bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen-15 and Oxygen-18 Characteristics of Nitrous Oxide: A Global Perspective
Authors: Kim K.-R. , Craig H.
Published: October 2006

The global budget of N2O shows a significant imbalance between the known rate of destruction in the stratosphere and the estimated rates of natural and anthropogenic production in soils and the ocean. Measurements of the15N/14N and18O/16O ratios in two major tropospheric sources of N2O, tropical rain forest soils and fertilized soils, show that soil N2O from a tropical rain forest in Costa Rica and from sugar-cane fields in Maui is strongly depleted in both15N and18O relative to mean tropospheric N2O. A major source of heavy N2O, enriched in both15N and18O, must therefore be present to balance the light N2O from soils. One such source is the back-mixing flux of N2O from the stratosphere, which is enriched in15N and18O by photolysis and chemistry. However these return fluxes of15N and18O are so great that a large oceanic flux of N2O is required to balance the heavy isotope—enriched stratospheric flux. All these effects will be reflected in climatically related isotopic variations in trapped N2O in polar ice cores.
AIDS-Kaposi's Sarcoma-Derived Cells Express Cytokines with Autocrine and Paracrine Growth Effects
Authors: Ensoli Barbara , Nakamura Shuji , Salahuddin S. Zaki , Biberfeld Peter , Larsson Lena , Beaver Barbara , Wong-Staal Flossie , Gallo Robert C.
Published: October 2006

When grown in vitro, cells from Kaposi's sarcoma lesions of AIDS patients (AIDS-KS cells) constitutively release several growth promoting activities. When inoculated into nude mice, the AIDS-KS cells induce a KS-like lesion of mouse origin. Here it is shown that the AIDS-KS cells express messenger RNA for a complex mixture of cytokines that correlate with several of the biological activities of these cells. Basic fibroblast growth factor, which is a potent angiogenic factor, and interleukin-1 messenger RNAs are expressed at very high levels and seem to account for a large proportion of the activities, since their corresponding proteins are released in biologically active form into the culture media where they induce autocrine and paracrine growth effects.
Glial Cell Diversification in the Rat Optic Nerve
Authors: Raff Martin C.
Published: October 2006

A central challenge in developmental neurobiology is to understand how an apparently homogeneous population of neuroepithelial cells in the early mammalian embryo gives rise to the great diversity of nerve cells (neurons) and supporting cells (glial cells) in the mature central nervous system. Because the optic nerve is one of the simplest parts of the central nervous system, containing several types of glial cells but no intrinsic neurons, it is an attractive place to investigate how neuroepithelial cells diversify. Studies of developing rat optic nerve cells in culture suggest that both cell-cell interactions and intrinsic cellular programs play important parts in glial cell diversification.
The Pathway of Infection of
Autographa californica
Nuclear Polyhedrosis Virus in an Insect Host
Authors: Keddie B. Andrew , Aponte Gregory W. , Volkman Loy E.
Published: October 2006

An immunohistochemical study was conducted to detect the temporal infection sequence of
Autographa californica
M nuclear polyhedrosis virus in
Trichoplusia ni
larvae. Staining patterns indicated that the initial infection occurred in the midgut, simultaneously in columnar epithelial and regenerative cells, but that subsequently this tissue recovered. A major envelope glycoprotein stained in a polar fashion when it was expressed in columnar epithelial cells, but not when expressed in other cells types. Systemic infection was mediated by free virus for some tissues whereas infected hemocytes appeared to spread virus to other tissues by an unknown mechanism. A cell to cell spread within several tissues was detected. These results have important implications for baculoviruses engineered for improving their pesticide potential.
Production of Mammastatin, a Tissue-Specific Growth Inhibitor, by Normal Human Mammary Cells
Authors: Ervin P. R. , Kaminski M. S. , Cody R. L. , Wicha M. S.
Published: October 2006

The growth of human mammary cells may be regulated by a balance between growth stimulatory and growth inhibitory pathways. Polypeptides of 47 and 65 kilodaltons (mammastatin) were isolated from conditioned medium of normal human mammary cells. Monoclonal antibodies against mammastatin were generated that blocked its activity and were used for purification and further characterization of the protein. Mammastatin inhibited the growth of 5 transformed human mammary cell lines, but had no effect on the growth of 11 transformed human cell lines derived from nonmammary tissues. Mammastatin appeared to be a heat-labile protein distinct from transforming growth factor-β (TGF-β). By immunoperoxidase staining it was detected in cultured normal human mammary cells, but was decreased in transformed mammary cells.
Pretranslational Suppression of an Insulin-Responsive Glucose Transporter in Rats with Diabetes Mellitus
Authors: Garvey W. Timothy , Huecksteadt Thomas P. , Birnbaum Morris J.
Published: October 2006

A prominent feature of diabetes mellitus is the inability of insulin to appropriately increase the transport of glucose into target tissues. The contributions of different glucose transport proteins to insulin resistance in rats with streptozotocin-induced diabetes was evaluated. A glucose transporter messenger RNA and its cognate protein that are exclusively expressed in muscle and adipose tissue were specifically depleted in diabetic animals, and these effects were reversed after insulin therapy; a different glucose transporter and its messenger RNA that exhibit a less restricted tissue distribution were not specifically modulated in this way. Depletion of the muscle- and adipose-specific glucose transporter species correlates with and may account for the major portion of cellular insulin resistance in diabetes in these animals.
Transcriptional Regulation in Mammalian Cells by Sequence-Specific DNA Binding Proteins
Authors: Mitchell Pamela J. , Tjian Robert
Published: October 2006

