0.9 mmol/L] P < 0.05). Similarly, systolic and diastolic blood pressures were significantly higher in the incipient and overt nephropathy groups compared to the normal group. This study confirms the high incidence of incipient and overt nephropathy in adolescents with IDDM early in the course of the disease.

Applying decision analysis to management of adolescent idiopathic nephrotic syndrome

Due to the concern that adolescents presenting with nephrotic syndrome are less likely to have minimal change disease than younger children, pediatric nephrologists have tended toward renal biopsy-tailored treatment rather than corticosteroid use in this population. The need for biopsy prior to treatment of nephrotic syndrome in adults has been challenged. A similar challenge to the clinical need for this procedure in adolescents with idiopathic nephrotic syndrome is raised here. The principles of medical decision analysis were applied and calculations were made with the Decision Maker computer program. The life expectancy of an adolescent who receives biopsy-tailored treatment was found to be no different from that of an adolescent who receives empiric corticosteroid treatment. We conclude that renal biopsy is not mandatory for the clinical management of adolescents with idiopathic nephrotic syndrome. Prognostically, a response, or lack thereof, to empiric corticosteroid therapy may be just as informative as a histological diagnosis.

A proposed method for the noninvasive evaluation of renal asymmetry in a living-related donor candidate

This report proposes an adjunctive technique for the evaluation of asymmetry of renal size and function of undetermined etiology, discovered during the assessment of two living-related donor candidates. The method utilizes the observation of renal functional reserve measurement as demonstrated by oral protein loading in patients with normal and diseased kidneys. Renal function was measured as timed Ccr and estimation of differential GFR by technetium-99m diethylenetriaminepentaacetic acid (99mTcDTPA) scintigraphy. A comparison of renal function before and after protein loading in two such patients demonstrated the anticipated increase in GFR. No change in differential GFR as determined by renal scan in one patient was interpreted as supportive evidence for bilaterally normal parenchymal function. Follow-up of both donors shows continued normal renal function.

Changing pattern of glomerular disease at Beijing Children's Hospital

Current clinical experience with glomerular disease at a pediatric referral center in Beijing, China, was reviewed. In 1992, renal disorders accounted for 505 of a total 6,885 (7.3%) pediatric medical discharges. Acute glomerulonephritis accounted for 30% of renal diagnoses, while nephrotic syndrome accounted for 28% and Henoch-Schönlein purpura nephritis accounted for 16% of renal disease. Mortality in children with renal disease was 0.4% (two of 505). All children with acute glomerulonephritis recovered or improved at last follow-up, regardless of the relationship to a streptococcal infection. In children with uncomplicated nephrotic syndrome, 91% had a complete or partial response to corticosteroids. Nephritis developed in 81 of 278 patients with Henoch-Schönlein purpura (29%). Since 1956, a dramatic decrease in the diagnosis of acute glomerulonephritis has occurred at this pediatric hospital. Nephrotic syndrome, in contrast, has increased from 45.3 cases per year in the 1956-to-1965 decade to 146 cases annually in the period from 1986 to 1992. Similarly, Henoch-Schönlein purpura has increased from 45.3 cases annually in the 1956-to-1965 period to 238 cases per year in the past 6 years. The incidence of nephritis in patients with Henoch-Schönlein purpura has remained constant at 29% in the past 36 years. These data should be helpful for individuals and institutions who are planning educational or clinical collaborations with pediatric nephrologists in China.

Atrial septal aneurysm in a patient with autosomal dominant polycystic kidney disease

We describe a 6-year-old patient with autosomal dominant polycystic kidney disease, normal renal function, hypertension, and serial echocardiograms showing an aneurysm of the atrial septum. Intracardiac aneurysms have not previously been reported in patients with autosomal dominant polycystic kidney disease.

