PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Functional perturbation”

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

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

At least 325 records · Page 18Linked to original sources
PubMed1999

In vivo UVA-1 and UVB irradiation differentially perturbs the antigen-presenting function of human epidermal Langerhans cells.

Ultraviolet B (UVB, 290-320 nm) radiation is known to suppress the immune function of epidermal Langerhans cells. We have recently described that in vitro UVB irradiation perturbs the antigen-presenting cell function of Langerhans cells by inhibiting their expression of functional B7 costimulatory molecules (B7-1, B7-2). The aim of this study was to determine wavelength-specific UV effects on Langerhans cells function in vivo, specifically UVB and UVA-1. To address this issue, volunteers were irradiated on the sun protected volar aspects of their forearms with 3 x minimal erythema dose of UVB (Philips TL-12) and UVA-1 (UVASUN 5000 Mutzhaas). Langerhans cells were isolated from suction blister roofs immediately following irradiation. Langerhans cells isolated from UVB- but not from UVA-1-irradiated skin failed to activate naïve resting allogeneic T cells (mixed epidermal cell leukocyte reaction) or primed tetanus toxoid reactive autologous T cells. Langerhans cells isolated from sham-irradiated or UVA-1-irradiated skin strongly upregulated B7-2 molecules during short-term tissue culture. By contrast, Langerhans cells from UVB-irradiated skin did not upregulate B7-2 molecules. Furthermore, exogenous stimulation of the B7 pathway by anti-CD28 stimulatory monoclonal antibodies restored the capacity of UVB-irradiated Langerhans cells to activate both alloreactive and tetanus toxoid-reactive T cells, implying suppressed antigen-presenting cell activities and perturbed B7 expression of Langerhans cells isolated from UVB-irradiated skin are related. Those studies demonstrate that in vivo UVB, but not UVA-1, interferes with the activation-dependent upregulation of B7 molecules on Langerhans cells, which in turn is of functional relevance for the perturbed antigen-presenting cell function of Langerhans cells within UVB- but not UVA-1-irradiated skin.

Antigen Presentation↗
PubMed2003

Gene expression profiling and functional proteomic analysis reveal perturbed kinase-mediated signaling in genetic stroke susceptibility.

The stroke-prone spontaneously hypertensive rat (SHRSP) is a model of heritable hypertension-associated cerebrovascular injury. This study sought to compare SHRSP to the stroke-resistant SHR strain to identify genes and protein pathways whose expression and/or function was significantly altered between the strains prior to the onset of stroke. Cerebral cortex gene expression profiles from male SHRSPs and matched SHRs were examined by Affymetrix microarray analysis. mRNAs encoding the brain-derived neurotrophic factor receptor (TrkB) and multiple kinases of the MAPK/AKT signaling pathways, including JNK2, AKT2, and PI3K, were differentially expressed between SHRSP and SHR. Because these data suggest altered function in pathways involving MAP and AKT kinase activity, we performed Western blot using phosphorylation state-specific antibodies to characterize activity of MAP kinase and PI3K/AKT pathways. Changes in the levels of the phosphorylated forms of these kinases paralleled the changes in transcript levels observed between the strains. Two-dimensional gel electrophoresis and peptide fragment mass fingerprinting were used to identify altered protein substrates of these kinases. Protein profiling of kinase substrates further supported the notion of perturbed kinase-mediated signaling in SHRSP and identified adenylyl cyclase associated protein 2, TOAD-64, propionyl CoA carboxylase, APG-1, and valosin-containing protein as kinase targets whose phosphorylation state is altered between these strains. Altered gene and protein expression patterns in SHRSP are consistent with increased vulnerability of this strain to cerebrovascular injury.

Animals↗
PubMed2026

Mapping convergent regulators of melanoma drug resistance by PerturbFate.

High-throughput genomic studies have uncovered associations between diverse genetic alterations and disease phenotypes. However, elucidating how perturbations in functionally disparate genes give rise to convergent cellular states remains challenging. Here we present PerturbFate, a high-throughput, cost-effective, combinatorial-indexing single-cell platform that enables systematic interrogation of massively parallel CRISPR interference1 perturbations across the full spectrum of gene regulation, from chromatin remodelling and nascent transcription to steady-state transcriptomic phenotypes. Using PerturbFate, we profiled more than 300,000 cultured melanoma cells to characterize multimodal phenotypic and gene regulatory responses to perturbations in more than 140 vemurafenib resistance-associated genes. We uncovered a shared dedifferentiated cell state marked by convergent cooperative transcription factor activities across diverse genetic perturbations. We further dissected phenotypic responses to perturbations in Mediator complex components, linking module-specific biochemical properties to convergent transcriptional activations. We identified common regulatory nodes that drive similar phenotypic outcomes across distinct genetic perturbations. We also delineated how perturbations in functionally unrelated genes reshape cell state. Thus, PerturbFate establishes a versatile platform for identifying key molecular regulators by anchoring multimodal regulatory dynamics to disease-relevant phenotypes.

