Targeting of cyclic AMP degradation to beta 2-adrenergic receptors by beta-arrestins

Catecholamines signal through the beta2-adrenergic receptor by promoting production of the second messenger adenosine 3',5'-monophosphate (cAMP). The magnitude of this signal is restricted by desensitization of the receptors through their binding to beta-arrestins and by cAMP degradation by phosphodiesterase (PDE) enzymes. We show that beta-arrestins coordinate both processes by recruiting PDEs to activated beta2-adrenergic receptors in the plasma membrane of mammalian cells. In doing so, the beta-arrestins limit activation of membrane-associated cAMP-activated protein kinase by simultaneously slowing the rate of cAMP production through receptor desensitization and increasing the rate of its degradation at the membrane.     

Reduced numbers of somatostatin receptors in the cerebral cortex in Alzheimer's disease

Somatostatin receptor concentrations were measured in patients with Alzheimer's disease and controls. In the frontal cortex (Brodmann areas 6, 9, and 10) and temporal cortex (Brodmann area 21), the concentrations of somatostatin in receptors in the patients were reduced to approximately 50 percent of control values. A 40 percent reduction was seen in the hippocampus, while no significant changes were found in the cingulate cortex, postcentral gyrus, temporal pole, and superior temporal gyrus. Scatchard analysis showed a reduction in receptor number rather than a change in affinity. Somatostatin-like immunoreactivity was significantly reduced in both the frontal and temporal cortex. Somatostatin-like immunoreactivity was linearly related to somatostatin-receptor binding in the cortices of Alzheimer's patients. These findings may reflect degeneration of postsynaptic neurons or cortical afferents in the patients' cerebral cortices. Alternatively, decreased somatostatin-like immunoreactivity in Alzheimer's disease might indicate increased release of somatostatin and down regulation of postsynaptic receptors.     

A cyclic carbanionic valence isomer of a carbocation: diphosphino analogs of diaminocarbocations

Diaminocarbocations (or amidinium salts) feature a three-center 4pi electron system with an open planar structure. Their 2pi electron three-membered cyclic valence isomers, in which the carbon atom bears a negative charge, are predicted to be about 541 kilojoules per mole higher in energy than the open form. This isomer has not been identified yet. In contrast, the attempted synthesis of a diphosphorus analog of amidinium salts leads to the cyclic carbanionic form. There is no precedent for such a transformation of a carbocationic center into a carbanionic center, but with the help of heavier main-group elements, numerous examples can be imagined. This approach will enable the preparation of many unknown structural moieties that are difficult or even impossible to access in the corresponding carbon and nitrogen series.     

GC-MS法分析比较新疆2种玫瑰花酱的香气成分

【目的】分析比较香气成分,研究新疆玫瑰花品种的香气物质。【目的】为新疆特色玫瑰产业的加工技术及产品品质提供一定的理论基础。【方法】采用顶空固相微萃取法(HS-SPME),提取新疆和田地区两种玫瑰花酱中的香气成分,结合气相色谱-质谱联用仪分析香气成分。【结果】和田大马士革玫瑰花酱香气成分的种类主要为醇类(28.57%)、醛酮类(17.14%)、烷类(31.43%)、酸类(2.86%)、酯类(5.71%)、烯烃类(8.57%)、胺类(5.71%)。和田紫枝玫瑰花酱香气成分主要为醛酮类(12.90%)、醇类(22.58%)、烷类(35.48%)、酯类(19.35%)、芳香族化合物(9.68%)。【结论】不同品种的玫瑰花虽含有一定的香气物质,但由于香气成分及含量存在差异,使得其拥有不同的结构及香味。     

两种细菌粗多糖对草鱼的免疫调节作用

目的检测细菌多糖对草鱼的免疫调节作用。方法用酚水法分别从大肠杆菌和根癌农杆菌细胞壁中提取出粗多糖，注射草鱼,测定受试草鱼血液中白细胞数量，血清中抗体效价，肝脏、肾脏、脾脏、血清和粘液中过氧化物酶的活力。结果受试草鱼中的白细胞数量、血清抗体效价及过氧化物酶活力均具有明显提高。结论大肠杆菌和根癌农杆菌粗多糖对草鱼有免疫促进作用。     

Habitat selection by chemically differentiated races of lichens

The maritime European lichens of the aggregate species Ramalina siliquosa represent six chemical races. Where the races are sympatric they populate different habitats. Such intensive local ecological sorting of morphologically similar individuals accumulating different, highly specialized metabolic end products appears to be unknown in other plants.     

