Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “cell state transition”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 37 records · Page 2Linked to original sources
PubMed1977

PH-dependent changes of 2,3-bisphosphoglycerate in human red cells during transitional and steady states in vitro.

A systematic study of the pH-dependent changes in the range 6.6--7.4 of 2,3-bisphosphoglycerate and the adenine nucleotides was performed in the presence and absence of glucose during transitional and steady states. 1. The results indicatethat 2,3-gisphosphoglycerate phosphatase breaks down 2,3-bisphosphoglycerate nearly independent of pH at a rate of 480 mumol 2,3-bisphosphoglycerate x1 cells-1xh-1.2,3-Bisphosphoglycerate mutase is practically completely inhibited below pH value increases in long-term experiments with lower 2,3-bisphosphoglycerate levels. The formation of pyruvate corresponds to the breakdown of 2,3-bisphosphoglycerate afterconsumption of an unknown reducing substance.

Adenosine Diphosphate↗
PubMed1986

Stage-Specific State I-State II Transitions during the Cell Cycle of Euglena gracilis.

In synchronized Euglena gracilis (light-dark regime of 14:10 hours) the successive formation of the photosynthetic apparatus during cell ontogeny is correlated with large changes in photosynthetic efficiency (P Brandt, B von Kessel 1983 Plant Physiol 72: 616-619; B Kohnke, P Brandt 1984 Biochim Biophys Acta 766: 156-160). This observation led us to investigate the functional association of the chlorophyll a/b light-harvesting protein complex (LHCP) with photosystem I or II, because changes in energy flow to photosystem I or II and in energy transfer between the two photosystems can be a reason for these alterations. As criterion for the association of the LHCP with photosystem I or II, state transitions were determined after 15 minutes preillumination using wave-lengths of 725 or 620 nanometers. The state transitions were determined from measurements of fluorescence induction at room temperature, and fluorescence kinetics at 77 K. According to the obtained data (a) mobile LHCP is present only between the 6th and the 10th hour of the light-time of the cell cycle and (b) this functional relation of the LHCP to photosystem I only at this stage of Euglena chloroplast development is not accompanied by a decrease in stacking. A model for the organization of the newly inserted LHCP within the photosynthetic apparatus of E. gracilis is discussed.

Journal Article↗
PubMed1995

Human microvascular endothelial cell-extracellular matrix interaction in cellular growth state determination.

We introduce two methods, both of which are based on cellular-extracellular matrix interaction, which will facilitate the study of human microvascular endothelial cells. One method describes the means to obtain a G1 population baseline in human microvascular endothelial cells. Because of the contribution of the extracellular matrix in endothelial cell growth, synchronization in G1 was possible only after the incorporation of angiostatic levels of heparin and hydrocortisone into the extracellular matrix. In the second method, we demonstrate that selective perturbation of human microvascular endothelial cell-extracellular matrix interactions results in the induction of a transitional growth state, between proliferative and differentiated growth states, in human microvascular endothelial cells. In the functional, microtubule formation assays, transitional growth state endothelial cells display rates that are indermediate between those obtained from differentiated and proliferative endothelial cells. Our results demonstrate the importance of the human microvascular endothelial cell-extracellular matrix interaction in the determination of cellular growth state. Our findings also imply that responsiveness of microvascular endothelial cells to their cellular-extracellular matrix environs is highest during the differentiated growth state.

Adolescent↗
PubMed1999

Isolation and characterization of photoautotrophic mutants of Chlamydomonas reinhardtii deficient in state transition.

