bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Effects of
nef
on HIV Replication: Implications for Viral Pathogenesis in the Host
Authors: Cheng-Mayer Cecilia , Iannello Pina , Shaw Karen , Luciw Paul A. , Levy Jay A.
Published: October 2006

Stable lymphoid cell lines expressing the human immunodeficiency virus type 1 (HIV-1)
nef
gene product, p27, were established. The presence of p27 in the lymphoid cells suppressed replication of some strains of both HIV-1 and HIV-2. This observation indicates that
nef
could be important in the establishment of HIV latency. In contrast, fast replicating and highly cytopathic HIV-1 isolates recovered from patients with advanced disease states were not affected by the negative effect of
nef
present in these lymphoid cell lines. This lack of response to
nef
appears to constitute another viral feature that correlates with disease progression. Thus, manipulating expression of the
nef
gene in vivo might influence pathogenesis in the host.
In Situ Scanning Tunneling Microscopy of Corrosion of Silver-Gold Alloys
Authors: Oppenheim Ivette C. , Trevor Dennis J. , Chidsey Christopher E. D. , Trevor Paula L. , Sieradzki Karl
Published: October 2006

An in situ scanning tunneling microscope (STM) was used to observe the morphological changes accompanying the selective dissolution of Ag from low-Ag content Ag-Au alloys in dilute perchloric acid. This study was undertaken to explore the role of surface diffusion in alloy corrosion processes. These results are interpreted within the framework of the kink-ledge-terrace model of a crystal surface and a recent model of alloy corrosion based on a variant of percolation theory. The corrosion process leads to roughening of the surface by dissolution of Ag atoms from terrace sites. Annealing or smoothening of the surface occurs by vacancy migration through clusters and the subsequent annihilation of clusters at terrace ledges.
Orientational Disorder in Solvent-Free Solid C
70
Authors: Vaughan Gavin B. M. , Heiey Paul A. , Luzzi David E. , Ricketts-Foot Deborah A. , McGhie Andrew R. , Fischer John E. , Hui Yiu-Wing , Smith Allan L. , Cox David E. , Romanow William J. , Allen Brent H. , Coustel Nicole , McCauley John P. , Smith Amos B.
Published: October 2006

The high-temperature structure of solvent-free C
70
has been determined with high-resolution x-ray powder diffraction and electron microscopy. Samples crystallized from solution form hexagonal close-packed crystals that retain an appreciable amount of residual toluene, even after prolonged heating. Samples prepared by sublimation, which contain no detectable solvent, are primarily face-centered cubic with some admixture of a hexagonal phase. The relative volume of the hexagonal phase can be further reduced by annealing. The structures of both phases are described by a model of complete orientational disorder. The cubic phase contains an appreciable density of stacking faults along the [111] direction.
Lunar Impact Basins and Crustal Heterogeneity: New Western Limb and Far Side Data from Galileo
Authors: Belton Michael J. S. , Head James W. , Pieters Carle M. , Greeley Ronald , McEwen Alfred S. , Neukum Gerhard , Klaasen Kenneth P. , Anger Clifford D. , Carr Michael H. , Chapman Clark R. , Davies Merton E. , Fanale Fraser P. , Gierasch Peter J. , Greenberg Richard , Ingersoll Andrew P. , Johnson Torrence , Paczkowski Brian , Pilcher Carl B. , Veverka Joseph
Published: October 2006

Multispectral images of the lunar western limb and far side obtained from Galileo reveal the compositional nature of several prominent lunar features and provide new information on lunar evolution. The data reveal that the ejecta from the Orientale impact basin (900 kilometers in diameter) lying outside the Cordillera Mountains was excavated from the crust, not the mantle, and covers pre-Orientale terrain that consisted of both highland materials and relatively large expanses of ancient mare basalts. The inside of the far side South Pole—Aitken basin (>2000 kilometers in diameter) has low albedo, red color, and a relatively high abundance of iron- and magnesium-rich materials. These features suggest that the impact may have penetrated into the deep crust or lunar mantle or that the basin contains ancient mare basalts that were later covered by highlands ejecta.
Topographic and Magnetic-Sensitive Scanning Tunneling Microscope Study of Magnetite
Authors: Wiesendanger R. , Shvets I. V. , Bürgler D. , Tarrach G. , Güntherodt H. J. , Coey J. M. D. , Gräser S.
Published: October 2006

The topographic and magnetic surface structure of a natural single crystal of magnetite (Fe
3
O
4
), a common mineral, has been studied from the submicrometer scale down to the atomic scale with a scanning tunneling microscope having nonmagnetic tungsten as well as ferromagnetic iron probe tips. Several different (001) crystal planes were imaged to atomic resolution with both kinds of tips. A selective imaging of the octahedrally coordinated Fe B-sites in the Fe-O planes, and even a selective imaging of the different magnetic ions Fe
2+
and Fe
3+
, has been achieved, demonstrating for the first time that magnetic imaging can be realized at the atomic level.
Refuges as a Predictor of Parasitoid Diversity
Authors: Hochberg Michael E. , Hawkins Bradford A.
Published: October 2006

A central problem in ecology is predicting the diversity of communities. Insect parasitoids may encompass 20 percent of all insect species; hence, establishing the mechanisms that drive parasitoid species richness represents a major step in understanding the diversity of terrestrial communities. An assemblage model, based on population dynamic constructs, shows how the presence of refuges from parasitoid attack can generate diversity patterns that are in good accord with global data on structural protection from parasitism resulting from host feeding biology. This theory offers a simple ecological explanation for the range of diversities observed in real parasitoid assemblages. Predicting parasitoid diversity may be a realistic goal, at least for those systems in which the basic demography is well understood.
Rapid Solid-State Precursor Synthesis of Materials
Authors: Wiley John B. , Kaner Richard B.
Published: October 2006

