bluuebunny/crossref_metadata_2025 huggingface dataset:
Resource Partitioning in Ecological Communities
Authors: Schoener Thomas W.
Published: October 2006

To understand resource partitioning, essentially a community phenomenon, we require a holistic theory that draws upon models at the individual and population level. Yet some investigators are still content mainly to document differences between species, a procedure of only limited interest. Therefore, it may be useful to conclude with a list of questions appropriate for studies of resource partitioning, questions this article has related to the theory in a preliminary way.

1) What is the mechanism of competition? What is the relative importance of predation? Are differences likely to be caused by pressures toward reproductive isolation?

2) Are niches (utilizations) regularly spaced along a single dimension?

3) How many dimensions are important, and is there a tendency for more dimensions to be added as species number increases?

4) Is dimensional separation complementary?

5) Which dimensions are utilized, how do they rank in importance, and why? How do particular dimensions change in rank as species number increases?

6) What is the relation of dimensional separation to difference in phenotypic indicators? To what extent does the functional relation of phenotype to resource characteristics constrain partitioning?

7) What is the distance between mean position of niches, what is the niche standard deviation, and what is the ratio of the two? What is the niche shape?
Expression of the Familial Hypercholesterolemia Gene in Heterozygotes: Mechanism for a Dominant Disorder in Man
Authors: Brown Michael S. , Goldstein Joseph L.
Published: October 2006

Studies in cultured fibroblasts indicate that the primary genetic abnormality in familial hypercholesterolemia involves a deficiency in a cell surface receptor for low density lipoproteins (LDL). In normal cells, binding of LDL to this receptor regulates cholesterol metabolism by suppressing cholesterol synthesis and increasing LDL degradation. In cells from heterozygotes, a 60 percent reduction in LDL receptors leads to a concentration-dependent defect in regulation, so that attainment of equal rates of cholesterol synthesis and LDL degradation in normal and heterozygous cells requires a two- to threefold higher concentration of LDL in the heterozygote. The identification of this genetic regulatory defect in fibroblasts of heterozygotes makes available an in vitro system for studying the effects of a dominant mutation on gene expression in mammalian cells.
Lassa Virus Isolation from
Mastomys natalensis
Rodents during an Epidemic in Sierra Leone
Authors: Monath Thomas P. , Newhouse Verne F. , Kemp Graham E. , Setzer Henry W. , Cacciapuoti Anthony
Published: October 2006

Lassa fever is a severe febrile illness of man, first recognized in West Africa in 1969. During an epidemic in Sierra Leone, Lassa virus was isolated for the first time from wild rodents of
Mastomys natalensis
. A high prevalence of infected
Mastomys
was found in houses occupied by patients with Lassa fever. The data presented provide the first demonstration of an extra-human cycle of Lassa virus transmission and suggest that rodent control may be an effective method of limiting the disease.
Three-Dimensional Tertiary Structure of Yeast Phenylalanine Transfer RNA
Authors: Kim S. H. , Suddath F. L. , Quigley G. J. , McPherson A. , Sussman J. L. , Wang A. H. J. , Seeman N. C. , Rich Alexander
Published: October 2006

The 3-angstrom electron density map of crystalline yeast phenylalanine transfer RNA has provided us with a complete three-dimensional model which defines the positions of all of the nucleotide residues in the molecule. The overall features of the molecule are virtually the same as those seen at a resolution of 4 angstroms except that many additional details of tertiary structure are now visualized. Ten types of hydrogen bonding are identified which define the specificity of tertiary interactions. The molecule is also stabilized by considerable stacking of the planar purines and pyrimidines. This tertiary structure explains, in a simple and direct fashion, chemical modification studies of transfer RNA. Since most of the tertiary interactions involve nucleotides which are common to all transfer RNA's, it is likely that this three-dimensional structure provides a basic pattern of folding which may help to clarify the three-dimensional structure of all transfer RNA's.
Lysosomal and Microsomal Glucuronidase: Genetic Variant Alters Electrophoretic Mobility of Both Hydrolases
Authors: Lalley Peter A. , Shows Thomas B.
Published: October 2006

An electrophoretic variant of β-glucuronidase is present in certain inbred mouse lines. The variant simultaneously affects the mobility of the lysosomal and microsomal forms of the enzyme. The difference is inherited as a single gene mapping at the position of the structural gene on chromosome 5. This confirms that β-glucuronidase at both intracellular sites is coded by the same structural gene.
Brave New World?
Authors: Motulsky Arno G.
Published: October 2006

Recent developments in biology and medicine are raising new problems in the prevention and treatment of birth defects, and in research on these diseases. The problems include immediate issues such as genetic counseling, abortion for birth defects, the withholding of complex treatments from individuals in some situations, screening for genetic and other diseases, artificial insemination, and fertilization in vitro. Other problems, such as the dysgenic effects of modern medicine and the possibilities of cloning and gene therapy, are more remote. Each of these issues should be considered on its own merits and by its immediate and remote consequences rather than by a priori absolute criteria. Ways must be found to deal with these issues in a manner acceptable to most human beings. Open discussions and freedom from coercion are the best guarantees for ultimate success. The ethical human brain is the highest accomplishment of biologic evolution. By harmonizing our scientific, cultural, and ethical capabilities, the potentially achievable results can place us at the threshold of a new era of better health and less human suffering.
Eolian Biogenic Detritus in Deep Sea Sediments: A Possible Index of Equatorial Ice Age Aridity
Authors: Parmenter Carol , Folger D. W.
Published: October 2006

