bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistent Noncytopathic Infection of Normal Human T Lymphocytes with AIDS-Associated Retrovirus
Authors: Hoxie James A. , Haggarty Beth S. , Rackowski Jerome L. , Pillsbury Nan , Levy Jay A.
Published: October 2006

Infection of normal peripheral blood T cells by the acquired immune deficiency syndrome (AIDS)-associated retrovirus (ARV) was evaluated in long-term cultures of helper-inducer T cells (T4 cells). Cells that were inoculated with ARV and maintained in medium supplemented with interleukin-2 remained productively infected with this virus for more than 4 months in culture, although they showed no cytopathic effects characteristic of acute ARV infection. The presence of replicating virus was demonstrated by reverse transcriptase activity of culture fluids and by viral antigens and budding particles detected on cells by immunofluorescence and electron microscopy. Virus produced in these cultures remained infectious and could induce cytopathic effects and viral antigens in uninfected lymphoid cells. The finding that normal lymphocytes may be productively infected by an AIDS retrovirus in the absence of cell death suggests that a range of biologic effects may occur after infection in vivo.
The 36-Kilodalton Substrate of pp60

v-
src

Is Myristylated in a Transformation-Sensitive Manner
Authors: Soric Jasna , Gordon Julius A.
Published: October 2006

A primary intracellular substrate for pp60

v-
src

kinase in a variety of avian and mammalian cells is a protein of 34 to 39 kilodaltons (kD). After incubation of chicken embryo fibroblasts (CEF) with [
3
H]myristic acid for 4 hours, the 36-kD protein contained covalently bound myristic acid by several criteria: (i) the radioactively labeled material comigrated with the 36-kD protein on sodium dodecyl sulfate-polyacrylamide gels in one and two dimensions, (ii) the labeled material was insoluble in chloroform-methanol, and (iii) radioactively labeled myristate could be recovered from the purified 36-kD protein. The resistance of the acyl fatty acid moiety to hydrolysis by hydroxylamine suggested that the covalent linkage to the 36-kD protein may be through an amide linkage. The [
3
H]myristic-acid labeling of the 36-kD protein in Rous sarcoma virus-transformed CEF showed a reduction of up to 45 percent when compared to an identical amount of 36-kD protein derived from normal cells; this reduction was not due to general changes in myristic acid metabolism in transformed cells.
Histocompatibility Antigens on Murine Tumors
Authors: Goodenow Robert S. , Vogel Julie M. , Linsk Richard L.
Published: October 2006

Recent advances in tumor immunology suggest that the expression of the histocompatibility antigens, encoded by the major histocompatibility complex, is important in controlling the metastatic growth of certain murine tumors. The anomalous expression of histocompatibility antigens in many neoplasms appears to be associated with the ability of these cells to evade the immune system and progress to metastasis. This review examines some of the underlying molecular and immunobiological interactions that might determine the metastatic outcome of cellular transformation.
Identification of a Missense Mutation in the Factor VIII Gene of a Mild Hemophiliac
Authors: Gitschier Jane , Wood William I. , Shuman Marc A. , Lawn Richard M.
Published: October 2006

DNA probes derived from the cloned factor VIII gene can be used to detect mutations in the factor VIII gene of hemophiliacs. DNA hybridization analysis led to the identification of two contrasting point mutations in the same codon. In a severe hemophiliac with no detectable factor VIII activity, the normal arginine codon (number 2307) is converted to a stop codon, while in a mild hemophiliac with 10 percent of normal activity, this same codon is converted to glutamine.
Viral Shedding and Transmission Between Hosts Determined by Reovirus L2 Gene
Authors: Keroack Mark , Fields Bernard N.
Published: October 2006

Two reovirus isolates (type 1 Lang and type 3 Dearing) differ in their transmissibility between littermates of newborn mice. They also differ in the amounts of virus excreted by the gastrointestinal tract. With the use of reassortant viruses, these properties were mapped to the L2 gene. Thus environmental spread of reovirus is a genetic property.
Estrogen Memory Effect in Human Hepatocytes During Repeated Cell Division Without Hormone
Authors: Tam S.-P. , Haché R. J. G. , Deeley R. G.
Published: October 2006

Transient stimulation of target tissues by sex steroids can cause long-lasting changes that may facilitate or alter responses to subsequent hormonal treatment. How these altered characteristics are propagated during cell division in the absence of the stimulating hormone is unknown. The human hepatocarcinoma cell line HepG2 was used as a model to examine the effects of estrogen on the synthesis of serum apolipoproteins in vitro. Treatment with low concentrations of estrogen for 24 to 48 hours resulted in long-lasting alterations in the kinetics with which the cells responded to subsequent stimulation with estrogen. Manifestation of this memory effect was correlated quantitatively with the induction and propagation of a moderate-affinity, nuclear, estrogen-binding protein with the characteristics of a type II estrogen receptor. The data indicate that transient exposure of these cells to estrogen can induce changes in their response characteristics and composition of nuclear proteins that are inherited by daughter cells grown in the absence of hormone for more than ten generations.
A Promoter with an Internal Regulatory Domain Is Part of the Origin of Replication in BPV-1
Authors: Stenlund Arne , Bream Gary L. , Botchan Michael R.
Published: October 2006

