Biomedical subjects

D Broekaert

Publications and source records attributed to D Broekaert.

At least 19 recordsLinked to original sources

PubMed2006

Influence of citalopram, a selective serotonin reuptake inhibitor, on oesophageal hypersensitivity: a double-blind, placebo-controlled study.

Background Tricyclic antidepressants, which have multiple pharmacological influences, have a therapeutic effect in non-cardiac chest pain, but selective serotonin reuptake inhibitors have a single pharmacological effect. Aim To evaluate the acute effect of citalopram on oesophageal hypersensitivity. Methods On two separate occasions, 10 healthy subjects (seven men, mean age 25 years) with established oesophageal hypersensitivity, underwent oesophageal manometry with evaluation of mechanical and chemical sensitivity. Subjects received placebo or citalopram 20 mg i.v. in a randomized, crossover, double-blind fashion. Results Citalopram did not alter oesophageal motility. Citalopram significantly increased the threshold inducing first perception (4.6+/-0.3 vs. 6.7+/-0.4 mL, P<0.005) and discomfort (8.6+/-0.4 vs. 9.9+/-0.6 mL, P<0.01) during balloon distention. It also significantly prolonged the acid perfusion time to induce perception of heartburn (6.0+/-0.9 vs. 10.7+/-0.6 min, P<0.005) and discomfort (12.2+/-0.8 vs. 16.7+/-0.7 mL, P<0.001). Seven subjects experienced a retrosternal sensation during edrophonium provocation with placebo, and this was reduced to two of 10 after citalopram (P=0.02). Conclusions Acute administration of citalopram significantly lowers chemical and mechanical oesophageal sensitivity in oesophageal hypersensitivity, without altering the motility.

Adult↗

PubMed2006

Influence of acute serotonin reuptake inhibition on colonic sensorimotor function in man.

BACKGROUND: It is unclear whether decreased serotonin transporter function contributes to sensorimotor abnormalities in irritable bowel syndrome. AIM: To study the influence of acute serotonin transporter inhibition on colonic sensorimotor function in man. METHODS: Ten healthy subjects (five men, aged 20-29 years) underwent a combined manometry/barostat study of the descending colon on two occasions. Stepwise distentions by 2 mmHg increments were performed until discomfort. Subsequently, placebo or citalopram 20 mg were administered i.v. over 20 min and distentions were repeated. Afterwards, isobaric tone measurements were performed 30 min before and 90 min after ingestion of a meal. High-amplitude propagated contractions, colonic motility index, colonic compliance, sensitivity and colonic response to a meal after placebo or citalopram were compared by t-test and two-way ANOVA. RESULTS: Citalopram induced a significant increase in colonic motility index (5.6 +/- 0.9 to 0.8 +/- 1.9 mL*min, P < 0.005) and high-amplitude propagated contractions (32 after citalopram vs. 2 after placebo, P < 0.05), which were associated with abdominal cramping. Administration of citalopram increased colonic compliance (10.3 +/- 1.5 vs. 14.5 +/- 2.2 mL/mmHg, P < 0.01) and inhibited colonic response to a meal (volume decrease 48 +/- 12 vs. 16 +/- 12 mL, P < 0.01). CONCLUSIONS: Acute serotonin transporter inhibition in man increases colonic phasic contractility and the occurrence of high-amplitude propagated contractions, increases colonic compliance and suppresses the colonic tonic response to a meal. These data suggest that both release and elimination of 5-hydroxytryptamine by serotonin transporter are involved in the control of colonic motility in man.

Adult↗

PubMed2006

A controlled crossover study of the selective serotonin reuptake inhibitor citalopram in irritable bowel syndrome.