Opal phytoliths and freshwater diatoms, transported mainly in dust to the equatorial Atlantic, are common in sediments deposited when ocean waters were cool, and sparse in those deposited when waters were warm, during the last 1.8 million years. Climate in source areas of the southern Sahara apparently was more arid during glacials and more humid during interglacials.
Hemoglobin Switching in Sheep and Goats: Occurrence of Hemoglobins A and C in the Same Red Cell
Authors: Nienhuis Arthur W. , Bunn H. Franklin
Published: October 2006

Sheep and goats switch from the synthesis of hemoglobin A (α
2
β
2
A
) to hemoglobin C (α
2
β
2
C
) when made anemic. We have demonstrated the existence of the asymmetrical hybrid hemoglobin, α
2
β
A
β
C
, in the circulating red cells of anemic sheep. These erythroid cells, therefore, synthesized both A and C hemoglobin simultaneously. Thus, the switch appears to be mediated by selective gene expression rather than by a clonal or cellular selective mechanism.
Centric Fusion, Satellite DNA, and DNA Polarity in Mouse Chromosomes
Authors: Lin M. S. , Davidson R. L.
Published: October 2006

A fluorescent staining technique has demonstrated a contralateral arrangement of fluorescent spots in the centromeric region of mouse metacentric chromosomes which have resulted from centric fusion. The results suggest that centric fusion involves the maintenance of DNA polarity through the centromere and that the thymidine-rich chain of satellite DNA in the centromeric region is associated with the same DNA chain in every mouse autosome.
Pulmonary Alveolar Hypoxia: Release of Prostaglandins and Other Humoral Mediators
Authors: Said Sami I. , Yoshida Takero , Kitamura Satoshi , Vreim Carol
Published: October 2006

Hypoxic ventilation of isolated perfused cat lungs caused the frequent appearance in pulmonary perfusates of biologically active substances, which included prostaglandins or prostaglandin-like compounds. In anesthetized cats, inhibition of prostaglandin biosynthesis with infusions of aspirin (more than 50 milligrams per kilogram) reduced the pulmonary vasoconstrictor and bronchoconstrictor responses to hypoxic breathing.
Spectroscopic Observation of Acid Sulfate in Atmospheric Particulate Samples
Authors: Cunningham P. T. , Johnson S. A.
Published: October 2006

Infrared spectra of time- and size-classified atmospheric particulate samples collected with an inertial impactor reveal the presence of acid sulfate in the submicrometer-sized fraction. Although the degree of acidity is highly variable with time, the acidic nature of the particles is observed at all times of the day and may persist for several days in urban areas.
Skin Lipids: Their Biochemical Uniqueness
Authors: Nicolaides N.
Published: October 2006

Two key words characterize the uniqueness of skin lipids: complexity and perversity. Each suggests a function. Complexity manifests itself in the large number and variety of both saturated and unsaturated fatty chains synthesized by human skin. Functionally, this allows each individual to have a distinct odor or chemical fingerprint. Perversity manifests itself when one compares the lipids synthesized by skin with those synthesized by internal tissues. For example, skin makes odd instead of only even chains, branched instead of only straight chains, free instead of only esterified acids, places double bonds in unusual positions in the fatty chains, extends chains to extreme lengths, and accumulates intermediates in the synthesis of a biologically valuable compound such as cholesterol. Functionally, these products may pose metabolic problems to potential pathogens and thus contribute to the survival of only compatible microorganisms.
Thermal Blanketing: A Case for Aerosol-Induced Climatic Alteration
Authors: Idso Sherwood B.
Published: October 2006

Long-term temperature records at Phoenix, Arizona, indicate the existence of a post-1946 warming trend that may be attributed to the buildup of pollution in the lower layers of the atmosphere. The causative mechanism appears to be an enhancement of the so-called "greenhouse effect," induced by the interaction of aerosol with long-wavelength thermal radiation in the lower atmosphere.
Development of the Circum-Antarctic Current
Authors: Kennett J. P. , Houtz R. E. , Andrews P. B. , Edwards A. R. , Gostin V. A. , Hajos M. , Hampton M. A. , Jenkins D. G. , Margolis S. V. , Ovenshine A. T. , Perch-Nielsen K.
Published: October 2006

Deep-sea drilling in the Southern Ocean south of Australia and New Zealand shows that the Circum-Antarctic Current developed about 30 million years ago in the middle to late Oligocene when final separation occurred between Antarctica and the continental South Tasman Rise. Australia had commenced drifting northward from Antarctica 20 million years before this.
Bone Foreshafts from a Clovis Burial in Southwestern Montana
Authors: Lahren Larry , Bonnichsen Robson
Published: October 2006

Formal and functional analyses of bone artifacts from a Clovis burial in southwestern Montana suggest that they were constructed to serve as (detachable or nondetachable) foreshafts for attaching fluted projectile points to lance shafts.
Monocularly Deprived Cats: Improvement of the Deprived Eye's Vision by Visual Decortication
Authors: Sherman S. Murray
Published: October 2006