Extrachromosomal elements that are stably maintained at a constant copy number through cell doublings are a good model system for the study of the regulation of DNA replication in higher eukaryotes. Previous studies have defined both cis and trans functions required for the regulated plasmid replication of the bovine papilloma virus in stably transformed cells. Here, a sequence known to be a cis-dominant element of the replication origin of the plasmid is shown to contain a promoter for transcription. Both in vitro and in vivo assays have been used to define this promoter and show that a sequence located just 3′ to the transcriptional start site is required for activity. This DNA sequence element, which has been defined through deletions, coincides with a binding site for a cellular factor and is also required for a functional origin of replication. Possible models for how a transcription factor may play a role in the regulation of DNA replication are discussed.
Variable Occurrence of the
nrd
B Intron in the T-Even Phages Suggests Intron Mobility
Authors: Pedersen-Lane Joan , Belfort Marlene
Published: October 2006

The bacteriophage T4
erb
B gene, encoding nucleoside diphosphate reductase subunit B, contains a self-splicing group I intervening sequence. The
erb
B intron was shown to be absent from the genomes of the closely related T-even phages T2 and T6. Evidence for variable intron distribution was provided by autocatalytic
32
P-guanosine 5′-triphosphate labeling of T-even RNAs, DNA and RNA hybridization analyses, and DNA sequencing studies. The results indicate the nonessential nature of the intron in
erb
B expression and phage viability. Furthermore, they suggest that either precise intron loss from T2 and T6 or lateral intron acquisition by T4 occurred since the evolution of these phages from a common ancestor. Intron movement in the course of T-even phage divergence raises provocative questions about the origin of these self-splicing elements in prokaryotes.
Human Factor VIII: Morphometric Analysis of Purified Material in Solution
Authors: Tan Henry K. , Andersen Judith C.
Published: October 2006

Study of purified human factor VIII in buffer by freeze-etch electron microscopy reveals rounded, rod-shaped particles measuring 22 by 42 nanometers. When thrombin was added to purified normal factor VIII, there was a rapid loss of rod-shaped particles during the first 15 minutes of incubation at 37°C. Purified plasma from two patients with severe hemophilia contained spherical particles measuring 10 to 50 nanometers in diameter, with no evidence of significant numbers of rod-shaped forms. Negatively stained and unstained air-dried samples of factor VIII corroborate the relative shape and size differences between normal and hemophiliac material.
Escherichia coli
Aspartate Transcarbamylase: the Relation Between Structure and Function
Authors: Kantrowitz Evan R. , Lipscomb William N.
Published: October 2006

The x-ray structures of the allosteric enzyme aspartate transcarbamylase from
Escherichia coli
have been solved and refined for both allosteric forms. The T form was determined in the presence of the heterotropic inhibitor cytidine triphosphate, CTP, while the R form was determined in the presence of the bisubstrate analog
N
-phosphonacetyl-L-aspartate. These two x-ray structures provide the starting point for an understanding of how allosteric enzymes are able to control the rates of metabolic pathways. Insights into the mechanisms of both catalysis and homotropic cooperativity have been obtained by using site-directed mutagenesis to probe residues thought to be critical to the function of the enzyme based on these x-ray structures.
Time-Resolved Photoacoustic Calorimetry: Probing the Energetics and Dynamics of Fast Chemical and Biochemical Reactions
Authors: Peters Kevin S. , Snyder Gary J.
Published: October 2006

Time-resolved photoacoustic calorimetry is a new experimental technique that measures the dynamics of enthalpy changes on the time scale of nanoseconds to microseconds for reactions initiated by absorption of light. When the reaction is carried out in water, it is also possible to obtain the dynamics of the corresponding volume changes. This method has been applied to a variety of biochemical, organic, and organometallic reactions.
Site-Specific Integration of H-
ras
in Transformed Rat Embryo Cells
Authors: McKenna W. Gillies , Nakahara Ken , Muschel Ruth J.
Published: October 2006

A karyotypic analysis was performed on seven independently derived clones of primary rat embryo cells transformed by the
ras
oncogene plus the cooperating oncogene
myc
. The transfected oncogenes were sometimes present in amplified copy number, with heterogeneity in the levels of amplification. Some chromosomal features, such as aberrantly banding regions and double-minute chromosomes, typical of cells carrying amplified genes, were also seen in three of the seven cell lines. Underlying this heterogeneity there was an unexpected finding. All seven lines showed a common integration site for
ras
on the q arm of rat chromosome 3 (3q12), though some lines also had other sites of integration. In four of the lines integration of
ras
was accompanied by deletion of the p arm of chromosome 3 or its possible translocation to chromosome 12.
Intron Existence Predated the Divergence of Eukaryotes and Prokaryotes
Authors: Shih Ming-Che , Heinrich Peter , Goodman Howard M.
Published: October 2006

Nucleotide sequences for the nuclear genes encoding chloroplast (GapA and GapB) and cytosolic (GapC) glyceraldehyde-3-phosphate dehydrogenases (GAPDHs) from
Arabidopsis thaliana
were determined. Comparison of nucleotide sequences indicates that the divergence of chloroplast and cytosolic GAPDH genes preceded the divergence of prokaryotes and eukaryotes. In addition, some intron-exon junctions are conserved among GapB, GapC, and chicken GAPDH genes. These results provide evidence at the molecular level to support the idea that introns existed before the divergence of prokaryotes and eukaryotes.
Identification of Paramyosin as Schistosome Antigen Recognized by Intradermally Vaccinated Mice
Authors: Lanar David E. , Pearce Edward J. , James Stephanie L. , Sher Alan
Published: October 2006

