bluuebunny/crossref_metadata_2025 huggingface dataset:
The Predicted Structure of Immunoglobulin D1.3 and Its Comparison with the Crystal Structure
Authors: Chothia Cyrus , Lesk Arthur M. , Levitt Michael , Amit Adolfo G. , Mariuzza Roy A. , Phillips Simon E. V. , Poljak Roberto J.
Published: October 2006

Predictions of the structures of the antigen-binding domains of an antibody, recorded before its experimental structure determination and tested subsequently, were based on comparative analysis of known antibody structures or on conformational energy calculations. The framework, the relative positions of the hypervariable regions, and the folds of four of the hypervariable loops were predicted correctly. This portion includes all residues in contact with the antigen, in this case hen egg white lysozyme, implying that the main chain conformation of the antibody combining site does not change upon ligation. The conformations of three residues in each of the other two hypervariable loops are different in the predicted models and the experimental structure.
Protein-Binding Sites in Ig Gene Enhancers Determine Transcriptional Activity and Inducibility
Authors: Lenardo Michael , Pierce Jacqueline W. , Baltimore David
Published: October 2006

Individual protein-binding sites within the mouse immunoglobulin heavy chain and kappa light chain gene enhancers were altered, making it possible to examine the functional role of the sites during transcription. The E motifs, which bind factors that are present in many if not all cells, mostly behave as transcriptional activating sites. The only known heavy chain enhancer site that binds a lymphocyte-specific factor, the "octamer" site, plays a critical role in transcription but only in a truncated form of the enhancer. In the full enhancer, no one site is crucial because of an apparent functional redundancy. The site in the kappa enhancer that binds a factor specific to mature B cells, κB, was crucial to the constitutive activity of the enhancer in B cells. This factor is also inducible in pre-B cells, and the site was necessary for inducibility of the kappa enhancer. Thus, the sites defined by protein binding are important for the functional activity of immunoglobulin enhancers, with the sites that bind proteins restricted in their cellular distribution playing the most important roles.
The Use of a Charge-Coupled Device for Quantitative Optical Microscopy of Biological Structures
Authors: Hiraoka Yasushi , Sedat John W. , Agard David A.
Published: October 2006

The properties of a charge-coupled device (CCD) and its application to the high-resolution analysis of biological structures by optical microscopy are described. The CCD, with its high resolution, high sensitivity, wide dynamic range, photometric accuracy, and geometric stability, can provide data of such high quality that quantitative analysis on two- and three-dimensional microscopic images is possible. For example, the three-dimensional imaging properties of an epifluorescence microscope have been quantitatively determined with the CCD. This description of the imaging properties of the microscope, and the high-quality image data provided by the CCD, allow sophisticated computational image processing methods to be used that greatly improve the effective resolution obtainable for biological structures. Image processing techniques revealed fine substructures in
Drosophila
embryonic diploid chromosomes in two and three dimensions. The same approach can be extended to structures as small as yeast chromosomes or to other problems in structural cell biology.
Voltage Dependence of Junctional Conductance in Early Amphibian Embryos
Authors: Spray D. C. , Harris A. L. , Bennett M. V. L.
Published: October 2006

Isolated pairs of blastomeres from early amphibian embryos (
Ambystoma
,
Rana
,
Xenopus
) are electrotonically coupled. Junctional conductance and permeability to the dye Lucifer Yellow are markeldy and reversibly decreased by moderate transjunctional polarization in either direction. The relationship between junctional conductance and transjunctional voltage is sufficiently steep that a physiological role in regulation of intercellular communication is plausible.
Genetic and Fossil Evidence for the Origin of Modern Humans
Authors: Stringer C. B. , Andrews P.
Published: October 2006

The origin of living
Homo sapiens
has once again been the subject of much debate. Genetic data on present human population relationships and data from the Pleistocene fossil hominid record are used to compare two contrasting models for the origin of modern humans. Both genetics and paleontology support a recent African origin for modern humans rather than a long period of multiregional evolution accompanied by gene flow.
Accuracy of in Vivo Aminoacylation Requires Proper Balance of tRNA and Aminoacyl-tRNA Synthetase
Authors: Swanson Robert , Hoben Patricia , Sumner-Smith Martin , Uemura Haruki , Watson Lynley , Söll Dieter
Published: October 2006

The fidelity of protein biosynthesis in any cell rests on the accuracy of aminoacylation of tRNA. The exquisite specificity of this reaction is critically dependent on the correct recognition of tRNA by aminoacyl-tRNA synthetases. It is shown here that the relative concentrations of a tRNA and its cognate aminoacyl-tRNA synthetase are normally well balanced and crucial for maintenance of accurate aminoacylation. When
Escherichia coli
Gln-tRNA synthetase is overproduced in vivo, it incorrectly acylates the
supF
amber suppressor tRNA
Tyr
with Gln. This effect is abolished when the intracellular concentration of the cognate tRNA
2
Gln
is also elevated. These data indicate that the presence of aminoacyl-tRNA synthetase and the cognate tRNAs in complexed form, which requires the proper balance of the two macromolecules, is critical in maintaining the fidelity of protein biosynthesis. Thus, limits exist on the relative levels of tRNAs and aminoacyl-tRNA synthetases within a cell.
Mutation in LDL Receptor: Alu-Alu Recombination Deletes Exons Encoding Transmembrane and Cytoplasmic Domains
Authors: Lehrman Mark A. , Schneider Wolfgang J. , Südhof Thomas C. , Brown Michael S. , Goldstein Joseph L. , Russell David W.
Published: October 2006

