bluuebunny/crossref_metadata_2025 huggingface dataset:
Agrarian Potential, Population, and the Tarascan State
Authors: Pollard Helen Perlstein , Gorenstein Shirley
Published: October 2006

Estimates based on potential maize crops and maize consumption patterns of the 15th-century Mesoamerican protohistoric Tarascan population living within its geopolitical core (Lake Pátzcuaro Basin) indicate that this population had not maintained itself through agricultural- and lacustrine-carrying capacity alone. It was through having to obtain basic resources such as maize from outside the basin that the Tarascans developed mechanisms that formed the particular character of their state.
Patterning and Assembly of Ciliature Are Independent Processes in Hypotrich Ciliates
Authors: Grimes Gary W. , McKenna Maureen E. , Goldsmith-Spoegler Christina M. , Knaupp Elizabeth A.
Published: October 2006

Mirror-imaged doublets of the hypotrich ciliate
Pleurotricha lanceolata
were induced and analyzed with respect to the overall patterning (structural asymmetry and polarity) of the individual components of the ciliature. The overall pattern is arranged as a mirror image, but the individual components in the two halves of the doublet show the same organizational asymmetry. These data demonstrate the independence of the mechanisms for this kind of large-scale (global) patterning and control of assembly of the individual ciliary components.
Disruptive Coloration in Butterflies: Lack of Support in
Anartia fatima
Authors: Silberglied Robert E. , Aiello Annette , Windsor Donald M.
Published: October 2006

Experimental obliteration of high-contrast wing stripes of the neotropical butterfly
Anartia fatima
affected neither survival nor wing damage in a natural population over a 5-month period. There is no direct evidence supporting the hypothesis that so-called disruptive wing patterns function as protective coloration in butterflies.
Induction of Follicle Separation in the Mosquito by Physiological Amounts of Ecdysterone
Authors: Beckemeyer Elizabeth F. , Lea Arden O.
Published: October 2006

Physiological quantities of the molting hormone, ecdysterone, injected into female
Aedes aegypti
prematurely induced separation of incipient follicles in the ovarioles, an event that normally occurs only in blood-fed females. It was possible to stimulate this morphological event with physiological amounts of hormone by mimicking, with two injections, the timing of normal increases in endogenous hormone of blood-fed females.
Influence of Siphonophore Behavior upon Their Natural Diets: Evidence for Aggressive Mimicry
Authors: Purcell Jennifer E.
Published: October 2006

Collection by divers permitted determination of the natural diets of siphonophore species within 11 genera. Siphonophores that swim rapidly to spread their tentacles capture small prey, whereas those that swim very weakly capture much larger prey. Nematocyst batteries of two species of weak swimmers closely resemble copepods and fish larvae. Morphology, behavior, and diet suggest that these two species attract large prey by mimicking other zooplankton.
A Comparison of Thermal Observations of Mount St. Helens Before and During the First Week of the Initial 1980 Eruption
Authors: St. Lawrence William , Qamar Anthony , Moore Johnnie , Kendrick George
Published: October 2006

Before and during the first week of the March-April 1980 eruptions of Mount St. Helens, Washington, infrared thermal surveys were conducted to monitor the thermal activity of the volcano. The purpose was to determine if an increase in thermal activity had taken place since an earlier airborne survey in 1966. Nine months before the eruption there was no evidence of an increase in thermal activity. The survey during the first week of the 1980 eruptions indicated that little or no change in thermal activity had taken place up to 4 April. Temperatures of ejected ash and steam were low and never exceeded 15°C directly above the vent.
Aminophylline Increases Cerebral Metabolic Rate and Decreases Anoxic Survival in Young Mice
Authors: Thurston Jean Holowach , Hauhard Richard E. , Dirgo John A.
Published: October 2006

In weanling mice treated with pharmacologic doses of aminophylline, the concentrations of adenosine 3′,5′-monophosphate and guanosine 3′,5′-monophosphate in the brain increased 44 and 36 percent, respectively, and the cerebral metabolic rate was three times that in controls. In neonatal mice, therapeutic doses of aminophylline greatly decreased the rate of anoxic survival in vivo and the duration of gasping of the isolated head. The findings suggest caution in the use of this drug and other methylxanthines in hypoxic human newborns.
Geochronology of Wadi Tushka: Lost Tributary of the Nile
Authors: Haynes C. Vance
Published: October 2006

The Sadat Canal, now under construction, is designed to drain excess water from Lake Nasser to the Western Desert by way of Wadi Tushka, a sand-filled, dry-wash tributary of the Nile 34 kilometers north of Abu Simbel. Core-drilling logs made by the Aswan High Dam Authority prior to excavation of the Sadat Canal and along 48 kilometers of its axis reveal as much as 33 meters of unconsolidated sand and gravel over Mesozoic bedrock and under surficial dune sand and playa muds of Holocene age. Excavation of the canal revealed Acheulean artifacts 6.7 meters below the surface in fluvial sediments capped by a buried, red calcic paleosol. These data are interpreted as evidence for the existence of a major tributary of the Nile during the late middle Pleistocene. The tributary drained the Kiseiba-Dungul Depression and possibly the Kharga Depression as well. Chalcedony-armored mudstones in the depressions are believed to be saline lake deposits possibly related to a lake that drained to the Nile by way of Wadi Tushka, thus entrenching the divide between the depression and the valley. Gross correlations with Pleistocene deposits of the Nile Valley and the Kharga Depression are based upon archeological evidence only until more precise geochronology can be applied to the problem.
Upper Wisconsinan Till Recovered on the Continental Shelf Southeast of New England
Authors: Bothner Michael H. , Spiker Elliott C.
Published: October 2006

