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Biomedical subjects

R Didier

Publications and source records attributed to R Didier.

At least 19 recordsLinked to original sources
PubMed2000

SCO-spondin and RF-GlyI: two designations for the same glycoprotein secreted by the subcommissural organ.

SCO-spondin and RF-GlyI are two designations for cDNAs strongly expressed in the bovine subcommissural organ (SCO), characterized, respectively, in 1996 and 1998 by two different research groups. Because both cDNAs were partial sequences and exhibited close similarities in their nucleotide and deduced amino acid sequences, it was thought that they might be part of the same encoding sequence. To find out, we performed 3'RACE using a SCO-spondin-specific upstream primer. From the RT-PCR product generated and by nested PCR techniques, we amplified both SCO-spondin and RF-GlyI specific products with the expected length. Also, probes generated from both PCR products hybridized to the same major 14 kb transcript in Northern blot analyses, clearly showing that SCO-spondin and RF-GlyI cDNAs do belong to the same encoding sequence. In addition, we amplified, cloned, and sequenced a PCR product of 3 kb spanning both the known SCO-spondin and RF-GlyI sequences. The deduced amino acid sequence contains nine thrombospondin type 1 repeats that alternate with sequences sharing similarities with the D-domain of von Willebrand factor. Taken together, these findings show that SCO-spondin and RF-GlyI are two designations of the same gene encoding proteins secreted by the bovine SCO and forming Reissner's fiber. In addition, compared to the sequence provided by Nualart et al. (1998), we extended the reading frame and identified new conserved domains in the 3' end of SCO-spondin. The putative function of SCO-spondin on axonal pathfinding is discussed regarding the presence of a great number of thrombospondin type 1 repeats.

Amino Acid Motifs↗
PubMed2000

Subcommissural organ/Reissner's fiber complex: characterization of SCO-spondin, a glycoprotein with potent activity on neurite outgrowth.

In the developing vertebrate nervous system, several proteins of the thrombospondin superfamily act on axonal pathfinding. By successive screening of a SCO-cDNA library, we have characterized a new member of this superfamily, which we call SCO-spondin. This extracellular matrix glycoprotein of 4,560 amino acids is expressed and secreted early in development by the subcommissural organ (SCO), an ependymal differentiation located in the roof of the Sylvian aqueduct. Furthermore, SCO-spondin makes part of Reissner's fiber (RF), a thread-like structure present in the central canal of the spinal cord. This novel protein shows a unique arrangement of several conserved domains, including 26 thrombospondin type 1 repeats (TSR), nine low-density lipoprotein receptor (LDLr) type A domains, two epidermal growth factor (EGF)-like domains, and N- and C-terminal von Willebrand factor (vWF) cysteine-rich domains, all of which are potent sites of protein-protein interaction. Regarding the huge number of TSR, the putative function of SCO-spondin on axonal guidance is discussed in comparison with other developmental molecules of the CNS exhibiting TSR. To correlate SCO-spondin molecular feature and function, we tested the effect of oligopeptides, whose sequences include highly conserved amino acids of the consensus domains on a neuroblastoma cell line B 104. One of these peptides (WSGWSSCSRSCG) markedly increased neurite outgrowth of B 104 cells and this effect was dose dependent. Thus, SCO-spondin is a favorable substrate for neurite outgrowth and may participate in the posterior commissure formation and spinal cord differentiation during ontogenesis of the central nervous system.

Age Factors↗
PubMed1999

SCO-spondin is evolutionarily conserved in the central nervous system of the chordate phylum.

Bovine SCO-spondin was shown to be a brain-secreted glycoprotein specifically expressed in the subcommissural organ, an ependymal differentiation located in the roof of the Sylvian aqueduct. Also, SCO-spondin makes part of Reissner's fiber, a phylogenetically and ontogenetically conserved structure present in the central canal of the spinal cord of chordates. This secretion is a large multidomain protein probably involved in axonal growth and/or guidance. As Reissner's fiber is highly conserved in the chordate central nervous system, we sought genes orthologous to the bovine SCO-spondin gene by Southern blot analysis in several members of the chordate phylum: urochordates, cephalochordates, cyclostomes, and lower and higher vertebrates, including humans. In addition, conserved glycoproteins present in the subcommissural organ and Reissner's fiber were revealed by immunohistochemistry using antibodies raised against bovine Reissner's fiber. Variation in the sites of Reissner's fiber production according to chordate subphylum, presence of this structure in the spinal cord, and conservation of the SCO-spondin gene are discussed in the context of chordate central nervous system development. These results indicate that SCO-spondin is an ancient ependymal secretion, making part of Reissner's fiber, that may have had an important function during the evolution of the central nervous system in chordates, including that of the spinal cord.

