bluuebunny/crossref_metadata_2025 huggingface dataset:
Δ9-Tetrahydrocannabinol: Effects on Mammalian Nonmyelinated Nerve Fibers
Authors: Byck R. , Ritchie J. M.
Published: October 2006

Δ9-Tetrahydrocannabinol can be applied to tissue in vitro by dissolving it in Pluronic F68 and ethanol. It causes a decrease in size of the compound action potential of the nonmyelinated fibers of the vagus nerve of the rabbit. This effect appears to be dose-related and chloride-dependent. Effects on other measurable parameters of nerve function seem to be minimal. Although the amounts required seem to be higher than those required to produce hallucinogenic effects in man, this effect is consistent with other work on Δ9-tetrahydrocannabinol and may ultimately account for a significant portion of the pharmacological activity of this drug.
Acanthaster
: Effect on Coral Reef Growth in Panama
Authors: Glynn Peter W.
Published: October 2006

Analysis of data on coral abundance and growth, and the population size (26 individuals per hectare) and feeding rate of
Acanthaster
indicates that
Pocillopora
reefs on the Pacific coast of Panama are undergoing vigorous growth in the presence of this predator. Prediction of the effects of a population increase in
Acanthaster
to plague proportions (2.5 times that presently observed) suggests that reefs could still maintain a positive growth. However,
Acanthaster
at ten times the present population density would lead to rapid destruction of reefs. It is argued that coral destruction due to
Acanthaster
represents only one of several factors affecting coral reef progression.
Iguanid Lizard from the Upper Cretaceous of Brazil
Authors: Estes Richard , Price Llewellyn I.
Published: October 2006

Pristiguana brasiliensis
, new genus and species, from the Upper Cretaceous Baurú Formation of Brazil, is the oldest fossil referable to the living lizard family Iguanidae. It resembles living primitive South American iguanids in some features, but also shows similarity to members of the related family Teiidae. Iguanid fossils do not appear in North America until the early Eocene, probably by waif dispersal from South America during the late Paleocene or early Eocene. A southern continental (Gondwanan) origin of iguanids is more plausible than the northern one often suggested.
Macrophage Nonimmunologic Recognition: Target Cell Factors Related to Contact Inhibition
Authors: Hibbs John B.
Published: October 2006

Activated mouse macrophages were not cytotoxic to contact-inhibited nontumorigenic 3T3 fibroblasts, but caused marked destruction to non-contact-inhibited, tumorigenic 3T12 and simian virus 40-transformed fibroblasts. Nonimmunologic recognition and destruction of target cells by activated macrophages is independent of altered morphology, abnormal karyotype, and ability for continuous multiplication in vitro—all characteristics of 3T3 fibroblasts. A modification of the target cell surface that results in a high in vitro saturation density, agglutinability by plant lectins, and tumorigenicity appears to evoke a cytotoxic response by activated macrophages.
Rejection of Tumor Cells in vitro
Authors: Berczi I. , Strausbauch P. , Sehon A. H.
Published: October 2006

The emergence of lymphoblast-like cells, capable of rapidly destroying tumor cells, was observed in primary cultures of an antigenic sarcoma transplantable in strain 13 guinea pigs. It is likely that these cytotoxic cells represent the progeny of lymphocytes sensitive to tumor antigens that had infiltrated the tumor tissue.
Size of the Great White Shark (
Carcharodon
)
Authors: Randall John E.
Published: October 2006

The maximum length of 36.5 feet (11.1 meters) attributed to the white shark (
Carcharodon carcharias
) by Günther and others is a mistake. Examination of the jaws and teeth of the specimen referred to by Günther and comparison with the jaws of white sharks of known length revealed a length of about 17 feet (∼5 meters). The largest white shark reliably measured was a 21-foot (6.4-meter) individual from Cuba. Bites on whale carcasses found off southern Australia suggest that white sharks as long as 25 or 26 feet (7½ or 8 meters) exist today. The size of extinct
Carcharodon
has also been grossly exaggerated. Based on a projection of a curve of tooth size of Recent
Carcharodon carcharias
, the largest fossil
Carcharodon
were about 43 feet (∼13 meters) long.
Exocytosis-Endocytosis Coupling in the Pancreatic Beta Cell
Authors: Orci L. , Malaisse-Lagae F. , Ravazzola M. , Amherdt M. , Renold A. E.
Published: October 2006

The stimulation of the release of insulin by glucose is accompanied by an enhanced uptake of cytochemically demonstrable horseradish peroxidase into endocytotic vesicles within the beta cells. An exocytosis-endocytosis coupling might represent a mechanism by which membrane constituents are recycled within the beta cells under conditions of increased secretory activity.
Depressive Disorders: Toward a Unified Hypothesis
Authors: Akiskal Hagop S. , McKinney William T.
Published: October 2006

Our scientific understanding of psychiatric syndromes, including the phenomena of depression, has been hampered because of: (i) the use of metapsychological concepts that are difficult to test; (ii) methodological and linguistic barriers that prevent communication among psychoanalysts, behaviorists, experimental psychologists, and psychiatrists; and (iii) the reluctance of psychiatrists to accept animal models as possible approximations of certain aspects of human psychopathology.

We have attempted to demonstrate that the animal models simulate some of the central features of clinical depression (for example, helplessness and object loss), thereby allowing one to rigorously investigate them from developmental, behavioral, and biochemical perspectives.

