Development of the signal in sensory rhodopsin and its transfer to the cognate transducer

The microbial phototaxis receptor sensory rhodopsin II (NpSRII, also named phoborhodopsin) mediates the photophobic response of the haloarchaeon Natronomonas pharaonis by modulating the swimming behaviour of the bacterium. After excitation by blue-green light NpSRII triggers, by means of a tightly bound transducer protein (NpHtrII), a signal transduction chain homologous with the two-component system of eubacterial chemotaxis. Two molecules of NpSRII and two molecules of NpHtrII form a 2:2 complex in membranes as shown by electron paramagnetic resonance and X-ray structure analysis. Here we present X-ray structures of the photocycle intermediates K and late M (M2) explaining the evolution of the signal in the receptor after retinal isomerization and the transfer of the signal to the transducer in the complex. The formation of late M has been correlated with the formation of the signalling state. The observed structural rearrangements allow us to propose the following mechanism for the light-induced activation of the signalling complex. On excitation by light, retinal isomerization leads in the K state to a rearrangement of a water cluster that partly disconnects two helices of the receptor. In the transition to late M the changes in the hydrogen bond network proceed further. Thus, in late M state an altered tertiary structure establishes the signalling state of the receptor. The transducer responds to the activation of the receptor by a clockwise rotation of about 15 degrees of helix TM2 and a displacement of this helix by 0.9 A at the cytoplasmic surface.     

Light-dependent phosphorylation of rhodopsin by beta-adrenergic receptor kinase

The structural components involved in transduction of extracellular signals as diverse as a photon of light impinging on the retina or a hormone molecule impinging on a cell have been highly conserved. These components include a recognition unit or receptor (for example, the beta-adrenergic receptor (beta AR) for catecholamines or the 'light receptor' rhodopsin), a guanine nucleotide regulatory or transducing protein, and an effector enzyme (for example, adenylate cyclase or cyclic GMP phosphodiesterase). Molecular cloning has revealed that the beta AR shares significant sequence and three-dimensional homology with rhodopsin. The function of the beta AR is diminished by exposure to stimulatory agonists, leading to desensitization. Similarly, 'light adaptation' involves decreased coupling of photoactivated rhodopsin to cGMP phosphodiesterase activation. Both forms of desensitization involve receptor phosphorylation. The latter is mediated by a unique protein kinase, rhodopsin kinase, which phosphorylates only the light-bleached form of rhodopsin. An analogous enzyme (termed beta AR kinase or beta ARK) phosphorylates only the agonist-occupied beta AR. We report here that beta ARK is also capable of phosphorylating rhodopsin in a totally light-dependent fashion. Moreover, rhodopsin kinase can phosphorylate the agonist-occupied beta AR. Thus the mechanisms which regulate the function of these disparate signalling systems also appear to be similar.     

Palaeobiology: calcification of early vertebrate cartilage

Hagfish and lampreys are unusual for modern vertebrates in that they have no jaws and their skeletons are neither calcified nor strengthened by collagen the cartilaginous elements of their endoskeleton are composed of huge, clumped chondrocytes (cartilage cells). We have discovered that the cartilage in a 370-million-year-old jawless fish, Euphanerops longaevus, was extensively calcified, even though its cellular organization was similar to the non-mineralized type found in lampreys. The calcification of this early lamprey-type cartilage differs from that seen in modern jawed vertebrates, and may represent a parallel evolutionary move towards a mineralized endoskeleton.     

The potential of vertebrate microfossils for marine to non-marine correlation in the Late Jurassic

Fish (cartilaginous: elasmobranch and bony: osteichthyan actinopterygian) and reptile (crocodile) microfossils comprising scales and teeth have been examined from a series of limestone samples in the Upper Jurassic of France and Germany to gauge the possibilities of using them for correlation between fully marine and hypo-or hyper-saline (non-marine) deposits.     