Precursor reactions based on metathetical (exchange) pathways have been found to be an effective synthetic route for the preparation of a large number of materials. These solid-solid reactions are extremely rapid (typically less than 1 second) and often can be initiated at or near room temperature. They are potentially useful for controlling product particle size and for preparing high-quality cationic or anionic solid solutions. The frequently self-propagating and sometimes explosive behavior exhibited by these reactions can be attributed to the large amount of heat they release. As a consequence, thermodynamic considerations can be used to help select the best set of precursors as judged from reaction enthalpies. The factors that influence these reactions are illustrated by a discussion of MoS
2
, ZrN, MoSi
2
, and GaAs, examples of the many compounds accessible by this synthetic route.
An Efficient Antibody-Catalyzed Aminoacylation Reaction
Authors: Jacobsen John R. , Prudent James R. , Kochersperger Lynn , Yonkovich Shirlee , Schultz Peter G.
Published: October 2006

An antibody generated against a neutral phosphonate diester transition-state analog was found to catalyze the aminoacylation of the 3′-hydroxyl group of thymidine with an alanyl ester. A comparison of the apparent second-order rate constant of the antibody-catalyzed reaction [5.4 × 10
4
molar
-1
minute
-1
(M
-1
min
-1
)] with that of the uncatalyzed reaction (2.6 × 10
-4
M
-1
min
-1
) revealed this to be a remarkably efficient catalyst. Moreover, although the concentration of water (55 M) greatly exceeds that of the secondary alcohol, the antibody selectively catalyzes acyl transfer to thymidine. The antibody exhibits sequential binding, with Michaelis constants of 770 μM and 260 μM for acyl acceptor and donor, respectively, and a dissociation constant of 240 pM for hapten. This antibody-catalyzed reaction provides increased insight into the requirements for efficient aminoacylation catalysts and may represent a first step toward the generation of "aminoacyl transfer RNA synthetases" with novel specificities.
An Intercomparison of Tropospheric OH Measurements at Fritz Peak Observatory, Colorado
Authors: Mount George H. , Eisele Fred L.
Published: October 2006

The hydroxyl radical (OH) controls the lifetimes and therefore the concentrations of many important chemical species in Earth's lower atmosphere including several greenhouse and ozone-depleting species. Two completely different measurement techniques were used in an informal intercomparison to determine tropospheric OH concentrations at Fritz Peak Observatory, Colorado, from 15 July to 24 August 1991. One technique determined OH concentrations by chemical analysis; the other used spectroscopic absorption on a long path. The intercomparison showed that ambient OH concentrations can now be measured with sufficient sensitivity to provide a test for photochemical models, with the derived OH concentrations agreeing well under both polluted and clean atmospheric conditions. Concentrations of OH on all days were significantly lower than model predictions, perhaps indicating the presence of an unknown scavenger. The change in OH concentration from early morning to noon on a clear day was found to be only a factor of 2.
Mechanism of the Rhodium Porphyrin-Catalyzed Cyclopropanation of Alkenes
Authors: Maxwell Jana L. , Brown Kathlynn C. , Bartley David W. , Kodadek Thomas
Published: October 2006

The rhodium porphyrin-catalyzed cyclopropanation of alkenes by ethyl diazoacetate (EDA) is representative of a number of metal-mediated cyclopropanation reactions used widely in organic synthesis. The active intermediate in these reactions is thought to be a metal carbene complex, but evidence for the involvement of metal-olefin π complexes has also been presented. Low-temperature infrared and nuclear magnetic resonance spectroscopies have been used to characterize a rhodium porphyrin-diazoalkyl adduct that results from the stoichiometric condensation of the catalyst and EDA. Optical spectroscopy suggests that this complex is the dominant steady-state species in the catalytic reaction. This compound decomposes thermally to provide cyclopropanes in the presence of styrene, suggesting that the carbene is indeed the active intermediate. Metal-alkene π complexes have also been detected spectroscopically. Kinetic studies suggest that they mediate the rate of carbene formation from the diazoalkyl complex but are not attacked directly by EDA.
A Genetic Polymorphism in the Renin Gene of Dahl Rats Cosegregates with Blood Pressure
Authors: Rapp John P. , Wang Sue-May , Dene Howard
Published: October 2006

Blood pressure is influenced by multiple genetic loci whose identities are largely unknown. A restriction fragment length polymorphism (RFLP) in the renin gene was found between Dahl salt-hypertension-sensitive (S) and Dahl salt-hypertension-resistant (R) rats. In an F
2
population derived from crossing S and R rats, the renin RFLP cosegregated with blood pressure. One dose of the S-rat renin allele was associated with an increment in blood pressure of approximately 10 mmHg, and two doses of this allele increased blood pressure approximately 20 mmHg. From this it can be definitively concluded that in the rat the renin gene is, or is closely linked to, one of the genes regulating blood pressure.
NMDA Antagonists Differentiate Epileptogenesis from Seizure Expression in an in Vitro Model
Authors: Stasheff Steven F. , Anderson William W. , Clark Suzanne , Wilson Wilkie A.
Published: October 2006

