Biomedical subjects

S Sundaram

Publications and source records attributed to S Sundaram.

At least 19 recordsLinked to original sources

PubMed1996

A point mutation causes mistargeting of Golgi GlcNAc-TV in the Lec4A Chinese hamster ovary glycosylation mutant.

The Lec4A and Lec4 Chinese hamster ovary glycosylation mutants lack N-linked glycans with GlcNAcbeta(1,6)Manalpha(1,6) branches that are initiated by the transferase termed GlcNAc-TV. Detergent extracts of Lec4 cells have no detectable GlcNAc-TV activity, but Lec4A extracts have activity equivalent to that of parental Chinese hamster ovary cells. This discrepancy occurs because Lec4A GlcNAc-TV activity co-localizes with membranes of the endoplasmic reticulum (ER) instead of with Golgi membranes (Chaney, W., Sundaram, S., Friedman, N., and Stanley, P. (1989) J. Cell. Biol. 109, 2089-2096). cDNAs from the coding region of the GlcNAc-TV gene have now been isolated from each mutant line. Lec4 GlcNAc-TV cDNA was found to possess two insertions, the first of which shifts the open reading frame and codes for a truncated transferase missing 585 amino acids from the catalytic domain. By contrast, Lec4A GlcNAc-TV cDNA possesses a single point mutation from T to G, which results in a change from Leu to Arg at position 188. When transfected into Lec4 cells, both cDNAs gave the appropriate phenotype; Lec4 cDNA was unable to restore GlcNAc-TV activity, whereas Lec4A cDNA converted Lec4 cells to the Lec4A phenotype, with an active GlcNAc-TV mislocalized to ER membranes. Moreover, Lec4A cDNA cured of its mutation restored a functional, Golgi-localized GlcNAc-TV to Lec4 cells. The results demonstrate that a single change in the 740 amino acids of GlcNAc-TV serves to functionally inactivate the transferase in an intact cell by causing it to localize to the ER instead of the Golgi compartment. The mislocalized transferase retains full enzyme activity, showing that it is well folded and stable and suggesting that the L188R mutation either prevents association with exit complexes from the ER or causes retrograde transport from a Golgi compartment.

Amino Acid Sequence↗

PubMed1996

Determination of contact phase activation by the measurement of the activity of supernatant and membrane surface-adsorbed factor XII (FXII): its relevance as a useful parameter for the in vitro assessment of haemodialysis membranes.

We investigated hemodialysis membrane biocompatibility with respect to contact phase activation by determination of FXII-like activity (FXIIA) on the membrane surface and in the supernatant phase, during plasma contact with various hemodialysis membranes using an in vitro incubation test cell. The results were compared to the influence of these membranes on the activation of purified FXII. A time course for the generation of activated FXII using purified FXII solution at physiologic concentrations on two similar negatively charged polymers was performed. The membranes assessed were regenerated cellulose (Cuprophan; Akzo Faser AG, Germany), modified cellulosic (Hemophan; Akzo Faser AG), acrylonitrile-sodium methallyl copolymer-based membrane AN69S (Hospal, France), and SPAN, a new polyacrylonitrile-based copolymer (akzo Nobel AG). The plasma FXIIA at the membranes surface was significantly different between the membranes, while the supernatant phase FXIIA exhibited no significant differences. In contrast, activation of purified FXII in a plasma-free system with respect to supernatant activity indicated significant differences between the materials. A similar finding for the membrane-bound factor XIIA was also observed when purified factor XII was used. The membrane-bound FXIIA values observed in the plasma system containing heparin were significantly greater than in citrated plasma. This demonstrated the strong influence of heparin and the interaction of other plasma components to the membrane surface on the activation of contact phase of coagulation.

Adsorption↗

PubMed1996

Role of leucocytes in coagulation induced by artificial surfaces: investigation of expression of Mac-1, granulocyte elastase release and leucocyte adhesion on modified polyurethanes.

