Endodermal Components Research Articles

The effect of retinoic acid on the proportion of insulin cells in the developing chick pancreas.

We assessed the potential role of all-trans-retinoic acid on the developing chick pancreas, specifically with regard to the proportions of insulin cells. The endodermal component of the dorsal pancreatic bud of 5-d-old chick embryos was cultured on Matrigel. Retinoic acid (10(-6) or 10(-5) M) was added to a standard serum-free medium, Ham's F12 containing insulin, transferrin and selenium (F12.ITS). Control grafts were cultured in F12.ITS alone or in F12.ITS with DMSO (the diluent for retinoic acid). After 7 d the explants were retrieved, freeze-dried, vapor-fixed, and embedded in resin. Endocrine cell types were identified by immunocytochemistry. The numbers of insulin cells were expressed as a proportion of the sum of insulin plus glucagon cells. Retinoic acid had a dose-related effect; the proportion of insulin cells in explants treated with the lower dose of retinoic acid (10(-6) M) was more than twice the proportion of insulin cells in explants treated with the higher dose (10(-5) M) of retinoic acid and more than three times that of the control grafts.

OtxExpression during Lamprey Embryogenesis Provides Insights into the Evolution of the Vertebrate Head and Jaw

Agnathan or jawless vertebrates, such as lampreys, occupy a critical phylogenetic position between the gnathostome or jawed vertebrates and the cephalochordates, represented by amphioxus. In order to gain insight into the evolution of the vertebrate head, we have cloned and characterized a homolog of the head-specific geneOtxfrom the lampreyPetromyzon marinus.This lampreyOtxgene is a clear phylogenetic outgroup to both the gnathostomeOtx1andOtx2genes. Like its gnathostome counterparts, lampreyOtxis expressed throughout the presumptive forebrain and midbrain. Together, these results indicate that the divergence ofOtx1andOtx2took place after the gnathostome/agnathan divergence and does not correlate with the origin of the vertebrate brain. Intriguingly,Otxis also expressed in the cephalic neural crest cells as well as mesenchymal and endodermal components of the first pharyngeal arch in lampreys, providing molecular evidence of homology with the gnathostome mandibular arch and insights into the evolution of the gnathostome jaw.

Effects of tri-iodothyronine (T3), insulin, insulin-like growth factor I (IGF-I) and transforming growth factor beta1 (TGFbeta1) on the proportion of insulin cells in cultured embryonic chick pancreas.

With a view to ultimately identifying factors involved in the development of pancreatic insulin cells, we have cultured dorsal pancreatic buds from 5-day chick embryos on a basement membrane matrix (Matrigel) in a serum-free medium supplemented with selected factors. The endodermal components of the buds were freed of almost all the mesenchyme so as to eradicate as much as possible of this source of some such factors. In 7-day cultures, insulin and glucagon cells were demonstrated immunocytochemically; numbers of insulin cells were expressed as a percentage of insulin plus glucagon cell counts. Our standard medium contained insulin. Addition of tri-iodothyronine to this medium did not increase the proportion of insulin cells, but in combination with raised concentrations of glucose and essential amino acids it improved somewhat the marked increase previously recorded for these nutrient conditions. Omission of insulin from the standard medium greatly reduced the proportion of these cells; substitution of insulin by insulin-like growth factor I increased the proportion considerably more than did insulin. To test for an overall effect of growth factors, explants were cultured in standard medium on Matrigel containing reduced amounts of growth factors: the proportion of insulin cells proved to be increased over that reached on normal Matrigel. The suspicion that transforming growth factor beta1, a component of Matrigel, might act to reduce the proportion of insulin cells was tested and found to be correct. It is suggested that the different factors studied here may affect either or both of proliferation and determination in the differentiation pathway of insulin vis-à-vis glucagon cells.

Recurrent immature teratoma: Lack of correlation between serum level and immunohistochemical detection of serum alpha-fetoprotein

We present the clinicopathologic and immunohistochemical features of a pure immature ovarian teratoma that had arisen in a 15-year-old girl. At original diagnosis immature extra ovarian implants were noted (grade 3) accompanied by moderately elevated serum alpha-fetoprotein (AFP) levels. AFP was immunohistochemically demonstrable in immature endodermal elements. The immature neural tissue present was negative for AFP, and no other tumor elements were recognisable. Serum AFP fell post-operatively to within normal limits. Despite five courses of chemotherapy and asymptomatic status, the patient re-presented 15 months after original diagnosis with a massive abdominal and pelvic tumor recurrence with predominantly mature glial tissue, but some persistent immature foci. There was no associated increase in serum AFP at this time. AFP was, however, persistently detectable immunohistochemically in immature endodermal components only. Immature neural elements were no longer identified. Disappearance of immature neural tissue in the tumor recurrence may have been related to chemotherapy. This case demonstrates the lack of correlative ability of serum AFP levels with both clinical behaviour and immunohistochemical demonstration of AFP expression in the tumor recurrence.

