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C Desbois

Publications and source records attributed to C Desbois.

At least 19 recordsLinked to original sources
PubMed2002

The integrative role of the rat medullary subnucleus reticularis dorsalis in nociception.

Neurons within the medullary subnucleus reticularis dorsalis (SRD) of the rat convey selectively nociceptive information from all parts of the body. We have sought to define the neuronal networks that convey information from widespread noxious stimuli to the diffuse thalamocortical system and also modulate spinal outflow. The experiments, which were performed in rats, were designed to determine whether efferents from the SRD issue collaterals to the thalamus and spinal cord. Injections of the tracers fluorogold and tetramethylrhodamine-labelled dextran were centred stereotaxically in two areas that receive dense projections from the SRD: the cervical spinal cord and the lateral ventromedial thalamus (VMl), respectively. In other experimental series, SRD neurons were characterized electrophysiologically and individually labelled in a Golgi-like manner following juxtacellular iontophoresis of biotin-dextran. More than half reticulothalamic neurons within the SRD provided monosynaptic connections to the spinal cord. SRD neurons that responded to Adelta- or Adelta- and C-fibre activation from any area of the body had axons that gave both ascending and descending collaterals. Because the SRD innervates several areas involved in motor processing and receives strong, direct influences from several cortical regions, it could provide a structural basis for the processing of nociceptive and motor activities.

Animals↗
PubMed2001

The organization of lateral ventromedial thalamic connections in the rat: a link for the distribution of nociceptive signals to widespread cortical regions.

We have used several anatomical tracing techniques to study the organization of the lateral ventromedial thalamic nucleus in the rat, a region that is selectively activated by cutaneous nociceptive inputs from any part of the body. The lateral ventromedial thalamic projections are organized as a widespread dense band covering mainly layer I of the dorsolateral anterior-most aspect of the cortex. This band diminishes progressively as one moves caudally, disappearing completely at 1mm caudal to bregma level. These widespread projections contrast with the circumscribed projections to the deep layers of the primary somatosensory and insular cortices from the adjacent ventral posteromedial and ventroposterior parvicellular thalamic regions, respectively. Injections into the lateral part of the ventromedial thalamic nucleus of an anterograde/retrograde tracer showed that the cortical layer I areas showing the densest projections from this thalamic region also contain the greatest number of retrogradely labeled cells in cortical layers V and VI. The same injections retrogradely labeled numerous cells which were confined to the dorsal subnucleus reticularis dorsalis in an area that contains a concentration of neurons with widespread nociceptive convergence. Finally, the lateral part of the ventromedial thalamic nucleus was also differentially labeled following a topical application of tetramethylrhodamine-labeled dextran on the dorsolateral anterior cortex. These findings suggest that lateral ventromedial thalamic neurons could be part of a spino-reticulo-thalamo-cortical network that allows signals of pain from any part of the body surface to spread across widespread cortical areas.

Animals↗
PubMed2001

Alteration of the stability of Bag-1 protein in the control of olfactory neuronal apoptosis.

Normal apoptosis occurs continuously in the olfactory neuroepithelium of adult vertebrates, making it a useful model for studying neuronal apoptosis. Here we demonstrate that overexpression of the anti-apoptotic Bag-1 gene in olfactory neuronal cells confers a strong resistance to apoptosis. Conversely decreased levels of Bag-1 were found to precede a massive wave of olfactory neuronal apoptosis triggered by synaptic target ablation. We show that the decrease is brought about by ubiquitination and subsequent degradation of the Bag-1 protein. The ring finger protein Siah-2 is a likely candidate for the ubiquitination reaction since Siah-2 mRNA accumulated in lesioned olfactory neuroepithelium and overexpression of Siah-2 stimulated Bag-1 ubiquitination and degradation in transient expression assays. These results together identify destabilization of Bag-1 as a necessary step in olfactory neuronal apoptosis.

Amino Acid Sequence↗
PubMed2000

COUP-TFI (chicken ovalbumin upstream promoter-transcription factor I) regulates cell migration and axogenesis in differentiating P19 embryonal carcinoma cells.