Use of chemokine receptors by poxviruses

Chemokine receptors serve as portals of entry for certain intracellular pathogens, most notably human immunodeficiency virus (HIV). Myxoma virus is a member of the poxvirus family that induces a lethal systemic disease in rabbits, but no poxvirus receptor has ever been defined. Rodent fibroblasts (3T3) that cannot be infected with myxoma virus could be made fully permissive for myxoma virus infection by expression of any one of several human chemokine receptors, including CCR1, CCR5, and CXCR4. Conversely, infection of 3T3-CCR5 cells can be inhibited by RANTES, anti-CCR5 polyclonal antibody, or herbimycin A but not by monoclonal antibodies that block HIV-1 infection or by pertussis toxin. These findings suggest that poxviruses, like HIV, are able to use chemokine receptors to infect specific cell subtypes, notably migratory leukocytes, but that their mechanisms of receptor interactions are distinct.     

Paradoxical elevation of growth hormone by intraventricular somatostatin: possible ultrashort-loop feedback

Somatostatin, the growth hormone-inhibiting factor, when microinjected into the third ventricle of the rat brain, paradoxically induced the release of growth hormone. A pituitary site of action having been ruled out, this result supports the concept that exogenous somatostatin within the hypothalamus acts either to suppress the release of somatostatin from somatostatin-containing neurons, possibly via an ultrashort-loop feedback mechanism, or to augment release of hypothalamic growth hormone-releasing factor, thereby inducing a release of growth hormone. Injection of somatostatin into the third ventricle also decreased plasma concentrations of luteinizing hormone, follicle-stimulating hormone, and thyroid-stimulating hormone, probably by inhibiting the release of luteinizing hormone-releasing factor and thyrotropin-releasing factor.     

Plasticity of the differentiated state

Heterokaryons provide a model system in which to examine how tissue-specific phenotypes arise and are maintained. When muscle cells are fused with nonmuscle cells, muscle gene expression is activated in the nonmuscle cell type. Gene expression was studied either at a single cell level with monoclonal antibodies or in mass cultures at a biochemical and molecular level. In all of the nonmuscle cell types tested, including representatives of different embryonic lineages, phenotypes, and developmental stages, muscle gene expression was induced. Differences among cell types in the kinetics, frequency, and gene dosage requirements for gene expression provide clues to the underlying regulatory mechanisms. These results show that the expression of genes in the nuclei of differentiated cells is remarkably plastic and susceptible to modulation by the cytoplasm. The isolation of the genes encoding the tissue-specific trans-acting regulators responsible for muscle gene activation should now be possible.     

Pulsatile growth hormone secretion: suppression by hypothalamic ventromedial lesions and by long-acting somatostatin

Sequential blood samples, obtained from freely behaving, nonstressed male rats, showed a pulsatile pattern of growth hormone secretion with a mean interval between peaks of 68 minutes. The bursts of secretion were blocked by lesions of the hypothalamic ventromedial nuclei and by administration of a longacting preparation of synthetic somatostatin.     

培育胶合板材二种密度分布对间作年限和收益大小的影响

通过不同栽植密度分布2×8(m)和2×2×14(m),连续进行间作(年限)和收益大小的研究.结果表明,2×2×14(m)是窄冠幅杨树品种培育胶合板材的理想密度分布,农作物可间作6年,牧草互间作5年.总间作收益达52 742.4元/hm2.林地农林产品总收入和利润均可达到和超过单纯农业的收入且生态效益显著.     

