Proteinuria in focal segmental glomerulosclerosis: role of circulating factors and therapeutic approach

The clinical course of primary Focal Segmental Glomerulosclerosis (FSGS) is frequently complicated by nephrotic range proteinuria and progression to renal failure. The high recurrence rate of the disease in transplanted kidney suggests the hypothesis that such patients have a circulating factor that alters glomerular capillary permeability. In recent years some authors found that serum from patients with FSGS increases glomerular permeability to albumin and partially identified the permeability factor (PF) as a protein of 30-50 Kd m.w. The removal of this protein by means of Plasma Exchange (PE) or plasma Immunoadsorption by Protein A (IA) decreased proteinuria. In this report we provide preliminary data about the prevalence of PF and the therapeutic effect of its removal by IA, in 3 pts with recurrence in the transplanted kidney, and 4 with FSGS of the native kidneys. They were resistant to corticosteroids (CS) and immunosuppressive (IS) therapy. 10 IA sessions were performed in 4 weeks: if a remission was achieved IA was gradually tapered. The level of PF in the serum was measured by an in vitro assay to determine the glomerular permeability to albumin. The FSGS was histologically proven in all cases and the degree of evolution was evaluated. PF levels, serum creatinine, daily proteinuria and serum albumin were monitored. The 3 patients with recurrent FSGS had a normalization of the PF levels; 2 had a clinical remission. In FSGS of native kidneys PF was elevated in 3/4 cases; 1 had a clinical remission; 2 with extensive sclerohyalinosis and 1 without PF levels did not improve. Our results confirm that most patients with FSGS have high PF serum levels and suggest that its removal can be beneficial.

Apheresis in primary focal segmental glomerulosclerosis of native and transplanted kidneys: a therapeutic protocol

BACKGROUND

Patients with focal segmental glomerulosclerosis (FSGS) develop nephrotic syndrome and terminal renal failure in most cases. FSGS reappears in 15-50% of transplanted kidneys and frequently causes the graft loss. Sera from patients with FSGS of native or transplanted kidneys contain some proteinuric or permeability factors (PF) which can be removed by means of plasma exchange (PE) or protein A Immunoadsorption (IA).

METHODS

We suggest a therapeutic protocol, for patients with biopsy proven FSGS of native or transplanted kidneys, resistant to steroid and immunosuppressive therapy, based on the association of PE or IA to conventional drug therapy. Daily proteinuria, renal function, serum albumin and circulating level of proteinuric factors (permeability test) will be monitored at regular time intervals during the apheresis cycle, which will be intensive at the beginning (8-10 sessions in 4 weeks) and very gradually discontinued. Results. We will consider satisfactory remission the reduction of proteinuria below 1 g/day, improvement of renal function, normalization of serum albumin level (> 3.5 g/dl). Partial remission will be considered: proteinuria below 3 g/day, stable renal function, serum albumin level between 3 and 3.5 g/dl. Permeability test, if positive at baseline examination, should be negative after apheresis.

CONCLUSIONS

The primary endpoint of our protocol is: lasting remission (satisfactory or partial) after the apheresis suspension. Secondary endpoints are: maintained remission with continuing apheresis sessions, correlation between permeability activity and disease activity, identification of responders and non responders patients on the basis of positive permeability test.

Models for the active site of vanadium-dependent haloperoxidases: insight into the solution structure of peroxo vanadium compounds

A combined use of electrospray ionization-mass spectrometry (ESI-MS), 51V NMR spectroscopy and ab initio calculations has been proved to be a powerful tool for obtaining direct information of the structure and the chemistry of peroxo vanadates in solutions. The analysis of acid solutions containing monoperoxo vanadates showed the occurrence of exchange reactions between solvent molecules in the coordination sphere of the metal. On the other hand, bisperoxo vanadates appear to be less prone to coordinate more than one water or alcohol molecule. The bisperoxo complex [VO5]- in the presence of histidine and histidine-like ligands, at near neutral conditions, has been studied. Coordination of one and two molecules of ligand is observed affording [VO5L]- and [VO5L2]-, respectively. Characterization of these species has been obtained by MSn experiments, which allowed us to distinguish specific fragmentations of the peroxidic moiety.

