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At least 577 records · Page 32Linked to original sources
PubMed2005

Isolation of precursor cells (PCs) from human dental follicle of wisdom teeth.

The dental follicle is an ectomesenchymal tissue surrounding the developing tooth germ. It is believed that this tissue contains stem cells and lineage committed progenitor cells or precursor cells (PCs) for cementoblasts, periodontal ligament cells, and osteoblasts. In this study, we report the isolation of PCs derived from dental follicle of human third molar teeth. These fibroblast-like, colony forming and plastic adherent cells expressed putative stem cell markers Notch-1 and Nestin. We compared gene expressions of PCs, human mesenchymal stem cells (hMSCs), periodontal ligament cells (PDL-cells) and osteoblasts (MG63) for delimitation of PCs. Interestingly, PCs expressed higher amounts of insulin-like growth factor-2 (IGF-2) transcripts than hMSCs. Differentiation capacity was demonstrated under in vitro conditions for PCs. Long-term cultures with dexamethasone produced compact calcified nodules or appeared as plain membrane structures of different dimensions consisting of a connective tissue like matrix encapsulated by a mesothelium-like cellular structure. PCs differentially express osteocalcin (OCN) and bone sialoprotein (BS) after transplantation in immunocompromised mice but without any sign of cementum or bone formation. Therefore, our results demonstrate that cultured PCs are unique undifferentiated lineage committed cells residing in the periodontium prior or during tooth eruption.

Adolescent↗
PubMed2001

Clustering of missense mutations in the C-terminal region of factor H in atypical hemolytic uremic syndrome.

Hemolytic-uremic syndrome (HUS) is a microvasculature disorder leading to microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. Most cases of HUS are associated with epidemics of diarrhea caused by verocytotoxin-producing bacteria, but atypical cases of HUS not associated with diarrhea (aHUS) also occur. Early studies describing the association of aHUS with deficiencies of factor H suggested a role for this complement regulator in aHUS. Molecular evidence of factor H involvement in aHUS was first provided by Warwicker et al., who demonstrated that aHUS segregated with the chromosome 1q region containing the factor H gene (HF1) and who identified a mutation in HF1 in a case of familial aHUS with normal levels of factor H. We have performed the mutational screening of the HF1 gene in a novel series of 13 Spanish patients with aHUS who present normal complement profiles and whose plasma levels of factor H are, with one exception, within the normal range. These studies have resulted in the identification of five novel HF1 mutations in four of the patients. Allele HF1 Delta exon2, a genomic deletion of exon 2, produces a null HF1 allele and results in plasma levels of factor H that are 50% of normal. T956M, W1183L, L1189R, and V1197A are missense mutations that alter amino acid residues in the C-terminal portion of factor H, within a region--SCR16-SCR20--that is involved in the binding to solid-phase C3b and to negatively charged cellular structures. This remarkable clustering of mutations in HF1 suggests that a specific dysfunction in the protection of cellular surfaces by factor H is a major pathogenic condition underlying aHUS.

Base Sequence↗
PubMed1995

Calcium-mediated cell injury and cell death.

The effect of intracellular ion deregulation, particularly of [Ca2+], on the events following acute cell injury and the progression of change from initiation (reversible) to maintenance (reversible-irreversible) phases and finally to cell death has been the major thrust of experimentation in our laboratory for over 20 years. Cell death, which plays an important role in both normal and pathological phenomena, has been classified into two principal types, accidental and programmed. Recent exploration of programmed cell death (or apoptosis) has revealed extensive data showing it is an important mechanism for the normal maintenance and also differentiation of a variety of cell types and organs. From the results from our laboratory and those of others, we continue to expand and refine our working hypothesis: deregulation of [Ca2+] results in a number of phenomena from activation of signaling mechanisms and alterations in cellular structure to alterations in gene expression, all of which contribute to or play a critical role in cellular toxicity, including carcinogenesis and cell death. Therefore, although much more experimentation is needed to clarify some of these phenomena, the implications of such data for understanding the mechanisms and processes involved in carcinogenesis and the chemotherapeutic killing of cancer cells are extremely exciting. These relationships between [Ca2+], cell injury, and cell death are briefly reviewed here within the framework of our hypothesis.

Animals↗
PubMed1992

Human papillomavirus detection in cervical cells by in situ hybridization with biotinylated probes.