INTRODUCTION: Selective serotonin reuptake inhibitors (SSRIs) are frequently used in the treatment of irritable bowel syndrome (IBS) although evidence of their efficacy is scarce. AIM: Twenty three non-depressed IBS patients were recruited from a tertiary care centre and included in a crossover trial comparing six weeks of treatment with the SSRI citalopram (20 mg for three weeks, 40 mg for three weeks) with placebo. IBS symptom severity was the primary outcome measure, and depression and anxiety scores were also measured. The effect of acute administration of citalopram on colonic sensitivity and on colonic response to feeding was investigated as a putative predictor of symptomatic response to the drug. RESULTS: After three and six weeks of treatment, citalopram significantly improved abdominal pain, bloating, impact of symptoms on daily life, and overall well being compared with placebo. There was only a modest effect on stool pattern. Changes in depression or anxiety scores were not related to symptom improvement. The effect of acute administration of citalopram during a colonic barostat study did not predict clinical outcome. Analysis of the first treatment period as a double blind parallel arm study confirmed the benefit of citalopram over placebo. CONCLUSIONS: The SSRI citalopram significantly improves IBS symptoms, including abdominal pain, compared with placebo. The therapeutic effect is independent of effects on anxiety, depression, and colonic sensorimotor function.

Abdominal Pain↗

PubMed2006

A role for leptin in the systemic inflammatory response syndrome (SIRS) and in immune response, an update.

Leptin was originally identified as an adipocyte-derived cytokine with a key role in the regulation of the energy balance. Subsequent research revealed that leptin's biological action is not restricted to its effects on appetite and food intake, but instead has a much more pleiotropic character. There is now ample evidence that leptin has important functions in reproduction, hematopoiesis, HPA-axis endocrinology and angiogenesis. In this review we have focused on the effects of leptin in the antigen-specific immunity and in the inflammatory effector system.

Adaptation, Physiological↗

PubMed2003

Influence of the selective serotonin re-uptake inhibitor, paroxetine, on gastric sensorimotor function in humans.

BACKGROUND: The role of 5-hydroxytryptamine in the control of gastric fundus tone in humans is still unknown. Selective 5-hydroxytryptamine re-uptake inhibitors act both centrally and peripherally to enhance the availability of physiologically released 5-hydroxytryptamine. AIM: To study the influence of a selective 5-hydroxytryptamine re-uptake inhibitor, paroxetine, on gastric fundus tone, on the perception to gastric distension and on gastric accommodation to a meal. METHODS: Sixteen healthy volunteers underwent a gastric barostat study on two occasions, after pre-treatment with placebo or paroxetine, 20 mg/day. Graded isobaric and isovolumetric distensions were performed and perception was scored by a questionnaire. Subsequently, the amplitude of the gastric accommodation to a mixed liquid meal was also measured. RESULTS: Pre-treatment with paroxetine did not alter the thresholds for perception and discomfort during isobaric (4.7 +/- 2.3 vs. 4.0 +/- 2.0 mmHg and 13.3 +/- 3.1 vs. 12.7 +/- 2.3 mmHg above the minimum intragastric distending pressure, N.S.) and isovolumetric (307 +/- 90 vs. 417 +/- 114 mL and 772 +/- 74 vs. 750 +/- 76 mL, N.S.) distensions. Paroxetine significantly enhanced the amplitude of the meal-induced fundus relaxation (136 +/- 51 vs. 255 +/- 43 mL, P < 0.05). CONCLUSIONS: Pre-treatment with paroxetine enhances gastric accommodation to a meal. These data suggest that the release of 5-hydroxytryptamine, probably at the level of the enteric nervous system, is involved in the control of the accommodation reflex in humans, and that paroxetine may be beneficial to patients with impaired post-prandial fundus relaxation.

Adult↗

PubMed2002

A role for leptin in the systemic inflammatory response syndrome (SIRS) and in immune response.

Leptin was originally identified as an adipocyte-derived cytokine with a key role in the regulation of the energy balance. Subsequent research has, however, revealed that leptin's biological action is not restricted to its effects on appetite and food intake, but rather has a much more pleiotropic character. Evidence is now accumulating that it has important functions in reproduction, hematopoiesis, HPA-axis endocrinology and angiogenesis. In this review, we have focused on the effects of leptin in the immune system, which can be found in both the antigen-specific immunity and in the inflammatory effector system.