Evidence for a thymus-dependent form of tolerance that is not based on elimination or anergy of reactive T cells.

The avian embryo has provided an appropriate model to study the ontogeny of the primary lymphoid organs, thymus and bursa of Fabricius. By using the quail-chick marker system the embryonic origin of the highly intricate cell components which form these organs could be traced back to the initial endodermal, mesodermal and ectodermal germ layers. The timing and dynamics of the incoming and outcoming flows of hemopoietic cells which characterize their lymphopoietic activity could be revealed in both quail and chick embryos. This knowledge served as a basis for an investigation on the role of the epithelial component of the thymus (derived from the pharyngeal endoderm) on tolerance to tissue graft and, by extension, tolerance to self. When this work was undertaken, the prevailing view was that exposure of the developing immune system to foreign antigens in the embryo allows them to be assimilated to self components in the mature animal. In fact, this was found to be true for allogeneic grafts between MHC-distinct chickens, of certain tissues, such as for instance wing tissues. However, in heterospecific transplantations, i.e. when a limb bud was grafted from quail to chick embryos, the chick host acutely rejected the foreign limb soon after birth. In contrast, grafts of the quail thymic epithelial (TE) rudiment resulted in the development of a chimeric thymus in which the foreign epithelial component was not only tolerated but able to induce full tolerance of the grafted wing from the same donor. By monitoring the amount of quail TE implanted we showed in addition that only part of the peripheral T-cell population had to differentiate in the context of the quail epithelial cells to induce tolerance to quail tissues. This pointed to the generation in the thymus of regulatory T cells, coexisting with specific anti-quail reactive T cells, but able to inhibit them from reacting against the quail wing antigenic determinants. A mammalian model was then devised to further study this mechanism of tolerance that we have qualified as "dominant" by opposition to the current model based on either clonal elimination or anergy which can be considered as recessive or passive. Nude mice of MHC type A were grafted with TE of E10 type B embryos. They became reconstituted for T-cell function but tolerant for B skin allografts. Spleen cells from such tolerant animals injected to naive A nude mice reconstituted T cell function in the recipient and transferred the tolerance to B skin grafts. Reducing the number of donor cells resulted in the segregation of the two phenomena. For low numbers the recipients were restored but not tolerant, thus showing the coexistence in the tolerant donor of anti-B reactive T cells together with regulatory cells able to abolish their reactivity against B determinants. Other experiments demonstrated that TE-induced tolerance does not rely on clonal deletion or anergy. This was shown on systems where elimination of cells directed toward superantigens was screened. It turned out that tolerance to skin grafts and superantigen T-cell deletion are unrelated phenomena. These observations strongly suggest that tolerance to self results at least in part from the interplay between cells potentially harmful for self component and others which exert a strong control on their reactivity. The latter cell type depends upon interactions of thymocytes with the endodermal component of the thymus.

Ovarian teratomas in mice lacking the protooncogene c-mos.

Parthenogenesis has been suggested to be tightly coupled with development of ovarian teratomas. Indeed, ovarian tumors developed in c‐mos‐delieicnt female mice, which are characterized by the parthenogenetic activation of oocytes. The tumors appeared at a frequency of 30% between 4 and 8 months of age, and did not develop in younger or older mice. Most of the tumors were benign and consisted of multi‐focal cysts most notably with mature ectodermal components, but also with mesodermal and endodermal components. One among 17 tumors observed consisted of extraembryonic tissues alone, and two bore malignant components with metastasis to peritoneal organs. The results strongly suggest the involvement of c‐mos mutations in human germ cell tumors.

Monoclonal antibodies against human germ cell tumors: usefulness as tumor markers and differentiation markers.

AbstractEstablishment of monoclonal antibodies against human germ cell tumors which detected cell surface antigens, 2A2 and 2G10 (subclass; IgM) are described. Distributions of these antigens in human tumors were studied immunohisto‐chemically. They were expressed on immature endodermal components often seen in yolk sac tumors but not on the other solid tumors in childhood. Regarding their specificities on human germ cell tumor, we have established an ELISA system to detect these antigens from patient's sera. In normal and fetal tissue, on the other hand, they showed quite different distributions. In the kidney, for example, 2A2 and 2G10 were present on collecting tubules and proximal/distal tubules respectively which were already observed in fetal kidney, gestational ages 10 weeks. These results indicate the usefulness of these antibodies as the markers for human germ cell tumors and also for somatic cell differentiation.

Localization of H blood group antigen in ectoblastic derivatives of murine teratocarcinoma.