Monocularly deprived cats were tested for visual perimetry before and after visual cortex lesions. Such a lesion greatly enhances the deprived eye's performance and impairs that of the nondeprived eye so that the pronounced preoperative interocular asymmetry is lost postoperatively. Apparently this destruction of abnormal corticotectal pathways allows the expression of previously suppressed, normal retinotectal pathways.
Molluscan Phylogeny: The Paleontological Viewpoint
Authors: Runnegar Bruce , Pojeta John
Published: October 2006

Stasek theorized that the extant mollusks are the progeny of three separate lineages that separated before the phylum was well established. He wrote that no known intermediate forms, fossil or living, bridge the "enormous gaps between any two of the three lineages," and therefore treated each as a separate subphylum. These subphyla are (i) the subphylum Aculifera Hatscheck 1891, containing only the class Aplacophora, derived from the most primitive ancestors of the Mollusca; (ii) the subphylum Placophora von Jhering 1876, containing only the class Polyplacophora, and emphasizing the pseudometamerism of its more advanced premollusk ancestor; and (iii) the subphylum Conchifera Gegenbaur 1878, containing the Monoplacophora and the other classes derived from it.

We point out that the Polyplacophora may be derived from the Monoplacophora instead of a more primitive ancestral stock. We also suggest that the Conchifera can be separated into two major lineages, each worthy of the rank of subphylum. The fossil record indicates that the Monoplacophora gave rise to the Gastropoda, Cephalopoda, Rostroconchia, and possibly Polyplacophora, and that the Pelecypoda and Scaphopoda are derived from the Rostroconchia. These last three classes thus form a lineage that diverged from the Monoplacophora in the Early Cambrian. They emphasized a shell form that in all groups is primitively open at both ends, allowing the gut to remain relatively straight, with an anterior mouth and posterior anus. They became burrowing (infaunal) deposit or filter feeders. We coin the term Diasoma (through-body) for the subphylum containing these three classes (Rostroconchia, Pelecypoda, and Scaphopoda). The remaining three classes (Monoplacophora, Gastropoda, and Cephalopoda) emphasize a conical univalved shell, usually twisted into a spiral. The relatively small single aperture forces the anus to lie close to the mouth, and the gut is bent into a "U." Most are surface-dwelling (epifaunal) grazers or carnivores. We coin the name
Cyrtosoma
(hunchback-body) for the subphylum containing these three classes. Strictly speaking, the cyrtosomes are the ancestors of the diasomes but, in fact, both subphyla appeared and began to diversify within a few million years in the Early Cambrian.

Note added in proof
: After proofs were corrected we were informed that the new genus Opikella is preoccupied by (pikella = Oepikella) Thorslund 1940, an Ordovican ostracod. We rename the mollusk genus Oepikila.
Geniculate Neural Plasticity in Kittens after Exposure to Periodic Gratings
Authors: Maffei L. , Fiorentini A.
Published: October 2006

Kittens were exposed for 2 hours a day to a periodic vertical grating during the first 10 weeks after birth, and otherwise kept in darkness. The spatial frequency of the grating fell in the range of highest contrast sensitivity of normal cats. After the 10-week exposure period, cortical evoked potentials and lateral geniculate mass responses to alternating gratings showed a reduced amplitude for the spatial frequency of exposure. This reduction was independent of grating orientation. An analysis of orientational sensitivity of cortical units did not show any bias in favor of the vertical orientation.
Baring High-Albedo Soils by Overgrazing: A Hypothesized Desertification Mechanism
Authors: Otterman Joseph
Published: October 2006

Observations are reported of high-albedo soils denuded by overgrazing which appear bright, in high contrast to regions covered by natural vegetation. Measurements and modeling show that the denuded surfaces are cooler, when compared under sunlit conditions. This observed "thermal depression" effect should, on theoretical grounds, result in a decreased lifting of air necessary for cloud formation and precipitation, and thus lead to regional climatic desertification.
Gamma-Aminobutyric Acid Effects on Pituitary Gonadotropin Secretion
Authors: Ondo Jerome G.
Published: October 2006

Gamma-aminobutyric acid (GABA) injected into the third ventricle of male rats promotes the release of pituitary luteinizing hormone (LH) but not follicle-stimulating hormone. When GABA was injected directly into the pituitary it was ineffective in promoting LH release. This evidence suggests that GABA may play a role in controlling the discharge of hypothalamic luteinizing hormone releasing factor.
Viability of Stored Seed: Extension by Cathodic Protection
Authors: Pammenter N. W. , Adamson J. H. , Berjak Patricia
Published: October 2006

Placing seeds on a negatively charged conductor extended their viability during artificial aging. Such cathodic protection may reduce free radical attack by providing a source of electrons. The results support the hypothesis of free radical damage to cellular components and are consistent with such damage being important in deteriorative senescence changes.
Atmospheric Trace Metals at Remote Northern and Southern Hemisphere Sites: Pollution or Natural?
Authors: Duce Robert A. , Hoffman Gerald L. , Zoller William H.
Published: October 2006

The chemical composition of atmospheric particles collected near sea level over the North Atlantic indicates that Al, Sc, Mn, Fe, Co, Cr, Na, Mg, Ca, K, and Sr are derived from either crustal weathering or the ocean. The elements V, Zn, Cu, Cd, Pb, Sb, and Se are present in concentrations higher than expected from these sources. Although the V is probably derived from pollution sources on the North American continent, a comparison of enrichment factors relative to average crustal material for the remainder of these elements over the North Atlantic with enrichment factors for similar samples collected at the geographic South Pole suggests that the anomalously high enrichment factors may be due to natural rather than anthropogenic sources. A vapor phase for these metals may be involved at their source.
Mount St. Helens Volcano: Recent and Future Behavior
Authors: Crandell Dwight R. , Mullineaux Donal R. , Rubin Meyer
Published: October 2006

