bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of Alloreactivity in Vivo by a Soluble Form of the Interleukin-1 Receptor
Authors: Fanslow William C. , Sims John E. , Sassenfeld Helmut , Morrissey Philip J. , Gillis Steven , Dower Steven K. , Widmer Michael B.
Published: October 2006

In vitro studies have shown that cytokines are involved in the regulation of the immune response, but their role in vivo is less well defined. Specific cytokine antagonists enable the identification of particular cytokines involved in the response and offer a means for modifying it. Systemic administration of a soluble, extracellular portion of the receptor for interleukin-1 (sIL-1R) had profound inhibitory effects on the development of in vivo alloreactivity. Survival of heterotopic heart allografts was prolonged from 12 days in controls to 17 days in mice treated with sIL-1R. Lymph node hyperplasia in response to a localized injection of allogeneic cells was completely blocked by sIL-1R treatment. The inhibition was overcome by simultaneous administration of interleukin-1 (IL-1); thus, sIL-1R acts by neutralizing IL-1. These results implicate IL-1 as a regulator of allograft rejection and demonstrate the in vivo biological efficacy of a soluble cytokine receptor.
Interiors of the Giant Planets
Authors: Hubbard W. B.
Published: October 2006

Unlike the terrestrial planets, the giant planets—Jupiter, Saturn, Uranus, and Neptune—have retained large amounts of the carbon, nitrogen, and oxygen compounds that were present in their zone of formation. A smaller fraction of the available hydrogen and helium was retained. The distribution and relative amounts of these components in the interiors of the Jovian planets can be inferred from theoretical and experimental data on equations of state and from the planets' hydrostatic equilibrium response to rotation.
Biological Classification: Toward a Synthesis of Opposing Methodologies
Authors: Mayr Ernst
Published: October 2006

Currently a controversy is raging as to which of three competing methodologies of biological classification is the best: phenetics, cladistics, or evolutionary classification. The merits and seeming deficiencies of the three approaches are analyzed. Since classifying is a multiple-step procedure, it is suggested that the best components of the three methods be used at each step. By such a synthetic approach, classifications can be constructed that are equally suited as the basis of generalizations and as an index to information storage and retrieval systems.
Late Quaternary Environmental History of Lake Valencia, Venezuela
Authors: Bradbury J. Platt , Leyden B. , Salgado-Labouriau M. , Lewis W. M. , Schubert C. , Binford M. W. , Frey D. G. , Whitehead D. R. , Weibezahn F. H.
Published: October 2006

Chemical, paleontological, and mineralogical analyses of a 7.5-meter core from the middle of Lake Valencia, Venezuela, have provided information on the paleoclimatic history of this low-elevation, low-latitude site for the last 13,000 years. The data show that dry climates existed in this region from 13,000 years before present (B.P.) until about 10,000 years B.P. The Lake Valencia Basin was occupied by intermittent saline marshes at that time. About 10,000 years B.P., a permanent lake of fluctuating salinity formed and arboreal plant communities replaced the earlier dominant xeric herbaceous vegetation and marsh plants. By 8500 years B.P., Lake Valencia reached moderate to low salinities and discharged water; the modern vegetation became established at that time. After 8500 years B.P., the lake twice ceased discharging as a result of reduced watershed moisture. The second of these drying episodes is still in progress and has been aggravated by human activities in the watershed.
Chemical Self-Defense by Termite Workers: Prevention of Autotoxication in Two Rhinotermitids
Authors: Spanton S. G. , Prestwich G. D.
Published: October 2006

Soldiers of the lower termites
Prorhinotermes simplex
and
Schedorhinotermes lamanianus
(Isoptera, Rhinotermitidae) have electrophilic contact poisons used in colony defense. Workers of these termites die when exposed to the defense secretion of the other species, but survive when exposed to chemicals from conspecific soldiers. Detoxication occurs by an initial substrate-specific reduction of the electron-deficient double bond of the nitroalkene (
Prorhinotermes simplex
) or vinyl ketone (
Schedorhinotermes lamanianus
) followed by complete catabolism to acetate.
Direct Measurement of Forces Between Linear Polysaccharides Xanthan and Schizophyllan
Authors: Rau Donald C. , Parsegian V. Adrian
Published: October 2006

Direct osmotic stress measurements have been made of forces between helices of xanthan, an industrially important charged polysaccharide. Exponentially decaying hydration forces, much like those already measured between lipid bilayer membranes or DNA double helices, dominate the interactions at close separation. Interactions between uncharged schizophyllans also show the same kind of hydration force seen between xanthans. In addition to the practical possibilities for modifying solution and suspension properties through recognition and control of molecular forces, there is now finally the opportunity for theorists to relate macroscopic properties of a polymer solution to the microscopic properties that underlie them.
Synaptic Phosphoproteins: Specific Changes After Repetitive Stimulation of the Hippocampal Slice
Authors: Browning Michael , Dunwiddie Thomas , Bennett William , Gispen Willem , Lynch Gary
Published: October 2006

Repetitive stimulation (100 pulses per second for 1 second) of the Schaffer collateral-commissural system of the rat hippocampus induces long-term potentiation of synaptic strength and produces significant changes in the subsequent endogenous phosphorylation of a 40,000-dalton protein from synaptic plasma membranes. This effect is not observed after stimulation in calcium-deficient media or after simulation at the rate of one pulse per second for 100 seconds. These findings provide evidence that repetitive synaptic activation can alter the phosphorylation machinery of the synaptic region and suggest a biochemical process which may be involved in the production of neuronal plasticity.
Prescribed Fire: Effects on Water Quality and Forest Nutrient Cycling
Authors: Richter D. D. , Ralston C. W. , Harms W. R.
Published: October 2006

