Plasma pseudouridine levels reflect body size in children on hemodialysis

BACKGROUND

Dialysis in children as well as adults is prescribed to achieve a target spKt/V_urea, where V_urea is the volume of distribution of urea. Waste solute production may however be more closely correlated with body surface area (BSA) than V_urea which rises in proportion with body weight. Plasma levels of waste solutes may thus be higher in smaller patients when targeting spKt/V_urea since they have higher BSA relative to body weight. This study measured levels of pseudouridine (PU), a novel marker solute whose production is closely proportional to BSA, to test whether prescription of dialysis to a target spKt/V_urea results in higher plasma levels of PU in smaller children.

METHODS

PU and urea nitrogen (ureaN) were measured in plasma and dialysate at the midweek hemodialysis session in 20 pediatric patients, with BSA ranging from 0.65-1.87m². Mathematical modeling was employed to estimate solute production rates and average plasma solute levels.

RESULTS

The dialytic clearance (K_d) of PU was proportional to that of ureaN (average K_dPU/K_dUreaN 0.69 ± 0.13, r² 0.84, p < 0.001). Production of PU rose in proportion with BSA (r² 0.57, p < 0.001). The pretreatment plasma level of PU was significantly higher in smaller children (r² 0.20, p = 0.051) while the pretreatment level of ureaN did not vary with size.

CONCLUSIONS

Prescribing dialysis based on urea kinetics may leave uremic solutes at higher levels in small children. Measurement of a solute produced proportional to BSA may provide a better index of dialysis adequacy than measurement of urea.

Residual Function Effectively Controls Plasma Concentrations of Secreted Solutes in Patients on Twice Weekly Hemodialysis

Background Most patients on hemodialysis are treated thrice weekly even if they have residual kidney function, in part because uncertainty remains as to how residual function should be valued and incorporated into the dialysis prescription. Recent guidelines, however, have increased the weight assigned to residual function and thus reduced the treatment time required when it is present. Increasing the weight assigned to residual function may be justified by knowledge that the native kidney performs functions not replicated by dialysis, including solute removal by secretion. This study tested whether plasma concentrations of secreted solutes are as well controlled in patients with residual function on twice weekly hemodialysis as in anuric patients on thrice weekly hemodialysis.Methods We measured the plasma concentration and residual clearance, dialytic clearance, and removal rates for urea and the secreted solutes hippurate, phenylacetylglutamine, indoxyl sulfate, and p-cresol sulfate in nine patients on twice weekly hemodialysis and nine patients on thrice weekly hemodialysis.Results Compared with anuric patients on thrice weekly dialysis with the same standard Kt/V_urea, patients on twice weekly hemodialysis had lower hippurate and phenylacetylglutamine concentrations and similar indoxyl sulfate and p-cresol sulfate concentrations. Mathematical modeling revealed that residual secretory function accounted for the observed pattern of solute concentrations.Conclusions Plasma concentrations of secreted solutes can be well controlled by twice weekly hemodialysis in patients with residual kidney function. This result supports further study of residual kidney function value and the inclusion of this function in dialysis adequacy measures.

First experience with hybrid percutaneous transmyocardial laser revascularization and angioplasty in patients with lesions at high risk for restenosis: Results of a phase I feasibility study

BACKGROUND

Prior studies have suggested that percutaneous transmyocardial laser revascularization (PTMR) may be effective as a sole treatment modality in reducing angina in patients with severe coronary artery disease and no revascularization alternatives. The safety and efficacy of the hybrid or adjunctive use of PTMR during the same procedure as percutaneous intervention (PCI) has not previously been reported.

METHODS

A US phase I feasibility study was therefore performed to determine whether PTMR performed in the same myocardial territory as PCI is able to ameliorate symptomatic recurrence from restenosis.

RESULTS

After successful and uncomplicated PCI in 26 patients with class III-IV angina and lesion(s) at high risk for restenosis, PTMR was performed in the same myocardial territories subtended by the treated vessel(s). Major periprocedural adverse events (death, Q-wave myocardial infarction, and bypass surgery) occurred in 3 (11.5%) patients, as the result of subacute vessel closure in 2 patients, and tamponade in the third. Cumulative 6-month mortality rate was 19.2%, including 2 late deaths between 3 and 4 months after discharge (1 death caused by late stent closure and 1 unexplained death during sleep.) Late repeat revascularization for restenosis in the PCI plus PTMR treated target vessel was required in 19.2% of patients, and an additional 11.5% of patients had class III-IV angina at 6-month follow-up.

CONCLUSIONS

These data demonstrate that in a patient population at high risk for restenosis, recently created PTMR channels are not protective against severe ischemia caused by acute vessel closure and that late symptomatic restenosis after PCI may still frequently occur despite PTMR in the same region.

