Biomedical subjects

J Bergström

Publications and source records attributed to J Bergström.

At least 109 records · Page 6Linked to original sources

PubMed1997

Recognition of glycoconjugates by Helicobacter pylori. Comparison of two sialic acid-dependent specificities based on haemagglutination and binding to human erythrocyte glycoconjugates.

Helicobacter pylori expresses separate binding characteristics depending on growth conditions, as documented by binding to human erythrocyte glycoconjugates. Cells grown in Ham's F12 liquid medium exhibited a selective sialic acid-dependent binding to polyglycosylceramides, PGCs (Miller-Podraza et al.(1996) Glycoconjugate J13:453-60). There was no binding to traditional sialylated glycoconjugates like shorter-chain gangliosides, glycophorin or fetuin. However, cells grown on Brucella agar bound both to PGCs and other sialylated glycoconjugates. Fetuin was an effective inhibitor of haemagglutination caused by agar-grown cells, but had no or a very weak inhibitory effect on haemagglutination by F12-grown bacteria. PGCs were strong inhibitors in both cases, while asialofetuin was completely ineffective. The results indicate that H. pylori is able to express two separate sialic acid-dependent specificities, one represented by binding to fetuin, as described before, and another represented by a selective binding to PGCs.

Bacterial Adhesion↗

PubMed1997

Uremic serum enhances scavenger receptor expression and activity in the human monocytic cell line U937.

The macrophage scavenger receptor (SR) plays a leading role in atherogenesis, but little is known about the relevance of SR to atherosclerosis in uremia. In this study, the impact of uremic serum on SR expression and activity was examined in the human monocytic cell line U937. The cells were cultured with serum from ten healthy subjects, ten hemodialysis (HD) and ten continuous ambulatory peritoneal dialysis (CAPD) patients. SR mRNA expression was examined using reverse transcriptase-polymerase chain reaction followed by Southern blot. SR protein amount was evaluated by ligand blot. SR activity was analyzed by cellular uptake of fluorescently labeled acetylated low-density lipoprotein using flow cytometry. Uremic serum dose-dependently enhanced SR activity primarily by increasing the amount of receptor protein. Heat-inactivated uremic serum had a stimulatory effect, but ultrafiltrate of uremic serum, which included molecules with a molecular weight less than ten kDa, had no effect. The serum levels of macrophage-colony stimulating factor (M-CSF), an activator of SR, were fourfold higher in uremia and significantly correlated with SR activity in cells treated with uremic serum. Pre-treatment of uremic serum with a neutralizing antibody to M-CSF abolished the effect of uremic serum on SR activity. In conclusion, uremic serum contains a factor(s) that enhances SR expression and activity in U937 cells. Elevated M-CSF in uremic serum could be responsible for this enhancement.

Antibodies↗

PubMed1997

Effect of increased dialysate fill volume on peritoneal fluid and solute transport.

It has recently been recommended that the peritoneal dialysate volume should in general be increased to increase the peritoneal small solute clearances. However, the net ultrafiltration volume may decrease due to higher intraperitoneal hydrostatic pressure (IPP) and higher peritoneal fluid absorption induced by higher fill volume. In the present study, we investigated the effects of increasing the fill volume on peritoneal fluid and solute transport. A four-hour dwell study with frequent dialysate and blood sampling was performed in 32 male Sprague-Dawley rats using 16 ml, 25 ml, 30 ml or 40 ml (8 rats in each group) of 3.86% glucose solution with 131I albumin as an intraperitoneal volume marker. The peritoneal transport of fluid, glucose, urea, sodium, potassium, phosphate and total protein as well as IPP with different fill volume were evaluated. The IPP and peritoneal fluid absorption rate (as estimated from the 131I albumin elimination coefficient, KE) significantly increased with increase in fill volume (P < 0.05), whereas the direct lymphatic absorption did not change with increasing fill volume. There was a strong correlation between IPP and KE. However, the net ultrafiltration volume was significantly higher in the high fill volume groups compared to the low fill volume groups, mainly due to a better maintenance of the dialysate to plasma glucose concentration gradient in the high fill volume groups. There was no significant difference in the diffusive mass transport coefficients (KBD) and sieving coefficients for any of the investigated solutes, although KBD values tended to be lower in the 16 ml group. The clearances for small solutes increased with increased fill volume, although these increases were slightly smaller than predicted from the increase in fill volume. We conclude that: (1) An increase in dialysate fill volume using 3.86% glucose solution results in higher intraperitoneal hydrostatic pressure and higher peritoneal fluid absorption, but, on the other hand, a higher net ultrafiltration; (2) The increase in net ultrafiltration with increased fill volume is mainly due to a better maintenance of glucose concentration in the dialysate, inducing an increased transcapillary ultrafiltration rate; (3) Solute clearances increase although not quite to the same extent as predicted from the increase in fill volume. Our results indicate that decreased net ultrafiltration volume associated with higher dialysate fill volume (due to higher IPP and higher peritoneal fluid absorption) could be avoided if hypertonic glucose solutions are used.

