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61.
Shao Zezhi Li Yuping Krishnamoorthy Ramesh Chermak Todd Mitra Ashim K. 《Pharmaceutical research》1993,10(2):243-251
Various surfactants were investigated to compare their effects on insulin dissociation, -chymotryptic degradation, and rat enteral absorption. With a circular dichroism technique, sodium dodecyl sulfate (SDS) at a 5 mM concentration was found to completely dissociate procine-zinc insulin hexamers (0.5 mg/ml) into monomers. The catalytic activity of -chymotrypsin (0.5 µM) was also abolished by 5 mM SDS. When insulin was injected into the distal jejunum/ proximal ileum segment of the rat, 5 mM SDS greatly enhanced its pharmacological availability, from a negligible value to 2.8%. Being a cationic surfactant, hexadecyl trimethylammonium bromide (CTAB) also efficiently dissociated insulin hexamers at concentrations of 1–5 mM. However, extensive charge–charge interaction was observed below a CTAB concentration of 0.6 mM, leading to insulin precipitation at a molar CTAB:insulin ratio of 1:1 to 2:1. An -chymotryptic degradation study also revealed near-complete dissociation of insulin hexamers at 1 mM CTAB. Above 1 mM, however, CTAB acted as an enzyme inhibitor, most likely by means of charge repulsion. Enteral absorption studies showed a much lower pharmacological availability, only 0.29%. Nonionic surfactants such as Tween 80 and polyoxyethylene 9 lauryl ether were ineffective in dissociating insulin hexamers. Tween 80, at 5 mM, neither significantly altered the -chymotryptic degradation pattern nor enhanced the enteral absorption of insulin. The relative effectiveness of different species of bile salts on insulin hexamer dissociation appeared to be similar. Sodium glycocholate at a 30 mM concentration also significantly increased insulin pharmacological availability, to 2.3%. A morphological study did not reveal any significant alteration of the rat intestinal mucosal integrity after exposure to 5 mM SDS for 30 min. The results further emphasize the importance of the degree of insulin aggregation on its enteral transport. 相似文献
62.
Ba2+ differentially inhibits the Rb+ efflux promoting and the vasorelaxant effects of levcromakalim and minoxidil sulfate in rat isolated aorta 总被引:1,自引:0,他引:1
Ulrich Quast Yves Baumlin Cornelia Löffler 《Naunyn-Schmiedeberg's archives of pharmacology》1995,353(1):86-93
The K+ channel openers activate ATP-sensitive K+ channels (KATP) in vascular smooth muscle and induce relaxation. In this study, the relationship between these two effects was examined in rings of rat aorta using levcromakalim and minoxidil sulfate as the openers and Ba2+ as the K+ channel blocker; K+ channel opening was assessed by determining the rate constant of 86Rb+ efflux from the preparation.Ba2+ inhibited the 86Rb+ efflux stimulated by levcromakalim in a noncompetitive manner with an IC50 value of 29 M and a Hill-coefficient of 1.2. At concentrations > 300 M, Ba2+ increased the tension of rat aortic rings concentration-dependently. Levcromakalim relaxed contractions to Ba2+ (0.5 and 1 mM) with potencies similar to those determined against KCl (25 mM) or noradrenaline as spasmogens (EC50 values 15–40 nM). The vasorelaxant effect against Ba2+ was inhibited by the KATP channel blockers, glibenclamide and tedisamil, and abolished in depolarizing medium (55 mM KCl). At 3 mM Ba2+, levcromakalim was still able to transiently induce complete relaxation; however, within 1 h oscillations in tension developed, leading to a stable level of only 15% relaxation. A similar level of relaxation was achieved against 10 mM Ba2+ whereas the combination of 0.5 mM Ba2+ and 3 M tedisamil blocked the relaxant effect of levcromakalim completely. With minoxidil sulfate as the KATP channel opener the results of the 86Rb+ efflux and tension experiments were similar to those obtained with levcromakalim.It is concluded that Ba2+ is more potent in inhibiting the K+ channel opening than the vasorelaxant effects of the openers. On the basis of the 86Rb+ efflux experiments it is estimated that at least 97% of the channels opened by the activators can be blocked without major effects on vasorelaxation suggesting a dissociation between the two effects. However, if the block is pushed to extremes ( 99.95%) the vasorelaxant effect of the openers is also abolished suggesting a link between both effects. This paradoxon remains to be solved. 相似文献
63.