The molecular size of the plasma LDL (low density lipoprotein) receptor synthesized by cultured fibroblasts from a patient with the internalization-defective form of familial hypercholesterolemia (FH 274) was smaller by 10,000 daltons than the size of the normal LDL receptor. The segment of the gene encoding the truncated portion of the FH 274 receptor was cloned into bacteriophage lambda. Comparison of the nucleotide sequences of the normal and FH 274 genes revealed a 5-kilobase deletion, which eliminated the exons encoding the membrane-spanning region and the carboxyl terminal cytoplasmic domain of the receptor. The deletion appeared to be caused by a novel intrastrand recombination between two repetitive sequences of the Alu family that were oriented in opposite directions. The truncated receptors lack membrane-spanning regions and cytoplasmic domains; they are largely secreted into the culture medium, but a small fraction remains adherent to the cell surface. The surface-adherent receptors bind LDL, but they are unable to cluster in coated pits, thus explaining the internalization-defective phenotype.
Staphylococcal Enterotoxin A Is Encoded by Phage
Authors: Betley Marsha J. , Mekalanos John J.
Published: October 2006

The gene for staphylococcal enterotoxin A (
entA
), in two wild-type strains, is carried by related temperate bacteriophages. Hybridization analysis of DNA from
entA
-converting phage PS42-D and its bacterial host suggests that this phage integrates into the bacterial chromosome by circularization and reciprocal crossover (the Campbell model) and that the
entA
gene is located near the phage attachment site. DNA from three of eight staphylococcal strains that did not produce enterotoxin A and seven wild-type enterotoxin A-producing (EntA
+
) strains had extensive homology to the
entA
-converting phage PS42-D DNA, although there was a high degree of restriction-fragment length polymorphisms. At least one EntA+ strain did not produce detectable viable phage after induction. These data indicate that a polymorphic family of
Staphylococcus aureus
phages (some of which may be defective) can carry the
entA
gene.
Hyperthermia Protects Against Light Damage in the Rat Retina
Authors: Barbe Mary F. , Tytell Michael , Gower David J. , Welch William J.
Published: October 2006

An increase in the synthesis of heat shock proteins that is induced in cells in vitro by hyperthermia or other types of metabolic stress correlates with enhanced cell survival upon further stress. To determine if a similar increase in stress tolerance could be elicited in vivo, rats were made hyperthermic, and then their retinas were tested for sensitivity to light damage. This treatment resulted in a marked decrease in photoreceptor degeneration after exposure to bright light as compared to normothermic animals. Concomitant with such protection was an increase in retinal synthesis of three heat shock proteins. Thus, a physiological rise in body temperature enhances the stress tolerance of nerve tissue, perhaps by increasing heat shock protein production.
Endothelial Adhesiveness for Blood Neutrophils Is Inhibited by Transforming Growth Factor-β
Authors: Gamble Jennifer R. , Vadas Matthew A.
Published: October 2006

Adhesion of blood cells to endothelial cells is an essential component of all inflammatory responses. The capacity of the endothelium to support adhesion of neutrophils is increased by cytokines such as tumor necrosis factor-α, interleukin-1, and endotoxin. Another cytokine, transforming growth factor-β (TGF-β), was a strong inhibitor of basalneutrophil adhesion and also decreased the adhesive response of endothelial cells to tumor necrosis factor-α (TNF-α). The ability of cells to respond to TGF-β was related to the duration of culture of endothelial cells after explantation from umbilical veins. TGF-β is likely to serve an anti-inflammatory role at sites of blood vessel injury undergoing active endothelial regeneration.
Growth Cone Guidance in Insects: Fasciclin II Is a Member of the Immunoglobulin Superfamily
Authors: Harrelson Allan L. , Goodman Corey S.
Published: October 2006

The cellular cues that guide neuronal growth cones toward their targets are highly conserved in such diverse organisms as insects and vertebrates. Evidence presented here suggests that the molecular mechanisms underlying these events may be equally conserved. This article describes the structure and function of fasciclin II, a glycoprotein expressed on a subset of fasciculating axons in the grasshopper embryo. Antibody perturbation experiments suggest that fasciclin II functions in mediating one form of neuronal recognition: selective fasciculation. Fasciclin II is a member of the immunoglobulin gene superfamily and is homologous in structure and function to the neural cell adhesion molecule N-CAM and to several other vertebrate cell adhesion molecules.
Tris(2,3-Dibromopropyl) Phosphate: Mutagenicity of a Widely Used Flame Retardant
Authors: Prival Michael J. , McCoy Elena C. , Gutter Bezalel , Rosendranz Herbert S.
Published: October 2006

Tris(2,3-dibromopropyl) phosphate, a widely used flame-retardant additive for textiles, is mutagenic to histidine-requiring strains of
Salmonella typhimurium
. Extracts of fabrics treated with this compound are also capable of inducing mutations in these bacterial strains.
Novel Regulators of Bone Formation: Molecular Clones and Activities
Authors: Wozney John M. , Rosen Vicki , Celeste Anthony J. , Mitsock Lisa M. , Whitters Matthew J. , Kriz Ronald W. , Hewick Rodney M. , Wang Elizabeth A.
Published: October 2006