Vanadium catalyzed reduction of dioxygen to hydrogen peroxide: an oscillating process

In acid isopropanol/water solution and aerobic conditions, (Bu)4N+VO3- in the presence of an initial amount of H2O2, catalyzes the autoxidation of isopropanol to acetone and the contextual dioxygen reduction to hydrogen peroxide, which accumulates in solution. We have observed that, in the system under examination, the build-up of H2O2 concentration shows an oscillatory behavior. Speciation of the peroxovanadium complexes in iPrOH/H2O has been explored with the combined use of 51V NMR, UV-Vis and ESI-MS techniques.

Albumin permeability in isolated glomeruli in incipient experimental diabetes mellitus

AIMS/HYPOTHESIS

The pre-clinical phase of diabetic nephropathy is characterised by increased glomerular filtration rate and episodes of microalbuminuria. The cause of the microalbuminuria has been variably ascribed to alterations of the size or charge selective barriers of the glomerulus or both or as a consequence of the haemodynamic changes. Our aim was to investigate very early albumin permeability alterations in isolated glomeruli which were not subject to perfusion pressure.

METHODS

Isolated glomeruli were studied from 120 male Wistar rats, divided into three groups: streptozotocin-treated, streptozotocin-treated with insulin pellet implants, and controls. From each group ten animals were killed at 7, 14, 28, and 56 days after induction. Study variables included blood pressure, proteinuria, iopamidol clearance, albumin permeability and glomerular area. Subsequently, albumin permeability, proteinuria, and iopamidol clearance were determined in an additional group of 40 diabetic animals studied at 24, 72, 96, and 120 h after induction.

RESULTS

Albumin permeability increased steadily from induction in streptozotocin-treated animals, reaching a plateau at approximately 120 h. Glomerular filtration rate was shown to increase significantly at approximately 7 days and proteinuria correlated with it. Glomerular hypertrophy was observed both in streptozotocin-treated animals and in streptozotocin-treated rats with insulin pellet implants. Strict blood glucose control delayed the appearance of the permeability defect in isolated glomeruli and inhibited the increase in glomerular filtration in intact animals. It did not prevent glomerular hypertrophy.

CONCLUSION/INTERPRETATION

An albumin permeability defect exists early in isolated non-perfused glomeruli from streptozotocin-treated rats and seems to be independent of glomerular filtration rate alterations.

Prediction and treatment of recurrent focal segmental glomerulosclerosis after renal transplantation in children

The recurrence of focal segmental glomerulosclerosis (FSGS) after renal transplantation has a potentially detrimental course toward the loss of renal function. To identify prognostic markers for recurrence and efficacy of treatment, we evaluated the outcome of 32 renal allografts in 29 pediatric patients with FSGS who underwent transplantation from 1987 to 1998 in the North Italy Transplant program. Recurrence was observed in 15 of 29 patients (52%) after the first transplant and in 3 of 3 patients (100%) after the second graft. No significant differences in sex, age at FSGS onset, age at transplantation, or length of dialysis were noted between patients with recurrent and nonrecurrent FSGS. Those with recurrence originally developed end-stage renal failure faster (3.9 years) than those without recurrence (6.2 years). Pretransplantation serum samples from 25 patients were tested in an in vitro assay that evaluates glomerular permeability to albumin. FSGS recurred in 11 of 13 children who tested positive for the permeability factor and in 4 of 12 patients with a negative test result; the odds ratio for developing recurrence was 10.99 (95% confidence limit, 1.6 to 75.47) in the former group. The immediate onset of proteinuria after transplantation was a negative prognostic factor for the outcome; 6 of 9 patients in whom proteinuria appeared within 2 days of transplantation returned to dialysis in less than 24 months. In 9 of 11 patients who were treated with plasmapheresis plus cyclophosphamide after recurrence, proteinuria was successfully reversed and persistent remission was obtained in 7 patients. These data show that the glomerular permeability test has a significant predictive value for the recurrence of proteinuria in children with FSGS who have received a renal allograft. Of the clinical parameters considered, only the duration of disease was significantly different in patients with recurrent versus nonrecurrent FSGS. Treatment with plasmapheresis plus cyclophosphamide can be effective in the control of FSGS relapse after renal transplantation.

