Communicating junctions

Tree like networks of nerve fiber called dendrites protrude outward from the neuron s cell body, or soma. Extending outward from the soma is also a long fiber called the axon that itself eventually branches out into a set of strands and sub strands. At the ends of these strands are the transmitting ends of communication junctions between nerve fibers called synapses. The receiving ends of these junctions exist both on dendrites and on the somas themselves. Each neuron is typically connected to several thousand other neurons. 

There are also numerous important variations in the microvasculature bed (i.e., arterioles, capillaries, and venules) that affect permeability. For example, venular portions of the capillaries have thin endothelial cells (170 nm), with frequent interendothelial discontinuities. About 30% of venular junctions are believed to have gaps of about 6 nm. Arterioles, in contrast, have endothelial cells that are linked by the tight junctions and communicating junctions, whereas the capillary endothelium contains... 

Another example of molecular communication is found in a neuronal synapse, which is a communication junction between two neurons as shown in Fig.2. The presynaptic membrane releases the neurotransmitter molecule that is recognized and captured by the receptor located on the surface of the postsynaptic membrane. 

Peracchia C Calmodulin-like proteins and communicating junctions - electrical uncoupling of crayfish septate axons is inhibited by the calmodulin inhibitor W7 and is not affected by cyclic nucleotides. Pfliigers Arch 1987 408 379-385. 

The gap junctions are communicating junctions, kinds of tunnels enabling the molecular exchanges between neighboring cells. They are spread in an anarchic way on the lateral and basal faces. 

Another type of communicating junction is also found in synapses of the nervous system. At these specialized contacts a nerve impulse transmitted along the membrane of one neuron triggers the release of a neurotransmitter, a chemical substance that passes across the gap between cells of the synapse and initiates a nerve impulse in the second neuron (Chapter 30). 

Polypeptides of mouse liver plasma membrane gap (communicating) junctions 132 NG ... 

The supplanting of germanium-based semiconductor devices by shicon devices has almost eliminated the use of indium in the related ahoy junction (see Semiconductors). Indium, however, is finding increased use in III—V compound semiconductors such as indium phosphide [22398-80-7] for laser diodes used in fiber optic communication systems (see Electronic materials Fiber optics Light generation). Other important indium-containing semiconductors include indium arsenide [1303-11-3] indium antimonide [1312-41 -0] and copper—indium—diselenide [12018-95-0]. 

Two specialties of the nervous system are speed and localization, accompHshed using highly developed electrical signaling and close cellular apposition. At specialized points of communication, such as the synapse and the neuromuscular junction, the cells are separated by a nanometer or less. 

When cells lie adjacent to each other in animal tissues, they are often connected by gap junction structures, which permit the passive flow of small molecules from one cell to the other. Such junctions essentially connect the cells metabolically, providing a means of chemical transfer and communication. In certain tissues, such as heart muscle that is not innervated, gap junctions permit very large numbers of cells to act synchronously. Gap junctions also provide a means for transport of nutrients to cells disconnected from the circulatory system, such as the lens cells of the eye. 

Although gap junctions allow cells to communicate metabolically under normal conditions, the ability to close gap junctions provides the tissue with an important intercellular regulation mechanism. In addition, gap junctions provide a means to protect adjacent cells if one or more cells are damaged or... 

Functions of nNOS include long-term regulation of synaptic transmission in the CNS (long-term potentiation, long-term depression), whereas there is no evidence for an involvement of nNOS-derived NO in acute neurotransmission. Retrograde communication across synaptic junctions is presumed to be involved in memory... 