Renal function in hypertensive rats transgenic for mouse renin gene

The recent development of a transgenic rat strain carrying the mouse ren-2 renin gene [TGR(mRen2)27] has provided a new model of hypertension characterized by suppressed plasma renin levels and marked hyperproreninemia. In this long-term study, we examined the kidney function of these animals. Transgenic rats had significantly (P < 0.01) higher blood pressures than control animals at 2, 4, and 8 mo of age. However, the severity of their hypertension diminished over time (225 +/- 8 mmHg at age 2 mo vs. 169 +/- 5 mmHg at age 8 mo, P < 0.001), indicating age-dependent transgene regulation. Whole kidney and single-nephron blood flows and glomerular filtration rates did not differ between control and TGR(mRen2)27 animals studied with micropuncture techniques at 4 and 8 mo of age. Preglomerular vasoconstriction was responsible for this normal autoregulatory response. Elevated preglomerular vascular resistance of transgenic rats prevented transmission of systemic hypertension to glomeruli at 4 but not 8 mo of age leading to increased glomerular capillary pressures in these older animals (53 +/- 1 vs. 48 +/- 1 mmHg, P < 0.05). Pathological albuminuria appeared as early as 2 mo of age but did not increase over the subsequent 6 mo of follow-up. The incidence of glomerulosclerosis, assessed at 4 and 8 mo of age, was greater in TGR(mRen2)27 than control animals (6.6 +/- 1.4% vs. 0.9 +/- 0.3%, P = 0.01) but did not differ between 4- and 8-mo-old transgenic rats. Glomerular ultrafiltration coefficients were significantly elevated (P < 0.05) in transgenic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Type III posterior urethral valves: presentation and management

The clinical and radiographic presentation of infants with type III posterior urethral valves help to distinguish them from patients with the more common type I valves. The diaphragmatic valvular obstruction may make catheterization impossible. Percutaneous cystography can confirm the diagnosis and allow for short-term decompression. The presence of smooth-walled bladders with narrow posterior urethras is unique to type III valves but is not always present. Type III valves present within a spectrum of clinical severity; however, the majority involve significant renal impairment. The prognosis for survival and renal function appears poorer for patients with type III valves than for those with type I valves.

Two-day therapy with cefuroxime axetil is effective for urinary tract infections in children

Short-course therapy for pediatric urinary tract infection (UTI) remains controversial. The present study was undertaken to compare the effectiveness of cefuroxime axetil (Ceftin) as short-course (2-day) versus conventional (10-day) therapy for uncomplicated pediatric UTIs. In a randomized, controlled, prospective study, we enrolled 50 children, 2-11 years of age, to receive oral cefuroxime axetil, 125 mg twice a day, for either 2 or 10 days. UTI was defined as at least 10(5) colonies/ml of a single pathogen isolated on clean catch, or at least 10(4) colonies/ml on a catheterized specimen. A 10-fold or greater reduction in colony count of the initially isolated organism (3-5) days after stopping therapy was considered a bacteriologic success, as long as the absolute colony count was below the threshold for UTI described above. Patients were followed for 15 months with multiple repeat urine cultures and radiologic studies. Twenty-five of the 50 patients enrolled were withdrawn, including 12 for initially inadequate colony counts. Eight of 12 patients in the short-course group (67%), versus 12 of 14 in the conventional-therapy group (86%), were initial bacteriological successes, a nonsignificant difference. All 37 initially isolated uropathogens were sensitive to cefuroxime axetil in vitro. Cefuroxime axetil is an effective antimicrobial for uncomplicated pediatric UTIs. Two-day therapy with cefuroxime axetil appears to be as effective as 10-day therapy, although sample size was limited in this study.

Insurability for asymptomatic hematuria or proteinuria during childhood

The objective of this survey was to describe life insurance underwriting practices concerning children with asymptomatic hematuria and proteinuria. A questionnaire was sent to 200 companies licensed to issue life insurance policies in the state of New York. The medical director of each company was asked to respond to the insurability of children with asymptomatic hematuria and proteinuria. Two case summaries were provided with the questionnaire. Of 97 companies, 66 would offer insurance to the patient with hematuria, although 38 (58%) would charge additional premiums. In response to the problem of proteinuria, 61 companies would offer life insurance, although 50 (82%) would require higher premium charges (P < 0.002 compared with hematuria). We conclude that children with asymptomatic hematuria and proteinuria can usually obtain life insurance, although often at higher cost. Invasive diagnostic tests are not necessary for insurers to offer insurance.

