bluuebunny/crossref_metadata_2025 huggingface dataset:
Atrionatriuretic Peptide Transforms Cardiac Sodium Channels into Calcium-Conducting Channels
Authors: Sorbera Lisa Ann , Morad Martin
Published: October 2006

The atrionatriuretic peptide (ANP) is released from atrial cells in response to increased extracellular fluid volume and reduces sodium absorption by the kidney, thus reducing the blood volume. In this report, ANP suppressed the calcium and sodium currents in rat and guinea pig ventricular myocytes. The suppression of sodium current was caused by enhanced permeability of the sodium channel to calcium without significant changes in the kinetics or the tetrodotoxin sensitivity of the channel. Thus, ANP may regulate the sodium channel by altering its cationic selectivity site to calcium, thereby repressing the sodium current. The suppression of sodium and calcium channels and the resultant depressed excitability of the atrial cells may help to regulate ANP secretion.
Primary Structure of the γ Subunit of the DHP-Sensitive Calcium Channel from Skeletal Muscle
Authors: Jay Scott D. , Ellis Steven B. , McCue Ann F. , Williams Mark E. , Vedvick Thomas S. , Harpold Michael M. , Campbell Kevin P.
Published: October 2006

Affinity-purified, polyclonal antibodies to the γ subunit of the dihydropyridine (DHP)-sensitive, voltage-dependent calcium channel have been used to isolate complementary DNAs to the rabbit skeletal muscle protein from an expression library. The deduced primary structure indicates that the γ subunit is a 25,058-dalton protein that contains four transmembrane domains and two N-linked glycosylation sites, consistent with biochemical analyses showing that the γ subunit is a glycosylated hydrophobic protein. Nucleic acid hybridization studies indicate that there is a 1200-nucleotide transcript in skeletal muscle but not in brain or heart. The γ subunit may play a role in assembly, modulation, or the structure of the skeletal muscle calcium channel.
Microscale Patchiness of Nutrients in Plankton Communities
Authors: Lehman John T. , Scavia Donald
Published: October 2006

Autoradiography was used to identify the presence of nutrient patches produced by zooplankton. Algal cells which encounter patches of phosphorus-33 released by swimming animals accumulate more label than cells that do not enter the patches. Differential labeling of algae does not occur when turbulence in the fluid is increased by stirring. Nutrient patchiness at the scale of millimeters or less in nature probably influences the course of competition and coexistence among the phytoplankton.
Meteorological Analysis of the Eruption of Soufriere in April 1979
Authors: Barr Sumner , Heffter Jerome L.
Published: October 2006

Meteorological upper-air data, in conjunction with satellite imagery, lidar light detection and ranging returns, and aircraft sampling, aid in the determination of plume altitude and transport. The estimated trajectories indicate that the ash was transported eastward across the Atlantic to Africa in 3 to 5 days and that there was modest meridional transport as far as 15° poleward during the first week of travel.
Fibroblast Growth Factor Receptor Is a Portal of Cellular Entry for Herpes Simplex Virus Type 1
Authors: Kaner Robert J. , Baird Andrew , Mansukhani Alka , Basilico Claudio , Summers Barbara D. , Florkiewicz Robert Z. , Hajjar David P.
Published: October 2006

Herpes simplex virus type 1 (HSV-1) is a ubiquitous pathogen responsible for considerable morbidity in the general population. The results presented herein establish the basic fibroblast growth factor (FGF) receptor as a means of entry of HSV-1 into vertebrate cells. Inhibitors of basic FGF binding to its receptor and competitive polypeptide antagonists of basic FGF prevented HSV-1 uptake. Chinese hamster ovary (CHO) cells that do not express FGF receptors are resistant to HSV-1 entry; however, HSV-1 uptake is dramatically increased in CHO cells transfected with a complementary DNA encoding a basic FGF receptor. The distribution of this integral membrane protein in vivo may explain the tissue and cell tropism of HSV-1.
Protein Tyrosine Phosphatase Activity of an Essential Virulence Determinant in
Yersinia
Authors: Guan Kunliang , Dixon Jack E.
Published: October 2006

Yersinia
is the genus of bacteria that is the causative agent in plague or the black death, and on several occasions this organism has killed a significant portion of the world's population. An essential virulence determinant of
Yersinia
was shown to be a protein tyrosine phosphatase. The recombinant 50-kilodalton
Yersinia
phosphatase had a specificity for removal of phosphate from Tyr-containing as opposed to Ser/Thr-containing phosphopeptides and proteins. Site-directed mutagenesis was used to show that the
Yersinia
phosphatase possesses an essential Cys residue required for catalysis. Amino acids surrounding an essential Cys residue are highly conserved, as are other amino acids in the
Yersinia
and mammalian protein tyrosine phosphatases, suggesting that they use a common catalytic mechanism.
Odor Stimuli Trigger Influx of Calcium Into Olfactory Neurons of the Channel Catfish
Authors: Restrepo Diego , Miyamoto Takenori , Bryant Bruce P. , Teeter John H.
Published: October 2006