Basal till was identified in two sediment cores collected about 69 kilometers southeast of Nantucket Island on the east and west sides of Great South Channel. These are the first samples of till collected on the outer continental shelf off the northeastern United States. The carbon-14 age of the total organic carbon in the tills provides a "no older than" age of about 20,000 years before present and suggests that the tills were deposited during the late Wisconsinan glaciation. This conclusion is in support of the hypothesis of an extensive Laurentide ice sheet that extended to the northern side of Georges Bank.
Infectious Diseases and Population Cycles of Forest Insects
Authors: Anderson Roy M. , May Robert M.
Published: October 2006

The regulation of natural populations of invertebrate hosts by viral, bacterial, protozoan, or helminth infections is discussed, using models that combine elements of conventional epidemiology (where the host population is assumed constant) with dynamic elements drawn from predator-prey studies; the apparent absence of acquired immunity in invertebrates simplifies the analysis. Highly pathogenic infections, with long-lived infective stages, tend to produce cyclic behavior in their host populations. The models give an explanation of the 9- to 10-year population cycles of the larch bud moth (
Zeiraphera diniana
) in the European Alps and suggest that microsporidian protozoan and baculovirus infections may be responsible for the 5- to 12-year population cycles observed in many temperate forest insects.
Possible Fluid Dynamical Interpretation of Some Reported Features in the Jovian Atmosphere
Authors: Maxworthy Tony , Redekopp Larry G.
Published: October 2006

Flow patterns of some of the features in the Voyager 1 imaging data for Jupiter appear to be consistent with those predicted by a solitary-wave theory.
Repression of c-
fos
Transcription and an Altered Genetic Program in Senescent Human Fibroblasts
Authors: Seshadri Tara. , Campisi Judith.
Published: October 2006

Normal cells in culture invariably undergo senescence, whereby they cease proliferation after a finite number of doublings. Irreversible changes in gene expression occurred in senescent human fetal lung fibroblasts: a non-cell cycle-regulated mRNA was partially repressed; an unusual polyadenylated histone mRNA was expressed; although serum induced c-H-
ras
, c-
myc
, and ornithine decarboxylase mRNA normally, ornithine decarboxylase activity was deficient; and serum did not induce mRNA for a replication-dependent histone and for the c-
fos
proto-oncogene. The loss of c-
fos
inducibility was the result of a specific, transcriptional block. The results suggest that senescent fibroblasts were unable to proliferate because of, at least in part, selective repression of c-
fos
; moreover, the multiple changes in gene expression support the view that cellular senescence is a process of terminal differentiation.
Growth Inhibition of Transformed Cells with Succinylated Concanavalin A
Authors: Mannino Raphael J. , Ballmer Kurt , Burger Max M.
Published: October 2006

Succinylated concanavalin A reversibly inhibits the growth of SV40 transformed mouse 3T3 cells and thus causes an accumulation of the cells in the G
1
phase of the cell cycle. In a soft substrate (methylcellulose) succinylated concanavalin A also restores in transformed cells the growth behavior typical of untransformed cells.
Cytidine 3′,5′-Monophosphate Phosphodiesterase: Decreased Activity in the Regenerating and Developing Liver
Authors: Shoji Mamoru , Brackett Nancy L. , Kuo J. F.
Published: October 2006

A decrease in the activity of the enzyme cytidine 3′,5′-monophosphate (cyclic CMP) phosphodiesterase was noted in the regenerating liver of young rats as early as 8 hours after partial hepatectomy, with a maximum decrease occurring 12 hours after the surgery. In comparison, in old rats which showed a slower liver growth, the maximum decrease in the activity of cyclic CMP phosphodiesterase was smaller and occurred at a much later time (2 days after surgery). A similar decrease in the enzyme activity was observed in the fetal liver of guinea pigs. These findings suggest that regulation of tissue concentration of cyclic CMP may be crucial for the regeneration and development of the liver.
Novel Fluorogenic Substrates for Assaying Retroviral Proteases by Resonance Energy Transfer
Authors: Matayoshi Edmuund D. , Wang Gary T. , Krafft Grant A. , Erickson John
Published: October 2006

The 11-kD protease (PR) encoded by the human immunodeficiency virus 1 (HIV-1) is essential for the correct processing of viral polyproteins and the maturation of infectious virus, and is therefore a target for the design of selective acquired immunodeficiency syndrome (AIDS) therapeutics. To facilitate the identification of novel inhibitors of HIV-1 PR, as well as to permit detailed studies on the enzymology and inhibition of this enzyme, a continuous assay for its activity was developed that was based on intramolecular fluorescence resonance energy transfer (RET). The assay used the quenched fluorogenic substrate 4-(4-dimethylaminophenylazo)benzoic acid (DABCYL)—Ser Gln Asn Tyr Pro Ile Val Gln—5-[(2-aminoethyl)amino]naphthalene-1 sulfonic acid (EDANS), whose peptide sequence is derived from a natural processing site for HIV-1 PR. Incubation of recombinant HIV-1 PR with the fluorogenic substrate resulted in specific cleavage at the Tyr-Pro bond and a time-dependent increase in fluorescence intensity that was linearly related to the extent of substrate hydrolysis. An internally quenched fluorogenic substrate was also designed that was selectively cleaved by the related PR from avian myeloblastosis virus (AMV). The fluorescence quantum yields of the HIV-1 PR and AMV PR substrates in the RET assay increased by 40.0- and 34.4-fold, respectively, per mole of substrate cleaved. Because of its simplicity, rapidity, and precision in the determination of reaction rates required for kinetic analysis, this method offers many advantages over the commonly used high-performance liquid chromatography- or electrophoresis-based assays for peptide substrate hydrolysis by retroviral PRs.
Isolation of a G Protein that Is Modified by Learning and Reduces Potassium Currents in
Hermissenda
Authors: Nelson Thomas J. , Collin Carlos , Alkon Daniel L.
Published: October 2006

