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Biomedical subjects

C Philippe

Publications and source records attributed to C Philippe.

At least 73 records · Page 4Linked to original sources
PubMed1993

Cytokine formation within rat glomeruli during experimental endotoxemia.

Increasing evidence supports a role of cytokines, tumor necrosis factor alpha (TNF alpha), interleukin-1 (IL-1), and IL-6 in the development of endotoxin-induced acute renal failure. Several activities of these cytokines require a local rather than a systemic production and function. Thus, this study investigates the chronology of cytokine expression in glomeruli isolated from normal rats or rats given iv lipopolysaccharide injections. Detectable levels of TNF alpha could be found in glomeruli isolated from normal rats as assessed by L-929 fibroblast lytic assay and ELISA. Glomeruli isolated from rats given lipopolysaccharide transiently released increased amounts of TNF alpha in relation to the dose of lipopolysaccharide (10 to 500 micrograms/kg body wt) and the lag period between lipopolysaccharide injection and glomerular isolation (20 to 120 min). TNF alpha was released in similar amounts by glomeruli from normal rats that were exposed in vitro to lipopolysaccharide challenge (0.01 to 10 micrograms/mL), indicating that lipopolysaccharide had direct effects on the release of TNF alpha from glomerular cells. These cells consisted mainly of resident cells because reduction of glomerular infiltration by bone marrow-derived cells after the irradiation of normal rats did not affect TNF alpha release. Glomerular IL-1 and IL-6 production was evaluated by specific bioassays under identical conditions. No IL-1 activity could be detected in the medium or within the glomerular cells at any time within 120 min after lipopolysaccharide injection. By contrast, glomerular IL-6 production was induced after lipopolysaccharide challenge both in vivo and in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Glomerular expression of tumor necrosis factor alpha (TNF-alpha) and of its receptors].

TNF alpha is generated in inflammatory lesions of the glomerulus. Both resident mesangial cells and infiltrating macrophages contribute to this generation, when exposed to bacterial lipopolysaccharide and immune complexes, respectively. TNF alpha has multiple actions on glomerular cells and on distant target cells that appear to promote in turn either amplification or limitation of TNF alpha release and TNF alpha binding. For instance, there is in vitro evidence that locally generated reactive oxygen metabolites: 1) cause increased release of TNF alpha into the extracellular space by accelerating the cleavage of its cell-associated precursor, and 2) reduce the expression of both cell-associated and soluble TNF alpha receptors. Thus it might be expected that reactive oxygen metabolites released at the site of glomerular inflammation limit autocrine, juxtacrine and paracrine effects of TNF alpha and simultaneously increase its widespread release into the circulation.

Humans↗
PubMed1993

Protection from tumor necrosis factor-mediated cytolysis by platelets.

Infiltrating macrophages elicit tumor-destructive reactions by releasing cytolytic factors including tumor necrosis factor alpha (TNF-alpha). Because platelets represent another major component of the cell infiltrate in tumors, we examined whether they could affect TNF alpha-induced cell death. Exposure of L-929 fibrosarcoma cells to human platelets reduced TNF alpha-induced cytotoxicity and cytolysis, as determined by 51Cr release assay and DNA fragmentation assay. This inhibitory effect, which depended on the concentration of platelets (0.1 to 10 x 10(6)/0.1 ml), was as high as 50%. The decrease in responsiveness to TNF-alpha reflected neither a degradation of TNF-alpha nor an inability of L-929 cells to bind TNF-alpha. Indeed, even though Scatchard analysis indicated the presence of 100 to 150 125I-TNF-alpha binding sites/platelet with a kd of 3.8 to 6.4 nM, addition of platelets up to 5 x 10(6)/0.1 ml did not compete with 125I-TNF-alpha binding to L-929 cells. Furthermore, addition of platelets 1 or 2 hours after that of TNF-alpha was still protective suggesting that platelets rather promoted hyporesponsiveness of L-929 cells to a postbinding effect of TNF-alpha Platelet-induced reduction of TNF-alpha response could be reproduced with supernatant fluids from platelets incubated at 37 degrees C for 24 hours. The platelet-derived factor responsible for this effect was found to be a lipid of low molecular weight with high affinity for albumin and charcoal. A role for 12(S) hydroxyeicosatetraenoic acid is proposed because this metabolite reduced TNF-alpha-induced cytolysis in a dose-dependent manner, whereas other platelet-derived lipids including thromboxane A2 and platelet activating factor were inactive. These observations indicate that the role of associated platelets has to be considered when analyzing the cytotoxic and cytolytic activity of macrophage-derived TNF-alpha on tumor cells.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1993

Membrane expression and shedding of tumour necrosis factor receptors during activation of human blood monocytes: regulation by desferrioxamine.

