bluuebunny/crossref_metadata_2025 huggingface dataset:
Chloroplast Transformation in
Chlamydomonas
with High Velocity Microprojectiles
Authors: Boynton John E. , Gillham Nicholas W. , Harris Elizabeth H. , Hosler Jonathan P. , Johnson Anita M. , Jones Allan R. , Randolph-Anderson Barbara L. , Robertson Dominique , Klein Ted M. , Shark Katherine B. , Sanford John C.
Published: October 2006

Bombardment of three mutants of the chloroplast
atpB
gene of
Chlamydomonas reinhardtii
with high-velocity tungsten microprojectiles that were coated with cloned chloroplast DNA carrying the wild-type gene permanently restored the photosynthetic capacity of the algae. In most transformants of one of the mutants, a fragment with a 2.5-kilobase deletion was restored to normal size by a homologous replacement event; in about 25 percent of the transformants the restored restriction fragment was 50 to 100 base pairs smaller or larger than that of wild type. About one-fourth of the transformants of this mutant contained unintegrated donor plasmid when first examined. This plasmid persisted in four different transformants after 65 cell generations of continuous liquid culture but was lost from all transformants maintained on plates of selective medium. The restored wild-type
atpB
gene remains in all transformants as an integral part of the chloroplast genome and is expressed and inherited normally.
HIV-1-Infected T Cells Show a Selective Signaling Defect After Perturbation of CD3/Antigen Receptor
Authors: Linette Gerald P. , Hartzman Robert J. , Ledbetter Jeffrey A. , June Carl H.
Published: October 2006

The binding of antigen or monoclonal antibody to the T cell receptor for antigen or the closely associated CD3 complex causes increases in the concentration of intracellular ionized calcium and subsequent cell proliferation. By measuring second messenger production in primary cultures of human immunodeficiency virus (HIV-1)-infected T cells stimulated with monoclonal antibodies specific for either CD3 or CD2, a specific impairment of membrane signaling was revealed. The HIV-1-infected T cells were unable to mobilize Ca
2+
after stimulation with anti-CD3, whereas CD2-induced calcium mobilization remained intact. Furthermore, the HIV-1-infected cells proliferated poorly after CD3 stimulation, although the cells retained normal DNA synthesis in response to interleukin-2 stimulation. These results show that the signals initiated by CD2 and CD3 can be regulated independently within the same T cell; uncoupling of signal transduction after antigen-specific stimulation provides a biochemical mechanism to explain, in part, the profound immunodeficiency of patients with HIV-1 infection.
Dynamic Expression Pattern of the
myc
Protooncogene in Midgestation Mouse Embryos
Authors: Schmid Peter , Schulz Wolfgang A. , Hameister H.
Published: October 2006

The c-
myc
protooncogene in mouse embryos was shown by RNA in situ hybridization to be preferentially expressed in tissues of endodermal and mesodermal origin. Most organs developing from the ectoderm, such as skin, brain, and spinal cord, displayed low levels of c-
myc
RNA. The thymus represented the only hematopoietic organ with high c-
myc
expression. In organs and structures strongly hybridizing to c-
myc
probes, for example the fetal part of the placenta, gut, liver, kidney, pancreas, submandibular glands, enamel organs of the molars, and skeletal cartilage, the level of expression depended on the stage of development. Expression was observed to be correlated with proliferation, particularly during expansion and folding of partially differentiated epithelial cells.
Evidence That the Leucine Zipper Is a Coiled Coil
Authors: O'Shea Erin K. , Rutkowski Rheba , Kim Peter S.
Published: October 2006

Recently, a hypothetical structure called a leucine zipper was proposed that defines a new class of DNA binding proteins. The common feature of these proteins is a region spanning approximately 30 amino acids that contains a periodic repeat of leucines every seven residues. A peptide corresponding to the leucine zipper region of the yeast transcriptional activator GCN4 was synthesized and characterized. This peptide associates in the micromolar concentration range to form a very stable dimer of α helices with a parallel orientation. Although some features of the leucine zipper model are supported by our experimental data, the peptide has the characteristics of a coiled coil.
Amyloid β Protein Enhances the Survival of Hippocampal Neurons in Vitro
Authors: Whitson Janet S. , Selkoe Dennis J. , Cotman Carl W.
Published: October 2006

The β-amyloid protein is progressively deposited in Alzheimer's disease as vascular amyloid and as the amyloid cores of neuritic plaques. Contrary to its metabolically inert appearance, this peptide may have biological activity. To evaluate this possibility, a peptide ligand homologous to the first 28 residues of the β-amyloid protein (β1-28) was tested in cultures of hippocampal pyramidal neurons for neurotrophic or neurotoxic effects. The β1-28 appeared to have neurotrophic activity because it enhanced neuronal survival under the culture conditions examined. This finding may help elucidate the sequence of events leading to plaque formation and neuronal damage in Alzheimer's disease.
Biosynthesis and Secretion of Proatrial Natriuretic Factor by Cultured Rat Cardiocytes
Authors: Bloch Kenneth D. , Scott James A. , Zisfein Jerome B. , Fallon John T. , Margolies Michael N. , Seidman Christine E. , Matsueda Gary R. , Homcy Charles J. , Graham Robert M. , Seidman J. G.
Published: October 2006