The object loss model, as a concrete version of a metapsychological-psychoanalytic concept, has enabled primatologists to study the disruption of an attachment bond. The behavioral model accommodates this concept to a broader generalization: loss of reinforcement or loss of control over reinforcement. We have reviewed the evidence that these processes involve the diencephalic centers of reward or reinforcement, thereby permitting integration of the psychoanalytical and behavioral formulations with the biochemical hypotheses. Also, we have presented data strongly suggesting that the breaking of an attachment bond in the primate represents significant loss of reinforcement that induces helplessness and disrupts motivated behavior.

Finally, we have argued that the depressive syndrome could be caused by interactions of genetic, chemical, developmental, and interpersonal factors, all of which impinge on the diencephalic centers of reinforcement.
Student Ratings of Teaching: Validity of Several Rating Factors
Authors: Frey Peter W.
Published: October 2006

Students' ratings of their instructors in undergraduate classes in calculus were correlated with class performance on a common final examination. Ratings on several instructional factors were highly related to class performance even though they appeared to be independent of the students' own grades.
The 25-km Discontinuity: Implications for Lunar History
Authors: Simmons Gene , Todd Terry , Wang Herbert
Published: October 2006

The lunar velocity profile and laboratory data on terrestrial and lunar rocks are constraints on models of lunar history. They show that shock-induced microcracks are absent from the rocks present in the moon today at depths of 25 to 60 kilometers. All possible causes of this observation are examined, and the most likely explanations are that either the rocks at depths of 25 to 60 kilometers formed after the major impacts ceased or the microcracks have annealed at temperatures of about 600°C over geologically long times.
Air Pollution Monitoring by Advanced Spectroscopic Techniques
Authors: Hodgeson J. A. , McClenny W. A. , Hanst P. L.
Published: October 2006

The monitoring requirements related to air pollution are many and varied. The molecules of concern differ greatly in their chemical and physical properties, in the nature of their environment, and in their concentration ranges. Furthermore, the application may have specific requirements such as rapid response time, ultrasensitivity, multipollutant capability, or capability for remote measurements. For these reasons, no single spectroscopic technique appears to offer a panacea for all monitoring needs. Instead we have attempted to demonstrate in the above discussion that, regardless of the difficulty and complexity of the monitoring problems, spectroscopy offers many tools by which such problems may be solved.
Role of Relative Humidity in the Synergistic Effect of a Sulfur Dioxide-Aerosol Mixture on the Lung
Authors: McJilton Charles , Frank Robert , Charlson Robert
Published: October 2006

Experimental evidence concerning the physicochemical and biological factors involved in the potentiation of the irritant property of sulfur dioxide in combination with an aerosol is reported. Relative humidity is an important variable for those aerosols capable of absorbing water at relative humidities below 95 percent.
Rabbit Blood Lymphocytes May Be T Cells with Surface Immunoglobulins
Authors: Sell Stewart , Sheppard Haynes W.
Published: October 2006

Rabbit peripheral blood lymphocytes and thymus cells do not respond to lipopolysaccharide mitogen in vitro, whereas spleen cells do. Soluble concanavalin A consistently stimulates 80 to 90 percent of rabbit peripheral blood lymphocytes, and the morphologic changes associated with such transformation may be observed within 18 hours after stimulation. Approximately 80 percent of rabbit peripheral blood lymphocytes have demonstrable immunoglobulin markers. These and other observations suggest that most rabbit peripheral blood lymphocytes are T cells with surface immunoglobulins.
Rapid Viral Induction of Plasmacytomas in Pristane-Primed BALB/c Mice
Authors: Potter Michael , Sklar Marshall D. , Rowe Wallace P.
Published: October 2006

Strain BALB/c mice were injected intraperitoneally with 0.5 milliliter of pristane, and 39 to 56 days later they were infected with Abelson murine leukemia virus, which is a lymphosarcomagenic variant of Moloney virus. Fifty-eight percent of the mice developed lymphosarcoma, and 28 percent developed immunoglobulin-producing plasmacytomas within 20 to 93 days (77 to 149 days after the pristane injection). Two of 57 control mice developed plasmacytomas at days 138 and 166 after a single injection of pristane; no plasmacytomas were found in mice treated with virus alone.
Spiroplasmas and Acholeplasmas: Multiplication in Insects
Authors: Whitcomb R. F. , Tully J. G. , Bové J. M. , Saglio P.
Published: October 2006

The helical wall-free microorganism,
Spiroplasma citri
, which is associated with citrus stubborn, a disease with no known vector, multiplied in the leafhopper vector of corn stunt but multiplied to higher titer in the vector of aster yellows and decreased the longevity of that insect.
Acholeplasma laidlawii
and
A. granularum
also multiplied in both leafhoppers.
Beta Cell Protection to Alloxan Necrosis by Anomers of D-Glucose
Authors: Rossini Aldo A. , Berger Michael , Shadden James , Cahill George F.
Published: October 2006

Various concentrations of either the α or β anomers of D-glucose were injected into fasted rats prior to a diabetogenic dose of alloxan. Plasma concentrations of glucose were measured 24 hours later. There was a significantly greater protection of the pancreatic beta cells by the α anomer of D-glucose as compared to the β anomer, which was evidenced by concentrations of glucose in the plasma, and morphology of beta cells.
Cyclic Adenosine Monophosphate: Selective Increase in Caudate Nucleus after Administration of L-Dopa
Authors: Garelis E. , Neff N. H.
Published: October 2006