Humans↗
PubMed2006

Local work function of Pt clusters vacuum-deposited on a TiO2 surface.

Surface topography and work function maps were simultaneously obtained for Pt-evaporated titanium dioxide (TiO(2)) surfaces by using a Kelvin probe force microscope (KPFM). Platinum clusters with diameters of 2-3 nm and heights of 0.2-0.4 nm were obtained on rutile TiO(2)(110)-(1 x 1) surfaces. The work function on the Pt clusters was smaller than that on the surrounding TiO(2) surface. With the assumption that the work function was perturbed by electric dipole moments created at the Pt-TiO(2) interface, the work function decrease indicates that dipole moments were created at the interface and directed toward the vacuum. Such dipole moments can be formed by electron transfer from the originally neutral Pt atoms to the Ti cations exposed on the (1 x 1) surface. A simple model is constructed by assuming a uniform dipole moment per unit interface area. Using this model, the size-dependent perturbation of the work function can be interpreted. The electrostatic potential is more perturbed above the Pt clusters with a larger interface area since the number density of dipole moments is equal to that of the Ti cations and is uniform. A similar correlation between the work function decrease and interface area was observed for the clusters formed on terraces and on step edges. The work function maps showed no peculiar contribution for Ti atoms exposed at the step edges. Vacuum annealing caused a considerable change in the work function on the clusters. The work function was decreased on some clusters relative to the TiO(2) substrate, while it increased on the other clusters. The atomistic structure of the interface may be modified upon annealing, thus perturbing the electron transfer across the interface.

Journal Article↗
PubMed1981

Differential perturbation of erythrocyte membrane function by structurally related polycyclic aromatic hydrocarbons.

Examination of the interaction of a number of structurally related polycyclic aromatic hydrocarbons with the erythrocyte plasma membrane indicated that the presence and position of methyl groups on the lipophilic hydrocarbon nucleus determined whether the compound acted as an inhibitor of membrane function. 7,12-Dimethylbenz(a)anthracene, a potent carcinogen, acted as a noncompetitive inhibitor of membrane acetylcholinesterase. The inhibition depended on the anion composition of the buffer at the time of exposure of the cells to inhibitor, i.e., it was only manifest in the presence of an anion gradient. The temperature dependence of the intact cell enzyme in the presence of inhibitor was influenced by the temperature at which the compound was added prior to assay and may involve the perturbation of tightly associated lipids. Glucose exchange across the membrane was inhibited by the same compounds which inhibit acetylcholinesterase. The temperature dependence of the exchange was not grossly altered by the presence of 7,12-dimethylbenz(a)anthracene. The observed inhibition of two membrane functions by the polycyclic aromatic hydrocarbons does not correlate simply with their theoretical octanol/water partition coefficients, water solubilities, or ability to confer membrane stabilization against osmotic hemolysis. This demonstration of differential inhibition by compounds having the same overall hydrophobicity was unexpected and suggests a more complex mode of interaction with the cell membrane.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2000

When pyramidal neurons lock, when they respond chaotically, and when they like to synchronize.

We give an overview on the locking properties of perturbed regularly firing pyramidal neurons, as a function of perturbation strength, self-spiking frequency and perturbation frequency. For inhibitory perturbations, instead of locking chaotic response emerges for a whole range of parameters. This suggests that global synchronization on the set of inhibitory connections may easily be achieved.

Action Potentials↗
PubMed1990

Mechanisms of cytomegalovirus-mediated myelosuppression: perturbation of stromal cell function versus direct infection of myeloid cells.