The potential of vertebrate microfossils for marine to non-marine correlation in the Late Jurassic

Fish (cartilaginous: elasmobranch and bony: osteichthyan actinopterygian) and reptile (crocodile) microfossils comprising scales and teeth have been examined from a series of limestone samples in the Upper Jurassic of France and Germany to gauge the possibilities of using them for correlation between fully marine and hypo-or hyper-saline (non-marine) deposits.     

Growth potential of human hepatocarcinoma cells in the liver of neonatal immunocompetent mice and its relation to immunological tolerance

To determine the pathological behavior of human hepatocarcinoma cells in the liver microenvironment of neonatal non-immunode-ficient mice, three human hepatocarcinoma cell lines (Bel7402, HepG2, and SK-Hep-1), traced by DiI, were transplanted into the intrahepatic or subcutaneous tissue of neonatal and adult Kunming mice. Histopathological observations showed that cells in the adult liver induced a severe immune response as early as the second day after the implantation, while the subcutaneous neoplasm underwent extensive necrosis by the end of the study. Only the cells injected into the neonatal liver underwent a delayed immunologic rejection in the organ microenvironment. These cells retained recognizable tumor features over the first seven days, and displayed an intrahepatic invasive pattern. The expression of tumor markers including alpha-fetoprotein and survivin was maintained. The quantitative ELISA for the expression patterns of IL-2 and IL-10 also confirmed that the intrahepatic immunity was non-susceptive during this period. The high serum alpha-fetoprotein level was inversely correlated with the change in immune response. Our study provided a bio-system for the research of immune responses to xenografts in the liver.     

关中早期城市群及其与环境关系探讨

目的 为了探讨关中地区早期城市群的形成和发展规律及其与环境的相互关系。方法 在野外实地考察及查阅有关献资料的基础上，运用定性描述与定量分析相结合的手法，结合现代城市地理学中的相关理论进行探讨。结果 揭示了关中早期城市分布、发展的一般规律及其与环境的关系，并从区域城市数量、人口等级规模、职能分工诸方面说明当时该区城市群雏形已经形成。结论 ①优越的自然地理环境是城市形成与发展的基础，特殊的政治环境是区域城市得以发展的契机；②关中城市群的形成与发展则不断地改变着本区域的环境特征。     

地震预警系统的实践及与实时地震学发展之间的关系

 地震预警系统在过去30年里逐渐从科学界的讨论变成了防震减灾的实践。在调研地震预警系统的发展的基础上,梳理了近年来不同国家、不同机构围绕地震预警开展的研究。介绍了采用简易烈度计（MEMS）和智能手机来实现地震预警的一种尝试性方法。在传统分析地震预警系统发展空间范围的基础上,分析预警系统发展时间节点信息,讨论地震预警系统的实践与实时地震学发展之间的关系。     

山东早期城市群及其与环境关系研究

目的为了深入研究山东早期城市群的形成和发展规律及其与环境的相互关系。方法在野外实地考察及查阅有关文献资料的基础上,运用定性描述与定量分析相结合的手法,结合现代城市地理学中的相关理论进行探讨。结果揭示了山东早期城市群分布、发展的一般规律及其与环境的关系。结论区域自然环境、人文环境,尤其是早期政治地缘结构演变是影响区域城市群发展的关键性因素;早期城市群的形成与发展改变着区域的环境特征。     

Cloning of the gene and cDNA for mammalian beta-adrenergic receptor and homology with rhodopsin

The adenylate cyclase system, which consists of a catalytic moiety and regulatory guanine nucleotide-binding proteins, provides the effector mechanism for the intracellular actions of many hormones and drugs. The tissue specificity of the system is determined by the particular receptors that a cell expresses. Of the many receptors known to modulate adenylate cyclase activity, the best characterized and one of the most pharmacologically important is the beta-adrenergic receptor (beta AR). The pharmacologically distinguishable subtypes of the beta-adrenergic receptor, beta 1 and beta 2 receptors, stimulate adenylate cyclase on binding specific catecholamines. Recently, the avian erythrocyte beta 1, the amphibian erythrocyte beta 2 and the mammalian lung beta 2 receptors have been purified to homogeneity and demonstrated to retain binding activity in detergent-solubilized form. Moreover, the beta-adrenergic receptor has been reconstituted with the other components of the adenylate cyclase system in vitro, thus making this hormone receptor particularly attractive for studies of the mechanism of receptor action. This situation is in contrast to that for the receptors for growth factors and insulin, where the primary biochemical effectors of receptor action are unknown. Here, we report the cloning of the gene and cDNA for the mammalian beta 2AR. Analysis of the amino-acid sequence predicted for the beta AR indicates significant amino-acid homology with bovine rhodopsin and suggests that, like rhodopsin, beta AR possesses multiple membrane-spanning regions.     

