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At least 793 records · Page 44Linked to original sources
PubMed1998

Blastoderm structure, cell migration and formation of the embryonic shield during gastrulation in the carp (Cyprinus Carpio); a scanning electron microscopic study.

This paper describes an ultrastructural study of the cell movements during the gastrulation of the common carp, Cyprinus carpio, using scanning electron microscopy. The morphology of the deep cells was studied in several consecutive stages ranging from 0-100% epiboly. Furthermore, the formation of the embryonic shield was followed from its earliest appearance at 50% epiboly onwards. This paper gives morphological evidence for the existence of two different pathways for involving and convergent movements. Firstly, cells may move along the inner surface of the not (yet) involuted cells. Secondly, a much smaller group may use the YSL as their substrate. These results are discussed in the light of the hypothesis that the two migrating cell populations may be differently induced, subsequently leading to the formation of mesoderm and endoderm.

Animals↗
PubMed2001

Stage- and tissue-specific expression of a beta-1,4-galactosyltransferase in the embryonic epidermis.

Changes in oligosaccharide structures of glycoconjugates have been observed, and are postulated to have key roles in embryonic development and differentiation. N-Acetylglucosamine (GlcNAc) beta-1,4-galactosyltransferase (beta4GalT) AKI showed different expression patterns in time and space, and different enzymatic activity from the other known family members. The epidermis of mouse embryo included a high level of AKI activities, which transferred galactose (Gal) to endogenous glycoprotein (molecular weight 130 kDa) (GP130). The maximum activity was for 13.5-d postcoitum embryos. Specific antibody against AKI inhibited 81% of GlcNAc betaGalT activities, which indicates that AKI represents the major part of the embryonic epidermis enzymes. AKI shows 2.2 times higher galactosyltransferase activity toward Gal-acceptor glucose with alpha-lactalbumin (alpha-LA) than toward GlcNAc without alpha-LA. AKI is also expressed in mouse melanoma and leukemia cell lines and in human basal cell carcinoma specimens. The GP130 Gal acceptor once galactosylated by AKI may be directly involved in epidermal differentiation and oncogenesis.

Aged↗
PubMed1975

[Embryonal rhabdomyosarcoma of the larynx in a 63 year-old man].

A case of embryonal rabromyosarcoma localized in the larynx in the region of the left vocal bands in an elderly man is described, the tumour represented a hardly discernable delimited greyish-pinkish node with 1 cm diametre. Microscopic investigation of the tumour revealed the structure typical of embryonal rabromyosarcoma. The patient died two days after laryngectomy of thromboembolism of the pulmonary artery. At autopsy no metastases were observed. The peculiar features of the case are an extremely rare localization of embryonal rabromyosarcoma and advanced age of the patient.

Age Factors↗
PubMed1997

[The structural organization of suspension grafts of human embryonic midbrain in the rat brain].

Dynamics of survival, differentiation and migration of human fetal cells after their transplantation into the rat brain without immunosuppression was studied using routine histology, electron microscopy and immunocytochemistry. A cell suspension prepared from the ventral mesencephalon of human embryos 7-8 weeks of gestation was injected into the striatum of rats-recipients. The graft development depends on the intensity of immune reaction. Under a weak reaction, the viability and differentiation of human embryo cells in the rat brain were observed within the three months of the experiment. The grafted cells conserve their mediator specificity, some of them being seen to migrate into the host (rat) tissue beyond the graft. In the transplant neuropil various types of cell contacts were observed, including synapses. The described method makes its possible to study the human nervous tissue histogenesis in an abnormal environment.

Animals↗
PubMed1998

[Structure of long-term transplants of embryonal anlages of the rat central nervous system].

Morphological investigation of transplants of the rat 14-15 d embryonal neocortical and spinal anlages after long term transplantation into the adult animal sciatic nerve was conducted. Transplants were shown to retain viability on 19th month postoperatively, with the part of neurons demonstrating dystrophic changes and death. Neocortical neurons were shown to preserve higher viability in sciatic transplants. Increase in number of neurons showing irreversible changes correlates well with the development of degenerative changes in blood vessels, their calcification and formation of psammoma-like bodies.

Animals↗
PubMed1990

Embryonic and neonatal development of the vomeronasal and olfactory systems in garter snakes (Thamnophis spp.).