In an electrographic model of seizures in the hippocampal slice, both of the N-methyl-D-aspartate (NMDA) antagonists 2-amino-5-phosphonovaleric acid and 5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine maleate (MK-801) prevented the progressive development of seizures but did not block previously induced seizures. Thus, a process dependent on the NMDA receptor-ionophore complex establishes a long-lasting, seizure-prone state; thereafter the seizures depend on non-NMDA receptor-ionophore mechanisms. This suggests that there is an important distinction between epileptogenesis and seizure expression and between antiepileptogenic and anticonvulsant pharmacological agents.
Manipulating Chlorine Atom Bonding on the Si(100)-(2 × 1) Surface with the STM
Authors: Boland John J.
Published: October 2006

Chlorine atoms strongly chemisorbed at dangling bond sites on the Si(100)-(2 × 1) surface are observed by scanning tunneling microscopy (STM) to hop between adjacent sites. The origin of this behavior is suggested to be an interaction between the field of the probe tip and the dipole moment of the silicon—chlorine bond. Chlorine atom migration is shown to be facilitated by the presence of a metastable chlorine bridge—bonded minimum. The STM probe was used to excite single chlorine atoms into this bridging configuration, resulting in a local population inversion. Selective application of voltage pulses between the probe tip and the surface rearranged the local bonding and induced transformations between different types of chlorine sites. In this manner, adsorbed species can be dissected and their composition and structure directly probed.
Genetic Control of Differentiation of the
Caenorhabditis elegans
Touch Receptor Neurons
Authors: Chalfie Martin , Au Macy
Published: October 2006

The genetic control of neuronal differentiation has been studied by examining mutations that affect the development and function of the six touch receptor neurons of the nematode
Caenorhabditis elegans
. By screening for touch-insensitive mutants, it has been possible to identify 18 genes (represented by 417 mutations) that are required at various stages in the developmental program for touch cell differentiation. Two of the genes are needed for the generation of precursors in the touch cell lineages; without the precursors, touch cells are not made. A third gene,
mec-3
, specifies the differentiation of the touch cells, probably by acting as a transcription factor. The remaining 15 genes are likely targets of
mec-3
action; mutants defective in these genes have nonfunctioning, yet differentiated, touch cells. Some of these latter genes are needed for the formation of cell-specific components of the touch cells, such as a set of microtubules that are only found in these cells. The study of the touch genes should help us understand how touch cell fate is determined, how microtubule form is specified, and, perhaps, how mechanical stimuli are transduced.
Endothelial Cell Gene Expression of a Neutrophil Chemotactic Factor by TNF-α, LPS, and IL-1β
Authors: Strieter R. M. , Kunkel S. L. , Showell H. J. , Remick D. G. , Phan S. H. , Ward P. A. , Marks R. M.
Published: October 2006

Human endothelial cells produced a neutrophil chemotactic factor (NCF) upon stimulation with tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), or lipopolysaccharide (LPS). The expression of endothelial cell-derived NCF messenger RNA and biological activity was both time- and concentration-dependent. Maximal NCF mRNA expression occurred at 10 and at 2 nanograms per milliliter for TNF and IL-1β, respectively; mRNA expression was first observed 1 hour after stimulation and was maintained for at least 24 hours. In situ hybridization analysis showed that NCF mRNA peaked in treated cells by 24 hours, whereas unstimulated cells were negative. These studies demonstrated that endothelial cells may participate in neutrophil-mediated inflammation by synthesizing a chemotactic factor in response to specific monokines and LPS.
Lymphocyte Ecto-5′-Nucleotidase Deficiency in Agammaglobulinemia
Authors: Edwards N. Lawrence , Magilavy Daniel B. , Cassidy James T. , Fox Irving H.
Published: October 2006

Fresh peripheral blood lymphocytes from eight patients with congenital agammaglobulinemia demonstrate reduced ecto-5′-nucleotidase activity when compared to the mean activity of normal subjects and patients with other forms of immunoglobulin deficiency. A specific defect of ecto-5′-nucleotidase is further suggested by normal values for lymphocyte ecto-adenosinetriphosphatase and ecto-nonspecific phosphatase. The data provide evidence for an enzyme deficiency in this X-linked, B lymphocyte deficiency syndrome.
Effects of Extracellular Egg Factors on Sperm Guanylate Cyclase
Authors: Ward Gary E. , Garbers David L. , Vacquier Victor D.
Published: October 2006

Extracellular factors from the sea urchin egg induce a change in the electrophoretic mobility of an abundant sperm membrane phosphoprotein. The modified protein was identified as guanylate cyclase. The mobility shift of the cyclase was shown to be associated with a decrease in its enzymatic activity.
Carboxyl Rerminal Domain of G
sα
Specifies Coupling of Receptors to Stimulation of Adenylyl Cyclase
Authors: Masters Susan B. , Sullivan Kathleen A. , Miller R. Tyler , Beiderman Barry , Lopez Ninfa G. , Ramachandran J. , Bourne Henry R.
Published: October 2006

The α subunits of G
s
and G
i
link different sets of hormone receptors to stimulation and inhibition, respectively, of adenylyl cyclase. A chimeric α
i
/α
s
cDNA was constructed that encodes a polypeptide composed of the amino terminal 60% of an α
i
chain and the carboxyl terminal 40% of α
s
. The cDNA was introduced via a retroviral vector into S49
cyc
-
cells, which lack endogenous α
s
. Although less than half of the hybrid α chain is derived from α
s
, its ability to mediate β-adrenoceptor stimulation of adenylyl cyclase matched that of the normal α
s
polypeptide expressed from the same retroviral vector in
cyc
-
cells. This result indicates that carboxyl terminal amino acid sequences of α
s
contain the structural features that are required for specificity of interactions with the effector enzyme, adenylyl cyclase, as well as with the hormone receptor.
Overexpression of Transforming Growth Factor α in Psoriatic Epidermis
Authors: Elder James T. , Fisher Gary J. , Lindquist Patricia B. , Bennett Gregory L. , Pittelkow Mark R. , Coffey Robert J. , Ellingsworth Larry , Derynck Rik , Voorhees John J.
Published: October 2006

