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Biomedical subjects

S M Mauer

Publications and source records attributed to S M Mauer.

At least 37 records · Page 2Linked to original sources
PubMed1994

Application of electron microscopic immunocytochemistry to the human kidney: distribution of type IV and type VI collagen in normal human kidney.

We used immunogold electron microscopic (IEM) techniques with periodate-lysine-paraformaldehyde-fixed and Lowicryl-embedded or cryopreserved tissues to study the distribution of alpha 1(IV) and alpha 3(IV) chains of Types IV and VI collagen in glomerular basement membrane (GBM) and mesangial matrix of glomeruli in normal human kidneys. Monoclonal antibodies to alpha 1(IV) and alpha 3(IV) collagen chains and Type VI collagen could be detected only with cryoultramicrotomy, whereas polyclonal anti-Type IV collagen antibody was detectable in Lowicryl-embedded tissue. Ultrastructural detail was better preserved in the Lowicryl-embedded tissue. IEM labeling provided more detailed information as to the site-specific array of these extracellular matrix molecules in glomeruli than did immunofluorescent microscopy. The labeling of alpha 1(IV) collagen chain was distributed mainly along the endothelial side of glomerular basement membrane and the mesangial matrix. Mesangial GBM was relatively poorly labeled compared with that of mesangial matrix. In contrast, the alpha 3(IV) chain was detected throughout the thickness of the GBM, but there was no labeling of mesangial matrix. Type VI collagen distribution was identical to that of the alpha 1(IV) chain within the glomerulus but was also associated with interstitial collagen fibrils. This study documents and details the heterogeneous distribution of Type IV and VI collagen chains within the normal human glomerulus and provides the framework for the study of these matrix components in human glomerular diseases.

Basement Membrane↗
PubMed1994

Relationship between retinal and glomerular lesions in IDDM patients.

Current knowledge regarding the concordance and discordance of the eye and kidney complications of diabetes is based on observations by ophthalmoscopy of retinal structural changes, which may be present at early stages of the disorder, and renal functional changes, which only become apparent at the later stages of the disease. For this reason we investigated the relationship between retinal structural lesions and quantitative measures of glomerular structure in patients with insulin-dependent diabetes mellitus (IDDM). Renal biopsies were evaluated using morphometric techniques, and retinopathy classification was determined by retinal fundus photography in 86 patients with IDDM: age 30.4 +/- 7.3 years and duration of IDDM 18.9 +/- 6.3 years (mean +/- SD). Retinopathy score correlated with glomerular basement membrane width (r = 0.39, P = 0.0002), mesangial volume fraction (VvMes/Glom) (r = 0.35, P = 0.0009), surface density of the peripheral capillary wall (SvPGBM/Glom) (r = 0.34, P = 0.0013), and index of arteriolar hyalinosis (r = 0.36, P = 0.0008). Abnormalities in VvMes/Glom and SvPGBM/Glom were more pronounced in patients with both retinopathy and hypertension. Four of the 15 patients (27%) with either normal urinary albumin excretion (UAE) or low-level microalbuminuria had advanced retinopathy but normal VvMes/Glom. In conclusion, the presence of advanced retinal disease with or without hypertension in patients with IDDM indicates a greater likelihood of advanced nephropathy as evidenced by increased VvMes/Glom and decreased SvPGBM/Glom. However, marked discordance between retinopathy and nephropathy occurs, as illustrated by patients with normal UAE or low-level microalbuminuria, normal glomerular structural measures, and advanced retinopathy.

Adolescent↗
PubMed1994

Outcome of dialysis for acute renal failure in pediatric bone marrow transplant patients.

We have reviewed the clinical course of 30 pediatric bone marrow transplant (BMT) recipients requiring dialysis for acute renal failure early after BMT. Patients requiring dialysis were not significantly different from the general pediatric BMT population except for: (1) a greater proportion of neuroblastoma patients in the dialysis group, and (2) fewer autologous and more unrelated BMT donors in the dialysis group. Twenty-three patients (77%) died without recovering renal function 1-72 days (mean 12 days) after dialysis was begun. Sepsis was the most commonly cited cause of renal failure and death in these patients. Seven patients (23%) recovered sufficient renal function to stop dialysis; all long-term survivors were in this group. Factors at the onset of dialysis associated with persistent renal failure were weight gain of > or = 10% of baseline body weight, requirement of three or more drugs for blood pressure support and hyperbilirubinemia. Although acute renal failure requiring dialysis is an ominous development following BMT, recovery of renal function is possible with aggressive supportive care.