Renal biopsy in children with asymptomatic hematuria or proteinuria: survey of pediatric nephrologists

The decision to perform a renal biopsy on children with asymptomatic hematuria or proteinuria remains a problem for clinicians. To assess the current opinion of 349 pediatric nephrologists on this issue, case summaries of a 9-year-old boy with 20 urinary red blood cells per high power field without proteinuria and a 9-year-old boy with 2+ proteinuria (600 mg/day) without hematuria were distributed to each specialist. Seventy-three percent (n = 256; 3:1, male:female) responded. Five percent would biopsy the child with asymptomatic hematuria. The main reasons were academic interest, parental pressure for a diagnosis/prognosis and concern for future economic impact on the child (i.e., life insurance). The determinations to biopsy for hematuria were not related to age or sex of the nephrologist. In contrast, 38% (n = 96) of the pediatric nephrologists would perform a biopsy on the child with proteinuria. The major reasons for biopsy were academic interest and potential for drug therapy. With a normal history, physical examination and laboratory/radiographic evaluation, the vast majority of pediatric nephrologists in North America support a conservative approach to the child with asymptomatic hematuria or proteinuria.

Serum creatinine, height, and weight do not predict glomerular filtration rate in children with IDDM

OBJECTIVE

To assess the validity of two equations: K x height/serum creatinine (KL/Cr; K = 0.55 for females 1-18 yr of age and 0.7 for males 12-18 yr of age) and (140 - age) x weight/72 x creatinine (x0.85 for women; Cockroft-Gault) in estimating glomerular filtration rate in children and adolescents with IDDM.

RESEARCH DESIGN AND METHODS

From the records of the Children's Hospital Diabetes Clinic, we selected 70 patients with GFR determined by 99mTc-labeled DTPA plasma clearance, stable renal function, and simultaneous measurements of height, weight, blood pressure, HbA1c, and plasma creatinine. We compared DTPA-GFR with estimated GFR from KL/Cr and Cockroft-Gault equations for three groups: all patients, patients with DTPA-GFR < or = 140 ml.min-1 x 1.73 m-2, and patients with DTPA-GFR > 140 ml.min-1 x 1.73 m-2.

RESULTS

For all patients, mean values for DTPA-GFR = 147 (95% confidence interval, 139-155), for KL/Cr = 118 (110-125), and for Cockroft-Gault = 84 ml.min-1 x 1.73 m-2 (78-90). For patients with DTPA-GFR < or = 140, DTPA-GFR = 123 (117-128), KL/Cr = 110 (100-119), and Cockroft-Gault = 92 (82-102). For patients with DTPA-GFR > 140, DTPA-GFR = 167 (158-177), KL/Cr = 125 (114-136), and Cockroft-Gault = 77 (71-84). Linear regression analysis showed significant (P < 0.05) relationships for KL/Cr only in patients with DTPA-GFR < or = 140 (r = 0.29), for Cockroft-Gault in all patients (r = -0.46), and for patients with DTPA-GFR < or = 140 (r = -0.31). Determination of a revised K for use in KL/Cr from individual calculations of K (DTPA-GFR x Cr/L) yielded an average value of 0.70 (SD = 0.11). With the use of K = 0.7, the mean KL/Cr value for patients with DTPA-GFR < or = 140 ml.min-1 x 1.73 m-2 was 125 +/- 27 (95% confidence interval, 115-135), compared with a DTPA-GFR value of 123 +/- 14 (95% confidence interval, 117-128).