Treatment with the dopamine precursor L-dopa produced a significant accumulation of adenosine 3′,5′-monophosphate (cyclic AMP) in the caudate nucleus of the rat. In contrast, there was no change in the amount of cyclic AMP in the cerebellum. Accumulation of cyclic AMP in the caudate nucleus after administration of L-dopa was prevented by prior treatment with the decarboxylase inhibitor RO 4-4602. These observations and those in other laboratories support the assumption that dopamine formed from L-dopa selectively activates striatal adenylate cyclase. The in vivo activation of adenylate cyclase after treatment with L-dopa may be a useful model for studying neurological and psychiatric disorders that are thought to involve the dopaminergic system of the brain.
Bumblebee
Ocelli
and Navigation at Dusk
Authors: Wellington W. G.
Published: October 2006

Western bumblebees fly straight while homing by polarized light, but zigzag when they use landmarks. That flight difference was used to determine the roles of the dorsal ocelli and parts of the compound eyes in homing. Polarized light and ocelli can prolong foraging at twilight, when landmarks are no longer visible.
Coupling between Cortical Potentials from Different Areas
Authors: Callaway Enoch , Harris Peter R.
Published: October 2006

At any instant, the electroencephalogram can be classified as to (i) polarity and (ii) direction of change in polarity. This classification provides a way to measure coupling between cortical areas. The technique is simple, yet of wide potential utility for studying functional relationships between cortical areas. The results of applying this technique suggest how the potentials giving rise to the electroencephalogram may play a role in information processing in the central nervous system.
Electronic Structure and Catalytic Behavior of Tungsten Carbide
Authors: Bennett L. H. , Cuthill J. R. , McAlister A. J. , Erickson N. E. , Watson R. E.
Published: October 2006

Tungsten carbide has been shown to be an effective catalyst for a number of reactions that are readily catalyzed by platinum, but not at all by tungsten, and it was speculated that this behavior is due to changes in the electron distribution when carbon is added to tungsten. A test of this hypothesis, made by measuring the valence band x-ray photoelectron spectrum of tungsten carbide and comparing it with the spectra of tungsten and platinum, shows that, near the Fermi level, the electronic density of states of tungsten carbide more nearly resembles that of platinum than that of tungsten.
Asbestiform Amphibole Minerals: Detection and Measurement of High Concentrations in Municipal Water Supplies
Authors: Cook Philip M. , Glass Gary E. , Tucker James H.
Published: October 2006

Asbestiform amphibole minerals, which have been demonstrated to be associated with human health problems, have been detected in substantial quantities in municipal water supplies taken from western Lake Superior water. The total concentration of amphibole minerals in the Duluth, Minnesota, water supply, as measured by x-ray diffraction for daily samples of suspended solids, averages 0.19 milligram per liter with large fluctuations due to seasonal and climatological effects on lake circulation. Electron microscopic examination of these water samples confirms the presence of asbestiform amphibole fibers. A conservative estimate of the fiber count for 1973 Duluth water supply samples is (1 to 30) × 10
6
amphibole fibers identifiable by electron diffraction per liter of water with a mass concentration of 1 to 30 micrograms per liter.
Novel Enzymic Hydrolytic Dehalogenation of a Chlorinated Aromatic
Authors: Scholten Jeffrey D. , Chang Kai-Hsuan , Babbitt Patricia C. , Charest Hugues , Sylvestre Michel , Dunaway-Mariano Debra
Published: October 2006

Microbial enzyme systems may be used in the biodegradation of persistent environmental pollutants. The three polypeptide components of one such system, the 4-chlorobenzoate dehalogenase system, have been isolated, and the chemical steps of the 4-hydroxybenzoate-forming reaction that they catalyze have been identified. The genes contained within a 4.5-kilobase
Pseudomonas
sp. strain CBS3 chromosomal DNA fragment that encode dehalogenase activity were selectively expressed in transformed
Escherichia coli
. Oligonucleotide sequencing revealed a stretch of homology between the 57-kilodalton (kD) polypeptide and several magnesium adenosine triphosphate (MgATP)-cleaving enzymes that allowed MgATP and coenzyme A (CoA) to be identified as the dehalogenase cosubstrate and cofactor, respectively. The dehalogenase activity arises from two components, a 4-chlorobenzoate:CoA ligase-dehalogenase (an αβ dimer of the 57- and 30-kD polypeptides) and a thioesterase (the 16-kD polypeptide).
Electrotonic Coupling: Effective Sign Reversal by Inhibitory Neurons
Authors: Spira M. E. , Spray D. C. , Bennett M. V. L.
Published: October 2006

Neurons in the buccal ganglia of
Navanax inermis
which control circumferential muscles of the pharynx showed typical electrotonic coupling when there was little synaptic activity in them. When there was much inhibitory activity, the effective sign of coupling was reversed; that is, hyperpolarization and depolarization of one cell caused depolarization and hyperpolarization of the others. A neural circuit explaining these results involves inhibitory neurons electrotonically coupled to and also inhibitory to the circumferential neurons that are themselves coupled. This circuit offers considerable flexibility for mediation of different activity patterns in this simple neuronal system.
Sunday and Workday Variations in Photochemical Air Pollutants in New Jersey and New York
Authors: Cleveland W. S. , Graedel T. E. , Kleiner B. , Warner J. L.
Published: October 2006

