Interleukin-8 in chronic renal failure and dialysis patients

A total of 105 patients participated in this study, including 10 with chronic glomerulonephritis with normal renal function (CGN patients), 36 uraemic patients (CRF patients), 19 continuous ambulatory peritoneal dialysis patients (CAPD) without peritonitis, three CAPD patients with peritonitis, 37 patients undergoing chronic haemodialysis (HD) divided into short-term HD, 15 patients; medium-term HD, 12 patients; and long-term HD, 10 patients. IL-8 and two other proinflammatory cytokines, IL-6 and TNF alpha were tested using a specific immunoassay. IL-8, IL-6, and TNF alpha serum levels were significantly increased in patients with chronic renal failure compared to their levels in normal individuals (P < 0.0001, P < 0.05 and P < 0.0001 respectively). The most pronounced increment in IL-8, IL-6 and TNF alpha serum levels was observed in CAPD patients (P < 0.0001). CAPD patients without peritonitis showed relatively low levels of IL-8 or IL-6 in peritoneal dialysate effluents (PDE), whereas PDE-TNF alpha were not detectable in almost all patients tested. Patients with peritonitis showed very high serum and PDE levels of IL-8, IL-6 and TNF alpha. The clinical recovery from peritonitis was characterized by a rapid fall in IL-8, IL-6 and TNF alpha in serum and dialysate. HD patients showed a significant increase in serum levels of IL-8 and also IL-6 and TNF alpha compared to normal individuals (P < 0.05, P < 0.05 and P < 0.01 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Peritonitis in continuous ambulatory peritoneal dialysis. Culture of peritoneal dialysate fluid

Conventional aerobic and anaerobic culture of peritoneal dialysate effluent from patients in continuous peritoneal dialysis (CAPD) was compared to culture in a semiautomated blood culture system. During a two-year period 78 of 79 consecutive episodes of peritonitis among 45 Danish CAPD patients were cultured and the etiology of the infection found in 73 (94%). The sensitivity of the blood culture system was 88%, whereas the sensitivity of the conventional culture of the dialysate effluent was 81%. This difference is not significant (McNemar test; 0.5 > p > 0.3). The majority of isolates were Gram-positive bacteria dominated by coagulase-negative staphylococci (38%). In comparison, only 2% of the cultures of peritoneal dialysate effluent taken within the same period from patients without clinical signs of peritonitis were positive. All the Gram-positive aerobic bacteria were sensitive to vancomycin whereas 97% of the Gram-negative aerobic bacteria were sensitive to gentamicin. An initial empiric treatment of peritonitis with a combination of vancomycin and gentamicin is recommended.     

Lys75 of Anabaena ferredoxin-NADP+ reductase is a critical residue for binding ferredoxin and flavodoxin during electron transfer

Previous studies, and the three-dimensional structure of Anabaena PCC 7119 ferredoxin-NADP+ reductase (FNR), indicate that the positive charge of Lys75 might be directly involved in the interaction between FNR and its protein partners, ferredoxin (Fd) and flavodoxin (Fld). To assess this possibility, this residue has been replaced by another positively charged residue, Arg, by two uncharged residues, Gln and Ser, and by a negatively charged residue, Glu. UV-vis absorption, fluorescence, and CD spectroscopies of these FNR mutants (Lys75Arg, Lys75Gln, Lys75Ser, and Lys75Glu) indicate that all the mutated proteins folded properly and that significant protein structural rearrangements did not occur. Steady-state kinetic parameters for these FNR mutants, utilizing the diaphorase activity with DCPIP, indicate that Lys75 is not a critical residue for complex formation and electron transfer (ET) between FNR and NADP+ or NADPH. However, steady-state kinetic activities requiring complex formation and ET between FNR and Fd or Fld were appreciably affected when the positive charge at position of Lys75 was removed, and the ET reaction was not even measurable if a negatively charged residue was placed at this position. These kinetic parameters also suggest that it is complex formation that is affected by mutation. Consistent with this, when dissociation constants (Kd) for FNRox-Fdox (differential spectroscopy) and FNRox-Fdrd (laser flash photolysis) were measured, it was found that neutralization of the positive charge at position 75 increased the Kd values by 50-100-fold, and that no complex formation could be detected upon introduction of a negative charge at this position. Fast transient kinetic studies also corroborated the fact that removal of the positive charge at position 75 of FNR appreciably affects the complex formation process with its protein partners but indicates that ET is still achieved in all the reactions. This study thus clearly establishes the requirement of a positive charge at position Lys75 for complex formation during ET between FNR and its physiological protein partners. The results also suggest that the interaction of this residue with its protein partners is not structurally specific, since Lys75 can still be efficiently substituted by an arginine, but is definitely charge specific.     

