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Biomedical subjects

C Queirolo

Publications and source records attributed to C Queirolo.

At least 19 recordsLinked to original sources
PubMed1989

Endogenous albumin as a marker of renal selectivity in steroid-unresponsive nephrotic syndrome.

Albumin electrical charge, conformation and hydrophobicity taken as indexes of renal selectivity were evaluated in 8 children affected by steroid-unresponsive nephrotic syndrome associated with glomerulosclerosis or mesangial hypercellularity. These characteristics related to urinary albumin have already been reported to vary markedly in steroid-responsive nephrotic syndrome of minimal-change nephropathy giving rise to new pathogenetic possibilities in this disease. In the steroid-unresponsive nephrotic children albumin was found to be more microheterogenous and cationic in urine than in serum and at the same time it was conformationally altered. Regarding these characteristics, the selectivity properties of the renal filter are similar in steroid-unresponsive nephrotic syndrome, suggesting a pathogenetic connection between these two renal disorders.

Albuminuria↗
PubMed1988

Hemodynamic changes during acetate dialysis, bicarbonate dialysis and hemofiltration.

Twenty uremic patients submitted to three different dialytic procedures (6 patients to acetate dialysis, 8 patients to bicarbonate dialysis, 6 patients to hemofiltration) were monitored in respect to the hemodynamic parameters recorded with a thermistor Swan-Ganz catheter. During acetate dialysis there was an increment of cardiac index (CI) up to positive values (+4.8%), while resistance index (RI) decreased progressively until it reached -16.5%. During bicarbonate dialysis CI, after an initial fall, remained constant and RI increased (+8.6%). During hemofiltration CI decreased constantly throughout the entire procedure while RI increased until +12.9%. We concluded that during diffusive transport the buffer used plays an important role in determining hemodynamic responses to fluid removal; during convective transport vascular resistance increases in spite of acetate.

Acetates↗
PubMed1987

Renal selectivity properties towards endogenous albumin in minimal change nephropathy.

It is well accepted that the molecular charge and conformation of serum proteins are major determinants of their glomerular filtration, but few studies characterizing the molecular features of circulating proteins in renal diseases are currently available. In 11 children affected by minimal change nephropathy (MCN) we determined the electrical charge and the fluorescence quantum yield of Tyrosine (Tyr) and Tryptophan (Trp) (taken as index of conformation) of serum and urinary albumin before and after steroid-induced remission of proteinuria. In all proteinuric children at the onset of the disease, urinary albumin was formed by one band with an isoelectric point (pI) of 4.7 (pI of the native protein), and by numerous other, less anionic bands with pIs between 4.8 and 5.5 accounting for about 50% of the total amount of this protein. The normalization of proteinuria which followed steroid therapy was characterized by the disappearance in urines of the less anionic fraction and by the appearance of numerous isoforms with a pI still more anionic (pI less than 4.7) than normal. At the same time, in the proteinuric phase, the fluorescence quantum yield of Trp of urinary albumin was markedly quenched, returning to near normal levels after steroid-induced remission of proteinuria. These data indicate that in MCN the charge-dependent renal selectivity properties are partially maintained and that the less anionic isoforms of albumin are a main component of urinary albumin. Together with the electrical charge, the conformation of albumin as a major determinant of its urinary excretion in MCN must also be considered.

Adolescent↗
PubMed1987

Characterization of cationic albumin in minimal change nephropathy.

The presence of isoalbumins with a less anionic charge than the normal protein (pI = 4.7) is the hallmark of proteinuria in minimal change nephropathy (MCN). Steroid-induced restoration of near normal levels of proteinuria is characterized by the appearance in urines of isoalbumins with a pI still more anionic than the normal. In our search for an explanation for the pI changes, we used preparative isoelectric focusing in granulated gels to split the microheterogeneous bands obtained from nine MCN-affected children into four fractions (A1, A2, A3, A4) with decreasing pI from 5.8 to 4.0 and we have determined their fatty acid content. The least anionic fraction, A1, was the most defatted, followed by A2, A3 and A4 in which fatty acid content progressively increased, A4 being the most fatted fraction. Accordingly, the mean content of fatty acids in urinary albumin in proteinuric children was lower than in both the remission phase and in normal children (2.17 +/- 0.03 vs. 20.91 +/- 0.38 and 20.94 +/- 0.39, respectively) and was lower by a factor of 4 compared to serum albumin in the same phase of the disease (2.17 +/- 0.03 vs. 8.59 +/- 1.64). Among medium and long-chain fatty acids, the ratio between serum and urinary albumin was the highest for linoleic acid (approximately 7), followed by that of oleic acid, palmitic acid and lauric acid. At variance in five other patients affected by non-MCN nephrotic syndrome this ratio was for practically all FAs about 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Reactivity with diazonium salts of albumin from micro and macroalbuminuric diabetic patients.