Animals↗

PubMed1997

Resting membrane potential of skeletal muscle calculated from plasma and muscle electrolyte and water contents.

1. A method is described that enables the calculation of resting membrane potential from the electrolyte and water contents in blood plasma and in a sample of human muscle tissue obtained by the percutaneous needle-biopsy technique. In this calculation, the previously described equations for calculating resting membrane potential via the intra- and extra-cellular distribution of chloride were combined with the equation utilizing potassium distribution over the cell membrane. 2. The method of calculation was applied to 60 healthy subjects divided into three groups aged 19-40, 41-60 and 61-85 years. The calculated resting membrane potential in the subjects as a whole was -88.4 mV (SD 1.35; n = 60). A lower value was observed in the group aged 61-85 years (-87.7 mV, SD 1.0; n = 12) than in the group aged 19-40 years (-88.6 mV; SD 1.4; n = 32). No difference was observed between female and male subjects. 3. The RMP calculated with the present method in 60 healthy subjects was also compared with previously published values in healthy subjects, measured by the Clarke electrode method, and with values calculated from electrolyte and water distribution measured by isotope-dilution techniques. The results obtained in healthy subjects with different techniques were very similar. Data were analysed from earlier published studies in experimental animals in which resting membrane potential ranged from -91 to -65 mV. The resting membrane potential calculated from electrolytes in plasma and muscle showed a very good agreement with resting membrane potential recorded directly.

Adult↗

PubMed1997

Total, free, and protein-bound sulphur amino acids in uraemic patients.

Fasting plasma concentrations of sulphur amino acids (sAA) were measured in nine non-dialysed (ND) chronic uraemic patients on conservative treatment, 10 patients on continuous ambulatory peritoneal dialysis (CAPD), nine patients on haemodialysis (HD) treatment, and 10 healthy subjects (HS). Methionine and taurine concentrations were significantly decreased in the CAPD and HD patients and tended to be low in the ND patients. Cysteine sulphinic acid (CSA) levels were significantly higher in all patient groups. Total (t), free (f), and protein-bound (pb) homocysteine (Hcy) and cysteine (Cys) were significantly increased in all patient groups. Serine, a substrate for cystathionine synthesis from Hcy, showed significantly lower concentrations in all patient groups. The percentages of pbHcy were significantly higher in the CAPD and HD patients than in the ND patients (P < 0.0001, P = 0.002 respectively) or in the HS (P < 0.0001, P = 0.008 respectively), whereas the percentages of pbCys in CAPD and HD patients were significantly higher than in ND patients (P = 0.0006, P = 0.009 respectively) and tended to be high without reaching statistical significance compared to the HS. A single HD treatment decreased tHcy by 26%, fHcy by 39%, and pbHcy by 22%, as well as tCys by 40%, fCys by 54%, and pbCys by 27%. The tHcy concentration, although decreased by HD treatment, remained higher than in HS, whereas tCys was normalized by the dialysis session. In addition, HD treatment significantly decreased the plasma concentrations of methionine, CSA, taurine, and serine. We conclude that, except for methionine and taurine, the plasma sAA in their different forms are markedly increased in dialysed and non-dialysed uraemic patients. The percentages of pbHcy and pbCys were significantly higher in dialysed than in ND uraemic patients. HD treatment can normalize the tCys concentration, and decrease the tHcy concentration but not normalize it. The observed hyperhomocysteineaemia and low taurine levels may contribute to the high incidence of cardiovascular disease in uraemic patients.

Adult↗

PubMed1997

Free amino-acid levels simultaneously collected in plasma, muscle, and erythrocytes of uraemic patients.