Transforming growth factor α (TGF-α) is produced by and required for the growth of epithelial cells and is angiogenic in vivo. Since epidermal hyperplasia and angiogenesis are hallmarks of psoriasis, TGF-α gene expression was analyzed in epidermal biopsies of normal and psoriatic skin. TGF-α messenger RNA and protein are much more abundant in lesional psoriatic epidermis than in normal-appearing skin of psoriatic patients or in normal epidermis. In contrast, messenger RNA levels of transforming growth factor β1 (TGF-β1), which inhibits epithelial cell growth, are not significantly different in normal, uninvolved, and lesional psoriatic epidermis. Thus, psoriatic epidermal hyperplasia may involve increased expression of a keratinocyte mitogen (TGF-α) rather than deficient expression of a growth inhibitor (TGF-β1).
Construction of a General Human Chromosome Jumping Library, with Application to Cystic Fibrosis
Authors: Collins Francis S. , Drumm Mitchell L. , Cole Jeffery L. , Lockwood Wendy K. , Vande Woude George F. , Iannuzzi Michael C.
Published: October 2006

In many genetic disorders, the responsible gene and its protein product are unknown. The technique known as "reverse genetics," in which chromosomal map positions and genetically linked DNA markers are used to identify and clone such genes, is complicated by the fact that the molecular distances from the closest DNA markers to the gene itself are often too large to traverse by standard cloning techniques. To address this situation, a general human chromosome jumping library was constructed that allows the cloning of DNA sequences approximately 100 kilobases away from any starting point in genomic DNA. As an illustration of its usefulness, this library was searched for a jumping clone, starting at the
met
oncogene, which is a marker tightly linked to the cystic fibrosis gene that is located on human chromosome 7. Mapping of the new genomic fragment by pulsed field gel electrophoresis confirmed that it resides on chromosome 7 within 240 kilobases downstream of the
met
gene. The use of chromosome jumping should now be applicable to any genetic locus for which a closely linked DNA marker is available.
D
1
Dopamine Receptor Activation Required for Postsynaptic Expression of D
2
Agonist Effects
Authors: Walters Judith R. , Bergstrom Debra A. , Carlson Joanne H. , Chase Thomas N. , Braun Allen R.
Published: October 2006

D
1
and D
2
dopamine receptors exert synergistic effects on the firing rates of basal ganglia neurons and on the expression of stereotyped behavior in rats. Moreover, the ability of D
2
agonists to induce changes in basal ganglia single unit activity and spontaneous motor activity is dependent upon the presence of endogenous dopamine to stimulate D
1
receptors; in rats treated with α-methyl-
p
-tyrosine to reduce endogenous dopamine levels, the neurophysiological and behavioral effects of the D
2
agonist quinpirole are significantly attenuated, while the effects of nonselective agonists like apomorphine, which stimulate both D
1
and D
2
receptors, or combinations of a D
2
agonist and a D
1
agonist are not attenuated. Thus, the previously held view that D
2
receptors alone are responsible for evoking the changes in behavior and basal ganglia output induced by nonselective dopamine agonists and endogenous dopamine is not supported by these results, which indicate that these phenomena require concurrent stimulation of both dopamine receptor subtypes.
Gene Encoding the β Subunit of S100 Protein Is on Chromosome 21: Implications for Down Syndrome
Authors: Allore R. , O'Hanlon D. , Price R. , Neilson K. , Willard H. F. , Cox D. R. , Marks A. , Dunn R. J.
Published: October 2006

S100 protein is a calcium-binding protein found predominantly in the vertebrate nervous system. Genomic and complementary DNA probes were used in conjunction with a panel of rodent-human somatic cell hybrids to assign the gene for the β subunit of S100 protein to the distal half of the long arm of human chromosome 21. This gene was identified as a candidate sequence which, when expressed in the trisomic state, may underlie the neurologic disturbances in Down syndrome.
Magnetic Resonance Imaging of Biological Specimens by Electron Paramagnetic Resonance of Nitroxide Spin Labels
Authors: Berliner Lawrence J. , Fujii Hirotada
Published: October 2006

Electron paramagnetic resonance imaging was demonstrated on two plant species,
Apium graveolens
and
Coleus blumei
. This was accomplished by soaking stems of these plants in the paramagnetic nitroxide imaging agent 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl. The experiments were accomplished at L-band frequency (1.4 to 1.9 gigahertz) with single-turn, flat-loop surface coils. One-dimensional imaging spectra were diagnostic of capillary structure and long-term stability.
Subcellular Localization of the Product of the Long Open Reading Frame of Human T-Cell Leukemia Virus Type I
Authors: Goh Wei Chun , Sodroski Joseph , Rosen Craig , Essex Max , Haseltine William A.
Published: October 2006