We have investigated the applicability of human papillomavirus (HPV) DNA detection by in situ hybridization with biotinylated probes in epithelial cells obtained from the cervix using a cotton tip swab. We describe a simple procedure for obtaining homogeneous cell samples and good preservation of cellular structure. This is achieved by pretreatment of cells with L-cysteine before hybridization. Separate denaturation of cellular DNA and probe DNA is also necessary for satisfactory results. Both benign HPV DNA 6/11 and potentially oncogenic HPV DNA 16/18 could be identified in our series. In situ hybridization on cervical scrapes is a rapid, simple and very specific method for detecting patients infected with oncogenic HPV types.

Adult↗
PubMed1984

[Comparison of superslow activity with changes in the function of the neocortical cytostructures].

Effects of ethimizole on the infraslow ascillations of the brain electrical activity were correlated with the pattern of its distribution within cellular structures. A negative wave of the infraslow activity was found to occur after the drug administration at the moment of its maximal inclusion into the two cellular fractions: the nuclei and the surface proteins of the endoplasmatic net. These structures seem to play part in changes of the central nervous system's functional state.

Animals↗
PubMed2001

Cellular pathophysiology of portal hypertension and prospects for management with gene therapy.

In summary, regulation of sinusoidal blood flow in normal and injured liver involves structural, cellular, and humoral components. Available data suggest that stellate cells, resident perisinusoidal mesenchymal cells with a histologic orientation in the sinusoid analogous to [figure: see text] vasoregulatory pericytes, modulate sinusoidal blood flow. This regulation by stellate cells is most evident in the context of liver injury but may apply also to the normal liver. The endothelin and NO systems are important in modulating stellate cell contractility, and their degree of equilibrium is significant in determining the level of local intrahepatic resistance, especially in the injured liver. Manipulation of either or both of these systems is feasible and effective in experimental models. Such findings have obvious clinical implications and are expected to set the [figure: see text] stage for novel gene therapy approaches for treatment of patients with portal hypertension.

Endothelins↗
PubMedDate not supplied

Confocal spectral imaging analysis of intracellular interactions of mitoxantrone at different phases of the cell cycle.

It is suggested that the cytotoxicity of anticancer agent mitoxantrone (MITOX) is related to a complex combination of molecular interactions which lead to slowing of S phase traverse and arresting of cells in G2 phase of the cell cycle or even to an apoptosis at high concentration of MITOX. Here intracellular molecular interactions of MITOX were visualised and studied using the confocal spectral imaging technique in synchronised K562 cells. Localisation, quantitative distributions of MITOX in the polar environment, MITOX bound to hydrophobic cellular structures (MITOXphob), nucleic acid-related complexes of MITOX (MITOXNA) and relative distributions of naphthoquinoxaline (NQX) metabolite and intrinsic cellular fluorescence of porphyrins were measured within cytoplasmic and nuclear compartments (chromosomes) of the G2, S, and M cells treated with 10 or 2 microM of MITOX for 1 hour. Colocalisation of MITOX, NQX metabolite and sites of intrinsic cellular fluorescence indicates an accumulation of MITOX within or near mitochondria. One may suppose that due to high concentration MITOX can compete with natural substrates for binding to the enzymes thus affecting the normal functioning of a mitochondria. A remarkable redistribution of MITOX and its complexes occurs in the M cells. In particular, a prominent amount of MITOX is associated with the surface of chromatids but not with the cytoplasmic structures in M cells. At the present time the exact location of the sites of MITOX accumulation in the M cells is not known. It is thought to be some cytoskeleton/microtubule structures associated directly with the chromosomes. Selective labelling of particular cytoskeleton structures and/or proteins in MITOX treated cells is in the progress now and the question will be addressed using the CSI technique.

Antineoplastic Agents↗
PubMed1991

Where is the glycolytic complex? A critical evaluation of present data from muscle tissue.

Associations between glycolytic enzymes and subcellular structures have been interpreted as presenting a novel mechanism of glycolytic control; reversible enzyme binding to subcellular structural components is believed to regulate enzyme activity in vivo through the formation of a multi-enzyme complex. However, three lines of evidence suggest that enzyme binding to cellular structures is not involved in the control of glycolysis. (i) Calculations of the distribution of glycolytic enzymes under the physiological cellular conditions of higher ionic strength and higher enzyme concentrations indicate that a large multi-enzyme complex would not exist. (ii) In many cases, binding to subcellular structures is accompanied by changes in enzyme kinetic parameters brought about by allosteric modification, but these changes often inhibit enzyme activity. (iii) In the case where formation of binary enzyme/enzyme complexes activates enzymes, the overall increase in flux through the enzyme reaction is negligible.