Adaptation, Physiological↗

PubMed2001

A mediator role for metallothionein in tumor necrosis factor-induced lethal shock.

Tumor necrosis factor (TNF) is a proinflammatory cytokine, which is centrally involved in several inflammatory disorders. Administration of TNF leads to a potentially lethal systemic inflammatory response syndrome (SIRS). We observed that (a) mice lacking functional genes for metallothionein 1 and 2 (MT-null) were protected compared with wild-type controls (P = 0.0078), and (b) mice overexpressing MT-1 (MT-TG) were more sensitized for the lethal effect of TNF than control mice (P = 0.0003), indicating a mediating role for MT in TNF induced SIRS. As MT is involved in the body zinc homeostasis, we tested whether zinc-deprivation or -supplementation alters the response to TNF. Although zinc-depletion strongly sensitized (P = 0.036), and pretreatment with zinc sulfate (ZnSO4) conferred protection against the deleterious effects of TNF (P < 0.0002), it was also found that the protection provided by zinc is independent of MT. Our observation that hsp70 is strongly induced in jejunum after ZnSO4 treatment, suggests a contribution of hsp70 in the protection against TNF. In addition, ZnSO4 cotreatment allowed complete regression of inoculated tumors with TNF and interferon gamma, leading to a significantly better survival (P = 0.0045).

Animals↗

PubMed2001

Neutralizing monoclonal antibodies can potentiate IL-5 signaling.

IL-5 is a major determinant in the survival, differentiation and effector-functions of eosinophils. It mediates its effect upon binding and activation of a membrane bound receptor (R), composed of a ligand-specific alpha-chain and a beta-chain, shared with the receptors for IL-3 and granulocyte-macrophage colony-stimulating factor. We have generated and mapped the epitopes of three monoclonal antibodies (mAb) directed against this cytokine: the strong neutralizing mAb 5A5 and 1E1, and the very weak neutralizing mAb H30. We found that H30 as well as 5A5 can increase proliferation above the level induced by human (h)IL-5 alone, in a JAK-2-dependent manner, and at every sub-optimal hIL-5 concentration analyzed. This effect is dependent on mAb-mediated cross-linking of IL-5R complexes, and is only observed on cell lines expressing a hybrid human/mouse IL-5Ralpha-chain. We discuss these findings in view of the stoichiometric and topological requirements for an activated IL-5R. Since humanized anti-IL-5 mAb are currently in clinical testing, our findings imply that such mAb should be carefully evaluated for their potentiating effects.

Animals↗

PubMed2000

Identification of the Y985 and Y1077 motifs as SOCS3 recruitment sites in the murine leptin receptor.

The leptin system provides a link between adipose mass and the central nervous system. The appetite suppressing effects of leptin are impaired in most obese patients and some mutant mice strains. Herein we describe how suppressor of cytokine signalling 3 (SOCS3), a potential mediator of this leptin resistance is recruited into the activated murine leptin receptor complex. Using a functional assay based on inhibition of leptin mediated reporter induction, and using phosphopeptide affinity chromatography we show binding of SOCS3 to the highly conserved phosphorylated Tyr-985 and Tyr-1077 motifs within the mouse leptin receptor.

Amino Acid Motifs↗

PubMed2000

Identification and expression analysis of leptin-regulated immediate early response and late target genes.

