维生素D的最新进展

1.最近的研究表明了1,25-(OH)_2-D_3在靶组织中的特异性定位。在多种以前未知的维生素 D 的靶组织中,证明了特异性核内定位。在核内定位的细胞和许多肿瘤及癌细胞中,发现了与1,25-(OH)_2-D_3特异结合的大分子受体。2.适量有意义的1,-羟化酶除存在子肾脏外,已在胚胎中发现。虽有肾外合成1,25-(OH)_2-D_3,的报导,假如这些部位能生成1,25-(OH)_2-D_3,而其量也是不足的。肾的1-羟化酶已溶解,是三种成分的酶系。肝内的25-羟化酶也巳溶解,也是三种成分的酶系。3,维生素 D 代谢的新途径,包括23位氧化形成23,25-(OH)_2-D_3或1,25-(OH)2-D_5的23-羟化形式。23,25-(OH)_2-D_3进一步氧化产生25-(OH)_2-D_3-26,23-内酯。这个途径虽有重要意义,但其作用还不了解,因为这个产物白姓物活性很低。4.维生素 D 代谢物的重要类似物,包括24,24,-F_2-25-OH-D_3和26,26,26,27,27,27,-F6-25-OH-D_3。曾使用这些化合物证明了,24-羟化作用、26-羟化作用和内酯的形成,这些途径在维生素 D 的功能中不起重要作用。这些化合物的1-羟基类似物已经制备,它们有很高的生物活性,比天然1,25-(OH)_2-D_3的生物活性大10倍。     

羟基-D_3的生理功能和机理研究

维生素D3及其活性代谢物25-羟基D3和1,25-羟基D3对畜禽营养具有很重要的意义。从它们的生理功能、代谢过程、作用机理和在畜禽养殖中的应用系统地进行了探讨。     

1,25二羟维生素D_3和甲状旁腺素在钙代谢中的作用(综述)

参与钙代谢的激素有许多,如1,25二羟维生素D_3(l,25(OH)_2D_3)、甲状旁腺素(PTH)、性激素、生长激素、甲状腺素、肾上腺素、促乳素、降钙素等。本文仅就近年来有关l,25(OH)_2D_3和PTH对钙代谢的调控研究作简单综述。1,252二羟维生素D_3(1,25(OH)_2D_3)1.1 1,25(OH)_2D_3刺激钙吸收运转的机理     

用维生素D3代谢物提高牛肉柔嫩度

最新研究表明，维生素D3(VD3)可以提高牛肉柔嫩度，但在牛肉和血浆中会有大量残留而引起软组织和动脉钙化。因此，用VD3提高牛肉柔嫩度令人担忧。为此，美国研究人员试验测定给牛饲喂VD3代谢物25-羟VD3(25-POH D3)或1，25-二羟VD3(1，25-(OH)2D3)提高柔嫩度的效果和是否有残留。     

植物多糖免疫活性研究进展

植物多糖是一类具有多种生物学活性的天然产物,调节免疫功能是其主要生物学活性之一。分别从细胞、分子及器官水平就近几年对植物多糖的免疫调节作用研究进行归纳综述,可为植物多糖免疫调节活性研究提供参考。     

畜禽干扰素-γ研究进展

干扰素-γ(interferon-γ,IFN-γ)是一种具有抗病毒、抗肿瘤和免疫调节功能的细胞因子,主要由活化的T细胞和自然杀伤(Natural killer)细胞产生。干扰素因其重要的免疫调节功能而被广泛地应用于疾病的诊断及治疗过程。本研究主要对干扰素-γ诱生、作用机制、生物学活性、畜禽IFN-γ基因多态性与疾病的关系以及畜禽干扰素开发等的研究现状进行综述,以期为畜禽干扰素-γ的深入研究及其在畜禽生产中的应用奠定一定的理论基础。     