Mount St. Helens volcano in southern Washington has erupted many times during the last 4000 years, usually after brief dormant periods. This behavior pattern suggests that the volcano, last active in 1857, will erupt again—perhaps within the next few decades. Potential volcanic hazards of several kinds should be considered in planning for land use near the volcano.
Pterosaur from the Latest Cretaceous of West Texas: Discovery of the Largest Flying Creature
Authors: Lawson Douglas A.
Published: October 2006

Three partial skeletons of a large pterosaur have been found in the latest Cretaceous nonmarine rock of West Texas. This flying reptile had thin, elongate, perhaps toothless jaws and a long neck similar to
Pterodaustro
and
Pterodactylus
. With an estimated wingspan of 15.5 meters, it is undoubtedly the largest flying creature presently known.
Preparation of Native Chromatin and Damage Caused by Shearing
Authors: Noll Markus , Thomas Jean O. , Kornberg Roger D.
Published: October 2006

Chromatin prepared by a method involving limited nuclease digestion contains the same repeating structure as chromatin in the nucleus, whereas chromatin prepared by conventional methods involving shear does not.
Design and Synthesis of a Mimetic from an Antibody Complementarity-Determining Region
Authors: Saragovi Horacio Uri , Fitzpatrick Dennis , Raktabutr Apichaya , Nakanishi Hiroshi , Kahn Michael , Greene Mark I.
Published: October 2006

A technique for producing non-peptide compounds (mimetics) of designed specificities was developed that permitted the synthesis of a conformationally restricted molecule that mimicked the binding and functional properties of monoclonal antibody (MAb) 87.92.6, which recognizes the reovirus type 3 cellular receptor. Binding of either MAb 87.92.6, peptide analogs, or 87.1-mimetic to the cellular receptor inhibited cellular proliferation. The mimetic was a synthetic β-loop structure that mimics the second complementarity-determining region of the MAb. These studies may lead to strategies for the synthetic design of antibody complementarity regions, ligands, and other pharmacologically active agents that are water soluble, resistant to proteolysis, and nonimmunogenic.
Localization of Heart Poisons in the Monarch Butterfly
Authors: Brower Lincoln P. , Glazier Susan C.
Published: October 2006

The cardiac glycosides that monarch butterflies sequester from milkweed plants during the larval stage differ remarkably in their emetic potency and are concentrated to different degrees in the various parts of the body as well as in the two sexes. The very high concentrations of these compounds in the wings probably facilitate learned taste rejection in predators and account for the relatively high frequency of Danaid butterflies with beak-marked wings in natural populations. The cardiac glycosides in the abdomen have a much higher emetic potency than those in the rest of the body. Consequently, naive, extremely hungry, or forgetful birds which capture and peck off the wings but eat the abdomen discard the least emetic glycosides and ingest the most emetic, and thus again experience emesis. The nonrandom distribution of cardenolides in the wings, abdomen, and thorax, together with the fact that monarch males not only contain lower concentrations of cardiac glycosides than females but also contain cardenolides that are overall less emetic than those in females, is interpreted as evidence that these poisons are incorporated at a physiological cost. This cost, balanced against the benefits of protection from predation, provides a selective basis for the occurrence of both emetic and nonemetic individuals in natural populations. Since birds can discriminate emetic from nonemetic monarchs on the basis of taste, it is not necessary to invoke theories of kin or group selection to explain the evolution of this kind of unpalatability.
Soils of the Tropics and the World Food Crisis
Authors: Sanchez P. A. , Buol S. W.
Published: October 2006

The properties and potential of soils of the tropics are poorly understood. The old idea that laterite is formed when tropical soils are cleared is true of only a small proportion of the area. In most features, soils in the tropics are similar or equivalent to soils in the temperate regions. Specifically, soil organic matter contents, commonly believed to be low in the tropics, are essentially similar to those of the temperate regions. While the basic concepts about physical and chemical behavior developed in the nonglaciated temperate regions are directly applicable to the tropics, the development of soil management practices for sustained food production involves different strategies because of environmental and economic constraints. A major distinction is made between the development of high base status and low base status soils. With the former, soil management practices should be aimed at maximizing the potential of high-yielding varieties and improving intercropping systems with relatively intensive fertilizer inputs. With the low base status soils of the vast savanna and jungle areas energy-related inputs should be optimized by (i) selecting of crop varieties and species more tolerant to nutritional deficiencies or toxicities, (ii) applying fertilizers at lower rates than those recommended by classic marginal analysis, and (iii) increasing the efficiency of applied fertilizers in such soils.
Weyl's Theory of Glaciation Supported by Isotopic Study of Norwegian Core K 11
Authors: Duplessy Jean Claude , Chenouard Lydie , Vila Françoise
Published: October 2006