Previous studies have shown that desferrioxamine (DFX), an iron chelator preventing the synthesis of hydroxyl radical (OH.), up-regulates the cell-surface expression of tumour necrosis factor-alpha (TNF-alpha) receptors on unactivated human blood monocytes. In the present study, we investigated the regulatory action of DFX on 125I-TNF-alpha binding to monocytes upon exposure to bacterial lipopolysaccharide (LPS). Exposure to LPS (1 microgram/ml) resulted in almost complete loss of 125I-TNF-alpha binding to the surface of monocytes. This down-regulation was reversible and the recovery observed after 18 hr was enhanced by addition of DFX (5 mM). However, binding studies on monocytes pre-exposed to low pH suggested that the DFX-induced increase of 125I-TNF-alpha binding was not due to differences in the number of receptors available but was probably due to a reduction of receptor occupancy by endogenously generated TNF-alpha. Time-course studies of TNF-alpha release from monocytes confirmed the ability of DFX to reduce the extracellular concentration of bioactive TNF-alpha through a decrease of its synthesis and an increase of its inactivation. The latter process was associated with an increased expression of the soluble form of TNF-alpha receptor type II. These results indicate that, in the presence of LPS, DFX increases the release of soluble TNF-alpha receptors from monocytes. Thus, conversely, OH. generated in situ could reduce the shedding of soluble TNF-alpha receptors and, hence, increase the widespread release of bioactive TNF-alpha.

Cell Membrane↗
PubMed1993

The Noonan syndrome. The Nancy experience revisited.

67 patients with Noonan syndrome seen over the last 29 years were selected preferentially on cardiac involvement. The cardiac anomalies consisted in the association of dysplastic pulmonary stenosis with asymmetric cardiomyopathy. In one patient, a translocation (3;22) was found. The relationship with cardio-facio-cutaneous syndrome and with the group of phacomatoses is discussed. The familial occurrence (10 families) seems compatible with autosomal dominant inheritance. A gene location on chromosome 22 cannot be excluded.

Adolescent↗
PubMed1992

Heat shock prevents lipopolysaccharide-induced tumor necrosis factor-alpha synthesis by rat mononuclear phagocytes.

Tumor necrosis factor-alpha (TNF-alpha), a mononuclear phagocyte-derived peptide is known to participate in the pathogenesis of fever. To determine whether a feedback mechanism exists by which elevated temperatures influence TNF-alpha generation, we have examined the effects of heat shock on the in vitro synthesis of TNF-alpha by rat glomeruli, inflammatory peritoneal macrophages and blood monocytes. Preexposure of peritoneal macrophages to elevated temperatures for 20 min decreased the subsequent lipopolysaccharide-induced release of TNF-alpha bioactivity. The mean reductions were 11.9 +/- 5.0%, 86.3 +/- 12.0%, and 95.2 +/- 3.5% after pretreatment at 39, 41 and 43 degrees C, respectively. Reductions, that were transient, were maximum when lipopolysaccharide was added 0-2 h after heat shock. They correlated with the decreased release of immunoreactive TNF-alpha and the decreased expression of both cell-associated TNF-alpha molecule and TNF-alpha mRNA. Heat shock-induced inhibition of TNF-alpha release was independent of variations of prostaglandin synthesis, but was possibly related to the induction of heat-shock proteins since (a) macrophages exposed to heat shock synthesized the major 70- and 90-kDa heat-shock proteins, and (b) chemical inducers of the heat-shock response were also effective inhibitors of TNF-alpha release. The mean reduction of TNF-alpha release after pretreatment at 41 degrees C was found to be identical in glomerular tissue (82.0 +/- 7.5%), but significantly less in blood monocytes (43.9 +/- 10.9%). This supports the hypothesis that a negative-feedback mechanism exists between elevated temperature and lipopolysaccharide-induced TNF-alpha synthesis, and suggests that this regulation is less active in blood monocytes than in tissue macrophages.

