Pathogenesis of dialysis-related amyloidosis

Beta 2-microglobulin has been demonstrated to be a major constituent of amyloid fibrils in dialysis-related amyloidosis. However, the molecular pathogenesis of this complication remains unknown. Several lines of evidence suggest that beta 2-microglobulin is not an innocent bystander, but plays an active role in the development of dialysis-related amyloidosis. The evidence remains inconclusive, however, as to whether it is intact or modified beta 2-microglobulin which is amyloidogenic and contributes to bone and joint destruction. Recent biochemical and immunohistological studies have revealed a new modification of beta 2-microglobulin in amyloid fibrils, the advanced glycation end products formed nonenzymatically between aldoses and proteins. Further study has suggested that the interaction of advanced glycation end product-modified beta 2-microglobulin with monocytes/macrophages gives a plausible, albeit incomplete, explanation for the mechanism of bone and joint destruction in dialysis-related amyloidosis. This review focuses on new aspects of the pathogenesis of dialysis-related amyloidosis.     

N epsilon-(carboxymethyl)lysine in blood from maintenance hemodialysis patients may contribute to dialysis-related amyloidosis

BACKGROUND: Recent studies demonstrated not only that advanced glycation end product could be found in amyloid tissue from patient with dialysis related amyloidosis, but also that amyloid beta2-microglobulin was modified with N(epsilon)-(carboxymethyl)lysine (CML). We wanted to determine if CML could be a biomarker in these patients. METHODS: To raise polyclonal anti-carboxymethyllysine antibody, human serum albumin was carboxymethylated by glyoxylic acid and was immunized to rabbits as antigen. Carboxymethyllysine-hemoglobin (CML-Hb) levels were measured by the dot blotting method using this antibody. RESULTS: The levels of CML-Hb were 6.68 +/- 3.10 nmol CML/mg Hb in nondiabetic hemodialysis patients (N = 70), 6.39 +/- 3.43 nmol CML/mg Hb in diabetic hemodialysis patient (N = 21), and 3.13 +/- 0.88 nmol CML/mg Hb in 47 healthy volunteers. For clinical signs of dialysis-related amyloidosis, 70 nondiabetic hemodialysis patients were scored according Gejyo's criteria. The CML-Hb levels in patients with a high amyloid score as well as a low amyloid score were significantly higher than in patients with negative amyloid score (8.89 +/- 3.53 nmol CMLmg Hb, 7.28 +/- 2.32 nmol CML/mg Hb vs. 5.11 +/- 2.09 nmol CML/mg Hb, P < 0.001, P < 0.05). Furthermore, the CML-Hb levels correlated significantly with serum values of the methylguanidine over creatinine ratio and hyaluronate. CONCLUSIONS: We suggest that CML-Hb is increased in blood from patients on maintenance hemodialysis and is thus a potential biomarker of oxidative damage in these patients. Moreover, CML-modification of protein may play a pathogenic role in the development of dialysis related amyloidosis.     

Colonic pseudo-obstruction due to beta2-microglobulin amyloidosis after long-term haemodialysis

Beta2-microglobulin (A beta2M) amyloidosis is a relatively new secondary amyloidosis associated with renal failure and haemo- and peritoneal dialysis. Although beta2-microglobulin depositions are systemic, clinical manifestations are limited to articular and para-articular disease in most cases. A very limited number of patients have been reported with extra-articular manifestations including those of the gastrointestinal tract. We report on a patient who was treated with haemodialysis for 23 years and developed colonic pseudo-obstruction due to A beta2M amyloidosis.     