Concentration distributions of air contaminants and meteorological variables in New Jersey and New York for workdays (Mondays through Fridays, omitting holidays) and Sundays are compared by means of quantile-quantile plots. The ozone distributions are slightly higher on Sundays, and the primary pollutant distributions are lower. These results raise serious questions about the validity of current concepts underlying ozone reduction in urban atmospheres.
Dendritic Spine "Dysgenesis" and Mental Retardation
Authors: Purpura Dominick P.
Published: October 2006

Golgi studies reveal abnormally long, thin spines and the absence of short, thick spines on dendrites of cortical neurons in retarded children with normal karyotypes. The degree of dendritic spine loss and abnormality appears to be related to age and the severity of developmental retardation. Dendritic spine "dysgenesis" is a common feature of the microstructural pathology that occurs in profound mental retardation of unknown etiology.
Reversal of Catecholamine Refractoriness by Inhibitors of RNA and Protein Synthesis
Authors: de Vellis Jean , Brooker Gary
Published: October 2006

The generation of adenosine 3′,5′-monophosphate (cyclic AMP) in response to catecholamines in the 2B subclone of RGC6 rat glioma cells previously exposed to norepinephrine and refractory to further norepinephrine addition is substantially increased by addition of inhibitors of RNA and protein synthesis. The time course of the effect of these inhibitors on cyclic AMP concentration suggests that rapid protein synthesis and turnover are involved in catecholamine refractoriness. Norepinephrine induction of cyclic nucleotide phosphodiesterase is demonstrable in RGC6 cells but not in the 2B subclone. Thus, catecholamine refractoriness cannot be attributed to induction of phosphodiesterase. This implies that induction of a protein or proteins, important in catecholamine refractoriness, affects the synthesis rather than the degradation of cyclic AMP.
Nitrogen Fixation in a Coral Reef Community
Authors: Wiebe W. J. , Johannes R. E. , Webb K. L.
Published: October 2006

Algal reef flats at Enewetak Atoll, Marshall Islands, fix atmospheric nitrogen at rates comparable to those in managed agriculture. The dominant nitrogen fixer appears to be the blue-green alga
Calothrix crustacea
. Since this nutrient enrichment contributes to the high productivity of adjacent coral reefs and undoubtedly to atoll lagoons, it is recommended that the algal reef flats receive increased conservation priority.
Arsenic Tolerance in a Population of the Grass
Andropogon scoparius
Michx.
Authors: Rocovich Sue Ellen , West David A.
Published: October 2006

Samples of
Andropogon scoparius
Michx. collected on an arsenic mine exhibited a wide range of tolerance to arsenic in solution, whereas plants of the same species growing in uncontaminated soil showed no tolerance. Arsenic tolerance must be an evolved character under genetic control. Furthermore, the degree of tolerance is related to the amount of arsenic in which the plant was growing.
Sentence Perception as an Interactive Parallel Process
Authors: Marslen-Wilson William D.
Published: October 2006

The restoration of disrupted words to their original form in a sentence shadowing task is dependent upon semantic and syntactic context variables, thus demonstrating an on-line interaction between the structural and the lexical and phonetic levels of sentence processing.
High Cristobalite and High Tridymite in a Middle Eocene Deep-Sea Chert
Authors: Klasik John A.
Published: October 2006

The high-temperature forms of cristobalite and tridymite have been found occurring in a Middle Eocene, radiolarian-rich claystone. Evidence indicates that these crystals formed at low temperature and were chemical precipitates. Scanning electron microscopy, energy-dispersive x-ray analysis (microprobe), and x-ray diffraction provided the data upon which the determinative mineralogy was based.
A Genetic Tool Used to Identify Thioredoxin as a Mediator of a Growth Inhibitory Signal
Authors: Deiss Louis P. , Kimchi Adi
Published: October 2006

Loss of sensitivity to growth inhibitory polypeptides is likely to be one of the events that participates in the formation of some tumors and might be caused by inactivation or loss of the genetic elements that transduce these extracellular signals. The isolation of such a gene was achieved by randomly inactivating genes by an anti-sense complementary DNA expression library followed by direct selection for growth in the presence of an inhibitory polypeptide. Thus, a gene whose inactivation conveyed growth resistance to interferon-γ (IFN-γ) was isolated. Sequence analysis showed complete identity with human thioredoxin, a dithiol reducing agent, implicated here in the IFN-γ-mediated growth arrest of HeLa cells.
Surface/Volume Ratio: Implications for Phytoplankton Morphology
Authors: Lewis William M.
Published: October 2006

Plankton autotrophs vary greatly in size and shape. Computation of surface/volume ratios for biomass units of 27 coexisting phytoplankton species in a tropical lake indicates that these ratios are conserved within a range much narrower than expected by random choice of shapes. Conservation of surface/volume ratios suggests new explanations for the shapes of phytoplankton biomass units.
Viking Magnetic Properties Investigation: Further Results
Authors: Hargraves R. B. , Collinson D. W. , Arvidson R. E. , Spitzer C. R.
Published: October 2006

The amounts of magnetic particles held on the reference test chart and backhoe magnets on lander 2 and lander 1 are comparable, indicating the presence of an estimated 3 to 7 percent by weight of relatively pure, strongly magnetic particles in the soil at the lander 2 sampling site. Preliminary spectrophotometric analysis of the material held on the backhoe magnets on lander 1 indicates that its reflectance characteristics are indistinguishable from material within a sampling trench with which it has been compared. The material on the RTC magnet shows a different spectrum, but it is suspected that the difference is the result of a reflectance contribution from the magnesium metal covering on the magnet. It is argued that the results indicate the presence, now or originally, of magnetite, which may be titaniferous.
1,25-Dihydroxycholecalciferol and Parathormone: Effects on Isolated Osteoclast-Like and Osteoblast-Like Cells
Authors: Wong Glenda Lyn , Luben Richard A. , Cohn David V.
Published: October 2006