Thrombus formation on artificial surfaces can be viewed as the sequential and concomitant involvement of protein adsorption, platelet reactions, activation of the coagulation system, participation of complement, fibrinolytic and kallikrein-kinin systems, and the interaction of cellular elements. This study examines the activation of leucocytes on a series of well-characterized polyurethanes with different ionic groups [sulphonate groups (negatively charged); quaterinary amine groups (positively charged)], in terms of adhesion, degranulation and cell surface integrin receptor expression. Leucocyte adhesion was monitored with radiolabelled neutrophils and scanning electron microscopy (SEM), degranulation by measurement of human neutrophil elastase using an indirect enzyme-linked immunosorbent assay and cell surface expression of the integrin receptor Mac-1, using fluorescent-activated cell sorting (FACS). Our results indicate a trend towards enhanced adhesion and degranulation with respect to the negatively charged polyurethane. Similar results were observed with respect to the integrin Mac-1 from recovered adherent cells. The findings of enhanced adhesion and spreading, Mac-1 up-regulation and granulocyte elastase release from the negatively charged sulphonated polyurethane indicate the potential of leucocytes to contribute towards thrombus formation on such surfaces.

Biocompatible Materials↗

PubMed1996

Transmembrane passage of cytokine-inducing bacterial products across new and reprocessed polysulfone dialyzers.

The widespread use of bicarbonate dialysate and reprocessed high-efficiency and "high-flux" dialyzers has raised concerns about the increased risk of reverse-transfer of dialysate contaminants into the blood compartment. To evaluate this concern, the reverse-transfer of bacterial products from contaminated bicarbonate dialysate into the blood compartment was compared during in vitro dialysis with new or reprocessed high-flux polysulfone dialyzers. In vitro dialysis was carried out at 37 degrees C by use of a counter-current recirculating loop dialysis circuit with either new high-flux polysulfone dialyzers or dialyzers reprocessed once or 20 times with formaldehyde (0.75%) and bleach (< 1%) with an automated system. Heparinized whole blood from healthy volunteers was circulated through the blood compartment, and bicarbonate dialysate was circulated in the dialysate compartment. The dialysate was challenged sequentially by 1:1000 and 1:100 dilutions of a sterile Pseudomonas aeruginosa culture supernatant (bacterial challenge). Samples were drawn from the blood and dialysate compartments 1 h after each challenge. Peripheral blood mononuclear cells (PBMC) were harvested by Ficoll-Hypaque separation from whole blood in the blood compartment and a 5 x 10(6) PBMC/mL cell suspension was prepared. Likewise, dialysate samples (0.5 mL) were added to 0.5 mL suspension of 5 x 10(6) PBMC/mL drawn at baseline. All PBMC suspensions were incubated upright in a humidified atmosphere at 37 degrees C with 5% CO2 for 24 h, and total interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF alpha) cytokine production (cell-associated and secreted) was measured by radioimmunoassay. Eight experiments were performed for each arm of the study with the same donor for each arm. One hour after contaminating the dialysate with a 1:1000 dilution of the bacterial challenge, IL-1 alpha production by PBMC harvested from the blood compartment was 160 +/- 0, 171 +/- 11, and 270 +/- 35 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.004). One hour after challenging the dialysate with 1:100 dilution, IL-1 alpha production by PBMC harvested from the blood compartment was 188 +/- 20, 228 +/- 35, and 427 +/- 67 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.006). IL-1 alpha production by PBMC from dialyzers reprocessed 20 times was significantly greater than both new and dialyzers reprocessed once. However, there were no significant differences between new dialyzers and dialyzers reprocessed once. Similarly, after the 1:1000 challenge, TNF alpha production by PBMC harvested from the blood compartment was 160 +/- 0, 160 +/- 0, and 213 +/- 22 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.008). After the 1:100 challenge, TNF alpha production was 168 +/- 8, 188 +/- 20, and 225 +/- 32 pg, respectively, for new dialyzers, dialyzers reprocessed once, and dialyzers reprocessed 20 times (P = 0.20). These results demonstrate that reprocessing of high-flux polysulfone dialyzers with bleach increases the risk of reverse-transfer of bacterial products from contaminated dialysate, and this risk appears to increase with the number of reuses. Consequently, units that reprocess membranes with bleach and have suboptimal water quality might subject their patients to a higher risk of cytokine-related morbidity.

Anti-Bacterial Agents↗

PubMed1996

Plasma lipopolysaccharide binding protein and bactericidal/permeability increasing factor in CRF and HD patients.