Olfactory transduction is thought to be mediated by a G protein-coupled increase in intracellular adenosine 3′,5′-monophosphate (cAMP) that triggers the opening of cAMP-gated cation channels and results in depolarization of the plasma membrane of olfactory neurons. In olfactory neurons isolated from the channel catfish,
Ictalurus punctatus
, stimulation with olfactory stimuli (amino acids) elicits an influx of calcium that leads to a rapid increase in intracellular calcium. In addition, in a reconstitution assay a plasma membrane calcium channel has been identified that is gated by inositol-1,4,5-trisphosphate (IP
3
), which could mediate this calcium influx. Together with previous studies indicating that stimulation with olfactory stimuli leads to stimulation of phosphoinositide turnover in olfactory cilia, these data suggest that an influx of calcium triggered by odor stimulation of phosphoinositide turnover may be an alternate or additional mechanism of olfactory transduction.
Spatial Learning as an Adaptation in Hummingbirds
Authors: Cole Susan , Hainsworth F. Reed , Kamil Alan C. , Mercier Terre , Wolf Larry L.
Published: October 2006

An ecological approach based on food distribution suggests that hummingbirds should more easily learn to visit a flower in a new location than to learn to return to a flower in a position just visited, for a food reward. Experimental results support this hypothesis as well as the general view that differences in learning within and among species represent adaptations.
Ecological Correlates of Paternal Investment of Urates in a Tropical Cockroach
Authors: Schal Coby , Bell William J.
Published: October 2006

Females of the tropical cockroach
Xestoblatta hamata
feed on urates offered by the male after copulation. Females on nitrogen-deficient diets ingest and transfer to their maturing oocytes more male-derived uric acid than do females on high-protein diets. In isolated females, the greatest uptake of uric acid by the ovaries occurs during the mating stage in the reproductive cycle. Uric acid from males contributes significantly to the female's nitrogen pool and may help shorten the time between mating and oviposition. In both field and laboratory experiments males choose high-protein foods and dietary uric acid.
Liquid Chromatography in 1982
Authors: Freeman David H.
Published: October 2006

Classical liquid chromatography gave rise 15 years ago to new ideas about high-speed separations. Today, difficult separations can be made almost routinely by use of liquid chromatography instruments with automated controls and sensitive detectors. Sorptive effects are often best achieved with small, porous, "bonded phase" particles. The trend is to control the chemical selectivity by means of the liquid phase. These techniques are easily learned, and they have been widely accepted throughout chemistry and its allied disciplines. As a result, liquid chromatography has become the most rapidly expanding branch of the chemical instrumentation field.
Surface Analysis and Atomic Physics with Slow Positron Beams
Authors: Mills Allen P.
Published: October 2006

Recent advances in slow positron beam techniques are making it possible to study the interactions of low-energy positrons with gas molecules and solid surfaces and to measure the properties of free positronium atoms. New surface related results include the observation of surfaces with negative positron affinity and the thermionic emission of slow positronium atoms, low-energy positron diffraction measurements, and the sensitive detection of near-surface crystalline imperfections. Two recent successful experiments in atomic physics are the formation of the positronium negative ion and the optical excitation of positronium for high precision spectroscopy. Prospects for a positron microscope and the study of exotic antimatter systems such as the two-component Fermi gas are based on the imminent possibility of enormous increases in the brightness and instantaneous intensity of positron beams.
Japanese Supercomputer Technology
Authors: Buzbee B. L. , Ewald R. H. , Worlton W. J.
Published: October 2006

Under the auspices of the Ministry for International Trade and Industry the Japanese have launched a National Superspeed Computer Project intended to produce high-performance computers for scientific computation and a Fifth-Generation Computer Project intended to incorporate and exploit concepts of artificial intelligence. If these projects are successful, which appears likely, advanced economic and military research in the United States may become dependent on access to supercomputers of foreign manufacture.
Transcriptional Regulator of Oxidative Stress-Inducible Genes: Direct Activation by Oxidation
Authors: Storz Gisela , Tartaglia Louis A. , Ames Bruce N.
Published: October 2006

The
oxyR
gene positively regulates genes induced by oxidative stress in
Salmonella typhimurium
and
Escherichia coli
. Purification of the OxyR protein showed that oxidized but not reduced OxyR activates transcription of oxidative stress-inducible genes in vitro. Conversion between the two forms of OxyR is rapid and reversible. Both the oxidized and the reduced forms of the OxyR protein are capable of binding to three diverse sequences upstream of OxyR-regulated promoters, but the interactions of the two forms of OxyR with the promoter regions are different. The results suggest that direct oxidation of the OxyR protein brings about a conformational change by which OxyR transduces an oxidative stress signal to RNA polymerase.
Interaction of Hsp 70 with Newly Synthesized Proteins: Implications for Protein Folding and Assembly
Authors: Beckmann Richard P. , Mizzen Lee E. , Welch William J.
Published: October 2006

The 70-kilodalton family of heat shock proteins (Hsp 70) has been implicated in posttranslational protein assembly and translocation. Binding of cytosolic forms of Hsp 70 (Hsp 72,73) with nascent proteins in the normal cell was investigated and found to be transient and adenosine triphosphate (ATP)-dependent. Interaction of Hsp 72,73 with newly synthesized proteins appeared to occur cotranslationally, because nascent polypeptides released prematurely from polysomes in vivo can be isolated in a complex with Hsp 72,73. Moreover, isolation of polysomes from short-term [
35
S]Met-labeled cells (pulsed) revealed that Hsp 72,73 associated with nascent polypeptide chains. In cells experiencing stress, newly synthesized proteins coimmunoprecipitated with Hsp 72,73; however, in contrast to normal cells, interaction with Hsp 72,73 was not transient. A model consistent with these data suggests that under normal growth conditions, cytosolic Hsp 72,73 interact transiently with nascent polypeptides to facilitate proper folding, and that metabolic stress interferes with these events.
Environmental Effects of an Impact-Generated Dust Cloud: Implications for the Cretaceous-Tertiary Extinctions
Authors: Pollack James B. , Toon Owen B. , Ackerman Thomas P. , McKay Christopher P. , Turco Richard P.
Published: October 2006

