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1.
TV Hoang EU Choe HL Lippton AL Hyman LM Flint JJ Ferrara 《Canadian Metallurgical Quarterly》1996,61(2):330-338
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. 相似文献
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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. 相似文献
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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. 相似文献
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Summary
This article reports the synthesis of novel hydrophilic end-branched poly(ethylene glycol)s, in aqueous media by atom transfer
radical polymerization (ATRP). Poly(ethylene glycol)s with molecular weights 10,000 and 16,000 were end-functionalized and
used as bifunctional initiators for the polymerization of a poly(ethylene glycol) macromonomer with a molecular weight of
2,000 (PEGMA), either by aqueous ATRP or in a watedmethanol (l/l V/V) mixture. For both macroinitiators a DP of 10 was the
target, giving an average of 5 branches in each end. The rates of polymerization were of the same order of magnitude when
the polymerizations were initiated by either of the two macroinitiators in watedmethanol (l/l V/V). When a bifunctional oligo(ethy1ene
glycol) initiator (Mn = 600) was used to study the polymerization of PEGMA in water/methanol a reduction in the rate of polymerization was observed
indicating an influence of the molecular weight of the initiator on the rate of polymerization.
Received 25 Maich 2002/Revised 8 November 2002/Accepted 8 November 2002
Correspondence to Jorgen Kops 相似文献
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Biological membranes are often poorly visible with the electron microscope after high‐pressure freezing and freeze‐substitution. The water content of the sample and of the substitution medium is one factor among others that strongly influences membrane visibility. In order to investigate this effect, high‐pressure frozen yeast cells, rat‐pancreas tissue and arthropod tissue were freeze‐substituted with and without adding water to the substitution medium. The visibility of the biological membranes was generally improved if the substitution medium contained 1–5% water. The effect was especially pronounced in yeast cells, where membrane visibility was poor after freeze‐substitution with water‐free medium but good after addition of 5% water to the substitution medium. 相似文献
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