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Biomedical subjects

A H Naber

Publications and source records attributed to A H Naber.

17 recordsLinked to original sources
PubMed2000

Effects of structurally different lipid emulsions on human neutrophil migration.

AIM: To test the hypothesis that structurally different lipid emulsions have distinct immunomodulatory properties, we analysed neutrophil migration in the presence of various lipid emulsions. METHOD: Neutrophils of 8 volunteers were pre-incubated in medium or physiological 2.5 mM emulsions containing long-chain (LCT), medium-chain (MCT), mixed LCT/MCT, alpha -tocopherol-enriched LCT/MCT (LCT/MCT-E) or structured triglycerides (SL). Thereafter, the cells were put on top of 3 microm-pore-sized cell culture filters and incubated for one hour in the presence or absence of a chemo-attractant. Neutrophil migration was measured as the percentage of cells that had passed the filter in the presence (chemotaxis) or absence (random migration) of a chemotactic factor. RESULTS: Compared to lipid-free incubation (19+/-1%) random neutrophil migration significantly decreased with LCT/MCT (11+/-2%), LCT/MCT-E (12+/-2) and MCT (5+/-2%), while LCT (18+/-3%) and SL (20+/-1%) had no effect. N-formyl-methionyl-leucyl-phenylalanine- (fMLP, 10(-8)M) or zymosan-activated-serum-induced (ZAS, 10%) filter passage under lipid-free conditions amounted to 61+/-14% and 70+/-13%, respectively. These values decreased with LCT/MCT to 11+/-9% and 15+/-7%; with LCT/MCT-E to 18+/-10% and 28+/-12%; with SL to 39+/-18% and 57+/-14%, and with MCT to 5+/-2% and 10+/-6%, (all P<0.01), while LCT had no effect. Compared to LCT/MCT, the alpha -tocopherol-enriched formulation significantly increased ZAS- and fMLP-induced chemotaxis. fMLP-induced chemotaxis decreased in direct proportion to LCT/MCT triglyceride concentration. CONCLUSIONS: Human neutrophil migration is distinctively inhibited by structurally different lipid emulsions, depending on triglyceride chain-length and concentration as well as alpha -tocopherol content.

Adult↗
PubMed1999

Depression of plasma levels of cytokines and ex-vivo cytokine production in relation to the activity of the pituitary-adrenal axis, in patients undergoing major vascular surgery.

The relation between the immune and neuroendocrine response during surgery was studied. In 18 patients undergoing major vascular surgery, circulating interleukin (IL)-1beta and ex-vivo production of IL-1beta and tumour necrosis factor (TNF)-alpha were lower on day 1 after surgery compared to pre-operation values (-14+/-5%, P<0.05; -62+/-9%, P<0.05; and -31+/-54%, P<0.005, respectively). Circulating IL-1 receptor antagonist (IL-1ra) was higher on the 5th day post-operatively compared to pre-operation values (mean +640%+/-400, P<0.05). In a more detailed study in six patients, the ex-vivo production of IL-1beta and TNF-alpha started to decrease at induction of general anaesthesia and dropped to under 10% of initial values at the end of surgery. Circulating IL-1ra and ex-vivo production of IL-1ra started to increase at the end of surgery and remained elevated up to 6 days post-operatively. Plasma antidiuretic hormone (ADH) and adrenocorticotropic hormone (ACTH) increased during surgery, but cortisol remained unchanged. We demonstrate a depression of circulating pro-inflammatory IL-1beta and an increase of circulating anti-inflammatory IL-1ra during surgical stress. The ex-vivo production of IL-1beta and TNF-alpha was suppressed, indicating a downregulation of the production of these cytokines. This parallelled the hormonal reaction with high ADH and ACTH, but not of cortisol, suggesting that glucocorticoid is not the key-factor in downregulation of production and release of pro-inflammatory cytokines.

Adrenocorticotropic Hormone↗
PubMed1999

Influence of structurally different lipid emulsions on human neutrophil oxygen radical production.