A model of the evolution and radiative effects of a debris cloud from a hypothesized impact event at the Cretaceous-Tertiary boundary suggests that the cloud could have reduced the amount of light at the earth's surface below that required for photosynthesis for several months and, for a somewhat shorter interval, even below that needed for many animals to see. For 6 months to 1 year, the surface would cool; the oceans would cool only a few degrees Celsius at most, but the continents might cool a maximum of 40 Kelvin. Extinctions in the ocean may have been caused primarily by the temporary cessation of photosynthesis, but those on land may have been primarily induced by a combination of lowered temperatures and reduced light.
Prorocentrin: An Extracellular Siderophore Produced by the Marine Dinoflagellate
Prorocentrum minimum
Authors: Trick Charles G. , Andersen Raymond J. , Gillam Andrew , Harrison Paul J.
Published: October 2006

Prorocentrin, a putative iron transport compound, has been extracted from the filtrates of
Prorocentrum minimum
cultures by XAD-2 resin. Production of prorocentrin can be stimulated by culturing
Prorocentrum minimum
under conditions of iron deficiency. The iron(III) complex of prorocentrin has an ultraviolet-visible absorption spectrum typical of hydroxamate siderophores
.
The Threat of Soil Erosion to Long-Term Crop Production
Authors: Larson W. E. , Pierce F. J. , Dowdy R. H.
Published: October 2006

National increases in row crops at the expense of hay and pasture crops, particularly on steeper slopes, have made the control of erosion a difficult prospect. Management practices that fit the various field conditions are needed to accomplish effective erosion control. These measures should be selected on the basis of soil characteristics, landscape type, and the amount of ongoing erosion. The maintenance of a cropland base adequate to our needs must be a primary national goal.
Thermal Vent Clam (
Calyptogena magnifica
) Hemoglobin
Authors: Terwilliger Robert C. , Terwilliger Nora B. , Arp Alissa
Published: October 2006

A heterodont bivalve mollusk
Calyptogena magnifica
, from the East Pacific Rise and the Galápagos Rift hydrothermal vent areas, contains abundant hemoglobin in circulating erythrocytes. No other known heterodont clam contains a circulating intracellular hemoglobin. The hemoglobin is tetrameric and has a relatively high oxygen affinity, which varies only slightly between 2° and 10°C. The presence of hemoglobin in the clam may facilitate the transport of oxygen to be used in chemoautotrophic hydrogen sulfide metabolism.
Light-Evoked Changes in the Interphotoreceptor Matrix
Authors: Uehara Fumiyuki , Matthes Michael T. , Yasumura Douglas , LaVail Matthew M.
Published: October 2006

The normal function of vertebrate photoreceptor cells depends on multiple interactions and transfer of substances between the photoreceptors and the retinal pigment epithelium (RPE), but the mechanisms of these interactions are poorly understood. Many are thought to be mediated by the interphotoreceptor matrix (IPM), a complex extracellular matrix that surrounds the photoreceptors and lies between them and the RPE. Histochemical, immunocytochemical, and lectin probes for several IPM constituents revealed that components of the IPM in the rat undergo a major shift in distribution or molecular conformation after the transition between light and dark. In the light, various IPM constituents concentrated in bands at the apical and basal regions of the outer segment zone; in the dark, they distributed much more uniformly throughout the zone. The change in IPM distribution was triggered by the light-dark transition; it was not a circadian event, and it was not driven by a systemic factor. The light-evoked change in IPM distribution may facilitate the transfer of substances between the photoreceptors and the RPE.
Cloning of a Transcriptionally Active Human TATA Binding Factor
Authors: Kao C. Cheng , Lieberman Paul M. , Schmidt Martin C. , Zhou Qiang , Pei Rui , Berk Arnold J.
Published: October 2006

Transcription factor IID (TFIID) binds to the TATA box promoter element and regulates the expression of most eukaryotic genes transcribed by RNA polymerase II. Complementary DNA (cDNA) encoding a human TFIID protein has been cloned. The human TFIID polypeptide has 339 amino acids and a molecular size of 37,745 daltons. The carboxyl-terminal 181 amino acids of the human TFIID protein shares 80% identity with the TFIID protein from
Saccharomyces cerevisiae
. The amino terminus contains an unusual repeat of 38 consecutive glutamine residues and an X-Thr-Pro repeat. Expression of DNA in reticulocyte lysates or in
Escherichia coli
yielded a protein that was competent for both DNA binding and transcription activation.
Prolactin Receptors in
Rana catesbeiana
During Development and Metamorphosis
Authors: White Bruce A. , Nicoll Charles S.
Published: October 2006

Specific binding of ovine prolactin was found in microsomal preparations of tail, gill, and kidney of the bullfrog
Rana catesbeiana
. Binding by larval and adult liver and by kidney before larval stage XVII was low or nondetectable. Renal binding increased during metamorphic climax and in response to treatment with thyroid hormone. The emergence of renal binding of prolactin may signify a shift in the hormone's participation in the control of hydromineral homeostasis from the gill, which is resorbed, to the kidney. A renal action of prolactin during climax may facilitate metamorphosis.
An Altered aroA Gene Product Confers Resistance to the Herbicide Glyphosate
Authors: Comai Luca , Sen Louvminia C. , Stalker David M.
Published: October 2006