The recent characterization of lipopolysaccharide binding protein (LBP) and bactericidal/permeability increasing factor (BPI) have provided the opportunity to examine the natural factors that regulate cytokine production in response to endotoxin in patients on hemodialysis (HD). Whole blood was collected in EDTA from 28 undialyzed patients with chronic renal failure (undialyzed CRF), 36 patients on chronic HD (HD) and 15 healthy controls, and plasma levels of LBP and BPI were measured by a sandwich ELISA. Plasma LBP levels in undialyzed patients with CRF (P = 0.04) and patients on HD (P = 0.01) were significantly higher than those in healthy controls, but not significantly different from each other. Plasma BPI levels in undialyzed patients with CRF and patients on HD were not significantly different from those in healthy controls. There was no correlation between serum creatinine and plasma levels of either LBP or BPI. Peripheral blood mononuclear cells (PBMC) were harvested from healthy volunteers by FLcoll-Hypaque separation, and 0.125 mL of 10 x 10(6)/mL suspensions were incubated with 0.125 mL of test plasma (containing different LBP/BPI ratios) and 0.25 mL of RPMI, containing 1 ng/mL of endotoxin, for 24 h at 37 degrees C. Samples were subjected to three freeze-thaw cycles, and total interleukin-1 receptor antagonist (IL-1Ra) or interleukin-1 alpha (IL-1 alpha) production was measured by a specific non-crossreactive RIA. The results of this study showed: (1) IL-1Ra production by endotoxin-stimulated PBMC incubated with pooled plasma from HD patients with LBP/BPI ratios of 11 x 10(2), 167 x 10(2), 379 x 10(2), and 778 x 10(2), respectively was 1466 +/- 195 pg, 3105 +/- 462 pg, 8179 +/- 1020 pg, and 4770 +/- 1185 pg (P < 0.001); (2) Paired plasma collected before dialysis (predialysis) and at 15 min after the start of dialysis (15 minute) with cellulose membranes showed a negligible change in plasma LBP levels (-3 +/- 5%), but a 6681 +/- 1788% increase in plasma BPI levels. Consequently, compared with predialysis plasma, there was a 35 +/- 6% decrease in endotoxin-stimulated IL-1 alpha production by PBMC incubated with plasma drawn at 15 min (P = 0.001); (3) Compared with the PBMC incubated with predialysis plasma from HD patients, there was a 39 +/- 5%, 53 +/- 5%, and 60 +/- 5% decrease in endotoxin-stimulated IL-1 alpha production in the presence of 1 ng/ mL, 10 ng/mL, or 1 microgram/mL of recombinant BPI, respectively (P < 0.003). These results suggest that the plasma LBP:BPI ratio could influence cytokine production in response to bacterial endotoxin; the high LBP:BPI ratios observed in patients with chronic renal failure probably imparts an increased susceptibility to endotoxin-stimulated cytokine production; and natural or pharmacological increases in plasma BPI levels and the consequent decrease in LBP:BPI ratios could attenuate this susceptibility to endotoxin-stimulated cytokine production.

Acute-Phase Proteins↗

PubMed1996

Impact of single use versus reuse of cellulose dialyzers on clinical parameters and indices of biocompatibility.

Hemodialysis with reprocessed dialyzers has been associated with an increased mortality in patients on chronic dialysis, but the causes for this increased mortality have not been identified thus far. The aim of this study was to compare the qualitative and/or quantitative differences in activation of cellular and plasma elements, intradialytic signs and symptoms, adequacy of dialysis, and serum biochemistry and hematology in patients dialyzed with new or reprocessed cellulose dialyzers. This study measured the plasma levels and production of interleukin-1 receptor antagonist (IL-1Ra) by peripheral blood mononuclear cells (PBMC), indices of cytokine synthesis; plasma C3a levels, an index of complement activation; plasma levels of lipopolysaccharide binding protein (LBP), an acute phase reactant; and plasma levels of bactericidal-permeability increasing factor (BPI), a neutrophil primary granule protein, in 37 patients on chronic hemodialysis with glutaraldehyde and bleach-reprocessed cellulose dialyzers after random assignment to 12 wk of dialysis with new (single use) or reprocessed (reuse) cellulose dialyzers. These indices were studied before dialysis, 15 min after the start of dialysis, and at the conclusion of dialysis in both groups. Intradialytic clinical symptoms and signs, urea reduction ratios, monthly blood chemistry, and hematology were also studied during the 12-wk period. Before randomization, clinical and laboratory characteristics and IL-1Ra production by PBMC were similar in the two groups. During the 12-wk study, the mean number of dialyzer reuses was 7 +/- 1 in the reuse group and there were no breaks in protocol in the single-use group. At the end of the study, plasma levels of IL-1Ra, cell content and production of IL-1Ra by unstimulated, endotoxin-stimulated, and lgG-stimulated PBMC among patients assigned to reuse were not significantly different from those in the single-use group either before dialysis, at 15 min, or at the conclusion of dialysis. Similarly, plasma levels of C3a, LBP, and BPl were not significantly different between groups at any of the three time points. During the 12-wk study, none of the patients in either arm of the study experienced chills, rigors, or fever, and there were no differences in the number of episodes of symptomatic hypotension in patients on reused dialyzers (11 +/- 3) compared with patients on single-use dialyzers (8 +/- 2). The mean monthly urea reduction ratio during the 3 months of the study was 63 +/- 2% and 65 +/- 2% for reuse and single-use dialyzers, respectively (not significant). Similarly, the hematocrit, white blood cell count, serum calcium, phosphorus, cholesterol, triglycerides, total protein, and albumin levels were also not significantly different between the two groups at the end of the 12-wk study period. These results suggest that the reprocessing of cellulose dialyzers with glutaraldehyde and bleach does not affect indices of blocompatibility, intradialytic symptoms and signs, adequacy of dialysis, or serum biochemistry and hematology.