BACKGROUND: The aim of this study was to evaluate immunomodulatory properties of lipid emulsions applied in parenteral nutrition by measuring neutrophil oxygen radical production (the 'respiratory burst') after lipid incubation. MATERIALS AND METHODS: Neutrophils, isolated from the blood of 10 healthy individuals, were incubated in medium or in lipid emulsions in a physiological concentration (2.5 mmol L-1) containing long-chain [Intralipid (LCT)], mixed medium and long-chain [Lipofundin (LCT/MCT)] or structured triglycerides (SL). After washing and stimulation with phorbol 12-myristate 13-acetate (PMA) or serum-treated zymosan (STZ) particles, the respiratory burst was evaluated by measuring maximum oxygen uptake, superoxide and hydrogen peroxide production rates and chemiluminescence. RESULTS: Unlike LCT and SL, LCT/MCT increased PMA- and STZ-induced oxygen uptake rate by 45% and 31% respectively (both P = 0.006 compared with medium) as well as superoxide (+56%, P = 0.006) and hydrogen peroxide (+14%, P = 0.04) production, within 5 min after stimulation. Increased LCT/MCT-mediated early respiratory burst was confirmed by decreased PMA- (-65%) and STZ-stimulated (-54%) chemiluminescence peak time (time after stimulation to peak) in combination with unchanged peak height (maximum rate of radical production). Late respiratory burst (within 2 h) of LCT/MCT, indicated by overall luminescence (overall radical production), remained unchanged (PMA) or decreased (STZ, P = 0.02). The addition of 2.5 mmol L-1 LCT/MCT or MCT emulsion to unstimulated neutrophils, in contrast to LCT and SL, resulted in significant luminescence. CONCLUSIONS: Early neutrophil respiratory burst is accelerated by the LCT/MCT emulsion Lipofundin, whereas LCT (Intralipid) and structured lipid emulsions exert no effect. MCT-containing emulsions, contrary to LCT and structured lipid emulsions, can induce oxygen radical production in unstimulated neutrophils.

Adult↗
PubMed1997

Role of bacteria in the pathogenesis of short bowel syndrome-associated D-lactic acidemia.

Previously, we have demonstrated that short bowel syndrome (SBS) patients suffer daily from D-lactic acidemia; in these patients rather high amounts of (bacterial) D-lactate emerge in blood and urine with a circadian rhythm. The aim of this study was to establish the microbial basis of D-lactic acidemia in SBS. Therefore, faecal flora of (young and adult) SBS-patients was analysed qualitatively and quantitatively, and compared to that of controls. The isolated bacterial species were screened for massive D- and/or L-lactate production after in vitro growth. After introduction of oral feeding in SBS-infants shortly after the resection, lactobacilli increased from < or = 1% up to 60 +/- 5% of the faecal flora within 2-3 weeks. In the faeces of patients with oral feeding the lactate producers Lactobacillus acidophilus and Lactobacillus fermentum were the major resident bacteria (each with 10(10)-10(12) cfu/g faeces). During active growth in vitro these lactobacilli produced massive amounts of D- and L-lactic acid from glucose. Use of oral antibiotics in two SBS-children did not reduce the total numbers of lactobacilli, but caused shifts within the intestinal populations of at least lactobacilli. It is concluded that the strongly reduced intestinal capacity for carbohydrate absorption and the oral consumption of easily fermentable carbohydrates form the physiological basis for D-lactic acidemia in SBS, and that the fermentative D-lactate production by intestinal bacteria, especially the abundant, resident lactobacilli, forms its microbial basis. In these patients the antimicrobial and therapeutic effects of antibiotics are unpredictable.

Acidosis, Lactic↗
PubMed1995

[Generalized histoplasmosis due to endogenous reactivation of a latent infection in an HIV-seronegative man].

