On the ordinality of numbers: A review of neural and behavioral studies.

The last several years have seen steady growth in research on the cognitive and neuronal mechanisms underlying how numbers are represented as part of ordered sequences. In the present review, we synthesize what is currently known about numerical ordinality from behavioral and neuroimaging research, point out major gaps in our current knowledge, and propose several hypotheses that may bear further investigation. Evidence suggests that how we process ordinality differs from how we process cardinality, but that this difference depends strongly on context-in particular, whether numbers are presented symbolically or nonsymbolically. Results also reveal many commonalities between numerical and nonnumerical ordinal processing; however, the degree to which numerical ordinality can be reduced to domain-general mechanisms remains unclear. One proposal is that numerical ordinality relies upon more general short-term memory mechanisms as well as more numerically specific long-term memory representations. It is also evident that numerical ordinality is highly multifaceted, with symbolic representations in particular allowing for a wide range of different types of ordinal relations, the complexity of which appears to increase over development. We examine the proposal that these relations may form the basis of a richer set of associations that may prove crucial to the emergence of more complex math abilities and concepts. In sum, ordinality appears to be an important and relatively understudied facet of numerical cognition that presents substantial opportunities for new and ground-breaking research.

Dialysate iron therapy: infusion of soluble ferric pyrophosphate via the dialysate during hemodialysis.

BACKGROUND: Soluble iron salts are toxic for parenteral administration because free iron catalyzes free radical generation. Pyrophosphate strongly complexes iron and enhances iron transport between transferrin, ferritin, and tissues. Hemodialysis patients need iron to replenish ongoing losses. We evaluated the short-term safety and efficacy of infusing soluble ferric pyrophosphate by dialysate. METHODS: Maintenance hemodialysis patients receiving erythropoietin were stabilized on regular doses of intravenous (i.v.) iron dextran after oral iron supplements were discontinued. During the treatment phase, 10 patients received ferric pyrophosphate via hemodialysis as monthly dialysate iron concentrations were progressively increased from 2, 4, 8, to 12 micrograms/dl and were then sustained for two additional months at 12 micrograms/dl (dialysate iron group); 11 control patients were continued on i.v. iron dextran (i.v. iron group). RESULTS: Hemoglobin, serum iron parameters, and the erythropoietin dose did not change significantly from month 0 to month 6, both within and between the two groups. The weekly dose of i.v. iron (mean +/- SD) needed to maintain iron balance during month 6 was 56 +/- 37 mg in the i.v. iron group compared with 10 +/- 23 mg in the dialysate iron group (P = 0.001). Intravenous iron was required by all 11 patients in the i.v. iron group compared with only 2 of the 10 patients receiving 12 micrograms/dl dialysate iron. The incidence of adverse effects was similar in both groups. CONCLUSIONS: Slow infusion of soluble iron pyrophosphate by hemodialysis may be a safe and effective alternative to the i.v. administration of colloidal iron dextran in maintenance hemodialysis patients.

Symptomatic interleukin-2-induced cholecystopathy in patients with HIV infection.

OBJECTIVE: This study reports the clinical and radiologic findings in seven patients infected with HIV who had 10 consecutive episodes of symptomatic cholecystopathy induced by infusion of interleukin-2. SUBJECTS AND METHODS: Ten episodes of right upper quadrant pain associated with gallbladder wall thickening were seen in seven of 29 HIV-infected patients who received IV interleukin-2. Patients received 6-18 million IU/day of continuous interleukin-2 infusion for 5 days. Patients with right upper quadrant pain underwent sonographic examinations, which were interpreted prospectively. Medical records and previous sonographic studies were reviewed retrospectively. Follow-up was obtained through outpatient visits and sonography. RESULTS: Right upper quadrant pain during these 10 episodes of cholecystopathy usually developed 4-5 days after starting infusion of interleukin-2. Sonography during that time showed gallbladder wall thickening (mean thickness, 12.4 mm; range, 5-18 mm) and a wide variety of sonographic appearances. Tenderness during sonography was focal in six episodes, diffuse in one, and absent in three. Sludge was identified in one episode; calculi were not seen. Findings on radionuclide biliary scans were normal in three cases. Symptoms abated rapidly in every case after infusion of interleukin-2 was reduced or stopped. No surgery was necessary. When treatment was repeated, three patients had recurrent episodes, with clinical courses and sonographic aberrations showing little variance from the initial episodes. Follow-up sonography in three episodes showed a maximal thickness of the gallbladder wall of 4 mm. No patient had a history or laboratory evidence of intrinsic biliary disease. CONCLUSION: Symptomatic thickening of the gallbladder wall during infusion of interleukin-2 can exactly mimic other forms of acalculous cholecystitis, except that when associated with interleukin-2 the thickening is rapidly reversible and surgery is not required. Radionuclide scans can be useful in clinical decision making. The process appears to be benign, and cessation of interleukin-2 therapy, along with close clinical observation, appears to be the appropriate treatment.