bluuebunny/crossref_metadata_2025 huggingface dataset:
Legless, a Novel Mutation Found in PHT1-1 Transgenic Mice
Authors: McNeish John D. , Scott William J. , Potter S. Steven
Published: October 2006

In this report it is shown that the PHT1-1 line of transgenic mice exhibited a pattern of developmental abnormalities when the mice were homozygous for the transgene insertion. Hindlimbs were uniformly truncated at the distal end of the femur, resulting in a "legless" appearance. Forelimbs lacked anterior structures including digits and the radius. The brains had many defects, particularly in the anterior structures of the cerebrum, including the olfactory lobes. Craniofacial malformations in the form of facial clefts also commonly occurred. Furthermore, heterozygotes of this line, with only one copy of the DNA insertion, and other transgenic lines carrying the same DNA construct appeared normal, suggesting that in the PHT1-1 line a gene significant in mammalian development has been disrupted.
Mesoderm Induction in Amphibians: the Role of TGF-β2-Like Factors
Authors: Rosa Frédéric , Roberts Anita B. , Danielpour David , Dart Linda L. , Sporn Michael B. , Dawid Igor B.
Published: October 2006

Mesoderm induction in the amphibian embryo can be studied by exposing animal region explants (destined to become ectoderm) to appropriate stimuli and assaying the appearance of mesodermal products like α-actin messenger RNA. Transforming growth factor β2 (TGF-β2), but not TGF-β1, was active in α-actin induction, while addition of fibroblast growth factor had a small synergistic effect. Medium conditioned by
Xenopus
XTC cells (XTC-CM), known to have powerful mesoderm-inducing activity, was shown to contain TGF-β-like activity as measured by a radioreceptor binding assay, colony formation in NRK cells, and growth inhibition in CCL64 cells. The activity of XTC-CM in mesoderm induction and in growth inhibition of CCL64 cells was inhibited partially by antibodies to TGF-β2 but not by antibodies to TGF-β1. Thus, a TGF-β2-like molecule may be involved in mesoderm induction.
Gene Interaction at HLA-DQ Enhances Autoantibody Production in Primary Sjögren's Syndrome
Authors: Harley John B. , Reichlin Morris , Arnett Frank C. , Alexander Elaine L. , Bias Wilma B. , Provost Thomas T.
Published: October 2006

Primary Sjögren's syndrome is an autoimmune disorder characterized by dryness of the mouth and eyes. The human leukocyte antigen (HLA) locus DQ is related to the primary Sjögren's syndrome autoantibodies that bind the RNA proteins Ro/SSA and La/SSB. Both DQ1 and DQ2 alleles are associated with high concentrations of these autoantibodies. An analysis of all possible combinations at DQ has shown that the entire effect was due to heterozygotes expressing the DQ1 and DQ2 alleles. These data suggest that gene interaction between DQ1 and DQ2 (or alleles at associated loci), possibly from gene complementation of
trans
-associated surface molecules, influences the autoimmune response in primary Sjögren's syndrome.
Redesigning Metabolic Routes: Manipulation of TOL Plasmid Pathway for Catabolism of Alkylbenzoates
Authors: Ramos Juan L. , Wasserfallen Alain , Rose Keith , Timmis Kenneth N.
Published: October 2006

Increasing quantities of man-made organic chemicals are released each year into the biosphere. Some of these compounds are both toxic and relatively resistant to physical, chemical, or biological degradation, and they thus constitute an environmental burden of considerable magnitude. Genetic manipulation of microbial catabolic pathways offers a powerful means by which to accelerate evolution of biodegradative routes through which such compounds might be eliminated from the environment. In the experiments described here, a catabolic pathway for alkylbenzoates specified by the TOL plasmid of
Pseudomonas
was restructured to produce a pathway capable of processing a new substrate, 4-ethylbenzoate. Analysis of critical steps in the TOL pathway that prevent metabolism of 4-ethylbenzoate revealed that this compound fails to induce synthesis of the catabolic enzymes and that one of its metabolic intermediates inactivates catechol 2,3-dioxygenase (C23O), the enzyme that cleaves the aromatic ring. Consequently, the pathway was sequentially modified by recruitment of genes from mutant bacteria selected for their production of either an altered pathway operon regulator that is activated by 4-ethylbenzoate or an altered C23O that is less sensitive to metabolite inactivation. The redesigned pathway was stably expressed and enabled host bacteria to degrade 4-ethylbenzoate in addition to the normal substrates of the TOL pathway.
T-Lymphocyte Priming and Protection Against Friend Leukemia by Vaccinia-Retrovirus
env
Gene Recombinant
Authors: Earl Patricia L. , Moss Bernard , Morrison Richard P. , Wehrly Kathy , Nishio Jane , Chesebro Bruce
Published: October 2006

The current prevalence of the acquired immune deficiency syndrome in humans has provoked renewed interest in methods of protective immunization against retrovirus-induced diseases. In this study, a vaccinia-retrovirus recombinant vector was constructed to study mechanisms of immune protection against Friend virus leukemia in mice. The envelope (
env
) gene from Friend murine leukemia virus (F-MuLV) was inserted into the genome of a vaccinia virus expression vector. Infected cells synthesized gp85, the glycosylated primary product of the
env
gene. Processing to gp70 and p15E, and cell surface localization, were similar to that occurring in cells infected with F-MuLV. Mice inoculated with live recombinant vaccinia virus had an envelope-specific T-cell proliferative response and, after challenge with Friend virus complex, developed neutralizing antibody and cytotoxic T cells (CTL) and were protected against leukemia. In contrast, unimmunized and control groups developed a delayed neutralizing antibody response, but no detectable CTL, and succumbed to leukemia. Genes of the major histocompatibility complex influenced protection induced by the vaccinia recombinant but not that induced by attenuated N-tropic Friend virus.
A Common Mechanism of Chromosomal Translocation in T- and B-Cell Neoplasia
Authors: Finger Lawrence R. , Harvey Richard C. , Moore Robert C. A. , Showe Louise C. , Croce Carlo M.
Published: October 2006

