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At least 433 records · Page 24Linked to original sources
PubMed2005

Temporal expression patterns and corresponding protein inductions of early responsive genes in rabbit bone marrow-derived mesenchymal stem cells under cyclic compressive loading.

Our recent study suggested that cyclic compressive loading may promote chondrogenesis of rabbit bone-marrow mesenchymal stem cells (BM-MSCs) in agarose cultures through the transforming growth factor (TGF)-beta signaling pathway. It has been shown that the activating protein 1 (AP-1) (Jun-Fos) complex mediated autoinduction of TGF-beta1 and its binding activity was essential for promoting chondrogenesis of mesenchymal cells, whereas Sox9 was identified as an essential transcription factor for chondrogenesis of embryonic mesenchymal cells. The objective of this study was to examine temporal expression patterns of early responsive genes (Sox9, c-Fos, c-Jun, and TGF-beta type I and II receptors) and induction of their corresponding proteins in agarose culture of rabbit BM-MSCs subjected to cyclic compressive loading. The rabbit BM-MSCs were obtained from the tibias and femurs of New Zealand White rabbits. Cell-agarose constructs were made by suspending BM-MSCs in 2% agarose gel (10(7) cells/ml) for cyclic, unconfined compression tests performed in a custom-made bioreactor. In the loading experiment, specimens were subjected to sinusoidal loading with a magnitude of 15% strain at a frequency of 1 hertz for 4 hours per day. Experiments were conducted for 2 consecutive days. This study showed that cyclic compressive loading promoted gene expressions of Sox9, c-Jun, and both TGF-beta receptors and productions of their corresponding proteins, whereas those gene expressions exhibited different temporal expression patterns among genes and between 2 days of testing. The gene expression of c-Fos was detected only in the samples subjected to1-hour dynamic compressive loading. These findings suggest that the TGF-beta signal transduction and activities of AP-1 and Sox9 are involved in the early stage of BM-MSC chondrogenesis promoted by dynamic compressive loading.

Animals↗
PubMed1999

Effects of jarastatin, a novel snake venom disintegrin, on neutrophil migration and actin cytoskeleton dynamics.

A new disintegrin, an RGD-containing peptide of 6 kDa called jarastatin, was purified from Bothrops jararaca venom. It is a potent inhibitor of platelet aggregation induced by ADP, collagen, and thrombin. The effect of jarastatin on neutrophil migration in vivo and in vitro and on the actin cytoskeleton dynamics of these cells was investigated. Incubation in vitro with jarastatin significantly inhibited, in a concentration-dependent manner, the chemotaxis of human neutrophils toward fMLP, IL-8, and jarastatin itself. Despite this inhibitory effect, jarastatin induced neutrophil chemotaxis. A significant increase of F-actin content was observed in jarastatin-treated neutrophils. Furthermore, as demonstrated by confocal microscopy after FITC-phalloidin labeling, these cells accumulated F-actin at the plasmalemma, a distribution similar to that observed in fMLP-stimulated cells. Pretreatment of mice with jarastatin inhibited neutrophil migration into peritoneal cavities induced by carrageenan injection. The results suggest that binding of jarastatin to neutrophil integrins promotes cellular activation and triggers a dynamic alteration of the actin filament system and that this is one of the first event in integrin-mediated signaling.

Actins↗
PubMed2004

Dynamics of compartmented and reticulate food webs in relation to energetic flows.

Using simple food webs, we address how the interactions of food web structure and energetic flows influence dynamics. We examine the effect of food web topologies with equivalent energetics (i.e., trophic interactions are equivalent at each trophic level), following which we vary energetic flows to include weak and strong interactions or nonequivalent energetics. In contrast to some work (Pimm 1979), we find that compartmented webs are more stable than reticulate webs. However, we find that nonequivalent energetics can stabilize previously unstable reticulate structures. It is not only weak flows that can be stabilizing but also the arrangement of the flows that emphasizes stabilizing mechanisms. We find that the main stabilizing mechanism is asynchrony, where structures and energetic arrangements that decrease synchrony such as internal segregation or competition will stabilize dynamics. Since compartments allow prey dynamics to behave somewhat independently, compartmentation readily promotes stability. In addition, these results can be scaled from simple food webs to more complex webs with many interacting subsystems so that linking weak subsystems to strong ones can stabilize dynamics. We show that food web dynamics are determined not only by topology but also the arrangement of weak and strong energetic flows.