Long-term survival (10 years or more) in 30 patients with primary amyloidosis

The median survival in primary systemic (AL) amyloidosis is less than 18 months. No published series of patients with AL amyloidosis have reported survival of more than 10 years. The records of all Mayo Clinic patients with a diagnosis of AL amyloidosis between January 1, 1966 and March 1, 1987 were reviewed. Patients with secondary amyloidosis, familial amyloidosis, senile systemic amyloidosis, and localized amyloidosis were excluded. During the 21 years of the study, 841 patients with AL amyloidosis were seen. Of these, 29 were excluded because the diagnosis was made at autopsy, and 2 others were excluded because no follow-up data were available. Actuarial survival for the 810 patients was 51% at 1 year, 16% at 5 years, and 4.7% at 10 years. Thirty patients survived for 10 years or more after the histologic diagnosis of AL amyloidosis; all received alkylating-agent therapy. In 14 patients, the monoclonal protein disappeared from the serum or urine. Of 10 patients with nephrotic syndrome, 4 had an objective response. Congestive heart failure, older age, creatinine value of 2 mg/dL or more, bone marrow plasma cell value of 20% or more, platelet count of 500 x 10(9)/L or less, and the presence of peripheral neuropathy were underrepresented in the 10-year survivors and are unfavorable prognostic features. Five percent of patients with AL amyloidosis survived for 10 years or more.     

Development of gastrointestinal beta2-microglobulin amyloidosis correlates with time on dialysis

Dialysis-associated beta2-microglobulin (beta2m) amyloidosis affects predominantly musculoskeletal tissue, but visceral involvement also occurs. To evaluate the clinical significance and prevalence of gastrointestinal beta2m amyloidosis, we studied hemodialysis patients admitted for gastrointestinal-related complaints. Hemodialysis patients (excluding those with non-beta2m amyloidosis) who were admitted with gastrointestinal complaints from 1984 to 1994 were identified. Gastrointestinal tissues from patients with available autopsy or surgical specimens were examined using hematoxylin and eosin stain, Congo red stain, and beta2m immunostain. Each case was evaluated independently by two pathologists and scored for quantity and location of beta2m amyloid and associated pathology. Of 24 patients, eight (four men and 4 women) had beta2m amyloid deposits within the gastrointestinal tract. Acute clinical presentation ranged from abdominal pain to gastrointestinal bleeding and was not significantly different for patients with or without gastrointestinal beta2m amyloid deposits. However, the mean time on dialysis of 15.3 +/- 5.7 years (range 6-24 years) for patients with gastrointestinal beta2m amyloidosis was significantly greater than that of patients without gastrointestinal beta2m amyloidosis (10.5 +/- 7.0 years, range <1 to 22 years, p < 0.05). Vascular histopathology ranged from mild focal thickening of vessel walls to massive vascular beta2m amyloid deposition with thrombosis. Extravascular beta2m amyloid ranged from mild to severe with marked expansion of the submucosa. Mucosal pathology ranged from none to severe ulceration. The degree of beta2m amyloid and the associated pathology tended to increase in severity with time on dialysis. Gastrointestinal beta2m amyloid deposition is an underappreciated complication of chronic hemodialysis that is significantly associated with increased time on dialysis. Gastrointestinal beta2m amyloidosis should be considered in any patient on hemodialysis 10 years or more who has gastrointestinal symptoms and can be identified in resection specimens as well as some biopsy specimens. Congo red stain and beta2m immunostains may be necessary for sensitive histopathologic evaluation of gastrointestinal beta2m amyloidosis.     

Beta 2-microglobulin as a predictor of death in HIV-infected women from Kigali, Rwanda

OBJECTIVE: To determine if beta 2-microglobulin (beta 2M) predicts death among HIV-infected African women. DESIGN: Nested case-control study. SETTING: Kigali, Rwanda. PARTICIPANTS: Two hundred and five seroprevalent women known to be HIV-infected since 1986-1987; 67 of whom died of HIV disease (cases) and 138 were alive (controls) as of November 1991. In addition, 128 women who seroconverted between 1986 and 1991. MAIN OUTCOME MEASURES: HIV serology, clinical signs and symptoms of HIV disease, hematology variables, and beta 2M concentration. RESULTS: beta 2M concentration increased over time (P < 0.001) in the seroprevalent women and seroconvertors. The average rate of beta 2M increase in women who died was 0.5 compared with 0.3 mg/l/year in the vital, seroprevalent women (P = 0.07). The strongest independent predictors of death were the rate of change of beta 2M (mg/l/year) [odds ratio (OR), 3.4; 95% confidence interval (CI), 1.7-6.8] and baseline beta 2M concentration (mg/l) [OR, 1.6; 95% CI, 1.2-2.1]. The rate of death for women with beta 2M concentration > or = 7.0 mg/l and a rate of change of beta 2M > or = 0.4 mg/l/year was 7.3 times higher than for women with beta 2M concentration < 7.0 mg/l and a rate of change of beta 2M of < 0.4 mg/l/year (95% CI, 3.1-17.2). The estimated median time from seroconversion to death assuming a constant rate of change of beta 2M was 10.6 years (95% CI, 9.9-11.2) for this cohort of HIV-infected women. CONCLUSIONS: Elevated beta 2M and a high rate of beta 2M increase were strongly associated with mortality among HIV-infected African women. Based on survival estimates using the rate of change of beta 2M, HIV-infected African women have similar survival compared with HIV-infected adults in the United States.     

