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At least 703 records · Page 39Linked to original sources
PubMed1993

[Intercellular communication within the anterior pituitary].

Paracrine and autocrine interactions within the anterior pituitary have been studied in the last few years. The adaptation of novel methodology to the study of the physiology of the anterior pituitary has yielded convincing evidence for cell-cell communication. Another reason for expanded interest in this field is the discovery of a growing member of substances that likely play a role in cell-cell communication. The various types of secretory cells within the anterior pituitary, gonadotroph, thyrotroph, somatotroph, lactotroph and corticotroph, have been addressed as sources, and then targets of intercellular factors. We need have more a collection of observations than a system of delineated pathways. Moreover, care must be exercised in interpretations of these observations.

Activins↗
PubMed1988

Novel method for selective killing of transformed rodent cells through intercellular communication, with possible therapeutic applications.

A novel method for killing transformed cells selectively, without affecting surrounding nontransformed cells, has been developed. The method is based on our finding that transformed cells form their own gap-junctional communication compartment which is independent of that of adjacent nontransformed cells; transformed cells and adjacent normal cells transfer molecules through gap junctions among their homologous cells, but there is no heterologous transfer. Thus, when Lucifer Yellow CH is microinjected into transformed cells, it spreads only among the transformed cells and not to surrounding nontransformed cells. Subsequent irradiation of cells with blue light (around 430 nm) kills only those cells containing Lucifer Yellow CH (i.e., transformed cells), and surrounding normal cells continue to grow after treatment. We succeeded in killing BALB/c 3T3 transformed foci induced in situ by a chemical carcinogen or by an activated oncogene, and in killing tumorigenic rat liver epithelial cells cocultured with nontumorigenic counterparts. Potential development of this phenomenon for cancer therapy is suggested.

Animals↗
PubMed2004

Intercellular communication within the rat anterior pituitary gland: X. Immunohistocytochemistry of S-100 and connexin 43 of folliculo-stellate cells in the rat anterior pituitary gland.

Since Rinehart and Farquhar reported the presence of agranulated cells in the anterior pituitary gland in 1953, the functions of the folliculo-stellate cell remain to be clarified. Intercellular junctions have been described in the monkey, rat, and teleost anterior pituitary glands, indicating the existence of cell-to-cell communication within the organ. We pointed to their possible role in the rapid dissemination of information through a complex interconnecting system of follicles involving gap junctions. The gap junctional/folliculo-stellate cellular network was essential in the maturation and regulation of the pituitary gland system such as the hypothalamic-pituitary-gonadal axis. It has been was shown that a network participated in the conduction of electrophysiological information over a long distance using the ion Ca(++), which propagates to other folliculo-stellate cells by signaling through gap junctions. Sixty-day-old male rats were used in this study for light microscopic immunohistochemistry of S-100 protein, type I collagen, and connexin 43, and for electron microscopy to observe the morphological relationships between the cellular networks of folliculo-stellate cells and granulated pituitary cells. Clusters of anti-S-100 protein-positive cells were clearly observed in a region of the hypophysis tentatively named the transition zone. Anti-S-100 protein-positive cells and their cytoplasmic processes were also present in the anterior lobe and assembled together to form follicular lumina. Type I collagen was clearly shown outlining the incomplete lobular or ductule-like structure making cell cords in the anterior pituitary gland. Numerous microvilli were present within the follicular lumen while around the lumina, junctional specializations including gap junctions were positive for the connexin 43 protein. A nonuniform distribution of the connexin 43-positive sites were observed. Small or dot-shaped positive sites were noted where two clusters of cells were connected; the cells were identified as S-100 cells. Double immunohistochemical staining of the connexin 43 and growth hormone (GH) or connexin 43 and luteinizing hormone (LH) was also performed, demonstrating no direct relationship between the connexin 43 and either the GH or LH cells. These findings indicate that there are two kinds of messages necessary for the hormone release in the pituitary gland. One is via the portal vein system, the other is through the gap junction-mediated networks of folliculo-stellate cells. The granulated cells directly associate with cell membrane of folliculo-stellate cells are able to discharge secretory granules through communication via gap junctions, while those granulated cells that are more distant from the folliculo-stellate cells are only able to discharge hormones via the pituitary hormone-releasing hormone from the portal vein system.

Animals↗
PubMed1996

Dominant inhibition of intercellular communication by two chimeric connexins.

1. The physiological significance of communication through gap junction channels has been difficult to assess because channel activity cannot be experimentally modulated in a specific manner. To address this problem we have constructed chimeric connexins that function as dominant-negative inhibitors of intercellular channel activity.

