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At least 217 records · Page 12Linked to original sources
PubMed1991

DNA-damaging, mutagenic, clastogenic and cell-cell communication inhibitory properties of gamma-oryzanol.

As a part of short-term safety assessment of gamma-Oryzanol, the genotoxic or the carcinogenic initiation activity was studied in three genetic toxicity tests and the promotion activity was studied in a cell-cell communication inhibitory test. gamma-Oryzanol showed the negative response in the bacterial DNA repair test (Rec-assay), the bacterial reverse mutation tests (Ames test) and the rat bone marrow chromosome aberration test. Also, gamma-Oryzanol showed the negative response in the metabolic cooperation inhibition test using Chinese hamster V79 cells.

Animals↗
PubMed2002

Connexin-GFPs shed light on regulation of cell-cell communication by gap junctions.

Important roles for connexins have emerged from studies linking connexin mutations to human disease. Use of connexins tagged with GFP have provided a clearer picture of the mechanisms that govern connexin channel function and it is now evident that functional forms of connexin channel include cell-cell channels and unapposed hemichannels. Clustering appears to be a requirement for opening of cell-cell channels and suggests that dynamic changes occur in plaques (clusters) as they form and grow that are critical for channel function. In particular, recruitment or generation of 'silent' channels has gained support as a mechanism by which coupling can be dynamically regulated within formed plaques. Two distinct voltage sensitive gating mechanisms appear to be built-into each hemichannel, one putatively located at the cytoplasmic entrance and the other at the extracellular end, each differing in sensitivity, kinetics and degree of channel/hemichannel closure. The extracellular gate may also be that which opens unapposed hemichannels in the plasma membrane and be the final target of many known chemical agents that act as uncouplers of cell-cell communication. An understanding of the structural requirements for regulation via gating and clustering represents an important preclinical step in the design of therapeutic agents to treat disorders arising from connexin channel and hemichannel dysfunction.

Animals↗
PubMed1999

Proximal to distal cell communication in the Drosophila leg provides a basis for an intercalary mechanism of limb patterning.

Proximodistal patterning in the Drosophila leg is elaborated from the circular arrangement of the proximal domain expressing escargot and homothorax, and the distal domain expressing Distal-less that are allocated during embryogenesis. The distal domain differentiates multiply segmented distal appendages by activating additional genes such as dachshund. Secreted signaling molecules Wingless and Decapentaplegic, expressed along the anterior-posterior compartment boundary, are required for activation of Distal-less and dachshund and repression of homothorax in the distal domain. However, whether Wingless and Decapentaplegic are sufficient for the circular pattern of gene expression is not known. Here we show that a proximal gene escargot and its activator homothorax regulate proximodistal patterning in the distal domain. Clones of cells expressing escargot or homothorax placed in the distal domain induce intercalary expression of dachshund in surrounding cells and reorient planar cell polarity of those cells. Escargot and homothorax-expressing cells also sort out from other cells in the distal domain. We suggest that inductive cell communication between the proximodistal domains, which is maintained in part by a cell-sorting mechanism, is the cellular basis for an intercalary mechanism of the proximodistal axis patterning of the limb.

Animals↗
PubMed1987

Gap junction structure and the control of cell-to-cell communication.

Gap junctions are collections of oligomeric membrane proteins (connexons), which interact across the space between neighbouring cells to form continuous cell-to-cell pathways for ions and small molecules. The connexon is constructed from six identical subunits, arranged symmetrically in the plane of the membrane and delineating the channel along their common sixfold axis. The subunits are rod-shaped and 7-8 nm long; they protrude about 1.5 nm into the extracellular space, but somewhat less into the cell interior. Their cross-section within the membrane corresponds most closely to that of four closely packed alpha-helical rods. The channel is narrowest near the cytoplasmic surface and widest in the extracellular region. Changes between alternative quaternary configurations are most pronounced in the cytoplasmic region, and involve a coordinated tilting of the subunits, predominantly tangential to the central symmetry axis. The observed molecular details suggest that switching between open and closed states of the channel may entail a cooperative mechanism in which a localized effect induced by ligand binding triggers a long-range concerted rearrangement of the subunits. Other membrane channels have similar molecular designs and may act in an analogous way.

Animals↗
PubMed1975

Effect of intracellular injection of calcium and strontium on cell communication in heart.

1. The influence of Ca and Sr on the electrical coupling of canine Purkinje cells was investigated by injecting the ions electrophoretically into the cytoplasm. 2. It was found that the intracellular injection produced electrical uncoupling which was spontaneously reversed. 3. No change in resting potential of the cell adjacent to the injection site was found except in those fibres not completely healed. 4. The input resistance of the injected cell increased concomitantly with the establishment of the electrical uncoupling. 5. Caffeine (6mM), added to the extracellular fluid, reduced the rate of spontaneous recoupling. Reduction of temperature of the Tyrode solution had the same effect. 6. The abolition of cell communication produced by Ca injection seems to indicate that the ion plays an important role in the control of junctional conductance in heart fibres.

Animals↗
PubMed1997

Cell-cell communication in gram-positive bacteria.

