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J J Picard

Publications and source records attributed to J J Picard.

At least 19 recordsLinked to original sources
PubMed2003

Maternal diabetes in the rat impairs the formation of neural-crest derived cranial nerve ganglia in the offspring.

AIMS/HYPOTHESIS: Maternal diabetes mellitus increases the risk for fetal malformations. Several of these malformations are found in organs and tissues derived from the neural crest. Previous studies have shown changes in fetal organs of neural crest origin in experimental diabetes and changes in migration of neural crest cells exposed to high glucose in vitro. METHODS: We used whole-mount neurofilament staining of embryos from normal and diabetic mothers to investigate the development of cranial nerve ganglia. Neural tube explants were cultured in 10 and 40 mmol/l glucose and cell death and caspase activity was measured with flow cytometry. RESULTS: The development of cranial ganglia V, VII, VIII, IX and X was impaired in day 10-11 embryos of diabetic rats. There was also a higher rate of cell death of neural crest derived cells cultured in 40 mmol/l glucose for 20 h (35% compared to 12% in 10 mmol/l). However, exposure of cells to 40 mmol/l glucose in culture did not increase the activation of the cell death effector proteins-caspases-measured as cellular binding of the activated caspase marker VAD-FMK. This suggests that the cell death is not caused by caspase-dependent apoptosis or that the caspases are activated at an earlier stage. CONCLUSION/INTERPRETATION: The development of neural crest-derived structures is disturbed already at the organogenic period in embryos of diabetic rats and this deteriorated development could be due to high-glucose induced increase in cell death of neural crest derived cells.

Animals↗
PubMed2001

Expression of Sonic Hedgehog downstream genes is modified in rat embryos exposed in utero to a distal inhibitor of cholesterol biosynthesis.

Holoprosencephaly is a common developmental anomaly of the forebrain and midface, that has been associated with mutations in the Sonic Hedgehog gene, and with perturbations of cholesterol synthesis and metabolism in mammalian embryos. The study presented here was aimed to evaluate the functional relationship between these two causal agents in the genesis of the phenotype. Therefore, we used rat embryos exposed in utero to a distal inhibitor of cholesterol biosynthesis (AY9944) in which we analyzed different Shh-dependent processes, as evaluated by the expression of eight target genes. In addition, to delineate between the impact of cholesterol shortage and/or sterol precursors accumulation on the Shh signaling cascade we exposed rat embryos to AY9944 and we provided complementary diets rich in cholesterol and 7-DHC. At the early-somite stage we observed a reduction of Shh signaling in AY9944 treated embryos, resulting in the definition of a narrower ventral domain. Later in development this reduction of Shh signaling led to a complete interruption of the pathway in the rostral hindbrain and caudal midbrain. Other regions such as the forebrain and the spinal cord appeared less sensitive to the reduction of Shh signaling and interruption of the pathway was only observed in a subset of embryos. Finally, we did provide evidence that 7-DHC accumulation is compatible with normal activity of Shh, as long as cholesterol levels in embryonic tissue is sufficient.

Abnormalities, Drug-Induced↗
PubMed1999

Absence of ventral cell populations in the developing brain in a rat model of the Smith-Lemli-Opitz syndrome.

The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive condition involving craniofacial and central nervous system malformations with occasional holoprosencephaly (HPE). It is caused by a defect in the 7-dehydrocholesterol (7-DHC) reductase, the enzyme catalyzing the last step of cholesterol biosynthesis. Treatment of pregnant rats with inhibitors of 7-DHC reductase, either AY9944 or BM15.766, has provided a valuable model to study the pathogenesis in SLOS. Recently, cholesterol has been shown to be involved in the post-translational activation of the signaling protein Sonic Hedgehog. To identify the early defects associated with HPE in a rat model of SLOS, and to compare the phenotype of the treated embryos with that of the Shh(-/-) mutants, we examined brain morphology and expression of three developmental genes (Shh, Otx2, and Pax6 ) in 23-somite stage embryos from AY9944-treated dams. We report clearly abnormal morphology of the developing brain, concerning primarily the ventral aspect of the neural tube. We observed a reduced or absent expression of Shh and Otx2 in their ventral domain associated with extended ventral expression of Pax6. The results suggest an absence of the midline ventral cell type at all levels of the cranial neural tube. They provide further evidence that cholesterol-deficiency-induced HPE originates from impaired Shh signaling activity in the ventral neural tube.