Animals↗
PubMed1995

The secretory material of the subcommissural organ of the chick embryo. Characterization of a specific polypeptide by two-dimensional electrophoresis.

The subcommissural organ (SCO) is a cerebral gland that releases into the cerebrospinal fluid a carbohydrate-rich glycoprotein which condenses to form Reissner's fiber (RF). Western blots from two-dimensional gel electrophoresis were stained with lectins (Concanavalin-A, wheat germ agglutinin) and anti-bovine RF serum to identify the secretory products of the chick embryo SCO. Immunohistochemical investigations showed that the anti-bovine RF serum reacted exclusively with the secretion of the SCO. Comparative protein patterns of SCO, pineal organ and cerebral hemisphere extracts allowed us to characterize a specific polypeptide in the SCO electrophoretic profiles. The polypeptide was a highly acid compound (isoelectric point of 4.7) with a high molecular weight (390 kDa). On Western blots only this component was immunoreactive with the RF antiserum and it exhibited an affinity for the two lectins. On the basis of these results, this polypeptide may be considered as a specific component of the secretory material synthesized by the SCO cells of the chick embryo.

Animals↗
PubMed1992

A radioautographic study of [3H]-A 23187 (calcimycin) in components of the brain. Distribution in different cell types of the diencephalo-mesencephalic roof.

The distribution of the ionophore [3H]-A 23187 was examined by means of light and electron microscopy in elements of the central nervous system located in the diencephalo-mesencephalic roof. A 23187 is not evenly distributed in the components studied (ependyma, secretory ependyma of the subcommissural organ and neurons of the mesencephalon). At the cellular level, A 23187 appears preferentially associated with the cytoplasmic membrane as well as with the internal membranous system.

Animals↗
PubMed1992

Monoclonal antibodies as probes for the analysis of the secretory ependymal differentiation in the subcommissural organ of the chick embryo.

Monoclonal antibodies directed against components of the subcommissural organ (SCO) of the chick embryo were produced by immunizing mice with SCO homogenate. In three series of production, 788 hybridomas were screened by immunofluorescence microscopy. Four hybridoma cell lines producing antibodies that specifically recognize both SCO cells and Reissner's fiber (RF) were selected and cloned. Using these immunological probes, the ontogenetic development of the SCO and RF was investigated in the chick embryo. Immunoreactive material could be detected in the SCO anlage from stage 17 on and RF was first observed in the central canal of the thoracal part of the spinal cord in 10-day-old embryos. Monoclonal antibodies can be useful as markers for analyzing molecular mechanisms involved in the specific function of these ependymal cells.

Animals↗
PubMed1989

Detection of sex-specific proteins in chick embryo gonads and mesonephros: effects of estradiol benzoate or tamoxifen on their expression.

Gonadal and mesonephric protein patterns from 19 day old normal chick embryos were investigated by two-dimensional polyacrylamide gel electrophoresis. Under these conditions, several sex-specific polypeptides were detected. As concerns gonadal extracts, four sex-specific polypeptides, all restricted to the cytosol, were present in the testis, whereas three sex-specific polypeptides, two localized in the cytosol, the other being membrane-bound, were identified in the ovary. Among the ovary-specific polypeptides two proved to be estrogen-dependent. They appeared in the left testis of embryos after early estradiol benzoate treatment and their expression was reduced in the ovary after early exposure to the antiestrogen, tamoxifen. Mesonephros extracts of both sexes also differed in their protein composition since three additional polypeptides (one in both the cytosolic and membrane fractions, the others in the cytosol) not found in females were found to be present in males. None appeared to be affected after either estradiol or tamoxifen treatment.

