1,721,056 research outputs found
Multipotent neuroepithelial stem cell differentiation: some caveats for future clinical applications.
No full text
Lineage specification of olfactory neural precursor cells depends on continuous cell interactions.
No full textWe transplanted, as a single cell suspension, cells dissociated from the mature and immature olfactory epithelium of rats or TgR(ROSA26)26Sor mice expressing constitutively the LacZ gene into the developing brain (cerebellum, striatum, inferior colliculus, lateral ventricles) of E15 rat fetuses. Grafted cells or their descendants were still present in the central nervous system more than a month after transplantation. Transplanted cells either integrated as isolated cells or, during the first day after transplantation, reaggregated into clusters. Scattered cells, despite their placodal origin, differentiated into neuron or glial cells with a central phenotype. This was demonstrated by anatomical methods and selective amplification of cDNA encoding for neuronal specific transcripts (microtubule-associated protein 2 and middle-molecular-mass neurofilament protein) expressed by the engrafted cells. Cells in large clusters generated an epithelium containing mature olfactory neurons. Some of them were immunoreactive for the olfactory marker protein. Our findings show that cells dissociated from the developing and adult olfactory organs when transplanted into the rat fetal brain can either completely change their fate and differentiate according to their final position or generate an olfactory epithelium if they reaggregate into large clusters
Cell death in the olfactory epithelium
No full textIn the nervous system of vertebrates the olfactory epithelium presents unique cytological characteristics. In the olfactory mucosa, olfactory neurons die and are replaced from undifferentiated neuroblasts over the entire life span of the animal. It remains unclear whether these neurons die as a result of a direct insult from the environment or in fulfillment of a physiological program of cell death. We have studied the distribution and the characteristics of cell death in the olfactory epithelium of normal, adult rats. The olfactory epithelium contains pycnotic bodies resembling those described for thymocytes undergoing terminal apoptotic changes. These appear at all levels in the epithelium, under both light and electron microscopes and can also be demonstrated after vital staining with acridine orange. Chromatin condensation into large blocks, often located at the nuclear periphery, is a morphological hallmark of the nuclei of mature olfactory neurons, which also present an increase in electron density of the cytoplasm. After non-radioactive in situ labeling of fragmented DNA, the nuclei of olfactory neurons are positive. Under the same reaction conditions (mild protease digestion), most of the nuclei of the supporting and basal cells are negative. In vivo incorporation of 5-bromouridine, a marker of RNA synthesis, is also lower in olfactory neurons than in basal and supporting cells. These findings suggest that olfactory neurons are committed very early to physiological cell death
Single olfactory organ associated with prosencephalic malformation and cyclopia in a Xenopus laevis tadpole.
No full textA cyclops Xenopus laevis tadpole with a single olfactory organ is described. At a stage comparable to 48, the telencephalon was severely atrophic and only the region where the olfactory fibres terminated appeared to have the cytoarchitecture of the olfactory bulb. In this animal the central nervous system (CNS) appeared normally developed only posterior to the preoptic area. The hypothesis of a diencephalic origin of the region where the olfactory fibres terminated is discussed in the light of our previous results of olfactory placode transplantation. By analogy between this case and other malformations (cyclopia, holoprosencephaly) in higher vertebrates and humans, the need is emphasized for a more precise anatomical description of the olfactory input in related malformations
Interaction of the transplanted olfactory placode with the optic stalk and the diencephalon in Xenopus laevis embryos.
No full textThe effect of olfactory placode transplantation on the differentiation of the optic vesicle and stalk has been studied in Xenopus laevis embryos. Host embryos (stages 23-24) received the transplant of two olfactory placodes from same-stage donors in place of a partially or totally removed optic vesicle. All tadpoles were sacrificed at stages 47-50. The host tadpoles were subdivided in three groups according to the amount of optic vesicle removed. In the first group all of the optic vesicle was removed. At sacrifice a lobar mass of nervous tissue, continuous with and protruding from the diencephalic wall, was penetrated by the olfactory nerves from the transplanted placodes and a well-defined glomerular layer was present at the entrance zone of the olfactory nerves. The lobar protrusion contained a normal ventricular cavity, connected by a foramen to the third ventricle. The ventricle was lined by a mitotically active ependymal layer. In the second group the host embryos were deprived of two-thirds of the optic vesicle. In these animals we observed the development of a round mass of nervous tissue connected by a peduncle to the diencephalic wall. A ventricle lined by ependyma was present in the formation; however, the cavity was not continuous with the third ventricle. Olfactory nerves from the transplanted placodes penetrated the rostral portion of the nervous mass and formed a distinct glomerular layer. In the third group of embryos only one-third of the optic vesicle was removed. These animals developed irregularly shaped structures where ocular tissue and nervous tissue coexisted. The termination of the supranumerary olfactory nerves and the glomerular layer were restricted to the non-ocular nervous tissue. The interpretation of the histogenetic phenomena determining the protrusions is difficult and further studies are needed. It seems highly probable, however, that the fate of such determined structures as the optic peduncle and vesicle can be influenced by the olfactory input, supporting the hypothesis that the ectopically directed olfactory fibres interfere with the differentiation of the optic structures
The pattern of cell death in fushi tarazu, a segmentation gene of Drosophila.
No full textThe pair-rule mutant, fushi tarazu, causes deletion of alternate metameres. Here we show that there is cell death in the mutant which begins at the completion of germ band extension. We map the dying cells in the epidermis; they occur scattered all over those regions that, in the wild type, would form the even-numbered parasegments and are also found in posterior parts of the odd-numbered parasegments. In the affected zones, dying and dividing cells are intermingled; we suggest that cells from these zones may still give descendents that contribute to the larval cuticle. Cell death is not limited to those cells that would normally express ftz+, suggesting that it is some indirect consequence of the abnormal situation in the mutant embryo
VISION-GUIDED TECHNIQUE FOR CELL TRANSPLANTATION AND INJECTION OF ACTIVE MOLECULES INTO RAT AND MOUSE EMBRYOS
No full text
- …
