Coordinated intercellular calcium waves induced by noradrenaline in rat hepatocytes: dual control by gap junction permeability and agonist

Calcium-mobilizing agonists induce intracellular Ca2+ concentration ([Ca2+]i) changes thought to trigger cellular responses. In connected cells, rises in [Ca2+]i can propagate from cell to cell as intercellular Ca2+ waves, the mechanisms of which are not elucidated. Using fura2-loaded rat hepatocytes, we studied the mechanisms controlling coordination and intercellular propagation of noradrenaline-induced Ca2+ signals. Gap junction blockade with 18 alpha-glycyrrhetinic acid resulted in a loss of coordination between connected cells. We found that second messengers and [Ca2+]i rises in one hepatocyte cannot trigger Ca2+ responses in connected cells, suggesting that diffusion across gap junctions, while required for coordination, is not sufficient by itself for the propagation of intercellular Ca2+ waves. In addition, our experiments revealed functional differences between noradrenaline-induced Ca2+ signals in connected hepatocytes. These results demonstrate that intercellular Ca2+ signals in multicellular systems of rat hepatocytes are propagated and highly organized through complex mechanisms involving at least three factors. First, gap junction coupling ensures coordination of [Ca2+]i oscillations between the different cells; second, the presence of hormone at each hepatocyte is required for cell-cell Ca2+ signal propagation; and third, functional differences between adjacent connected hepatocytes could allow a 'pacemaker-like' intercellular spread of Ca2+ waves.     

Adhesive intercellular interactions

The process of intercellular interactions during morphogenesis, inflammation and malignant growth are considered from the point of view of possible intercellular contacts provided by cell adhesion molecules. The system analysis of different cell adhesion molecules classes? their structure and influence on functional cell activity is performed. Clinical importance of expression disturbances of cell adhesion molecules at various pathological processes is considered.     

The molecular structure of mitochondrial contact sites. Their role in regulation of energy metabolism and permeability transition

Contact sites between the outer and peripheral inner membrane of mitochondria are involved in protein precursor uptake and energy transfer. Hexokinase and mitochondrial creatine kinase could be attributed by different techniques to the energy transfer contacts. Kinetic analyses suggested a functional interaction between the kinases, outer membrane pore protein, and inner membrane adenylate translocator (ANT). This suggestion was strongly supported by isolation of hexokinase and creatine kinase complexes that were constituted of kinase oligomers, porin and ANT. Phospholipid vesicles carrying reconstituted kinase-porin-ANT complexes enclosed internal ATP in contrast to vesicles containing free porin only. This indicated that unspecific transport through porin was regulated by its interaction with a specific antiporter, ANT. A direct interaction between porin and ANT in the hexokinase complex conferred the reconstituted system with permeability properties reminiscent of the mitochondrial permeability transition (PT) pore. In the creatine kinase complex this interaction between porin and ANT was replaced by contact of both with the kinase octamer. Thus PT-pore-like functions were not observed unless the creatine kinase octamer was dissociated, suggesting that the ANT was locked in the antiporter state by interaction with the octamer. Indeed, reconstituted pure ANT showed PT-pore-like properties concerning Ca2+ sensitivity. However, as cyclophilin was missing, sensitivity against cyclosporin was not observed.     

Structure of gap junction intercellular channels

The water durability at adhesion interfaces was investigated by measurement of the peeled area of thin resin films bonded with 4-META resin on metal surfaces after imposing thermal stress using liquid nitrogen. Thermal stress at the adhesion interface was calculated by a computer-aided finite element method. On 18-8 stainless-steel specimens which bond strongly with 4-META resin, total interface failure occurs on specimens with resin thicker than 0.55 mm in dry condition. A resin layer of 0.25 mm was chosen to study degradation of the adhesion interface by water. The shearing stress was calculated as 16 MPa for a 0.25 mm thick resin layer. On mild-steel adherent interface with 4-META resin which degrades rapidly by water molecule, the relationship between water immersion time and degradation at the adhesion interface was discussed together with the amount of water penetrated at the interface. The method proposed in the present study is effective as a quick evaluation method for water durability at the adhesion interface.     

High levels of soluble intercellular adhesion molecule-1 (ICAM-1) in crevicular fluid of periodontitis patients with plaque

The intercellular adhesion molecule-1 (ICAM-1) is a membrane-bound molecule involved in cell-cell adhesive interactions which is upregulated on inflammatory epithelial cells. The levels of soluble ICAM-1 (sICAM-1) shed into the gingival crevicular fluid (GCF) were studied in healthy patients and patients with gingivitis, adult periodontitis or rapidly progressive periodontitis, using an ELISA technique. Clinical parameters including plaque index, gingival index, probing depth, and bleeding on probing were recorded following careful sampling of GCF with standardised filter strips. In GCF, sICAM-1 levels were higher for patients with plaque (p=0.04) and for patients with inflammation (p=0.02), but did not correlate with disease classifications. These results suggest that elevated GCF sICAM-1 levels may represent increased shedding of this molecule in the interstitial fluid as a result of membrane-bound ICAM-1 upregulation on ICAM-1 gingival-bearing cells in relation with plaque accumulation and inflammation.     

