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Biomedical subjects

J Bonnet

Publications and source records attributed to J Bonnet.

At least 19 recordsLinked to original sources
PubMed1998

Purification of guinea pig YKL40 and modulation of its secretion by cultured articular chondrocytes.

The aim of this study was to purify, characterize, and study the regulation at the chondrocyte level of the guinea pig (gp) homologue of human (R) YKL40, a putative marker of arthritic disorders. Studying YKL40 in guinea pigs is of particular interest, as age-related osteoarthritis develops in this species spontaneously. Both N-terminal sequencing and total amino acid composition of gpYKL40 purified from the secretion medium of cultured articular chondrocytes indicate a high degree of identity with hYKL40. gpYKL40 was found to contain complex N-linked carbohydrate, as demonstrated by N-glycosidase F and endoglycosidase F digestion. Isoelectric focusing demonstrated the presence of a major band at pI 6.7. The secretion of gpYKL40 by confluent articular chondrocytes in the extracellular medium was studied by immunoblotting. gpYKL40 was released by chondrocytes continuously over a 7 day period and did not appear to be degraded by proteinases, as its signal intensity in cell-free medium at 37 degrees C did not decrease with time. Thus, gpYKL40 displays high stability and accumulates in extracellular medium without reaching a steady-state level. Among the main factors known to regulate cartilage metabolism, IL-1beta, TNF-alpha, bFGF, or 1,25(OH)2D3 did not alter the basal level of gpYKL40, and retinoic acid had a slight inhibitory effect; TGF-beta and IGF-I and -II dose-dependently and inversely modulated this basal level. TGF-beta at 5 ng/ml decreased extracellular gpYKL40 2.9-fold, whereas IGF-I and IGF-II at 50 ng/ml increased extracellular gpYKL40 3.6- and 3.4-fold, respectively. The present biochemical and biological findings give new insights for studying the function of YKL40 in cartilage.

Adipokines↗
PubMed1998

Vitronectin expression and interaction with receptors in smooth muscle cells from human atheromatous plaque.

Vitronectin (VN) is a plasma glycoprotein that promotes cell attachment and induces migration of human smooth muscle cells (SMCs) in culture. VN has been observed to accumulate in human atherosclerotic plaques, although its origin and role in atherosclerosis are not yet established. In the present experiments, synthesis of VN by intimal cells and its colocalization with receptors, alphavbeta3 and alphavbeta5, were studied by in situ hybridization and immunohistochemistry on 15 human atherosclerotic plaques from carotid arteries obtained after surgery. Strong VN protein and mRNA expression was observed in the intima and in the media. In the intima, VN mRNA expression was colocalized with SMCs, indicating that these cells produce VN, which may account for its accumulation in atherosclerotic plaques. In SMCs in culture, immunoprecipitation after metabolic labeling demonstrated that human SMCs do synthesize vitronectin. Confocal microscopic examination showed that VN colocalized with its receptors, alphavbeta3 and alphavbeta5, in the atherosclerotic intima. However, the distribution of the VN receptors on SMCs in culture in contact with VN was different. These observations suggest that VN plays various parts in atherogenesis via different SMC membrane receptors.

Arteriosclerosis↗
PubMed1998

Fibronectin expression and aortic wall elastic modulus in spontaneously hypertensive rats.

Recent studies have shown that large-artery wall remodeling per se does not reduce distensibility in hypertension, indicating qualitative or quantitative changes in arterial components. The aim of the study was to determine in 1-year-old spontaneously hypertensive rats (SHRs) the changes in the elastic properties of large arteries, as assessed by the incremental elastic modulus (E(inc)), and the changes in the extracellular matrix, including fibronectin (FN) and alpha5beta1-integrin. The relationship between E(inc) and circumferential wall stress was calculated from in vivo pulsatile changes in blood pressure and arterial diameter by using a high-resolution echo-tracking system at the site of the abdominal aorta and in vitro medial cross-sectional area. E(inc)-stress curves and FN and integrin alpha5-subunit contents were determined for each animal. Mean stress and E(inc) were higher in SHRs than in Wistar rats. However, in a common range of stress, E(inc)-stress curves for SHRs were superimposable on those for Wistar rats, indicating that wall materials in both strains have equivalent mechanical behavior. Immunohistochemistry indicated that total FN, EIIIA FN isoform, and alpha5-integrin increased in the SHRs aortas without changes in elastin and collagen densities. Total FN was also increased in SHRs as determined by Western blot analysis. No differences in FN and alpha5-subunit mRNAs were detected between SHRs and Wistar rats. These results indicate that the aortic wall material of SHRs and Wistar rats have equivalent mechanical properties, although in SHRs it is subjected to a higher level of stress. By increasing cell-matrix attachment sites, FN may participate in the mechanical adaptation of both cellular and matrix components in SHRs.