In photosynthetic cells of higher plants and algae, the distribution of light energy between photosystem I and photosystem II is controlled by light quality through a process called state transition. It involves a reorganization of the light-harvesting complex of photosystem II (LHCII) within the thylakoid membrane whereby light energy captured preferentially by photosystem II is redirected toward photosystem I or vice versa. State transition is correlated with the reversible phosphorylation of several LHCII proteins and requires the presence of functional cytochrome b(6)f complex. Most factors controlling state transition are still not identified. Here we describe the isolation of photoautotrophic mutants of the unicellular alga Chlamydomonas reinhardtii, which are deficient in state transition. Mutant stt7 is unable to undergo state transition and remains blocked in state I as assayed by fluorescence and photoacoustic measurements. Immunocytochemical studies indicate that the distribution of LHCII and of the cytochrome b(6)f complex between appressed and nonappressed thylakoid membranes does not change significantly during state transition in stt7, in contrast to the wild type. This mutant displays the same deficiency in LHCII phosphorylation as observed for mutants deficient in cytochrome b(6)f complex that are known to be unable to undergo state transition. The stt7 mutant grows photoautotrophically, although at a slower rate than wild type, and does not appear to be more sensitive to photoinactivation than the wild-type strain. Mutant stt3-4b is partially deficient in state transition but is still able to phosphorylate LHCII. Potential factors affected in these mutant strains and the function of state transition in C. reinhardtii are discussed.

Animals↗
PubMed2003

Ultrastructural basis for the transition of cell death mode from apoptosis to necrosis in menadione-treated osteosarcoma 143B cells.

Time-dependent ultrastructural changes of menadione-treated human osteosarcoma 143B cells were correlated with those in their stainability to Annexin V and propidium iodide (PI). Populations of both apoptotic (Annexin V(+)/PI(-)) and necrotic (Annexin V(+)/PI(+)) cells, judged by flow cytometry, began to increase at 2 h after menadione treatment. The former reached a maximum at 6 h followed by abrupt decreases thereafter, while the latter continued to increase. Electron microscopically, cells obtained at 6 h after the menadione treatment consisted of mixed populations of cells with typical apoptotic features and those with a mixture of apoptotic and necrotic features, while cells obtained at 8-24 h consisted exclusively of cells with a mixture of apoptotic and necrotic features. Thus, necrotic cells, as judged by flow cytometry, were in a transitional state of cell death mode from apoptosis to necrosis and are thus designated as 'intermediate cells'. Lack of apoptotic bodies, judged by flow cytometric analysis on sub-G1 nuclei and by electron microscopy in menadione-treated cells, suggested that the transition of cell death mode from apoptosis to necrosis occurred before the apoptotic processes were completed. Effects of N-acetylcysteine and Z-VAD-fmk on menadione-induced ultrastructural changes were also studied.

Antifibrinolytic Agents↗
PubMed2003

Kinetic analyses of state transitions of the cyanobacterium Synechococcus sp. PCC 7002 and its mutant strains impaired in electron transport.

The state transitions of the cyanobacterium Synechococcus sp. PCC 7002 and of three mutant strains, which were impaired in PsaE-dependent cyclic electron transport (psaE(-)), respiratory electron transport (ndhF(-)) and both activities (psaE(-)ndhF(-)), were analyzed. Dark incubation of the wild type and psaE(-) cells led to a transition to state 2, while the ndhF(-) strains remained in state 1 after dark incubation. The ndhF(-) cells adapted to state 2 when the cells were incubated under anaerobic conditions or in the presence of potassium cyanide; these results suggest that the ndhF(-) cells were inefficient in performing state 1 to state 2 transitions in the dark unless cytochrome oxidase activity was inhibited. In the state 2 to state 1 transition of wild-type cells induced by light in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), there was still a significant reduction of the interphotosystem electron carriers by both respiration and cyclic electron flow around PSI. Kinetic analysis of the state 2 to state 1 transition shows that, in the absence of PSII activity, the relative contribution to the reduced state of the interphotosystem electron carriers by respiratory and cyclic electron transfer is about 72% and 28%, respectively. The state 2 to state 1 transition was prevented by the cytochrome b(6)f inhibitor 2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB). On the other hand, the state 1 to state 2 transition was induced by DBMIB with half times of approximately 8 s in all strains. The externally added electron acceptor 2,5-dimethyl-benzoquinone (DMBQ) induced a state 2 to state 1 transition in the dark and this transition could be prevented by DBMIB. The light-induced oxidation of P700 showed that approximately 50% of PSI could be excited by 630-nm light absorbed by phycobilisomes (PBS) under state 2 conditions. P700 oxidation measurements with light absorbed by PBS also showed that the dark-induced state 1 to state 2 transition occurred in wild-type cells but not in the ndhF(-) cells. The possible mechanism for sensing an imbalanced light regime in cyanobacterial state transitions is discussed.