Newborn, unfed garter snakes (Thamnophis spp.) respond preferentially to aqueous extracts of natural prey items, and these responses are mediated by the vomeronasal system (VNS). Since the VNS, and possibly the olfactory system (OS), are functional at birth, we examined the ontogeny of VNS and OS structures in four embryonic stages and two postnatal ages in garter snakes. The results of this study show 1) significant changes in thickness of the receptor epithelia for both systems; 2) temporal differences in the innervation of the telencephalon for each system; and 3) concurrent development of primary and secondary projection sites in both systems. Possible interactions between different cell populations and their significance for morphogenesis are discussed.

Animals↗
PubMed1988

Structure of myofibrils at extra-junctional membrane attachment sites in cultured cardiac muscle cells.

The composition and organization of myofibrils at extra-junctional membrane attachment sites in cultured neonatal rat cardiac muscle cells were analysed by immunofluorescence and electron microscopy. When myofibril terminals attached to the cell membrane via focal contacts at regions of the sarcolemma that lacked intercalated discs, they appeared to be non-striated and resembled thick actin cables. Although the non-striated terminals contained actin, myosin and alpha-actinin, the proteins were not organized into recognizable sarcomeres at the light microscopic level. Analysis of the structure of the terminals in the electron microscope confirmed that the usual sarcomeric organization and attachments to the sarcolemma were markedly modified. The non-striated myofibril terminals differed in structure from both stress fibres in non-muscle cells and stress fibre-like structures present in embryonic heart cells in culture. Non-striated myofibril terminals attached to the cell membrane by lateral contact with extra-junctional electron-dense membrane plaques rather than by insertion by their ends into the fascia adherens. It is proposed that the structure and composition of membrane-attachment points for myofibrils may have an influence on the structure, organization or stability of contractile elements in cardiac muscle.

Animals↗
PubMed2001

Human embryonic stem cells can differentiate into myocytes with structural and functional properties of cardiomyocytes.

The study of human cardiac tissue development is hampered by the lack of a suitable in vitro model. We describe the phenotypic properties of cardiomyocytes derived from human embryonic stem (ES) cells. Human ES cells were cultivated in suspension and plated to form aggregates termed embryoid bodies (EBs). Spontaneously contracting areas appeared in 8.1% of the EBs. Cells from the spontaneously contracting areas within EBs were stained positively with anti-cardiac myosin heavy chain, anti--alpha-actinin, anti-desmin, anti--cardiac troponin I (anti-cTnI), and anti-ANP antibodies. Electron microscopy revealed varying degrees of myofibrillar organization, consistent with early-stage cardiomyocytes. RT-PCR studies demonstrated the expression of several cardiac-specific genes and transcription factors. Extracellular electrograms were characterized by a sharp component lasting 30 +/- 25 milliseconds, followed by a slow component of 347 +/- 120 milliseconds. Intracellular Ca(2+) transients displayed a sharp rise lasting 130 +/- 27 milliseconds and a relaxation component lasting 200--300 milliseconds. Positive and negative chronotropic effects were induced by application of isoproterenol and carbamylcholine, respectively. In conclusion, the human ES cell--derived cardiomyocytes displayed structural and functional properties of early-stage cardiomyocytes. Establishment of this unique differentiation system may have significant impact on the study of early human cardiac differentiation, functional genomics, pharmacological testing, cell therapy, and tissue engineering.

Actinin↗
PubMed1991

Incorporation of 3H-thymidine in telencephalic structures of the vomeronasal and olfactory systems of embryonic garter snakes.

Previous studies have shown that the vomeronasal and, possibly, olfactory systems are functional in newborn garter snakes. However, little is known about neurogenesis in these chemosensory pathways. In the companion paper, we describe the embryonic growth of the sensory epithelia for both the vomeronasal and olfactory systems. In the present study, we examine neurogenesis in the telencephalic structures of these chemosensory systems by using 3H-thymidine autoradiography (ARG). The majority of neurogenesis appears to occur before birth in the accessory and main olfactory bulbs and their principal projection sites, the nucleus sphericus and lateral cortex, respectively. The data suggest that some postnatal neurogenesis may occur in the accessory and main olfactory bulbs and in the nucleus sphericus. Although the neuronal constituents of the accessory and main olfactory bulbs appear to mature concurrently, those of the lateral cortex appear to mature before those of the nucleus sphericus. Along with previous findings, this latter result supports the hypothesis that the olfactory system develops before the vomeronasal system in garter snakes. There appears to be a rostral to caudal gradient of neurogenesis within the mural layer of the nucleus sphericus. However, an "outside to inside" gradient of neurogenesis was not observed in the mantle layer of the lateral cortex, as described for other reptiles. Similarities and differences observed by other investigators in other reptilian species and mammals are discussed.

