Semi-Quantitative Evaluation of Asymmetricity of Dialysis Membrane Using Forward and Backward Ultrafiltration.

Performance of the dialysis membrane is strongly dependent upon the physicochemical structure of the membrane. The objective of this study is to devise a new in vitro evaluation technique to quantify the physicochemical structures of the membrane. Three commercial dialyzers with cellulose triacetate (CTA), asymmetric CTA (termed ATA®), and polyether sulfone (PES) membranes (Nipro Co., Osaka, Japan) were employed for investigation. Forward and backward ultrafiltration experiments were performed separately with aqueous vitamin B12 (MW 1355), α-chymotrypsin (MW 25,000), albumin (MW 66,000) and dextran solutions, introducing the test solution inside or outside the hollow fiber (HF), respectively. Sieving coefficients (s.c.) for these solutes were measured under the test solution flow rate of 200 mL/min and the ultrafiltration rate of 10 mL/min at 310 K, according to the guidelines provided by Japanese academic societies. We defined the ratio of s.c. in the backward ultrafiltration to that in the forward ultrafiltration and termed it the index for asymmetricity (IA). The IA values were unity for vitamin B12 and α-chymotrypsin in all three of the dialyzers. The IA values for albumin, however, were 1.0 in CTA, 1.9 in ATA®, and 3.9 in PES membranes, respectively, which corresponded well with the fact that CTA is homogeneous, whereas ATA® and PES are asymmetrical in structure. Moreover, the asymmetricity of ATA® and PES may be different by twofold. This fact was verified in continuous basis by employing dextran solution before and after being fouled with albumin. These findings may contribute to the development of a novel membrane for improved success of dialysis therapy.

Comparison of biocompatibility in polysulfone dialysis membranes with different sterilization.

INTRODUCTION: Polysulfone (PSf) membrane has been widely used for hemodialysis. A few studies have been reported in which a method of sterilization may affect biocompatibility. In this study, the comparison was made between two PSf membranes in order to evaluate the effect of sterilization from the biocompatibility point of view. METHODS: We investigated the biocompatibility of the following two dialyzers, that is, APS-11SA (Asahi Kasei medical Co., Tokyo, Japan), sterilized by gamma-ray irradiation, and RENAK PS-1.0 (Kawasumi laboratories, Tokyo, Japan), sterilized by autoclave. Heparin of 40 units/mL was put in a syringe, and test blood was collected from healthy volunteers. Then, the dialyzer and blood circuit were filled with the test blood. Subsequently, the blood was circulated by a roller pump at the rate of 200 mL/min. We measured the platelet counts, CD41 and CD42b platelet surface markers, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) at 30, 120, and 240 minutes, respectively. FINDINGS: The platelet counts at 30, 120, and 240 minutes decreased significantly from the initiation of blood circulation in both dialyzers. The average beta-TG and PF4 increased from 61.3 ± 22.1 and 17.0 ± 6.4 ng/mL to 680.7 ± 217.1 and 550.7 ± 116.7 ng/mL with APS-11SA and to 454.3 ± 85.6 and 402.0 ± 58.0 ng/mL with RENAK PS-1.0, respectively. The average expression of CD41 and CD42b in APS-11SA and RENAK PS-1.0 was similar. DISCUSSION: There are some reports that the gamma-ray irradiation changes the membrane structure of the PSf membrane, crosslinking the polyvinylpyrrolidone (PVP), a hydrophilic agent, on to the membrane. On the other hand, excess amount of PVP may have been eluted during the rinsing procedure in RENAK PS-1.0 because it was sterilized with autoclave. Because both these factors influenced on our results, APS-11SA and RENAK PS-1.0 dialyzers showed excellent blood compatibility.

Verification of physicochemical structures of dialysis membrane using reversal dialysis technique.