Bacterial Proteins↗
PubMed2003

Achieving the ultimate physiological goal in transition state analogue inhibitors for purine nucleoside phosphorylase.

Genetic deficiency of human purine nucleoside phosphorylase (PNP) causes T-cell immunodeficiency. The enzyme is therefore a target for autoimmunity disorders, tissue transplant rejection and T-cell malignancies. Transition state analysis of bovine PNP led to the development of immucillin-H (ImmH), a powerful inhibitor of bovine PNP but less effective for human PNP. The transition state of human PNP differs from that of the bovine enzyme and transition state analogues specific for the human enzyme were synthesized. Three first generation transition state analogues, ImmG (Kd = 42 pM), ImmH (Kd = 56 pM), and 8-aza-ImmH (Kd = 180 pM), are compared with three second generation DADMe compounds (4'-deaza-1'-aza-2'-deoxy-1'-(9-methylene)-immucillins) tailored to the transition state of human PNP. The second generation compounds, DADMe-ImmG (Kd = 7pM), DADMe-ImmH (Kd = 16 pM), and 8-aza-DADMe-ImmH (Kd = 2.0 nM), are superior for inhibition of human PNP by binding up to 6-fold tighter. The DADMe-immucillins are the most powerful PNP inhibitors yet described, with Km/Kd ratios up to 5,400,000. ImmH and DADMe-ImmH are orally available in mice; DADMe-ImmH is more efficient than ImmH. DADMe-ImmH achieves the ultimate goal in transition state inhibitor design in mice. A single oral dose causes inhibition of the target enzyme for the approximate lifetime of circulating erythrocytes.

Enzyme Inhibitors↗
PubMed2000

Molecular tectonic model of virus structural transitions: the putative cell entry states of poliovirus.

Upon interacting with its receptor, poliovirus undergoes conformational changes that are implicated in cell entry, including the externalization of the viral protein VP4 and the N terminus of VP1. We have determined the structures of native virions and of two putative cell entry intermediates, the 135S and 80S particles, at approximately 22-A resolution by cryo-electron microscopy. The 135S and 80S particles are both approximately 4% larger than the virion. Pseudoatomic models were constructed by adjusting the beta-barrel domains of the three capsid proteins VP1, VP2, and VP3 from their known positions in the virion to fit the 135S and 80S reconstructions. Domain movements of up to 9 A were detected, analogous to the shifting of tectonic plates. These movements create gaps between adjacent subunits. The gaps at the sites where VP1, VP2, and VP3 subunits meet are plausible candidates for the emergence of VP4 and the N terminus of VP1. The implications of these observations are discussed for models in which the externalized components form a transmembrane pore through which viral RNA enters the infected cell.

Capsid↗
PubMed2002

Analysis of the temporal expression of nestin in human fetal brain derived neuronal and glial progenitor cells.

Nestin expression in the developing human brain was examined with the use of unique human specific anti-nestin antibodies. Double immunostaining of cell cultures and tissue sections derived from first and second trimester human fetal brain (HFB) examined the co-expression of nestin with other cell type specific phenotypic markers. The immunocytochemical analysis shows that from first to second trimester, the majority of developing glial cells exhibited a transitional state marked by co-expression of nestin and GFAP. However, the corresponding transitional state for developing neuronal cells, co-expressing nestin and MAP-2, was rarely detected. These results imply different temporal patterns of nestin expression in cells of glial and neuronal lineages. Confocal microscopy of HFB tissue section staining also revealed a similar pattern of nestin co-expression with glial and neuronal markers. Our results suggest that nestin expression alone may not identify an undifferentiated stem cell, and that progenitor cells in glial and neuronal lineages express nestin in different temporal patterns.

Astrocytes↗
PubMed1988

[DNA synthesis in heterokaryons obtained by the fusion of proliferating cells of the NIH 3T3 line with cells in transition to the resting state].