Protein extracts derived from bone can initiate the process that begins with cartilage formation and ends in de novo bone formation. The critical components of this extract, termed bone morphogenetic protein (BMP), that direct cartilage and bone formation as well as the constitutive elements supplied by the animal during this process have long remained unclear. Amino acid sequence has been derived from a highly purified preparation of BMP from bovine bone. Now, human complementary DNA clones corresponding to three polypeptides present in this BMP preparation have been isolated, and expression of the recombinant human proteins have been obtained. Each of the three (BMP-1, BMP-2A, and BMP-3) appears to be independently capable of inducing the formation of cartilage in vivo. Two of the encoded proteins (BMP-2A and BMP-3) are new members of the TGF-β supergene family, while the third, BMP-1, appears to be a novel regulatory molecule.
Unexpectedly High Levels of HIV-1 RNA and Protein Synthesis in a Cytocidal Infection
Authors: Somasundaran M. , Robinson H. L.
Published: October 2006

The expression of a laboratory strain of HIV-1 (HTLV-IIIB) has been studied in mitogen-stimulated peripheral blood lymphocytes (PBLs) and in two lymphoid cell lines (CEM cells and C8166 cells). HIV-expressing cells contained from 300,000 to 2,500,000 copies of viral RNA per cell. Near-synchronous expression of an active infection could be achieved in C8166 cells. In these cells, the high copy numbers of viral RNA used as much as 40% of total protein synthesis for the production of viral
gag
protein, with high levels of viral RNA and protein synthesis preceding cell death by 2 to 4 days.
Complementary Hemispheric Specialization in Monkeys
Authors: Hamilton Charles R. , Vermeire Betty A.
Published: October 2006

Twenty-five split-brain monkeys were taught to discriminate two types of visual stimuli that engage lateralized cerebral processing in human subjects. Differential lateralization for the two kinds of discriminations was found; the left hemisphere was better at distinguishing between tilted lines and the right hemisphere was better at discriminating faces. These results indicate that lateralization of cognitive processing appeared in primates independently of language or handedness. In addition, cerebral lateralization in monkeys may provide an appropriate model for studying the biological basis of hemispheric specialization.
Rat Insulin Genes: Construction of Plasmids Containing the Coding Sequences
Authors: Ullrich Axel , Shine John , Chirgwin John , Pictet Raymond , Tischer Edmund , Rutter William J. , Goodman Howard M.
Published: October 2006

Recombinant bacterial plasmids have been constructed that contain complementary DNA prepared from rat islets of Langerhans messenger RNA. Three plasmids contain cloned sequences representing the complete coding region of rat proinsulin I, part of the preproinsulin I prepeptide, and the untranslated 3′ terminal region of the mRNA. A fourth plasmid contains sequences derived from the A chain region of rat preproinsulin II.
Intravenous Naloxone Administration in Schizophrenia and Affective Illness
Authors: Davis Glenn C. , Bunney William E. , DeFraites Emanuel G. , Kleinman Joel E. , van Kammen Daniel P. , Post Robert M. , Wyatt Richard J.
Published: October 2006

Fourteen schizophrenic patients and five patients with affective disorders were given naloxone (0.4 to 10 milligrams) or placebo intravenously in a double-blind fashion. Physicians' ratings of hallucinations, mannerisms and posturing, conceptual disorganization, psychosis, and mood did not change significantly. A single item, unusual thought content, improved significantly on the naloxone day compared to the placebo day. There was no improvement in mood in affectively ill patients rated either by themselves or by physicians. Naloxone did not markedly improve any patient studied, which suggests that the acute blockade of opiate receptors is not associated with global improvement in psychotic symptomatology.
Cachectin/TNF and IL-1 Induced by Glucose-Modified Proteins: Role in Normal Tissue Remodeling
Authors: Vlassara Helen , Brownlee Michael , Manogue Kirk R. , Dinarello Charles A. , Pasagian Araxi
Published: October 2006

Proteins undergo a series of nonenzymatic reactions with glucose over time to form advanced glycosylation end products (AGEs). Macrophages have a receptor that recognizes the AGE moiety and mediates the uptake and degradation of AGE proteins. This removal process is associated with the production and secretion of cachectin (tumor necrosis factor) and interleukin-1, two cytokines with diverse and seemingly paradoxical biological activities. The localized release and action of these cytokines could account for the coordinated removal and replacement of senescent extracellular matrix components in normal tissue homeostasis.
2-Aminopurine Selectively Inhibits the Induction of β-Interferon, c-
fos
, and c-
myc
Gene Expression
Authors: Zinn Kai , Keller Andrew , Whittemore Lisa-Anne , Maniatis Tom
Published: October 2006

The protein kinase inhibitor 2-aminopurine (2AP) blocks the induction of the human β-interferon gene by virus or poly(I)-poly(C) at the level of transcription. This inhibition is specific, since 2AP does not inhibit induction of either the
hsp
70 heat-shock gene by high temperature or the metallothionein gene by cadmium or dexamethasone. However, 2AP does block the induction of the
fos
and c-
myc
proto-oncogenes by serum growth factors or virus, suggesting that a protein kinase may be involved in the regulation of these genes, as well as of the β-interferon gene. However, different factors must be required for the induction of these three genes, since they are not coordinately regulated by the same inducers in most of the cell lines examined.
DNA Damage and Oxygen Radical Toxicity
Authors: Imlay James A. , Linn Stuart
Published: October 2006