Oxygen-18 analyses of pelagic and benthic foraminifera from core K 11 indicate that during the last glaciation Norwegian Sea bottom waters were warmer than in modern times and had the same physical parameters (temperature, oxygen isotope ratio, and salinity) as the North Atlantic deep water. This result indicates that the glacial Norwegian Sea was not a sink for dense surface water, as it is now, and that during glacial times North Atlantic deep water invaded the deep Norwegian basin.
Nectar: Its Production and Functions in Trumpet Creeper
Authors: Elias Thomas S. , Gelband Hellen
Published: October 2006

Studies of the trumpet creeper,
Campsis radicans
(L.) Seem. (Bignoniaceae), reveal five distinct nectary systems, a phenomenon never before reported among temperate zone plants. Ant activity, centered around the four extrafloral systems, clearly demonstrates the ant-guard symbiosis usually associated only with tropical or subtropical species. Floral nectar, an attractant for hummingbird and bumblebee pollinators, differs chemically from the ant-attracting nectar produced extraflorally.
Sun-Tracking Solar Furnaces in High Arctic Flowers: Significance for Pollination and Insects
Authors: Kevan Peter G.
Published: October 2006

Heliotropic flowers (Dryas integrifolia,Papaver radicatum) act, in sunshine, as solar reflectors, their corollas focusing heat on the sporophylls. Considerable intrafloral temperatures are generated. Winds above 3.8 meters per second and cloud abolish the effect. Insects that bask in the flowers also gain heat. The phenomena are important in maximizing the small heat budget.
Scanning Proton-Induced X-ray Microspectrometry in an Atmospheric Environment
Authors: Horowitz P. , Grodzins L.
Published: October 2006

Collimated million-electron-volt proton beams, brought out into air, can be used as a scanning microprobe to examine specimens with a spatial resolution of the order of 1 micrometer. Trace elements at concentrations as low as 1 part per million can be detected. Some preliminary results based on the use of this simple method are presented.
Controlling Urban Air Pollution: A Benefit-Cost Assessment
Authors: Krupnick Alan J. , Portney Paul R.
Published: October 2006

To help focus debate about the best use of society's resources, it is important to have estimates of the benefits and costs of further improvements in air quality. Such estimates are developed, with focus primarily on reductions in ground-level ozone resulting from the control of volatile organic compounds; to a lesser extent, particulate control also is considered. Proposed controls are evaluated for both the nation as a whole and for the Los Angeles metropolitan area, where violations of air quality standards are most frequent and severe. Subject to a number of uncertainties, the costs of proposed new controls are found to exceed the benefits, perhaps by a considerable margin.
Control of
doublesex
Alternative Splicing by
transformer
and
transformer-2
in
Drosophila
Authors: Hoshijima Kazuyuki , Inoue Kunio , Higuchi Ikuko , Sakamoto Hiroshi , Shimura Yoshiro
Published: October 2006

Sex-specific alternative processing of
doublesex
(
dsx
) precursor messenger RNA (pre-mRNA) regulates somatic sexual differentiation in
Drosophila melanogaster
. Cotransfection analyses in which the
dsx
gene and the female-specific transformer (tra) and
transformer-2
(
tra-2
) complementary DNAs were expressed in
Drosophila
Kc cells revealed that female-specific splicing of the
dsx
transcript was positively regulated by the products of the
tra
and
tra-2
genes. Furthermore, analyses of mutant constructs of
dsx
showed that a portion of the female-specific exon sequence was required for regulation of
dsx
pre-messenger RNA splicing.
Amplitude Spectrum Representation in the Doppler-Shifted-CF Processing Area of the Auditory Cortex of the Mustache Bat
Authors: Suga Nobuo
Published: October 2006

The mustache bat,
Pteronotus parnellii rubiginosus
, emits orientation sounds containing a long constant-frequency (CF) component that is ideal for echo detection and Doppler shift measurement. About 30 percent of the primary auditory cortex of this bat is chiefly devoted to processing the second harmonic of the CF component in Doppler-shifted echoes. In this Doppler-shifted-CF processing area, single neurons recorded in any electrode penetration perpendicular to the cortical surface have nearly identical best frequencies and best amplitudes (or best pressure levels) at which the neurons show maximum excitation. The best frequency and best amplitude vary systematically with the location of the neurons in the cerebral cortex, so that there are tonotopic and "amplitopic" representation axes, which are radial and eccentric, respectively. In other words, the best-frequency and best-amplitude contours are eccentric and radial, respectively. The amplitude spectrum of a signal is thus represented in the coordinates of amplitude and frequency parallel to the cortical surface. This amplitude spectrum representation is disproportionate according to perceptual significance, so that a signal of 61.5 to 62.0 kilohertz and 30 to 50 decibels SPL (sound pressure level) is projected to a larger area than other signals. Just outside this Doppler-shifted-CF processing area, neurons are found which are specialized for responding to a particular information-bearing element or a particular combination of information-bearing elements in orientation sounds and echoes consisting of CF and frequency-modulated components.
Ca
2+
-Induced Ca
2+
Release in Sea Urchin Egg Homogenates: Modulation by Cyclic ADP-Ribose
Authors: Galione Antony , Lee Hon Cheung , Busa William B.
Published: October 2006