In
Hermissenda crassicornis
conditioned to associate light and rotation, type B photoreceptor neurons exhibit pairing-specific decreases in the potassium currents
I
A
and
I
K-Ca
, which account for many of the behavioral changes elicited by associative conditioning. To determine which proteins are involved in storage of this memory, high-performance liquid chromatography was used to examine proteins from
Hermissenda
eyes. Conditioning-specific changes in four phosphoproteins were observed 24 hours after conditioning. One of these proteins, cp20, was purified to apparent homogeneity and found to be a G protein. When injected back into
Hermissenda
type B cells, cp20 reduced
I
K
and
I
K-Ca
in a manner indistinguishable from the reduction caused by conditioning, suggesting that this protein may play a crucial role in memory acquisition or retention.
A Pleistocene Sand Sea on the Alaskan Arctic Coastal Plain
Authors: Carter L. David
Published: October 2006

A ridge and thermokarst-basin landscape that is strikingly portrayed in Landsat winter imagery consists of large Pleistocene dunes that have been modified by younger eolian activity and thermokarst processes. This is the most extensive area of large stabilized dunes yet reported in the North American Arctic; the landscape is of particular interest because it has been proposed as a first-order analog for martian fretted terrain. Recognition of the large dunes permits a new interpretation for linear and curvilinear trends visible in Landsat summer imagery.
The Great Tumaco, Colombia Earthquake of 12 December 1979
Authors: Herd Darrell G. , Youd T. Leslie , Meyer Hansjürgen , Arango C. Jorge Luis , Person Waverly J. , Mendoza Carlos
Published: October 2006

Southwestern Colombia and northern Ecuador were shaken by a shallow-focus earthquake on 12 December 1979. The magnitude 8 shock, located near Tumaco, Colombia, was the largest in northwestern South America since 1942 and had been forecast to fill a seismic gap. Thrust faulting occurred on a 280- by 130-kilometer rectangular patch of a subduction zone that dips east beneath the Pacific coast of Colombia. A 200-kilometer stretch of the coast tectonically subsided as much as 1.6 meters; uplift occurred offshore on the continental slope. A tsunami swept inland immediately after the earthquake. Ground shaking (intensity VI to IX) caused many buildings to collapse and generated liquefaction in sand fills and in Holocene beach, lagoonal, and fluvial deposits.
Effects of Trace Gases and Water Vapor on the Diffusion Coefficient of Polonium-218
Authors: Frey Gregory , Hopke Philip K. , Stukel James J.
Published: October 2006

The two-filter method described by Thomas and LeClare was used to investigate the effects of trace concentrations of nitric oxide and nitrogen dioxide in dry nitrogen on the diffusion coefficient of radium A (polonium-218). Charged radium A was neutralized in 10 parts per million (ppm) nitrogen dioxide in dry nitrogen, in 8.3 ppm nitric oxide in dry 92 percent nitrogen and 8 percent oxygen, and in nitrogen with 20 and 80 percent relative humidity. No neutralization was seen in dry nitrogen, dry oxygen, dry air, or 10 ppm nitric oxide in dry nitrogen. The diffusion coefficient of the neutral radium A species was found to be 0.079 square centimeters per second, regardless of the relative humidity of the nitrogen gas atmosphere. Lower values were observed for charged species.
Oxygen Isotope Ratios in Trees Reflect Mean Annual Temperature and Humidity
Authors: Burk R. L. , Stuiver M.
Published: October 2006

Values of the oxygen isotope ratios (δ
18
O) in tree-ring cellulose closely reflect the δ
18
O values in atmospheric precipitation and hence mean annual temperature. The change in δ
18
O in cellulose is 0.41 per mil per degree Celsius for selected near-coastal stations. The values of δ
18
O in precipitation and cellulose also change with altitude, as demonstrated for Mount Rainier, Washington. A temperature lapse rate of 5.2° ± 0.5°C per 1000 meters calculated from cellulose δ
18
O values agrees with the accepted mean annual lapse rate of 5°C per 1000 meters for this region. Cellulose δ
18
O values and δ
18
O values of carbon dioxide equilibrated with leaf water differ by a fixed 16 per mil.
Cleavage of Amyloid β Peptide During Constitutive Processing of Its Precursor
Authors: Esch Fred S. , Keim Pamela S. , Beattie Eric C. , Blacher Russell W. , Culwell Alan R. , Oltersdorf Tilman , McClure Donald , Ward Pamela J.
Published: October 2006

The amyloid β peptide (AβP) is a small fragment of the much larger, broadly distributed amyloid precursor protein (APP). Abundant AβP deposition in the brains of patients with Alzheimer's disease suggests that altered APP processing may represent a key pathogenic event. Direct protein structural analyses showed that constitutive processing in human embryonic kidney 293 cells cleaves APP in the interior of the AβP, thus preventing AβP deposition. A deficiency of this processing event may ultimately prove to be the etiological event in Alzheimer's disease that gives rise to senile plaque formation.
Evidence of Sea Spray Produced by Bursting Bubbles
Authors: Wu Jin
Published: October 2006

Measurements of air bubbles and sea spray are compared, showing that bubble bursting is the major mechanism for producing spray.
Biomass Energy from Crop and Forest Residues
Authors: Pimentel David , Moran Mary Ann , Fast Sarah , Weber Georg , Bukantis Robert , Balliett Lisa , Boveng Peter , Cleveland Cutler , Hindman Sally , Young Martin
Published: October 2006

