Secretion of human interferons by yeast   总被引：27，自引：0，他引：27  

R A Hitzeman  D W Leung  L J Perry  W J Kohr  H L Levine  D V Goeddel 《Science (New York, N.Y.)》1983,219(4585):620-625

Plasmids were constructed to direct synthesis of the human interferons IFN-alpha 1, IFN-alpha 2, and IFN-gamma in the yeast Saccharomyces cerevisiae. Expression of IFN genes containing coding sequences for secretion signals resulted in the secretion of IFN activity. A large proportion of the IFN-alpha 1 and IFN-alpha 2 isolated from the yeast cell growth media had the same amino termini as the natural mature interferons, suggesting a removal of the signal sequences identical to that of human cells. These results show that a lower eukaryote, such as yeast, can utilize and process a human signal sequence.  相似文献   

Rapid identification of nonessential genes of herpes simplex virus type 1 by Tn5 mutagenesis   总被引：27，自引：0，他引：27  

P C Weber  M Levine  J C Glorioso 《Science (New York, N.Y.)》1987,236(4801):576-579

The large genome of herpes simplex virus type of (HSV-1) encodes at least 80 polypeptides, the majority of which have no recognized function. A subgroup of these gene products appears to be nonessential for virus replication in cell culture, but contributes to the complex life cycle of the virus in the host. To identify such functions, a simple insertional mutagenesis method has been used for selective inactivation of individual HSV-1 genes. The bacterial transposon Tn5 was allowed to insert randomly into cloned restriction fragments representing the entire short unique (US) region of the HSV-1 genome. Of the 12 open reading frames that were mutagenized with Tn5, mutant derivatives of US2, US4, and US5 were recombined into the virus. These three genes proved to be nonessential for HSV-1 replication in Vero (African Green monkey kidney) cells and the US4 gene appeared to be involved in viral pathogenesis in the central nervous system of mice. This rapid mutagenesis procedure should prove useful in exploring the entire HSV-1 genome as well as the genomes of other complex animal viruses.  相似文献   

Very-Long-Baseline Radio Interferometry: The Mark III System for Geodesy, Astrometry, and Aperture Synthesis     

Rogers AE  Cappallo RJ  Hinteregger HF  Levine JI  Nesman EF  Webber JC  Whitney AR  Clark TA  Ma C  Ryan J  Corey BE  Counselman CC  Herring TA  Shapiro II  Knight CA  Shaffer DB  Vandenberg NR  Lacasse R  Mauzy R  Rayhrer B  Schupler BR  Pigg JC 《Science (New York, N.Y.)》1983,219(4580):51-54

The Mark III very-long-baseline interferometry (VLBI) system allows recording and later processing of up to 112 megabits per second from each radio telescope of an interferometer array. For astrometric and geodetic measurements, signals from two radio-frequency bands (2.2 to 2.3 and 8.2 to 8.6 gigahertz) are sampled and recorded simultaneously at all antenna sites. From these dual-band recordings the relative group delays of signals arriving at each pair of sites can be corrected for the contributions due to the ionosphere. For many radio sources for which the signals are sufficiently intense, these group delays can be determined with uncertainties under 50 picoseconds. Relative positions of widely separated antennas and celestial coordinates of radio sources have been determined from such measurements with 1 standard deviation uncertainties of about 5 centimeters and 3 milliseconds of arc, respectively. Sample results are given for the lengths of baselines between three antennas in the United States and three in Europe as well as for the arc lengths between the positions of six extragalactic radio sources. There is no significant evidence of change in any of these quantities. For mapping the brightness distribution of such compact radio sources, signals of a given polarization, or of pairs of orthogonal polarizations, can be recorded in up to 28 contiguous bands each nearly 2 megahertz wide. The ability to record large bandwidths and to link together many large radio telescopes allows detection and study of compact sources with flux densities under 1 millijansky.  相似文献   

Cell-surface changes after infection with oncogenic viruses: requirement for synthesis of host DNA   总被引：2，自引：0，他引：2  

J R Sheppard  A J Levine  M M Burger 《Science (New York, N.Y.)》1971,172(990):1345-1346