Fracture strength of type IV and type V die stone as a function of time

OBJECTIVE: To evaluate risk/benefit of various continuous ambulatory peritoneal dialysis (CAPD) dialysate calcium concentrations. DATA SOURCES: A review of the literature on the effects of various CAPD dialysate Ca concentrations on plasma Ca, plasma phosphate, plasma parathyroid hormone (PTH), doses of calcium carbonate, doses of vitamin D analogs, and requirements of aluminum-containing phosphate binders. STUDY SELECTION: Eleven studies of nonselected CAPD patients, and 13 studies of CAPD patients with hypercalcemia were reviewed. RESULTS:In nonselected CAPD patients, treatment with a reduced dialysate Ca concentration (1.00, 1.25, or 1.35 mmol/L) improved the tolerance to calcium carbonate and/or vitamin D metabolites and reduced the need for Al-containing phosphate binders. When using dialysate Ca 1.25 or 1.35 mmol/L, the initial decrease of plasma Ca and increase of PTH could easily be reversed with an immediate adjustment of the treatment. After 3 months, stable plasma Ca and PTH levels could be maintained using only monthly investigations. In patients with hypercalcemia and elevated PTH levels, treatment with dialysate Ca concentrations below 1.25 mmol/L implied a considerable risk for the progression of secondary hyperparathyroidism. When hypercalcemia was present in combination with suppressed PTH levels, a controlled increase of PTH could be obtained with a temporary discontinuation of vitamin D and/or a reduction of calcium carbonate treatment in combination with a dialysate Ca concentration of 1.25 or 1.35 mmol/L. CONCLUSION: Most CAPD patients can be treated effectively and safely with a reduced dialysate Ca concentration of 1.35 or 1.25 mmol/L. Treatment with dialysate Ca concentrations below 1.25 mmol/L should not be used. A small fraction of patients with persistent hypocalcemia need treatment with high dialysate Ca, such as 1.75 mmol/L.     

A study of cis-diamminedichloroplatinum(II) suppositories for the treatment of rabbit uterine endometrial carcinoma

OBJECTIVE: To determine the effects of continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) on endothelin-1 (ET-1) levels in patients with end-stage renal disease (ESRD) and to assess the relationship between plasma ET-1 levels and selected patient parameters. DESIGN: Prospective, nonrandomized comparison study. SETTING: Outpatient CAPD and HD units of a university medical center. PARTICIPANTS: Twelve ESRD patients (6 on CAPD and 6 on HD) and 5 healthy normotensive subjects. INTERVENTIONS: CAPD patients had blood and peritoneal dialysate samples collected and measurements made following an overnight exchange. HD patients had blood collected and measurements made at 0 hours (basal) and again at 3 hours during a midweek HD session. Blood samples were also collected from normal subjects and served as ET-1 controls. MEASUREMENTS: ET-1 and patient parameters (creatinine, peritoneal dialysate volume, blood pressure, body weight, age, and treatment duration) were determined. Data are reported as the mean +/- one standard deviation. RESULTS: Plasma and dialysate ET-1 levels in the CAPD group were 19.5 +/- 4.2 pg/mL and 9.2 +/- 4.2 pg/mL, respectively. The control group plasma and unused dialysate contained no detectable ET-1 (< 3.0 pg/mL, the limit of detection). The peritoneal clearance of ET-1 was less than that of creatinine (2.29 +/- 0.69 mL/minute vs 4.22 +/- 0.66 mL/minute, p = 0.005). The basal (0 hour) plasma ET-1 level in the HD group (16.5 +/- 7.8 pg/mL) did not differ from that of the CAPD group, p = 0.423. Furthermore, no differences in patient parameters were detected between the CAPD and basal HD groups. Although the mean arterial pressure (MAP) decreased during HD, the plasma ET-1 level at 3 hours (13.5 +/- 5.4 pg/mL) remained unchanged from the basal level, p = 0.307. An analysis of pooled data from the CAPD and HD groups revealed no significant correlation between plasma ET-1 and MAP, body weight, creatinine, or treatment duration. There was, however, a positive correlation between plasma ET-1 and age (r = 0.643, p = 0.024).     

