Effect of somatostatin on intestinal absorption of nutrients the rat

Effects of somatostatin on absorption of D-glucose, L-leucine and triacylglycerols by the small intestine were studied in rats after treatment with the peptide in vivo and in everted jejunal segments in vitro.Absorption of glucose was not affected in vitro by somatostatin or the analogue [D-Trp⁸, D-Cys¹⁴]somatostatin at concentrations up to 0.006 mM. Addition of various peptidase inhibitors had no influence, suggesting that failure of somatostatins to inhibit absorption was not due to inactivation by peptidases. Glucose absorption in vitro by jejunum from rats treated with high doses of somatostatin in vivo was not different from that of untreated rats. The biguanide phenformin inhibited glucose absorption, whether added in vitro (IC₅₀ ≈ 1 mM) of after treatment in vivo (3–100 mg/kg per os). The blood glucose increase following oral glucose administration in fasted rats was not affected by somatostatin, but significantly suppressed by phenformin.Absorption of leucine in vitro was not affected by somatostatin (up to 0.03 mM) or [D-Trp⁸, D-Cys¹⁴]somatostatin (0.01 mM), but inhibited by phenformin (IC₅₀ = 2 mM).Absorption of acylglycerols (glycerol tri[1-¹⁴C]oleate) administered orally was significantly inhibited by somatostatin (twice 5 mg/kg subcutaneously) and phenformin (100 mg/kg per os).In rats — apparently in contrast to man — somatostatin does not decrease role of somatostatin in carbohydrate absorption remains controversial. Investigations in healthy [9] and diabetic [20] human subjects suggest that the peptide inhibits (directly or indirectly) the intestinal absorption of glucose in man. On the other hand, our results and those of others obtained in experiments in rats [4,11,21] and Rhesus monkeys [7] clearly do not support such a role in these species. Further studies are therefore needed to resolve this problem.     

Sterols of some red algae

The sterol composition of 17 red algae has been determined. Only C-27 sterols have been found in substantial amounts; details of the structural elucidation of liagosterol (cholesta-5,23-diene-3β,25-diol) are given. The possible taxonomic significance of the sterol distribution is briefly discussed.     

Purification of the blood groupH gene associated α-2-l-fucosyltransferase from human plasma

The -2-l-fucosyltransferase in human plasma has been freed from -3-l-fucosyltransferase activity and purified approximately 200,000-fold by a series of steps involving ammonium sulphate precipitation, hydrophobic chromatography on Phenyl Sepharose 4B and affinity chromatography first on GDP-adipate-Sepharose and then on GDP-hexanolamine-Sepharose. The purified -2-l-fucosyltransferase had a M_r on gel filtration HPLC of 158,000 and showed optimal activity in the pH range 6.5–7.0. The enzyme transferred fucose equally well to Type 1 (Gal1-3GlcNAc) and Type 2 (Gal1-4GlcNAc) substrates but Type 3 (Gal1-3GalNAc) structures were less efficient acceptors. Competition experiments indicated that a single enzyme species in the purified preparation was responsible for reactivity with the Type 1 and Type 2 structures. Thus the differences in conformation between the Type 1 and Type 2 disaccharides do not appear to influence the capacities of their terminal non-reducing -d-galactosyl residues to function as acceptor substrates for the -2-l-fucosyltransferase expressed by the blood groupH gene in haemopoietic tissue.     

Ca2+-Induced Mitochondrial ROS Regulate the Early Embryonic Cell Cycle

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孕早期妇女血清25-羟维生素D水平的表达及与甲状腺功能的相关性研究