Human T-cell leukemia virus type I (HTLV-I) is a retrovirus associated with adult T-cell leukemia and lymphoma. In addition to containing the
gag
,
pol
, and
env
genes of the chronic leukemia viruses, the genome of HTLV-I contains a long open reading frame (LOR) located between the 3′ end of the envelope gene and the 3′ long terminal repeat sequence (LTR). It has been suggested that a protein of 42 kilodaltons that is encoded by the LOR region may participate in both trans-acting transcriptional regulation of the viral LTR as well as in the transforming properties of HTLV-I. It is reported here that a significant fraction of the 42-kilodalton HTLV LOR product is located in the nucleus of HTLV-I-infected transformed lymphocytes, a finding that is consistent with its proposed functions.
Expression of the
pX
Gene of HTLV-I: General Splicing Mechanism in the HTLV Family
Authors: Seiki Motoharu , Hikikoshi Atsuko , Taniguchi Tadatsugu , Yoshida Mitsuaki
Published: October 2006

Human T-cell leukemia virus type I (HTLV-I) is an etiological agent of adult T-cell leukemia. A viral gene
pX
encodes for p40

x

and it has been proposed that this protein trans-activates the viral long terminal repeat and possibly some cellular genes; this activation may be associated with T-cell transformation. The mechanism of
pX
gene expression and the primary structure of p40

x

are now reported. Two-step splicing generates the 2.1-kilobase
pX
mRNA; the initiator methionine for
env
becomes part of the
pX
protein. These splicing signals are conserved among all members of the HTLV family except for the acquired immune deficiency syndrome-associated viruses.
A Role for Glycosylation of the α Subunit in Transduction of Biological Signal in Glycoprotein Hormones
Authors: Sairam M. R. , Bhargavi G. N.
Published: October 2006

The biological properties of recombinants of glycoprotein hormones in which the α and β subunits were differentially deglycosylated have been investigated. Specific deglycosylation of the α subunit generated a recombinant that had more receptor-binding activity but did not produce hormone response in the target cells. The deglycosylated α + β recombinant was also an antagonist of the action of the native hormone. Thus, the carbohydrates in the α subunit play a dominant role in the transduction of the hormone signal into the cell.
The pX Protein of HTLV-I Is a Transcriptional Activator of Its Long Terminal Repeats
Authors: Felber Barbara K. , Paskalis Harry , Kleinman-Ewing Carol , Wong-Staal Flossie , Pavlakis George N.
Published: October 2006

Expression of the pX protein of human T-cell leukemia virus type I (HTLV-I) in animal cells demonstrates that this protein is a specific transcriptional activator of the long terminal repeats (LTR) of HTLV-I. Several other promoters are not affected by pX. No lymphocyte-specific factors are required for this activation. pX can be detected in the nucleus of transfected monkey kidney cells (line CV1) by indirect immunofluorescence. These results indicate that the pX protein is essential for the replication cycle of the virus and that it may be directly involved in the immortalization of human lymphocytes by HTLV-I.
A New HTLV-III/LAV Protein Encoded by a Gene Found in Cytopathic Retroviruses
Authors: Lee Tun-Hou , Coligan John E. , Allan Jonathan S. , McLane Mary F. , Groopman Jerome E. , Essex M.
Published: October 2006

The DNA of the HTLV-III/LAV group of retroviruses contains certain additional open reading frames that are not found in typical avian or mammalian retroviruses. The role of these sequences in encoding for gene products that may be related to pathogenesis remains to be resolved. An open reading frame whose 5′ end overlaps with the
pol
gene, but is unrelated to the
env
gene, has been observed in HTLV-III/LAV and visna virus, both cytopathic mammalian retroviruses. Evidence presented here shows that this open reading frame is a bona fide coding sequence of HTLV-III/LAV and that its product, a protein with a molecular weight of 23,000, induces antibody production in the natural course of infection.
Replicative and Cytopathic Potential of HTLV-III/LAV with
sor
Gene Deletions
Authors: Sodroski Joseph , Goh Wei Chun , Rosen Craig , Tartar Andre , Portetelle Daniel , Burny Arsene , Haseltine William
Published: October 2006

The genome of the human T-lymphotropic virus type III (HTLV-III/LAV) has the potential to encode at least three polypeptides in addition to those encoded by the
gag
,
pol
, and
env
genes. In this study, the product of the sor (short open reading frame) region, which overlaps the 3′ end of the
pol
gene, was found to be a protein with a molecular weight of 23,000. An assay was developed for testing the ability of cloned HTLV-III proviruses to produce viruses cytopathic for T4
+
lymphocytes. In the cell line used, C8166, neither the HTLV-III
sor
gene product nor the complete 3′-
orf
gene product were necessary for the replication or cytopathic effects of the HTLV-III.
Clonally Related Cortical Cells Show Several Migration Patterns
Authors: Walsh C. , Cepko C. L.
Published: October 2006

The mammalian cerebral cortex is organized into columns of cells with common functional properties. During embryogenesis, cortical neurons are formed deep, near the lateral ventricles, and migrate radially to their final position. This observation led to the suggestion that the cortex consists of radial, ontogenetic units of clonally related neurons. In the experiments reported here, this hypothesis was tested by studying cell lineage in the rat cortex with a retroviral vector carrying the
Escherichia coli
β-galactosidase gene, which can be easily visualized. Labeled, clonally related cortical neurons did not occur in simple columnar arrays. Instead, clonally related neurons entered several different radial columns, apparently by migrating along different radial glial fibers.
Unusual Immunoglobulin Gene Rearrangement Leads to Replacement of Recombinational Signal Sequences
Authors: Morzycka-Wroblewska Ewa , Lee F. Eun Hyung , Desiderio Stephen V.
Published: October 2006