Animals↗
PubMed1999

[In Process Citation]

The soil dynamics of old-fields, characterized by the early establishment of broom (Cytisus scoparius L.), is analysed in the Breton bocage. The role of former land use practices is estimated by comparing two similar plant successions, post cultivation and post pasture. Different variables (organic matter, mineral N content, microbial biomass, total microbial activity and mineralization) are measured within the soil layer disturbed by farming (between -5 and -25 cm). One year after abandonment, the parameters taken into account show similar values for both series. After 8 years, in broom thickets, the two soil series are characterized by an increase in microbial activity, organic matter and mineral N contents. However, the post cultivation thicket differed by higher N content and mineralization rate than the post pasture thicket, but also by a smaller microbial biomass. It appears that, if the development of similar vegetational communities promotes the same kind of soil dynamics, the former land use practices significantly modify this evolution, for at least the first 8 years following abandonment.

Journal Article↗
PubMed1993

The effects of tobacco sales promotion on initiation of smoking--experiences from Finland and Norway.

Norway and Finland were among the first countries to adopt a total ban on tobacco sales promotion. Such legislation came into force in Norway and Finland in 1975 and 1978 respectively. These two countries are sometimes referred to as illustrations that such legislation has been successfully used as a means to reduce tobacco consumption. Tobacco industry spokesmen seem to interpret available evidence in the opposite way and maintain that the prohibition has not contributed to reducing the use of tobacco. Among the publications referred to and misused by tobacco industry spokesmen are publications from the authors of the present report. The effects of a ban on advertising can only be properly examined after describing a reasonable conceptual model. Such a model has to take into account (i) other social and cultural predictors of smoking, (ii) tobacco sales promotion in the contexts of all other mass communication, (iii) control measures other than a ban, and (iv) the degree of success in implementing the ban on advertising. Like any other kind of mass communication tobacco advertising influences the individual in a rather complex way. Behaviour change may be regarded as the outcome of an interpersonal and intrapersonal process. Social science research on tobacco advertising and the effects of banning such advertising has a short history, most studies having been carried out in the late 1980s. After examining available evidence related to the effects of tobacco advertising on the smoking habits of adolescents we conclude as follows: the few scientifically valid reports available today give both theoretical and empirical evidence for a causal relationship. Tobacco sales promotion seems both to promote and to reinforce smoking among young people. The dynamic tobacco market represented by children and adolescents is probably the main target of tobacco sales promotion. In Finland, there have been few studies explicitly addressing the causal links between tobacco sales promotion and the smoking habits of adolescents. In Norway, no such studies have been carried out. If we examine the changes in the use of tobacco over time, the data available do not lend support to the conclusions drawn by the tobacco industry spokesmen. In Norway the prevalence of daily smokers was higher in 1975, when the ban on tobacco advertising came into force than either before or after. The strongest decrease in the prevalence of daily smokers took place during the first five-year period after the ban was introduced.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed2005

Promoter methylation and differential expression of pi-class glutathione S-transferase in endometrial carcinoma.