Infection with cytomegalovirus (CMV) continues to be one of the most common complications following allogeneic bone marrow transplantation. To study the role of CMV in the suppression of hemopoiesis that frequently accompanies infection, we investigated the effect of CMV on the growth of isolated committed myeloid progenitors and on hemopoiesis in long-term bone marrow cultures. Laboratory strain AD169 had no effect on the growth and development of progenitor cells. In contrast, 40% of clinical isolates of CMV inhibited colony formation by up to 100%. In long-term bone marrow cultures all CMV isolates resulted in myelosuppression, which in the majority of cases was associated with the infection of stromal elements. Analysis of RNA from stromal cells infected with AD169 and one clinical isolate demonstrated a specific deficiency of granulocyte colony-stimulating factor transcripts. For a small proportion of the clinical isolates tested in long-term bone marrow cultures, suppression of hemopoiesis was correlated with infection of developing granulocytes. These studies suggest that CMV can impair hemopoiesis either through infection of stromal cells and consequent perturbation of growth factor production or by direct infection of myeloid cells.

Antigens, Viral↗
PubMed1997

Involvement of the protein of Xenopus vasa homolog (Xenopus vasa-like gene 1, XVLG1) in the differentiation of primordial germ cells.

In order to understand the role of the protein of Xenopus vasa homolog (Xenopus vasa-like gene 1, XVLG1) in germ line cells, an attempt was made to perturb the function of the protein with the anti-vasa antibody 2L-13. The 2L-13 or the control antibody was microinjected with a lineage tracer (FITC-dextran-lysine, FDL) into single vegetal blastomeres containing the germ plasm of Xenopus 32-cell embryos, the descendants of which were destined to differentiate into a small number of primordial germ cells (PGC) and a large number of somatic cells, mostly of endodermal tissues at the tadpole stage. No significant effect of the injection of the antibodies on FDL-labeled, presumptive PGC (pPGC) was observed in embryos until stage 37/38. However, FDL-labeled PGC were not observed in almost all the 2L-13 antibody-injected tadpoles, although a similar number of labeled somatic cells were always present. As 2L-13 antibody specifically reacts with XVLG1 protein in the embryos by immunoblotting, the present results suggest that the antibody perturbed the function of XVLG1 protein in the pPGC, resulting in failure of PGC differentiation at the tadpole stage.

Animals↗
PubMed2000

Perturbation of mitochondrial structure and function plays a central role in Actinobacillus actinomycetemcomitans leukotoxin-induced apoptosis.

Certain pore-forming bacterial toxins, including the leukotoxin (Ltx) produced by Actinobacillus actinomycetemcomitans, induce apoptosis in susceptible target cells. Although binding to the target cell surface represents the first step in the initiation of this process, the downstream events leading to toxin-induced apoptotic cell death have not been identified. Perturbation of mitochondrial function has been shown to have a major role in regulating progression of apoptosis initiated by exposure to numerous stimuli. Using Ltx as a model, the aim of this study was to evaluate whether induction of apoptosis by pore-forming toxins follows a similar paradigm. After exposure to Ltx, Epstein-Barr virus transformed B cells (JY cell line) exhibited the classical morphological features of apoptosis including decreased cell size, plasma membrane blebbing, selective alterations in plasma membrane permeability and condensation of nuclear DNA. The morphologic changes were accompanied by swelling of the mitochondria, a decrease in mitochondrial transmembrane potential (Psi(m)), hyperproduction of reactive oxygen intermediates (ROIs) and release of cytochrome c from the intermembrane space. Subsequently, we detected activation of the c ysteine asp artate-specific prote ases (caspases)-3 and -9, cleavage of the nuclear DNA repair enzyme, poly(ADP-ribose)polymerase (PARP) and internucleosomal DNA fragmentation. These results indicate that perturbation of mitochondrial structure and function, in concert with activation of specific caspases, initiate the effector phase of Ltx-induced apoptosis.

Aggregatibacter actinomycetemcomitans↗
PubMed1994

Perturbation of epidermal barrier function correlates with initiation of cytokine cascade in human skin.