The actions of 1,25-dihydroxycholecalciferol [1,25-(OH)
2
D
3
] and parathormone, both effective bone-resorptive agents in vivo and in vitro, were tested on CT (osteoclast-like) and PT (osteoblast-like) bone cells maintained in culture. Both agents stimulated acid phosphatase activity and hyaluronate synthesis in the CT cells and decreased alkaline phosphatase, citrate decarboxylation, and collagen synthesis in the PT cells. Calcitonin inhibited the changes induced in the CT but not in the PT cells. The activity of 1,25-(OH)
2
D
3
differed from that of parathormone in one key respect: it did not increase cellular cyclic adenosine monophosphate, whereas parathormone did. Prior incubation of the bone cells with 1,25-(OH)
2
D
3
for 6 to 24 hours made the cells refractory to the effect of parathormone on cyclic adenosine monophosphate formation. These data suggest that 1,25-(OH)
2
D
3
and parathormone induce bone resorption by affecting the same cell types (osteoblasts and osteoclasts) although at different cellular sites.
Harvesting Natural Populations in a Randomly Fluctuating Environment
Authors: Beddington J. R. , May Robert M.
Published: October 2006

As harvesting effort and yield are increased, animal populations that are being harvested for sustained yield will take longer to recover from environmentally imposed disturbances. One consequence is that the coefficient of variation (the relative variance) of the yield increases as the point of maximum sustained yield (MSY) is approached. When overexploitation has resulted in a population smaller than that for MSY, high effort produces a low average yield with high variance. These observations accord with observed trends in several fish and whaling industries. We expect these effects to be more pronounced for a harvesting strategy based on constant quotas than for one based on constant effort. Although developed in a MSY context, the conclusions also apply if the aim is to maximize the present value of (discounted) net economic revenue.
Compressional and Surface Waves in Sand: Used by Desert Scorpions to Locate Prey
Authors: Brownell Philip H.
Published: October 2006

Loose sand conducts compressional and surface (Rayleigh) waves at relatively low velocities (95 to 120 meters per second and 40 to 50 meters per second, respectively) compared to other natural substrates. For frequencies between 1 and 5 kilohertz, the specific attenuation factor,
Q
, for sand is 18. Compound slit sensilla on basitarsal leg segments of sand-dwelling scorpions respond to surface waves generated by movements of insects as far as 50 centimeters away, and tarsal sensory hairs respond to higher-frequency (mostly compressional-wave) components of the signal.
Man-Made Dogs
Authors: Clutton-Brock Juliet
Published: October 2006

The origins of the domestic dog are discussed in relation to the hunting and nurturing behavioral patterns of man and the social canids. While it is accepted that the wolf was the progenitor of the dog the possibility that other species of canid were tamed and interbred with early domestic dogs is not disputed. A description is given of the recently extinct
Dusicyon australis
and it is suggested that this South American canid may have been tamed and then introduced and domesticated by man in the Falkland Islands during the early Holocene.
Self-Nonself Discrimination by T Cells
Authors: von Boehmer Harald , Kisielow Pawel
Published: October 2006

The αβ T cell receptor (TCR) recognizes antigens that are presented by major histocompatibility complex (MHC)-encoded cell surface molecules by binding to both the antigen and the MHC molecules. Discrimination of self from nonself antigens and MHC molecules is achieved by negative and positive selection of T cells in the thymus: potentially harmful T cells with receptors that bind to self antigens plus self MHC molecules are deleted before they can mount immune responses. In contrast, the maturation of useful T cells with receptors that bind foreign antigens plus self MHC molecules requires the binding of their receptor to MHC molecules on thymic epithelium in the absence of foreign antigen. The binding of the TCR to either class I or class II MHC molecules directs differentiation of the selected cells into either CD4
-
8
+
(killer) or CD4
+
8
-
(helper) T cells, respectively.
Plant Crops as a Source of Fuel and Hydrocarbon-Like Materials
Authors: Nielsen Peter E. , Nishimura Hiroyuki , Otvos John W. , Calvin Melvin
Published: October 2006

Chemical analyses have been made of a number of plant species in order to assess their suitability as renewable sources of hydrocarbon-like photosynthetic products. Yields of rubber and wax, glycerides, isoprenoids, and other terpenoids were estimated. Individual sterols were identified in latex from some species.
Cholinergic Vesicles: Ability to Empty and Refill Independently of Cytoplasmic Acetylcholine
Authors: Carroll Paul T. , Nelson Stephen H.
Published: October 2006

Incubation of minced mouse-forebrain tissues in lithium Krebs solution reduces the acetylcholine content of the vesicular fraction 70 percent without altering that of the cytoplasmic fraction. Depleted vesicular-bound acetylcholine can be restored with newly synthesized acetylcholine (formed from extracellular choline) independently of the cytoplasmic pool. Depletion of vesicular-bound acetylcholine does not facilitate the movement of preformed extracellular acetylcholine into vesicles.
Changing Atmospheric Fallout of Magnetic Particles Recorded in Recent Ombrotrophic Peat Sections
Authors: Oldfield F. , Thompson R. , Barber K. E.
Published: October 2006