The developmental expression patterns of the nuclear orphan receptors COUP-TFs (chicken ovalbumin upstream promoter-transcription factors) have been correlated to neurogenesis in several animal species. Nevertheless, the role of COUP-TFs in neurogenesis remains unknown. We have studied the functional involvement of COUP-TFI in retinoic acid (RA)-induced neuronal differentiation of P19 embryonal carcinoma cells through two complementary approaches: 1) deregulated expression of COUP-TFI, and 2) inactivation of endogenous COUP-TFs by means of a dominant-negative COUP-TFI mutant. Low levels of wild-type (wt)COUP-TFI transgene expression did not inhibit neural cell fate and primarily enhanced neuron outgrowth from RA-treated P19 aggregates. In contrast, high COUP-TFI expression impeded the neuronal differentiation of P19 cells induced with RA, resulting in cell cultures lacking neurons. This morphological effect was correlated to an elevated level of E-cadherin mRNA. The dominant-negative COUP-TFI mutant induced cell packing after RA treatment and inhibited neurite extension and neuron outgrowth from aggregates. A RGD peptide interference assay indicated that endogenous COUP-TFs could favor migration of neurons through an integrin-dependent mechanism. Accordingly, vitronectin mRNA levels were shown to be up-regulated by COUP-TFI by RT-PCR analysis, and COUP-TFI stimulated the mouse vitronectin promoter activity in transient transfection assays. Taken together, these data indicate that COUP-TFI is not simply a global repressor of retinoid functions, but shows a high selectivity for regulating genes involved in cellular adhesion and migration processes that are particularly important for neuronal differentiation.

Animals↗
PubMed1999

Organization of cortical projections to the medullary subnucleus reticularis dorsalis: a retrograde and anterograde tracing study in the rat.

The distribution and organization of cortical projections to the subnucleus reticularis dorsalis (SRD), the neighboring cuneate nucleus (Cu), and trigeminal nucleus caudalis (Sp5C) were studied in the rat using microinjections of wheat germ agglutinin-apo horseradish peroxidase-gold and Biotin-Dextran. Cortical cells projecting to the caudal medulla were confined to the contralateral layer V with their descending axons crossing the midline at the level of pyramidal decussation. Cortical afferents to Sp5C originated from cells located mainly in the primary somatosensory cortex (S1) and the insular cortex, whereas cortical projections to the Cu originated mainly from the primary motor cortex (M1), the primary and secondary somatosensory cortex (S1 and S2). The SRD received dense cortical afferents from larger, widespread cortical areas: M1, M2, S1, S2, and the insular cortex. The existence of dense cortico-SRD connections supports the possibility of a pyramidal influence over SRD neurons, which might modify nociceptive information ascending to the cortex itself. This proposal is consistent with the fact that SRD efferents terminate densely in thalamic areas that influence sensorimotor cortical regions which in turn project to the SRD. Moreover, these corticofugal mechanisms could allow the cortex to select its own input by suppressing or augmenting transmission of signals through SRD-hindbrain/forebrain pathways or by coordinating activities in spino-SRD-spinal circuits and thus selecting the relevant information produced by the noxious stimulus.

Animals↗
PubMed1999

Exogenous CCK and gastrin stimulate pancreatic exocrine secretion via CCK-A but also via CCK-B/gastrin receptors in the calf.

A predominance of the pancreatic cholecystokinin (CCK) receptor of the B/gastrin subtype (CCK-B/G) was reported in calves older than 1 month. Specific CCK-A and CCK-B/G receptor antagonists (SR 27897 and PD 135158, respectively) were used to identify the CCK receptor subtype involved in exogenous CCK- and gastrin-induced exocrine pancreatic responses. Conscious calves (2 months old) with catheterized pancreas, jugular vein and duodenum were used; the pancreatic juice was continuously reinfused. CCK (30 pmol kg-1 min-1, 40 min) evoked an increase in pancreatic juice flow and enzyme secretion, while the same dose of gastrin increased enzyme secretion alone. CCK-induced pancreatic secretion was abolished by SR 27897 (15 nmol kg-1 min-1, 55 min) and reduced by PD 135158 (0.15 nmol kg-1 min-1, 55 min). Gastrin-induced enzyme secretion was reduced by PD 135158 (50% to 90%) and to a lesser extent by SR 27897 (50% to 60%). These results demonstrate that CCK and gastrin in the physiological range stimulate pancreatic exocrine secretion in calves and that these effects are partly mediated by CCK-B/G receptors. Although CCK-A receptors are not predominantly expressed, they seem to play a major role in the response of pancreatic exocrine secretion to CCK.

Animals↗
PubMed1999

The CCKB/gastrin receptor is coupled to the regulation of enzyme secretion, protein synthesis and p70 S6 kinase activity in acinar cells from ElasCCKB transgenic mice.

