Plakoglobin, or an 83-kD homologue distinct from beta-catenin, interacts with E-cadherin and N-cadherin.

E- and N-cadherin are members of a family of calcium-dependent, cell surface glycoproteins involved in cell-cell adhesion. Extracellularly, the transmembrane cadherins self-associate, while, intracellularly, they interact with the actin-based cytoskeleton. Several intracellular proteins, collectively termed catenins, have been noted to co-immunoprecipitate with E- and N-cadherin and are thought to be involved in linking the cadherins to the cytoskeleton.

Effects of acute vs. chronic phorbol ester exposure on transepithelial permeability and epithelial morphology.

In previous experiments we have shown that acute (30 minutes) exposure to phorbol esters or other protein kinase C activators causes increased transepithelial permeability, specifically by the increased paracellular permeability through tight junctions. However, the role of protein kinase C activators in carcinogenesis is predicted upon a chronic exposure of an effective dose at frequent intervals for a prolonged period of time. We therefore sought to determine the effect of chronic phorbol ester exposure on transepithelial permeability by exposing cells of the polar renal epithelial cell line, LLC-PK1, to phorbol esters for time periods as long as 16 weeks.

Basolateral 3-O-methylglucose transport by cultured kidney (LLC-PK1) epithelial cells.

In previous work we demonstrated the similarity of basolateral sugar transport of LLC-PK1 renal epithelia to basolateral kidney sugar transport using 2-deoxy-D-glucose as a substrate. In this study we first examine a central limitation to use of 2-deoxyglucose for basolateral sugar transport study in LLC-PK1 epithelia, namely, a shift of the rate-limiting step in uptake from transport to phosphorylation. Use of 3-O-methylglucose avoids this complication because it is not phosphorylated.

Induction of ornithine decarboxylase in specific subpopulations of murine epidermal cells following multiple exposures to 12-O-tetradecanoylphorbol-13-acetate, mezerein and ethyl phenylpropriolate.

Single applications of 12-O-tetradecanoylphorbol-13-acetate (TPA), mezerein or ethyl phenylpropriolate (EPP) to mouse skin at appropriate doses cause similar degrees of hyperplasia and comparable levels of induction of epidermal ornithine decarboxylase (ODC) activity. Multiple (n = 5) treatments with these agents, in contrast, resulted in large differences in induced ODC activity (TPA much greater than mezerein greater than EPP) with no differences in the degree of hyperplasia or [3H]thymidine pulse-labeling among the multiple treatment groups. To attempt to explain the cellular basis for the greater ODC-inducing ability of TPA relative to mezerein and EPP in chronic exposure protocols, immunocytochemical and flow cytometric analyses were performed.

Suppression of renal vein renin profiles by mannitol prophylaxis: implications in the evaluation of renovascular hypertension.

Renal arteriography with concomitant renal vein renin profiling remains the diagnostic standard for evaluating the anatomic and physiologic significance of stenotic renal artery lesions in hypertensive patients. False-negative renal vein renin profiles with failure of lateralization in patients with anatomically apparent high-grade stenosis complicate the diagnostic process. Mannitol is frequently administered prophylactically to minimize the risk of dye nephropathy in these patients.

Effects of exogenous putrescine on murine preimplantation development in vitro.

After first demonstrating that murine embryos take up putrescine from the medium in which they are cultured in vitro, fertilized eggs were placed in culture and maintained for 4 days in medium supplemented with varying amounts of putrescine. Their development was monitored each day. While embryos that were cultured in putrescine-supplemented medium developed at the same rate as control embryos, a significantly higher percentage of the putrescine-treated embryos attained the blastocyst stage as compared to the control group.

Colocalization of N-CAM and N-cadherin in avian skeletal myoblasts.

The cell-cell adhesion molecules, N-CAM and N-cadherin, have been shown previously to mediate myoblast interaction during cell fusion accompanying skeletal myogenesis. To study the localization of both molecules in fusion-competent myoblasts, we used antigen-specific primary antibodies and a double-labeling preembedding immuno-electron microscopy technique. Ultrastructural observations and quantitative analysis of the results reveal that N-CAM and N-cadherin frequently colocalize in clusters on the myoblast plasma membrane.