Mice immunized intradermally with extracts of
Schistosoma mansoni
in combination with the adjuvant BCG are significantly protected against subsequent infection with living larval forms of the parasite. Remarkably, these vaccinated animals produce antibodies predominantly against a single parasite protein of molecular weight 97 kilodaltons (Sm-97). A complementary DNA that encodes about half of the Sm-97 molecule has now been cloned and sequenced. Analysis of the deduced amino acid sequence reveals a protein containing periodic repeats of hydrophobic amino acids characteristic of an α-helical coiled-coil structure. The deduced amino acid composition of the cloned gene and several properties of the native protein are similar to that of paramyosin, an α-helical protein that forms the core for myosin filaments in invertebrate muscle. Paramyosin was isolated from
Schistosoma mansoni
adult worms and antibodies to Sm-97 were shown to react with this molecule as well as with a known paramyosin from molluscan muscle.
Sequence-Specific Cleavage of Double Helical DNA by Triple Helix Formation
Authors: Moser Heinz E. , Dervan Peter B.
Published: October 2006

Homopyrimidine oligodeoxyribonucleotides with EDTA⋅Fe attached at a single position bind the corresponding homopyrimidine-homopurine tracts within large double-stranded DNA by triple helix formation and cleave at that site. Oligonucleotides with EDTA⋅Fe at the 5′ end cause a sequence specific double strand break. The location and asymmetry of the cleavage pattern reveal that the homopyrimidine-EDTA probes bind in the major groove parallel to the homopurine strand of Watson-Crick double helical DNA. The sequence-specific recognition of double helical DNA by homopyrimidine probes is sensitive to single base mismatches. Homopyrimidine probes equipped with DNA cleaving moieties could be useful tools for mapping chromosomes.
Protein Carbon-13 Spin Systems by a Single Two-Dimensional Nuclear Magnetic Resonance Experiment
Authors: Oh Byung Ha , Westler William M. , Darba Prashanth , Markley John L.
Published: October 2006

By applying a two-dimensional double-quantum carbon-13 nuclear magnetic resonance experiment to a protein uniformly enriched to 26 percent carbon-13, networks of directly bonded carbon atoms were identified by virtue of their one-bond spin-spin couplings and were classified by amino acid type according to their particular single- and double-quantum chemical shift patterns. Spin systems of 75 of the 98 amino acid residues in a protein, oxidized
Anabaena
7120 ferredoxin (molecular weight 11,000), were identified by this approach, which represents a key step in an improved methodology for assigning protein nuclear magnetic resonance spectra. Missing spin systems corresponded primarily to residues located adjacent to the paramagnetic iron-sulfur cluster.
Identification and Characterization of a Neuron-Specific Nuclear Antigen in
Drosophila
Authors: Bier Ethan , Ackerman Larry , Barbel Sandra , Jan Lily , Jan Yuh Nung
Published: October 2006

An antigen found only in neuronal nuclei of
Drosophila melanogaster
is revealed by staining with a monoclonal antibody (Mab44C11). This antigen appears early in development, before neurons show any other signs of antigenic or morphologic differentiation, and persists throughout development. This nuclear staining permits reliable detection of neurons in developmental studies of wild-type and mutant flies. Protein immunoblot analyses and immune precipitation experiments show that the neuronal nuclear antigen is a 50-kilodalton polypeptide.
Preferential Transmission of the Z Deficient Allele of α
1
-Antitrypsin
Authors: Chapuis-Cellier Colette , Arnaud Philippe
Published: October 2006

The transmission of the Z deficient allele of α
1
-antitrypsin was studied in 23 families, each with a single parent heterozygous for this allele. When the mother carried the Z allele, the distribution of phenotypes in the children did not differ significantly from the expected frequency. In contrast, when the father was the carrier, a significant increase of heterozygous phenotypes was observed in the children. This observation suggests that a selective advantage is associated with the expression of the Z allele in male gametes.
Beta-
N
-Methylamino-L-Alanine Neurotoxicity: Requirement for Bicarbonate as a Cofactor
Authors: Weiss John H. , Choi Dennis W.
Published: October 2006

Ingestion of the excitotoxic cycad seed amino acid β-
N
-methylamino-L-alanine may be responsible for the neuronal degeneration associated with Guam amyotrophic lateral sclerosis-parkinsonism-dementia in man. However, the basis for the central neurotoxicity of β-
N
-methylamino-L-alanine has been unclear, as it lacks the omega acidic (or equivalent electronegative) moiety characteristic of other excitatory amino acids. β-
N
-methylamino-L-alanine produced neurotoxic and neuroexcitatory effects in murine cortical cell cultures only when physiological concentrations of bicarbonate were available in the extracellular bathing medium. Bicarbonate may interact noncovalently with β-
N
-methylamino-L-alanine to produce, in combination, a molecular configuration that activates glutamate receptors.
Heavy Metals Affect Rod, But Not Cone, Photoreceptors
Authors: Fox D. A. , Sillman A. J.
Published: October 2006

Low concentrations of lead, mercury, or cadmium depress the amplitude of the rod receptor potential in the perfused bullfrog retina. Responses from the cones were not affected. The data implicate the rods as a lesion site in animals exhibiting scotopic vision deficits as a result of heavy metal poisoning.
DNA Elements Are Asymmetrically Joined During the Site-Specific Recombination of Kappa Immunoglobulin Genes
Authors: Lewis Susanna , Gifford Ann , Baltimore David
Published: October 2006

Immunoglobulin K genes are constructed during lymphocyte differentiation by the joining of two DNA elements, V
K
and J
K
, to form both a V
K
J
K
coding unit and a reciprocal recombination product. The two products formed in single V
K
-to-J
K
joining events can be directly isolated through the use of a retrovirally introduced recombination substrate. The structural analysis of a number of recombinants and the derivation of secondary recombination products define some of the basic features of the mechanism of immunoglobulin gene assembly.
Structural Rearrangement of the Retinoblastoma Gene in Human Breast Carcinoma
Authors: T'Ang Anne , Varley Jennifer M. , Chakraborty Shikha , Murphree A. Linn , Fung Yuen-Kai T.
Published: October 2006

