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OBJECTIVERegulation of obesity development is an important issue to prevent metabolic syndromes. Gene-disrupted mice of phospholipase Cδ1 (PLCδ1), a key enzyme of phosphoinositide turnover, seemed to show leanness. Here we examined whether and how PLCδ1 is involved in obesity.RESEARCH DESIGN AND METHODSWeight gain, insulin sensitivity, and metabolic rate in PLCδ1−/− mice were compared with PLCδ1+/− littermate mice on a high-fat diet. Thermogenic and adipogenetic potentials of PLCδ1−/− immortalized brown adipocytes and adipogenesis of PLCδ1-knockdown (KD) 3T3L1 cells, or PLCδ1−/− white adipose tissue (WAT) stromal-vascular fraction (SVF) cells, were also investigated.RESULTSPLCδ1−/− mice showed marked decreases in weight gain and mass of epididymal WAT and preserved insulin sensitivity compared with PLCδ1+/− mice on a high-fat diet. In addition, PLCδ1−/− mice have a higher metabolic rate such as higher oxygen consumption and heat production. When control immortalized brown adipocytes were treated with thermogenic inducers, expression of PLCδ1 was decreased and thermogenic gene uncoupling protein 1 (UCP1) was upregulated to a greater extent in PLCδ1−/− immortalized brown adipocytes. In contrast, ectopic expression of PLCδ1 in PLCδ1−/− brown adipocytes induced a decrease in UCP expression, indicating that PLCδ1 negatively regulates thermogenesis. Importantly, accumulation of lipid droplets was severely decreased when PLCδ1-KD 3T3L1 cells, or PLCδ1−/− WAT SVF cells, were differentiated, whereas differentiation of PLCδ1−/− brown preadipocytes was promoted.CONCLUSIONSPLCδ1 has essential roles in thermogenesis and adipogenesis and thereby contributes to the development of obesity.

The Holstein's theory of the imprisonment of resonance radiation for pressure-broadened Lorentzian profiles is extended to the Xe-based binary gas mixtures which are widely employed in practical discharge devices. In the binary mixtures, collisions between radiating and buffer atoms modify the emission and absorption spectrum profiles, affecting the imprisonment characteristics. It is found that the imprisonment time Tp is independent of total or partial pressures, provided that the Xe mixture ratio m and discharge tube diameter D are kept constant. Tp is proportional to D1/2. It is also proportional to m1/2 when m is sufficiently small, and becomes independent of m when m approaches unity. The 'broadening coefficients' xi Xe, xi He and xi Ne are defined as degrees of broadening of the Xe emission/absorption profiles due to collisions with Xe, He and Ne, respectively, in terms of half-widths at half-maxima per unit ground state atom density. By measuring Tp using cylindrical discharge tubes of diameters D=2, 5, 10 and 25 mm filled with various mixtures of He-Xe and Ne-Xe, the unknown coefficients are determined to be xi He=1.2*10-16 m3 s-1 and xi Ne=8.0*10-17 m3 s-1. These are 0.059 and 0.039 times that of xi X3, respectively. Knowledge of the coefficients allows us to calculate imprisonment times for any gas mixture and discharge space configuration. A reduction in Tp favours an increase of luminance and luminous efficiency in two ways. One is that luminance saturation with respect to the discharge current becomes less likely to occur, and the other is that, even under the fully saturated condition, luminance is higher with smaller Tp. Smaller Xe mixture ratios and tube diameters favour shortening of Tp. A reduction of m from 1 to 0.01 results, for any value of D, in a decrease in Tp by a factor of 2.6, assuring quicker escape of VUV from the volume. Since neither the total pressure nor Xe, He or Ne partial pressures affect Tp as long as the Xe mixture ratio is kept constant, these pressures can be chosen by considering only the conditions that provide the best discharge.

Fluctuation-free electron emission is obtained from MIM (Al-Al2O3-Au) cathodes. The Al2O3 layer is fabricated by anodic oxidation with a reduced electrolysis current density, i.e., a reduced oxidation rate. The slow oxidation process improves the insulating effect of the Al2O3 layer, and enables the MIM cathodes to operate in the non-formed state. The fluctuation-free emission is reproducible when the diode voltage is cut off instantaneously. With a thin Al2O3 layer, the diode voltage reguired for the cathode operation is reduced to values slightly above the work function of the top electrode.