bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Field Observations During the Ulysses Flyby of Jupiter
Authors: Balogh A. , Dougherty M. K. , Forsyth R. J. , Southwood D. J. , Smith E. J. , Tsurutani B. T. , Murphy N. , Burton M. E.
Published: October 2006

The Jovian flyby of the Ulysses spacecraft presented the opportunity to confirm and complement the findings of the four previous missions that investigated the structure and dynamics of the Jovian magnetosphere and magnetic field, as well as to explore for the first time the high-latitude dusk side of the magnetosphere and its boundary regions. In addition to confirming the general structure of the dayside magnetosphere, the Ulysses magnetic field measurements also showed that the importance of the current sheet dynamics extends well into the middle and outer magnetosphere. On the dusk side, the magnetic field is swept back significantly toward the magnetotail. The importance of current systems, both azimuthal and field-aligned, in determining the configuration of the field has been strongly highlighted by the Ulysses data. No significant changes have been found in the internal planetary field; however, the need to modify the external current densities with respect to previous observations on the inbound pass shows that Jovian magnetic and magnetospheric models are highly sensitive to both the intensity and the structure assumed for the current sheet and to any time dependence that may be assigned to these. The observations show that all boundaries and boundary layers in the magnetosphere have a very complex microstructure. Waves and wave-like structures were observed throughout the magnetosphere; these included the longest lasting mirror-mode wave trains observed in space.
Change in Failure Stress on the Southern San Andreas Fault System Caused by the 1992 Magnitude = 7.4 Landers Earthquake
Authors: Stein Ross S. , King Geoffrey C. P. , Lin Jian
Published: October 2006

The 28 June Landers earthquake brought the San Andreas fault significantly closer to failure near San Bernardino, a site that has not sustained a large shock since 1812. Stress also increased on the San Jacinto fault near San Bernardino and on the San Andreas fault southeast of Palm Springs. Unless creep or moderate earthquakes relieve these stress changes, the next great earthquake on the southern San Andreas fault is likely to be advanced by one to two decades. In contrast, stress on the San Andreas north of Los Angeles dropped, potentially delaying the next great earthquake there by 2 to 10 years.
Prehistoric Rock Avalanches in the Olympic Mountains, Washington
Authors: Schuster Robert L. , Logan Robert L. , Pringle Patrick T.
Published: October 2006

Rock avalanches blocked streams in the Olympic Mountains southwest of Puget Sound during the past few thousand years. Limiting radiocarbon ages indicated that three or four of six avalanches occurred from 1000 to 1300 years ago or shortly thereafter. Most of the dates were from the outer preserved rings of trees drowned behind avalanche dams. These three or four avalanches may be coeval not only with one another but also with abrupt tectonic deformation in western Washington. No rock avalanches in the Olympic Mountains are known to have resulted from storms or earthquakes during the past century. The avalanches strengthen the case that a large prehistoric earthquake occurred in the Puget Sound region.
Biological Control of Crystal Texture: A Widespread Strategy for Adapting Crystal Properties to Function
Authors: Berman Amir , Hanson Jonathan , Leiserowitz Leslie , Koetzle Thomas F. , Weiner Stephen , Addadi Lia
Published: October 2006

Textures of calcite crystals from a variety of mineralized tissues belonging to organisms from four phyla were examined with high-resolution synchrotron x-ray radiation. Significant differences in coherence length and angular spread were observed between taxonomic groups. Crystals from polycrystalline skeletal ensembles were more perfect than those that function as single-crystal elements. Different anisotropic effects on crystal texture were observed for sea urchin and mollusk calcite crystals, whereas none was found for the foraminifer,
Patellina
, and the control calcite crystals. These results show that the manipulation of crystal texture in different organisms is under biological control and that crystal textures in some tissues are adapted to function. A better understanding of this apparently widespread biological phenomenon may provide new insights for improving synthetic crystal-containing materials.
Multiple Evolutionary Origins of Magnetotaxis in Bacteria
Authors: DeLong Edward F. , Frankel Richard B. , Bazylinski Dennis A.
Published: October 2006

Magnetosomes are intracellular, iron-rich, membrane-enclosed magnetic particles that allow magnetotactic bacteria to orient in the earth's geomagnetic field as they swim. The magnetosomes of most magnetotactic bacteria contain iron oxide particles, but some magnetotactic species contain iron sulfide particles instead. Phylogenetic analyses of small subunit ribosomal RNA sequences showed that all known magnetotactic bacteria of the iron oxide type are associated with the α subgroup of the Proteobacteria in the domain Bacteria. In contrast, uncultured magnetotactic bacteria of the iron sulfide type are specifically related to the dissimilatory sulfate-reducing bacteria within the δ subdivision of the Proteobacteria. These findings indicate a polyphyletic origin for magnetotactic bacteria and suggest that magnetotaxis based on iron oxides and iron sulfides evolved independently.
Diversity of Atlantic Coastal Plain Mollusks Since the Pliocene
Authors: Allmon Warren D. , Rosenberg Gary , Portell Roger W. , Schindler Kevin S.
Published: October 2006

