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PubMed1982

Inhibition of intercellular communication in Chinese hamster V79 cells by teleocidin.

Teleocidin, a mixture of teleocidin A and teleocidin B, was found to block metabolic cooperation between the 6-thioguanine-resistant and the 6-thioguanine-sensitive cells in the Chinese hamster V79 cell system. A teleocidin B preparation containing two isomers exerted the same effect. The dose-response curves of these two compounds were, in general, similar to that of 12-O-tetradecanoyl-phorbol-13-acetate, a powerful mouse skin tumor promoter. Upon hydrolysis with 6M hydrochloric acid containing 4% thioglycolic acid, teleocidin lost most of its ability to block metabolic cooperation. This was probably caused by the conformational change resulting from the rupture of the nine-membered lactam ring of teleocidin.

Alkaloids↗
PubMed1994

Modulation of hepatic sinusoidal endothelial cell function by Kupffer cells: an example of intercellular communication in the liver.

We tested the hypothesis that Kupffer cells modulate sinusoidal endothelial cell function in the liver. Rats were treated with Kupffer cell-depleting agents (gadolinium chloride and liposome-encapsulated dichloromethylene diphosphonate) or with inhibitors of phospholipase A2 or leukotriene A4 synthase (dexamethasone and diethylcarbamazine, respectively). Hyaluronan uptake by the isolated, perfused liver was measured as an index of the functional state of the sinusoidal endothelial cell. Plasma hyaluronan concentration was also determined. Three hours after Escherichia coli lipopolysaccharide administration (100 micrograms/100 gm body wt, intravenously) plasma hyaluronan levels were significantly increased (280% to 320%), whereas hepatic hyaluronan uptake was markedly decreased (approximately 76%). Pretreatment with gadolinium chloride (0.5 mg/100 gm body wt, intravenously, 21 hr before saline solution or lipopolysaccharide administration), liposome-encapsulated dichloromethylene diphosphonate (40 mumol/100 gm body wt, intravenously, 44 hr before saline solution or lipopolysaccharide injection), dexamethasone (40 micrograms/100 gm body wt, intravenously, 1 hr before saline solution or lipopolysaccharide administration) or diethylcarbamazine (repeated doses, 10 mg/100 gm body wt, intravenously, 1 hr before saline solution or lipopolysaccharide injection) counteracted the lipopolysaccharide inhibitory effect on hepatic hyaluronan uptake. With the exception of gadolinium chloride, all other agents also prevented the lipopolysaccharide-induced increase in plasma hyaluronan concentration. Gadolinium chloride only attenuated the lipopolysaccharide effect on plasma hyaluronan level. Taken together with earlier results from our laboratory, these data indicate that: (a) Kupffer cell activation by lipopolysaccharide results in suppression of hyaluronan uptake by sinusoidal endothelial cells and (b) such modulation of endothelial cell function is likely mediated by products of the lipoxygenase pathway of arachidonate metabolism.

Animals↗
PubMed1993

Intercellular communication and maintenance of islet cell mass--implications for islet transplantation.

BACKGROUND: The major emphasis in islet transplantation has been the development of methods to enhance islet purity. This focus assumes that islets do not require support from other cellular elements of the pancreas. We chose to examine a possible duct-islet interaction because of the embryologic origin of islets from ductal epithelium. METHODS: Duct and islet cells were prepared by collagenization of hamster pancreas and purified on a bovine serum albumin gradient. Primary duct cultures were passaged twice. Duct-conditioned medium was collected from the tertiary cultures. Three groups of cultures were established: group 1, 100 islets/plate in minimal medium (Dulbecco's modified Eagle medium/F12); group 2, 100 islets + 40 duct fragments/plate in Dulbecco's modified Eagle medium/F12; and group 3, 100 islets/plate+duct-conditioned medium. After a 3-day incubation, tritiated thymidine (1 microCi/ml) was added for 24 hours. The islets were separated from the ducts by handpicking and then sonicated. DNA was measured (microgram) fluorometrically and tritiated thymidine incorporation, a measure of cell proliferation, was determined in trichloroacetic acid-precipitated material by liquid scintillation. Data (mean +/- SEM) were compared by two-tailed Student's t test. RESULTS: Tritiated thymidine incorporation into islet cells in minimal medium (81.1 +/- 24.6 disintegrations per minute [dpm]/microgram DNA [n = 8 plates]) was less than 25% (p < 0.001) of that of islet cells cocultured with ducts (323.2 +/- 54.5 dpm/micrograms DNA [n = 6]) or with duct-conditioned medium (389.7 +/- 27.6 dpm/micrograms DNA [n = 5]). CONCLUSIONS: Pancreatic duct epithelium can stimulate islet cell proliferation in a paracrine manner.

Animals↗
PubMed1993

[Intercellular communication and signal transduction mechanisms].

Cells in multicellular organisms coordinate their functions by signalling molecules serving as means of communication. Specific receptors enable transduction of chemical information from extracellular environment into a cell. Inside the cell the signal is multiplied and transduced further by intracellular signalling molecules and enzymatic cascades. Phosphorylation of proteins on tyrosine, serine or threonine residues, guanosine triphosphate binding by special G proteins and regulation of DNA transcription seem to be the most important biochemical mechanisms of signal transduction. Products of cellular protooncogenes are involved in all levels of signal transduction, the detailed knowledge of signal pathways is therefore important for our understanding of pathophysiology of malignant disease and strategies for the therapeutic use of growth factors in oncology and haematology.

Cell Communication↗
PubMed1996

[Receptors--one component of intercellular communication pathways].

Every event, which occurs in the cell, can be an information capable to propagate. The existence of the structures which are capable of transmission (i.e. RECEPTORS) is necessary for the effective signal propagation. In this review the receptors are divided according their localization in the cell, genetic and structural similarity to cytoplasmatic, organelic and membrane receptors. Structure and function (including basic characteristics of intracellular signalization) of the main representatives of the previously mentioned groups are described. The possible interactions between receptors are mentioned too.

Cell Communication↗
PubMed1996

[Role of intercellular communication via gap junctions in insulin secretion].

Alike most other cell types of eukaryotic organisms, the insulin-producing beta-cells of pancreatic islets are functionally interconnected by specialized regions of their cell membrane, referred to as gap junctions. These structures represent concentrations of channels which are formed by the proteins of the connexin family, and that are specialized for the exchange between neighboring cells of cytoplasmic ions and small molecules. This exchange is referred to as junctional coupling. Increasing evidence indicates that a normal expression of connexins and junctional coupling is essential to ensure proper insulin biosynthesis and secretion.

Connexin 43↗
PubMed1997

Carotenoids and intercellular communication via gap junctions.

Stimulation of gap junctional communication has been suggested to be one of the biochemical mechanisms underlying the cancer-preventive activity of carotenoids. The stimulatory activity is associated with structural properties of the carotenoids. It appears that the presence of a six-membered ring substituent at the end of the conjugated system of double bonds is required for the effects; five-membered ring carotenoids are less active. There is increasing evidence that oxidation products of carotenoids, especially retinoic acid analogs, significantly contribute to this biological property.

Animals↗