Animals↗
PubMed1992

Chromosomal mapping of the human (MACS) and mouse (Macs) genes encoding the MARCKS protein.

The myristoylated, alanine-rich C-kinase substrate, or MARCKS protein, is a major cellular substrate for protein kinase C that is also a high-affinity calmodulin-binding protein. In addition, it is the prototype of a small family of myristoylated, calmodulin-binding protein kinase C substrate proteins. We isolated a phage clone from a mouse genomic library that spanned the entire coding sequence of the mouse MARCKS protein. The first 612 bp of the putative promoter was 89% identical to a corresponding region of the human promoter, and contained at least 59 potential transcription factor binding sites in analogous locations; both human and mouse promoters lacked TATA boxes. The mouse genomic probe was used to localize the mouse gene to chromosome 10, in the middle of a linkage group that corresponds to a region on human chromosome 6q. These data strongly suggested that the human gene would localize to 6q21. This was confirmed by studies of DNA from a patient with del(6)(q21), in which expression of the human gene encoding MARCKS, MACS, was only about 50% of normal; MARCKS mRNA expression in lymphoblast RNA from this patient was only 22% of normal. These studies confirm that the mouse and human MARCKS proteins are products of the same genes in their respective species; differences in their primary sequence can therefore be attributed to species variation rather than to the existence of related genes.

Animals↗
PubMed1992

Up-regulation of tumour necrosis factor-alpha receptors on monocytes by desferrioxamine.

The effect of endogenously generated reactive oxygen metabolites on the interaction of human blood monocytes with tumour necrosis factor-alpha (TNF-alpha) was investigated. Pre-exposure of unactivated human blood monocytes to dimethylthiourea, a scavenger of hydroxyl radical (OH.), or to desferrioxamine (DFX), an iron chelator preventing the synthesis of OH., enhanced the specific binding of 125I-TNF-alpha to its receptors. Scavengers of superoxide anion or hydrogen peroxide were without effect. DFX-induced up-regulation of 125I-TNF-alpha binding depended on the concentration of the drug (1-5 mM) and on the duration of the treatment (1-18 h). It was not due to a reduction of receptor occupancy by endogenously generated TNF-alpha. Scatchard analysis of binding data revealed that DFX caused an approximately two-fold increase in the number of type II TNF-alpha receptors, with no change in their affinity. This up-regulation, that did not require synthesis of new proteins, was associated with a decrease in the internalization rate of TNF-alpha receptors, the half-life of which was doubled. Conversely, these findings suggest that OH. generation by monocytes may have a physiological role in reducing the activity of membrane-associated TNF-alpha receptors.

Binding, Competitive↗
PubMed1992

Reactive oxygen species as glomerular autacoids.

There is considerable evidence suggesting that reactive oxygen species (ROS; superoxide anion, hydrogen peroxide, hydroxyl radical, hypochlorous acid) are implicated in the pathogenesis of toxic, ischemic, and immunologically mediated glomerular injury. The capacity of glomerular cells, especially mesangial cells, to generate ROS in response to several stimuli suggests that these autacoids may play a role in models of glomerular injury that are independent of infiltrating polymorphonuclear leukocytes and monocytes. The mechanisms whereby ROS formation results in morphologic lesions and in modifications of glomerular permeability, blood flow, and filtration rate have been inferred from in vitro studies. They involve direct and indirect injury to resident cells (mesangiolysis) and glomerular basement membrane (in concert with metalloproteases) and alteration of both the release and binding of vasoactive substances, such as bioactive lipids (e.g., prostaglandin E2, prostacyclin, thromboxane), cytokines (e.g., tumor necrosis factor alpha), and possibly endothelium-derived relaxing factor. The importance of such processes appears to be modulated by the intrinsic antioxidant defenses of the glomeruli. Further studies are needed to address the role of ROS in human glomerular diseases.

Animals↗
PubMed1992

Incontinentia pigmenti (type 1) and X;5 translocation.

The authors present a 5-year-old girl with total absence of speech, dysmorphic features, pigmented lesions on the legs, an abnormal EEG and otherwise normal intelligence representing a mild form of type 1 Incontinentia pigmenti associated with an (X;5) (p11.2;q35.2) apparently balanced translocation prenatally diagnosed. The seven previous translocation type 1 IP patients are reviewed and all have the same Xp11 breakpoint. Somatic cell hybrids have been made to further study this breakpoint and further define the putative type 1 IP gene.