The change in the surface structure of cultutred mammalian cells infected with oncogenic DNA viruses was similar to that described for the fully and permanently transformed cell surfaces. The course of appearance of this change was established. Synthesis of host DNA is required for expression of the surface change triggered by infection with the oncogenic virus.  相似文献   

Inescapable versus escapable shock modulates long-term potentiation in the rat hippocampus   总被引：10，自引：0，他引：10  

T J Shors  T B Seib  S Levine  R F Thompson 《Science (New York, N.Y.)》1989,244(4901):224-226

A group of rats was trained to escape low-intensity shock in a shuttle-box test, while another group of yoked controls could not escape but was exposed to the same amount and regime of shock. After 1 week of training, long-term potentiation (LTP) was measured in vitro in hippocampal slices. Exposure to uncontrollable shock massively impaired LTP relative to exposure to the same amount and regime of controllable shock. These results provide evidence that controllability modulates plasticity at the cellular-neuronal level.  相似文献   

Vacuum Squeezing of Solids: Macroscopic Quantum States Driven by Light Pulses     

GA Garrett  AG Rojo  AK Sood  JF Whitaker  R Merlin 《Science (New York, N.Y.)》1997,275(5306):1638-1640

Femtosecond laser pulses and coherent two-phonon Raman scattering were used to excite KTaO3 into a squeezed state, nearly periodic in time, in which the variance of the atomic displacements dips below the standard quantum limit for half of a cycle. This nonclassical state involves a continuum of transverse acoustic modes that leads to oscillations in the refractive index associated with the frequency of a van Hove singularity in the phonon density of states.  相似文献   

Ellipsosomes: organelles containing a cytochrome-like pigment in the retinal cones of certain fishes   总被引：1，自引：0，他引：1  

E F MacNichol  Y W Kunz  J S Levine  F I Hárosi  B A Collins 《Science (New York, N.Y.)》1978,200(4341):549-552

Ellipsosomes are dense spherical bodies containing a very large concentration of a heme pigment spectroscopically resembling pure cytochrome c. They are located at the outer ends of the inner segments of the cones of certain fishes. Although, superficially, they resemble the similarly located oil droplets in the cones of birds and reptiles, their ultrastructure and staining properties resemble those of the neighboring mitochondria. However, like the oil droplets, they may serve as intracellular color filters.  相似文献   

Stochastic gene expression in a single cell   总被引：1，自引：0，他引：1  

Elowitz MB  Levine AJ  Siggia ED  Swain PS 《Science (New York, N.Y.)》2002,297(5584):1183-1186

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Stress-induced eating is mediated through endogenous opiates   总被引：1，自引：0，他引：1  

J E Morley  A S Levine 《Science (New York, N.Y.)》1980,209(4462):1259-1261

The interaction of endogenous opiates and stress-induced eating in rats was evaluated by pharmacological manipulation. Eating induced by the tail-pinch method was inhibited by the opitate antagonist naloxone; after being repeatedly stressed over a 10-day period and then given nalozone, the rats behaved in a manner indistinguishable from the "wet-dog" shakes of opiate withdrawal. Thus endogenous opiates may have a role in the control of stress-related eating, a finding that may have therapeutic implications for humans.  相似文献   

Antibodies to photoproducts of deoxyribonucleic acids irradiated with ultraviolet light   总被引：5，自引：0，他引：5  

L Levine  E Seaman  E Hammerschlag  H Van Vunakis 《Science (New York, N.Y.)》1966,153(744):1666-1667

A rabbit immunized with complexes of methylated bovine serum albumin and ultraviolet-irradiated DNA from calf thymus produced antibodies directed toward the photoproducts in the DNA. Serologic activity appeared after irradiation of DNA at 270 mmicro and decreased upon irradiation at 235 mmicro. The antigenic determinants of the ultraviolet-treated DNA appear to be photoproducts associated primarily with thymine, as measured by direct dependence of serologic activity on the adenine-thymine content of the DNA, and by inhibition of the Serlolgic reaction by the irradiated di-,tri-,and tetra-(thymidine-5'-phosphate nucleotides.  相似文献