About 70 percent of tropical western Atlantic mollusk species have become extinct since the Pliocene, which has led to perceptions of a corresponding decline in diversity. However, a compilation of gastropod species from Plio-Pleistocene faunas of the United States Atlantic coastal plain and from Recent western Atlantic faunas indicates that regional diversity has not changed since the Pliocene. Gastropod diversity in the Pliocene Pinecrest Beds in Florida approximates that seen today on either coast of Florida. Gastropod diversity is not demonstrably different in the Recent tropical western Atlantic than in the Recent tropical eastern Pacific. High extinction rates must have been balanced by high origination rates.
Achieving Acceptable Air Quality: Some Reflections on Controlling Vehicle Emissions
Authors: Calvert J. G. , Heywood J. B. , Sawyer R. F. , Seinfeld J. H.
Published: October 2006

Motor vehicle emissions have been and are being controlled in an effort to abate urban air pollution. This article addresses the question: Will the vehicle exhaust emission control and fuel requirements in the 1990 Clean Air Act Amendments and the California Air Resources Board regulations on vehicles and fuels have a significant impact? The effective control of in-use vehicle emissions is the key to a solution to the motor vehicle part of the urban air pollution problem for the next decade or so. It is not necessary, except perhaps in Southern California, to implement extremely low new car emission standards before the end of the 20th century. Some of the proposed gasoline volatility and composition changes in reformulated gasoline will produce significant reductions in vehicle emissions (for example, reduced vapor pressure, sulfur, and light olefin and improved high end volatility), whereas others (such as substantial oxygenate addition and aromatics reduction) will not.
The Genesis and Collapse of Third Millennium North Mesopotamian Civilization
Authors: Weiss H. , Courty M. -A. , Wetterstrom W. , Guichard F. , Senior L. , Meadow R. , Curnow A.
Published: October 2006

Archaeological and soil-stratigraphic data define the origin, growth, and collapse of Subir, the third millennium rain-fed agriculture civilization of northern Mesopotamia on the Habur Plains of Syria. At 2200 B. C., a marked increase in aridity and wind circulation, subsequent to a volcanic eruption, induced a considerable degradation of land-use conditions. After four centuries of urban life, this abrupt climatic change evidently caused abandonment of Tell Leilan, regional desertion, and collapse of the Akkadian empire based in southern Mesopotamia. Synchronous collapse in adjacent regions suggests that the impact of the abrupt climatic change was extensive.
Why Silicon Is Hard
Authors: Gilman John J.
Published: October 2006

Compared with pure metals and ionic salts, covalent solids such as silicon are hard and brittle because dislocations do not move in them except at high temperatures. A satisfactory explanation for this behavior has been lacking in spite of its great importance for the mechanics of materials and structures. It is shown here that the critical atomic process leading to the observed brittleness is analogous to a chemical substitution reaction. Analysis of this analogy with the aid of a correlation diagram yields the observed high resistive stress and high activation energy. When a kink on a dislocation line moves, it breaks the atomic bonding symmetry, a forbidden process.
Laser-Focused Atomic Deposition
Authors: McClelland J. J. , Scholten R. E. , Palm E. C. , Celotta R. J.
Published: October 2006

The ability to fabricate nanometer-sized structures that are stable in air has the potential to contribute significantly to the advancement of new nanotechnologies and our understanding of nanoscale systems. Laser light can be used to control the motion of atoms on a nanoscopic scale. Chromium atoms were focused by a standing-wave laser field as they deposited onto a silicon substrate. The resulting nanostructure consisted of a series of narrow lines covering 0.4 millimeter by 1 millimeter. Atomic force microscopy measurements showed a line width of 65 ± 6 nanometers, a spacing of 212.78 nanometers, and a height of 34 ± 10 nanometers. The observed line widths and shapes are compared with the predictions of a semiclassical atom optical model.
Picosecond Resolution in Scanning Tunneling Microscopy
Authors: Nunes G. , Freeman M. R.
Published: October 2006

A method has been developed for performing fast time-resolved experiments with a scanning tunneling microscope. The method uses the intrinsic nonlinearity in the microscope's current versus voltage characteristics to resolve optically generated transient signals on picosecond time scales. The ability to combine the spatial resolution of tunneling microscopy with the time resolution of ultrafast optics yields a powerful tool for the investigation of dynamic phenomena on the atomic scale.
Greenland Ice Sheet Surface Properties and Ice Dynamics from ERS-1 SAR Imagery
Authors: Fahnestock Mark , Bindschadler Robert , Kwok Ron , Jezek Ken
Published: October 2006

C-band synthetic aperture radar (SAR) imagery from the European Space Agency's ERS-1 satellite reveals the basic zonation of the surface of the Greenland Ice Sheet. The zones have backscatter signatures related to the structure of the snowpack, which varies with the balance of accumulation and melt at various elevations. The boundaries of zones can be accurately located with the use of this high-resolution imagery. The images also reveal a large flow feature in northeast Greenland that is similar to ice streams in Antarctica and may play a major role in the discharge of ice from the ice sheet.
Long-Term Changes in Dopaminergic Innervation of Caudate Nucleus After Continuous Amphetamine Administration
Authors: Ellison Gaylord , Eison Michael S. , Huberman Harris S. , Daniel Frank
Published: October 2006

Silicone pellets containing
d
-amphetamine base were implanted subcutaneously in rats. These pellets release amphetamine continuously for at least 10 days. Several days after implantation, swollen dopamine axons concomitant with large decreases in tyrosine hydroxylase activity were observed in the caudate nucleus. Decreased tyrosine hydroxylase activity was still present 110 days after pellet removal in the caudate but not in several other brain regions, nor in the caudate of rats injected with an equivalent amount of amphetamine in daily injections. This implies that continuous amphetamine administration has a selective neurotoxic effect on dopamine terminals in the caudate.
Odor-Induced Membrane Currents in Vertebrate-Olfactory Receptor Neurons
Authors: Firestein Stuart , Werblin Frank
Published: October 2006