Animals↗
PubMed1997

HNF-6 is expressed in endoderm derivatives and nervous system of the mouse embryo and participates to the cross-regulatory network of liver-enriched transcription factors.

Hepatocyte nuclear factor-6 (HNF-6) is a liver-enriched transcription factor that contains a single cut domain and a novel type of homeodomain. Here we have studied the developmental expression pattern of HNF-6 in the mouse. In situ hybridization experiments showed that HNF-6 mRNA is detected in the liver at embryonic day (E) 9, at the onset of liver differentiation. HNF-6 mRNA disappeared transiently from the liver between E12.5 and E15. In transfection experiments HNF-6 stimulated the expression of HNF-4 and of HNF-3 beta, two transcription factors known to be involved in liver development and differentiation. HNF-6 was detected in the pancreas from E10.5 onward, where it was restricted to the exocrine cells. HNF-6 was also detected in the developing nervous system. Both the brain and the spinal cord started to express HNF-6 at E9-9.5 in postmitotic neuroblasts. Later on, HNF-6 was restricted to brain nuclei, to the retina, to the ventral horn of the spinal cord, and to dorsal root ganglia. Our observations that HNF-6 contributes to the control of the expression of transcription factors and is expressed at early stages of liver, pancreas, and neuronal differentiation suggest that HNF-6 regulates several developmental programs.

Animals↗
PubMed1997

Postimplantation mouse embryos cultured in vitro. Assessment with whole-mount immunostaining and in situ hybridization.

The postimplantation embryos of rodents have been particularly convenient to study in culture using the whole embryo culture (WEC) system developed by New. Two serious limitations of the method will be illustrated in the present paper and proposals will be made to improve the quality of the information. The first limitation is that the developmental period amenable to culture has not been significantly extended in recent years. In the present paper, we show that the culture of mouse presomitic stages for 48 h leads to poorly reproducible results and frequent dysmorphogenic embryos. We also show that early somite stages cultured for 54 h or less have a normal growth and differentiation. In contrast, the culture of these embryos for 72 h results in subtle abnormalities of the head and the first branchial arch. The second limitation is that the gross morphology and histology are often not informative enough to distinguish between overall toxicity and developmental toxicity. We suggest some improvements by the association of WEC with two specific techniques: 1) whole-mount immunostaining of sensory ganglia and nerves and 2) in situ hybridization on histological sections using molecular probes for some developmental genes. Embryos reaching about the 30 somite stage at the end of the culture were processed for whole-mount immunostaining of sensory ganglia and nerves. We show that these structures are very sensitive to the noxious effects of HgCl2 and valproate. Both developmental retardations and dysmorphogeneses of the cervical ganglia and nerves were observed. Embryos were also exposed in vitro to low concentrations of all-trans-retinoic acid (AT-RA) and processed for in situ hybridization with radiolabeled anti-sense RNA probes for the Hoxb-1 and Hoxb-2 developmental genes. Three-dimensional reconstructions of the expression domains were performed. The data show that AT-RA induces ectopic expression domains of Hoxb-1. Our experiments demonstrate that techniques such as immunostaining and in situ hybridization can significantly expand the information obtained from whole postimplantation embryo culture.

Animals↗
PubMed1996

Cranial nerves and ganglia are altered after in vitro treatment of mouse embryos with valproic acid (VPA) and 4-en-VPA.