Using PC12 cells as an in vitro model system, we have identified a series of transcripts induced through activation of the leptin receptor. On the basis of kinetic studies, two distinct gene sets could be discerned: signal transducer and activator of transciption-3 (STAT-3), suppressor of cytokine signalling-3 (SOCS-3), MT-II (metallothionein-II), the serine/threonine kinase fibroblast-growth-factor-inducible kinase (Fnk) and modulator recognition factor (MRF-1), which are immediate early response genes, and pancreatitis-associated protein I (PAP I), squalene epoxidase, uridine diphosphate glucuronosyltransferase and annexin VIII, which are late induced target genes. At late time points a strong co-stimulation with beta-nerve growth factor or with the adenylate cyclase activator forskolin was observed. To assess the validity of the PC12-cell model system, we examined the effect of leptin administration on the gene transcription of STAT-3, MT-II, Fnk and PAP I in vivo. Leptin treatment of leptin-deficient ob/ob mice increased the STAT-3, SOCS-3, MT-II and Fnk mRNA, and MT-I protein levels in liver, whereas, in jejunum, expression of PAP I mRNA was down-regulated. Furthermore, administration of leptin to starved wild-type mice enhanced the expression of MT-II and Fnk mRNA in liver, but decreased MT-II and PAP I mRNA expression in jejunum. These findings may help to explain the obese phenotype observed in some colonies of MT-I- and MT-II-null mice and/or the observation that leptin protects against tumour-necrosis-factor toxicity in vivo.

Acute-Phase Proteins↗

PubMed1999

Analysis of Tyr to Phe and fa/fa leptin receptor mutations in the PC12 cell line.

Weight regulation through body-fat content and energy homeostasis, is regulated mainly through the actions of leptin. Herein, we analyse the effect of mutations in the mouse leptin receptor using the PC12 pheochromocytoma cell line as a model system. Both the induction of pancreatitis associated protein 1 and metallothionein-II, two leptin regulated genes in PC12, was evaluated. Tyr to Phe mutations in the cytoplasmic tail of the mouse leptin receptor confirmed the critical role of Tyr1138 (a YxxQ motif) and STAT-3 activation for induction of leptin-induced genes in PC12. In addition, the Tyr985Phe mutation showed enhanced responsiveness to leptin, which was even more pronounced in combination with Tyr1077Phe. The short isoform of the leptin receptor showed complete loss of stimulation of both genes. In contrast, a leptin receptor devoid of all Tyr residues in its cytoplasmic tail was still capable of a limited induction of the PAP 1 gene. A mutant mouse leptin receptor containing the fa/fa mutation showed constitutive signalling and impaired responsiveness to leptin. Treatment with the adenylate cyclase activator forskolin alone, in the absence of leptin was sufficient to obtain full induction of both genes.

Acute-Phase Proteins↗

PubMed1997

Peptides adsorbed on reverse-phase chromatographic beads as targets for femtomole sequencing by post-source decay matrix assisted laser desorption ionization-reflectron time of flight mass spectrometry (MALDI-RETOF-MS).

We here describe a procedure for concentrating peptides from solutions by adsorbing them onto reverse-phase beads that were added to these solutions. The beads are then transferred to the target disc of the matrix assisted laser desorption ionization-reflectron time of flight (MALDI-RETOF) mass spectrometer. Because of their hydrophobic nature, these beads cluster in a very small area on the target disc assuring an important concentration step. After drying, peptides are desorbed from the beads by adding a small volume of 50% acetonitrile in 0.1% trifluroacetic acid in water containing the matrix components. Hereby we focus the original amount of peptide material on the target disc on a very small surface, producing highly concentrated peptide-matrix mixtures. This permits high yield identification and sequence tagging by post-source-decay analysis on peptides derived from proteins only available in the femtomole range from one-dimensional (1-D) or two-dimensional (2-D) gels. The procedure is illustrated by the identification of 38 proteins from human thrombocyte membrane skeletons.

Acetonitriles↗

PubMed1995

The tympanic membrane: a biochemical updating of structural components.

