解剖学和形态学
麻醉学
听力与言语-语言病理学
行为科学
心脏和心血管系统
细胞和组织工程学
临床神经病学
危重症监护医学
牙科,口腔外科和医学
皮肤病学
急诊医学
内分泌学和新陈代谢
肠胃学和肝脏学
老人病学和老年医学
卫生保健科学和服务
血液学
免疫学
传染病
综合和补充性医学
医学伦理学
医学信息学
医学实验室技术
医学,全科和内科
医学,法律
医学,研究和试验
神经系统科学
护理
营养学和饮食学
产科医学和妇科医学
肿瘤学
眼科学
整形外科学
耳鼻喉科学
病理学
儿科学
周围血管疾病
药理学和药剂学
生理学
基本医疗保健
精神病学
公共、环境和职业卫生
放射学,核医学和医学成像
康复学
生殖生物学
呼吸系统
风湿病学
运动科学
外科学
毒理学
热带医学
泌尿学和肾脏学
病毒学
老年医学
健康政策和服务
心理学,临床
abstract::Octopamine is highly concentrated in neurones of several invertebrate species. Unlike in mammals, octopaminergic neurones in invertebrates are spatially separated from catecholaminergic neurons. In identified nerve cells of Aplysia, however, this amine coexists with other putative neurotransmitters. Octopamine is synt...
journal_title:Nature
pub_type: 杂志文章,评审
doi:10.1038/265501a0
更新日期:1977-02-10 00:00:00
abstract::Eukaryotic structural gene mutations occurring spontaneously in a mouse myeloma cell line offer the opportunity to study somatic mutation in animal cells at the molecular level. Studies on the myeloma protein and on mRNA have enabled us to characterise four such mutants representing four different mutation mechanisms....
journal_title:Nature
pub_type: 杂志文章,评审
doi:10.1038/265299a0
更新日期:1977-01-27 00:00:00
abstract::The chemical induction of malignant transformation in BHK cells seems to result from a somatic mutation. Stable transformants, whose frequency is significantly increased by mutagenic carcinogens, can revert to normal and often display temperature-restricted phenotypes indicative of an altered gene product. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/264722a0
更新日期:1976-12-23 00:00:00
abstract::A re-analysis of published data on mouse mutation rates induced by X and gamma rays suggests that the kinetics of induction can be analysed by fitting the data to a parabolic curve. We interpret this to mean that a substantial proportion of the induced mutations results from gross chromosomal changes such as deletions...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/264715a0
更新日期:1976-12-23 00:00:00
abstract::Transposable elements of DNA that are structurally defined and genetically discrete units seem to have an important role in the evolution of bacterial plasmids. Recombination occurring at the termini of such elements can result in the joining together of unrelated DNA segments that lack extensive nucleotide sequence h...
journal_title:Nature
pub_type: 杂志文章,评审
doi:10.1038/263731a0
更新日期:1976-10-28 00:00:00
abstract::Microsomes prepared from rabbit or pig aortas transformed endoperoxides (PGG2 or PGH2) to an unstable substance (PGX) that inhibited human platelet aggregation. PGX was 30 times more potent in this respect than prostaglandin E1. PGX contracted some gastrointestinal smooth muscle and relaxed certain isolated blood vess...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/263663a0
更新日期:1976-10-21 00:00:00
abstract::In Drosophila melanogaster, the rRNA genes (rDNA) are clustered at single sites on two non-homologous chromosomes, the X and Y. Examination of the structure of X and Y rDNAs with restriction endonucleases reveals that the X rDNA contains repeating units not present in the Y. Such observations, as well as genetic evide...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/263027a0
更新日期:1976-09-02 00:00:00
abstract::oop RNA, which is initiated at the po promoter and is 81 nucleotides long, can function as a leader sequence for the lambda immunity establishment transcription, previously believed to originate at a special promoter pre located in the y region. Thus, oop RNA seems to have a dual role, either favouring the lytic cycle...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/262112a0
更新日期:1976-07-08 00:00:00
abstract::A short exposure of primary cultures of mouse mammary tumour cells to glucocorticoids results in at least a three-fold stimulation of mammary tumour virus (MTV) production. Specific interaction of glucocorticoids with the cytoplasmic and nuclear receptors can also be demonstrated. The biological potency of various ste...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/262107a0
更新日期:1976-07-08 00:00:00
abstract::First-order difference equations arise in many contexts in the biological, economic and social sciences. Such equations, even though simple and deterministic, can exhibit a surprising array of dynamical behaviour, from stable points, to a bifurcating hiearchy of stable cycles, to apparently random fluctuations. There ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/261459a0
更新日期:1976-06-10 00:00:00
abstract::Elongation factor Tu is present in a fourfold excess over the amount seemingly involved in protein synthesis. It is identical to a major protein which we have found associated with the plasma membrane. The possibility of a specific role in that location is considered. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/261023a0
更新日期:1976-05-06 00:00:00
abstract::TMV RNA is not an efficient template for translation of the viral coat protein, in spite of containing nucleotide sequences coding for the protein. Efficient translation requires the prior synthesis within infected cells of a smaller RNA carrying only a portion of the information encoded in the whole genome. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/260759a0
更新日期:1976-04-29 00:00:00
abstract::Noradrenaline releases prostaglandins in the kidney, and in rats these augment rather than reduce vasoconstriction produced by the amine. Homogenates of kidneys of New Zealand rats inbred for hypertension exhibit lower prostaglandin inactivation by 15-hydroxydehydrogenase than controls. At the same time, augmentation ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/260582a0
更新日期:1976-04-15 00:00:00
abstract::Five new double-mutant haemoglobins composed of betaS chains and alpha chains with different substitutions, which are located at the surface of the tetramer, have been prepared. Although all the hybrids are more soluble than deoxyhaemoglobin S, the individual differences between these molecules make it possible to eva...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/260219a0
更新日期:1976-03-18 00:00:00
abstract::A model catalyst is described which has properties in common with carbonic anhydrase. The model demonstrates the availability of a mechanism, previously only hypothetical, for the action of the enzyme. It also shows, however, that this mechanism alone is not adequate to produce the high activity of the enzyme. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/258677a0
