Biomedical subjects

O Kellermann

Publications and source records attributed to O Kellermann.

At least 37 records · Page 2Linked to original sources

PubMed1998

Cross-talk between 5-hydroxytryptamine receptors in a serotonergic cell line. Involvement of arachidonic acid metabolism.

The study of signaling cascades and of functional interactions between 5-hydroxytryptamine (5-HT) receptor pathways with heterogenous brain cell populations remains an arduous task. We took advantage of a serotonergic cell line to elucidate cross-talks between 5-HT receptors and to demonstrate the involvement of two 5-HT2 receptor subtypes in the regulation of 5-HT1B/1D function. The inducible 1C11 cell line has the unique property of acquiring within 4 days a complete serotonergic phenotype (1C11* cells), including three 5-HT receptors. 5-HT1B/1D and 5-HT2B receptors are expressed since day 2 of the serotonergic differentiation while 5-HT2A receptors are induced at day 4. We first established that 5-HT2B receptors are coupled with the phospholipase A2 (PLA2)-mediated release of arachidonic acid (AA) and that the activation of 5-HT2B receptors in 1C11*d2 cells inhibits the 5-HT1B/1D receptor function via a cyclooxygenase-dependent AA metabolite. At day 4, this 5-HT2B-mediated inhibition of the 5-HT1B/1D function can be blocked upon concomitant 5-HT2A activation although a 5-HT2A/PLA2 positive coupling was evidenced. This suggests the existence in 1C11*d4 cells of pathway(s) for 5-HT2A receptors, distinct from PLC and PLA2. Finally, this study reveals the antagonistic roles of 5-HT2A and 5-HT2B receptors in regulating the function of 5-HT1B/1D, a receptor involved in neuropsychiatric disorders and migraine pathogenesis.

Arachidonic Acid↗

PubMed1997

Perturbation of BMP signaling in somitogenesis resulted in vertebral and rib malformations in the axial skeletal formation.

Axial skeletons such as vertebrae, ribs, and scapulae develop from the embryonic somitic mesoderm through interactions with neural tube/notochord and skin ectoderm. Bone morphogenetic proteins (BMPs) seem to play important roles in these tissue interactions; however, the relationship between BMP signaling and the early development of axial skeletons is poorly understood. In this report, we investigated possible roles of BMP signaling in axial skeletal formation. First, we describe the expression patterns of BMP4 and type I receptors for BMP during somitogenesis in chick embryos based on whole mount in situ hybridization. Next, the effects of BMP on axial skeletal morphogenesis were investigated by implantation of BMP proteins into the dorsal mesoderm at the time of somitogenesis. Transcripts for both BMP4 ligand and its receptors are expressed in the dorsal ectoderm and mesoderm. Implantation of BMP4 and BMP2 into the dorsal regions of embryos result in subsequent anomalies of vertebrae, ribs, and scapulae. The effects of BMP implantation on the skeleton are shown to be dependent upon the somitic stage. Vertebral anomalies are restricted to the dorsolateral elements of the vertebrae and specifically observed after BMP implantation into embryonic day 2 (E2) embryos, but not E3 embryos. These results indicate that implantation of BMP into the dorsal part of embryos where endogenous BMP ligand and BMP receptors are expressed perturbs BMP signaling and causes axial skeletal malformations. The findings presented here suggest that BMP signaling may be involved in the early developmental process of the axial skeleton.

Amino Acid Sequence↗

PubMed1996

The mouse 5-HT2B receptor: homologous subtype or species variant?

The recently characterized 5-HT2B subfamily of serotonin receptors has now been reported from three different species: human, rat and mouse. Their genomic structures include 2 introns present at identical positions. Despite this similarity, their respective protein sequences show some diversities. In addition, the pharmacology of these receptors is distantly related, and their sites of expression vary amongst species. Thus, it appears difficult at present to unambiguously classify these receptors into the same subfamily, raising the possibility of the existence of other 5-HT2B-like receptors, yet to be discovered.