In gram-positive bacteria, many important processes are controlled by cell-to-cell communication, which is mediated by extracellular signal molecules produced by the bacteria. Most of these signaling molecules are peptides or modified peptides. Signal processing, in most cases, involves either transduction across the cytoplasmic membrane or import of the signal and subsequent interaction with intracellular effectors. Concentrations of signal in the nanomolar range or below are frequently sufficient for biological activity. The microbial processes controlled by extracellular signaling include the expression of virulence factors, the expression of gene transfer functions, and the production of antibiotics.

4-Butyrolactone↗
PubMed1993

Expression of Pseudomonas aeruginosa virulence genes requires cell-to-cell communication.

Pseudomonas aeruginosa is an opportunistic human pathogen that causes a variety of infections in immunocompromised hosts and individuals with cystic fibrosis. Expression of elastase, one of the virulence factors produced by this organism, requires the transcriptional activator LasR. Experiments with gene fusions show that gene lasl is essential for high expression of elastase. The lasl gene is involved in the synthesis of a diffusible molecule termed Pseudomonas autoinducer (PAI). PAI provides P. aeruginosa with a means of cell-to-cell communication that is required for the expression of virulence genes and may provide a target for therapeutic approaches.

Amino Acid Sequence↗
PubMed2005

Cell-cell communication in Gram-negative bacteria.

Over the last decade or so, a wealth of research has established that bacteria communicate with one another using small molecules. These signals enable the individuals in a population to coordinate their behaviour. In the case of pathogens, this behaviour may include decisions such as when to attack a host organism or form a biofilm. Consequently, such signalling systems are excellent targets for the development of new antibacterial therapies. In this review, we assess how Gram-negative bacteria use small molecules for cell-cell communication, and discuss the main approaches that have been developed to interfere with it.

Cell Communication↗
PubMed2003

Identification and sequence of seventy-nine new transcripts expressed in hemocytes of Ciona intestinalis, three of which may be involved in characteristic cell-cell communication.

Ascidian is a useful experimental animal for studying body planning principles and host defense mechanisms employed by the phylum chordata. Toward this goal, genome and cDNA/EST projects of Ciona intestinalis have been undertaken. Using cDNAs and ESTs derived from Ciona hemocytes, we identified 79 possible hemocyte-preferential transcripts and determined the cDNA sequence of each clone. The amino acid sequence of each encoded polypeptide was predicted as well. Among these cDNAs, we identified three transcripts that may be involved in characteristic cell-cell communication in Ciona. These transcripts encoded leucine-rich repeat-containing RP105-like, IL-17 receptor/similar expression to FGF-like, and ectodysplasin-like polypeptide of the tunmr necrosis factor famlly, and they are expressed abundantly in hemocytes.

Animals↗
PubMed1992

tra-2 encodes a membrane protein and may mediate cell communication in the Caenorhabditis elegans sex determination pathway.

The Caenorhabditis elegans sex-determining gene, tra-2, promotes female development in XX animals. In this paper we report the cDNA sequence corresponding to a 4.7 kb tra-2 mRNA and show that it is composed of 23 exons, is trans-spliced to SL2, and contains a perfect direct repeat in the 3' untranslated region. This mRNA is predicted to encode a 1475 amino acid protein, named pTra2A, that has a secretory signal and several potential membrane-spanning domains. The molecular analysis of tra-2 loss-of-function mutations supports our open reading frame identification and suggests that the carboxy-terminal domain is important for tra-2 activity. We propose that in XX animals the carboxy-terminal domain of pTra2A negatively regulates the downstream male promoting fem genes. In XO animals, tra-2 is negatively regulated by her-1, which acts cell nonautonomously. Because hydropathy predictions suggest that pTra2A is an integral membrane protein, pTra2A might act as a receptor for the her-1 protein. We propose that in XO animals, the her-1 protein promotes male development by binding and inactivating pTra2A. The role of cell communication in C. elegans sex determination might be to ensure unified sexual development throughout the animal. If so, then regulation of sexual fate by her-1 and tra-2 might provide a general model for the coordination of groups of cells to follow a single cell fate.

Amino Acid Sequence↗
PubMed1998

Quorum sensing and the cell-cell communication dependent regulation of gene expression in pathogenic and non-pathogenic bacteria.

Although it has been clear for some time that individual bacterial cells employ intra-cellular signalling systems to sense, integrate and process information from their surroundings, their widespread capacity to perceive information from other bacterial cells is only just beginning to be recognised. Recent work has established that diverse bacteria exploit a cell-cell communication device to regulate the transcription of multiple target genes. This communication device termed 'quorum sensing', depends on the production of one or more diffusible signal molecules termed 'autoinducers' or 'pheromones' which enable a bacterium to monitor its own cell population density. Quorum sensing is thus an example of multicellular behaviour in prokaryotes and regulates diverse physiological processes including bioluminescence, swarming, antibiotic biosynthesis, plasmid conjugal transfer and the production of virulence determinants in animal, fish and plant pathogens. In Gram-negative bacteria, the best understood family of signal molecules are the N-acylhomoserine lactones (AHLs) which vary predominantly in the presence or absence of an acyl chain C3 substituent (oxo- or hydroxy-) and length of the N-acyl side chain. However not all quorum sensing signal molecules are AHLs; in Gram-positive bacteria, they are often post-translationally modified peptides. Irrespective of the chemical 'language' employed, interference with either the synthesis or transmission of a quorum sensing signal molecule in pathogenic bacteria offers an exciting new strategy for controlling infection.

Gene Expression Regulation, Bacterial↗