In olfactory receptor neurons, odor molecules cause a depolarization that leads to action potential generation. Underlying the depolarization is an ionic current that is the earliest electrical event in the transduction process. In two preparations, olfactory receptor neurons were voltage-clamped and stimulated with odors and this generator current was measured. In addition, a method was developed to estimate the time course and absolute concentration of odorants delivered to the receptor sites. With this method, olfactory neurons were found to have relatively high stimulus thresholds, steep dose-response relations, long latencies, and an apparent requirement for cooperativity at one or more steps in the pathway from odorant binding to activation of the generator current.
Sex Pheromones in Snakes
Authors: Mason Robert T. , Fales Henry M. , Jones Tappey H. , Pannell Lewis K. , Chinn John W. , Crews David
Published: October 2006

The majority of pheromones identified to date are insect pheromones, which are volatile in nature. Identification of nonvolatile pheromones have been relatively rare, especially in vertebrates. Male and female garter snakes use pheromones to mediate sexual behavior. The female sex attractiveness pheromone of the Canadian red-sided garter snake,
Thamnophis sirtalis parietalis
, consists of a novel series of nonvolatile saturated and monounsaturated long-chain methyl ketones, whereas the male sex recognition pheromone contains squalene. These compounds were isolated, identified, and partially synthesized, and field tests show them to be biologically active.
The Fc and not CD4 Receptor Mediates Antibody Enhancement of HIV Infection in Human Cells
Authors: Homsy Jacques , Meyer Mia , Tateno Masatoshi , Clarkson Sarah , Levy Jay A.
Published: October 2006

Antibodies that enhance human immunodeficiency virus (HIV) infectivity have been found in the blood of infected individuals and in infected or immunized animals. These findings raise serious concern for the development of a safe vaccine against acquired immunodeficiency syndrome. To address the in vivo relevance and mechanism of this phenomenon, antibody-dependent enhancement of HIV infectivity in peripheral blood macrophages, lymphocytes, and human fibroblastoid cells was studied. Neither Leu3a, a monoclonal antibody directed against the CD4 receptor, nor soluble recombinant CD4 even at high concentrations prevented this enhancement. The addition of monoclonal antibody to the Fc receptor III (anti-FcRIII), but not of antibodies that react with FcRI or FcRII, inhibited HIV type 1 and HIV type 2 enhancement in peripheral blood macrophages. Although enhancement of HIV infection in CD4+ lymphocytes could not be blocked by anti-FcRIII, it was inhibited by the addition of human immunoglobulin G aggregates. The results indicate that the FcRIII receptor on human macrophages and possibly another Fc receptor on human CD4
+
lymphocytes mediate antibody-dependent enhancement of HIV infectivity and that this phenomenon proceeds through a mechanism independent of the CD4 protein.
Lithium Blocks a Phosphoinositide-Mediated Cholinergic Response in Hippocampal Slices
Authors: Worley Paul F. , Heller William A. , Snyder Solomon H. , Baraban Jay M.
Published: October 2006

The effects of lithium on inositol phosphate metabolism may account for the therapeutic actions of lithium in affective disorder. Muscarinic stimulation of the phosphoinositide system blocks synaptic inhibitory actions of adenosine in the hippocampal slice. At therapeutic concentrations, lithium diminished this muscarinic response, whereas rubidium, which does not affect phosphoinositide metabolism, had no effect. A dampening of phosphoinositide-mediated neurotransmission may explain the normalizing effects of lithium in treating both mania and depression.
Amino Acid Sequences Common to Rapidly Degraded Proteins: The PEST Hypothesis
Authors: Rogers Scott , Wells Rodney , Rechsteiner Martin
Published: October 2006

The amino acid sequences of ten proteins with intracellular half-lives less than 2 hours contain one or more regions rich in proline (P), glutamic acid (E), serine (S), and threonine (T). These PEST regions are generally, but not always, flanked by clusters containing several positively charged amino acids. Similar inspection of 35 proteins with intracellular half-lives between 20 and 220 hours revealed that only three contain a PEST region. On the basis of this information, it was anticipated that caseins, which contain several PEST sequences, would be rapidly degraded within eukaryotic cells. This expectation was confirmed by red blood cell-mediated microinjection of
125
I-labeled caseins into HeLa cells where they exhibited half-lives of less than 2 hours. The rapid degradation of injected α- and β-casein as well as the inverse correlation of PEST regions with intracellular stability indicate that the presence of these regions can result in the rapid intracellular degradation of the proteins containing them.
Seroprevalence and Epidemiological Correlates of HTLV-I Infection in U.S. Blood Donors
Authors: Williams Alan E. , Fang Chang T. , Slamon Dennis J. , Poiesz Bernard J. , Sandler S. Gerald , Darr W. Frederick , Shulman Gerald , McGowan Eoline I. , Douglas Deborah K. , Bowman Robert J. , Peetoom Frans , Kleinman Steven H. , Lenes Bruce , Dodd Roger Y.
Published: October 2006