Constitutively elevated levels of ornithine and polyamines in mouse epidermal papillomas.

Epidermal papillomas were induced in CD-1 mice by a single topical application of 7,12-dimethylbenzanthracene (DMBA) followed by twice weekly applications of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) in acetone. Control groups consisted of mice treated singly or chronically with acetone or TPA. TPA induced a rapid, yet transient 500- to 1000-fold increase in ornithine decarboxylase (ODC) activity which resulted in a 2- to 8.

Inhibition of murine melanoma cell-matrix adhesion and experimental metastasis by albolabrin, an RGD-containing peptide isolated from the venom of Trimeresurus albolabris.

Albolabrin, a 7.5-kDa cysteine-rich protein isolated from the venom of Trimeresurus albolabris, contains the arginine-glycine-aspartic acid (RGD) cell recognition sequence found in many cell adhesion-promoting extracellular matrix proteins, such as fibronectin and laminin. Albolabrin belongs to a family of RGD-containing peptides, termed disintegrins, recently isolated from the venom of various vipers and discovered to be potent inhibitors of both platelet aggregation and cell-substratum adhesion.

Intradialytic parenteral nutrition in chronic hemodialysis patients.

The effects of intradialytic parenteral nutrition (IDPN) were studied in chronic hemodialysis (CHD) patients who had a normalized protein catabolic rate (PCRN) of less than or equal to 0.8 g/kg/day, and KT/V = 0.94 +/- 0.

Effects of apical vs. basolateral palytoxin on LLC-PK1 renal epithelia.

Research on palytoxin focuses on its action as a tumor promoter and its ionophoretic action in cell membranes. The first property is unusual because palytoxin is not a protein kinase C activator. The second property is remarkable in that it may require interaction with the Na(+)-K(+)-adenosinetriphosphatase (ATPase).

Differential sensitivity of cardiac pacemakers to exogenous adenosine in vivo.

Adenosine exerts pronounced depressant effects on cardiac pacemakers. Previous studies in vitro have indicated that different pacemakers exhibit variable sensitivity to adenosine: ventricular greater than junctional greater than sinus node pacemakers. This study tested the hypothesis that ventricular pacemakers are more sensitive to adenosine than sinus node pacemakers in vivo in an experimental canine model and determined the mechanism involved in this phenomenon using specific pharmacological interventions.

A role for the Ca2(+)-dependent adhesion molecule, N-cadherin, in myoblast interaction during myogenesis.

The formation of multinucleate skeletal muscle cells (myotubes) is a Ca2(+)-dependent process involving the interaction and fusion of mononucleate muscle cells (myoblasts). Specific cell-cell adhesion precedes lipid bilayer union during myoblast fusion and has been shown to involve both Ca2(+)-independent (CI)2 and Ca2(+)-dependent (CD) mechanisms. In this paper we present evidence that CD myoblast adhesion involves a molecule similar or identical to two known CD adhesion glycoproteins, N-cadherin and A-CAM.

Acetone and acetol inhibition of insulin-stimulated glucose oxidation in adipose tissue and isolated adipocytes.

The response of peripheral tissues to insulin is reduced in fasting and diabetes mellitus. The experiments described herein were designed to determine whether insulin-stimulated glucose oxidation is affected by the free-fatty acid-derived plasma metabolites acetone, acetol, and propylene glycol (1,2-propanediol [1,2-PD]), concentrations of which are elevated in both starvation and diabetic ketosis. In epididymal adipose tissue from fed and 48-h--fasted rats given 3% acetone drinking water for 7 days, insulin-stimulated glucose oxidation was reduced by approximately 30-40%.

Effect of tumor necrosis factor on epithelial tight junctions and transepithelial permeability.

The serum factor inducing hemorrhagic necrosis of transplantable tumors [tumor necrosis factor (TNF)], and the macrophage hormone associated with cachexia in cancer and certain infectious diseases [cachectin] are known to be the same protein. Because an association may exist between TNF and the cachectic state, we wished to examine the effect of TNF on the permeability of epithelial barriers. We present data showing that TNF affects the tight junctional region between epithelial cells, lowering the transepithelial resistance and potential difference, and increasing the flow of solute between cells and across the epithelium.