NIH 3T3 mouse fibroblasts cultured in the medium containing 0.5% serum for 2, 4, 8, 24, 48 and 72 hours were fused to cells stimulated for proliferation by replacing the medium with a fresh one containing 10% serum; DNA synthesis was studied in monokaryons, homo- and heterodikaryons using radioautography and double-labelling technique. Cells that were cultured in the medium with a low serum content for 72 hours exerted their inhibitory effect on the entry of stimulated nuclei into the S period in heterodikaryons, whereas cells deprived of serum for shorter periods failed to exert this effect. It thus appears that in cell fusion studies with NIH 3T3 cells, the effects of endogenous growth inhibitor(s) produced by resting cells may be revealed not earlier than by the 3rd day of serum depletion.

Animals↗
PubMed1985

Regulation of myelination: Schwann cell transition from a myelin-maintaining state to a quiescent state after permanent nerve transection.

Permanent nerve transection of the adult rat sciatic nerve forces Schwann cells in the distal nerve segment from a myelin-maintaining to a quiescent state. This transition was followed by serial morphometric evaluation of the percentage fascicular area having myelin (myelin percent of area) in transverse sections of the distal nerve segment and revealed a rapid decline from a normal value of 36.6% to 3.2% by 14 days for the sciatic nerve to less than 1.0% throughout the remaining time course (up to 105 days). No evidence of axonal reentry into the distal nerve segment or new myelin formation was observed at times under 70 days. In some of the distal nerve segments at 70, 90, and 105 days, new myelinated fibers were observed that usually consisted of only a few myelinated fibers at the periphery and in the worst case amounted to 1.6% (myelin percent of area). Radioactive precursor incorporation of [3H]mannose into endoneurial slices at 4 and 7 days after transection revealed two species of the major myelin glycoprotein, P0, with Mr of 28,500 and 27,700. By 14 days after nerve transection, only the 27,700 Mr species remained. Incorporation of [3H]mannose into the 27,700 Mr species increased progressively to 35 days after transection and then began to decline at 70 and 105 days. Alterations in the oligosaccharide structure of this down-regulated myelin glycoprotein accounted for the progressive increase in mannose incorporation. Lectin affinity chromatography of pronase-digested P0 glycopeptides on concanavalin A-Sepharose revealed that the 28,500 Mr species of P0 had the complex-type oligosaccharide as the predominant oligosaccharide structure (92%). In contrast, the high mannose-type oligosaccharide was the predominate structure for the 27,700 Mr form, which increased to 70% of the total radioactivity by 35 days after nerve transection. Since the biosynthesis of the complex-type oligosaccharide chains on glycoproteins involves high mannose-type intermediates, the mechanism of down-regulation in the biosynthesis of this major myelin glycoprotein, therefore, results in a biosynthetic switch from the complex-type oligosaccharide structure as an end product to the predominantly high mannose-type oligosaccharide structure as a biosynthetic intermediate. This biosynthetic switch occurs gradually between 7 and 14 days after nerve transection and likely reflects a decreased rate of processing through the Golgi apparatus. It remains to be determined if the high mannose-type oligosaccharide chain on P0 can undergo additional processing steps in this permanent nerve transection model.

Animals↗
PubMed2026

Identification of Drug-resistant Cell Subpopulations in Colorectal Cancer Through Single-cell Analysis and Exploration of Potential Therapeutic Strategies.

INTRODUCTION: The therapeutic efficacy of Colorectal Cancer (CRC) is often compromised by resistance to the standard chemotherapy agent oxaliplatin. METHODS: This study obtained single-cell RNA sequencing (scRNA-seq) data from the Gene Expression Omnibus (GEO) database. Differentially Expressed Genes (DEGs) between resistant and sensitive epithelial subpopulations were identified, followed by enrichment analysis. Pseudotemporal trajectory and cell-cell communication were analyzed using Monocle2 and CellChat, respectively. The candidate drug was predicted by Connectivity Map (cMAP) analysis. External validation included assessment of the EpC2 signature in an oxaliplatin-resistant cell line dataset (GSE76092), survival analysis using The Cancer Genome Atlas (TCGA) cohorts, and re-analysis of the GSE179784 dataset to assess the reproducibility of EpC2-like subpopulations and their DNA Damage Repair (DDR) scores. RESULTS: Cell subpopulations were divided into 10 clusters. Among them, epithelial cells comprised 5 subpopulations, with EPC2 identified as a potential oxaliplatin-resistant subset. DEGs were enriched in the TNF and IL-17 pathways. External validation confirmed the enrichment of EpC2 in resistant cell lines and its association with poor survival. Pseudotemporal trajectory revealed that epithelial cells underwent state transitions, forming two distinct branches. The resistant group exhibited enrichment in RNA splicing and NF-κB pathways. Cell-cell communication analysis revealed interactions involving MDK- NCL and PPIA-BSG. Dasatinib was predicted as a candidate drug. DISCUSSION: We identified an oxaliplatin-resistant subpopulation of Epithelial Cells (EpC2) in CRC, elucidated its multi-layered resistance mechanisms, and integrated multi- omics and cMAP database analyses to predict a potential intervention drug. CONCLUSION: This study provided potential therapeutic possibilities for oxaliplatin resistance, contributing to CRC treatment.