Screening for human T-lymphotropic virus type I (HTLV-I) antibodies was performed on sera from 39,898 blood donors at eight blood centers in geographically distinct areas of the United States. Ten donors (0.025 percent) showed evidence of HTLV-I seropositivity by enzyme immunoassays; this was confirmed by protein immunoblot and radioimmunoprecipitation. Seroprevalence rates ranged from 0 to 0.10 percent at the locations sampled, with HTLV-I antibodies found predominantly in donors from the southeastern and southwestern United States. Matched case-control interviews and laboratory studies were performed on five seropositive women and two seropositive men who participated in an identity-linked collection of sera from a subset of 33,893 donors at six of the eight blood centers. Four of the women and both men are black; one woman is Caucasian. Four of the seven seropositive individuals admitted to prior intravenous drug abuse or sexual contact with an intravenous drug user. Sexual contact with native inhabitants of an HTLV-I endemic area was the only identified risk factor for one male. The distribution of HTLV-I antibodies in this U.S. blood donor sample corroborates the previously reported epidemiology of this agent and suggests that additional donor screening measures, including the testing of donated blood for HTLV-I markers, may be necessary to prevent the spread of HTLV-I to transfusion recipients.
Nimodipine Facilitates Associative Learning in Aging Rabbits
Authors: Deyo Richard A. , Straube Karen T. , Disterhoft John F.
Published: October 2006

Nimodipine is one of several dihydropyridines that block calcium channels. Originally administered to improve cerebral blood flow in elderly patients with chronic cerebrovascular disorders, nimodipine was noted to facilitate learning. These observations led to the present investigation of the effects of nimodipine on associative learning in aging rabbits. Nimodipine accelerated acquisition of conditioned eye-blink in both young and aging rabbits without altering the amplitude of responses to the conditioned or unconditioned stimuli or causing nonspecific responding. Thus, nimodipine may be a candidate for an effective treatment for age-related learning deficits.
Prooxidant States and Tumor Promotion
Authors: Cerutti Peter A.
Published: October 2006

There is convincing evidence that cellular prooxidant states—that is, increased concentrations of active oxygen and organic peroxides and radicals—can promote initiated cells to neoplastic growth. Prooxidant states can be caused by different classes of agents, including hyperbaric oxygen, radiation, xenobiotic metabolites and Fenton-type reagents, modulators of the cytochrome P-450 electron-transport chain, peroxisome proliferators, inhibitors of the antioxidant defense, and membrane-active agents. Many of these agents are promoters or complete carcinogens. They cause chromosomal damage by indirect action, but the role of this damage in carcinogenesis remains unclear. Prooxidant states can be prevented or suppressed by the enzymes of the cellular antioxidant defense and low molecular weight scavenger molecules, and many antioxidants are antipromoters and anticarcinogens. Finally, prooxidant states may modulate the expression of a family of prooxidant genes, which are related to cell growth and differentiation, by inducing alterations in DNA structure or by epigenetic mechanisms, for example, by polyadenosine diphosphate-ribosylation of chromosomal proteins.
Measuring Gene Expression with Light
Authors: Engebrecht JoAnne , Simon Melvin , Silverman Michael
Published: October 2006

Light is produced by recombinant
Escherichia coli
that contain
lux
genes cloned from the marine bacterium
Vibrio fischeri
. The bioluminescence phenotype requires genes for regulatory and biochemical functions, the latter encoded by five
lux
genes contained in a single operon. These
lux
genes were disconnected from their native promoter and inserted into the transposon mini-Mu. The resulting transposon, mini-Mu
lux
, could induce mutations by insertional inactivation of a target gene, and the
lux
DNA was oriented to align target gene transcription with that of the
lux
genes. Genes in
Escherichia coli
and
Vibrio parahaemolyticus
were mutagenized, and mutants containing transposon-generated
lux
gene fusions produced light as a function of target gene transcription. Light production offers a simple, sensitive, in vivo indicator of gene expression.
Location of the
Trans
-Activating Region on the Genome of Human T-Cell Lymphotropic Virus Type III
Authors: Sodroski Joseph , Patarca Roberto , Rosen Craig , Wong-Staal Flossie , Haseltine William
Published: October 2006

The retrovirus involved in acquired immune deficiency syndrome (HTLV-III/LAV) contains a region that is necessary for stimulation of gene expression directed by the viral long terminal repeat. This region is located between nucleotides 5365 and 5607, immediately 5′ to the envelope gene. A doubly-spliced message containing this region could encode an 86-amino acid protein with structural features similar to those of nucleic acid-binding proteins.
Discovery of a Predicted DNA Knot Substantiates a Model for Site-Specific Recombination
Authors: Wasserman Steven A. , Dungan Jan M. , Cozzarelli Nicholas R.
Published: October 2006

The mechanism of site-specific genetic recombination mediated by Tn3 resolvase has been investigated by a topological approach. Extrapolation of a detailed model of synapsis and strand exchange predicts the formation of an additional DNA product with a specific knotted structure. Two-dimensional gel electrophoresis of DNA reacted in vitro revealed a product, about 0.1 percent of the total, with the appropriate mobility. A technique for determining DNA topology by electron microscopy was improved such that less than a nanogram of DNA was required. The structure of the knot was as predicted, providing strong evidence for the model and showing the power of the topological method.
Regeneration of Functional Synapses Between Individual Recognizable Neurons in the Lamprey Spinal Cord
Authors: Mackler Scott A. , Selzer Michael E.
Published: October 2006