Acute-Phase Proteins↗

PubMed1996

Nafamostat mesilate, a broad spectrum protease inhibitor, modulates platelet, neutrophil and contact activation in simulated extracorporeal circulation.

Activation of humoral and cellular participants in inflammation enhances the risk of postoperative bleeding and multiple organ damage in cardiopulmonary bypass (CPB). We now compare the effects of heparin alone in combination with nafamostat mesilate (NM), a protease inhibitor with specificity of trypsin-like enzymes, in an extracorporeal circuit which simulates CPB. NM significantly inhibits the release of platelet beta-thromboglobulin (beta TG) at 60 and 120 min. Platelet counts do not differ. ADP-induced aggregation decreases in circuits with NM, which is due to a direct effect of NM on platelet function. NM prevents any significant release of neutrophil elastase; at 120 min, plasma elastase-alpha 1-antitrypsin complex is 0.16 micrograms/ml in the NM group and 1.24 micrograms/ml in the control group. NM completely inhibits formation of complexes of C1 inhibitor with kallikrein and FXIIa. NM does not alter markers of complement activation (C1-C1-inhibitor complex and C5b-9), or indicators of thrombin formation (F1.2). However, at 120 min, thrombin activity as measured by release of fibrinopeptide A is significantly decreased. The data indicate that complement activation during CPB correlates poorly with neutrophil activation and that either kallikrein or FXIIa or both may be more important agonists. The ability of NM to inhibit two important contact system proteins and platelet and neutrophil release raises the possibility of suppressing the inflammatory response during clinical CPB.

Anticoagulants↗

PubMed1996

Cytokine production by human peripheral blood mononuclear cells stimulated by a Pseudomonas aeruginosa culture filtrate: role of plasma and polymyxin B.

The lack of consensus regarding the significance of transmembrane passage of bacterial products across hemodialysis membranes can be related to several methodological differences in the various studies, including the choice of circulating fluid in the blood compartment of the model, nature and concentration of the bacterial products employed to challenge the dialysate compartment and whether cytokine production by PMBC or the limulus amebocyte lysate (LAL) assay was used as the index of transfer and the cytokine used as the read-out. In this study, we examined the production of interleukin-1 alpha (IL-1 alpha), interleukin-1 receptor antagonist (IL-1Ra) and interleukin-8 (IL-8) by peripheral blood mononuclear cells (PBMC) incubated with a Pseudomonas aeruginosa culture filtrate. Further, the effects of 10% autologous human plasma and Polymyxin B sulfate (PmB) on cytokine production by PBMC were also characterized. The results of our study indicate that the Ps. aeruginosa culture filtrate had both PmB suppressible and PmB non-suppressible components and that the addition of 10% human plasma significantly enhanced cytokine production by both PmB suppressible and PmB non-suppressible components. The enhancing effect of plasma was most evident at low concentrations of the filtrate. The inhibitory effect of PmB was most evident in samples cultured in the presence of 10% plasma. There was a direct correlation between the production of IL-1 alpha and IL-1Ra suggesting that both pro-inflammatory cytokines and cytokine-specific inhibitory proteins are concurrently produced. There results have direct relevance to selection of study conditions for in vitro models used to study the transmembrane passage of bacterial products across hemodialysis membranes.

