Muscarinic cholinergic inhibition of cyclic AMP formation and adrenocorticotropin secretion in mouse pituitary tumor cells

Cholinergic muscarinic receptors were identified in AtT-20/D16-16 (AtT-20) cell membranes by receptor binding techniques and the effect of carbachol on basal and stimulated cyclic AMP formation and ACTH release was investigated. Carbachol markedly decreased the stimulatory effect of the adenylate cyclase activator, forskolin, on both cyclic AMP formation and ACTH secretion. Carbachol also reduced forskolin-stimulated adenylate cyclase activity. The stimulatory effects of (-) isoproterenol on cyclic nucleotide formation and ACTH secretion were also blocked by carbachol. The inhibitory effects of carbachol on (-) isoproterenol-stimulated cyclic AMP synthesis and ACTH secretion were reversed by the muscarinic antagonist, atropine, and not by the nicotinic antagonist, gallamine. These data suggest that in AtT-20 cells, inhibition of ACTH secretion may be regulated by activation of muscarinic receptors coupled negatively to adenylate cyclase.     

控释肥硫膜降解对微域土壤性质的影响

硫包膜控释肥在农业上的大面积应用,引起了硫膜降解产物对土壤环境影响的广泛关注。选用山东有代表性的耕作土壤棕壤和潮土,设置处理包括硫加树脂残膜、硫残膜、硫磺片,采用尼龙滤网分隔法获取受控释肥硫膜影响较强的微域土壤,对比研究了硫膜对微域和非微域土壤某些化学性质的影响。结果表明,在棕壤上施用各含硫材料会显著影响微域土壤的pH值,微域各含硫材料的氧化高峰期出现在60d左右。硫膜降解对潮土pH值影响与棕壤相比不显著,但肥际微域与非微域相比下降明显。硫残膜对土壤中的微量元素能起到一定的活化作用,尤其是对潮土肥际微域有效铁的影响最为显著,培养结束时硫加树脂残膜处理是空白处理的6.58倍。潮土中施用含硫包膜控释肥可活化土壤养分,从而提高土壤中有效硫和有效磷的含量。控释肥硫膜降解对土壤性质影响显著的区域是在硫膜≤5mm范围内的土壤,而对非肥际微域土壤的化学性质无显著影响。     

Structural-Functional Analysis of the Third Transmembrane Domain of the Corticotropin-releasing Factor Type 1 Receptor: ROLE IN ACTIVATION AND ALLOSTERIC ANTAGONISM*

The corticotropin-releasing factor (CRF) type 1 receptor (CRF₁R) for the 41-amino acid peptide CRF is a class B G protein-coupled receptor, which plays a key role in the response of our body to stressful stimuli and the maintenance of homeostasis by regulating neural and endocrine functions. CRF and related peptides, such as sauvagine, bind to the extracellular regions of CRF₁R and activate the receptor. In contrast, small nonpeptide antagonists, which are effective against stress-related disorders, such as depression and anxiety, have been proposed to interact with the helical transmembrane domains (TMs) of CRF₁R and allosterically antagonize peptide binding and receptor activation. Here, we aimed to elucidate the role of the third TM (TM3) in the molecular mechanisms underlying activation of CRF₁R. TM3 was selected because its tilted orientation, relative to the membrane, allows its residues to establish key interactions with ligands, other TM helices, and the G protein. Using a combination of pharmacological, biochemical, and computational approaches, we found that Phe-203^3.40 and Gly-210^3.47 in TM3 play an important role in receptor activation. Our experimental findings also suggest that Phe-203^3.40 interacts with nonpeptide antagonists.     

Corticotropin-releasing factor type-1 receptor antagonists: the next class of antidepressants?

Corticotropin-releasing factor (CRF) is a neuropeptide that plays a primary role in the neuroendocrine, autonomic, and behavioral responses to stressors. Numerous reports suggest that alterations in CRF function contribute to the pathogenesis of depression. Recently, selective nonpeptide CRF type 1 (CRF1) receptor antagonists have been discovered and several of these CRF1 receptor antagonists have demonstrated antidepressant-like efficacy in animals. The CRF1 receptor antagonists appear to be unique, as they exhibit antidepressant-like activity principally in animal models that are hyperresponsive to stress or under experimental conditions that alter endogenous stress-hormone activity. A nonpeptide CRF1 receptor antagonist has also been shown to reduce symptoms of major depression in an open-label clinical trial. Accumulating evidence supports a role for nonpeptide CRF1 receptor antagonists among the future pharmacotherapies for the treatment of depression.     