The chromosomal breakpoint involved in the t(8;14)(q24;q11) chromosome translocation in the SKW-3 cell line, which directly involves the 3′ flanking region of the c-
myc
gene, was cloned and sequenced. The breakpoint on chromosome 8 mapped to a position 3 kb 3′ of c-
myc
while the chromosome 14 breakpoint occurred 36 kb 5′ of the gene for the constant region of the α chain of the T-cell receptor (TCR). The translocation resulted in a precise rearrangement of sequences on chromosome 8 and what appears to be a functional J
α
segment on chromosome 14. Signal sequences for V-J joining occurred at the breakpoint positions on both chromosomes 14 and 8, suggesting that the translocation occurs during TCR gene rearrangement and that it is catalyzed by the enzymatic systems involved in V-J joining reactions. The involvement of c-
myc
in the translocation and the association of joining signals at the breakpoints provides a parallel to the situation observed in the translocations involving c-
myc
and the immunoglobulin loci in B-cell neoplasms and suggests that common mechanisms of translocation and oncogene deregulation are involved in B- and T-cell malignancies.
Epidermal-Growth-Factor-Dependent Transformation by a Human EGF Receptor Proto-Oncogene
Authors: Velu Thierry J. , Beguinot Laura , Vass William C. , Willingham Mark C. , Merlino Glenn T. , Pastan Ira , Lowy Douglas R.
Published: October 2006

The epidermal growth factor (EGF) receptor gene
EGFR
has been placed in a retrovirus vector to examine the growth properties of cells that experimentally overproduce a full-length EGF receptor. NIH 3T3 cells transfected with the viral DNA or infected with the corresponding rescued retrovirus developed a fully transformed phenotype in vitro that required both functional
EGFR
expression and the presence of EGF in the growth medium. Cells expressing 4 × 10
5
EGF receptors formed tumors in nude mice, while control cells did not. Therefore, the
EGFR
retrovirus, which had a titer on NIH 3T3 cells that was greater than 10
7
focus-forming units per milliliter, can efficiently transfer and express this gene, and increased numbers of EGF receptors can contribute to the transformed phenotype.
Blocking of HIV-1 Infectivity by a Soluble, Secreted Form of the CD4 Antigen
Authors: Smith Douglas H. , Byrn Randal A. , Marsters Scot A. , Gregory Timothy , Groopman Jerome E. , Capon Daniel J.
Published: October 2006

The initial event in the infection of human T lymphocytes, macrophages, and other cells by human immunodeficiency virus (HIV-1) is the attachment of the HIV-1 envelope glycoprotein gp120 to its cellular receptor, CD4. As a step toward designing antagonists of this binding event, soluble, secreted forms of CD4 were produced by transfection of mammalian cells with vectors encoding versions of CD4 lacking its transmembrane and cytoplasmic domains. The soluble CD4 so produced binds gp120 with an affinity and specificity comparable to intact CD4 and is capable of neutralizing the infectivity of HIV-1. These studies reveal that the high-affinity CD4-gp120 interaction does not require other cell or viral components and may establish a novel basis for therapeutic intervention in the acquired immune deficiency syndrome (AIDS).
Obesity, Overeating, and Rapid Gastric Emptying in Rats with Ventromedial Hypothalamic Lesions
Authors: Duggan J. P. , Booth D. A.
Published: October 2006

Measurements confirm the quantitative theoretical prediction that the autonomic nonendocrine abnormality of rapid daytime gastric emptying is the major primary cause of the obesity resulting from ventromedial hypothalamic lesions in rats. Therapy for obesity could include slowing of stomach emptying.
Specific DNA Probe for the Diagnosis of
Plasmodium falciparum
Malaria
Authors: Barker Robert H. , Suebsaeng Laksami , Rooney William , Alecrim Graca C. , Dourado Heitor V. , Wirth Dyann F.
Published: October 2006

Malaria can be diagnosed either by direct microscopic examination of blood smears, which is time consuming and requires expertise, or by immunological techniques, which are effective but do not distinguish between past and present infections. In this study, a simple procedure was developed for spotting lysed blood from infected patients directly onto nitrocellulose paper and identifying the malaria species on the basis of hybridization of parasite DNA with a species-specific probe. A genomic DNA library of
Plasmodium falciparum
was screened to detect clones containing DNA sequences that are highly repeated within the parasite genome. Several such clones were further analyzed to identify those that hybridize specifically with
P. falciparum
DNA but not with DNA from humans,
P. vivax
, or
P. cynomolgi
. This technique appears to be sensitive enough to detect 10 picograms of purified
P. falciparum
DNA (equivalent to 100 parasites) and in field studies is able to detect approximately 40 parasites per microliter of blood.
Distribution of Protein and RNA in the 30
S
Ribosomal Subunit
Authors: Ramakrishnan V.
Published: October 2006