Structural changes of the human retinoblastoma gene have been demonstrated previously in retinoblastoma and some clinically related tumors including osteosarcoma. Structural aberrations of the retinoblastoma locus (RB1) were observed in 25% of breast tumor cell lines studied and 7% of the primary tumors. These changes include homozygous internal deletions and total deletion of RB1; a duplication of an exon was observed in one of the cell lines. In all cases, structural changes either resulted in the absence or truncation of the RB1 transcript. No obvious defect in RB1 was detected by DNA blot analysis in primary tumors or cell lines from Wilms' tumor, cervical carcinoma, or hepatoma. These results further support the concept that the human RB1 gene has pleiotropic effects on specific types of cancer.
Behavioral Neurophysiology: Insights into Seeing and Grasping
Authors: Wise Steven P. , Desimone Robert
Published: October 2006

One marvels at a batter's ability to hit a baseball traveling at 150 kilometers per hour or a monkey's skill in snatching a flying insect. Indeed, the ability of many animals to reach out, grasp, and manipulate objects is a feat of biological engineering unmatched by even state-of-the-art robots. But how are the objects of our attention chosen and how are the eyes and hands directed to it? Recent progress in behavioral neurophysiology has clarified some of the brain mechanisms at work.
Novel Screening Procedure for Recombinant Plasmids
Authors: Telford John , Boseley Paul , Schaffner Walter , Birnstiel Max
Published: October 2006

Lysed bacterial colonies containing potential recombinant plasmids were mixed with molten agar and sealed into slots of an agarose gel. After electrophoresis overnight, the gel was stained with ethidium bromide, which clearly reveals recombinant plasmids.
Xenopus laevis
ribosomal DNA and histone DNA of
Psammechinus miliaris
were ligated into pCRI plasmids and screened by this method.
Cloning of Cauliflower Mosaic Virus (CLMV) DNA in
Escherichia coli
Authors: Szeto W. W. , Hamer D. H. , Carlson P. S. , Thomas C. A.
Published: October 2006

A plasmid containing cauliflower mosaic virus DNA can be faithfully cloned in
Escherichia coli
, but proved to be noninfective in test plants.
Theta-Sensitive Cell and Erythropoiesis: Identification of a Defect in
W
/

W
v

Anemic Mice
Authors: Wiktor-Jedrzejczak Wieslaw , Sharkie Saul , Ahmed Aftab , Sell Kenneth W. , Santos George W.
Published: October 2006

Nonirradiated mice of the
W
/
W

v

genotype were injected with normal (+/+) bone marrow cells that had been treated with antiserum to Thy 1.2 and complement (C′). Such bone marrow cells had no effect on the number of macroscopic colonies formed in the spleens of these mice, but did not cure the anemia. The addition of +/+ thymocytes to these bone marrow cells restored their ability to cure the anemia in
W
/
W

v

mice. These data suggest that a theta-sensitive cell is required in the promotion of differentiation of murine hematopoietic stem cells into erythrocytes, and that there is a deficiency of such a cell in the
W
/
W

v

mouse.
One Factor Recognizes the Liver-Specific Enhancers in α
1
-Antitrypsin and Transthyretin Genes
Authors: Grayson Dennis R. , Costa Robert H. , Xanthopoulos Kleanthis G. , Darnell James E.
Published: October 2006

Four different regulatory sites required for transcriptional stimulation by the enhancers of two unrelated liver-specific genes α
1
-antitrypsin and transthyretin appear to bind the same nuclear protein that is found mainly in the liver. Such proteins may provide a basis for a coordinated, hepatocyte-specific control of gene transcription.
Time-Resolved X-Ray Diffraction of Biological Materials
Authors: Gruner Sol M.
Published: October 2006

Instrumental and specimen considerations pertinent to performing time-resolved x-ray diffraction on biological materials are discussed. Existing synchrotron x-ray sources, in conjunction with integrating x-ray detectors, have made millisecond diffraction experiments feasible; exposure times several orders of magnitude shorter than this will be possible with synchrotron sources now on the drawing boards. Experience gained from time-resolved studies together with order-of-magnitude estimates of specimen requirements can be used to determine the instrumental capabilities needed for various time-resolved experiments. Existing instrumental capabilities and methods of dealing with time-resolved specimens are reviewed.
Neuroregulatory and Neuropathological Actions of the Ether-Phospholipid Platelet-Activating Factor
Authors: Kornecki Elizabeth , Ehrlich Yigal H.
Published: October 2006

Platelet-activating factor (PAF) is a naturally occurring phospholipid that serves as a critical mediator in diverse biological and pathophysiological processes. In this study of the interactions of PAF with neuronal cells, it was found that PAF increased the intracellular levels of free calcium ions in cells of the clones NG108-15 and PC12. The increase was dependent on extracellular calcium and was inhibited by the antagonistic PAF analog CV-3988 and by the calcium-influx blockers prenylamine and diltiazem. A functional consequence of this interaction was revealed by measuring a PAF-elicited, Ca
2+
-dependent secretion of adenosine triphosphate from PC12 cells. Exposure of NG108-15 cells for 3 to 4 days to low concentrations of PAF induced neuronal differentiation; higher concentrations were neurotoxic. Thus, by influencing Ca
2+
fluxes, PAF may play a physiological role in neuronal development and a pathophysiological role in the degeneration that occurs when neurons are exposed to circulatory factors as a result of trauma, stroke, or spinal cord injury.
Immunization Against Infectious Disease
Authors: Mortimer Edward A.
Published: October 2006

