bluuebunny/crossref_metadata_2025 huggingface dataset:
An Insulin-Stimulated Protein Kinase Similar to Yeast Kinases Involved in Cell Cycle Control
Authors: Boulton Teri G. , Yancopoulos George D. , Gregory Jill S. , Slaughter Clive , Moomaw Carolyn , Hsu Joan , Cobb Melanie H.
Published: October 2006

A protein kinase characterized by its ability to phosphorylate microtubule-associated protein-2 (MAP2), is thought to be an early intermediate in an insulin-stimulated phosphorylation cascade and in a variety of other mammalian cell responses to extracellular signals. A complementary DNA that encodes this protein serine-threonine kinase has been cloned, and the protein designated extracellular signal-regulated kinase 1 (ERK1). ERK1 has striking similarity to two protein kinases, KSS1 and FUS3, from yeast. The yeast kinases function in an antagonistic manner to regulate the cell cycle in response to mating factors. Thus, ERK1 and the two yeast kinases constitute a family of evolutionarily conserved enzymes involved in regulating the response of eukaryotic cells to extracellular signals.
Feature Identification and Location Experiment
Authors: Sivertson W. E. , Wilson R. Gale , Bullock Gordon F. , Schappell R. T.
Published: October 2006

The feature identification and location experiment (FILE) senses radiation from the earth in spectral bands centered at 0.65 and 0.85 micrometers and compares ratios of the reflected solar radiation in the two wavelengths to make real-time classification decisions about four primary features: water, vegetation, bare land, and a cloud-snow-ice class. The radiance ratio classification algorithm successfully made automatic data-selection decisions. The classification image obtained on the mission is providing information needed to evaluate the FILE algorithm and system performance.
Enhancement of the GDP-GTP Exchange of RAS Proteins by the Carboxyl-Terminal Domain of SCD25
Authors: Créchet Jean-Bernard , Poullet Patrick , Mistou Michel-Yves , Parmeggiani Andrea , Camonis Jacques , Boy-Marcotte Emmanuelle , Damak Faten , Jacquet Michel
Published: October 2006

In
Saccharomyces cerevisiae
, the product of the
CDC25
gene controls the RAS-mediated production of adenosine 3′,5′-monophosphate (cAMP). In vivo the carboxyl-terminal third of the
CDC25
gene product is sufficient for the activation of adenylate cyclase. The 3′-terminal part of
SCD25
, a gene of
S. cerevisiae
structurally related to
CDC25
, can suppress the requirement for
CDC25
. Partially purified preparations of the carboxyl-terminal domain of the
SCD25
gene product enhanced the exchange rate of guanosine diphosphate (GDP) to guanosine triphosphate (GTP) of pure RAS2 protein by stimulating the release of GDP. This protein fragment had a similar effect on the human c-H-
ras
-encoded p21 protein. Thus, the SCD25 carboxyl-terminal domain can enhance the regeneration of the active form of RAS proteins.
Molecular Biological Mechanisms of Speciation
Authors: Rose Michael R. , Doolittle W. Ford
Published: October 2006

Growing recognition that much of the evolutionary history of eukaryotic genomes reflects the operation of turnover processes involving repetitive DNA sequences has led to the recent formulation of models describing speciation as a consequence of such turnover. These models are of three general kinds: those attributing hybrid infertility to the process of transposition, those attributing hybrid infertility to mispairing between chromosomes of divergent repetitive DNA composition, and those assuming that change in repetitive DNA's can reset coordinated gene regulation. These models are discussed with respect to the kinds of evidence needed for their corroboration and to their significance for questions related to macroevolutionary punctuated equilibria and genetic revolutions.
Death of a Hadal Deep-Sea Bacterium After Decompression
Authors: Yayanos A. Aristides , Dietz Allan S.
Published: October 2006

An obligately barophilic bacterium that was recovered from a depth of 10,476 meters in the Pacific Ocean slowly lost colony-forming ability (assayed at 101.3 megapascals and 2°C) during incubation at atmospheric pressure and 0°C.
Sex Pheromone Biosynthesis in
Trichoplusia ni
: Key Steps Involve Delta-11 Desaturation and Chain-Shortening
Authors: Bjostad L. B. , Roelofs W. L.
Published: October 2006

In addition to the primary pheromone component (
Z
)-7-dodecenyl acetate, the sex pheromone gland of
Trichoplusia ni
contains the immediate fatty acyl precursor (
Z
)-7-dodecenoate and a large quantity of (
Z
)-11-hexadecenoate. Labeling experiments showed that (
Z
)-11-hexadecenoate is chain-shortened to (
Z
)-9-tetradecenoate, and that this in turn is chain-shortened to (
Z
)-7-dodecenoate. The same mechanism appears to explain the sex pheromone compositions of many other moth species.
Differentiation of Mouse Erythroleukemia Cells Enhanced by Alternatively Spliced c-
myb
mRNA
Authors: Weber Barbara L. , Westin Eric H. , Clarke Michael F.
Published: October 2006