Rat atrial natriuretic factor (ANF) is translated as a 152-amino acid precursor preproANF. PreproANF is converted to the 126-amino acid proANF, the storage form of ANF in the atria. ANF isolated from the blood is approximately 25 amino acids long. It is demonstrated here that rat cardiocytes in culture store and secrete proANF. Incubation of proANF with serum produced a smaller ANF peptide. PreproANF seems to be processed to proANF in the atria, and proANF appears to be released into the blood, where it is converted by a protease to a smaller peptide.
A Single Receptor Binds Both Insulin-Like Growth Factor II and Mannose-6-Phosphate
Authors: MacDonald Richard G. , Pfeffer Suzanne R. , Coussens Lisa , Tepper Mark A. , Brocklebank Carol M. , Mole John E. , Anderson Jacqueline K. , Chen Ellson , Czech Michael P. , Ullrich Axel
Published: October 2006

Amino acid sequences deduced from rat complementary DNA clones encoding the insulin-like growth factor II (IGF-II) receptor closely resemble those of the bovine cation-independent mannose-6-phosphate receptor (Man-6-P receptor
CI
), suggesting they are identical structures. It is also shown that IGF-II receptors are adsorbed by immobilized pentamannosyl-6-phosphate and are specifically eluted with Man-6-P. Furthermore, Man-6-P specifically increases by about two times the apparent affinity of the purified rat placental receptor for
125
I-labeled IGF-II. These results indicate that the type II IGF receptor contains cooperative, high-affinity binding sites for both IGF-II and Man-6-P-containing proteins.
Trans
Activation of the Bovine Leukemia Virus Long Terminal Repeat in BLV-Infected Cells
Authors: Rosen Craig A. , Sodroski Joseph G. , Kettman Richard , Burny Arsene , Haseltine William A.
Published: October 2006

The transcription initiation signals for retroviruses lie within the long terminal repeat (LTR) sequences that flank the integrated provirus. This study shows that factors present in cells infected with bovine leukemia virus (BLV) mediate transcriptional trans activation of the BLV LTR. This phenomenon is similar to that reported for the human T-cell leukemia virus LTR and establishes both structural and functional criteria for inclusion of BLV and human T-cell leukemia viruses in the same family of transforming retroviruses.
Coupling of
Tetrahymena
Ribosomal RNA Splicing to β-Galactosidase Expression in
Escherichia coli
Authors: Price James V. , Cech Thomas R.
Published: October 2006

Splicing of the
Tetrahymena
ribosomal RNA precursor is mediated by the folded structure of the RNA molecule and therefore occurs in the absence of any protein in vitro. The
Tetrahymena
intervening sequence (IVS) has been inserted into the gene for the α-donor fragment of β-galactosidase in a recombinant plasmid. Production of functional β-galactosidase is dependent on RNA splicing in vivo in
Escherichia coli
. Thus RNA self-splicing can occur at a rate sufficient to support gene expression in a prokaryote, despite the likely presence of ribosomes on the nascent RNA. The β-galactosidase messenger RNA splicing system provides a useful method for screening for splicing-defective mutations, several of which have been characterized.
The Unusual
varl
Gene of Yeast Mitochondrial DNA
Authors: Butow Ronald A. , Perlman Philip S. , Grossman Lawrence I.
Published: October 2006

The
var1
gene specifies the only mitochondrial ribosomal protein known to be encoded by yeast mitochondrial DNA. The gene is unusual in that its base composition is nearly 90 percent adenine plus thymine. It and its expression product show a strain-dependent variation in size of up to 7 percent; this variation does not detectably interfere with function. Furthermore,
var1
is an expandable gene that participates in a novel recombinational event resembling gene conversion whereby shorter alleles are preferentially converted to longer ones. The remarkable features of
var1
indicate that it may have evolved by a mechanism analogous to exon shuffling, although no introns are actually present.
The Granulocyte-Macrophage Colony-Stimulating Factors
Authors: Metcalf Donald
Published: October 2006

The granulocyte-macrophage colony-stimulating factors are well-characterized specific glycoproteins that interact to control the production, differentiation, and function of two related white cell populations of the blood, the granulocytes and monocyte-macrophages. Widely produced in the body, these regulators probably play an important role in resistance to infections. The proliferation of myeloid leukemia cells remains dependent on stimulation by colony-stimulating factors, although one of them also has the ability to suppress leukemic populations by inducing terminal differentiation.
Effects of Genomic Position on the Expression of Transduced Copies of the
white
Gene of
Drosophila
Authors: Levis Robert , Hazelrigg Tulle , Rubin Gerald M.
Published: October 2006

The white gene of
Drosophila
is expressed normally when introduced at many different sites in the genome by P-element-mediated DNA transformation, but is expressed abnormally when inserted at two particular genomic positions. It is now demonstrated that the mutant expression in these two cases is caused by the surrounding chromosomal region into which the white gene has been inserted. The white gene could be moved from these two positions, where it confers a mutant phenotype, to other positions in the genome where it confers a wild-type phenotype. However, flies in which white has been moved to one new location have an unusual mosaic phenotype.
Bidirectional SV40 Transcription Mediated by Tandem Sp1 Binding Interactions
Authors: Gidoni David , Kadonaga James T. , Barrera-Saldaña Hugo , Takahashi Keikichi , Chambon Pierre , Tjian Robert
Published: October 2006

The 21-base pair repeat elements of the SV40 promoter contain six tandem copies of the GGGCGG hexanucleotide (GC-box), each of which can bind, with varying affinity, to the cellular transcription factor, Sp1. In vitro SV40 early RNA synthesis is mediated by interaction of Sp1 with GC-boxes I, II, and III, whereas transcription in the late direction is mediated by binding to GC-boxes III, V, and VI.
Tyrosine Kinase Receptor with Extensive Homology to EGF Receptor Shares Chromosomal Location with
neu
Oncogene
Authors: Coussens Lisa , Yang-Feng Teresa L. , Liao Yu-Cheng , Chen Ellson , Gray Alane , McGrath John , Seeburg Peter H. , Libermann Towia A. , Schlessinger Joseph , Francke Uta , Levinson Arthur , Ullrich Axel
Published: October 2006