The hypothesis that the herbicide glyphosate (
N
-phosphonomethylglycine) acts on plants and microorganisms by inhibiting synthesis of 5-enolpyruvyl-3-phosphoshikimate, a precursor to aromatic amino acids, was tested.
Salmonella typhimurium
was treated with ethyl methanesulfonate, and mutants mapping at the aroA locus, which encodes 5-enolpyruvyl-3-phosphoshikimate synthetase, were isolated by selection for glyphosate resistance. One of the mutants results in the synthesis of a 5-enolpyruvyl-3-phosphoshikimate synthetase that is resistant to inhibition by glyphosate. The mutant aroA gene and the corresponding wild-type allele were cloned. The mutation confers high resistance to glyphosate when introduced in
Escherichia coli
in the presence or absence of the wild-type aroA allele.
Social Wasps: Discrimination Between Kin and Nonkin Brood
Authors: Klahn Jeff E. , Gamboa George J.
Published: October 2006

In experiments in which nest boxes were switched, colony foundresses of the social wasp
Polistes fuscatus
accepted sisters' combs with little brood destruction but destroyed younger brood in the combs of less closely related females and sometimes deserted these combs. Discrimination between related and unrelated brood does not appear to depend on prior brood contact or environmentally acquired cues.
Cadmium-113 Magnetic Resonance Spectroscopy
Authors: Ellis Paul D.
Published: October 2006

Cadmium-113 nuclear magnetic resonance spectroscopy has been used in studies of the structure and dynamics of inorganic and bioinorganic molecules. Chemical dynamics play an important role in the analysis of relaxation and chemical shift data. Naïve interpretations of relaxation data can be checked by performing these experiments at a variety of temperatures and magnetic field strengths. A combination of solid- and liquid-state nuclear magnetic resonance measurements can provide the user with unambiguous data on chemical shielding. These data can be used to characterize zinc and calcium ion binding sites in metalloproteins.
Monitoring the 1980-1982 Eruptions of Mount St. Helens: Compositions and Abundances of Glass
Authors: Melson William G.
Published: October 2006

The Mount St. Helens eruptive sequence of 1980 through 1982 reflects the tapping of successively less water-rich, more highly crystallized, and more viscous, highly phyric dacitic magmas. These changes reflect both syn- and preeruption processes. The decreasing water content points to a continued decline in the volume and intensity of explosive pyroclastic activity. This decreasing water content appears to be composed of a long-term trend established during a long period of repose (about 130 years) imposed on short-term trends established during short periods (about 7 to 100 days) of repose between eruptions in the present eruptive cycle. The last two eruptive cycles of this volcano, the T (A.D. 1800) and W cycles (about A.D. 1500), exhibited similar trends. These changes are inferred from a combination of petrographic, bulk chemical, and electron- and ion-microprobe analyses of matrix and melt-inclusion glasses.
Extrageniculate Vision in Hemianopic Humans: Saccade Inhibition by Signals in the Blind Field
Authors: Rafal R. , Smith J. , Krantz J. , Cohen A. , Brennan C.
Published: October 2006

The functional competence of extrageniculate visual pathways in hemianopic humans was demonstrated by showing that distractor signals in the blind half of the visual field could inhibit saccades toward targets in the intact visual field. This inhibitory effect of unseen distractors in patients occurred only when distractors were presented in the temporal half of the visual field, was specific to oculomotor responses, and did not occur in normal subjects. These results show that a peripheral visual signal activates retinotectal pathways to prime the oculomotor system and that these pathways can mediate orienting behavior in hemianopic humans.
Historic Volcanism, European Dry Fogs, and Greenland Acid Precipitation, 1500 B.C. to A.D. 1500
Authors: Stothers Richard B. , Rampino Michael R.
Published: October 2006

Historic dry fogs in Europe, acid precipitation in Greenland, and major explosive volcanic eruptions correlate well with each other between 1500 B.C. and A.D. 1500. European (Mediterranean and Icelandic) volcanic eruptions appear to be the source of at least five of the nine largest acidity signals found in Greenland ice for this period. Between 152 B.C. and A.D. 43, eruptions of sulfur-rich Mount Etna probably supplied about 15 percent of the smaller acidity signals.
Chlorine-36 Dating of Saline Sediments: Preliminary Results from Searles Lake, California
Authors: Phillips Fred M. , Smith George I. , Bentley Harold W. , Elmore David , Gove Harry E.
Published: October 2006

Measurements have been made of the ratios of chlorine-36 to chlorine in five halite samples from Searles Lake sediments, previously dated by carbon-14, thorium-230, and magnetostratigraphic techniques. The ages calculated from the chlorine ratios are generally concordant with those from the other methods, implying the constancy of the chlorine input ratio over the last million years.
Samarium-146 in the Early Solar System: Evidence from Neodymium in the Allende Meteorite
Authors: Lugmair G. W. , Shimamura T. , Lewis R. S. , Anders Edward
Published: October 2006

A carbon-chromite fraction from the Allende C3V chondrite shows strikingly large isotopic enrichments of neodymium-142 (0.47 percent) and neodymium- 143 (36 percent). Both apparently formed by alpha decay of samarium-146 and samarium-147 (half-lives 1.03 × 10
8
and 1.06 × 10
11
years), but the isotopic enrichment was greatly magnified by recoil of residual nuclei into a carbon film surrounding the samarium-bearing grains. These data provide an improved estimate of the original abundance of extinct samarium-146 in the early solar system [
146
Sm/
144
Sm = (4.5 ± 0.5) × 10
-3
], higher than predicted by some models of
p
-process nucleosynthesis. It may be possible to use this isotopic pair as a chronometer of the early solar system.
Solidification and Ostwald Ripening of Near-Monotectic Zinc-Lead Alloys
Authors: Kneissl Albert , Fischmeister Hellmut
Published: October 2006