C-
myb
, the normal cellular homolog of the retroviral transforming gene v-
myb
, encodes a nuclear, transcriptional regulatory protein (p75

c-
myb

). C-
myb
is involved in regulating normal human hematopoiesis, and inhibits dimethyl sulfoxide-induced differentiation of Friend murine erythroleukemia (F-MEL) cells. An alternately spliced c-
myb
mRNA encodes a truncated version of p75

c-
myb

(
mbm2
) that includes the DNA binding region and nuclear localization signal present in the c-
myb
protein, but does not contain the transcriptional regulatory regions. Constitutive expression of
mbm2
, in contrast to c-
myb
, here resulted in enhanced differentiation of F-MEL cells. These data suggest that the c-
myb
protooncogene encodes alternately spliced mRNA species with opposing effects on differentiation.
Chitin in Sea Anemone Shells
Authors: Dunn Daphne Fautin , Liberman Martin H.
Published: October 2006

Chitin, which is widely distributed among life forms, is well documented in the coelenterate class Hydrozoa and is contained in one member of class Scyphozoa. In class Anthozoa, hard corals synthesize it but soft corals do not. Chitin was identified by infrared spectrophotometry in the trochoid shell of the actinian
Stylobates
. It constitutes 1.7 percent of the shell by weight, the rest probably being protein. The ability of sea anemones to synthesize chitin is thereby confirmed.
Adaptive Complexity of Interactions Between Feeding and Escape in Crayfish
Authors: Bellman Kirstie L. , Krasne Franklin B.
Published: October 2006

If crayfish (
Procambarus clarkii
) are presented with food or threat stimuli, or both, their feeding behavior and escape from threat by tail flips show flexible patterns of interaction. If they are engaged in eating large, relatively immovable pieces of food, escape is inhibited, whereas if small pieces of food are being eaten, the probability of escape is enhanced. If escape occurs during a feeding bout, large pieces of food are usually released, but small ones are not. These observations suggest that the neural circuitry responsible for coordination of behavior in invertebrates may not be as simple as usually assumed.
Phosphorus Cycling in a Northern Hardwood Forest: Biological and Chemical Control
Authors: Wood Tim , Bormann F. H. , Voigt G. K.
Published: October 2006

Phosphorus is tightly conserved within the northern hardwood forest ecosystems at Hubbard Brook, New Hampshire. Detailed analyses of the soil system indicate that biological and geochemical processes, stratified within the profile, regulate phosphorus retention.
Circadian Changes in Enzyme Concentration Account for Rhythm of Enzyme Activity in
Gonyaulax
Authors: Johnson Carl Hirschie , Roeber James F. , Hastings J. W.
Published: October 2006

A circadian rhythm in the activity of luciferase is partly responsible for rhythmic bioluminescence in the dinoflagellate alga
Gonyaulax polyedra
. The cyclic activity of this enzyme can be attributed to a corresponding rhythm in the concentration of immunologically reactive luciferase protein. Hence protein turnover (synthesis or degradation or both) is used by the endogenous clock to control the daily rhythm of bioluminescence.
cdc2
Gene Expression at the G
1
to S Transition in Human T Lymphocytes
Authors: Furukawa Yusuke , Piwnica-Worms Helen , Ernst Timothy J. , Kanakura Yuzuru , Griffin James D.
Published: October 2006

The product of the
cdc2
gene, designated p34

cdc2

, is a serine-threonine protein kinase that controls entry of eukaryotic cells into mitosis. Freshly isolated human T lymphocytes (G
0
phase) were found to have very low amounts of p34

cdc2

and
cdc2
messenger RNA. Expression of
cdc2
increased 18 to 24 hours after exposure of T cells to phytohemagglutinin, coincident with the G
1
to S transition. Antisense oligodeoxynucleotides could reduce the increase in
cdc2
expression and inhibited DNA synthesis, but had no effect on several early and mid-G
1
events, including blastogenesis and expression of interleukin-2 receptors, transferrin receptors, c-
myb
, and c-
myc
. Induction of
cdc2
required prior induction of c-
myb
and c-
myc
. These results suggest that
cdc2
induction is part of an orderly sequence of events that occurs at the G
1
to S transition in T cells.
Mississippi Deltaic Wetland Survival: Sedimentation Versus Coastal Submergence
Authors: Baumann Robert H. , Day John W. , Miller Carolyn A.
Published: October 2006

Seasonal sedimentation, measured with the aid of artificial marker horizons, was markedly different in deteriorating as compared with stable marshes in the Mississippi River deltaic plain. Deteriorating marshes receive most sediment during storm events, whereas stable marshes receive substantial amounts of sediments during the spring river flood. The deteriorating marshes are accreting at a faster rate (1.5 centimeters per year at streamside, 0.9 centimeter per year at inland areas) than the stable marshes (1.3 centimeters per year at streamside, 0.6 centimeter per year at inland areas). However, relative to local apparent sea-level rise as measured by tide gauges in each area, the deteriorating marshes are not maintaining their intertidal elevation as well as the stable marshes. These results indicate the importance of considering accretion relative to submergence.
Polychlorinated Dibenzo-
p
-dioxins and Dibenzofurans in Sediments from Siskiwit Lake, Isle Royale
Authors: Czuczwa Jean M. , McVeety Bruce D. , Hites Ronald A.
Published: October 2006

Polychlorinated dibenzo-
p
-dioxins and dibenzofurans were found in sediment from Siskiwit Lake on Isle Royale, Lake Superior, a location which can receive only atmospheric inputs. The source of these compounds is the atmospheric transport of dioxins and furans formed by combustion of domestic and chemical waste.
Acid Precipitation: Natural Versus Anthropogenic Components
Authors: Galloway James N. , Likens Gene E. , Hawley Mark E.
Published: October 2006

