The international entrepreneurial firm's social networks

This paper investigates theoretically the importance and impact of the international entrepreneurial firms’ (IEFs) social networks on selected firms’ strategies. We focus specifically on some core attributes of IEFs and the impact of social networks on such strategies as the choice of the foreign markets to operate and the foreign entry modes. The social networks are a major driver of the internationalization from inception and help in overcoming a variety of physical and social resource limitations as well as transactional hazards. We conclude that it is likely that both some fundamental characteristics of the IEFs and those of the foreign markets entered account for these firms reliance on their social networks

CHARACTERIZATION OF ISOLATED RAT-LIVER CELLS MADE PERMEABLE WITH FILIPIN

When isolated rat-liver cells were incubated for 1 min at 37 degrees C with filipin at a concentration of 50 microM, the plasma membrane became permeable to sucrose, inulin, glycerol 3-phosphate and other low-molecular-weight compounds. Upon removal of the filipin and subsequent incubation of the cells at 37 degrees C there was a gradual leakage of lactate dehydrogenase from the cells. However, the leakage of lactate dehydrogenase could be prevented for about 10 min by including glutathione and ATP in the incubation medium. The filipin-treated cells were able to metabolize phosphorylated sugars. The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate, glucose-6-phosphate and glucose was inhibited by AMP but not by high concentrations of fructose 1,6-bisphosphate. The results indicate that filipin-treated cells can be used to study the kinetic parameters of enzymes in their macromolecular environment in sit

Measurement of binding of adenine nucleotides and phosphate to cytosolic proteins in permeabilized rat-liver cells

1. A method is described for measuring the binding of metabolites to cytosolic proteins in situ in isolated rat-liver cells treated with filipin to render the plasma membrane permeable to compounds of low molecular weight. 2. There is no binding of ATP or inorganic phosphate to cytosolic proteins, either in the presence or in the absence of Mg2+. 3. Binding of ADP to cytosolic proteins occurs both in the absence and in the presence of Mg2+. The concentration of binding sites was 0.68 and 0.52 mumol/g dry weight of cells (n = 3-4) in the absence and presence of Mg2+, respectively. The corresponding Kd values were 320 microM and 235 micro

Enterotoxigenic Escherichia coli vesicles target toxin delivery into mammalian cells

Enterotoxigenic Escherichia coli (ETEC) is a prevalent cause of traveler's diarrhea and infant mortality in third-world countries. Heat-labile enterotoxin (LT) is secreted from ETEC via vesicles composed of outer membrane and periplasm. We investigated the role of ETEC vesicles in pathogenesis by analyzing vesicle association and entry into eukaryotic cells. Fluorescently labeled vesicles from LT-producing and LT-nonproducing strains were compared in their ability to bind adrenal and intestinal epithelial cells. ETEC-derived vesicles, but not control nonpathogen-derived vesicles, associated with cells in a time-, temperature-, and receptor-dependent manner. Vesicles were visualized on the cell surface at 4°C and detected intracellularly at 37°C. ETEC vesicle endocytosis depended on cholesterol-rich lipid rafts. Entering vesicles partially colocalized with caveolin, and the internalized vesicles accumulated in a nonacidified compartment. We conclude that ETEC vesicles serve as specifically targeted transport vehicles that mediate entry of active enterotoxin and other bacterial envelope components into host cells. These data demonstrate a role in virulence for ETEC vesicles