Differentiating abilities of avian somatopleural mesoderm

Summary Quail-to-chick grafting experiments were performed on 2-day embryos in order to test the differentiating abilities of the somatopleure. After orthotopic and heterotopic transplantations of different parts of quail somatopleural mesoderm into chick embryos it is demonstrated that avian somatopleural cells differentiate into skeletal elements, smooth muscles, tendons and connective tissues. However, skeletal muscle fibres do not originate from somatopleural cells.Supported by a grant from the Deutsche Forschungsgemeinschaft (Ch 44/3).     

Electron microscopic study of the penetration and distribution of somitic cells in the mesoblast of the limb buds of reptiles (Anguis fragilis and Lacerta viridis)]

Based on characteristics of mitochondria and on the amount of lipid inclusions, a distinction between somitic cells and mesoblastic somatopleural cells is possible, at the early stages of the development of the limb bud in Reptiles (Anguis fragilis and Lacerta viridis). The dislocation of the ventral processes of the somites and the localisation of the somitic cells in the mesoblast of the anterior limb buds could be studied.     

The inhibitory effect of D-glucosamine on thymidine kinase in chick embryo retinas and HeLa cells

Summary D-Glucosamine markedly inhibits thymidine incorporation into the TCA-insoluble fraction and thymidine kinase activity in HeLa cells. Both the inhibitory effects are also observed in isolated retinas of chick embryos. In this case the inhibitory effects are age-dependent and the magnitude of the responses decreases with embryonic development. In addition the time of exposure to D-glucosamine which is necessary to reveal the inhibitory effect on thymidine kinase increases with the age of the embryos.     

The inhibitory effect of D-glucosamine on thymidine kinase in chick embryo retinas and HeLa cells

D-Glucosamine markedly inhibits thymidine incorporation into the TCA-insoluble fraction and thymidine kinase activity in HeLa cells. Both the inhibitory effects are also observed in isolated retinas of chick embryos. In this case the inhibitory effects are age-dependent and the magnitude of the responses decreases with embryonic development. In addition the time of exposure to D-glucosamine which is necessary to reveal the inhibitory effect on thymidine kinase increases with the age of the embryos.     

Permeable embryonic cells of sea urchins as a model for studying nucleus-cytoplasm interactions

Sea urchin embryonic cells were made permeable by treating them with glycerol solution for the purpose of exchanging cytoplasmic components. When proteoglycans prepared from embryos of advanced stages of development permeated into these glycerinated cells, these substances accumulated rapidly in the nucleus, being bound with chromatin.     

Scanning electron microscopy of cells from hydroxyurea-arrested blastulae ofXenopus laevis

Summary Cells fromXenopus embryos blocked at the blastula stage by treatment with hydroxyurea have been isolated and cultured in vitro. The morphology of these cells has been compared with that of cells from normal embryos using scanning electron microscopy. Cells from such hydroxyurea-blocked embryos do not show the features, or changes in features, in culture shown by cells from normal embryos.Acknowledgments. We wish to thank Mr C. Veltkamp for his help with the electron microscopy, and Mrs J. Clumpus for technical assistance.     

Lipid peroxidation caused by chinoform-ferric chelate in cultured neural retinal cells

Incorporation of chinoform-ferric chelate was demonstrable in cultured neural retinal cells of chick embryos after 1 h of incubation, and the lipid peroxide level in the cells was increased strikingly 1 h thereafter. On the other hand, free ferric ions were scarcely incorporated into the cells, and a significant increase in the lipid peroxide level in the cells was not observed. These data indicate that chinoform is carrier of iron for its passage through cell membranes and that the incorporated iron induces lipid peroxidation which in turn leads to neural cell degeneration.     

Mouse egg cylinders developed in vitro may form benign and malignant teratoid tumors

Summary Egg cylinders developed in vitro from explanted mouse blastocysts were transplanted under the kidney capsules of adult mice to assess their developmental potential. In vitro grown egg cylinders are capable of differentiation into somatic tissues and may give rise to stem cells of teratocarcinoma like the developmentally equivalent 7 day mouse embryos grown in vivo.     