Actins↗
PubMed2002

Deficiency of microvascular thrombomodulin and up-regulation of protease-activated receptor-1 in irradiated rat intestine: possible link between endothelial dysfunction and chronic radiation fibrosis.

Microvascular injury is believed to be mechanistically involved in radiation fibrosis, but direct molecular links between endothelial dysfunction and radiation fibrosis have not been established in vivo. We examined radiation-induced changes in endothelial thrombomodulin (TM) and protease-activated receptor-1 (PAR-1) in irradiated intestine, and their relationship to structural, cellular, and molecular aspects of radiation injury. Rat small intestine was locally exposed to fractionated X-radiation. Structural injury was assessed 24 hours and 2, 6, and 26 weeks after the last radiation fraction using quantitative histology and morphometry. TM, neutrophils, transforming growth factor-beta, and collagens I and III were assessed by quantitative immunohistochemistry. PAR-1 protein was localized immunohistochemically, and cells expressing TM or PAR-1 transcript were identified by in situ hybridization. Steady-state PAR-1 mRNA levels in intestinal smooth muscle were determined using laser capture microdissection and competitive reverse transcriptase-polymerase chain reaction. Radiation caused a sustained, dose-dependent decrease in microvascular TM. The number of TM-positive vessels correlated with all parameters of radiation enteropathy and, after adjusting for radiation dose and observation time in a statistical model, remained independently associated with neutrophil infiltration, intestinal wall thickening, and collagen I accumulation. PAR-1 immunoreactivity and transcript increased in vascular and intestinal smooth muscle cells in irradiated intestine. PAR-1 mRNA increased twofold in irradiated intestinal smooth muscle. Intestinal irradiation up-regulates PAR-1 and causes a dose-dependent, sustained deficiency of microvascular TM that is independently associated with the severity of radiation toxicity. Interventions aimed at preserving or restoring endothelial TM or blocking PAR-1 should be explored as strategies to increase the therapeutic ratio in clinical radiation therapy.

Animals↗
PubMed2002

Polarized angular dependent spectroscopy of epithelial cells and epithelial cell nuclei to determine the size scale of scattering structures.

An understanding of the relationship between tissue structures and light scattering from tissue will help facilitate the development and acceptance of noninvasive optical diagnostics including elastic scattering spectroscopy, diffuse reflectance, and optical coherence tomography. For example, a quantitative model of the structures that scatter light in epithelial cells would allow determination of what structures control the characteristics of in vivo light transport measurements and subsequently could provide a detailed relationship between cellular structures and optical measurements. We have determined the size distribution of refractive index structure variations in epithelial cells as well as in nuclei isolated from epithelial cells from measurements of the angular dependence of polarized light scattering. The quantitative size distributions we obtained for both whole cells and isolated nuclei include particles with effective radii of 2 microm to 10 nm or less and contain orders of magnitude more small particles than large particles. These results demonstrate that not only are biological cells very heterogeneous, but so are the nuclei within them. Light scattering is likely sensitive to structures smaller than those commonly investigated by standard pathology methods.

Animals↗
PubMed2000

[Morphometric analysis of erythrocyte aggregates in vitro: pharmacological application with buflomedil].

Erythrocyte aggregation is usually evaluated through indirect measurements such as the sedimentation rate and rheometric measurements of aggregation and disaggregation thresholds. The aim of this study was a preliminary evaluation of a morphometric approach of aggregates in vitro. A sample of blood (on EDTA) was examined under the microscope, and a picture with magnification X 640 was obtained after stabilization of the cellular structure. The digital image was analyzed with a home made dedicated software that allows the measurement of the cellular density and the evaluation of several shape parameters. Ten samples obtained from different donors were analysed within one hour after blood withdrawal and 24 hours later (preservation temperature: 4 degrees C), with and without adjunction of Buflomedil (4 microg/ml). Results showed an important anti-aggregant effect of Buflomedil administrated in these conditions, both on fresh and preserved blood (p<10(-3)). These results illustrate the potential interest of a morphometric approach to erythrocyte aggregation. They show new pharmacological properties of Buflomedil administered in vitro, which have to be confirmed with a therapeutic administration of the compound.

Densitometry↗
PubMed1991

[Histopathologic study of cardiac myxoma. Apropos of 80 surgical cases].

