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Results 601 - 650 of 1399
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Neuhof Dirk - - 2004
BACKGROUND: Telomerase activity in a human lymphoblastoid cell line with wild-type p53 status (TK6) was previously shown to be rapidly induced by ionizing radiation doses as low as 10 cGy. Since this low-dose response was absent in a closely related cell line overexpressing a mutant form of p53 (WTK1), the ...
Flanary Barry - - 2004
Normal somatic cells have a finite replicative capacity. With each cell division, telomeres (the physical ends of linear chromosomes) progressively shorten until they reach a critical length, at which point the cells enter replicative senescence. Some cells can maintain telomere length by the action of the telomerase enzyme. A recent ...
Enomoto Shinichiro - - 2004
Cells lacking telomerase undergo senescence, a progressive reduction in cell division that involves a cell cycle delay and culminates in "crisis," a period when most cells become inviable. In telomerase-deficient Saccharomyces cerevisiae cells lacking components of the nonsense-mediated mRNA decay (NMD) pathway (Upf1,Upf2, or Upf3 proteins), senescence is delayed, with ...
Gordon Katrina E - - 2004
Telomeres are the structures at the ends of chromosomes, composed of repetitive sequences and associated proteins, which cap chromosome ends to maintain genomic stability. These structures are maintained by the enzyme complex telomerase in germ cells and some stem cells, but are absent in the majority of somatic cells. The ...
Peitsaro Panu - - 2004
Expression of the viral oncogenes E6 and E7, and telomerase, was investigated, using a cell line from a mild dysplastic vaginal lesion containing human papillomavirus (HPV) type 33. During passaging of the cells, there was a change towards a cancer phenotype, and a shift from episomal to integrated HPV. Levels ...
Cordero Julio F - - 2004
The distribution of intramembrane particles in human erythrocytes was studied by freeze-fracture on young and old cells and compared to that obtained after ATP depletion or following addition of a clustering agent. It was shown that intramembrane particles became aggregated and the mean particle density increased as the cells aged. ...
Yin Fei - - 2004
Telomerase, which is required to maintain telomeres, has attracted considerable attention as a target for anticancer therapy. In this study, we investigated the inhibition of HeLa cell telomerase activity and cell cycle progression by triethylene tetraamine (TETA), using a modified telomeric repeat amplification protocol (TRAP) assay, and flow cytometry. TETA ...
Wai Lin Kah - - 2004
Human telomeres function as a protective structure capping both ends of the chromosome. They are composed of long, repetitive sequences of TTAGGG, associated with a variety of telomere-binding proteins. Telomeres protect the chromosomes from end-to-end fusion, recombination, and degradation, all events that can lead to cell death. At cell replication, ...
Okabe Jun - - 2004
The maintenance of telomere integrity is essential for prolonged cell proliferation, and failure in this mechanism is a most consistent manifestation of cellular senescence. In this study, we investigated the role of telomere repeat binding factor (TRF1) in the proliferation of human fibroblasts. TRF1 expression is upregulated in a large ...
Zeng Xiao-li - - 2003
The aim of this study was to investigate the effects of ginsenoside Rh(2) (G-Rh(2)) on differentiation of SMMC-7721 hepatocarcinoma cell line in culture. We studied G-Rh(2)-induced differentiation of SMMC-7721 cells through cell proliferation, cell morphology, ultrastructure, cell cycle, cell function and metabolism. The proliferation of treated cells was inhibited, the ...
Wang Peichang - - 2003
Astragalus membranceus (Fish) Bunge Var. mongholicus (Bge) Hsiao is a Chinese herb considered as an effective traditional anti-ageing material. The two isomers of 4-hydroxy-5-hydroxymethyl-[1,3]dioxolan-2,6'-spirane-5',6',7',8'-tetrahydro-indolizine-3'-carbaldehyde (HDTIC), HDTIC-1 and HDTIC-2, were extracted from the herb. We chose them to investigate their effects on replicative senescence in vitro. In this study, we observed ...
Swynghedauw B - - 2003
In all mammals including humans, adult cardiocytes become post mitotic cells, while cardiac non muscle cells still have the capacity to proliferate, and cardiac hypertrophy in adults is known to be due to cardiocyte hypertrophy and non muscle cell hyperplasia. Such a dogma was supported by several, rather ancient, observations, ...