Prescribed fire, a practice applied annually to about 106hectares of forests in the southeastern United States, had limited effects on soils, nutrient cycling, and hydrologic systems of a coastal plain pine forest. Hydrologic fluxes of nitrogen, phosphorus, sulfur, and basic cations, from burned pine litter to ground and stream waters, are not likely to have appreciable impacts on water quality in the Atlantic and Gulf Coastal Plain.
Radiuin-226 and Radon-222 in the Coastal Waters of West Florida: High Concentrations and Atmospheric Degassing
Authors: Fanning Kent A. , Breland Jabe A. , Byrne Robert H.
Published: October 2006

On the central portion of the west Florida continental shelf, radionuclide activities show unusually wide variations: radium-226 activities up to 350 disintegrations per minute per 100 liters, radon-222 activities up to 1300 disintegrations per minute per 100 liters, and deficiencies of radon-222 as low as –10 disintegrations per minute per 100 liters. Florida's phosphate-rich strata seem to be the principal source of the radionuclides, with the transfer occurring directly from sediments or indirectly in streams, ground-water flow, and geothermal springs. Winter storm fronts may enhance radon degassing in the shelf waters.
Microcolonial Fungi: Common Inhabitants on Desert Rocks?
Authors: Staley James T. , Palmer Fred , Adams John B.
Published: October 2006

Microcolonial structures have been harvested from desert rock samples for cultivation and ultrastructural examination. The results indicate that these microcolonial structures are fungi previously unrecognized as inhabitants of desert rocks.
Maternally Inherited Sex Ratio in the Parasitoid Wasp
Nasonia vitripennis
Authors: Skinner Samuel W.
Published: October 2006

Facultative control of the sex ratio has been reported in the wasp
Nasonia vitripennis
. In a newly wild-caught strain, females produced few or no male offspring and did not show the usual alterations of sex ratio in response to external conditions. The aberrant trait is inherited through females.
Pollen-Stigma Interaction and Cross-Incompatibility in the Grasses
Authors: Heslop-Harrison J.
Published: October 2006

The failure of interspecific and intergeneric crosses in the grasses is commonly due to zygotic inviability, embryo abortion, or endosperm abnormalities, all of which occur after fertilization. Often, however, there is difficulty in obtaining fertilization because the pollen tube fails to reach the embryo sac. This article concerns recent research on pollen-stigma interaction in the grasses and the light it is beginning to throw on prefertilization self- and cross-incompatibilities.
Dating of a Fault by Electron Spin Resonance on Intrafault Materials
Authors: Ikeya Motoji , Miki Toshikatsu , Tanaka Kazuhiro
Published: October 2006

The total dose of natural radiation and the age were determined from paramagnetic defects in quartz grains at a fractured fault zone. Young age at the fault indicates that the accumulated defects in rocks were destroyed by high stress or high temperature at the time of the last fault movement, setting the clock time to zero. The technique was applied to quartz grains crushed by uniaxial compression in the laboratory to verify this interpretation.
Influence of Land-Surface Evapotranspiration on the Earth's Climate
Authors: Shukla J. , Mintz Y.
Published: October 2006

Calculations with a numerical model of the atmosphere show that the global fields of rainfall, temperature, and motion strongly depend on the land-surface evapotranspiration. This confirms the long-held idea that the surface vegetation, which produces the evapotransporation, is an important factor in the earth's climate.
Bronze Age Copper Sources in the Mediterranean: A New Approach
Authors: Gale Noël H. , Stos-Gale Zofia A.
Published: October 2006

Efforts by scientists to locate the sources of copper used in ancient Mediterranean and Near Eastern cultures through comparative chemical analyses of copper ores and archeological artifacts have largely failed for various mineralogical and metallurgical reasons. The isotopic composition of lead, an element present in a minor amount in many copper ores and bronze objects, is unchanged through metallurgical processes and may in principle be used to determine the sources of the copper used in Bronze Age artifacts. Results suggest that for Late Bronze Age Crete the Laurion region in Attica, Greece, may have been a more important copper source than Cyprus.
Venus: Chemical Weathering of Igneous Rocks and Buffering of Atmospheric Composition
Authors: Nozette Stewart , Lewis John S.
Published: October 2006

Data from the Pioneer Venus radar mapper, combined with measurements of wind velocity and atmospheric composition, suggest that surface erosion on Venus varies with altitude. Calcium- and magnesium-rich weathering products are produced at high altitudes by gas-solid reactions with igneous minerals, then removed into the hotter lowlands by surface winds. These fine-grained weathering products may then rereact with the lower atmosphere and buffer the composition of the observed gases carbon dioxide, water vapor, sulfur dioxide, and hydrogen fluoride in some regions of the surface. This process is a plausible mechanism for the establishment in the lowlands of a calcium-rich mineral assemblage, which had previously been found necessary for the buffering of these species.
Steel Recycling and Energy Conservation
Authors: Hannon Bruce , Brodrick James R.
Published: October 2006