Animals↗

PubMed1996

Sequential onset of three 5-HT receptors during the 5-hydroxytryptaminergic differentiation of the murine 1C11 cell line.

1. The murine 1C11 clone, which derives from a multipotential embryonal carcinoma cell line, has the features of a neuroectodermal precursor. When cultured in the presence of dibutyryl cyclic AMP, the 1C11 cells extend bipolar extensions and express neurone-associated markers. After 4 days, the resulting cells have acquired the ability to synthesize, take up, store and catabolize 5-hydroxytryptamine (5-HT). We have thus investigated the presence of 5-HT receptors during the 5-hydroxytryptaminergic differentiation of this inducible 1C11 cell line. 2. As shown by the binding of [125I]-GTI and the CGS 12066-dependent inhibition of the forskolin-induced cyclic AMP production, functional 5-HT1B/1D receptors become expressed on day 2 of 1C11 cell differentiation. The density of these receptors remained unchanged until day 4. 3. The same holds true for the 5-HT2B receptor, also identified by its pharmacological profile and its positive coupling to the phosphoinositide cascade. 4. On day 4 of 1C11 cell differentiation, a third 5-HT receptor, pharmacologically and functionally similar to 5-HT2A, had become induced. 5. Strikingly, the amounts of each transcript encoding 5-HT1B, 5-HT2A and 5-HT2B receptor did not very significantly during the time course of the 1C11 5-hydroxytryptaminergic differentiation. 6. The clone 1C11 may thus provide a useful in vitro model for studying regulation(s) between multiple G-linked receptors as well as the possible role of 5-HT upon the expression of a complete 5-hydroxytryptamine phenotype.

Animals↗

PubMed1996

Immortalised mouse submandibular epithelial cell lines retain polarised structural and functional properties.

The mouse submandibular gland (SMG) is an excellent model for the study of many important biological phenomena such as hormonal regulation of differentiation, neurotransmitter control of secretion, epithelial transport, exocytosis and endocytosis as well as the regulation of mouse SMG specific gene expression, in particular, NGF, EGF and renin. The postnatal development and sexual dimorphism of the mouse gland permits the isolation of male SMGs of different ages, corresponding to different stages of differentiation, particularly with respect to the cytodifferentiation of ductal cell types. We have immortalized SMG epithelial cell lines using mice transgenic for the large T antigen of SV40 or polyoma viruses. Epithelial clusters from the dissected glands were placed in culture and cell lines were established from the immortalized population. Two cell lines, SIMS and SIMP, which retain structural and functional characteristics, are described here. The cell lines are immortalised but not transformed, as judged by the absence of anchorage independent growth potential and the lack of tumour formation in athymic nude mice. Confocal and electron microscopy examination demonstrate that SIMP and SIMS cells express E-cadherin and ZO-1 and have features of polarised epithelial cells. In addition, they form spherical cysts with a wide lumen when grown in type I collagen gels. When grown on a filter support SIMS cells form a tight monolayer, exhibit vectorial transport function and show exclusive Na+, K(+)-ATPase localisation to the basolateral domain. We determined the cell type restricted expression of cytokeratin markers in the mouse SMG in vivo and we demonstrate that SIMS and SIMP cell lines express duct-specific cytokeratins. Finally, the expression of a set of differentiation markers, including EGF, NGF and renin, was detected by RT-PCR and by indirect immunofluorescence staining in these lines. Thus, these polarised ductal cell lines, as well as having important intrinsic properties, represent well characterised mouse epithelial models which, until now, have not been readily available for cellular studies.

Animals↗

PubMed1995

Drosophila 5-HT2 serotonin receptor: coexpression with fushi-tarazu during segmentation.

