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Biomedical subjects

R Benner

Publications and source records attributed to R Benner.

At least 19 recordsLinked to original sources
PubMed2005

Dissection of systems, cell populations and molecules.

This paper summarizes studies on antibody formation in the bone marrow and the suppressive effects of intravenous immunization with allogeneic blood cells on T-cell function in mice. The latter studies were extended by employing the limiting dilution culture system developed in Ivan Lefkovits' laboratory and implemented in collaboration with Lucien Aarden. Thereby, the functional data were complemented with frequencies of alloantigen-activated helper (Th) and suppressor T cells after intravenous alloimmunization. These results led the Rotterdam group to studies on the prevention of rejection of the foetal 'allograft'. Th cells are central in foetal allograft rejection and pregnancy success. Characteristic for human pregnancy is the production of the glycoprotein chorionic gonadotropin (hCG) hormone. The in vivo liberated peptide fragments originating from nicking of the sequence MTRVLQGVLPALPQ in the beta-chain of hCG were considered for their immunoregulating capacity related to pregnancy success. These peptides - prepared synthetically - (MTR, MTRV, LQG, LQGV, VLPALP and others) indeed showed a remarkable spectrum of biological effects (e.g. modulation of angiogenesis, inhibition of septic shock syndrome, prevention of diabetes and reduction of ischaemia-reperfusion damage). The paper interprets and generalizes these findings and projects them into various research directions, especially towards the proteomics framework studies built up in Ivan Lefkovits' laboratory in the nineties. During the time period, when Ivan spent a mini-sabbatical in Rotterdam (months after closing down the BII) more detailed discussions were intiated. This paper is meant to keep the discussions between the involved research groups going on.

Animals↗
PubMed2001

Production of refractory dissolved organic matter by bacteria.

Most of the oceanic reservoir of dissolved organic matter (DOM) is of marine origin and is resistant to microbial oxidation, but little is known about the mechanisms of its formation. In a laboratory study, natural assemblages of marine bacteria rapidly (in <48 hours) utilized labile compounds (glucose, glutamate) and produced refractory DOM that persisted for more than a year. Only 10 to 15% of the bacterially derived DOM was identified as hydrolyzable amino acids and sugars, a feature consistent with marine DOM. These results suggest that microbial processes alter the molecular structure of DOM, making it resistant to further degradation and thereby preserving fixed carbon in the ocean.

Amino Acids↗
PubMed2001

Inhibition of diabetes in NOD mice by human pregnancy factor.

Clinical symptoms of Th1 mediated autoimmune diseases regress in many patients during pregnancy. A prominent feature of pregnancy is the presence of human chorionic gonadotrophin hormone (hCG) in blood and urine. In this report we tested the effect of clinical grade hCG (c-hCG) on the development of diabetes, a Th1 mediated autoimmune disease, in nonobese diabetic (NOD) mice. We show that treatment of NOD mice with c-hCG before the onset of clinical symptoms lowered the increased blood glucose levels, reversed the established inflammatory infiltrate of pancreatic tissue, and profoundly inhibited the development of diabetes for prolonged time. c-hCG also induced profound inhibition of the functional activity (i.e. production of IFN-gamma) of Th1 cells. Transfer of spleen cells from c-hCG-treated NOD mice into immunocompromised NOD.SCID mice inhibited the development of diabetes in these otherwise nontreated mice. This shows that the treatment of the donor NOD mice induced persistent changes in the immune system. The antidiabetic activity of c-hCG was not caused by heterodimeric hCG or its subunits. Instead, this antidiabetic activity resided in a fraction of c-hCG preparation that contains a 400-2000 Dalton natural (immuno) modulatory pregnancy factor (NMPF).

Animals↗
PubMed2000

A randomized, double-blind trial comparing azithromycin and clarithromycin in the treatment of disseminated Mycobacterium avium infection in patients with human immunodeficiency virus.

Two hundred and forty-six patients infected with human immunodeficiency virus (HIV) who also had disseminated Mycobacterium avium complex received either azithromycin 250 mg every day, azithromycin 600 mg every day, or clarithromycin 500 mg twice a day, each combined with ethambutol, for 24 weeks. Samples drawn from patients were cultured and clinically assessed every 3 weeks up to week 12, then monthly thereafter through week 24 of double-blind therapy and every 3 months while on open-label therapy through the conclusion of the trial. The azithromycin 250 mg arm of the study was dropped after an interim analysis showed a lower rate of clearance of bacteremia. At 24 weeks of therapy, the likelihood of patients' developing 2 consecutive negative cultures (46% vs. 56%, P=.24) or 1 negative culture (59% vs. 61%, P=.80) was similar for azithromycin 600 mg (n=68) and clarithromycin (n=57), respectively. The likelihood of relapse was 39% versus 27% (P=.21) on azithromycin compared with clarithromycin, respectively. Of the 6 patients who experienced relapse, none of those randomized to receive azithromycin developed isolates resistant to macrolides, compared with 2 of 3 patients randomized to receive clarithromycin [corrected]. Mortality was similar in patients comprising each arm of the study (69% vs. 63%; hazard, 95.1% confidence interval, 1.1 [0.7, 1.7]). Azithromycin 600 mg, when given in combination with ethambutol, is an effective agent for the treatment of disseminated M. avium disease in patients infected with HIV.