Magnetic measurements of ombrotrophic peat allow a reconstruction of changes in the past fallout of magnetic particles through the atmosphere. In recent peat profiles from three sites in Britain and Northern Ireland, a marked increase in saturated isothermal remanent magnetization of the peat is recorded in levels which can be shown to postdate the onset of the Industrial Revolution. Furthermore the spatial variation in contemporary isothermal remanent magnetization values is consistent with a recent industrial and urban origin for the bulk of the magnetic minerals present. Pre-Industrial Revolution values are between two and three orders of magnitude lower, suggesting that the natural cosmic and terrestrial sources previously cited for such material have been dominated in recent times by the products of human activity. Magnetic measurements provide a simple, rapid, and nondestructive method of monitoring and differentiating various types of particulate atmospheric fallout for both recent and preindustrial times.
Continuous and Discontinuous Perturbations
Authors: Klauder John R.
Published: October 2006

Perturbations of quantum systems ranging from oscillators to fields can be either continuous or discontinuous functions of the coupling. Even nonrenormalizable fields may now find a natural interpretation.
Stereospecific and Nonstereospecific Effects of (+)- and (—)-Morphine: Evidence for a New Class of Receptors?
Authors: Jacquet Yasuko F. , Klee Werner A. , Rice Kenner C. , Iijima Ikuo , Minamikawa Junichi
Published: October 2006

The unnatural (+) enantiomer of morphine had minimal activity in three opiate assays in vitro: the rat brain homogenate binding assay, the electrically stimulated guinea pig ileum assay, and the inhibition of adenylate cyclase in neuroblastoma × glioma hybrid cell homogenates. When (+)-morphine was microinjected into the periaqueductal gray (a site known to mediate morphine analgesia) of drug-naive rats, there was only minimal analgesia, but the hyperresponsivity usually observed after microinjection of (-)-morphine occurred. Also, when (+)-morphine was microinjected into the midbrain reticular formation of drug-naive rats, rotation similar to that following microinjection of (-)-morphine occurred. These behaviors were not blocked by naloxone. Significantly, they typically occur in precipitated abstinence in morphine-dependent rats. These observations suggest that there are at least two classes of receptors, one stereospecific and blocked by naloxone and the other only weakly stereospecific and not blocked by naloxone, and that precipitated abstinence may be due, in part, to a selective blockade of receptors of the former class but not of the latter.
An El Jobo Mastodon Kill at Taima-taima, Venezuela
Authors: Bryan Alan L. , Casamiquela Rodolfo M. , Cruxent José M. , Gruhn Ruth , Ochsenius Claudio
Published: October 2006

Excavation at Taima-taima in 1976 recovered artifacts of the El Jobo complex in direct association with the butchered remains of a juvenile mastodon. Radiocarbon dates on associated wood twigs indicate a minimum age of 13,000 years before the present for the mastodon kill, a dating significantly older than that of the Clovis complex in North America. The El Jobo complex must have evolved independently in northern South America.
Coral Reef Morphogenesis: A Multidimensional Model
Authors: Adey Walter H.
Published: October 2006

Windward reef morphogenesis is a dynamic process directly controlled by the growth potential of dominant corals and coralline algae relative to wave energy and sea level rise. Moderate wave energy favors vertically rapid growth that is porous and uncemented; high wave energy favors slow but compact growth. Growth potentials of Caribbean and Indo-Pacific reefs are probably equivalent. Major differences are probably not due to biological or direct climatic factors but are in part related to differing patterns of sea level rise resulting from Holocene crustal adjustment. The nature and position of antecedent foundations developed by high interglacial and interstadial sea levels is especially critical and is largely controlled by regional tectonic factors, especially long-term subsidence.
Conservation of Liquid and Solid Quantity by the Chimpanzee
Authors: Woodruff Guy , Premack David , Kennel Keith
Published: October 2006

Sarah, an adult "language"-trained chimpanzee, made accurate same-different judgments on quantities of liquid and solid matter and conserved both types of quantity despite a transformation in an irrelevant property (shape). Control tests showed that she judged on the basis of inference rather than perceptual evaluation of the quantities. She failed to make accurate same-different judgments on the basis of number, and she was not tested for conservation of this type of quantity.
Tricyclic Antidepressants: Therapeutic Properties and Affinity for α-Noradrenergic Receptor Binding Sites in the Brain
Authors: U'Prichard David C. , Greenberg David A. , Sheehan Peter P. , Snyder Solomon H.
Published: October 2006

Tricyclic antidepressants vary in their capacity to cause psychomotor activation, to relieve agitated depressive states, and to cause sedation and hypotension. We have quantified relative potencies of tricyclic antidepressants in competing for the binding of
3
H-labeled WB-4101 to α-noradrenergic receptor sites in rat brain membranes. Affinities of tricyclic drugs for α-noradrenergic receptor sites in the brain correlate well with the capacity of these agents to relieve psychomotor agitation and to induce sedation and hypotension; these affinities also correlate inversely with tendencies to elicit psychomotor activation.
Little Salt Spring, Florida: A Unique Underwater Site
Authors: Clausen C. J. , Cohen A. D. , Emiliani Cesare , Holman J. A. , Stipp J. J.
Published: October 2006