Design, synthesis, and anticonvulsant activity of 1-(pyrid-3-ylsulfonamido)-2-nitroethylenes

The lipophilic 1-cycloalkylamino-1-(pyrid-3-yl-sulfonamido)-2-nitr oethylenes were synthesized as bioisosteres of BM-34, an anticonvulsant sulfonylthiourea. Compound 17 (ip) emerged from the maximal electroshock seizure (MES) test with a 50% effective dose (ED50) of 8.25 mg/kg. Its anticonvulsant profile was similar to that of phenytoin (ED50 = 9.51 mg/kg) and of BM-34 (ED50 = 1.19 mg/kg): active in the MES test and inactive in seizures induced by subcutaneous injection of pentetrazole, strychnine, bicuculline, picrotoxin, or N-methyl-D,L-aspartate. The neurotoxicity of 17 (TD50 = 113.8 mg/kg) was lower than that of phenytoin (TD50 = 65.5 mg/kg) but higher than that of BM-34 (TD50 = 147.2 mg/kg). Crystallographic study revealed that BM-401 (17) was a zwitterionic structure. Its sulfonamido nitroethylene side chain adopted a conformation which placed the two cycloalkyl rings face to face to form a single hydrophobic area.     

Influence of long-term, low-dose, diuretic-based, antihypertensive therapy on glucose, lipid, uric acid, and potassium levels in older men and women with isolated systolic hypertension: The Systolic Hypertension in the Elderly Program. SHEP Cooperative Research Group

BACKGROUND: Previous studies often of short duration have raised concerns that antihypertensive therapy with diuretics and beta-blockers adversely alters levels of other cardiovascular disease risk factors. METHODS: The Systolic Hypertension in the Elderly Program was a community-based, multicenter, randomized, double-blind, placebo-controlled clinical trial of treatment of isolated systolic hypertension in men and women aged 60 years and older. This retrospective analysis evaluated development of diabetes mellitus in all 4736 participants in the Systolic Hypertension in the Elderly Program, including changes in serum chemistry test results in a subgroup for 3 years. Patients were randomized to receive placebo or treatment with active drugs, with the dose increased in stepwise fashion if blood pressure control goals were not attained: step 1, 12.5 mg of chlorthalidone or 25.0 mg of chlorthalidone; and step 2, the addition of 25 mg of atenolol or 50 mg of atenolol or reserpine or matching placebo. RESULTS: After 3 years, the active treatment group had a 13/4 mm Hg greater reduction in systolic and diastolic blood pressure than the placebo group (both groups, P<.001). New cases of diabetes were reported by 8.6% of the participants in the active treatment group and 7.5% of the participants in the placebo group (P=.25). Small effects of active treatment compared with placebo were observed with fasting levels of glucose (+0.20 mmol/L [+3.6 mg/dL]; P<.01), total cholesterol (+0.09 mmol/L [+3.5 mg/dL]; P<.01), high-density lipoprotein cholesterol (-0.02 mmol/L [-0.77 mg/dL]; P<.01) and creatinine (+2.8 micromol/L [+0.03 mg/dL]; P<.001). Larger effects were seen with fasting levels of triglycerides (+0.9 mmol/L [+17 mg/dL]; P<.001), uric acid (+35 micromol/L [+.06 mg/dL]; P<.001), and potassium (-0.3 mmol/L; P<.001). No evidence was found for a subgroup at higher risk of risk factor changes with active treatment. CONCLUSIONS: Antihypertensive therapy with low-dose chlorthalidone (supplemented if necessary) for isolated systolic hypertension lowers blood pressure and its cardiovascular disease complications and has relatively mild effects on other cardiovascular disease risk factor levels.     