BACKGROUND: An important function of skin is to serve as a barrier and thus provide protection from the external environment. The epidermal keratinocyte establishes this barrier by producing an intact stratum corneum. In the past, keratinocytes were appreciated only for this rather inert, passive structural responsibility and not for their potential dynamic contribution to inflammatory or immune-mediated reactions. OBJECTIVE: Our purpose was to examine the cascade of molecular and cellular events that occur when the barrier function of human skin is abrogated by repeated tape stripping, which physically removes the stratum corneum without inducing any cytopathic effects on the underlying epidermal keratinocytes. METHODS: Eight healthy human volunteers underwent repeated tape stripping and sequential punch biopsy specimens of skin obtained between 1 and 24 hours after tape stripping were analyzed for protein antigens by immunostaining of cryostat-cut sections. The presence or absence of various messenger RNAs (mRNAs) were detected by polymerase chain reaction. RESULTS: After repeated tape stripping, keratinocytes became activated within hours. The responses included up-regulation of keratin-16 expression and keratinocyte proliferation accompanied by production of a specific profile of cytokine and adhesion molecule mRNAs and proteins in both epidermal and dermal compartments. Polymerase chain reaction amplification of RNA species isolated from the epidermal portion of skin revealed increases 6 hours after tape stripping in mRNA coding for tumor necrosis factor-alpha, IL-8, IL-10, interferon gamma, intercellular adhesion molecule-1, transforming growth factor-alpha, and transforming growth factor-beta. There was no increase in tumor necrosis factor-alpha, IL-8, IL-10, or transforming growth factor-alpha mRNAs in the dermal samples. Immunostaining revealed that keratinocyte intercellular adhesion molecule-1 was increased 6 hours after stripping and was accompanied by endothelial cell expression of E-selectin (endothelial cell adhesion molecule-1) and vascular cell adhesion molecule-1. These molecular events, which occurred after 6 hours in tape-stripped skin, preceded any movement of inflammatory cells from the circulation into dermis or epidermis and hence reflect changes that occur in cells indigenous to normal human skin. None of these changes occurred in persons who underwent limited tape strippings without barrier perturbation. CONCLUSION: The results highlight the rapid and distinctive responses of epidermal keratinocytes and demonstrate that these cells can actively participate in a far greater number of homeostatic responses other than the production of the epidermal barrier.

Adult↗
PubMed1995

Altering the expression of cell surface beta 1,4-galactosyltransferase modulates cell growth.

beta 1,4-Galactosyltransferase (GalTase) is unusual among the glycosyltransferases in that it is localized both in the Golgi complex and on the cell surface. Most studies of surface GalTase function have focused on its role in cellular interactions; however, surface GalTase has also been suggested to function during cellular proliferation. Consistent with this hypothesis, a variety of GalTase-specific perturbants inhibit cell growth in vitro and in vivo. However, all of these studies have been limited to the use of exogenous reagents to perturb GalTase function. Furthermore, all of these perturbants inhibit cell growth, irrespective of whether they stimulate or inhibit GalTase enzyme activity. Therefore, it remains unclear whether surface GalTase delivers a growth inhibitory or growth stimulatory signal. In this study, we took a more direct approach to defining surface GalTase function during growth by examining its expression during the cell cycle and by molecularly altering its expression in stably transfected cell lines. The expression of GalTase was shown to be cell cycle specific, with the cell surface and intracellular GalTase pools displaying independent expression patterns. Furthermore, multiple, independent, stably transfected cell lines with reduced levels of cytoskeletally associated surface GalTase grew faster than control cells, whereas cell lines that over-expressed surface GalTase grew slower than controls. These observations directly support the concept that surface GalTase delivers a growth inhibitory signal. Evidence is presented suggesting that surface GalTase interacts with the epidermal growth factor (EGF) receptor, as suggested by others. The activity of the EGF receptor was shown to be directly proportional to the growth rate of the various GalTase-transfected cell lines. Thus, the expression of surface GalTase directly affects cell proliferation rate and may do so by modulating the ability of the EGF receptor to transduce EGF-dependent signals.

3T3 Cells↗
PubMed1996

Vibrio cholerae hemagglutinin/protease (HA/protease) causes morphological changes in cultured epithelial cells and perturbs their paracellular barrier function.

In this report, we describe the cytotoxic activity of the cholera hemagglutinin/protease (HA/protease). A concentrated protein sample from the 37 degrees C overnight culture supernatant of CVD110, a delta ctxA, delta zot, delta Ace and hlyA::(ctxB mer) mutant of El Tor biotype Ogawa serotype strain E7946 caused morphological changes in cultured MDCK-I epithelial cells and altered their arrangement of filamentous actin (F-actin) and Zonula occludens-associated protein ZO-1. The drastic morphological changes can be inhibited by Zincov, a specific bacterial metalloprotease inhibitor. The cytotoxic fractions of the sample after FPLC gelfiltration fractionation showed two visible protein bands with molecular weights of approximately 34- and 32 kDa. Microsequencing of these two proteins revealed that they were the cholera HA/protease.