A major portion of the toxicity of hydrogen peroxide in
Escherichia coli
is attributed to DNA damage mediated by a Fenton reaction that generates active forms of hydroxyl radicals from hydrogen peroxide, DNA-bound iron, and a constant source of reducing equivalents. Kinetic peculiarities of DNA damage production by hydrogen peroxide in vivo can be reproduced by including DNA in an in vitro Fenton reaction system in which iron catalyzes the univalent reduction of hydrogen peroxide by the reduced form of nicotinamide adenine dinucleotide (NADH). To minimize the toxicity of oxygen radicals, the cell utilizes scavengers of these radicals and DNA repair enzymes. On the basis of observations with the model system, it is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.
Plants: Novel Developmental Processes
Authors: Goldberg Roberrt B.
Published: October 2006

Plants represent a diverse group of organisms that have unique reproductive, developmental, and physiological processes. Although morphologically simple, plants have molecular genetic processes that are equivalent in complexity to those found in animals. Sophisticated gene transfer procedures, transposon mutagenesis in homologous and heterologous plants, and development of model organisms such as
Arabidopsis
permit almost any gene that is associated with an observable phenotype to be isolated and studied. These advances, coupled with general advances in molecular biology, now make it possible to dissect the molecular and cellular events responsible for controlling plant-specific processes.
Primates
Authors: King Frederick A. , Yarbrough Cathy J. , Anderson Daniel C. , Gordon Thomas P. , Gould Kenneth G.
Published: October 2006

Nonhuman primates demonstrate marked similarities to humans in almost all aspects of their anatomy, endocrinology, and physiology. These similarities underlie the value of these animals for appropriate studies in neurobiology, immunology, pathology, reproductive biology, teratology, neonatology, endocrinology, cardiology, and psychology. Investigations with nonhuman primates has made, and continues to make, significant contributions to biomedical and behavioral research. This review provides an overview of basic and applied studies for which primates are appropriate subjects and a summary of the advantages and problems of using nonhuman primates in research.
The National Institutes of Health in Its Centennial Year
Authors: Wyngaarden James B.
Published: October 2006

The laboratory of which the National Institutes of Health (NIH) is a lineal descendant was founded in 1887. During discussions of our plans for a year-long centennial observance with members of our House and Senate appropriations subcommittees, congressional members urged us to set two specific objectives: making NIH better known to the American people, and presenting the attractions of the many roles in health-related research to young people who have not yet formulated career plans. When I was invited to prepare an article for
Science
dealing with my personal experiences as director of NIH since April 1982, it seemed an opportunity to address the same objectives for the scientific community, for in my view there is much misinformation and far too much pessimism throughout the country about the state of biomedical research and its support.
The Catalytic Role of the Active Site Aspartic Acid in Serine Proteases
Authors: Craik Charles S. , Roczniak Steven , Largman Corey , Rutter William J.
Published: October 2006

The role of the aspartic acid residue in the serine protease catalytic triad Asp, His, and Ser has been tested by replacing Asp
102
of trypsin with Asn by site-directed mutagenesis. The naturally occurring and mutant enzymes were produced in a heterologous expression system, purified to homogeneity, and characterized. At neutral
p
H the mutant enzyme activity with an ester substrate and with the Ser
195
-specific reagent diisopropylfluorophosphate is approximately 10
4
times less than that of the unmodified enzyme. In contrast to the dramatic loss in reactivity of Ser
195
, the mutant trypsin reacts with the His
57
-specific reagent, tosyl-L-lysine chloromethylketone, only five times less efficiently than the unmodified enzyme. Thus, the ability of His
57
to react with this affinity label is not severely compromised. The catalytic activity of the mutant enzyme increases with increasing
p
H so that at
p
H 10.2 the
k
cat
is 6 percent that of trypsin. Kinetic analysis of this novel activity suggests this is due in part to participation of either a titratable base or of hydroxide ion in the catalytic mechanism. By demonstrating the importance of the aspartate residue in catalysis, especially at physiological
p
H, these experiments provide a rationalization for the evolutionary conservation of the catalytic triad.
Saccharomyces cerevisiae
Has a U1-Like Small Nuclear RNA with Unexpected Properties
Authors: Siliciano Paul G. , Jones Michele Haltiner , Guthrie Christine
Published: October 2006

Previous experiments indicated that only a small subset of the ≃ 24 small nuclear RNAs (snRNAs) in
Saccharomyces cerevisiae
have binding sites for the Sm antigen, a hallmark of metazoan small nuclear ribonucleoproteins (snRNPs) involved in pre-messenger RNA splicing. Antibodies from human serum to Sm proteins were used to show that four snRNAs (snR7, snR14, snR19, and snR20) can be immunoprecipitated from yeast extracts. Three of these four, snR7, snR14, and snR20, have been shown to be analogs of mammalian U5, U4, and U2, respectively. Several regions of significant homology to U1 (164 nucleotides) have now been found in cloned and sequenced snR19 (568 nucleotides). These include ten out of ten matches to the 5′ end of U1, the site known to interact with the 5′ splice site of mammalian introns. Surprisingly, the precise conservation of this sequence precludes perfect complementarity between snR19 and the invariant yeast 5′ junction (GTA
T
GT), which differs from the mammalian consensus at the fourth position (GTPu
A
GT).
Evidence for Dispensable Sequences Inserted into a Nucleotide Fold
Authors: Starzyk Ruth M. , Webster Teresa A. , Schimmel Paul
Published: October 2006