The potential for energy conservation through increased use of steel scrap by the U.S. steel industry is examined. It is concluded that increased use of scrap would reduce energy use, but it is not economical, due mainly to volatile scrap prices. Other energy-saving technologies exist, but it is likely that energy will be conserved through reduced use of steel as rising energy costs are passed through to consumers.
Deep Advective Transport of Lithogenic Particles in Panama Basin
Authors: Honjo Susumu , Spencer Derek W. , Farrington John W.
Published: October 2006

Sediment traps were deployed at several depths between 660 and 3800 meters in the Panama Basin. The flux of lithogenic particles increased with increasing depth. This increase was due primarily to particles of beidellite (a smectite clay), which was identical to the clay occurring in bottom sediment on the continental slope to the west of the sediment trap mooring. The beidellite vertical flux at the Panama Basin station increased when an easterly current prevailed and decreased when the current reversed, indicating that a major portion of smectite was transported horizontally at mid-water depth to the mooring site from the nearby continental slope.
Energy and the Oil-Importing Developing Countries
Authors: Dunkerley Joy , Ramsay William
Published: October 2006

Oil-importing developing countries will need more energy during the 1980's to sustain development and to support their subsistence sectors. Development plans must be revised to reflect the potentially disastrous effects of high-cost oil on foreign exchange reserves and on national indebtedness. Energy use efficiency must be increased, and wider use must be made of domestic sources of energy—of conventional fossil and hydro sources and of new and renewable options such as biomass and other solar resources. The international community can help by careful management of world financial flows and trade agreements, expansion of capital assistance, and provision of technical assistance. The importance of improving levels of scientific and technical expertise in the less-developed countries is a challenge to the worldwide scientific and engineering community.
Variables on Scatterplots Look More Highly Correlated When the Scales Are Increased
Authors: Cleveland William S. , Diaconis Persi , McGill Robert
Published: October 2006

Judged association between two variables represented on scatterplots increased when the scales on the horizontal and vertical axes were simultaneously increased so that the size of the point cloud within the frame of the plot decreased. Judged association was very different from the correlation coefficient,r, which is the most widely used measure of association.
Regulated Splicing of the
Drosophila
P Transposable Element Third Intron in Vitro: Somatic Repression
Authors: Siebel Christian W. , Rio Donald C.
Published: October 2006

In eukaryotic cells alternative splicing of messenger RNA precursors (pre-mRNA′s) is a means of regulating gene expression. Although a number of the components that participate in regulating some alternative splicing events have been identified by molecular genetic procedures, the elucidation of the biochemical mechanisms governing alternative splicing requires in vitro reaction systems. The tissue specificity of P element transposition in
Drosophila
depends on the germline restriction of pre-mRNA splicing of the P element third intron (IVS3).
Drosophila
P element IVS3 pre-mRNA substrates were spliced accurately in vitro in heterologous human cell extracts but not in
Drosophila
somatic cell splicing extracts. Components in
Drosophila
somatic cell extracts that specifically inhibited IVS3 splicing in vitro were detected by a complementation assay. Biochemical assays for
Drosophila
RNA binding proteins were then used to detect a 97-kilodalton protein that interacts specifically with 5′ exon sequences previously implicated in the control of IVS3 splicing in vivo. Inhibition of IVS3 splicing in vitro could be correlated with binding of the 97-kD protein to 5′ exon sequences, suggesting that one aspect of IVS3 tissue-specific splicing involves somatic repression by specific RNA-protein interactions.
Long-Term Synaptic Changes Produced by a Cellular Analog of Classical Conditioning in
Aplysia
Authors: Buonomano Dean V. , Byrne John H.
Published: October 2006

A change in synaptic strength arising from the activation of two neuronal pathways at approximately the same time is a form of associative plasticity and may underlie classical or Pavlovian conditioning. A cellular analog of a classical conditioning protocol produces short-term associative plasticity at the connections between sensory and motor neurons in
Aplysia
. A similar training protocol produced long-term (24-hour) enhancement of excitatory postsynaptic potentials (EPSPs). EPSPs produced by sensory neurons in which activity was paired with a reinforcing stimulus were significantly larger than unpaired controls 24 hours after training. Thus, associative plasticity at the sensory to motor neuron connection can occur in a long-term form in addition to the short-term form. In this system, it should be possible to analyze the molecular mechanisms underlying long-term associative plasticity and classical conditioning.
Hypertriglyceridemia as a Result of Human apo
CII
Gene Expression in Transgenic Mice
Authors: Ito Yasushi , Azrolan Neal , O'Connell Anita , Walsh Annemarie , Breslow Jan L.
Published: October 2006

Primary and secondary hypertriglyceridemia is common in the general population, but the biochemical basis for this disease is largely unknown. With the use of transgenic technology, two lines of mice were created that express the human apolipoprotein
CIII
gene. One of these mouse lines with 100 copies of the gene was found to express large amounts of the protein and to be severely hypertriglyceridemic. The other mouse line with one to two copies of the gene expressed low amounts of the protein, but nevertheless manifested mild hypertriglyceridemia. Thus, overexpression of apolipoprotein
CIII
can be a primary cause of hypertriglyceridemia in vivo and may provide one possible etiology for this common disorder in humans.
Molecular Cloning and Functional Expression of Glutamate Receptor Subunit Genes
Authors: Boulter Jim , Hollmann Michael , O'Shea-Greenfield Anne , Hartley Melissa , Deneris Evan , Maron Cornelia , Heinemann Stephen
Published: October 2006