A 63-year-old, Dutch, HIV-seronegative man presented with anal pain and itch of 6 months' duration, a perianal ulcer and a solitary colon ulcer. Crohn's disease was suspected; the patient was treated with corticosteroids, but later died. Autopsy revealed disseminated histoplasmosis, a fungal disease rare in the Netherlands. The patient had visited Honduras. This case report illustrates that disseminated histoplasmosis may mimic Crohn's disease leading to a delay in the diagnosis.

Crohn Disease↗
PubMed1995

Undefined malabsorption syndrome with villous atrophy successfully reversed by treatment with cyclosporine.

A 47-year-old man with a flat jejunal mucosa complicated by malabsorption, diarrhoea and lymphocytic colitis is presented. There was no response to gluten withdrawal alone, combination of a gluten-free diet and prednisone therapy, or total parenteral nutrition. Complete clinical remission was only achieved after simultaneous treatment with cyclosporine and a gluten-free diet. Rechallenge with a gluten-containing diet while cyclosporine treatment continued resulted in a relapse of diarrhoea and malabsorption. We conclude that cyclosporine may be an effective agent for the treatment of undefined, refractory forms of malabsorption.

Atrophy↗
PubMed1993

Oxidation resistance, oxidation rate, and extent of oxidation of human low-density lipoprotein depend on the ratio of oleic acid content to linoleic acid content: studies in vitamin E deficient subjects.

The purpose of this study was to understand better the factors providing oxidation resistance to human low-density lipoprotein (LDL). Therefore, the susceptibility to copper-induced in vitro oxidation of LDL from vitamin E deficient patients and normal healthy subjects was studied. Surprisingly, the LDL of vitamin E deficient patients appeared less susceptible to oxidation than control LDL. Both oxidation rate and extent of oxidation, measured as diene production, were reduced when compared to control LDL. The lag time, a measure of resistance to oxidation, was not different from the lag time of LDL from healthy subjects. No relation was found between vitamin E content and resistance against oxidation. LDL from vitamin E deficient patients contained lower amounts of vitamin E, less cholesteryl esters, and increased amounts of triglycerides. Furthermore, its oleic acid content was increased and its linoleic acid content decreased. Linear regression analyses revealed that the ratio of oleic acid content to linoleic acid content was strongly correlated with the lag time, and inversely correlated with oxidation rate and extent of oxidation. Thus, LDL rich in oleic acid and poor in linoleic acid was less easily oxidized. It is concluded that the susceptibility of LDL to oxidation is determined not only by its antioxidant content, but also by other compositional factors, and more specifically by the ratio of oleic acid content to linoleic acid content.

Adult↗
PubMed1993

[Endosonography of the esophagus and the stomach].

Endosonography of the oesophagus and stomach is important for staging of carcinomas, for judging the degree of thickening of the wall, and for assessment of submucosal and intramural lesions and of space-occupying processes in extra-oesophageal and extragastric organs.

Endoscopy↗
PubMed1991

Nodular regenerative hyperplasia of the liver: an important cause of portal hypertension in non-cirrhotic patients.

In our hospital over the last 10 years a diagnosis of nodular regenerative hyperplasia was made for 13 patients. Sixty-nine percent of these patients had portal hypertension, representing 27% of all our patients with portal hypertension and a non-cirrhotic liver. Nodular regenerative hyperplasia was the second most frequent cause of portal hypertension in patients without cirrhosis. To make the diagnosis, a reticulin staining of a surgical biopsy is most helpful. However, the characteristic derangement of the liver architecture on histology may still be overlooked. In this study a suggestive relation was found between malignant disease (multiple myeloma, chronic myelogenous leukaemia, Leydig cell tumour and Hodgkin's disease), the use of cytotoxic or immunosuppressive drugs and nodular regenerative hyperplasia. Furthermore, a high rate of symptomatic nodular regenerative hyperplasia was observed in patients following kidney transplantation. Liver function abnormalities developed in these patients after a period ranging from 8 months to 3 years of immunosuppressive- or chemotherapy. These liver function abnormalities were, however, usually mild. Since hepatic encephalopathy is not likely to develop in these patients with nodular regenerative hyperplasia a decompressive shunt operation is a good alternative approach, if not the treatment of choice, for the prevention of recurrent variceal haemorrhage.