Development and maintenance of bile canaliculi in vitro and in vivo

Four types of high-flux hemodialyzers, Primus 2000 (high-flux polysulfone 2.0 m2), Altra-Flux 170 G (cellulose diacetate 1.7 m2), FLX-15 GW (polyester-polymer alloy 1.5 m2) and PAN-85 DX (polyacrylonitrile 1.7 m2) were evaluated in vivo. A total of 12 stable chronic hemodialysis patients participated in the study and each type of dialyzer was tested once in 9 of them. Blood samples for the measurement of BUN, creatinine, phosphate, uric acid, albumin and beta2-microglobulin (beta2M) were drawn before and 5 min after the end of the study dialysis. During dialysis, which was performed in all patients with a blood flow rate of 250 ml/min for 240 min, the dialysate (550-600 ml/min) was collected every hour and samples were drawn for the measurements of all the above substances. The mean total amount of low-molecular substances removed per session by each dialyzer was very close to 19.5 g for urea, 2.0 g for creatinine, 0.9 g for phosphate and 1 g for uric acid. The one-third (30-33%) of the above amounts were removed during the first hour of dialysis. Dialyzers' clearances for creatinine and uric acid were significantly higher in Primus dialyzer comparing to FLX-15 GW (p < 0.05) while the clearance for urea showed a borderline significance (p = 0.055). No difference was found either among Altra-Flux 170 G, FLX-15 GW and PAN-85 DX or between Primus and PAN-85 DX dialyzers. Phosphate clearance did not show any difference among the four dialyzers. The lowest amount of albumin removed per session was 0.75 g by PAN-85 DX and the highest 1.8 g by FLX-15 GW, while the equivalents for beta2M were 80 mg by Altra-Flux 170 G and 142 mg by PAN-85 DX. A significant adsorption of beta2M on these dialysis membranes was indicated by the combination of a satisfactory serum beta2M reduction ratio (post-/predialysis values = 0.52, 0.77, 0.60, 0.55) with a reduced beta2M clearance (23.9, 13.6, 20.2, 25.1 ml/min). During the first hour of dialysis, in comparison to the following time, the highest amounts of albumin and beta2M (expressed as percentage of total) were removed by the Primus 2000 dialyzer. Our results indicate that under conventional conditions small differences in the surface area of the high-flux dialyzers are unimportant regarding the removal of low molecules. However, the composition of the membrane seems to play an important role in the removal of high-molecular substances.     

Biliary metabolites of levonorgestrel in rats

The metabolism of levonorgestrel (LNG) in the bile following oral administration of the drug was examined in female rat. 1) Within 48 h after administration of 14C-labelled LNG (LNG-14C), 67-82% of the radioactivity was excreted into the bile. 2) Almost all the metabolites in the bile were conjugated with glucuronic acid or sulfuric acid and only a small amount of the unchanged compound was found. 3) After treatment of these metabolites in the bile with beta-glucuronidase and arylsulfatase, more than ten aglycones were detected on TLC. Three main aglycones, M1, M2 and M3, were isolated. They accounted for 68.0, 0.8 and 11.5% of the radioactivity excreted into the bile, respectively. 4) The structures of M1 and M2 were assumed to be 13-ethyl-18,19-dinor-5 alpha,17 beta-pregn-20-yne-3 alpha,17- diol and 13-ethyl-18,19-dinor-5 beta,17 beta-pregn-20-yne-3 alpha,17-diol, respectively, by NMR and LC/MS analyses, and confirmed by direct comparison with respective authentic samples. M3 was assigned to be 13-ethyl-18,19-dinor-5 alpha,17 beta-pregn-20-yne-3 alpha,16 beta,17-triol by NMR, LC/MS and GC/MS analyses and acetonide derivation. 5) Isolation of the glucuronide metabolite, M4, from the bile, was achieved by column chromatography using Amberlite XAD-2 and Sephadex LH-20. Hydrolysis of this compound with beta-glucuronidase released M1 and glucuronic acid. After M4 was converted to an acetylated-methyl ester derivative, the definite structural assignment of M4 was established to be M1-3-O-yl glucuronic acid by NMR analysis. The NOE effect and the value of the corresponding coupling constant of the anomeric proton showed that the glucoside moiety was in the beta configuration. These findings suggested that LNG was predominantly converted to 5 alpha-reduced metabolites and that the 5 beta-metabolite accounted for less than 1% of the total metabolites in female rats. These metabolites were excreted as glucuronides into the bile.     