Three closely related genes, GluR1, GluR2, and GluR3, encode receptor subunits for the excitatory neurotransmitter glutamate. The proteins encoded by the individual genes form homomeric ion channels in
Xenopus
oocytes that are sensitive to glutamatergic agonists such as kainate and quisqualate but not to
N
-methyl-D-aspartate, indicating that binding sites for kainate and quisqualate exist on single receptor polypeptides. In addition, kainate-evoked conductances are potentiated in oocytes expressing two or more of the cloned receptor subunits. Electrophysiological responses obtained with certain subunit combinations show agonist profiles and current-voltage relations that are similar to those obtained in vivo. Finally, in situ hybridization histochemistry reveals that these genes are transcribed in shared neuroanatomical loci. Thus, as with γ-aminobutyric acid, glycine, and nicotinic acetylcholine receptors, native kainate-quisqualate-sensitive glutamate receptors form a family of heteromeric proteins.
Spiroplasmas: Diversity of Arthropod Reservoirs and Host-Parasite Relationships
Authors: Clark Truman B.
Published: October 2006

Spiroplasmas were found in 11 new insect hosts representing four orders: Hymenoptera, Hemiptera, Diptera, and Coleoptera. Three of the new spiroplasmas were serologically distinct from all existing groups or subgroups. A spiroplasma that infects digestive tracts of Colorado potato beetles may be transmitted to uninfected insects that feed on contaminated plants. This simple type of spiroplasma-insect relationship may explain a growing list of isolations of spiroplasmas and other wall-less prokaryotes from plant surfaces.
Manipulations of Endosperm Balance Number Overcome Crossing Barriers Between Diploid
Solanum
Species
Authors: Johnston S. A. , Hanneman R. E.
Published: October 2006

Abortion of the hybrid endosperm is the basis for the inability to hybridize many angiosperm species. This has made it nearly impossible to incorporate the valuable characteristics from several wild, diploid
Solanum
species into the cultivated potato
Solanum tuberosum
But some wild species have "endosperm balance numbers" different from those of most
Solanum
diploid species, and these numbers or "effective ploidies" can be manipulated to create new hybrids.
Magnetostratigraphy of Sediments in Mammoth Cave, Kentucky
Authors: Schmidt Victor A.
Published: October 2006

Clastic sediment deposits found within the caves of Mammoth Cave National Park have yielded a magnetostratigraphic pattern of magnetic polarity reversals which indicates-that they were deposited over a range of at least 1 million and most likely 2 million years.
Functional Morphology of
Homo habilis
Authors: Susman Randall L. , Stern Jack T.
Published: October 2006

Olduvai hominid (O.H.) fossils 7, 8, and 35 represent the earliest species of the genus
Homo
dated at 1.76 million years. The O.H. 7 hand, jaw, and skull and the O.H. 8 foot come from one subadult individual, and the O.H. 35 leg are also those of
Homo habilis
. The skeleton represents a mosaic of primitive and derived features, indicating an early hominid which walked bipedally and could fabricate stone tools but also retained the generalized hominoid capacity to climb trees.
Endomycorrhizal Role for Interspecific Transfer of Phosphorus in a Community of Annual Plants
Authors: Chiariello Nona , Hickman James C. , Mooney Harold A.
Published: October 2006

Phosphorus-32 applied to leaves of
Plantago erecta
in a serpentine annual grassland reached the shoots of about 20 percent of the close neighbors. Vesicular-arbuscular mycorrhizae connect the root systems of neighbors of different species and probably mediate nutrient transfers among them. Spatial patterns of transfer show that taxonomic affinity, distance from donor, and size of recipient do not serve as predictors of transfer and that models of transfer by simple diffusion are not appropriate. No alternative predictor was discovered. The results underscore the importance of belowground interactions in explaining neighbor effects, but the factors controlling nutrient transfer and its consequences for community structure appear complex.
Molecular Cloning of Polyoma Virus DNA in
Escherichia coli
: Plasmid Vector System
Authors: Israel Mark A. , Chan Hardy W. , Rowe Wallace P. , Martin Malcolm A.
Published: October 2006

A series of recombinant plasmids containing polyoma virus (PY) DNA were constructed, and their biological activity was evaluated in mice and in cultured mouse cells. While all of the recombinants studied contain the complete, potentially infectious viral DNA, in no case was the intact recombinant PY-plasmid DNA, or live
Escherichia coli
containing the recombinant plasmids, capable of inducing PY infection of mice, either by feeding or by parenteral injection.
Expression of Interleukin-10 Activity by Epstein-Barr Virus Protein BCRF1
Authors: Hsu Di-Hwei , Malefyt Rene de Waal , Fiorentino David F. , Dang Minh-Ngoc , Vieira Paulo , deVries Jan , Spits Hergen , Mosmann Timothy R. , Moore Kevin W.
Published: October 2006

Cytokine synthesis inhibitory factor (CSIF; interleukin-10), a product of mouse TH
2
T cell clones that inhibits synthesis of cytokines by mouse TH
1
T cell clones, exhibits extensive sequence similarity to an uncharacterized open reading frame in the Epstein-Barr virus BCRF1. Recombinant BCRF1 protein mimics the activity of interleukin-10, suggesting that BCRF1 may have a role in the interaction of the virus with the host's immune system.
Calcium Mobilization and Exocytosis After One Mechanical Stretch of Lung Epithelial Cells
Authors: Wirtz Hubert R. W. , Dobbs Leland G.
Published: October 2006

