Biosynthesis of ascorbic acid in chick embryos

Summary Biosynthesis of ascorbic acid was found in the kidneys (mesonephros and metanephros) of the chick embryo as well as in the yolk sac membrane. The activity of L-gulonolactone oxidase in the yolk sac membrane suggested that it was the major source of ascorbic acid in the chick embryo.I am grateful to Dr R. Jenness (Univ. of Minnesota) for the generous gift of L-gulonolactone and to Dr B. Sanders (Univ. of Texas) for the chick embryo samples     

Lymphocytes, but not cancer cells are able to penetrate into the rat embryo yolk sac wall

Normal rat lymphocytes and cells of 2 highly invasive tumors, the L5222 rat leukemia and the VW rabbit carcinoma, were inoculated in vitro on the mesothelial surface of the visceral wall of the rat embryo yolk sac. After 48 h, lymphocytes, without any damage being inflicted on the mesothelial cells, had penetrated deeply into the yolk sac wall, whereas both kinds of cancer cells had destroyed the mesothelial cells, but not advanced beyond the basal lamina.     

Lymphocytes,but not cancer cells are able to penetrate into the rat embryo yolk sac wall

Summary Normal rat lymphocytes and cells of 2 highly invasive tumors, the L5222 rat leukemia and the V2 rabbit carcinoma, were inoculated in vitro on the mesothelial surface of the visceral wall of the rat embryo yolk sac. After 48 h, lymphocytes, without any damage being inflicted on the mesothelial cells, had penetrated deeply into the yolk sac wall, whereas both kinds of cancer cells had destroyed the mesothelial cells, but not advanced beyond the basal lamina.     

Effect of different methods of exposure to cyproterone acetate on mortality in chick embryos

Summary 33-h chick embryos exposed to 0.25 mg or 0.50 mg cyproterone acetate injected into the yolk sac showed a significantly lower mortality rate than embryos receiving the same dosage applied directly onto the developing blastodisc.This work was supported by a Government Research Support Grant awarded to Louisiana State University School of Medicine. Cyproterone acetate supplied through courtesy of Schering AG, Berlin, West Germany.     

Receptor-mediated transport and deposition of complement component C3 into developing chicken oocytes

Immunological resistance of the chick embryo is dependent upon IgG present in the yolk of the layed egg. Here we show that complement factor 3 (C3), a key component of the humoral complement system, is a yolk component of chicken eggs. C3 is transported into oocytes by LR8-mediated endocytosis. LR8 also binds and transports other major yolk components such as vitellogenin, very-low-density lipoprotein, and α₂-macroglobulin. Expression studies of LR8 during chicken development and oocyte maturation, in combination with studies on the uptake of individual yolk components, suggest the following model for oocyte maturation in the chicken: all oocytes present in the ovary contain high levels of LR8 mRNA and protein long before the onset of oocyte maturation. Selected oocytes gain access to yolk precursors, and LR8 binds, internalizes, and deposits the major yolk components in the ratio of their relative abundance in the accessible pool.Received 9 May 2005; received after revision 6 June 2005; accepted 13 June 2005     

Effect of ascorbic acid on pigmentation of toad (Bufo melanostictus).

Administration of ascorbic acid in toad during breeding season results an increase in melanin pigments in skin, liver and vocal sac.     

Utilization of ascorbic acid during post-embryonic development of chick skeletal muscle.

Ascorbic acid is utilized during the post-embryonic differentiation of skeletal muscle fibres in chick. While the fibres lose their heterogeneity with regard to ascorbic acid, they continue to exhibit differences in their metabolic rates in terms of the succinate dehydrogenase activity throughout life.     

Latent differentiation in the endoderm of the young chick embryo]

Initiation and localization of the capacity of self-differentiation in the 1-2 day old chick embryo were studied by means of culturing endoderm fragments, wrapped in a piece of viteline membrane and completely deprived of mesenchyme.     

Effect of ascorbic acid on pigmentation of toad (Bufo melanostictus)

Summary Administration of ascorbic acid in toad during breeding season results an increase in melanin pigments in skin, liver and vocal sac.Acknowledgment. The authors' thanks are due to Prof.C. Deb, Head of the Department of Physiology, Calcutta University, for encouragements.     

Method for long term delivery of soluble agents to the chick chorioallantoic membrane

Summary Osmotic minipumps were used to administer thyroxine to the chick embryo. This technique proved to be a convenient and efficacious method for the delivery of soluble agents to the chorioallantoic membrane. The thyroxine induced the precocious appearance of extensive cell sloughing by the corneal epithelium.     

Epitheliophagy: intrauterine cell nourishment in the viviparous alpine salamander, Salamandra atra (Laur.)

The intrauterine nourishment of the viviparous alpine salamander, Salamandra atra, has been demonstrated to consist of two phases: oophagy - after hatching from the jelly membrane, the developing embryo ingests the remaining disintegrated, unfertilized egg mass. Epitheliophagy - a special cranial portion of the uterus wall, the zona trophica, is stimulated by the presence of the embryo. After the yolk mass has been exhausted, the developing embryo is supplied with epithelial cells as nourishment until the end of pregnancy. The epithelial cells of the zona trophica are released into the uterus lumen by partial necrosis of the underlying connective tissue. Regeneration and detachment of the uterine epithelium occur simultaneously in different regions of the zona trophica. A special dentition enables the embryo, according to its position in the uterus, to feed directly on the zona trophica.     