The nitric oxide donor nitroprusside intraperitoneally affects peritoneal permeability in CAPD

Nitroprusside is a nitric oxide (NO) donor. To investigate effects of nitroprusside i.p. on peritoneal permeability and perfusion, standard peritoneal permeability analyses were performed. Ten stable CAPD patients were studied twice within one week with glucose based dialysate (1.36% Dianeal) with and without addition of nitroprusside 4.5 mg/liter. Mass transfer area coefficients (MTAC) of CO2 were calculated to estimate peritoneal blood flow. Nitrate, a stable metabolite of NO, and cGMP, a second messenger of NO synthesis, were measured in plasma and dialysate. The MTACs of low molecular weight solutes were greater with nitroprusside (NP) compared to the control dwell (C): creatinine median 14.1 (NP) versus 9.9 ml/min (C), urea 21.7 (NP) versus 18.5 ml/min (C) and urate 10.5 (NP) versus 8.6 ml/min (C) (P < 0.05 for all). This points to an increased effective peritoneal surface area with nitroprusside. Furthermore, the restriction coefficient for the low molecular weight solutes decreased from 1.28 (C) to 1.23 (NP) (P = 0.02), suggesting some effect also on the size selectivity to these solutes. The effect of nitroprusside on the clearances of serum proteins was more pronounced. The increase with nitroprusside was 34% for beta 2-microglobulin, 70% for albumin, 77% for IgG and 143% for alpha 2-macroglobulin. This reduction in size selectivity was reflected in a decrease in the restriction coefficient for macromolecules from 2.29 (C) to 1.86 (NP), P < 0.01. This implies an increase in the intrinsic permeability of the peritoneal membrane. Kinetic modeling, using computer simulations, was done to analyze these effects in terms of the pore theory, using a convection model and a diffusion model for the transport of macromolecules. Nitroprusside led to an increase of both the large pore radius and the small pore radius and of the unrestricted area over diffusion distance. These effects were more pronounced with the diffusion model. The MTAC CO2 was not different: NP 76.9 and C 84.1 ml/min. MTACs of nitrate were not greater than expected on the basis of the molecular weight during both dwells. The dialysate/plasma (D/P) ratio of cGMP was greater after addition of nitroprusside: 0.36, range 0.21 to 0.77 (C) and 0.74, 0.23 to 2.50 (NP), P = 0.02. With nitroprusside the D/P ratio of cGMP was greater than expected on the basis of its molecular weight (P < 0.001). This points to local generation of cGMP after the addition of nitroprusside, induced by NO. No differences were found in the dialysate concentrations of the prostaglandins (PG) PGE2 and 6-keto-PGF1 alpha and thromboxane B2 after addition of nitroprusside. The transcapillary ultrafiltration rate and the net ultrafiltration rate during four hours were not different with nitroprusside. In conclusion, nitroprusside i.p. increased the effective peritoneal surface area and the intrinsic permeability, but the peritoneal blood flow did not change. The greater than expected D/P ratios of cGMP point to local generation of cGMP with nitroprusside, induced by NO.     

Interleukin-10, interferon gamma, interleukin-2, and soluble interleukin-2 receptor alpha detected during peritonitis in the dialysate and serum of patients on continuous ambulatory peritoneal dialysis