Deep inflation of the lung stimulates surfactant secretion by unknown mechanisms. The hypothesis that mechanical distension directly stimulates type II cells to secrete surfactant was tested by stretching type II cells cultured on silastic membranes. The intracellular Ca2+concentration was measured in single cells, before and after stretching. A single stretch of alveolar type II cells caused a transient (less than 60 seconds) increase in cytosolic Ca2+followed by a sustained (15 to 30 minutes) stimulation of surfactant secretion. Both Ca2+mobilization and exocytosis exhibited dose-dependence to the magnitude of the stretch-stimulus. Thus, mechanical factors can trigger complex cellular events in nonneuron, nonmuscle cells and may be involved in regulating normal lung functions.
Mass Spectrometry of Large, Fragile, and Involatile Molecules
Authors: Busch Kenneth L. , Cooks R. Graham
Published: October 2006

Desorption ionization makes it possible to obtain mass spectra of molecules whose vaporization by heating may lead to thermal degradation. Several methods are in use, but in general desorption is achieved by particle or photon bombardment of the sample and the mass spectra obtained by different methods are fundamentally similar. Desorption ionization techniques have been used to obtain mass spectra of biomolecules, including peptides, antibiotics, and oligosaccharides, for which normal mass spectral methods have been of limited power. Several examples are given of recent applications of these new techniques, and prospects for their further evolution are discussed.
Fossil Land Mammal from Antarctica
Authors: Woodburne Michael O. , Zinsmeister William J.
Published: October 2006

A fossil land mammal, apparently the first found in Antarctica, belongs to the extinct marsupial family Polydolopidae. The fossils were recovered from rocks about 40 million years old on Seymour Island, in the northern Antarctic Peninsula. The newly discovered marsupials support theories that predicted their former presence in Antarctica and strengthen proposals that Australian marsupials perhaps originated from South American species that dispersed across Antarctica when Australia still was attached to it, prior to 56 million years ago.
Heterotrophic Bacteria and Bacterivorous Protozoa in Oceanic Macroaggregates
Authors: Caron David A. , Davis Paul G. , Madin Laurence P. , Sieburth John McN.
Published: October 2006

Oceanic macroaggregates (marine snow and
Rhizosolenia
mats) sampled from the Sargasso Sea are associated with bacterial and protozoan populations up to four orders of magnitude greater than those present in samples from the surrounding water. Filamentous, curved, and spiral bacteria constituted a higher proportion of the bacteria associated with the particles than were found among bacteria in the surrounding water. Protozoan populations were dominated numerically by heterotrophic microflagellates, but ciliates and amoebas were also observed. Macroaggregates are highly enriched heterotrophic microenvironments in the oceans and may be significant for the cycling of particulate organic matter in planktonic food chains.
Chemical Mimicry in the Myrmecophilous BeetleMyrmecaphodius excavaticollis
Authors: Vander Meer Robert K. , Wojcik Daniel P.
Published: October 2006

The myrmecophilus beetleMyrmecaphodius excavaticollis(Blanchard) was found to have species-specific cuticular hydrocarbons acquired-from one of its hosts, the antSolenopsis richteriForel. Removal from its ant host resulted in loss of the host hydrocarbons, leaving a cuticular pattern innate to the beetle. When beetles were transferred to colonies of three otherSolenopsisspecies, they acquired the specific hydrocarbons associated with each of the new hosts. This passive integration mechanism is coupled with the beetle's armored exterior to enable it to cope with multiple aggressive hosts.
Subsurface Valleys and Geoarcheology of the Eastern Sahara Revealed by Shuttle Radar
Authors: McCauley J. F. , Schaber G. G. , Breed C. S. , Grolier M. J. , Haynes C. V. , Issawi B. , Elachi C. , Blom R.
Published: October 2006

The shuttle imaging radar (SIR-A) carried on the space shuttle Columbia in November 1981 penetrated the extremely dry Selima Sand Sheet, dunes, and drift sand of the eastern Sahara, revealing previously unknown buried valleys, geologic structures, and possible Stone Age occupation sites. Radar responses from bedrock and gravel surfaces beneath windblown sand several centimeters to possibly meters thick delineate sand- and alluvium-filled valleys, some nearly as wide as the Nile Valley and perhaps as old as middle Tertiary. The now-vanished major river systems that carved these large valleys probably accomplished most of the erosional stripping of this extraordinarily flat, hyperarid region. Underfit and incised dry wadis, many superimposed on the large valleys, represent erosion by intermittent running water, probably during Quaternary pluvials. Stone Age artifacts associated with soils in the alluvium suggest that areas near the wadis may have been sites of early human occupation. The presence of old drainage networks beneath the sand sheet provides a geologic explanation for the locations of many playas and present-day oases which have been centers of episodic human habitation. Radar penetration of dry sand and soils varies with the wavelength of the incident signals (24 centimeters for the SIR-A system), incidence angle, and the electrical properties of the materials, which are largely determined by moisture content. The calculated depth of radar penetration of dry sand and granules, based on laboratory measurements of the electrical properties of samples from the Selima Sand Sheet, is at least 5 meters. Recent (September 1982) field studies in Egypt verified SIR-A signal penetration depths of at least 1 meter in the Selima Sand Sheet and in drift sand and 2 or more meters in sand dunes.
Leaf Closure in the Venus Flytrap: An Acid Growth Response
Authors: Williams Stephen E. , Bennett Alan B.
Published: October 2006