Intestinal permeability of ophthalmic beta-blockers for predicting ocular permeability

The purpose of this study was to investigate the intestinal permeability of ophthalmic beta-blockers and evaluate the utility of intestinal membrane for predicting the ocular permeability. The penetrations of beta-blockers were measured across the isolated jejunum and colon of the albino rabbit using a two-chamber glass diffusion cell. beta-Blockers tested include atenolol, carteolol, tilisolol, timolol, and befunolol. Colonic membrane showed lower permeability of hydrophilic drugs than jejunal membrane. Scraping the entire cell monolayer of jejunum increased the drug permeability. There was a significant correlation between colonic permeability coefficients and lipophilicities of beta-blockers. The permeability coefficients through jejunum and scraped jejunum were not susceptible to drug lipophilicities. Jejunum, scraped jejunum, and colon showed permeability coefficients almost equal to those of sclera, conjunctiva, and cornea, respectively. There was a significant correlation between permeability coefficients through colon and cornea. These results indicate that the steady-state permeability of ophthalmic beta-blockers through ocular membranes may be predicted by measuring the permeability through certain intestinal membranes. However, the analyses of intestinal permeability using Fick's equation showed the functional difference of intestinal permeability from ocular permeability of ophthalmic beta-blockers.     

Mechanisms and function of intercellular calcium signaling

Intercellular Ca2+ waves initiated by mechanical or chemical stimuli propagate between cells via gap junctions. The ability of a wide diversity of cells to display intercellular Ca2+ waves suggests that these Ca2+ waves may represent a general mechanism by which cells communicate. Although Ca2+ may permeate gap junctions, the intercellular movement of Ca2+ is not essential for the propagation of Ca2+ waves. The messenger that moves from one cell to the next through gap junctions appears to be IP3 and a regenerative mechanism for IP3 may be required to effect multicellular communication. Extracellularly mediated Ca2+ signaling also exists and this could be employed to supplement or replace gap junctional communication. The function of intercellular Ca2+ waves may be the coordination of cooperative cellular responses to local stimuli.     

Cytoplasmic tail regulates the intercellular adhesion function of the epithelial cell adhesion molecule

Ep-CAM, an epithelium-specific cell-cell adhesion molecule (CAM) not structurally related to the major families of CAMs, contains a cytoplasmic domain of 26 amino acids. The chemical disruption of the actin microfilaments, but not of the microtubuli or intermediate filaments, affected the localization of Ep-CAM at the cell-cell boundaries, suggesting that the molecule interacts with the actin-based cytoskeleton. Mutated forms of Ep-CAM were generated with the cytoplasmic domain truncated at various lengths. All of the mutants were transported to the cell surface in the transfectants; however, the mutant lacking the complete cytoplasmic domain was not able to localize to the cell-cell boundaries, in contrast to mutants with partial deletions. Both the disruption of the actin microfilaments and a complete truncation of the cytoplasmic tail strongly affected the ability of Ep-CAM to mediate aggregation of L cells. The capability of direct aggregation was reduced for the partially truncated mutants but remained cytochalasin D sensitive. The tail truncation did not affect the ability of the transfectants to adhere to solid-phase-adsorbed Ep-CAM, suggesting that the ability to form stable adhesions and not the ligand specificity of the molecule was affected by the truncation. The formation of intercellular adhesions mediated by Ep-CAM induced a redistribution to the cell-cell boundaries of alpha-actinin, but not of vinculin, talin, filamin, spectrin, or catenins. Coprecipitation demonstrated direct association of Ep-CAM with alpha-actinin. Binding of alpha-actinin to purified mutated and wild-type Ep-CAMs and to peptides representing different domains of the cytoplasmic tail of Ep-CAM demonstrates two binding sites for alpha-actinin at positions 289 to 296 and 304 to 314 of the amino acid sequence. The results demonstrate that the cytoplasmic domain of Ep-CAM regulates the adhesion function of the molecule through interaction with the actin cytoskeleton via alpha-actinin.     

改善烧结料层透气性途径的探讨

介绍韶关冶炼厂烧结机烧结料层透气性的情况以及改造途径．     

Carotenoids and intercellular communication via gap junctions

Long-term cultured murine embryonic yolk sac cells that are capable of forming capillary structures when cultured on base membrane proteins (Matrigel) were successfully transfected with a human growth hormone antagonist (G120R) gene. Cells that stably express relatively high levels of G120R were co-implanted s.c. with Matrigel into BALB/c mice. G120R can be detected in the sera of those implanted mice for more than 14 days at levels from 4 ng/ml to 28 ng/ml. The insulin-like growth factor-1 levels in the sera of those implanted mice were significantly affected by the delivered G120R. One of the physiological effects of G120R delivered by this murine embryonic yolk sac cell-derived mini-organ system is to decrease the growth rate of the implanted mice. This gene delivery system can also be used as an alternative to transgenic animals to study protein function in vivo.     