The cloning of genes encoding mammalian DNA binding transcription factors for RNA polymerase II has provided the opportunity to analyze the structure and function of these proteins. This review summarizes recent studies that define structural domains for DNA binding and transcriptional activation functions in sequence-specific transcription factors. The mechanisms by which these factors may activate transcriptional initiation and by which they may be regulated to achieve differential gene expression are also discussed.
Directing Cell Division During Development
Authors: O'Farrell Patrick H. , Edgar Bruce A. , Lakich Delia , Lehner Christian F.
Published: October 2006

Several evolutionarily conserved proteins constitute a universal mitotic trigger that is precisely controlled during the orderly cell divisions of embryogenesis. As development progresses, the mechanisms controlling this trigger change. Early divisions are executed by maternally synthesized gene products, and in
Xenopus
they are timed by the accumulation and periodic degradation of cyclin, a trigger component. Later, the zygotic genome assumes control, and in
Drosophila
, zygotic transcription is required for production of another trigger protein, the product of
string
. After this transition to zygotic control, pulses of
string
transcription define the timing of highly patterned embryonic cell divisions and cyclin accumulation is not rate limiting.
Chromosomal Location and Evolutionary Rate Variation in Enterobacterial Genes
Authors: Sharp Paul M. , Shields Denis C. , Wolfe Kenneth H. , Li Wen-Hsiung
Published: October 2006

The basal rate of DNA sequence evolution in enterobacteria, as seen in the extent of divergence between
Escherichia coli
and
Salmonella typhimurium
, varies greatly among genes, even when only "silent" sites are considered. The degree of divergence is clearly related to the level of gene expression, reflecting constraints on synonymous codon choice. However, where this constraint is weak, among genes not expressed at high levels, divergence is also related to the chromosomal location of the gene; it appears that genes furthest away from
oriC
, the origin of replication, have a mutation rate approximately two times that of genes near
oriC
.
Structural Basis for Misaminoacylation by Mutant
E. coli
Glutaminyl-tRNA Synthetase Enzymes
Authors: Perona John J. , Swanson Robert N. , Rould Mark A. , Steitz Thomas A. , Söll Dieter
Published: October 2006

A single-site mutant of
Escherichia coli
glutaminyl-synthetase (D235N, GlnRS7) that incorrectly acylates in vivo the amber suppressor
supF
tyrosine transfer RNA (tRNA
Tyr
) with glutamine has been described. Two additional mutant forms of the enzyme showing this misacylation property have now been isolated in vivo (D235G, GlnRS10; I129T, GlnRS15). All three mischarging mutant enzymes still retain a certain degree of tRNA specificity; in vivo they acylate
supE
glutaminyl tRNA (tRNA(Gln] and
supF
tRNA
Tyr
but not a number of other suppressor tRNA's. These genetic experiments define two positions in GlnRS where amino acid substitution results in a relaxed specificity of tRNA discrimination. The crystal structure of the GlnRS:tRNA
Gln
complex provides a structural basis for interpreting these data. In the wild-type enzyme Asp
235
makes sequence-specific hydrogen bonds through its side chain carboxylate group with base pair G3 ⋅ C70 in the minor groove of the acceptor stem of the tRNA. This observation implicates base pair 3 ⋅ 70 as one of the identity determinants of tRNA
Gln
. Isoleucine 129 is positioned adjacent to the phosphate of nucleotide C74, which forms part of a hairpin structure adopted by the acceptor end of the complexed tRNA molecule. These results identify specific areas in the structure of the complex that are critical to accurate tRNA discrimination by GlnRS.
Binocular Depth Reversals Despite Familiarity Cues
Authors: van den Enden Aad , Spekreijse Henk
Published: October 2006

Stereoscopic depth can be reversed by interchanging the left- and right-eye views (pseudoscopy) when abstract stereograms are used, but not when stereograms contain natural objects or scenes. This resistance to reversal of depth has traditionally been attributed to familiarity with the shape of objects and the presence of monocular depth cues. However, when texture disparity is neutralized by making the texture perspective of surfaces identical for both eyes, even a highly familiar object, like a monocularly recognizable human face, appears as concave (nose pointing inwards) when viewed pseudoscopically.
Hidden Thermodynamics of Mutant Proteins: A Molecular Dynamics Analysis
Authors: Gao Jiali , Kuczera Krzysztof , Tidor Bruce , Karplus Martin
Published: October 2006

A molecular dynamics simulation method is used to determine the contributions of individual amino acid residues and solvent molecules to free energy changes in proteins. Its application to the hemoglobin interface mutant Asp G1(99) β→Ala shows that some of the contributions to the difference in the free energy of cooperativity are as large as 60 kilocalories (kcal) per mole. Since the overall free energy change is only -5.5 kcal/mole (versus the experimental value of -3.4 kcal/mole), essential elements of the thermodynamics are hidden in the measured results. By exposing the individual contributions, the free energy simulation provides new insights into the origin of thermodynamic changes in mutant proteins and demonstrates the role of effects beyond those usually considered in structural analyses.
Scale Invariance in Food Web Properties
Authors: Sugihara George , Schoenly Kenneth , Trombla Alan
Published: October 2006