Serotonin, first described as a neurotransmitter in invertebrates, has been investigated mostly for its functions in the mature central nervous system of higher vertebrates. Serotonin receptor diversity has been described in the mammalian brain and in insects. We report the isolation of a cDNA coding for a Drosophila melanogaster serotonin receptor that displays a sequence, a gene organization, and pharmacological properties typical of the mammalian 5-HT2 serotonin receptor subtype. Its mRNA can be detected in the adult fly; moreover, a high level of expression occurs at 3 hr of Drosophila embryogenesis. This early embryonic expression is surprisingly organized in a seven-stripe pattern that appears at the cellular blastoderm stage. In addition, this pattern is in phase with that of the even-parasegment-expressed pair-rule gene fushi-tarazu and is similarly modified by mutations affecting segmentation genes. Simultaneously with this pair-rule expression, the complete machinery of serotonin synthesis is present and leads to a peak of ligand concomitant with a peak of 5-HT2-specific receptor sites in blastoderm embryos.

Amino Acid Sequence↗

PubMed1995

Controlled conversion of an immortalized mesodermal progenitor cell towards osteogenic, chondrogenic, or adipogenic pathways.

The teratocarcinoma-derived C1 clone behaves as a mesodermal tripotential progenitor cell whose choice of fate, either osteoblast, chondroblast, or adipoblast, is strictly dependent on the spatial organization of the cells and the nature of the induction. In the absence of cell contact before the addition of inducers, the C1 cells maintain a stable undifferentiated phenotype while expressing potential regulators of embryonic mesodermal stem cell fate such a M-twist and Id1. Upon establishment of cell contacts before the induction of differentiation, the early genes characteristic of the three fates become expressed. In the presence of beta glycerophosphate and ascorbate, provided the cells have formed aggregates, 95% of the C1 cells mineralize with a kinetics of gene expression close to that of osteoblasts (Poliard, A., D. Lamblin, P. J. Marie, M. H. Buc, and O. Kellerman. 1993. J. Cell Sci. 106:503-512). With 10(-6)M dexamethasone, 80% of the same aggregates differentiate into foci of chondroblast-like cells. The kinetics of expression of the genes encoding type II, IX, X, and XI collagens, aggrecan and link protein during the conversion toward cartilage hypertrophy resembles that accompanying in vivo chondrogenesis. The synergistic action of dexamethasone and insulin convert most confluent C1 cells into functional adipocytes and induce a pattern of gene expression close to that reported for adipoblast cell lines. The C1 clone with its capacity to differentiate along three alternative pathways with high frequency, therefore appears as a valid in vitro model for deciphering the molecular basis of mesoblast ontogeny.

Adipocytes↗

PubMed1995

Functional serotonin-2B receptors are expressed by a teratocarcinoma-derived cell line during serotoninergic differentiation.

Among immortalized teratocarcinoma-derived cells, the clone 1C11 is a committed precursor of the neuronal lineage. On day 2 of its serotoninergic differentiation, this clone expresses only one subtype of serotonin [5-hydroxytryptamine (5-HT)] receptor, which is functionally coupled to phosphatidylinositol hydrolysis. The identity of these receptors was established by comparing their properties with those of 5-HT2B receptors expressed by LMTK- fibroblasts stably transfected with the recently cloned murine cDNA NP75 (LM5 cells). In both cell types, the analysis of (+/-)-1-(2,5-dimethoxy-4-[125I]iodophenyl)- 2-aminopropane HCl ([125I]DOI) binding revealed the presence of a single class of sites, the affinity of which was 1 order of magnitude lower than that reported for 5-HT2A receptors. In 1C11 cells differentiated for 2 days, as well as in LM5 cells, DOI binding was decreased by nonhydrolyzable analogs of GTP, indicating that the 5-HT2B receptor is functionally coupled to a G protein. The DOI-induced increase of phosphoinositide hydrolysis, which was correlated with both GTPase activity and binding data, is mediated by a Gq protein. This work demonstrates that the 5-HT2B receptor is functionally expressed before complete serotoninergic differentiation of 1C11 cells. The inducible 1C11 clone thus provides an in vitro model to investigate the possible role of the 5-HT2B receptor in the expression of the serotoninergic phenotype.

Animals↗

PubMed1994

The mouse 5-HT2B receptor: possible involvement in trophic functions of serotonin.

