This article draws on theories about the internationalization process of small-and mediumsized enterprises (SMEs) and feminist arguments to explain gender differences in export propensity. Findings are based on a large-scale survey of Canadian SMEs. After controlling for sector, firm, and owner attributes, female majority-owned firms were significantly less likely to export than firms owned by men. The implications for entrepreneurship and feminist theory, export policy, and research are considered.

1 The effects of various sulphonylureas and diazoxide on insulin secretion and the activity of various channels have been studied using tissue culture and patch-clamp methods in an insulinsecreting cell line derived from a rat islet cell tumour. 2 Tolbutamide, glibenclamide and HB699 increased the rate of insulin release by 2-5 fold. The concentrations of tolbutamide and glibenclamide giving half-maximum effects on insulin secretion were approximately 40pM and 0.2pm, respectively. 3 Diazoxide (0.6-1.0mM) per se, had either no effect or produced a small increase in insulin secretion, whereas when secretion was maximally stimulated by the combination of glucose (3 mM) and leucine (20mM), it produced inhibition. Tolbutamide-induced release was also inhibited by diazoxide. 4 Tolbutamide, glibenclamide, HB699 and HB985 reduced the open-state probability of the ATP-K+ channel in a dose-dependent manner. Tolbutamide and glibenclamide were shown to be effective regardless of which side of the membrane they were applied. 5 In whole cell recording, in which the total ATP-sensitive K+ conductance of the cell could be measured, dose-inhibition curves for tolbutamide and glibenclamide were constructed, resulting in Ki values of 17pM and 27nm, respectively. The value of Ki for tolbutamide was unchanged when ATP (0.1 mM) was present in the electrode. 6 Diazoxide (0.6mM) activated the ATP-K+ channels only when they had first been inhibited by intracellular ATP (0.1 mM) or bath applied tolbutamide (3-30 pM). The inhibition produced by glibenclamide could not be reversed by diazoxide. 7 Neither tolbutamide (1.0mM) nor glibenclamide (10 M) altered the open-state probability of the Ca2 + -activated K+ channel or the Ca2 + -activated non-selective cation channel which are present in this cell line. 8 It is concluded that the sulphonylureas and related hypoglycaemic drugs and diazoxide regulate insulin secretion by direct effects on the ATP-K+ channel or a protein closely associated with this channel.

Thus, pigs transgenic for multiple transgenes provide a greater degree of human complement regulation and hence might be more suitable for xenotransplantation.

Polyelectrolyte complex (PEC) nanoparticles assembled from plasmid DNA (pDNA) and polycations such as linear polyethylenimine (lPEI) represent a major nonviral delivery vehicle for gene therapy tested thus far. Efforts to control the size, shape, and surface properties of pDNA/polycation nanoparticles have been primarily focused on fine-tuning the molecular structures of the polycationic carriers and on assembly conditions such as medium polarity, pH, and temperature. However, reproducible production of these nanoparticles hinges on the ability to control the assembly kinetics, given the nonequilibrium nature of the assembly process and nanoparticle composition. Here we adopt a kinetically controlled mixing process, termed flash nanocomplexation (FNC), that accelerates the mixing of pDNA solution with polycation lPEI solution to match the PEC assembly kinetics through turbulent mixing in a microchamber. This achieves explicit control of the kinetic conditions for pDNA/lPEI nanoparticle assembly, as demonstrated by the tunability of nanoparticle size, composition, and pDNA payload. Through a combined experimental and simulation approach, we prepared pDNA/lPEI nanoparticles having an average of 1.3 to 21.8 copies of pDNA per nanoparticle and average size of 35 to 130 nm in a more uniform and scalable manner than bulk mixing methods. Using these nanoparticles with defined compositions and sizes, we showed the correlation of pDNA payload and nanoparticle formulation composition with the transfection efficiencies and toxicity in vivo. These nanoparticles exhibited long-term stability at −20 °C for at least 9 months in a lyophilized formulation, validating scalable manufacture of an off-the-shelf nanoparticle product with well-defined characteristics as a gene medicine.

Five cell lines have been derived from a rat transplantable islet cell tumour using two different methods. The lines differ in morphology and contain and release different amounts of insulin and glucagon (insulin content, 1-90 pmol/10(6) cells; insulin release, 6-250 pmol/10(6) cells per 24 h; glucagon content, less than 0.005-35 pmol/10(6) cells; glucagon release, less than 0.05-10 pmol/10(6) cells per 24 h). All the lines responded to the presence of the secretagogues leucine (20 mmol/l) plus theophylline (5 mmol/l) by increasing the rate of release of insulin approximately twofold. A high extracellular concentration of potassium (40 mmol/l) caused a three- to tenfold calcium-dependent increase in release of insulin and a parallel release of glucagon. Increasing the concentration of glucose from 2.8 to 16.7 mmol/l did not alter the rate of insulin release by any of the cell lines.