Studies of melting and resolidification were carried out on Spacelab 1 on the zinc-lead binary, an alloy which exhibits a miscibility gap in the liquid state. The possibility of maintaining the state of homogeneous dispersion of lead in the zinc matrix in a microgravity environment was verified. The second objective of the experiment was to study Ostwald ripening of the lead droplets (manifested as slow coarsening of the droplets) within the region of immiscibility. An increase in droplet size was observed and may have been due to Ostwald ripening, although the effect on droplet size of precipitation during cooling must be analyzed before this can be determined conclusively.
Thermogenic Gas Hydrates in the Gulf of Mexico
Authors: Brooks J. M. , Kennicutt M. C. , Fay R. R. , McDonald T. J. , Sassen Roger
Published: October 2006

Thermogenic gas hydrates were recovered from the upper few meters of bottom sediments in the northwestern Gulf of Mexico. The hydrates were associated with oil-stained cores at a water depth of 530 meters. The hydrates apparently occur sporadically in seismic "wipeout" zones of sediments in a region of the Gulf continental slope at least several hundred square kilometers in area.
Siblicidal Aggression and Resource Monopolization in Birds
Authors: Mock Douglas W.
Published: October 2006

In Texas, great egret
Casmerodius albus
chicks attack younger nestmates, often fatally (siblicide). By contrast, the young of neighboring great blue herons
Ardea herodias
seldom strike or kill siblings. These interspecific differences seem related to prey size: only fish provided by egret parents are small enough for chicks to monopolize (a process facilitated by aggression). Experimentally cross-fostered heron chicks raised on small prey by egret parents became siblicidal, but the reverse procedure of cross-fostering egret chicks did not reduce aggression or siblicide.
Isolable Compounds Containing a Silicon-Silicon Double Bond
Authors: West Robert
Published: October 2006

After 70 years of unsuccessful attempts, several stable disilenes—compounds with double bonds between silicon atoms—have now been made. The silicon-silicon double bond resembles in many ways the well-known carbon-carbon double bond of organic chemistry. However, striking dissimilarities are also found between disilenes and alkenes in both their structures and chemical reactions.
Recent Sedimentation on the New Jersey Slope and Rise
Authors: Stanley Daniel Jean , Nelsen Terry A. , Stuckenrath Robert
Published: October 2006

Radiocarbon dating and sedimentological studies of closely spaced cores indicate movement during the Holocene of sediments on the New Jersey continental slope and upper rise between Wilmington and Lindenkohl canyons. The uneven time-stratigraphic thickness of the late Quaternary sediment sections between cores and the nonuniform deposition rate at any given core site and among core sites show that the sediment blanket in canyon and intercanyon areas has been affected by downslope, gravity-driven processes during the Holocene to the present. The reduced rate of deposition on the slope and upper rise between the late Pleistocene and the present is largely due to decreased off-shelf transport in response to the eustatic rise in sea level. Very old radiocarbon dates at core tops result from emplacement of older reworked materials from upslope or from truncation of sections by mass wasting processes exposing older material at the sea floor. These processes also account for an irregular sequence of dated sections within cores and stratigraphic irregularities of the surficial cover from core to core. Marked variability in deposition rates on the slope and upper rise is largely a function of topographic configuration, proximity and accessibility to sediment source, and transport processes seaward of the shelf break. Moreover, higher accumulation rates on the upper rise are attributed primarily to slope bypassing. Bypassing, prevalent during the late Pleistocene, has continued periodically to the present.
A New Basis for Recognizing the Paleocene/Eocene Boundary in Western Interior North America
Authors: Wing Scott L.
Published: October 2006

Fossil pollen grains from Paleocene-Eocene rocks of the Bighorn Basin of Wyoming allow important sequences of terrestrial vertebrate fossils to be correlated with standard marine microfossil zonations. The Paleocene/Eocene boundary as based on pollen evidence falls within the Wasatchian land mammal age, much higher than the boundary used by some fossil mammal workers. This discrepancy partly results from multiple definitions of the Paleocene/Eocene boundary but may also indicate faulty mammal-based correlations to the type Sparnacian of France.
Densities of Liquid Silicates at High Pressures
Authors: Rigden Sally M. , Ahrens Thomas J. , Stolper Edward M.
Published: October 2006

Densities of molten silicates at high pressures (up to ∼230 kilobars) have been measured for the first time with shock-wave techniques. For a model basaltic composition (36 mole percent anorthite and 64 mole percent diopside), a bulk modulus
K
s
of ∼230 kilobars and a pressure derivative (
dK
s
/
dP
) of ∼4 were derived. Some implications of these results are as follows: (i) basic to ultrabasic melts become denser than olivine- and pyroxene-rich host mantle at pressures of 60 to 100 kilobars; (ii) there is a maximum depth from which basaltic melt can rise within terrestrial planetary interiors; (iii) the slopes of silicate solidi [(
dT
m
/
dP
), where
T
m
is the temperature] may become less steep at high pressures; and (iv) enriched mantle reservoirs may have developed by downward segregation of melt early in Earth history.
The Variability of Holocene Climate Change: Evidence from Varved Lake Sediments
Authors: Dean Walter E. , Bradbury J. Platt , Anderson Roger Y. , Barnosky Cathy W.
Published: October 2006