In order to determine which physiological functions can be regulated by the pancreatic CCKB/gastrin receptor, studies were carried out on pancreatic acini from mice expressing transgenic CCKB/gastrin receptors in the exocrine pancreas (ElasCCKB mice). Acini were stimulated by sulfated gastrin in the presence of SR 27897 (1.8 microM), blocking endogenous CCKA receptors. After 30 min incubation with gastrin, the secretion of chymotrypsinogen and amylase showed superimposable monophasic dose-response curves. Enzyme secretion was detectable and maximal at 100 pM and 1 nM of gastrin, respectively. No increase in chymotrypsinogen and amylase mRNAs was detected for doses of gastrin which specifically occupy the CCKB/gastrin receptor. In contrast, gastrin stimulated total protein synthesis in isolated acini from ElasCCKB mice. [35S]Methionine incorporation into total proteins was increased dose-dependently to a maximum for 30 pM gastrin and inhibited with higher doses (> 300 pM). Gastrin stimulated p70 S6 kinase activity for concentrations ranging from 10 pM to 1 nM. Gastrin-stimulated p70 S6 kinase activity and protein synthesis were blocked by rapamycin and wortmannin. Therefore, in ElasCCKB mice acinar cells, the CCKB/gastrin receptor mediates enzyme release and protein synthesis. However, a more efficient coupling of the CCKB/gastrin receptor to protein synthesis than to enzyme secretion was demonstrated. CCKB/gastrin receptor-stimulated protein synthesis likely results from an enhancement of mRNA translation and involves phosphatidyl inositol 3-kinase and p70 S6 kinase.

Amino Acid Sequence↗
PubMed1998

The C-terminus of the HTLV-1 Tax oncoprotein mediates interaction with the PDZ domain of cellular proteins.

Infection by HTLV-1 has been correlated with the appearance of various proliferative or degenerative diseases. Some of these disorders have been observed in transgenic mice expressing the Tax protein, which is known to transactivate various viral and cellular promoters through interactions with several transcription factors. In this study we show that the C-terminus of this viral oncoprotein represents a motif permitting binding of Tax to the PDZ domains of several cellular proteins. A two-hybrid screen with Tax as bait indeed yielded complementary DNAs coding for six proteins including PDZ domains. Two of them correspond to truncated forms of the PSD-95 and beta1-syntrophin proteins, another clone codes for a protein homologous to the product of the C. elegans gene lin-7. The other three clones code for new human members of the PDZ family of cellular proteins. The interaction of Tax with the products of these clones was confirmed by immunoprecipitation assays in mammalian cells, and analysis of various mutants of Tax established the importance of the C-terminal amino acids for several of these interactions. These data suggest that Tax could perturb the normal function of targeted cellular proteins by strongly interacting with their PDZ domains.

Amino Acid Sequence↗
PubMed1998

Organization of diencephalic projections from the medullary subnucleus reticularis dorsalis and the adjacent cuneate nucleus: a retrograde and anterograde tracer study in the rat.

The distribution and organization of diencephalic projections from the subnucleus reticularis dorsalis (SRD) and the neighbouring cuneate nucleus (Cu) were studied in the rat by using microinjections of Phaseolus vulgaris leucoagglutinin in SRD and Cu and wheat germ agglutinin-apo horseradish peroxidase-gold in some selected thalamic areas. As previously reported, the efferent projections from the Cu were essentially contralateral and terminated mainly in the ventroposterolateral thalamic nucleus. Less dense terminals from the Cu were also observed in the posterior thalamic group, the ventral aspect of the zona incerta and the caudal and dorsal portion of the reuniens area. Retrograde tracer injections in the medial ventroposterolateral thalamic nucleus labeled numerous cells in the contralateral Cu, with a smaller number in the gracile nucleus. From the SRD, terminals were observed in the lateral aspect of the ventromedial thalamic nucleus, the lateral parafascicular area and, to a lesser extent, in the ventral aspect of the zona incerta and the core of the reuniens area. Retrograde tracer injections in the lateral part of the ventromedial thalamic nucleus labeled cells in the caudal medulla, many of which were located in the dorsal-most aspect of the SRD throughout its caudo-rostral extent. The existence of SRD-thalamic connections reinforces the idea that the caudal reticular formation is an important nociceptive relay to the thalamus. Our data shed new light on old hypotheses suggesting that, in addition to spino-thalamic pathways, spino-reticulo-thalamic pathways may play an important role in distributing pain signals to the forebrain.

Animals↗
PubMed1998

Differential tissular expression of the CCK(A) and CCK(B) gastrin receptor genes during postnatal development in the calf.

