PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Cellular differentiation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1988

Gap junctions in goldfish preoptic ependyma: regional variation in cellular differentiation.

Ependyma adjacent to the goldfish preoptic neurosecretory nucleus was examined with transmission electron microscopy. Ependymal cells adjoining the rostroventral end of the nucleus were spindle-shaped with their long axes perpendicular to the ventricular surface. Gap junctions and desmosomes were common near the apical (ventricular) ends of these cells, and less frequent laterally in the ependymal layer. Ependymal cells in more caudodorsal preoptic regions (adjacent to large neurosecretory cells) were progressively more pleomorphic. The frequent occurrence of apparently internalized gap junctions and of gap junction fragments enclosed within lysosome-like organelles indicated extensive turnover of these junctions, or uncoupling. Ependymal cells in the caudodorsal region formed gap junctions on their lateral and basal (abluminal) surfaces with glial processes containing bundles of intermediate filaments. Subependymally, these processes (presumptive radial glia) were parallel to one another and coupled together by gap junctions. Neurites containing dense core vesicles occasionally invaginated into ependymal cells in the caudal region, but did not appear to form gap junctions. Previous observations indicate continuing maturation and growth of the goldfish preoptic area with neurosecretory cell formation rostroventrally and a rostroventral to caudodorsal gradient of maturation. The present findings suggest a parallel and related gradient in preoptic ependyma. Ependymal cell differentiation possibly involves loss of gap junctions, and radial migration or differentiation into underlying neurons and glia.

Animals↗
PubMed1989

Cellular differentiation in the embryonic rat pancreas, with special reference to the co-existence of substances immunoreactive to both insulin and glucagon antibodies in the same cells.

We used light and electron microscopy and immunohistochemistry to examine the pancreas primordium in 11- to-20-day-old rat embryos. Cells that were immunoreactive to glucagon-like antibodies (G-like cells) first appeared under light microscopy on day 11, and those immunoreactive to insulin-like antibodies (I-like cells) appeared on day 13. All the I-like cells also reacted to G-like substance antibody. From the 13th to the 17th day of gestation, the G-like cells proliferated rapidly while the I-like cells increased in number very slowly. All the I-like cells continued to react with G-like substance antibody as well. The I-like cells began increasing rapidly on the 18th day and soon occupied about half of the islet-constituting cells. They no longer reacted with G-like substance antibody. Using double-label immunostaining with protein A-colloidal gold, the pancreatic endocrine cells became visible in 15-day-old embryos as large polygonal cells containing numerous secretion granules 180-200 nm in diameter. Some of these cells reacted to both I-like and G-like substance antibodies. These findings show the co-existence of G-like and I-like substances in rat embryo pancreatic endocrine cells between the 13th and 17th days of gestation, after which the I-like cells proliferate rapidly, and undergo definitive differentiation from the G-like cells.

Animals↗
PubMedDate not supplied

Non-classical actions of cholinesterases: role in cellular differentiation, tumorigenesis and Alzheimer's disease.

The cholinesterases are members of the serine hydrolase family, which utilize a serine residue at the active site. Acetylcholinesterase (AChE) is distinguished from butyrylcholinesterase (BChE) by its greater specificity for hydrolysing acetylcholine. The function of AChE at cholinergic synapses is to terminate cholinergic neurotransmission. However, AChE is expressed in tissues that are not directly innervated by cholinergic nerves. AChE and BChE are found in several types of haematopoietic cells. Transient expression of AChE in the brain during embryogenesis suggests that AChE may function in the regulation of neurite outgrowth. Overexpression of cholinesterases has also been correlated with tumorigenesis and abnormal megakaryocytopoiesis. Acetylcholine has been shown to influence cell proliferation and neurite outgrowth through nicotinic and muscarinic receptor-mediated mechanisms and thus, that the expression of AChE and BChE at non-synaptic sites may be associated with a cholinergic function. However, structural homologies between cholinesterases and adhesion proteins indicate that cholinesterases could also function as cell-cell or cell-substrate adhesion molecules. Abnormal expression of AChE and BChE has been detected around the amyloid plaques and neurofibrillary tangles in the brains of patients with Alzheimer's disease. The function of the cholinesterases in these regions of the Alzheimer brain is unknown, but this function is probably unrelated to cholinergic neurotransmission. The presence of abnormal cholinesterase expression in the Alzheimer brain has implications for the pathogenesis of Alzheimer's disease and for therapeutic strategies using cholinesterase inhibitors.