A novel potential cell surface receptor of the tyrosine kinase gene family has been identified and characterized by molecular cloning. Its primary sequence is very similar to that of the human epidermal growth factor receptor and the v-erbB oncogene product; the chromosomal location of the gene for this protein is coincident with the
neu
oncogene, which suggests that the two genes may be identical.
The Human Gene Encoding GM-CSF Is at 5q21-q32, the Chromosome Region Deleted in the 5q
-
Anomaly
Authors: Huebner Kay , Isobe Masaharu , Croce Carlo M. , Golde David W. , Kaufman Susan E. , Gasson Judith C.
Published: October 2006

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) is a 22,000-dalton glycoprotein that stimulates the growth of myeloid progenitor cells and acts directly on mature neutrophils. A full-length complementary DNA clone encoding human GM-CSF was used as a probe to screen a human genomic library and isolate the gene encoding human GM-CSF. The human GM-CSF gene is approximately 2.5 kilobase pairs in length with at least three intervening sequences. The GM-CSF gene was localized by somatic cell hybrid analysis and in situ hybridization to human chromosome region 5q21-5q32, which is involved in interstitial deletions in the 5q
-
syndrome and acute myelogenous leukemia. An established, human promyelocytic leukemia cell line, HL60, contains a rearranged, partially deleted GM-CSF allele and a candidate 5q
-
marker chromosome, indicating that the truncated GM-CSF allele may reside at the rejoining point for the interstitial deletion on the HL60 marker chromosome.
A human Y-Linked DNA Polymorphism and Its Potential for Estimating Genetic and Evolutionary Distance
Authors: Casanova Myriam , Leroy Pascale , Boucekkine Chafika , Weissenbach Jean , Bishop Colin , Fellous Marc , Purrello Michele , Fiori Gianmario , Siniscalco Marcello
Published: October 2006

A human DNA sequence (p12f
2
), derived from a partial Y-chromosome genomic library and showing homology with the X and Y chromosomes and with an undetermined number of autosomes, detected two Y-specific restriction fragment length variants on male DNA that had been digested with Taq I and Eco RI. These variants may have been generated through a deletion-insertion mechanism and their pattern of holoandric transmission indicates that they represent a two-allele Y-linked polymorphism (RFLP). By means of DNA from patients with inborn deletions in chromosome Y, this polymorphic DNA site was mapped to the interval Yq11.1-Yq11.22. The frequency of the rarest allele was about 35 percent in Algerian and Sardinian human males, whereas it was only 4 percent among Northern Europeans. The p12f
2
probe also detected Y-specific DNA fragments in the gorilla and chimpanzee. In view of the monosomy of the Y chromosome in mammalian species, Y-linked RFLP's may prove to be more useful than autosomal or X-linked markers in estimating genetic distances within and between species.
Detection of Papillomavirus DNA in Human Semen
Authors: Ostrow Ronald S. , Zachow Karen R. , Niimura Michihito , Okagaki Takashi , Muller Sigfrid , Bender Mitchell , Faras Anthony J.
Published: October 2006

Human papillomavirus DNA has been detected in the semen of three patients, two of whom have severe chronic wart disease. These data support the contention that sexual transmission of human papillomavirus DNA could occur via semen, a possibility suggested by epidemiological data on the sexual transmission of human papillomavirus.
Three-Year Incidence of AIDS in Five Cohorts of HTLV-III-Infected Risk Group Members
Authors: Goedert James J. , Biggar Robert J. , Weiss Stanley H. , Eyster M. Elaine , Melbye Mads , Wilson Susan , Ginzburg Harold M. , Grossman Ronald J. , DiGioia Richard A. , Sanchez William C. , Giron José A. , Ebbesen Peter , Gallo Robert C. , Blattner William A.
Published: October 2006

The incidence of the acquired immune deficiency syndrome (AIDS) among persons infected with human T-lymphotropic virus type III (HTLV-III) was evaluated prospectively among 725 persons who were at high risk of AIDS and had enrolled before October 1982 in cohort studies of homosexual men, parenteral drug users, and hemophiliacs. A total of 276 (38.1 percent) of the subjects were either HTLV-III seropositive at enrollment or developed HTLV-III antibodies subsequently. AIDS had developed in 28 (10.1 percent) of the seropositive subjects before August 1985. By actuarial survival calculations, the 3-year incidence of AIDS among all HTLV-III seropositive subjects was 34.2 percent in the cohort of homosexual men in Manhattan, New York, and 14.9 percent (range 8.0 to 17.2 percent) in the four other cohorts. Out of 117 subjects followed for a mean of 31 months after documented seroconversion, five (all hemophiliacs) developed AIDS 28 to 62 months after the estimated date of seroconversion, supporting the hypothesis that there is a long latency between acquisition of viral infection and the development of clinical AIDS. This long latency could account for the significantly higher AIDS incidence in the New York cohort compared with other cohorts if the virus entered the New York homosexual population before it entered the populations from which the other cohorts were drawn. However, risk of AIDS development in different populations may also depend on the presence of as yet unidentified cofactors.
Endonucleolytic Activity That Cleaves Immunoglobulin Recombination Sequences
Authors: Hope Thomas J. , Aguilera Renato J. , Minie Mark E. , Sakano Hitoshi
Published: October 2006