BACKGROUND: Disturbances in amino acid (AA) metabolism in uraemia have mainly been reported to occur in plasma and muscle. The erythrocytes (RBC) constitute a large proportion of the free AA in blood and may play an important role in the interogan transport of AA. This report presents the first data on AA levels obtained simultaneously from three different compartments in uraemic patients. METHODS: Muscle biopsy and blood samples were obtained from 38 haemodialysis (HD), 22 continuous peritoneal dialysis (CPD) and 10 end-stage renal failure patients for determination of free amino acids by reversed-phase HPLC. The results are compared to data obtained from 27 healthy subjects under the same conditions. RESULTS: For a number of non-essential AA (alanine, glycine, asparagine, arginine) and for lysine, elevated concentrations were present simultaneously in RBC and in muscle but not in plasma. On the other hand, low concentration of some essential AA (leucine, valine, phenylalanine, tyrosine) were observed in RBC and in plasma, while the concentrations in muscle were normal. Most of the non-essential AA (NEAA), especially taurine and glutamine, had much higher muscle/plasma gradients than RBC/plasma gradients, although an accumulation in RBC of glycine, serine, arginine, asparagine, ornithine, glutamate and taurine was observed. Most of the essential AA (EAA) showed higher muscle/plasma gradients, whereas the RBC/ plasma gradients were approximately 1.0. CONCLUSION: Our findings are in agreement with studies that have shown that RBC and plasma play independent and opposing roles in AA interorgan transport. The results indicate that there are several AA abnormalities in all three compartments in uraemic patients. They also suggest that there may be some specific common changes of selected transport systems for both RBC and muscle in uraemia. Determination of AA in RBC should be considered when undertaking metabolic and clinical studies of AA disturbances.

Adult↗

PubMed1997

Dioctyl sodium sulphosuccinate increases net ultrafiltration in peritoneal dialysis.

BACKGROUND: The surface-active substance dioctyl sodium sulphosuccinate (DSS) has been reported to increase the peritoneal clearances of urea and creatinine. This study investigated the effects of DSS on the fluid and solute transport characteristics of the peritoneum. DESIGN: A 4-h single-dwell experiment session of peritoneal dialysis using 25 ml of 3.86% glucose dialysis solution with an intraperitoneal volume maker was performed in 16 male Sprague-Dawley rats. In eight rats, 0.005% (50 p.p.m.) DSS was added to the dialysis fluid. No DSS was given to the other eight rats (control group). The transport of fluid, glucose, potassium, sodium, urea, phosphate and urate were analysed. RESULTS: There was a significant increase in the intraperitoneal volume in the DSS group. At 240 min, the drain volume in DSS group (33.0 +/- 2.9 ml) was significantly higher compared to the control group (28.8 +/- 2.1 ml, P < 0.01). This increase in the drain volume was mainly due to a decrease in peritoneal fluid absorption rate in the DSS group (0.040 +/- 0.013 ml/min) as compared to the control group (0.054 +/- 0.010 ml/min, P < 0.05). There was no significant difference in the diffusive permeability and sieving coefficient for the small solutes between these two groups. However, the clearances for urea and sodium were higher in the DSS group, mainly due to the increase in the dialysate volume. CONCLUSION: Our results suggest that DSS significantly increases the net ultrafiltration of peritoneal dialysis. This effect, which was mainly due to a decrease in the fluid absorption rate, contributed to the increased clearances for urea and sodium. DSS did not alter the diffusive permeability and sieving coefficient for the small solutes.

Animals↗

PubMed1997

Minimum periodontal bone loss in dentally-aware adults. A 10-year prospective study.

A prospective study was performed on periodontal bone height changes over 10 years in dentally aware subjects. 94 subjects, aged 20-60 year, were radiographically examined by means of full mouth surveys at baseline in 1982 and 10 years later. The periodontal bone height evaluated by means of a computerized method was expressed as % of the root length. The mean of all measurements in the individual constituted the bone height value. The mean (SEM) periodontal bone height was 82.8% (0.64) at baseline and 82.0% (0.61) at follow-up. Although small, the periodontal bone height reduction over the 10 year period was statistically significant (p < 0.05). The reduction in periodontal bone height over time ranged from 0.4% (0.87) for subjects aged 30-39 years to 1.3% (0.80) for subjects aged 60-69 year. Only 15% of the subjects exhibited a bone loss > 5% and none > 10%. It is concluded that the rate of periodontal bone height reduction in dentally aware subjects is low. In the vast majority of these subjects, the 10 year bone loss may be considered clinically negligible.