The concentrations of H
+
, SO
4
2-
, and NO
3
-
in the precipitation of eastern North America are greater now than they were historically as a result of fossil-fuel combustion. Because of a lack of data prior to 1950, the absolute increases in the concentrations of these three ions are unknown. This problem can be addressed by comparing the composition of precipitation from areas sensitive to acidic deposition with that of precipitation from remote areas. An analysis of precipitation data indicates that many areas of eastern North America receive precipitation with substantially greater H
+
, SO
4
2-
, and NO
3
-
concentrations than remote areas. For example, SO
4
2-
, the most ecologically significant indicator of change, is enriched 2 to 16 times in eastern North American precipitation relative to its concentration in remote areas.
The Pollination of
Zygogynum
(Winteraceae) by a Moth,
Sabatinca
(Micropterigidae): An Ancient Association?
Authors: Thien Leonard B. , Bernhardt Peter , Gibbs George W. , Pellmyr Olle , Bergström Gunnar , Groth Inga , McPherson Gordon
Published: October 2006

The primitive and vesselless angiosperm
Zygogynum
(Winteraceae), which is restricted to New Caledonia, is pollinated by a moth,
Sabatinca
(Micropterigidae). Fossil records of both the moth and the plant families extend to the Early Cretaceous. Adult
Sabatinca
have grinding mandibles and usually feed on the spores of ferns and on pollen. The insects use the flowers as mating sites and eat the pollen which is immersed in a dense pollenkitt. This mode of pollination in which flowers serve as mating and feeding stations with floral odors acting as cues may have been common in the early evolution of flowering plants.
Strain Accumulation in the Shumagin and Yakataga Seismic Gaps, Alaska
Authors: Savage J. C. , Lisowski M. , Prescott W. H.
Published: October 2006

Strain accumulation during the 1980-85 interval has been measured by means of trilateration surveys in the Shumagin and Yakataga seismic gaps, which are the two regions identified as the most likely sites for the next great thrust earthquakes along the Alaska-Aleutian arc. No significant strain accumulation was detected in the Shumagin gap, but experience at similar subduction zones and simple models of the subduction process suggest that a measurable amount of strain should have accumulated. The most likely explanation of the observation is that subduction there is either aseismic or episodic. The strain accumulation measured in the Yakataga gap is consistent with that expected for the plate convergence rate, although the direction of maximum compression may suggest a somewhat more oblique convergence than expected.
Dynamics of Fractal Networks
Authors: Orbach R.
Published: October 2006

Random structures often exhibit fractal geometry, defined in terms of the mass scaling exponent,
D
, the fractal dimension. The vibrational dynamics of fractal networks are expressed in terms of the exponent d̿, the fracton dimensionality. The eigenstates on a fractal network are spatially localized for d̿ less than or equal to 2. The implications of fractal geometry are discussed for thermal transport on fractal networks. The electron-fracton interaction is developed, with a brief outline given for the time dependence of the electronic relaxation on fractal networks. It is suggested that amorphous or glassy materials may exhibit fractal properties at short length scales or, equivalently, at high energies. The calculations of physical properties can be used to test the fractal character of the vibrational excitations in these materials.
Thallphytic Alleopathy: Isolation and Identification of Laetisaric Acid
Authors: Bowers William S. , Hoch Harvey C. , Evans Philip H. , Katayama Masato
Published: October 2006

Laetisaria arvalis
, a soil-dwelling basidiomycete fungus, secretes an allelopathic agent that induces rapid hyphal lysis in several phytopathogenic fungi. The active compound was isolated from chloroform:methanol extracts of
L. arvalis
mycelia and characterized as a previously unknown hydroxy fatty acid, (
Z
,
Z
)-9,12-8-hydroxyoctadecadienoic acid.
Comet Giacobini-Zinner: Plasma Description
Authors: Bame S. J. , Anderson R. C. , Asbridge J. R. , Baker D. N. , Feldman W. C. , Fuselier S. A. , Gosling J. T. , McComas D. J. , Thomsen M. F. , Young D. T. , Zwickl R. D.
Published: October 2006

A strong interaction between the solar wind and comet Giacobini-Zinner was observed oh 11 September 1985 with the Los Alamos plasma electron experiment on the International Cometary Explorer (ICE) spacecraft. As ICE approached an intercept point 7800 kilometers behind the nucleus from the south and receded to the north, upstream phenomena due to the comet were observed. Periods of enhanced electron heat flux from the comet as well as almost continuous electron density fluctuations were measured. These effects are related to the strong electron heating observed in the cometary interaction region and to cometary ion pickup by the solar wind, respectively. No evidence for a conventional bow shock was found as ICE entered and exited the regions of strongest interaction of the solar wind with the cometary environment. The outer extent of this strong interaction zone was a transition region in which the solar wind plasma was heated, compressed, and slowed. Inside the inner boundary of the transition region was a sheath that enclosed a cold intermediate coma. In the transition region and sheath, small-scale enhancements in density were observed. These density spikes may be due to an instability associated with cometary ion pickup or to the passage of ICE through cometary ray structures. In the center of the cold intermediate coma a narrow, high-density core of plasma, presumably the developing plasma tail, was found. In some ways this tail can be compared to the plasma sheet in Earth's magnetotail and to the current sheet in the tail at Venus. This type of configuration is expected in the double-lobe magnetic topology detected at the comet, possibly caused by the theoretically expected draping of the interplanetary magnetic field around its ionosphere.
A Toxic Dipeptide from the Defense Glands of the Colorado Beetle
Authors: Daloze D. , Braekman J. C. , Pasteels J. M.
Published: October 2006