Animals↗
PubMed1998

Morphometry of the human splenic artery: muscular columns, morphofunctional aspects and developmental implications.

There is a paucity of studies in the literature concerning the structural characteristics of the arterial wall in the abdominal region using human material and specialized morphometric techniques. In the present study we carry out the morphometric study, describing a series of structural peculiarities in 12 segments of the human splenic artery. Among these the presence of length-wise or spiral-shaped muscular columns in the medial layer which mark and reduce the diameter of the arterial lumen is of major importance. In its underlying intima small localized thickenings appear which, with age may become generalized. We also analyze the different intimal thickenings and such indices as the Intimal Thickening Index, Lumen Reduction Index and Pathologic Thickening Index, with differences among the groups we have considered. The study of elastin in the various parietal structures help us to understand the possible pathogenesis of the thickenings, and to clarify the important morphological-functional correlation for the regulation of blood flow which exists in this arterial region.

Adolescent↗
PubMed1998

Amino derivatives of phenyl alkyl thiophene as inhibitors of bone resorption. Structure-activity relationship.

Metabolism of arachidonic acid through the 5-lipoxygenase (LO) pathway generates compounds that stimulate osteoclastic bone resorption; since LO metabolites might play a role in bone loss due to excessive resorption it was tried to develop a series of antiresorptive agents starting from an already known LO inhibitor. Of the 35 compounds synthesized, 11 strongly inhibited (10 mumol/l) retinoic acid-induced bone resorption in cultured mouse calvariae; they were also tested for their effect on LO activity using rat peritoneal neutrophils, but no correlation could be drawn between inhibition of LO and bone resorption. Other pathways, still to be identified, must therefore be targeted by these compounds even though LO inhibition might contribute to their effects on bone. Two compounds selected for further studies were found active on parathyroid hormone-induced osteolysis, while they had no effect on basal resorption; they must, therefore, act at some key point in the process of activation of osteoclastic resorption. This series of compounds may represent a new way for the treatment of bone loss due to excessive resorption.

Animals↗
PubMed1997

Selection of down-regulated sequences along the monocytic differentiation of leukemic HL60 cells.

In order to dissect the molecular mechanisms of monocytic differentiation we have developed a subtractive hybridisation method based on a simplified 'representational difference analysis'. We have selected 16 sequences and confirmed their down-regulation along the TPA-induced monocytic differentiation of HL60 cells. Among these sequences we have identified the alpha-tubulin, the TaxREB protein and two ribosomal protein sequences which had not been previously described as differentially expressed. These results add to our knowledge about the molecules implicated along the monocytic differentiation and growth arrest of leukemic cells and provide a first step in the study of their respective roles.

Cell Differentiation↗
PubMed1997

Restenosis or rapid progression in non-dilated sites are not predictors of late spontaneous coronary events.