The robustness of five common food web properties is examined by varying the resolution of the data through aggregation of trophic groupings. A surprising constancy in each of these properties is revealed as webs are collapsed down to approximately half their original size. This analysis of 60 invertebrate-dominated community food webs confirms the existence of all but one of these properties in such webs and addresses a common concern held by critics of food web theory that observed food web properties may be sensitive to trophic aggregation. The food web statistics (chain length; predator/prey ratio; fraction of top, intermediate, and bottom species; and rigid circuits) are scaling in the sense that they remain roughly invariant over a wide range of data resolution. As such, within present standards of reporting food web data, these statistics may be used to compare systems whose trophic data are resolved differently within a factor of 2.
Domain Separation in the Activation of Glycogen Phosphorylase
a
Authors: Goldsmith E. J. , Sprang S. R. , Hamlin R. , Xuong N.-H. , Fletterick R. J.
Published: October 2006

The crystal structure of glycogen phosphorylase
a
complexed with its substrates, orthophosphate and maltopentaose, has been determined and refined at a resolution of 2.8 angstroms. With oligosaccaride bound at the glycogen storage site, the phosphate ion binds at the catalytic site and causes the regulatory and catalytic domains to separate with the loss of stabilizing interactions between them. Homotropic cooperativity between the active sites of the allosteric dimer results from rearrangements in isologous contacts between symmetry-related helices in the subunit interface. The conformational changes in the core of the interface are correlated with those observed on covalent activation by phosphorylation at Ser
14
(phosphorylase
b
→
a
).
Ocular Dominance Column Development: Analysis and Simulation
Authors: Miller Kenneth D. , Keller Joseph B. , Stryker Michael P.
Published: October 2006

The visual cortex of many adult mammals has patches of cells that receive inputs driven by the right eye alternating with patches that receive inputs driven by the left eye. These ocular dominance patches (or "columns") form during early life as a consequence of competition between the activity patterns of the two eyes. A mathematical model of several biological mechanisms that can account for this development is presented. Analysis of this model reveals the conditions under which ocular dominance segregation will occur and determines the resulting patch width. Simulations of the model also exhibit other phenomena associated with early visual development, such as topographic refinement of cortical receptive fields, the confinement of input cell connections to patches, monocular deprivation plasticity including a critical period, and the effect of artificially induced strabismus. The model can be used to predict the results of proposed experiments and to discriminate among various mechanisms of plasticity.
Fitness Differences Among Remnant Populations of the Endangered Sonoran Topminnow
Authors: Quattro J. M. , Vrijenhoek R. C.
Published: October 2006

Four correlates of fitness were measured in three stocks of the endangered Sonoran topminnow,
Poeciliopsis occidentalis
, from Arizona. Survival, growth, early fecundity, and developmental stability were greatest in laboratory-reared fish from the most heterozygous natural population studied. Conversely, all four traits were poorest in fish from a population with no electrophoretically detectable genetic variation. These results emphasize the need for genetic as well as demographic information for the development of comprehensive species recovery programs.
Identification of Monocyte Chemotactic Activity Produced by Malignant Cells
Authors: Graves D. T. , Jiang Y. L. , Williamson M. J. , Valente A. J.
Published: October 2006

Human malignant cells secrete low molecular size proteins that attract peripheral blood monocytes and may be responsible for the accumulation of tumor-associated macrophages observed in vivo. Similar chemotactic proteins are secreted by cultured vascular smooth muscle cells. The predominant monocyte chemoattractants produced by tumor cells of differing origin were demonstrated to be related to smooth muscle cell-derived chemotactic factor. Thus, a single class of chemotactic proteins is produced by different cell types, which suggests a common mechanism for the recruitment of monocytes and macrophages. These results are significant in view of the potential of macrophages to affect tumor growth.
Spatial Buffering of Light-Evoked Potassium Increases by Retinal Müller (Glial) Cells
Authors: Karwoski Chester J. , Lu Hong-Kai , Newman Eric A.
Published: October 2006

Activity-dependent variations in extracellular potassium concentration in the central nervous system may be regulated, in part, by potassium spatial buffering currents in glial cells. The role of spatial buffering in the retina was assessed by measuring light-evoked potassium changes in amphibian eyecups. The amplitude of potassium increases in the vitreous humor was reduced to ∼10 percent by 50 micromolar barium, while potassium increases in the inner plexiform layer were largely unchanged. The decrease in the vitreal potassium response was accurately simulated with a numerical model of potassium current flow through Müller cells, the principal glial cells of the retina. Barium also substantially increased the input resistance of Müller cells and blocked the Müller cell-generated M-wave, indicating that barium blocks the potassium channels of Müller cells. Thus, after a light-evoked potassium increase within the retina, there is a substantial transfer of potassium from the retina to the vitreous humor by potassium current flow through Müller cells.
Antibody to Interleukin-5 Inhibits Helminth-Induced Eosinophilia in Mice
Authors: Coffman Robert L. , Seymour Brian W. P. , Hudak Susan , Jackson John , Rennick Donna
Published: October 2006

When rodents are infected with the nematode
Nippostrongylus brasiliensis
, large numbers of eosinophils appear in their blood and lungs and their serum immunoglobulin E (IgE) is increased. Injection of a monoclonal antibody to interleukin-5 completely suppressed the blood eosinophilia and the infiltration of eosinophils in the lungs of parasitized mice but had no effect on serum IgE. In contrast, an antibody to interleukin-4 inhibited parasite-induced IgE but not the eosinophilia. These results show that interleukin-5 is important in eosinophil production in vivo and that IgE and eosinophil production are regulated by different cytokines produced by the T
H
2 subset of CD4-expressing T cells.
Prevention of Allogeneic Bone Marrow Graft Rejection by H-2 Transgene in Donor Mice
Authors: Öhlén Claes , Kling Gunilla , Höglund Petter , Hansson Mona , Scangos George , Bieberich Charles , Jay Gilbert , Kärre Klas
Published: October 2006