An endonucleolytic activity has been identified in nuclear extracts of chick embryo bursa and mouse fetal liver cells. The activity introduces a double-strand cut in the vicinity of the recombination site of immunoglobulin joining gene segments. The cleavage occurs at the dinucleotide pair TG-AC. This activity is a good candidate for the putative endonuclease involved in recombination of the immunoglobulin variable, diversity, and joining regions. It is distinct from the endonuclease activities previously reported by others.
Antiserum to a Synthetic Peptide Recognizes the HTLV-III Envelope Glycoprotein
Authors: Kennedy R. C. , Henkel R. D. , Pauletti D. , Allan J. S. , Lee T. H. , Essex M. , Dreesman G. R.
Published: October 2006

In a study performed to determine which regions of the human T-cell lymphotrophic virus type III (HTLV-III) may represent vaccine candidates to prevent the acquired immune deficiency syndrome (AIDS), a synthetic peptide corresponding to amino acid sequence 735 to 752 of the precursor envelope glycoprotein of HTLV-III was used to immunize rabbits. The resulting rabbit antiserum to the synthetic peptide specifically recognized the precursor envelope glycoprotein (gp160) of HTLV-III. Human sera positive for antibody to HTLV-III reacted with this peptide. These findings indicate that synthetic peptides can be used to induce an immune response directed against a native envelope glycoprotein epitope of HTLV-III. The data are discussed in terms of using synthetic peptides to identify antigenic determinants involved in the induction of protective immunity and possibly as vaccine candidates against the etiologic agent of AIDS.
The Role of Mononuclear Phagocytes in HTLV-III/LAV Infection
Authors: Gartner Suzanne , Markovits Paul , Markovitz David M. , Kaplan Mark H. , Gallo Robert C. , Popovic Mikulas
Published: October 2006

Cells with properties characteristic of mononuclear phagocytes were evaluated for infectivity with five different isolates of the AIDS virus, HTLV-III/LAV. Mononuclear phagocytes cultured from brain and lung tissues of AIDS patients harbored the virus. In vitro-infected macrophages from the peripheral blood, bone marrow, or cord blood of healthy donors produced large quantities of virus. Virus production persisted for at least 40 days and was not dependent on host cell proliferation. Giant multinucleated cells were frequently observed in the macrophage cultures and numerous virus particles, often located within vacuole-like structures, were present in infected cells. The different virus isolates were compared for their ability to infect macrophages and T cells. Isolates from lung- and brain-derived macrophages had a significantly higher ability to infect macrophages than T cells. In contrast, the prototype HTLV-III
B
showed a 10,000-fold lower ability to infect macrophages than T cells and virus production was one-tenth that in macrophage cultures infected with other isolates, indicating that a particular variant of HTLV-III/LAV may have a preferential tropism for macrophages or T cells. These results suggest that mononuclear phagocytes may serve as primary targets for infection and agents for virus dissemination and that these virus-infected cells may play a role in the pathogenesis of the disease.
Direct Polyclonal Activation of Human B Lymphocytes by the Acquired Immune Deficiency Syndrome Virus
Authors: Schnittman Steven M. , Lane H. Clifford , Higgins Sandra E. , Folks Thomas , Fauci Anthony S.
Published: October 2006

When B lymphocytes from normal human peripheral blood were incubated for 1 hour with the retrovirus that causes the acquired immune deficiency syndrome (AIDS), the B cells showed marked proliferation and differentiation. Proliferative responses to the virus peaked on day 4 and appeared to be independent of accessory cells. This finding was repeated with three separate viral isolates, one of which was from a patient from Zaire. The magnitude of the observed responses was comparable to that seen with standard polyclonal B-cell activators. This phenomenon may be at least partially responsible for the polyclonal B-cell activation seen in patients with AIDS.
Genomic Analysis of the Human B-Lymphotropic Virus (HBLV)
Authors: Josephs Steven F. , Salahuddin S. Zaki , Ablashi Dharam V. , Schachter Francois , Wong-Staal Flossie , Gallo Robert C.
Published: October 2006

The human B-lymphotropic virus (HBLV) has a double-stranded DNA genome of greater than 110 kilobase pairs, which is consistent with its morphological classification as a herpesvirus. A 9000-base pair cloned probe of HBLV detected specific sequences in DNA and RNA of infected cells but did not hybridize to the genomic DNA of other human herpesviruses including the Epstein-Barr virus, human cytomegalovirus, herpes simplex type I, and varicella-zoster virus. Conversely, while probes obtained from each of the known human herpesvirus readily detected the homologous viral DNA, they did not hybridize to genomic HBLV DNA. This evidence, in addition to serological and morphological distinctions and the biological effects of this virus demonstrate that HBLV is a novel human herpesvirus.
Myosin Rod Phosphorylation and the Catch State of Molluscan Muscles
Authors: Castellani Loriana , Cohen Carolyn
Published: October 2006

"Catch" is a prolonged state of tension in molluscan smooth muscles shown by mechanical measurements to be associated with the level of protein phosphorylation. Myosin isolated from these muscles is unusual in being phosphorylated in the rod portion by an endogenous kinase, like certain nonmuscle myosins. These findings suggest that the myosin rod is a target for phosphorylation and that this reaction may control the transition from catch to relaxation.
Computational Neuroscience
Authors: Sejnowski Terrence J. , Koch Christof , Churchland Patricia S.
Published: October 2006

The ultimate aim of computational neuroscience is to explain how electrical and chemical signals are used in the brain to represent and process information. This goal is not new, but much has changed in the last decade. More is known now about the brain because of advances in neuroscience, more computing power is available for performing realistic simulations of neural systems, and new insights are available from the study of simplifying models of large networks of neurons. Brain models are being used to connect the microscopic level accessible by molecular and cellular techniques with the systems level accessible by the study of behavior.
Axon Guidance and the Patterning of Neuronal Projections in Vertebrates
Authors: Dodd Jane , Jessell Thomas M.
Published: October 2006