Imidazole antimycotics, ketoconazole, clotrimazole, and miconazole are potent inhibitors of various cytochrome P450-isoenzymes that also affect the metabolism of retinoids. They were fust shown to inhibit the metabolism of RA in F9 embryonal carcinoma cells. When tested in vitm liarazole, a potent CYP-inhibitor, suppressed neoplastic transformation and upregulated gap junctional communication in murine and human fibroblasts, which appeared to be due to the presence of retinoids in the serum component of the cell culture medium. Furthermore, liarazole magnified the cancer chemopreventive activity of RA and (3-carotene in these experiments by inhibiting RA-catabolism as demonstrated by absence of a decrease in RA-levels in the culture medium in the presence of liarazole over 48 h, whereas without liarazole 99% of RA was catabolized. In vivo, treatment with liarazole and ketoconazole reduced the accelerated catabolism of retinoids and increased the mean plasma all-irans-RA-concentration in patients with acute promyelocytic leukemia and other cancels. 

Josephson junctions for passive microwave devices, satellite-communication systems, and computer logic gates. 

Fransson-Steen R, Warngard L. 1992. Inhibitory effects of endosulfan on gap junctional intercellular communication in WB-F344 rat liver cells and primary rat hepatocytes. Carcinogenesis 13(4) 657-662. 

Kenne K, Fransson-Steen R, Honkasalo S, et al. 1994. Two inhibitors of gap junctional intercellular communication, TPA and endosulfan Different effects on phosphorylation of connexin 43 in the rat liver epithelial cell line, lAR 20. Carcinogenesis 15(6) 1161-1165. 

Musil LS et al. 1990. Differential phosphorylation of the gap junction protein connexin43 in junctional communication-competent and -deficient cell lines. J Cell Biol 111 2077-2088. 

Whilst finite-element modelling of gap junctions occurs at a sub-cellular level, these models do not consider the operation of intact organs. Conversely, in models of the complete heart the discretisation is usually on a milhmetre scale. However, the cochlea (see Figure 9.3) is already being simulated on a 0.01 mm, or cellular, scale. Although cochlear malfunction is not hfe threatening, damage to it does adversely affect the ability of almost 1000000000 people to communicate. 

In the Unites States, the daily intake of 3-carotene is around 2 mg/day Several epidemiological studies have reported that consumption of carotenoid-rich foods is associated with reduced risks of certain chronic diseases such as cancers, cardiovascular disease, and age-related macular degeneration. These preventive effects of carotenoids may be related to their major function as vitamin A precursors and/or their actions as antioxidants, modulators of the immune response, and inducers of gap-junction communications. Not all carotenoids exert similar protective effects against specific diseases. By reason of the potential use of carotenoids as natural food colorants and/or for their health-promoting effects, research has focused on better understanding how they are absorbed by and metabolized in the human body. 

In atherosclerosis and other heart diseases, the role of carotenoids as antioxidants is probable, but for these types of diseases and also for other degenerative diseases such as cancers, non-antioxidant activities constitute other possible prevention mechanisms. These activities are, for example, stimulation of gap junction communications between cells, and the induction of detoxifying enzymes. The... 

Different types of apparently beneficial activities have been demonstrated in vitro for carotenoid oxidation products, including induction of gap-junctional communications, " growth inhibition of leukemia and cancer cells, induction of apoptosis... 

Another study showed that a mixture of oxidative metabolites of P-carotene, but not P-carotene, was able to increase the binding of benzo[a]pyrene to DNA. Other mixtures of P-carotene cleavage products have been shown to induce oxidative stress in vitro,exert cytotoxic and genotoxic effects, and inhibit gap junction intercellular communications. It has been suggested that these detrimental effects could possibly occur in vivo following the intake of high doses of carotenoids. 

Stahl, W. and Sies, H., Effects of carotenoids and retinoids on gap junctional communication, Biofactors, 15, 95, 2001. 

Yeh, S.L. and Hu, M.L., Oxidized [beta]-carotene inhibits gap junction intercellular communication in the human lung adenocarcinoma cell line A549, Food Chem. Toxicol., 41, 1677, 2003. 

Ozone attacks the rings of PAHs rather indiscriminately with fission of the rings to prodnce aldehyde gronps. There has been concern, however, since the products may be more harmful than their precursors. In the studies that are used as illustration, in vitro gap junctional intracellular communication (GJIC) was used to assess adverse alteration on the expression of genes at the transcription, translational, or posttranslational level ... 

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