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PubMed1978

Membrane potential, resistance, and intercellular communication in the lacrimal gland: effects of acetylcholine and adrenaline.

1. Intracellular micro-electrode recordings were made from surface acini of mouse exorbital lacrimal glands placed in a Perspex bath through which oxygenated physiological saline solutions were circulated. Two micro-electrodes were inserted into neighbouring communicating cells. Through one of the electrodes, current pulses could be injected. The cells impaled were stimulated by iontophoresis of acetylcholine (ACh), adrenaline or isoprenaline from an extracellular micropipette. 2. During exposure to standard Krebs solution the resting membrane potential was -42.5 mV +/- 1.2 and the resting input resistance 3.3 Momega +/- 0.3. When the tips of the two intracellular micro-electrodes were more than 100 micrometer apart no electrical coupling between two impaled cells could be detected. At intertip distances below about 80 micrometer coupling was frequently observed. In all such cases the coupling ratio was 1. The resting current-voltage relation was almost linear within the membrane potential range of -30 to -80 mV. 3. During exposure to standard Krebs solution the resting membrane potential was -42.5 mV +/- 1.2 and the resting input resistance 3.3 Momega +/- 0.3. When the tips of the two intracellular micro-electrodes were more than 100 micrometer apart no electrical coupling between two impaled cells could be detected. At intertip distances below about 80 micrometer coupling was frequently observed. In all such cases the coupling ratio was 1. The resting current-voltage relation was almost linear within the membrane potential range of -30 to -80mV. 3. During exposure to standard Krebs solution short iontophoretic pulses of ACh or adrenaline caused fully reversible hyperpolarizations accompanied by marked reduction of surface cell membrane resistance and membrane time constant. The effects of ACh were blocked by atropine (1.4 x 10(-6)M). Iontophoresis of isoprenaline never had any detectable effect on membrane potential or resistance. 4. Applying de- or hyperpolarizing direct currents through one of the two intracellular micro-electrodes the effect of ACh or adrenaline could be observed at different lvels of resting potential. Depolarizing the acinar cell membrane resulted in an enhanced stimulant-evoked hyperpolarization whereas hyperpolarizing the acinar cell membrane resulted in a reduction, and at potentials more negative than -60 mV in a reversal of the stimulant-evoked potential change. The ACh equilibrium potential (EACh) under control conditions was -56.6 mV +/- 1.1 and EAdrenaline was -61.4 mV +/- 1.0. 5. Replacing the control superfusion solution by a Clfree sulphate solution resulted in an immediate shift of EACh towards more negative values. At steady state in the Cl-free solution the resting input resistance was 6.8 Momega +/- 1.3 EACh was -95.9 mV +/- 3.4. 6. Reducing [K]o from the usual 4.7 to 1.0 mM resulted in an immediate marked increase in the amplitude of ACh-evoked hyperpolarization whereas increasing [K]o to 10 mM almost abolished the ACh-evoked potential, but not resistance change. 7...

Acetylcholine↗
PubMed2002

Intercellular communication in the mammalian ovary: oocytes carry the conversation.

The production of functional female gametes is essential for the propagation of all vertebrate species. The growth of oocytes within ovarian follicles and their development to mature eggs have fascinated biologists for centuries, and scientists have long realized the importance of the ovarian follicle's somatic cells in nurturing oogenesis and delivering the oocyte to the oviduct by ovulation. Recent studies have revealed key roles of the oocyte in folliculogenesis and established that bidirectional communication between the oocyte and companion somatic cells is essential for development of an egg competent to undergo fertilization and embryogenesis. The challenge for the future is to identify the factors that participate in this communication and their mechanisms of action.

Animals↗
PubMed1979

Intercellular communication in pancreatic islet monolayer cultures: a microfluorometric study.

Single islet cells in monolayer cultures of neonatal rat pancreas were microinjected with fluorescein and scanned topographically by microfluorometry. Fluorescein spread from an injected islet cell directly into neighboring islet cells, and, in the presence of 16.7 millimolar glucose, significantly more islet cells communicated with the injected cell than in glucose-free medium. Islet cells were also microinjected with glycolytic substrates and activators that produced transient changes in cellular levels of reduced pyridine nucleotides-nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate [NAD(P)H]. Changes in NAD(P)H fluorescence were observed in islet cells incubated first for 18 hours in very low glucose concentrations and then in a glucose-free medium and injected with glycolytic substrates and activators; however, little change of fluorescence occurred in adjacent islet cells. In contrast, after adding 16.7 millimolar glucose to the medium, injection of glycolytic substrates and activators produced transient changes in NAD(P)H fluorescence in the injected cell and in neighboring cells.

Animals↗
PubMed2000

Intercellular communication in Helicobacter pylori: luxS is essential for the production of an extracellular signaling molecule.

