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Biomedical subjects

A W Yu

Publications and source records attributed to A W Yu.

At least 19 recordsLinked to original sources
PubMed2001

Urea reduction ratio that considers effects of ultrafiltration and intradialytic urea generation.

We modified the urea reduction ratio (URR) equation to correct the effects of ultrafiltration and intradialytic urea generation on the delivered dose of hemodialysis: mURR = [1 - (R/1 + 2*UF/BW) + 0.01*t] x 100% where mURR is modified URR, R is postdialysis plasma urea nitrogen (PUN) to predialysis PUN ratio, UF is ultrafiltrate volume in liters, BW is postdialysis body weight in kilograms, and t is dialysis session length in hours. The equation was validated against 145 hemodialysis treatments on 33 stable maintenance dialysis patients. The mURR values obtained closely predicted single-pool Kt/V (spKt/V) values. In contrast to conventional URR, the range of spKt/V values at each mURR value is narrow over a wide range of UF, t, and R values. Based on the mURR equation, mURR values of 64%, 70%, and 76% are mathematically equivalent to spKt/V levels of 1.0, 1.2, and 1.4, respectively. This equation can be a useful bedside tool to quantify hemodialysis dose.

Blood Urea Nitrogen↗
PubMed2001

Recurrent IgA nephropathy in renal transplant allografts.

Previous reports of renal transplantation for patients with underlying immunoglobulin A (IgA) nephropathy suggested a recurrence rate greater than 50% for transplant IgA nephropathy. Initially regarded as a benign condition, more recent data showed that recurrent transplant IgA nephropathy may be a significant contributor to graft loss. We performed a retrospective analysis in a single center of 48 kidney transplant recipients, all of Chinese origin, with biopsy-proven IgA nephropathy as the cause of end-stage renal failure to determine the recurrence rate of IgA nephropathy in the transplant allograft and subsequent clinical course in Chinese patients. Median duration of follow-up was 52 months (range, 18 to 155 months). Fourteen patients (29%) had biopsy-confirmed recurrent transplant IgA nephropathy after a median of 52 months (interquartile range, 23 to 82 months) posttransplantation. Recurrent transplant IgA nephropathy was associated with greater serum IgA levels (P = 0.01). The presence of HLA-A2 in transplant recipients (P = 0.002) appeared to protect them from developing recurrent IgA nephropathy in the transplant allograft. Twenty-nine percent of patients with recurrent transplant IgA nephropathy had progressive deterioration of graft function. The progressive graft dysfunction (GD) rate was greater in patients with a transplant from a living related donor (LRD; 21%) compared with those with a transplant from a cadaveric or living unrelated donor (URD; 3%; P = 0.062). Although the cumulative graft survival rate was 100% at 5 years for transplants from both LRDs and URDs, the 10-year graft survival rate was only 63% for a graft from an LRD versus 93% for a URD (log-rank test, P = 0.19). A review of other reported series of recurrent transplant IgA nephropathy also showed an apparently greater incidence of GD for a graft from an LRD (28%) compared with a URD (15%). Our data suggest that although recurrent transplant IgA nephropathy is highly prevalent among the Chinese population, the risk for disease recurrence is not particularly increased compared with other ethnic groups. The trend toward a greater risk for GD for living related compared with unrelated allografts in patients with IgA nephropathy needs to be confirmed with further prospective study.

Adult↗
PubMed2000

Posttransplant Epstein-Barr virus-associated myogenic tumors involving bone.