The Colorado beetle is protected against predators by the secretions of defensive glands located on the pronotum and the elytra. The single major compound of the secretion was identified as γ-L-glutamyl-L-2-amino-3(
Z
),5-hexadienoic acid by spectroscopic and chemical methods. This compound, which contains a nonprotein β,γ-unsaturated amino acid, is toxic to ants (
Myrmica rubra
) at a concentration 10
-2
molar, which is less than its estimated concentration in the secretion (1.8 × 10
-1
molar).
GT-1 Binding Site Confers Light Responsive Expression in Transgenic Tobacco
Authors: Lam Eric , Chua Nam-Hai
Published: October 2006

Light-dependent expression of
rbcS
, the gene encoding the small subunit of ribulose-1,5-bisphosphate carboxylase, which is the key enzyme involved in carbon fixation in higher plants, is regulated at the transcriptional level. Sequence analysis of the gene has uncovered a conserved GT motif in the -150 to -100 region of many
rbcS
promoters. This motif serves as the binding site of a nuclear factor, designated GT-1. Analysis of site-specific mutants of pea
rbcS-3A
promoter demonstrated that GT-1 binding in vitro is correlated with light-responsive expression of the
rbcS
promoter in transgenic plants. However, it is not known whether factors other than GT-1 might also be required for activation of transcription by light. A synthetic tetramer of box II (TGTGTGGTTAATATG), the GT-1 binding site located between -152 to -138 of the
rbcS-3A
promoter, inserted upstream of a truncated cauliflower mosaic virus 35
S
promoter is sufficient to confer expression in leaves of transgenic tobacco. This expression occurs principally in chloroplast-containing cells, is induced by light, and is correlated with the ability of box II to bind GT-1 in vitro. The data show that the binding site for GT-1 is likely to be a part of the molecular light switch for
rbcS
activation.
An Amylose Antiparallel Double Helix at Atomic Resolution
Authors: Hinrichs W. , Büttner G. , Steifa M. , Betzel CH. , Zabel V. , Pfannemüller B. , Saenger W.
Published: October 2006

In the crystal structure of the polyiodide complex (
p
-nitrophenyl-α-maltohexaose
2
) ⋅ Ba(I
3
)
2
⋅ 22H
2
O, the maltohexaose units form an antiparallel, left-handed double helix with O-2 ... O-3 and O-6 ... O-6 hydrogen bonding and a central cavity that encloses two triiodide units. This structure contrasts with the parallel, left-handed double helix with no central cavity proposed for the A- and B-starch helix and the left-handed single helix in V-amylose and may be relevant for the stabilization of glycogen Structure.
A Rapid Cold-Hardening Process in Insects
Authors: Lee Richard E. , Chen Cheng-Ping , Denlinger David L.
Published: October 2006

Traditionally studies of cold tolerance in insects have focused on seasonal adaptations related to overwintering that are observed after weeks or months of exposure to low temperature. In contrast, an extremely rapid cold-hardening response was observed in nonoverwintering stages that confers protection against injury due to cold shock at temperatures above the supercooling point. This response was observed in nondiapausing larvae and pharate adults of the flesh fly,
Sarcophaga crassipalpis
, nondiapausing adults of the elm leaf beetle,
Xanthogaleruca luteola
, and the milkweed bug,
Oncopeltus fasciatus
. The rapid hardening response is correlated with the accumulation of glycerol.
Increased Life-Span of
age
-1 Mutants in
Caenorhabditis elegans
and Lower Gompertz Rate of Aging
Authors: Johnson Thomas E.
Published: October 2006

A mutation in the
age-1
gene of the nematode
Caenorhabditis elegans
has been shown to result in a 65 percent increase in mean life-span and a 110 percent increase in maximum life-span at 25°C. One of the hallmarks of organismic aging and senescent processes is an exponential acceleration of age-specific mortality rate with chronological age. This exponential acceleration is under genetic control:
age-1
mutant hermaphrodites show a 50 percent slower rate of acceleration of mortality with chronological age than wild-type strains. Mutant males also show a lengthening of life and a slowing of the rate of acceleration of mortality, although
age-1
mutant males still have significantly shorter life-spans than do hermaphrodites of the same genotype. The slower rates of acceleration of mortality are recessive characteristics of the
age-1
mutant alleles examined.
A New Class of Endogenous Human Retroviral Genomes
Authors: Callahan Robert , Chiu Ing-Ming , Wong James F. H. , Tronick Stephen R. , Roe Bruce A. , Aaronson Stuart A. , Schlom Jeffrey
Published: October 2006