Local and temporal expression of CCK(A) and CCK(B)/gastrin receptor genes was studied in the calf with a quantitative Reverse Transcription-Polymerase Chain Reaction (RT-PCR) method. Cerebral cortex, antrum, fundus, gall bladder, pancreas and liver were analyzed in calves at 0, 2, 7, 21, 28 and 150 days of age. Cerebral cortex and pancreas expressed both receptor genes with a ratio between CCK(A) and CCK(B)/gastrin receptor transcripts varying according to the age. Gall bladder and fundus showed an exclusive expression of CCK(A) and CCK(B)/gastrin receptor mRNAs, respectively, with the highest levels of transcripts in newborn and 28-day-old calves. The rank order for CCK(A) receptor mRNA expression was gall bladder > pancreas > cerebral cortex >>> antrum and that for CCK(B)/gastrin receptor mRNA expression was cerebral cortex / pancreas / fundus >> antrum. No CCK(A) and CCK(B)/gastrin receptor mRNA was detected in liver, regardless of the age of calves. The present data represent a basis for a better understanding of the ontogeny of physiological functions linked to the CCK(A) and CCK(B)/gastrin receptors.

Aging↗
PubMed1997

Method of measurement of pancreatic elastase II activity and postnatal development of proteases in human duodenal juice and bovine and porcine pancreatic tissue.

A specific method for pancreatic elastase II activity analysis was developed. True elastase II activity could be discriminated from that of elastase I and chymotrypsin. The postnatal development of four pancreatic proteases in the duodenal juice of children and in the pancreatic homogenates of calves and piglets was measured. The study was carried out on patients without (14 children) and with (5 children) pancreatic insufficiency. Calves and piglets were either milk-fed or weaned until slaughter at different ages. Profiles of enzyme development were globally similar in milk-fed piglets and calves, while in children without pancreatic insufficiency, no significant change was observed between 4 and 168 months. In children with pancreatic insufficiency, enzyme activity was low. In animals, elastase II and chymotrypsin activities were maximal at birth, decreased with age, and probably were associated with the digestion of milk protein. In contrast, elastase I and trypsin activities increased markedly after weaning in connection with the intake of solid food.

Adolescent↗
PubMed1996

Exclusion of Int-6 from PML nuclear bodies by binding to the HTLV-I Tax oncoprotein.

The Tax transactivator of the human T cell leukemia virus type I (HTLV-I) exhibits oncogenic properties. A screen for proteins interacting with Tax yielded a complementary DNA (cDNA) encoding the human Int-6 protein. In mice, the Int-6 gene can be converted into a putative dominant negative oncogene after retroviral insertion. Here, Int-6 was localized in the cell nucleus to give a speckled staining pattern superposed to that of the promyelocytic leukemia (PML) protein. The binding of Tax to Int-6 caused its redistribution from the nuclear domains to the cytoplasm. Thus, Int-6 is a component of the PML nuclear bodies and Tax disrupts its normal cellular localization by binding to it.

Animals↗
PubMed1996

Increased bone formation in osteocalcin-deficient mice.

Vertebrates constantly remodel bone. The resorption of preexisting bone by osteoclasts and the formation of new bone by osteoblasts is strictly coordinated to maintain bone mass within defined limits. A few molecular determinants of bone remodelling that affect osteoclast activity have been characterized, but the molecular determinants of osteoblast activity are unknown. To investigate the role of osteocalcin, the most abundant osteoblast-specific non-collagenous protein, we have generated osteocalcin-deficient mice. These mice develop a phenotype marked by higher bone mass and bones of improved functional quality. Histomorphometric studies done before and after ovariectomy showed that the absence of osteocalcin leads to an increase in bone formation without impairing bone resorption. To our knowledge, this study provides the first evidence that osteocalcin is a determinant of bone formation.

Animals↗
PubMed1996

Effects on NF-kappa B1/p105 processing of the interaction between the HTLV-1 transactivator Tax and the proteasome.

The viral Tax protein, which is encoded by human T-cell leukaemia virus HTLV-I, activates nuclear translocation of the NF-kappa B/Rel transcription factors and relieves cytoplasmic sequestration of RelA and Rel by heterodimerization with NF-kappa B1/p1O5 (refs 1,2). Proteolytic maturation of this precursor protein is performed by the proteasome complex. Here we show that Tax binds specifically to two subunits of the 20S proteasome, HsN3 and HC9. This interaction is weakened with HsN3 and lost for HC9 when a mutant of Tax is substituted that is selectively defective for NF-kappa B activation. Immunoprecipitation shows that p1O5 binds weakly to HC9 and that this interaction is reinforced by Tax. No bridging function of Tax between p1O5 and HsN3 was observed. From these results, we propose that Tax accelerates the proteolytic maturation of P105 by favouring its anchorage to the proteasome.