Amyloid beta 2-microglobulin is modified with imidazolone, a novel advanced glycation end product, in dialysis-related amyloidosis

We have recently demonstrated by immunohistochemistry that amyloid beta 2-microglobulin (beta 2m) is modified with advanced glycation end products (AGEs) in dialysis-related amyloidosis (DRA). To further investigate the role of the Maillard reaction in the pathogenesis of DRA, we produced a monoclonal antibody to imidazolone, a novel AGE, and a reaction product of arginine and 3-deoxyglucosone (3-DG) which was accumulated in uremic serum. Then we determined the localization of imidazolone in the amyloid tissues by immunohistochemistry using the antibody. The connective tissues in carpal tunnel and ligamentum flavum were obtained from six patients with carpal tunnel syndrome and two patients with destructive spondyloarthropathy. Imidazolone was localized to all the beta 2m-positive amyloid deposits in these patients. Western blotting using the antibody demonstrated that beta 2m extracted from the synovium amyloid of hemodialysis patients was modified with imidazolone. Further, beta 2m isolated from the blood ultrafiltrate of hemodialyzed patients was also modified with imidazolone. In vitro incubation of beta 2m with 3-DG produced imidazolone-modified beta 2m. In conclusion, amyloid tissue beta2m is modified with imidazolone in patients with DRA. 3-DG accumulating in uremic serum may be involved in the modification of beta 2m with imidazolone.     

A clinical study of dialysis-related osteoarthropathy in long-term hemodialysis patients

Amyloid osteoarthropathy has been seen frequently in long-term hemodialysis (HD) patients, in which the bone X-ray examination reveals characteristic cystic radiolucency (CRL) of the carpal bone, shoulder joint, hip joint and knee joint, and destructive spondylarthropathy (DSA) of cervical vertebrae. To clarify the clinico-pathological significance of CRL and DSA in HD-related amyloidosis, we investigated the grade and frequency of CRL or DSA and these relationship with age, HD duration, primary diseases, osteoarticular symptoms and blood analysis in 817 HD patients (492 male and 325 female, age: 52.6 + 15.5 years, dialysis duration: 6.8 + 5.4 years). The number of cases with osteoarticular symptoms increased with the prolongation of HD duration. CRL and DSA were observed even in patients without osteoarticular symptoms: 26.7% for carpal bone, 26.2% for shoulder joint, 17.3% for hip joint and 22.2% for DSA. The grade and frequency of CRL and DSA also increased in accordance with age and HD duration. In patients with CRL of the carpal bone, shoulder CRL was noticed in 39.7%, hip CRL in 25.8%, and DSA in 14.3% of cases, respectively, and these frequencies increased with the prolongation of HD duration. In the carpal CRL negative group, shoulder CRL was noticed in 14.6%, hip CRL in 7.5%, and DSA in 6.0%, respectively. Although there was no relationship between CRL or DSA and serum beta 2-MG level in any of the cases, the serum beta 2-MG level was lower in patients with HD showing shoulder CRL (+2) and DSA (+) for more than 16 years. No significant relationship was noticed between CRL or DSA and serum C-PTH and aluminum level. These results suggested that aging was related to CRL or DSA formation in dialysis-related amyloidosis. The findings also suggested that systemic bone X-ray examination should be considered in patients with carpal bone CRL, high-age patients and long-term HD patients even without osteoarticular symptoms.     