Golubev A - - 2003
In telomerase-negative cell populations the mean telomere length (TL) decreases with increasing population doubling number (PD). A critically small TL is believed to stop cell proliferation at a cell-, age- and species-specific PD thus defining the Hayflick limit. However, positively skewed TL distributions are broad compared to differences between initial ...
Kraveka Jacqueline M - - 2003
In this study, we examined the role of endogenous ceramide in the inhibition of telomerase and induction of morphologic differentiation in response to all-trans-retinoic acid (ATRA) in the SK-N-SH and SK-N-AS human neuroblastoma cell lines. The results showed that ATRA inhibited the activity of telomerase significantly in a time- and ...
Bechter Oliver E - - 2003
Homologous recombination is thought to be the molecular mechanism for maintaining telomere length in alternative lengthening of telomeres (ALT) cells. We used a recombination reporter system to show that the frequency of homologous recombination is the same for ALT- and telomerase-positive cells, suggesting that if ALT cells have a recombination ...
Young A T L - - 2003
Telomerase activation is a means to delay in vitro replicative senescence in human cells via telomere maintainence; however, this enzymatic activity is virtually absent in almost all normal somatic cells. As a result, cell senesce, leading to an eventual loss of graft function. Aging allografts, either due to cell injury ...
Hayflick Leonard - - 2003
Since the first cell culture was set at the beginning of the twentieth century it was believed that all cultured cells, if provided with the proper conditions, would replicate indefinitely. Sixty years later we overthrew this dogma by finding that normal cells have a finite capacity to replicate and that ...
Bird Joseph - - 2003
Replicative senescence, the irreversible loss of proliferative capacity, is a common feature of somatic cells derived from many different species. The molecular mechanisms controlling senescence in mammals, and especially in humans, have now been substantively elucidated. However, to date, attempts to link the senescence of cells with the ageing of ...
Powell Chris D - - 2003
Ageing in budding yeast is not determined by chronological lifespan, but by the number of times an individual cell is capable of dividing, termed its replicative capacity. As cells age they are subject to characteristic cell surface changes. Saccharomyces cerevisiae reproduces asexually by budding and as a consequence of this ...
Sharma Girdhar G - - 2003
Telomeres are associated with the nuclear matrix and are thought to be heterochromatic. We show here that in human cells the overexpression of green fluorescent protein-tagged heterochromatin protein 1 (GFP-HP1) or nontagged HP1 isoforms HP1(Hsalpha) or HP1(Hsbeta), but not HP1(Hsgamma), results in decreased association of a catalytic unit of telomerase ...
Piliero Lisa M - - 2004
Patients with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome) typically exhibit thymic hypoplasia, conotruncal cardiac defects, and hypoparathyroidism. The immunodeficiency that results from the thymic hypoplasia has been extensively described and consists primarily of T-cell lymphopenia. A curious feature of the T-cell lymphopenia is that the age-related rate of decline ...
Gomez Dennis - - 2003
The molecular mechanisms induced by G-quadruplex ligands to trigger senescence in mammalian cells are still unknown, although the critical role of telomerase is highly suspected. JFA2 cells selected for resistance to senescence induced by the G-quadruplex ligand 12459 presented an overexpression of hTERT transcript that correlated to a functional increase ...
Akiyama Masaharu - - 2003
Telomeres are specialized nucleoprotein complexes that protect against fusion and degradation of linear chromosomes. Critical shortening of telomeres leads to irreversible cessation of cell division, whereas telomerase elongates telomere sequences to compensate for losses that occur with each round of DNA replication. Continued proliferation of tumor cells requires this enzyme ...
Reber F - - 2003
INTRODUCTION: The extracellular effects caused by advanced glycation end products (AGEs) themselves formed by the Maillard-reaction from proteins and sugars, are well known. Less is known about the effects of AGEs on cellular function. Cellular dysfunctions accumulate with increasing age and can be found as a pathogenetic principle of different ...
Velicescu Mihaela - - 2003
Replicative immortality is achieved in vitro by overcoming two mortality checkpoints, M1 (senescence) and M2 (crisis). Cancer cells are thought to overcome M2 by activating telomerase, an enzyme believed to confer genomic stability in addition to maintaining telomeric sequences above a critical length. Here we show that a subset of ...