Ectoblastic derivatives (ectodermal and neuroectodermal components) constitute more than 90% of all structures in the murine teratocarcinoma derived from the PCC4-aza-1 line. This tumor was labeled immunocytochemically with fluoresceinated antibodies to A, B and H blood groups. A and B antigens were always noted to be absent from all structures of the three germ layers. With anti-H, however, embryonic and fetal endodermal components, e.g. alimentary or respiratory duct-like structures, gave positive staining. Mesodermal components, i.e. bone and cartilage structures, fibroblasts and myocytes of mature or embryonal type, were negative. Immature and mature ectodermal components, viz. epidermoid cysts or islets, were always positive. Neuroectodermal components, neuroblastic cysts and differentiated neuronal, glial and ependymal elements were always negative. Ectoblastic and/or neuroectoblastic individual cells or cell clusters, observed in the vicinity of positive differentiating ectodermal and neuroectodermal structures, were positive. Similar cells or clusters were negative when located close to negative neuroectodermal components. The undifferentiated, embryonal carcinoma cells and structures were always negative. These observations are compared to the staining patterns of H antigen in murine embryos and adult mice and in human teratocarcinomas. It is suggested that poorly differentiated, morphologically similar ectoblastic and/or neuroectoblastic structures are positive, if they concern ectodermal components, and negative, if they belong to neuroectodermal components, with the exception of some primary sensory cells that are positive. These last cells are also positive in normal fetal and adult tissues.

Periventricular Metastases of a Primary Intracranial α-Fetoprotein-Producing Germ Cell Tumor

Periventricular subependymal lesions were found on CT scan in a young man with growth failure, diabetes insipidus, mental deterioration, and hypogonadism with delayed puberty. An initial very good response to radiotherapy was followed a few months later by a relapse, presenting as a very large tumor in the base of the frontal lobes. Serum alpha-fetoprotein at the time of the relapse was very elevated suggesting that the tumor was largely composed of an endodermal sinus tumor component, which was confirmed at autopsy. The purpose of this report is to stress the importance of the use of tumor markers in a particular clinical and neuroradiological setting.

Investigation of the fate of 4·5 daypost-coitummouse inner cell mass cells by blastocyst injection

Two distinct patterns of chimaerism were found in conceptuses produced by injecting dissociated 4.5-day inner cell mass cells into genetically dissimilar blastocysts. Pattern 1: donor cells were found in the endoderm layer of the visceral yolk sac, but not in the adjacent mesoderm layer of this organ or in the foetus itself. Pattern 2: donor cells were found in the mesoderm layer of the visceral yolk sac and/or foetus, but never in the yolk-sac endoderm as well. Primitive endoderm cells of donor inner cell masses are responsible for the first pattern and primitive ectoderm cells for the second. These results, together with those of previous studies, suggest that the entire foetus, including its endodermal components, is formed from the primitive ectoderm, and that primitive endoderm forms only extra-embryonic endoderm of the conceptus.

The induction of the primordial germ cells in the urodeles.

Xenoplastic recombinates of animal ectodermal caps with the ventral vegetative yolk mass of blastulae of stage 81/2-83/4 ofA. mexicanum, T. alpestris, T. cristatus carnifex andP. waltlii have demonstrated unambiguously that in the urodeles the primordial germ cells-together with other ventro-caudal mesodermal structures-develop from the animal ectodermal moiety of the blastula under an inductive influence emanating from the ventral vegetative yolk mass. Similar recombinates of3H-labeled and unlabeled ectodermal and endodermal components fully support this conclusion.Recombinates of the ventral vegetative yolk mass with different regions of the animal ectodermal hemisphere show that primordial germ cells can be formed by any region of the animal ectodermal hemisphere, including those regions which in normal development will never form them. The number of primordial germ cells formed differs significantly among the various regions, that of the ventral peripheral region being the highest and that of the central, animal region the lowest. The capacity for primordial germ cell formation shows two increasing gradients, one animal-vegetative and the other dorse-ventral (in the peripheral zone). Although accurate measurements could not be made, there seems to be a relation between the number of primordial germ cells formed and the amount of ventro-caudal mesoderm induced.The experiments, moreover, show that notochord differentiation largely or entirely suppresses primordial germ cell formation. Notochord differentiation shows a similar animalvegetative, but an opposite ventro-dorsal increase in frequency (in the peripheral zone) as compared with the capacity for primordial germ cell formation. The notochord-forming gradient in the peripheral regions is mainly due to the inductive action already exerted by the dorsal vegetative yolk mass in the intact blastula prior to isolation and recombination (see control explants). The ventro-dorsal decline in primordial germ cell formation in the peripheral regions is very probably due only to the inhibition of primordial germ cell formation by notochord differentiation (as an expression of dorsal mesoderm induction). Therefore, in the animal ectodermal moiety of the blastula there exists only an animal-vegetative gradient in mesodermal competence.These results make it very likely that in urodeles the primordial germ cells do not arise from predetermined elements such as those demonstrated in anurans, but develop from common, totipotent animal ectodermal cells. The discrepancy in the mode of origin of the primordial germ cells between anurans and urodeles could be due only to pronounced differences in the time of appearance of the germinal cytoplasm (in anurans during oogenesis, in urodeles possibly during determination of the primordial germ cells within the ventro-caudal mesoderm).The differences in site and mode of origin of the primordial germ cells between urodeles and anurans favor a dual phylogenetic origin of the two groups.