The maternal protection reaction against a mother's rejection of her own larva in Salamandra salamandra L]

In vitro experiments have shown that maternal spleen cells from Salamandra salamandra are cytotoxic to cells from their embryos. This reaction can be inhibited by maternal serum. In this paper, we show that maternal serum protection acts through two effects: by inactivating spleen cells and by protecting embryonic cells. The more numerous the embryos are in a female, the stronger the protection is. The effect of the maternal serum does not appear to be individual specific.     

The effect of 5-bromodeoxyuridine on mouse embryos during neurulation in vitro

Mouse embryos explanted at various stages during neurulation were cultured for 20-28 h in the presence of 25-900 micrograms/ml of 5-bromodeoxyuridine (BUdR). BUdR strongly inhibited closure of the cranial neural tube, which was found to be stage-dependent. When mouse embryos were exposed to BUdR after development of the concave curvature in the neuroepithelium of the midbrain to the upper hindbrain regions, they became insensitive to the drug-induced open cranial neural tube. Histological observations showed that BUdR interfered with interkinetic migration and cytokinesis of the neuroepithelial cells. These cellular abnormalities were not dependent on the morphological development of the cranial neural folds. The 3H-BUdR experiment confirmed that the label was mostly incorporated into the DNA fraction.     

Lipid peroxidation caused by chinoform-ferric chelate in cultured neural retinal cells

Summary Incorporation of chinoform-ferric chelate was demonstrable in cultured neural retinal cells of chick embryos after 1 h of incubation, and the lipid peroxide level in the cells was increased strikingly 1 h thereafter. On the other hand, free ferric ions were scarcely incorporated into the cells, and a significant increase in the lipid peroxide level in the cells was not observed. These data indicate that chinoform is carrier of iron for its passage through cell membranes and that the incorporated iron induces lipid peroxidation which in turn leads to neural cell degeneration.This work was supported in part by a grant from the Ministry of Health and Welfare of Japan     

A comparative study of the differentiation of dissociated nerve cells under different culture conditions.

In vitro differentiation of chick embryo brain cells was compared under several culture conditions. Morphological observations and acetylcholinesterase histochemical staining revealed that the development was similar in all conditions tested if cells have been derived from 7 days embryos. Considering the cultures from 11 days embryos, the cell dissociation by trypsin and the plastic surface proved to be the most favourable conditions in contrast to mechanical dissection and collagen surface.     

Germ cell colonization of gonads in experimental quail twin embryos (Coturnix coturnix japonica)]

At the same development stage, two Quail twin embryos from right and left halves of a blastoderm contain together as many germ cells as a normal embryol. These are asymmetricaly distributed between the twins as between the right and left genital ridges of control embryos.     

Enzymatic activities of muscle fibres differentiated,in vitro,from pectoralis major (white) and adductor magnus (red) muscles of chick embryos

Summary Specific activities of NADP isocitrate dehydrogenase and acetylcholinesterase were significantly higher in muscle fibres differentiated, in vitro, from myoblasts of adductor magnus (red) than pectoralis major (white) muscles 10-day-old chick embryos. This is evidence, as far as enzyme activities, are concerned, that myoblasts from different types of skeletal muscles are able to give, in tissue culture, muscle fibres of different properties, even in the absence of nerve supply.Supported by a grant No. 75 7 1641 from the French Délégation à la Recherche scientifique et technique.     

Role of grafted Schwann cells in the regeneration of intraspinal nerve fibers when peripheral nerve, skeletal muscle or submandibular gland fragments are transplanted into the spinal cord of the mouse

Small pieces of peripheral nerve, skeletal muscle or submandibular gland, taken from young or new-born mice, were grafted into the non-transected spinal cord of young albino mice, at the thoracic level, through a punctiform meningeal opening. Neighbouring intraspinal nerve fibres, severed during the grafting process, regenerate into and eventually throughout the transplants. In this regenerative process, sedentary or migrating Schwann cells of the transplants probably have a prominent influence in guiding the growth of the axonal sprouts they ensheathe and eventually myelinate.     