Little Salt Spring in southwest Florida, consisting of a shallow, water-filled basin above a deep, vertical underwater cavern, was a freshwater cenote in the peninsula's drier past. It collected and preserved perishable organic artifacts and other evidence of Paleo-Indian and Archaic Indian origin ranging in age from 12,000 to 9000 and from 6800 to 5200 years ago. An Archaic Period cemetery containing an estimated 1000 burials occupies an adjoining muck-filled slough and presently drowned portions of the basin of the spring. Artifacts and the nature of interment suggest a cultural link between the Archaic people and the much later Glades Tradition of southern Florida.
Trace Chemicals: The Essence of Sexual Communication Systems in
Heliothis
Species
Authors: Klun J. A. , Plimmer J. R. , Bierl-Leonhardt B. A. , Sparks A. N. , Chapman O. L.
Published: October 2006

Analysis of heptane-soluble compounds from ovipositors of
Heliothis zea
and
Heliothis virescens
shows that both species produce relatively large amounts of (
Z
)-11-hexadecenal, with traces of (
Z
)-9-hexadecenal, (
Z
)-7-hexadecenal, and hexadecanal.
Heliothis virescens
females differ from
Heliothis zea
in that they also produce trace amounts of tetradecanal, (
Z
)-9-tetradecenal, and (
Z
)-11-hexadecen-1-ol. In both species, trace compounds are essential to pheromonal activity and specificity of chemical signals.
Seasat Mission Overview
Authors: Born G. H. , Dunne J. A. , Lame D. B.
Published: October 2006

During some 3 months of orbital operations, Seasat collected a unique set of global synoptic data on ocean winds, waves, temperature, and topography. All indications from a preliminary analysis of these data are that most of the mission's proof-of-concept objective—the demonstration of nearly all-weather microwave surveillance of the world's oceans—will be met.
The Cheetah: Native American
Authors: Adams Daniel B.
Published: October 2006

Two North American fossil species of large felids, hitherto regarded as Late Cenozoic pumas (mountain lion), are in fact closely related to the living cheetah,
Acinonyx
, of Africa and Eurasia. A new subgenus (
Miracinonyx
) is proposed for the American species. Cheetahs and pumas may have had a common ancestor in the Miocene of North America.
Catalysis by Small Metal Clusters
Authors: Hamilton J. F. , Baetzold R. C.
Published: October 2006

Experimental and theoretical studies of small clusters of metal atoms are aimed at revealing how properties change in the ultrafinely divided state. Thermodynamic, electronic, and structural features can be size-dependent and may be involved in determining the activity of small-particle catalysts. Correlations between these properties give indications of the features important in catalysis.
Inner-Shell Electron Spectroscopy for Microanalysis
Authors: Joy David C. , Maher Dennis M.
Published: October 2006

The transmission electron energy-loss spectrum shows characteristic "edges" corresponding to the excitation of inner-shell electrons of atoms in a thin sample. Analysis of these edges provides detailed chemical, structural, and electronic data from the radiated volume. By combining electron spectroscopy and electron microscopy, this microanalytical technique can be performed in conjunction with high-resolution imaging of the sample. It is shown that this approach has advantages of sensitivity, spatial resolution, and convenience over other comparable techniques.
Archean Rocks in Antarctica: 2.5-Billion-Year Uranium-Lead Ages of Pegmatites in Enderby Land
Authors: Grew Edward S. , Manton William I.
Published: October 2006

Uranium-lead isotopic data indicate that the granulite-facies Napier complex of Enderby Land, Antarctica, was cut by charnockitic pegmatites 2.5 billion years ago and by pegmatites lacking hypersthene 0.52 billion years ago. The 4-billion-year lead-lead ages (whole rock) reported for the Napier complex are rejected since these leads developed in three stages. Reconstructions of Gondwanaland suggest that the Napier complex may be a continuation of the Archean granulitic terrain of southern India.
Ecology and Acculturation Among Native Peoples of Central Brazil
Authors: Gross Daniel R. , Eiten George , Flowers Nancy M. , Leoi Francisca M. , Ritter Madeline Lattman , Werner Dennis W.
Published: October 2006

Simple exposure to Western goods may not be a sufficient explanation of why isolated village communities increase their participation in external market economies. The degree of market participation by four native villages in central Brazil is related to the difficulty of making a living from slash-and-burn subsistence agriculture as measured by the ratio of labor input to food output.
Biogenic Amine Synthesis Defect in Dihydropteridine Reductase Deficiency
Authors: Koslow Stephen H. , Butler Ian J.
Published: October 2006

In the enzymatic hydroxylation of aromatic amino acids, tetrahydrobiopterin is the essential cofactor. Regeneration of tetrahydrobiopterin requires dihydropteridine reductase, without which there should be a deficiency of hydroxylated amino acids and their products, biogenic amines. Assay of biopsied brain cortex of a patient with a deficiency of dihydropteridine reductase showed low concentrations of serotonin and dopamine, and this was reflected in the concentrations of their major metabolites measured in cerebrospinal fluid from lumbar, ventricular, and subarachnoid spaces. The metabolite concentrations were restored to normal, or above normal, by treatment with specific amino acids which bypass the metabolic block at the hydroxylation step. It is postulated that the seizures and neurological deterioration of the patient were related to a deficiency in the synthesis of biogenic amine neurotransmitters.
Changes in Atmospheric Carbon-14 Attributed to a Variable Sun
Authors: Stuiver Minze , Quay Paul D.
Published: October 2006