Prenatal valproic acid (VPA) exposure results in neural tube defects and in the fetal valproate syndrome (FVS), associated with developmental delay. In the present study we investigate the alterations induced by VPA and one of its metabolite, 4-en-VPA, on specific neural structures: branchial nerves and ganglia. This study was performed on 8-9 pairs of somites mouse embryos exposed in vitro for 24 h to 0.75 mM of VPA or 1 mM of 4-en-VPA. After an additional culture period of 20 h without drug, the embryos were processed for whole mount immunostaining using the monoclonal antibody 2H3, directed against the 155 kDa neurofilament protein. This technique makes it possible to visualise the branchial nerves/ganglia. VPA and 4-en-VPA induced a delay in the development of the trigeminal (V), glossopharyngeal (IX) and vagus (X) nerves/ganglia. The development of the facial (VII) nerve was delayed to a lesser extend. These treatments also induced defects in the four ganglia. The main abnormalities were a reduced dorsal component of ganglion V, the absence of the dorsal root of ganglion IX, a disorganised dorsal part of ganglion X and diffuse ventral fibres in nerves VII-VIII. In addition, scattered fibres were observed around and between ganglia. In conclusion, VPA and 4-en-VPA deeply altered the differentiation of branchial nerves/ganglia. The dorsal part of the ganglia, arising from the rhombencephalic neural crest, was particularly sensitive. The disorganisation of fibres could possibly be explained by alteration of the extracellular matrix.

Animals↗
PubMed1996

Defects in the development of branchial nerves and ganglia induced by in vitro exposure of mouse embryos to mercuric chloride.

The embryotoxic and dysmorphogenic effects of mercuric chloride (HgCl2) have been studied in mouse embryos cultured in vitro. In addition, the alterations induced in the developing branchial nerves and ganglia were analyzed. Mouse embryos with 6-8 pairs of somites were exposed for 26 hr to increasing concentrations (0, 12.5, 25, 50 microM) of HgCl2. After this period, a first set of embryos was removed and a second set of embryos transferred to culture medium without HgCl2 and remained in culture for an additional 22 hr. Both sets of embryos were examined for (1) survival, (2) presence of external dysmorphogenesis, (3) growth, and (4) differentiation. Dose-related alterations of these parameters were observed. The main target was the cephalic neural tube (mainly the forebrain), but several other systems were also affected (e.g., the turning of the embryos, the optic system). The 48-hr cultured embryos were immunostained using a monoclonal antineurofilament antibody to visualize defects in the development of branchial nerves and ganglia. HgCl2 induced a pronounced retardation in the differentiation of ganglion/nerve V and a slight retardation in the differentiation of ganglia/nerves VII and IX. The ganglia/nerves VIII and X were not retarded. In addition, hight percentages of abnormalities of ganglion/nerve V and fusions between ganglia/nerves IX and X were observed in these embryos. Disorganized fibers between ganglia/nerves VII-VIII and IX and between ganglia/nerves IX and X were also more frequently observed. At the highest concentration, asymmetric defects were induced by HgCl2 with a more pronounced effect observed on the right side of the embryos. These results demonstrate the usefulness of this approach in evaluating the susceptibility of the developing branchial nerves to the adverse effects of developmental toxicants.

Abnormalities, Drug-Induced↗
PubMed1992

Early neurogenesis and teratogenesis in whole mouse embryo cultures. Histochemical, immunocytological and ultrastructural study of the premigratory neuronal-glial units in normal mouse embryo and in mouse embryos influenced by cocaine and retinoic acid.