Individual bacteria of numerous species can communicate and coordinate their actions via the production, release, and detection of extracellular signaling molecules. In this study, we used the Vibrio harveyi luminescence bioassay to determine whether Helicobacter pylori produces such a factor. Cell-free conditioned media from H. pylori strains 60190 and 26695 each induced >100-fold-greater luminescence in V. harveyi than did sterile culture medium. The H. pylori signaling molecule had a molecular mass of <10 kDa, and its activity was unaffected by heating to 80 degrees C for 5 min or protease treatment. The genome sequence of H. pylori 26695 does not contain any gene predicted to encode an acyl homoserine lactone synthase but does contain an orthologue of luxS, which is required for production of autoinducer-2 (AI-2) in V. harveyi. To evaluate the role of luxS in H. pylori, we constructed luxS null mutants derived from H. pylori 60190 and 26695. Conditioned media from the wild-type H. pylori strains induced >100-fold-greater luminescence in the V. harveyi bioassay than did conditioned medium from either mutant strain. Production of the signaling molecule was restored in an H. pylori luxS null mutant strain by complementation with a single intact copy of luxS placed in a heterologous site on the chromosome. In addition, Escherichia coli DH5alpha produced autoinducer activity following the introduction of an intact copy of luxS from H. pylori. Production of the signaling molecule by H. pylori was growth phase dependent, with maximal production occurring in the mid-exponential phase of growth. Transcription of H. pylori vacA also was growth phase dependent, but this phenomenon was not dependent on luxS activity. These data indicate that H. pylori produces an extracellular signaling molecule related to AI-2 from V. harveyi. We speculate that this signaling molecule may play a role in regulating H. pylori gene expression.

Amino Acid Sequence↗
PubMed1994

Intercellular communication between mouse Leydig cells.

In this paper we describe the basic features of gap junctions in pairs of Leydig cells mechanically dissociated from mouse testes, studied with the double whole cell patch-clamp technique. These cells are extensively coupled with regard to dye injection and electrophysiological measurements. The mean junctional conductance (gj) measured in 61 pairs of cells was 10.6 +/- 1.5 (SE) nS. In most pairs gj was voltage dependent when transjunctional voltage exceeded +/- 50 mV. On imposition of a voltage gradient across the junction the transjunctional current decayed exponentially to a lower level, with a time constant of 3.3 s at 50 mV and 430 ms at 100 mV. As in other systems, octanol (600 microM final concentration) uncoupled the cells within approximately 2 min. In a few cell pairs, gj was low enough to permit recording of single channel currents without the use of uncoupling agents. Single channel conductance fluctuations measured using pipettes containing potassium aspartate were distributed mainly around three peaks, at 21, 39, and 60 pS, suggesting the presence of channels formed by connexin 43. Western blots of Percoll gradient purified Leydig cells using specific antibodies indicate that connexin 43 is indeed expressed in these cells, whereas connexin 26 and connexin 32 are not.

Animals↗
PubMed1990

Intercellular communication in bronchial epithelial cells: review of evidence for a possible role in lung carcinogenesis.

A challenging aspect of lung carcinogenesis is the elucidation of the mechanisms which permit initiated bronchial epithelial cells to attain a growth advantage over normal bronchial epithelial cells, and subsequently evolve into a malignant phenotype. In this review, the effects of interactions between normal and transformed cells, and the potential role of representative extrinsic factors on cell-cell communication are discussed. Evidence is presented to show how cell injury and the effects of serum and calcium may affect morphology and communication, and tumor development. A large number of autocrine-paracrine factors (e.g., TGF beta, TGF alpha) are released by bronchial epithelial cells. These factors may inhibit or promote the proliferation of normal and transformed bronchial epithelial cells, respectively. The ability of certain injurious and tumor promoting agents (e.g., formaldehyde, TPA) to select for the transformed phenotype may involve selective cell injury, the induction of terminal differentiation and an inhibition of gap junction communication among normal BE cells.

Bronchi↗
PubMed2000

Intercellular communication in the anterior pituitary.

In addition to hypothalamic and feedback inputs, the secretory cells of the anterior pituitary are influenced by the activity of factors secreted within the gland. The list of putative intrapituitary factors has been expanding steadily over the past decade, although until recently much of the work was limited to descriptions of potential interactions. This took the form of evidence of production within the pituitary of factors already known to influence activity of secretory cells, or further descriptions of actions on pituitary cells by such factors when added exogenously. A new phase of discovery has been entered, with extensive efforts being made to delineate the control of the synthesis and secretion of the pituitary factors within the gland, regulation of the receptors and response mechanisms for the factors in pituitary cells, and measurements of the endogenous actions of the factors through the use of specific immunoneutralization, receptor blockade, tissue from transgenic animals, and other means. Taken together, these findings are producing blueprints of the intrapituitary interactions that influence each of the individual types of secretory cells, leading toward an understanding of the physiological significance of the interactions. The purpose of this article is to review the recent literature on many of the factors acting as intrapituitary signals and to present such finding in the context of the physiology of the secretory cells.