Mortality and morbidity from infectious diseases in the United States have declined more than 90 percent since 1900. Factors believed to be responsible for this decline include changes in the natural history of disease, sanitation, quarantine measures, control of nonhuman vectors, antibacterial drugs, and immunization. The contributions of each of these factors differ among the various infectious diseases; except for smallpox and diphtheria control, immunization had little effect until after World War II. The success of present and future immunization programs is endangered by public and physician complacency and by complex legal and ethical problems related to informed consent and responsibility for rare, vaccine-related injury.
T-Cell Recognition of Ia Molecules Selectively Altered by a Single Amino Acid Substitution
Authors: Brown Melissa A. , Glimcher Laurie A. , Nielsen Ellen A. , Paul William E. , Germain Ronald N.
Published: October 2006

T lymphocytes recognize foreign antigen together with allele-specific determinants on membrane-bound class I and class II (Ia) gene products of the major histocompatibility complex. To identify amino acids of class II molecules critical to this recognition process, the genes encoding the β chains of the I-A
k
molecule were cloned from a wild-type B-cell hybridoma and from an immunoselected variant subline showing distinct serological and T-cell stimulatory properties. Nucleotide sequencing and DNA-mediated gene transfer established that a single base transition (G → A) encoding a change from glutamic acid to lysine at position 67 in the I-A
k
β
molecule accounted for all the observed phenotypic changes of the variant cells. These results confirm the importance of residues 62 to 78 in the amino terminal domain of I-A
β
for class II-restricted T-cell recognition of antigen and demonstrate the ability of a single substitution in this region to alter this recognition event.
Novel Serine Proteases Encoded by Two Cytotoxic T Lymphocyte-Specific Genes
Authors: Lobe Corrinne G. , Finlay B. Brett , Paranchych William , Paetkau Verner H. , Bleackley R. Chris
Published: October 2006

Genes that are expressed exclusively in cytotoxic T cells should encode proteins that are essential for target cell lysis in cell-mediated immune responses. The sequences of two cytotoxic T lymphocyte-specific complementary DNA's (cDNA's) suggest that the two genes encode serine proteases. A full-length cDNA corresponding to one of the genes was isolated and sequenced. The predicted protein resembles serine proteases in that it includes all the residues that form the catalytic triad of the active site of serine proteases. Moreover, it has sequence characteristics thought to occur only in rat mast cell protease type II. These results are in accord with the view that a protease cascade plays a key role in cytotoxic T-cell activation.
Evidence for Increased Somatic Cell Mutations at the Glycophorin A Locus in Atomic Bomb Survivors
Authors: Langlois Richard G. , Bigbee William L. , Kyoizumi Seishi , Nakamura Nori , Bean Michael A. , Akiyama Mitoshi , Jensen Ronald H.
Published: October 2006

A recently developed assay for somatic cell mutations was used to study survivors of the atomic bomb at Hiroshima. This assay measures the frequency of variant erythrocytes produced by erythroid precursor cells with mutations that result in a loss of gene expression at the polymorphic glycophorin A (GPA) locus. Significant linear relations between variant frequency (VF) and radiation exposure were observed for three different variant cell phenotypes. The spontaneous and induced VFs agree with previous measurements of radiation-induced mutagenesis in other systems; this evidence supports a mutational origin for variant cells characterized by a loss of GPA expression and suggests that the GPA assay system may provide a cumulative dosimeter of past radiation exposures. VFs for some survivors differ dramatically from the calculated dose response, and these deviations appear to result primarily from statistical fluctuations in the number of mutations in the stem-cell pool. These fluctuations allow one to estimate the number of long-lived hemopoietic stem cells in humans.
Sequence and Expression of Human Estrogen Receptor Complementary DNA
Authors: Greene Geoffrey L. , Gilna Paul , Waterfield Michael , Baker Andrew , Hort Yvonne , Shine John
Published: October 2006

The mechanism by which the estrogen receptor and other steroid hormone receptors regulate gene expression in eukaryotic cells is not well understood. In this study, a complementary DNA clone containing the entire translated portion of the messenger RNA for the estrogen receptor from MCF-7 human breast cancer cells was sequenced and then expressed in Chinese hamster ovary (CHO-K1) cells to give a functional protein. An open reading frame of 1785 nucleotides in the complementary DNA corresponded to a polypeptide of 595 amino acids and a molecular weight of 66,200, which is in good agreement with published molecular weight values of 65,000 to 70,000 for the estrogen receptor. Homogenates of transformed Chinese hamster ovary cells contained a protein that bound [
3
H]estradiol and sedimented as a 4S complex in salt-containing sucrose gradients and as an 8 to 9S complex in the absence of salt. Interaction of this receptor-[
3
H]estradiol complex with a monoclonal antibody that is specific for primate ER confirms the identity of the expressed complementary DNA as human estrogen receptor. Amino acid sequence comparisons revealed significant regional homology among the human estrogen receptor, the human glucocorticoid receptor, and the putative v-
erb
A oncogene product. This suggests that steroid receptor genes and the avian erythroblastosis viral oncogene are derived from a common primordial gene. The homologous region, which is rich in cysteine, lysine, and arginine, may represent the DNA-binding domain of these proteins.
Expression and Cell Type—Specific Processing of Human Preproenkephalin with a Vaccinia Recombinant
Authors: Thomas Gary , Herbert Edward , Hruby Dennis E.
Published: October 2006