The histological features of eighty cardiac myxomas removed by surgery between 1959 and 1988 were evaluated by the usual staining techniques and also by identification of immunohistological markers (vimentin, desmin, factor VIII, actin). Myxoma cells present various forms (polygonal, round, spindle, stellate) when isolated but are characterized by their tubular angioid structures: cellular masses, elementary tubes, organoid formations with several parietal layers and abundant "myxoid" matrix, denser around the angioid structures. Sometimes they are located on the surface forming crypts and vegetations, replaced in old myxomas by hyalinization. Other constituents such as vascular spaces, fibrinous exudate, hemosiderosis pigments, necrobiotic areas, various calcifications, plasma cell infiltrates are also frequently found. The insertion on the endocardium is usually an interesting structure. The presence of mucous epithelial structures and clusters of smooth muscle cells is uncommon but constitutes an additional argument in favour of the present explanation concerning its histogenosis i.e. a tumor derived from vestigial cells, usually confined to the floor of the fossa ovalis. On the basis of these various characteristics, myxomas can be classified as being active or inactive (more or less mummified), poorly differentiated or mature, which may correspond to the duration of the lesion prior to its resection. A precise histological examination of myxoma avoids confusion with more malignant myxomatous cardiac tumors.

Heart Neoplasms↗
PubMed1990

[Cytoskeletal principles of the functional organization of cells].

The paper provides basic information on cytoskeletal structures [microtubules, microfilaments and intermediate filaments] which form a very dynamic system in the cytoplasm and in specialized cellular structures. The cytoskeleton comprises also the membrane and nuclear skeleton. The cytoskeleton performs all motor functions of the cell, incl. intracellular transport, some morphogenic processes and it is the carrier of positional information in the cell and probably also the memory structure of non-genetic cell memory. The author mentions some molecular mechanisms of transformation of the chemical energy into mechanical energy. The article indicates also some perspectives of the application of findings in the sphere of medicine, in particular in the biology of tumour cells, in the pathogenesis of some diseases, in cytostatic treatment, in toxicology and in diagnostic applications.

Cytoskeleton↗
PubMed2001

Improved Technique for Electron Microscope Visualization of Yeast Membrane Structure.

Yeast cells represent a powerful model system in cell biology mainly due to their amenability to genetic manipulations. Increasingly, studies focus on mutant genes resulting in alterations of cellular structures and organelles. To ascertain the phenotypic changes involved, it is often desirable to use the resolving power of electron microscopy. In contrast to higher eukaryotic cells, yeast cells are particularly difficult to preserve mainly due to the presence of a thick cell wall that acts as a barrier against diffusion of fixatives. Although several procedures are targeted to overcome these difficulties, none of them have become established as a standard procedure. As a consequence, electron microscopy is still not used routinely as a tool in yeast cell biology. This prompted us to develop an easy-to-follow protocol for yeast transmission electron microscopy that should be useful in all cases where membrane integrity and organelle morphology is emphasized. One means of making the yeast cytoplasm more attainable to fixation and staining solutions is by enzymatic digestion of the cell wall. Following this approach, we were able to reliably preserve yeast cells and their cellular organelles. Enzymatic treatment with zymolyase 20T to partially remove the yeast cell wall allowed the fixation, preservation, and visualization of the yeast cytoplasm revealing detailed ultrastructure. The advancement of this technique is demonstrated with mitochondria as a model organelle. Our studies on various yeast mutants clearly show the power of the enzymatic digestion technique in visualizing subtle changes of membrane structure and organelle morphology.

Journal Article↗
PubMed2002

Structure and dynamics of the fusion pores in live GH-secreting cells revealed using atomic force microscopy.

Earlier studies in live pancreatic acinar cells identified new cellular structures at the cell plasma membrane called 'pits' and 'depressions', where membrane-bound secretory vesicles dock and fuse to release vesicular contents. In the current study, using atomic force microscopy we identify similar structures at the plasma membrane of GH-secreting cells of the pituitary and implicate their involvement in hormone release. Pits containing 100-200 nm in diameter depressions or fusion pores were identified in resting GH-secreting cells. Following stimulation of secretion the size of depression enlarged and gold-tagged GH antibody were found to bind to the pit structures in the stimulated GH cells. This study documents for the first time the presence of these structures and their involvement in secretions in a neuroendocrine cell.

Actins↗
PubMed2005

Costameres, focal adhesions, and cardiomyocyte mechanotransduction.