Implication of an increased oxidative stress in the formation of advanced glycation end products in patients with end-stage renal failure

Recent studies have demonstrated a marked increase in the level of advanced glycation end products (AGEs) in the plasma, skin and amyloid fibrils of hemodialysis (HD) patients. The presence of AGEs in (beta2m) forming amyloid fibrils has been established in a previous immunochemical study relying on a monoclonal anti-AGE antibody. In the present study, Western blot analysis and immunohistochemistry reveal that the epitope recognized by this antibody is N epsilon-(carboxymethyl)lysine (CML) and that CML is one of the AGE structures present in amyloid fibrils. Thus, two AGE structures, CML and pentosidine, are now recognized in dialysis-related amyloidosis. AGE accumulation in uremia is not accounted for by elevated glucose levels. Since CML and pentosidine formation are closely linked to oxidative processes, we tested the hypothesis that a high oxidative stress enhanced AGE formation in HD patients. We focused on ascorbic acid (AA) because AA is easily oxidized under oxidative stress and its oxidized form (oxiAA) is a source of CML and pentosidine. In vitro incubation of beta2m with AA under atmospheric oxygen resulted in: (1) the rapid appearance of characteristic physicochemical properties of AGEs (brown color, fluorescence, polymerization tendency); (2) the transformation of beta2m into AGE-modified beta2m recognized by a specific monoclonal antibody; and (3) the accelerated formation of CML in beta2m and beta2m-peptide, recognized by mass spectrometry. A similar in vitro incubation of human serum albumin disclosed a parallel production of pentosidine measured by high-performance liquid chromatographic assay. In HD patients, the degree of AA oxidation, assessed as the ratio of oxiAA to total ascorbate, was more than twice as high as that of normal subjects (0.87 +/- 0.16 vs. 0.35 +/- 0.11, P < 0.0001), suggesting the presence of an increased oxidative stress. Interestingly, plasma level of oxiAA was correlated with the plasma levels of protein linked (P < 0.01, r2 = 0.25) and free (P < 0.05, r2 = 0.22) pentosidine. Altogether these results demonstrate that AGE, that is, CML and pentosidine, production is accelerated under oxidative stress, even in the absence of glucose. They suggest that, in uremia, CML and pentosidine production is determined both by an increased oxidative stress and the availability of precursors such as oxiAA. Finally, both CML and pentosidine contribute to the AGEs present in dialysis-related amyloid fibrils.     

Hemofiltration or hemodiafiltration with on-line production of substitution fluid: clinical observation of safety and effectiveness

OBJECTIVE: To observe the safety and cardiovascular stability of on-line hemofiltration (HF) or hemodiafiltration (HDF) and evaluate the clinical effectiveness of one HF or HDF session in addition to two hemodialysis (HD) sessions weekly. METHODS: Forty patients were randomly divided into four groups: group predilutional (PRD) HF (filtration rate: 259-333 ml/min) group predilutional HDF (filtration rate: 167 ml/min) group postdilutional (POD) HDF (filtration rate: 83 ml/min) and group bicarbonate HD. The reduction rate of parathyroid hormone (PTH), beta 2-microglobulin (beta 2MG), alpha 1-microglobulin (alpha 1MG) and KT/V in the initial treatment of every month was observed, and the incidence of hypotension and pyretic reaction during each treatment was evaluated. RESULTS: After 4-month observation, the KT/V for Group POD HDF is better than that for the other three groups, and for Group PRD HDF is better than that for Group HF and HD. Serum level of PTH and beta 2MG was not decreased after every treatment in Group HD, and so was serum level of alpha 1MG in all groups. Significant removal of PTH and beta 2MG was observed in Group HF, PRD HDF and POD HDF. The monthly serum level of beta 2MG and KT/V were stable in all groups, but the monthly serum level of PTH tended to be decreased in Group HF, PRD, HDF, and POD HDF. The incidence of pyretic reaction in HF or HDF was the same as in HD. Although the ultrafiltration volume was significantly higher during HF or PRD HDF than during HD, the incidence of hypotension in HF or PRD HDF was similar to that in HD. CONCLUSIONS: On-line HF or HDF proved to be a safe and reliable method. POD HDF mode seems to have the best KT/V, HF or PRD HDF offers a better choice for preventing intradialytic hypotension. One HF or HDF session in addition to two HD sessions weekly is similarly effective to decrease the serum level of PTH and the proof of the clinical effectiveness of such a therapy awaits a long-term observation.     