The rapid closure of leaves in the Venus flytrap (
Dionaea muscipula
) involves irreversible cell enlargement, which can be initiated by acidifying the cell walls to
p
H 4.50 and below. Leaves infiltrated with neutral buffers that keep the
p
H above 4.50 to 4.75 will not close in response to stimulation of their trigger hairs even though the action potentials that ordinarily cause closure are produced. During the 1 to 3 seconds required for closure about 29 percent of the cellular adenosine triphosphate is lost. It is likely that this adenosine triphosphate is used in very rapid transport of hydrogen ions from the motor cells and that the movement is due to a mechanism of "acid growth."
HIP-70: a Protein Induced by Estrogen in the Brain and LH-RH in the Pituitary
Authors: Mobbs C. V. , Fink G. , Pfaff D. W.
Published: October 2006

Estrogen and luteinizing hormone-releasing hormone (LH-RH) interact to influence both behavior and gonadotropin release. However, little is known about the biochemical mechanisms that mediate the effects of these hormones or their interactions. The most prominent protein induced by estrogen in the ventromedial hypothalamus has the same amino-terminal sequence as the most prominent protein induced by LH-RH in the pituitary in vitro and in vivo; these proteins comigrate on two-dimensional gels. Furthermore, the hormonal induction may be caused by modification of a constitutive protein with the same molecular weight (70,000) but a slightly more acidic isoelectric point, whose level is inversely related to the level of the induced form after estrogen treatment. Thus estrogen and LH-RH may interact by additively or synergistically inducing this protein, which is called HIP-70.
Rational Design of Peptide-Based HIV Proteinase Inhibitors
Authors: Roberts Noel A. , Martin Joseph A. , Kinchington Derek , Broadhurst Anne V. , Craig J. Charles , Duncan Ian B. , Galpin Sarah A. , Handa Balraj K. , Kay John , Kröhn Antonin , Lambert Robert W. , Merrett John H. , Mills John S. , Parkes Kevin E. B. , Redshaw Sally , Ritchie Alison J. , Taylor Debra L. , Thomas Gareth J. , Machin Peter J.
Published: October 2006

A series of peptide derivatives based on the transition-state mimetic concept has been designed that inhibit the proteinase from the human immunodeficiency virus (HIV). The more active compounds inhibit both HIV-1 and HIV-2 proteinases in the nanomolar range with little effect at 10 micromolar against the structurally related human aspartic proteinases. Proteolytic cleavage of the HIV-1
gag
polyprotein (p55) to the viral structural protein p24 was inhibited in chronically infected CEM cells. Antiviral activity was observed in the nanomolar range (with one compound active below 10 nanomolar) in three different cell systems, as assessed by p24 antigen and syncytium formation. Cytotoxicity was not detected at 10 and 5 micromolar in C8166 and JM cells, respectively, indicating a high therapeutic index for this new class of HIV proteinase inhibitors.
L-Cysteine, a Bicarbonate-Sensitive Endogenous Excitotoxin
Authors: Olney John W. , Zorumski Charles , Price Madelon T. , Labruyere Joann
Published: October 2006

After systemic administration to immature rodents, L-cysteine destroys neurons in the cerebral cortex, hippocampus, thalamus, and striatum, but the underlying mechanism has never been clarified. This neurotoxicity of L-cysteine, in vitro or in vivo, has now been shown to be mediated primarily through the
N
-methyl-D-aspartate subtype of glutamate receptor (with quisqualate receptor participation at higher concentrations). In addition, the excitotoxic potency of L-cysteine was substantially increased in the presence of physiological concentrations of bicarbonate ion. L-Cysteine is naturally present in the human brain and in the environment, and is much more powerful than β-
N
-methylamino-L-alanine, a bicarbonate-dependent excitotoxin, which has been implicated in an adult neurodegenerative disorder endemic to Guam. Thus, the potential involvement of this common sulfur-containing amino acid in neurodegenerative processes affecting the central nervous system warrants consideration.
Obsidian Dating and East African Archeology
Authors: Michels Joseph W. , Tsong Ignatius S. T. , Nelson Charles M.
Published: October 2006

New experimental procedures have made it possible to establish specific hydration rates for the numerous compositional types of obsidian to be found at archeological sites in Kenya. Two rates are applied to artifacts from the Prospect Farm site, revealing a history of occupation extending back 120,000 years.
Leaf Dimorphism in Aquatic Angiosperms: Significance of Turgor Pressure and Cell Expansion
Authors: Deschamp Paula A. , Cooke Todd J.
Published: October 2006

Depending on environmental conditions, the aquatic angiosperm
Callitriche heterophylia
can develop two different leaf types with distinctive morphological characteristics. Cellular turgor pressure seems to act as the biophysical mechanism responsible for the selection of leaf form in control conditions designed to mimic the natural habitat of this plant. The experimental induction of leaf form involves the ability of various treatments to mediate cell expansion through their effects on turgor pressure or wall extensibility.
Isolation of Agronomically Useful Mutants from Plant Cell Cultures
Authors: Chaleff R. S.
Published: October 2006

Enormous genetic variability is accumulated by plant cells proliferating in culture. Additional variability can be induced in cultured cell populations by exposure to mutagens. This pool of genetic diversity can be examined for agronomically desirable traits at two levels of differentiation. Populations of plants regenerated from callus cultures can be screened by conventional methods. Alternatively, selective culture conditions favoring growth of specific mutant types can be applied at the cellular level. The several characteristics that have been introduced by these methods to date are a harbinger of future contributions to be made by cell culture to the genetic improvement of crops.
Immobilized Enzymes and Cells as Practical Catalysts
Authors: Klibanov Alexander M.
Published: October 2006