Electron microscopic observations on the morphogenesis of the albino rat lung, with special reference to pulmonary epithelial cells.

AbstractElectron microscopic observations of developing albino rat lung provide further evidence for the endodermal origin of the type I and II pulmonary epithelial cells, and for the mesodermal origin of the interstitial pulmonary cells.Cytoplasmic glycogen increased in the fetal endodermal cells from day 16 to the twentieth day of gestation. Further development revealed a decrease of this substance in the differentiating pulmonary epithelial cells, and a concurrent increase in the mesodermal interstitial pulmonary cells, these being cells formerly characterized by their high lipid content. A continuous basement membrane delineated the mesodermal and endodermal components of the developing rat lung from day 16 to the third postnatal day. Tight junctions between adjacent endodermal epithelial cells were present throughout this same gestational period. Lamellar bodies, which are characteristic of the type II pulmonary epithelial cell, may be found simultaneously with large quantities of cytoplasmic glycogen. This feature is considered characteristic of fetal endodermal components.A definite continuum of ultrastructural changes may be traced from the endodermal, columnar epithelial cells to the definitive type I and II pulmonary epithelial cells. Comparable observations for the mesodermal components reveal a progression leading to mature interstitial pulmonary cells.

The formation of the mesoderm in urodelean amphibians : III. The vegetalizing action of the Li ion.

Strong Li treatment leads to auto-activation of blastula and gastrula ectoderm due to lethal and sublethal cytolysis, resulting in adirect meso- and endodermization of the ectoderm. In contrast, a mild Li treatment-0.04 M LiCl in Holtfreter solution for only two hours-which does not show cytolizing effects, has no or only a weak mesodermizing effect upon blastula ectoderm. However, when the explant contains endoderm as well the same treatment leads to a marked transformation of ectoderm into mesoderm and subsequently into endoderm (vegetalization). Thisindirect action of the Li ion under "physiological" conditions apparently represents an enhancement of the normally occurring mesoderm formation from the ectodermal component of the blastula under the inducing action of the endodermal component and its subsequent transformation into endodermal structures, probably due to a rise in competence. The question is raised in how far the direct meso-and endodermization of gastrula ectoderm by heterogeneous inductors is open to the same criticsm as in the case of auto-activation of the ectoderm by a strong Li treatment. Finally, the experiments of Ave, Kawakami and Sameshima (1968) are briefly discussed.

Shell gland formation in the Ilyanassa embryo

The topography of the shell gland in relation to endodermal components in the Ilyanassa embryo has been described. It was concluded that the development of the archenteron, the position of the 4D macromere, or the proliferation of the enteroblasts does not influence shell gland formation in the Ilyanassa embryo. The RNA content of the cells of the shell gland was briefly discussed.

THE HISTOLOGY OF THE BLOOD SYSTEM IN OLIGOCHAETA and POLYCHAETA

THE HISTOLOGY OF THE BLOOD SYSTEM IN OLIGOCHAETA and POLYCHAETA

THE EFFECTS OF LITHIUM CHLORIDE ON THE FERTILIZED EGGS OF NEREIS LIMBATA

1. The fertilized eggs of Nereis limbata were treated with mixtures of sea water and a 0.54 M stock solution of LiCl, ranging from 2 per cent to 100 per cent for periods of 15 minutes to 36 hours. Treatment was begun 75 minutes after insemination of the eggs, shortly before the appearance of the first cleavage.2. No exogastrulae were observed. There were a few cases of marked abnormalities in the endodermal components of the trochophores within a very narrow range of treatment (15 per cent for 6, 8 and 10 hours).3. The main abnormalities observed in the experimental larvae were: Absence of the apical tuft, lengthening of the prototrochal cilia, absence of these cilia in varying degrees, abnormalities in the anal and prototrochal pigments, absence or abnormality of the eye spots, deficiencies in the number of prototrochal cells, atypical seta sacs, abnormalities in the number and position of oil droplets. The degree of abnormality in these cases seemed to be roughly proportional to the severity of treatment.