Adult↗

PubMed1997

Cholecystokinin octapeptide inhibits carbohydrate but not protein intake.

Male rats ingested about half as much of an intraorally infused (1 ml/min) carbohydrate solution compared with a protein solution. Blood levels of cholecystokinin octapeptide (CCK-8) had increased to 13.6 +/- 1.4 and 16.7 +/- 1.7 pmol/l when the rats stopped ingesting carbohydrate or protein and continued to increase to 35.6 +/- 3.2 pmol/l 30 min after the carbohydrate meal and 34.4 +/- 3.5 pmol/l 60 min after the protein meal. Intraperitoneal injection of CCK-8 (0.6-5.0 micrograms) inhibited and injection of the CCKA-receptor antagonist L-364, 718 (20-80 micrograms) facilitated carbohydrate intake, but neither CCK-8 nor L-364,718 affected protein intake. The results suggest that CCK-8 is not involved in regulating the duration of a protein meal but may be involved in regulating carbohydrate intake. The postprandial period of suppression of protein intake correlated with the disappearance of some amino acids, e.g., Arg, Tyr, and Trp, in the blood, and this may be of importance for protein ingestion, since these amino acids are neurotransmitter precursors.

Amino Acids↗

PubMed1997

Hyaluronan decreases peritoneal fluid absorption in peritoneal dialysis.

Hyaluronan, exhibiting a high resistance against water flow, acts in the tissue as a barrier against rapid changes in water content. To test whether hyaluronan has any effect on the peritoneal fluid and solute transport, and, in particular, on the peritoneal fluid absorption, a 4-h dwell study with an intraperitoneal volume marker (radiolabeled human serum albumin [RISA]) was conducted in 21 male Sprague Dawley rats (three groups, seven rats in each group). Each rat was injected intraperitoneally with 25 ml of 1.36% glucose solution alone (control group), with 0.005% hyaluronan (HA1 group), or with 0.01% hyaluronan (HA2 group). Dialysate and blood samples were taken frequently for analyses of fluid and solute (urea, glucose, and protein) transport. The intraperitoneal volume was calculated from the dilution of RISA with a correction for RISA disappearance from the peritoneal cavity. This study shows that adding hyaluronan to peritoneal dialysis solution significantly (P < 0.01) increased the net peritoneal fluid removal, mainly due to a significant decrease in the peritoneal fluid absorption rate (P < 0.01). The diffusive mass transfer coefficients for glucose, urea, and protein did not differ between the three groups. The peritoneal clearance of urea increased significantly in the two hyaluronan groups compared with the control group, due to the increased net fluid removal in the hyaluronan groups. These results suggest that intraperitoneal administration of hyaluronan during a single peritoneal dialysis exchange may significantly increase the peritoneal fluid and solute removal by decreasing peritoneal fluid absorption.

Absorption↗

PubMed1997

Serum levels of NG, NG-dimethyl-L-arginine, a potential endogenous nitric oxide inhibitor in dialysis patients.

Nitric oxide (NO) is involved in blood pressure regulation, and its synthesis is inhibited by methylarginines. It has been hypothesized that one of these, asymmetrical dimethylarginine (ADMA), may contribute to dialysis-associated hypertension because it accumulates in the plasma of hemodialysis (HD) patients in a concentration high enough (4 mumol/L) to inhibit NO synthesis in experimental model systems. A precolumn HPLC technique was used to quantify methylarginines (ADMA and symmetrical dimethylarginine [SDMA]) in plasma from HD patients before and after dialysis, from continuous ambulatory peritoneal dialysis (CAPD) patients, and from healthy subjects. Plasma ADMA concentrations were 0.59 +/- 0.22 (SD) mumol/L in HD patients predialysis (n = 19) and 0.70 +/- 0.27 mumol/L in CAPD patients (n = 11), versus about half of the concentration in control subjects (0.36 +/- 0.08 mumol/L, n = 7). The concentrations of SDMA (not an inhibitor of NO formation) were approximately four to five times the ADMA concentrations in both HD and CAPD patients, in contrast to a ratio of 1:1 in the control subjects. Methylarginine concentrations were reduced by 23% and 40% postdialysis, as calculated from ADMA and SDMA values, respectively. No significant correlations were observed between ADMA concentrations, on the one had, and blood pressure, creatinine and dialysis dose (Kt/V urea), on the other hand. It is concluded that plasma levels of ADMA are considerably lower than those reported earlier in patients treated with HD and also below the levels that hitherto have been thought to have clinical relevance. The role of ADMA in inhibiting NO in dialysis-associated hypertension is questioned.