Alzheimer Disease↗
PubMed1986

[Cellular differentiation and proliferation in corn roots grown in microgravity (Biocosmos 1985)].

A cytological study was performed on Maize roots (Zea mays) which were grown in space (flight Biocosmos 1985) and on control roots on earth. Two criteria were selected: cell elongation in the cortical zone in the four mm of the extremity of the root and mitotic activity of the meristem. The results show that in microgravity the length of the meristem is reduced of 1/3 and that its mitotic activity increases of about twofold comparatively to the synchronous control. In parallel the cell differentiation begin closer to the root cap junction. These results are discussed relative to the influence of gravistimulation on cell proliferation and cell differentiation in roots.

Cell Differentiation↗
PubMed1991

Growth factor requirements of human colorectal tumour cells: relations to cellular differentiation.

Human colorectal tumour lines that exhibit different degrees of differentiation were studied to define their growth requirements. The poorly differentiated cell lines SW620, SW480, SW48 and SW837 proliferated in Dulbecco's modified Eagle's medium without exogenously added growth factors. In contrast, the moderately differentiated cell lines SW1222, HT29, PC/JW and LS174T proliferated only in medium supplemented with growth factor. SW1222 and HT29 cells required transferrin for growth, which was improved by other growth-promoting factors including epidermal growth factor (SW1222) and sodium selenite (HT29). PC/JW and LS174T required both insulin and transferrin for optimal growth. The tumour cell lines could be passaged continuously in serum-free medium supplemented with growth factor and in some cases they grew better than in serum-supplemented medium. The serum-free growth conditions should prove useful for studies on differentiation in colorectal cell lines and their interactions with growth factors.

Cell Count↗
PubMed1995

Differential cellular localization of oestrogen receptor immunoreactivity and oxytocin mRNA and immunoreactivity in the rat preoptic area.

Oestrogen influences both oxytocin mRNA and peptide immunoreactivity in the preoptic area and the rat oxytocin gene contains functional oestrogen response elements. However, using combinations of immunocytochemistry and in situ hybridization for oxytocin and oestrogen receptor, we found that preoptic oxytocin neurons do not possess oestrogen receptors. This finding implies oestrogen actions on oxytocin synthesis in preoptic neurones are unlikely to be mediated directly.

Animals↗
PubMed1996

Differential cellular pattern of gene expression for two distinct cGMP-inhibited cyclic nucleotide phosphodiesterases in developing and mature rat brain.