Fate choice of post-natal mesoderm progenitors: skeletal versus cardiac muscle plasticity

Regenerative medicine for skeletal and cardiac muscles still constitutes a fascinating and ambitious frontier. In this perspective, understanding the possibilities of intrinsic cell plasticity, present in post-natal muscles, is vital to define and improve novel therapeutic strategies for acute and chronic diseases. In addition, many somatic stem cells are now crossing the boundaries of basic/translational research to enter the first clinical trials. However, it is still an open question whether a lineage switch between skeletal and cardiac adult myogenesis is possible. Therefore, this review focuses on resident somatic stem cells of post-natal skeletal and cardiac muscles and their plastic potential toward the two lineages. Furthermore, examples of myogenic lineage switch in adult stem cells are also reported and discussed.     

Development of rhythmic melatonin synthesis in cultured pineal glands and pineal cells isolated from chick embryo

The chick pineal gland exhibits circadian rhythms in melatonin synthesis under in vivo and in vitro conditions. A daily rhythm of melatonin production was first detectable in pineal glands isolated from chick embryos at embryonic day 16 and incubated under a LD cycle. All pineal glands isolated from 17-day-old and older embryos were rhythmic while no gland isolated at embryonic day 14 and 15 exhibited a daily rhythm in melatonin synthesis. Melatonin production in static cultures of embryonic pineal cells was rhythmic over 48 h if the cells were kept under a LD cycle. When embryonic pineal cells were incubated in constant darkness the rhythm in melatonin production was damped within 48 h. These results suggest that chick pineal cells from embryonic day 16 onwards are photosensitive but that the endogenous component of the melatonin rhythm is not completely developed at that age. A soluble analogue of cAMP stimulated and norepinephrine inhibited melatonin synthesis in cultured embryonic pineal cells. These findings indicate that the stimulatory and inhibitory pathways controlling melatonin synthesis in the mature pineal gland are effective in pineal cells isolated from chick embryos at least 2 days before hatching.     

A comparative study of the differentiation of dissociated nerve cells under different culture conditions

Summary In vitro differentiation of chick embryo brain cells was compared under several culture conditions. Morphological observations and acetylcholinesterase histochemical staining revealed that the development was similar in all conditions tested if cells have been derived from 7 days embryos. Considering the cultures from 11 days embryos, the cell dissociation by trypsin and the plastic surface proved to be the most favourable conditions in contrast to mechanical dissection and collagen surface.M. Sensenbrenner is Maitre de Recherche au CNRS.     

Pleiotropic effects of sphingolipids in skeletal muscle

Studies of the last two decades have demonstrated that sphingolipids are important signalling molecules exerting key roles in the control of fundamental biological processes including proliferation, differentiation, motility and survival. Here we review the role of bioactive sphingolipids such as ceramide, sphingosine, sphingosine 1-phosphate, ganglioside GM3, in the regulation of skeletal muscle biology. The emerging picture is in favour of a complex role of these molecules, which appear implicated in the activation of muscle resident stem cells, their proliferation and differentiation, finalized at skeletal muscle regeneration. Moreover, they are involved in the regulation of contractile properties, tissue responsiveness to insulin and muscle fiber trophism. Hopefully, this article will provide a framework for future investigation into the field, aimed at establishing whether altered sphingolipid metabolism is implicated in the onset of skeletal muscle diseases and identifying new pharmacological targets for the therapy of multiple illnesses, including muscular dystrophies and diabetes. Received 30 April 2008; received after revision 19 June 2008; accepted 14 July 2008     

Ventral neural tube cells differentiate into hepatocytes in the chick embryo

A population of ventral neural tube cells has recently been shown to migrate out of the hind brain neural tube via the vagus nerve and contribute to the developing gastrointestinal tract. Since liver is also innervated by the vagus nerve, we sought to determine if these cells also migrate into the liver. Ventral neural tube cells in the caudal hindbrain of chick embryos were tagged with a replication-deficient retroviral vector containing the LacZ gene on embryonic day 2. Embryos were processed for detection of labeled cells on embryonic day 5 and 11. Labeled cells were seen in the liver on both days and identified as hepatocytes. Previously, it was believed that all hepatocytes develop from the gut endoderm. Results of the present study show an additional source for the formation of liver cells. Received 25 August 1998; received after revision 5 November 1998; accepted 5 November 1998