A role for the neural cell adhesion molecule, NCAM, in myoblast interaction during myogenesis.

The Ca2(+)-independent neural cell adhesion molecule, NCAM, is expressed by both nerve and muscle cells and has been shown to mediate both nerve-nerve and nerve-muscle cell interaction. A role for NCAM in muscle-muscle cell interaction has been proposed but not demonstrated. Here we report evidence that NCAM is expressed by embryonic chick muscle cells during in vitro development and functions together with Ca2(+)-dependent adhesion molecules in mediating myoblast interaction during the formation of multinucleate cells.

The effects of teleocidin and aplysiatoxin tumor promoters on epithelial tight junctions and transepithelial permeability: comparison to phorbol esters.

Control of transepithelial permeability by regulation of tight junctions is exerted by the non-phorbol ester tumor promoters, teleocidin and aplysiatoxin. Similar to the phorbol esters, tetradecanoylphorbol-13-acetate (TPA) and phorbol dibutyrate (PDBU), both teleocidin and aplysiatoxin cause a reversible decrease of transepithelial voltage and transepithelial resistance across LLC-PK1 renal epithelial cell sheets at concentrations as low as 10(-8) M. These compounds are effective from either side of these polar epithelial cells, i.

Effect of tight junctional resistance on penetration of LLC-PK1 epithelial cell layers by metastatic B16-F10 melanoma cells.

The relationship between tight junctional resistance of a tissue and its penetration by metastatic cells was examined in vitro using LLC-PK1 cells, an epithelial cell line derived from pig kidney, and B16-F10 cells, a murine melanoma cell line metastatic in syngeneic C57BL/6 mice. When grown to confluence on 8.0-microns pore size polycarbonate filters, LLC-PK1 cells formed tight junctions between adjacent cells which offered an electrical resistance to a nondestructive 20-mu ampere alternating current passed across the cell layer.

Involvement of cell surface phosphatidylinositol-anchored glycoproteins in cell-cell adhesion of chick embryo myoblasts.

During myogenesis myoblasts fuse to form multinucleate cells that express muscle-specific proteins. A specific cell-cell adhesion process precedes lipid bilayer union during myoblast fusion (Knudsen, K. A.

Na+-independent sugar transport by cultured renal (LLC-PK1) epithelial cells.

The LLC-PK1 cell line has been well characterized concerning its proximal tubule-like Na+-dependent active sugar transporter in the apical membrane. In this study, we investigated the uptake of the glucose analogue, 2-deoxy-D-glucose (2DOG), a paradigm substrate for the facilitated diffusion, Na+-independent sugar transporter in the renal basolateral membrane. The uptake of 0.

The GPIIB-IIIa-like complex may function as a human melanoma cell adhesion receptor for thrombospondin.

The purpose of this study was to determine whether a heterodimeric complex immunologically related to the fibrinogen receptor could function as a thrombospondin (TSP) receptor in TSP-mediated cell-substratum adhesion of human melanoma cells. We found that polyclonal antibodies to the platelet GPIIb-IIIa complex, GPIIIa, and the human vitronectin receptor inhibited TSP-mediated cell adhesion by 63-68%. Immunoprecipitation of detergent extracts of 125I-surface-labeled melanoma cells using either anti-human platelet GPIIb-IIIa or anti-human vitronectin receptor antibody revealed the presence of a single heterodimeric complex, suggesting that both antisera recognize the same integrin receptor, GPIIb-IIIa-like antigen.

Extracellular potassium ion dynamics and ventricular arrhythmias in the canine heart.

The relation between extracellular potassium ion activity [( K+]o) and ventricular tachyarrhythmias was studied in an open chest canine model with the use of two protocols. In Protocol I, potassium chloride was administered into the proximal left anterior descending coronary artery at a rate of 0.125 mEq/min for either 20 min or until [K+]o = 20 mEq/liter, whichever came first.