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  • 1
    Publication Date: 1991-06-21
    Description: The sequence of a Pst I restriction fragment was determined that demonstrate instability in fragile X syndrome pedigrees. The region of instability was localized to a trinucleotide repeat p(CCG)n. The sequence flanking this repeat were identical in normal and affected individuals. The breakpoints in two somatic cell hybrids constructed to break at the fragile site also mapped to this repeat sequence. The repeat exhibits instability both when cloned in a nonhomologous host and after amplification by the polymerase chain reaction. These results suggest variation in the trinucleotide repeat copy number as the molecular basis for the instability and possibly the fragile site. This would account for the observed properties of this region in vivo and in vitro.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kremer, E J -- Pritchard, M -- Lynch, M -- Yu, S -- Holman, K -- Baker, E -- Warren, S T -- Schlessinger, D -- Sutherland, G R -- Richards, R I -- New York, N.Y. -- Science. 1991 Jun 21;252(5013):1711-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cytogenetics and Molecular Genetics, Adelaide Children's Hospital, South Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1675488" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Blotting, Southern ; Chromosome Mapping ; Fragile X Syndrome/*genetics ; Humans ; Molecular Sequence Data ; Pedigree ; Polymerase Chain Reaction ; Polymorphism, Restriction Fragment Length ; Repetitive Sequences, Nucleic Acid ; Restriction Mapping ; X Chromosome/ultrastructure
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1992-11-27
    Description: The cystic fibrosis gene product (CFTR) is a complex protein that functions as an adenosine 3,5-monophosphate (cAMP)-stimulated ion channel and possibly as a regulator of intracellular processes. In order to determine whether the CFTR molecule contains a functional aqueous pathway, anion, water, and urea transport were measured in Xenopus oocytes expressing CFTR. Cyclic AMP agonists induced a Cl- conductance of 94 microsiemens and an increase in water permeability of 4 x 10(-4) centimeter per second that was inhibited by a Cl- channel blocker and was dependent on anion composition. CFTR has a calculated single channel water conductance of 9 x 10(-13) cubic centimeter per second, suggesting a pore-like aqueous pathway. Oocytes expressing CFTR also showed cAMP-stimulated transport of urea but not the larger solute sucrose. Thus CFTR contains a cAMP-stimulated aqueous pore that can transport anions, water, and small solutes. The results also provide functional evidence for water movement through an ion channel.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hasegawa, H -- Skach, W -- Baker, O -- Calayag, M C -- Lingappa, V -- Verkman, A S -- DK35124/DK/NIDDK NIH HHS/ -- DK43840/DK/NIDDK NIH HHS/ -- HL42368/HL/NHLBI NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1992 Nov 27;258(5087):1477-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine, University of California, San Francisco 94143-0532.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1279809" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; Biological Transport/physiology ; Chlorides/metabolism ; Cyclic AMP/physiology ; Cystic Fibrosis Transmembrane Conductance Regulator ; Female ; Humans ; In Vitro Techniques ; Ion Channels/*physiology ; Membrane Proteins/*physiology ; Molecular Sequence Data ; Oocytes ; Urea/metabolism ; Water/metabolism ; Xenopus
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 1990-12-07
    Description: In the development of multicellular organisms a diversity of cell types differentiate at specific positions. Spacing patterns, in which an array of two or more cell types forms from a uniform field of cells, are a common feature of development. Identical precursor cells may adopt different fates because of competition and inhibition between them. Such a pattern in the developing Drosophila eye is the evenly spaced array of R8 cells, around which other cell types are subsequently recruited. Genetic studies suggest that the scabrous mutation disrupts a signal produced by R8 cells that inhibits other cells from also becoming R8 cells. The scabrous locus was cloned, and it appears to encode a secreted protein partly related to the beta and gamma chains of fibrinogen. It is proposed that the sca locus encodes a lateral inhibitor of R8 differentiation. The roles of the Drosophila EGF-receptor homologue (DER) and Notch genes in this process were also investigated.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Baker, N E -- Mlodzik, M -- Rubin, G M -- New York, N.Y. -- Science. 1990 Dec 7;250(4986):1370-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, University of California, Berkeley 94720.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2175046" target="_blank"〉PubMed〈/a〉