AIDS-Related Opportunistic Infections↗
PubMed2000

Isolation and quantification of dissolved lignin from natural waters using solid-phase extraction and GC/MS.

Solid-phase extraction (SPE) was tested for the isolation of dissolved lignin from diverse natural waters (fresh, estuarine, and marine) in preparation for CuO oxidation. Capillary GC coupled to selected-ion monitoring mass spectrometry (SIM-MS) of CuO oxidation products provides the high sensitivity and precision required for the identification and quantification of trace levels of lignin in seawater. The low blanks and quick cleanup of C18 cartridges support SPE for processing such samples. Comparison of SPE with other isolation procedures (direct dry-down and ultrafiltration) has shown that this method quantitatively recovers dissolved lignin and preserves its compositional parameters. The concentration and nature of dissolved organic matter appear to be primary factors that constrain the amount of water that should be processed to obtain quantitative and reproducible recoveries of dissolved lignin using SPE. Highest recoveries of dissolved lignin were obtained at low pH (1.5-4.0) with substantial decreases at pH > 4. Extraction efficiencies were independent of flow rate within a range of five to fifteen bed volumes per minute (50-150 mL min(-1)), and both refrigeration and freezing were appropriate long-term storage methods for processed cartridges prior to elution of retained dissolved lignin.

Gas Chromatography-Mass Spectrometry↗
PubMed2000

Determination of amino sugars in environmental samples with high salt content by high-performance anion-exchange chromatography and pulsed amperometric detection.

Amino sugars were determined in natural samples, including seawater, using high-performance anion-exchange chromatography with pulsed amperometric detection and a new-off-line sample cleanup procedure. Samples were hydrolyzed with 3 M HCl for 5 h (100 degrees C) and neutralized with anion retardation resin. Before injection, salts and organic contaminants were removed with a strong cation exchanger in the Na+ form. Detection limits for amino sugars were between 1 and 4 nM (signal-to-noise ratio 3), allowing for the first time quantification of amino sugars in seawater without preconcentration. Precision was 2-11% at the 20 nM level. The relatively simple and rapid sample preparation makes it suitable for routine analyses.

Amino Sugars↗
PubMed2000

Human keratinocytes are major producers of IL-18: predominant expression of the unprocessed form.

The cytokine network in the skin is a tightly regulated system in which IL-1 isoforms, as well as their receptors and antagonists have a central role. The recently discovered IL-1 isoform IL-18 (also known as interferon gamma-inducing factor (IGIF) or IL-1gamma), promotes IFN-gamma expression by T cells in concert with IL-12. Because IFN-gamma plays an important role in many inflammatory skin diseases by facilitating the development of Th1 cells, it is important to elucidate the role of mediators which regulate the production of this cytokine. We demonstrate that human keratinocytes constitutively express IL-18 at the mRNA as well as at the protein level. The protein was mainly expressed intracellularly in the 24 kD unprocessed pro-form, but was also secreted. Histochemistry revealed a diffuse staining of IL-18 in the epidermis of normal skin, which is in line with our in vitro data. Furthermore, we show that the level of IL-18 expressed in freshly isolated normal human epidermal cells, whether or not containing HLA-DR+ cells, significantly exceeded the expression levels of other cell types such as monocytes and bronchial epithelial cells. Finally, our results show that stimulation of the keratinocyte cell line HaCaT with PMA LPS or IL-1beta, does not significantly affect intracellular or released (pro) IL-18 levels. These experiments show for the first time that human keratinocytes relative to monocytes, PBMC or leukocytes produce a considerably larger amount of pro-IL-18, which is also readily released. High constitutive levels of IL-18 may contribute to the skewing towards a Th1-like environment, which is apparent in many human inflammatory skin diseases.

Cell Line↗
PubMed1999

IL-1 beta and IFN-gamma induce the regenerative epidermal phenotype of psoriasis in the transwell skin organ culture system. IFN-gamma up-regulates the expression of keratin 17 and keratinocyte transglutaminase via endogenous IL-1 production.