Human DNA contains multiple copies of a novel class of endogenous retroviral genomes. Analysis of a human recombinant DNA clone (HLM-2) containing one such proviral genome revealed that it is a mosaic of retroviral-related sequences with the organization and length of known endogenous retroviral genomes. The HLM-2 long terminal repeat hybridized with the long terminal repeat of the squirrel monkey virus, a type D retrovirus. The HLM-2
gag
and
pol
genes share extensive nucleotide sequence homology with those of the M432 retrovirus (a type A-related retrovirus), mouse mammary tumor virus (a type B retrovirus), and the avian Rous sarcoma virus (a type C retrovirus). Nucleotide sequence analysis revealed regions in the HLM-2
pol
gene that were as much as 70 percent identical to the mouse mammary tumor virus
pol
gene. A portion of the putative HLM-2
env
gene hybridized with the corresponding region of the M432 viral genome.
A Molecular Shift Register Based on Electron Transfer
Authors: Hopfield J. J. , Onuchic José Nelson , Beratan David N.
Published: October 2006

An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a "molecular electronic device" that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density.
Neoplastic Conversion of Human Keratinocytes by Adenovirus 12-SV40 Virus and Chemical Carcinogens
Authors: Rhim Johng S. , Fujita Jun , Arnstein Paul , Aaronson Stuart A.
Published: October 2006

Efforts to investigate the progression of events that lead human cells of epithelial origin to become neoplastic in response to carcinogenic agents have been aided by the development of tissue culture systems for propagation of epithelial cells. In the present study, nontumorigenic human epidermal keratinocytes immortalized by adenovirus 12 and simian virus 40 (Ad 12-SV40) were transformed by treatment with the chemical carcinogens
N
-methyl-
N
′-nitro-
N
-nitrosoguanidine or 4-nitroquinoline-1-oxide. Such transformants showed morphological alterations and induced carcinomas when transplanted into nude mice, whereas primary human epidermal keratinocytes treated with these chemical carcinogens failed to show any evidence of transformation. This in vitro system may be useful in assessing environmental carcinogens for human epithelial cells and in detecting new human oncogenes.
Amplification and Expression of Genes Associated with Multidrug Resistance in Mammalian Cells
Authors: Scotto Kathleen W. , Biedler June L. , Melera Peter W.
Published: October 2006

In multidrug resistance, which is observed clinically and in tissue culture, cells that are challenged with certain cytotoxic drugs develop resistance not only to the selective agent but also to other, seemingly unrelated, agents. The multidrug-resistant phenotype is associated with DNA sequence amplification and with the overproduction of a number of cytosolic and membrane glycoproteins. The differential amplification and altered expression of at least two related genes, termed multidrug-resistant associated genes has been shown in multidrug-resistant Chinese hamster cells. In multidrug-resistant mouse and human cells, genes homologous to those in Chinese hamster cells are also amplified. The level of expression of these genes varied and did not correlate with their copy number. Furthermore, in Chinese hamster cells, the development of resistance to a single drug and multidrug resistance were closely related, but uncoupled, events. The overexpression of the multidrug-resistant genes was better correlated with the degree of resistance to the selective agent than it was with the extent of multidrug resistance.
Slow Transport of Tubulin in the Neurites of Differentiated PC12 Cells
Authors: Keith Charles H.
Published: October 2006

In order to study the rate and form of tubulin transport in cultured neuronal cells, the fluorescence recovery after the photobleaching of a fluorescent tubulin analog has been followed within the neuritic processes of differentiated PC12 cells. In these cells, as in peripheral axons, tubulin is transported in coherent, nondiffusing waves at two different slow rates that are within the range of the slow components a and b of axonal transport measured in vivo. Finally, it appears that most, if not all, of the tubulin analog is moving out these processes. Thus, slow neuroplasmic transport in cultured neuron-like cells is a good model of axonal transport, in which experimental manipulations of the system can be performed that would be difficult in the whole animal.
Skeleton of the Oldest Known Pinniped,
Enaliarctos mealsi
Authors: Berta Annalisa , Ray Clayton E. , Wyss André R.
Published: October 2006

A nearly complete skeleton of the archaic pinniped
Enaliarctos
, found in late Oligocene or early Miocene rocks (approximately 23 million years old) of California, provides new evidence on the origin of pinnipeds.
Enaliarctos
retains many primitive features expected in the hypothesized common ancestor of pinnipeds. Skeletal modifications seen in
Enaliarctos
document swimming adaptations and indicate that pinnipeds primitively used the axial skeleton and both fore and hindflippers as sources of propulsion. Elongate hindlimbs with prominent bony processes (reflecting powerful musculature) suggest that
Enaliarctos
was more active on land than modern pinnipeds.
A Glycan-Phosphatidylinositol-Specific Phospholipase D in Human Serum
Authors: Davitz Michael A. , Hereld Dale , Shak Steve , Krakow Jessica , Englund Paul T. , Nussenzweig Victor
Published: October 2006

A group of proteins anchored to the cell by phosphatidylinositol (PI) has recently been identified. The significance of this new class of membrane anchor is unknown; one possibility is that it facilitates release of the molecule by phospholipases. In fact, phospholipase C enzymes specific for the complex carboxyl-terminal glycolipids of these proteins have been isolated from African trypanosomes and from hepatocyte plasma membranes. This study reports the discovery of a glycan-PI-specific phospholipase D in human serum that cleaves both the membrane form of the variant surface glycoprotein of African trypanosomes and its glycolipid precursor, but not phosphatidylethanolamine, phosphatidylcholine, or phosphatidylinositol. Decay-accelerating factor, another PI-anchored molecule, is also cleaved by the enzyme and converted from a hydrophobic to a soluble protein. The enzyme is Ca
2+
-dependent, heat labile, and not affected by the inhibitor of serine proteases, phenylmethylsulfonylfluoride. Its function is not known, but the present findings indicate that it participates in the metabolism of glycolipid-anchored membrane proteins.
Anti-Idiotypic Network Induced by T Cell Vaccination Against Experimental Autoimmune Encephalomyelitis
Authors: Lider Ofer , Reshef Tamara , Beraud Evelyne , Ben-Nun Avraham , Cohen Irun R.
Published: October 2006