Rejection of bone marrow grafts in irradiated mice is mediated by natural killer (NK) cells and is controlled by genes linked to the major histocompatibility complex (MHC). It has, however, not been possible to identify the genes or their products. An MHC class I (D
d
) transgene introduced in C57BL donors prevented the rejection of their bone marrow by NK cells in irradiated allogeneic and F
1
hybrid mice expressing the D
d
gene. Conversely, H-2D
d
transgenic C57BL recipients acquired the ability to reject bone marrow from C57BL donors but not from H-2D
d
transgenic C57BL donors. These results provide formal evidence that NK cells are part of a system capable of rejecting cells because they lack normal genes of the host type, in contrast to T cells, which recognize cells that contain abnormal or novel sequences of non-host type.
Assembly of the Native Heterodimer of
Rana esculenta
Tropomyosin by Chain Exchange
Authors: Lehrer Sherwin S. , Qian Yude , Hvidt Søren
Published: October 2006

Rana esculenta
tropomyosin assembles in vivo into a coiled-coil α helix from two different subunits, α and β, which are present in about equal concentrations. Although the native composition is αβ, a mixture of equal amounts of αα and ββ is produced by refolding dissociated α and β at low temperature in vitro. Refolding kinetics showed that αα formed first and was relatively stable with regard to chain exchange below approximately 20°C. Equilibration of the homodimer mixture at 30° and 34°C for long times, however, resulted in the formation of the native αβ molecule by chain exchange. Biosynthesis of αβ from separate α and β genes is, therefore, favored thermodynamically over the formation of homodimers, and biological factors need not be invoked to explain the preferred native αβ composition.
Human Proto-Oncogene c-
jun
Encodes a DNA Binding Protein with Structural and Functional Properties of Transcription Factor AP-1
Authors: Bohmann Dirk , Bos Timothy J. , Admon Arie , Nishimura Tetsuji , Vogt Peter K. , Tjian Robert
Published: October 2006

Nuclear oncogene products have the potential to induce alterations in gene regulation leading to the genesis of cancer. The biochemical mechanisms by which nuclear oncoproteins act remain unknown. Recently, an oncogene, v-
jun
, was found to share homology with the DNA binding domain of a yeast transcription factor, GCN4. Furthermore, GCN4 and the phorbol ester-inducible enhancer binding protein, AP-1, recognize very similar DNA sequences. The human proto-oncogene c-
jun
has now been isolated, and the deduced amino acid sequence indicates more than 80 percent identity with v-
jun
. Expression of cloned c-
jun
in bacteria produced a protein with sequence-specific DNA binding properties identical to AP-1. Antibodies raised against two distinct peptides derived from v-
jun
reacted specifically with human AP-1. In addition, partial amino acid sequence of purified AP-1 revealed tryptic peptides in common with the c-
jun
protein. The structural and functional similarities between the c-
jun
product and the enhancer binding protein suggest that AP-1 may be encoded by c-
jun
. These findings demonstrate that the proto-oncogene product of c-
jun
interacts directly with specific target DNA sequences to regulate gene expression, and therefore it may now be possible to identify genes under the control of c-
jun
that affect cell growth and neoplasia.
Functional Expression of a New Pharmacological Subtype of Brain Nicotinic Acetylcholine Receptor
Authors: Wada Keiji , Ballivet Marc , Boulter Jim , Connolly John , Wada Etsuko , Deneris Evan S. , Swanson Larry W. , Heinemann Steve , Patrick Jim
Published: October 2006

A new type of agonist-binding subunit of rat neuronal nicotinic acetylcholine receptors (nAChRs) was identified. Rat genomic DNA and complementary DNA encoding this subunit (alpha2) were cloned and analyzed. Complementary DNA expression studies in
Xenopus
oocytes revealed that the injection of messenger RNAs (mRNAs) for alpha2 and beta2 (a neuronal nAChR subunit) led to the generation of a functional nAChR. In contrast to the other known neuronal nAChRs, the receptor produced by the injection of alpha2 and beta2 mRNAs was resistant to the α-neurotoxin Bgt3.1. In situ hybridization histochemistry showed that alpha2 mRNA was expressed in a small number of regions, in contrast to the wide distribution of the other known agonist-binding subunits (alpha3 and alpha4) mRNAs. These results demonstrate that the alpha2 subunit differs from other known agonist-binding α-subunits of nAChRs in its distribution in the brain and in its pharmacology.
Characterization of a Noncytopathic HIV-2 Strain with Unusual Effects on CD4 Expression
Authors: Evans Louise A. , Moreau Jacques , Odehouri Koudou , Legg Harold , Barboza Ashley , Cheng-Mayer Cecilia , Levy Jay A.
Published: October 2006