Residues remaining after the harvest of crop and forestry products are being proposed as a substantial energy source for the nation. An estimated 22 percent of the residues might be utilized, providing a renewable source of high-grade energy with the potential of supplying 1 percent of the current U.S. gasoline consumption as ethanol or 4 percent of the total electrical energy used. These net energy benefits are limited by high energy costs to collect, transport, and process the residues. Environmental threats include soil erosion, water runoff, and nutrient loss.
Melting of Normal Hydrogen Under High Pressures Between 20 and 300 Kelvins
Authors: Diatschenko V. , Chu C. W.
Published: October 2006

The melting curve of normal hydrogen has been determined up to 52 kilobars between 20 and 300 Kelvins. The results are in excellent agreement with the modified Simon equation proposed for hydrogen below 19 kilobars, but not with the existing theoretical predictions. The results also provide an independent check on the validity of the ruby high-pressure scale at low temperature.
Invertebrate Collagens
Authors: Adams Elijah
Published: October 2006

The collagens of all major invertebrate phyla have been studied, but characterization has been thorough in only a few classes and in no case in the detail (such as sequence analysis) known for vertebrate collagen. Biochemical data on insect collagen are particularly sparse. Invertebrate and vertebrate collagens are strikingly similar, with some notably unique features in annelids and nematodes. Present data do not support the suggestion that invertebrate collagens resemble vertebrate basement membrane collagen. In invertebrates, as in vertebrates, collagens of specific tissues show differences that probably reflect individual tissue requirements.
State of Stress and Intraplate Earthquakes in the United States
Authors: Zoback Mark D. , Zoback Mary Lou
Published: October 2006

Recently compiled data on the state of stress have been used to define stress provinces in the conterminous United States in which the orientation and relative magnitude of the horizontal principal stresses are fairly uniform. The observed patterns of stress constrain mechanisms for generating intraplate lithospheric stresses. Coupled with new information on geologic structure and tectonism in seismically active areas of the Midcontinent and East, these data help to define some characteristics common to these areas and to identify key questions regarding why certain faults seem to be seismically active.
Evidence for Extensive Overlap of Sporophytic and Gametophytic Gene Expression in
Lycopersicon esculentum
Authors: Tanksley Steven D. , Zamir Daniel , Rick Charles M.
Published: October 2006

Male gametophyte (pollen) isozyme profiles were compared with those of the sporophyte for nine enzyme systems. Sixty percent of the structural genes coding for these enzymes in the sporophyte were also found to be expressed by the gametophyte. All the genes tested were found to be expressed after meiosis, apparently transcribed and translated in the haploid gametophytes.
Cellular Interactions Uncouple β-Adrenergic Receptors from Adenylate Cyclase
Authors: Ciment Gary , de Vellis Jean
Published: October 2006

C6 glioma cells and B104 neuroblastoma cells both possess adenylate cyclase activity, but only C6 cells have β-adrenergic receptors. However, when cocultured with B104 cells, C6 cells show a marked decrease in their ability to accumulate adenosine 3′,5′-monophosphate upon stimulation with β receptor agonists. Since both β receptors and cholera toxin-stimulated adenylate cyclase activities are present in C6/B104 cocultures, we conclude that the β receptor/adenylate cyclase transduction mechanism in cocultured C6 cells is uncoupled.
Interaction Between the Antibiotic Trichothecenes and the Higher Plant
Baccharis megapotamica
Authors: Jarvis Bruce B. , Midiwo Jacob O. , Tuthill David , Bean George A.
Published: October 2006

The Brazilian shrub
Baccharis megapotamica
contains significant amounts of antibiotic trichothecenes. When these plants are grown in the United States, they are devoid of the mycotoxins. Feeding experiments with fungus-produced trichothecenes show that
Baccharis megapotamica
absorbs, translocates, and chemically alters these compounds to ones with structures analogous to those found in the plant in its native habitat. The mycotoxins, which have no apparent ill effect in
Baccharis megapotamica,
kill tomatoes, peppers, and artichokes
.
Bat Predation and the Evolution of Frog Vocalizations in the Neotropics
Authors: Tuttle Merlin D. , Ryan Michael J.
Published: October 2006

Bat predation has probably had an important influence on the evolution of frog vocalizations in the Neotropics. The rate at which fringe-lipped bats capture frogs is significantly higher when the frogs are calling. These bats respond to a wide variety of calls from edible frogs, and, when simultaneously presented with a choice, choose the recorded call of a palatable species over that of a poisonous species and the call of a small species over that of one too large to capture. Thus the selective advantages of loud, rapid mating calls in anurans are balanced by an increased risk of predation.
Large-Scale Air-Sea Interactions and Short-Period Climatic Fluctuations
Authors: Namias Jerome , Cayan Daniel R.
Published: October 2006

Research during the last 15 years has shown that there is order in large-scale air-sea interactions, so that space scales of abnormalities of the lower atmosphere's circulation and the upper oceanic thermal structure are comparable. Because of this air-sea coupling, each oceanic or atmospheric pattern can be reasonably well specified by the other. Patterns of oceanic thermal anomalies are about an order of magnitude more persistent than those of atmospheric circulations, and empirical studies have had some success in using sea surface temperature patterns in long-range weather prediction. In addition to empirical studies, efforts continue in the development of numerical-dynamical models in order to understand the complex linkages of the large-scale air-sea system.
Plasma Observations Near Saturn: Initial Results from Voyager 2
Authors: Bridge H. S. , Bagenal F. , Belcher J. W. , Lazarus A. J. , McNutt R. L. , Sullivan J. D. , Gazis P. R. , Hartle R. E. , Ogilvie K. W. , Scudder J. D. , Sittler E. C. , Eviatar A. , Siscoe G. L. , Goertz C. K. , Vasyliunas V. M.
Published: October 2006