BACKGROUND: Epstein-Barr virus (EBV)-associated myogenic tumors in immunocompromised patients were recently recognized, but their biologic behavior remains only partially understood. Although observations so far have permitted the recognition of similarities between posttransplant myogenic tumors and posttransplant lymphoproliferative disorders (PTLD), the number of reports are still few, and new experiences continue to be informative. METHODS: The authors describe what they believe is the first example of posttransplant EBV-associated myogenic tumor involving bone, which is also remarkable for its multicentric symmetric limb distribution. Immunohistochemistry of tumor cells for myogenic antigens (desmin and smooth muscle actin), EBV antigens (latency proteins latent membrane protein-1 [LMP-1], Epstein-Barr nuclear antigen-2 [EBNA-2], and ZEBRA), p53, and bcl-2 was examined by standard avidin-biotin-peroxidase complex methods. Molecular techniques investigated in situ hybridization for Epstein-Barr virus-encoded messenger RNAs (EBERs) and single-strand conformation polymorphism analysis for p53 mutation. RESULTS: Although the biologic behavior of this tumor was uncertain, the reduction of immunosuppression arrested tumor growth for 5 years, at the expense of some loss in renal function. The occurrence of episodes of acute cellular rejection required pulse therapy, resulting in the appearance of new lesions in both liver and lungs. Despite these complications, a balance between control of this multicentric tumor growth and allograft survival has been maintained for 8 years. CONCLUSIONS: To the authors' knowledge, this example of posttransplant myogenic tumor is the first described in the bone. It shows partial response to immunomodulation with persistent tumor, with prolonged survival of the renal allograft.

Adult↗
PubMed2000

Factors predicting outcome of fungal peritonitis in peritoneal dialysis: analysis of a 9-year experience of fungal peritonitis in a single center.

Fungal peritonitis causes significant morbidity and mortality for patients undergoing continuous ambulatory peritoneal dialysis (CAPD). We retrospectively reviewed 70 episodes of fungal peritonitis in a single center over the last 9 years in 896 CAPD patients. Seventy percent of the episodes of fungal peritonitis were caused by Candida species, among which 50% were Candida parapsilosis. As a result of fungal peritonitis, 44% of the patients died, whereas further peritoneal dialysis failed in 14%, requiring a change to long-term hemodialysis. Only 37% managed to continue CAPD. The remaining 5% either underwent transplantation or were lost to follow-up. We identified the factors associated with poor outcome, namely mortality and technique failure. The presence of abdominal pain, bowel obstruction, and a catheter remaining in situ were significantly associated with greater mortality. Abdominal pain, antibiotic use within 3 months before fungal peritonitis, and complication by bowel obstruction were associated with greater technique failure. In choosing antifungal agents with catheter removal, oral fluconazole alone appears equally as effective as combined oral fluconazole with 5-flucytosine for peritonitis caused by Candida species. For peritonitis caused by species other than Candida, the choice of antifungal therapy needs to be individualized, based on fungal species and sensitivities.

Antifungal Agents↗
PubMed1999

Independent effects of residual renal function and dialysis adequacy on nutritional status and patient outcome in continuous ambulatory peritoneal dialysis.

Dialysis adequacy has a major impact on outcome of continuous ambulatory peritoneal dialysis (CAPD) patients. However, there is a substantial confounding effect by residual renal function in most studies. We differentiated the effects of dialysis adequacy from those of residual renal function on nutritional status and outcome of CAPD patients. We identified 168 CAPD patients treated in our center between September 1995 and December 1996 and categorized them into three groups: 49 patients with an average total Kt/V of 1.93 +/- 0.18 and a median residual glomerular filtration rate (GFR) of 0. 07 mL/min/1.73 m(2) in the dialysis-dependent (DD) group; 48 patients with an average total Kt/V of 2.03 +/- 0.25 and a residual GFR of 2. 33 mL/min/1.73 m(2) in the residual renal function (RRF) group; and 71 patients with an average total Kt/V of 1.38 +/- 0.22 and a residual GFR of 0.05 mL/min/1.73 m(2) in the control (CTL) group. They were followed-up for 1 year to compare baseline nutritional status and 1-year morbidity. Baseline normalized protein catabolic rates (NPCR) are 1.00 +/- 0.20 and 0.96 +/- 0.19 (for RRF and DD, respectively) versus 0.89 +/- 0.16 g/kg/d for CTL (P < 0.01). Percentage lean body mass (%LBM) was 71.6 +/- 9.8 and 71.5 +/- 10.0 (for RRF and DD, respectively) versus 65.2 +/- 8.5% for CTL (P < 0. 001). No difference was seen in the nutritional status between RRF and DD groups. Duration of hospitalization for 1 year was 6.9 +/- 11. 8 days in the RRF group versus 14.9 +/- 25.1 in the DD and 10.6 +/- 11.6 days in the CTL groups (P < 0.05). The peritonitis rate was 44. 4 patient-months for the RRF group, versus 13.6 for the DD and 12.9 for the CTL groups (P < 0.05). There also was a trend toward superior 1-year technique survival in the RRF group, but the number of observations was small. There was no difference in duration of hospitalization, peritonitis rate, and technique survival between the DD and CTL groups. Short-term morbidity in patients without residual renal function appears to be independent of total Kt/V, although Kt/V may have some effects on nutritional status. The assumption that renal and peritoneal clearances are equivalent must be carefully reexamined. Further studies on the effect of dialysis adequacy in patients without residual renal function are urgently needed.

