Effect of maturation on alpha-adrenoceptor activity in newborn piglet mesentery

To characterize the mesenteric alpha1- and alpha2-adrenoceptor populations in newborn piglets, an extracorporeal circuit was established to control intestinal blood flow in 0- to 2-day old and 10- to 14-day old animals. In both groups, alpha-adrenoceptor activation was first documented by observing dose-dependent increases in mesenteric perfusion pressure after intramesenteric arterial injection of alpha-adrenoceptor agonists. In the 10- to 14-day old piglets, mesenteric vasoconstrictor responses to alpha1-adrenoceptor agonists (methoxamine and norepinephrine) and an alpha2-adrenoceptor agonist (BHT-933) were each blunted (P < 0.05, analysis of variance) by peripheral intravenous injections of prazosin (an alpha1-adrenoceptor antagonist) and yohimbine (an alpha2-adrenoceptor antagonist), respectively. The mesenteric vasoconstrictor responses to those agonists were not significantly attenuated by prazosin or yohimbine in 0- to 2-day old animals, nor were they blunted by YM-12617 (alpha1-adrenoceptor antagonist) or idazoxan (alpha2-adrenoceptor antagonist)--compounds that are structurally unrelated to prazosin and yohimbine, respectively. In addition, mesenteric vasoconstrictor responses to other known vasoconstrictor agents--angiotensin II, neuropeptide Y, and a thromboxane A2 mimic (U-46619)--were not effected in either age group by prazosin or yohimbine, implying these agents act independently of alpha-adrenoceptor mechanisms. These data suggest that (1) there exists functional mesenteric alpha1- and alpha2-adrenoceptor-like activity in 10- to 14-day old piglets that, in 0- to 2-day old animals, is not specifically expressed; and (2) mesenteric alpha-adrenoceptor function becomes more selective as newborn piglets mature.     

A novel model to study the effects of burn lymph on pulmonary vascular hemodynamic variables

The possible hypocholesterolaemic properties of milk and fermented milk products have been investigated in groups of albino rats given a basal diet, basal diet plus cholesterol, and basal diet plus cholesterol together with whole milk or standard or bifidus yogurt. The yogurts were fortified with skim milk powder, condensed whey or lactose-hydrolysed condensed whey. After 30 d, triacylglycerols, total cholesterol, HDL-cholesterol and LDL-cholesterol were measured in serum. Whole milk and ordinary yogurt had no hypocholesterolaemic effect, but standard yogurt containing lactose-hydrolysed condensed whey and all bifidus yogurts lowered serum cholesterol. In general, yogurts changed HDL-cholesterol little, but tended to raise triacylglycerols. There was marked lowering of LDL-cholesterol in rats given either type of yogurt fortified with whey proteins. This study has demonstrated in a rat model that bifidus yogurts and yogurts fortified with whey proteins can reduce total and LDL-cholesterol, and suggests that if they have the same effect in human subjects they have potential value in cholesterol-lowering diets.     

ST/b and DBA/2 mice differ in brain alpha-bungarotoxin binding and alpha 7 nicotinic receptor subunit mRNA levels: a quantitative autoradiographic analysis

Inbred mouse strains vary in sensitivity to a number of behavioral and physiological effects produced by nicotine. Differences in sensitivity to nicotine are correlated with variance in the number of brain nicotinic receptors as measured in regionally dissected brain tissue. The studies reported here used quantitative autoradiography and in-situ hybridization methods to measure regional levels of alpha-bungarotoxin (alpha BTX) binding and alpha 7 mRNA levels. Two inbred mouse strains, ST/b and DBA/2, were compared because these strains differ maximally in sensitivity to nicotine-induced seizures and in alpha BTX binding measured in regional brain homogenates. The binding of alpha BTX was significantly greater in the St/b strain in 42 of 127 brain regions that were analyzed, and a trend towards increased binding was seen in many additional brain regions. The most consistent strain differences were found in hippocampal, thalamic and pontine nuclei. Strain differences in alpha 7 mRNA levels were also detected, but these were not as widespread as were the alpha BTX binding differences. The alpha 7 mRNA levels were significantly correlated with alpha BTX binding in both mouse strains which suggests that the strain differences in binding are related, in part, to the levels of alpha 7 mRNA.     

Stable mode-locked operation up to 80 /spl deg/C from an InGaAs quantum-dot laser

We demonstrate the mode-locked operation of a two-section quantum-dot laser in a broad temperature range. Stable mode-locking was observed at temperatures ranging from 20 /spl deg/C to 70 /spl deg/C, with signal-to-noise ratios well over 20 dB and a -3-dB linewidth smaller than 80 kHz. In the temperature range between 70 /spl deg/C and 80 /spl deg/C, the mode-locking was less stable. It was found that in order to provide stable mode-locked operation with increasing temperature, the reverse bias on the absorber section must be reduced accordingly.     