Pi-class glutathione S-transferase (GSTP1), located on chromosome 11q13, codes for a phase II metabolic enzyme that detoxifies reactive electrophilic intermediates. The protein also interacts with steroid hormones in the human body. The role of GSTP1 in endometrial carcinoma has not been reported. In this study, we aimed at determining the expression of GSTP1 in relation to the epigenetic and genetic changes of the gene in endometrial carcinoma. The GSTP1 protein and mRNA expression was assessed by immunohistochemistry on tissue microarray and quantitative real-time reverse transcriptase-polymerase chain reaction, respectively. Its methylation status was studied by methylation-specific polymerase chain reaction and bisulfite sequencing. Possible mutations in coding region of GSTP1 were assessed by cDNA sequencing. Ninety-seven cases of endometrial carcinoma with available tissue blocks and clinical data were studied. Our results showed that 68.0% (66 of 97) of the cases showed reduced protein expression while 64% (16 of 25) showed reduced mRNA expression; 30.9% (30 of 97) of the cases demonstrated methylated alleles in at least one of the six methylation-specific polymerase chain reaction reactions. The methylation status significantly correlated with reduced protein expression (P = 0.008) and reduced mRNA expression (P = 0.003). Methylation at non-CpG sites including CpCpG trinucleotides and CpT dinucleotides were also observed. cDNA sequencing did not reveal genetic alterations in coding region of the gene. The extent of myometrial invasion was found to be significantly correlated with both the methylation status (P = 0.009) and the protein expression (P = 0.036) of the GSTP1 gene. We postulated that hypermethylation of the GSTP1 gene promoter region may act as a dynamic regulation mechanism contributing to reduced GSTP1 expression, which is associated with myometrial invasion potential of the endometrial carcinoma.

Adult↗
PubMed1996

Prelymphomatous B cell hyperplasia in the bone marrow of interleukin-7 transgenic mice: precursor B cell dynamics, microenvironmental organization and osteolysis.

Transgenic mice carrying mouse interleukin-7 (IL-7) cDNA under the control of MHC class II (E alpha) promoter develop B lymphoid tumors. We have analyzed population dynamics of early precursor B cells and electron microscopic organization of bone marrow (BM) during the prelymphomatous phase. Immunofluorescence labeling of terminal deoxynucleotidyl transferase (TdT), B220 glycoprotein, and mu heavy chains have been used to quantitate three populations of pro-B cells lacking mu chains, cytoplasmic mu-bearing pre-B cells, and surface mu-bearing B lymphocytes. Proliferative activity was assayed by metaphase arrest. In BM of IL-7 transgenic mice, the number and proliferative activity of cells in each of the pro-B and pre-B cell populations were markedly increased. B lymphocytes increased to a lesser extent. The BM cavity was considerably expanded and cortical bone showed focal osteolysis. Immature lymphoid cells compressed the venous sinusoids and exuded through eroded bone. Apoptotic bodies, macrophages, and plasma cells were unusually prominent. B lymphocytes and cells of B precursor phenotype were also much increased in the spleen. These results demonstrate that overexpression of IL-7 causes excessive proliferation of a wide range of precursor B cells in BM. Such prolonged stimulation at early stages of B cell development, prone to genetic errors, may predispose to neoplasia. The bone resorption in these transgenic mice provides a model for bone lesions in BM malignancies.

Animals↗
PubMed1997

An endogenous calcium oscillator may control early embryonic division.

Transient elevations in the concentration of free cytosolic calcium ion ([Ca2+]i) promote cell phase transitions in early embryonic division and persist even if these transitions are blocked. These observations suggest that a [Ca2+]i oscillator is an essential timing element of the early embryonic "master clock." We explore this possibility by coupling a [Ca2+]i oscillator model to an early embryonic cell cycle model based on the protein interactions that govern the activity of the M-phase-promoting factor (MPF). We hypothesize three dynamical states of the MPF system and choose parameter sets to represent each. We then investigate how [Ca2+]i dynamics may control early embryonic division in both sea urchin and Xenopus embryos. To investigate both systems, distinct [Ca2+]i profiles matching those observed in sea urchin embryos (in which [Ca2+]i exhibits sharp transients) and Xenopus embryos (in which [Ca2+]i is elevated and oscillates sinusoidally) are imposed on each of the hypothesized dynamical states of MPF. In the first hypothesis, [Ca2+]i oscillations entrain the autonomous MPF oscillator. In the second and third hypotheses, where the MPF system rests in excitatory and bistable states, respectively, [Ca2+]i oscillations drive MPF activation cycles. Simulation results show that hypotheses two and three, in which a [Ca2+]i oscillator is a fundamental timing element of the master clock, best account for key experimental observations and the questions that they raise. Finally, we propose experiments to elucidate further [Ca2+]i regulation and the fundamental components of the early embryonic master clock.