Acute Kidney Injury↗
PubMed1993

Effects of pancreas transplantation on glomerular structure in insulin-dependent diabetic patients with their own kidneys.

Pancreas transplantation prevents or retards development of early diabetic glomerular lesions in renal allografts transplanted to patients with insulin-dependent diabetes mellitus (IDDM), but its effect on established renal lesions in native kidneys of such patients is unknown. Renal biopsy samples were taken before and 5 years after pancreas transplantation from 13 non-uraemic IDDM patients and compared with baseline and 5-year biopsy samples from 10 persistently hyperglycaemic IDDM patients who did not undergo transplantation. The two groups were similar in age, duration of diabetes, metabolic control, renal function, and blood pressure. Glomerular structures were measured by standard morphometric techniques. Haemoglobin A1 concentrations fell to within the normal range after pancreas transplantation but did not change in the comparison group. Glomerular basement membrane width did not significantly change in either group. Glomerular volume decreased and mesangial fractional volume increased in the pancreas transplant recipients but there was no significant change in total mesangial volume over 5 years. By contrast, both glomerular volume and mesangial fractional volume increased in the comparison patients, resulting in increased total mesangial volume. Diabetic glomerular lesions in patients with their own kidneys were not ameliorated by pancreas transplantation, despite 5 years of normoglycaemia. Pancreas transplantation can correct severe metabolic instability and thus improve quality of life, but it cannot yet be recommended for the treatment of established lesions of diabetic nephropathy.

Adolescent↗
PubMed1993

Interstitial fibrosis in obstructive nephropathy.

Interstitial fibrosis and tubular basement membrane (TBM) thickening are evident within 16 days of unilateral ureteral obstruction (UUO) in the rabbit, and resemble the changes previously reported in hydronephrotic human kidneys. The cortical interstitial volume fraction in this rabbit model at 16 days is 43.3 +/- 6.1% (+/- 1 SD) in UUO kidneys, 4.9 +/- 3.1% in contralateral kidneys (CLK), and 2.8 +/- 0.8% in kidneys from sham-operated animals (ANOVA, P < 0.0001). Immunohistochemically, UUO is associated with increased interstitial collagens I and III, fibronectin, heparan sulfate proteoglycan and tubulointerstitial nephritis antigen. Aberrant collagen expression is also evident as interstitial collagen IV becomes prominent. Focal, peritubular accumulation of collagens I and II also appear to encircle the TBM. These changes are accompanied by an early, transient increase in renal cortical mRNA encoding the alpha 1 monomers of collagens I, III and IV, implicating increased matrix synthesis in the pathogenesis of obstructive nephropathy. In situ hybridization localized increased expression of alpha 1 (I) and alpha 1 (IV) mRNA to cells in the interstitial space, with clusters of alpha 1(I) positive cells associated with dilated tubules, muscular arteries and the periglomerular interstitium.

Animals↗
PubMed1993

Structural-functional relationships in type I mesangiocapillary glomerulonephritis.

We quantitated glomerular and cortical interstitial structures in nine type I mesangiocapillary glomerulonephritis (MCGN) patients aged 6 to 20 years whose creatinine clearance (CCr) was 10 to 129 ml/min/1.73 m,2 as compared to age-matched normal controls. Mean glomerular volume and mesangial volume fraction [Vv(mes/glom)] were increased and the percentage of the capillary endothelial circumference which was defined as filtration surface was decreased in type I MCGN patients. Vv(mes/glom) was inversely related to filtration surface area per glomerulus (r = -0.73, P < 0.05) and directly to volume density of cortical interstitium [Vv(int/cortex)] (r = +0.90; P < 0.01). Vv(mes/glom) (r = -0.87; P < 0.01), filtration surface area per glomerulus (r = +0.83; P < 0.01) and Vv(int/cortex) (r = -0.86; P < 0.01) were correlated with CCr. Thus, in type I MCGN, measures both of glomerular and of cortical interstitial structure are highly correlated with glomerular function.