Adult↗
PubMed1999

Neutrophilic transient acidification and superoxide production in peritoneal dialysate.

AIM: To elucidate whether an inhibited superoxide production (O2-) of neutrophils induced by commercial lactate-based peritoneal dialysates (PDS) could be corrected after a transient intracellular acidosis. METHODS: The intracellular pH ([pHi]) of human neutrophils incubated in PDS was monitored with a spectrofluorometer with a pH-sensitive dye (BCECF-AM). Neutrophilic O2- stimulated by zymosan was determined in PDS with the superoxide dismutase inhibitable ferricytochrome c reduction, using a spectrophotometer. RESULTS: The severe intracellular acidosis induced within 5 min by PDS at an extracellular pH of 5.2 could be promptly and completely recovered by a neutralization of the pH of media. However, O2- by neutrophils exposed to the PDS for as little as 5 min was drastically and persistently inhibited, even the acidic [pHi] of cells had been fully returned for 1 h. CONCLUSIONS: The intracellular acidification of cells in the initial phase could be transient and reversible, but impaired cell functions, at least in part including O2- generating system, might be consistent and irreversible in the early stage of the cellular acidosis in the peritoneal cavity of CAPD patients. The findings above may be of particular importance in both clinic and cell biology.

Acidosis↗
PubMed1998

The effects of perinatal hypoxic risk on developmental outcome in early and middle childhood: a twin study.

The goal of this study of 66 twins was to determine whether motor and cognitive functions assessed in early and middle childhood are vulnerable to perinatal hypoxic risk. In an earlier study of 76 infant and toddler twins (S. Raz, F. Shah, & C. Sander, 1996), the authors found that intrapair discrepancy on the Mental Developmental Index, but not on the Psychomotor Developmental Index, of the Bayley Scales of Infant Development was associated with discordance for perinatal hypoxic risk. The twins at lower risk outperformed their higher risk co-twins. In the present study the authors sought to establish in a new sample of preschool and school-age twins whether gaps in performance persist into early and middle childhood. Although the disparity in hypoxic risk between the co-twins was typically moderate, significant intrapair differences were observed on the measure of motor performance. Among the motor abilities examined, skills involving visually guided ballistic arm movements appeared to be the most vulnerable to perinatal risk.

Analysis of Variance↗
PubMed1998

A simple assessment of peritoneal transport in stable continuous ambulatory peritoneal dialysis patients.