A recent theory of the pathogenesis of diabetic microalbuminuria points to an involvement of glycated albumin, which has been demonstrated as being able to fluetrate the renal filter. The chemical characterization of urinary albumin, initially performed on the electrical charge and conformation of the protein has now been extended to the affinity properties for specific chemical probes. In this context, urinary albumin from Albustix-negative diabetic patients was found to be highly reactive towards diazonium salts (a dye specific for pyrrole rings) while the same protein purified from macroproteinuric diabetics showed no difference in reactivity towards diazonium salts compared to serum or normal albumin. These data indicate that, beside being highly anionic and conformationally deranged, urinary albumin in conditions of normal renal selectivity contains pyrrole structures. The reasons for considering this reactivity as an indirect sign of rearranged structure are presented here.

Adult↗
PubMed1986

Isoelectric focusing in low-denaturing media: visualization in renal disease of variation of the isoelectric point of albumin not related to a remarkable conformational variation.

The isoelectric properties of serum and urinary albumin from normal subjects and patients with nephrotic syndrome have been investigated in various conditions of denaturation, obtained by using urea (0-8 M) as a support in isoelectric focusing. In normal human serum, albumin is rather acidic (pI = 4.7) when focused in glycerol while the denatured form obtained by exposing the protein to 8 M urea has a much higher pI (6.1). Albumin from nephrotic patients is acidic in glycerol but at very low levels of urea (2M) it shifts from pI 4.7 to pI 6.1; the same effect has been induced by treating albumin with activated charcoal at low pH. In order to obtain more information on urea-induced changes, we have recorded the circular dichroic spectra of albumin when exposed to the concentration of urea used in gels, and we found that no conformational transition occurs for urea concentrations less than 5 M. Taken together, these observations reveal that variation of the pI of albumin in nephrotic syndrome occurs mainly due to a dissociating effect of urea on charged substances bound to this protein.

Albumins↗
PubMed1986

Conformational mediated renal selectivity towards albumin in diabetes mellitus.

In an attempt to define the nature of renal selectivity in diabetes mellitus, we have determined the free sulfhydryl (SH) groups of serum and urinary albumin in 9 normal subjects and 24 diabetic patients with various grades of renal involvement, as defined by their urinary excretion rates of albumin (alb. UER): 8 with alb. UER less than 10 micrograms/min (Group A), 6 with alb. UER between 10 and 30 micrograms/min (Group B), 5 with alb. UER between 30 and 200 micrograms/min (Group C) and 5 with alb. UER greater than 200 micrograms/min (Group D). The free SH group content of urinary albumin was three to four fold increased in comparison with its serum homologue in normal subjects and in diabetics with normal or slightly increased alb. UERs (Groups A and B). Diabetics in Group C showed a two-fold increase in free SH groups of urinary albumin compared to serum albumin and diabetics with clinical nephropathy (Group D) showed no increase at all. The SH group content of urinary albumin correlated in all diabetics with the concentration of glycosyl albumin and the of urinary/serum albumin SH groups ratio was inversely correlated with alb. UER. From these observations concerning the selectivity properties of the renal filter in normal and diabetic subjects, it is concluded that the mechanism for progression of diabetic nephropathy may be the hyperfiltration of albumin with an altered conformational state.

Adolescent↗
PubMed1985

Reaction of human serum albumin with aldoses.

The reaction of human serum albumin (HSA) with aldoses (C3-C6) and acetaldehyde has been studied. U.v. and fluorescent spectra of the HSA-glyceraldehyde and HSA-GlcN adducts reveal yellow chromophores absorbing at 300-350 nm and emitting at 435 nm. However, even limited reaction of HSA with acetaldehyde induced perturbation in the Trp microenvironment. C.d. spectra of the adducts show an average 20% decrement in mean residual ellipticity [theta], which is independent of the extent of the reaction and the aldose used. It is concluded that most of the reactions with aldoses occur at the surface of the HSA molecule. With the exception of the GlcN adduct, the HSA adducts rearrange to produce pyrrole rings on the protein surface. I.e.f. analysis shows that the pI values of the modified HSA are almost linearly correlated with the chain length of the reacting aldose: from pI 4.2 for HSA-glyceraldehyde up to pI 5.0 for HSA-GlcN.