Actins↗
PubMed1992

Prothrombotic and fibrinolytic function of normal and perturbed endothelium.

Endothelium mediates thrombosis and fibrinolysis in part through cell-based production and binding of coagulation factors and anticoagulant moieties. A variety of biologically active agents (homocysteine, interleukin-1, and endotoxin) and environmental factors (mechanical injury and hypoxia) can upset the homeostasis of the coagulation system leading in vitro and in vivo to abnormal propensity for thrombin formation. None of the above agents or any similar agents have been demonstrated to inhibit clotting factors or thrombosis formation. As one would expect, injury to endothelium even on a sublethal basis promotes a procoagulant response. This procoagulant response appears to be multifactorial and multiphasic. Gross injury leads to factor release by dead or dying cells with rapid promotion of thrombosis by neighboring infact cells. A more subtle prothrombotic state promulgated by viable cells appears after sublethal perturbation and is characterized by protein synthesis-dependent production of endothelial-produced clotting factors in the early stages of injury with subsequent return to normal levels of these factors by 24 hr. A second phase of abnormal levels of fibrinolysis inhibitors and possible reduction in fibrinolysis promoters appears to follow up to 48 hr after the initial injury. Thus the cell can be viewed as producing means of promoting thrombus formation followed by preventing thrombus dissolution. The data presented in this article are primarily cell culture data and are thus limited both in physiologic applicability and in ability to define over long periods the relevance of those findings to other cells in the hemostatic system. Nonetheless, in vivo data of endothelial perturbation correlate with the in vitro findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗
PubMed2005

Perturbation of leukocyte function-associated antigen-1/intercellular adhesion molecule-1 results in differential outcomes in cardiac vs islet allograft survival.

BACKGROUND: Various studies indicate the requirements for tolerance induction may vary between different transplanted tissues and organs. Consequently, we compared the efficacy of anti-leukocyte function-associated antigen-1 (LFA-1)/anti-intercellular adhesion molecule-1 (ICAM-1) monoclonal antibody therapy for facilitating cardiac vs islet long-term allograft acceptance in mice. METHODS: BALB/c (H-2d) mouse cardiac or islet allografts were transplanted into recipient CBA/J (H-2k) mice. Monoclonal anti-body therapy with anti-LFA-1, anti-ICAM-1, the combination, or control rat immunoglobulin (Ig) was administered intraperitoneally on Days 0 to 5. Cardiac allograft function was assessed by palpation and islet graft function by blood glucose monitoring. Mixed lymphocyte assays were performed to assess proliferation of CD4 and CD8 T-cells under conditions of stimulator-cell ICAM-1 and/or LFA-1 deficiency. RESULTS: Anti-ICAM-1 therapy resulted in a modest prolongation of cardiac allografts but in pronounced survival of islet allografts. Anti-LFA-1 therapy promoted significant long-term survival of both cardiac and islet allografts. Surprisingly, combined anti-LFA-1/anti-ICAM-1 therapy abrogated long-term islet, but not cardiac, allograft acceptance relative to either monotherapy. Mixed lymphocyte reactions demonstrated complete blockade of CD4 and CD8 T-cell proliferation under conditions of ICAM-1 deficiency alone or in combination with anti-LFA-1 therapy. CONCLUSION: These results indicate that optimal therapies for some allografts (vascularized-heart) may not translate to other types of allografts (cellular-islet). Thus, the type of transplant represents an independent variable for optimizing strategies to promote indefinite allograft acceptance. Complete inhibition of CD4 and CD8 T-cell proliferation during ICAM-1/LFA-1 blockade suggests a threshold signal may be dependent upon ICAM-1/LFA-1 for regulatory tolerance to occur and that this signal may be lost under conditions of minimal graft cellular mass.

Animals↗
PubMed2006

Interaction energy contributions of H-bonded and stacked structures of the AT and GC DNA base pairs from the combined density functional theory and intermolecular perturbation theory approach.

Stacked and Watson-Crick structures of DNA base pairs are investigated with the DFT-SAPT variant of intermolecular perturbation theory, yielding a rigorous decomposition of the interaction energy into electrostatic, induction, dispersion, and exchange contributions. Their interplay in the various structures is analyzed. Total interaction energies extrapolated to the complete basis set limit are compared with corresponding second-order Møller-Plesset and estimated coupled-cluster theory results.

Adenine↗