Arginine↗

PubMed1997

Correction of acidosis in dialysis patients increases branched-chain and total essential amino acid levels in muscle.

Earlier studies have shown increased oxidation of the branched-chain amino acids (BCAA), valine, isoleucine and leucine, in experimental acidosis and low levels of valine in the muscle of acidotic HD patients. Using HPLC, free amino acids in plasma and muscle were studied before and after correction of acidosis in 9 HD patients over 6 months by dialysis with a high bicarbonate solution. The predialysis standard bicarbonate concentration in blood increased from 20.6 +/- 1.3 mmol/l (mean +/- SD) before correction of acidosis to 25.9 +/- 1.8 mmol/l after correction. Correction of acidosis resulted in a significant increase in the i.c. concentrations of valine, isoleucine and leucine by 48%, 28% and 32%, as well as for the sum of BCAA and EAA, from a level lower than controls. The intra- and extracellular gradient increased for several amino acids and for the sum of EAA and BCAA, suggesting an increased influx or reduced efflux of amino acids across the cell membrane. Anthropometric data and the levels of S-albumin and transferrin did not change after correction of acidosis. The increases in the i.c. concentrations of BCAA after correction of acidosis suggest that the catabolism of these amino acids had been reduced. The effects of correction of acidosis on the concentrations of essential amino acids could be beneficial since low concentrations in muscle may reduce protein synthesis.

Acidosis↗

PubMed1997

Time dependence of solute removal during a single exchange.

The viability of long-term peritoneal dialysis (PD), especially once residual renal function is lost, has been challenged since recently recommended weekly targets of Kt/V of 2.1 and creatine clearance (Ccr) of 70 L/1.73 m2 may be difficult to reach. This study demonstrates the theoretical possibility of achieving these targets in PD patients even without residual renal function. A 6-hour dwell study was performed in 68 PD patients with frequent dialysate and plasma sampling using 2 L of 1.36% (n = 13), 2.27% (n = 9), or 3.86% glucose dialysate (n = 46) with 131I albumin as an intraperitoneal volume marker. Alterations in fluid balance, Kt/V, and Ccr with dwell time (t) as well as the impact of peritoneal fluid absorption on peritoneal fluid and solute removal were evaluated. Kt/V and Ccr did not follow an exponential function with t and, in fact, decreased after 4-5 hours, especially in high transporters. All patients could achieve either weekly Kt/V (especially low transporters) or Ccr target (especially high transporters) if they are treated with automated PD. Calculations showed that eliminating fluid absorption could increase mean fluid removal by 43%-179%, increase mean Kt/V by 17%-32%, and mean Ccr by 16%-30% (depending on the solution used and the patient's peritoneal transport pattern) during a 6-hour dialysis exchange. We reached the following conclusions: (1) Kt/V(urea) and Ccr are markedly time-dependent during a single exchange due to the substantial impact of peritoneal absorption and may, in fact, decline after 4 hours, especially in high transporters. (2) Extrapolating Kt/V and Ccr values from short dwell times [i.e., peritoneal equilibration test (PET) results] to long dwell times will overestimate the peritoneal clearances. (3) Enough fluid removal must be considered as an important target of adequate dialysis along with small solute clearances. (4) If fluid absorption could be eliminated, most continuous ambulatory peritoneal dialysis (CAPD) patients could achieve the recommended Kt/V and/or Ccr targets even without residual renal function.

Absorption↗

PubMed1997

Serum ferritin and tissue iron in anemic dialysis patients.