Animals↗
PubMed2025

Circadian clock control of ribosome composition promotes rhythmic translation and termination fidelity.

Ribosome composition is dynamic, shifting with cell state and stress, but whether it varies with circadian time is unknown. Here, we uncover circadian clock-driven changes in ribosome composition in Neurospora crassa. Mass spectrometry of ribosomes across circadian time identified six ribosomal proteins and one associated factor under clock control. Rhythms in eL31 abundance were validated in purified ribosomes, and deletion of el31 disrupted translation rhythms in nearly half of rhythmically translated mRNAs. N. crassa eL31 promotes circadian control of translation termination and impacts elongation fidelity while maintaining Mg homeostasis, a key determinant of translational accuracy. These findings reveal that the circadian clock reprograms ribosome composition to orchestrate rhythmic translation and fidelity, temporally expanding the proteome beyond the static genome to align cellular function with time of day.

Neurospora crassa↗
PubMed1988

Detection of single fluorescent microtubules and methods for determining their dynamics in living cells.

The ability to tag biological molecules fluorescently and to detect their distribution in living cells has promoted the study of cytoplasmic organization in general and microtubule dynamics in particular. The techniques that we have selected and developed allowed the determination of spatial and temporal changes of the microtubule network in living fibroblasts at the level of individual microtubules. We have employed two general approaches for determining pattern changes: direct video microscopy and photobleaching and subsequent observation. Direct observation of fluorescent microtubules by high-definition video microscopy provided good spatial resolution at several time points, but was limited to the less congested and thinner periphery of the cell. This approach was made possible by a relatively bright, photostable reporter, xrhodamine-tubulin, and showed that microtubules underwent rounds of assembly and disassembly from their ends. Bleaching and subsequent observation of lysed cells improved the signal to noise ratio by extracting soluble chromophore and permitted observations in congested areas, but was limited to a single time interval. This approach demonstrated that microtubule domains were replaced one by one and that turnover was most rapid at the cell periphery. Antibodies specific for nonbleached chromophore can be used to enhance the signal to noise ratio further or to extend spatial resolution by the use of immunoelectron microscopy. Direct video microscopy and photobleaching are two approaches to the study of dynamics that have complementary strengths and wide application to the biology of living cells.

Cell Movement↗
PubMed2006

A comprehensive library of fluorescent transcriptional reporters for Escherichia coli.

E. coli is widely used for systems biology research; there exists a need, however, for tools that can be used to accurately and comprehensively measure expression dynamics in individual living cells. To address this we present a library of transcriptional fusions of gfp to each of about 2,000 different promoters in E. coli K12, covering the great majority of the promoters in the organism. Each promoter fusion is expressed from a low-copy plasmid. We demonstrate that this library can be used to obtain highly accurate dynamic measurements of promoter activity on a genomic scale, in a glucose-lactose diauxic shift experiment. The library allowed detection of about 80 previously uncharacterized transcription units in E. coli, including putative internal promoters within previously known operons, such as the lac operon. This library can serve as a tool for accurate, high-resolution analysis of transcription networks in living E. coli cells.

Escherichia coli↗
PubMed2005

The dynamics of cardiac fibrillation.