Varved sediments from a lake near the present forest-prairie border in northwestern Minnesota provide an annual record of climate change for the last 10,400 years. Climate-sensitive mineral, chemical, and biological components show that the mid-Holocene dry interval between 8500 and 4000 years ago is asymmetrical and actually consists of two distinct drier pulses separated by a moister interval that lasted about 600 years. Cyclic fluctuations with periods of several hundred years were abrupt and persistent throughout the Holocene and are most clearly recorded within the two drier pulses.
Generation and Migration of Light Hydrocarbons
Authors: Hunt John M.
Published: October 2006

Light hydrocarbons (containing from 1 to 14 carbon atoms) are formed from disseminated organic matter in sediments at the parts-per-billion level by biological and low-temperature (< 50°C) chemical reactions and at the parts-permillion level by high-temperature (> 50°C) cracking reactions. The cooler reactions produce mainly branched hydrocarbons, whereas the hotter reactions yield more straight chains. Hydrocarbon generation zones in the subsurface can be recognized on the basis of hydrocarbon distribution patterns. Hydrocarbons with tertiary carbon atoms form at lower temperatures than those with quaternary carbons. Methane and ethane migrate vertically through fine-grained shales by diffusion and solution, whereas many of the C
3+
hydrocarbons show little or no vertical migration. Concentrations of light hydrocarbons, including methane, in fine-grained source rocks decrease to low values in deep, high-temperature (>200°C) sediments. This decrease may be one reason why no economic accumulation of gas has been found to date deeper than 8.2 kilometers (27,000 feet).
Dinoflagellate with Blue-Green Chloroplasts Derived from an Endosymbiotic Eukaryote
Authors: Wilcox Lee W. , Wedemayer Gary J.
Published: October 2006

The dinoflagellate,
Amphidinium wigrense
, contains triple membrane-bound bodies we have termed "blue-green chloroplasts." We believe these chloroplasts were derived from a cryptomonad endosymbiont similar to that present in another blue-green dinoflagellate,
Gymnodinium acidotum
. These dinoflagellates provide evidence that a chloroplast has evolved from an endosymbiotic eukaryote.
How Bees Remember Flower Shapes
Authors: Gould James L.
Published: October 2006

Bees are able to learn to distinguish between flowers with different shapes or patterns. Some studies have suggested that bees remember only isolated features such as spatial frequency and line angles, rather than the photographic search images that are characteristic of vertebrates. New data indicate that this presumptive vertebrate-invertebrate dichotomy is false; bees can store flower patterns as a low-resolution eidetic image or photograph.
A Model for a Seismic Computerized Alert Network
Authors: Heaton Thomas H.
Published: October 2006

In large earthquakes, damaging ground motions may occur at large epicentral distances. Because of the relatively slow speed of seismic waves, it is possible to construct a system to provide short-term warning (as much as several tens of seconds) of imminent strong ground motions from major earthquakes. Automated safety responses could be triggered by users after receiving estimates of the arrival time and strength of shaking expected at an individual site. Although warning times are likely to be short for areas greatly damaged by relatively numerous earthquakes of moderate size, large areas that experience very strong shaking during great earthquakes would receive longer warning times.
Crassulacean Acid Metabolism in the Strangler
Clusia rosea
Jacq.
Authors: Ting Irwin P. , Lord Elizabeth M. , Sternberg Leonel da S. L. , DeNiro Michael J.
Published: October 2006

Observations of malic acid fluctuation, leaf anatomy, and stable carbon isotopic composition showed that the epiphytic strangler
Clusia rosea
, growing on Saint John, U.S. Virgin Islands, has crassulacean acid metabolism. This hemiepiphyte may be the only woody dicotyledonous tree species among the many thousands of flowering species in the 30 or more plant families that shows this type of metabolism. The finding has implications with respect to water balance during the process whereby
Clusia rosea
establishes itself as a tree, since crassulacean acid metabolism is a photosynthetic adaptation to water-stressed environments.
Prenylated Proteins: the Structure of the Isoprenoid Group
Authors: Rilling H. C. , Breunger E. , Epstein W. W. , Crain P. F.
Published: October 2006

The mevalonate-derived portion of a prenylated protein from Chinese hamster ovary cells has been established as diterpenoid (C
20
). This group is linked to a carboxyl-terminal cysteine as a thioether. It was removed from the protein by hydrazinolysis followed by Raney nickel desulfurization, and the resulting hydrocarbon fraction was analyzed by gas chromatography-mass spectrometry.
Induction of Cellular Senescence in Immortalized Cells by Human Chromosome 1
Authors: Sugawara Osamu , Oshimura Mitsuo , Koi Minoru , Annab Lois A. , Barrett J. Carl
Published: October 2006

The control of cellular senescence by specific human chromosomes was examined in interspecies cell hybrids between diploid human fibroblasts and an immortal, Syrian hamster cell line. Most such hybrids exhibited a limited life span comparable to that of the human fibroblasts, indicating that cellular senescence is dominant in these hybrids. Karyotypic analyses of the hybrid clones that did not senesce revealed that all these clones had lost both copies of human chromosome 1, whereas all other human chromosomes were observed in at least some of the immortal hybrids. The application of selective pressure for retention of human chromosome 1 to the cell hybrids resulted in an increased percentage of hybrids that senesced. Further, the introduction of a single copy of human chromosome 1 to the hamster cells by microcell fusion caused typical signs of cellular senescence. Transfer of chromosome 11 had no effect on the growth of the cells. These findings indicate that human chromosome 1 may participate in the control of cellular senescence and further support a genetic basis for cellular senescence.
Glucose, Sulfonylureas, and Neurotransmitter Release: Role of ATP-Sensitive K
+
Channels
Authors: Amoroso Salvatore , Schmid-Antomarchi Heidy , Fosset Michel , Lazdunski Michel
Published: October 2006