Yolk sacs of postimplantation mouse embryos were cultured in a mixture of human and rat sera. The central nervous system of these cultured normal embryos was studied from the stage of 5-9 somites (approximately 8.5 postcoital days) to 20-21 somites (approximately 9.5 postcoital days) and compared with in vivo embryos at the same stages. This developmental period covers most of the neural tube closure, the early premigratory differentiation of the neuroectodermal epithelium, and the glial commitment of a population of germinative cells. The neuronal and glial elements of the in vitro cultivated embryos were found to be identical to the corresponding neural tissue in in vivo embryos (light and electron microscopic comparisons); the morphological identity between the in vivo and in vitro embryos was confirmed by morphometry and by stainings revealing the differentiation of the glial elements and precursors. The study of the neuronal-glial units in this material revealed that the fascicular organization of the radial glial cells occurs before the stage of 20 somites. When submitted to a single low dose of retinoic acid at the 7-somite stage, the expression of the epitope recognized by radial cell 2 (RC2), a glial marker, is delayed in the in vitro embryos 12-16 hours, but the glycogen and the other glial parameters mature in time. The in vitro embryos exposed to cocaine at the 7-somite stage displayed a prosencephalon remaining deprived of almost all glial cytological features during the entire culture period, although the other developmental parameters evolved normally. This in vitro whole embryo model seems to be a powerful tool for studying early neurogenesis and teratogenesis.

Animals↗
PubMed1992

Ethanol-induced disturbances of gliogenesis and neuronogenesis in the developing murine brain: an in vitro and in vivo immunohistochemical and ultrastructural study.

The effects of ethanol on murine brain development were studied in a model of whole embryo culture and in vivo. Ethanol locally enhances cell death in the primitive neuroepithelium. During neuronal migration, ethanol induces a premature transformation of the radial glial guides into astrocytes. Ethanol also inhibits the late gliogenesis. The resulting postmigratory neocortex displays an abnormal neuronal pattern almost completely deprived of vertical columnization. These glial-neuronal disturbances can explain neuropathological and clinical features of the fetal alcohol syndrome. Our study provides also an experimental tool for the study of cell death in normal and abnormal conditions at early stages of neurogenesis.

Animals↗
PubMed1992

Evolution of the developmental scores of sixteen morphological features in mouse embryos displaying 0 to 30 somites.

A precise framework of morphological developmental events observed macroscopically in early postimplantation mouse embryos aged 8-10 days (0-30 somites) is established. The quantitative evolution of the developmental score of 16 features as a function of the developmental stage of the embryos (expressed in number of somites) is presented. Thirty-one groups of ten embryos, each with 0 to 30 somites, were scored for each feature according to the previous description of the authors. In addition, the variation of individual structures as a function of embryonic developmental stages is evaluated. It is suggested that the framework of differentiating individual structures at given developmental stages will help to plan experiments in developmental biology of rodents and will facilitate the interpretation of results in developmental toxicity.

Age Factors↗
PubMed1991

Interlaboratory evaluation of three culture media for postimplantation rodent embryos.

The first aim of the study was to compare the ability of rat serum, human serum, and a mixture of human and rat serum (4:1) to support in vitro development of rodent postimplantation embryos. The comparison was made in three laboratories using rat embryos and in one laboratory using mouse embryos. Batches of sera, initial developmental stage, duration of culture, and endpoints were identical in the laboratories. The second aim of the study was to evaluate if other variables that could not be standardized would significantly influence the results of the laboratories. No reproducible difference was observed among the culture media or among the laboratories except that growth and differentiation were slower in the laboratory using mouse embryos. Further experiments are needed to exclude small differences in performance of the media.

Animals↗
PubMed1990

Plasminogen activator activity of normal and retinoic acid-treated post-implantation embryos.

Urokinase-type plasminogen activator (uPA) has been implicated in cellular migration accompanying different biological phenomena including organogenesis. An increase in uPA activity was observed in mouse post-implantation embryos during the early organogenesis period. Since we have previously shown that all-trans retinoic acid (RA) prevented the induction of uPA in mouse peritoneal macrophages, we have now assessed whether teratogenic doses of this agent could also interfere with uPA activity in mouse embryo in vitro and in vivo. Post-implantation embryos (8.5 days) were incubated for up to 24 hr with micromolar concentration of RA resulting in the occurrence of malformations. No significant difference in uPA activity was found between control and treated embryos. Likewise, uPA activity was not altered in embryos explanted on day 9.5 from dams treated 24 hr before with a teratogenic dose of RA. This study indicates that the teratogenic activity of RA is not caused by an inhibition of the induction of uPA in embryos.