The novel serotonin receptor 5-HT2B shows the highest homology to the 5-HT2 family of receptors. The pharmacological profile of membranes from 5-HT2B cDNA stably transfected LMTK- cell line, corresponds to a new 5-HT2-like receptor named 5-HT2B, although some difference exists between the mouse and rat pharmacology. A similar pharmacological profile is detected on the immortalized teratocarcinoma-derived cell line 1C11 upon 2 days of serotoninergic differenciation by cAMP. In both cell lines, the analysis 125I-DOI binding reveals the presence of a single class of sites, the affinity of which is one order of magnitude lower than the one reported for the 5-HT2A receptor. This demonstrates that the 5-HT2B receptor is functionally expressed before the complete serotoninergic differentiation of 1C11 cells. These observations are in good agreement with the presence of 5-HT2B mRNA in early mouse embryonic development. Furthermore, the major sites of 5-HT2B mRNA embryonic expression are in the heart, and in the neural fold before the closure of the neural tube. Therefore, this receptor could account at least in part for the trophic functions attributed to the 5-HT2-like receptors.

Animals↗

PubMed1993

Kinetics of in vitro mineralization by an osteogenic clonal cell line (C1) derived from mouse teratocarcinoma.

We have previously reported the isolation of an osteogenic clonal cell line (C1) derived from mouse teratocarcinoma and immortalized by the SV 40 oncogenes. In this report we describe the kinetics of osteogenic differentiation of aggregated C1 cells by following the matrix deposition and mineralization and the expression of alkaline phosphatase. We show that after addition of beta-glycerophosphate and ascorbic acid, more than 95% of C1 aggregates synthesize a bone matrix which is deposited as early as 2 days and increases progressively with time in culture. Matrix calcification is evidenced by von Kossa staining and tetracycline incorporation into the mineral whereas no calcification appears in control cultures. Calcium is detectable in mineralizing aggregates at 2 days and calcium content increases linearly with time in culture, being 125-fold higher in mineralizing nodules than in control aggregates at 30 days. Aggregated C1 cells are characterized by a high activity of the bone type isoenzyme of alkaline phosphatase, a marker of osteoblast phenotype. Upon addition of inducers, alkaline phosphatase activity decreases by five-fold after the onset of mineralization and remains stable thereafter. The down-regulation of alkaline phosphatase activity is confirmed at the cellular level by histochemical staining. The mRNA levels for alkaline phosphatase decline during osteogenesis, following a pattern similar to the decrease in protein activity. Analysis of DNA synthesis by (3H)-thymidine incorporation and quantification of labelled nuclei on autoradiographs shows that C1 cells proliferation is not down-regulated during the time course of differentiation and that proliferating C1 cells still express alkaline phosphatase activity during osteogenic differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗

PubMed1993

Commitment of the teratocarcinoma-derived mesodermal clone C1 towards terminal osteogenic differentiation.

The mesodermal clone C1 was derived from the multipotent embryonal carcinoma 1003 cell line transformed with the plasmid pK4 carrying SV40 oncogenes under the control of the adenovirus E1A promoter. We have shown that the C1 clone becomes committed to the osteogenic pathway when cultured in aggregates in the presence of mediators of the osteogenic differentiation. To further validate C1 as a model with which to study osteogenesis in vitro the kinetics of its differentiation was studied, focusing on the histology of the aggregates and on the expression of a set of genes corresponding to representative bone matrix proteins. The presence of ascorbic acid and beta- glycerophosphate specifically leads to mineralization in almost 100% of the aggregates. Transcription of the above genes, silent in exponentially growing cells, specifically occurred with the establishment of cell-cell contacts independently of the presence of ascorbic acid and inorganic phosphate. The latter, however, were absolutely required for matrix deposition and mineralization. In their presence, one observed an overall decline in type I collagen and alkaline phosphatase transcripts while osteocalcin and osteopontin transcripts preferentially accumulated in cells lining the mineralizing foci. Concomitantly, type I collagen and osteocalcin became extracellularly deposited. The osteogenic differentiation of C1 occurred while cells were still proliferating. The C1 clone thus behaves as a mesodermal stem cell, becoming committed to the osteogenic pathway upon: firstly, establishment of cellular contacts; and secondly, addition of ascorbate and beta-glycerophosphate. It therefore appears to be a promising in vitro system for deciphering the molecular basis of osteoblast ontogeny.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗

PubMed1992

High expression of stathmin in multipotential teratocarcinoma and normal embryonic cells versus their early differentiated derivatives.