The posttranslational maturation of a complex precursor polyprotein, human proenkephalin, was assessed by infection of a wide spectrum of cell types with a recombinant vaccinia virus that expressed human proenkephalin. The infected cells rapidly produced both cellular and secreted Met-enkephalin immunoreactivity. Although each cell line could secrete intact proenkephalin, only a mouse pituitary line was capable of processing proenkephalin to mature enkephalin peptides. The quantity of intact proenkephalin secreted from BSC-40 cells (derived from African Green monkey kidney) was sufficient to establish the value of vaccinia virus as a mammalian cell expression vector.
Metabolite Transfer via Enzyme-Enzyme Complexes
Authors: Srivastava D. K. , Bernhard Sidney A.
Published: October 2006

The concentrations of enzyme sites in cells are usually higher than the concentrations of cognate intermediary metabolites. Therefore metabolic pathways or substantial segments of pathways may proceed by the direct transfer of metabolites from one enzyme site to the next by means of enzyme-enzyme complex formation. This mechanism of metabolite transfer differs from that usually assumed where dissociation and random diffusion of metabolite through the aqueous environment is responsible for the transfer to the next enzyme site. Since the direct transfer mechanism does not involve the aqueous environment, the energetics of metabolite interconversion can differ from expectations based on aqueous solution data. Evidence is summarized suggesting that metabolite is transformed and transferred with equal facility everywhere in the direct transfer pathway.
Molecular Models for DNA Damaged by Photoreaction
Authors: Pearlman David A. , Holbrook Stephen R. , Pirkle David H. , Kim Sung-Hou
Published: October 2006

Structural models of a DNA molecule containing a radiation-induced psoralen cross-link and of a DNA containing a thymine photodimer were constructed by applying energy-minimization techniques and model-building procedures to data from x-ray crystallographic studies. The helical axes of the models show substantial kinking and unwinding at the sites of the damage, which may have long-range as well as local effects arising from the concomitant changes in the supercoiling and overall structure of the DNA. The damaged areas may also serve as recognition sites for repair enzymes. These results should help in understanding the biologic effects of radiation-induced damage on cells.
Basal Ganglia Cooling Disables Learned Arm Movements of Monkeys in the Absence of Visual Guidance
Authors: Hore J. , Meyer-Lohmann J. , Brooks V. B.
Published: October 2006

Unilateral local cooling in the region of the globus pallidus of Cebus monkeys produced a severe breakdown in the performance of learned flexion-extension elbow movements when animals had no visual information about arm position but not when such information was displayed to them. This result indicates that visual information enables an animal to compensate to a large degree for the motor disorder produced by globus pallidus dysfunction, and it may explain why some previous workers have failed to see motor impairments in monkeys with lesions in the globus pallidus who were observed in their cages.
Morphological Novelty in the Limb Skeleton Accompanies Miniaturization in Salamanders
Authors: Hanken James
Published: October 2006

Salamanders of the genus
Thorius
(Plethodontidae) are among the smallest tetrapods. Hypotheses of limb skeletal evolution in these vertebrates were evaluated on the basis of estimates of natural variation, comparisons of skeletal homology, and analysis of molecular phylogeny. Nine carpal arrangements occur in
Thorius
, more than in all twelve related genera of typically larger salamanders; six of these arrangements are unique. They represent a trend toward a decrease in the number of separate cartilages that is independent of locomotor and ecological specialization. Miniaturization may be an important source of morphological novelty, distinct from local adaptation, in vertebrates.
Disorganization of Cultured Vascular Endothelial Cell Monolayers by Fibrinogen Fragment D
Authors: Dang Chi V. , Bell William R. , Kaiser Donald , Wong Albert
Published: October 2006

Fibrinogen fragment D, which is heterogeneous, has several important biological functions. Human fibrinogen fragments D
94
(molecular weight, 94,000), D
78
(78,000), and E (52,000) were purified. Fragments D
78
and D
94
but not purified fibrinogen or fragment E specifically caused disorganization of bovine aortic endothelial cells cultured as monolayers. Within 2 hours of exposure to pathophysiological concentrations of fragment D, the confluent endothelial cells retracted from each other and projected pseudopodia. These disturbed cells subsequently became rounded and detached from the substrate. The actin present in stress fibers in stationary monolayer cells was diffusely redistributed in cells with fragment D-induced alterations in morphology. This effect was not observed in monolayers of kidney epithelial cells. The results demonstrate a specific effect of fibrinogen fragment D on the disorganization of cultured vascular endothelial cell monolayers and suggest that fragment D plays a role in the pathogenesis of syndromes with vascular endothelial damage.
Brain-Derived Acidic Fibroblast Growth Factor: Complete Amino Acid Sequence and Homologies
Authors: Gimenez-Gallego Guillermo , Rodkey John , Bennett Carl , Rios-Candelore Mari , DiSalvo Jerry , Thomas Kenneth
Published: October 2006

Bovine brain-derived acidic fibroblast growth factor (aFGF) is a protein mitogen originally identified in partially purified preparations of whole brain. The protein was purified to homogeneity and shown to be a potent vascular endothelial cell mitogen in culture and angiogenic substance in vivo. The homology of aFGF to human interleukin-1β was inferred from partial sequence data. The complete amino acid sequence of aFGF has now been determined and observed to be similar to both basic FGF and interleukin-1's. A neuropeptide-like sequence, flanked by basic dipeptides, was observed within the aFGF sequence.
Phthalate Ester Plasticizers: A New Class of Marine Pollutant
Authors: Giam C. S. , Chan H. S. , Neff G. S. , Atlas E. L.
Published: October 2006