In a study of the mechanism of resistance to autoimmune disease induced by T cell vaccination, rats were vaccinated against experimental autoimmune encephalomyelitis (EAE) by injecting them once in the hind footpads with a subencephalitogenic dose (10
4
) of a clone of T lymphocytes specific for myelin basic protein (BP). The response to vaccination was assayed by challenging the rats with an encephalitogenic dose (3 × 10
6
) of T lymphocytes of this BP-specific clone. Five to six days after vaccination, the cells responsible for mediating resistance to adoptively transferred EAE were concentrated in the popliteal lymph nodes draining the vaccination site. Transfer of the draining lymph node cells to unvaccinated rats led to loss of resistance in the donor rats and acquisition of resistance by the recipient rats. Limiting-dilution cultures of the draining lymph node cells were established with irradiated cells of the BP-specific clone as stimulators. Two sets of T lymphocytes specifically responsive to the BP-specific T cells from the clone were isolated: CD4
+
CD8
-
helper and CD4
-
CD8
+
suppressor cells. The helper T cells, like the BP antigen, specifically stimulated the BP-specific vaccinating clone. In contrast, the suppressor T cells specifically suppressed the response of the BP-specific vaccinating clone to its BP antigen. These results suggest that T cell vaccination induces resistance to autoimmune disease by activating an antiidiotypic network.
The CD14 Monocyte Differentiation Antigen Maps to a Region Encoding Growth Factors and Receptors
Authors: Goyert Sanna M. , Ferrero Enza , Rettig Wolfgang J. , Yenamandra Aswani K. , Obata Fumiya , Le Beau Michelle M.
Published: October 2006

CD14 is a myelomonocytic differentiation antigen expressed by monocytes, macrophages, and activated granulocytes and is detectable with the monoclonal antibodies MO2, MY4, and LeuM3. Analyses of complementary DNA and genomic clones of CD14 show that it has a novel structure and that it maps to chromosome 5 within a region containing other genes encoding growth factors and receptors; it may therefore represent a new receptor important for myeloid differentiation. In addition, the
CD14
gene is included in the "critical" region that is frequently deleted in certain myeloid leukemias.
RNA as an RNA Polymerase: Net Elongation of an RNA Primer Catalyzed by the
Tetrahymena
Ribozyme
Authors: Been Michael D. , Cech Thomas R.
Published: October 2006

A catalytic RNA (ribozyme) derived from an intervening sequence (IVS) RNA of
Tetrahymena thermophila
will catalyze an RNA polymerization reaction in which pentacytidylic acid (C
5
) is extended by the successive addition of mononucleotides derived from a guanylyl-(3′,5′)-nucleotide (GpN). Cytidines or uridines are added to C
5
to generate chain lengths of 10 to 11 nucleotides, with longer products being generated at greatly reduced efficiency. The reaction is analogous to that catalyzed by a replicase with C
5
acting as the primer, GpNs as the nucleoside triphosphates, and a sequence in the ribozyme providing a template. The demonstration that an RNA enzyme can catalyze net elongation of an RNA primer supports theories of prebiotic RNA self-replication.
A 115-kD Polypeptide Immunologically Eelated to Erythrocyte Band 3 Is Present in Golgi Membranes
Authors: Kellokumpu Sakari , Neff Lyn , Jämsä-Kellokumpu Sirpa , Kopito Ron , Baron Roland
Published: October 2006

Band 3 multigene family consists of several distinct but structurally related polypeptides which are probably involved in the transport of anions across the plasma membrane of both erythrocytes and nonerythroid cells. A novel member of this family of polypeptides that resides in the Golgi complex was identified with antibodies to Band 3. The Golgi antigen had a larger molecular size and was antigenically distinct from Band 3 in the amino-terminal domain. It was expressed most prominently in cells that secrete large amounts of sulfated proteins and proteoglycans. This polypeptide may participate in sulfate transport across Golgi membranes.
Receptor and Antibody Epitopes in Human Growth Hormone Identified by Homolog-Scanning Mutagenesis
Authors: Cunningham Brian C. , Jhurani Parkash , Ng Peter , Wells James A.
Published: October 2006