Humans↗
PubMed2000

Cyclin-dependent kinase inhibitors: novel anticancer agents.

In current models of cell cycle control, the transition between different cell cycle states is regulated at checkpoints. Transition through the cell-cycle is induced by a family of protein kinase holoenzymes, the cyclin-dependent kinases (CDKs) and their heterodimeric cyclin partner. Orderly progression through the cell-cycle involves co-ordinated activation of the CDKs, which in the presence of an associated CDK-activating kinase, phosphorylate target substrates including members of the 'pocket protein' family. This family includes the product of the retinoblastoma susceptibility gene (the pRb protein) and the related p107 and p130 proteins. Activity of these holoenzymes is regulated by post-translational modification. Phosphorylation of inhibitory sites on a conserved threonine residue within the activation segment is regulated by CDK7/cyclin H, referred to as CDK-activating kinase [1]. In addition, the cdc25 phosphatases activate the CDKs by dephosphorylating their inhibitory tyrosine and threonine phosphorylated residues [2,3]. Among the many roles for endogenous inhibitors (CDKIs), including members of the p21(CIP1/Waf1) family and the p16 family, one role is to regulate cyclin activity. Cellular neoplastic transformation is accompanied by loss of regulation of cell cycle checkpoints in conjunction with aberrant expression of CDKs and/or cyclins and the loss or mutation of the negative regulators (the CDKIs or the pocket protein pRb). One strategy to inhibit malignant cellular proliferation involves inhibiting CDK activity or enhancing function of the CDKI. Novel inhibitors of CDKs showing promise in the clinic include flavopiridol and UCN-01, which show early evidence of human tolerability in clinical trials. This review examines pertinent advances in the field of CDK inhibitors.

Animals↗
PubMed2001

Drug design with a new transition state analog of the hydrated carbonyl: silicon-based inhibitors of the HIV protease.

BACKGROUND: Silicon is the element most similar to carbon, and bioactive organosilanes have therefore been of longstanding interest. Design of bioactive organosilanes has often involved a systematic replacement of a bioactive molecule's stable carbon atoms with silicon. Silanediols, which are best known as unstable precursors of the robust and ubiquitous silicone polymers, have the potential to mimic an unstable carbon, the hydrated carbonyl. As a bioisostere of the tetrahedral intermediate of amide hydrolysis, a silanediol could act as a transition state analog inhibitor of protease enzymes. RESULTS: Silanediol analogs of a carbinol-based inhibitor of the HIV protease were prepared as single enantiomers, with up to six stereogenic centers. As inhibitors of this aspartic protease, the silanediols were nearly equivalent to both their carbinol analogs and indinavir, a current treatment for AIDS, with low nanomolar K(i) values. IC(90) data from a cell culture assay mirrored the K(i) data, demonstrating that the silanediols can also cross cell membranes and deliver their antiviral effects. CONCLUSIONS: In their first evaluation as inhibitors of an aspartic protease, silanediol peptidomimetics have been found to be nearly as potent as currently available pharmaceutical agents, in enzyme and cell protection assays. These neutral, cell-permeable transition state analogs therefore provide a novel foundation for the design of therapeutic agents.

Cells, Cultured↗
PubMed1995

Glycosylation of CD44 negatively regulates its recognition of hyaluronan.