Influence of blood flow on adsorption of beta2-microglobulin onto AN69 dialyzer membrane

Adsorption onto the dialyzer membrane is a contributing factor to the elimination of beta2-microglobulin (beta2M) from the sera of uremic patients. The purpose of this prospective study was to ascertain the influence of the blood flow rate on adsorption of beta2M onto the polyacrylonitrile (AN69) hollow-fiber dialyzer membrane in 8 patients during regular hemodialysis (HD). Blood first passed through a low-flux polysulfone dialyzer and then through an AN69 dialyzer, which was not in contact with the dialysis fluid. During the investigation period (first hour of the HD session), the blood flow rate was 100 ml/ min (first part of the study), 200 ml/min (second part of the study), and 300 ml/min (third part of the study). Ultrafiltration was not performed during the investigation period. At the start of the HD sessions, the serum concentration of beta2M in the afferent blood line did not differ significantly among the 3 parts of the study. Serum beta2M was measured in samples taken from the afferent and efferent blood lines of the AN69 dialyzer at 5, 10, 15, 30, 45, and 60 min. The serum beta2M concentration decreased significantly in blood that had passed through the AN69 dialyzer. This decrease, indicating membrane adsorption, was maximal during the first part and minimal during the third part of study. The decrease in the contact time between the blood and the AN69 could be the underlying cause. The calculated quantities of beta2M adsorbed onto the AN69 membrane (44.2 +/- 10.2, 43.2 +/- 12.1, and 42.6 +/- 17.3 mg) did not differ significantly among the 3 parts of the study. These results suggest that an increase in blood flow rate from 100 to 300 ml/min did not significantly affect the quantity of beta2M adsorbed onto the AN69 membrane.     

Development of a Response Surface for Prediction of Nitrate Removal in Sulfur–Limestone Autotrophic Denitrification Fixed-Bed Reactors

Sulfur–limestone autotrophic denitrification (SLAD) processes are very efficient for treatment of ground or surface water contaminated with nitrate. However, detailed information is not available on the interaction among some major variables on the design and performance of the SLAD process. In this study, the response surface method was used by designing a rotatable central composite test scheme with 12 SLAD column tests. A polynomial linear regression model was set up to quantitatively describe the relationship of the effluent and influent nitrate–nitrogen concentration and hydraulic retention time (HRT) in the SLAD column reactors. This model may be used for estimating the effluent nitrate–nitrogen concentration when the influent nitrate–nitrogen concentration ranges between 20 and 110?mg/L and the HRT ranges between 2 and 9?h. Based on our model and the requirement for nitrite control, we recommend that the HRT of the SLAD column reactor be kept ≥ 6?h and the nitrate loading rate less than 200 g NO3?–N/day?m3 media to achieve high nitrate removal efficiency (>99%) and prevent nitrite accumulation from being >1?mg/L NO2?–N.     

Pharmacokinetics of ceftizoxime in renal failure patients without dialysis

AIM: To investigate the pharmacokinetics of ceftizoxime (Cef) in renal failure patients without any dialysis and supply the basis for a suitable clinical regimen. METHODS: Cef in plasma and urine was assayed by HPLC. RESULTS: After injecting Cef 16.7 mg kg-1, Cef concentration in blood was described as a 2-compartment open model. The main pharmacokinetic parameters were Vd 0.55 +/- 0.17 L kg-1; AUC 879 +/- 460 mg L-1 h; Cl 27 +/- 11 mL kg-1 h-1. T1/2 beta was 15 +/- 4 h. CONCLUSION: T1/2 beta in renal failure patients was about 10 times longer than that in normal volunteers. The clinical regimen should be adjusted in renal failure patients with infection, either prolonging the interval between Cef administration, or decreasing Cef dosage.     