In 4- to 5-year-old sea lamprey larvae that had recovered from complete transection of the spinal cord, pairs of giant interneurons on opposite sides of the scar were impaled with microelectrodes. In 4 of 30 pairs, stimulation of the caudal cell elicited a monosynaptic electrochemical excitatory postsynaptic potential in the rostral cell. Fifty percent of such pairs were synaptically linked in control lampreys without transections. These results show regeneration of functional synaptic connections between individual neurons in a vertebrate central nervous system.
Induction of HTLV-III/LAV from a Nonvirus-Producing T-Cell Line: Implications for Latency
Authors: Folks Thomas , Powell Douglas M. , Lightfoote Marilyn M. , Benn Steven , Martin Malcolm A. , Fauci Anthony S.
Published: October 2006

When the human T-cell line A3.01 is infected with HTLV-III/LAV, the virus associated with the acquired immune deficiency syndrome (AIDS), most of the cells are killed. However, a small number of cells that lack the Leu-3 surface marker survive. Under normal conditions these surviving cells do not produce virus, nor can they be infected by the virus, but they can be induced to produce virus by treatment with 5-iodo-2′-deoxyuridine. This response can be induced for as long as 3 months after the initial infection, suggesting that the cells may harbor a latent form of HTLV-III/LAV.
Immunoregulatory Feedback Between Interleukin-1 and Glucocorticoid Hormones
Authors: Besedovsky Hugo , del Rey Adriana , Sorkin Ernst , Dinarello Charles A.
Published: October 2006

The production and action of immunoregulatory cytokines, including interleukin-1 (IL-1), are inhibited by glucocorticoid hormones in vivo and in vitro. Conversely, glucocorticoid blood levels were increased by factors released by human leukocytes exposed to Newcastle disease virus preparations. This activity was neutralized by an antibody to IL-1. Therefore the capacity of IL-1 to stimulate the pituitary-adrenal axis was tested. Administration of subpyrogenic doses of homogeneous human monocyte-derived IL-1 or the
p
I 7 form of human recombinant IL-1 to mice and rats increased blood levels of adrenocorticotropic hormone (ACTH) and glucocorticoids. Another monokine, tumor necrosis factor, and the lymphokines IL-2 and γ-interferon had no such effects when administered in doses equivalent to or higher than those of IL-1. The stimulatory effect of IL-1 on the pituitary-adrenal axis seemed not to be mediated by the secondary release of products from mature T lymphocytes since IL-1 was endocrinologically active when injected into athymic nude mice. These results strongly support the existence of an immunoregulatory feedback circuit in which IL-1 acts as an afferent and glucocorticoid as an efferent hormonal signal.
The Site of Attachment in Human Rhinovirus 14 for Antiviral Agents That Inhibit Uncoating
Authors: Smith Thomas J. , Kremer Marcia J. , Luo Ming , Vriend Gerrit , Arnold Edward , Kamer Greg , Rossmann Michael G. , McKinlay Mark A. , Diana Guy D. , Otto Michael J.
Published: October 2006

WIN 51711 and WIN 52084 are structurally related, antiviral compounds that inhibit the replication of rhino (common cold) viruses and related picornaviruses. They prevent thepH-mediated uncoating of the viral RNA. The compounds consist of a 3-methylisoxazole group that inserts itself into the hydrophobic interior of the VP1 β-barrel, a connecting seven-membered aliphatic chain, and a 4-oxazolinylphenoxy group (OP) that covers the entrance to an ion channel in the floor of the "canyon." Viral disassembly may be inhibited by preventing the collapse of the VP1 hydrophobic pocket or by blocking the flow of ions into the virus interior.
Nuclear and Mitochondrial DNA Comparisons Reveal Extreme Rate Variation in the Molecular Clock
Authors: Vawter Lisa , Brown Wesley M.
Published: October 2006

The discovery that the rate of evolution of vertebrate mitochondrial DNA is rapid, compared to the rate for vertebrate nuclear DNA, has resulted in its widespread use in evolutionary studies. Comparison of mitochondrial and nuclear DNA divergences among echinoid and vertebrate taxa of similar ages indicates that the rapid rate of vertebrate mitochondrial DNA evolution is, in part, an artifact of a widely divergent rate of nuclear DNA evolution. This disparity in relative rates of mitochondrial and nuclear DNA divergence suggests that the controls and constraints under which the mitochondrial and nuclear genomes operate are evolving independently, and provides evidence that is independent of fossil dating for a robust rejection of a generalized molecular clock hypothesis of DNA evolution.
Molecular Cloning of Complementary DNA Encoding the Avian Receptor for Vitamin D
Authors: McDonnell Donal P. , Mangelsdorf David J. , Pike J. Wesley , Haussler Mark R. , O'Malley Bert W.
Published: October 2006

Vitamin D
3
receptors are intracellular proteins that mediate the nuclear action of the active metabolite 1,25-dihydroxyvitamin D
3
[1,25(OH)
2
D
3
]. Two receptor-specific monoclonal antibodies were used to recover the complementary DNA (cDNA) of this regulatory protein from a chicken intestinal λgt11 cDNA expression library. The amino acid sequences that were deduced from this cDNA revealed a highly conserved cysteine-rich region that displayed homology with a domain characteristic of other steroid receptors and with the
gag-erbA
oncogene product of avian erythroblastosis virus. RNA selected via hybridization with this DNA sequence directed the cell-free synthesis of immunoprecipitable vitamin D
3
receptor. Northern blot analysis of polyadenylated RNA with these cDNA probes revealed two vitamin D receptor messenger RNAs (mRNAs) of 2.6 and 3.2 kilobases in receptor-containing chicken tissues and a major cross-hybridizing receptor mRNA species of 4.2 kilobases in mouse 3T6 fibroblasts. The 4.2-kilobase species was substantially increased by prior exposure of 3T6 cells to 1,25(OH)
2
D
3
. This cDNA represents perhaps the rarest mRNA cloned to date in eukaryotes, as well as the first receptor sequence described for an authentic vitamin.
Clustering of Genes Dispensable for Growth in Culture in the S Component of the HSV-1 Genome
Authors: Longnecker Richard , Roizman Bernard
Published: October 2006