Skin biopsies from healthy human skin and non-lesional skin from patients with psoriasis were cultured for 24 h and stimulated with interleukin-1 beta (IL-1 beta) and interferon-gamma (IFN-gamma) in a skin organ culture model and the induction of the psoriasiform regenerative epidermal phenotype was analysed using immunostaining. In the presence of IL-1 beta, the psoriasiform regenerative epidermal phenotype was clearly induced. This involved strong up-regulation of the expression of keratin 16, keratin 17, and keratinocyte transglutaminase (TGk) in the suprabasal layers, strong up-regulation and a shift of the expression of keratin 5 and integrin beta 1 from the basal to suprabasal keratinocytes, and induction of the expression of ICAM-1 and HLA-DR on basal keratinocytes. The effects of IL-1 beta in the organ cultures of normal skin could be completely neutralized by anti-IL-1 polyclonal antibodies. The effects of IFN-gamma in healthy and non-lesional psoriatic skin were qualitatively similar to those of IL-1 beta. The IFN-gamma-induced epidermal expression of keratin 17 and TGk could be completely blocked by culturing the biopsies in the presence of IL-1ra or anti-IL-1 antibodies, while the induction of HLA-DR and ICAM-1 was not inhibited. The induction of the psoriasiform regenerative epidermal phenotype by IFN-gamma is partially mediated via endogenous epidermal IL-1.

Adult↗
PubMed1999

Epidermal participation in post-burn hypertrophic scar development.

The reconstruction of epidermal architecture over time in normotrophic and hypertrophic scars in untransplanted, spontaneously healed partial-thickness burns has scarcely been studied, unlike the regeneration of epidermal grafts used to cover burn wounds and the regeneration of the dermis during hypertrophic scarring. The expression of markers of epidermal proliferation, differentiation and activation in normotrophic and hypertrophic scars in spontaneously healed partial-thickness burns was assessed and compared with the expression of these markers in normal control skin of healthy persons to determine whether hypertrophic scarring is associated with abnormalities in the phenotype of keratinocytes. Punch biopsies were taken both of partial-thickness burns after re-epithelialisation and of matched unburned skin. At 4 and 7 months post-burn, biopsies were taken of normotrophic and hypertrophic scars that had developed in these wounds. The biopsies were analysed using immunostaining for markers of keratinocyte proliferation, differentiation and activation (keratins 5, 10, 16 and 17, filaggrin, transglutaminase and CD36). We observed a higher expression of markers for proliferation, differentiation and activation in the epidermis of scars at 1 month post-burn than in normal control skin of healthy persons. There was a striking difference between normotrophic and hypertrophic scars at 4 months post-burn. Keratinocytes in hypertrophic scars displayed a higher level of proliferation, differentiation and activation than did normotrophic scars. At 7 months post-burn all keratinocyte proliferation and differentiation markers showed normal expression, but the activation marker CD36 remained upregulated in both normotrophic and hypertrophic scars. Surprisingly, in matched unburned skin of burn patients, a state of hyperactivation was observed at 1 month. Our results suggest that keratinocytes may be involved in the pathogenesis of hypertrophic scarring.

Adult↗
PubMed1998

Major bacterial contribution to marine dissolved organic nitrogen

Next to N2 gas, the largest pool of reduced nitrogen in the ocean resides in the enormous reservoir of dissolved organic nitrogen (DON). The chemical identity of most of this material, and the mechanisms by which it is cycled, remain fundamental questions in contemporary oceanography. Amino acid enantiomeric ratios in the high molecular weight fraction of DON from surface and deep water in three ocean basins show substantial enrichment in D enantiomers of four amino acids. The magnitude and pattern of these D/L enrichments indicate that peptidoglycan remnants derived from bacterial cell walls constitute a major source of DON throughout the sea. These observations suggest that structural properties of specific bacterial biopolymers, and the mechanisms for their accumulation, are among the central controls on long-term cycling of dissolved organic nitrogen in the sea.

Journal Article↗
PubMed1997

[Immunology in medical practice. I. Introduction].

Fundamental immunology has seen a tremendous development in the past decades. This has resulted in a large body of knowledge, part of which has led to applications in laboratory diagnosis, but of which little has made its way to the clinic in terms of new therapies. The progress in understanding pathogenesis of diseases is also slow. This journal is planning a series of articles that highlight the recent achievements of immunology and their consequences for understanding and treating disease.

Allergy and Immunology↗
PubMed1997

The IL-1 system in psoriatic skin: IL-1 antagonist sphere of influence in lesional psoriatic epidermis.