An unexpected immunoglobulin gene rearrangement, signal sequence replacement, was observed in which the recombinational signal sequences of a V
H
gene segment are fused intact to the 5′ end of a DJ
H
element. Nucleotides are not lost from the signal sequences, but they may be lost from the DJ
H
coding sequence. Signal sequence replacement may result from the alternative resolution of an intermediate in V
H
-to-DJ
H
recombination. This type of rearrangement provides a means to alter the targeting of immunoglobulin gene segments and suggests a mechanism for the occurrence of V
H
-J
H
junctions in vivo. Signal sequence replacement may represent an additional pathway for the generation of antibody diversity.
Transcriptional Regulation in the Yeast Life Cycle
Authors: Nasmyth Kim , Shore David
Published: October 2006

The transition from haploid to diploid in homothallic yeast involves a defined sequence of events which are regulated at the level of transcription. Transcription factors encoded by
SWI
genes activate the
HO
endonuclease gene at a precise stage in the cell cycle of mother cells. The
HO
endonuclease initiates a transposition event which activates genes of the opposite mating type by causing them to move away from a silencer element. The activated mating type genes then regulate genes involved in cell signaling such as the mating type-specific pheromones and their receptors. Since
HO
is only activated in one of the sister cells after division (the mother), adjacent cells of opposite mating type are generated which respond to each others' secreted pheromones by inducing genes involved in conjugation. This leads to the formation of a diploid in which many of the genes involved in mating and mating-type switching become repressed due to the heterozygosity of the mating-type locus. This article summarizes what is known about these transcriptional controls and discusses possible parallels in higher eukaryotes.
Causes of the Liability Insurance Crisis
Authors: Harrington Scott , Litan Robert E.
Published: October 2006

In this article the reasons for recent dramatic premium increases for liability insurance are explored by examination of available data on industry premiums, losses, and expenses. The suggestions that the premium increases were primarily caused by collusion among insurers, cyclical behavior, or systematic errors in forecasting losses are rejected. Instead, the evidence indicates that the jump in liability insurance premiums is most plausibly due to the growth in the discounted value of expected liability losses.
Hair Cell Regeneration After Acoustic Trauma in Adult
Coturnix
Quail
Authors: Ryals Brenda M. , Rubel Edwin W.
Published: October 2006

Recovery of hair cells was studied at various times after acoustic trauma in adult quail. An initial loss of hair cells recovered to within 5 percent of the original number of cells. Tritium-labeled thymidine was injected after this acoustic trauma to determine if mitosis played a role in recovery of hair cells. Within 10 days of acoustic trauma, incorporation of [
3
H]thymidine was seen over the nuclei of hair cells and supporting cells in the region of initial hair cell loss. Thus, hair cell regeneration can occur after embryonic terminal mitosis.
The Context Effect Does Not Require a Fourth Base Pair
Authors: Ayer Don , Yarus Michael
Published: October 2006

The translational activity of a transfer RNA at a codon varies at different message sites, although the codon does not vary. The source of this effect, which may help to determine the level of gene expression, is generally agreed to be in nearby message sequences. By making every possible nucleotide combination between position 33 of the transfer RNA and the major context nucleotide of the message, it was shown that base-pairing between the two nucleotides is not the source of this context effect on translation in vivo.
Proteolytic Self-Cleavage of Hepatitis B Virus Core Protein May Generate Serum e Antigen
Authors: Miller Roger H.
Published: October 2006

A model is proposed to explain the presence of the e antigen (HBeAg) of hepatitis B virus (HBV) in the serum of individuals infected with this virus. The e antigen, which has only recently been characterized, is a fragment of the virus core, or nucleocapsid, protein. Serum HBeAg is a valuable clinical marker for active HBV infection because its appearance correlates both with virus replication in the liver and with the presence of circulating virions. In this study a protease-like amino acid sequence was identified at the amino terminus of the core protein sequence. Experimental evidence indicates that HBeAg may be produced by proteolytic self-cleavage of the core protein.
Health and Safety Risk Analyses: Information for Better Decisions
Authors: Lave Lester B.
Published: October 2006

Knowing the nature and magnitude of health and safety risks is helpful in setting priorities as well as in making decisions about pursuing recreational activities, foods, jobs, and other aspects of everyday living. "Risk-risk" situations require a choice among risky alternatives. "How safe" situations involve a more general choice as to how much of other desired activities to sacrifice for increased safety. "How safe" situations are inherently more difficult to manage, because they are subject to fuzzy thinking and rhetoric. The large uncertainties of current estimates must be conveyed explicitly to arrive at sensible decisions.
Formation of Retinal Ganglion Cell Topography During Prenatal Development
Authors: Lia Barry , Williams Robert W. , Chalupa Leo M.
Published: October 2006

A fundamental feature of the mammalian visual system is the nonuniform distribution of ganglion cells across the retinal surface. To understand the ontogenetic processes leading to the formation of retinal ganglion cell topography, changes in the regional density of these neurons were studied in relation to ganglion cell loss and the pattern of retinal growth in the fetal cat. Midway through the gestation period, the density of these neurons was only two to three times greater in the area centralis than in the peripheral retina, whereas shortly before birth this central-to-peripheral difference was nearly 20-fold. Age-related changes in the ganglion cell distribution were found not to correspond in time or magnitude to the massive loss of ganglion cells that occurs during prenatal development. Rather, the formation of ganglion cell density gradients can be accounted for by unequal expansion of the growing fetal retina-peripheral regions expand more than the central region, thereby diluting the peripheral density of ganglion cells to a greater degree. Nonuniform growth, in conjunction with differential periods of neurogenesis of the different types of retinal cells, appears to be a dominant factor regulating overall retinal topography. These results suggest that the differential regional expansion of the fetal retina underlies the formation of magnification factors in the developing visual system.
Concanavalin A Alters Synaptic Specificity Between Cultured
Aplysia
Neurons
Authors: Lin Stephen S. , Levitan Irwin B.
Published: October 2006