CONCLUSIONS

KL/Cr and Cockroft-Gault do not accurately estimate DTPA plasma clearance. We recommend the use of K equal to 0.70 when estimating GFR in children and adolescents with IDDM and DTPA-GFR < or = 140 using KL/Cr and do not recommend the use of the KL/Cr (for patients with DTPA-GFR > 140) or the Cockroft-Gault equation in this population.

Endogenous creatinine clearance in the rat: strain variation

The clearance of endogenous creatinine was examined in five strains of rats (Wistar, Wistar Kyoto, Spontaneously Hypertensive Rats, Biobreeding/Worcester diabetic prone and diabetic resistant rats). Creatinine clearance was compared with inulin clearance as the standard. Conditions for clearance measurements were also varied (anesthesia with constant infusion, overnight collection of urine, fed vs. unfed state, single-injection technique). The clearance of creatinine adequately reflects the glomerular filtration rate in three strains (Wistar, Wistar-Kyoto and the Spontaneously Hypertensive Rat). In the two strains of the Biobreeding/Worcester rat creatinine clearance is consistently lower than the inulin clearance. When creatinine clearance is measured from an overnight collection of urine with food withheld it is always lower than when food is present. This clearance should always be validated by comparison with inulin clearance measured simultaneously or under comparable conditions. The ease with which endogenous creatinine clearance can be measured makes it a reasonable method when large numbers of repeated determinations of glomerular filtration rate are required.

Serum creatinine level and renal function in children

OBJECTIVE

To evaluate the accuracy of serum creatinine and height/serum creatinine glomerular filtration rate (Cr-GFR) formula as screening tests for abnormal renal function defined by plasma diethylenetriaminepenta-acetic acid (DTPA) clearance.

DESIGN

Patient series.

SETTING

The Children's Hospital of Buffalo (NY).

PATIENTS

Eighty-seven consecutive patients ranging in age from 2 to 20 years.

MEASUREMENTS

The Cr-GFR was calculated by means of the formula GFR (milliliters per minute per 1.73 m2) = kL/serum creatinine (milligrams per deciliter), where L is body length in centimeters and k is a constant dependent on age and sex. Plasma clearance of technetium Tc 99m-labeled DTPA was our reference method for determination of GFR (DTPA-GFR).

RESULTS

The Cr-GFR formula identified children with impaired renal function (DTPA clearance, less than 80 mL/min per 1.73 m2) with a sensitivity of 95% and a specificity of 93%. In contrast, the sensitivity and specificity of elevated serum creatinine level for this purpose were 80% and 96%, respectively. Of the children with renal insufficiency (DTPA clearance, 40 to 79 mL/min per 1.73 m2), 91% were correctly identified by the Cr-GFR formula. However, only 65% of these children had elevated serum creatinine levels. Although all children with renal failure (DTPA clearance, less than 40 mL/min per 1.73 m2) had abnormally high serum creatinine levels, the specificity of this test was significantly lower than that of the Cr-GFR formula (75% vs 100%, respectively).

CONCLUSIONS

The Cr-GFR formula is superior to serum creatinine level for estimating GFR. This formula provides a simple, reasonably accurate screening test for the presence and severity of impaired renal function.

Association of Kawasaki disease and interstitial nephritis

Renal insufficiency is a rare manifestation of Kawasaki disease. We report a 2.5-year-old boy with Kawasaki disease who developed acute renal failure during the acute phase of his illness. A percutaneous renal biopsy revealed acute interstitial nephritis. No etiological agent could be identified and renal recovery occurred with supportive care alone.

Long-term renal handling of sodium and calcium in spontaneously hypertensive rats

The renal handling of sodium and calcium in spontaneously hypertensive rats (SHR) was investigated over an extended period (10-75 weeks of age) and compared with age-matched normotensive Wistar-Kyoto controls. The animals were fed a standard rat chow except during screening periods when liquid diet that matched the pellet chow was substituted. Sodium balance, urinary excretion of sodium and calcium, fractional excretion of sodium (FENa), and renal cortical dopamine receptors (DA1 and DA2) were measured at 10, 30, 60 and 75 weeks of age. The results showed no difference between the two strains except for FENa, which was significantly higher in the SHR at 75 weeks coincident with decreased glomerular filtration rate. We conclude that a defect in renal handling of sodium and/or calcium is not a major factor in the maintenance of hypertension in the SHR.