Animals↗
PubMed1983

Structure of the egg funiculus and deposition of embryonic envelopes in a crab.

The newly laid egg of Carcinus maenas is attached to a maternal ovigerous seta by a funiculus which consists of the two superimposed vitelline envelopes 1a + 1b, highly stretched and concurrently showing important structural alterations. The funiculus is glued to the specialized seta merely owing to the strong adhesiveness of its external face comprising the outermost vitelline envelope 1a, without any added adhesive. The subjacent envelope 2, originated from the cortical reaction, is not involved in such a funiculus elaboration. In the course of the embryonic development, four new coatings are successively secreted from the ectodermal embryonic cells, underneath the (1a + 1b + 2) fertilization envelope or embryonic capsule. They will remain until hatching in this concentric order, thus giving evidence of successive embryonic moulting cycles, with apolysis but without exuviation. In addition, the successive secretory phases, regarding to the embryonic envelope elaborations, happen in presence of high concentrations of the ecdysteroid ponasterone A which might be involved consequently in such secretory processes.

Animals↗
PubMed2002

Endothelial cells derived from human embryonic stem cells.

Human embryonic stem cells have the potential to differentiate into various cell types and, thus, may be useful as a source of cells for transplantation or tissue engineering. We describe here the differentiation steps of human embryonic stem cells into endothelial cells forming vascular-like structures. The human embryonic-derived endothelial cells were isolated by using platelet endothelial cell-adhesion molecule-1 (PECAM1) antibodies, their behavior was characterized in vitro and in vivo, and their potential in tissue engineering was examined. We show that the isolated embryonic PECAM1+ cells, grown in culture, display characteristics similar to vessel endothelium. The cells express endothelial cell markers in a pattern similar to human umbilical vein endothelial cells, their junctions are correctly organized, and they have high metabolism of acetylated low-density lipoprotein. In addition, the cells are able to differentiate and form tube-like structures when cultured on matrigel. In vivo, when transplanted into SCID mice, the cells appeared to form microvessels containing mouse blood cells. With further studies, these cells could provide a source of human endothelial cells that could be beneficial for potential applications such as engineering new blood vessels, endothelial cell transplantation into the heart for myocardial regeneration, and induction of angiogenesis for treatment of regional ischemia.

Cell Differentiation↗
PubMedDate not supplied

Congenital hemangioma with milialike structures: a case report.

A 4-month-old infant had two 3 cm x 4 cm hemangiomatous lesions on the scalp and back, present since birth, which contained peculiar white-yellowish small nodules. Histologically the lesions proved to have a hemangiomatous (capillary-type) component together with small keratin-containing epidermal cysts (milia-like) which progressively extruded their contents. The lesions also contained embryonic-like hair structures. The hemangiomas resolved spontaneously. We were unable to find any reference in the literature describing this peculiar combination of features.

Back↗
PubMed1999

Functional analysis of chromatin assembled in synthetic nuclei.

Numerous regulatory mechanisms contribute to the control of eukaryotic transcription. These controls are manifested through higher-order protein-DNA structure within the nucleus. In vitro assays have proven extremely useful in deciphering the potential regulatory roles of chromatin and nuclear structure in transcription. Embryonic egg extracts of Xenopus with their vast maternal stores and rapid cell-cycle oscillations can be exploited to recapitulate multiple layers of nuclear regulation. Incubation of cloned DNA templates in Xenopus egg extracts promotes a self-ordered assembly of physiologically spaced nucleosomes and synthetic nuclei structure formation. Interaction of membrane vesicles with chromatin leads to formation of a bilayer nuclear envelope encapsulating the DNA. These synthetic nuclei are functional organelles capable of active protein transport and a single round of semiconservative DNA synthesis. This system can be used to directly test the mechanisms by which trans-acting factors promote transcription on nucleosomal DNA, either during chromatin assembly or postassembly or in conjunction with remodeling machinery and/or DNA replication. The functional consequences of trans-acting factor interaction within synthetic nuclei are determined by a coupled in vitro transcription analysis. Immobilizing biotin end-labeled DNA templates on paramagnetic streptavidin beads greatly improves the flexibility of the system. The ease of chromatin-assembled template recovery allows the introduction of wash steps, buffer changes, and specific reaction optimization. These methods for reconstituting gene regulatory mechanisms in vitro are an attempt to strike a balance between biochemical accessibility and physiological relevance.

Animals↗