Cell Line↗
PubMed1996

Genetic characterization of transactivation of the human T-cell leukemia virus type 1 promoter: Binding of Tax to Tax-responsive element 1 is mediated by the cyclic AMP-responsive members of the CREB/ATF family of transcription factors.

To achieve a better understanding of the mechanism of transactivation by Tax of human T-cell leukemia virus type 1 Tax-responsive element 1 (TRE-1), we developed a genetic approach with Saccharomyces cerevisiae. We constructed a yeast reporter strain containing the lacZ gene under the control of the CYC1 promoter associated with three copies of TRE-1. Expression of either the cyclic AMP response element-binding protein (CREB) or CREB fused to the GAL4 activation domain (GAD) in this strain did not modify the expression of the reporter gene. Tax alone was also inactive. However, expression of the reporter gene was induced by coexpression of Tax and CREB. This effect was stronger with the GAD-CREB fusion protein. Analysis of different CREB mutants with this genetic system indicated that the C-terminal 92 amino acid residues, which include the basic domain and the leucine zipper, are necessary and sufficient to mediate transactivation by Tax. To identify cellular proteins binding to TRE-1 in a Tax-dependent manner, this strain was also used to screen a library of human cDNAs fused to GAD. Of five positive clones isolated from 0.75 x 10(6) yeast colonies, four were members of the CREB/activating transcription factor (ATF) family: CREB, two isoforms of the cyclic AMP-responsive element modulator (CREM), and ATF-1. Interestingly, these three proteins can be phosphorylated by protein kinase A and thus form a particular subgroup within the CREB/ATF family. Expression of ATF-2 in S. cerevisiae did not activate TRE-1 in the presence of Tax. This shows that in a eukaryotic nucleus, Tax specifically interacts with the basic domain-leucine zipper region of ATF-1, CREB, and CREM. The fifth clone identified in this screening corresponded to the Ku autoantigen p70 subunit. When fused to GAD, the C-terminal region of Ku was able to activate transcription via TRE-1 but this activation was not dependent on Tax.

Activating Transcription Factors↗
PubMed1995

Osteocalcin cluster: implications for functional studies.

Osteocalcin is a skeletal member of the family of extracellular mineral binding Gla protein. Osteocalcin is synthesized only by the osteoblast and it is secreted into the bone matrix at the time of bone mineralization. The mineral binding properties of osteocalcin as well as its spatial and temporal pattern of expression suggest that it plays a role during bone mineralization, however until now its biological function is unclear. To understand osteocalcin function during skeletogenesis we mutated the two osteocalcin genes by homologous recombination in embryonic stem (ES) cells. Eight targeted clones were identified by Southern analysis using external probes. One of these clones contributed to the germ line of mouse chimera. Interbreeding of heterozygotes is currently in progress. Mutant mice will be useful to understand osteocalcin function in vivo.

Animals↗
PubMed1994

The mouse osteocalcin gene cluster contains three genes with two separate spatial and temporal patterns of expression.

Osteocalcin is the most abundant noncollagenous protein of bone. Here we report that the mouse genome contains an osteocalcin cluster composed of three genes arranged within a 23-kilobase span of genomic DNA. We named them osteocalcin gene 1 (OG1), osteocalcin gene 2 (OG2), and osteocalcin-related gene (ORG) in order from the 5' end to the 3' end of the cluster. Hybridization of polymerase chain reaction-amplified cDNAs with specific oligonucleotides and RNase protection assays showed that OG1 and OG2 are expressed only in bone, whereas ORG is transcribed in kidney but not in bone. Furthermore, during embryogenesis, OG1 and OG2 begin to be expressed at day 15.5, while ORG is transcribed as early as day 10.5. The protein encoded by ORG has a similar pattern of expression and identical structural features to nephrocalcin, a calcium-binding protein partially purified from kidney that plays a role in calcium reabsorption and in prevention of nephrolithiasis. The nephrocalcin gene has not been cloned in any species; we propose that ORG is the mouse nephrocalcin gene. The existence of several osteocalcin or osteocalcin-related sequences is not restricted to mouse but is present in every species we examined.

Age Factors↗