Performance of enzymes and whole cells in commercial applications can often be dramatically improved by immobilization of the biocatalysts, for instance, by their covalent attachment to or adsorption on solid supports, entrapment in polymeric gels, encapsulation, and cross-linking. The effect of immobilization on enzymatic properties and stability of biocatalysts is considered. Applications of immobilized enzymes and cells in the chemical, pharmaceutical, and food industries, in clinical and chemical analyses, and in medicine, as well as probable future trends in enzyme technology are discussed.
Carbon-13 and Carbon-14 Abundances in Alaskan Aquatic Organisms: Delayed Production from Peat in Arctic Food Webs
Authors: Schell Donald M.
Published: October 2006

Inputs of terrestrial peat carbon to the nearshore Alaskan Beaufort Sea from erosion and fluvial transport are of the same magnitude as in situ primary production within 10 kilometers of shore. Nevertheless, carbon-13/carbon-12 ratios and carbon-14 abundances in marine organisms show that only small amounts of the terrestrial carbon are transferred beyond the microbial level. Freshwater organisms, however, are heavily dependent on peat, as shown by pronounced seasonal radiocarbon depressions in resident fish and ducks. Tundra ponds and lakes are areas where accumulated terrestrial peat carbon is apparently transferred to aquatic insect larvae and passed on to higher organisms. The lack of functionally analogous abundant marine prey organisms may explain why peat carbon is not efficiently transferred to apical food web species in the marine environment.
Spider Populations: Extraordinarily High Densities on Islands Without Top Predators
Authors: Schoener Thomas W. , Toft Catherine A.
Published: October 2006

Distributions and densities of orb spiders on small islands are extremely variable. Species occurrences are far more irregular for spiders than vertebrates on the same islands. Much variation in spider density is explainable by distance from the presumed source of colonists and presence or absence of vertebrate predators. As has been predicted for passive dispersers, densities decline exponentially with distance. For a given distance, spider densities are about ten times greater on islands without vertebrate predators than on those with such predators.
The Process of Formation of Ocean Crust
Authors: Lewis Brian T. R.
Published: October 2006

Ocean crust is the outermost layer of earth under the oceans. It is separated from the underlying mantle by a seismic transition zone called the Moho. A widely held view is that the Moho represents a petrologic change from basaltic-type rocks to a mantle composed mostly of olivine and pyroxene. According to this view, crust is formed by a steady segregation of basaltic melt, derived from partial melting of the mantle, into a crustal magma chamber wherein cooling and crystallization bring about steady-state accretion to the continuously spreading plates. There is sufficient disagreement between the predictions of this hypothesis and marine geophysical data to cause one to doubt the validity of this formation process. At least two other processes are more compatible with the geophysical data. In one, the crust is formed from the episodic injection of basaltic dikes from a mantle reservoir and the Moho is a primary petrologic boundary. In the other, the crust is treated as a mechanical boundary layer in which thermal contraction results in cracking; by comparison, in the mantle thermal contraction is accommodated by flow. The upper part of the crust is formed from episodic extrusion and intrusion of basaltic melt. The lower crust is formed by rapid hydrothermal alteration of mantle that may be continuously or episodically injected by viscous flow at temperatures below the melting temperature.
The "Decade of the Environment" in the U.S.S.R.
Authors: Pryde Philip R.
Published: October 2006

The decade of the 1970's was for the U.S.S.R, as for the United States, a period of increased awareness of environmental deterioration. In response, new laws were passed, pollution control funding was increased, and natural resource conservation was heavily stressed. Despite such good intentions, the cumulative effects of new technologies, inadequate budgets and enforcement, the primacy of production goals, and various institutional impediments resulted in an uneven and in some places inadequate level of environmental enhancement.
Damselfish as Keystone Species in Reverse: Intermediate Disturbance and Diversity of Reef Algae
Authors: Hixon Mark A. , Brostoff William N.
Published: October 2006

Substrates located within the defended territories of Hawaiian damselfish for 1 year were subjected to intermediate grazing intensity and, as a result, showed greater diversity of algae than substrates either protected within fish-exclusion cages or exposed to intense fish grazing outside territories. Thus, this damselfish enhances local diversity on reefs through "intermediate-disturbance" effects, and is a keystone species that decreases rather than increases overall predation intensity relative to areas where it is absent.
Toward a Theory of Bargaining: An Experimental Study in Economics
Authors: Roth Alvin E.
Published: October 2006

Contemporary economic theories of bargaining depend on aspects of the bargainers' preferences that are difficult to observe. This makes these theories difficult to test in natural environments. It has proved possible, however, to design experiments to test these theories in a controlled, laboratory environment. The results of these experiments reveal shortcomings and incompleteness in the descriptive power of currently available theories of bargaining. However, these results also suggest important regularities in bargaining behavior. Together with recent theoretical developments, these results suggest some directions in which a more descriptively powerful theory of bargaining might be developed.
Ferroelectric Polymers
Authors: Lovinger Andrew J.
Published: October 2006