In
Escherichia coli
, the small ribosomal subunit has a sedimentation coefficient of 30
S
, and consists of a 16
S
RNA molecule of 1541 nucleotides complexed with 21 proteins. Over the last few years, a controversy has emerged regarding the spatial distribution of RNA and protein in the 30
S
subunit. Contrast variation with neutron scattering was used to suggest that the RNA was located in a central core of the subunit and the proteins mainly in the periphery, with virtually no separation between the centers of mass of protein and RNA. However, these findings are incompatible with the results of efforts to locate individual ribosomal proteins by immune electron microscopy and triangulation with interprotein distance measurements. The conflict between these two views is resolved in this report of small-angle neutron scattering measurements on 30
S
subunits with and without protein S1, and on subunits reconstituted from deuterated 16
S
RNA and unlabeled proteins. The results show that (i) the proteins and RNA are intermingled, with neither component dominating at the core or the periphery, and (ii) the spatial distribution of protein and RNA is asymmetrical, with a separation between their centers of mass of about 25 angstroms.
Chloroquine Resistance Produced in Vitro in an African Strain of Human Malaria
Authors: Nguyen-Dinh Phuc , Trager William
Published: October 2006

After continuous cultivation in the presence of chloroquine, an African strain of the malaria parasite,
Plasmodium falciparum
, acquired resistance to the drug. The resistance was stable and comparable in vitro to that occurring naturally in a strain from Southeast Asia. This suggests that chloroquine resistance, absent until now in Africa, might arise in the future.
Active Human-Yeast Chimeric Phosphoglycerate Kinases Engineered by Domain Interchange
Authors: Mas Maria T. , Chen Christina Y. , Hitzeman Ronald A. , Riggs Arthur D.
Published: October 2006

Phosphoglycerate kinase (PGK) is a monomeric protein composed of two domains of approximately equal size, connected by a hinge. Substrate-induced conformational change results in the closure of the active site cleft, which is situated between these two domains. In a study of the relations between structure and function of this enzyme, two interspecies hybrids were constructed, each composed of one domain from the human enzyme and one domain from the yeast enzyme. Despite a 35% difference in the amino acid composition between human and yeast PGK, catalytic properties of the hybrid enzymes are very similar to those of the parental proteins. This result demonstrates that the evolutionary substitutions within these two distantly related molecules do not significantly affect formation of the active site cleft, mechanism of domain closure, or enzyme activity itself.
Differentiation-Linked Leukemogenesis in Lymphocytes
Authors: Greaves Melvyn F.
Published: October 2006

Most human lymphoid malignancies preserve a pattern of gene expression reflecting their proliferative activity and the developmental level of clonal expansion and maturation arrest. Characteristics of leukemia and other cancer cells frequently considered to reflect aberrant differentiation may more often reflect clonal selection of cell types that are normally infrequent and transitory. The differentiation status of progenitor or mature lymphoid cells influences which genetic elements are at risk of being exploited, via mutation, recombination, or deletion, for clonal advantage. These alterations may frequently arise spontaneously as a consequence of the unique developmental and functional programs of lymphoid cells and have as a major phenotypic consequence the stabilization of transitory cellular phenotypes.
Efficacy of Murine Malaria Sporozoite Vaccines: Implications for Human Vaccine Development
Authors: Egan James E. , Weber James L. , Ballou W. Ripley , Hollingdale Michael R. , Majarian William R. , Gordon Daniel M. , Maloy W. Lee , Hoffman Stephen L. , Wirtz Robert A. , Schneider Imogene , Woollett Gillian R. , Young James F. , Hockmeyer Wayne T.
Published: October 2006

As part of a study of potential vaccines against malaria, the protective efficacy of sporozoite subunit vaccines was determined by using the
Plasmodium berghei
murine malaria model. Mice were immunized with recombinant DNA-produced or synthetic peptide-carrier subunit vaccines derived from the repetitive epitopes of the
Plasmodium berghei
circumsporozoite gene, or with radiation-attenuated sporozoites. Immunization with subunit vaccines elicited humoral responses that were equivalent to or greater than those elicited by irradiated sporozoites, yet the protection against sporozoite challenge induced by either of the subunit vaccines was far less than that achieved by immunization with attenuated sporozoites. Passive and adoptive transfer studies demonstrated that subunit vaccines elicited predominantly antibody-mediated protection that was easily overcome whereas irradiated sporozoites induced potent cell-mediated immunity that protected against high challenge doses of sporozoites. These studies indicate that new strategies designed to induce cellular immunity will be required for efficacious sporozoite vaccines.
The Safety Goals of the U.S. Nuclear Regulatory Commission
Authors: Okrent David
Published: October 2006

In August 1986, after 6 years of effort, the U.S. Nuclear Regulatory Commission adopted a Policy Statement on safety goals for nuclear power reactors. The commission's qualitative goals state that (i) individual members of the public should be provided a level of protection from the consequences of nuclear power plant operation such that they bear no significant additional risk to life and health, and (ii) societal risks to life and health from nuclear power should be comparable to or less than the risks of generating electricity by viable competing technologies and should not be a significant addition to other societal risks. The commission's safety goal Policy Statement also includes quantitative design objectives.
Carbon Tetrachloride at Hepatotoxic Levels Blocks Reversibly Gap Junctions Between Rat Hepatocytes
Authors: Sáez J. C. , Bennett M. V. L. , Spray D. C.
Published: October 2006