Sulfonylurea-sensitive adenosine triphosphate (ATP)-regulated potassium (K
ATP
) channels are present in brain cells and play a role in neurosecretion at nerve terminals. K
ATP
channels in substantia nigra, a brain region that shows high sulfonylurea binding, are inactivated by high glucose concentrations and by antidiabetic sulfonylureas and are activated by ATP depletion and anoxia. K
ATP
channel inhibition leads to activation of γ-aminobutyric acid (GABA) release, whereas K
ATP
channel activation leads to inhibition of GABA release. These channels may be involved in the response of the brain to hyper- and hypoglycemia (in diabetes) and ischemia or anoxia.
Experiments on Salt Fingers in a Hele Shaw Cell
Authors: Taylor J. , Veronis G.
Published: October 2006

"Salt fingers" are generated when a slowly diffusing solute overlies a more rapidly diffusing solute in a gravitationally stable fluid. The phenomenon is important in many areas of science; for example, it affects the temperature and salinity structure in the upper half of the ocean, the production of crystals when liquid alloys solidify, and the distribution of properties in magma chambers below the earth's crust. The evolution of a salt finger from initial instability to a fully developed feature is difficult to follow in a fluid because of the close-packed array of cells that is formed. However, when the fluid is contained in a Hele Shaw cell, individual fingers occupy the entire gap width, thereby enabling the experimenter to monitor and record the evolution much more easily. The instability of an array of wide fingers to disturbances that lead to (preferred) smaller scales is documented in a sequence of photographs, and a qualitative, physically consistent argument is offered to explain the instability.
Southern Hemisphere Origin of the Cretaceous Laytonville Limestone of California
Authors: Tarduno J. A. , McWilliams M. , Sliter W. V. , Cook H. E. , Blake M. C. , Premoli-Silva I.
Published: October 2006

New paleomagnetic, paleontologic, and stratigraphic data from outcrops of the Laytonville Limestone (101 to 88 million years old) support a Southern Hemisphere origin. A paleomagnetic megaconglomerate test is statistically significant and suggests magnetization at 14° ± 5° south, predating Late Cretaceous to Eocene (70 to 50 million years ago) accretion. Rapid Kula plate movement or the existence and demise of a now vanished oceanic plate (or both) are required to accommodate the greater than 50° of poleward displacement implied by the paleomagnetic data. This rapid motion brings into question the validity of a "speed limit" for absolute plate velocity based on present-day plate motions.
Decrease in Deformation Rate Observed by Two-Color Laser Ranging in Long Valley Caldera
Authors: Linker M. F. , Langbein J. O. , McGarr A.
Published: October 2006

After the January 1983 earthquake swarm, the last period of notable seismicity, the rapid rate of deformation of the south moat and resurgent dome of the Long Valley caldera diminished. Frequently repeated two-color laser ranging measurements made within a geodetic network in the caldera during the interval June 1983 to November 1984 reveal that, although the deformation accumulated smoothly in time, the rate of extension of many of the baselines decreased by factors of 2 to 3 from mid-1983 to mid-1984. Areal dilatation was the dominant signal during this period, with rates of extension of several baselines reaching as high as 5 parts per million per annum during the summer of 1983. Within the south moat, shear deformation also was apparent. The cumulative deformation can be modeled as the result of injection of material into two points located beneath the resurgent dome in addition to shallow right lateral slip on a vertical fault in the south moat.
International Cometary Explorer Encounter with Giacobini-Zinner: Magnetic Field Observations
Authors: Smith Edward J. , Tsurutani Bruce T. , Slavin James A. , Jones Douglas E. , Siscoe George L. , Mendis D. Asoka
Published: October 2006

The vector helium magnetometer on the International Cometary Explorer observed the magnetic fields induced by the interaction of comet Giacobini-Zinner with the solar wind. A magnetic tail was penetrated ∼7800 kilometers downstream from the comet and was found to be 10
4
kilometers wide. It consisted of two lobes, containing oppositely directed fields with strengths up to 60 nanoteslas, separated by a plasma sheet ∼10
3
kilometers thick containing a thin current sheet. The magnetotail was enclosed in an extended ionosheath characterized by intense hydromagnetic turbulence and interplanetary fields draped around the comet. A distant bow wave, which may or may not have been a bow shock, was observed at both edges of the ionosheath. Weak turbulence was observed well upstream of the bow wave.
Melittin-Like Peptides from the Shark-Repelling Defense Secretion of the Sole
Pardachirus pavoninus
Authors: Thompson Stewart A. , Tachibana Kazuo , Nakanishi Koji , Kubota Ichiro
Published: October 2006

Three ichthyotoxic peptides, pardaxins P-1 to P-3, have been isolated from the defense secretion of the sole
Pardachirus pavoninus.
Pavoninins, the steroid glycosides with shark-repelling ability, had previously been isolated therefrom. Each pardaxin consists of 33 amino acid residues having a distinctly hydrophilic carboxyl terminal region and a predominantly hydrophobic remainder; the pardaxin is thus strongly surfactant. These peptides show marked physical and pharmacological similarities to melittin, the major active constituent of bee venom, yet they lack sequence homology. They are probably also responsible for the predator-repelling property of the sole.
A Budget for Continental Growth and Denudation
Authors: Howell David G. , Murray Richard W.
Published: October 2006