更新日期:1975-12-25 00:00:00
abstract::The extreme resistance of bacterial endospores to heat may result from dehydration of the central protoplast brought about and maintained by osmotic activity of expanded electronegative peptidoglycan polymer, and positively charged counterions associated with it, in the surrounding cortex. The cortex may thus act as a...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/258402a0
更新日期:1975-12-04 00:00:00
abstract::Tectal polarity for retinal connections remains reversible long after the anatomical pattern of neural structures has been determined. Cells in the diencephalon seem to control this polarity. Following certain embryonic operations, the diencephalon developed behind the tectum. In such cases, the polarity of the retino...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/258126a0
更新日期:1975-11-13 00:00:00
abstract::A 7-A resolution map of the purple membrane has been obtained by electron microscopy of tilted, unstained specimens. The protein in the membrane contains seven, closely packed, alpha-helical segments which extend roughly perpendicular to the plane of the membrane for most of its width. Lipid bilayer regions fill the s...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/257028a0
更新日期:1975-09-04 00:00:00
abstract::The process of DNA recognition by the activated form of the restriction endonuclease from E. coli K involves three enzyme-DNA complexes which can be differentiated experimentally. These are: an initial complex formed at a nonspecific site; a recognition complex involving the host specificity site; and a cleavage compl...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/256556a0
更新日期:1975-08-14 00:00:00
abstract::Corticosteroids as well as non-steroid anti-inflammatory drugs inhibit the prostaglandin-mediated vasodilatation accompanying lipolysis in subcutaneous fat. Whereas the non-steroids produce their effect by inhibition of prostaglandin synthesis, however, corticosteroids inhibit their release. This mechanism may be the ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/254308a0
更新日期:1975-03-27 00:00:00
abstract::An analysis of 15 protein structures indicates: First, the loss of accessible surface area by monomeric proteins on folding-proportional to hydrophobic energy-is a simple function of molecular weight; second, the proportion of polar groups forming intramolecular hydrogen bonds is constant; and third, protein interiors...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/254304a0
更新日期:1975-03-27 00:00:00
abstract::The nucleotide sequence of the RNA polymerase binding site at a promotor on fd RF DNA has been determined in comparison with the starting sequence of RNA initiated at this promoter. The RNA polymerase binding site contained the startpoint of transcription in the centre and a region with twofold symmetry in the non-tra...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/253410a0
更新日期:1975-02-06 00:00:00
abstract::Lord Rothschild presents his personal views about the terminology used to describe research and development. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/239373a0
更新日期:1972-10-13 00:00:00
abstract::Published data from X-ray telescopes are not adequate to reveal the fluctuations in the surface brightness of the background radiation caused by clustering or superclustering of the sources giving rise to the background. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/238020a0
更新日期:1972-07-07 00:00:00
abstract::Oxygen isotope analyses of Spondylus shells from neolithic sites suggest that the source for the shells used as ornaments in the Balkans and central Europe during the fourth millennium BC was the Aegean and not the Black Sea. The trade in Spondylus may have taken the form of an exchange of gifts. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/2281062a0
更新日期:1970-12-12 00:00:00
abstract::Helium-neon lasers emitting at 632.8 nm can influence the phytochrome controlled growth and development of plants more than a quarter of a mile away. It may therefore be possible to control the growth of crops using lasers to activate the phytochrome system. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/228970a0
更新日期:1970-12-05 00:00:00
abstract::An attempt is made to understand the characteristics of pulsar slowdown in terms of various possible emission mechanisms. Though magnetic-dipole radiation seems to be dominant, the deviations from a pure dipolar decay are large compared with errors in measurement and indicate the presence of more complicated braking m...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/228445a0
更新日期:1970-10-31 00:00:00
abstract::Is the big-bang hot, warm or cold? And are galactic masses determined by the interplay of gravitational and strong interactions in the very early universe? ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/228258a0
更新日期:1970-10-17 00:00:00
abstract::The neutron superfluid in most neutron stars should be in a highly turbulent state. If so, this turbulence drastically alters its rotational properties. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/227791a0
更新日期:1970-08-22 00:00:00
abstract::Data from a rocket experiment show details which were not known from ground-based observations. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/226526a0
更新日期:1970-05-09 00:00:00
abstract::A rapid decrease in shear velocity in the suboceanic mantle is used to infer the thickness of the lithosphere. It is proposed that new and highly precise group velocity data constrain the solutions and imply a thickness near 70 km. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/226330a0
更新日期:1970-04-25 00:00:00
abstract::Flash spectra of the total solar eclipse throughout all its phases have been obtained in the extreme ultraviolet for the first time. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/226249a0
更新日期:1970-04-18 00:00:00
abstract::The subsidence history of the Bahamian Platform points to a non-uniform rate of sea-floor spreading since the beginning of the Cretaceous. Lower Cretaceous rates of perhaps 5 cm/yr led to an active trench system at the boundary between the American and Caribbean lithosphere plates, and the rapid subsidence of the cont...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/2251226a0
更新日期:1970-03-28 00:00:00
abstract::A first step towards somatic hybridization in plants has been achieved. Protoplasts have been isolated and seen to fuse. ...
journal_title:Nature
pub_type: 杂志文章
doi:10.1038/2251016a0
更新日期:1970-03-14 00:00:00