Electrical coupling and dye coupling between pairs of rat hepatocytes were reversibly reduced by brief exposure to halogenated methanes (CBrCl
3
, CCl
4
, and CHCl
3
). The potency of different halomethanes in uncoupling hepatocytes was comparable to their hepatotoxicity in vivo, and the rank order was the same as that of their tendency to form free radicals. The effect of carbon tetrachloride (CCl
4
) on hepatocytes was substantially reduced by prior treatment with SKF 525A, an inhibitor of cytochrome P-450, and by exposure to the reducing reagent β-mercaptoethanol. Halomethane uncoupling occurred with or without extracellular calcium and did not change intracellular concentrations of calcium and hydrogen ions or the phosphorylation state of the main gap-junctional protein. Thus the uncoupling appears to depend on cytochrome P-450 oxidative metabolism in which free radicals are generated and may result from oxidation of the gap-junctional protein or of a regulatory molecule that leads to closure of gap-junctional channels. Decreases in junctional conductance may be a rapid cellular response to injury that protects healthy cells by uncoupling them from unhealthy ones.
Frequency Dependence of Electric Field Modulation of Fibroblast Protein Synthesis
Authors: McLeod Kenneth J. , Lee Raphael C. , Ehrlich H. Paul
Published: October 2006

The effect of electric current on protein biosynthesis in mammalian fibroblasts was investigated with neonatal bovine fibroblast-populated collagen matrices. The field strength dependence of electric field modulation of proline incorporation into extracellular and intracellular protein was measured over a frequency range from 0.1 to 1000 hertz. A frequency- and amplitude-dependent reduction in the rate of incorporation was observed. In tissues containing cells aligned either parallel or perpendicular to the electric field, this response was dependent on the orientation of the cells relative to the direction of the applied electric field. This study demonstrates that currents of physiological strength can stimulate alterations in biosynthesis and thereby may influence tissue growth, remodeling, and repair.
New Early Jurassic Tetrapod Assemblages Constrain Triassic-Jurassic Tetrapod Extinction Event
Authors: Olsen P. E. , Shubin N. H. , Anders M. H.
Published: October 2006

The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all "typical Triassic" forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.
A Stereospecific Cyclization Catalyzed by an Antibody
Authors: Napper Andrew D. , Benkovic Stephen J. , Tramontano Alfonso , Lerner Richard A.
Published: October 2006

A monoclonal antibody elicited by a transition-state analog that is representative of an intramolecular six-membered ring cyclization reaction acted as a stereospecific, enzyme-like catalyst for the appropriate substrate. Formation of a single enantiomer of a δ-lactone from the corresponding racemic δ-hydroxyester was accelerated by the antibody by about a factor of 170, which permitted isolation of the lactone in an enantiomeric excess of about 94 percent. This finding demonstrates the feasibility of catalytic-antibody generation for chemical transformations that require stereochemical control.
Activated Oncogenes in B6C3F1 Mouse Liver Tumors: Implications for Risk Assessment
Authors: Reynolds Steven H. , Stowers Shari J. , Patterson Rachel M. , Maronpot Robert R. , Aaronson Stuart A. , Anderson Marshall W.
Published: October 2006

The validity of mouse liver tumor end points in assessing the potential hazards of chemical exposure to humans is a controversial but important issue, since liver neoplasia in mice is the most frequent tumor target tissue end point in 2-year carcinogenicity studies. The ability to distinguish between promotion of background tumors versus a genotoxic mechanism of tumor initiation by chemical treatment would aid in the interpretation of rodent carcinogenesis data. Activated oncogenes in chemically induced and spontaneously occurring mouse liver tumors were examined and compared as one approach to determine the mechanism by which chemical treatment caused an increased incidence of mouse liver tumors. Data suggest that furan and furfural caused an increased incidence in mouse liver tumors at least in part by induction of novel weakly activating point mutations in
ras
genes even though both chemicals did not induce mutations in
Salmonella
assays. In addition to
ras
oncogenes, two activated
raf
genes and four non-
ras
transforming genes were detected. The B6C3F1 mouse liver may thus provide a sensitive assay system to detect various classes of proto-oncogenes that are susceptible to activation by carcinogenic insult. As illustrated with mouse liver tumors, analysis of activated oncogenes in spontaneously occurring and chemically induced rodent tumors will provide information at a molecular level to aid in the use of rodent carcinogenesis data for risk assessment.
Biomaterial-Centered Infection: Microbial Adhesion Versus Tissue Integration
Authors: Gristina Anthony G.
Published: October 2006

Biomaterials are being used with increasing frequency for tissue substitution. Complex devices such as total joint replacements and the total artificial heart represent combinations of polymers and metal alloys for system and organ replacement. The major barriers to the extended use of these devices are the possibility of bacterial adhesion to biomaterials, which causes biomaterial-centered infection, and the lack of successful tissue integration or compatibility with biomaterial surfaces. Interactions of biomaterials with bacteria and tissue cells are directed not only by specific receptors and outer membrane molecules on the cell surface, but also by the atomic geometry and electronic state of the biomaterial surface. An understanding of these mechanisms is important to all fields of medicine and is derived from and relevant to studies in microbiology, biochemistry, and physics. Modifications to biomaterial surfaces at an atomic level will allow the programming of cell-to-substratum events, thereby diminishing infection by enhancing tissue compatibility or integration, or by directly inhibiting bacterial adhesion.
Embryonic Development of Identified Neurons: Temporal Pattern of Morphological and Biochemical Differentiation
Authors: Goodman Corey S. , O'Shea Michael , McCaman Richard , Spitzer Nicholas C.
Published: October 2006