A strategy, termed homolog-scanning mutagenesis, was used to identify the epitopes on human growth hormone (hGH) for binding to its cloned liver receptor and eight different monoclonal antibodies (Mab's). Segments of sequences (7 to 30 residues long) that were derived from homologous hormones known not to bind to the hGH receptor or Mab's, were systematically substituted throughout the hGH gene to produce a set of 17 chimeric hormones. Each Mab or receptor was categorized by a particular subset of mutant hormones that disrupted binding. Each subset of the disruptive mutations mapped within close proximity on a three-dimensional model of hGH, even though the residues changed within each subset were usually distant in the primary sequence. The mapping analysis correctly predicted those Mab's which could or could not block binding of the receptor to hGH and further suggested (along with other data) that the folding of these chimeric hormones is like that of hGH. By this analysis, three discontinuous polypeptide determinants in hGH—the loop between residues 54 and 74, the central portion of helix 4 to the carboxyl terminus, and to a lesser extent the amino-terminal region of helix 1—modulate binding to the liver receptor. Homolog-scanning mutagenesis should be of general use in identifying sequences that cause functional variation among homologous proteins.
HIV with Reduced Sensitivity to Zidovudine (AZT) Isolated During Prolonged Therapy
Authors: Larder Bredan A. , Darby Graham , Richman Douglas D.
Published: October 2006

The drug sensitivities of human immunodeficiency virus (HIV) isolates from a group of patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) who were receiving zidovudine (3′-azido-3′-deoythymidine, AZT) therapy were tested by means of a newly developed plaque assay in CD4
+
HeLa cells. Fifty percent inhibitory dose (ID
50
) values of 18 isolates from untreated individuals ranged between 0.01 μ
M
and 0.05 μ
M
. In contrast, most isolates from patients who had received zidovudine for 6 months or more exhibited decreased sensitivity characterized by changes in ID
50
or ID
95
values (or both), with isolates from several patients (5/15) showing 100-fold increases in ID
50
. The latter isolates were also insensitive to 3′-azido-2′,3′-dideoxyuridine; however, the isolates were still sensitive to 2′,3′-dideoxycytidine, 2′,3′-dideoxy-2′,3′-didehydrothymidine, or phosphonoformate. It cannot be determined from this small sample of patients whether development of a less sensitive virus phenotype results in clinical resistance. Appearance of such variants was not associated with a consistent increase in viral p24 concentrations in patient plasma and did not herald any sudden deterioration in clinical status. More extensive studies are required to determine the clinical significance. Thus, it would be premature to alter any treatment protocols for HIV-infected individuals at present.
The Dynamics of the Oceanic Subtropical Gyres
Authors: Pedlosky Joseph
Published: October 2006

Recent theoretical advances in physical oceanography have produced plausible models for the structure of the circulation in the oceans' subtropical gyres. These theoretical ideas are reviewed and assessed in the light of present observational evidence. The dominant role of potential vorticity is emphasized in describing the strong interplay between three-dimensional distributions of density and velocity. In particular, the complementary processes of subduction and recirculation jointly act to shape the circulation pattern of the subtropical gyre.
Triassic Vertebrates of Gondwanan Aspect from the Richmond Basin of Virginia
Authors: Sues Hans-Dieter , Olsen Paul E.
Published: October 2006

A new locality of early Late Triassic age in the Richmond basin of east-central Virginia has yielded abundant remains of a diversified assemblage of small to medium-sized tetrapods that closely resembles Southern Hemisphere (Gondwanan) assemblages in the predominance of certain synapsids. Associated palynomorphs indicate an early middle Carnian age for the fossiliferous strata. The discovery suggests that previously recognized differences between tetrapod assemblages of early Late Triassic age from Gondwana and Laurasia at least in part reflect differences in stratigraphic age, rather than geographic separation.
Field-Induced Nanometer- to Atomic-Scale Manipulation of Silicon Surfaces with the STM
Authors: Lyo In-Whan , AVOURIS PHAEDON
Published: October 2006

The controlled manipulation of silicon at the nanometer scale will facilitate the fabrication of new types of electronic devices. The scanning tunneling microscope (STM) can be used to manipulate strongly bound silicon atoms or clusters at room temperature. Specifically, by using a combination of electrostatic and chemical forces, surface atoms can be removed and deposited on the STM tip. The tip can then move to a predetermined surface site, and the atom or cluster can be redeposited. The magnitude of such forces and the amount of material removed can be controlled by applying voltage pulses at different tip-surface separations.
Reversible Decrease of Gel-Solvent Friction
Authors: Tokita Masayuki , Tanaka Toyoighi
Published: October 2006

The friction between water and the polymer network of a gel is found to decrease reversibly by three orders of magnitude and appears to diminish as the gel approaches a certain temperature at constant volume and network structure.
Lightning and Plasma Wave Observations from the Galileo Flyby of Venus
Authors: Gurnett D. A. , Kurth W. S. , Roux A. , Gendrin R. , Kennel C. F. , Bolton S. J.
Published: October 2006

During the Galileo flyby of Venus the plasma wave instrument was used to search for impulsive radio signals from lightning and to investigate locally generated plasma waves. A total of nine events were detected in the frequency range from 100 kilohertz to 5.6 megahertz. Although the signals are weak, lightning is the only known source of these signals. Near the bow shock two types of locally generated plasma waves were observed, low-frequency electromagnetic waves from about 5 to 50 hertz and electron plasma oscillation at about 45 kilohertz. The plasma oscillations have considerable fine structure, possibly because of the formation of soliton-like wave packets.
Direct Brønsted Analysis of the Restoration of Activity to a Mutant Enzyme by Exogenous Amines
Authors: Toney Michael D. , Kirsch Jack F.
Published: October 2006