Previous experimental results along with the structural modeling presented indicate that a nucleotide fold starts in the amino-terminal part of
Escherichia coli
isoleucyl-transfer RNA synthetase, a single chain polypeptide of 939 amino acids. Internal deletions were created in the region of the nucleotide fold. A set of deletions that collectively span 145 contiguous amino acids yielded active enzymes. Further extensions of the deletions yielded inactive or unstable proteins. The three-dimensional structure of an evidently homologous protein suggests that the active deletions lack portions of a segment that connects two parts of the nucleotide fold. Therefore, the results imply that removal of major sections of the polypeptide that connects these two parts of the fold does not result in major perturbation of the nucleotide binding site.
Magnetoencephalography and Epilepsy Research
Authors: Rose D. F. , Smith P. D. , Sato S.
Published: October 2006

Magnetoencephalography is the detection of the magnetic field distribution across the surface of the head, which is generated by a neuronal discharge within the brain. Magnetoencephalography is used in clinical epilepsy to localize the epileptogenic region prior to its surgical removal. A discussion of the instrumentation based on the superconducting quantum interference device that is used for detecting the magnetic field distribution, the analytical techniques, current research, and future directions of magnetoencephalography in epilepsy research is presented.
Transmission of HIV in Belle Glade, Florida: Lessons for Other Communities in the United States
Authors: Castro Kenneth G. , Lieb Spencer , Jaffe Harold W. , Narkunas John P. , Calisher Charles H. , Bush Timothy J. , Witte John J. ,   The Belle Glade Field-Study Group
Published: October 2006

The high cumulative incidence of AIDS and the large percentage of AIDS patients with no identified risks in Belle Glade, Florida, were evaluated through case interviews and neighborhood-based seroepidemiologic studies. It was found that of 93 AIDS patients reported between July 1982 and 1 August 1987, 34 could be directly linked to at least one other AIDS patient or to a person with AIDS-related complex by sexual contact, sharing of needles during intravenous drug abuse (or both), or perinatal exposure; of 877 randomly selected adults, 28 had antibodies to HIV; no person over age 60 and none of 138 children aged 2 to 10 years had antibodies to HIV; no clustering of infected persons within households occurred, except in sex partners; and HIV-seropositive adults were more likely than HIV-seronegative adults to be from Haiti, have a lower income, report sex with intravenous drug abusers, and have a history of previous treatment for sexually transmitted diseases. The presence of antibodies to five arboviruses prevalent in South Florida or the Caribbean did not correlate significantly with HIV infection. The high cumulative rate of AIDS in Belle Glade appears to be the result of HIV transmission through sexual contact and intravenous drug abuse; the evidence does not suggest transmission of HIV through insects.
Ethical Issues in the Prevention and Treatment of HIV Infection and AIDS
Authors: Walters LeRoy
Published: October 2006

The epidemic of infection with the human immunodeficiency virus (HIV) and the acquired immunodeficiency syndrome (AIDS) poses a major ethical question: How can we control the epidemic and the harm that it causes without unjustly discriminating against particular social groups and without unnecessarily infringing on the freedom of individuals? This question pertains to three spheres of public policy in the United States: public health, the delivery of health care, and research. In the public health sphere, vigorous educational efforts will be required, as will modified approaches to intravenous drug use, prostitution, and homosexual and bisexual sexual activity. Carefully targeted, voluntary testing and screening programs should be coupled with counseling and with guarantees of confidentiality and nondiscrimination where these are appropriate. Both health care workers and the health care system have a moral obligation to provide care to people with HIV infection, but heroic self-sacrifice should not be required provided that infection control precautions are observed. Patients with neurological involvement and terminally ill patients will benefit from statutes allowing recognition of advance directives about preferred modes of care or nontreatment. There is a moral imperative to perform intensive research directed toward the understanding, treatment, and prevention of HIV infection and AIDS. The research process will raise challenging ethical questions.
Expression of the Murine Duchenne Muscular Dystrophy Gene in Muscle and Brain
Authors: Chamberlain Jeffrey S. , Pearlman Joel A. , Muzny Donna M. , Gibbs Richard A. , Ranier Joel E. , Reeves Alice A. , Caskey C. Thomas
Published: October 2006

Complementary DNA clones were isolated that represent the 5′ terminal 2.5 kilobases of the murine Duchenne muscular dystrophy (Dmd) messenger RNA (mRNA). Mouse Dmd mRNA was detectable in skeletal and cardiac muscle and at a level approximately 90 percent lower in brain. Dmd mRNA is also present, but at much lower than normal levels, in both the muscle and brain of three different strains of dystrophicmdxmice. The identification of Dmd mRNA in brain raises the possibility of a relation between human Duchenne muscular dystrophy (DMD) gene expression and the mental retardation found in some DMD males. These results also provide evidence that themdxmutations are allelic variants of mouseDmdgene mutations.
Game Depletion Hypothesis of Amazonian Adaptation: Data from a Native Community
Authors: Vickers William T.
Published: October 2006