Calcium-induced calcium release (CICR) may function widely in calcium-mediated cell signaling, but has been most thoroughly characterized in muscle cells. In a homogenate of sea urchin eggs, which display transients in the intracellular free calcium concentration ([Ca
2+
]
i
) during fertilization and anaphase, addition of Ca
2+
triggered CICR. Ca
2+
release was also induced by the CICR modulators ryanodine and caffeine. Responses to both Ca
2+
and CICR modulators (but not Ca
2+
release mediated by inositol 1,4,5-trisphosphate) were inhibited by procaine and ruthenium red, inhibitors of CICR. Intact eggs also displayed transients of [Ca
2+
]
i
when microinjected with ryanodine. Cyclic ADP-ribose, a metabolite with potent Ca
2+
-releasing properties, appears to act by way of the CICR mechanism and may thus be an endogenous modulator of CICR. A CICR mechanism is present in these nonmuscle cells as is assumed in various models of intracellular Ca
2+
wave propagation.
Serengeti Migratory Wildebeest: Facilitation of Energy Flow by Grazing
Authors: McNaughton S. J.
Published: October 2006

Dense concentrations of migratory wildebeest leaving the Serengeti Plains in late May 1974 reduced green plant biomass by almost 400 grams per square meter, 85 percent of the initial standing crop. However, this grazing prevented senescence and stimulated net primary productivity of the grasslands. Thomson's gazelles leaving the plains a month later were significantly associated with areas previously grazed by wildebeest, and this association was still evident at the end of the dry season, 6 months later.
Septal Pores in
Prototaxites
, an Enigmatic Devonian Plant
Authors: Schmid Rudolf
Published: October 2006

Prototaxites southworthii
, an Upper Devonian, nonvascular plant of unknown affinity that is commonly ascribed to the brown algae, has filaments with septal pores. These superficially resemble various pores and pit connections of the higher algae and fungi and suggest that very elaborate cell wall structure had evolved by Devonian times.
Venus: Microwave Detection of Carbon Monoxide
Authors: Kakar R. K. , Waters J. W. , Wilson W. J.
Published: October 2006

The 115-gigahertz microwave line of carbon monoxide has been detected in the spectrum of Venus. The measurement proves that the carbon monoxide mixing ratio increases above an altitude of 85 kilometers in the Venus stratosphere and provides quantitative information on carbon monoxide in the altitude region from 80 to 110 kilometers. This altitude region is well above that which has been previously sensed.
The Surface of the Ice-Age Earth
Authors:   CLIMAP Project Members
Published: October 2006

In the Northern Hemisphere the 18,000 B.P. world differed strikingly from the present in the huge land-based ice sheets, reaching approximately 3 km in thickness, and in a dramatic increase in the extent of pack ice and marine-based ice sheets. In the Southern Hemisphere the most striking contrast was the greater extent of sea ice. On land, grasslands, steppes, and deserts spread at the expense of forests. This change in vegetation, together with extensive areas of permanent ice and sandy outwash plains, caused an increase in global surface albedo over modern values. Sea level was lower by at least 85 m.

The 18,000 B.P. oceans were characterized by: (i) marked steepening of thermal gradients along polar frontal systems, particularly in the North Atlantic and Antarctic; (ii) an equatorward displacement of polar frontal systems; (iii) general cooling of most surface waters, with a global average of –2.3°C; (iv) increased cooling and up-welling along equatorial divergences in the Pacific and Atlantic; (v) low temperatures extending equatorward along the western coast of Africa, Australia, and South America, indicating increased upwelling and advection of cool waters; and (vi) nearly stable positions and temperatures of the central gyres in the subtropical Atlantic, Pacific, and Indian oceans.
Stratospheric Aluminum Oxide
Authors: Brownlee D. E. , Ferry G. V. , Tomandl D.
Published: October 2006

Balloons and U-2 aircraft were used to collect micrometer-sized stratospheric aerosols. It was discovered that for the past 6 years at least, aluminum oxide spheres have been the major stratospheric particulate in the size range 3 to 8 micrometers. The most probable source of the spheres is the exhaust from solid-fuel rockets.
Depletion of CD4
+
T Cells in Major Histocompatibility Complex Class II-Deficient Mice
Authors: Grusby Michael J. , Johnson Randall S. , Papaioannou Virginia E. , Glimcher Laurie H.
Published: October 2006

The maturation of T cells in the thymus is dependent on the expression of major histocompatibility complex (MHC) molecules. By disruption of the MHC class II A
β
b
gene in embryonic stem cells, mice were generated that lack cell surface expression of class II molecules. These MHC class II-deficient mice were depleted of mature CD4
+
T cells and were deficient in cell-mediated immune responses. These results provide genetic evidence that class II molecules are required for the maturation and function of mature CD4
+
T cells.
Oroville Earthquakes: Normal Faulting in the Sierra Nevada Foothills
Authors: Bufe Charles G. , Lester Fredrick W. , Lahr Karen M. , Lahr John C. , Seekins Linda C. , Hanks Thomas C.
Published: October 2006

Aftershocks of the Oroville, California, earthquake of 1 August 1975 define a 16- by 12-kilometer fault plane striking north-south and dipping 60 degrees to the west to a depth of 10 kilometers. Focal mechanisms from P-wave first motions indicate normal faulting with the western, Great Valley side downdropped relative to the Sierra Nevada block. The northward projection of the fault plane passes beneath Oroville Dam and crops out under the reservoir.
Ecological Competition Between Algae: Experimental Confirmation of Resource-Based Competition Theory
Authors: Titman David
Published: October 2006