Reentry occurs when the electrical wave propagating through the atria or ventricles breaks locally and forms a rotor (also called a scroll wave or functional reentry). If the waves propagating outward from a rotor develop additional wavebreaks (which may form new rotors), fibrillation results. Tissue heterogeneity, exacerbated by electrical and structural remodeling from cardiac disease, has traditionally been considered the major factor promoting wavebreak and its degeneration to fibrillation. Recently, however, dynamic factors have also been recognized to play a key role. Dynamic factors refer to cellular properties of the cardiac action potential and Ca(i) cycling, which dynamically generate wave instability and wavebreak, even in tissue that is initially completely homogeneous. Although the latter situation can only be created in computer simulations, its relevance to real (heterogeneous) cardiac tissue has been unequivocally demonstrated. Dynamic factors are related to membrane voltage (Vm) and Ca(i). Vm factors include electrical restitution of action potential duration and conduction velocity, short-term cardiac memory, and electrotonic currents. Ca(i) factors are related to dynamic Ca(i) cycling properties. They act synergistically, as well as with tissue heterogeneity, to promote wavebreak and fibrillation. As global properties, rather than local electrophysiological characteristics, dynamic factors represent an attractive target for novel therapies to prevent ventricular fibrillation.

Action Potentials↗
PubMed2004

Coordination of cell signaling, chromatin remodeling, histone modifications, and regulator recruitment in human matrix metalloproteinase 9 gene transcription.

Transcriptional activation of eukaryotic genes depends on the precise and ordered recruitment of activators, chromatin modifiers/remodelers, coactivators, and general transcription factors to the promoters of target genes. Using the human matrix metalloproteinase 9 (MMP-9) gene as a model system, we investigated the sequential assembly and dynamic formation of transcription complexes on a human promoter under the influence of mitogen signaling. We find that, coincident with activation of the MMP-9 gene, activators, chromatin remodeling complexes, and coactivators are recruited to the preassembled MMP-9 promoter in a stepwise and coordinated order, which is dependent on activation of MEK-1/extracellular signal-regulated kinase and NF-kappa B signaling pathways. Conversely, corepressor complexes are released from the MMP-9 promoter after transcriptional activation. Histone modifications shift from repressive to permissive modifications concurrent with activation of the MMP-9 gene. Chromatin remodeling induced by Brg-1 is required for MMP-9 gene transcription, which is concomitant with initiation of transcription. Therefore, coordination of cell signaling, chromatin remodeling, histone modifications, and stepwise recruitment of transcription regulators is critical to precisely regulate MMP-9 gene transcription in a temporally and spatially dependent manner. Given the important role of MMP-9 in both normal development and pathological conditions, understanding MMP-9 gene regulation is of great relevance.

Binding Sites↗
PubMed2003

The multicoloured world of promoter recognition complexes.

The expression pattern of regulated genes changes dynamically depending on the developmental stage and the differentiation state of the cell. Transcription factors regulate cellular events at the gene expression level by communicating signals to the general transcription machinery that forms a preinitiation complex (PIC) at class II core promoters. Recent data strongly suggest that PICs are composed of different sets of factors at distinct promoters, reflecting the spatiotemporal profile of gene expression in multicellular organisms. Thus, today it is important to ask the question: how universal are the promoter recognition factors? This review will focus on findings that support the new idea that core promoter recognition by distinct factors is an additional level of transcriptional regulation and that this step is developmentally regulated.

Animals↗
PubMed1979

Group dynamics in community health teams.

The work of community mental health centers is typically organized into heterogeneous groups of professionals and nonprofessionals. These groups suffer from numerous strains and conflicts and infrequently achieve group cohesiveness or a sense of community. This paper analyzes the source of this problem from the points of view of group dynamics and social organization. Implications for promoting group cohesiveness through group design are discussed.

Community Mental Health Centers↗
PubMed1994

Reduced surface area in apoptotic rounding of human Chang liver cells from serum deprivation.