Piezoelectricity and pyroelectricity, traditionally encountered in certain single crystals and ceramics, have now also been documented in a number of polymers. Recently, one such polymer—poly(vinylidene fluoride)—and some of its copolymers have been shown to be ferroelectric as well. The extraordinary molecular and supermolecular structural requirements for ferroelectric behavior in polymers are discussed in detail, with particular emphasis on poly(vinylidene fluoride). Piezoelectric, pyroelectric, and ferroelectric properties are also briefly reviewed, as are some promising applications of such polymers.
Interphase and Metaphase Resolution of Different Distances Within the Human Dystrophin Gene
Authors: Lawrence Jeanne Bentley , Singer Robert H. , McNeil John A.
Published: October 2006

Fluorescence in situ hybridization makes possible direct visualization of single sequences not only on chromosomes, but within decondensed interphase nuclei, providing a potentially powerful approach for high-resolution (1 Mb and below) gene mapping and the analysis of nuclear organization. Interphase mapping was able to extend the ability to resolve and order sequences up to two orders of magnitude beyond localization on banded or unbanded chromosomes. Sequences within the human dystrophin gene separated by <100 kb to 1 Mb were visually resolved at interphase by means of standard microscopy. In contrast, distances in the 1-Mb range could not be ordered on the metaphase chromosome length. Analysis of sequences 100 kb to 1 Mb apart indicates a strong correlation between interphase distance and linear DNA distance, which could facilitate a variety of gene-mapping efforts. Results estimate chromatin condensation up to 1 Mb and indicate a comparable condensation for different cell types prepared by different techniques.
No Excess of Homozygosity at Loci Used for DNA Fingerprinting
Authors: Devlin B. , Risch Neil , Roeder Kathryn
Published: October 2006

Variable number of tandem repeat (VNTR) loci are extremely valuable for the forensic technique known as DNA fingerprinting because of their hypervariability. Nevertheless, the use of these loci in forensics has been controversial. One criticism of DNA fingerprinting is that the VNTR loci used for the "fingerprints" violate the assumption of Hardy-Weinberg equilibrium (H-W), making it difficult to calculate the probability of observing a genotype in the population. If one can assume H-W, the probability of observing the pair of alleles constituting an individual's genotype can be calculated by taking the product of the alleles' frequencies in the population and multiplying by two if the alleles are different. The evidence cited against assuming H-W is homozygote excess, which is presumed to be caused by an undetected mixture of two or more populations with limited interpopulational mating and distinct allele frequencies. For most VNTR loci, measurement error makes it impossible to test these claims by standard methods. The Lifecodes database of three VNTR loci used for forensics was used to show that the claimed excess of homozygotes is not necessarily real because many heterozygotes with similar allele sizes are misclassified as homozygotes. A simple test of H-W that takes such misclassifications into account was developed to test for an overall excess or dearth of heterozygotes in the sample (the complement of homozygote dearth or excess). The application of this test to the Lifecodes database revealed that there was no consistent evidence of violation of H-W for the Caucasian, black, or Hispanic populations.
Acceleration of Diabetes in Young Nod Mice with a CD4
+
Islet-specific T Cell Clone
Authors: Haskins Kathryn , McDuffie Marcia
Published: October 2006

Nonobese diabetic (NOD) mice develop an autoimmune form of diabetes, becoming hyperglycemic after 3 months of age. This process was accelerated by injecting young NOD mice with CD4
+
islet-specific T cell clones derived from NOD mice. Overt diabetes developed in 10 of 19 experimental animals by 7 weeks of age, with the remaining mice showing marked signs of the disease in progress. Control mice did not become diabetic and had no significant pancreatic infiltration. This work demonstrates that a CD4 T cell clone is sufficient to initiate the disease process in the diabetes-prone NOD mouse.
Venera 13 and Venera 14: Sedimentary Rocks on Venus?
Authors: Florensky C. P. , Basilevsky A. T. , Kryuchkov V. P. , Kusmin R. O. , Nikolaeva O. V. , Pronin A. A. , Chernaya I. M. , Tyuflin Yu. S. , Selivanov A. S. , Naraeva M. K. , Ronca L. B.
Published: October 2006

Venera 13 and Venera 14 transmitted almost complete panoramic views of their landing sites. Analyses of the photographs show the presence of rock formations undergoing geomorphic degradation. The formations display ripple marks, thin layering, differential erosion, and curvilinear fracturings. Some of them are interpreted as lithified clastic sediments. The lithification could have taken place at depth or at the surface, resulting in a type of duricrust. The origin of the sediments is unknown but could be aeolian, volcanic, or related to impacts or to turbidity currents.
Circumglobal Transport of the El Chichón Volcanic Dust Cloud
Authors: Robock Alan , Matson Michael
Published: October 2006

The stratospheric dust cloud from the 4 April 1982 eruption of El Chichón volcano in southern Mexico was observed to travel completely around the world in a 3-week period. Images from satellites operated by the National Oceanic and Atmospheric Administration were used to prepare daily maps of the location of the volcanic dust cloud, which is the largest and longest-lasting one so far observed with satellite imagery.
Direct Embryogenesis from Mesophyll Cells of Orchardgrass
Authors: Conger B. V. , Hanning G. E. , Gray D. J. , McDaniel J. K.
Published: October 2006

Segments taken from the basal 15 to 20 millimeters of the two innermost leaves of an orchardgrass (
Dactylis glomerata
L.) genotype produced somatic (nonzygotic) embryos directly from mesophyll cells without an intervening callus when cultured on an agar medium with 30 micromolar 3,6-dichloro-
o
-anisic acid (dicamba). This demonstration of high-frequency embryogenesis from mesophyll cells in Gramineae is strong evidence for totipotency of the cells.