The low population densities and impermanent settlements of Amazonian Indians are often interpreted as adaptations to a fauna that offers limited protein resources and is rapidly depleted by hunting. Data spanning the 10-year life cycle of one northwestern Amazonian settlement show that variations in hunt yields result from temporal variations in peccary (
Tayassu pecari
and
T. tajacu
) kills that appear extrinsic to native population size. After 10 years, hunting success remained high and the kill rates for most prey did not suggest depletion. An array of environmental factors accounts for the incipient settlement relocation observed.
A Previously Undetected MHC Gene with an Unusual Periodic Structure
Authors: Lévi-Strauss Matthieu , Carroll Michael C. , Steinmetz Michael , Meo Tommaso
Published: October 2006

The major histocompatibility complex is a chromosomal segment embodying several gene clusters among which those with immune functions are the best characterized. This region is suspected to host other as yet undetected genes whose characterization may shed light on the population genetics and evolution of the whole gene complex and thus on its unexplained character of marker locus for a number of diseases of nonimmune or unknown pathogenesis. A novel gene was identified that is transcribed in all tissues tested and is located in mouse and man between the
C4
and Bƒ genes of the H-2 and HLA complexes, respectively. From the nucleotide sequence, derived from liver complementary DNA clones, it is predicted that this novel single-copy gene encodes a 42-kilodalton polypeptide that bears no recognizable relation to the protein families known so far, but it displays striking hallmarks of natural selection.
A "Selfish" B Chromosome That Enhances Its Transmission by Eliminating the Paternal Genome
Authors: Nur Uzi , Werren John H. , Eickbush Danna G. , Burke William D. , Eickbush Thomas H.
Published: October 2006

In the parasitic wasp,
Nasonia vitripennis
, males are haploid and usually develop from unfertilized eggs, whereas females are diploid and develop from fertilized eggs. Some individuals in this species carry a genetic element, termed
psr
(paternal sex ratio), which is transmitted through sperm and causes condensation and subsequent loss of paternal chromosomes in fertilized eggs, thus converting diploid females into haploid males. In this report the
psr
trait was shown to be caused by a supernumerary chromosome. This B chromosome contains at least three repetitive DNA sequences that do not cross-hybridize to each other or to the host genome. The
psr
chromosome apparently produces a trans-acting product responsible for condensation of the paternal chromosomes, but is itself insensitive to the effect. Because the
psr
chromosome enhances its transmission by eliminating the rest of the genome, it can be considered the most "selfish" genetic element yet described.
Reduction of Naturally Occurring Motoneuron Death in Vivo by a Target-Derived Neurotrophic Factor
Authors: Oppenheim Ronald W. , Haverkamp Lanny J. , Prevette David , McManaman James L. , Appel Stanley H.
Published: October 2006

Treatment of chick embryos in ovo with crude and partially purified extracts from embryonic hindlimbs (days 8 to 9) during the normal cell death period (days 5 to 10) rescues a significant number of motoneurons from degeneration. The survival activity of partially purified extract was dose-dependent and developmentally regulated. The survival of sensory, sympathetic, parasympathetic, and a population of cholinergic sympathetic preganglionic neurons was unaffected by treatment with hindlimb extract. The massive motoneuron death that occurs after early target (hindlimb) removal was partially ameliorated by daily treatment with the hindlimb extract. These results indicate that a target-derived neurotrophic factor is involved in the regulation of motoneuron survival in vivo.
Immunofluorescence Localization of Proteins of High Molecular Weight Along Intracellular Microtubules
Authors: Sherline Peter , Schiavone Karen
Published: October 2006

To help clarify the role, in cytoplasmic microtubule function, of the proteins of high molecular weight that coassemble with tubulin in vitro, a monospecific antibody against the proteins of high molecular weight was prepared from the serum of immunized rabbits by affinity chromatography. With indirect immunofluorescence we found that the protein in both cultured neuroblastoma cells and 3T3 cells is distributed in an extensive filamentous array that originates at sites near the nucleus and extends to the cell periphery or, in neuroblastoma cells, gathers into bundles which enter neurites. No filaments were seen with nonspecific antibodies from serum taken before immunization, and prior incubation of the specific antibody with purified protein of high molecular weight (but not tubulin) prevented filament visualization. The filamentous pattern in 3T3 cells was disrupted by colchicine. This evidence indicates that the proteins of high molecular weight are found in cells in association with cytoplasmic microtubules.
Potassium Salt Microinjection into
Xenopus
Oocytes Mimics Gonadotropin Treatment
Authors: Lau Ying-Tung , Yassin Rihab R. , Horowitz Samuel B.
Published: October 2006

Gonadotropin stimulates protein synthesis and growth in ovarian oocytes. The hormone is also known to modify transfollicular K
+
fluxes and is now shown to cause increased intraoocytic K
+
activity (
a
K
). The hormone's effect on
a
K
was duplicated by microinjecting K
+
salts into oocytes which were incubated in paraffin oil. This treatment mimicked the influence of gonadotropin on both the rate of protein synthesis and the synthesis of specific polypeptides. These findings suggest that gonadotropin-stimulated oocyte growth is attributable largely to the hormone's influence on transfollicular K
+
fluxes. They support the hypothesis that the K
+
flux and
a
K
changes observed during cell activation are critical in causing subsequent increases in protein synthesis and growth.
Familial Imprinting Determines H-2 Selective Mating Preferences
Authors: Yamazaki K. , Beauchamp G. K. , Kupniewski D. , Bard J. , Thomas L. , Boyse E. A.
Published: October 2006