Cyclic GMP-inhibited phosphodiesterases are characterized by sensitivity of cAMP hydrolysis to inhibition by cGMP. This phosphodiesterase family contains at least two different isoforms (PDE3A and PDE3B) encoded by distinct genes and serving tissue-specific roles in regulation of lipolysis, glycogenolysis, myocardial contractility, and smooth muscle relaxation. Our previous work indicated an abundance of these two phosphodiesterase messenger RNAs in the embryonic rat brain, and therefore, to elucidate the potential functions of these enzymes in brain development as well as in mature brain function, the present study mapped cellular patterns of gene expression for these two enzymes from embryonic day 15 to adulthood using in situ hybridization histochemistry. Phosphodiesterase 3B isoform messenger RNA is uniformly expressed in germinal neuroepithelium and mature neurons, with distribution generally reflecting cell density. Phosphodiesterase isoform 3A messenger RNA, in contrast, demonstrates striking spatiotemporal specificity of expression, with three distinct patterns being evident. Firstly, this mRNA is highly abundant in both primary and secondary neuroepithelial germinal zones. Secondly, during early postnatal development PDE3A mRNA is transiently but highly expressed in neurons localized in basal forebrain, deep cerebellar, pontine, interpeduncular and a variety of thalamic, midbrain and brainstem nuclei. Thirdly, PDE3A mRNA is focally expressed in isolated large striatal and hippocampal neurons from the perinatal period without attenuation into adulthood. In summary, two cGMP-inhibited phosphodiesterase isoforms show distinctive patterns of gene expression in brain: PDE3B gene expression is uniform without evidence of system specificity or developmental stage specificity, suggesting that this isoform has a constitutive role in neuroepithelial metabolism, while PDE3B gene expression demonstrates a high level of spatiotemporal heterogeneity, suggesting that this isoform subserves a variety of developmental stage-specific and system-specific functions.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1993

Cellular differentiation: a theory based on simulation with computer graphics.

Rules are outlined in order to construct graphically a computer model that deals with cell growth, multiplication and differentiation. The process starts with a multicoloured stem cell and the end product will be differentiated cells represented by different colours. Various biological processes and neoplastic transformation can also be simulated. Based on the idea that the model corresponds to real events, predictions are made about the possible results of future experiments.

Animals↗
PubMed1995

Mechanism of active DNA demethylation during embryonic development and cellular differentiation in vertebrates.

Incubation of hemimethylated and labelled oligodeoxynucleotides with nuclear extracts from differentiating chicken embryos and mouse myoblasts resulted in the replacement of m5C by C. One of the enzymes involved is m5CpG endonuclease. It cleaves only m5CpG and not, m5CpT, m5CpA, m5CpC or m6ApT. The enzyme is not sequence specific and catalyses the reaction in the presence of high concentrations of EDTA or EGTA.

Animals↗
PubMed1989

Development of the cerebellum with particular reference to cellular differentiation in the external granular layer.

Immunocytochemical evidence of differentiation in developing human cerebellum is presented in this study. Antibodies to neuron specific enolase, neurofilament protein, glial fibrillary acidic protein, vimentin, cytokeratin, epithelial membrane antigen and lymphoid markers, DLC and Leu 7 were used. The external granular layer showed positivity with neuronal markers between 27 weeks gestation and 4 months postnatal, but was negative for all other markers including glial fibrillary acidic protein. Characteristic staining reactions were noted in the other cerebellar layers. Monoclonal antibodies, UJ13A (pan-neuroectodermal marker) and G10 (localising microtubule-associated protein MAP1x) were also used in a limited number of cryostat sections and were positive and negative, respectively, in the external granular layer. The results of this study are discussed in relation to the theory that the external granular layer may be one source of medulloblastomas.

Biomarkers↗
PubMed2004

Nickel, lead, and cadmium induce differential cellular responses in sea urchin embryos by activating the synthesis of different HSP70s.

Treatment with heavy metals, such as nickel, lead or cadmium, elicits different cellular stress responses according to the metal used and the length of treatment. In Paracentrotus lividus embryos the inducible forms of HSP70 (HSP70/72) are different in molecular mass from the constitutively expressed HSP75, and they can be used as markers of cellular stress. Even a short treatment with each metal induces the synthesis of HSP70/72 which remain stable for at least 20h and differ little in their isoelectric points. Continuous treatment from fertilization with nickel or lead produces late irregular pluteus embryos, with peak HSP70/72 synthesis at blastula followed by the arrest of synthesis by pluteus. On the contrary, the same treatment with cadmium induces continuous HSP70/72 synthesis and produces irregular gastrula embryos which then degenerate. Moreover, a long treatment induces over control embryos a slight increase in the amount of constitutive HSP75 during development while lead treatment depresses constitutive HSP75 at early stages and doubles its quantity at late stages.

Animals↗