The epidermal expression of IL-1 in psoriasis is clearly altered, but data are still incomplete and poorly understood. To thoroughly study the IL-1 system in psoriasis, we semiquantitatively analyzed the expression of all currently characterized IL-1 isoforms and their receptors in parallel in both lesional (PP) and nonlesional psoriatic (PN) epidermis. Immunostaining of skin sections showed that IL-1alpha, located in the basal keratinocytes of normal control (NN) and PN epidermis, was significantly decreased to negligible levels in PP epidermis. IL-1 receptor antagonist (IL-1ra) and IL-1R type II (IL-1RII) were both significantly overexpressed in mutually exclusive compartments of PP epidermis, the suprabasal and basal compartment, respectively. A significant inverse correlation was found between the expressions of IL-1alpha and these two IL-1 antagonists, which may be inherent to the accelerated terminal differentiation of the psoriatic keratinocyte. In situ hybridization of IL-1(R) mRNAs confirmed the staining results. Levels of IL-1ra mRNA, however, were not increased in PP epidermis, suggesting that the overexpression of IL-1ra protein may be explained at the level of translation. The more sensitive PCR demonstrated a clearly increased expression of IL-1beta mRNA in PP epidermal cells (EC), which may be related to the inflammatory response in psoriasis. IL-1RI mRNA was clearly present in both PP and NN EC. The mRNA levels of the secreted IL-1ra isoform, but not intracellular IL-1raI and II, and IL-1RII were elevated in PP EC and paralleled those of IL-1beta. In summary, this study provides a defined phenotype of the complete epidermal IL-1 system in psoriasis; it shows that the expressions of IL-1(R) isoforms are coordinately altered, resulting in a predominance of IL-1 antagonists, which may represent a negative feedback response to IL-1 agonists, leading to a decreased IL-1 responsiveness.

Epidermis↗
PubMed1997

Monoclonal gammopathies in aging mu, kappa-transgenic mice: involvement of the B-1 cell lineage.

Monoclonal gammopathies (MG) are monoclonal proliferative disorders of B cells at the differentiation stage of Ig production. They can be detected in the serum, either as transient or as persistent homogenous immunoglobulin (H-Ig) components. The exact phenotype, localization, and cell lineage origin of the precursor cells of MG are unknown, but may be crucial for both the correct diagnosis and for timely efficient treatment of the malignant forms. We used for the first time transgenic (Tg) mice (Sp6; mu/kappa) to study the origin of MG. In the mu, kappa Tg mice a small proportion of B cells can still produce endogenous IgM. These cells are of B-1 cell origin. The MG in Tg mice showed a later onset and a lower frequency than those in littermate control mice, mainly due to a four times lower frequency of benign monoclonal gammopathy. The 10% of B-1 cells that were able to produce endogenous Ig led to the development of MG in a frequency that was half the number of MG found in normal littermates. None of the MG in Tg mice produced an Ig of the Tg origin and therefore it can be concluded that they originated from B-1 cells.

Aging↗
PubMed1997

Impaired T cell functions preceding lymphoproliferative disorders in mice neonatally tolerized to transplantation antigens.

In A/J (H-2a) (A) mice, the neonatal i.v. injection of (B10 x A)F1 spleen cells (SC) induces partial transplantation tolerance (TT) to C57BL/10ScSn (H-2b) (B10) skin allografts, chronic host-versus-graft disease (HVGD) and lethal lymphoproliferative disorders (LPD). They produce anti-T-cell autoantibodies (ATA), and the proliferative responses of their SC to the T cell mitogen Con A are decreased. We found that, similar to ATA, the hyporeactivity of T cells developed earlier (at 1-2 weeks of age) than splenomegaly. The proportions of both CD4+ and CD8+ T cells were not reduced in the spleens of tolerized mice without manifest LPD. The supernatants (SN) of Con A-stimulated tolerized SC contained no, or only small amounts of interleukin-2 (IL-2). Thus, in the tolerized mice, ATA and T cell deficiency preceded the development of LPD. ATA and the decreased amount of the T cell growth factor IL-2 might play a role in the defective T cell activation.

Age Factors↗
PubMed1997

Host-versus-graft disease in mice after the induction of neonatal transplantation tolerance by two different methods.