Manipulation of microparticles using Bessel beams from semiconductor lasers

Optical manipulation of microscopic objects (including living cells) using Bessel beams from semiconductor lasers has been demonstrated for the first time. In addition, it has been found in the experiments that a Bessel beam of sufficient power from a semiconductor laser makes it possible to manipulate simultaneously several microscopic objects captured into its central lobe and the first ring.     

High-power (1W,CW) single-lobe operation of LPE-grown GaInAsP/GaInP ( lambda =0.8 mu m) separate-confinement single-quantum-well broad-area lasers

Liquid-phase epitaxy was used to grow single-quantum-well separate-confinement laser structures with a GaInAsP active layer. Broad-area devices with 100 mu m-wide stripes that were fabricated from these structures emit over 1 W of optical power per facet at a wavelength of 0.8 mu m in continuous room-temperature operation. A stable single-lobed far-field pattern with a beam divergence as low as 0.6 degrees is obtained in pulsed operation.<>     

Shelf-life of prepeeled potato cultivated, stored, and processed by various methods

The present study was aimed to investigate the effects of indigestible dextrin and polydextrose, soluble dietary fibers with low molecular weight, on lipid metabolism and disaccharidase activities of intestinal mucosa in rats fed a high sucrose diet. Their effects were compared with those of well-known soluble fibers, pectin, and guar gum, and also with an insoluble fiber, cellulose. Dietary fibers added to diets at the 5% (w/w) level were alpha-cellulose, pectin, guar gum, indigestible dextrin, and polydextrose. Male Sprague-Dawley rats were given free access to test diets for 6 weeks. Body weight gain was the lowest in rats fed guar gum, the highest in rats fed cellulose, and in-between in rats fed other diets. Although guar gum, pectin, and indigestible feeding dextrin had lower plasma lipid values than cellulose feeding did, the differences were statistically insignificant. Liver triglyceride of the guar gum-fed group was about a third that of the cellulose-fed group, but although those of rats fed polydextrose, indigestible dextrin, and pectin were lower than that of cellulose, the differences were insignificant. Liver cholesterol and phospholipid concentrations were similar among groups. Daily fecal excretion of total lipid, cholesterol, and bile acids were highest in rats fed guar gum, followed by pectin-fed and cellulose-fed rats, and the lowest in rats fed indigestible dextrin and polydextrose. Jejunal sucrase activity was low in the order of guar-gum, polydextrose, indigestible dextrin, pectin, and cellulose. The results indicate that the hypolipidemic effect of soluble dietary fibers would be lessened with reduction in molecular weight, but that the lower sucrase activity by soluble fibers with low molecular weight might be beneficial for hypoglycemic effect.     

Bessel beams from semiconductor light sources

We report on recent progress in the generation of non-diffracting (Bessel) beams from semiconductor light sources including both edge-emitting and surface-emitting semiconductor lasers as well as light-emitting diodes (LEDs). Bessel beams at the power level of Watts with central lobe diameters of a few to tens of micrometers were achieved from compact and highly efficient lasers. The practicality of reducing the central lobe size of the Bessel beam generated with high-power broad-stripe semiconductor lasers and LEDs to a level unachievable by means of traditional focusing has been demonstrated. We also discuss an approach to exceed the limit of power density for the focusing of radiation with high beam propagation parameter M². Finally, we consider the potential of the semiconductor lasers for applications in optical trapping/tweezing and the perspectives to replace their gas and solid-state laser counterparts for a range of implementations in optical manipulation towards lab-on-chip configurations.     

Extended-cavity surface-emitting diode laser as active mirror controlling modelocked Ti:sapphire laser

Directly controlled, stable modelocking of a Ti:sapphire oscillator is demonstrated using a commercially available electrically pumped vertical extended-cavity surface-emitting laser as an active saturable absorber mirror. Modelocking is controlled by applying a pulsed current to the saturable absorber. Pulse durations of /spl sim/330 ps are observed.     

Amplification of femtosecond pulses over by 18 dB in a quantum-dot semiconductor optical amplifier

We demonstrate amplification (> 18 dB) of 200-fs pulses in a quantum-dot (QD) semiconductor amplifier. Our measurements have shown that such QD devices can provide amplification of femtosecond pulses over a spectral range that exceeds 100 nm.