Prevention of metamorphosis by exposure of insect eggs to juvenile hormone analogs

Metamorphosis of the bugs Pyrrhocoris apterus and Oncopeltus fasciatus is blocked by the application of juvenile hormone analogs to the eqgs 4 weeks earlier. One or more supernumerary larval molts occur to form "giant" larvae which routinely die without undergoing netamorphosis. When the corpora allatta were excised at the outset of the fifth larval stage, the entire phenomenon vanished and all individuals underwent normal metamorphosis. The inhibition of metamorphosis can therefoore be attributed to a continuation of the secretion of endogenous juvenile hormone by the corpora allata of mature larvae deried from eggs treated with juvenile hormone.     

Circulating somatostatin acts on the islets of Langerhans by way of a somatostatin-poor compartment

Somatostatin perfused in canine pancreases at 10 to 20 picograms per milliliter or 10 to 20 percent of the pancreatic vein somatostatin concentration inhibited insulin and glucagon secretion. This suggests that the high local concentration of endogenous somatostatin is not in contact with somatostatin receptors of the islets. The integrity of this separation may determine the sensitivity of islet cells to circulating somatostatin.     

Psychotomimesis mediated by kappa opiate receptors

The kappa opioid agonists are analgesics that seem to be free of undesired morphine-like effects. Their dysphoric actions observed with the kappa agonist cyclazocine are thought to be mediated by an action at sigma-phencyclidine receptors. The benzomorphan kappa agonist MR 2033 is inactive at sigma-phencyclidine receptors. In male subjects, the opiate-active (-)-isomer, but not the (+)-isomer, elicited dose-dependent dysphoric and psychotomimetic effects that were antagonized by naloxone. Thus, kappa opiate receptors seem to mediate psychotomimetic effects. In view of the euphorigenic properties of mu agonists, our results imply the existence of opposed opioid systems affecting emotional and perceptual experiences.     

Antigen recognition by variable lymphocyte receptors

Variable lymphocyte receptors (VLRs) rather than antibodies play the primary role in recognition of antigens in the adaptive immune system of jawless vertebrates. Combinatorial assembly of leucine-rich repeat (LRR) gene segments achieves the required repertoire for antigen recognition. We have determined a crystal structure for a VLR-antigen complex, VLR RBC36 in complex with the H-antigen trisaccharide from human blood type O erythrocytes, at 1.67 angstrom resolution. RBC36 binds the H-trisaccharide on the concave surface of the LRR modules of the solenoid structure where three key hydrophilic residues, multiple van der Waals interactions, and the highly variable insert of the carboxyl-terminal LRR module determine antigen recognition and specificity. The concave surface assembled from the most highly variable regions of the LRRs, along with diversity in the sequence and length of the highly variable insert, can account for the recognition of diverse antigens by VLRs.     

“两田制”与农业双层经营

虽然双层经营体制已经得到确立,但至今其经营客体或对象在实践中仍然是不清楚的,而且就统分结合两方面来看,统的职能也严重不足,致使家庭经营的弊端依然存在,双层经营的功能难以充分发挥.为此.笔者提出,“两田制”是完善双层经营体制的有效形式。它有利于实现农业的适度规模经营,可大幅度地提高农业劳动生产率和农产品商品率,还形成了农村劳动力合理流动的机制,有利于农村经济的全面发展和农业机械化的推广。所以,笔者主张,“两田制”应谈有计划地加以推广.     

Compartmentalization of cyclic AMP during phagocytosis by human neutrophilic granulocytes

Immunocytochemistry shows that early during phagocytosis of zymosan, adenosine 3',5'-monophosphate (cyclic AMP) appears on the cell surface before the phagosome is internalized. The appearance of cyclic AMP on the cell surface is coincident with that of granule products and regulatory subunit of type I cyclic AMP-dependent protein kinase. Guanosine 3',5'-monophosphate is not associated with the initiation site of phagocytosis, but is observed throughout the granular cytoplasmic region. This sharply localized accumulation of cyclic AMP may serve as a signal for the initiation of phagocytosis.