    Keywords: Alleles ; Amino Acid Sequence ; Animals ; Cell Differentiation ; DNA Transposable Elements ; Drosophila/anatomy & histology/*genetics/growth & development ; *Drosophila Proteins ; Eye/anatomy & histology/growth & development ; Fibrinogen/*genetics ; *Glycoproteins ; Humans ; Molecular Sequence Data ; Mosaicism ; *Mutation ; Phenotype ; Proteins/*genetics ; Receptor, Epidermal Growth Factor/genetics ; Sequence Homology, Nucleic Acid
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
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  • 4
    Publication Date: 1990-05-04
    Description: The Drosophila Shaker gene on the X chromosome has three sister genes, Shal, Shab, and Shaw, which map to the second and third chromosomes. This extended gene family encodes voltage-gated potassium channels with widely varying kinetics (rate of macroscopic current activation and inactivation) and voltage sensitivity of steady-state inactivation. The differences in the currents of the various gene products are greater than the differences produced by alternative splicing of the Shaker gene. In Drosophila, the transient (A current) subtype of the potassium channel (Shaker and Shal) and the delayed-rectifier subtype (Shab and Shaw) are encoded by homologous genes, and there is more than one gene for each subtype of channel. Homologs of Shaker, Shal, Shab, and Shaw are present in mammals; each Drosophila potassium-channel gene may be represented as a multigene subfamily in mammals.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wei, A -- Covarrubias, M -- Butler, A -- Baker, K -- Pak, M -- Salkoff, L -- 1 RO1-NS24785-01/NS/NINDS NIH HHS/ -- GMO 7200/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1990 May 4;248(4955):599-603.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2333511" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; *Chromosome Mapping ; Drosophila/*genetics ; Drosophila Proteins ; Female ; Membrane Proteins/*genetics/physiology ; Mice/*genetics ; Molecular Sequence Data ; *Multigene Family ; Oocytes/physiology ; Potassium Channels/*physiology ; Sequence Homology, Nucleic Acid ; Shab Potassium Channels ; Transcription, Genetic ; *X Chromosome ; Xenopus
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    Electronic ISSN: 1095-9203
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  • 5
    Publication Date: 1993-06-04
    Description: Biological variability of human immunodeficiency virus type-1 (HIV-1) is involved in the pathogenesis of acquired immunodeficiency syndrome (AIDS). Syncytium-inducing (SI) HIV-1 variants emerge in 50 percent of infected individuals during infection, preceding accelerated CD4+ T cell loss and rapid progression to AIDS. The V1 to V2 and V3 region of the viral envelope glycoprotein gp120 contained the major determinants of SI capacity. The configuration of a hypervariable locus in the V2 domain appeared to be predictive for non-SI to SI phenotype conversion. Early prediction of HIV-1 phenotype evolution may be useful for clinical monitoring and treatment of asymptomatic infection.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Groenink, M -- Fouchier, R A -- Broersen, S -- Baker, C H -- Koot, M -- van't Wout, A B -- Huisman, H G -- Miedema, F -- Tersmette, M -- Schuitemaker, H -- New York, N.Y. -- Science. 1993 Jun 4;260(5113):1513-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Clinical Viro-Immunology, Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Amsterdam.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8502996" target="_blank"〉PubMed〈/a〉
    Keywords: Acquired Immunodeficiency Syndrome/microbiology ; Amino Acid Sequence ; Base Sequence ; Biological Evolution ; Consensus Sequence ; Genetic Variation ; Giant Cells/microbiology ; HIV Envelope Protein gp120/*chemistry ; HIV Seropositivity/microbiology ; HIV-1/*chemistry/*genetics/pathogenicity ; Humans ; Male ; Molecular Sequence Data ; Phenotype ; Protein Conformation ; Recombination, Genetic
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  • 6
    Publication Date: 2004-12-03
    Description: The thinning and intensification of the cross tail current sheet during the substorm growth phase are analyzed during the CDAW 6 substorm (22 Mar. 1979) using two complementary methods. The magnetic field and current sheet development are determined using data from two spacecraft and a global magnetic field model with several free parameters. These results are compared with the local calculation of the current sheet location and structure previously done by McPherron et al. Both methods lead to the conclusion that an extremely thin current sheet existed prior to the substorm onset, and the thicknesses estimated by the two methods at substorm onset agree relatively well. The plasma data from the ISEE 1 spacecraft at 13 R(sub E) show an anisotropy in the low energy electrons during the growth phase which disappears just before the substorm onset. The global magnetic model results suggest that the field is sufficiently stretched to scatter such low energy electrons. The strong stretching may improve the conditions for the growth of the ion tearing instability in the near Earth tail at substorm onset.