OBJECTIVE: To analyze interleukin (IL)-10, interferon gamma (IFN-gamma), IL-2, and soluble IL-2 receptor alpha (sIL-2R alpha) in the dialysate and serum of patients on continuous ambulatory peritoneal dialysis (CAPD). DESIGN AND PATIENTS: Samples from dialysate bags were collected during the initial month of dialysis. During peritonitis, samples were collected from the first three bags on the day of admittance to the hospital and from the night bags on days 3 and 10. Serum samples were drawn on days 1 and 10. RESULTS: IL-10 was detected in all dialysate samples except one on the first day of infection, with a peak median level of 50 pg/mL and a slow decrease thereafter. In serum the median levels never exceeded detectable levels. Patients infected with Escherichia coli or Staphylococcus aureus had higher IL-10 levels in dialysate on day 3 as compared to the remaining patients (p < 0.05). If the catheter had to be drawn, because of persistent cloudy dialysate, the IL-10 levels remained elevated for a longer time (p < 0.05). IFN-gamma and IL-2 were detected only in the dialysate of patients infected with either S. aureus or S. epidermidis. Only one serum sample showed increased IFN-gamma. SIL-2R alpha was found in all the serum and dialysis samples from the first day of infection. Contrary to the analyzed cytokines, the receptor showed severalfold higher levels in serum as compared to the dialysate. During the infection the receptor levels in the dialysate increased, while they remained stationary in the serum, indicating a local production. CONCLUSION: This is the first time IL-10 has been demonstrated in the dialysate during peritonitis in CAPD patients. In view of its role as a suppressor of the immune and inflammatory responses, it is a potentially important observation, which might have clinical implications in the future.     

Optimum electrode geometry for spinal cord stimulation: the narrow bipole and tripole

From a pathophysiological perspective, several studies have been performed on cytokines in chronic renal failure patients treated with continuous ambulatory peritoneal dialysis (CAPD). Because the peritoneal macrophages in CAPD patients produce some cytokines and the urinary secretion route for cytokines lost in those patients, CAPD patients are considered to have different plasma cytokine levels. Among the various cytokines, research on certain inflammatory cytokine levels has been reported. In studies of CAPD patients, peripheral blood and dialysate can be used as specimens. There are two methods of research. One involves determining the cytokine concentration in specimens and culture supernatant, while the other is to determine the mRNA expression of mononuclear cells in specimens and cultured mononuclear cells. The plasma levels of macrophage colony stimulating factor (M-CSF), granulocyte macrophage colony stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) were measured in CAPD patients without peritonitis. Plasma M CSF, GM CSF and G-CSF levels in CAPD patients were higher than those in healthy volunteers (p < 0.0001).     

Commonly prescribed salt intake in continuous ambulatory peritoneal dialysis patients is too restrictive: results of a double-blind crossover study

Salt restriction in continuous ambulatory peritoneal dialysis (CAPD) patients is widely prescribed and thereby may reduce quality of life. It is presumed that this has a beneficial effect on BP and reduces the need for hypertonic dialysate. However, this has never been formally evaluated. A double-blind crossover study of placebo versus sodium chloride pills (60 mEq of sodium per day) is presented in 20 stable CAPD patients, 10 of whom were hypertensive. Dietary sodium was quantified throughout the study by 3-d dietary histories and remained unaltered throughout. There was a clinically unimportant but statistically significant rise in BP with added salt: 135/77 to 144/82 (P < 0.05). No rise in BP occurred in the hypertensive patients. Weights, use of hypertonic dialysate, and BP medications remained unaltered throughout the study. In conclusion, 200 mEq of sodium per day, i.e., a normal sodium intake, is easily tolerated in stable CAPD patients, and the recommended sodium intake commonly prescribed is too restrictive.     

Clinical experience of automated peritoneal dialysis

For uremic patients on continuous ambulatory peritoneal dialysis who are complicated with peritonitis, hernia or burn out of meticulous procedure, automated peritoneal dialysis (APD) is a new alternative therapy. We started our APD program by continuous cyclic peritoneal dialysis (CCPD) method from October, 1991 and this study included 3 CAPD patients. Our studies showed high dose CCPD was better than CAPD in ultrafiltration and urea clearance with similar weekly creatinine clearance and weekly KT/V urea. During the one year treatment course, there was no signs of fluid overload. We performed once to twice day time exchange by low volume dialysate (1500-1600ml) There was no events of abdomen discomfort due to increase intraabdominal pressure or recurrent hernia in susceptible patient. The decrease in day time exchange frequency obviously reduced patients'loading. One patient changed to high dose CCPD due to underdialysis after stand CCPD therapy. Two patients returned to hemodialysis due to severe peritonitis and technique method, but careful assessment of dialysis adequacy with PET test and KT/V evaluation is mandatory.     