A cross-section of the tympanic membrane is discussed at the molecular level. Actually, the tympanic membrane can be described as a continuation of a vast number of structural proteins and molecular interactions. The epidermal layer is subject to soft keratinization, a differentiation process implying the genesis of a chemically resistant cell matrix (cytokeratins, filaggrin) and cornified membrane (involucrin, keratolinin, loricrin, transglutaminase). The epidermis is anchored in the connective tissue by means of hemidesmosomes whose biochemical nature begun to be elucidated rapidly in recent years. Of the first importance are the HD1 inner plaque protein, supposed to be associated with intermediate filaments, and the transmembrane components in the dense plaque (BPAG2 and alpha 6 beta 4 integrin), whose extracellular domains directly interact with basement membrane components. Though the complete characterization of the basement membrane has not yet been achieved, the molecular catalogue of its three distinct layers is really impressive (laminin, fibronectin, nidogen, kalinin, K-laminin, type IV collagen, heparan sulphate proteoglycan, type III and VII collagen, ...). Besides numerous mutual interactions, it appears that mainly laminin and kalinin (anchoring filaments) promote binding of epidermal cells. Furthermore, a continuation may exist between anchoring fibrils in the deepest layer and anchoring filaments in the upper layer of the basement membrane. Finally, the lamina propria, a specific type of extracellular matrix, is perhaps the most difficult to dissect, though substantial progress has been made in the last few years (fibronectin, type I, III, V and VI collagen, fibrillin, ...).

Basement Membrane↗

PubMed1993

Cytokeratin expression patterns in the human tympanic membrane and external ear canal.

Immunohistochemical investigations were carried out to further reveal the pattern of cytokeratin (CK) expression in middle ear cholesteatoma. Using chain-specific monoclonal antibodies and the indirect immunoperoxidase technique, 10 out of 19 CK polypeptides were screened in cryoslices of fresh postmortem eardrums and external ear canal specimens. Our data, combined with those published before, indicate an intimate relationship between middle ear cholesteatoma lesions and epidermal tissues in the immediate vicinity. Our CK data do not favor the metaplastic origin of cholesteatoma, because the CK complement of cholesteatoma lesions does not include major and typical CK constituents of the middle ear mucosa.

Antibodies, Monoclonal↗

PubMed1993

An immunohistochemical and histochemical study of cytokeratin, involucrin and transglutaminase in seborrhoeic keratosis.

The mode of differentiation of seborrhoeic keratoses was investigated by immunohistochemical staining using cytokeratin (CK) polypeptide-specific monoclonal antibodies and an antibody specific for the particulate form of epidermal transglutaminase (ETgase), and by applying an anti-human involucrin serum. The role played by (E)Tgase was further evaluated using an activity assay based on the covalent attachment of monodansylcadaverine. Samples of uninvolved epidermis served as reference tissue. CK reactivities suggested that seborrhoeic keratoses is a hyperproliferative disease with an epidermal CK composition. CK5 and CK14 were prominent markers of basal and basaloid keratinocytes, whereas a decrease in staining occurred in advanced maturation stages and areas of terminal keratinization. In contrast, CK1 and CK10 were prominent markers of suprabasaloid differentiation stages and produced complementary stainings to those of CK5 and 14. Generally, CK10 staining was more impressive than CK1 staining and seemed to start before CK1 staining. In contrast to CK10 staining, cornified areas lost CK1 reactivity. These staining patterns were similar to those observed in uninvolved reference tissues. The epidermal CK subset was further supplemented with the 'hyperproliferative' CK6 and 16 which occur sequentially. Positive staining for CK6 was noted from basal and proximal basaloid cells onwards, whereas distal basaloid cells additionally showed CK16 staining. The presence of other non-epidermal CK polypeptides could not be shown. The competence for other differentiation markers belonging to the group of (E)Tgase and cornifying cell membranes also evolved with a typical epidermal pattern. (E)Tgase activity was restricted to advanced and terminal stages of keratinization and was dual in nature, i.e. a diffuse cytoplasmic staining occurred together with a prominent staining of cornifying cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗

PubMed1993

Cytoskeletal polypeptides: cell-type specific markers useful in investigative otorhinolaryngology.