Stathmin is a ubiquitous cytoplasmic protein, phosphorylated in response to agents regulating the proliferation, the differentiation and the specialized functions of cells, in a way possibly integrating the actions of diverse concomitant regulatory signals. Its expression is also regulated in relation with cell proliferation and differentiation and reaches a peak at the neonatal stage. To assess the possible role of stathmin at earlier stages of development, we examined its expression and regulation in embryonal carcinoma (EC) and derived cell lines as well as in the early mouse embryo. Interestingly, stathmin is highly abundant in the undifferentiated, multipotential cells of the F9, 1003 and 1009 EC cell lines. Its high expression markedly decreased, both at the protein and mRNA levels, when F9 cells were induced to differentiate into endodermal-like cells with retinoic acid and dibutyryl-cAMP. Stathmin was also much less abundant in differentiated cell lines such as the trophectodermal line TDM-1, as well as in several F9- and 1003-derived cell lines committed to differentiate towards the mesodermal and neuroectodermal lineages but still proliferating. Therefore, the observed decrease of stathmin expression is not related to the reduced proliferation rate but rather to the differentiation of the multipotential EC cells. The immunocytochemical pattern of stathmin expression during early mouse development indicated that stathmin is also highly abundant in the multipotential cells of the inner cell mass of the blastula, whereas it is much lower in the differentiated trophectodermal cells. These results confirm the physiological relevance of the observations with EC cells, and suggest that stathmin, in addition to its high expression at later stages of development and in the adult nervous system, may be considered as a new marker of the multipotential cells of the early mouse embryo.

Animals↗

PubMed1990

Serotonin uptake, storage, and synthesis in an immortalized committed cell line derived from mouse teratocarcinoma.

We report the isolation and characterization of a serotoninergic cell line, 1C11, derived from a mouse teratocarcinoma. The clone 1C11 was immortalized through the expression of the simian virus 40 oncogenes. 1C11 presents two states: an immature epithelial-like state (1C11 precursor) and a more differentiated state (1C11). After induction by dibutyryl cyclic AMP and cyclohexanecarboxylic acid, almost 100% of 1C11 cells continue to divide and have acquired a neural-like phenotype. 1C11* cells coexpress several neural markers, such as synaptophysin (the membrane constituent of synaptic vesicles), the neuropeptide [Met5]enkephalin, and the neurotransmitter serotonin. 1C11* cells store endogenous serotonin and are able to synthesize serotonin from L-tryptophan and to catabolize it by monoamine oxidase B. Moreover, the cells take up serotonin by a carrier-mediated mechanism very similar to that of serotoninergic neurons. The expression of the simian virus 40 oncogenes, which promoted immortalization, does not therefore prevent further differentiation. This inducible cell line constitutes a valuable model for cellular and molecular studies concerning the physiology and the pharmacological modulation of the serotoninergic phenotype.

Animals↗

PubMed1990

An immortalized osteogenic cell line derived from mouse teratocarcinoma is able to mineralize in vivo and in vitro.