The relationship between serum ferritin and tissue iron was investigated in 26 dialysis patients (17 hemodialysis patients. 9 chronic peritoneal dialysis patients) with anemia (median hemoglobin 74 g/l, range 56-92 g/l). Serum ferritin ranged from 18 to 9,435 micrograms/l (median 450 micrograms/l). Tissue iron was assessed in the liver biopsies of 4 hemodialysis patients with iron overload (serum ferritin 1,150-9,435 micrograms/l), in the muscle biopsies of 5 patients with serum ferritin 170-9,435 micrograms/l, and in bone marrow aspirations (semiquantitative assessment). The mean liver iron concentration was 15.4 +/- 8.0 micrograms Fe/mg protein (mean +/- SD), which is similar to that previously found in patients with untreated idiopathic hemochromatosis. Four patients with serum ferritin 170-620 micrograms/l had muscle iron concentrations (0.33 +/- 0.10 microgram Fe/mg protein) similar to those found in controls (0.23 +/- 0.10, means +/- SD). One patient with serum ferritin 9,435 micrograms/l had a markedly increased muscle iron concentration (1.3 micrograms Fe/mg protein). The bone marrow iron was assessed as negative in 3 patients (serum ferritin 44-85 micrograms/l), positive in 8 (serum ferritin 18-379 micrograms/l), increased in 11 patients (serum ferritin 222-4,210 micrograms/l), and was markedly increased in 2 patients (serum ferritin 4,550 and 9,435 micrograms/l). Bone marrow iron correlated significantly with serum ferritin concentrations (spearman rank correlation coefficient rho = 0.89, p < 0.001). These results show that in dialysis patients with a stable iron balance and unstimulated erythropoiesis, i.e., patients without erythropoietin treatment and parenteral iron, serum ferritin is a useful indicator of iron stores. Our findings also suggest that the relationship between tissue iron and serum ferritin levels in end-stage renal disease is altered, i.e. a relative increase in serum ferritin levels unrelated to iron stores is observed in dialysis patients.

Adult↗

PubMed1996

A multispecific saline-soluble lectin from the parasitic fungus Arthrobotrys oligospora. Similarities in the binding specificities compared with a lectin from the mushroom agaricus bisporus.

Several fungi can express high levels of saline-soluble and low-molecular-mass lectins that bind to glycoproteins such as fetuin and different mucins but not bind to any monosaccharides. In this paper, we report the binding specificities of such a lectin (designated AOL) isolated from the nematophagous fungus Arthrobotrys oligospora. The results show that AOL is a multispecific lectin that interacts with the following ligands: (a) Several sulfated glycoconjugates including sulfatide, dextran sulfate, and fucoidan. The specificity of this binding was indicated by experiments showing that none of the tested neutral- and sialic-acid-containing glycolipids, chondroitin sulfates B and C, heparin, and polyvinyl sulfate bound to AOL; (b) Phosphatidic acid and phospatidylglycerol, two out of several tested phospholipids. (c) N-linked and O-linked sugar chains bound to intact fetuin. The involvement of such sugar structures was demonstrated by analyzing the binding of AOL to chemically deglycosylated (trifluoromethanesulfonic acid) fetuin. Treating fetuin with O-glycosidase and N-glycosidase indicated that AOL bound to Gal beta GaLNAc alpha-Ser/Thr and to some N-linked complex sugars, respectively. Further assays demonstrated that AOL could interact with several other glycoproteins containing O-linked and/or N-linked sugar chains. The observations that AOL did not bind to free N-linked sugars isolated from fetuin, or to fetuin treated with trypsin or pronase, or to any of the tested neoglycoproteins and glycolipids with neutral- or sialic acid-containing sugars, indicated that the sugar chains need to be bound to an intact peptide backbone to interact with AOL. We have recently shown that the deduced primary structure of AOL has a high similarity to the sequence of a saline-soluble lectin isolated from the mushroom Agaricus bisporus (ABL) (Rosén, S., Kata, M., Persson, Y., Lipniunas, P. H., Wikström, M., van den Hondel, C. A. M. J. J., van den Brink, J. M., Rask, L., Hedén L.-O. and Tunlid, A., see companion paper). It is well known that ABL binds to Gal beta 3GaLNAc alpha-Ser/Thr, and in this paper we demonstrate that ABL binds to sulfatide, phosphatidic acid, phospatidylglycerol, and possibly also to the same N-linked complex sugars as AOL. The above data indicate that AOL and ABL are members of a novel family of fungal lectins sharing similar primary structure and binding properties.