Anti-Bacterial Agents↗

PubMed1996

Transfer of cytokine-inducing bacterial products across hemodialyzer membranes in the presence of plasma or whole blood.

Cytokine production by peripheral blood mononuclear cells (PBMC) is a sensitive indicator of cytokine-inducing substances which may cross from contaminated dialysate into the blood compartment. The objective of this study was to compare the transfer of cytokine-inducing substances from dialysate contaminated with a culture filtrate from Pseudomonas aeruginosa across dialyzers with low (hemophan) or intermediate ultrafiltration coefficients (modified cellulose triacetate, CTA), under conditions where either 10% plasma or whole blood was circulated in the blood compartment. Eight paired experiments of in vitro dialysis were carried out at 37 degrees C using a countercurrent recirculating loop dialysis circuit with either a new CTA or hemophan dialyzer. 10% plasma in standard tissue culture medium was circulated through the blood compartment and bicarbonate dialysate was circulated in the dialysate compartment. The dialysate was challenged sequentially by log-fold dilutions (10(2), 10(3) or 10(4)) of a Ps. aeruginosa culture filtrate. Samples were drawn from the blood compartment 5 and 15 minutes after each challenge and incubated with suspensions of PBMC in the absence or presence of polymyxin B, in order to block endotoxin. After 24 h at 37 degrees C, total interleukin-1 alpha (IL-1 alpha) was measured by RIA. Although the dialysate contained potent cytokine-inducing substances, there was no significant IL-1 alpha production by PBMC incubated with the plasma mixture from the blood compartment in the majority of experiments with both dialyzers and with each of the three dilutions of the bacterial challenge. Eight experiments were also performed with CTA dialzyers using heparinized whole blood in the blood compartment. Samples of whole blood and dialysate were drawn at baseline, after one hour of dialysis with uncontaminated dialysate and 15 minutes and three hours after dialysis with dialysate contaminated with Ps. aeruginosa filtrate. There was no significant IL-1 alpha production by PBMC isolated from the whole blood 1 h after dialysis with uncontaminated dialysate, and 15 min and 2 h after adding the Ps. aeruginosa filtrate to the dialysate side. In contrast, production of IL-1 alpha by PBMC from the same donors incubated with samples from the dialysate were 263 +/- 50, 1074 +/- 306, 2333 +/- 774 and 2602 +/- 702 pg/2.5 x 10(6) PBMC, respectively at the same four time points. These data suggest that although the Ps. aeruginosa culture filtrate present in the dialysate was a potent inducer of IL-1 alpha, neither dialyzer permitted transfer of cytokine inducing substances from the dialysate into the blood compartment.

Bacterial Toxins↗

PubMed1995

In vitro contact phase activation with haemodialysis membranes: role of pharmaceutical agents.

Contact phase activation was investigated in vitro using flat sheet type of haemodialysis membranes, Cuprophan (Akzo, Faser, Germany) and AN69S (Hospal, France), and a negatively charged polyamide Ultipor NR 14225 membrane as a control. The investigation focussed on the determination of factor XII-like activity (FXIIA) as an indicator of contact phase activation in the supernatant phase and at the membrane surface after plasma-membrane contact using an incubation test cell. The findings were compared with the observations from a plasma-free system utilizing purified unactivated factor XII. The plasma FXIIA bound to the membrane surface was significantly different between the membranes, while the supernatant phase FXIIA exhibited no significant differences. In contrast, the plasma-free system exhibited significant differences in the supernatant FXIIA and membrane-bound FXIIA for all the materials used and the magnitude of the activity was significantly greater for negatively charged materials. This finding demonstrated the strong influence of the interaction of other plasma constituents on the membrane surface and as such the binding and subsequent activation of factor XII may be altered possibly due to competitive binding and steric hindrance. On the addition of anticoagulants such as heparin, low-molecular-weight heparin, citrate and hirudin, no significant differences were observed in plasma supernatant phase FXIIA. However, each anticoagulant appears to have a distinct influence on the magnitude of plasma membrane-bound FXIIA. On the addition of aprotinin (a kallikrein inhibitor), no significant differences were observed in the plasma supernatant FXIIA. In contrast, aprotinin appears to significantly reduce membrane-bound FXIIA on Cuprophan and polyamide NR, but significantly increase the magnitude of the membrane-bound FXIIA on AN69S.