Phthalate ester plasticizers have been detected in the open-ocean environment. Samples consisting of water, sediment, air, and biota from the Gulf of Mexico and of water and air from the North Atlantic were analyzed and found to contain two phthalate esters, di-(2-ethylhexyl) phthalate (DEHP) and di-
n
-dibutyl phthalate (DBP); the concentrations of polychlorinated biphenyls (PCB's) and DDT's (
p
,
p
′-DDT and
p
,
p
′-DDE) were also determined. Like the ubiquitous PCB's and DDT's, the phthalate plasticizers were found in almost all samples analyzed; DEHP was present at higher concentrations than the PCB's or DDT's in water and sediment. The environmental impact of the concentrations found in these studies, coupled with the continued high production and wide use of these plasticizers, requires assessment.
Evaluation of Medical Practices
Authors: Frazier Howard S. , Hiatt Howard H.
Published: October 2006

Evaluation of the efficacy of a medical intervention requires valid measurements of both its benefits and risks as compared to those of alternative forms of management. The requisite measurements are more difficult to make than this simple description suggests, and the accumulation of information is further inhibited by certain characteristics of our pattern of health care. These features include, for example, discontinuous care by a variety of unrelated providers, inadequate records, the autonomy of physicians as decision-makers, financial disincentives, ambiguities in what we mean by "experimental" and "accepted" forms of therapy, and failure to see continuing evaluation as a necessary component of the cost of providing good medical care. Although no single change will solve all the problems of evaluation, several offer promise of improving our ability to choose from among medical interventions those most likely to be useful.
Methylation of Mouse Liver DNA Studied by Means of the Restriction Enzymes Msp I and Hpa II
Authors: Singer Judith , Roberts-Ems Joan , Riggs Arthur D.
Published: October 2006

The restriction enzymes Hpa II and Msp I both recognize the sequence 5′-CCGG (C, cytosine; G, guanine). However, Hpa II cuts mouse liver DNA to fragments four times larger than does Msp I. The size of DNA cut by Msp I is close to that predicted from base composition and nearest neighbor analysis. The most probable explanation of these results is that in mouse the site 5′-CCGG is highly methylated.
Auditory Brainstem Frequency Following Responses to Waveform Envelope Periodicity
Authors: Hall Joseph W.
Published: October 2006

An auditory frequency following response (FFR) was recorded to four complex stimuli. The FFR corresponded to the waveform envelope periodicity but not to the "missing fundamental" pitch of the stimuli. The FFR may be significant for timbre perception and sound lateralization.
Alpha-Adrenergic Receptor Identification by [
3
H]Dihydroergocryptine Binding
Authors: Williams Lewis T. , Lefkowitz Robert J.
Published: October 2006

A radioactively labeled α-adrenergic antagonist, [
3
H]dihydroergocryptine, binds specifically to a site on rabbit uterine membranes. Binding is rapid, reaching equilibrium in less than 17 minutes at 25°C. Adrenergic agonists compete for this binding site with an order of affinities identical to the pharmacological potency order of these agents as α-adrenergic agonists (epinephrine > norepinephrine ⪢ isoprotereonl). The (-) stereoisomers of epinephrine and norepinephrine are 30 times more potent in competing for the site than the corresponding (+) stereoisomers. α-Adrenergic antagonists, such as phentolamine and phenoxybenzamine, potently compete for the binding sites while the β-adrenergic antagonist propranolol does not. Structural analogs of catecholamines that are devoid of α-adrenergic physiological activity do not compete for [
3
H]dihydroergocryptine binding sites. These data suggest that α-adrenergic receptors can be directly identified and studied by [
3
H]dihydroergocryptine binding.
Phenylethylamine in Paranoid Chronic Schizophrenia
Authors: Potkin Steven G. , Karoum Farouk , Chuang Lin-Whei , Cannon-Spoor H. E. , Phillips Ingrid , Wyatt Richard Jed
Published: October 2006

Phenylethylamine (PEA) is an endogenous amine that is structurally and pharmacologically related to amphetamine. Urinary PEA excretion is significantly higher in paranoid chronic schizophrenics than in nonparanoid chronic schizophrenics and normal controls. Diet, hospitalization, and medication do not account for differences in PEA concentrations. These findings offer some indication that PEA may be an endogenous amphetamine.
Dopamine-Related Tetrahydroisoquinolines: Significant Urinary Excretion by Alcoholics After Alcohol Consumption
Authors: Collins Michael A. , Nijm William P. , Borge George F. , Teas Gregory , Goldfarb Clara
Published: October 2006

Concentrations of dopamine-related tetrahydroisoquinolines (salsolinol and
O
-methylated salsolinol) were significantly higher in the daily urine samples of alcoholic subjects admitted for alcohol detoxification than in the daily urine samples of nonalcoholic control subjects. Salsolinol concentrations in alcoholic subjects appeared to drop to trace (control) values 2 to 3 days after admission, following the disappearance of ethanol and its reactive metabolite acetaldehyde from the blood. These results indicate that physiologically active tetrahydroisoquinolines increase in humans during long-term alcohol consumption, presumably because of acetaldehyde's direct condensation with catecholamines. The presence of these or similar condensation products in the urine could be useful as clinical indicators of prior blood acetaldehyde concentrations in chronic alcoholics.
Temporal Lobe Aggression in Rats
Authors: Pinel John P. J. , Treit Dallas , Rovner Louis I.
Published: October 2006