Individually identified neurons can be recognized in grasshopper embryos, and are accessible to examination by morphological, physiological, and biochemical techniques from their birth to their maturation. Only after the axon of an identified neuron reaches its postsynaptic target does the neurotransmitter accumulate, the soma rapidly enlarge, and the central arborizations greatly expand.
Acylation of Proteins with Myristic Acid Occurs Cotranslationally
Authors: Wilcox Celeste , Hu Jing-Shan , Olson Eric N.
Published: October 2006

Several proteins of viral and cellular origin are acylated with myristic acid early during their biogenesis. To investigate the possibility that myristylation occurred cotranslationally, the BC
3
H1 muscle cell line, which contains a broad array of myristylated proteins, was pulse-labeled with [
3
H]myristic acid. Nascent polypeptide chains covalently associated with transfer RNA were isolated subsequently by ion-exchange chromatography. [
3
H]Myristate was attached to nascent chains through an amide linkage and was identified by thin-layer chromatography after its release from nascent chains by acid methanolysis. Inhibition of cellular protein synthesis with puromycin resulted in cessation of [
3
H]myristate-labeling of nascent chains, in agreement with the dependence of this modification on protein synthesis in vivo. These data represent a direct demonstration that myristylation of proteins is a cotranslational modification.
Parathyroid Hormone-Related Protein of Malignancy: Active Synthetic Fragments
Authors: Kemp Bruce E. , Moseley Jane M. , Rodda Christine P. , Ebeling Peter R. , Wettenhall Richard E. H. , Stapleton David , Diefenbach-Jagger Hannelore , Ure Fiona , Michelangeli Valdo P. , Simmons Hollis A. , Raisz Lawrence G. , Martin T. John
Published: October 2006

Peptides corresponding to the amino-terminal region of the parathyroid hormone-related protein (PTHrP) of humoral hypercalcemia of malignancy were synthesized. A 34-amino acid peptide, PTHrP(1-34), was two to four times more potent than bovine or human PTH(1-34) in bioassays promoting the formation of adenosine 3′,5′-monophosphate (cAMP) and plasminogen activator activity in osteogenic sarcoma cells and adenylate cyclase activity in chick kidney membranes. Like parathyroid hormone itself, in which the activity resides in the first 34 residues, PTHrP peptides of less than 30 residues from the amino terminus showed substantially reduced activity. PTHrP(1-34) had only 6% of the potency of bovine PTH(1-34) in promoting bone resorption in vitro. PTHrP(1-34) strongly promoted the excretion of cAMP and phosphorus and reduced the excretion of calcium in the isolated, perfused rat kidney consistent with the symptoms seen in malignant hypercalcemia.
Identification of the Iron-Responsive Element for the Translational Regulation of Human Ferritin mRNA
Authors: Hentze Matthias W. , Caughman S. Wright , Rouault Tracey A. , Barriocanal Javier G. , Dancis Andrew , Harford Joe B. , Klausner Richard D.
Published: October 2006

Regulated translation of messenger RNA offers an important mechanism for the control of gene expression. The biosynthesis of the intracellular iron storage protein ferritin is translationally regulated by iron. A
cis
-acting element that is both necessary and sufficient for this translational regulation is present within the 5′ nontranslated leader region of the human ferritin H-chain messenger RNA. In this report the iron-responsive element (IRE) was identified by deletional analysis. Moreover, a synthetic oligodeoxynucleotide was shown to be able to transfer iron regulation to a construct that would otherwise not be able to respond to iron. The IRE has been highly conserved and predates the evolutionary segregation between amphibians, birds, and man. The IRE may prove to be useful for the design of translationally regulated expression systems.
Neuronal Population Coding of Movement Direction
Authors: Georgopoulos Apostolos P. , Schwartz Andrew B. , Kettner Ronald E.
Published: October 2006

Although individual neurons in the arm area of the primate motor cortex are only broadly tuned to a particular direction in three-dimensional space, the animal can very precisely control the movement of its arm. The direction of movement was found to be uniquely predicted by the action of a population of motor cortical neurons. When individual cells were represented as vectors that make weighted contributions along the axis of their preferred direction (according to changes in their activity during the movement under consideration) the resulting vector sum of all cell vectors (population vector) was in a direction congruent with the direction of movement. This population vector can be monitored during various tasks, and similar measures in other neuronal populations could be of heuristic value where there is a neural representation of variables with vectorial attributes.
Extrapituitary Action of Gonadotropin-Releasing Hormone: Direct Inhibition Ovarian Steroidogenesis
Authors: Hsueh A. J. W. , Erickson G. F.
Published: October 2006

Gonadotropin-releasing hormone (GnRH) and its agonistic analogs inhibited the follicle-stimulating hormone (FSH)-induced increase of estrogen and progesterone production in vitro by rat ovarian granulosa cells. Likewise, GnRH analogs inhibited FSH-induced changes in ovarian function in hypophysectomized rats in vivo. These results indicate that GnRH, in addition to its well-known gonadotropin-releasing action in the pituitary, exerts a direct inhibition of ovarian steroidogenesis.
Different Mutations in Ashkenazi Jewish and Non-Jewish French Canadians with Tay-Sachs Disease
Authors: Myerowitz Rachel , Hogikyan Norman D.
Published: October 2006