Results of measurements of plasma electrons and positive ions made during the Voyager 2 encounter with Saturn have been combined with measurements from Voyager 1 and Pioneer 11 to define more clearly the configuration of plasma in the Saturnian magnetosphere. The general morphology is well represented by four regions: (i) the shocked solar wind plasma in the magnetosheath, observed between about 30 and 22 Saturn radii (
R
S
) near the noon meridian; (ii) a variable density region between ∼17
R
S
and the magnetopause; (iii) an extended thick plasma sheet between ∼17 and ∼7
R
S
symmetrical with respect to Saturn's equatorial plane and rotation axis; and (iv) an inner plasma torus that probably originates from local sources and extends inward from
L
≈ 7 to less than
L
≈ 2.7 (
L
is the magnetic shell parameter). In general, the heavy ions, probably O
+
, are more closely confined to the equatorial plane than H
+
, so that the ratio of heavy to light ions varies along the trajectory according to the distance of the spacecraft from the equatorial plane. The general configuration of the plasma sheet at Saturn found by Voyager 1 is confirmed, with some notable differences and additions. The "extended plasma sheet," observed between
L
≈ 7 and
L
≈ 15 by Voyager 1 is considerably thicker as observed by Voyager 2. Inward of
L
≈ 4, the plasma sheet collapses to a thin region about the equatorial plane. At the ring plane crossing,
L
≈ 2.7, the observations are consistent with a density of O
+
of ∼100 per cubic centimeter, with a temperature of ∼10 electron volts. The location of the bow shock and magnetopause crossings were consistent with those previously observed. The entire magnetosphere was larger during the outbound passage of Voyager 2 than had been previously observed; however, a magnetosphere of this size or larger is expected ∼3 percent of the time.
Energetic Charged Particles in Saturn's Magnetosphere: Voyager 2 Results
Authors: Vogt R. E. , Chenette D. L. , Cummings A. C. , Garrard T. L. , Stone E. C. , Schardt A. W. , Trainor J. H. , Lal N. , McDonald F. B.
Published: October 2006

Results from the cosmic-ray system on Voyager 2 in Saturn's magnetosphere are presented. During the inbound pass through the outer magnetosphere, the ≥ 0.43-million-electron-volt proton flux was more intense, and both the proton and electron fluxes were more variable, than previously observed. These changes are attributed to the influence on the magnetosphere of variations in the solar wind conditions. Outbound, beyond 18 Saturn radii, impulsive bursts of 0.14- to > 1.0-million-electron-volt electrons were observed. In the inner magnetosphere, the charged particle absorption signatures of Mimas, Enceladus, and Tethys are used to constrain the possible tilt and offset of Saturn's internal magnetic dipole. At ∼ 3 Saturn radii, a transient decrease was observed in the electron flux which was not due to Mimas. Characteristics of this decrease suggest the existence of additional material, perhaps another satellite, in the orbit of Mimas.
Expression of β-Nerve Growth Factor Receptor mRNA in Sertoli Cells Downregulated by Testosterone
Authors: Persson Håkan , Ayer-Le Lievre Christiane , Söder Olof , Villar Marcelo J. , Metsis Madis , Olson Lars , Ritzen Martin , Hökfelt Tomas
Published: October 2006

Nerve growth factor (NGF) is synthesized in male germ cells. The NGF receptor (NGFR) mRNA was found in the Sertoli cells of rat testis. Hypophysectomy increased both NGFR mRNA in testis and the number of NGFR hybridizing cells in seminiferous tubules. This was suppressed by treatment with chorionic gonadotropin or testosterone, but not with follicle-stimulating hormone. The NGFR mRNA also increased after destruction of Leydig cells or blocking of the androgen receptor. This suggests that NGF produced by male germ cells regulates testicular function in an androgen-modulated fashion by mediating an interaction germ and Sertoli cells.
Uptake of Dissolved Sulfide by
Spartina alterniflora
: Evidence from Natural Sulfur Isotope Abundance Ratios
Authors: Carlson Paul R. , Forrest Joseph
Published: October 2006

The difference in the stable sulfur isotope ratios of sulfate and sulfide in marsh pore water was used to verify the uptake of hydrogen sulfide by the salt marsh cordgrass
Spartina alterniflora
in a North Carolina salt marsh. Most of the plant sulfur derived from pore-water sulfide was recovered as sulfate, an indication that the sulfide had been oxidized within the plant. The analysis of the sulfur isotope ratios of other coastal halophytes may be a useful technique for determining whether sulfide is taken up by plants in saline wetlands.
Is Sperm Cheap? Limited Male Fertility and Female Choice in the Lemon Tetra (Pisces, Characidae)
Authors: Nakatsuru Ken , Kramer Donald L.
Published: October 2006

In the laboratory, fertilization rates achieved by male lemon tetras decline with spawning frequency. Even when the number of females is not limited, males can produce only four times as many offspring as females. Females show a preference for males that have not recently spawned as opposed to those that have. The cost of producing sufficient sperm to maximize fertilization rates may therefore reduce the intensity of sexual selection in this polygamous fish species.
Stable-Carbon Isotope Ratios as a Measure of Marine Versus Terrestrial Protein in Ancient Diets
Authors: Chisholm Brian S. , Nelson D. Erle , Schwarcz Henry P.
Published: October 2006