Animals↗
PubMed1996

Intercellular communication: relative importance of cellular adhesion and paracrine signaling to hormonal gene expression.

Although there is a consensus that a cell's microenvironment can have a dramatic influence on its ability to express a particular gene, the relative contribution of physical interaction (cell to cell adhesion) and paracrine signaling to this phenomenon has been difficult to discern. Here, we addressed this problem in mammotropes by making "real-time" measurements of prolactin (PRL) gene expression followed by immunocytochemistry (for post facto identification of a neighbor's phenotype). Our results show that it is the nature (phenotype) rather than the physical presence of a neighboring cell that dictates the degree to which the PRL gene is expressed.

Animals↗
PubMed1998

Gap junctional intercellular communication contributes to the contraction of rat osteoblast populated collagen lattices.

The contraction of native collagen lattices by resident mesenchymal cells mimics the organization of collagen during development and repair. Lattice contraction is cell density dependent, suggesting that cell-to-cell communications may contribute to the process. This possibility was investigated by comparing lattice contraction by four rat osteoblastic cell lines: ROS 17/2.8 cells (ROS); ROS transfected with an antisense cDNA sequence of the gap junctional protein connexin 43 (RCx16); ROS transfected with connexin 45 cDNA, a connexin not normally expressed in ROS cells (ROS/Cx45); and ROS transfected with cDNA encoding carboxy-terminal truncated Cx45 (ROS/Cx45tr). The cell coupling indices, which reflect gap junctional communication, were quantitated by the fluorescent dye scrape loading. ROS cells were well coupled (index 3.0), ROS/Cx45tr were better coupled (index 4.2), ROS/Cx45 were poorly coupled (index 1.7), and RCx16 showed no coupling (index 1.1). As determined by immunoblotting, the level of connexin 43 protein was increased in both ROS/Cx45tr and ROS/Cx45 cell lines compared with ROS cells, while the level in RCx16 cells was reduced. ROS populated collagen lattices (PCLs) contracted significantly more at day 5 (177 mm2 to 67 mm2) than ROS/Cx45tr (84 mm2), ROS/Cx45 (108 mm2), or RCx16 (114 mm2). Myosin ATPase activity, which is required for lattice contraction, was equivalent in all four cell lines, indicating that it was not responsible for inhibiting PCL contraction. ROS cells in collagen appeared elongated compared with the other cell lines which were more rounded. These experiments suggest gap junctional communication contributes to PCL contraction by resident osteoblasts.

Animals↗
PubMed2003

Drosophila free-running rhythms require intercellular communication.

Robust self-sustained oscillations are a ubiquitous characteristic of circadian rhythms. These include Drosophila locomotor activity rhythms, which persist for weeks in constant darkness (DD). Yet the molecular oscillations that underlie circadian rhythms damp rapidly in many Drosophila tissues. Although much progress has been made in understanding the biochemical and cellular basis of circadian rhythms, the mechanisms that underlie the differences between damped and self-sustaining oscillations remain largely unknown. A small cluster of neurons in adult Drosophila brain, the ventral lateral neurons (LN(v)s), is essential for self-sustained behavioral rhythms and has been proposed to be the primary pacemaker for locomotor activity rhythms. With an LN(v)-specific driver, we restricted functional clocks to these neurons and showed that they are not sufficient to drive circadian locomotor activity rhythms. Also contrary to expectation, we found that all brain clock neurons manifest robust circadian oscillations of timeless and cryptochrome RNA for many days in DD. This persistent molecular rhythm requires pigment-dispersing factor (PDF), an LN(v)-specific neuropeptide, because the molecular oscillations are gradually lost when Pdf(01) mutant flies are exposed to free-running conditions. This observation precisely parallels the previously reported effect on behavioral rhythms of the Pdf(01) mutant. PDF is likely to affect some clock neurons directly, since the peptide appears to bind to the surface of many clock neurons, including the LN(v)s themselves. We showed that the brain circadian clock in Drosophila is clearly distinguishable from the eyes and other rapidly damping peripheral tissues, as it sustains robust molecular oscillations in DD. At the same time, different clock neurons are likely to work cooperatively within the brain, because the LN(v)s alone are insufficient to support the circadian program. Based on the damping results with Pdf(01) mutant flies, we propose that LN(v)s, and specifically the PDF neuropeptide that it synthesizes, are important in coordinating a circadian cellular network within the brain. The cooperative function of this network appears to be necessary for maintaining robust molecular oscillations in DD and is the basis of sustained circadian locomotor activity rhythms.

Animals↗