Animals↗
PubMed1978

[Structural diversity of communicating intercellular junctions (gap junctions) in the posterior cecal epithelium of the crustacean Orchestis].

Two types of gap junction are described, they are different in the size, the spacing and the polarity of their intramembrane particles. The dense type shows two kinds of particles which rather remain joined to the P fracture face. The loose type shows larger and more spaced out particles which rather are held by the E fracture face. These observations demonstrate that one needs to shade the distinction between P-type gap (Vertebrate) and E-type gap (Arthropoda).

Animals↗
PubMed2001

Aspects of the intercellular communication in aged hearts: effects of the gap junction uncoupler palmitoleic acid.

Although cardiac arrhythmia is among the most common causes of death and the percentage of aged people in our population is steadily increasing, only little is known on age-dependent changes in intercellular coupling, anisotropy and electrophysiology in mammalian heart. Thus, we wanted to investigate electrophysiology and anisotropy in aged vs. young rabbit heart, as well as the response to the gap junction uncoupler palmitoleic acid. Spontaneously beating hearts of young mature (6+/-1 months, n=14) and aged (32+/-5 months, n=9) male White New Zealand rabbits (Langendorff technique) were submitted to epicardial 256-channel potential mapping. Cumulative concentration-response curves for palmitoleic acid (0.2-20.0 microM) were carried out. At certain time points anisotropy was measured by application of rectangular pulses and the determination of longitudinal and transversal conduction velocity. Finally, hearts were processed histologically for Van Gieson staining or connexin43 immunostaining. In spontaneously beating aged hearts we found enhanced dispersion of activation-recovery intervals (15.9+/-1.6 ms vs. 10.8+/-2.0 ms, P<0.05), prolonged (31.2+/-1.4 ms vs. 25.2+/-1.8 ms, P<0.05) and fractionated QRS complexes. We found reduced transversal velocity (0.22+/-0.01 m/s vs. 0.27+/-0.02 m/s, P<0.05) and enhanced anisotropy (2.6+/-0.2 vs. 2.0+/-0.1, P<0.05) in aged hearts, while longitudinal velocity was not changed. Histologically, in ventricles from aged hearts we found diffuse deposition of collagen lateral to the fibers and more pronounced expression of connexin43 at lateral cell borders. The functional changes in ventricles from aged hearts were mimicked by application of palmitoleic acid to young hearts in a concentration-dependent manner. In aged hearts this concentration-response curve started at higher initial values, but finally reached similar maximum values. In aged hearts ventricular intercellular coupling transverse to the fiber axis is reduced. Correlates are increased dispersion, slowed transverse conduction and increased anisotropy, and enhanced Cx43 immunostaining at the lateral cell borders. The functional age-dependent changes can be mimicked in young hearts by the gap junction uncoupler palmitoleic acid.

Aging↗
PubMed2005

Immunoactivation and altered intercellular communication mediate the pathophysiology of spinal cord injury.

Evidence and inferences from clinical research, clinical observation, and literature review support an etiologic paradigm for the pathophysiology of spinal cord injury (SCI). According to this paradigm, changes in immunoregulation and in the activation of cytokines or intercellular adhesion molecules (ICAMs) contribute to many of the comorbidities, metabolic changes, and pathophysiologic sequelae observed after traumatic SCI. Cytokines and ICAMs are endogenously secreted molecules that serve as intercellular signals and immunoregulators. They modulate the activity of cells and influence the organization and function of tissues or organs. These intercellular signals are posited as molecular links between the damaged, decentralized nervous system of SCI and the acquired autonomic failure, neuroendocrine-immunoregulatory dysfunction, diminished central nervous system (CNS) regenerative capacity, and broad spectrum of pathology, organ failure, and generalized impairment of homeostasis caused by trauma to the spinal cord. These highly bioactive molecules may also mediate or facilitate the intralesional CNS axonal damage and peripheral neurologic deficits sustained at time of acute CNS injury. Ultimately, it should be possible to develop treatments that will block or modulate the local and systemic expression of cytokine or ICAM bioactivity. Such treatments might aid victims of SCI by diminishing overall morbidity or mortality, helping restore sensorimotor function and homeostasis, and enhancing longevity and quality of life.

Biotransformation↗
PubMed1992

Intercellular communication between cultured granulosa cells of the marmoset (Callithrix jacchus).