Tay-Sachs disease patients of Ashkenazi Jewish and non-Jewish French Canadian origin are affected with a clinically identical form of this inherited disease. Both have a similar gene frequency for the disorder, which is tenfold higher than that found in the general population. Unlike other patients with the disease, who often display variation at the clinical or biochemical level, the absence of such differences between these two groups has prompted the idea that they may harbor the same mutation. In this report, a complementary DNA clone coding for the α chain of human β-hexosaminidase has been used to analyze the genetic lesions in the α-chain locus of two patients with Tay-Sachs disease from each of these groups. On the basis of DNA hybridization analyses, the α-chain gene of the Ashkenazi patients appears intact while the α-chain gene of French Canadian patients has a 5′ deletion of approximately 5 to 8 kilobases.
The Complete Primary Structure of Protein Kinase C—the Major Phorbol Ester Receptor
Authors: Parker Peter J. , Coussens Lisa , Totty Nick , Rhee Lucy , Young Susan , Chen Ellson , Stabel Silvia , Waterfield Michael D. , Ullrich Axel
Published: October 2006

Protein kinase C, the major phorbol ester receptor, was purified from bovine brain and through the use of oligonucleotide probes based on partial amino acid sequence, complementary DNA clones were derived from bovine brain complementary DNA libraries. Thus, the complete amino acid sequence of bovine protein kinase C was determined, revealing a domain structure. At the amino terminal is a cysteine-rich domain with an internal duplication; a putative calcium-binding domain follows, and there is at the carboxyl terminal a domain that shows substantial homology, but not identity, to sequences of other protein kinase.
Ablation of Polymers and Biological Tissue by Ultraviolet Lasers
Authors: Srinivasan R.
Published: October 2006

When pulsed, ultraviolet laser radiation falls on the surface of an organic polymer or biological tissue, the material at the surface is spontaneously etched away to a depth of 0.1 to several micrometers. In the process, the depth of etching is controlled by the width of the pulse and the fluence of the laser, and there is no detectable thermal damage to the substrate. The material that is removed by etching consists of products ranging from atoms to small fragments of the polymer. They are ejected at supersonic velocities. This dry photoetching technique is useful in patterning polymer films. It is also under serious investigation in several areas in surgery.
DNA Organization of
Methanobacterium thermoautotrophicum
Authors: Mitchell Ralph M. , Loeblich Laurel A. , Klotz Lynn C. , Loeblich Alfred R.
Published: October 2006

The organism
Methanobacterium thermoautotrophicum
, an archaebacterium, is evolutionarily very distant from both traditional prokaryotes and eukaryotes. Its genome (DNA) has physical characteristics typical of most prokaryotes except that it is quite small (about 10
9
daltons, less than half the size of the genome of
Escherichia coli
) and contains a significant amount (6 percent) of DNA which renatures extremely rapidly.
A Low Threshold Calcium Spike Mediates Firing Pattern Alterations in Pontine Reticular Neurons
Authors: Greene Robert W. , Haas Helmut L. , McCarley Robert W.
Published: October 2006

Intracellular electrical recordings in an in vitro slice preparation of the brainstem medial pontine reticular formation, a region thought to be important in mediation of desynchronized sleep phenomena, demonstrate a population of neurons that have a calcium-dependent, low threshold spike. This low threshold spike was inactivated at relatively depolarized membrane potential levels and, when this spike was deinactivated, it induced a burst of action potentials. The membrane potential dependence of the spike may underlie changes in action potential firing patterns associated with behavioral state change because the baseline membrane potential in neurons of the medial pontine reticular population depolarizes during passage from waking and slow wave sleep to desynchronized sleep, which is characterized by the absence of burst firing.
Flow Control Among Microvessels Coordinated by Intercellular Conduction
Authors: Segal Steven S. , Duling Brain R.
Published: October 2006

Optimal distribution of blood flow requires coordination of vasodilation among resistance vessels. During hyperemia, blood vessels dilate upstream from the initiating stimulus. Spreading vasodilation independent of flow changes has not been previously demonstrated. In the present study, iontophoresis of acetylcholine adjacent to single hamster cheek pouch arterioles in situ (diameter, 20 to 37 micrometers) induced a rapid bidirectional dilation that was not attenuated when blood flow was eliminated with vascular occlusion. This finding indicates that a vasodilatory stimulus is conducted along the arteriole and demonstrates the existence of a mechanism of intercellular communication that is capable of coordinating diameter changes among resistance vessels.
Long-Term Potentiation in Dentate Gyrus: Induction by Asynchronous Volleys in Separate Afferents
Authors: Winson Jonathan , Dahl Dennis
Published: October 2006

Long-term potentiation (LTP), a long-lasting enhancement of synaptic efficacy, is considered a model for learning and memory. In anesthetized rats, activation of dentate granule cells by stimulating either the medial or lateral perforant pathway at frequencies of 100 to 400 Hz produced LTP of the stimulated pathway preferentially at 400 Hz. However, hippocampal pathways do not normally fire at this high rate. Stimuli at 200 Hz were then applied to either the medial or lateral pathway separately, to both pathways simultaneously, or to the two pathways asynchronously so that the composite stimulus applied to the granule cell dendrite was 400 Hz. LTP was produced preferentially in the asynchronous condition. Thus, lower frequency, physiological input volleys arriving asynchronously at medial and lateral synapses can induce LTP by activating a 400-Hz sensitive mechanism capable of integrating spatially separated granule cell inputs. This may reflect how LTP is normally produced in the dentate gyrus.
Cytotaxins After the Sedimentation Behavior of Human Granulocytes
Authors: Catsimpoolas Nicholas , Kurtz Sanford R. , Skrabut Eugene M. , Griffith Ann L. , Valeri C. Robert
Published: October 2006