Pulmonary hypertension associated with human immunodeficiency virus infection. Report of two cases and review of the literature

Recent reports have suggested a possible association between HIV-1 infection and "idiopathic" pulmonary hypertension (PH), but the pathogenetic role of the viral agent has not been fully defined yet. We report the cases of two white males positive for human immunodeficiency virus type 1 (HIV-1) who presented with clinical and hemodynamic diagnosis of pulmonary hypertension. They were heterosexual, non-hemophiliac, heroin abusers with no signs of clinical AIDS. Neither one of the patients had opportunistic lung infections or any other cause of secondary pulmonary hypertension. In one case, peculiar clinical and electrocardiographic features of PH were associated with signs of thrombotic thrombocytopenic purpura (TTP). The association between PH and HIV-1 infection might be explained by a severe alteration of pulmonary endothelial cell homeostasis secondary to HIV-1 viral infection.

Relationship between whole-body protein turnover and serum creatinine in chronically uremic patients

To investigate the relationship between decline in renal function and alterations of protein metabolism we determined the rate of whole-body protein turnover in a group of 15 postabsorptive chronically uremic patients (9 males and 6 females) with different levels of serum creatinine concentrations (average 5.7 +/- 0.4 (SE) mg x dl(-1); range 3.3-9.1). Patients' age and body mass index were 53 +/- 4 years (range 26-73) and 24.7 +/- 0.6 kg/m2 (range 20.3-28.7), respectively. Nutritional status (plasma albumin 3.6 +/- 0.4 g x dl[-1]) and acid-base equilibrium (arterial pH 7.38 +/- 0.01) were fairly controlled by therapy. Whole-body leucine rate of appearance (Ra), an index of whole-body protein turnover, was assessed using a stable isotope technique. L-[1-(13)C]leucine was continuously infused and plasma [1-(13)C]alpha-ketoisocaproic acid enrichment was determined in steady-state conditions as a marker of the intracellular leucine enrichment. The average leucine Rawas 2.03 +/- 0.13 micromol x kg(-1) x min(-1) (range 1.29-3.19). Using simple linear regression analysis, the coefficient of correlation between the individual values of serum creatinine concentration and leucine Ra was 0.59 (n = 15; p = 0.02). Leucine Ra did not significantly correlate with blood pH or plasma albumin. In conclusion, we found a positive linear relationship between the values of plasma creatinine concentration and the rate of whole-body protein degradation. This correlation suggests that the progression of renal insufficiency is associated with accelerated rates of turnover of body proteins.

Effects of a dimeric vs a monomeric nonionic contrast medium on renal function in patients with mild to moderate renal insufficiency: a double-blind, randomized clinical trial

The efficacy and safety of nonionic dimeric contrast media in subjects with impaired renal function is largely unknown. The present study was aimed at determining the risk of tubular nephrotoxicity in patients with mild to moderate renal insufficiency who underwent intravenous urography (IVU) with the nonionic dimeric contrast agent iodixanol (Visipaque, Nycomed Imaging, Oslo, Norway). In a double-blind protocol 64 patients (55 males; mean age 68.3 years) with serum creatinine between 135 and 265 micromol/l who were to undergo IVU were randomized to receive iodixanol (a nonionic dimer) or iopromide (a nonionic monomer), 600 mg I/kg b. w. Renal function was evaluated before and 1 h, 6 h, 24 h, 48 h and 7 days after IVU with analysis of serum creatinine, urinary enzymes alanylaminopeptidase and N-acetyl-beta-glucosaminidase, and urinary microproteins alpha-1-microglobulin and albumin. Renal function remained stable in both contrast medium groups during the follow-up period. No statistically significant differences were observed between the monomer and the dimer in terms of urinary enzyme and microprotein excretion or serum creatinine. Transient radiocontrast-induced nephropathy developed in 1 patient who had received iodixanol. The administration of the nonionic dimeric contrast medium iodixanol, or of the nonionic monomer iopromide, entailed a low nephrotoxic potential in patients with mild to moderate renal insufficiency undergoing excretory urography.

[Morpho-functional study of the kidney in patients with kidney disease and liver disease with magnetic resonance]

INTRODUCTION

We studied renal function and perfusion after the i.v. injection of Gd-DTPA-BMA, a nonionic paramagnetic contrast agent, to assess renal morphology and function in normal subjects, in renal insufficiency patients and in patients with hepatic failure and normal renal function. The latter were chosen because some patients with advanced hepatic failure may suffer from the hepatorenal syndrome, characterized by severe vasoconstriction in the renal cortical vessels. We investigated if dynamic MRI can detect early renal perfusion abnormalities in the patients who will eventually develop this syndrome.