Glomerular function in spontaneously diabetic rats

This study was undertaken to determine whether hyperfiltration exists at the single nephron level and whether albumin excretion is increased early in the course of diabetes in Biobreeding rats. Diabetic rats were studied at 8-12 weeks after the onset of diabetes. Control animals were age-matched, diabetes-resistant rats. Urinary and tubular fluid albumin concentrations were measured by polyacrylamide gel electrophoresis. Clearance and micropuncture techniques were used to determine whole kidney and single nephron glomerular filtration rate, renal blood flow, and glomerular capillary pressure. The urinary albumin excretion rate (1.3 +/- 0.1 mg/24 hr) and the tubular fluid albumin concentration (4.7 +/- 0.7 mg/dl) in the diabetic group were significantly elevated when compared with urinary albumin excretion (0.9 +/- 0.1 mg/24 hr) and tubular fluid albumin concentration (2.5 +/- 0.5 mg/dl) in the control group. There were no significant differences in glomerular hemodynamics (whole kidney or single nephron glomerular filtration rate or glomerular capillary pressure) between diabetic and control rats. The kidney weight and kidney weight to body weight ratio were significantly higher in diabetic rats when compared with control rats. Early diabetes in Biobreeding rats is characterized by mild albuminuria and increased kidney size, but not glomerular hyperfiltration.

Progressive glomerular injury after recovery from acute glomerulonephritis in rats

To determine if an acute immunologic injury resembling poststreptococcal nephritis could lead to chronic renal injury, rats with immune-complex glomerulonephritis produced with cationic human gammaglobulin were followed for 48 weeks. During Week 1, animals developed severe proteinuria, hypoalbuminemia, and a diffuse proliferative/exudative glomerulitis. Substantial recovery, characterized by a significant decline in urinary protein excretion and normalization of plasma albumin concentration, occurred by Week 4. Subsequently, rats developed significantly elevated blood pressures and increasing proteinuria. Glomerular histology at Week 48 revealed minimal inflammation, significant hypertrophy, and considerable sclerosis. We conclude that chronic, progressive renal disease can evolve after apparent recovery from an acute immunologic insult. Further study of this model should provide clinically relevant information about the mechanisms underlying this process.

Degenerated intramural pericytes ('ghost cells') in the retinal capillaries of diabetic rats

One of the earliest histopathological signs of diabetic retinopathy is a selective loss of intramural pericytes from retinal capillaries. In the present study, the retinal vessels of rats with streptozotocin-induced diabetes (STZ Wistar) and rats with genetically-induced insulin dependent diabetes mellitus (BB Wistar) and non-insulin dependent diabetes mellitus (SHR/N-corpulent) were examined after 6 to 8 months duration for diabetes-related retinal microangiopathies. The SHR/N-corpulent (cp) rats were fed a 54% sucrose diet, whereas the STZ Wistar and BB Wistar rats were fed laboratory chow for 32 to 36 weeks. In all the diabetic rats, the retinal capillaries in enzyme-digested flat mounts exhibited an increase in periodic-acid-Schiff (PAS) staining and loss of pericytes compared to their respective euglycemic controls. Pericyte "ghosts", like those defined in human diabetes as intramural pockets lacking normal cell contents, were documented by high resolution micrographs in all the diabetic rats. Endothelial cell proliferation, capillary dilation, and varicose loop formation were noted in some of the diabetic rats. Hence, similar capillary lesions were found in very different groups of diabetic rats. The findings suggest that a chronic high tissue concentration of glucose is the underlying factor which triggers pathogenesis in the pericyte. Hyperglycemia-induced activation of endogenous aldose reductase of the polyol pathway is probably the initial insult, but other factors such as advanced glycosylation products may affect the final outcome.