猪抗病毒特异性免疫调节因子的制备及其相关性质的分析

通过获取抗人乙肝病毒特异性免疫调节因子并对其有关活性的研究,进一步探索在家畜疫苗接种过程中低分子量抗病毒免疫调节因子的特异性功能基础及免疫效应机制。用乙肝疫苗接种幼猪,致其产生特异性免疫应答,然后从其脾脏淋巴细胞中制备抗病毒免疫活性调节因子进行理化鉴定。MTT法活性检测和氨基酸组分及其含量的对比分析结果表明,制备的免疫调节因子为低分子量多肽与核酸复合物;具有特异性粘附抑制活性;在氨基酸组成上与非特异性免疫调节因子相同,但在所含氨基酸的百分含量上却有一定差异。检测结果提示,这种差异是决定其抗病毒特异性功能的化学基础。     

DWARF14响应独角金内酯信号的分子机制

独脚金内酯是一类由类胡萝卜素衍生而来的新型植物生长调节因子,能够从抑制根部分生、诱导侧根形成、促进根毛伸长、介导根部与共生真菌和寄生植物信号通讯等多个方面调控植物生长发育。独角金内酯受体DWARF14(D14)起源于α/β水解酶,其信号转导机制不同于传统植物生长调节因子受体,它遵循新型的"底物-酶-活性分子-受体"识别规律,具有生成和感知生长调节因子活性分子的双重功能。综述了独脚金内酯受体D14结构及信号转导机制最新研究进展。     

维生素A和维生素D_3对菲律宾蛤仔3种水解酶活性的影响

分别用0、5000、10000、15000、20000 IU.L-1维生素A和维生素D3浸浴菲律宾蛤仔96 h,研究维生素A和维生素D3对蛤仔内脏团酸性磷酸酶(ACP)、碱性磷酸酶(ALP)和溶菌酶(LSZ)活性的影响.结果表明:维生素A能提高蛤仔内脏团ACP、ALP和LSZ的活性,在一定剂量范围内随着维生素A剂量的增加,ACP、ALP和LSZ活性显著提高(P0.05),但到96h时20000 IU.L-1维生素A会抑制ACP和LSZ的活性;维生素D3能提高ACP、ALP和LSZ的活性,在一定剂量范围内随着维生素D3剂量的增加,ACP、ALP和LSZ活性提高;维生素A和维生素D3微粒悬浮于水层中被蛤仔滤食,可在一定程度上提高3种水解酶的活性,以10000和15000 IU.L-1剂量的效果较好.     

单纯性肥胖儿童血清维生素D水平检测及干预效果观察

目的了解单纯性肥胖儿童体内维生素D的水平及干预效果。方法对212例6～12岁单纯性肥胖儿童（肥胖组）和235例体质量指数（BMI）正常儿童（对照组）,晨起空腹采集静脉血并采用酶联免疫吸附法（ELISA）检测其血清中25-羟维生素D浓度。对62例BMI异常的维生素D缺乏患儿补充维生素D制剂,1个月后复查25-羟维生素D浓度。结果肥胖组中维生素D不足及缺乏的有140例（66.0%）;对照组中维生素D不足及缺乏的有66例（28.1%）,两组间差异有统计学意义（P〈0.01）。62例维生素D治疗干预者中,维生素D水平达到适宜水平的超重患儿占91.7%（33/36）,而肥胖患儿只占65.4%（17/26）,两者间差异有统计学意义（P〈0.01）。结论单纯性肥胖儿童血清25-（OH）D浓度低于正常儿童,超重儿童补充维生素D制剂的效果较明显。     

1,25-dihydroxyvitamin D-responsive element and glucocorticoid repression in the osteocalcin gene

The active hormonal form of vitamin D3, 1,25-dihydroxyvitamin D3[1,25(OH), which regulates cellular replication and function in many tissues and has a role in bone and calcium homeostasis, acts through a hormone receptor homologous with other steroid and thyroid hormone receptors. A 1,25(OH)2D3-responsive element (VDRE), which is within the promoter for osteocalcin [a bone protein induced by 1,25(OH)2D3] is unresponsive to other steroid hormones, can function in a heterologous promoter, and contains a doubly palindromic DNA sequence (TTGGTGACTCACCGGGTGAAC; -513 to -493 bp), with nucleotide sequence homology to other hormone responsive elements. The potent glucocorticoid repression of 1,25(OH)2D3 induction and of basal activity of this promoter acts through a region between -196 and +34 bp, distinct from the VDRE.     