MATERIAL AND METHODS

Thirty MR examinations were carried out on 30 subjects after the i.v. injection of Gd-DTPA-BMA. Our series consisted of: 10 normal subjects; 10 renal insufficiency patients; 10 patients with hepatic failure and normal renal function. MR examinations were performed on a Philips ACS II scanner operating at 1.5 T. Two sequences were carried out in all cases: T1-weighted SE and T1-weighted TGE sequences after the bolus injection of .1 mmol/kg contrast agent. Renal longitudinal diameter and parenchymal thickness were measured in all cases and signal intensity time curves were always made. The signal intensity of the cortex, corticomedullary junction, medulla and pyelocaliceal system of each kidney was measured using a region of interest (ROI). The signal intensity curves were made considering quantitative parameters, including the area below the curve (ASC), the peak (P) and the time to peak (T-P).

RESULTS

Longitudinal diameter and parenchymal thickness values were significantly lower in renal insufficiency patients than in normal subjects. Four phases were demonstrated after i.v. contrast agent injection in normal subjects, namely A) the cortical phase, B) the corticomedullary junction phase, C) the medullary phase, D) the pyelocaliceal phase. No signal intensity decrease in the medullary and pyelocaliceal curves was observed in renal insufficiency patients. Signal intensity curves values were lower in hepatic failure patients than in those with normal renal function. Hepatic failure patients could be divided into two groups: 5 patients had low P and ASC values and 4 had normal P and ASC values. The patients with lower P and ASC values developed the hepatorenal syndrome within a few months of the MR examination.

DISCUSSION

Signal intensity decreased in the pyelocaliceal system phase in normal subjects because of the high paramagnetic contrast agent concentration. The lack of signal intensity decrease in renal insufficiency patients was caused by the reduced capability of concentrating Gd-DTPA-BMA. Lower signal intensity values in hepatic failure patients may be considered an early sign of the hepatorenal syndrome.

Mechanisms of malnutrition in uremia

The pathogenesis of protein wasting in chronic renal failure is multifactorial. Potential mediators of protein catabolism in chronic uremia include anorexia, low protein-energy intake, increased cortisol and parathyroid hormone secretion, insulin resistance, metabolic acidosis and unidentified uremic toxins. In non-acidotic uremic patients the rate of protein turnover (that is, synthesis and degradation) has often been found to be decreased. Malnutrition also decreases both protein synthesis and degradation. In contrast, during acidosis protein degradation is primarily accelerated and results in rapid loss of body proteins. Cytokine concentrations have often been found increased in both dialyzed and undialyzed chronically uremic patients. Our study determined the circulating levels of TNF-alpha and of type I (60 kDa) and type II (80 kDa) soluble TNF-alpha receptors in undialyzed uremic patients, and found that their plasma levels were greatly increased. Serum creatinine correlated with TNF-alpha soluble receptors but not with the TNF-alpha. Thus, TNF-alpha is potentially an important mediator of protein wasting in chronically uremic patients. Pharmacological therapy of protein catabolism in chronic uremia may include the administration of pentoxifylline, which has been shown to decrease protein degradation by interfering with the TNF-alpha system (that is, TNF-alpha and its soluble receptors) in experimental models. Growth hormone and insulin-like growth factor-1 administration may also be beneficial in these patients, but further evaluation of the hormone effects on glucose and glutamine metabolism is called for.

[A comparison between an ionic paramagnetic contrast agent (Gd-DTPA) and a nonionic one (Gd-DTPA-BMA) in functional kidney evaluation with magnetic resonance]

INTRODUCTION

The combination of TGE sequences with bolus injection of paramagnetic contrast agents permits to study renal function and perfusion. We studied renal function with both an ionic (Gd-DTPA) and a nonionic paramagnetic contrast agent (Gd-DTPA-BMA) to compare their kinetics in normal kidneys.

MATERIAL AND METHODS

Twenty MR examinations were performed on 20 subjects with normal renal function. Ten subjects were examined after i.v. injection of Gd-DTPA and the other ten subjects after i.v. injection of Gd-DTPA-BMA. MR examinations were performed on a Philips ACS II unit (1.5 T). Two sequences were acquired in all cases; an SE coronal T1-weighted sequence (TR/TE = 600/19 ms) and a TGE coronal T1-weighted sequence (TR/TE = 12/5 ms, flip angle = 25 degrees) performed after bolus injection of the contrast agent at 0.1 mmol/kg. Signal intensity time curves were obtained in all the cases. The signal intensity of the cortex, corticomedullary junction, medulla and the pyelocaliceal system of each kidney was measured using a region of interest (ROI). Signal intensity curves were analyzed considering some quantitative parameters such as the area under the curve (AUC), the peak (P) and the time to peak (T-P).