The hybrid plasmid pK4 containing the early genes of the simian virus SV-40, under the control of the adenovirus type 5 E1a promoter, was introduced into the multipotent embryonal carcinoma (EC) 1003. Expression of the SV-40 oncogenes was observed at the EC cell stage, and this allowed the derivation of immortalized cells corresponding to early stages of differentiation. Among the immortalized mesodermal derivatives obtained, one clone, C1, is committed to the osteogenic pathway. C1 cells have a stable phenotype, synthesize type I collagen, and express alkaline phosphatase activity. Although immortalized and expressing the SV-40 T antigen, the cells continue to be able to differentiate in vivo and in vitro. In vivo, after injection into syngeneic mice, they produce osteosarcomas. In vitro, the cells form nodules and deposit a collagenous matrix that mineralizes, going to hydroxyapatite crystal formation, in the presence of beta-glycerophosphate. This clonal cell line, which originates from an embryonal carcinoma, therefore differentiates into osteogenic cells in vivo and in vitro. This immortalized cell line will be useful in identifying specific molecular markers of the osteogenic pathway, to investigate gene regulation during osteogenesis and to study the ontogeny of osteoblasts.

Acid Phosphatase↗

PubMed1990

[A strategy for immortalizing lines committed to endoderm, neuroectoderm or mesoderm from mouse teratocarcinoma].

With the aim of immortalizing embryonic cells fixed at early embryonic stages, various plasmids carrying the SV40 early region were introduced into the mouse embryonal carcinomas (EC) F9 and 1003. Only the construction PK4, in which the SV40 oncogenes are placed under the control of the adenovirus E1A promoter, led to the immortalization of the cells at the onset of differentiation. Clones corresponding to committed precursors of each embryonic lineage (neuroectoderm, mesoderm and endoderm) were then selected with high efficiency according to the following strategy: selection of immature cells which: have lost EC cell markers, keep a stable phenotype, are immortalized by the expression of the SV40 oncogenes and are still able to differentiate along a restricted lineage in vitro or in vivo. Examples of an endodermal precursor (H7) which differentiates into extraembryonic and embryonic endoderm, of a neuroectodermic clone (ICII) committed to a serotoninergic differentiation, and of a mesodermal osteogenic clone (CI) which gives rise to bone in vivo and in vitro, are given.

Adenoviridae↗

PubMed1989

F9 teratocarcinoma aggregates express villin upon differentiation into visceral endoderm-like cells.

The visceral endoderm of the mouse embryo is a polarized epithelium which has recently been shown to express villin, a major actin binding component of absorptive epitheliums. We report here that villin is induced during differentiation of aggregates of the mouse embryonal carcinoma F9, an in vitro system widely used to study extraembryonic endoderm differentiation. Identical results were obtained with a variant of F9 which carries an immortalizing vector. Villin is coexpressed with F-actin and with alpha-foetoprotein, in most of the visceral endoderm-like cells lining the aggregates. This system is potentially useful to study (i) the induction of villin expression and (ii) the establishment of polarity in the visceral endoderm epithelium.

Animals↗

PubMed1988

[Results of magnetic resonance tomography of the temporomandibular joint using optimized surface coils].

One hundred temporo-mandibular joints were examined with a super-conducting nuclear resonance tomograph (1.0 Tesla) using various high resolution surface coils. The optimal method proved to be a spin echo sequence with a repetition time of 1,000 msec and an echo period of 28 msec with a 4 mm slice width. There were significant advantages from the non-invasive MRT diagnosis of the temporo-mandibular joints when compared with CT and with arthrography in recognising abnormal discs, changes in the tissues and for post-operative control.

Adult↗

PubMed1988

[Magnetic resonance tomography in tumors of the salivary glands--a diagnostic advantage?].

40 patients with clinically palpable salivary gland masses were included in a prospective study to compare magnetic resonance imaging to computed tomography. MRI has proved superior to CT not only in imaging primary lesions but also in diagnosing local and regional recurrences. In evaluating border structures, signal intensity, T1- and T2-values of space occupying lesions, we can determine the tumour status. Besides, we can define to some extent the internal architecture of the salivary gland or intra-resp. periglandular lymph node masses. Better contrast resolution and more specificity can be obtained by the use of contrast medium gadolinium-DTPA. Even small intraglandular and periglandular masses can be clearly distinguished from the sourrounding structures. At present, magnetic resonance imaging offers the diagnostic potency of both sonography and computed tomography. The advantages of MRI and our present indications in imaging salivary gland masses are discussed.

Adenocarcinoma↗