In the last decade, it has been established that eukaryotic cells possess a cytoskeleton, i.e. an integrated cytoplasmic network of microfilaments (MFs), microtubules (MTs) and intermediate filaments (IFs). Moreover, certain cell membrane specializations as well as the inner lamina of the nuclear membrane also participate in the cytoskeletal structure. Although this definition of the cytoskeleton is up to date it is obvious that the future course of cell biology will be reflected in a revised definition. While the bulk of structural polypeptides involved were characterized at regular intervals, surprisingly, the function of the cytoskeleton remained largely speculative and is still less precisely defined. The most widely postulated function concerns mechanical support and integration of diverse cellular activities and thus refers to cellular architecture. Briefly, the mechanical function is thought to involve cell movement, adhesive interaction with the extracellular matrix and neighbouring cells, as well as the stabilization of cell shape. The integrative function refers to intracellular movement, i.e. transport and positioning to the appropriate locations of organelles, intracellular particles, RNA and proteins. It has been established from numerous investigations that (certain) cytoskeletal polypeptides provide significant information about the cellular origin and differentiation state. This consideration constitutes the most prominent reflection underlying this review. Furthermore, this appreciation encourages additional efforts to explore these markers in normal and pathological conditions. The first purpose of this review is briefly to summarize our present comprehension of the molecular components of the cytoskeleton, restricted to the filamentous trinity for practical reasons. The second and main aim is to survey the field with respect to otorhinolaryngology-related issues. To the author's knowledge, this has not been dealt with in the past. In bridging this gap in the literature, I hope to provoke additional interest in one of the fastest moving areas of cell biology. A comprehensive review covering the whole cytoskeleton has been covered by Preston et al. (The Cytoskeleton and Cell Motility. Blackie, Glasgow and London, 1990, pp. 7-69, 188-191). Additional information on the participating substructures is provided in the text, inclusive of last year's reviews.

Animals↗

PubMed1993

The proliferative capacity of the keratinizing annular epithelium.

Using monoclonal antibodies specific for CK chains and the indirect immunoperoxidase technique, the expression of 10 CK polypeptides was investigated. The external stratified squamous epithelium of the tympanic membrane generally expressed CKs 5, 10 and 14. In addition, basal keratinocytes in the annular region, both tympanic and deep meatal, expressed CK19 (a simple epithelium marker). Suprabasally the hyperproliferative marker CK16 (known to have a limited distribution in healthy epidermis) was expressed in the same area. These data reflect the unusually proliferative nature of this transitional area.

Adult↗

PubMed1992

Immunohistochemical analysis of the cytokeratin expression in middle ear cholesteatoma and related epithelial tissues.

Immunohistochemical investigations were carried out to determine the pattern of cytokeratin (CK) expression in middle ear cholesteatoma and related epithelia. Using monoclonal antibodies specific for CK chains and the indirect immunoperoxidase technique, we examined 10 CK polypeptides for expression. The external stratified squamous epithelium of the tympanic membrane generally expressed CKs 5, 10, and 14. In addition, basal keratinocytes in the annular region of the pars tensa expressed CK 19 (a simple epithelium marker), while suprabasally the hyperproliferative marker CK 16 was expressed. These data reflect the unusual proliferative nature of this region. The unexpected appearance of CK 16 (known to have a limited distribution in healthy epidermis) clearly relates to its expression in the neighboring deep meatus. The medial simple epithelium of the eardrum revealed mucosal CKs 7, 8, 14, 18, and 19. Acquired cholesteatoma lesions, besides CKs 5, 10, and 14, consistently expressed CK 16 in suprabasal layers. These results constitute the first direct molecular evidence for the hyperproliferative nature of the cholesteatoma matrix. Overall, our CK data suggest that aural cholesteatoma lesions and epidermal tissue in this area are related. However, they do not explain the mechanism(s) by which the eardrum or meatal epithelia might invade the middle ear cavity. Congenital cholesteatomas expressed CKs 5, 10, 14, and 16 equally. These CK data do not support the idea of a metaplastic origin from middle ear mucosa; instead, they suggest activation of an ectodermal rest in the middle ear cavity.

Adult↗