A new isolate of the human immunodeficiency virus type 2, designated HIV-2
UC1
, was recovered from an Ivory Coast patient with normal lymphocyte numbers who died with neurologic symptoms. Like some HIV-1 isolates, HIV-2
UC1
grows rapidly to high titers in human peripheral blood lymphocytes and macrophages and has a differential ability to productively infect established human cell lines of lymphocytic and monocytic origin. Moreover, infection with this isolate also appears to involve the CD4 antigen. However, unlike other HIV isolates, HIV-2
UC1
does not cause cytopathic effects in susceptible T cells nor does it lead to loss of CD4 antigen expression on the cell surface. These results indicate that HIV-2 may be found in individuals with neurologic symptoms and that the biological characteristics of this heterogeneous subgroup can differ from those typical of HIV-1.
Brownian Dynamics of Cytochrome c and Cytochrome c Peroxidase Association
Authors: Northrup Scott H. , Boles Jeffrey O. , Reynolds John C. L.
Published: October 2006

Brownian dynamics computer simulations of the diffusional association of electron transport proteins cytochrome c (cyt c) and cytochrome c peroxidase (cyt c per) were performed. A highly detailed and realistic model of the protein structures and their electrostatic interactions was used that was based on an atomic-level spatial description. Several structural features played a role in enhancing and optimizing the electron transfer efficiency of this reaction. Favorable electrostatic interactions facilitated long-lived nonspecific encounters between the proteins that allowed the severe orientational criteria for reaction to be overcome by rotational diffusion during encounters. Thus a "reduction-in-dimensionality" effect operated. The proteins achieved plausible electron transfer orientations in a multitude of electrostatically stable encounter complexes, rather than in a single dominant complex.
Negative Regulation by Glucocorticoids Through Interference with a cAMP Responsive Enhancer
Authors: Akerblom Ingrid E. , Slater Emily P. , Beato Miguel , Baxter John D. , Mellon Pamela L.
Published: October 2006

Although steroid hormone receptors are known to activate gene expression by binding to specific hormone-dependent enhancers, the mechanisms by which steroids inhibit the transcription of specific genes are unknown. It is shown here by gene transfer studies that the same glucocorticoid receptor that activates gene expression can negatively regulate expression of the human glycoprotein hormone α-subunit gene. Glucocorticoid inhibition was conferred by a 52-nucleotide region that also contains elements crucial both for adenosine 3′,5′-monophosphate (cAMP) responsiveness and for placental-specific expression of this gene and was observed only under conditions in which these elements were functioning as enhancers. Purified glucocorticoid receptor was found to bind to DNA that overlap the cAMP responsive elements sites in this region. It is hypothesized that steroid receptors negatively regulate gene expression by interfering with the activity or binding of other important transcription factors.
From Epinephrine to Cyclic AMP
Authors: Levitzki Alexander
Published: October 2006

Binding of catecholamines to the β-adrenergic receptor results in the activation of adenylate cyclase and the intracellular formation of adenosine 3′,5′-monophosphate (cAMP). In the past 20 years the events that lead from hormone binding at the cell surface receptor site to the synthesis of cAMP at the inner layer of the membrane have been intensively studied. Signal transduction in this system involves the sequential interaction of the β-adrenergic receptor with the guanine nucleotide-binding protein (G
s
) and the adenylate cyclase catalyst (C). The mechanism of signal transduction from the receptor through G
s
to C, as well as the role of the adenylate cyclase inhibitory G protein G
i
, is discussed.
A Defective HSV-1 Vector Expresses
Escherichia coli
β-Galactosidase in Cultured Peripheral Neurons
Authors: Geller Alfred I. , Breakefield Xandra O.
Published: October 2006

A defective herpes simplex virus 1 (HSV-1) vector, pHSVlac, has been developed that contains a transcription unit that places the
Escherichia coli
lacZ
gene under the control of the HSV-1 immediate early 4/5 promoter. The vector pHSVlac was propagated with the HSV-1 temperature-sensitive mutant ts K as helper virus. Infection of neurons from rat superior cervical ganglia and dorsal root ganglia in primary culture resulted in stable expression of high levels of β-galactosidase without cell death. These HSV-1 vectors should be useful for introducing genes into postmitotic cells, such as neurons, in vitro and in vivo.
T Cell CD3-ζη Heterodimer Expression and Coupling to Phosphoinositide Hydrolysis
Authors: Merćep Mladen , Bonifacino Juan S. , Garcia-Morales Pilar , Samelson Lawrence E. , Klausner Richard D. , Ashwell Jonathan D.
Published: October 2006

The T cell antigen receptor consists of an antigen-binding heterodimer that is noncovalently associated with at least five CD3 subunits (γ, δ, ε, ζ, and η). The CD3-ζ chains are either disulfide-linked homodimers (CD3-ζ
2
) or disulfide-linked heterodimers with η (CD3-ζη). Variants of a murine antigen-specific T cell hybridoma that express normal amounts of CD3-ζ
2
but decreased amounts of CD3-ζη were isolated. When activated, the parental cell line increased both phosphatidylinositol hydrolysis and serine-specific protein kinase activity to a much greater extent than the variants. In contrast, the activation of a tyrosine-specific kinase after stimulation with a cross-linking antibody to CD3 was similar among these cells. There was a positive linear relation between the expression of CD3-ζη and phosphoinositide hydrolysis stimulated by the TCR, suggesting a differential coupling of the T cell αβ heterodimer to signal transduction mechanisms due to αβ association with either CD3-ζ
2
or CD3-ζη.
Point mutations in the Human Vitamin D Receptor Gene Associated with Hypocalcemic Rickets
Authors: Hughes Mark R. , Malloy Peter J. , Kieback Dirk G. , Kesterson Robert A. , Pike J. Wesley , Feldman David , O'Malley Bert W.
Published: October 2006