In vivo determination of very-low-density lipoprotein-apolipoprotein B100 secretion rates in humans with a low dose of l-[1-13C]valine and isotope ratio mass spectrometry

Beta2-Microglobulin (beta2-m) is a polypeptide that is freely filtered and then mostly reabsorbed and degraded in the proximal renal tubule. Beta2-m is a marker of glomerular filtration (GFR) in renal failure, whereas urinary beta2-m is a marker of proximal renal tubular dysfunction. Preeclampsia (PE) (ie, de novo hypertension in pregnancy with accompanying renal, cerebral, or liver disease or thrombocytopenia) often has renal involvement characterized by proteinuria, decreasing glomerular filtration, or renal tubular dysfunction. The aim of this study was to determine whether serum beta2-m concentration or urinary beta2-m excretion were greater in women with PE than in women with gestational hypertension (GH) (ie, isolated de novo hypertension in the second half of pregnancy) and normal pregnant women. Seventy-five pregnant women (35 with PE, 22 with GH, and 18 normotensives) were studied prospectively. Serum creatinine and beta2-m concentrations, 24-hour proteinuria, and fractional excretion (FE) of beta2-m were measured. Preeclamptics had similar serum creatinine but higher serum beta2-m (3.26+/-0.99 mg/L) than gestational hypertensives (2.44+/-0.77 mg/L; P = 0.016), and both groups had higher serum beta2-m than controls (1.62+/-0.54 mg/L; P = 0.001). FE of beta2-m was similar amongst groups (PE: 0.27%; interquartile range [IQR]: 0.20-0.86; GH: 0.21%; IQR: 0.11-0.40; controls: 0.26%, IQR: 0.12-0.69). PE is characterized by higher serum beta2-m but similar serum creatinine to GH. Because FE beta2-m is similar in these groups, this implies reduced filtering of beta2-m in PE rather than altered tubular handling of beta2-m. Further studies are now necessary to assess whether measurement of serum beta2-m is helpful in the clinical management of the hypertensive disorders of pregnancy.     

Comparative activity of azithromycin against clinical isolates of mycobacteria

Azithromycin exhibited in-vitro activity against 20 clinical isolates of Mycobacterium avium complex for which the MIC90 was 32 mg/L and 22 clinical isolates of other mycobacteria but showed no activity against 20 isolates of Mycobacterium tuberculosis (MIC90 > 128 mg/L) nor against the single isolate of Mycobacterium marinum tested (MIC 128 mg/L). These results suggest that the drug may prove useful for the prophylaxis and treatment of infections due to non-tuberculous mycobacteria, including M. avium complex in patients with AIDS.     

Application of Ce(IV) in industrial wastewater treatment

At present,rare earth application in wastewater treatment has become more and more widely,according to the fact that the Ce(IV) has the strong oxidation ability under acid condition,we have studied the application of Ce(IV) in industrial wastewater treatment originally.Results showed that oxidation-reduction reaction occurred between Ce(IV) and the organic compounds or other reducing substances in industrial wastewater,thereby the colority and CODcr reduced effectively.Ce(IV) formed [Ce(OH)x·nH2O](4-x)+ after hydrolyzation and Ce(III) obtained after Ce(IV) reduction formed [Ce(OH)x·nH2O](3-x)+ after hydrolyzation,these hydrate had big specific surface area,could adsorb the suspension substances and removed toxic or harmful ions in industrial wastewater.After treatment by Ce(IV),the analytical results of industrial wastewater are as follows:The CODcr became 58 mg/L from 1646 mg/L,the total COD removal efficiency was more than 95.0%.Turbidity reduced to no more than 10NTU from 87NTU.The chroma became 6 degree from 26 degree,suspension substances content decreased to no more than 2 mg/L from 36 mg/L,and total arsenic and fluorion became <0.05 mg/L and <0.10 mg/L from 0.60 and 15.3 mg/L.Total cadmium reduced to 0.01 mg/L from the 0.58 mg/L.These all indicated that Ce(IV) was one kind of latent good water treatment chemical.