Distally based fasciocutaneous flaps: a versatile option for coverage of difficult war wounds of the foot and ankle

Addition of the nitric oxide (NO) donor nitroprusside to 1.36% glucose dialysate enlarges the effective peritoneal surface area during four-hour dwells. The theoretical positive effect on ultrafiltration is, however, counteracted by an increase in glucose absorption. The absorption of the glucose polymer icodextrin is much lower in comparison with glucose-based dialysis solutions, due to its high molecular weight. In the present study 7.5% icodextrin dialysis solution with and without the addition of 4.5 mg/liter nitroprusside was studied during eight-hour CAPD dwells. Two Standard Peritoneal permeability Analyses, adapted for eight-hour dwells, were performed in 10 stable CAPD patients. Nitrate and cGMP were measured as parameters of NO synthesis. The transcapillary ultrafiltration increased in a linear way with icodextrin (ICO) and was even higher after the addition of nitroprusside (NP): 666 (ICO) versus 834 (NP) ml/8 hr, P = 0.03. The effective lymphatic absorption rate was not different. The resulting net ultrafiltration increased with nitroprusside: 344 (ICO) versus 540 (NP) ml/8 hr, P < 0.01. The mass transfer area coefficient of urea increased 15% and that of creatinine 26% with nitroprusside, consistent with the expected enlargement of the vascular peritoneal surface area. The increase in protein clearances was more pronounced the larger the protein: beta 2-microglobulin 19%, albumin 47%, IgG 63% and alpha 2-macroglobulin 95%. Dialysate/plasma (D/P) ratios of nitrate were not higher than the expected values on the basis of its molecular weight (P < 0.001). They increased 19% with nitroprusside. Also, the D/P ratio cyclic guanosine monophosphate (cGMP) after four hours increased with nitroprusside (0.39, range 0.13 to 0.55 ICO, and 0.82, range 0.36 to 1.39 NP, P = 0.01). With nitroprusside the D/P ratio cGMP was higher than expected after four and eight hours (P < 0.001). This points to local generation of NO after addition of nitroprusside. The nitroprusside induced increase in the mass transfer area coefficients (MTAC) of creatinine and in the ultrafiltration caused an increase in the creatinine clearance from 4.2 ml/min to 5.0 ml/min during the eight-hour dwell. This means that nitroprusside adds 3 liters/week to the peritoneal clearance of creatinine. The adequacy of peritoneal dialysis can therefore be improved by the addition of nitroprusside to 7.5% icodextrin, used for the long exchange.     

The history of occupational health service in Korea

Dialysate and serum levels of granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage colony stimulating factor (GM-CSF) and leukemia inhibitory factor (LIF) were analyzed in patients with continuous ambulatory peritoneal dialysis (CAPD). Samples from the peritoneal effluent and from serum were obtained during the first months of dialysis and during peritonitis from the first three dialysate bags drained on the day of admittance and form nightbags on days three and ten. Serum samples were drawn on days one and ten. On the first day of infection G-CSF was detected in twelve out of fifteen samples in the dialysate and reached its peak median level, 443 pg/ml, in the first drained bag and thereafter decreased significantly. Also in serum a peak, 190 pg/ml, was observed on the first day. LIF was found in six of ten analyzed dialysate samples, with a peak median level of 77 pg/ml on day one, while only four of ten patients had detectable GM-CSF. Peripheral blood mononuclear cells from non-infected CAPD patients were stimulated with lipopolysaccharide and G-CSF levels in the supernatants increased significantly (P < 0.05) after 6 h stimulation. We conclude that G-CSF is produced locally in the dialysate during the acute stage of peritonitis and to a lesser extent also systemically. These findings are in line with G-CSF production after LPS stimulation of peripheral blood mononuclear cells.     