Adolescent↗
PubMed1993

Renal interstitial expansion in insulin-dependent diabetes mellitus.

Eighty-four patients with insulin-dependent diabetes mellitus had studies of renal function and quantitative renal morphometry including mesangial volume fraction (Vvmes/glom), index of arteriolar hyalinosis, percentage of globally sclerosed glomeruli (%GS), and interstitial volume fraction for total renal cortex (Vvint/T). There was significant correlation among these four parameters, and all four structural parameters correlated with glomerular filtration rate and the log of urinary albumin excretion. Stepwise multiple regression analysis showed that Vvmes/glom and Vvint/T were additive, suggesting that they are partially independent. Arteriolar hyalinosis and %GS did not improve the correlations further. We hypothesize that Vvmes/glom, Vvint/T, arteriolar hyalinosis, and %GS represent multiple but probably interrelated pathologic mechanisms leading to the functional disturbances of diabetic nephropathy. Longitudinal studies of patients with diabetes and studies of patients with diseases producing interstitial expansion in the absence of glomerular disease may help clarify the independent role of interstitial expansion in the kidney disease of diabetes mellitus.

Arterioles↗
PubMed1993

Abnormal renal hemodynamic response to reduced renal perfusion pressure in diabetic rats: role of NO.

Diabetic rats manifest abnormal renal hemodynamic responses, with persistent renal vasodilation at reduced renal perfusion pressures. We hypothesized that in diabetes, renal hemodynamics are modulated by increased activity of the endogenous vasodilator, NO. In anesthetized Munich-Wistar rats, after 6 wk of streptozotocin-induced, insulin-treated diabetes, and in age-matched, nondiabetic littermates (n = 7-8), basal renal hemodynamics and responses to graded reductions in renal perfusion pressure were determined before and after intrarenal arterial infusion of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). An identical protocol was followed in a second cohort of rats pretreated with indomethacin (4 mg/kg iv). Diabetic rats demonstrated hyperglycemia, renal enlargement, hyperfiltration, and increased urinary excretion of the stable NO metabolites, NO2 and NO3. L-NAME eliminated basal hyperfiltration in diabetic rats, and L-NAME, but not indomethacin, also eliminated persistent renal vasodilation at reduced renal perfusion pressure. We conclude that in a rat model of diabetes, increased endogenous NO activity may play a role in basal hyperfiltration and in the persistent renal vasodilatation manifested at reduced renal perfusion pressures.

Amino Acid Oxidoreductases↗
PubMed1993

Enzymological and mutational analysis of a complex primary hyperoxaluria type 1 phenotype involving alanine:glyoxylate aminotransferase peroxisome-to-mitochondrion mistargeting and intraperoxisomal aggregation.

Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive disease caused by a deficiency of the liver-specific peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT). Three unrelated PH1 patients, who possess a novel complex phenotype, are described. At the enzymological level, this phenotype is characterized by a complete, or nearly complete, absence of AGT catalytic activity and reduced AGT immunoreactivity. Unlike normal individuals in whom the AGT is confined to the peroxisomal matrix, the immunoreactive AGT in these three patients was distributed approximately equally between the peroxisomes and mitochondria. The peroxisomal AGT appeared to be aggregated into amorphous core-like structures in which no other peroxisomal enzymes could be identified. Mutational analysis of the AGT gene showed that two of the three patients were compound heterozygotes for two previously unrecognized point mutations which caused Gly41-->Arg and Phe152-->Iso amino acid substitutions. The third patient was shown to be a compound heterozygote for the Gly41-->Arg mutation and a previously recognized Gly170-->Arg mutation. All three patients were homozygous for the Pro11-->Leu polymorphism that had been found previously with a high allelic frequency in normal populations. It is suggested that the Phe152-->Iso and Gly170-->Arg substitutions, which are only eighteen residues apart and located in the same highly conserved internal region of 58 amino acids, might be involved in the inhibition of peroxisomal targeting and/or import of AGT and, in combination with the Pro11-->Leu polymorphism, be responsible for its aberrant mitochondrial compartmentalization. On the other hand, the Gly41-->Arg substitution, either in combination with the Pro11-->Leu polymorphism or by itself, is predicted to be responsible for the intraperoxisomal aggregation of the AGT protein.