Utilization of ascorbic acid during post-embryonic development of chick skeletal muscle

Summary Ascorbic acid is utilized during the post-embryonic differentiation of skeletal muscle fibres in chick. While the fibres lose their heterogeneity with regard to ascorbic acid, they continue to exhibit differences in their metabolic rates in terms of the succinate dehydrogenase activity throughout life.The investigations were carried out at the Department of Zoology, Panjab University, Chandigarh. We thank ProfessorG. P. Sharma, Head of the Department, for providing the necessary loboratory facilities.     

Morphofunctional changes in the mitochondrial subpopulations of conceptus tissues during the placentation process

To establish the role of mitochondrial subpopulations in the mitochondrial maturation process, we studied morphological and functional changes in the mitochondria of different mammalian conceptus tissues during the organogenic and the placentation processes. Mitochondrial subpopulations of three different conceptus tissues, embryo and visceral yolk sac placenta on gestational days 11, 12 and 13 and placenta on days 12 and 13, were examined morphologically by transmission electron microscopy. Cytochrome oxidase activity and protein levels were also measured in each mitochondrial subpopulation. The results indicate two different mitochondrial subpopulation profiles: a homogeneous one, which corresponds to immature mitochondria, and a heterogeneous one, which represents the mature mitochondria. The three tissues studied show different morphologic and metabolic patterns of mitochondrial maturation during the placentation process, rendering them suitable as experimental models to establish the p ossible relationship between mitochondrial maturation and the mitochondrial subpopulations. Received 5 August 2002; received after revision 23 September 2002; accepted 8 October 2002 RID="*" ID="*"Corresponding author.     

Side effects of Ricinus lectin (RCA 120) on nucleic acid synthesis in chick embryo fibroblasts

When fibroblasts from chick embryos were treated with Ricinus lectin, the effects observed depended on the stage of development of the embryo from which the cells were prepared. Thus, in 16-day fibroblasts, which have a weak proliferative capacity, nucleic acid synthesis was less sensitive to the effect of this lectin than that in 8-day fibroblasts, whose proliferative capacity is high.     

Deconvoluting the ontogeny of hematopoietic stem cells

Two different models describe the development of definitive hematopoiesis and hematopoietic stem cells (HSCs). In one of these, the visceral yolk sac serves as a starting point of relatively lengthy developmental process culminating in the fetal liver hematopoiesis. In another, the origin of adult hematopoiesis is split between the yolk sac and the dorsal aorta, which has a peculiar capacity to generate definitive HSCs. Despite a large amount of experimental data consistent with the latter view, it becomes increasingly unsustainable in the light of recent cell tracing studies. Moreover, analysis of the published studies supporting the aorta-centered version uncovers significant caveats in standard experimental approach and argumentation. As a result, the theory cannot offer feasible cellular mechanisms of the HSC emergence. This review summarizes key efforts to discern the developmental pathway of the adult-type HSCs and attempts to put forward a hypothesis on the inflammatory mechanisms of hematopoietic ontogenesis.     

Methods of experimental yolk removal fromBrachydanio rerio eggs

Summary The yolk ofBrachydanio rerio eggs was removed by pipettation, bursting and cutting off with a scalpel. The total yolk removal before the 8-cell stage led to a germ with irregular groups of cells, at the 8-cell stage to a topologically irregular differentiation, at the 64-cell stage to a nearly normal embryo, which is not viable.     

The localization of acetylcholinesterase in the optic lobe in the developing chick embryo

Summary The localization of acetylcholinesterase (AChE) in the optic lobe in the developing chick embryo was studied histochemically and biochemically. The histochemical reaction of AChE increased remarkably between stage 42 and 44 especially in the neuropile. The increase of the biochemical activity of the AChE in the synaptic membrane fraction occurred at a later stage than that in the microsomal fraction. These findings can be interpreted as the result of axonal transport of the enzyme from the synthetic to the synaptic site.Acknowledgments. The authors wish to thank Prof. Yasuharu Kuwahara, Cataract Research Institute, for the use of his cryostat and other laboratory facilities, Dr. Koji Kami, Department of Anatomy, Keio University School of Medicine, for his valuable advice regarding histochemistry.     

Cell death and phagocytosis in the neuroepithelium of the developing retina. A TEM and SEM study.

Phagocytosis by neuroepithelial cells independent of the presence of pseudopodes is observed as the main mechanism of elimination of physiologically degenerating cells during the early development of the retina in the chick embryo.     

Acetylcholine receptors in the gastrulating chick embryo

Summary Muscarinic acetylcholine receptors are present in the gastrulating chick embryo.     

Development of oxidative metabolism in the non-innervated optic lobe of the chick.

Early removal of the optic cup of the chick embryo prevents innervation of the contralateral optic lobe. This reduces the rate of development od citrate synthetase. The posthatch increase of the level of this enzyme related to oxidative metabolism is not impaired by denervation of the chick optic lobe.