Sudden deafness: a randomized comparative study of 2 administration modalities of hyperbaric oxygenotherapy combined with naftidrofuryl

The pharmacokinetics of a single, oral dose of 750 mg of ciprofloxacin were studied in 35 subjects with various degrees of renal function (Group 1, Clcr > or = 80 ml/min; Group II, Clcr 50-79 ml/min; Group III, Clcr 10-49 ml/min) and on hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). Blood, urine and CAPD dialysate samples were collected over a period of 48 hours after dosing. Data were fitted using non-linear, least squares regression. The mean Cmax was 3.4 +/- 1.0 mg/l and tmax was 2.3 +/- 0.9 hours. The mean AUC in Group I was 14.7 mg.h/l, Group II was 33.7 (p < 0.001), Group III 63.8 (p < 0.001), HD 57.9 (p < 0.0001) and CAPD 44.3 (p < 0.001). Half-life in Group I was 4.6 h, and was shorter than Group III (11.1 h, p < 0.001), HD (13.4 h, p < 0.001) and CAPD (8.9 h, p < 0.001). Total body clearance and renal clearance demonstrated significant differences also. The dialysis clearance in CAPD patients was 0.53 +/- 0.39 l/h. Peritoneal effluent concentrations varied from 0.6 mg/l during the first exchange, to a peak of 2.2 mg/l during the second, to 0.13 mg/l in the 48 hour (9th) exchange. Dosage adjustments of ciprofloxacin in the presence of renal insufficiency are indicated for subjects with a Clcr < 20 ml/min/1.73m2.     

Icodextrin use in CCPD patients during peritonitis: ultrafiltration and serum disaccharide concentrations

BACKGROUND AND METHODS: In a randomized study on the biocompatibility of icodextrin (I) versus glucose (G) in CCPD we used icodextrin or glucose for the long daytime dwell. During the night-time dwells glucose was used in all patients. In case of peritonitis icodextrin was continued. In all patients ultrafiltration (UF) was recorded and serum icodextrin metabolites were determined every 3 months and during peritonitis in I-users when available. RESULTS: Thirty-eight patients ( 19 G, 19 I) entered the study and suffered 30 peritonitis episodes (16 G, 14 I). During peritonitis (P), daytime dwell UF decreased significantly in G (P=0.001), but remained stable in I patients compared to non-peritonitis (NP) episodes. Total 24-h UF decreased in G (P=0.001) and in I patients (P=0.04), as the result of a decreased daytime UF and night-time UF, respectively. There was no difference in the used glucose concentrations during the P versus NP episodes. In five I-patients serum disaccharides increased from 0.05+/-0.01 to 1.26+/-0.23mg/ml during follow up. During peritonitis serum disaccharide concentrations did not increase further (1.47+/-0.24 mg/ml, P= 0.56). In I patients total carbohydrate minus glucose rose to 5.72 +/- 1.2 mg/ml during follow up, and to 6.63 +/- 1.04 mg/ml during peritonitis (P=0.7). These concentrations are comparable to CAPD patients despite the longer dwelltime in CCPD (8-10 versus 14-16 h, respectively). Adverse reactions attributable to icodextrin were not encountered. CONCLUSIONS: In contrast to glucose, icodextrin preserved the daytime dwell ultrafiltration during peritonitis. Serum icodextrin metabolites increased during icodextrin use, but remained stable during peritonitis. Adverse effects were not observed.     

Cysteine-scanning mutagenesis of helix IV and the adjoining loops in the lactose permease of Escherichia coli: Glu126 and Arg144 are essential. off

Cys-scanning mutagenesis has been applied to the remaining 45 residues in lactose permease that have not been mutagenized previously (from Gln100 to Arg144 which comprise helix IV and adjoining loops). Of the 45 single-Cys mutants, 26 accumulate lactose to > 75% of the steady state observed with Cys-less permease, and 14 mutants exhibit lower but significant levels of accumulation (35-65% of Cys-less permease). Permease with Phe140-->Cys or Lys131-->Cys exhibits low activity (15-20% of Cys-less permease), while mutants Gly115-->Cys, Glu126-->Cys and Arg144-->Cys are completely unable to accumulate the dissacharide. However, Cys-less permease with Ala or Pro in place of Gly115 is highly active, and replacement of Lys131 or Phe140 with Cys in wild-type permease has a less deleterious effect on activity. In contrast, mutant Glu126-->Cys or Arg144-->Cys is inactive with respect to both uphill and downhill transport in either Cys-less or wild-type permease. Furthermore, mutants Glu126-->Ala or Gln and Arg144-->Ala or Gln are also inactive in both backgrounds, and activity is not rescued by double neutral replacements or inversion of the charged residues at these positions. Finally, a mutant with Lys in place of Arg144 accumulates lactose to about 25% of the steady state of wild-type, but at a slow rate. Replacement of Glu126 with Asp, in contrast, has relatively little effect on activity. None of the effects can be attributed to decreased expression of the mutants, as judged by immunoblot analysis. Although the activity of most of the single-Cys mutants is unaffected by N-ethylmaleimide, Cys replacement at three positions (Ala127, Val132, or Phe138) renders the permease highly sensitive to alkylation. The results indicate that the cytoplasmic loop between helices IV and V, where insertional mutagenesis has little effect on activity [McKenna, E., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 11954-11958], contains residues that play an important role in permease activity and that a carboxyl group at position 126 and a positive charge at position 144 are absolutely required.     

