Atrial natriuretic factor: a hormone produced by the heart

Systematic studies on the significance of the secretory-like morphological characteristic of cardiac atrial muscle cells of mammals led to the finding that these cells produce a polypeptide hormone. This hormone, described in 1981 as atrial natriuretic factor (ANF), is diuretic (natriuretic), hypotensive, and has an inhibitory effect on renin and aldosterone secretion. Thus, ANF probably intervenes in the short- and long-term control of water and electrolyte balance and of blood pressure. Phylogenetically, ANF appears early, suggesting different functions for this peptide in accordance with each species' environment. Knowledge of the properties of the hormone should provide insights into the pathophysiology of important clinical entities and lead to the development of new pharmaceutical products.     

An LRR receptor kinase involved in perception of a peptide plant hormone,phytosulfokine

The sulfated peptide phytosulfokine (PSK) is an intercellular signal that plays a key role in cellular dedifferentiation and proliferation in plants. Using ligand-based affinity chromatography, we purified a 120-kilodalton membrane protein, specifically interacting with PSK, from carrot microsomal fractions. The corresponding complementary DNA encodes a 1021-amino acid receptor kinase that contains extracellular leucine-rich repeats, a single transmembrane domain, and a cytoplasmic kinase domain. Overexpression of this receptor kinase in carrot cells caused enhanced callus growth in response to PSK and a substantial increase in the number of tritium-labeled PSK binding sites, suggesting that PSK and this receptor kinase act as a ligand-receptor pair.     

Dimerization of the extracellular domain of the human growth hormone receptor by a single hormone molecule

Human growth hormone (hGH) forms a 1:2 complex with the extracellular domain of its receptor-binding protein (hGHbp) as studied by crystallization, size exclusion chromatography, calorimetry, and a previously undescribed fluorescence quenching assay. These and other experiments with protein engineered variants of hGH have led to the identification of the binding determinants for two distinct but adjacent sites on hGH for the hGHbp, and the data indicated that there are two overlapping binding sites on the hGHbp for hGH. Furthermore, the binding of hGH to the hGHbp occurred sequentially; a first hGHbp molecule bound to site 1 on hGH and then a second hGHbp bound to site 2. Hormone-induced receptor dimerization is proposed to be relevant to the signal transduction mechanism for the hGH receptor and other related cytokine receptors.     

Identification of a thyroid hormone receptor that is pituitary-specific

Three cellular homologs of the v-erbA oncogene were previously identified in the rat; two of them encode high affinity receptors for the thyroid hormone triiodothyronine (T3). A rat complementary DNA clone encoding a T3 receptor form of the ErbA protein, called r-ErbA beta-2, was isolated. The r-ErbA beta-2 protein differs at its amino terminus from the previously described rat protein encoded by c-erbA beta and referred to as r-ErbA beta-1. Unlike the other members of the c-erbA proto-oncogene family, which have a wide tissue distribution, r-erbA beta-2 appears to be expressed only in the anterior pituitary gland. In addition, thyroid hormone downregulates r-erbA beta-2 messenger RNA but not r-erbA beta-1 messenger RNA in a pituitary tumor-derived cell line. The presence of a pituitary-specific form of the thyroid hormone receptor that may be selectively regulated by thyroid hormone could be important for the differential regulation of gene expression by T3 in the pituitary gland.     

Atrial natriuretic peptide inhibits a cation channel in renal inner medullary collecting duct cells

The patch-clamp technique was used to examine the effects of atrial natriuretic peptide (ANP) and its second messenger guanosine 3',5'-monophosphate (cGMP) on an amiloride-sensitive cation channel in the apical membrane of renal inner medullary collecting duct cells. Both ANP (10(-11) M) and dibutyryl guanosine 3',5'-monophosphate (10(-4) M) inhibited the channel in cell-attached patches, and cGMP (10(-5) M) inhibited the channel in inside-out patches. The inner medullary collecting duct is the first tissue in which ANP, via its second messenger cGMP, has been shown to regulate single ion channels. The results suggest that the natriuretic action of ANP is related in part to cGMP-mediated inhibition of electrogenic Na+ absorption by the inner medullary collecting duct.     

Coexistence of guanylate cyclase and atrial natriuretic factor receptor in a 180-kD protein

Atrial natriuretic factor (ANF) is a peptide hormone that is released from atria and regulates a number of physiological processes, including steroidogenesis in adrenal cortex and testes. The parallel stimulation of membrane guanylate cyclase and corticosterone production in isolated fasciculata cells of rat adrenal cortex has supported the hypothesis of a mediatory role for cyclic guanosine monophosphate (cyclic GMP) in signal transduction. A novel particulate guanylate cyclase tightly coupled with ANF receptor was purified approximately 273,000-fold by two-step affinity chromatography. The enzyme had a molecular size of 180 kilodaltons and was acidic in nature with a pI of 4.7. Its specific activity was 1800 nanomoles of cyclic GMP formed per minute per milligram of protein. The purified enzyme bound ANF with a specific binding activity of 4.01 nanomoles per milligram of protein, a value that is close to the theoretical binding activity of 5.55 nanomoles per milligram of protein for 1 mole of the ligand binding 1 mole of the receptor protein. These results indicate that the guanylate cyclase-coupled ANF receptor exists in a 180-kilodalton protein of rat adrenocortical carcinoma and represent a step toward the elucidation of the basic mechanism of cyclic GMP-mediated transmembrane signal transduction in response to a hormone.     