Hypocalcemic vitamin D-resistant rickets is a human genetic disease resulting from target organ resistance to the action of 1,25-dihydroxyvitamin D3. Two families with affected children homozygous for this autosomal recessive disorder were studied for abnormalities in the intracellular vitamin D receptor (VDR) and its gene. Although the receptor displays normal binding of 1,25-dihydroxyvitamin D3 hormone, VDR from affected family members has a decreased affinity for DNA. Genomic DNA isolated from these families was subjected to oligonucleotide-primed DNA amplification, and each of the nine exons encoding the receptor protein was sequenced for a genetic mutation. In each family, a different single nucleotide mutation was found in the DNA binding domain of the protein; one family near the tip of the first zinc finger (Gly→Asp) and one at the tip of the second zinc finger (Arg→Gly). The mutant residues were created in vitro by oligonucleotide directed point mutagenesis of wild-type VDR complementary DNA and this cDNA was transfected into COS-1 cells. The produced protein is biochemically indistinguishable from the receptor isolated from patients.
Quantitative Analysis of D2 Dopamine Receptor Binding in the Living Human Brain by PET
Authors: Farde Lars , Hall Håkan , Ehrin Erling , Sedvall Göran
Published: October 2006

D2 dopamine receptors in the putamen of living human subjects were characterized by using the selective, high-affinity D2 dopamine receptor antagonist carbon-11-labeled raclopride and positron emission tomography. Experiments in four healthy men demonstrated saturability of [
11
C]raclopride binding to an apparently homogeneous population of sites with Hill coefficients close to unity. In the normal putamen, maximum binding ranged from 12 to 17 picomoles per cubic centimeter and dissociation constants from 3.4 to 4.7 nanomolar. Maximum binding for human putamen at autopsy was 15 picomoles per cubic centimeter. Studies of [
11
C]raclopride binding indicate that clinically effective doses of chemically distinct neuroleptic drugs result in 85 to 90 percent occupancy of D2 dopamine receptors in the putamen of schizophrenic patients.
Neurogenetic Adaptive Mechanisms in Alcoholism
Authors: Cloninger C. Robert
Published: October 2006

Clinical, genetic, and neuropsychopharmacological studies of developmental factors in alcoholism are providing a better understanding of the neurobiological bases of personality and learning. Studies of the adopted-away children of alcoholics show that the predisposition to initiate alcohol-seeking behavior is genetically different from susceptibility to loss of control after drinking begins. Alcohol-seeking behavior is a special case of exploratory appetitive behavior and involves different neurogenetic processes than do susceptibility to behavioral tolerance and dependence on the antianxiety or sedative effects of alcohol. Three dimensions of personality have been described that may reflect individual differences in brain systems modulating the activation, maintenance, and inhibition of behavioral responses to the effects of alcohol and other environmental stimuli. These personality traits distinguish alcoholics with different patterns of behavioral, neurophysiological, and neuropharmacological responses to alcohol.
A Transgenic Mouse Model for Human Neurofibromatosis
Authors: Hinrichs Steven H. , Nerenberg Michael , Reynolds R. Kay , Khoury George , Jay Gilbert
Published: October 2006

Human T-lymphotropic virus type 1 (HTLV-1) has been associated with the neurologic disorder tropical spastic paraparesis and possibly with multiple sclerosis. Thetatgene of HTLV-1 under control of its own long terminal repeat is capable of inducing tumors in transgenic mice. The morphologic and biologic properties of these tumors indicate their close resemblance to human neurofibromatosis (von Recklinghausen's disease), the most common single gene disorder to affect the nervous system. The high spontaneous incidence of this disease, together with the diverse clinical and pathologic features associated with it, suggests that environmental factors may account for some of the observed cases. Multiple tumors developed simultaneously in the transgenictatmice at approximately 3 months of age, and the phenotype was successfully passed through three generations. The tumors arise from the nerve sheaths of peripheral nerves and are composed of perineural cells and fibroblasts. Tumor cells from these mice adapt easily to propagation in culture and continue to express the tat protein in significant amounts. When transplanted into nude mice, these cultured cells efficiently induce tumors. Evidence of HTLV-1 infection in patients with neural and other soft tissue tumors is needed in order to establish a link between infection by this human retrovirus and von Recklinghausen's disease and other nonlymphoid tumors.
Molecular Genetics: Applications to the Clinical Neurosciences
Authors: Martin Joseph B.
Published: October 2006

Application of molecular biology, by means of linkage analysis and DNA probes that demonstrate restriction fragment length polymorphisms (RFLPs), has resulted in the chromosomal localization of the genes responsible for a number of neurological disorders. Characterization of the structure and function of individual genes for these diseases is in an early stage, but information available indicates that the molecular mechanisms underlying phenotypic expression of neurological diseases encompass a wide range of genetic errors ranging from the most minor (a single-base pair mutation) to large chromosomal deletions. Linkage analysis can now be used for genetic counseling in several of these disorders.
Inhibition of Cellular Proliferation by Antisense Oligodeoxynucleotides to PCNA Cyclin
Authors: Jaskulski Dariusz , deRiel J. Kim , Mercer W. Edward , Calabretta Bruno , Baserga Renato
Published: October 2006