目的:探讨孕早期妇女血清25-羟维生素D[25(OH)D]水平及与甲状腺功能的相关性。方法:选取2015年12月至2016年12月期间来我院进行常规产前检查的孕早期(≤12周)妇女90例为观察组,根据妊娠时间将观察组分为A组(4-6周)、B组(7-9周)和C组(10-12周),另选取同期在我院进行健康体检的妇女30例为对照组。采用电化学发光免疫分析法测定所有研究对象血清中的25(OH)D、促甲状腺激素(TSH)、游离甲状腺素(FT4)、游离三碘甲状腺原氨酸(FT3)水平,并分析观察组妇女血清25(OH)D水平与TSH、FT4、FT3之间的相关性。结果:A组、B组、C组出现维生素D缺乏的比例高于对照组,维生素D充足的比例低于对照组,C组出现维生素D不足的比例高于对照组,差异均有统计学意义(P0.05)。A组、B组、C组维生素D缺乏、维生素D不足、维生素D充足的比例之间差异无统计学意义(P0.05)。A组、B组、C组出现甲状腺功能异常的比例比较差异无统计学意义(P0.05)。三种甲状腺功能减退的患病率由低到高分别为临床甲减、亚临床甲减、低T4血症,且A组、B组、C组临床甲减、亚临床甲减及低T4血症组间整体比较差异无统计学意义(P0.05)。不同血清25(OH)D水平的观察组孕妇血清中TSH、FT4、FT3水平之间的差异无统计学意义(P0.05)。直线回归分析显示,观察组血清中25(OH)D水平与TSH、FT4无明显相关性(P0.05),与FT3呈正相关关系(P0.05),多元线性回归模型分析显示血清中25(OH)D水平与TSH、FT4、FT3均无相关性(P0.05)。结论:孕早期妇女普遍存在维生素D缺乏的现象,血清25(OH)D水平及与甲状腺功能无明显相关性,但仍应注意加强维生素D的补充。     

Stereochemistry of naturally-occurring 25-hydroxyvitamin D3-26,23 lactone as determined by radioligand binding analysis and high-performance liquid chromatography

The four stereoisomers of 25-hydroxyvitamin D₃-26,23 lactone (25-OHD₃-26,23 lactone) were tested against in vivo 25-OHD₃-26,23 lactone to determine their relative competition in the radioligand binding assays for 25-OHD₃ and 1,25-(OH)₂D₃. The 25R-OHD₃-26,23S lactone and in vivo 25-OHD₃-26,23 lactone behaved identically in the radioligand binding assay for 25-OHD₃ and were ～5-fold more potent than 25-OHD₃ at displacing 25-OH[³H]D₃. The 25S-OHD₃-26,23S lactone was the poorest competitor in this assay, requiring a 10-fold excess relative to 25-OHD₃ to displace 50% of the 25-OH[³H]D₃. The order of competition in the 25-OHD₃ radioligand binding assay was 25R-OHD₃-26,23S lactone = in vivo 25-OHD₃-26,23 lactone ? 25S-OHD₃-26,23R lactone > 25-OHD₃ ? 25R-OHD₃-26,23R lactone > 25S-OHD₃-26,23S lactone. The order of competition in the 1,25-(OH)₂D₃ cytosol receptor assay was essentially reversed from the competition in the 25-OHD₃ assay and was 25S-OHD₃-26,23S lactone > 25-OHD₃ ? 25S-OHD₃-26,23R lactone > 25R-OHD₃-26,23S lactone = in vivo 25-OHD₃-26,23 lactone. When tested in a high-performance liquid chromatographic system which separates all four stereoisomers, the in vivo 25-OHD₃-26,23 lactone comigrated with synthetic 25R-OHD₃-26,23S lactone. These data firmly establish that the naturally-occurring 25-OHD₃-26,23 lactone has the 25R, 23S stereochemistry. In addition, these data are the first to demonstrate that the four stereoisomers of 25-OHD₃-26,23 lactone have different affinities for the plasma vitamin D binding protein and the 1,25-(OH)₂D cytosol receptor.     

A binding assay for 25-hydroxycalciferols and 24R,25-dihydroxycalciferols using bovine plasma globulin

The concentrations of the 25-hydroxy and 24R,25-dihydroxy derivatives of vitamin D were determined in 100 μ1 plasma samples using calciferol binding globulin from bovine plasma. Sufficient quantities of 24R,25-dihydroxy vitamin D were found in bovine, porcine, chicken and human plasma to interfere in the assay of 25-hydroxy vitamin D in unfractionated extracts. No metabolites of vitamin D could be found in rainbow trout plasma.