The influence of follicle-stimulating hormone, forskolin, insulin-like growth factor type I, epidermal growth factor, and 12-tetradecanoyl-phorbol-13-acetate on marmoset granulosa cell communication via gap junctions was investigated by morphological means and microinjection of carboxyfluorescein. Gap junctions between neighbouring granulosa cells were present in all groups. The number, but not length, of gap junctions between marmoset granulosa cells increased when the cells had been treated with follicle-stimulating hormone, insulin-like growth factor type I, and follicle-stimulating hormone plus insulin-like growth factor type I. No effect on gap junctions was seen, after exposure of the cells to the other three substances. Carboxyfluorescein and counting of the surrounding labelled cells showed that supplementation with follicle-stimulating hormone, forskolin, insulin-like growth factor type I and epidermal growth factor from the beginning of cultivation led to an increase in stained cells after 48 h. When treatment was started in 48 h cultures the substances reached their maximal activity within 30 min (forskolin and epidermal growth factor) or 3 h (follicle-stimulating hormone and insulin-like growth factor type I). Spreading of the fluorescent dye was inhibited when the medium was supplemented with 12-tetradecanoyl-phorbol-13-acetate. This effect was maximal after 30 min. Additive effects regarding the coupling of the cells were seen by combining of epidermal growth factor with follicle-stimulating hormone, but not with insulin-like growth factor type I or forskolin plus follicle-stimulating hormone.

Animals↗
PubMed1984

Intercellular communication and the control of growth: X. Alteration of junctional permeability by the src gene. A study with temperature-sensitive mutant Rous sarcoma virus.

To study changes of junctional membrane permeability associated with transformation, the junctions and the nonjunctional membranes of quail embryo-, chick embryo- and mouse-3T3 cell cultures, infected with temperature-sensitive mutant Rous sarcoma virus, were probed with fluorescent-labelled glutamate. Junctional permeability fell in the transformed state. In the quail cells, the fall was detectable within 25 min of shifting the temperature down to the level (permissive) at which tyrosine-phosphorylation by the viral src gene product is expressed. This reduction of junctional permeability is one of the earliest manifestations of viral transformation. Normal permeability was restored within 30 min of raising the temperature to the nonpermissive level, a reversibility that could be displayed several times during the span of a cell generation. The reversal seems to reflect a reopening of cell-to-cell channels rather than a synthesis of new ones; it is not blocked by protein-synthesis inhibition. Treatments with cyclic AMP and phosphodiesterase inhibitor or with forskolin, which stimulate serine and threonine phosphorylation--the type of phosphorylation on which normal junctional permeability depends (Wiener & Loewenstein, 1983, Nature 305:433)--did not abolish, in general, the junctional effect of the virus; src tyrosine-phosphorylation apparently overrides the junctional upregulation mediated by cyclic AMP. Nonjunctional membrane permeability was not sensibly affected by the virus. It was affected, however, by temperature: lowering the temperature from the nonpermissive to the permissive level caused the nonjunctional permeability to fall, and vice versa. This change was unrelated to transformation. Its secondary effect on junctional transfer is in the opposite direction to that produced by the temperature-activated viral transformation.

Animals↗
PubMed1992

Intercellular communication between follicular angiotensin receptors and Xenopus laevis oocytes: medication by an inositol 1,4,5-trisphosphate-dependent mechanism.

In Xenopus laevis oocytes, activation of angiotensin II (AII) receptors on the surrounding follicular cells sends a signal through gap junctions to elevate cytoplasmic calcium concentration ([Ca2+]i) within the oocyte. The two major candidates for signal transfer through gap junctions into the oocyte during AII receptor stimulation are Ins(1,4,5)P3 and Ca2+. In [3H]inositol-injected follicular oocytes, AII stimulated two- to fourfold increases in phosphoinositide hydrolysis and production of inositol phosphates. Injection of the glycosaminoglycan, heparin, which selectively blocks Ins(1,4,5)P3 receptors, prevented both AII-stimulated and Ins(1,4,5)P3-induced Ca2+ mobilization in Xenopus follicular oocytes but did not affect mobilization of Ca2+ by ionomycin or GTP. These results indicate that the AII-regulated process of gap junction communication between follicular cells and the oocyte operates through an Ins(1,4,5)P3-dependent mechanism rather than through transfer of Ca2+ into the ooplasm and subsequent Ca(2+)-induced Ca2+ release.

Angiotensin II↗
PubMed1975

The structure of cell membranes involved in intercellular communication.

The molecular structure of mouse hepatocyte gap junctions is investigated with corrlated electron microscopy, biochemistry, and x-ray diffraction technics. These studies reveal that the gap junction is composed of a hexagonal lattice of protein subunits, connexons, which pierce the hydrophobic membrane and establish a structural basis for intercellular hydrophilic channels or pores. By digesting liver-cell membranes with trypsin, a preparation of open- and closed-gap junction vesicles can be generated; this preparation will permit direct permeability measurements across the gap junction membranes in an in-vitro system.

Animals↗