Over the past decade, new insights have been obtained into the cellular strategies and molecular mechanisms that guide axons to their targets in the developing vertebrate nervous system. Axons select pathways by recognizing specific cues in their environment. These cues include cell surface and extracellular matrix molecules that mediate cell and substrate adhesion and axon fasciculation, molecules with contact-dependent inhibitory properties, and diffusible tropic factors. Several guidance cues may operate in a coordinated way to generate the distinct axonal trajectories of individual neurons.
Frame-Shift Deletions in Patients with Duchenne and Becker Muscular Dystrophy
Authors: Malhotra S. B. , Hart K. A. , Klamut H. J. , Thomas N. S. T. , Bodrug S. E. , Burghes A. H. M. , Bobrow M. , Harper P. S. , Thompson M. W. , Ray P. N. , Worton R. G.
Published: October 2006

Duchenne muscular dystrophy (DMD) and its less severe form Becker muscular dystrophy (BMD) are allelic disorders. It has been suggested that in the mutations involving BMD, the translational reading frame of messenger RNA is maintained and a smaller, though partially functional, protein is produced. In order to test this, the exon-intron boundaries of the first ten exons of the DMD gene were determined, and 29 patients were analyzed. In a number of BMD patients (mild and severe BMD), the reading frame of messenger RNA was not maintained. On the basis of these findings, a model for reinitiation from an internal start codon is suggested.
Rat Resistance to Schistosomiasis: Platelet-Mediated Cytotoxicity Induced by C-Reactive Protein
Authors: Bout Daniel , Joseph Michel , Pontet Michel , Vorng Han , Deslée Didier , Capron André
Published: October 2006

In rats infected with the parasite
Schistosoma mansoni
, the concentration of C-reactive protein in the serum increases after the lung stage of infection and is at its highest at the time of terminal worm rejection. The peak of platelet-mediated cytotoxicity induced by infected serum that has been heated (and is free of immunoglobulin E) as well as the time course for the development of platelet cytotoxic activity in infected rats was found to be correlated with the concentration of C-reactive protein. Rat and human platelets treated with homologous serum obtained during an acute phase of inflammation or with purified C-reactive protein were able to kill the immature forms of the worm in vitro. Platelets treated with C-reactive protein were furthermore capable of conferring significant protection against schistosomiasis in transfer experiments. Collectively these data indicate that a system that includes C-reactive protein and platelets participates in the natural resistance of the rat to schistosomal infection.
Novel Interleukin-2 Receptor Subunit Detected by Cross-Linking Under High-Affinity Conditions
Authors: Sharon Michael , Klausner Richard D. , Cullen Bryan R. , Chizzonite Richard , Leonard Warren J.
Published: October 2006

Interleukin-2 (IL-2) binds to both high- and low-affinity classes of IL-2 receptors on activated T lymphocytes. Only the high-affinity receptors are involved in receptor-mediated endocytosis and normally transduce the mitogenic signals of IL-2; however, the structural features distinguishing the high- and low-affinity receptors are unknown. When
125
I-labeled IL-2 was chemically cross-linked to activated human T lymphocytes, two major bands were identified. First, as predicted, a 68- to 72-kilodalton band, consisting of IL-2 (15.5 kilodaltons) cross-linked to the IL-2 receptor (55 kilodaltons), was observed. Second, an unpredicted 85- to 92-kilodalton moiety was detected. This band was not present when IL-2 was cross-linked to transfected C127 cells, which exclusively express low-affinity receptors. The data presented are most consistent with the existence of a 70- to 77-kilodalton glycoprotein subunit (p70) which, upon associating with the 55-kilodalton low-affinity receptor (p55), transforms it into a high-affinity site. It is proposed that p55 and p70 be referred to as the α and β subunits, respectively, of the high-affinity IL-2 receptor.
Tumor Necrosis Factor Reduces c-
myc
Expression and Cooperates with Interferon-γ in HeLa Cells
Authors: Yarden Anat , Kimchi Adi
Published: October 2006

The suppression of the c-
myc
nuclear oncogene is associated with growth arrest and may therefore be directly controlled by naturally occurring growth inhibitors. The effect of tumor necrosis factor (TNF) and of interferon-γ (IFN-γ) on c-
myc
expression was investigated in HeLa cells, which respond to these cytokines by a specific arrest in the G
0
/G
1
phase of the cell cycle. Northern blot and nuclear transcription analyses indicated that each cytokine reduced within 1 to 3 hours the c-
myc
messenger RNA levels as a result of transcriptional inhibition. Adding the two cytokines together at saturating levels resulted in enhanced inhibition of c-
myc
transcription and of the c-
myc
messenger RNA steady-state levels. While the reduction of c-
myc
messenger RNA by IFN-γ was dependent on new protein synthesis, the inhibitory effect of TNF on c-
myc
messenger RNA was direct and was not abrogated by cycloheximide. The differential effect of the protein synthesis inhibitor and the cooperative inhibitory effects of the two cytokines when added together suggest that IFN-γ and TNF reduce c-
myc
transcription through different molecular mechanisms.
Detection of an Auditory Nerve—Activating Substance
Authors: Sewell William F. , Norris Charles H. , Tachibana Masayoshi , Guth Paul S.
Published: October 2006