Agaricus↗

PubMed1996

Recognition of glycoconjugates by Helicobacter pylori: an apparently high-affinity binding of human polyglycosylceramides, a second sialic acid-based specificity.

Helicobacter pylori has been reported to agglutinate erythrocytes and to bind to various other cells in a sialic acid-dependent way. The binding was inhibited by sialyllactose or fetuin and other sialylated glycoproteins. The specificity apparently requires bacterial growth on agar, since we found that it was lost after growth in the nutrient mixture Ham's F12. Instead, the bacteria bound with high affinity and in a sialic acid-dependent way to polyglycosylceramides of human erythrocytes, a still incompletely characterized group of complex glycolipids. Bacteria grown in F12 medium were metabolically labelled with 35S-methionine and analysed for binding to glycolipids on thin-layer chromatograms and to glycoproteins on blots after electrophoresis, with human erythrocyte glycoconjugates in focus. There was no binding to simpler gangliosides including GM3 or sialylparagloboside, or to a mixture of brain gangliosides. In contrast, polyglycosylceramides of human erythrocyte membranes bound at a pmol level. The activity was eliminated by mild acid treatment, mild periodate oxidation or sialidase hydrolysis. Erythrocyte proteins as well as a range of reference glycoproteins did not bind except band 3, which was weakly active. However, this activity was resistant to periodate oxidation. These results indicate a second and novel sialic acid-recognizing specificity which is expressed independently of the previously described specificity.

Binding Sites↗

PubMed1996

Enhanced scavenger receptor expression in monocyte-macrophages in dialysis patients.

The macrophage scavenger receptor (SR), which has two isoforms named type I and II, plays a leading role in the atherosclerotic process. To elucidate the mechanism of atherosclerosis in dialysis patients, SR expression was studied in monocyte-macrophages from thirteen dialysis patients and eight healthy controls. SR mRNA expression was examined in four hemodialysis patients and four controls matched for age and sex. Monocytes were allowed to differentiate into macrophages in in vitro cultures for seven days and SR type I and II mRNA expression were analyzed with the reverse transcription-polymerase chain reaction and quantitated using radiation densities of Southern blots. Only SR type I expression increased during differentiation and was accelerated by one or two days and enhanced after five days in patients, as compared to controls. To detect SR protein expression, uptake of fluorescently labeled acetylated low-density lipoprotein (Ac-LDL) was evaluated by flow cytometry. The mean fluorescence intensity of labeled cells was significantly higher in hemodialysis and continuous ambulatory peritoneal dialysis patients than in controls, although the number of SR-positive cells remained constant. In conclusion, SR expression is enhanced in macrophages from dialysis patients, probably by up-regulation of type I, which may contribute to the development of atherosclerosis in these patients.

Adult↗

PubMed1996

Influence of peritoneal dialysis solutions with glucose and amino acids on ingestive behavior in rats.

Continuous ambulatory peritoneal dialysis (CAPD) is often associated with malnutrition; reduced intake of nutrients due to anorexia is an important factor. The glucose load from glucose-based peritoneal dialysis (PD) solutions and amino acids from amino acid-based solutions may favor suppression of the appetite. To study this matter we used a new experimental model in free-moving, unstressed male Wistar rats (300 to 350 g) with feeding catheters channeled from the top of the skull to the oral cavity. When the rats recovered from surgery they were tested under standardized conditions by giving them an intraoral infusion (1 ml/min) of a solution containing 342 g/liter of the sucrose or 97 g/liter protein solutions while recording the time (volume) of ingestion. Control rats consumed 18.8 +/- 0.9 ml of the sucrose and 39.8 +/- 0.8 ml of the protein solutions. Injections of PD solutions with 13.6, 22.7, and 38.6 g/liter of glucose reduced the ingestion of sucrose by 12.4%, 23.6% and 36.1%, respectively, but did not affect the ingestion of protein. Injections of 30 ml of PD solutions containing 11, 18 and 31 g/liter of amino acids reduced the ingestion of both sucrose by 9.7%, 17.1% and 33.2% and of protein by 13.5%, 25.9% and 33.1%, respectively. We conclude that in our experimental model, the inhibition of appetite caused by peritoneal solutions containing glucose or amino acids seems to be specific for each nutritional constituent and not simply an effect of hyperosmolality or large filling volumes.

Adaptation, Physiological↗