Adult↗
PubMed1992

Prospective versus clinical diagnosis and therapy of acute neonatal hyperammonaemia in two sisters with carbamyl phosphate synthetase deficiency.

Two female siblings were treated for acute neonatal hyperammonaemia due to complete carbamyl phosphate synthetase I deficiency. The first child was detected clinically at 65 hours of age and therapy started at 79 hours. The second child was followed from birth and therapy started at 5 hours of age. The extrapolated rate of increase of blood ammonia, in the first hours of life before therapy started, was 19 mumol L-1 h-1 in both babies. Peak blood ammonia level was 2235 mumol/L in the first (clinically detected) child and 271 mumol/L in the second (prospectively followed) child. The second child became symptomatic at 3 hours of age when blood ammonia level was as low as 90 mumol/L, whereas blood ammonia levels above 100 mumol/L caused no symptoms during recovery. The child detected clinically required haemodialysis and peritoneal dialysis to treat the hyperammonaemia. In the prospectively treated child, early therapy with intravenous sodium benzoate and sodium phenylacetate slowed the rate of increase in blood ammonia level, but this therapy did not prevent the need for peritoneal dialysis.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

An overview of renal pathology in insulin-dependent diabetes mellitus in relationship to altered glomerular hemodynamics.

Clinical diabetic nephropathy in man is the consequence of the development of a specific constellation of glomerular, tubular, vascular, and interstitial structural abnormalities accompanied by highly characteristic immunohistochemical alterations that, together, are unique to diabetes. Because changes resembling the specific pathology of diabetes do not develop in patients with conditions that lead to long-standing glomerular hyperfunction (such as unilateral nephrectomy), it is unlikely that glomerular hemodynamic abnormalities per se can be the cause of diabetic nephropathy. Whether hemodynamic abnormalities represent a risk factor that, in the presence of the diabetic state, can accelerate the rate of development of the basic lesions of diabetic nephropathy is currently unclear. However, there is considerable evidence that when the renal lesions of diabetes are far advanced, factors such as systemic hypertension can determine the rate of renal functional deterioration in diabetes as in other disorders. Although the diabetic rat may be a useful model for the study of aspects of the pathogenesis of diabetic nephropathy, much confusion has resulted from the inclusion of focal segmental glomerular sclerosis as a diabetic lesion. Similarly, the acceptance of all increases in urinary protein excretions in this model as resulting from or reflecting of diabetic nephropathology can be misleading. It is concluded that treatment aimed at manipulating renal hemodynamics in diabetic patients without evidence of renal disease should remain in the realm of clinical research.

Animals↗
PubMed1992

Relationship of systemic blood pressure to nephropathology in insulin-dependent diabetes mellitus.

Although hypertension is an important complication of diabetes it is unclear whether its association with other diabetic complications represents cause or consequence. Our study is a cross sectional evaluation of the relationship of blood pressure to renal structural and functional parameters. In 139 patients with insulin dependent diabetes for 18.9 +/- 7.4 years (mean +/- SD), we divided the patients into those with markedly increased mesangial volume fraction [Vv(mes/glom) greater than or equal to 0.37] and those with less [Vv(mes/glom) less than 0.37]. Hypertension (systolic BP greater than or equal to 160 and/or diastolic BP greater than 90 mm Hg or receiving BP medications) occurred in 29/40 with Vv(mes/glom) greater than or equal to 0.37. All 40 had clinical nephropathy with urinary albumin excretion (UAE) greater than 200 mg/24 hr. By two-way ANOVA creatinine clearance was lower and albuminuria was increased with both hypertension and the expanded mesangium. Also other measures of renal structure including filtration surface, index of interstitial fibrosis and index of arteriolar hyalinosis were increased by hypertension and mesangial expansion. Most patients with hypertension had other criteria for clinical nephropathy. Since, in these studies, we could not determine if hypertension contributed to or resulted from the renal lesions, we developed an estimate of the rate of mesangial expansion. We found that patients with normal BP (119 +/- 11/78 +/- 7 mm Hg) can be rapidly developing mesangial expansion. These studies support the view that the development of serious renal lesions can be independent of hypertension in IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Heparan sulfate proteoglycan in the glomerular basement membrane in type 1 diabetes mellitus.