The herpes simplex virus 1 genome consists of one long and one short stretch of unique sequences flanked by inverted repeat sequences. The nucleotide sequence and RNA map predict 12 open reading frames designated as US1 through US12 within the short stretch of unique sequences. This paper reports the construction of virus mutants from which US2, US3, or US4 had been deleted that are capable of growth in cell culture. One of the three deleted genes, US4, specifies the viral envelope glycoprotein G. Mutants with deletions in US1, US8, US9, US10, US11, and US12 have been previously reported. The nine genes deleted from this region form two clusters, US1 through US4 and US8 through US12, and encode at least two and possibly more structural proteins. The presence of so many genes dispensable for growth in cell culture suggests several hypotheses regarding their function and evolution.
Mapping Human Brain Monoamine Oxidase A and B with11C-Labeled Suicide Inactivators and PET
Authors: Fowler J. S. , MacGregor R. R. , Wolf A. P. , Arnett C. D. , Dewey S. L. , Schlyer D. , Christman D. , Logan J. , Smith M. , Sachs H. , Aquilonius S. M. , Bjurling P. , Halldin C. , Hartvig P. , Leenders K. L. , Lundqvist H. , Oreland L. , Stålnacke C.-G. , Långström B.
Published: October 2006

The regional distributions of monoamine oxidase (MAO) types A and B have been identified in human brain in vivo with intravenously injected11C-labeled suicide enzyme inactivators, clorgyline and L-deprenyl, and positron emission tomography. The rapid brain uptake and retention of radioactivity for both11C tracers indicated irreversible trapping. The anatomical distribution of11C paralleled the distribution of MAO A and MAO B in human brain in autopsy material. The corpus striatum, thalamus, and brainstem contained high MAO activity. The magnitudes of uptake of both [11C]clorgyline and L-[11C]deprenyl were markedly reduced in one subject treated with the antidepressant MAO inhibitor phenelzine. A comparison of the brain uptake and retention of the11C-labeled inactive (D-) and active (L-) enantiomers of deprenyl showed rapid clearance of the inactive enantiomer and retention of the active enantiomer within MAO B-rich brain structures, in agreement with the known stereoselectivity of MAO B for L-deprenyl. Prior treatment with unlabeled L-deprenyl prevented retention of L-[11C]deprenyl. Thus, suicide enzyme inactivators labeled with positron emitters can be used to quantitate the distribution and kinetic characteristics of MAO in human brain structures.
A Small Viral RNA Is Required for in Vitro Packaging of Bacteriophage φ29 DNA
Authors: Guo Peixuan , Erickson Stephen , Anderson Dwight
Published: October 2006

A small RNA of
Bacillus subtilis
bacteriophage φ29 is shown to have a novel and essential role in viral DNA packaging in vitro. This requirement for RNA in the encapsidation of viral DNA provides a new dimension of complexity to the attendant protein-DNA interactions. The RNA is a constituent of the viral precursor shell of the DNA-packaging machine but is not a component of the mature virion. Studies of the sequential interactions involving this RNA molecule are likely to provide new insight into the structural and possible catalytic roles of small RNA molecules. The φ29 assembly in extracts and φ29 DNA packaging in the defined in vitro system were strongly inhibited by treatment with the ribonucleases A or T1. However, phage assembly occurred normally in the presence of ribonuclease A that had been treated with a ribonuclease inhibitor. An RNA of approximately 120 nucleotides co-purified with the φ29 precursor protein shell (prohead), and this particle was the target of ribonuclease action. Removal of RNA from the prohead by ribonuclease rendered it inactive for DNA packaging. By RNA-DNA hybridization analysis, the RNA was shown to originate from a viral DNA segment very near the left end of the genome, the end packaged first during in vitro assembly.
Suppression of Macrophage Activation and T-Lymphocyte Function in Hypoprolactinemic Mice
Authors: Bernton Edward W. , Meltzer Monte S. , Holaday John W.
Published: October 2006

The effects of prolactin on lactation and reproductive organs are well known. However, the other possible target organs and physiological consequences of altered levels of circulating prolactin remain poorly understood. In this study, mice were treated with bromocryptine, a dopamine receptor agonist that inhibits pituitary prolactin secretion. Bromocryptine treatment prevented T-cell-dependent induction of macrophage tumoricidal activity after the intraperitoneal injection of
Listeria monocytogenes
or
Mycobacterium bovis
. Coincident treatment with ovine prolactin reversed this effect. Of the multiple events leading to macrophage activation in vivo, the production by T-lymphocytes of γ-interferon was the most impaired in bromocryptine-treated mice. Lymphocyte proliferation after stimulation with mitogens in vitro was also depressed in spleens of bromocryptine-treated mice, and coadministration of prolactin also reversed this effect. Bromocryptine treatment also reduced the number of deaths resulting from inoculation of mice with
Listeria
; exogenous prolactin significantly reversed this effect. The critical influence of pituitary prolactin release on maintenance of lymphocyte function and on lymphokine-dependent macrophage activation suggests that, in mice, lymphocytes are an important target tissue for circulating prolactin.
Expression of a Calcium-Mobilizing Parathyroid Hormone-Like Peptide in Lactating Mammary Tissue
Authors: Thiede Mark A. , Rodan Gideon A.
Published: October 2006