Factors that regulate synaptic specificity were investigated with
Aplysia
buccal and bag cell neurons in primary cell culture. In the presence of fetal calf serum electrical synapses are formed between buccal-buccal or bag-bag cell pairs, but not between buccal-bag cell pairs. Instead, buccal neurons make inhibitory chemical synapses on bag cells. However, in the presence of nanomolar concentrations of the lectin concanavalin A this pattern changes, such that more than 75 percent of buccal-bag pairs exhibit electrical synapses and the frequency of occurrence of buccal-bag chemical synapses is reduced. Such changes in synaptic specificity may be important in determining the types of synapses formed during neuronal development and neurite regeneration.
Human Growth Hormone: Complementary DNA Cloning and Expression in Bacteria
Authors: Martial Joseph A. , Hallewell Robert A. , Baxter John D. , Goodman Howard M.
Published: October 2006

The nucleotide sequence of a DNA complementary to human growth hormone messenger RNA was cloned; it contains 29 nucleotides in its 5′ untranslated region, the 651 nucleotides coding for the prehormone, and the entire 3′ untranslated region (108 nucleotides). The data reported predict the previously unknown sequence of the signal peptide of human growth hormone and, by comparison with the previously determined sequences of rat growth hormone and human chorionic somatomammotropin, strengthens the hypothesis that these genes evolved by gene duplication from a common ancestral sequence. The human growth hormone gene sequences have been linked in phase to a fragment of the
trp
D gene of
Escherichia coli
in a plasmid vehicle, and a fusion protein is synthesized at high level (approximately 3 percent of bacterial protein) under the control of the regulatory region of the
trp
operon. This fusion protein (70 percent of whose amino acids are coded for by the human growth hormone gene) reacts specifically with antibodies to human growth hormone and is stable in
E. coli
.
Rapid Killing of Single Neurons by Irradiation of Intracellularly Injected Dye
Authors: Miller John P. , Selverston Allen I.
Published: October 2006

A simple technique for rapidly killing all or part of single neurons consists of filling the cell with Lucifer Yellow CH and irradiating all or part of it with intense blue light. Such treatment kills the irradiated part of the cell within a few minutes. Adjacent cells are not affected.
Spatially Regulated Expression of Homeotic Genes in
Drosophila
Authors: Harding Katherine , Wedeen Cathy , McGinnis William , Levine Michael
Published: October 2006

The sites of transcript accumulation for six different homeotic loci of the Antennapedia and bithorax gene complexes (ANT-C and BX-C) were identified within embryo tissue sections by in situ hybridization. These six loci belong to the Antennapedia class of the homeo box gene family. Transcripts encoded by each locus are detected primarily in discrete, nonoverlapping regions of the embryonic central nervous system (CNS). The regions of the CNS that contain transcripts encoded by each of these loci correspond to the embryonic segments that are disrupted in mutants for these genes. The maintenance of spatially restricted expression of each ANT-C and BX-C locus could involve hierarchical, cross-regulatory interactions that are mediated by the homeo box protein domains encoded by these genes.
Crystal Structure of Cd,Zn Metallothionein
Authors: Furey W. F. , Robbins A. H. , Clancy L. L. , Winge D. R. , Wang B. C. , Stout C. D.
Published: October 2006

The anomalous scattering data from five Cd in the native protein were used to determine the crystal structure of cadmium, zinc (Cd,Zn) metallothionein isoform II from rat liver. The structure of a 4-Cd cluster was solved by direct methods. A 2.3 Å resolution electron density map was calculated by iterative single-wavelength anomalous scattering. The structure is folded into two domains. The amino terminal domain (β) of residues 1 to 29 enfolds a three-metal cluster of one Cd and two Zn atoms coordinated by six terminal cysteine thiolate ligands and three bridging cysteine thiolates. The carboxyl terminal domain (α) of residues 30 to 61 enfolds a 4-Cd cluster coordinated by six terminal and five bridging cysteine thiolates. All seven metal sites have tetrahedral coordination geometry. The domains are roughly spherical, and the diameter is 15 to 20 Å; there is limited contact between domains. The folding of α and β is topologically similar but with opposite chirality. Redundant, short cysteine-containing sequences have similar roles in cluster formation in both α and β.
Matrix-Driven Translocation of Cells and Nonliving Particles
Authors: Newman Stuart A. , Frenz Dorothy A. , Tomasek James J. , Rabuzzi Daniel D.
Published: October 2006

Cells of metazoan organisms produce and react to complex macromolecular microenvironments known as extracellular matrices. Assembly in vitro of native, compositionally nonuniform collagen-fibronectin matrices caused translocation of certain types of cells or polystyrene-latex beads from regions lacking fibronectin into regions containing it. The translocation process was not due to diffusion, convection, or electrostatic distribution effects, but may depend on nonequilibrium phenomena at the interface of contiguous collagen matrices formed in the presence and absence of fibronectin or particles. Extracellular matrix formation alone was sufficient to drive translocation by a biophysical process that may play a role in cellular migration during embryogenesis, as well as in other types of tissue reorganization such as inflammation, wound healing, and tumor invasion.
Trans
-4-Hydroxy-2-Hexenal: a Reactive Metabolite from the Macrocyclic Pyrrolizidine Alkaloid Senecionine
Authors: Segall H. J. , Wilson D. W. , Dallas J. L. , Haddon William F.
Published: October 2006