Interference of bcl-2 with intercellular control of carcinogenesis

Induction of apoptosis in transformed fibroblasts by surrounding normal cells has been discussed as a potent early control step in carcinogenesis. According to this hypothesis, tumor progression should require resistance of transformed cells against this TGF-beta-triggered control mechanism. Here we show that Bcl-2, a protein involved in inhibition of apoptosis, can protect transformed cells from induction of apoptosis by surrounding cells. Rather than acting on the transformation process itself, Bcl-2 may thus represent an efficient modulator of carcinogenesis at an intercellular level.     

Mechanical properties of intercellular contacts of small intestinal epithelium

It has been shown that when long-acting forces are applied, the intercellular contacts in the small intestine epithelium are destroyed at the values of these forces lower than the adhesion ones obtained at the application of short-term loads. Starting with some threshold value of the load viscose-elastic properties of intercellular contacts are shown up. Thus the threshold varies essentially for different cells of the population: 4 variations are observed. A removal of bivalent cations from the tissue significantly decreases the threshold value of the forces and decreases the viscosity while the excessive concentrations of bivalent cations increase the threshold value of forces, the membrane viscosity and contact components.     

Properties of stochastic permeability

When modeled at macroscopic length scales, the complex dendritic network in the solid-plus-liquid region of a solidifying alloy (the “mushy zone”) has been modeled as a continuum based on the theory of porous media. The most important property of a porous medium is its permeability, which relates the macroscopic pressure gradient to the throughput of fluid flow. Knowledge of the permeability of the mushy zone as a function of the local volume-fraction of liquid and other morphological parameters is thus essential to successfully modeling the flow of interdendritic liquid during alloy solidification. Permeability is usually treated as a deterministic function of parameters that can be calculated by the model (e.g., local solid fraction, dendrite arm spacing). However, recent results show that the length scales that must be resolved are too small for the assumption of deterministic behavior to be valid, and investigators must confront the stochastic behavior of the permeability field. We describe early work to investigate the spatial structure of the stochastic permeability at these small scales, with a view to develop a comprehensive treatment of stochastic permeability to enable improved modeling.     

Energy and metabolic intercellular interaction in the growth region of Neurospora crassa

A major group of systemic autoimmune diseases is associated with abnormal lymphoproliferation, as a result of defects in the termination of lymphocyte activation and growth. Recent progress has been made in understanding the causes and consequences of these abnormalities. At the molecular level, the defects in CD95 and its ligand are only the most obvious reasons for the breakdown of 'clonal contraction' which in fact requires the participation of multiple gene products, including the IL-2-IL-2-receptor system, to set up a functional apoptotic machinery.     

High in situ rat intestinal permeability of artemisinin unaffected by multiple dosing and with no evidence of P-glycoprotein involvement

PURPOSE: To evaluate inflammation after clear corneal incision (CCI) cataract surgery in patients with noninsulin-dependent diabetes mellitus and no retinopathy. METHODS: Forty patients with diabetes and 40 age-matched controls had standardized temporal CCI cataract surgery with implantation of a foldable intraocular lens. Anterior chamber flare was evaluated in an undilated eye with a laser flare-cell meter preoperatively and 1, 3, 7, 14, and 28 days postoperatively. RESULTS: In both groups, flare and cell values increased on the first postoperative day and successively decreased on the following days. Flare had not recovered to preoperative values by day 28. At no time was there a significant mean difference in cell and flare between the 2 groups. CONCLUSION: It does not appear necessary to alter the postoperative therapeutic regimen in patients with type 2 diabetes mellitus and no retinopathy.     

Essential functional role of the polysaccharide intercellular adhesin of Staphylococcus epidermidis in hemagglutination

Hemagglutination of erythrocytes is a common property of Staphylococcus epidermidis strains, which is related to adherence and biofilm formation and may be essential for the pathogenesis of biomaterial-associated infections caused by S. epidermidis. In three independent biofilm-producing, hemagglutination-positive S. epidermidis isolates, interruption of the icaADBC operon essential for polysaccharide intercellular adhesin (PIA) synthesis by Tn917 insertions led to a hemagglutination-negative phenotype. An immunoglobulin G fraction of antiserum to PIA greatly reduced hemagglutination. Purified PIA led to a 64-fold decrease of hemagglutination titers of these strains; however, it did not mediate hemagglutination by itself. These observations define PIA as the hemagglutinin of S. epidermidis or at least as its major functional component.