A substance or substances capable of increasing the firing rate of primary auditory fibers is detectable in the perilymph of frogs and guinea pigs subjected to sound stimulation. The increase in firing rate occurs in single units of the frog auditory nerve after perilymph obtained from frogs or guinea pigs during sound stimulation is infused into the frog perilymphatic sac. Perilymph collected from animals maintained in silence failed to cause an increase in firing rate of primary auditory fibers of the frog.
Eosinophils Cocultured with Endothelial Cells Have Increased Survival and Functional Properties
Authors: Rothenberg Marc E. , Owen William F. , Silberstein David S. , Soberman Roy J. , Austen K. Frank , Stevens Richard L.
Published: October 2006

Human peripheral blood eosinophils, cells often associated with allergic and parasitic diseases, were maintained in vitro for at least 14 days when they were cocultured with bovine endothelial cells and for at least 7 days when cultured with either bovine or human endothelial cell-derived conditioned medium. The cocultured eosinophils became hypodense and generated about three times as much leukotriene C
4
upon activation with calcium ionophore and killed about three times as many antibody-coated larvae of
Schistosoma mansoni
as freshly isolated normodense eosinophils. That these cells can be maintained in vitro by coculture with endothelial cells, and the surprising finding that the cocultured eosinophils have biochemical, cytotoxic, and density properties similar to those of eosinophils in patients with allergic and other disorders, will facilitate investigation of the regulation and role of these cells in health and disease.
The Three-Dimensional Structure of Asn
102
Mutant of Trypsin: Role of Asp
102
in Serine Protease Catalysis
Authors: Sprang S. , Standing T. , Fletterick R. J. , Stroud R. M. , Finer-Moore J. , Xuong N-H. , Hamlin R. , Rutter W. J. , Craik C. S.
Published: October 2006

The structure of the Asn
102
mutant of trypsin was determined in order to distinguish whether the reduced activity of the mutant at neutral
p
H results from an altered active site conformation or from an inability to stabilize a positive charge on the active site histidine. The active site structure of the Asn
102
mutant of trypsin is identical to the native enzyme with respect to the specificity pocket, the oxyanion hole, and the orientation of the nucleophilic serine. The observed decrease in rate results from the loss of nucleophilicity of the active site serine. This decreased nucleophilicity may result from stabilization of a His
57
tautomer that is unable to accept the serine hydroxyl proton.
Two Pairs of Recombination Signals Are Sufficient to Cause Immunoglobulin V-(D)-J Joining
Authors: Akira Shizuo , Okazaki Kenji , Sakano Hitoshi
Published: October 2006

The minimum sequence requirements for antigen receptor V-(D)-J joining were studied by constructing recombination-substrates containing synthetic recombination signals and introducing them into a recombination-competent pre-B cell line. Two sets of heptamer (CACTGTG) and nonamer (GGTTTTTGT) sequences were shown to be sufficient to cause the V-(D)-J joining, if the 12- and 23-base pair spacer rule is satisfied. A point mutation in the heptamer sequence, or a change in the combination of the two spacer lengths, drastically reduced the recombination.
Monoclonal Antibodies Defining Distinctive Human T Cell Surface Antigens
Authors: Kung Patrick C. , Goldstein Gideon , Reinherz Ellis L. , Schlossman Stuart F.
Published: October 2006

Three novel monoclonal antibodies (designated OKT1, OKT3, and OKT4) were generated against surface determinants of human peripheral T cells. Both OKT1 and OKT3 reacted with all human peripheral T cells and 5 to 10 percent of thymocytes but differed in their reactivities with T cell lines. By contrast, OKT4 reacted with 55 percent of human peripheral T cells and 80 percent of thymocytes. All three antibodies were selective for T cells in the peripheral blood in that they did not react with normal B cells, null cells, monocytes, or granulocytes.
Effect of Vanadate on Elevated Blood Glucose and Depressed Cardiac Performance of Diabetic Rats
Authors: Heyliger Clayton E. , Tahiliani Arun G. , McNeill John H.
Published: October 2006

The trace element vanadium has an unclear biological function. Vanadate, an oxidized form of vanadium, appears to have an insulin-like action. The effect of vanadate on blood glucose and cardiac performance was assessed in female Wistar rats 6 weeks after they were made diabetic with streptozotocin. When vanadate was administered for a 4-week period to the diabetic rats, their blood glucose was not significantly different from that of nondiabetic controls despite a low serum insulin. In contrast, blood glucose was increased about threefold in the diabetic rats that were not treated with vanadate; these rats also had low insulin levels. Cardiac performance was depressed in the untreated diabetic animals, but the cardiac performance of the vanadate-treated diabetic animals was not significantly different from that of nondiabetic controls. Thus vanadate controlled the high blood glucose and prevented the decline in cardiac performance due to diabetes.
Inhibition of Interferon-Gamma May Suppress Allograft Reactivity by T Lymphocytes in Vitro and in Vivo
Authors: Landolfo Santo , Cofano Franca , Giovarelli Mirella , Prat Maria , Cavallo Giorgio , Forni Guido
Published: October 2006

The addition to mixed-leukocyte reactions of monoclonal antibodies to interferon-γ abrogated alloantigen recognition and induction of cytotoxic T lymphocytes by inducing early and highly effective suppressor T lymphocytes. This inhibitory activity was not confined to in vitro models, since daily injection of the antibodies into CBA/J mice blocked the usual rejection of allogenic tumor cells.
Nucleotide Sequences from the Rabbit Beta Globin Gene Inserted into
Escherichia coli
Plasmids
Authors: Browne Jeffrey K. , Paddock Gary V. , Liu Alvin , Clarke Pat , Heindell Howard C. , Salser Winston
Published: October 2006