A true Brønsted analysis of proton transfer in an enzyme mechanism is made possible by the chemical rescue of an inactive mutant of aspartate aminotransferase, where the endogenous general base, Lys
258
, is replaced with Ala by site-directed mutagenesis. Catalytic activity is restored to this inactive mutant by exogenous amines. The eleven amines studied generate a Brønsted correlation with β of 0.4 for the transamination of cysteine sulfinate, when steric effects are included in the regression analysis. Localized mutagenesis thus allows the classical Brønsted analysis of transition-state structure to be applied to enzyme-catalyzed reactions.
Haplodiploidy and the Evolution of Facultative Sex Ratios in a Primitively Eusocial Bee
Authors: Mueller Ulrich G.
Published: October 2006

In eusocial Hymenoptera, the haplodiploid system of sex determination creates relatedness asymmetries such that workers are more closely related on average to their sisters than to their brothers. For such societies, kin-selection theory and sex-ratio theory predict that workers maximize their inclusive fitness by biasing the investment sex ratio toward females. To test the prediction of sex-ratio biasing, relatedness asymmetries were experimentally manipulated in colonies of the primitively eusocial bee
Augochlorella striata
(Halictidae: Hymenoptera) by removing or not removing foundress queens. Queenright colonies (relatedness asymmetry present) produced a more female-biased sex ratio than did queenless colonies (relatedness asymmetry absent). Worker reproduction and unmated replacement queens can be discounted as alternative explanations. Workers therefore facultatively adjusted their colony's sex ratio and, in the presence of a relatedness asymmetry, biased the investment sex ratio toward their more closely related sisters and away from their more distantly related brothers.
β-Adrenergic Inhibition of Cardiac Sodium Channels by Dual G-Protein Pathways
Authors: Schubert Bernd , VanDongen Antonius M. J. , Kirsch Glenn E. , Brown Arthur M.
Published: October 2006

The signaling pathways by which β-adrenergic agonists modulate voltage-dependent cardiac sodium currents are unknown, although it is likely that adenosine 3′5′-monophosphate (cAMP) is involved. Single-channel and whole-cell sodium currents were measured in cardiac myocytes and the signal transducing G protein G
s
was found to couple β-adrenergic receptors to sodium channels by both cytoplasmic (indirect) and membrane-delimited (direct) pathways. Hence, G
s
can act on at least three effectors in the heart: sodium channels, calcium channels, and adenylyl cyclase. The effect on sodium currents was inhibitory and was enhanced by membrane depolarization. During myocardial ischemia the sodium currents of depolarized cells may be further inhibited by the accompanying increase in catecholamine levels.
Medical Treatment of Mental Illness
Authors: Berger Philip A.
Published: October 2006

Psychotherapeutic drugs have dramatically improved the prognosis for patients with severe mental illness. The drug treatments are not a panacea. The medications sometimes cause irreversible side effects, and they are not helpful for all patients. They allow large numbers of individuals to leave the hospital, but to return to communities that are often poorly prepared to provide continuing care. Despite their limitations, psychotherapeutic drugs relieve a great deal of human suffering. They also involve psychiatry in modern biological science. This has led to the continuing search for more effective medications based on the study of possible biochemical substrates of psychiatric disorders.
Evidence of a Pre-Angiosperm Origin of Endosperm: Implications for the Evolution of Flowering Plants
Authors: Friedman William E.
Published: October 2006

The formation of a polyploid endosperm tissue has long been considered a unique and defining feature (autapomorphy) of angiosperms. Contemporaneous with the fertilization of an egg nucleus by a sperm nucleus in
Ephedra trifurca
(a nonflowering seed plant closely related to angiosperms), a second fertilization event has previously been shown to occur between a second sperm nucleus and the sister nucleus of the egg nucleus. Development of the second fertilization product is now shown to be fundamentally similar to that of endosperm in primitive flowering plants: both are characterized by an initial period of free nuclear proliferation followed by a process of cellularization. In
Ephedra
, however, the second fertilization product ultimately yields additional embryos. If double fertilization in
Ephedra
and angiosperms is evolutionarily homologous, it is likely that endosperm evolved from a supernumerary fertilization event that originally produced embryos into one that produced a specialized nonembryo tissue dedicated to the nourishment of the zygotic embryo.
Competition, Cooperation, and Mutation: Improving a Synthetic Replicator by Light Irradiation
Authors: Hong Jong-In , Feng Qing , Rotello Vincent , Rebek Julius
Published: October 2006

Replication and mutation are necessary elements of evolution, and some properties of self-replicating molecules (replicators) can be explored with synthetic structures. Selection and evolution at the molecular level require systems capable of competition and inheritable change. These phenomena have now been observed with synthetic molecules. Two such molecules were prepared having sufficient structural similarity that they catalyzed each other's formation as well as their own. One of the replicators bears a photochemically active function that is cleaved on irradiation. The resulting species is more effective at replication than the original and rapidly takes over the system's resources.
The Hot Plasma Environment at Jupiter: Ulysses Results
Authors: Lanzerotti L. J. , Armstrong T. P. , Gold R. E. , Anderson K. A. , Krimigis S. M. , Lin R. P. , Pick M. , Roelof E. C. , Sarris E. T. , Simnett G. M. , Maclennan C. G. , Choo H. T. , Tappin S. J.
Published: October 2006

Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at ∼105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at ∼86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically ∼1.6 × 10
-4
microamperes per square meter or ∼8 × 10
5
amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.