Child, Preschool↗
PubMed1991

Adrenoleukodystrophy: a complex chromosomal rearrangement in the Xq28 red/green-color-pigment gene region indicates two possible gene localizations.

We have characterized a complex chromosomal rearrangement in band Xq28, in an adrenoleukodystrophy patient who also has blue-cone monochromacy. A 130-kb region upstream from the color-vision pigment genes was isolated as yeast artificial chromosome or cosmid clones. Another Xq28 sequence, not included in the above region, was obtained by cloning a deletion breakpoint from the patient. Using probes derived from the cloned sequences, we have shown that the rearrangement affects the color-pigment genes and includes two deletions, most likely separated by a large (greater than 110-kb) inversion. One deletion encompasses part of the pigment gene cluster and 33 kb of upstream sequences and accounts for the patient's blue-cone monochromacy. If this rearrangement also caused ALD, the disease gene would be expected to lie within or close to one of the deletions. However, deletions were not detected in a 50-kb region upstream of the red-color-pigment gene in 81 other ALD patients. Two CpG islands were mapped, at 46 and 115 kb upstream from the pigment genes.

Adrenoleukodystrophy↗
PubMed1990

Translational control of ribosomal protein S15.

The expression of ribosomal protein S15 is shown to be translationally and negatively autocontrolled using a fusion within a reporter gene. Isolation and characterization of several deregulated mutants indicate that the regulatory site (the translational operator site) overlaps the ribosome loading site of the S15 messenger. In this region, three domains, each exhibiting a stem-loop structure, were determined using chemical and enzymatic probes. The most downstream hairpin carries the Shine-Dalgarno sequence and the initiation codon. Genetic and structural data derived from mutants constructed by site-directed mutagenesis show that the operator is a dynamic structure, two domains of which can form a pseudoknot. Binding of S15 to these two domains suggests that the pseudoknot could be stabilized by S15. A model is presented in which two alternative structures would explain the molecular basis of the S15 autocontrol.

Base Sequence↗
PubMed1990

Target site of Escherichia coli ribosomal protein S15 on its messenger RNA. Conformation and interaction with the protein.

The regulatory site of ribosomal protein S15 has been located in the 5' non-coding region of the messenger, overlapping with the ribosome loading site. The conformation of an in vitro synthesized mRNA fragment, covering the 105 nucleotides upstream from the initiation codon and the four first codons of protein S15, has been monitored using chemical probes and RNase V1. Our results show that the RNA is organized into three domains. Domains I and II, located in the 5' part of the mRNA transcript, are folded into stable stem-loop structures. The 3'-terminal domain (III), which contains the Shine-Dalgarno sequence and the AUG initiation codon, appears to adopt alternative conformations. One of them corresponds to a rather unstable stem-loop structure in which the Shine-Dalgarno sequence is paired. An alternative potential structure involves a "pseudo-knot" interaction between bases of this domain and bases in the loop of domain II. The conformation of several RNA variants has also been investigated. The deletion of the 5'-proximal stem-loop structure (domain I), which has no effect on the regulation, does not perturb the conformation of the two other domains. The deletion of domain II, leading to a loss of regulatory control, prevents the formation of the potential helix involved in the pseudo-knot structure and results in a stabilization of the alternative stem-loop structure in domain III. The replacement of another base in domain III involved in pairing in the two alternative structures mentioned above should induce a destabilization of both structures and results in a loss of the translational control. However, the replacement of another base in domain III, which does not abolish the control, results in the loss of the conformational heterogeneity in this domain and yields a stable conformation corresponding to the pseudo-knot structure. Thus, it appears that any mutation that disrupts or alters the formation of the pseudo-knot impairs the regulatory mechanism. Footprinting experiments show that protein S15 is able to bind to the synthesized fragment and provide evidence that the protein triggers the formation of the pseudo-knot conformation. A mechanism can be postulated in which the regulatory protein stabilizes this particular structure, thus impeding ribosome initiation.

Base Composition↗
PubMed1990

In vitro production of tumour necrosis factor and prostaglandin E2 by peripheral blood mononuclear cells from tuberculosis patients.