The proliferating cell nuclear antigen (PCNA or cyclin) is a nuclear protein recently identified as a cofactor of DNA polymerase δ. When exponentially growing Balb/c3T3 cells are exposed to antisense oligodeoxynucleotides to PCNA, both DNA synthesis and mitosis are completely suppressed. A corresponding sense oligodeoxynucleotide has no inhibitory effects. These experiments indicate that PCNA (cyclin) is important in cellular DNA synthesis and in cell cycle progression.
Engraftment of Immune-Deficient Mice with Human Hematopoietic Stem Cells
Authors: Kamel-Reid Suzanne , Dick John E.
Published: October 2006

A system in which immune-deficient mice are repopulated with cells from the human myeloid lineage, and that provides an in vivo stem cell assay for human hematopoietic cells is described. Generation of the chimeric human/immune-deficient (HID) mice was dependent on the use of immune-deficient
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/
xid
mice. Infusion of these mice with human bone marrow gave rise to increases in human macrophage progenitors during more than 5 weeks of in vivo growth, indicating the seeding, proliferation, and differentiation of human stem cells. The human identity of the progenitors was confirmed by sequence analysis and their dependence on human growth factors. The creation of HID mice lays the foundation for establishing animal models for a wide variety of human hemopathies, from leukemia to infectious disease.
High-Level Recombinant Gene Expression in Rabbit Endothelial Cells Transduced by Retroviral Vectors
Authors: Zwiebel James A. , Freeman Scott M. , Kantoff Philip W. , Cornetta Ken , Ryan Una S. , Anderson W. French
Published: October 2006

By virtue of its immediate contact with the circulating blood, the endothelium provides an attractive target for retroviral vector transduction for the purpose of gene therapy. To see whether efficient gene transfer and expression was feasible, rabbit aortic endothelial cells were infected with three Moloney murine leukemia virus-derived retroviral vectors. Two of these vectors carry genes encoding products that are not secreted: N2, containing only the selectable marker gene
neo
R
, and SAX, containing both neo
R
gene and an SV40-promoted adenosine deaminase (ADA) gene. The third vector, G2N, contains a secretory rat growth hormone (rGH) gene and an SV40-promoted neo
R
gene. Infection with all three vectors resulted in expression of the respective genes. A high level of human ADA expression was observed in infected endothelial cell populations both before and after selection in G418. G2N-infected rabbit aortic endothelial cells that were grown on a synthetic vascular graft continued to secrete rGH into the culture medium. These studies suggest that endothelial cells may serve as vehicles for the introduction in vivo of functioning recombinant genes.
Isolation and Expression of Functional High-Affinity Fc Receptor Complementary DNAs
Authors: Allen Janet M. , Seed Brian
Published: October 2006

Human and murine mononuclear phagocytes express a high-affinity receptor for immunoglobulin G that plays a central role in macrophage antibody-dependent cellular cytotoxicity and clearance of immune complexes. The receptor (FcRI) may also be involved in CD4-independent infection of human macrophages by human immunodeficiency virus. This report describes the isolation of cDNA clones encoding the human FcRI by a ligand-mediated selection technique. Expression of the cDNAs in COS cells gave rise to immunoglobulin G binding of the expected affinity and subtype specificity. RNA blot analysis revealed expression of a 1.7-kilobase transcript in macrophages and in cells of the promonocytic cell line U937 induced with interferon-γ. The extracellular region of FcRI consists of three immunoglobulin-like domains, two of which share homology with low-affinity receptor domains.
Molecular Dynamics Simulation of a Phospholipid Micelle
Authors: Wendoloski J. J. , Kimatian S. J. , Schutt C. E. , Salemme F. R.
Published: October 2006

The dynamic character of phospholipid aggregates limits conventional structural studies to the determination of average molecular features. In order to develop more detailed descriptions of phospholipid structure for comparison with experiment, the molecular dynamics of a hydrated lysophosphatidylethanolamine (LPE) micelle, incorporating 85 LPE and 1591 water molecules, have been simulated. Comparison of the initial and equilibrated micelles shows substantial differences both in LPE hydrocarbon chain conformation and polar head-group-solvent interactions. Although these changes produce only subtle effects on the averaged structural properties of the system, the alterations in hydrocarbon chain packing and head-group solvation appear to mimic a polymorphic pretransition from a spherical toward a cylindrical micelle structure.
Reciprocal Effects of Hyper- and Hypoactivity Mutations in the
Drosophila
Pattern Gene
torso
Authors: Strecker Teresa R. , Halsell Susan R. , Fisher William W. , Lipshitz Howard D.
Published: October 2006

In
Drosophila
, five "terminal" polarity genes must be active in females in order for them to produce embryos with normal anterior and posterior ends. Hypoactivity mutations in one such gene,
torso
, result in the loss of the most posterior domain of
fushi tarazu
expression and the terminal cuticular structures. In contrast, a
torso
hyperactivity mutation causes the loss of central
fushi tarazu
expression and central cuticular structures. Cytoplasmic leakage, transplantation, and temperature-shift experiments suggest that the latter effect is caused by abnormal persistence of the
torso
product in the central region of the embryo during early development. Thus, the amount and timing of
torso
activity is key to distinguishing the central and terminal regions of the embryo. Mutations in the
tailless
terminal gene act as dominant maternal suppressors of the hyperactive
torso
allele, indicating that the
torso
product acts through, or in concert with, the
tailless
product.
Coronary Vasoconstrictor Effects of Atriopeptin II
Authors: Wangler R. D. , Breuhaus B. A. , Otero H. O. , Hastings D. A. , Holzman M. D. , Saneii H. H. , Sparks H. V. , Chimoskey J. E.
Published: October 2006