Ultrastructural characteristics of immunolabelled,corticotropin releasing factor (CRF)-synthesizing neurons in the rat brain

Summary The corticotropin releasing factor (CRF)-synthesizing perikarya and neural processes were detected at ultrastructural level in the hypothalamic paraventricular nucleus and in the median eminence of control and colchicine-pretreated rats. The unlabelled antibody peroxidase-antiperoxidase complex (PAP) immunohistochemical method was used in a pre-embedding manner, on thick, non-frozen sections. In CRF-perikarya, neurosecretory granules (80–120 nm in diameter), free ribosomes, and the rough endoplasmic reticulum were labelled. Unlabelled axon terminals formed asymmetric synapses on CRF-containing perikarya and dendrites. Immunolabelled axons terminated in the palisadic zone of the median eminence.     

Comparison of the effects of CRF and stress on levels of pituitary cyclic AMP and plasma ACTH in vivo

We have previously reported that acute stress increases levels of rat pituitary cyclic AMP in vivo. The present study was conducted to test the hypothesis that stress-induced increases in pituitary cyclic AMP in vivo were mediated via CRF. We compared the effects of various stressors with the effects of CRF or epinephrine administration on pituitary cyclic AMP and plasma ACTH responses in vivo. Stressors, epinephrine or CRF increased levels of pituitary cyclic AMP. Pituitary cyclic AMP response to either immobilization or CRF was much greater at light onset than at lights off in rats maintained on at 12 hr light: 12 hr dark lighting regimen. In rats with pituitary stalk transections, footshock did not increase levels of pituitary cyclic AMP, suggesting that some factor of central origin was required for this stress response. Exogenous CRF administration did increase levels of pituitary cyclic AMP in stalk-transected rats, while epinephrine increased levels in sham-operated but not in stalk-transected rats. Antisera to CRF markedly decreased pituitary cyclic AMP response to exogenous CRF administered 6 min following antisera and partially attenuated pituitary cyclic AMP response to forced running. Taken as a whole these data support a major role for CRF in the pituitary cyclic AMP response to stress.     

Characterization of human immunodeficiency virus type 1 CRF01_AE env genes derived from recently infected Thai individuals

Transmitted/founder virus is responsible for the establishment of human immunodeficiency virus type 1 (HIV-1) infection and induces primary anti-HIV-1 immune responses; therefore, it is important to study the viral population to understand the early events of HIV-1 infection. We amplified HIV-1 env genes from sera derived from recently infected Thai individuals, and established envelope glycoproteins (Env)-recombinant viruses. Generated Env-recombinant viruses were tested for their neutralization susceptibility to neutralizing human monoclonal antibodies (NHMAbs) and entry inhibitors, as well as being subjected to genotypic analysis. Most recombinant viruses were susceptible to neutralization by NHMAbs to Env gp41, whereas approximately one-third of the recombinant viruses were susceptible to a NHMAb against the CD4 binding site of gp120. In addition, all env genes were classified into CRF01_AE genes and showed low genetic divergence. Taken together with our previous studies on CRF01_AE env genes derived from chronically infected Thai individuals, these results suggested that the immunological and genetic characteristics of CRF01_AE Env derived from recently infected Thai individuals were different from those derived from chronically infected individuals.     

The Peptidergic Brain-Gut Axis: Influence on Gastric Ulcer Formation

The existence of a relationship between the brain and the formation of gastric ulcers has been suspected since the last century. The advancement of stereotaxic procedures and the use of electrical lesion or stimulation have allowed localization within the limbic system, hypothalamus and brain stem, of discrete nuclei that influence the formation of gastric ulceration in experimental animals. Recently, further progress in the understanding of how the brain may influence gastric pathogenesis has been made by the demonstration that specific peptides act in the central nervous system to induce or prevent the formation of gastric ulcers and to markedly alter gastric secretory and motor function. Peptides established to have a centrally mediated protective effect are bombesin, calcitonin, corticotropin-releasing factor, neurotensin and opioid peptides. Growing evidence suggests a possible role for endogenous thyroptropin-releasing hormone in mediating cold-restraint stress induced gastric lesions. Circadian variations of the content and release of these peptides have been demonstrated in specific brain structures. To what extent such rhythms of peptide secretion are potentially linked to the circadian changes in the susceptibility to ulcer formation is worth investigating.     

中国树鼠句伏隔核促肾上腺皮质激素释放激素能神经元免疫组织化学研究

应用免疫组织化学碱性磷酸酶标Ａ蛋白（ＰＡＡＰ）技术在光镜水平研究中国树鼠句伏隔核内促肾上腺皮质激素释放激素（ＣＲＦ）能神经元的形态和分布特点。结果显示,该核内ＣＲＦ免疫反应阳性神经元胞体多数呈多边形、圆形或卵圆形,梭形极少;直径多数为１３－１９ｕｍ,少数＜１３ｕｍ;胞质免疫反应强度不等。对左右侧伏隔核内ＣＲＦ免疫反应阳性神经元数目、胞体大小、形态和免疫反应强度进行分析,除免疫反应强阳性神经元计数项（Ｐ＜００１）外,其他项都无显著意义。ＣＲＦ免疫反应阳性神经元在伏隔核内分布不均,主要位于该核的前半段背侧区,核芯区较少