十二烷基硫酸钠在天然水体中的降解作用 总被引:1,自引:0,他引:1
本文研究了十二烷基硫酸钠在天然水体中的降解作用,结果表明十二烷基硫酸钠在天然水体中的降解主要依赖于微生物的降解。微生物最适降解条件为pH6.5~9.4和36℃左右。降解作用随温度升高(4~36.5℃)和微生物浓度增大而加快,用十二烷基硫酸钠预先驯化微... 相似文献
64.
为研究镁在脑缺血早期对神经元保护作用的机制,用电凝法建立大鼠大脑中动脉缺血模型,在造模前给大鼠注射20g/L硫酸镁,观察镁对脑组织中谷氨酸(Glu)及一氧化氮(NO)含量的影响。结果显示,高浓度镁可明显降低脑缺血皮质中Glu、NO含量,在缺血组Glu、NO的峰值浓度分别为9.87、44.97nmol/g,而在加镁组两者浓度分别为7.68、33.92nmol/g。提示:镁对脑缺血早期神经元的保护作用与其降低脑组织中Glu及NO含量有关。 相似文献
65.
硫酸奈替米星注射液与硫酸丁胺卡那注射液临床疗效及安全性的比较 总被引:5,自引:0,他引:5
为评价硫酸奈替米星的临床疗效及安全性,在170例急性细菌感染性病人中作多中心临床研究。结果显示:硫酸奈替米星的有效率(95.3%)显著高于对照药硫酸丁胺卡那的有效率(84.1%),试验组病人咳痰和腰痛症状的平均下降显著高于对照组;硫酸奈替米星治疗后细菌清除率达97.2%;2组病人不良反应发生率均为4.8%,对照组中有2例(3.2%)出现耳鸣、1例(1.6%)听力减退,但试验组病人用药后未发现听力异常。结论:硫酸奈替米星临床疗效优于硫酸丁胺卡那且较少耳毒性。 相似文献
66.
67.
A. W. Vorbrodt H. Lassmann H. M. Wisniewski A. S. Lossinsky 《Acta neuropathologica》1981,55(2):113-123
Summary Alkaline phosphatase(AP),5-nucleotidase(5N) and nucleoside diphosphatase (NDPase) activities were studied by cytochemical methods applied to light and electron microscopy in the microvasculature of spinal cord leptomeningeal strips of normal and protamine sulfate (PS) treated rats. The increased permeability to intravenously injected horseradish peroxidase was observed in some segments of microvessels of PS treated rats. Enhanced formation of plasmalemmal pits and deep invaginations, formation of numerous pinocytic vesicles and the appearance of channel-like structures in the cytoplasm of endothelial cells were the most striking ultrastructural evidence of increased permeability of the affected microvessels. All of these structures also showed activity of AP, and to lesser extent, of NDPase; 5N activity was mainly associated with the delimiting membranes of pinocytic vesicles. Our data present evidence that a shift of enzymatic activity from luminal to abluminal surface of affected endothelial cells results from membrane flow accompanying increased transport activity via formation of pinocytic vesicles and channel-like structures.Supported in part by a grant from NINCDS No. 17271-01Visiting scientist from the Neurological Institute of the University of Vienna, Vienna, Austria 相似文献
68.
69.
70.
Natalie Baziuk Charles M. Gremillion Jr. Gholam A. Peyman Ho Kyun Cho 《International ophthalmology》1992,16(2):101-107
Five albino New Zealand rabbits underwent bilateral lensectomy and vitrectomy. All left eyes were fitted with a collagen shield that had been soaked for 5 min in 2.0 mL of gentamicin solution (40 mg/mL for IV use). Right eyes were treated with fortified gentamicin drops (13.6 mg/mL) every 30 min for 12 hrs. Aqueous and vitreous specimens were obtained at the following time intervals: 1, 2, 4, 8, 12 and 24 hrs.We found the gentamicin concentrations to be higher in the aqueous of all eyes treated with fortified gentamicin drops. Only those eyes treated with fortified gentamicin drops attained a therapeutic drug level (4g–9g/mL) in the aqueous. Therapeutic drug levels were not attained in the vitreous of either treatment group. 相似文献