On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota

Protopteryx, a monotypic fossil bird discovered from the Sichakou basin in Fengning, Hebei, is the most primitive enantiornithine currently known. The bird-bearing strata do not contain the index fossils of the Yixian Formation in western Liaoning; the fish and bird fossils have more primitive features than the related forms found in the Yixian Formation, and the conchostracans are those usually distributed in the Dabeigou and Dadianzi formations in northern Hebei. Besides, the Protopteryx-bearing strata underlie the deposits bearing the index fossils of the Yixian Formation in the neighboring basin. Thus, it could be confirmed that the horizon of Protopteryx should be lower than the Yixian Formation, and Is approximately equivalent to the Dadianzi Formation in northern Hebei. This is the lowest horizon of the known fossil birds in China and Mesozoic enantiornithine birds in the world. Accompanying Protopteryx, there are other birds, acipenseriform fishes, salamanders, and mammals, which compose the Peipiaosteus fengningensis-Protopteryx fengningensis assemblage. This new assemblage traces the vertebrate evolution history of the Jehol Biota back to 130.7 Ma before. It is suggested that the demarcation of the Jehol Biota should be based on the large-scale tectonic-sedimentary cycles, and Peipiaosteus, instead of Lycoptera, could be taken as the vertebrate representative of the Jehol Biota.     

Generation of cat retinal ganglion cells in relation to central pathways

The ganglion cells of the cat retina form classes distinguishable in terms of perikaryal size, dendritic morphology and functional properties. Further, the axons differ in their diameters, patterns of chiasmatic crossing and in their central connections. Here we define, by 3H-thymidine autoradiography, the order of production of cells of each class and relate the order of the 'birthdates' to the known axonal pathways. The ganglion cell classes are produced in broad waves, which overlap as cells are produced first for central then for peripheral retina. Medium-sized cells are produced before the largest cells, and small ganglion cells are produced throughout the period of cell generation. This sequence of cell production relates to the orderly arrangement of axons in the optic tract, and can also be related to the rules of chiasmatic crossing observed for each ganglion cell class.     

On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota

Protopteryx, a monotypic fossil bird discovered from the Sichakou basin in Fengning, Hebei, is the most primitive enantiornithine currently known. The bird-bearing strata do not contain the index fossils of the Yixian Formation in western Liaoning; the fish and bird fossils have more primitive features than the related forms found in the Yixian Formation, and the conchostracans are those usually distributed in the Dabeigou and Dadianzi formations in northern Hebei. Besides, the Protopteryx-bearing strata underlie the deposits bearing the index fossils of the Yixian Formation in the neighboring basin. Thus, it could be confirmed that the horizon of Protopteryx should be lower than the Yixian Formation, and is approximately equivalent to the Dadianzi Formation in northern Hebei. This is the lowest horizon of the known fossil birds in China and Mesozoic enantiornithine birds in the world. Accompanying Protop- teryx, there are other birds, acipenseriform fishes, salamanders, and mammals, which compose the Peipiaosteus fengningensis-Protopteryx fengningensis assemblage. This new assemblage traces the vertebrate evolution history of the Jehol Biota back to 130.7 Ma before. It is suggested that the de- marcation of the Jehol Biota should be based on the large-scale tectonic-sedimentary cycles, and Peipiaosteus, instead of Lycoptera, could be taken as the vertebrate representative of the Jehol Biota.