All possible outcomes of ecological competition, including stable coexistence, were observed in laboratory studies of two species of freshwater diatoms potentially limited by phosphate and silicate. The relative abundance of these nutrients determined the outcome of competition. The observed conditions of coexistence and competitive displacement agree with those predicted solely from the abilities of each species to acquire and utilize limiting nutrients. Coexistence occurred only when the growth rate of each species was limited by a different resource. These results may help explain the regional coexistence in nature of an otherwise paradoxically high number of algal species.
Fly Ash Collected from Electrostatic Precipitators: Microcrystalline Structures and the Mystery of the Spheres
Authors: Fisher G. L. , Chang D. P. Y. , Brummer Margaret
Published: October 2006

Scanning electron micrographs demonstrate the presence of microcrystalline structures on the surface of coal-derived fly ash samples taken from electrostatic precipitator hoppers. Cenospheres (hollow spheres) were found to be packed with smaller cenospheres, which were also packed with spheres. Microspheres, apparently formed by uneven heating, are encapsulated in the parent sphere. Chemical analyses provide a basis for the postulation of a mechanism of formation for plerospheres (hollow spheres packed with spheres) and microcrystals.
Atomic Structure of Adenosine Deaminase Complexed with a Transition-State Analog: Understanding Catalysis and Immunodeficiency Mutations
Authors: Wilson David K. , Rudolph Frederick B. , Quiocho Florante A.
Published: October 2006

The crystal structure of a murine adenosine deaminase complexed with 6-hydroxyl-1,6-dihydropurine ribonucleoside, a nearly ideal transition-state analog, has been determined and refined at 2.4 angstrom resolution. The structure is folded as an eight-stranded parallel α/β barrel with a deep pocket at the β-barrel COOH-terminal end wherein the inhibitor and a zinc are bound and completely sequestered. The presence of the zinc cofactor and the precise structure of the bound analog were not previously known. The 6
R
isomer of the analog is very tightly held in place by the coordination of the 6-hydroxyl to the zinc and the formation of nine hydrogen bonds. On the basis of the structure of the complex a stereoselective addition-elimination or S
N
2 mechanism of the enzyme is proposed with the zinc atom and the Glu and Asp residues playing key roles. A molecular explanation of a hereditary disease caused by several point mutations of an enzyme is also presented.
Identification of the DNA Binding Site for NGFI-B by Genetic Selection in Yeast
Authors: Wilson Thomas E. , Fahrner Timothy J. , Johnston Mark , Milbrandt Jeffrey
Published: October 2006

An in vivo selection system for isolating targets of DNA binding proteins in yeast was developed and used to identify the DNA binding site for the NGFI-B protein, a member of the steroid-thyroid hormone receptor superfamily. The feasibility of the technique was verified by selecting DNA fragments that contained binding sites for GCN4, a well-characterized yeast transcriptional activator. The DNA binding domain of NGFI-B, expressed as part of a LexA-NGFI-B-GAL4 chimeric activator, was then used to isolate a rat genomic DNA fragment that contained an NGFI-B binding site. The NGFI-B response element (NBRE) is similar to but functionally distinct from elements recognized by the estrogen and thyroid hormone receptors and the hormone receptor-like proteins COUP-TF, CF1, and H-2RIIBP. Cotransfection experiments in mammalian cells demonstrated that NGFI-B can activate transcription from the NBRE with or without its putative ligand binding domain.
NMR Studies of the Structure and Dynamics of Membrane-Bound Bacteriophage Pf1 coat protein
Authors: Shon Ki-Joon , Kim Yongae , Colnago Luiz A. , Opella Stanley J.
Published: October 2006

Filamentous bacteriophage coat protein undergoes a remarkable structural transition during the viral assembly process as it is transferred from the membrane environment of the cell, where it spans the phospholipid bilayer, to the newly extruded virus particles. Nuclear magnetic resonance (NMR) studies show the membrane-bound form of the 46-residue Pf1 coat protein to be surprisingly complex with five distinct regions. The secondary structure consists of a long hydrophobic helix (residues 19 to 42) that spans the bilayer and a short amphipathic helix (residues 6 to 13) parallel to the plane of the bilayer. The NH
2
-terminus (residues 1 to 5), the COOH-terminus (residues 43 to 46), and residues 14 to 18 connecting the two helices are mobile. By comparing the structure and dynamics of the membrane-bound coat protein with that of the viral form as determined by NMR and neutron diffraction, essential features of assembly process can be identified.
Membrane-Mediated Assembly of Filamentous Bacteriophage Pf1 Coat Protein
Authors: Nambudripad Raman , Stark Wilhelm , Opella Stanley J. , Makowski Lee
Published: October 2006

Filamentous bacteriophage Pf1 assembles by a membrane-mediated process during which the viral DNA is secreted through the membrane while being encapsulated by the major coat protein. Neutron diffraction studies showed that in the virus most of the coat protein consists of two α-helical segments arranged end-to-end with an intervening mobile surface loop. Nuclear magnetic resonance studies of the coat protein in the membrane-bound form have shown that the secondary structure is essentially identical to that in the intact virus. A comparison indicates that during membrane-mediated viral assembly, while the secondary structure of the coat protein is largely conserved, its tertiary structure changes substantially.
Toward Cloning And Mapping the Genome of
Drosophila
Authors: Merriam J. , Ashburner M. , Hartl D. L. , Kafatos F. C.
Published: October 2006