We studied the peritoneal transport properties in 175 stable continuous ambulatory peritoneal dialysis (CAPD) patients seeking a simple and handy assessment of peritoneal permeability to small solutes. Measurement of creatinine in biological fluid was known to suffer from interference by high glucose concentration in the sample. Furthermore, the interference is also affected by the creatinine concentration of the specimen. Peritoneal transport properties were studied by determining the dialysate to plasma ratio of creatinine concentration (D/P) at the fourth hour of the peritoneal equilibration test, and the mass transfer area coefficient of creatinine (MTACCr) or glucose (MTACGlu). The ratio of glucose concentration in peritoneal dialysate effluent (PDE) at 4 and 0 h (G4/G0) was examined and compared with various peritoneal parameters. There were significant logarithmic correlations between D/P or G4/G0 with MTACCr (r=0.96 and 0.79, respectively, p < 0.0001). The correlation between G4/G0 and D/P was linear (r=-0.82, p < 0.0001). A fairly good agreement was present between G4/G0 and D/P by Bland and Altman's method. The bias was -0.93% with 95% confidence interval -23.29% to 21.43% of the measured value. Systematic error was found when D/P or G4/G0 were compared with MTACCr. D/P under estimated MTACCr in the high range. The reverse happened for G4/G0. Net ultrafiltration (NUF) also correlated with MTACCr, D/P and G4/G0 (r=-0.32, p < 0.001; -0.26, p < 0.01; and 0.16, p < 0.05, respectively. In conclusion, the use of G4/G0 as a measure of peritoneal transport in CAPD is an acceptable alternative to D/P. It is highly reproducible and avoids correction of interference when creatinine transport parameters are measured. Because of the logarithmic relations of G4/G0 (or D/P) with MTACCr, the former should not be directly converted to MTACCr. Such a simple measure of peritoneal permeability is, however, most convenient for serial monitoring and can be useful to detect early loss of ultrafiltration or solute clearance.

Creatinine↗
PubMed1998

Treatment of pulmonary embolism by subcutaneous low-molecular-weight heparin in a hemodialysis patient.

Low-molecular-weight heparin (LMWH) has been used in the prophylaxis and treatment of deep vein thrombosis. Data regarding the efficacy of this drug without subsequent use of oral anticoagulant in the treatment of pulmonary embolism is limited. Pulmonary embolism may complicate the use of central venous catheter in hemodialysis. We report a case of acute submassive pulmonary embolism complicating a central venous hemodialysis catheter in a dialysis patient. After the catheter was removed, the patient was treated successfully with subcutaneous injection of LMWH for three months. We conclude that LMWH is safe and effective for treatment of pulmonary embolism in patient on hemodialysis.

Adult↗
PubMed1998

Pyruvate-based peritoneal dialysate preserves neutrophilic oxygen consumption.

AIM: To investigate effects of pyruvate- or lactate-based peritoneal dialysis solutions (P-PDS or L-PDS) on neutrophilic oxygen consumption and the role of the extracellular pH (pHe) in cells' oxygen uptake. METHODS: Human neutrophils were incubated in P-PDS or L-PDS containing pyruvate or lactate 35-38 mmol.L-1 at various pHe, respectively. Oxygen consumption rates by opsonized zymosan (OZ)-stimulated cells were measured polarographically, using a Clark-type oxygen electrode. RESULTS: L-PDS at an initial pH 5.2 dramatically inhibited the rate of oxygen consumption (2.2 nmol.min-1/10(6) cells) by neutrophils, while the equally acidic P-PDS markedly improved the rate (6.4 nmol.min-1/10(6) cells) (P < 0.01). However, P-PDS at pHe 5.2 severely impaired the rate by cells, the same as pHe 5.2 L-PDS. CONCLUSION: P-PDS preserved an oxygen consumption rate by OZ-stimulated human neutrophils, but in an acidi milieu it comparably deteriorated the ability of cells to consume oxygen, indicating that the pHe of PDS plays an essential role in cellular oxidative metabolism. The superior biocompatibility of an acidic P-PDS was associated with its lower buffering capacity.

Dialysis Solutions↗
PubMed1997

Xanthomonas maltophilia peritonitis in uremic patients receiving continuous ambulatory peritoneal dialysis.

Xanthomonas maltophilia peritonitis has been only occasionally reported in patients receiving continuous ambulatory peritoneal dialysis. We present a series of six cases of peritonitis caused by such bacteria, accounting for 1.5% of all peritonitis episodes encountered in our renal unit over the past 5 years. Recent bacterial peritonitis treated with broad-spectrum antibiotics was the major risk factor, and the outcome was poor with medical treatment alone. Secondary peritonitis, especially fungal, was common and probably related to the prolonged course of antibiotics. All patients eventually required removal of the catheter, either because the effluent failed to clear up or because of secondary peritonitis. We suggest that X maltophilia peritonitis be treated with double antibiotics as soon as it is diagnosed. To prevent the development of superimposed infection after prolonged administration of antibiotics, the Tenckhoff catheter should be removed if the peritonitis fails to respond to a short course of antibiotics.