A survey of rat tissues by RNA analysis, aimed at uncovering the physiological function of the parathyroid hormone-like peptide (PTH-LP) associated with hypercalcemia of malignancy, revealed the presence of a 1.5-kilobase messenger RNA encoding this peptide in lactating mammary glands. PTH-LP messenger RNA is expressed in mammary tissue only during lactation; it appears and disappears rapidly (2 to 4 hours) as a function of the sucking stimulus. The identity of this messenger RNA was confirmed by cloning the rat PTH-LP complementary DNA, which predicts a peptide with strong similarity to the human homolog. Moreover, extracts from lactating mammary tissue stimulated parathyroid hormone-dependent adenylate cyclase. These findings suggest that PTH-LP plays a physiological role in lactation, possibly as a hormone for the mobilization or transfer (or both) of calcium to the milk.
An in Vitro System for Accurate Methylation of Internal Adenosine Residues in Messenger RNA
Authors: Narayan Prema , Rottman Fritz M.
Published: October 2006

Some internal adenosine residues in messenger RNA are methylated posttranscriptionally in the nucleus. Most of the methylated adenosine residues in prolactin mRNA are in the 3′ untranslated region. The site of methylation in the 3′ end of prolactin mRNA was determined. This methylation reaction is highly specific; of the three adenosine residues in consensus sequences located in the 3′ end, only one is methylated. An in vitro methylation system was developed in which bovine prolactin mRNA, synthesized in vitro with T7 RNA polymerase, was accurately methylated in a HeLa cell nuclear extract. The adenosine residue that was methylated in vitro was the same as the one methylated in vivo. This cell-free system, which accurately methylates the N
6
-position of adenosine residues in mRNA, will allow further study of the mechanism of adenosine methylation.
Introduction of Nucleophiles and Spectroscopic Probes into Antibody Combining Sites
Authors: Pollack Scott J. , Nakayama Grace R. , Schultz Peter G.
Published: October 2006

A general chemical strategy has been developed whereby antibody combining sites can be selectively derivatized with natural or synthetic molecules, such as catalytic groups, drugs, metals, or reporter molecules. Cleavable affinity labels were used to selectively introduce a thiol into the combining site of the immunoglobulin A MOPC 315. This thiol acted both as a nucleophile to accelerate ester thiolysis 60,000-fold and as a handle for selectively derivatizing the antibody with additional functional groups. For example, derivatization of the antibody with a fluorophore made possible a direct spectroscopic assay of antibody-ligand complexation. This chemistry should not only extend our ability to exploit antibody specificity in chemical catalysis, diagnostics, and therapeutics, but may also prove generally applicable to the functional modification of other proteins for which detailed structural information is unavailable.
Mitochondrial DNA Mutation Associated with Leber's Hereditary Optic Neuropathy
Authors: Wallace Douglas C. , Singh Gurparkash , Lott Marie T. , Hodge Judy A. , Schurr Theodore G. , Lezza Angela M. S. , Elsas Louis J. , Nikoskelainen Eeva K.
Published: October 2006

Leber's hereditary optic neuropathy is a maternally inherited disease resulting in optic nerve degeneration and cardiac dysrhythmia. A mitochondrial DNA replacement mutation was identified that correlated with this disease in multiple families. This mutation converted a highly conserved arginine to a histidine at codon 340 in the NADH dehydrogenase subunit 4 gene and eliminated an Sfa NI site, thus providing a simple diagnostic test. This finding demonstrated that a nucleotide change in a mitochondrial DNA energy production gene can result in a neurological disease.
Calicheamicin γ
1
I
: an Antitumor Antibiotic That Cleaves Double-Stranded DNA Site Specifically
Authors: Zein Nada , Sinha Achyut M. , McGahren William J. , Ellestad George A.
Published: October 2006

Calicheamicin γ
1
I
is a recently discovered diyne-ene—containing antitumor antibiotic with considerable potency against murine tumors. In vitro, this drug interacts with double-helical DNA in the minor groove and causes site-specific double-stranded cleavage. It is proposed that the observed cleavage specificity is a result of a unique fit of the drug and DNA followed by the generation of a nondiffusible 1,4-dehydrobenzene—diradical species that initiates oxidative strand scission by hydrogen abstraction on the deoxyribose ring. The ability of calicheamicin γ
1
I
to cause double-strand cuts at very low concentrations may account for its potent antitumor activity.
Effects of Cyclosporine A on T Cell Development and Clonal Deletion
Authors: Jenkins Marc K. , Schwartz Ronald H. , Pardoll Drew M.
Published: October 2006

Cyclosporine A (CsA) is an important immunosuppressive drug that is widely used in transplantation medicine. Many of its suppressive effects on T cells appear to be related to the inhibition of T cell receptor (TCR)-mediated activation events. Paradoxically, in certain situations CsA is responsible for the induction of a T cell-mediated autoimmunity. The effects of CsA on T cell development in the thymus were investigated to elucidate the physiologic events underlying this phenomenon. Two major effects were revealed: (i) CsA inhibits the development of mature single positive (CD4
+
8
-
or CD4
-
8
+
) TCR-α β
+
thymocytes without discernibly affecting CD4
-
8
-
TCR-γδ
+
thymocytes and (ii) CsA interferes with the deletion of cells bearing self-reactive TCRs in the population of single positive thymocytes that do develop. This suggests a direct mechanism for CsA-induced autoimmunity and may have implications for the relative contribution of TCR-mediated signaling events in the development of the various T cell lineages.
The Expert Witness in Psychology and Psychiatry
Authors: Faust David , Ziskin Jay
Published: October 2006