The present study was designed to assess the prognostic value of clinical and angiographic factors, and especially restenosis or rapid progression in non-dilated sites, on major spontaneous coronary events at long-term follow-up after a first successful coronary angioplasty performed for angina pectoris. A second aim was to assess the prognostic factors and especially restenosis in asymptomatic patients after angioplasty. The first 352 consecutive patients undergoing a successful coronary angioplasty were selected and followed-up. The following variables: age, sex, unstable angina, previous myocardial infarction, diabetes, hypercholesterolemia, tobacco consumption, hypertension, fibrinogen, coronary extent, single or multiple dilatation, restenosis, new progression, clinical deterioration of anginal status just before angiographic restudy or asymptomatic status were subjected to a stepwise regression analysis. Restenosis (a loss of 30% in diameter and/or a return to a >50% stenosis) and progression in non-dilated segments (a 20% reduction in diameter) were assessed by a computer-assisted method. Cardiac death, new myocardial infarction or new unstable angina, at long-term follow-up after angiographic restudy, were regarded as spontaneous coronary events and pooled in a single dependent variable. Thus 41 patients had a coronary event. In the overall population, clinical deterioration of anginal status (p<0.001, relative risk: 3.65) and fibrinogen (p<0.05, relative risk: 1.03) were independent predictors of spontaneous coronary events. Restenosis or new progression were not predictors. In asymptomatic patients (n=187), fibrinogen (p<0.01, relative risk=1.06) was the only predictor and restenosis was not an independent predictor of spontaneous coronary events. The best predictor of spontaneous coronary events at long-term follow-up after a first successful coronary angioplasty is clinical deterioration in anginal status in the months following the procedure. Restenosis does not appear as an independent predictor. Rapid progression observed in non-dilated sites is not an important prognostic factor.

Adult↗
PubMed1997

Enzyme immunoassay for myelin basic protein in cerebrospinal fluid.

Myelin basic proteins (MBPs) are a set of proteins making up about 30% of the protein content of the central nervous system myelin. Four human isoforms have been identified. The most abundant is a highly conserved 18.5 kDa polypeptide. For this species, the amino acid sequence homologies between human and monkey or human and chick are 98.2% and 71.1%, respectively. As a consequence, there is a very good immunological cross-reactivity between the mammalian MBP. This protein has been extensively used to induce experimental allergic encephalomyelits (EAE) in numerous animals. The evolution of chronic EAE in animal is similar to that of multiple sclerosis (MS), a demyelinating human pathology, and chronic EAE is considered to be an animal model of MS. In demyelinating pathologies, MBP concentration in the cerebrospinal fluid (CSF) is considered to be a good marker of demyelination. MBP concentration, in biological fluids, is generally determined by radioimmunoassay (RIA). The RIA technique currently used is highly sensitive (0.1-2.5 ng/ml) but has the drawback of requiring the handling of radioactivity and frequent labelling of MBP. So we developed a new enzyme immunoassay (EIA) technique. Our technique has the same sensitivity as RIA, needs only small volumes of CSF (50 microliters) and the enzyme-labelled MBP tracer is stable for at least 12 months.

Alkaline Phosphatase↗
PubMed1997

Validation of reconstructed bremsstrahlung spectra between 6 MV and 25 MV from measured transmission data.

We have previously investigated a method of high-energy x-ray spectral reconstruction from transmission data by direct resolution of a matrix system. This technique uses the spectral vectorial algebra formalism. The resolution has previously been tested on a 12 MV photon beam. To extend and to test the validity of the results to the entire radiotherapy energy range, we have performed the method on photon beams with nominal energies of 6, 12, 15, and 25 MV. The influence on the 6 MV spectrum of a 60 degrees built-in wedge has also been investigated to test the sensitivity of the method and the results are reported. To validate our reconstructed spectra, dosimetric quantities such as tissue phantom ratios (TPR), water-to-air stopping power ratios (S/p) air water, and quality indexes TPR 10 (20) have been calculated. The results show good agreement between the measured and calculated data. Mean mass energy absorption coefficient ratios for different materials have also been computed and compared to data published recently and the results are very close (within +/- 0.5%). Primary depth dose functions in water have also been computed to deduce primary dose attenuation coefficients.

Evaluation Studies as Topic↗
PubMed1997

Complex polysaccharides as PCR inhibitors in feces: Helicobacter pylori model.

A model was developed to study inhibitors present in feces which prevent the use of PCR for the detection of Helicobacter pylori. A DNA fragment amplified with the same primers as H. pylori was used to spike samples before extraction by a modified QIAamp tissue method. Inhibitors, separated on an Ultrogel AcA44 column, were characterized. Inhibitors in feces are complex polysaccharides possibly originating from vegetable material in the diet.

Feces↗
PubMed1997

The integrin very late antigen-4 is expressed in human smooth muscle cell. Involvement of alpha 4 and vascular cell adhesion molecule-1 during smooth muscle cell differentiation.