Animals↗
PubMed1984

Magnesium deficiency in the Japanese quail.

Morphological effects of magnesium deficiency on liver cells and general aspects of its influence on the metabolism were investigated in young quails. Magnesium deficiency was characterized by a depressed growth, a high mortality rate, a decrease in hematocrit and magnesium and calcium plasma concentrations. Magnesium deficiency reduced the magnesium concentration in heart by 44%, but did not affect the concentration in liver. Ultrastructural aspect of liver parenchymal cells revealed that the number of mitochondria per cell section was decreased and the average area of a mitochondrion was greater in deficient quails than in control animals. The significance of these morphological changes was discussed in relation to disturbances in energy metabolism of these organelles. From these results, japanese quail appeared as an interesting experimental model for studies on metabolic disturbances in magnesium deficiency.

Animals↗
PubMed1983

Changes in glucose and lipid metabolism in starved or starved-refed Japanese quail (coturnix coturnix japonica) in relation to fine structure of liver cells.

1. Metabolic response of adult quail to fasting or refeeding was studied by measuring the main blood and hepatic metabolites. Moreover, the fine structure of hepatocytes in these physiological conditions was described. 2. Starvation or refeeding did not affect glycemia in male as in female quails. 3. Fasting had no effect on plasma free fatty acids in female quails, whereas plasma triglycerides were markedly decreased. 4. In fasted quails, there was an active ketogenesis with a high 3-hydroxybutyrate/acetoacetate ratio. 5. Ultrastructural aspect of liver parenchymal cells from fasted quails revealed alterations in the quantity of glycogen, smooth endoplasmic reticulum, lysosomes and in the form of the rough endoplasmic reticulum. 6. The significance of these morphological changes was discussed in relation to an hormonal stimulation.

Animals↗
PubMed1983

[Hepatotoxicity of 2,4,5-trichlorophenoxyacetic acid. Cytologic and biochemical study in quail embryos].

The effects of 2,4,5-T on the hepatic cell in the 13 day old quail embryo have been studied. When injected at the dose level of 80 or 240 mg/kg into non-incubated eggs, this herbicide induces a proliferation of the smooth endoplasmic reticulum. The ergastoplasmic cisternae are dilated and feature a decrease in ribosomic covering. The mitochondria are swollen showing a pale matrix and a deficiency in cristae. One also observes an increase in the amount and size of lipidic inclusions and a dilatation of bile canaliculi. Moreover, biochemical analysis reveals a significant decrease in the glycogen content indicating that 2,4,5-T disturbs the glycogenic function of the liver.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1982

[Toxicity and certain physiopathologic effects of 2,4,5-trichlorophenoxyacetic acid, an organo-chlorine herbicide, in the adult domestic quail (Coturnix coturnix japonica)].

The effects of 2,4,5-T on adult japanese quail have been studied. The herbicide was administered daily in oral dosages at level of 100 mg/kg per day for two weeks (five days a week). In these experimental conditions, this compound was moderately toxic, the rate of mortality was low. However, we noticed a significant reduction in food consumption, body weight and egg production. The physiological disturbances resulting from the toxicological treatment are reversible.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1981

[Effect of fasting on the main blood and liver metabolites of gluconeogenesis and ketogenesis in the adult domestic quail (Coturnix coturnix japonica)].

The changes in the main plasma and liver metabolites of gluconeogenesis and ketogenesis have been studied in quails during 72-hr starvation. In those conditions, glycaemia barely decreased, whereas liver glycogen and plasma and liver lactate dropped, suggesting that lactate was utilized extensively for gluconeogenesis. In contrast, plasma alanine decreased only slightly. During starvation, plasma free fatty acids and cholesterol were significantly enhanced, whereas plasma triglycerides decreased. Ketogenesis seemed very active. Hydroxybutyrate concentrations were markedly higher in the plasma than in the liver, indicating that mechanisms other than simple diffusion processes should be considered for hepatic ketone body release. The present results suggest that metabolic response to prolonged starvation in the quail does not differ markedly from that observed in other birds. However, the utilization of glucose and ketone bodies by peripheral tissue and of some substrates, such as alanine or pyruvate, for gluconeogenesis must be further investigated.

Animals↗