Inbred male mice typically prefer to mate with females of a different, non-self H-2 haplotype. To determine whether this natural preference is irrevocable or results from familial imprinting, a test system was used which relied on previous observations that B6 males (H-2
b
) mate preferentially with congenic B6-H-2
k
rather than B6 females, and B6-H-2
k
males with B6 females. This preference was reversed in B6 males fostered by B6-H-2
k
parents and in B6-H-2
k
males fostered by B6 parents, preference in these cases favoring the same H-2 type. Thus, H-2 selective mating preference is acquired by imprinting on familial H-2 types.
Conversion of a PI-Anchored Protein to an Integral Membrane Protein by a Single Amino Acid Mutation
Authors: Waneck Gerald L. , Stein Monica E. , Flavell Richard A.
Published: October 2006

Qa-2, a cell-surface glycoprotein anchored by phosphatidylinositol (PI), is structurally related to the class I transplantation antigens H-2 K, D, and L, which are integral membrane glycoproteins. The predicted transmembrane segment of Qa-2 differs from those of H-2 K, D, and L by the presence of an aspartate in place of a valine at position 295. A single base change that replaced this aspartate with valine resulted in cell-surface Qa-2 molecules that were insensitive to hydrolysis by a PI-specific phospholipase C and more resistant to papain cleavage, properties shared by H-2D. Cells expressing Asp → Val mutant Qa-2 proteins were still able to attach a PI anchor to endogenous proteins such as Thy-1 and J11D. It therefore appears that this single amino acid change converts Qa-2 from a PI-linked form into an integral membrane protein.
Models for the Specific Adhesion of Cells to Cells
Authors: Bell George I.
Published: October 2006

A theoretical framework is proposed for the analysis of adhesion between cells or of cells to surfaces when the adhesion is mediated by reversible bonds between specific molecules such as antigen and antibody, lectin and carbohydrate, or enzyme and substrate. From a knowledge of the reaction rates for reactants in solution and of their diffusion constants both in solution and on membranes, it is possible to estimate reaction rates for membrane-bound reactants. Two models are developed for predicting the rate of bond formation between cells and are compared with experiments. The force required to separate two cells is shown to be greater than the expected electrical forces between cells, and of the same order of magnitude as the forces required to pull gangliosides and perhaps some integral membrane proteins out of the cell membrane.
Surgical Innovation and Its Evaluation
Authors: Bunker J. P. , Hinkley D. , McDermott W. V.
Published: October 2006

Early clinical trials, observational or randomized, hasten the prompt evaluation of new operations. Early clinical surveillance facilitates the design and implementation of randomized clinical trials when they are necessary. Of equal or greater importance, long-term surveillance of operations allows continuing evaluation when their use becomes widespread. Standards, coordination, review, and funding of the evaluation of new operations we believe should be centralized in a single national agency, for which an Institute of Health Care Assessment might be created. Implementation and regulation of the evaluation we believe should remain at the local or regional level with existing mechanisms and agencies being used, such as institutional human research committees and local health systems agencies.
Deregulation of c-
myc
by Translocation of the α-Locus of the T-Cell Receptor in T-Cell Leukemias
Authors: Erikson Jan , Finger Lawrence , Sun Lee , ar-Rushdi Abbas , Nishikura Kazuko , Minowada Jun , Finan Janet , Emanuel Beverly S. , Nowell Peter C. , Croce Carlo M.
Published: October 2006

Two human T-cell leukemias carrying a t(8;14)(q24;q11) chromosome translocation were studied for rearrangements and expression of the c-
myc
oncogene. For one leukemia, rearrangement was detected in a region immediately distal (3′) to the c-
myc
locus; no rearrangements of c-
myc
were observed in the second case (DeF). However, studies with hybrids between human and mouse leukemic T cells indicated that in the leukemic cells of DeF, the breakpoint in chromosome 14 occurred between genes for the variable (V
α
) and the constant (C
α
) regions for the α chain of the T-cell receptor. The C
α
locus had translocated to a region more than 38 kilobases 3′ to the involved c-
myc
oncogene. Since human c-
myc
transcripts were expressed only in hybrids carrying the 8q+ chromosome but not in hybrids containing the normal chromosome 8, it is concluded that the translocation of the C
α
locus 3′ to the c-
myc
oncogene can result in its transcriptional deregulation.
The Oncogenic Activation of Human p21

ras

by a Novel Mechanism
Authors: Walter Maureen , Clark Scott G. , Levinson Arthur D.
Published: October 2006

Single amino acid changes were introduced into normal (non-oncogenic) and activated forms of the human H-
ras
protein at a position (residue 116) proposed on structural grounds to represent a contact site with guanine nucleotides. Substitutions at this site could significantly reduce the ability of both forms to bind and hydrolyze guanosine 5′-triphosphate; these substitutions, however, did not necessarily diminish the transforming capacity of activated derivatives. One substitution that severely impairs these functions activated the transforming potential of the otherwise normal polypeptide.
Structure-Activity Studies of Interleukin-2
Authors: Cohen F. E. , Kosen P. A. , Kuntz I. D. , Epstein L. B. , Ciardelli T. L. , Smith K. A.
Published: October 2006