Buckley S - - 2004
Lung cancer is the most common visceral malignancy in males, with rapidly increasing incidence in females, and a devastatingly poor prognosis. Transforming growth factor (TGF)-beta has been shown to induce senescence in A549 lung cancer cells, and both TGF-beta and bone morphogenetic protein (BMP) 2 can suppress the transformed phenotype ...
Chimenti Cristina - - 2003
Chronological myocardial aging is viewed as the inevitable effect of time on the functional reserve of the heart. Cardiac failure in elderly patients is commonly interpreted as an idiopathic or secondary myopathy superimposed on the old heart independently from the aging process. Thus, aged diseased hearts were studied to determine ...
Jiang Ying-An - - 2003
AIM: To evaluate the effect of human telomerase reverse transcriptase (hTERT) gene antisense oligodeoxynucleotide (As-ODN) on telomerase activity and cell apoptosis in colon cancer cell line SW480. METHODS: As-ODN was transfected into cells SW480 by liposomal transfection. Cultured cells were divided into three groups: ASODN (5'GGAGCGCGCGGCATCGCGGG-3'), sense oligodeoxynucleotide (5'-CCCGCGATGCCGCGCGCTCC-3', S-ODN) ...
Kraemer Kai - - 2003
PURPOSE: The expression of human telomerase reverse transcriptase (hTERT) is associated with cellular aging and tumorigenesis. It was found in nearly all cancer types but not in most normal, somatic cells. The aim of this study was to investigate whether hTERT inhibition by antisense oligodeoxynucleotides (AS-ODN) can act as an ...
Baerlocher Gabriela M - - 2003
BACKGROUND: Telomeres are essential protein-DNA structures at the end of chromosomes which are implicated in genome stability and cell replication. The average length of telomere repeats can be measured by in situ hybridization and flow cytometry [flow-FISH]. Such telomere length values reflect telomere shortening (resulting from cell divisions, oxidative damage ...
Shammas Masood A - - 2003
OBJECTIVE: The aim of this study was to test the efficacy of telomerase inhibitor (TMPyP4 [tetra(N-methyl-4-pyridyl)-porphyrin chloride]; a G-quadruplex-intercalating porphyrin) as a potential therapeutic agent for multiple myeloma. MATERIALS AND METHODS: We studied telomere length, telomerase activity, and effect of telomerase inhibition in multiple myeloma cells. Several myeloma cell lines ...
Kim Seung-Ki - - 2003
In gliomas, a high frequency of homozygous p16 gene deletions have been demonstrated, which are believed to be linked with malignant progression. The aim of this study was to assess the role of p16 in growth, invasion, and senescence. The human glioma cell lines U87 MG and U373 MG were ...
Aoshiba K - - 2003
Cellular senescence is a state of irreversible growth arrest. In this paper the authors examined whether bleomycin, an agent that causes pulmonary fibrosis, induces the senescence of alveolar epithelial cells. Type II-like alveolar epithelial (A549) cells or rat primary type II cells were exposed to bleomycin and then evaluated for ...
Kashino Genro - - 2003
Primary human cells have a definite life span and enter into cellular senescence before ceasing cell growth. Oxidative stress produced by aerobic metabolism has been shown to accelerate cellular senescence. Here, we demonstrated that ascorbic acid, used as an antioxygenic reagent, delayed cellular senescence in a continuous culture of normal ...
Kim Moses - - 2003
Expression of the catalytic subunit of human telomerase, hTERT, extends human primary fibroblast life span. Such life span extension has generally been reported to be accompanied by net telomere lengthening, which led to the hypothesis that it is the telomere lengthening that causes the life span extension. Here we show ...
Davies Barry R - - 2003
Epithelial ovarian cancer is the most common form of gynaecological malignancy. This lethal disease is thought to arise in ovarian surface epithelial (OSE) cells. The biology of these cells is not well understood, due to the limited amount of tissue that can be obtained from a single biopsy and their ...
Harada Hideki - - 2003
Normal human somatic cells have a finite life span and undergo replicative senescence after a limited number of cell divisions. Erosion of telomeric DNA has emerged as a key factor in senescence, which is antagonized during cell immortalization and transformation. To clarify the involvement of telomerase in the immortalization of ...