The toxicity of macrocyclic pyrrolizidine alkaloids in the livers of man and animals has been attributed to the formation of reactive pyrroles from dihydropyrrolizines. Now a novel metabolite,
trans
-4-hydroxy-2-hexenal, has been isolated from the macrocyclic pyrrolizidine alkaloid senecionine, in an in vitro hepatic microsomal system. Other alkenals such as
trans
-4-hydroxy-2-nonenal have previously been isolated from microsomal systems when treated with halogenated hydrocarbons or subjected to lipid peroxidation. The in vivo pathology caused by
trans
-4-hydroxy-2-hexenal appears to be identical to that previously attributed to reactive pyrroles. There are similarities between the toxic effects of this alkenal and those of centrilobular hepatotoxins such as CCl
4
and other alkenals formed during lipid peroxidation.
A Brain Event Related to the Making of a Sensory Discrimination
Authors: Ritter Walter , Simson Richard , Vaughan Herbert G. , Friedman David
Published: October 2006

Event-related potentials associated with detected targets in a vigilance task were analyzed in two ways: (i) by sorting the potentials in terms of sequential reaction time bins of 50 milliseconds and (ii) by examining the single trial waveforms. A negative component (N2) covaried in latency with reaction time. These results support the hypothesis that N2 reflects a decision process which controls behavioral responses in sensory discrimination tasks.
Partially Modified Retro-Inverso-Enkephalinamides: Topochemical Long-Acting Analogs in Vitro and in Vivo
Authors: Chorev Michael , Shavitz Rick , Goodman Murray , Minick Scott , Guillemin Roger
Published: October 2006

The synthesis of four enkephalinamide analogs is described in which the peptide bond between residues 4 and 5 is reversed with or without simultaneous reversal of the carboxyl-terminal amide bond. These so-called partially modified retro-inverso-isomers are new, potent, topochemical analogs of the enkephalins. Tests, both in vitro and in vivo, have shown that these analogs are considerably longer acting than any previously studied enkephalins. Thus, partial reversal of the peptide bonds of the backbone can result in peptides with enhanced activity compared to a parent compound, provided that the structural complementarity of both the side chains and end groups are conserved.
Neonatal Rat Surgery: Avoiding Maternal Cannibalism
Authors: Libbin Richard M. , Person Philip
Published: October 2006

A simple program of handling and care of pregnant rats before delivery makes it possible to carry out surgical procedures on newborn pups without resultant cannibalism or rejection of the operated animals by their mothers.
Lens Epithelial Cell Elongation in the Absence of Microtubules: Evidence for a New Effect of Colchicine
Authors: Beebe David C. , Feagans Douglas E. , Blanchette-Mackie E. Joan , Nau Martin E.
Published: October 2006

Embryonic chick lens epithelial cells cultured in serum-supplemented medium elongated in the absence of microtubules after treatment with the antimicrotubule drug nocodazole. Colchicine, at concentrations lower than those that dissociate microtubules, blocks cell elongation and the associated increase in cell volume. These results indicate that an increase in cell volume, not microtubules, is responsible for lens cell elongation and suggest a previously undescribed effect of colchicine on cell volume regulation.
Differential Mortality by Sex in Fetal and Neonatal Deaths
Authors: McMillen Marilyn M.
Published: October 2006

Vital statistics data for the United States from 1922 to 1936 and from 1950 to 1972 were used to analyze fetal and early neonatal mortality. This analysis corroborates the previously established pattern of the sex ratio of fetal deaths—highest from months 3 to 5, lower from months 6 to 7 or 8, and increasing at term. It also indicates a postponement of late fetal deaths into the early infant period. Whereas earlier research reports have described the pattern of the sex ratio of fetal deaths, this report repeats this analysis for a recent national data base. This line of analysis is extended by using the patterns observed in the data to produce an empirical estimate of the primary sex ratio. For 1950 to 1972, this ratio (male to female) is conservatively estimated to be 120:100.
Release of Luteinizing Hormone in Male Mice During Exposure to Females: Habituation of the Response
Authors: Coquelin Arthur , Bronson F. H.
Published: October 2006

Male mice release luteinizing hormone when exposed for a short time to a female. In this experiment, multiple blood samples were withdrawn by atrial cannulas from tethered males during either continuous or intermittent exposure to nonreceptive females. After an immediate, transient release of luteinizing hormone, continuous exposure to the same female was accompanied by only random, spontaneous elevations in plasma levels of this hormone. Successive presentations of the same female at 2-hour intervals elicited gradually diminishing luteinizing hormone responses. Exposing such unresponsive males to novel, diestrous females, however, dramatically stimulated their release of the hormone. These results demonstrate habituation of a socially induced, neuroendocrine response involving reproductive hormones.
Activation of the c-
myb
Locus by Viral Insertional Mutagenesis in Plasmacytoid Lymphosarcomas
Authors: Shen-Ong Grace L. C. , Potter Michael , Mushinski J. Frederic , Lavu Sukadev , Reddy E. Premkumar
Published: October 2006

Rearrangement in the c-
myb
locus of each of four independently derived BALB/c plasmacytoid lymphosarcoma (ABPL's) is due to the insertion of a defective Moloney murine leukemia virus (M-MuLV) into a 1.5-kilobase-pair stretch of cellular DNA at the 5′ end of the v-
myb
-related sequences. This retroviral insertion is associated with abnormal transcription of
myb
sequences and probably represents a step in the neoplastic transformation of ABPL cells.