We investigated the production of tumour necrosis factor-alpha (TNF-alpha) and prostaglandin E2 (PGE2) by peripheral blood mononuclear cells (PBMC) from tuberculosis patients and healthy controls. PBMC from tuberculosis patients generated constitutively more TNF-alpha than did control PBMC. This production was significantly higher for patients with high-grade fever and cachexia. The increase of TNF-alpha production by PBMC from tuberculosis patients was associated with a comparatively weaker elevation of PGE2 synthesis which did not parallel fever or weight loss. In vitro treatment of control PBMC with the tuberculin purified protein derivative (PPD) promoted an increased TNF-alpha production which was similar to that of untreated PBMC from tuberculosis patients. Thus, the increased TNF-alpha production in tuberculosis could be explained by the in vivo exposure of PBMC to mycobacterial antigens. In contrast, the concentration of PGE2 was weaker in the medium of untreated PBMC from tuberculosis patients than in the medium of PPD-treated control PBMC, suggesting that PGE2 synthesis by PBMC was limited in tuberculosis by unidentified factors.

Adult↗
PubMed1990

Plasma neurotensin in the conscious pig: release by individual food components and effects on exocrine pancreas secretion.

In conscious pigs, i.v. infusion of serial doses of neurotensin (NT, actual doses of 0.24-59.4 pmol.kg-1.min-1) on a background of secretin resulted in a linear increase of plasma NT-like immunoreactivity (NT-LI), as measured with an antiserum that requires the biologically active C-terminal part of the molecule for recognition. The NT infusions were accompanied by a dose-related increase of pancreatic volume and bicarbonate and protein output. The threshold plasma NT-LI concentrations for significant increases of pancreatic enzymes and of pancreatic fluid and bicarbonate were 46.6 +/- 7.0 and 161.3 +/- 10.8 pM, respectively. Food intake was followed by a sharp pancreatic response and a progressive increase of plasma NT-LI level to a peak of about 27.7 +/- 3.0 pM from the basal level 11.8 +/- 1.6 pM. The carbohydrate fraction of the meal was predominantly responsible for the NT release observed after meal intake. High-performance liquid chromatography analysis of plasma samples collected during NT infusion or after meal ingestion revealed one immunoreactive peak coeluting with intact NT. Pancreatic polypeptide was released on infusion of high, supraphysiological doses of NT, while plasma somatostatin remained at low basal values. It is concluded that in the pig, intact NT is released after a standard meal predominantly through the carbohydrate fraction of the diet, NT is a stimulant of exocrine pancreas secretion, and the modest pancreatic response to physiologic increments of plasma NT-LI on peptide infusion is not attributable to indirect inhibition of the exocrine pancreas by NT-released pancreatic polypeptide or somatostatin.

Animals↗
PubMed1988

The E. coli 16S rRNA binding site of ribosomal protein S15: higher-order structure in the absence and in the presence of the protein.

We have investigated in detail the secondary and tertiary structures of E. coli 16S rRNA binding site of protein S15 using a variety of enzymatic and chemical probes. RNase T1 and nuclease S1 were used to probe unpaired nucleotides and RNase V1 to monitor base-paired or stacked nucleotides. Bases were probed with dimethylsulfate (at A(N-1), C(N-3) and G(N-7)), with 1-cyclohexyl-3 (2-(1-methylmorpholino)-ethyl)-carboiimide-p- toluenesulfonate (at U(N-3) and G(N-1)) and with diethylpyrocarbonate (at A(N-7)). The RNA region corresponding to nucleotides 652 to 753 was tested within: (1) the complete 16S rRNA molecule; (2) a 16S rRNA fragment corresponding to nucleotides 578 to 756 obtained by transcription in vitro; (3) the S15-16S rRNA complex; (4) the S15-fragment complex. Cleavage and modification sites were detected by primer extension with reverse transcriptase. Our results show that: (1) The synthetized fragment folds into the same overall secondary structure as in the complete 16S rRNA, with the exception of the large asymmetrical internal loop (nucleotides 673-676/714-733) which is fully accessible in the fragment while it appears conformationally heterogeneous in the 16S rRNA; (2) the reactivity patterns of the S15-16S rRNA and S15-fragment complexes are identical; (3) the protein protects defined RNA regions, located in the large interior loop and in the 3'-end strand of helix [655-672]-[734-751]; (4) the protein also causes enhanced chemical reactivity and enzyme accessibility interpreted as resulting from a local conformational rearrangement, induced by S15 binding.

Base Sequence↗