Human granulocytes from the peripheral blood of healthy donors were subjected to transient gravity sedimentation analysis in Ficoll density gradient columns (37°C) containing different concentrations of
Escherichia coli
endotoxin-activated serum and medium 199. A dramatic serum concentration-dependent dispersion of the cells based on changes in sedimentation velocity was observed as a function of time, using a new optical scanning instrument. The phenomenon was virtually abolished in the presence of cytochalasin B, a known inhibitor of cellular chemotaxis. The width (second statistical moment) of the sedimenting cell distribution increased in a sigmoid fashion as a function of time regardless of cytotaxin concentration. This indicates that a slow and nonlinear response of the granulocytes to the cytotaxins occurs. This new kinetic method should be useful in examining an alternate manifestation of the chemoresponsiveness of phagocytic cells and of cell interactions in general.
Sporozoite-Induced Malaria: Therapeutic Effects of Glycolipids in Liposomes
Authors: Alving Carl R. , Schneider Imogene , Swartz Glenn M. , Steck Edgar A.
Published: October 2006

Liposomes containing neutral glycolipids with a terminal glucose or galactose, when injected intravenously, prevented the appearance of erythrocytic forms of malaria (
Plasmodium berghei
) in mice previously injected with sporozoites. Inhibitory glycolipids included glucosyl, galactosyl, or lactosyl ceramide. Inhibition was not observed with liposomes containing ceramide, phosphocholine ceramide, sulfogalactosyl ceramide (sulfatide), or ganglioside G
M1
. Liposomes containing glycolipids did not inhibit infection transmitted by injecting blood containing erythrocytic stages of malaria. These results may have therapeutic implications in the treatment of malaria. Analysis of the mechanism of interference with the life cycle of malaria by liposomal glycolipids may yield information about the interactions of parasites with cellular membranes.
Hierarchical Structure in Polymeric Materials
Authors: Baer E. , Hiltner A. , Keith H. D.
Published: October 2006

The diversity of monomers available for synthesis of high polymers makes it possible to prepare a wide variety of long-chain macromolecular compounds. It is instructive to consider a hierarchical organization of structure in polymers at four successive levels—the molecular, nano-, micro-, and macrolevels—and to examine how interactions at and between these various levels of structure have important and often quite specific influences. Examples are drawn from semicrystalline polymers with flexible chains, liquid-crystalline polymers composed of rigid macromolecules, and amorphous polymers. Structural hierarchies in biocomposite systems are also discussed, particularly in soft connective tissues such as tendon and intervertebral disk.
Aromatic Cross-Links in Insect Cuticle: Detection by Solid-State
13
C and
15
N NMR
Authors: Schaefer Jacob , Kramer Karl J. , Garbow Joel R. , Jacob Gary S. , Stejskal Edward O. , Hopkins Theodore L. , Speirs Roy D.
Published: October 2006

Cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy has been used to determine insect cuticle composition and cross-link structure during sclerotization or tanning. Unsclerotized cuticle from newly ecdysed pupae of the tobacco hornworm,
Manduca sexta
L., had a high protein content with lesser amounts of lipid and chitin. Concentrations of chitin, protein, and catechol increased substantially as dehydration and sclerotization progressed. Analysis of intact cuticle specifically labeled with carbon-13 and nitrogen-15 revealed direct covalent linkages between ring nitrogens of protein histidyl residues and ring carbons derived from the catecholamine dopamine. This carbon-nitrogen adduct was present in chitin isolated from cuticle by alkaline extraction and is probably bound covalently to chitin. These data support the hypothesis that the stiffening of insect cuticle during sclerotization results primarily from the deposition of protein and chitin polymers and their crosslinking by quinonoid derivatives of catecholamines.
Post-Transcriptional Control of Class I MHC mRNA Expression in Adenovirus 12-Transformed Cells
Authors: Vaessen Ruud T. M. J. , Houweling Ada , van der Eb Alex J.
Published: October 2006

Expression of the class I transplantation antigens of the major histocompatibility complex (MHC) is suppressed in cells transformed by the oncogenic human adenovirus 12 (Ad12). This suppression of class I antigen expression, which contributes to the tumorigenic phenotype of the transformed cells, has also been observed in some naturally occurring cancers. In the present study, the rate of transcription initiation of class I genes was measured by a nuclear run-on assay in Ad5- and Ad12-transformed cells of three different types. The rate of transcription was the same in all three. The stability of the class I messenger RNA was also examined and found to be the same in all three cell types. The results indicate that in Ad12-transformed cells the suppression is caused by an inhibition of the post-transcriptional processing of class I MHC messenger RNA in the nucleus.
Redesigning Trypsin: Alteration of Substrate Specificity
Authors: Craik Charles S. , Largman Corey , Fletcher Thomas , Roczniak Steven , Barr Philip J. , Fletterick Robert , Rutter William J.
Published: October 2006