The stable-carbon isotope ratios for the flesh of marine and terrestrial animals from Canada's Pacific coast differ by 7.9 ± 0.4 per mil, reflecting the ∼ 7 per mil difference between oceanic and atmospheric carbon. This difference is passed on to human consumers. The carbon isotopic values (δ
13
C) for human collagen thus yield direct information on the relative amounts of marine and terrestrial foods in prehistoric diets.
Venus: Halide Cloud Condensation and Volatile Element Inventories
Authors: Lewis John S. , Fegley Bruce
Published: October 2006

Several recently suggested Venus cloud condensates, including aluminum chloride and halides, oxides, and sulfides of arsenic and antimony, are assessed for their thermodynamic and geochemical plausibility. Aluminum chloride can confidently be ruled out, and condensation of arsenic sulfides on the surface will cause arsenic compounds to be too rare to produce the observed clouds. Antimony may be sufficiently volatile, but the expected molecular form is gaseous antimony sulfide, not the chloride. Arsenic and antimony compounds in the atmosphere will be regulated at very low levels by sulfide precipitation, irrespective of the planetary inventory of arsenic and antimony. Thus arguments for a volatile-deficient origin for Venus based on depletion of water and mercury (relative to the earth) cannot be tested by a search for atmospheric arsenic or antimony.
A Receptor for Tumor Necrosis Factor Defines an Unusual Family of Cellular and Viral Proteins
Authors: Smith Craig A. , Davis Terri , Anderson Dirk , Solam Lisabeth , Beckmann M. Patricia , Jerzy Rita , Dower Steven K. , Cosman David , Goodwin Raymond G.
Published: October 2006

Tumor necrosis factor α and β (TNF-α and TNF-β) bind surface receptors on a variety of cell types to mediate a wide range of immunological responses, inflammatory reactions, and anti-tumor effects. A cDNA clone encoding an integral membrane protein of 461 amino acids was isolated from a human lung fibroblast library by direct expression screening with radiolabeled TNF-α. The encoded receptor was also able to bind TNF-β. The predicted cysteine-rich extracellular domain has extensive sequence similarity with five proteins, including nerve growth factor receptor and a transcriptionally active open reading frame from Shope fibroma virus, and thus defines a family of receptors.
Pollination and Airflow Patterns Around Conifer Ovulate Cones
Authors: Niklas Karl J. , Paw U Kyaw Tha
Published: October 2006

Wind-tunnel studies indicate that the geometry of
Pinus
ovulate cones may enhance the probability of pollen entrapment by aerodynamically predetermining airflow patterns around scale-bract complexes. Pollination experiments reveal that pollen from a particular species has the highest probability of reaching the ovules of its own species. The phenomenon of species-specific pollination appears to be related to the specific morphometry of scale-bract complexes and the terminal settling velocity of pollen of the same species. These data are interpreted as evidence for a reciprocity between the aerodynamic characteristics of airborne pollen and ovulate cones of some conifer species.
Changes in the Cell Membranes of the Bullfrog Gastric Mucosa with Acid Secretion
Authors: Clausen Chris , Machen Terry E. , Diamond Jared M.
Published: October 2006

The effective area, resistance, and configuration of the apical and basolateral cell membranes of the bullfrog gastric mucosa were studied as a function of acid secretion rate, by alternating-current impedance methods. The drop in transepithelial resistance with acid secretion is attributed to the great increase in apical membrane area (hence conductance) associated with tubulovesicles. There is no evidence of a change in basolateral membrane resistance or of apical membrane permeability per unit area.
Early Enhancement of Calcium Currents by H-
ras
Oncoproteins Injected into
Hermissenda
Neurons
Authors: Collin Carlos , Papageorge Alex G. , Lowy Douglas R. , Alkon Daniel L.
Published: October 2006

Influx of calcium through membrane channels is an important initial step in signal transduction of growth signals. Therefore, the effects of Ras protein injection on calcium currents across the soma membrane of an identified neuron of the snail
Hermissenda
were examined. With the use of these post-mitotic cells, a voltage-sensitive, inward calcium current was increased 10 to 20 minutes after Harvey-
ras
oncoproteins were injected. The effects of oncogenic Harvey
ras
p21 protein (v-Ras) occurred quickly and were sustained, whereas the effects of proto-oncogenic
ras
protein (c-Ras) were transient. This relative potency is consistent with the activities of these oncoproteins in stimulating cell proliferation. Thus, this calcium channel may be a target for Ras action.
Collapse of Gels in an Electric Field
Authors: Tanaka Toyoichi , Nishio Izumi , Sun Shao-Tang , Ueno-Nishio Shizue
Published: October 2006

An infinitesimal change in electric potential across a polyelectrolyte gel produces a discrete, reversible volume change. The volume of the collapsed gel can be several hundred times smaller than that of the swollen gel.
The Sperm Attractant of the Marine Brown Alga
Ascophyllum nodosum
(Phaeophyceae)
Authors: Müller D. G. , Gassmann G. , Marner F.-J. , Boland W. , Jaenicke L.
Published: October 2006

Spermatozoids of the intertidal seaweed
Ascophyllum nodosum
(Fucales, Phaeophyceae) are attracted to eggs prior to fertilization. The attractant has been isolated and its structure identified as 1(3
E
,5
Z
,8
Z
)-undecatetraene (finavarrene). The relation of finavarrene to sex hormones in other brown algae is discussed.
The Use of Strontium-87/Strontium-86 Ratios to Measure Atmospheric Transport into Forested Watersheds
Authors: Graustein William C. , Armstrong Richard L.
Published: October 2006