A 169-nucleotide region from the rabbit beta globin gene has been sequenced by analysis of complementary DNA's cloned in bacterial plasmids. Comparison of these sequences with those established for this gene by other techniques provides evidence of a high degree of fidelity and allows the unambiguous establishment that these plasmids do not contain harmful sequences.
Multiple Principal Sigma Factor Homologs in Eubacteria: Identification of the "
rpoD
Box"
Authors: Tanaka Kan , Shiina Tetsuo , Takahashi Hideo
Published: October 2006

Genes for the principal sigma factor (
rpoD
genes) of various eubacteria were identified with a synthetic oligonucleotide probe corresponding to a conserved sequence in
rpoD
gene products of
Escherichia coli
and
Bacillus subtilis
. Multiple
rpoD
homologs were found in the strains of
Micrococcus
,
Pseudomonas
, and
Streptomyces
, whereas single genes were detected in
E. coli
,
B. subtilis
, and
Staphylococcus aureus
. The four
rpoD
homologs of
Streptomyces coelicolor
A3(2) were cloned and sequenced. A homologous portion with 13 amino acids was found in the
rpoD
genes of
S. coelicolor
A3(2),
E. coli
, and
B. subtilis
and was named the "
rpoD
box."
Serum Complement-Like Opsonic Activities in Human, Animal, Vegetable, and Proprietary Milks
Authors: Miller Michael E. , Ganges Roland G.
Published: October 2006

Human, animal, proprietary, and soy milks are comparable to human serum C5 in opsonization of baker's yeast. Bovine milk and human serum opsonically reconstitute C5-deficient mouse serum. Such reconstitution is selectively inhibited by antiserum to human C5. Further characterization suggests that bovine milk contains material structurally and functionally similar, but not identical, to human C5.
Methylazoxymethanol Treatment of Fetal Rats Results in Abnormally Dense Noradrenergic Innervation of Neocortex
Authors: Johnston Michael V. , Grzanna Reinhard , Coyle Joseph T.
Published: October 2006

A single injection of methylazoxymethanol in pregnant rats at 15 days of gestation results in severe cortical atrophy in the offspring. In the adult offspring, the neurochemical markers for the cortical γ-aminobutyric acid-containing neurons are severely reduced, whereas the noradrenergic markers are minimally altered. Immunohistofluorescence microscopy demonstrates a marked increase in the density of noradrenergic axons which have an abnormal pattern of distribution in the atrophic cortex. The results suggest that the central noradrenergic neurons determine the number of axons to be formed early in brain development, but local factors in the terminal field regulate the ultimate distribution of the noradrenergic axons.
Fertilization: A Uterine Glycosaminoglycan Stimulates the Conversion of Sperm Proacrosin to Acrosin
Authors: Wincek Thomas J. , Parrish Richard F. , Polakoski Kenneth L.
Published: October 2006

Acrosin is a proteinase required for mammalian fertilization, and in freshly ejaculated spermatozoa exists as an inactive zymogen, proacrosin. A factor present in uterine flushings of gilts stimulates the conversion of highly purified boar proacrosin to acrosin. Characterization of this factor indicates that its active component is a glycosaminoglycan.
Biochemical Identification of Homogentisic Acid Pigment in an Ochronotic Egyptian Mummy
Authors: Stenn Frederick F. , Milgram James W. , Lee Sandra L. , Weigand Raymond J. , Veis Arthur
Published: October 2006

Roentgenograms of an Egyptian mummy, dating from 1500 B.C., showed extensive calcification of the intervertebral discs and articular narrowing in both hip and knee joints. Biopsy cores from the right hip showed parallel black zones in the region of the articular surfaces, leading to a clinical diagnosis of ochrinosis. The black pigment was extracted, analyzed, and compared to an air-oxidized homogentisic acid polymer. The two substances apparently were identical. The chemical evidence thus confirms the clinical finding of ochronosis, an autosomal recessive disorder. This is, so far as known, the earliest verified case of this disorder.
The Syphilis Epidemic and Its Relation to AIDS
Authors: Brandt Allan M.
Published: October 2006

This article presents an overview of the history of medical and public health responses to syphilis in the 20th-century United States and briefly evaluates the relevance and significance of these approaches for the AIDS epidemic. The parallels are numerous: they relate to science, public health, civil liberties, and social attitudes concerning sexually transmitted infection. The strengths and limits of past approaches to controlling sexually transmitted diseases are explored as a possible guide for AIDS policy.
Pathogenesis of Dengue: Challenges to Molecular Biology
Authors: Halstead Scott B.
Published: October 2006

Dengue viruses occur as four antigenically related but distinct serotypes transmitted to humans by
Aedes aegypti
mosquitoes. These viruses generally cause a benign syndrome, dengue fever, in the American and African tropics, and a severe syndrome, dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), in Southeast Asian children. This severe syndrome, which recently has also been identified in children infected with the virus in Puerto Rico, is characterized by increased vascular permeability and abnormal hemostasis. It occurs in infants less than 1 year of age born to dengue-immune mothers and in children 1 year and older who are immune to one serotype of dengue virus and are experiencing infection with a second serotype. Dengue viruses replicate in cells of mononuclear phagocyte lineage, and subneutralizing concentrations of dengue antibody enhance dengue virus infection in these cells. This antibody-dependent enhancement of infection regulates dengue disease in human beings, although disease severity may also be controlled genetically, possibly by permitting and restricting the growth of virus in monocytes. Monoclonal antibodies show heterogeneous distribution of antigenic epitopes on dengue viruses. These epitopes serve to regulate disease: when antibodies to shared antigens partially neutralize heterotypic virus, infection and disease are dampened; enhancing antibodies alone result in heightened disease response. Further knowledge of the structure of dengue genomes should permit rapid advances in understanding the pathogenetic mechanisms of dengue.
Cortical Flow in Animal Cells
Authors: Bray D. , White J. G.
Published: October 2006