Mechanotransduction refers to the cellular mechanisms by which load-bearing cells sense physical forces, transduce the forces into biochemical signals, and generate appropriate responses leading to alterations in cellular structure and function. This process affects the beat-to-beat regulation of cardiac performance but also affects the proliferation, differentiation, growth, and survival of the cellular components that comprise the human myocardium. This review focuses on the experimental evidence indicating that the costamere and its structurally related structure the focal adhesion complex are critical cytoskeletal elements involved in cardiomyocyte mechanotransduction. Biochemical signals originating from the extracellular matrix-integrin-costameric protein complex share many common features with those signals generated by growth factor receptors. The roles of key regulatory kinases and other muscle-specific proteins involved in mechanotransduction and growth factor signaling are discussed, and issues requiring further study in this field are outlined.

Animals↗
PubMed1997

Phenotypic characterization of neurotensin messenger RNA-expressing cells in the neuroleptic-treated rat striatum: a detailed cellular co-expression study.

The chemical phenotype of proneurotensin messenger RNA-expressing cells was determined in the acute haloperidol-treated rat striatum using a combination of (35S)-labelled and alkaline phosphatase-labelled oligonucleotides. Cellular sites of proneurotensin messenger RNA expression were visualized simultaneously on tissue sections processed to reveal cellular sites of preproenkephalin A messenger RNA or the dopamine and adenylate cyclase phosphoprotein-32, messenger RNA. The cellular co-expression of preproenkepahlin A (enkephalin) and preprotachykinin (substance P) messenger RNA was also examined within forebrain structures. Cellular sites of enkephalin (substance P) and dopamine and adenylate cyclase phosphoprotein-32 messenger RNAs were visualized using alkaline phosphatase-labelled oligonucleotides whilst sites of substance P and proneurotensin messenger RNA expression were detected using (35S)-labelled oligos. Cellular sites of enkephalin and dopamine and adenylate cyclase phosphoprotein-32 gene expression were identified microscopically by the concentration of purple alkaline phosphatase reaction product within the cell cytoplasm, whereas sites of substance P and proneurotensin gene expression were identified by the dense clustering of silver grains overlying cells. An intense hybridization signal was detected for all three neuropeptide messenger RNAs in the striatum, the nucleus accumbens and septum. Dopamine and adenylate cyclase phosphoprotein-32 messenger RNA was detected within the neostriatum but not within the septum. In all forebrain regions examined, with the exception of the islands of Calleja, the cellular expression of enkephalin messenger RNA and substance P messenger RNA was discordant; the two neuropeptide messenger RNAs were detected essentially in different cells, although in the striatum and nucleus accumbens occasional isolated cells were detected which contained both hybridization signals; dense clusters of silver grains overlay alkaline phosphatase-positive cells, demonstrating clearly that these dual-labelled cells expressed both messenger RNAs. By contrast, the hybridization signals for proneurotensin and enkephalin, and proneurotensin and dopamine and adenylate cyclase phosphoprotein-32 were generally coincident, at least within the neostriatum; most proneurotensin messenger RNA-positive cells expressed enkephalin messenger RNA and were also positive for dopamine and adenylate cyclase phosphoprotein-32 messenger RNA. However, occasional proneurotensin messenger RNA-positive striatal cells were identified that were single-labelled and did not express enkephalin messenger RNA. Within the septal nucleus, enkephalin messenger RNA and substance P messenger RNA were expressed essentially within segregated cell populations. These studies illustrate further the utility of co-expression techniques for investigating the chemical phenotype of cells within the CNS and demonstrate that the distribution of neuropeptide co-expressing cells is different within different brain regions. That several populations of proneurotensin messenger RNA-positive striatal cells may exist, of which one population is sensitive to haloperidol, co-expresses enkephalin messenger RNA and is positive for dopamine and adenylate cyclase phosphoprotein-32 messenger RNA may be of some significance in neuropsychiatric/neurological disorders given that the translated peptide, neurotensin, is known to influence and interact closely with the dopamine systems.

Animals↗
PubMed1996

Micro-imaging by magnetic resonance on flexible polyurethane foams.

Flexible polyurethane foams are mainly used for their particular mechanical properties such as hardness and resilience. The correlation of the foam properties with the material structure is believed to be important but it has always been difficult to identify the individual contributions of the cellular structure and of the polymer to the foam physical properties.

Image Processing, Computer-Assisted↗