The
14
C production rate in the upper atmosphere changes with time because the galactic cosmic-ray flux responsible for
14
C production is modulated by the changes in solar wind magnetic properties. The resulting changes in the atmospheric
14
C level are recorded in tree rings and are used to calculate past
14
C production rates from a carbon reservoir model that describes terrestrial carbon exchange between the atmosphere, ocean, and biosphere. These past
14
C production rate changes are compared with
14
C production rates determined from 20th-century neutron flux measurements, and a theory relating
14
C production and solar variability, as given by geomagnetic
Aa
indices and sunspot numbers, is developed. This theory takes into account long-term solar changes that were previously neglected. The 860-year
14
C record indicates three episodes when sunspots apparently were absent: A.D. 1654 to 1714 (Maunder minimum), 1416 to 1534 (Spörer minimum), and 1282 to 1342 (Wolf minimum). A less precisely defined minimum occurred near A.D. 1040. The part of this record after A.D. 1645 correlates well with the basic features of the historical record of sunspot numbers. The magnitude of the calculated
14
C production rates points to a further increase in cosmic-ray flux when sunspots are absent. This flux was greatest during the Spörer minimum. A record of approximate sunspot numbers and
Aa
indices for the current millennium is also presented.
Sex Ratio Adaptations to Local Mate Competition in a Parasitic Wasp
Authors: Werren John H.
Published: October 2006

Females of the parasitic wasp
Nasonia vitripennis
adjust the sex ratio of their broods according to whether they are a first or second wasp to parasitize a host. The first wasp produces a strong daughter bias. The second wasp adjusts the proportion of sons to the relative level of local mate competition, as predicted by a natural selection model. The results provide a quantitative test of sex ratio theory.
Arctic Steppe-Tundra: A Yukon Perspective
Authors: Cwynar L. C. , Ritchie J. C.
Published: October 2006

The first reliable, securely dated full- and late-glacial pollen stratigraphy from Eastern Beringia forces the rejection of the widely held hypothesis of a steppe-tundra or grassland associated with extinct vertebrates and early humans. The arctic-alpine fossil flora and low pollen influx suggest a sparse tundra similar to modern herb fell-field vegetation.
The Einstein Observatory: New Perspectives in Astronomy
Authors: Giacconi Riccardo , Tananbaum Harvey
Published: October 2006

High-sensitivity x-ray measurements with the recently launched Einstein Observatory are having a major impact on wide areas of astronomical research. The x-ray luminosity of young O, B, and A stars and late K and M stars is found to be several orders of magnitude greater than predicted by current theories of coronal heating. Detailed x-ray images and spectra of supernova remnants are providing new information on the temperature, composition, and distribution of material ejected in supernova explosions as well as of the material comprising the interstellar medium. Observations of galaxies are yielding insights on the formation and evolution of stellar systems and galaxies over a wide range of variables. X-ray time variations are being used to probe the underlying energy source in quasars and active galactic nuclei. The distribution of mass in clusters of galaxies is being traced through detailed x-ray images, and the data are being used to classify clusters and trace their formation and evolution. Substantial progress is being made in several areas of cosmological research, particularly in the study of the diffuse x-ray background.
The National System of Scientific Measurement
Authors: Hunter J. S.
Published: October 2006

Mandated measurement methods are required by regulatory agencies and other government groups. These methods exist for measuring almost all physical, chemical, and biological phenomena. The methods have been culled from the literature, from the organizations that write voluntary standards, and some have been developed by the agencies. Few provide adequate estimates of precision, and fewer still provide any evaluation of interlaboratory bias. The societal costs of these poor measurements are large. Much needs to be done to meet the physical and statistical requirements for establishing and maintaining dependable measurements. Excepting those directly supported by the National Bureau of Standards, most of the nation's measurement systems are uncontrolled.
Annual Growth Increments in Shells of
Spisula solidissima
Record Marine Temperature Variability
Authors: Jones Douglas S.
Published: October 2006

Systematic variations in annual growth increments, formed over a 16-year period in shells of the marine bivalve mollusc
Spisula solidissima
, reveal more growth in some years than others. Favorable years are indicated by larger than expected annual growth increments and successful recruitment of juveniles. Variations in the size of growth increments correlate negatively with sea surface temperatures. The results suggest that the annual growth increments in the shells of certain molluscs record changes in the marine environment and may be useful monitors of pollution and indicators of paleotemperatures.
Scheiner's Halo: Evidence for Ice Ic in the Atmosphere
Authors: Whalley E.
Published: October 2006

Refraction of sunlight at the angle of minimum deviation between octahedral faces of crystals of ice Ic in the upper atmosphere could produce a halo around the sun or the moon at 27.46°. Crystals of hexagonal ice having low-index faces cannot produce a halo of this radius. It is therefore suggested that Scheiner's halo, which has been reported at least four times since 1629 at 28° from the sun, is due to ice Ic. If this is correct, it is apparently the first evidence that ice Ic occurs naturally and that liquid water can freeze to ice Ic.
A Cell Culture Model for T Lymphocyte Clonal Anergy
Authors: Schwartz Ronald H.
Published: October 2006

T lymphocytes respond to foreign antigens both by producing protein effector molecules known as lymphokines and by multiplying. Complete activation requires two signaling events, one through the antigen-specific receptor and one through the receptor for a costimulatory molecule. In the absence of the latter signal, the T cell makes only a partial response and, more importantly, enters an unresponsive state known as clonal anergy in which the T cell is incapable of producing its own growth hormone, interleukin-2, on restimulation. Our current understanding at the molecular level of this modulatory process and its relevance to T cell tolerance are reviewed.