The involvement of psychologists and psychiatrists within the legal arena continues to grow rapidly but remains highly controversial. Extensive research on clinical judgment provides a scientific basis for clarifying the growing disputes about the values of such professional activities. Studies show that professionals often fail to reach reliable or valid conclusions and that the accuracy of their judgments does not necessarily surpass that of laypersons, thus raising substantial doubt that psychologists or psychiatrists meet legal standards for expertise. Factors that underlie the research findings and implications for courtroom testimony are discussed.
Neural Model of Adaptive Hand-Eye Coordination for Single Postures
Authors: Kuperstein Michael
Published: October 2006

A neural network model has been developed that achieves adaptive visual-motor coordination of a multijoint arm, without a teacher. The model learns to position an arm so that it reaches a cylinder arbitrarily positioned in space. The model uses a new neural architecture and a new algorithm for modifying neural-connection strengths. Computer simulations show that the model performs with an average position error of 4% of the arm's length and with an average orientation error of 4°. The model is designed to be generalized for coordinating any number of topographic sensory inputs with limbs of any number of joints.
Biological Bases of Childhood Shyness
Authors: Kagan Jerome , Reznick J. Steven , Snidman Nancy
Published: October 2006

The initial behavioral reaction to unfamiliar events is a distinctive source of intraspecific variation in humans and other animals. Two longitudinal studies of 2-year-old children who were extreme in the display of either behavioral restraint or spontaneity in unfamiliar contexts revealed that by 7 years of age a majority of the restrained group were quiet and socially avoidant with unfamiliar children and adults whereas a majority of the more spontaneous children were talkative and interactive. The group differences in peripheral physiological reactions suggest that inherited variation in the threshold of arousal in selected limbic sites may contribute to shyness in childhood and even extreme degrees of social avoidance in adults.
Social Relationships and Health
Authors: House James S. , Landis Karl R. , Umberson Debra
Published: October 2006

Recent scientific work has established both a theoretical basis and strong empirical evidence for a causal impact of social relationships on health. Prospective studies, which control for baseline health status, consistently show increased risk of death among persons with a low quantity, and sometimes low quality, of social relationships. Experimental and quasi-experimental studies of humans and animals also suggest that social isolation is a major risk factor for mortality from widely varying causes. The mechanisms through which social relationships affect health and the factors that promote or inhibit the development and maintenance of social relationships remain to be explored.
Functional Cooperativity Between Transcription Factors UBF1 and SL1 Mediates Human Ribosomal RNA Synthesis
Authors: Bell Stephen P. , Learned R. Marc , Jantzen Hans-Michael , Tjian Robert
Published: October 2006

The human ribosomal RNA promoter contains two distinct control elements (UCE and core) both of which are recognized by the sequence-specific DNA binding protein UBF1, which has now been purified to apparent homogeneity. The purified factor activates RNA polymerase I (RNA pol I) transcription through direct interactions with either control element. A second RNA pol I transcription factor, designated SL1, participates in the promoter recognition process and is required to reconstitute transcription in vitro. Although SL1 alone has no sequence-specific DNA binding activity, deoxyribonuclease I footprinting experiments reveal that a cooperative interaction between UBF1 and SL1 leads to the formation of a new protein-DNA complex at the UCE and core elements. In vitro transcription experiments indicate that formation of the UBF1-SL1 complex is vital for transcriptional activation by UBF1. Thus, protein-protein interactions between UBF1 and SL1 are required for targeting of SL1 to cis-control sequences of the promoter.
Schizophrenic Symptoms Improve with Apomorphine
Authors: Tamminga Carol A. , Schaffer Martin H. , Smith Robert C. , Davis John M.
Published: October 2006

Eighteen chronic schizophrenic patients received subcutaneous doses of apomorphine, a dopamine receptor agonist, and of placebo in separate trials. A significant improvement in psychotic symptoms occurred after apomorphine compared to placebo. The results are interpreted as a consequence of presynaptic dopamine receptor activation by apomorphine with a subsequent decrease in dopamine-mediated neural transmission.
Innervation of Periosteum and Bone by Sympathetic Vasoactive Intestinal Peptide-Containing Nerve Fibers
Authors: Hohmann Elizabeth L. , Elde Robert P. , Rysavy Joseph A. , Einzig Stanley , Gebhard Roger L.
Published: October 2006

Neural control of bone metabolism and growth has been suggested, although the identity of participating neurons and neurotransmitters effecting this control has not been established. Immunohistochemical studies demonstrated a system of vasoactive intestinal peptide (VIP)-immunoreactive nerve fibers that innervate periosteum and bone in several mammalian species. Thoracic sympathetic chain ganglionectomy resulted in an ipsilateral loss of VIP-immunoreactive fibers in the periosteum of ribs, whereas dorsal root ganglionectomy had no effect. Injection of fast blue into rib periosteum labeled a population of VIP-immunoreactive sympathetic postganglionic neurons. Thus, postganglionic sympathetic neurons may provide an important means by which VIP regulates bone mineralization.