Anticoagulants↗

PubMed1995

Characterization of a zwf mutant of Synechococcus sp. strain PCC 7942.

A mutant of the cyanobacterium Synechococcus sp. strain PCC 7942 carrying a disrupted gene encoding glucose-6-phosphate dehydrogenase (zwf) produced no detectable glucose-6-phosphate dehydrogenase as assessed by enzyme assay and Western blot (immunoblot) analysis. This mutant exhibited significantly impaired dark viability.

Cyanobacteria↗

PubMed1995

Modeling and optimising dextrose fermentation using a fluorosensor.

Dextrose has been fermented in a Tokyo Rikakikai Fermentor at 32 degree celsius using seven different concentrations of yeast as seeding. The progress of the reaction was followed by measuring the fluorescent signal due to NADH with a Dr. Ingold (Switzerland) fluorosensor which has an excitation wavelength of 360 nm and measurement wavelength of 450 nm. The optimum concentration for this fermentation reaction is 30 percent seeding. At this concentration the biomass growth rate and final biomass concentration are a maximum. The fluorescent voltage vs time data fitted a first order model with an error of less than one percent. Further work on optimising the temperature is in progress.

Biomedical Engineering↗

PubMed1994

Differential expression of an E-selectin ligand (SLex) by two Chinese hamster ovary cell lines transfected with the same alpha (1,3)-fucosyltransferase gene (ELFT).

The mammalian cDNA encoding alpha (1,3)-fucosyltransferase (alpha (1,3)Fuc-T) termed ELAM-1 ligand fucosyltransferase (ELFT) or Fuc-TIV was previously cloned by three groups who reported different results from transfection studies Goelz et al. (Goelz, S. E., Hession, C., Goff, D., Griffiths, B., Tizard, R., Newman, B., Chi-Rosso, G., and Lobb, R. (1990) Cell 63, 1349-1356) found that Chinese hamster ovary (CHO) cells expressing the ELFT cDNA had alpha (1,3)Fuc-T activity and were able to bind to E-selectin. In contrast, Lowe et al. (Lowe, J. B., Kukowska-Latallo, J. F., Nair, R. P., Larsen, R. D., Marks, R. M., Macher, B. A., Kelly, R. J., and Ernst, L. K. (1991) J. Biol. Chem. 266, 17467-17477) and Kumar et al. (Kumar, R., Potvin, B., Muller, W. A., and Stanley, P. (1991) J. Biol. Chem. 266, 21777-21783) found no binding to E-selectin of CHO transfectants expressing the same alpha (1,3)Fuc-T gene; nor did the latter transfectants synthesize a known E-selectin ligand, sialylated Lex (SLex), although they had substantial alpha (1,3)Fuc-T activity. We now show that these discrepant results were due to a difference between the parental CHO cell lines. Following transfection of ELFT cDNA into Pro-5 or dihydrofolate reductase (DHFR)- CHO cells, only the DHFR- transfectants expressed SLex and bound to E-selectin. Indirect evidence from monoclonal antibody and lectin binding studies indicates that the range of carbohydrate structures synthesized by the Pro-5 and DHFR- CHO cell lines differs. Since DHFR-/ELFT transfectants expressed cell surface SLex but transferred fucose poorly to sialylated substrates in vitro, ELFT may be able to fucosylate a complex carbohydrate missing from Pro-5 cells. Alternatively, either CHO line may have an activity (such as an alpha (2,3)-sialyltransferase), that modifies alpha (1,3)-fucosylated lactosamines.

Animals↗

PubMed1994

Endotoxemia, complement, and white blood cell activation in cardiac surgery: a randomized trial of laxatives and pulsatile perfusion.