A general method for modifying eukaryotic genes by site-specific mutagenesis and subsequent expression in mammalian cells was developed to study the relation between structure and function of the proteolytic enzyme trypsin. Glycine residues at positions 216 and 226 in the binding cavity of trypsin were replaced by alanine residues, resulting in three trypsin mutants. Computer graphic analysis suggested that these substitutions would differentially affect arginine and lysine substrate binding of the enzyme. Although the mutant enzymes were reduced in catalytic rate, they showed enhanced substrate specificity relative to the native enzyme. This increased specificity was achieved by the unexpected differential effects on the catalytic activity toward arginine and lysine substrates. Mutants containing alanine at position 226 exhibited an altered conformation that may be converted to a trypsin-like structure upon binding of a substrate analog.
Molecular Cloning of a Gene Sequence Regulated by Nerve Growth Factor
Authors: Levi Andrea , Eldridge Juanita D. , Paterson Bruce M.
Published: October 2006

Nerve growth factor (NGF) is essential for the development and differentiation of sympathetic or sensory neurons. A complementary DNA was cloned that corresponds to a gene sequence induced more than 50-fold in a cultured target cell line of pheochromocytoma cells (PC12 cells) 5 hours after the addition of NGF. The induced messenger RNA encodes a 90,000-dalton polypeptide that may represent one of the primary events in NGF-induced differentiation of neurons.
Coexpression of Translocated and Normal c-
myc
Oncogenes in Hybrids Between Daudi and Lymphoblastoid Cells
Authors: Croce Carlo M. , Erikson Jan , Huebner Kay , Nishikura Kazuko
Published: October 2006

Mechanisms that affect the transcription of the c-
myc
oncogene take part in the development of B-cell neoplasias such as Burkitt's lymphoma. Daudi Burkitt lymphoma cells, which express only the translocated c-
myc
oncogene, were hybridized with human lymphoblastoid cells, which express the normal c-
myc
gene; the hybrids were phenotypically lymphoblastoid and expressed both the translocated and the normal c-
myc
gene. This result contrasts with the findings that the decapitated c-
myc
gene, translocated to an immunoglobulin switch μ or α region, is transcriptionally silent in lymphoblastoid hybrids. Thus, there may be at least two distinct enhancer-like elements capable of deregulating c-
myc
transcription in lymphomas and leukemias with t(8;14) chromosome translocations. In addition, since the Daudi × lymphoblastoid hybrids express both the translocated and the normal c-
myc
gene, the c-
myc
gene product does not autoregulate c-
myc
transcription.
Molecular Cloning of the Complementary DNA for Human Tumor Necrosis Factor
Authors: Wang Alice M. , Creasey Abla A. , Ladner Martha B. , Lin Leo S. , Strickler James , Van Arsdell Janelle N. , Yamamoto Ralph , Mark David F.
Published: October 2006

Tumor necrosis factor (TNF) is a soluble protein that causes damage to tumor cells but has no effect on normal cells. Human TNF was purified to apparent homogeneity as a 17.3-kilodalton protein from HL-60 leukemia cells and showed cytotoxic and cytostatic activities against various human tumor cell lines. The amino acid sequence was determined for the amino terminal end of the purified protein, and oligodeoxyribonucleotide probes were synthesized on the basis of this sequence. Complementary DNA (cDNA) encoding human TNF was cloned from induced HL-60 messenger RNA and was confirmed by hybrid-selection assay, direct expression in COS-7 cells, and nucleotide sequence analysis. The human TNF cDNA is 1585 base pairs in length and encodes a protein of 233 amino acids. The mature protein begins at residue 77, leaving a long leader sequence of 76 amino acids. Expression of high levels of human TNF in Escherichia coli was accomplished under control of the bacteriophage λP
L
promoter and gene N ribosome binding site.
Human T-Cell Clones from Autoimmune Thyroid Glands: Specific Recognition of Autologous Thyroid Cells
Authors: Londei Marco , Bottazzo G. Franco , Feldmann Marc
Published: October 2006

The thyroid glands of patients with autoimmune diseases such as Graves' disease and certain forms of goiter contain infiltrating activated T lymphocytes and, unlike cells of normal glands, the epithelial follicular cells strongly express histocompatibility antigens of the HLA-DR type. In a study of such autoimmune disorders, the infiltrating T cells from the thyroid glands of two patients with Graves' disease were cloned in mitogen-free interleukin-2 (T-cell growth factor). The clones were expanded and their specificity was tested. Three types of clones were found. One group, of T4 phenotype, specifically recognized autologous thyroid cells. Another, also of T4 phenotype, recognized autologous thyroid or blood cells and thus responded positively in the autologous mixed lymphocyte reaction. Other clones derived from cells that were activated in vivo were of no known specificity. These clones provide a model of a human autoimmune disease and their analysis should clarify mechanisms of pathogenesis and provide clues to abrogating these undesirable immune responses.
Evidence for a Malarial Parasite Interaction Site on the Major Transmembrane Protein of the Human Erythrocyte
Authors: Friedman Milton J. , Fukuda Minoru , Laine Roger A.
Published: October 2006

Soluble oligosaccharides derived from the surface of human erythrocytes were tested for their ability to competitively inhibit invasion of erythrocytes by
Plasmodium falciparum
, a malarial parasite. Invasion was most effectively inhibited by erythroglycan, a carbohydrate component of the band 3 transmembrane protein. The lactosamine chains of erythroglycan contributed much of the inhibitory activity. This indication of a primary parasite interaction site on band 3 supports a role for this protein in mediating the radical alterations of the erythrocyte cytoskeleton that accompany invasion.