Oceanic crustal material on a global scale is re-created every 110 million years. From the data presented it is inferred that potential sialic material is formed at a rate of about 1.35 cubic kilometers per year, including hemipelagic volcanic sediments that accumulate at a rate of about 0.05 cubic kilometer per year. It is estimated that the influx of 1.65 cubic kilometers per year of terrigenous and biogenic sediment is deposited on the deep ocean, and this represents continental denudation. Because all this material is brought into a subduction zone, continental accretion rates, which could include all this material, may be as high as 3.0 cubic kilometers per year with a potential net growth for continents of 1.35 cubic kilometers per year.
Colors of Objects in the Field of the Double Quasi-Stellar Object 1146+111B,C
Authors: Tyson J. Anthony , Gullixson Craig A.
Published: October 2006

Color images of faint objects were used to test two hypotheses for the quasi-stellar object (QSO) pair 1146+ 111B,C: gravitational lens or massive string. Blue, red, and near-infrared CCD (charge-coupled device) images of the field of this QSO pair were examined for gravitational lens multiple-image candidates for all four QSO's in the field (B, C, D, and E). No third image of 1146+111B,C was found, down to 4 magnitudes fainter than BC. This result implies a compact lens mass distribution, if B and C are images of the same QSO. C appears to be redder than B in the wavelength region from 700 to 1100 nanometers. This raises the question of whether B and C are images of the same QSO. Three blue stellar objects of unusual color were found at plausible locations for multiple images of the other two QSO's in the field. A very red object was found at a plausible lens position. Under the hypothesis that B and C are lensed images, these color data severely restrict the possible lens models and imaged QSO multiplicities. One possibility is a compact lens mass of 4 × 10
15
solar masses at a redshift of 0.8. Another is an S-shaped massive string. If the spectrum of any of the three anomalous blue objects were available, it would be possible to distinguish between these two models. However, it is difficult to fit the color and intensity data reported here to either simple string or black hole models. Overall, the simplest model consistent with all the data is the no-lens, no-string hypothesis: B and C probably are separate QSO's, but with some spectral similarities.
Crystal Structures of an Antibody to a Peptide and Its Complex with Peptide Antigen at 2.8 Å
Authors: Stanfield Robyn L. , Fieser Terry M. , Lerner Richard A. , Wilson Ian A.
Published: October 2006

The three-dimensional structures of an antibody to a peptide and its complex with the peptide antigen have been determined at 2.8 Å resolution. The antigen is a synthetic 19-amino acid peptide homolog of the C helix of myohemerythrin (Mhr). The unliganded Fab′ crystals are orthorhombic with two molecules per asymmetric unit, whereas the complex crystals are hexagonal with one molecule per asymmetric unit. The Fab′ and the Fab′-peptide complex structures have been solved independently by molecular replacement methods and have crystallographic R factors of 0.197 and 0.215, respectively, with no water molecules included. The amino-terminal portion of the peptide sequence (NH
2
-Glu-Val-Val-Pro-His-Lys-Lys) is clearly interpretable in the electron density map of the Fab′-peptide complex and adopts a well-defined type II β-turn in the concave antigen binding pocket. This same peptide amino acid sequence in native Mhr is α-helical. The peptide conformation when bound to the Fab′ is inconsistent with binding of the Fab′ to native Mhr, and suggests that binding can only occur to conformationally altered forms of the native Mhr or to apo-Mhr. Immunological mapping previously identified this sequence as the peptide epitope, and its fine specificity correlates well with the structural analysis. The binding pocket includes a large percentage of hydrophobic residues. The buried surfaces of the peptide and the antibody are complementary in shape and cover 460 Å
2
and 540 Å
2
, respectively. These two structures now enable a comparison of a specific monoclonal Fab′ both in its free and antigen complexed state. While no major changes in the antibody were observed when peptide was bound, there were some small but significant side chain and main chain rearrangements.
Petroleum Associated with Polymetallic Sulfide in Sediment from Gorda Ridge
Authors: Kvenvolden Keith A. , Rapp John B. , Hostettler Frances D. , Morton Janet L. , King J. David , Claypool George E.
Published: October 2006

A sediment sample, impregnated with asphaltic petroleum and polymetallic sulfide, was dredged from the southern end of Gorda Ridge (the Escanaba Trough) off northern California, within the offshore Exclusive Economic Zone of the United States. The molecular distributions of hydrocarbons in this petroleum show that it was probably derived from terrestrial organic matter in turbidite sediment filling the Escanaba Trough. Hydrothermal activity at the Gorda Ridge spreading center provided the heat for petroleum formation and was the source of fluids for sulfide mineralization.
Superconductivity at 52.5 K in the Lanthanum-Barium-Copper-Oxide System
Authors: Chu C. W. , Hor P. H. , Meng R. L. , Gao L. , Huang Z. J.
Published: October 2006

A superconducting transition with an onset temperature of 52.5 K has been observed under hydrostatic pressure in compounds with nominal compositions given by (La
0.9
Ba
0.1
)
2
CuO

4-
y

Possible causes for the high-temperature superconductivity are discussed.
The Economic Consequences of Immigration
Authors: Borjas George J. , Tienda Marta
Published: October 2006

Available research supports several major conclusions about the economic consequences of immigration. (i) The aggregate impacts of foreign workers on the earnings and employment of native workers are quite small, but differ for selected population subgroups and high ethnic density labor markets. (ii) Immigrants who arrived during the 1970s are less skilled than earlier arrivals, and their earnings will remain substantially below those of natives throughout their working lives. (iii) The evidence on immigrants' receipt of public assistance income is inconclusive.