Endotoxin activates complement and white blood cells and all are implicated in the pathologic effects of cardiopulmonary bypass (CPB). We investigated if reduction in intestinal bacterial load with a laxative and/or pulsatile perfusion to improve bowel circulation during CPB reduced endotoxemia and complement and white blood cell activation. Sixty patients were randomized to four groups in a 2 x 2 factorial structure: group 1 (no laxative, nonpulsatile perfusion); group 2 (laxative, nonpulsatile perfusion); group 3 (no laxative, pulsatile perfusion); and group 4 (laxative, pulsatile perfusion). Plasma concentrations of endotoxin, C3a and C5a, and granulocyte elastase (GE) were measured before anesthesia, skin incision, and heparin administration; during CPB (1, 30, 60, 90, and 120 minutes and after protamine administration); and after CPB at 3, 6, 12, 24, and 48 hours and 7 days. In all groups there was a small increase in the concentration of endotoxin (overall from 6 ng/L before CPB to 11 ng/L at 90 to 120 minutes; p < 0.001) and significant increases in C3a, C5a, and GE levels but no significant differences among the groups. Endotoxin levels did not correlate with activation of complement or white blood cells. There was a weak correlation between duration of CPB and levels of C3a (r = 0.14; p < 0.03) and GE (r = 0.25; p = 0.001) but not endotoxin or C5a. There was a general correlation between levels of C3a and GE but not in individual patients. In conclusion, CPB results in statistically significant increases in endotoxin, C3a, C5a, and GE during CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Surgical Procedures↗

PubMed1994

Biomaterials for blood-contacting applications.

Consideration of biomaterials for blood-contacting applications should take into account blood-biomaterial interactions, factors influencing the blood response and evaluation procedures. Examination of blood-biomaterial interactions indicates that relevant features are protein adsorption, platelet reactions, intrinsic coagulation, fibrinolytic activity, erythrocytes, leucocytes and complement activation. Factors influencing the blood response to a biomaterial in clinical application are the biomaterial structure, the presence of an antithrombotic agent, the patient status as determined by the disease and drug therapy, and the nature of the application. Evaluation options for biomaterials are clinical, in vivo, ex vivo and in vitro, with ex vivo and in vitro procedures relevant for biomaterial development.

Biocompatible Materials↗

PubMed1994

Biomaterials in cardiopulmonary bypass.

The improved utilization of biomaterials in cardiopulmonary bypass is dependent on polymer science and technology, procedures for blood compatibility assessment, optimization of biomaterial/antithrombotic agent combinations and the interpretation of clinical data.

Biocompatible Materials↗

PubMed1994

Modeling and optimising lactose fermentation using a fluorosensor.

Lactose has been fermented in a Tokyo Rikakikai Fermentor using two percent seeding at various temperatures. The progress of the reaction was followed by measuring the fluorescent signal due to NADH with a Dr. Ingold (Switzerland) fluorosensor which has an excitation wave length of 360 nm and measurement wavelength of 450 nm. The optimum temperature for this fermentation reaction is 34 degree celsius. At this temperature while biomass growth rate and final biomass concentration are a maximum the time taken to reach the final biomass concentration and lag time are a minimum. The fluorescent voltage vs time data fitted a first order plus dead time model with an error of less than one percent. The present work is in good agreement with earlier work on glucose and lactose fermentation with one percent seeding. The increase in seeding from one to two percent has improved the optimum parameters studied. Further work on higher seeding concentration and higher order models is in progress.

Fermentation↗

PubMed1994

Biocompatibility of cardiopulmonary bypass: influence on blood compatibility of device type, mode of blood flow and duration of application.

The biocompatibility of artificial organs is recognised as an area presenting difficulties in terms of the complexity of the situation. The nature of the blood response involving interactions of systems, pattern and extent of change, patient status and the influence of the whole device contribute to the complexity. Recognising these, the profile of the blood response to cardiopulmonary bypass (CPB), with respect to type of device, mode of blood flow, duration of the procedure and patient status, has been evaluated by monitoring contact phase activation [Factor XII-like activity (FXIIA)], fibrinolytic activity [Fibrin degradation products (X-FDP's)], complement activation (C3a, C5a), leucocyte activation [Granulocyte elastase (GE)] and platelet and white cell imaging. FXIIA, X-FDP's, and GE rose gradually during CPB, with levels remaining elevated post-operatively for up to 48 h. In contrast, C3a levels rose sharply with no significant elevation in the post-operative period, while C5a did not show significant changes during bypass. The use of pulsatile perfusion resulted in lesser activation of the parameters, although these were significantly less only for GE. The alterations in FXIIA, X-FDP's, C3a and GE correlated positively with the duration of CPB, with this effect pronounced in the post-operative period for FXIIA, X-FDP's and GE. However, these changes had no apparent influence on clinical outcome and the majority of patients had uncomplicated post-operative recoveries. With respect to the use of bubble/membrane oxygenators, platelet and white cell deposition and the patterns of change for FXIIA and C3a were similar in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatible Materials↗