BACKGROUND: The early stages of apoptosis (programmed cell death) are said to be characterized by internucleosomal DNA fragmentation and "condensation of the cytoplasm" in which cells round up, detach, and increase in density. We studied the causation of apoptotic rounding. METHODS: Human Chang liver cells in normal monolayer culture were compared with apoptotic counterparts derived from serum growth factor deprivation. Cell-by-cell analysis using the Coulter EPICS PROFILE II flow cytometer studied 1) the cell cycle from propidium iodide-DNA bindings, 2) uptake of neutral red (NR) dye, a viable cell marker, and 3) cytosolic pH (pHi) modulations from 2',7'-bis(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF) fluorescence ratios with NH4Cl prepulsing and forward scatter bitmapping of cell surface area. Morphometric studies were done in the Quantimet 570 image analyser. Uptake of trypan blue, neutral red, and 2 million mol.wt fluoresceinated dextrans was studied by light microscopy. Cytological profiles were examined in light microscopy and transmission and scanning electron microscopy. RESULTS: Three days of serum growth factor deprivation caused confluent flat substrate-attached cells to retract and round up, tethering tenuously to the substrate via thin microvillus attachments only. Ninety percent of cell surface area was lost with this flat-to-round change. There was high trypan blue staining with total loss of proliferative potential, and the entire genome was just fragmented DNA making up the solitary Ao (apoptotic) peak in cell cycle profiles. However, these rounded apoptotic cells also internalized huge 2 million mol.wt dextran particles and impermeant neutral red which is an established viable cell marker. The rounded apoptotic cells had an intensely acidic (pH 5.6) cytosol and therefore a steep [H+]i/[H+]o gradient promoting proton extrusion. The pHi upshifted dynamically upon acidification, recovering and even exceeding resting level by a whole pH unit. Surface area reduction occurred concomitantly in real time with pHi upshifts in these apoptotic cells. Acidification and recovery in apoptotic cells also produced enhanced uptake of neutral red. Cytological profiles showed abundant large endocytic channels and endosomes in the rounded apoptotic cells. CONCLUSIONS: Gross surface area reduction with evidence of distinctive endocytic activity including uptake of huge 2 million mol.wt dextran particles suggested large channel endocytic internalization as a causal factor in apoptotic rounding, in common with rounding in M-phase and interphase cells with pHi upshifting where concomitant surface area reduction and uptake of impermeant particles were similarly demonstrable. The reduction in size of the cell envelope, together with consequential concentration pressures, could account for the observed rise in cell density and shrinkage in cell size. As a symptom of continual pHi upshifting, apoptotic rounding appears to be a recovery-associated response rather than a direct consequence of the disruptive forces causing its death.

Apoptosis↗
PubMed2001

Expression of SCG10 and stathmin proteins in the rat olfactory system during development and axonal regeneration.

The membrane-associated protein SCG10 is expressed specifically by neuronal cells. Recent experiments have suggested that it promotes neurite outgrowth by increasing microtubule dynamics in growth cones. SCG10 is related to the ubiquitous but neuron-enriched cytosolic protein stathmin. To better understand the role played by SCG10 and stathmin in vivo, we have analyzed the expression and localization of these proteins in both the olfactory epithelium and the olfactory bulb in developing and adult rats, as well as in adult bulbectomized rats. The olfactory epithelium is exceptional in that olfactory receptor neurons constantly regenerate and reinnervate the olfactory bulb throughout animal life-span. SCG10 and stathmin expression in the olfactory receptor neurons was found to be regulated during embryonic and postnatal development and to correlate with neuronal maturation. Whereas SCG10 expression was restricted to immature olfactory receptor neurons (GAP-43-positive, olfactory marker protein-negative), stathmin was also expressed by the basal cells. In the olfactory bulb of postnatal and adult rats, a moderate to strong SCG10 immunoreactivity was present in the olfactory nerve layer, whereas no labeling was detected in the glomerular layer. Olfactory glomeruli also showed no apparent immunoreactivity for several cytoskeletal proteins such as tubulin and microtubule-associated proteins. In unilaterally bulbectomized rats, SCG10 and stathmin were seen to be up-regulated in the regenerating olfactory epithelium at postsurgery stages corresponding to olfactory axon regeneration. Our data strongly suggest that, in vivo, both SCG10 and stathmin may play a role in axonal outgrowth during ontogenesis as well as during axonal regeneration.

Aging↗