Atrial natriuretic peptides lower arterial pressure, cardiac filling pressure, and cardiac output. In isolated, Langendorff-perfused guinea pig hearts, atriopeptin II, the 23-amino acid atrial natriuretic peptide, is also a potent coronary vasoconstrictor. The median effective dose for atriopeptin II in guinea pig hearts is 26 nanomoles, the threshold constrictor dose is 5 nanomoles, and flow nearly ceases at a dose of 100 nanomoles in perfused hearts at constant pressure. Similar concentrations of atriopeptin II also cause coronary vasoconstriction in rat and dog heart preparations. The disulfide bridge is necessary for vasoconstrictor activity; reduction of this bridge abolishes the activity, as it does the other biological activities of atrial natriuretic peptides.
A Blood Vessel Model Constructed from Collagen and Cultured Vascular Cells
Authors: Weinberg Crispin B. , Bell Eugene
Published: October 2006

A model of a blood vessel was constructed in vitro. Its multilayered structure resembled that of an artery and it withstood physiological pressures. Electron microscopy showed that the endothelial cells lining the lumen and the smooth muscle cells in the wall were healthy and well differentiated. The lining of endothelial cells functioned physically, as a permeability barrier, and biosynthetically, producing von Willebrand's factor and prostacyclin. The strength of the model depended on its multiple layers of collagen integrated with a Dacron mesh.
Activation of Mouse T-Helper Cells Induces Abundant Preproenkephalin mRNA Synthesis
Authors: Zurawski Gerard , Benedik Michael , Kamb Barkley J. , Abrams John S. , Zurawski Sandra M. , Lee Frank D.
Published: October 2006

Antigenic or mitogenic stimulation of T cells induces the secretion of an array of protein hormones that regulate immune responses. Molecular cloning has contributed strongly to our present understanding of the nature of this regulation. A complementary DNA (cDNA) library prepared from a cloned concanavalin A-activated mouse T-helper cell line was screened for abundant and induction-specific cDNA's. One such randomly chosen cDNA was found to encode mouse preproenkephalin messenger RNA (mRNA). Preproenkephalin mRNA represented about 0.4 percent of the mRNA in the activated cell line but was absent in resting cells of this line. Other induced T-helper cell lines have 0.1 to 0.5 percent of their mRNA as preproenkephalin mRNA. Induced T-helper cell culture supernatants have [Met]enkephalin-immunoreactive material. The production by activated T cells of a peptide neurotransmitter identifies a signal that can potentially permit T cells to modulate the nervous system.
Islet Allograft Survival After a Single Course of Treatment of Recipient with Antibody to L3T4
Authors: Shizuru Judith A. , Gregory Anita K. , Chao C. Tien-Bao , Fathman C. Garrison
Published: October 2006

Allografts of pancreatic islets of Langerhans were induced to survive for an indefinite period in diabetic mice if, at the time of engraftment, the mice received a single course of treatment with a monoclonal antibody directed against the L3T4 determinant, a nonpolymorphic cell surface glycoprotein present on the cell surface of the murine T helper-inducer lymphocyte subset. This treatment allowed the survival of islets of Langerhans transplanted across a major histocompatibility barrier without additional immunosuppression. The results demonstrate that the lymphocyte subset defined by the expression of the L3T4 molecules is central to the induction of allograft rejection and provides a model for tolerance induction for organ allograft transplantation.
Structure of the Receptor for Insulin-Like Growth Factor II: The Puzzle Amplified
Authors: Roth Richard A.
Published: October 2006

The insulin-like growth factor II (IGF-II) is a polypeptide hormone with structural homologies to insulin and insulin-like growth factor I (IGF-I). In contrast to these other hormones, the in vivo function of IGF-II is not known. Although IGF-II can stimulate a broad range of biological responses in isolated cells, these responses have usually been found to be mediated by the insulin and IGF-I receptors. Recently, the receptor for IGF-II was found to also be the receptor for mannose-6-phosphate. Since this latter receptor has been implicated in targeting of lysosomal enzymes, the question is now raised of whether the same protein can also mediate metabolic responses to IGF-II.
Antibody-Enhanced Infection by HIV-1 Via Fc Receptor-Mediated Entry
Authors: Takeda Akira , Tuazon Carmelita U. , Ennis Francis A.
Published: October 2006

Monocytes and macrophages, which may play a central role in the pathogenesis of infection with human immunodeficiency virus type 1 (HIV-1), express the CD4 molecule and Fc receptors (FcR) for immunoglobulin G (IgG). To explore the possibility that FcR mediate HIV-1 infection of monocytes, studies were conducted with the human monocytic cell line U937. These cells were exposed to HIV-1 complexed with various concentrations of serum from HIV-1 antibody-positive individuals and monitored for HIV-1 replication. Serum samples from antibody-negative normal individuals did not affect virus yields. High concentrations of antibody-positive sera showed virus-neutralizing activity; however, cells infected with HIV-1 in the presence of antibody-positive sera at subneutralizing concentrations significantly enhanced virus replication. This infection enhancement was blocked by heat-aggregated γ-globulin. Moreover, the IgG fraction from an HIV-1 antibody-positive serum enhanced HIV-1 infection at the same serum dilution equivalents. In contrast, IgG-F(abγ)
2
did not enhance HIV-1 infection but showed neutralizing activity with HIV-1. These results are compatible with the concept of FcR-mediated infection enhancement and suggest that this immunological response to HIV-1, instead of protecting the host, potentially facilitates the infection.