    Keywords: GEOPHYSICS
    Type: ESA, Substorms 1; p 131-135
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  • 7
    Publication Date: 2004-12-03
    Description: Issues concerning the 'driven' versus 'unloading' nature of substorms are presented. The original concepts attendant to this debate are presented and substorms are concluded to inextricably combine aspects that are driven with aspects that represent a loading-unloading system. For isolated substorms, the magnetosphere-ionosphere system is shown to exhibit a bimodal response to solar wind changes. A 20 min response characteristic is associated with the driven aspect of substorms, while a 1 hr response time is associated with unloading. It is found that for strong solar wind input conditions, the magnetospheric response becomes more nearly unimodal. This is interpreted in terms of a nonlinear dynamical evolution of the system. Simple analog models are described which capture the essence of the nonlinear magnetospheric behavior. These models exhibit chaotic transitions for strong driving conditions: this may explain the observed behavior of the magnetosphere during strong geomagnetic activity.
    Keywords: GEOPHYSICS
    Type: ESA, Substorms 1; p 185-191
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  • 8
    Publication Date: 2004-12-03
    Description: A pseudobreakup is a phenomenon similar to the substorm expansive phase onset, including an activation of an auroral arc, a burst of Pi2 micropulsations, and enhancement of the westward electrojet. However, these effects are weak and a pseudobreak is generally assumed to be very localized. The pseudobreakups are discussed based on simultaneous observations made in space and on the ground during the substorm growth phase. In the events studied the main features listed above are found, but the significance of the localization is unclear. The optical pseudobreakup, with associated magnetic perturbations, is highly localized, but simultaneously a wide local time sector of the auroral oval may be activated. The major differences between pseudobreakups and substorm expansive phase onsets are concluded to be the intensity and the development that follows. Careful study of pseudobreakups may help to determine phase initiation, and the role of the ionosphere-magnetosphere coupling in the substorm process.
    Keywords: GEOPHYSICS
    Type: ESA, Substorms 1; p 111-116
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  • 9
    Publication Date: 2011-08-24
    Description: High-energy electrons have been measured systematically in a low-altitude (520 x 675 km), nearly polar (inclination = 82 deg) orbit by sensitive instruments onboard the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX). Count rate channels with electron energy thresholds ranging from 0.4 MeV to 3.5 MeV in three different instruments have been used to examine relativistic electron variations as a function of L-shell parameter and time. A long run of essentially continuous data (July 1992 - July 1993) shows substantial acceleration of energetic electrons throughout much of the magnetosphere on rapid time scales. This acceleration appears to be due to solar wind velocity enhancements and is surprisingly large in that the radiation belt 'slot' region often is filled temporarily and electron fluxes are strongly enhanced even at very low L-values (L aprroximately 2). A superposed epoch analysis shows that electron fluxes rise rapidly for 2.5 is approximately less than L is approximately less than 5. These increases occur on a time scale of order 1-2 days and are most abrupt for L-values near 3. The temporal decay rate of the fluxes is dependent on energy and L-value and may be described by J = Ke-t/to with t(sub o) approximately equals 5-10 days. Thus, these results suggest that the Earth's magnetosphere is a cosmic electron accelerator of substantial strength and efficiency.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 6; p. 409-412
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  • 10
    Publication Date: 2011-08-24
    Description: Rocket data have been used to evaluate the characteristics of precipitating relativistic electrons and their effects on the electrodynamic structure of the middle atmosphere. These data were obtained at Poker Flat, Alaska, on May 13 and 14, 1990, during a midday, highly relativistic electron (HRE) precipitation event. Solid state detectors were used to measure the electron fluxes and their energy spectra. An X ray scintillator was included on each flight to measure bremsstrahlung X rays produced by energetic electrons impacting on the upper atmosphere. However, these were found the be of negligible importance for this particular event. The energy deposition by the electrons has been determined from the flux measurements and compared with in situ measurements of the atmospheric electrical response. The electrodynamic measurements were obtained by the same rockets and additionally on May 13, with an accompanying rocket. The impact flux was highly irregular, containing short-lived bursts of relativistic electrons, mainly with energies below 0.5 MeV and with fluxes most enhanced between pitch angles of 0 deg - 20 deg. Although the geostationary counterpart of this measured event was considered to be of relatively low intensity and hardness, energy deposition peaked near 75 km with fluxes approaching an ion pair production rate in excess of 100/cu cm s. This exceeds peak fluxes in relativistic electron precipitation (REP) events as observed by us in numerous rocket soundings since 1976. Conductivity measurements from a blunt probe showed that negative electrical conductivities exceeded positive conductivities down to 50 km or lower, consistent with steady ionization by precipitating electrons above 1 MeV. These findings imply that the electrons from the outer radiation zone can modulate the electrical properties of the middle atmosphere to altitudes below 50 km. During the decline and activity minimum of the current solar cycle, we anticipate the occurence of similar events but with fluxes 1-2 orders of magnitude above that reported here, based on studies of earlier solar cycles (e.g., Baker et al., 1993).
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D10; p. 21,071-21,081
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