Strontium-87/strontium-86 ratios indicate the sources of strontium in samples of natural waters, vegetation, and soil material taken from watersheds in the Sangre de Cristo Mountains of New Mexico. More than 75 percent of the strontium in the vegetation is ultimately derived from atmospheric transport and less than 25 percent from the weathering of the underlying rock. Much of the airborne strontium enters the watersheds by impacting on coniferous foliage, but deciduous foliage apparently traps little, if any, strontium-bearing aerosol. The strontium and presumably other nutrients are continuously recycled in a nearly closed system consisting of upper soil horizons, forest litter, and the standing crop of vegetation.
Regulation of Queen Number by Workers in Colonies of Social Insects
Authors: Fletcher David J. C. , Blum Murray S.
Published: October 2006

Experiments with fire ants suggest that queen pheromones act quantitatively in the regulation of queen number in colonies of social insects. Specific mechanisms probably include recognition by workers of unique quantitative blends of pheromones produced by queens, and quantitative effects of pheromones acting at the level of the colony on workers and at the level of the individual on queens. Several aspects of this quantitative hypothesis of pheromone action were tested.
Quaternary Pollen Record from Laguna de Tagua Tagua, Chile
Authors: Heusser Calvin J.
Published: October 2006

Pollen of southern beech and podocarp at Laguna de Tagua Tagua during the late Pleistocene indicates that cooler and more humid intervals were a feature of Ice Age climate at this subtropical latitude in Chile. The influence of the southern westerlies may have been greater at this time, and the effect of the Pacific anticyclone was apparently weakened. The climate today, wet in winter and dry in summer, supports broad sclerophyll vegetation that developed during the Holocene with the arrival of paleo-Indians and the extinction of mastodon and horse.
Selection, Outbreeding Depression, and the Sex Ratio of Scale Insects
Authors: Alstad D. N. , Edmunds G. F.
Published: October 2006

The black pineleaf scale insect has haploid males and diploid females. Ratios of males to females late in development ranged from 0.005 to 0.320 among insect subpopulations that were infesting different host trees. Demes well adapted to an individual ponderosa pine had a higher proportion of males than did demes that were poorly adapted to the host. Ratios of males to females rose in successive annual samples as natural selection increased insect adaptation. Gene flow between demes on different host trees produced predictable changes in the sex ratio.
Behavior of Antarctic Krill,
Euphausia superba:
Chemoreception, Feeding, Schooling, and Molting
Authors: Hamner William M. , Hamner Peggy P. , Strand Steven W. , Gilmer Ronald W.
Published: October 2006

Krill do not feed by passive, continuous filtration but use area-intensive searching and various rapid feeding behaviors to exploit local high food concentrations. Chemicals alone at low concentrations, not particles, trigger feeding. Krill form dense schools that move rapidly and migrate primarily horizontally. Abrupt disruption of a school can trigger mass molting, and molts may act as decoys.
Van der Waals Picture of Liquids, Solids, and Phase Transformations
Authors: Chandler David , Weeks John D. , Andersen Hans C.
Published: October 2006

The van der Waals picture focuses on the differing roles of the strong short-ranged repulsive intermolecular forces and the longer ranged attractions in determining the structure and dynamics of dense fluids and solids. According to this physical picture, the attractive interactions help fix the volume of the system, but the arrangements and motions of molecules within that volume are determined primarily by the local packing and steric effects produced by the repulsive forces. This very useful approach, its limitations, and its successful application to a wide variety of static and dynamic phenomena in condensed matter systems are reviewed.
Acquisition of Digestive Enzymes by Siricid Woodwasps from Their Fungal Symbiont
Authors: Kukor Jerome J. , Martin Michael M.
Published: October 2006

Larvae of the woodwasp.
Sirex cyaneus
, contain midgut digestive enzymes that enable them to utilize the major fungal and plant polysaccharides found in their food. At least two classes of enzymes, the C
x
-cellulases and the xylanases, are not produced by the larvae. Instead, larvae acquire these enzymes while ingesting tissue of
Amylostereum chailletii
, the fungal symbiont that occurs in the wood on which the larvae feed.
Bovine Growth Hormone: Human Food Safety Evaluation
Authors: Juskevich Judith C. , Guyer C. Greg
Published: October 2006

Scientists in the Food and Drug Administration (FDA), after reviewing the scientific literature and evaluating studies conducted by pharmaceutical companies, have concluded that the use of recombinant bovine growth hormone (rbGH) in dairy cattle presents no increased health risk to consumers. Bovine GH is not biologically active in humans, and oral toxicity studies have demonstrated that rbGH is not orally active in rats, a species responsive to parenterally administered bGH. Recombinant bGH treatment produces an increase in the concentration of insulin-like growth factor-I (IGF-I) in cow's milk. However, oral toxicity studies have shown that bovine IGF-I lacks oral activity in rats. Additionally, the concentration of IGF-I in milk of rbGH-treated cows is within the normal physiological range found in human breast milk, and IGF-I is denatured under conditions used to process cow's milk for infant formula. On the basis of estimates of the amount of protein absorbed intact in humans and the concentration of IGF-I in cow's milk during rbGH treatment, biologically significant levels of intact IGF-I would not be absorbed.
Environmental Component of Morphological Differentiation in Birds
Authors: James Frances C.
Published: October 2006

Geographic character variation in birds is usually attributed to natural selection for phenotypes that reflect locally adapted genetic differences. However, experimental transplants of red-winged blackbird eggs between nests in northern and southern Florida, and from Colorado to Minnesota, show that in this species a significant proportion of the regional differences in nestling development is nongenetic. If natural selection is maintaining the clines of character variation that are observed in adult phenotypes, the genetic and nongenetic components of phenotypic variation must covary.
Sequence of the 16
S
Ribosomal RNA from
Halobacterium volcanii
, an Archaebacterium
Authors: Gupta Ramesh , Lanter Jan M. , Woese Carl R.
Published: October 2006