Adult↗
PubMed1997

Association of IgA nephropathy with T-cell receptor constant alpha chain gene polymorphism.

T-cell receptor (TCR) proteins recognize a complex of an antigen-derived peptide bound to the cell surface products of the major histocompatibility complex (MHC) that could be of importance in the immunopathogenesis of IgA nephropathy (IgAN). Previous studies found no difference on TCR constant beta chain gene frequencies in IgAN compared with control. Yet no study on the TCR alpha gene in IgAN was reported. We studied the TCR C alpha gene polymorphisms by restriction fragment length polymorphism (RFLP) in 53 patients with IgAN and in comparison with 67 healthy controls. The patients were also classified into different histopathological grading (I, II, and III with increasing histological severity) and renal functions. The extracted DNA were digested with Taq I enzymes and probed with a full-length TCR-alpha cDNA clone p1.2alpha probe. A 7-kb C-alpha Taq 1 fragment is found in 32 of 53 patients (60.3%) compared with 26 of 67 controls (38.8%) (P < 0.05). There was no association of any polymorphic fragment, including the 7-kb fragment, with either the histological grading or renal function. It is concluded that the TCR C-alpha gene is associated with IgAN but not with the prognosis of the disease.

Adult↗
PubMed1997

Splanchnic erythrocyte content decreases during hemodialysis: a new compensatory mechanism for hypovolemia.

Splanchnic and splenic erythrocyte volumes decrease during postural changes and exercise to help maintain central blood volume and cardiac output. The contribution of this compensatory mechanism to hemodynamic stability during dialysis has not been studied, however. In 8 ESRD patients, age 51.0 +/- 4.5 years old, we measured changes in the splanchnic/splenic erythrocyte volume during dialysis by tagging the patients' erythrocytes with technetium and following abdominal radioactivity over time. Splanchnic radioactivity decreased to 90.2 +/- 3.8% (mean +/- SEM) of the baseline value after 2 hr of accelerated fluid removal (3.7 +/- 0.4 liters) during dialysis (DUF), while it remained relatively unchanged after two hours of dialysis without fluid removal (DD) [106.5 +/- 2.3%, P (DUF vs. DD) = 0.03]. Splenic radioactivity decreased to 89.2 +/- 5.0% of the initial value during DUF versus 103 +/- 3.8% during DD, but the decrease was noted only during the last 30 minutes of DUF and did not attain statistical significance. Autonomic nervous system integrity was measured by the spontaneous variation of the R-R interval during deep respiration (E/I ratio) and by the Valsalva ratio. The mean E/I and Valsalva ratios in the eight patients were 1.13 +/- 0.03 (+/-SEM) and 1.42 +/- 0.1 respectively, suggesting reasonably adequate autonomic nervous system functioning. The results suggest that contraction of the splanchnic, and possibly the splenic, vascular beds occurs during fluid removal associated with hemodialysis. The resultant addition of erythrocytes to the circulation may help maintain central blood volume and cardiac output.

Adaptation, Physiological↗
PubMed1997

Effects of pyruvate-based or lactate-based peritoneal dialysis solutions on neutrophil intracellular pH.

Acidic (pH 5.2) incubation mixtures containing pyruvate-based or lactate-based peritoneal dialysis solutions (PDSN's) induced comparable degrees of intracellular acidosis in neutrophils. However, addition of an acidic (pH 5.2), pyruvate-based PDSN to a pH-7.4, neutrophil/phosphate-buffered saline mixture brought about higher extracellular and intracellular (neutrophil) pH values when compared to the introduction of an equally acidic, lactate-based PDSN. This poor ability of acidic (pH 5.0-5.5), pyruvate-based PDSN's to resist alkalinizing influences is the cause for the above higher pH values. The higher intracellular pH levels so obtained may be a reason behind why acidic, pyruvate-based PDSN's appear to be more biocompatible than their equally acidic, lactate-based counterparts.

Adult↗