Newborn A mice were injected either with a single i.v. dose (Group A) or with repeated doses of (B10 x A)F1 semiallogeneic spleen cells (SSC) (Group B). A similar degree of partial transplantation tolerance (TT) to B10 skin allografts was revealed in both groups. No signs of acute, rapidly fatal host-versus-graft disease (HVGD) (anemia, leukocytosis, severe thrombocytopenia, hepatic infarcts, gastrointestinal bleedings) were found, rather a chronic HVGD developed [moderate thrombocytopenia, autoimmune antithymocyte antibodies (ATA)] in both groups. The mortality due to lymphoproliferative disorders (LPD) was significantly higher in Group A. Thus, repeated perinatal injections of (B10 x A)F1 SSC into A mice did not increase the tolerogenic and the LPD-inducing effect either, and they did not elicit acute HVGD in contrast to observations in other F1 donor-recipient combinations [1]. Consequently, the development of acute HVGD depends on immunogenetic factors and not on the repeated administration of SSC.

Acute Disease↗
PubMed1996

Expression of platelet-derived growth factor (PDGF) and PDGF receptors in human malignant mesothelioma in vitro and in vivo.

The expression of platelet-derived growth factor (PDGF) and PDGF receptors was studied in human normal and malignant mesothelial cells in vitro and in vivo. Staining with anti-cytokeratin and ME1 antibodies and ultrastructural analysis confirmed the mesothelial nature of the cell lines used to study PDGF and PDGF receptor expression in vitro. Using antibodies, mesothelioma cell lines were found to express PDGF and both the PDGF alpha- and the PDGF beta-receptor, whereas cultured normal mesothelial cells expressed PDGF and PDGF alpha-receptor. This PDGF and PDGF receptor staining pattern largely reflects the earlier described mRNA expression in these cell lines. The only exception was the immunocytochemical detection of PDGF alpha-receptors in the mesothelioma cell lines, which is different from the inability to detect alpha-receptor transcripts on Northern blots. Expression was also investigated in mesothelial cells in vivo. Expression of PDGF was observed in malignant mesothelioma cells on frozen tissue sections. In pleural effusions, a double immunofluorescence staining procedure for PDGF and epithelial membrane antigen (EMA) revealed PDGF expression by EMA-positive malignant mesothelioma cells. PDGF beta-receptors and occasionally PDGF alpha-receptors were detected in frozen tissue sections of malignant mesotheliomas, whereas mesothelioma cells in effusions showed faint expression of only the PDGF beta-receptor. In contrast, in effusions containing non-malignant mesothelial cells, only a very low level of PDGF alpha-receptor could be detected. Taken together, these results indicate that the pattern of PDGF and PDGF receptor expression in mesothelial cells in vivo largely corresponds to expression of PDGF and its receptors in vitro. Malignant mesothelioma cell lines thus constitute a good model system for studies on the role of PDGF in this malignancy. Furthermore, the data reported in this paper are consistent with the idea that an autocrine growth stimulatory effect of PDGF via PDGF receptors may play a role in the pathogenesis of malignant mesothelioma.

Cryopreservation↗
PubMed1996

Expression of cytokines and their receptors by psoriatic fibroblast. I. Altered IL-6 synthesis.

Interleukin(IL-)6 is overproduced in psoriatic lesions. We investigated the contribution of dermal fibroblasts to the local IL-6 production. Fibroblasts (passageno. 2 to 6) derived from lesional psoriatic (PP) and normal human (NN) skin were used to analyse the secretion of IL-6, and the related cytokines IL-1, IL-8 and TNF-alpha, and the expression of their corresponding mRNA by bioassay, ELISA and Northern hybridization, respectively. PP fibroblasts cultured under serum-free conditions produced increased amounts of bioactive IL-6 when compared to NN fibroblasts. Differences were partially restored in the presence of growth factors or serum. The serum-induced IL-6 production reached a maximum within 24 h after seeding and remained unchanged in PP fibroblasts, whereas comparable amounts of IL-6 were produced only 6 days later in NN fibroblasts. There was a clear expression of IL-6 mRNA in both types of fibroblasts under serum-free conditions. Unexpectedly, fetal calf serum, inactivated fetal calf serum as well as human serum completely inhibited the expression of IL-6 mRNA in all the PP fibroblast cultures investigated. NN fibroblasts were clearly less sensitive to this inhibiting effect of serum. Furthermore, medium supplemented with serum-free component or calcium also repressed IL-6 mRNA expression in PP fibroblasts in contrast to NN fibroblasts. Cycloheximide fully restored the repressing effect of serum indicating that serum induced a labile repressor protein. PP and NN fibroblasts produced negligible amounts of IL-1 and TNF-alpha, but the production of IL-8, however, was comparable to that of IL-6. Our results show a differently regulated IL-6 synthesis in PP fibroblasts in vitro, suggesting an active contribution of dermal fibroblasts to the local IL-6 production in psoriasis.

Blotting, Northern↗