A concerted flow of actin filaments associated with the inner face of the plasma membrane may provide the basis for many animal cell movements. The flow is driven by gradients of tension in the cell cortex, which pull cortical components from regions of relaxation to regions of contraction. In some cases cortical components return through the cytoplasm to establish a continuous cycle. This cortically located motor may drive cell locomotion, growth cone migration, the capping of antigens on a lymphocyte surface, and cytokinesis.
Transgenic Animals
Authors: Jaenisch Rudolf
Published: October 2006

The ability to introduce foreign genes into the germ line and the successful expression of the inserted gene in the organism have allowed the genetic manipulation of animals on an unprecedented scale. The information gained from the use of the transgenic technology is relevant to almost any aspect of modern biology including developmental gene regulation, the action of oncogenes, the immune system, and mammalian development. Because specific mutations can be introduced into transgenic mice, it becomes feasible to generate precise animal models for human genetic diseases and to begin a systematic genetic dissection of the mammalian genome.
The Human as an Experimental System in Molecular Genetics
Authors: White Ray , Caskey C. Thomas
Published: October 2006

There are compelling reasons for choosing to develop the human as the highest-order experimental system in genetics: an obvious social context that stirs interest, wide medical observation of the population that permits identification of an abundance of genetic defects, and our ability to perceive in the human subtle or complex variations that may not be observable in other species. Various lines of genetic inquiry that are based on research in other systems--cytogenetic analysis, biochemical studies, mapping of defective loci by linkage analysis in affected families, and in vitro techniques such as the creation of transgenic organisms--complement and enrich each other. New phenomena that would not have been predicted from investigations in other organisms have been found in humans, such as the discovery of the "giant" Duchenne muscular dystrophy gene and the identification of recessive cancer genes. Genetic research is yielding insights into human biology that are raising new possibilities for therapy and prevention of disease, as well as challenges to society in the form of ethical decisions about the appropriate application of genetic information.
Tumor Necrosis Factor (Cachectin) as an Essential Mediator in Murine Cerebral Malaria
Authors: Grau Georges E. , Fajardo Luis F. , Piguet Pierre-François , Allet Bernard , Lambert Paul-Henri , Vassalli Pierre
Published: October 2006

Tumor necrosis factor, or cachectin (TNF-α), a protein with a wide range of biological activities, is produced mainly by macrophages and may be important in inflammatory processes. The role of TNF-α in the pathogenesis of cerebral malaria was investigated in a murine model. Most CBA mice infected with
Plasmodium berghei
anka die between days 6 and 14 with acute neurological manifestations unrelated to the level of parasitemia, whereas mice of some other strains have malaria of the same severity that ends in death after 3 to 4 weeks without neurological manifestations. The activity of serum TNF-α was considerably increased in CBA/Ca mice with cerebral malaria but not in
Plasmodium berghei
-infected mice that did not develop this complication. One injection of rabbit antibody to TNF-α on day 4 or 7 fully protected infected mice from cerebral malaria without modifying the parasitemia, whereas immunoglobulins from normal rabbit had no effect. In mice with cerebral malaria, the cerebral vessels showed focal accumulations of packed macrophages often containing infected erythrocytes; this lesion was not seen in mice treated with antibody to TNF-α or in untreated mice without cerebral malaria. These findings indicate that TNF-α has an important role in the pathogenesis of cerebral malaria in this murine model and suggest that local accumulation and activation of macrophages may lead to the predominance of lesions in the central nervous system.
Helix Geometry, Hydration, and G ⋅ A Mismatch in a B-DNA Decamer
Authors: Privé Gilbert G. , Heinemann Udo , Chandrasegaran Srinivasan , Kan Lou-Sing , Kopka Mary L. , Dickerson Richard E.
Published: October 2006

The DNA double helix is not a regular, featureless barberpole molecule. Different base sequences have their own special signature, in the way that they influence groove width, helical twist, bending, and mechanical rigidity or resistance to bending. These special features probably help other molecules such as repressors to read and recognize one base sequence in preference to another. Single crystal x-ray structure analysis is beginning to show us the various structures possible in the B-DNA family. The DNA decamer C-C-A-A-G-A-T-T-G-G appears to be a better model for mixed-sequence B-DNA than was the earlier C-G-C-G-A-A-T-T-C-G-C-G, which is more akin to regions of poly(dA).poly(dT). The G⋅A mismatch base pairs at the center of the decamer are in the
anti-anti
conformation about their bonds from base to sugar, in agreement with nuclear magnetic resonance evidence on this and other sequences, and in contrast to the
anti-syn
geometry reported for G⋅A pairs in C-G-C-G-A-A-T-T-A-G-C-G. The ordered spine of hydration seen earlier in the narrow-grooved dodecamer has its counterpart, in this wide-grooved decamer, in two strings of water molecules lining the walls of the minor groove, bridging from purine N3 or pyrimidine O2, to the following sugar O4′. The same strings of hydration are present in the phosphorothioate analog of G-C-G-C-G-C. Unlike the spine, which is broken up by the intrusion of amine groups at guanines, these water strings are found in general, mixed-sequence DNA because they can pass by unimpeded to either side of a guanine N2 amine. The spine and strings are perceived as two extremes of a general pattern of hydration of the minor groove, which probably is the dominant factor in making B-DNA the preferred form at high hydration.