The sequence of the 16
S
ribosomal RNA (rRNA) from the archaebacterium
Halobacterium volcanii
has been determined by DNA sequencing methods. The archaebacterial rRNA is similar to its eubacterial counterpart in secondary structure. Although it is closer in sequence to the eubacterial 16
S
rRNA than to the eukaryotic 16
S
-like rRNA, the
H. volcanii
sequence also shows certain points of specific similarity to its eukaryotic counterpart. Since the
H. volcanii
sequence is closer to both the eubacterial and eukaryotic sequences than these two are to one another, it follows that the archaebacterial sequence is more like the common ancestral sequence than at least one of the other two versions.
Direct Interaction of a Ligand for the
erb
B2 Oncogene Product with the EGF Receptor and p185

erb
B2
Authors: Lupu Ruth , Colomer Ramon , Zugmaier Gerhard , Sarup Jay , Shepard Michael , Slamon Dennis , Lippman Marc E.
Published: October 2006

The
erb
B2 oncogene encodes a 185-kilodalton transmembrane protein whose sequence is similar to the epidermal growth factor receptor (EGFR). A 30-kilodalton factor (gp30) secreted from MDA-MB-231 human breast cancer cells was shown to be a ligand for p185

erb
B2

. An antibody to EGFR abolished the tyrosine phosphorylation induced by EGF and transforming growth factor-α (TGF-α) but only partially blocked that produced by gp30 in SK-BR-3 breast cancer cells. In two cell lines that overexpress
erb
B2 but do not express EGFR (MDA-MB-453 breast cancer cells and a Chinese hamster ovary cell line that had been transfected with
erb
B2), phosphorylation of p185

erb
B2

was induced only by gp30. The gp30 specifically inhibited the growth of cells that overexpressed p185

erb
B2

. An antibody to EGFR had no effect on the inhibition of SK-BR-3 cell colony formation obtained with gp30. Thus, it appeared that gp30 interacted directly with the EGFR and
erb
B2. Direct binding of gp30 to p185

erb
B2

was confirmed by binding competition experiments, where gp30 was found to displace the p185

erb
B2

binding of a specific antibody to p185

erb
B2

. The evidence described here suggests that gp30 is a ligand for p185

erb
B2

.
ACTH and Vasopressin Treatments Immediately After a Defeat Increase Future Submissiveness in Male Mice
Authors: Roche Kerry E. , Leshner Alan I.
Published: October 2006

Male mice were given a single injection of either adrenocorticotropic hormone (ACTH) or lysine vasopressin immediately after a defeat in an encounter with an aggressive male mouse. The defeated mice were tested for submissiveness at either 24 hours, 48 hours, or 7 days after the initial encounter. Both hormone treatments increased future submissiveness, although the time courses of the effects were different: The effects of ACTH disappeared after 48 hours, whereas those of vasopressin persisted for 7 days. These results suggest that changes in peptide hormone levels following naturally stressful experiences can affect the memory of those experiences, as expressed in future adaptive responses.
Morphogenesis in
Dictyostelium
: An Orbital Hypothesis
Authors: Clark Robert L. , Steck Theodore L.
Published: October 2006

Free-living amoebae of
Dictyostelium discoideum
aggregate when deprived of food, guided by the intercellular transmission of signals of adenosine 3′,5′-monophosphate. A succession of multicellular forms is then constructed, each with a circular cross section in every plane normal to its central axis. Amoebae are in constant circular and helical motion around the circumference of these structures. A theory is proposed wherein the sustained propagation of waves of cyclic adenosine 3′,5′-monophosphate secretion in cellular loops determines their circumference and thereby organizes morphogenesis in this organism.
Terminal Cretaceous Extinctions in the Hell Creek Area, Montana: Compatible with Catastrophic Extinction
Authors: Smit J. , van der Kaars S.
Published: October 2006

Inaccurate stratigraphic correlations in the Hell Creek area, Montana, have led to the assumption that transitional vertebrate faunas (Bug Creek Anthills) exist in the latest Cretaceous, refuting a catastrophic turnover at the Cretaceous-Tertiary boundary. Establishment of the transitional faunas in Paleocene channels that cut down through the Cretaceous-Tertiary boundary renders the terrestrial faunal record compatible with the marine record and with catastrophic extinction.
Catastrophic Storms, El Niño, and Patch Stability in a Southern California Kelp Community
Authors: Dayton Paul K. , Tegner Mia J.
Published: October 2006

Strong winter storms in southern California destroyed most of the canopy of the giant kelp
Macrocystis pyrifera
but not the patches of understory kelps in the Point Loma kelp forest near San Diego. Subsequent massive recruitment of
Macrocystis
juveniles and adults that survived the storms had low survival in the summer during the California El Niño of 1983. The combined disturbance may have long-lasting structural consequences for this community because, once established, the understory patches can resist invasion by
Macrocystis
.
Chromosome Organization and Heterochromatin Elimination in
Parascaris
Authors: Goday Clara , Pimpinelli Sergio
Published: October 2006

A cytological analysis by modern banding techniques of gonial metaphases in two
Parascaris
forms that have been considered varieties but now seem to be two species [
P. univalens
(karyotype 2
n
= 2) and
P. equorum
(karyotype 2
n
= 4)] reveals a different chromosome organization in each.
Parascaris univalens
chromosomes contain only terminal heterochromatin, while
P. equorum
chromosomes also contain intercalary heterochromatin. In the somatic cells of both species during early embryogenesis, chromatin diminution occurs in and consists of the elimination of all heterochromatin independent of its localization in the chromosomes.