Heparan sulfate proteoglycans (HSPG) are negatively charged constituents of the renal extracellular matrix including the glomerular basement membrane (GBM) and mesangial matrix. Biochemical and functional studies of patients with type-1 insulin dependent diabetes mellitus (IDDM) suggest that alterations of HSPG may occur in diabetic nephropathy. We have utilized a specific cytochemical method and electron microscopy to quantitate the distribution of HSPG in the GBM of 10 normal people and in 16 IDDM patients with a spectrum of clinical and structural changes. Enzyme incubation studies of normal infant kidney demonstrated that heparitinase removed 94% of the stainable anionic sites in the lamina rara externa (LRE) and 77% of the sites in the lamina rara interna (LRI) of the GBM. In contrast, incubation in the enzyme chondroitinase ABC did not reduce the number of sites in the LRE but reduced the number of sites in the LRI by 26%. The HSPG anionic sites in normal subjects were distributed in the LRE as 20.9 +/- 1.3, and in the LRI as 13.1 +/- 2.2 per micron GBM length. Anionic sites were slightly reduced (19.6 +/- 1.3, P less than 0.04) in the LRE of IDDM patients with normal urinary albumin excretion rates (UAE), or microalbuminuria, and were reduced in both the LRE and LRI of IDDM patients with clinical proteinuria (13.1 +/- 2.3, P less than 0.001 and 8.9 +/- 2.1, P less than 0.001, respectively). The number of anionic sites in the LRE and LRI, respectively, correlated with UAE (r = +0.78, P less than 0.001, r = +0.58, P less than 0.02), with GBM thickness (LRE, r = +0.81, P less than 0.001; LRI, r = +0.67, P less than 0.01) and with the volume fraction of mesangium (LRE, r = +0.59, P less than 0.02; LRI, r = +0.58, P less than 0.03). These data confirm earlier biochemical findings of a reduction of HSPG in the GBM in advanced diabetic nephropathy but do not provide evidence for the loss of HSPG in the GBM as a mechanism for early microalbuminuria.

Adolescent↗
PubMed1992

Estimation of glomerular volume: a comparison of four methods.

Methods for estimating glomerular volume were compared in Zenker-fixed, paraffin-embedded biopsies from 10 patients with insulin-dependent diabetes mellitus and 6 normal kidney donors. Two methods of measurement of individual glomerular volumes were used: the Cavalieri method (considered the "gold standard") and the maximal profile area (MPA) method. Also studied were the method of Weibel and Gomez and a method based on the disector principle; both estimate mean volume (VG). MPA and Cavalieri showed strong correlation (r = 0.93; P less than 0.001), although the MPA method consistently overestimated the true volume; six glomeruli were necessary for a reliable estimate of VG. The disector method did not correlate with VG determined by Cavalieri. Weibel-Gomez did correlate with Cavalieri (r = 0.68; P less than 0.05), but overestimated VG. At least 15 profiles were needed to provide a dependable estimate of VG by Weibel-Gomez. The Cavalieri, MPA, and Weibel-Gomez methods all can provide reliable estimates of VG, the latter two with appropriate correction factors. The individual glomerular volume methods, while more time consuming, provide information on variation and distribution of the glomerular population and are the methods of choice for studies of glomerular volume.

Adult↗
PubMed1992

Success of kidney transplantation in oxalosis is unrelated to residual hepatic enzyme activity.

We evaluated hepatic alanine glyoxylate aminotransferase (AGT) activity in percutaneous hepatic biopsy material obtained from four children with long-term renal allograft function following transplantation for primary hyperoxaluria type 1 (PH 1). The study was performed to determine whether these successes had occurred because relatively high residual levels of AGT activity had introduced a selection bias. The children ranged from seven months to eight years at transplant and are currently well 7 to 11 years later, with no oxalate deposition on repeated allograft biopsies and creatinine clearances of 80 to 128 ml/min/1.73 m2. AGT activity ranged from 0 to 13.8%, and in two of three patients with detectable levels the AGT was in mitochondria rather than peroxisomes. These results indicate that long-term renal allograft success can occur in spite of severe AGT deficiency. Thus, the therapeutic choice of kidney alone versus combined kidney-liver transplant cannot currently be made by measuring residual hepatic AGT in PH 1. Kidney transplant alone remains a reasonable initial therapeutic alternative for patients with recent onset of renal insufficiency due to PH 1.

Adolescent↗