An ultimate goal of
Drosophila
genetics is to identify and define the functions of all the genes in the organism. Traditional approaches based on the isolation of mutant genes have been extraordinary fruitful. Recent advances in the manipulation and analysis of large DNA fragments have made it possible to develop detailed molecular maps of the
Drosophila
genome as the initial steps in determining the complete DNA sequence.
Stereospecific Effects of Inhalational General Anesthetic Optical Isomers on Nerve Ion Channels
Authors: Franks N. P. , Lieb W. R.
Published: October 2006

Although it is generally agreed that general anesthetics ultimately act on neuronal ion channels, there is considerable controversy over whether this occurs by direct binding to protein or secondarily by nonspecific perturbation of lipids. Very pure optical isomers of the inhalational general anesthetic isoflurane exhibited clear stereoselectivity in their effects on particularly sensitive ion channels in identified molluscan central nervous system neurons. At the human median effect dose (ED
50
) for general anesthesia, the (+)-isomer was about twofold more effective than the (-)-isomer both in eliciting the anesthetic-activated potassium current
I

K
(An)

and in inhibiting a current mediated by neuronal nicotinic acetylcholine receptors. For inhibiting the much less sensitive transient potassium current
I
A
, the (-)-isomer was marginally more potent than the (+)-isomer. Both isomers were equally effective at disrupting lipid bilayers.
Combustion Metamorphism in Southern California
Authors: Bentor Y. K. , Kastner M.
Published: October 2006

In several places in Southern California bituminous sediments of the Monterey Formation—siliceous shales, phosphatic rocks, dolomites, and arkoses—were affected during the Pleistocene and as late as the 19th century by spontaneous subsurface combustion of organic matter, during which temperatures up to 1600°C were reached. This oxidative heating (combustion metamorphism) affected rock complexes over areas of tens of square kilometers that tend to occur in clusters. As a result of these processes, the rocks recrystallized and partially melted to form pseudomagmas which intruded the country rocks. The chemical compositions of these melts differ from those of igneous magmas. Acid and intermediate siliceous melts as well as phosphatic melts have formed. These two types are generally immiscible. The following high-temperature minerals were determined: α- and β-cristobalite, quartz, calcic plagioclase, diopsidic pyroxene, wollastonite, cordierite, graphite, fluorapatite, and fluorite; at lower temperature pyrite, gypsum, aragonite, calcite, jarosite, and hexahydrite crystallized.
Composition and Structure of the Martian Atmosphere: Preliminary Results from Viking 1
Authors: Nier A. O. , Hanson W. B. , Seiff A. , McElroy M. B. , Spencer N. W. , Duckett R. J. , Knight T. C. D. , Cook W. S.
Published: October 2006

Results from the aeroshell-mounted neutral mass spectrometer on Viking I indicate that the upper atmosphere of Mars is composed mainly of CO
2
with trace quantities of N
2
, Ar, O, O
2
, and CO. The mixing ratios by volume relative to CO
2
for N
2
, Ar, and O
2
are about 0.06, 0.015, and 0.003, respectively, at an altitude near 135 kilometers. Molecular oxygen (O
2
+
) is a major component of the ionosphere according to results from the retarding potential analyzer. The atmosphere between 140 and 200 kilometers has an average temperature of about 180° ± 20°K. Atmospheric pressure at the landing site for Viking 1 was 7.3 millibars at an air temperature of 241°K. The descent data are consistent with the view that CO
2
should be the major constituent of the lower martian atmosphere.
Snowfall Observations from Natural-Draft Cooling Tower Plumes
Authors: Kramer Mark L. , Seymour David E. , Smith Maynard E. , Reeves Robert W. , Frankenberg Theodore T.
Published: October 2006

During the winter of 1975-1976, snowfall from the plumes of large natural-draft cooling towers of power plants has been observed. Snow accumulations up to 2.5 centimeters have been found on the ground at extended distances from the cooling towers, and visibility has been restricted to less than 1600 meters in the tower plume near ground level.
Entropy Estimates for Some Silicates at 298°K from Molar Volumes
Authors: Saxena Surendra K.
Published: October 2006

Third law entropies for silicates of Be, Mg, Ca, Zn, Na, and K containing the same anion group, for example, SiO
4
or SiO
3
or AlSi
3
O
8
, are found to be linearly related to their molar volumes. The relationship between the molar volume and the entropy of silicates of Fe and Mn, atoms with unfilled
d
electron subshells, is different from that of other silicates. The linear correlations yield a useful method of estimating the entropies of ortho-, meta-, and framework silicates (feldspars and feldspathoids). The estimated entropies of pyrope and almandine at 298°K are 47.47 and 68.13 gibbs per mole, respectively.
Cytochrome c: Immunofluorescent Localization of the Testis-Specific Form
Authors: Goldberg Erwin , Sberna Donna , Wheat Thomas E. , Urbanski Gregory J. , Margoliash E.
Published: October 2006

Mouse testes contain a unique form of cytochrome c. As demonstrated by the indirect immunofluorescence technique, the testis-specific cytochrome c is detectable in the primary spermatocyte and in cell types comprising the later stages of spermatogenesis. Interstitial cells, Sertoli cells, and spermatogonia contain the somatic form of cytochrome c, as does heart muscle.