1,25-dihydroxyvitamin D3: a novel immunoregulatory hormone

The hormonal form of vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], at picomolar concentrations, inhibited the growth-promoting lymphokine interleukin-2, which is produced by human T lymphocytes activated in vitro by the mitogen phytohemagglutinin. Other metabolites of vitamin D3 were less effective than 1,25(OH)2D3 in suppressing interleukin-2; their order of potency corresponded to their respective affinity for the 1,25(OH)2D3 receptor, suggesting that the effect on interleukin-2 was mediated by this specific receptor. The proliferation of mitogen-activated lymphocytes was also inhibited by 1,25(OH)2D3. This effect of the hormone became more pronounced at later stages of the culture. These findings demonstrate that 1,25(OH)2D3 is an immunoregulatory hormone.     

Molecular cloning of complementary DNA encoding the avian receptor for vitamin D

Vitamin D3 receptors are intracellular proteins that mediate the nuclear action of the active metabolite 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. Two receptor-specific monoclonal antibodies were used to recover the complementary DNA (cDNA) of this regulatory protein from a chicken intestinal lambda gt11 cDNA expression library. The amino acid sequences that were deduced from this cDNA revealed a highly conserved cysteine-rich region that displayed homology with a domain characteristic of other steroid receptors and with the gag-erbA oncogene product of avian erythroblastosis virus. RNA selected via hybridization with this DNA sequence directed the cell-free synthesis of immunoprecipitable vitamin D3 receptor. Northern blot analysis of polyadenylated RNA with these cDNA probes revealed two vitamin D receptor messenger RNAs (mRNAs) of 2.6 and 3.2 kilobases in receptor-containing chicken tissues and a major cross-hybridizing receptor mRNA species of 4.2 kilobases in mouse 3T6 fibroblasts. The 4.2-kilobase species was substantially increased by prior exposure of 3T6 cells to 1,25(OH)2D3. This cDNA represents perhaps the rarest mRNA cloned to date in eukaryotes, as well as the first receptor sequence described for an authentic vitamin.     

Strontium induced rickets: metabolic basis

Dietary strontium inhibits both the synthesis of 1,25-dihydroxycholecalciferol and intestinal calcium absorption in vitamin D(3)-repleted chicks. 1,25-Dihydroxycholecalciferol restores calcium absorption to normal, while 25-hydroxycholecalciferol is without effect in the strontium-fed chick. It is suggested that strontium induces rickets by blocking the biosynthesis of 1,25-dihydroxycholecalciferol, the metabolically active form of vitamin D in the intestine.     

1,25-dihydroxycholecalciferol: metabolite of vitamin D3 active on bone in anephric rats

Nephrectomy prevents completely the bone calcium mobilization response to 25-hydroxycholecalciferol. In contrast it does not prevent this response to 1,25-dihydroxycholecalciferol. Because it is known that the kidney is the site of 1,25-dihydroxycholecalciferol formation, these results provide evidence that 1,25-dihydroxycholecalciferol or a further metabolite thereof and not 25-hydroxycholecalciferol is the metabolically active form of vitamin D(3) responsible for bone calcium mobilization.     