OBJECTIVE: Solute removal performance of the dialyzer is closely related to physicochemical structures of the membrane. The objective of this study is to devise a new in vitro evaluation technique to directly correlate the physicochemical structures of the membrane to the dialysis performance. MATERIALS AND METHODS: Commercial 11 dialyzers with cellulose triacetate (CTA), ethylene vinylalcohol co-polymer (EVAL), asymmetry CTA (termed ATA), 4 polysulfone (PSf), polyether sulfone (PES), and 3 polyester polymer alloy (PEPA) membranes were employed for investigation. Normal dialysis experiments were performed with aqueous creatinine (MW 113), bromophenol blue (MW 670), vitamin B12 (MW 1355), chymotrypsin (MW 25,000) test solutions. Reversal dialysis experiments were devised introducing the test solution outside the hollow fiber (HF) and the dialysate inside the HF, respectively. Clearances were measured under QB = 200 mL/min and QD = 500 mL/min at 310 K. The ratio of clearance in the reversal dialysis to that in the normal dialysis termed the yielding factor of asymmetry, fYA , was defined for evaluation. RESULTS AND DISCUSSION: According to the classic mass transfer theory, clearance in the normal dialysis and that in the reversal dialysis are expected to be identical; however, the average fYA was 0.96 for creatinine and was always slightly lower than unity in 10 dialyzers out of 11. This may be caused by un-uniform distribution of the test solution outside the HF, which was more likely to occur than when it flowed inside the HF. Unlike creatinine, the average fYA for vitamin B12 was 1.0 and that for chymotrypsin was 1.06 to 1.45 in membranes with heterogeneous structures (ATA, PSf, PEPA, and PES), but was almost unity (1.02) in homogeneous membrane (CTA). This must be based on the fact that the membrane permeability in the reversal dialysis is much larger than that in the normal dialysis due to the physicochemical structures of the heterogeneous membrane that has a wedge-like pore size distribution in the radial direction. CONCLUSIONS: A wedge-like pore size distribution in the radial direction in heterogeneous membrane was semiquantitatively evaluated by introducing a reversal dialysis technique with a new index.

[Hypersensitivity pneumonitis induced by Aspergillus niger--a case report].

A 52-year-old woman was hospitalized because of severe cough in August 1994. She had engaged in culturing roses in greenhouses since 1968, and had developed a cough during the summer of 1990. Chest radiography showed diffuse ground-glass opacity in both lung fields, and she suffered from hypoxemia (PaO2 = 45.6 torr) while breathing room air. The lymphocyte count in the bronchoalveolar lavage fluid was increased, and transbronchial lung biopsy specimens showed lymphocyte alveolitis in the alveolar spaces. After admission, the patient's symptoms improved rapidly without medication. However, on her return to work, the cough and hypoxemia reappeared. In her rose culture, she had used Rockwool, and Aspergillus niger was detected predominantly in the Rockwool. Precipitins against the extracts of Aspergillus niger were detected with the double immunodiffusion test and the inhalation provocation test yielded clinical symptoms. Our diagnosis was hypersensitivity pneumonitis caused by Aspergillus niger.

[A case of primary pulmonary MALT lymphoma as a nodular shadow on CT scan, and relapsed with diffuse micronodular shadows after surgical resection at 7 years ago].

A 76-year-old man without symptoms was admitted to our hospital for investigation of an abnormal chest shadow in 1994. His chest radiograph showed a nodular shadow in the lingual lobe. Segmentectomy was performed and the histological diagnosis was MALT (mucosa-associated lymphoid tissue) lymphoma. In June 2001, there were no abnormal shadows on the chest radiograph or in 10 mm slice CT. However, high-resolution CT with 2-mm slice thickness revealed diffuse micronodular shadows in both lungs. A relapse of MALT lymphoma was diagnosed by immunohistochemical analysis of tissue specimens obtained by transbronchial lung biopsy. It was observed that the patterns of radiological findings in primary pulmonary MALT lymphoma cases may differ between the initial state and a relapse.