RESULTS

In the subjects with normal renal function, four phases were demonstrated after the i.v. injection of either Gd-DTPA or Gd-DTPA-BMA, namely the cortical phase, the cortico-medullary junction phase, the medullary phase and the pyelocaliceal system phase. No statistically significant differences between the two agents were demonstrated in signal intensity time curves and quantitative parameters.

CONCLUSIONS

Gd-DTPA and Gd-DTPA-BMA showed the same efficacy in renal function studies.

[Bolus thrombolysis in pulmonary embolism. Review of experimental and clinical data]

Although heparin is the primary drug used to treat pulmonary embolism, its limits include poor prevention of recurrence, and slow and delayed normalization of hemodynamic parameters. Over the past decades, thrombolysis has proved to be the most rapid and effective therapy to normalize hemodynamic parameters and angiographic and scintigraphic indexes of obstruction. Studies conducted up to the present have not, however, demonstrated a significant advantage over heparin with respect to mortality. Moreover, thrombolytic drugs carry a greater risk of hemorrhage than heparin. Various experimental studies have demonstrated that the short-term administration of recombinant tissue plasminogen activator (rt-PA) is more effective and decreases risk of hemorrhage. To our knowledge, only a few uncontrolled clinical studies on bolus thrombolysis with urokinase have been done. Studies comparing a 0.6 mg/Kg bolus of intravenous rt-PA versus the infusion of 100 mg over 2 hours have given conflicting results. Of these, some have demonstrated that bolus administration is safer and more effective while others have provided nearly overlapping results regarding safety and the reduction of pulmonary resistances. One study reports higher mortality in a group receiving 0.6 mg/Kg bolus rt-PA. Until these questions are clarified, administration of thrombolytics in the following doses is advised: streptokinase bolus 250,000 U over 30 min + 100,000 U/hour for 24 hours; urokinase bolus 4400 U/Kg for 10 min + 4400 U/Kg/hour for 12-24 hours; rt-PA 100 mg for 2 hours.

Dose effect of nitrendipine on urinary enzymes and microproteins following non-ionic radiocontrast administration

BACKGROUND

Although calcium-channel antagonists have been proposed as prophylaxis to prevent radiocontrast-induced nephropathy, the dose and dose interval to achieve a protective effect have not been quantified in humans.

METHODS

In a randomized, double-blind protocol we studied urinary enzyme and microprotein excretion in 121 outpatients (mean age 65.3 +/- 9.3 years, 62% male) with normal renal function who were to undergo digital subtraction arteriography with iohexol or iopentol. The subjects were treated with a single dose of placebo (group 1) or nitrendipine 10 mg (group 2) or 20 mg (group 3) p.o. 1 h before the procedure. Blood and urine samples were collected 1 h before, 1 h after, and 24 h after contrast administration. Study variables included contrast volume and serum creatinine, and urinary creatinine, osmolality, albumin, alanylamino-peptidase (AAP, a brush border enzyme), N-acetyl-beta-glucosaminidase (NAG, a lysosomal enzyme), and alpha-1-microglobulin (alpha-1-micro, a filtered microprotein).

RESULTS

Serum values of creatinine remained unchanged during the study period. Albuminuria was not affected by contrast administration, whereas AAP, NAG, and alpha-1-micro increased significantly, all except AAP returning to baseline at 24 h. Pretreatment with nitrendipine did not reduce enzyme excretion, although AAP levels were lower in general in the group assigned to the 20-mg dose. Acute renal failure, defined as a 50% increase of serum creatinine 24 h after radiocontrast administration, was found in eight patients: four from group 1 (8.3%), three from group 2 (6.5%), and one from group 3 (3.7%).

CONCLUSIONS

Neither the course of enzyme excretion nor the incidence of acute renal failure following radiocontrast administration were affected by single doses of calcium antagonists. AAP levels were lower in general in subjects taking the 20-mg dose of nitrendipine. This study also indicates that a single low or normal dose of nitrendipine per os is not effective prophylaxis before radiocontrast administration. The designs of future studies investigating the "nephroprotective' effect of calcium-channel antagonists per os should incorporate (1) the use of repeated doses to saturate hepatic metabolic pathways, and (2) the control of confounding variables in the measurement of urinary enzymes.