Effect of thromboxane A2 blockade on clinical outcome and restenosis after successful coronary angioplasty. Multi-Hospital Eastern Atlantic Restenosis Trial (M-HEART II)

BACKGROUND

Antithromboxane therapy with aspirin reduces acute procedural complications of coronary angioplasty (PTCA) but has not been shown to prevent restenosis. The effect of chronic aspirin therapy on long-term clinical events after PTCA is unknown, and the utility of more specific antithromboxane agents is uncertain. The goal of this study was to assess the effects of aspirin (a nonselective inhibitor of thromboxane A2 synthesis) and sulotroban (a selective blocker of the thromboxane A2 receptor) on late clinical events and restenosis after PTCA.

METHODS AND RESULTS

Patients (n = 752) were randomly assigned to aspirin (325 mg daily), sulotroban (800 mg QID), or placebo, started within 6 hours before PTCA and continued for 6 months. The primary outcome was clinical failure at 6 months after successful PTCA, defined as (1) death, (2) myocardial infarction, or (3) restenosis associated with recurrent angina or need for repeat revascularization. Neither active treatment differed significantly from placebo in the rate of angiographic restenosis: 39% (73 of 188) in the aspirin-assigned group, 53% (100 of 189) in the sulotroban group, and 43% (85 of 196) in the placebo group. In contrast, aspirin therapy significantly improved clinical outcome in comparison to placebo (P = .046) and sulotroban (P = .006). Clinical failure occurred in 30% (49 of 162) of the aspirin group, 44% (73 of 166) of the sulotroban group, and 41% (71 of 175) of the placebo group. Myocardial infarction was significantly reduced by antithromboxane therapy: 1.2% in the aspirin group, 1.8% in the sulotroban group, and 5.7% in the placebo group (P = .030).

CONCLUSIONS

Thromboxane A2 blockade protects against late ischemic events after angioplasty even though angiographic restenosis is not significantly reduced. While both aspirin and sulotroban prevent the occurrence of myocardial infarction, overall clinical outcome appears superior for aspirin compared with sulotroban. Therefore, aspirin should be continued for at least 6 months after coronary angioplasty.

Patient-related variables and restenosis after percutaneous transluminal coronary angioplasty--a report from the M-HEART Group

As part of a randomized prospective study designed to investigate the restenosis process after percutaneous transluminal coronary angioplasty (PTCA), the relation between patient-related variables and restenosis rate was examined. A total of 722 patients had successful PTCA. Angiographic follow-up was scheduled for 6 +/- 2 months after the procedure and achieved in 510 patients (71%), yielding 598 lesions for analysis. The overall restenosis rate was 40%. The rate was higher in patients undergoing early restudy for a clinical event than in those undergoing routinely scheduled follow-up restudy (71 vs 22%, p less than 0.0001). Age, sex, cigarette smoking history, diabetes mellitus and history of previous myocardial infarction were not associated with restenosis rate. Angina duration and severity before PTCA were also unrelated to restenosis rate. In summary, these variables, many of which have been previously implicated in restenosis, were not found to be predictors of restenosis. The decision to perform PTCA in individual patients should not be negatively influenced by the presence of these factors.

The effect of chloramphenicol on the induction of cyanase in Escherichia coli

The early stages of cyanase induction were studied. It was found that 30 s elapsed at 37 °C and 60 s elapsed at 22 °C before cyanase-forming capacity of Escherichia coli could be demonstrated. This period was termed inducer-dependent stage (i.d.s.). An additional period of 120 s at 22 °C was needed for demonstration of enzyme synthesis. This period was termed inducer-independent stage (i.i.s.). It was found that in contrast to β-galactosidase, the i.d.s. as well as the i.i.s. were inhibited by chloramphenicol. Pulse-labelling experiments showed an increase in m-RNA obtained from induced bacteria in the presence of chloramphenicol compared with noninduced bacteria treated with chloramphenicol, indicating that chloramphenicol does not interfere with transcription. However, the m-RNA formed in the presence of chloramphenicol did not participate in translation upon removal of the antibiotic. This evidence, in addition to the time course of the inhibition, suggests that the inhibition of induction is caused by chloramphenicol preventing the attachment of the ribosomes to cyanase-specific m-RNA.

Some properties of the induced enzyme cyanase

The inhibitory action of various anions on cyanase activity is described and it is shown that halides inhibit the enzyme competitively. The previously reported Kmvalue of cyanase was measured in the presence of NaCl and was therefore erroneous. The molecular weight of a partially purified enzyme was determined by gradient centrifugation in sucrose, but it seems probable that this molecular weight is that of a polymer. The high specificity and the heat stability of cyanase are also described.