低磷条件下VD_3对大鼠小肠NaPi-Ⅱb mRNA表达及磷吸收的调控

【目的】本试验旨在研究低磷条件下VD3对磷吸收的调节作用。【方法】选择40只断奶后大白鼠(雄),随机分为0.2%(低磷组)和0.6%(正常磷组)两磷(总磷)水平组,每组5个重复,每重复4只大白鼠,试验期7d。试验前6d,每组每只大白鼠肌注VD3代谢抗干忧药物EHDP(二磷酸盐);宰前的12h,每组2只老鼠以600ng/kg.wt剂量注射VD3,为试验组;另2只不注射,为对照组。第7天早晨屠宰、取样。测定血清和骨组织中钙磷及小肠NaPi-Ⅱb载体蛋白mRNA表达量和磷的吸收等指标。【结果】(1)低磷水平对照组骨钙、骨磷分别比正常磷水平低3.33倍(P0.01)和3.03倍(P0.01)。两磷水平试验组VD3含量比对照组高3.08倍和2.32倍,差异极显著;(2)0.2%磷水平小肠各段和肾脏Na+/PiⅡb mRNA表达量试验组皆极显著高于对照组;(3)两磷水平试验组4个部位磷的吸收皆显著或极显著高于对照组,0.2%磷水平试验组较对照组磷吸收4个部位分别提高:51.76%、62.68%、57.79%、47.37%。0.6%磷水平组分别提高18.19%、39.22%、54.72%、39.83%。【结论】(1)低磷情况下,VD3是调节磷吸收的一个重要因素,补充VD3可提高NaPi-Ⅱb转运蛋白mRNA的表达和磷的吸收;(2)VD3对磷吸收的提高作用随着磷水平的增加而减弱。     

Intestinal calcium transport: stimulation by low phosphorus diets

Rats maintained on a low phosphorus diet supplemented with 25-hydroxyvitamin D(3) show high intestinal calcium transport activity as compared to rats similarly treated but fed a diet containing adequate phosphorus. This increased transport activity is correlated with an increased biosynthesis of 1,25-dihydroxyvitamin D(3), the probable metabolically active form of the vitamin in the intestine.     

4-氨基-3,5二-（4-吡啶基）-1,2,4三-氮唑-Cu（Ⅰ）配合物的溶剂热合成及结构表征

采用CuBr与4-氨基-3,5-二（4-吡啶基）-1,2,4-三氮唑配体（4-abpt）在溶剂热条件下合成了配合物[CuBr（4-abpt）],并用红外光谱、元素分析及X-射线单晶衍射对其进行了结构表征.结果表明,该配合物中Cu（Ⅰ）呈现四面体配位几何,4-abpt采取μ3-桥连模式与μ3-Cu（Ⅰ）在ab平面形成了具有（4.82）拓扑结构的[Cu-（4-abpt）]层,相邻层间通过N-H…Br氢键作用和π-π堆积构筑成三维超分子网络.配合物结晶于单斜晶系,P2（1）/n空间群,a=0.768 97（6）nm,b=1.332 70（10）nm,c=1.263 38（9）nm,β=91.388（2）,V=1.294 34（17）nm3,Z=4,S=1.050,R1=0.023 1,wR2=0.056 7[I〉2σ（I）].     

Vitamin D receptor as an intestinal bile acid sensor

The vitamin D receptor (VDR) mediates the effects of the calcemic hormone 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We show that VDR also functions as a receptor for the secondary bile acid lithocholic acid (LCA), which is hepatotoxic and a potential enteric carcinogen. VDR is an order of magnitude more sensitive to LCA and its metabolites than are other nuclear receptors. Activation of VDR by LCA or vitamin D induced expression in vivo of CYP3A, a cytochrome P450 enzyme that detoxifies LCA in the liver and intestine. These studies offer a mechanism that may explain the proposed protective effects of vitamin D and its receptor against colon cancer.     

4-氨基-3,5二-（4-吡啶基）-1,2,4三-氮唑-Cu（Ⅰ）配合物的溶剂热合成及结构表征

采用CuBr与4-氨基-3,5-二（4-吡啶基）-1,2,4-三氮唑配体（4-abpt）在溶剂热条件下合成了配合物[CuBr（4-abpt）],并用红外光谱、元素分析及X-射线单晶衍射对其进行了结构表征.结果表明,该配合物中Cu（Ⅰ）呈现四面体配位几何,4-abpt采取μ3-桥连模式与μ3-Cu（Ⅰ）在ab平面形成了具有（4.82）拓扑结构的[Cu-（4-abpt）]层,相邻层间通过N-H…Br氢键作用和π-π堆积构筑成三维超分子网络.配合物结晶于单斜晶系,P2（1）/n空间群,a=0.768 97（6）nm,b=1.332 70（10）nm,c=1.263 38（9）nm,β=91.388（2）,V=1.294 34（17）nm3,Z=4,S=1.050,R1=0.023 1,wR2=0.056 7[I〉2σ（I）].