Although CD44 is expressed on a wide variety of cell types, few of them use it to recognize the ligand hyaluronan (HA). A glycosylation-defective clone of Chinese hamster ovary cells (Lec 8) bound HA, demonstrating that complete processing of glycoproteins with addition of a full complement of sialic acid is not required. On the contrary, subsequent findings revealed that complex sugars on CD44 can actually inhibit ligand recognition. Two subclones of wild-type Chinese hamster ovary cells with similar amounts of surface CD44 were isolated on the basis of HA binding and found to differ with respect to CD44 size as well as staining with fluorescent lectins. Treatment of the nonbinding clone with tunicamycin reduced the size of the protein and allowed the cells to recognize HA via CD44. This function was also induced by treatment with deglycosylating enzymes (either a mixture of endoglycosidase F and N-glycosidase F or neuraminidase alone). A possible role for glycosylation in regulation of adhesion was then sought with a series of normal and transformed murine cells. Disruption of glycosylation or treatment with deglycosylating enzymes did not induce ligand binding in an interleukin 7-dependent pre-B cell line, and splenic B cells also appeared to be in an inactive state. Some normal B cells acquired the ability to recognize HA after stimulation with lipopolysaccharide or interleukin 5 and had distinctive surface characteristics (loss of immunoglobulin D and acquisition of CD43). An additional subset of activated cells might have been in a transitional state, because the cells bound ligand after neuraminidase treatment. The ligand-binding ability of a purified CD44-immunoglobulin fusion protein dramatically increased after neuraminidase treatment. Thus, differential glycosylation of this molecule is sufficient to influence its recognition function. Cell adhesion involving HA can be regulated by multiple mechanisms, one of which involves variable glycosylation of CD44.

Animals↗
PubMed1998

Effects of perturbations of pools of deoxyribonucleoside triphosphates on expression of ribonucleotide reductase, a G1/S transition state enzyme, in p53-mutated cells.

Effects of drug treatment with antimetabolites on a human colon cancer cell line, SW480, were studied. Cells were treated with 10 microM of 5-fluorouracil (5FU), an inhibitor of pyrimidine synthesis, or 1000 microM of hydroxyurea (HU), an inhibitor of both purine and pyrimidine syntheses, or the combination. Recombinant alpha-2a-interferon (IFN), 500 U/mL, also was employed, as this augments the effects of both antimetabolites in vitro and in vivo. The predominant effect of this combination was to block cells in early S phase as measured by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation. By 24 hr, 86% of the cells had accumulated in S phase, but failed to progress to G2/M. This was accompanied by an early, rapid decline in all four deoxyribonucleoside triphosphates (dNTPs) by 38-86% at 4-24 hr. Despite these effects, expression of the G1/S transition state enzyme, ribonucleotide reductase (RR), increased at 24 hr as measured by a 3 to 5-fold increase in mRNA levels for the M2 subunit, in the absence of a measurable effect on protein levels. The rise in levels of RR mRNA and the continued progression of cells into S phase were associated with a synergistic inhibition of cell cycle proliferation resulting from treatment with the three-drug combination. This suggests that in the presence of antimetabolite-induced depletion of dNTPs, SW480 cells, which lack a normal p53 gene, will proceed into S phase, and that this is associated with a rise in expression of the G1/S transition state enzyme, RR. Cells arrested in S phase by a p53-independent mechanism will undergo a synergistic enhancement of cell death.

Cell Cycle↗
PubMed1981

The role of respiration in tumor cell transition from the noncycling to the cycling state.

Resting Yoshida AH130 hepatoma cells, harvested at the plateau of tumor development in vivo, were recruited into the cycling state following transfer to an in vitro system whereby these cells were incubated in the autologous ascites plasma diluted with buffered saline and enriched with glucose. In this system, cell recruitment into the phase of DNA synthesis (S phase) strictly depends on the activity of the respiratory chain and is abolished by anaerobiosis as well as by antimycin A, although the intracellular levels of ATP and the rate of protein synthesis are practically unaffected by these treatments. Furthermore, 2,4-dinitrophenol, at concentrations which uncouple the respiratory phosphorylation and hence enhance both glycolysis and oxygen consumption, does not hinder cell promotion into S phase. Thus, the absolute respiration dependence of cycling resumption by resting ascites cells does not seem to rely on respiratory ATP supply, but rather is linked to the electron flow through the respiratory chain.

Adenosine Triphosphate↗