Free energy simulations of axial contacts in sickle-cell hemoglobin

Molecular dynamics simulations have been used to investigate the thermodynamic stability of axial contacts in sickle-cell hemoglobin (HbS). Free energy changes were evaluated for the point mutation beta 121 Glu --> Gln in the axial contact region of HbS crystals. The calculations predict a free energy change of-3.6 kcal/mol per contact for the mutation, which is in qualitative agreement with experimental observations of aggravated sickling found in the double mutant Hb D Los Angeles (beta 6 Glu --> Val. beta 121 Glu --> Gln) relative to HbS (beta 6 Glu --> Val). The beta 121 Glu is sequestered in a salt link with beta 17 Lys located on the same polypeptide chain, making the Glu interactions with its surroundings similar in aggregates and individual hemoglobins. Due to this cancellation of the large electrostatic Glu contributions, the weak nonspecific interactions between the Gln and the neighboring polypeptide chain are the main contributing factor to the enhanced aggregation of Hb D Los Angeles relative to HbS. Together with the previous study of the lateral contact [K. Kuczera et al. (1990) Proceedings of the National Academy of Science USA, Vol. 87, pp, 8481-8485], the present results provide a more complete picture of the forces driving the sickling aggregation. A comparison of different treatments of internal flexibility in free energy simulations and analysis of rate of convergence of the different calculated properties has also been performed.     

Modulation of the catalytic rate of Cu,Zn superoxide dismutase in single and double mutants of conserved positively and negatively charged residues

The catalytic rate of four single and three double mutants of Xenopus laevis Cu,Zn superoxide dismutase B, neutralized at Lys120, Asp130, Glu131, and Lys134, has been determined by pulse radiolysis as a function of ionic strength. Neutralization of Glu131 increases the catalytic rate by 80% at low ionic strength, but the effect is reduced to 50% at physiological ionic strength. The rate is unperturbed upon neutralization of Asp130, while neutralization of either of the two lysines drastically decreases the enzyme activity. The Lys120Leu-Lys134Thr and Lys134Thr-Asp130Gln double mutations have an additive and a compensative effect, respectively, on the activity values, while neutralization of the Glu131-Lys134 pair, which also has a compensative effect, gives rise to a faster enzyme at any ionic strength value. The effects observed in the single Asp130Gln and Lys120Leu mutants differ from those reported on human or bovine enzymes [Getzoff et al. (1992) Nature (London) 358, 347-351; Sines et al. (1990) Biochemistry 29, 9403-9412], indicating that some residues occupying the same position in the linear sequence of different Cu,Zn superoxide dismutases have a different functional weight. Our results also suggest that the strategy of multiple charge mutation may be a promising approach in order to increase the catalytic rate of Cu,Zn SODs independently of ionic strength.     