Although reports of aggressive behavior in temporal lobe epileptics are common, it has proven difficult in clinical settings to gain the experimental control necessary to systematically investigate temporal lobe aggression or even to provide unequivocal evidence of its existence. Increases in aggressive behavior were observed in rats with experimentally induced epileptic foci in temporal lobe structures but not in control rats or those with foci in the caudate.
β-Adrenergic Mechanism of Insulin-Induced Adrenocorticotropin Release from the Anterior Pituitary
Authors: Mezey E. , Reisine T. D. , Brownstein M. J. , Palkovits M. , Axelrod J.
Published: October 2006

Intraperitoneal administration of insulin to control rats and to rats with pituitary stalk transections or with lesions of the median eminence resulted in increased plasma adrenocorticotropin (ACTH) levels. The insulin-induced stimulation of ACTH release was blocked in both the control and lesioned animals by prior treatment with either the β-adrenergic antagonist propranolol or the glucocorticoid analog dexamethasone. The direct application of insulin to primary cultures of the anterior pituitary did not evoke ACTH release or affect the maximal ability of corticotropin-releasing factor or epinephrine to stimulate ACTH secretion. The results suggest that insulin stimulates ACTH release by a mechanism in which catecholamines of peripheral origin act directly on the anterior pituitary.
A Conjugate of α-Amanitin and Monoclonal Immunoglobulin G to Thy 1.2 Antigen Is Selectively Toxic to T Lymphoma Cells
Authors: Davis Minh-Tam B. , Preston James F.
Published: October 2006

A covalent conjugate of an α-amanitin azo derivative and a monoclonal immunoglobulin G to the Thy 1.2 antigen on murine T lymphocytes was synthesized. The conjugate was 375- to 750-fold more inhibitory to murine T lymphoma S49.1 cells than the unconjugated derivative. At 0.7 × 10
-7
to 1.5 × 10
-7
M
and at 4 × 10
-7
M
amanitin equivalents, the conjugate inhibited protein synthesis in S49.1 cells by 50 percent and 80 to 96 percent, respectively. At these concentrations, mutant Thy 1-deficient S49 cells and other murine lymphomas lacking Thy 1 altogether or carrying Thy 1.1 antigens were unaffected. This result demonstrates the potential for targeting amanitin to specific cell types.
Estradiol Is Concentrated in Tyrosine Hydroxylase-Containing Neurons of the Hypothalamus
Authors: Sar Madhabananda
Published: October 2006

Localization of [
3
H]estradiol in tyrosine hydroxylase-containing neurons of rat brain was shown by a combined technique of autoradiography and immunohistochemistry. [
3
H]Estradiol was concentrated in the nuclei of tyrosine hydroxylase-containing neurons in the nucleus arcuatus, nucleus periventricularis hypothalami, and the zona incerta. These results suggest that estradiol acts directly on dopamine-producing neurons of the tuberoinfundibular system and incertohypothalamic system.
Excitatory and Inhibitory Effects of Opiates in the Rat Vas Deferens: A Dual Mechanism of Opiate Action
Authors: Jacquet Yasuko F.
Published: October 2006

Both natural (-)-morphine and its unnatural enantiomer (+)-morphine exert an excitatory action on electrically stimulated contractions of rat vas deferens. Preexposure to (-)-morphine results in cross-tolerance to the inhibitory action of β-endorphin. (-)-Naloxone and its stereoisomer (+)-naloxone also exert an excitatory action, but only (-)-naloxone blocks the inhibitory action of β-endorphin. Thus morphine exerts a dual action on a peripheral organ: one an inhibitory action mediated by the stereospecific endorphin receptor that is blocked stereospecifically by naloxone, the other an excitatory action mediated by a nonstereospecific receptor that is not blocked by naloxone. The opiate abstinence syndrome is seen as due to the unmasking of the excitatory action of opiates when its concomitant inhibitory influence is removed by selective blockade by naloxone or weakened by selective tolerance. The view that the rat vas deferens is devoid of morphine receptors is now seen as arising from a reverse example of morphine's dual action: the masking of the inhibitory action of morphine by its concomitant and more potent excitatory action.
Reassortant Virus Derived from Avian and Human Influenza A Viruses Is Attenuated and Immunogenic in Monkeys
Authors: Murphy Brian R. , Sly D. Lewis , Tierney Eveline L. , Hosier Nanette T. , Massicot Judith G. , London William T. , Chanock Robert M. , Webster Robert G. , Hinshaw Virginia S.
Published: October 2006

An influenza A reassortant virus that contained the hemagglutinin and neuraminidase genes of a virulent human virus, A/Udorn/72 (H3N2), and the six other influenza A virus genome segments from an avirulent avian virus, A/Mallard/New York/6750/78 (H2N2), was evaluated for its level of replication in squirrel monkeys and hamsters. In monkeys, the reassortant virus was as attenuated and as restricted in its level of replication in the upper and lower respiratory tract as its avian influenza virus parent. Nonetheless, infection with the reassortant induced significant resistance to challenge with virulent human influenza virus. In hamsters, the reassortant virus replicated to a level intermediate between that of its parents. These findings suggest that the nonsurface antigen genes of the avian parental virus are the primary determinants of restriction of replication of the reassortant virus in monkeys. Attenuation of the reassortant virus for primates is achieved by the inefficient functioning of the avian influenza genes in primate cells, while antigenic specificity of the human influenza virus is provided by the neuraminidase and hemagglutinin genes derived from the human virus. This approach could lead to the development of a live influenza A virus vaccine that is attenuated for man if the avian influenza genes are similarly restricted in human cells.