Acetaldehyde↗
PubMed1985

Electrical charge of serum and urinary albumin in normal and diabetic humans.

The isoelectric points of albumin purified by pseudo-ligand chromatography on Affi-Gel Blue were determined simultaneously in serum and urine of 11 normal subjects and 25 diabetic patients, subdivided in groups according to their urinary excretion rates of albumin. Serum albumin was constituted by a single homogeneous peak at 4.7 (pI) in normal subjects, whereas the levels for diabetic patients covered this band and some other microheterogeneous levels, ranging from 3.5 to 7 pI. By affinity chromatography with Concanavalin A-Sepharose and immunoelectrophoretic techniques, all these micro-heterogeneous bands were characterized as glycosyl albumin. In normal subjects and diabetic patients whose urinary excretion rate of albumin was normal or increased only slightly (10 to 100 micrograms/min), the pattern of urinary albumin included a main band with normal pI (4.7) and some remarkable amounts of more anionic bands (pI between 4.0 and 4.7) if compared to the native protein, which was characterized as glycosyl albumin. Such a difference was not detected in urines of diabetic patients with clinical nephropathy. These results indicate that the non-enzymatic glycosylation of albumin is a main determinant of the excretion of this protein into urine, in spite of the anionic electrical charge. We describe also the renal selectivity properties in humans that may be viewed as a model for the study of renal disease, but the role of such a mechanism in early diabetic nephropathy remains unknown.

Adolescent↗
PubMed1985

Glycosylation of serum albumin in diabetic humans with osmolar and acid-base disorders.

The rate of nonenzymatic glycosylation of serum albumin was determined in 7 diabetic patients at the onset and during the recovery of an acute metabolic derangement as defined by hyperglycemia, hyperosmolality and metabolic acidosis of various degrees. Serum glycosyl albumin concentration (chemically determined) was decreased after 1 day in 5 patients (mean -6%) and increased in the remaining 2 (+11% and +22% respectively). The same variance was decreased in the whole group after 7 days of therapy (-18.6%). A negative statistical correlation was found by plotting initial values of serum glycosyl albumin against arterial H+ concentration and the same relationship was confirmed by multiple regression analysis which gave the following curve: t (glycosyl albumin) = 1.57 - 0.004 X (H+) + 0.000225 y (Mean blood glucose concentration) - 0.00285 z (serum osmolality) (the regression coefficients were 0.24 for x, 0.18 for y and 0.23 for z). Finally, a number of albumin isoforms with a cationic charge up to 7 pH have been detected in all patients by isoelectric focusing. Taken together all the data presented herein indicate that beside serum glucose concentration other factors (such as H+ concentration and serum osmolality) influence the rate of glycosylation of albumin, their effects being prominent and opposite to hyperglycemia.

Acid-Base Imbalance↗
PubMed1985

Microheterogeneity of serum glycosyl albumin in diabetes mellitus.

Proteins purified by affinity chromatography on Blue-Sepharose CL-6B from serum of 10 normal controls and 19 Type I diabetic patients were studied by means of combined ultrathin isoelectric focusing and photochemical silver stain. While only a single band of protein (characterized as albumin by crossed immunoelectrophoresis) with a pI of 4.7 was found in serum of normal subjects, 10 out of the diabetic group showed some bands of proteins with a pI greater than 4.7 and a single one with a pI less than 4.7. Concanavalin A-Sepharose removed all these bands with altered pIs which were further characterized as albumin by fused rocket immunoelectrophoresis of the eluates from Concanavalin A-Sepharose, direct immunofixation after isoelectric focusing of proteins with high purified anti-albumin antibodies, SDS-polyacrylamide gradient pore electrophoresis, aminoacidic analysis. The gas-chromatographic analysis of carbohydrates released from both the albumin bound to Concanavalin A-Sepharose and that not bound, revealed in addition to two unidentified peaks, the presence of glucose, galactose and mannose whose contents were greatly increased in albumin with affinity for the lectin. Serum glycosyl albumin concentration was not statistically different in serum of diabetic patients displaying cationic glycosyl albumin in comparison to patients without these proteins (0.2261 +/- 0.0186 versus 0.1874 +/- 0.015 nmole HMF/nmole albumin), whereas the first group showed statistically higher urinary excretion rates of albumin (28.6 +/- 1.2 micrograms/min versus 4.6 +/- 0.2 micrograms/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