Vascular cell adhesion molecule-1 (VCAM-1) and its counterreceptor, the integrin very late antigen-4 (VLA-4), have recently been identified in smooth muscle cells during intimal thickening in humans and in newly forming vessels during ontogeny in mice, respectively. We examined the coexpression of VCAM-1 and the alpha 4 integrin subunit in human smooth muscle cells. The expression of VCAM-1 and alpha 4 subunit were studied during development of the aorta. In the 10-week-old human fetal aorta, VCAM-1 and alpha 4 were strongly expressed in smooth muscle cells. Their expression was dramatically reduced within the 24th week of gestation and disappeared in the adult aortic media. However, smooth muscle cells from intimal atherosclerotic thickening of adult aorta reexpressed both VCAM-1 and alpha 4. In a culture model mimicking smooth muscle differentiation, VCAM-1 mRNA and protein and alpha 4 integrin protein were coexpressed with smooth muscle-specific variants of cytoskeletal and contractile proteins, smooth muscle myosin heavy chain, caldesmon heavy chain, and desmin. Treatment with antibodies against VCAM-1 or alpha 4 integrin subunit interfered with the mRNA induction of smooth muscle-specific markers of differentiation. These results in vitro, associated with the transitory expression of VCAM-1 and VLA-4 during vascular ontogeny and the atherosclerosis process, point to a possible role of VCAM-1 and VLA-4 in the induction of smooth muscle differentiation.

Adult↗
PubMed1997

Platinum porphyrins as phosphorescent label for time-resolved microscopy.

We investigated phosphorescent metalloporphyrins as potential labels for time-resolved microscopy. On the basis of spectroscopic analysis of their physicochemical properties (quantum yield, molar absorption coefficient, decay times) the best candidates were selected. Next, we synthesized antibody and avidin metalloporphyrin conjugates. The optimal F/P ratio with respect to quantum yield, decay time, and retention of biological activity of these immunoreagents was determined. The reagents were then evaluated by in situ hybridization and immunocytochemical procedures for demonstration of hapten-labeled DNA probes, membrane antigens (CD type), and 28S rRNA. All stained samples exhibited bright phosphorescence that could be selectively detected using time-resolved microscopy, especially when glucose/glucose oxidase was added to the embedding medium to deplete oxygen. Applications of time-resolved detection of phosphorescent porphyrins in strongly autofluorescent material (histological sections) are discussed.

Affinity Labels↗
PubMed1996

Mechanism of inhibition of tumor necrosis factor production by chlorpromazine and its derivatives in mice.

In previous work, we reported that chlorpromazine inhibits tumor necrosis factor (TNF) production in endotoxin lipopolysaccharide-treated mice, and protects against lipopolysaccharide toxicity. Chlorpromazine is used as an antipsychotic and has several effects on the central nervous system. It acts on different neurotransmitter receptors and has other biochemical activities some of which, like inhibition of phospholipase A2, might be responsible for the inhibitory effect on TNF production. To investigate the role of these actions in the inhibition of TNF production by chlorpromazine, we have synthesized some chlorpromazine derivatives that do not have central activities. Some of these analogs have lost their affinity for various receptors and their phospholipase A2 inhibitory activity, but still inhibit TNF production. No correlation was found between TNF inhibition and the ability to inhibit nitric oxide (NO) synthase, whereas a good correlation was evident between TNF inhibition and antioxidant activity.

Animals↗
PubMed1996

A water-soluble, stable dipeptide NK1 receptor-selective neurokinin receptor antagonist with potent in vivo pharmacological effects: S18523.