Adolescent↗
PubMed1991

Total parenteral nutrition: practical recommendations and new developments.

In this article the general guidelines for a nutrition schedule and new developments in the field of parenteral nutrition are discussed. The present possibilities for parenteral nutrition do not imitate the normal physiologic diet completely. The most frequently used calculation of the energy expenditure is estimated by a formula using weight, height, and age and was developed in healthy persons. It does not always represent the real caloric demands of a patient. Complications, partly due to parenteral nutrition, are noted. In severely ill patients hyperglycaemia and liver function disorders are frequently observed. Parenteral nutrition results in atrophy of the intestinal mucosa. Deficiencies in trace elements and vitamins are diagnosed despite calculated adequate nutritional support because the demands are underestimated. New developments in parenteral nutrition include a better method to determine the nutritional demands in clinical practice, administration of hormones to improve the nitrogen balance, and development of new lipid emulsions and amino-acid solutions. Studies provide more insight into the physiologic process of trace element metabolism, and methods are being developed to define a real deficiency.

Amino Acids↗
PubMedDate not supplied

With medium-chain triglycerides, higher and faster oxygen radical production by stimulated polymorphonuclear leukocytes occurs.

BACKGROUND: Parenteral lipid emulsions are suspected of suppressing the immune function. However, study results are contradictory and mainly concern the conventional long-chain triglyceride emulsions. METHODS: Polymorphonuclear leukocytes were preincubated with parenteral lipid emulsions. The influence of the lipid emulsions on the production of oxygen radicals by these stimulated leukocytes was studied by measuring chemiluminescence. Three different parenteral lipid emulsions were tested: long-chain triglycerides, a physical mixture of medium- and long-chain triglycerides, and structured triglycerides. Structured triglycerides consist of triglycerides where the medium- and long-chain fatty acids are attached to the same glycerol molecule. RESULTS: Stimulated polymorphonuclear leukocytes preincubated with the physical mixture of medium- and long-chain triglycerides showed higher levels of oxygen radicals (p < .005) and faster production of oxygen radicals (p < .005) compared with polymorphonuclear leukocytes preincubated with long-chain triglycerides or structured triglycerides. Additional studies indicated that differences in results of various lipid emulsions were not caused by differences in emulsifier. The overall production of oxygen radicals was significantly lower after preincubation with the three lipid emulsions compared with controls without lipid emulsion. CONCLUSIONS: A physical mixture of medium- and long-chain triglycerides induced faster production of oxygen radicals, resulting in higher levels of oxygen radicals, compared with long-chain triglycerides or structured triglycerides. This can be detrimental in cases where oxygen radicals play either a pathogenic role or a beneficial one, such as when rapid phagocytosis and killing of bacteria is needed. The observed lower production of oxygen radicals by polymorphonuclear leukocytes in the presence of parenteral lipid emulsions may result in immunosuppression by these lipids.

Adult↗
PubMedDate not supplied

Medium-chain, triglyceride-containing lipid emulsions increase human neutrophil beta2 integrin expression, adhesion, and degranulation.