The critical role of interleukin-2 (IL-2) in immune response heightens the need to know its structure in order to understand its activity. New computer-assisted predictive methods for the assignment of secondary structure together with a method to predict the tertiary structure of a protein from data on its primary sequence and secondary structure were applied to IL-2. This method generated four topological families of structures, of which the most plausible is a right-handed fourfold α-helical bundle. Members of this family were shown to be compatible with existing structural data on disulfide bridges and monoclonal antibody binding for IL-2. Experimental estimates of secondary structure from circular dichroism and site-directed mutagenesis data support the model. A region likely to be important in IL-2 binding to its receptor was identified as residues Leu
36
, Met
38
, Leu
40
, Phe
42
, Phe
44
, and Met
46
.
Gap Junctional Conductance and Permeability Are Linearly Related
Authors: Verselis V. , White R. L. , Spray D. C. , Bennett M. V. L.
Published: October 2006

The permeability of gap junctions to tetraethylammonium ions was measured in isolated pairs of blastomeres from
Rana pipiens
L. and compared to the junctional conductance. In this system, the junctional conductance is voltage-dependent and decreases with moderate transjunctional voltage of either sign. The permeability to tetraethylammonium ions was determined by injecting one cell of a pair with tetraethylammonium and monitoring its changing concentration in the prejunctional and postjunctional cells with ion-selective electrodes. Junctional conductance was determined by current-clamp and voltage-clamp techniques. For different cell pairs in which the transjunctional voltage was small and the junctional conductance at its maximum value, the permeability to tetraethylammonium ions was proportional to the junctional conductance. In individual cell pairs, a reduction in the junctional conductance induced by voltage was accompanied by a proportional reduction in the permeability of the gap junction over a wide range. The diameter of the tetraethylammonium ion (8.0 to 8.5 Å, unhydrated) is larger than that of the potassium ion (4.6 Å, hydrated), the predominant current-carrying species. The proportionality between the permeability to tetraethylammonium ions and the junctional conductance, measured here with exceptionally fine time resolution, indicates that a common gap junctional pathway mediates both electrical and chemical fluxes between cells, and that closure of single gap junction channels by voltage is all or none.
Epidemiology of Drug Abuse: An Overview
Authors: Kozel Nicholas J. , Adams Edgar H.
Published: October 2006

Issues regarding the use of epidemiology in drug abuse research are discussed and systems for monitoring national trends and identifying risk factors are described. Data indicate a general decline in marijuana use among youth, a cohort aging effect among heroin and marijuana users, and increased prevalence and health consequences associated with cocaine use.
Clonal Gene Therapy: Transplanted Mouse Fibroblast Clones Express Human α1-Antitrypsin Gene in Vivo
Authors: Garver Robert I. , Chytil Anna , Courtney Michael , Crystal Ronald G.
Published: October 2006

A retroviral vector was used to insert human α1-antitrypsin (α1AT) complementary DNA into the genome of mouse fibroblasts to create a clonal population of mouse fibroblasts secreting human α1AT. After demonstrating that this clone of fibroblasts produced α1AT after more than 100 population doublings in the absence of selection pressure, the clone was transplanted into the peritoneal cavities of nude mice. When the animals were evaluated 4 weeks later, human α1AT was detected in both sera and the epithelial surface of the lungs. The transplanted clone of fibroblasts could be recovered from the peritoneal cavities of those mice and demonstrated to still be producing human α1AT. Thus, even after removal of selective pressure, a single clone of retroviral vector-infected cells that expressed an exogenous gene in vitro, continued to do so in vivo, and when recovered, continued to produce the product of the exogenous gene.
Measuring the Human T Cell Receptor γ-Chain Locus
Authors: Strauss William M. , Quertermous T. , Seidman J. G.
Published: October 2006

The human T cell receptor γ locus, including eleven variable-region, five joining-region, and two constant-region segments, is contained in 160 kilobases. During T cell somatic development these genes undergo rearrangement by deletion of the sequences separating the variable and joining regions. The molecular map of this locus was completely defined by deletion mapping and restriction mapping. Restriction fragments were resolved by standard agarose electrophoresis and field inversion electrophoresis. These studies demonstrate that the deletions in this locus, which occur during the formation of a functional T cell receptor γ-chain gene, range from 50 to 145 kilobases in length. These studies also provide a structural basis for understanding the development of the γ-chain peptide repertoire, and extends the potential of the emerging pulsed-field electrophoretic technology.
Molecular Basis for the Auxin-Independent Phenotype of Crown Gall Tumor Tissues
Authors: Thomashow Michael F. , Hugly Suzanne , Buchholz Wallace G. , Thomashow Linda S.
Published: October 2006

The transfer of specific Ti (tumor-inducing) plasmid sequences, the T-DNA, from
Agrobacterium tumefaciens
to a wide range of plants results in the formation of crown gall tumors. These tissues differ from most plant cells in that they can be grown in vitro in the absence of added phytohormones. Here, data are presented that offer an explanation for the auxin-independent phenotype of crown gall tissues. It is shown that crude cell-free extracts prepared from three bacterial species harboring pTiA6 gene 1 could convert L-tryptophan to indole-3-acetamide; control extracts lacking gene 1 could not carry out the reaction. Other reports indicate that the pTiA6 gene 2 product can convert indole-3-acetamide to indole-3-acetic acid, a naturally occurring auxin of plants. It is concluded that the auxin-independent phenotype of crown gall tissue involves the introduction of Ti plasmid sequences encoding a two-step pathway for auxin synthesis.