Abnormalities, Drug-Induced↗
PubMed1987

A new method to express embryotoxic data obtained in vitro on whole murine embryos.

This report proposes to express the effect of drugs in the whole embryo culture system by a new method using an intrinsic reference. Percentages of malformed embryos or other defects in development, expressed as percentages of controls, are plotted against concentrations of the drug expressed as percentages of the concentration inducing 50% embryolethality (ELC50). It is suggested that the slope generated by this method is directly related to the intensity of the in vitro teratogenic potential of the agent and allows an estimation of the specific interference with developmental processes. The method has been applied to data obtained from the literature and pertaining to 22 drugs. The slope generated by these drugs varied widely. The effect of these drugs could be meaningfully compared in spite of the wide range of ELC50 displayed by the drugs. In addition, results obtained for two drugs in different laboratories using different methods and species were in fair agreement when they were compared by using the proposed method. Finally, it is suggested that the method provides an improved means to inquire if there is any relevance of in vitro data to teratological results obtained in vivo.

Animals↗
PubMed1987

Evaluation of the embryotoxic potential of ten chemicals in the whole mouse embryo culture.

Ten widely different chemicals, actinomycin D, mithramycin, podophyllotoxin, vincristine sulfate, triaziquone, chlorambucil, mercaptopurine riboside, methyl-mercaptopurine riboside, dimethylsulfoxide, and L-lysine were tested in the whole mouse embryo culture system. The highest concentration was always the concentration that induced 100% lethality (ELC100). The lowest concentration varied from 1/2 to 1/10 of the ELC100. The chemicals that had the most noxious effect on embryonic growth and differentiation were actinomycin D, triaziquone, and mercaptopurine riboside. Podophyllotoxin, methyl-mercaptopurine riboside, and L-lysine were the less embryotoxic. As a whole, no significant discrepancies were observed between the results and the teratological data obtained from the literature. These observations support the assumption that the whole murine embryo culture system can give valuable information on the teratogenicity of chemicals.

Abnormalities, Drug-Induced↗
PubMed1986

Tumorigenic Xenopus cells express several maternal and early embryonic mRNAs.

Recombinant cDNA libraries were constructed from poly(A)+ RNA isolated from different stages of oogenesis and embryogenesis from the clawed toad Xenopus laevis. Hybridization analyses were used to describe the accumulation of specific RNAs represented by these cDNA clones in oocytes, embryos, adult liver, a cell line derived from Xenopus borealis embryos (Xb693), and a tumorigenic substrain of that cell line (Xb693T). It was found that from 550 cDNA clones analysed, six sequences accumulate to higher titers in poly(A)+ RNA isolated from the tumorigenic cell line compared with the non-tumorigenic cell line. All six sequences were expressed at high levels during oogenesis, and the titers of three of these sequences decreased considerably during oogenesis. DNA sequencing of these three sequences followed by a computer search of protein data banks has identified them as coding for the glycolytic enzyme enolase, the ATP-ADP carrier protein, and a-tubulin.

Animals↗
PubMed1985

A partially histocompatible family of Xenopus borealis.

Reciprocal skin allografts were made between siblings of three successive generations in a family of Xenopus borealis and mutually tolerant animals were mated. In the F3 generation of one subfamily, 92% of the siblings were histocompatible.

Animal Husbandry↗
PubMed1983

An oncogenic cell line inducing transplantable metastasizing adeno-carcinomas in Xenopus borealis.

Three epithelioid cell lines were initiated from stage 35 tadpoles of Xenopus borealis. Cell strain XB693-M1 was obtained by incubation of one of these cell lines in MNNG. The strain is hypotetraploid with a modal chromosome number of 62. It is tumorigenic when 4 X 10(6) cells are injected into hosts belonging to a partially histocompatible family. The tumors are very invasive, metastasizing adenocarcinomas that kill the host within 5 to 38 weeks. The tumor can be propagated in vivo by serial transplantation.

Adenocarcinoma↗