BACKGROUND: To test the hypothesis that lipid emulsions with different triglyceride structures have distinct immunomodulatory properties, we analyzed human neutrophil adhesion and degranulation after lipid incubation. METHODS: Neutrophils, isolated from the blood of 10 healthy volunteers, were incubated in medium or physiologic (2.5 mmol/L) emulsions containing long-chain (LCT), medium-chain (MCT), mixed LCT/MCT, or structured (SL) triglycerides. Expression of adhesion molecules and degranulation markers was evaluated by flow cytometry. Also, functional adhesion was investigated by means of a flow cytometric assay using fluorescent beads coated with the integrin ligand intercellular adhesion molecule (ICAM)-1. RESULTS: Although LCT and SL had no effect, LCT/MCT significantly increased expression of the beta2 integrins lymphocyte-function-associated antigen 1 (+18%), macrophage antigen 1 (+387%), p150,95 (+82%), and (alphaDbeta2 (+230%). Degranulation marker expression for azurophilic (CD63, +210%) and specific granules (CD66b, +370%) also significantly increased, whereas L-selectin (CD62L, -70%) decreased. The effects of LCT/MCT were mimicked by the MCT emulsion. ICAM-1 adhesion (% beads bound) was increased by LCT/MCT (34% +/- 4%), whereas LCT (19% +/-3%) and SL (20% +/- 2%) had no effect compared with medium (17% +/- 3%). CONCLUSIONS: LCT/MCT and MCT, contrary to LCT and SL emulsions, increased neutrophil beta2 integrin expression, adhesion, and degranulation. Apart from other emulsion constituents, triglyceride chain length might therefore be a key feature in the interaction of lipid emulsions and the phagocyte immune system.

Adult↗
PubMedDate not supplied

Phagocytosis and killing of Candida albicans by human neutrophils after exposure to structurally different lipid emulsions.

BACKGROUND: To test the hypothesis that structurally different lipid emulsions have distinct immune-modulating properties, we analyzed the elimination of Candida albicans by neutrophils after exposure to various emulsions. METHODS: Neutrophils from 8 volunteers were incubated in physiologic 5 mmol/L emulsions containing long-chain- (LCT), medium-chain- (MCT), mixed LCT/MCT-, alpha-tocopherol-enriched LCT/MCT (LCT/MCT-E), or structured lipids (SL). After washing, the neutrophils were incubated with C. albicans. Phagocytosis was measured as the number of yeast-associated neutrophils relative to the total neutrophil count. Killing was expressed as the percentage of Candida survival relative to the initial yeast cell count. RESULTS: No significant differences in yeast-neutrophil association could be demonstrated after neutrophil incubation in various lipid emulsions or medium, after correction for non-specific adhesion. However, although Candida survival after 1 hour incubation with non-lipid-exposed neutrophils amounted to 53% +/- 11% and was not influenced by LCT (60% +/- 11%), LCT/MCT (78% +/- 7%), LCT/MCT-E (72% +/- 12%), and SL (67% +/- 6%), pure MCT (70% +/- 13%) significantly impaired the killing capacity of neutrophils. CONCLUSIONS: The decreased killing capacity of neutrophils after exposure to medium-chain fatty acid-containing emulsions and the absence of this effect with LCT suggest that lipid emulsions influence the elimination of C. albicans depending on the triglyceride chain length.

Adjuvants, Immunologic↗
PubMedDate not supplied

Human neutrophil membrane fluidity after exposure to structurally different lipid emulsions.

BACKGROUND: We have previously reported that medium-chain triglyceride (MCT)-containing lipid emulsions, contrary to long-chain triglyceride (LCT) emulsions, activate human neutrophils. This activation might result from functional alterations in cellular membranes induced by MCT. Membrane fluidity is such a feature with known clinical implications and can be assessed by fluorescence polarization measurements. This study was performed to investigate whether exposure to various emulsions distinctively influences neutrophil membrane fluidity. METHODS: Neutrophils from 8 volunteers were incubated in medium or physiologic 2.5 mmol/L emulsions containing LCT, mixed LCT/MCT, or structured lipids (SL). Subsequently, the cells were washed and anisotropy, ie, the reciprocal of fluidity, was measured using the fluorescent probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethyl-ammonium (TMA)-DPH. RESULTS: Compared with nonlipid-exposed neutrophils, LCT/MCT and, to a lesser degree, SL decreased fluorescence anisotropy and thus increased membrane fluidity, which was measured by DPH anisotropy, whereas LCT had no effect. Similar results were obtained with the more polar probe TMA-DPH. CONCLUSIONS: These data suggest that the neutrophil-activating effect of MCT-containing emulsions may, at least in part, be mediated by an effect on cellular membrane fluidity.

Adult↗