Satyanarayana A - - 2003
Telomere shortening limits the regenerative capacity of primary cells in vitro by inducing cellular senescence characterized by a permanent growth arrest of cells with critically short telomeres. To test whether this in vitro model of cellular senescence applies to impaired organ regeneration induced by telomere shortening in vivo, we monitored ...
Ferlicot Sophie - - 2003
Loss of telomere repeat sequences occurs after each cell division and telomere shortening has been implicated in cellular senescence. The measurement of telomere length might therefore assess the lifespan of a cell. The aim of this study was to set up and validate a technique enabling the assessment of telomere ...
Montanaro L - - 2003
AIM: Dyskeratosis congenita (DC) is characterised by the failure of those tissues that are rapidly dividing in the adult, particularly the skin, mucosae, and haemopoietic system. The X linked form of the disease is caused by mutations of the DKC1 gene, which encodes dyskerin, a protein that is necessary for ...
Alexander Kamilah - - 2003
Senescent cells in which pRb is inactivated undergo apoptosis on attempted reinitiation of DNA synthesis. To further explore the cell death resulting from loss of pRb function in senescent cells, we employed a temperature-sensitive pRb mutant protein (tspRb). We found that tspRb inactivation results in rapid E2F reactivation and subsequent ...
Hornsby Peter J - - 2003
Mice and humans are at opposite ends of the mammalian spectrum of longevity. A major question in biology is whether this difference can be accounted for by differences in the properties of cells from these two species. A new publication from Judith Campisi's lab reports that human cells in culture ...
Masutomi Kenkichi - - 2003
In normal human cells, telomeres shorten with successive rounds of cell division, and immortalization correlates with stabilization of telomere length. These observations suggest that human cancer cells achieve immortalization in large part through the illegitimate activation of telomerase expression. Here, we demonstrate that the rate-limiting telomerase catalytic subunit hTERT is ...
Huang Hsu-Shan - - 2003
As a part of our program aimed at exploring the biological activity of symmetrical substitution of side chains into the anthracene-9,10-dione chromophore, we have synthesized a series of 1,5-bisthioanthraquinones 2 and 1,5-bisacyloxyanthraquinones 3 that are related to the antitumor agent mitoxantrone. Since the telomerase enzyme is a novel target for ...
Barrett Michael T - - 2003
Elevated 4N (G(2)-tetraploid) cell populations are unstable intermediates in the development of many human cancers. However, 4N cell populations are intermixed with larger diploid fractions in vivo, limiting investigation of these key intermediates of neoplastic progression. Therefore, to study elevated 4N cell populations in human neoplasia, we used flow cytometry ...
Hayashi Masanobu - - 2003
Amounts of DNA strand breaks were estimated by the proportion of cells without tails (PCWT) and the average lengths of tail momentum (ALTM) in comet images of tissue cells of senescence-accelerated prone (SAMP1) mouse and senescence-accelerated resistant (SAMR1) mouse. The PCWT and ALTM of brain cells from SAMR1 were unchanged ...
Péterszegi G - - 2003
Skin aging represents an important chapter of connective tissue aging and concerns an organ of vital importance. Here we describe the preparation as well as the biological properties of fucose-rich oligo- and polysaccharides (FROPs), composed of polymers of a trisaccharide containing galactose, acetyl galacturonic acid and fucose, from the original ...
Horrocks Carolyn - - 2003
In the current drug discovery paradigm, validated recombinant targets form the basis of in vitro high-throughput screening (HTS) assays. Isolated proteins cannot, however, be regarded as representative of complex biological systems; hence, cell-based systems can be employed to complement in vitro data, providing greater confidence in compound activity in an ...
Vogt Saskia - - 2003
BACKGROUND: Replicative senescence describes the fact that somatic cells undergo a finite and predictable number of cell divisions before entering an irreversible state of growth arrest. Progressive shortening of the telomeres, a consequence of cell division, is a reliable indicator of replicative senescence. METHOD: We analyzed telomere length of DNA ...
Kameta Ayako - - 2003
This study describes the first example of spontaneously immortalized, telomerase-negative hamster cells which replicated in the absence of telomere shortening. Primary hamster buccal pouch epithelial (HBPE) cells were subcultured for approximately 10 population doublings (PDs) before they ceased to divide. Among the non-replicating HBPE cells, a colony of proliferating cells ...
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