[An atypical presentation of a case of Horton's giant-cell arteritis]

Horton giant cell arteritis can present with an atypical clinical picture that often resembles other diseases. In the case described below, the patient initially demonstrated clinical and laboratory evidence of a Candida albicans sepsis, and therefore we started antimycotic treatment with amphotericin B. Because of an adverse reaction to that drug, we added parenteral steroids before every administration of the antimycotic which led to an unexpected improvement of symptoms. This result caused us to reconsider some clinical aspects that could have been interpreted also as vasculitis, in particular for a giant cell arteritis: throbbing temporal headache, diffuse weakness, important rise in ESR, myoarthralgias. We performed a biopsy of the temporal artery that confirmed our diagnosis.

Nifedipine reduces postexercise proteinuria in young volunteers

Previous studies have demonstrated that it is possible to prevent postexercise proteinuria with angiotensin-converting enzyme inhibitors. To determine whether calcium antagonists have the same effect, 40 young healthy volunteers underwent maximal aerobic exercise with and without nifedipine 10 mg per os 1 h before the first or second trial. Urinary excretion of albumin (UAE), transferrin (UTE) and alpha 1-microglobulin (UME) were examined before and after each trial. UAE, UTE and UME were significantly increased after exercise. Nifedipine significantly decreased UAE (p = 0.001) and UTE (p = 0.02) after exercise, and slightly decreased the maximal work load and the basal excretion of albumin. UME was unchanged. Therefore, the results of this study demonstrate that nifedipine administration before exercise significantly reduces postexercise proteinuria.

Involvement of the renin angiotensin system in the pathogenesis of postexercise proteinuria

Proteinuria after strenuous exercise is common in healthy subjects. The pathophysiologic mechanism of postexercise proteinuria (PEP) is not clear, although the phenomenon has long been known and many explanatory theories have been proposed. It is widely recognized that angiotensin II may increase filtration of protein through the glomerular membrane, and that its concentration in plasma increases during exercise. The aim of this study was to evaluate possible involvement of angiotensin II in the pathogenesis of PEP. Of 25 young volunteers who performed maximal aerobic exercise, eight showed PEP. The exercise was repeated after an interval of at least one week, now 90 minutes after administration of captopril (25 mg). Captopril did not affect the achieved work load of the maximal blood pressure and heart rate during the exercise, but PEP was not found. As it was possible to prevent PEP by administering an angiotensin-converting enzyme inhibitor, the study supports the theory that the renin angiotensin system is involved in the pathogenesis of PEP.

Power spectral analysis of heart-rate variations improves assessment of diabetic cardiac autonomic neuropathy

Power spectral analysis (PSA) of heart-rate variations has recently proved a useful tool in evaluating cardiovascular autonomic activity. It offers the possibility of examining both the functioning of parasympathetic and sympathetic pathways through breakdown into two frequency bands, and of their effects on heart-rate cyclic variability. We applied an autoregressive model for PSA to study overall autonomic tone in 20 male age-matched control subjects and 53 insulin-dependent (type I) diabetic subjects, subdivided into three groups of 20, 15, and 18, each group presenting different degrees of autonomic involvement. We found that: 1) power spectrum density (PSD) values at high-frequency bands (parasympathetic dependent) were similar in diabetic subjects without cardiac autonomic neuropathy (CAN) and in control subjects, but differed significantly from diabetic subjects with mild CAN and severe CAN, both standing and lying; 2) PSD values at low frequency (mainly sympathetic dependent) were similar, or slightly different, in diabetic subjects without CAN and in control subjects, but differed significantly from diabetic subjects with mild and severe CAN, both standing and lying; 3) as an expression of parasympathetic versus sympathetic coherence, correlations, both standing and lying, existed between PSD values at low- and high-frequency bands in control and diabetic subjects without CAN, but not in diabetic subjects with CAN; and 4) different degrees of correlation characterized the PSD values of high and low frequencies versus traditional cardiovascular test values in the diabetic subjects. The best correlation was between PSD low-frequency values and the lying-to-standing maneuver.(ABSTRACT TRUNCATED AT 250 WORDS)