Docking of nitrogenase iron- and molybdenum-iron proteins for electron transfer and MgATP hydrolysis: the role of arginine 140 and lysine 143 of the Azotobacter vinelandii iron protein

Docking of the nitrogenase component proteins, the iron protein (FeP) and the molybdenum-iron protein (MoFeP), is required for MgATP hydrolysis, electron transfer between the component proteins, and substrate reductions catalyzed by nitrogenase. The present work examines the function of 3 charged amino acids, Arg 140, Glu 141, and Lys 143, of the Azotobacter vinelandii FeP in nitrogenase component protein docking. The function of these amino acids was probed by changing each to the neutral amino acid glutamine using site-directed mutagenesis. The altered FePs were expressed in A. vinelandii in place of the wild-type FeP. Changing Glu 141 to Gln (E141Q) had no adverse effects on the function of nitrogenase in whole cells, indicating that this charged residue is not essential to nitrogenase function. In contrast, changing Arg 140 or Lys 143 to Gln (R140Q and K143Q) resulted in a significant decrease in nitrogenase activity, suggesting that these charged amino acid residues play an important role in some function of the FeP. The function of each amino acid was deduced by analysis of the properties of the purified R140Q and K143Q FePs. Both altered proteins were found to support reduced substrate reduction rates when coupled to wild-type MoFeP. Detailed analysis revealed that changing these residues to Gln resulted in a dramatic reduction in the affinity of the altered FeP for binding to the MoFeP. This was deduced in FeP titration, NaCl inhibition, and MoFeP protection from Fe2+ chelation experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

IgG glycation and function during continuous ambulatory peritoneal dialysis

IgG in dialysate may have an important role in anti-infection mechanisms during continuous ambulatory peritoneal dialysis (CAPD). As Fc fragment oligosaccharidic chains are crucial for IgG effector functions, we have tested the hypothesis that IgG glycation might occur during CAPD and modify IgG properties. Purified normal IgG was incubated with glucose solutions of different concentrations and pH. Separation of glycated IgG was performed by affinity chromatography. Complement activation (C3c deposition) and phagocytosis by polymorphonuclear leucocytes (PMN) were studied in vitro using Staphylococcus aureus Wood (STAW) as antigen. In addition, we compared the percentages of glycated IgG in IgG purified from sera and dialysates of 12 CAPD patients. The percentage of glycated IgG after in vitro incubation of normal IgG with glucose solutions was directly proportional to glucose concentrations, incubation time and pH. Glycated IgG anti-STAW induced a higher C3c deposition than non-glycated IgG anti-STAW (C3c/IgG (mean +/- SD) 0.96 +/- 0.06 vs 0.79 +/- 0.08; P = 0.027). PMN phagocytosis was not affected by IgG glycation. The percentages of glycated IgG in dialysates of CAPD patients were greater than those in corresponding sera (5.38 +/- 2.36% vs 4.56 +/- 2.47%; P = 0.006). It is concluded that IgG glycation may take place in the peritoneal cavity during CAPD and lead to enhanced complement activation. This could explain the high degree of complement activation previously described in dialysate of CAPD patients and might theoretically result in a reduction of complement factors available in dialysate for adequate anti-infection mechanisms.     

Increased peritoneal permeability is associated with decreased fluid and small-solute removal and higher mortality in CAPD patients

BACKGROUND: Recent studies suggest that increased peritoneal membrane permeability is associated with higher morbidity and mortality in peritoneal dialysis patients. It is not known, however, whether the difference in clinical outcome among different peritoneal transport groups is due to differences in peritoneal fluid and solute removal. In the present study, we compared the peritoneal fluid and solute transport and clinical outcome in CAPD patients with high (H), high-average (H-A), low-average (L-A) and low (L) peritoneal transport patterns. DESIGN: A 6-h dwell study was performed in 46 patients with frequent dialysate and plasma samples using 2 l of 3.86% glucose dialysate with 131I albumin as an intraperitoneal volume marker. The patients were divided into four transport groups according to their D/P of creatinine at 240 min. RESULTS: The results showed that high transporters had significantly lower peritoneal fluid and small-solute removal but high glucose absorption and high protein loss during a 6-h exchange. The serum albumin was lower and blood pressure and triglycerides were higher in high transporters compared with the other groups. Two-year patient survival from the start of CAPD treatment was significantly lower for high transporters (64, 85, 90 and 100% for H, H-A, L-A and L respectively, P < 0.01). The 1-year patient survival from the dwell study was also significantly lower in high transporters (16, 63, 90 and 100% for each group, P<0.01). CONCLUSION: Our results suggest that high transporters remove less fluid and small solutes and have higher protein loss and increased glucose absorption. These alterations may contribute to fluid overload, malnutrition and lipid abnormalities that perhaps contribute to the increased mortality among the high transporters.