The potassium salt of a chemically stabilized dipeptide, {1-[4-(1 H-tetrazol-5-yl)butyl]indol-3-yl}carbonyl-Hyp-Nal-N(methyl)-Bzl , (Hyp = (R)-4-hydroxy-L-proline; Nal = 3-L-(beta-naphthyl)-alanine), S18523, is described as a new water-soluble, potent and selective NK1 receptor antagonist. The low molecular weight antagonist (M(r) = 736) displays nanomolar potency (pA2 = 9.6) in the rabbit vena cava (NK1) bioassay and nanomolar affinity (pKi = 9.1) on the human NK1 receptor expressed by lymphoblastoma cells. It is devoid of mu-opiate affinity (Ki > 10(-4) M with respect to tritiated Tyr-DAla-Gly-MePhe-Gly-ol), has negligible calcium-channel affinity (estimated Ki = 2.6 x 10(-5) M, with respect to isradipine) and does not cause peritoneal mast-cell degranulation. S18523 has strong antinociceptive effects in three classical pain tests in vivo both by i.v. and p.o. routes. The dipeptide potently antagonizes bronchoconstriction provoked by exogenous substance P in the guinea-pig and acts longer than the non-peptide antagonist CP99994, when administered as aerosol. Finally, S18523 displays antiinflammatory properties, since it dose-dependently inhibits substance P-induced plasma extravasation both in the bladder (ID50 = 0.18 mg/kg i.v.) and bronchi (ID50 = 0.14 mg/kg i.v.) of the guinea-pig.

Animals↗
PubMed1996

Monocyte/macrophage recruitment and expression of endothelial adhesion proteins in human atherosclerotic lesions.

Since mononuclear cells are recruited in atherosclerotic lesions, the expression of adhesion proteins by the arterial endothelium may play a major role in atherogenesis. The relationships between ICAM-1, E-selectin, and VCAM-1 expression on the arterial endothelium and the presence and degree of maturation of intimal macrophages in human atherosclerotic lesions was investigated. By quantitative double immunostaining with a pan-macrophage-specific monoclonal antibody, HAM-56, and a recently developed monoclonal antibody that is specific for mature macrophages, 3MA-B38, arterial sections were classified as (I) normal, (II) thickened without macrophage infiltration, (III) atherosclerotic with recent macrophage infiltration or (IV) atherosclerotic with infiltration of mature differentiated macrophages. A marked increase in the expression of ICAM-1, E-selectin, and VCAM-1 was observed on endothelial cells adjacent to recently recruited macrophages. Endothelial cells overlying differentiated macrophages exhibited a lower but significant increase in VCAM-1 expression, with no difference in ICAM-1 and E-selectin expression with respect to that observed in endothelium of normal arteries. These findings indicate that the endothelium covering the human arterial wall exhibits different states of activation as reflected by the expression of adhesion proteins, and that intimal monocyte/macrophage recruitment appears to depend on the level of expression of adhesion proteins.

Adult↗
PubMed1996

Effects of parathyroid hormone and agonists of the adenylyl cyclase and protein kinase C pathways on bone cell proliferation.

The anabolic effect of parathyroid hormone (PTH) on bone is partly due to a stimulation of osteoblast proliferation. The PTH signal is transduced by the pathways of adenylyl cyclase (AC)/protein kinase (PK) A and phospholipase C/PKC/Ca++. There is still uncertainty about the relative contribution of the two pathways to the proliferative effects of the hormone. In our study, PTH(1-34), AC/PKA agonists, and phorbol 12-myristate-13-acetate (PMA, a PKC activator) stimulated cell proliferation in cultured mouse calvariae. In isolated osteoblasts, only PMA stimulated proliferation, whereas AC/PKA agonists and PTH(1-34) inhibited it. As already known, PTH in the presence of supramaximal concentrations of transforming growth factor-beta (TGF-beta) stimulated osteoblast growth; under these same conditions, AC/PKA agonists reproduced the stimulatory effect of PTH(1-34), whereas PMA became inhibitory. PTH(1-31), which stimulates AC without affecting PKC, acted similarly to the fully active PTH(1-34) in both calvaria and isolated osteoblasts. On the contrary, midregion fragments that activate only PKC stimulated calvaria cell proliferation faintly in comparison with PTH(1-34); no effect was seen in osteoblasts, either with or without TGF-beta. Our study shows that the effects of PTH on proliferation can be mimicked by agonists of the AC/cAMP pathway. Although PMA is indeed able to stimulate cell growth in tissue explants, its effects on isolated osteoblasts markedly diverge from those of PTH. We conclude that activation of the AC/PKA pathway is the main component of the proliferative effects of PTH.

1-Methyl-3-isobutylxanthine↗