重组人脑利钠肽治疗急性心力衰竭的近期效果观察

目的 观察重组人脑利钠肽(rhBNP)治疗急性心力衰竭的近期效果.方法 60例急性心力衰竭患者随机分为观察组与对照组.两组均予以常规抗心衰治疗,观察组加用rhBNP治疗,对照组加用硝酸甘油治疗.对比两组近期疗效.结果 观察组总有效率、左室射血分数明显高于对照组(P＜0.01),而治疗后心率、血浆NT-proBNP水平低于对照组(P＜0.01).两组不良反应发生率比较差异无统计学意义(P＞0.05).结论 rhBNP辅助治疗急性心力衰竭近期疗效显著,可有效降低血浆NT-proBNP水平.     

Toll-like receptor 4-dependent activation of dendritic cells by beta-defensin 2

beta-Defensins are small antimicrobial peptides of the innate immune system produced in response to microbial infection of mucosal tissue and skin. We demonstrate that murine beta-defensin 2 (mDF2beta) acts directly on immature dendritic cells as an endogenous ligand for Toll-like receptor 4 (TLR-4), inducing up-regulation of costimulatory molecules and dendritic cell maturation. These events, in turn, trigger robust, type 1 polarized adaptive immune responses in vivo, suggesting that mDF2beta may play an important role in immunosurveillance against pathogens and, possibly, self antigens or tumor antigens.     

A G protein-coupled receptor is a plasma membrane receptor for the plant hormone abscisic acid

The plant hormone abscisic acid (ABA) regulates many physiological and developmental processes in plants. The mechanism of ABA perception at the cell surface is not understood. Here, we report that a G protein-coupled receptor genetically and physically interacts with the G protein alpha subunit GPA1 to mediate all known ABA responses in Arabidopsis. Overexpressing this receptor results in an ABA-hypersensitive phenotype. This receptor binds ABA with high affinity at physiological concentration with expected kinetics and stereospecificity. The binding of ABA to the receptor leads to the dissociation of the receptor-GPA1 complex in yeast. Our results demonstrate that this G protein-coupled receptor is a plasma membrane ABA receptor.     

不同甲状腺功能状态患者血浆B型钠尿肽的检测及其临床意义

目的 了解不同甲状腺功能状态患者血浆B型钠尿肽浓度及B型钠尿肽与血浆FT3、FT4的关系.方法 采用酶联免疫法(ELISA)检测72例甲状腺功能亢进和60例甲状腺功能减退症患者血浆B型钠尿肽(BNP)水平.结果 血浆FT3、FT4、BNP甲亢未治组高于甲亢缓解组和对照组,差异有统计学意义(P＜0.01);甲亢缓解组与对照组比较,差异无统计学意义(P＞0.05).血浆FT3、FT4甲减未治组低于甲减治疗组和对照组,差异有统计学意义(P＜0.01);甲减治疗组与对照组比较,差异无统计学意义(P＞0.05);但甲减未治组、甲减治疗组和对照组BNP比较,差异均无统计学意义(P＞0.05).甲亢未治组患者血浆BNP与FT3、FT4两者呈量依赖关系,r分别为0.9919和0.9999996(均P＜0.01),回归方程分别为y=193.8 3.191x,y=198.0 0.8353x.结论 BNP对甲亢的辅助诊断和疗效观察具有一定临床价值.     

Thyrotropin releasing hormone: enhancement of dopa activity by a hypothalamic hormone

Thyrotropin releasing hormone potentiates the behaviorial effects of dopa plus pargyline in mice. Because the potentiation occurs in hypophysectomized mice, as well as in normal mice, the phenomenon is independent of the release of thyroid stimulating hormone from the pituitary. Possible mechanisms and clinical implications are discussed.     

B型钠尿肽与急性ST段抬高型心肌梗死预后关系的临床研究

目的观察血浆B型钠尿肽（BNP）对急性ST段抬高型心肌梗死（STEMI）预后的意义。方法选取2005年3月至2008年12月间首次在本院住院的STEMI患者100例（STEMI组）,以60例体检健康者作对照（健康组）,用竞争酶联免疫分析法测定这两组BNP的质量浓度并进行比较;同时对100例STEMI患者随访12个月,比较心血管事件发生者和未发生者的BNP质量浓度。结果STEMI血浆BNP质量浓度比健康者高,发生心血管事件的患者血浆BNP质量浓度明显高于未发生者。结论BNP质量浓度高提示心血管事件发生率高;BNP可作为STEMI后心血管事件的预测因子。     

血浆脑钠肽在急性冠脉综合征患者中的变化及其临床意义

目的探讨血浆脑钠肽（BNP）变化与急性冠脉综合征（ACS）血管病变的关系。方法采用免疫荧光法测定98例ACS患者[不稳定心绞痛（UAP）36例、ST抬高心梗（STEMI）34例、非ST抬高心梗（NSTEMI）28例]发病20 h内血浆BNP水平,分析BNP变化与临床亚型和冠脉病变的关系。结果对照、UAP、NSTEMI、STEMI组血浆BNP水平分别是（51.34±11.27）、（155.06±39.12）、（247.05±68.34）、（513.17±127.88）μg/L,多支、2支、1支、0支血管病变组的BNP水平则分别为（612.34±155.87）、（299.81±166.09）、（177.86±143.65）、（25.78±14.49）μg/L,组间比较差异均有统计学意义（P〈0.01）。结论血浆BNP水平升高与冠脉病变的严重程度有关,可作为ACS病情的评估指标之一。